TNF-α mediates SDF-1α–induced NF-κB activation and cytotoxic effects in primary astrocytes
Yulong Han, … , Carlos A. Pardo, Richard M. Ransohoff
Yulong Han, … , Carlos A. Pardo, Richard M. Ransohoff
Published August 1, 2001
Citation Information: J Clin Invest. 2001;108(3):425-435. https://doi.org/10.1172/JCI12629.
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Article

TNF-α mediates SDF-1α–induced NF-κB activation and cytotoxic effects in primary astrocytes

Abstract

Stromal-derived cell factor-1α (SDF-1α; CXCL12) and its receptor, CXCR4, are constitutively expressed on neuroepithelial cells and are believed to be involved in both development and pathological processes, such as AIDS-associated neurologic disorders. Here, we demonstrate that SDF-1α activates NF-κB, stimulates production of chemokines and cytokines, and induces cell death in primary astrocytes, effects that depend on ongoing secretion of TNF-α. SDF-1α upregulated TNF-α mRNA and protein secretion, as well as TNF receptor 2 expression. TNF-α treatment mimicked SDF-1α induction of NF-κB, IL-1α/β, and RANTES, as well as cell death; neutralizing antibodies against TNF-α opposed these responses. We also found that SDF-1α activated Erk1 and Erk2 (Erk1/2) MAPK in a biphasic fashion. Early Erk1/2 activation was stimulated directly by SDF-1α and late activation was mediated by TNF-α. PD98059 suppression of early Erk1/2 activation correlated with reduction of SDF-1α–induced TNF-α expression. Late Erk1/2 activation was involved in TNF-α–stimulated NF-κB activation and cytokine induction. SDF-1α was induced in reactive CXCR4-positive astrocytes near axotomized spinal cord motor neurons, consistent with autocrine SDF-1/CXCR4 signaling in these cells. We propose that these novel effects of SDF-1α are relevant to the pathogenic and developmental roles of SDF-1α in the CNS.

Authors

Yulong Han, Tao He, DeRen Huang, Carlos A. Pardo, Richard M. Ransohoff

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SDF-1α–induced Erk1/2 activation is involved in TNF-α induction and NF-κ...
SDF-1α–induced Erk1/2 activation is involved in TNF-α induction and NF-κB activation. (a) PD98059, but not PTX, suppresses SDF-1α–induced cytokine and chemokine mRNA expression. Murine primary astrocytes were incubated with medium alone, with PTX for 20 hours, or with PD98059 for 1 hour. Incubation was followed by SDF-1α stimulation for 2 hours. RNA was then prepared and analyzed by RPA. Unprotected probe bands are indicated with arrows on the right, and protected bands are shown with arrows on the left. Data represent four experiments. (b) PD98059, but not PTX, suppresses SDF-1α–induced TNF-α promoter reporter activity. Primary astrocytes in the presence or absence of PTX or PD98059 were transiently cotransfected with pGL3-mTNF (–1260) (0.5 μg) and pRL-TK (0.05 μg) constructs followed by SDF-1α stimulation for 6 hours. Cells were then lysed and subjected to luciferase activity assay. After normalization, mean ± SD relative luciferase activity was obtained from triplicate independent transfection (Student’s t test: *treatment with PTX + SDF-1α vs. SDF-1α alone, P = 0.1097; #treatment with PD + SDF-1α vs. SDF-1α alone, P = 0.0015). Data represent three independent experiments. (c) PD98059 suppresses SDF-1α–induced NF-κB activation. Murine primary astrocytes were treated with SDF-1α (lane 2) for 2 hours, with PD98059 for 3 hours (lane 3), or with PD98059 for 1 hour followed by SDF-1α for 2 hours (lane 4). Shown are results of EMSA with the IP-10 κB2 probes. Data represent three experiments.