Targeting the transmembrane cytokine co-receptor neuropilin-1 in distal tubules improves renal injury and fibrosis.

Neuropilin-1 (NRP1), a co-receptor for various cytokines, including TGF-ß, has been identified as a potential therapeutic target for fibrosis. However, its role and mechanism in renal fibrosis remains elusive. Here, we show that NRP1 is upregulated in distal tubular (DT) cells of patients with transplant renal insufficiency and mice with renal ischemia-reperfusion (I-R) injury. Knockout of Nrp1 reduces multiple endpoints of renal injury and fibrosis. We find that Nrp1 facilitates the binding of TNF-α to its receptor in DT cells after renal injury. This signaling results in a downregulation of lysine crotonylation of the metabolic enzyme Cox4i1, decreases cellular energetics and exacerbation of renal injury. Furthermore, by single-cell RNA-sequencing we find that Nrp1-positive DT cells secrete collagen and communicate with myofibroblasts, exacerbating acute kidney injury (AKI)-induced renal fibrosis by activating Smad3. Dual genetic deletion of Nrp1 and Tgfbr1 in DT cells better improves renal injury and fibrosis than either single knockout. Together, these results reveal that targeting of NRP1 represents a promising strategy for the treatment of AKI and subsequent chronic kidney disease.

Comprehensive Pan-Cancer Analysis of Connexin 43 as a Potential Biomarker and Therapeutic Target in Human Kidney Renal Clear Cell Carcinoma (KIRC).

Background and Objectives: Connexin 43 (Cx43) is involved in the transfer of small signaling molecules between neighboring cells, thereby exerting a major influence on the initiation and progression of tumorigenesis. However, there is a lack of systematic research on Cx43 expression and its predictive role in clinical diagnosis and prognosis in pan-cancer. Materials and Methods: Several biological databases were used to evaluate the expression levels of GJA1 (encoding Cx43) and its diagnostic and prognostic significance in pan-cancer. We targeted kidney renal clear cell carcinoma (KIRC) and investigated the relationship between GJA1 expression and different clinical features of KIRC patients. Then, we performed cell-based experiments to partially confirm our results and predicted several proteins that were functionally related to Cx43. Results: The expression of GJA1 has a high level of accuracy in predicting KIRC. High GJA1 expression was remarkably correlated with a favorable prognosis, and this expression was reduced in groups with poor clinical features in KIRC. Cell experiments confirmed the inhibitory effects of increased GJA1 expression on the migratory capacity of human renal cancer (RCC) cell lines, and protein-protein interaction (PPI) analysis predicted that CDH1 and CTNNB1 were closely related to Cx43. Conclusions: GJA1 could be a promising independent favorable prognostic factor for KIRC, and upregulation of GJA1 expression could inhibit the migratory capacity of renal cancer cells.

The probiotic Lactobacillus casei Zhang-mediated correction of gut dysbiosis ameliorates peritoneal fibrosis by suppressing macrophage-related inflammation via the butyrate/PPAR-γ/NF-κB pathway.

Peritoneal fibrosis is a complication of long-term peritoneal dialysis (PD) that restricts its clinical application for the treatment of end-stage renal disease. Lactobacillus casei Zhang (LCZ), a probiotic strain isolated from traditional fermented koumiss, exhibits health benefits such as anti-inflammatory and antioxidative effects, improvement of insulin resistance and mitigation of renal injury. However, whether LCZ can prevent peritoneal fibrosis remains unknown. Here, we assessed the effects of LCZ in a mouse model of PD-induced peritoneal fibrosis. Our results showed that the administration of LCZ significantly ameliorated peritoneal fibrosis in experimental mice. Macrophage infiltration, inflammatory M1 polarization and inflammatory cytokines in peritoneal dialysis effluents were effectively reduced by LCZ. Meanwhile, LCZ corrected gut dysbiosis and enriched beneficial bacteria that produce short-chain fatty acids, specifically Dubosiella, Lachnospiraceae, Parvibacter, and Butyricicoccus. Correspondingly, the local butyrate level in peritoneal dialysis effluents was significantly elevated by LCZ. Mechanistically, we found activation of PPARγ and inhibition of the NF-κB pathway in LCZ-treated mice, an observation that was replicated in a butyrate-treated macrophage cell line. In conclusion, our study suggests that LCZ is beneficial for preventing PD-induced peritoneal fibrosis through modulating the gut microbiota, enhancing butyrate production, activating PPARγ, and suppressing NF-κB-mediated inflammation.

Effects of probiotics on non-alcoholic fatty liver disease: a review of human clinical trials.

Non-alcoholic fatty liver disease (NAFLD) is a global public health issue, of which the prevalence is about 25% worldwide. The incidence of NAFLD is increasing in patients with obesity, type 2 diabetes (T2DM) and the metabolic syndrome. The crosstalk between gut microbiota and metabolism-related diseases has been raised great concern. Patients with NAPLD were observed with disruption of gut microbiota. Several researches showed that gut microbiota was the determination in the progression of NAFLD by the experiments using fecal microbiota transplants. The application of probiotics, as one of the most important strategies for the regulation of gut microbiota disorder, have been explored whether it is beneficial to gut-related diseases of intestine-distal organs. Some probiotics were showed to improve the liver parameters and phenotype in patients with NAFLD. The oral intake of them might become the effective management for the prevention and treatment of NAFLD. In this review, we summarized the human clinical trials focusing on the effects of probiotics on NAFLD to give some evidential reference for the administration of NAFLD.

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.

Gut Dysbiosis and Kidney Diseases.

Gut dysbiosis is defined as disorders of gut microbiota and loss of barrier integrity, which are ubiquitous on pathological conditions and associated with the development of various diseases. Kidney diseases are accompanied with gut dysbiosis and metabolic disorders, which in turn contribute to the pathogenesis and progression of kidney diseases. Microbial alterations trigger production of harmful metabolites such as uremic toxins and a decrease in the number of beneficial ones such as SCFAs, which is the major mechanism of gut dysbiosis on kidney diseases according to current studies. In addition, the activation of immune responses and mitochondrial dysfunction by gut dysbiosis, also lead to the development of kidney diseases. Based on the molecular mechanisms, modification of gut dysbiosis via probiotics, prebiotics and synbiotics is a potential approach to slow kidney disease progression. Fecal microbiota transplantation (FMT) and genetic manipulation of the gut microbiota are also promising choices. However, the clinical use of probiotics in kidney disease is not supported by the current clinical evidence. Further studies are necessary to explore the causal relationships of gut dysbiosis and kidney diseases, the efficiency and safety of therapeutic strategies targeting gut-kidney axis.

Lymphocytes: Versatile Participants in Acute Kidney Injury and Progression to Chronic Kidney Disease.

Background: Acute kidney injury (AKI) remains a major global public health concern due to its high morbidity and mortality. The progression from AKI to chronic kidney disease (CKD) makes it a scientific problem to be solved. However, it is with lack of effective treatments. Summary: Both innate and adaptive immune systems participate in the inflammatory process during AKI, and excessive or dysregulated immune responses play a pathogenic role in renal fibrosis, which is an important hallmark of CKD. Studies on the pathogenesis of AKI and CKD have clarified that renal injury induces the production of various chemokines by renal parenchyma cells or resident immune cells, which recruits multiple-subtype lymphocytes in circulation. Some infiltrated lymphocytes exacerbate injury by proinflammatory cytokine production, cytotoxicity, and interaction with renal resident cells, which constructs the inflammatory environment and induces further injury, even death of renal parenchyma cells. Others promote tissue repair by producing protective cytokines. In this review, we outline the diversity of these lymphocytes and their mechanisms to regulate the whole pathogenic stages of AKI and CKD; discuss the chronological responses and the plasticity of lymphocytes related to AKI and CKD progression; and introduce the potential therapies targeting lymphocytes of AKI and CKD, including the interventions of chemokines, cytokines, and lymphocyte frequency regulation in vivo, adaptive transfer of ex-expanded lymphocytes, and the treatments of gut microbiota or metabolite regulations based on gut-kidney axis. Key Message: In the process of AKI and CKD, T helper (Th) cells, innate, and innate-like lymphocytes exert mainly pathogenic roles, while double-negative T (DNT) cells and regulatory T cells (Tregs) are confirmed to be protective. Understanding the mechanisms by which lymphocytes mediate renal injury and renal fibrosis is necessary to promote the development of specific therapeutic strategies to protect from AKI and prevent the progression of CKD.

Combination of ultra-low dose rituximab and low dose tacrolimus versus tacrolimus alone in the treatment of non-responsive idiopathic membranous nephropathy: a Chinese retrospective cohort study.

INTRODUCTION: Some patients with idiopathic membranous nephropathy (iMN) do not respond to cyclophosphamide plus steroids treatment, and we define them as non-responsive iMN. The combined regimen of rituximab (RTX) and tacrolimus (TAC) has an excellent effect on this kind of non-responsive iMN patients; however, the optimal dose is still unclear. In this retrospective study, we comapred the efficacy and safety of ultra-low dose RTX plus low-dose TAC therapy versus standard TAC monotherapy in patients with non-responsive iMN. MATERIALS AND METHODS: Sixty-seven Chinese non-responsive iMN patients were included. There were 41 patients received standard tacrolimus monotherapy (TAC) and 26 patients received ultra-low dose rituximab plus low dose tacrolimus (RTX/TAC) combination therapy. All patients were observed for 12 months. RESULTS: 18 patients (18/26, 69.2%) in the RTX/TAC group and 17 patients (17/41, 41.5%) in the TAC group achieved clinical response after 12-month follow-up (P=0.044). The median time for achieving response in the two groups was 3.0 months. As indicated by Kaplan-Meier curve, the response rate in the RTX/TAC group was higher than that in the TAC group (P=0.015). 24-hour proteinuria, serum albumin, estimated glomerular filtration rate (eGFR) and serum creatinine in the two groups were comparable at baseline; howerver, after 12-month follow up, they were significantly improved in the RTX/TAC group compared with the TAC group (P<0.05). B-cell depletion was achieved in all patients in the RTX/TAC group during the whole follow-up period. Pneumonia, urinary tract infections and glucose intolerance were the major side effects observed in this study. All adverse events were mild, and the cumulative incidence was lower in the RTX/TAC group compared with that in the TAC group (9 (34.6%) vs 27 (65.9%), P=0.023). CONCLUSION: The combination of ultra-low dose rituximab and low dose tacrolimus is more effective in inducing proteinuria response, improving eGFR and serum albumin in non-responsive iMN patients than standard tacrolimus monotherapy. The combined treatment also has higher safty.

The probiotic L. casei Zhang slows the progression of acute and chronic kidney disease.

The relationship between gut microbial dysbiosis and acute or chronic kidney disease (CKD) is still unclear. Here, we show that oral administration of the probiotic Lactobacillus casei Zhang (L. casei Zhang) corrected bilateral renal ischemia-reperfusion (I/R)-induced gut microbial dysbiosis, alleviated kidney injury, and delayed its progression to CKD in mice. L. casei Zhang elevated the levels of short-chain fatty acids (SCFAs) and nicotinamide in the serum and kidney, resulting in reduced renal inflammation and damage to renal tubular epithelial cells. We also performed a 1-year phase 1 placebo-controlled study of oral L. casei Zhang use (Chinese clinical trial registry, ChiCTR-INR-17013952), which was well tolerated and slowed the decline of kidney function in individuals with stage 3-5 CKD. These results show that oral administration of L. casei Zhang, by altering SCFAs and nicotinamide metabolism, is a potential therapy to mitigate kidney injury and slow the progression of renal decline.

Exogenous bone marrow derived-putative endothelial progenitor cells attenuate ischemia reperfusion-induced vascular injury and renal fibrosis in mice dependent on pericytes.

Rationale: Capillaries are composed of endothelial cells and the surrounding mural cells, pericytes. Microvascular repair after injury involves not only the proliferation of endothelial cells but also pericyte-based vessel stabilization. Exogenous bone marrow derived-putative endothelial progenitor cells (b-pEPCs) have the potential for vascular repair; however, their effect on vascular structure stabilization and pericyte-related pathobiological outcomes in the injured kidney has not been fully examined. Methods: We applied ischemia-reperfusion (IR) to induce renal vascular injury and renal fibrosis in mice. Platelet-derived growth factor receptor ß (PDGFR-ß)-DTR-positive mice were generated to deplete pericytes, and exogenous b-pEPCs and the PDGFR-ß ligand, PDGF chain B (PDGF-BB), were employed to explore the relationship among b-pEPCs, pericytes, vascular repair, and early renal fibrosis. Results: Administration of b-pEPCs reduced IR-induced pericyte-endothelial detachment, pericyte proliferation, and myofibroblast transition via a paracrine mode, which preserved not only vascular stabilization but also ameliorated IR-initiated renal fibrosis. PDGF-BB upregulated the expression of PDGFR-ß, exacerbated vascular abnormality, and pericyte-myofibroblast transition, which were ameliorated by b-pEPCs administration. The exogenous b-pEPCs and their culture medium (CM) induced vascular injury protection, and renal fibrosis was blocked by selective deletion of pericytes. Conclusion: Exogenous b-pEPCs directly protect against IR-induced vascular injury and prevent renal fibrosis by inhibiting the activation of PDGFR-ß-positive pericytes.

Putative endothelial progenitor cells do not promote vascular repair but attenuate pericyte-myofibroblast transition in UUO-induced renal fibrosis.

BACKGROUND: Putative endothelial progenitor cells (pEPCs) have been confirmed to participate in alleviation of renal fibrosis in several ischaemic diseases. However, their mechanistic effect on renal fibrosis, which is characterized by vascular regression and further rarefaction-related pathology, remains unknown. METHODS: To explore the effect and molecular mechanisms by which pEPCs act on unilateral ureteral obstruction (UUO)-induced renal fibrosis, we isolated pEPCs from murine bone marrow. In vivo, pEPCs (2 × 105 cells/day) and pEPC-MVs (microvesicles) were injected into UUO mice via the tail vein. In vitro, pEPCs were co-cultured with renal-derived pericytes. Pericyte-myofibroblast transition was evaluated using the myofibroblast marker α-smooth muscle actin (α-SMA) and pericyte marker platelet-derived growth factor receptor ß (PDGFR-ß). RESULTS: Exogenous supply of bone marrow-derived pEPCs attenuated renal fibrosis by decreasing pericyte-myofibroblast transition without significant vascular repair in the UUO model. Our results indicated that pEPCs regulated pericytes and their transition into myofibroblasts via pEPC-MVs. Co-culture of pericytes with pEPCs in vitro suggested that pEPCs inhibit transforming growth factor-ß (TGF-ß)-induced pericyte-myofibroblast transition via a paracrine pathway. CONCLUSION: pEPCs effectively attenuated UUO-induced renal fibrosis by inhibiting pericyte-myofibroblast transition via a paracrine pathway, without promoting vascular repair.

GAG and collagen II attenuate glucocorticoid-induced osteoporosis by regulating NF-κB and MAPK signaling.

As a component of collagen II, glycosaminoglycan (GAG) has a relatively close relationship with bone metabolism. GAG and collagen II have been proven to promote connection of the bone trabecular structure. However, the exact mechanism remains unknown. In this study, we aimed to determine the concrete effect and the mechanism of GAG and collagen II on glucocorticoid-induced osteoporosis. We implanted prednisolone pellets subcutaneously in mice to mimic glucocorticoid-induced osteoporosis. GAG was administered intragastrically every day for 60 days. The results demonstrated a protective effect of GAG and collagen II on glucocorticoid-induced osteoporosis. Trabecular number and connection density increased after treatment with GAG and collagen II. We generated bone marrow-derived macrophages to explore the effect of GAG and collagen II on osteoclast differentiation. We collected cell protein and RNA in the presence of macrophage colony-stimulating factor (M-CSF) and receptor activator for nuclear factor-κB ligand (RANKL) and found that GAG and collagen II inhibited the NF-κB and MAPK pathways, thereby down-regulating osteoclast differentiation molecules such as matrix metallopeptidase 9 (MMP 9) and nuclear factor of activated T-cells, cytoplasmic 1 (NFATc-1). Our findings suggest that GAG and collagen II may have therapeutic potential of patients with glucocorticoid-induced osteoporosis in clinical settings.