Background & Aims

Traumatic stress exposures (TSE) affect >90% of individuals in their lifetime. While most individuals recover following TSE, a substantial subset develops chronic posttraumatic musculoskeletal pain (CPMP) (1,2). Increasing evidence indicates that dysregulation of the body’s physiological response to TSE via repeated or chronic stressors substantially increases vulnerability for CPMP. Further, existing evidence indicates that repeated stress exposures lead to epigenetic changes to DNA in genes critical to stress and pain resolution (3,4). For example, in a recently published study, we showed across four independent longitudinal studies of adult trauma survivors that DNA methylation levels at CpG sites in the promoter region of the stress-response gene POMC strongly predicts CPMP development (5). Here, we aimed to assess this relationship in a fifth trauma cohort, and to test the hypothesis that repeated stress exposures are responsible for increased POMC methylation levels.

Methods

Biological samples and data were derived from the AURORA study, a large longitudinal cohort of adult TSE survivors. Blood samples were collected from participants in the early aftermath of TSE. DNA methylation levels were processed for a subset of samples (n=707) using the Illumina MethylationEPIC array. The relationship between POMC promoter methylation levels and CPMP was assessed using repeated measures mixed models. We assessed whether acute stress vs repeated/chronic stress might influence POMC promoter methylation using the Peritraumatic Distress Inventory (PDI) and the Area Deprivation Index (ADI), respectively. We also analyzed CpG methylation levels in the POMC promoter and related POMC mRNA expression levels in vitro in a cell culture model of chronic stress (100nM cortisol for 51 days) (6).

Results

Consistent with our previously published results, we showed using AURORA cohort data that increased methylation levels at three POMC promoter CpGs within 160 nucleotides of the transcription start site, cg24425171, cg20387815 and cg13025668, predicted more severe CPMP outcomes following TSE. Further, we found that individuals with ADI scores in the highest tertile have significantly higher methylation levels at each of the three pain-associated CpGs compared to those individuals with scores in the lowest tertile (cg24425171: t(447)=3.317; p<0.001, cg20387815: t(447)=3.369, p<0.001; cg13025668: t(447)=4.083, p<0.001). No increase in methylation level was observed when comparing upper and lower tertiles of PDI scores. In cell culture, prolonged cortisol exposure resulted in an increase in methylation levels at POMC promoter CpGs, with the greatest increase in methylation observed at cg24425171, located in the binding region of the POMC-activating transcription factor NF-?B.

Conclusions

Here we validated our previous findings indicating that increased CpG methylation levels in the POMC promoter increases risk for CPMP. We also showed via both human cohort and cell culture studies that prolonged stress exposure increases methylation levels at these same CpG sites in POMC. These data suggest that exposure to chronic stress, but not necessarily acute stress (approximated by ADI and PDI, respectively), results in aberrant epigenetic patterning at the POMC promoter, which may impair physiological stress-regulatory mechanisms and increase vulnerability to CPMP development. These results are consistent with previous findings that chronic environmental stress related to living in socioeconomically disadvantaged areas is known to increase vulnerability to CPMP via dysregulation of stress system function (7). Future studies should further explore the causal and mechanistic relationship between physiological stress, POMC methylation, and CPMP.

References

1.Norris FH. Epidemiology of trauma: frequency and impact of different potentially traumatic events on different demographic groups. Journal of consulting and clinical psychology 1992;60(3):409.
2.McLean SA, Clauw DJ, Abelson JL, Liberzon I. The development of persistent pain and psychological morbidity after motor vehicle collision: integrating the potential role of stress response systems into a biopsychosocial model. Psychosomatic medicine 2005;67(5):783-790.
3.Liang L, Lutz BM, Bekker A, Tao Y-X. Epigenetic regulation of chronic pain Epigenomics 2015;7(2):235-245.
4.Mourtzi N, Sertedaki A, Charmandari E. Glucocorticoid Signaling and Epigenetic Alterations in Stress-Related Disorders. International Journal of Molecular Sciences 2021;22(11):5964
5.Branham EM, McLean SA, Deliwala I, et al. CpG methylation levels in HPA axis genes predict chronic pain outcomes following trauma exposure. The Journal of Pain 2023:S1526-5900. DOI: 10.1016/j.jpain.2023.03.001.
6.Leung CS, Kosyk O, Welter EM, Dietrich N, Archer TK, Zannas AS. Chronic stress-driven glucocorticoid receptor activation programs key cell phenotypes and functional epigenomic patterns in human fibroblasts. Iscience 2022;25(9):104960.
7.Ulirsch JC, Weaver MA, Bortsov AV, et al. No man is an island: living in a disadvantaged neighborhood influences chronic pain development after motor vehicle collision. Pain. 2014;155(10):2116-2123. doi:10.1016/j.pain.2014.07.025

Presenting Author

Erica M Branham

Poster Authors

Erica Branham

BSc

University of North Carolina Chapel Hill

Lead Author

Anthony Zannas MD PhD

University of North Carolina, Chapel Hill, NC, USA

Lead Author

Ying Zhao

MPH MS

The University of North Carolina at Chapel Hill

Lead Author

Oksana Kosyk

University of North Carolina, Chapel Hill, NC, USA.

Lead Author

Samuel McLean

MD MPH

The University of North Carolina at Chapel Hill

Lead Author

Sarah Linnstaedt

PhD

The University of North Carolina at Chapel Hill

Lead Author

Topics

  • Mechanisms: Psychosocial and Biopsychosocial