Rapid changes in histone deacetylases and inflammatory gene expression in expert meditators

Abstract

Background: A growing body of research shows that mindfulness meditation can alter neural, behavioral and biochemical processes. However, the mechanisms responsible for such clinically relevant effects remain elusive.

Methods: Here we explored the impact of a day of intensive practice of mindfulness meditation in experienced subjects (n=19) on the expression of circadian, chromatin modulatory and inflammatory genes in peripheral blood mononuclear cells (PBMC). In parallel, we analyzed a control group of subjects with no meditation experience who engaged in leisure activities in the same environment (n=21). PBMC from all participants were obtained before (t1) and after (t2) the intervention (t2-t1=8h) and gene expression was analyzed using custom pathway focused quantitative-real time PCR assays. Both groups were also presented with the Trier Social Stress Test (TSST).

Results: Core clock gene expression at baseline (t1) was similar between groups and their rhythmicity was not influenced in meditators by the intensive day of practice. Similarly, we found that all the epigenetic regulatory enzymes and inflammatory genes analyzed exhibited similar basal expression levels in the two groups. In contrast, after the brief intervention we detected reduced expression of histone deacetylase genes (HDAC 2, 3 and 9), alterations in global modification of histones (H4ac; H3K4me3) and decreased expression of pro-inflammatory genes (RIPK2 and COX2) in meditators compared with controls. We found that the expression of RIPK2 and HDAC2 genes was associated with a faster cortisol recovery to the TSST in both groups.

Conclusions: The regulation of HDACs and inflammatory pathways may represent some of the mechanisms underlying the therapeutic potential of mindfulness-based interventions. Our findings set the foundation for future studies to further assess meditation strategies for the treatment of chronic inflammatory conditions.

Keywords: Epigenetics; HDAC; Inflammation; Meditation; Mindfulness; Stress.

Conflict of interest statement

Conflict of interest statement

None declared.

Copyright © 2013 Elsevier Ltd. All rights reserved.

Figures

FIGURE 1. Effect of mindfulness meditation on circadian gene expression

Gene expression analysis by real-time RT-PCR from PBMC mRNA using TaqMan FAM-labeled specific probes and expressed relative to TBP (mean ± SE). A, DBP (albumin D-site binding protein). B, BMAL1 (brain and muscle ARNT -like 1). C, D, CRY1 and 2 (Cryptochrome 1 and 2). E–G, PER 1–3 (Period 1–3).

FIGURE 2. Effect of mindfulness meditation on gene expression of chromatin modulatory enzymes and histone-tail modifications

A–H, Gene expression analysis by real-time RT-PCR analyses from PBMC mRNA using TaqMan FAM-labeled specific probes and expressed relative to TBP (mean ± SE; * p<0.05; ** p<0.01; *** p<0,001). A–F, histone deacetylases HDACs 1, 2, 3, 5, 9 and sirtuin 1 (SIRT1). G–H, histone methyltransferases SET7/9and G9a.I, lysine -specific demethylase 1 (LSD1). J, DNA -methyl transferase 3a (DNMT3a). K–O, PBMC nuclear acidic lysates were probed with antibodies detecting histone-tail modifications. K, representative Western blot images. L–O, quantification of Western blots by scanning densitometry. L, global acetylation of histone H4 (H4ac). M, trimethylation of histone H3 lysine 4 (H3K4me3). N, global acetylation of histone H3 (H3ac). O, phosphorylation of serine 10 in histone H3 (H3S10ph). Histone modifications were corrected by total histone, and data were expressed as t2/t1; #, p<0.05, one tail t-test for unpaired data and p=0,064, two tail t-test; *, p<0.05, 2 tails t-test for unpaired data (mean ± SE; n=10–14/group).

FIGURE 3. Effect of mindfulness meditation on inflammatory pathways: correlation with HDAC gene expression and social stress recovery

A, receptor-interacting serine-threonine kinase 2 (RIPK2) gene expression (mean ± SE; ** p<0.01). B–D, partial correlations between RIPK2 and HDAC gene expression. P values (p) and partial correlation coefficients (ρr) are indicated. HDAC3 was normalized using inverse-transformed values. Partial correlations were controlled for group variable (n=40). E, cyclooxygenase 2 (COX2) gene expression (mean ± SE; * p< 0.05). F, PBMC cell lysates were probed with Cox2 antibody, representative Western blot images are shown. G, Quantification of Western blots by scanning densitometry. Cox2 protein was corrected by β-actin, and data were expressed as (t2-t1) (mean ± SE; n=6/group; #, p=0.05, two-tailed Mann Whitney U test). H–I HDAC2 and RIPK2 gene expression correlation with cortisol recovery after acute psychological stress. Participants completed the Trier Social Stress Test twice. T2-T1 was calculated, which reflects the post-intervention response (T1) controlling for the response at baseline, 12 weeks before (T2). Cortisol was determined in saliva samples and recovery was defined as the percentage of the baseline value that cortisol levels returned to after the peak. For HDAC2 and RIPK2, a difference score (t2-t1) was calculated, which reflects the intervention response controlling for baseline levels (t1). Pearson correlations were used to test the association between changes in cortisol recovery with changes in gene expression.