Research progress on the mechanism of cholesterol-25-hydroxylase in intestinal immunity

Antiviral role of cholesterol 25-hydroxylase in inhibiting porcine circovirus 3 replication

Cholesterol 25-hydroxylase (CH25H) has significant antiviral effects through the production of 25-hydroxycholesterol (25HC). In this study, we investigated the effects of CH25H, its catalytic product 25HC, and its catalytic mutant lacking hydroxylase activity (CH25H-M) on porcine circovirus 3 (PCV3) replication. By transfecting PCV3 persistently infected PK-15 cells with the pCAGGS-CH25H-Flag plasmid, the results demonstrated that overexpression of CH25H significantly inhibited PCV3 Cap protein expression, Cap mRNA levels, and viral titers in a dose-dependent manner. Moreover, its catalytic product 25HC inhibited PCV3 replication in PK-15 cells at concentrations below 10 µM without affecting cell viability. In contrast, knockdown of endogenous CH25H using small interfering RNA (siRNA) enhanced PCV3 replication, further confirming its antiviral role. Interestingly, the CH25H-M mutant also exhibited inhibitory effects on PCV3 replication, although the inhibition was much less effective compared with CH25H. In conclusion, CH25H plays a critical role in regulating PCV3 replication, and its antiviral effect is not entirely dependent on its enzymatic activity. These findings provide new insights into both the enzymatic and non-enzymatic antiviral mechanisms of CH25H and revealed some mechanistic immune evasion for PCV3.

Hypoxia-induced ALKBH5 aggravates synovial aggression and inflammation in rheumatoid arthritis by regulating the m6A modification of CH25H

Previous studies have shown that epigenetic factors are involved in the occurrence and development of rheumatoid arthritis (RA). However, the role of N6-methyladenosine (m6A) methylation in RA has not been determined. The aim of this study was to investigate the role and regulatory mechanisms of hypoxia-induced expression of the m6A demethylase alkB homolog 5 (ALKBH5) in RA fibroblast-like synoviocytes (FLSs). Synovial tissues were collected from RA and osteoarthritis (OA) patients, and RA FLSs were obtained. ALKBH5 expression in RA FLSs and collagen-induced arthritis (CIA) model rats was determined using quantitative reverse transcription-PCR (qRT-PCR), western blotting and immunohistochemistry (IHC). Using ALKBH5 overexpression and knockdown, we determined the role of ALKBH5 in RA FLS aggression and inflammation. The role of ALKBH5 in RA FLS regulation was explored using m6A-methylated RNA sequencing and methylated RNA immunoprecipitation coupled with quantitative real-time PCR. The expression of ALKBH5 was increased in RA synovial tissues, CIA model rats and RA FLSs, and a hypoxic environment increased the expression of ALKBH5 in FLSs. Increased expression of ALKBH5 promoted the proliferation and migration of RA-FLSs and inflammation. Conversely, decreased ALKBH5 expression inhibited the migration of RA-FLSs and inflammation. Mechanistically, hypoxia-induced ALKBH5 expression promoted FLS aggression and inflammation by regulating CH25H mRNA stability. Our study elucidated the functional roles of ALKBH5 and mRNA m6A methylation in RA and revealed that the HIF1α/2α-ALKBH5-CH25H pathway may be key for FLS aggression and inflammation. This study provides a novel approach for the treatment of RA by targeting the HIF1α/2α-ALKBH5-CH25H pathway.

Anemoside B4, a new pyruvate carboxylase inhibitor, alleviates colitis by reprogramming macrophage function

OBJECTIVES

Colitis is a global disease usually accompanied by intestinal epithelial damage and intestinal inflammation, and an increasing number of studies have found natural products to be highly effective in treating colitis. Anemoside B4 (AB4), an abundant saponin isolated from Pulsatilla chinensis (Bunge), which was found to have strong anti-inflammatory activity. However, the exact molecular mechanisms and direct targets of AB4 in the treatment of colitis remain to be discovered.

METHODS

The anti-inflammatory activities of AB4 were verified in LPS-induced cell models and 2, 4, 6-trinitrobenzene sulfonic (TNBS) or dextran sulfate sodium (DSS)-induced colitis mice and rat models. The molecular target of AB4 was identified by affinity chromatography analysis using chemical probes derived from AB4. Experiments including proteomics, molecular docking, biotin pull-down, surface plasmon resonance (SPR), and cellular thermal shift assay (CETSA) were used to confirm the binding of AB4 to its molecular target. Overexpression of pyruvate carboxylase (PC) and PC agonist were used to study the effects of PC on the anti-inflammatory and metabolic regulation of AB4 in vitro and in vivo.

RESULTS

AB4 not only significantly inhibited LPS-induced NF-κB activation and increased ROS levels in THP-1 cells, but also suppressed TNBS/DSS-induced colonic inflammation in mice and rats. The molecular target of AB4 was identified as PC, a key enzyme related to fatty acid, amino acid and tricarboxylic acid (TCA) cycle. We next demonstrated that AB4 specifically bound to the His879 site of PC and altered the protein's spatial conformation, thereby affecting the enzymatic activity of PC. LPS activated NF-κB pathway and increased PC activity, which caused metabolic reprogramming, while AB4 reversed this phenomenon by inhibiting the PC activity. In vivo studies showed that diisopropylamine dichloroacetate (DADA), a PC agonist, eliminated the therapeutic effects of AB4 by changing the metabolic rearrangement of intestinal tissues in colitis mice.

CONCLUSION

We identified PC as a direct cellular target of AB4 in the modulation of inflammation, especially colitis. Moreover, PC/pyruvate metabolism/NF-κB is crucial for LPS-driven inflammation and oxidative stress. These findings shed more light on the possibilities of PC as a potential new target for treating colitis.

Houttuynia cordata thunb. alleviates inflammatory bowel disease by modulating intestinal microenvironment: a research review

Inflammatory bowel disease (IBD) is a complex group of chronic intestinal diseases, the cause of which has not yet been clarified, but it is widely believed that the disorder of the intestinal microenvironment and its related functional changes are key factors in the development of the disease. Houttuynia cordata thunb. is a traditional plant with abundant resources and long history of utilization in China, which has attracted widespread attention in recent years due to its potential in the treatment of IBD. However, its development and utilization are limited owing to the aristolochic acid alkaloids contained in it. Therefore, based on the relationship between the intestinal microenvironment and IBD, this article summarizes the potential mechanisms by which the main active ingredients of Houttuynia cordata thunb., such as volatile oils, polysaccharides, and flavonoids, and related traditional Chinese medicine preparations, such as Xiezhuo Jiedu Formula, alleviate IBD by regulating the intestinal microenvironment. At the same time, combined with current reports, the medicinal and edible safety of Houttuynia cordata thunb. is explained for providing ideas for further research and development of Houttuynia chordate thunb. in IBD disease, more treatment options for IBD patients, and more insights into the therapeutic potential of plants with homology of medicine and food in intestinal diseases, and even more diseases.