Magnesium reverses the LTP deficiency induced by ICV-STZ.

<p>Rats were divided into sham-operated control (Con), sham-operated plus 100 mg/kg magnesium control (Mg), and STZ ICV (STZ) or STZ ICV plus 100 mg/kg magnesium (STZ+Mg) groups. During the 3^rd week after ICV-STZ treatment, the hippocampal slices were prepared and an ideographic electrophysiology recording set-up with a stimulating electrode and recording electrode were placed in the CA3 and CA1 regions (A). The representative analog traces of evoked potentials before (solid line) and after (broken line) high-frequency stimulation (HFS) were recorded (B). Normalized field excitatory postsynaptic potential (fEPSP) slopes were measured in four groups (C), and the relative ratio of fEPSP increments after HFS (D) was calculated. Data were presented as means ± SD. *<i>P</i><0.05 versus the control group, <i>#P</i><0.05 versus the STZ group.</p

Magnesium reverses ICV-STZ-induced dendritic spines and synapse impairments.

<p>Rats were divided into sham-operated control (Con), sham-operated plus 100 mg/kg magnesium control (Mg), STZ ICV (STZ) or STZ ICV plus 100 mg/kg magnesium (STZ+Mg) groups and treated as shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0108645#pone-0108645-g001" target="_blank">Figure 1A</a>. The representative morphology alterations of neurons in the hippocampal CA1 regions were displayed by Golgi staining. Representative photomicrographs of primary dendrites in the hippocampal CA1 region were shown (A). Quantification of dendrite number (B) and mushroom-type dendrites (C) were calculated. The number of dendritic branches and mushroom percentage in the hippocampus of ICV-STZ-treated rats decreased markedly, and supplement of magnesium almost fully reversed the dendritic complexity. Data were presented as means ± SD. *<i>P</i><0.05 versus the control group, <i>#P</i><0.05 versus the STZ group.</p

Intraperitoneal supplementation of magnesium rescues ICV-STZ-induced learning and memory deficits with elevation of brain magnesium level.

<p>The experiments were designed as shown in panel A. Rats were divided into six groups, i.e., sham-operated control (Con), sham-operated plus 100 mg/kg magnesium control (Mg), STZ ICV (STZ), STZ ICV plus 50 mg/kg magnesium (STZ+Mg50), STZ ICV plus 100 mg/kg magnesium (STZ+Mg100) and STZ ICV plus 200 mg/kg magnesium (STZ+Mg200) groups, as described in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0108645#s2" target="_blank">Methods</a>. During the 3^rd week after ICV-STZ treatment, the rats were trained in Morris watwe maze for six consecutive days to measure the learning capacity, and memory was tested on the 7^th day via removal of the hidden platform. The escape latencies to find the hidden platform were recorded daily (B). For the memory test, the time spent in the target quadrant (C), the swimming tracks (D) and numbers of crossings (E) in the target quadrant were calculated. The rats were sacrificed after the behavioral tests, and the magnesium levels in the cerebral cortex (F) and hippocampus (G) were measured. Data were presented as means ± SD. *<i>P</i><0.05 versus the control group, <i>#P</i><0.05 versus the STZ group.</p

Magnesium Protects Cognitive Functions and Synaptic Plasticity in Streptozotocin-Induced Sporadic Alzheimer’s Model

<div><p>Alzheimer’s disease (AD) is characterized by profound synapse loss and impairments of learning and memory. Magnesium affects many biochemical mechanisms that are vital for neuronal properties and synaptic plasticity. Recent studies have demonstrated that the serum and brain magnesium levels are decreased in AD patients; however, the exact role of magnesium in AD pathogenesis remains unclear. Here, we found that the intraperitoneal administration of magnesium sulfate increased the brain magnesium levels and protected learning and memory capacities in streptozotocin-induced sporadic AD model rats. We also found that magnesium sulfate reversed impairments in long-term potentiation (LTP), dendritic abnormalities, and the impaired recruitment of synaptic proteins. Magnesium sulfate treatment also decreased tau hyperphosphorylation by increasing the inhibitory phosphorylation of GSK-3β at serine 9, thereby increasing the activity of Akt at Ser473 and PI3K at Tyr458/199, and improving insulin sensitivity. We conclude that magnesium treatment protects cognitive function and synaptic plasticity by inhibiting GSK-3β in sporadic AD model rats, which suggests a potential role for magnesium in AD therapy.</p></div

Magnesium suppresses GSK-3β with no effect on PP2A in the hippocampus of ICV-STZ-treated rats.

<p>Rats were divided into sham-operated control (Con), sham-operated plus 100 mg/kg magnesium control (Mg), STZ ICV (STZ) or STZ ICV plus 100 mg/kg magnesium (STZ+Mg) groups and treated as shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0108645#pone-0108645-g001" target="_blank">Figure 1A</a>. The total GSK-3β, GSK-3β (Ser9), GSK-3β (Tyr216), total PP2A and PP2A (pY307) levels in whole hippocampus extracts were measured using Western blotting (A, C) and quantitative analysis (B, D). The level of p-GSK-3β (Ser9) was significantly decreased in ICV-STZ-treated rats, and magnesium supplementation restored the levels. No alterations in total GSK-3β, p-GSK-3β (Y216), total PP2A and PP2A (pY307) levels were detected in these groups. Data were presented as means ± SD. *<i>P</i><0.05 versus the control group, <i>#P</i><0.05 versus the STZ group.</p

Magnesium prevents tau hyperphosphorylation in the hippocampus of ICV-STZ-treated rats.

<p>Rats were divided into sham-operated control (Con), sham-operated plus 100 mg/kg magnesium control (Mg), STZ ICV (STZ) or STZ ICV plus 100 mg/kg magnesium (STZ+Mg) groups and treated as shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0108645#pone-0108645-g001" target="_blank">Figure 1A</a>. The levels of total tau (tau-5) and phosphorylated tau at Thr205, Thr231, Ser396, and Ser404 in whole hippocampus extracts were measured using Western blotting (A) and quantitative analysis (B). The accumulation of Tau214 in the hippocampus neuron was detected using immunohistochemistry (C). The phosphorylation levels of tau at Thr205, Thr231, Ser396 and Ser404 sites increased significantly in the hippocampus of ICV-STZ-treated rats, while supplementation of magnesium attenuated tau hyperphosphorylation. The level of the total tau probed by tau-5 did not change. Attenuation of the STZ-induced tau hyperphosphorylation at Ser214 by magnesium was also detected using immunohistochemistry. Data were presented as means ± SD. *<i>P</i><0.05 versus the control group, <i>#P</i><0.05 versus the STZ group.</p

Magnesium increases synaptic proteins in the hippocampus of ICV-STZ-treated rats.

<p>Rats were divided into sham operated control (Con), sham operated plus 100 mg/kg magnesium control (Mg), STZ ICV (STZ) or STZ ICV plus 100 mg/kg magnesium (STZ+Mg) groups and treated as shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0108645#pone-0108645-g001" target="_blank">Figure 1A</a>. The levels of presynaptic and postsynaptic proteins in whole hippocampal extracts were measured using Western blotting (A) and quantitative analysis (B). The expression of synapsin I, PSD95, PSD93, GluR1 and GluR2 was significantly reduced in the hippocampus of ICV-STZ-treated rats, while supplementation of magnesium restored the levels. Levels of synaptophysin, NR2A and NR2B were not significantly changed. Data were presented as means ± SD. *<i>P</i><0.05 versus the control group, <i>#P</i><0.05 versus the STZ group.</p

Magnesium stimulates the activity of Akt and PI3K in the hippocampus of ICV-STZ-treated rats.

<p>Rats were divided into sham-operated control (Con), sham-operated plus 100 mg/kg magnesium control (Mg), STZ ICV (STZ) or STZ ICV plus 100 mg/kg magnesium (STZ+Mg) groups and treated as shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0108645#pone-0108645-g001" target="_blank">Figure 1A</a>. The total Akt, Akt (Thr308), Akt (Ser473), total PI3K and PI3K (Tyr458/199) levels in whole hippocampus extracts were measured using Western blotting (A, C) and quantitative analysis (B, D), respectively. The p-Akt (Ser473) and p-PI3K (Tyr458/199) levels decreased significantly in ICV-STZ-treated rats, and these changes were fully restored by magnesium supplement. There was no change in total Akt, Akt (Thr308) and PI3K. Data were presented as means ± SD. *<i>P</i><0.05 versus the control group, <i>#P</i><0.05 versus the STZ group.</p

Additional file 1 of Targeting vulnerable microcircuits in the ventral hippocampus of male transgenic mice to rescue Alzheimer-like social memory loss

Additional file 1: Materials and methods. Table S1 Virus strains and their applications. Table S2. Antibody list. Fig. S1 A realistic picture for the social memory test. Fig. S2 Schematic representation of the dissection of vCA1 and dCA1. Fig. S3 Prominent accumulation of hyper-phosphorylated tau (p-Tau, AT8) in the ventral hippocampal CA1 (vCA1) of 3xTg-AD mice. Fig. S4 Accumulation of hyper-phosphorylated tau (p-Tau) in the vCA1 of 3-month-old female P301L and 8-month-old male P301S mice. Fig. S5 Differential proteins detected in the ventral hippocampal CA1 (vCA1) and dorsal hippocampal CA1 (dCA1) in WT and P301L mice. Fig. S6 Number of differentially phosphorylated proteins/sites detected in the ventral hippocampal CA1 (vCA1) and dorsal hippocampal CA1 (dCA1) in WT and P301L mice. Fig. S7 Male 3xTg-AD and P301L mice displayed social memory deficits. Fig. S8 Injection sites of AAV-hSyn-hTau-eGFP virus into the vCA1. Fig. S9 Overexpression hTau in vCA1 has no effect on anxiety-like behaviors. Fig. S10 Tau accumulation in the dCA1 has no effect on social memory. Fig. S11 Hyper-phosphorylated tau (p-Tau) is accumulated in excitatory and PV neurons of 3xTg-AD mice. Fig. S12 hTau accumulation increases the action potential threshold of CaMKII+ and PV+ neurons in the vCA1. Fig. S13 No transmission of hTau occurs from excitatory neurons (CaMKII+) to PV neurons in vCA1-hTauCaMKII mice. Fig. S14 hTau overexpression in PV or excitatory neurons does not affect the electrophysiological properties of excitatory or PV neurons. Fig. S15 Quantitative analysis of co-location of GCaMP6f and hTau in excitatory and PV neurons. Fig. S16 Tau accumulation has no effects on eGFP signals of CaMKII and PV neurons during bouts of social interaction. Fig. S17 Accumulation of vCA1-hTauPV disinhibits excitatory neurons during novel conspecific identification. Fig. S18 Accumulation of vCA1-hTauPV has no effect on eGFP signals of CaMKII neurons during bouts of social interaction. Fig. S19 ChR2 is highly expressed in excitatory and PV neurons. Fig. S20 Photostimulation of excitatory neurons during social exploration has no improvement on social discrimination in vCA1-hTauCaMKII mice. Fig. S21 Photoactivation of excitatory and PV neurons expressing eYFP had no effects on tau-impaired social memory. Fig. S22 Photoactivation of excitatory neurons in physical condition at different rhythm has no improvements on social memory. Fig. S23 Photoactivation of PV neurons in physical condition at different rhythm has no improvements on social memory. Fig. S24 Ursolic acid (UA) at 30 μmol/L effectively reduces pathological tau without changing tau mRNA. Fig. S25 CCK-8 assay on cytotoxicity of UA in HEK293-hTau cells. Fig. S26 Low-dose UA treatment remarkably reduces tau load and ameliorates social memory deficits in vCA1-tau mice. Fig. S27 Low-dose UA treatment has no toxic effect on social memory in C57BL/6 mice. Fig. S28 Low-dose UA treatment improves the excitability of excitatory and PV neurons in vCA1-hTau mice