MECHANICAL STRAIN INCREASES ENDOTHELIN-1 GENE-EXPRESSION VIA PROTEIN-KINASE-C PATHWAY IN HUMAN ENDOTHELIAL-CELLS

Vascular endothelial cells (ECs) are constantly subjected to mechanica l strain due to relaxation and contraction of vessel walls. The effect s of cyclical strain on endothelin-1 (Et-1) secretion and Et-1 mRNA le vels in human umbilical vein ECs were examined. Cultured ECs grown on a flexible membrane base were deformed by negative pressure (16 kPa at 60 cycles/min). Cells subjected to strain showed increased Et-1 secre tion (0.54 ng/hr/10(6) cells) compared with unstrained control cells ( 0.22 ng/hr/10(6) cells). Northern blot analysis of cells strained for 2 hours or longer demonstrated a sustained elevated Et-1 mRNA level at more than double the level in unstrained controls. This strain-induce d ET-1 mRNA level returned to its basal level 2 hours after the releas e of strain. Cells treated with actinomycin D before or during strain treatment showed no strain-induced gene expression. Pretreatment of EC s with a protein kinase C (PKC) inhibitor, Calphostin C, strongly inhi bited the strain-induced Et-1 gene expression. Pretreatment of ECs wit h cAMP- or cGMP-dependent protein kinase inhibitors (KT5720 or KT5823) only partially inhibited the increased Et-1 mRNA levels in strain-tre ated cells. EGTA strongly inhibited the Et-1 gene expression. The intr acellular calcium chelator BAPTA/AM also showed an inhibitory effect o n Et-1 mRNA levels. We conclude that mechanical strain can stimulate t he secretion of Et-1 from ECs by increasing Et-1 mRNA levels via trans cription, and that this gene induction is mediated predominantly via t he PKC pathway and requires extracellular Ca2+ This strain-induced Et- 1 gene expression in ECs may contribute to the regulation of vascular tone and structure in normal and pathological states of the cardiovasc ular system. (C) 1995 Wiley-Liss, Inc.