ICAM-1-induced expression of proinflammatory cytokines in astrocytes: Involvement of extracellular signal-regulated kinase and p38 mitogen-activated protein kinase pathways

Academic Article

Abstract

  • ICAM-1 is a transmembrane glycoprotein of the Ig superfamily involved in cell adhesion. ICAM-1 is aberrantly expressed by astrocytes in CNS pathologies such as multiple sclerosis, experimental allergic encephalomyelitis, and Alzheimer's disease, suggesting a possible role for ICAM-1 in these disorders. ICAM-1 has been shown to be important for leukocyte diapedesis through brain microvessels and subsequent binding to astrocytes. However, other functional roles for ICAM-1 expression on astrocytes have not been well elucidated. Therefore, we investigated the intracellular signals generated upon ICAM-1 engagement on astrocytes. ICAM-1 ligation by a mAb to rat ICAM-1 induced mRNA expression of proinflammatory cytokines such as IL-lα, IL-1β, IL-6, and TNF-α. Examination of cytokine protein production revealed that ICAM-1 ligation results in IL-6 secretion by astrocytes, whereas IL-1β and IL-1α protein is expressed intracellularly in astrocytes. The involvement of mitogen-activated protein kinases (MAPKs) in ICAM-1-mediated cytokine expression in astrocytes was tested, as the MAPK extracellular signal-regulated kinase (ERK) was previously shown to be activated upon ICAM-1 engagement. Our results indicate that ERK1/ERK2, as well as p38 MAPK, are activated upon ligation of ICAM-1. Studies using pharmacological inhibitors demonstrate that both p38 MAPK and ERK1/2 are involved in ICAM-1-induced IL-6 expression, whereas only ERK1/2 is important for IL-1α and IL-1β expression. Our data support the role of ICAM-1 on astrocytes as an inflammatory mediator in the CNS and also uncover a novel signal transduction pathway through p38 MAPK upon ICAM-1 ligation.
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    Digital Object Identifier (doi)

    Author List

  • Sung Joong Lee; Drabik K; Van Wagoner NJ; Lee S; Choi C; Dong Y; Benveniste EN
  • Start Page

  • 4658
  • End Page

  • 4666
  • Volume

  • 165
  • Issue

  • 8