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

Abstract

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.

Enhanced fibrillin-2 expression is a general feature of wound healing and sclerosis: potential alteration of cell attachment and storage of TGF-β

“…53 Altered TGF-b storage on fibrilllin-2 containing microfibrils might be responsible for such changes as it was shown that TGF-b influences the cross-linking pathway. 54 In summary, our data show that the enhanced expression of fibrillin-2 is a general feature of activated fibroblasts found either in vivo in wound healing and sclerotic tissues or in cell culture after induction with serum, TGF-b or IL-4. The elevated expression of fibrillin-2 in wound healing and sclerotic tissue is another example for the 'embryonic reprogramming' of fibroblasts in these conditions.…”

Procollagen Lysyl Hydroxylase 2 Expression Is Regulated by an Alternative Downstream Transforming Growth Factor β-1 Activation Mechanism

“…PLOD2 is considered a fibrotic marker since its expression and the resulting pyridinoline cross-links are increased in various scarred tissues and in vitro in fibroblast by profibrotic cytokines such as TGF␤1 (4,5,38,43,44). In addition, PLOD2 expression is enhanced in various types of cancers (e.g.…”

“…The results clearly indicate that the transcriptional effects of both inhibitors were TGF␤1 pathway NOVEMBER 20, 2015 • VOLUME 290 • NUMBER 47 related, since no significant effects were observed on the basal PLOD2 expression in unstimulated fibroblasts. The other PLOD family members, PLOD1 and PLOD3, are not responsive to TGF␤1 stimulation (38). To prove that their transcriptional activation is independent on SP1 and SMAD3, we analyzed mRNA expression of PLOD1 and PLOD3 after treatment with SIS3 and Mithramycin A.…”

Gene Expression Analysis of Murine and Human Osteoarthritis Synovium Reveals Elevation of Transforming Growth Factor β–Responsive Genes in Osteoarthritis‐Related Fibrosis

“…LH2b converts the lysine in the telopeptides into hydroxylysine, thereby inducing the hydroxyallysine route. This route lead to an elevation in pyridinoline crosslinks that results in greater resistance of collagen to enzymatic degradation (14,34,37). Interestingly, both LH2b and pyridinolines are elevated in various fibrotic tissues and organs (34,38).…”