Astragaloside IV alleviates renal fibrosis by inhibiting renal tubular epithelial cell pyroptosis induced by urotensin II through regulating the cAMP/PKA signaling pathway.

OBJECTIVE: To explore the molecular mechanism of Astragaloside IV (AS-IV) in alleviating renal fibrosis by inhibiting Urotensin II-induced pyroptosis and epithelial-mesenchymal transition of renal tubular epithelial cells. METHODS: Forty SD rats were randomly divided into control group without operation: gavage with 5ml/kg/d water for injection and UUO model group: gavage with 5ml/kg/d water for injection; UUO+ AS-IV group (gavage with AS-IV 20mg/kg/d; and UUO+ losartan potassium group (gavage with losartan potassium 10.3mg/kg/d, with 10 rats in each group. After 2 weeks, Kidney pathology, serum Urotensin II, and cAMP concentration were detected, and the expressions of NLRP3, GSDMD-N, Caspase-1, and IL-1ß were detected by immunohistochemistry. Rat renal tubular epithelial cells were cultured in vitro, and different concentrations of Urotensin II were used to intervene for 24h and 48h. Cell proliferation activity was detected using the CCK8 assay. Suitable concentrations of Urotensin II and intervention time were selected, and Urotensin II receptor antagonist (SB-611812), inhibitor of PKA(H-89), and AS-IV (15ug/ml) were simultaneously administered. After 24 hours, cells and cell supernatants from each group were collected. The cAMP concentration was detected using the ELISA kit, and the expression of PKA, α-SMA, FN, IL-1ß, NLRP3, GSDMD-N, and Caspase-1 was detected using cell immunofluorescence, Western blotting, and RT-PCR. RESULTS: Renal tissue of UUO rats showed renal interstitial infiltration, tubule dilation and atrophy, renal interstitial collagen fiber hyperplasia, and serum Urotensin II and cAMP concentrations were significantly higher than those in the sham operation group (p <0.05). AS-IV and losartan potassium intervention could alleviate renal pathological changes, and decrease serum Urotensin II, cAMP concentration levels, and the expressions of NLRP3, GSDMD-N, Caspase-1, and IL-1ß in renal tissues (p <0.05). Urotensin II at a concentration of 10-8 mol/L could lead to the decrease of cell proliferation, (p<0.05). Compared with the normal group, the cAMP level and the PKA expression were significantly increased (p<0.05). After intervention with AS-IV and Urotensin II receptor antagonist, the cAMP level and the expression of PKA were remarkably decreased (p<0.05). Compared with the normal group, the expression of IL-1ß, NLRP3, GSDMD-N, and Caspase-1 in the Urotensin II group was increased (p<0.05), which decreased in the AS-IV and H-89 groups. CONCLUSION: AS-IV can alleviate renal fibrosis by inhibiting Urotensin II-induced pyroptosis of renal tubular epithelial cells by regulating the cAMP/PKA signaling pathway.

Fatty Acid Binding Protein-4 Silencing Inhibits Ferroptosis to Alleviate Lipopolysaccharide-induced Injury of Renal Tubular Epithelial Cells by Blocking Janus Kinase 2/Signal Transducer and Activator of Transcription 3 Signaling.

Sepsis-induced kidney injury (SAKI) has been frequently established as a prevailing complication of sepsis which is linked to unfavorable outcomes. Fatty acid-binding protein-4 (FABP4) has been proposed as a possible target for the treatment of SAKI. In the current work, we aimed to explore the role and underlying mechanism of FABP4 in lipopolysaccharide (LPS)-induced human renal tubular epithelial cell damage. In LPS-induced human kidney 2 (HK2) cells, FABP4 expression was tested by the reverse transcription-quantitative polymerase chain reaction and Western blot. Cell counting kit-8 method assayed cell viability. Inflammatory levels were detected using the enzyme-linked immunosorbent assay. Immunofluorescence staining measured the nuclear translocation of nuclear factor kappa B p65. Thiobarbituric acid-reactive substances assay and C11 BODIPY 581/591 probe were used to estimate the level of cellular lipid peroxidation. Fe2+ content was examined by the kit. In addition, the expression of proteins related to inflammation-, ferroptosis- and Janus kinase 2 (JAK2)/signal transducer, and activator of transcription 3 (STAT3) signaling was detected by the Western blot analysis. The results revealed that FABP4 was significantly upregulated in LPS-treated HK2 cells, the knockdown of which elevated the viability, whereas alleviated the inflammation and ferroptosis in HK2 cells challenged with LPS. In addition, down-regulation of FABP4 inactivated JAK2/STAT3 signaling. JAK2/STAT3 stimulator (colivelin) and ferroptosis activator (Erastin) partially restored the effects of FABP4 interference on LPS-triggered inflammation and ferroptosis in HK2 cells. Together, FABP4 knockdown inhibited ferroptosis to alleviate LPS-induced injury of renal tubular epithelial cells through suppressing JAK2/STAT3 signaling.

Activation of the Nrf2/ARE signaling pathway ameliorates hyperlipidemia-induced renal tubular epithelial cell injury by inhibiting mtROS-mediated NLRP3 inflammasome activation.

Dyslipidemia is the most prevalent independent risk factor for patients with chronic kidney disease (CKD). Lipid-induced NLRP3 inflammasome activation in kidney-resident cells exacerbates renal injury by causing sterile inflammation. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that modulates the cellular redox balance; however, the exact role of Nrf2 signaling and its regulation of the NLRP3 inflammasome in hyperlipidemia-induced kidney injury are poorly understood. In this study, we demonstrated that activation of the mtROS-NLRP3 inflammasome pathway is a critical contributor to renal tubular epithelial cell (RTEC) apoptosis under hyperlipidemia. In addition, the Nrf2/ARE signaling pathway is activated in renal tubular epithelial cells under hyperlipidemia conditions both in vivo and in vitro, and Nrf2 silencing accelerated palmitic acid (PA)-induced mtROS production, mitochondrial injury, and NLRP3 inflammasome activation. However, the activation of Nrf2 with tBHQ ameliorated mtROS production, mitochondrial injury, NLRP3 inflammasome activation, and cell apoptosis in PA-induced HK-2 cells and in the kidneys of HFD-induced obese rats. Furthermore, mechanistic studies showed that the potential mechanism of Nrf2-induced NLRP3 inflammasome inhibition involved reducing mtROS generation. Taken together, our results demonstrate that the Nrf2/ARE signaling pathway attenuates hyperlipidemia-induced renal injury through its antioxidative and anti-inflammatory effects through the downregulation of mtROS-mediated NLRP3 inflammasome activation.

Tubular expression of Toll-like receptor 9 in lupus and primary membranous nephropathy.

INTRODUCTION: Toll-like- receptors (TLR) control important aspects of innate and adaptive immune responses. Renal cells are among the non-immune cells that express (TLR). Therefore, their activation might be implicated in renal tubulo-interstitial injury. AIM: The study aimed to compare TLR9 expression in patients with primary membranous nephropathy (MN) to patients with lupus membranous nephropathy. METHODS: Kidney sections from 10 Lupus nephritis (LN) patients and ten patients with primary MN were analyzed by immunohistochemistry using anti-human TLR9 antibody. RESULTS: Results showed that TLR9 expression was weak and exclusively tubular in primary MN patients' biopsies. There was a significant difference between LN patients' biopsies and primary MN patients' biopsies. TLR9 expression was more diffused in LN patients' specimen than in those with primary MN. CONCLUSION: This study focuses on molecular level pathogenesis of MN. The data suggest that the receptors TLR9 may play role in tubulointerstitial injury in the pathogenesis of LN but not primary membranous nephropathy.

VDR restores the expression of PINK1 and BNIP3 in TECs of streptozotocin-induced diabetic mice.

Defective mitophagy in renal tubular epithelial cells is one of the main drivers of renal fibrosis in diabetic kidney disease. Our gene sequencing data showed the expression of PINK1 and BNIP3, two key molecules of mitophagy, was decreased in renal tissues of VDR-knockout mice. Herein, streptozotocin (STZ) was used to induce renal interstitial fibrosis in mice. VDR deficiency exacerbated STZ-induced renal impairment and defective mitophagy. Paricalcitol (pari, a VDR agonist) and the tubular epithelial cell-specific overexpression of VDR restored the expression of PINK1 and BNIP3 in the renal cortex and attenuated STZ-induced kidney fibrosis and mitochondrial dysfunction. In HK-2 cells under high glucose conditions, an increased level of α-SMA, COL1, and FN and a decreased expression of PINK1 and BNIP3 with severe mitochondrial damage were observed, and these alterations could be largely reversed by pari treatment. ChIP-qPCR and luciferase reporter assays showed VDR could positively regulate the transcription of Pink1 and Bnip3 genes. These findings reveal that VDR could restore mitophagy defects and attenuate STZ-induced fibrosis in diabetic mice through regulation of PINK1 and BNIP3.

Transport activity regulates mitochondrial bioenergetics and biogenesis in renal tubules.

Renal tubules are featured with copious mitochondria and robust transport activity. Mutations in mitochondrial genes cause congenital renal tubulopathies, and changes in transport activity affect mitochondrial morphology, suggesting mitochondrial function and transport activity are tightly coupled. Current methods of using bulk kidney tissues or cultured cells to study mitochondrial bioenergetics are limited. Here, we optimized an extracellular flux analysis (EFA) to study mitochondrial respiration and energy metabolism using microdissected mouse renal tubule segments. EFA detects mitochondrial respiration and glycolysis by measuring oxygen consumption and extracellular acidification rates, respectively. We show that both measurements positively correlate with sample sizes of a few centimeter-length renal tubules. The thick ascending limbs (TALs) and distal convoluted tubules (DCTs) critically utilize glucose/pyruvate as energy substrates, whereas proximal tubules (PTs) are significantly much less so. Acute inhibition of TALs' transport activity by ouabain treatment reduces basal and ATP-linked mitochondrial respiration. Chronic inhibition of transport activity by 2-week furosemide treatment or deletion of with-no-lysine kinase 4 (Wnk4) decreases maximal mitochondrial capacity. In addition, chronic inhibition downregulates mitochondrial DNA mass and mitochondrial length/density in TALs and DCTs. Conversely, gain-of-function Wnk4 mutation increases maximal mitochondrial capacity and mitochondrial length/density without increasing mitochondrial DNA mass. In conclusion, EFA is a sensitive and reliable method to investigate mitochondrial functions in isolated renal tubules. Transport activity tightly regulates mitochondrial bioenergetics and biogenesis to meet the energy demand in renal tubules. The system allows future investigation into whether and how mitochondria contribute to tubular remodeling adapted to changes in transport activity.

Lipid nephrotoxicity mediated by HIF-1α activation accelerates tubular injury in diabetic nephropathy.

This study is intended to explore the effect of hypoxia-inducible factor-1α (HIF-1α) activation on lipid accumulation in the diabetic kidney. A type 1 diabetic rat model was established by STZ intraperitoneal injection. Cobalt chloride (CoCl2) and YC-1 were used as the HIF-1α activator and antagonist, respectively. CoCl2 treatment significantly increased HIF-1α expression, accelerated lipid deposition, and accelerated tubular injury in diabetic kidneys. In vitro, CoCl2 effectively stabilized HIF-1α and increased its transportation from the cytoplasm to the nucleus, which was accompanied by significantly increased lipid accumulation in HK-2 cells. Furthermore, results obtained in vivo showed that HIF-1α protein expression in the renal tubules of diabetic rats was significantly downregulated by YC-1 treatment. Meanwhile, lipid accumulation in the tubules of the DM + YC-1 group was markedly decreased in comparison to the DM + DMSO group. Accordingly, PAS staining revealed that the pathological injury caused to the tubular epithelial cells was alleviated by YC-1 treatment. Furthermore, the blood glucose level, urine albumin creatinine ratio, and NAG creatinine ratio in the DM + YC-1 group were significantly decreased compared to the DM + DMSO group. Moreover, the protein expression levels of transforming growth factor ß1 (TGF-ß1) and connective tissue growth factor (CTGF) in diabetic kidneys were decreased by YC-1 treatment. Our findings demonstrate that the activation of HIF-1α contributed to interstitial injury in a rat model of diabetic nephropathy and that the underlying mechanism involved the induction of lipid accumulation.

Autophagy-deficient macrophages exacerbate cisplatin-induced mitochondrial dysfunction and kidney injury via miR-195a-5p-SIRT3 axis.

Macrophages (Mφ) autophagy is a pivotal contributor to inflammation-related diseases. However, the mechanistic details of its direct role in acute kidney injury (AKI) were unclear. Here, we show that Mφ promote AKI progression via crosstalk with tubular epithelial cells (TECs), and autophagy of Mφ was activated and then inhibited in cisplatin-induced AKI mice. Mφ-specific depletion of ATG7 (Atg7Δmye) aggravated kidney injury in AKI mice, which was associated with tubulointerstitial inflammation. Moreover, Mφ-derived exosomes from Atg7Δmye mice impaired TEC mitochondria in vitro, which may be attributable to miR-195a-5p enrichment in exosomes and its interaction with SIRT3 in TECs. Consistently, either miR-195a-5p inhibition or SIRT3 overexpression improved mitochondrial bioenergetics and renal function in vivo. Finally, adoptive transfer of Mφ from AKI mice to Mφ-depleted mice promotes the kidney injury response to cisplatin, which is alleviated when Mφ autophagy is activated with trehalose. We conclude that exosomal miR-195a-5p mediate the communication between autophagy-deficient Mφ and TECs, leading to impaired mitochondrial biogenetic in TECs and subsequent exacerbation of kidney injury in AKI mice via miR-195a-5p-SIRT3 axis.

The NLRP3 Inflammasome Is a Major Cause of Acute Renal Failure Induced by Polypeptide Antibiotics.

Drug-induced acute renal failure (ARF) is a public health concern that hinders optimal drug therapy. However, pathological mechanisms of drug-induced ARF remain to be elucidated. Here, we show that a pathological process of drug-induced ARF is mediated by proinflammatory cross-talk between kidney tubular cells and macrophages. Both polymyxin B and colistin, polypeptide antibiotics, frequently cause ARF, stimulated the ERK and NF-κB pathways in kidney tubular cells, and thereby upregulated M-CSF and MCP-1, leading to infiltration of macrophages into the kidneys. Thereafter, the kidney-infiltrated macrophages were exposed to polypeptide antibiotics, which initiated activation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome. Interestingly, blockade of the NLRP3 activation clearly ameliorated the pathology of ARF induced by polypeptide antibiotics, suggesting that a combination of the distinct cellular responses to polypeptide antibiotics in kidney tubular cells and macrophages plays a key role in the pathogenesis of colistin-induced ARF. Thus, our results provide a concrete example of how drugs initiate ARF, which may give insight into the underlying pathological process of drug-induced ARF.

Double-negative T cells have a reparative role after experimental severe ischemic acute kidney injury.

T cells mediate organ injury and repair. A proportion of unconventional kidney T cells called double-negative (DN) T cells (TCR+ CD4- CD8-), with anti-inflammatory properties, were previously demonstrated to protect from early injury in moderate experimental acute kidney injury (AKI). However, their role in repair after AKI has not been studied. We hypothesized that DN T cells mediate repair after severe AKI. C57B6 mice underwent severe (40 min) unilateral ischemia-reperfusion injury (IRI). Kidney DN T cells were studied by flow cytometry and compared with gold-standard anti-inflammatory CD4+ regulatory T cells (Tregs). In vitro effects of DN T cells and Tregs on renal tubular epithelial cell (RTEC) repair after injury were quantified with live-cell analysis. DN T cells, Tregs, CD4, or vehicle were adoptively transferred after severe AKI. Glomerular filtration rate (GFR) was measured using fluorescein isothiocyanate (FITC)-sinistrin. Fibrosis was assessed with Masson's trichrome staining. Profibrotic genes were measured with qRT-PCR. Percentages and the numbers of DN T cells substantially decreased during repair phase after severe AKI, as well as their activation and proliferation. Both DN T cells and Tregs accelerated RTEC cell repair in vitro. Post-AKI transfer of DN T cells reduced kidney fibrosis and improved GFR, as did Treg transfer. DN T cell transfer lowered transforming growth factor (TGF)ß1 and α-smooth muscle actin (αSMA) expression. DN T cells reduced effector-memory CD4+ T cells and IL-17 expression. DN T cells undergo quantitative and phenotypical changes after severe AKI, accelerate RTEC repair in vitro as well as improve GFR and renal fibrosis in vivo. DN T cells have potential as immunotherapy to accelerate repair after AKI.NEW & NOTEWORTHY Double-negative (DN) T cells (CD4- CD8-) are unconventional kidney T cells with regulatory abilities. Their role in repair from acute kidney injury (AKI) is unknown. Kidney DN T cell population decreased during repair after ischemic AKI, in contrast to regulatory T cells (Tregs) which increased. DN T cell administration accelerated tubular repair in vitro, while after severe in vivo ischemic injury reduced kidney fibrosis and increased glomerular filtration rate (GFR). DN T cell infusion is a potential therapeutic agent to improve outcome from severe AKI.

Autophagic-lysosomal damage induced by swainsonine is protected by trehalose through activation of TFEB-regulated pathway in renal tubular epithelial cells.

Swainsonine (SW) is the main toxic component of locoweed. Previous studies have shown that kidney damage is an early pathologic change in locoweed poisoning in animals. Trehalose induces autophagy and alleviates lysosomal damage, while its protective effect and mechanism against the toxic injury induced by SW is not clear. Based on the published literature, we hypothesize that transcription factor EB(TFEB) -regulated is targeted by SW and activating TFEB by trehalose would reverse the toxic effects. In this study, we investigate the mechanism of protective effects of trehalose using renal tubular epithelial cells. The results showed that SW induced an increase in the expression level of microtubule-associated protein light chain 3-II and p62 proteins and a decrease in the expression level of ATPase H+ transporting V1 Subunit A, Cathepsin B, Cathepsin D, lysosome-associated membrane protein 2 and TFEB proteins in renal tubular epithelial cells in a time and dose-dependent manner suggesting TFEB-regulated lysosomal pathway is adversely affected by SW. Conversely, treatment with trehalose, a known activator of TFEB promote TFEB nuclear translocation suggesting that TFEB plays an important role in protection against SW toxicity. We demonstrated in lysosome staining that SW reduced the number of lysosomes and increased the luminal pH, while trehalose could counteract these SW-induced effects. In summary, our results demonstrated for the first time that trehalose could alleviate the autophagy degradation disorder and lysosomal damage induced by SW. Our results provide an interesting method for reversion of SW-induced toxicity in farm animals and furthermore, activation of TFEB by trehalose suggesting novel mechanism of treating lysosomal storage diseases.

Butyrate promotes kidney resilience through a coordinated kidney protective response in tubular cells.

Acute kidney injury (AKI) is common in hospitalized patients and increases short-term and long-term mortality. Treatment options for AKI are limited. Gut microbiota products such as the short-chain fatty acid butyrate have anti-inflammatory actions that may protect tissues, including the kidney, from injury. However, the molecular mechanisms of tissue protection by butyrate are poorly understood. Treatment with oral butyrate for two weeks prior to folic acid-induced AKI and during AKI improved kidney function and decreased tubular injury and kidney inflammation while stopping butyrate before AKI was not protective. Continuous butyrate preserved the expression of kidney protective factors such as Klotho, PGC-1α and Nlrp6 which were otherwise downregulated. In cultured tubular cells, butyrate blunted the maladaptive tubular cell response to a proinflammatory milieu, preserving the expression of kidney protective factors. Kidney protection afforded by this continuous butyrate schedule was confirmed in a second model of nephrotoxic AKI, cisplatin nephrotoxicity, where the expression of kidney protective factors was also preserved. To assess the contribution of preservation of kidney protective factors to kidney resilience, recombinant Klotho was administered to mice with cisplatin-AKI and shown to preserve the expression of PGC-1α and Nlrp6, decrease kidney inflammation and protect from AKI. In conclusion, butyrate promotes kidney resilience to AKI and decreases inflammation by preventing the downregulation of kidney protective genes such as Klotho. This information may be relevant to optimize antibiotic management during hospitalization.

Calcium signaling induces partial EMT and renal fibrosis in a Wnt4mCherry knock-in mouse model.

The renal tubular epithelial cells (TEC) have a strong capacity for repair after acute injury, but when this mechanism becomes uncontrollable, it leads to chronic kidney diseases (CKD). Indeed, in progress toward CKDs, the TECs may dedifferentiate, undergo epithelial-to-mesenchyme transition (EMT), and promote inflammation and fibrosis. Given the critical role of Wnt4 signaling in kidney ontogenesis, we addressed whether changes in this signaling are connected to renal inflammation and fibrosis by taking advantage of a knock-in Wnt4mCh/mCh mouse. While the Wnt4mCh/mCh embryos appeared normal, the corresponding mice, within one month, developed CKD-related phenotypes, such as pro-inflammatory responses including T-cell/macrophage influx, expression of fibrotic markers, and epithelial cell damage with a partial EMT. The Wnt signal transduction component ß-catenin remained unchanged, while calcium signaling is induced in the injured TECs involving Nfat and Tfeb transcription factors. We propose that the Wnt4 signaling pathway is involved in repairing the renal injury, and when the signal is overdriven, CKD is established.

Mitochondrial bioenergetics: coupling of transport to tubular mitochondrial metabolism.

PURPOSE OF REVIEW: Renal tubules have robust active transport and mitochondrial metabolism, which are functionally coupled to maintain energy homeostasis. Here, I review the current literature and our recent efforts to examine mitochondrial adaptation to different transport activities in renal tubules. RECENT FINDINGS: The advance of extracellular flux analysis (EFA) allows real-time assessments of mitochondrial respiration, glycolysis, and oxidation of energy substrates. We applied EFA assays to freshly isolated mouse proximal tubules, thick ascending limbs (TALs), and distal convoluted tubules (DCTs) and successfully differentiated their unique metabolic features. We found that TALs and DCTs adjusted their mitochondrial bioenergetics and biogenesis in response to acute and chronic alterations of transport activity. Based on the literature and our recent findings, I discuss working models and mechanisms underlying acute and chronic tubular adaptations to transport activity. The potential roles of peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α), AMP-activated protein kinase (AMPK), and uncoupling protein 2 (UCP2) are discussed. SUMMARY: Mitochondria in renal tubules are highly plastic to accommodate different transport activities. Understanding the mechanisms may improve the treatment of renal tubulopathies.

The role of mitophagy in the development of chronic kidney disease.

Chronic kidney disease (CKD) represents a significant global health concern, with renal fibrosis emerging as a prevalent and ultimate manifestation of this condition. The absence of targeted therapies presents an ongoing and substantial challenge. Accumulating evidence suggests that the integrity and functionality of mitochondria within renal tubular epithelial cells (RTECs) often become compromised during CKD development, playing a pivotal role in the progression of renal fibrosis. Mitophagy, a specific form of autophagy, assumes responsibility for eliminating damaged mitochondria to uphold mitochondrial equilibrium. Dysregulated mitophagy not only correlates with disrupted mitochondrial dynamics but also contributes to the advancement of renal fibrosis in CKD. While numerous studies have examined mitochondrial metabolism, ROS (reactive oxygen species) production, inflammation, and apoptosis in kidney diseases, the precise pathogenic mechanisms underlying mitophagy in CKD remain elusive. The exact mechanisms through which modulating mitophagy mitigates renal fibrosis, as well as its influence on CKD progression and prognosis, have not undergone systematic investigation. The role of mitophagy in AKI has been relatively clear, but the role of mitophagy in CKD is still rare. This article presents a comprehensive review of the current state of research on regulating mitophagy as a potential treatment for CKD. The objective is to provide fresh perspectives, viable strategies, and practical insights into CKD therapy, thereby contributing to the enhancement of human living conditions and patient well-being.

Renal lipid accumulation and aging linked to tubular cells injury via ANGPTL4.

Renal tubular epithelial cells are vulnerable to stress-induced damage, including excessive lipid accumulation and aging, with ANGPTL4 potentially playing a crucial bridging role between these factors. In this study, RNA-sequencing was used to identify a marked increase in ANGPTL4 expression in kidneys of diet-induced obese and aging mice. Overexpression and knockout of ANGPTL4 in renal tubular epithelial cells (HK-2) was used to investigate the underlying mechanism. Subsequently, ANGPTL4 expression in plasma and kidney tissues of normal young controls and elderly individuals was analyzed using ELISA and immunohistochemical techniques. RNA sequencing results showed that ANGPTL4 expression was significantly upregulated in the kidney tissue of diet-induced obesity and aging mice. In vitro experiments demonstrated that overexpression of ANGPTL4 in HK-2 cells led to increased lipid deposition and senescence. Conversely, the absence of ANGPTL4 appears to alleviate the impact of free fatty acids (FFA) on aging in HK-2 cells. Additionally, aging HK-2 cells exhibited elevated ANGPTL4 expression, and stress response markers associated with cell cycle arrest. Furthermore, our clinical evidence revealed dysregulation of ANGPTL4 expression in serum and kidney tissue samples obtained from elderly individuals compared to young subjects. Our study findings indicate a potential association between ANGPTL4 and age-related metabolic disorders, as well as injury to renal tubular epithelial cells. This suggests that targeting ANGPTL4 could be a viable strategy for the clinical treatment of renal aging.

MicroRNA-5010-5p ameliorates high-glucose induced inflammation in renal tubular epithelial cells by modulating the expression of PPP2R2D.

INTRODUCTION: We previously reported the significant upregulation of eight circulating exosomal microRNAs (miRNAs) in patients with diabetic kidney disease (DKD). However, their specific roles and molecular mechanisms in the kidney remain unknown. Among the eight miRNAs, we evaluated the effects of miR-5010-5p on renal tubular epithelial cells under diabetic conditions in this study. RESEARCH DESIGN AND METHODS: We transfected the renal tubular epithelial cell line, HK-2, with an miR-5010-5p mimic using recombinant plasmids. The target gene of hsa-miR-5010-5p was identified using a dual-luciferase assay. Cell viability was assessed via the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay. Moreover, mRNA and protein expression levels were determined via real-time PCR and western blotting, respectively. RESULTS: High glucose levels did not significantly affect the intracellular expression of miR-5010-5p in HK-2 cells. Transfection of the miR-5010-5p mimic caused no change in cell viability. However, miR-5010-5p-transfected HK-2 cells exhibited significantly decreased expression levels of inflammatory cytokines, such as the monocyte chemoattractant protein-1, interleukin-1ß, and tumor necrosis factor-ɑ, under high-glucose conditions. These changes were accompanied by the restored expression of phosphorylated AMP-activated protein kinase (AMPK) and decreased phosphorylation of nuclear factor-kappa B. Dual-luciferase assay revealed that miR-5010-5p targeted the gene, protein phosphatase 2 regulatory subunit B delta (PPP2R2D), a subunit of protein phosphatase 2A, which modulates AMPK phosphorylation. CONCLUSIONS: Our findings suggest that increased miR-5010-5p expression reduces high glucose-induced inflammatory responses in renal tubular epithelial cells via the regulation of the target gene, PPP2R2D, which modulates AMPK phosphorylation. Therefore, miR-5010-5p may be a promising therapeutic target for DKD.

Blockade of aryl hydrocarbon receptor restricts omeprazole-induced chronic kidney disease.

Chronic kidney disease (CKD) is the 16th leading cause of mortality worldwide. Clinical studies have raised that long-term use of omeprazole (OME) is associated with the morbidity of CKD. OME is commonly used in clinical practice to treat peptic ulcers and gastroesophageal reflux disease. However, the mechanism underlying renal failure following OME treatment remains mostly unknown and the rodent model of OME-induced CKD is yet to be established. We described the process of renal injury after exposure to OME in mice; the early renal injury markers were increased in renal tubular epithelial cells (RTECs). And after long-term OME treatment, the OME-induced CKD mice model was established. Herein, aryl hydrocarbon receptor (AHR) translocation appeared after exposure to OME in HK-2 cells. Then for both in vivo and in vitro, we found that Ahr-knockout (KO) and AHR small interfering RNA (siRNA) substantially alleviated the OME-induced renal function impairment and tubular cell damage. Furthermore, our data demonstrate that antagonists of AHR and CYP1A1 could attenuate OME-induced tubular cell impairment in HK-2 cells. Taken together, these data indicate that OME induces CKD through the activation of the AHR-CYP axis in RTECs. Our findings suggest that blocking the AHR-CYP1A1 pathway acts as a potential strategy for the treatment of CKD caused by OME. KEY MESSAGES: We provide an omeprazole-induced chronic kidney disease (CKD) mice model. AHR activation and translocation process was involved in renal tubular damage and promoted the occurrence of CKD. The process of omeprazole nephrotoxicity can be ameliorated by blockade of the AHR-CYP1A1 axis.

Tubular CPT1A deletion minimally affects aging and chronic kidney injury.

Kidney tubules use fatty acid oxidation (FAO) to support their high energetic requirements. Carnitine palmitoyltransferase 1A (CPT1A) is the rate-limiting enzyme for FAO, and it is necessary to transport long-chain fatty acids into mitochondria. To define the role of tubular CPT1A in aging and injury, we generated mice with tubule-specific deletion of Cpt1a (Cpt1aCKO mice), and the mice were either aged for 2 years or injured by aristolochic acid or unilateral ureteral obstruction. Surprisingly, Cpt1aCKO mice had no significant differences in kidney function or fibrosis compared with wild-type mice after aging or chronic injury. Primary tubule cells from aged Cpt1aCKO mice had a modest decrease in palmitate oxidation but retained the ability to metabolize long-chain fatty acids. Very-long-chain fatty acids, exclusively oxidized by peroxisomes, were reduced in kidneys lacking tubular CPT1A, consistent with increased peroxisomal activity. Single-nuclear RNA-Seq showed significantly increased expression of peroxisomal FAO enzymes in proximal tubules of mice lacking tubular CPT1A. These data suggest that peroxisomal FAO may compensate in the absence of CPT1A, and future genetic studies are needed to confirm the role of peroxisomal ß-oxidation when mitochondrial FAO is impaired.