Gemfibrozil Pretreatment Resulted in a Sexually Dimorphic Outcome in the Rat Models of Global Cerebral Ischemia–Reperfusion via Modulation of Mitochondrial Pro-survival and Apoptotic Cell Death Factors as well as MAPKs

Effects of methylphenidate on mitochondrial dynamics and bioenergetics in the prefrontal cortex of juvenile rats are sex-dependent

Methylphenidate (MPH) is a central nervous system stimulant drug and a first order prescription in the treatment of Attention Deficit Hyperactivity Disorder (ADHD). Although MPH biochemistry in neurodevelopment is not completely understood, studies showed it alters energy metabolism in rat brains. ADHD prevalence during neurodevelopment is related to males and the investigation has been mainly done in these subjects, therefore, little is known about MPH action in females and, consequently, about sexual dimorphism. In the present study we evaluated markers of mitochondrial dynamics (DRP1 and MFN2, fission and fusion, respectively), biogenesis (mtTFA) and bioenergetics (respiratory chain complexes) in prefrontal cortex of male and female juvenile rats submitted to exposure to MPH to better understand MPH effect during postnatal neurodevelopment. ATP and oxidative stress levels were also evaluated. Wistar rats received intraperitoneal injection of MPH (2.0 mg/kg) or control (saline), once a day, from 15th to 45th day of age. Results showed that MPH increased DRP1 and decreased MFN2, as well as increased mtTFA in prefrontal cortex of male rats. In female, MPH decreased NRF1 and increased Parkin, which are mitochondrial regulatory proteins. Respiratory chain complexes (complex I, SDH, complexes III and IV), ATP production and oxidative stress parameters were altered and shown to be sex-dependent. Taken together, results suggest that chronic MPH exposure at an early age in healthy animals changes mitochondrial dynamics, biogenesis and bioenergetics differently depending on the sex of the subjects.

Neuroprotective effects of gemfibrozil in neurological disorders: Focus on inflammation and molecular mechanisms

BACKGROUND

Gemfibrozil (Gem) is a drug that has been shown to activate PPAR-α, a nuclear receptor that plays a key role in regulating lipid metabolism. Gem is used to lower the levels of triglycerides and reduce the risk of coronary heart disease in patients. Experimental studies in vitro and in vivo have shown that Gem can prevent or slow the progression of neurological disorders (NDs), including cerebral ischemia (CI), Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS). Neuroinflammation is known to play a significant role in these disorders.

METHOD

The literature review for this study was conducted by searching Scopus, Science Direct, PubMed, and Google Scholar databases.

RESULT

The results of this study show that Gem has neuroprotective effects through several cellular and molecular mechanisms such as: (1) Gem has the ability to upregulate pro-survival factors (PGC-1α and TFAM), promoting the survival and function of mitochondria in the brain, (2) Gem strongly inhibits the activation of NF-κB, AP-1, and C/EBPβ in cytokine-stimulated astroglial cells, which are known to increase the expression of iNOS and the production of NO in response to proinflammatory cytokines, (3) Gem protects dopamine neurons in the MPTP mouse model of PD by increasing the expression of PPARα, which in turn stimulates the production of GDNF in astrocytes, (4) Gem reduces amyloid plaque pathology, reduces the activity of glial cells, and improves memory, (5) Gem increases myelin genes expression (MBP and CNPase) via PPAR-β, and (6) Gem increases hippocampal BDNF to counteract depression.

CONCLUSION

According to the study, Gem was investigated for its potential therapeutic effect in NDs. Further research is needed to fully understand the therapeutic potential of Gem in NDs.

Role of fenofibrate in multiple sclerosis

Multiple sclerosis (MS) is the most frequent inflammatory and demyelinating disease of the central nervous system (CNS). The underlying pathophysiology of MS is the destruction of myelin sheath by immune cells. The formation of myelin plaques, inflammation, and injury of neuronal myelin sheath characterizes its neuropathology. MS plaques are multiple focal regions of demyelination disseminated in the brain's white matter, spinal cords, deep grey matter, and cerebral cortex. Fenofibrate is a peroxisome proliferative activated receptor alpha (PPAR-α) that attenuates the inflammatory reactions in MS. Fenofibrate inhibits differentiation of Th17 by inhibiting the expression of pro-inflammatory signaling. According to these findings, this review intended to illuminate the mechanistic immunoinflammatory role of fenofibrate in mitigating MS neuropathology. In conclusion, fenofibrate can attenuate MS neuropathology by modulating different pathways, including oxidative stress, autophagy, mitochondrial dysfunction, inflammatory-signaling pathways, and neuroinflammation.

Peroxisome Proliferator-Activated Receptors and Caloric Restriction-Common Pathways Affecting Metabolism, Health, and Longevity

Caloric restriction (CR) is a traditional but scientifically verified approach to promoting health and increasing lifespan. CR exerts its effects through multiple molecular pathways that trigger major metabolic adaptations. It influences key nutrient and energy-sensing pathways including mammalian target of rapamycin, Sirtuin 1, AMP-activated protein kinase, and insulin signaling, ultimately resulting in reductions in basic metabolic rate, inflammation, and oxidative stress, as well as increased autophagy and mitochondrial efficiency. CR shares multiple overlapping pathways with peroxisome proliferator-activated receptors (PPARs), particularly in energy metabolism and inflammation. Consequently, several lines of evidence suggest that PPARs might be indispensable for beneficial outcomes related to CR. In this review, we present the available evidence for the interconnection between CR and PPARs, highlighting their shared pathways and analyzing their interaction. We also discuss the possible contributions of PPARs to the effects of CR on whole organism outcomes.

Inhibition of IL-32 Expression Ameliorates Cerebral Ischemia-Reperfusion Injury via the NOD/MAPK/NF-κB Signaling Pathway

Cerebral ischemia represents a major cause of disability, yet its precise mechanism remains unknown. In addition, ischemia-reperfusion injury which occurs during the blood recovery process increases the risk of mortality, and is not adequately addressed with current treatment. To improve therapeutic options, it is important to explore the vital substances that play a pivotal role in ischemia-reperfusion injury. This study is the first to investigate the role of IL-32, a vital pro-inflammatory factor, in models of cerebral ischemia-reperfusion injury. The results showed that IL-32 was highly expressed in both in vivo and in vitro models. The proteins of the NOD/MAPK/NF-κB pathway were also up-regulated, indicating a potential signaling pathway mechanism. Inhibition of IL-32 and blocking of the NOD/MAPK/NF-κB pathway increased cell survival, decreased the level of inflammatory factors and inflammasomes, and attenuated nitrosative stress. Taken together, the results show that inhibition of IL-32 expression ameliorates cerebral ischemia-reperfusion injury via the NOD/MAPK/NF-κB signaling pathway. The findings in this study reveal that IL-32 is a vital target of ischemia-reperfusion injury, providing a new avenue for treatment development.

Emerging role of transcription factor EB in mitochondrial quality control

Mitochondria are energy producers that play a vital role in cell survival. Mitochondrial dysfunction is involved in many diseases, including metabolic syndrome, neurodegenerative disorders, cardiomyopathies, cancer, obesity, and diabetic kidney disease, and challenges still remain in terms of treatments for these diseases. Mitochondrial quality control (MQC), which is defined as the maintenance of the quantity, morphology, and function of mitochondria, plays a pivotal role in maintaining cellular metabolic homeostasis and cell survival. Recently, growing evidence suggests that the transcription factor EB (TFEB) plays a pivotal role in MQC. Here, we systemically investigate the potential role and mechanisms of TFEB in MQC, which include the activation of mitophagy, regulation of mitochondrial biogenesis, reactive oxygen species (ROS) clearance, and the balance of mitochondria fission-fusion cycle. Importantly, we further discuss the therapeutic measures and effects aimed at TFEB on mitochondrial dysfunction-related diseases. Taken together, targeting TFEB to regulate MQC may represent an appealing therapeutic strategy for mitochondrial dysfunction related-diseases.

Temporal Pattern and Crosstalk of Necroptosis Markers with Autophagy and Apoptosis Associated Proteins in Ischemic Hippocampus

Necroptosis, a novel type of programmed cell death, has been recently implicated as a possible mechanism for cerebral ischemia-reperfusion (I/R) injury. We herein studied time-dependent changes of necroptosis markers along with apoptosis- and autophagy-associated proteins in rat hippocampus at 1, 3, 6, 12, 24, and 48 h after global cerebral I/R injury. Furthermore, to determine the cross talk between autophagy and necroptosis, we examined the effects of pretreatment with bafilomycin-A1 (Baf-A1), as a late-stage autophagy inhibitor, on necroptosis. Highest levels of receptor-interacting protein 1 and 3 (RIP1 and RIP3), as key mediators of necroptosis, were observed at 24 h after reperfusion. Alongside, activity of glutamate dehydrogenase (GLUD1), downstream enzyme of RIP3, was increased. Peak time of necroptosis was subsequent to caspase-3-dependent cell death that peaked at 12 h of reperfusion but concurrent with autophagy. Administration of Baf-A1 could attenuate necroptosis, verified by decrease in RIP1 and RIP3 protein levels, as well as GLUD1 activity. However, there was no significant change in caspase-3-dependent cell death. Taken together, our results highlight that global cerebral I/R activates necroptosis that could be triggered by autophagy and interacts reversely with caspase-3-dependent apoptosis.

Gemfibrozil has antidepressant effects in mice: Involvement of the hippocampal brain-derived neurotrophic factor system

Major depressive disorder has become one of the most serious neuropsychiatric disorders worldwide. However, currently available antidepressants used in clinical practice are ineffective for a substantial proportion of patients and always have side effects. Besides being a lipid-regulating agent, gemfibrozil is an agonist of peroxisome proliferator-activated receptor-α (PPAR-α). We investigated the antidepressant effects of gemfibrozil on C57BL/6J mice using the forced swim test (FST) and tail suspension test (TST), as well as the chronic unpredictable mild stress (CUMS) model of depression. The changes in brain-derived neurotrophic factor (BDNF) signaling cascade in the brain after CUMS and gemfibrozil treatment were further assessed. Pharmacological inhibitors and lentivirus-expressed short hairpin RNA (shRNA) were also used to clarify the antidepressant mechanisms of gemfibrozil. Gemfibrozil exhibited significant antidepressant actions in the FST and TST without affecting the locomotor activity of mice. Chronic gemfibrozil administration fully reversed CUMS-induced depressive-like behaviors in the FST, TST and sucrose preference test. Gemfibrozil treatment also restored CUMS-induced inhibition of the hippocampal BDNF signaling pathway. Blocking PPAR-α and BDNF but not the serotonergic system abolished the antidepressant effects of gemfibrozil on mice. Gemfibrozil produced antidepressant effects in mice by promoting the hippocampal BDNF system.

Sex differences in brain mitochondrial metabolism: influence of endogenous steroids and stroke

Steroids are neuroprotective and a growing body of evidence indicates that mitochondria are a potential target of their effects. The mitochondria are the site of cellular energy synthesis, regulate oxidative stress and play a key role in cell death after brain injury and neurodegenerative diseases. After providing a summary of the literature on the general functions of mitochondria and the effects of sex steroid administrations on mitochondrial metabolism, we summarise and discuss our recent findings concerning sex differences in brain mitochondrial function under physiological and pathological conditions. To analyse the influence of endogenous sex steroids, the oxidative phosphorylation system, mitochondrial oxidative stress and brain steroid levels were compared between male and female mice, either intact or gonadectomised. The results obtained show that females have higher a mitochondrial respiration and lower oxidative stress compared to males and also that these differences were suppressed by ovariectomy but not orchidectomy. We have also shown that the decrease in brain mitochondrial respiration induced by ischaemia/reperfusion is different according to sex. In both sexes, treatment with progesterone reduced the ischaemia/reperfusion-induced mitochondrial alterations. Our findings indicate sex differences in brain mitochondrial function under physiological conditions, as well as after stroke, and identify mitochondria as a target of the neuroprotective properties of progesterone. Thus, it is necessary to investigate sex specificity in brain physiopathological mechanisms, especially when mitochondria impairment is involved.

Sex differences in ischaemic stroke: potential cellular mechanisms

Stroke remains a leading cause of mortality and disability worldwide. More women than men have strokes each year, in part because women live longer. Women have poorer functional outcomes, are more likely to need nursing home care and have higher rates of recurrent stroke compared with men. Despite continued advancements in primary prevention, innovative acute therapies and ongoing developments in neurorehabilitation, stroke incidence and mortality continue to increase due to the aging of the U.S.

POPULATION

Sex chromosomes (XX compared with XY), sex hormones (oestrogen and androgen), epigenetic regulation and environmental factors all contribute to sex differences. Ischaemic sensitivity varies over the lifespan, with females having an "ischaemia resistant" phenotype that wanes after menopause, which has recently been modelled in the laboratory. Pharmacological therapies for acute ischaemic stroke are limited. The only pharmacological treatment for stroke approved by the Food and Drug Administration (FDA) is tissue plasminogen activator (tPA), which must be used within hours of stroke onset and has a number of contraindications. Pre-clinical studies have identified a number of potentially efficacious neuroprotective agents; however, nothing has been effectively translated into therapy in clinical practice. This may be due, in part, to the overwhelming use of young male rodents in pre-clinical research, as well as lack of sex-specific design and analysis in clinical trials. The review will summarize the current clinical evidence for sex differences in ischaemic stroke, and will discuss sex differences in the cellular mechanisms of acute ischaemic injury, highlighting cell death and immune/inflammatory pathways that may contribute to these clinical differences.

PPARs modulate cardiac metabolism and mitochondrial function in diabetes

Diabetic cardiomyopathy is a major complication of diabetes mellitus (DM). Currently, effective treatments for diabetic cardiomyopathy are limited. The pathophysiology of diabetic cardiomyopathy is complex, whereas mitochondrial dysfunction plays a vital role in the genesis of diabetic cardiomyopathy. Metabolic regulation targeting mitochondrial dysfunction is expected to be a reasonable strategy for treating diabetic cardiomyopathy. Peroxisome proliferator-activated receptors (PPARs) are master executors in regulating glucose and lipid homeostasis and also modulate mitochondrial function. However, synthetic PPAR agonists used for treating hyperlipidemia and DM have shown controversial effects on cardiovascular regulation. This article reviews our updated understanding of the beneficial and detrimental effects of PPARs on mitochondria in diabetic hearts.

Prevention of Cyclophilin D-Mediated mPTP Opening Using Cyclosporine-A Alleviates the Elevation of Necroptosis, Autophagy and Apoptosis-Related Markers Following Global Cerebral Ischemia-Reperfusion

The mitochondrial permeability transition pore (mPTP) is a complex channel of the inner membrane, the opening of which leads to mitochondrial swelling and dissipation of mitochondrial membrane potential (MMP). Here, we aimed to evaluate the role of the cyclophilin D (CypD) as a prominent mediator of mPTP, on necroptosis and autophagy as well as apoptosis, beyond the global cerebral ischemia-reperfusion (I/R) injury. We showed that while cerebral I/R injury is accompanied by loss of MMP, mitochondrial swelling and programmed cell death, pretreatment with cyclosporine-A (CsA) as a potent inhibitor of CypD, led to partial but significant reduction in necroptosis markers, RIP1 and RIP3 as well as activity of glutamate-ammonia ligase (GLUL) and glutamate dehydrogenase 1 (GLUD1), downstream enzymes of RIP3. Administration of CsA also partially decreased autophagy associated proteins. Furthermore, we demonstrated that Bax/Bcl-2 ratio as well as caspase-3 activation, as the executioner of apoptosis, noticeably decreased by CsA pretreatment. Taken together, our results suggest that the CypD alongside the apoptosis regulation plays a partial role in inducing necroptosis and autophagy.

Sex dependent alterations in mitochondrial electron transport chain proteins following neonatal rat cerebral hypoxic-ischemia

Males are more susceptible to brain mitochondrial bioenergetic dysfunction following neonatal cerebral hypoxic-ischemia (HI) than females. Mitochondrial biogenesis has been implicated in the cellular response to HI injury, but sex differences in biogenesis following HI have not been described. We tested the hypothesis that mitochondrial biogenesis or the expression of mitochondrial electron transport chain (ETC) proteins are differentially stimulated in the brains of 8 day old male and female rats one day following HI, and promoted by treatment with acetyl-L-carnitine (ALCAR). There were no sex differences in mitochondrial mass, as reflected by the ratio of mitochondrial to nuclear DNA (mtDNA/nDNA) and citrate synthase enzyme activity present one day following HI or sham surgery. There was an increase in mtDNA/nDNA, however, in the hypoxic and ischemic (ipsilateral) hemisphere after HI in both male and female brains at one day post-injury, which was suppressed by ALCAR. Citrate synthase activity was increased in the ipsilateral hemisphere of ALCAR treated male and female brain. Most importantly, the levels of representative mitochondrial proteins present in ETC complexes I, II and IV increased substantially one day following HI in female, but not male brain. This sex difference is consistent with the increase in the mitochondrial biogenesis-associated transcription factor NRF-2/GABPα following HI in females, in contrast to the decrease observed with males. In conclusion, the female sex-selective increase in ETC proteins following HI may at least partially explain the relative female resilience to mitochondrial respiratory impairment and neuronal death that occur after HI.

Dehydroepiandrosterone protects male and female hippocampal neurons and neuroblastoma cells from glucose deprivation

Dehydroepiandrosterone (DHEA) modulates neurogenesis, neuronal function, neuronal survival and metabolism, enhancing mitochondrial oxidative capacity. Glucose deprivation and hypometabolism have been implicated in the mechanisms that mediate neuronal damage in neurological disorders, and some studies have shown that these mechanisms are sexually dimorphic. It was also demonstrated that DHEA is able to attenuate the hypometabolism that is related to some neurodegenerative diseases, eliciting neuroprotective effects in different experimental models of neurodegeneration. The aim of this study was to evaluate the effect of DHEA on the viability of male and female hippocampal neurons and SH-SY5Y neuroblastoma cells exposed to glucose deprivation. It was observed that after 12h of pre-treatment, DHEA was able to protect SH-SY5Y cells from glucose deprivation for 6h (DHEA 10(-12), 10(-8) and 10(-6)M) and 8h (DHEA 10(-8)M). In contrast, DHEA was not neuroprotective against glucose deprivation for 12 or 24h. DHEA (10(-8)M) also protected SH-SY5Y cells when added together or even 1h after the beginning of glucose deprivation (6h). Furthermore, DHEA (10(-8)M) also protected primary neurons from both sexes against glucose deprivation. In summary, our findings indicate that DHEA is neuroprotective against glucose deprivation in human neuroblastoma cells and in male and female mouse hippocampal neurons. These results suggest that DHEA could be a promising candidate to be used in clinical studies aiming to reduce neuronal damage in people from both sexes.

Sex differences in mitochondrial (dys)function: Implications for neuroprotection

Decades of research have revealed numerous differences in brain structure size, connectivity and metabolism between males and females. Sex differences in neurobehavioral and cognitive function after various forms of central nervous system (CNS) injury are observed in clinical practice and animal research studies. Sources of sex differences include early life exposure to gonadal hormones, chromosome compliment and adult hormonal modulation. It is becoming increasingly apparent that mitochondrial metabolism and cell death signaling are also sexually dimorphic. Mitochondrial metabolic dysfunction is a common feature of CNS injury. Evidence suggests males predominantly utilize proteins while females predominantly use lipids as a fuel source within mitochondria and that these differences may significantly affect cellular survival following injury. These fundamental biochemical differences have a profound impact on energy production and many cellular processes in health and disease. This review will focus on the accumulated evidence revealing sex differences in mitochondrial function and cellular signaling pathways in the context of CNS injury mechanisms and the potential implications for neuroprotective therapy development.

Activation of AMP-activated protein kinase by metformin protects against global cerebral ischemia in male rats: interference of AMPK/PGC-1α pathway

Here, we have investigated the effect of metformin pretreatment in the rat models of global cerebral ischemia. Cerebral ischemia which leads to brain dysfunction is one of the main causes of neurodegeneration and death worldwide. Metformin is used in clinical drug therapy protocols of diabetes. It is suggested that metformin protects cells under hypoxia and ischemia in non-neuronal contexts. Protective effects of metformin may be modulated via activating the AMP activated protein kinase (AMPK). Our results showed that induction of 30 min global cerebral I/R injury using 4-vesseles occlusion model led to significant cell death in the rat brain. Metformin pretreatment (200 mg kg/once/day, p.o., 2 weeks) attenuated apoptotic cell death and induced mitochondrial biogenesis proteins in the ischemic rats, analyzed using histological and Western blot assays. Besides, inhibition of AMPK by compound c showed that metformin resulted in apoptosis attenuation via AMPK activation. Interestingly, AMPK activation was also involved in the induction of mitochondrial biogenesis proteins using metformin, inhibition of AMPK by compound c reversed such effect, further supporting the role of AMPK upstream of mitochondrial biogenesis proteins. In summary, Metformin pretreatment is able to modulate mitochondrial biogenesis and apoptotic cell death pathways through AMPK activation in the context of global cerebral ischemia, conducting the outcome towards neuroprotection.