Natural polyphenols as proteasome modulators and their role as anti-cancer compounds

The purpose of this review is to discuss the effect of natural antioxidant compounds as modulators of the 20S proteasome, a multi-enzymatic multi-catalytic complex present in the cytoplasm and nucleus of eukaryotic cells and involved in several cellular activities such as cell-cycle progression, proliferation and the degradation of oxidized and damaged proteins. From this perspective, proteasome inhibition is a promising approach to anticancer therapy and such natural antioxidant effectors can be considered as potential relevant adjuvants and pharmacological models in the study of new drugs.     

Influence of Prior Coronary Stenting on the Immediate and Mid-term Outcome of Isolated Coronary Artery Bypass Surgery

BACKGROUND:: There has been little emphasis on the possible consequences of prior stent placement on the outcome of coronary bypass surgery (CABG). We compared the results of isolated CABG patients who had prior stents with those who had not with respect to preoperative status, operative procedure, and postoperative immediate and long-term outcome. METHODS:: Records of 1471 patients undergoing isolated CABG at our institution between January 1, 2000, and March 31, 2005, were reviewed. Patients were divided into three groups. Group I had no stents (n = 1317). Group II had one to three stents (n = 137). Group III had more than three stents (n = 17). Groups were compared with respect to preoperative risk factors, operative procedures, and postoperative results. Long-term survival data were obtained on 97.6% of patients with a mean follow-up, 4.1 ± 2.3 years. RESULTS:: Stented patients were younger (66.1 ± 10.8 vs. 69.1 ± 10.8 years, P = 0.006), had more unstable angina (68.2% vs. 58.9%, P = 0.02), hypercholesterolemia (83.8% vs. 61.2%, P = 0.00), chronic obstructive pulmonary disease (13.6% vs. 8.4%, P = 0.03), peripheral vascular disease (15.2% vs. 8.4%, P = 0.00), and previous CABG (10.1% vs. 4.2%, P = 0.00), fewer low ejection fractions (1.3% vs. 5.2%, P = 0.02), left main disease (25.3% vs. 32.6%, P = 0.04), diabetes (31.2% vs. 40.8%, P = 0.01), or diffuse disease (19.5 ± 10.5 vs. 22.5 ± 10.9, P = 0.00), had more off pump procedures (53.2% vs. 45.3%, P = 0.03), fewer internal thoracic artery grafts (80.5% vs. 86.6%, P = 0.03), fewer grafts placed (>3: 52.6% vs. 61.8%, P = 0.02), more complications (76.5% vs. 42.6%, P = 0.005), atrial fibrillation (47.1% vs. 19.7%, P = 0.011), longer hospital stays (12.2 vs. 8.3 days, P = 0.019). Percentage survival for groups I, II, and III at 60 months was 82.1%, 84.7%, and 72.6%, respectively. CONCLUSIONS:: Stents placed before surgery in isolated CABG patients may be associated with higher preoperative risk, altered operative procedures, more postoperative complications, longer hospitalizations, and more readmissions. Overall, stented patients experienced more preoperative hospitalizations, catheterizations, and percutaneous coronary interventions (PCIs) than nonstented patients. Survival for those with more than three stents may be diminished.     

Preference for Male Traits Differ in Two Female Morphs of the Tree Lizard,Urosaurus ornatus

Non-random female mating preferences may contribute to the maintenance of phenotypic variation in color polymorphic species. However, the effect of female preference depends on the types of male traits used as signals by receptive females. If preference signals derive from discrete male traits (i.e., morph-specific), female preferences may rapidly fix to a morph. However, female preference signals may also include condition-dependent male traits. In this scenario, female preference may differ depending on the social context (i.e., male morph availability). Male tree lizards (Urosaurus ornatus) exhibit a dewlap color polymorphism that covaries with mating behavior. Blue morph males are aggressive and defend territories, yellow males are less aggressive and defend smaller territories, and orange males are typically nomadic. Female U. ornatus are also polymorphic in dewlap color, but the covariation between dewlap color and female behavior is unknown. We performed an experiment to determine how female mate choice depends on the visual and chemical signals produced by males. We also tested whether female morphs differ in their preferences for these signals. Female preferences involved both male dewlap color and size of the ventral color patch. However, the female morphs responded to these signals differently and depended on the choice between the types of male morphs. Our experiment revealed that females may be capable of distinguishing among the male morphs using chemical signals alone. Yellow females exhibit preferences based on both chemical and visual signals, which may be a strategy to avoid ultra-dominant males. In contrast, orange females may prefer dominant males. We conclude that female U. ornatus morphs differ in mating behavior. Our findings also provide evidence for a chemical polymorphism among male lizards in femoral pore secretions.     

Nephrocystin-1 Forms a Complex with Polycystin-1 via a Polyproline Motif/SH3 Domain Interaction and Regulates the Apoptotic Response in Mammals

Mutations in PKD1, the gene encoding for the receptor Polycystin-1 (PC-1), cause autosomal dominant polycystic kidney disease (ADPKD). The cytoplasmic C-terminus of PC-1 contains a coiled-coil domain that mediates an interaction with the PKD2 gene product, Polycystin-2 (PC-2). Here we identify a novel domain in the PC-1 C-terminal tail, a polyproline motif mediating an interaction with Src homology domain 3 (SH3). A screen for interactions using the PC-1 C-terminal tail identified the SH3 domain of nephrocystin-1 (NPHP1) as a potential binding partner of PC-1. NPHP1 is the product of a gene that is mutated in a different form of renal cystic disease, nephronophthisis (NPHP). We show that in vitro pull-down assays and NMR structural studies confirmed the interaction between the PC-1 polyproline motif and the NPHP1 SH3 domain. Furthermore, the two full-length proteins interact through these domains; using a recently generated model system allowing us to track endogenous PC-1, we confirm the interaction between the endogenous proteins. Finally, we show that NPHP1 trafficking to cilia does not require PC-1 and that PC-1 may require NPHP1 to regulate resistance to apoptosis, but not to regulate cell cycle progression. In line with this, we find high levels of apoptosis in renal specimens of NPHP patients. Our data uncover a link between two different ciliopathies, ADPKD and NPHP, supporting the notion that common pathogenetic defects, possibly involving de-regulated apoptosis, underlie renal cyst formation.     

Protein oxidation and cellular homeostasis: Emphasis on metabolism

Reactive oxygen species (ROS) are generated as the result of a number of physiological and pathological processes. Once formed ROS can promote multiple forms of oxidative damage, including protein oxidation, and thereby influence the function of a diverse array of cellular processes. This review summarizes the mechanisms by which ROS are generated in a variety of cell types, outlines the mechanisms which control the levels of ROS, and describes specific proteins which are common targets of ROS. Additionally, this review outlines cellular processes which can degrade or repair oxidized proteins, and ultimately describes the potential outcomes of protein oxidation on cellular homeostasis. In particular, this review focuses on the relationship between elevations in protein oxidation and multiple aspects of cellular metabolism. Together, this review describes a potential role for elevated levels of protein oxidation contributing to cellular dysfunction and oxidative stress via impacts on cellular metabolism.     

Modifying the Frequency and Characteristics of Involuntary Autobiographical Memories

Recent studies have shown that involuntary autobiographical memories (IAMs) can be elicited in the laboratory. Here we assessed whether the specific instructions given to participants can change the nature of the IAMs reported, in terms of both their frequency and their characteristics. People were either made or not made aware that the aim of the study was to examine IAMs. They reported mental contents either whenever they became aware of them or following a predetermined schedule. Both making people aware of the aim of the study and following a fixed schedule of interruptions increased significantly the number of IAMs reported. When aware of the aim of the study, participants reported more specific memories that had been retrieved and rehearsed more often in the past. These findings demonstrate that the number and characteristics of memories depend on the procedure used. Explanations of these effects and their implications for research on IAMs are discussed.     

Mitochondria accumulate large amounts of quercetin: prevention of mitochondrial damage and release upon oxidation of the extramitochondrial fraction of the flavonoid

Quercetin uptake in Jurkat cells is extremely rapid and associated with a remarkable accumulation of the flavonoid, dependent on its binding to intracellular components. Cell-associated quercetin is biologically active, quantitatively consumed to promote survival in the presence of reactive species, such as peroxynitrite (ONOO^?), or reduction of extracellular oxidants via activation of plasma membrane oxidoreductases. In alternative, quercetin is very slowly released upon post-incubation in drug-free medium, an event significantly accelerated by extracellular albumin. Quercetin uptake is also observed in isolated mitochondria, resulting in an enormous accumulation of the flavonoid, consumed under conditions associated with prevention of lipid peroxidation induced by ONOO^?. Interestingly, remarkable quercetin accumulation is also detected in the mitochondria isolated from quercetin-pre-loaded cells, and exposure to either ONOO^? or extracellular oxidants caused the parallel loss of both the mitochondrial and cytosolic fractions of the flavonoid. In conclusion, Jurkat cells accumulate large amounts of quercetin and even larger amounts of the flavonoid further accumulate in their mitochondria. Intramitochondrial quercetin appears to be functional for prevention of mitochondrial damage as well as for redistribution to the cytosol, when the fraction of the flavonoid therein retained is progressively consumed either by cell-permeant oxidants or by activation of plasma membrane oxidoreductases.     

Binding of recombinant PrPc to human plasminogen: kinetic and thermodynamic study using a resonant mirror biosensor

Transmissible spongiform encephalopathies are a class of sporadic, genetic and transmissible neurodegenerative diseases that affect both humans and animals. Propagation of these diseases is thought to be due to the misfolding of a neuronal glyco-protein, PrP(c), into a pathological insoluble conformer, PrP(Sc). In earlier works, some serum components were identified as exclusive PrP(Sc)-interacting proteins (Fisher et al., Nature 2000;408:479), and thus those macromolecules were thought to represent a potential diagnostic endogenous factor discriminating between normal and pathological prion proteins. In contrast, in agreement with a recent work (Kornblatt et al., Biochem Biophys Res Commun 2003;305:518), in this paper we present a detailed thermodynamic and kinetic characterization of the interaction between recombinant bovine PrP(c 25-242) and the human serum component plasminogen, measured using a resonant mirror technique: our results reveal a high-affinity interaction between the two binding partners. For comparison, the complex obtained from the purified full-length PrP(c) and human plasminogen was also studied: both prion proteins (the recombinant bovine PrP(c 25-242) and the purified full-length PrP(c)) are able to bind human plasminogen. Both kinetic and thermodynamic parameters are affected by the modulation exerted by the H(+) ions in solution. Moreover, the analysis of binding, according to canonical linkage relationships, suggests the involvement of a His residue, consistent with the interaction between other serine (pro)enzymes and their ligands.     

Peroxynitrite-induced oxidation and its effects on isolated proteasomal systems

The proteasomes are the major intracellular proteolytic systems involved in the removal of altered proteins. In this study, we examined different susceptibilities of constitutive (XYZ) and interferon-gamma inducible (LMP) 20S proteasomes, isolated from bovine brain and thymus, respectively, to peroxynitrite-mediated oxidation. Exposure of XYZ and LMP proteasomes to increasing amounts of peroxynitrite resulted in different levels, in the two enzymes, of 3-nitrotyrosine groups and tryptophan residues oxidation. 1-Anilino-8-naphtalene-sulfonic acid binding studies and quenching of tryptophan residues indicated that the LMP complex was more sensitive to peroxynitrite. Regarding the proteolytic activities, the XYZ proteasome showed an overall activation (even if the trypsin-like (T-L) component was 20% inhibited), with the peptidyl-glutamyl peptide-hydrolyzing (PGPH) and branched-chain amino acid-preferring (BrAAP) activities being the most stimulated. On the other end, the LMP proteasome was inhibited, especially the BrAAP activity, whereas the T-L activity was not affected. Furthermore, exposure to increasing amounts of peroxynitrite induced a gradual decrease of beta-casein degrading rate by the LMP proteasome, whereas it did not influence the constitutive complex. Our results indicated that peroxynitrite caused a mild modification of the XYZ complex, leading to activation of its catalytic activities. Differently, the LMP proteasome showed a more significant conformational change resulting in the inhibition of the proteolytic functions.