Hypoxemia induces expression of heme oxygenase-1 and heme oxygenase-2 proteins in the mouse myocardium

F Han, K Takeda, M Ono, F Date, K Ishikawa, S Yokoyama, Y Shinozawa, K Furuyama and S. Shibahara

The Journal of Biochemistry, 2010, 147(1), 143-151. DOI: 10.1093/jb/mvp153

Abstract

Heme oxygenase (HO) catalyzes oxidative breakdown of heme, and constitutes two isozymes, HO-1 and HO-2. Here, we explored the tissue-specific regulation of expression of HO-1 and HO-2 under hypoxemia. There was no significant change in the overall expression levels of HO-1 and HO-2 mRNAs and proteins in the lung during adaptation of C57BL/6 mice to normobaric hypoxia (10% O2). However, immunohistochemical analysis revealed the increased expression of HO-1 and HO-2 proteins after 28 days of normobaric hypoxia in the pulmonary venous myocardium that is the extension of the left atrial myocardium into pulmonary venous walls. Moreover, the expression of HO-2 protein was increased in the sub-endocardial myocardium of ventricles under hypoxia, while HO-1 protein level was increased in the full-thickness walls. Thus, hypoxemia induces expression of both HO-1 and HO-2 proteins in the myocardium. Using C57BL/6 mice lacking HO-2 (HO-2–/–), which manifest chronic hypoxemia, we also showed that the HO-1 protein level in the lung was similar between HO-2–/– mice and wild-type mice. Unexpectedly, HO-1 protein level was lower by 35% in the HO-2–/– mouse liver than the wild-type liver. These results indicate that the expression of HO-1 protein is regulated in a tissue-specific manner under hypoxemia.

ASCI-ID: 1088-148