Interação das vias da ciclo-oxigenase-2 e da hemeoxigenase-1 / biliverdina / monóxido de carbono no controle da nocicepção e da inflamação

Abstract

Heme oxygenase-1 (HO-1) plays a preventive role in oxidative stress. In contrast, COX-2 is involved in the pathogenesis of many inflammatory diseases and COX-2 selective inhibition has been shown to be effective in reversing inflammation without gastric side effects. However, serious cardiovascular effects of some selective COX-2 inhibitors emerged from clinical studies. Purpose: To assess the interaction between heme oxygenase -1/ biliverdin/ carbon monoxide (HO-1/BVD/CO) and cyclooxygenase-2 (COX-2) pathways for nociception and inflammation control in rats and mice. Methods: Protocol 1: In the abdominal writhe model induced by acetic acid, mice were pretreated with etoricoxib (selective COX-2 inhibitor; 0.1, 1 or 10mg/Kg; i.p) or with HO-1/BVD/CO pathway modulators, knowingly: Hemin (substrate of HO-1/BVD/CO pathway; 0.3, 1 or 3mg/Kg; s.c), DMDC (CO donor; 0.00025, 0.025 or 2.5µMol/Kg; s.c) or ZnPP-IX (specific HO-1 inhibitor; 1, 3 or 9mg/Kg; s.c). Animals pretreated with etoricoxib or HO-1/BVD/CO pathway modulators received the acetic acid injection (i.p.) after 30 and 60 min, respectively. Next, the number of abdominal contortions was quantified. In the same model, ineffective doses of etoricoxib were coadministered with hemin or DMDC and an effective dose of etoricoxib with ZnPP-IX. Four hours after the acetic acid injection, bilirubin levels (product of BVD conversion by the BVD reductase enzyme) were diagnosed in the peritoneal lavage. Protocol 2: In the hot-plate model, mice were pretreated with hemin (0.3, 1 or 3mg/Kg; s.c), DMDC (0.00025, 0.025 or 2.5µMol/Kg; s.c) or ZnPP-IX (1, 3 or 9mg/Kg; s.c) and, after 30, 60 and 90 min, the animals’ response latency on the hot plate (55ºC) was measured. Protocol 3: In the paw edema model induced by carrageenin (Cg), rats were pretreated with etoricoxib (0.1, 1 or 10mg/Kg; i.p) 30 min before receiving the subplantar injection of Cg in the right back paw, or 60 min before receiving injections with Hemin (0.3, 1 or 3mg/Kg; s.c), DMDC (0.25, 2.5 or 25µMol/Kg; s.c) or ZnPP-IX (1, 3 or 9mg/Kg; s.c). In the same model, ineffective doses of etoricoxib were coadministered with hemin or DMDC and an effective dose of etoricoxib with ZnPP-IX. Next, the paw edema was measured with a plethysmometer 1, 2, 3 and 4 h at 60 min after the Cg injection. Four hours after the Cg injection, paw tissue samples were collected for immunohistochemical analysis with anti-COX-2 and anti-HO-1 antibodies. Results: Hemin or DMDC reduced (p<0.05) the number of writhes and the paw edema in the 3rd h, while ZnPP-IX potentiated (p<0.05) the effect of acetic acid by increasing (p<0.05) the number of writhes and the paw edema in the 3rd h, intensifying Cg action. The coadministration of etoricoxib with hemin or DMDC reduced (p<0.05) the number of writhes. Coadministration of etoricoxib with DMDC reduced (p<0.05) the paw edema in the 3rd h, which was not significantly observed (p>0.05) when etoricoxib was coadministered with hemin. When etoricoxib was coadministered with ZnPP-IX, it was observed that ZnPP-IX reduced the analgesic and antiedematogenic effects of etoricoxib. In the hot-plate model, hemin, DMDC or ZnPP-IX administration did not affect the mice’s response latency on the plate. Conclusion: The HO-1/BVD/CO pathway is activated in the abdominal writhe model induced by acetic acid and paw edema by Cg, but does not seem to participate in the central mediation of nociception. The analgesic and antiedematogenic effect of etoricoxib at least partially depends on the participation of the HO-1/BVD/CO pathway.