The inhibitory effects of H+K+ATPase inhibitors on human neutrophils in vitro:: Restoration by a K+ ionophore

Objective: This study investigated the ability of proton pump inhibitors (PPI), such as omeprazole and pantoprazole, to inhibit neutrophil migration, calcium mobilization and the mechanisms involved in this inhibition. Methods: Neutrophils were incubated with different concentrations of omeprazole and pantoprazole for 30 min and stimulated to migrate with fMLP and IL-8. Treatment toxicity was assessed by MTT assay. The intracellular calcium levels were analyzed in neutrophils pre-treated with omeprazole and pre-loaded with FURA-2AM, when stimulated with fMLP. The activity of p38 MAP Kinase was evaluated by Western blot after treatment with omeprazole. Results: Omeprazole is able to inhibit neutrophil chemotaxis to fMLP and IL-8. Pantoprazole demonstrated the same ability. This inhibitory effect was not due to a toxic effect of the proton pump inhibitors. Inhibition of v-ATPase by bafilomycin did not modify the ability of fMLP or IL-8 to induce neutrophil migration. Omeprazole was also able to decrease intracellular calcium availability. The addition of a potassium ionophore, nigericin, restored the migratory ability, as well as the intracellular calcium levels. The activity of p38 MAP Kinase was decreased in neutrophils pretreated with omeprazole. Conclusion: Proton pump inhibitors promote inhibition of H(+)K(+)ATPase in neutrophils, resulting in cationic flow disturbances through the cellular membrane that, consequently, inhibit migratory and intracellular events such as calcium influx and p38 MAP Kinase activation.