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epigenetics

Rosenberg, T.- Volcani Center, Institute of Animal Science, Agricultural Research Organization, Rishon LeZiyyon, Israel; Department of Animal Science, the Robert H, Smith Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot, Israel. 
Ben-Nun, O. - Volcani Center, Institute of Animal Science, Agricultural Research Organization, Rishon LeZiyyon, Israel; Department of Animal Science, the Robert H, Smith Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot, Israel. 
Cramer, T. - Volcani Center, Institute of Animal Science, Agricultural Research Organization, Rishon LeZiyyon, Israel; Department of Animal Science, the Robert H, Smith Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot, Israel


 

A stressor can induce resilience in another, different stressor, a phenomenon known as cross-tolerance. To learn if cross-tolerance is governed by epigenetic regulation, we used embryonic heat conditioning (EHC) in chicks, during the development of the hypothalamus, to increase the immunization response. Indeed, EHC induced a lifelong systemic antibody response to immunization, in addition to reduced hypothalamic IL6 inflammatory expression following LPS challenge. Since the outcome of EHC was long-term cross-tolerance with the immune system, we studied possible epigenetic mechanisms. We first analysed the methylation and hydroxymethylation patterns of IL6. We found reduced hydroxymethylation on IL6 intron 1 in the EHC group, a segment enriched with CpGs and NFkB-binding sites. Luciferase assay in cell lines expressing NFkB showed that IL6 intron 1 is indeed an enhancer. ChiP in the same segment against NFkB in the hypothalamus presented reduced binding to IL6 intron 1 in the EHC group, before and during LPS challenge. In parallel, EHC chicks’ IL6 intron 1 presented increased H3K27me3, a repressive translational modification mediated by EZH2. This histone modification occurred during embryonic conditioning and persisted later in life. Moreover, we showed reduced expression of miR-26a, which inhibits EZH2 transcription, during conditioning along with increased EZH2 expression. We demonstrate that stress cross-tolerance, which was indicated by EHC-induced inflammatory resilience and displayed by attenuated inflammatory expression of IL6, is regulated by different epigenetic layers. 

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Cross-tolerance: embryonic heat conditioning induces inflammatory resilience by affecting different layers of epigenetic mechanisms regulating IL6 expression later in life
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Rosenberg, T.- Volcani Center, Institute of Animal Science, Agricultural Research Organization, Rishon LeZiyyon, Israel; Department of Animal Science, the Robert H, Smith Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot, Israel. 
Ben-Nun, O. - Volcani Center, Institute of Animal Science, Agricultural Research Organization, Rishon LeZiyyon, Israel; Department of Animal Science, the Robert H, Smith Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot, Israel. 
Cramer, T. - Volcani Center, Institute of Animal Science, Agricultural Research Organization, Rishon LeZiyyon, Israel; Department of Animal Science, the Robert H, Smith Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot, Israel


 

Cross-tolerance: embryonic heat conditioning induces inflammatory resilience by affecting different layers of epigenetic mechanisms regulating IL6 expression later in life

A stressor can induce resilience in another, different stressor, a phenomenon known as cross-tolerance. To learn if cross-tolerance is governed by epigenetic regulation, we used embryonic heat conditioning (EHC) in chicks, during the development of the hypothalamus, to increase the immunization response. Indeed, EHC induced a lifelong systemic antibody response to immunization, in addition to reduced hypothalamic IL6 inflammatory expression following LPS challenge. Since the outcome of EHC was long-term cross-tolerance with the immune system, we studied possible epigenetic mechanisms. We first analysed the methylation and hydroxymethylation patterns of IL6. We found reduced hydroxymethylation on IL6 intron 1 in the EHC group, a segment enriched with CpGs and NFkB-binding sites. Luciferase assay in cell lines expressing NFkB showed that IL6 intron 1 is indeed an enhancer. ChiP in the same segment against NFkB in the hypothalamus presented reduced binding to IL6 intron 1 in the EHC group, before and during LPS challenge. In parallel, EHC chicks’ IL6 intron 1 presented increased H3K27me3, a repressive translational modification mediated by EZH2. This histone modification occurred during embryonic conditioning and persisted later in life. Moreover, we showed reduced expression of miR-26a, which inhibits EZH2 transcription, during conditioning along with increased EZH2 expression. We demonstrate that stress cross-tolerance, which was indicated by EHC-induced inflammatory resilience and displayed by attenuated inflammatory expression of IL6, is regulated by different epigenetic layers. 

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