Caffeic acid phenethyl ester suppresses monocyte adhesion to the endothelium by inhibiting NF-κB/NOX2-derived ROS signaling

Recent progresses in the pharmacological activities of caffeic acid phenethyl ester

The past decades have seen a growing interest in natural products. Caffeic acid phenethyl ester (CAPE), a flavonoid isolated from honeybee propolis, has shown multiple pharmacological potentials, including anti-cancer, anti-inflammatory, antioxidant, antibacterial, antifungal, and protective effects on nervous systems and multiple organs, since it was found as a potent nuclear factor κB (NF-κB) inhibitor. This review summarizes the advances in these beneficial effects of CAPE, as well as the underlying mechanisms, and proposes that CAPE offers an opportunity for developing therapeutics in multiple diseases. However, clinical trials on CAPE are necessary and encouraged to obtain certain clinically relevant conclusions.

Caffeic acid phenethyl ester potentiates gastric cancer cell sensitivity to doxorubicin and cisplatin by decreasing proteasome function

Caffeic acid phenethyl ester (CAPE) is a major propolis component that possesses a variety of pharmacological properties such as antioxidant and anticancer effects. Herein, we investigated the effectiveness of CAPE on cytotoxicity of clinically used anticancer drugs, doxorubicin (DXR) and cisplatin (CDDP), in parental and the drug-resistant cells of stomach (MKN45) and colon (LoVo) cancers. Concomitant treatment with CAPE potentiated apoptotic effects of DXR and CDDP against the parental cells. The treatment significantly reduced the production of reactive oxygen species elicited by DXR but did not affect the DXR-mediated accumulation of 4-hydroxy-2-nonenal, a lipid peroxidation-derived aldehyde. Intriguingly, treatment of parental MKN45 cells with CAPE alone reduced 26S proteasome-based proteolytic activities, in which a chymotrypsin-like activity was most affected. This effect of CAPE was the most prominent among those of eight flavonoids and nine cinnamic acid derivatives and was also observed in parental LoVo cells. In the DXR-resistant or CDDP-resistant cells, the chymotrypsin-like activity was highly up-regulated and significantly decreased by CAPE treatment, which sensitized the resistant cells to DXR and CDDP. Reverse transcription-PCR analysis showed that CAPE treatment led to downregulation of five proteasome subunits (PSMB1-PSMB5) and three immunoproteasome subunits (PSMB8-PSMB10) in DXR-resistant MKN45 cells. The results suggest that CAPE enhances sensitivity of these cancer cells and their chemoresistant cells to DXR and CDDP, most notably through decreasing proteasome function. Thus, CAPE may be valuable as an adjuvant for DXR or CDDP chemotherapy in gastric cancer.

Dexmedetomidine Attenuates LPS-Induced Monocyte-Endothelial Adherence via Inhibiting Cx43/PKC-α/NOX2/ROS Signaling Pathway in Monocytes

Dexmedetomidine is widely used for sedating patients in operation rooms or intensive care units. Its protective functions against oxidative stress, inflammation reaction, and apoptosis have been widely reported. In present study, we explored the effects of dexmedetomidine on monocyte-endothelial adherence. We built lipopolysaccharide- (LPS-) induced monocyte-endothelial adherence models with U937 monocytes and human umbilical vein endothelial cells (HUVECs) and observed the effects of dexmedetomidine on U937-HUVEC adhesion. Specific siRNA was designed to knock-down Connexin43 (Cx43) expression in U937 monocytes. Gö6976, GSK2795039, and NAC were used to inhibit PKC-α, NOX2, and ROS, respectively. Then, we detected whether dexmedetomidine could downregulate Cx43 expression and its downstream PKC-α/NOX2/ROS signaling pathway activation and ultimately result in the decrease of U937-HUVEC adhesion. The results showed that dexmedetomidine, at its clinically relevant concentrations (0.1 nM and 1 nM), could inhibit adhesion of molecule expression (VLA-4 and LFA-1) and U937-HUVEC adhesion. Simultaneously, it also attenuated Cx43 expression in U937 monocytes. With the downregulation of Cx43 expression, the activity of PKC-α and its related NOX2/ROS signaling pathway were reduced. Inhibiting PKC-α/NOX2/ROS signaling pathway with Gö6976, GSK2795039, and NAC, respectively, VLA-4, LFA-1 expression, and U937-HUVEC adhesion were all decreased. In summary, we concluded that dexmedetomidine, at its clinically relevant concentrations (0.1 nM and 1 nM), decreased Cx43 expression in U937 monocytes and PKC-α associated with carboxyl-terminal domain of Cx43 protein. With the downregulation of PKC-α, the NOX2/ROS signaling pathway was inhibited, resulting in the decrease of VLA-4 and LFA-1 expression. Ultimately, U937-HUVEC adhesion was reduced.

Lunasin abrogates monocytes to endothelial cells

The adherence of monocytes to endothelial cells plays a causal role in the early development of atherosclerosis and is driven by several inflammatory stimuli, which includes oxidized low-density lipoprotein (ox-LDL). Lunasin, a natural peptide identified in soybean seeds, soy-derived food products, other grains and herbal plants, has been found to exert numerous biological activities, including anti-inflammatory and antioxidant properties. However, little is known regarding the mechanism of action of lunasin in ox-LDL-induced endothelial inflammation. The results of the present study indicate that lunasin significantly ameliorated ox-LDL-induced adhesion of THP-1 monocytes to the surface of human umbilical vein endothelial cells (HUVECs). Lunasin also suppressed expression of the adhesion molecules VCAM-1 and E-selectin, but not ICAM-1. Notably, the inhibitory mechanism of lunasin is associated with its stimulatory effects on expression of the KLF2 transcriptional factor. In addition, lunasin treatment could reverse the effects of ox-LDL on the expression of eNOS and PAI-1, the direct target genes of KLF2. Mechanistically, it was proven that the MEK5/ERK5 pathway mediates the effects of lunasin on KLF2 expression. Taken together, the results of this study suggest that dietary or supplementary intake of lunasin may have a prophylactic or therapeutic capacity in cardiovascular diseases such as atherosclerosis.

CAPE increases the expression of SOD3 through epigenetics in human retinal endothelial cells

Extracellular-superoxide dismutase (EC-SOD or SOD3), which catalyzes the dismutation of superoxide anions into hydrogen peroxide, plays a key role in vascular protection against reactive oxygen species (ROS). The excess generation of ROS is closely involved in the pathogenesis of diabetic retinopathy (DR); therefore, the maintenance of SOD3 expression at high levels is important for the prevention of DR. In the present study, we showed that caffeic acid phenethyl ester (CAPE) increased the expression of SOD3 through the acetylation of histone within the SOD3 promoter region in human retinal endothelial cells (HRECs). Histone acetylation within its promoter was focused on the inhibition of histone deacetylase (HDAC), and we examined the involvement of myocyte enhancer factor 2 (MEF2) and HDAC1 in CAPE-elicited SOD3 expression. Our results demonstrate that SOD3 silencing in basal HRECs is regulated by HDAC1 composed with MEF2A/2D hetero dimers. Moreover, phosphorylation of threonine 312 in MEF2A and dissociation of HDAC1 from SOD3 promoter play pivotal roles in CAPE-elicited SOD3 expression. Overall, our findings provide that CAPE may be one of the seed compounds that maintain redox homeostasis.