To evaluate the effects of avocado soybean unsaponifiables (ASU) on proinflammatory mediators in chondrocytes and monocyte/macrophage-like cells.
To determine the dose response of ASU, chondrocytes (5 x 10(5) cells/well) were incubated at 5% CO(2), 37 degrees C for 72 h with (1) control media alone or (2) ASU at concentrations of 0.3, 0.9, 2.7, 8.3, and 25 microg/ml. Cells were activated with 20 ng/ml lipopolysaccharide (LPS) for 24 h and cell supernatants were analyzed for prostaglandin E(2) (PGE(2)) and nitrite content. Chondrocytes and THP-1 monocyte/macrophages (5 x 10(5) cells/well) were incubated at 5% CO(2), 37 degrees C for 72 h with (1) control media alone or (2) ASU (25 mug/ml). One set of cells was activated for 1 h with LPS (20 ng/ml) for both reverse-transcriptase PCR and real-time PCR analysis of tumor necrosis factor-alpha (TNF-alpha), interleukin-1-beta (IL-1beta), cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS) expression. One set of cells was activated for 24 h to analyze secreted PGE(2) and nitrite levels in the cellular supernatant.
ASU reduced TNF-alpha, IL-1beta, COX-2, and iNOS expression in LPS-activated chondrocytes to levels similar to nonactivated control levels. The suppression of COX-2 and iNOS expression was paralleled by a significant reduction in PGE(2) and nitrite, respectively, in the cellular supernatant. ASU also reduced TNF-alpha and IL-1beta expression in LPS-activated monocyte/macrophage-like cells.
The present study demonstrates that the anti-inflammatory activity of ASU is not restricted to chondrocytes, but also affects monocyte/macrophage-like cells that serve as a prototype for macrophages in the synovial membrane. These observations provide a scientific rationale for the pain-reducing and anti-inflammatory effects of ASU observed in osteoarthritis patients.