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From studies of individual families to global collaborative efforts, the NLRP3 inflammasome is now recognized to be a key regulator of innate immunity. Activated by a panoply of pathogen-associated and endogenous triggers, NLRP3 serves as an intracellular sensor that drives carefully coordinated assembly of the inflammasome, and downstream inflammation mediated by IL-1 and IL-18. Initially discovered as the cause of the autoinflammatory spectrum of cryopyrin-associated periodic syndrome (CAPS), NLRP3 is now also known to play a role in more common diseases including cardiovascular disease, gout, and liver disease. We have seen cohesion in results from clinical studies in CAPS patients, ex vivo studies of human cells and murine cells, and in vivo murine models leading to our understanding of the downstream pathways, cytokine secretion, and cell death pathways that has solidified the role of autoinflammation in the pathogenesis of human disease. Recent advances in our understanding of the structure of the inflammasome have provided ways for us to visualize normal and mutant protein function and pharmacologic inhibition. The subsequent development of targeted therapies successfully used in the treatment of patients with CAPS completes the bench to bedside translational loop which has defined the study of this unique protein.

Background & aimsBreast regression protein 39 (BRP39) (Chi3L1) and its human homolog YKL-40, is an established biomarker of liver fibrosis in nonalcoholic steatohepatitis (NASH) patients, but its role in NASH pathogenesis remains unclear. We recently identified Chi3L1 as one of the top up-regulated genes in mice with inducible gain-of-function NOD-like receptor protein 3 (NLRP3) activation that mimics several liver features of NASH. This study aimed to investigate the effects of BRP39 deficiency on NLRP3-induced liver inflammation using tamoxifen-inducible Nlrp3 knockin mice sufficient (Nlrp3A350V CRT) and deficient for BRP39 (Nlrp3A350V/BRP-/- CRT).MethodsUsing Nlrp3A350V CRT mice and Nlrp3A350V BRP-/- CRT, we investigated the consequences of BRP39 deficiency influencing NLRP3-induced liver inflammation.ResultsOur results showed that BRP39 deficiency in NLRP3-induced inflammation improved body weight and liver weight. Moreover, liver inflammation, fibrosis, and hepatic stellate cell activation were reduced significantly, corresponding to significantly decreased Ly6C+ infiltrating macrophages, CD68+ osteopontin-positive hepatic lipid-associated macrophages, and activated Lymphocyte antigen 6 complex locus G6D positive (Ly6G+) and citrullinated histone H3 postivie (H3Cit+) neutrophil accumulation in the liver. Further investigation showed that circulatory neutrophils from NLRP3-induced BRP39-deficient mice have impaired chemotaxis and migration ability, and this was confirmed by RNA bulk sequencing showing reduced immune activation, migration, and signaling responses in neutrophils.ConclusionsThese data showcase the importance of BRP39 in regulating the NLRP3 inflammasome during liver inflammation and fibrotic NASH by altering cellular activation, recruitment, and infiltration during disease progression, and revealing BRP39 to be a potential therapeutic target for future treatment of inflammatory NASH and its associated diseases.

Cell death is crucial for maintaining tissue balance and responding to diseases. However, under pathological conditions, the surge in dying cells results in an overwhelming presence of cell debris and the release of danger signals. In the liver, this gives rise to hepatic inflammation and hepatocellular cell death, which are key factors in various liver diseases caused by viruses, toxins, metabolic issues, or autoimmune factors. Both clinical and in vivo studies strongly affirm that hepatocyte death serves as a catalyst in the progression of liver disease. This advancement is characterized by successive stages of inflammation, fibrosis, and cirrhosis, culminating in a higher risk of tumor development. In this review, we explore pivotal forms of cell death, including apoptosis, pyroptosis, and necroptosis, examining their roles in both acute and chronic liver conditions, including liver cancer. Furthermore, we discuss the significance of cell death in liver surgery and ischemia-reperfusion injury. Our objective is to illuminate the molecular mechanisms governing cell death in liver diseases, as this understanding is crucial for identifying therapeutic opportunities aimed at modulating cell death pathways. [ABSTRACT FROM AUTHOR]

Macrophages contribute to the induction and resolution of inflammation and play a central role in chronic low-grade inflammation in cardiovascular diseases caused by atherosclerosis. Human milk oligosaccharides (HMOs) are complex unconjugated glycans unique to human milk that benefit infant health and act as innate immune modulators. Here, we identify the HMO 3'sialyllactose (3'SL) as a natural inhibitor of Toll-Like Receptor (TLR) 4-induced low-grade inflammation in macrophages and endothelium. Transcriptome analysis in macrophages revealed that 3'SL attenuates mRNA levels of a selected set of inflammatory genes and promotes the activity of Liver X Receptor (LXR) and Sterol Regulatory Element-binding Protein-1 (SREBP). These acute anti-inflammatory effects of 3'SL were associated with reduced histone H3K27 acetylation at a subset of lipopolysaccharide (LPS)-inducible enhancers distinguished by preferential enrichment for CCCTC-binding factor (CTCF), Interferon Regulatory Factor 2 (IRF2), B-cell lymphoma 6 (BCL6), and other transcription factor recognition motifs. In a murine atherosclerosis model, both subcutaneous and oral administration of 3'SL significantly reduced atherosclerosis development and the associated inflammation. This study provides evidence that 3'SL attenuates inflammation by a transcriptional mechanism to reduce atherosclerosis development in the context of cardiovascular disease.

Inflammation has an essential role in healing. However, over-active inflammation disrupts normal cellular functions and can be life-threatening when not resolved. The NLRP3 inflammasome, a component of the innate immune system, is an intracellular multiprotein complex that senses stress-associated signals, and, for this reason is a promising therapeutic target for treating unresolved, pathogenic inflammation. Alternative splicing of NLRP3 RNA has been suggested as a regulatory mechanism for inflammasome activation, as some spliced isoforms encode NLRP3 proteins with compromised function. Here, we take advantage of this natural regulatory mechanism and devise a way to control pathogenic inflammation using splice-switching antisense oligonucleotides (ASOs). To identify and induce NLRP3 spliced isoforms lacking inflammatory activity, we tested a series of ASOs, each targeting a different exon, to determine the most effective strategy for down-regulating NLRP3. We identify several ASOs that modulate NLRP3 splicing, reduce NLRP3 protein, and decrease inflammasome signaling in vitro . The most effective ASO suppresses systemic inflammation in vivo in mouse models of acute inflammation and cryopyrin-associated periodic syndrome (CAPS). Our results demonstrate a systematic approach to protein engineering using splice-switching ASOs to generate isoforms with altered activity, and identify an ASO that can treat pathological inflammation in mice by reducing functional NLRP3.