We recently reported that glucosamine reversed the decrease in proteoglycan synthesis and in UDP-glucuronosyltransferase I mRNA expression induced by interleukin-1L L (IL-1L L) [Arthritis Rheum. 44 (2001) 351^360]. In the present work, we show that glucosamine does not exert the same effects when chondrocytes were stimulated with reactive oxygen species (ROS). In order to better understand its mechanism of action, we determined if glucosamine could prevent the binding of IL-1L L to its cellular receptors or could interfere with its signaling pathway at a post-receptor level. Addition of glucosamine to rat chondrocytes treated with IL-1L L or with ROS decreased the activation of the nuclear factor U UB, but not the activator protein-1. After treatment with IL-1L L, glucosamine increased the expression of mRNA encoding the type II IL-1L L receptor. These results emphasize the potential role of two regulating proteins of the IL-1L L signaling pathway that could account for the beneficial effect of glucosamine in osteoarthritis. ß

Manganese superoxide dismutase (MnSOD) is known to play a role in cancer. MnSOD exerts a tumor suppressive effect in estrogen-dependent human breast cancer cells. In the present study we investigated the in vitro role of MnSOD in the growth of some aggressive and highly metastatic estrogen-independent breast cancer cells, i.e., MDA-MB231 and SKBR3 cells. We show that estrogen-independent cells expressed a significantly higher basal MnSOD level compared to estrogen-dependent human breast cancer cell lines (MCF-7 and T47D). For MDA-MB231 cells, the high-MnSOD level was accompanied by an overproduction of intracellular hydrogen peroxide (H2O2) and by a low expression of the major H2O2-detoxifying enzymes, catalase, and peroxiredoxin 3, compared to MCF-7 cells. Suppression of MnSOD expression by antisense RNA was associated with a decrease of H2O2 content and caused a stimulation of growth with a reduced cell doubling time but induced a decrease of colony formation. Furthermore, treatment of MDA-MB231 cells with H2O2 scavengers markedly reduced tumor cell growth and colony formation. In addition, MnSOD suppression or treatment with H2O2 scavengers reduced the invasive properties of MDA-MB231 cells up to 43%, with a concomitant decrease of metalloproteinase-9 activity. We conclude that MnSOD plays a role in regulating tumor cell growth and invasive properties of estrogen-independent metastatic breast cancer cells. These action are mediated by MnSOD-dependent H2O2 production. In addition, these results suggest that MnSOD up-regulation may be one mechanism that contributes to the development of metastatic breast cancers.

The activation of peroxisome proliferator-activated receptor Q Q (PPARQ Q) has been shown to inhibit the production and the effects of proinflammatory cytokines. Since interleukin-1L L (IL-1L L) directly mediates cartilage degradation in osteoarthritis, we investigated the capability of PPARQ Q ligands to modulate IL-1L L effects on human chondrocytes. RT-PCR and Western blot analysis revealed that PPARQ Q expression was decreased by IL-1L L. 15-Deoxy-v v 12Y14 -prostaglandin J 2 (15d-PGJ 2 ), in contrast to troglitazone, was highly potent to counteract IL-1L L-induced cyclooxygenase-2 and inductible nitric oxide synthase expression, NO production and the decrease in proteoglycan synthesis. Western blot and gel-shift analyses demonstrated that 15d-PGJ 2 inhibited NF-U UB activation, while troglitazone was ineffective. Although 15d-PGJ 2 attenuated activator protein-1 binding on the DNA, it potentiated c-jun migration in the nucleus. The absence or the low effect of troglitazone suggests that 15d-PGJ 2 action in human chondrocytes is mainly PPARQ Q-independent. ß

SUMMARY We investigated the spatiotemporal distributions of the different peroxisome proliferator-activated receptor (PPAR) isotypes (α, β, and α) during development (Week 7 to Week 22 of gestation) of the human fetal digestive tract by immunohistochemistry using specific polyclonal antibodies. The PPAR subtypes, including PPARα, are expressed as early as 7 weeks of development in cell types of endodermal and mesodermal origin. The presence of PPARα was also found by Western blotting and nuclease-S1 protection assay, confirming that this subtype is not adipocyte-specific. PPARα, PPARβ, and PPARα exhibit different patterns of expression during morphogenesis of the digestive tract. Whatever the stage and the gut region (except the stomach) examined, PPARα is expressed at a high level, suggesting some fundamental role for this receptor in development and/or physiology of the human digestive tract.

This work demonstrated the constitutive expression of peroxisome proliferator-activated receptor (PPAR)-gamma and PPAR-alpha in rat synovial fibroblasts at both mRNA and protein levels. A decrease in PPAR-gamma expression induced by 10 microg/ml lipopolysaccharide (LPS) was observed, whereas PPAR-alpha mRNA expression was not modified. 15-Deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) dose-dependently decreased LPS-induced cyclooxygenase (COX)-2 (-80%) and inducible nitric oxide synthase (iNOS) mRNA expression (-80%), whereas troglitazone (10 microM) only inhibited iNOS mRNA expression (-50%). 15d-PGJ(2) decreased LPS-induced interleukin (IL)-1 beta (-25%) and tumor necrosis factor (TNF)-alpha (-40%) expression. Interestingly, troglitazone strongly decreased TNF-alpha expression (-50%) but had no significant effect on IL-1 beta expression. 15d-PGJ(2) was able to inhibit DNA-binding activity of both nuclear factor (NF)-kappa B and AP-1. Troglitazone had no effect on NF-kappa B activation and was shown to increase LPS-induced AP-1 activation. 15d-PGJ(2) and troglitazone modulated the expression of LPS-induced iNOS, COX-2, and proinflammatory cytokines differently. Indeed, troglitazone seems to specifically target TNF-alpha and iNOS pathways. These results offer new insights in regard to the anti-inflammatory potential of the PPAR-gamma ligands and underline different mechanisms of action of 15d-PGJ(2) and troglitazone in synovial fibroblasts.