Ouabain inhibitor rostafuroxin attenuates dextromethorphan-induced manic potential.

Dextromethorphan (DM) abuse produces mania-like symptoms in humans. ERK/Akt signaling activation involved in manic potential can be attenuated by the inhibition of ouabain-like cardiac steroids. In this study, increased phosphorylations of ERK/Akt and hyperlocomotion induced by DM (30 mg/kg, i.p./day × 7) were significantly protected by the ouabain inhibitor rostafuroxin (ROSTA), suggesting that DM induces the manic potential. ROSTA significantly attenuated DM-induced protein kinase C δ (PKCδ) phosphorylation, GluN2B (i.e., MDA receptor subunit) expression, and phospho-PKCδ/GluN2B interaction. DM instantly upregulated the nuclear factor erythroid-2-related factor 2 (Nrf2)-dependent system. However, DM reduced Nrf2 nuclear translocation, Nrf2 DNA binding activity, γ-glutamylcysteine mRNA expression, and subsequent GSH/GSSG level and enhanced oxidative parameters following 1-h of administration. ROSTA, PKCδ inhibitor rottlerin, and GluN2B inhibitor traxoprodil significantly attenuated DM-induced alterations in Nrf2-related redox parameters and locomotor activity induced by DM in wild-type mice. Importantly, in PKCδ knockout mice, DM failed to alter the above parameters. Further, ROSTA and traxoprodil also failed to enhance PKCδ depletion effect, suggesting that PKCδ is a critical target for the anti-manic potential of ROSTA or GluN2B antagonism. Our results suggest that ROSTA inhibits DM-induced manic potential by attenuating ERK/Akt activation, GluN2B/PKCδ signalings, and Nrf2-dependent system.

5-HT1A receptor agonist 8-OH-DPAT induces serotonergic behaviors in mice via interaction between PKCδ and p47phox.

Serotonin syndrome is an adverse reaction due to increased serotonin (5-hydroxytryptophan: 5-HT) concentrations in the central nervous system (CNS). The full 5-HT1A receptor (5-HT1AR) agonist (±)-8-hydroxy-dipropylaminotetralin (8-OH-DPAT) has been recognized to elicit traditional serotonergic behaviors. Treatment with 8-OH-DPAT selectively increased PKCδ expression out of PKC isoforms and 5-HT turnover rate in the hypothalamus of wild-type mice. Treatment with 8-OH-DPAT resulted in oxidative burdens, co-immunoprecipitation of 5-HT1AR and PKCδ, and phosphorylation and membrane translocation of p47phox. Importantly, p47phox also interacted with 5-HT1AR or PKCδ in the presence of 8-OH-DPAT. Consistently, the interaction and oxidative burdens were attenuated by 5-HT1AR antagonism (i.e., WAY100635), PKCδ inhibition (i.e., rottlerin and genetic depletion of PKCδ), or NADPH oxidase/p47phox inhibition (i.e., apocynin and genetic depletion of p47phox). However, WAY100635, apocynin, or rottlerin did not exhibit any additive effects against the protective effect by inhibition of PKCδ or p47phox. Furthermore, apocynin, rottlerin, or WAY100635 also significantly protected from pro-inflammatory/pro-apoptotic changes induced by 8-OH-DPAT. Therefore, we suggest that 8-OH-DPAT-induced serotonergic behaviors requires oxidative stress, pro-inflammatory, and pro-apoptotic changes, that PKCδ or p47phox mediates the serotonergic behaviors induced by 8-OH-DPAT, and that the inhibition of PKCδ-dependent p47phox activation is critical for protecting against serotonergic behaviors.