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      Lysyl Hydroxylase Inhibition by Minoxidil Blocks Collagen Deposition and Prevents Pulmonary Fibrosis via TGF-β 1/Smad3 Signaling Pathway

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          Abstract

          Background

          Idiopathic pulmonary fibrosis (IPF) is a deadly disease characterized by excessive collagen in the extracellular matrix (ECM) of the lungs. Collagen is the primary protein component of the ECM. However, the exact mechanisms underlying the formation and deposition of collagen in the ECM under normal and pathological conditions remain unclear. Previous studies showed that lysyl hydroxylase (LH) plays a crucial role in the formation of collagen. Minoxidil is an FDA-approved anti-hypertensive agent that inhibits LH that reduces fibrosis. In this study, we investigated the functional roles of LHs (LH1, LH2, and LH3) in pulmonary fibrosis and the anti-fibrotic effects of minoxidil.

          Material/Methods

          Patient serum samples were examined for their expression of procollagen-lysine, 2-oxoglutarate 5-dioxygenases (PLOD) 1–3, the genes encoding LH 1–3. Mice with bleomycin (BLM 2.5 mg/kg)-induced pulmonary fibrosis were administered a minoxidil solution (30 mg/kg) by oral gavage.

          Results

          The PLOD mRNA levels were significantly higher in the IPF patients than in the healthy control subjects. Minoxidil suppressed the BLM-induced pulmonary fibrosis in vivo. These effects were associated with blocking TGF-β 1/Smad3 signal transduction and attenuating the expression and activity of LHs, resulting in decreased collagen formation, thus reducing the pulmonary fibrosis. The anti-fibrotic effects of minoxidil may be mediated through competitive inhibition of LHs activity, resulting in decreased pyridine cross-link formation and collagen production and deposition.

          Conclusions

          The results of this study suggest that LH represents a target to prevent or treat pulmonary fibrosis, and minoxidil may provide an effective agent to inhibit LHs.

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          Most cited references15

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          Increased formation of pyridinoline cross-links due to higher telopeptide lysyl hydroxylase levels is a general fibrotic phenomenon.

          Fibrosis is characterized by an excessive accumulation of collagen which contains increased levels of pyridinoline cross-links. The occurrence of pyridinolines in the matrix is an important criterion in assessing the irreversibility of fibrosis, which suggests that collagen containing pyridinoline cross-links significantly contributes to the unwanted collagen accumulation. Pyridinoline cross-links are derived from hydroxylated lysine residues located within the collagen telopeptides (hydroxyallysine pathway). Here, we have investigated whether the increase in hydroxyallysine-derived cross-links in fibrotic conditions can be ascribed to an increased expression of one of the lysyl hydroxylases (LH1, LH2 with its splice variants LH2a and LH2b, or LH3) and/or to an increased expression of lysyl oxidase (LOX). In fibroblast cultures of hypertrophic scars, keloid and palmar fascia of Dupuytren's patients, as well as in activated hepatic stellate cells, increased levels of LH2b mRNA expression were observed. Only minor amounts of LH2a were present. In addition, no consistent increase in the mRNA expression levels of LH1, LH3 and LOX could be detected, suggesting that LH2b is responsible for the overhydroxylation of the collagen telopeptides and the concomitant formation of pyridinolines as found in the collagen matrix deposited in long-term cultures by the same fibrotic cells. This is consistent with our previous observation that LH2b is a telopeptide lysyl hydroxylase. We conclude that the increased expression of LH2b, leading to the increased formation of pyridinoline cross-links, is present in a wide variety of fibrotic disorders and thus represents a general fibrotic phenomenon.
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            The type of collagen cross-link determines the reversibility of experimental skin fibrosis.

            Fibrotic processes in humans are characterised by an excessive accumulation of collagen containing increased levels of hydroxyallysine-derived cross-links. The occurrence of these cross-links appears to be an important criterion in assessing the irreversibility of fibrosis. We hypothesise that increased hydroxyallysine cross-linking results in a collagenous matrix that is less susceptible to proteolytic degradation and therefore the collagen deposition is no longer reversible. In this report, we show that collagen matrices with increased hydroxyallysine cross-link levels were less susceptible to matrix metalloproteinase 1 degradation than are collagen matrices containing low hydroxyallysine levels. These data indicate that the type of collagen cross-link influences collagen catabolism. In vivo evidence for the importance of the cross-linking type in determining the reversibility of the fibrotic process was found using the bleomycin-induced skin fibrosis mouse model. The analysis of the accumulated collagen in the fibrotic skin of bleomycin-treated mice did not reveal an increase in hydroxyallysine cross-link levels. In concurrence with our hypothesis, the collagen accumulation resolved in time when the mice were no longer receiving bleomycin treatment, showing the reversibility of the fibrosis. In conclusion, our data indicate that the type of collagen cross-linking is an important factor in determining whether the outcome of the fibrotic process is reversible or not.
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              Transforming growth factors-beta 1, -beta 2, and -beta 3 stimulate fibroblast procollagen production in vitro but are differentially expressed during bleomycin-induced lung fibrosis.

              Transforming growth factor (TGF)-beta 1 may potentiate wound healing and fibrosis by stimulating fibroblast collagen deposition. TGF-beta 1 is implicated in the pathogenesis of pulmonary fibrosis, but the role of TGF-beta 2 and TGF-beta 3 remains unclear. We examined their effects on lung fibroblast procollagen metabolism in vitro and localized their gene expression during bleomycin-induced lung fibrosis using in situ hybridization with digoxigenin-labeled riboprobes. All three isoforms stimulated fibroblast procollagen production. TGF-beta 3 was the most potent and also reduced procollagen degradation. In normal mouse lung, TGF-beta 1 and TGF-beta 3 mRNA transcripts were abundant in bronchiolar epithelium. After bleomycin, TGF-beta 1 gene expression was maximally enhanced at 10 days, with the signal being predominant in macrophages. Signal was also enhanced in mesenchymal, pulmonary endothelial, and mesothelial cells. After 35 days, the pattern of TGF-beta 1 gene expression returned to that of control lung. TGF-beta 3 gene expression remained unchanged throughout compared with controls. TGF-beta 2 mRNA was not detected with the antisense probe, but signal obtained with the sense probe suggests the presence of a naturally occurring antisense. This study demonstrates that TGF-beta 1, -beta 2, and -beta 3 all exert profibrotic effects in vitro. However, TGF-beta isoform gene expression is differentially controlled during experimental pulmonary fibrosis with TGF-beta 1 the predominant isoform expressed during pathogenesis.
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                Author and article information

                Journal
                Med Sci Monit
                Med. Sci. Monit
                Medical Science Monitor
                Medical Science Monitor : International Medical Journal of Experimental and Clinical Research
                International Scientific Literature, Inc.
                1234-1010
                1643-3750
                2018
                27 November 2018
                : 24
                : 8592-8601
                Affiliations
                [1 ]Department of Pathophysiology, Guizhou Medical University, Guiyang, Guizhou, P.R. China
                [2 ]Department of Respiratory and Critical Medicine, Guizhou Provincial People’s Hospital, Guiyang, Guizhou, P.R. China
                [3 ]Department of Pathophysiology, Guangdong Medical University, Dongguan, Guangdong, P.R. China
                [4 ]Department of Psychological Medicine, The Second People’s Hospital of Guizhou Province, Guiyang, Guizhou, P.R. China
                Author notes
                Corresponding Authors: Xiangyan Zhang, e-mail: zxy35762@ 123456126.com , Weijia Liu, e-mail: weijia902@ 123456126.com , Bing Guo, e-mail: guobingbs@ 123456126.com
                [A]

                Study Design

                [B]

                Data Collection

                [C]

                Statistical Analysis

                [D]

                Data Interpretation

                [E]

                Manuscript Preparation

                [F]

                Literature Search

                [G]

                Funds Collection

                [*]

                Contributed equally to the work

                Article
                910761
                10.12659/MSM.910761
                6278642
                30481795
                a2be8594-8cae-42b1-a3d6-18f80f65ae1d
                © Med Sci Monit, 2018

                This work is licensed under Creative Common Attribution-NonCommercial-NoDerivatives 4.0 International ( CC BY-NC-ND 4.0)

                History
                : 23 April 2018
                : 20 June 2018
                Categories
                Clinical Research

                idiopathic pulmonary fibrosis,minoxidil,procollagen-lysine, 2-oxoglutarate 5-dioxygenase,smad3 protein,transforming growth factor beta1

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