Lack of effect of α-tocopherol on in vitro angiogenesis

A novel 2,3-diphenyl-4H-pyrido[1,2-a]pyrimidin-4-one derivative inhibits endothelial cell dysfunction and smooth muscle cell proliferation/activation

Hyper-proliferation and migration of vascular smooth muscle cells and endothelial cell dysfunction are central events in the development of neo-intimal lesions. Pursuing our interest in the synthesis of bioisosters of flavonoids, we studied in depth a novel synthetic 2,3-diphenyl-4H-pyrido[1,2-a]pyrimidin-4-one derivative, examining its effects in vitro on induced-cell proliferation and activation in human aortic smooth muscle cells (HAoSMCs) and in human umbilical vein endothelial cells (HUVECs). Compared with two well known flavonoids, apigenin and quercetin, the novel compound, 2-(3,4-dimethoxyphenyl)-3-phenyl-4H-pyrido[1,2-a]pyrimidin-4-one, 3, was not toxic for HUVECs, even at high concentrations and for long incubation times, while the two flavonoids were not tolerated, even at concentrations as low as 10 μmol/L. Compound 3 inhibited selectively, and in a concentration-dependent manner, the proliferation of HAoSMCs but not that of HUVECs. In HUVECs, it inhibited the cytokine-induced vascular cell adhesion molecule-1 expression, but not the cyclooxygenase-2 (COX-2) expression. Instead, in HAoSMC, it inhibited the induction of COX-2 expression and the relative release of prostaglandin E2. In addition, it inhibited the transcription of the matrix metalloproteinase-9 and its activity. Thanks to its multiple and tissue-specific function, 2-(3,4-dimethoxyphenyl)-3-phenyl-4H-pyrido[1,2-a]pyrimidin-4-one might replace or assist the action of current drugs eluted by coronary stents, in order to promote a functional repair of damaged wall.

Nitroxides and a nitroxide-based UV filter have the potential to photoprotect UVA-irradiated human skin fibroblasts against oxidative damage

BACKGROUND

Antioxidants are now being incorporated into sunscreens as additional topical measure for delaying the aging process and reducing photo-damage to skin induced by excessive UVA exposure. UVA radiation reaching the skin leads to the generation of ROS (reactive oxygen species) implicated in DNA damage and activation of matrix metalloproteinase-1 (MMP-1) responsible for collagen damage and photo-aging. Nitroxides are a class of compounds endowed with versatile antioxidant activity and recently, nitroxide-based UV filters in which a nitroxide moiety has been attached to the most popular UV filter present in sunscreens have been developed.

OBJECTIVE

This study explores the potential photo-protective effects of these compounds on ROS production and induction of MMP-1 in cultured human dermal fibroblasts exposed to UVA. For comparison, vitamin E was also tested.

METHODS

The effects were assessed by measuring intracellular ROS production using a ROS-index probe and MMP-1 mRNA expression levels using quantitative real-time PCR (qPCR).

RESULTS

Exposure of fibroblasts to 18J/cm(2) UVA lead to a two-fold increase in ROS production which was reduced to non-irradiated control levels in the presence of 50μM nitroxide compounds and vitamin E. Under the same conditions, a ten-fold increase in MMP-1 mRNA expression levels was observed 24h post-UVA treatment which was significantly reduced by all nitroxide compounds but not vitamin E.

CONCLUSION

The results of this study support the potential use of nitroxide compounds, including novel nitroxide-based UV filters, as a useful and alternative strategy for improving the efficacy of topical formulations against photo-aging and possibly photo-carcinogenesis.

Vitamins E and C may increase collagen turnover by intramuscular fibroblasts. Potential for improved meat quality

Vitamins influence collagen metabolism in animals grown for meat. This study investigated whether vitamins E and C regulate collagen turnover in muscle by the balance of effects on the synthesis of collagen and its degradation by secretion of matrix metalloproteinases (MMPs) by bovine intramuscular fibroblasts. Fibroblasts isolated from longissimus dorsi (LD) and semitendinosus (ST) muscle were treated with different concentrations of vitamins. Pro-MMP-2, MMP-2, and total soluble collagen (TSC) synthesis were determined. Vitamins E and C each preferentially increased (P < 0.05) MMP-2 in cells derived from LD relative to those derived from ST. Higher TSC values (P < 0.05) were found for ST cells than for LD cells. Both vitamins may increase collagen turnover exerted by intramuscular connective tissue fibroblasts. These results may have implications in vivo on animal production, as a high rate of collagen turnover may lead to increased collagen solubility in muscles, which can affect meat tenderness.

Alterations in the Notch4 pathway in cerebral endothelial cells by the HIV aspartyl protease inhibitor, nelfinavir

Background

Aspartyl protease inhibitors (PIs) used to treat HIV belong to an important group of drugs that influence significantly endothelial cell functioning and angiogenic capacity, although specific mechanisms are poorly understood. Recently, PIs, particularly Nelfinavir, were reported to disrupt Notch signaling in the HIV-related endothelial cell neoplasm, Kaposi's sarcoma. Given the importance of maintaining proper cerebral endothelial cell signaling at the blood brain barrier during HIV infection, we considered potential signaling pathways such as Notch, that may be vulnerable to dysregulation during exposure to PI-based anti-retroviral regimens. Notch processing by γ-secretase results in cleavage of the notch intracellular domain that travels to the nucleus to regulate expression of genes such as vascular endothelial cell growth factor and NFκB that are critical in endothelial cell functioning. Since, the effects of HIV PIs on γ-secretase substrate pathways in cerebral endothelial cell signaling have not been addressed, we sought to determine the effects of HIV PIs on Notch and amyloid precursor protein.

Results

Exposure to reported physiological levels of Saquinavir, Indinavir, Nelfinavir and Ritonavir, significantly increased reactive oxygen species in cerebral endothelial cells, but had no effect on cell survival. Likewise, PIs decreased Notch 4-protein expression, but had no effect on Notch 1 or amyloid precursor protein expression. On the other hand, only Nelfinavir increased significantly Notch 4 processing, Notch4 intracellular domain nuclear localization and the expression of notch intracellular domain targets NFκB and matrix metalloproteinase 2. Pre-treatment with the antioxidant Vitamin E prevented PI-induced reactive oxygen species generation and partially prevented Nelfinavir-induced changes in both Notch 4 processing, and cellular localization patterns. Moreover, in support of increased expression of pro-angiogenic genes after Nelfinavir treatment, Nelfinavir did not inhibit angiogenic capacity.

Conclusion

Nelfinavir affects Notch 4 processing that results in induction of expression of the pro-angiogenic genes NFκB and matrix metalloproteinase 2 in cerebral endothelial cells.

Cellular, molecular and clinical aspects of vitamin E on atherosclerosis prevention

Randomised clinical trials and epidemiologic studies addressing the preventive effects of vitamin E supplementation against cardiovascular disease reported both positive and negative effects, and recent meta-analyses of the clinical studies were rather disappointing. In contrast to that, many animal studies clearly show a preventive action of vitamin E in several experimental settings, which can be explained by the molecular and cellular effects of vitamin E observed in cell cultures. This review is focusing on the molecular effects of vitamin E on the cells playing a role during atherosclerosis, in particular on the endothelial cells, vascular smooth muscle cells, monocytes/macrophages, T cells, and mast cells. Vitamin E may act by normalizing aberrant signal transduction and gene expression in antioxidant and non-antioxidant manners; in particular, over-expression of scavenger receptors and consequent foam cell formation can be prevented by vitamin E. In addition to that, the cellular effects of alpha-tocopheryl phosphate and of EPC-K1, a composite molecule between alpha-tocopheryl phosphate and l-ascorbic acid, are summarized.