The online version of this article (doi:10.1186/1476-9255-9-1) contains supplementary material, which is available to authorized users.
The authors declare that they have no competing interests.
AN participated in the experimental work and drafting the manuscript. KM participated in the experimental work. MY and IA participated in the study design and drafting of the manuscript. PK conceived the study, participated in its design and coordination and drafting of the manuscript. All authors read and approved the final manuscript.
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 H2O2, 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 (IC50 ~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.
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Sweet MJ, Hume DA: Endotoxin signal transduction in macrophages. J Leukoc Biol. 1996, 60 (1): 8-26. PubMed
Marwick JA, Chung KF, Adcock IM: Phosphatidylinositol 3-kinase isoforms as targets in respiratory disease. Ther Adv Respir Dis. 4 (1): 19-34.
Seldon PM, et al.: Suppression of lipopolysaccharide-induced tumor necrosis factor-alpha generation from human peripheral blood monocytes by inhibitors of phosphodiesterase 4: interaction with stimulants of adenylyl cyclase. Mol Pharmacol. 1995, 48 (4): 747-57. PubMed
Liang BT, Galper JB: Differential sensitivity of alpha o and alpha i to ADP-ribosylation by pertussis toxin in the intact cultured embryonic chick ventricular myocyte. Relationship to the role of G proteins in the coupling of muscarinic cholinergic receptors to inhibition of adenylate cyclase activity. Biochem Pharmacol. 1988, 37 (23): 4549-55. 10.1016/0006-2952(88)90671-5. CrossRefPubMed
Weingarten R, et al.: Mastoparan interacts with the carboxyl terminus of the alpha subunit of Gi. J Biol Chem. 1990, 265 (19): 11044-9. PubMed
- LPS induced inflammatory responses in human peripheral blood mononuclear cells is mediated through NOX4 and Giα dependent PI-3kinase signalling
Paul A Kirkham
- BioMed Central
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