Figure 1. Clinical and histological correlations in mice with experimental colitides treated with nicotine.

A. Representative images of colons dissected from control BALB/c mice treated i.r. with 47.5% ethanol in saline (Control), mice with oxazolone-induced colitis either untreated (Ox) or treated with 7.5 mg/kg/day of nicotine (Ox+N), and untreated (T) vs. nicotine-treated (T+N) mice with TNBS colitis. The treatment with nicotine started from the day before instillation of a haptenating agent (i.e., at the day “zero”) and ended on the 4^th day of experiment, i.e., the day before mice were sacrificed. Note: the colon from untreated mouse with oxazolone colitis has several necrotic areas, whereas in the nicotine-treated animal the inflammation is visible only in the distal segment. While the colon of mouse with TNBS colitis is diffusely hyperemic, it lacks overt necrosis. In contrast, the mouse with TNBS colitis treated by nicotine has developed necrotic areas, as seen in the proximal segment of colon.

B. Clinical evaluation of the effects of nicotine treatment on the severity of colitis in mice with oxazolone- and TNBS-induced colitides. The DAI values were computed as described in detail in Materials and Methods (Table 1). In oxazolone colitis, the differences are statistically significant (p<0.05) on days 4 and 5. In TNBS colitis, the statistical differences between the DAI values of nicotine-treated vs. untreated mice are significant (p<0.05) starting from the 3^rd day after instillation of the haptenating agent. Each point represents the mean ± SD of data obtained in 20 mice. The DAI values in control mice instilled with the ethanol solution without haptenating agents were equal or close to zero (data not shown).

C. The representative images of the histologic findings in nicotine-treated vs. untreated mice with oxazolone- and TNBS-indiceds colities. The photomicrographs of H&E stained 5 μm sections of matching segments of colons were made at 10x magnification. Abbreviations are the same as as in panel “A”. Note: the extensive goblet cell depletion with submucosal involvement and lymphocytic infiltrations characteristic of oxazolone colitis were not present in mice treated with nicotine. In contrast, nicotine treatment aggravated colonic inflammation in TNBS colitis, leading to crypt destruction, goblet cells depletion and extensive lymphocytic infiltration.

D. Histopathologic analysis of the effects of treatment with nicotine on the colonic inflammation in mice with oxazolone- and TNBS-induced cotises. The HAI values were computed as described in detail in Materials and Methods (Table 2). Nicotine treatment protected the colons from inflammation induced by oxazolone, as can be judged from an approximately 2-fold decrease of HAI. Vice versa, the HAI value computed in mice with TNBS colitis treated by nicotine significantly increased, indicating that nicotine worsened TNBS-induced colonic inflammation. Asterisk = p<0.05 compared to the HAI value computed in colons of the nicotne-untreated mice with the respective form of colitis.