Diazoxide induces delayed pre‐conditioning in cultured rat cortical neurons

Abstract

We investigated the effect of diazoxide on neuronal survival in primary cultures of rat cortical neurons against oxygenglucose deprivation (OGD). Diazoxide pre-treatment induced delayed pre-conditioning and almost entirely attenuated the OGD-induced neuronal death. Diazoxide inhibited succinate dehydrogenase and induced mitochondrial depolarization, free radical production and protein kinase C activation. The putative mitochondrial ATP-sensitive potassium channel blocker 5-hydroxydecanoate abolished the protective effect of diazoxide while the non-selective K ATP channel blocker glibenclamide did not. The non-selective K ATP channel openers nicorandil and cromakalim did not improve viability. Superoxide dismutase mimetic, M40401, or protein kinase C inhibitor, chelerythrine, prevented the neuroprotective effect of diazoxide. Diazoxide did not increase reduced glutathione and manganese-superoxide dismutase levels but we found significantly higher reduced glutathione levels in diazoxidepre-conditioned neurons after OGD. In pre-conditioned neurons free radical production was reduced upon glutamate stimulation. The succinate dehydrogenase inhibitor 3-nitropropionic acid also induced pre-conditioning and free radical production in neurons. Here, we provide the first evidence that diazoxide induces delayed pre-conditioning in neurons via acute generation of superoxide anion and activation of protein kinases and subsequent attenuation of oxidant stress following OGD. The succinate dehydrogenase-inhibiting effect of diazoxide is more likely to be involved in this neuroprotection than the opening of mitochondrial ATP-sensitive potassium channels.

Mitochondrial ATP-sensitive potassium channels enhance angiotensin-induced oxidative damage and dopaminergic neuron degeneration. Relevance for aging-associated susceptibility to Parkinson’s disease

“…When Δψ M is depressed, as occurs during ischemia or treatment with the complex I blocker rotenone, mitoK(ATP) opening may add a parallel K + conductance that counteracts the decrease in K + influx and matrix contraction that otherwise occur, and therefore mitoK(ATP) opening may maintain constant volume of the mitochondrial matrix and the intermembrane space (Bajgar et al 2001;Garlid et al 2003;Kowaltowski et al 2001). It is interesting to note that activation of mitoK(ATP) channels and ROS production lead to delayed protection against subsequent intense and potentially lethal insults such as ischemia by activation of adaptive cell responses in several types of cells (i.e., preconditioning; Kis et al 2003;Oldenburg et al 2002). Conversely, the present study shows that ROS induced by activation of mitoK (ATP) channels contribute to dopaminergic cell death.…”

Mitochondrial Complex II Prevents Hypoxic but Not Calcium- and Proapoptotic Bcl-2 Protein-induced Mitochondrial Membrane Potential Loss

“…In contrast to the organized electron flow by respiratory supercomplexes, mitochondrial complex II (succinate dehydrogenase) can function as an independent enzyme whose activity is limited only by substrate availability (25). However, inhibition of mitochondrial complex II also leads to mitochondrial depolarization (26,27) and mimics hypoxia in cells (28). As a result, the discrete roles of complex I and II in the establishment and maintenance of the ⌬⌿ m both under normoxic and hypoxic conditions are unclear.…”

Effects of Systemic Administration of Iptakalim on Extracellular Neurotransmitter Levels in the Striatum of Unilateral 6-Hydroxydopamine-Lesioned Rats

“…Opening of K ATP channels may result in the preservation of intracellular ATP production, hence, subsequently elevate activity of glutamate transporter. Moreover, activation of K ATP channels leads to almost immediate activation of protein kinase C (Kis et al, 2003). Activator of protein kinase C such as phorbol esters rapidly stimulates glutamate transporter activity (Davis et al, 1998;Dowd and Robinson, 1996;Yao et al, 2005).…”