Vascular inflammation plays a significant role in the pathogenesis of atherosclerosis. Luteolin, a naturally occurring flavonoid present in many medicinal plants and some commonly consumed fruits and vegetables, has received wide attention for its potential to improve vascular function in vitro. However, its effect in vivo and the molecular mechanism of luteolin at physiological concentrations remain unclear. Here, we report that luteolin as low as 0.5 μM significantly inhibited tumor necrosis factor (TNF)-α-induced adhesion of monocytes to human EA.hy 926 endothelial cells, a key event in triggering vascular inflammation. Luteolin potently suppressed TNF-α-induced expression of the chemokine monocyte chemotactic protein-1 (MCP-1) and adhesion molecules intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1), key mediators involved in enhancing endothelial cell–monocyte interaction. Furthermore, luteolin inhibited TNF-α-induced nuclear factor (NF)-κB transcriptional activity, IκBα degradation, expression of IκB kinase β and subsequent NF-κB p65 nuclear translocation in endothelial cells, suggesting that luteolin can inhibit inflammation by suppressing NF-κB signaling. In an animal study, C57BL/6 mice were fed a diet containing 0% or 0.6% luteolin for 3 weeks, and luteolin supplementation greatly suppressed TNF-α-induced increase in circulating levels of MCP-1/JE, CXCL1/KC and sICAM-1 in C57BL/6 mice. Consistently, dietary intake of luteolin significantly reduced TNF-α-stimulated adhesion of monocytes to aortic endothelial cells ex vivo. Histology shows that luteolin treatment prevented the eruption of endothelial lining in the intima layer of the aorta and preserved elastin fibers' delicate organization as shown by Verhoeff–Van Gieson staining. Immunohistochemistry studies further show that luteolin treatment also reduced VCAM-1 and monocyte-derived F4/80-positive macrophages in the aorta of TNF-α-treated mice. In conclusion, luteolin protects against TNF-α-induced vascular inflammation in both in vitro and in vivo models. This anti-inflammatory effect of luteolin may be mediated via inhibition of the NF-κB-mediated pathway.

Acrolein is a ubiquitous unsaturated aldehyde has been implicated in the pathogenesis of various neurological disorders. However, limited study has been conducted into potential therapeutic protection and underlying mechanism against acrolein-induced cytotoxicity via upregulation of cellular aldehyde-detoxification defenses. In this study we have utilized RA-differentiated human SH-SY5Y cells and primary human astrocytes to investigate the induction of glutathione (GSH) by the synthetic triterpenoid 2-cyano-3,12-dixooleana-1,9-dien-28-imidazolide (CDDO-Im) and the protective effects CDDO-Im-mediated antioxidant defenses on acrolein toxicity. Acrolein exposure to RA-differentiated SH-SY5Y cells resulted in a significant time dependent depletion of cellular GSH preceding a reduction in cell viability and LDH release. Further, we demonstrated the predominance of cellular GSH in protection against acrolein-induced cytotoxicity. Buthionine sulfoximine (BSO) at 25μM dramatically depleted GSH and significantly potentiated acrolein-induced cytotoxicity. Pretreatment of the cells with 100nM CDDO-Im afforded a dramatic protection against acrolein-induced cytotoxicity. Pretreatment of BSO and CDDO was found to prevent the CDDO-Im-mediated GSH induction and partially reversed the cytoprotective effects of CDDO-Im against acrolein cytotoxicity. Overall, this study represents for the first time the CDDO-Im mediated upregulation of GSH is a predominant mechanism against acrolein-induced neurotoxicity.

Acrolein is an environmental toxicant, mainly found in smoke released from incomplete combustion of organic matter. Several studies showed that exposure to acrolein can lead to liver damage. The mechanisms involved in acrolein-induced hepatocellular toxicity, however, are not completely understood. This study examined the cytotoxic mechanisms of acrolein on HepG2 cells. Acrolein at pathophysiological concentrations was shown to cause apoptotic cell death and an increase in levels of protein carbonyl and thiobarbituric acid reactive acid substances. Acrolein also rapidly depleted intracellular glutathione (GSH), GSH-linked glutathione-S-transferases, and aldose reductase, three critical cellular defenses that detoxify reactive aldehydes. Results further showed that depletion of cellular GSH by acrolein preceded the loss of cell viability. To further determine the role of cellular GSH in acrolein-mediated cytotoxicity, buthionine sulfoximine (BSO) was used to inhibit cellular GSH biosynthesis. It was observed that depletion of cellular GSH by BSO led to a marked potentiation of acrolein-mediated cytotoxicity in HepG2 cells. To further assess the contribution of these events to acrolein-induced cytotoxicity, triterpenoid compound 2-cyano-3,12-dioxooleana-1,9-dien-28-imidazolide (CDDO-Im) was used for induction of GSH. Induction of GSH by CDDO-Im afforded cytoprotection against acrolein toxicity in HepG2 cells. Furthermore, BSO significantly inhibited CDDO-Im-mediated induction in cellular GSH levels and also reversed cytoprotective effects of CDDO-Im in HepG2 cells. These results suggest that GSH is a predominant mechanism underlying acrolein-induced cytotoxicity as well as CDDO-Im-mediated cytoprotection. This study may provide understanding on the molecular action of acrolein which may be important to develop novel strategies for the prevention of acrolein-mediated toxicity.

Sulforaphane, a naturally occurring isothiocyanate present in cruciferous vegetables, has received wide attention for its potential to improve vascular function in vitro. However, its effect in vivo and the molecular mechanism of sulforaphane at physiological concentrations remain unclear. Here, we report that a sulforaphane concentration as low as 0.5 μM significantly inhibited tumor necrosis factor-α (TNF-α)-induced adhesion of monocytes to human umbilical vein endothelial cells, a key event in the pathogenesis of atherosclerosis both in static and under flow conditions. Such physiological concentrations of sulforaphane also significantly suppressed TNF-α-induced production of monocyte chemotactic protein-1 and adhesion molecules including soluble vascular adhesion molecule-1 and soluble E-selectin, key mediators in the regulation of enhanced endothelial cell-monocyte interaction. Furthermore, sulforaphane inhibited TNF-α-induced nuclear factor (NF)-κB transcriptional activity, Inhibitor of NF-κB alpha (IκBα) degradation and subsequent NF-κB p65 nuclear translocation in endothelial cells, suggesting that sulforaphane can inhibit inflammation by suppressing NF-κB signaling. In an animal study, sulforaphane (300 ppm) in a mouse diet significantly abolished TNF-α-increased ex vivo monocyte adhesion and circulating adhesion molecules and chemokines in C57BL/6 mice. Histology showed that sulforaphane treatment significantly prevented the eruption of endothelial lining in the intima layer of the aorta and preserved elastin fibers' delicate organization, as shown by Verhoeff-van Gieson staining. Immunohistochemistry studies showed that sulforaphane treatment also reduced vascular adhesion molecule-1 and monocyte-derived F4/80-positive macrophages in the aorta of TNF-α-treated mice. In conclusion, sulforaphane at physiological concentrations protects against TNF-α-induced vascular endothelial inflammation, in both in vitro and in vivo models. This anti-inflammatory effect of sulforaphane may be, at least in part, associated with interfering with the NF-κB pathway.

Introduction: TNF-α, plays an important role in endothelial dysfunction and is involved in the pathogenesis of atherosclerosis. Aim: We investigated the protective effect of cruciferous vegetable phytochemical sulforaphane at physiological concentrations on TNF-α-induced vascular inflammation. Methods: Human umbilical vascular endothelial cells (HUVEC) were pretreated with sulforaphane (0.5 - 8 μM) before addition of TNF-α for 6 h. Cell adhesion was measured with calcein-AM labeled human monocytes. In animal study, ten weeks old male C57BL/6 mice were fed a diet containing 0 or 300 ppm sulforaphane for 2 weeks followed by TNF-α administration. The chemokines and adhesion molecules in the serum were measured using ELISA Kit. VCAM-1 and F4/80 expressions in mice aorta were performed using immunohistochemistry. Results: Sulforaphane at physiological concentrations (0.5 - 2 μM) significantly inhibited TNF-α-induced adhesion of monocytes to HUVECs and suppressed TNF-α-induced production of monocyte chemoattractant protein -1 (MCP-1) and interleukin-8 (IL-8). Furthermore, sulforaphane inhibited TNF-α-induced NF-κB transcriptional activity, IκBα degradation and subsequent NF-κB p65 nuclear translocation in endothelial cells, suggesting that sulforaphane can inhibit endothelial inflammation by suppressing NF-κB signaling. In animal study, dietary sulforaphane (300 ppm in the diet) significantly suppressed TNF-α-induced increase in circulating chemokines and adhesion molecules in C57BL/6 mice. Sulforaphane treatment also reduced the presence of VCAM-1 and monocytes-derived F4/80-positive macrophages in the aorta of TNF-α treated mice. Histology showed that sulforaphane treatment significantly prevented the eruption of endothelial lining in the intima layer of the aorta and preserved elastin fibers' delicate organization as shown by Verhoeff-van Gieson staining. Conclusion: sulforaphane at physiological concentrations protects against TNF-α-induced vascular endothelial inflammation, in both in vitro and in vivo models. This anti-inflammatory effect of sulforaphane may be, at least in part, associated with interfering with the NF-κB pathway.

Acrolein is an environmental toxicant, mainly found in smoke released from incomplete combustion of organic matter. The compound is ubiquitously found in endogenous as well as exogenous environment. Several studies showed that exposure to acrolein can lead to liver damage. The mechanisms involved in acrolein-induced hepatocellular toxicity, however, are not completely understood. This study examines the toxic effects and cytotoxic mechanisms of acrolein on HepG2 cells. Acrolein at pathophysiological concentrations was shown to cause a concentration-dependent decrease in cell viability as measured by MTT and LDH assays. Acrolein exposure was also found to cause apoptotic cell death and an increase in levels of protein carbonyl and TBARS, markers of protein damage and lipid peroxidation, respectively, in HepG2 cells. Acrolein also rapidly depleted intracellular glutathione (GSH), phase II enzyme GSH-linked glutathione-S-transferases (GST) and aldose reductase (AR) -- three critical cellular defenses that detoxify reactive aldehydes. Results further showed that depletion of cellular GSH by acrolein preceded the loss of cell viability, which suggests that cellular GSH depletion may be an important event in acrolein-induced cytotoxicity. To further determine the role of cellular GSH in protecting against acrolein-mediated cytotoxicity, buthionine sulfoximine (BSO) was used to inhibit cellular GSH biosynthesis. It was observed that depletion of cellular GSH by BSO led to a marked potentiation of acrolein-mediated cytotoxicity in HepG2cells. Furthermore, induction of GSH levels by CDDO-Im, a triterpenoid compound, afforded protection against acrolein toxicity in a concentration-dependent manner. Notably, incubation of HepG2 cells with CDDO-Im at a concentration as low as 10 nM leads to a significant increase in GSH content. To further determine the role of GSH in CDDO-Im-mediated cytoprotection against acrolein-mediated cytotoxicity, BSO was used to inhibit cellular GSH induction by CDDO-Im. Pretreatment of HepG2 cells with BSO and CDDO-Im significantly inhibited CDDO-Im-mediated induction in cellular GSH levels and also reversed cytoprotective effects of CDDO-Im on acrolein-mediated toxicity. In summary, this study demonstrates that exposure to acrolein results in a faster depletion of GSH, an important phase II defense, and causes an increase in apoptosis, lipid peroxidation and protein carbonylation. Furthermore, the endogenous antioxidant GSH can be induced by CDDO-Im. The CDDO-Im-mediated elevated GSH appears to afford a marked protection against acrolein toxicity suggesting that GSH plays a predominant role in CDDO-Im-mediated protection against acrolein-induced toxicity in HepG2 cells. This study may provide understanding on the molecular action of acrolein which may be important to develop novel strategies for the prevention of acrolein-mediated toxicity.