Abstract
HIV-1 protein Tat is neurotoxic and increases macrophage and microglia production of TNF-alpha, a cytopathic cytokine linked to the neuropathogenesis of HIV dementia. Others have shown that intracellular calcium regulates TNF-alpha production in macrophages, and we have shown that Tat releases calcium from inositol 1,4, 5-trisphosphate (IP3) receptor-regulated stores in neurons and astrocytes. Accordingly, we tested the hypothesis that Tat-induced TNF-alpha production was dependent on the release of intracellular calcium from IP3-regulated calcium stores in primary macrophages. We found that Tat transiently and dose-dependently increased levels of intracellular calcium and that this increase was blocked by xestospongin C, pertussis toxin, and by phospholipase C and type 1 protein kinase C inhibitors but not by protein kinase A or phospholipase A2 inhibitors. Xestospongin C, BAPTA-AM, U73122, and bisindolylmalemide significantly inhibited Tat-induced TNF-alpha production. These results demonstrate that in macrophages, Tat-induced release of calcium from IP3-sensitive intracellular stores and activation of nonconventional PKC isoforms play an important role in Tat-induced TNF-alpha production.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Calcium / metabolism*
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Calcium Channels / physiology*
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Calcium Signaling / immunology
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Cells, Cultured
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Dose-Response Relationship, Immunologic
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Estrenes / pharmacology
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Gene Products, tat / physiology*
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HIV-1 / physiology*
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Humans
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Inositol 1,4,5-Trisphosphate / metabolism
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Inositol 1,4,5-Trisphosphate Receptors
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Intracellular Fluid / metabolism
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Macrophages / drug effects
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Macrophages / immunology
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Macrophages / metabolism*
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Pertussis Toxin
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Pyrrolidinones / pharmacology
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Receptors, Cytoplasmic and Nuclear / physiology*
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Time Factors
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Tumor Necrosis Factor-alpha / antagonists & inhibitors
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Tumor Necrosis Factor-alpha / biosynthesis*
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Type C Phospholipases / physiology
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Virulence Factors, Bordetella / pharmacology
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tat Gene Products, Human Immunodeficiency Virus
Substances
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Calcium Channels
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Estrenes
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Gene Products, tat
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ITPR1 protein, human
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Inositol 1,4,5-Trisphosphate Receptors
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Pyrrolidinones
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Receptors, Cytoplasmic and Nuclear
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Tumor Necrosis Factor-alpha
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Virulence Factors, Bordetella
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tat Gene Products, Human Immunodeficiency Virus
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1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione
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Inositol 1,4,5-Trisphosphate
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Pertussis Toxin
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Type C Phospholipases
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Calcium