Exacerbated response to oxidative stress in the Retinitis Pigmentosa CerklKD/KO mouse model triggers retinal degeneration pathways upon acute light stress.

The retina is particularly vulnerable to genetic and environmental alterations that generate oxidative stress and cause cellular damage in photoreceptors and other retinal neurons, eventually leading to cell death. CERKL (CERamide Kinase-Like) mutations cause Retinitis Pigmentosa and Cone-Rod Dystrophy in humans, two disorders characterized by photoreceptor degeneration and progressive vision loss. CERKL is a resilience gene against oxidative stress, and its overexpression protects cells from oxidative stress-induced apoptosis. Besides, CERKL contributes to stress granule-formation and regulates mitochondrial dynamics in the retina. Using the CerklKD/KO albino mouse model, which recapitulates the human disease, we aimed to study the impact of Cerkl knockdown on stress response and activation of photoreceptor death mechanisms upon light/oxidative stress. After acute light injury, we assessed immediate or late retinal stress response, by combining both omic and non-omic approaches. Our results show that Cerkl knockdown increases ROS levels and causes a basal exacerbated stress state in the retina, through alterations in glutathione metabolism and stress granule production, overall compromising an adequate response to additional oxidative damage. As a consequence, several cell death mechanisms are triggered in CerklKD/KO retinas after acute light stress. Our studies indicate that Cerkl gene is a pivotal player in regulating light-challenged retinal homeostasis and shed light on how mutations in CERKL lead to blindness by dysregulation of the basal oxidative stress response in the retina.

Nanotechnology-Based Strategies to Overcome Current Barriers in Gene Delivery.

Nanomaterials are currently being developed for the specific cell/tissue/organ delivery of genetic material. Nanomaterials are considered as non-viral vectors for gene therapy use. However, there are several requirements for developing a device small enough to become an efficient gene-delivery tool. Considering that the non-viral vectors tested so far show very low efficiency of gene delivery, there is a need to develop nanotechnology-based strategies to overcome current barriers in gene delivery. Selected nanostructures can incorporate several genetic materials, such as plasmid DNA, mRNA, and siRNA. In the field of nanotechnologies, there are still some limitations yet to be resolved for their use as gene delivery systems, such as potential toxicity and low transfection efficiency. Undeniably, novel properties at the nanoscale are essential to overcome these limitations. In this paper, we will explore the latest advances in nanotechnology in the gene delivery field.

CERKL, a retinal dystrophy gene, regulates mitochondrial function and dynamics in the mammalian retina.

The retina is a highly active metabolic organ that displays a particular vulnerability to genetic and environmental factors causing stress and homeostatic imbalance. Mitochondria constitute a bioenergetic hub that coordinates stress response and cellular homeostasis, therefore structural and functional regulation of the mitochondrial dynamic network is essential for the mammalian retina. CERKL (ceramide kinase like) is a retinal degeneration gene whose mutations cause Retinitis Pigmentosa in humans, a visual disorder characterized by photoreceptors neurodegeneration and progressive vision loss. CERKL produces multiple isoforms with a dynamic subcellular localization. Here we show that a pool of CERKL isoforms localizes at mitochondria in mouse retinal ganglion cells. The depletion of CERKL levels in CerklKD/KO(knockdown/knockout) mouse retinas cause increase of autophagy, mitochondrial fragmentation, alteration of mitochondrial distribution, and dysfunction of mitochondrial-dependent bioenergetics and metabolism. Our results support CERKL as a regulator of autophagy and mitochondrial biology in the mammalian retina.

A New Cerkl Mouse Model Generated by CRISPR-Cas9 Shows Progressive Retinal Degeneration and Altered Morphological and Electrophysiological Phenotype.

Purpose: Close to 100 genes cause retinitis pigmentosa, a Mendelian rare disease that affects 1 out of 4000 people worldwide. Mutations in the ceramide kinase-like gene (CERKL) are a prevalent cause of autosomal recessive cause retinitis pigmentosa and cone-rod dystrophy, but the functional role of this gene in the retina has yet to be fully determined. We aimed to generate a mouse model that resembles the phenotypic traits of patients carrying CERKL mutations to undertake functional studies and assay therapeutic approaches. Methods: The Cerkl locus has been deleted (around 97 kb of genomic DNA) by gene editing using the CRISPR-Cas9 D10A nickase. Because the deletion of the Cerkl locus is lethal in mice in homozygosis, a double heterozygote mouse model with less than 10% residual Cerkl expression has been generated. The phenotypic alterations of the retina of this new model have been characterized at the morphological and electrophysiological levels. Results: This CerklKD/KO model shows retinal degeneration, with a decreased number of cones and progressive photoreceptor loss, poorly stacked photoreceptor outer segment membranes, defective retinal pigment epithelium phagocytosis, and altered electrophysiological recordings in aged retinas. Conclusions: To our knowledge, this is the first Cerkl mouse model to mimic many of the phenotypic traits, including the slow but progressive retinal degeneration, shown by human patients carrying CERKL mutations. This useful model will provide unprecedented insights into the retinal molecular pathways altered in these patients and will contribute to the design of effective treatments.

The Relevance of Oxidative Stress in the Pathogenesis and Therapy of Retinal Dystrophies.

Retinal cell survival requires an equilibrium between oxygen, reactive oxygen species, and antioxidant molecules that counteract oxidative stress damage. Oxidative stress alters cell homeostasis and elicits a protective cell response, which is most relevant in photoreceptors and retinal ganglion cells, neurons with a high metabolic rate that are continuously subject to light/oxidative stress insults. We analyze how the alteration of cellular endogenous pathways for protection against oxidative stress leads to retinal dysfunction in prevalent (age-related macular degeneration, glaucoma) as well as in rare genetic visual disorders (Retinitis pigmentosa, Leber hereditary optic neuropathy). We also highlight some of the key molecular actors and discuss potential therapies using antioxidants agents, modulators of gene expression and inducers of cytoprotective signaling pathways to treat damaging oxidative stress effects and ameliorate severe phenotypic symptoms in multifactorial and rare retinal dystrophies.

In Vitro Gene Delivery in Retinal Pigment Epithelium Cells by Plasmid DNA-Wrapped Gold Nanoparticles.

Many rare diseases course with affectation of neurosensory organs. Among them, the neuroepithelial retina is very vulnerable due to constant light/oxidative stress, but it is also the most accessible and amenable to gene manipulation. Currently, gene addition therapies targeting retinal tissue (either photoreceptors or the retinal pigment epithelium), as a therapy for inherited retinal dystrophies, use adeno-associated virus (AAV)-based approaches. However, efficiency and safety of therapeutic strategies are relevant issues that are not always resolved in virus-based gene delivery and alternative methodologies should be explored. Based on our experience, we are currently assessing the novel physical properties at the nanoscale of inorganic gold nanoparticles for delivering genes to the retinal pigment epithelium (RPE) as a safe and efficient alternative approach. In this work, we present our preliminary results using DNA-wrapped gold nanoparticles (DNA-gold NPs) for successful in vitro gene delivery on human retinal pigment epithelium cell cultures, as a proof-of-principle to assess its feasibility for retina in vivo gene delivery. Our results show faster expression of a reporter gene in cells transfected with DNA-gold NPs compared to DNA-liposome complexes. Furthermore, we show that the DNA-gold NPs follow different uptake, internalization and intracellular vesicle trafficking routes compared to pristine NPs.

Two distinct molecular subtypes of chronic lymphocytic leukemia give new insights on the pathogenesis of the disease and identify novel therapeutic targets.

Biopsy samples of lymph nodes from 38 patients with CLL were analyzed. We found differential expression in 1092 genes in two different subgroups: 418 overexpressed in one subgroup and 674 in another. Molecular pathways identified in one subgroup appear to be characterized by greater dependence of signaling by cytokines and activation of the NFkB pathway, while in the other seem to depend on cell cycle. Despite having found a differential expression between both subgroups, none of these genes reached FDR < 0.25. We have not found significant association with survival or any prognostic factors. Analysis of the differences between normal lymph node and CLL in 253 genes with difference in the intensity of expression revealed upregulated genes different to BCR: CD40, TCL1, IL-7, and PAX5. Using large-scale molecular analysis, we may obtain information about molecular mechanisms of CLL pathogenesis and may contribute to the identification of new therapeutic targets.

AMPK and PFKFB3 mediate glycolysis and survival in response to mitophagy during mitotic arrest.

Blocking mitotic progression has been proposed as an attractive therapeutic strategy to impair proliferation of tumour cells. However, how cells survive during prolonged mitotic arrest is not well understood. We show here that survival during mitotic arrest is affected by the special energetic requirements of mitotic cells. Prolonged mitotic arrest results in mitophagy-dependent loss of mitochondria, accompanied by reduced ATP levels and the activation of AMPK. Oxidative respiration is replaced by glycolysis owing to AMPK-dependent phosphorylation of PFKFB3 and increased production of this protein as a consequence of mitotic-specific translational activation of its mRNA. Induction of autophagy or inhibition of AMPK or PFKFB3 results in enhanced cell death in mitosis and improves the anti-tumoral efficiency of microtubule poisons in breast cancer cells. Thus, survival of mitotic-arrested cells is limited by their metabolic requirements, a feature with potential implications in cancer therapies aimed to impair mitosis or metabolism in tumour cells.

mRNA expression analysis of the SUMO pathway genes in the adult mouse retina.

Sumoylation is a reversible post-translational modification that regulates different cellular processes by conjugation/deconjugation of SUMO moieties to target proteins. Most work on the functional relevance of SUMO has focused on cell cycle, DNA repair and cancer in cultured cells, but data on the inter-dependence of separate components of the SUMO pathway in highly specialized tissues, such as the retina, is still scanty. Nonetheless, several retinal transcription factors (TFs) relevant for cone and rod fate, as well as some circadian rhythm regulators, are regulated by sumoylation. Here we present a comprehensive survey of SUMO pathway gene expression in the murine retina by quantitative RT-PCR and in situ hybridization (ISH). The mRNA expression levels were quantified in retinas obtained under four different light/dark conditions, revealing distinct levels of gene expression. In addition, a SUMO pathway retinal gene atlas based on the mRNA expression pattern was drawn. Although most genes are ubiquitously expressed, some patterns could be defined in a first step to determine its biological significance and interdependence. The wide expression of the SUMO pathway genes, the transcriptional response under several light/dark conditions, and the diversity of expression patterns in different cell layers clearly support sumoylation as a relevant post-translational modification in the retina. This expression atlas intends to be a reference framework for retinal researchers and to depict a more comprehensive view of the SUMO-regulated processes in the retina.

Mitosis-targeting therapies: a troubleshooting guide.

Several mitotic kinases and kinesins are currently considered as cancer targets based on their critical role during the cell division cycle and their significant level of expression in human tumors. Yet, their use is limited by the lack of selectivity against tumor cells, the low percentage of mitotic cells in many human tumors, and dose-limiting side-effects. As a consequence, initial clinical trials have shown limited responses. Despite these drawbacks, inhibiting mitosis is a promising strategy that deserves further development. Future advances will benefit from more specific inhibitors with better pharmacodynamic properties, a clear physiological characterization and cell-type-specific requirements of old and new mitotic targets, and rational strategies based on synthetic lethal interactions to improve selectivity against tumor cells.

New mutations in chronic lymphocytic leukemia identified by target enrichment and deep sequencing.

Chronic lymphocytic leukemia (CLL) is a heterogeneous disease without a well-defined genetic alteration responsible for the onset of the disease. Several lines of evidence coincide in identifying stimulatory and growth signals delivered by B-cell receptor (BCR), and co-receptors together with NFkB pathway, as being the driving force in B-cell survival in CLL. However, the molecular mechanism responsible for this activation has not been identified. Based on the hypothesis that BCR activation may depend on somatic mutations of the BCR and related pathways we have performed a complete mutational screening of 301 selected genes associated with BCR signaling and related pathways using massive parallel sequencing technology in 10 CLL cases. Four mutated genes in coding regions (KRAS, SMARCA2, NFKBIE and PRKD3) have been confirmed by capillary sequencing. In conclusion, this study identifies new genes mutated in CLL, all of them in cases with progressive disease, and demonstrates that next-generation sequencing technologies applied to selected genes or pathways of interest are powerful tools for identifying novel mutational changes.

Low pH acts as inhibitor of membrane damage induced by human islet amyloid polypeptide.

Human islet amyloid polypeptide (IAPP) is the major component of the amyloid deposits found in the pancreatic islets of patients with type 2 diabetes mellitus. After synthesis, IAPP is stored in the ß-cell granules of the pancreas at a pH of approximately 5.5 and released into the extracellular compartment at a pH of 7.4. To gain insight into the possible consequences of pH differences for properties and membrane interaction of IAPP, we here compared the aggregational and conformational behavior of IAPP as well as IAPP-membrane interactions at pH 5.5 and pH 7.4. Our data reveal that a low pH decreases the rate of fibril formation both in solution and in the presence of membranes. We observed by CD spectroscopy that these differences in kinetics are directly linked to changes in the conformational behavior of the peptide. Mechanistically, the processes that occur at pH 5.5 and pH 7.4 appear to be similar. At both pH values, we found that the kinetic profile of IAPP fibril growth matches the kinetic profile of IAPP-induced membrane damage, and that both are characterized by a lag phase and a sigmoidal transition. Furthermore, monolayer studies as well as solid-state NMR experiments indicate that the differences in kinetics and conformational behavior as function of pH are not due to a different mode of membrane insertion. Our study suggests that a low pH prevents aggregation and membrane damage of IAPP in the secretory granules, most likely by affecting the ionization properties of the peptide.

Increased oxidative stress levels and normal antioxidant enzyme activity in circulating mononuclear cells from patients of familial hypercholesterolemia.

Familial hypercholesterolemia (FH) is a clinical condition with high risk for developing atherosclerosis. Increased oxidative stress (OS) and FH have been related to atherosclerosis, but no data are available on levels of OS and antioxidant enzyme activity in circulating mononuclear cells (CMCs) from FH patients. Circulating mononuclear cells are important mediators in atherosclerosis development, and chronically increased blood OS present in FH can induce modification in CMC activity. The objective of the study was to analyze the OS levels in CMCs from FH patients and controls. We have selected 30 nonrelated FH index patients and 30 normoglycemic and normocholesterolemic controls matched by age, sex, body mass index, abdominal circumference, and homeostasis model assessment index. Production of free radicals was analyzed by measurement of xanthine oxidase activity in plasma, reduced and oxidized glutathione (GSH and GSSG, respectively), and malonyldialdehyde in levels CMCs. Antioxidant status was analyzed by measuring antioxidant enzyme activity as superoxide dismutase, catalase, and glutathione peroxidase. We have found that FH patients showed significantly higher xanthine oxidase and malonyldialdehyde enzyme activities, as well as increased GSSG and lower GSH values resulting in a higher GSSG/GSH ratio. These data indicate a higher free radical production in plasma and increased OS levels in CMCs from patients than from controls. No significant differences were found in superoxide dismutase, catalase, and glutathione peroxidase activities between both groups. These data show an important alteration of OS regulation in FH and the absence of antioxidant response in CMCs mediated by some of the major antioxidant enzymes.

Bemiparin improves the total antioxidant status in plasma.

The aim of this work is to test the protective effect of bemiparin (3500 I.U., s.c.) against oxidative stress in plasma from healthy volunteers. We have evaluated the total antioxidant activity in plasma, superoxide dismutase and glutathione peroxidase activities, and oxidized glutathione and malondialdehyde levels, in two groups: treated (n=20) and control (n=15). Blood samples were collected at: basal, 2, 4, 6, 8 and 10 h. Total antioxidant activity and antioxidant enzymes activity were higher in the treated group at 2-6 h. However, oxidized glutathione and malondialdehyde levels were lower in the treated group at same times. The results suggest that bemiparin exerts an early beneficial effect against oxidative stress in plasma.

Moderate exercise is an antioxidant: upregulation of antioxidant genes by training.

Exercise causes oxidative stress only when exhaustive. Strenuous exercise causes oxidation of glutathione, release of cytosolic enzymes, and other signs of cell damage. However, there is increasing evidence that reactive oxygen species (ROS) not only are toxic but also play an important role in cell signaling and in the regulation of gene expression. Xanthine oxidase is involved in the generation of superoxide associated with exhaustive exercise. Allopurinol (an inhibitor of this enzyme) prevents muscle damage after exhaustive exercise, but also modifies cell signaling pathways associated with both moderate and exhaustive exercise in rats and humans. In gastrocnemius muscle from rats, exercise caused an activation of MAP kinases. This in turn activated the NF-kappaB pathway and consequently the expression of important enzymes associated with defense against ROS (superoxide dismutase) and adaptation to exercise (eNOS and iNOS). All these changes were abolished when ROS production was prevented by allopurinol. Thus ROS act as signals in exercise because decreasing their formation prevents activation of important signaling pathways that cause useful adaptations in cells. Because these signals result in an upregulation of powerful antioxidant enzymes, exercise itself can be considered an antioxidant. We have found that interfering with free radical metabolism with antioxidants may hamper useful adaptations to training.

Oral administration of vitamin C decreases muscle mitochondrial biogenesis and hampers training-induced adaptations in endurance performance.

BACKGROUND: Exercise practitioners often take vitamin C supplements because intense muscular contractile activity can result in oxidative stress, as indicated by altered muscle and blood glutathione concentrations and increases in protein, DNA, and lipid peroxidation. There is, however, considerable debate regarding the beneficial health effects of vitamin C supplementation. OBJECTIVE: This study was designed to study the effect of vitamin C on training efficiency in rats and in humans. DESIGN: The human study was double-blind and randomized. Fourteen men (27-36 y old) were trained for 8 wk. Five of the men were supplemented daily with an oral dose of 1 g vitamin C. In the animal study, 24 male Wistar rats were exercised under 2 different protocols for 3 and 6 wk. Twelve of the rats were treated with a daily dose of vitamin C (0.24 mg/cm2 body surface area). RESULTS: The administration of vitamin C significantly (P=0.014) hampered endurance capacity. The adverse effects of vitamin C may result from its capacity to reduce the exercise-induced expression of key transcription factors involved in mitochondrial biogenesis. These factors are peroxisome proliferator-activated receptor co-activator 1, nuclear respiratory factor 1, and mitochondrial transcription factor A. Vitamin C also prevented the exercise-induced expression of cytochrome C (a marker of mitochondrial content) and of the antioxidant enzymes superoxide dismutase and glutathione peroxidase. CONCLUSION: Vitamin C supplementation decreases training efficiency because it prevents some cellular adaptations to exercise.

Age-related increase in xanthine oxidase activity in human plasma and rat tissues.

This study assessed the role of xanthine oxidase in vascular ageing. A positive correlation between xanthine oxidase activity and age was found in human plasma. Similar results were found in rat plasma. Xanthine oxidase expression and activity in homogenates from the aortic wall were significantly higher in samples from old rats than in their young counterparts (p < 0.01). In rat skeletal muscle homogenates both xanthine oxidase expression and activity showed a similar age-related profile. Superoxide production by xanthine oxidase in aortic rings was higher in aged rats. Uric acid, the final product of xanthine oxidase has been proposed as a risk factor for coronary heart disease and an independent marker of worse prognosis in patients with moderate-to-severe chronic heart failure. These results give a possible explanation for this correlation and underscore the role of xanthine oxidase in ageing.