| First Author | Fan H | Year | 2011 |
| Journal | Biochim Biophys Acta | Volume | 1813 |
| Issue | 3 | Pages | 466-72 |
| PubMed ID | 21255617 | Mgi Jnum | J:170605 |
| Mgi Id | MGI:4946970 | Doi | 10.1016/j.bbamcr.2011.01.012 |
| Citation | Fan H, et al. (2011) Heterotrimeric Galpha(i) proteins are regulated by lipopolysaccharide and are anti-inflammatory in endotoxemia and polymicrobial sepsis. Biochim Biophys Acta 1813(3):466-72 |
| abstractText | Previous studies have implicated a role of heterotrimeric Galpha(i) proteins in lipopolysaccharide (LPS)-induced inflammatory responses. We hypothesized that Toll-like receptor (TLR) signaling regulates Galpha(i) proteins, which are anti-inflammatory in endotoxemia and polymicrobial sepsis. RAW 264.7 cells were stimulated with LPS and the Galpha(i)-GTP protein complex was immunoprecipitated with a Galpha(i) protein activation assay. In subsequent in vivo studies, the Galpha(i) protein inhibitor pertussis toxin (PTx) or G(i) protein agonist mastoparan (MP-7) were administrated prior to endotoxemia. LPS-induced pro-inflammatory cytokines and mortality were determined. To examine the role of Galpha(i2) in sepsis, Galpha(i2) (-/-) and wildtype (WT) mice were subjected to cecal ligation and puncture (CLP) and monitored every 24 h for 120 h. Other mice were sacrificed 24 h after CLP. Peritoneal fluid, blood, and tissue samples were collected. Plasma pro-inflammatory cytokine production, bacterial load in peritoneal fluid, blood and lung tissue, myeloperoxidase (MPO) activity in lung and liver and different immune cell populations in spleen were studied. We found that Galpha(i) proteins are rapidly activated by LPS followed by rapid inactivation. These studies provide the first direct evidence that Galpha(i) proteins are modulated by TLR signaling. In following studies, PTx augmented LPS-induced plasma TNFalpha, IL-6, whereas MP-7 suppressed LPS-induced TNFalpha and decreased LPS-induced mortality. In sepsis studies, the survival rate post-CLP was significantly decreased in the Galpha(i2) (-/-) mice compared to WT mice. CLP-induced plasma TNFalpha, IL-6, bacterial load in peritoneal fluid, blood and lung tissue and lung and liver MPO activity were significantly increased in Galpha(i2) (-/-) compared to WT mice. Galpha(i2) (-/-) mice also exhibited increased Th1 and Th2 responses compared to WT mice. Taken together, Galpha(i) proteins are activated by LPS and negatively regulate endotoxemia and sepsis. Understanding the role of Galpha(i2) protein in regulation of the inflammatory response in sepsis may provide novel targets for treatment of sepsis. |
