Membrane Attack Complex C5b-9 Promotes Renal Tubular Epithelial Cell Pyroptosis in Trichloroethylene-Sensitized Mice

Tanshinone IIA reduces tubulointerstitial fibrosis by suppressing GSDMD-mediated pyroptosis

CONTEXT

Tanshinone IIA (Tan IIA), a bioactive compound derived from the traditional Chinese herb Salvia miltiorrhiza (Family Lamiaceae, Authority Bunge), is well-known for its protective effects in various kidney diseases. However, its role in obstructive nephropathy has not been thoroughly investigated.

OBJECTIVE

This study aimed to explore the protective effects of Tan IIA in a mouse model of unilateral ureteral obstruction (UUO) and to elucidate the cellular and molecular mechanisms underlying these effects.

MATERIALS AND METHODS

Gasdermin D (GSDMD) knockout mice and their wild-type (WT) littermates underwent UUO surgery, with Tan IIA treatment administered 24 h prior. Human proximal tubular cells (HK-2 cells) were treated with TGF-β1 to induce fibrosis (50 ng/mL for 24 h), followed by Tan IIA treatment (5 μM) for an additional 3 h.

RESULTS

Tan IIA significantly reduced the expression of extracellular matrix (ECM) components, including collagen I, α-smooth muscle actin (α-SMA), vimentin and fibronectin, in UUO mice. Tan IIA attenuated GSDMD-mediated pyroptosis. However, in GSDMD knockout mice subjected to UUO, the protective effects of Tan IIA on ECM gene expression and collagen deposition in the tubular interstitium were reduced. In vitro studies showed that Tan IIA reduced GSDMD activation and fibronectin protein expression in HK-2 cells.

DISCUSSION AND CONCLUSIONS

Tan IIA may mitigate GSDMD-mediated pyroptosis in renal tubular epithelial cells (RTECs) and reduce kidney fibrosis, highlighting its potential as a therapeutic strategy to prevent the progression of kidney disease after ureteral obstruction.

Monocyte/macrophage pyroptosis and C5b-9-induced cyst enlargement in Pkd1-/- mice

BACKGROUND AND HYPOTHESIS

The levels of C5b-9, terminal products of complement activation, were significantly elevated in autosomal dominant polycystic kidney disease (ADPKD). However, the precise mechanisms by which C5b-9 facilitates cyst growth remain incompletely elucidated.

METHODS

Three groups of chronic-onset Pkd1-/- mice were established: one group received intravenous injections of 0.5 mg/kg C5b-9, another was administered 1.0 mg/kg monoclonal anti-C9 antibodies, and a control group received 1 mg/kg IgG isotype control. All treatments were administered biweekly for two months (postnatal day 180-240). Renal macrophages from distinct subsets were sorted using fluorescence-activated cell sorting. To deplete macrophages, liposome clodronate was injected intraperitoneally. Sublethal irradiation followed by bone marrow reconstruction was performed in Pkd1-/- mice to evaluate the role of bone marrow-derived macrophages (BMDMs) in ADPKD progression.

RESULTS

(i) In vitro, sublytic C5b-9 did not affect the viability of renal tubular epithelial cells, but significantly induced M1-like polarization and pyroptosis of BMDMs. (ii) In vivo, C5b-9 notably triggered pyroptosis of Ly6C+ monocytes and a reduction in circulating monocyte numbers as cysts enlarged. (iii) Residual Ly6C+ monocytes infiltrated renal tissues and differentiated into Ly6C+ macrophages, which exhibited a greater susceptibility to pyroptosis compared to Ly6C- macrophages. (iv) Although limited evidence has recently suggested that Ly6C- monocytes may also be affected by C5b-9, upregulation of CCR2 in Ly6C- macrophages was observed in C5b-9-treated Pkd1-/- mice, implying that Ly6C- monocytes could represent a significant source of M2 macrophages.

CONCLUSIONS

C5b-9 infusion promoted renal tubular epithelial cell proliferation by inducing pyroptosis of Ly6C+ monocytes/macrophages, contributing to progressive cyst enlargement in chronic-onset PKD mice.

Advances in Research on the Release of von Willebrand Factor from Endothelial Cells through the Membrane Attack Complex C5b-9 in Sepsis

Sepsis, a lethal organ dysfunction syndrome driven by aberrant host responses to infection, intertwines excessive inflammatory responses and dysregulated coagulation processes in its pathophysiology. Emerging research reveals the complement terminal membrane attack complex C5b-9 orchestrates ultralarge von Willebrand factor (ULVWF) release from vascular endothelial cells (ECs) through multifaceted mechanisms: C5b-9 compromises EC membrane integrity, activates calcium influx cascades, and provokes NLRP3 inflammasome signaling, triggering massive exocytosis of ULVWF stored within Weibel-Palade bodies (WPBs). When ADAMTS13 activity falters, undegraded ULVWF complexes with platelets to spawn microthrombi, precipitating microvascular occlusion and multiorgan collapse. Strikingly, elevated plasma von Willebrand factor (vWF) antigen levels in sepsis patients correlate robustly with endothelial injury, thrombocytopenia, and mortality-underscoring C5b-9-driven vWF release as a linchpin of septic coagulopathy. Current therapeutic strategies targeting these pathways, including recombinant ADAMTS13 (rhADAMTS13), N-acetylcysteine (NAC), and complement inhibitors like eculizumab, face limitations in clinical translation, necessitating further validation of their efficacy. Additionally, investigating complement regulatory molecules such as CD59 may unlock novel therapeutic avenues. Deciphering the intricate interplay within the C5b-9-vWF axis and advancing precision therapies hold transformative potential for ameliorating sepsis outcomes.

FTO mediates the diabetic kidney disease progression through regulating the m6A modification of NLRP3

BACKGROUND

The objective of our research was to investigate the specific mechanism of FTO in diabetic kidney disease (DKD) progression.

METHODS

The DKD model was established with renal tubular epithelial HK-2 cells and mice in vitro and in vivo. The N6-methyladenosine (m6A) content in cells was detected using dot plot assay and the m6A levels of NLRP3 was detected with the MeRIP assay. The mRNA and protein levels were tested with real-time reverse transcriptase-polymerase chain reaction (RT-qPCR) and western blot. The IL-1β and IL-18 levels were assessed with enzyme-linked immunosorbent assay (ELISA). The cell viability was measured by cell counting kit (CCK)-8 assay and cell pyroptosis was determined with Annexin V and propidium iodide (PI) double staining followed by flow cytometry analysis. RNA-binding protein immunoprecipitation (RIP) and dual luciferase reporter assays were conducted to detect the interaction between FTO and NLRP3. m6A levels were detected by Me-RIP assay. The renal injury was measured by observing the renal morphology and urine and blood levels of relevant indicators.

RESULTS

The results indicated that high glucose treatment induced HK-2 cell pyroptosis. m6A levels were prominently elevated in high glucose treated HK-2 cells while FTO expression were significantly down-regulated. FTO over-expression promoted cell viability but inhibited pyroptosis of HK-2 cells under high glucose (HG) treatment. Moreover, FTO could inhibit NLRP3 expression. RIP and Me-RIP assays indicated that FTO could bind with NLRP3 and regulate its m6A modification level. Further luciferase assay confirmed that FTO binds with the 233-237 bp region of NLRP3. NLRP3 neutralized the function of FTO in the HG stimulated HK-2 cells. In vivo, the H&E staining showed that FTO over-expression alleviated the kidney injury and suppressed the pyroptosis induced by DKD.

CONCLUSION

We found that FTO could inhibit the DKD progression in vivo and in vitro by regulated the m6A modification of NLRP3.

IP3R-dependent mitochondrial dysfunction mediates C5b-9-induced ferroptosis in trichloroethylene-caused immune kidney injury

Patients with occupational medicamentose-like dermatitis due to trichloroethylene often suffer from immune kidney injury. Our previous study reveals that C5b-9-dependent cytosolic Ca2+ overload-induced ferroptosis is involved in trichloroethylene sensitized kidney injury. However, how C5b-9 causes cytosolic Ca2+ rise and the specific mechanism whereby overloaded Ca2+ induces ferroptosis remain unknown. The purpose of our study was to explore the role of IP3R-dependent mitochondrial dysfunction in C5b-9 mediated ferroptosis in trichloroethylene sensitized kidney. Our results showed that IP3R was activated, and mitochondrial membrane potential was decreased in the renal epithelial cells of trichloroethylene-sensitized mice, and these changes were antagonized by CD59, a C5b-9 inhibitory protein. Moreover, this phenomenon was reproduced in a C5b-9-attacked HK-2 cell model. Further investigation showed that RNA interference with IP3R not only alleviated C5b-9-induced cytosolic Ca2+ overload and mitochondrial membrane potential loss but also attenuated C5b-9-induced ferroptosis in HK-2 cells. Mechanistically, IP3R-dependent cytosolic Ca2+ overload activated the mitochondrial permeability transition pore, resulting in the loss of mitochondrial membrane potential and ferroptosis of HK-2 cells. Finally, cyclosporin A, a mitochondrial permeability transition pore inhibitor, not only ameliorated IP3R-dependent mitochondrial dysfunction but also blocked C5b-9-induced ferroptosis. Taken together, these results suggest that IP3R-dependent mitochondrial dysfunction plays an important role in trichloroethylene sensitized renal tubular ferroptosis.