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Homocysteine Induces Collagen I Expression by Downregulating Histone Methyltransferase G9a.

Lei W, Long Y, Li S, Liu Z, Zhu F, Hou FF, Nie J - PLoS ONE (2015)

Bottom Line: Conversely, overexpressing G9a inhibited the promoter activity of COL1A1.Hcy treatment decreased the binding of G9a on NRSE, which in turn decreased the level of H3K9me2 on the promoter of COL1A1, led to upregulation of COL1A1.Taken together, these results provide a novel mechanism on explaining how HHcy promotes ECM production.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Organ Failure Research, National Clinical Research Center of Kidney Disease, Division of Nephrology, Nanfang Hospital, Southern Medical University, Guangzhou, P.R. China.

ABSTRACT
Hyperhomocysteinemia (HHcy) leads to several clinical manifestations including hepatic fibrosis. Excess deposition of extracellular matrix (ECM) components including collagen is the eponymous lesion of liver fibrosis. In this study, we demonstrated that elevated concentration of Hcy induced the expression of collagen type I in cultured human liver cells as well as in liver tissue of HHcy mice. Meanwhile, Hcy inhibited the expression of histone methyltransferase G9a. Mechanistically, silencing endogenous G9a by siRNA enhanced the promoter activity of COL1A1 in LO2 cells. Conversely, overexpressing G9a inhibited the promoter activity of COL1A1. CHIP assay demonstrated that G9a binds to the neuron-restrictive silencer element (NRSE) on the promoter of COL1A1. Hcy treatment decreased the binding of G9a on NRSE, which in turn decreased the level of H3K9me2 on the promoter of COL1A1, led to upregulation of COL1A1. Taken together, these results provide a novel mechanism on explaining how HHcy promotes ECM production.

No MeSH data available.


Related in: MedlinePlus

Hcy decreased the level of H3K9me2 on the COL1A1 promoter.(A) (A-B) LO2 cells were treated with 100μM of Hcy for indicated time period (A), or indicated concentration of Hcy for 48 h (B), and then harvested for ChIP assay by using anti-H3K9me2 antibody. The changes of H3K9me2 on the COL1A1 promoter were examined by q-ChIP PCR. Data are means±SD of three independent experiments. *p<0.05 versus untreated cells. (C) Liver tissues of wild type mice and HHcy mice were collected for ChIP assay by using anti-H3K9me2 antibody. The changes in H3K9me2 on the Col1α1 promoter were examined by q-ChIP PCR. Data are expressed as mean±SD, n = 6. *p<0.05 versus mice fed with regular rodent chow.
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pone.0130421.g005: Hcy decreased the level of H3K9me2 on the COL1A1 promoter.(A) (A-B) LO2 cells were treated with 100μM of Hcy for indicated time period (A), or indicated concentration of Hcy for 48 h (B), and then harvested for ChIP assay by using anti-H3K9me2 antibody. The changes of H3K9me2 on the COL1A1 promoter were examined by q-ChIP PCR. Data are means±SD of three independent experiments. *p<0.05 versus untreated cells. (C) Liver tissues of wild type mice and HHcy mice were collected for ChIP assay by using anti-H3K9me2 antibody. The changes in H3K9me2 on the Col1α1 promoter were examined by q-ChIP PCR. Data are expressed as mean±SD, n = 6. *p<0.05 versus mice fed with regular rodent chow.

Mentions: Since G9a is the primary enzyme for dimethylation of histone H3 lysine 9 (H3K9me2), we next examined whether histone H3 lysine methylation levels were also altered by Hcy. ChIP assay using H3K9me2-specific antibodies revealed that Hcy decreased the level of H3K9me2 on COL1A1 promoter in a time- and dose-dependent manner (Fig 5A and 5B). Similarly, the level of H3K9me2 on Col1α1 promoter was also dramatically decreased in the liver of HHcy mice (Fig 5C). These results suggest that upregulation of Col I might be caused, at least partially, by a loss of repressive epigenetic histone modification on its promoter.


Homocysteine Induces Collagen I Expression by Downregulating Histone Methyltransferase G9a.

Lei W, Long Y, Li S, Liu Z, Zhu F, Hou FF, Nie J - PLoS ONE (2015)

Hcy decreased the level of H3K9me2 on the COL1A1 promoter.(A) (A-B) LO2 cells were treated with 100μM of Hcy for indicated time period (A), or indicated concentration of Hcy for 48 h (B), and then harvested for ChIP assay by using anti-H3K9me2 antibody. The changes of H3K9me2 on the COL1A1 promoter were examined by q-ChIP PCR. Data are means±SD of three independent experiments. *p<0.05 versus untreated cells. (C) Liver tissues of wild type mice and HHcy mice were collected for ChIP assay by using anti-H3K9me2 antibody. The changes in H3K9me2 on the Col1α1 promoter were examined by q-ChIP PCR. Data are expressed as mean±SD, n = 6. *p<0.05 versus mice fed with regular rodent chow.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4508059&req=5

pone.0130421.g005: Hcy decreased the level of H3K9me2 on the COL1A1 promoter.(A) (A-B) LO2 cells were treated with 100μM of Hcy for indicated time period (A), or indicated concentration of Hcy for 48 h (B), and then harvested for ChIP assay by using anti-H3K9me2 antibody. The changes of H3K9me2 on the COL1A1 promoter were examined by q-ChIP PCR. Data are means±SD of three independent experiments. *p<0.05 versus untreated cells. (C) Liver tissues of wild type mice and HHcy mice were collected for ChIP assay by using anti-H3K9me2 antibody. The changes in H3K9me2 on the Col1α1 promoter were examined by q-ChIP PCR. Data are expressed as mean±SD, n = 6. *p<0.05 versus mice fed with regular rodent chow.
Mentions: Since G9a is the primary enzyme for dimethylation of histone H3 lysine 9 (H3K9me2), we next examined whether histone H3 lysine methylation levels were also altered by Hcy. ChIP assay using H3K9me2-specific antibodies revealed that Hcy decreased the level of H3K9me2 on COL1A1 promoter in a time- and dose-dependent manner (Fig 5A and 5B). Similarly, the level of H3K9me2 on Col1α1 promoter was also dramatically decreased in the liver of HHcy mice (Fig 5C). These results suggest that upregulation of Col I might be caused, at least partially, by a loss of repressive epigenetic histone modification on its promoter.

Bottom Line: Conversely, overexpressing G9a inhibited the promoter activity of COL1A1.Hcy treatment decreased the binding of G9a on NRSE, which in turn decreased the level of H3K9me2 on the promoter of COL1A1, led to upregulation of COL1A1.Taken together, these results provide a novel mechanism on explaining how HHcy promotes ECM production.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Organ Failure Research, National Clinical Research Center of Kidney Disease, Division of Nephrology, Nanfang Hospital, Southern Medical University, Guangzhou, P.R. China.

ABSTRACT
Hyperhomocysteinemia (HHcy) leads to several clinical manifestations including hepatic fibrosis. Excess deposition of extracellular matrix (ECM) components including collagen is the eponymous lesion of liver fibrosis. In this study, we demonstrated that elevated concentration of Hcy induced the expression of collagen type I in cultured human liver cells as well as in liver tissue of HHcy mice. Meanwhile, Hcy inhibited the expression of histone methyltransferase G9a. Mechanistically, silencing endogenous G9a by siRNA enhanced the promoter activity of COL1A1 in LO2 cells. Conversely, overexpressing G9a inhibited the promoter activity of COL1A1. CHIP assay demonstrated that G9a binds to the neuron-restrictive silencer element (NRSE) on the promoter of COL1A1. Hcy treatment decreased the binding of G9a on NRSE, which in turn decreased the level of H3K9me2 on the promoter of COL1A1, led to upregulation of COL1A1. Taken together, these results provide a novel mechanism on explaining how HHcy promotes ECM production.

No MeSH data available.


Related in: MedlinePlus