ABSTRACT
HIV-1 Nef is expressed in astrocytes, but a contribution to neuropathogenesis and the development of HIV-associated dementia (HAD) remains uncertain. To determine the neuropathogenic actions of the HIV-1 Nef protein, the brain-derived (YU-2) and blood-derived (NL4-3) Nef proteins were expressed in neural cells using an alphavirus vector, which resulted in astrocyte death (P < 0.001). Supernatants from Nef-expressing astrocytes also caused neuronal death, suggesting the release of neurotoxic molecules by astrocytes. Analysis of pro-inflammatory gene induction in astrocytes expressing Nef revealed increased IP-10 mRNA expression (4000-fold) that was Nef sequence dependent. Recombinant IP-10 caused selective cell death in neurons (P < 0.001) but not astrocytes, and the cytotoxicity of supernatant from astrocytes expressing Nef YU-2 was blocked by an antibody directed against the chemokine receptor CXCR3 (P < 0.001). SCID/NOD mice implanted with a Nef YU-2-expressing vector displayed abnormal motor behavior (P < 0.05), neuroinflammation, and neuronal loss relative to controls. Analysis of mRNA levels in brains from patients with HAD also revealed increased expression of IP-10 (P < 0.05), which was confirmed by immunoreactivity detected principally in astrocytes. Phylogenetic and protein structure analyses of Nef sequences derived from HIV/AIDS patients with and without HAD suggested viral evolution toward a neurotropic Nef protein. These results indicate that HIV-1 Nef contributes to neuropathogenesis by directly causing astrocyte death together with indirect neuronal death through the cytotoxic actions of IP-10 on neurons. Furthermore, Nef molecular diversity was evident in brain tissue among patients with neurological disease and which may influence IP-10 production by astrocytes.
Subject(s)
Chemokines, CXC/physiology , Gene Products, nef/genetics , HIV-1 , AIDS Dementia Complex/metabolism , AIDS Dementia Complex/physiopathology , Animals , Animals, Genetically Modified , Astrocytes/metabolism , Astrocytes/virology , Cell Death , Cells, Cultured , Chemokine CCL2/biosynthesis , Chemokine CCL2/genetics , Chemokine CXCL10 , Chemokines, CXC/biosynthesis , Chemokines, CXC/pharmacology , Gene Products, nef/biosynthesis , Genetic Vectors , HIV-1/genetics , HIV-1/pathogenicity , Humans , Interleukin-1/biosynthesis , Interleukin-1/genetics , Interleukin-1beta , Male , Mice , Mice, Inbred NOD , Mice, SCID , Molecular Sequence Data , Neurons/drug effects , Neurons/metabolism , Neurons/pathology , Neurotoxins/pharmacology , Peptide Fragments/biosynthesis , Peptide Fragments/genetics , RNA, Messenger/analysis , Recombinant Proteins/pharmacology , nef Gene Products, Human Immunodeficiency VirusABSTRACT
The kinetics of water uptake and redistribution in several soils and their components are studied using NMR relaxometry. Unlike the normal behavior observed in stable porous media, entry into micropores in the soil is a slow process as compared to entry into macro- and mesopores. This indicates that soils air-dried at ambient temperature include gel phases that have collapsed or reoriented, closing micropores, during drying. Wetting must then include the swelling processes that re-open micropores. This can even exhibit temperature dependence giving an "apparent activation energy" comparable to that of a chemical reaction, for example, ester hydrolysis. The processes of micropore opening may play a role in slow uptake of contaminants into soils.
Subject(s)
Soil/analysis , Humic Substances , Hydrophobic and Hydrophilic Interactions , Kinetics , Magnetic Resonance Spectroscopy , Porosity , Silicon Dioxide , Solubility , Water , WettabilityABSTRACT
Soil from the Ellerslie site of experimental oil contamination in Alberta developed water repellency some years after initial remediation. The water-repellent soils were compared to clean soils and contaminated but wettable soils by solid-state nuclear magnetic resonance (NMR). The effects of extraction with CH2Cl2 (for petroleum hydrocarbons), NaOH (for natural organic matter), and 2-propanol/ammonia (IPA/NH3) on wettability were evaluated by the molarity of the ethanol droplet (MED) test. Soil extracts and whole soils, after extraction, were examined using NMR and Fourier transform infrared spectroscopy (FTIR). On the basis of the structure--MED correlations, a model of a thin-layer natural organic matter--petroleum products complex formed under strong drying conditions is proposed to account for the development of water repellency. Studies of two similar soils from accidental oil spills are supportive.
Subject(s)
Environmental Pollution/prevention & control , Petroleum , Soil Pollutants/analysis , Magnetic Resonance Spectroscopy , Solubility , Spectroscopy, Fourier Transform InfraredABSTRACT
Petroleum-induced water repellency in soils is a problem that has been thought to develop randomly following contamination and then remediation of a site with petroleum. The emergence of the phenomenon can occur within months or years of original contamination and with seemingly no warning. Low-field NMR has been used to study these soils and, specifically, the processes of water uptake that occur in them. Critical aspects in the development of this phenomenon have been identified as well--specifically, a dependence on climatic events in the area and contamination levels that contribute are suggested.
