Minoxidil exerts different inhibitory effects on gene expression of lysyl hydroxylase 1, 2, and 3: Implications for collagen cross-linking and treatment of fibrosis

• Published in: Matrix biology 2005-06, Vol.24 (4), p.261-270
• Main Authors: Zuurmond, Anne-Marie, van der Slot-Verhoeven, Annemarie J., van Dura, Ernst A., De Groot, Jeroen, Bank, Ruud A.
• Format: Article
• Language: English
• Subjects: 2-Aminoadipic Acid - analogs & derivatives; 2-Aminoadipic Acid - metabolism; Cells, Cultured; Chromatography, High Pressure Liquid; Collagen; Collagen - metabolism; Fibrosis; Fibrosis - drug therapy; Gene Expression Regulation, Enzymologic - drug effects; Humans; Hydroxylation; Lysyl hydroxylase; Minoxidil; Minoxidil - pharmacology; Procollagen-Lysine, 2-Oxoglutarate 5-Dioxygenase - genetics; Procollagen-Lysine, 2-Oxoglutarate 5-Dioxygenase - metabolism; Pyridinoline cross-links
• ISSN: 0945-053X; 1569-1802
• DOI: 10.1016/j.matbio.2005.04.002

Collagen deposits in fibrotic lesions often display elevated levels of hydroxyallysine (pyridinoline) cross-links. The relation between the occurrence of pyridinoline cross-links and the irreversibility of fibrosis suggests that these cross-links contribute to the aberrant accumulation of collagen. Based on its inhibitory effect on lysyl hydroxylase activity minoxidil has been postulated to possess anti-fibrotic properties by limiting the hydroxylysine supply for hydroxyallysine cross-linking. However, to interfere with hydroxyallysine cross-linking specifically lysyl hydroxylation of the collagen telopeptide should be inhibited, a reaction predominantly catalysed by lysyl hydroxylase (LH) 2b. In this study, we demonstrate that minoxidil treatment of cultured fibroblasts reduces LH1>>LH2b>LH3 mRNA levels dose-and time-dependently, but has essentially no effect on the total number of pyridinoline cross-links in the collagen matrix. Still the collagen produced in the presence of minoxidil displays some remarkable features: hydroxylation of triple helical lysine residues is reduced to 50% and lysylpyridinoline cross-linking is increased at the expense of hydroxylysylpyridinoline cross-linking. These observations can be explained by our finding that LH1 mRNA levels are the most sensitive to minoxidil treatment, corroborating that LH1 has a preference for triple helical lysine residues as substrate. In addition, the non-proportional increase in cross-links (20-fold) with respect to the decrease in lysyl hydroxylation state of the triple helix (2-fold) even suggests that LH1 preferentially hydroxylates triple helical lysine residues at the cross-link positions. We conclude that minoxidil is unlikely to serve as an anti-fibroticum, but confers features to the collagen matrix, which provide insight into the substrate specificity of LH1.