Expression of apolipoprotein E by mouse brain astrocytes and its modulation by interferon-gamma

We have found that mouse brain astrocytes in culture synthesize and secrete apolipoprotein E (ApoE) and that its expression is modulated by interferon-gamma, which influences the functional state of astrocytes. Interferon-gamma, which induces expression of Ia determinants on the surface of the astrocyte, reduced secretion of ApoE while enhancing intracellular expression of ApoE. Our data suggest that the synthesis and secretion phases of the ApoE pathway are regulated independently. It is possible that, by the production of ApoE, astrocytes may perform functions that are usually ascribed to macrophages and that may be important in immune reactivity in the brain.