HYDROXYL RADICAL GENERATION BY RHEUMATOID BLOOD AND KNEE-JOINT SYNOVIAL-FLUID

Objective-To demonstrate directly that highly reactive hydroxyl radica ls (OH.) can be generated in patients with rheumatoid arthritis and co ntribute to joint damage, and to examine the ability of blood to cause OH. generation. Methods-The sensitive and specific technique of hydro xylation of aromatic compounds (salicylate and phenylalanine) was used to measure OH.. Synovial fluid and blood from patients with active rh eumatoid arthritis were aspirated and immediately added to tubes conta ining salicylate and phenylalanine as detectors of OH., or to tubes co ntaining saline as a control. Levels of specific products of attack of OH. upon salicylate (2,3- and 2,5-dihydroxybenzoates) and phenylalani ne (ortho- and meta-tyrosines) were measured by high performance liqui d chromatography. Results-Synovial fluid samples aspirated into saline never contained ortho- or meta-tyrosines or 2,3-dihydroxybenzoate. Of 53 patients examined, synovial fluid and blood from 36 caused formati on of ortho- and meta-tyrosines when aspirated into solutions containi ng phenylalanine. Repeated sampling from three ((positive)) patients s howed consistent evidence of these hydroxylation products. Similarly, of 22 patients examined, synovial fluid and blood from 18 caused forma tion of 2,3- and 2,5- dihydroxybenzoates when aspirated into salicylat e solutions. Further evidence for the role of OH. was provided by inhi bition of the hydroxylation by the specific OH. scavengers mannitol an d sodium formate. Conclusions-Aspirated knee joint fluids and blood fr om rheumatoid arthritis patients can generate OH., consistent with cur rent views on the importance of this radical as a cytotoxic agent in r heumatoid disease. The ability of body fluids to cause OH. formation i s not correlated with simple laboratory indices of disease activity, b ut is reproducible on sequential sampling from the same patients. The mechanism and significance of the phenomenon in rheumatoid arthritis p athology remain to be established.