Mast Cell Deficiency Leads to Decreased Expression of Cyclooxygenase-1 (COX1), COX2, Toll-Like Receptor-4 (TLR4) and Endothelial Nitric Oxide Synthase (eNOS) mRNA in Mouse Aorta (100.8)

Abstract

Abstract Mast cells (MC) are well known for their contribution to vascular inflammation and atherosclerosis. We have shown that MC proteases and histamine amplify lipopolysaccharide (LPS)-induced inflammatory responses in human coronary artery endothelial cells via stimulation of TLR4 expression. This study examined mRNA levels of COX1, COX2, TLR4 and eNOS in aortic tissues of MC-deficient (W/Wv) mice and wild type controls (WT) to gain insight into the role of MC in vascular pathophysiology. We also determined the effect of MC degranulation on gene expression in aortas 24 h after intraperitoneal injection of MC degranulation agent compound 48/80 (1 μg/g body wt). We found that, in comparison to WT, aortic tissues of W/Wv mice express lower levels of COX1, COX2, TLR4 and eNOS mRNA. Injection of compound 48/80 resulted in marked stimulation of expression of these genes in aortas of WT, but not in W/Wv mice, confirming the involvement of MC degranulation products in this process. To determine whether a deficiency of MC and/or decreased COX expression in W/Wv mice is associated with changes in prostanoid homoeostasis, the levels of prostacyclin and thromboxane A2 metabolites in urine samples were analyzed. The levels of 6-keto PGF1α and 11-dehydro TXB2 in 24 h urine of both genotypes were comparable when normalized for the volume and creatinine excretion. These results suggest that, although MC deficiency suppresses the expression of COX1 and COX2 genes in the vasculature, the systemic prostanoid homeostasis remains protected. (Supported by NIH R01-HL070101 and Carey Arthritis Fund)