Inducible nitric oxide synthase (iNOS) is one rate-limiting enzyme in nitric oxide (NO) synthesis, and plays a role in mediating cell proliferation, apoptosis, and inflammation. Post-traumatic arthritis (PTA) is secondary after osteoarthritis (OA). This study thus established rat PTA model, on which the role of iNOS in PTA pathogenesis was investigated.
Chondrocytes and synovial fluids were collected for comparing NO content and iNOS activity. In vitro cultured PTA rat chondrocytes were tested for expression of iNOS, matrix metallopeptidase 13 (MMP-13), and alpha-1 chain of type II collagen (COL2A1) expression with or without Interleukin 1β (IL-1β) treatment. NO content and iNOS activity in the supernatant were measured, followed by flow cytometry for Ki-67 expression and apoptosis. IL-1β treated cells were transfected with small interfere iNOS (si-iNOS), followed by expressional assay of iNOS, MMP-13 and Col2A1, activity assay of NO and iNOS, plus Ki-67 level and apoptosis.
Compared to Sham group, PTA model rats had higher iNOS expression, NO content, and iNOS activity. IL-1β treatment remarkably elevated iNOS and MMP-13 expression in chondrocytes, it decreased COL2A1 expression, increased NO content and iNOS activity, whilst suppressed cell proliferation to facilitate apoptosis. Silencing of iNOS expression decreased iNOS or MMP-13 expression, increased COL2A1 expression, suppressed NO or iNOS content, potentiated proliferation and decreased apoptosis.
iNOS expression and NO content were elevated in PTA rat chondrocyte. iNOS and NO production can facilitate chondrocyte apoptosis and matrix degradation, and suppress chondrocyte proliferation, thus playing a role in PTA pathogenesis.