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Repeated vapor ethanol exposure induces transient histone modifications in the brain that are modified by genotype and brain region.

Finegersh A, Ferguson C, Maxwell S, Mazariegos D, Farrell D, Homanics GE - Front Mol Neurosci (2015)

Bottom Line: In CCx, CIE had a significant effect on levels of H3K18ac; there was also a significant effect of the α1SHLA mutation on levels of H3K27me3, H3K14ac, and H3K18ac as well as a trend for H3S10pK14ac.A genetic mutation that altered sensitivity to EtOH was associated with altered induction of histone modifications during CIE.These results have implications for studying EtOH-induced histone modifications and EtOH sensitivity.

View Article: PubMed Central - PubMed

Affiliation: Departments of Anesthesiology, Pharmacology and Chemical Biology, University of Pittsburgh Pittsburgh, PA, USA.

ABSTRACT

Background: Emerging research implicates ethanol (EtOH)-induced epigenetic modifications in regulating gene expression and EtOH consumption. However, consensus on specific epigenetic modifications induced by EtOH has not yet emerged, making it challenging to identify mechanisms and develop targeted treatments. We hypothesized that chronic intermittent EtOH (CIE) induces persistent changes in histone modifications across the cerebral cortex (CCx), nucleus accumbens (NAc), and prefrontal cortex (PFC), and that these histone modifications are altered in a knock-in mouse strain with altered sensitivity to EtOH.

Methods: C57BL/6J (B6) mice and α1SHLA knockin mice on a B6 background were exposed to 16 h of vapor EtOH or room air followed by 8 h of room air for 4 consecutive days and sacrificed at multiple time points up to 72 h following exposure. Histone modifications were assessed using Western blot and dot blot. RT-qPCR was used to study expression of chromatin modifying enzymes in NAc and PFC.

Results: In NAc, CIE significantly increased acetylation of histone subunit H3 at lysine 9 (H3K9ac) but not lysine 14 (H3K14ac) or lysine 27 (H3K27ac). In PFC, CIE significantly increased H3K9ac but not H3K14 or H3K27ac. There were no significant changes at 8 or 72 h after EtOH exposure in either NAc or PFC. CIE was also associated with increased expression of Kat2b, Kat5, and Tet1 in NAc but not PFC. In CCx, CIE had a significant effect on levels of H3K18ac; there was also a significant effect of the α1SHLA mutation on levels of H3K27me3, H3K14ac, and H3K18ac as well as a trend for H3S10pK14ac.

Conclusions: The EtOH-induced histone modifications observed were transient and varied significantly between brain regions. A genetic mutation that altered sensitivity to EtOH was associated with altered induction of histone modifications during CIE. These results have implications for studying EtOH-induced histone modifications and EtOH sensitivity.

No MeSH data available.


Related in: MedlinePlus

Chronic intermittent EtOH alters expression of select chromatin modifying enzymes in NAc but not PFC. Gene expression of a diverse set of chromatin modifying enzyme expression was assessed using RT-qPCR. (A) There was no significant effect of EtOH on expression of enzymes in the mPFC. (B) There was a significant effect of chronic EtOH exposure on gene expression (p < 0.05) and post-hoc analysis revealed significantly increased expression of Kat5 and Tet1 as well as a trend for increased expression of Kat2b. **p < 0.01, *p < 0.05, #p = 0.08, n = 4–5/group, data presented as mean ± SEM.
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Figure 4: Chronic intermittent EtOH alters expression of select chromatin modifying enzymes in NAc but not PFC. Gene expression of a diverse set of chromatin modifying enzyme expression was assessed using RT-qPCR. (A) There was no significant effect of EtOH on expression of enzymes in the mPFC. (B) There was a significant effect of chronic EtOH exposure on gene expression (p < 0.05) and post-hoc analysis revealed significantly increased expression of Kat5 and Tet1 as well as a trend for increased expression of Kat2b. **p < 0.01, *p < 0.05, #p = 0.08, n = 4–5/group, data presented as mean ± SEM.

Mentions: Chromatin modifications are carried out by a diverse group of enzymes that are rapidly induced by environmental stimuli (Smith and Shilatifard, 2010). We performed RT-qPCR in the chronic EtOH group to assess expression of chromatin modifying enzymes that may be involved in mediating the epigenetic effects of EtOH. These included the histone deacetylases (HDAC) Hdac2 and Hdac11 previously shown to be down-regulated by acute EtOH (Finegersh and Homanics, 2014), the histone acetyltransferases Kat2b and Kat5 that are associated with the cAMP-response element binding protein (CREB), the histone lysine methyltransferase Ehmt2, and a component of an active DNA demethylation pathway Tet1. In PFC, there was no significant effect of chronic EtOH exposure on expression of these enzymes (Figure 4A). In NAc, there was a significant effect of chronic EtOH exposure on gene expression [F(1, 7) = 11.66, p < 0.05]; post-hoc analysis revealed significantly increased expression of Kat5 (p < 0.05) and Tet1 (p < 0.01) and a trend for increased expression of Kat2b (p = 0.08) (Figure 4B).


Repeated vapor ethanol exposure induces transient histone modifications in the brain that are modified by genotype and brain region.

Finegersh A, Ferguson C, Maxwell S, Mazariegos D, Farrell D, Homanics GE - Front Mol Neurosci (2015)

Chronic intermittent EtOH alters expression of select chromatin modifying enzymes in NAc but not PFC. Gene expression of a diverse set of chromatin modifying enzyme expression was assessed using RT-qPCR. (A) There was no significant effect of EtOH on expression of enzymes in the mPFC. (B) There was a significant effect of chronic EtOH exposure on gene expression (p < 0.05) and post-hoc analysis revealed significantly increased expression of Kat5 and Tet1 as well as a trend for increased expression of Kat2b. **p < 0.01, *p < 0.05, #p = 0.08, n = 4–5/group, data presented as mean ± SEM.
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Figure 4: Chronic intermittent EtOH alters expression of select chromatin modifying enzymes in NAc but not PFC. Gene expression of a diverse set of chromatin modifying enzyme expression was assessed using RT-qPCR. (A) There was no significant effect of EtOH on expression of enzymes in the mPFC. (B) There was a significant effect of chronic EtOH exposure on gene expression (p < 0.05) and post-hoc analysis revealed significantly increased expression of Kat5 and Tet1 as well as a trend for increased expression of Kat2b. **p < 0.01, *p < 0.05, #p = 0.08, n = 4–5/group, data presented as mean ± SEM.
Mentions: Chromatin modifications are carried out by a diverse group of enzymes that are rapidly induced by environmental stimuli (Smith and Shilatifard, 2010). We performed RT-qPCR in the chronic EtOH group to assess expression of chromatin modifying enzymes that may be involved in mediating the epigenetic effects of EtOH. These included the histone deacetylases (HDAC) Hdac2 and Hdac11 previously shown to be down-regulated by acute EtOH (Finegersh and Homanics, 2014), the histone acetyltransferases Kat2b and Kat5 that are associated with the cAMP-response element binding protein (CREB), the histone lysine methyltransferase Ehmt2, and a component of an active DNA demethylation pathway Tet1. In PFC, there was no significant effect of chronic EtOH exposure on expression of these enzymes (Figure 4A). In NAc, there was a significant effect of chronic EtOH exposure on gene expression [F(1, 7) = 11.66, p < 0.05]; post-hoc analysis revealed significantly increased expression of Kat5 (p < 0.05) and Tet1 (p < 0.01) and a trend for increased expression of Kat2b (p = 0.08) (Figure 4B).

Bottom Line: In CCx, CIE had a significant effect on levels of H3K18ac; there was also a significant effect of the α1SHLA mutation on levels of H3K27me3, H3K14ac, and H3K18ac as well as a trend for H3S10pK14ac.A genetic mutation that altered sensitivity to EtOH was associated with altered induction of histone modifications during CIE.These results have implications for studying EtOH-induced histone modifications and EtOH sensitivity.

View Article: PubMed Central - PubMed

Affiliation: Departments of Anesthesiology, Pharmacology and Chemical Biology, University of Pittsburgh Pittsburgh, PA, USA.

ABSTRACT

Background: Emerging research implicates ethanol (EtOH)-induced epigenetic modifications in regulating gene expression and EtOH consumption. However, consensus on specific epigenetic modifications induced by EtOH has not yet emerged, making it challenging to identify mechanisms and develop targeted treatments. We hypothesized that chronic intermittent EtOH (CIE) induces persistent changes in histone modifications across the cerebral cortex (CCx), nucleus accumbens (NAc), and prefrontal cortex (PFC), and that these histone modifications are altered in a knock-in mouse strain with altered sensitivity to EtOH.

Methods: C57BL/6J (B6) mice and α1SHLA knockin mice on a B6 background were exposed to 16 h of vapor EtOH or room air followed by 8 h of room air for 4 consecutive days and sacrificed at multiple time points up to 72 h following exposure. Histone modifications were assessed using Western blot and dot blot. RT-qPCR was used to study expression of chromatin modifying enzymes in NAc and PFC.

Results: In NAc, CIE significantly increased acetylation of histone subunit H3 at lysine 9 (H3K9ac) but not lysine 14 (H3K14ac) or lysine 27 (H3K27ac). In PFC, CIE significantly increased H3K9ac but not H3K14 or H3K27ac. There were no significant changes at 8 or 72 h after EtOH exposure in either NAc or PFC. CIE was also associated with increased expression of Kat2b, Kat5, and Tet1 in NAc but not PFC. In CCx, CIE had a significant effect on levels of H3K18ac; there was also a significant effect of the α1SHLA mutation on levels of H3K27me3, H3K14ac, and H3K18ac as well as a trend for H3S10pK14ac.

Conclusions: The EtOH-induced histone modifications observed were transient and varied significantly between brain regions. A genetic mutation that altered sensitivity to EtOH was associated with altered induction of histone modifications during CIE. These results have implications for studying EtOH-induced histone modifications and EtOH sensitivity.

No MeSH data available.


Related in: MedlinePlus