Endothelial cell and podocyte autophagy synergistically protect from diabetes-induced glomerulosclerosis

Chinese herbal medicine and its active compounds in attenuating renal injury via regulating autophagy in diabetic kidney disease

Diabetic kidney disease (DKD) is the main cause of end-stage renal disease worldwide, and there is a lack of effective treatment strategies. Autophagy is a highly conserved lysosomal degradation process that maintains homeostasis and energy balance by removing protein aggregates and damaged organelles. Increasing evidence suggests that dysregulated autophagy may contribute to glomerular and tubulointerstitial lesions in the kidney under diabetic conditions. Emerging studies have shown that Chinese herbal medicine and its active compounds may ameliorate diabetic kidney injury by regulating autophagy. In this review, we summarize that dysregulation or insufficiency of autophagy in renal cells, including podocytes, glomerular mesangial cells, and proximal tubular epithelial cells, is a key mechanism for the development of DKD, and focus on the protective effects of Chinese herbal medicine and its active compounds. Moreover, we systematically reviewed the mechanism of autophagy in DKD regulated by Chinese herb compound preparations, single herb and active compounds, so as to provide new drug candidates for clinical treatment of DKD. Finally, we also reviewed the candidate targets of Chinese herbal medicine regulating autophagy for DKD. Therefore, further research on Chinese herbal medicine with autophagy regulation and their targets is of great significance for the realization of new targeted therapies for DKD.

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.

LncRNA X Inactive Specific Transcript Exerts a Protective Effect on High Glucose-Induced Podocytes by Promoting the Podocyte Autophagy via miR-30d-5p/BECN-1 Axis

Inhibiting podocyte autophagy promotes the development of diabetic nephropathy (DN). This study aims to explore the upstream regulatory mechanism of the autophagy-related gene BECN1 in high glucose (HG)-induced podocytes. C57BL/6 mice were treated with 50 mg/kg streptozotocin to construct a DN model. Biochemical indexes, pathological morphology of renal tissue, the morphology of renal podocytes, and the expressions of autophagy-related proteins in DN mice and normal mice were detected. The upstream miRNAs of BECN1 and the upstream long noncoding RNAs (lncRNAs) of miR-30d-5p were predicted by bioinformatics analysis and verified by dual-luciferase reporter assay. Mouse podocyte clone 5 (MPC5) cells were exposed to HG to construct a DN cell model. The levels of miR-30d-5p, X inactive specific transcript (XIST), and BECN1 in mouse kidney and MPC5 cells were detected by quantitative real-time polymerase chain reaction (qRT-PCR). The regulation of XIST/miR-30d-5p on the viability, apoptosis as well as proteins related to apoptosis, epithelial-mesenchymal transition (EMT), and autophagy in MPC5 cells were determined by rescue experiments. The levels of glucose, urinary protein, serum creatinine, and blood urea nitrogen were upregulated, but the kidney tissues and podocytes were damaged in DN mice. XIST targeted miR-30d-5p to promote viability while suppressing the apoptosis of HG-induced MPC5 cells. In kidney tissues or HG-induced MPC5 cells, the expressions of Beclin-1, light chain 3 (LC3) II/I, XIST, B-celllymphoma-2 (Bcl-2), and E-cadherin were downregulated, while the expressions of P62, miR-30d-5p, Bcl-2-associated X protein (Bax), cleaved-caspase-3, vimentin, and alpha-smooth muscle actin (α-SMA) were upregulated, which were reversed by XIST overexpression. The reversal effect of XIST overexpression was offset by miR-30d-5p mimic. Collectively, XIST promotes the autophagy of podocytes by regulating the miR-30d-5p/BECN1 axis to protect podocytes from HG-induced injury.

Chronic kidney disease and NLRP3 inflammasome: Pathogenesis, development and targeted therapeutic strategies

Chronic kidney disease (CKD) is a global health concern and public health priority. The condition often involves inflammation due to the accumulation of toxins and the reduced clearance of inflammatory cytokines, leading to gradual loss of kidney function. Because of the tremendous burden of CKD, finding effective treatment strategies against inflammation is crucial. Substantial evidence suggests an association between kidney disease and the inflammasome. As a well-known multiprotein signaling complex, the NLR family pyrin domain containing 3 (NLRP3) inflammasome plays an important role in inducing renal inflammation and fibrosis. Small molecule inhibitors targeting the NLRP3 inflammasome are potential agents for the treatment of CKD.The NLRP3 inflammasome activation amplifies the inflammation response, promoting pyroptotic cell death. Thus, it may contribute to the onset and progression of CKD, but the mechanism behind inflammasome activation in CKD remains obscure.In this review, we summarized recent findings on the role of the NLRP3 inflammasome in CKD and new strategies targeting the NLRP3 inflammasome.

Kaempferol attenuated diabetic nephropathy by reducing apoptosis and promoting autophagy through AMPK/mTOR pathways

INTRODUCTION

Renal podocyte injury, apoptosis and autophagy are involved in the occurrence and development of diabetic nephropathy (DN). Kaempferol (KPF) has the promotion of autophagy and inhibition of apoptosis properties in the development of miscellaneous diseases, but these functions in DN have not yet been elucidated.

METHODS

We used db/db mice to evaluate the protective role of KPF on DN. The anti-DN effect of KPF was evaluated by urine albumin-to-creatinine ratio and pathological changes of kidney tissue. Injury of podocytes was observed through Transmission electron microscopy. Immunofluorescence, Western blot, and Immunohistochemistry were used to detect the protein expression of podocyte-associated molecules, autophagy, and AMPK/mTOR pathway.

RESULTS

We demonstrated that KPF treatment significantly attenuated diabetes-induced albuminuria and glycolipid metabolism dysfunction. In addition, KPF alleviated mesangial matrix expansion, glomerular basement membrane thickening and loss or fusion of podocytes. Mechanistically, KPF treatment regulated the expression of autophagic proteins (upregulated LC3II, Beclin-1, Atg7 and Atg 5, and downregulated p62/SQSTM1), accompanied by inhibited renal apoptosis (downregulated Caspase 3 and Bax, and upregulated Bcl-2). KPF could significantly regulate the AMPK/mTOR signaling pathways by increasing p-AMPK and decreasing p-mTOR expressions.

DISCUSSION

In conclusion, KPF might have a protective effect on DN through reduced apoptosis and enhanced podocytes autophagy, which were correlated with regulating AMPK/mTOR pathways.

Glucosamine delays the progression of osteoporosis in senile mice by promoting osteoblast autophagy

Background

Senile osteoporosis (SOP) is one of the most prevalent diseases that afflict the elderly population, which characterized by decreased osteogenic ability. Glucosamine (GlcN) is an over-the-counter dietary supplement. Our previous study reported that GlcN promotes osteoblast proliferation by activating autophagy in vitro. The purpose of this study is to determine the effects and mechanisms of GlcN on senile osteoporosis and osteogenic differentiation in vivo.

Methods

Aging was induced by subcutaneous injection of d-Galactose (d-Gal), and treated with GlcN or vehicle. The anti-senile-osteoporosis effect of GlcN was explored by examining changes in micro-CT, serum indicators, body weight, protein and gene expression of aging and apoptosis. Additionally, the effects of GlcN on protein and gene expression of osteogenesis and autophagy were observed by inhibiting autophagy with 3-methyladenine (3-MA).

Results

GlcN significantly improved bone mineral density (BMD) and bone micro-architecture, decreased skeletal senescence and apoptosis and increased osteogenesis in d-Gal induced osteoporotic mice. While all effect was reversed with 3-MA.

Conclusion

GlcN effectively delayed the progression of osteoporosis in senile osteoporotic mice by promoting osteoblast autophagy. This study suggested that GlcN may be a prospective candidate drug for the treatment of SOP.

REDD1 Ablation Attenuates the Development of Renal Complications in Diabetic Mice

Chronic hyperglycemia contributes to development of diabetic kidney disease by promoting glomerular injury. In this study, we evaluated the hypothesis that hyperglycemic conditions promote expression of the stress response protein regulated in development and DNA damage response 1 (REDD1) in the kidney in a manner that contributes to the development of oxidative stress and renal injury. After 16 weeks of streptozotocin-induced diabetes, albuminuria and renal hypertrophy were observed in wild-type (WT) mice coincident with increased renal REDD1 expression. In contrast, diabetic REDD1 knockout (KO) mice did not exhibit impaired renal physiology. Histopathologic examination revealed that glomerular damage including mesangial expansion, matrix deposition, and podocytopenia in the kidneys of diabetic WT mice was reduced or absent in diabetic REDD1 KO mice. In cultured human podocytes, exposure to hyperglycemic conditions enhanced REDD1 expression, increased reactive oxygen species (ROS) levels, and promoted cell death. In both the kidney of diabetic mice and in podocyte cultures exposed to hyperglycemic conditions, REDD1 deletion reduced ROS and prevented podocyte loss. Benefits of REDD1 deletion were recapitulated by pharmacological GSK3β suppression, supporting a role for REDD1-dependent GSK3β activation in diabetes-induced oxidative stress and renal defects. The results support a role for REDD1 in diabetes-induced renal complications.

The Effect of Allograft Inflammatory Factor-1 on Inflammation, Oxidative Stress, and Autophagy via miR-34a/ATG4B Pathway in Diabetic Kidney Disease

Increasing evidence suggests that disorders of inflammation, oxidative stress, and autophagy contribute to the pathogenesis of diabetic kidney disease (DKD). This study attempted to clarify the effect of allograft inflammatory factor-1 (AIF-1), miR-34a, and ATG4B on inflammation, oxidative stress, and autophagy in DKD both in vitro and in vivo experiments. In vivo, it was found that the levels of AIF-1, miR-34a, oxidative stress, and inflammatory factors were significantly increased in blood and urine samples of DKD patients and mouse models and correlated with the level of urinary protein. In vitro, it was also found that the expressions of AIF-1, miR-34a, ROS, and inflammatory factors were increased, while ATG4B and other autophagy related proteins were decreased in human renal glomerular endothelial cells (HRGECs) cultured with high concentration glucose medium (30 mmol/L). When AIF-1 gene was overexpressed, the levels of miR-34a, ROS, and inflammatory factors were significantly upregulated, and autophagy-related proteins such as ATG4B were downregulated, while downregulation of AIF-1 gene had the opposite effect. In addition, miR-34a inhibited the expression of ATG4B and autophagy-related proteins and increased the levels of ROS and inflammation. Furthermore, the result of luciferase reporter assay suggested that ATG4B was the target gene of miR-34a. When ATG4B gene was overexpressed, the level of autophagy was upregulated, and inflammatory factors were downregulated. Conversely, when ATG4B gene was inhibited, the level of autophagy was downregulated, and inflammatory factors were upregulated. Then, autophagy inducers inhibited the levels of inflammation and ROS, whereas autophagy inhibitors had the opposite function in HRGECs induced by glucose (30 mmol/L). In conclusion, the above data suggested that AIF-1 regulated the levels of inflammation, oxidative stress, and autophagy in HRGECs via miR-34a/ATG4B pathway to contribute to the pathogenesis of diabetic kidney disease.

Ameliorative Effects of Camel Milk and Its Exosomes on Diabetic Nephropathy in Rats

Contradictory results were obtained regarding the effects of extracellular vesicles such as exosomes (EXOs) on diabetes and diabetic nephropathy (DN). Some studies showed that EXOs, including milk EXOs, were involved in the pathogenesis of DN, whereas other studies revealed ameliorative effects. Compared to other animals, camel milk had unique components that lower blood glucose levels. However, little is known regarding the effect of camel milk and its EXOs on DN. Thus, the present study was conducted to evaluate this effect on a rat model of DN induced by streptozotocin. Treatment with camel milk and/or its EXOs ameliorated DN as evidenced by (1) reduced levels of kidney function parameters (urea, creatinine, retinol-binding protein (RBP), and urinary proteins), (2) restored redox balance (decreased lipid peroxide malondialdehyde (MDA) and increased the activity of antioxidants enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx)), (3) downregulated expression of DN-related genes (transforming growth factor-beta 1 (TGFβ1), intercellular adhesion molecules 1 (ICAM1), and transformation specific 1 (ETS1), integrin subunit beta 2 (ITGβ2), tissue inhibitors of matrix metalloproteinase 2 (TIMP2), and kidney injury molecule-1 (KIM1)), and (4) decreased renal damage histological score. These results concluded that the treatment with camel milk and/or its EXOs could ameliorate DN with a better effect for the combined therapy.

NLRP3-mediated pyroptosis in diabetic nephropathy

Diabetic nephropathy (DN) is the main cause of end-stage renal disease (ESRD), which is characterized by a series of abnormal changes such as glomerulosclerosis, podocyte loss, renal tubular atrophy and excessive deposition of extracellular matrix. Simultaneously, the occurrence of inflammatory reaction can promote the aggravation of DN-induced kidney injury. The most important processes in the canonical inflammasome pathway are inflammasome activation and membrane pore formation mediated by gasdermin family. Converging studies shows that pyroptosis can occur in renal intrinsic cells and participate in the development of DN, and its activation mechanism involves a variety of signaling pathways. Meanwhile, the activation of the NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome can not only lead to the occurrence of inflammatory response, but also induce pyroptosis. In addition, a number of drugs targeting pyroptosis-associated proteins have been shown to have potential for treating DN. Consequently, the pathogenesis of pyroptosis and several possible activation pathways of NLRP3 inflammasome were reviewed, and the potential drugs used to treat pyroptosis in DN were summarized in this review. Although relevant studies are still not thorough and comprehensive, these findings still have certain reference value for the understanding, treatment and prognosis of DN.

Podocyte as the link between sterile inflammation and diabetic kidney disease

Shahzad et al. examined the underlying mechanisms of sterile inflammation in diabetic kidney disease, specifically the role of NLRP3 inflammasome activation in podocytes. Using mouse models with gain-of-function and loss-of-function mutations in podocyte Nlrp3, or caspase-1 loss-of-function mutations in podocytes, they identified that Nlrp3 activation in these cells is central for development of diabetic kidney disease but not solely dependent on canonical mechanisms and caspase-1. These findings position podocyte-mediated immune cell-like functions as potential therapeutic targets for diabetic kidney disease.

Potential therapeutic effects of natural compounds targeting autophagy to alleviate podocyte injury in glomerular diseases

Podocyte injury is a common cause of proteinuric kidney diseases. Uncontrollable progressive podocyte loss accelerates glomerulosclerosis and increases the risk of end-stage renal disease. To date, owing to the complex pathological mechanism, effective therapies for podocyte injury have been limited. Accumulating evidence supports the indispensable role of autophagy in the maintenance of podocyte homeostasis. A variety of natural compounds and their derivatives have been found to regulate autophagy through multiple targets, including promotes nuclear transfer of transcription factor EB and lysosomal repair. Here, we reviewed the recent studies on the use of natural compounds and their derivatives as autophagy regulators and discussed their potential applications in ameliorating podocyte injury. Several known natural compounds with autophagy-regulatory properties, such as quercetin, silibinin, kaempferol, and artemisinin, and their medical uses were also discussed. This review will help in improving the understanding of the podocyte protective mechanism of natural compounds and promote their development for clinical use.

Tenovin-1 Ameliorates Renal Fibrosis in High-Fat-Diet-Induced Diabetic Nephropathy via Antioxidant and Anti-Inflammatory Pathways

High-fat diet (HFD)-induced obesity has been involved in the development of diabetic nephropathy (DN). Tenovin-1, a potent selective SIRT1/2 inhibitor, regulates various target proteins. The present study evaluated the protective effect of Tenovin-1 against renal fibrosis in HFD-induced Zucker diabetic fatty (ZDF) rats. Rats were fed a normal chow diet or HFD. Tenovin-1 (45 mg/kg) administered to HFD-fed rats decreased inflammatory cytokine expression in the serum of the rats. The antioxidant status and oxidative damage to lipids or DNA were significantly restored by Tenovin-1. Additionally, Tenovin-1 reduced the levels of blood urea nitrogen (BUN), serum creatinine (sCr), microalbumin, and urinary protein-based biomarkers in the urine of HFD-fed rats. The abnormal architecture of the kidney and pancreas was restored by Tenovin-1 administration. Tenovin-1 also reduced apoptosis in the kidneys of the HFD-fed rats and HG-treated NRK-52E cells. It significantly lowered the levels of ECM proteins in the kidneys of HFD-fed rats and HG-treated NRK-52E cells. Additionally, Tenovin-1 markedly reduced claudin-1, SIRT1, and SIRT2, but increased SIRT3 and SIRT4 in HFD-fed rats and NRK-52E cells treated with HG. Furthermore, Tenovin-1 altered epidermal growth factor receptor (EGFR), platelet-derived growth factor receptor-β (PDGFR-β), and signal transducer and activator of transcription 3 (STAT3) levels in the kidneys of HFD-fed rats. Conclusively, this study shows that Tenovin-1 can be a potential candidate drug for the treatment of HFD-induced renal fibrosis, in vivo and in vitro models.

ATG5: A central autophagy regulator implicated in various human diseases

Autophagy, an intracellular conserved degradative process, plays a central role in the renewal/recycling of a cell to maintain the homeostasis of nutrients and energy within the cell. ATG5, a key component of autophagy, regulates the formation of the autophagosome, a hallmark of autophagy. ATG5 binds with ATG12 and ATG16L1 resulting in E3 like ligase complex, which is necessary for autophagosome expansion. Available data suggest that ATG5 is indispensable for autophagy and has an imperative role in several essential biological processes. Moreover, ATG5 has also been demonstrated to possess autophagy-independent functions that magnify its significance and therapeutic potential. ATG5 interacts with various molecules for the execution of different processes implicated during physiological and pathological conditions. Furthermore, ATG5 genetic variants are associated with various ailments. This review discusses various autophagy-dependent and autophagy-independent roles of ATG5, highlights its various deleterious genetic variants reported until now, and various studies supporting it as a potential drug target.

Solasonine alleviates high glucose-induced podocyte injury through increasing Nrf2-medicated inhibition of NLRP3 activation

The worldwide high prevalence of diabetic nephropathy is one of the common causes of renal failure in diabetic patients. Hyperglycemia-caused podocyte injury is considered as a major contributor to diabetic kidney disease, accompanied by a chronic inflammatory condition. Pyroptosis, a characterized inflammatory form of programmed cell death, is believed to be involved in the pathogenesis of diabetic nephropathy. Solasonine (SS) is a natural alkaloid and received attention as a potential anticancer agent. However, its protective effect against hyperglycemia-caused podocyte injury remains to be determined. Our study found that SS alleviates cell apoptosis, and reduces pyroptosis and oxidative damage in high glucose (HG)-treated MPC5 podocytes. Pro-inflammatory cytokines, including interleukin (IL)-1β and IL-18, and caspase-1 activity were markedly suppressed by SS in HG-treated MPC5 podocytes. SS also reduced HG-induced oxidative damage in MPC5 podocytes. Nrf2 expression was activated by SS in vitro under a HG condition. In addition, Nrf2 silencing attenuated the protective effect of SS against apoptosis, pro-inflammatory cytokines release, caspase-1 activity, and oxidative damage in MPC5 podocytes under a HG condition. Taken together, our findings revealed for the first time that SS alleviated high glucose-induced podocyte apoptosis, pyroptosis, and oxidative damage via regulating the Nrf2/NLRP3 signaling pathway. Our results indicate that SS has the potential as a therapeutic agent for podocyte injury in diabetic nephropathy.

The critical role of dysregulated autophagy in the progression of diabetic kidney disease

Diabetic kidney disease (DKD) is one of the major public health problems in society today. It is a renal complication caused by diabetes mellitus with predominantly microangiopathy and is a major cause of end-stage renal disease (ESRD). Autophagy is a metabolic pathway for the intracellular degradation of cytoplasmic products and damaged organelles and plays a vital role in maintaining homeostasis and function of the renal cells. The dysregulation of autophagy in the hyperglycaemic state of diabetes mellitus can lead to the progression of DKD, and the activation or restoration of autophagy through drugs is beneficial to the recovery of renal function. This review summarizes the physiological process of autophagy, illustrates the close link between DKD and autophagy, and discusses the effects of drugs on autophagy and the signaling pathways involved from the perspective of podocytes, renal tubular epithelial cells, and mesangial cells, in the hope that this will be useful for clinical treatment.

Autophagy in renal fibrosis: Protection or promotion?

Autophagy is a process that degrades endogenous cellular protein aggregates and damaged organelles via the lysosomal pathway to maintain cellular homeostasis and energy production. Baseline autophagy in the kidney, which serves as a quality control system, is essential for cellular metabolism and organelle homeostasis. Renal fibrosis is the ultimate pathological manifestation of progressive chronic kidney disease. In several experimental models of renal fibrosis, different time points, stimulus intensities, factors, and molecular mechanisms mediating the upregulation or downregulation of autophagy may have different effects on renal fibrosis. Autophagy occurring in a single lesion may also exert several distinct biological effects on renal fibrosis. Thus, whether autophagy prevents or facilitates renal fibrosis remains a complex and challenging question. This review explores the different effects of the dual regulatory function of autophagy on renal fibrosis in different renal fibrosis models, providing ideas for future work in related basic and clinical research.

Urolithins Modulate the Viability, Autophagy, Apoptosis, and Nephrin Turnover in Podocytes Exposed to High Glucose

Urolithins are bioactive compounds generated in human and animal intestines because of the bacterial metabolism of dietary ellagitannins (and their constituent, ellagic acid). Due to their multidirectional effects, including anti-inflammatory, antioxidant, anti-cancer, neuroprotective, and antiglycative properties, urolithins are potential novel therapeutic agents. In this study, while considering the future possibility of using urolithins to improve podocyte function in diabetes, we assessed the results of exposing mouse podocytes cultured in normal (NG, 5.5 mM) and high (HG, 25 mM) glucose concentrations to urolithin A (UA) and urolithin B (UB). Podocytes metabolized UA to form glucuronides in a time-dependent manner; however, in HG conditions, the metabolism was lower than in NG conditions. In HG milieu, UA improved podocyte viability more efficiently than UB and reduced the reactive oxygen species level. Both types of urolithins showed cytotoxic activity at high (100 µM) concentration. The UA upregulated total and surface nephrin expression, which was paralleled by enhanced nephrin internalization. Regulation of nephrin turnover was independent of ambient glucose concentration. We conclude that UA affects podocytes in different metabolic and functional aspects. With respect to its pro-survival effects in HG-induced toxicity, UA could be considered as a potent therapeutic candidate against diabetic podocytopathy.

Research progress on the relationship between autophagy and chronic complications of diabetes

Diabetes is a common metabolic disease whose hyperglycemic state can induce diverse complications and even threaten human health and life security. Currently, the treatment of diabetes is restricted to drugs that regulate blood glucose and have certain accompanying side effects. Autophagy, a research hotspot, has been proven to be involved in the occurrence and progression of the chronic complications of diabetes. Autophagy, as an essential organismal defense mechanism, refers to the wrapping of cytoplasmic proteins, broken organelles or pathogens by vesicles, which are then degraded by lysosomes to maintain the stability of the intracellular environment. Here, we review the relevant aspects of autophagy and the molecular mechanisms of autophagy in diabetic chronic complications, and further analyze the impact of improving autophagy on diabetic chronic complications, which will contribute to a new direction for further prevention and treatment of diabetic chronic complications.

Potential Therapeutic Strategies for Renal Fibrosis: Cordyceps and Related Products

At present, there is no effective drug for the treatment of renal fibrosis; in particular, a safe and effective treatment for renal fibrosis should be established. Cordyceps has several medical effects, including immunoregulatory, antitumor, anti-inflammatory, and antioxidant effects, and may prevent kidney, liver, and heart diseases. Cordyceps has also been reported to be effective in the treatment of renal fibrosis. In this paper, we review the potential mechanisms of Cordyceps against renal fibrosis, focusing on the effects of Cordyceps on inflammation, oxidative stress, apoptosis, regulation of autophagy, reduction of extracellular matrix deposition, and fibroblast activation. We also discuss relevant published clinical trials and meta-analyses. Available clinical studies support the possibility that Cordyceps and related products provide benefits to patients with chronic kidney diseases as adjuvants to conventional drugs. However, the existing clinical studies are limited by low quality and significant heterogeneity. The use of Cordyceps and related products may be a potential strategy for the treatment of renal fibrosis. Randomized controlled trial studies with good methodological quality, favorable experimental design, and large sample size are needed to evaluate the efficacy and safety of Cordyceps.

Progranulin Preserves Autophagy Flux and Mitochondrial Function in Rat Cortical Neurons Under High Glucose Stress

Chronic hyperglycemia in type II diabetes results in impaired autophagy function, accumulation of protein aggregates, and neurodegeneration. However, little is known about how to preserve autophagy function under hyperglycemic conditions. In this study, we tested whether progranulin (PGRN), a neurotrophic factor required for proper lysosome function, can restore autophagy function in neurons under high-glucose stress. We cultured primary cortical neurons derived from E18 Sprague-Dawley rat pups to maturity at 10 days in vitro (DIV) before incubation in high glucose medium and PGRN for 24-72 h before testing for autophagy flux, protein turnover, and mitochondrial function. We found that although PGRN by itself did not upregulate autophagy, it attenuated impairments in autophagy seen under high-glucose conditions. Additionally, buildup of the autophagosome marker light chain 3B (LC3B) and lysosome marker lysosome-associated membrane protein 2A (LAMP2A) changed in both neurons and astrocytes, indicating a possible role for glia in autophagy flux. Protein turnover, assessed by remaining advanced glycation end-product levels after a 6-h incubation, was preserved with PGRN treatment. Mitochondrial activity differed by complex, although PGRN appeared to increase overall activity in high glucose. We also found that activation of extracellular signal-regulated kinase 1/2 (ERK1/2) and glycogen synthase kinase 3β (GSK3β), kinases implicated in autophagy function, increased with PGRN treatment under stress. Together, our data suggest that PGRN prevents hyperglycemia-induced decreases in autophagy by increasing autophagy flux via increased ERK1/2 kinase activity in primary rat cortical neurons.

mTOR-Dependent Autophagy Regulates Slit Diaphragm Density in Podocyte-like Drosophila Nephrocytes

Both mTOR signaling and autophagy are important modulators of podocyte homeostasis, regeneration, and aging and have been implicated in glomerular diseases. However, the mechanistic role of these pathways for the glomerular filtration barrier remains poorly understood. We used Drosophila nephrocytes as an established podocyte model and found that inhibition of mTOR signaling resulted in increased spacing between slit diaphragms. Gain-of-function of mTOR signaling did not affect spacing, suggesting that additional cues limit the maximal slit diaphragm density. Interestingly, both activation and inhibition of mTOR signaling led to decreased nephrocyte function, indicating that a fine balance of signaling activity is needed for proper function. Furthermore, mTOR positively controlled cell size, survival, and the extent of the subcortical actin network. We also showed that basal autophagy in nephrocytes is required for survival and limits the expression of the sns (nephrin) but does not directly affect slit diaphragm formation or endocytic activity. However, using a genetic rescue approach, we demonstrated that excessive, mTOR-dependent autophagy is primarily responsible for slit diaphragm misspacing. In conclusion, we established this invertebrate podocyte model for mechanistic studies on the role of mTOR signaling and autophagy, and we discovered a direct mTOR/autophagy-dependent regulation of the slit diaphragm architecture.

Inhibition of the lncRNA MIAT prevents podocyte injury and mitotic catastrophe in diabetic nephropathy

Podocyte damage is strongly associated with the progression of diabetic nephropathy. Mitotic catastrophe plays an essential role in accelerating podocyte loss and detachment from the glomerular basement membrane. In the current study, we observed that the long non-coding RNA (lncRNA) MIAT was noticeably upregulated in the plasma and kidney tissues of patients with diabetic nephropathy, and this upregulation was accompanied by higher albumin/creatinine ratios and serum creatinine levels. By generating CRISPR-Cas9 Miat-knockout (KO) mice in vivo and employing vectors in vitro, we found that the depletion of Miat expression significantly restored slit-diaphragm integrity, attenuated foot process effacement, prevented dedifferentiation, and suppressed mitotic catastrophe in podocytes during hyperglycemia. The mechanistic investigation revealed that Miat increased Sox4 expression and subsequently regulated p53 ubiquitination and acetylation, thereby inhibiting the downstream factors CyclinB/cdc2 by enhancing p21^cip1/waf1 activity, and that Miat interacted with Sox4 by sponging miR-130b-3p. Additionally, the inhibition of miR-130b-3p with an antagomir in vivo effectively enhanced glomerular podocyte injury and mitotic dysfunction, eventually exacerbating proteinuria. Based on these findings, MIAT may represent a therapeutic target for diabetic nephropathy.

Autophagy in lupus nephritis: A delicate balance between regulation and disease

Autophagy is a highly regulated process wherein an unwanted cargo of damaged and dysfunctional cytoplasmic components is removed, delivered to lysosomes for degradation, and released back into the cytoplasm. Accumulating evidence suggests an important role of autophagy in the pathophysiology of systemic lupus erythematosus, with profound effects on both innate and adaptive immunity. Autophagy downregulation results in the inhibition of antigen presenting cells, reduced release of neutrophil extracellular traps and decreased activation of effector T and B cells, leading to reduced autoantibody production and attenuated type 1 interferon signaling. However, defective autophagy may accelerate the production of other inflammatory cytokines and reduce the clearance of apoptotic cells, promoting lupus development. In addition, autophagy dysfunction can concur to the pathogenesis of kidney injury in lupus nephritis. Autophagy is a pivotal mechanism to maintain podocyte integrity and endothelial cell survival. Several animal models have demonstrated that defective autophagy leads to podocyte injury and can promote an endothelial pro-inflammatory and atherogenic phenotype. Moreover, autophagy is a key homeostatic regulator of renal tubular cells, and recent evidence has pointed out that chronic autophagy deficiency may accelerate kidney fibrosis. Targeting autophagy may theoretically improve lupus nephritis outcomes, but novel, non-invasive methods to measure and monitor autophagic activity are urgently needed. In addition, the extent and timing of autophagy inhibition still require additional studies before clinical translation may be attempted. In this review, we will also discuss the effect of several clinically available drugs that can regulate the autophagic flux and their effect in lupus nephritis patients.

Extravascular rapamycin film inhibits the endothelial-to-mesenchymal transition through the autophagy pathway to prevent vein graft restenosis

Following vein grafting, the vein must adapt to arterial hemodynamics, which can lead to intimal hyperplasia (IH) and restenosis. Moreover, endothelial-to-mesenchymal transition (EndMT) components are highly associated with IH. Therefore, in this study, we aimed to design an extravascular film loaded with rapamycin (extravascular rapamycin film [ERF]) to limit vein graft stenosis. The film exhibited stable physicochemical properties as well as in vivo and in vitro biocompatibility. In vivo, the film inhibited the EndMT by activating the autophagy pathway. Moreover, rapamycin enhanced this biological effect. Collectively, these findings highlighted the applicability of ERF as a new therapeutic target for preventing vein graft restenosis.

Autophagy and Renal Fibrosis

Renal fibrosis is a common process of almost all the chronic kidney diseases progressing to end-stage kidney disease. As a highly conserved lysosomal protein degradation pathway, autophagy is responsible for degrading protein aggregates, damaged organelles, or invading pathogens to maintain intracellular homeostasis. Growing evidence reveals that autophagy is involved in the progression of renal fibrosis, both in the tubulointerstitial compartment and in the glomeruli. Nevertheless, the specific role of autophagy in renal fibrosis has still not been fully understood. Therefore, in this review we will describe the characteristics of autophagy and summarize the recent advances in understanding the functions of autophagy in renal fibrosis. Moreover, the problem existing in this field and the possibility of autophagy as the potential therapeutic target for renal fibrosis have also been discussed.

C-reactive protein inhibits C3a/C3aR-dependent podocyte autophagy in favor of diabetic kidney disease

Numerous studies have reported the pathogenic roles of C-reactive protein (CRP) and complement activation in diabetic kidney disease (DKD) individually. However, considering the potent regulatory effect of CRP on complement activation, it remains unclear whether CRP participates in DKD pathogenesis by regulating complement activation. Moreover, this work focuses on complement activation in rats, which aims at settling the dispute that whether rat CRP can activate the complement system. To address this question, the complement effectors C3a, C5a, and C5b-9 were examined in human patients with diabetic nephropathy (DN) and wt, Crp^-/- , and huCRPtg rats with STZ-diabetic DKD. The Crp^-/- rats showed more C3a accumulation in blood and glomeruli than wt and huCRPtg rats. The balance between autophagy and apoptosis was evaluated in DKD rats, and Crp^-/- rats showed increased podocyte autophagy compared with wt and huCRPtg rats. Meanwhile, stable CRP-overexpression and CRP-knockout cell lines were established and used to demonstrate that CRP suppresses C3a-induced podocyte autophagy under high-glucose conditions. We further verified that the inhibition of C3a-induced podocyte autophagy by CRP was dependent on C3aR expression and that this effect could be reversed with a C3aR antagonist and agonist. Therefore, our findings provide evidence that CRP suppresses podocyte autophagy to accelerate the development of DKD by inhibiting C3a/C3aR axis signaling, which may help in the development of a new therapeutic strategy for the management of podocyte autophagy and DKD. In addition, rat CRP has been shown to be identical to human CRP in the activation of autologous complement and interspecific complement.

Mutation of Beclin1 acetylation site at K414 alleviates high glucose-induced podocyte impairment in the early stage of diabetic nephropathy by inhibiting hyperactivated autophagy

BACKGROUND

Our group recently reported that a mutation of the novel Beclin1 K414R acetylation site impacts the stability of Beclin1 protein, which decreases autophagy in adipocytes and further impedes adipocyte differentiation and lipolysis. This study was to explore whether Beclin1 acetylation plays a role in the early renal injury induced by high glucose and to further investigate the K414R mutation site in podocytes.

METHODS

Male Sprague-Dawley rats were randomized to con (control) and diabetic nephropathy (DN) groups. The DN group was induced by a single 55 mg/kg intraperitoneal injection of streptozotocin and fed a high-fat and high-sugar diet (the con group received an equal volume of the vehicle and fed a plain diet), after 3 days of induction, blood glucose levels were measured to confirm the onset of diabetes. Then, at weeks 0 and 4, the biochemical index was assayed and renal cortex tissues were harvested. MPC5 podocytes were cultured in vitro. Beclin1 (K414R)-pLVX-ZsGreen1-N1(wild-type or mutant) lentiviral plasmids were transfected into podocytes. Western blot or immunoprecipitation was used to test proteins or the acetylation levels respectively, and immunohistochemistry was used to analyze morphological changes of podocytes. Immunofluorescence was used to detect the aggregation of LC3 puncta.

RESULTS

The acetylation level of Beclin1 was upregulated with podocyte injury exacerbated in high glucose at 24 h and that a mutation at K414R could inhibit hyperactivated autophagy, which ameliorated podocyte impairment.

CONCLUSION

These findings suggest that the acetylation site at K414 is a critical molecule and drug target and that further research into this area is warranted.

Glucolipotoxicity induces endothelial cell dysfunction by activating autophagy and inhibiting autophagic flow

OBJECTIVES

This study aims to determine the role and mechanism of autophagy in endothelial cell dysfunction by glucolipotoxicity.

METHODS

Human umbilical vein endothelial cells (HUVECs) were treated with high glucose and high palmitic acid. The number of autophagosomes was evaluated by monodansylcadaverine (MDC) staining and transmission electron microscopy (TEM). The expression of autophagy-related proteins (LC3 and P62) was assessed by Western blotting. Capillary tube-like formation was evaluated on Matrigel. Reactive oxygen species (ROS) production was detected by DCFH-DA. Cell apoptosis was measured by Hoechst 33258 staining and flow cytometry. Phosphorylation of AMPK, mTOR, and ULK1 was also analyzed by Western blotting.

RESULTS

We found that glucolipotoxicity induced autophagy initiation and hindered autophagosomes degradation. Moreover, glucolipotoxicity increased the production of intracellular ROS, decreased the ability of tubular formation, and increased cell apoptosis. However, endothelial cell dysfunction was alleviated by 3-methyladenine, an early-stage autophagy inhibitor. Additionally, glucolipotoxicity promoted the phosphorylation of AMPK and ULK1 and inhibited the phosphorylation of mTOR.

CONCLUSIONS

Glucolipotoxicity initiates autophagy through the AMPK/mTOR/ULK1 signaling pathway and inhibits autophagic flow, leading to the accumulation of autophagosomes, thereby inducing apoptosis and impairing endothelial cell function.

Long Non-Coding RNAs in the Pathogenesis of Diabetic Kidney Disease

Diabetic kidney disease (DKD) is one of the major microvascular complications of diabetes mellitus, with relatively high morbidity and mortality globally but still in short therapeutic options. Over the decades, a large body of data has demonstrated that oxidative stress, inflammatory responses, and hemodynamic disorders might exert critical influence in the initiation and development of DKD, whereas the delicate pathogenesis of DKD remains profoundly elusive. Recently, long non-coding RNAs (lncRNAs), extensively studied in the field of cancer, are attracting increasing attentions on the development of diabetes mellitus and its complications including DKD, diabetic retinopathy, and diabetic cardiomyopathy. In this review, we chiefly focused on abnormal expression and function of lncRNAs in major resident cells (mesangial cell, endothelial cell, podocyte, and tubular epithelial cell) in the kidney, summarized the critical roles of lncRNAs in the pathogenesis of DKD, and elaborated their potential therapeutic significance, in order to advance our knowledge in this field, which might help in future research and clinical treatment for the disease.

Docosahexaenoic Acid Suppresses Oxidative Stress-Induced Autophagy and Cell Death via the AMPK-Dependent Signaling Pathway in Immortalized Fischer Rat Schwann Cells 1

Autophagy is the process by which intracellular components are degraded by lysosomes. It is also activated by oxidative stress; hence, autophagy is thought to be closely related to oxidative stress, one of the major causes of diabetic neuropathy. We previously reported that docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) induced antioxidant enzymes and protected Schwann cells from oxidative stress. However, the relationship between autophagy and oxidative stress-induced cell death in diabetic neuropathy has not been elucidated. Treatment with tert-butyl hydroperoxide (tBHP) decreased the cell survival rate, as measured by an MTT assay in immortalized Fischer rat Schwann cells 1 (IFRS1). A DHA pretreatment significantly prevented tBHP-induced cytotoxicity. tBHP increased autophagy, which was revealed by the ratio of the initiation markers, AMP-activated protein kinase, and UNC51-like kinase phosphorylation. Conversely, the DHA pretreatment suppressed excessive tBHP-induced autophagy signaling. Autophagosomes induced by tBHP in IFRS1 cells were decreased to control levels by the DHA pretreatment whereas autolysosomes were only partially decreased. These results suggest that DHA attenuated excessive autophagy induced by oxidative stress in Schwann cells and may be useful to prevent or reduce cell death in vitro. However, its potentiality to treat diabetic neuropathy must be validated in in vivo studies.

Mechanisms of podocyte injury and implications for diabetic nephropathy

Albuminuria is the hallmark of both primary and secondary proteinuric glomerulopathies, including focal segmental glomerulosclerosis (FSGS), obesity-related nephropathy, and diabetic nephropathy (DN). Moreover, albuminuria is an important feature of all chronic kidney diseases (CKDs). Podocytes play a key role in maintaining the permselectivity of the glomerular filtration barrier (GFB) and injury of the podocyte, leading to foot process (FP) effacement and podocyte loss, the unifying underlying mechanism of proteinuric glomerulopathies. The metabolic insult of hyperglycemia is of paramount importance in the pathogenesis of DN, while insults leading to podocyte damage are poorly defined in other proteinuric glomerulopathies. However, shared mechanisms of podocyte damage have been identified. Herein, we will review the role of haemodynamic and oxidative stress, inflammation, lipotoxicity, endocannabinoid (EC) hypertone, and both mitochondrial and autophagic dysfunction in the pathogenesis of the podocyte damage, focussing particularly on their role in the pathogenesis of DN. Gaining a better insight into the mechanisms of podocyte injury may provide novel targets for treatment. Moreover, novel strategies for boosting podocyte repair may open the way to podocyte regenerative medicine.

BECLIN1 Is Essential for Podocyte Secretory Pathways Mediating VEGF Secretion and Podocyte-Endothelial Crosstalk

Vascular endothelial growth factor A (VEGFA) secretion from podocytes is crucial for maintaining endothelial integrity within the glomerular filtration barrier. However, until now, the molecular mechanisms underlying podocyte secretory function remained unclear. Through podocyte-specific deletion of BECLIN1 (ATG6 or Becn1), a key protein in autophagy initiation, we identified a major role for this molecule in anterograde Golgi trafficking. The Becn1-deficient podocytes displayed aberrant vesicle formation in the trans-Golgi network (TGN), leading to dramatic vesicle accumulation and complex disrupted patterns of intracellular vesicle trafficking and membrane dynamics. Phenotypically, podocyte-specific deletion of Becn1 resulted in early-onset glomerulosclerosis, which rapidly progressed and dramatically reduced mouse life span. Further, in vivo and in vitro studies clearly showed that VEGFA secretion, and thereby endothelial integrity, greatly depended on BECLIN1 availability and function. Being the first to demonstrate the importance of a secretory pathway for podocyte integrity and function, we identified BECLIN1 as a key component in this complex cellular process. Functionally, by promoting VEGFA secretion, a specific secretory pathway emerged as an essential component for the podocyte-endothelial crosstalk that maintains the glomerular filtration barrier.

GPR43 activation-mediated lipotoxicity contributes to podocyte injury in diabetic nephropathy by modulating the ERK/EGR1 pathway

Background: G-protein-coupled receptor 43 (GPR43) is a posttranscriptional regulator involved in cholesterol metabolism. This study aimed to investigate the possible roles of GPR43 activation in podocyte lipotoxicity in diabetic nephropathy (DN) and explore the potential mechanisms.

Methods: The experiments were conducted by using diabetic GPR43-knockout mice and a podocyte cell culture model. Lipid deposition and free cholesterol levels in kidney tissues were measured by BODIPY staining and quantitative cholesterol assays, respectively. The protein expression of GPR43, LC3II, p62, beclin1, low-density lipoprotein receptor (LDLR) and early growth response protein 1 (EGR1) in kidney tissues and podocytes was measured by real-time PCR, immunofluorescent staining and Western blotting.

Results: There were increased LDL cholesterol levels in plasma and cholesterol accumulation in the kidneys of diabetic mice. However, GPR43 gene knockout inhibited these changes. An in vitro study further demonstrated that acetate treatment induced cholesterol accumulation in high glucose-stimulated podocytes, which was correlated with increased cholesterol uptake mediated by LDLR and reduced cholesterol autophagic degradation, as characterized by the inhibition of LC3 maturation, p62 degradation and autophagosome formation. Gene knockdown or pharmacological inhibition of GPR43 prevented these effects on podocytes. Furthermore, GPR43 activation increased extracellular regulated protein kinases 1/2 (ERK1/2) activity and EGR1 expression in podocytes, which resulted in an increase in cholesterol influx and autophagy inhibition. In contrast, after GPR43 deletion, these changes in podocytes were improved, as shown by the in vivo and in vitro results.

Conclusion: GPR43 activation-mediated lipotoxicity contributes to podocyte injury in DN by modulating the ERK/EGR1 pathway.

Effects of Shenkang Pills on Early-Stage Diabetic Nephropathy in db/db Mice via Inhibiting AURKB/RacGAP1/RhoA Signaling Pathway

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease, so there is an urgent need to suppress its development at early stage. Shenkang pills (SKP) are a hospital prescription selected and optimized from effective traditional Chinese medicinal formulas for clinical treatment of DN. In the present study, liquid chromatography-quadrupole-time of flight-mass spectrometry (LC-Q-TOF-MS) and total contents qualification were applied to generate a quality control standard of SKP. For verifying the therapeutic effects of SKP, db/db mice were administered intragastrically with SKP at a human-equivalent dose (1.82 g/kg) for 4 weeks. Moreover, the underlying mechanism of SKP were analyzed by the renal RNA sequencing and network pharmacology. LC-Q-TOF-MS identified 46 compounds in SKP. The total polysaccharide and organic acid content in SKP were 4.60 and 0.11 mg/ml, respectively, while the total flavonoid, saponin, and protein content were 0.25, 0.31, and 0.42 mg/ml, respectively. Treatment of SKP significantly reduced fasting blood glucose, improved renal function, and ameliorated glomerulosclerosis and focal foot processes effacement in db/db mice. In addition, SKP protected podocytes from injury by increasing nephrin and podocin expression. Furthermore, transcriptome analyses revealed that 430 and 288 genes were up and down-regulated in mice treated with SKP, relative to untreated controls. Gene ontology enrichment analysis revealed that the differentially expressed genes mainly involved in modulation of cell division and chromosome segregation. Weighted gene co-expression network analysis and network pharmacology analysis indicated that aurora kinase B (AURKB), Rac GTPase activating protein 1 (RacGAP1) and SHC binding, and spindle associated 1 (shcbp1) might be the core targets of SKP. This protein and Ras homolog family member A (RhoA) were found overexpression in db/db mice, but significantly decreased with SKP treatment. We conclude that SKP can effectively treat early-stage DN and improve renal podocyte dysfunction. The mechanism may involve down-regulation of the AURKB/RacGAP1/RhoA pathway.

Evaluation of renal fibrosis in patients with chronic kidney disease by shear wave elastography: a comparative analysis with pathological findings

PURPOSE

To explore the elastic values obtained by shear wave elastography (SWE) in assessing renal fibrosis in chronic kidney disease (CKD).

METHODS

One hundred and twenty-four patients with CKD who underwent renal biopsy were prospectively enrolled between April 2019 and June 2021. SWE was performed to measure the renal cortex stiffness, presented as SWE parameters, including the minimum, mean, and maximum elasticity (namely Emin, Emean, and Emax). Then, the patients with different kidney pathological impairment (mild, moderate, and severe groups) were compared in SWE elasticity and the discriminative capacity was also analyzed.

RESULTS

For the pathology impaired grade, SWE parameter was significantly reduced in the moderately and severely impaired group than the mild one. Emax parameter achieved the best discriminative ability toward differentiating moderate-severe impairment from mild one, yielding an area under the curve (AUC) of 0.764 (95%CI: 0.681-0.848). Regarding interstitial fibrosis/tubular atrophy and global glomerular sclerosis, the Emax values were significantly reduced across the group of patients with moderate grade compared to those with mild grade. Patients in severe group were also with reduced elastic value than those in mild one, while the difference was non-significant in interstitial fibrosis/tubular atrophy but a borderline statistical significance was achieved in global glomerular sclerosis. For grade of vessel wall thickening, patients in moderate (33.04 ± 9.86 kPa, P = 0.009) and severe (31.42 ± 9.16 kPa, P < 0.001) group were with significantly lower elastic value compared with those in the mild one (39.58 ± 9.67 kPa). The SWE parameter was linearly reduced as grade of vessel wall thickening elevated (P for trend: < 0.001).

CONCLUSION

SWE derived elastic values reduced as pathology grade of renal fibrosis or grade of vessel wall thickening progresses in patients with CKD, which may be attributed to renal hypo-perfusion rather than tubulo-interstitial fibrosis progression.

Application of weighted gene co-expression network analysis to identify novel key genes in diabetic nephropathy

AIMS/INTRODUCTION

Diabetic nephropathy (DN) is among the leading causes of end-stage renal disease worldwide. DN pathogenesis remains largely unknown. Weighted gene co-expression network analysis is a powerful bioinformatic tool for identifying key genes in diseases.

MATERIALS AND METHODS

The datasets GSE30122, GSE104948, GSE37463 and GSE47185 containing 23 DN and 23 normal glomeruli samples were obtained from the National Center for Biotechnology Information Gene Expression Omnibus database. After data pre-processing, weighted gene co-expression network analysis was carried out to cluster significant modules. Then, Gene Set Enrichment Analysis-based Gene Ontology analysis and visualization of network were carried out to screen the key genes in the most significant modules. The connectivity map analysis was carried out to find the significant chemical compounds. Finally, some key genes were validated in in vivo and in vitro experiments.

RESULTS

A total of 454 upregulated and 392 downregulated genes were identified. A total of 16 modules were clustered, and the most significant modules (green, red and yellow modules) were determined. The green module was associated with extracellular matrix organization, the red module was associated with immunity reaction and the yellow module was associated with kidney development. We found several key genes in these three modules separately, and part of them were validated in vivo and in vitro successfully. We found the top 15 chemical compounds that could perturb the overall expression of key genes in DN.

CONCLUSION

Weighted gene co-expression network analysis was applied to DN expression profiling in combination with connectivity map analysis. Several novel key genes and chemical compounds were screened out, providing new molecular targets for DN.

Sirtuin Family and Diabetic Kidney Disease

Diabetes mellitus (DM) is gradually attacking the health and life of people all over the world. Diabetic kidney disease (DKD) is one of the most common chronic microvascular complications of DM, whose mechanism is complex and still lacks research. Sirtuin family is a class III histone deacetylase with highly conserved NAD⁺ binding domain and catalytic functional domain, while different N-terminal and C-terminal structures enable them to bind different deacetylated substrates to participate in the cellular NAD⁺ metabolism. The kidney is an organ rich in NAD⁺ and database exploration of literature shows that the Sirtuin family has different expression localization in renal, cellular, and subcellular structures. With the progress of modern technology, a variety of animal models and reagents for the Sirtuin family and DKD emerged. Machine learning in the literature shows that the Sirtuin family can regulate pathophysiological injury mainly in the glomerular filtration membrane, renal tubular absorption, and immune inflammation through various mechanisms such as epigenetics, multiple signaling pathways, and mitochondrial function. These mechanisms are the key nodes participating in DKD. Thus, it is of great significance for target therapy to study biological functions of the Sirtuin family and DKD regulation mechanism in-depth.

Knowledge Domain and Emerging Trends in Podocyte Injury Research From 1994 to 2021: A Bibliometric and Visualized Analysis

Background: Podocyte injury has a direct causal relationship with proteinuria and glomerulosclerosis and, on a chronic level, can lead to irreversible disease progression. Podocyte injury plays a critically decisive role in the development of proteinuric kidney disease. In recent years, the research on podocyte injury has developed rapidly all over the world. However, no report has summarized the field of podocyte injury as a whole to date. Using bibliometric analysis, this study aimed to evaluate the current state of worldwide podocyte injury research in the last 30 years and identify important achievements, primary research fields, and emerging trends.

Methods: Publications related to podocyte injury were retrieved from Web of Science Core Collection. HistCite, VOSviewer, CiteSpace, and the Bibliometrix Package were used for bibliometric analysis and visualization, including the analysis of the overall distribution of annual outputs, leading countries, active institutions and authors, core journals, co-cited references, and keywords. Total global citation score and total local citation score were used to assess the quality and impact of publications.

Results: A total of 2,669 publications related to podocyte injury were identified. Publications related to podocyte injury tended to increase continuously. A total of 10,328 authors from 2,171 institutions in 69 countries published studies related to podocyte injury. China (39.46%) was the most prolific country, and the number of citations of studies in the United States (cited 36,896 times) ranked first. Moin A Saleem, John Cijiang He, and Zhihong Liu were the top three contributing authors, and Journal of the American Society of Nephrology and Kidney International were the most popular journals in the field. “Diabetic nephropathy” is the primary focus area of podocyte injury research, and “autophagy,” “microRNA,” and “inflammation” were the top keywords of emerging research hotspots, and traditional Chinese medicine monomer may be a neglected research gap.

Conclusion: Our research found that global publications on podocyte injury have increased dramatically. Diabetic nephropathy is the main research field of podocyte injury, whereas autophagy, microRNA, and inflammation are the top topics getting current attention from scholars and which may become the next focus in podocyte injury research.

Therapeutic potential of resveratrol in diabetic nephropathy according to molecular signaling

BACKGROUND

Diabetic nephropathy (DN) as a severe complication of diabetes mellitus (DM), is a crucial menace for human health and survival and remarkably elevates the healthcare systems' costs. Therefore, it is worth noting to identify novel preventive and therapeutic strategies to alleviate the disease conditions. Resveratrol, as a well-defined anti-diabetic/ antioxidant agent has capabilities to counteract diabetic complications. It has been predicted that resveratrol will be a fantastic natural polyphenol for diabetes therapy in the next few years.

OBJECTIVE

Accordingly, the current review aims to depict the role of resveratrol in the regulation of different signaling pathways that are involved in the reactive oxygen species (ROS) production, inflammatory processes, autophagy, and mitochondrial dysfunction, as critical contributors to DN pathophysiology.

RESULTS

The pathogenesis of DN can be multifactorial; hyperglycemia is one of the prominent risk factors of DN development that is closely related to oxidative stress. Resveratrol, as a well-defined polyphenol, has various biological and medicinal properties, including anti-diabetic, anti-inflammatory, and anti-oxidative effects.

CONCLUSION

Resveratrol prevents kidney damages that are caused by oxidative stress, enhances antioxidant capacity, and attenuates the inflammatory and fibrotic responses. For this reason, resveratrol is considered an interesting target in DN research due to its therapeutic possibilities during diabetic disorders and renal protection.

Co-culture of peripheral blood mononuclear cell (PBMC) and human coronary artery endothelial cell (HCAEC) reveals the important role of autophagy implicated in Kawasaki disease

BACKGROUND

Kawasaki disease (KD) is a systemic vasculitis syndrome that commonly occurs in children. Autophagy has been increasingly shown to be involved in various cardiovascular diseases, including endothelial dysfunction and vascular endothelial injury. However, whether autophagy is implicated in the pathogenesis of KD remains poorly understood, and particularly, how the dysfunction of human coronary artery endothelial cells (HCAECs) is associated with autophagy in peripheral blood mononuclear cells (PBMCs) from KD patients awaits further investigation.

METHODS

Peripheral blood samples were collected from KD patients, common fever patients, and healthy controls. The PBMC samples were isolated from KD blood samples collected at three different phases: the acute phase before therapy (acute-KD), 1 week (subacute-KD), and 4 weeks (convalescent-KD) after drug administration.

RESULTS

The autophagy flux was significantly increased in the PBMCs of KD patients at acute phase. The PBMCs of acute KD patients could induce autophagy in HCAECs and promote the secretion of chemokines and pro-inflammatory factors after cocultured with HCAECs whereas 3-methyladenine (3-MA) drug could partly reverse this process.

CONCLUSIONS

Autophagy is involved in the inflammatory injury of vascular endothelial cells associated with PBMCs in KD patients, and may play a crucial role in regulating inflammation. Hence, we identify a novel regulatory mechanism of vascular injury in this disease.

Dysfunction of the circadian clock in the kidney tubule leads to enhanced kidney gluconeogenesis and exacerbated hyperglycemia in diabetes

The circadian clock is a ubiquitous molecular time-keeping mechanism which synchronizes cellular, tissue, and systemic biological functions with 24-hour environmental cycles. Local circadian clocks drive cell type- and tissue-specific rhythms and their dysregulation has been implicated in pathogenesis and/or progression of a broad spectrum of diseases. However, the pathophysiological role of intrinsic circadian clocks in the kidney of diabetics remains unknown. To address this question, we induced type I diabetes with streptozotocin in mice devoid of the circadian transcriptional regulator BMAL1 in podocytes (cKOp mice) or in the kidney tubule (cKOt mice). There was no association between dysfunction of the circadian clock and the development of diabetic nephropathy in cKOp and cKOt mice with diabetes. However, cKOt mice with diabetes exhibited exacerbated hyperglycemia, increased fractional excretion of glucose in the urine, enhanced polyuria, and a more pronounced kidney hypertrophy compared to streptozotocin-treated control mice. mRNA and protein expression analyses revealed substantial enhancement of the gluconeogenic pathway in kidneys of cKOt mice with diabetes as compared to diabetic control mice. Transcriptomic analysis along with functional analysis of cKOt mice with diabetes identified changes in multiple mechanisms directly or indirectly affecting the gluconeogenic pathway. Thus, we demonstrate that dysfunction of the intrinsic kidney tubule circadian clock can aggravate diabetic hyperglycemia via enhancement of gluconeogenesis in the kidney proximal tubule and further highlight the importance of circadian behavior in patients with diabetes.

Calcium Signaling Mediates Cell Death and Crosstalk with Autophagy in Kidney Disease

The kidney is an important organ for the maintenance of Ca²⁺ homeostasis in the body. However, disruption of Ca²⁺ homeostasis will cause a series of kidney diseases, such as acute kidney injury (AKI), chronic kidney disease (CKD), renal ischemia/reperfusion (I/R) injury, autosomal dominant polycystic kidney disease (ADPKD), podocytopathy, and diabetic nephropathy. During the progression of kidney disease, Ca²⁺ signaling plays key roles in various cell activities such as necrosis, apoptosis, eryptosis and autophagy. Importantly, there are complex Ca²⁺ flux networks between the endoplasmic reticulum (ER), mitochondria and lysosomes which regulate intracellular Ca²⁺ signaling in renal cells and contribute to kidney disease. In addition, Ca²⁺ signaling also links the crosstalk between various cell deaths and autophagy under the stress of heavy metals or high glucose. In this regard, we present a review of Ca²⁺ signaling in cell death and crosstalk with autophagy and its potential as a therapeutic target for the development of new and efficient drugs against kidney diseases.

Pathomorphological sequence of nephron loss in diabetic nephropathy

Following our previous reports on mesangial sclerosis and vascular proliferation in diabetic nephropathy (DN) (Kriz W, Löwen J, Federico G, van den Born J, Gröne E, Gröne HJ. Am J Physiol Renal Physiol 312: F1101-F1111, 2017; Löwen J, Gröne E, Gröne HJ, Kriz W. Am J Physiol Renal Physiol 317: F399-F410, 2019), we now describe the advanced stages of DN terminating in glomerular obsolescence and tubulointerstitial fibrosis based on a total of 918 biopsies. The structural aberrations emerged from two defects: 1) increased synthesis of glomerular basement membrane (GBM) components by podocytes and endothelial cells leading to an accumulation of GBM material in the mesangium and 2) a defect of glomerular vessels consisting of increased leakiness and an increased propensity to proliferate. Both defects may lead to glomerular degeneration. The progressing compaction of accumulated worn-out GBM material together with the retraction of podocytes out of the tuft and the collapse and hyalinosis of capillaries results in a shrunken tuft that fuses with Bowman's capsule (BC) to glomerular sclerosis. The most frequent pathway to glomerular decay starts with local tuft expansions that result in contacts of structurally intact podocytes to the parietal epithelium initiating the formation of tuft adhesions, which include the penetration of glomerular capillaries into BC. Exudation of plasma from such capillaries into the space between the parietal epithelium and its basement membrane causes the formation of insudative fluid accumulations within BC spreading around the glomerular circumference and, via the glomerulotubular junction, onto the tubule. Degeneration of the corresponding tubule develops secondarily to the glomerular damage, either due to cessation of filtration in cases of global sclerosis or due to encroachment of the insudative spaces. The degenerating tubules induce the proliferation of myofibroblasts resulting in interstitial fibrosis.NEW & NOTEWORTHY Based on analysis of 918 human biopsies, essential derangement in diabetic nephropathy consists of accumulation of worn-out glomerular basement membrane in the mesangium that may advance to global sclerosis. The most frequent pathway to nephron dropout starts with the penetration of glomerular capillaries into Bowman's capsule (BC), delivering an exudate into BC that spreads around the entire glomerular circumference and via the glomerulotubular junction onto the tubule, resulting in glomerular sclerosis and chronic tubulointerstitial damage.

Protective Effect of Keluoxin against Diabetic Nephropathy in Type 2 Diabetic Mellitus Models

Diabetic nephropathy (DN) is a chronic kidney disease that develops in patients with diabetes mellitus (DM). Renal dysfunction and persistent proteinuria are the main clinical features of DN. Podocyte injury is an important cause of persistent proteinuria and diabetic kidney disease (DKD) progression. Traditional Chinese patent medicines can improve renal function by enhancing autophagy and promoting apoptosis. Keluoxin is a Chinese patent medicine that has the effect of invigorating qi and nourishing yin, activating blood, and eliminating blood stasis. Therefore, we hypothesized that Keluoxin may have a protective effect against diabetic nephropathy in rats with type 2 DM. Rats induced with diabetes through streptozocin (STZ) injection and a high-fat and high-sugar diet were treated with Keluoxin (0.63 g/kg/day) for 8 weeks, and renal function, biochemical indicators, and histopathological changes in renal tissues were observed. Immunofluorescence staining and western blot analysis were used to detect the expression of autophagy-related proteins. The results showed that Keluoxin reduced blood glucose and lipid levels, improved renal function, and alleviated renal histopathological changes in rats with DN. The therapeutic effect was similar to that of Irbesartan (15.6 mg/kg/day). It is inferred that the mechanism works through reducing the obstruction of downstream pathways of autophagy by improving the lysosomal degradation function and alleviating podocyte injury. This study demonstrates that Keluoxin could regulate autophagy in podocytes, alleviate kidney injury in rats with DN, and have a protective effect on renal function; its mechanism can thus be a potential therapy for DN.

Relationship between lysosomal dyshomeostasis and progression of diabetic kidney disease

Lysosomes are organelles involved in cell metabolism, waste degradation, and cellular material circulation. They play a key role in the maintenance of cellular physiological homeostasis. Compared with the lysosomal content of other organs, that of the kidney is abundant, and lysosomal abnormalities are associated with the occurrence and development of certain renal diseases. Lysosomal structure and function in intrinsic renal cells are impaired in diabetic kidney disease (DKD). Promoting lysosomal biosynthesis and/or restoring lysosomal function can repair damaged podocytes and proximal tubular epithelial cells, and delay the progression of DKD. Lysosomal homeostasis maintenance may be advantageous in alleviating DKD. Here, we systematically reviewed the latest advances in the relationship between lysosomal dyshomeostasis and progression of DKD based on recent literature to further elucidate the mechanism of renal injury in diabetes mellitus and to highlight the application potential of lysosomal homeostasis maintenance as a new prevention and treatment strategy for DKD. However, research on screening effective interventions for lysosomal dyshomeostasis is still in its infancy, and thus should be the focus of future research studies. The screening out of cell-specific lysosomal function regulation targets according to the different stages of DKD, so as to realize the controllable targeted regulation of cell lysosomal function during DKD, is the key to the successful clinical development of this therapeutic strategy.

Mitochondrial Regulation of Diabetic Kidney Disease

The role and nature of mitochondrial dysfunction in diabetic kidney disease (DKD) has been extensively studied. Yet, the molecular drivers of mitochondrial remodeling in DKD are poorly understood. Diabetic kidney cells exhibit a cascade of mitochondrial dysfunction ranging from changes in mitochondrial morphology to significant alterations in mitochondrial biogenesis, biosynthetic, bioenergetics and production of reactive oxygen species (ROS). How these changes individually or in aggregate contribute to progression of DKD remain to be fully elucidated. Nevertheless, because of the remarkable progress in our basic understanding of the role of mitochondrial biology and its dysfunction in DKD, there is great excitement on future targeted therapies based on improving mitochondrial function in DKD. This review will highlight the latest advances in understanding the nature of mitochondria dysfunction and its role in progression of DKD, and the development of mitochondrial targets that could be potentially used to prevent its progression.

Autophagy in major human diseases

Autophagy is a core molecular pathway for the preservation of cellular and organismal homeostasis. Pharmacological and genetic interventions impairing autophagy responses promote or aggravate disease in a plethora of experimental models. Consistently, mutations in autophagy-related processes cause severe human pathologies. Here, we review and discuss preclinical data linking autophagy dysfunction to the pathogenesis of major human disorders including cancer as well as cardiovascular, neurodegenerative, metabolic, pulmonary, renal, infectious, musculoskeletal, and ocular disorders.