DIFFERENTIAL EXPRESSION OF HEME OXYGENASE-1 IN CULTURED CORTICAL-NEURONS AND ASTROCYTES DETERMINED BY THE AID OF A NEW HEME OXYGENASE ANTIBODY - RESPONSE TO OXIDATIVE STRESS

Heme oxygenase exists as two isoenzymes designated heme oxygenase-1 (H O-1) and heme oxygenase-2 (HO-2). HO-2 is made constitutively in many cell types whereas HO-1 is a stress protein inducible by heat, heavy m etals, ultraviolet irradiation, and oxidative stress. Recombinant rat HO-1 was expressed in bacteria and antiserum designated HO-1713 was ra ised against the purified protein, HO-1713 detected recombinant rat HO -1 and recombinant rat HO-2. In rat tissues it detected HO-1 and a sec ond, unidentified band designated HO-L (heme oxygenase-like immunoreac tivity) which was not HO-2. Cultured rat cortical neurons and forebrai n astrocytes were exposed to hydrogen peroxide (0.14-0.7 micromolar fo r 30 or 60 min). Neurons which contained little detectable HO-1 and wh ich were sensitive to hydrogen peroxide at the high end of the dose cu rve failed to induce HO-1 by Western blot analysis. In contrast, cultu red rat forebrain astrocytes which contained HO-1 under normal culture conditions and which were resistant to injury by hydrogen peroxide, i ncreased their content of immunoreactive HO-1 by 7-fold within 3 h aft er exposure. Our results support a protective role for HO-1 in oxidati ve injury and suggest that the relative inability of neurons to increa se HO-1 after oxidative stress may contribute to their selective vulne rability vis-a-vis astrocytes. They also suggest that differential exp ression of heme oxygenase in studies utilizing CNS cultures may alter normal cell physiology and cell survival.