Comparison of the Safety and Efficacy of Tofacitinib and Fingolimod in TNBS-Induced Colitis Model in Adult Zebrafish: The Role of Myd88/NF-κB/TNF-α Signaling Pathway.

Due to the inadequate response, side effects, parenteral route of administration, and immunogenicity, oral targeted small molecules seem to replace monoclonal antibodies in the future management of ulcerative colitis (UC). In order to pave the way for clinical translations of small molecules in UC, for the first time, we compared the efficacy of fingolimod and tofacitinib in preclinical model of colitis, and uncovered another mechanism of action that these medicines may act through. We implicated adult zebrafish to find out its pros/cons, investigated aquatic toxicity of the mentioned compounds, and designed a procedure to evaluate compound's efficacy in adult zebrafish colitis model; hence, facilitating screening of further agents. Tofacitinib and fingolimod were investigated to be in category 1 of Globally Harmonized System (GHS) aquatic toxicity classification with the LC50 of 0.9014 and 0.36 mg/L, respectively, based on the acute toxicity assessment within 96 h. Considering efficacy assessments, colitis was induced through intrarectal administration of 160 mM TNBS for 48 h. Then, animals were exposed to different concentrations of tofacitinib (0.25, 0.57, 0.72, 0.90 mg/L) and fingolimod (0.23, 0.28, 0.36, 0.45 mg/L) for 96 h. Subsequent analyses revealed that TNBS significantly reduced length of villi, number of goblet cells, level of TNF-α, MyD88, and NF-κB2, increased thickness of villi and necrosis, and induced histopathological changes, including intestinal edema, submucosal hemorrhage/hyperemia with the presence of inflammatory cells. All the aforementioned parameters were considerably enhanced almost dose-dependently with both agents, wherein the effect of 0.45 mg/L fingolimod was superior to other groups. As well, there were no signs of hyperemia/hemorrhage in harvested intestinal samples. Resultantly, we revealed that these medications may suppress canonical and non-canonical NF-κB pathways through targeting toll-like receptors and MyD88. Given the better efficacy and multi-targeted action of fingolimod, it worth to focus on sphingosine-1 phosphate receptor modulators in clinical trials of UC and compare them with other classes of medications; albeit, their ecotoxicity aspect should not be overlooked.