ABSTRACT: Exposure to immune stress or lipopolysaccharide (LPS) during critical developmental stages, particularly puberty, may result in gut microbiome dysbiosis and disturb epigenetic regulation in mammary glands. This disruption can affect gene expression and potentially increase breast cancer susceptibility later in life. While the adverse effects of LPS on intestinal and brain function are documented, its impact on mammary glands is not well understood. An immunocompetent murine model (BALB/c mice) was administered an acute dosage of LPS during the pubertal stage. The study aimed to comprehensively evaluate the enduring effects of LPS exposure, as well as LPS exposure in combination with AHCC (Lentinula Edodes Cultured Extract), on various parameters, including DNA methylation patterns, cytokine profiles, and microRNA expression within the mammary gland during adulthood, at the age of 9 weeks. Analysis was carried out using DNA methylation sequencing, multiplex immunoassays, quantitative PCR, and image processing.Our findings revealed significant and enduring dysregulation in DNA methylation patterns, cytokine levels, and microRNA expression in the mammary glands exposed to LPS during puberty. These dysregulations significantly impacted critical signaling pathways related to mammary gland growth and potential breast cancer development. Notably, we observed hypermethylation of the transcriptional start sites (TSS), promoters, and 5' UTRs of critical genes, including Vav3, Pdgfa, Pdgfc, Jag2, Hras, Ksr1, Il2rb, Il17b, and Il17rb in the LPS group, whereas hypomethylation was evident in the prebiotic+LPS group. The multiplex immunoassays and quantitative PCR confirmed these findings. LPS exposure during puberty causes long-lasting epigenetic and inflammatory alterations in the mammary glands, which could influence breast cancer risk. The use of AHCC as a mitigating factor suggests potential for dietary interventions to prevent or reduce these effects.
