L. Bueno et al.
Gelatine (GEL) stabilised by cross-linking with tannic acid (TA) forms gelatine tannate (GT). GT is approved as medical device for the oral treatment of diarrhoea as Tasectan®. GT is considered as a protective biofilm on the gut mucosa and has been shown to cure diarrhoea but the mechanism of action needs further investigation.
We aimed at investigating the effect of GT and its components (GEL and TA) on the intestinal mucosa using both in-vitro and in-vivo models.
The in-vitro “filming” activity was evaluated by Corrositex®, a standard measure of chemical aggression, and on Caco-Goblet monolayers. The effect of GT (5 or 20 mg/ml) on Caco-Goblet cell permeability was assessed by Trans-Epithelial Electrical Resistance (TEER) and Lucifer Yellow (LY) before and after apical S. typhimurium. The tight-junction (TJ) proteins acquaporin-3 (AQP3) and occludin (OCL) were assayed by RT-PCR as markers of TJ integrity.
In-vivo, Wistar rats received orally either GT (250 mg/kg), Gel (125 mg/kg), or TA (125mg/kg), and 2 h. later were injected IP with LPS from E. coli. Jejunal strips were collected 6 hours later for in vitro TJ permeability measurement using FITC-dextran and mucosal myelo-peroxidase (MPO) activity as a marker of inflammation.
GT increased the corrosion time (hydrochloric ac. 37%) from 400 to 699 sec (p <0.001) suggesting a chemical biofilm protection. In addition, GT (5 mg/ml) increased TEER of CACO-goblet at 4 hours (from 180.1 to 269.2 ohm*cm2, p<0.05) and decreased the basal permeability to LY in basal conditions at both 2 and 4h. The LY permeability increased from 1.18 to 7.54 after 2 hours of exposure to S. typhimurium however a pre-treatment with GT suppressed this increase and decreased bacterial invasion by 72%, such been associated with overexpression of AQP3 and OCL at 4 hours (350 and 200% respectively for GT at 20mg/kg.
Six hours after LPS injection in rats, both jejunal TJ permeability and MPO activity were dramatically increased. Oral pretreatment with GT reduced by 78.1% the jejunal increase of permeability whereas GEL and TA did not affected it and subsequently reduced significantly the LPS-induced increase in MPO.
Our results confirm that GT acts by mechanical protection of the gut mucosa. The protective biofilm formed by GT prevents the leakiness of the tight Junctions both in basal conditions and after insult by bacteria (in-vitro) and by LPS (in-vivo). These effects cannot be replicated by either tannic acid or gelatine confirming that GT is the active form to prevent gut leakiness and subsequent inflammation.
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