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

Abstract

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 (p I=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 μl 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 hyperplasia, 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 μg 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.