Efeito protetor do bloqueio de peroxinitrito sobre a lesão da cartilagem articular na artrite induzida por Zymosan

Abstract

Although excessive nitric oxide (NO) release has been associated with disease severity in arthritis, the administration of NO synthase (NOS) inhibitors was not protective in experimental arthritis. PN, formed by the combination of NO and 02", may be linked to tissue lesions associated with increased NO release. We investigated the effect of the administration of NOS inhibitors orthe PN scanvenger uric acid (UA) in the acute (6h) and chronic (7d or 14d) ZyA. Wistar rats were subjected to the intraarticular (iart) injection of 1mg Zy into both knees. After 6h, 7 or 14d the articular exsudate was collected for evaluation of the cell influx (Cl), nitrite (Griess reaction) and the PN marker 3-nitrotyrosine (3-NT) release, using ELISA. The synovial membranes were excised for histopathological analysis, after hematoxylin-eosin staining. The cartilage lesion was assessed by the determination of the glycosaminoglycan (GAG) content obtained from the distai femoral extremities, using agarose gel electrophoresis followed by densitometry (525nm). Groups received either L-NAME (LN 25 or 75 mg/kg/d, p.o) or aminoguanidine (Ag 50 or 100 mg/kg/d, p.o), starting prior (prophylactic) or 3d (therapeutic) after Zy injection, and daily, until sacrifice, at 7d. A group received the selective iNOS inhibitor 1400W (0.5 or 1 mg/kg/d, s.c) as a prophylactic intervention and was killed at 7d. For the acute experiments (6h), other groups received LN (100 mg/kg, s.c) or 1400W (1mg/kg, s.c) 30 min before Zy. To study the role of neutrophils in NO and PN release, a group received an antineutrophil antibody before the Zy and was killed at 6h. Other groups received UA (100 or 250 mg/kg/d/14d, i.p) before the Zy and were killed at 14d. Controls (CT) received saline. Non-treated (NT) groups received just the Zy i.art. ZyA led to increased NO and PN release into the joints. Prophylactic or therapeutic administration of the NOS inhibitors did significantly inhibited the cell influx and the synovitis, as compared to NT rats (p<0.05), though being able to reduced NO release. However, the reduction of GAG content seen in the NT group was unaltered by the NOS inhibitors. Surprisingly, NOS inhibitors did worsen the GAG loss, as compared to NT (p<0,05). Zy injection significantly increase the 3-NT leveis in the NT group, measured 14d after injection of the Zy, as compared to control (p<0.05), that were significantly decreased by UA (p<0.05). Both UA regimens significantly reversed the Cl, the synovitis and also the GAG loss, as compared to NT (p<0,05). Neutropenic animais displayed significantly lower NO and 3-NT leveis, measured 6h after injection of the Zy (p<0,05). In the acute phase, neutrophils are at least partially responsible for the increased NO and 3-NT leveis in ZyA. PN scavenging rather than NOS inhibition protects from the articular cartilage lesion in ZyA. NO seems to be essential to cartilage metabolism, at least during arthritis.