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The NLRP3 inflammasome plays a critical role in the innate immune response, and its excessive activation will cause pyroptotic cell death and be associated with the onset of inflammatory diseases. However, NLRP3 inflammasome targeting therapies are still to be implemented in the clinic setting. Here, we first isolated, purified and characterized a novel Vitenegu acid from V. negundo L. herb that specifically inhibits NLRP3 inflammasome activation, without affecting NLRC4 or AIM2 inflammasomes. Vitenegu acid blocks the oligomerization of NLRP3, thus inhibiting NLRP3 inflammasome assembly and activation. In vivo data show that Vitenegu acid exerts therapeutic effects on NLRP3 inflammasome-dependent inflammation. Taken together, our results suggest that Vitenegu acid is a candidate therapeutic agent for treating NLRP3 inflammasome related diseases.

Inflammatory bowel diseases (IBDs) are increasingly common diseases characterized by chronic and relapsing inflammation of the gastrointestinal tract. NLRP3 might be a crucial regulator of the homeostatic balance of the intestine, but its upregulation leads to pyroptosis. Munronoid I is extracted and purified from Munronia sinica, which has shown an anti-inflammatory effect, but the efficacy of Munronoid I in IBD remains unproven. In this study, we attempted to determine the effect of Munronoid I on NLRP3 to regulate the inflammasome activation and pyroptosis in IBD. Our data demonstrated that Munronoid I treatment attenuated DSS-induced body weight loss, pathological injury of the colon, the production of IL-1β and IL-18, and the expression of pyroptosis-associated proteins in colon tissue in mice. Moreover, Munronoid I inhibited LPS/ATP-induced pyroptosis in mouse peritoneal macrophages, MODE-K cells, and DSS-induced pyroptosis in mouse colonic epithelial cells, and decreased the release of inflammatory cytokines IL-1β and IL-18 in mouse peritoneal macrophages. Mechanically, Munronoid I could suppress the NLRP3 inflammasome activation and pyroptosis by promoting the K48-linked ubiquitination and NLRP3 degradation. It is suggested that Munronoid I might be a potential therapeutic candidate for IBD.

Succinate is at the crossroads of multiple metabolic pathways and plays a role in several immune responses acting as an inflammation signal. However, whether succinate regulates antiviral immune response remains unclear. Here, we found that the production of succinate was reduced in RAW264.7 cells during vesicular stomatitis virus (VSV) infection. Using diethyl succinate to pretreat the mouse peritoneal macrophages and RAW264.7 cells before VSV infection, the production of interferon-β (IFN-β), chemokine (C–X–C motif) ligand 10 (CXCL-10), and IFN-stimulated genes 15 (ISG15) was significantly decreased, following which the VSV replication in diethyl succinate-pretreated cells was obviously increased. Moreover, succinate decreased the expression of IFN-β in serum, lung, and spleen derived from the VSV-infected mice. The overall survival rate in the VSV-infected mice with diethyl succinate pretreatment was also remarkably downregulated. Furthermore, we identified that succinate inhibited the activation of MAVS-TBK1-IRF3 signaling by suppressing the formation of MAVS aggregates. Our findings provide previously unrecognized roles of succinate in antiviral immune response and establish a novel link between metabolism and innate immune response.

Fibrotic animal models are critical for the pathogenesis investigations and drug explorations in systemic sclerosis (SSc). The bleomycin (BLM)-induced mouse model is the classical and most widely used fibrosis model. However, traditional subcutaneous injection of BLM rarely induced diffuse skin and lung lesions. Hypochlorous acid (HOCl)-induced mice are a more representative model that have diffuse cutaneous lesions, lung fibrosis and renal involvement. However, the fibrotic and immunological features of this model are not fully elucidated. Here, we injected BALB/c mice subcutaneously with HOCl used at different concentrations of HOCl (1:55, 1:70, and 1:110 NaClO: KH2PO4, hereafter named HOCl55, HOCl70, and HOCl110, respectively) for 6 weeks to induce fibrosis, and also used HOCl110 at different time course (4, 5, and 6 weeks). Morphological changes were observed via HE and Masson's trichrome staining. Immunohistochemistry or real-time PCR was used to detect inflammatory infiltrates, important fibrosis pathways and pro-inflammatory mediator expression. Flow cytometry was used to detect the alteration of immune cells in mouse spleen. Skin and lung fibrosis were most obvious in the HOCl55 group compared to lower concentration groups. In the HOCl110 group, dominant inflammatory infiltrates were found after 5 weeks, and significant fibrosis was found after 6 weeks. Then we explored the fibrosis and immunological profiles in the HOCl110 (6 weeks) group. Important fibrosis pathway proteins such as TGF-β, NF-κB, Smad3, p-Smad3, STAT3, and p-STAT3 were significantly elevated at week 6 in the HOCl110 group. Increased infiltration of CD4+T cells, CD8+T cells, CD20+B cells, and myofibroblasts was found both in skin and lung tissues. However, decreased CD4+T cells, CD8+T cells, monocytes and macrophages and increased CD19+B cells were found in the spleen tissues. The mRNA expression of fibrosis mediators such as IL-1β, IL-6, IL-17, IL-33, TNF-α, and CTGF was also upregulated in skin and lung tissues. In conclusion, HOCl induced fibrosis mouse model displayed systemic immune cell infiltration, pro-inflammatory mediator release, vasculopathy and fibrosis, which better mimicked human SSc than BLM-induced mice.

Scleroderma (systemic sclerosis, SSc) is a highly heterogeneous rheumatic disease, and uncontrolled fibrosis in visceral organs is the major cause of death in patients. The transforming growth factor-β (TGF-β) and WNT/β-catenin signaling pathways, along with signal transducer and activator of transcription 3 (STAT3), play crucial roles in this fibrotic process. Currently, no therapy is available that effectively arrests or reverses the progression of fibrosis in patients with SSc. Ubiquitination is an important post-translational modification that controls many critical cellular functions. Dysregulated ubiquitination events have been observed in patients with systemic lupus erythematosus, rheumatoid arthritis and fibrotic diseases. Inhibitors targeting the ubiquitination pathway have considerable potential for the treatment of rheumatic diseases. However, very few studies have examined the role and mechanism of ubiquitination in patients with SSc. In this review, we will summarize the molecular mechanisms of ubiquitination in patients with SSc and explore the potential targets for treatment.