MicroRNA-365 Knockdown Prevents Ischemic Neuronal Injury by Activating Oxidation Resistance 1-Mediated Antioxidant Signals / 神经科学通报·英文版

MicroRNA-365 (miR-365) is upregulated in the ischemic brain and is involved in oxidative damage in the diabetic rat. However, it is unclear whether miR-365 regulates oxidative stress (OS)-mediated neuronal damage after ischemia. Here, we used a transient middle cerebral artery occlusion model in rats and the hydrogen peroxide-induced OS model in primary cultured neurons to assess the roles of miR-365 in neuronal damage. We found that miR-365 exacerbated ischemic brain injury and OS-induced neuronal damage and was associated with a reduced expression of OXR1 (Oxidation Resistance 1). In contrast, miR-365 antagomir alleviated both the brain injury and OXR1 reduction. Luciferase assays indicated that miR-365 inhibited OXR1 expression by directly targeting the 3'-untranslated region of Oxr1. Furthermore, knockdown of OXR1 abolished the neuroprotective and antioxidant effects of the miR-365 antagomir. Our results suggest that miR-365 upregulation increases oxidative injury by inhibiting OXR1 expression, while its downregulation protects neurons from oxidative death by enhancing OXR1-mediated antioxidant signals.

VEGF enhances reconstruction of neurovascular units in the brain after injury / 生理学报

Vascular endothelial growth factor (VEGF) was originally recognized as a substance predominantly with vascular permeability and angiogenesis. Recently, more and more evidence indicated that VEGF is expressed in the neurons of the developing and adult brains. Functional investigation demonstrated that VEGF shows several important effects on the neuronal development and physiological function. For example, VEGF accelerates the development of neurons and neural dendritic and axon growth. Besides, VEGF directly and acutely regulates the functions of multiple ion channels of the neuron membrane and changes neural excitability. In traumatic or ischemic injured brains, VEGF produces neuroprotection, enhances capacity of adult neurogenesis and transformation of astroglial cells into new neurons, which are fundamental basis for re-establishment of neural network. Based on the knowledge obtained from the literatures, we propose that VEGF may play very important roles in neural plasticity in the normal brain, and the reconstruction of neurovascular units and neural repair in the traumatic injured brain. This review mainly focuses on neural activity and repair roles of VEGF in adult mammalian brains. Further study on the mechanism of VEGF's neurobiological effects in the brain will be helpful for understanding the regulation of brain functions and developing new therapeutic strategy for prevention of neurodegeneration of the brain.

GABAergic neurons innervating the preganglionic cardiac vagal neurons in the dorsal motor nucleus receive tonic glutamatergic control / 生理学报

The glutamatergic innervations and the GABAergic innervations are respectively the major excitatory and inhibitory inputs of preganglionic cardiac vagal neurons (CVNs). Whether and how these two kinds of innervations interact in the regulation of CVNs is unknown. Using retrograde fluorescent labeling of CVNs and voltage patch-clamp technique, we demonstrated that mixed global application of glutamatergic NMDA and non-NMDA antagonists AP(5) and CNQX, while had no effect on the GABAergic synaptic events of the CVNs in the nucleus ambiguus (NA), significantly decreased the GABAergic synaptic events of the CVNs in the dorsal motor nucleus of the vagus (DMNX). These results suggest that the GABAergic neurons preceding the CVNs in the DMNX receive tonic glutamatergic control, whereas the GABAergic neurons preceding the CVNs in the NA receive little, if any, glutamatergic innervations. This differential central regulation of the CVNs in the DMNX from those in the NA might be a possible mechanism that enables the CVNs in the DMNX play different roles from those in the NA in the parasympathetic control of heart rate and cardiac functions.

Expression of transient receptor potential channel 4 in striatum and hippocampus of rats is increased after focal cerebral ischemia / 生理学报

This paper was designed in middle cerebral artery occlusion (MCAO) model of rats, to explore the role of transient receptor potential channel 4 (TRPC4) as Ca(2+) selective channel by detecting the changes of the expression of TRPC4 in different parts of cerebral tissues under the condition of focal cerebral ischemia. The rats were sacrificed after MCAO surviving time 6 h, 12 h, 1 d, 3 d. As determined by Western blot, the expressions of TRPC4 in striatum and hippocampus of 12 h, 1 d, 3 d groups were significant higher than that in the control group (P<0.05). Immunohistochemical staining showed that the TRPC4 immunoreactive substances were present in the membrane of neurons. Compared with the control group, immunostaining positive cells increased in hippocampus and striatum of cerebral ischemia groups. The TRPC4 immunostaining positive cells increased significantly in 1d-group and 3d-group (P<0.05). It suggests that as a Ca(2+) selective channel, the variance of the expression of TRPC4 may play a role in acute and delayed neuronal injury in focal cerebral ischemia.

Aberrant neuronal expression of mitotic protein, tau and Bax in the rat brain after injection of Abeta(25-35) into the amygdala / 生理学报

Recent evidence indicates that the aberrant neuronal expression of mitotic proteins in Alzheimer's disease (AD) brain may be related to AD pathological changes. To investigate whether the toxicity of beta-amyloid protein (Abeta) induces mitotic proteins expression in adult rat brain, we used immunohistochemical and integral optical density analytic method to analyze the adult rat brains, which had been injected with Abeta(25-35) into unilateral amygdala. Results showed that the levels of neurofibrillary tangle (NFT) related phosphorylated tau protein and apoptosis related protein Bax were increased in Abeta(25-35) injected rat brains, meanwhile the aberrantly expression of mitotic protein cyclin A and cyclin B1 was also detected at 7 d after operation, but the level of cyclin A decreased and cyclin B1 disappeared at 21 d. Immunofluorescence double labeling presented that cyclin B1 was partially co-localized with Bax or phosphorylated tau protein, whereas Bax and phosphorylated tau protein seldom co-localized. These results suggest that Abeta causes mitotic protein expression in adult brain neurons, which may die through apoptosis or may be affected by AD NFT-related tau phosphorylation.

Okadaic acid induces the expression of glutamate transporter EAAT1 in the neurons of rat brain / 生理学报

To study the relationship between tau hyperphosphorylation and the function of glutamate transporter okadaic acid (OA), a protein phosphatase inhibitor, 20 ng in a 0.5 microl volume, was injected into the frontal cortex of rat brain and immunostaining was used to observe the phosphorylation of tau protein and the expression of excitatory amino acid transporter 1 (EAAT1) in the brain following the injection. The results showed that (1) the neurons in the center of the injection region displayed cytoplasmic shrinkage, swelling, nuclear pyknosis, and dislocation at the early stage, and necrosis appeared 3 d after the injection. However, most neurons in the peri-injected areas showed normal morphological characters with immuno positive reaction for AT8, a tau phosphorylated marker; (2) morphological analysis showed that tau hyperphosphorylation caused by OA treatment was mainly observed in the axons and dendrites of neuronal cells at 6 h in the cell body at 1 d, which brought about dystrophic neurites and neurofibrillary tangle (NFT)-like pathological changes; (3) the induction of glutamate transporter EAAT1 was observed in the involved areas corresponding to that with AT8 immunopositive staining, and the number of EAAT1-positive staining cells markedly increased at 12 h (P<0.01), peaked at 1 d (P<0.001), then decreased at 3 d following the injection. Combined with a confocal laser scanning microscopic analysis, double fluorescent immunostaining showed that EAAT1 positive staining appeared in neurons as well as astrocytes in the peri-injected areas of the frontal cortex. These results demonstrate that OA increases glutamate transporter EAAT1 expression in neurons while it induces tau hyperphosphorylation. However, the mechanism and significance of the induction of glutamate transporter EAAT1 expression remain to be further elucidated.

The expression of nestin in ischemia-injured brain of adult rat / 生理学报

Immunohistochemistry and double immunofluorescent labeling techniques combined with confocal laser scanning microscope analysis were used to investigate the characteristic spatial induction profile of nestin following a transient middle cerebral artery occlusion in adult rat brain. The results showed that nestin was induced in ischemic core at 1 day after reperfusion. In addition to ischemic core, the expression of nestin increased in peri-ischemic I, II and III regions at 3 days and 1 week, then it decreased and narrowed along the rim of ischemic core 2 weeks after reperfusion. Double immunofluorescent labeling showed that nestin positive cells were mostly co-stained with GFAP,a astrocyte marker, in peri-ischemic I region 3 days after reperfusion. At 2 weeks, however nestin cells showed a long process and the cells double stained with nestin and NSE,a neuonal specific marker,increased in the ischemic brain. The results suggest that cerebral ischemia induces nestin expression in damaged neurons which might favor the neuroprotection against ischemic damage.