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Background and Purpose-Human umbilical cord blood cells (HUCBC) are rich in stem and progenitor cells. In this study we tested whether intravenously infused HUCBC enter brain, survive, differentiate, and improve neurological functional recovery after stroke in rats. In addition, we tested whether ischemic brain tissue extract selectively induces chemotaxis of HUCBC in vitro. Methods-Adult male Wistar rats were subjected to transient (2-hour) middle cerebral artery occlusion (MCAO).Experimental groups were as follows: group 1, MCAO alone (nϭ5); group 2, 3ϫ10 6 HUCBC injected into tail vein at 24 hours after MCAO (nϭ6) (animals of groups 1 and 2 were killed at 14 days after MCAO); group 3, MCAO alone (nϭ5); group 4, MCAO injected with PBS at 1 day after stroke (nϭ8); and group 5, 3ϫ10 6 HUCBC injected into tail vein at 7 days after MCAO (nϭ5). Rats of groups 3, 4, and 5 were killed at 35 days after MCAO.

Almost all degenerative diseases of the CNS are associated with chronic inflammation. A central step in this process is the activation of brain mononuclear phagocyte cells, called microglia. While it is recognized that healthy neurons and astrocytes regulate the magnitude of microglia-mediated innate immune responses and limit excessive CNS inflammation, the endogenous signals governing this process are not fully understood. In the peripheral nervous system, recent studies suggest that an endogenous 'cholinergic anti-inflammatory pathway' regulates systemic inflammatory responses via a7 nicotinic acetylcholinergic receptors (nAChR) found on blood-borne macrophages. These data led us to investigate whether a similar cholinergic pathway exists in the brain that could regulate microglial activation. Here we report for the first time that cultured microglial cells express a7 nAChR subunit as determined by RT-PCR, western blot, immunofluorescent, and immunochistochemistry analyses. Acetylcholine and nicotine pre-treatment inhibit lipopolysaccharide (LPS)-induced TNF-a release in murine-derived microglial cells, an effect attenuated by a7 selective nicotinic antagonist, a-bungarotoxin. Furthermore, this inhibition appears to be mediated by a reduction in phosphorylation of p44/42 and p38 mitogen-activated protein kinase (MAPK). Though preliminary, our findings suggest the existence of a brain cholinergic pathway that regulates microglial activation through a7 nicotinic receptors. Negative regulation of microglia activation may also represent additional mechanism underlying nicotine's reported neuroprotective properties.

Grafts of fetal mesencephalic tissue can survive for a long period in the human brain and restore dopaminergic innervation to the striatum in patients with Parkinson's disease. In the patient we studied, clinical improvement and enhanced fluorodopa with uptake on PET scanning were associated the survival of the grafts and dopaminergic reinnervation of the striatum.

Background and Purpose-To date, stem cell graft-mediated neuroprotection is equated with graft survival and secretion of neurotrophic factors in the brain. Here, we examined whether neuroprotection by systemically delivered human umbilical cord blood (HUCB) cells was dependent on their entry into the central nervous system in a rodent model of acute stroke. Methods-Adult male Sprague-Dawley rats were subjected to right middle cerebral artery occlusion for 60 minutes. During the 1-hour occlusion, animals were randomly assigned to 1 of the following treatments: intravenous injection of HUCB (a subtherapeutic dose of 200 000 cells in 10 L) with blood-brain barrier (BBB) permeabilizer (1.1 mol/L mannitol at 4°C) or vehicle, intravenous vehicle alone, or intravenous mannitol alone. Behavioral tests, using elevated body swing test and passive avoidance test, were conducted at day 3 poststroke, and thereafter, animals were euthanized for: (1) immunohistochemical examination of HUCB, which were lentivirally labeled with green fluorescent protein; (2) cerebral infarction analysis using 2,3,5-triphenyl-tetrazolium chloride; and (3) enzyme-linked immunosorbent assay of trophic factors within the striatal region. Results-We did not detect intravenously administered low dose of HUCB cells in the brains of animals at day 3 after stroke even when cells were coinfused with a BBB permeabilizer (mannitol). However, HUCB-mannitol treatment significantly increased brain levels of neurotrophic factors, which correlated positively with reduced cerebral infarcts and improved behavioral functions. Conclusions-Our data show that central nervous system availability of grafted cells is not a prerequisite for acute neuroprotection provided that therapeutic molecules secreted by these cells could cross the BBB.

Background and Purpose-Intravenously delivered human umbilical cord blood cells (HUCBC) have been previouslyshown to improve functional recovery of stroked rats. To extend these findings, we examined the behavioral recovery and stroke infarct volume in the presence of increasing doses of HUCBC after permanent middle cerebral artery occlusion (MCAO). Methods-Rats were subjected to MCAO and allowed to recover for 24 hours before intravenous infusion of 10 4 up to 3 to 5ϫ10 7 HUCBC. Behavioral tests (spontaneous activity, step test, elevated body swing test) were performed 1 week before MCAO and at 2 and 4 weeks after HUCBC infusion. On completion of behavioral testing, animals were euthanized and brain infarct volumes quantified. HUCBC were identified by immunofluorescence for human nuclei and by polymerase chain reaction (PCR) using primers specific for human glycerol 3-phosphate dehydrogenase. Results-At 4 weeks after infusion, there was a significant recovery in behavioral performance when 10 6 or more HUCBC were delivered (pϭ0.001 to pϭ0.05). Infarct volume measurements revealed an inverse relationship between HUCBC dose and damage volume, which reached significance at the higher HUCBC doses (10 7 cells, pϽ0.01; 3 to 5ϫ10 7 cells, pϽ0.05). Moreover, HUCBC were localized by immunohistochemistry and PCR analysis only in the injured brain hemisphere and spleen. Conclusions-These results extend previous observations of HUCBC infusion in the MCAO rat stroke model by demonstrating a dose relationship between HUCBC, behavioral improvement, and neuronal sparing.

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While the monoamine deficiency hypothesis of depression is still most commonly used to explain the actions of antidepressant drugs, a growing body of evidence has accumulated that is not adequately explained by the hypothesis. This article draws attention to contributions from another apparently common pharmacological property of antidepressant medications-the inhibition of nicotinic acetylcholine receptors (nAChR). Evidence is presented suggesting the hypercholinergic neurotransmission, which is associated with depressed mood states, may be mediated through excessive neuronal nicotinic receptor activation and that the therapeutic actions of many antidepressants may be, in part, mediated through inhibition of these receptors. In support of this hypothesis, preliminary evidence is presented suggesting that the potent, centrally acting nAChR antagonist, mecamylamine, which is devoid of monoamine reuptake inhibition, may reduce symptoms of depression and mood instability in patients with comorbid depression and bipolar disorder. If this hypothesis is supported by further preclinical and clinical research, nicotinic acetylcholine receptor antagonists may represent a novel class of therapeutic agents for treating mood disorders.