L-732,138

The NK-1 Receptor Antagonist L-732,138 Induces Apoptosis and Counteracts Substance P-Related Mitogenesis in Human Melanoma Cell Lines.[Pubmed:24281084]

Cancers (Basel). 2010 Apr 20;2(2):611-23.

It has been recently demonstrated that substance P (SP) and neurokinin-1 (NK-1) receptor antagonists induce cell proliferation and cell inhibition in human melanoma cells, respectively. However, the antitumor action of the NK-1 receptor antagonist L-732,138 on such cells is unknown. The aim of this study was to demonstrate an antitumor action of L-732,138 against three human melanoma cell lines (COLO 858, MEL HO, COLO 679). We found that L-732,138 elicits cell growth inhibition in a concentration dependent manner in the melanoma cells studied. Moreover, L-732,138 blocks SP mitogen stimulation. The specific antitumor action of L-732,138 occurred through the NK-1 receptor and melanoma cell death was by apoptosis. These findings indicate that the NK-1 receptor antagonist L-732,138 could be a new antitumor agent in the treatment of human melanoma.

Neurokinin-1 receptors located in human retinoblastoma cell lines: antitumor action of its antagonist, L-732,138.[Pubmed:17525212]

Invest Ophthalmol Vis Sci. 2007 Jun;48(6):2775-81.

PURPOSE: The authors have recently demonstrated that substance P and L-733,060 induce cell proliferation and cell inhibition, respectively, in human retinoblastoma cell lines. However, the presence of neurokinin-1 receptors has not been demonstrated in such cell lines, nor is it known whether other neurokinin-1 receptor antagonists exert antitumoral action against retinoblastoma cell lines. The purpose of this study was to demonstrate the presence of neurokinin-1 receptors in the human retinoblastoma cell lines WERI-Rb-1 and Y-79 and to study the growth inhibitory capacity of the neurokinin-1 receptor antagonist L-732,138 against those cell lines. The authors also sought to demonstrate that the administration of L-732,138 or L-733,060 induces apoptosis in retinoblastoma cells and that neurokinin-1 receptors and substance P are present in primary retinoblastoma. METHODS: Immunoblot analysis was used to determine neurokinin-1 receptors, and a Coulter counter was used to determine viable cell numbers; this was followed by application of the tetrazolium compound WST-8, a colorimetric method, to evaluate cell viability. DAPI stain was applied to assess chromatin condensation, characteristic of apoptosis, and immunoperoxidase was used to demonstrate neurokinin-1 receptors and substance P in eyes with primary retinoblastoma. RESULTS: Neurokinin-1 receptors were present in both retinoblastoma cell lines studied. Three identical bands (isoforms of approximately 33, 58, and 75 kDa) were observed in both cell lines. Moreover, L-732,138 inhibited the growth of both cell lines studied, with and without previous administration of substance P. This inhibition occurred in a dose-dependent manner, with the IC50 values of 60.47 microM for WERI-Rb1 and 56.78 microM for Y-79. Moreover, apoptosis was observed in both cell lines after the administration of L-732,138 or L-733,060. In fixed eyes with primary retinoblastoma, a high density of neurokinin-1 receptors was observed in tumor cells, whereas a very low number of such cells contained substance P. CONCLUSIONS: This study showed that the same isoforms of the neurokinin-1 receptor are present in human retinoblastoma cell lines WERI-Rb-1 and Y-79. Both L-732,138 and L-733,060 can induce apoptosis in these cell lines and therefore can act as antitumoral agents. Primary retinoblastoma specimens display neurokinin-1 receptor immunolabeling. These results suggest that the neurokinin-1 receptor may be a promising new target for the treatment of retinoblastoma.

Lipopolysaccharide enhances neurogenic plasma exudation in guinea-pig airways.[Pubmed:9831906]

Br J Pharmacol. 1998 Oct;125(4):711-6.

1. Lipopolysaccharide (LPS) is implicated in many pulmonary and airway inflammatory diseases. Tachykinins released from nerve endings increase vascular permeability. In this study, we have assessed the enhancement by LPS of tachykinin-mediated plasma exudation in guinea-pig airways, and examined the role of oxidants as well as leukocyte adherence. 2. LPS (100 microg kg(-1), i.v.) was administered 0-3 h before bilateral electrical stimulation of the cervical vagus nerves in animals anaesthetized with urethane and ventilated. Vagal stimulation increased vascular permeability in the airways. LPS enhanced the vagally-mediated plasma exudation with the peak effect at 1 h after LPS administration. LPS alone induced no significant plasma exudation. LPS also enhanced exogenous substance P (10(-8) mol kg(-1), i.v.)-induced plasma exudation. 3. The NK-1 receptor antagonist L-732,138 abolished vagally-induced plasma exudation and significantly inhibited the enhancement by LPS. Pretreatment with superoxide dismutase (SOD, 5000 U kg(-1), i.p.) did not affect the vagally-induced plasma exudation, but inhibited the LPS-enhanced neurogenic plasma leakage. The LPS-enhanced vagally-induced plasma exudation was not completely inhibited by either L-732,138 or SOD pretreatment alone, but was blocked by the combination of both pretreatments. 4. Neutrophil depletion by cyclophosphamide alone did not influence vagally-induced plasma exudation, but significantly inhibited the LPS-enhanced response. 5. In conclusion, we have demonstrated LPS enhanced neurogenic plasma exudation by augmenting the response to tachykinins, partly through NK-1 receptors, to directly increase vascular permeability or to enhance leukocyte adhesion-mediated endothelial cell injury. Tachykinins released from nerve endings may contribute to endotoxin-related airway inflammatory responses.

Characterization of the interaction of N-acyl-L-tryptophan benzyl ester neurokinin antagonists with the human neurokinin-1 receptor.[Pubmed:7509807]

J Biol Chem. 1994 Mar 4;269(9):6587-91.

We have recently shown that a series of N-acyl-L-tryptophan benzyl esters are potent substance P antagonists (Macleod, A. M., Merchant, K. J., Cascieri, M. A., Sadowski, S., Ber, E., Swain, C. J., and Baker, R. (1993) J. Med Chem. 14, 2044-2045). We now report the detailed characterization of the interaction of N-acetyl-L-tryptophan-3,5-bistrifluoromethyl benzyl ester (L-732,138) with the human neurokinin-1 (NK-1) receptor. L-732,138 inhibits the binding of 125I-substance P to the cloned human NK1 receptor expressed in Chinese hamster ovary cells with an IC50 of 2.3 +/- 0.7 nM. In contrast, it has 200-fold lower affinity for the cloned rat NK-1 receptor and has > 1000-fold lower affinity for the human NK-2 and NK-3 receptors. L-732,138 acts as a competitive antagonist of substance P, as shown by functional Schild analysis of the inhibition of substance P-induced inositol phosphate synthesis, by kinetic analysis of the dissociation rate, and by thermodynamic analysis of the equilibrium binding of 125I-substance P to the NK-1 receptor. L-732,138 also competitively inhibits the binding of the quinuclidine amine antagonist, [125I]L-703,606, to the receptor. The compound has 230- and 10-fold reduced affinity for mutant NK-1 receptors in which histidine 265 or histidine 197, respectively, are replaced with alanine. We have previously shown that these residues play key roles in the binding of quinuclidine antagonists to the NK-1 receptor. These results suggest that the tryptophan and quinuclidine series of NK-1 antagonists bind to similar binding sites on the human NK-1 receptor.

Identification of L-tryptophan derivatives with potent and selective antagonist activity at the NK1 receptor.[Pubmed:7513763]

J Med Chem. 1994 Apr 29;37(9):1269-74.

As part of a program of screening the Merck sample collection, N-ethyl-L-tryptophan benzyl ester was identified as a weak antagonist at the substance P (NK1) receptor. Structure-activity studies showed that the indole ring system could be replaced by 3,4-dichlorophenyl, alpha- or beta-naphthyl, or benzthiophene with retention or only small loss of affinity. It was found that acylation of the tryptophan nitrogen gave compounds with higher affinity than N-ethyl or other basic amines. Optimization of substitution on the benzyl ester led to the identification of the 3,5-bis-(trifluoromethyl)benzyl ester of N-acetyl-L-tryptophan 26 as a potent and selective substance P receptor antagonist. Compound 26 blocked substance P induced dermal extravasation in vivo and was the most potent compound from this structurally novel class of antagonists which further adds to the diversity of small molecules that bind to the (NK1) receptor.

L-732138 is a selective, potent and competitive neurokinin-1 (NK-1) receptor antagonist with an IC50 of 2.3 nM. L-732138 has 200-fold more potent in cloned human NK-1 receptors than cloned rat NK-1 receptors, and has > 1000-fold more potent than human NK-2 and NK-3 receptors. L-732138 can reduce hyperalgesia and has antitumor action.

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