The NLRP3 inhibitor Mcc950 attenuates acute allograft damage in rat kidney transplants

NLRP3 inflammasome: significance and potential therapeutic targets to advance solid organ transplantation

INTRODUCTION

NOD-like receptor (NLR) family pyrin domain-containing 3 (NLRP3) inflammasome, integral to innate immunity, has become a pivotal figure in the inflammatory cascade.

AREAS COVERED

This article provides an overview of the NLRP3 inflammasome, reviewing its complicated structure, as well as the diverse signals that trigger its assembly. Furthermore, we explored the intricate relationship between the NLRP3 inflammasome and acute and chronic rejection in solid organ transplantation. Solid organ transplantation stands as a crucial medical intervention, yet its efficacy is challenged by immune-mediated complications, including acute rejection, ischemia-reperfusion injury, and chronic allograft rejection. We also investigated the encouraging potential of immunosuppressive therapies targeting NLRP3 signaling to alleviate inflammatory responses linked to transplantation.

EXPERT OPINION

In recent years, the NLRP3 inflammasome has garnered considerable attention owing to its critical functions spanning diverse fields. This study highlights the critical function of the NLRP3 inflammasome and presents insights, offering fresh perspectives on how its modulation might help to improve the outcomes among patients who undergo solid organ transplantations.

Gasdermin D mutation protects against renal ischemia reperfusion injury

Pyroptosis, the most inflammatory form of cell death, is dependent on membrane pore formation governed by the assembly of cleaved Gasdermin D (GSDMD). We hypothesized that regulated necrosis pathways are crucial in the pathophysiology of acute kidney injury (AKI). Mice with an isoleucine-to-asparagine loss-of-function mutation in the Gasdermin D gene (GSDMDI105N/I105N) generated by ethylnitrosourea-mutagenesis were subjected to bilateral renal ischemia-reperfusion injury (IRI) with bio-molecular readouts performed at 24 h. IRI was also performed in mice pretreated with disulfiram. Whole-body irradiation followed by syngeneic bone marrow transplantation generated chimeric mice prior to IRI. Mice homozygous for the GSDMD I105N mutation were protected from IRI, demonstrating lower serum creatinine and reduced histological injury, as well as decreased pro-inflammatory cytokine expression and oxidative stress. Chimeric mice showed that this protection was predominantly governed by mutations in the parenchymal tissue, with a potential contribution from the hematopoietic compartment. Pharmacological inhibition of GSDMD pore formation using disulfiram protected against IRI. Manipulation of GSDMD is an attractive target to mitigate inflammation and cellular death following AKI.

Targeting Kidney Inflammation After Brain Death and Cold Storage: Investigating the Potential of an NLRP3 Inflammasome Inhibitor (MCC950) for Preconditioning Donor Kidneys

BACKGROUND

Brain death (BD) and cold storage (CS) are critical factors that induce inflammation in donor kidneys, compromising organ quality. We investigated whether treating kidneys from BD rats with an inflammasome Nod-like receptor family pyrin domain containing 3 (NLRP3) inhibitor (MCC950) followed by CS could reduce kidney inflammation.

METHODS

BD rats were assigned to MCC950-treated or nontreated (NT) groups. Kidneys were evaluated immediately before CS (T0) and after 12 h (T12) and 24 h (T24) of CS. Mean arterial pressure, serum creatinine, gene/protein expression, and histology were evaluated.

RESULTS

At T0, MCC950 treatment did not affect mean arterial pressure but tended to reduce serum creatinine and ameliorated the histological score of acute tubular necrosis. However, MCC950 reduced NLRP3 , caspase-1 , interleukin (IL)-1β , IL-6 , Kim-1 , nuclear factor kappa B , tumor necrosis factor alpha , and caspase-3 gene expression while increasing IL-10 cytokine gene expression. After 12 h of CS, only the expression of the NLRP3 and caspase-1 genes decreased, and after 24 h of CS, no further changes in the gene expression profile were observed. The levels of the inflammasome proteins NLRP3, caspase-1, and IL-1β consistently decreased across all time points (T0, T12, and T24).

CONCLUSIONS

These findings suggest that MCC950 treatment holds promise for mitigating the proinflammatory state observed in kidneys after BD and CS.

Purinoreceptor P2X7 in Extracellular ATP-Mediated Inflammation through the Spectrum of Kidney Diseases and Kidney Transplantation

Extracellular purines not only play a critical role in maintaining a balanced inflammatory response but may also trigger disproportionate inflammation in various kidney pathologies. Extracellular ATP is the most well-characterized inflammatory purine, which serves as a potent extracellular danger-associated molecular pattern ( i.e ., danger-associated molecular pattern). It signals through the P2 purinoreceptors during both acute and chronic kidney damage. The purinoreceptor P2X7 (P2X7R) has been extensively studied in kidney disease because of its potent ability to enhance inflammation by activating the nucleotide-binding oligomerization domain, leucine rich repeat family pyrin domain containing 3 inflammasome in both immune and parenchymal tubular cells and potential role in immunometabolic reprogramming. We will explore how, following a primary insult to the kidney, disturbance of purinergic balance characterized by extracellular ATP-mediated P2X7R activation exacerbates AKI. Second, we will describe how persistent purinergic disbalance promotes a P2X7R-mediated protracted inflammatory reaction leading to the progression of CKD of different etiologies. Finally, we will also highlight the relevant and emerging role of P2X7R signaling in both antigen-presenting cells and adaptive immune cells to modulate cellular and humoral immune responses in kidney transplantation and hypertension. This review underscores that ATP-P2X7R axis is a key driver of pathologic purinergic signaling, representing a largely unexplored but highly promising clinical target against a wide spectrum of kidney diseases.

Neferine Targeted the NLRC5/NLRP3 Pathway to Inhibit M1-type Polarization and Pyroptosis of Macrophages to Improve Hyperuricemic Nephropathy

BACKGROUND

Neferine (Nef) has a renal protective effect. This research intended to explore the impact of Nef on hyperuricemic nephropathy (HN).

METHODS

Adenine and potassium oxonate were administered to SD rats to induce the HN model. Bone marrow macrophages (BMDM) and NRK-52E were used to construct a transwell co-culture system. The polarization of BMDM and apoptosis levels were detected using immunofluorescence and flow cytometry. Renal pathological changes were detected using hematoxylin-eosin (HE) and Masson staining. Biochemical methods were adopted to detect serum in rats. CCK-8 and EDU staining were used to assess cell activity and proliferation. RT-qPCR and western blot were adopted to detect NLRC5, NLRP3, pyroptosis, proliferation, and apoptosis-related factor levels.

RESULTS

After Nef treatment, renal injury and fibrosis in HN rats were inhibited, and UA concentration, urinary protein, BUN, and CRE levels were decreased. After Nef intervention, M1 markers, pyroptosis-related factors, and NLRC5 levels in BMDM stimulated with uric acid (UA) treatment were decreased. Meanwhile, the proliferation level of NRK-52E cells co-cultured with UA-treated BMDM was increased, but the apoptosis level was decreased. After NLRC5 overexpression, Nef-induced regulation was reversed, accompanied by increased NLRP3 levels. After NLRP3 was knocked down, the levels of M1-type markers and pyroptosis-related factors were reduced in BMDM.

CONCLUSION

Nef improved HN by inhibiting macrophages polarized to M1-type and pyroptosis by targeting the NLRC5/NLRP3 pathway. This research provides a scientific theoretical basis for the treatment of HN.

Inflammasome pathway in kidney transplantation

Kidney transplantation is the best available renal replacement therapy for patients with end-stage kidney disease and is associated with better quality of life and patient survival compared with dialysis. However, despite the significant technical and pharmaceutical advances in this field, kidney transplant recipients are still characterized by reduced long-term graft survival. In fact, almost half of the patients lose their allograft after 15-20 years. Most of the conditions leading to graft loss are triggered by the activation of a large immune-inflammatory machinery. In this context, several inflammatory markers have been identified, and the deregulation of the inflammasome (NLRP3, NLRP1, NLRC4, AIM2), a multiprotein complex activated by either whole pathogens (including fungi, bacteria, and viruses) or host-derived molecules, seems to play a pivotal pathogenetic role. However, the biological mechanisms leading to inflammasome activation in patients developing post-transplant complications (including, ischemia-reperfusion injury, rejections, infections) are still largely unrecognized, and only a few research reports, reviewed in this manuscript, have addressed the association between abnormal activation of this pathway and the onset/development of major clinical effects. Finally, the regulation of the inflammasome machinery could represent in future a valuable therapeutic target in kidney transplantation.

Normothermic ex vivo heart perfusion with NLRP3 inflammasome inhibitor Mcc950 treatment improves cardiac function of circulatory death hearts after transplantation

Background

The utilization of donation after circulatory death (DCD) hearts can enlarge the donor pool. However, DCD hearts suffer from serious ischemia/reperfusion injury (IRI). Recent studies found that the activation of NLRP3 inflammasome could play a significant role in organ IRI. Mcc950, which is a novel inhibitor of the NLRP3 inflammasome, can be applied to treat various kinds of cardiovascular diseases. Therefore, we hypothesized that the treatment of mcc950 could protect DCD hearts preserved with normothermic ex vivo heart perfusion (EVHP) against myocardial IRI via inhibiting NLRP3 inflammasome in a rat heart transplantation model of DCD.

Methods

Donor-heart rats were randomly divided into four groups: Control group; Vehicle group; MP-mcc950 group; and MP + PO-mcc950 group. Mcc950 was added into the perfusate of normothermic EVHP in the MP-mcc950 and MP + PO-mcc950 groups, and was injected into the left external jugular vein after heart transplantation in the MP + PO-mcc950 group. Cardiac functional assessment was performed. The level of oxidative stress, inflammatory response, apoptosis, and NLRP3 inflammasome-associated protein of donor hearts were evaluated.

Results

The treatment with mcc950 significantly increased the developed pressure (DP), dP/dtmax, and dP/dtmin of the left ventricular of DCD hearts at 90 min after heart transplantation in both MP-mcc950 and MP + PO-mcc950 groups. Furthermore, mcc950 added into perfusate and injected after transplantation in both MP-mcc950 and MP + PO-mcc950 groups significantly attenuated the level of oxidative stress, inflammatory response, apoptosis, and NLRP3 inflammasome compared with the vehicle group.

Conclusions

Normothermic EVHP combined with mcc950 treatment can be a promising and novel DCD heart preservation strategy, which can alleviate myocardial IRI via inhibiting NLRP3 inflammasome.

Gasdermins and pyroptosis in the kidney

Pyroptosis is a form of regulated cell death that is mediated by the membrane-targeting, pore-forming gasdermin family of proteins. Pyroptosis was initially described as a caspase 1- and inflammasome-dependent cell death pathway typified by the loss of membrane integrity and the secretion of cytokines such as IL-1β. However, gasdermins are now recognized as the principal effectors of this form of regulated cell death; activated gasdermins insert into cell membranes, where they form pores that result in the secretion of cytokines, alarmins and damage-associated molecular patterns and cause cell membrane rupture. It is now evident that gasdermins can be activated by inflammasome- and caspase-independent mechanisms in multiple cell types and that crosstalk occurs between pyroptosis and other cell death pathways. Although they are important for host antimicrobial defence, a growing body of evidence supports the notion that pyroptosis and gasdermins have pathological roles in cancer and several non-microbial diseases involving the gut, liver and skin. The well-documented roles of inflammasome activity and apoptosis pathways in kidney diseases suggests that gasdermins and pyroptosis may also be involved to some extent. However, despite some evidence for involvement of pyroptosis in the context of acute kidney injury and chronic kidney disease, our understanding of gasdermin biology and pyroptosis in the kidney remains limited.

NLRP3 inflammasome: A potential therapeutic target to minimize renal ischemia/reperfusion injury during transplantation

Renal transplantation is currently the best treatment option for patients with end-stage kidney disease. Ischemia/reperfusion injury (IRI), which is an inevitable event during renal transplantation, has a profound impact on the function of transplanted kidneys. It has been well demonstrated that innate immune system plays an important role in the process of renal IRI. As a critical component of innate immune system, Nod-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome has received great attention from scientific community over the past decade. The main function of NLRP3 inflammasome is mediating activation of caspase-1 and maturation of interleukin (IL)-1β and IL-18. In this review, we summarize the associated molecular signaling events about NLRP3 inflammasome in renal IRI, and highlight the possibility of targeting NLRP3 inflammasome to minimize renal IRI during transplantation.

Novel insights into NOD-like receptors in renal diseases

Nucleotide-binding oligomerization domain-like receptors (NLRs), including NLRAs, NLRBs (also known as NAIPs), NLRCs, and NLRPs, are a major subfamily of pattern recognition receptors (PRRs). Owing to a recent surge in research, NLRs have gained considerable attention due to their involvement in mediating the innate immune response and perpetuating inflammatory pathways, which is a central phenomenon in the pathogenesis of multiple diseases, including renal diseases. NLRs are expressed in different renal tissues during pathological conditions, which suggest that these receptors play roles in acute kidney injury, obstructive nephropathy, diabetic nephropathy, IgA nephropathy, lupus nephritis, crystal nephropathy, uric acid nephropathy, and renal cell carcinoma, among others. This review summarises recent progress on the functions of NLRs and their mechanisms in the pathophysiological processes of different types of renal diseases to help us better understand the role of NLRs in the kidney and provide a theoretical basis for NLR-targeted therapy for renal diseases.

Pyroptosis in Kidney Disease

In the last several decades, apoptosis interference has been considered clinically irrelevant in the context of renal injury. Recent discovery of programmed necrotic cell death, including necroptosis, ferroptosis, and pyroptosis refreshed our understanding of the role of cell death in kidney disease. Pyroptosis is characterized by a lytic pro- inflammatory type of cell death resulting from gasdermin-induced membrane permeabilization via activation of inflammatory caspases and inflammasomes. The danger-associated molecular patterns (DAMPs), alarmins and pro-inflammatory cytokines are released from pyroptotic cells in an uncontrolled manner, which provoke inflammation, resulting in secondary organ or tissue injuries. The caspases and inflammasome activation-related proteins and pore-forming effector proteins known as GSDMD and GSDME have been implicated in a variety of acute and chronic microbial and non-microbial kidney diseases. Here, we review the recent advances in pathological mechanisms of pyroptosis in kidney disease and highlight the potential therapeutic strategies in future.

Pharmacological Inhibition of the Nod-Like Receptor Family Pyrin Domain Containing 3 Inflammasome with MCC950

Activation of the Nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome drives release of the proinflammatory cytokines interleukin (IL)-1β and IL-18 and induces pyroptosis (lytic cell death). These events drive chronic inflammation, and as such, NLRP3 has been implicated in a large number of human diseases. These range from autoimmune conditions, the simplest of which is NLRP3 gain-of-function mutations leading to an orphan disease, cryopyrin-associated period syndrome, to large disease burden indications, such as atherosclerosis, heart failure, stroke, neurodegeneration, asthma, ulcerative colitis, and arthritis. The potential clinical utility of NLRP3 inhibitors is substantiated by an expanding list of indications in which NLRP3 activation has been shown to play a detrimental role. Studies of pharmacological inhibition of NLRP3 in nonclinical models of disease using MCC950 in combination with human genetics, epigenetics, and analyses of the efficacy of biologic inhibitors of IL-1β, such as anakinra and canakinumab, can help to prioritize clinical trials of NLRP3-directed therapeutics. Although MCC950 shows excellent (nanomolar) potency and high target selectivity, its pharmacokinetic and toxicokinetic properties limited its therapeutic development in the clinic. Several improved, next-generation inhibitors are now in clinical trials. Hence the body of research in a plethora of conditions reviewed herein may inform analysis of the potential translational value of NLRP3 inhibition in diseases with significant unmet medical need. SIGNIFICANCE STATEMENT: The nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome is one of the most widely studied and best validated biological targets in innate immunity. Activation of NLRP3 can be inhibited with MCC950, resulting in efficacy in more than 100 nonclinical models of inflammatory diseases. As several next-generation NLRP3 inhibitors are entering proof-of-concept clinical trials in 2020, a review of the pharmacology of MCC950 is timely and significant.

The roles of NLRP3 inflammasome-mediated signaling pathways in hyperuricemic nephropathy

Hyperuricemic nephropathy (HN) is a common clinical complication of hyperuricemia. High-serum uric acid can trigger renal inflammation. The inflammasome family has several members and shows a significant effect on inflammatory responses. NLRP3 (NOD-, LRR-, and pyrin domain-containing 3) senses the stimuli signal of excessive uric acid and then it recruits apoptosis-related specular protein (ASC) as well as aspartic acid-specific cysteine protease (caspase)-1 precursor to form NLRP3 inflammasome. NLRP3 inflammasome is activated in acute kidney injury (AKI), chronic kidney diseases (CKD), diabetic nephropathy (DN), and HN. This review focuses on important role for the involvement of NLRP3 inflammasome and associated signaling pathways in the pathogenesis of hyperuricemia-induced renal injury and the potential therapeutic implications. Additionally, several inhibitors targeting NLRP3 inflammasome are under development, most of them for experiment. Therefore, researches into NLRP3 inflammasome modulators may provide novel therapies for HN.

Protective effect of Aster tataricus extract on NLRP3-mediated pyroptosis of bladder urothelial cells

Aster tataricus L.f. is a traditional Eastern Asian herbal medicine used for the relief of uroschesis‐related illnesses and has been demonstrated clinically to exert satisfied effects. However, the mechanism of its therapeutic action remains unclear. The present study aimed to evaluate the protective mechanism of Aster tataricus extract (ATE) on CYP or LPS + ATP‐induced interstitial cystitis (IC), we successfully constructed the induced IC Sprague‐Dawley (SD) rat model and IC human urothelium cell (SV‐HUC‐1) model. The main compounds of ATE were determined by LC‐MS. After intervention, the changes on the bladder wall morphology and inflammation were observed in each group. SV‐HUC1 cell viability was measured by MTT and double stained with Hoechst 33342 and propidium iodide (PI). The expression levels of NLRP3, Pro‐caspase‐1, Caspsae‐1 p20, GSDMD, GSDMD‐N and Cleave‐IL‐1β in vivo and in vitro in different groups were detected by Western blotting. ATE significantly alleviated oedema and haemorrhage and reduced the inflammation index and histopathological score in SD rat bladder. The results of cell revealed that ATE could improve cell viability and decrease pyroptosis ratio. The expression of NLRP3 and other pyroptosis‐related protein was remarkably decreased by ATE both in vivo and in vitro. ATE may be used as an inhibitor of NLRP3 in treating IC. The discovery of NLRP3/Caspase‐1/GSDMD‐N as a new protective pathway provides a new direction for protecting cell against IC.