Metallothioneins involment in the pathogenesis of synovial tissue inflammation in rats with acute gonarthritis

Zinc (Zn) is involving in the suppressing of inflammation. However, its functionality in the knee joint under the gonarthritis (GA) is not elucidated. The aim of this study was to investigate the participation of Zn-buffering and stress responsive proteins metallothioneins (MTs) in the pathogenesis of the synovial tissues under the experimental acute GA. The inflammation was induced in rats by intra-articular administration of carrageenan. The concentrations of MTs total protein (MTSH), Zn-bound protein (Zn-MTs), total Zn concentration in the tissue, the indexes of oxidative stress and cholinesterase activity were determined. The level of sialic acids was indicated in the blood serum. The enhancing of sialic acids concentration by 42% and cholinesterase depletion confirmed the pathology. In the animals with GA, total level of Zn in the tissue was correspondent to control. However, the MTSH and Zn-MT levels were elevated (by 79 and 46% respectively). This disproportionate rate can be due to partial oxidation of thiols. The superoxide dismutase activity was elevated, radical scavenging activity and protein carbonylation were correspondent to control, but the levels of catalase, glutathione–S-transferase and glutathione were decreased by 28-44%, and lipid peroxidation (TBARS) was increased by 59% compared to control group. Principal Component Analysis confirmed the strong interrelations between MTs and peroxide-related oxidative stress indexes. This preliminary study provides the basis for the understanding of the reason for Zn imbalance in the acute GA as the result of the impairment of thiol redox balance and proposes these biomarkers for the evaluation of knee joint pathologies.