Mouse Model Of Chronic Kidney Disease Research Articles

ULK1-regulated AMP sensing by AMPK and its application for the treatment of chronic kidney disease

Adenosine monophosphate (AMP)-activated protein kinase (AMPK) is a central kinase involved in energy homeostasis. Increased intracellular AMP levels result in AMPK activation through the binding of AMP to the γ-subunit of AMPK. Recently, we reported that AMP-induced AMPK activation is impaired in the kidneys in chronic kidney disease (CKD) despite an increase in the AMP/ATP ratio. However, the mechanisms by which AMP sensing is disrupted in CKD are unclear. Here, we identified mechanisms of energy homeostasis in which Unc-51-like kinase 1 (ULK1)-dependent phosphorylation of AMPKγ1 at Ser260/Thr262 promoting AMP sensitivity of AMPK. AMPK activation by AMP was impaired in Ulk1 knockout mice despite an increased AMP/ATP ratio. ULK1 expression is markedly downregulated in CKD kidneys, leading to AMP sensing failure. Additionally, MK8722, an allosteric AMPK activator, stimulated AMPK in the kidneys of a CKD mouse model (5/6th nephrectomy) via a pathway that is independent of AMP sensing. Thus, our study shows that MK8722 treatment significantly attenuates the deterioration of kidney function in CKD and may be a potential therapeutic option in CKD therapeutics.

Dysregulation of the 3β-hydroxysteroid dehydrogenase type 2 enzyme and steroid hormone biosynthesis in chronic kidney disease.

Chronic kidney disease (CKD) presents a critical global health challenge, marked by the progressive decline of renal function. This study explores the role of the 3β-hydroxysteroid dehydrogenase type 2 enzyme (HSD3B2) and the steroid hormone biosynthesis pathway in CKD pathogenesis and progression. Using an adenine-induced CKD mouse model, we conducted an untargeted metabolomic analysis of plasma samples to identify key metabolite alterations associated with CKD. Immunohistochemistry, Western blotting, and qPCR analyses were performed to confirm HSD3B2 expression in both human and mouse tissues. Additionally, Nephroseq and Human Protein Atlas data were utilized to assess the correlation between HSD3B2 and kidney function. Functional studies were conducted on HK2 cells with HSD3B2 knockdown to evaluate the impact on cell proliferation and apoptosis. Metabolic characteristics revealed significant shifts in CKD, with 61 metabolites increased and 65 metabolites decreased, highlighting the disruption in steroid hormone biosynthesis pathways influenced by HSD3B2. A detailed examination of seven key metabolites underscored the enzyme's central role. HSD3B2 exhibited a strong correlation with kidney function, supported by data from Nephroseq and the Human Protein Atlas. Immunohistochemistry, Western blotting, and qPCR analyses confirmed a drastic reduction in HSD3B2 expression in CKD-affected kidneys. Suppressed proliferation and increased apoptosis rates in HSD3B2 knocked down HK2 cells further demonstrated the enzyme's significance in regulating renal pathophysiology. These findings underscore the potential of HSD3B2 as a clinical diagnostic and therapeutic target in CKD. While further studies are warranted to fully elucidate the mechanisms, our results provide valuable insights into the intricate interplay between steroid hormone biosynthesis and CKD. This offers a promising avenue for precision medicine approaches and personalized treatment strategies.

VCAM-1 mediates proximal tubule-immune cell cross talk in failed tubule recovery during AKI-to-CKD transition.

Studies in animal models have suggested a linkage between the inflammatory response to injury and subsequent nephron loss during the acute kidney injury (AKI) to chronic kidney disease (CKD) transition. Failure of normal repair during the CKD transition correlates with de novo expression of vascular cell adhesion protein-1 (VCAM-1) by a subset of injured proximal tubule cells. This study identified the role of VCAM-1 expression in promoting the failed repair state. Single-cell transcriptome analysis of patients with AKI and CKD and whole kidney RNA and protein analyses of mouse models of CKD confirmed a marked increase of VCAM-1 expression in the proximal tubules of injured kidneys. In immortalized mouse proximal tubular cells and primary cultured renal cells (PCRCs), VCAM-1 expression was induced by proinflammatory cytokines including tumor necrosis factor (TNF)-α and interleukin (IL)-1β. Analyses of bulk RNA sequencing of TNF-α-treated primary cultured renal cells or pseudo-bulk RNA sequencing of biopsies from Kidney Precision Medicine Project datasets indicated activation of NF-κB and an enrichment of inflammatory response and cell adhesion pathways in VCAM-1-positive cells. Pharmacological inhibition of NF-κB signaling or genetic deletion of myeloid differentiation factor 88 and TIR domain-containing adapter-inducing interferon-β suppressed TNF-α- and IL-1β-induced VCAM-1 expression in vitro. TNF-α stimulation or overexpression of VCAM-1 significantly increased splenocyte adhesion to the mouse proximal tubular monolayer in culture. These results demonstrate that persistence of proinflammatory cytokines after AKI can induce NF-κB-dependent VCAM-1 expression by proximal tubule cells, mediating increased immune cell adhesion to the tubule and thus promoting further tubule injury and greater risk of progression from AKI to CKD.NEW & NOTEWORTHY We demonstrated the induction of VCAM-1 and its biological function in proximal tubules. We found that proinflammatory cytokines (TNF-α and IL-1β) significantly induced VCAM-1 expression via NF-κB signaling pathway. TNF-α treatment or overexpression of VCAM-1 in immortalized MPT cells increased CD45+ splenocyte adhesion. Pharmacological inhibition of NF-κB or genetic deletion of Vcam1 suppressed TNF-α-induced splenocyte adhesion in vitro, suggesting that VCAM-1 mediates proximal tubular-immune cell cross talk in failed tubule recovery during AKI-to-CKD transition.

Single-cell RNA sequencing data locate ALDH1A2-mediated retinoic acid synthetic pathway to glomerular parietal epithelial cells.

Aldehyde dehydrogenase 1, family member A2, is a retinoic acid-synthesizing enzyme encoded by Aldh1a2 in mice and ALDH1A2 in humans. This enzyme is indispensable for kidney development, but its role in kidney physiology and pathophysiology remains to be fully defined. In this review, we mined single-cell and single-nucleus RNA sequencing databases of mouse and human kidneys and found that glomerular parietal epithelial cells (PECs) express a full set of genes encoding proteins needed for cellular vitamin A uptake, intracellular transport, and metabolism into retinoic acid. In particular, Aldh1a2/ALDH1A2 mRNAs are selectively enriched in mouse and human PECs. Aldh1a2 expression in PECs is greatly increased in a mouse model of anti-glomerular basement membrane glomerulonephritis and moderately induced in a mouse model of ischemia-reperfusion acute kidney injury. Aldh1a2 expression in PECs is substantially repressed in a chronic kidney disease mouse model combining diabetes, hypertension, and partial nephrectomy and is moderately repressed in mouse models of focal segmental glomerulosclerosis and diabetic nephropathy. Single-nucleus RNA sequencing data show that ALDH1A2 mRNA expression in PECs is diminished in patients with chronic kidney disease associated with diabetes, hypertension and polycystic kidney disease. In addition to data mining, we also performed Spearman's rank correlation coefficient analyses and identified gene transcripts correlated with Aldh1a2/ALDH1A2 transcripts in mouse PECs and PEC subtypes, and in human PECs of healthy subjects and patients with AKI or CKD. Furthermore, we conducted Gene Ontology pathway analyses and identified the biological pathways enriched among these Aldh1a2/ALDH1A2-correlated genes. Our data mining and analyses led us to hypothesize that ALDH1A2-mediated retinoic acid synthesis in PECs plays a yet-undefined role in the kidney and that its dysregulation mediates injury. Conditional, PEC-selective Aldh1a2 knockout, RNA silencing and transgenic mouse models will be useful tools to test this hypothesis. Clinical studies on genetics, epigenetics, expression and functions of ALDH1A2 and other genes needed for retinoic acid biosynthesis and signaling are also warranted.

Imperatorin ameliorates ferroptotic cell death, inflammation, and renal fibrosis in a unilateral ureteral obstruction mouse model

BackgroundImperatorin is a naturally occurring furocoumarin derivative found in traditional Chinese medicine Angelica dahurica for its anticancer, antihypertensive, and antidiabetic properties. Chronic kidney disease (CKD) is a global health issue, characterized by a high prevalence, significant morbidity and mortality, and a range of related complications. ObjectiveThis study aims to investigate the protective effects of imperatorin treatment and the specific underlying mechanisms in progressive CKD. MethodsImperatorin was orally administrated for 14 consecutive days to mice with unilateral ureteral obstruction (UUO) to investigate the renal pathological alternations, pro-inflammatory mediators, antioxidant response, and ferroptotic death signaling. Imperatorin was also tested in the erastin-induced injury of renal proximal tubular cells (NRK-52E). Cell viability, ferroptosis protein markers, erastin-induced oxidative stress, and lipid peroxidation were assessed. ResultsIn vivo, imperatorin treatment alleviated kidney histology alternations and attenuated the protein expression of fibrotic markers. Furthermore, imperatorin administration reduced inflammatory cell infiltration, and alleviated the oxidative stress burden by downregulating protein markers such as catalase, superoxide dismutase 2 (SOD-2), NADPH oxidase 4 (NOX-4), and thioredoxin reductase 1 (Trxr-1). It also mitigated ferroptosis markers such as glutathione peroxidase 4 (GPX4), solute carrier family 7 member 11/cystine transporter (SLC7A11/xCT), and transferrin receptor 1 (TFR-1), and attenuated renal cell apoptosis. In vitro, imperatorin treatment effectively decreased erastin-induced feroptotic cell death, restored the antioxidant enzyme levels, and mitigated lipid peroxidation as well as the expression of ferroptosis-related markers (XCT, GPX4, and p-p53) in a dose-dependent manner. ConclusionOur finding demonstrated for the first time, that imperatorin treatment holds therapeutic potential in a UUO mouse model of CKD and inhibits the erastin-induced oxidative stress, ferroptosis, and subsequent lipid peroxidation in vitro. This highlights the potential of imperatorin as a future therapeutic target for ferroptosis to improve the progression of CKD.

Irisin Ameliorates Muscle Atrophy by Inhibiting the Upregulation of the Ubiquitin‒Proteasome System in Chronic Kidney Disease.

Muscle atrophy is a common complication of chronic kidney disease (CKD). Irisin, a novel muscle cytokine, protects against muscle atrophy, but its specific role in CKD-associated muscle atrophy requires further elucidation. Because the ubiquitin-proteasome system (UPS) plays an important role in CKD muscle atrophy, our study will explore whether irisin affects UPS and alleviate CKD-associated muscle atrophy. In this study, an adenine-fed mouse model of CKD and urotension II (UII)-induced C2C12 myotubes were used as in vivo and in vitro models of muscle atrophy. The results showed that renal function, mouse weight, and the cross-sectional area (CSA) of skeletal muscles were significantly improved in CKD mice treated with irisin. Moreover, irisin effectively mitigated the decreases in phosphorylated Forkhead box O 3a (p-FOXO3A) levels and increases in the levels of E3 ubiquitin ligases, such as muscle RING finger 1 (MuRF1) and muscle atrophy F-box (MAFbx/atrogin1), in both the muscles of CKD mice and UII-induced C2C12 myotubes. In addition, irisin significantly increased the expression levels of myogenic differentiation factor D (MyoD) in the muscles of CKD mice. Our study is the first to demonstrate that irisin ameliorates skeletal muscle atrophy by inhibiting UPS upregulation and improving satellite cell differentiation in CKD.

Interleukin‐6 induces cognitive impairment via toll‐like receptor 4 (TLR4)‐mediated neuroinflammation and neurodegeneration in mice with chronic kidney disease

AbstractBackgroundsPast epidemiological and experimental studies in rodents have demonstrated that chronic kidney disease (CKD) leads to cognitive impairment. However, the underlying mechanism requires further investigation. Herein, a mouse model of CKD was established using conventional 5/6 nephrectomy. We aimed to examine the relationship between CKD and cognitive impairment and elucidate the underlying mechanisms.MethodsCognitive behavior was assessed using the Morris water maze, novel object recognition test, and fear conditioning test. Further experiments were also conducted to investigate the underlying molecular mechanisms.ResultsOur clinical data revealed a decrease in cognitive function among patients with CKD, accompanied by elevated plasma levels of pro‐inflammatory cytokines. A positive correlation between cytokine concentrations and serum creatinine levels, as well as a significant positive correlation with cognitive dysfunction, were observed. Correlation analyzes demonstrated that hippocampal cytokine levels were positively correlated with serum creatinine levels and cognitive dysfunction in CKD model mice. Furthermore, 20 mg/mL interleukin‐6 (IL‐6) significantly decreased HT22 cell activity in vitro. Further, HT22 cells treated with IL‐6 showed increased expression levels of toll‐like receptor 4 (TLR4) and myeloid differentiation primary response gene 88 (MyD88), thereby inducing the nuclear factor kappa‐B p65 inflammatory pathway and mitochondria‐dependent apoptosis. The CKD mouse model showed increased expression of TLR4 and cytokines in the hippocampus. TLR4 knockdown antagonized the IL‐6‐mediated pro‐inflammatory and pro‐apoptotic effects in HT22 cells. TLR4 knockdown in the CKD model mice decreased hippocampal inflammation and increased the number of neuron dendrites, thus ameliorated cognitive impairment.ConclusionThese results suggest that IL‐6 triggers TLR4 activation to induce neuroinflammation and neurodegeneration in CKD, ultimately culminate in cognitive impairment.

Identifying biochemical changes in the kidney using proton nuclear magnetic resonance in an adenine diet chronic kidney disease mouse model.

This study aimed to investigate the metabolic changes in the kidneys in a murine adenine-diet model of chronic kidney disease (CKD). Kidney fibrosis is the common pathological manifestation across CKD aetiologies. Sustained inflammation and fibrosis cause changes in preferred energy metabolic pathways in the cells of the kidney. Kidney cortical tissue from mice receiving a control or adenine-supplemented diet for 8weeks (late inflammation and fibrosis) and 12 weeks (8weeks of treatment followed by 4weeks recovery) were analysed by 2D-correlated nuclear magnetic resonance spectroscopy and compared with histopathology and biomarkers of kidney damage. Tissue metabolite and lipid levels were assessed using the MestreNova software. Expression of genes related to inflammation, fibrosis, and metabolism were measured using quantitative polymerase chain reaction. Animals showed indicators of severely impaired kidney function at 8 and 12 weeks. Significantly increased fibrosis was present at 8weeks but not in the recovery group suggesting some reversal of fibrosis and amelioration of inflammation. At 8weeks, metabolites associated with glycolysis were increased, while lipid signatures were decreased. Genes involved in fatty acid oxidation were decreased at 8weeks but not 12 weeks while genes associated with glycolysis were significantly increased at 8weeks but not at 12 weeks. In this murine model of CKD, kidney fibrosis was associated with the accumulation of triglyceride and free lactate. There was an up-regulation of glycolytic enzymes and down-regulation of lipolytic enzymes. These metabolic changes reflect the energy demands associated with progressive kidney disease where there is a switch from fatty acid oxidation to that of glycolysis.

Glycolysis in Peritubular Endothelial Cells and Microvascular Rarefaction in CKD.

Peritubular endothelial cell dropout leading to microvascular rarefaction is a common manifestation of chronic kidney disease (CKD). The role of metabolism reprogramming in peritubular endothelial cell loss in CKD is undetermined. Single-cell sequencing and metabolic analysis were used to characterize metabolic profile of peritubular endothelial cells from CKD patients and from CKD mouse models. In vivo and in vitro models demonstrated metabolic reprogramming in peritubular endothelial cells in conditions of CKD and its contribution to microvascular rarefaction. Here, we identified glycolysis as a top dysregulated metabolic pathway in peritubular endothelial cells from CKD patients. Specifically, CKD peritubular endothelial cells were hypoglycolytic while displaying an anti-angiogenic response with decreased proliferation and increased apoptosis. The hypoglycolytic phenotype of peritubular endothelial cells was recapitulated in CKD mouse models and in peritubular endothelial cells stimulated by hydrogen peroxide (H2O2). Mechanically, oxidative stress, through activating a redox sensor kruppel-like transcription factor 9, downregulated the glycolytic activator 6-phosphofructo-2-kinase/fructose-2, 6-bisphosphatase (PFKFB3) expression, thereby reprogramming peritubular endothelial cells towards a hypoglycolytic phenotype. PFKFB3 overexpression in peritubular endothelial cells restored H2O2-induced reduction in glycolysis and cellular ATP levels, and enhanced the G1/S cell cycle transition, enabling peritubular endothelial cells to improve proliferation and reduce apoptosis. Consistently, restoration of peritubular endothelial cell glycolysis in CKD mice, via overexpressing endothelial Pfkfb3, reversed the anti-angiogenic response in peritubular endothelial cells and protected the kidney from microvascular rarefaction and fibrosis. In contrast, suppression of glycolysis by endothelial Pfkfb3 deletion exacerbated microvascular rarefaction and fibrosis in CKD mice. Our study revealed a disrupted regulation of glycolysis in peritubular endothelial cells as an initiator of microvascular rarefaction in CKD. Restoration of peritubular endothelial cell glycolysis in CKD kidney improved microvascular rarefaction and ameliorated fibrotic lesions.

Mineralocorticoid receptor (MR) antagonist eplerenone and MR modulator balcinrenone prevent renal extracellular matrix remodeling and inflammation via the MR/proteoglycan/TLR4 pathway.

Excessive activation of the mineralocorticoid receptor (MR) is implicated in cardiovascular and renal disease. Decreasing MR activation with MR antagonists (MRA) is effective to slow chronic kidney disease (CKD) progression and its cardiovascular comorbidities in animal models and patients. The present study evaluates the effects of the MR modulator balcinrenone and the MRA eplerenone on kidney damage in a metabolic CKD mouse model combining nephron reduction and a 60% high-fat diet. Balcinrenone and eplerenone prevented the progression of renal damages, extracellular matrix remodeling and inflammation to a similar extent. We identified a novel mechanism linking MR activation to the renal proteoglycan deposition and inflammation via the TLR4 pathway activation. Balcinrenone and eplerenone similarly blunted this pathway activation.

Chronic Kidney Disease-associated Lung Injury Is Mediated by Phosphate-induced MAPK/AKT Signaling.

Chronic kidney disease (CKD) is associated with systemic phosphate elevations, called hyperphosphatemia. Translational studies have shown that hyperphosphatemia contributes to CKD-associated inflammation and injury in various tissues, including the kidney, heart, liver, and parathyroid gland. Mechanisms underlying pathologic actions of elevated phosphate on cells are not well understood but seem to involve uptake of phosphate through sodium-phosphate cotransporters and phosphate-induced signaling via fibroblast growth factor receptor (FGFR) 1. Clinical studies indicate CKD patients are more likely to develop inflammatory and restrictive lung diseases, such as fibrotic interstitial lung diseases, and here we aimed to determine whether hyperphosphatemia can cause lung injury. We found that a mouse model of CKD and hyperphosphatemia, induced by an adenine-rich diet, develops lung fibrosis and inflammation. Elevation of systemic phosphate levels by administration of a high-phosphate diet in a mouse model of primary lung inflammation and fibrosis, induced by bleomycin, exacerbated lung injury in the absence of kidney damage. Our in vitro studies identified increases of proinflammatory cytokines in human lung fibroblasts exposed to phosphate elevations. Phosphate activated extracellular signal related kinase (ERK) 1/2 and protein kinase B (PKB/AKT) signaling, and pharmacological inhibition of ERK, AKT, FGFR1, or sodium-phosphate cotransporters prevented phosphate-induced proinflammatory cytokine upregulation. Additionally, inhibition of FGFR1 or sodium-phosphate cotransporters decreased the phosphate-induced activation of ERK and AKT. Our study suggests that phosphate can directly target lung fibroblasts and induce an inflammatory response and that hyperphosphatemia in CKD and non-CKD models contributes to lung injury. Phosphate-lowering strategies might protect from CKD-associated lung injury.

Diffusion tensor MRI is sensitive to fibrotic injury in a mouse model of oxalate-induced chronic kidney disease.

Chronic kidney disease (CKD) is characterized by inflammation and fibrosis in the kidney. Renal biopsies and estimated glomerular filtration rate (eGFR) remain the standard of care, but these endpoints have limitations in detecting the stage, progression, and spatial distribution of fibrotic pathology in the kidney. MRI diffusion tensor imaging (DTI) has emerged as a promising noninvasive technology to evaluate renal fibrosis in vivo both in clinical and preclinical studies. However, these imaging studies have not systematically identified fibrosis particularly deeper in the kidney where biopsy sampling is limited, or completed an extensive analysis of whole organ histology, blood biomarkers, and gene expression to evaluate the relative strengths and weaknesses of MRI for evaluating renal fibrosis. In this study, we performed DTI in the sodium oxalate mouse model of CKD. The DTI parameters fractional anisotropy, apparent diffusion coefficient, and axial diffusivity were compared between the control and oxalate groups with region of interest (ROI) analysis to determine changes in the cortex and medulla. In addition, voxel-based analysis (VBA) was implemented to systematically identify local regions of injury over the whole kidney. DTI parameters were found to be significantly different in the medulla by both ROI analysis and VBA, which also spatially matched with collagen III immunohistochemistry (IHC). The DTI parameters in this medullary region exhibited moderate to strong correlations with histology, blood biomarkers, hydroxyproline, and gene expression. Our results thus highlight the sensitivity of DTI to the heterogeneity of renal fibrosis and importance of whole kidney noninvasive imaging.NEW & NOTEWORTHY Chronic kidney disease (CKD) can be characterized by inflammation and fibrosis of the kidney. Although standard of care methods have been limited in scope, safety, and spatial distribution, MRI diffusion tensor imaging (DTI) has emerged as a promising noninvasive technology to evaluate renal fibrosis in vivo. In this study, we performed DTI in an oxalate mouse model of CKD to systematically identify local kidney injury. DTI parameters strongly correlated with histology, blood biomarkers, hydroxyproline, and gene expression.

Natural antagonistic flavones for AhR inhibit indoxyl sulfate-induced inflammatory gene expression in vitro and renal pathological damages in vivo.

Uremic toxin indoxyl sulfate (IS) induces vascular inflammation, a crucial event in renal failure, and vascular complications in patients with chronic kidney disease (CKD). In endothelial cells, IS increases the production of inflammatory cytokines partially via the activation of the aryl hydrocarbon receptor (AhR), and several food flavonoids have been reported to act as antagonists of AhR. This study aimed to investigate whether antagonistic flavonoids can attenuate IS-induced inflammatory responses in vascular endothelial cells in vitro and renal failure in vivo. Human umbilical vein endothelial cells (HUVECs) pretreated with the flavones apigenin, chrysin, or luteolin were stimulated with IS. Expression levels of genes involved in AhR signaling, inflammatory cytokine production, and reactive oxygen species (ROS) production were analyzed. Uninephrectomized mice were orally administered chrysin and received daily intraperitoneal injections of IS for 4 weeks. In HUVECs, IS upregulated the mRNA expression of AhR-targeted genes (CYP1A1 and AhRR), and genes involved in inflammation (NOX4, MCP-1, IL-6, and COX2) and monocyte invasion/adhesion (ICAM1). All three flavones attenuated the IS-induced increase in the expression of these mRNAs. They also suppressed the IS-induced nuclear translocation of AhR and intracellular ROS production. Furthermore, IS-induced phosphorylation of the signal transducer and activator of transcription 3 (STAT3) was inhibited by treatment with these flavones. The results of in-vivo experiments showed that administration with chrysin attenuated the elevation of blood urea nitrogen levels and AhR-target gene expression and the pathological impairment of renal tissues in mice, regardless of higher serum levels of IS. Natural food flavones antagonizing AhR exerted protective effects against IS-induced inflammation through the inhibition of the AhR-STAT3 pathway in HUVECs. Moreover, chrysin ameliorated IS-induced renal dysfunction in a mouse model of CKD. These flavonoids could be a therapeutic strategy for vascular inflammation in CKD.

Activation of PERK/eIF2α/ATF4/CHOP branch of endoplasmic reticulum stress response and cooperation between HIF-1α and ATF4 promotes Daprodustat-induced vascular calcification.

Introduction: Vascular calcification is accelerated in patients with chronic kidney disease (CKD) and increases the risk of cardiovascular events. CKD is frequently associated with anemia. Daprodustat (DPD) is a prolyl hydroxylase inhibitor for the treatment of CKD-associated anemia that enhances erythropoiesis through the activation of the hypoxia-inducible factor 1 (HIF-1) pathway. Studies showed that DPD promotes osteogenic differentiation of human aortic smooth muscle cells (HAoSMCs) and increases aorta calcification in mice with CKD. HIF-1 activation has been linked with endoplasmic reticulum (ER) stress; therefore, here we investigated the potential contribution of ER stress, particularly activating transcription factor 4 (ATF4), to the pro-calcification effect of DPD. Methods: Here, we used an adenine-induced CKD mouse model and HAoSMCs as an in vitro vascular calcification model to study the effect of DPD. Results: DPD treatment (15mg/kg/day) corrects anemia but increases the expression of hypoxia (Glut1, VEGFA), ER stress (ATF4, CHOP, and GRP78), and osteo-/chondrogenic (Runx2, Sox9, BMP2, and Msx2) markers and accelerates aorta and kidney calcification in CKD mice. DPD activates the PERK/eIF2α/ATF4/CHOP pathway and promotes high phosphate-induced osteo-/chondrogenic differentiation of HAoSMCs. Inhibition of ER stress with 4-PBA or silencing of ATF4 attenuates HAoSMC calcification. DPD-induced ATF4 expression is abolished in the absence of HIF-1α; however, knockdown of ATF4 does not affect HIF-1α expression. Conclusion: We concluded that DPD induces ER stress in vitro and in vivo, in which ATF4 serves as a downstream effector of HIF-1 activation. Targeting ATF4 could be a potential therapeutic approach to attenuate the pro-calcific effect of DPD.

Knockout of integrin αvβ6 protects against renal inflammation in chronic kidney disease by reduction of pro-inflammatory macrophages

Integrin αvβ6 holds promise as a therapeutic target for organ fibrosis, yet targeted therapies are hampered by concerns over inflammatory-related side effects. The role of αvβ6 in renal inflammation remains unknown, and clarifying this issue is crucial for αvβ6-targeted treatment of chronic kidney disease (CKD). Here, we revealed a remarkable positive correlation between overexpressed αvβ6 in proximal tubule cells (PTCs) and renal inflammation in CKD patients and mouse models. Notably, knockout of αvβ6 not only significantly alleviated renal fibrosis but also reduced inflammatory responses in mice, especially the infiltration of pro-inflammatory macrophages. Furthermore, conditional knockout of αvβ6 in PTCs in vivo and co-culture of PTCs with macrophages in vitro showed that depleting αvβ6 in PTCs suppressed the migration and pro-inflammatory differentiation of macrophages. Screening of macrophage activators showed that αvβ6 in PTCs activates macrophages via secreting IL-34. IL-34 produced by PTCs was significantly diminished by αvβ6 silencing, and reintroduction of IL-34 restored macrophage activities, while anti-IL-34 antibody restrained macrophage activities enhanced by αvβ6 overexpression. Moreover, RNA-sequencing of PTCs and verification experiments demonstrated that silencing αvβ6 in PTCs blocked hypoxia-stimulated IL-34 upregulation and secretion by inhibiting YAP expression, dephosphorylation, and nuclear translocation, which resulted in the activation of Hippo signaling. While application of a YAP agonist effectively recurred IL-34 production by PTCs, enhancing the subsequent macrophage migration and activation. Besides, reduced IL-34 expression and YAP activation were also observed in global or PTCs-specific αvβ6-deficient injured kidneys. Collectively, our research elucidates the pro-inflammatory function and YAP/IL-34/macrophage axis-mediated mechanism of αvβ6 in renal inflammation, providing a solid rationale for the use of αvβ6 inhibition to treat kidney inflammation and fibrosis.

Effects of Yacon Leaf Extract on MCP-1 and IL-10 Expressions and Macrophage Phenotypes in CKD Mouse Model

Macrophages are essential in tissue homeostasis and immunity, but also contribute to disease development and progression. Chronic kidney disease (CKD) is characterized by interstitial infiltration of macrophages, the density of which correlates inversely with kidney survival. Studies have shown that yacon (Smallanthus sonchifolius) has beneficial effects on CKD. Therefore, this study aimed to investigate the effects of yacon leaf extract on mice with subtotal nephrectomy by evaluating the M1 and M2 macrophage counts and mRNA expressions of monocyte chemoattractant protein-1 (MCP-1 and IL-10. The mice were randomly divided into five groups: SO (negative control: underwent sham operation), SN (positive control: underwent subtotal nephrectomy), and yacon-treated groups: YK1, YK2, and YK3 (underwent subtotal nephrectomy, given peroral yacon leaf extract for 14 days with doses of 24,5 mg/kgBW/day, 49 mg/kgBW/day, and 98 mg/kgBW/day, respectively). The macrophage subtypes were assessed using immunohistochemistry anti-CD68 for M1 and anti-Arginase I for M2. MCP-1 and IL-10 mRNA expressions were analyzed using semi-quantitative PCR. Results showed that yacon leaf extract could significantly lower the M2 macrophage count (p<0.001) and the mRNA expressions of MCP-1 and IL-10 in all yacon-treated groups when compared to the SN group. However, the M1 macrophage count was only lower in the YK2 group (p=0.009). In conclusion, the administration of yacon leaf extract could attenuate kidney injury by lowering the macrophage count and the expression of MCP-1 and IL-10.

#571 Vitamin D receptor from VSMCs regulates vascular calcification during CKD: a potential role for miR-145a

Abstract Background and Aims Vascular calcification (VC) is a highly prevalent complication of chronic kidney disease (CKD) and is associated with the higher morbidity-mortality of patients with CKD. Vitamin D receptor (VDR) has been proposed to play a role in the osteoblastic differentiation of vascular smooth muscle cells (VSMCs), but the involvement of vitamin D (1, 25D) in VC associated to CKD is controversial. Accumulating evidence points to microRNAs as important players in the process of VC and recent studies show that miR-145a expression decreases in VSMCs during VC. In addition, VDR has been considered as a potent regulator of these small molecules, while miR-145a was identified as a target for 1, 25D. Our aim was to determine the role of local vitamin D signalling in VSMCs during CKD-induced VC and the involvement of miR-145a in this process. Method We used epigastric arteries from CKD-affected patients and from individuals with normal renal function. In vivo, we employed an experimental model of CKD-induced VC in mice with conditional deletion of VDR in VSMC (Myh11-CreERT2+ VDRlox/lox), while in vitro, we used mouse VSMC with (VDRwt) or without VDR (VDRko) incubated in calcification media. Transfection experiments with mmu-miR-145a-5p mimic or mmu-miR-145a-5p inhibitor were carried out in mouse VDRwt VSMCs. Results CKD-affected patients showed an increase in VC, alongside an increased arterial expression of VDR compared with controls with normal renal function. Conditional gene silencing of VDR in arterial VSMCs led to a significant decrease of VC in the mouse model of CKD, despite similar levels of renal impairment and serum calcium and phosphate levels. This was accompanied by lower arterial expression of osteopontin (OPN) and lamin A, and a higher expression of sclerostin (SOST). Runx2 was increased in arteries of both CKD groups independently of the presence of VDR in VSMCs. Furthermore, CKD-affected mice showed a reduction of miR-145a expression in calcified arteries, which was significantly recovered in animals with deletion of VDR in VSMCs. In vitro, the absence of VDR prevented VC, inhibited the increase of OPN, and re-established the expression of miR-145a. Forced expression of miR-145a in vitro in VDRwt VSMCs blunted VC and decreased OPN levels. Mir-145a levels markedly decreased both in human and mouse VDRwt VSMCs incubated in calcification media and 1, 25D. Overexpression of miR-145a suppressed the levels of OPN induced by 1, 25D, while the inhibition of mir-145a led to a significant increase in OPN levels, even higher than in cells treated solely with 1, 25D. A predicted miR-145a-binding site was detected at the 3’UTR of OPN mRNA transcript, through the extended seed region of the miRNA, pointing to OPN as a possible target of mir-145a during VC in CKD. There were no significant differences in Runx2 levels in 1, 25D-treated cells after transfection with mir-145a mimic or inhibitor. Conclusion VDR is induced in calcified VSMCs during CKD where it can modulate the expression of promoters and inhibitors of VSMC transdifferentiation, as well as small noncoding RNA molecules such as mir-145a that modulate VC. The regulation of these pathways by VDR seems to be essential for the settings of CKD-induced VC, as deletion of VDR from VSMCs prevented it.

Magnoflorine Ameliorates Chronic Kidney Disease in High-Fat and High-Fructose-Fed Mice by Promoting Parkin/PINK1-Dependent Mitophagy to Inhibit NLRP3/Caspase-1-Mediated Pyroptosis.

Excessive intake of fat and fructose in Western diets has been confirmed to induce renal lipotoxicity, thereby driving the progression of chronic kidney disease (CKD). This study was conducted to evaluate the efficacy of magnoflorine in a CKD mouse model subjected to high-fat and high-fructose diets. Our results demonstrated that magnoflorine treatment ameliorated abnormal renal function indices (serum creatinine, urea nitrogen, uric acid, and urine protein) in high-fat- and high-fructose-fed mice. Histologically, renal tubular cell steatosis, lipid deposition, tubular dilatation, and glomerular fibrosis were significantly reduced by the magnoflorine treatment in these mice. Mechanistically, magnoflorine promotes Parkin/PINK1-mediated mitophagy, thereby inhibiting NLRP3/Caspase-1-mediated pyroptosis. Consistent findings were observed in the palmitic acid-incubated HK-2 cell model. Notably, both silencing of Parkin and the use of a mitophagy inhibitor reversed the inhibitory effect of magnoflorine on NLRP3 inflammasome activation in vitro. Therefore, the present study provides compelling evidence that magnoflorine improves renal injury in high-fat- and high-fructose-fed mice by promoting Parkin/PINK1-dependent mitophagy to inhibit NLRP3 inflammasome activation and pyroptosis. Our findings suggest that dietary supplementation with magnoflorine and magnoflorine-rich foods (such as magnolia) might be an effective strategy for the prevention of CKD.

Empagliflozin Mitigates TMAO-Induced NLRP3 Inflammation and Alters Transporter Expression in Renal Proximal Tubular Cells

The gut-microbe-derived metabolite, trimethylamine N-oxide (TMAO), not only exhibits elevated levels but also serves as a predictor of higher mortality in patients with chronic kidney disease (CKD). In additional to CKD, elevated TMAO levels were also observed in organic anion transporter 3 (OAT 3) knockout mice and in the presence of trimethoprim, an antibiotic known for inhibiting multiple transporters on renal proximal tubule (PT) cells. These findings suggest that plasma TMAO level is a marker for diminished transporter function in PT cells. Moreover, the pro-inflammatory effects of TMAO on PT cells is relatively underexplored. Besides reno-protective effect, a recent study has shown that the sodium-glucose cotransporter 2 (SGLT2) inhibitor empagliflozin attenuates hyperuricemia by enhancing efflux transporter function. Therefore, we propose that empagliflozin can ameliorate TMAO-induced inflammation in PT cells by regulating the expression of membrane transporters. Western blotting results revealed that empagliflozin mitigated TMAO-induced NLRP3 inflammatory cytokines IL-1β, and IL-18. Additionally, empagliflozin reduced the elevated serum levels of TMAO in a CKD mouse model resulting from 5/6 nephrectomy (5/6Nx). Immuno-fluorescent staining demonstrated that TMAO decreased the expression of the basolateral transporter organic anion transporter 1 (OAT1) but increased the expression of apical membrane transporters ATP-binding cassette super-family G member 2 (ABCG2) on the PT cells of 5/6Nx mice. Our in vitro study indicated that TMAO reduced the expression of basolateral membrane transporters OAT1 and OAT3. But empagliflozin significantly increased the expression of OAT3 and ABCG2 in TMAO-treated HK-2 cells. In summary, TMAO induced NLRP3 inflammation in PT cells, while empagliflozin ameliorated the inflammation. Empagliflozin also lowered TMAO levels and influenced transporter expressions in a CKD mouse model. In conclusion, we have shown that empagliflozin mitigate TMAO-induced NLRP3 inflammation. Beyond inhibiting SGLT2, empagliflozin possesses additional effect on the expression of membrane transporters in PT, particularly in CKD mice. This research was funded by Chang Gung Medical Foundation CMRPG8K0011 and CMRPG8M0311. 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.

Cold atmospheric plasma for chronic kidney disease-related skin disorders.

An estimated 80% of individuals with chronic kidney disease (CKD) experience concomitant skin disorders, yet experimental research that elucidates the pathological changes in CKD-affected skin is limited. Cold atmospheric plasma (CAP) has shown promise in regulating keratinocyte proliferation, skin barrier function, and anti-inflammatory activity. We hypothesize that CAP emerges as a promising therapeutic avenue for CKD-related skin diseases. Male and female C57/BL6 mice were administered a 0.2% adenine diet to generate a CKD mouse model. Skin samples from dialysis patients were also collected. These models were used to investigate the pathological alterations in the renal glomeruli, tubules, and epidermis. Subsequently, the potential impact of CAP on the stratum corneum, keratinocytes, skin hydration, and inflammation in mice with CKD were examined. Renal biopsies revealed glomerular and tubular atrophy, epithelial degeneration and necrosis in uriniferous tubules, and significant renal interstitial fibrosis. Skin biopsies from patients with CKD and mice showed stratum corneum thickening, epidermis atrophy, skin hydration dysfunction, and excessive inflammation. CAP attenuated skin atrophy, hydration dysfunction, and inflammation in mice with CKD, as evidenced by the activated level of YAP1/β-catenin and Nrf-2/OH-1, enhanced expression of K5 and Ki67, increased levels of AQP3, collagen I, and GLUT1, reduced infiltration of CD3+ T cells, and diminished levels of IL-6 and TNF-α. This study provides valuable insights into the pathological changes in skin associated with CKD in both patients and animal models. It also establishes that CAP has the potential to effectively mitigate skin atrophy, hydration dysfunction, and inflammation, suggesting a novel therapeutic avenue for the treatment of CKD-related skin disorders.