Neuroprotective Effects of Ferrostatin and Necrostatin Against Entorhinal Amyloidopathy-Induced Electrophysiological Alterations Mediated by voltage-gated Ca2+ Channels in the Dentate Gyrus Granular Cells.

Alzheimer's disease (AD) is a progressive neurodegenerative disease that is the main form of dementia. Abnormal deposition of amyloid-beta (Aß) peptides in neurons and synapses cause neuronal loss and cognitive deficits. We have previously reported that ferroptosis and necroptosis were implicated in Aß25-35 neurotoxicity, and their specific inhibitors had attenuating effects on cognitive impairment induced by Aß25-35 neurotoxicity. Here, we aimed to examine the impact of ferroptosis and necroptosis inhibition following the Aß25-35 neurotoxicity on the neuronal excitability of dentate gyrus (DG) and the possible involvement of voltage-gated Ca2+ channels in their effects. After inducing Aß25-35 neurotoxicity, electrophysiological alterations in the intrinsic properties and excitability were recorded by the whole-cell patch-clamp under current-clamp condition. Voltage-clamp recordings were also performed to shed light on the involvement of calcium channel currents. Aß25-35 neurotoxicity induced a considerable reduction in input resistance (Rin), accompanied by a profoundly decreased excitability and a reduction in the amplitude of voltage-gated calcium channel currents in the DG granule cells. However, three days of administration of either ferrostatin-1 (Fer-1), a ferroptosis inhibitor, or Necrostatin-1 (Nec-1), a necroptosis inhibitor, in the entorhinal cortex could almost preserve the normal excitability and the Ca2+ currents. In conclusion, these findings suggest that ferroptosis and necroptosis involvement in EC amyloidopathy could be a potential candidate to prevent the suppressive effect of Aß on the Ca2+ channel current and neuronal function, which might take place in neurons during the development of AD.

Role of amyloid beta (25-35) neurotoxicity in the ferroptosis and necroptosis as modalities of regulated cell death in Alzheimer's disease.

Neuronal cell death as a prominent pathological feature contributes to cognitive decline and memory loss in Alzheimer's disease. We investigated the role of two forms of cell death pathways, ferroptosis and necroptosis, and their interactions following entorhinal cortex (EC) amyloidopathy. The Aß25-35 was bilaterally injected into the rat's EC, and Morris Water Maze was applied to determine spatial performance one week after Aß injection. For evaluation of ferroptosis and necroptosis involvement in Aß induced pathology, ferroptosis inhibitor, Ferrostatin (Fer-1), and necroptosis inhibitor, Necrostatin (Nec-1), were injected into the EC during training days of behavioral test. Our behavioral and histological assessment showed spatial learning and memory impairment, along with neuropathology changes such as cell survival and intracellular Aß deposits in response to EC amyloidopathy, which were ameliorated by treatment with Fer-1 or Nec-1. The expression of ferroptosis key factors GPX4 and SLC7A11 were decreased and the level of TfR was increased following Aß toxicity. Also, Necroptosis pathway related factors RIP1, RIP3, and MLKL were modulated by Aß neurotoxicity. However, application of Fer-1 or Nec-1 could inhibit the hippocampal ferroptosis and necroptosis pathways due to EC amyloidopathy. Our data also demonstrated that Aß-induced necroptosis suppressed by Fer-1, although Nec-1 had no effect on ferroptosis, indicating that ferroptosis pathway is upstream of necroptosis process in the Aß neurotoxicity. Moreover, Aß induced hippocampal mGLUR5 overexpression and reduced level of STIM1/2 recovered by Fer-1 or Nec-1. According to our findings ferroptosis and necroptosis pathways are involved in Aß neurotoxicity through modulation of mGLUR5 and STIM1/2 signaling.

Phosphonate analog of 2-oxoglutarate regulates glutamate-glutamine homeostasis and counteracts amyloid beta induced learning and memory deficits in rats.

BACKGROUND: Metabolic alteration is a mainstream concept underlying the cognitive decline in neurodegenerative disorders including Alzheimer's disease (AD). Mitochondrial enzyme α-ketoglutarate dehydrogenase complex (α-KGDHC) seems to play a dual-edged sword role in cytotoxic insult. Here, using succinyl phosphonate (SP), a specific α-KGDHC inhibitor, we aimed to examine its potential action on AD progression. METHODS: Male Wistar rats were assigned to two separate experiments. First, they were bilaterally microinjected into the dorsal CA1 area by amyloid-beta (Aß)25-35 for four consecutive days. Seven days after the last injection, they were trained to acquire Morris Water Maze (MWM) task for three successive days when they were treated with SP after each training session. In the second experiment, SP was administered 30 min after the first Aß microinjection and behavioral tests were performed one week after the last Aß administration. The activity of glutamate dehydrogenase (GDH), and glutamine synthetase (GS), as key enzymes involved in glutamate-glutamine homeostasis and histological assays were evaluated in the hippocampi. RESULTS: Our behavioral results indicated that post-training SP treatment enhanced task acquisition but did not change memory performance in Aß-treated rats. However, administration of SP at the time of Aß injection precludes the deteriorative effect of Aß and neuronal injury on both spatial learning and memory performances indicating its preventive action against Aß pathology at its early stages. Measurement of enzymes activity shows that α-KGDHC activity was reduced in the Aß treated group, and SP administration restored its activity; also, GDH and GS activities were increased and decreased respectively due to Aß, and SP reversed the action of Aß on these enzymes. CONCLUSIONS: This study proposes that SP possibly a promising therapeutic approach to improve memory impairment in AD, especially in the early phases of this disease.

Protective effects of Vitex agnus-castus in ovariectomy mice following permanent middle cerebral artery occlusion.

OBJECTIVES: Previous studies have indicated that phytoestrogens induce estrogenic as well as anti-inflammatory effects, and they are found in high abundance in the extracts of some herbs such as Vitex Agnus Castus (VAC). Therefore, we investigated the effect of VAC extract on ovariectomized mice after the induction of permanent middle cerebral artery occlusion (PMCAO) model. MATERIALS AND METHODS: In this study, 50 mice ranging from 25 to 35 g were divided into five experimental groups as follows: Control, VAC, Estrogen, Tamoxifen, and Tamoxifen-VAC. Animals were ovariectomized, and after 30 days of treatment, they were given PMCAO induction. Behavioral assessment (adhesive removal and wire hanging tests) was evaluated 24 hr, 48 hr, and one week after induction of stroke. The infarct volume, as well as serum levels of matrix metalloproteinase-9 (MMP-9) and interleukin-10 (IL-10), were measured one week after stroke. RESULTS: One week after stroke, in both VAC and estrogen groups, the infarct size reduced in comparison with the control group. Estrogen and VAC extract improved adhesive removal and wire hanging test, increased the level of IL-10, and decreased the level of MMP-9 compared with the control group. In addition, co-administration of tamoxifen and VCA extract had no significant effect on measured indices compared with control and tamoxifen groups. CONCLUSION: Based on our findings, VAC extract has neuroprotective properties and can reduce stroke injuries in PMCAO-induced ovariectomized mice via anti-inflammatory and estrogenic properties.

The effect of exercise preconditioning on stroke outcome in ovariectomized mice with permanent middle cerebral artery occlusion.

Exercise preconditioning has been shown to be effective in improving behavioral and neuropathological indices after cerebral ischemia. We evaluated the effect of exercise preconditioning, 17ß-estradiol, and their combination on stroke outcome using an experimental model of stroke in ovariectomized (OVX) mice. OVX mice were randomly assigned to 4 groups as follows: control (stroke), exercise (exercise and stroke), estradiol (17ß-estradiol and stroke), and exercise+estradiol (exercise and 17ß-estradiol and stroke). Exercise preconditioning was performed on a treadmill 5 days/week, 40 min/day, at a speed of 18 m/min for 4 weeks. 17ß-estradiol was gavaged (40 µg/kg per day) for 4 weeks. Stroke was induced by permanent middle cerebral artery occlusion (pMCAO), and neurological deficits were evaluated 1, 2, and 7 days after stroke. Then, the serum concentrations of matrix metalloproteinase-9 (MMP-9) and interleukin-10 (IL-10) and infarct volumes were assessed. Exercise preconditioning and 17ß-estradiol induced a better outcome compared with the control ischemic mice, which was manifested by decrease in MMP-9, increase in IL-10, diminished infarct volume, and improved neurological deficits. Concomitant administration of 17ß-estradiol and exercise also significantly improved these parameters. Exercise preconditioning or administration of 17ß-estradiol alone or in combination before pMCAO induced significant neuroprotection in OVX mice.