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K Boumediene

Publications and source records attributed to K Boumediene.

8 recordsLinked to original sources
PubMed1999

Avocado/soya unsaponifiables enhance the expression of transforming growth factor beta1 and beta2 in cultured articular chondrocytes.

OBJECTIVE: Avocado and soya unsaponifiables (ASU) have been reported to exert beneficial effects in the treatment of periodontal and osteoarticular diseases. They are supposed to stimulate deposition and repair of extracellular matrix components, but the mechanisms underlying their action are not well understood. In view of the repair potential of osteoarthritic (OA) cartilage and the role that the transforming growth factor beta (TGFbeta) system could play in that process, we carried out in vitro studies to determine the mechanism of action of ASU on articular chondrocytes that may account for the beneficial effects on cartilage metabolism. METHODS: Cultured bovine articular chondrocytes were treated with various concentrations of ASU, and the expression of both TGFbeta isoforms, 1 and 2, and their receptors (TGFbetaRI and TGFbetaRII) was determined by Northern blot and reverse transcriptase-polymerase chain reaction. Cell transfection with TGFbeta1 promoter constructs was also used to delineate the cis-acting sequences mediating ASU responsiveness in chondrocytes. The level of plasminogen activator inhibitor 1 (PAI-1) was also evaluated by Northern blotting and protein radiolabeling. RESULTS: The data indicated that ASU stimulate the expression of TGFbeta1, TGFbeta2, and PAI-1 by articular chondrocytes. In contrast, the levels of TGFbetaRI and TGFbetaRII were not significantly affected by the compound. Treatment of bovine articular chondrocytes transiently transfected with TGFbeta1 promoter constructs suggested that the effect on TGFbeta1 expression is mediated by the region located between -732 and -1132 bp. CONCLUSION: The results indicate that the ASU-induced stimulation of matrix synthesis previously reported in cultured articular chondrocytes could be explained by the ability to enhance TGFbeta expression in these cells. Further, ASU increase the production of PAI-1, an effect that could help in blocking the plasmin cascade that leads to metalloprotease activation. These data suggest that the compound has properties that might promote TGFbeta-induced matrix repair mechanisms in articular cartilage.

5' Untranslated Regions↗
PubMed1999

Stimulating effect of diacerein on TGF-beta1 and beta2 expression in articular chondrocytes cultured with and without interleukin-1.

OBJECTIVE: Diacetylrhein or diacerein has shown efficacy in the treatment of both major forms of osteoarthritis (OA), coxarthrosis as well as gonarthrosis, improving clinical symptoms of the disease (pain reduction and algo-functional index). Both in-vitro and animal models studies suggest that diacerein may have also disease-modifying effects. The drug exerts inhibitory effects on interleukin-1-induced expression of cartilage degrading enzymes. However, its mechanism of action is not completely understood. In view of the role that could play the transforming growth factor (TGF)-beta system in the repair potentialities of OA cartilage, we studied the effect of diacerein on the expression of TGF-beta isoforms 1, 2 and 3 and that of their receptor types I and II in cultured bovine chondrocytes. METHODS: Cultured bovine articular chondrocytes were treated with 10(-5) m diacerein, 10 ng/ml IL-1beta or the combination diacerein+interleukin (IL)-1, and the expression of both TGF-beta isoforms 1, 2 and 3 and that of their receptors TbetaR-I and TbetaR-II was determined by Northern-blot and reverse transcriptase-polymerase chain reaction (RT-PCR). Cell transfections of cDNA constructs containing sequences of the 5'-upstream region of TGF-beta1 promoter were also performed to determine their transcriptional activity in diacerein-treated cultures. RESULTS: The data indicated that diacerein enhances the expression of TGF-beta1 and TGF-beta2. This effect was also found in the presence of IL-1, albeit with smaller intensity. In contrast, the levels of TGF-beta3 and receptors I and II remained unaffected or slighty modified by the compound. Treatment of cells transiently transfected with TGF-beta1 promoter constructs suggested that the stimulating effect on TGF-beta1 expression is mediated by the region -1038 to -1132 base pars. CONCLUSION: The results suggest that diacerein effects on matrix synthesis and turn-over previously reported in cultured articular chondrocytes might be explained in part by the ability of the drug to enhance TGF-beta1 and TGF-beta2 expression in these cells. This mechanism of action may account for the potential disease-modifying properties of diacerein and might give clues as to how future anti-osteoarthritic drugs should be designed.

Animals↗
PubMed1998

Cell-cycle-dependent expression of transforming growth factor beta type I receptor correlates with differential proliferative effects of TGFbeta1 in articular chondrocytes.

We previously found that transforming growth factor beta type 1 (TGFbeta1) had bifunctional effects on articular chondrocytes in culture depending on the proliferative state of the cells. Here, TGFbeta1 responses and the expression of TGFbeta receptors I and II were investigated as a function of growth state in rabbit articular chondrocytes (RAC) and Mv1Lu cells, a cell line which is growth inhibited by TGFbeta1. In contrast to these latter cells, in which DNA synthesis was decreased by TGFbeta1 independently of the cell cycle phases, exponentially growing RAC responded with a stimulation of DNA synthesis while confluent or quiescent cells were growth inhibited. Using synchronized RAC cultures, we showed that inhibitory responses were associated with the G0/G1 phase, whereas proliferative effects were S-phase dependent. Type I receptor mRNA level was severalfold greater in quiescent and slowly proliferating than in exponentially growing cells. In contrast, the expression of type II mRNA did not change. 125I-TGFbeta1 binding to RI in G0/G1-arrested cells was greater than in S-phase, suggesting a correlation with the growth-inhibitory effect of TGFbeta1. Transfection of an RI expression vector in exponentially growing RAC, which normally are growth stimulated by TGFbeta1, induced an inhibitory response, supporting the idea that this effect was due to increased RI expression. These results indicate that the ratio of type I to type II levels is cell cycle dependent and could lead to either negative or positive proliferative responses. In contrast, no influence on the TGFbeta1-induced stimulation of matrix gene transcriptional activity was seen, confirming that TGFbeta cell growth and matrix effects are controlled by separate pathways.

Activin Receptors, Type I↗
PubMed1995

Modulation of rabbit articular chondrocyte (RAC) proliferation by TGF-beta isoforms.

We have previously shown that TGF-beta 1 exerts a bifunctional effect on RAC proliferation. Added to quiescent cultures, it inhibits the entry of G0/G1 cells into S phase whereas in S phase synchronized populations, it stimulates the DNA replication rate with a delayed G2 + M phase and a subsequent transient increase of cell number. As TGF-beta 2 and beta 3 isoforms are also expressed in bone and cartilage tissues, it was of interest to study their effect on RAC proliferation, in comparison to that of TGF-beta 1. Using cell counting and tritiated thymidine incorporation, we found that all the TGF-beta s used here induced an increase of RAC proliferation rate occurring between 24 and 48 h of exposure. TGF-beta 2 appeared as the most efficient form as judged from the maximum of thymidine labelling. However, TGF-beta 3 induced an increase of cell number slightly higher than both TGF-beta 1 and TGF-beta 2 (+30% versus 20% for TGF-beta 1 and beta 2). TGF-beta 2 and beta 3 were able to stimulate the DNA replication rate as previously demonstrated for TGF-beta 1. However, the effect occurred later for TGF-beta 2 and beta 3 (12 h) than for TGF-beta 1 (6 h). This was confirmed by flow cytometric analysis of DNA content. In addition, immunodetection by flow cytometry demonstrated that all TGF-beta isoforms enhanced endogenous expression of TGF-beta-related peptides. The effect was shown to be associated with the cell cycle S phase and was greater for TGF-beta 3 than for TGF-beta 1 and beta 2. These findings suggest that TGF-beta s could act on RAC functions via autocrine and paracrine ways. Taken together, these data indicate that TGF-beta s may modulate proliferation of articular chondrocytes and therefore could play a role in the activation of these cells in the early stages of osteoarthritis.

Animals↗
PubMed1994

Different phosphorylated forms of inositolphosphate glycan could be involved in the transforming growth factor-beta 1 (TGF-beta 1) signalling pathway.

Labelling with [3H]glucosamine was used to prepare a transforming growth factor-beta 1 (TGF-beta 1)-sensitive glycosylphosphatidylinositol (GPI) from monolayer cultures of rabbit articular chondrocytes (RAC), which may be involved in control of the cell cycle. The polar headgroup of this glycosylphosphatidylinositol was generated by both phosphatidylinositol-specific phospholipase C (PI-PLC) and pronase E digestion. The molecule emerged in only one peak on a Dowex AG1-X8 chromatogram, eluted at 0.1 N ammonium formate. In contrast, similar experiments performed on cellular extract from cultures previously labelled with [3H]glucosamine displayed four radioactive peaks eluting at 0.1, 0.2, 0.5 and 1 N ammonium formate, respectively. Evidence that the eluting position of these peaks was dependent on the number of phosphate residues present in each fraction was demonstrated by both [32P]phosphorus labelling and change in the position of alkaline phosphatase-induced shift in elution volume. We also demonstrated that the GPI-derived inositolphosphate glycan (IPG) could be hyperphosphorylated into the cell under the action of a kinase whose activity was enhanced by TGF-beta 1 itself. We have also shown that all of these IPG forms could mimic the TGF-beta-induced increase of DNA replication rate of RAC, with a higher activity for peaks III and IV than peaks I and II.

Animals↗
PubMed1994

Transforming growth factor-beta (TGF-beta) and articular chondrocytes.

Transforming growth factor-beta (TGF-beta) has a dual effect on the proliferation of joint chondrocytes. In medium with a low serum concentration, it inhibits cell growth, while in medium supplemented with 10% fetal calf serum it stimulates cell growth. This stimulation leads to a higher replication rate an a larger number of cells in the G2/M phase of the cell cycle. Since these cells have already replicated their DNA, they can begin mitosis when stimulated by a EGF type factor. This mechanism involves the systems of the TGF-beta receptors which appear to vary with the cell cycle. In addition, a glycane inositophosphate may play a role as a second messenger for TGG-beta in this action. Finally, TGF-beta cannot restore the chondrocyte phenotype in dedifferentiated cells nor limit the dedifferentiation process. It exerts a opposing effect to the deleterious effects of interleukin-1 by inhibiting the expression of the receptors of this cytokine at the level of transcription. These in vitro effects would suggest that TGF-beta plays an important role in the repair potentiality of joint cartilage especially in arthrosis. In vivo studies are however necessary to verify this hypothesis.

Animals↗