Antonietta Esposito

Decreased carotid atherosclerotic process by control of daily acute glucose fluctuations in diabetic patients treated by DPP-IV inhibitors

OBJECTIVE Blood glucose fluctuations have been found to be relevant to the progression of atherosclerosis in patients with type 2 diabetes and to be more detrimental for the development of atherosclerosis than the sustained hyperglycemia. We aim at evaluating the effect of blunted daily acute glucose fluctuations by DPP-IV inhibitors on intima-media thickness (IMT), a surrogate marker for early atherosclerosis. METHODS Data from a 12-week prospective, randomized, open-label parallel group trial with a blinded-endopoint study on 90 patients with DMT2, assessing the role of Dipeptidyl Peptidase-4 inhibition in lowering oxidative stress and inflammation by reducing daily acute glucose fluctuations (MAGE), were included in the present analysis. RESULTS Administration of both sitagliptin and vildagliptin treatment resulted in a significant decline in IMT. Indeed, vs baseline data Vildagliptin vs Sitagliptin resulted in a greater IMT reduction. After 3 months therapy changes in IMT significantly correlated with changes in MAGE but not with change in HbA1c in the whole population. Only change in MAGE and LDL plasma levels resulted to be independent predictors of the reduced carotid intima-media thickness after adjusting for conventional cardiovascular risk factors in patients with type 2 diabetes. Significant correlations between change in MAGE, change in IMT and change in fasting and interprandial inflammation score and nitrotyrosine plasma levels were found. CONCLUSION Reduction of glucose excursion due to DPP-IV inhibitors administration, may prevent atherosclerosis progression in patients with type 2 diabetes probably through the reduction of daily inflammation and oxidative stress.

Mediterranean diet, telomere maintenance and health status among elderly.

Leukocyte telomere length (LTL) and rate of telomere shortening are known biomarkers of aging while, numerous studies showed that Mediterranean diet (MD) may boost longevity. We studied association between telomere length, telomerase activity and different adherence to MD and its effects on healthy status. The study was conducted in 217 elderly subjects stratified according Mediterranean diet score (MDS) in low adherence (MDS≤3), medium adherence (MDS 4–5) and high adherence (MDS≥6) groups. LTL was measured by quantitative polymerase chain reaction and telomerase activity by a PCR-ELISA protocol. High adherence group showed longer LTL (p = 0.003) and higher telomerase activity (p = 0.013) compared to others. Linear regression analysis including age, gender, smoking habit and MDS showed that MDS was independently associated with LTL (p = 0.024) and telomerase activity levels (p = 0.006). Telomerase activity was independently associated with LTL (p = 0.007) and negatively modulated by inflammation and oxidative stress. Indeed, telomerase levels were associated with healthy status independently of multiple covariates (p = 0.048). These results support a novel role of MD in promoting health-span suggesting that telomere maintenance, rather than LTL variability is the major determinant of healthy status among elderly.

Poor glycaemic control in type 2 diabetes patients reduces endothelial progenitor cell number by influencing SIRT1 signalling via platelet-activating factor receptor activation

Aims/hypothesisDownregulation of levels of endothelial progenitor cells (EPCs) during in-vitro short-term exposure to high glucose concentrations relates to reduced activity of silent information regulator 1 (SIRT1) and increased synthesis of platelet-activating factor (PAF). We investigated the possible relationship between PAF and SIRT1 pathways in EPCs during altered glucose homeostasis.MethodsSIRT1 and PAF receptor (PAF-R) levels were determined by western blot, RT-PCR and confocal laser-scanning microscopy. In-vivo experiments were performed on 48 type 2 diabetic patients (25 with poor glycaemic control and 23 with good glycaemic control) and 20 control individuals. In-vitro experiments with the PAF-R antagonist CV3988 were performed on EPCs isolated from leucocyte-rich buffy coat of healthy human donors.ResultsDecreased SIRT1 protein levels were observed in EPCs from type 2 diabetic patients compared with control individuals (p < 0.01). Notably, the SIRT1 level was consistently lower in patients with poor glycaemic control than in those with good glycaemic control (p < 0.01). Diabetic patients also showed an upregulation of PAF-Rs; this response occurred to a greater extent in individuals with poor glycaemic control than in those with good glycaemic control. In-vitro experiments confirmed that EPCs respond to PAF stimulation with decreased SIRT1 protein and SIRT1 mRNA levels. Moreover, reduction of SIRT1 levels and activity were abolished by CV3988.Conclusions/interpretationThese findings unveil a link between PAF and SIRT1 pathways in EPCs that contributes to the deleterious effect of hyperglycaemia on the functional properties of EPCs, crucial in diabetes and peripheral vascular complications.

A new pleiotropic effect of statins in elderly: modulation of telomerase activity

Recent evidence suggests a link between statins and telomere biology. Whether statin treatment may modulate telomerase activity and affect telomere erosion rate is unknown. We aimed at investigating the potential impact of statin therapy on peripheral blood mononuclear cells telomerase activity, its implication on LTL variability, and its association with telomere shortening rates along with aging. The cross‐sectional study was conducted in 230 subjects (age range: 30‐86 y) stratified according to statins treatment. LTL was measured by quantitative polymerase chain reaction and telomerase activity by a PCR‐ELISA protocol. Subjects on statin treatment showed higher telomerase activity (P<0.0001) and longer LTL (P= 0.028) levels compared to the nonstatin group. Statin therapy was associated with higher telomerase activity independently of multiple covariates, including age, gender, smoking habits, lipid, systemic inflammation, glucose, and blood pressure levels (P=0.019). Indeed, subjects on statin treatment showed significant lower telomere erosion along with aging. Every 1 y increment in age, LTL decreases by 0.058 Kb in no statin and 0.033 Kb in statin groups, respectively, as well as the major difference in telomere attrition between groups was found after the age of 65 yr (P<0.0001). In summary, statins, modulating telomerase activity, affect telomere erosion along with aging.—Boccardi, V., Barbieri, M., Rizzo, M. R., Marfella, R., Esposito, A., Marano, L., Paolisso, G., A new pleiotropic effect of statins in elderly: modulation of telomerase activity FASEB J. 27, 3879–3885 (2013). www.fasebj.org

Inorganic phosphate enhances sensitivity of human osteosarcoma U2OS cells to doxorubicin via a p53-dependent pathway.

Osteosarcoma is the most common malignant primary bone tumor in children and adolescents. The clinical outcome for osteosarcoma remains discouraging despite aggressive surgery and intensive radiotherapy and chemotherapy regimens. Thus, novel therapeutic approaches are needed. Previously, we have shown that inorganic phosphate (Pi) inhibits proliferation and aggressiveness of human osteosarcoma U2OS cells identifying adenylate cyclase, beta3 integrin, Rap1, ERK1/2 as proteins whose expression and function are relevantly affected in response to Pi. In this study, we investigated whether Pi could affect chemosensitivity of osteosarcoma cells and the underlying molecular mechanisms. Here, we report that Pi inhibits proliferation of p53‐wild type U2OS cells (and not of p53‐null Saos and p53‐mutant MG63 cells) by slowing‐down cell cycle progression, without apoptosis occurrence. Interestingly, we found that Pi strongly enhances doxorubicin‐induced cytotoxicity in U2OS, and not in Saos and MG63 cells, by apoptosis induction, as revealed by a marked increase of sub‐G1 population, Bcl‐2 downregulation, caspase‐3 activation, and PARP cleavage. Remarkably, Pi/doxorubicin combination‐induced cytotoxicity was accompanied by an increase of p53 protein levels and of p53 target genes mdm2, p21 and Bax, and was significantly reduced by the p53 inhibitor pifithrine‐alpha. Moreover, the doxorubicin‐induced cytotoxicity was associated with ERK1/2 pathway inhibition in response to Pi. Altogether, our data enforce the evidence of Pi as a novel signaling molecule capable of inhibiting ERK pathway and inducing sensitization to doxorubicin of osteosarcoma cells by p53‐dependent apoptosis, implying that targeting Pi levels might represent a rational strategy for improving osteosarcoma therapy. J. Cell. Physiol. 228: 198–206, 2013.

Targeting protein kinase A in cancer therapy: an update.

Protein Kinase A (PKA) is a well known member of the serine-threonin protein kinase superfamily. PKA, also known as cAMP-dependent protein kinase, is a multi-unit protein kinase that mediates signal transduction of G-protein coupled receptors through its activation upon cAMP binding. The widespread expression of PKA subunit genes, and the myriad of mechanisms by which cAMP is regulated within a cell suggest that PKA signaling is one of extreme importance to cellular function. It is involved in the control of a wide variety of cellular processes from metabolism to ion channel activation, cell growth and differentiation, gene expression and apoptosis. Importantly, since it has been implicated in the initiation and progression of many tumors, PKA has been proposed as a novel biomarker for cancer detection, and as a potential molecular target for cancer therapy. Here, we highlight some features of cAMP/PKA signaling that are relevant to cancer biology and present an update on targeting PKA in cancer therapy.

cAMP Elevation Down-Regulates β3 Integrin and Focal Adhesion Kinase and Inhibits Leptin-Induced Migration of MDA-MB-231 Breast Cancer Cells.

Abstract Breast cancer is one of the most common malignancies and a major cause of cancer death among women worldwide. The high mortality rate associated with breast cancer is mainly due to a propensity of the tumor to metastasize, even if small or undetectable. Given the relevant role of leptin in breast cancer growth and metastasis, novel strategies to counteract biological effects of this obesity-linked cytokine are warranted. Recently, we demonstrated that in MDA-MB-231 breast cancer cells, intracellular cAMP elevation completely abrogates both ERK1/2 and STAT3 phosphorylation in response to leptin. Very surprisingly, this provided evidence that when cAMP levels are increased, leptin drives cells towards apoptosis associated with a marked decrease of Bcl2 protein levels and accompanied by down-regulation of protein kinase A (PKA). The aim of the current study was to investigate the role of cAMP in leptin-associated motility of breast cancer cells. Here we show that cAMP elevation completely prevents leptin-induced migration of MDA-MB-231 breast cancer cells. Interestingly, the inhibition by cAMP-elevating agents of leptin-mediated cell migration is accompanied by a strong decrease of β3 integrin subunit and focal adhesion kinase (FAK) protein levels. Analysis of the underlying cAMP-dependent molecular mechanisms revealed that PKA blockers partly counteract the inhibition of leptin-induced migration and completely prevent the antiproliferative action by cAMP elevation. Moreover, a cAMP analogue that specifically activates Epac and not PKA has an inhibitory effect on leptin-induced cell migration as well. The present study confirms initial evidence for the efficacy of cAMP elevation against oncogenic effects of leptin, identifies β3 integrin subunit and FAK as proteins strongly down-regulated by cAMP elevation, and suggests that both cAMP/PKA- and cAMP/Epac-dependent pathways are involved in inhibition of leptin-induced migration of MDA-MB-231 breast cancer cells. The potential clinical significance and therapeutic applications of our data are discussed.

Integrating leptin and cAMP signalling pathways in triple-negative breast cancer cells.

Breast cancer is a major cause of cancer death in women in the world. Triple-negative breast cancers, which accounts for 10-20% of all mammary tumours, are characterised by an aggressive phenotype, are often found in younger women and have been associated with poor prognosis. Obesity increases the risk for triple-negative breast cancer occurrence. Because triple-negative breast cancer patients are unresponsive to current targeted therapies and other treatment options are only partially effective, new pharmacological approaches are warranted. The obesity-linked adipokine, leptin, is a well known mitogen/survival factor in breast cancer cells and several studies have addressed the role of leptin in breast cancer pathogenesis and progression. Surprisingly, recent in vitro studies have shown that leptin enhances the anti-proliferative effects of cAMP elevation in triple-negative breast cancer cells by apoptosis induction. In the current review, we discuss on the role of cAMP as a growth suppressor and of leptin as a growth promoting factor in breast cancer cells and we will focus on the molecular pathways involved in the antiproliferative interaction between leptin and cAMP elevation. The rationale for the possible development of a simple, cheap and innovative approach for therapeutic intervention in triple-negative breast cancer, based on the use of cAMP elevating drugs at lower and tolerable doses, will be also discussed.

Synergistic cytotoxic effects of inorganic phosphate and chemotherapeutic drugs on human osteosarcoma cells

Novel therapeutic approaches are required for the treatment of osteosarcoma. Combination chemotherapy is receiving increased attention in order to identify compounds that may increase the therapeutic index of clinical anticancer drugs. In this regard, naturally occurring molecules with antitumor activity and with limited toxicity to normal tissues have been suggested as possible candidates for investigation of their synergistic efficacy in combination with antineoplastic drugs. Inorganic phosphate (Pi) is an essential nutrient for living organisms. Relevantly, Pi has emerged as an important signaling molecule capable of modulating multiple cellular functions by altering signal transduction pathways, gene expression and protein abundance in many cell types. Previously, we showed that Pi inhibits proliferation and aggressiveness of U2OS human osteosarcoma cells and that Pi is capable of inducing sensitization of osteosarcoma cells to doxorubicin in a p53-dependent manner. In this study, we extended the role of Pi in the chemosensitivity of osteosarcoma cells to other anticancer drugs. Specifically, we report and compare the antiproliferative effects of a combination between Pi and doxorubicin, Taxol® and 5-fluorouracil (5-FU) treatments. We found that Pi increases the antiproliferative response to both Taxol and doxorubicin to a similar extent. On the other hand, Pi did not potentiate the anticancer effects induced by 5-FU. These effects were paralleled by apoptosis induction and were cell cycle-dependent. The clinical significance of our data and their potential therapeutic applications for improving osteosarcoma treatment are discussed.

Inorganic Phosphate as a Novel Signaling Molecule with Antiproliferative Action in MDA-MB-231 Breast Cancer Cells

Abstract Inorganic phosphate (Pi) is an essential nutrient for living organisms. It plays a key role in diverse physiological functions, including osteoblast differentiation and skeletal mineralization. Relevantly, Pi is emerging as an important signaling molecule capable of modulating multiple cellular functions by altering signal transduction pathways, gene expression, and protein abundance in many cell types. To our knowledge, the consequences of elevated Pi on behavior of breast cancer cells have been poorly addressed. In this study we investigate the effects of Pi on proliferation of MDA-MB-231 breast cancer cells. We report that Pi inhibits proliferation of MDA-MB-231 cells by slowing cell cycle progression, without apoptosis occurrence. We found that Pi causes cells to accumulate in G1 phase in a time-dependent manner. Accordingly, G1 accumulation was associated with a decrease of cyclin A and cyclin E and an increase of cell cycle inhibitors p21 and p27 protein levels, respectively. Moreover, the Pi-induced antiproliferative effect was dynamically accompanied by profound changes in ERK1/2 and STAT3 protein and phosphorylation levels in response to Pi. Altogether, our data represent the first evidence of Pi acting as a novel signaling molecule in MDA-MB-231 breast cancer cells, capable of eliciting a strong antiproliferative action and suggest that targeting Pi levels at local sites might represent the rationale for developing novel strategies for therapeutic intervention in triple-negative breast cancer.