Potential biomarkers of addiction identified by real-time PCR in human peripheral blood lymphocytes: a narrative review

Addiction-related neurobiological factors could be considered as potential biomarkers. The concentration of peripheral biomarkers in tissues like blood lymphocytes may mirror their brain levels. This review is focused on the mRNA expression of potential addiction biomarkers in human peripheral blood lymphocytes (PBLs). PubMed, EMBASE, Web of Science, Scopus and Google Scholar were searched using the keywords 'addiction', 'biomarker', 'peripheral blood lymphocyte', 'gene expression' and 'real-time PCR'. The results showed the alterations in the regulation of genes such as dopamine receptors, opioid receptors, NMDA receptors, cannabinoid receptors, alpha-synuclein, DYN, MAO-A, FosB and orexin-A as PBLs biomarkers in addiction stages. Such variations could also be found during abstinence and relapse. PBLs biomarkers may help in drug development and have clinical implications. Plain language summary There are some peptides and proteins that are considered as non-invasive biomarkers in addiction. The level of such biomarkers in peripheral tissues like blood may be parallel to their concentrations in the brain. Here, we have reviewed the articles that have studied these biomarkers' expression levels in human peripheral blood lymphocytes (PBLs) using the real-time PCR technique. Previous studies have shown that in the process of addiction, some changes might occur in PBLs expression level of factors like dopamine, glutamate and opioid receptors, which are crucial in reward circuits and neurobiology of addiction. Studying the alterations in PBLs concentrations of these parameters (in stages of drug abuse, abstinence and relapse) could help investigators find a promising biomarker, which can help design new treatment strategies.