Although most studies have focused on the cholesterol-lowering activity of stigmasterol,
other bioactivities have been ascribed to this plant sterol compound, one of which
is a potential anti-inflammatory effect. To investigate the effects of stigmasterol,
a plant sterol, on the inflammatory mediators and metalloproteinases produced by chondrocytes.
We used a model of newborn mouse chondrocytes and human osteoarthritis (OA) chondrocytes
in primary culture stimulated with or without IL-1beta (10 ng/ml), for 18 h. Cells
were pre-incubated for 48 h with stigmasterol (20 microg/ml) compared to untreated
cells. We initially investigated the presence of stigmasterol in chondrocyte, compared
to other phytosterols. We then assessed the role of stigmasterol on the expression
of various genes involved in inflammation (IL-6) and cartilage turn-over (MMP-3, -13,
ADAMTS-4, -5, type II collagen, aggrecan) by quantitative Reverse Transcriptase-Polymerase
Chain Reaction (RT-PCR). Additional experiments were carried out to monitor the production
of MMP-3 and prostaglandin E2 (PGE(2)) by specific immuno-enzymatic assays. We eventually
looked at the role of stigmasterol on NF-kappaB activation by western blot, using
an anti-IkappaBalpha antibody.
After 18 h of IL-1beta treatment, MMP-3, MMP-13, ADAMTS-4, but not ADAMTS-5 RNA expression
were elevated, as well as MMP-3 and PGE(2) protein levels in mouse and human chondrocytes.
Type II collagen and aggrecan mRNA levels were significatively reduced. Pre-incubation
of stigmasterol to IL-1beta-treated cells significantly decreased these effects described
above (significant reduction of MMP-3 mRNA in human and mouse, MMP-3 protein in mouse,
MMP-13 mRNA in mouse and human, ADAMTS-4 mRNA in human, PGE(2) protein in human and
mouse) Finally, stigmasterol was capable of counteracting the IL-1beta-induced NF-kappaB
pathway.
This study shows that stigmasterol inhibits several pro-inflammatory and matrix degradation
mediators typically involved in OA-induced cartilage degradation, at least in part
through the inhibition of the NF-kappaB pathway. These promising results justify further
ex vivo and in vivo investigations with stigmasterol.
Copyright 2009 Osteoarthritis Research Society International. Published by Elsevier
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