Neuropeptide Y promotes neurogenesis and protection against methamphetamine-induced toxicity in mouse dentate gyrus-derived neurosphere cultures

Abstract

Methamphetamine (METH) is a psychostimulant drug of abuse that causes severe brain damage. However, the mechanisms responsible for these effects are poorly understood, particularly regarding the impact of METH on hippocampal neurogenesis. Moreover, neuropeptide Y (NPY) is known to be neuroprotective under several pathological conditions. Here, we investigated the effect of METH on dentate gyrus (DG) neurogenesis, regarding cell death, proliferation and differentiation, as well as the role of NPY by itself and against METH-induced toxicity. DG-derived neurosphere cultures were used to evaluate the effect of METH or NPY on cell death, proliferation or neuronal differentiation. Moreover, the role of NPY and its receptors (Y₁, Y₂ and Y₅) was investigated under conditions of METH-induced DG cell death. METH-induced cell death by both apoptosis and necrosis at concentrations above 10 nM, without affecting cell proliferation. Furthermore, at a non-toxic concentration (1 nM), METH decreased neuronal differentiation. NPY's protective effect was mainly due to the reduction of glutamate release, and it also increased DG cell proliferation and neuronal differentiation via Y₁ receptors. In addition, while the activation of Y₁ or Y₂ receptors was able to prevent METH-induced cell death, the Y₁ subtype alone was responsible for blocking the decrease in neuronal differentiation induced by the drug. Taken together, METH negatively affects DG cell viability and neurogenesis, and NPY is revealed to be a promising protective tool against the deleterious effects of METH on hippocampal neurogenesis.

Introduction

Methamphetamine (METH) is an addictive psychostimulant drug of abuse highly toxic to different brain regions, including the hippocampus, and it was previously shown to induce working memory deficits (Simon et al., 2000; Thompson et al., 2004; Simões et al., 2007). Moreover, oxidative stress (Mirecki et al., 2004; Fitzmaurice et al., 2006), increase of glutamate release (Mark et al., 2004; Tata and Yamamoto, 2008), mitochondrial dysfunction (Jayanthi et al., 2004; Brown et al., 2005; Wu et al., 2007; Tian et al., 2009), neuroinflammation (Thomas et al., 2004; Gonçalves et al., 2008, 2010), hyperthermia (Bowyer et al., 1994) and disruption of the blood–brain barrier (BBB) (Bowyer et al., 2008; Ramirez et al., 2009; Silva et al., 2010; Martins et al., 2011) are some of the well-known neurotoxic features of this drug. However, the mechanisms underlying METH toxicity are still poorly understood, particularly its effect(s) on adult brain neurogenesis.

Adult hippocampal neurogenesis is an important modulator of brain plasticity (Prickaerts et al., 2004; Lledo et al., 2006) and plays a key role in learning and memory functions (Garthe et al., 2009; Clelland et al., 2009; Jessberger et al., 2009). This is a process that persists throughout life but several factors may impair the formation of new functional neurons. In fact, drugs of abuse generally have a negative impact on neurogenesis (Mandyam et al., 2008; Silva et al., 2010; Bento et al., 2011). Chronic exposure to cocaine decreases proliferation in the subgranular zone (SGZ), but has no effect on immature cell survival or cell death (Domínguez-Escribà et al., 2006). Furthermore, a binge alcohol administration to adolescent nonhuman primates decreases both proliferation and neurogenesis with an increase in neural degeneration (Taffe et al., 2010). On the other hand, 3,4-methylenedioxymethamphetamine (MDMA) administered to adolescent Sprague–Dawley rats increases proliferation, whereas neuronal differentiation is compromised (Catlow et al., 2010). Chronic administration of morphine and chronic self-administration of heroin impair cell proliferation and neurogenesis (Eisch et al., 2000). Concerning METH, the little information available points to a negative effect on cell proliferation (Tian et al., 2009; Teuchert-Noodt et al., 2000), neuronal differentiation, migration and survival of hippocampal neuronal cells (Mandyam et al., 2008). Additionally, we recently demonstrated that METH is toxic to stem/progenitor cells and decreases proliferation, neuronal differentiation and maturation in the subventricular zone (SVZ) (Bento et al., 2011).

Neuropeptide Y (NPY) is a 36 amino acid peptide widely distributed in both central and peripheral nervous systems (Dumont and Quirion, 2006). In fact, NPY regulates several physiological functions, such as feeding, anxiety, circadian rhythms, body temperature, sexual behavior and cognition (reviewed by Silva et al., 2005a), and has also an important neuroprotective role under pathological conditions (Woldbye et al., 2005; Silva et al., 2005b, 2007). Previously, Thiriet et al. (2005) demonstrated that METH-induced cell death in mouse striatum was prevented by NPY. Furthermore, this neuropeptide is able to increase proliferation and neuronal differentiation in the SGZ (Howell et al., 2003; Decressac et al., 2010), in the olfactory epithelium and in the SVZ through Y₁ receptors activation (Hansel et al., 2001; Agasse et al., 2008; Decressac et al., 2009; Thiriet et al., 2011).

The present study aimed to characterize the effects of METH on DG stem/progenitor cell survival, proliferation and neuronal differentiation, as well as to evaluate the protective role of NPY system. Overall, our results demonstrate that NPY is protective against METH-induced DG cell death and prevents the decrease of neurogenesis induced by this drug of abuse.