Inverse Agonist Activity of Selected Ligands of the Cysteinyl-Leukotriene Receptor 1

Abstract

Cysteinyl leukotrienes (CysLTs) are associated with several inflammatory processes, including asthma. Due to this association, considerable effort has been invested in the development of antagonists to the CysLT receptors (CysLT 1 R). Many of these molecules have been shown to specifically interact with CysLT 1 R, but little is known about their impact on the conformation of the receptor and its activity. We were especially interested in possible inverse agonist activity of the antagonists. Using a constitutively active mutant (N106A) of the human CysLT 1 R and the wild-type (WT) receptor coexpressed with the G ␣q subunit of the trimeric G protein, we were able to address this issue with ligands commonly used in therapy. We demonstrated that some of these molecules are inverse agonists, whereas others act as partial agonists. In cells expressing the CysLT 1 R mutant N106A exposed to Montelukast, Zafirlukast, or 3-[[3-[2-(7-chloroquinolin-2-yl)vinyl]phenyl]-(2-dimethylcarbamoylethylsulfanyl)methylsulfanyl] propionic acid (MK571), the basal inositol phosphate production was reduced by 53 Ϯ 6, 44 Ϯ 3, and 54 Ϯ 4%, respectively. On the other hand, 6(R)-(4-carboxyphenylthio)-5(S)-hydroxy-7(E),9(E),11(Z),14(Z)-eicosatetraenoic acid (BayU9773) and 1-[2-hydroxy-3-propyl-4-[4-(1H-tetrazole-5-YL)-butoxy]-phenyl ethanone] (LY171883) acted as partial agonists and ␣-pentyl-3-[2-quinolinylmethoxy] benzyl alcohol (REV 5901) as a neutral antagonist. However, in cells expressing CysLT 1 R and G ␣q , all antagonists used had inverse agonist activity. The decrease in basal inositol phosphate production by ligands with inverse agonist activity could be inhibited by a more neutral antagonist, confirming the specificity of the reaction. We demonstrate here that Montelukast, MK571, and Zafirlukast can act as inverse agonists on the human CysLT 1 receptor.

Montelukast potentiates the anticonvulsant effect of phenobarbital in mice: An isobolographic analysis

“…Moreover, phenidone and BW755C, dual inhibitors of LOX/COX pathways, decrease kainic acid-induced seizures, suggesting the involvement of leukotrienes in this effect [10,11]. In line with this view, Rehni and Singh (2011) have shown that montelukast, a CysLT 1 receptor inverse agonist [12] and1,2,3,4-tetrahydroisoquinoline, regarded as a LTD 4 synthetic pathway inhibitor, dose-dependently suppress the development of kindled seizures, as well as pilocarpine-induced spontaneous recurrent seizures [13]. Similarly, Liu and colleagues (2014) have shown that zileuton, a 5-LOX inhibitor, decreases spike-wave discharges in pilocarpine epileptic rats [14].…”

“…wakefulness) from basal and after treatment periods were identified in EEG recording and divided in 15 s segments and a 4 s epoch from each segment (without artifacts) was used to carry out the power analysis by the conversion into frequency domain by fast Fourier transformation (FFT) method. The resultant power values displayed for each frequency were grouped into 5 bands represented by delta (0.1-4 Hz), theta (4-8 Hz), alpha (8-12 Hz), beta (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) and gamma . For power analysis of decomposed waves, the power sum from all frequencies (0.1-80 Hz) was considered as 100%.…”

Montelukast regulates eosinophil protease activity through a leukotriene-independent mechanism

“…It has been demonstrated that montelukast, possibly as an inverse agonist, reduces the intracellular level of phosphatidyl inositol triphosphate and diminished the intracellular calcium flux essential for a number of functions in eosinophils. 28 Intracellular calcium is essential for cell migration. [29][30][31] However, further studies are needed to better understand the role of calcium in protease activation or expression.…”

Leukotriene antagonists attenuate late phase nitric oxide production during the hypersensitivity response in the conjunctiva

“…By quantifying two important signaling molecules of the inflammatory response, the present study showed the effectiveness of the pharmacologically classified as cysLT receptor antagonist zafirlukast to attenuate NO induction during the delayed hypersensitivity reaction in the rat conjunctiva, without inducing significant alterations either in the basal histamine content or in the nitrite levels in the lavage fluid in the unchallenged eye. Although it has been shown that zafirlukast can block LT-induced NO release in other tissues [19,20], this study aimed neither at correlating NO release with LT levels, nor at determining the molecular mechanisms of the cysLT receptor antagonists, which may act as inverse agonists [21] and/or as modulators of inducible NOS via pathways independent of cysLTs [22]. This first report on the interaction between cysLT-receptor antagonists and NO in the conjunctiva may provide the lead for the evaluation of the leukotrienic component in the treatment of ocular hypersensitivity disorders.…”