Date on Master's Thesis/Doctoral Dissertation

5-2020

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Pharmacology and Toxicology

Degree Program

Pharmacology and Toxicology, PhD

Committee Chair

Feng, Wenke

Committee Co-Chair (if applicable)

McClain, Craig

Committee Member

McClain, Craig

Committee Member

Gobejishvili, Leila

Committee Member

Matoba, Nobuyuki

Committee Member

Deng, Zhongbin

Author's Keywords

antimicrobial peptide; cathelicidin; alcoholic liver disease; inflammasome activation; neutrophil infiltration

Abstract

Patients with alcohol-associated liver disease (ALD) have high morbidity and mortality in its severe forms. One of the major features in different forms of ALD is the altered gut microbiota. Antimicrobial peptides (AMPs) play a crucial role in maintaining gut microbiota homeostasis. LL-37 (known as CRAMP in mouse) is the sole member of the human cathelicidin family and has piqued great research interest for its dual role in modulating microbiota and the immune response in metabolic diseases. Inflammasome activation is an important component of the liver pathophysiology in ALD and requires two signals for its full activation to induce the maturation and release of IL-1β, to induce inflammation. Whether LL-37/CRAMP is involved in the regulation of inflammasome activation in ALD remains unclear. The first aim of this dissertation was to investigate whether CRAMP protects the liver from alcohol-induced injury and whether the effect is mediated through regulation of gut microbiota and inflammasome activation inhibition. Indeed, CRAMP deficiency exacerbated, while exogenous CRAMP peptide alleviated, alcohol-induced liver injury through inhibition of inflammasome activation by decreasing LPS function and uric acid (UA) production. Obese alcoholic subjects have elevated serum ALT levels and are often at high risk of progressing from simple fatty liver to advanced ALD. Increased neutrophil infiltration and chemokine expression were linked to the synergistic effects of alcohol consumption and obesity. LL-37 and CRAMP has been recognized as chemoattractants to neutrophils and inflammatory monocytes through membrane chemokine receptors. The second aim was to investigate the role of CRAMP in binge alcohol-induced liver injury in high fat diet (HFD)-fed mice. CRAMP knockout (Camp-/-) mice were protected from HFD feeding induced weight gain and adipocyte enlargement, liver injury and steatosis; importantly, Camp-/- mice had significantly fewer infiltrated neutrophils in the liver and decreased chemokine expression compared to WT mice. High fat diet plus ethanol (HFD+E) treatment significantly increased hepatic protein levels of CRAMP, which co-localized with Ly6G-positive neutrophils. In summary, the dual effects of CRAMP in alcohol-associated liver disease have been explored. CRAMP plays a protective role in binge alcohol-induced liver injury in chronic alcohol-fed mice, through the inhibition of LPS function and UA-induced inflammasome activation. In contrast, CRAMP acts as a chemoattractant for neutrophil infiltration in HFD-fed mice challenged with binge alcohol, exacerbating liver injury. The present study suggested that the role of CRAMP in alcohol-associated liver disease is dependent on the disease status and targeting CRAMP may represent a novel therapeutic strategy for alcohol-associated liver disease.

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