AQP5-1364A/C Polymorphism Affects AQP5 Promoter Methylation

Abstract

The quantity of aquaporin 5 protein in neutrophil granulocytes is associated with human sepsis-survival. The C-allele of the aquaporin (AQP5)-1364A/C polymorphism was shown to be associated with decreased AQP5 expression, which was shown to be relevant in this context leading towards improved outcomes in sepsis. To date, the underlying mechanism of the C-allele—leading to lower AQP5 expression—has been unknown. Knowing the detailed mechanism depicts a crucial step with a target to further interventions. Genotype-dependent regulation of AQP5 expression might be mediated by the epigenetic mechanism of promoter methylation and treatment with epigenetic-drugs could maybe provide benefit. Hence, we tested the hypothesis that AQP5 promoter methylation differs between genotypes in specific types of immune cells.: AQP5 promoter methylation was quantified in cells of septic patients and controls by methylation-specific polymerase chain reaction and quantified by a standard curve. In cell-line models, AQP5 expression was analyzed after demethylation to determine the impact of promoter methylation on AQP5 expression. C-allele of AQP5-1364 A/C promoter polymorphism is associated with a five-fold increased promoter methylation in neutrophils (p = 0.0055) and a four-fold increase in monocytes (p = 0.0005) and lymphocytes (p = 0.0184) in septic patients and healthy controls as well. In addition, a decreased AQP5 promoter methylation was accompanied by an increased AQP5 expression in HL-60 (p = 0.0102) and REH cells (p = 0.0102). The C-allele which is associated with lower gene expression in sepsis is accompanied by a higher methylation level of the AQP5 promoter. Hence, AQP5 promoter methylation could depict a key mechanism in genotype-dependent expression.

The Aquaporin 3 Polymorphism (rs17553719) Is Associated with Sepsis Survival and Correlated with IL-33 Secretion

“…Thus, the link between the AQP5-1364A/C polymorphism and sepsis survival could be due to AQP5 expression and its impact on neutrophil cell migration [28]. It was demonstrated mechanistically that the CpG methylation of the AQP5 promoter correlates strongly with the AQP5 A/C-1364 genotype, and, hence, this could represent the mechanistic explanation for the decreased AQP5 expression in C allele carriers [29].…”

Methazolamide Reduces the AQP5 mRNA Expression and Immune Cell Migration—A New Potential Drug in Sepsis Therapy?

“…However, the exact mechanisms preventing the inhibition of AQP5 expression cannot be elucidated here. It is possible that genetic or epigenetic factors may play a role here since LPS inhibits methylation at the AQP5 promotor [ 49 , 50 ] and they contribute to the differential disease severity [ 51 , 52 ].…”

Aquaporin Expression and Regulation in Clinical and Experimental Sepsis

“…Methylation of the AQP5 promoter was examined in neutrophils, monocytes, and lymphocytes from healthy individuals and septic patients. Carries of the AC genotype exhibited increased methylation in both groups [ 88 ].…”