The role of the gut microbiome and bile acid metabolism in chronic liver diseases

Abstract

Atherosclerosis, characterized by the deposition of fatty materials underneath the arterial wall, is a chronic inflammatory disease responsible for several fatal cardiovascular events, including myocardial infarction and stroke which rank the top causes of mortality globally. Emerging animal studies and clinical trials confirmed that unresolved inflammation is contributing to all stages of atherosclerosis. Leukocytes infiltration is indispensable for the chronic inflammation and evidence points to neutrophil recently. As a major effector of neutrophil, proteinase-3 (PR3), a neutrophil derived granule protein, possesses antimicrobial activity and modulates inflammation by different means. The pathophysiological roles of PR3 are complicated in many inflammatory and autoimmune diseases while the use of its inhibitors can reverse the adverse conditions. PR3 protein and its enzymatic activity are correlated with the severity of plaque in cardiovascular disease (CVD) patients, however the functional role of PR3 in the pathogenesis of atherosclerosis remains elusive. To this end, our current study sought to address whether PR3 played a contributing role in the animal model of atherosclerosis. The current study revealed the expression profile of neutrophil serine protease, PR3, in high fat high cholesterol (HFHC) diet-induced ApoE knockout (KO) atherosclerotic mice. In line with the significant plaque development and advancement, the circulating level of PR3 and the proteolytic activity of the enzyme were elevated in HFHC group when compared with standard chow-fed mice. We then generated PR3 KO mice in C57 BL/6J ApoE-KO genetic background to study the role of PR3 in atherosclerosis. The knockdown of PR3 was confirmed by genotyping and western blot analysis. Histological evaluation of atherosclerotic lesions in aorta demonstrated the improvement in atherosclerotic plaque development and progression in PR3-KO animals after 12-week HFHC diet induction, as compared with littermates. The genetic ablation of PR3 significantly attenuated macrophage infiltration and vascular smooth muscle cell proliferation in the lesion. Moreover, the expression of pro-inflammatory cytokines was significantly reduced in PR3-deficient mice than in their WT littermates. Despite ameliorated atherosclerosis was found in the PR3-KO animals, the other metabolic phenotypes including body weight gain, fat mass, serum lipid profiles and glucose tolerance were not different between the PR3-KO mice and their WT littermates. In conclusion, PR3 levels and its activity were significantly enriched in the animal with significant plaque development while genetic ablation of PR3 hindered the progression of the disease. These findings collectively indicate that PR3 is actively involved in the pathogenesis of atherosclerosis and further study regarding its potential as a therapeutic target is warranted.