Angiotensin-converting-enzyme inhibition counteracts angiotensin II-mediated endothelial cell dysfunction by modulating the p38/SirT1 axis.

OBJECTIVE: Oxidative stress has been linked to endothelial dysfunction and angiotensin II stimulates the reactive oxygen species production contributing to several cardiovascular diseases. We have studied the chain of events induced by angiotensin-converting-enzyme (ACE) activation in vascular umbilical vein endothelial cells (HUVECs) by using an ACE inhibitor such as zofenoprilat. METHODS: We used specific assay to measure the superoxide anion production, tetrazolium bromide (MTT) assay for cell viability, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay for cell apoptosis, and western blot for protein analysis in the study. RESULTS: Zofenoprilat counteracts the superoxide anion production and cell apoptosis induced by angiotensin I treatment by blocking the extrinsic caspase cascade, NF-kB and p38 activation. p38 inhibitor SB203580 reverted the angiotensin II oxidant effects while the p38 constitutively activation, by MKK6 transfection, abrogated the zofenoprilat effects. Characterizing the zofenoprilat downstream effector we found that zofenoprilat reverted the SirT-1 downregulation induced by angiotensin II. p38 activation by angiotensin II was strictly correlated with SirT1 protein downregulation; SB203580 significantly prevented SirT1 downregulation induced by angiotensin II while the p38 constitutive activation abolished SIRT1 protein basal levels. p38 directly bound SirT1 sequestering it in the cytoplasm. SirT1 inhibition by sirtinol annulled zofenoprilat action while SirT1 overexpression reverted the cytotoxic effects of angiotensin II. Finally, zofenoprilat negatively controlled angiotensin I receptor protein expression through SirT1. CONCLUSION: The p38-SirT1 axis is found markedly relevant in modulating the cardiovascular benefit deriving from ACE-inhibitors and might represent a novel target for innovative drugs in cardiovascular prevention.

Vitamin D protects human endothelial cells from H2O2 oxidant injury through the Mek/Erk-Sirt1 axis activation.

Endothelium homeostasis alterations govern the pathogenesis of cardiovascular diseases. Several studies show that vitamins anti-oxidant proprieties rescue the endothelial functions adversely affected by oxidative stress in several diseases. We investigated the vitamin D anti-oxidant potential in human endothelial cells exposed to H2O2 oxidative stress. Vitamin D protected endothelial cells against H2O2 oxidative stress counteracting the superoxide anion generation, the apoptosis and blocking the extrinsic caspase cascade by positively controlling phospho-active ERKs level. MEKs/ERKs inhibitor U0126 reverted the vitamin D anti-oxidant effects. Characterizing the vitamin D downstream effector, we found that vitamin D up-regulated SirT-1 and reverted the SirT-1 down-regulation induced by H2O2. ERKs activation by vitamin D strictly correlated with SirT-1 protein accumulation since both MEKs/ERKs inhibition and ERK1/2 silencing decreased SIRT-1. SirT-1 inhibition by Sirtinol reverted the vitamin D anti-oxidant effects. Thus, vitamin D significantly reduced the endothelial malfunction and damage caused by oxidative stress, through the activation of MEKs/ERKs/SirT-1 axis.

MEK/ERK inhibitor U0126 increases the radiosensitivity of rhabdomyosarcoma cells in vitro and in vivo by downregulating growth and DNA repair signals.

Multimodal treatment has improved the outcome of many solid tumors, and in some cases the use of radiosensitizers has significantly contributed to this gain. Activation of the extracellular signaling kinase pathway (MEK/ERK) generally results in stimulation of cell growth and confers a survival advantage playing the major role in human cancer. The potential involvement of this pathway in cellular radiosensitivity remains unclear. We previously reported that the disruption of c-Myc through MEK/ERK inhibition blocks the expression of the transformed phenotype; affects in vitro and in vivo growth and angiogenic signaling; and induces myogenic differentiation in the embryonal rhabdomyosarcoma (ERMS) cell lines (RD). This study was designed to examine whether the ERK pathway affects intrinsic radiosensitivity of rhabdomyosarcoma cancer cells. Exponentially growing human ERMS, RD, xenograft-derived RD-M1, and TE671 cell lines were used. The specific MEK/ERK inhibitor, U0126, reduced the clonogenic potential of the three cell lines, and was affected by radiation. U0126 inhibited phospho-active ERK1/2 and reduced DNA protein kinase catalytic subunit (DNA-PKcs) suggesting that ERKs and DNA-PKcs cooperate in radioprotection of rhabdomyosarcoma cells. The TE671 cell line xenotransplanted in mice showed a reduction in tumor mass and increase in the time of tumor progression with U0126 treatment associated with reduced DNA-PKcs, an effect enhanced by radiotherapy. Thus, our results show that MEK/ERK inhibition enhances radiosensitivity of rhabdomyosarcoma cells suggesting a rational approach in combination with radiotherapy.

Cardiovascular risk and cardiometabolic protection: role of glitazones.

Thiazolidinediones (TZDs) are widely used in the type 2 diabetes mellitus (DMT2) treatment but have also been tested in cardiovascular prevention. DMT2 is associated with a marked increment in cardiovascular risk, and its prevention represents a main target in cardiometabolic protection. Both Troglitazone (Troglitazone in Prevention of Diabetes study) and Rosiglitazone (Diabetes Reduction Assessment with Ramipril and Rosiglitazone Medication study) significantly reduced new-onset diabetes. A similar topic will be investigated with pioglitazone (Actos Now for Prevention of Diabetes). In the Prospective Pioglitazone Clinical Trial in Macrovascular events the primary end point (all-cause mortality, nonfatal myocardial infarction, stroke, acute coronary syndromes, endovascular or surgical intervention in the coronary/leg arteries and amputation above ankles) was unaffected, whereas the secondary one (all-cause mortality, nonfatal myocardial infarction and stroke) was reduced by pioglitazone (-16%, p=0.027) compared to placebo in 5,238 patients with DMT2 and macrovascular disease. In contrast, a meta-analysis (Nissen and Wolski, N Engl J Med. 2007;356:2457-2471) reported that rosiglitazone treatment is associated with a significant increase in myocardial infarction risk (p=0.03) and a borderline significant increase in the risk of death from cardiovascular causes (p=0.06). Nevertheless, the possibility that rosiglitazone might affect cardiovascular events should be evaluated by the ongoing trial Rosiglitazone Evaluated for Cardiac Outcomes and Regulation of Glycemia in Diabetes (RECORD). Interim findings early from RECORD did not show significant differences between the rosiglitazone and the control group regarding myocardial infarction and death from cardiovascular and any cause. Additional large-scale trials are awaited to clarify the of role TZDs in cardiovascular outcomes.