Inhibition of Ca2+ induced Macrophage Oxidative Stress Cascade in Mice With Ulcerative Colitis.

ABSTRACT

Context In the context of ulcerative coloproctitis (UC), a chronic and non-specific inflammatory condition of the colon and rectum with an elusive etiology, the therapeutic potential of G protein-coupled receptor 109a (GPR109a) has gained prominence. GPR109a is expressed in various cell types including colonic epithelium, adipocytes, neutrophils, and macrophages, positioning it as a promising candidate for pharmacological intervention in colitis. Objective: the mechanistic role of GPR109a in a mouse model of UC and to assess its capacity to mitigate the disease's progression. Design: The research team performed an animal study. Setting: Conducted by a research team in the biomedical setting of the People's Hospital of Dongxihu District in Wuhan, Hubei province of China. Animals This animal study engaged 16 specific pathogen-free (SPF) male BALB/c mice, aged between 4 to 6 weeks and weighing 20-24 grams each. Outcome Measures: (1) analysis of rectal lesions via hematoxylin-eosin (HE) staining, (2) the use of transmission electron microscopy to examine suborganelle spatial relationships, (3) Western blot analysis to evaluate a spectrum of protein expressions such as phosphorylated IP3R, p-PERK, p-IRE-1α, mitofusins, NADPH oxidases, TNF-α, and IL-1ß, and (4) determination of intracellular calcium concentrations to gauge intestinal barrier function impairment involving specific calcium pathway signals. Results: Results from the study painted a picture of significant infiltration by inflammatory cells within the mucosal and submucosal layers, compounded by pronounced endoplasmic reticulum expansion. Abundant interfaces between the ER and the mitochondria formed multiple structures known as mitochondria-associated membranes or MAMs. When evaluated under calcium-rich conditions, the protein levels mentioned earlier were notably elevated in the GPR109a knockdown (KD) group versus the infection control (NC) counterparts. However, this differential expression disappeared under calcium-depleted conditions or when treated with 2-aminoethyl diphenyl borinate (2-APB). Additionally, fluorescence intensity assays showed marked suppression in the GPR109a-KD plus lipopolysaccharide (LPS) group compared to the control. Conclusions: Drawing these observations to a close, the study concluded that GPR109a has an inhibitory effect on the advancement of ulcerative coloproctitis in mice. This is mediated through the activation of a calcium-induced oxidative stress cascade within macrophages, delineating a promising therapeutic pathway for the management of this inflammatory disease.