Fragiska Sigala

Downregulation of the KIP family members p27KIP1 and p57KIP2 by SKP2 and the role of methylation in p57KIP2 inactivation in nonsmall cell lung cancer

Knowing the status of molecules involved in cell cycle control in cancer is vital for therapeutic approaches aiming at their restoration. The p27KIP1 and p57KIP2 cyclin‐dependent kinase inhibitors are nodal factors controlling normal cell cycle. Their expression in normal lung raises the question whether they have a mutual exclusive or redundant role in nonsmall cell lung cancer (NSCLC). A comparative comprehensive analysis was performed in a series of 70 NSCLCs. The majority of cases showed significantly reduced expression of both members compared to normal counterparts. Low KIP protein levels correlated with increased proliferation, which seems to be histological subtype preponderant. At mechanistic level, degradation by SKP2 was demonstrated, in vivo and in vitro, by siRNA‐methodology, to be the most important downregulating mechanism of both KIPs in NSCLC. Decreased p57KIP2‐transcription complements the above procedure in lowering p57KIP2‐protein levels. Methylation was the main cause of decreased p57KIP2‐mRNA levels. Allelic loss and imprinting from LIT1 mRNA contribute also to decreased p57KIP2 transcription. In vitro recapitulation of the in vivo findings, in A549 lung cells (INK4A‐B(−/−)), suggested that inhibition of the SKP2‐degradation mechanism restores p27KIP1 and p57KIP2 expression. Double siRNA treatments demonstrated that each KIP is independently capable of restraining cell growth. An additional demethylation step is required for complete reconstitution of p57KIP2 expression in NSCLC.

p53-Dependent ICAM-1 overexpression in senescent human cells identified in atherosclerotic lesions

Most normal somatic cells enter a state called replicative senescence after a certain number of divisions, characterized by irreversible growth arrest. Moreover, they express a pronounced inflammatory phenotype that could contribute to the aging process and the development of age-related pathologies. Among the molecules involved in the inflammatory response that are overexpressed in senescent cells and aged tissues is intercellular adhesion molecule-1 (ICAM-1). Furthermore, ICAM-1 is overexpressed in atherosclerosis, an age-related, chronic inflammatory disease. We have recently reported that the transcriptional activator p53 can trigger ICAM-1 expression in an nuclear factor-kappa B (NF-κB)-independent manner (Gorgoulis et al, EMBO J. 2003; 22: 1567–1578). As p53 exhibits an increased transcriptional activity in senescent cells, we investigated whether p53 activation is responsible for the senescence-associated ICAM-1 overexpression. To this end, we used two model systems of cellular senescence: (a) human fibroblasts and (b) conditionally immortalized human vascular smooth muscle cells. Here, we present evidence from both cell systems to support a p53-mediated ICAM-1 overexpression in senescent cells that is independent of NF-κB. We also demonstrate in atherosclerotic lesions the presence of cells coexpressing activated p53, ICAM-1, and stained with the senescence-associated β-galactosidase, a biomarker of replicative senescence. Collectively, our data suggest a direct functional link between p53 and ICAM-1 in senescence and age-related disorders.

Toll-Like Receptor 7 Protects From Atherosclerosis by Constraining “Inflammatory” Macrophage Activation

Background Toll-like receptors (TLRs) have long been considered to be major culprits in the development of atherosclerosis, contributing both to its progression and clinical complications. However, evidence for most TLRs beyond TLR2 and TLR4 is lacking. Methods and Results We used experimental mouse models, human atheroma cultures, and well-established human biobanks to investigate the role of TLR7 in atherosclerosis. We report the unexpected finding that TLR7, a receptor recognizing self–nucleic acid complexes, is protective in atherosclerosis. In Apoe−/− mice, functional inactivation of TLR7 resulted in accelerated lesion development, increased stenosis, and enhanced plaque vulnerability as revealed by Doppler ultrasound and/or histopathology. Mechanistically, TLR7 interfered with macrophage proinflammatory responses to TLR2 and TLR4 ligands, reduced monocyte chemoattractant protein-1 production, and prevented expansion of Ly6Chi inflammatory monocytes and accumulation of inflammatory M1 macrophages into developing atherosclerotic lesions. In human carotid endarterectomy specimens TLR7 levels were consistently associated with an M2 anti-inflammatory macrophage signature (interleukin [IL]-10, IL-1RA, CD163, scavenger and C-type lectin receptors) and collagen genes, whereas they were inversely related or unrelated to proinflammatory mediators (IL-12/IL-23, interferon beta, interferon gamma, CD40L) and platelet markers. Moreover, in human atheroma cultures, TLR7 activation selectively suppressed the production of key proatherogenic factors such as monocyte chemoattractant protein-1 and tumor necrosis factor without affecting IL-10. Conclusions These findings provide evidence for a beneficial role of TLR7 in atherosclerosis by constraining inflammatory macrophage activation and cytokine production. This challenges the prevailing concept that all TLRs are pathogenic and supports the exploitation of the TLR7 pathway for therapy.

Metabonomic identification of novel biomarkers in doxorubicin cardiotoxicity and protective effect of the natural antioxidant oleuropein.

Doxorubicin (DXR) is a commonly used antineoplastic agent; however, its use is limited due to cardiotoxicity. Oxidative stress and consequent alterations of cardiac energetics are involved in the development of DXR toxicity. Oleuropein (Oleu) is a phenolic antioxidant, present in olive tree, reported to confer protection against DXR cardiotoxicity. In this study, NMR based‐metabonomics was applied to characterize the metabolic profile of the acute DXR cardiotoxicity in rats and to evaluate the metabolic alterations conferred by co‐treatment with Oleu. Wistar rats were divided into six groups and treated as follows: control group with a single injection of 2 mL normal saline intraperitoneally (i.p.), DXR group with a single dose of 20 mg/kg, i.p and DXR plus Oleu groups with 20mg/kg DXR i.p., and 100 or 200 mg/kg/BW of Oleu i.p. for 5 or 3 consecutive days starting either 2 days before or on the day of DXR administration. Hearts were excised 72 h after DXR treatment and 1H‐NMR spectra of aqueous myocardium extracts were recorded. Principal Component Analysis (PCA) and Partial Least Square Discriminant Analysis (PLS‐DA) revealed differences in the metabolic profile between control and DXR attributed to several metabolites. A number of them were quantified by integration of the NMR spectra. Myocardial levels of acetate and succinate were increased in DXR compared to controls, while branched amino acids were decreased. These results correlate with nonenzymatic conversion of pyruvate to acetate and of α‐ketoglutarate to succinate by DXR free radicals. Oleu completely restored the changes of metabolites to the normal levels. Acetate and succinate constitute novel biomarkers related to DXR, and Oleu treatment aids the compensation of distressed energy metabolic pathways. Copyright

Short-term statin administration in hypercholesterolaemic rabbits resistant to postconditioning: effects on infarct size, endothelial nitric oxide synthase, and nitro-oxidative stress

AIMS The effectiveness of postconditioning (POC) in hypercholesterolaemia is in dispute. We investigated the effects of 3-day lipophilc (simvastatin) or hydrophilic (pravastatin) statin treatment, without or with POC in normocholesterolaemic (Norm) and hypercholesterolaemic (Chol) rabbits. METHODS AND RESULTS Norm or Chol rabbits were subjected to 30 min ischaemia and randomized in two series of 12 groups each: control, simvastatin (Sim), pravastatin (Prav), POC, Sim-POC, Prav-POC, Chol, Sim-Chol, Prav-Chol, POC-Chol, Sim-POC-Chol, Prav-POC-Chol. After ischaemia, rabbits of the first series underwent 3 h reperfusion, followed by infarct size, total cholesterol, and low density lipoprotein plasma level evaluation; animals of the second series underwent 10 min reperfusion followed by tissue sampling for nitrotyrosine (NT), malondialdehyde, endothelial nitric oxide synthase (eNOS), and Akt analyses. N-nitro-l-arginine methylester (L-NAME) was given in two additional groups (POC-L-NAME and Prav-Chol-L-NAME) for infarct size assessment. All interventions reduced infarction in Norm (24.3 ± 1.3, 25.9 ± 2.8, 27.9 ± 3.1, 23.3 ± 2.3, and 33.4 ± 2.5%, in POC, Sim, Prav, Sim-POC, and Prav-POC groups, respectively, vs. 49.3 ± 1.9% in control, P < 0.05), but only Prav did so in Chol animals (25.7 ± 3.3 and 25.3 ± 3.9% in Prav-Chol and Prav-POC-Chol vs. 50.9 ± 1.7, 44.8 ± 4.3, 41.5 ± 3.5, and 49.3 ± 5.5% in Chol, Sim-Chol, POC-Chol, and Sim-POC-Chol, respectively, P < 0.05). L-NAME abolished the infarct size-limiting effect of POC and Prav-Chol. Prav induced the greatest reduction in NT, while it was the only intervention that increased myocardial eNOS and Akt in Chol rabbits (P < 0.05 vs. all others). CONCLUSION Prav, in contrast to same-dose Sim or POC, reduces infarction in Chol rabbits independently of lipid lowering, potentially through eNOS activation and nitro-oxidative stress attenuation.

Oleuropein prevents doxorubicin-induced cardiomyopathy interfering with signaling molecules and cardiomyocyte metabolism

Oleuropein, a natural phenolic compound, prevents acute doxorubicin (DXR)-induced cardiotoxicity but there is no evidence regarding its role in chronic DXR-induced cardiomyopathy (DXR-CM). In the present study, we investigated the role of oleuropein in DXR-CM by addressing cardiac geometry and function (transthoracic echocardiography), cardiac histopathology, nitro-oxidative stress (MDA, PCs, NT), inflammatory cytokines (IL-6, Big ET-1), NO homeostasis (iNOS and eNOS expressions), kinases involved in apoptosis and metabolism (Akt, AMPK) and myocardial metabonomics. Rats were randomly divided into 6 groups: Control, OLEU-1 and OLEU-2 [oleuropein at 1000 and 2000 mg/kg in total, respectively, intraperitoneally (i.p.) for 14 days], DXR (18 mg/kg, i.p. divided into 6 equal doses for 2 weeks), DXR-OLEU-1 and DXR-OLEU-2 (both oleuropein and DXR as previously described). Impaired left ventricular contractility and inflammatory and degenerative pathology lesions were encountered only in the DXR group. The DXR group also had higher MDA, PCs, NT, IL-6 and Big ET-1 levels, higher iNOS and lower eNOS, Akt and AMPK activation compared to controls and the oleuropein-treated groups. Metabonomics depicted significant metabolite alterations in the DXR group suggesting perturbed energy metabolism and protein biosynthesis. The effectiveness of DXR in inhibiting cell proliferation is not compromised when oleuropein is present. We documented an imbalance between iNOS and eNOS expressions and a disturbed protein biosynthesis and metabolism in DXR-CM; these newly recognized pathways in DXR cardiotoxicity may help identifying novel therapeutic targets. Activation of AMPK and suppression of iNOS by oleuropein seem to prevent the structural, functional and histopathological cardiac effects of chronic DXR toxicity.

Oxidized LDL in human carotid plaques is related to symptomatic carotid disease and lesion instability

BACKGROUND Oxidative stress is an important determinant in atherosclerosis development. Various markers of oxidative stress, such as oxidation of low-density lipoprotein (LDL), nitrosative stress, lipid peroxidation, and protein oxidation, have been implicated in the initiation and/or progression of atherosclerosis, but their association with plaque erosion and symptomatic carotid disease has not been fully defined. In addition, certain oxidative markers have been shown in various models to promote plaque remodeling through matrix metalloproteinase (MMP) activation. OBJECTIVE To perform a global investigation of various oxidative stress markers and assess for potential relationships with destabilization and symptomatic development in human carotid plaques. METHODS Thirty-six patients undergoing endarterectomy were evaluated and compared with 20 control specimens obtained at the time of autopsy. Differences between stable and unstable plaques, symptomatic and asymptomatic patients, and >or=90% and <90% stenosis were evaluated. Oxidized LDL (ox-LDL), nitrotyrosine (NT), malondialdehyde (MDA), and protein carbonyls (PCs) levels were determined in atheromatic plaques homogenates by corresponding biochemical assays. Immunohistochemical (IHC) analysis was also employed to determine the percentage and topological distribution of cells expressing NT and metalloproteinase-9 (MMP-9) in serial sections from corresponding atheromatic plaques. MMP-9 expression was further verified using Western blot analysis. RESULTS Ox-LDL was increased in symptomatic patients (P < .05). Also, ox-LDL and NT levels were significantly higher in unstable versus stable carotid plaques (P < .05, respectively). Furthermore, IHC serial section analysis, corroborated by statistical analysis, showed a topological and expressional correlation between NT and MMP-9 (P < .05). MDA and PCs levels, although increased in carotid plaques, did not distinguish stable from unstable carotid plaques as well as symptomatic from asymptomatic patients with various degrees of stenosis. CONCLUSION All types of investigated oxidative stress markers were significantly increased in human carotid plaques, but only ox-LDL levels were associated with clinical symptoms, while peroxynitrite products and MMP-9 were specifically related to plaque instability.

Quantitative analysis of carotid plaque vasa vasorum by CEUS and correlation with histology after endarterectomy

BACKGROUND Intraplaque neovascularization and vasa vasorum (VV) proliferation contribute in the progression and rupture of atherosclerotic lesions. Contrast enhanced ultrasonography (CEUS) has been reported to attain data regarding intraplaque neovessels and VV. However, whether the detection of microbubbles by CEUS within atherosclerotic plaques truly represents microvessels is a point of concern. We aimed to evaluate stable and unstable carotid artery plaque (CAP) VV pattern by CEUS and its correlation with histology and immunochemistry. PATIENTS AND METHODS Patients with CAP scheduled for plaque endarterectomy were enrolled. CAP was initially identified by conventional ultrasonography and subsequently CEUS (harmonic ultrasound imaging with simultaneous intravenous contrast agent injection) was performed. The recorded image loops were evaluated by a semi-automated method. Plaque specimens were excised and underwent histological and immunochemical (for CD34, Vascular Endothelial Growth Factor, CD68 and CD3 antibodies) analysis. RESULTS Fourteen patients (67.6 ± 10.2 years, 10 males) with a 86.9 ± 11.5 % degree of carotid artery stenosis were evaluated. Histology showed that half of the plaques were unstable. Enhancement of plaque brightness on CEUS was significant for both stable and unstable plaque subgroups (p = 0.018 for both). Immunochemistry showed that microvessels, as assessed by CD34 antibody, were more dense in unstable vs. stable plaques (36.6 ± 17.4 vs. 13.0 ± 7.2 respectively, p = 0.002). However, correlation between plaque brigthness enhancement on CEUS and microvessel density was significant only for stable (r = 0.800, p = 0.031) plaques. CONCLUSIONS The identification of brightness enhacement during CEUS in carotid atherosclerotic plaques may not always reflect the presence of VV.

Therapeutic value of melatonin in an experimental model of liver injury and regeneration

Abstract:  Melatonin has marked antioxidant properties. The aim of the present study was to evaluate the therapeutic effect of melatonin on acute liver injury induced in rats by carbon tetrachloride (CCl4), allyl alcohol (AA) and their combination. A total of 108 male Wistar rats were divided into 12 experimental groups according to their treatment regimen (n = 5–10 rats in each group). Melatonin (100 mg/kg body weight, BW) was administered 6 hr (a) after a single dose of CCl4 (intragastrically 0. 66 mL/kg BW diluted 1:1 v/v with corn oil); (b) a single dose of AA (intraperitonealy, 0.62 mmol/kg BW 1:50 v/v in 0.9% saline solution); and (c) a combination of the above substances. Rats were sacrificed at 24 and 48 hr post‐toxin administration and the therapeutic effect of melatonin was investigated by assessment of histopathological changes and lipid peroxidation alterations determined by measuring tissue malondialdehyde plus 4‐hydroxy‐nonenal (MDA + 4‐HNE), plasma MDA and plasma levels of liver enzymes. The levels of a key antioxidant, glutathione (GSH), were measured in liver tissue homogenates. Hepatic necrosis was significantly reduced in the melatonin‐treated rats 48 hr after administration of CCl4, AA and CCl4 + AA. The levels of hepatic enzymes in plasma were found to be significantly reduced at 24 and 48 hr in the CCl4 + AA treated rats after melatonin administration. Additionally, MDA and MDA + 4‐HNE concentrations were significantly reduced at 24 and 48 hr time‐points in all groups that received melatonin. GSH levels were decreased in liver after the toxic substances administration, whereas melatonin reversed this effect. In conclusion, a single dose of melatonin decreased hepatic injury induced by CCl4, AA and CCl4 + AA. The inhibition of the oxidative stress and therefore lipid peroxidation by melatonin in CCl4 and AA administered animals, may constitute the protective mechanism of melatonin against acute liver injury.

Expression of Heregulin in Human Coronary Atherosclerotic Lesions

Background: Endothelial cells, monocytes/macrophages, and vascular smooth muscle cells contribute to the establishment and progression of atherosclerotic lesions by expressing growth and inflammatory factors. The aim of the present study was to determine whether heregulin (HRG) is associated with human coronary artery disease. Methods: Twenty-six fresh human coronary artery segments were collected at autopsy. Expression of cysteine-rich 61 (CYR61) and VEGF in response to HRG was studied in the human endothelial cell line EA.hy926, and expression of CYR61 and HRG was evaluated in activated macrophages isolated from peripheral blood of healthy donors. Results: We found that HRG was overexpressed at the protein and mRNA level in all lesions analyzed and gradually increased as the stages of the lesions progressed. Expression of HRG was observed in the intima primarily in macrophages. The same specimens were analyzed for the expression of CYR61, an angiogenetic factor regulated by HRG in breast cancer epithelial cells. CYR61 was expressed in both normal and atheromatic specimens, but its expression was significantly enhanced in macrophages of the intima. Activation of primary human macrophages results in increased expression of both HRG and CYR61. In addition, studies in endothelial cells where no endogenous HRG is present showed that HRG induces expression of CYR61 and secretion of VEGF. Conclusions: HRG may, therefore, play an important role in the development of coronary artery disease and the expansion of the atherosclerotic plaque and may locally regulate the expression of the angiogenetic factor CYR61.