Specific effects of ethanol on neurite-promoting proteoglycans of neuronal origin

Quantitative analysis of proteoglycan synthesis and release by neurons indicated that of the total incorporation of 35SO4 and [3H]glucosamine into proteoglycan, approximately 75% was chondroitin sulphate while approximately 25% was heparan sulphate. Using a biological assay it has been shown that heparan sulphate proteoglycans (HSPGs) in conditioned medium promote neurite outgrowth from sensory neurons when complexed to a laminin substrate. Culture media conditioned in the presence of ethanol did not enhance neurite formation over control levels. Co-incubation of neurons with beta-D-xyloside, an inhibitor of proteoglycan synthesis, reduced neurite outgrowth after 20 h in culture and the combination of ethanol and beta-D-xyloside produced no further inhibition than with either ethanol or beta-D-xyloside used alone. If the laminin substrate was coated with medium conditioned by neurons, the direct inhibitory effects on process formation seen when ethanol was co-incubated with neurons were no longer observed. Ethanol inhibited the incorporation of 35SO4 and [3H]glucosamine into HSPG by neurons while having little or no effect on incorporation into chondroitin sulphate. These results suggest that inhibition of neuronal synthesis of HSPGs by ethanol is responsible for the decrease in neurite promoting activity of medium conditioned in the presence of ethanol.