Evaluation of the effect of losartan and methotrexate combined therapy in adjuvant-induced arthritis in rats.

There is increasing body of evidence documenting the involvement of angiotensin II in inflammatory diseases. Moreover the up-regulation of angiotensin II AT(1) receptors in the synovium of rheumatoid arthritis patients has been previously described. This study aimed at investigating the anti-inflammatory effect of losartan, the selective angiotensin II AT(1) receptor blocker, and comparing the efficacy of methotrexate alone and in combination with losartan in adjuvant arthritis in rats. Twelve days post adjuvant injection, Sprague-Dawley rats were treated with methotrexate (1mg/kg/week), losartan (20mg/kg/day) and their combination for 15 days. Severity of arthritis was assessed by hind paw swelling, arthrogram scores. Serum was analyzed for measurement of albumin, C-reactive protein (CRP), nitrite/nitrate concentrations, interleukin 1β (IL-1β), tumor necrosis factor-α (TNF-α), vascular endothelial growth factor (VEGF), aspartate transaminase (AST) and alanine transaminase (ALT). Histopathological examination was done for hind paws and livers. Methotrexate and losartan monotherapies significantly reduced all parameters of inflammation and arthritis with better results in the methotrexate group except for the transaminases where losartan caused more significant reduction in their serum levels. The combined therapy showed better results than methotrexate and losartan alone. Hind paws showed better improvement of inflammatory cell infiltration and bone resorption in the combined therapy group. Disturbances in liver architecture and fibrosis caused by adjuvant arthritis were reverted to normal status in the combined therapy group in contrast to losartan and methotrexate monotherapies. In conclusion, methotrexate and losartan combined therapy provided more effective anti-inflammatory and hepatoprotective effects than either drug alone.