Littermate Control Mice Research Articles

Dendritic cell mineralocorticoid receptor controls blood pressure by regulating T helper 17 differentiation: role of the Plcβ1/4-Stat5-NF-κB pathway.

Dendritic cells (DCs) are closely related to blood pressure (BP) regulation. Mineralocorticoid receptor (MR) is an important drug target for antihypertensive treatment. However, the role of DC MR in the pathogenesis of hypertension has not been fully elucidated. This study aimed to determine the role of DC MR in BP regulation and to explore the mechanism. Renal biopsy and peripheral blood samples were collected from hypertensive patients (HTN) for immunostaining and flow cytometry. Dendritic cell MR knockout (DCMRKO) mice, DC MR overexpressing (DCMROV) mice, DCMROV/IL-17A knockout (DCMROV/IL-17AKO) mice and finerenone-treated C57BL/6 mice were infused with angiotensin II (Ang II) to establish hypertensive models. Western blotting, chromatin immunoprecipitation, co-immunoprecipitation, and in vivo DC depletion or adoptive transfer were used to delineate the functional importance of DC MR in hypertension development. Mineralocorticoid receptor antagonists (spironolactone and finerenone) suppressed DC aggregation and activation, as well as hypertension in HTN and mice. Compared with littermate control (LC) mice, dendritic cell MR knockout mice had strikingly decreased BPs and attenuated target organ damage after Ang II infusion. Flow cytometry showed that DC MR deficiency mitigated Ang II-induced DC activation and T helper 17 (Th17) cell differentiation. RNA sequencing revealed that MR-deficient DCs had elevated expression of Plcβ1 and Plcβ4, knockdown of which reversed the inhibitory effect of MR deficiency on DC activation and Th17 differentiation. Adoptive transfer of MR-deficient DCs protected Ang II-induced hypertension, whereas knockdown of Plcβ1/4 eliminated the protective effects. At the molecular level, MR negatively regulated Plcβ1/4, which recruited SHP-1 to inactivate of Stat5 activity, resulting in enhanced NF-κB activation and Th17 polarization. Furthermore, DCMROV mice manifested more elevated BPs and target organ damage than control mice after Ang II infusion, and these differences were abolished in DCMROV/IL-17AKO mice. Finally, MR antagonists decreased the aggregation of Th17 in HTN and mice. Dendritic cell MR plays important roles in the pathogenesis of hypertension by regulating Th17 through Plcβ1/4-Stat5-NF-κB signalling, and blockade of DC MR is beneficial for treating hypertension.

Oral low-dose rapamycin treatment prevents aortic aneurysms in marfan mice

Abstract Background/Introduction Marfan syndrome (MFS) is a hereditary connective tissue disorder caused by fibrillin-1 (FBN1) gene mutations. Life-threatening complications are cardiovascular, e.g. thoracic aortic aneurysms and dissections. The pathophysiological cause is the increased release of transforming growth factor β-1 (TGF-β1) from the FBN1-deficient extracellular matrix (ECM) and structural disintegrity. Overactivation of the mechanistic target of rapamycin (mTOR) pathway has been demonstrated in the murine mgR/mgR model of MFS. Short-term administration of rapamycin significantly reduced aortic aneurysm formation and increased the life span in these mice. Purpose To assess the effect of an early continuous oral low-dose rapamycin treatment on the aortic aneurysm formation in the FBN1 hypomorphic mgR/mgR mouse model. Methods Male and female 3-4 week-old mgR/mgR mice were orally administered vehicle or rapamycin through diet (8mg/kg/KG) and sacrificed after 11 weeks. Rapamycin concentration was measured by liquid chromatography-mass spectrometry in whole blood. Aortic diameter was studied using echocardiography. Histopathological and immunofluorescence analyses were performed using aortic tissue sections and techniques. Results Blood rapamycin concentration following oral administration remained below detection level. Rapamycin normalized the aortic wall thickness and the diameter in female mgR/mgR mice to levels of the littermate control mice but not in male mgR/mgR mice. The circumferentially distributed elastin fibres remained significantly intact in sections of the ascending aorta of female mice. Echocardiography revealed that rapamycin-treated female mice stayed below a cut-off value for aortic aneurysms of 2 mm inner aortic diameter eight weeks after starting therapy. In contrast, vehicle-treated female animals already exceeded this value after five weeks. In female but not in male mice, the abundance of the mTOR downstream target phosphorylated ribosomal protein S6 was effectively suppressed by low-dose rapamycin up to levels detected in control animals. At the same time, extracellular matrix proteins like the proteoglycan aggrecan (ACAN) and the related chondroitin sulfate were significantly decreased in female mice. The abundance of ADAMTS5 transglutaminase-2 and xylosyltransferase-1, key enzymes involved in the turnover of proteoglycans and biosynthesis of glycosaminoglycan chains, was improved by the rapamycin treatment in female mice. No decrease in mTOR activity could be detected in male mgR/mgR animals. Here, the ACAN and chondroitin sulphate levels also remained at the level of the vehicle-treated animals. Conclusions Chronic low-dose rapamycin treatment reduced aneurysm formation only in female mgR/mgR mice, since the dose was too low for male mgR/mgR mice, by affecting the composition and organization of key ECM components essential for maintaining aortic homeostasis and mechanical properties.

Macrophage-expressed coagulation factor 7 promotes adverse cardiac remodeling

Abstract Background Excess fibrotic remodeling leads to cardiac dysfunction in ischemic heart disease and is driven by MAP kinase-dependent transforming growth factor-ß1 (TGF-ß1) activation by coagulation signaling of myeloid cells. How coagulation-inflammatory circuits can be specifically targeted to achieve beneficial macrophage reprogramming after myocardial infarction (MI) is incompletely understood. Methods Mice with permanent ligation of the proximal left anterior descending artery (LAD) were used to model ischemic heart disease and analyzed by single cell RNA sequencing, protein expression changes, confocal microscopy, and longitudinal monitoring of recovery. We probed the role of the tissue factor (TF)-factor 7 (F7)-integrin ß1-protease activated receptor (PAR) 2 signaling complex by utilizing genetic mouse models and pharmacological intervention. Results Cleavage-insensitive PAR2R38E and myeloid cell integrin ß1-deficient mice had improved cardiac function after MI compared to controls. Proximity ligation assays of monocytic cells in the infarcted myocardium demonstrated that colocalization of F7 with integrin ß1 was diminished in monocyte/macrophage F7-deficient mice. F7fl/fl CX3CR1Cre relative to littermate control mice showed reduced TGF-ß1 and MAP kinase activation, as well as cardiac dysfunction after MI, despite unaltered overall recruitment of myeloid cells into the infarct zone. Single cell mRNA sequencing of CD45+ cells 3 and 7 days after MI uncovered a trajectory from ischemic myocardium-recruited monocytes to inflammatory TF+/F7+/TREM1+ macrophages. As early as 7 days after MI, macrophage F7-deletion led to an expansion of Olfml3+ macrophages with a reparative phenotype and, conversely, to a reduction of TF+/F7+/TREM1+ macrophages, which were also attenuated in activation-resistant PAR2R38E mice. To demonstrate the therapeutic potential of inhibiting the TF-F7-PAR2 signaling complex, we injected a specific monoclonal anti-TF antibody that lacks anticoagulant activity. Short-term treatment from day 1-5 after non-reperfused MI improved cardiac dysfunction, decreased excess fibrosis, attenuated vascular endothelial dysfunction, and increased survival 28 days after MI. Conclusion Extravascular TF-F7-PAR2 complex signaling drives inflammatory macrophage polarization in ischemic heart disease. Targeting this signaling complex for specific therapeutic macrophage reprogramming following MI attenuates cardiac fibrosis and improves cardiovascular function.

ALDH2 mediates the effects of sodium-glucose cotransporter 2 inhibitors (SGLT2i) on improving cardiac remodeling

BackgroundSodium-glucose cotransporter-2 inhibitors (SGLT2i) are now recommended for patients with heart failure, but the mechanisms that underlie the protective role of SGLT2i in cardiac remodeling remain unclear. Aldehyde dehydrogenase 2 (ALDH2) effectively prevents cardiac remodeling. Here, the key role of ALDH2 in the efficacy of SGLT2i on cardiac remodeling was studied.MethodsAnalysis of multiple transcriptomic datasets and two-sample Mendelian randomization were performed to find out the differentially expressed genes between pathological cardiac hypertrophy models (patients) and controls. A pathological cardiac hypertrophy mouse model was established via transverse aortic constriction (TAC) or isoproterenol (ISO). Cardiomyocyte-specific ALDH2 knockout mice (ALDH2CMKO) and littermate control mice (ALDH2flox/flox) were generated to determine the critical role of ALDH2 in the preventive effects of dapagliflozin (DAPA) on cardiac remodeling. RNA sequencing, gene knockdown or overexpression, bisulfite sequencing PCR, and luciferase reporter assays were performed to explore the underlying molecular mechanisms involved.ResultsOnly ALDH2 was differentially expressed when the differentially expressed genes obtained via Mendelian analysis and the differentially expressed genes obtained from the multiple transcriptome datasets were combined. Mendelian analysis revealed that ALDH2 was negatively related to the severity of myocardial hypertrophy in patients. DAPA alleviated cardiac remodeling in mouse hearts subjected to TAC or ISO. ALDH2 expression was reduced, whereas ALDH2 expression was restored by DAPA in hypertrophic hearts. Cardiomyocyte specific ALDH2 knockout abolished the protective role of DAPA in preventing cardiac remodeling. ALDH2 expression and activity were increased in DAPA-treated neonatal rat primary cardiomyocytes (NRCMs), H9C2 cells and AC16 cells. Moreover, DAPA upregulated ALDH2 in peripheral blood mononuclear cells (PBMCs) from patients with type 2 diabetes. Sodium/proton exchanger 1 (NHE1) inhibition contributed to the regulation of ALDH2 by DAPA. DAPA suppressed the production of reactive oxygen species (ROS), downregulated DNA methyltransferase 1 (DNMT1) and subsequently reduced the ALDH2 promoter methylation level. Further studies revealed that DAPA enhanced the binding of nuclear transcription factor Y, subunit A (NFYA) to the promoter region of ALDH2, which was due to the decreased promoter methylation level of ALDH2.ConclusionsThe upregulation of ALDH2 plays a critical role in the protection of DAPA against cardiac remodeling. DAPA enhances the binding of NFYA to the ALDH2 promoter by reducing the ALDH2 promoter methylation level through NHE1/ROS/DNMT1 pathway.Graphical abstract

Elevated plasma and CSF neurofilament light chain concentrations are stabilized in response to mutant huntingtin lowering in the brains of Huntington’s disease mice

BackgroundTherapeutic approaches aimed at lowering toxic mutant huntingtin (mHTT) levels in the brain can reverse disease phenotypes in animal models of Huntington's disease (HD) and are currently being evaluated in clinical trials. Sensitive and dynamic response biomarkers are needed to assess the efficacy of such candidate therapies. Neurofilament light chain (NfL) is a biomarker of neurodegeneration that increases in cerebrospinal fluid (CSF) and blood with progression of HD. However, it remains unknown whether NfL in biofluids could serve as a response biomarker for assessing the efficacy of disease-modifying therapies for HD.MethodsLongitudinal plasma and cross-sectional CSF samples were collected from the YAC128 transgenic mouse model of HD and wild-type (WT) littermate control mice throughout the natural history of disease. Additionally, biofluids were collected from YAC128 mice following intracerebroventricular administration of an antisense oligonucleotide (ASO) targeting the mutant HTT transgene (HTT ASO), at ages both before and after the onset of disease phenotypes. NfL concentrations in plasma and CSF were quantified using ultrasensitive single-molecule array technology.ResultsPlasma and CSF NfL concentrations were significantly elevated in YAC128 compared to WT littermate control mice from 9 months of age. Treatment of YAC128 mice with either 15 or 50 µg HTT ASO resulted in a dose-dependent, allele-selective reduction of mHTT throughout the brain at a 3-month interval, which was sustained with high-dose HTT ASO treatment for up to 6 months. Lowering of brain mHTT prior to the onset of regional brain atrophy and HD-like motor deficits in this model had minimal effect on plasma NfL at either dose, but led to a dose-dependent reduction of CSF NfL. In contrast, initiating mHTT lowering in the brain after the onset of neuropathological and behavioural phenotypes in YAC128 mice resulted in a dose-dependent stabilization of NfL increases in both plasma and CSF.ConclusionsOur data provide evidence that the response of NfL in biofluids is influenced by the magnitude of mHTT lowering in the brain and the timing of intervention, suggesting that NfL may serve as a promising exploratory response biomarker for HD.

NINJ1-mediated Macrophage Plasma Membrane Rupture and Neutrophil Extracellular Trap Formation Contribute to Oxalate Nephropathy.

Oxalate nephropathy is characterized by calcium oxalate crystals deposition, which triggers necrosis of renal tubular epithelial cells, initiates an inflammatory cascade characterized by neutrophil and macrophage activation within the renal microenvironment. Despite the close association of immune cells with acute oxalate nephropathy, the underlying mechanisms still remain unclear. Nerve injury-induced protein 1 (NINJ1) plays an essential role in the induction of plasma membrane rupture (PMR), leading to damage-associated molecular patterns (DAMPs) release and triggering inflammation. We hypothesize that NINJ1-mediated high mobility group box 1 (HMGB1) release from macrophage PMR and neutrophil extracellular traps (NETs) formation synergistically contribute to the progression of acute oxalate nephropathy. Using a murine model of acute oxalate nephropathy, myeloid cell-specific deletion of Ninj1 mice (Ninj1fl/flvavcre) and their wild-type littermate control mice (Ninj1wt/wtvavcre) were administered intraperitoneal injection of 100 mg/kg sodium oxalate followed by drinking water with 3% sodium oxalate. Evaluation was conducted on tubular injury and inflammatory cell infiltration. In vitro studies involved isolation and culture of renal proximal tubular epithelial cells (RTECs), bone marrow-derived macrophages, and neutrophils to investigate NETs formation and HMGB1 release. Targeted deletion of Ninj1 in myeloid cells significantly mitigated oxalate-induced acute kidney injury by suppressing both HMGB1 release and NETs formation in vivo. In vitro investigations demonstrated that HMGB1 release from macrophage PMR and NETs formation in neutrophils mediated by NINJ1 oligomerization, which consequently coordinated to enhance renal tubular epithelial cell death. Our findings elucidate the pivotal role of NINJ1-dependent macrophage PMR and NETs formation in the progression of acute oxalate nephropathy, providing novel insights for its prevention and therapeutic targets.

Fas (CD95) expression in adipocytes contributes to diet-induced obesity.

Induction of browning in white adipose tissue (WAT) increases energy expenditure and may be an attractive target for the treatment of obesity. Since activation of Fas (CD95) induces pathways known to blunt expression of uncoupling protein 1 (UCP1), we hypothesized that Fas expression in adipocytes inhibits WAT browning and thus contributes to the development of obesity. Adipocyte-specific Fas knockout (FasΔadipo) and control littermate (FasF/F) mice were fed a regular chow diet or a high-fat diet (HFD) for 20 weeks. Energy expenditure was assessed by indirect calorimetry, and browning was determined in subcutaneous WAT. In vitro, UCP1 was analyzed in subcutaneous murine adipocytes treated with or without Fas ligand. Moreover, FAS expression in WAT was correlated to UCP1 and percentage of body fat in human individuals. HFD-fed FasΔadipo mice displayed reduced body weight gain and blunted adiposity compared to control littermates. Concomitantly, whole-body energy expenditure and WAT browning were elevated. In cultured adipocytes, Fas ligand treatment blunted isoproterenol-induced UCP1 protein levels. In support of these findings in rodents, FAS expression in WAT correlated negatively with UCP1 but positively with adiposity in human individuals. Fas activation in adipocytes contributes to HFD-associated adiposity in rodents and may be a therapeutic target to reduce obesity and associated diseases.

Revealing the Novel Role of Purinergic Receptor P2X4 in Phagocytic Uptake After Ischemic Stroke.

Purinergic receptor P2X4 (P2X4R), highly expressed on microglia and macrophages, is activated by ATP released from damaged cells and linked to poststroke inflammation. Previous studies showed that short-term P2X4R inhibition reduces inflammation and promotes long term recovery, but the mechanism underlying P2X4R and inflammation remains unclear. We hypothesized that P2X4R absence or pharmacological blockade can enhance macrophage phagocytic function by alleviating excessive inflammation after stroke. We divided P2X4R knockout and littermate control mice into 2 groups either naive or mice subjected to ischemic stroke surgery. Additionally, the regular WT mice subjected to ischemic stroke were treated with 5-(3-Bromophenyl)-1,3-dihydro-2H-Benzofuro[3,2-e]-1,4-diazepin-2-one BD (a P2X4R inhibitor) or vehicle. We isolated phagocytic cells from mice in each group and assayed phagocytic activity by quantifying uptake of fluorescent beads and bioparticles using flow cytometry or confocal microscopy and by measuring protein expression related to phagocytosis. Short-term inhibition of P2X4R with with 5-(3-Bromophenyl)-1,3-dihydro-2H-Benzofuro[3,2-e]-1,4-diazepin-2-one treatment upregulated ANXA1 (annexinA1). P2X4R absence prevented ATP-induced decline in phagocytic uptake in macrophages. Microglia or macrophages derived from P2X4R knockout mice showed significantly increased phagocytic activity compared with microglia/macrophages taken from littermate control mice. Cell surface expression of CD36, a scavenger receptor protein, increased after stroke, and was higher in P2X4R knockout mice. This study suggests that blockade or absence of P2X4R increases phagocytic uptake of damaged tissue following ischemic stroke. Taken together with previous reports detailing how P2X4R inhibition is protective following stroke, our results demonstrate P2X4R may mediate long-term resolution after ischemic stroke by enhancing phagocytic clearance.

Transcriptional and morphological responses following distinct muscle contraction protocols for Snell dwarf (Pit1dw/dw) mice.

The Snell dwarf mouse (Pit1dw/dw), an animal model of congenital combined pituitary hormone deficiency, displays skeletal muscle weakness. While enhanced responsivity to repeated exposures of muscle contractions have been documented for Snell dwarf mice, the response following single exposure to distinct contraction protocols remained uncharacterized. The purpose of this study was to investigate the muscle recovery of Snell dwarf and control littermate mice following a single exposure to two separate protocols-an intermittent slow velocity (30°/s) contraction protocol or a continuous rapid velocity (500°/s) contraction protocol. Following both protocols for control mice, torque values were 30% and 80% of pre-protocol values at 5 min and 3 days, respectively. At 10 days, performance returned to baseline for the 30°/s protocol and were depressed for the 500°/s protocol. For Snell dwarf mice following both protocols, torques were depressed to 5% of pre-protocol values at 5 min and returned to baseline by 3 days. Recovery following the 30°/s protocol for control mice and both protocols for Snell dwarf mice coincided with increased transcriptional output, upregulation of cytokine-mediated signaling genes, and a distribution shift to smaller muscle fibers with reduced area per nucleus. These features represent efficacious remodeling ubiquitous across distinct contraction paradigms in the context of the Pit1 mutation.

Dysbiosis-activated IL-17-producing T cells promote skin immunopathological progression in mice deficient of the Notch ligand Jag1 in keratinocytes

BackgroundThe Notch signaling pathway is an evolutionarily conserved regulatory cascade critical in skin development and homeostasis. Mice deficient of Notch signaling molecules have impaired skin and hair follicle development associated with local tissue inflammation. However, mechanisms underlying skin inflammation and pathology resulting from defective Notch signals are not well understood. ObjectiveTo dissect molecular and cellular mechanisms underlying development of skin immunopathology in mice defective of the Notch ligand Jagged-1 (Jag1). MethodsWe assessed involvement of microbiota and immune cell subsets in skin pathogenic symptoms in Foxn1CreJag1fl/fl mice that were deficient of Jag1 in keratinocytes. We also used RNA-seq and 16S rRNA gene-seq analyses to identify molecular factors and bacterial species contributing to skin pathologic symptoms in Foxn1CreJag1fl/fl mice. ResultsCompared to Jag1-sufficient littermate control mice, Foxn1CreJag1fl/fl mice had specific expansion of IL-17a-producing T cells accompanying follicular and epidermal hyperkeratosis and cyst formation while antibody blockage of IL-17a reduced the skin pathology. RNA-sequencing and 16S rRNA gene-sequencing analyses revealed dysregulated immune responses and altered microbiota compositions in the skin of Foxn1CreJag1fl/fl mice. Antibiotic treatment completely prevented over-activation of IL-17a-producing T cells and alleviated skin pathology in Foxn1CreJag1fl/fl mice. ConclusionDysbiosis-induced over-activation of IL-17a-producing T cells is critically involved in development of skin pathology in Foxn1CreJag1fl/fl mice, establishing Foxn1CreJag1fl/fl mice as a useful model to study pathogenesis and therapeutic targets in microbiota-IL-17-mediated skin inflammatory diseases such as hidradenitis suppurativa (HS) and psoriasis.

Exon 1-targeting miRNA reduces the pathogenic exon 1 HTT protein in Huntington disease models.

Huntington disease (HD) is a fatal neurodegenerative disease caused by a trinucleotide repeat expansion in exon 1 of the huntingtin gene (HTT) resulting in toxic gain-of-function and cell death. Despite its monogenic cause, the pathogenesis of HD is highly complex and increasing evidence indicates that, in addition to the full-length (FL) mutant HTT protein, the expanded exon 1 HTT (HTTexon1) protein that is translated from the HTT1a transcript generated by aberrant splicing is prone to aggregate and may contribute to HD pathology. This finding suggests that reducing the expression of HTT1a may achieve a greater therapeutic benefit than targeting only FL mutant HTT. Conversely, strategies that exclusively target FL HTT may not fully prevent the pathogenesis of HD. We have developed an engineered microRNA targeting the HTT exon 1 sequence (miHTT), delivered via adeno-associated virus serotype 5 (AAV5). The target sequence of miHTT is present in both FL HTT and HTT1a transcripts. Preclinical studies with AAV5-miHTT have demonstrated efficacy in several rodent and large animal models by reducing FL HTT mRNA and protein and rescuing HD-like phenotypes, and have been the rationale for phase I/II clinical studies now ongoing in the US and Europe. In the present study, we evaluated the ability of AAV5-miHTT to reduce the levels of aberrantly spliced HTT1a mRNA and the HTTexon1 protein in the brain of two mouse models of HD (heterozygous zQ175 knock-in mice and humanized Hu128/21 mice). Polyadenylated HTT1a mRNA and HTTexon1 protein were detected in the striatum and cortex of heterozygous zQ175 knock-in mice, but not in wild-type, littermate control mice. Intrastriatal administration of AAV5-miHTT resulted in dose-dependent expression of mature miHTT microRNA in cortical brain regions, accompanied by significant lowering of both FL HTT and HTT1a mRNA expression at two months post-injection. Mutant HTT and HTTexon1 protein levels were also significantly reduced in the striatum and cortex of heterozygous zQ175 knock-in at 2 months after AAV5-miHTT treatment and in humanized Hu128/21 mice 7 months post-treatment. The effects were confirmed in primary Hu128/21 neuronal cultures. These results demonstrate that AAV5-miHTT gene therapy is an effective approach to lower both FL HTT and the pathogenic HTTexon1 levels, which could potentially have an additive therapeutic benefit compared to other HTT-targeting modalities.

Tartrate-resistant acid phosphatase (TRAP/ACP5) promotes bone length, regulates cortical and trabecular bone mass, and maintains growth plate architecture and width in a sex- and site-specific manner in mice

Tartrate-resistant acid phosphatase (TRAP) serum levels reflect osteoclast number, bone remodeling activity, and fracture risk. Deletion or loss of function of TRAP results in short stature in mice and man. Yet, the impact and mechanisms of TRAP for the site- and sex-specific development of bone and cartilage is not well understood. Here, we use a global TRAP knockout (TRAPKO) and wildtype littermate control (WT) mice of both sexes to investigate TRAP as a possible sex- and site-specific regulator of bone and growth plate development. TRAPKO mice of both sexes weighed less and had shorter tibial length than their WT, features that were more accentuated in male than female TRAPKO mice. These changes were not associated with a general reduction in growth as not all organs displayed a proportionally lower mass, and serum IGF-1 was unchanged. Using μCT and site-specificity analysis of the cortical bone revealed wider proximal tibia, a higher trabecular thickness, and lower trabecular separation in male TRAPKO compared to WT mice, an effect not seen in female mice. Histomorphometric analysis revealed that the growth plate height as well as height of terminal hypertrophic chondrocytes were markedly increased, and the number of columns was decreased in TRAPKO mice of both sexes. These effects were more accentuated in female mice. Proliferation and differentiation of bone marrow derived macrophages into osteoclasts, as well as C-terminal cross links were normal in TRAPKO mice of both sexes. Collectively, our results show that TRAP regulates bone and cartilage development in a sex-and site-specific manner in mice.

Abstract We060: Hypoxia Inducible Factor-2α Enhances Neutrophil Survival and Promotes Cardiac Injury Following Myocardial Infarction via cIAP-1 Signaling

Rationale: Heart failure is a major cause of mortality following myocardial infarction (MI). Neutrophils (PMNs) are among the first immune cells to accumulate in the infarcted region. While some long-term beneficial functions of PMN in heart injury are now appreciated, en mase PMN accumulation in injured hearts is still associated with worsened resolution of inflammation and disease outcomes. MI causes extensive hypoxic injury to heart tissue, where hypoxia-inducible factors (HIFs) play critical roles in cellular functions. While HIF1α regulation of cell survival, migration and metabolism have been well-studied, the role of HIF-2α in these processes is not well-understood. Even less is known of HIF-2α contributions to PMN effector functions, especially in the context of MI. Objectives: The current study aimed to 1. Mechanistically explore how HIF-2α regulates survival of tissue infiltrating PMNs post-MI and 2. Determine how HIF-2α activity in PMNs impacts heart injury resolution post-MI, and whether specific HIF-2α deletion in PMNs can alleviate MI-induced tissue injury. Methods & Results: Infarct size, cardiac functions monitored by echocardiography, and scar tissue formation after left anterior descending coronary ligation injury model were compared between littermate control and specific PMN HIF-2α depletion (Ly6G-cre +/- HIF-2α fl/fl ) mice. Myocardial infarction size, cardiac dysfunction, scare tissue deposit and survival of tissue infiltrating PMNs post-MI were substantially attenuated in mice with PMN HIF-2α deletion. A significantly reduced lifespan of HIF-2α knockout PMNs was further confirmed by fate-mapping EdU pulse chase experiments. Mechanistically, molecular studies revealed that HIF-2α transcriptionally regulates expression of the pro-survival factor cIAP1 in PMNs binding to an HRE located in the promoter region of BIRC2 , in a hypoxia-inducible manner. Ex-vivo pharmacological inhibition of cIAP1 expression in PMNs using Birinapant resulted in dramatic cell death, establishing the critical role of cIAP1 in PMN survival. Finally, our data demonstrate that the protective effect of HIF-2α deletion in PMNs on MI outcomes was due to elevated recruitment of reparative macrophages into infarcted hearts. Conclusion: HIF-2α, through cIAP1 regulation, promotes PMN survival and tissue retention post-MI, leading to worsen cardiac functions and scar formation.

Tissue material properties, whole-bone morphology and mechanical behavior in the Fbn1C1041G/+ mouse model of Marfan syndrome

Marfan syndrome (MFS) is a connective tissue disorder caused by pathogenic mutations in FBN1. In bone, the protein fibrillin-1 is found in the extracellular matrix where it provides structural support of elastic fiber formation, stability for basement membrane, and regulates the bioavailability of growth factors. Individuals with MFS exhibit a range of skeletal complications including low bone mineral density and long bone overgrowth. However, it remains unknown if the bone phenotype is caused by alteration of fibrillin-1′s structural function or distortion of its interactions with bone cells. To assess the structural effects of the fibrillin-1 mutation, we characterized bone curvature, microarchitecture, composition, porosity, and mechanical behavior in the Fbn1C1041G/+ mouse model of MFS. Tibiae of 10, 26, and 52-week-old female Fbn1C1041G/+ and littermate control (LC) mice were analyzed. Mechanical behavior was assessed via in vivo strain gauging, finite element analysis, ex vivo three-point bending, and nanoindentation. Tibial bone morphology and curvature were assessed with micro computed tomography (μCT). Bone composition was measured with Fourier transform infrared (FTIR) imaging. Vascular and osteocyte lacunar porosity were assessed by synchrotron computed tomography. Fbn1C1041G/+ mice exhibited long bone overgrowth and osteopenia consistent with the MFS phenotype. Trabecular thickness was lower in Fbn1C1041G/+ mice but cortical bone microarchitecture was similar in Fbn1C1041G/+ and LC mice. Whole bone curvature was straighter below the tibio-fibular junction in the medial–lateral direction and more curved above in LC compared to Fbn1C1041G/+ mice. The bone matrix crystallinity was 4 % lower in Fbn1C1041G/+ mice compared to LC, implying that mineral platelets in LCs have greater crystal size and perfection than Fbn1C1041G/+ mice. Structural and mechanical properties were similar between genotypes. Cortical diaphyseal lacunar porosity was lower in Fbn1C1041G/+ mice compared to LC; this was a result of the average volume of an individual osteocyte lacunae being smaller. These data provide valuable insights into the bone phenotype and its contribution to fracture risk in this commonly used mouse model of MFS.

Adipocyte-specific Nrf2 deletion negates nitro-oleic acid benefits on glucose tolerance in diet-induced obesity

Obesity is commonly linked with white adipose tissue (WAT) dysfunction, setting off inflammation and oxidative stress, both key contributors to the cardiometabolic complications associated with obesity. To improve metabolic and cardiovascular health, countering these inflammatory and oxidative signaling processes is crucial. Offering potential in this context, the activation of nuclear factor erythroid 2-related factor 2 (Nrf2) by nitro-fatty acids (NO2-FA) promote diverse anti-inflammatory signaling and counteract oxidative stress. Additionally, we previously highlighted that nitro-oleic acid (NO2-OA) preferentially accumulates in WAT and provides protection against already established high fat diet (HFD)-mediated impaired glucose tolerance. The precise mechanism accounting for these protective effects remained largely unexplored until now. Herein, we reveal that protective effects of improved glucose tolerance by NO2-OA is absent when Nrf2 is specifically ablated in adipocytes (ANKO mice). NO2-OA treatment did not alter body weight between ANKO and littermate controls (Nrf2fl/fl) mice on both the HFD and low-fat diet (LFD). As expected, at day 76 (before NO2-OA treatment) and notably at day 125 (daily treatment of 15 mg/kg NO2-OA for 48 days), both HFD-fed Nrf2fl/fl and ANKO mice exhibited increased fat mass and reduced lean mass compared to LFD controls. However, throughout the NO2-OA treatment, no distinction was observed between Nrf2fl/fl and ANKO in the HFD-fed mice as well as in the Nrf2fl/fl mice fed a LFD. Glucose tolerance tests revealed impaired glucose tolerance in HFD-fed Nrf2fl/fl and ANKO compared to LFD-fed Nrf2fl/fl mice. Notably, NO2-OA treatment improved glucose tolerance in HFD-fed Nrf2fl/fl but did not yield the same improvement in ANKO mice at days 15, 30, and 55 of treatment. Unraveling the pathways linked to NO2-OA's protective effects in obesity-mediated impairment in glucose tolerance is pivotal within the realm of precision medicine, crucially propelling future applications and refining novel drug-based strategies.

Role of ADAR2-mediated innate immune responses in vascular inflammation and atherosclerosis

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Deutsche Forschungsgemeinschaft (DFG) Background Adenosine-to-inosine (A-to-I) RNA editing is an epitranscriptional regulator of RNA metabolism, catalyzed by the adenosine deaminases acting on RNA-1/-2 (ADAR1/2). Whether ADAR2 play a role in atherosclerotic processes remains elusive. Aim We examined the role of ADAR2 in vascular endothelial cell (EC) immunomodulatory responses and its biological relevance in murine and human atherosclerosis. Methods The role of ADAR2 in atherosclerosis was determined in a double ADAR2 and ApoE knockout mice fed with Western diet for 20 weeks. Three mouse genetic models (global and inducible vascular endothelial cell (iEC)-restricted ADAR2 and IL6ST knockout) were used to determine the role of ADAR2 in IL-6-related innate immunity. Expression levels of ADAR2 were measured in peripheral blood mononuclear cells derived from 533 individuals at risk for atherosclerotic vascular disease. Structural vascular measurements were used, including intima-media thickness (IMT), carotid wall maximum thickness (maxWT), and the number of atheromatous plaques by carotid and femoral artery ultrasonography as surrogate markers of subclinical arterial disease. Study participants were followed for major adverse cardiovascular events (MACE). Results Genetic ablation of ADAR2 resulted in a reduction of atherosclerotic plaque burden and necrotic core in the aorta and brachiocephalic trunk as well as reduced leukocyte infiltration in atherosclerotic plaques without affecting cholesterol levels in mice. Blood analysis revealed decreased pro-inflammatory cytokine levels including IL-6 after treatment of ADAR2/APOE KO mice compared to littermate control mice. Intravital imaging of IL-6-inflamed vascular endothelium showed that rolling and adhesion of leukocyte subsets to vascular wall were impaired by 2-fold in ADAR2-/- or iEC-ADAR2-/- KO mice. In vivo and ex vivo histological examination revealed that endothelial ADAR2 controls endothelial vascular adhesion molecule expression induced by gp130 signaling. ADAR2-deficient transcriptome revealed a selective upregulation of a conserved group of miRNAs targeting the IL6ST mRNA. Multilayered rescue studies including miR-inhibitors restored IL6ST levels after ADAR2 deficiency. In humans, increased ADAR2 expression was independently associated with the presence of CAD, higher C-reactive protein and mean carotid IMT after adjustment for traditional risk factors. Increased ADAR2 at baseline was prospectively associated with accelerated progression of subclinical atherosclerosis reflected by the increased number of carotid plaques at follow-up (OR=3.74, P<0.05). Finally, high ADAR2 levels were independently associated with higher MACE incidence across a median follow-up period of 54 months. Conclusion Posttranscriptional control of vascular inflammation by ADAR2 is integral for the development and progression of atherosclerosis in mice and humans. Our findings suggest that ADAR2 may serve as a promising therapeutic target for atherosclerosis.Role of ADAR2 in atherosclerosis

Defining the In Vivo Role of mTORC1 in Thyrocytes by Studying the TSC2 Conditional Knockout Mouse Model.

Background: The thyroid gland is susceptible to abnormal epithelial cell growth, often resulting in thyroid dysfunction. The serine-threonine protein kinase mechanistic target of rapamycin (mTOR) regulates cellular metabolism, proliferation, and growth through two different protein complexes, mTORC1 and mTORC2. The PI3K-Akt-mTORC1 pathway's overactivity is well associated with heightened aggressiveness in thyroid cancer, but recent studies indicate the involvement of mTORC2 as well. Methods: To elucidate mTORC1's role in thyrocytes, we developed a novel mouse model with mTORC1 gain of function in thyrocytes by deleting tuberous sclerosis complex 2 (TSC2), an intracellular inhibitor of mTORC1. Results: The resulting TPO-TSC2KO mice exhibited a 70-80% reduction in TSC2 levels, leading to a sixfold increase in mTORC1 activity. Thyroid glands of both male and female TPO-TSC2KO mice displayed rapid enlargement and continued growth throughout life, with larger follicles and increased colloid and epithelium areas. We observed elevated thyrocyte proliferation as indicated by Ki67 staining and elevated cyclin D3 expression in the TPO-TSC2KO mice. mTORC1 activation resulted in a progressive downregulation of key genes involved in thyroid hormone biosynthesis, including thyroglobulin (Tg), thyroid peroxidase (Tpo), and sodium-iodide symporter (Nis), while Tff1, Pax8, and Mct8 mRNA levels remained unaffected. NIS protein expression was also diminished in TPO-TSC2KO mice. Treatment with the mTORC1 inhibitor rapamycin prevented thyroid mass expansion and restored the gene expression alterations in TPO-TSC2KO mice. Although total thyroxine (T4), total triiodothyronine (T3), and TSH plasma levels were normal at 2 months of age, a slight decrease in T4 and an increase in TSH levels were observed at 6 and 12 months of age while T3 remained similar in TPO-TSC2KO compared with littermate control mice. Conclusions: Our thyrocyte-specific mouse model reveals that mTORC1 activation inhibits thyroid hormone (TH) biosynthesis, suppresses thyrocyte gene expression, and promotes growth and proliferation.

Cardiomyocyte Ketone Metabolism Regulates Myocardial Hyperemia

Myocardial perfusion is inextricably coupled to metabolism, with increases in physiologic cardiac demand promoting coronary vasodilation. Despite its wide acceptance, the hypothesis that cardiomyocyte metabolism autoregulates myocardial perfusion lacks mechanistic detail; however, clinical and preclinical studies suggest a signaling role for intermediary metabolites in the vasodilatory response. In particular, the ketone body precursor, β-hydroxybutyrate (3-OHB), enhances myocardial blood flow in humans, but the mechanism by which it does so remains unclear. Here, we determined the extent to which 3-OHB influences myocardial hyperemia in mice. Intravenous 3-OHB infusion (0.5 g/kg) in adult mice (12–24 wks) raised circulating 3-OHB levels (0.5 ± 0.1 to 5.1 ± 0.6 mM; p=0.005) and increased myocardial perfusion (18.6 ± 4.4 to 50.9 ± 10.4 mL/min/g; p=0.024), as measured by myocardial contrast echocardiography. Enhanced perfusion induced by 3-OHB occurred in the absence of changes in cardiac output or systolic performance. Next, to determine if 3-OHB directly dilates the coronary vasculature, we exposed pressurized (80 mmHg), small-diameter (100–260 μm) coronary arteries from mice (C57/Bl6J and 6N) to 3-OHB (0.1–5 mM) but found no significant changes in diameter. Based on these results, we tested whether cardiomyocyte metabolism of 3-OHB is required for the vasodilatory response. We deleted β-hydroxybutyrate dehydrogenase (BDH1) selectively in cardiomyocytes using Bdh1fl/fl mice crossed with tamoxifen-inducible Cre recombinase mice (csBDH1−/−). Although 3-OHB robustly enhanced myocardial perfusion (6.9 ± 1.4 to 21.3 ± 5.6 mL/min/g; p=0.031) at sustained cardiac workloads and peripheral vascular resistance in Cre-negative littermate (control) mice, csBDH1−/− mice completely lacked the 3-OHB-induced hyperemic response (8.0 ± 2.5 to 6.3 ± 2.8 mL/min/g; p>0.999). Together, these data indicate that 3-OHB evokes workload-independent enhancement of myocardial perfusion through a mechanism that requires cardiomyocyte metabolism of 3-OHB. Our results support the general concept that acute changes in metabolic substrate availability may influence oxygen delivery to cardiomyocytes via a cardiomyocyte-vascular signaling nexus. R01HL163818, R01HL142710, R01HL163003, P30GM127607, P30GM127607-05S1, Jewish Heritage Fund for Excellence (JHFE), S10OD025178. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Deletion of ADAM17 on microglia attenuates salt-sensitive hypertension

Previous work from our group identified ADAM17-mediated shedding as a major mechanism responsible for ACE2 shedding, thus impairing ACE2 compensatory activity and contributing to the development of salt sensitive hypertension. While microglia have been shown to contribute to salt sensitive hypertension, the mechanisms responsible are unknown. Accordingly, we hypothesize that ADAM17 promotes microglia priming, sympatho-excitation and neuro-inflammation in salt sensitive hypertension, and thus targeting ADAM17 or its maturation, via iRhom2, provides a multi-pronged strategy to normalize BP. Here, we aimed to evaluate whether deletion of ADAM17 on microglia attenuates hypertension. Uninephrectomized male and female mice (14–16-week-old, n=10/group) with selective deletion of ADAM17 in microglia (Cx3CR1-ADAM17tom) or with global deletion of iRhom2 (iRhom2-KO) and littermate controls (Cx3CR1-Cretom) mice were used to monitor blood pressure (BP telemetry, DSI) at baseline and following the initiation of salt sensitive hypertension (DOCA 1mg/g body weight sc + 1% saline po for 3 weeks). Following the establishment of hypertension (7 days post DOCA implantation) mice were injected with tamoxifen (200 nl ICV) and monitored for 2 more weeks. At the end of the treatment, mice were euthanized, and their brains were collected. Baseline mean arterial pressure (MAP) was not different in Cx3CR1-ADAM17tom, iRhom2-KO compared to controls (102±1, 106±1 and 104±1 mmHg, respectively). Surprisingly, all mice developed hypertension following DOCA implantation, including iRhom2 KO (Cx3CR1-ADAM17tom: 131±1, iRhom2 KO: 131±1, control: 126±1 mmHg, respectively. p<0.05). Interestingly, following tamoxifen injection Cx3CR1-ADAM17tom mice showed a blunted hypertension compared to the control group (MAP: 122±0.2 vs. 146±0.5 mmHg, one way ANOVA, p<0.05) suggesting that ADAM17 in microglia contributes to salt sensitive hypertension. In vitro, human microglia cells (iCell microglia — hIPSC) were shown to express lower ACE2 protein (0.03 ± 0.1 vs. 1.18 ± 0.3, Student’s t test, p<0.05) when exposed to Ang-II (100 ng) with a trend for ADAM17 upregulation (1.5 ± 0.3 vs. 1.1 ± 0.1, p<0.05). Together, our data suggest that overactivity of the renin-angiotensin system is associated with overexpression of ADAM17 in microglia and a simultaneous downregulation of ACE2. In addition, knockdown of ADAM17 specifically on microglia blunted the development of hypertension. We conclude that ADAM17 expression in microglia plays a pivotal role in salt sensitive hypertension. This work was supported in part by a research grant from the National Institutes of Health (HL163588). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Cardiac lipotoxicity and fibrosis underlie impaired contractility in a mouse model of metabolic dysfunction-associated steatotic liver disease.

The leading cause of death among patients with metabolic dysfunction-associated steatotic liver disease (MASLD) is cardiovascular disease. A significant percentage of MASLD patients develop heart failure driven by functional and structural alterations in the heart. Previously, we observed cardiac dysfunction in hepatocyte-specific peroxisome proliferator-activated receptor alpha knockout (Ppara HepKO), a mouse model that exhibits hepatic steatosis independent of obesity and insulin resistance. The goal of the present study was to determine mechanisms that underlie hepatic steatosis-induced cardiac dysfunction in Ppara HepKO mice. Experiments were performed in 30-week-old Ppara HepKO and littermate control mice fed regular chow. We observed decreased cardiomyocyte contractility (0.17 ± 0.02 vs. 0.24 ± 0.02 μm, p < 0.05), increased cardiac triglyceride content (0.96 ± 0.13 vs. 0.68 ± 0.06 mM, p < 0.05), collagen type 1 (4.65 ± 0.25 vs. 0.31 ± 0.01 AU, p < 0.001), and collagen type 3 deposition (1.32 ± 0.46 vs. 0.05 ± 0.03 AU, p < 0.05). These changes were associated with increased apoptosis as indicated by terminal deoxynucleotidyl transferase dUTP nick end labeling staining (30.9 ± 4.7 vs. 13.1 ± 0.8%, p < 0.006) and western blots showing increased cleaved caspase-3 (0.27 ± 0.006 vs. 0.08 ± 0.01 AU, p < 0.003) and pro-caspase-3 (5.4 ± 1.5 vs. 0.5 ± 0.3 AU, p < 0.02), B-cell lymphoma protein 2-associated X (0.68 ± 0.07 vs. 0.04 ± 0.04 AU, p < 0.001), and reduced B-cell lymphoma protein 2 (0.29 ± 0.01 vs. 1.47 ± 0.54 AU, p < 0.05). We further observed elevated circulating natriuretic peptides and exercise intolerance in Ppara HepKO mice when compared to controls. Our data demonstrated that lipotoxicity, and fibrosis underlie cardiac dysfunction in MASLD.