mRNA expression of nuclear receptor RZR/RORalpha, melatonin membrane receptor MT, and hydroxindole-O-methyltransferase in different populations of human immune cells.

We characterized the expression levels of the retinoid Z receptor alpha (RZR alpha), RORalpha mRNA isoforms (RORalpha1, RORalpha2, and RORalpha3), and both melatonin receptor MT1 and hydroxindole-O-methyltransferase (HIOMT) genes. For this purpose, the following human peripheral blood mononuclear cells populations were isolated: monocytes (CD14+ cells), B lymphocytes (CD19+ cells), T helper lymphocytes (CD14(-) CD4+), cytotoxic T lymphocytes (CD56(-) CD8+ cells), and natural killer (NK) lymphocytes (CD56+ cells). PBMCs subsets were obtained by Dynabeads M-450 (Dynal) isolation procedure. We observed a strong gene expression signal for RZRalpha in all subpopulations studied, whereas both RORalpha1 and RORalpha2 transcripts were amplified only in CD8+ cells. Specific signal for RORalpha2 was obtained in all subpopulations studied, but we were not able to detect the RORalpha3 mRNA transcript in human immune cells studied. A weaker signal (especially in CD19+ cells) was also detected in all subsets of cells for the MT1 gene. With regard to HIOMT, a strong signal was achieved among all but one subpopulation of cells; the only exception was CD14+ cells. Thus, in addition to its classical function in the nervous and endocrine system, melatonin could act directly as a paracrine and/or autocrine agent in the human immune system.