Detection of substance P and its receptor in human fetal microglia

Substance P, the most abundant neurokinin in the CNS, is a major modulator of the immune system. We have examined the gene expression of substance P a nd its receptor in human fetal brain microglia. Using reverse transcription -polymerase chain reaction and Southern blotting assay, the four isoforms o f preprotachykinin-A gene transcripts (alpha, beta, gamma and delta) were d etected in the microglia. The human fetal microglia produced significantly higher levels of endogenous substance P protein (640-850 pg/10(6) cells) th an did human peripheral blood monocyte-derived macrophages (25-50pg/10(6) c ells), as determined by an enzyme immunoassay. Using immunohistochemical st aining with an anti-substance P antibody, cell membrane substance P immunor eactivity was observed. In addition, we identified the presence of messenge r RNA for neurokinin-1 receptor, a primary receptor for substance P in huma n fetal microglia. From these data, we propose that substance P and its receptor are biologica lly involved in regulating the functions of microglia, and potentially play an important role in host defense of the central nervous system. (C) 2000 IBRO. Published by Elsevier Science Ltd. All rights reserved.