Calcium, mitochondria and oxidative stress in neuronal pathology. Novel aspects of an enduring theme

High intracellular calcium amounts inhibit activation-induced proliferation of mouse T cells: Tert-butyl hydroquinone as an additive enhancer of intracellular calcium

Optimal T cell activation is critical to orchestrate adaptive immune responses. Calcium is critical for T cell activation and integrates signaling pathways necessary to activate key transcription factors. In fact, patients with calcium channelopathies are immunodeficient. Here, we investigated the effects of different concentrations of intracellular calcium on activation of mouse T cells. High intracellular calcium amounts inhibited in vitro T cell proliferation as evidenced by a decreased cell cycling-to-hypodiploidy ratio in two models of activation: the combination of phorbol 12-myristate 13-acetate (PMA) and Ionomycin (an ionophore)/Thapsigargin (a SERCA inhibitor) or plate bound anti-CD3 and anti-CD28. High intracellular calcium amounts increased the production of reactive oxygen species (ROS) in T cells activated with PMA and Ionomycin and scavenging excess ROS using N-acetyl cysteine (NAC) rescued the decrease in cycling-to-hypodiploidy ratio. To test the universality of our observations, we studied the effects of tert-Butylhydroquinone (tBHQ), a SERCA inhibitor and Nrf2 activator. tBHQ alone did not increase intracellular calcium amounts but the intracellular calcium amounts increased when tBHQ was used in combination with PMA. Also, tBHQ inhibited T cell activation in a dose-dependent manner in both in vitro models of T cell activation. Importantly, intraperitoneal injection of tBHQ ameliorated Dextran Sodium Sulfate (DSS)-induced colitis in mice as evidenced by rescue of colon length shortening and lower disease activity index. Overall, this study identifies high calcium amounts as a potential target to lower T cell activation. The implications of these observations are discussed in the context of calcium modulating drugs that are used to treat various diseases.

Antimicrobial and Antioxidant Activity of Some Nitrogen-Containing Heterocycles and Their Acyclic Analogues

We investigated antimicrobial and antioxidant activity of nitrogen-containing heterocycles and their acyclic analogues, some of which can be considered as promising in terms of biological activity. Based on structure, 26 tested compounds were divided into 4 groups. In the test with 2,2-diphenyl-1-picrylhydrazyl (DPPH), the compounds of the group 2 had the highest radical-binding activity (RBA) (53-78%), while those of group 3 had the lowest values (1.5-5.2%). In oxygen radical absorbance capacity assay, all compounds from groups 1, 2 and 3 showed high RBA: 44-94% at 50 µM. The highest bacteriostatic activity against Escherichia coli was found for four compounds in group 2 (MIC = 0.25-1 mM) and low bacteriostatic activity for group 3 (MIC > 4 mM). Some relationships between the structure of compounds and the values of the MIC are revealed. It was also found that four substances from different groups had the ability to inhibit the formation of colonies in E. coli from 1.3 to 5.7 times. Four compounds reduced specific biofilm formation by 40-60%. The tested substances did not induce the expression of the sulA gene controlled by the SOS system, which indicates the lack of genotoxic activity. None of the tested compounds had pro-oxidant activity. This was shown by both the absence of production hydrogen peroxide in a bacteria-free medium and inability to induce expression of the katG gene encoding HPI catalase in growing E. coli. The data obtained could be useful in the development of new drugs.

Oxidative Stress-Induced Platelet Apoptosis/Activation: Alleviation by Purified Curcumin via ASK1-JNK/p-38 Pathway

Platelets are known for their indispensable role in hemostasis and thrombosis. However, alteration in platelet function due to oxidative stress is known to mediate various health complications, including cardiovascular diseases and other health complications. To date, several synthetic molecules have displayed antiplatelet activity; however, their uses are associated with bleeding and other adverse effects. The commercially available curcumin is generally a mixture of three curcuminoids: curcumin, demethoxycurcumin, and bisdemethoxycurcumin. Although crude curcumin is known to inhibit platelet aggregation, the effect of purified curcumin on platelet apoptosis, activation, and aggregation remains unclear. Therefore, in this study, curcumin was purified from a crude curcumin mixture and the effects of this preparation on the oxidative stress-induced platelet apoptosis and activation was evaluated. 2,2'-Azobis(2-methylpropionamidine) dihydrochloride (AAPH) compound was used as an inducer of oxidative stress. Purified curcumin restored AAPH-induced platelet apoptotic markers like reactive oxygen species, intracellular calcium level, mitochondrial membrane potential, cardiolipin peroxidation, cytochrome c release from mitochondria to the cytosol, and phosphatidyl serine externalization. Further, it inhibited the agonist-induced platelet activation and aggregation, demonstrating its antiplatelet activity. Western blot analysis confirms protective effect of the purified curcumin against oxidative stress-induced platelet apoptosis and activation via downregulation of MAPKs protein activation, including ASK1, JNK, and p-38. Together, these results suggest that the purified curcumin could be a potential therapeutic bioactive molecule to treat the oxidative stress-induced platelet activation, apoptosis, and associated complications.

Neuroprotective Effects of Noncanonical PAR1 Agonists on Cultured Neurons in Excitotoxicity

Serine proteases regulate cell functions through G protein-coupled protease-activated receptors (PARs). Cleavage of one peptide bond of the receptor amino terminus results in the formation of a new N-terminus ("tethered ligand") that can specifically interact with the second extracellular loop of the PAR receptor and activate it. Activation of PAR1 by thrombin (canonical agonist) and activated protein C (APC, noncanonical agonist) was described as a biased agonism. Here, we have supposed that synthetic peptide analogs to the PAR1 tethered ligand liberated by APC could have neuroprotective effects like APC. To verify this hypothesis, a model of the ischemic brain impairment based on glutamate (Glu) excitotoxicity in primary neuronal cultures of neonatal rats has been used. It was shown that the nanopeptide NPNDKYEPF-NH2 (AP9) effectively reduced the neuronal death induced by Glu. The influence of AP9 on cell survival was comparable to that of APC. Both APC and AP9 reduced the dysregulation of intracellular calcium homeostasis in cultured neurons induced by excitotoxic Glu (100 µM) or NMDA (200 µM) concentrations. PAR1 agonist synthetic peptides might be noncanonical PAR1 agonists and a basis for novel neuroprotective drugs for disorders related to Glu excitotoxicity such as brain ischemia, trauma and some neurodegenerative diseases.

Mitochondrial Alpha-Keto Acid Dehydrogenase Complexes: Recent Developments on Structure and Function in Health and Disease

The present work delves into the enigmatic world of mitochondrial alpha-keto acid dehydrogenase complexes discussing their metabolic significance, enzymatic operation, moonlighting activities, and pathological relevance with links to underlying structural features. This ubiquitous family of related but diverse multienzyme complexes is involved in carbohydrate metabolism (pyruvate dehydrogenase complex), the citric acid cycle (α-ketoglutarate dehydrogenase complex), and amino acid catabolism (branched-chain α-keto acid dehydrogenase complex, α-ketoadipate dehydrogenase complex); the complexes all function at strategic points and also participate in regulation in these metabolic pathways. These systems are among the largest multienzyme complexes with at times more than 100 protein chains and weights ranging up to ~10 million Daltons. Our chapter offers a wealth of up-to-date information on these multienzyme complexes for a comprehensive understanding of their significance in health and disease.

Disturbing cytoskeleton by engineered nanomaterials for enhanced cancer therapeutics

Cytoskeleton plays a significant role in the shape change, migration, movement, adhesion, cytokinesis, and phagocytosis of tumor cells. In clinical practice, some anti-cancer drugs achieve cytoskeletal therapeutic effects by acting on different cytoskeletal protein components. However, in the absence of cell-specific targeting, unnecessary cytoskeletal recombination in organisms would be disastrous, which would also bring about severe side effects during anticancer process. Nanomedicine have been proven to be superior to some small molecule drugs in cancer treatment due to better stability and targeting, and lower side effects. Therefore, this review summarized the recent developments of various nanomaterials disturbing cytoskeleton for enhanced cancer therapeutics, including carbon, noble metals, metal oxides, black phosphorus, calcium, silicon, polymers, peptides, and metal-organic frameworks, etc. A comprehensive analysis of the characteristics of cytoskeleton therapy as well as the future prospects and challenges towards clinical application were also discussed. We aim to drive on this emerging topic through refreshing perspectives based on our own work and what we have also learnt from others. This review will help researchers quickly understand relevant cytoskeletal therapeutic information to further advance the development of cancer nanomedicine.

Cellular Uptake of Catharanthus roseus-Silver Nanoparticles in Human Hepatocellular Carcinoma HepG2 Cells

Introduction: Nanoparticles exhibit unique features and currently at the forefront of cutting-edge research. Silver nanoparticles (AgNPs) are among the most promising and widely commercialised nanoproducts in various fields. The interaction of these AgNPs with cells remain unclear to connect with its toxicological endpoints. The aim of this study was to investigate the cellular uptake of C. roseus-AgNPs in hepatocellular carcinoma cells HepG2. Methods: The HepG2 cells were treated with the mean IC50 value of C. roseus-AgNPs which was 4.95±0.26 µg/mL for 24, 48 and 72 hours. The effects were compared with the untreated cells and other treatments which include camptothecin, C. roseus-aqueous extract, and AgNO3. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used to quantify the intracellular Ag+ and Ca2+, while transmission electron microscopy (TEM) imaging was used to visualise the nanoparticle distribution. Results: The HepG2 cells have significantly taken up Ag+ from C. roseus-AgNPs with at least six times higher compared to Ag+ from AgNO3. The intracellular Ca2+ detected in HepG2 cells for all treatments were significantly higher than the untreated cells, in time-dependent manner. TEM images indicated the endocytosis of C. roseus-AgNPs with the presence of endosomes and exocytic vesicles. Conclusion: The significant accumulation of intracellular Ag+ demonstrated the efficiency of the C. roseus-AgNPs uptake while the increased Ca2+ indicated the early sign of cell injury. The cellular uptake was mainly through endocytosis. These findings are crucial to correlate the physicochemical properties of C. roseus-AgNPs with the anticancer mechanisms towards the development of liver cancer therapy.

L- and T-type Ca2+ channels dichotomously contribute to retinal ganglion cell injury in experimental glaucoma

Retinal ganglion cell apoptotic death is the main pathological characteristic of glaucoma, which is the leading cause of irreversible blindness. Disruption of Ca²⁺ homeostasis plays an important role in glaucoma. Voltage-gated Ca²⁺ channel blockers have been shown to improve vision in patients with glaucoma. However, whether and how voltage-gated Ca²⁺ channels are involved in retinal ganglion cell apoptotic death are largely unknown. In this study, we found that total Ca²⁺ current densities in retinal ganglion cells were reduced in a rat model of chronic ocular hypertension experimental glaucoma, as determined by whole-cell patch-clamp electrophysiological recordings. Further analysis showed that L-type Ca²⁺ currents were downregulated while T-type Ca²⁺ currents were upregulated at the later stage of glaucoma. Western blot assay and immunofluorescence experiments confirmed that expression of the Ca_V1.2 subunit of L-type Ca²⁺ channels was reduced and expression of the Ca_V3.3 subunit of T-type Ca²⁺ channels was increased in retinas of the chronic ocular hypertension model. Soluble tumor necrosis factor-α, an important inflammatory factor, inhibited the L-type Ca²⁺ current of isolated retinal ganglion cells from control rats and enhanced the T-type Ca²⁺ current. These changes were blocked by the tumor necrosis factor-α inhibitor XPro1595, indicating that both types of Ca²⁺ currents may be mediated by soluble tumor necrosis factor-α. The intracellular mitogen-activated protein kinase/extracellular signal-regulated kinase pathway and nuclear factor kappa-B signaling pathway mediate the effects of tumor necrosis factor-α. TUNEL assays revealed that mibefradil, a T-type calcium channel blocker, reduced the number of apoptotic retinal ganglion cells in the rat model of chronic ocular hypertension. These results suggest that T-type Ca²⁺ channels are involved in disrupted Ca²⁺ homeostasis and apoptosis of retinal ganglion cells in glaucoma, and application of T-type Ca²⁺ channel blockers, especially a specific Ca_V3.3 blocker, may be a potential strategy for the treatment of glaucoma.

TWEAK-Fn14 Axis Induces Calcium-Associated Autophagy and Cell Death To Control Mycobacterial Survival in Macrophages

Autophagy is a natural defense mechanism that protects the host against pathogens. We previously demonstrated that mycobacterial infection upregulated tumor necrosis factor-like weak inducer of apoptosis (TWEAK) to promote autophagy and mycobacterial autophagosome maturation through activation of AMP-activated protein kinase (AMPK). Fibroblast growth factor-inducible 14 (Fn14) is the receptor of TWEAK. But the role of Fn14 in mycobacterial infection remains elusive. Herein, we observed increased expression of Fn14 in peripheral blood mononuclear cells of active tuberculosis (TB) patients. Downregulation of cellular Fn14 enhanced mycobacterial survival in macrophages. Conversely, Fn14 overexpression inhibited mycobacterial growth, suggesting that Fn14 can inhibit mycobacterial infection. The in vitro results revealed that TWEAK-promoted mycobacterial phagosome maturation is Fn14-dependent. We demonstrated that TWEAK-Fn14 signaling promotes oxidative stress to enhance the expression of stromal interaction molecule 1 (STIM1) and its activation of the Ca2+ channel ORAI1. Elevated calcium influx stimulated the activation of CaMCCK2 (calcium/calmodulin-dependent protein kinase kinase 2) and its downstream effector AMPK, thus inducing autophagy in early infection. Persistently TWEAK-Fn14 signaling caused cell death in late infection by reducing mitochondrial membrane potential, leading to mitochondrial ROS accumulation, and activating cell death-associated proteins. Genetic Fn14 deficiency or TWEAK blockers decreased oxidative stress-induced calcium influx, thus suppressing autophagy and cell death in mycobacteria-infected macrophages, and resulting in elevated mycobacterial survival. We propose that the TWEAK-Fn14 axis and calcium influx could be manipulated for anti-TB therapeutic purposes. Our results offer a new molecular machinery to understand the association between the TWEAK-Fn14 axis, calcium influx, and mycobacterial infection. IMPORTANCE Tuberculosis remains a major cause of morbidity and mortality worldwide. We previously demonstrated a relationship between TWEAK and activation of the autophagic machinery, which promotes anti-mycobacterial immunity. The TWEAK-Fn14 axis is multi-functional and involved in the pathogenesis of many diseases, thus blockade of TWEAK-Fn14 axis has been considered as a potential therapeutic target. Here, we demonstrated that the TWEAK-Fn14 axis plays a novel role in anti-mycobacterial infection by regulating calcium-associated autophagy. Persistently, TWEAK-Fn14 signaling caused cell death in late infection by reducing mitochondrial membrane potential, leading to mitochondrial ROS accumulation, and activating cell death-associated proteins. TWEAK blocker or Fn14 deficiency could suppress oxidative stress and calcium-associated autophagy, resulting in elevated mycobacterial survival. We propose that the TWEAK-Fn14 axis and calcium influx could be manipulated for anti-TB therapeutic purposes. This study offers a new molecular machinery to understand the association between the TWEAK-Fn14 axis, calcium influx, and mycobacterial infection.

Bridging the gap of axonal regeneration in the central nervous system: A state of the art review on central axonal regeneration

Neuronal regeneration in the central nervous system (CNS) is an important field of research with relevance to all types of neuronal injuries, including neurodegenerative diseases. The glial scar is a result of the astrocyte response to CNS injury. It is made up of many components creating a complex environment in which astrocytes play various key roles. The glial scar is heterogeneous, diverse and its composition depends upon the injury type and location. The heterogeneity of the glial scar observed in different situations of CNS damage and the consequent implications for axon regeneration have not been reviewed in depth. The gap in this knowledge will be addressed in this review which will also focus on our current understanding of central axonal regeneration and the molecular mechanisms involved. The multifactorial context of CNS regeneration is discussed, and we review newly identified roles for components previously thought to solely play an inhibitory role in central regeneration: astrocytes and p75NTR and discuss their potential and relevance for deciding therapeutic interventions. The article ends with a comprehensive review of promising new therapeutic targets identified for axonal regeneration in CNS and a discussion of novel ways of looking at therapeutic interventions for several brain diseases and injuries.

Substrate stiffness effect on molecular crosstalk of epithelial-mesenchymal transition mediators of human glioblastoma cells

The complexity of the microenvironment effects on cell response, show accumulating evidence that glioblastoma (GBM) migration and invasiveness are influenced by the mechanical rigidity of their surroundings. The epithelial–mesenchymal transition (EMT) is a well-recognized driving force of the invasive behavior of cancer. However, the primary mechanisms of EMT initiation and progression remain unclear. We have previously showed that certain substrate stiffness can selectively stimulate human GBM U251-MG and GL15 glioblastoma cell lines motility. The present study unifies several known EMT mediators to uncover the reason of the regulation and response to these stiffnesses. Our results revealed that changing the rigidity of the mechanical environment tuned the response of both cell lines through change in morphological features, epithelial-mesenchymal markers (E-, N-Cadherin), EGFR and ROS expressions in an interrelated manner. Specifically, a stiffer microenvironment induced a mesenchymal cell shape, a more fragmented morphology, higher intracellular cytosolic ROS expression and lower mitochondrial ROS. Finally, we observed that cells more motile showed a more depolarized mitochondrial membrane potential. Unravelling the process that regulates GBM cells’ infiltrative behavior could provide new opportunities for identification of new targets and less invasive approaches for treatment.

Evaluation of mitochondrial dysfunction due to oxidative stress in therapeutic, toxic and lethal concentrations of tramadol

Tramadol (TR) is a centrally acting analgesic drug that is used to relieve pain. The therapeutic (0.1-0.8 mg/l), toxic (1-2 mg/l) and lethal (>2 mg/l) ranges were reported for TR. The present study was designed to evaluate which doses of TR can induce liver mitochondrial toxicity. Mitochondria were isolated from the five rats' liver and were incubated with therapeutic to lethal concentrations (1.7-600 μM) of TR. Biomarkers of oxidative stress including: reactive oxygen species (ROS), lipid peroxidation (LPO), protein carbonyl content, glutathione (GSH) content, mitochondrial function, mitochondrial membrane potential (MMP) and mitochondrial swelling were assessed. Our results showed that ROS and LPO at 100 μM and protein carbonylation at 600 μM concentrations of TR were significantly increased. GSH was decreased specifically at 600 μM concentration. Mitochondrial function, MMP and mitochondrial swelling decreased in isolated rat liver mitochondria after exposure to 100 and 300 μM, respectively. This study suggested that TR at therapeutic and toxic levels by single exposure could not induce mitochondrial toxicity. But, in lethal concentration (≥100 μM), TR induced oxidative damage and mitochondria dysfunction. This study suggested that ROS overproduction by increasing of TR concentration induced mitochondrial dysfunction and caused mitochondrial damage via Complex II and membrane permeability transition pores disorders, MMP collapse and mitochondria swelling.

Impacts of oxidants and antioxidants on the emergence and progression of Alzheimer's disease

The brain shows a high sensitivity to oxidative stress (OS). Thus, the maintenance of homeostasis of the brain regarding the reduction-oxidation (redox) situation is crucial for the regular function of the central nervous systems (CNS). The imbalance between the reactive oxygen species (ROS) and the cellular mechanism might lead to the emergence of OS, causing profound cell death as well as tissue damages and initiating neurodegenerative disorders (NDDs). Characterized by the cytoplasmic growth of neurofibrillary tangles and extracellular β-amyloid plaques, Alzheimer's disease (AD) is a complex NDD that causes dementia in adult life with severe manifestations. Nuclear factor erythroid 2-related factor 2 (NRF2) is a key transcription factor that regulates the functional expression of OS-related genes and the functionality of endogenous antioxidants. In the case of oxidative damage, NRF2 is transferred to the nucleus and attached to the antioxidant response element (ARE) that enhances the sequence to initiate transcription of the cell-protecting genes. This review articulates various mechanisms engaged with the generation of active and reactive species of endogenous and exogenous oxidants and focuses on the antioxidants as a body defense system regarding the NRF2-ARE signaling path in the CNS.

Hydrogen-rich saline reduces tissue injury and improves skin flap survival on a rat hindlimb degloving injury model

BACKGROUND

Degloving injuries represent a challenge in plastic surgery. The aim of this study is to acknowledge the protective effects of hydrogen-rich saline (HRS) solution on a rat hindlimb degloved skin flap.

METHODS

Twenty-one Sprague-Dawley rats were divided into three groups (control, saline and HRS). Degloving injury model was established, and flaps were sutured back following 5 min of ischemia. The control group did not receive any treatment. The saline group received intraperitoneal physiological saline (10 ml/kg) and the HRS group received intraperitoneal HRS solution (10 ml/kg) postoperatively and daily for 5 days after the operation. Skin samples were obtained for histological, immunohistochemical and biochemical evaluations.

RESULTS

Inflammation was lower in the HRS compared with saline (p = 0.02) and control (p = 0.004) groups. Edema was lower in the HRS compared with saline (p = 0.02) and control (p = 0.001) groups. Malondialdehyde (MDA) level was lower in the HRS than the control group (p = 0.01). Total antioxidant level was higher in the HRS compared with saline (p = 0.009) and control (p = 0.03) groups. Total oxidant level was lower in the HRS than the control group (p = 0.02). Oxidative stress index was lower in the HRS compared with saline (p = 0.001) and control (p = 0.0001) groups`. Vascular proliferation was higher in the HRS compared with the control group (p = 0.01).

CONCLUSION

Repeated HRS injections after trauma increased the viability of skin flap in rat degloving injury model by decreasing local tissue injury, due to its antioxidant, anti-inflammatory and angiogenic effects.

Drug-Induced Vanishing Bile Duct Syndrome: From Pathogenesis to Diagnosis and Therapeutics

The most concerned issue in the context of drug/herb-induced chronic cholestasis is vanishing bile duct syndrome. The progressive destruction of intrahepatic bile ducts leading to ductopenia is usually not dose dependent, and has a delayed onset that should be suspected when abnormal serum cholestasis enzyme levels persist despite drug withdrawal. Immune-mediated cholangiocyte injury, direct cholangiocyte damage by drugs or their metabolites once in bile, and sustained exposure to toxic bile salts when biliary epithelium protective defenses are impaired are the main mechanisms of cholangiolar damage. Current therapeutic alternatives are scarce and have not shown consistent beneficial effects so far. This review will summarize the current literature on the main diagnostic tools of ductopenia and its histological features, and the differential diagnostic with other ductopenic diseases. In addition, pathomechanisms will be addressed, as well as the connection between them and the supportive and curative strategies for ductopenia management.

Calcium-Induced Autonomic Denervation in Patients With Post-Operative Atrial Fibrillation

BACKGROUND

Post-operative atrial fibrillation (POAF) is associated with worse long-term cardiovascular outcomes.

OBJECTIVES

This study hypothesized that injecting calcium chloride (CaCl₂) into the major atrial ganglionated plexi (GPs) during isolated coronary artery bypass grafting (CABG) can reduce the incidence of POAF by calcium-induced autonomic neurotoxicity.

METHODS

This proof-of-concept study randomized 200 patients undergoing isolated, off-pump CABG to CaCl₂ (n = 100) or sodium chloride (sham, n = 100) injection. Two milliliters of CaCl₂ (5%) or sodium chloride (0.9%) was injected into the 4 major atrial GPs during CABG. All patients received 7-day continuous telemetry and Holter monitoring. The primary outcome was incidence of POAF (≥30 s) in 7 days. Secondary outcomes included length of hospitalization, POAF burden, average ventricular rate during AF, plasma level of inflammatory markers, and actionable antiarrhythmic therapy to treat POAF.

RESULTS

The POAF incidence was reduced from 36% to 15% (hazard ratio: 0.366; 95% confidence interval: 0.211 to 0.635; p = 0.001). Length of hospitalization did not differ between the 2 groups. POAF burden (first 7 post-operative days), the use of amiodarone or esmolol, and the incidence of atrial couplets and nonsustained atrial tachyarrhythmias were significantly reduced in the CaCl₂ group. Heart rate variability data showed a decrease in both high-frequency and low-frequency power in the CaCl₂ group with a preserved low-frequency/high-frequency ratio, suggesting that the sympathetic/parasympathetic balance was not perturbed by CaCl₂ injection.

CONCLUSIONS

Injection of CaCl₂ into the 4 major atrial GPs reduced the POAF hazard by 63%. Inhibition of GP function by Ca-mediated neurotoxicity may underlie the therapeutic effect. (Calcium Autonomic Denervation Prevents Postoperative Atrial Fibrillation; ChiCTR1800019276).

An Unbalanced Synaptic Transmission: Cause or Consequence of the Amyloid Oligomers Neurotoxicity?

Amyloid-β (Aβ) 1-40 and 1-42 peptides are key mediators of synaptic and cognitive dysfunction in Alzheimer's disease (AD). Whereas in AD, Aβ is found to act as a pro-epileptogenic factor even before plaque formation, amyloid pathology has been detected among patients with epilepsy with increased risk of developing AD. Among Aβ aggregated species, soluble oligomers are suggested to be responsible for most of Aβ's toxic effects. Aβ oligomers exert extracellular and intracellular toxicity through different mechanisms, including interaction with membrane receptors and the formation of ion-permeable channels in cellular membranes. These damages, linked to an unbalance between excitatory and inhibitory neurotransmission, often result in neuronal hyperexcitability and neural circuit dysfunction, which in turn increase Aβ deposition and facilitate neurodegeneration, resulting in an Aβ-driven vicious loop. In this review, we summarize the most representative literature on the effects that oligomeric Aβ induces on synaptic dysfunction and network disorganization.

Photobiomodulation and Oxidative Stress: 980 nm Diode Laser Light Regulates Mitochondrial Activity and Reactive Oxygen Species Production

Photobiomodulation with 808 nm laser light electively stimulates Complexes III and IV of the mitochondrial respiratory chain, while Complexes I and II are not affected. At the wavelength of 1064 nm, Complexes I, III, and IV are excited, while Complex II and some mitochondrial matrix enzymes seem to be not receptive to photons at that wavelength. Complex IV was also activated by 633 nm. The mechanism of action of wavelengths in the range 900–1000 nm on mitochondria is less understood or not described. Oxidative stress from reactive oxygen species (ROS) generated by mitochondrial activity is an inescapable consequence of aerobic metabolism. The antioxidant enzyme system for ROS scavenging can keep them under control. However, alterations in mitochondrial activity can cause an increment of ROS production. ROS and ATP can play a role in cell death, cell proliferation, and cell cycle arrest. In our work, bovine liver isolated mitochondria were irradiated for 60 sec, in continuous wave mode with 980 nm and powers from 0.1 to 1.4 W (0.1 W increment at every step) to generate energies from 6 to 84 J, fluences from 7.7 to 107.7 J/cm², power densities from 0.13 to 1.79 W/cm², and spot size 0.78 cm². The control was equal to 0 W. The activity of the mitochondria's complexes, Krebs cycle enzymes, ATP production, oxygen consumption, generation of ROS, and oxidative stress were detected. Lower powers (0.1–0.2 W) showed an inhibitory effect; those that were intermediate (0.3–0.7 W) did not display an effect, and the higher powers (0.8–1.1 W) induced an increment of ATP synthesis. Increasing the power (1.2–1.4 W) recovered the ATP production to the control level. The interaction occurred on Complexes III and IV, as well as ATP production and oxygen consumption. Results showed that 0.1 W uncoupled the respiratory chain and induced higher oxidative stress and drastic inhibition of ATP production. Conversely, 0.8 W kept mitochondria coupled and induced an increase of ATP production by increments of Complex III and IV activities. An augmentation of oxidative stress was also observed, probably as a consequence of the increased oxygen consumption and mitochondrial isolation experimental conditions. No effect was observed using 0.5 W, and no effect was observed on the enzymes of the Krebs cycle.

Rapid and Targeted Photoactivation of Ca2+ Channels Mediated by Squaraine To Regulate Intracellular and Intercellular Signaling Processes

As an important cellular signal transduction messenger, Ca²⁺ has the capability to regulate cell function and control many biochemical processes, including metabolism, gene expression, and cell survival and death. Here, we introduce an accessible method for the photoactivation of Ca²⁺ channels mediated by squaraine (SQ) to rapidly induce cellular Ca²⁺ release and activate signal transduction. With a short preparation time, the maximum Ca²⁺ concentration increase could reach approximately 450% in 30 s, resulting from marked Ca²⁺ release channel opening in the endoplasmic reticulum (ER). This release was enhanced by another target location of SQ, that is, the outer mitochondrial-associated membrane where Ca²⁺ channels accumulate, and by the consequent large amounts of reactive oxygen species resulting from the respiratory chain activity stimulated by Ca²⁺ load. We used this method to investigate cellular signal transduction in different cancer cells and revealed rapid intracellular Ca²⁺ flow, unidirectional intercellular signaling processes, and neuronal signaling activity, which demonstrated the potential and convenience of the method for routine Ca²⁺ research.

Verapamil attenuates scopolamine induced cognitive deficits by averting oxidative stress and mitochondrial injury - A potential therapeutic agent for Alzheimer's Disease

Alzheimer's disease (AD) is a multifactorial disorder where amyloid beta (Aβ) plaques, Ca2+ dysregulation, excessive oxidative stress, mitochondrial dysfunction and synaptic loss operate synergistically to bring about cholinergic deficits and dementia. New therapeutic interventions are gaining prominence as the morbidity and mortality of AD increases exponentially every year. Treating AD with antihypertensive drugs is thought to be a promising intervention; however, its mechanism of action of ameliorating AD needs further investigation. In this context, the present study explores the protective effect of verapamil, an antihypertensive agent of Ca2+ channel blocker (CCB) class against scopolamine-induced in vitro neurotoxicity and in vivo cognitive impairment. Supplementation of verapamil was found to attenuate oxidative stress by preventing mitochondrial injury, and augment the expression of genes involved in the cholinergic function (mACR1), synaptic plasticity (GAP43, SYP) and Ca2+-dependent memory-related genes (CREB1, CREBBP, BDNF). Further, verapamil treatment in mice attenuated the cognitive and behavioural deficits induced by scopolamine as measured by the elevated plus maze and passive avoidance test (P < 0.05). Thus, the present study demonstrates the neuroprotective effect of verapamil against the pathogenesis of AD such as oxidative stress, mitochondrial dysfunction and cognitive decline. These observations emphasize the importance of ‛Ca2+ dysregulation' and ‛mitochondrial dysfunction' theories in AD and recommends the supplementation of compounds that regulate Ca2+ homeostasis and mitochondrial function in susceptible AD individuals.

Shengmai injection alleviates H2O2‑induced oxidative stress through activation of AKT and inhibition of ERK pathways in neonatal rat cardiomyocytes

ETHNOPHARMACOLOGICAL RELEVANCE

Shengmai injection (SMI) is a classical traditional Chinese medicine (TCM) officially recorded in Pharmacopoeia of the People's Republic of China (version 2015) and has long been used to treat heart failure in China. However scientific evidence for the anti-oxidative stress potential of SMI used in traditional medicine is lacking.

AIM OF STUDY

The present study aimed to evaluate the efficacy of SMI in alleviating H₂O₂‑induced Oxidative Stress the underlying mechanisms MATERIALS AND METHODS: H₂O₂-induced oxidative stress model of cardiomyocytes was established with primary cultured neonatal rat cardiomyocytes. CCK8 cell viability assay and lacatate dehydrogenase cytotoxicity assay were performed to ensure the safety dose and lowest effective dose for the mode employing CCK-8 cell viability assay kit and lactate dehydrogenase cytotoxicity assay kit. ROS levels were determined using CM-H2DCFDA fluorescent probe in cardiomyocytes with H₂O₂-induced oxidative stress. The change of NAD(P)H level in cardiomyocytes was evaluated during the process of oxidative stress. The content of myocardial cytosolic Ca²⁺ and Ca²⁺ was determined using Fura-2/AM and Rhod 2-AM fluorescent probe in mitochondrial in the process of oxidative stress. Annexin V-FITC/PI double staining was applied to examine the apoptotic cells in cardiomyocytes with oxidative stress. To identify the apoptosis after oxidative stress myocardial cells with the application of Annexin V-FITC/PI double staining apoptosis detection kit. Quantitative polymerase chain reaction (RT-PCR) was applied to measure the expression of antioxidant enzymes: catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GSR). Western blot was performed to observe the phosphorylation of AKT and ERK1/2.

RESULTS

SMI was shown to significantly attenuate oxidative stress-induced cell proliferation arrest and apoptosis in neonatal rat cardiomyocytes. In addition, SMI treatment could decrease the production of reactive oxygen species (ROS), nicotinamide adenine dinucleotide (NADH) and malondialdehyde (MDA), and reduce the overloads of cytoplasmic Ca²⁺ and mitochondrial Ca²⁺ induced by H₂O₂. SMI could also restore the mRNA expression and activities of SOD, GSR, and CAT suppressed by H₂O₂. Mechanistically, SMI upregulated intracellular AKT phosphorylation and downregulate ERK1/2 phosphorylation in H₂O₂-treated cardiomyocytes. Pretreatment with LY294002, an AKT phosphorylation inhibitor, suppressed the protective role of SMI in cardiomyocytes, while pretreatment with PD98059, an ERK1/2 phosphorylation inhibitor, enhanced the effect of SMI.

CONCLUSIONS

In conclusion, SMI may attenuate oxidative stress-induced damage in cardiomyocytes potentially through the AKT and ERK1/2 pathway and can function as a promising injectable traditional Chinese medicine to treat oxidative stress-induced injury.

Noninvasive Ultrasound Deep Brain Stimulation for the Treatment of Parkinson's Disease Model Mouse

Modulating basal ganglia circuitry is of great significance in the improvement of motor function in Parkinson's disease (PD). Here, for the first time, we demonstrate that noninvasive ultrasound deep brain stimulation (UDBS) of the subthalamic nucleus (STN) or the globus pallidus (GP) improves motor behavior in a subacute mouse model of PD induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Immunohistochemical c-Fos protein expression confirms that there is a relatively high level of c-Fos expression in the STN-UDBS and GP-UDBS group compared with sham group (both p < 0.05). Furthermore, STN-UDBS or GP-UDBS significantly increases the latency to fall in the rotarod test on day 9 (p < 0.05) and decreases the time spent climbing down a vertical rod in the pole test on day 12 (p < 0.05). Moreover, our results reveal that STN-UDBS or GP-UDBS protects the dopamine (DA) neurons from MPTP neurotoxicity by downregulating Bax (p < 0.001), upregulating Bcl-2 (p < 0.01), blocking cytochrome c (Cyt C) release from mitochondria (p < 0.05), and reducing cleaved-caspase 3 activity (p < 0.01) in the ipsilateral substantia nigra (SN). Additionally, the safety of ultrasound stimulation is characterized by hematoxylin and eosin (HE) and Nissl staining; no hemorrhage or tissue damage is detected. These data demonstrate that UDBS enables modulation of STN or GP neural activity and leads to neuroprotection in PD mice, potentially serving as a noninvasive strategy for the clinical treatment of PD.

Photobiomodulation preconditioning prevents cognitive impairment in a neonatal rat model of hypoxia-ischemia

Neonatal hypoxia-ischemia (HI) injury caused by oxygen deprivation is the most common cause of mortality and severe neurologic deficits in neonates. The present work evaluated the preventative effect of photobiomodulation (PBM) preconditioning, and its underlying mechanism of action on brain damage in an HI model in neonatal rats. According to the optimal time response of ATP levels in brain samples removed from normal rats, a PBM preconditioning (PBM-P) regimen (808 nm CW laser, 1 cm2 spot, 100 mW/cm2 , 12 J/cm2 ) was delivered to the scalp 6 hours before HI. PBM-P significantly attenuated cognitive impairment, volume shrinkage in the brain, neuron loss, dendritic and synaptic injury after HI. Further mechanistic investigation found that PBM-P could restore HI-induced mitochondrial dynamics and inhibit mitochondrial fragmentation, followed by a robust suppression of cytochrome c release, and prevention of neuronal apoptosis by inhibition of caspase activation. Our work suggests that PBM-P can attenuate HI-induced brain injury by maintaining mitochondrial dynamics and inhibiting the mitochondrial apoptotic pathway.

The Protective Effects of Levetiracetam on a Human iPSCs-Derived Spinal Muscular Atrophy Model

Spinal muscular atrophy (SMA) is an inherited disease characterized by progressive motor neuron death and subsequent muscle weakness and is caused by deletion or mutation of survival motor neuron (SMN) 1 gene. Protecting spinal motor neuron is an effective clinical strategy for SMA. The purpose of this study was to investigate the potential effect of an anti-epileptic drug levetiracetam on SMA. In the present study, we used differentiated spinal motor neurons (MNs) from SMA patient-derived induced pluripotent stem cells (SMA-iPSCs) to investigate the effect of levetiracetam. Levetiracetam promoted neurite elongation in SMA-iPSCs-MNs. TUNEL-positive spinal motor neurons were significantly reduced by levetiracetam in SMA-iPSCs-MNs. In addition, the expression level of cleaved-caspase 3 was decreased by levetiracetam in SMA-iPSCs-MNs. Furthermore, levetiracetam improved impaired mitochondrial function in SMA-iPSCs-MNs. On the other hand, levetiracetam did not affect the expression level of SMN protein in SMA-iPSCs-MNs. These findings indicate that levetiracetam has a neuroprotective effect for SMA.

The Effects of Sodium Dichloroacetate on Mitochondrial Dysfunction and Neuronal Death Following Hypoglycemia-Induced Injury

Our previous studies demonstrated that some degree of neuronal death is caused by hypoglycemia, but a subsequent and more severe wave of neuronal cell death occurs due to glucose reperfusion, which results from the rapid restoration of low blood glucose levels. Mitochondrial dysfunction caused by hypoglycemia leads to increased levels of pyruvate dehydrogenase kinase (PDK) and suppresses the formation of ATP by inhibiting pyruvate dehydrogenase (PDH) activation, which can convert pyruvate into acetyl-coenzyme A (acetyl-CoA). Sodium dichloroacetate (DCA) is a PDK inhibitor and activates PDH, the gatekeeper of glucose oxidation. However, no studies about the effect of DCA on hypoglycemia have been published. In the present study, we hypothesized that DCA treatment could reduce neuronal death through improvement of glycolysis and prevention of reactive oxygen species production after hypoglycemia. To test this, we used an animal model of insulin-induced hypoglycemia and injected DCA (100 mg/kg, i.v., two days) following hypoglycemic insult. Histological evaluation was performed one week after hypoglycemia. DCA treatment reduced hypoglycemia-induced oxidative stress, microglial activation, blood–brain barrier disruption, and neuronal death compared to the vehicle-treated hypoglycemia group. Therefore, our findings suggest that DCA may have the therapeutic potential to reduce hippocampal neuronal death after hypoglycemia.

Perioperatively Inhaled Hydrogen Gas Diminishes Neurologic Injury Following Experimental Circulatory Arrest in Swine

This study used a swine model of mildly hypothermic prolonged circulatory arrest and found that the addition of 2.4% inhaled hydrogen gas to inspiratory gases during and after the ischemic insult significantly decreased neurologic and renal injury compared with controls. With proper precautions, inhalational hydrogen may be administered safely through conventional ventilators and may represent a complementary therapy that can be easily incorporated into current workflows. In the future, inhaled hydrogen may diminish the sequelae of ischemia that occurs in congenital heart surgery, cardiac arrest, extracorporeal life-support events, acute myocardial infarction, stroke, and organ transplantation.

Noxious Iron-Calcium Connections in Neurodegeneration

Iron and calcium share the common feature of being essential for normal neuronal function. Iron is required for mitochondrial function, synaptic plasticity, and the development of cognitive functions whereas cellular calcium signals mediate neurotransmitter exocytosis, axonal growth and synaptic plasticity, and control the expression of genes involved in learning and memory processes. Recent studies have revealed that cellular iron stimulates calcium signaling, leading to downstream activation of kinase cascades engaged in synaptic plasticity. The relationship between calcium and iron is Janus-faced, however. While under physiological conditions iron-mediated reactive oxygen species generation boosts normal calcium-dependent signaling pathways, excessive iron levels promote oxidative stress leading to the upsurge of unrestrained calcium signals that damage mitochondrial function, among other downstream targets. Similarly, increases in mitochondrial calcium to non-physiological levels result in mitochondrial dysfunction and a predicted loss of iron homeostasis. Hence, if uncontrolled, the iron/calcium self-feeding cycle becomes deleterious to neuronal function, leading eventually to neuronal death. Here, we review the multiple cell-damaging responses generated by the unregulated iron/calcium self-feeding cycle, such as excitotoxicity, free radical-mediated lipid peroxidation, and the oxidative modification of crucial components of iron and calcium homeostasis/signaling: the iron transporter DMT1, plasma membrane, and intracellular calcium channels and pumps. We discuss also how iron-induced dysregulation of mitochondrial calcium contributes to the generation of neurodegenerative conditions, including Alzheimer’s disease (AD) and Parkinson’s disease (PD).

Intermittent hypoxia training: Powerful, non-invasive cerebroprotection against ethanol withdrawal excitotoxicity

Ethanol intoxication and withdrawal exact a devastating toll on the central nervous system. Abrupt ethanol withdrawal provokes massive release of the excitatory neurotransmitter glutamate, which over-activates its postsynaptic receptors, causing intense Ca2+ loading, p38 mitogen activated protein kinase activation and oxidative stress, culminating in ATP depletion, mitochondrial injury, amyloid β deposition and neuronal death. Collectively, these mechanisms produce neurocognitive and sensorimotor dysfunction that discourages continued abstinence. Although the brain is heavily dependent on blood-borne O2 to sustain its aerobic ATP production, brief, cyclic episodes of moderate hypoxia and reoxygenation, when judiciously applied over the course of days or weeks, evoke adaptations that protect the brain from ethanol withdrawal-induced glutamate excitotoxicity, mitochondrial damage, oxidative stress and amyloid β accumulation. This review summarizes evidence from ongoing preclinical research that demonstrates intermittent hypoxia training to be a potentially powerful yet non-invasive intervention capable of affording robust, sustained neuroprotection during ethanol withdrawal.

Emerging mechanisms and novel applications of hydrogen gas therapy

Clinical and pre-clinical studies have reported a broad range of applications for hydrogen gas therapy. Classically, conventional antioxidant therapy is limited because it neutralizes both the detrimental and protective effects of reactive oxygen species. As a weak reducing agent, hydrogen gas avoids this paradox by reacting with strong oxidants while leaving other beneficial oxidants reactive. This review gathers a promising list of hydrogen gas applications that merit further mechanistic investigation and additional therapeutic trials. Reports support the ability of hydrogen gas to downregulate the expression of pro-inflammatory cytokines and pro-apoptotic factors. Mechanistically, hydrogen gas has been shown to downregulate miR-9 and miR-21, while upregulating miR-199 to reduce inflammatory injury. In angiogenic pathways, hydrogen's inhibition of cyclic guanosine monophosphate-degrading phosphodiesterase led to higher levels of cyclic guanosine monophosphate, activation of protein kinase, and angiogenesis; next, as hydrogen gas increased the levels of intracellular calcium, stimulated vascular endothelial growth factor increased nitric oxide production. In conjunction, hydrogen gas opened adenosine triphosphate-sensitive potassium channel channels, which activate downstream mitogen-activated protein kinase pathways. Growing molecular mechanisms have discovered a plethora of downstream targets for hydrogen gas therapy that include autophagy (via the adenosine 5’-monophosphate-activated protein kinase/mammalian target of rapamycin pathway), histone modification, mitochondrial unfolded protein response, acute oxidative stress after exercise, and oxidative stress secondary to aging. In conclusion, evolving research has discovered novel molecular connections that will continue to widen applications for hydrogen therapy.

Targeted Ganglionated Plexi Denervation Using Magnetic Nanoparticles Carrying Calcium Chloride Payload

OBJECTIVES

This study sought to develop a novel targeted delivery therapy to ablate the major atrial ganglionated plexi (GP) using magnetic nanoparticles carrying a CaCl₂ payload.

BACKGROUND

Prior studies indicated the role of hyperactivity of the cardiac autonomic nervous system in the genesis of atrial fibrillation.

METHODS

Twenty-eight male mongrel dogs underwent a bilateral thoracotomy. CaCl₂-encapsulated magnetic nanoparticles (Ca-MNP) included magnetite in a sphere of biocompatible, biodegradable poly(lactic-co-glycolic acid). A custom external electromagnet focusing the magnetic field gradient (2,600 G) on the epicardial surface of the targeted GP was used to pull Ca-MNP into and release CaCl₂ within the GP. The ventricular rate slowing response to high frequency stimulation (20 Hz, 0.1 ms) of the GP was used to assess the GP function.

RESULTS

The minimal effective concentration of CaCl₂ to inhibit the GP function was 0.5 mmol/l. Three weeks after CaCl₂ (0.5 mmol/l, n = 18 GP) or saline (n = 18 GP) microinjection into GP, the increased GP function, neural activity, and atrial fibrillation inducibility, as well as shortened effective refractory period in response to 6 h of rapid atrial pacing (1,200 beats/min) were suppressed by CaCl₂ microinjection. After intracoronary infusion of Ca-MNP, the external electromagnet pulled Ca-MNP to the targeted GP and suppressed the GP function (n = 6 GP) within 15 min.

CONCLUSIONS

Ca-MNP can be magnetically targeted to suppress GP function by calcium-mediated neurotoxicity. This novel approach may be used to treat arrhythmias related to hyperactivity of the cardiac autonomic nervous system, such as early stage of atrial fibrillation, with minimal myocardial injury.

Photocatalytic Activity of Polymer Nanoparticles Modulates Intracellular Calcium Dynamics and Reactive Oxygen Species in HEK-293 Cells

Optical modulation of living cells activity by light-absorbing exogenous materials is gaining increasing interest, due to the possibility both to achieve high spatial and temporal resolution with a minimally invasive and reversible technique and to avoid the need of viral transfection with light-sensitive proteins. In this context, conjugated polymers represent ideal candidates for photo-transduction, due to their excellent optoelectronic and biocompatibility properties. In this work, we demonstrate that organic polymer nanoparticles, based on poly(3-hexylthiophene) conjugated polymer, establish a functional interaction with an in vitro cell model (Human Embryonic Kidney cells, HEK-293). They display photocatalytic activity in aqueous environment and, once internalized within the cell cytosol, efficiently generate reactive oxygen species (ROS) upon visible light excitation, without affecting cell viability. Interestingly, light-activated ROS generation deterministically triggers modulation of intracellular calcium ion flux, successfully controlled at the single cell level. In perspective, the capability of polymer NPs to produce ROS and to modulate Ca2+ dynamics by illumination on-demand, at non-toxic levels, may open the path to the study of biological processes with a gene-less approach and unprecedented spatio-temporal resolution, as well as to the development of new biotechnology tools for cell optical modulation.

Monomethyl fumarate inhibits pain behaviors and amygdala activity in a rat arthritis model

Neuroplasticity in the amygdala, a brain center for emotions, leads to increased neuronal activity and output that can generate emotional-affective behaviors and modulate nocifensive responses. Mechanisms of increased activity in the amygdala output region (central nucleus, CeA) include increased reactive oxygen species, and so we explored beneficial effects of monomethyl fumarate (MMF), which can have neuroprotective effects through the nuclear factor (erythroid-derived 2)-like 2 (Nrf2) antioxidant response pathway. Systemic (intraperitoneal) MMF dose-dependently inhibited vocalizations and mechanosensitivity (hindlimb withdrawal reflexes) of rats in an arthritis pain model (kaolin-carrageenan-induced monoarthritis in the knee). Stereotaxic administration of MMF into the CeA by microdialysis also inhibited vocalizations but had a limited effect on mechanosensitivity, suggesting a differential contribution to emotional-affective vs sensory pain aspects. Extracellular single-unit recordings of CeA neurons in anesthetized rats showed that stereotaxic administration of MMF into the CeA by microdialysis inhibited background activity and responses of CeA neurons to knee joint stimulation in the arthritis pain model. Monomethyl fumarate had no effect on behaviors and neuronal activity under normal conditions. The results suggest that MMF can inhibit emotional-affective responses in an arthritis pain model through an action that involves the amygdala (CeA).

Prohibitin is a positive modulator of mitochondrial function in PC12 cells under oxidative stress

Prohibitin (PHB) is a ubiquitously expressed and evolutionarily conserved mitochondrial protein with multiple functions. We have recently shown that PHB up-regulation offers robust protection against neuronal injury in models of cerebral ischemia in vitro and in vivo, but the mechanism by which PHB affords neuroprotection remains to be elucidated. Here, we manipulated PHB expression in PC12 neural cells to investigate its impact on mitochondrial function and the mechanisms whereby it protects cells exposed to oxidative stress. PHB over-expression promoted cell survival, whereas PHB down-regulation diminished cell viability. Functionally, manipulation of PHB levels did not affect basal mitochondrial respiration, but it increased spare respiratory capacity. Moreover, PHB over-expression preserved mitochondrial respiratory function of cells exposed to oxidative stress. Preserved respiratory capacity in differentiated PHB over-expressing cells exposed to oxidative stress was associated with an elongated mitochondrial morphology, whereas PHB down-regulation enhanced fragmentation. Mitochondrial complex I oxidative degradation was attenuated by PHB over-expression and increased in PHB knockdown cells. Changes in complex I degradation were associated with alterations of respiratory chain supercomplexes. Furthermore, we showed that PHB directly interacts with cardiolipin and that down-regulation of PHB results in loss of cardiolipin in mitochondria, which may contribute to destabilizing respiratory chain supercomplexes. Taken together, these data demonstrate that PHB modulates mitochondrial integrity and bioenergetics under oxidative stress, and suggest that the protective effect of PHB is mediated by stabilization of the mitochondrial respiratory machinery and its functional capacity, by the regulation of cardiolipin content. Open Data: Materials are available on https://cos.io/our-services/open-science-badges/ https://osf.io/93n6m/.

Oxidative stress, caspase-3 activation and cleavage of ROCK-1 play an essential role in MeHg-induced cell death in primary astroglial cells

Methylmercury is a toxic environmental contaminant that elicits significant toxicity in humans. The central nervous system is the primary target of toxicity, and is particularly vulnerable during development. Rho-associated protein kinase 1 (ROCK-1) is a major downstream effector of the small GTPase RhoA and a direct substrate of caspase-3. The activation of ROCK-1 is necessary for membrane blebbing during apoptosis. In this work, we examined whether MeHg could affect the RhoA/ROCK-1 signaling pathway in primary cultures of mouse astrocytes. Exposure of cells with 10 μM MeHg decreased cellular viability after 24 h of incubation. This reduction in viability was preceded by a significant increase in intracellular and mitochondrial reactive oxygen species levels, as well as a reduced NAD⁺/NADH ratio. MeHg also induced an increase in mitochondrial-dependent caspase-9 and caspase-3, while the levels of RhoA protein expression were reduced or unchanged. We further found that MeHg induced ROCK-1 cleavage/activation and promoted LIMK1 and MYPT1 phosphorylation, both of which are the best characterized ROCK-1 downstream targets. Inhibiting ROCK-1 and caspases activation attenuated the MeHg-induced cell death. Collectively, these findings are the first to show that astrocytes exposed to MeHg showed increased cleavage/activation of ROCK-1, which was independent of the small GTPase RhoA.

Chronic Administration of S-Allylcysteine Activates Nrf2 Factor and Enhances the Activity of Antioxidant Enzymes in the Striatum, Frontal Cortex and Hippocampus

Oxidative stress plays an important role in neurodegenerative diseases and aging. The cellular defense mechanisms to deal with oxidative damage involve the activation of transcription factor related to NF-E2 (Nrf2), which enhances the transcription of antioxidant and phase II enzyme genes. S-allylcysteine (SAC) is an antioxidant with neuroprotective properties, and the main organosulfur compound in aged garlic extract. The ability of SAC to activate the Nrf2 factor has been previously reported in hepatic cells; however this effect has not been studied in normal brain. In order to determine if the chronic administration of SAC is able to activate Nrf2 factor and enhance antioxidant defense in the brain, male Wistar rats were administered with SAC (25, 50, 100 and 200 mg/kg-body weight each 24 h, i.g.) for 90 days. The activation of Nrf2, the levels of p65 and 8-hydroxy-2-deoxyguanosine (8-OHdG) as well as the activities of the enzymes glutathione peroxidase (GPx), glutathione reductase (GR), catalase (CAT), superoxide dismutase (SOD), and glutathione S-transferase (GST) were evaluated in the hippocampus, striatum and frontal cortex. Results showed that SAC activated Nrf2 factor in the hippocampus (25-200 mg/kg) and striatum (100 mg/kg) and significantly decreased p65 levels in the frontal cortex (25-200 mg/kg). On the other hand, SAC increased GPx, GR, CAT and SOD activities mainly in the hippocampus and striatum, but it did not change GST activity. Finally, no changes were observed in 8-OHdG levels mediated by SAC in any brain region, but the hippocampus showed a major level of 8-OHdG compared with the striatum and frontal cortex. All these results suggest that in the hippocampus, the observed increase in the activity of antioxidant enzymes could be associated with the ability of SAC to activate Nrf2 factor; however, a different mechanism could be involved in the striatum and frontal cortex, since no changes were found in Nrf2 activation and p65 levels.

Effects of ischemic preconditioning on PDGF-BB expression in the gerbil hippocampal CA1 region following transient cerebral ischemia

Ischemic preconditioning (IPC) is induced by exposure to brief durations of transient ischemia, which results in ischemic tolerance to a subsequent longer or lethal period of ischemia. In the present study, the effects of IPC (2 min of transient cerebral ischemia) were examined on immunoreactivity of platelet‑derived growth factor (PDGF)‑BB and on neuroprotection in the gerbil hippocampal CA1 region following lethal transient cerebral ischemia (LTCI; 5 min of transient cerebral ischemia). IPC was subjected to a 2‑min sublethal ischemia and a LTCI was given 5‑min transient ischemia. The animals in all of the groups were given recovery times of 1, 2 and 5 days and change in PDGF‑BB immunoreactivity was examined as was the neuronal damage/death in the hippocampus induced by LTCI. LTCI induced a significant loss of pyramidal neurons in the hippocampal CA1 region 5 days after LTCI, and significantly decreased PDGF‑BB immunoreactivity in the CA1 pyramidal neurons from day 1 after LTCI. Conversely, IPC effectively protected the CA1 pyramidal neurons from LTCI and increased PDGF‑BB immunoreactivity in the CA1 pyramidal neurons post‑LTCI. In conclusion, the results demonstrated that LTCI significantly altered PDGF‑BB immunoreactivity in pyramidal neurons in the hippocampal CA1 region, whereas IPC increased the immunoreactivity. These findings indicated that PDGF‑BB may be associated with IPC‑mediated neuroprotection.

Increase of reactive oxygen species generation in cerebral cortex slices after the transiently enhanced metabolic activity

Under certain conditions such as hypoxia-reoxygenation, the generation of reactive oxygen species (ROS) increases following hypoxia caused by a decreased oxygen supply. As another hypoxic condition, an excess neural activity status including epileptic seizure induces a decrease in tissue oxygen partial pressure (pO₂) caused by enhanced oxygen utilization; however, whether ROS generation increases following the hypoxic status induced by transiently enhanced energy metabolism in brain tissue currently remains unknown. We herein investigated ROS-dependent chemiluminescence in cerebral cortex slices during the restoration of transiently enhanced energy metabolism induced by a high-potassium treatment with tissue pO₂ changes and redox balance. ROS generation in the tissue was enhanced after high-potassium-induced hypoxia, but not by the reversed order of the treatment: control-potassium then high-potassium treatment, high-potassium treatment alone, and control-potassium treatment alone. The high-potassium treatment induced a transient decrease in tissue pO₂ and a shift in the tissue redox balance towards reduction. The transient shift in the tissue redox balance towards reduction with enhanced metabolic activity and its recovery may correlate with ROS generation. This phenomenon may mimic ROS generation following the hypoxic status induced by transiently enhanced energy metabolism.

The Role of Mitochondria in the Activation/Maintenance of SOCE: Store-Operated Ca2+ Entry and Mitochondria

Mitochondria extensively modify virtually all cellular Ca²⁺ transport processes, and store-operated Ca²⁺ entry (SOCE) is no exception to this rule. The interaction between SOCE and mitochondria is complex and reciprocal, substantially altering and, ultimately, fine-tuning both capacitative Ca²⁺ influx and mitochondrial function. Mitochondria, owing to their considerable Ca²⁺ accumulation ability, extensively buffer the cytosolic Ca²⁺ in their vicinity. In turn, the accumulated ion is released back into the neighboring cytosol during net Ca²⁺ efflux. Since store depletion itself and the successive SOCE are both Ca²⁺-regulated phenomena, mitochondrial Ca²⁺ handling may have wide-ranging effects on capacitative Ca²⁺ influx at any given time. In addition, mitochondria may also produce or consume soluble factors known to affect store-operated channels. On the other hand, Ca²⁺ entering the cell during SOCE is sensed by mitochondria, and the ensuing mitochondrial Ca²⁺ uptake boosts mitochondrial energy metabolism and, if Ca²⁺ overload occurs, may even lead to apoptosis or cell death. In several cell types, mitochondria seem to be sterically excluded from the confined space that forms between the plasma membrane (PM) and endoplasmic reticulum (ER) during SOCE. This implies that high-Ca²⁺ microdomains comparable to those observed between the ER and mitochondria do not form here. In the following chapter, the above aspects of the many-sided SOCE-mitochondrion interplay will be discussed in greater detail.

Acetaminophen toxicity in rat and mouse hepatocytes in vitro

CONTEXT

Acetaminophen (APAP) hepatotoxicity is often studied in primary cultures of hepatocytes of various species, but there are only few works comparing interspecies differences in susceptibility of hepatocytes to APAP in vitro.

OBJECTIVES

The aim of our work was to compare hepatotoxicity of APAP in rat and mouse hepatocytes in primary cultures.

MATERIALS AND METHODS

Hepatocytes isolated from male Wistar rats and C57Bl/6J mice were exposed to APAP for up to 24 h. We determined lactate dehydrogenase (LDH) activity in culture medium, activity of cellular dehydrogenases (WST-1) and activity of caspases 3 in cell lysate as markers of cell damage/death. We assessed content of intracellular reduced glutathione, production of reactive oxygen species (ROS) and malondialdehyde (MDA). Respiration of digitonin-permeabilized hepatocytes was measured by high resolution respirometry and mitochondrial membrane potential (MMP) was visualized (JC-1).

RESULTS

APAP from concentrations of 2.5 and 0.75 mmol/L induced a decrease in viability of rat (p < 0.001) and mouse (p < 0.001) hepatocytes (WST-1), respectively. In contrast to rat hepatocytes, there was no activation of caspase-3 in mouse hepatocytes after APAP treatment. Earlier damage to plasma membrane and faster depletion of reduced glutathione were detected in mouse hepatocytes. Mouse hepatocytes showed increased glutamate + malate-driven respiration in state 4 and higher susceptibility of the outer mitochondrial membrane (OMM) to APAP-induced injury.

CONCLUSION

APAP displayed dose-dependent toxicity in hepatocytes of both species. Mouse hepatocytes in primary culture however had approximately three-fold higher susceptibility to the toxic effect of APAP when compared to rat hepatocytes.

Considerations in Fluids and Electrolytes After Traumatic Brain Injury

Appropriate fluid management of patients with traumatic brain injury (TBI) presents a challenge for many clinicians. Many of these patients may receive osmotic diuretics for the treatment of increased intracranial pressure or develop sodium disturbances, which act to alter fluid balance. However, establishment of fluid balance is extremely important for improving patient outcomes after neurologic injury. The use of hyperosmolar fluids, such as hypertonic saline, has gained significant interest because they are devoid of dehydrating properties and may have other beneficial properties for patients with TBI. Electrolyte derangements are also common after neurologic injury, with many having neurologic manifestations. In addition, the role of electrolyte abnormalities in the secondary neurologic injury cascade is being delineated and may offer a potential future therapeutic intervention.

Enhanced Oxidative Stress Is Responsible for TRPV4-Induced Neurotoxicity

Transient receptor potential vanilloid 4 (TRPV4) has been reported to be responsible for neuronal injury in pathological conditions. Excessive oxidative stress can lead to neuronal damage, and activation of TRPV4 increases the production of reactive oxygen species (ROS) and nitric oxide (NO) in many types of cells. The present study explored whether TRPV4-induced neuronal injury is mediated through enhancing oxidative stress. We found that intracerebroventricular injection of the TRPV4 agonist GSK1016790A increased the content of methane dicarboxylic aldehyde (MDA) and NO in the hippocampus, which was blocked by administration of the TRPV4 specific antagonist HC-067047. The activities of catalase (CAT) and glutathione peroxidase (GSH-Px) were decreased by GSK1016790A, whereas the activity of superoxide dismutase (SOD) remained unchanged. Moreover, the protein level and activity of neuronal nitric oxide synthase (nNOS) were increased by GSK1016790A, and the GSK1016790A-induced increase in NO content was blocked by an nNOS specific antagonist ARL-17477. The GSK1016790A-induced modulations of CAT, GSH-Px and nNOS activities and the protein level of nNOS were significantly inhibited by HC-067047. Finally, GSK1016790A-induced neuronal death and apoptosis in the hippocampal CA1 area were markedly attenuated by administration of a ROS scavenger Trolox or ARL-17477. We conclude that activation of TRPV4 enhances oxidative stress by inhibiting CAT and GSH-Px and increasing nNOS, which is responsible, at least in part, for TRPV4-induced neurotoxicity.

Physical exercise, reactive oxygen species and neuroprotection

Regular exercise has systemic beneficial effects, including the promotion of brain function. The adaptive response to regular exercise involves the up-regulation of the enzymatic antioxidant system and modulation of oxidative damage. Reactive oxygen species (ROS) are important regulators of cell signaling. Exercise, via intensity-dependent modulation of metabolism and/or directly activated ROS generating enzymes, regulates the cellular redox state of the brain. ROS are also involved in the self-renewal and differentiation of neuronal stem cells and the exercise-mediated neurogenesis could be partly associated with ROS production. Exercise has strong effects on the immune system and readily alters the production of cytokines. Certain cytokines, especially IL-6, IL-1, TNF-α, IL-18 and IFN gamma, are actively involved in the modulation of synaptic plasticity and neurogenesis. Cytokines can also contribute to ROS production. ROS-mediated alteration of lipids, protein, and DNA could directly affect brain function, while exercise modulates the accumulation of oxidative damage. Oxidative alteration of macromolecules can activate signaling processes, membrane remodeling, and gene transcription. The well known neuroprotective effects of exercise are partly due to redox-associated adaptation.

Allogeneic/xenogeneic transplantation of peptide-labeled mitochondria in Parkinson's disease: restoration of mitochondria functions and attenuation of 6-hydroxydopamine-induced neurotoxicity

Although restoration of mitochondrial function in mitochondrial diseases through peptide-mediated allogeneic mitochondrial delivery (PMD) has been demonstrated in vitro, the in vivo therapeutic efficacy of PMD in Parkinson's disease (PD) has yet to be determined. In this study, we compared the functionality of mitochondrial transfer with or without Pep-1 conjugation in neurotoxin (6-hydroxydopamine, 6-OHDA)-induced PC12 cells and PD rat models. We injected mitochondria into the medial forebrain bundle (MFB) of the PD rats after subjecting the nigrostriatal pathway to a unilateral 6-OHDA lesion for 21 days, and we verified the effectiveness of the mitochondrial graft in enhancing mitochondrial function in the soma of the substantia nigra (SN) neuron through mitochondrial transport dynamics in the nigrostriatal circuit. The result demonstrated that only PMD with allogeneic and xenogeneic sources significantly sustained mitochondrial function to resist the neurotoxin-induced oxidative stress and apoptotic death in the rat PC12 cells. The remaining cells exhibited a greater capability of neurite outgrowth. Furthermore, allogeneic and xenogeneic transplantation of peptide-labeled mitochondria after 3 months improved the locomotive activity in the PD rats. This increase was accompanied by a marked decrease in dopaminergic neuron loss in the substantia nigra pars compacta (SNc) and consistent enhancement of tyrosine hydroxylase-positive immunoreaction of dopaminergic neurons in the SNc and striatum. We also observed that in the SN dopaminergic neuron in the treated PD rats, mitochondrial complex I protein and mitochondrial dynamics were restored, thus ameliorating the oxidative DNA damage. Moreover, we determined signal translocation of graft allogeneic mitochondria from the MFB to the calbindin-positive SN neuron, which demonstrated the regulatory role of mitochondrial transport in alleviating 6-OHDA-induced degeneration of dopaminergic neurons.

Distinct contributions of reactive oxygen species in amygdala to bee venom-induced spontaneous pain-related behaviors

Reactive oxygen species (ROS), such as superoxide and hydrogen peroxide, play essential roles in physiological plasticity and are also involved in the pathogenesis of persistent pain. Roles of peripheral and spinal ROS in pain have been well established, but much less is known about ROS in the amygdala, a brain region that plays an important role in pain modulation. The present study explored the contribution of ROS in the amygdala to bee venom (BV)-induced pain behaviors. Our data show that the amygdala is activated following subcutaneous BV injection into the left hindpaw, which is reflected in the increased number of c-Fos positive cells in the central and basolateral amygdala nuclei in the right hemisphere. Stereotaxic administration of a ROS scavenger (tempol, 10mM), NADPH oxidase inhibitor (baicalein, 5mM) or lipoxygenase inhibitor (apocynin, 10mM) into the right amygdala attenuated the BV-induced spontaneous licking and lifting behaviors, but had no effect on BV-induced paw flinch reflexes. Our study provides further evidence for the involvement of the amygdala in nociceptive processing and pain behaviors, and that ROS in amygdala may be a potential target for treatment strategies to inhibit pain.

Reactive oxygen species mediate visceral pain-related amygdala plasticity and behaviors

Accumulating evidence suggests an important contribution of reactive oxygen species (ROS) to pain and neuropsychiatric disorders, but their role in pain-related plasticity in the brain is largely unknown. Neuroplasticity in the central nucleus of the amygdala (CeA) correlates positively with pain behaviors in different models. Little is known, however, about mechanisms of visceral pain-related amygdala changes. The electrophysiological and behavioral studies reported here addressed the role of ROS in the CeA in a visceral pain model induced by intracolonic zymosan. Vocalizations to colorectal distension and anxiety-like behavior increased after intracolonic zymosan and were inhibited by intra-CeA application of a ROS scavenger (tempol, a superoxide dismutase mimetic). Tempol also induced a place preference in zymosan-treated rats but not in controls. Single-unit recordings of CeA neurons in anesthetized rats showed increases of background activity and responses to visceral stimuli after intracolonic zymosan. Intra-CeA application of tempol inhibited the increased activity but had no effect under normal conditions. Whole-cell patch-clamp recordings of CeA neurons in brain slices from zymosan-treated rats showed that tempol decreased neuronal excitability and excitatory synaptic transmission of presumed nociceptive inputs from the brainstem (parabrachial area) through a combination of presynaptic and postsynaptic actions. Tempol had no effect in brain slices from sham controls. The results suggest that ROS contribute to visceral pain-related hyperactivity of amygdala neurons and amygdala-dependent behaviors through a mechanism that involves increased excitatory transmission and excitability of CeA neurons.

Ion Channels and Oxidative Stress as a Potential Link for the Diagnosis or Treatment of Liver Diseases

Oxidative stress results from a disturbed balance between oxidation and antioxidant systems. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) may be either harmful or beneficial to the cells. Ion channels are transmembrane proteins that participate in a large variety of cellular functions and have been implicated in the development of a variety of diseases. A significant amount of the available drugs in the market targets ion channels. These proteins have sulfhydryl groups of cysteine and methionine residues in their structure that can be targeted by ROS and RNS altering channel function including gating and conducting properties, as well as the corresponding signaling pathways associated. The regulation of ion channels by ROS has been suggested to be associated with some pathological conditions including liver diseases. This review focuses on understanding the role and the potential association of ion channels and oxidative stress in liver diseases including fibrosis, alcoholic liver disease, and cancer. The potential association between ion channels and oxidative stress conditions could be used to develop new treatments for major liver diseases.