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Homocysteine Triggers Inflammatory Responses in Macrophages through Inhibiting CSE-H2S Signaling via DNA Hypermethylation of CSE Promoter.

Li JJ, Li Q, Du HP, Wang YL, You SJ, Wang F, Xu XS, Cheng J, Cao YJ, Liu CF, Hu LF - Int J Mol Sci (2015)

Bottom Line: Unfortunately, Hcy-lowering strategies were found to have limited effects in reducing cardiovascular events.DNMT inhibition or knockdown reversed the decrease of CSE transcription induced by Hcy in macrophages.In sum, our findings demonstrate that Hcy may trigger inflammation through inhibiting CSE-H2S signaling, associated with increased promoter DNA methylation and transcriptional repression of cse in macrophages.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases, the Second Affiliated Hospital of Soochow University, Soochow University, Suzhou 215004, China. dragonrabbit@163.com.

ABSTRACT
Hyperhomocysteinemia (HHcy) is an independent risk factor of atherosclerosis and other cardiovascular diseases. Unfortunately, Hcy-lowering strategies were found to have limited effects in reducing cardiovascular events. The underlying mechanisms remain unclear. Increasing evidence reveals a role of inflammation in the pathogenesis of HHcy. Homocysteine (Hcy) is a precursor of hydrogen sulfide (H2S), which is formed via the transsulfuration pathway catalyzed by cystathionine β-synthase and cystathionine γ-lyase (CSE) and serves as a novel modulator of inflammation. In the present study, we showed that methionine supplementation induced mild HHcy in mice, associated with the elevations of TNF-α and IL-1β in the plasma and reductions of plasma H2S level and CSE expression in the peritoneal macrophages. H2S-releasing compound GYY4137 attenuated the increases of TNF-α and IL-1β in the plasma of HHcy mice and Hcy-treated raw264.7 cells while CSE inhibitor PAG exacerbated it. Moreover, the in vitro study showed that Hcy inhibited CSE expression and H2S production in macrophages, accompanied by the increases of DNA methyltransferase (DNMT) expression and DNA hypermethylation in cse promoter region. DNMT inhibition or knockdown reversed the decrease of CSE transcription induced by Hcy in macrophages. In sum, our findings demonstrate that Hcy may trigger inflammation through inhibiting CSE-H2S signaling, associated with increased promoter DNA methylation and transcriptional repression of cse in macrophages.

No MeSH data available.


Related in: MedlinePlus

DNMTs inhibition reversed the repression of Hcy on CSE expression. DNMTs inhibition with its inhibitor Aza (A,B) or DNMT1 siRNA (C) almost reversed the decreases of CSE expression induced by Hcy treatment. The knockdown efficiency of DNMT1 siRNA was determined by immunoblotting analysis (D). n = 3–4. *p < 0.05, **p < 0.01, ***p < 0.001. N.S., not significant.
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ijms-16-12560-f005: DNMTs inhibition reversed the repression of Hcy on CSE expression. DNMTs inhibition with its inhibitor Aza (A,B) or DNMT1 siRNA (C) almost reversed the decreases of CSE expression induced by Hcy treatment. The knockdown efficiency of DNMT1 siRNA was determined by immunoblotting analysis (D). n = 3–4. *p < 0.05, **p < 0.01, ***p < 0.001. N.S., not significant.

Mentions: To confirm whether DNMT1 was responsible for DNA hypermethylation of cse gene in Hcy-treated macrophages, we studied the expression of CSE protein and mRNA in DNMT1-suppressed cells. As shown in Figure 5, Hcy caused about 50% reduction of CSE protein and mRNA levels, which were reversed by DNMT inhibitor 5-Aza-2′-deoxycytidine (Aza) co-treatment (Figure 5A,B). Moreover, DNMT1 knockdown with siRNAs also alleviated the decrease of cse transcription caused by Hcy treatment, compared with scrambled siRNA-transfected cells. One hundred micromoles Hcy failed to significantly reduce CSE mRNA expression in DNMT1-deficient cells (Figure 5C). The knockdown efficiency of DNMT1 siRNA reached about 50% as determined by its protein expression (Figure 5D).


Homocysteine Triggers Inflammatory Responses in Macrophages through Inhibiting CSE-H2S Signaling via DNA Hypermethylation of CSE Promoter.

Li JJ, Li Q, Du HP, Wang YL, You SJ, Wang F, Xu XS, Cheng J, Cao YJ, Liu CF, Hu LF - Int J Mol Sci (2015)

DNMTs inhibition reversed the repression of Hcy on CSE expression. DNMTs inhibition with its inhibitor Aza (A,B) or DNMT1 siRNA (C) almost reversed the decreases of CSE expression induced by Hcy treatment. The knockdown efficiency of DNMT1 siRNA was determined by immunoblotting analysis (D). n = 3–4. *p < 0.05, **p < 0.01, ***p < 0.001. N.S., not significant.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4490461&req=5

ijms-16-12560-f005: DNMTs inhibition reversed the repression of Hcy on CSE expression. DNMTs inhibition with its inhibitor Aza (A,B) or DNMT1 siRNA (C) almost reversed the decreases of CSE expression induced by Hcy treatment. The knockdown efficiency of DNMT1 siRNA was determined by immunoblotting analysis (D). n = 3–4. *p < 0.05, **p < 0.01, ***p < 0.001. N.S., not significant.
Mentions: To confirm whether DNMT1 was responsible for DNA hypermethylation of cse gene in Hcy-treated macrophages, we studied the expression of CSE protein and mRNA in DNMT1-suppressed cells. As shown in Figure 5, Hcy caused about 50% reduction of CSE protein and mRNA levels, which were reversed by DNMT inhibitor 5-Aza-2′-deoxycytidine (Aza) co-treatment (Figure 5A,B). Moreover, DNMT1 knockdown with siRNAs also alleviated the decrease of cse transcription caused by Hcy treatment, compared with scrambled siRNA-transfected cells. One hundred micromoles Hcy failed to significantly reduce CSE mRNA expression in DNMT1-deficient cells (Figure 5C). The knockdown efficiency of DNMT1 siRNA reached about 50% as determined by its protein expression (Figure 5D).

Bottom Line: Unfortunately, Hcy-lowering strategies were found to have limited effects in reducing cardiovascular events.DNMT inhibition or knockdown reversed the decrease of CSE transcription induced by Hcy in macrophages.In sum, our findings demonstrate that Hcy may trigger inflammation through inhibiting CSE-H2S signaling, associated with increased promoter DNA methylation and transcriptional repression of cse in macrophages.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases, the Second Affiliated Hospital of Soochow University, Soochow University, Suzhou 215004, China. dragonrabbit@163.com.

ABSTRACT
Hyperhomocysteinemia (HHcy) is an independent risk factor of atherosclerosis and other cardiovascular diseases. Unfortunately, Hcy-lowering strategies were found to have limited effects in reducing cardiovascular events. The underlying mechanisms remain unclear. Increasing evidence reveals a role of inflammation in the pathogenesis of HHcy. Homocysteine (Hcy) is a precursor of hydrogen sulfide (H2S), which is formed via the transsulfuration pathway catalyzed by cystathionine β-synthase and cystathionine γ-lyase (CSE) and serves as a novel modulator of inflammation. In the present study, we showed that methionine supplementation induced mild HHcy in mice, associated with the elevations of TNF-α and IL-1β in the plasma and reductions of plasma H2S level and CSE expression in the peritoneal macrophages. H2S-releasing compound GYY4137 attenuated the increases of TNF-α and IL-1β in the plasma of HHcy mice and Hcy-treated raw264.7 cells while CSE inhibitor PAG exacerbated it. Moreover, the in vitro study showed that Hcy inhibited CSE expression and H2S production in macrophages, accompanied by the increases of DNA methyltransferase (DNMT) expression and DNA hypermethylation in cse promoter region. DNMT inhibition or knockdown reversed the decrease of CSE transcription induced by Hcy in macrophages. In sum, our findings demonstrate that Hcy may trigger inflammation through inhibiting CSE-H2S signaling, associated with increased promoter DNA methylation and transcriptional repression of cse in macrophages.

No MeSH data available.


Related in: MedlinePlus