Crocin is a water-soluble carotenoid pigment that is primarily used in various 
cuisines as a seasoning and coloring agent, as well as in traditional medicines 
for the treatment of edema, fever, and hepatic disorder. In this study, we 
demonstrated that crocin markedly induces the expression of heme oxygenase-1 
(HO-1) which leads to an anti-inflammatory response. Crocin inhibited inducible 
nitric oxide synthase (iNOS) expression and nitric oxide production via 
downregulation of nuclear factor kappa B activity in lipopolysaccharide- (LPS-) 
stimulated RAW 264.7 macrophages. These effects were abrogated by blocking of 
HO-1 expression or activity. Crocin also induced Ca(2+) mobilization from 
intracellular pools and phosphorylation of Ca(2+)/calmodulin-dependent protein 
kinase 4 (CAMK4). CAMK4 knockdown and kinase-dead mutant inhibited 
crocin-mediated HO-1 expression, Nrf2 activation, and phosphorylation of Akt, 
indicating that HO-1 expression is mediated by CAMK4 and that Akt is a 
downstream mediator of CAMK4 in crocin signaling. Moreover, crocin-mediated 
suppression of iNOS expression was blocked by CAMK4 inhibition. Overall, these 
results suggest that crocin suppresses LPS-stimulated expression of iNOS by 
inducing HO-1 expression via Ca(2+)/calmodulin-CAMK4-PI3K/Akt-Nrf2 signaling 
cascades. Our findings provide a novel molecular mechanism for the inhibitory 
effects of crocin against endotoxin-mediated inflammation.