AUTHOR=Liu Xiaozhen , Jiang Leming , Li Linyan , Yu Hai , Nie Shaoping , Xie Mingyong , Gong Joshua 

TITLE=The Role of Neurotransmitters in the Protection of Caenorhabditis Elegans for Salmonella Infection by Lactobacillus

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=10

YEAR=2020

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2020.554052

DOI=10.3389/fcimb.2020.554052

ISSN=2235-2988

ABSTRACT=<p>Salmonellosis is a common foodborne disease. We previously reported the protection of <italic>Caenorhabditis elegans</italic> from <italic>Salmonella</italic> Typhimurium DT104 infection by <italic>Lactobacillus zeae</italic> LB1. However, the mechanism is not fully understood. <italic>C. elegans</italic> exhibits behavior plasticity when presented with diverse pathogenic or commensal bacteria. Whether it can exert approach avoidance to <italic>S</italic>. Typhimurium through altering its neurological activity remains to be determined. In the current study, both the wild type and mutants defective in serotonin or dopamine production of <italic>C. elegans</italic> were used to investigate olfactory preference of the nematode to <italic>L. zeae</italic> LB1, DT104, and <italic>Escherichia coli</italic> OP50 by choice assays, and its resistance to DT104 infection and the protection offered by <italic>L. zeae</italic> LB1 using a life-span assay. The expression of target genes in <italic>C. elegans</italic> was also examined by real-time quantitative PCR. Results showed that pre-exposure to <italic>L. zeae</italic> LB1 did not elicit aversive olfactory behavior of the nematode toward DT104. Both mutants <italic>tph-1</italic> and <italic>cat-2</italic> succumbed faster than the wild type when infected with DT104. While pre-exposure to <italic>L. zeae</italic> LB1 significantly increased the survival of both the wild type and mutant <italic>tph-1</italic>, it provided no protection to mutant <italic>cat-2</italic>. Supplementation of dopamine resulted in both the resistance of mutant <italic>cat-2</italic> to <italic>S</italic>. Typhimurium infection and the protection from <italic>L. zeae</italic> LB1 to the same mutant. Gene expression data also supported the observations in the life-span assay. These results suggest that both serotonin and dopamine play a positive role in the host defense of <italic>C. elegans</italic> to <italic>S</italic>. Typhimurium infection and that the <italic>L. zeae</italic> LB1 protection is not dependent on modifying olfactory preference of the nematode but mediated by dopamine that may have involved the regulation of p38-mitogen-activated protein kinase and insulin/insulin-like growth factor signaling pathways.</p>