N-(3-Ethoxy-phenyl)-4-pyrrolidin-1-yl-3-trifluoromethyl-benzamide (EPPTB) prevents 3-iodothyronamine (T1AM)-induced neuroprotection against kainic acid toxicity

Abstract

Thyroid hormone and thyroid hormone metabolites, including 3-iodothyronamine (T1AM) and 3-iodothyroacetic acid (TA1), activate AKT signaling in hippocampal neurons affording protection from excitotoxic damage. We aim to explore whether the mechanism of T1AM neuroprotection against kainic acid (KA)-induced excitotoxicity included the activation of the trace amine associated receptor isoform 1 (TAAR1), one of T1AM targets. Rat organotypic hippocampal slices were exposed to vehicle (Veh) or to 5 μM kA for 24 h in the absence or presence of 0.1, 1 and 10 μM T1AM or to 0.1, 1 and 10 μM T1AM and 1 μM N-(3-Ethoxy-phenyl)-4-pyrrolidin-1yl-3-trifluoromethyl-benzamide (EPPTB), the only available TAAR1 antagonist, or to 1 μM T1AM in the absence or in the presence of 10 μM LY294002, an inhibitor of phosphoinositide 3-kinases (PI3Ks). Cell death was evaluated by measuring propidium iodide (PI) levels of fluorescence 24 h after treatment. In parallel, the expression levels of p-AKT and p-PKA were evaluated by Western blot analysis of slice lysates. The activity of mitochondrial monoamine oxidases (MAO) was assayed fluorimetrically. 24 h exposure of slices to T1AM resulted in the activation of AKT and PKA. KA exposure induced cell death in the CA3 region and significantly reduced p-AKT and p-PKA levels. The presence of 1 and 10 μM T1AM significantly protected neurons from death and conserved both kinase levels with the essential role of AKT in neuroprotection. Furthermore, EPPTB prevented T1AM-induced neuroprotection, activation of PKA and AKT. Of note, in the presence of EPPTB T1AM degradation by MAO was reduced. Our results indicate that the neuroprotection offered by T1AM depends, as for TA1, on AKT activation but do not allow to conclusively indicate TAAR1 as the target implicated.

Enhanced Neuroprotective Effects of Panax ginseng G115® and Ginkgo biloba GK501® Combinations In Vitro Models of Excitotoxicity

“…Activation of these pathways may, in part, increase the ability of neuronal cells to survive toxic insults such as the excitotoxic treatment that was mimicked by exposing hippocampal slices to NMDA and kainic acid. In this study, NMDA and kainic acid consistently induced death of neurons of the CA1 and CA3 regions of organotypic hippocampal slices, which correlated to the reduced hippocampal levels of p-Akt that we have previously observed [32] but also of p-Erk1/2. In the presence of the both extracts, NMDA- and kainate-induced cell death was reduced and, in parallel, the levels of p-Akt and p-Erk1/2 remained high in the hippocampus.…”

Neuroprotective Effects of Thymoquinone by the Modulation of ER Stress and Apoptotic Pathway in In Vitro Model of Excitotoxicity

“…The neuronal degeneration mediated by KA involves ER stress and the activation of ER sensors [45]. In organotypic hippocampal slices, KA induces a selective death in the CA3 region [27,28,46]. We observed that at a concentration of 10 or 20 µM, TQ was able to reduce neuronal damage induced by KA (Figure 2F).…”

“…KA triggers a delayed type of excitotoxic cell death in the CA3 area of organotypic hippocampal slices through activation of ionotropic glutamate receptors [27,28]. Additionally, it has been shown that KA induces cell death through caspases activation [29], increase expression of pro-apoptotic proteins, such as Bim and Bax, which lead to a decrease in the Bcl-2-Bad ratio, paralleled release of cytochrome c and cleavage of poly(ADP-ribose)polymerase (PARP) [30].…”

3-Iodothyronamine Affects Thermogenic Substrates’ Mobilization in Brown Adipocytes

“…When administered to rodents, T1AM induces neurological and metabolic effects similar, but also opposite to those induced by T3. Among these, T1AM activates neuroprotective signaling including the activation of the AKT and PKA signaling [2,3]; it stimulates neuronal plasticity [4,5] and induces central-mediated reduction of body temperature without activating the brown adipose tissue [6][7][8]. Most of the pharmacological effects of T1AM, including the effect on body temperature, have been described following acute administration of the amine.…”