LPS induced inflammatory responses in human peripheral blood mononuclear cells is mediated through NOX4 and G iα dependent PI-3kinase signalling

Copd is a disease of innate immunity and bacterial infections are a dominant cause of exacerbations in the later stages resulting in poor health and high mortality. the pathogen-associated molecular pattern (pamp) lipopolysaccharide (lps) is sensed by immune cells through activation of the toll-like receptor 4 (tlr4). this leads to the activation of nadph oxidase (nox) and nf-κb which together drive copd inflammation. in this study we show in human pbmcs that lps stimulated proinflammatory cytokine release (cxcl8 and il6) was inhibited by approximately 50% by the broad specificity phosphatidylinositol 3-kinase (pi3k) inhibitor,wortmannin. our results also demonstrate that activation of pi3k following lps stimulation is mediated by a nox4 dependent mechanism releasing endogenous h 2o 2,as the nox4 inhibitor apocynin blocked lps induced akt phosphorylation. moreover,lps-induced pi3k activation was inhibited by the anti-oxidant n-acetylcysteine in a concentration dependent manner (ic 50∼100 μm). in addition,our data demonstrated that inhibition of small g proteins,by pre-treatment with pertussis toxin,inhibited lps-induced akt phosphorylation. furthermore,the g-protein inhibitors pertussis toxin and mastoparan both inhibited lps-induced cxcl8 and il-6 release by approximately 50%. together,these data indicate there is a mechanism in human pbmcs where tlr4 activation by lps leads to ros generation through nox4 and activation of the pi3k pathway. this effect is apparently mediated through small g proteins facilitating the release of pro-inflammatory cytokines. © 2012 ngkelo et al; licensee biomed central ltd.