299P Granada Congress and Exhibitions Centre
6th European Congress of Pharmacology (EPHAR 2012)

 

 

Intestinal anti-inflammatory effects of doxycycline in the TNBS model of rat colitis.

J Garrido-Mesa1, N Garrido-Mesa1, F Algieri1, ME Rodriguez-Cabezas1, P Zorrilla1, MP Utrilla1, M Comalada2, A Zarzuelo1, J Galvez1. 1University of Granada, Department of Pharmacology, Spain, 2Institute of Biomedical Research Barcelona, Macrophage Biology Group, Spain

 

Introduction: Tetracyclines have been reported to exert immunomodulatory activities in addition to their antimicrobial properties which could contribute to their therapeutic use in inflammatory bowel disease (1,2). The aim of this study was to evaluate the intestinal anti-inflammatory properties of doxycyline in the trinitrobenzenesulphonic acid (TNBS) model of rat colitis.

Methods: Wistar rats were randomly assigned to five groups (n=10): Non colitic group, Control colitic group (without treatment) and colitic groups treated orally with different doses of doxycycline (5, 10 and 25 mg/kg/day), starting the same day of TNBS colitis induction (10 mg). Rats were sacrificed one week after, and colonic damage was assessed histologically and biochemically: myeloperoxidase activity (MPO), glutathione content and IL-1β levels (ELISA). In addition, in vitro studies were also performed in Caco-2 and RAW 264.7 cells, pre-treated with different concentrations of doxycycline (1 – 50 µg/ml), and stimulated with IL-1β (1 ng/ml) or LPS (100 ng/ml), respectively. IL-8 production (Caco-2 cells) and nitrite levels (RAW 264.7 cells) were determined. Statistical analyses was carried out with Statgraphics 5.0, with statistical significance set at p<0.05 using a one-way analysis of variance (ANOVA) and post hoc least significance tests.

Results: The intestinal anti-inflammatory effect of doxycycline was evidenced macroscopically by a significant reduction in the extension of damage tissue (5 and 10 mg/kg) as well as in the colonic weight/length ratio (5 mg/kg) (Table 1). The antibiotic decreased MPO activity at the doses of 5 mg/kg (42%) and 25 mg/kg (32%), as a marker of neutrophil infiltration of the inflamed colon. The antibiotic treatment, at all doses assayed, was also able to partially counteract glutathione depletion, thus ameliorating the oxidative stress induced in the colonic tissue after colitis induction. It also significantly reduced the levels of the pro-inflammatory cytokine IL-1β levels (approximately 45%), which were modified after colonic insult with TNBS. Finally, doxycycline was able to reduce dose-dependently the production of either IL-8 (Caco-2 cells) or nitrites (RAW 264.7), when compared with untreated cells.

Table 1. Effects of doxycycline in TBNS rat colitis

Group(n=10) Score(0-10) Weight/length(mg/cm) MPO activity(mU/g tissue) GSH content(nmol/g tissue) IL-1β(pg/g tissue)
Healthy 0.0 ± 0.0 77.5 ± 4.8 45.1 ± 11.6 1256 ± 78 372 ± 140
Colitic Control 7.3 ± 0.4 274.3 ± 15.2 607.7 ± 728 340 ± 75 24101 ± 3824
Doxycycline(5 mg/kg) 5.0 ± 0.3* 179.9 ± 20.3* 370.5 ± 54.2* 631 ± 101* 13330 ± 3093*
Doxycycline(10 mg/kg) 5.7 ± 0.3* 234.8 ± 38.6 541.9 ± 35.6 731 ± 137* 19856 ± 2317
Doxycycline(25 mg/kg) 6.4 ± 0.3 192.5 ± 27.8 427.2 ± 49.2* 878 ± 138* 13232 ± 186*

Data are expressed as mean ± SEM. *p<0.05 vs. Control group.

Conclusion: Doxycycline exhibits immunomodulatory properties that can collaborate in its efficacy in the amelioration of the intestinal damage induced by TNBS in rats.

References: (1) Pharmacol Res. 2011;63:308-19. (2) Biochem Pharmacol. 2011;82:1891-900.