The bisphosphonate alendronate improves the damage associated with trinitrobenzenesulfonic acid-induced colitis in rats

Abstract

Background and purpose: The nitrogen-containing bisphosphonates are drugs used successfully in the treatment of osteoporosis. They act inhibiting farnesyl diphosphate synthase. This mechanism may also produce anti-inflammatory effects. The therapeutic activity of alendronate was tested in vivo using a model of inflammatory bowel disease.

Experimental approach: The trinitrobenzenesulfonic acid model of colitis in the rat was used. Rats were treated orally with alendronate and its efficacy compared with that of oral sulphasalazine or vehicle, starting 2 h after colitis induction. The status of the animals was assessed 5 days later.

Key results: Alendronate treatment (25 or 75 mg kg(-1) day(-1)) resulted in a decrease in the colonic damage score and loss of body weight (at 25 mg kg(-1) day(-1) only). This was associated to a dramatic reduction in the mRNA levels of interleukin 1 beta (IL-1 beta), monocyte chemoattractant protein 1 (MCP-1) and interleukin 1 receptor antagonist (IL-1 ra). The magnitude of the beneficial effect was comparable to that of sulphasalazine (at a 6-20 fold higher dose). Thus sulphasalazine post-treatment reduced the mRNA levels of IL-1 beta/IL-1 ra and MCP-1 to the same extent as alendronate and additionally lowered colonic alkaline phosphatase activity, but failed to affect body weight loss or colonic damage score. Alendronate failed to exert beneficial effects when administered intraperitoneally.

Conclusions and implications: Oral but not intraperitoneal alendronate significantly protected the colon in experimental rat colitis. Inflammatory bowel disease patients might benefit from exposure to oral alendronate.

Figure 1

Macroscopic appearance of rat TNBS colitis in the different experimental groups. Photographs are representative of the macroscopic features of the large intestine in each group. Uninflamed: noncolitic group; TNBS: colitic animals treated with vehicle; alendronate: colitic animals treated with alendronate (25 mg kg⁻¹ day⁻¹); sulphasalazine: colitic animals treated with sulphasalazine (500 mg kg⁻¹ day⁻¹). Darkened areas correspond to epithelial necrosis.

Figure 2

Colonic protein expression of COX-2 (70 kilodaltons) in the different experimental groups. Uninflamed: noncolitic group; TNBS: colitic animals treated with vehicle; alendronate: colitic animals treated with alendronate (25 mg kg⁻¹ day⁻¹); sulphasalazine: colitic animals treated with sulphasalazine (500 mg kg⁻¹ day⁻¹). Expression was assessed by Western blot and densitometry was performed with the Scion Image software. A representative gel is shown. ⁺P<0.05 vs uninflamed group; ^*P<0.05 vs TNBS group.

Figure 3

Effect of alendronate on IL-1β, IL-1ra and TGF-β (a), MUC2, MUC3 and TFF-3 (b) mRNA levels in colon specimens. Representative gels (of at least triplicate experiments) and densitometric analysis are shown. Uninflamed: noncolitic group; TNBS: colitic animals treated with vehicle; alendronate: colitic animals treated with alendronate (25 mg kg⁻¹ day⁻¹); sulphasalazine: colitic animals treated with sulphasalazine (500 mg kg⁻¹ day⁻¹). Expression was assessed by semiquantitative RT-PCR and densitometry was performed with the Scion Image software. Bars represent mean±s.e.m.; ⁺P<0.05 vs uninflamed group, ^*P<0.05 vs TNBS group.

Figure 4

Effect of alendronate (Fosamax) on TNBS colitis. Control values were: 2.6±0.1 U g⁻¹ tissue (myeloperoxidase; MPO), 83.4±4.5 mU mg⁻¹ protein (AP), 16.5±1.9% (AP sensitivity). TNBS: vehicle-treated colitic rats; SAZ: colitic rats treated with sulphasalazine (500 mg kg⁻¹); Ale: colitic rats treated with alendronate (75 mg kg⁻¹). ^*Different from TNBS group, P<0.05. All means in the TNBS group are significantly different from the control (not shown).

Figure 5

Immunohistochemical analysis of the effect of alendronate (Fosamax) on rat TNBS colitis. A piece of the distal colon was fixed in formaldehyde and stained with antibodies specific for either COX2 (a–d) or iNOS (e–h). The images are representative of the groups of control rats (a, e) and TNBS colitic rats treated with vehicle (b, f), sulphasalazine 500 mg kg⁻¹ (c, g) or alendronate 75 mg kg⁻¹ (d, h). Original magnification: × 5.