Date of Award

2012

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Sociology

Abstract

Ethanol is a common factor in traumatic injury, including burn injury. Previous studies from our laboratory indicate that ethanol increases both pulmonary and gastrointestinal inflammation as well as susceptibility to infection in burn-injured mice; however, the mechanisms of these responses are not entirely known. Moreover, after burn injury, bacteria and their products leak out of the intestinal lumen and into the bloodstream. These bacteria can disperse throughout the body leading to pulmonary damage, acute lung injury, sepsis, and death. Ethanol in combination with burn injury has been shown to decrease intestinal barrier function greater than either insult alone. Long (210 kDa) smooth muscle myosin light chain kinase (MLCK), an enzyme important for epithelial tight junction maintenance, has been implicated in barrier alterations after burn injury or ethanol exposure alone. With this knowledge, we hypothesize that the combination of binge ethanol exposure and burn injury causes an increase in intestinal barrier dysfunction due to inflammation-mediated activation of myosin light chain kinase. To test this hypothesis, three aims are proposed: 1) to determine whether elevated myosin light chain kinase activation mediates the intestinal permeability alterations in mice receiving binge ethanol and burn injury treatment, 2) if interleukin–6 (IL–6) activates myosin light chain kinase and, 3) the signaling mechanism leading to MLCK activation after ethanol exposure and burn injury. Bacterial translocation along with immunofluorescent staining for tight junction protein localization will be performed to investigate intestinal barrier function and integrity. MLCK activation will be determined by Western blot analysis. Inhibition and knock out of MLCK will be employed as well to examine the role of this molecule on intestinal permeability after acute ethanol and burn injury exposure. We will investigate MLCK activation and tight junction integrity in IL–6 knockout mice and wild type mice given an IL–6 neutralizing antibody. Finally, we will examine the signaling mechanism leading to MLCK activation in our model of ethanol and burn. To do this, activation of other mediators of the MLCK pathway, including Rho kinase (ROCK), myosin light chain phosphatase (MLCP) and Src kinase, will be determined. These studies will help gain an understanding for how even binge ethanol in combination with burn injury can result in decreased barrier function that has been clinically observed and can result in increased morbidity and mortality.

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Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.

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