IMMUNOACTIVATION ENHANCES THE CONCENTRATION OF LUTEINIZING-HORMONE-RELEASING HORMONE PEPTIDE AND ITS GENE-EXPRESSION IN HUMAN PERIPHERAL T-LYMPHOCYTES

An immunomodulatory role for LHRH was suggested when we reported the presence of immunoactive and bioactive LHRH and its mRNA in rat splenic and thymic lymphocytes. In this paper we report that human peripheral T-cells as well as its subsets CD4+ and CD8+ contained immunoactive and bioactive LHRH. Furthermore, analysis of phytohemagglutinin (PHA)-activated T-cell lysates for LHRH by RIA demonstrated that the mean concentration of LHRH in PHA-activated T-cells increased from 45 +/- 4.5 to 64 +/- 7 pg/10(6) cells after 24 h of culture and from 47 +/- 3.6 to 117 +/- 11.8 pg/10(6) cells (P < 0.01) after 48 h. While the LHRH concentration in PHA-activated cells increased over the last 24 h of culture h from 64 +/- 7 to 117 +/- 11.8 pg/10(6) cells (P < 0.001), there was no change in mean concentration of LHRH in T-cells kept in medium alone. In a preliminary study we found that fresh T-cells contain 20 +/- 1.4 pg pro-LHRH/10(6) cells, and PHA stimulation increased the pro-LHRH content similar to the increase in LHRH. As with unfractionated T-cells, a significant PHA-induced time-dependent enhancement of intracellular LHRH was noted in CD4+ and CD8+ T-cells. RNA extracted from lymphocytes was subjected to reverse transcription-polymerase chain reaction analysis using LHRH and histone-3.3, primers, the latter as an internal control. The polymerase chain reaction-generated data demonstrated that the relative amount of LHRH mRNA in cultured, but non-PHA-stimulated (resting), cells diminished dramatically between 5-24 h, but recovered by 48 h of culture. The relative amount of LHRH mRNA in PHA-stimulated cells revealed a markedly different pattern. LHRH message expression in PHA-activated cells increased slightly at 5 h of culture and was maximally stimulated by 24 h, but declined by 48 h of culture. The PHA activation-induced time-dependent enhancement of intracellular accumulation of LHRH peptide at 5 and 24 h was accompanied by increased LHRH message. However, the increased concentration of LHRH peptide at 48 h coincided with decreased LHRH message expression. The data from total protein synthesis in PHA-activated cells showed a progressive increase in protein synthesis, a pattern entirely similar to the changes in the cell content of LHRH. Activation of the interleukin-2 (IL-2) system, assessed by an increase in the percentage of IL-2 receptor-positive T-cells and IL-2 release from PHA-activated cells, demonstrated a temporal discordance from increased LHRH, in that the cellular content of LHRH peptide and mRNA increased at 5 h, well before the increased IL-2 system activation that occurred at 24 h. T-Cell LHRH production was also independent of T-cell DNA synthesis, which began well after the increased LHRH production. In summary, human peripheral T-cells and their subsets produced LHRH. LHRH production increased in T-cells activated by PHA. Enhancement of LHRH production in activated T-cells started before IL-2 system activation and was independent of DNA synthesis. Further, this is the first finding of LHRH gene expression in human lymphocytes, as evidenced by LHRH mRNA presence, and parallels our previous finding of LHRH mRNA in rat lymphocytes. These findings further support the idea that LHRH is an important immunomodulator, and endogenous lymphocyte LHRH may exert its immune functional role in a paracrine/autocrine fashion.