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Protein kinase FA/glycogen synthase kinase-3 alpha after heparin potentiation phosphorylates tau on sites abnormally phosphorylated in Alzheimer's disease brain.

Previously, we identified protein kinase FA/glycogen synthase kinase-3 alpha (GSK-3 alpha) as a brain microtubule-associated tau kinase that phosphorylates Ser235 and Ser404 of tau and causes its electrophoretic mobility shift in gels, a unique property characteristic of paired helical filament-associated pathological tau (PHF-tau) in Alzheimer's disease brains. In this study, we found that the activity of kinase FA/GSK-3 alpha towards phosphorylation of brain tau could be stimulated approximately fourfold by heparin. The phosphorylation molar ratio was increased simultaneously up to 9 mol of phosphates/mol of tau, resulting in a reduced mobility of tau with an apparent molecular mass shift to approximately 68 kDa in sodium dodecyl sulfate gels, which is very similar to that observed in Alzheimer-tau. Tryptic digestion of 32P-labelled tau, followed by HPLC and two-dimensional separation on TLC cellulose plates, revealed eight major phosphopeptides. Phosphoamino acid analysis together with sequential manual Edman degradation and protein sequence analysis further revealed that, in addition to Ser235 and Ser404, heparin generated Thr212, Thr231, Ser262, Ser324, and Ser356, the five extra phosphorylation sites in tau. As Ser235, Ser262, Ser324, Ser356, and Ser404 (particularly the site of Ser262) have been identified as five of the most potent sites in tau responsible for reducing microtubule binding possibly involved in neuronal degeneration, and Thr231, Ser235, Ser262, and Ser404 are four of the most well documented sites abnormally phosphorylated in Alzheimer-tau, the results provide initial evidence that protein kinase FA/GSK-3 alpha after heparin potentiation may represent one of the most potent systems possibly involved in the abnormal phosphorylation of PHF-tau in Alzheimer's disease brains.

Alzheimer Disease↗

Alcoholic organic brain disease: nosology and pathophysiologic mechanisms.

Study of alcoholic chronic organic brain syndrome may have applicability to the large population of alcoholics with less severe cerebral dysfunction. Brain impairment in alcoholics may be conceptualized as two clinically and neuropathologically distinguishable organic brain syndromes: alcohol amnestic disorder or Korsakoff's psychosis (KP) and alcoholic dementia. Alcoholic organic brain disease may result from two interacting pathophysiological processes: nutritional (thiamine) deficiency and ethanol neurotoxicity. Subcortical periventricular lesions associated with KP result primarily from thiamine deficiency, whereas ethanol neurotoxicity and various secondary effects of alcoholism may contribute to the cortical neuropathological changes associated with alcoholic dementia. These two patterns of brain damage may be differentiable in individual alcoholics using cognitive tests and other measures of CNS function and, therefore, allow selection of a treatment strategy based on pathophysiological considerations. Studies in animals and humans suggest that a genetic predisposition to thiamine deficiency may contribute to alcoholism-associated dysfunction of brain and other organ systems and possibly have a causative role in the development of alcoholism.

Alcohol Amnestic Disorder↗

Reaction time and brain disease: relations to location, etiology and progression of cerebral dysfunction.

Using the results from 485 patients with various forms of cerebral dysfunctions and from 60 hospitalized controls, it was shown that measurement of continuous reaction times (CRT) is sensitive to cerebral lesions. Reaction times were more impaired by progressive than by non-progressive brain diseases. The test did not distinguish between patients with right- or left-hemisphere lesions and was not influenced either by etiology, chronicity, age or sex. Our conclusion is that CRT is useful as a "screening" test for the presence of cerebral dysfunction and is especially sensitive to progressive diseases. Its discrimination power is equivalent to more sophisticated and complex psychological tests.

Adolescent↗

Cell mediators of inflammation in the Alzheimer disease brain.

Lesions of Alzheimer disease are associated with low-grade but sustained inflammatory responses. Activated microglia agglomerate in the center of senile plaques. Reactive astrocytes marginate the amyloid beta-protein (A beta) deposits and extend their processes toward the center of plaques. Both microglia and astrocytes are known to secrete a wide variety of molecules involved in inflammation and are potential sources of proinflammatory elements in the brain. Dystrophic neurites occur in senile plaques with such glial reactions, suggesting the relevance of inflammatory responses to the neuronal degeneration in Alzheimer disease. Activated glial cells are, therefore, targets of anti-inflammatory therapy of Alzheimer disease. However, evidence also indicates that these cells eliminate A beta from the brain. A beta is produced continuously in both the normal and the AD brain. Under normal conditions, A beta is removed successfully before it accumulates as extracellular amyloid fibrils. Even in Alzheimer disease, a large portion of A beta may be cleared from the brain with a small portion being left and deposited as neurotoxic senile plaques. Both in vivo and in vitro studies showed the effective uptake of A beta by microglia. Before clinical application, it must be determined whether the treatment that suppresses glial activation and inflammatory responses inhibits A beta removal by glial cells.

Alzheimer Disease↗

Neuron-specific enolase in cerebrospinal fluid and plasma of patients with acute ischemic brain disease.

The objective of this research was to determine the dynamics of change of neuron-specific enolase concentration in patients with acute ischemic brain disease in cerebrospinal fluid and plasma. The study included 103 patients, their mean age 58-66 years. The control group consisted of 16 patients, of matching age and sex, with radicular lesions of discal origin, subjected to diagnostic radiculography. Concentration of neuron-specific enolase was measured by a flouroimmunometric method. The results showed that the concentration of neuron-specific enolase in cerebrospinal fluid and plasma of patients with brain ischemic disease within first seven days significantly increased compared to the control. The highest increase of concentration was established in brain infarction, somewhat lower in reversible ischemic attack, and the lowest in transient ischemic attack. Maximal concentration was established on the 3rd-4th day upon the brain infarction. Neuron-specific enolase concentration in cerebrospinal fluid and plasma may be an indicator of pathophysiological processes in the acute phase of brain ischemia and is significant in early diagnostics and therapy of the disease.

Acute Disease↗

APP-BP1 mediates APP-induced apoptosis and DNA synthesis and is increased in Alzheimer's disease brain.

APP-BP1, first identified as an amyloid precursor protein (APP) binding protein, is the regulatory subunit of the activating enzyme for the small ubiquitin-like protein NEDD8. We have shown that APP-BP1 drives the S- to M-phase transition in dividing cells, and causes apoptosis in neurons. We now demonstrate that APP-BP1 binds to the COOH-terminal 31 amino acids of APP (C31) and colocalizes with APP in a lipid-enriched fraction called lipid rafts. We show that coexpression of a peptide representing the domain of APP-BP1 that binds to APP, abolishes the ability of overexpressed APP or the V642I mutant of APP to cause neuronal apoptosis and DNA synthesis. A dominant negative mutant of the NEDD8 conjugating enzyme hUbc12, which participates in the ubiquitin-like pathway initiated by APP-BP1, blocks neuronal apoptosis caused by APP, APP(V642I), C31, or overexpression of APP-BP1. Neurons overexpressing APP or APP(V642I) show increased APP-BP1 protein levels in lipid rafts. A similar increase in APP-BP1 in lipid rafts is observed in the Alzheimer's disease brain hippocampus, but not in less-affected areas of Alzheimer's disease brain. This translocation of APP-BP1 to lipid rafts is accompanied by a change in the subcellular localization of the ubiquitin-like protein NEDD8, which is activated by APP-BP1.

Alzheimer Disease↗

The brain erythropoietin system and its potential for therapeutic exploitation in brain disease.

The discovery of the broad neuroprotective potential of erythropoietin (EPO), an endogenous hematopoietic growth factor, has opened new therapeutic avenues in the treatment of brain diseases. EPO expression in the brain is induced by hypoxia. Practically all brain cells are capable of production and release of EPO and expression of its receptor. EPO exerts multifaceted protective effects on brain cells. It protects neuronal cells from noxious stimuli such as hypoxia, excess glutamate, serum deprivation or kainic acid exposure in vitro by targeting a variety of mechanisms and involves neuronal, glial and endothelial cell functions. In rodent models of ischemic stroke, EPO reduces infarct volume and improves functional outcome, but beneficial effects have also been observed in animal models of subarachnoid hemorrhage, intracerebral hemorrhage, traumatic brain injury, and spinal cord injury. EPO has a convenient therapeutic window upon ischemic stroke and favorable pharmacokinetics. Results from first therapeutic trials in humans are promising, but will need to be validated in larger trials. The safety profile and effectiveness of EPO in a wide variety of neurologic disease models make EPO a candidate compound for a potential first-line therapeutic for neurologic emergencies.

Animals↗