Disruption of phospholipase Cgamma1 signalling attenuates cardiac tumor necrosis factor-alpha expression and improves myocardial function during endotoxemia.

AIMS

Lipopolysaccharide (LPS) induces tumor necrosis factor-alpha (TNF-alpha) expression in cardiomyocytes, which contributes to myocardial dysfunction during sepsis. The purpose of this study was to investigate the role of phosphatidylinositol (PI) phospholipase Cgamma1 (PLCgamma1) in cardiac TNF-alpha expression, and myocardial dysfunction during endotoxemia.

METHODS AND RESULTS

In cultured mouse neonatal cardiomyocytes, LPS increased PLCgamma1 phosphorylation. Knockdown of PLCgamma1 with specific siRNA or inhibition of PLCgamma1 with U73122 attenuated TNF-alpha expression induced by LPS. This action of PLCgamma1 was mediated through inositol-1,4,5-trisphosphate (IP3)/IP3 receptor (IP3R) pathways since blocking either IP3 or IP3R decreased LPS-induced TNF-alpha expression. In contrast, neither diacylglycerol agonist nor antagonist had any evident effect on LPS-induced TNF-alpha expression in cardiomyocytes. To investigate the role of PLCgamma1 in endotoxemia in vivo, wild-type and heterozygous PLCgamma1 knockout (PLCgamma1(+/-)) mice were pre-treated with either U73122, or its inactive analog U73343, or vehicle for 15 min, followed by LPS for 4 h. Inhibition of PLCgamma1 by U73122 or by heterozygous deletion of the PLCgamma1 gene decreased cardiac TNF-alpha expression. More importantly, LPS-induced myocardial dysfunction was also attenuated in PLCgamma1(+/-) mice or by U73122 treatment.

CONCLUSION

PLCgamma1 signalling induces cardiac TNF-alpha expression and myocardial dysfunction during LPS stimulation. The action of PLCgamma1 on TNF-alpha expression is mediated through IP3/IP3R pathways. The present results suggest that PLCgamma1 may be a potential therapeutic target for myocardial dysfunction in sepsis.