tacrolimus and Hypoxia-Ischemia--Brain

Although, astrocytes are more resistant than neurons to ischemic injury, astrocyte death has been demonstrated in animal models of brain ischemia. Astrocytes death after ischemia/reperfusion may strongly affect neuronal survival because of the absence of their trophic and metabolic support to neurons, and astrocytic glutamate uptake. Early signals involved in astrocytes death are poorly understood. We demonstrated enhanced and mostly cytoplasmic activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) during glutamate-induced apoptosis of cultured astrocytes. Treatment with UO126, inhibitor of MEK1, threo-beta-benzyloxyaspartic acid, glutamate transporter inhibitor, and FK506, a cytoprotective drug prevented ERK activation and glutamate-induced apoptosis. Over-expression of ERK dual specificity phosphatases 5 and 6 reduced apoptosis in transfected astrocytes. Prolonged ERK1/2 activation was observed in ischemic brain: in the nucleus and cytoplasm of astrocytes in the cerebral cortex, and exclusively in the cytoplasm of astrocytes in the striatum. Global gene expression profiling in the cortex revealed that FK506 blocks middle cerebral artery occlusion-induced expression of numerous genes associated with ERK signaling pathway and apoptosis. The results demonstrate a pro-apoptotic role of sustained activation of ERK1/2 signaling in glutamate-induced death of astrocytes and the ability of FK506 to block both ERK activation and astrocytic cell death in vitro and in ischemic brains.

Topics: Amino Acid Transport System X-AG; Animals; Animals, Newborn; Apoptosis; Astrocytes; Butadienes; Cells, Cultured; Enzyme Activation; Enzyme Inhibitors; Glutamic Acid; Hypoxia-Ischemia, Brain; Immunosuppressive Agents; Infarction, Middle Cerebral Artery; Male; MAP Kinase Kinase 1; MAP Kinase Signaling System; Mitogen-Activated Protein Kinase 3; Neuroprotective Agents; Nitriles; Rats; Rats, Wistar; Tacrolimus

Immunosuppressant tacrolimus (FK506) has shown neuroprotective effects on hypoxic-ischemic brain damage (HIBD) in the adult animal model. This study investigated whether FK506 has a protection against HIBD in neonatal rats by examining growthjassociated protein-43 (GAP-43) expression in the hippocampus.. Ninety-six seven-day-old Sprague-Dawley rats were randomly divided into three groups: sham-operation, HIBD and FK506 intervention group. HIBD was induced in the later two groups. The FK506 intervention group was intraperitoneally injected with FK506 immediately after HIBD, at a dosage of 1 mg/kg daily, for three days. The HIBD group was injected with normal saline. Immunohistochemical technical was applied to examine GAP-43 expression in the hippocampus 24 and 72 hrs and 7 and 14 days after HIBD.. Compared with the HIBD group, hematoxylin-eosin staining showed attenuated neuronal necrosis in the FK506 intervention group. In the HIBD group, the expression of GAP-43 increased significantly 72 hrs, and 7 and 14 days after HIBD compared with that in the sham-operation group. The GAP-43 expression in the FK506 intervention group was significantly higher than that in the HIBD group 72 hrs and 7 days after HIBD.. FK506 might have neuroprotective effects against HIBD in neonatal rats.

Topics: Animals; Animals, Newborn; GAP-43 Protein; Hippocampus; Hypoxia-Ischemia, Brain; Immunosuppressive Agents; Rats; Rats, Sprague-Dawley; Tacrolimus

Many practical therapies have been explored as clinical applications for ischemic cerebral infarction; however, most are still insufficient to treat acute stroke. We show here a potential combination therapy in a rat focal ischemic model to improve neurological symptoms as well as to reduce infarct volumes at the maximum level. We applied protein transduction technology using artificial anti-death Bcl-xl derivative with three amino acid-substitutions (Y22F, Q26N and R165K) (FNK) protein fused with a protein-transduction-domain peptide (PTD-FNK). When PTD-FNK was administrated 1 h after initiating ischemia followed by the administration of an immunosuppressant FK506 with a 30-min time lag, infarct volumes of the total brain and cortex were markedly reduced to 27% and 14%, respectively. This procedure not only reduced the infarct volume and edema, but also markedly improved neurological symptoms. The therapeutic effect continued for at least 1 week after ischemia. FK506 inhibited the transduction of PTD-FNK in vitro, which explains the requirement of a time lag for the administration of FK506. An additional in vitro experiment showed that PTD-FNK, when administered 30 min before FK506, gave the maximal protective effect by reducing the intracellular calcium concentration. We propose that this combination therapy would provide a synergistic protective effect by both drugs, reducing adverse the effects of FK506.

Topics: Animals; Apoptosis; Brain Infarction; Calcium Signaling; Disease Models, Animal; Drug Synergism; Drug Therapy, Combination; Hypoxia-Ischemia, Brain; Immunosuppressive Agents; Ischemic Attack, Transient; Male; Peptide Fragments; Protein Serine-Threonine Kinases; Rats; Rats, Sprague-Dawley; Recombinant Fusion Proteins; Tacrolimus; Transduction, Genetic; Treatment Outcome

We examined the effects of the immunosuppressant tacrolimus (FK506) on the discrimination learning impairment induced by chronic cerebral hypoperfusion in rats. Chronic cerebral hypoperfusion was prepared by permanent ligation of bilateral common carotid arteries for male Wistar rats aged 9 weeks. FK506 (0.05 mg/kg, s.c.) recovered the learning impairment and also prevented the rarefaction of white matter and striatal neuronal cell damage. Our findings suggest that FK506 ameliorates the learning impairment mainly due to preventing neuropathological alterations.

Topics: Animals; Brain; Cerebrovascular Circulation; Chronic Disease; Corpus Callosum; Dementia, Vascular; Frontal Lobe; Hypoxia-Ischemia, Brain; Immunosuppressive Agents; Learning Disabilities; Male; Neostriatum; Nerve Degeneration; Nerve Fibers, Myelinated; Rats; Rats, Wistar; Recovery of Function; Tacrolimus