Effect of retinoic acid on chondrocyte glycosaminoglycan biosynthesis

An agarose gel electrophoretic method for analysis of sulfated glycosaminoglycans of cultured cells

Agarose disc gel electrophoresis has been adapted to achieve the separation of the major sulfated glycosaminoglycans produced by cells in culture. By use of buffers containing barium ion, mixtures of chondroitin sulfate, dermatan sulfate, and heparan sulfate are well resolved into discrete bands. The technique can be used preparatively as well as analytically to separate quantities of glycosaminoglycans up to a milligram in a 6-mm diameter gel.

Effect of retinyl acetate on sulfated glycosaminoglycan biosynthesis in dermal and epidermal cells in vitro

The effects of retinyl acetate on the biosynthesis of sulfated glycosaminoglycans in dermal and epidermal cells isolated from newborn mice was investigated. Three compartments were analysed for [35S]-glycosaminoglycans; the culture medium, the cellular matrix, and the cells. The individual levels of chondroitin 4-sulfate, dermatan sulfate and heparin and/or heparan sulfate in these compartments as a function of retinyl acetate was also analysed. The addition of retinyl acetate resulted in a dose dependent increase 35SO4 incorporation in the cellular and matrix compartments of the dermis in vitro. At the optimum concentration of 1.8 X 10(-6) M, this increase was 50%. The levels of35SO4 incorporated into medium glycosaminoglycans were relatively constant. There were also changes in the levels of the individual sulfated glycosaminoglycans. The glycosaminoglycan profile was modified differently in each of the three compartments analysed. In the epidermal cells, retinyl acetate at an optimum concentration of 1.8 X 10(-6) M resulted in a dose dependent increase in 35SO4 incorporation in the cellular, matrix and medium compartments. There was no apparent change in the glycosaminoglycan profile, with heparin and/or heparan sulfate being the major sulfated glycosaminoglycan.

Effects of retinoic acid on the immune system: stimulation of T killer cell induction

Retinoic acid (RA), a vitamin A derivative with anti-tumor activity, was assayed for its effects on the immune system in mice. High doses of this compound (1000 microgram/mouse/day) have toxic effects and cause depletion on the peripheral lymphoid organs (spleen, thymus) while leaving the bone marrow cells unaffected. Both the in vivo and in vitro induction of cell-mediated cytotoxicity (CMC) to allogeneic tumor cells is stimulated at least tenfold by low doses (25--300 microgram/mouse/day) of RA while high doses suppress CMC induction. RA is shown to be a specific adjuvant for the induction of cytotoxic thymus-derived lymphocytes (T cells) and not a general T cell mitogen or adjuvant. It does not enhance the proliferative response in the mixed lymphocyte culture nor does it stimulate lymphocyte proliferation in response to the mitogens concanavalin A and phytohemagglutinin. The induction of cooperating T cells and the delayed-type hypersensitivity reaction are also not stimulated by RA. In contrast to the reported stimulatory effects of retinyl palmitate and retinyl acetate, RA does not stimulate the humoral response to erythrocytes. The strong adjuvant effects that RA has on the induction of CMC at low doses may be responsible for its anti-tumor activity.

The effect of beta-D-xylosides on chondroitin sulphate biosynthesis in embryonic chicken cartilage in the absence of protein synthesis inhibitors

Incorporation of [35S]]sulphate, [3H]glucose and [3H]serine into glycosaminoglycans and proteoglycans of embryonic-chicken sternum was measured in vitro in incubation medium containing 4-methylumbelliferyl beta-D-xyloside or p-nitrophenyl beta-D-xyloside at low concentrations, and in the absence of inhibitors of protein synthesis. Incorporation of sulphate was decreased by 80% in incubations in which 1mM-4-methylumbelliferyl beta-xyloside or 2.5 mM-p-nitrophenyl beta-xyloside was present; under these conditions, serum factors stimulated incorporation to only a small extent. When the concentration of the xyloside was decreased tenfold, incorporation of sulphate was inhibited by 60-70%, but when normal human serum or L-3,3',5-tri-iodothyronine or both were also added to the incubation medium, incorporation was markedly stimulated. Experiments in which [35S]sulphate and [3H]glucose were incorporated simultaneously, and enzymic analysis of glycosaminoglycans formed in such experiments, indicated that chondroitin sulphate formed in the presence of 0.1 mM-4-methylumbelliferyl beta-xyloside contained 30-40% less sulphate than did chondrotin sulphate synthesized in the absence of xylosides. Similar experiments, with [3H]serine instead of [3H]glucose, suggested also a 20-30% decrease in chain length of the chondroitin sulphate; this was confirmed by direct gel filtration of labelled glycosaminoglycans on a calibrated column. Incorporation of [3H]glucose or [3H]serine was stimulated by serum and tri-iodothyronine in parallel with incorporation of sulphate. The changes seen in the total chondroitin sulphate were mirrored in the major proteoglycan fraction, purified by isopycnic centrifugation of salt-extracted proteoglycans. The labelling pattern of chondroitin sulphate from this proteoglycan indicated that decreased sulphation of chondroitin sulphate was largely due to the inferior ability of short polysaccharide chains to accept sulphate, with some direct interference with transfer of sulphate to all chains. The results also suggested that the action of serum factors on synthesis of proteochondroitin sulphate is exercised at the level of either protein synthesis or transport to the sites of initiation of polysaccharide synthesis.