The effect of patulin on adrenergic receptor signalling and DNA methylation in C57BL/6 mouse livers.

Abstract

Background: Secondary metabolic products of fungi and mould are called mycotoxins, and they are usually hazardous to organisms. Patulin (PAT) is a mycotoxin most prevalent in apples and their products, such as juice and cider. PAT may threaten animal and human health by causing chronic effects including immunotoxicity, genotoxicity, teratogenicity, and carcinogenicity. Research demonstrates that PAT is hepatotoxic; however, its mechanism of action is unclear. The adrenergic receptors are altered during liver injury. The adrenergic receptors utilise the mitogen- activated protein kinases/extracellular signal-regulated kinase (MAPK/ERK) and phosphatidylinositol-3-kinase/protein kinase B (PI3K/AKT) pathways. It is unclear if ARs are modulated by DNA methylation. DNA methylation is crucial for cell differentiation. Hence its dysregulation can lead to diseases such as cancer. Aim: To determine the effect of PAT on global DNA methylation and adrenergic receptor signalling in C57BL/6 mouse livers. Methods: In the livers of four C57BL/6 mice fed PAT (2.5 mg/kg BW) for 10 days: qPCR determined the mRNA expression of alpha and beta-adrenergic receptors, as well as MAPK, MAPK14, ERK1/2, PI3K and AKT, DNMT1, DNMT3A, DNMT3B and MBD2. Western blot determined the protein expression of P38, ERK1/2, PI3K, DNMT1, DNMT3A, and MBD2. The ELISA assay was used to determine global DNA methylation levels. Results: PAT significantly increased alpha-1A adrenergic receptor mRNA levels whilst decreasing alpha-2A, 2B, and all beta-adrenergic receptor expression, with beta-2 reduced significantly. PI3K’s decline was PAT-induced. PAT significantly increased AKT, MAPK, MAPK14, and ERK1 expression but significantly reduced ERK2 levels. PAT increased MBD2 and DNMT1 expression while significantly decreasing DNMT3A and 3B levels. PAT significantly increased and decreased the protein levels of P38 and ERK1/2 respectively. Additionally, a PAT- mediated increase in PI3K protein levels was observed. PAT significantly increased DNMT1 and increased DNMT3A and MBD2 expression. Significant global hypermethylation was PAT- induced. Discussion/Conclusion: PAT significantly impacted alpha-1A and beta-2 adrenergic receptors which also utilise the MAPK/ERK/PI3K/AKT pathway. The dysregulation of these signalling cascades has been associated with altered expression of the adrenergic receptors. PAT-induced global hypermethylation. PAT disrupts adrenergic receptor signalling and modifies global DNA methylation, thus resulting in liver injury.