An optimal redox status for the survival of axotomized ganglion cells in the developing retina

Oxidative Stress and Male Infertility: The Protective Role of Antioxidants

Oxidative stress is a significant factor in male infertility, compromising sperm function and overall reproductive health. As male infertility garners increasing attention, effective therapeutic interventions become paramount. This review investigates the therapeutic role of antioxidants in addressing male infertility. A detailed examination was conducted on antioxidants such as vitamin C, E, B12, D, coenzyme Q10, zinc, folic acid, selenium, l-carnitine, l-arginine, inositols, and alpha-lipoic acid. This analysis examines the methodologies, outcomes, and constraints of current clinical studies. Antioxidants show notable potential in counteracting the negative effects of oxidative stress on sperm. Based on the evidence, these antioxidants, individually or synergistically, can enhance sperm health and reproductive outcomes. However, certain limitations in the studies call for careful interpretation. Antioxidants are integral in tackling male infertility attributed to oxidative stress. The current findings underscore their therapeutic value, yet there's a pressing need for deeper, comprehensive research. Future studies should focus on refining dosage guidelines, identifying potential side effects, and discerning the most efficacious antioxidant combinations for male infertility solutions.

Sex differences in neuroimmunoendocrine communication. Involvement on longevity

Endocrine, nervous, and immune systems work coordinately to maintain the global homeostasis of the organism. They show sex differences in their functions that, in turn, contribute to sex differences beyond reproductive function. Females display a better control of the energetic metabolism and improved neuroprotection and have more antioxidant defenses and a better inflammatory status than males, which is associated with a more robust immune response than that of males. These differences are present from the early stages of life, being more relevant in adulthood and influencing the aging trajectory in each sex and may contribute to the different life lifespan between sexes.

Antioxidant Intervention against Male Infertility: Time to Design Novel Strategies

Infertility is a highly prevalent condition, affecting 9-20% of couples worldwide. Among the identifiable causes, the male factor stands out in about half of infertile couples, representing a growing problem. Accordingly, there has been a decline in both global fertility rates and sperm counts in recent years. Remarkably, nearly 80% of cases of male infertility (MI) have no clinically identifiable aetiology. Among the mechanisms likely plausible to account for idiopathic cases, oxidative stress (OS) has currently been increasingly recognized as a key factor in MI, through phenomena such as mitochondrial dysfunction, lipid peroxidation, DNA damage and fragmentation and finally, sperm apoptosis. In addition, elevated reactive oxygen species (ROS) levels in semen are associated with worse reproductive outcomes. However, despite an increasing understanding on the role of OS in the pathophysiology of MI, therapeutic interventions based on antioxidants have not yet provided a consistent benefit for MI, and there is currently no clear consensus on the optimal antioxidant constituents or regimen. Therefore, there is currently no applicable antioxidant treatment against this problem. This review presents an approach aimed at designing an antioxidant strategy based on the particular biological properties of sperm and their relationships with OS.

Antioxidant Paradox in Male Infertility: 'A Blind Eye' on Inflammation

The pathophysiology of male infertility involves various interlinked endogenous pathways. About 50% of the cases of infertility in men are idiopathic, and oxidative stress (OS) reportedly serves as a central mechanism in impairing male fertility parameters. The endogenous antioxidant system operates to conserve the seminal redox homeostasis required for normal male reproduction. OS strikes when a generation of seminal reactive oxygen species (ROS) overwhelms endogenous antioxidant capacity. Thus, antioxidant treatment finds remarkable relevance in the case of idiopathic male infertility or subfertility. However, due to lack of proper detection of OS in male infertility, use of antioxidant(s) in some cases may be arbitrary or lead to overuse and induction of 'reductive stress'. Moreover, inflammation is closely linked to OS and may establish a vicious loop that is capable of disruption to male reproductive tissues. The result is exaggeration of cellular damage and disruption of male reproductive tissues. Therefore, limitations of antioxidant therapy in treating male infertility are the failure in the selection of specific treatments targeting inflammation and OS simultaneously, two of the core mechanisms of male infertility. The present review aims to elucidate the antioxidant paradox in male infertility treatment, from the viewpoints of both induction of reductive stress as well as overlooking the inflammatory consequences.

Oxidative Stress and Toxicity in Reproductive Biology and Medicine: A Comprehensive Update on Male Infertility Volume II - Conclusion

Infertility is a globally under-recognized public health problem significantly impacting individual health and socioeconomics affecting millions of couples. The reasons for infertility are manifold and not only include many couples decision to postpone having children but also diseases (e.g., diabetes, infections, or varicocele), lifestyle (e.g., obesity), and environmental factors (e.g., bisphenol A, DTT or dioxin). In the pathology of many causes of infertility, oxidative stress plays a significant role as reactive oxygen species (ROS) exert significant detrimental effects. On the other hand, a small amount of ROS is essential to trigger physiological events such as capacitation. Therefore, a fine balance between oxidation and reduction has to be maintained. Apart from treating the underlying disease or correcting the cause of the infertility, oxidative stress can be treated by antioxidant supplementation. Since plants and their extracts contain numerous phytochemicals which exhibit antioxidant activity, many people tend to use herbal products. Alternatively, isolated antioxidants such as vitamin C or E are also used. However, when using purified antioxidants, it is essential that the redox balance is maintained to avoid a "reductive stress" situation, which is as harmful as oxidative stress.

Reductive Stress and Male Infertility

Male infertility research and clinical advances had vast progress in the last few decades. Strong research evidence underpinned the concepts of oxidative stress (OS)-mediated male reproductive disruptions, which bear answers to several cases of idiopathic male infertility. Antioxidant treatment held the prime solution for OS-mediated male infertility. But excess use of antioxidants is challenged by the research breakthrough that reductive stress also predisposes to male infertility, resolutely instituting that any biological extremes of the redox spectrum are deleterious to male fertility. Superfluity of reducing agents may hinder essential oxidation mechanisms, affecting physiological homeostasis. These mechanisms need to be explicated and updated time and again to identify the fine thread between OS-mediated male infertility treatment and induction of reductive stress. This chapter thus presents the evidence-based concepts pertaining to the antioxidants actions to combat OS-induced male infertility, the mechanism of induction of reductive stress and its impact on male reproduction.

Extracellular Reactive Oxygen Species (ROS) Production in Fresh Donkey Sperm Exposed to Reductive Stress, Oxidative Stress and NETosis

Jenny shows a large endometrial reaction after semen influx to the uterus with a large amount of polymorphonuclear neutrophils (PMN) migrating into the uterine lumen. PMN act as a sperm selection mechanism through phagocytosis and NETosis (DNA extrudes and, together with proteins, trap spermatozoa). While a reduced percentage of spermatozoa are phagocytosed by PMN, most are found to be attached to neutrophil extracellular traps (NETs). This selection process together with sperm metabolism produces a large amount of reactive oxygen species (ROS) that influence the reproductive success. The present study aimed to determine the extracellular ROS production in both sperm and PMN. With this purpose, (1) donkey sperm were exposed to reductive and oxidative stresses, through adding different concentrations of reduced glutathione (GSH) and hydrogen peroxide (H₂O₂), respectively; and (2) PMN were subjected to NETosis in the presence of the whole semen, sperm, seminal plasma (SP) or other activators such as formyl-methionyl-leucyl-phenylalanine (FMLP). Extracellular ROS production (measured as H₂O₂ levels) was determined with the Amplex^® Red Hydrogen Peroxide/Peroxidase Assay Kit. Donkey sperm showed more resilience to oxidative stress than to the reductive one, and GSH treatments led to greater H₂O₂ extracellular production. Moreover, not only did SP appear to be the main inducer of NETosis in PMN, but it was also able to maintain the extracellular H₂O₂ levels produced by sperm and NETosis.

A Global Survey of Reproductive Specialists to Determine the Clinical Utility of Oxidative Stress Testing and Antioxidant Use in Male Infertility

Purpose

The use of antioxidants is common practice in the management of infertile patients. However, there are no established guidelines by professional societies on antioxidant use for male infertility.

Materials and Methods

Using an online survey, this study aimed to evaluate the practice pattern of reproductive specialists to determine the clinical utility of oxidative stress (OS) testing and antioxidant prescriptions to treat male infertility.

Results

Responses from 1,327 participants representing 6 continents, showed the largest participant representation being from Asia (46.8%). The majority of participants were attending physicians (59.6%), with 61.3% having more than 10 years of experience in the field of male infertility. Approximately two-thirds of clinicians (65.7%) participated in this survey did not order any diagnostic tests for OS. Sperm DNA fragmentation was the most common infertility test beyond a semen analysis that was prescribed to study oxidative stress-related dysfunctions (53.4%). OS was mainly tested in the presence of lifestyle risk factors (24.6%) or sperm abnormalities (16.3%). Interestingly, antioxidants were prescribed by 85.6% of clinicians, for a duration of 3 (43.7%) or 3–6 months (38.6%). A large variety of antioxidants and dietary supplements were prescribed, and scientific evidence were mostly considered to be modest to support their clinical use. Results were not influenced by the physician's age, geographic origin, experience or training in male infertility.

Conclusions

This study is the largest online survey performed to date on this topic and demonstrates 1) a worldwide understanding of the importance of this therapeutic option, and 2) a widely prevalent use of antioxidants to treat male infertility. Finally, the necessity of evidence-based clinical practice guidelines from professional societies is highlighted.

Utility of Antioxidants in the Treatment of Male Infertility: Clinical Guidelines Based on a Systematic Review and Analysis of Evidence

It is widely accepted that oxidative stress plays an important role in the pathophysiology of male infertility and that antioxidants could have a significant role in the treatment of male infertility. The main objectives of this study are: 1) to systematically review the current evidence for the utility of antioxidants in the treatment of male infertility; and 2) propose evidence-based clinical guidelines for the use of antioxidants in the treatment of male infertility. A systematic review of the available clinical evidence was performed, with articles published on Scopus being manually screened. Data extracted included the type of antioxidant used, the clinical conditions under investigation, the evaluation of semen parameters and reproductive outcomes. The adherence to the Cambridge Quality Checklist, Cochrane Risk of Bias for randomized controlled trials (RCTs), CONSORT guidelines and JADAD score were analyzed for each included study. Further, we provided a Strength Weakness Opportunity Threat (SWOT) analysis to analyze the current and future value of antioxidants in male infertility. Of the 1,978 articles identified, 97 articles were included in the study. Of these, 52 (53.6%) were uncontrolled (open label), 12 (12.4%) unblinded RCTs, and 33 (34.0%) blinded RCTs, whereas 44 (45.4%) articles tested individual antioxidants, 31 (32.0%) a combination of several products in variable dosages, and 22 (22.6%) registered antioxidant products. Based on the published evidence, we 1) critically examined the necessity of additional double-blind, randomized, placebo-controlled trials, and 2) proposed updated evidence-based clinical guidelines for antioxidant therapy in male infertility. The current systematic review on antioxidants and male infertility clearly shows that antioxidant supplementation improves semen parameters. In addition, it provides the indications for antioxidant treatment in specific clinical conditions, including varicocele, unexplained and idiopathic male infertility, as well as in cases of altered semen quality.

The effect of oxidative and reductive stress on semen parameters and functions of physiologically normal human spermatozoa

Both oxidative stress (OS) and reductive stress (RS) are the two extreme facets of redox imbalance that can have deleterious effects on sperm function. However, there is a lack of information on the physiological range of oxidation-reduction potential (ORP). The aim of this study was to investigate the effect of OS and RS on functions and associated molecular changes in normal spermatozoa in order to establish the physiological range of ORP. In the current study, total and progressive motility remained unchanged in spermatozoa exposed to ORP values 0.33 and 0.72 mV/10⁶ sperm/mL. However, a significant (P < 0.05) decline in total and progressive motility were observed at ORP values 1.48, 2.75, -11.24, -9.76 and -9.35 mV/10⁶ sperm/mL. Sperm vitality also decreased significantly (P < 0.0001) at 2.75, -11.24 and -9.76 mV/10⁶ sperm/mL. Spermatozoa exposed to ORP levels 2.75 and -11.24 mV/10⁶ sperm/mL showed a significant (P < 0.01) decrease in mitochondrial membrane potential. Intracellular reactive oxygen species (iROS) production increased (P < 0.05) in spermatozoa exposed to ORP levels of 1.48 and 2.75 mV/10⁶ sperm/mL, while iROS decreased (P < 0.05) at ORP levels -9.76 and -11.24 mV/10⁶ sperm/mL. No significant change in sperm DNA fragmentation was noted in sperm exposed to OS/RS and the values were below the reference range (<19.25%). Western blot analysis revealed decreased expression of CV-ATPA, CIII-UQCRC2 and CIV-MTCO1 proteins at 60 and 120 min (P < 0.05) in both OS and RS conditions. This is the first study to report physiological range of ORP (between -9.76 and 1.48 mV/10⁶ sperm/mL) and to elucidate the role of altered expression of oxidative phosphorylation (OXPHOS) complexes proteins in mediating detrimental effects of oxidative and reductive conditions on sperm functions. A decreased expression of OXPHOS proteins and associated mitochondrial dysfunction contributes to decreased sperm motility and vitality under oxidative and reductive stress.

Noninvasive Detection of Mitochondrial Dysfunction in Ocular Hypertension and Primary Open-angle Glaucoma

PURPOSE

To assess mitochondrial dysfunction in vivo in ocular hypertension (OHT) and primary open-angle glaucoma (POAG) using retinal metabolic analysis.

PATIENTS AND METHODS

This was an observational, cross-sectional study performed from November 2015 to October 2016 at the New York Eye and Ear Infirmary of Mount Sinai. Thirty-eight eyes with varying stages of POAG, 16 eyes with OHT, and 32 control eyes were imaged on a custom fundus camera modified to measure full retinal thickness fluorescence at a wavelength optimized to detect flavoprotein fluorescence (FPF). Optical coherence tomography was used to measure the retinal ganglion cell-plus layer (RGC+) thickness. Macular FPF and the ratio of macular FPF to RGC+ thickness were the primary outcome variables and were compared among the three groups using an age-adjusted linear regression model. A mixed-effects model was used to assess correlations between FPF variables and clinical characteristics.

RESULTS

Both macular FPF and the macular FPF/RGC+ thickness ratio were significantly increased in OHT compared with control eyes (P<0.05 and <0.01, respectively). In POAG eyes, macular FPF was not significantly increased compared with controls (P=0.24). However, the macular FPF/RGC+ thickness ratio in POAG eyes was significantly increased compared with controls (P<0.001). FPF was significantly correlated to age in POAG eyes.

CONCLUSIONS

Despite lacking clinical evidence of glaucomatous deterioration, OHT eyes displayed significantly elevated macular FPF, suggesting that mitochondrial dysfunction may be detected before structural changes visible on current clinical imaging. Our preliminary results suggest that macular FPF analysis may prove to be a useful tool in assessing and evaluating OHT and POAG eyes.

Male Oxidative Stress Infertility (MOSI): Proposed Terminology and Clinical Practice Guidelines for Management of Idiopathic Male Infertility

Despite advances in the field of male reproductive health, idiopathic male infertility, in which a man has altered semen characteristics without an identifiable cause and there is no female factor infertility, remains a challenging condition to diagnose and manage. Increasing evidence suggests that oxidative stress (OS) plays an independent role in the etiology of male infertility, with 30% to 80% of infertile men having elevated seminal reactive oxygen species levels. OS can negatively affect fertility via a number of pathways, including interference with capacitation and possible damage to sperm membrane and DNA, which may impair the sperm's potential to fertilize an egg and develop into a healthy embryo. Adequate evaluation of male reproductive potential should therefore include an assessment of sperm OS. We propose the term Male Oxidative Stress Infertility, or MOSI, as a novel descriptor for infertile men with abnormal semen characteristics and OS, including many patients who were previously classified as having idiopathic male infertility. Oxidation-reduction potential (ORP) can be a useful clinical biomarker for the classification of MOSI, as it takes into account the levels of both oxidants and reductants (antioxidants). Current treatment protocols for OS, including the use of antioxidants, are not evidence-based and have the potential for complications and increased healthcare-related expenditures. Utilizing an easy, reproducible, and cost-effective test to measure ORP may provide a more targeted, reliable approach for administering antioxidant therapy while minimizing the risk of antioxidant overdose. With the increasing awareness and understanding of MOSI as a distinct male infertility diagnosis, future research endeavors can facilitate the development of evidence-based treatments that target its underlying cause.

The excessive use of antioxidant therapy: A possible cause of male infertility?

Reactive oxygen species and oxidative stress are closely associated with various pathologies such as neurodegenerative diseases, ageing and male infertility. Hence, antioxidants such as vitamin C, vitamin E, N-acetyl cysteine, L-carnitine and folic acid are regularly used in various treatment regimens to protect cells from the damage induced by free radicals. However, given their over-the-counter availability at unnaturally high concentrations and also the fact that they are commonly added to various food products, patients may run a risk of consuming excessive dosages of these compounds, which may then be toxic. The few studies that have assessed antioxidant overuse and the associated adverse effects found that large doses of dietary antioxidant supplements have varying-if any-therapeutic effects even though free radicals clearly damage cells-a phenomenon that has been termed the "antioxidant paradox." Furthermore, overuse of antioxidants such as vitamin C, vitamin E, N-acetyl cysteine may lead to reductive stress, which is reported to be as dangerous to cells as oxidative stress and can be the cause of diseases such as cancer or cardiomyopathy. Therefore, we feel that there is a need for more elaborate research to establish the clear benefits and risks involved in antioxidant therapy for male infertility.

Role of Antioxidants in Assisted Reproductive Techniques

Oxidative stress (OS) has been recognized as a significant cause of suboptimal assisted reproductive outcome. Many of the sperm preparation and manipulation procedures that are necessary in the in vitro environment can result in excessive production of reactive oxygen species (ROS) thereby exposing the gametes and growing embryos to significant oxidative damage. Antioxidants have long been utilized in the management of male subfertility as they can counterbalance the elevated levels of ROS inducing a high state of OS. Few studies have looked into the clinical effectiveness of antioxidants in patients undergoing assisted reproduction. While an overall favorable outcome has been perceived, the specific clinical indication and optimal antioxidant regimen remain unknown. The goal of our review is to explore the sources of ROS in the in vitro environment and provide a clinical scenario-based approach to identify the circumstances where antioxidant supplementation is most beneficial to enhance the outcome of assisted reproduction.

Folic Acid and Grape Seed Extract Prevent Azathioprine-induced Fetal Malformations and Renal Toxicity in Rats

Azathioprine (AZA) is an important drug commonly used in the therapy of the autoimmune system disorders. It induces many hazard effects that restrict its use. The present study was designed to investigate the influence of AZA on the fetal development and renal function and its co-administration with either folic acid (FA) or grape seed extract (GSE). The effects of administration of GSE or FA on AZA toxicity by gavage simultaneously for 4 weeks were studied by determining the changes in kidney histology, the glutathione level (GSH), and lipid per oxidation content as malondialdehyde in the kidney tissue. Additionally, their effects on the fetal development were investigated. Azathioprine induced a renal damage as indicated from the pronounced changes in histological structure, a significant increase in serum urea and creatinine, and malondialdehyde content in the kidney tissue. Meanwhile, the GSH activity was significantly decreased. Co-treatment with GSE significantly minimized the previously mentioned hazard effects of AZA by ameliorating the antioxidant activity. At this point, FA induced a nonsignificant protective activity. The results also revealed that administration of FA or GSE at 6th to 15th day of gestation did not altered fetal development. While, AZA administration clearly disturbed fetal development as indicated from a significant decrease in fetal weights. Furthermore, co-administration of both drugs significantly minimized similarly the hazards of AZA on the fetal development. It may be concluded that GSE and FA are a useful remedies. Maternal administrations of either both are protective agents against AZA-induced fetal malformations. Grape seed extract was more active than FA in potentiating the antioxidative defenses for controlling AZA-induced oxidative renal damages. Copyright © 2016 John Wiley & Sons, Ltd.

Social behavioral testing and brain magnetic resonance imaging in chicks exposed to mobile phone radiation during development

Background

The potential adverse effect of mobile phone radiation is currently an area of great concern in the field of public health. In the present study, we aimed to investigate the effect of mobile phone radiation (900 MHz radiofrequency) during hatching on postnatal social behaviors in chicks, as well as the effect on brain size and structural maturity estimated using 3.0 T magnetic resonance imaging. At day 4 of incubation, 76 normally developing chick embryos were divided into the control group (n = 39) and the radiation group (n = 37). Eggs in the radiation group were exposed to mobile phone radiation for 10 h each day from day 4 to 19 of incubation. Behavioral tests were performed 4 days after hatching. T2-weighted MR imaging and diffusion tensor imaging (DTI) were subsequently performed. The size of different brain subdivisions (telencephalon, optic lobe, brain stem, and cerebellum) and corresponding DTI parameters were measured. The Chi-square test and the student’s t test were used for statistical analysis. P < 0.05 was considered statistically significant.

Results

Compared with controls, chicks in the radiation group showed significantly slower aggregation responses (14.87 ± 10.06 vs. 7.48 ± 4.31 s, respectively; P < 0.05), lower belongingness (23.71 ± 8.72 vs. 11.45 ± 6.53 s, respectively; P < 0.05), and weaker vocalization (53.23 ± 8.60 vs. 60.01 ± 10.45 dB/30 s, respectively; P < 0.05). No significant differences were found between the radiation and control group for brain size and structural maturity, except for cerebellum size, which was significantly smaller in the radiation group (28.40 ± 1.95 vs. 29.95 ± 1.41 cm², P < 0.05). The hatching and heteroplasia rates were also calculated and no significant difference was found between the two groups.

Conclusions

Mobile phone radiation exposure during chick embryogenesis impaired social behaviors after hatching and possibly induced cerebellar retardation. This indicates potential adverse effects of mobile phone radiation on brain development.

Dietary Alpha-Lipoic Acid Alters Piglet Neurodevelopment

INTRODUCTION

Alpha-lipoic acid (a-LA) is an antioxidant shown to ameliorate age-associated impairments of brain and cardiovascular function. Human milk is known to have high antioxidant capacity; however, the role of antioxidants in the developing brain is largely uncharacterized. This exploratory study aimed to examine the dose-response effects of a-LA on piglet growth and neurodevelopment.

METHODS

Beginning at 2 days of age, 31 male pigs received 1 of 3 diets: control (CONT) (0 mg a-LA/100 g), low a-LA (LOW) (120 mg a-LA/100 g), or high a-LA (HIGH) (240 mg a-LA/100 g). From 14 to 28 days of age, pigs were subjected to spatial T-maze assessment, and macrostructural and microstructural neuroimaging procedures were performed at 31 days of age.

RESULTS

No differences due to diet were observed for bodyweight gain or intestinal weight and length. Spatial T-maze assessment did not reveal learning differences due to diet in proportion of correct choices or latency to choice measures. Diffusion tensor imaging revealed decreased (P = 0.01) fractional anisotropy (FA) in the internal capsule of HIGH-fed pigs compared with both the CONT (P < 0.01)- and LOW (P = 0.03)-fed pigs, which were not different from one another. Analysis of axial diffusivity (AD) within the internal capsule revealed a main effect of diet (P < 0.01) in which HIGH-fed piglets exhibited smaller (P < 0.01) rates of diffusion compared with CONT piglets, but HIGH-fed piglets were not different (P = 0.12) than LOW-fed piglets. Tract-based spatial statistics, a comparison of FA values along white matter tracts, revealed 1,650 voxels where CONT piglets exhibited higher (P < 0.05) values compared with HIGH-fed piglets.

CONCLUSION

The lack of differences in intestinal and bodyweight measures among piglets indicate a-LA supplementation does not impact overall growth, regardless of concentration. Additionally, no observed differences between CONT- and LOW-fed piglets in behavior and neuroimaging measures indicate a low concentration of a-LA does not affect normal brain development. Supplementation of a-LA at a high concentration appeared to alter white matter maturation in the internal capsule, which may indicate delayed neurodevelopment in these piglets.

Expression of peroxiredoxins and thioredoxins in the mouse spinal cord during embryonic development

Reactive oxygen and nitrogen species (ROS/RNS) are natural byproducts of cellular metabolism. Although these molecules are deleterious at high concentrations, moderate levels of ROS/RNS are essential for normal cell function and take part in numerous cellular processes. The regulation of ROS/RNS is largely attended by peroxiredoxins (Prdxs) and their main reductants, thioredoxins (Trxs). Through their oxidoreductase activities, the members of the Trx/Prdx system can also affect certain cellular processes, notably many implicated in central nervous system (CNS) development. Although several studies have investigated the expression of Prdxs and Trxs in mouse, rat, and human adult CNS, few data are available concerning embryonic stages. In this work, we use immunofluorescence analyses to study the distribution of these enzymes during prenatal mouse spinal cord development. Our results highlight several patterns that contrast with available data for the adult. Indeed, Prdx1, Prdx4, and Prdx6, which are expressed in glial cells in the adult CNS, present clear neuronal localization in mouse spinal cord during embryonic development. Additionally, Prdx1, Prdx2, and to a lesser extent Prdx4, Prdx6, and Trx1 are localized mainly in the nucleus of neural cells. Finally, we identified a consistent, intense expression of all Prdxs and Trxs in groups of cells located in ventral regions of the spinal cord that express motor neuronal markers. These striking expression patterns suggest novel functions of these enzymes at these stages and offer clues to the role of the Trx/Prdx system during embryonic development of the spinal cord.

Impact of oxidative stress in fetal programming

Intrauterine stress induces increased risk of adult disease through fetal programming mechanisms. Oxidative stress can be generated by several conditions, such as, prenatal hypoxia, maternal under- and overnutrition, and excessive glucocorticoid exposure. The role of oxidant molecules as signaling factors in fetal programming via epigenetic mechanisms is discussed. By linking oxidative stress with dysregulation of specific target genes, we may be able to develop therapeutic strategies that protect against organ dysfunction in the programmed offspring.

A cell-permeable phosphine-borane complex delays retinal ganglion cell death after axonal injury through activation of the pro-survival extracellular signal-regulated kinases 1/2 pathway

The reactive oxygen species (ROS) superoxide has been recognized as a critical signal triggering retinal ganglion cell (RGC) death after axonal injury. Although the downstream targets of superoxide are unknown, chemical reduction of oxidized sulfhydryls has been shown to be neuroprotective for injured RGCs. On the basis of this, we developed novel phosphine-borane complex compounds that are cell permeable and highly stable. Here, we report that our lead compound, bis (3-propionic acid methyl ester) phenylphosphine borane complex 1 (PB1) promotes RGC survival in rat models of optic nerve axotomy and in experimental glaucoma. PB1-mediated RGC neuroprotection did not correlate with inhibition of stress-activated protein kinase signaling, including apoptosis stimulating kinase 1 (ASK1), c-jun NH2-terminal kinase (JNK) or p38. Instead, PB1 led to a striking increase in retinal BDNF levels and downstream activation of the extracellular signal-regulated kinases 1/2 (ERK1/2) pathway. Pharmacological inhibition of ERK1/2 entirely blocked RGC neuroprotection induced by PB1. We conclude that PB1 protects damaged RGCs through activation of pro-survival signals. These data support a potential cross-talk between redox homeostasis and neurotrophin-related pathways leading to RGC survival after axonal injury.

The Roles of Glutathione Peroxidases during Embryo Development

Embryo development relies on the complex interplay of the basic cellular processes including proliferation, differentiation, and apoptotic cell death. Precise regulation of these events is the basis for the establishment of embryonic structures and the organ development. Beginning with fertilization of the oocyte until delivery the developing embryo encounters changing environmental conditions such as varying levels of oxygen, which can give rise to reactive oxygen species (ROS). These challenges are met by the embryo with metabolic adaptations and by an array of anti-oxidative mechanisms. ROS can be deleterious by modifying biological molecules including lipids, proteins, and nucleic acids and may induce abnormal development or even embryonic lethality. On the other hand ROS are vital players of various signaling cascades that affect the balance between cell growth, differentiation, and death. An imbalance or dysregulation of these biological processes may generate cells with abnormal growth and is therefore potentially teratogenic and tumorigenic. Thus, a precise balance between processes generating ROS and those decomposing ROS is critical for normal embryo development. One tier of the cellular protective system against ROS constitutes the family of selenium-dependent glutathione peroxidases (GPx). These enzymes reduce hydroperoxides to the corresponding alcohols at the expense of reduced glutathione. Of special interest within this protein family is the moonlighting enzyme glutathione peroxidase 4 (Gpx4). This enzyme is a scavenger of lipophilic hydroperoxides on one hand, but on the other hand can be transformed into an enzymatically inactive cellular structural component. GPx4 deficiency - in contrast to all other GPx family members - leads to abnormal embryo development and finally produces a lethal phenotype in mice. This review is aimed at summarizing the current knowledge on GPx isoforms during embryo development and tumor development with an emphasis on GPx4.

Redox control in mammalian embryo development

The development of an embryo constitutes a complex choreography of regulatory events that underlies precise temporal and spatial control. Throughout this process the embryo encounters ever changing environments, which challenge its metabolism. Oxygen is required for embryogenesis but it also poses a potential hazard via formation of reactive oxygen and reactive nitrogen species (ROS/RNS). These metabolites are capable of modifying macromolecules (lipids, proteins, nucleic acids) and altering their biological functions. On one hand, such modifications may have deleterious consequences and must be counteracted by antioxidant defense systems. On the other hand, ROS/RNS function as essential signal transducers regulating the cellular phenotype. In this context the combined maternal/embryonic redox homeostasis is of major importance and dysregulations in the equilibrium of pro- and antioxidative processes retard embryo development, leading to organ malformation and embryo lethality. Silencing the in vivo expression of pro- and antioxidative enzymes provided deeper insights into the role of the embryonic redox equilibrium. Moreover, novel mechanisms linking the cellular redox homeostasis to gene expression regulation have recently been discovered (oxygen sensing DNA demethylases and protein phosphatases, redox-sensitive microRNAs and transcription factors, moonlighting enzymes of the cellular redox homeostasis) and their contribution to embryo development is critically reviewed.

Effectiveness of Novel Borane-Phosphine Complexes In Inhibiting Cell Death Depends on the Source of Superoxide Production Induced by Blockade of Mitochondrial Electron Transport

Central neurons undergo cell death after axotomy. One of the signaling pathways for this process is oxidative modification of one or more critical sulfhydryls in association with superoxide generation within mitochondria. Agents that reduce oxidized sulfhydryls are neuroprotective of axotomized retinal ganglion cells, and we hypothesized that this occurs via reversal of the effects of mitochondrial-produced superoxide. To study this, we measured the ability of the novel borane-phosphine complex drugs bis(3-propionic acid methyl ester)phenylphosphine borane complex (PB1) and (3-propionic acid methyl ester)diphenylphosphine borane complex (PB2) to inhibit the death of neuron-like RGC-5 cells induced by perturbation of the mitochondrial electron transport chain. We found that borane-phosphine complexes prevent neuronal cell death from superoxide produced by the redox-cycling agent menadione and the complex III inhibitor antimycin A, which produce superoxide towards the cytoplasm and matrix, but not the complex I inhibitor rotenone, which produces superoxide in the matrix alone. The ability of these disulfide reductants to prevent cell death may be predicted by the topology of superoxide production with respect to the mitochondrial matrix and extramitochondrial space.

The impact of human superoxide dismutase 1 expression in a mouse model on the embryotoxicity of hydroxyurea

BACKGROUND

Oxidative stress is hypothesized to mediate embryotoxicity during organogenesis, yet the reactive oxygen species involved are not defined. The superoxide oxygen radical is converted to hydrogen peroxide, a less reactive species, by superoxide dismutases (SODs). If superoxide is important in mediating embryotoxicity, increased SOD expression should protect embryos against insult. Exposure to hydroxyurea during organogenesis causes brain defects, cleft palate, tail anomalies, and limb defects; administration of D-mannitol, a free radical scavenger, ameliorates hydroxyurea embryotoxicity, suggesting that oxidative stress is important. To elucidate the role of superoxide in mediating hydroxyurea embryotoxicity, we assessed the impact of human SOD1 expression in a murine model.

METHODS

hSOD1 hemizygous male mice, carrying the human SOD1 gene, were mated to wild-type or hSOD1 hemizygous females. Dams were treated on gestation day (GD) 9 with saline (control) or 400 (low) or 600 (high) mg/kg hydroxyurea (n = 8-13/group). Mice were euthanized on GD 18 and developmental toxicity was assessed.

RESULTS

Exposure to hydroxyurea caused a dose-dependent increase in fetal deaths that was not affected by hSOD1 expression; hydroxyurea decreased fetal weights in litters from wild-type but not hemizygous dams. Hydroxyurea increased the incidence of external and skeletal malformations; fetuses from hemizygous dams treated with high-dose hydroxyurea had fewer malformations compared to wild-type dams. There was no correlation between embryonic phenotype and genotype or SOD activity.

CONCLUSION

Maternal hSOD1 expression protected fetuses against malformations induced by hydroxyurea, providing evidence that superoxide plays a role in mediating the response of organogenesis stage embryos to this teratogen.

Effects of oxidative stress on embryonic development

Oxygen radicals, or reactive oxygen species (ROS) act as primary or secondary messengers to promote cell growth or death. Many instances demonstrate an important direct role of ROS in development because redox status regulates key transcription factors that influence cell signaling pathways involved in proliferation, differentiation, and apoptosis. Therefore, oxidative stress can alter many important reactions that affect embryonic development both positively and negatively. During particular periods in development, the embryo is more or less susceptible to oxidative stress, and teratogens, which can modify redox status, such as thalidomide, phenytoin, and ethanol, will disrupt fetal development. Various events in pregnancy such as diabetes also alter the redox state. Fortunately, antioxidants can obviate these effects through modification of gene expression, transcription factor signaling, and cell cycle alterations. A better understanding of ROS-mediated reactions and their impact on embryonic development is important to ensure optimal outcomes.

Neuroprotective effect of STAZN, a novel azulenyl nitrone antioxidant, in focal cerebral ischemia in rats: dose-response and therapeutic window

Stilbazulenyl nitrone (STAZN) is a potent antioxidant that, in a rat model of transient focal cerebral ischemia, confers significant enduring functional and morphological neuroprotection. This study investigated the influence of dose and time of administration on the neuroprotective effects of STAZN in the intraluminal suture model of middle cerebral artery occlusion (MCAo). Dose response: At 2 and 4 h after the onset of MCAo, animals received intravenously either STAZN (low dose=0.07 mg/kg, n=8; medium dose=0.7 mg/kg, n=9; high dose=3.5 mg/kg, n=9), an equivalent volume of vehicle (30% Solutol HS15 and 70% isotonic saline, 0.37 ml/kg, n=5) or saline (0.37 ml/kg, n=5). Only the medium dose improved scores (p<0.05) on a standardized neurobehavioral test at 1, 2 and 3 days after MCAo. Only the medium dose reduced the total infarction (51%, p=0.014) compared to controls. These results indicate that STAZN exhibits maximal neuroprotection at the 0.7 mg/kg dose. Therapeutic window: STAZN (0.6 mg/kg) dissolved in dimethylsulfoxide was given intra-peritoneally at 2 and 4 h (n=11), 3 and 5 h (n=10), 4 and 6 h (n=10) or 5 and 7 h (n=7) after the onset of MCAo. Additional doses were given at 24 and 48 h. Vehicle (dimethylsulfoxide, 2.0 ml/kg, n=6) was administered at 3, 5, 24 and 48 h. STAZN treatment initiated at 2 or 3 h after the onset of MCAo improved neurological scores (p<0.001) and reduced total infarction (42.2%, p<0.05) compared to controls.

Synthesis and characterization of a novel class of reducing agents that are highly neuroprotective for retinal ganglion cells

Retinal ganglion cells (RGCs) undergo apoptosis after axonal injury, in part regulated by an intracellular superoxide anion burst, for which the target(s) are unknown. Shifting the RGC redox state towards reduction and preventing sulfhydryl oxidation is neuroprotective in vitro and in vivo, implying that one or more sulfhydryls on one or more critical proteins may be involved. We synthesized novel borane-protected analogues of the reductant tris(2-carboxyethyl)phosphine (TCEP) with the intent of increasing cell permeability and improving chemical stability, and tested their ability to increase RGC survival in vitro. Retinal ganglion cells of postnatal day 2-4 Long-Evans rats were retrogradely labeled with 4',6-diamidino-2-phenylindole (DAPI). At postnatal days 11-13 the animals were sacrificed, the retinas enzymatically dissociated and plated on poly-L-lysine-coated 96-well flat-bottomed tissue culture plates for 72 h in Neurobasal-A, B27 supplement lacking antioxidants, and TCEP, bis(3-propionic acid methyl ester)phenylphosphine borane complex (PB1), (3-propionic acid methyl ester)diphenylphosphine borane complex (PB2), or three commercially available phosphines. Viable DAPI-positive RGCs were identified by calcein-AM staining. At 72 h, PB1 was effective at rescuing acutely axotomized RGCs at concentrations from 1 nM to 100 microM. RGC survival with 1 nM PB1 was 174+/-12% of control (p=0.002). Another compound, PB2, rescued RGCs at 10 pM (177+/-24%; p=0.006) and 10 nM (251+/-34%; p=0.004) at 72 h. A PAMPA assay demonstrated that PB1 and PB2 were substantially more permeable than TCEP. These data demonstrate that modified reductants are effective RGC neuroprotectants at picomolar-nanomolar concentrations. We propose that these novel molecules may act by inhibiting the sulfhydryl oxidation effect of an intracellular superoxide burst.

Amplification of a reactive oxygen species signal in axotomized retinal ganglion cells

Retinal ganglion cells (RGCs) undergo apoptosis after axonal injury. Elucidation of the sequence of intracellular events proximal to caspase activation may allow development of effective neuroprotective strategies. In this study, we explored the role that reactive oxygen species may have in signaling RGC apoptosis after axonal injury. Using the fluorescent probe dihydroethidium, we were able to measure intracellular superoxide anion production. We found that axotomized RGCs exposed to oxidative stress exhibited a secondary superoxide burst. The broad-spectrum caspase inhibitor Z-Val-Ala-DL-Asp-fluoromethyl ketone did not block the burst, suggesting it is proximal to caspase activation, but it was inhibited by cycloheximide, consistent with a requirement for protein synthesis. These results are consistent with RGC axotomy inducing synthesis of one or more proteins that mediate oxidative amplification. This could be an early event in signaling of RGC apoptosis after axonal injury.

Stilbazulenyl nitrone, a novel antioxidant, is highly neuroprotective in focal ischemia

Azulenyl nitrones are novel chain-breaking antioxidants with low oxidation potentials and high lipophilicity-properties favoring their efficacy as neuroprotectants. We tested the second-generation azulenyl nitrone, stilbazunenlyl nitrone (STAZN), in focal ischemic stroke. Physiologically monitored rats received 2 hours of middle cerebral artery occlusion by intraluminal suture, resulting in substantial cortical and striatal infarcation. Neurobehavior was quantified on a standard battery, and brains were perfusion-fixed for quantitative histopathology at 3 days. In 3 independent series, rats were treated at either 2h + 4h, or 2h + 4h + 24h + 48h, after onset of ischemia; vehicle-treated rats received dimethylsulfoxide or saline. All animals (n = 52) developed high-grade neurological deficits (score 11 of 12) during ischemia, which improved, in STAZN-treated rats, within 1-1.5 h of the initial dose and fell to a median score of 3 at 72 h, compared to 8 in vehicle rats. STAZN treatment reduced mean cortical infarct volume by 64-97%, and total infarct volume by 42-72%. In over one-half of STAZN-treated animals, cortical infarction was virtually abolished. Regression analysis predicted that STAZN would confer approximately 50% cortical neuroprotection even in the most severely affected cases. The potency of STAZN was orders-of-magnitude greater than other nitrones such as NXY-059. These results suggest that STAZN has great promise for ischemic stroke.

Early events of target deprivation/axotomy-induced neuronal apoptosis in vivo: oxidative stress, DNA damage, p53 phosphorylation and subcellular redistribution of death proteins

The mechanisms of injury- and disease-associated apoptosis of neurons within the CNS are not understood. We used a model of cortical injury in rat and mouse to induce retrograde neuronal apoptosis in thalamus. In this animal model, unilateral ablation of the occipital cortex induces apoptosis of corticopetal projection neurons in the dorsal lateral geniculate nucleus (LGN), by 7 days post-lesion, that is p53 modulated and Bax dependent. We tested the hypothesis that this degenerative process is initiated by oxidative stress and early formation of DNA damage and is accompanied by changes in the levels of pro-apoptotic mediators of cell death. Immunoblotting revealed that the protein profiles of Bax, Bak and Bad were different during the progression of neuronal apoptosis in the LGN. Bax underwent a subcellular redistribution by 1 day post-lesion, while Bak increased later. Bad showed an early sustained increase. Cleaved caspase-3 was elevated maximally at 5 and 6 days. Active caspase-3 underwent a subcellular translocation to the nucleus. A dramatic phosphorylation of p53 was detected at 4 days post-lesion. DNA damage was assessed immunocytochemically as hydroxyl radical adducts (8-hydroxy-2-deoxyguanosine) and single-stranded DNA. Both forms of DNA damage accumulated early in target-deprived LGN neurons. Transgenic overexpression of superoxide dismutase-1 provided significant protection against the apoptosis but antioxidant pharmacotreatments with trolox and ascorbate were ineffective. We conclude that overlapping and sequential signaling pathways are involved in the apoptosis of adult brain neurons and that DNA damage generated by superoxide derivatives is an upstream mechanism for p53-regulated, Bax-dependent apoptosis of target-deprived neurons.

Ultrastructure of retinal ganglion cell death after axotomy in chick embryos

Axotomy often leads to neuronal death, which occurs after a particularly short delay in immature animals. Tectal lesions were made in embryonic day (E) 12 chick embryos, thereby axotomizing the retinal ganglion cells of the contralateral eye, which then died within 3 days. We here describe the ultrastructural changes in the axotomized ganglion cells. The main changes were nuclear invagination and type 3B (cytoplasmic type) cell death characterized by dilation of the perinuclear space, endoplasmic reticulum, and Golgi apparatus. However, nuclear invagination was never seen in type 3B dying cells. All the axotomy-induced retinal ganglion cell death appears to have been of type 3B; apoptosis was not induced by axotomy, as was confirmed by additional light microscopic experiments showing that it did not increase the frequency of apoptotic markers revealed by terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling (the TUNEL method) labeling and immunoreactivity for activated caspase-3. However, the latter methods did show small numbers of apoptotic cells dying naturally even in control retinas. After the death of the axotomized ganglion cells, they were phagocytosed mainly in Müller processes. The present findings open up the chick tectal lesion model as a system for analyzing type 3B neuronal death in vivo.

Stilbazulenyl nitrone, a novel azulenyl nitrone antioxidant: improved neurological deficit and reduced contusion size after traumatic brain injury in rats

OBJECT

Stilbazulenyl nitrone (STAZN) is a second-generation azulenyl nitrone that has markedly enhanced antioxidant properties compared with those of conventional alpha-phenyl nitrones. In this study, the authors assessed the potential efficacy of STAZN in a rodent model of fluid-percussion brain injury, which results in a consistent cortical contusion.

METHODS

After anesthesia had been induced in normothermic Sprague-Dawley rats (brain temperature 36-36.5 degrees C) by halothane-nitrous oxide, the animals were subjected to a right parietooccipital parasagittal fluid-percussion injury (1.5-2 atm). The agent (STAZN, 30 mg/kg: eight animals) or vehicle (dimethyl sulfoxide; eight animals) was administered intraperitoneally at 5 minutes and 4 hours after trauma. The neurological status of each rat was evaluated on Days 1, 2, and 7 postinjury (normal score 0, maximum injury 12). Seven days after trauma, the rat brains were perfusion fixed, coronal sections at various levels were digitized, and areas of contusion were measured. Treatment with STAZN significantly improved neurological scores on Days 2 and 7 postinjury compared with vehicle-treated rats. Administration of STAZN also significantly reduced the total contusion area by 63% (1.8 +/- 0.5 mm2 in STAZN-treated animals compared with 4.8 +/- 2.1 mm2 in vehicle-treated animals; p = 0.04) and the deep cortical contusion area by 60% (1.2 +/- 0.2 mm2 in STAZN-treated animals compared with 2.9 +/- 1.2 mm2 in vehicle-treated animals; p = 0.03). By contrast, hippocampal cell loss in the CA3 sector was unaffected by STAZN treatment.

CONCLUSIONS

Therapy with STAZN, a novel potent antioxidant, administered following traumatic brain injury, markedly improves neurological and histological outcomes. Azulenyl nitrones appear to represent a promising class of neuroprotective agents for combating this devastating condition.

Involvement of cyclin-dependent kinases in axotomy-induced retinal ganglion cell death

We have tested the role of cyclin-dependent kinases (CDKs) in the type 3B death of axotomized retinal ganglion cells, by injecting intraocularly olomoucine, roscovitine, or butyrolactone I. Each of these inhibits CDK1, CDK2, and CDK5; CDK1 and CDK2 are involved in cell proliferation, whereas CDK5 is involved in neuronal differentiation. The inhibitors partially protected ganglion cells against the effects of axotomy. These agents may affect the ganglion cells directly, because CDK1, its regulatory subunit cyclin B1, and CDK5 were identified immunohistochemically in the perikarya of ganglion cells, and this was confirmed for CDK1 and CDK5 in Western blots of the ganglion cell layer. These blots showed an axotomy-induced phosphorylation of CDK5 occurring remarkably quickly (within 6 hours of axotomy) but little if any change in the phosphorylation state of CDK1. In addition, we studied the expression of proliferation markers, including proliferating cell nuclear antigen (PCNA) and the synthesis of DNA, by immunohistochemical and autoradiographic methods. Normal or axotomized ganglion cells did not express PCNA and did not synthesize DNA. Although we cannot exclude the possibility that axotomized ganglion cells may leave their quiescent state, our data show that they did not progress beyond the G1 phase of the cell cycle. Finally, in contrast to inhibitors of CDKs, cell cycle blockers with different targets than CDKs did not protect ganglion cells. Globally, our results suggest that axotomy-induced death of ganglion cells involves the activation of CDK1, CDK2, or CDK5 (most probably CDK5) but not the full cell cycle machinery.

Reduced redox state allows prolonged survival of axotomized neonatal retinal ganglion cells

Axonal injury to CNS neurons results in apoptotic cell death. The processes by which axotomy signals apoptosis are diverse, and may include deprivation of target-derived factors, induction of injury factors, bursts of reactive oxygen species (ROS), and other mechanisms. Our previous studies demonstrated that death of a dissociated retinal ganglion cell, an identified CNS neuron, is ROS-dependent. To better define the mechanisms by which ROS induce retinal ganglion cell death after axotomy, we studied their effects in dissociated neonatal rat retinal cultures. Postnatal day 2-4 Long-Evans rat retinal ganglion cells were retrogradely labeled with the fluorescent tracer 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine (DiI). Postnatal day 7-9 retinas were dissociated and cultured in the presence of specific ROS generating systems, scavengers, or redox modulators. Retinal ganglion cells were identified by DiI positivity and viability determined by metabolism of calcein-acetoxymethyl ester. We found that ROS scavengers protected against retinal ganglion cell death after acute dissociation, and the effects of ROS appeared to be due to shifts in the redox potential, as retinal ganglion cell survival was critically dependent on redox state, with greatest survival under mildly reducing conditions. Culture of retinal ganglion cell with the non-thiol-containing reducing agent tris(carboxyethyl)phosphine resulted in long-term survival equivalent to or better than with neurotrophic factors. Our data suggest that axotomy-associated neuronal death induced by acute dissociation may be partly dependent on ROS production, acting to shift the redox state and oxidize one or more key thiols. Understanding the mechanisms by which ROS signal neuronal death could result in strategies for increasing their long-term survival after axonal injury.

Dual role of the NF-kappaB transcription factor in the death of immature neurons

We have previously shown that the extent of axotomy-induced death of retinal ganglion cells is reduced by cycloheximide, an inhibitor of protein synthesis, and that an earlier sublethal oxidative insult induced by buthionine sulfoximine, a glutathione synthesis inhibitor, enhances the protective effects of cycloheximide. Thus, axotomy-induced ganglion cell death seems to involve an interaction between the redox status and genetic expression. The redox-sensitive transcription factor nuclear factor-kappaB (NF-kappaB) is a logical candidate for providing this interaction. In the present study, we injected intraocularly selective inhibitors of NF-kappaB in chick embryos either unlesioned, or after a unilateral tectal lesion, which axotomizes ganglion cells. The number of dying cells in the retina contralateral to the lesion was reduced in embryos receiving NF-kappaB inhibitors as compared with vehicle-injected controls. In contrast, the same NF-kappaB inhibitors administered as pretreatment before intraocular injection of buthionine sulfoximine and cycloheximide drastically raised neuronal death and induced fulgurant degenerative changes in the retina. The most parsimonious interpretation of our results is that in axotomized retinal ganglion cells of chick embryos NF-kappaB may have either death-promoting or death-inhibiting effects. We propose a theoretical model to explain these dual effects assuming the existence of parallel death pathways differently affected by NF-kappaB. These results may have implications for future redox-based therapeutic strategies for neuroprotection.

Neuroprotective effects of a new glutathione peroxidase mimetic on neurons of the chick embryo's retina

During their period of naturally occurring neuronal death, retinal ganglion cells are particularly vulnerable to axotomy. The resulting cell death requires protein synthesis and is redox-regulated, since antioxidants protect axotomized-ganglion cells when given in doses that maintain the redox status near an optimal set-point. Here we report the effects of BXT-51072, a new glutathione peroxidase mimetic, on ganglion cell death induced in various ways in the retinas of chick embryos. The intraocular injection of BXT-51072 protected axotomized neurons at doses in a narrow (tenfold) range. It also reduced the deleterious effects of intraocular tert-butyl hydroperoxide, an inducer of lipid peroxidation, and diminished the excitotoxic degeneration induced by N-methyl-D-aspartate. However, BXT-51072 did not noticeably reduce naturally occurring cell death. Globally, our results show that BXT-51072 has numerous protective effects in the retina. In accordance with published data, the present report indicates that glutathione peroxidase mimetics may have potential applications for neurologic or degenerative diseases.

Inhibitors of mitogen-activated protein kinases protect axotomized developing neurons

Axotomy kills developing neurons by mechanisms dependent on protein synthesis and influenced by the redox status. Amongst the redox-regulated transduction systems regulating gene expression are the mitogen-activated protein kinases (MAPKs). In the chick embryo, inhibitors of two different MAPK pathways, including notably the p38 kinase pathway, reduce the number of dying axotomized retinal ganglion cells. The regulation of the genetic events associated to axotomy-induced death thus seems to involve MAPKs.