THE EFFECT OF CITRUS SINENSIS POLYPHENOLS ON ADULT ZEBRAFISH GUT INFLAMMATION INDUCED BY ORAL INFECTION WITH VIBRIO ANGUILLARUM

The polyphenols present in plants and their fruits have several biological and pharmacological activities, including anti-inflammatory properties. The Tarocco orange (Citrus sinensis) is a typical fruit of the southern part of Italy, especially present in Sicily, but also in California, (USA), and Spain. Citrus fruits and juices can be considered among the most common dietary sources rich in poliphenols. We have analyzed whether or not a natural extract from Tarocco orange (C. sinensis) is able to counteract the enteritis induced in adult zebrafish by Vibrio anguillarum, through live feed (Artemia nauplii). It is hypothesized that polyphenols from these fruits are able to play a role in attenuating inflammation due to a gram-negative infection. Adult male and female zebrafish (n=80) were divided into four groups. The first group was used as control; the second group as positive control for enteritis induced by V. anguillarum loaded Artemia; the third group, treated with Citrus Juices extract (CJe) (30 days), in order to detect the effects of extract on the intestine; the fourth group, treated with CJe (30 days), before the induction of enteritis using V. anguillarum-loaded Artemia. At the end of the experiment all fish were sacrificed and the gut was rapidly removed and dissected for the histological assay, immunohistochemistry and qRT-PCR. The third and fourth groups were sampled at 1, 3, 5 days post infection. Histological evaluation and qRT-PCR for IL-1β, IL-6, as well as TNFα, were performed to analyze the severity of inflammation in fish exposed to different experimental conditions. Fish infected through V. anguillarum-loaded Artemia showed histo-pathological evidence of enteritis in anterior and medium segments of the intestine and an over-expression of the main inflammatory cytokines. A previous treatment with CJe resulted in a remarkable reduction of tissutal inflammatory events, as well as a molecular down regulation of the inflammatory signs. The present findings strongly suggest that the treatment with natural extract of C. sinensis is able to counteract the structural evidence of enteritis and to modulate the expression of the main pro-inflammatory cytokines in adult zebrafish. Therefore, these natural polyphenols could be useful for the prevention of enteric pathologies.