The study of cinnamaldehyde in anti-inflammatory mechanism in endothelial cells

• Main Authors: Being-Chyuan Liao, 廖炳泉
• Other Authors: Being-Sun Wung
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/74324355264129916761

碩士 === 國立嘉義大學 === 微生物免疫與生物藥學系研究所 === 96 === 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 TNFα-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 TNFα-treated ECs, the principal downstream signal of VCAM-1 and ICAM-1, NF-□B, 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 IκB-α, 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 TNF□-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 Nrf-2 related gene. Moreover, Cinnamaldehyde exposure rapidly reduces the cellular GSH levels in ECs over short term treatments but increases these levels after 9 hours exposure. We also found that cinnamaldehyde can upregulate Nrf-2 in nuclear extracts and upregulate □-glutamate-cysteine ligase (□-GCL) gene expression. To understand the anti-inflammation by GSH, we studied effects on glutaredoxin-1 (Grx-1), which catalyze GSH-dependent thiol-disulfide reactions, particularly in glutathionylation of protein sulfhydryl group. We found cinnamaldehyde increased Grx-1 gene expression and enzyme activity in ECs. The anti-inflammatory effect was reduced in ECs treated with buthionine sulfoximine (BSO), a specific inhibitor of □-glutamate-cysteine ligase, cadmium chloride (CdCl2), a Grx-1 inhibitor or small interference RNA of Grx-1. Cinnamaldehyde increased S-glutathionlation of p65, however; the S-glutathionylation could be reversed by CdCl2-treated ECs. The results suggest that Grx-dependent S-glutathionlation of p65 regulates p65 activity in cinnamaldehyde-treated ECs. Taken together, these data suggest cinnamaldehyde suppresses TNFα-induced singling pathways via two distinct mechanisms that are mediated by dynamic of intracellular GSH level.