PAR4 Inhibition Reduces Coronary Artery Atherosclerosis and Myocardial Fibrosis in SR-B1/LDLR Double Knockout Mice.

BACKGROUND: SR-B1 (scavenger receptor class B type 1)/LDLR (low-density lipoprotein receptor) double knockout mice fed a high-fat, high-cholesterol diet containing cholate exhibit coronary artery disease characterized by occlusive coronary artery atherosclerosis, platelet accumulation in coronary arteries, and myocardial fibrosis. Platelets are involved in atherosclerosis development, and PAR (protease-activated receptor) 4 has a prominent role in platelet function in mice. However, the role of PAR4 on coronary artery disease in mice has not been tested. METHODS: We tested the effects of a PAR4 inhibitory pepducin (RAG8) on diet-induced aortic sinus and coronary artery atherosclerosis, platelet accumulation in atherosclerotic coronary arteries, and myocardial fibrosis in SR-B1/LDLR double knockout mice. SR-B1/LDLR double knockout mice were fed a high-fat, high-cholesterol diet containing cholate and injected daily with 20 mg/kg of either the RAG8 pepducin or a control reverse-sequence pepducin (SRQ8) for 20 days. RESULTS: Platelets from the RAG8-treated mice exhibited reduced thrombin and PAR4 agonist peptide-mediated activation compared with those from control SRQ8-treated mice when tested ex vivo. Although aortic sinus atherosclerosis levels did not differ, RAG8-treated mice exhibited reduced coronary artery atherosclerosis, reduced platelet accumulation in atherosclerotic coronary arteries, and reduced myocardial fibrosis. These protective effects were not accompanied by changes in circulating lipids, inflammatory cytokines, or immune cells. However, RAG8-treated mice exhibited reduced VCAM-1 (vascular cell adhesion molecule 1) protein levels in nonatherosclerotic coronary artery cross sections and reduced leukocyte accumulation in atherosclerotic coronary artery cross sections compared with those from SRQ8-treated mice. CONCLUSIONS: The PAR4 inhibitory RAG8 pepducin reduced coronary artery atherosclerosis and myocardial fibrosis in SR-B1/LDLR double knockout mice fed a high-fat, high-cholesterol diet containing cholate. Furthermore, RAG8 reduced VCAM-1 in nonatherosclerotic coronary arteries and reduced leukocyte and platelet accumulation in atherosclerotic coronary arteries. These findings identify PAR4 as an attractive target in reducing coronary artery disease development, and the use of RAG8 may potentially be beneficial in cardiovascular disease.

Protease activated receptor-1 targeted 99Tcm-(HYNIC-BMS-200261) (tricine) (TPPTS) imaging on nude mice bearing human breast cancer / 中华核医学与分子影像杂志

Objective To study the reliability of 99Tcm-(hydrazinonicotinamide (HYNIC)-BMS-200261) (tricine) (trisodium triphenylphosphine-3,3',3"-trisulfonate (TPPTS)) as a radiotracer for protease activated receptor-1 (PAR-1) expression in breast cancer.Methods Fifteen nude mice bearing MDA-MB-435,MDA-MB-231 and MCF-7 human breast cancer xenografts (5 mice for each cell line) with different PAR-1 expression were used for 99Tcm-(HYNIC-BMS-200261) (tricine) (TPPTS) γ imaging,and tumor/non-tumor (T/NT) ratios were obtained with region of interest (ROI) technique.Afterwards,the biodistribution of 99Tcm-(HYNIC-BMS-200261) (tricine) (TPPTS) was analyzed in tumor-bearing nude mice,and the radioactivity in tumor (percentage activity of injection dose per gram of tissue,％ID/g) was calculated.The immunostaining was performed to examine PAR-1 expression in tumor tissue and semi-quantitative analysis was used.One-way analysis of variance and Pearson correlation analysis were used to analyze data.Results At 2 h postinjection,the T/NT ratios were 3.03±0.32,2.27±0.25 and 1.51±0.13 respectively in nude mice bearing MDA-MB-435,MDA-MB-231 and MCF-7 xenografts;the tumor uptakes of 99Tcm-(HYNIC-BMS-200261)(tricine)(TPPTS) were (1.03±0.15),(0.56±0.14) and (0.30±0.06) ％ID/g;PAR-1 expression levels were (17.22±2.71) ％,(10.78± 1.95) ％ and (2.80± 1.18) ％,respectively (F values:47.66,46.36,62.35,all P＜0.05).The T/NT ratios and tumor uptake of 99Tcm-(HYNIC-BMS-200261) (tricine) (TPPTS) at 2 h post-injection were correlated with PAR-1 expression (r values:0.934 and 0.929,both P＜0.05).Conclusions 99Tcm-(HYNIC-BMS-200261) (tricine) (TPPTS) imaging could be a noninvasive and effective method for monitoring PAR-1 expression in human breast cancer.

Targeting coagulation factor receptors - protease-activated receptors in idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a lethal lung disease with a 5-year mortality rate of > 50% and unknown etiology. Treatment options remain limited and, currently, only two drugs are available, i.e. nintedanib and pirfenidone. However, both of these antifibrotic agents only slow down the progression of the disease, and do not remarkably prolong the survival of IPF patients. Hence, the discovery of new therapeutic targets for IPF is crucial. Studies exploring the mechanisms that are involved in IPF have identified several possible targets for therapeutic interventions. Among these, blood coagulation factor receptors, i.e. protease-activated receptors (PARs), are key candidates, as these receptors mediate the cellular effects of coagulation factors and play central roles in influencing inflammatory and fibrotic responses. In this review, we will focus on the controversial role of the coagulation cascade in the pathogenesis of IPF. In the light of novel data, we will attempt to reconciliate the apparently conflicting data and discuss the possibility of pharmacologic targeting of PARs for the treatment of fibroproliferative diseases.

The expression of protease-activated receptors in colon mucosa tissue of patients with diarrhea-predominant irritable bowel syndrome and its significance / 中华消化杂志

Objective To investigate the expression of protease-activated receptors (PARs) in colon mucosal tissue of patients with diarrhea-predominant irritable bowel syndrome (D-IBS). Methods Colon mucosa tissues were obtained from 28 D-IBS patients and 18 normal controls by colonoscopy.The expression of PARs was detected using Western blotting and real-time PCR. Data were analysed by SPSS 18. 0 softwave, and comparisons between groups were done using Mann-Whitney U test.Results There was no difference in expression of PAR1 between D-IBS patients and normal controls (P=0. 300). The expressions of PAR2 and PAR4 were higher in D-IBS patients than those in normal controls (0.99±0.67 vs 0.63±0.38, P=0.038 and 0.37±0. 14 vs 0.25±0. 11, P=0.013,respectively). The results of real-time PCR were in accordance with those of Western blotting.Conclusion The increased expressions of PAR2 and PAR4 in colon mucosa of D-IBS patients indicate that these two PAR receptors may be involved in the process of D-IBS.