Tg Mice Research Articles

Abstract We123: Cardiomyocyte Specific Sustained Atg7 Overexpression Activates Mitochondrial Autophagy in the Heart

Introduction: Accumulating evidence indicates that autophagy-related protein 7 (Atg7) is essential in cellular autophagy. Our earlier studies showed that Atg7 is required to promote macro-autophagy in the heart. However, it is unknown if the activation of Atg7 has a role in the heart to regulate selective mitochondrial autophagy (mitophagy). Objectives: We employed in vitro and in vivo approaches to delineate the molecular function and mechanisms of Atg7-mediated activation of mitophagy in the heart. Methods and Results: Subcellular fractionation and quantum dot-labeled electron microscopy revealed Atg7’s localization on the mitochondrial fraction in the heart. Atg7 co-localization to Mitotracker-labeled mitochondria was confirmed using isolated heart mitochondria. To quantitate the mitophagy, we overexpressed Atg7 in cultured primary cardiomyocytes, treated with cyanide 3-chlorophenylhydrazone (CCCP) to induce mitophagy, and stained with pH-sensitive fluorescent mitophagy dye to enumerate mitophagy dots by microscopy. We found significantly increased mitophagy dots in Atg7 overexpressed cardiomyocytes than in β-gal expressing control. To assess the activation of mitophagy in vivo , we treated the cardiac-specific Atg7 overexpressing transgenic (αMHC-Atg7 Tg) and their littermate non-transgenic (Ntg) mice with CCCP. We found an increased accumulation of mature autophagolysosomal marker protein LC3-II in isolated mitochondria from Atg7 Tg mice hearts post-CCCP treatment. To assess the extent of mitochondrial lysosomal delivery in Atg7 overexpressing hearts, we crossed αMHC-Atg7 Tg mice with cardiac-specific Mito-Keima transgenic (Mt-Keima Tg) mice. Mt-Keima Tg mice bear mitochondria-targeted pH-dependent fluorescent lysosomal protease-resistance Keima protein, enabling the measurement of mitophagy activation in vivo . We observed increased Mt-Keima high red-to-green areas in αMHC-Atg7xMt-Keima Tg mice hearts compared to Mt-Keima mice. Conclusions: Our biochemical and genetic approaches revealed that Atg7 localizes to the mitochondria, leading to the recruitment and initiation of mitophagy machinery. Our data further confirm that genetic activation of Atg7 leads to increased mitophagy activity in the heart.

Abstract Tu047: Carbonic anhydrase inhibitors (CAIs) mitigate cardiac amyloid β pathology, attenuating neuro-signaling adverse remodeling and improving cardiac function in the Tg2676- AD mouse model.

FDA-approved carbonic anhydrase inhibitors (CAIs) have been shown to attenuate Aβ pathology, neurodegeneration, and cerebrovascular dysfunction in models of Alzheimer’s disease (AD) and cerebral amyloid angiopathy (CAA), suggesting a key role for CAs as a novel and previously unexplored target for AD therapy. Amyloid-β accumulation severely impairs the cerebral neuro-signaling pathway with a progressive loss in neurotrophic factors (like BDNF), potentially also affecting the cardiac nervous system and culminating in lethal heart dysfunction. Yet, no studies have proposed the use of CAIs for treating and preventing the systemic and cardiac effects of amyloidosis and AD. Here, we explored for the first time, the protective effects of a chronic CAIs therapeutic regimen against cardiac amyloid pathology, neuronal fibers’ loss, and heart neurotrophic dysregulation in Tg2576 mice, a widely used model of AD and cerebral amyloidosis. Cardiac fibrosis enhancement along with progressive Aβ deposition in the heart seriously affected the cardiac neuro-signaling pathway culminating in a robust decline of BDNF expression associated with myocardial adrenergic nerve fibers and regenerated nerve endings impoverishment (stained with TH and GAP-43 respectively) in 13-month-old Tg2576 mice compared to age-matched WT littermates. These degenerative mechanisms severely compromised heart function, evidenced by a decline of both ejection fraction and fraction shortening percentage in Tg2576 animals. Accordingly, we observed that human Aβ40 or Aβ42 oligomers’ treatment drastically reduced BDNF and GAP-43 expression in human neuronal cells and human cardiomyocytes. Notably, long-term CAIs treatment in Tg2576 mice reduced Aβ accumulation in the heart tissue and reverted cardiac neuro-signaling pathway adverse remodeling, thus ameliorating heart function, as evidenced through speckle tracking-based strain echocardiography analysis. These in vivo results were validated by in vitro experiments both in neuronal and cardiac cells. These findings suggest a new beneficial role of CAIs in preventing the Aβ induced cardiovascular remodeling and neuro-signaling deregulation for the first time in the Tg2576 model of AD. Taken together with the positive effects of CAIs on cerebrovascular function and cognition, this study paves the way for future clinical trials aimed at repurposing FDA-approved CAIs to prevent and correct both central and peripheral pathologies induced by AD and amyloidosis.

Investigation of the Impact of the H310A FcRn Region Mutation on 89Zr-Immuno-PET Brain Imaging with a BBB-Shuttle Anti‑Amyloid Beta Antibody

PurposeIn the emerging field of antibody treatments for neurodegenerative diseases, reliable tools are needed to evaluate new therapeutics, diagnose and select patients, monitor disease progression, and assess therapy response. Immuno-PET combines the high affinity and exceptional specificity of monoclonal antibodies with the non-invasive imaging technique positron emission tomography (PET). Its application in neurodegenerative disease brain imaging has been limited due to the marginal uptake across the blood–brain barrier (BBB). The emergence of BBB-shuttle antibodies with enhanced uptake across the BBB extended immuno-PET to brain imaging. We recently reported about specific brain uptake of a bispecific aducanumab mTfR antibody in APP/PS1 TG mice using 89Zr-immuno-PET. However, a sufficient target-to-background ratio was reached at a relatively late scanning time point of 7 days post-injection. To investigate if a better target-to-background ratio could be achieved earlier, an aducanumab BBB-shuttle with a mutated Fc region for reduced FcRn affinity was evaluated.ProceduresAduH310A-8D3 and Adu-8D3 were modified with DFO*-NCS and subsequently radiolabeled with 89Zr. The potential influence of the H310A mutation, modification with DFO*-NCS, and subsequent radiolabeling on the in vitro binding to amyloid-beta and mTfR1 was investigated via amyloid-beta peptide ELISA and FACS analysis using mTfR1 transfected CHO-S cells. Blood kinetics, brain uptake, in vivo PET imaging and target engagement of radiolabeled AduH310A-8D3 were evaluated and compared to non-mutated Adu-8D3 in APP/PS1 TG mice and wild-type animals as controls.ResultsRadiolabeling was performed with sufficient radiochemical yields and radiochemical purity. In vitro binding to amyloid-beta and mTfR1 showed no impairment. [89Zr]Zr-AduH310A-8D3 showed faster blood clearance and earlier differentiation of amyloid-beta-related brain uptake compared to [89Zr]Zr-Adu-8D3. However, only half of the brain uptake was observed for [89Zr]Zr-AduH310A-8D3.ConclusionsAlthough a faster blood clearance of AduH310A-8D3 was observed, it was concluded that no beneficial effects for 89Zr-immuno-PET imaging of brain uptake were obtained.Graphical

Abstract Mo120: Overexpression of Prostaglandin E2 EP3 Receptor Subtype Alters Calcium-Handling Proteins in Mouse Hearts

Prostaglandin E2 (PGE2) is an autacoid that acts through G-protein coupled receptors (EP1-EP4) in various cell types within the heart, including cardiomyocytes in which EP3 and EP4 predominate. We previously reported that mice with cardiomyocyte-specific overexpression of the EP3 receptor (EP3 TG) demonstrate reduced cardiac function and diminished cardiomyocyte contractility in isolated cardiomyocytes. We therefore hypothesized that PGE2 via the EP3 receptor regulates calcium handling proteins to reduce contractility. To test our hypothesis, we performed RNA sequencing (RNA seq) on the left ventricle of fifteen-week-old male EP3 TG mice along with their WT controls. Western blots were used to confirm changes in the expression of calcium-handling proteins such as Sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA2a), Ryanodine receptor 2 (RYR2), Phospholamban (PLB), Troponins (C, I, T) and voltage-gated calcium channel (CACNB2). For RNA seq, all data is reported as Log2Fold change, adjusted P value, and western blot data is reported as mean ± standard error (SE) of the mean. Additionally, isolated cardiomyocyte contractility was assessed using the IonOptix system, and data is reported as the mean ± SE. RNA seq data shows that SERCA2a and RYR2 expression were significantly downregulated in TG mice (SERCA2a -0.44, p=4.72 x 10 -6 ; RYR2: -0.86, p=4.08 x 10 -5 ) in addition to significant reductions in Troponin I (-0.43, p=0.038) and the Voltage-gated calcium channel (CACNB2: -0.71,p=0.0055). Western blot analyses confirmed the reductions in SERCA2a, RYR2, and CACNB2 although these changes were only significant for CACNB2 (1.0 ± 0.03 for WT vs 0.59 ± 0.04 for TG, p = 0.016). Expression of Troponins did not change in TG mice. Consistent with our previous data, IonOptix analysis shows reduced contractility of myocytes from EP3 TG mice (bl% peak h is 3.47 ± 0.20 for WT vs 1.0 ± 0.14 for TG, p<0.0001) despite a similar increase in the Ca 2+ transients (Ca 2+ peak h for WT= 0.86 ± 0.04 and TG=0.86 ± 0.07) suggesting potential changes in the sensitivity of the myofilament to Ca 2+ . In conclusion, the reduced contractility observed in EP3 TG mice may be due to alterations in calcium handling proteins and/or changes in calcium sensitivity at the level of the myofilament.

Abstract Tu114: Prostaglandin E2 Alters Mitochondrial Energy Metabolism in the Murine Heart

Prostaglandin E 2 (PGE2) is an autacoid that acts via 4 receptors (EP1-EP4), with EP3 and EP4 being the most prominent in the heart. We previously reported that cardiomyocyte specific knockout of EP4 (EP4 KO) results in dilated cardiomyopathy. Additionally, transgenic mice that overexpress EP3 in the cardiomyocyte (EP3 TG) develop heart failure. Recently published data from our laboratory suggests EP4 KO results in mitochondrial dysfunction, likely via EP3 receptor signaling. We therefore hypothesized that PGE2 alters energy metabolism in the heart via EP3. To test our hypothesis, we performed gene array analysis on left ventricles from adult EP4 KO and wild type (WT) mice. Significant reductions (2.1-fold) in carnitine palmitoyltransferase 2 ( Cpt2 ) were observed in EP4 KO vs. EP4 WT. CPT2 is a key enzyme in fatty acid oxidation and deficiencies in humans have been shown to cause cardiomyopathy. Substantial reductions in CPT2 were also observed in C57 mice after 2 weeks of myocardial infarction (0.22 ± 0.04 a.u. in sham controls vs. 0.039 ± 0.06 a.u. after MI. p<0.01) by western blot analysis. Moreover, treatment with the EP3 receptor agonist, sulprostone, reduced CPT2 protein expression significantly in cardiomyocytes isolated from C57 mice (1.0 ± 0.0 a.u. in vehicle control vs. 0.67 ± 0.07 a.u. in sulprostone treated. p<0.005). These data suggest that PGE2 via its EP3 receptor reduces CPT2 expression. In fact, RNAseq analysis on left ventricles from EP3 TG and EP3 WT mice showed significant reductions in Cpt 2 expression as early as 5 wks of age (log 2 FC = -1.17. p<0.01). RNAseq also showed reductions in other key fatty acid oxidation/transport genes in EP3 TG mice ( Acsl1 ; log 2 FC= -0.73, Acads , log 2 FC= -0.59, Cd36 , log 2 FC= -0.64. p<0.005). Lastly, to further investigate the role of the EP receptors on energy metabolism in the heart, we isolated cardiomyocytes from EP4 KO and EP4 WT mice and performed metabolomics. As anticipated, we observed significant reductions in L-carnitine (7.6 ± 1.13 fmol/cell in EP4 WT vs. 2.1 ± 0.32 fmol/cell in EP4 KO. p<0.005) and several acyl carnitine products. Altogether our data supports our hypothesis that PGE2 signaling via its EP3 receptor impairs mitochondrial energy metabolism in the heart by reducing fatty acid oxidation.

Abstract We106: Long Non-Coding RNA LIPTER Regulates Lipid Metabolism of Human Cardiomyocytes and Preserves Cardiac Function

Background: Recently, long non-coding RNAs (lncRNAs) have emerged as novel human-specific (i.e. non-conserved) regulators of cardiovascular development and disease, which possess diverse functions through interacting with other molecules, including DNA, RNA, protein, and lipid. We identified a human lncRNA, LIPTER, which mediates lipid droplet (LD) transport to regulate lipid metabilism of human cardiomyocytes (CMs). Mechanistically, LIPTER binds phospholipids PA and PI4P on the LD membranes and the MYH10 protein, connecting LDs to the cytoskeleton and facilitating LD transport to mitochondria. LIPTER deficiencies led to prominent LD accumulation, mitochondrial dysfunction, and death of human iPS cell-derived CMs. Since downregulation of LIPTER and enahnced LD accumulation are associated with cardiac dysfunction and heart failure in patients with metabolic disorders, such as obesity and diabetes mellitus, we thereby seek to explore the preclinical potential of LIPTER for the therapy of human metabolic disorder associated cardiac dysfunction and heart failure. Hypothesis: We hypothesize that transgenic overexpression of the human lncRNA LIPTER in mouse heart could attenuate metabolic syndrome-associated myocardium lipid accumulation and cardiac dysfunction, as well as prevent isoproterenol-induced heart failure through increasing the fatty acid oxidation (FAO) of mouse heart. Goals: To evaluate the preclinical potential of human lncRNA LIPTER for the therapy of cardiac dysfunction and heart failure by using mouse cardiac dysfunction and heart failure models. Methods: We established a LIPTER transgenic overexpression mouse line (LIPTER Tg ). Both WT and LIPTER Tg mice were fed with high fat diet for 10 months to induce cardiac lipid accumulation and dysfunction. Additionally, heart failure was induced by the chronic isoproterenol administration. After treatment, mice were subjected to histological and molecular analyses. Results: We found LIPTER Tg significantly enhanced FAO of mouse heart, reduced cardiac lipid accumulation and fibrosis, and alleviated cardiac dysfunction of high-fat-diet fed mice, as well as preserved cardiac function of mice post isoproterenol administration. Conclusions: We unveil a crucial role of human lncRNA LIPTER in regulating lipid metabolism of human CMs and testify its clinical potential for treating cardiac dysfunction and heart failure.

Abstract Tu050: Deficiency Of Mitochondrial Disulfide Relay Carrier Leads To Cardiac Hypertrophy

Background: Innate immune activation is critical for cardiac hypertrophy; however, its upstream regulation is less well understood. Coiled-coil-helix-coiled-coil-helix domain 4 (CHCHD4) is an essential carrier for the import of various mitochondrial proteins including TP53 -regulated inhibitor of apoptosis 1 (TRIAP1). CHCHD4 was recently identified as a dysregulated gene in patients with dilated cardiomyopathy and was separately found to mediate innate immune signaling in skeletal muscle. Therefore, we hypothesized that CHCHD4 may play a role in the development of cardiac hypertrophy by regulating innate immunity. Methods: Genetically modified C57BL/6 mice overexpressing CHCHD4 (CHCHD4 Tg) or haploinsufficient in CHCHD4 ( CHCHD4 +/- ) were utilized. Mice were injected either with low dose (2 mg/kg) or high dose (30 mg/kg) isoproterenol (ISO) daily for up to 3 wk to induce hypertrophy. Results: CHCHD4 +/- mice developed cardiac hypertrophy (HW/BW (mg/g): 3.62 ± 0.15 CHCHD4 +/- vs 2.70 ± 0.13 wild-type (WT) or 2.55 ± 0.16 CHCHD4 Tg, p<0.0001) when allowed to age to 28 wk and showed reduced left ventricular ejection fraction (EF) at 1 year when compared with wild-type or CHCHD4 Tg mice (EF (%): 50.94 ± 0.94 CHCHD4 +/- vs 58.33 ± 0.78 wild-type or 57.88 ± 1.32 CHCHD4 Tg, p<0.0001). After low dose ISO treatment, CHCHD4 +/- mice had reduced EF at 2 wk compared to WT or CHCHD4 Tg mice (EF (%): 44.60 ± 1.74 CHCHD4 +/- vs 54.28 ± 0.86 wild-type, p<0.0001; or vs 52.76 ± 1.33 CHCHD4 Tg, p=0.0006). After high dose ISO treatment, WT mice developed cardiac hypertrophy by 1 wk and impaired EF by 3 wk, while CHCHD4 Tg mice remained normal. ISO treatment caused reduction of CHCHD4 levels in both the 24 hr and 1 wk states. This reduction was associated with decreased TRIAP1 and activation of the cGAS-STING-NFkB pathway in wild-type, but not CHCHD4 Tg mice. Further, plasma mitochondrial DNA (mtDNA) was 2.3 times higher in WT mice treated with high dose ISO for 1 wk compared to WT control (n=8-11/group, p=0.011), while that of CHCHD4 Tg mice was not significantly changed by ISO treatment. Conclusions: Our findings suggest that CHCHD4 may be a key upstream regulator of innate immune activation mediating cardiac hypertrophy and that cell-free mtDNA in blood could be a potential biomarker of pathogenesis.

The 5HT4R agonist velusetrag efficacy on neuropathic chronic intestinal pseudo-obstruction in PrP-SCA7-92Q transgenic mice.

Chronic intestinal pseudo-obstruction (CIPO) is a type of intestinal dysfunction with symptoms of intestinal blockage but without the actual mechanical obstruction. Currently, there are no drugs available to treat this disease. Herein, we report the characterization of the PrP-SCA7-92Q transgenic (Tg) line as a valuable CIPO mouse model and investigated the tolerability and efficacy of the 5-hydroxytryptamine type-4 receptor (5HT4R) agonist velusetrag as a promising pharmacological treatment for CIPO. To test the pharmacodynamics of velusetrag, 8-week-old SCA7 Tg mice, which express human mutated Ataxin-7 gene containing 92 CAG repeats under the mouse prion protein promoter, were treated for 5weeks by oral route with velusetrag at 1 and 3mg/kg doses or vehicle. Body weight was monitored throughout the treatment. After sacrifice, the small intestine and proximal colon were collected for whole-mount immunostaining. Untreated, age-matched, C57BL/6J mice were also used as controls in comparison with the other experimental groups. Analysis of SCA7 Tg mice showed tissue damage and alterations, mucosal abnormalities, and ulcers in the distal small intestine and proximal colon. Morphological changes were associated with significant neuronal loss, as shown by decreased staining of pan-neuronal markers, and with accumulation of ataxin-7-positive inclusions in cholinergic neurons. Administration of velusetrag reversed intestinal abnormalities, by normalizing tissue damage and re-establishing the normal level of glia/neuron's count in both the small and large intestines. We demonstrated that the PrP-SCA7-92Q Tg line, a model originally developed to mimic spinocerebellar ataxia, is suitable to study CIPO pathology and can be useful in establishing new therapeutic strategies, such as in the case of velusetrag. Our results suggest that velusetrag is a promising compound to treat patients affected by CIPO or intestinal dysmotility disease.

Integrated Genome-Wide Analysis of DNA Methylation and Gene Expression in the Hippocampi of 5xFAD Alzheimer's Disease Mouse Model.

DNA methylation forms 5-methylcytosine and its regulation in the hippocampus is critical for learning and memory. Indeed, dysregulation of DNA methylation is associated with neurological diseases. Alzheimer's disease (AD) is the predominant of dementia and a neurodegenerative disorder. We examined the learning and memory function in 3- and 9-month-old wild-type and 5xfamiliar Alzheimer's disease (5xFAD) transgenic mice by performing the object recognition memory and Y-maze tests, and identified the hippocampal amyloid beta burden. To investigate the epigenetically regulated genes involved in the development or neuropathology of AD, we performed genome-wide DNA methylation sequencing and RNA sequencing analyses in the hippocampus of 9-month-old wild-type and 5xFAD tg mice. To validate the genes inversely regulated by epigenetics, we confirmed their methylation status and mRNA levels. At 9 months of age, 5xFAD tg mice showed significant cognitive impairment and amyloid-beta plaques in the hippocampus. DNA methylation sequencing identified a total of 13,777 differentially methylated regions, including 4484 of hyper- and 9293 of hypomethylated regions, that are associated with several gene ontology (GO) terms including 'nervous system development' and 'axon guidance'. In RNA sequencing analysis, we confirmed a total of 101 differentially expressed genes, including 52 up- and 49 downregulated genes, associated with GO functions such as 'positive regulation of synaptic transmission, glutamatergic' and 'actin filament organization'. Through further integrated analysis of DNA methylation and RNA sequencing, three epigenetically regulated genes were selected: thymus cell antigen 1, theta (Thy1), myosin VI (Myo6), and filamin A-interacting protein 1-like (Filip1l). The methylation level of Thy1 decreased and its mRNA levels increased, whereas that of Myo6 and Filip1l increased and their mRNA levels decreased. The common functions of these three genes may be associated with the neural cytoskeleton and synaptic plasticity. We suggest that the candidate genes epigenetically play a role in AD-associated neuropathology (i.e., amyloid-beta plaques) and memory deficit by influencing neural structure and synaptic plasticity. Furthermore, counteracting dysregulated epigenetic changes may delay or ameliorate AD onset or symptoms.

Moderate-Intensity Treadmill Exercise Regulates GSK3α/β Activity in the Cortex and Hippocampus of APP/PS1 Transgenic Mice.

Physical exercise has been shown to be beneficial for individuals with Alzheimer's disease (AD), although the underlying mechanisms are not fully understood. Six-month-old Amyloid precursor protein/Presenilin 1 (APP/PS1) transgenic (Tg) mice and wild-type (Wt) mice were randomly assigned to either a sedentary group (Tg-Sed, Wt-Sed) or an exercise group (Tg-Ex, Wt-Ex) undertaking a 12-week, moderate-intensity treadmill running program. Consequently, all mice were tested for memory function and amyloid β (Aβ) levels and phosphorylation of tau and protein kinase B (Akt)/glycogen synthase kinase-3 (GSK3) were examined in tissues of both the cortex and hippocampus. Tg-Sed mice had severely impaired memory, higher levels of Aβ, and increased phosphorylation of tau, GSK3α tyrosine279, and GSK3β tyrosine216, but less phosphorylation of GSK3α serine21, GSK3β serine9, and Akt serine473 in both tissues than Wt-Sed mice in respective tissues. Tg-Ex mice showed significant improvement in memory function along with lower levels of Aβ and less phosphorylation of tau (both tissues), GSK3α tyrosine279 (both tissues), and GSK3β tyrosine216 (hippocampus only), but increased phosphorylation of GSK3α serine21 (both tissues), GSK3β serine9 (hippocampus only), and Akt serine473 (both tissues) compared with Tg-Sed mice in respective tissues. Moderate-intensity aerobic exercise is highly effective in improving memory function in 9-month-old APP/PS1 mice, most likely through differential modulation of GSK3α/β phosphorylation in the cortex and hippocampus.

Diastolic dysfunction in Alzheimer’s disease model mice is associated with Aβ-amyloid aggregate formation and mitochondrial dysfunction

Alzheimer's Disease (AD) is a progressive neurodegenerative disease caused by the deposition of Aβ aggregates or neurofibrillary tangles. AD patients are primarily diagnosed with the concurrent development of several cardiovascular dysfunctions. While few studies have indicated the presence of intramyocardial Aβ aggregates, none of the studies have performed detailed analyses for pathomechanism of cardiac dysfunction in AD patients. This manuscript used aged APPSWE/PS1 Tg and littermate age-matched wildtype (Wt) mice to characterize cardiac dysfunction and analyze associated pathophysiology. Detailed assessment of cardiac functional parameters demonstrated the development of diastolic dysfunction in APPSWE/PS1 Tg hearts compared to Wt hearts. Muscle function evaluation showed functional impairment (decreased exercise tolerance and muscle strength) in APPSWE/PS1 Tg mice. Biochemical and histochemical analysis revealed Aβ aggregate accumulation in APPSWE/PS1 Tg mice myocardium. APPSWE/PS1 Tg mice hearts also demonstrated histopathological remodeling (increased collagen deposition and myocyte cross-sectional area). Additionally, APPSWE/PS1 Tg hearts showed altered mitochondrial dynamics, reduced antioxidant protein levels, and impaired mitochondrial proteostasis compared to Wt mice. APPSWE/PS1 Tg hearts also developed mitochondrial dysfunction with decreased OXPHOS and PDH protein complex expressions, altered ETC complex dynamics, decreased complex activities, and reduced mitochondrial respiration. Our results indicated that Aβ aggregates in APPSWE/PS1 Tg hearts are associated with defects in mitochondrial respiration and complex activities, which may collectively lead to cardiac diastolic dysfunction and myocardial pathological remodeling.

Higher-order interactions between hippocampal CA1 neurons are disrupted in amnestic mice.

Across systems, higher-order interactions between components govern emergent dynamics. Here we tested whether contextual threat memory retrieval in mice relies on higher-order interactions between dorsal CA1 hippocampal neurons requiring learning-induced dendritic spine plasticity. We compared population-level Ca2+ transients as wild-type mice (with intact learning-induced spine plasticity and memory) and amnestic mice (TgCRND8 mice with high levels of amyloid-β and deficits in learning-induced spine plasticity and memory) were tested for memory. Using machine-learning classifiers with different capacities to use input data with complex interactions, our findings indicate complex neuronal interactions in the memory representation of wild-type, but not amnestic, mice. Moreover, a peptide that partially restored learning-induced spine plasticity also restored the statistical complexity of the memory representation and memory behavior in Tg mice. These findings provide a previously missing bridge between levels of analysis in memory research, linking receptors, spines, higher-order neuronal dynamics and behavior.

Single-Nucleus RNA Sequencing Reveals Loss of Distal Convoluted Tubule 1 Renal Tubules in HIV Viral Protein R Transgenic Mice

Hyponatremia and salt wasting is a common occurance in patients with HIV/AIDS, however, the understanding of its contributing factors is limited. HIV viral protein R (Vpr) contributes to HIV-associated nephropathy. To investigate the effects of Vpr on the distal tubules and on the expression level of the Slc12a3 gene, encoding the Na-Cl cotransporter, which is responsible for sodium reabsorption in distal nephron segments, single-nucleus RNA sequencing was performed on kidney cortices from three wild-type (WT) and three Vpr-transgenic (Vpr Tg) mice. The results showed that the percentage of distal convoluted tubule (DCT) cells was significantly lower in Vpr Tg mice compared with WT mice (P < 0.05), and that in Vpr Tg mice, Slc12a3 expression was not significantly different in DCT cells. The Pvalb+ DCT1 subcluster had fewer cells in Vpr Tg mice compared with WT mice (P < 0.01). Immunohistochemistry demonstrated fewer Slc12a3+Pvalb+ DCT1 segments in Vpr Tg mice. Differential gene expression analysis between Vpr Tg and WT in the DCT cluster showed downregulation of Ier3 gene, which is an inhibitor of apoptosis. The in vitro knockdown of Ier3 by siRNA transfection induced apoptosis in mouse DCT cells. These observations suggest that the salt-wasting effect of Vpr in Vpr Tg mice is likely mediated by Ier3 downregulation in DCT1 cells and loss of Slc12a3+Pvalb+ DCT1 segments.

Preliminary Analysis of Potentially Overlapping Differentially Expressed Proteins in Both the Spinal Cord and Brain of SOD1 G93A Mice.

Proteomic elucidation is an essential step in improving our understanding of the biological properties of proteins in amyotrophic lateral sclerosis (ALS). Preliminary proteomic analysis was performed on the spinal cord and brain of SOD1 G93A (TG) and wild-type (WT) mice using isobaric tags for relative and absolute quantitation. Partial up- and downregulated proteins showing significant differences between TG and WT mice were identified, of which 105 proteins overlapped with differentially expressed proteins in both the spinal cord and brain of progression mice. Bioinformatic analyses using Gene Ontology, a cluster of orthologous groups, and Kyoto Encyclopedia of Genes and Genomes pathway revealed that the significantly up- and downregulated proteins represented multiple biological functions closely related to ALS, with 105 overlapping differentially expressed proteins in the spinal cord and brain at the progression stage of TG mice closely related to 122 pathways. Differentially expressed proteins involved in a set of molecular functions play essential roles in maintaining neural cell survival. This study provides additional proteomic profiles of TG mice, including potential overlapping proteins in both the spinal cord and brain that participate in pathogenesis, as well as novel insights into the up- and downregulation of proteins involved in the pathogenesis of ALS.

Exercise mitigates reductive stress-induced cardiac remodeling in mice

The endoplasmic reticulum (ER) regulates protein folding and maintains proteostasis in cells. We observed that the ER transcriptome is impaired during chronic reductive stress (RS) in cardiomyocytes. Here, we hypothesized that a prolonged moderate treadmill exercise mitigates the RS-induced ER dysfunction and cardiac remodeling in cardiac-specific constitutively active Nrf2 mice (CaNrf2-TG). RNA sequencing showed notable alterations in the ER transcriptome of TG hearts at 4, 12, and 24 weeks (16, 28, and 35 genes, respectively). Notably, the downregulation of ER genes was significant at 12 weeks, and further pronounced at 24 weeks, at which the cardiac pathology is evident. We also observed increased levels of ubiquitinated proteins in CaNrf2-TG hearts across all ages, along with VCP, a marker of ERAD function, at 24 weeks. These findings indicate that constitutive Nrf2 activation and RS impair protein-folding activity and augments ERAD function over time. Exercise intervention for 20 weeks (beginning at 6 weeks of age), reduced cardiomyocyte hypertrophy (from 448 μm2 to 280 μm2) in TG mice, through adaptive remodeling, and preserved the cardiac function. However, while exercise did not influence antioxidants or ER stress protein levels, it significantly improved ERAD function and autophagy flux (LC-I to LC-II) in the TG-EXE hearts. Collectively, our findings underscore the prophylactic potential of exercise in mitigating RS-associated pathology, highlighting its essential role in maintaining cellular proteostasis through ER-independent mechanisms.

Norboldine improves cognitive impairment and pathological features in Alzheimer's disease by activating AMPK/GSK3β/Nrf2 signaling pathway

Ethnopharmacological relevanceLindera aggregata (Sims) Kosterm is a common traditional herb that has multiple bioactivities. Radix Linderae (LR), the dry roots of Lindera aggregata (Sims) Kosterm, is a traditional Chinese herbal medicine with antioxidant, anti-inflammatory and immunomodulatory properties, first found in Kaibao Era. Norboldine (Nor) is an alkaloid extracted from LR and is one of the primary active ingredients of LR. However, the pharmacological functions and mechanism of Nor in Alzheimer's disease (AD) are still unknown. Aim of the studyThis study aims to investigate the effect and mechanism of Nor therapy in improving the cognitive impairment and pathological features of 3 × Tg mice. Materials and methods3 × Tg mice were treated with two concentrations of Nor for one month and then the memory and cognitive abilities of mice were assessed by novel object recognition experiment and Morris water maze. The impact of Nor on the pathology of ADwere examined in PC12 cells and animal tissues using western blotting and immunofluorescence. Finally, western blotting was used to verify the anti-apoptotic effect of Nor by activating AMPK/GSK3β/Nrf2 signaling pathway at animal and cellular levels. ResultsIn this study, we showed that Nor treatment improved the capacity of the learning and memory of 3 × Tg mice and alleviated AD pathology such as Aβ deposition. In addition, Nor restored the abnormalities of mitochondrial membrane potential, significantly reduced the production of intracellular ROS and neuronal cell apoptosis. Mechanistically, we combined network pharmacology and experimental verification to show that Nor may exert antioxidant stress and anti-apoptotic through the AMPK/GSK3β/Nrf2 signaling pathway. ConclusionOur data provide some evidence that Nor exerts a neuroprotective effect through the AMPK/GSK3β/Nrf2 pathway, thereby improving cognitive impairment in AD model mice. Natural products derived from traditional Chinese medicines are becoming increasingly popular in the process of new drug development and discovery, and our findings provide new perspectives for the discovery of improved treatment strategies for AD.

Brexpiprazole: A new option in treating agitation in Alzheimer's dementia-Insights from transgenic mouse models.

Brexpiprazole is the first FDA-approved treatment for agitation associated with dementia due to Alzheimer's disease. Agitation in Alzheimer's dementia (AAD) occurs in high prevalence and is a great burden for patients and caregivers. Efficacy, safety, and tolerability of brexpiprazole were demonstrated in the AAD clinical trials. To demonstrate the agitation-ameliorating effect of brexpiprazole in animals, we evaluated brexpiprazole in two AAD mouse models. The resident-intruder test was conducted in 5- to 6-month-old Tg2576 mice, given vehicle or brexpiprazole (0.01 or 0.03 mg/kg) orally 1 h before the test. Locomotor activity was measured in 6-month-old APPSL-Tg mice given vehicle or brexpiprazole (0.01 or 0.03 mg/kg) orally the evening before the start of locomotor measurement for 3 days. In the resident-intruder test, Tg2576 mice showed significantly higher attack number and shorter latency to first attack compared to non-Tg mice. In the Tg mice, brexpiprazole treatment (0.03 mg/kg) significantly delayed the latency to first attack and showed a trend toward a decrease in attack number. APPSL-Tg mice (≧6 months old) showed significantly higher locomotion during dark period Phase II (Zeitgeber time [ZT] 16-20) and Phase III (ZT20-24) compared to non-Tg mice, correlating with the clinical observations of late afternoon agitation in Alzheimer's disease. Brexpiprazole treatment (0.01 and 0.03 mg/kg) significantly decreased hyperlocomotion during the Phase III in APPSL-Tg mice. The suppression of attack behavior and the reduction of nocturnal hyperlocomotion in these Tg mice may be indicative of the therapeutic effect of brexpiprazole on AAD, as demonstrated in the clinical trials.

Characterization of Unique Pathological Features of COVID-Associated Coagulopathy: Studies with AC70 hACE2 Transgenic Mice Highly Permissive to SARS-CoV-2 Infection.

COVID-associated coagulopathy seemly plays a key role in post-acute sequelae of SARS- CoV-2 infection. However, the underlying pathophysiological mechanisms are poorly understood, largely due to the lack of suitable animal models that recapitulate key clinical and pathological symptoms. Here, we fully characterized AC70 line of human ACE2 transgenic (AC70 hACE2 Tg) mice for SARS-CoV-2 infection. We noted that this model is highly permissive to SARS-CoV-2 with values of 50% lethal dose and infectious dose as ~ 3 and ~ 0.5 TCID50 of SARS-CoV-2, respectively. Mice infected with 105 TCID50 of SARS-CoV-2 rapidly succumbed to infection with 100% mortality within 5 days. Lung and brain were the prime tissues harboring high viral titers, accompanied by histopathology. However, viral RNA and inflammatory mediators could be detectable in other organs, suggesting the nature of a systemic infection. Lethal challenge of AC70 hACE2 Tg mice caused acute onset of leukopenia, lymphopenia, along with an increased neutrophil-to-lymphocyte ratio (NLR). Importantly, infected animals recapitulated key features of COVID-19-associated coagulopathy. SARS-CoV-2 could induce the release of circulating neutrophil extracellular traps (NETs), along with activated platelet/endothelium marker. Immunohistochemical staining with anti-platelet factor-4 (PF4) antibody revealed profound platelet aggregates especially within blocked veins of the lungs. We showed that acute SARS-CoV-2 infection triggered a hypercoagulable state coexisting with ill-regulated fibrinolysis. Finally, we highlighted the potential role of Annexin A2 (ANXA2) in fibrinolytic failure. ANXA2 is a calcium-dependent phospholipid-binding protein that forms a heterotertrameric complexes localized at the extracellular membranes with two S100A10 small molecules acting as a co-receptor for tissue-plasminogen activator (t-PA), tightly involved in cell surface fibrinolysis. Thus, our results revealing elevated IgG type anti-ANXA2 antibody production, downregulated de novo ANXA2/S100A10 synthesis, and reduced ANXA2/S100A10 association in infected mice, this protein might serve as druggable targets for development of antithrombotic and/or anti-fibrinolytic agents to attenuate pathogenesis of COVID-19.

Choline supplementation in early life improves and low levels of choline can impair outcomes in a mouse model of Alzheimer's disease.

Maternal choline supplementation (MCS) improves cognition in Alzheimer's disease (AD) models. However, the effects of MCS on neuronal hyperexcitability in AD are unknown. We investigated the effects of MCS in a well-established mouse model of AD with hyperexcitability, the Tg2576 mouse. The most common type of hyperexcitability in Tg2576 mice are generalized EEG spikes (interictal spikes [IIS]). IIS also are common in other mouse models and occur in AD patients. In mouse models, hyperexcitability is also reflected by elevated expression of the transcription factor ∆FosB in the granule cells (GCs) of the dentate gyrus (DG), which are the principal cell type. Therefore, we studied ΔFosB expression in GCs. We also studied the neuronal marker NeuN within hilar neurons of the DG because reduced NeuN protein expression is a sign of oxidative stress or other pathology. This is potentially important because hilar neurons regulate GC excitability. Tg2576 breeding pairs received a diet with a relatively low, intermediate, or high concentration of choline. After weaning, all mice received the intermediate diet. In offspring of mice fed the high choline diet, IIS frequency declined, GC ∆FosB expression was reduced, and hilar NeuN expression was restored. Using the novel object location task, spatial memory improved. In contrast, offspring exposed to the relatively low choline diet had several adverse effects, such as increased mortality. They had the weakest hilar NeuN immunoreactivity and greatest GC ΔFosB protein expression. However, their IIS frequency was low, which was surprising. The results provide new evidence that a diet high in choline in early life can improve outcomes in a mouse model of AD, and relatively low choline can have mixed effects. This is the first study showing that dietary choline can regulate hyperexcitability, hilar neurons, ΔFosB, and spatial memory in an animal model of AD.

TPA supplementation preserves neurovascular and cognitive function in Tg2576 mice.

Amyloid beta (Aβ) impairs the cerebral blood flow (CBF) increase induced by neural activity (functional hyperemia). Tissue plasminogen activator (tPA) is required for functional hyperemia, and in mouse models of Aβ accumulation tPA deficiency contributes to neurovascular and cognitive impairment. However, it remains unknown if tPA supplementation can rescue Aβ-induced neurovascular and cognitive dysfunction. Tg2576 mice and wild-type littermates received intranasal tPA (0.8mg/kg/day) or vehicle 5 days a week starting at 11 to 12 months of age and were assessed 3 months later. Treatment of Tg2576 mice with tPA restored resting CBF, prevented the attenuation in functional hyperemia, and improved nesting behavior. These effects were associated with reduced cerebral atrophy and cerebral amyloid angiopathy, but not parenchymal amyloid. These findings highlight the key role of tPA deficiency in the neurovascular and cognitive dysfunction associated with amyloid pathology, and suggest potential therapeutic strategies involving tPA reconstitution. Amyloid beta (Aβ) induces neurovascular dysfunction and impairs the increase of cerebral blood flow induced by neural activity (functional hyperemia). Tissue plasminogen activator (tPA) deficiency contributes to the neurovascular and cognitive dysfunction caused by Aβ. In mice with florid amyloid pathology intranasal administration of tPA rescues the neurovascular and cognitive dysfunction and reduces brain atrophy and cerebral amyloid angiopathy. tPA deficiency plays a crucial role in neurovascular and cognitive dysfunction induced by Aβ and tPA reconstitution may be of therapeutic value.