HMOX1 and acute respiratory distress syndrome: In addition, a series of genes such as TLR4,Arg-1 and HMOX1 have been shown to be involved in immune regulation and antioxidant activity HO-1 is an antioxidant enzyme that can inhibit apoptosis, inflammation and cell proliferation to reduce cell death in ALI animal models by inducing several detoxification enzymes and antioxidant proteins (25).