Suppression of Ca²⁺ influx in endotoxin-treated mouse cerebral cortex endothelial bEND.3 cells

Release of nitric oxide (NO) is triggered by a rise in endothelial cell (EC) cytosolic Ca²⁺ concentration ([Ca²⁺]_i) and is of prime importance in vascular tone regulation as NO relaxes vascular smooth muscle. Agonists could stimulate EC [Ca²⁺]_i elevation by triggering Ca²⁺ influx via plasma membrane ion channels, one of which is the store-operated Ca²⁺ channel; the latter opens as a result of agonist-triggered internal Ca²⁺ release. Endotoxin (lipopolysaccharide, LPS) could cause sepsis, which is often the fatal cause in critically ill patients. One of the LPS-induced damages is EC dysfunction, eventually leading to perturbations in hemodynamics. We obtained data showing that LPS-challenged mouse cerebral cortex endothelial bEND.3 cells did not suffer from apoptotic death, and in fact had intact agonist-triggered intracellular Ca²⁺ release; however, they had reduced store-operated Ca²⁺ entry (SOCE) after LPS treatment for 3 h or more. Using real-time PCR, we did not find a decrease in gene expression of stromal interaction molecule 1 (STIM1) and Orai1 (two SOCE protein components) in bEND.3 cells treated with LPS for 15 h. LPS inhibitory effects could be largely prevented by sodium salicylate (an inhibitor of nuclear factor-κB; NF-κB) or SB203580 (an inhibitor of p38 mitogen-activated protein kinases; p38 MAPK), suggesting that the p38 MAPK-NF-κB pathway is involved in SOCE inhibition.