BACKGROUND: Clinical studies have shown that rose hip powder (RHP) alleviates osteoarthritis (OA). This might be due to anti-inflammatory and cartilage-protective properties of the complete RHP or specific constituents of RHP. Cellular systems (macrophages, peripheral blood leukocytes and chondrocytes), which respond to inflammatory and OA-inducing stimuli, are used as in vitro surrogates to evaluate the possible pain-relief and disease-modifying effects of RHP. METHODS: (1) Inflammatory processes were induced in RAW264.7 cells or human peripheral blood leukocytes (PBL) with LPS. Inflammatory mediators (nitric oxide (NO), prostaglandin E(2) (PGE(2)) and cytokines/chemokines) were determined by the Griess reaction, EIA and multiplex ELISA, respectively. Gene expression was quantified by RT-PCR. RHP or its constituent galactolipid, GLGPG (galactolipid (2S)-1, 2-di-O-[(9Z, 12Z, 15Z)-octadeca-9, 12, 15-trienoyl]-3-O-ß-D-galactopyranosyl glycerol), were added at various concentrations and the effects on biochemical and molecular parameters were evaluated. (2) SW1353 chondrosarcoma cells and primary human knee articular chondrocytes (NHAC-kn) were treated with interleukin (IL)-1ß to induce in vitro processes similar to those occurring during in vivo degradation of cartilage. Biomarkers related to OA (NO, PGE(2), cytokines, chemokines, metalloproteinases) were measured by multiplex ELISA and gene expression analysis in chondrocytes. We investigated the modulation of these events by RHP and GLGPG. RESULTS: In macrophages and PBL, RHP and GLGPG inhibited NO and PGE(2) production and reduced the secretion of cytokines (TNF-a, IFN-?, IL-1ß, IL-6, IL-12) and chemokines (CCL5/RANTES, CXCL10/IP-10). In SW1353 cells and primary chondrocytes, RHP and GLGPG diminished catabolic gene expression and inflammatory protein secretion as shown by lower mRNA levels of matrix metalloproteinases (MMP-1, MMP-3, MMP-13), aggrecanase (ADAMTS-4), macrophage inflammatory protein (MIP-2, MIP-3a), CCL5/RANTES, CXCL10/IP-10, IL-8, IL-1a and IL-6. The effects of GLGPG were weaker than those of RHP, which presumably contains other chondro-protective substances besides GLGPG. CONCLUSIONS: RHP and GLGPG attenuate inflammatory responses in different cellular systems (macrophages, PBLs and chondrocytes). The effects on cytokine production and MMP expression indicate that RHP and its constituent GLGPG down-regulate catabolic processes associated with osteoarthritis (OA) or rheumatoid arthritis (RA). These data provide a molecular and biochemical basis for cartilage protection provided by RHP.