HIF-1α ameliorates tubular injury in diabetic nephropathy via HO-1-mediated control of mitochondrial dynamics

Methyltransferase-like 3 mediates m6A modification of heme oxygenase 1 mRNA to induce ferroptosis of renal tubular epithelial cells in acute kidney injury

Acute kidney injury (AKI) involves a series of syndromes characterized by a rapid increase in creatinine levels. Ferroptosis, as an iron-dependent mode of programmed cell death, reportedly participates in the pathogenesis of AKI. Methyltransferase-like 3 (METTL3)-mediated N6-methyladenosine (m6A) modification has been recently associated with various kidney diseases; however, the mechanism of METTL3 crosstalk with the molecules involved in ferroptosis is not clearly understood. Here, we investigated the crosstalk between METTL3-mediated m6A modification and ferroptosis in AKI. METTL3-mediated m6A modification was elevated in patients with AKI, folic acid-AKI mice, and tert-butyl hydrogen peroxide-stimulated TCMK-1 cells. Inhibition of METTL3 expression in vivo and in vitro alleviated the damage and ferroptosis in renal tubular cells. Methylated RNA immunoprecipitation sequencing showed that heme oxygenase 1 (Hmox1/HO-1) was the METTL3 target. RNA immunoprecipitation-qPCR indicated that anti-insulin-like growth factor 2 mRNA binding protein 3 (IGF2BP3) could be used as a reader to bind to the methylated site of Hmox1 mRNA to maintain its stability. Hmox1 knockdown in vitro reduced the accumulation of iron ions and alleviated ferroptosis. METTL3 mediates the m6A modification of Hmox1 mRNA and maintains its stability in an IGF2BP3-dependent manner, which causes iron overload in renal tubular epithelial cells, leading to ferroptosis and AKI.

The Physiological Functions and Therapeutic Potential of Hypoxia-Inducible Factor-1α in Vascular Calcification

HIF-1α plays a crucial regulatory role in vascular calcification (VC), primarily influencing the osteogenic differentiation of VSMCs through oxygen-sensing mechanisms. Under hypoxic conditions, the stability of HIF-1α increases, avoiding PHD and VHL protein-mediated degradation, which promotes its accumulation in cells and then activates gene expressions related to calcification. Additionally, HIF-1α modulates the metabolic state of VSMCs by regulating the pathways that govern the switch between glycolysis and oxidative phosphorylation, thereby further advancing the calcification process. The interaction between HIF-1α and other signaling pathways, such as nuclear factor-κB, Notch, and Wnt/β-catenin, creates a complex regulatory network that serves as a critical driving force in VC. Therefore, a deeper understanding of the role and regulatory mechanism of the HIF-1α signaling during the development and progression of VC is of great significance, as it is not only a key molecular marker for understanding the pathological mechanisms of VC but also represents a promising target for future anti-calcification therapies.

The role of hypoxia-inducible factors 1 and 2 in the pathogenesis of diabetic kidney disease

According to the 10th edition of the IDF Diabetes Atlas, 537 million people suffered from diabetes in 2021, and this number will increase by 47% by 2045. It is estimated that even 30-40% of these individuals may develop diabetic kidney disease (DKD) in the course of diabetes. DKD is one of the most important complications of diabetes, both in terms of impact and magnitude. It leads to high morbidity and mortality, which subsequently impacts on quality of life, and it carries a high financial burden. Diabetic kidney disease is considered a complex and heterogeneous entity involving disturbances in vascular, glomerular, podocyte, and tubular function. It would appear that hypoxia-inducible factors (HIF)-1 and HIF-2 may be important players in the pathogenesis of this disease. However, their exact role is still not fully investigated. In this article, we summarize the current knowledge about HIF signaling and its role in DKD. In addition, we focus on the possible effects of nephroprotective drugs on HIF expression and activity in various tissues.

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 β1 (TGF-β1) 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.

Diagnostic value of TRIM22 in diabetic kidney disease and its mechanism

PURPOSE

Diabetic kidney disease (DKD) is the primary reason of chronic kidney disease. Our objective was to discover potential autophagy-related biomarkers of tubulointerstitial injury in DKD and assess their clinical value.

METHODS

We retrieved four datasets (GSE104954, GSE30122, GSE30529, and GSE99340) of renal tubule samples from Gene Expression Omnibus (GEO) and used two algorithms (LASSO and SVM-RFE) to screen for autophagy-related differentially expressed genes (ARDEGs) in DKD. Tripartite motif containing 22 (TRIM22) was identified for subsequent validation. Validation of TRIM22 and autophagic indicators expression in clinical samples and HK-2 cells stimulated by high glucose using immunohistochemistry, immunofluorescence, and western blot.

RESULTS

We identified four ARDEGs (TRIM22, PLK2, HTR2B, and FAS) using a diagnostic gene model. ROC curves further confirmed that TRIM22 had the best diagnostic efficacy for DKD. Both clinical samples and HK-2 cells stimulated by high glucose showed high protein expression of TRIM22. The correlation analysis revealed that TRIM22 correlates with SQSTM1, NGAL, and some clinical and pathological indicators in patients with DKD.

CONCLUSION

We identified TRIM22 as a potential diagnostic biomarker for DKD, revealing its high diagnostic value in patients with DKD with moderate-to-severe interstitial fibrosis and tubular atrophy (IFTA). TRIM22 is involved in tubulointerstitial injury and autophagy dysregulation in DKD.

Effective protective mechanisms of HO-1 in diabetic complications: a narrative review

Diabetes mellitus is a metabolic disorder with persistent hyperglycemia caused by a variety of underlying factors. Chronic hyperglycemia can lead to diverse serious consequences and diversified complications, which pose a serious threat to patients. Among the major complications are cardiovascular disease, kidney disease, diabetic foot ulcers, diabetic retinopathy, and neurological disorders. Heme oxygenase 1 (HO-1) is a protective enzyme with antioxidant, anti-inflammatory and anti-apoptotic effects, which has been intensively studied and plays an important role in diabetic complications. By inducing the expression and activity of HO-1, it can enhance the antioxidant, anti-inflammatory, and anti-apoptotic capacity of tissues, and thus reduce the degree of damage in diabetic complications. The present study aims to review the relationship between HO-1 and the pathogenesis of diabetes and its complications. HO-1 is involved in the regulation of macrophage polarization and promotes the M1 state (pro-inflammatory) towards to the M2 state (anti-inflammatory). Induction of HO-1 expression in dendritic cells inhibits them maturation and secretion of pro-inflammatory cytokines and promotes regulatory T cell (Treg cell) responses. The induction of HO-1 can reduce the production of reactive oxygen species, thereby reducing oxidative stress and inflammation. Besides, HO-1 also has an important effect in novel programmed cell death such as pyroptosis and ferroptosis, thereby playing a protective role against diabetes. In conclusion, HO-1 plays a significant role in the occurrence and development of diabetic complications and is closely associated with a variety of complications. HO-1 is anticipated to serve as a novel target for addressing diabetic complications, and it holds promise as a potential therapeutic agent for diabetes and its associated complications. We hope to provide inspiration and ideas for future studies in the mechanism and targets of HO-1 through this review.

ESRRA modulation by empagliflozin mitigates diabetic tubular injury via mitochondrial restoration

BACKGROUND

The protection of the diabetic kidney by Empagliflozin (EMPA) is attributed to its interaction with the sodium glucose cotransporter 2 located on proximal tubular epithelial cells (PTECs). Estrogen-related receptor α (ESRRA), known for its high expression in PTECs and association with mitochondrial biogenesis, plays a crucial role in this process. This study aimed to explore the impact of ESRRA on mitochondrial mass in diabetic tubular injury and elucidate the mechanism underlying the protective effects of EMPA.

METHODS

Mitochondrial changes in PTECs of 16-week-old diabetic mice were assessed using transmission electron microscopy (TEM) and RNA-sequences. In vivo, EMPA administration was carried out in db/db mice for 8 weeks, while in vitro experiments involved modifying ESRRA expression in HK2 cells using pcDNA-ESRRA or EMPA.

RESULTS

Evaluation through TEM revealed reduced mitochondrial mass and swollen mitochondria in PTECs, whereas no significant changes were observed under light microscopy. Analysis of RNA-sequences identified 110 downregulated genes, including Esrra, associated with mitochondrial function. Notably, ESRRA overexpression rescued the loss of mitochondrial mass induced by high glucose (HG) in HK2 cells. EMPA treatment ameliorated the ultrastructural alterations and mitigated the downregulation of ESRRA both in db/db mice and HG-treated HK2 cells.

CONCLUSION

The diminished expression of ESRRA is implicated in the decline of mitochondrial mass in PTECs during the early stages of diabetes, highlighting it as a key target of EMPA for preventing the progression of diabetic kidney injury.

Hypoxia Modulates Sodium Chloride Co-transporter via CaMKII-β Pathway: An In Vitro Study with mDCT15 Cells

BACKGROUND

Hypoxia plays a crucial role in regulating various cellular functions, including ion-transport mechanisms in the kidney. The sodium-chloride co-transporter (NCC) is essential for sodium reabsorption in the distal convoluted tubule (DCT). However, the effects of hypoxia on NCC expression and its regulatory pathways remain unclear. We aimed to explore the effects and potential mechanisms of hypoxia on NCC in vitro.

METHODS

mDCT15 cells were treated with cobalt chloride (CoCl2) at a concentration of 300 μmol/L to induce hypoxia. The cells were harvested at different time points, namely 30 min, 1 h, 6 h, and 24 h, and the expression of NCC and CaMKII-β was analyzed using Western blot.

RESULTS

A time-dependent upregulation of NCC and CaMKII-β expression in response to CoCl2-induced hypoxia. KN93 reversed the effect of CoCl2 on NCC and phosphorylated NCC expression.

CONCLUSIONS

Hypoxia, mediated through cobalt chloride treatment, upregulates NCC expression via the CaMKII-β pathway in mDCT15 cells.

Uncovering the Role of Anoikis-Related Genes in Modulating Immune Infiltration and Pathogenesis of Diabetic Kidney Disease

Background

Diabetic kidney disease (DKD) is an intricate complication of diabetes with limited treatment options. Anoikis, a programmed cell death activated by loss of cell anchorage to the extracellular matrix, participated in various physiological and pathological processes. Our study aimed to elucidate the role of anoikis-related genes in DKD pathogenesis.

Methods

Differentially expressed genes (DEGs) associated with anoikis in DKD were identified. Weighted gene co-expression network analysis (WGCNA) was conducted to identify DKD-correlated modules and assess their functional implications. A diagnostic model for DKD was developed using LASSO regression and Gene set variation analysis (GSVA) was performed for enrichment analysis. Experimental validation was employed to validate the significance of selected genes in the progression of DKD.

Results

We identified 10 anoikis-related DEGs involved in key signaling pathways impacting DKD progression. WGCNA highlighted the yellow module's significant enrichment in immune response and regulatory pathways. Correlation analysis further revealed the association between immune infiltration and anoikis-related DEGs. Our LASSO regression-based diagnostic model demonstrated a well-predictive efficacy with seven identified genes. GSVA indicated that gene function in the high-risk group was primarily associated with immune regulation. Further experimental validation using diabetic mouse models and data analysis in the single-cell dataset confirmed the significance of PYCARD and SFN in DKD progression. High glucose stimulation in RAW264.7 and TCMK-1 cells showed significantly increased expression levels of both Pycard and Sfn. Co-expression analysis demonstrated distinct functions of PYCARD and SFN, with KEGG pathway analysis showing significant enrichment in immune regulation and cell proliferation pathway.

Conclusion

In conclusion, our study provides valuable insights into the molecular mechanisms involved in DKD pathogenesis, specifically highlighting the role of anoikis-related genes in modulating immune infiltration. These findings suggest that targeting these genes may hold promise for future diagnostic and therapeutic approaches in DKD management.

The role of hypoxia in chronic kidney disease: a nuanced perspective

PURPOSE OF REVIEW

This review critically examines the role of hypoxia in chronic kidney disease (CKD). While traditionally viewed as detrimental, recent insights suggest a more nuanced understanding of hypoxia's role during renal disease.

RECENT FINDINGS

Emerging evidence challenges the traditional view that hypoxia is universally harmful in CKD context. We review here the recent evidence about hypoxia and HIF activation in CKD. We also discuss the effect of hypoxia on the renal tissue, and the relative inhibition of different HIF isoforms. Recent advancements in therapies, such as HIF prolyl hydroxylase inhibitors (HIF-PHIs) and sodium-glucose cotransporter 2 (SGLT2) inhibitors seem to target the HIF pathway. These drugs impact anemia associated with CKDbut also renoprotection, hinting at a more complex interplay between hypoxia, HIF activation, and renal health.

SUMMARY

A certain level of hypoxia and specific HIF pathway activation, especially HIF-α, can be beneficial in CKD progression. Therapeutic strategies targeting HIF stabilization, such as with HIF-PHIs and SGLT2 inhibitors, offer promising avenues for enhancing renal protection. Future investigations should aim at better understanding the precise effects on HIF pathway and optimize their clinical application to improve outcomes for CKD patients.

Advances of Iron and Ferroptosis in Diabetic Kidney Disease

Diabetes mellitus presents a significant threat to human health because it disrupts energy metabolism and gives rise to various complications, including diabetic kidney disease (DKD). Metabolic adaptations occurring in the kidney in response to diabetes contribute to the pathogenesis of DKD. Iron metabolism and ferroptosis, a recently defined form of cell death resulting from iron-dependent excessive accumulation of lipid peroxides, have emerged as crucial players in the progression of DKD. In this comprehensive review, we highlight the profound impact of adaptive and maladaptive responses regulating iron metabolism on the progression of kidney damage in diabetes. We summarize the current understanding of iron homeostasis and ferroptosis in DKD. Finally, we propose that precise manipulation of iron metabolism and ferroptosis may serve as potential strategies for kidney management in diabetes.

ACSF2 and lysine lactylation contribute to renal tubule injury in diabetes

AIMS

Lactate accumulation is reported to be a biomarker for diabetic nephropathy progression. Lactate drives lysine lactylation, a newly discovered post-translational modification that is involved in the pathogenesis of cancers and metabolic and inflammatory disease. Here, we aimed to determine whether lysine lactylation is involved in the pathogenesis of diabetic nephropathy.

METHODS

Renal biopsy samples from individuals with diabetic nephropathy (n=22) and control samples from individuals without diabetes and kidney disease (n=9) were obtained from the First Affiliated Hospital of Zhengzhou University for immunohistochemical staining. In addition, we carried out global lactylome profiling of kidney tissues from db/m and db/db mice using LC-MS/MS. Furthermore, we assessed the role of lysine lactylation and acyl-CoA synthetase family member 2 (ACSF2) in mitochondrial function in human proximal tubular epithelial cells (HK-2).

RESULTS

The expression level of lysine lactylation was significantly increased in the kidneys of individuals with diabetes as well as in kidneys from db/db mice. Integrative lactylome analysis of the kidneys of db/db and db/m mice identified 165 upregulated proteins and 17 downregulated proteins, with an increase in 356 lysine lactylation sites and a decrease in 22 lysine lactylation sites decreased. Subcellular localisation analysis revealed that most lactylated proteins were found in the mitochondria (115 proteins, 269 sites). We further found that lactylation of the K182 site in ACSF2 contributes to mitochondrial dysfunction. Finally, the expression of ACSF2 was notably increased in the kidneys of db/db mice and individuals with diabetic nephropathy.

CONCLUSIONS

Our study strongly suggests that lysine lactylation and ACSF2 are mediators of mitochondrial dysfunction and may contribute to the progression of diabetic nephropathy.

DATA AVAILABILITY

The LC-MS/MS proteomics data have been deposited in the ProteomeXchange Consortium database ( https://proteomecentral.proteomexchange.org ) via the iProX partner repository with the dataset identifier PXD050070.

JinChan YiShen TongLuo Formula ameliorate mitochondrial dysfunction and apoptosis in diabetic nephropathy through the HIF-1α-PINK1-Parkin pathway

ETHNOPHARMACOLOGICAL RELEVANCE

The JinChan YiShen TongLuo (JCYSTL) formula, a traditional Chinese medicine (TCM), has been used clinically for decades to treat diabetic nephropathy (DN). TCM believes that the core pathogenesis of DN is "kidney deficiency and collateral obstruction," and JCYSTL has the effect of "tonifying kidney and clearing collateral," thus alleviating the damage to kidney structure and function caused by diabetes. From the perspective of modern medicine, mitochondrial damage is an important factor in DN pathogenesis. Our study suggests that the regulation of mitophagy and mitochondrial function by JCYSTL may be one of the internal mechanisms underlying its good clinical efficacy.

AIM OF THE STUDY

This study aimed to investigate the mechanisms underlying the renoprotective effects of JCYSTL.

MATERIALS AND METHODS

Unilateral nephrectomy combined with low-dose streptozotocin intraperitoneally injected in a DN rat model and high glucose (HG) plus hypoxia-induced HK-2 cells were used to explore the effects of JCYSTL on the HIF-1α/mitophagy pathway, mitochondrial function and apoptosis.

RESULTS

JCYSTL treatment significantly decreased albuminuria, serum creatinine, blood urea nitrogen, and uric acid levels and increased creatinine clearance levels in DN rats. In vitro, medicated serum containing JCYSTL formula increased mitochondrial membrane potential (MMP); improved activities of mitochondrial respiratory chain complexes I, III, and IV; decreased the apoptotic cell percentage and apoptotic protein Bax expression; and increased anti-apoptotic protein Bcl-2 expression in HG/hypoxia-induced HK-2 cells. The treatment group exhibited increased accumulation of PINK1, Parkin, and LC3-II and reduced P62 levels in HG/hypoxia-induced HK-2 cells, whereas in PINK1 knockdown HK-2 cells, JCYSTL did not improve the HG/hypoxia-induced changes in Parkin, LC3-II, and P62. When mitophagy was impaired by PINK1 knockdown, the inhibitory effect of JCYSTL on Bax and its promoting effect on MMP and Bcl-2 disappeared. The JCYSTL-treated group displayed significantly higher HIF-1α expression than the model group in vivo, which was comparable to the effects of FG-4592 in DN rats. PINK1 knockdown did not affect HIF-1α accumulation in JCYSTL-treated HK-2 cells exposed to HG/hypoxia. Both JCYSTL and FG-4592 ameliorated mitochondrial morphological abnormalities and reduced the mitochondrial respiratory chain complex activity in the renal tubules of DN rats. Mitochondrial apoptosis signals in DN rats, such as increased Bax and Caspase-3 expression and apoptosis ratio, were weakened by JCYSTL or FG-4592 administration.

CONCLUSION

This study demonstrates that the JCYSTL formula activates PINK1/Parkin-mediated mitophagy by stabilizing HIF-1α to protect renal tubules from mitochondrial dysfunction and apoptosis in diabetic conditions, presenting a promising therapy for the treatment of DN.

Roles of Mitochondrial Dysfunction in Diabetic Kidney Disease: New Perspectives from Mechanism to Therapy

Diabetic kidney disease (DKD) is a common microvascular complication of diabetes and the main cause of end-stage renal disease around the world. Mitochondria are the main organelles responsible for producing energy in cells and are closely involved in maintaining normal organ function. Studies have found that a high-sugar environment can damage glomeruli and tubules and trigger mitochondrial dysfunction. Meanwhile, animal experiments have shown that DKD symptoms are alleviated when mitochondrial damage is targeted, suggesting that mitochondrial dysfunction is inextricably linked to the development of DKD. This article describes the mechanisms of mitochondrial dysfunction and the progression and onset of DKD. The relationship between DKD and mitochondrial dysfunction is discussed. At the same time, the progress of DKD treatment targeting mitochondrial dysfunction is summarized. We hope to provide new insights into the progress and treatment of DKD.

Renal aging and mitochondrial quality control

Mitochondria are dynamic organelles that participate in different cellular process that control metabolism, cell division, and survival, and the kidney is one of the most metabolically active organs that contains abundant mitochondria. Perturbations in mitochondrial homeostasis in the kidney can accelerate kidney aging, and maintaining mitochondrial homeostasis can effectively delay aging in the kidney. Kidney aging is a degenerative process linked to detrimental processes. The significance of aberrant mitochondrial homeostasis in renal aging has received increasing attention. However, the contribution of mitochondrial quality control (MQC) to renal aging has not been reviewed in detail. Here, we generalize the current factors contributing to renal aging, review the alterations in MQC during renal injury and aging, and analyze the relationship between mitochondria and intrinsic renal cells. We also introduce MQC in the context of renal aging, and discuss the study of mitochondria in the intrinsic cells of the kidney, which is the innovation of our paper. In addition, during kidney injury and repair, the specific functions and regulatory mechanisms of MQC systems in resident and circulating cell types remain unclear. Currently, most of the studies we reviewed are based on animal and cellular models, the relationship between renal tissue aging and mitochondria has not been adequately investigated in clinical studies, and there is still a long way to go.

Network analysis to explore the anti-senescence mechanism of Jinchan Yishen Tongluo Formula (JCYSTLF) in diabetic kidneys

Background

The Jinchan Yishen Tongluo Formula (JCYSTLF) has the effect of delaying senescence in diabetic kidneys. However, the mechanism is not clear.

Purpose

Combination methods to investigate the anti-senescence mechanism of JCYSTLF in diabetic kidneys.

Methods

The main compounds of JCYSTLF were characterized by LC-MS/MS, and the anti-senescence targets of JCYSTLF were screened via network analysis. Then, we performed in vivo and in vitro experiments to validate the results.

Results

The target profiles of compounds were obtained by LC-MS/MS to characterize the primary function of JCYSTLF. Senescence was identified as a key biological functional module of JCYSTLF in the treatment of DN via constructing compounds-target-biological network analysis. Further analysis of senescence-related targets recognized the HIF-1α/autophagy pathway as the core anti-senescence mechanism of JCYSTLF in diabetic kidneys. Animal experiments showed, in comparison with valsartan, JCYSTLF showed an improvement in urinary albumin and renal pathological damage. JCYSTLF enhanced the ability of diabetic kidneys to clear senescence-related proteins via regulating autophagy confirmed by autophagy inhibitor CQ. However, HIF-1α inhibitor 2-ME weakened the role of JCYSLTF in regulating autophagy in diabetic kidneys. Meanwhile, over-expressed HIF-1α in HK-2 cells decreased the levels of SA-β-gal, p21 and p53 induced by AGEs. Upregulated HIF-1α could reverse the blocking of autophagy induced by AGEs in HK-2 cells evaluated by ptfLC3.

Conclusion

We provided in vitro and in vivo evidence for the anti-senescence role of JCYSTLF in regulating the HIF-1α/autophagy pathway.

Salvianolic acid B attenuates diabetic nephropathy through alleviating ADORA2B, NALP3 in flammasome, and NFκB activity

Diabetic nephropathy is one of the microvascular complications of diabetes. This study is aimed at investigating the role and mechanisms of salvianolic acid B (Sal B) in diabetic nephropathy. High glucose (HG)-induced human renal tubular epithelial HK-2 cells were treated with Sal B, BAY-60-6583 (agonist of adenosine 2B receptor), or PSB-603 (antagonist of adenosine 2B receptor) for 24 h. Adenosine A2b receptor (ADORA2B), NACHT, leucine-rich repeat (LRR), and pyrin (PYD) domains-containing protein 3 (NALP3), and nuclear factor Kappa B (NFκB) expressions, mitochondrial membrane potential (MMP), and reactive oxygen species (ROS) levels were examined. Following 6 weeks of Sal B treatment, db/db mice blood and kidney tissue were harvested for biochemical detection with hematoxylin-eosin (H&E), Masson's, periodic acid schiff (PAS), and Sirius red staining and detection of ADORA2B, NALP3, NFκB, interleukin 1β (IL-1β), and toll-like receptor 4 (TLR4) activity. NFκB, NALP3, and ADORA2B were found to be downregulated in Sal B treated HK-2 cells exposed to high glucose (HG), accompanied by elevated levels of MMPs and reduced intracellular ROS production. Sal B-treated diabetic mice had the improvement in body weight, water intake, hyperglycemia, hyperlipidemia, and liver and kidney function. Altogether, Sal B attenuates HG-induced kidney tubule cell injury and diabetic nephropathy in diabetic mice, providing clues to other novel mechanisms by which Sal B is beneficial in diabetic nephropathy.

Astragaloside IV attenuates renal tubule injury in DKD rats via suppression of CD36-mediated NLRP3 inflammasome activation

Background

In recent years, diabetic kidney disease (DKD) has emerged as a prominent factor contributing to end-stage renal disease. Tubulointerstitial inflammation and lipid accumulation have been identified as key factors in the development of DKD. Earlier research indicated that Astragaloside IV (AS-IV) reduces inflammation and oxidative stress, controls lipid accumulation, and provides protection to the kidneys. Nevertheless, the mechanisms responsible for its protective effects against DKD have not yet been completely elucidated.

Purpose

The primary objective of this research was to examine the protective properties of AS-IV against DKD and investigate the underlying mechanism, which involves CD36, reactive oxygen species (ROS), NLR family pyrin domain containing 3 (NLRP3), and interleukin-1β (IL-1β).

Methods

The DKD rat model was created by administering streptozotocin along with a high-fat diet. Subsequently, the DKD rats and palmitic acid (PA)-induced HK-2 cells were treated with AS-IV. Atorvastatin was used as the positive control. To assess the therapeutic effects of AS-IV on DKD, various tests including blood sugar levels, the lipid profile, renal function, and histopathological examinations were conducted. The levels of CD36, ROS, NLRP3, Caspase-1, and IL-1β were detected using western blot analysis, PCR, and flow cytometry. Furthermore, adenovirus-mediated CD36 overexpression was applied to explore the underlying mechanisms through in vitro experiments.

Results

In vivo experiments demonstrated that AS-IV significantly reduced hyperglycemia, dyslipidemia, urinary albumin excretion, and serum creatinine levels in DKD rats. Additionally, it improved renal structural abnormalities and suppressed the expression of CD36, NLRP3, IL-1β, TNF-α, and MCP-1. In vitro experiments showed that AS-IV decreased CD36 expression, lipid accumulation, and lipid ROS production while inhibiting NLRP3 activation and IL-1β secretion in PA-induced HK-2 cells.

Conclusion

AS-IV alleviated renal tubule interstitial inflammation and tubule epithelial cell apoptosis in DKD rats by inhibiting CD36-mediated lipid accumulation and NLRP3 inflammasome activation.

Nrf2 knockout attenuates the astragaloside IV therapeutic effect on kidney fibrosis from liver cancer by regulating pSmad3C/3L pathways

Fibrotic kidney injury from hepatocarcinogenesis seriously impacts treatment effect. Astragaloside IV (AS-IV), an extract of Astragalus membranaceus, has several pharmacological activities, which are useful in the treatment of edema and fibrosis. Nrf2/HO-1 is a key antioxidant stress pathway and help treatment of kidney injury. Smad3 phosphorylation is implicated in hepatocarcinogenesis. Our previous study clarified that Smad3 is differentially regulated by different phosphorylated forms of Smad3 on hepatocarcinogenesis. Therefore, we investigated the contribution of AS-IV on the therapy of kidney fibrosis from hepatocarcinogenesis. And the focus was on whether the phosphorylation of Smad3 and the regulation of Nrf2/HO-1 pathway were involved during AS-IV therapy and whether there is an effect of Nrf2 knockout on the phosphorylation of Smad3. We performed TGF-β1 stimulation on HK-2 cells and intervened with AS-IV. Furtherly, we investigated renal injury of AS-IV on Nrf2 knockout mice during hepatocarcinogenesis and its mechanism of action. On the one hand, in vitro results showed that AS-IV reduced the ROS and α-SMA expression of HK-2 by promoting the expression pSmad3C/p21 of and Nrf2/HO-1 and suppressed the expression of pSmad3L/PAI-1. On the other hand, the in vivo results of histopathological features, serological biomarkers, and oxidative damage indicators showed that Nrf2 knockout aggravated renal injury. Besides, Nrf2 deletion decreased the nephroprotective effect of AS-IV by suppressing the pSmad3C/p21 pathway and promoting the pSmad3L/PAI-1 pathway. The experimental results were as we suspected. And we identify for the first time that Nrf2 deficiency increases renal fibrosis from hepatocarcinogenesis and attenuates the therapeutic effects of AS-IV via regulating pSmad3C/3L signal pathway.

IGF2BP3-stabilized CAMK1 regulates the mitochondrial dynamics of renal tubule to alleviate diabetic nephropathy

BACKGROUND

CAMK1 has been shown to be involved in human disease progression via regulating mitochondrial dynamics. However, whether CAMK1 mediates mitochondrial dynamics to regulate diabetic nephropathy (DN) process remains unclear.

METHODS

Mice were injected with streptozotocin (STZ) to mimic diabetic mice models in vivo, and mice with proximal tubule-specific knockout of CAMK1 (CAMK1-KO) were generated. HK-2 cells were treated with high-glucose (HG) to mimic DN cell model in vitro. Histopathological analysis was performed to confirm kidney injury in mice. ROS production and apoptosis were assessed by DHE staining and TUNEL staining. Mitochondria morphology was observed and analyzed by electron microscopy. Mitochondrial membrane potential was detected by JC-1 staining, and cell proliferation was measured by EdU assay. The mRNA and protein expression were examined by qRT-PCR, western blot and immunostaining. RNA interaction was confirmed by RIP assay and dual-luciferase reporter assay. The mRNA stability was tested by actinomycin D treatment, and m6A level was examined by MeRIP assay.

RESULTS

CAMK1 was reduced in DN patients and STZ-induced diabetic mice. Conditional deletion of CAMK1 aggravated kidney injury and promoted mitochondrial fission in diabetic mice. CAMK1 overexpression inhibited mitochondrial fission to alleviate HG-induced HK-2 cell apoptosis. IGF2BP3 promoted the stability of CAMK1 mRNA by m6A modification. IGF2BP3 inhibited mitochondrial fission to repress cell apoptosis in vitro and kidney injury in vivo by increasing CAMK1 expression.

CONCLUSION

IGF2BP3-mediated CAMK1 mRNA stability alleviated DN progression by inhibiting mitochondria fission.

Correction to: YY1 inactivated transcription co-regulator PGC-1α to promote mitochondrial dysfunction of early diabetic nephropathy-associated tubulointerstitial fibrosis

The development of diabetic nephropathy (DN) could be promoted by the occurrence of tubulointerstitial fibrosis (TIF), which has a close relationship with mitochondrial dysfunction of renal tubular epithelial cells (RTECs). As a key regulator of metabolic homeostasis, Yin Yang 1 (YY1) plays an important role not only in regulating the fibrosis process but also in maintaining the mitochondrial function of pancreatic β-cells. However, it was not clear whether YY1 participated in maintaining mitochondrial function of RTECs in early DN-associated TIF. In this study, we dynamically detected mitochondrial functions and protein expression of YY1 in db/db mice and high glucose (HG)-cultured HK-2 cells. Our results showed that comparing with the occurrence of TIF, the emergence of mitochondrial dysfunction of RTECs was an earlier even, besides the up-regulated and nuclear translocated YY1. Correlation analysis showed YY1 expressions were negatively associated with PGC-1α in vitro and in vivo. Further mechanism research demonstrated the formation of mTOR-YY1 heterodimer induced by HG up-regulated YY1, the nuclear translocation of which inactivated PGC-1α by binding to the PGC-1α promoter. Overexpression of YY1 induced mitochondrial dysfunctions in normal glucose-cultured HK-2 cells and 8-weeks-old db/m mice. While, dysfunctional mitochondria induced by HG could be improved by knockdown of YY1. Finally, downregulation of YY1 could retard the progression of TIF by preventing mitochondrial functions, resulting in the improvement of epithelial-mesenchymal transition (EMT) in early DN. These findings suggested that YY1 was a novel regulator of mitochondrial function of RTECs and contributed to the occurrence of early DN-associated TIF.

[Role of SPP1 in acute kidney injury induced by renal ischemia-reperfusion in rats]

OBJECTIVE

To investigate the role of SPP1 gene in acute kidney injury induced by renal ischemia-reperfusion injury (IRI).

METHODS

Twelve Sprague-Dawley rats were randomly divided into sham group and IRI group (n=6) and subjected to sham operation and renal ischemia for 30 min induced by penal pedicle clamping using non-traumatic microvascular clamps, respectively.Serum creatinine and blood urea nitrogen levels were detected, and PAS staining was used for pathological examination of the kidneys in the two groups.The renal expressions of SPP1, α-SMA and caspase-3 were detected using immunohistochemistry and immunofluorescent staining.In cultured renal tubular epithelial cells (HK-2 cells), Western blotting was performed to detect the changes in expressions of SPP1, caspase-3, and Kim-1 proteins following hypoxiareoxygenation (H/R) and transfection with si-NC or si-SPP1;flow cytometry was employed to analyze apoptosis of the treated cells.

RESULTS

Renal IRI caused significant elevations of serum creatinine and blood urea nitrogen levels (P<0.05) and induced severe shedding and necrosis of the renal tubular epithelial cells in the rats, resulting also in significantly up-regulated renal expressions of SPP1, α-SMA and caspase-3(P<0.05).In HK-2 cells, H/R significantly increased the protein expression levels of SPP1, caspase-3, and Kim-1(P<0.05), and compared si-NC transfection, transfection with SPP1 obviously reduced caspase-3 and Kim-1 expressions and lowered apoptosis rate of the cells with H/R exposure (P<0.05).

CONCLUSION

SPP1 is up-regulated in the kidneys of rats with renal IRI, and down-regulation of SPP1 expression can inhibit H/R-induced apoptosis of renal tubular epithelial cells.

GLIS1 alleviates cell senescence and renal fibrosis through PGC1-α mediated mitochondrial quality control in kidney aging

Mitochondrial dysfunction is implied as a crucial factor in age-related chronic kidney disease. It is confirmed that Gli-like transcription factor 1 (GLIS1) is involved in age-related renal fibrosis, however, the correlation between mitochondrial disturbances and GLIS1-driven kidney aging are not clearly clarified. Thus, we investigated the regulatory mechanism of GLIS1 in the homeostasis of mitochondrial quality control both in vivo and in vitro. The lower expression of GLIS1 was identified in natural and accelerated kidney aged models, accompanied by the dysfunctions of mitochondrial quality control, including enhanced mitochondrial fission, reduced mitochondrial biogenesis and mitophagy, whereas, GLIS1 could maintain mitochondrial stability by interacting with peroxisome proliferator-activated receptor γ coactivator-1α (PGC1-α). Additionally, the over-expressed GLIS1 inhibited extracellular matrix accumulation and alleviated renal fibrosis while siGLIS1 inhibited PGC1-α transcription, as well as affecting its mitochondria-protective functions. Collectively, we demonstrated that GLIS1 mediated mitochondrial quality control through targeting PGC1-α in kidney aging, which might be a promising therapeutic target for attenuating cell senescence and age-related renal fibrosis.

HIF-1α promotes kidney organoid vascularization and applications in disease modeling

BACKGROUND

Kidney organoids derived from human pluripotent stem cells (HiPSCs) hold huge applications for drug screening, disease modeling, and cell transplanting therapy. However, these applications are limited since kidney organoid cannot maintain complete morphology and function like human kidney. Kidney organoids are not well differentiated since the core of the organoid lacked oxygen, nutrition, and vasculature, which creates essential niches. Hypoxia-inducible factor-1 α (HIF-1α) serves as a critical regulator in vascularization and cell survival under hypoxia environment. Less is known about the role of HIF-1α in kidney organoids in this regard. This study tried to investigate the effect of HIF-1α in kidney organoid vascularization and related disease modeling.

METHODS

For the vascularization study, kidney organoids were generated from human induced pluripotent stem cells. We overexpressed HIF-1α via plasmid transfection or treated DMOG (Dimethyloxallyl Glycine, an agent for HIF-1α stabilization and accumulation) in kidney progenitor cells to detect the endothelium. For the disease modeling study, we treated kidney organoid with cisplatin under hypoxia environment, with additional HIF-1α transfection.

RESULT

HIF-1α overexpression elicited kidney organoid vascularization. The endothelial cells and angiotool analysis parameters were increased in HIF-1α plasmid-transfected and DMOG-treated organoids. These angiogenesis processes were partially blocked by VEGFR inhibitors, semaxanib or axitinib. Cisplatin-induced kidney injury (Cleaved caspase 3) was protected by HIF-1α through the upregulation of CD31 and SOD2.

CONCLUSION

We demonstrated that HIF-1α elicited the process of kidney organoid vascularization and protected against cisplatin-induced kidney organoid injury in hypoxia environment.

Sex Difference in the Association Between Serum Versican and Albuminuria in Patients with Type 2 Diabetes Mellitus

Introduction

Diabetic kidney disease (DKD) is one of the major microvascular complications of diabetes. DKD is associated with oxidative stress and inflammation. Versican (VCAN), a chondroitin sulphate proteoglycan, has been proven to participate in oxidative stress and inflammation. This study aimed to explore the overall and sex-based relationship between serum VCAN levels and albuminuria in patients with type 2 diabetes mellitus (T2DM).

Methods

428 patients with T2DM and 84 healthy individuals were enrolled. Patients with diabetes were separated into normal albuminuria, microalbuminuria, and macroalbuminuria groups, according to their urinary albumin/creatinine ratio (UACR). Serum VCAN levels were tested using an enzyme-linked immunosorbent assay.

Results

Compared with males, female patients were older, and had higher total cholesterol and high-density lipoprotein cholesterol, but lower body mass index, diastolic blood pressure, glycated hemoglobin A1, alanine aminotransferase, urinary albumin (UA), and serum creatinine (SCr) (P < 0.05). The VCAN levels in male patients with T2DM were significantly higher than those in the healthy individuals. Male patients with T2DM with albuminuria (micro and macro) had higher levels of VCAN than in patients with normal albuminuria; the highest level was seen in patients with macroalbuminuria (P < 0.05). In male patients with T2DM, serum VCAN correlated positively with systolic blood pressure, blood urea nitrogen, UA, SCr, and UACR, but correlated negatively with the estimated glomerular filtration rate. The area under the receiver operating characteristic curve of serum VCAN to diagnose albuminuria was 0.702, with a corresponding cut-off value of 0.399 ng/mL (P < 0.001). However, the association between serum VCAN and UACR was not observed in female patients with T2DM.

Conclusion

Serum VCAN levels correlated positively with the severity of albuminuria in male patients with T2DM.

Heme oxygenase-1: The roles of both good and evil in neurodegenerative diseases

Heme oxygenase-1 (HO-1) is the only way for cells to decompose heme. It can cleave heme to produce carbon monoxide (CO), ferrous iron (Fe2+ ), and biliverdin (BV). BV is reduced to bilirubin (BR) by biliverdin reductase(BVR). In previous studies, HO-1 was considered to have protective effects because of its anti-inflammatory, anti-apoptosis, and antiproliferation functions. However, emerging experimental studies have found that the metabolites derived from HO-1 can cause increase iin intracellular oxidative stress, mitochondrial damage, iron death, and autophagy. Because of its particularity, it is very meaningful to understand its exact mechanism. In this review, we summarized the protective and toxic effects of HO-1, its potential mechanism, its role in neurodegenerative diseases and related drug research. This knowledge may be beneficial to the development of new therapies for neurodegenerative diseases and is crucial to the development of new therapeutic strategies and biomarkers.

Cellular crosstalk of mesangial cells and tubular epithelial cells in diabetic kidney disease

Diabetic kidney disease (DKD) is a major cause of end-stage renal disease and imposes a heavy global economic burden; however, little is known about its complicated pathophysiology. Investigating the cellular crosstalk involved in DKD is a promising avenue for gaining a better understanding of its pathogenesis. Nonetheless, the cellular crosstalk of podocytes and endothelial cells in DKD is better understood than that of mesangial cells (MCs) and renal tubular epithelial cells (TECs). As the significance of MCs and TECs in DKD pathophysiology has recently become more apparent, we reviewed the existing literature on the cellular crosstalk of MCs and TECs in the context of DKD to acquire a comprehensive understanding of their cellular communication. Insights into the complicated mechanisms underlying the pathophysiology of DKD would improve its early detection, care, and prognosis. Video Abstract.

TRPA1 promotes cisplatin-induced acute kidney injury via regulating the endoplasmic reticulum stress-mitochondrial damage

BACKGROUND

Cisplatin is a widely used and effective chemotherapeutic agent against cancer. However, nephrotoxicity is one of the most common side effects of cisplatin, and it can proceed to acute kidney injury (AKI). Studies have reported that activation of transient receptor potential ankyrin-1 (TRPA1) mediates cisplatin-induced renal tubular cytotoxic injury. The aim of this study was to investigate the mechanism of TRPA1 in promoting cisplatin-induced AKI through modulation of the endoplasmic reticulum stress (ERS)-mitochondrial damage.

METHODS

A cisplatin-induced HK-2 cell model in vitro and mouse model in vivo were established. The mechanism of TRPA1 promotes AKI was elucidated by H&E staining, TUNEL staining, transmission electron microscope (TEM), immunofluorescence, CCK-8 viability assays, flow cytometry, Western blotting, JC-1 assay, and enzyme linked immunosorbent assay (ELISA).

RESULT

In vivo and in vitro, HC-030031 reduced cisplatin-induced Scr and BUN level elevations; improved cisplatin-induced renal tissue injury, apoptosis, and mitochondrial dysfunction; elevated the reduced ERS-associated proteins glucose-regulated protein 78 (GRP78), glucose-regulated protein 75 (GRP75), and C/EBP homologous protein (CHOP) levels induced by cisplatin; reduced the elevated optic atrophy 1 (OPA1), mito-fusion 1 (MFN1), and mito-fusion 2 (MFN2) protein levels, and elevated phospho-dynamin-related protein 1 (p-DRP1) and mitochondrial fission factor (MFF) protein levels. HC-030031 also reduced the mitochondria-associated endoplasmic reticulum membrane (MAM) structure. In addition, TRPA1 agonists also decreased cell proliferation, increased apoptosis, and triggered mitochondrial dysfunction and calcium overload in HK-2 cells via modulation of MAM. ERS inhibitors and GRP75 inhibitors reversed these changes caused by TRPA1 agonists.

CONCLUSION

Our findings suggest that TRPA1 enhances cisplatin-induced AKI via modulation of ERS and mitochondrial damage.

PACS-2 deficiency aggravates tubular injury in diabetic kidney disease by inhibiting ER-phagy

Autophagy of endoplasmic reticulum (ER-phagy) selectively removes damaged ER through autophagy-lysosome pathway, acting as an adaptive mechanism to alleviate ER stress and restore ER homeostasis. However, the role and precise mechanism of ER-phagy in tubular injury of diabetic kidney disease (DKD) remain obscure. In the present study, we demonstrated that ER-phagy of renal tubular cells was severely impaired in streptozocin (STZ)-induced diabetic mice, with a decreased expression of phosphofurin acidic cluster sorting protein 2 (PACS-2), a membrane trafficking protein which was involved in autophagy, and a reduction of family with sequence similarity 134 member B (FAM134B), one ER-phagy receptor. These changes were further aggravated in mice with proximal tubule specific knockout of Pacs-2 gene. In vitro, transfection of HK-2 cells with PACS-2 overexpression plasmid partially improved the impairment of ER-phagy and the reduction of FAM134B, both of which were induced in high glucose ambience; while the effect was blocked by FAM134B siRNA. Mechanistically, PACS-2 interacted with and promoted the nuclear translocation of transcription factor EB (TFEB), which was reported to activate the expression of FAM134B. Collectively, these data unveiled that PACS-2 deficiency aggravates renal tubular injury in DKD via inhibiting ER-phagy through TFEB/FAM134B pathway.

The neuroprotective effects of FG-4592, a hypoxia-inducible factor-prolyl hydroxylase inhibitor, against oxidative stress induced by alpha-synuclein in N2a cells

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra. The pathological hallmark of PD is the appearance of intraneuronal cytoplasmic α-synuclein (α-Syn) aggregation, called Lewy bodies. α-Syn aggregation is deeply involved in the pathogenesis of PD. Oxidative stress is also associated with the progression of PD. In the present study, to investigate whether a hypoxia-inducible factor (HIF)-prolyl hydroxylase (PH) inhibitor, FG-4592 (also called roxadustat), has neuroprotective effects against α-Syn-induced neurotoxicity, we employed a novel α-Syn stably expressing cell line (named α-Syn-N2a cells) utilizing a piggyBac transposon system. In α-Syn-N2a cells, oxidative stress and cell death were induced by α-Syn, and FG-4592 showed significant protection against this neurotoxicity. However, FG-4592 did not affect α-Syn protein levels. FG-4592 triggered heme oxygenase-1 (HO-1) expression downstream of HIF-1α in a concentration-dependent manner. In addition, FG-4592 decreased the production of reactive oxygen species possibly via the activation of HO-1 and subsequently suppressed α-Syn-induced neurotoxicity. Moreover, FG-4592 regulated mitochondrial biogenesis and respiration via the induction of the peroxisome proliferator-activated receptor-γ coactivator-1α. As FG-4592 has various neuroprotective effects against α-Syn and is involved in drug repositioning, it may have novel therapeutic potential for PD.

Environmental and behavioral regulation of HIF-mitochondria crosstalk

Reduced oxygen availability (hypoxia) can lead to cell and organ damage. Therefore, aerobic species depend on efficient mechanisms to counteract detrimental consequences of hypoxia. Hypoxia inducible factors (HIFs) and mitochondria are integral components of the cellular response to hypoxia and coordinate both distinct and highly intertwined adaptations. This leads to reduced dependence on oxygen, improved oxygen supply, maintained energy provision by metabolic remodeling and tapping into alternative pathways and increased resilience to hypoxic injuries. On one hand, many pathologies are associated with hypoxia and hypoxia can drive disease progression, for example in many cancer and neurological diseases. But on the other hand, controlled induction of hypoxia responses via HIFs and mitochondria can elicit profound health benefits and increase resilience. To tackle pathological hypoxia conditions or to apply health-promoting hypoxia exposures efficiently, cellular and systemic responses to hypoxia need to be well understood. Here we first summarize the well-established link between HIFs and mitochondria in orchestrating hypoxia-induced adaptations and then outline major environmental and behavioral modulators of their interaction that remain poorly understood.

Mitochondrial quality control and its emerging role in the pathogenesis of diabetic kidney disease

Most eukaryotic cells have mitochondrial networks that can change in shape, distribution, and size depending on cellular metabolic demands and environments. Mitochondrial quality control is critical for various mitochondrial functions including energy production, redox homeostasis, intracellular calcium handling, cell differentiation, proliferation, and cell death. Quality control mechanisms within mitochondria consist of antioxidant defenses, protein quality control, DNA damage repair systems, mitochondrial fusion and fission, mitophagy, and mitochondrial biogenesis. Defects in mitochondrial quality control and disruption of mitochondrial homeostasis are common characteristics of various kidney cell types under hyperglycemic conditions. Such defects contribute to diabetes-induced pathologies in renal tubular cells, podocytes, endothelial cells, and immune cells. In this review, we focus on the roles of mitochondrial quality control in diabetic kidney disease pathogenesis and discuss current research evidence and future directions.

Mitochondrial iron regulation as an emerging target in ischemia/reperfusion injury during kidney transplantation

The injury caused by ischemia and subsequent reperfusion (I/R) is inevitable during kidney transplantation and its current management remains unsatisfactory. Iron is considered to play a remarkable pathologic role in the initiation or progression of tissue damage induced by I/R, whereas the effects of iron-related therapy remain controversial owing to the complicated nature of iron's involvement in multiple biological processes. A significant portion of the cellular iron is located in the mitochondria, which exerts a central role in the development and progression of I/R injury. Recent studies of iron regulation associated with mitochondrial function represents a unique opportunity to improve our knowledge on the pathophysiology of I/R injury. However, the molecular mechanisms linking mitochondria to the iron homeostasis remain unclear. In this review, we provide a comprehensive analysis of the alterations to iron metabolism in I/R injury during kidney transplantation, analyze the current understanding of mitochondrial regulation of iron homeostasis and discussed its potential application in I/R injury. The elucidation of regulatory mechanisms regulating mitochondrial iron homeostasis will offer valuable insights into potential therapeutic targets for alleviating I/R injury with the ultimate aim of improving kidney graft outcomes, with potential implications that could also extend to acute kidney injury or other I/R injuries.

New therapeutic directions in type II diabetes and its complications: mitochondrial dynamics

As important organelles of energetic and metabolism, changes in the dynamic state of mitochondria affect the homeostasis of cellular metabolism. Mitochondrial dynamics include mitochondrial fusion and mitochondrial fission. The former is coordinated by mitofusin-1 (Mfn1), mitofusin-2 (Mfn2), and optic atrophy 1 (Opa1), and the latter is mediated by dynamin related protein 1 (Drp1), mitochondrial fission 1 (Fis1) and mitochondrial fission factor (MFF). Mitochondrial fusion and fission are generally in dynamic balance and this balance is important to preserve the proper mitochondrial morphology, function and distribution. Diabetic conditions lead to disturbances in mitochondrial dynamics, which in return causes a series of abnormalities in metabolism, including decreased bioenergy production, excessive production of reactive oxygen species (ROS), defective mitophagy and apoptosis, which are ultimately closely linked to multiple chronic complications of diabetes. Multiple researches have shown that the incidence of diabetic complications is connected with increased mitochondrial fission, for example, there is an excessive mitochondrial fission and impaired mitochondrial fusion in diabetic cardiomyocytes, and that the development of cardiac dysfunction induced by diabetes can be attenuated by inhibiting mitochondrial fission. Therefore, targeting the restoration of mitochondrial dynamics would be a promising therapeutic target within type II diabetes (T2D) and its complications. The molecular approaches to mitochondrial dynamics, their impairment in the context of T2D and its complications, and pharmacological approaches targeting mitochondrial dynamics are discussed in this review and promise benefits for the therapy of T2D and its comorbidities.

Ferroptosis: new insight into the mechanisms of diabetic nephropathy and retinopathy

Diabetic nephropathy (DN) and diabetic retinopathy (DR) are the most serious and common diabetes-associated complications. DN and DR are all highly prevalent and dangerous global diseases, but the underlying mechanism remains to be elucidated. Ferroptosis, a relatively recently described type of cell death, has been confirmed to be involved in the occurrence and development of various diabetic complications. The disturbance of cellular iron metabolism directly triggers ferroptosis, and abnormal iron metabolism is closely related to diabetes. However, the molecular mechanism underlying the role of ferroptosis in DN and DR is still unclear, and needs further study. In this review article, we summarize and evaluate the mechanism of ferroptosis and its role and progress in DN and DR, it provides new ideas for the diagnosis and treatment of DN and DR.

Ferroptosis: a new strategy for Chinese herbal medicine treatment of diabetic nephropathy

Diabetic nephropathy (DN) is a serious microvascular complication of diabetes. It has become a leading cause of death in patients with diabetes and end-stage renal disease. Ferroptosis is a newly discovered pattern of programmed cell death. Its main manifestation is the excessive accumulation of intracellular iron ion-dependent lipid peroxides. Recent studies have shown that ferroptosis is an important driving factor in the onset and development of DN. Ferroptosis is closely associated with renal intrinsic cell (including renal tubular epithelial cells, podocytes, and mesangial cells) damage in diabetes. Chinese herbal medicine is widely used in the treatment of DN, with a long history and definite curative effect. Accumulating evidence suggests that Chinese herbal medicine can modulate ferroptosis in renal intrinsic cells and show great potential for improving DN. In this review, we outline the key regulators and pathways of ferroptosis in DN and summarize the herbs, mainly monomers and extracts, that target the inhibition of ferroptosis.

Ameliorative Effects of Extracellular Vesicles Derived from Mesenchymal Stem Cells on Apoptosis and Differentiation of Osteoblasts Treated with CoCl2

Severe osteoporotic fracture occurring in sites with inadequate blood supply can cause irreversible damage to cells, particularly osteoblasts, with current drug and surgical interventions exhibiting limitations for elderly individuals. As participants mediating intercellular communication, extracellular vesicles (EVs) are rarely reported to play functional roles in osteoblasts under hypoxia. Our study mainly investigated the effects of bone marrow mesenchymal stem cells-derived EVs (BMSCs-EVs) on apoptosis and differentiation of osteoblasts treated with CoCl2. Primary rat BMSCs and osteoblasts were extracted as required for the following experiments. Cell counting kit 8 assay was used to explore the concentration of CoCl2 for treating osteoblasts, and we found that 100 μM CoCl2 was appropriate to treat osteoblasts for 48 hours. The analysis of flow cytometer showed that CoCl2-treated osteoblasts apoptosis can be ameliorated when cocultured with BMSCs-EVs. Further findings revealed that reactive oxygen species (ROS) was related to CoCl2-induced apoptosis. In addition, our results demonstrated that EVs exerted an important role in increasing expression levels of ALP, BMP-2, OCN, and OSTERIX under hypoxia. Similarly, the functional effects of BMSCs-EVs were observed on the osteoblasts mineralization. In summary, these findings provide insight that BMSCs-EVs might decrease the effect of CoCl2-induced apoptosis through inhibiting ROS, and promote osteogenic differentiation under hypoxia.

Emerging Role of Ferroptosis in Diabetic Kidney Disease: Molecular Mechanisms and Therapeutic Opportunities

Diabetic kidney disease (DKD) is one of the most common and severe microvascular complications of diabetes mellitus (DM), and has become the leading cause of end-stage renal disease (ESRD) worldwide. Although the exact pathogenic mechanism of DKD is still unclear, programmed cell death has been demonstrated to participate in the occurrence and development of diabetic kidney injury, including ferroptosis. Ferroptosis, an iron-dependent form of cell death driven by lipid peroxidation, has been identified to play a vital role in the development and therapeutic responses of a variety of kidney diseases, such as acute kidney injury (AKI), renal cell carcinoma and DKD. In the past two years, ferroptosis has been well investigated in DKD patients and animal models, but the specific mechanisms and therapeutic effects have not been fully revealed. Herein, we reviewed the regulatory mechanisms of ferroptosis, summarized the recent findings associated with the involvement of ferroptosis in DKD, and discussed the potential of ferroptosis as a promising target for DKD treatment, thereby providing a valuable reference for basic study and clinical therapy of DKD.

4-Octyl itaconate attenuates LPS-induced acute kidney injury by activating Nrf2 and inhibiting STAT3 signaling

BACKGROUND

Septic acute kidney injury (S-AKI) is the leading form of acute kidney failure among hospitalized patients, and the inflammatory response is involved in this process. 4-octyl itaconate (4-OI) is a multi-target itaconate derivative with potent anti-inflammatory action. However, it remains elusive whether and how 4-OI contributes to the regulation of S-AKI.

METHODS

We employed a lipopolysaccharide (LPS)-induced AKI murine model and explored the potential renoprotective effect of 4-OI in vivo. In vitro experiments, BUMPT cells, a murine renal tubular cell line, were conducted to examine the effects of 4-OI on inflammation, oxidative stress, and mitophagy. Moreover, STAT3 plasmid was transfected in BUMPT cells to investigate the role of STAT3 signaling in the 4-OI-administrated state.

RESULTS

We demonstrate that 4-OI protects against S-AKI through suppressing inflammation and oxidative stress and enhancing mitophagy. 4-OI significantly reduced the levels of Scr, BUN, Ngal as well as the tubular injury in LPS-induced AKI mice. 4-OI restrained inflammation by reducing macrophage infiltration and suppressing the expression of IL-1β and NLRP3 in the septic kidney. 4-OI also reduced ROS levels, as well as cleaved caspase-3 and boosted antioxidants such as HO-1, and NQO1 in mice. In addition, the 4-OI treatment significantly promoted mitophagy. Mechanistically, 4-OI activated Nrf2 signaling and suppressed phosphorylated STAT3 in vivo and vitro. Molecular docking revealed the binding affinity of 4-OI towards STAT3. ML385, a specific Nrf2 inhibitor, partially repressed the anti-inflammatory and anti-oxidative effects of 4-OI and partially restricted the mitophagy induced by 4-OI in vivo and in vitro. Transfected with STAT3 plasmid partially suppressed mitophagy and the anti-inflammatory effect provoked by 4-OI in vitro.

CONCLUSION

These data suggest that 4-OI ameliorates LPS-induced AKI by suppressing inflammation and oxidative stress and enhancing mitophagy through the overactivation of the Nrf2 signaling pathway, and inactivation of STAT3. Our study identifies 4-OI as a promising pharmacologic for S-AKI.

Cardiac and Kidney Adverse Effects of HIF Prolyl-Hydroxylase Inhibitors for Anemia in Patients With CKD Not Receiving Dialysis: A Systematic Review and Meta-analysis

RATIONALE & OBJECTIVE

Hypoxia-inducible factor prolyl hydroxylase inhibitors (HIF-PHIs) are novel, orally administered agents for anemia management in chronic kidney disease (CKD). We evaluated the cardiac and kidney-related adverse effects of HIF-PHIs among patients with CKD and anemia.

STUDY DESIGN

Systematic review and meta-analysis of randomized controlled trials (RCTs).

SETTING & STUDY POPULATIONS

Patients with anemia and CKD not receiving maintenance dialysis.

SELECTION CRITERIA FOR STUDIES

RCTs comparing HIF-PHIs to placebo or an erythropoiesis-stimulating agent (ESA) with primary outcomes of cardiac and kidney-related adverse events (AEs).

DATA EXTRACTION

Two independent reviewers evaluated RCTs for eligibility and extracted relevant data.

ANALYTICAL APPROACH

Dichotomous variables were pooled using the Mantel-Haenszel method and presented as risk ratios (RRs). Subgroup analyses evaluated different intervention times and HIF-PHIs, as well as phase 2 versus phase 3 trials. The certainty of findings was rated according to GRADE criteria.

RESULTS

Twenty-three studies with 15,144 participants were included. No significant difference in the risk of cardiac AEs was observed between the HIF-PHIs group and the placebo (RR, 1.02 [95% CI, 0.89-1.16]; moderate certainty) or ESA (RR, 1.06 [95% CI, 0.98-1.14]; low certainty) groups. No significant difference in the risk of kidney-related AEs was observed between the HIF-PHIs group and the placebo (RR, 1.09 [95% CI, 0.98-1.20]; moderate certainty) or ESA (RR, 1.00 [95% CI, 0.94-1.06]; low certainty) groups. The occurrence of hypertension and hyperkalemia was higher in the HIF-PHIs group than in the placebo group (RRs of 1.35 [95% CI, 1.14-1.60] and 1.25 [95% CI, 1.03-1.51], respectively; both findings had high certainty). The occurrence of hypertension was lower in the HIF-PHIs group than in the ESA group (RR, 0.89 [95% CI, 0.81-0.98]; moderate certainty).

LIMITATIONS

The reporting criteria of cardiac and kidney-related AEs and dosage of HIF-PHIs were inconsistent across trials.

CONCLUSIONS

The occurrence of cardiac or kidney-related AEs in the HIF-PHI groups were not different compared with placebo or ESA groups.

REGISTRATION

Registered at PROSPERO with registration number CRD42021228243.

Identification of transcription factors related to diabetic tubulointerstitial injury

BACKGROUND

Diabetic nephropathy (DN) is a main cause of chronic renal failure. Despite decades of extensive study, the molecular mechanisms underlying diabetic tubulointerstitial injury remain unclear. We aim to identify key transcription factor genes involved in diabetic tubulointerstitial injury.

METHODS

A microarray dataset (GSE30122) from Gene Expression Omnibus (GEO) was downloaded. A total of 38 transcription factor genes based on 166 differentially expressed genes (DEGs) were identified by UCSC_TFBS.

RESULTS

The regulatory network showed connections between the top 10 transcription factors and their target DEGs. Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of targeted DEGs indicated that extracellular space, extracellular exosome, cell surface and complement and coagulation cascades were most significantly enriched. Utilizing Nephroseq v5 online platform, the mRNA expression pattern analysis of transcription factor genes demonstrated that mRNA expression of CDC5, CEBPA, FAC1, HFH1, IRF1, NFE2 and TGIF1 increased in renal tubulointerstitium of DN patients compared with normal controls while that of CEBPB and FOXO4 decreased in renal tubulointerstitium of DN patients compared with normal controls. Correlation analysis between mRNA expression of transcription factor genes in renal tubulointerstitium and clinical features showed that AP1, BACH1, CDC5, FAC1, FOXD1, FOXJ2, FOXO1, FOXO4, HFH1, IRF1, POU3F2, SOX5, SOX9, RSRFC4, S8 and TGIF1 may be related to diabetic tubulointerstitial injury.

CONCLUSIONS

(1) CDC5, FAC1, FOXO4, HFH1, IRF1 and TGIF1 may be key transcription factor genes. (2)Transcription factors involved in diabetic tubulointerstitial injury may become prospective targets for diagnosis and treatment of DN.

Rutin alleviates colon lesions and regulates gut microbiota in diabetic mice

Diabetes is a common metabolic disorder that has become a major health problem worldwide. In this study, we investigated the role of rutin in attenuating diabetes and preventing diabetes-related colon lesions in mice potentially through regulation of gut microbiota. The rutin from tartary buckwheat as analyzed by HPLC was administered intragastrically to diabetic mice, and then the biochemical parameters, overall community structure and composition of gut microbiota in diabetic mice were assayed. The results showed that rutin lowered serum glucose and improved serum total cholesterol, low-density lipoprotein, high-density lipoprotein, triglyceride concentrations, tumor necrosis factor-α, interleukin-6, and serum insulin in diabetic mice. Notably, rutin obviously alleviated colon lesions in diabetic mice. Moreover, rutin also significantly regulated gut microbiota dysbiosis and enriched beneficial microbiota, such as Akkermansia (p < 0.05). Rutin selectively increased short-chain fatty acid producing bacteria, such as Alistipes (p < 0.05) and Roseburia (p < 0.05), and decreased the abundance of diabetes-related gut microbiota, such as Escherichia (p < 0.05) and Mucispirillum (p < 0.05). Our data suggested that rutin exerted an antidiabetic effect and alleviated colon lesions in diabetic mice possibly by regulating gut microbiota dysbiosis, which might be a potential mechanism through which rutin alleviates diabetes-related symptoms.

Natural products for kidney disease treatment: Focus on targeting mitochondrial dysfunction

The patients with kidney diseases are increasing rapidly all over the world. With the rich abundance of mitochondria, kidney is an organ with a high consumption of energy. Hence, renal failure is highly correlated with the breakup of mitochondrial homeostasis. However, the potential drugs targeting mitochondrial dysfunction are still in mystery. The natural products have the superiorities to explore the potential drugs regulating energy metabolism. However, their roles in targeting mitochondrial dysfunction in kidney diseases have not been extensively reviewed. Herein, we reviewed a series of natural products targeting mitochondrial oxidative stress, mitochondrial biogenesis, mitophagy, and mitochondrial dynamics. We found lots of them with great medicinal values in kidney disease. Our review provides a wide prospect for seeking the effective drugs targeting kidney diseases.

Roxadustat, a HIF-PHD inhibitor with exploitable potential on diabetes-related complications

Diabetes mellitus (DM) is a group of metabolic diseases caused by absolute or relative deficiency of insulin secretion and characterized by chronic hyperglycemia. Its complications affect almost every tissue of the body, usually leading to blindness, renal failure, amputation, etc. and in the final stage, it mostly develops into cardiac failure, which is the main reason why diabetes mellitus manifests itself as a high clinical lethality. The pathogenesis of diabetes mellitus and its complications involves various pathological processes including excessive production of mitochondrial reactive oxygen species (ROS) and metabolic imbalance. Hypoxia-inducible Factor (HIF) signaling pathway plays an important role in both of the above processes. Roxadustat is an activator of Hypoxia-inducible Factor-1α, which increases the transcriptional activity of Hypoxia-inducible Factor-1α by inhibiting hypoxia-inducible factor prolyl hydroxylase (HIF-PHD). Roxadustat showed regulatory effects on maintaining metabolic stability in the hypoxic state of the body by activating many downstream signaling pathways such as vascular endothelial growth factor (VEGF), glucose transporter protein-1 (GLUT1), lactate dehydrogenase (LDHA), etc. This review summarizes the current research findings of roxadustat on the diseases of cardiomyopathy, nephropathy, retinal damage and impaired wound healing, which also occur at different stages of diabetes and greatly contribute to the damage caused by diabetes to the organism. We attempts to uncover a more comprehensive picture of the therapeutic effects of roxadustat, and inform its expanding research about diabetic complications treatment.

Autophagy and its therapeutic potential in diabetic nephropathy

Diabetic nephropathy (DN), the leading cause of end-stage renal disease, is the most significant microvascular complication of diabetes and poses a severe public health concern due to a lack of effective clinical treatments. Autophagy is a lysosomal process that degrades damaged proteins and organelles to preserve cellular homeostasis. Emerging studies have shown that disorder in autophagy results in the accumulation of damaged proteins and organelles in diabetic renal cells and promotes the development of DN. Autophagy is regulated by nutrient-sensing pathways including AMPK, mTOR, and Sirt1, and several intracellular stress signaling pathways such as oxidative stress and endoplasmic reticulum stress. An abnormal nutritional status and excess cellular stresses caused by diabetes-related metabolic disorders disturb the autophagic flux, leading to cellular dysfunction and DN. Here, we summarized the role of autophagy in DN focusing on signaling pathways to modulate autophagy and therapeutic interferences of autophagy in DN.

Hypoxia-Inducible Factor 1 and Mitochondria: An Intimate Connection

The general objective of the review is to explain the interaction between HIF-1 and mitochondria. On the one hand, this review describes the effects of HIF-1 on mitochondrial structure, including quantity, distribution, and morphology, as well as on mitochondrial metabolism and respiratory function. On the other hand, various factors, including mitochondrial activation of enzymes, the respiratory chain, complex and decoupling proteins, affect the stability and activity of HIF-1. It is possible to develop future molecular therapeutic interventions by understanding the interrelationships between HIF-1 and mitochondria.

Exploring the mechanisms underlying the therapeutic effect of the drug pair Rhubarb-Coptis in diabetic nephropathy using network pharmacology and molecular docking analysis

Background

To use network pharmacology to explore the mechanism of the drug pair Rhubarb-Coptis in the treatment of diabetic nephropathy (DN).

Methods

The Traditional Chinese Medicine Systems Pharmacology (TCMSP) database was used to screen active ingredients of drug pair Rhubarb-Coptis. Targets were obtained using the TCMSP and SwissTargetPrediction databases. DN disease targets were extracted from the Online Mendelian Inheritance in Man (OMIM), GeneCards, and Therapeutic Target database (TTD) databases. A "drug-compound-target" network and protein-protein interaction (PPI) network were constructed and analyzed through the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) database and Cytoscape software. Gene Ontology (GO) functional and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed in the Database for Annotation, Visualization, and Integrated Discovery (DAVID) database. Molecular docking was performed using AutoDock Vina and PyMOL software.

Results

A total of 30 active components and 609 targets of Rhubarb-Coptis were screened out, and 98 common targets of DN and Rhubarb-Coptis were obtained. Quercetin, berberine, epiruberine, epautin, and moupinamide were the main active components in the treatment of DN. The STAT3, CTNNB1, PIK3R1, PIK3CA, and TP53 genes were identified as the potential 5 key targets. The GO enrichment analysis showed that these 5 key targets mainly involved in inflammation, oxidative stress, and apoptosis. KEGG enrichment analysis showed that the pathways were mainly enriched in the AGE-RAGE and HIF-1 signaling pathways. Molecular docking revealed that the 5 key targets could combine well with their corresponding active compounds.

Conclusions

This study expounds the therapeutic effect of Rhubarb-Coptis on DN from a holistic perspective, and provides a valuable basis for clinical application and academic research.

The Role of Hypoxia-Inducible Factor-1 Alpha in Renal Disease

Partial pressure of oxygen (pO₂) in the kidney is maintained at a relatively stable level by a unique and complex functional interplay between renal blood flow, glomerular filtration rate (GFR), oxygen consumption, and arteriovenous oxygen shunting. The vulnerability of this interaction renders the kidney vulnerable to hypoxic injury, leading to different renal diseases. Hypoxia has long been recognized as an important factor in the pathogenesis of acute kidney injury (AKI), especially renal ischemia/reperfusion injury. Accumulating evidence suggests that hypoxia also plays an important role in the pathogenesis and progression of chronic kidney disease (CKD) and CKD-related complications, such as anemia, cardiovascular events, and sarcopenia. In addition, renal cancer is linked to the deregulation of hypoxia pathways. Renal cancer utilizes various molecular pathways to respond and adapt to changes in renal oxygenation. Particularly, hypoxia-inducible factor (HIF) (including HIF-1, 2, 3) has been shown to be activated in renal disease and plays a major role in the protective response to hypoxia. HIF-1 is a heterodimer that is composed of an oxygen-regulated HIF-1α subunit and a constitutively expressed HIF-1β subunit. In renal diseases, the critical characteristic of HIF-1α is protective, but it also has a negative effect, such as in sarcopenia. This review summarizes the mechanisms of HIF-1α regulation in renal disease.

Downregulation of SIRT3 Aggravates Lung Ischemia Reperfusion Injury by Increasing Mitochondrial Fission and Oxidative Stress through HIF-1α-Dependent Mechanisms

Lung ischemia-reperfusion injury (LIRI) is a severe multifaceted pathological condition that can lead to poor patient outcome where oxidative stress and the resulting inflammatory response can trigger and exacerbate tissue damage in LIRI patients. Sirtuin3 (SIRT3), a member of the sirtuin family, protects against oxidative stress-related diseases. However, it remains unclear if and how SIRT3 alleviates lung injury induced by ischemia/reperfusion (I/R). Our previous study showed that lung tissue structures were severely damaged at 6 h after lung I/R in mice, however, repair of the injured lung tissue was significant at 24 h. In this study, we found that both SIRT3 mRNA and protein levels were markedly increased at 24 h after lung I/R in vivo. Meanwhile, inhibition of SIRT3 aggravated lung injury and inflammation, augmented mitochondrial fission and oxidative stress and increased Hypoxia-inducible factor-1α (HIF-1α) expression in vivo. The results suggest that SIRT3 may be an upstream regulator of HIF-1α expression. Knockdown of SIRT3 resulted in excessive mitochondrial fission and increased oxidative stress in vitro, and we found that knocking down the expression of HIF-1α alleviated these changes. This suggests that the SIRT3-HIF-1α signaling pathway is involved in regulating mitochondrial function and oxidative stress. Furthermore, inhibition of dynamin-related protein 1 (Drp-1) by the inhibitor of mitophagy, Mdivi-1, blocked mitochondrial fission and alleviated oxidative stress in vitro. Taken together, our results demonstrated that downregulation of SIRT3 aggravates LIRI by increasing mitochondrial fission and oxidative stress. Activation of SIRT3 inhibits mitochondrial fission and this mechanism may serve as a new therapeutic strategy to treat LIRI.

Hypoxia-Inducible Factors and Diabetic Kidney Disease—How Deep Can We Go?

Diabetes is one of the leading causes of chronic kidney disease (CKD), and multiple underlying mechanisms involved in pathogenesis of diabetic nephropathy (DN) have been described. Although various treatments and diagnosis applications are available, DN remains a clinical and economic burden, considering that about 40% of type 2 diabetes patients will develop nephropathy. In the past years, some research found that hypoxia response and hypoxia-inducible factors (HIFs) play critical roles in the pathogenesis of DN. Hypoxia-inducible factors (HIFs) HIF-1, HIF-2, and HIF-3 are the main mediators of metabolic responses to the state of hypoxia, which seems to be the one of the earliest events in the occurrence and progression of diabetic kidney disease (DKD). The abnormal activity of HIFs seems to be of crucial importance in the pathogenesis of diseases, including nephropathies. Studies using transcriptome analysis confirmed by metabolome analysis revealed that HIF stabilizers (HIF-prolyl hydroxylase inhibitors) are novel therapeutic agents used to treat anemia in CKD patients that not only increase endogenous erythropoietin production, but also could act by counteracting the metabolic alterations in incipient diabetic kidney disease and relieve oxidative stress in the renal tissue. In this review, we present the newest data regarding hypoxia response and HIF involvement in the pathogenesis of diabetic nephropathy and new therapeutic insights, starting from improving kidney oxygen homeostasis.