Date of Award

Fall 2017

Document Type

Open Access Dissertation

Department

Pharmacology, Physiology and Neuroscience

Sub-Department

College of Pharmacy

First Advisor

Lorne J. Hofseth

Abstract

Inflammatory bowel diseases (IBD), mainly ulcerative colitis (UC), Crohn’s disease (CD), are chronic, idiopathic, inflammatory diseases of the gastrointestinal tract affecting millions of people worldwide. The incidence of IBD is steadily increasing in the modern world due to changes in dietary habits and other environmental influences that originated from industrialization. The etiology is poorly understood but is believed to be a combination of genetic predisposition, environmental factors, and overactive immune system. UC is characterized by inflammation and ulceration of colonic mucosa and rectum and has a higher incidence than CD. Aside from severely affecting the quality of life of the patients, IBD also increases the risk of developing colorectal cancer (CRC). Hence, it is imperative to find a treatment that not only treats colitis but can also act as a chemopreventive agent. Current medications that include aminosalicylates, TNFα inhibitors, and corticosteroids help patients cope with the symptoms and induce temporary remission, but are paired with a risk of serious side effects and people become refractory. Many patients, therefore, turn to unconventional treatments for relief and plant-based products provide a safe, alternative option.

Many studies have shown that American Ginseng (AG), an herb native to North America is effective in the treatment of diabetes, cancer, cardiovascular diseases, and neurodegenerative diseases. Our lab has previously shown that AG treats colitis and prevents colon cancer in mice. This indicates the potential for AG to become part of mainstream medicine like other drugs that have natural antecedents, e.g., taxol, vincristine, digoxin, etc. Drug discovery from plant products involves phytochemical and biological characterization of plants used in alternative medicine. This dissertation aims to address these issues by identifying the bioactive component of AG and elucidating the mechanism of action in the treatment of UC and prevention of CRC.

We used bioassay-guided fractionation to identify the most potent fraction of AG. A hexane fraction of AG (HAG) has shown remarkable anti-inflammatory and anti-cancer properties both in vitro and in vivo. Sub-fractionation of HAG revealed that Panaxynol (PA), a polyacetylene is the most abundant compound in this fraction and also showed antiinflammatory potential in vitro as indicated by suppression of iNOS, an inflammation marker. PA effectively suppressed DSS induced colitis in mice and showed potential as a chemopreventive agent. PA targets macrophages (mФ) for DNA damage and apoptosis while it requires >10X dosage to sustain cause similar effects in other cell types.

AG has been shown to decrease oxidative stress and Nuclear factor (erythroidderived 2)-like 2 (NFE2L2 or Nrf2)-a transcription factor that is a master regulator of antioxidant response), we hypothesized that AG, HAG, and PA treat colitis by activating the Nrf2 pathway. AG, HAG, and PA decreased oxidative stress and activated the Nrf2 pathway in vitro and in vivo. Accordingly, in vivo experiments indicate that AG, HAG, and PA were not very effective in the treatment of DSS induced colitis in Nrf2 knockout mice.

We further delineated the mechanism of action of AG in the absence of inflammation using gene expression profiling of primary peritoneal mФ by microarray. We found that AG and its compounds showed distinct immunomodulatory properties, as shown by the activation of both pro-inflammatory cytokines and anti-inflammatory molecules. These results will bring AG a step closer to being used as a conventional drug for the treatment of colitis and pave the way for its use in the treatment of other inflammatory and autoimmune diseases with a similar genesis.

Available for download on Wednesday, December 18, 2019

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