Sex-biased autophagy as a potential mechanism mediating sex differences in ischemic stroke outcome

Endoplasmic reticulum stress and autophagy in cerebral ischemia/reperfusion injury: PERK as a potential target for intervention

JOURNAL/nrgr/04.03/01300535-202505000-00028/figure1/v/2024-07-28T173839Z/r/image-tiff Several studies have shown that activation of unfolded protein response and endoplasmic reticulum (ER) stress plays a crucial role in severe cerebral ischemia/reperfusion injury. Autophagy occurs within hours after cerebral ischemia, but the relationship between ER stress and autophagy remains unclear. In this study, we established experimental models using oxygen-glucose deprivation/reoxygenation in PC12 cells and primary neurons to simulate cerebral ischemia/reperfusion injury. We found that prolongation of oxygen-glucose deprivation activated the ER stress pathway protein kinase-like endoplasmic reticulum kinase (PERK)/eukaryotic translation initiation factor 2 subunit alpha (eIF2α)-activating transcription factor 4 (ATF4)-C/EBP homologous protein (CHOP), increased neuronal apoptosis, and induced autophagy. Furthermore, inhibition of ER stress using inhibitors or by siRNA knockdown of the PERK gene significantly attenuated excessive autophagy and neuronal apoptosis, indicating an interaction between autophagy and ER stress and suggesting PERK as an essential target for regulating autophagy. Blocking autophagy with chloroquine exacerbated ER stress-induced apoptosis, indicating that normal levels of autophagy play a protective role in neuronal injury following cerebral ischemia/reperfusion injury. Findings from this study indicate that cerebral ischemia/reperfusion injury can trigger neuronal ER stress and promote autophagy, and suggest that PERK is a possible target for inhibiting excessive autophagy in cerebral ischemia/reperfusion injury.

Exosomes: the next-generation therapeutic platform for ischemic stroke

Current therapeutic strategies for ischemic stroke fall short of the desired objective of neurological functional recovery. Therefore, there is an urgent need to develop new methods for the treatment of this condition. Exosomes are natural cell-derived vesicles that mediate signal transduction between cells under physiological and pathological conditions. They have low immunogenicity, good stability, high delivery efficiency, and the ability to cross the blood-brain barrier. These physiological properties of exosomes have the potential to lead to new breakthroughs in the treatment of ischemic stroke. The rapid development of nanotechnology has advanced the application of engineered exosomes, which can effectively improve targeting ability, enhance therapeutic efficacy, and minimize the dosages needed. Advances in technology have also driven clinical translational research on exosomes. In this review, we describe the therapeutic effects of exosomes and their positive roles in current treatment strategies for ischemic stroke, including their anti-inflammation, anti-apoptosis, autophagy-regulation, angiogenesis, neurogenesis, and glial scar formation reduction effects. However, it is worth noting that, despite their significant therapeutic potential, there remains a dearth of standardized characterization methods and efficient isolation techniques capable of producing highly purified exosomes. Future optimization strategies should prioritize the exploration of suitable isolation techniques and the establishment of unified workflows to effectively harness exosomes for diagnostic or therapeutic applications in ischemic stroke. Ultimately, our review aims to summarize our understanding of exosome-based treatment prospects in ischemic stroke and foster innovative ideas for the development of exosome-based therapies.

A core scientific problem in the treatment of central nervous system diseases: newborn neurons

It has long been asserted that failure to recover from central nervous system diseases is due to the system's intricate structure and the regenerative incapacity of adult neurons. Yet over recent decades, numerous studies have established that endogenous neurogenesis occurs in the adult central nervous system, including humans'. This has challenged the long-held scientific consensus that the number of adult neurons remains constant, and that new central nervous system neurons cannot be created or renewed. Herein, we present a comprehensive overview of the alterations and regulatory mechanisms of endogenous neurogenesis following central nervous system injury, and describe novel treatment strategies that target endogenous neurogenesis and newborn neurons in the treatment of central nervous system injury. Central nervous system injury frequently results in alterations of endogenous neurogenesis, encompassing the activation, proliferation, ectopic migration, differentiation, and functional integration of endogenous neural stem cells. Because of the unfavorable local microenvironment, most activated neural stem cells differentiate into glial cells rather than neurons. Consequently, the injury-induced endogenous neurogenesis response is inadequate for repairing impaired neural function. Scientists have attempted to enhance endogenous neurogenesis using various strategies, including using neurotrophic factors, bioactive materials, and cell reprogramming techniques. Used alone or in combination, these therapeutic strategies can promote targeted migration of neural stem cells to an injured area, ensure their survival and differentiation into mature functional neurons, and facilitate their integration into the neural circuit. Thus can integration replenish lost neurons after central nervous system injury, by improving the local microenvironment. By regulating each phase of endogenous neurogenesis, endogenous neural stem cells can be harnessed to promote effective regeneration of newborn neurons. This offers a novel approach for treating central nervous system injury.

Sex as a biological variable in ageing: insights and perspectives on the molecular and cellular hallmarks

Sex-specific differences in lifespan and ageing are observed in various species. In humans, women generally live longer but are frailer and suffer from different age-related diseases compared to men. The hallmarks of ageing, such as genomic instability, telomere attrition or loss of proteostasis, exhibit sex-specific patterns. Sex chromosomes and sex hormones, as well as the epigenetic regulation of the inactive X chromosome, have been shown to affect lifespan and age-related diseases. Here we review the current knowledge on the biological basis of sex-biased ageing. While our review is focused on humans, we also discuss examples of model organisms such as the mouse, fruit fly or the killifish. Understanding these molecular differences is crucial as the elderly population is expected to double worldwide by 2050, making sex-specific approaches in the diagnosis, treatment, therapeutic development and prevention of age-related diseases a pressing need.

Global, regional, and national burden of stroke attributable to diet high in sodium from 1990 to 2019: a systematic analysis from the global burden of disease study 2019

Purpose

Given the increasing occurrence of stroke and high-sodium diets (DHIS) over the past 30 years, it is crucial to assess the global, national, and regional impact of DHIS on the burden of stroke.

Methods and materials

The Global Burden of Diseases Study 2019 provided the study's data. We used the Bayesian meta-regression tool DisMod-MR 2.1 to evaluate the burden of stroke attributable to DHIS. Age-standardized disability-adjusted life years (ASDR) and age-standardized mortality rate (ASMR) were used to quantify the burden. We perform correlation analysis utilizing the Spearman rank-order correlation method, and we calculate the estimated annual percentage change (EAPC) to evaluate temporal trends.

Results

Globally, DHIS accounts for 17,673.33 thousand disability-adjusted life years (DALYs) and 700.98 thousand deaths of stroke in 2019. The burden of stroke attributable to DHIS has declined between 1990 and 2019 globally and in the majority of regions, with the largest declines seen in regions with high sociodemographic indexes (SDI). Both ASMR and ASDR were higher regionally in regions with moderate SDI than those in developed regions. Furthermore, the absolute values of EAPC, reflecting the rate of decrease, were notably lower in these regions compared to developed nations. High-income North America, categorized within the SDI regions, notably witnessed the smallest decline in ASDR over the last three decades. Additionally, from 1990 to 2019, males consistently bore a larger burden of stroke attributable to DHIS.

Conclusion

The burden of stroke attributable to DHIS remained a major concern despite advancements in public knowledge of stroke and their utilization of emergency medical services. Over the past 30 years, more burden has been placed on males and regions with moderate SDI values; in males, higher EAPC values for both ASMR and ASDR have been found. This underscores the urgent need for effective interventions to alleviate the burden of stroke associated with DHIS.

Trend analysis of stroke subtypes mortality attributable to high body-mass index in China from 1990 to 2019

BACKGROUND

The prevalence of stroke disability associated with high BMI has significantly increased over the past three decades. However, it remains uncertain whether high body-mass index (BMI) exerts a similar impact on the disease burden of different stroke subtypes. The aim of this study is to assess the long-term trends of stroke and subtypes mortality attributable to high BMI in China between 1990 and 2019.

METHODS

Data on stroke and subtypes mortality attributable to high BMI in China was extracted in the Global Burden of Disease (GBD) 2019. The trends of age-standardized mortality rate (ASMR) were calculated using the linear regression and age-period-cohort framework.

RESULTS

The changing trend of ASMR on stroke attributable to high BMI in China differed among subtypes, with an estimated annual percentage change (EAPC) and 95%CI of 2.04 (1.86 to 2.21) for ischemic stroke (IS), 0.36 (-0.03 to 0.75) for intracerebral hemorrhage (ICH), and - 4.62 (-5.44 to -3.78) for subarachnoid hemorrhage (SAH). Net and local drift analyses revealed a gradual increase in the proportion of older people with IS and a gradual increase in the proportion of younger people with hemorrhagic strokes. The cohort and period rate ratios varied by subtype, showing an increasing trend for IS and ICH but a decreasing trend for SAH. The stroke mortality attributable to high BMI increased significantly with age for IS and ICH, peaking between ages 50-70 for SAH. Notably, males had higher ASMR related to stroke but exhibited slighter declines or higher growth compared to females in China. Moreover, the population affected by fatal strokes tended to be older among females but more evenly distributed across a wider age range encompassing both younger and older individuals.

CONCLUSION

The research findings indicate a rising trend in the ASMR of stroke and subtypes attributable to high BMI in China from 1990 to 2019, with different patterns of change for different subtypes, genders and ages. Consequently, it is imperative for public health authorities in China to formulate guidelines for specific stroke subtypes, genders and ages to prevent the burden of stroke attributable to high BMI.

Brain structure alterations following neonatal exposure to low-frequency electromagnetic fields: A histological analysis

Nitric oxide (NO) and electromagnetic fields (EMF) have been extensively studied for their roles in neurobiology, particularly in regulating cerebral functions and synaptic plasticity. This study investigates the impact of EMFs on NO modulation and its subsequent effects on neurodevelopment, building upon prior research examining EMF exposure's consequences on Wistar albino rats. Rats were exposed perinatally to either tap water, 1 g/L of L-arginine (LA) or 0.5 g/L of N-methylarginine (NMA). Half of the rats in each group were also exposed to a 7-Hz square-wave EMF at three separate intensities (5, 50 and 500 nT) for 2-14 days following birth. Animals were allowed to develop, and their brains were harvested later in adulthood (mean age = 568.17 days, SD = 162.73). Histological analyses were used to elucidate structural changes in key brain regions. All brains were stained with Toluidine Blue O (TBO), enabling the visualization of neurons. Neuronal counts were then conducted in specific regions of interest (e.g. hippocampus, cortices, amygdala and hypothalamus). Histological analyses revealed significant alterations in neuronal density in specific brain regions, particularly in response to EMF exposure and pharmacological interventions. Notable findings include a main EMF exposure effect where increased neuronal counts were observed in the secondary somatosensory cortex under low EMF intensities (p < 0.001) and sex-specific responses in the hippocampus, where a significant increase in neuronal counts was observed in the left CA3 region in female rats exposed to EMF compared to unexposed females (t(18) = 2.371, p = 0.029). Additionally, a significant increase in neuronal counts in the right entorhinal cortex was seen in male rats exposed to EMF compared to unexposed males (t(18) = 2.216, p = 0.040). These findings emphasize the complex interaction among sex, EMF exposure and pharmacological agents on neuronal dynamics across brain regions, highlighting the need for further research to identify underlying mechanisms and potential implications for cognitive function and neurological health in clinical and environmental contexts.

Analysis and projections of disease burden for different risk factors and sexes of ischemic stroke in young adults in China

To estimate the rate of death, and disability-adjusted life years (DALYs) and project the disease burden of ischemic stroke due to relevant risk factors in young adults age 20-49 years by sex in China. Data from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019 were used. The age-standardized mortality (ASMR), age-standardized DALYs rate (ASDR), and estimated annual percentage changes (EAPC) were calculated to evaluate the temporal trends from 1990 to 2019. We also used the NORDPRED model to predict ASMR for ischemic stroke due to related risk factors in Chinese young adults over the next 10 years. From 1990 to 2019, the general age-standardized mortality [from 2.39 (1.97 to 2.99) in 1990 to 1.8 (1.41 to 2.18) in 2019, EAPC = - 1.23] and DALYs rates (from 171.7 (140.34 to 212.36) in 1990 to 144.4 (114.29 to 177.37) in 2019, EAPC = - 0.86) decreased for ischemic stroke in young adults in China. ASMR and ASDR decreased for all level 1 risk factors (including behavioral, environmental/occupational, and metabolic) from 1990 to 2019, with the slightest decrease for metabolic risks [ASMR from 1.86 (1.39 to 2.41) in 1990 to 1.53 (1.15 to 1.92) in 2019, ASDR from 133.68 (99.96 to 173.89) in 1990 to 123.54 (92.96 to 156.98) in 2019] and the largest decrease for environmental/occupational risks [ASMR from 1.57 (1.26 to 1.98) in 1990 to 1.03 (0.78 to 1.29) in 2019, ASDR from 110.91 (88.44 to 138.34) in 1990 to 80.03 (61.87 to 100.33) in 2019]. In general, high body-mass index, high red meat intake, and ambient particulate matter pollution contributed to the large increase in ASMR and ASDR between 1990 and 2019. Significant reductions in ASMR and ASDR were observed in low vegetables intake, household air pollution from solid fuels, lead exposure, and low fiber intake. In addition, there were sex differences in the ranking of ASMR attributable to risks in ischemic stroke. The disease burden of ischemic stroke attributable to relevant risk factors in young adults in China is greater and has a faster growth trend or a slower decline trend in males than in females (except for secondhand smoke). The apparent increasing trend of ASMR attributable to high fasting plasma glucose, high systolic blood pressure, high body-mass index, and high red meat intake was observed in males but not in females. The projected analysis showed an increasing trend in ASMR between 1990 and 2030 for all specific metabolic risks for males, but a decreasing trend for females. ASMR attributable to ambient particulate matter pollution showed an increasing trend from 1990 to 2030 for both males and females. The burden of ischemic stroke in young adults in China showed a downward trend from 1990 to 2019. Specific risk factors associated with the burden of ischemic stroke varied between the sexes. Corresponding measures need to be developed in China to reduce the disease burden of ischemic stroke among young adults.

Genetically predicted high serum sex hormone-binding globulin levels are associated with lower ischemic stroke risk: A sex-stratified Mendelian randomization study

OBJECTIVE

Cross-sectional and cohort studies have found insufficient evidence of a causal relationship between sex hormone-binding globulin and ischemic stroke, only associations. Here, we performed a sex-stratified, bidirectional, two-sample Mendelian randomization analysis to evaluate whether a causal relationship exists between sex hormone-binding globulin and ischemic stroke.

METHODS

Single-nucleotide polymorphisms associated with sex hormone-binding globulin and ischemic stroke were screened from genome-wide association studies summary data as instrumental variables to enable a bidirectional, two-sample Mendelian randomization study design. Inverse-variance weighted analysis was used as the main method to evaluate potential causality, and additional methods, including the weighted median and MR-Egger tests, were used to validate the Mendelian randomization results. Cochran's Q statistic, MR-Egger intercept test, and Mendelian Randomization-Pleiotropy Residual Sum and Outlier global test were used as sensitivity analysis techniques to assure the reliability of the results. Multivariable analysis was used to show the robustness of the results with key theorized confounders.

RESULTS

Inverse-variance weighted analysis showed that genetically predicted higher serum sex hormone-binding globulin levels were associated with significantly decreased risk of ischemic stroke in males (odds radio = 0.934, 95 % confidence interval = 0.885-0.985, P = 0.012) and females (odds radio = 0.924, 95 % confidence interval = 0.868-0.983, P = 0.013). In an analysis of ischemic stroke subtypes, genetically predicted higher serum sex hormone-binding globulin levels were also associated with significantly decreased risk of small-vessel occlusion in both males (odds radio = 0.849, 95 % confidence interval = 0.759-0.949, P = 0.004) and females (odds radio = 0.829, 95 % confidence interval = 0.724-0.949, P = 0.006). The association remained in sensitivity analyses and multivariable analyses. The reverse analysis suggested an association between genetically predicted risk of cardioembolism and increased serum sex hormone-binding globulin in females (Beta = 0.029 nmol/L, Standard Error = 0.010, P = 0.003).

CONCLUSION

Our findings provide new insight into the etiology of ischemic stroke and suggest that modulating serum sex hormone-binding globulin may be a therapeutic strategy to protect against ischemic stroke.

Succinylation modification: a potential therapeutic target in stroke

Stroke is a leading cause of mortality and disability worldwide. Ischemic cell death triggered by the compromised supply of blood oxygen and glucose is one of the major pathophysiology of stroke-induced brain injury. Impaired mitochondrial energy metabolism is observed minutes after stroke and is closely associated with the progression of neuropathology. Recently, a new type of post-translational modification, known as lysine succinylation, has been recognized to play a significant role in mitochondrial energy metabolism after ischemia. However, the role of succinylation modification in cell metabolism after stroke and its regulation are not well understood. We aimed to review the effects of succinylation on energy metabolism, reactive oxygen species generation, and neuroinflammation, as well as Sirtuin 5 mediated desuccinylation after stroke. We also highlight the potential of targeting succinylation/desuccinylation as a promising strategy for the treatment of stroke. The succinylation level is dynamically regulated by the nonenzymatic or enzymatic transfer of a succinyl group to a protein on lysine residues and the removal of succinyl catalyzed by desuccinylases. Mounting evidence has suggested that succinylation can regulate the metabolic pathway through modulating the activity or stability of metabolic enzymes. Sirtuins, especially Sirtuin 5, are characterized for their desuccinylation activity and have been recognized as a critical regulator of metabolism through desuccinylating numerous metabolic enzymes. Imbalance between succinylation and desuccinylation has been implicated in the pathophysiology of stroke. Pharmacological agents that enhance the activity of Sirtuin 5 have been employed to promote desuccinylation and improve mitochondrial metabolism, and neuroprotective effects of these agents have been observed in experimental stroke studies. However, their therapeutic efficacy in stroke patients should be validated.

Changing Patterns of Stroke and Subtypes Attributable to High Systolic Blood Pressure in China From 1990 to 2019

BACKGROUND

It is unknown whether high systolic blood pressure had a similar effect on the disease burden of stroke subtypes. The aim of our study is to compare the long-term trends of stroke subtypes and sex groups attributable to high systolic blood pressure in China from 1990 to 2019.

METHODS

Data about the age-standardized mortality rate and the age-standardized disability-adjusted life-year rate of stroke subtypes attributable to high systolic blood pressure in China were extracted in GBD (Global Burden of Disease) 2019. The trends in the age-standardized mortality rate and the age-standardized disability-adjusted life-year rate were calculated using the liner regression and age-period-cohort method, adjusted for age, period, and cohort.

RESULTS

The estimated annual percentage change for mortality of stroke attributable to high systolic blood pressure was different from subtypes, with an estimated annual percentage change and 95% CI of 0.56 (0.37-0.74) for ischemic stroke (IS), -1.52 (-1.97 to -1.07) for intracerebral hemorrhage, and -7.02 (-7.86 to -6.17) for subarachnoid hemorrhage (SAH). The curve of the net drifts showed a downward trend for intracerebral hemorrhage and SAH, but that showed a stable trend for IS. The curve of local drifts showed a slow upward trend with age for IS, a slow downward trend for intracerebral hemorrhage, and a sharp downward trend for SAH. The drift curves showed different trends for males and females. The proportion of stroke mortality in young males was gradually increasing. The cohort rate ratio varied by subtypes, with the greatest decline for SAH, a slight decrease for intracerebral hemorrhage, and a slight increase for IS. The period rate ratio had decreased over the past 3 decades, with the greatest decline for SAH and the weakest decrease for IS. Moreover, both the period and cohort rate ratios for IS mortality due to high systolic blood pressure in males have increased significantly over the past 3 decades.

CONCLUSIONS

Our results provided strong evidence that the disease burden of stroke attributable to high systolic blood pressure varied by subtypes and sex in China from 1990 to 2019. The age-standardized mortality rate and the age-standardized disability-adjusted life-year rate decreased for hemorrhagic stroke but increased for IS. Males had a higher mortality and exposure risk but a slighter decreasing trend than females. Our study suggested that greater attention should be given to the prevention of the burden of IS attributable to systolic blood pressure in China, especially for males.

Translatome analysis reveals microglia and astrocytes to be distinct regulators of inflammation in the hyperacute and acute phases after stroke

Neuroinflammation is a hallmark of ischemic stroke, which is a leading cause of death and long-term disability. Understanding the exact cellular signaling pathways that initiate and propagate neuroinflammation after stroke will be critical for developing immunomodulatory stroke therapies. In particular, the precise mechanisms of inflammatory signaling in the clinically relevant hyperacute period, hours after stroke, have not been elucidated. We used the RiboTag technique to obtain microglia and astrocyte-derived mRNA transcripts in a hyperacute (4 h) and acute (3 days) period after stroke, as these two cell types are key modulators of acute neuroinflammation. Microglia initiated a rapid response to stroke at 4 h by adopting an inflammatory profile associated with the recruitment of immune cells. The hyperacute astrocyte profile was marked by stress response genes and transcription factors, such as Fos and Jun, involved in pro-inflammatory pathways such as TNF-α. By 3 days, microglia shift to a proliferative state and astrocytes strengthen their inflammatory response. The astrocyte pro-inflammatory response at 3 days is partially driven by the upregulation of the transcription factors C/EBPβ, Spi1, and Rel, which comprise 25% of upregulated transcription factor-target interactions. Surprisingly, few sex differences across all groups were observed. Expression and log2 fold data for all sequenced genes are available on a user-friendly website for researchers to examine gene changes and generate hypotheses for stroke targets. Taken together, our data comprehensively describe the microglia and astrocyte-specific translatome response in the hyperacute and acute period after stroke and identify pathways critical for initiating neuroinflammation.

Translatome analysis reveals microglia and astrocytes to be distinct regulators of inflammation in the hyperacute and acute phases after stroke

Neuroinflammation is a hallmark of ischemic stroke, which is a leading cause of death and long-term disability. Understanding the exact cellular signaling pathways that initiate and propagate neuroinflammation after stroke will be critical for developing immunomodulatory stroke therapies. In particular, the precise mechanisms of inflammatory signaling in the clinically relevant hyperacute period, hours after stroke, have not been elucidated. We used the RiboTag technique to obtain astrocyte and microglia-derived mRNA transcripts in a hyperacute (4 hours) and acute (3 days) period after stroke, as these two cell types are key modulators of acute neuroinflammation. Microglia initiated a rapid response to stroke at 4 hours by adopting an inflammatory profile associated with the recruitment of immune cells. The hyperacute astrocyte profile was marked by stress response genes and transcription factors, such as Fos and Jun , involved in pro-inflammatory pathways such as TNF-α. By 3 days, microglia shift to a proliferative state and astrocytes strengthen their inflammatory response. The astrocyte pro-inflammatory response at 3 days is partially driven by the upregulation of the transcription factors C/EBPβ, Spi1 , and Rel , which comprise 25% of upregulated transcription factor-target interactions. Surprisingly, few sex differences across all groups were observed. Expression and log ₂ fold data for all sequenced genes are available on a user-friendly website for researchers to examine gene changes and generate hypotheses for stroke targets. Taken together our data comprehensively describe the astrocyte and microglia-specific translatome response in the hyperacute and acute period after stroke and identify pathways critical for initiating neuroinflammation.

A Bibliometric Analysis for Global Trends and Full View of the Autophagy in Ischemic Stroke from 2006 to 2022

Autophagy plays a key role in ischemic stroke, but its mechanism remains to be elucidated. In order to explore the effect of autophagy on ischemic stroke, bibliometric analysis and view tools are used to identify the directions of the global research trends and construct full view of the autophagy in ischemic stroke from 2006 to 2022. The research hotspots of autophagy related to ischemic stroke are visually analyzed and generated various visual maps to display publications, authors, sources, countries, organizations, and keywords. By bibliometric analysis, it can be seen that the investigations of autophagy in ischemic stroke is focused on both brain injury and neuroprotection. The impact of a variety of inflammatory factors and signaling pathways on autophagy following an ischemic stroke is also studied. Autophagy plays an important role in all phases of ischemic stroke. It is of great significance to guide the development of treatment plans for ischemic stroke.