© 2001 Blackwell Science Ltd, Helicobacter , 6, 110–115 110 Volume 6 • Number 2 • 2001 HELICOBACTER Blackwell Science, Ltd Helicobacter pylori Induces Apoptosis in Human Epithelial Gastric Cells by Stress Activated Protein Kinase Pathway Matthew J. Domek, Peter Netzer, Bruce Prins, Trang Nguyen, Dan Liang, Frederic A. Wyle and Alberta Warner VA Medical Center, Long Beach and the University of California, Irvine, CA, USA ABSTRACT Background. The pathway by which Helicobacter pylori induces apoptosis in gastric epithelial cells is not known. The aim of this study was to determine whether H. pylori-induced apoptosis is associated with SAPK / JNK activity in human gastric cancer KATO III cells. Materials and Methods. H. pylori VacA toxin positive strain was incubated with KATO III cells for 0.5, 1, 2 or 24 hours. The SAPK/JNK protein was harvested from the KATO III cell lysate by precipitation with a C-jun fusion protein and its activity was measured by C-jun phosphorylation utilizing transblotting and phospho- serine antibody. Cellular apoptosis was demonstrated by DNA fragmentation. In addition, cell growth in coculture with H. pylori was determined over 72 hours. Results. H. pylori significantly stimulated SAPK / JNK activity in KATO III cells with a peak at the 0.5 hour time point (3.6-fold vs. control, p < .05), but a return to basal levels by 2 hours. In addition, significant DNA fragmentation was observed after 24 hours in these cells but not in the control KATO III cells. Cell growth was inhibited in a dose dependent fashion in coculture with H. pylori. Conclusion. These results show that H. pylori triggers an increase in apoptosis in KATO III cells as reflected by DNA fragmentation. This effect was preceded and correlated with an increase in SAPK/JNK activity suggesting that the H. pylori-induced apoptosis in human gastric epithelial cells may be mediated by the SAPK/JNK pathway. Keywords. Helicobacter pylori, apoptosis, stress activated protein kinase, SAPK/JNK, cell growth inhibitor. H elicobacter pylori infection is associated with chronic gastritis, peptic ulceration, gastric lymphoma and gastric cancer [1–3]. The World Health Organization has listed H. pylori as a type I carcinogen [4]. However, the underlying mech- anism of H. pylori-induced carcinogenesis is not, so far, entirely understood [5]. It is assumed that an increased cell turnover, coupled with a chronic state of inflammation due to the chronic H. pylori infection, may cause an increased mutagenesis rate [6 –12]. In normal tissue, the cell turnover caused by apoptosis (programmed cell death) is neces- sary to preserve homeostasis [13–15]. Although a short-term increase in apoptosis is not accom- panied by a matched increase in cell prolifera- tion, a chronic or prolonged increase in the rate of apoptosis appears to stimulate cell proliferation [6 –11]. Recent studies have shown that H. pylori can directly induce apoptosis through coculture with epithelial cells and indirectly through inflam- matory mediators such as TNF-alpha or inducible nitric oxide synthase (iNOS) [7,16,17]. While the indirect induction of apoptosis through TNF- alpha or iNOS has been well characterized, the mechanism by which H. pylori directly induces apoptosis remains elusive [6,7,16,17]. There are several related pathways that are able to induce apoptosis [13–15,18]. Recent studies have shown that the stress-activated protein kinase, also known as the c-Jun N-terminal kinase (SAPK/ JNK) pathway, induces apoptosis in several cell lines through a variety of environmental stresses [19–21]. Even though several reports about various cellular signal transudation pathway induced by H. pylori exist, data on induction of the SAPK/JNK by H. pylori are scant [22 – 29]. The aim of this study was to determine whether H. pylori-induced apoptosis is associated with increased SAPK/JNK activity in human gastric KATO III cells. Methods KATO III Cell Culture KATO III cells were obtained from the American Type Culture Collection and the culture was Reprint requests to: Peter Netzer, MD, Gastrointestinal Unit, Inselspital, University of Berne, CH-3010 Berne, Switzerland.