Epigenetic Connection of the Calcitonin Gene-Related Peptide and Its Potential in Migraine

The calcitonin gene-related peptide (CGRP) is implicated in the pathogenesis of several pain-related syndromes, including migraine. Targeting CGRP and its receptor by their antagonists and antibodies was a breakthrough in migraine therapy, but the need to improve efficacy and limit the side effects of these drugs justify further studies on the regulation of CGRP in migraine. The expression of the CGRP encoding gene, CALCA, is modulated by epigenetic modifications, including the DNA methylation, histone modification, and effects of micro RNAs (miRNAs), circular RNAs, and long-coding RNAs (lncRNAs). On the other hand, CGRP can change the epigenetic profile of neuronal and glial cells. The promoter of the CALCA gene has two CpG islands that may be specifically methylated in migraine patients. DNA methylation and lncRNAs were shown to play a role in the cell-specific alternative splicing of the CALCA primary transcript. CGRP may be involved in changes in neural cytoarchitecture that are controlled by histone deacetylase 6 (HDAC6) and can be related to migraine. Inhibition of HDAC6 results in reduced cortical-spreading depression and a blockade of the CGRP receptor. CGRP levels are associated with the expression of several miRNAs in plasma, making them useful peripheral markers of migraine. The fundamental role of CGRP in inflammatory pain transmission may be epigenetically regulated. In conclusion, epigenetic connections of CGRP should be further explored for efficient and safe antimigraine therapy.

DNA methylation and fluoride exposure in school-age children: Epigenome-wide screening and population-based validation

Excessive fluoride exposure and epigenetic change can induce numerous adverse health outcomes, but the role of epigenetics underneath the harmful health effects induced by fluoride exposure is unclear. In such gap, we evaluated the associations between fluoride exposure and genome-wide DNA methylation, and identified that novel candidate genes associated with fluoride exposure. A total of 931 school-age children (8-12 years) in Tongxu County of Henan Province (China) were recruited in 2017. Urinary fluoride (UF) concentrations were measured using the national standardized ion selective electrode method. Participants were divided into a high fluoride-exposure group (HFG) and control group (CG) according to the UF concentrations. Candidate differentially methylated regions (DMRs) were screened by Infinium-Methylation EPIC BeadChip of DNA samples collected from 16 participants (eight each from each group). Differentially methylated genes (DMGs) containing DMRs associated with skeletal and neuronal development influenced by fluoride exposure were confirmed using MethylTarget™ technology from 100 participants (fifty each from each group). DMGs were verified by quantitative methylation specific PCR from 815 participants. Serum levels of hormones were measured by auto biochemical analyzer. The mediation analysis of methylation in the effect of fluoride exposure on hormone levels was also performed. A total of 237 differentially methylated sites (DMSs) and 212 DMRs were found in different fluoride-exposure groups in the epigenome-wide phase. Methylation of the target sequences of neuronatin (NNAT), calcitonin-related polypeptide alpha (CALCA) and methylenetetrahydrofolate dehydrogenase 1 showed significant difference between the HFG and CG. Each 0.06% (95% CI: -0.11%, -0.01%) decreased in NNAT methylation status correlated with each increase of 1.0 mg/L in UF concentration in 815 school-age children using QMSP. Also, each 1.88% (95% CI: 0.04%, 3.72%) increase in CALCA methylation status correlated with each increase of 1.0 mg/L in UF concentration. The mediating effect of NNAT methylation was found in alterations of ACTH levels influenced by fluoride exposure, with a β value of 11.7% (95% CI: 3.4%, 33.4%). In conclusion, long-term fluoride exposure affected the methylation pattern of genomic DNA. NNAT and CALCA as DMGs might be susceptible to fluoride exposure in school-age children.

Preeclampsia/Eclampsia candidate genes show altered methylation in maternal leukocytes of preeclamptic women at the time of delivery

OBJECTIVE

To analyze methylation profiles of known preeclampsia/eclampsia (PE) candidate genes in normal (NL) and preeclamptic (PE) women at delivery.

METHODS

A matched case-control study comparing methylation in 79 CpG sites/33 genes from an independent gene set in maternal leukocyte DNA in PE and NL (n = 14 each) on an Illumina BeadChip platform. Replication performed on second cohort (PE = 12; NL = 32).

RESULTS

PE demonstrates differential methylation in POMC, AGT, CALCA, and DDAH1 compared with NL.

CONCLUSION

Differential methylation in four genes associated with PE may represent a potential biomarker or an epigenetic pathophysiologic mechanism altering gene transcription.

DNA methylation pattern of CALCA in preterm neonates with bacterial sepsis as a putative epigenetic biomarker

Diagnosis of bacterial sepsis in preterm neonates can be difficult when using serum markers that rely on physiological changes because these changes may not necessarily be the result of bacterial infections alone. This retrospective investigation explores the potential use of the DNA methylation pattern of CpG sites in the promoter region of the calcitonin-related polypeptide α (CALCA) gene as an epigenetic biomarker for bacterial sepsis in preterm newborns. Four novel changes in the DNA methylation of eight CpG sites were detected in this gene and are present only in neonates with bacterial sepsis: (1) partial methylation at -769 CpG in gram-negative or gram-positive early onset sepsis (EOS) and late onset sepsis (LOS) episodes; (2) demethylation of 8 CpGs in gram-negative EOS followed by LOS (ELS) and in gram-negative EOS; (3) demethylation of 7 CpGs in gram-positive ELS and gram-positive EOS; (4) -771 C:G>T:A; 5' de novo -778 CpG mutation on both alleles in EOS. These changes were not detected in birth weight and gestational age matched controls or in newborns with isolated infections. Our results indicate that the DNA methylation pattern of the promoter region of the CALCA gene varies in different types of bacterial preterm sepsis, thus suggesting a potential use as an epigenetic biomarker. A prospective confirmation of these results is essential.