John R. Lever

Bombesin functionalized gold nanoparticles show in vitro and in vivo cancer receptor specificity.

Development of cancer receptor-specific gold nanoparticles will allow efficient targeting/optimum retention of engineered gold nanoparticles within tumors and thus provide synergistic advantages in oncology as it relates to molecular imaging and therapy. Bombesin (BBN) peptides have demonstrated high affinity toward gastrin-releasing peptide (GRP) receptors in vivo that are overexpressed in prostate, breast, and small-cell lung carcinoma. We have synthesized a library of GRP receptor-avid nanoplatforms by conjugating gold nanoparticles (AuNPs) with BBN peptides. Cellular interactions and binding affinities (IC50) of AuNP–BBN conjugates toward GRP receptors on human prostate cancer cells have been investigated in detail. In vivo studies using AuNP–BBN and its radiolabeled surrogate 198AuNP–BBN, exhibiting high binding affinity (IC50 in microgram ranges), provide unequivocal evidence that AuNP–BBN constructs are GRP-receptor-specific showing accumulation with high selectivity in GRP-receptor-rich pancreatic acne in normal mice and also in tumors in prostate-tumor-bearing, severe combined immunodeficient mice. The i.p. mode of delivery has been found to be efficient as AuNP–BBN conjugates showed reduced RES organ uptake with concomitant increase in uptake at tumor targets. The selective uptake of this new generation of GRP-receptor-specific AuNP–BBN peptide analogs has demonstrated realistic clinical potential in molecular imaging via x-ray computed tomography techniques as the contrast numbers in prostate tumor sites are severalfold higher as compared to the pretreatment group (Hounsfield unit = 150).

The sigma receptor agonist SA4503 both attenuates and enhances the effects of methamphetamine

BACKGROUNDnMethamphetamines behavioral effects have been attributed to its interaction with monoamine transporters; however, methamphetamine also has affinity for sigma receptors.nnnMETHODnThe present study investigated the effect of the sigma receptor agonist SA 4503 and the sigma receptor antagonists BD-1047 and BD-1063 on methamphetamine-evoked [(3)H]dopamine release from preloaded rat striatal slices. The effect of SA 4503 on methamphetamine-induced hyperactivity and on the discriminative stimulus properties of methamphetamine also was determined.nnnRESULTSnSA 4503 attenuated methamphetamine-evoked [(3)H]dopamine release in a concentration-dependent manner. BD-1047 and BD-1063 did not affect release. SA 4503 dose-dependently potentiated and attenuated methamphetamine-induced hyperactivity. SA 4503 pretreatment augmented the stimulus properties of methamphetamine.nnnCONCLUSIONSnOur findings indicate that SA 4503 both enhances and inhibits methamphetamines effects and that sigma receptors are involved in the neurochemical, locomotor stimulatory and discriminative stimulus properties of methamphetamine.

Effect of structural modification in the amine portion of substituted aminobutyl-benzamides as ligands for binding σ1 and σ2 receptors

5-Bromo-N-[4-(6,7-dimethoxy-3,4-dihydro-1H-isoquinolin-2-yl)-butyl)]-2,3-dimethoxy-benzamide (1) is one of the most potent and selective σ(2) receptor ligands reported to date. A series of new analogs, where the amine ring fused to the aromatic ring was varied in size (5-7) and the location of the nitrogen in this ring was modified, has been synthesized and assessed for their σ(1)/σ(2) binding affinity and selectivity. The binding affinity of an open-chained variant of 1 was also evaluated. Only the five-membered ring congener of 1 displayed a higher σ(1)/σ(2) selectivity, derived from a higher σ(2) affinity and a lower σ(1) affinity. Positioning the nitrogen adjacent to the aromatic ring in the five-membered and six-membered ring congeners dramatically decreased affinity for both subtypes. Thus, location of the nitrogen within a constrained ring is confirmed to be key to the exceptional σ(2) receptor binding affinity and selectivity for this active series.

(±)-2-(N-tert-Butylamino)-3′-[125I]-iodo-4′-azidopropiophenone: a dopamine transporter and nicotinic acetylcholine receptor photoaffinity ligand based on bupropion (Wellbutrin, Zyban)

Towards addressing the knowledge gap of how bupropion interacts with the dopamine transporter (DAT) and nicotinic acetylcholine receptors (nAChRs), a ligand was synthesized in which the chlorine of bupropion was isosterically replaced with an iodine and a photoreactive azide was added to the 4-position of the aromatic ring. Analog (±)-3 (SADU-3-72) demonstrated modest DAT and α4β2 nAChR affinity. A radioiodinated version was shown to bind covalently to hDAT expressed in cultured cells and affinity-purified, lipid-reincorporated human α4β2 neuronal nAChRs. Co-incubation of (±)-[(125)I]-3 with non-radioactive (±)-bupropion or (-)-cocaine blocked labeling of these proteins. Compound (±)-[(125)I]-3 represents the first successful example of a DAT and nAChR photoaffinity ligand based on the bupropion scaffold. Such ligands are expected to assist in mapping bupropion-binding pockets within plasma membrane monoamine transporters and ligand-gated nAChR ion channels.

Effects of N-phenylpropyl-N'-substituted piperazine sigma receptor ligands on cocaine-induced hyperactivity in mice.

The present study examined N-phenylpropyl-N-substituted piperazine sigma receptor ligands on cocaine-induced changes in locomotor activity in mice. Previous reports indicate that N-phenylpropyl-N-(4-methoxybenzyl)piperazine (Nahas-3h), N-phenylpropyl-N-(4-methoxyphenethyl)piperazine (YZ-067), and N-phenylpropyl-N-(3-methoxyphenethyl)piperazine (YZ-185) bind with high affinity (Ki values≈1 nM) to σ1 sigma receptors. YZ-067 and YZ-185 are known to attenuate cocaine-induced convulsions, while Nahas-3h has not been tested in behavioral studies. Nahas-3h significantly attenuated cocaine-induced hyperactivity. YZ-067 decreased the effect of cocaine in a dose-dependent manner. Interestingly, YZ-185 inhibited cocaines effect at higher doses, but enhanced cocaines effect at a low dose. The YZ-185 inhibition of cocaine-induced hyperactivity was not surmounted by increasing the cocaine dose. Overall, this study is consistent with previous work showing the ability of certain sigma receptor ligands to affect cocaine-induced hyperactivity. Further, subtle alterations of ligand structure and the specific dosage levels employed influence the behavioral effects observed, with a 3-methoxy substituent apparently conferring the ability of a ligand to enhance cocaines locomotor stimulatory effects.

Azido-iodo-N-benzyl derivatives of threo-methylphenidate (Ritalin, Concerta): Rational design, synthesis, pharmacological evaluation, and dopamine transporter photoaffinity labeling

In contrast to tropane-based compounds such as benztropine and cocaine, non-tropane-based photoaffinity ligands for the dopamine transporter (DAT) are relatively unexplored. Towards addressing this knowledge gap, ligands were synthesized in which the piperidine nitrogen of 3- and 4-iodomethylphenidate was substituted with a benzyl group bearing a photoreactive azide. Analog (±)-3a demonstrated modest DAT affinity and a radioiodinated version was shown to bind covalently to rat striatal DAT and hDAT expressed in cultured cells. Co-incubation of (±)-3a with nonradioactive d-(+)-methylphenidate or (-)-2-β-carbomethoxy-3-β-(4-fluorophenyl)tropane (β-CFT, WIN-35,428, a cocaine analog) blocked DAT labeling. Compound (±)-3a represents the first successful example of a DAT photoaffinity ligand based on the methylphenidate scaffold. Such ligands are expected to assist in mapping non-tropane ligand-binding pockets within plasma membrane monoamine transporters.

Fischer indole synthesis in water: simple, efficient preparation of naltrindole, naltriben and analogs

Naltrindole, naltrindole analogs and the benzofuran congener naltriben have been prepared by Fischer syntheses using mildly acidic, purely aqueous conditions. The preparation of naltrindole and several analogs was accomplished under almost neutral conditions using just the hydrochloride salts of naltrexone and various electron-rich and electron-poor phenylhydrazines in boiling water. The products were obtained by simple filtration in good to excellent yields and with high purities in the majority of cases. The route is suited to gram-scale synthesis, does not require the use of organic solvents, minimizes the use of corrosive acids, and is simple, efficient and environmentally friendly. Naltriben was prepared efficiently from the hydrochloride salts of naltrexone and O-phenylhydroxylamine but more forcing conditions, 6.0 N HCl, were required. A limitation to the method is the failure of Fischer cyclization between naltrexone and nitro-substituted phenylhydrazines under aqueous conditions.

N-Phenylpropyl-N′-(3-methoxyphenethyl)piperazine (YZ-185) Attenuates the Conditioned-Rewarding Properties of Cocaine in Mice

Sigma receptor antagonists diminish the effects of cocaine in behavioral assays, including conditioned place preference. Previous locomotor activity experiments in mice determined that the sigma receptor ligand YZ-185 (N-phenylpropyl-N′-(3-methoxyphenethyl)piperazine) enhanced cocaine-induced hyperactivity at a lower (0.1u2009μmol/kg) dose and dose-dependently attenuated cocaine-induced hyperactivity at higher (3.16–31.6u2009μmol/kg) doses. The present study investigated the effect of YZ-185 on cocaines conditioned-rewarding properties in mice. YZ-185 (0.1, 0.316, 3.16, and 31.6u2009μmol/kg) did not have intrinsic activity to produce conditioned place preference or aversion. A higher (31.6u2009μmol/kg) YZ-185 dose, but not lower (0.1–3.16u2009μmol/kg) YZ-185 doses, prevented the development of place preference to cocaine (66u2009μmol/kg). YZ-185 did not alter the expression of cocaine place preference. To further characterize YZ-185s behavioral profile, its effects in the elevated zero maze and rotarod procedures were also determined; YZ-185 produced no significant change from baseline in either assay, indicating that the sigma receptors probed by YZ-185 do not regulate anxiety-like or coordinated motor skill behaviors. Overall, these results suggest that YZ-185 is a sigma receptor antagonist at the 31.6u2009μmol/kg dose and demonstrate that sigma receptors can mediate the development of the conditioned-rewarding properties of cocaine.