Sex differences in antioxidant defence and the regulation of redox homeostasis in physiology and pathology

Sepsis after middle cerebral artery occlusion exacerbates peripheral oxidative stress in a sex-specific manner

Ischemic stroke occurs due a blockage in the blood flow to the brain, leading to damage to the nervous system. The prevalent morbidities resulting from stroke include post-stroke infection, as sepsis. Additionally, oxidative stress is recognized for inducing functional deficits in peripheral organs during sepsis. Therefore, sex differences in stroke exist and we aimed to investigate the peripheral oxidative stress caused by sepsis after stroke in male and female rats. Wistar rats (male and female) were divided into sham+sham, middle cerebral artery occlusion (MCAO) + sham, sham+ cecal ligation and perforation (CLP) and MCAO+CLP groups to males and female rats. Animals were subjected to MCAO or sham and after 7 days, were subjected to sepsis by CLP or sham. After 24 h, serum, total brain, lung, liver, heart, and spleen were collected. Brain edema, myeloperoxidase (MPO) activity, nitrite/nitrate (N/N) concentration, oxidative damage to lipids and proteins, and catalase activity were evaluated. Brain edema was observed only in male rats in MCAO+CLP group compared to MCAO+sham. Regarding MPO activity, an increase was verified in male in different organs and serum in MCAO+CLP group. For N/N levels, the increase was more pronounced in females submitted to MCAO+CLP. In general, to oxidative stress, an increase was only observed in animals exposed to MCAO+CLP, or with a greater increase in this group compared to the others. The findings provided the first indication that animals exposed to MCAO exhibit a heightened vulnerability to the harmful impacts of sepsis, as evidenced by brain edema and peripheral oxidative stress, and this susceptibility is dependent of sex.

Sex Differences in Impacts of Early Gestational and Peri-Adolescent Ozone Exposure on Lung Development in Rats: Implications for Later Life Disease in Humans

Air pollution exposure during pregnancy may affect fetal growth. Fetal growth restriction (FGR) is associated with reduced lung function in children that can persist into adulthood. Using an established model of asymmetrical FGR in Long-Evans rats, this study investigated sex differences in effects of early life ozone exposure on lung development and maturation. Adverse health effects for i) gestational exposure (with impacts on primary alveolarization), ii) peri-adolescent exposure (with impacts on secondary alveolarization), and iii) cumulative exposure across both periods were evaluated. Notably, female offspring were most affected by gestational ozone exposure, likely because of impaired angiogenesis and corresponding decreases in primary alveolarization. Females had diminished lung capacity, fewer mature alveoli, and medial hypertrophy of small and large pulmonary arteries. Males, especially FGR-prone offspring, were more affected by peri-adolescent ozone exposure. Males had increased ductal areas, likely due to disrupted secondary alveolarization. Altered lung development may increase risk of developing diseases, such as pulmonary arterial hypertension or chronic obstructive pulmonary disease. Pulmonary arterial hypertension disproportionately affects women. In the United States, chronic obstructive pulmonary disease prevalence is increasing, especially in women; and prevalence for both men and women is highest in urbanized areas. This investigation underlines the importance of evaluating results separately by sex, and provides biologic plausibility for later consequences of early-life exposure to ozone, a ubiquitous urban air pollutant.

Time of day differences in the regulation of glutathione levels in the rat lens

Introduction

Evidence in non-ocular tissues indicate that the antioxidant glutathione (GSH) may be regulated in a circadian manner leading to the idea that GSH levels in the lens may also be controlled in a circadian manner to anticipate periods of oxidative stress.

Methods

Male rat Wistar lenses (6 weeks) were collected every 4 hours over a 24-hour period at 6am, 10am, 2pm, 6pm, 10pm and 2am and quantitative-PCR, western blotting and immunohistochemistry performed to examine the expression of core clock genes and proteins (BMAL1, CLOCK, CRY1-2, PER 1-3) and their subcellular localisation over a 24-hour period. Western blotting of lenses was also performed to examine the expression of NRF2, a transcription factor involved in regulating genes involved in GSH homeostasis and GSH related enzymes (GCLC, GS and GR) over the 24-hour period. Finally, HLPC was used to measure GSH levels in the aqueous humour and lenses every 4 hours over a 24-hour period.

Results

The rat lens contains the core molecular components of a circadian clock with the expression of core clock proteins, NRF2 and GSH related enzymes fluctuating over a 24-hour period. BMAL1 expression was highest during the day, with BMAL1 localised to the nuclei at 10am. NRF2 expression remained constant over the 24-hour period, although appeared to move in and out of the nuclei every 4 hours. GSH related enzyme expression tended to peak at the start of night which correlated with high levels of GSH in the lens and lower levels of GSH in the aqueous humour.

Conclusion

The lens contains the key components of a circadian clock, and time-of-day differences exist in the expression of GSH and GSH related enzymes involved in maintaining GSH homeostasis. GSH levels in the rat lens were highest at the start of night which represents the active phase of the rat when high GSH levels may be required to counteract oxidative stress induced by cellular metabolism. Future work to directly link the clock to regulation of GSH levels in the lens will be important in determining whether the clock can be used to help restore GSH levels in the lens.

Glutathione overproduction mediates lymphoma initiating cells survival and has a sex-dependent effect on lymphomagenesis

Lymphoid tumor patients often exhibit resistance to standard therapies or experience relapse post-remission. Relapse is driven by Tumor Initiating Cells (TICs), a subset of tumor cells capable of regrowing the tumor and highly resistant to therapy. Growing cells in 3D gels is a method to discern tumorigenic cells because it strongly correlates with tumorigenicity. The finding that TICs, rather than differentiated tumor cells, grow in 3D gels offers a unique opportunity to unveil TIC-specific signaling pathways and therapeutic targets common to various cancer types. Here, we show that culturing lymphoid cells in 3D gels triggers reactive oxygen species (ROS) production, leading to non-tumor lymphoid cell death while enabling the survival and proliferation of a subset of lymphoma/leukemia cells, TICs or TIC-like cells. Treatment with the antioxidant N-acetylcysteine inhibits this lethality and promotes the growth of primary non-tumor lymphoid cells in 3D gels. A subset of lymphoma cells, characterized by an increased abundance of the antioxidant glutathione, escape ROS-induced lethality, a response not seen in non-tumor cells. Reducing glutathione production in lymphoma cells, either through pharmacological inhibition of glutamate cysteine ligase (GCL), the enzyme catalyzing the rate-limiting step in glutathione biosynthesis, or via knockdown of GCLC, the GCL catalytic subunit, sharply decreased cell growth in 3D gels and xenografts. Tumor cells from B-cell lymphoma/leukemia patients and λ-MYC mice, a B-cell lymphoma mouse model, overproduce glutathione. Importantly, pharmacological GCL inhibition hindered lymphoma growth in female λ-MYC mice, suggesting that this treatment holds promise as a therapeutic strategy for female lymphoma/leukemia patients.

The impact of high-fat diet consumption and inulin fiber supplementation on anxiety-related behaviors and liver oxidative status in female Wistar rats

BACKGROUND

Obesity is a worldwide public health problem associated with cognitive and mental health problems in both humans and rats. Studies assessing the effect of fiber supplementation on behavioral deficits and oxidative stress caused by high-fat diet (HFD) consumption in female rats are still scarce. We hypothesized that HFD consumption would lead to anxiety-related behavior and hepatic oxidative stress and that inulin would protect against these changes. We analyzed the impact of HFD-induced obesity combined with fiber supplementation (inulin) on anxiety-related defensive behavior and hepatic oxidative stress.

RESULTS

Female rats were fed a high-fat diet (HFD; 45%) for nine weeks to induce obesity. The administration of inulin was found to decrease the adiposity index in both the control and obese groups. The consumption of a HFD combined with inulin supplementation resulted in a reduction in both CAT activity and carbonylated protein levels, leading to a shift in the hepatic redox balance. Interestingly, the behavioral data were conflicting. Specifically, animals that consumed a high-fat diet and received inulin showed signs of impaired learning and memory caused by obesity. The HFD did not impact anxiety-related behaviors in the female rats. However, inulin appears to have an anxiolytic effect, in the ETM, when associated with the HFD. On the other hand, inulin appears to have affected the locomotor activity in the HFD in both open field and light-dark box.

CONCLUSION

Our results show that consumption of a HFD induced obesity in female rats, similar to males. However, HFD consumption did not cause a consistent increase in anxiety-related behaviors in female Wistar rats. Treatment with inulin at the dosage used did not exert consistent changes on the behavior of the animals, but attenuated the abdominal WAT expansion and the hepatic redox imbalance elicited by high-fat diet-induced obesity.

The impact of physical activity on promoter-specific methylation of genes involved in the redox-status and disease progression: A longitudinal study on post-surgery female breast cancer patients undergoing medical treatment

Most anticancer treatments act on oxidative-stress pathways by producing reactive oxygen species (ROS) to kill cancer cells, commonly resulting in consequential drug-induced systemic cytotoxicity. Physical activity (PA) has arisen as an integrative cancer therapy, having positive health effects, including in redox-homeostasis. Here, we investigated the impact of an online supervised PA program on promoter-specific DNA methylation, and corresponding gene expression/activity, in 3 antioxidants- (SOD1, SOD2, and CAT) and 3 breast cancer (BC)-related genes (BRCA1, L3MBTL1 and RASSF1A) in a population-based sample of women diagnosed with primary BC, undergoing medical treatment. We further examined mechanisms involved in methylating and demethylating pathways, predicted biological pathways and interactions of exercise-modulated molecules, and the functional relevance of modulated antioxidant markers on parameters related to aerobic capacity/endurance, physical fatigue and quality of life (QoL). PA maintained levels of SOD activity in blood plasma, and at the cellular level significantly increased SOD2 mRNA (≈+77 %), contrary to their depletion due to medical treatment. This change was inversely correlated with DNA methylation in SOD2 promoter (≈-20 %). Similarly, we found a significant effect of PA only on L3MBTL1 promoter methylation (≈-25 %), which was inversely correlated with its mRNA (≈+43 %). Finally, PA increased TET1 mRNA levels (≈+15 %) and decreased expression of DNMT3B mRNA (≈-28 %). Our results suggest that PA-modulated DNA methylation affects several signalling pathways/biological activities involved in the cellular oxidative stress response, chromatin organization/regulation, antioxidant activity and DNA/protein binding. These changes may positively impact clinical outcomes and improve the response to cancer treatment in post-surgery BC patients.

WDR23 mediates NRF2 proteostasis and cytoprotective capacity in the hippocampus

Pathogenic brain aging and neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease are characterized by chronic neuroinflammation and the accumulation of dysfunctional or misfolded proteins that lead to progressive neuronal cell death. Here we demonstrate that a murine model with global loss of the CUL4-DDB1 substrate receptor WDR23 (Wdr23KO) results in changes in multiple age-related hippocampal-dependent behaviors. The behavioral differences observed in Wdr23KO animals accompany the stabilization of the NRF2/NFE2L2 protein, an increase in RNA transcripts regulated by this cytoprotective transcription factor, and an increase in the steady state level of antioxidant defense proteins. Taken together, these findings reveal a role for WDR23-proteostasis in mediating cytoprotective capacity in the hippocampus and reveal the potential for targeting WDR23-NRF2 signaling interactions for development of therapies for neurodegenerative disorders.

Sex differences in the susceptibility to valproic acid-associated liver injury in epileptic patients

BACKGROUND

Valproic acid has been widely used as an antiepileptic drug for several decades. Long-term valproic acid treatment is usually accompanied by liver injury. Although both men and women are susceptible to valproic acid-associated liver injury, hepatotoxicity differs between the sexes. However, the mechanisms underlying sex differences in valproic acid-associated liver injury remain unclear.

METHODS

To explore potential risk factors for the susceptibility to valproic acid-associated liver injury, 231 pediatric patients with epilepsy (119 males, 112 females) were enrolled for laboratory and genetic analysis.

RESULTS

Heterozygous genotype of catalase C-262T (P = 0.045) and the concentrations of glutathione (P = 0.002) and thiobarbituric acid-reactive substances (P = 0.011) were associated with the sex-specific susceptibility to valproic acid-associated liver injury. Meanwhile, logistic regression analysis revealed that carriers of heterozygous genotype of catalase C-262T (P = 0.010, odds ratio: 4.163; 95 percent confidence interval 1.400 - 7.378), glutathione concentration (P = 0.001, odds ratio: 2.421; 95 percent confidence interval 2.262 - 2.591) and male patients (P = 0.005, odds ratio: 1.344; 95% confidence interval 0.782 - 2.309) had a higher risk for valproic acid-associated liver injury.

DISCUSSION

The mechanism underlying valproic acid-induced hepatotoxicity remains unclear. Additionally, factors that may contribute to the observed differences in the incidence of hepatotoxicity between males and females have yet to be defined. This study identifies several genetic factors that may predispose patients to valproic acid-associated hepatotoxicity.

LIMITATIONS

This relatively small sample size of children with one ethnicity some of whom were taking other antiepileptics that are potentially hepatotoxic.

CONCLUSION

Catalase C-262T genotype, glutathione concentration and gender (male) are potential risk factors for the susceptibility to valproic acid-associated liver injury.

WDR23 mediates NRF2 proteostasis and cytoprotective capacity in the hippocampus

Pathogenic brain aging and neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease are characterized by chronic neuroinflammation and the accumulation of dysfunctional or misfolded proteins that lead to progressive neuronal cell death. Here we demonstrate that a murine model with global loss of the CUL4-DDB1 substrate receptor WDR23 ( Wdr23KO ) results in changes in multiple age-related hippocampal-dependent behaviors. The behavioral differences observed in Wdr23KO animals accompany the stabilization of the NRF2/NFE2L2 protein, an increase in RNA transcripts regulated by this cytoprotective transcription factor, and an increase in the steady state level of antioxidant defense proteins. Taken together, these findings reveal a role for WDR23-proteostasis in mediating cytoprotective capacity in the hippocampus and reveal the potential for targeting WDR23-NRF2 signaling interactions for development of therapies for neurodegenerative disorders.

HIGHLIGHTS

WDR23 regulates NRF2/NFE2L2 stability in the mouse hippocampus Loss of Wdr23 significantly increases the expression of NFE2L2/NRF2 target genes Global loss of WDR23 influences age-related behaviors differentially in males and females.

Oxidative Stress Linking Obesity and Cancer: Is Obesity a 'Radical Trigger' to Cancer?

Obesity is on the rise worldwide, and consequently, obesity-related non-communicable diseases are as well. Nutritional overload induces metabolic adaptations in an attempt to restore the disturbed balance, and the byproducts of the mechanisms at hand include an increased generation of reactive species. Obesity-related oxidative stress causes damage to vulnerable systems and ultimately contributes to neoplastic transformation. Dysfunctional obese adipose tissue releases cytokines and induces changes in the cell microenvironment, promoting cell survival and progression of the transformed cancer cells. Other than the increased risk of cancer development, obese cancer patients experience higher mortality rates and reduced therapy efficiency as well. The fact that obesity is considered the second leading preventable cause of cancer prioritizes the research on the mechanisms connecting obesity to cancerogenesis and finding the solutions to break the link. Oxidative stress is integral at different stages of cancer development and advancement in obese patients. Hypocaloric, balanced nutrition, and structured physical activity are some tools for relieving this burden. However, the sensitivity of simultaneously treating cancer and obesity poses a challenge. Further research on the obesity-cancer liaison would offer new perspectives on prevention programs and treatment development.