title: Cinnamaldehyde inhibits the tumor necrosis factor-alpha-induced expression of cell adhesion molecules in endothelial cells by suppressing NF-kappaB activation: effects upon IkappaB and Nrf2.
abstract: The production of adhesion molecules and subsequent attachment of leukocytes to endothelial cells (ECs) are critical early events in atherogenesis. These adhesion molecules thus play an important role in the development of this disease. Recent studies have highlighted the chemoprotective and anti-inflammatory effects of cinnamaldehyde, a Cinnamomum cassia Presl-specific diterpene. In our current study, we have examined the effects of both cinnamaldehyde and extracts of C. cassia on cytokine-induced monocyte/human endothelial cell interactions. We find that these compounds inhibit the adhesion of TNFalpha-induced monocytes to endothelial cells and suppress the expression of the cell adhesion molecules, VCAM-1 and ICAM-1, at the transcriptional level. Moreover, in TNFalpha-treated ECs, the principal downstream signal of VCAM-1 and ICAM-1, NF-kappaB, was also found to be abolished in a time-dependent manner. Interestingly, cinnamaldehyde exerts its anti-inflammatory effects by blocking the degradation of the inhibitory protein IkappaB-alpha, but only in short term pretreatments, whereas it does so via the induction of Nrf2-related genes, including heme-oxygenase-1 (HO-1), over long term pretreatments. Treating ECs with zinc protoporphyrin, a HO-1 inhibitor, partially blocks the anti-inflammatory effects of cinnamaldehyde. Elevated HO-1 protein levels were associated with the inhibition of TNFalpha-induced ICAM-1 expression. In addition to HO-1, we also found that cinnamaldehyde can upregulate Nrf2 in nuclear extracts, and can increase ARE-luciferase activity and upregulate thioredoxin reductase-1, another Nrf2-related gene. Moreover, cinnamaldehyde exposure rapidly reduces the cellular GSH levels in ECs over short term treatments but increases these levels after 9 h exposure. Hence, our present findings indicate that cinnamaldehyde suppresses TNF-induced singling pathways via two distinct mechanisms that are activated by different pretreatment periods.
authors.affiliation: Department of Microbiology and Immunology, National Chiayi University, Chiayi, Taiwan.
authors.forename: Being-Chyuan
authors.initials: BC
authors.lastname: Liao
authors.forename: Chia-Wen
authors.initials: CW
authors.lastname: Hsieh
authors.forename: Yen-Chin
authors.initials: YC
authors.lastname: Liu
authors.forename: Tsai-Teng
authors.initials: TT
authors.lastname: Tzeng
authors.forename: Yung-Wei
authors.initials: YW
authors.lastname: Sun
authors.forename: Being-Sun
authors.initials: BS
authors.lastname: Wung
mesh_terms: D000171:Acrolein / Q000031:analogs & derivatives* / Q000494:pharmacology; D001483:Base Sequence; D002448:Cell Adhesion / Q000502:physiology*; D002460:Cell Line; D017931:DNA Primers; D006801:Humans; D020672:I-kappa B Proteins / Q000502:physiology*; D051267:NF-E2-Related Factor 2 / Q000502:physiology*; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors* / Q000502:physiology
chemical_list: D017931:DNA Primers; D020672:I-kappa B Proteins; D051267:NF-E2-Related Factor 2; D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; D000171:Acrolein; C012843:cinnamaldehyde