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Sirt6 deficiency aggravates angiotensin II-induced cholesterol accumulation and injury in podocytes.

ABSTRACT: Disturbed renal lipid metabolism, especially cholesterol dysregulation plays a crucial role in the pathogenesis of chronic kidney disease (CKD). We recently reported that angiotensin (Ang) II could induce cholesterol accumulation and injury in podocytes. However, the underlying mechanisms for these alterations remain unknown.Methods: Bioinformatics analysis of renal biopsy specimens from patients with hypertensive nephropathy (HN) suggests the involvement of Sirtuin 6 (Sirt6) in Ang II-induced dysregulation of glomerular cholesterol. Using a podocyte-specific Sirt6 knockout mouse model, the effects of Sirt6 on Ang II-induced cholesterol accumulation in podocytes and the therapeutic efficacies of cholesterol-lowering agents were evaluated.Results: Cholesterol accumulation was detected in the podocytes of Ang II-infused mice, whereas selective deletion of Sirt6 in podocytes not only increased cholesterol accumulation in these cells but also exacerbated Ang II-induced kidney injury. Deletion of Sirt6 also attenuated the protective effect of cyclodextrin (CD) on Ang II-induced urinary albumin excretion, glomerulosclerosis and podocyte injury. In addition, we demonstrated that Sirt6 affected cholesterol efflux in podocytes by regulating the expression of ATP-binding cassette transporter G1 (ABCG1).Conclusions: These findings provide evidence that Sirt6 is a potential target for renin-angiotensin system (RAS)-associated podocyte injury and provide a rationale for the application of cholesterol-lowering agents in patients with CKD.

SUBMITTER: Yang Q

PROVIDER: S-EPMC7330847 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Angiotensin II induces cholesterol accumulation and injury in podocytes.

Project description:Angiotensin II (Ang II) is a risk factor for the initiation and progression of chronic kidney disease (CKD), as elevated Ang II levels can lead to podocyte injury. However, there have been no studies on the role of Ang II in lipid metabolism or on podocyte injury caused by lipid dysfunction. Our study showed that Ang II induced lipid droplet (LD) accumulation and expression of the LD marker adipose differentiation-related protein (ADRP) in podocytes, and the extent of lipid deposition could be alleviated by losartan. Our study also demonstrated that Ang II increased the content of cholesterol in podocytes, which is an LD component, and this change was accompanied by decreased expression of the cholesterol efflux-related molecule ATP-binding cassette transporter-1 (ABCA1) and increased expression of the cholesterol uptake-related molecule LDL receptor (LDLR) and the cholesterol synthesis-related molecules sterol regulatory element-binding protein (SREBP1 and SREBP2) and 3-hydroxy-3-methylglutaryl CoA reductase (HMGCR). Pretreating podocytes with methyl-β-cyclodextrin (CD), which induces cholesterol efflux, decreased Ang II-mediated cholesterol accumulation and Ang II-induced podocyte apoptosis and maintained the podocyte cytoskeleton and spreading. These results suggested that Ang II induced podocyte cholesterol accumulation by regulating the expression of cholesterol metabolism-related molecules and that the subsequent cholesterol metabolism dysfunction resulted in podocyte injury.

| S-EPMC5587570 | biostudies-literature

Alteration in Rab11-mediated endocytic trafficking of LDL receptor contributes to angiotensin II-induced cholesterol accumulation and injury in podocytes.

Project description:ObjectivesExposure of podocytes to angiotensin II (Ang II) enhances the abundance of the cell surface glycoprotein, low-density lipoprotein receptor (LDLR) and promotes significant changes in the cellular cholesterol content. Recent investigation provides evidence that the small GTPase Rab11 is involved in the regulation of LDLR, but the exact mechanisms remain unknown. In this study, the role of Rab11 in post-transcriptional regulation of LDLR was evaluated to investigate potential mechanisms of podocyte cholesterol dysregulation in chronic kidney disease.Materials and methodsCholesterol content, LDLR and Rab11 expression were assessed in podocytes from Ang II-infused mice. In vitro, the intracellular localization of LDLR was detected under different conditions. Rab11 expression was modulated and we then explored the effect of anti-lipid cytotoxicity by detecting LDLR expression and trafficking, cholesterol content and apoptosis in podocytes.ResultsCholesterol accumulation, upregulated expression of LDLR and Rab11 were discovered in podocytes from Ang II-infused mice. Ang II enhanced the co-precipitation of LDLR with Rab11 and accelerated the endocytic recycling of LDLR to the plasma membrane. Additionally, silencing Rab11 promoted lysosomal degradation of LDLR and alleviated Ang II-induced cholesterol accumulation and apoptosis in podocytes. Conversely, overexpression of Rab11 or inhibition of lysosomal degradation up-regulated the abundance of LDLR and aggravated podocyte cholesterol deposition.ConclusionsRab11 triggers the endocytic trafficking and recycling of LDLR; overactivation of this pathway contributes to Ang II-induced podocyte cholesterol accumulation and injury.

| S-EPMC9201372 | biostudies-literature

Sirtuin 3 deficiency aggravates angiotensin II-induced hypertensive cardiac injury by the impairment of lymphangiogenesis.

Project description:Lymphangiogenesis is possibly capable of attenuating hypertension-induced cardiac injury. Sirtuin 3 (SIRT3) is an effective mitochondrial deacetylase that has the potential to modulate this process; however, its role in hypertension-induced cardiac lymphangiogenesis to date has not been investigated. Our experiments were performed on 8-week-old wild-type (WT), SIRT3 knockout (SIRT3-KO) and SIRT3 overexpression (SIRT3-LV) mice infused with angiotensin II (Ang II) (1000 ng/kg per minute) or saline for 28 days. After Ang II infusion, SIRT3-KO mice developed a more severe cardiac remodelling, less lymphatic capillaries and lower expression of lymphatic marker when compared to wild-type mice. In comparison, SIRT3-LV restored lymphangiogenesis and attenuated cardiac injury. Furthermore, lymphatic endothelial cells (LECs) exposed to Ang II in vitro exhibited decreased migration and proliferation. Silencing SIRT3 induced functional decrease in LECs, while SIRT3 overexpression LECs facilitated. Moreover, SIRT3 may up-regulate lymphangiogenesis by affecting vascular endothelial growth factor receptor 3 (VEGFR3) and ERK pathway. These findings suggest that SIRT3 could promote lymphangiogenesis and attenuate hypertensive cardiac injury.

| S-EPMC8358873 | biostudies-literature

MMP-12 deficiency attenuates angiotensin II-induced vascular injury, M2 macrophage accumulation, and skin and heart fibrosis.

Project description:MMP-12, a macrophage-secreted elastase, is elevated in fibrotic diseases, including systemic sclerosis (SSc) and correlates with vasculopathy and fibrosis. The goal of this study was to investigate the role of MMP-12 in cardiac and cutaneous fibrosis induced by angiotensin II infusion. Ang II-induced heart and skin fibrosis was accompanied by a marked increase of vascular injury markers, including vWF, Thrombospondin-1 (TSP-1) and MMP-12, as well as increased number of PDGFRβ+ cells. Furthermore Ang II infusion led to an accumulation of macrophages (Mac3+) in the skin and in the perivascular and interstitial fibrotic regions of the heart. However, alternatively activated (Arg 1+) macrophages were mainly present in the Ang II infused mice and were localized to the perivascular heart regions and to the skin, but were not detected in the interstitial heart regions. Elevated expression of MMP-12 was primarily found in macrophages and endothelial cells (CD31+) cells, but MMP-12 was not expressed in the collagen producing cells. MMP-12 deficient mice (MMP12KO) showed markedly reduced expression of vWF, TSP1, and PDGFRβ around vessels and attenuation of dermal fibrosis, as well as the perivascular fibrosis in the heart. However, MMP-12 deficiency did not affect interstitial heart fibrosis, suggesting a heterogeneous nature of the fibrotic response in the heart. Furthermore, MMP-12 deficiency almost completely prevented accumulation of Arg 1+ cells, whereas the number of Mac3+ cells was partially reduced. Moreover production of profibrotic mediators such as PDGFBB, TGFβ1 and pSMAD2 in the skin and perivascular regions of the heart was also inhibited. Together, the results of this study show a close correlation between vascular injury markers, Arg 1+ macrophage accumulation and fibrosis and suggest an important role of MMP-12 in regulating these processes.

| S-EPMC4193823 | biostudies-literature

PFKFB3 downregulation aggravates Angiotensin II-induced podocyte detachment.

Project description:Podocytes play a critical role in maintaining normal glomerular filtration, and podocyte loss from the glomerular basement membrane (GBM) initiates and worsens chronic kidney disease (CKD). However, the exact mechanism underlying podocyte loss remains unclear. Fructose-2,6-biphosphatase 3 (PFKFB3) is a bifunctional enzyme that plays crucial roles in glycolysis, cell proliferation, cell survival, and cell adhesion. This study aimed to determine the role of PFKFB3 in angiotensin II (Ang II) kidney damage. We found that mice infused with Ang II developed glomerular podocyte detachment and impaired renal function accompanied by decreased PFKFB3 expression in vivo and in vitro. Inhibition of PFKFB3 with the PFKFB3 inhibitor 3PO further aggravated podocyte loss induced by Ang II. In contrast, activating PFKFB3 with the PFKFB3 agonist meclizine alleviated the podocyte loss induced by Ang II. Mechanistically, PFKFB3 knockdown likely aggravate Ang II-induced podocyte loss by suppressing talin1 phosphorylation and integrin beta1 subunit (ITGB1) activity. Conversely, PFKFB3 overexpression protected against Ang II-induced podocyte loss. These findings suggest that Ang II leads to a decrease in podocyte adhesion by suppressing PFKFB3 expression, and indicates a potential therapeutic target for podocyte injury in CKD.

| S-EPMC10334864 | biostudies-literature

TIGAR deficiency sensitizes angiotensin-II-induced renal fibrosis and glomerular injury.

Project description:Angiotensin II (Ang-II) is one of the major contributors to the progression of renal fibrosis, inflammation, glomerular injury, and chronic kidney disease. Emerging evidence suggests that renal glycolysis plays an important role in renal fibrosis and injury. TP53-induced glycolysis and apoptosis regulator (TIGAR) has been shown to regulate glycolysis. In the present study, we investigated the role of TIGAR in renal glycolysis, fibrosis, and glomerular injury during Ang-II-induced hypertension. Wild-type (WT) and TIGAR knockout (KO) mice were infused with Ang-II (1 µg/kg/min) via mini-pumps for 4 weeks. The mean arterial pressure was similar between the WT and TIGAR KO mice, associated with a comparable increase in plasma creatinine level. Ang-II infusion resulted in a significant increase in renal interstitial fibrosis and more mesangial expansion and collapsed glomerular structure in the TIGAR KO mice. These were associated with elevated expression of hypoxia-inducible factor-1 alpha, glycolytic enzymes, and transforming growth factor beta 1 in the TIGAR KO mice after Ang-II infusion when compared to that of the WT mice. The coupled-enzyme method revealed that PFK-1 activity was similarly increased in WT and TIGAR KO mice after Ang-II infusion. Our present study suggests that TIGAR is involved in Ang-II-induced renal fibrosis and glomerular injury, although it has little effect on blood pressure and renal function. Knockout of TIGAR sensitizes Ang-II-induced renal fibrosis and injury. This study provides new insights into the role of TIGAR in renal metabolism and pathological remodeling during Ang-II-induced hypertension.

| S-EPMC9020173 | biostudies-literature

C/EBP? deficiency in podocytes aggravates podocyte senescence and kidney injury in aging mice.

Project description:Kidney aging leads to an increased incidence of end-stage renal disease (ESRD) in the elderly, and aging is a complex biological process controlled by signaling pathways and transcription factors. Podocyte senescence plays a central role in injury resulting from kidney aging. Here, we demonstrated the critical role of C/EBP? in podocyte senescence and kidney aging by generating a genetically modified mouse model of chronological aging in which C/EBP? was selectively deleted in podocytes and by overexpressing C/EBP? in cultured podocytes, in which premature senescence was induced by treatment with adriamycin. Moreover, we illuminated the mechanisms by which podocyte senescence causes tubular impairment by stimulating HK-2 cells with bovine serum albumin (BSA) and chloroquine. Our findings suggest that C/EBP? knockout in podocytes aggravates podocyte senescence through the AMPK/mTOR pathway, leading to glomerulosclerosis, and that subsequent albuminuria exacerbates the epithelial-mesenchymal transdifferentiation of senescent tubular cells by suppressing autophagy. These observations highlight the importance of C/EBP? as a new potential target in kidney aging.

| S-EPMC6746733 | biostudies-literature

Injured Podocytes Are Sensitized to Angiotensin II-Induced Calcium Signaling.

Project description:BackgroundInhibition of angiotensin II (AngII) signaling, a therapeutic mainstay of glomerular kidney diseases, is thought to act primarily through regulating glomerular blood flow and reducing filtration pressure. Although extravascular actions of AngII have been suggested, a direct effect of AngII on podocytes has not been demonstrated in vivo.MethodsTo study the effects of AngII on podocyte calcium levels in vivo, we used intravital microscopy of the kidney in mice expressing the calcium indicator protein GCaMP3.ResultsIn healthy animals, podocytes displayed limited responsiveness to AngII stimulation. In contrast, in animals subjected to either adriamycin-induced acute chemical injury or genetic deletion of the podocin-encoding gene Nphs2, the consequent podocyte damage and proteinuria rendered the cells responsive to AngII and resulted in AngII-induced calcium transients in significantly more podocytes. The angiotensin type 1 receptor blocker losartan could fully inhibit this response. Also, responsiveness to AngII was at least partly mediated through the transient receptor potential channel 6, which has been implicated in podocyte calcium handling. Interestingly, loss of a single Nphs2 allele also increased podocytes' responsiveness to AngII signaling. This direct effect of AngII on injured podocytes results in increased calcium transients, which can further aggravate the underlying kidney disease.ConclusionsOur discovery that podocytes become sensitized to AngII-induced calcium signaling upon injury might explain results from large, randomized, controlled trials in which improved renal outcomes occur only in the subgroup of patients with proteinuria, indicating podocyte damage. Our findings also emphasize the need to treat every patient with a glomerular disease with either an angiotensin-converting enzyme inhibitor or an angiotensin type 1 receptor blocker.

| S-EPMC7062224 | biostudies-literature

Mitoquinone Protects Podocytes from Angiotensin II-Induced Mitochondrial Dysfunction and Injury via the Keap1-Nrf2 Signaling Pathway.

Project description:Podocyte mitochondrial dysfunction plays a critical role in the pathogenesis of chronic kidney disease (CKD). Previous studies demonstrated that excessive mitochondrial fission could lead to the overproduction of reactive oxygen species (ROS) and promote podocyte apoptosis. Therefore, the maintenance of stable mitochondrial function is a newly identified way to protect podocytes and prevent the progression of CKD. As a mitochondria-targeted antioxidant, mitoquinone (MitoQ) has been proven to be a promising agent for the prevention of mitochondrial injury in cardiovascular disease and Parkinson's disease. The present study examined the effects of MitoQ on angiotensin II- (Ang II-) induced podocyte injury both in vivo and in vitro. Podocyte mitochondria in Ang II-infused mice exhibited morphological and functional alterations. The observed mitochondrial fragmentation and ROS production were alleviated with MitoQ treatment. In vitro, alterations in mitochondrial morphology and function in Ang II-stimulated podocytes, including mitochondrial membrane potential reduction, ROS overproduction, and adenosine triphosphate (ATP) deficiency, were significantly reversed by MitoQ. Moreover, MitoQ rescued the expression and translocation of Nrf2 (nuclear factor E2-related factor 2) and decreased the expression of Keap1 (Kelch-like ECH-associated protein 1) in Ang II-stimulated podocytes. Nrf2 knockdown partially blocked the protective effects of MitoQ on Ang II-induced mitochondrial fission and oxidative stress in podocytes. These results demonstrate that MitoQ exerts a protective effect in Ang II-induced mitochondrial injury in podocytes via the Keap1-Nrf2 signaling pathway.

| S-EPMC8380182 | biostudies-literature

Intravital Imaging Reveals Angiotensin II-Induced Transcytosis of Albumin by Podocytes.

Project description:Albuminuria is a hallmark of kidney disease of various etiologies and usually caused by deterioration of glomerular filtration barrier integrity. We recently showed that angiotensin II (Ang II) acutely increases albumin filtration in the healthy kidney. Here, we used intravital microscopy to assess the effects of Ang II on podocyte function in rats. Acute infusion of 30, 60, or 80 ng/kg per minute Ang II enhanced the endocytosis of albumin by activation of the type 1 Ang II receptor and resulted in an average (±SEM) of 3.7±2.2, 72.3±18.6 (P<0.001), and 239.4±34.6 µm(3) (P<0.001) albumin-containing vesicles per glomerulus, respectively, compared with none at baseline or 10 ng/kg per minute Ang II. Immunostaining of Ang II-infused kidneys confirmed the presence of albumin-containing vesicles, which colocalized with megalin, in podocin-positive cells. Furthermore, podocyte endocytosis of albumin was markedly reduced in the presence of gentamicin, a competitive inhibitor of megalin-dependent endocytosis. Ang II infusion increased the concentration of albumin in the subpodocyte space, a potential source for endocytic protein uptake, and gentamicin further increased this concentration. Some endocytic vesicles were acidified and colocalized with LysoTracker. Most vesicles migrated from the capillary to the apical aspect of the podocyte and were eventually released into the urinary space. This transcytosis accounted for approximately 10% of total albumin filtration. In summary, the transcellular transport of proteins across the podocyte constitutes a new pathway of glomerular protein filtration. Ang II enhances the endocytosis and transcytosis of plasma albumin by podocytes, which may eventually impair podocyte function.

| S-EPMC4769192 | biostudies-literature

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