Location: Produce Safety and Microbiology ResearchTitle: Composition of herba pogostemonis water extract and protection of infected mice against salmonella typhimurium-induced liver damage and mortality by stimulation of innate immune cells Author
|Kim, Sung Phil|
|Nam, Seok Hyun|
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2012
Publication Date: 11/27/2012
Citation: Kim, S., Moon, E., Nam, S., Friedman, M. 2012. Composition of herba pogostemonis water extract and protection of infected mice against salmonella typhimurium-induced liver damage and mortality by stimulation of innate immune cells. Journal of Agricultural and Food Chemistry. 60(49):12122-12130. doi:10.1021/jf304466t. Interpretive Summary: The immune response to pathogenic microorganisms occurs in two stages. Cells of the innate immune system respond rapidly to an infection, block the invading pathogen, and signal to lymphocytes. These cells and the adaptive immune system then neutralize the infection. In previous studies, we reported that rice hull smoke and mushroom extracts protected mice against Salmonella-induced liver necrosis and mortality. The main objective of the present study was to find out whether a water extract of dried leaves of the herbal medicine Herba Pogostemonis, widely used in traditional Chinese medicine to treat inflammation and other disorders, would also protect mice against adverse effects of lethal infections by the foodborne Salmonella bacteria. We used a series of in vitro and in vivo bacterial bioassays to demonstrate the protective effect of a water extract of the medicinal herb Herba Pogostemonis containing 31 characterized compounds against adverse effects of the virulent foodborne pathogen Salmonella Typhimurium in macrophage cells and against liver necrosis and mortality in infected mice. Liver morphology and life expectancy were improved in Salmonella-infected mice by administration of the extract. The beneficial effects were accompanied by changes in several biomarkers in cultured murine macrophage cells associated with the immune system. Because the bioactive extracts protected mice administered a lethal dose of the bacteria against liver damage and mortality,it seems that the protective effect is associated with a potentiating of the immune system. These beneficial results suggest that the bioactive extract merits further study for its potential to improve microbial food safety and to protect animals and humans against adverse effects associated with infectious salmonellosis.
Technical Abstract: We investigated the composition and antibacterial effects of a lyophilized hot water extract of the medicinal herb Herba Pogostemonis (HP) against murine salmonellosis. The extract contained 31 compounds characterized by GC/MS. Although the extract showed significant inhibitory activity on Salmonella enterica ser. Typhimurium (S. Typhimurium) growth in culture, it did not exhibit high cytotoxicity against RAW264.7 murine macrophage cells up to a concentration of 1 mg/mL. The extract stimulated uptake of the bacteria into cells, as indicated by both increased fluorescence by internalized FITC-Dextran and increased colony-forming unit (CFU) bacterial counts of the lysed macrophages incubated with S. Typhimurium for 30 and 60 min. Two hours post-infection, the bacterial counts increased in the macrophages; however, 4 and 8 h post-infection the extract-treated cells showed lower bacterial counts than the phosphate buffer (PBS) vehicle-treated control. The extract altered the morphology and elevated inducible nitric oxide synthase (iNOS) mRNA expression in macrophage cells in the absence of S.Typhimurium infection. In the presence of S. Typhimurium, inducible nitric oxide synthase (iNOS) mRNA expression was further increased along with cognate polypeptide expression, accompanied by an increase in NO production. Histology of the livers of mice infected with a sublethal dose (1 × 104 CFU) of S. Typhimurium showed that intraperitoneal daily injection of the extract protected against liver necrosis, a biomarker of salmonellosis. The lifespan of mice similarly infected with a lethal dose (1 × 105 CFU) was significantly extended by the extract. The activity of the extract against bacterial infection in mice seems to occur mainly through the activation of innate immune macrophage cells. The herb water extract has the potential to protect animals and humans against adverse effects associated with salmonellosis.