Fluid shear stress induces upregulation of COX-2 and PGI₂release in endothelial cells via a pathway involving PECAM-1, PI3K, FAK, and p38

Abstract

Vascular endothelial cells play an important role in the regulation of vascular function in response to mechanical stimuli in both healthy and diseased states. Prostaglandin I (PGI) is an important antiatherogenic prostanoid and vasodilator produced in endothelial cells through the action of the cyclooxygenase (COX) isoenzymes COX-1 and COX-2. However, the mechanisms involved in sustained, shear-induced production of COX-2 and PGI have not been elucidated but are determined in the present study. We used cultured endothelial cells exposed to steady fluid shear stress (FSS) of 10 dyn/cm for 5 h to examine shear stress-induced induction of COX-2/PGI Our results demonstrate the relationship between the mechanosensor platelet endothelial cell adhesion molecule-1 (PECAM-1) and the intracellular mechanoresponsive molecules phosphatidylinositol 3-kinase (PI3K), focal adhesion kinase (FAK), and mitogen-activated protein kinase p38 in the FSS induction of COX-2 expression and PGI release. Knockdown of PECAM-1 (small interference RNA) expression inhibited FSS-induced activation of αβ-integrin, upregulation of COX-2, and release of PGI in both bovine aortic endothelial cells (BAECs) and human umbilical vein endothelial cells (HUVECs). Furthermore, inhibition of the PI3K pathway (LY294002) substantially inhibited FSS activation of αβ-integrin, upregulation of COX-2 gene and protein expression, and release of PGI in BAECs. Inhibition of integrin-associated FAK (PF573228) and MAPK p38 (SB203580) also inhibited the shear-induced upregulation of COX-2. Finally, a PECAM-1 mouse model was characterized by reduced COX-2 immunostaining in the aorta and reduced plasma PGI levels compared with wild-type mice, as well as complete inhibition of acute flow-induced PGI release compared with wild-type animals. In this study we determined the major mechanotransduction pathway by which blood flow-driven shear stress activates cyclooxygenase-2 (COX-2) and prostaglandin I (PGI) release in endothelial cells. Our work has demonstrated for the first time that COX-2/PGI mechanotransduction is mediated by the mechanosensor platelet endothelial cell adhesion molecule-1 (PECAM-1).

Focal adhesion kinase signaling regulates anti-inflammatory function of bone marrow mesenchymal stromal cells induced by biomechanical force

“…ERK and Akt have been shown to be sensitive to mechanosensors such as caveolae, cadherins, cell-cell adhesion molecules, and Ca 2+ signaling [33,35–38]. Fluid shear stress elevated PTGS2 expression in osteoblasts through activation of phosphatidylinositol 3-kinase (PI3K)-Akt [39], and was recently shown to induce COX2 expression and prostacyclin release from endothelial cells via a platelet endothelial cell adhesion molecule (PECAM-1)-PI3K-dependent pathway [40]. Thus, we hypothesized that PI3K/Akt may contribute to regulation of COX2 in MSCs.…”

“…The tyrosine kinase FAK is one of many constituents that localize to focal adhesions, where integrins, actin, and various other scaffolding molecules, GTPases, and enzymes such as kinases, phosphatases, proteases, and lipases gather and interact [41]. FAK has been shown in previous reports to be required for shear-induced PTGS2 and COX2 in endothelium and osteoblasts [39,40]. We therefore hypothesized that FAK might also mediate COX2 mechanoresponse in MSCs.…”

Mechanoregulation of p38 activity enhances endoplasmic reticulum stress‐mediated inflammation by arterial endothelium

“…We next examined the signal pathways responsible for SS‐mediated differential expression between VCAM‐1 and ICAM‐1. PECAM‐1 is known to mechanotransduce signals derived from fluid SS via the downstream kinase PI3K (17). Employing shRNA‐loaded lentivirus to knock down PECAM‐1, transfected HAECs were confirmed to be 75‐80% deficient in PECAM‐1 protein by Western blot as previously reported in Bailey et al .…”

“…Values are means 6 SE; n = 3-6 experiments. *P , 0.05, **P , 0.005. that plays a central role in initiating flow-induced signaling (15)(16)(17). We reported that the shear modulation of both VCAM-1 and ICAM-1 in TNF-a-stimulated HAEC was dependent upon a PECAM-1-mediated mechanism (7).…”

“…In contrast, deactivation of p38 occurred more rapidly in HAECs exposed to high SS, leading to differential activity levels at 2 h. This response was attributable to enhanced early expression of MKP‐1 under high SS. Although there is evidence in the literature supporting p38 activation by SS and TNF‐α, less is known regarding how SS‐modulated p38 signaling affects downstream targets to modulate VCAM‐1 transcription (17, 19, 23, 24). Several reports in animal models link SS modulation of p38 to regulation of VCAM‐1.…”