Innate Immune Memory refers to the ability of innate immune cells to display altered responses upon secondary exposure to pathogens. This phenomenon is driven by dynamic and heritable histone protein modifications, which influence post-translational gene transcription. Currently, while the broader MAPK and PI3K/AKT pathways of α-MSH are well established, there is little existing research on the direct link between α-MSH and histone modifications. Our study aims to investigate the effects of alpha-melanocyte-stimulating hormone (α-MSH), a neuropeptide with notable anti-inflammatory properties, on Histone 3 (H3) post-translational markers and their epigenetic impact on mouse macrophages.

We conducted a comprehensive analysis of H3 modifications to identify key changes, focusing on H3K4 global methylation, H3K9 dimethylation, and H3K14 acetylation levels in response to varying concentrations of α-MSH. Methylation and acetylation of histone proteins, such as H3K4, H3K9, and H3K14, regulate the accessibility of transcriptional start sites and promoters, thereby influencing gene transcription. In immune cells, these histone modifications alter the transcription of genes associated with immune responses, particularly inflammation.

Utilizing enzyme-linked immunosorbent assays (ELISA) to quantify the H3 methylation and acetylation levels, the response of histone modifications to α-MSH treatment was measured, highlighting the potential of α-MSH as a modulator of epigenetic marks in innate immune cells. Such findings enhance our understanding of how neuropeptides like α-MSH can influence immune responses through epigenetic mechanisms, providing insights into new therapeutic strategies for controlling inflammation and enhancing immune memory.

Our results demonstrate significant effects of α-MSH on histone modifications, with notable demethylation of H3K4, increased dimethylation of H3K9, and elevated acetylation of H3K14 observed in treated macrophages. Specifically, significant changes in H3K4 global methylation and H3K14 acetylation were detected at 1 ng/mL and 10 ng/mL α-MSH, while H3K9 dimethylation was significantly affected at 30 pg/mL α-MSH. Additionally, low-dose α-MSH (30 pg/mL) induced demethylation and deacetylation of H3K4 and H3K14, respectively.

These findings suggest that α-MSH exerts anti-inflammatory effects by modulating histone methylation and acetylation patterns. Changes in H3 histone modifications decrease the expression of proinflammatory molecules and enhance the expression of anti-inflammatory molecules in macrophages. This epigenetic regulation may contribute to the innate immune memory, eliciting trained responses to subsequent exposures.

In summary, α-MSH modulates histone H3 post-translational modifications in a concentration-dependent manner, altering the epigenetic landscape of macrophages to promote anti-inflammatory responses. This research underscores the significance of histone modifications in the regulation of innate immune memory and the potential for targeting these pathways in immunotherapy.