gms | German Medical Science

Objective: Pain is the most basic sign of illness, being an overture to start diagnostics and treatment. However, more and more often in medicine we meet chronic pain, accompanying e.g. neoplastic disease, diabetes or degenerative spine disease, that lacks its warning character and becomes a disease itself. Such pain doesn’t react on standard therapeutic methods, results in lowering quality of life, has a negative impact on patient’s emotional and physical functioning and generates socio-economic costs. However, the cause of chronic pain as well as the objective assessment of pain intensity sensed by the patient, are still a challenge in medicine. Currently used methods rely only on the subjective feeling of the patient. Therefore there is a need for precise description of pain on the molecular level, for characterization of its various forms, what can be a base for personalized treatment assessment.

Methods: Peripheral blood samples were taken from patients with pain syndrome operated on lumbar discopathy before and after performing the procedure. DNA was hydrolyzed with micrococcal nuclease and snake venom phosphodiesterase, and then radioactively labeled using T4 polynucleotide kinase and [γ-³²P]ATP. Hot nucleotides’ mixture was separated with thin layer chromatography (TLC). The chromatograms were assessed using Phosphoimager, and the amount of m⁵C represented as a ratio (R) of intensity of spots of m⁵C to m⁵C+C+T. For the analysis of the results statistical methods were used. The amount of m⁵C was correlated with pain intensity assessed by the patient (in VAS), pain duration, advancement of primary disease, comorbidities, treatment applied thus far and lifestyle, as well as laboratory tests' results.

Results: Our preliminary studies on a group of 50 subjects operated on lumbar discopathy show that the intensity of pain is associated with the decrease of global DNA methylation. The level of m⁵C in peripheral blood DNA of patients complaining about pain depends on its type and time of duration. Because there are no known specific human DNA demethylases, pain-associated DNA demethylation can be a result of changes in red-ox potential of the cell, as a consequence of oxidative stress. Therefore the decrease of m⁵C level has a great informative potential and can be widely used in the clinical setting. DNA analysis provides the precise global m⁵C content depending on the intensity and type of pain, allow the estimation of the extent and speed of global DNA methylation changes, impact of irritating factors and correlation with subjective pain assessment scale.

Conclusion: The obtained results showing a different range of DNA demethylation contribute to a better understanding of the molecular basis of pain. There is a possibility that in the future that epigenetic method will be used in clinical diagnostics and therapy design.