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Luteinizing hormone-releasing hormone signaling at the lymphocyte involves stimulation of interleukin-2 receptor
N Batticane1, M C Morale, F Gallo
1Department of Pharmacology, University of Catania Medical School, Italy.
Insights
The hypothalamic decapeptide LHRH and its agonists stimulate lymphocyte proliferation and interleukin-2 (IL-2) receptor expression in rat cells. LHRH antagonists block these effects, suggesting LHRH signaling influences lymphocyte activation.
Area of Science:
- Immunology
- Neuroendocrinology
- Molecular Biology
Background:
- Lymphocyte function is modulated by various signaling molecules.
- Interleukin-2 (IL-2) receptor expression is a key step in lymphocyte proliferation.
- The hypothalamic decapeptide LHRH's role in lymphocyte function requires further elucidation.
Purpose of the Study:
- To investigate the involvement of LHRH in lymphocyte proliferation.
- To determine the effect of LHRH on interleukin-2 (IL-2) receptor expression in rat lymphocytes.
- To explore the role of LHRH agonists and antagonists in modulating lymphocyte activation.
Main Methods:
- In vitro treatment of rat splenocytes and thymocytes with LHRH, its agonists, antagonists, and fragments.
- Assessment of lymphocyte proliferative activity and blastogenesis.
- Quantification of IL-2 receptor expression on lymphocytes using flow cytometry.
Main Results:
- LHRH and LHRH agonists significantly stimulated basal lymphocyte proliferation and IL-2 receptor expression.
- LHRH amplified Concanavalin-A-induced lymphocyte blastogenesis and IL-2 receptor expression.
- LHRH antagonists inhibited LHRH-induced IL-2 receptor expression, confirming specificity.
Conclusions:
- LHRH signaling specifically increases IL-2 receptor expression on lymphocytes, promoting activation.
- Endogenous LHRH may play a role in regulating IL-2 receptor expression under basal and stimulated conditions.
- LHRH signaling on lymphocytes may synergize with intracellular pathways involved in lymphocyte activation.
Abstract:
The marked modulation of lymphocyte function exerted by the hypothalamic decapetide LHRH prompted us to study the possible involvement of the neuropeptide in one of the major steps of lymphocyte proliferation, namely the expression of interleukin-2 (IL-2) receptor during in vitro treatment of rat lymphocytes with LHRH agonists (LHRH-A) or antagonists (LHRH-ANTA). The basal proliferative activity of splenocytes and thymocytes from proestrous female rats was significantly stimulated after incubation with LHRH and LHRH-A, but not LHRH fragments [LHRH-(1-3), LHRH-(1-5), and LHRH-(2-6)]. Similarly, in the absence of the mitogenic stimulus, IL-2 receptor expression was significantly stimulated in thymocyte and splenocyte cultures incubated with increasing doses of LHRH or its agonists. The amplification of Concanavalin-A-induced increase in blastogenic transformation of lymphocytes by LHRH was paralleled by a significant stimulation of IL-2 receptor expression. The specificity of such effect was demonstrated by 1) the failure of LHRH fragments [LHRH-(1-6)] to mimick the LHRH stimulatory effect; and 2) the complete reversal produced by simultaneous addition of a potent LHRH-ANTA on IL-2 receptor expression induced by LHRH. Moreover, basal and lectin stimulation of IL-2 receptor-positive cells were significantly inhibited by treatment with the LHRH-ANTA. These data clearly demonstrate that 1) LHRH induction of lymphocyte activation in vitro is accompanied by a specific increase in IL-2 receptor-positive cells; 2) endogenous lymphocyte LHRH may participate in stimulation of IL-2 receptor expression under both basal and stimulated conditions, suggesting that LHRH signaling at the lymphocyte may interact synergistically with intracellular mechanisms responsible for lymphocyte activation.