Effects of the Hybridization of Opioid and Neurotensin Pharmacophores on Cell Survival in Rat Organotypic Hippocampal Slice Cultures.

Patrycja Kleczkowska,Maria Kawalec,Małgorzata Filip,Magdalena Bujalska-Zadrozny,Andrzej W Lipkowski,Barbara Zablocka

doi:10.1007/s12640-015-9553-9

Abstract

Several neurotransmitter and neuromodulatory systems can control physiological glutamatergic activity. For example, opioid receptor ligands were shown to partially inhibit N-methyl-D-aspartic acid (NMDA) receptor-dependent glutamatergic excitotoxicity. Also, the endogenous tridecapeptide neurotensin (NT) was found to modulate excessive glutamate release and glutamate receptor activity in neurons. Alternatively to the one target-one drug approach, it has been well documented that hybrid compounds encompassing two pharmacophores in one molecular scaffold can represent more potent drugs. Moreover, such structures with dual activity can potentially enable a reduction of undesirable side effects and/or improved bioavailability. Herein, we describe the neuroprotective potential of an opioid-NT hybrid peptide (PK20), which was recently designed and synthesized within our group. The protective properties of PK20, assessed in an in vitro model of excitotoxic injury in organotypic hippocampal slice cultures subjected to NMDA, were compared to the effects caused by NT. Our results indicate that PK20 is a potent anti-neurodegenerative agent. Moreover, co-administered with NMDA, PK20 (25-100 ng/ml) dose-dependently reduced hippocampal cell death, determined by a decrease in the propidium iodide signal. We also report for the first time the significant NT-induced neuroprotective effect, as its application (50-100 ng/ml) to hippocampal slice cultures protected CA1 damage against neurotoxicity caused by NMDA.

Highlights

Glutamate, being the main excitatory neurotransmitter in the brain, is responsible for neurodegeneration and neuronal damage (Arundine and Tymianski 2004; Hynd et al 2004; Olney et al 1972)
The number of dead cells labeled with propidium iodide (PI) was counted in order to assess the effects of NT and PK20 on N-methyl-D-aspartic acid (NMDA)-induced cell death
In the field of neurodegenerative disease treatment, there have been a few articles describing the use of compounds containing at least two chemically connected drugs, known as hybrids, chimeras, designed multifunctional drugs or bi/multifunctional drugs

Summary

Introduction

Glutamate, being the main excitatory neurotransmitter in the brain, is responsible for neurodegeneration and neuronal damage (Arundine and Tymianski 2004; Hynd et al 2004; Olney et al 1972). Glutamate’s prolonged and excessive release causes over-stimulation of its Neurotox Res (2015) 28:352–360 receptors, especially the N-methyl-D-aspartic acid (NMDA) receptors, which leads to excitotoxicity (Mark et al 2001) This pathological process, by which neurons are damaged, is well-established and is well-observed in, for example hippocampal pyramidal cells (CA1 region), which are known to be one of the most sensitive to excitotoxicity. By use of the hippocampal slice/NMDA model, previous studies have shown that opioid ligands, including morphine and the peptide biphalin, express neuroprotective properties (Liu et al 2008; Kawalec et al 2011) Both morphine and biphalin express a ceiling protective effect that was proposed to be directly related to the proportion of cells containing particular neuropeptide receptor types on their membranes. We hypothesized that the activation of other neuropeptide receptors may result in independent protection and may result in additive or synergic effects when applied together with opioids

Objectives

Methods

Results

Conclusion