Substance P enhances the secretion of tumor necrosis factor-alpha from neuroglial cells stimulated with lipopolysaccharide.
The neuropeptide, substance P (SP), can stimulate secretion of TNF-alpha from macrophages. Neuroglia have SP receptors and subserve various macrophage-like functions in the central nervous system. We investigated whether SP stimulates secretion of TNF-alpha from primary cultures of neuroglial cells containing both astrocytes (approximately 90%) and microglia (approximately 10%). SP alone had no effect; however in the presence of LPS (10 ng/ml), SP (1 to 10 nM) caused a dose-dependent increase in TNF-alpha secretion above the level measured in response to LPS alone. The effective doses of SP correlated with 125I-labeled Bolton Hunter-conjugated SP binding (Kd 0.2 nM) to these cultures. Incubation with LPS did not change the number or affinity of SP-binding sites. In cultures enriched for microglia (> 99% pure), LPS stimulated the secretion of TNF-alpha but SP caused no enhancement. Microglia have no detectable 125I-labeled Bolton-Hunter-conjugated SP binding sites in the presence or absence of LPS. These results indicate that the action of SP is mediated through astrocytes. We investigated whether IL-1 mediates the SP enhancement of TNF-alpha secretion. Addition of IL-1-neutralizing antisera to mixed cultures stimulated with both LPS and 10 nM SP decreased TNF-alpha secretion to the level observed with LPS alone. LPS alone stimulated the secretion of IL-1 in a dose-dependent manner in the primary cultures, and this LPS-mediated IL-1 secretion was enhanced by SP. This enhancement was not observed in microglial cultures. SP may therefore play a role in neuropathologies in which these cytokines have been implicated.
Luber-Narod
J
J
Department of Surgery, University of Massachusetts Medical School, Worcester 01655.
Kage
R
R
Leeman
S E
SE
D000818:Animals; D002478:Cells, Cultured; D066298:In Vitro Techniques; D007375:Interleukin-1 / Q000502:physiology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D009457:Neuroglia / Q000378:metabolism*; D051381:Rats; D018040:Receptors, Neurokinin-1 / Q000378:metabolism; D013373:Substance P / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
D007375:Interleukin-1; D008070:Lipopolysaccharides; D018040:Receptors, Neurokinin-1; D014409:Tumor Necrosis Factor-alpha; D013373:Substance P