Molecular mechanisms of ischemia-reperfusion injury in brain: pivotal role of the mitochondrial membrane potential in reactive oxygen species generation

Energy metabolism disturbance in migraine: From a mitochondrial point of view

Migraine is a serious central nervous system disease with a high incidence rate. Its pathogenesis is very complex, which brings great difficulties for clinical treatment. Recently, many studies have revealed that mitochondrial dysfunction may play a key role in migraine, which affects the hyperosmotic of Ca²⁺, the excessive production of free radicals, the decrease of mitochondrial membrane potential, the imbalance of mPTP opening and closing, and the decrease of oxidative phosphorylation level, which leads to neuronal energy exhaustion and apoptosis, and finally lessens the pain threshold and migraine attack. This article mainly introduces cortical spreading depression, a pathogenesis of migraine, and then damages the related function of mitochondria, which leads to migraine. Oxidative phosphorylation and the tricarboxylic acid cycle are the main ways to provide energy for the body. 95 percent of the energy needed for cell survival is provided by the mitochondrial respiratory chain. At the same time, hypoxia can lead to cell death and migraine. The pathological opening of the mitochondrial permeability transition pore can promote the interaction between pro-apoptotic protein and mitochondrial, destroy the structure of mPTP, and further lead to cell death. The increase of mPTP permeability can promote the accumulation of reactive oxygen species, which leads to a series of changes in the expression of proteins related to energy metabolism. Both Nitric oxide and Calcitonin gene-related peptide are closely related to the attack of migraine. Recent studies have shown that changes in their contents can also affect the energy metabolism of the body, so this paper reviews the above mechanisms and discusses the mechanism of brain energy metabolism of migraine, to provide new strategies for the prevention and treatment of migraine and promote the development of individualized and accurate treatment of migraine.

Therapeutic Administration of Oxcarbazepine Saves Cerebellar Purkinje Cells from Ischemia and Reperfusion Injury Induced by Cardiac Arrest through Attenuation of Oxidative Stress

Research reports using animal models of ischemic insults have demonstrated that oxcarbazepine (a carbamazepine analog: one of the anticonvulsant compounds) extends neuroprotective effects against cerebral or forebrain injury induced by ischemia and reperfusion. However, research on protective effects against ischemia and reperfusion cerebellar injury induced by cardiac arrest (CA) and the return of spontaneous circulation has been poor. Rats were assigned to four groups as follows: (Groups 1 and 2) sham asphyxial CA and vehicle- or oxcarbazepine-treated, and (Groups 3 and 4) CA and vehicle- or oxcarbazepine-treated. Vehicle (0.3% dimethyl sulfoxide/saline) or oxcarbazepine (200 mg/kg) was administered intravenously ten minutes after the return of spontaneous circulation. In this study, CA was induced by asphyxia using vecuronium bromide (2 mg/kg). We conducted immunohistochemistry for calbindin D-28kDa and Fluoro-Jade B histofluorescence to examine Purkinje cell death induced by CA. In addition, immunohistochemistry for 4-hydroxy-2-nonenal (4HNE) was carried out to investigate CA-induced oxidative stress, and immunohistochemistry for Cu, Zn-superoxide dismutase (SOD1) and Mn-superoxide dismutase (SOD2) was performed to examine changes in endogenous antioxidant enzymes. Oxcarbazepine treatment after CA significantly increased the survival rate and improved neurological deficit when compared with vehicle-treated rats with CA (survival rates ≥ 63.6 versus 6.5%), showing that oxcarbazepine treatment dramatically protected cerebellar Purkinje cells from ischemia and reperfusion injury induced by CA. The salvation of the Purkinje cells from ischemic injury by oxcarbazepine treatment paralleled a dramatic reduction in 4HNE (an end-product of lipid peroxidation) and increased or maintained the endogenous antioxidant enzymes (SOD1 and SOD2). In brief, this study shows that therapeutic treatment with oxcarbazepine after CA apparently saved cerebellar neurons (Purkinje cells) from CA-induced neuronal death by attenuating oxidative stress and suggests that oxcarbazepine can be utilized as a therapeutic medicine for ischemia and reperfusion brain (cerebellar) injury induced by CA.

Nrf2 Regulates Oxidative Stress and Its Role in Cerebral Ischemic Stroke

Cerebral ischemic stroke is characterized by acute ischemia in a certain part of the brain, which leads to brain cells necrosis, apoptosis, ferroptosis, pyroptosis, etc. At present, there are limited effective clinical treatments for cerebral ischemic stroke, and the recovery of cerebral blood circulation will lead to cerebral ischemia-reperfusion injury (CIRI). Cerebral ischemic stroke involves many pathological processes such as oxidative stress, inflammation, and mitochondrial dysfunction. Nuclear factor erythroid 2-related factor 2 (Nrf2), as one of the most critical antioxidant transcription factors in cells, can coordinate various cytoprotective factors to inhibit oxidative stress. Targeting Nrf2 is considered as a potential strategy to prevent and treat cerebral ischemia injury. During cerebral ischemia, Nrf2 participates in signaling pathways such as Keap1, PI3K/AKT, MAPK, NF-κB, and HO-1, and then alleviates cerebral ischemia injury or CIRI by inhibiting oxidative stress, anti-inflammation, maintaining mitochondrial homeostasis, protecting the blood-brain barrier, and inhibiting ferroptosis. In this review, we have discussed the structure of Nrf2, the mechanisms of Nrf2 in cerebral ischemic stroke, the related research on the treatment of cerebral ischemia through the Nrf2 signaling pathway in recent years, and expounded the important role and future potential of the Nrf2 pathway in cerebral ischemic stroke.

Modulation of oxidative neurometabolism in ischemia/reperfusion by nitrite

Nitrite has been viewed essentially as an inert metabolic endpoint of nitric oxide (^•NO). However, under certain conditions, nitrite can be a source of ^•NO. In the brain, this alternative source of ^•NO production independent of nitric oxide synthase activity may be particularly relevant in ischemia/reperfusion (I/R), where low oxygen availability limits enzymatic production of ^•NO. Notably, in vivo concentration of nitrite can be easily increased with diet, through the ingestion of nitrate-rich foods, opening the window for a therapeutic intervention based on diet. Considering the modulation of mitochondrial respiration by ^•NO, we have hypothesized that the protective action of nitrite in I/R may also result from modulation of mitochondrial function. We used high-resolution respirometry to evaluate the effects of nitrite in two in vitro models of I/R. In both cases, an increase in oxygen flux was observed following reoxygenation, a phenomenon that has been coined "oxidative burst". The amplitude of this "oxidative burst" was decreased by nitrite in a concentration-dependent manner. Additionally, a pilot in vivo study in which animals received a nitrate-rich diet as a strategy to increase circulating and tissue levels of nitrite also revealed that the "oxidative burst" was decreased in the nitrate-treated animals. These results may provide mechanistic support to the observation of a protective effect of nitrite in situations of brain ischemia.

Delivery of the reduced form of vitamin K2(20) to NIH/3T3 cells partially protects against rotenone induced cell death

Mitochondria generate energy through the action of the electron transport chain (ETC) and ATP synthase. Mitochondrial malfunction can lead to various disorders, including neurodegenerative diseases. Several reports have shown that menaquinone-4 (MK-4, vitamin K₂₍₂₀₎), a safe drug for osteoporosis, may improve mitochondrial function. Here, we hypothesized that the efficient delivery of menahydroquinone-4 (MKH), an active form of MK-4, could exert a supporting effect. We verified the effects of MKH delivery on mitochondrial dysfunction by using MK-4 and MKH ester derivatives in NIH/3T3 mouse fibroblast cells treated with mitochondrial inhibitors. MK-4 and MKH derivatives suppressed cell death, the decline in mitochondrial membrane potential (MMP), excessive reactive oxygen species (ROS) production, and a decrease in intrinsic coenzyme Q₉ (CoQ₉) induced by rotenone (ROT, complex I inhibitor). MK-4 and MKH derivatives delivered MKH to NIH/3T3 cells, acting as an effective MKH prodrug, proving that the delivered MKH may reflect the mitigation effects on ROT-induced mitochondrial dysfunction. MKH prodrugs are also effective against 3-nitropropionic acid (3-NP, complex II inhibitor) and carbonyl cyanide-m-chlorophenylhydrazone (CCCP, uncoupler)-induced cell death. In conclusion, MKH delivery may mitigate mitochondrial dysfunction by maintaining MMP, ROS, and CoQ₉, indicating that MKH prodrugs may be good candidates for treating mitochondrial disorders.

Prophylactic Treatment with Hydrogen Sulphide Can Prevent Renal Ischemia-Reperfusion Injury in L-NAME Induced Hypertensive Rats with Cisplatin-Induced Acute Renal Failure

(Background and Objectives): Renal ischemia perfusion injury is one of the major issues in kidney transplant. The aim of the study was to investigate the hypothesis that prophylactic treatment-with a hydrogen sulphide donor to an acute renal failure case of hypertensive rats-can minimize the ischemia reperfusion injury of the kidney which is beneficial for kidney transplant. To check this hypothesis, the present study was designed to investigate the effect of chronic administration of a hydrogen sulphide (H2S) donor and sodium hydrosulfide (NaHS) on nuclear factor kappa B (NF-kB) and inter cellular adhesion molecule-1 (ICAM-1) concentration in non-renal failure (NRF) and acute renal failure (ARF) rats in the ischemia-reperfusion injury (IRI) model of the kidney in both normotensive WKY and hypertensive rats (L-nitro arginine methyl ester (L-NAME-induced); (Materials and Methods): A total number of 48 Sprague-Dawley rats were recruited into eight groups each consisting of six animals. Each of these eight groups was used to measure systemic and renal parameters, H2S, antioxidant parameters in plasma, plasma concentration of NF-kB and ICAM-1 and renal cortical blood pressure. ARF was induced by single intraperitoneal (i.p.) cisplatin injection (5 mg/kg). Hypertension was induced by oral administration of L-NAME in drinking water for four weeks at 40 mg/kg/day. NaHS was administered (i.p) at 56 µmol/kg for five weeks while dL-propargylglycine (PAG), a H2S generation inhibitor, was administered as a single intra-peritoneal injection (50 mg/kg). An acute surgical experiment was performed for the induction of renal ischemia for 30 min by renal artery clamping followed by reperfusion for three hours; (Results): Chronic administration of NaHS attenuated the severity of ARF in both normotensive and hypertensive animals (L-NAME) along with lowering the blood pressure in hypertensive groups. NaHS improved the oxidative stress parameters such as total superoxide dismutase (T-SOD), glutathione (GSH) and reduced the malondialdehyde (MDA) concentration along with reduction of NF-kB and ICAM-1 following renal IRI; Conclusions: These findings demonstrate that H2S not only reduced the severity of cisplatin induced ARF but also reduced the severity of renal IRI by upregulating antioxidants along with decreased concentrations of NF-kB and ICAM-1 in normotensive and L-NAME induced hypertensive rats.

Sometimes less is more: inhibitory infrared light during early reperfusion calms hyperactive mitochondria and suppresses reperfusion injury

Ischemic stroke affects over 77 million people annually around the globe. Due to the blockage of a blood vessel caused by a stroke, brain tissue becomes ischemic. While prompt restoration of blood flow is necessary to save brain tissue, it also causes reperfusion injury. Mitochondria play a crucial role in early ischemia-reperfusion injury due to the generation of reactive oxygen species (ROS). During ischemia, mitochondria sense energy depletion and futilely attempt to up-regulate energy production. When reperfusion occurs, mitochondria become hyperactive and produce large amounts of ROS which damages neuronal tissue. This ROS burst damages mitochondria and the cell, which results in an eventual decrease in mitochondrial activity and pushes the fate of the cell toward death. This review covers the relationship between the mitochondrial membrane potential (ΔΨm) and ROS production. We also discuss physiological mechanisms that couple mitochondrial energy production to cellular energy demand, focusing on serine 47 dephosphorylation of cytochrome c (Cytc) in the brain during ischemia, which contributes to ischemia-reperfusion injury. Finally, we discuss the use of near infrared light (IRL) to treat stroke. IRL can both stimulate or inhibit mitochondrial activity depending on the wavelength. We emphasize that the use of the correct wavelength is crucial for outcome: inhibitory IRL, applied early during reperfusion, can prevent the ROS burst from occurring, thus preserving neurological tissue.

Carboxylate-Capped Analogues of Ru265 Are MCU Inhibitor Prodrugs

The mitochondrial calcium uniporter (MCU) is a transmembrane protein that resides on the inner membrane of the mitochondria and mediates calcium uptake into this organelle. Given the critical role of mitochondrial calcium trafficking in cellular function, inhibitors of this channel have arisen as tools for studying the biological relevance of this process and as potential therapeutic agents. In this study, four new analogues of the previously reported Ru-based MCU inhibitor [ClRu(NH3)4(μ-N)Ru(NH3)4Cl]Cl3 (Ru265) are reported. These compounds, which bear axial carboxylate ligands, are of the general formula [(RCO2)Ru(NH3)4(μ-N)Ru(NH3)4(O2CR)]X3, where X = NO3- or CF3SO3- and R = H (1), CH3 (2), CH2CH3 (3), and (CH2)2CH3 (4). These complexes were fully characterized by IR spectroscopy, NMR spectroscopy, and elemental analysis. X-ray crystal structures of 1 and 3 were obtained, revealing the expected presence of both the linear Ru(μ-N)Ru core and axial formate and propionate ligands. The axial carboxylate ligands of complexes 1-4 are displaced by water in buffered aqueous solution to give the aquated compound Ru265'. The kinetics of these processes were measured by 1H NMR spectroscopy, revealing half-lives that span 5.9-9.9 h at 37 °C. Complex 1 with axial formate ligands underwent aquation approximately twice as fast as the other compounds. In vitro cytotoxicity and mitochondrial membrane potential measurements carried out in HeLa and HEK293T cells demonstrated that none of these four complexes negatively affects cell viability or mitochondrial function. The abilities of 1-4 to inhibit mitochondrial calcium uptake in permeabilized HEK293T cells were assessed and compared to that of Ru265. Fresh solutions of 1-4 are approximately 2-fold less potent than Ru265 with IC50 values in the range of 14.7-19.1 nM. Preincubating 1-4 in aqueous buffers for longer time periods to allow for the aquation reactions to proceed increases their potency of mitochondrial uptake inhibition to match that of Ru265. This result indicates that 1-4 are aquation-activated prodrugs of Ru265'. Finally, 1-4 were shown to inhibit mitochondrial calcium uptake in intact, nonpermeabilized cells, revealing their value as tools and potential therapeutic agents for mitochondrial calcium-related disorders.

Ischemia-Selective Cardioprotection by Malonate for Ischemia/Reperfusion Injury

BACKGROUND

Inhibiting SDH (succinate dehydrogenase), with the competitive inhibitor malonate, has shown promise in ameliorating ischemia/reperfusion injury. However, key for translation to the clinic is understanding the mechanism of malonate entry into cells to enable inhibition of SDH, its mitochondrial target, as malonate itself poorly permeates cellular membranes. The possibility of malonate selectively entering the at-risk heart tissue on reperfusion, however, remains unexplored.

METHODS

C57BL/6J mice, C2C12 and H9c2 myoblasts, and HeLa cells were used to elucidate the mechanism of selective malonate uptake into the ischemic heart upon reperfusion. Cells were treated with malonate while varying pH or together with transport inhibitors. Mouse hearts were either perfused ex vivo (Langendorff) or subjected to in vivo left anterior descending coronary artery ligation as models of ischemia/reperfusion injury. Succinate and malonate levels were assessed by liquid chromatography-tandem mass spectrometry LC-MS/MS, in vivo by mass spectrometry imaging, and infarct size by TTC (2,3,5-triphenyl-2H-tetrazolium chloride) staining.

RESULTS

Malonate was robustly protective against cardiac ischemia/reperfusion injury, but only if administered at reperfusion and not when infused before ischemia. The extent of malonate uptake into the heart was proportional to the duration of ischemia. Malonate entry into cardiomyocytes in vivo and in vitro was dramatically increased at the low pH (≈6.5) associated with ischemia. This increased uptake of malonate was blocked by selective inhibition of MCT1 (monocarboxylate transporter 1). Reperfusion of the ischemic heart region with malonate led to selective SDH inhibition in the at-risk region. Acid-formulation greatly enhances the cardioprotective potency of malonate.

CONCLUSIONS

Cardioprotection by malonate is dependent on its entry into cardiomyocytes. This is facilitated by the local decrease in pH that occurs during ischemia, leading to its selective uptake upon reperfusion into the at-risk tissue, via MCT1. Thus, malonate's preferential uptake in reperfused tissue means it is an at-risk tissue-selective drug that protects against cardiac ischemia/reperfusion injury.

Parecoxib sodium alleviates ischemia reperfusion-induced pulmonary injury via inhibiting ERK/NF-κB and further activating the HIF-1α pathway

INTRODUCTION

The lungs are extremely vulnerable to ischemia/reperfusion (I/R), which is characterized by intense inflammation, oxidative stress, alveolar damage, and vascular permeability. Parecoxib sodium (Pare) has been shown to exert protective effects against multiple I/R-induced tissue injuries. However, its role in I/R-induced lung injury remains unknown. This study aimed to reveal the roles and mechanisms of Pare in pulmonary I/R injury.

METHODS

Sixty-six rats were randomly divided into three groups: The sham-operated group, the pulmonary I/R group, and the Pare-pretreated I/R group. Pare at 10 mg/kg or saline (vehicle control) were intraperitoneally administered to rats once per day for 5 consecutive days before ischemia. Serum and tissue samples were harvested following 2 h of reperfusion. The oxygenation index (OI) and alveolar-arterial oxygen partial pressure difference (PA-aO2 ) were analyzed. The levels or activities of malondialdehyde, superoxidase dismutase, catalase, glutathione peroxidase, intracellular reactive oxygen species, tumor necrosis factor-α, interleukin (IL)-6, and IL-8 were examined. The mitochondrial membrane potential was measured. The protein expression levels of the extracellular signal-regulated kinase (ERK), nuclear factor-κB (NF-κB) and their phosphorylated forms, and hypoxia-inducible factor-1α (HIF-1α) were detected. Histological changes were observed using hematoxylin and eosin staining. Moreover, the survival rate following pulmonary I/R injury was recorded daily.

RESULTS

Pare significantly increased the OI, decreased the PA-aO2 , increased the levels of antioxidants, while decreasing the levels of oxidants, and alleviated mitochondrial dysfunction and the histopathological damage induced by I/R. Furthermore, Pare inhibited the expression of proinflammatory cytokines, suppressed the activation of ERK and NF-κB, further increased HIF-1α expression, and significantly improved the rat survival rate.

CONCLUSIONS

Pare pretreatment attenuated lung I/R injury by inhibiting oxidative stress and the inflammatory response possibly via inhibiting the activation of the ERK/NF-κB pathway and further activating the HIF-1α pathway.

Identification of changed proteins by retinoic acid in cerebral ischemic damage: a proteomic study

Ischemic stroke is a severe neurodegenerative disease with a high mortality rate. Retinoic acid is a representative metabolite of vitamin A. It has many beneficial effects including anti-inflammatory, anti-apoptotic, and neuroprotective effects. The purpose of this study is to identify specific proteins that are regulated by retinoic acid in ischemic stroke. Middle cerebral artery occlusion (MCAO) was performed to induce focal cerebral ischemia. Retinoic acid (5 mg/kg) or vehicle was injected intraperitoneally into male rats for four days prior to MCAO operation. Neurobehavioral tests were performed 24 hr after MCAO and the cerebral cortex was collected for proteomic study. Retinoic acid alleviates neurobehavioral deficits and histopathological changes caused by MCAO. Furthermore, we identified various proteins that were altered by retinoic acid in MCAO damage. Among these identified proteins, adenosylhomocysteinase, isocitrate dehydrogenase [NAD+] subunit α, glycerol-3-phosphate dehydrogenase, Rab GDP dissociation inhibitor β, and apolipoprotein A1 were down-regulated in MCAO animals with vehicle treatment, whereas retinoic acid treatment alleviated these reductions. However, heat shock protein 60 was up-regulated in MCAO animals with vehicle, while retinoic acid treatment attenuated this increase. The changes in these expressions were confirmed by reverse transcription-PCR. These proteins regulate cell metabolism and mediate stress responses. Our results demonstrated that retinoic acid attenuates the neuronal damage by MCAO and regulates the various protein expressions that are involved in the survival of cells. Thus, we can suggest that retinoic acid exerts neuroprotective effects on focal cerebral ischemia by modulation of specific proteins.

Quantitative Fluorescence Imaging of the Intracellular Redox State by Real-Time Spatial and Temporal Simultaneous Analysis of O2•- Levels and Keap1 Translocation

Dysregulated redox homeostasis under pathological conditions can eventually culminate in oxidative stress and associated disease damage. Spatial and temporal regulation of intracellular redox states involves two crucial parameters for elucidating oxidative stress-related molecular mechanisms. However, the lack of methods for real-time analysis of redox states is a considerable hurdle for the in-depth interpretation of pathogenic mechanisms. Herein, given the over-produced reactive oxygen species (ROS) and the translocation of redox-sensitive proteins as the potential biomarkers of oxidative stress, we developed a novel ROS-macromolecular protein synergistic imaging strategy that relied on a small-molecule fluorescent CPR-SK probe. The CPR-SK specifically activated the caffeic acid moieties or targeting peptides (EWWW) toward the biomarkers, including superoxide (O₂^•-) fluctuations and Keap1 translocation, achieving simultaneous real-time imaging of dual molecular events during oxidative stress. Importantly, in situ, CPR-SK exhibited both gentle elevation of O₂^•- and subsequent migration of Keap1 from the cytoplasm to the nucleus, which were key indicators for determining slight injuries induced by hepatic ischemia-reperfusion. The results clearly demonstrated that this spatiotemporal imaging method was a reliable tool for analyzing dynamic intracellular changes of the redox state and elucidating the molecular mechanisms of oxidative stress-related diseases.

Capacitation promotes a shift in energy metabolism in murine sperm

In mammals, sperm acquire fertilization ability after a series of physiological and biochemical changes, collectively known as capacitation, that occur inside the female reproductive tract. In addition to other requirements, sperm bioenergetic metabolism has been identified as a fundamental component in the acquisition of capacitation. Mammalian sperm produce ATP through two main metabolic processes, oxidative phosphorylation (OXPHOS) and aerobic glycolysis that are localized to two different flagellar compartments, the midpiece, and the principal piece, respectively. In mouse sperm, the occurrence of many events associated with capacitation relies on the activity of these two energy-producing pathways, leading to the hypothesis that some of these events may impose changes in sperm energetic demands. In the present study, we used extracellular flux analysis to evaluate changes in glycolytic and respiratory parameters of murine sperm that occur as a consequence of capacitation. Furthermore, we examined whether these variations affect sperm ATP sustainability. Our results show that capacitation promotes a shift in the usage ratio of the two main metabolic pathways, from oxidative to glycolytic. However, this metabolic rewiring does not seem to affect the rate at which the sperm consume ATP. We conclude that the probable function of the metabolic switch is to increase the ATP supply in the distal flagellar regions, thus sustaining the energetic demands that arise from capacitation.

The mechanism underlying the TC-G 1008 rescue of reactive oxygen species (ROS)-induced osteoblast apoptosis by the upregulation of peroxiredoxin 1

Osteoporosis is a common bone disease in the elderly with high morbidity and mortality. Previous studies have shown ROS-revulsive osteoblast apoptosis to be involved in the pathogenesis of osteoporosis. At present, a research hotspot exists on the topic of the ROS-targeted clinical treatment of osteoporosis. TC-G 1008, a potent and selective GPR39 agonist, exerts a conspicuous influence on a myriad of cellular processes, ranging from cellular redox status, to gene expression, to cell apoptosis. However, the underlying mechanism by which TC-G 1008 regulates osteoblast function under oxidative stress has not yet been elucidated. The purpose of this study was to investigate the effect and underlying mechanism of TC-G 1008 in the rescue of ROS-induced apoptosis by upregulating peroxiredoxin (Prx1). In this study, experimental results demonstrated that TC-G 1008 could activate GPR39, which then accelerated ROS obliteration and apoptosis inhibition in osteoblasts via Prx1 upregulation through the nuclear factor (erythroid-derived 2)-related factor 2 (Nrf2). Interestingly, being regarded as an 'information' molecule rather than an anti-oxidase molecule, Prx1 was shown to restrict the dissociation of the apoptosis signal-regulating kinase 1 (ASK1)/thioredoxin (Trx) under oxidative stress, which signified the activation of the ASK1 pathway, thereby resulting in the suppression of apoptosis. In summary, this study explores the double mechanism of TC-G 1008 in osteoblast apoptosis amelioration under oxidative stress through (i) ROS elimination and (ii) ASK1/Trx signal suppression, both of which contribute to increased Prx1 expression, and the results suggest that TC-G 1008 has great potential in the clinical treatment of osteoporosis.

Brain Energy Metabolism in Ischemic Stroke: Effects of Smoking and Diabetes

Proper regulation of energy metabolism in the brain is crucial for maintaining brain activity in physiological and different pathophysiological conditions. Ischemic stroke has a complex pathophysiology which includes perturbations in the brain energy metabolism processes which can contribute to worsening of brain injury and stroke outcome. Smoking and diabetes are common risk factors and comorbid conditions for ischemic stroke which have also been associated with disruptions in brain energy metabolism. Simultaneous presence of these conditions may further alter energy metabolism in the brain leading to a poor clinical prognosis after an ischemic stroke event. In this review, we discuss the possible effects of smoking and/or diabetes on brain glucose utilization and mitochondrial energy metabolism which, when present concurrently, may exacerbate energy metabolism in the ischemic brain. More research is needed to investigate brain glucose utilization and mitochondrial oxidative metabolism in ischemic stroke in the presence of smoking and/or diabetes, which would provide further insights on the pathophysiology of these comorbid conditions and facilitate the development of therapeutic interventions.

Calix[4]arene chalcone amide C-1011 elicits differential effects on the viability of 4T1 mouse breast adenocarcinoma cells with different levels of adaptor protein Ruk/CIN85 expression

According to our earlier data, calix[4]arene chalcone amides modulate Ca ions exchange in the myometrium mitochondria and the level of inner membrane polarization that can potentially affect cell survival. To test this hypothesis, we studied the effect of calix[4]arene with 4 chalcone amide groups on mitochondria membrane polarization and viability of 4T1 mouse breast adenocarcinoma cells, a surrogate model of human triple-negative breast cancer, and on its highly malignant subline overexpressing the adaptor protein Ruk/CIN85. Mitochondria membrane potential was measured by flow cytometry, and cell viability was assessed using Trypan blue dye exclusion. It was shown that mitochondrial membranes of control (Mock) cells had a higher polarization level (67.80 ± 8.82 r.u., n = 5) compared to 4T1 cells with up-regulation of Ruk/CIN85 (RukUp cells) (25.42 ± 2.58 r.u., n = 4). Upon incubation of cells with 1 μM calix[4]arene C-1011, the CCCP-sensitive component of mitochondrial membranes polarization decreased (by almost 50%) in 4T1 Mock cells and did not change in RukUp cells compared with the control. It was demonstrated that 1 μM calix[4]arene C-1011 suppressed the viability of 4T1 Mock cells by 45%, but did not affect RukUp cells considerably. It was suggested that calix[4]arene chalcone amide С-1011 decreased mouse breast adenocarcinoma 4T1 cell viability­ at least by affecting mitochondrial membrane polarization.The data obtained indicate the prospects of further studies of calix[4]arene chalcone amide as a potential anticancer drug candidate.

miRNA Involvement in Cerebral Ischemia-Reperfusion Injury

Cerebral ischemia reperfusion injury is a debilitating medical condition, currently with only a limited amount of therapies aimed at protecting the cerebral parenchyma. Micro RNAs (miRNAs) are small, non-coding RNA molecules that via the RNA-induced silencing complex either degrade or prevent target messenger RNAs from being translated and thus, can modulate the synthesis of target proteins. In the neurological field, miRNAs have been evaluated as potential regulators in brain development processes and pathological events. Following ischemic hypoxic stress, the cellular and molecular events initiated dysregulate different miRNAs, responsible for long-terming progression and extension of neuronal damage. Because of their ability to regulate the synthesis of target proteins, miRNAs emerge as a possible therapeutic strategy in limiting the neuronal damage following a cerebral ischemic event. This review aims to summarize the recent literature evidence of the miRNAs involved in signaling and modulating cerebral ischemia-reperfusion injuries, thus pointing their potential in limiting neuronal damage and repair mechanisms. An in-depth overview of the molecular pathways involved in ischemia reperfusion injury and the involvement of specific miRNAs, could provide future perspectives in the development of neuroprotective agents targeting these specific miRNAs.

Tracking autophagy process with a through bond energy transfer-based ratiometric two-photon viscosity probe

Autophagy is a self-degradation process in cells, which is of vital significance to the health and operation of organisms. Due to the increase of lysosomal viscosity during autophagy, viscosity probes that specifically accumulate in lysosome are powerful tools for monitoring autophagy and investigating related diseases. However, there is still a lack of viscosity-sensitive ratiometric autophagy probes, which restricts the tracking of autophagy with high accuracy in complex physiological environment. Herein, a viscosity-responsive, lysosome targeted two-photon fluorescent probe Lyso-Vis was designed based on through bond energy transfer (TBET) mechanism. The TBET-based probe achieved the separation of two emission baselines, which greatly improved the resolution and reliability of sensing and imaging. Under 810 nm two-photon excitation, the emission intensity ratio of the red and green channel increased with a viscosity dependent manner. Lyso-Vis not only for the first time realized ratiometric sensing of lysosomal viscosity during autophagy process, but also visualized the association of autophagy with inflammation and stroke, and it was applied to explore the activation and inhibition of autophagy during stroke in mice.

Neuroprotection of everolimus against focal cerebral ischemia-reperfusion injury in rats

BACKGROUND

Mammalian target of rapamycin (mTOR) is a serine/threonine kinase that regulates cell growth and metabolism and integrates various signals under physiological and pathological conditions. Altered signaling of mTOR has been shown to play pathogenic roles in ischemic stroke. In the present study, the protective effect of everolimus, the selective mTOR inhibitor, in the middle cerebral artery occlusion (MCAO) model of ischemic stroke was evaluated.

METHODS

Wistar rats were exposed to MCAO (30 min) followed by reperfusion for 24 h. Everolimus (100, and 500 µg/kg) was administered at the time of reperfusion, intraperitoneally. 24 h post operation, the neurological function, infarct volume, histopathological alterations and the markers of oxidative stress including superoxide dismutase (SOD) activity, malondialdehyde (MDA), and total thiol levels were analyzed in the peri-infarct region.

RESULTS

In the rats subjected to MCAO, everolimus ameliorated neurological deficits, neuronal cell loss, and infarct volume, as compared to the stroke group. Also, everolimus significantly increased SOD activity and total thiol content, while markedly decreased the MDA level, as compared to MCAO group.

CONCLUSION

Single-dose administration of everolimus significantly improved neurological deficits and inhibited cortical cell loss by enhancing redox status, subsequently protected cerebral ischemia-reperfusion injury in rats.

Discovery of Natural Rosin Derivatives Containing Oxime Ester Moieties as Potential Antifungal Agents to Control Tomato Gray Mold Caused by Botrytis cinerea

Inspired by the application of natural products against pathogenic fungi, two series of dehydroabietyl oxime ester derivatives were synthesized using rosin as a raw material. Based on the evaluation and screening of in vitro antifungal activities against Botrytis cinerea (B. cinerea), Sclerotinia sclerotiorum, Valsa mali, Rhizoctonia solani, Fusarium oxysporum, and Alternaria alternata, compound 4f exhibited the best antifungal activity against B. cinerea, and its EC₅₀ was 0.798 mg/L, which was lower than that of the positive control trifloxystrobin (1.112 mg/L). The in vivo antifungal activity results showed that 4f had satisfactory protective and curative effects on tomato. Physiological and biochemical studies showed that the action mechanism of compound 4f against B. cinerea is to change the morphology and the ultrastructure of the mycelium, increase the permeability of the cell membrane, and cause nucleus and mitochondrial dysfunction, thus leading to apoptosis. In addition, qualitative and quantitative structure-activity relationship studies showed that the inductive and conjugative interactions between compound 4f and the target receptor form an electron transfer process, thereby achieving an antifungal effect. These results indicated that compound 4f, which was derived from the natural product rosin, is a novel potential fungicidal candidate against B. cinerea.

Targeting vascular inflammation through emerging methods and drug carriers

Acute inflammation is a common dangerous component of pathogenesis of many prevalent conditions with high morbidity and mortality including sepsis, thrombosis, acute respiratory distress syndrome (ARDS), COVID-19, myocardial and cerebral ischemia-reperfusion, infection, and trauma. Inflammatory changes of the vasculature and blood mediate the course and outcome of the pathology in the tissue site of insult, remote organs and systemically. Endothelial cells lining the luminal surface of the vasculature play the key regulatory functions in the body, distinct under normal vs. pathological conditions. In theory, pharmacological interventions in the endothelial cells might enable therapeutic correction of the overzealous damaging pro-inflammatory and pro-thrombotic changes in the vasculature. However, current agents and drug delivery systems (DDS) have inadequate pharmacokinetics and lack the spatiotemporal precision of vascular delivery in the context of acute inflammation. To attain this level of precision, many groups design DDS targeted to specific endothelial surface determinants. These DDS are able to provide specificity for desired tissues, organs, cells, and sub-cellular compartments needed for a particular intervention. We provide a brief overview of endothelial determinants, design of DDS targeted to these molecules, their performance in experimental models with focus on animal studies and appraisal of emerging new approaches. Particular attention is paid to challenges and perspectives of targeted therapeutics and nanomedicine for advanced management of acute inflammation.

Neuroprotective Effect of Piclamilast-Induced Post-Ischemia Pharmacological Treatment in Mice

Various studies have evidenced the neuroprotective role of PDE4 inhibitors. However, whether PDE4 inhibitor, Piclamilast pharmacological post-treatment is protective during cerebral ischemia reperfusion-induced injury remains unknown. Therefore, this study design included testing the hypothesis that Piclamilast administered at the beginning of a reperfusion phase (Piclamilast pPost-trt) shows protective effects and explores & probes underlying downstream mechanisms. Swiss albino male mice were subjected to global ischemic and reperfusion injury for 17 min. The animals examined cerebral infarct size, biochemical parameters, inflammatory mediators, and motor coordination. For memory, assessment mice were subjected to morris water maze (MWM) and elevated plus maze (EPM) test. Histological changes were assessed using HE staining. Piclamilast pPost-trt significantly reduced I/R injury-induced deleterious effects on biochemical parameters of oxidative stress, inflammatory parameters, infarct size, and histopathological changes, according to the findings. These neuroprotective effects of pPost-trt are significantly abolished by pre-treatment with selective CREB inhibitor, 666-15. Current study concluded that induced neuroprotective benefits of Piclamilast Post-trt, in all probability, maybe mediated through CREB activation. Hence, its neuroprotective effects can be further explored in clinical settings.

Therapeutic Targets for Regulating Oxidative Damage Induced by Ischemia-Reperfusion Injury: A Study from a Pharmacological Perspective

Ischemia-reperfusion (I-R) injury is damage caused by restoring blood flow into ischemic tissues or organs. This complex and characteristic lesion accelerates cell death induced by signaling pathways such as apoptosis, necrosis, and even ferroptosis. In addition to the direct association between I-R and the release of reactive oxygen species and reactive nitrogen species, it is involved in developing mitochondrial oxidative damage. Thus, its mechanism plays a critical role via reactive species scavenging, calcium overload modulation, electron transport chain blocking, mitochondrial permeability transition pore activation, or noncoding RNA transcription. Other receptors and molecules reduce tissue and organ damage caused by this pathology and other related diseases. These molecular targets have been gradually discovered and have essential roles in I-R resolution. Therefore, the current study is aimed at highlighting the importance of these discoveries. In this review, we inquire about the oxidative damage receptors that are relevant to reducing the damage induced by oxidative stress associated with I-R. Several complications on surgical techniques and pathology interventions do not mitigate the damage caused by I-R. Nevertheless, these therapies developed using alternative targets could work as coadjuvants in tissue transplants or I-R-related pathologies

Metformin Protects Against Diabetes-Induced Cognitive Dysfunction by Inhibiting Mitochondrial Fission Protein DRP1

Objectives: Diabetes is an independent risk factor for dementia. Mitochondrial dysfunction is a critical player in diabetes and diabetic complications. The present study aimed to investigate the role of mitochondrial dynamic changes in diabetes-associated cognitive impairment.

Methods: Cognitive functions were examined by novel object recognition and T-maze tests. Mice hippocampi were collected for electron microscopy and immunofluorescence examination. Neuron cell line HT22 and primary hippocampal neurons were challenged with high glucose in vitro. Mitotracker-Red CM-H2X ROS was used to detect mitochondrial-derived free radicals.

Results: Diabetic mice exhibited memory loss and spatial disorientation. Electron microscopy revealed that diabetic mice had larger synaptic gaps, attenuated postsynaptic density and fewer dendritic spines in the hippocampus. More round-shape mitochondria were observed in hippocampal neurons in diabetic mice than those in control mice. In cultured neurons, high glucose induced a high phosphorylated level of dynamin-related protein 1 (DRP1) and increased oxidative stress, resulting in cell apoptosis. Inhibition of mitochondrial fission by Mdivi-1 and metformin significantly decreased oxidative stress and prevented cell apoptosis in cultured cells. Treatment of Mdivi-1 and metformin restored cognitive function in diabetic mice.

Conclusion: Metformin restores cognitive function by inhibiting mitochondrial fission, reducing mitochondrial-derived oxidative stress, and mitigating neuron loss in hippocampi of diabetic mice. The protective effects of metformin shed light on the therapeutic strategy of cognitive impairment.

Laminarin Alleviates the Ischemia/Reperfusion Injury in PC12 Cells via Regulation of PTEN/PI3K/AKT Pathway

Objective. To investigate the protective effect of laminarin on PC12 cells damaged by oxygen glucose deprivation/reoxygenation (OGD/R) and its molecular mechanism. Methods. PC12 cells in the logarithmic phase were randomly divided into the control group, OGD/R group, and OGD/R+laminarin (0.5, 2.5, and 5 μg/ml) group. CCK-8 activity assay kit was used to detect cell viability. ELISA kit was performed to examine the levels of proinflammatory factors (TNF-α, IL-1β, and IL-6) and oxidative stress markers (ROS, LDH, and MPO). In addition, flow cytometry was employed to determine cell cycle and apoptosis. The expression of cell proliferation-related proteins (PCNA and Ki67), apoptosis-related proteins (Bcl-2, Bax, and Caspase-3), and PTEN/PI3K/AKT pathway-related proteins was evaluated by Western blot. Results. Compared with the control group, the cell viability was decreased significantly in the OGD/R group. CCK-8 results showed that laminarin could attenuate the damage of PC12 cell viability induced by OGD/R in a concentration-dependent manner. Meanwhile, the highest concentration of 5 μg/ml laminarin could significantly promote the viability of PC12 cells and the expression of PCNA and Ki67 than the OGD/R group. Additionally, ELISA assays showed that laminarin significantly inhibited the expression of proinflammatory factors (TNF-α, IL-1β, and IL-6) and the levels of oxidative stress markers (ROS, LDH, and MPO). Flow cytometry results demonstrated that laminarin promoted the cell cycle. And laminin upregulated the expression of apoptotic protein Bcl-2, while downregulated the expression of apoptotic proteins Bax and Caspase-3. Finally, laminarin significantly suppressed the expression of PTEN and facilitated the expression of PI3K and p-AKT compared to the OGD/R group. Conclusion. Laminarin could alleviate the OGD/R-induced PC12 cell neuronal injury via promoting cell activity and cycle and inhibiting inflammation, oxidative stress, and apoptosis. The mechanism may be related to the downregulation of PTEN protein and the activation of the PI3K/AKT pathway.

Fast Imaging of Mitochondrial Thioredoxin Reductase Using a Styrylpyridinium-Based Two-Photon Ratiometric Fluorescent Probe

Thioredoxin reductase (TrxR) is a pivotal antioxidant enzyme, but there remains a challenge for its fast imaging. This work describes the combination of a hydroxyl styrylpyridinium scaffold as the push-pull fluorophore with a carbonate-bridged 1,2-dithiolane unit as the reaction site to develop a fast mitochondrial TrxR2 probe, DSMP. It manifested a plethora of excellent properties including a rapid specific response (12 min), large Stokes shift (170 nm), ratiometric two-photon imaging, favorable binding with TrxR (K_m = 12.5 ± 0.2 μM), and the ability to cross the blood-brain barrier. With the aid of DSMP, we visualized the increased mitochondrial TrxR2 activity in cancer cells compared to normal cells. This offers the direct imaging evidence of the connection between the increased TrxR2 activity and the development of cancer. Additionally, the probe allowed the visualization of the loss in TrxR2 activity in a cellular Parkinson's disease model and, more importantly, in mouse brain tissues of a middle cerebral artery occlusion model for ischemic stroke.

Oxidative Stress in Ischemia/Reperfusion Injuries following Acute Ischemic Stroke

Recanalization therapy is increasingly used in the treatment of acute ischemic stroke. However, in about one third of these patients, recanalization is followed by ischemia/reperfusion injuries, and clinically to worsening of the neurological status. Much research has focused on unraveling the involved mechanisms in order to prevent or efficiently treat these injuries. What we know so far is that oxidative stress and mitochondrial dysfunction are significantly involved in the pathogenesis of ischemia/reperfusion injury. However, despite promising results obtained in experimental research, clinical studies trying to interfere with the oxidative pathways have mostly failed. The current article discusses the main mechanisms leading to ischemia/reperfusion injuries, such as mitochondrial dysfunction, excitotoxicity, and oxidative stress, and reviews the clinical trials with antioxidant molecules highlighting recent developments and future strategies.

Role of CRF and the hypothalamic-pituitary-adrenal axis in stroke: revisiting temporal considerations and targeting a new generation of therapeutics

Ischaemic neurovascular stroke represents a leading cause of death in the developed world. Preclinical and human epidemiological evidence implicates the corticotropin-releasing factor (CRF) family of neuropeptides as mediators of acute neurovascular injury pathology. Preclinical investigations of the role of CRF, CRF receptors and CRF-dependent activation of the hypothalamic-pituitary-adrenal (HPA) axis have pointed toward a tissue-specific and temporal relationship between activation of these pathways and physiological outcomes. Based on the literature, the major phases of ischaemic stroke aetiology may be separated into an acute phase in which CRF and anti-inflammatory stress signalling are beneficial and a chronic phase in which these contribute to neural degeneration, toxicity and apoptotic signalling. Significant gaps in knowledge remain regarding the pathway, temporality and systemic impact of CRF signalling and stress biology in neurovascular injury progression. Heterogeneity among experimental designs poses a challenge to defining the apparent reciprocal relationship between neurological injury and stress metabolism. Despite these challenges, it is our opinion that the elucidated temporality may be best matched with an antibody against CRF with a half-life of days to weeks as opposed to minutes to hours as with small-molecule CRF receptor antagonists. This state-of-the-art review will take a multipronged approach to explore the expected potential benefit of a CRF antibody by modulating CRF and corticotropin-releasing factor receptor 1 signalling, glucocorticoids and autonomic nervous system activity. Additionally, this review compares the modulation of CRF and HPA axis activity in neuropsychiatric diseases and their counterpart outcomes post-stroke and assess lessons learned from antibody therapies in neurodegenerative diseases.

Ester Prodrugs of Malonate with Enhanced Intracellular Delivery Protect Against Cardiac Ischemia-Reperfusion Injury In Vivo

PURPOSE

Mitochondrial reactive oxygen species (ROS) production upon reperfusion of ischemic tissue initiates the ischemia/reperfusion (I/R) injury associated with heart attack. During ischemia, succinate accumulates and its oxidation upon reperfusion by succinate dehydrogenase (SDH) drives ROS production. Inhibition of succinate accumulation and/or oxidation by dimethyl malonate (DMM), a cell permeable prodrug of the SDH inhibitor malonate, can decrease I/R injury. However, DMM is hydrolysed slowly, requiring administration to the heart prior to ischemia, precluding its administration to patients at the point of reperfusion, for example at the same time as unblocking a coronary artery following a heart attack. To accelerate malonate delivery, here we developed more rapidly hydrolysable malonate esters.

METHODS

We synthesised a series of malonate esters and assessed their uptake and hydrolysis by isolated mitochondria, C2C12 cells and in mice in vivo. In addition, we assessed protection against cardiac I/R injury by the esters using an in vivo mouse model of acute myocardial infarction.

RESULTS

We found that the diacetoxymethyl malonate diester (MAM) most rapidly delivered large amounts of malonate to cells in vivo. Furthermore, MAM could inhibit mitochondrial ROS production from succinate oxidation and was protective against I/R injury in vivo when added at reperfusion.

CONCLUSIONS

The rapidly hydrolysed malonate prodrug MAM can protect against cardiac I/R injury in a clinically relevant mouse model.

Role of Creatine Supplementation in Conditions Involving Mitochondrial Dysfunction: A Narrative Review

Creatine monohydrate (CrM) is one of the most widely used nutritional supplements among active individuals and athletes to improve high-intensity exercise performance and training adaptations. However, research suggests that CrM supplementation may also serve as a therapeutic tool in the management of some chronic and traumatic diseases. Creatine supplementation has been reported to improve high-energy phosphate availability as well as have antioxidative, neuroprotective, anti-lactatic, and calcium-homoeostatic effects. These characteristics may have a direct impact on mitochondrion's survival and health particularly during stressful conditions such as ischemia and injury. This narrative review discusses current scientific evidence for use or supplemental CrM as a therapeutic agent during conditions associated with mitochondrial dysfunction. Based on this analysis, it appears that CrM supplementation may have a role in improving cellular bioenergetics in several mitochondrial dysfunction-related diseases, ischemic conditions, and injury pathology and thereby could provide therapeutic benefit in the management of these conditions. However, larger clinical trials are needed to explore these potential therapeutic applications before definitive conclusions can be drawn.

The dynamin-related protein 1 is decreased and the mitochondrial network is altered in Friedreich's ataxia cardiomyopathy

Friedreich ataxia is an autosomal recessive congenital neurodegenerative disease caused by a deficiency in the frataxin protein and is often diagnosed in young adulthood. An expansion of guanine-adenine-adenine repeats in the first intron of the FXN gene leads to decreased frataxin expression. Frataxin plays an essential role in mitochondrial metabolism. Most Friedreich ataxia patients are diagnosed with left ventricular hypertrophic cardiomyopathy, and 60% of patients die with hypertrophic cardiomyopathy. However, the mitochondrial anatomy in Friedreich ataxia hypertrophic cardiomyopathy is still poorly understood. We investigated mitochondrial fission, fusion, and function using biochemical, microscopy, and computational stochastic analysis in human induced pluripotent stem cell derived cardiomyocytes from a patient with Friedreich ataxia hypertrophic cardiomyopathy and a healthy individual. We found a significantly higher mitochondrial footprint, decreased mitochondrial fission protein dynamin-related protein, and mitochondrial fission rate over fusion with more giant mitochondrial clusters in human induced pluripotent stem cell derived cardiomyocytes from a patient with Friedreich ataxia hypertrophic cardiomyopathy, compared to an unaffected individual. We also found significantly depolarized mitochondrial membrane potential and higher reactive oxygen species levels in Friedreich ataxia human induced pluripotent stem cell cardiomyocytes. Our results show that frataxin's depletion may dampen the mitochondrial fission machinery by reducing dynamin-related protein1. The loss of mitochondrial fission might lead to elevated reactive oxygen species and depolarized mitochondrial membrane potential, which may cause oxidative damage in Friedreich ataxia hypertrophic cardiomyopathy. Further investigations are needed to identify the mechanism of downregulating dynamin-related protein1 due to the frataxin deficiency in Friedreich ataxia hypertrophic cardiomyopathy.

Physico-Chemical Characterization and Assessment of Cytotoxic and Genotoxic Effects of Poly-Ethylene-Glycol Coated and Uncoated Gold Nanoparticles on Human Kidney (HK-2) Cells

Although gold nanoparticles (Au-NPs) have been widely used in medicine for the diagnosis and treatment of patients due to their unique physicochemical properties, chemical stability and biocompatibility, recent reports have also highlighted their potential to induce toxicity to humans. In the present study, we investigated the toxic effects of uncoated and polyethylene glycol (PEG)-coated AuNPs on human kidney (HK-2) cells. Both forms of AuNP were synthesized and characterized using standard protocols. Dynamic Light Scattering (DLS), Zeta Sizer Nano ZS analyzer, Transmission Electron Microscopy (TEM), and Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) were used to measure their distribution, zeta potential/surface charge, morphological size, and Au concentrations, respectively. Cytotoxicity was measured by Cyto-Tox assay and trypan blue exclusion test. Oxidative stress (OS) was assessed by quantifying the levels of Glutathione (GSH), and Mitochondria Membrane Potential (MMP). Genotoxicity was assessed by single cell gel electrophoresis (Comet assay) and Chromosomal Aberration (CA) assay. Uncoated AuNPs significantly reduced cell viability, increased ROS, decreased GSH, depolarized the MMP, and induced significant DNA damage and chromosomal alterations including chromosome gaps, centric rings, breaks, deletions, and intra and inter-chromosome exchanges, in a concentration-dependent manner. PEG-coated AuNPs displayed lower cytotoxic and genotoxic effects, and did not produce any significant increase in ROS or significant decrease in GSH along with negligible polarization of the MMP. Hence, PEG-coated AuNPs are relatively less toxic than uncoated AuNPs and therefore, may have potential applications in nanomedicine.

Oxidative Stress in the Brain: Basic Concepts and Treatment Strategies in Stroke

The production of free radicals is inevitably associated with metabolism and other enzymatic processes. Under physiological conditions, however, free radicals are effectively eliminated by numerous antioxidant mechanisms. Oxidative stress occurs due to an imbalance between the production and elimination of free radicals under pathological conditions. Oxidative stress is also associated with ageing. The brain is prone to oxidative damage because of its high metabolic activity and high vulnerability to ischemic damage. Oxidative stress, thus, plays a major role in the pathophysiology of both acute and chronic pathologies in the brain, such as stroke, traumatic brain injury or neurodegenerative diseases. The goal of this article is to summarize the basic concepts of oxidative stress and its significance in brain pathologies, as well as to discuss treatment strategies for dealing with oxidative stress in stroke.

The cardioprotective actions of statins in targeting mitochondrial dysfunction associated with myocardial ischaemia-reperfusion injury

During cardiac reperfusion after myocardial infarction, the heart is subjected to cascading cycles of ischaemia reperfusion injury (IRI). Patients presenting with this injury succumb to myocardial dysfunction resulting in myocardial cell death, which contributes to morbidity and mortality. New targeted therapies are required if the myocardium is to be protected from this injury and improve patient outcomes. Extensive research into the role of mitochondria during ischaemia and reperfusion has unveiled one of the most important sites contributing towards this injury; specifically, the opening of the mitochondrial permeability transition pore. The opening of this pore occurs during reperfusion and results in mitochondria swelling and dysfunction, promoting apoptotic cell death. Activation of mitochondrial ATP-sensitive potassium channels (mitoK_ATP) channels, uncoupling proteins, and inhibition of glycogen synthase kinase-3β (GSK3β) phosphorylation have been identified to delay mitochondrial permeability transition pore opening and reduce reactive oxygen species formation, thereby decreasing infarct size. Statins have recently been identified to provide a direct cardioprotective effect on these specific mitochondrial components, all of which reduce the severity of myocardial IRI, promoting the ability of statins to be a considerate preconditioning agent. This review will outline what has currently been shown in regard to statins cardioprotective effects on mitochondria during myocardial IRI.

A unique red-emitting molecular rotor for high-fidelity visualizing and long-term tracking mitochondria

Visualizing and tracking mitochondrial changes is the key to understand the processes of diseases related to mitochondria, which is meaningful to physiology, pathology, and pharmacology. So, a great deal of mitochondrial probes was designed and synthesized according to the principle that probes with a positive charge can target mitochondria through mitochondrial membrane potential (MMP). However, these traditional mitochondrial probes are not able to visualize and track mitochondrial changes, because their targeting abilities depend on high MMP. Once MMP decreases, they will leak from mitochondria. Herein, we designed and synthesized a red-emitting molecule rotor (SQ, sensitive to viscosity) that could visualize mitochondria with high-fidelity. The rotor was able to firmly immobilize in mitochondrial inner membrane through the cooperation of MMP and the high viscosity property of mitochondrial membrane, and it could still stain mitochondria with long-term regardless of MMP changes. Hence, the probe is able to real-time image and distinguish four kinds of mitochondria with high-fidelity in muscle tissues. In addition, SQ can monitor mitochondrial autophagy in real time. These results demonstrate that SQ is a powerful tool for high-fidelity visualizing and long-term tracking mitochondria in vitro and in vivo.

Moderate mechanical stress suppresses the IL-1β-induced chondrocyte apoptosis by regulating mitochondrial dynamics

Mitochondrial dysfunction contributes to osteoarthritis (OA) onset and progress. Mitochondrial dynamics, coupled with mitophagy, is critical for the maintenance of mitochondrial fitness, involving many cellular processes, such as proliferation and apoptosis. Excessive mechanical stress induces chondrocyte apoptosis; however, the effects of mechanical stress on mitochondrial dynamics remain elusive. In this study, we performed fluorescence staining, flow cytometry, transmission electron microscope, Western blot analysis, and RNA-sequencing to assess the effects of different strength of mechanical stimulation on mitochondrial functions of chondrocyte treated with interleukin-1β (IL-1β). We found that moderate mechanical stress reduced the IL-1β-induced apoptosis by maintaining mitochondrial function and scavenging the reactive oxygen species, while excessive mechanical stress induced strong mitochondrial dysfunction and apoptosis. Moreover, RNAsequencing revealed that mitophagy and mitochondrial dynamics were involved in the regulation of mechanical stress on chondrocyte biology. In addition to the elevated mitophagy, moderate mechanical stress also promoted mitochondrial dynamics by enhancing the expression of MFN1/2 and OPA1 and the translocation of dynamin-related protein 1 from the cytoplasm to the mitochondria. However, an uncoupling of mitochondrial dynamics, characterized by strongly elevated fission, resulted in the unfavorable apoptosis of excessive mechanical stress-stimulated chondrocytes. This study revealed the effects of mechanical stress upon mitochondrial dynamics in chondrocyte.

Erythrocytes of Little Ground Squirrels Undergo Reversible Oxidative Stress During Arousal From Hibernation

The hibernation of small mammals is characterized by long torpor bouts alternating with short periods of arousal. During arousal, due to a significant increase in oxygen consumption, tissue perfusion, and the launch of thermogenesis in cells, a large amount of reactive oxygen species (ROS) and nitrogen (RNS) can be formed, which can trigger oxidative stress in cells. To estimate this possibility, we studied the intensity of free-radical processes in the red blood cells (RBCs) of little ground squirrels (LGS; Spermophilus pygmaeus) in the dynamics of arousal from hibernation. We found that in the torpid state, the degree of generation of ROS and RNS (8.3%, p>0.09; 20.7%, p<0.001, respectively), the degree of oxidative modification of membrane lipids and RBC proteins is at a low level (47%, p<0.001; 82.7%, p<0.001, respectively) compared to the summer control. At the same time, the activity of superoxide dismutase (SOD) and catalase (CAT) in RBC is significantly reduced (32.8%, p<0.001; 22.2%, p<0.001, respectively), but not the level of glutathione (GSH). In the torpid state, SOD is activated by exogenous GSH in concentration-dependent manner, which indicates reversible enzyme inhibition. During the arousal of ground squirrels, when the body temperature reaches 25°C, RBCs are exposed oxidative stress. This is confirmed by the maximum increase in the level of uric acid (25.4%, p<0.001) in plasma, a marker of oxidative modification of lipids [thiobarbituric acid reactive substances (TBARS); 82%, p < 0.001] and proteins (carbonyl groups; 499%, p < 0.001) in RBC membranes, as well as the decrease in the level of GSH (19.7%, p < 0.001) in erythrocytes relative to the torpid state and activity of SOD and CAT in erythrocytes to values at the Tb 20°C. After full recovery of body temperature, the level of GSH increases, the ratio of SOD/CAT is restored, which significantly reduces the degree of oxidative damage of lipids and proteins of RBC membranes. Thus, the oxidative stress detected at Tb 25°C was transient and physiologically regulated.

Effects of Lipoic Acid on Ischemia-Reperfusion Injury

Ischemia-reperfusion (I/R) injury often occurred in some pathologies and surgeries. I/R injury not only harmed to physiological functions of corresponding organ and tissue but also induced multiple tissue or organ dysfunctions (even these in distant locations). Although the reperfusion of blood attenuated I/R injury to a certain degree, the risk of secondary damages was difficult to be controlled and it even caused failures of these tissues and organs. Lipoic acid (LA), as an endogenous active substance and a functional agent in food, owns better safety and effects in our body (e.g., enhancing antioxidant activity, improving cognition and dementia, controlling weight, and preventing multiple sclerosis, diabetes complication, and cancer). The literature searching was conducted in PubMed, Embase, Cochrane Library, Web of Science, and SCOPUS from inception to 20 May 2021. It had showed that endogenous LA was exhausted in the process of I/R, which further aggravated I/R injury. Thus, supplements with LA timely (especially pretreatments) may be the prospective way to prevent I/R injury. Recently, studies had demonstrated that LA supplements significantly attenuated I/R injuries of many organs, though clinic investigations were short at present. Hence, it was urgent to summarize these progresses about the effects of LA on different I/R organs as well as the potential mechanisms, which would enlighten further investigations and prepare for clinic applications in the future.

Regulation of STAT3 and its role in cardioprotection by conditioning: focus on non-genomic roles targeting mitochondrial function

Ischemia–reperfusion injury (IRI) is one of the biggest challenges for cardiovascular researchers given the huge death toll caused by myocardial ischemic disease. Cardioprotective conditioning strategies, namely pre- and post-conditioning maneuvers, represent the most important strategies for stimulating pro-survival pathways essential to preserve cardiac health. Conditioning maneuvers have proved to be fundamental for the knowledge of the molecular basis of both IRI and cardioprotection. Among this evidence, the importance of signal transducer and activator of transcription 3 (STAT3) emerged. STAT3 is not only a transcription factor but also exhibits non-genomic pro-survival functions preserving mitochondrial function from IRI. Indeed, STAT3 is emerging as an influencer of mitochondrial function to explain the cardioprotection phenomena. Studying cardioprotection, STAT3 proved to be crucial as an element of the survivor activating factor enhancement (SAFE) pathway, which converges on mitochondria and influences their function by cross-talking with other cardioprotective pathways. Clearly there are still some functional properties of STAT3 to be discovered. Therefore, in this review, we highlight the evidence that places STAT3 as a promoter of the metabolic network. In particular, we focus on the possible interactions of STAT3 with processes aimed at maintaining mitochondrial functions, including the regulation of the electron transport chain, the production of reactive oxygen species, the homeostasis of Ca²⁺ and the inhibition of opening of mitochondrial permeability transition pore. Then we consider the role of STAT3 and the parallels between STA3/STAT5 in cardioprotection by conditioning, giving emphasis to the human heart and confounders.

How cytosolic compartments play safeguard functions against neuroinflammation and cell death in cerebral ischemia

Ischemic stroke is the second leading cause of mortality and disability globally. Neuronal damage following ischemic stroke is rapid and irreversible, and eventually results in neuronal death. In addition to activation of cell death signaling, neuroinflammation is also considered as another pathogenesis that can occur within hours after cerebral ischemia. Under physiological conditions, subcellular organelles play a substantial role in neuronal functionality and viability. However, their functions can be remarkably perturbed under neurological disorders, particularly cerebral ischemia. Therefore, their biochemical and structural response has a determining role in the sequel of neuronal cells and the progression of disease. However, their effects on cell death and neuroinflammation, as major underlying mechanisms of ischemic stroke, are still not understood. This review aims to provide a comprehensive overview of the contribution of each organelle on these pathological processes after ischemic stroke.

Withania coagulans extract attenuates oxidative stress-mediated apoptosis of cerebellar purkinje neurons after ischemia/reperfusion injury

Cerebral ischemia/reperfusion (I/R) is known to increase reactive oxygen species (ROS) generation, consequences of oxidative stress (OS), and neuronal death in the susceptible brain areas including the cerebellum. Newly, remarkable attention has been paid to a natural diet with the capability to scavenge ROS. Withania coagulans root extract (WCE) is rich in components with antioxidants properties. Therefore, this study aimed to evaluate the effect of WCE on cerebellar Purkinje cells (PCs) against OS-mediated apoptosis after I/R injury. In this experimental study 64 male adult Wistar rats were randomly divided into 4 groups (n = 16) as follows: control, sham, I/R, and WCE 1000 + I/R. I/R animals were pretreated with daily administration of hydro-alcoholic WCE (1000 mg/kg) or distilled water as a vehicle for 30 days before I/R injury. After 72 h, the animals were sacrificed, the cerebellum tissue was removed and used for biochemical (CAT, SOD, GPx, and MDA levels) and histopathological (Nissl and TUNEL staining) assays. Findings showed that the MDA level and the number of apoptotic neurons significantly increased and viable Purkinje neurons decreased in I/R injury (p < 0.05). Administration of 1000 mg/kg WCE reduced MDA level and enhanced antioxidants activity including CAT, SOD, and GPx significantly. In addition, intact surviving PCs increased. At the same time, TUNEL-positive neurons decreased significantly in the WCE pre-treated group (p < 0.05). These findings suggest that WCE can counteract cerebral I/R-induced OS and associated neuronal death by enhancement of ROS scavenging and antioxidant capacity. It appears that pre-treatment with 1000 mg/kg WCE for thirty days can protect PCs against OS-mediated apoptosis after I/R injury.

Maintaining blood retinal barrier homeostasis to attenuate retinal ischemia-reperfusion injury by targeting the KEAP1/NRF2/ARE pathway with lycopene

Retinal ischemia-reperfusion (I/R) often results in intractable visual impairments, where blood retinal barrier (BRB) homeostasis mediated by retinal pigment epithelium (RPE) and retinal microvascular endothelium (RME) is crucial. However, strategies targeting the BRB are limited. Thus, we investigated the inconclusive effect of lycopene (LYC) in retinal protection under I/R. LYC elevated cellular viability and reversed oxidative stress in aRPE-19 cells/hRME cells under I/R conditions based on oxygen-glucose deprivation (OGD) in vitro. Molecular analysis showed that LYC promoted NRF2 expression and enhanced the downstream factors of the KEAP1/NRF2/ARE pathway: LYC increased the activities of antioxidants, including SOD and CAT, whereas it enhanced the mRNA expression of HO-1 (ho-1) and NQO-1 (nqo-1). The activation resulted in restrained ROS and MDA. On the other hand, LYC ameliorated the damage to retinal function and morphology in a mouse I/R model, which was established by unilateral ligation of the left pterygopalatine artery/external carotid artery and reperfusion. LYC promoted the expression of NRF2 in both the neural retina and the RPE choroid in vivo. This evidence revealed the potential of LYC in retinal protection under I/R, uncovering the pharmacological effect of the KEAP1/NRF2/ARE pathway in BRB targeting. The study generates new insights into scientific practices in retinal research.

Controlling Reperfusion Injury With Controlled Reperfusion: Historical Perspectives and New Paradigms

Cardiac reperfusion injury is a well-established outcome following treatment of acute myocardial infarction and other types of ischemic heart conditions. Numerous cardioprotection protocols and therapies have been pursued with success in pre-clinical models. Unfortunately, there has been lack of successful large-scale clinical translation, perhaps in part due to the multiple pathways that reperfusion can contribute to cell death. The search continues for new cardioprotection protocols based on what has been learned from past results. One class of cardioprotection protocols that remain under active investigation is that of controlled reperfusion. This class consists of those approaches that modify, in a controlled manner, the content of the reperfusate or the mechanical properties of the reperfusate (e.g., pressure and flow). This review article first provides a basic overview of the primary pathways to cell death that have the potential to be addressed by various forms of controlled reperfusion, including no-reflow phenomenon, ion imbalances (particularly calcium overload), and oxidative stress. Descriptions of various controlled reperfusion approaches are described, along with summaries of both mechanistic and outcome-oriented studies at the pre-clinical and clinical phases. This review will constrain itself to approaches that modify endogenously-occurring blood components. These approaches include ischemic postconditioning, gentle reperfusion, controlled hypoxic reperfusion, controlled hyperoxic reperfusion, controlled acidotic reperfusion, and controlled ionic reperfusion. This review concludes with a discussion of the limitations of past approaches and how they point to potential directions of investigation for the future.