Afobazole Modulates Neuronal Response to Ischemia and Acidosis via Activation of σ-1 Receptors

Abstract

Afobazole is an anxiolytic medication that has been previously shown to be neuroprotective both in vitro and in vivo. However, the mechanism(s) by which afobazole can enhance neuronal survival remain poorly understood. Experiments were carried out to determine whether afobazole can decrease intracellular calcium overload associated with ischemia and acidosis and whether the effects of afobazole are mediated via interaction of the compound with receptors. Fluorometric Ca 2ϩ imaging was used to resolve how application of afobazole affects intracellular Ca 2ϩ handling in cortical neurons. Application of afobazole significantly depressed, in a concentration-dependent and reversible manner, the intracellular Ca 2ϩ overload resulting from in vitro ischemia and acidosis. The IC 50 for afobazole inhibition of ischemia-evoked intracellular Ca 2ϩ overload was considerably less than that for the inhibition of [Ca 2ϩ ] i increases induced by acidosis. However, afobazole maximally inhibited only 70% of the ischemia-evoked intracellular Ca 2ϩ overload but effectively abolished intracellular Ca 2ϩ increases produced by acidosis. The effects of afobazole on ischemia-and acidosis-induced intracellular Ca 2ϩ dysregulation were inhibited by preincubating the neurons in the irreversible, pan-selective -receptor antagonist, metaphit. Moreover, the effects of afobazole on intracellular Ca 2ϩ increases triggered by acidosis and ischemia were blocked by the selective -1-receptor antagonists, BD 1063 and BD 1047, respectively. Experiments examining the effects of afobazole on neuronal survival in response to ischemia showed that afobazole was neuroprotective. Taken together, these data suggest that afobazole regulates intracellular Ca 2ϩ overload during ischemia and acidosis via activation of -1 receptors. This mechanism is probably responsible for afobazole-mediated neuroprotection.

Afobazole Activation of σ-1 Receptors Modulates Neuronal Responses to Amyloid-β25–35

“…Incubation in the s-1-receptor antagonist BD-1047 reduced the effects of afobazole by ∼40%. The concentration and degree of block reported here is consistent with previous studies showing BD-1047 inhibition of s-1-receptor-mediated effects in cortical neurons and retinal ganglion cells (Katnik et al, 2006, Cuevas et al, 2011a, Mueller et al, 2013. The lack of involvement of s-2 receptors is confirmed by results obtained using the s-2 receptor antagonist rimcazole .…”

“…Unlike ANAVEX2-73, afobazole does not interact with muscarinic receptors (Seredenin and Voronin, 2009). Activation of s-1 receptors by afobazole results in a decrease in ischemia-induced Ca 21 overload, which is due in part to inhibition of NMDA channel activation (Katnik et al, 2006, Cuevas et al, 2011a. Previous studies have suggested other mechanisms for the neuroprotective properties of afobazole, including decreased caspase-3 activation and reduced oxidative stress (Zenina et al, 2005, Antipova et al, 2010.…”

“…Surprisingly, a second pan-selective s receptor agonist, DTG, failed to mimic the effects of afobazole on Ab 25-35 -evoked [Ca 21 ] i perturbation. DTG and afobazole both block acidosis-and ischemia-induced Ca 21 overload in neurons to a similar extent (Cuevas et al, 2011a). It was shown that ischemia-induced [Ca 21 ] i increases were due primarily to Ca 21 influxes through voltage-gated Ca 21 channels and NMDA receptors which were regulated by s receptor activation (Katnik et al, 2006 …”

In Vitro Evaluation of Guanidine Analogs as Sigma Receptor Ligands for Potential Anti-Stroke Therapeutics

“…Recent studies have shown that activation of s receptors inhibit acidosis-evoked [Ca 21 ] i overload (Herrera et al, 2008;Cuevas et al, 2011a). Experiments were conducted to determine whether migration or removal of the methyl moiety would alter the ability of the o-DTG derivatives to inhibit acidevoked elevations in [Ca 21 ] i .…”

Study of fabomotizole belonging to p-glycoprotein substrates

“…Кроме того, проникновение фабомо-тизола через гематоэнцефалический барь-ер, где активно функционирует данный транспортер, будет достаточным для дос-тижения минимальной терапевтической концентрации в ткани мозга, даже несмот-ря на его индукцию в условиях дефицита кислорода [6,10]. Это подтверждается ре-зультатами многочисленных исследований эффективности фабомотиазола в качестве анксиолитика и нейропротектора [13,14]. Вывод В эксперименте in vivo на кроликах породы Шиншилла установлено, что фа-бомотизол не является субстратом белка-транспортера гликопротеина-P. …”