Substance P C-terminal octapeptide analogues augment tumor necrosis factor-alpha release by human blood monocytes and...

We have investigated the effects of the substance P C-terminal octapeptide analogues [Pro4, Glu (OBzl)11] SP4-11, [Hyp4, Glu(OBzl)11] SP4-11, [cHyp4, Glu(OBzl)11] SP4-11 and [kPro4, Glu(OBzl)11] SP4-11 on the constitutive and/or lipopolysaccharide (LPS)-induced expression of tumor necrosis factor (TNF-alpha) in both freshly isolated human blood monocytes (FIBM) and monocyte-derived macrophages (MDM). The cells were treated with substance P and the substance P analogues at various concentrations (10-14 to 10-6 M) in the presence or absence of LPS and culture supernatants were analyzed for TNF-alpha as measured by an enzyme immunosorbent assay (ELISA). Monocytes and macrophages treated with the substance P analogues alone increased TNF-alpha secretion at a magnitude similar to the effect of entire undecapeptide substance P. The stimulatory effects of the substance P analogues on TNF-alpha secretion are inhibited by substance P antagonists, spantide ([D-Arg-1-D-Trp-7-D-Trp-9-Leu-11]-SP) and CP-96,345 (a nonpeptide antagonist of the substance P receptor), indicating that these effects are specific and substance P receptor-mediated. Treatment of monocytes and macrophages with the substance P analogues in combination with LPS, however, showed no synergistic interaction in upregulation of TNF-alpha. These data indicate that the biological effect of substance P on TNF-alpha production by human monocytes and macrophages depends mainly on the sequence of the C-terminal region of the molecule.