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The production of macrophage inflammatory protein‐2 induced by soluble intercellular adhesion molecule‐1 in mouse astrocytes is mediated by src tyrosine kinases and p42/44 mitogen‐activated protein kinase

Severe traumatic brain injury stimulates the release of soluble intercellular adhesion molecule‐1 (sICAM‐1) into CSF. Studies in cultured mouse astrocytes suggest that sICAM‐1 induces the production of macrophage inflammatory protein‐2 (MIP‐2). In the present study, we investigated the underlying mechanisms for MIP‐2 induction. sICAM‐1 induced MIP‐2 in astrocytes lacking membrane‐bound ICAM‐1, indicating that its action is due to heterophilic binding to an undescribed receptor rather than homophilic binding to surface ICAM‐1. Signal transduction may be mediated by src tyrosine kinases, as the src tyrosine kinase inhibitors herbimycin A and PP2 abolished MIP‐2 induction by sICAM‐1. Phosphorylation of p42/44 mitogen‐activated protein kinase (MAPK), but not of p38 MAPK, occurred further downstream, as evidenced by western blot analysis combined with the use of herbimycin A and specific MAPK inhibitors. By contrast, induction of MIP‐2 by tumour necrosis factor‐α (TNF‐α) involved both p42/44 MAPK and p38 MAPK. Following stimulation with either sICAM‐1 or TNF‐α, astrocyte supernatants promoted chemotaxis of human neutrophils and incubation of these supernatants with anti‐MIP‐2 antibodies more efficiently suppressed the migration induced by sICAM‐1 than by TNF‐α. These results show that sICAM‐1 induces the production of biologically active MIP‐2 in astrocytes by heterophilic binding to an undefined receptor and activation of src tyrosine kinases and p42/44 MAPK.