Induction of the cell survival kinase Sgk1: A possible novel mechanism for α-phenyl-N-tert-butyl nitrone in experimental stroke

Polyfunctionalized α-Phenyl-tert-butyl(benzyl)nitrones: Multifunctional Antioxidants for Stroke Treatment

Nowadays, most stroke patients are treated exclusively with recombinant tissue plasminogen activator, a drug with serious side effects and limited therapeutic window. For this reason, and because of the known effects of oxidative stress on stroke, a more tolerable and efficient therapy for stroke is being sought that focuses on the control and scavenging of highly toxic reactive oxygen species by appropriate small molecules, such as nitrones with antioxidant properties. In this context, herein we report here the synthesis, antioxidant, and neuroprotective properties of twelve novel polyfunctionalized α-phenyl-tert-butyl(benzyl)nitrones. The antioxidant capacity of these nitrones was investigated by various assays, including the inhibition of lipid peroxidation induced by AAPH, hydroxyl radical scavenging assay, ABTS+-decoloration assay, DPPH scavenging assay, and inhibition of soybean lipoxygenase. The inhibitory effect on monoamine oxidases and cholinesterases and inhibition of β-amyloid aggregation were also investigated. As a result, (Z)-N-benzyl-1-(2-(3-(piperidin-1-yl)propoxy)phenyl)methanimine oxide (5) was found to be one of the most potent antioxidants, with high ABTS+ scavenging activity (19%), and potent lipoxygenase inhibitory capacity (IC50 = 10 µM), selectively inhibiting butyrylcholinesterase (IC50 = 3.46 ± 0.27 µM), and exhibited neuroprotective profile against the neurotoxicant okadaic acid in a neuronal damage model. Overall, these results pave the way for the further in-depth analysis of the neuroprotection of nitrone 5 in in vitro and in vivo models of stroke and possibly other neurodegenerative diseases in which oxidative stress is identified as a critical player.

Inhibition of serum and glucocorticoid regulated kinases by GSK650394 reduced infarct size in early cerebral ischemia-reperfusion with decreased BBB disruption

Blood-brain barrier (BBB) disruption is one of the most important pathological changes following cerebral ischemia-reperfusion. We tested whether inhibition of the serum and glucocorticoid regulated kinase 1 (SGK1) would decrease BBB disruption and contribute to decreasing infarct size in the first few hours of cerebral ischemia-reperfusion within the thrombolysis therapy time window. After transient middle cerebral artery occlusion (MCAO), an SGK1 inhibitor GSK650394, or vehicle was administered into the lateral ventricle of rats. After one hour of MCAO and two hours of reperfusion, we determined BBB disruption using the transfer coefficient (K_i) of ¹⁴C-α-aminoisobutyric acid, and also determined infarct size, phosphorylation of NDRG1, and MMP2 protein level. Ischemia-reperfusion increased (+34%, p < 0.05) and GSK650394 decreased (-25%, p < 0.05) the K_i in the ischemic-reperfused cortex. GSK650394 decreased the percentage of cortical infarct (-31%, p < 0.001). At the same time GSK650394 reduced NDRG1 phosphorylation and MMP2 protein level in the ischemic-reperfused cortex suggesting that SGK1 was inhibited by GSK650394 and that lower MMP2 could be one of the mechanisms of decreased BBB disruption. Collectively our data suggest that GSK650394 could be neuroprotective and one of the mechanisms of the neuroprotection could be decreased BBB disruption. SGK1 inhibition within the thrombolysis therapy time window might reduce cerebral ischemia-reperfusion injury.

Intravenously delivered multilineage-differentiating stress enduring cells dampen excessive glutamate metabolism and microglial activation in experimental perinatal hypoxic ischemic encephalopathy

Perinatal hypoxic ischemic encephalopathy (HIE) results in serious neurological dysfunction and mortality. Clinical trials of multilineage-differentiating stress enduring cells (Muse cells) have commenced in stroke using intravenous delivery of donor-derived Muse cells. Here, we investigated the therapeutic effects of human Muse cells in an HIE model. Seven-day-old rats underwent ligation of the left carotid artery then were exposed to 8% oxygen for 60 min, and 72 hours later intravenously transplanted with 1 × 10⁴ of human-Muse and -non-Muse cells, collected from bone marrow-mesenchymal stem cells as stage-specific embryonic antigen-3 (SSEA-3)+ and -, respectively, or saline (vehicle) without immunosuppression. Human-specific probe revealed Muse cells distributed mainly to the injured brain at 2 and 4 weeks, and expressed neuronal and glial markers until 6 months. In contrast, non-Muse cells lodged in the lung at 2 weeks, but undetectable by 4 weeks. Magnetic resonance spectroscopy and positron emission tomography demonstrated that Muse cells dampened excitotoxic brain glutamatergic metabolites and suppressed microglial activation. Muse cell-treated group exhibited significant improvements in motor and cognitive functions at 4 weeks and 5 months. Intravenously transplanted Muse cells afforded functional benefits in experimental HIE possibly via regulation of glutamate metabolism and reduction of microglial activation.

Addition of Popular Exogenous Antioxidant Agent, PBN, to Culture Media May Be an Important Step to Optimization of Myogenic Stem/Progenitor Cell Preparation Protocol

The aim of the study was to modify human skeletal muscle-derived stem/progenitor cells (SkMDS/PCs) and demonstrate the optimal cell preparation protocol for application in post-infarction hearts. We used conditioned SkMDS/PC culture medium with α-phenyl-N-tert-butyl nitrone (PBN). SkMDS/PCs were cultured under hypoxic conditions and the results were compared to the standard ones. We observed a significant increase of CD-56 positive phenotypic marker the ability to form functional myotubes, increase in the proportion of young cells in cell primary suspensions, and a decrease in the percentage of apoptotic cells among PBN-conditioned cells in normoxia an hypoxia. We also observed significantly higher levels of SOD3 expression; maintained expression of SOD1, SOD2, and CAT; a higher level of BCL2 gene expression; and a rather significant decrease in Hsp70 gene expression in PBN-conditioned SkMDS/PCs compared to the WT population under hypoxic conditions. In addition, significant increase of myogenic genes expression was observed after PBN addition to culture medium, compared to WT population under hypoxia. Interestingly, PBN addition significantly increased the lengths of telomeres under hypoxia. Based on the data obtained, we can postulate that PBN conditioning of human SkMDS/PCs could be a promising step in improving myogenic cell preparation protocol for pro-regenerative treatment of post-infarction hearts.

SGK1.1 limits brain damage after status epilepticus through M current-dependent and independent mechanisms

Epilepsy is a neurological condition associated to significant brain damage produced by status epilepticus (SE) including neurodegeneration, gliosis and ectopic neurogenesis. Reduction of these processes constitutes a useful strategy to improve recovery and ameliorate negative outcomes after an initial insult. SGK1.1, the neuronal isoform of the serum and glucocorticoids-regulated kinase 1 (SGK1), has been shown to increase M-current density in neurons, leading to reduced excitability and protection against seizures. For this study, we used 4-5 months old male transgenic C57BL/6 J and FVB/NJ mice expressing near physiological levels of a constitutively active form of the kinase controlled by its endogenous promoter. Here we show that SGK1.1 activation potently reduces levels of neuronal death (assessed using Fluoro-Jade C staining) and reactive glial activation (reported by GFAP and Iba-1 markers) in limbic regions and cortex, 72 h after SE induced by kainate, even in the context of high seizure activity. This neuroprotective effect is not exclusively through M-current activation but is also directly linked to decreased apoptosis levels assessed by TUNEL assays and quantification of Bim and Bcl-x_L by western blot of hippocampal protein extracts. Our results demonstrate that this newly described antiapoptotic role of SGK1.1 activation acts synergistically with the regulation of cellular excitability, resulting in a significant reduction of SE-induced brain damage in areas relevant to epileptogenesis.

Ambient access to a new family of pyrrole-fused pyrazine nitrones via 2-carbonyl-N-allenylpyrroles

The chemo-, regio- and stereoselective synthesis of pyrrole-fused pyrazine nitrones via the direct reaction of 2-carbonyl-N-allenylpyrroles (readily accessible from the corresponding NH-pyrroles) with hydroxyl amine hydrochloride has been developed.