Nucleotide-Binding Domain Leucine-Rich Repeat Containing Proteins and Intestinal Microbiota: Pivotal Players in Colitis and Colitis-Associated Cancer Development

Vitamin D and Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD): Novel Mechanistic Insights

Metabolic dysfunction-associated steatotic liver disease (MASLD) is an increasingly prevalent condition characterized by abnormal fat accumulation in the liver, often associated with metabolic disorders. Emerging evidence suggests a potential link between vitamin D deficiency and the development and progression of MASLD. The current review provides a concise overview of recent studies uncovering novel mechanistic insights into the interplay between vitamin D and MASLD. Several epidemiological studies have highlighted a significant association between low vitamin D levels and an increased risk of MASLD. Vitamin D, traditionally known for its role in bone health, has now been recognized as a key player in various physiological processes, including immune regulation and inflammation. Experimental studies using animal models have demonstrated that vitamin D deficiency exacerbates liver steatosis and inflammation, suggesting a potential protective role against MASLD. Mechanistically, vitamin D appears to modulate MASLD through multiple pathways. Firstly, the vitamin D receptor (VDR) is abundantly expressed in liver cells, indicating a direct regulatory role in hepatic function. Activation of the VDR has been shown to suppress hepatic lipid accumulation and inflammation, providing a mechanistic basis for the observed protective effects. Additionally, vitamin D influences insulin sensitivity, a critical factor in MASLD pathogenesis. Improved insulin sensitivity may mitigate the excessive accumulation of fat in the liver, thus attenuating MASLD progression. In parallel, vitamin D exhibits anti-inflammatory properties by inhibiting pro-inflammatory cytokines implicated in MASLD pathophysiology. Experimental evidence suggests that the immunomodulatory effects of vitamin D extend to the liver, reducing inflammation and oxidative stress, key drivers of MASLD, and the likelihood of hepatocyte injury and fibrosis. Understanding the complex interplay between vitamin D and MASLD provides a basis for exploring targeted therapeutic strategies and preventive interventions. As vitamin D deficiency is a modifiable risk factor, addressing this nutritional concern may prove beneficial in mitigating the burden of MASLD and associated metabolic disorders.

Exploring the role of IL-1β in inflammatory bowel disease pathogenesis

Interleukin 1β (IL-1β) is a significant mediator of inflammation and tissue damage in IBD. The balance between IL-1β and its endogenous inhibitor-IL-1Ra-, plays a critical role in both initiation and regulation of inflammation. However, the precise role of IL-1β as a causative factor in IBD or simply a consequence of inflammation remains unclear. This review summarizes current knowledge on the molecular and cellular characteristics of IL-1β, describes the existing evidence on the role of this cytokine as a modulator of intestinal homeostasis and an activator of inflammatory responses, and also discusses the role of microRNAs in the regulation of IL-1β-related inflammatory responses in IBD. Current evidence indicates that IL-1β is involved in several aspects during IBD as it greatly contributes to the induction of pro-inflammatory responses through the recruitment and activation of immune cells to the gut mucosa. In parallel, IL-1β is involved in the intestinal barrier disruption and modulates the differentiation and function of T helper (Th) cells by activating the Th17 cell differentiation, known to be involved in the pathogenesis of IBD. Dysbiosis in the gut can also stimulate immune cells to release IL-1β, which, in turn, promotes inflammation. Lastly, increasing evidence pinpoints the central role of miRNAs involvement in IL-1β-related signaling during IBD, particularly in the maintenance of homeostasis within the intestinal epithelium. In conclusion, given the crucial role of IL-1β in the promotion of inflammation and immune responses in IBD, the targeting of this cytokine or its receptors represents a promising therapeutic approach. Further research into the IL-1β-associated post-transcriptional modifications may elucidate the intricate role of this cytokine in immunomodulation.

Microbiome and metabolome integrally reveal the anti-depression effects of Cistanche deserticola polysaccharides from the perspective of gut homeostasis

Polysaccharides are one of the active components of Cistanche deserticola (CD). Cistanche deserticola polysaccharides (CDPs) significantly regulate gut microbiota, immune activity, and neuroprotective functions. However, it merely scratches the surface that the anti-depression effects of CDPs. We aimed to demonstrate the anti-depression effects of CDPs and the underlying mechanisms from the perspectives of gut homeostasis by behavioral evaluations and applying integrally microbiome, metabolome, and molecular biology. CDPs showed significant effects on improving abnormal behaviors of depressed rats. Additionally, CDPs maintained Th17/Treg balance and modulated gut immunity of depressed rats. Comprehensive microbiome and metabolome analysis showed that CDPs significantly ameliorated abundances of beneficial bacteria, and increased the contents of SCFAs, consequently maintaining gut homeostasis. Besides, the anti-depression effects of CDPs involved in amino acid metabolism including BCAAs, glutamine, etc., maintaining metabolic balance. The current findings provide not only deep understanding of depression focusing on gut, but also evidence about the anti-depression effects of CDPs, broadening clinic applications of CDPs. Of note, the present study is of significance in a long run, in terms of providing novel strategies and protocols for revealing mechanisms of anti-depression drugs, and for the discovery of new antidepressants and functional foods from natural products.

Beyond allergic progression: From molecules to microbes as barrier modulators in the gut-lung axis functionality

The "epithelial barrier hypothesis" states that a barrier dysfunction can result in allergy development due to tolerance breakdown. This barrier alteration may come from the direct contact of epithelial and immune cells with the allergens, and indirectly, through deleterious effects caused by environmental changes triggered by industrialization, pollution, and changes in the lifestyle. Apart from their protective role, epithelial cells can respond to external factors secreting IL-25 IL-33, and TSLP, provoking the activation of ILC2 cells and a Th2-biased response. Several environmental agents that influence epithelial barrier function, such as allergenic proteases, food additives or certain xenobiotics are reviewed in this paper. In addition, dietary factors that influence the allergenic response in a positive or negative way will be also described here. Finally, we discuss how the gut microbiota, its composition, and microbe-derived metabolites, such as short-chain fatty acids, alter not only the gut but also the integrity of distant epithelial barriers, focusing this review on the gut-lung axis.

NLRP3 Promotes Colorectal Cancer Cell Proliferation and Metastasis via Regulating Epithelial Mesenchymal Transformation

BACKGROUND

Nucleotide-binding domain Leucine-rich Repeat Protein 3 (NLRP3) plays a regulatory role in the immune and inflammatory responses, and has been implicated in Colorectal Cancer (CRC) progression and metastasis. However, the underlying molecular mechanisms have not been fully elucidated.

METHODS

In this study, we analyzed the expression levels of NLRP3 in human CRC tissues, and performed functional assays in CRC cell lines and a subcutaneous tumor model to elucidate its role in the development and progression of CRC.

RESULTS

In this study, we found that NLRP3 was significantly upregulated in human CRC tissues and was associated with tumor size and invasion, lymph node metastasis, venous invasion, neural invasion and TNM staging. Furthermore, knockdown of NLRP3 in CRC cells inhibited their migration and growth in vitro and in vivo, and reversed Epithelial-Mesenchymal Transition (EMT) in vitro.

CONCLUSION

Our findings indicate that NLRP3 likely regulates CRC metastasis by activating the EMT program, and is a potential therapeutic target.

Interferon Type I Regulates Inflammasome Activation and High Mobility Group Box 1 Translocation in Hepatocytes During Ehrlichia-Induced Acute Liver Injury

Inflammasomes are an important innate immune host defense against intracellular microbial infection. Activation of inflammasomes by microbial or host ligands results in cleavage of caspase-1 (canonical pathway) or caspase-11 (noncanonical pathway), release of interleukin (IL)-1β, IL-18, high mobility group box 1 (HMGB1), and inflammatory cell death known as pyroptosis. Ehrlichia are obligate, intracellular, gram-negative bacteria that lack lipopolysaccharide but cause potentially life-threatening monocytic ehrlichiosis in humans and mice that is characterized by liver injury followed by sepsis and multiorgan failure. Employing murine models of mild and fatal ehrlichiosis caused by infection with mildly and highly virulent Ehrlichia muris (EM) and Ixodes ovatus Ehrlichia (IOE), respectively, we have previously shown that IOE infection triggers type I interferon (IFN-I) response and deleterious caspase-11 activation in liver tissues, which promotes liver injury and sepsis. In this study, we examined the contribution of IFN-I signaling in hepatocytes (HCs) to Ehrlichia-induced liver injury. Compared to EM infection, we found that IOE enter and replicate in vitro cultured primary murine HCs and induce secretion of IFNβ and several chemokines, including regulated upon activation, normal T-cell expressed, and secreted (RANTES), monocyte chemoattractant protein 1 (MCP1), monokine induced by gamma (MIG)/chemokine (C-X-C motif) ligand 9 (CXCL9), macrophage inflammatory protein 1 alpha (MIP1α), keratinocyte-derived chemokine (KC), and granulocyte-macrophage colony-stimulating factor (GM-CSF). Notably, in vitro stimulation of uninfected and Ehrlichia-infected HCs with recombinant IFNβ triggered activation of caspase-1/11, cytosolic translocation of HMGB1, and enhanced autophagy and intracellular bacterial replication. Secretion of HMGB1 by IOE-infected HCs was dependent on caspase-11. Primary HCs from IOE- but not EM-infected mice also expressed active caspase-1/11. Conclusion: HC-specific IFN-I signaling may exacerbate liver pathology during infection with obligate intracellular Ehrlichia by promoting bacterial replication and detrimental caspase-11-mediated inflammasome activation.

Role of NLRP3 inflammasome in inflammatory bowel diseases

Inflammasomes are multiprotein intracellular complexes which are responsible for the activation of inflammatory responses. Among various subtypes of inflammasomes, NLRP3 has been a subject of intensive investigation. NLRP3 is considered to be a sensor of microbial and other danger signals and plays a crucial role in mucosal immune responses, promoting the maturation of proinflammatory cytokines interleukin 1β (IL-1β) and IL-18. NLRP3 inflammasome has been associated with a variety of inflammatory and autoimmune conditions, including inflammatory bowel diseases (IBD). The role of NLRP3 in IBD is not yet fully elucidated as it seems to demonstrate both pathogenic and protective effects. Studies have shown a relationship between genetic variants and mutations in NLRP3 gene with IBD pathogenesis. A complex interaction between the NLRP3 inflammasome and the mucosal immune response has been reported. Activation of the inflammasome is a key function mediated by the innate immune response and in parallel the signaling through IL-1β and IL-18 is implicated in adaptive immunity. Further research is needed to delineate the precise mechanisms of NLRP3 function in regulating immune responses. Targeting NLRP3 inflammasome and its downstream signaling will provide new insights into the development of future therapeutic strategies.