L-lactic acid secreted from gastric mucosal cells enhances growth of Helicobacter pylori

Background: Helicobacter pylori mainly inhabit the mucus layer in the gastric mucosa. However, mechanisms involving H. pylori colonization and proliferation in gastric mucosa are not well established. This study focuses on elucidating the role of gastric mucosal cells on growth of H. pylori. Materials and methods: H. pylori was co-cultured with the murine gastric surface mucosal cells (GSM06), and the growth of H. pylori on the cells was assessed by enumerating the colony-forming units (CFU). The H. pylori growth factor in the culture media conditioned by GSM06 cell was purified by HPLC, and the chemical structure of the growth factor was identified by analyses of H-1- and C-13-NMR spectra. Results: A marked increase in the number of CFU of H. pylori was observed in the GSM06 cells. The enhanced H. pylori growth was also observed when indirectly incubated with GSM06 cells through semi-permeable membrane. In addition, culture media conditioned by GSM06 cell stimulated H. pylori growth approximately one thousand-fold. By bioassay-guided purification, the H. pylori growth factor was isolated from the conditioned medium of GSM06 cells and identified as L-lactic acid. The H. pylori growth-enhancing activity under microaerobic condition was well correlated with L-lactic acid concentrations in the conditioned media. Conclusions: This study demonstrates that L-lactic acid secreted by gastric mucosal cells enhances the growth of H. pylori, and this L-lactic acid-dependent growth of H. pylori may be important to the long-term colonization of H. pylori in the stomach.