The pathogenesis of inflammatory bowel disease is complex and multifactorial. Studies have led to the current concept that aryl hydrocarbon receptors have recently emerged as a critical physiological regulator of immune responses affecting both innate and adaptive systems. We studied the possibility of simvastatin and antagonist of receptors of interleukin-1 for pharmacological correction of colitis in rats with a focus on the expression intensity studies of AhR with lymphocytes of colon. Eight-month-old male Wistar rats (body mass 260-285 g) were purchased from Institution of Molecular Biology and Genetics (National Academy of Science of Ukraine, Kyiv) and kept in a 12-h light/dark cycle with controlled humidity (60–80%) and temperature (22°±1°C). Food and water were freely available. All animal experiments were performed according to international principles "of the European Convention for the Protection of vertebrate animals used for experimental and other scientific purposes" (Strasbourg, 18.03.1986) and "General ethical principles of animal research" (Ukraine, 2001). Rats were divided into four experimental groups: group 1 – control; group 2 – rats with oxazolone-induced colitis; group 3 – rats given simvastatin (20 mg/kg, for 5 days, intraperitoneally) ; group 4 – rats given antagonist of receptors of interleukin-1 (3 mg/kg, for 5 days, subcutaneously). Formalin-fixed, paraffin embedded colon sections (5-7 μm) placed on coated slides were sequentially deparaffinized and rehydrated using xylene and ethanol, washed in PBS (twice, 5 min each). The aryl hydrocarbon receptor immunopositive lymphocytes were determined using an indirect immunofluorescence technique with using a monoclonal rat antibody. After rinsing in 0.1 M PBS, the sections were incubated overnight at 4°C with the respective primary antibody: Aryl hydrocarbon Receptor. On the second day, after washing, sections were incubated for 1 h with a mixture of FITC-conjugated goat anti-rabbit IgG. Fluorescent images were obtained with a fluorescence microscope PrimoStar with a computer-assisted video system AxioCam 5c. The histological observation showed inflammatory cell infiltration, including polymorphonuclear leukocytes and multiple erosive lesions in the large intestine. Occasionally, crypt abscess and regenerated epithelium were seen in the colonic mucosa. We established that development of colitis was not accompanied with the change of amount of AhR+ lymphocytes. Drug administration during the development of experimental pathology was accompanied by changes in the expression of AhR on lymphocytes. Simvastatin and antagonist of receptors of interleukin-1 seemed to be beneficial in oxazolone -induced colitis rat model through modulate aryl hydrocarbon receptor expression with lymphocytes of colon.
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