Down-regulation of Homer1b/c protects against chemically induced seizures through inhibition of mTOR signaling.

BACKGROUND: Homer is a family of post synaptic density proteins functionally and physically attached to target proteins at proline-rich sequences. Reducing Homer1b/c expression has been shown in previous studies to be protective against excitotoxic insults, implicating Homer1b/c in the physiological regulation of aberrant neuronal excitability. METHODS: To test the efficacy of a Homer1b/c reducing therapy for disorders with a detrimental hyperexcitability profile in mice, we used small interfere RNA (siRNA) to decrease endogenous Homer1b/c expression in mouse hippocampus. The baseline motor and cognitive behavior was measured by sensorimotor tests, Morris water maze and elevated plus maze tasks. The anti-epileptic effects of Homer1b/c knockdown were determined in two chemically induced seizure models induced by Picrotoxin (PTX) or pentylenetetrazole (PTZ) administration. RESULTS: The results of sensorimotor tests, Morris water maze and elevated plus maze tasks showed that Homer1b/c reduction had no effect on baseline motor or cognitive behavior. In two chemically induced seizure models, mice with reduced Homerb/c protein had less severe seizures than control mice. Total Homer1b/c protein levels and seizure severity were highly correlated, such that those mice with the most severe seizures also had the highest levels of Homer1b/c. In addition, the phosphorylation of mammalian target of rapamycin (mTOR) and its target protein S6 was significantly inhibited in Homer1b/c down-regulated mice. Homer1b/c knockdown-induced inhibition of mTOR pathway was partially ablated by the metabotropic glutamate receptor 5 (mGluR5) agonist CHPG. CONCLUSION: Our results demonstrate that endogenous Homer1b/c is integral for regulating neuronal hyperexcitability in adult animals and suggest that reduction of Homer1b/c could protect against chemically induced seizures through inhibition mTOR pathway.

Dynamin-related protein 1 inhibitors protect against ischemic toxicity through attenuating mitochondrial Ca2+ uptake from endoplasmic reticulum store in PC12 cells.

Intracellular calcium homeostasis disorder and mitochondrial dysfunction are involved in many acute and chronic brain diseases, including ischemic brain injury. An imbalance in mitochondrial fission and fusion is one of the most important structural abnormalities found in a large number of mitochondrial dysfunction related diseases. Here, we investigated the effects of mitochondrial division inhibitor A (mdivi A) and mdivi B, two small molecule inhibitors of mitochondrial fission protein dunamin-related protein 1 (Drp-1), in neuronal injury induced by oxygen-glucose deprivation (OGD) in PC12 cells. We found that mdivi A and mdivi B inhibited OGD-induced neuronal injury through attenuating apoptotic cell death. These two inhibitors also preserved mitochondrial function, as evidenced by reduced reactive oxygen species (ROS) generation and cytochrome c release, as well as prevented loss of mitochondrial membrane potential (MMP). Moreover, mdivi A and mdivi B significantly suppressed mitochondrial Ca(2+) uptake, but had no effect on cytoplasmic Ca(2+) after OGD injury. The results of calcium imaging and immunofluorescence staining showed that Drp-1 inhibitors attenuated endoplasmic reticulum (ER) Ca(2+) release and prevented ER morphological changes induced by OGD. These results demonstrate that Drp-1 inhibitors protect against ischemic neuronal injury through inhibiting mitochondrial Ca(2+) uptake from the ER store and attenuating mitochondrial dysfunction.

Identification of metabolite biomarkers for L-DOPA-induced dyskinesia in a rat model of Parkinson's disease by metabolomic technology.

L-DOPA-induced dyskinesia (LID) is a frequent complication of chronic L-DOPA therapy in the clinical treatment of Parkinson's disease (PD). The pathogenesis of LID involves complex molecular mechanisms in the striatum. Metabolomics can shed light on striatal metabolic alterations in LID. In the present study, we compared metabolomics profiles of striatum tissue from Parkinsonian rats with or without dyskinetic symptoms after chronic L-DOPA administration. A liquid chromatography-mass spectrometry based global metabolomics method combined with multivariate statistical analyses were used to detect candidate metabolites associated with LID. 36 dysregulated metabolites in the striatum of LID rats, including anandamide, 2-arachidonoylglycerol, adenosine, glutamate and sphingosine1-phosphate were identified. Furthermore, IMPaLA metabolite set analysis software was used to identify differentially regulated metabolic pathways. The results showed that the metabolic pathways of "Retrograde endocannabinoid signaling", "Phospholipase D signaling pathway", "Glycerophospholipid metabolism" and "Sphingolipid signaling", etc. were dysregulated in LID rats compared to non-LID controls. Moreover, integrated pathway analysis based on results from the present metabolomics and our previous gene expression data in LID rats further demonstrates that aberrant "Retrograde endocannabinoid signaling" pathway might be involved in the development of LID. The present results provide a new profile for the understanding of the pathological mechanism of LID.

Exendin-4, a glucagon-like peptide 1 receptor agonist, protects against amyloid-ß peptide-induced impairment of spatial learning and memory in rats.

Type 2 diabetes mellitus (T2DM) and Alzheimer's disease (AD) share specific molecular mechanisms, and agents with proven efficacy in one may be useful against the other. The glucagon-like peptide-1 (GLP-1) receptor agonist exendin-4 has similar properties to GLP-1 and is currently in clinical use for T2DM treatment. Thus, this study was designed to characterize the effects of exendin-4 on the impairment of learning and memory induced by amyloid protein (Aß) and its probable molecular underlying mechanisms. The results showed that (1) intracerebroventricular (i.c.v.) injection of Aß1-42 resulted in a significant decline of spatial learning and memory of rats in water maze tests; (2) pretreatment with exendin-4 effectively and dose-dependently protected against the Aß1-42-induced impairment of spatial learning and memory; (3) exendin-4 treatment significantly decreased the expression of Bax and cleaved caspase-3 and increased the expression of Bcl2 in Aß1-42-induced Alzheimer's rats. The vision and swimming speed of the rats among all groups in the visible platform tests did not show any difference. These findings indicate that systemic pretreatment with exendin-4 can effectively prevent the behavioral impairment induced by neurotoxic Aß1-42, and the underlying protective mechanism of exendin-4 may be involved in the Bcl2, Bax and caspase-3 pathways. Thus, the application of exendin-4 or the activation of its signaling pathways may be a promising strategy to ameliorate the degenerative processes observed in AD.

[Diffusion characteristics of subcortical structures in patients with subcortical ischemic vascular disease and its correlation to cognitive function].

OBJECTIVE: To explore the diffusion-tensor imaging (DTI) characteristics of normal-appearing white matter (NAWM) and normal-appearing gray matter (NAGM) on conventional magnetic resonance imaging (MRI) in patients with subcortical ischemic vascular disease (SIVD) and examine the relation of such features with the general cognitive function of the patients. METHODS: DTI was performed in 46 SIVD patients and 34 age-matched control subjects with normal MRI findings. The apprarent diffusion coeeficient (ADC) and fractional anisotropy (FA) were measured within the regions of white matter lesions (WMLs), NAWM and NAGM. All the subjects were examined by neurologists with MMSE and clinical neurologic examination. RESULTS: Compared with normal controls, SIVD subjects showed increased ADC values in the subcortical NAGM and NAWM in anterior periventricular and centrum semiovale, with decreased FA values in the caudate nucleus, thalamus and centrum semiovale. An increased severity of the WMLs was associated with increased ADC and decreased FA in the NAWM of SIVD patients. After controlling for age, the ADC in the NAWM of the posterior periventricular, NAWM and WMLs in the centrum semiovale, caudate nucleus and thalamus showed significant inverse correlations to MMSE; FA values in NAWM of the anterior periventricular and WMLs of the centrum semiovale were positively correlated to MMSE. CONCLUSION: In SIVD patients, the NAWM and NAGM regions shown by MRI contain diffusion abnormalities, and these abnormalities shown by DTI are significantly correlated to the general cognitive function of the patients.

[Effect of Shuanghuanglian injection on cerebral nuclear factor-kappaB expression in mice with viral encephalitis].

OBJECTIVE: To observe the effect of Shuanghuanglian injection on cerebral expression of nuclear factor-kappaB (NF-kappaB) in mice with viral encephalitis. METHODS: The mice with experimental viral encephalitis received treatment with Shuanghuanglian injection at the dose of 0.2, 1.5, and 5 for 5, 10 or 20 consecutive days. The total RNA of the brain tissue was extracted to analyze the protein and mRNA expression of NF-kappaB using Western blotting and RT-PCR, respectively. RESULTS: Compared with the control group, the mice with experimental viral encephalitis showed significantly increased protein and mRNA expressions of NF-kappaB (P<0.01). Treatment with Shuanghuanglian injection at the doses of 0.2 and 1.5 mg/kg significantly lowered NF-kappaB protein and mRNA expressions in the brain of mice with viral encephalitis (P<0.05), and the effect was even more obvious at the dose of 5 mg/kg (P<0.01). CONCLUSION: Shuanghuanglian injection can reduce the expression of NF-kappaB in the brain of mice with viral encephalitis in a dose- and time-dependent manner.