Combination treatment for acute ischemic stroke: A ray of Hope?

Multiple interacting cell death mechanisms in the mediation of excitotoxicity and ischemic brain damage: a challenge for neuroprotection

There is currently no approved neuroprotective pharmacotherapy for acute conditions such as stroke and cerebral asphyxia. One of the reasons for this may be the multiplicity of cell death mechanisms, because inhibition of a particular mechanism leaves the brain vulnerable to alternative ones. It is therefore essential to understand the different cell death mechanisms and their interactions. We here review the multiple signaling pathways underlying each of the three main morphological types of cell death--apoptosis, autophagic cell death and necrosis--emphasizing their importance in the neuronal death that occurs during cerebral ischemia and hypoxia-ischemia, and we analyze the interactions between the different mechanisms. Finally, we discuss the implications of the multiplicity of cell death mechanisms for the design of neuroprotective strategies.

Long-term cerebral cortex protection and behavioral stabilization by gonadal steroid hormones after transient focal hypoxia

Sex steroids are neuroprotective following traumatic brain injury or during neurodegenerative processes. In a recent short-term study, we have shown that 17β-estradiol (E) and progesterone (P) applied directly after ischemia reduced the infarct volume by more than 70%. This protection might primarily result from the anti-inflammatory effects of steroids. Here, we focus on the long-term neuroprotection by both steroids with respect to the infarct volume, functional recovery, and vessel density in the penumbra. The application of E/P during the first 48h after stroke (transient middle cerebral artery occlusion, tMCAO) revealed neuroprotection after two weeks. The infarct area was reduced by 70% and motor activity was preserved compared to placebo-treated animals. Blood vessel density in the penumbra using immunohistochemistry for von Willebrand factor showed increased vessel density after tMCAO which was not affected by hormones. Expression of vascular endothelial growth factor (VEGF) and its receptor (R1) was increased at 24h after tMCAO and up-regulated by E/P but not changed 14 days after stroke. These findings suggest that the neuroprotective potency of both steroids is sustained and persists for at least two weeks. Besides anti-inflammatory and anti-apoptotic actions, angiogenesis in the damaged area appears to be initially affected early after ischemia and is manifested up to two weeks. This article is part of a Special Issue entitled 'Neurosteroids'.

Translating promising preclinical neuroprotective therapies to human stroke trials

Stroke is the third leading cause of mortality and carries the greatest socioeconomic burden of disease in North America. Despite several promising therapies discovered in the preclinical setting, there have been no positive results in human stroke clinical trials to date. In this article, we review the potential causes for failure and discuss strategies that have been proposed to overcome the barrier to translation of stroke therapies. To improve the chance of success in future human stroke trials, we propose that therapies be tested in stroke models that closely resemble the human condition with molecular, imaging and functional outcomes that relate to outcomes utilized in clinical trials. These strategies include higher-order, old-world, nonhuman primate models of stroke with clinically relevant outcome measures. Although stroke neuroprotection has been looked upon pessimistically given the many failures in clinical trials to date, we propose that neuroprotection in humans is feasible and will be realized with rigorous translational science.

Comparison between PACAP- and enriched environment-induced retinal protection in MSG-treated newborn rats

Pituitary adenylate cyclase activating polypeptide (PACAP) and its receptors occur throughout the nervous system, including the retina. PACAP exerts diverse actions in the eye: it influences ocular blood flow, contraction of the ciliary muscle, and has retinoprotective effects. This effect has been proven in different models of retinal degeneration. We have previously shown that PACAP protects against monosodium-glutamate (MSG)-induced damage in neonatal rats. The beneficial effects of enriched environment, another neuroprotective strategy, have long been known. Environmental enrichment has been shown to decrease different neuronal injuries. It also influences the development of the visual system. We have recently demonstrated that significant neuroprotection can be achieved in MSG-induced retinal degeneration in animals kept in an enriched environment. Combination of neuroprotective strategies often results in increased protection. Therefore, the aim of the present study was to compare the two neuroprotective strategies alone and in combination therapy. We found that both PACAP and environmental enrichment led to a similar degree of retinal protection, but the two treatments together did not lead to increased protection: their effects were not additive.