Expression of NK-1 receptor mRNA in murine T lymphocytes.

Abstract

Substance P (SP), one of the best characterized neurogenic mediators of immune hyperactivity, stimulates the production of a variety of cytokines, and acts as a general proinflammatory agent inducing proliferation and activation of immune cells Neurokinin 1 receptor (NK-1R), a G-protein-coupled receptor with high affinity for SP, has been cloned from nonlymphoid tissues. Although previous binding studies indicated the presence of high affinity SP receptors on immune cells, recent studies questioned the existence of specific NK-1R on lymphocytes and monocytes. In this study we investigate the expression of the NK-1R gene in murine T lymphocytes and T cell lines. The expression of NK-1R mRNA was determined by reverse transcription polymerase chain reaction (RT-PCR), with two separate sets of specific primers, and by nuclease protection assays. The NK-1R nature of the lymphocytic amplified fragments was confirmed by Southern blots with specific murine brain NK-1R probes. Both T cells lines (EL-4.IL-2 and LBRM-T6G) which were previously shown to respond to SP by increased IL-2 production express NK-1R mRNA constitutively. Normal spleen cells and purified CD4+ T lymphocytes which also responded to SP by increased IL-2 production express NK-1R mRNA. In addition to CD4+ T cells, NK-1R message is also expressed in murine splenic B lymphocytes. Sequencing of the RT-PCR amplified fragments from EL-4.IL-2 cells, purified CD4+ T lymphocytes, and murine brain showed complete identity to the published murine NK-1R sequence. This study indicates that murine CD4+ T lymphocytes possess the molecular template for the production of NK-1R. Together with previous binding studies, and with pharmacological studies regarding the effect of SP and of selective NK-1R antagonists on cytokine production, the present study supports the hypothesis that the response of CD4+ T cells to SP and related tachykinins is mediated through specific NK-1 receptors.