The mRNA and the activity of lysyl hydroxylase are up-regulated by the administration of ascorbate and hydralazine to human skin fibroblasts from a patient with Ehlers-Danlos syndrome type VI.
Lysyl hydroxylase (LH) catalyzes the formation of hydroxylysine required for the intermolecular cross-linking of collagen, which is an essential step in collagen biosynthesis. Dermal fibroblasts from patients with Ehlers-Danlos Syndrome type VI (EDS VI), an inherited connective tissue disorder, express decreased levels of LH activity. In the present study we have shown that both the mRNA and the enzyme activity of LH in skin fibroblasts from one EDS VI patient (AT750), a compound heterozygote for the LH gene, are increased by administration of ascorbate and hydralazine, either individually or in combination. Although the AT750 cells express only 24% of the LH activity found in normal cells, a similar fold increase in activities in both EDS VI and normal cells was observed following treatment with ascorbate (1.5- to 2-fold) and hydralazine (2- to 4-fold), which paralleled the increase in their steady state LH mRNAs. Ascorbate increased total collagen production by 2-fold from a similar basal level of collagen synthesis in each cell type. This was confirmed by protein gel analysis which showed increases in pro alpha 1(I), pro alpha 2(I), and pro alpha 1(III) collagen chains in both normal and EDS VI cells. This ascorbate-mediated increase of alpha 1(I) collagen resulted from increased mRNAs for alpha 1(I) collagen in both cell types. Hydralazine treatment, with or without ascorbate, severely decreased the alpha 1(I) collagen mRNAs in fibroblasts from both AT750 and the normal donor; total collagen synthesis was similarly reduced. This study shows that LH activity, which is severely deficient in fibroblasts from an EDS VI patient, can be upregulated by administration of ascorbate and hydralazine as a result of the increased mRNA for LH, suggesting that the mechanism for the regulation of the LH gene is functioning normally in this patient.
Yeowell, HN; Walker, LC; Marshall, MK; Murad, S; Pinnell, SR
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