TY - JOUR
T1 - Potential mechanisms for astrocyte-TIMP-1 downregulation in chronic inflammatory diseases
AU - Gardner, Jessica
AU - Borgmann, Kathleen
AU - Deshpande, Muralidhar S.
AU - Dhar, Alok
AU - Wu, Li
AU - Persidsky, Raisa
AU - Ghorpade, Anuja
PY - 2006/5/15
Y1 - 2006/5/15
N2 - The pathogenesis of many neurodegenerative disorders, including human immunodeficiency virus (HIV)-1 associated dementia, is exacerbated by an imbalance between matrix metalloproteinases (MMPs) and their inhibitors, tissue inhibitors of metalloproteinases (TIMPs). In the context of disease, TIMP-1 has emerged as an important multifunctional protein capable of regulating inflammation. We previously reported differential TIMP-1 expression in acute versus chronic activation of astrocytes. This study investigates possible mechanisms underlying TIMP-1 downregulation in chronic neuroinflammation. We used interleukin (IL)-1β as a model pro-inflammatory stimulus and measured TIMP-1 binding to extracellular matrix, cell death, receptor downregulation, TIMP-1 mRNA stability and transcriptional regulation in activated astrocytes. TIMP-1 remained localized to the cell body or was secreted into the cell supernatant. DNA fragmentation ELISA and MTT assay showed that prolonged IL-1β activation of astrocytes induced significant astrocyte death. In acute and chronic IL-1β-activated astrocytes, IL-1 receptor levels were not significantly different. TIMP-1 mRNA stability was measured in astrocytes and U87 astroglioma cells by real-time PCR, and TIMP-1 promoter activation was studied using TIMP-1-luciferase reporter constructs in transfected astrocytes. Our results indicated that TIMP-1 expression is regulated through multiple mechanisms. Transcriptional control and loss of mRNA stabilization are, however, the most likely primary contributors to chronic downregulation of TIMP-1. These data are important for unraveling the mechanisms underlying astrocyte responses during chronic neuroinflammation and have broader implications in other inflammatory diseases that involve MMP/TIMP imbalance.
AB - The pathogenesis of many neurodegenerative disorders, including human immunodeficiency virus (HIV)-1 associated dementia, is exacerbated by an imbalance between matrix metalloproteinases (MMPs) and their inhibitors, tissue inhibitors of metalloproteinases (TIMPs). In the context of disease, TIMP-1 has emerged as an important multifunctional protein capable of regulating inflammation. We previously reported differential TIMP-1 expression in acute versus chronic activation of astrocytes. This study investigates possible mechanisms underlying TIMP-1 downregulation in chronic neuroinflammation. We used interleukin (IL)-1β as a model pro-inflammatory stimulus and measured TIMP-1 binding to extracellular matrix, cell death, receptor downregulation, TIMP-1 mRNA stability and transcriptional regulation in activated astrocytes. TIMP-1 remained localized to the cell body or was secreted into the cell supernatant. DNA fragmentation ELISA and MTT assay showed that prolonged IL-1β activation of astrocytes induced significant astrocyte death. In acute and chronic IL-1β-activated astrocytes, IL-1 receptor levels were not significantly different. TIMP-1 mRNA stability was measured in astrocytes and U87 astroglioma cells by real-time PCR, and TIMP-1 promoter activation was studied using TIMP-1-luciferase reporter constructs in transfected astrocytes. Our results indicated that TIMP-1 expression is regulated through multiple mechanisms. Transcriptional control and loss of mRNA stabilization are, however, the most likely primary contributors to chronic downregulation of TIMP-1. These data are important for unraveling the mechanisms underlying astrocyte responses during chronic neuroinflammation and have broader implications in other inflammatory diseases that involve MMP/TIMP imbalance.
KW - HIV-1
KW - IL-1β
KW - Neurodegenerative disorders
KW - TIMP-1
UR - http://www.scopus.com/inward/record.url?scp=33646337422&partnerID=8YFLogxK
U2 - 10.1002/jnr.20823
DO - 10.1002/jnr.20823
M3 - Article
C2 - 16555295
AN - SCOPUS:33646337422
SN - 0360-4012
VL - 83
SP - 1281
EP - 1292
JO - Journal of Neuroscience Research
JF - Journal of Neuroscience Research
IS - 7
ER -