Inhibition of SOCs Attenuates Acute Lung Injury Induced by Severe Acute Pancreatitis in Rats and PMVECs Injury Induced by Lipopolysaccharide

Acute lung injury (ALI) is a critical complication of the severe acute pancreatitis (SAP), characterized by increased pulmonary permeability with high mortality. Pulmonary microvascular endothelial cells (PMVECs) injury and apoptosis play a key role in ALI. Previous studies indicated that store-operated calcium entry (SOCE) could regulate a variety of cellular processes. The present study was to investigate the effects of SOCE inhibition on ALI induced by SAP in Sprague-Dawley rats, and PMVECs injury induced by lipopolysaccharide (LPS). Rat model of SAP-associated ALI were established by the retrograde infusion of sodium deoxycholate. Serum levels of amylase, TNF-α, and IL-6, histological changes, water content of the lung, oxygenation index, and ultrastructural changes of PMVECs were examined in ALI rats with or without store-operated Ca²⁺ channels (SOCs) pharmacological inhibitor (2-aminoethoxydiphenyl borate, 2-APB) pretreatment. For in vitro studies, PMVECs were transiently transfected with or without small interfering RNA (siRNA) against calcium release-activated calcium channel protein1 (Orai1) and stromal interaction molecule1 (STIM1), the two main molecular constituents of SOCs, then exposed to LPS. The viability of PMVECs was determined. The expression of STIM1, Orai1, Bax, and caspase3, both in lung tissue and in PMVECs, were assessed by quantitative real-time PCR and western blot. Administration of sodium deoxycholate upregulated the expression of SOCs proteins in lung tissue. Similarly, the SOCs proteins were increased in PMVECs induced by LPS. 2-APB reduced the serum levels of amylase, TNF-α, and IL-6, and attenuated lung water content and histological findings. In addition, the decreased oxygenation index and ultrastructural damage in PMVECs associated with SAP were ameliorated after administration of 2-APB. Knockdown of STIM1 and Orai1 inhibited LPS-induced PMVECs death. Furthermore, blockade of SOCE significantly suppressed Orai1, STIM1, Bax, and caspase3 expression both in vivo and in vitro. These results suggest that SOCE may play a critical role in SAP-associated ALI and the protective effects of inhibition of SOCs could be mediated, at least partially, by restraining mitochondrial associated apoptosis of PMVECs.