ICAM-1 triggers liver regeneration through leukocyte recruitment and Kupffer cell-dependent release of TNF-alpha/IL-6 in mice

BACKGROUND & AIMS: Tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 mediate hepatocyte proliferation in vivo, suggesting that local and systemic inflammatory reactions may trigger hepatic regeneration after major tissue loss. METHODS: Wild-type, intercellular adhesion molecule (ICAM)-1-/-, and neutropenic-induced mice were subjected to 70% hepatectomy. Three different approaches to block and/or deplete liver macrophages (Kupffer cells) were used. RESULTS: We found that liver from ICAM-1-deficient mice exhibited impaired regeneration after partial hepatectomy. This finding is associated with dramatic decrease in leukocyte recruitment and tissue TNF-alpha and IL-6 levels. All markers of hepatocyte proliferation were restored in ICAM-/- mice by injections of recombinant IL-6. Neutropenic animals and liver macrophage (Kupffer cell) depletion resulted in similar failure of regeneration with low levels of TNF-alpha and IL-6. CONCLUSIONS: The data suggest a novel pathway in which ICAM-1 binds to leukocytes after hepatectomy, triggering hepatocyte proliferation through Kupffer cell-dependent release of TNF-alpha and IL-6.