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Varsha Singh,* Anoop Kumar,* Geetu Raheja, Arivarasu N. Anbazhagan, Shubha Priyamvada, Seema Saksena, Muhammad Nauman Jhandier, Ravinder K. Gill, Waddah A. Alrefai, Alip Borthakur, and Pradeep K. Dudeja Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago and Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois; and Singhania University, Pacheri Bari, Rajasthan, India

Background and Aim: Dysregulated epithelial secretory function can lead to the clinical manifestation of diarrhea. Intestinal fluid secretion is driven by active Clion secretion and is dependent on the availability of O2 for generation of cellular energy. Hydroxylases are the primary intracellular sensors of O2 availability, and we have previously shown that hydroxylase inhibition attenuates colonic epithelial secretory capacity. Here, we sought to investigate the molecular mechanisms involved and to test the efficacy of hydroxylase inhibitors in preventing diarrhea In Vivo.Methods: The pan-hydroxylase inhibitor dimethyloxallyl glycine (DMOG) was used to inhibit hydroxylase activity. Clsecretion was measured as changes in short circuit current across monolayers of T84 cells or muscle-stripped segments of mouse colon. Western blotting and biotinylation techniques were used to assess protein expression. DMOG effects were also tested In Vivo in a mouse allergic (ovalbumin) model of diarrhea. Results: As previously reported treatment of T84 cells with DMOG (1 mM) reduced Clsecretory responses to the Ca2+ and cAMP-dependent agonists, carbachol (CCh) and forskolin (FSK), to 20.2 ± 2.6% and 38.8 ± 4.8% of controls, respectively (n=16; p

The hypothesis that propylthiouracil (PTU)-induced hypothyroidism (HT) has a protective effect against the hepatic toxicity of acetaminophen (Tylenol or Paracetamol) was tested in a rat model. Toxic doses of acetaminophen (AAP) were administered to rats which had been made hypothyroid by oral administration of PTU for a period of 12 days, or by surgical thyroidectomy (STx) 3 wk before study, and to euthyroid controls. Hepatotoxicity was evaluated by the determination of serum glutamic oxaloacetic transaminase (SGOT) and serum glutamic pyruvic transaminase (SGPT) levels, and by light and electron microscopy. PTU treatment effectively prevented the increase of SGOT and SGPT levels, while controls had a 10-fold (1 g of AAP/kg body wt) to 70-fold increase (3 g/kg body wt) of transaminase levels. Only sporadic necrosis was observed in the PTU-treated rats, while the controls had extensive centrilobular necrosis. Electron microscopy showed slight changes in the hepatocytes of the PTU rats after 36 hr, which were considered to be reversible because these changes could not be detected after 6 days. A similar but less effective protective effect was observed 3 wk after STx. The protective effect was not mediated by delayed intestinal absorption; in contrast, the PTU rats absorbed, metabolized, and excreted the drug significantly faster than the euthyroid controls. However, the hepatic reduced glutathione (GSH) concentrations were significantly higher in the PTU-treated rats before AAP treatment, and, although decreased 6 hr after AAP treatment, they were still significantly higher than the AAP treated euthyroid controls. Higher GSH levels were inversely related to covalent binding of the toxic metabolite to hepatic tissue. Inflammatory response to necrotic hepatic tissue, as seen in all controls, was virtually absent in all HT rats. The mechanism of the protective effect of induced HT on hepatic toxicity of AAP was attributed to (a) induction of increased hepatic GSH levels resulting in decreased covalent binding of a toxic metabolite of AAP, (b) enhanced glucuronidation may prevent either formation or binding of a reactive metabolite to hepatocytes, and (c) prevention of inflammatory reaction to necrotic liver tissue.