Ghrelin-induced cSrc activation through constitutive nitric oxide synthase-dependent S-nitrosylation in modulation of salivary gland acinar cell inflammatory responses to <i>Porphyromonas gingivalis</i>

Abstract

A peptide hormone, ghrelin, recognized for its role in the regulation of nitric oxide production has emerged as an important modulator of oral mucosal inflammatory responses to periodontopathic bacterium, <i>P. gingivalis</i>. As cSrc kinase plays a major role in controlling the activity of nitric oxide synthase (NOS) system, in this study we investigated the influence of <i>P. gingivalis</i> LPS on the processes of Src activation in rat sublingual gland acinar cells. The LPS-induced enhancement in the activity of inducible (i) iNOS and the impairment in constitutive (c) cNOS were reflected in the suppression in cSrc activity and the extent of its phosphorylation at Tyr⁴¹⁶. Further, we show that the countering effect of ghrelin on the LPS-induced changes in cSrc activity and the extent of its phosphorylation was accompanied by a marked reduction in iNOS and the increase in cNOS activation through phosphorylation at Ser1179. Moreover, the effect of ghrelin on cSrc activation was associated with the kinase S-nitrosylation that was susceptible to the blockage by cNOS inhibition. Our findings suggest that <i>P. gingivalis</i>-induced up-regulation in iNOS leads to disturbances in cNOS phosphorylation that exerts the detrimental effect on the processes of cSrc activation through cNOS mediated S-nitrosylation. We also show that the effect of ghrelin on <i>P. gingivalis</i>-induced inflammatory changes are manifested in the enhancement in cSrc activation through S-nitrosylation and the increase in its phosphorylation at Tyr⁴¹⁶.