Michael Bailey, PhD

Pediatrics Assistant Professor
Pediatrics Associate Professor, Microbial Infection/Immunity
Associate Professor, Biosciences
Adjunct Associate Professor
Institute for Behavioral Medicine Research, Wexner Medical Center

Center for Microbial Pathogenesis
700 Children’s Drive, W410
Columbus, OH 43026

Michael.Bailey@osumc.edu
614-722-2764

Website

Studies in Dr. Bailey’s laboratory focus on determining the impact that the intestinal microbiota have on the local mucosal immune system, and on immune reactivity at systemic sites, particularly during periods of psychological stress. In past studies, they have shown that exposure to different types of psychological stressors change the community structure of microbiota in the intestines. Their goal now is to demonstrate that these changes have significant effects on the health of the host.

Impact of Microbiota on Mucosal Immunity: The inflammatory bowel diseases involve disrupted homeostatic interactions between the microbiota and the mucosal immune system. It is well recognized that symptom severity is worsened during periods of psychological stress, but whether the stress response is involved in these disrupted homeostatic interactions is not known. They have been studying Citrobacter rodentium infection in mice because the colonic inflammation resembles components of human inflammatory bowel disease. In their studies, exposing mice to an experimental stressor during oral challenge with C. rodentium significantly increases the pathogen-induced colitis. Their preliminary studies indicate that the stressor-induced increase in colitis is dependent upon stressor-induced alterations of the microbiota, thus demonstrating a link between stress, alterations in the microbiota, and exacerbation of colonic inflammation. Current studies are focused on further characterizing the colonic inflammation, including determining the impact of the stress response on colonic epithelial cells and lamina propria leukocytes. Studies are also focused on determining which members of the microbiota contribute to the enhanced colonic inflammation.

Impact of Microbiota on Systemic Immunity: The stress response is often thought of as suppressing immune activity. However, there is accumulating evidence that in addition to suppressing immune function, the stress response can also enhance immune activity. And, although many of the mechanisms by which the stress response suppresses immunity are known, such as by the action of stress-responsive glucocorticoid hormones, the mechanisms by which the stress response enhances immune activity are not well understood. They have been using a murine social stressor, called social disruption, to study how stressor exposure enhances the ability of splenic macrophages to kill a target microbe, namely Escherichia coli. Their data indicate that stressor exposure increases the splenic macrophage oxidative burst, resulting in increased production of superoxide, and increases iNOS gene expression, resulting in increased production of nitric oxide. This increased activity ultimately results in the production of the highly microbicidal compound, peroxynitrite. Their current studies are focused on determining how the stress response enhances macrophage peroxynitrite production, and indicate that the intestinal microbiota are involved. Their goal is to determine how the microbiota can enhance splenic macrophage activity during stressor exposure.

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