Neuronal Sirt3 Protects against Excitotoxic Injury in Mouse Cortical Neuron Culture

BACKGROUND: Sirtuins (Sirt), a family of nicotinamide adenine nucleotide (NAD) dependent deacetylases, are implicated in energy metabolism and life span. Among the known Sirt isoforms (Sirt1-7), Sirt3 was identified as a stress responsive deacetylase recently shown to play a role in protecting cells under stress conditions. Here, we demonstrated the presence of Sirt3 in neurons, and characterized the role of Sirt3 in neuron survival under NMDA-induced excitotoxicity. METHODOLOGY/PRINCIPAL FINDINGS: To induce excitotoxic injury, we exposed primary cultured mouse cortical neurons to NMDA (30 µM). NMDA induced a rapid decrease of cytoplasmic NAD (but not mitochondrial NAD) in neurons through poly (ADP-ribose) polymerase-1 (PARP-1) activation. Mitochondrial Sirt3 was increased following PARP-1 mediated NAD depletion, which was reversed by either inhibition of PARP-1 or exogenous NAD. We found that massive reactive oxygen species (ROS) produced under this NAD depleted condition mediated the increase in mitochondrial Sirt3. By transfecting primary neurons with a Sirt3 overexpressing plasmid or Sirt3 siRNA, we showed that Sirt3 is required for neuroprotection against excitotoxicity. CONCLUSIONS: This study demonstrated for the first time that mitochondrial Sirt3 acts as a prosurvival factor playing an essential role to protect neurons under excitotoxic injury

Metamorphosis of Subarachnoid Hemorrhage Research: from Delayed Vasospasm to Early Brain Injury

Delayed vasospasm that develops 3–7 days after aneurysmal subarachnoid hemorrhage (SAH) has traditionally been considered the most important determinant of delayed ischemic injury and poor outcome. Consequently, most therapies against delayed ischemic injury are directed towards reducing the incidence of vasospasm. The clinical trials based on this strategy, however, have so far claimed limited success; the incidence of vasospasm is reduced without reduction in delayed ischemic injury or improvement in the long-term outcome. This fact has shifted research interest to the early brain injury (first 72 h) evoked by SAH. In recent years, several pathological mechanisms that activate within minutes after the initial bleed and lead to early brain injury are identified. In addition, it is found that many of these mechanisms evolve with time and participate in the pathogenesis of delayed ischemic injury and poor outcome. Therefore, a therapy or therapies focused on these early mechanisms may not only prevent the early brain injury but may also help reduce the intensity of later developing neurological complications. This manuscript reviews the pathological mechanisms of early brain injury after SAH and summarizes the status of current therapies

Co-accumulation of vascular endothelial growth factor with beta-amyloid in the brain of patients with Alzheimer's disease

Alzheimer's disease (AD) is accompanied by the progressive deposition of beta-amyloid (Abeta) in both senile plaques and cerebral blood vessels, loss of central neurons, and vessel damage. Cerebral hypoperfusion is one of the major clinical features in AD and likely plays a critical role in its pathogenesis. In addition to its major roles in angiogenesis, vascular endothelial growth factor (VEGF) has neurotrophic and neuroprotective effects. VEGF is an ischemia-inducible factor and increased expression of VEGF often occurs in AD. Although the presence of VEGF inummoreactivity in the AD brain has been described previously, the direct interaction of VEGF with Abeta has not been established. Here, we show that VEGF is co-localized with Abeta plaques in the brains of patients with AD. In vitro experiments show that VEGF binds to Abeta with high affinity (K-D approximate to 50 pM). VEGF is co-aggregated with Abeta without any apparent effect on the rate of aggregation, strongly binds to pre-aggregated Abeta, and is very slowly released from the co-aggregated complex. Continuous deposition of VEGF in the amyloid plaques most likely results in deficiency of available VEGF under hypoperfusion and, thus, may contribute to neurodegeneration and vascular dysfunction in the progression of AD. (C) 2003 Elsevier Inc. All rights reserved.X11104sciescopu

A neuron-specific gene transfer by a recombinant defective Sindbis virus

We examined the possibility that Sindbis virus, an alpha virus with a single-stranded RNA genome, would be applied for neuronal gene transfer. The recombinant defective Sindbis viruses were constructed by replacing the structural genes of Sindbis virus with genes encoding beta-galactosidase (rdSind-lacZ) or enhanced green fluorescent protein (rdSind-EGFP). In neuron-glia cocultures prepared from the neocortex, hippocampus, and striatum, EGFP or beta-galactosidase was expressed selectively in neurons 24 h after infection with rdSind-EGFP or rdSind-lacZ. Most cortical neurons were infected with rdSind-lacZ at a multiplicity of infection (M.O.I.) of 5 while glial cells were little infected. In addition, transient neuron-specific expression of beta-galactosidase was observed near injection sites over the next 3 d following administration of rdSind-lacZ in adult rat. In the cortical neurons infected with rdSind-EGFP, treatment with NMDA induced neuritic blebs and cell body swelling in a Na+-dependent manner. Therefore, recombinant defective Sindbis viruses can be used as an efficient and selective vector for gene transfer into neurons and applied to investigate biological role of target genes delivered into neurons in vitro and in vivo. (C) 1998 Elsevier Science B.V. All rights reserved.X1126sciescopu