Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

During ischemic stroke, massive neural damage occurs due to excess release of glutamate which acts mainly through N-methyl-D-aspartate (NMDA) receptors. Activation of the NMDA receptor stimulates nitric oxide (NO) production by NO synthase (NOS). NO mediates glutamate neurotoxicity as inhibitors of NOS prevent neuronal death. FK506, an immunosuppressant drug, binds to FK506 binding protein (FKBP). One target of the FK506/FKBP complex is the calcium/calmodulin-dependent protein phosphatase calcineurin, whose activity is inhibited upon interaction with FK506/FKBP. FK506 treatment increases phosphorylation level of calcinurin substrates including NOS. As a potent neuroprotective agent in vitro and in vivo, FK506 increases NOS phosphorylation and decreases NO production. NO activates poly(ADP-ribose) synthetase (PARS), a nuclear enzyme that synthesizes poly(ADP-ribose) from NAD. Prolonged activation of PARS depletes NAD and lowers cellular energy levels. Inhibition of PARS also prevents NO toxicity. NOS inhibitors, immunosuppressants and PARS inhibitors may be useful agents to prevent neuronal damage during stroke.
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PMID:Nitric oxide synthase, immunophilins and poly(ADP-ribose) synthetase: novel targets for the development of neuroprotective drugs. 747 44

The immunosuppressive action of the drug FK506 involves inhibition of calcineurin in T-lymphocytes by a complex of FK506 and an FK506 binding protein, FKBP12, a member of the immunophilin protein family. The functional role of brain immunophilins is, however, unclear. We show here that FK506 is a powerful neuroprotective agent in an in vivo model of focal cerebral ischaemia when administered up to 60 min post-occlusion. The minimum effective neuroprotective dose is comparable with the immunosuppressant dose in humans, suggesting that FK506 may have clinical potential for the treatment of stroke. Although the related immunosuppressants rapamycin and cyclosporin failed to reduce brain damage, the finding that rapamycin pretreatment blocked the effect of FK506 confirms a role for immunophilins in the neuroprotective mechanism.
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PMID:Immunophilins mediate the neuroprotective effects of FK506 in focal cerebral ischaemia. 752 3

We reviewed retrospectively the clinical records, autopsy protocols and central nervous system tissue sections of 50 patients who underwent orthotopic liver transplantation for end-stage liver disease between 12/83 and 8/93. The postoperative survival period ranged from hours (6), weeks (17), months (17), to years (10). All patients received immunosuppressive drugs from the immediate postoperative period to the time of their death (cyclosporine, steroids; occasionally azathioprine, OKT3, FK506). Nineteen patients had neurological manifestations (hepatic encephalopathy) prior to surgery. Post-transplant neurologic signs and symptoms included: hepatic encephalopathy/altered mental status (11), focal or generalized seizures (9) and stroke (2). In the majority of cases (37) the cause of death was septicemia and/or bleeding diathesis. The neuropathologic findings present in 36 patients could be classified into 3 distinct categories: metabolic disorders: hepatic/anoxic encephalopathy, central pontine myelinolysis (15); cerebrovascular disease: subarachnoid and/or intracerebral hemorrhage, bland or hemorrhagic infarction (23); and infection: bacterial meningitis/cerebritis, multifocal fungal microabscesses, presumptive viral meningitis/encephalomyelitis (10). In conclusion, 72% of 50 patients who came to autopsy after liver transplantation were found to have neuropathologic abnormalities; these abnormalities were predominantly infections and vascular diseases.
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PMID:Neuropathology of liver transplantation. 760 96

Neurological complications are important contributors to morbidity and mortality after liver transplantation. We reviewed 391 patients who underwent 427 consecutive orthotopic liver transplantations to analyze the clinical features of patients who experienced one or more neurological complication (74 patients [19%]) and to compare postoperative neurological problems in adults versus children. Neurological complications were more frequent in adults (64 of 273 patients [23%]) than children (10 of 118 patients [8%]) (P < 0.01). The most common neurological complication was encephalopathy (59%), which ranged widely in severity and occurred with similar frequency in adults and children. Other common neurological complications were seizures (12 patients), brachial plexus and peripheral nerve injuries (16 patients, 15 of whom were adults), stroke (5 patients), and central nervous system infections (5 patients). In 27 patients, drug toxicity was the primary cause of neurological complications, all of which reversed with dosage reduction or discontinuation of drug. Cyclosporine and FK506, primarily during intravenous administration for induction of immunosuppression, accounted for 25 of 27 drug-induced neurological complications, which included encephalopathy, seizures, severe tremor, and severe headache. Despite a higher rate of neurological complications in adults, those in children were more severe and associated with a higher mortality rate. When compared with liver transplant recipients without neurological complications, patients with neurological complications had a higher posttransplant mortality rate (14% vs. 5% for adults, and 50% vs. 7% for children). In conclusion, neurological complications after liver transplantation are more common in adults, more severe and associated with a higher mortality rate in children, and associated with a higher mortality rate in both children and adults when compared with transplant recipients without neurological complications.
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PMID:Neurological complications of liver transplantation in adult versus pediatric patients. 807 14

The cellular mechanisms underlying the neuroprotective action of the immunosuppressant FK506 in experimental stroke remain uncertain, although in vitro studies have implicated an antiexcitotoxic action involving nitric oxide and calcineurin. The present in vivo study demonstrates that intraperitoneal pretreatment with 1 and 10 mg/kg FK506, doses that reduced the volume of ischemic cortical damage by 56-58%, did not decrease excitotoxic damage induced by quinolinate, NMDA, and AMPA. Similarly, intravenous FK506 did not reduce the volume of striatal quinolinate lesions at a dose (1 mg/kg) that decreased ischemic cortical damage by 63%. The temporal window for FK506 neuroprotection was defined in studies demonstrating efficacy using intravenous administration at 120 min, but not 180 min, after middle cerebral artery occlusion. The noncompetitive NMDA receptor antagonist MK801 reduced both ischemic and excitotoxic damage. Histopathological data concerning striatal quinolinate lesions were replicated in neurochemical experiments. MK801, but not FK506, attenuated the loss of glutamate decarboxylase and choline acetyltransferase activity induced by intrastriatal injection of quinolinate. The contrasting efficacy of FK506 in ischemic and excitotoxic lesion models cannot be explained by drug pharmacokinetics, because brain FK506 content rose rapidly using both treatment protocols and was sustained at a neuroprotective level for 3 d. Although these data indicate that an antiexcitotoxic mechanism is unlikely to mediate the neuroprotective action of FK506 in focal cerebral ischemia, the finding that intravenous cyclosporin A (20 mg/kg) reduced ischemic cortical damage is consistent with the proposed role of calcineurin.
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PMID:Neuroprotective actions of FK506 in experimental stroke: in vivo evidence against an antiexcitotoxic mechanism. 927 29

The neuroprotective properties of drugs binding to FKBP12, with and without subsequent inhibition of calcineurin, were investigated in rat models of ischemic embolic stroke. Drug effects on brain infarct volumes evoked by transient middle cerebral artery occlusion (MCAO) and by permanent MCAO were determined in vivo by T2-weighted magnetic resonance imaging and post mortem by triphenyltetrazolium chloride staining and histology. Drugs binding to FKBP12 and inhibiting calcineurin, such as FK506 and SDZ ASM 981, dose dependently reduced the infarct volumes, determined 48 h after MCAO by both magnetic resonance imaging and triphenyltetrazolium chloride staining but only in the transient MCAO model. In vivo potencies to reduce brain infarcts paralleled the in vitro potencies to inhibit calcineurin. Histological staining after 6 days of survival showed that the neuroprotective effects were permanent. Rapamycin, known to bind with similar affinity to FKBP12 but not to inhibit calcineurin, was not neuroprotective but abolished the neuroprotective effects of FK506 when coadministered. In the permanent MCAO models, FK506 showed no effect when injected before and little effect when injected after MCAO. Measurements of core temperatures after MCAO in controls and drug-treated rats do not support hypothermia being the mechanism responsible for neuroprotection. We conclude that drugs inhibiting calcineurin activity are neuroprotective in focal cerebral ischemia/reperfusion but not in permanent ischemia models, possibly by preventing reperfusion injury.
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PMID:Calcineurin inhibitors FK506 and SDZ ASM 981 alleviate the outcome of focal cerebral ischemic/reperfusion injury. 991 71

Ceramide is a key mediator of apoptosis during the cellular stress response which is also involved in stroke-induced death. Transient occlusion of the middle cerebral artery (MCA) in rats led to a strong generation of ceramide as measured in thalamus and entorhinal cortex of the ischemic brain tissue. Enhanced levels of ceramide may be involved in apoptosis signaling following stroke since exogenously added synthetic C2-ceramide increased expression of c-jun and the death-inducing ligands (DILs) CD95-L, TRAIL and TNF-alpha in neuroblastoma cells. DILs in turn mediated death via binding to their respective receptors as concluded from diminished apoptosis upon blocking of the common pathway by dominant negative FADD. C2-ceramide induced both necrosis and apoptosis in a concentration-dependent manner corresponding to the situation present in the ischemic brain. The immunosuppressant FK506 inhibited the release of ceramide, expression of CD95-L and apoptosis in an in vitro and in vivo model for ischemia/reperfusion. These data suggest that ceramide is a crucial initiator of death, e.g., by induction of DILs following stroke.
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PMID:FK506 prevents stroke-induced generation of ceramide and apoptosis signaling. 1022 98

Calcineurin is a Ca(2+)/calmodulin-dependent protein phosphatase that is abundantly expressed in several specific areas of the brain, which are exceptionally vulnerable to stroke, epilepsy, and neurodegenerative diseases. In this study, we assessed the effects of high level activity of calcineurin on neuronal cells. Virus-mediated high level constitutive activity of calcineurin rendered neuronal cells susceptible to apoptosis induced by serum reduction or by a brief exposure to calcium ionophore. Adenovirus-mediated, high level forced activity of calcineurin induced cytochrome c/caspase-3-dependent apoptosis in neurons. Preincubation with the calcineurin inhibitors cyclosporin A and FK506 reduced susceptibility to apoptosis. High level constitutive expression of Bcl-2 or CrmA or incubation with a specific caspase-3 inhibitor inhibited the calcineurin-induced apoptosis. These data indicate that high level constitutive activity of calcineurin predisposes neuronal cells to cytochrome c/caspase-3 dependent apoptosis even under sublethal conditions.
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PMID:High level calcineurin activity predisposes neuronal cells to apoptosis. 1056 26

In many types of cardiovascular pathophysiology such as hypercholesterolemia and atherosclerosis, diabetes, cigarette smoking, or hypertension (with its sequelae stroke and heart failure) the expression of endothelial NO synthase (eNOS) is altered. Both up- and downregulation of eNOS have been observed, depending on the underlying disease. When eNOS is upregulated, the upregulation is often futile and goes along with a reduction in bioactive NO. This is due to an increased production of superoxide generated by NAD(P)H oxidase and by an uncoupled eNOS. A number of drugs with favorable effects on cardiovascular disease upregulate eNOS expression. The resulting increase in vascular NO production may contribute to their beneficial effects. These compounds include statins, angiotensin-converting enzyme inhibitors, AT1 receptor antagonists, calcium channel blockers, and some antioxidants. Other drugs such as glucocorticoids, whose administration is associated with cardiovascular side effects, downregulate eNOS expression. Stills others such as the immunosuppressants cyclosporine A and FK506/tacrolimus or erythropoietin have inconsistent effects on eNOS. Thus regulation of eNOS expression and activity contributes to the overall action of several classes of drugs, and the development of compounds that specifically upregulate this protective enzyme appears as a desirable target for drug development.
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PMID:Regulation of endothelial-type NO synthase expression in pathophysiology and in response to drugs. 1238 13

Tacrolimus (FK506), a potent immunosuppressive drug, is effective in attenuating brain infarction after cerebral ischemia. However, there has been no report characterizing the neuroprotective action and therapeutic time window of tacrolimus systematically using different types of stroke models and extended observation periods. Therefore, we evaluated the neuroprotective effect of tacrolimus in three different animal models of cerebral ischemia: transient and permanent focal ischemia in rats and transient global ischemia in gerbils. Tacrolimus at doses higher than 0.1 mg/kg (i.v.) produced a statistically significant reduction in ischemic brain damage following permanent and transient focal ischemia in rats when administered immediately after the onset of ischemia. Tacrolimus (1 mg/kg, i.v.) demonstrated similar neuroprotective activity even after delayed administration (2 h after permanent or 1 h after transient focal ischemia). The neuroprotective effect of tacrolimus was still present 2 weeks after transient focal ischemia and 1 week after permanent focal ischemia. After transient global ischemia in gerbils, tacrolimus (1 mg/kg, i.v.) given immediately after reperfusion also produced long-lasting neuroprotective effects with a protective time-window of 1-2 h. Taken together, the results clearly indicate that tacrolimus exerts potent, long-term neuroprotective effects with a favorable therapeutic time-window, regardless of the model of cerebral ischemia. These results strengthen the notion that tacrolimus might be of clinical value for the treatment of acute stroke.
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PMID:Neuroprotective action of tacrolimus (FK506) in focal and global cerebral ischemia in rodents: dose dependency, therapeutic time window and long-term efficacy. 1259 Nov 30


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