Oxidative stress in cyanobacteria

Reactive oxygen species (ROS) are byproducts of aerobic metabolism and potent agents that cause oxidative damage. In oxygenic photosynthetic organisms such as cyanobacteria, ROS are inevitably generated by photosynthetic electron transport, especially when the intensity of light-driven electron transport outpaces the rate of electron consumption during CO₂ fixation. Because cyanobacteria in their natural habitat are often exposed to changing external conditions, such as drastic fluctuations of light intensities, their ability to perceive ROS and to rapidly initiate antioxidant defences is crucial for their survival. This review summarizes recent findings and outlines important perspectives in this field.     

Specific Role of Neuronal Nitric-oxide Synthase when Tethered to the Plasma Membrane Calcium Pump in Regulating the ��-Adrenergic Signal in the Myocardium

The cardiac neuronal nitric-oxide synthase (nNOS) has been described as a modulator of cardiac contractility. We have demonstrated previously that isoform 4b of the sarcolemmal calcium pump (PMCA4b) binds to nNOS in the heart and that this complex regulates β-adrenergic signal transmission in vivo. Here, we investigated whether the nNOS-PMCA4b complex serves as a specific signaling modulator in the heart. PMCA4b transgenic mice (PMCA4b-TG) showed a significant reduction in nNOS and total NOS activities as well as in cGMP levels in the heart compared with their wild type (WT) littermates. In contrast, PMCA4b-TG hearts showed an elevation in cAMP levels compared with the WT. Adult cardiomyocytes isolated from PMCA4b-TG mice demonstrated a 3-fold increase in Ser¹⁶ phospholamban (PLB) phosphorylation as well as Ser²² and Ser²³ cardiac troponin I (cTnI) phosphorylation at base line compared with the WT. In addition, the relative induction of PLB phosphorylation and cTnI phosphorylation following isoproterenol treatment was severely reduced in PMCA4b-TG myocytes, explaining the blunted physiological response to the β-adrenergic stimulation. In keeping with the data from the transgenic animals, neonatal rat cardiomyocytes overexpressing PMCA4b showed a significant reduction in nitric oxide and cGMP levels. This was accompanied by an increase in cAMP levels, which led to an increase in both PLB and cTnI phosphorylation at base line. Elevated cAMP levels were likely due to the modulation of cardiac phosphodiesterase, which determined the balance between cGMP and cAMP following PMCA4b overexpression. In conclusion, these results showed that the nNOS-PMCA4b complex regulates contractility via cAMP and phosphorylation of both PLB and cTnI.Neuronal nitric-oxide synthase (nNOS)⁵ is involved in a number of key processes in cardiomyocytes including calcium cycling (1), the β-adrenergic contractile response (2, 3), post-infarct left ventricular remodeling (4), and the regulation of redox equilibrium (5). Moreover, a polymorphism in an nNOS-interacting protein, CAPON, has been found to form a quantitative trait for the determination of the QT interval in humans (6), whereas a mutation in α1-syntrophin (SNTA1), another interacting partner of nNOS, has been associated with long QT syndrome (7). The signaling events downstream of the nNOS-CAPON (8) and nNOS-SNTA1 (7) complexes, which are responsible for mediating cardiac repolarization and sodium current respectively, have been elucidated. The nNOS-containing protein complex is therefore of immediate relevance to human pathology.In recent years, we have shown that the sarcolemmal calcium pump, which ejects calcium to the extracellular compartment (reviewed in Refs. 9 and 10), is an important molecule involved in signal regulation and transmission in the heart (11). We have demonstrated that isoform 4b of the sarcolemmal calcium pump (also known as PMCA4b for plasma membrane calcium/calmodulin-dependent ATPase 4b) modulates signaling through a tight molecular interaction with nNOS, leading to the modulation of β-adrenergic responsiveness in the heart (12). However, the events following signaling through the PMCA4b-nNOS complex remain unknown.In myocardial cells, nNOS has been localized to the sarcolemma (13), sarcoplasmic reticulum (2), and mitochondria (14), and translocation between compartments has been demonstrated (15). It has been speculated that these various localizations provide specificity to NO signaling, but the exact mechanisms have yet to be elucidated. In this study, we show a mechanism by which one fraction of nNOS serves highly specific functions through binding to PMCA4b. As PMCA4b is confined to the sarcolemma and is a calcium pump, it is the first identified protein to fulfill these aggregate functions. 1) It acts as an anchoring protein; 2) it regulates nNOS activity; and 3) it modulates a process at the plasma membrane, i.e. β-adrenergic signaling.     

Insights into in vitro spermatogenesis in mammals: Past,present, future

Considering the self‐renewal and differentiation ability of pluripotent stem cells, some studies have pointed out the possibility of stem cell‐derived sperm production. Most studies that test this hypothesis have been conducted on rodents, with some promising results; however, studies on humans are progressing slowly, and have encountered technical and ethical hurdles. Established methods to differentiate stem cells—including embryoid bodies, co‐culturing, and various feeder cells—may provide a niche that is similar to in vivo conditions and resolve epigenetic abnormalities, but a gonadal‐like three‐dimensional structure is still required to produce germ cells with the correct imprinting. In the last few years, sperm‐like cells with fertilizing capacity were produced from mouse embryonic stem cells, and the resulting embryos from these cells yielded live offspring. Future research should move towards the use of adult stem cells, however, owing to the unavailability of embryonic cells in adults. More intensive research and techniques are required since in vitro spermatogenesis provides hope to individuals without mature sperm who cannot be treated, and may be a useful system to study the precise mechanism of spermatogenesis. In this review, we describe recent studies of in vitro spermatogenesis mechanisms and related techniques in mammals. We also discuss the possible cell surface markers and culture conditions that might improve in vitro spermatogenesis.     

A eukaryotic-like sulfiredoxin involved in oxidative stress responses and in the reduction of the sulfinic form of 2-Cys peroxiredoxin in the cyanobacterium Anabaena PCC 7120

The overoxidation of 2-Cys peroxiredoxins (Prxs) into a sulfinic form was thought to be an irreversible protein inactivation process until sulfiredoxins (Srxs) were discovered. These are enzymes occurring among eukaryotes, which are able to reduce sulfinylated Prxs. Although Prxs are present in the three domains of life, their reduction by Srxs has been described only in eukaryotes so far. Here it was established that the cyanobacterium Anabaena PCC 7120 has a Srx homologue (SrxA), which is able to specifically reduce the sulfinic form of the 2-Cys Prx (PrxA) both in vivo and in vitro. A mutant lacking the srxA gene was found to be more sensitive than the wild type to oxidative stress. Sulfiredoxin homologues are restricted to the cyanobacterial and eukaryotic genomes sequenced so far. The present phylogenetic analysis of Srx and 2-Cys Prx sequences showed a pattern of coevolution of the enzyme and its substrate that must have involved an ancient gene transfer between ancestors of Cyanobacteria and Eukaryotes, followed by a more recent transfer from Cyanobacteria to Plantae through the chloroplastic endosymbiosis. This is the first functional characterization of a Srx enzyme in a prokaryotic organism.     

Critical scaffolding regions of the tumor suppressor Axin1 are natively unfolded

The Wnt pathway tumor-suppressor protein Axin coordinates the formation of a critical multiprotein destruction complex that serves to downregulate β-catenin protein levels, thereby preventing target gene activation. Given the lack of structural information on some of the major functional parts of Axin, it remains unresolved how the recruitment and positioning of Wnt pathway kinases, such as glycogen synthase kinase 3β, are coordinated to bring about β-catenin phosphorylation. Using various biochemical and biophysical methods, we demonstrate here that the central region of Axin that is implicated in binding glycogen synthase kinase 3β and β-catenin is natively unfolded. Our results support a model in which the unfolded nature of these critical scaffolding regions in Axin facilitates dynamic interactions with a kinase and its substrate, which in turn act upon each other.     

Cisplatin treatment of primary and metastatic epithelial ovarian carcinomas generates residual cells with mesenchymal stem cell-like profile

Epithelial mesenchymal transition (EMT) and cancer stem cells (CSC) have been associated with resistance to chemotherapy. Eighty percent of ovarian cancer patients initially respond to platinum-based combination therapy but most return with recurrence and ultimate demise. To better understand such chemoresistance we have assessed the potential role of EMT in tumor cells collected from advanced-stage ovarian cancer patients and the ovarian cancer cell line OVCA 433 in response to cisplatin in vitro. We demonstrate that cisplatin-induced transition from epithelial to mesenchymal morphology in residual cancer cells correlated with reduced E-cadherin, and increased N-cadherin and vimentin expression. The mRNA expression of Snail, Slug, Twist, and MMP-2 were significantly enhanced in response to cisplatin and correlated with increased migration. This coincided with increased cell surface expression of CSC-like markers such as CD44, α2 integrin subunit, CD117, CD133, EpCAM, and the expression of stem cell factors Nanog and Oct-4. EMT and CSC-like changes in response to cisplatin correlated with enhanced activation of extracellular signal-regulated kinase (ERK)1/2. The selective MEK inhibitor U0126 inhibited ERK2 activation and partially suppressed cisplatin-induced EMT and CSC markers. In vivo xenotransplantation of cisplatin-treated OVCA 433 cells in zebrafish embryos demonstrated significantly enhanced migration of cells compared to control untreated cells. U0126 inhibited cisplatin-induced migration of cells in vivo, suggesting that ERK2 signaling is critical to cisplatin-induced EMT and CSC phenotypes, and that targeting ERK2 in the presence of cisplatin may reduce the burden of residual tumor, the ultimate cause of recurrence in ovarian cancer patients.     

Serum Arsenic and Lipid Peroxidation Levels in Patients with Multiple Sclerosis

Oxidative stress plays a crucial role in the pathogenesis of multiple sclerosis (MS). Previous studies have shown that oxidative stress is one of the main underlying mechanisms of arsenic-induced cellular damage. The aim of this study was to assess the serum levels of arsenic and its relationship with lipid peroxidation in MS patients from Tabriz, as the third polluted city of Iran. The study population included 38 MS female patients and 38 age-matched healthy controls. Serum malondialdehyde (MDA) and arsenic levels were measured using thiobarbituric acid reactive substances (TBARS) assay and electrothermal atomic absorption spectrometry, respectively. The results showed that the arsenic (P?<?0.01) and MDA (P?=?0.03) levels were significantly higher in patients with MS than those in control. Moreover, serum levels of arsenic and MDA were positively correlated in MS patients. The elevated levels of serum arsenic might explain the increased oxidative stress in MS patients. We suggest that high arsenic levels in serum may lead to MS development, and therefore, exposure to this metal should be limited.     

Phylogenetic analysis of Aphanius from the endorheic Kor River Basin in the Zagros Mountains,South‐western Iran (Teleostei: Cyprinodontiformes: Cyprinodontidae)

Morphologically similar populations of Aphanius that are currently considered as A. sophiae inhabit the endorheic Kor River Basin in the Zagros Mountains. Using genetic analysis based on mtDNA (cytochrome b), combined with examination of morphology (morphometry, meristics, otoliths), we discovered that what is thought to be A. sophiae is actually two distinct species, one of which is described as A. shirini sp. n. The males of the new species can be distinguished from those of all other Iranian inland Aphanius species by having only 7–10 clearly defined white flank bars, which is the lowest number of flank bars among the Iranian inland Aphanius species. Both males and females differ from all other Iranian inland Aphanius species by having a significantly longer caudal peduncle and a smaller dorsal fin depth. Based on the PhyML and Bayesian likelihood trees, A. shirini is sister to A. vladykovi from the Karoun Basin in the Zagros Mountains. Our results indicate that an ancient exorheic Kor River Basin existed in the Late Miocene and Pliocene. The close phylogenetic relationship between A. shirini and A. vladykovi suggests that the pre‐Pliocene drainage in the ancient Kor River Basin was directed to the north‐west (to the Karoun Basin), and not to the south‐east as in the present‐day Kor Basin. Both A. shirini and A. vladykovi represent the highest altitude records for Aphanius. We conclude that the splits of A. shirini and A. vladykovi can be linked to tectonic events in the Middle to Late Miocene, which created the highest altitudes (>3000 m) in the Zagros Mountains, and led to isolation of populations. The present‐day endorheic Kor Basin is known to have formed in the Late Pleistocene or Early Holocene, and the ‘young’ age of A. sophiae is clearly related to this history. Our results contribute to elucidate the link between geological history and the present‐day species diversity in the tectonically still active Zagros Mountains of Iran.     

The effects of pulsed magnetic field exposure on the permeability of leukemia cancer cells

Purpose: The newer methods of cancer treatment require new idea of drug delivery in cancer cells. Due to numerous researches electromagnetic field affect on cell function and cell membrane for possible therapeutic and drug delivery. In this article, we determined in vitro uptake of fluorescent dyes into the attached K562 cells due to time-varying magnetic field exposure. Method and material: The K562 cells were exposed to magnetic pulses via Magstim stimulator and double 70?mm coil. The strength and duration of pulses in all experiments were the same and three different frequencies of 0.25, 1 and 10?Hz pulses for 56, 112 and 28 numbers of pulses were applied (nine experimental groups) and uptake of Ly and PI was measured in each group. Result: Our results show that magnetic field can efficiently increase permeability. Among the treatment groups, the system gives the optimal permeabilization when cells are exposed to a train of 28 pulses with 1?Hz frequency.