[D-Arg1,D-Phe5,D-Trp7,9,Leu11]-Substance P

Metabolism of the broad-spectrum neuropeptide growth factor antagonist: [D-Arg1, D-Phe5, D-Trp7,9, Leu11]-substance P.[Pubmed:8611370]

Br J Cancer. 1996 Mar;73(6):715-20.

Broad-spectrum neuropeptide growth factor antagonists, such as [D-Arg1, D-Phe5, D-Trp7,9, Leu11]substance P (antagonist D) and [Arg6, D-Trp7,9, NmePhe8]substance P(6-11) (antagonist G), are currently being investigated as possible anti-tumour agents. These compounds are hoped to be effective against neuropeptide-driven cancers such as small-cell lung cancer. Antagonist D possesses a broader antagonistic spectrum than antagonist G and hence may be of greater therapeutic use. The in vitro metabolism of antagonist D has been characterised and the structures of two major metabolites have been elucidated by amino acid analysis and mass spectrometry. Metabolism was confined to the C-terminus where serine carboxypeptidase action produced [deamidated]-antagonist D (metabolite 1) and [des-Leu11]-antagonist D (metabolite 2) as the major metabolites. Biological characterisation of the metabolites demonstrated that these relatively minor changes in structure resulted in a loss of antagonist activity. These results provide some of the first structure-activity information on the factors that determine which neuropeptides these compounds inhibit and on the relative potency of that inhibition.

Agonist function of the neurokinin receptor antagonist, [D-Arg1,D-Phe5,D-Trp7,9,Leu11]substance P, in monocytes.[Pubmed:12972327]

Regul Pept. 2003 Sep 15;115(2):123-9.

G-protein-coupled bombesin receptors are capable of signaling through the G(i) protein even when receptor-coupling to G(q) is blocked by [D-Arg1,D-Phe5,D-Trp7,9,Leu11]substance P (SpD), a neurokinin-1 receptor antagonist and "biased" agonist to bombesin receptors. As bombesin is a monocyte and tumor cell attractant, we were interested in the effects of SpD on cell migration. Chemotaxis of monocytes was tested in micropore filter assays. SpD was a dose-dependent agonist in monocyte migration and was not inhibited by antagonists to neurokinin-1 or -2 receptors. SpD failed to inhibit chemotaxis toward bombesin, suggesting that inhibition of bombesin receptor coupling to G(q) with SpD does not impair migratory responses elicited by bombesin. As pertussis toxin inhibited migration, coupling of receptors to G(i) may signal migration. Chemotaxis toward SpD was inhibited by bombesin receptor antagonists as well as by blocking signaling enzymes downstream of G(q) (phospholipase-3 and protein kinase C with wortmannin and bisindolylmaleimide, respectively), suggesting transactivation of G(q)-mediated chemotaxis signaling by SpD via bombesin receptors. Protein kinase C that induces sphingosine kinase activation and production of sphingosine-1-phosphate, which may lead to G(q)-dependent chemoattraction, was involved in SpD-dependent migration. Inhibition of sphingosine-1-phosphate production with dimethylsphingosine inhibited monocyte migration toward SpD. Data suggest that SpD induces migration in monocytes and signaling events involving activation of sphingosine kinase in a G(i) protein- and protein kinase C-dependent fashion. "Biased" agonism of SpD at bombesin receptors may affect normal and tumor cell migration.

Processing of [D-Arg1,D-Phe5,D-Trp7,9,Leu11]substance P in xenograft bearing Nu/Nu mice.[Pubmed:9357069]

Peptides. 1997;18(7):1073-7.

[D-Arg1,D-Phe5,D-Trp7,9,Leu11]Substance P is a broad-spectrum neuropeptide growth factor antagonist that has exhibited in vitro activity against a range of human cancer cell lines. The fate of this compound in vivo following i.p. administration at 12 micrograms/g to nu/nu mice bearing the H69 small-cell lung cancer xenograft has been studied. Metabolism was confined to the C-terminus producing [D-Arg1,D-Phe5,D-Trp7,9,Leu11]substance P acid and [D-Arg1,D-Phe5,D-Trp7,9]substance P(1-10). The peptide had a long half-life in plasma (45.9 min) and became widely distributed among the tissues studied with the highest accumulation observed in the liver (AUC 1102 micrograms/g x min) and the lowest in the brain (5 micrograms/g x min). Uptake into the tumor xenograft was poor (AUC 189 micrograms/g x min); however, uptake into the lungs was much greater (AUC 507 micrograms/g x min), offering encouragement that therapeutic concentrations may be targeted to primary lung tumors.

[D-Arg1,D-Phe5,D-Trp7,9,Leu11]Substance P acts as a biased agonist toward neuropeptide and chemokine receptors.[Pubmed:9446627]

J Biol Chem. 1998 Jan 30;273(5):3097-104.

Substance P derivatives are potential therapeutic compounds for the treatment of small cell lung cancer and can cause apoptosis in small cell lung cancer cells in culture. These peptides act as broad spectrum neuropeptide antagonists, blocking calcium mobilization induced by gastrin-releasing peptide, bradykinin, cholecystokinin, and other neuropeptides. We show that [D-Arg1,D-Phe5,D-Trp7,9, Leu11]substance P has unique agonist activities in addition to this described antagonist function. At doses that block calcium mobilization by neuropeptides, this peptide causes activation of c-Jun N-terminal kinase and cytoskeletal changes in Swiss 3T3 fibroblasts and stimulates migration and calcium flux in human neutrophils. Activation of c-Jun N-terminal kinase is dependent on the expression of the gastrin-releasing peptide receptor in rat 1A fibroblasts, demonstrating that the responses to the peptide are receptor-mediated. We hypothesize that [D-Arg1,D-Phe5,D-Trp7,9, Leu11]substance P acts as a biased agonist on neuropeptide and related receptors, activating certain guanine nucleotide-binding proteins through the receptor, but not others.

High constitutive signaling of the ghrelin receptor--identification of a potent inverse agonist.[Pubmed:12907757]

Mol Endocrinol. 2003 Nov;17(11):2201-10.

Ghrelin is a GH-releasing peptide that also has an important role as an orexigenic hormone-stimulating food intake. By measuring inositol phosphate turnover or by using a reporter assay for transcriptional activity controlled by cAMP-responsive elements, the ghrelin receptor showed strong, ligand-independent signaling in transfected COS-7 or human embryonic kidney 293 cells. Ghrelin and a number of the known nonpeptide GH secretagogues acted as agonists stimulating inositol phosphate turnover further. In contrast, the low potency ghrelin antagonist, [D-Arg1,D-Phe5,D-Trp7,9,Leu11]-Substance P was surprisingly found to be a high potency (EC50 = 5.2 nm) full inverse agonist as it decreased the constitutive signaling of the ghrelin receptor down to that observed in untransfected cells. The homologous motilin receptor functioned as a negative control as it did not display any sign of constitutive activity; however, upon agonist stimulation the motilin receptor signaled as strongly as the unstimulated ghrelin receptor. It is concluded that the ghrelin receptor is highly constitutively active and that this activity could be of physiological importance in its role as a regulator of both GH secretion and appetite control. It is suggested that inverse agonists for the ghrelin receptor could be particularly interesting for the treatment of obesity.

[D-Arg1, D-Phe5, D-Trp7,9, Leu11] substance P induces apoptosis in lung cancer cell lines in vitro.[Pubmed:7511895]

Biochem Biophys Res Commun. 1994 Mar 30;199(3):1313-9.

The broad spectrum antagonist [D-Arg1, D-Phe5, D-Trp7,9, Leu11] substance P has been shown previously to inhibit the growth of small cell lung cancer cells both in vitro and in vivo. To elucidate further the pathways involved in the growth inhibitory actions of [D-Arg1, D-Phe5, D-Trp7,9, Leu11] substance P we have examined the effect of this agent on cell viability and the induction of apoptosis in small cell and non-small cell lung cancer cells. Treatment of lung tumor cells with [D-Arg1, D-Phe5, D-Trp7,9, Leu11] substance P caused a concentration-dependent loss of cell viability which was accompanied by the onset of apoptosis, as defined by cytological criteria and DNA fragmentation. This effect occurred in both small cell and non-small cell lung cancer cells and was not dependent on de novo protein synthesis. Such findings indicate that the antiproliferative action of [D-Arg1, D-Phe5, D-Trp7,9, Leu11] substance P involves a signal transduction pathway for apoptosis.