Blockade of NOX2 and STIM1 signaling limits lipopolysaccharide-induced vascular inflammation

Abstract

During sepsis, acute lung injury (ALI) results from activation of innate immune cells and endothelial cells by endotoxins, leading to systemic inflammation through proinflammatory cytokine overproduction, oxidative stress, and intracellular Ca 2+ overload. Despite considerable investigation, the underlying molecular mechanism(s) leading to LPS-induced ALI remain elusive. To determine whether stromal interaction molecule 1-dependent (STIM1-dependent) signaling drives endothelial dysfunction in response to LPS, we investigated oxidative and STIM1 signaling of EC-specific Stim1-knockout mice. Here we report that LPSmediated Ca 2+ oscillations are ablated in ECs deficient in Nox2, Stim1, and type II inositol triphosphate receptor (Itpr2). LPS-induced nuclear factor of activated T cells (NFAT) nuclear accumulation was abrogated by either antioxidant supplementation or Ca 2+ chelation. Moreover, ECs lacking either Nox2 or Stim1 failed to trigger store-operated Ca 2+ entry (SOCe) and NFAT nuclear accumulation. LPS-induced vascular permeability changes were reduced in EC-specific Stim1 -/-mice, despite elevation of systemic cytokine levels. Additionally, inhibition of STIM1 signaling prevented receptor-interacting protein 3-dependent (RIP3-dependent) EC death. Remarkably, BTP2, a small-molecule calcium release-activated calcium (CRAC) channel blocker administered after insult, halted LPS-induced vascular leakage and pulmonary edema. These results indicate that ROS-driven Ca 2+ signaling promotes vascular barrier dysfunction and that the SOCe machinery may provide crucial therapeutic targets to limit sepsis-induced ALI.

Calcium flux and endothelial dysfunction during acute lung injury: a STIMulating target for therapy

“…By sensing the oxidant stress, STIM1 acts as a coincidence detector to activate SOCE and alter mitochondrial oxidative metabolism. In the present work, the authors extend these findings by identifying TLR4 and NADPH oxidase (NOX2) as key components in this pathway (5). LPS/TLR4 signaling can activate NOX2 and thus elevate oxidant stress through increased ROS production.…”

“…In addition to outlining the critical role of STIM1 in mediating calcium oscillations and vascular permeability after LPS injury, Gandhirajan et al tested a therapy that uncouples TLR4-mediated ROS from Ora1 channel calcium flux by blocking Oria1 channels (5). The authors utilized BTP2, a pyrazole-derived inhibitor of calcium release-activated calcium (CRAC) channels, which was originally described as a T cell immunosuppressant (13).…”

STIM1/ORAI1-mediated Ca2+ Influx Regulates Enolase-1 Exteriorization

“…We focused on STIM1, ORAI1, and Ca v 1.2 LTCC because these Ca 2ϩ channels have been found to control translocation of other PLG receptors to the cell surface and to regulate LPS-induced inflammatory responses (37)(38)(39). Whereas STIM1 and ORAI1 mRNA were detected in MDA-MB-231 cells, Ca v 1.2 was not expressed in this cell line (Fig.…”

Molecular pharmacology of store-operated CRAC channels

“…18,19 Ca 2+ influx through CRAC channels is essential to activate the transcription factor NFAT that regulates the expression of a variety of cytokines essential for T-cell function, a pathway that is defective in the SCID patients. 20 Since then, the importance of this pathway has been highlighted in a range of functions in many different cell types including various subsets of T cells, 21 B cells, 22,23 mast cells, 24,25 vascular smooth muscle, [26][27][28] endothelium, 29 platelets, 30,31 melanocytes, 32 and skeletal muscle. [33][34][35] Despite the biophysical characterization of CRAC channels, the molecular mechanism that linked store-depletion to channel activation as well as the molecular identity of the channel itself REVIEW REVIEW resting ER Ca 2+ concentration.…”