Elevated formation of pyridinoline cross-links by profibrotic cytokines is associated with enhanced lysyl hydroxylase 2b levels

Biochim Biophys Acta. 2005 Jun 30;1741(1-2):95-102. doi: 10.1016/j.bbadis.2004.09.009. Epub 2004 Oct 5.


The hallmark of fibrosis is the excessive accumulation of collagen. The deposited collagen contains increased pyridinoline cross-link levels due to an overhydroxylation of lysine residues within the collagen telopeptides. Lysyl hydroxylase 2b (LH2b) is the only lysyl hydroxylase consistently up-regulated in several forms of fibrosis, suggesting that an enhanced LH2b level is responsible for the overhydroxylation of collagen telopeptides. The present paper reports the effect of profibrotic cytokines on the expression of collagen, lysyl hydroxylases and lysyl oxidase in normal human skin fibroblasts, as well as the effect on pyridinoline formation in the deposited matrix. All three isoforms of TGF-beta induce a substantial increase in LH2b mRNA levels, also when expressed relatively to the mRNA levels of collagen type I alpha2 (COL1A2). The TGF-beta isoforms also clearly influence the collagen cross-linking pathway, since higher levels of pyridinoline cross-links were measured. Similar stimulatory effects on LH2b/COL1A2 mRNA expression and pyridinoline formation were observed for IL-4, activin A, and TNF-alpha. An exception was BMP-2, which has no effect on LH2b/COL1A2 mRNA levels nor on pyridinoline formation. Our data show for the first time that two processes, i.e., up-regulation of LH2b mRNA levels and increased formation of pyridinoline cross-links, previously recognized to be inherent to fibrotic processes, are induced by various profibrotic cytokines.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Activins / pharmacology
  • Amino Acids / chemistry*
  • Cells, Cultured
  • Collagen Type I / metabolism
  • Cross-Linking Reagents / pharmacology*
  • Cytokines / pharmacology*
  • Fibroblasts / drug effects
  • Fibroblasts / enzymology
  • Fibroblasts / metabolism
  • Fibrosis / pathology
  • Gene Expression Regulation, Enzymologic
  • Humans
  • Inhibin-beta Subunits / pharmacology
  • Interleukin-4 / pharmacology
  • Procollagen-Lysine, 2-Oxoglutarate 5-Dioxygenase / genetics
  • Procollagen-Lysine, 2-Oxoglutarate 5-Dioxygenase / metabolism*
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • Protein Isoforms / pharmacology
  • RNA, Messenger / metabolism
  • Skin / cytology
  • Time Factors
  • Transforming Growth Factor beta / genetics
  • Transforming Growth Factor beta / metabolism
  • Transforming Growth Factor beta / pharmacology
  • Tumor Necrosis Factor-alpha / pharmacology
  • Up-Regulation


  • Amino Acids
  • Collagen Type I
  • Cross-Linking Reagents
  • Cytokines
  • Protein Isoforms
  • RNA, Messenger
  • Transforming Growth Factor beta
  • Tumor Necrosis Factor-alpha
  • activin A
  • Activins
  • Interleukin-4
  • pyridinoline
  • Inhibin-beta Subunits
  • PLOD2 protein, human
  • Procollagen-Lysine, 2-Oxoglutarate 5-Dioxygenase