Figure 2.
Potential pathways for HO-1-dependent injury or resolution of neuroinflammation. Products formed by the degradation of haeme by haeme oxygenase-1 (HO-1) can be either beneficial or detrimental. Thin arrows: grey pathways indicate beneficial actions of HO-1 products. Black pathways indicate detrimental actions. The tetrapyrroles biliverdin and bilirubin possess antioxidant activity and help reduce oxidative stress. Ferrous iron can react with hydrogen peroxide by the Fenton reaction to generate damaging hydroxyl radicals, whereas evidence suggests that iron may also mediates an HO-1-dependent decrease in iNOS expression through a transcriptional inhibition. Carbon monoxide-releasing compounds also decrease iNOS expression, suggesting that HO-1-derived CO may act similarly. ROS, reactive oxygen species; sGC, soluble GC; iNOS, inducible NOS.