Renal fibrosis is a common consequence of various progressive nephropathies, including obstructive nephropathy, and ultimately leads to kidney failure. Infiltration of inflammatory cells is a prominent feature of renal injury after draining blockages from the kidney, and correlates closely with the development of renal fibrosis. However, the underlying molecular mechanism behind the promotion of renal fibrosis by inflammatory cells remains unclear. Herein, we showed that unilateral ureteral obstruction (UUO) induced Gasdermin D (GSDMD) activation in neutrophils, abundant neutrophil extracellular traps (NETs) formation and macrophage-to-myofibroblast transition (MMT) characterized by α-smooth muscle actin (α-SMA) expression in macrophages. Gsdmd deletion significantly reduced infiltration of inflammatory cells in the kidneys and inhibited NETs formation, MMT and thereby renal fibrosis. Chimera studies confirmed that Gsdmd deletion in bone marrow-derived cells, instead of renal parenchymal cells, provided protection against renal fibrosis. Further, specific deletion of Gsdmd in neutrophils instead of macrophages protected the kidney from undergoing fibrosis after UUO. Single-cell RNA sequencing identified robust crosstalk between neutrophils and macrophages. In vitro, GSDMD-dependent NETs triggered p65 translocation to the nucleus, which boosted the production of inflammatory cytokines and α-SMA expression in macrophages by activating TGF-β1/Smad pathway. In addition, we demonstrated that caspase-11, that could cleave GSDMD, was required for NETs formation and renal fibrosis after UUO. Collectively, our findings demonstrate that caspase-11/GSDMD-dependent NETs promote renal fibrosis by facilitating inflammation and MMT, therefore highlighting the role and mechanisms of NETs in renal fibrosis.

Acute kidney injury (AKI) could progress to chronic kidney disease (CKD) and the AKI-CKD transition has major clinical significance. A growing body of evidence has unveiled the role of pyroptosis in kidney injury. We postulate that GSDMD and GSDME exert cumulative effects on the AKI-CKD transition by modulating different cellular responses. We established an AKI-CKD transition model induced by folic acid in wildtype (WT), Gsdmd^−/−, Gsdme^−/−, and Gsdmd^−/−Gsdme^−/- mice. Tubular injury, renal fibrosis and inflammatory responses were evaluated. In vitro studies were conducted to investigate the interplay among tubular cells, neutrophils, and macrophages. Double deletion of Gsdmd and Gsdme conferred heightened protection against AKI, mitigating inflammatory responses, including the formation of neutrophil extracellular traps (NETs), macrophage polarization and differentiation, and ultimately renal fibrosis, compared with wildtype mice and mice with single deletion of either Gsdmd or Gsdme. Gsdme, but not Gsdmd deficiency, shielded tubular cells from pyroptosis. GSDME-dependent tubular cell death stimulated NETs formation and prompted macrophage polarization towards a pro-inflammatory phenotype. Gsdmd deficiency suppressed NETs formation and subsequently hindered NETs-induced macrophage-to-myofibroblast transition (MMT). GSDMD and GSDME collaborate to contribute to AKI and subsequent renal fibrosis induced by folic acid. Synchronous inhibition of GSDMD and GSDME could be an innovative therapeutic strategy for mitigating the AKI-CKD transition.

Key Points: Gene deletions of Zbp1, Ripk3, and Mlkl reduced severity of oxalate-induced AKI. Mice with mutation or deletion in the Z-nucleic acid sensing domain (Zα) of Z-DNA binding protein 1 were protected from AKI. Z-DNA binding protein 1 sensed mitochondrial Z-DNA through its Zα domain, recruited receptor-interacting protein kinase 3 through receptor-interacting protein homotypic interaction motif, and activated mixed lineage kinase domain-like to induce necroptosis. Background: Calcium oxalate–induced acute kidney injury is a severe condition in which the kidneys suffer rapid damage due to the deposition of oxalate crystals. Known factors contributing to cell death induced by calcium oxalate include receptor-interacting protein kinase 3 (RIPK3) and mixed lineage kinase domain-like (MLKL) protein–dependent necroptosis, as well as necrosis involving peptidylprolyl isomerase F–mediated mitochondrial permeability transition. However, the detailed molecular mechanisms linking mitochondrial dysfunction to RIPK3 activation are not fully understood. Methods: Mice with gene knockout of Zbp1, Ripk3, or Mlkl and mice with mutations in the Z-nucleic acid sensing domain of Z-DNA binding protein 1 (ZBP1) or deletion of Zα1 were used in an oxalate-induced AKI model. Proximal renal tubule cells were isolated and cultured for further investigation. Human oxalate nephropathy biopsy samples were analyzed. Results: Specific gene deletions of Zbp1, Ripk3, or Mlkl in proximal renal tubules significantly reduced the severity of oxalate-induced AKI by preventing necroptosis and subsequent inflammation. Notably, mice with mutations in the Z-nucleic acid sensing domain of ZBP1 or deletion of Zα1 were protected from AKI. In cultured proximal tubular cells, calcium oxalate damaged mitochondria, accompanied by an increase in Bax and a decrease in BCL2 and transcription factor A, mitochondrial (TFAM), leading to the release of mitochondrial Z-DNA. ZBP1 sensed this mitochondrial Z-DNA and then recruited RIPK3 through the receptor-interacting protein homotypic interaction motifs, which in turn activated MLKL through RIPK3 phosphorylation, leading to necroptosis and contributing to AKI. Conclusions: ZBP1 plays a critical role in sensing mitochondrial Z-DNA and initiating RIPK3/MLKL-mediated necroptosis, contributing to the development of oxalate-induced AKI.

Bladder cancer, predominantly urothelial carcinoma, is a global health issue with increasing incidences and mortality. It poses significant diagnostic and therapeutic challenges due to its molecular heterogeneity and the limitations of current detection methods. Extracellular vesicles (EVs), including exosomes, play a crucial role in intercellular communication and have emerged as potential biomarkers and therapeutic agents in bladder cancer. This review focuses on the multifaceted roles of EVs in bladder cancer biology, their potential as diagnostic biomarkers, and their use in therapeutic strategies. We discuss how EVs reflect molecular subtypes of bladder cancer, participate in metabolic reprogramming and angiogenesis, and modulate cellular behavior. The review also highlights the advances in proteomic analysis of urinary and tissue-exudative EVs, identifying specific proteins and RNAs that could serve as non-invasive diagnostic markers. Furthermore, we explore the innovative use of EVs as natural nanocarriers for drug delivery in bladder cancer treatment, demonstrating their potential to enhance the efficacy of chemotherapy and selectively target cancer cells. The integration of EV-based diagnostics with traditional methods could lead to more personalized and effective bladder cancer management, emphasizing the need for further research and clinical validation.

Objectives: Microscopic polyangiitis (MPA) is a subgroup of ANCA-associated vasculitis (AAV), which is characterized by vascular endothelial cell damage caused by abnormally activated neutrophils. Dyslipidemia is associated with vascular endothelial cell injury, and the relationship between blood lipid levels and renal prognosis in MPA patients is not clear. We aim to investigate the correlation between blood lipid levels at diagnosis and renal prognosis in MPA patients. Methods: Firstly, we retrospectively included 110 patients diagnosed with MPA and the primary endpoint was the occurrence of end stage renal disease (ESRD). The association between blood lipids at diagnosis and renal outcome was evaluated with Cox regression analysis and survival analysis. Secondly, we explored the potential underlying mechanism of poor renal prognosis in patients with high triglycerides (TG) levels at diagnosis using data independent acquisition (DIA) quantitative proteomics. Results: During a median follow-up period of 23 months, 44 out of 110 patients (40%) developed ESRD. High serum TG at diagnosis was associated with ESRD development after adjusting for several confounding factors including age, gender, body mass index (BMI), hypertension, diabetes mellitus, estimated glomerular filtration rate (eGFR) and Birmingham Vasculitis Activity Score (BVAS). Serum very low-density lipoprotein (VLDL) demonstrated a marginal trend towards association with ESRD development. MPA patients with TG >1.45 mmol/L or VLDL > 0.66 mmol/L had significantly higher risk of ESRD development than those with TG ≤ 1.45 mmol/L or VLDL ≤ 0.66 mmol/L. DIA quantitative proteomics analysis suggested that patients with elevated TG levels and severe MPA had an upregulation of profibrotic pathways, inflammatory signaling, and complement and coagulation cascades, in contrast to those with lower TG levels and milder disease severity. Conclusions: In MPA patients, high TG or VLDL at diagnosis is associated with an increased risk of ESRD development. The potential mechanisms may be associated with the upregulation of profibrotic and inflammatory signaling pathways, and the activation of complement and coagulation cascades.

Background: Hypertension-related chronic kidney disease (HT-CKD) represents a global health threat exacerbated by modifiable metabolic risks. Elevated body mass index (BMI) and low physical activity contribute to the development of hypertension and subsequent HT-CKD. This study quantified the global burden of HT-CKD attributable to elevated BMI or low physical activity from 1990 to 2021 and projected future trends to 2050. Methods: Based on the Global Burden of Disease (GBD) 2021 data, deaths, disability-adjusted life years (DALYs), and age-standardized rates (ASRs) of HT-CKD attributable to elevated BMI or physical inactivity were analyzed. Temporal trends of the disease burden from 1990 to 2021 were assessed using a linear regression model. Future burden was forecasted to 2050 using the autoregressive integrated moving average (ARIMA) model and the exponential smoothing (ES) model. Results: In 2021, HT-CKD attributable to elevated BMI caused 179,788 deaths and 4.26 million DALYs globally, representing increases of 392.9 and 322.2% since 1990. HT-CKD attributable to low physical activity caused 4,479 deaths and 77,879 DALYs, with similar substantial growth. ASRs for deaths and DALYs showed significant global upward trends from 1990 to 2021 for both risk factors. North Africa had the highest ASRs of death and DALYs for HT-CKD attributable to elevated BMI. For HT-CKD attributable to low physical activity, North Africa and South Africa recorded the highest ASRs of death and DALYs, respectively. The overall disease burden increased with age, peaking in populations aged ≥80 and reaching maximal ASRs in the ≥95-year age group for both metrics and risk factors. Gender disparities revealed higher absolute deaths and DALYs in men for HT-CKD attributable to elevated BMI, but ASR growth was rapid in women for HT-CKD attributable to low physical activity. Across all sociodemographic index (SDI) quintiles, disease burden increased significantly. High-SDI regions showed the steepest ASR growth for HT-CKD attributable to elevated BMI and to low physical activity, whereas low-SDI regions had the slowest growth. Both ARIMA and ES models indicated continued increases in deaths and DALYs attributable to both risk factors from 2022–2050, especially for elevated BMI. Conclusion: Elevated BMI is the dominant metabolic driver of HT-CKD burden, with physical inactivity playing a significant role. This burden demonstrates pronounced demographic and geographic disparities, highlighting the need for urgent, targeted public health interventions to combat obesity and promote physical activity.