Effects ofHelicobacter pylorion intracellular Ca2+signaling in normal human gastric mucous epithelial cells

Abstract

In stomach, Helicobacter pylori ( Hp) adheres to gastric mucous epithelial cells (GMEC) and initiates several different signal transduction events. Alteration of intracellular Ca2+concentration ([Ca2+]i) is an important signaling mechanism in numerous bacteria-host model systems. Changes in [Ca2+]iinduced by Hp in normal human GMEC have not yet been described; therefore, we examined effects of Hp on [Ca2+]iin normal human GMEC and a nontransformed GMEC line (HFE-145). Cultured cells were grown on glass slides, porous filters, or 96-well plates and loaded with fura 2 or fluo 4. Hp wild-type strain 60190 and vacA–, cagA–, and picB–/cagE–isogenic mutants were incubated with cells. Changes in [Ca2+]iwere recorded with a fluorimeter or fluorescence plate reader. Wild-type Hp produced dose-dependent biphasic transient [Ca2+]ipeak and plateau changes in both cell lines. Hp vacA–isogenic mutant produced changes in [Ca2+]isimilar to those produced by wild type. Compared with wild type, cagA–and picB–/cagE–isogenic mutants produced lower peak changes and did not generate a plateau change. Preloading cultures with intracellular Ca2+chelator BAPTA blocked all Hp-induced [Ca2+]ichanges. Thapsigargin pretreatment of cultures to release Ca2+from internal stores reduced peak change. Extracellular Ca2+removal reduced plateau response. Hp-induced peak response was sensitive to G proteins and PLC inhibitors. Hp-induced plateau change was sensitive to G protein inhibitors, src kinases, and PLA2. These findings are the first to show that H. pylori alters [Ca2+]iin normal GMEC through a Ca2+release/influx mechanism that depends on expression of cagA and picB/cagE genes.