Potential role of α-synuclein in neurodegeneration: studies in a rat animal model

Neuronal protein α-synuclein (α-syn) is an essential player in the development of neurodegenerative diseases called synucleinopathies. A spontaneous autosomal recessive rat model for neurodegeneration was developed in our laboratory. These rats demonstrate progressive increases in α-syn in the brain mesencephalon followed by loss of dopaminergic terminals in the basal ganglia (BG) and motor impairments. The severity of pathology is directly related to the overexpression of α-syn and parallel decrease in dopamine (DA) level in the striatum (ST) of affected rats. The neurodegeneration in this model is characterized by the presence of perikarya and neurites Lewis bodies (LB) and diffuse marked accumulation of perikaryal α-syn in the substantia nigra (SN), brain stem (BS), and striatum (ST) along with neuronal loss. Light and ultrastructural analyses revealed that the process of neuronal degeneration is a 'dying back' type. The disease process is accompanied by gliosis and release of inflammatory cytokines. This neurodegeneration is a multisystemic disease and implicate α-syn as a major factor in the pathogenesis of this inherited autosomal recessive animal model. Decrease dopamine (DA) and overexpression of α-syn in the brain mesencephalon may provide a naturally occurring animal model for Parkinson's disease (PD) and other synucleinopathies that reproduces significant pathological, neurochemical, and behavioral features of the human disease.     

Oxyleghemoglobin scavenges nitrogen monoxide and peroxynitrite: a possible role in functioning nodules?

It has been demonstrated that the NO^• produced by nitric oxide synthase or by the reduction of nitrite by nitrate reductase plays an important role in plants’ defense against microbial pathogens. The detection of nitrosyl Lb in nodules strongly suggests that NO^• is also formed in functional nodules. Moreover, NO^• may react with superoxide (which has been shown to be produced in nodules by various processes), leading to the formation of peroxynitrite. We have determined the second-order rate constants of the reactions of soybean oxyleghemoglobin with nitrogen monoxide and peroxynitrite. At pH 7.3 and 20 °C, the values are on the order of 10⁸ and 10⁴ M⁻¹ s⁻¹, respectively. In the presence of physiological amounts of CO₂ (1.2 mM), the second-order rate constant of the reaction of oxyleghemoglobin peroxynitrite is even larger (10⁵ M⁻¹ s⁻¹). The results presented here clearly show that oxyleghemoglobin is able to scavenge any NO^• and peroxynitrite formed in functional nodules. This may help to stop NO^• triggering a plant defense reaction.     

Xylem-borne cytokinins: still in search of a role?

Leaf expansion and xylem cytokinin concentration ([X-CK]) decrease in response to nitrogen (N) deprivation. Debate continues over cause, effect, and correlation. Supporting studies provide, at best, correlative evidence that [X-CK] controls leaf growth in response to N-deprivation, while dissenting studies indicate that leaf growth responses to N can be independent of changes in X-CK supply to leaves. A model is proposed to evaluate the physiological significance to leaf growth of changes in plant and environment N concentrations, and plant CK concentrations.     

A role of PPARgamma in reproduction?

Synthetic molecules of the glitazone family are currently used in the treatment of type II diabetes. Glitazones also improve secondary pathologies that are frequently associated with insulin resistance such as the polycystic ovary syndrome (PCOS). Glitazones bind to the peroxysome proliferator-activated receptor gamma (PPARgamma), a nuclear receptor which is highly expressed in adipose tissue. PPARgamma also binds natural ligands such as long-chain fatty acids. Recently, several groups have shown that PPARgamma is also highly expressed in ovarian granulosa cells, and that glitazones are able to modulate in vitro granulosa cell proliferation and steroidogenesis in several species. These recent data raise new questions concerning the underlying mechanism of the effect of glitazones on PCOS. One might hypothesize, as for other < glucophage > molecules such as metformin, that it is the general improvement of glucose metabolism and insulin sensitivity by glitazones which indirectly, and via an unknown mechanism, ameliorates ovarian functionality. The data discussed here suggest now an alternative possibility, that glitazones act directly at the ovarian level. Moreover, PPARgamma also seems to play a key role in the maturation of the placenta. In particular, inactivation of PPARgamma in mice is lethal, since the foetus is unable to develop because of alterations of placental maturation. In women, the activation of PPARgamma in placenta leads to an increase of placental hormone secretion. Overall, these results raise some questions about the role of natural ligands of PPARgamma such as long chain fatty acids on female fertility and the interactions between energy metabolism and reproduction in general.     

Receptor-specific mechanisms regulate phosphorylation of AKT at Ser473: role of RICTOR in β1 integrin-mediated cell survival

A tight control over AKT/PKB activation is essential for cells, and they realise this in part by regulating the phosphorylation of Ser473 in the "hydrophobic motif" of the AKT carboxy-terminal region. The RICTOR-mTOR complex (TORC2) is a major kinase for AKT Ser473 phosphorylation after stimulation by several growth factors, in a reaction proposed to require p21-activated kinase (PAK) as a scaffold. However, other kinases may catalyse this reaction in stimuli-specific manners. Here we characterised the requirement of RICTOR, ILK, and PAK for AKT Ser473 phosphorylation downstream of selected family members of integrins, G protein-coupled receptors, and tyrosine-kinase receptors and analysed the importance of this phosphorylation site for adhesion-mediated survival. siRNA-mediated knockdown in HeLa and MCF7 cells showed that RICTOR-mTOR was required for phosphorylation of AKT Ser473, and for efficient phosphorylation of the downstream AKT targets FOXO1 Thr24 and BAD Ser136, in response to β1 integrin-stimulation. ILK and PAK1/2 were dispensable for these reactions. RICTOR knockdown increased the number of apoptotic MCF7 cells on β1 integrin ligands up to 2-fold after 24 h in serum-free conditions. β1 integrin-stimulation induced phosphorylation of both AKT1 and AKT2 but markedly preferred AKT2. RICTOR-mTOR was required also for LPA-induced AKT Ser473 phosphorylation in MCF7 cells, but, interestingly, not in HeLa cells. PAK was needed for the AKT Ser473 phosphorylation in response to LPA and PDGF, but not to EGF. These results demonstrate that different receptors utilise different enzyme complexes to phosphorylate AKT at Ser473, and that AKT Ser473 phosphorylation significantly contributes to β1 integrin-mediated anchorage-dependent survival of cells.     

Gonadotropin levels in ovarian cyst fluids: a predictor of malignancy?

Gonadotropins can stimulate ovarian cancer growth in cell cultures. Corresponding LH/hCG receptors have been demonstrated in ovarian cancer. However, reduction of elevated serum gonadotropins by GnRH analogs in ovarian cancer patients did not lead to growth restriction, which means that serum levels of gonadotropins may not play the most important role in ovarian cancer. We therefore analyzed the LH and FSH concentrations in cyst fluids of ovarian cancer. Patients with preoperatively diagnosed cystic ovarian tumors were eligible for the study. Serum samples of the patients were obtained during surgery, while the fluids within the cysts were aspirated after surgical removal of the tumor. FSH and LH levels in serum and cyst fluids were measured using single antibody EIA (Boehringer Mannheim GmbH, Germany). Cyst fluids and sera of 108 patients were evaluated. While there were no significant differences in the FSH and LH serum concentrations, highly significant differences in the FSH and LH levels in cyst fluids were found. Only cancer cysts contained FSH and LH, while the corresponding concentrations in benign cysts were always below the measuring range of the assays. This clear division between high gonadotropin levels in cysts of serous ovarian cancer and low or absent concentrations in benign ovarian tumors further supports the hypothesis that FSH and LH may play a role in ovarian cancer; however, explanations for this surprising finding are still lacking.     

The role of corridors in conservation: Solution or bandwagon?

Corridors are currently a major buzzword in conservation biology and landscape ecology. These linear landscape features may perform numerous functions, but it is their role in facilitating movement of fauna that has attracted much recent debate. The database supporting the idea of corridors acting as faunal conduits is remarkably small, and few studies have actually demonstrated that movement along corridors is important for any given species. Such data are very difficult to obtain, and conservation biologists are thus faced with the problem of whether to recommend the allocation of resources to corridors on the assumption that they may be important.     

The role of necroptosis in cancer: A double-edged sword?

Necroptosis is a programmed, caspase-independent cell death that is morphologically similar to necrosis. Unlike apoptosis, necroptosis evokes inflammatory responses by releasing damage-associated molecular patterns. Recent studies suggest that tumor undergoes necroptosis in vivo and necroptosis has pro- or anti-tumoral effects in cancer development and progression. Furthermore, triggering necroptosis in tumor cells has been explored as a potential therapeutic strategy against cancer. Here, we will review the recent research progress of necroptosis in conferring anti- or pro-tumoral effects and its potential application in cancer therapy.     

Viral proteins functioning in organelles: a cryptic origin?

Although mitochondria derive from alpha-proteobacteria, many proteins acting in this organelle did not originate from bacteria. In particular, phylogenetic evidence indicates that RNA polymerase, DNA polymerase and DNA primase--with homologues encoded by T3/T7-like bacteriophages--have replaced the ancestral proteins of bacterial origin. To date, there was no clear explanation for this puzzling observation. Bacterial genomics has now revealed the presence of cryptic prophages that are related to T3/T7 in several genomes of proteobacteria. We propose that such a prophage was present in the ancestral alpha-proteobacterium at the origin of mitochondria and that RNA polymerase, DNA polymerase and DNA primase encoded by this prophage replaced the original bacterial enzymes to function in mitochondria. Another T3/T7 viral-like RNA polymerase is functional in the chloroplast, indicating that a strong selection pressure has favored replacement of some cellular proteins by viral proteins in organelle evolution.     

Potential problems of ascorbate and iron supplementation: pro-oxidant effect in vivo?

The comparison was undertaken between the effects of ascorbate versus ascorbate plus iron supplementation on DNA damage. Twenty healthy subjects with initial levels of plasma ascorbate of 67.2 +/- 23.3 micromol/l were randomly assigned to and cycled through one of three supplementation regimes: placebo, 260 mg/d ascorbate, 260 mg/d ascorbate plus 14 mg/d iron for 6 weeks separated by 8-week washout periods. Supplementation did not cause a rise in total oxidative DNA damage measured by GC-MS. However, a significant decrease occurred in levels of 8-oxo-7,8-dihydroguanine by ascorbate supplementation and 5-hydroxymethyl uracil by both ascorbate and ascorbate plus iron supplementation, relative to the pre-supplemental levels but not to the placebo group. In addition, levels of 5-hydroxymethyl hydantoin and 5-hydroxy cytosine increased significantly, only relative to pre-supplementation, by ascorbate plus iron treatment. No compelling evidence for a pro-oxidant effect of ascorbate supplementation, in the presence or absence of iron, on DNA base damage was observed.     

Potential role of miR-214 in β-catenin gene expression within hepatocellular carcinoma

Molecular Biology Reports - MicroRNAs (miRNAs) are important gene regulators whose dysregulations can be involved in tumorigenesis. β-catenin, the main agent in the Wnt/β-catenin pathway,...     

Changes in pituitary hormone levels induced by met-enkephalin in man—The role of dopamine

The interaction of dopamine with the effects of the opiate agonist peptide D-Ala²-MePhe⁴-met-enkephalin-O-o1 (DAMME) on anterior pituitary hormone secretion was investigated in normal male subjects. DAMME produced clear elevations in prolactin, growth hormone and thyroid-stimulating hormone, while inhibiting the release of luteinising hormone and cortisol. There was no change in follicle stimulating hormone. The elevations in prolactin and TSH were enhanced by the dopamine antagonist, domperidone, and blocked by an infusion of dopamine. Neither dopamine nor domperidone modulated the changes in growth hormone, luteinising hormone or cortisol. The data are comptible with the association of the release of prolactin and TSH by opiate peptides with decreased hypothalamic dopaminergic activity; changes in the other anterior pituitary hormones seem to involve different mechanisms.     

High levels of multiple paternity in Littorina saxatilis: hedging the bets?

The mating system of a species can have great effects on its genetic structure and evolution. We studied the extent of multiple paternity in a gastropod with internal fertilization, the intertidal snail Littorina saxatilis. Paternal genotype reconstruction based on microsatellite markers was performed on the offspring of wild, naturally fertilized females from 2 populations. The numbers of males contributing to the offspring per female were among the highest detected in invertebrates so far, with the exception of social insects. No reproductive skew in favor of males that were genetically more distant from the females was detected, and the pattern of fertilization appeared random. The result fits a hypothesis of indiscriminate mating, with genetic bet hedging as the most likely explanation. Bet hedging may have evolved as a form of inbreeding avoidance, if the snails are not able to recognize relatives. However, nutritional benefits from sperm or sexual conflict with males are additional possibilities that remain to be assessed in this species. Whatever the causes, such high levels of multiple paternity are remarkable and are likely to have a large impact on population structure and dynamics in a species in which migration between populations is spurious.     

Opinion: What is the role of protein aggregation in neurodegeneration?

Neurodegenerative diseases typically involve deposits of inclusion bodies that contain abnormal aggregated proteins. Therefore, it has been suggested that protein aggregation is pathogenic. However, several lines of evidence indicate that inclusion bodies are not the main cause of toxicity, and probably represent a cellular protective response. Aggregation is a complex multi-step process of protein conformational change and accretion. The early species in this process might be most toxic, perhaps through the exposure of buried moieties such as main chain NH and CO groups that could serve as hydrogen bond donors or acceptors in abnormal interactions with other cellular proteins. This model implies that the pathogenesis of diverse neurodegenerative diseases arises by common mechanisms, and might yield common therapeutic targets.     

Regulation of enzyme levels by phytochrome in mustard cotyledons: Multiple mechanisms?

Phytochrome controls the appearance of many enzymes in the mustard (Sinapis alba L.) cotyledons. The problem has been whether the effect of phytochrome on the appearance of enzymes in this organ is due to a common initial action of P_fr, e.g. due to the liberation of a second messenger. We have compared the modulation by light (phytochrome) of the appearance of phenylalanine ammonia lyase (PAL)⁺ and ribulosebisphosphate carboxylase (Carboxylase)⁺. PAL becomes detectable in the mustard cotyledons at 27 h after sowing while Carboxylase starts to appear only at 42 h after sowing (starting points, 25° C). The starting points cannot be shifted by light. As a major result, in the case of PAL the inductive effect of continuous red light (given from the time of sowing) remains fully reversible by 756 nm-light up to the starting point (27 h after sowing) while with Carboxylase full reversibility in continuous red light is lost at approximately 15 h after sowing. While the induction of Carboxylase is already saturated at a very low level of P_fr (e.g. continuous 756 nm-light saturates the response) and does not depend on irradiance (e.g. continuous 675 mW m^-2 red light and 67.5 mW m^-2 red light lead to the same time course), PAL induction is a graded response over a wide range of P_fr doses and depends strongly on the fluence rate (high irradiance response, HIR). It is concluded that PAL induction and Carboxylase induction are not only separated in time but differ in every regard except that both responses are mediated by phytochrome.The present data support the previous conclusion that the specification of the temporal and spatial pattern of development is independent of phytochrome even though the realization of the pattern of development can only occur in the presence of phytochrome (P_fr). It seems that there is no feedback from pattern realization to pattern specification.Abbreviations P_fr the far-red absorbing, physiologically active form of phytochrome - P_r the red absorbing physiologically inactive form of phytochrome - P_total [P_r]+[P_fr] - PAL phenylalanine ammonia-lyase (EC 4.3.1.5) - Carboxylase ribulosebisphosphate carboxylase (EC 4.1.1.39)