Naltrindole hydrochloride

Naltrindole hydrochloride is a highly potent and selective non-peptide δ opioid receptor antagonist with a Ki of 0.02 nM.

In Vitro:Opioid drugs exert a wide spectrum of physiological and behavioral effects. These effects are mediated via membrane-bound receptors, of which the best characterized are the kappa, delta, and mu receptors[1]. Naltrindole inhibits the proliferation of cultured human U266 MM cells in a time- and dose-dependent manner with an EC50 of 16 μM. Treatment of U266 cells with naltrindole significantly decreases the level of the active, phosphorylated form of the kinases, extracellular signal-regulated kinase and Akt, which may be related to its antiproliferative activity[2]. Naltrindole inhibits growth and induces apoptosis in the three characteristic SCLC cell lines, NCI-H69, NCI-H345, and NCI-H510. Naltrindole treatment reduces constitutive phosphorylation of Akt/PKB on serine 473 and threonine 308 in cells and also its downstream effectors glycogen synthase kinase-3β and the Forkhead transcription factors AFX and FKHR[3].

In Vivo:Naltrindole significantly decreases tumor cell volumes in human MM cell xenografts in severe combined immunodeficient mice[2]. In mice, naltrindole at 20 mg/kg s.c. antagonizes the δ-selective agonist effect of [D- Ser, Leu, Thr]enkephalin (DSLET) without blocking the antinociceptive effect of morphine or U50488H. Naltrindole is the only highly selective δ antagonist that is active upon peripheral administration[4]. Acute naltrindole induces significant decreases in external and total ambulation (horizontal activity) and rearing behaviour (vertical activity), as well as a significant increase in grooming frequency. In animals chronically treated with naltrindole there is an increase in total ambulation one day after the discontinuation of the treatment[5].

References:
[1]. Raynor K, et al. Pharmacological characterization of the cloned kappa-, delta-, and mu-opioid receptors. Mol Pharmacol. 1994 Feb;45(2):330-4. [2]. Mundra JJ, et al. Naltrindole inhibits human multiple myeloma cell proliferation in vitro and in a murine xenograft model in vivo. J Pharmacol Exp Ther. 2012 Aug;342(2):273-87. [3]. Chen YL, et al. Inhibition of akt/protein kinase B signaling by naltrindole in small cell lung cancer cells. [4]. Portoghese PS, et al. Naltrindole, a highly selective and potent non-peptide delta opioid receptor antagonist. Eur J Pharmacol. 1988 Jan 27;146(1):185-6. [5]. Fernández B, et al. Postnatal naltrindole treatments induce behavioural modifications in preweanling rats. Neurosci Lett. 2000 Mar 31;283(1):73-6.

Lipid Emulsion Inhibits Apoptosis Induced by a Toxic Dose of Verapamil via the Delta-Opioid Receptor in H9c2 Rat Cardiomyoblasts.[Pubmed:27990618]

Cardiovasc Toxicol. 2017 Jul;17(3):344-354.

The goals of this study were to investigate the effects of lipid emulsion (LE) on apoptosis induced by a toxic dose of verapamil in H9c2 cells and to elucidate the associated cellular mechanism. The effects of LE alone and combined with an inhibitor on the decreases in cell counts and viability induced by verapamil and diltiazem were examined using the MTT assay. The effects of verapamil alone, combined LE and verapamil treatment, and combined inhibitor, LE and verapamil treatment on cleaved caspase-3, caspase-8 and Bax expression, were examined using Western blotting. The effects of verapamil alone and combined with LE on the number of TUNEL-positive H9c2 cells were also examined. LE attenuated the decreases in cell counts and viability induced by verapamil and diltiazem. However, the magnitude of the LE-mediated attenuation of decreased cell viability was enhanced by verapamil compared with diltiazem treatment. Naloxone, Naltrindole hydrochloride, LY294002 and MK-2206 inhibited the LE-mediated attenuation of increased cleaved caspase-3 and caspase-8 expression induced by verapamil. LE attenuated the increase in the number of TUNEL-positive cell induced by verapamil. These results suggest that LE attenuates apoptosis induced by verapamil via activation of the delta-opioid receptor, phosphoinositide 3-kinase and Akt.

Hemokinin-1(4-11)-induced analgesia selectively up-regulates delta-opioid receptor expression in mice.[Pubmed:24587368]

PLoS One. 2014 Feb 28;9(2):e90446.

Our previous studies have shown that an active fragment of human tachykinins (hHK-1(4-11)) produced an opioid-independent analgesia after intracerebroventricular (i.c.v.) injection in mice, which has been markedly enhanced by a delta OR antagonist, Naltrindole hydrochloride (NTI). In this study, we have further characterized the in vivo analgesia after i.c.v. injection of hHK-1(4-11) in mouse model. Our qRT-PCR results showed that the mRNA levels of several ligands and receptors (e.g. PPT-A, PPT-C, KOR, PDYN and PENK) have not changed significantly. Furthermore, neither transcription nor expression of NK1 receptor, MOR and POMC have changed noticeably. In contrast, both mRNA and protein levels of DOR have been up-regulated significantly, indicating that the enhanced expression of delta opioid receptor negatively modulates the analgesia induced by i.c.v. injection of hHK-1(4-11). Additionally, the combinatorial data from our previous and present experiments strongly suggest that the discriminable distribution sites in the central nervous system between hHK-1(4-11) and r/mHK-1 may be attributed to their discriminable analgesic effects. Altogether, our findings will not only contribute to the understanding of the complicated mechanisms regarding the nociceptive modulation of hemokinin-1 as well as its active fragments at supraspinal level, but may also lead to novel pharmacological interventions.

Anti-hyperalgesic effect of a benzilidine-cyclohexanone analogue on a mouse model of chronic constriction injury-induced neuropathic pain: Participation of the kappa-opioid receptor and KATP.[Pubmed:24201054]

Pharmacol Biochem Behav. 2013 Dec;114-115:58-63.

The present study investigated the analgesic effect of a novel synthetic cyclohexanone derivative, 2,6-bis-4-(hydroxyl-3-methoxybenzilidine)-cyclohexanone or BHMC in a mouse model of chronic constriction injury-induced neuropathic pain. It was demonstrated that intraperitoneal administration of BHMC (0.03, 0.1, 0.3 and 1.0mg/kg) exhibited dose-dependent inhibition of chronic constriction injury-induced neuropathic pain in mice, when evaluated using Randall-Selitto mechanical analgesiometer. It was also demonstrated that pretreatment of naloxone (non-selective opioid receptor blocker), nor-binaltorphimine (nor-BNI, selective kappa-opioid receptor blocker), but not beta-funaltrexamine (beta-FN, selective mu-opioid receptor blocker) and Naltrindole hydrochloride (NTI, selective delta-opioid receptor blocker), reversed the anti-nociceptive effect of BHMC. In addition, the analgesic effect of BHMC was also reverted by pretreatment of 1H-[1,2,4]Oxadiazole[4,3-a]quinoxalin-1-one (ODQ, soluble guanosyl cyclase blocker) and glibenclamide (ATP-sensitive potassium channel blocker) but not Nomega-nitro-l-arginine (l-NAME, a nitric oxide synthase blocker). Taken together, the present study demonstrated that the systemic administration of BHMC attenuated chronic constriction, injury-induced neuropathic pain. We also suggested that the possible mechanisms include kappa-opioid receptor activation and nitric oxide-independent cyclic guanosine monophosphate activation of ATP-sensitive potassium channel opening.