OBJECTIVETo investigate the mechanism of high transcription of the glial cell-line derived neurotrophic factor (gdnf) gene induced by hyperacetylation of histone H3 lysine 9 (H3K9) at its promoter region II in rat C6 glioma cells.

METHODSThe acetylation level of H3K9 at Egr-1 binding site in gdnf gene promoter region II and the binding capacity of Egr-1 to its binding site in gdnf promoter were examined by ChIP-PCR in C6 astroglioma cells and normal rat astrocytes, and its changes were investigated in C6 astroglioma cells after treatment with histone acetyltransferase inhibitor curcumin or deacetylase inhibitor trichostatin A.

RESULTSCompared normal astrocytes, C6 astroglioma cells showed significantly increased acetylation level of H3K9 at Egr-1 binding site in gdnf gene promoter region II and Egr-1 binding capacity (P<0.01). Curcumin treatment significantly reduced H3K9 acetylation level at Egr-1 binding site and decreased both the binding of Egr-1 to promoter region II and gdnf mRNA levels in C6 astroglioma cells (P<0.05). Conversely, increased H3K9 acetylation at the Egr-1 binding site induced by trichostatin A significantly increased the binding of Egr-1 to promoter region II and gdnf mRNA expression levels (P<0.05).

CONCLUSIONH3K9 hyperacetylation induces increased Egr-1 binding to gdnf gene promoter II, which might be the reason for the high transcription level of gdnf gene in rat C6 glioma cells.

Acetylation ; Animals ; Astrocytes ; metabolism ; Binding Sites ; Cell Line, Tumor ; Early Growth Response Protein 1 ; metabolism ; Glial Cell Line-Derived Neurotrophic Factor ; genetics ; Glioma ; metabolism ; Histones ; chemistry ; Promoter Regions, Genetic ; Protein Processing, Post-Translational ; RNA, Messenger ; Rats ; Transcription, Genetic

Objective:To evaluate the inhibitory effect of a retinoid derivative ECPIRM on proliferation of a cutaneous T-cell lymphoma (CTCL) cell line HH, and to explore its potential mechanisms.Methods:Cultured HH cells were treated with ECPIRM at different concentrations of 0 (control group) , 5, 10 and 20 μmol/L separately for 72 hours, cell counting kit-8 (CCK8) assay was performed to evaluate the effect of ECPIRM on the proliferative activity of HH cells, and flow cytometry to investigate the effect of ECPIRM on apoptosis of HH cells. Some HH cells were treated with 10 μmol/L ECPIRM for 72 hours, transcriptome sequencing was performed to investigate gene expression changes triggered by ECPIRM in HH cells, and Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis and gene ontology (GO) enrichment analysis were then performed to analyze differentially expressed genes in HH cells induced by ECPIRM. Reverse transcription-qPCR was subsequently conducted to verify changes in key gene expression in related pathways. Intergroup differences were analyzed by using one-way analysis of variance, and least significant difference (LSD) - t test was used for multiple comparisons. Results:CCK8 assay showed that the 50% inhibitory concentration (IC50) of ECPIRM on HH cells was 4.91 ± 2.48 μmol/L, the viability of HH cells significantly differed among the control group, and 5-, 10-and 20-μmol/L ECPIRM groups (100.00% ± 2.87%, 49.58% ± 4.53%, 48.36% ± 2.88%, 31.44% ± 2.46%, respectively, F=162.86, P < 0.001) , and was significantly lower in the 5-, 10-and 20-μmol/L ECPIRM groups than in the control group ( t=15.36, 15.73, 20.89, respectively, all P < 0.001) . Flow cytometry showed that there was a significant difference in the apoptosis rate among the 4 groups (11.51% ± 1.84%, 23.83% ± 5.72%, 36.19% ± 8.33%, 49.75% ± 4.10%, respectively, F=17.62, P < 0.001) , and the 10-and 20-μmol/L groups showed significantly increased apoptosis rates compared with the control group ( t=4.46, 6.92 respectively, both P < 0.01) . Transcriptomics analysis revealed that the inhibitory effect of ECPIRM on the cellular proliferative activity may be related to the metabolic regulation of steroids. As reverse transcription-qPCR revealed, the 10-μmol/L ECPIRM group showed significantly decreased mRNA expression of L-amino acid oxidase (IL4I1) , acetyl-coenzyme A acetyltransferase 2 (ACAT2) , 3-hydroxy-3-methylglutaryl-coenzyme A synthase 1 (HMGCS1) , mevalonate diphosphate decarboxylase (MVD) , 3-β-hydroxysteroid-8,7-isomerase (EBP) , very low-density lipoprotein receptor (VLDLR) , 3-hydroxy 3-methylglutaryl-CoA reductase (HMGCR) compared with the control group (all P < 0.05) . Conclusion:The retinoid derivative ECPIRM exerted marked anti-proliferative and apoptosis-inducing effects on HH cells, which may be related to the decreased expression of key genes involved in steroid metabolism.