Ghrelin Protection against Lipopolysaccharide-Induced Gastric Mucosal Cell Apoptosis Involves Constitutive Nitric Oxide Synthase-Mediated Caspase-3 S-Nitrosylation

Bronislaw L Slomiany,Amalia Slomiany

doi:10.1155/2010/280464

Bronislaw L Slomiany, Amalia Slomiany

Open Access

https://doi.org/10.1155/2010/280464

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Abstract

Ghrelin, a peptide hormone produced mainly in the stomach, has emerged as an important modulator of the inflammatory responses that are of significance to the maintenance of gastric mucosal integrity. Here, we report on the role of ghrelin in controlling the apoptotic processes induced in gastric mucosal cells by H. pylori lipopolysaccharide (LPS). The countering effect of ghrelin on the LPS-induced mucosal cell apoptosis was associated with the increase in constitutive nitric oxide synthase (cNOS) activity, and the reduction in caspase-3 and inducible nitric oxide synthase (NOS-2). The loss in countering effect of ghrelin on the LPS-induced changes in apoptosis and caspase-3 activity was attained with Src kinase inhibitor, PP2, as well as Akt inhibitor, SH-5, and cNOS inhibitor, L-NAME. Moreover, the effect of ghrelin on the LPS-induced changes in cNOS activity was reflected in the increased cNOS phosphorylation that was sensitive to SH-5. Furthermore, the ghrelin-induced up-regulation in cNOS activity was associated with the increase in caspase-3 S-nitrosylation that was susceptible to the blockage by L-NAME. Therefore, ghrelin protection of gastric mucosal cells against H. pylori LPS-induced apoptosis involves Src/Akt-mediated up-regulation in cNOS activation that leads to the apoptotic signal inhibition through the NO-induced caspase-3 S-nitrosylation.

Highlights

Lipopolysaccharide (LPS), a component of the outer membrane of Gram-negative bacterium H. pylori colonizing the gastric mucosa, is recognized as a potent endotoxin responsible for eliciting mucosal inflammatory responses that characterize gastritis and duodenal ulcers [1, 2]
We found that significant loss in the preventive effect to ghrelin on the LPS-induced changes in the mucosal cell apoptosis and caspase-3 activity occurred with Src kinase inhibitor, PP2, as well as Akt inhibitor, SH-5, and constitutive nitric oxide synthase (cNOS) inhibitor, L-NAME, while selective nitric oxide synthase (NOS)-2 inhibitor, 1400 W, had no effect (Figure 5)
In keeping with recent evidence for the role of ghrelin in controlling gastric mucosal inflammatory responses through regulation of the mucosal NO production [15,16,17,18], in the present study we examined the influence of this peptide hormone on the apoptotic processes associated with H. pylori infection

Summary

Introduction

Lipopolysaccharide (LPS), a component of the outer membrane of Gram-negative bacterium H. pylori colonizing the gastric mucosa, is recognized as a potent endotoxin responsible for eliciting mucosal inflammatory responses that characterize gastritis and duodenal ulcers [1, 2]. The gastric mucosal response to H. pylori LPS or associated with gastritis caused by H. pylori infection is manifested by the increase in proinflammatory cytokine production, disturbances in nitric oxide generation system, and a massive rise in epithelial cell apoptosis [1, 3, 4]. Its massive and sustained activation may have cytotoxic consequences, causing transcriptional disturbances and the induction of apoptosis through the activation of a group of aspartatespecific cysteine proteases, caspases [6, 7]. Based on their function, the caspase proteases are categorized into initiator and executioner subtypes [6, 8]. The activation of executioner caspases is recognized as an irreversible commitment to the execution phase of apoptosis characterized by cytoplasmic shrinkage, breakdown of nuclear envelope, condensation of chromatin structure, and DNA fragmentation [8, 9]

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