Procyanidins from grape seeds protect endothelial cells from peroxynitrite damage and enhance endothelium-dependent relaxation in human artery: new evidences for cardio-protection

The peroxynitrite scavenging ability of Procyanidins from Vitis vinifera L. seeds was studied in homogeneous solution and in human umbilical endothelial cells (EA.hy926 cell line) using 3-morpholinosydnonimine (SIN-1) as peroxynitrite generator. In homogeneous phase procyanidins dose-dependently inhibited 2',7'-dichloro-dihydrofluorescein (DCFH) oxidation induced by SIN-1 with an IC50 value of 0.28 microM. When endothelial cells (EC) were exposed to 5 mM SIN-1, marked morphological alterations indicating a necrotic cell death (cell viability reduced to 16 +/- 2.5%) were observed. Cell damage was suppressed by procyanidins, with a minimal effective concentration of 1 microM (cell morphology and integrity completely recovered at 20 microM). Cellular localization of procyanidins in EC was confirmed using a new staining procedure and site-specific peroxyl radical inducers: AAPH and cumene hydroperoxide (CuOOH). Endothelial cells (EC) pre-incubated with procyanidins (20 microM) and exposed to FeCl3/K3Fe(CN)6 showed a characteristic blue staining, index of a site-specific binding of procyanidins to EC. Procyanidins dose-dependently inhibit the AAPH induced lipid oxidation and reverse the consequent loss of cell viability, but were ineffective when oxidation was driven at intracellular level (CuOOH). This demonstrates that the protective effect is due to their specific binding to the outer surface of EC thus to quench exogenous harmful radicals. Procyanidins dose-dependently relaxed human internal mammary aortic (IMA) rings (with intact endothelium) pre-contracted with norepinephrine (NE), showing a maximal vasorelaxant effect (85 +/- 9%) at 50 microM (catechin: 18 +/- 2% relaxation at 50 microM). This effect was completely abolished when IMA-rings were de-endothelized and when IMA-rings with intact endothelium were pretreated with L-NMMA or with the soluble guanylate cyclase inhibitor, ODQ. Pre-incubation with indomethacin reduces (by almost 50%) the vasodilating effect of procyanidins, indicating the involvement also of a COX-dependent mechanism. This was confirmed in another set of experiments, where procyanidins dose-dependently stimulate the prostacyclin (PGI2) release, reaching a plateau between 25 and 50 microM. Finally, pre-incubation of IMA-rings with procyanidins (from 6.25 to 25 microM) resulted in a dose-dependent prevention of the endothelin-1 (ET-1) vasoconstriction. The ability of procyanidins to prevent peroxynitrite attack to vascular cells, by layering on the surface of coronary EC, and to enhance endothelial NO-synthase-mediated relaxation in IMA rings provide further insight into the molecular mechanisms through which they exert cardioprotective activity in ischemia/reperfusion injury in vivo.     

Dietary polyphenols in chemoprevention and synergistic effect in cancer: Clinical evidences and molecular mechanisms of action

BackgroundEpidemiological studies has revealed that a diet rich in fruits and vegetables could lower the risk of certain cancers. In this setting, natural polyphenols are potent anticancer bioactive compounds to overcome the non-target specificity, undesirable cytotoxicity and high cost of treatment cancer chemotherapy.PurposeThe review focuses on diverse classifications of the chemical diversity of dietary polyphenol and their molecular targets, modes of action, as well as preclinical and clinical applications in cancer prevention.ResultsThe dietary polyphenols exhibit chemo-preventive activity through modulation of apoptosis, autophagy, cell cycle progression, inflammation, invasion and metastasis. Polyphenols possess strong antioxidant activity and control multiple molecular events through activation of tumor suppressor genes and inhibition of oncogenes involved in carcinogenesis. Numerous in vitro and in vivo studies have evidenced that these dietary phytochemicals regulate critical molecular targets and pathways to limit cancer initiation and progression. Moreover, natural polyphenols act synergistically with existing clinically approved drugs. The improved anticancer activity of combinations of polyphenols and anticancer drugs represents a promising perspective for clinical applications against many human cancers.ConclusionThe anticancer properties exhibited by dietary polyphenols are mainly attributed to their anti-metastatic, anti-proliferative, anti-angiogenic, anti-inflammatory, cell cycle arrest, apoptotic and autophagic effects. Hence, regular consumption of dietary polyphenols as food or food additives or adjuvants can be a promising tactic to preclude adjournment or cancer therapy.     

Deciphering bioactive peptides and their action mechanisms through proteomics

Introduction: Bioactive peptides such as antimicrobial peptides (AMPs), ribosomally synthesized and post translationally modified peptides (RiPPs) and the non-ribosomal peptides (NRPs) have emerged with promising applications in medicine, agriculture and industry. However, their development has been limited by several difficulties making it necessary to search for novel discovery methods. In this context, proteomics has been considered a reliable tool.

Areas covered: This review highlights recent developments in proteomic tools that facilitate the discovery of AMPs, RiPPs and NRPs as well as the elucidation of action mechanisms of AMPs and resistance mechanisms of pathogens to them.

Expert commentary: Proteomic approaches have emerged as useful tools for the study of bioactive peptides, especially mass spectrometry-based peptidomics profiling, a promising strategy for AMP discovery. Furthermore, the rapidly expanding fields of genome mining and genome sequencing techniques, as well as mass spectrometry, have revolutionized the discovery of novel RiPPs and NRPs from complex biological samples.     

Lithium neuroprotection: molecular mechanisms and clinical implications

Lithium has emerged as a neuroprotective agent efficacious in preventing apoptosis-dependent cellular death. Lithium neuroprotection is provided through multiple, intersecting mechanisms, although how lithium interacts with these mechanisms is still under investigation. Lithium increases cell survival by inducing brain-derived neurotrophic factor and thereby stimulating activity in anti-apoptotic pathways, including the phosphatidylinositol 3-kinase/Akt and the mitogen-activated protein kinase pathways. In addition, lithium reduces pro-apoptotic function by directly and indirectly inhibiting glycogen synthase kinase-3beta activity and indirectly inhibiting N-methyl-D-aspartate (NMDA)-receptor-mediated calcium influx. Lithium-induced regulation of anti- and pro-apoptotic pathways alters a wide variety of downstream effectors, including beta-catenin, heat shock factor 1, activator protein 1, cAMP-response-element-binding protein, and the Bcl-2 protein family. Lithium neuroprotection has a wide variety of clinical implications. Beyond its present use in bipolar mood disorder, lithium's neuroprotective abilities imply that it could be used to treat or prevent brain damage following traumatic injury, such as stroke, and neurodegenerative diseases such as Huntington's and Alzheimer's diseases.     

Medullary thyroid carcinoma: from molecular studies to clinical decision

The paper is focused on guidelines of practice in inherited medullary thyroid cancer, diagnosed on the basis of DNA analysis. Identification of RET mutation implies further steps of diagnostic procedure, some of them - USG, FNAB and calcitonin level tests - are common for all types of mutation, other are related to ascertained type of mutation. In asymptomatic RET mutation carriers, prophylactic thyroidectomy is indicated. In MEN2B inherited cancer reveals its symptoms quickly and shows dynamic progress. In MEN2A/FMTC the clinical picture is diversified - in some patients the course of disease is mild, however in some other cases the progression of disease and even death occur regardless of the proper treatment. Unfortunately, there are no molecular prognostic markers in medullary thyroid carcinoma. Recent papers and also our own unpublished results show that gene expression profile, is similar in MEN2A and sporadic cancer. This group differs from MEN2B by its expression profile. In conclusion it is to be emphasized that although inherited medullary thyroid carcinoma is a rare disease, the diagnostic algorithm is well established and maximizes the chance for early diagnosis. Moreover, it needs to be stressed that DNA analysis results inform us not only about the necessity of further therapy, but also suggest different ways of proceeding in particular type of mutation.     

The molecular mechanisms of interactions between bioactive peptides and angiotensin-converting enzyme

The ability of milk protein derived Ile-Pro-Ala (IPA), Phe-Pro (FP) and Gly-Lys-Pro (GKP) peptides to inhibit angiotensin I-converting enzyme (ACE), a protein with an important role in blood-pressure regulation, were verified in vitro and in vivo. This work elucidates the modes and molecular mechanisms of the interaction of IPA, FP and GKP with ACE, including mechanisms that bind the peptides to the cofactor Zn²⁺. It was observed that the best docking poses obtained for IPA, FP and GKP were at the ACE catalytic site with very similar modes of interaction, including the interaction with Zn²⁺. The interactions, including H-bonds, hydrophobic, hydrophilic, and electrostatic interactions, as well as the interaction with Zn²⁺, were responsible for the binding between the bioactive peptides and ACE.     

Glucocorticoid action on connective tissue: from molecular mechanisms to clinical practice

Glucocorticosteroids are highly effective in treating various acute and chronic diseases, but their long-term use is often accompanied by side effects, such as osteoporosis of skeleton and bones and atrophy of the skin. Clinically, many of these side effects involve changes in connective tissue. Glucocorticoid effects on connective tissue metabolism are, however, sometimes beneficial for instance, in the treatment of keloids or autoimmune connective tissue diseases. Recent advances in the biochemical technology have provided tools to examine the molecular mechanisms by which glucocorticoids affect connective tissue. These studies have shown distinct alterations in the extracellular matrix as a result of glucocorticoid treatment. This knowledge is useful for the further development of glucocorticosteroids with desirable action spectrum and with minimal side effects.     

ENPP1 affects insulin action and secretion: evidences from in vitro studies

The aim of this study was to deeper investigate the mechanisms through which ENPP1, a negative modulator of insulin receptor (IR) activation, plays a role on insulin signaling, insulin secretion and eventually glucose metabolism. ENPP1 cDNA (carrying either K121 or Q121 variant) was transfected in HepG2 liver-, L6 skeletal muscle- and INS1E beta-cells. Insulin-induced IR-autophosphorylation (HepG2, L6, INS1E), Akt-Ser(473), ERK1/2-Thr(202)/Tyr(204) and GSK3-beta Ser(9) phosphorylation (HepG2, L6), PEPCK mRNA levels (HepG2) and 2-deoxy-D-glucose uptake (L6) was studied. GLUT 4 mRNA (L6), insulin secretion and caspase-3 activation (INS1E) were also investigated. Insulin-induced IR-autophosphorylation was decreased in HepG2-K, L6-K, INS1E-K (20%, 52% and 11% reduction vs. untransfected cells) and twice as much in HepG2-Q, L6-Q, INS1E-Q (44%, 92% and 30%). Similar data were obtained with Akt-Ser(473), ERK1/2-Thr(202)/Tyr(204) and GSK3-beta Ser(9) in HepG2 and L6. Insulin-induced reduction of PEPCK mRNA was progressively lower in untransfected, HepG2-K and HepG2-Q cells (65%, 54%, 23%). Insulin-induced glucose uptake in untransfected L6 (60% increase over basal), was totally abolished in L6-K and L6-Q cells. GLUT 4 mRNA was slightly reduced in L6-K and twice as much in L6-Q (13% and 25% reduction vs. untransfected cells). Glucose-induced insulin secretion was 60% reduced in INS1E-K and almost abolished in INS1E-Q. Serum deficiency activated caspase-3 by two, three and four folds in untransfected INS1E, INS1E-K and INS1E-Q. Glyburide-induced insulin secretion was reduced by 50% in isolated human islets from homozygous QQ donors as compared to those from KK and KQ individuals. Our data clearly indicate that ENPP1, especially when the Q121 variant is operating, affects insulin signaling and glucose metabolism in skeletal muscle- and liver-cells and both function and survival of insulin secreting beta-cells, thus representing a strong pathogenic factor predisposing to insulin resistance, defective insulin secretion and glucose metabolism abnormalities.     

CRISPR-Cas adaptive immune systems in Sulfolobales: genetic studies and molecular mechanisms

CRISPR-Cas systems provide the small RNA-based adaptive immunity to defend against invasive genetic elements in archaea and bacteria. Organisms of Sulfolobales, an order of thermophilic acidophiles belonging to the Crenarchaeotal Phylum, usually contain both type I and type Ⅲ CRISPR-Cas systems. Two species, Saccharolobus solfataricus and Sulfolobus islandicus, have been important models for CRISPR study in archaea, and knowledge obtained from these studies has greatly expanded our understanding of molecular mechanisms of antiviral defense in all three steps: adaptation, expression and crRNA processing, and interference. Four subtypes of CRISPR-Cas systems are common in these organisms, including I-A, I-D, Ⅲ-B, and Ⅲ-D. These cas genes form functional modules, e.g., all genes required for adaptation and for interference in the I-A immune system are clustered together to form aCas and i Cas modules. Genetic assays have been developed to study mechanisms of adaptation and interference by different CRISPR-Cas systems in these model archaea, and these methodologies are useful in demonstration of the protospacer-adjacent motif(PAM)-dependent DNA interference by I-A interference modules and multiple interference activities by Ⅲ-B Cmr systems. Ribonucleoprotein effector complexes have been isolated for Sulfolobales Ⅲ-B and Ⅲ-D systems, and their biochemical characterization has greatly enriched the knowledge of molecular mechanisms of these novel antiviral immune responses.     

Horizontal transfer of microRNAs: molecular mechanisms and clinical applications

A new class of RNA regulatory genes known as microRNAs (miRNAs) has been found to introduce a whole new layer of gene regulation in eukaryotes. The intensive studies of the past several years have demonstrated that miRNAs are not only found intracellularly, but are also detectable outside cells, including in various body fluids (e.g. serum, plasma, saliva, urine and milk). This phenomenon raises questions about the biological function of such extracellular miRNAs. Substantial amounts of extracellular miRNAs are enclosed in small membranous vesicles (e.g. exosomes, shedding vesicles and apoptotic bodies) or packaged with RNA-binding proteins (e.g. high-density lipoprotein, Argonaute 2 and nucleophosmin 1). These miRNAs may function as secreted signaling molecules to influence the recipient cell phenotypes. Furthermore, secreted extracellular miRNAs may reflect molecular changes in the cells from which they are derived and can therefore potentially serve as diagnostic indicators of disease. Several studies also point to the potential application of siRNA/miRNA delivery as a new therapeutic strategy for treating diseases. In this review, we summarize what is known about the mechanism of miRNA secretion. In addition, we describe the pathophysiological roles of secreted miRNAs and their clinical potential as diagnostic biomarkers and therapeutic drugs. We believe that miRNA transfer between cells will have a significant impact on biological research in the coming years.     

Metal ion resistance in fungi: molecular mechanisms and their regulated expression

One stress response in cells is the ability to survive in an environment containing excessive concentrations of metal ions. This paper reviews current knowledge about cellular and molecular mechanisms involved in the response and adaptation of various fungal species to metal stress. Most cells contain a repertoire of mechanisms to maintain metal homeostasis and prevent metal toxicity. Roles played by glutathione, related (gamma-EC)nG peptides, metallothionein-like polypeptides, and sulfide ions are discussed. In response to cellular metal stress, the biosynthesis of some of these molecules are metalloregulated via intracellular metal sensors. The identify of the metal sensors and the role of metal ions in the regulation of biosynthesis of metallothionein and (gamma-EC)nG peptides are subjects of much current attention and are discussed herein.     

The role of anthocyanins as antidiabetic agents: from molecular mechanisms to in vivo and human studies

Journal of Physiology and Biochemistry - Diabetes mellitus is a chronic metabolic disease characterized by high blood glucose concentration. Nowadays, type 2 diabetes or insulin resistant diabetes...     

tRNA-targeting ribonucleases: molecular mechanisms and insights into their physiological roles

Most bacteria produce antibacterial proteins known as bacteriocins, which aid bacterial defence systems to provide a physiological advantage. To date, many kinds of bacteriocins have been characterized. Colicin has long been known as a plasmidborne bacteriocin that kills other Escherichia coli cells lacking the same plasmid. To defeat other cells, colicins exert specific activities such as ion-channel, DNase, and RNase activity. Colicin E5 and colicin D impair protein synthesis in sensitive E. coli cells; however, their physiological targets have not long been identified. This review describes our finding that colicins E5 and D are novel RNases targeting specific E. coli tRNAs and elucidates their enzymatic properties based on biochemical analyses and X-ray crystal structures. Moreover, tRNA cleavage mediates bacteriostasis, which depends on trans-translation. Based on these results and others, cell growth regulation depending on tRNA cleavage is also discussed.     

Glucocorticoid-induced apoptosis and glucocorticoid resistance: molecular mechanisms and clinical relevance

The ability of glucocorticoids (GC) to efficiently kill lymphoid cells has led to their inclusion in essentially all chemotherapy protocols for lymphoid malignancies. This review summarizes recent findings related to the molecular basis of GC-induced apoptosis and GC resistance, and discusses their potential clinical implications. Accumulating evidence suggests that GC may induce cell death via different pathways resulting in apoptotic or necrotic morphologies, depending on the availability/responsiveness of the apoptotic machinery. The former might result from regulation of typical apoptosis genes such as members of the Bcl-2 family, the latter from detrimental GC effects on essential cellular functions possibly perpetuated by GC receptor (GR) autoinduction. Although other possibilities exist, GC resistance might frequently result from defective GR expression, perhaps the most efficient means to target multiple antileukemic GC effects. Numerous novel drug combinations are currently being tested to prevent resistance and improve GC efficacy in the therapy of lymphoid malignancies.     

Multidrug resistance in lactic acid bacteria: molecular mechanisms and clinical relevance

The active extrusion of cytotoxic compounds from the cell by multidrug transporters is one of the major causes of failure of chemotherapeutic treatment of tumor cells and of infections by pathogenic microorganisms. The secondary multidrug transporter LmrP and the ATP-binding cassette (ABC) type multidrug transporter LmrA in Lactococcus lactis are representatives of the two major classes of multidrug transporters found in pro- and eukaryotic organisms. Therefore, knowledge of the molecular properties of LmrP and LmrA will have a wide significance for multidrug transporters in all living cells, and may enable the development of specific inhibitors and of new drugs which circumvent the action of multidrug transporters. Interestingly, LmrP and LmrA are transport proteins with very different protein structures, which use different mechanisms of energy coupling to transport drugs out of the cell. Surprisingly, both proteins have overlapping specificities for drugs, are inhibited by t he same set of modulators, and transport drugs via a similar transport mechanism. The structure-function relationships that dictate drug recognition and transport by LmrP and LmrA will represent an intriguing new area of research.     

Pleiotropic effects of statin therapy: molecular mechanisms and clinical results

Statins inhibit the enzyme 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, which is required for cholesterol biosynthesis, and are beneficial in the primary and secondary prevention of cardiovascular disease. Most of the benefits of statin therapy are owing to the lowering of serum cholesterol levels. However, by inhibiting HMG-CoA reductase, statins can also inhibit the synthesis of isoprenoids, which are important lipid attachments for intracellular signaling molecules, such as Rho, Rac and Cdc42. Therefore, it is possible that statins might exert cholesterol-independent or 'pleiotropic' effects through direct inhibition of these small GTP-binding proteins. Recent studies have shown that statins might have important roles in diseases that are not mediated by cholesterol. Here, we review data from recent clinical trials that support the concept of statin pleiotropy and provide a rationale for their clinical importance.     

Tunneling nanotubes: emerging view of their molecular components and formation mechanisms

Cell-to-cell communication is essential for the development and maintenance of multicellular organisms. The tunneling nanotube (TNT) is a recently recognized distinct type of intercellular communication device. TNTs are thin protrusions of the plasma membrane and allow direct physical connections of the plasma membranes between remote cells. The proposed functions for TNTs include the cell-to-cell transfer of large cellular structures such as membrane vesicles and organelles, as well as signal transduction molecules in a wide variety of cell types. Moreover TNT and TNT-related structures are thought to facilitate the intercellular spreading of virus and/or pathogenic proteins. Despite their contribution to normal cellular functions and importance in pathological conditions, virtually nothing is known about the molecular basis for their formation. We have recently shown that M-Sec (also called TNFaip2) is a key molecule for TNT formation. In cooperation with the RalA small GTPase and the exocyst complex, M-Sec can induce the formation of functional TNTs, indicating that the remodeling of the actin cytoskeleton and vesicle trafficking are involved in M-Sec-mediated TNT formation. Discovery of the role of M-Sec will accelerate our understanding of TNTs, both at the molecular and physiological levels.