Mitochondrial dysfunction and caspase activation in rat cortical neurons treated with cocaine or amphetamine

Abstract

Drug abuse is associated with brain dysfunction and neurodegeneration, and various recreational drugs induce apoptotic cell death. This study examined the role of the mitochondrial apoptotic pathway in psychostimulant-induced neuronal dysfunction. Using primary neuronal cultures, we observed that amphetamine (IC50=1.40 mM) was more potent than cocaine (IC50=4.30 mM) in inducing cell toxicity. Apoptotic cell death was further evaluated using cocaine and amphetamine concentrations that moderately decreased cell reduction capacity but did not affect plasma membrane integrity. Compared to cocaine, amphetamine highly decreased the mitochondrial membrane potential, as determined using the fluorescent probe rhodamine-123, whereas both drugs decreased mitochondrial cytochrome c. In contrast to amphetamine, cocaine cytotoxicity was partly mediated through effects on the electron transport chain, since cocaine toxicity was ameliorated in mitochondrial DNA-depleted cells lacking mitochondrially encoded electron transport chain subunits. Cocaine and amphetamine induced activation of caspases-2, -3 and -9 but did not affect activity of caspases-6 or -8. In addition, amphetamine, but not cocaine, was associated with the appearance of evident nuclear apoptotic morphology. These events were not accompanied by differences in the release of the apoptosis-inducing factor (AIF) from mitochondria. Our results demonstrate that although both amphetamine and cocaine activate the mitochondrial apoptotic pathway in cortical neurons, amphetamine is more likely to promote apoptosis.

Cellular and molecular mechanisms involved in the neurotoxicity of opioid and psychostimulant drugs

“…However, morphological features of apoptosis were not evident upon in vivo (Dietrich et al, 2005) or in vitro (Oliveira et al, 2002;Cunha-Oliveira et al, 2006a) exposure to cocaine, except in one study from Nassogne et al (1997). Cell death induced by cocaine in human neuronal progenitor cells, involving cytochrome c release, seems to be preceded by oxidative stress (Poon et al, 2007).…”

“…For more detailed explanation the reader is referred to the excellent review of Sulzer et al (2005). The weak base effect explains mitochondrial dysfunction induced by amphetamine in the absence of dopamine, due to disruption of mitochondrial potential (Cunha-Oliveira et al, 2006a), which may lead to a decrease in intracellular ATP (Oliveira et al, 2002).…”

“…been associated with the induction of biochemical features of apoptosis, such as activation of caspases (Dey et al, 2007;CunhaOliveira et al, 2006a;Imam et al, 2005;Oliveira et al, 2003;Mitchell and Snyder-Keller, 2003), loss of mitochondrial potential and cytochrome c release Cunha-Oliveira et al, 2006a). However, morphological features of apoptosis were not evident upon in vivo (Dietrich et al, 2005) or in vitro (Oliveira et al, 2002;Cunha-Oliveira et al, 2006a) exposure to cocaine, except in one study from Nassogne et al (1997).…”

“…Moreover, cocaine has been described to activate the mitochondrial apoptotic pathway (see Table 6). Cocaine seems to be less toxic than amphetamine, and in most studies apoptotic neurons were not observed upon exposure to cocaine (Dietrich et al, 2005;Cunha-Oliveira et al, 2006a;Oliveira et al, 2002). The differential effects of cocaine and amphetamine may be explained by the fact that these drugs have distinct effects in the mitochondria, as assessed by using NT-2 rho zero (depleted of mitochondrial DNA) versus NT-2 rho plus cells (CunhaOliveira et al, 2006a).…”

“…The activation of caspases upon amphetamine exposure has been reported in the rat frontal cortex (Warren et al, 2007) and medium spiny striatal neurons (Krasnova et al, 2005) of exposed animals, as well as in rat cortical neurons (Cunha-Oliveira et al, 2006a), rat cerebellar granule cells (Jimenez et al, 2004) and PC12 cells . Caspase activation mediated by D-amphetamine or methamphetamine has been suggested to be mediated by the mitochondrial apoptotic pathway, as indicated by the observation of cytochrome c release Jimenez et al, 2004), accompanied by a decrease in mitochondrial potential (Cunha-Oliveira et al, 2006a), and a decrease in Bcl-2/Bax levels (Krasnova et al, 2005;Imam et al, 2001). Moreover, Bcl-2 overexpression was shown to protect mesencephalic immortalized cells from methamphetamine-induced apoptosis (Cadet et al, 1997).…”