ABSTRACT
Endogenous, as well as exogenous, nitric oxide (NO) and carbon monoxide (CO) can act as signaling molecules via cGMP-dependent and -independent manners. Both hepatic parenchymal cells and hepatic nonparenchymal cells can express iNOS, whereas eNOS is constitutively expressed in hepatic endothelial cells. Although iNOS is not thought to be expressed constitutively in healthy liver, it is readily upregulated in the liver under diseases and is considered to play an important role in the pathophysiological responses to various insulting damages of the liver. On the other hand,
heme oxygenase-1 (HO-1) can be induced not only by hemecontaining compounds, but also by non-heme-containing substances or environmental conditions such as NO, endotoxin, hypoxia, heat shock, and is thought to play a key role in maintaining homeostasis in the case of cellular injury.
