Histopathological studies of the acute inflammation in synovial tissue of rat knee joint following intra-articular injection of PLA_2 from Chinese Cobra (Naja naja atra) venom

摘要

A phospholipase A_2 was purified from Chinese Cobra Naja naja atra by a two-step procedure: gel filtration on Superdex 75 and reverse-phase high-performance liquid chromatography (HPLC) on a NUCLEOSIL 5 C18 column. Purified phospholipase A_2 was homogeneous, as indicated by capillary electrophoresis and electrospray mass spectrometry. It was a basic protein (pI = 8.2 +- 0.03) with a molecular mass of 13,258 Da. Amino acid sequence analysis of the N-terminal demonstrated a high degree of homology with other related PLA_2 from elapid venoms. The histopathological effects of the purified PLA_2 on synovial tissue of knee joint were studied in Wistar rats. Rats were injected intra-articularly with 100 #mu#l solution of PLA_2 of different concentrations. Synovial tissue samples with patella were taken for light microscope study. Histopathological evaluation revealed a significant induction of acute inflammation in synovial tissue after injection, as indicated by synovial lining-cell hyperlasia, subsynovial cellular infiltration, and peri-articular soft-tissue cellular infiltration. Marked inflammatory and proliferative changes in synovial tissue were evident after repeated intra-articular injections of 100 #mu#g PLA_2. This study failed to show any significant histological changes in cartilage of patella as well as in the surrounding muscle tissue of the knee joints. These results suggest that PLA_2 purified from Chinese Cobra venom induce time- and dose-dependent inflammatory changes in the synovial tissue of rat knee joint.