Connexin 43 prevents the progression of diabetic renal tubulointerstitial fibrosis by regulating the SIRT1-HIF-1α signaling pathway

Involvement of oxidative stress-AMPK-Cx43-NLRP3 pathway in extracellular matrix remodeling of gastric smooth muscle cells in rats with diabetic gastroparesis

This study aimed to investigate the changes in oxidative stress, adenosine monophosphate-activated protein kinase (AMPK), connexin43 (Cx43), nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) expression, and extracellular matrix (ECM) in the gastric smooth muscle tissues of rats with diabetic gastroparesis (DGP) and high glucose-cultured gastric smooth muscle cells, determine the existence of oxidative stress-AMPK-Cx43-NLRP3 pathway under high glucose condition, and the involvement of this pathway in ECM remodeling in DGP rats. The results showed that with increasing duration of diabetes, oxidation stress levels gradually increased, the AMPK activity decreased first and then increased, NLRP3, CX43 expression, and membrane/cytoplasm ratio of Cx43 expression were increased in the gastric smooth muscle tissues of diabetic rats. Changes in ECM of gastric smooth muscle cells were observed in DGP rats. The DGP group showed higher collagen type I content, increased expression of Caspase-1, transforming growth factor-beta 3 (TGF-β3), and matrix metalloproteinase-2 (MMP-2), decreased tissue inhibitor of metalloproteinase-1 (TIMP-1) expression, and higher interleukin-1 beta content when compared with the control group. For gastric smooth muscle cells cultured under higher glucose, the MMP-2 and TGF-β3 expression was decreased, TGF-β1 and TIMP-1 expression was increased, the interleukin-1 beta content was decreased in cells after inhibition of NLRP3 expression; the NLRP3 and Caspase-1 expression was decreased, and adenosine triphosphate content was lower after inhibition of Cx43; the expression of NLRP3, Caspase-1, P2X7, and the membrane/cytoplasm ratio of CX43 expression was decreased in cells after inhibition of AMPK and oxidative stress, the phospho-AMPK expression was also decreased after suppressing oxidative stress. Our findings suggest that high glucose induced the activation of the AMPK-Cx43-NLRP3 pathway through oxidative stress, and this pathway was involved in the ECM remodeling of gastric smooth muscles in DGP rats by regulating the biological functions of TGF-β3, TGF-β1, MMP-2, and TIMP-1.

Roles of Sirt1 and its modulators in diabetic microangiopathy: A review

Diabetic vascular complications include diabetic macroangiopathy and diabetic microangiopathy. Diabetic microangiopathy is characterised by impaired microvascular endothelial function, basement membrane thickening, and microthrombosis, which may promote renal, ocular, cardiac, and peripheral system damage in diabetic patients. Therefore, new preventive and therapeutic strategies are urgently required. Sirt1, a member of the nicotinamide adenine dinucleotide-dependent histone deacetylase class III family, regulates different organ growth and development, oxidative stress, mitochondrial function, metabolism, inflammation, and aging. Sirt1 is downregulated in vascular injury and microangiopathy. Moreover, its expression and distribution in different organs correlate with age and play critical regulatory roles in oxidative stress and inflammation. This review introduces the background of diabetic microangiopathy and the main functions of Sirt1. Then, the relationship between Sirt1 and different diabetic microangiopathies and the regulatory roles mediated by different cells are described. Finally, we summarize the modulators that target Sirt1 to ameliorate diabetic microangiopathy as an essential preventive and therapeutic measure for diabetic microangiopathy. In conclusion, targeting Sirt1 may be a new therapeutic strategy for diabetic microangiopathy.

Pathogenesis of diabetic complications: Exploring hypoxic niche formation and HIF-1α activation

Hypoxia is a common feature of diabetic tissues, which highly correlates to the progression of diabetes. The formation of hypoxic context is induced by disrupted oxygen homeostasis that is predominantly driven by vascular remodeling in diabetes. While different types of vascular impairments have been reported, the specific features and underlying mechanisms are yet to be fully understood. Under hypoxic condition, cells upregulate hypoxia-inducible factor-1α (HIF-1α), an oxygen sensor that coordinates oxygen concentration and cell metabolism under hypoxic conditions. However, diabetic context exploits this machinery for pathogenic functions. Although HIF-1α protects cells from diabetic insult in multiple tissues, it also jeopardizes cell function in the retina. To gain a deeper understanding of hypoxia in diabetic complications, we focus on the formation of tissue hypoxia and the outcomes of HIF-1α dysregulation under diabetic context. Hopefully, this review can provide a better understanding on hypoxia biology in diabetes.

Sirtuins in kidney diseases: potential mechanism and therapeutic targets

Sirtuins, which are NAD+-dependent class III histone deacetylases, are involved in various biological processes, including DNA damage repair, immune inflammation, oxidative stress, mitochondrial homeostasis, autophagy, and apoptosis. Sirtuins are essential regulators of cellular function and organismal health. Increasing evidence suggests that the development of age-related diseases, including kidney diseases, is associated with aberrant expression of sirtuins, and that regulation of sirtuins expression and activity can effectively improve kidney function and delay the progression of kidney disease. In this review, we summarise current studies highlighting the role of sirtuins in renal diseases. First, we discuss sirtuin family members and their main mechanisms of action. We then outline the possible roles of sirtuins in various cell types in kidney diseases. Finally, we summarise the compounds that activate or inhibit sirtuin activity and that consequently ameliorate renal diseases. In conclusion, targeted modulation of sirtuins is a potential therapeutic strategy for kidney diseases. Video Abstract.

Potential therapeutic medicines for renal fibrosis: Small-molecule compounds and natural products

Renal fibrosis is the pathological change process of chronic kidney disease deteriorating continuously. When the renal organ is stimulated by external stimuli, it will trigger the damage and phenotypic changes of some intrinsic cells in the kidney. When the body's autoimmune regulation or external treatment is not prompted enough to restore the organ, the pathological process is gradually aggravating, inducing a large amount of intracellular collagen deposition, which leads to the appearance of fibrosis and scarring. The renal parenchyma (including glomeruli and tubules) begins to harden, making it difficult to repair the kidney lesions. In the process of gradual changes in the kidney tissue, the kidney units are severely damaged and the kidney function shows a progressive decline, eventually resulting in the clinical manifestation of end-stage renal failure, namely uremia. This review provides a brief description of the diagnosis, pathogenesis, and potential therapeutic inhibitors of renal fibrosis. Since renal fibrosis has not yet had a clear therapeutic target and related drugs, some potential targets and relevant inhibitors are discussed, especially pharmacological effects and interactions with targets. Some existing natural products have potential efficacy for renal fibrosis, which is also roughly summarized, hoping that this article would have reference significance for the treatment of renal fibrosis.

Therapeutic application of traditional Chinese medicine in kidney disease: Sirtuins as potential targets

Sirtuins are a family of NAD+ III-dependent histone deacetylases that consists of seven family members, Sirt1-Sirt7, which regulate various signalling pathways and are involved in many critical biological processes of kidney diseases. Traditional Chinese medicine (TCM), as an essential part of the global healthcare system, has multi-component and multi-pathway therapeutic characteristics and plays a role in preventing and controlling various diseases. Through ongoing collaboration with modern medicine, TCM has recently achieved many remarkable advancements in theoretical investigation, mechanistic research, and clinical applications related to kidney diseases. Therefore, a comprehensive and systematic summary of TCM that focuses on sirtuins as the intervention target for kidney diseases is necessary. This review introduces the relationship between abnormal sirtuins levels and common kidney diseases, such as diabetic kidney disease and acute kidney injury. Based on the standard biological processes, such as inflammation, oxidative stress, autophagy, mitochondrial homeostasis, and fibrosis, which are underlying kidney diseases, comprehensively describes the roles and regulatory effects of TCM targeting the sirtuins family in various kidney diseases.

Dibutyl phthalate induces epithelial-mesenchymal transition of renal tubular epithelial cells via the Ang II/AMPKα2/Cx43 signaling pathway

Maternal exposure to dibutyl phthalate (DBP) induces renal fibrosis in offspring. However, the specific roles of connexin 43 (Cx43) in DBP-induced renal fibrosis remain unknown. Therefore, in this study, we analysed the expression of Cx43 in renal tubular epithelial cells (RTECs) with or without DBP exposure using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blotting. A small interfering RNA against Cx43 was introduced to assess its role in epithelial-mesenchymal transition (EMT) of RTECs caused by 100 μmol/L DBP. Bioinformatics analysis was conducted with AMP-activated protein kinase (AMPK)-α2 and angiotensin (Ang) II inhibitors to determine the mechanisms involved in the expression of Cx43 in HK-2 cells. RT-qPCR and western blotting revealed that DBP increased the expression of Cx43 in vitro. Moreover, Cx43 knockdown significantly alleviated DBP-induced EMT caused by DBP in HK-2 cells. Bioinformatics analysis with AMPKα2 and Ang II inhibitors revealed that DBP upregulated Cx43 expression by activating the Ang II/AMPKα2 signaling pathway. Our findings indicate that DBP induces renal fibrosis by activating Ang II/AMPKα2/Cx43 signaling pathway and EMT in RETCs, suggesting a potential target for the treatment of renal fibrosis.

Regulation of SIRT1 in Ovarian Function: PCOS Treatment

The sirtuin family, a group of NAD+-dependent class 3 histone deacetylases (HDACs), was extensively studied initially as a group of longevity genes that are activated in caloric restriction and act in concert with nicotinamide adenine dinucleotides to extend the lifespan. Subsequent studies have found that sirtuins are involved in various physiological processes, including cell proliferation, apoptosis, cell cycle progression, and insulin signaling, and they have been extensively studied as cancer genes. In recent years, it has been found that caloric restriction increases ovarian reserves, suggesting that sirtuins may play a regulatory role in reproductive capacity, and interest in the sirtuin family has continued to increase. The purpose of this paper is to summarize the existing studies and analyze the role and mechanism of SIRT1, a member of the sirtuin family, in regulating ovarian function. Research and review on the positive regulation of SIRT1 in ovarian function and its therapeutic effect on PCOS syndrome.

USP22 aggravated diabetic renal tubulointerstitial fibrosis progression through deubiquitinating and stabilizing Snail1

Renal tubulointerstitial fibrosis (TIF) is one of the main pathological changes induced by diabetic kidney disease (DKD), and epithelial-to-mesenchymal transition (EMT) induced by high glucose (HG) can promote TIF. Our previous study has shown that ubiquitin-specific protease 22 (USP22) could affect the process of DKD by deubiquitinating and stabilizing Sirt1 in glomerular mesangial cells. However, whether USP22 could regulate EMT occurrence in renal tubular epithelial cells and further aggravate the pathological process of TIF in DKD remains to be elucidated. In this study, we found that USP22 expression was upregulated in kidney tissues of db/db mice and HG-treated NRK-52E cells. In vitro, USP22 overexpression promoted the EMT process of NRK-52E cells stimulated by HG and further increased the levels of extracellular matrix (ECM) components such as fibronectin, Collagen I, and Collagen Ⅳ. Meanwhile, USP22 deficiency exhibited the opposite effects. Mechanism studies showed that USP22, depending on its deubiquitinase activity, deubiquitinated and stabilized the EMT transcriptional factor Snail1. In vivo experiment showed that interfering with USP22 could improve the renal pathological damages and renal function of the db/db spontaneous diabetic mice by decreasing Snail1 expression, which could inhibit EMT occurrence, and reduce the production of ECM components. These results suggested that USP22 could accelerate renal EMT and promote the pathological progression of diabetic TIF by deubiquitinating Snail1, providing an experimental basis for using USP22 as a potential target for DKD.

Role of sirtuins in metabolic disease-related renal injury

Poor control of metabolic diseases induces kidney injury, resulting in microalbuminuria, renal insufficiency and, ultimately, chronic kidney disease. The potential pathogenetic mechanisms of renal injury caused by metabolic diseases remain unclear. Tubular cells and podocytes of the kidney show high expression of histone deacetylases known as sirtuins (SIRT1-7). Available evidence has shown that SIRTs participate in pathogenic processes of renal disorders caused by metabolic diseases. The present review addresses the regulatory roles of SIRTs and their implications for the initiation and development of kidney damage due to metabolic diseases. SIRTs are commonly dysregulated in renal disorders induced by metabolic diseases such as hypertensive nephropathy and diabetic nephropathy. This dysregulation is associated with disease progression. Previous literature has also suggested that abnormal expression of SIRTs affects cellular biology, such as oxidative stress, metabolism, inflammation, and apoptosis of renal cells, resulting in the promotion of invasive diseases. This literature reviews the research progress made in understanding the roles of dysregulated SIRTs in the pathogenesis of metabolic disease-related kidney disorders and describes the potential of SIRTs serve as biomarkers for early screening and diagnosis of these diseases and as therapeutic targets for their treatment.

Resveratrol attenuates cigarette smoke extract induced cellular senescence in human airway epithelial cells by regulating the miR-34a/SIRT1/NF-κB pathway

Chronic obstructive pulmonary disease (COPD) is characterized by accelerated lung aging. Smoking is the critical risk factor for COPD. Cellular senescence of airway epithelial cells is the cytological basis of accelerated lung aging in COPD, and the regulation of microRNAs (miRNAs) is the central epigenetic mechanism of cellular senescence. Resveratrol (Res) is a polyphenol with anti-aging properties. This study investigated whether Res attenuates cigarette smoke extract (CSE)-induced cellular senescence in human airway epithelial cells (BEAS-2B) through the miR-34a/SIRT1/nuclear factor-kappaB (NF-κB) pathway. BEAS-2B cells were treated with Res, CSE and transfected with miR-34a-5p mimics. Cellular senescence was evaluated by senescence -related β-galactosidase (SA-β-gal) staining and expression of senescence-related genes (p16, p21, and p53). The expressions of miR-34a-5p, SIRT1, and NF-κB p65 were examined using quantitative real time polymerase chain reaction and western blotting. The senescence-associated secretory phenotype (SASP) cytokines (IL-1β, IL-6, IL-8, TNF-α) were assessed by enzyme-linked immunosorbent assay. The binding between miR-34a-5p and SIRT1 was confirmed by dual-luciferase reporter assay. The results showed that CSE dose-dependently decreased cell viability and elevated cellular senescence, characterized by increased SA-β-gal staining and senescence-related gene expressions (p16, p21, and p53). Further, CSE dose-dependently increased the expression of miR-34a-5p and SASP cytokines (IL-1β, IL-6, IL-8, TNF-α) in BEAS-2B cells. Pretreatment with Res inhibited CSE-induced cellular senescence and secretion of SASP cytokines (IL-1β, IL-6, IL-8, TNF-α) in a dose-dependent manner. Moreover, Res reversed the CSE-induced down-regulation of SIRT1 and up-regulation of miR-34a-5p and NF-κB p65. SIRT1 is a target of miR-34a-5p. Overexpression of miR-34a-5p via transfection with miR-34a-5p mimic in BEAS-2B cells attenuated the inhibitory effect of Res on cellular senescence, accompanied by reversing the expression of SIRT1 and NF-κB p65. In conclusion, Res attenuated CSE-induced cellular senescence in BEAS-2B cells by regulating the miR-34a/SIRT1/NF-κB pathway, which may provide a new approach for COPD treatment.

The Role of Connexin 43 in Renal Disease: Insights from In Vivo Models of Experimental Nephropathy

Renal disease is a major public health challenge since its prevalence has continuously increased over the last decades. At the end stage, extrarenal replacement therapy and transplantation remain the only treatments currently available. To understand how the disease progresses, further knowledge of its pathophysiology is needed. For this purpose, experimental models, using mainly rodents, have been developed to unravel the mechanisms involved in the initiation and progression of renal disease, as well as to identify potential targets for therapy. The gap junction protein connexin 43 has recently been identified as a novel player in the development of kidney disease. Its expression has been found to be altered in many types of human renal pathologies, as well as in different animal models, contributing to the activation of inflammatory and fibrotic processes that lead to renal damage. Furthermore, Cx43 genetic, pharmacogenetic, or pharmacological inhibition preserved renal function and structure. This review summarizes the existing advances on the role of this protein in renal diseases, based mainly on different in vivo animal models of acute and chronic renal diseases.

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.

Intrarenal Single-Cell Sequencing of Hepatitis B Virus Associated Membranous Nephropathy

To date, the pathogenesis of hepatitis B virus (HBV)-associated membranous nephropathy (MN) remains elusive. This study aimed to decipher the etiopathogenesis of HBV-associated MN by performing single-cell RNA sequencing (scRNA-seq) of kidney biopsy specimens from a patient with HBV-associated MN and two healthy individuals. We generated 4,114 intrarenal single-cell transcriptomes from the HBV-associated MN patient by scRNA-seq. Compared to healthy individuals, podocytes in the HBV-associated MN patient showed an increased expression of extracellular matrix formation-related genes, including HSPA5, CTGF, and EDIL3. Kidney endothelial cells (ECs) in the HBV-associated MN were enriched in inflammatory pathways, including NF-kappa B signaling, IL-17 signaling, TNF signaling and NOD-like receptor signaling. Gene ontology (GO) functional enrichment analysis and Gene Set Variation Analysis (GSVA) further revealed that differentially expressed genes (DEGs) of ECs from the HBV-associated MN patients were enriched in apoptotic signaling pathway, response to cytokine and leukocyte cell-cell adhesion. The up-regulated DEGs in glomerular ECs of HBV-associated MN patients were involved in biological processes such as viral gene expression, and protein targeting to endoplasmic reticulum. We further verified that the overexpressed genes in ECs from HBV-associated MN were mainly enriched in regulation of protein targeting to endoplasmic reticulum, exocytosis, viral gene expression, IL-6 and IL-1 secretion when compared with anti-phospholipase A2 receptor (PLA2R)-positive idiopathic membranous nephropathy (IMN). The receptor-ligand crosstalk analysis revealed potential interactions between endothelial cells and other cells in HBV-associated-MN. These results offer new insight into the pathogenesis of HBV-associated MN and may identify new therapeutic targets for HBV-associated MN.

Longevity-Promoting Pathways and Transcription Factors Respond to and Control Extracellular Matrix Dynamics During Aging and Disease

Aging is one of the largest risk factors for cancer, type 2 diabetes, osteoarthritis, cardiovascular diseases, and other age-related pathologies. Here, we give a detailed description of the interplay of chronic age-related pathologies with the remodeling of the extracellular matrix during disease development and progression. Longevity-promoting signaling pathways slow or prevent age-related diseases. In particular, we focus on the mTOR signaling pathway, sirtuins, and canonical longevity-promoting transcription factors, such as FOXO, NF-κB, and Nrf2. We extend our analysis using chromatin immunoprecipitation (ChIP) sequencing and transcriptomic data and report that many established and emerging longevity-promoting transcription factors, such as CREB1, FOXO1,3, GATA1,2,3,4, HIF1A, JUN, KLF4, MYC, NFE2L2/Nrf2, RELA/NF-κB, REST, STAT3,5A, and TP53/p53, directly regulate many extracellular matrix genes and remodelers. We propose that modulation of these pathways increases lifespan and protects from age-related diseases in part due to their effects on extracellular matrix remodeling. Therefore, to successfully treat age-related diseases, it is necessary to better understand the connection between extracellular matrix components and longevity pathways.

GJA1 reverses arsenic-induced EMT via modulating MAPK/ERK signaling pathway

Arsenic is known as a well-established human carcinogen. Gap Junction Protein Alpha 1 (GJA1) is a multifunction protein that forms gap junction channels and is important for intercellular communication. Recently, its aberrant expression has been shown to associate with cancer recurrence and metastatic spread. However, whether GJA1 plays a role in arsenic carcinogenesis remains unknown. Here, we demonstrated that chronic exposure of human bronchial epithelial BEAS-2B cells to sodium arsenite promoted epithelial-mesenchymal transition (EMT) via increasing the expression of EMT inducer S100A4 and activation of MAPK/ERK signaling. In vitro and in vivo experiments showed that chronic exposure to sodium arsenite reduced GJA1 expression. Forced expression of GJA1 inhibited sodium arsenite-induced EMT via suppressing MAPK/ERK signaling whereas GJA1 knockdown produced an opposite effect. Intriguingly, chronic exposure to sodium arsenite increased autophagy flux. Inhibition of autophagy by pharmacological intervention or genetic deletion of autophagy core gene Beclin-1 upregulated GJA1 expression. These results suggested that GJA1 restrained the carcinogenic effect of sodium arsenite by limiting MAPK/ERK signaling, and GJA1 expression was decreased by arsenic-activated autophagy. In addition, interventions directed at enhancing the level or functional activity of GJA1 could be of preventive and therapeutic interest.

Blocking connexin 43 and its promotion of ATP release from renal tubular epithelial cells ameliorates renal fibrosis

Whether metabolites derived from injured renal tubular epithelial cells (TECs) participate in renal fibrosis is poorly explored. After TEC injury, various metabolites are released and among the most potent is adenosine triphosphate (ATP), which is released via ATP-permeable channels. In these hemichannels, connexin 43 (Cx43) is the most common member. However, its role in renal interstitial fibrosis (RIF) has not been fully examined. We analyzed renal samples from patients with obstructive nephropathy and mice with unilateral ureteral obstruction (UUO). Cx43-KSP mice were generated to deplete Cx43 in TECs. Through transcriptomics, metabolomics, and single-cell sequencing multi-omics analysis, the relationship among tubular Cx43, ATP, and macrophages in renal fibrosis was explored. The expression of Cx43 in TECs was upregulated in both patients and mice with obstructive nephropathy. Knockdown of Cx43 in TECs or using Cx43-specific inhibitors reduced UUO-induced inflammation and fibrosis in mice. Single-cell RNA sequencing showed that ATP specific receptors, including P2rx4 and P2rx7, were distributed mainly on macrophages. We found that P2rx4- or P2rx7-positive macrophages underwent pyroptosis after UUO, and in vitro ATP directly induced pyroptosis by macrophages. The administration of P2 receptor or P2X7 receptor blockers to UUO mice inhibited macrophage pyroptosis and demonstrated a similar degree of renoprotection as Cx43 genetic depletion. Further, we found that GAP 26 (a Cx43 hemichannel inhibitor) and A-839977 (an inhibitor of the pyroptosis receptor) alleviated UUO-induced fibrosis, while BzATP (the agonist of pyroptosis receptor) exacerbated fibrosis. Single-cell sequencing demonstrated that the pyroptotic macrophages upregulated the release of CXCL10, which activated intrarenal fibroblasts. Cx43 mediates the release of ATP from TECs during renal injury, inducing peritubular macrophage pyroptosis, which subsequently leads to the release of CXCL10 and activation of intrarenal fibroblasts and acceleration of renal fibrosis.

Expression of Pannexin 1 in the Human Kidney during Embryonal, Early Fetal and Postnatal Development and Its Prognostic Significance in Diabetic Nephropathy

Pannexins are transmembrane glycoproteins that constitute channels involved in purinergic signaling through ATP release from cells in various physiological and pathological processes. In this study, the distribution of Panx1 expression in different cell populations of healthy postnatal human kidneys and during human embryonic and early fetal development was investigated by double immunohistochemistry. In addition, the glomerular and tubular expression of Panx1 was examined in patients with type 2 diabetes mellitus (DM2) and the control group, and renal Panx1 expression was correlated with serum creatinine. In the 6th week of embryonic development (DW), Panx1 expression was found in mesonephric glomeruli and mesonephric tubules. At the transition from 6th to 7th DW, Panx1 immunoreactivity was found in the mesonephric tubules and mesonephric duct, as well as in the metanephric ureteric bud and ampullae. In the 7th DW, strong Panx1 immunoreactivity was observed in the developing ureteric bud in the metanephros, whereas no Panx1 immunoreactivity was found in the metanephric cup. In the 8th DW, Panx1 expression was also found in the ureteric bud of the metanephros, the renal vesicle and comma-shaped nephron, and the epithelial cells of Bowman’s capsule. Expression of Panx1 was found at an early stage in both the paramesonephric duct and the mesonephric duct and diminished toward the 8th DW. During the 6th–10th DW, colocalization of Panx1 with alpha smooth actin (aSMA) was found in developing blood vessels. In the postnatal kidney, strong Panx1 immunoreactivity was present in medullary and cortical collecting duct cells, renin-producing cells, and proximal tubules. Very weak Panx1 immunoreactivity was found in certain distal tubule cells and the thin descending limbs of the loop of Henle. Panx1 immunoreactivity was also found in nephrin-immunoreactive podocytes. Panx1 was not colocalized with aSMA immunoreactivity in the vessels of the postnatal human kidney, but it was present in the endothelium. A significant positive correlation was found between Panx1 expression in glomeruli and serum creatinine only in diabetic patients and was not found in the nondiabetic group. The spatiotemporal expression of Panx1 during the early stages of human kidney development supports its possible role in cellular differentiation, migration, and positioning in the developing human kidney. In addition, our data suggest that glomerular Panx1 expression is a potential indicator of worsening renal function in patients with type 2 diabetes.

Connexin32 ameliorates epithelial-to-mesenchymal-transition in diabetic renal tubular via inhibiting NOX4

Renal tubulointerstitial fibrosis (RIF), characterized by epithelial-to-mesenchymal transition (EMT) of renal tubular epithelial cells (TECs), is the main cause of diabetic renal fibrosis. Oxidative stress plays a pivotal role in the development of diabetic RIF. Connexin32 (Cx32), prominently expressed in renal TECs, has emerged as an important player in the regulation of oxidative stress. However, the role of Cx32 in diabetic RIF has not been explored yet. Here, we showed that adenovirus-mediated Cx32 overexpression suppressed EMT to ameliorate RIF and renal function in STZ-induced diabetic mice, while knockout (KO) of Cx32 exacerbated RIF in diabetic mice. Moreover, overexpression of Cx32 inhibited EMT and the production of extra cellular matrix (ECM) in high glucose (HG) induced NRK-52E cells, whereas knockdown of Cx32 showed the opposite effects. Furthermore, we showed that NOX4, the main source of ROS in renal tubular, was down-regulated by Cx32. Mechanistically, Cx32 down-regulated the expression of PKC alpha in a carboxyl-terminal-dependent manner, thereby inhibiting the phosphorylation at Thr147 of p22phox triggered by PKC alpha, which ultimately repressed the formation of the p22phox-NOX4 complex to reduce the protein level of NOX4. Thus, we establish Cx32 as a novel target and confirm the protection mechanism in RIF.

Regulation of lung epithelial cell senescence in smoking-induced COPD/emphysema by microR-125a-5p via Sp1 mediation of SIRT1/HIF-1a

Chronic obstructive pulmonary disease (COPD) affects the health of more than 300 million people worldwide; at present, there is no effective drug to treat COPD. Smoking is the most important risk factor, but the molecular mechanism by which smoking causes the disease is unclear. The senescence of lung epithelial cells is related to development of COPD. Regulation of miRNAs is the main epigenetic mechanism related to aging. β-Galactose staining showed that the lung tissues of smokers have a higher degree of cellular senescence, and the expression of miR-125a-5p is high. This effect is obvious for smokers with COPD/emphysema, and there is a negative correlation between miR-125a-5p levels and values for forced expiratory volume in one second (FEV1)/forced vital capacity (FVC). After Balb/c mice were chronically exposed to various concentrations of cigarette smoke (CS), plethysmography showed that lung function was impaired, lung tissue senescence was increased, and the senescence-associated secretory phenotype (SASP) in bronchoalveolar lavage fluid was increased. For mouse lung epithelial (MLE)-12 cells treated with cigarette smoke extract (CSE), Sp1 and SIRT1 levels were low, HIF-1α acetylation levels were high, and cell senescence and secretion of SASP factors were elevated. Down-regulation of miR-125a-5p or up-regulation of Sp1 reversed these effects. In addition, compared with mice exposed to CS, knockdown of miR-125a-5p reduced lung epithelial cell senescence and COPD/emphysema. Therefore, in smoking-induced COPD, elevated miR-125a-5p participates in the senescence of lung epithelial cells through Sp1/SIRT1/HIF-1α. These findings provide evidence related to the pathogenesis of COPD/emphysema caused by chronic smoking.

SIRT1-SIRT7 in Diabetic Kidney Disease: Biological Functions and Molecular Mechanisms

Diabetic kidney disease (DKD) is a severe microvascular complication in patients with diabetes and is one of the main causes of renal failure. The current clinical treatment methods for DKD are not completely effective, and further exploration of the molecular mechanisms underlying the pathology of DKD is necessary to improve and promote the treatment strategy. Sirtuins are class III histone deacetylases, which play an important role in many biological functions, including DNA repair, apoptosis, cell cycle, oxidative stress, mitochondrial function, energy metabolism, lifespan, and aging. In the last decade, research on sirtuins and DKD has gained increasing attention, and it is important to summarize the relationship between DKD and sirtuins to increase the awareness of DKD and improve the cure rates. We have found that miRNAs, lncRNAs, compounds, or drugs that up-regulate the activity and expression of sirtuins play protective roles in renal function. Therefore, in this review, we summarize the biological functions, molecular targets, mechanisms, and signaling pathways of SIRT1-SIRT7 in DKD models. Existing research has shown that sirtuins have the potential as effective targets for the clinical treatment of DKD. This review aims to lay a solid foundation for clinical research and provide a theoretical basis to slow the development of DKD in patients.

Exploring the Potential Mechanism of Tang-Shen-Ning Decoction against Diabetic Nephropathy Based on the Combination of Network Pharmacology and Experimental Validation

Background

Diabetic nephropathy (DN) has become one of the leading causes of the end-stage renal disease (ESRD). Tang-Shen-Ning (TSN) decoction, an effective Traditional Chinese formula for DN, can improve the renal function and inhibit renal fibrosis in DN. However, its potential mechanism is still unexplored.

Methods

A network pharmacology approach was employed in this study, including screening for differential expressed genes of DN (DN-DEGs), protein-protein interaction (PPI) network analysis, and GO and KEGG enrichment analysis. Besides, a rat model was established to verify the potential effect of TSN in DN.

Results

Twenty-three TSN-related DN-DEGs targets were identified. These genes were associated with decreased glomerular filtration rate (GFR) DN. The enrichment analysis suggested that the inhibition of renal fibrosis and inflammation through growth factors and chemokines is the potential mechanism through which TSN improves DN. TSN reduced renal fibrosis and improved pathological damage in the kidney in vivo through the regulation of GJA1, CTGF, MMP7, and CCL5, which are genes associated with ECM deposition.

Conclusion

This study revealed that TSN improves DN through a multicomponent, multitarget, and multipathway synergy. We provide a scientific basis for potential targets for TSN use to treat DN, yet further experimental validation is needed to investigate these targets and mechanisms.

USP9X deubiquitinates connexin43 to prevent high glucose-induced epithelial-to-mesenchymal transition in NRK-52E cells

Epithelial-to-mesenchymal transition (EMT) plays an important role in diabetic nephropathy (DN). Ubiquitin-specific protease 9X (USP9X/FAM) is closely linked to TGF-β and fibrosis signaling pathway. However, it remains unknown whether USP9X is involved in the process of EMT in DN. Our previous study has shown that connexin 43 (Cx43) activation attenuated the development of diabetic renal tubulointerstitial fibrosis (RIF). Here, we showed that USP9X is a novel negative regulator of EMT and the potential mechanism is related to the deubiquitination and degradation of Cx43. To explore the potential regulatory mechanism of USP9X, the expression and activity of USP9X were studied by CRISPR/Cas9-based synergistic activation mediator (SAM) system, short hairpin RNAs, and selective inhibitor. The following findings were observed: (1) Expression of USP9X was down-regulated in the kidney tissue of db/db diabetic mice; (2) overexpression of USP9X suppressed high glucose (HG)-induced expressions of EMT markers and extra cellular matrix (ECM) in NRK-52E cells; (3) depletion of USP9X further aggravated EMT process and ECM production in NRK-52E cells; (4) USP9X deubiquitinated Cx43 and suppressed its degradation to regulate EMT process; (5) USP9X deubiquitinated Cx43 by directly binding to the C-terminal Tyr²⁸⁶ of Cx43. The current study determined the protective role of USP9X in the process of EMT and the molecular mechanism clarified that the protective effects of USP9X on DN were associated with the deubiquitination of Cx43.

New insights into diabetes mellitus and its complications: a narrative review

Diabetes is a metabolic disorder accompanied by complications of multiple organs and systems. Diabetic nephropathy (DN) is one of the most prevalent lethal complications of diabetes. Although numerous biomarkers have be clarified for early diagnosis of DN, renal biopsy is still the gold standard. As a noninvasive imaging diagnostic method, blood oxygen level-dependent (BOLD) MRI can help understand the kidney oxygenation status and fibrosis process and monitor the efficacy of new drugs for DN via monitoring renal blood oxygen levels. Recent studies have shown that noncoding RNAs including microRNAs (miRNAs), long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs) were all involved in the development of DN, which could be exploited as therapeutic strategy to control DN. Dyslipidemia is also a common complication of diabetes. Apolipoprotein M (apoM), as a novel apolipoprotein, may be related to the development and progression of diabetes, which need to further investigation. Obstructive sleep apnea (OSA) is another common complication of diabetes and is an independent risk factor for cardiovascular disease (CVD). At present, there is no simple, effective and rapid diagnostic method to early identification of OSA in patients with diabetes. A nomogram consisted of waist-to-hip ratio, smoking status, body mass index, serum uric acid, HOMA-IR and history of fatty liver might be an alternative method to early assess the risk of OSA.