HMOX1 and hematoma: The results of the aforementioned studies suggest that HO-1 expression is rapidly induced following ICH, likely via one or more of the following mechanisms: (1) Heme released by damaged erythrocytes after ICH directly induces HO-1 expression; (2) HO-1 expression is induced by ischemia and hypoxia around the hematoma after ICH; (3) oxidative stress after ICH leads to upregulation of HO-1 expression via the Nrf2-ARE signaling pathway.