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Biomedical subjects

L G Epstein

Publications and source records attributed to L G Epstein.

At least 19 recordsLinked to original sources
PubMed2006

Monocyte chemoattractant protein-1 correlates with subcortical brain injury in HIV infection.

Various biomarkers have been suggested as associative or predictive of HIV-associated neurocognitive impairment. Plasma levels of monocyte chemoattractant protein 1 (MCP-1), tumor necrosis factor alpha (TNF-alpha), and hematocrit were evaluated for relationships with diffusion tensor imaging measurements of centrum semiovale, caudate, and putamen. MCP-1 levels correlated with tissue status (mean diffusivity) in all examined regions. Plasma markers were also significantly correlated with anisotropy measurements in centrum semiovale (TNF-alpha) and putamen (hematocrit).

Basal Ganglia↗
PubMed2006

Bone marrow diffusion measures correlate with dementia severity in HIV patients.

BACKGROUND AND PURPOSE: Escalation in monocyte trafficking from the bone marrow into the brain may play a critical role in central nervous system injury and cognitive deterioration in patients with HIV infection. This study tested the hypothesis that the mean diffusivity is sensitive to marrow changes in HIV patients and that these quantitative imaging measurements correlate with the severity of dementia. METHODS: The mean diffusivity (MD), determined for clival and calvarial marrow regions, was compared in 11 HIV-infected patients and 9 control subjects. The imaging measurements were also evaluated for relationships with dementia severity and markers of disease progression (CD4 and viral load in plasma). RESULTS: The MD was significantly reduced in both clival and calvarial marrow in HIV-infected patients (P =.006). Diffusion measurements for clival (P =.02) and for calvarial (P =.03) regions were significantly correlated with the severity of dementia. CONCLUSION: The results of this investigation support the utility of diffusion strategies for monitoring the marrow and provide further evidence of a relationship between marrow status changes and neurologic progression in HIV patients.

AIDS Dementia Complex↗
PubMed2006

Diffusion alterations in corpus callosum of patients with HIV.

BACKGROUND AND PURPOSE: Diffusion alterations have been identified in the corpus callosum and frontal white matter of patients infected with human immunodeficiency virus (HIV), though the relevance of these findings to cognitive deterioration has not yet been determined. This study tested the hypothesis that diffusion tensor imaging can detect tissue status alterations in these regions in cognitively impaired patients infected with HIV and the acquired measurements correlate with the severity of cognitive impairment. METHODS: Fractional anisotropy (FA) and mean diffusivity (MD) were determined for corpus callosum (genu and splenium) and frontal white matter (FWM). The DTI measurements were compared in 11 HIV and 11 control participants. Patterns of relationship were examined with cognitive status measures from concurrent neurologic and neuropsychologic evaluations. RESULTS: FA values for the splenium were significantly reduced in the patients infected with HIV and correlated with dementia severity and deficits in motor speed. MD values for the splenium were significantly increased in the patients infected with HIV and correlated with deficits in motor speed. FA measurements were also significantly correlated with performance on visual memory (genu), visuoconstruction (FWM), and verbal memory (FWM) tasks. CONCLUSION: Diffusion abnormalities were identified in the splenium of the corpus callosum in patients infected with HIV, and these alterations were associated with dementia severity and motor speed losses. In vivo assessment of callosal integrity by using quantitative neuroimaging may have potential utility as a marker of brain injury in patients infected with HIV.

Corpus Callosum↗
PubMed2005

Markers of immune activation and viral load in HIV-associated sensory neuropathy.

BACKGROUND: HIV infection is associated with a painful distal sensory polyneuropathy (DSP) that can severely limit the quality of life of affected subjects. The pathogenesis of DSP is unknown, although both HIV proteins and products of immune activation triggered by HIV infection have been implicated. OBJECTIVE: To assess the association between baseline markers of immune activation and HIV RNA levels (viral load) and time to symptomatic DSP (SDSP). METHODS: A cohort of 376 subjects, most receiving highly active antiretroviral therapy (HAART), were followed semiannually for up to 48 months. Blood and CSF levels of HIV viral load, monocyte chemotactic protein-1, macrophage colony-stimulating factor (M-CSF), matrix metalloproteinase-2, and tumor necrosis factor-alpha were measured in addition to CD4 lymphocyte cell count. RESULTS: In subjects without SDSP at baseline (62.5% of the cohort), among the virologic and immunologic markers, only baseline CSF M-CSF levels were associated with time to SDSP (hazard ratio = 2.97, p = 0.05). The Kaplan-Meier estimate of the 1-year incidence of SDSP was 21%, a 15% decrease from that observed in the Dana cohort, a pre-HAART cohort enrolled with the same inclusion/exclusion criteria. CONCLUSION: Highly active retroviral therapy (HAART) has changed the natural history of HIV-associated symptomatic distal sensory polyneuropathy (SDSP), which may explain, in contrast with studies from the pre-HAART era, the lack of association between SDSP and baseline HIV viral load and CD4 cell count.

Adult↗
PubMed2004

Disease burden in HIV-associated cognitive impairment: a study of whole-brain imaging measures.

OBJECTIVE: To study whole-brain MR measures derived from diffusion tensor imaging and magnetization transfer imaging (MTI) for the in vivo assessment of cumulative neuropathologic changes in HIV and to evaluate the quantitative imaging strategies with respect to cognitive status measures including the severity of dementia and the degree of impairment in specific cognitive domains including attention, memory, constructional abilities, and motor speed. METHODS: Quantitative whole-brain measurements, including fractional anisotropy (FA), apparent diffusion coefficient (ADC), and magnetization transfer ratio (MTR), were derived from histograms and compared in HIV and control participants. Relationships between the MR and cognitive status measures were examined. RESULTS: Whole-brain FA and MTR were reduced in patients with HIV and correlated with dementia severity. Whole-brain MTR and ADC were correlated with psychomotor deficits. Evaluation of relationships between the studied MR measures indicated a correlation between ADC and MTR; FA was not correlated with either ADC or MTR. CONCLUSIONS: Findings from this investigation support the use of quantitative whole-brain MR measures for evaluation of disease burden in HIV. Reductions in whole-brain fractional anisotropy and magnetization transfer ratio (MTR) distinguished HIV and control subjects, and these measures were associated with dementia severity. Relationships were identified between whole-brain MTR and apparent diffusion coefficient and psychomotor deficits. Combining these quantitative strategies in neuroimaging examinations may provide more comprehensive information concerning ongoing changes in the brains of HIV patients.

AIDS Dementia Complex↗
PubMed2004

Evaluation of HIV RNA and markers of immune activation as predictors of HIV-associated dementia.

OBJECTIVE: To evaluate whether baseline levels of plasma and CSF HIV RNA, tumor necrosis factor alpha (TNFalpha), monocyte chemoattractant protein-1 (MCP-1), matrix metalloproteinase-2 (MMP-2), or macrophage colony stimulating factor (M-CSF) are predictors of incident HIV-associated dementia (HIVD) in a cohort with advanced HIV infection. METHODS: A total of 203 nondemented subjects with CD4 lymphocyte counts less than 200/muL, or <300/microL but with cognitive impairment, underwent semiannual neurologic, cognitive, functional, and laboratory assessments. HIVD and minor cognitive motor disorder (MCMD) were defined using American Academy of Neurology criteria. The cumulative incidence of HIVD was estimated using Kaplan-Meier curves. Cox proportional hazards regression models were used to examine the associations between biologic variables and time to HIVD, adjusting for age, sex, years of education, duration of HIV infection, type of antiretroviral use, premorbid IQ score, and presence of MCMD. RESULTS: After a median follow-up time of 20.7 months, 74 (36%) subjects reached the HIVD endpoint. The dementia was mild in 70% of cases. The cumulative incidence of HIVD was 20% at 1 year and 33% at 2 years. Highly active antiretroviral therapy (HAART) was used by 73% of subjects at baseline. A plasma HIV RNA level was undetectable in 23% of subjects and a CSF HIV RNA level was undetectable in 48% of subjects. In adjusted analyses, neither plasma nor CSF HIV RNA levels (log10) were associated with time to HIVD; log10 levels of plasma TNFalpha (HR 3.07, p = 0.03) and CSF MCP-1 (HR = 3.36, p = 0.06) tended to be associated with time to HIVD. CONCLUSION: The lack of association between baseline plasma and CSF HIV RNA levels and incident dementia suggests highly active antiretroviral therapy may be affecting CNS viral dynamics, leading to lower HIV RNA levels, and therefore weakening the utility of baseline HIV RNA levels as predictors of HIV-associated dementia.

AIDS Dementia Complex↗
PubMed2003

Inter-rater reliability of a clinical staging of HIV-associated cognitive impairment.

OBJECTIVE: To determine the inter-rater reliability of a modification of the Memorial Sloan-Kettering (MSK) Staging for HIV-associated cognitive impairment. METHODS: Data were abstracted on neurologic, neuropsychological, and functional status on 100 individuals participating at four sites in the Northeast AIDS Dementia (NEAD) Consortium cohort study, a longitudinal study of predictors of cognitive impairment in HIV-infected individuals. Neuropsychological performance was defined 1) based on the neuropsychologist's global impression and 2) solely based on neuropsychological test scores. Raters at each site used the abstracted data to assign an MSK stage to each subject blind to any identifying information. Inter-rater reliability was assessed using kappa statistics. Agreement between computer-generated ratings and site-generated ratings was also assessed. RESULTS: Kappa statistics for pair-wise agreement among the sites regarding MSK stage ranged from 0.70-0.91, representing good to excellent agreement between sites. Agreement between computer-generated ratings and site-generated ratings was in the good to excellent range (0.62-0.79). CONCLUSIONS: The authors have modified the MSK rating scale and developed a reliable instrument that can be used in multicenter studies. This instrument will be useful in staging HIV-dementia in future longitudinal studies and will be valuable in increasing accuracy of clinicopathologic studies.

AIDS Dementia Complex↗
PubMed2000

Neuronal fractalkine expression in HIV-1 encephalitis: roles for macrophage recruitment and neuroprotection in the central nervous system.

HIV-1 infection of the brain results in chronic inflammation, contributing to the neuropathogenesis of HIV-1 associated neurologic disease. HIV-1-infected mononuclear phagocytes (MP) present in inflammatory infiltrates produce neurotoxins that mediate inflammation, dysfunction, and neuronal apoptosis. Neurologic disease is correlated with the relative number of MP in and around inflammatory infiltrates and not viral burden. It is unclear whether these cells also play a neuroprotective role. We show that the chemokine, fractalkine (FKN), is markedly up-regulated in neurons and neuropil in brain tissue from pediatric patients with HIV-1 encephalitis (HIVE) compared with those without HIVE, or that were HIV-1 seronegative. FKN receptors are expressed on both neurons and microglia in patients with HIVE. These receptors are localized to cytoplasmic structures which are characterized by a vesicular appearance in neurons which may be in cell-to-cell contact with MPs. FKN colocalizes with glutamate in these neurons. Similar findings are observed in brain tissue from an adult patient with HIVE. FKN is able to potently induce the migration of primary human monocytes across an endothelial cell/primary human fetal astrocyte trans-well bilayer, and is neuroprotective to cultured neurons when coadministered with either the HIV-1 neurotoxin platelet activating factor (PAF) or the regulatory HIV-1 gene product Tat. Thus focal inflammation in brain tissue with HIVE may up-regulate neuronal FKN levels, which in turn may be a neuroimmune modulator recruiting peripheral macrophages into the brain, and in a paracrine fashion protecting glutamatergic neurons.

Adult↗
PubMed2000

Release of the neuronal glycoprotein ICAM-5 in serum after hypoxic-ischemic injury.

Intercellular adhesion molecule (ICAM)-5 (telencephalin) is unique among the ICAMs, because it is only expressed in somatodendritic membranes of telencephalic neurons. To investigate the fate of ICAM-5 during focal brain injury, we induced hypoxia-ischemia (HI) damage in adult mice by right common carotid artery ligation followed by hypoxia. ICAM-5 was detectable in serum within a 48-hour window after HI injury. In HI brain, dendritic ICAM-5 immunore-activity was abolished, but it was present in the neuropil and soma of hippocampal pyramidal, dentate granule, and some cortical and striatal neurons. After HI injury, levels of ICAM-5 protein and messenger RNA initially increased, and ICAM-5 messenger RNA expression then decreased, although protein levels continued to increase. Because HI injury induces microglial activation with increases in CD11a/CD18 (lymphocyte function antigen [LFA]-1) counterreceptors to ICAM-5, we investigated whether modulation of interactions between LFA-1 receptors and brain ICAM-5 during HI injury are associated with changes in levels of serum ICAM-5. Intracerebroventricular administration of lipopolysaccharide to activate microglia before HI injury resulted in elevated serum ICAM-5 levels compared with those in mice with only HI injury. Pretreatment with anti-LFA-1 antibodies before HI injury or LFA-1 receptor knockout mice with HI injury had markedly reduced levels of serum ICAM-5. Lipopolysaccharide levels increased, whereas LFA-1 receptor blockade or LFA-1 knockout decreased HI injury in the first 12 hours. These data suggest that during the necrotic phase of HI injury, serum ICAM-5 may be a potential marker for somatodendritic neuronal damage.

Animals↗
PubMed1999

Randomized trial of the platelet-activating factor antagonist lexipafant in HIV-associated cognitive impairment. Neurological AIDS Research Consortium.

OBJECTIVE: To assess the safety and tolerability of lexipafant in HIV-associated cognitive impairment. BACKGROUND: Cognitive impairment is the most common neurologic complication of advanced HIV-1 infection. There is evidence that a variety of inflammatory mediators, including platelet-activating factor (PAF), may contribute to neuronal injury. We hypothesized that lexipafant, a PAF antagonist, might improve cognitive dysfunction in HIV-infected people. METHODS: We conducted a randomized, double-blind, placebo-controlled clinical trial to assess the safety and tolerability of lexipafant 500 mg/day. The primary outcome measure for tolerability was the ability to complete the study on the originally assigned dosage of medication. Thirty patients with cognitive impairment were enrolled. RESULTS: Lexipafant was safe and well tolerated. Ninety-three percent in the placebo group and 88% in the lexipafant group completed the study at the originally assigned dosage. Trends toward improvement were seen in neuropsychological performance, especially verbal memory, in the lexipafant treatment group. CONCLUSIONS: This study shows that lexipafant, the first PAF antagonist used in HIV-associated cognitive impairment, is a safe and well tolerated compound. The observed trends toward improvement in neuropsychological test scores warrant the pursuit of a larger and longer efficacy trial to assess the impact of lexipafant on cognitive performance.

Adult↗
PubMed1999

Coreceptor ligand inhibition of fetal brain cell infection by HIV type 1.

The capacity of a panel of HIV-1 isolates to infect primary mixed fetal brain cell cultures was estimated and their sensitivity to inhibition by a range of coreceptor ligands assessed. Our results show that (1) HIV-1 strains that predominantly use CCR5 or only CXCR4 are able to infect microglia in primary brain cell cultures, and (2) ligands to these two coreceptors can inhibit brain cell infection. CCR5 ligands (including AOP-RANTES, a potent inhibitor of CCR5-dependent infection), however, blocked infection only weakly, raising the possibility that alternative unidentified coreceptors are also used. Interestingly, vMIP-II, a chemokine encoded by the Kaposi sarcoma-associated herpes virus (KSHV), reduced brain cell infection by all HIV-1 strains tested, including both R5 and X4 viruses. Our results therefore indicate that novel drugs targeted to the major HIV-1 coreceptors will influence HIV replication in the brain, if they cross the blood-brain barrier.

Anti-HIV Agents↗
PubMed1999

Proteasome blockers inhibit TNF-alpha release by lipopolysaccharide stimulated macrophages and microglia: implications for HIV-1 dementia.

HIV-1 infection of the central nervous system can cause severe neurologic disease although only microglial cells and brain macrophages are susceptible to productive viral infection. Substances secreted by infected cells are thought to cause disease indirectly. Tumor necrosis factor alpha (TNF-alpha) is one candidate neurotoxin and is upregulated during HIV-1 infection of the brain, likely via activation of the transcription factor NF-kappaB. We used the proteasome inhibitors, MG132 and ALLN (N-acetyl-Leu-Leu-Norleucinal), to inhibit NF-kappaB activation in primary human fetal microglia (PHFM) and primary monocyte derived-macrophages, and showed that they could block TNF-alpha release stimulated by lipopolysaccharide (LPS) or TNF-alpha. In addition, we performed electrophoretic mobility shift analysis and determined that in microglia, the p50/p65 heterodimer of NF-kappaB is activated by LPS stimulation, and is inhibited by MG132. Thus, blockade of NF-kappaB activation in microglia in vitro can decrease production of TNF-alpha and may prove to be a novel strategy for treating HIV-1 dementia.

AIDS Dementia Complex↗
PubMed1999

HIV-1-induced neuronal injury in the developing brain.

HIV-1 infection of the nervous system causes neuronal injury and death, resulting in cognitive, motor, and behavioral dysfunction in both adults and children. In infants a characteristic feature of HIV-1 infection is impaired brain growth resulting in secondary microcephaly with onset between 2 and 4 months of age. This post-natal period of brain development is particularly vulnerable to excitotoxic neuronal injury due to the active synaptogenesis and pruning that takes place at this age associated with over-expression of excitatory amino acid (EAA) receptors. HIV-1 infection of brain microglia and perivascular macrophages results in chronic inflammation manifest pathologically as diffuse microglial activation and reactive astrogliosis. Several inflammatory products of activated microglia, including tumor necrosis factor alpha (TNF-alpha) and platelet-activating factor (PAF) have been shown to act as neuronal toxins. This toxic effect can be antagonized by blocking NMDA (or AMPA) glutamate receptors, suggesting that (weak) excitotoxicity leads to oxidative stress, neuronal injury, and apoptosis. HIV-1 infection and chronic inflammation may also contribute disruption of the blood-brain barrier and could result in further entry into the CNS of toxic viral or cellular products or additional HIV-1-infected cells. We hypothesize that prolonged microglial activation during HIV-1 infection underlies the neuronal injury and impaired brain growth in affected infants. Further investigation of the interaction between HIV-1-infected/activated microglia and developing neurons seems warranted. The current understanding of HIV neuropathogenesis implies that therapeutic strategies should target the sustained immune activation in microglia, attempt to repair the integrity of the blood-brain barrier, and provide "neuroprotection" from excitotoxic neuronal injury.

Animals↗
PubMed1999

Expression of caspase-3 in brains from paediatric patients with HIV-1 encephalitis.

Apoptosis of neurones, macrophages, and microglia occurs in the brains of paediatric patients with human immunodeficiency virus (HIV) type 1 encephalitis, which is often associated with pre-mortem neurological disease (progressive encephalopathy). We have previously reported that TUNEL-positive neurones in brain tissue from paediatric patients with HIV type 1 encephalitis and progressive encephalopathy are strikingly devoid of the pro-apoptotic gene product Bax, in marked contrast to brain-resident macrophages and microglia. Using immunocytochemical methods, the present study demonstrate that neurones in patients with HIV type 1 encephalitis and progressive encephalopathy, as well as macrophages and microglia, but not astrocytes, overexpress caspase-3, a pro-apoptotic enzyme that is proteolytically activated downstream of Bax-Bcl-2 dysregulation. Co-localization of neuronal cytoplasmic caspase-3 and nuclear TUNEL staining, a marker for fragmented DNA, was also infrequently observed in brain tissue from patients with HIV type 1 encephalitis and progressive encephalopathy. These findings suggest that vulnerable neurones in brain tissue from patients with HIV virus type 1 encephalitis and progressive encephalopathy undergo apoptosis by a mechanism that involves upregulation of caspase-3 in a pathway that is independent of Bax-Bcl-2 dysregulation. Furthermore, caspase-3 upregulation in apoptotic neurones likely occurs prior to DNA fragmentation.

AIDS Dementia Complex↗
PubMed1999

Association of human herpesvirus 6 with the demyelinative lesions of progressive multifocal leukoencephalopathy.

Progressive Multifocal Leukoencephalopathy (PML) is a primary demyelinating disease of the central nervous system occurring almost exclusively in individuals with impaired cell-mediated immunity. The JC polyoma virus has been accepted as the etiologic agent ofPML. Using a two-step in-situ polymerase chain reaction procedure to amplify and detect genomic DNA of human herpesvirus-6 (HHV6) in formalin-fixed paraffin-embedded archival brain tissues, a high frequency of infected cells was consistently detected in PML white matter both within and surrounding demyelinative lesions and HHV6 genome was found mainly within oligodendrocytes. Lesser amounts of HHV6 genome were detected in most normal, AIDS, and other neurological disease control tissues. Immunocytochemistry for HHV6 antigens showed actively infected nuclei of swollen oligodendrocytic morphology only within the demyelinative lesions of PML but not in adjacent uninvolved tissue. In addition, no HHV6 antigens were detectable in control tissues including brains of individuals with HIV-1 encephalopathy but without PML. Double immunohistochemical staining for JC virus large T antigen and HHV6 antigens demonstrated co-labeling of many swollen intralesional oligodendrocytes in the PML cases. The evidence suggests that HHV6 activation in conjunction with JC virus infection is associated with the demyelinative lesions of PML.

AIDS Dementia Complex↗
PubMed1998

Luciferase: a sensitive and quantitative probe for blood-brain barrier disruption.

A novel method for quantitative analysis of blood-brain barrier (BBB) disruption is described, using luciferase as a probe in a murine model system. Purified luciferase was delivered to mouse brain by osmotic BBB disruption with hypertonic mannitol; control animals received an intracarotid inoculation of saline prior to infusion of luciferase. Delivery of luciferase to brain tissue was then assessed by enzyme assay of tissue extracts, and by immunohistochemical staining. Luciferase activity in the brain of mannitol-treated animals was found to be significantly elevated (approx. sevenfold), when compared to activity in control (saline-treated) mice. This finding was confirmed by quantitative immunohistochemical staining of tissue sections, using a luciferase-specific antibody. These studies showed that there was an eight-fold elevation in the level of extravascular luciferase particles within the brain of mannitol-treated animals, as compared to controls. Taken together these data show that purified recombinant luciferase can be used as a sensitive probe, with which to study the integrity of the BBB.

Animals↗
PubMed1998

Platelet-activating factor receptor activation. An initiator step in HIV-1 neuropathogenesis.

Human immunodeficiency virus type 1 (HIV-1) infection of the central nervous system results in neuronal apoptosis. Activated HIV-1-infected monocytes secrete high levels of the proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) and the phospholipid mediator platelet-activating factor (PAF). TNF-alpha and PAF are elevated in the central nervous system of patients with HIV-1-associated dementia. We now demonstrate that conditioned media from activated HIV-1-infected monocytes induces neuronal apoptosis, which can be prevented by co-incubation with PAF acetylhydrolase, the enzyme that catabolizes PAF in the central nervous system. Preceding apoptosis is a TNF-alpha-induced increase in neuronal ceramide levels. TNF-alpha-mediated neuronal apoptosis can also be blocked by co-incubation with PAF acetylhydrolase, or a PAF receptor antagonist. Blocking pathologic activation of PAF receptors may therefore be a pivotal step in the treatment of HIV-1-associated dementia.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗