Date on Master's Thesis/Doctoral Dissertation

5-2016

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Pharmacology and Toxicology

Degree Program

Pharmacology and Toxicology, PhD

Committee Chair

Joshi-Barve, Swati

Committee Co-Chair (if applicable)

McClain, Craig

Committee Member

McClain, Craig

Committee Member

Barve, Shirish

Committee Member

Hein, David

Committee Member

Srivastava, Sanja

Author's Keywords

Acrolein; alcoholic liver disease

Abstract

Alcohol consumption can cause alcoholic liver disease (ALD), which remains a major cause of morbidity and mortality in the United States. Chronic alcohol consumption causes a pro-oxidant environment in the liver and increases hepatic lipid peroxidation. Acrolein is the most reactive and toxic aldehyde generated through lipid peroxidation. Acrolein forms protein adducts and triggers endoplasmic reticulum (ER) stress and hepatocyte apoptosis, which are recognized etiologic factors in ALD. Several studies have established the critical role of the gut-liver axis in ALD pathogenesis, wherein alcohol-induced gut barrier dysfunction contributes to liver injury. This study investigates, in vitro and in vivo, the pathogenic role of acrolein as a major mediator of intestinal barrier dysfunction, and hepatic ER stress and injury in ALD. Accumulation of acrolein adducts was seen in response to alcohol consumption in mouse livers and intestines. Intestinal acrolein accumulation correlated with serum lipopolysaccharides (LPS), suggesting that elevated acrolein is associated with gut permeability. Hepatic acrolein buildup correlated with ER stress, steatosis, JNK activation, apoptosis and liver injury. Further, hallmark ER chaperones GRP78 and GRP94 were minimally induced, suggesting that ER-adaptive/protective responses were insufficient; the underlying cause was lack of activation of relevant transcription factors. We used cultured hepatic and intestinal cells to examine the direct in vitro effects of acrolein in comparison to alcohol. The in vivo gut-liver effects of alcohol consumption were mimicked by direct in vitro acrolein exposure in intestinal Caco-2 and hepatic H4IIEC cells. Specifically, acrolein down-regulated tight junction proteins, altered their localization, and disrupted barrier function. Similarly, in vitro acrolein exposure in hepatic cells triggered ER stress and induced apoptosis. Notably, these alcohol-induced effects were attenuated by hydralazine, a known acrolein scavenger.