CD38/cyclic ADP-ribose regulates astrocyte calcium signaling: implications for neuroinflammation and HIV-1-associated dementia.
CD38 is a 45-kD ectoenzyme involved in the synthesis of potent calcium (Ca(2+))-mobilizing agents, cyclic adenosine diphosphate-ribose (cADPR), and nicotinic acid adenine dinucleotide phosphate (NAADP+). In HIV-1-infected patients, increased CD38 expression on CD8+ T cells is linked to immune system activation and progression of HIV-1 infection. However, the role of CD38 upregulation in astrocyte function and HIV-1-associated dementia (HAD-now called HAND: HIV-1-associated neurocognitive disorder) neuropathogenesis is unclear. To these ends, we used interleukin (IL)-1beta and HIV-1gp120 to activate primary human astrocytes and measured CD38 expression using real-time polymerase chain reaction and CD38 function by ADP-ribosyl cyclase activity. We also determined cADPR-mediated changes in single-cell intracellular Ca(2+) transients in activated astrocytes in presence or absence of ethylene glycol tetraacetic acid. CD38 levels were downregulated using CD38 small-interfering RNA (siRNA) and intracellular Ca(2+) concentration ([Ca(2+)](i)) was measured. We previously reported a approximately 20-fold rise in CD38 messenger RNA levels in IL-1beta-activated astrocytes. We extend this observation and report that HIV-1gp120 potentiated CD38 expression in a dose-dependent manner and also increased CD38 enzyme activity in control and IL-1beta-activated astrocytes. We demonstrate higher cADPR levels in IL-1beta-activated astrocytes with a corresponding rise in [Ca(2+)](i) upon cADPR application and its non-hydrolysable analog, 3-deaza-cADPR. In activated astrocytes, pre-treatment with the cADPR-specific antagonist 8-Br-cADPR and CD38 siRNA transfection returned elevated [Ca(2+)](i) to baseline, thus confirming a CD38-cADPR specific response. These data are important for unraveling the mechanisms underlying the role of astrocyte-CD38 in HAD and have broader implications in other inflammatory diseases involving astrocyte activation and CD38 dysregulation.
Banerjee
Sugato
S
Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE, USA.
Walseth
Timothy F
TF
Borgmann
Kathleen
K
Wu
Li
L
Bidasee
Keshore R
KR
Kannan
Mathur S
MS
Ghorpade
Anuja
A
D051997:ADP-ribosyl Cyclase 1 / Q000235:genetics / Q000502:physiology*; D015526:AIDS Dementia Complex / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D001253:Astrocytes / Q000378:metabolism / Q000473:pathology*; D020013:Calcium Signaling / Q000502:physiology*; D002478:Cells, Cultured; D036563:Cyclic ADP-Ribose / Q000235:genetics / Q000502:physiology*; D005333:Fetus; D015699:HIV Envelope Protein gp120 / Q000502:physiology; D015497:HIV-1 / Q000502:physiology*; D006801:Humans; D018836:Inflammation Mediators / Q000502:physiology*; D007424:Intracellular Fluid / Q000378:metabolism; D009474:Neurons / Q000378:metabolism / Q000473:pathology
D015699:HIV Envelope Protein gp120; D018836:Inflammation Mediators; C514793:gp120 protein, Human immunodeficiency virus 1; D036563:Cyclic ADP-Ribose; D051997:ADP-ribosyl Cyclase 1