Transcriptional regulation of inflammatory and extracellular matrix-regulating genes in cerebral arteries following experimental subarachnoid hemorrhage in rats. Laboratory investigation.
OBJECTIVE
Subarachnoid hemorrhage (SAH) results in the expression of inflammatory and extracellular matrix (ECM)-related genes and various G protein-coupled receptors. In the present study, the authors evaluated the time course and sequence of the transduction pathways, p38 mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase-1 and 2 (ERK1/2), and associated transcription factor activation as well as gene regulation and associated protein levels.


METHODS
Subarachnoid hemorrhage was induced in rats by injecting 250 microl of blood into the suprachiasmatic cistern, and gene regulation in the cerebral arteries was examined at various points in time following SAH by using quantitative polymerase chain reaction (PCR) and immunohistochemistry.


RESULTS
Immunohistochemical findings demonstrated that SAH phosphorylates and activates p38 and ERK1/2 as well as the downstream transcription factors Elk-1 and activating transcription factor-2. The pattern of activation consists of a rapid phase within the first few hours and a late phase that occurs from 24 to 48 hours. Activation is followed by an increase in the transcription of the inflammatory and ECM-related genes (IL6, TNFalpha, IL1beta, CXCL1, CXCL2, CCL20, MMP8, MMP9, MMP13, and iNOS), as demonstrated using real-time PCR. For MMP13 and iNOS, the changes in transcription were translated into functional proteins, as revealed on immunohistochemistry.


CONCLUSIONS
Activation of the p38 and ERK1/2 signaling pathways and their downstream transcription factors can explain the increase in the transcription of the genes studied. This increase and the subsequent augmentation in protein levels suggest that the inflammatory response may in part explain the remodeling that occurs in cerebral arteries following SAH.
Vikman
Petter
P
Department of Clinical Sciences, Experimental Vascular Research, Lund, Sweden. Petter.vikman@med.lu.se
Ansar
Saema
S
Edvinsson
Lars
L
D000818:Animals; D002536:Cerebral Arteries; D054418:Chemokine CCL20 / Q000032:analysis; D005109:Extracellular Matrix; D015870:Gene Expression; D007150:Immunohistochemistry; D019402:Macrophage Inflammatory Proteins / Q000032:analysis; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D013345:Subarachnoid Hemorrhage / Q000235:genetics*; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D014161:Transduction, Genetic; D050807:ets-Domain Protein Elk-1 / Q000378:metabolism / Q000502:physiology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
C108355:CCL20 protein, human; D054418:Chemokine CCL20; D019402:Macrophage Inflammatory Proteins; D014157:Transcription Factors; D050807:ets-Domain Protein Elk-1; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases