Neuropatogenia de HIV en la era HAART / Neuropathogenesis of HIV in the HAART era

La infección de tejidos cerebrales por HIV se asocia a desórdenes neurocognitivos identificados bajo la denominación HAND y categorizados en demencia, formas moderadas y formas asintomáticas. La introducción de terapia de alta efectividad ha implicado un notorio descenso de la demencia, pero no ha influido sobre las formas moderadas y asintomáticas que afectan alrededor del 50% de los pacientes bajo tratamiento. Esa disfunción cognitiva resulta de la pérdida de neuronas que, sin embargo, no han sido infectadas por el virus. De ahí la importancia de mecanismos indirectos en la neuropatogenia de HIV, ya que las citocinas/quimiocinas pro-inflamatorias liberadas por macrófagos/microglia infectados, la excitoxidad y el stress oxidativo se evidencian como principales causas de injuria neuronal, además de la directamente provocada por proteínas virales. Un mejor conocimiento de la interacción de HIV con su huésped humano está posibilitando el desarrollo de abordajes diganósticos más confiables y de estrategias terapéuticas más efectivas a nivel de SNC

HIV-1 associated neurocognitive disorders (HAND) result from brain infection. They are categorized as dementia, mild cases and asymptomatic cases. The introduction of HAART has markedly decreased dementia but no influence has been observed in mild and asymptomatic cases, since they are still identified in around 50 % of treated patients. Such cognitive dysfunction is the outcome of the loss of neurons which, however, have not been infected by the virus. hence, the importance of indirect mechanisms in HIV neuropathogenesis in which cytokines/chemokines released by infected macrophages/microglia, excitotoxic neuronal injury and oxidative stress are relevant causes of neurodegeneration besides that exerted by viral proteins. A better understanding of the HIV interaction with th human host is enabling the development of more reliable diagnostic biomarkers and more effective therapeutic strategies at CNS level

Neuropatogenia de HIV en la era HAART / Neuropathogenesis of HIV in the HAART era

La infección de tejidos cerebrales por HIV se asocia a desórdenes neurocognitivos identificados bajo la denominación HAND y categorizados en demencia, formas moderadas y formas asintomáticas. La introducción de terapia de alta efectividad ha implicado un notorio descenso de la demencia, pero no ha influido sobre las formas moderadas y asintomáticas que afectan alrededor del 50% de los pacientes bajo tratamiento. Esa disfunción cognitiva resulta de la pérdida de neuronas que, sin embargo, no han sido infectadas por el virus. De ahí la importancia de mecanismos indirectos en la neuropatogenia de HIV, ya que las citocinas/quimiocinas pro-inflamatorias liberadas por macrófagos/microglia infectados, la excitoxidad y el stress oxidativo se evidencian como principales causas de injuria neuronal, además de la directamente provocada por proteínas virales. Un mejor conocimiento de la interacción de HIV con su huésped humano está posibilitando el desarrollo de abordajes diganósticos más confiables y de estrategias terapéuticas más efectivas a nivel de SNC (AU)

HIV-1 associated neurocognitive disorders (HAND) result from brain infection. They are categorized as dementia, mild cases and asymptomatic cases. The introduction of HAART has markedly decreased dementia but no influence has been observed in mild and asymptomatic cases, since they are still identified in around 50 % of treated patients. Such cognitive dysfunction is the outcome of the loss of neurons which, however, have not been infected by the virus. hence, the importance of indirect mechanisms in HIV neuropathogenesis in which cytokines/chemokines released by infected macrophages/microglia, excitotoxic neuronal injury and oxidative stress are relevant causes of neurodegeneration besides that exerted by viral proteins. A better understanding of the HIV interaction with th human host is enabling the development of more reliable diagnostic biomarkers and more effective therapeutic strategies at CNS level (AU)

Regional differences in astrocyte activation in HIV-associated dementia.

Since astrogliosis is a histological marker usually observed in HIV-associated dementia (HIV-D), we decided to investigate the potential relationship between the expression of glial fibrillary acidic protein (GFAP) and the regional distribution of cells positive (+) for this specific marker of astrocyte activation. Histological sections of brain tissues obtained at necropsy from 5 HIV-D patients and 5 age-matched controls without history of neuropsychiatric illness were immunostained with peroxidase. Mean numbers of GFAP(+) astrocytes were significantly increased in entorhinal cortex, hippocampus and subcortical white matter of patients, but values in frontal cortex and basal ganglia were similar to those of controls. In contrast, surface density of immunoreactive GFAP was significantly increased in all tested brain areas from all patients, including unusually affected regions such as entorhinal cortex and hippocampus. Therefore, such consistent finding of hypertrophic astrocytes, ranging from highest cell percentajes in subcortical white matter to lowest in basal ganglia indicates that quantification of surface density in GFAP (+) cells appears to be a more reliable approach to score gliosis than the counting of their cell nuclei. Because astrocyte activation involves both protective and detrimental effects on adjacent neuronal subsets, the evidence of regional differences in this reactive potential highlights the importance of accurately defining their contribution to the neuropathogenesis not only of HIV-D, but of a wide range of neurodegenerative disorders.

Regional differences in astrocyte activation in HIV-associated dementia

Since astrogliosis is a histological marker usually observed in HIV-associated dementia (HIV-D),we decided to investigate the potential relationship between the expression of glial fibrillary acidicprotein (GFAP) and the regional distribution of cells positive (+) for this specific marker of astrocyte activation.Histological sections of brain tissues obtained at necropsy from 5 HIV-D patients and 5 age-matched controlswithout history of neuropsychiatric illness were immunostained with peroxidase. Mean numbers of GFAP(+)astrocytes were significantly increased in entorhinal cortex, hippocampus and subcortical white matter of patients,but values in frontal cortex and basal ganglia were similar to those of controls. In contrast, surface density ofimmunoreactive GFAP was significantly increased in all tested brain areas from all patients, including unusuallyaffected regions such as entorhinal cortex and hippocampus. Therefore, such consistent finding of hypertrophicastrocytes, ranging from highest cell percentajes in subcortical white matter to lowest in basal ganglia indicatesthat quantification of surface density in GFAP (+) cells appears to be a more reliable approach to score gliosisthan the counting of their cell nuclei. Because astrocyte activation involves both protective and detrimental effectson adjacent neuronal subsets, the evidence of regional differences in this reactive potential highlights theimportance of accurately defining their contribution to the neuropathogenesis not only of HIV-D, but of a widerange of neurodegenerative disorders. (AU)

Diferencias regionales en la activación astrocitaria en demencia asociada a HIV. Siendo laastrogliosis un signo histológico habitualmente presente en demencia asociada a HIV, se investigóla eventual relación entre expresión de proteína gliofibrilar ácida (GFAP) y localización regional de células positivaspara ese marcador específico de la activación astrocitaria. Por inmunoperoxidasa, se procesaron cortes histológicosde tejidos cerebrales obtenidos por necropsia de 5 pacientes y 5 controles de edades similares pero sin antecedentesneuropsiquiátricos. Según los valores de las medias registrados por conteo de astrocitos GFAP(+) en pacientes,el número fue significativamente mayor en corteza entorrinal, hipocampo y sustancia blanca subcortical, mientrasque en corteza frontal y ganglios basales no se encontraron diferencias con controles. En cambio, la densidad desuperficie del material GFAP inmunorreactivo en pacientes estuvo significativamente aumentada en todas las áreascerebrales analizadas, incluso en regiones inusualmente afectadas, como corteza entorrinal e hipocampo. Entreesos astrocitos hipertróficos, el mayor porcentaje correspondió a sustancia blanca subcortical, y el menor a gangliosbasales. Cabe concluir que el constante hallazgo de agrandamiento astrocitario señala a la medida de la superficieinmuno-reactiva como mejor índice de activación celular que el conteo de núcleos de las células marcadas. Dadoslos reconocidos efectos de la astrogliosis sobre las subpoblaciones neuronales vecinas, la comprobadaregionalización de ese potencial reactivo destaca el interés de precisar su contribución en la neuropatogenia, tantode demencia asociada a HIV como de otras enfermedades neurodegenerativas. (AU)

Regional differences in astrocyte activation in HIV-associated dementia

Since astrogliosis is a histological marker usually observed in HIV-associated dementia (HIV-D),we decided to investigate the potential relationship between the expression of glial fibrillary acidicprotein (GFAP) and the regional distribution of cells positive (+) for this specific marker of astrocyte activation.Histological sections of brain tissues obtained at necropsy from 5 HIV-D patients and 5 age-matched controlswithout history of neuropsychiatric illness were immunostained with peroxidase. Mean numbers of GFAP(+)astrocytes were significantly increased in entorhinal cortex, hippocampus and subcortical white matter of patients,but values in frontal cortex and basal ganglia were similar to those of controls. In contrast, surface density ofimmunoreactive GFAP was significantly increased in all tested brain areas from all patients, including unusuallyaffected regions such as entorhinal cortex and hippocampus. Therefore, such consistent finding of hypertrophicastrocytes, ranging from highest cell percentajes in subcortical white matter to lowest in basal ganglia indicatesthat quantification of surface density in GFAP (+) cells appears to be a more reliable approach to score gliosisthan the counting of their cell nuclei. Because astrocyte activation involves both protective and detrimental effectson adjacent neuronal subsets, the evidence of regional differences in this reactive potential highlights theimportance of accurately defining their contribution to the neuropathogenesis not only of HIV-D, but of a widerange of neurodegenerative disorders. (AU)

Diferencias regionales en la activación astrocitaria en demencia asociada a HIV. Siendo laastrogliosis un signo histológico habitualmente presente en demencia asociada a HIV, se investigóla eventual relación entre expresión de proteína gliofibrilar ácida (GFAP) y localización regional de células positivaspara ese marcador específico de la activación astrocitaria. Por inmunoperoxidasa, se procesaron cortes histológicosde tejidos cerebrales obtenidos por necropsia de 5 pacientes y 5 controles de edades similares pero sin antecedentesneuropsiquiátricos. Según los valores de las medias registrados por conteo de astrocitos GFAP(+) en pacientes,el número fue significativamente mayor en corteza entorrinal, hipocampo y sustancia blanca subcortical, mientrasque en corteza frontal y ganglios basales no se encontraron diferencias con controles. En cambio, la densidad desuperficie del material GFAP inmunorreactivo en pacientes estuvo significativamente aumentada en todas las áreascerebrales analizadas, incluso en regiones inusualmente afectadas, como corteza entorrinal e hipocampo. Entreesos astrocitos hipertróficos, el mayor porcentaje correspondió a sustancia blanca subcortical, y el menor a gangliosbasales. Cabe concluir que el constante hallazgo de agrandamiento astrocitario señala a la medida de la superficieinmuno-reactiva como mejor índice de activación celular que el conteo de núcleos de las células marcadas. Dadoslos reconocidos efectos de la astrogliosis sobre las subpoblaciones neuronales vecinas, la comprobadaregionalización de ese potencial reactivo destaca el interés de precisar su contribución en la neuropatogenia, tantode demencia asociada a HIV como de otras enfermedades neurodegenerativas. (AU)

Regional differences in astrocyte activation in HIV-associated dementia

Since astrogliosis is a histological marker usually observed in HIV-associated dementia (HIV-D),we decided to investigate the potential relationship between the expression of glial fibrillary acidicprotein (GFAP) and the regional distribution of cells positive (+) for this specific marker of astrocyte activation.Histological sections of brain tissues obtained at necropsy from 5 HIV-D patients and 5 age-matched controlswithout history of neuropsychiatric illness were immunostained with peroxidase. Mean numbers of GFAP(+)astrocytes were significantly increased in entorhinal cortex, hippocampus and subcortical white matter of patients,but values in frontal cortex and basal ganglia were similar to those of controls. In contrast, surface density ofimmunoreactive GFAP was significantly increased in all tested brain areas from all patients, including unusuallyaffected regions such as entorhinal cortex and hippocampus. Therefore, such consistent finding of hypertrophicastrocytes, ranging from highest cell percentajes in subcortical white matter to lowest in basal ganglia indicatesthat quantification of surface density in GFAP (+) cells appears to be a more reliable approach to score gliosisthan the counting of their cell nuclei. Because astrocyte activation involves both protective and detrimental effectson adjacent neuronal subsets, the evidence of regional differences in this reactive potential highlights theimportance of accurately defining their contribution to the neuropathogenesis not only of HIV-D, but of a widerange of neurodegenerative disorders.

Diferencias regionales en la activación astrocitaria en demencia asociada a HIV. Siendo laastrogliosis un signo histológico habitualmente presente en demencia asociada a HIV, se investigóla eventual relación entre expresión de proteína gliofibrilar ácida (GFAP) y localización regional de células positivaspara ese marcador específico de la activación astrocitaria. Por inmunoperoxidasa, se procesaron cortes histológicosde tejidos cerebrales obtenidos por necropsia de 5 pacientes y 5 controles de edades similares pero sin antecedentesneuropsiquiátricos. Según los valores de las medias registrados por conteo de astrocitos GFAP(+) en pacientes,el número fue significativamente mayor en corteza entorrinal, hipocampo y sustancia blanca subcortical, mientrasque en corteza frontal y ganglios basales no se encontraron diferencias con controles. En cambio, la densidad desuperficie del material GFAP inmunorreactivo en pacientes estuvo significativamente aumentada en todas las áreascerebrales analizadas, incluso en regiones inusualmente afectadas, como corteza entorrinal e hipocampo. Entreesos astrocitos hipertróficos, el mayor porcentaje correspondió a sustancia blanca subcortical, y el menor a gangliosbasales. Cabe concluir que el constante hallazgo de agrandamiento astrocitario señala a la medida de la superficieinmuno-reactiva como mejor índice de activación celular que el conteo de núcleos de las células marcadas. Dadoslos reconocidos efectos de la astrogliosis sobre las subpoblaciones neuronales vecinas, la comprobadaregionalización de ese potencial reactivo destaca el interés de precisar su contribución en la neuropatogenia, tantode demencia asociada a HIV como de otras enfermedades neurodegenerativas.

Immunochemical and morphometric features of astrocyte reactivity vs. plaque location in Alzheimer's disease.

The quantitative relationship between glial fibrillary acidic protein (GFAP) hyper-reactivity and beta-amyloid protein (betaAP) deposition was investigated by double immunoperoxidase labeling of hippocampal and entorhinal cortex sections from five Alzheimer's disease (AD) cases and five age-matched controls. betaAP plaques, which were absent in controls, were found in all AD samples, without significant differences in number or perimeter according to their location among the regions studied. In contrast, the mean number of GFAP (+) cells was significantly greater in the hippocampus than in the entorhinal cortex from AD cases (49 vs.39). Although at lower values (30 vs. 20), predominance of astrocyte hyperplasia in hippocampus as compared with entorhinal cortex was also found in control samples. Concomitant astrocyte hypertrophy, as defined by surface density (Sv) values of GFAP-immunoreactive material exceeding those of control means, affected a similar proportion of cells in the hippocampus (73%) and the entorhinal cortex (74%) from AD cases. Since an increased number of GFAP (+) cells in the hippocampus was not accompanied by an increased number and/or perimeter of neighbouring plaques, such differential hyper-reactivity in samples from AD patients, as well as in those with normal aging, seems to depend partially on the regional location of the involved astrocyte.

Differential astrocyte response to Theiler's murine encephalomyelitis virus infection.

OBJECTIVES: We aimed to address if selective astrocyte apoptosis is involved in the lack of murine demyelinating disease following infection by the L*-1 variant of Theiler's virus. In addition, we investigated whether L*-1-infected astrocytes were able to selectively express molecules whose effects would play a role as pathogenic factors. METHODS: Murine cultured astrocytes were infected with two Theiler viruses, the DA strain and the mutated DA variant L*-1, which does not synthesize the out of frame L* protein. RESULTS: Neither DA nor L*-1 provoked apoptosis, although they replicated in astrocytes inducing GFAP and iNOS expression, as well as subsequent nitric oxide production. In addition, both viruses caused an enhanced expression of ICAM-1, VCAM-1 and decay accelerating factor (DAF). In this connection, values of VCAM-1 and DAF induced by L*-1 were higher and lower, respectively, than those induced by DA. CONCLUSIONS: Since no apoptosis was found, such mechanism would not be involved in the lack of TMEV-induced demyelinating disease by L*-1. In contrast, selective expression of VCAM-1 and DAF molecules induced by L*-1 could have a role in virus clearance from the central nervous system.

Immunochemical and morphometric features of astrocyte reactivity vs. plaque location in Alzheimers disease.

The quantitative relationship between glial fibrillary acidic protein (GFAP) hyper-reactivity and beta-amyloid protein (betaAP) deposition was investigated by double immunoperoxidase labeling of hippocampal and entorhinal cortex sections from five Alzheimers disease (AD) cases and five age-matched controls. betaAP plaques, which were absent in controls, were found in all AD samples, without significant differences in number or perimeter according to their location among the regions studied. In contrast, the mean number of GFAP (+) cells was significantly greater in the hippocampus than in the entorhinal cortex from AD cases (49 vs.39). Although at lower values (30 vs. 20), predominance of astrocyte hyperplasia in hippocampus as compared with entorhinal cortex was also found in control samples. Concomitant astrocyte hypertrophy, as defined by surface density (Sv) values of GFAP-immunoreactive material exceeding those of control means, affected a similar proportion of cells in the hippocampus (73

) and the entorhinal cortex (74

) from AD cases. Since an increased number of GFAP (+) cells in the hippocampus was not accompanied by an increased number and/or perimeter of neighbouring plaques, such differential hyper-reactivity in samples from AD patients, as well as in those with normal aging, seems to depend partially on the regional location of the involved astrocyte.

Cholinergic modulation of baker's yeast cell phagocytosis by rat astrocytes.

Cholinergic regulation of baker's yeast cell phagocytosis in rat cultured astrocytes was studied. Phagocytic activity was reduced by 1 x 10(-5) M of atropine or pirenzepine, but not by AF-DX116 or 4-DAMP. In addition, carbachol stimulated phagocytosis in a dose-dependent manner. Furthermore, only 1 x 10(-5)M of atropine, pirenzepine and 4-DAMP significantly reduced enhanced activity induced by 1 x 10(-7)M carbachol. It was also observed that L-NMMA, staurosporine, or U-73122, reduced phagocytosis activity while TFP failed to do so. Nitrite levels in astrocyte supernatants increased after baker's yeast cells were incorporated to astrocyte cultures, correlating with enhanced phagocytosis induced by carbachol stimulation, and were reduced by 1 x 10(-5) M of atropine, pirenzepine or aminopiridine, but not by AF-DX116 or 4-DAMP. Enhanced NO production triggered by astrocyte phagocytosis may have pathological consequences.

Antibodies against astrocyte M1 and M2 muscarinic cholinoceptor from schizophrenic patients' sera.

We demonstrated the presence of circulating antibodies from schizophrenic patients able to interact with cultured astrocytes activating muscarinic acetylcholine receptors (mAChRs). Sera and purified IgG from 15 paranoid schizophrenic and 15 age-matched normal subjects were studied by indirect immunofluorescence (IFI), flow cytometry, dot blot, enzyme immunoassay (ELISA), and radioligand competition assays. Astrocyte membranes and/or a synthetic peptide, with identical amino acid sequence of human M(1) and M(2) mAChR, were used as antigens. By IFI and flow cytometry procedures, we proved that serum purified IgG fraction from schizophrenic patients, reacted to astrocyte cell surface. The same antibodies were able to inhibit the binding of the specific mAChR radioligand (3)H-QNB. Using synthetic peptide for dot blot and ELISA, we demonstrated that these antibodies reacted against the second extracellular loop of human cerebral M(1) and M(2) mAChR. Also, the corresponding affinity-purified antipeptide antibody displayed an agonistic-like activity associated to specific M(1) and M(2) mAChR activation, increasing inositol phosphates accumulation and decreasing cyclic AMP production, respectively. This article gives support to the participation of an autoimmune process in schizophrenia disease.

Immunochemical expression of proliferative cell nuclear antigen in aging cultured astrocytes.

Cell differentiation degree and mitotic activity were sequentially assessed by immunoperoxidase labeling of glial fibrillary acidic protein (GFAP) and proliferative cell nuclear antigen (PCNA), respectively, in rat brain cultured astrocytes maintained up to 60 days in vitro (DIV) of first subculture, or weekly passaged until their 12th subculture. Cell count was performed through a 0.01 mm2 section reticule and morphometric analysis with a stereological grid. The number of double immunoreactive cells peaked by 2 DIV to achieve its lowest value at 60 DIV. At 24 hs of cell seeding of successive passages, such values peaked by the 6th subculture to gradually decrease thereafter. Increasing cell hypertrophy was found during the long-term first subculture but not after passaging. At the end of the observation period, doubly immunolabeled astrocytes were still recorded, thus evidencing retention of proliferative potential despite aging.

A possible case of myelopathy/tropical spastic paraparesis in an Argentinian woman with human T lymphocyte virus type II.

A case of neurological disease featuring human T lymphocyte virus-associated myelopathy/tropical spastic paraparesis (HAM/TSP) was diagnosed by serological (Western blot) and molecular (polymerase chain reaction) criteria as related to human T lymphocyte virus (HTLV)-II infection. This is, to our knowledge, the first case of this kind found in Argentina and is additional evidence that HAM/TSP solely related to HTLV-II infection occurs in HTLV-I-negative subjects.

A cluster of human T-cell lymphotropic virus type I-associated myelopathy/tropical spastic paraparesis in Jujuy, Argentina.

Compared with other regions in Argentina, greater human T-cell lymphotropic virus type I (HTLV-I) seroprevalence has been reported in Jujuy Province, where it reaches 2.32% in the general population, so that a search for HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) cases deserved to be carried out. Accordingly, a clinically diagnosed and serologically confirmed cluster of cases in 1 man and 10 women, including 2 sisters, is described here. Most patients (9/11) were born in Cochinoca Department, located in an Andes highland area called Puna Jujeña, situated at more that 3400 m above sea level. No history of risk factors was disclosed, except for a single transfusion in 1 patient. In contrast to the Andean region of Bolivia, where high HTLV-I seroprevalence is in part attributable to Japanese immigrants, the Jujuy population mainly consists of aborigines, mestizos, and European descendants. Therefore, the long-term presence of virus in Jujuy natives may be taken for granted. Considering the HAM/TSP cluster described here plus previously reported isolated cases in neighboring Salta Province, we speculate that the Puna Jujeña region and regions in that vicinity would be a microepidemic focus of disease. To determine the role of possible pathogenic cofactors such as geographic, ethnic, genetic, and cultural features, further pertinent surveys are required in subtropical northwestern Argentina.

Junin virus-induced astrocytosis is impaired by iNOS inhibition.

Because Junin virus (JV) experimental encephalitis of mice and rats is characterized by mild histopathological changes that do not seem to justify per se lethality after intracerebral infection, such a murine model seems adequate to investigate the potential role of inducible nitric oxide synthase (iNOS) as a pathogenic factor. Concomitant with a predominant astrocyte reaction, increased immunoperoxidase expression of iNOS, mitochondrial superoxide dismutase (SODm) and glutathione peroxidase (GPX) was disclosed in brain of mice infected with JV strain #44. When specific inhibition of iNOS was achieved by intraperitoneal administration of amino guanidine (AG), significantly greater mortality was observed in treated animals (70% vs. 40%), together with similar infective titers ( approximately 10(7) PFU/g) but lower astrocytosis, as shown by glial fibrillary acidic (GFAP) labeling. As regards SODm and GPX immunochemical expression in neurons, no differences were found between mice with or without AG treatment. The present results suggest that the apparent protective role of nitric oxide (NO), when synthesized by iNOS, is unrelated to reduced viral replication but rather to enhanced astrocyte activation behaving as a beneficial cell response to virus-induced CNS damage.

Immunochemical expression of proliferative cell nuclear antigen in aging cultured astrocytes.

Cell differentiation degree and mitotic activity were sequentially assessed by immunoperoxidase labeling of glial fibrillary acidic protein (GFAP) and proliferative cell nuclear antigen (PCNA), respectively, in rat brain cultured astrocytes maintained up to 60 days in vitro (DIV) of first subculture, or weekly passaged until their 12th subculture. Cell count was performed through a 0.01 mm2 section reticule and morphometric analysis with a stereological grid. The number of double immunoreactive cells peaked by 2 DIV to achieve its lowest value at 60 DIV. At 24 hs of cell seeding of successive passages, such values peaked by the 6th subculture to gradually decrease thereafter. Increasing cell hypertrophy was found during the long-term first subculture but not after passaging. At the end of the observation period, doubly immunolabeled astrocytes were still recorded, thus evidencing retention of proliferative potential despite aging.