Endogenous carbon monoxide (CO) is produced by heme oxygenase-1 (HO)-1 which mediates the degradation of heme into CO, iron, and biliverdin. Also, CO ameliorates the human inflammatory bowel diseases and ulcerative colitis. However, the mechanism for the effect of CO on the inflammatory bowel disease has not yet been known. In this study, we showed that CO significantly increases survival percentage, body weight, colon length as well as histologic parameters in DSS-treated mice. In addition, CO inhalation significantly decreased DSS induced pro-inflammatory cytokines by inhibition of GSK-3β in mice model. To support the in vivo observation, TNF-α, iNOS and IL-10 after CO and LiCl treatment were measured in mesenteric lymph node cells (MLNs) and bone marrow-derived macrophages (BMMs) from DSS treated mice. In addition, we determined that CO potentially inhibited GSK-3β activation and decreased TNF-α and iNOS expression by inhibition of NF-κB activation in LPS-stimulated U937 and MLN cells pretreated with CO. Together, our findings indicate that CO attenuates DSS-induced colitis via inhibition of GSK-3β signaling in vitro and in vivo. Importantly, this is the first report that investigated the molecular mechanisms mediated the novel effects of CO via inhibition GSK-3β in DSS-induced colitis model.

Carbon monoxide (CO) may exert important roles in physiological and pathophysiological states through the regulation of cellular signaling pathways. CO can protect organ tissues from ischemia/reperfusion (I/R) injury by modulating intracellular redox status and by inhibiting inflammatory, apoptotic, and proliferative responses. However, the cellular mechanisms underlying the protective effects of CO in organ I/R injury remain incompletely understood. In this study, a murine model of hepatic warm I/R injury was employed to assess the role of glycogen synthase kinase-3 (GSK3) and phosphatidylinositol 3-kinase (PI3K)-dependent signaling pathways in the protective effects of CO against inflammation and injury. Inhibition of GSK3 through the PI3K/Akt pathway played a crucial role in CO-mediated protection. CO treatment increased the phosphorylation of Akt and GSK3-beta (GSK3β) in the liver after I/R injury. Furthermore, administration of LY294002, an inhibitor of PI3K, compromised the protective effect of CO and decreased the level of phospho-GSK3β after I/R injury. These results suggest that CO protects against liver damage by maintaining GSK3β phosphorylation, which may be mediated by the PI3K/Akt signaling pathway. Our study provides additional support for the therapeutic potential of CO in organ injury and identifies GSK3β as a therapeutic target for CO in the amelioration of hepatic injury.

Heme oxygenase-1 (HO-1) can exert anti-inflammatory and antioxidant effects. Acute lung injury (ALI) is associated with increased inflammation and influx of proinflammatory cells and mediators in the airspaces and lung parenchyma. In this study, we demonstrate that pterostilbene 4'-β-glucoside (4-PG), the glycosylated form of the antioxidant pterostilbene (PTER), can protect against lipopolysaccharide- (LPS-) or Pseudomonas aeruginosa- (P. aeruginosa-) induced ALI when applied as a pretreatment or therapeutic post-treatment, via the induction of HO-1. To determine whether HO-1 mediates the antioxidant and anti-inflammatory effects of 4-PG, we subjected mice genetically deficient in Hmox-1 to LPS-induced ALI and evaluated histological changes, HO-1 expression, and proinflammatory cytokine levels in bronchoalveolar lavage (BAL) fluid. 4-PG exhibited protective effects on LPS- or P. aeruginosa-induced ALI by ameliorating pathological changes in lung tissue and decreasing proinflammatory cytokines. In addition, HO-1 expression was significantly increased by 4-PG in cells and in mouse lung tissues. The glycosylated form of pterostilbene (4-PG) was more effective than PTER in inducing HO-1 expression. Genetic deletion of Hmox-1 abolished the protective effects of 4-PG against LPS-induced inflammatory responses. Furthermore, we found that 4-PG decreased both intracellular ROS levels and mitochondrial (mt) ROS production in a manner dependent on HO-1. Pharmacological application of the HO-1 reaction product carbon monoxide (CO), but not biliverdin or iron, conferred protection in Hmox-1-deficient macrophages. Taken together, these results demonstrate that 4-PG can increase HO-1 expression, which plays a critical role in ameliorating intracellular and mitochondrial ROS production, as well as in downregulating inflammatory responses induced by LPS. Therefore, these findings strongly suggest that HO-1 mediates the antioxidant and anti-inflammatory effects of 4-PG.