Dianne Langford

Fibroblast Growth Factor 1 Regulates Signaling via the Glycogen Synthase Kinase-3β Pathway IMPLICATIONS FOR NEUROPROTECTION

We hypothesize that in neurodegenerative disorders such as Alzheimers disease and human immunodeficiency virus encephalitis the neuroprotective activity of fibroblast growth factor 1 (FGF1) against several neurotoxic agents might involve regulation of glycogen synthase kinase-3β (GSK3β), a pathway important in determining cell fate. In primary rat neuronal and HT22 cells, FGF1 promoted a time-dependent inactivation of GSK3β by phosphorylation at serine 9. Blocking FGF1 receptors with heparinase reduced this effect. The effects of FGF1 on GSK3β were dependent on phosphatidylinositol 3-kinase (PI3K)-protein kinase B (Akt) because inhibitors of this pathway or infection with dominant negative Akt adenovirus blocked inactivation. Furthermore, treatment of neuronal cells with FGF1 resulted in ERK-independent Akt phosphorylation and β-catenin translocation into the nucleus. On the other hand, infection with wild-type GSK3β recombinant adenovirus-associated virus increased activity of GSK3β and cell death, both of which were reduced by FGF1 treatment. Moreover, FGF1 protection against glutamate toxicity was dependent on GSK3β inactivation by the PI3K-Akt but was independent of ERK. Taken together these results suggest that neuroprotective effects of FGF1 might involve inactivation of GSK3β by a pathway involving activation of the PI3K-Akt cascades.

Patterns of selective neuronal damage in methamphetamine-user AIDS patients

The risk for HIV infection attributable to methamphetamine (METH) use continues to increase. The combined effect of HIV and METH in the pathogenesis of HIV encephalitis (HIVE) is unclear, however. To better understand the neuropathology associated with HIV and METH use, the patterns of neurodegeneration were assessed in HIV-positive METH users and in HIV-positive non-METH users. Patients in the study met criteria for inclusion and received neuromedical and postmortem neuropathologic examinations. Immunocytochemical and polymerase chain reaction analyses were performed to determine brain HIV levels and to exclude the presence of other viruses. METH-using patients with HIVE showed significantly lower gp41 scores and less severe forms of encephalitis but a higher frequency of ischemic events, a more pronounced loss of synaptophysin immunoreactivity, and a more severe microglial reaction than HIVE non-METH users. Furthermore, in METH-using patients with HIVE, extensive loss of calbindin (CB)-immunoreactive interneurons displaying phylopodial neuritic processes suggestive of aberrant sprouting was observed. Taken together, these studies indicate that the combined effects of METH and HIV selectively damage CB immunoreactive nonpyramidal neurons. In combination, METH and HIV may increase neuronal cell injury and death, thereby enhancing brain metabolic disturbances observed in clinical populations of HIV-positive METH abusers.

Lithium Ameliorates HIV-gp120-Mediated Neurotoxicity

To investigate the protective effects of lithium against HIV-gp120-mediated toxicity in vivo, mice were exposed to lithium and gp120 and levels of the neuronal markers, microtubule-associated protein-2 and NeuN, and the astrocyte marker, glial fibrillary acidic protein, were determined. In addition, SH-SY5Y neuronal cells exposed to gp120 and lithium were assessed for cell viability. Lithium pretreatment protected the hippocampus of mice from gp120-mediated toxicity. Similarly, preexposure of neuronal cultures to lithium significantly reduced gp120-associated neurotoxicity. However, posttreatment with lithium had minimal neuroprotective effects against gp120, both in vivo and in vitro. The protective effects of lithium in vitro were blocked by LY294002, an inhibitor of the phosphatidylinositol 3-kinase/Akt pathway. Taken together, these results demonstrate that lithium might be neuroprotective against gp120-mediated toxicity and suggest that prophylactic treatment with lithium may prevent the onset/progression of HIV-associated cognitive impairments.

Crosstalk between components of the blood brain barrier and cells of the CNS in microglial activation in AIDS.

During the progression of AIDS, a majority of patients develop cognitive disorders such as HIV encephalitis (HIVE) and AIDS dementia complex (ADC), which correlate closely with macrophage infiltration into the brain and microglial activation. Microglial activation occurs in response to infection, inflammation and neurological disorders including HIVE, Alzheimers disease, Parkinsons disease and multiple sclerosis. Microglia can be activated by immunoreactive cells independent of, but enhanced by HIV infection, from at least two routes. Activation may occur from signals originating from activated monocytes and lymphocytes in the blood stream, which initiate a cascade of stimuli that ultimately reach microglia in the brain or from activated macrophages/microglia/astrocytes within the brain. Effects of microglial activation stemming from both systemic and CNS HIV infection act together to commence signaling feedback, leading to HIVE and increased neurodegeneration. Most recent data indicate that in AIDS patients, microglial activation in the brain with subsequent release of excitotoxins, cytokines and chemokines leads to neurodegeneration and cognitive impairment. Since the presence of HIV in the brain results from migration of infected monocytes and lymphocytes across the vascular boundary, the development of novel therapies aimed at protecting the integrity of the blood brain barrier (BBB) upon systemic HIV infection is critical for controlling CNS infection.

Cognitive deficits and degeneration of interneurons in HIV+ methamphetamine users

The cellular basis for cognitive deficits in HIV+ patients with and without a history of methamphetamine (METH) use is unclear. We found that HIV+ METH users had more severe loss of interneurons that was associated with cognitive impairment. Compared with other markers, loss of calbindin and parvalbumin interneurons in the frontal cortex was the most significant correlate to memory deficits, suggesting a role in neurobehavioral alterations of HIV+ METH users.

Relationship of antiretroviral treatment to postmortem brain tissue viral load in human immunodeficiency virus–infected patients

Human immunodeficiency virus (HIV)-1 invades the central nervous system (CNS) soon after infection and is partially protected there from host immunity and antiretroviral drugs (ARVs). Sanctuary from highly active antiretroviral therapy (HAART) in the CNS could result in ongoing viral replication, promoting the development of drug resistance and neurological disease. Despite the importance of these risks, no previous study has directly assessed HAART’s effects on brain tissue viral load (VL). The authors evaluated 61 HIV-infected individuals for whom both histories of HAART treatment and postmortem brain tissue VL measurements were available. Two groups were defined based on HAART use in the 3 months prior to death: HAART(+) subjects had received HAART, and HAART(−) subjects had not received HAART. HIV RNA was quantified in postmortem brain tissue (log10 copies/10 μg total tissue RNA) and antemortem plasma (log10 copies/ml) by reverse transcriptase—polymerase chain reaction (RT-PCR). Brain tissue VLs were significantly lower among HAART(+) subjects compared to HAART(−) subjects (median 2.6 versus 4.1; P = .0007). These findings suggest that despite the limited CNS penetration of many antiretroviral medications, HAART is at least partially effective in suppressing CNS viral replication. Because some HAART regimens may be better than others in this regard, regimen selection strategies could be used to impede CNS viral activity, limit neuronal dysfunction, and prevent or treat clinical neurocognitive disorders in HIV-infected patients. Furthermore, such strategies might help to prevent the development of ARV resistance.

Expression of stromal cell-derived factor 1α protein in HIV encephalitis

Abstract Analysis of the patterns of stromal cell-derived factor 1α (SDF-1α) expression in the brains from HIV-positive patients suggests that in neuronal cells, SDF-1α might play a role in neuroprotection and neurite extension in response to HIV infection. In all cases analyzed, SDF-1α immunoreactivity was primarily present in astroglial cells. Patients with HIV encephalitis (HIVE) showed intense somato-dendritic neuronal SDF-1α immunoreactivity, while HIVE negative patients with neurodegeneration had a significant decrease in neuronal SDF-1α immunoreactivity. Neuronal cells treated with SDF-1α displayed increased neurite outgrowth. Similarly, neurons treated with HIV-Tat, which induced SDF-1α expression, also showed neurite outgrowth. Tat-mediated neurite outgrowth was blocked by anti-SDF-1α antibody. These results suggest that SDF-1α may play a role in the neuronal response to HIV in the brains of AIDS patients.

The role of mitochondrial alterations in the combined toxic effects of human immunodeficiency virus Tat protein and methamphetamine on calbindin positive-neurons

The use of methamphetamine (METH) continues to increase the risk of human immunodeficiency virus (HIV) transmission within both homosexual and heterosexual drug abuser groups. Neurological studies indicate that the progression of HIV encephalitis is also enhanced by illicit drug use. Recently, the authors’ studies in the postmortem brains of HIV-positive METH users have shown that the combined effects of HIV and METH selectively damage calbindin (CB)-immunoreactive nonpyramidal neurons, which may contribute to the behavioral alterations observed in these patients. To better understand the mechanisms of toxicity associated with exposure to HIV and METH, neuronal survival, phenotypic markers, levels of oxidative stress, and mitochondrial potential were assessed in vitro in the hippocampal neuronal cell line, HT22, and in primary human neurons exposed to the HIV Tat protein and/or METH. Both Tat and METH were toxic to neurons in a time- and dose-dependent fashion. Neurons exposed to a combination of Tat and METH displayed early evidence of neuronal damage at 6 h, characterized by a decrease in CB and microtubuleassociated protein 2 (MAP2) immunoreactivity followed by more extensive cell death at 24 h. Loss of CB immunoreactivity associated with the combined exposure to Tat and METH was accompanied by mitochondrial damage with increased levels of oxidative stress. The toxic effects of Tat and METH were inhibited by blocking mitochondrial uptake of intracellular calcium, whereas blocking calcium flux in the endoplasmic reticulum or from the extracellular environment had no effect on Tat and METH toxicity. These studies indicate that in vitro, when combined, the HIV protein Tat and METH damage CB-immunoreactive nonpyramidal neurons by dysregulating the mitochondrial calcium potential. In combination, Tat and METH may increase cell injury and death, thereby enhancing brain metabolic disturbances observed in HIV-positive METH users in clinical populations.

Blood biomarkers for brain injury: What are we measuring?

Accurate diagnosis for mild traumatic brain injury (mTBI) remains challenging, as prognosis and return-to-play/work decisions are based largely on patient reports. Numerous investigations have identified and characterized cellular factors in the blood as potential biomarkers for TBI, in the hope that these factors may be used to gauge the severity of brain injury. None of these potential biomarkers have advanced to use in the clinical setting. Some of the most extensively studied blood biomarkers for TBI include S100β, neuron-specific enolase, glial fibrillary acidic protein, and Tau. Understanding the biological function of each of these factors may be imperative to achieve progress in the field. We address the basic question: what are we measuring? This review will discuss blood biomarkers in terms of cellular origin, normal and pathological function, and possible reasons for increased blood levels. Considerations in the selection, evaluation, and validation of potential biomarkers will also be addressed, along with mechanisms that allow brain-derived proteins to enter the bloodstream after TBI. Lastly, we will highlight perspectives and implications for repetitive neurotrauma in the field of blood biomarkers for brain injury.

Signalling crosstalk in FGF2-mediated protection of endothelial cells from HIV-gp120.

BackgroundThe blood brain barrier (BBB) is the first line of defence of the central nervous system (CNS) against circulating pathogens, such as HIV. The cytotoxic HIV protein, gp120, damages endothelial cells of the BBB, thereby compromising its integrity, which may lead to migration of HIV-infected cells into the brain. Fibroblast growth factor 2 (FGF2), produced primarily by astrocytes, promotes endothelial cell fitness and angiogenesis. We hypothesized that treatment of human umbilical vein endothelial cells (HUVEC) with FGF2 would protect the cells from gp120-mediated toxicity via endothelial cell survival signalling.ResultsExposure of HUVEC to gp120 resulted in dose- and time-dependent cell death; whereas, pre-treatment of endothelial cells with FGF2 protected cells from gp120 angiotoxicity. Treatment of HUVEC with FGF2 resulted in dose- and time-dependent activation of the extracellular regulated kinase (ERK), with moderate effects on phosphoinositol 3 kinase (PI3K) and protein kinase B (PKB), also known as AKT, but no effects on glycogen synthase kinase 3 (GSK3β) activity. Using pharmacological approaches, gene transfer and kinase activity assays, we show that FGF2-mediated angioprotection against gp120 toxicity is regulated by crosstalk among the ERK, PI3K-AKT and PKC signalling pathways.ConclusionsTaken together, these results suggest that FGF2 may play a significant role in maintaining the integrity of the BBB during the progress of HIV associated cerebral endothelial cell damage.