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  • Title: Enhanced synthesis of proteoglycans by vascular endothelial cells treated with phorbol ester.
    Author: Tao Z, Smart FW, Figueroa JE, Glancy DL, Vijayagopal P.
    Journal: Life Sci; 1997; 61(7):723-38. PubMed ID: 9252247.
    Abstract:
    We investigated the biosynthesis of proteoglycans (PG) in endothelial cells following their treatment with phorbol 12-myristate 13-acetate (PMA). Confluent cultures of bovine aortic endothelial cells were incubated in the presence and absence of PMA (100 ng/ml) and then pulsed with [35S]sulfate, [3H]glucosamine, or [35S]sulfate plus [3H]leucine for varying times in the absence of PMA. Alternatively, confluent endothelial cells were simultaneously incubated with PMA and [35S]sulfate for varying times. The metabolically labeled PG in the cell layer and medium were analyzed. Both short-term and prolonged exposure of endothelial cells to PMA significantly stimulated PG synthesis, regardless of the experimental conditions. [35S]sulfate incorporation into newly synthesized PG in PMA-treated cells also increased by 1.7-fold and 3.6-fold over control cells, following a 15-min and 30-min pulse, respectively. Cycloheximide markedly inhibited the increased synthesis of PG in PMA-treated cells, while actinomycin D produced a moderate inhibition. PG secretion was increased in PMA-treated cells compared with control cells, while there was no significant difference in PG degradation between the two cultures. PG from control and PMA-treated endothelial cell cultures did not differ in composition or hydrodynamic sizes. The incorporation of [3H]leucine into total cellular proteins decreased significantly following exposure of endothelial cells to PMA. Endothelial cells exposed to PMA for 3 h had significantly more protein kinase C (PKC) activity than did control cells. Inhibition of PKC by calphostin C abolished the PMA-mediated stimulation of PG synthesis in endothelial cells. The results indicate that PMA stimulates PG synthesis in endothelial cells either directly or indirectly through a PKC dependent mechanism.
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