H4K5 histone acetylation of BRG1 is associated with heroin administration rather than addiction

Abstract

Diacetylmorphine hydrochloride (heroin) addiction is a chronic relapsing brain disorder that is a heavy public health burden worldwide. Brm/SWI2-related gene-1 (BRG1) is a tumor suppressor gene that can influence embryogenesis and the development of the cerebellum. The current study aimed to investigate the effect of histone H4 lysine 5 (H4K5) modifications on the BRG1 gene in brain tissue of the ventral tegmental area (VTA) of heroin-addicted rats. A total of 21 male Sprague Dawley rats were raised in a standard manner and underwent heroin self-administration training. Rats were randomly divided into three equal groups: Group A, self-administered delivery of heroin; group B, yoked delivery of heroin; and group C, yoked delivery of saline. The VTA was harvested and subjected to chromatin immunoprecipitation (ChIP) analysis. Gene expression was evaluated by quantitative polymerase chain reaction. We calculated the recovery rate, which indicated the percentage of the total input BRG1 recovered by ChIP. Our results showed that BRG1 was less associated with H4K5 histone modification in the group of rats that underwent heroin self-administration than in the other two groups (A vs. B, P=0.031; A vs. C, P=0.067). The recovery fold changes of the self-administration group and the passive-administration group were significantly different from those of the group with yoked saline (A vs. C, P=0.013; B vs. C, P=0.009; A vs. B, P=0.731). The results of the current study demonstrated that H4K5 histone acetylation of BRG1 in the VTA may be associated with heroin administration, but not addiction.

Keywords: chromatin immunoprecipitation; heroin addiction; histone acetylation; ventral tegmental area.

Figure 1.

DNA fragmentation and quantitative polymerase chain reaction amplification. (A) DNA fragment size, as determined by electrophoresis after sonication. (B) Amplification curves of the samples with different antibodies. A, self-administered delivery of heroin; B, yoked delivery of heroin; C, yoked delivery of saline.

Figure 2.

(A) Recovery rate of H4K5 acetylation-associated DNA input and (B) fold enrichment over IgG of H4K5 acetylation-associated DNA. Recovery rate was calculated as recovery rate % (ChIP/total input)=2^[(Ct (x% input)-log (x%)/log2)-Ct (ChIP)] × 100%. Fold enrichment over IgG was calculated by the recovery of the target gene/GAPDH. A, self-administered delivery of heroin; B, yoked delivery of heroin; C, yoked delivery of saline. H4K5, histone H4 lysine 5; ChIP, chromatin immunoprecipitation.