Increased pulmonary vascular permeability due to endothelial cell (EC) barrier dysfunction is a major pathological feature of acute respiratory distress syndrome/acute lung injury (ARDS/ALI), which is a devastating critical illness with high incidence and excessive mortality. Activation of NADPH oxidase (NOX) induces EC dysfunction via production of reactive oxygen species (ROS). However, the role(s) of NOX isoform(s), and their downstream signaling events, in the development of ARDS/ALI have remained unclear. Cecal Ligation Puncture (CLP) was used to induce preclinical septic ALI in wild-type mice and mice deficient in NOX2 or p47phox, or mice transfected of control siRNA, NOX1 or NOX4 siRNA in vivo. The survival rate of the CLP group at 24 h (26.6%, control siRNA treated) was substantially improved by NOX4 knockdown (52.9%). Mice lacking NOX2 or p47phox, however, had worse outcomes after CLP (survival rates at 0% and 8.3% respectively), whereas NOX1-silenced mice had similar survival rate (30%). NOX4 knockdown attenuated lung ROS production in septic mice, whereas NOX1 knockdown, NOX2 knockout, or p47phox knockout in mice had no effects. In addition, NOX4 knockdown attenuated redox-sensitive activation of the CaMKII/ERK1/2/MLCK pathway, and restored expression of EC tight junction proteins ZO-1 and Occludin to maintain EC barrier integrity. Correspondingly, NOX4 knockdown in cultured human lung microvascular ECs also reduced LPS-induced ROS production, CaMKII/ERK1/2/MLCK activation and EC barrier dysfunction. Scavenging superoxide
in vitro
and
in vivo
with TEMPO, or inhibiting CaMKII activation with KN93, had similar effects as NOX4 knockdown in preserving EC barrier dysfunction. In summary, we have identified a novel, selective and causal role of NOX4 (versus other NOX isoforms) in inducing lung EC barrier dysfunction and injury/mortality in a preclinical CLP-induced septic model, which involves redox-sensitive activation of CaMKII/ERK1/2/MLCK pathway. Targeting NOX4 may therefore prove to an innovative therapeutic option that is markedly effective in treating ALI/ARDS.
Hydrogen-rich saline has been reported to prevent neointimal hyperplasia induced by carotid balloon injury. The purpose of the present study was to further investigate the molecular mechanisms underlying this phenomenon. Daily injection of a hydrogen-rich saline solution (HRSS) in rats was employed to study the effect of hydrogen on balloon injury-induced neointimal hyperplasia and the neointima/media ratio was assessed. HRSS significantly decreased the neointima area and neointima/media ratio in a dose-dependent manner. In vitro effects of hydrogen on fetal bovine serum (FBS)-induced vascular smooth muscle cell (VSMC) proliferation were also investigated. Hydrogen-rich medium (HRM) inhibited rat VSMC proliferation and migration induced by 10% FBS. FBS-induced reactive oxygen species (ROS) production and activation of intracellular Ras, MEK1/2, ERK1/2, proliferative cell nuclear antigen (PCNA), Akt were significantly inhibited by HRM. In addition, HRM blocked FBS-induced progression from the G0/G1 to the S-phase and increased the apoptosis rate of VSMCs. These results showed that hydrogen-rich saline was able to attenuate FBS-induced VSMC proliferation and neointimal hyperplasia by inhibiting ROS production and inactivating the Ras-ERK1/2-MEK1/2 and Akt pathways. Thus, HRSS may have potential therapeutic relevance for the prevention of human restenosis.
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