Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

During cerebral ischemia, there is excessive activity of excitatory amino acids, especially glutamate. Activation of glutamate receptors leads to a marked increase in intracellular calcium, which in turn leads to activation of intracellular enzymes and neuronal death--the so-called excitotoxic cascade. The calcium antagonist nimodipine, which acts at L-type calcium channels, was tested for a putative neuroprotectant effect in patients with acute ischemic stroke, but no beneficial effect was demonstrated. Glutamate receptors are attractive targets for neuroprotectant drugs because glutamate plays a central role in the excitotoxic cascade. Clinical trials of NMDA (N-methyl-D-aspartate) antagonists have been disappointing, however, and psychiatric side effects seem to be a general problem with this class of drug. Another strategy proposed for interfering with NMDA receptor function is the infusion of magnesium. The NMDA receptor is normally blocked by magnesium ions and will only respond to glutamate when this magnesium-induced block is removed on depolarization. A large clinical trial to investigate possible neuroprotection by magnesium is underway. The NMDA receptor also has a glycine-binding site and a polyamine-binding site, and the cation channel will only open in response to glutamate if glycine and polyamines are already bound to these obligatory modulatory sites. Gavestinel is selective for the glycine-binding site, and eliprodil for the polyamine site, but large international clinical trials have failed to find any beneficial effects in patients with acute ischemic stroke. Neurotoxic free radicals are also generated during cerebral ischemia. Laboratory stroke models suggest that free radical scavengers might be effective neuroprotectants. One of these, NXY-059, was effective in several animal studies, and preliminary studies in human subjects show that plasma concentrations that are neuroprotective in animal models can be achieved and are well tolerated. Lubeluzole interferes with the glutamate-induced neuronal damage mediated through the formation of nitric oxide. However, a meta-analysis of all clinical trials of lubeluzole was unable to detect a neuroprotectant effect of the drug. There is now some evidence that, in addition to necrosis, some neurons die as a result of apoptosis after cerebral ischemia. Several drugs that interfere with the apoptosis cascade, for example, caspase inhibitors, are under investigation. Clomethiazole ('ZENDRA'; a trademark, the property of the AstraZeneca group of companies) is also undergoing a second large clinical trial in patients with major ischemic strokes. This drug's mechanism of action is not completely clear, but it is known to activate a nonbenzodiazepine site on the GABA(A) (gamma-aminobutyric acid) receptor. This causes increased chloride conductance and hyperpolarization. In vitro clomethiazole inhibits ischemia-induced glutamate efflux from cerebral neurons. The first large controlled trial showed it to be well tolerated and suggested a clinically significant effect in patients with deficits of a major stroke.
 ...
PMID:Mechanisms of action of neuroprotectants in stroke. 1789 14

Ischemic stroke is a leading cause of adult disability and cognitive impairment worldwide. Neuroprotective therapy aims to save neurons by impeding the deleterious ischemic insults. However, the low efficiency of the neuroprotectants crossing blood brain barrier (BBB) prevents their clinical translation. In this work, a nanoagonist (NA) was developed to enhance neuroprotectant uptake by specifically increasing BBB permeability in brain ischemia. This NA first targeted ischemic brain vasculatures, temporarily opened local BBB by activating adenosine 2A receptors, and up-regulated the neuroprotectant uptake in brain ischemia. This NA significantly increased the delivery of superoxide dismutase (SOD), a free radical scavenger, into mouse brain ischemia. The combined treatment of NA/SOD achieved a five-fold ischemic volume reduction rate compared to the animal models treated with SOD alone. Non-invasive magnetic resonance imaging (MRI) confirmed the ischemia targeted BBB opening, increased brain drug delivery efficiency and up-regulated therapeutic response during the combined NA/SOD treatment. Since the inefficient brain drug delivery is a general problem for the treatment of central nervous system (CNS) diseases, this work provides a novel strategy to deliver therapeutics by crossing BBB with high efficiency and targeting specificity.
...
PMID:Salvaging brain ischemia by increasing neuroprotectant uptake via nanoagonist mediated blood brain barrier permeability enhancement. 2618 8