Mitochondrial ROS production and subsequent ERK phosphorylation are necessary for temperature preconditioning of isolated ventricular myocytes

ROS production by mitochondria: function or dysfunction?

In eukaryotic cells, ATP generation is generally viewed as the primary function of mitochondria under normoxic conditions. Reactive oxygen species (ROS), in contrast, are regarded as the by-products of respiration, and are widely associated with dysfunction and disease. Important signaling functions have been demonstrated for mitochondrial ROS in recent years. Still, their chemical reactivity and capacity to elicit oxidative damage have reinforced the idea that ROS are the products of dysfunctional mitochondria that accumulate during disease. Several studies support a different model, however, by showing that: (1) limited oxygen availability results in mitochondria prioritizing ROS production over ATP, (2) ROS is an essential adaptive mitochondrial signal triggered by various important stressors, and (3) while mitochondria-independent ATP production can be easily engaged by most cells, there is no known replacement for ROS-driven redox signaling. Based on these observations and other evidence reviewed here, we highlight the role of ROS production as a major mitochondrial function involved in cellular adaptation and stress resistance. As such, we propose a rekindled view of ROS production as a primary mitochondrial function as essential to life as ATP production itself.

Polystyrene nanoplastics induce apoptosis of human kidney proximal tubular epithelial cells via oxidative stress and MAPK signaling pathways

Polystyrene nanoplastics (PS-NPs) have recently been found to be present in human blood and kidney. However, the renal toxicity of PS-NPs and the underlying mechanisms have not been fully elucidated. Here, we found that exposure of PS-NPs induced apoptosis of human renal proximal tubular epithelial cells (HK-2) in a size- and dose-dependent manner as revealed by AnnexinV-FITC assay. In addition, PS-NPs promoted ROS production and caused structure changes of mitochondrial and endoplasmic reticulum. Mechanistically, transcriptional sequencing indicated the involvement of MAPK pathway in apoptosis, which was further confirmed by the upregulation of p-p38, p-ERK, CHOP, BAX, cytochrome C, and caspase 3 expression. This study clarified the molecular mechanism underlying PS-NP-induced apoptosis in HK-2 cells and contributed to our risk estimation of PS-NPs in human kidney.

Kuanoniamine C Suppresses Adipogenesis and White Adipose Tissue Expansion by Modulating Mitochondrial Function

Obesity is characterized by the excessive accumulation of fat to adipose tissue, which is related to abnormal increasing white adipose tissue (WAT) in the body, and it upregulates the risk of multiple diseases. Here, kuanoniamine C, which is a pyridoacridine alkaloid, suppressed the differentiation of pre-adipose cells into white adipocytes via the modulation of mitochondrial function, and inhibited WAT expansion in the early phase of high-fat-diet-induced obesity model. Pharmacological analysis revealed that inhibition of mitochondrial respiratory complex II, which new target of kuanoniamine C, activated reactive oxygen species (ROS)-extracellular signal-regulated kinase (ERK)-β-catenin signaling, and this signaling was antagonized by insulin-, IBMX-, and dexamethasone-induced adipogenesis. Therefore, the kuanoniamine C might prevent abnormal WAT expansion even when eating a diet that is not calorie restricted.

Baicalein Preconditioning Cardioprotection Involves Pro-Oxidant Signaling and Activation of Pyruvate Dehydrogenase

Preconditioning has a powerful protective potential against myocardial ischemia-reperfusion injury (I/R). Our prior work demonstrated that baicalein, a flavonoid derived from the root of Scatellaria baicalensis Georgi (also known as Huangqin), confers this preconditioning protection. This study further explored the mechanisms of baicalein preconditioning (BC-PC) in mouse cardiomyocytes. Cells were treated with baicalein (10 μM) for a brief period of time (10 min) prior to simulated ischemia 90 min/reperfusion for 180 min. Baicalein triggered an induction of a small amount of mitochondrial reactive oxygen species (ROS) prior to the initiation of ischemia, assessed by 6-carboxy-2^', 7^'-dichlorodihydrofluorescein diacetate (6-carboxy-H₂DCFDA). It also significantly increased cell viability measured by propidium iodide (PI) and lactate dehydrogenase and preserved mitochondrial membrane potential assessed by TMRM fluorescence intensity. Myxothiazol, a mitochondrial electron transport chain complex III inhibitor, partially blocked ROS generation induced by BC-PC and reduced cell viability. BC-PC increased phosphorylation of Akt (Thr308 and Ser473) and eNOS Ser1177, and nitric oxide (NO) production measured using 4,5-diaminofluorescein diacetate (DAF-2 DA, 1 μM). Akt inhibitor API-2 abolished Akt phosphorylation and reduced DAF-2 production and cell viability. In addition, BC-PC decreased phosphorylation of pyruvate dehydrogenase (PDH) reflecting upregulated PDH activity, and increased ATP production at 30 min during reperfusion. Taken together, baicalein preconditioning-induced cardioprotection involves pro-oxidant generation, activates survival signaling Akt/eNOS/NO, and improves metabolic recovery after I/R injury. Our work provides new perspectives on the effect of baicalein on cardiac preconditioning against I/R injury.

Phototoxicity-free blue light for enhancing therapeutic angiogenic efficacy of stem cells

Low-level light therapy (LLLT) is a safe and noninvasive technique that has drawn attention as a new therapeutic method to treat various diseases. However, little is known so far about the effect of blue light for LLLT due to the generation of reactive oxygen species (ROS) that can cause cell damage. We introduced a blue organic light-emitting diode (bOLED) as a safe and effective light source that could generate a low amount of heat and luminance compared to conventional light sources (e.g., light-emitting diodes). We compared phototoxicity of bOLED light with different light fluences to human adipose-derived stem cells (hADSC). We further explored molecular mechanisms involved in the therapeutic efficacy of bOLED for enhancing angiogenic properties of hADSC, including intracellular ROS control in hADSCs. Using optimum conditions of bOLED light proposed in this study, photobiomodulation and angiogenic properties of hADSCs were enhanced. These findings might open new methods for using blue light in LLLT. Such methods can be implemented in future treatments for ischemic disease.

High Levels of ROS Impair Lysosomal Acidity and Autophagy Flux in Glucose-Deprived Fibroblasts by Activating ATM and Erk Pathways

Under glucose deprivation, cells heavily mobilize oxidative phosphorylation to maintain energy homeostasis. This leads to the generation of high levels of ATP, as well as reactive oxygen species (ROS), from mitochondria. In nutrient starvation, autophagy is activated, likely to facilitate resource recycling, but recent studies suggest that autophagy flux is inhibited in cells undergoing glucose deprivation. In this study, we analyzed the status of autophagic flux in glucose-deprived human fibroblasts. Although lysosomes increased in quantity due in part to an increase of biogenesis, a large population of them suffered low acidity in the glucose-deprived cells. Autophagosomes also accumulated due to poor autolysis in these cells. A treatment of antioxidants not only restored lysosomal acidity but also released the flux blockade. The inhibition of ataxia telangiectasia mutated (ATM) serine/threonine kinase, which is activated by ROS, also attenuated the impairment of lysosomal acidity and autophagic flux, suggesting an effect of ROS that might be mediated through ATM activation. In addition, the activity of extracellular signal-regulated kinase (Erk) increased upon glucose deprivation, but this was also compromised by a treatment of antioxidants. Furthermore, the Erk inhibitor treatment also alleviated the failure in lysosomal acidity and autophagic flux. These together indicate that, upon glucose deprivation, cells undergo a failure of autophagy flux through an impairment of lysosomal acidity and that a high-level ROS-induced activation of Erk and ATM is involved in this impairment.

DiOHF Protects Against Doxorubicin-Induced Cardiotoxicity Through ERK1 Signaling Pathway

Doxorubicin (DOX) is an effective anticancer agent. Its clinical use is, however, limited due to its detrimental side effects, especially the cardiotoxicity caused by ROS, mitochondrial dysfunction and apoptosis. 3’,4’-dihydroxyflavonol (DiOHF) is a recently developed potent synthetic flavonoid which has been reported to exert anti-oxidative activity in myocardial ischemia–reperfusion injury and maintain the normal mitochondrial function. The aim of this study was to explore the protective effects of DiOHF on the DOX-induced cardiotoxicity. We established DOX-induced cardiotoxicity in H9C2 cells by incubation with 1 μM DOX and in BALB/c mice by DOX injection. DiOHF effectively prevented and reversed the DOX-induced cardiotoxicity, including ROS production, mitochondrial dysfunction, and apoptosis. The DOX-induced cardiotoxicity was accompanied by ERK1/2 activation and abolished by the silence of ERK1, rather than ERK2. Furthermore, DOX treatment in mice induced an increase in serum CK-MB level and myocardial fibrosis with a reduction in left ventricular (LV) function. These detrimental effects were blunted by DiOHF administration. Conclusion: DiOHF suppresses and reverses the DOX-induced cardiotoxicity by inhibiting ROS release, stabilizing mitochondrial function and reducing apoptosis through activation of the ERK1 signaling.

Comparative study on isolation and mitochondrial function of adult mouse and rat cardiomyocytes

BACKGROUND

Cultured adult mouse and rat cardiomyocytes are the best and low-cost cell model for cardiac cellular physiology, pathology, drug toxicity screening, and intervention. The functions of mouse cardiomyocytes decline faster than rat cardiomyocytes in culture conditions. However, little is known about the difference of mitochondrial function between cultured mouse and rat myocytes.

METHODS AND RESULTS

A large number of adult mouse and rat cardiomyocytes were comparative isolated using a simple perfusion system. Cardiomyocytes mitochondrial functions were measured after 2 h, 1 day, 2 days, 3 days, and 4 days culture by monitoring mitoflashes. We found that the mitochondrial function of mouse myocytes was remarkedly declined on the third day. Then, we focused on the third day cultured mouse and rat myocytes, comparatively analyzing the respiration function and superoxide generation stimulated by pyruvate/malate/ADP and the mitochondrial permeability transition pore (mPTP) opening induction. Mouse myocytes showed lower respiration and mitoflash activity, but without the change of maximum uncoupled respiration when compared with rat myocytes. Although the response to superoxide production stimulated by respiration substrates was slower than rat myocytes, the basal superoxide generation is faster than the rat. The faster mitochondrial reactive oxygen species (ROS) generation of mouse myocytes upon laser stimulation triggered the faster mPTP opening compared with the rat. Finally, antioxidant MitoTEMPO pretreatment preserved the mitochondrial function of mouse myocytes on the third day.

CONCLUSIONS

The mitochondrial function and stability are different between cultured mouse and rat cardiac myocytes beyond 3 days even though they both belong to Muridae. Mitochondrial ROS impairs the mitochondrial functions of mouse cardiomyocytes on the third day. Suppressing superoxide maintained the mitochondrial function of mouse myocytes on the third day.

Temperature dependence of mitoflash biogenesis in cardiac mitochondria

Mitochondrial flashes (mitoflashes) represent fundamental biochemical and biophysical dynamics of the organelle, involving sudden depolarization of mitochondrial membrane potential (ΔΨ_m), bursting production of reactive oxygen species (ROS), and accelerated extrusion of matrix protons. Here we investigated temperature dependence of mitoflash biogenesis as well as ΔΨ_m oscillations, a subset of which overlapping with mitoflashes, in both cardiac myocytes and isolated respiring cardiac mitochondria. Unexpectedly, we found that mitoflash biogenesis was essentially temperature-independent in intact cardiac myocytes, evidenced by the constancy of frequency as well as amplitude and rise speed over 5 °C-40 °C. Moderate temperature dependence was found in single mitochondria charged by respiratory substrates, where mitoflash frequency was decreased over 5 °C-20 °C with Q₁₀ of 0.74 for Complex I substrates and 0.83 for Complex II substrate. In contrast, ΔΨ_m oscillation frequency displayed a negative temperature dependence at 5 °C-20 °C with Q₁₀ of 0.82 in intact cells, but a positive temperature dependence at 25 °C - 40 °C with Q₁₀ of 1.62 in isolated mitochondria charged with either Complex I or Complex II substrates. Moreover, the recovery speed of individual mitoflashes exhibited mild temperature dependence (Q₁₀ = 1.14-1.22). These results suggest a temperature compensation of mitoflash frequency at both the mitochondrial and extra-organelle levels, and underscore that mitoflashes and ΔΨ_m oscillations are related but distinctly different mitochondrial functional dynamics.

Gastrin Protects Against Myocardial Ischemia/Reperfusion Injury via Activation of RISK (Reperfusion Injury Salvage Kinase) and SAFE (Survivor Activating Factor Enhancement) Pathways

BACKGROUND

Ischemia/reperfusion injury (IRI) is one of the most predominant complications of ischemic heart disease. Gastrin has emerged as a regulator of cardiovascular function, playing a key protective role in hypoxia. Serum gastrin levels are increased in patients with myocardial infarction, but the pathophysiogical significance of this finding is unknown. The purpose of this study was to determine whether and how gastrin protects cardiac myocytes from IRI.

METHODS AND RESULTS

Adult male Sprague-Dawley rats were used in the experiments. The hearts in living rats or isolated Langendorff-perfused rat hearts were subjected to ischemia followed by reperfusion to induce myocardial IRI. Gastrin, alone or with an antagonist, was administered before the induction of myocardial IRI. We found that gastrin improved myocardial function and reduced the expression of myocardial injury markers, infarct size, and cardiomyocyte apoptosis induced by IRI. Gastrin increased the phosphorylation levels of ERK1/2 (extracellular signal-regulated kinase 1/2), AKT (protein kinase B), and STAT3 (signal transducer and activator of transcription 3), indicating its ability to activate the RISK (reperfusion injury salvage kinase) and SAFE (survivor activating factor enhancement) pathways. The presence of inhibitors of ERK1/2, AKT, or STAT3 abrogated the gastrin-mediated protection. The protective effect of gastrin was via CCK2R (cholecystokinin 2 receptor) because the CCK2R blocker CI988 prevented the gastrin-mediated protection of the heart with IRI. Moreover, we found a negative correlation between serum levels of cardiac troponin I and gastrin in patients with unstable angina pectoris undergoing percutaneous coronary intervention, suggesting a protective effect of gastrin in human cardiomyocytes.

CONCLUSIONS

These results indicate that gastrin can reduce myocardial IRI by activation of the RISK and SAFE pathways.

Supplement of Betaine into Embryo Culture Medium Can Rescue Injury Effect of Ethanol on Mouse Embryo Development

Mammal embryos can be impaired by mother’s excessive ethanol uptake, which induces a higher level of reactive oxygen species (ROS) and interferes in one carbon unit metabolism. Here, our analysis by in vitro culture system reveals immediate effect of ethanol in medium on mouse embryo development presents concentration dependent. A preimplantation embryo culture using medium contained 1% ethanol could impact greatly early embryos development, and harmful effect of ethanol on preimplantation embryos would last during the whole development period including of reducing ratio of blastocyst formation and implantation, and deteriorating postimplantation development. Supplement of 50 μg/ml betaine into culture medium can effectively reduce the level of ROS caused by ethanol in embryo cells and rescue embryo development at each stage damaged by ethanol, but supplement of glycine can’t rescue embryo development as does betaine. Results of 5-methylcytosine immunodetection indicate that supplement of betaine into medium can reduce the rising global level of genome DNA methylation in blastocyst cells caused by 1% ethanol, but glycine can’t play the same impact. The current findings demonstrate that betaine can effectively rescue development of embryos harmed by ethanol, and possibly by restoring global level of genome DNA methylation in blastocysts.

[Cardioprotection in cardiac surgical patients : Everything good comes from the heart]

BACKGROUND

Despite substantial success in the anesthetic and surgical management of cardiac surgery, patients frequently show postoperative complications and organ dysfunctions. This is highly relevant for mid- to long-term outcomes.

OBJECTIVES

To evaluate cardioprotective strategies that may offer effective protection in vulnerable cardiac surgery patients.

METHODS

To demonstrate recent cardioprotective approaches for cardiac surgery patients, aiming to modulate the body's own protective mechanisms in cardiac surgery patients.

RESULTS

Both cardioplegia and hypothermia belong to the well-established protective strategies during myocardial ischemia. Volatile anesthetics have been repeatedly shown to improve the left ventricular function and reduce the extent of myocardial injury compared to a control group with intravenous anesthesia. Furthermore, patients receiving volatile anesthetics showed a significantly shortened stay in the ICU and in hospital after cardiac surgery. In contrast, numerous other protective strategies failed translation into the clinical practice. Despite the published reduction of troponin release after remote ischemic preconditioning, two recent large-scale randomized multicenter trials were unable to demonstrate a clinical benefit.

CONCLUSIONS

Beside the use of cardioplegia and hypothermia, the use of volatile anesthetics is well-established during cardiac surgery because of its conditioning and protective properties. Regardless of the promising results derived from experimental studies and small clinical trials, the majority of other approaches failed to translate their findings into the clinic. Therefore, systematic experimental studies are needed to identify potential confounding factors that may affect the protective effects.

13-Oxyingenol dodecanoate, a cytotoxic ingenol derivative, induces mitochondrial apoptosis and caspase-dependent Akt decrease in K562 cells

13-Oxyingenol dodecanoate (13OD) is an ingenol derivative prepared from Chinese traditional medicine Euphorbia kansui without any report about its bioactivity. The present study demonstrated for the first time that 13OD displayed potent cytotoxicity against chronic myeloid leukemia K562 cells in vitro. 13OD inhibited proliferation, induced G2/M phase arrest, and exhibited potent apoptotic activity in K562 cells. In K562 cells, 13OD disrupted the mitochondrial membrane potential and induced high level of ROS, which played an indispensable role in 13OD-induced apoptosis. Further investigations on the molecular mechanisms revealed that total Akt protein level was decreased in a caspase-dependent way after treatment with 13OD; in addition, ERK was activated by 13OD, and this activation played a protective role in 13OD stimulation. Altogether, these results revealed that the cytotoxic ingenol derivative 13OD induced apoptosis with novel mechanisms for the proapoptotic function in cancer cells, and suggested that 13OD may serve as a lead template for rational drug design and for future anticancer agent development.

TAp73 promotes anabolism

Metabolic adaptation has emerged as a hallmark of cancer and a promising therapeutic target, as rapidly proliferating cancer cells adapt their metabolism increasing nutrient uptake and reorganizing metabolic fluxes to support biosynthesis. The transcription factor p73 belongs to the p53-family and regulates tumorigenesis via its two N-terminal isoforms, with (TAp73) or without (ΔNp73) a transactivation domain. TAp73 acts as tumor suppressor, at least partially through induction of cell cycle arrest and apoptosis and through regulation of genomic stability. Here, we sought to investigate whether TAp73 also affects metabolic profiling of cancer cells. Using high throughput metabolomics, we unveil a thorough and unexpected role for TAp73 in promoting Warburg effect and cellular metabolism. TAp73-expressing cells show increased rate of glycolysis, higher amino acid uptake and increased levels and biosynthesis of acetyl-CoA. Moreover, we report an extensive TAp73-mediated upregulation of several anabolic pathways including polyamine and synthesis of membrane phospholipids. TAp73 expression also increases cellular methyl-donor S-adenosylmethionine (SAM), possibly influencing methylation and epigenetics, and promotes arginine metabolism, suggestive of a role in extracellular matrix (ECM) modeling. In summary, our data indicate that TAp73 regulates multiple metabolic pathways that impinge on numerous cellular functions, but that, overall, converge to sustain cell growth and proliferation.

IL-17 Induces MPTP opening through ERK2 and P53 signaling pathway in human platelets

The opening of mitochondrial permeability transition pore (MPTP) plays a critical role in platelet activation. However, the potential trigger of the MPTP opening in platelet activation remains unknown. Inflammation is the crucial trigger of platelet activation. In this study, we aimed to explore whether and how the important inflammatory cytokine IL-17 is associated with MPTP opening in platelets activation by using MPTP inhibitor cyclosporine-A (CsA). The mitochondrial membrane potential (ΔΨm) was detected to reflect MPTP opening levels. And the platelet aggregation, activation, and the primary signaling pathway were also tested. The results showed that the MPTP opening levels were increased and Δψm reduced in platelets administrated with IL-17. Moreover, the levels of aggregation, CD62P, PAC-1, P53 and the phosphorylation of ERK2 were enhanced along with the MPTP opening in platelets pre-stimulated with IL-17. However, CsA attenuated these effects triggered by IL-17. It was suggested that IL-17 could induce MPTP opening through ERK2 and P53 signaling pathway in platelet activation and aggregation.

Phosphoinositide and Erk signaling pathways mediate activity-driven rodent olfactory sensory neuronal survival and stress mitigation

Olfactory sensory neurons (OSNs) are the initial site for olfactory signal transduction. Therefore, their survival is essential to olfactory function. In the current study, we demonstrated that while odorant stimulation promoted rodent OSN survival, it induced generation of reactive oxygen species in a dose- and time-dependent manner as well as loss of membrane potential and fragmentation of mitochondria. The MEK-Erk pathway played a critical role in mediating these events, as its inhibition decreased odorant stimulation-dependent OSN survival and exacerbated intracellular stress measured by reactive oxygen species generation and heat-shock protein 70 expression. The phosphoinositide pathway, rather than the cyclic AMP pathway, mediated the odorant-induced activation of the MEK-Erk pathway. These findings provide important insights into the mechanisms of activity-driven OSN survival, the role of the phosphoinositide pathway in odorant signaling, and demonstrate that odorant detection and odorant stimulation-mediated survival proceed via independent signaling pathways. This mechanism, which permits independent regulation of odorant detection from survival signaling, may be advantageous if not diminished by repeated or prolonged odor exposure. We investigated the role of odorant stimulation in generating cellular stress and the molecular mechanisms mitigating such stress and promoting neuronal survival. Odorant stimulation promoted olfactory sensory neuron (OSN) survival and also induced intracellular oxidative stress, which was exacerbated when MEK/Erks pathway was inhibited. Sensory stimulation simultaneously activated at least two parallel pathways, the AC/cAMP cascade responsible for odorant detection, and phosphoinositide hydrolysis to promote odorant stimulation-dependent neuronal survival odorants may activate parallel signaling cascades to mediate sensory detection and sensory stimulation-dependent survival. AC, adenylyl cyclase; cAMP, cyclic adenosine monophosphate; Erk, extracellular signal-regulated kinase; MEK, MAPK/ERK kinase.

Interaction between neuronal nitric oxide synthase signaling and temperature influences sarcoplasmic reticulum calcium leak: role of nitroso-redox balance

RATIONALE

Although nitric oxide (NO) signaling modulates cardiac function and excitation-contraction coupling, opposing results because of inconsistent experimental conditions, particularly with respect to temperature, confound the ability to elucidate NO signaling pathways. Here, we show that temperature significantly modulates NO effects.

OBJECTIVE

To test the hypothesis that temperature profoundly affects nitroso-redox equilibrium, thereby affecting sarcoplasmic reticulum (SR) calcium (Ca(2+)) leak.

METHODS AND RESULTS

We measured SR Ca(2+) leak in cardiomyocytes from wild-type (WT), NO/redox imbalance (neuronal nitric oxide synthase-deficient mice-1 [NOS1(-/-)]), and hyper S-nitrosoglutathione reductase-deficient (GSNOR(-/-)) mice. In WT cardiomyocytes, SR Ca(2+) leak increased because temperature decreased from 37°C to 23°C, whereas in NOS1(-/-) cells, the leak suddenly increased when the temperature surpassed 30°C. GSNOR(-/-) cardiomyocytes exhibited low leak throughout the temperature range. Exogenously added NO had a biphasic effect on NOS1(-/-) cardiomyocytes; reducing leak at 37°C but increasing it at subphysiological temperatures. Oxypurinol and Tempol diminished the leak in NOS1(-/-) cardiomyocytes. Cooling from 37°C to 23°C increased reactive oxygen species generation in WT but decreased it in NOS1(-/-) cardiomyocytes. Oxypurinol further reduced reactive oxygen species generation. At 23°C in WT cells, leak was decreased by tetrahydrobiopterin, an essential NOS cofactor. Cooling significantly increased SR Ca(2+) content in NOS1(-/-) cells but had no effect in WT or GSNOR(-/-).

CONCLUSIONS

Ca(2+) leak and temperature are normally inversely proportional, whereas NOS1 deficiency reverses this effect, increasing leak and elevating reactive oxygen species production because temperature increases. Reduced denitrosylation (GSNOR deficiency) eliminates the temperature dependence of leak. Thus, temperature regulates the balance between NO and reactive oxygen species which in turn has a major effect on SR Ca(2+).

Resveratrol protects vascular smooth muscle cells against high glucose-induced oxidative stress and cell proliferation in vitro

Background

Resveratrol exhibits beneficial effects against numerous degenerative diseases at different stages of pathogenesis. This study investigated potential mechanisms and resveratrol effects on high glucose (HG)-induced oxidative stress (30 mM d-glucose, 30 min) and cell proliferation (30 mM d-glucose, 24 h) in vascular smooth muscle cells (VSMCs).

Material/Methods

Intracellular reactive oxygen species (ROS) generation was detected by 2′,7′-dichlorofluorescein diacetate (DCFH-DA). Total antioxidant capacity (TAC), malonyldialdehyde (MDA), glutathione (GSH), and superoxide dismutase (SOD) were measured to evaluate oxidative stress. VSMC proliferation was measured by CCK-8 assays and through propidium iodide-based cell cycle analysis. Expression of NAD(P)H oxidase, proliferation proteins, and cell signalling were assessed by immunoblot analysis.

Results

Co-treatment of primary cultures of VSMCs with 1–100 μM resveratrol decreased HG-induced ROS overproduction (P<0.05). Resveratrol also abolished HG-induced phosphorylation of oxidase subunit p47 phox and reduced HG-induced cyclin D1, cyclin E, and PCNA expression in a concentration-dependent manner. Furthermore, resveratrol (10 μM) attenuated HG-induced phosphorylation of Akt, p38 mitogen-activated protein kinase (MAPK), ERK 1/2, and JNK1/2 without affecting total levels. HG stimulation enhanced downstream IκB-α phosphorylation and NF-κB activity, and resveratrol repressed these effects.

Conclusions

Resveratrol inhibits HG-induced oxidative stress and VSMC proliferation by suppressing ROS generation, NADPH oxidase, Akt phosphorylation, p38 MAPK/JNK/ERK phosphorylation, and IκB-α and NF-κB activities.

Crosstalk between mitogen-activated protein kinases and mitochondria in cardiac diseases: therapeutic perspectives

Cardiovascular diseases cause more mortality and morbidity worldwide than any other diseases. Although many intracellular signaling pathways influence cardiac physiology and pathology, the mitogen-activated protein kinase (MAPK) family has garnered significant attention because of its vast implications in signaling and crosstalk with other signaling networks. The extensively studied MAPKs ERK1/2, p38, JNK, and ERK5, demonstrate unique intracellular signaling mechanisms, responding to a myriad of mitogens and stressors and influencing the signaling of cardiac development, metabolism, performance, and pathogenesis. Definitive relationships between MAPK signaling and cardiac dysfunction remain elusive, despite 30 years of extensive clinical studies and basic research of various animal/cell models, severities of stress, and types of stimuli. Still, several studies have proven the importance of MAPK crosstalk with mitochondria, powerhouses of the cell that provide over 80% of ATP for normal cardiomyocyte function and play a crucial role in cell death. Although many questions remain unanswered, there exists enough evidence to consider the possibility of targeting MAPK-mitochondria interactions in the prevention and treatment of heart disease. The goal of this review is to integrate previous studies into a discussion of MAPKs and MAPK-mitochondria signaling in cardiac diseases, such as myocardial infarction (ischemia), hypertrophy and heart failure. A comprehensive understanding of relevant molecular mechanisms, as well as challenges for studies in this area, will facilitate the development of new pharmacological agents and genetic manipulations for therapy of cardiovascular diseases.

Protein redox modification as a cellular defense mechanism against tissue ischemic injury

Protein oxidative or redox modifications induced by reactive oxygen species (ROS) or reactive nitrogen species (RNS) not only can impair protein function, but also can regulate and expand protein function under a variety of stressful conditions. Protein oxidative modifications can generally be classified into two categories: irreversible oxidation and reversible oxidation. While irreversible oxidation usually leads to protein aggregation and degradation, reversible oxidation that usually occurs on protein cysteine residues can often serve as an “on and off” switch that regulates protein function and redox signaling pathways upon stress challenges. In the context of ischemic tolerance, including preconditioning and postconditioning, increasing evidence has indicated that reversible cysteine redox modifications such as S-sulfonation, S-nitrosylation, S-glutathionylation, and disulfide bond formation can serve as a cellular defense mechanism against tissue ischemic injury. In this review, I highlight evidence of cysteine redox modifications as protective measures in ischemic injury, demonstrating that protein redox modifications can serve as a therapeutic target for attenuating tissue ischemic injury. Prospectively, more oxidatively modified proteins will need to be identified that can play protective roles in tissue ischemic injury, in particular, when the oxidative modifications of such identified proteins can be enhanced by pharmacological agents or drugs that are available or to be developed.

Akt and Erk1/2 activate the ornithine decarboxylase/polyamine system in cardioprotective ischemic preconditioning in rats: the role of mitochondrial permeability transition pores

Ornithine decarboxylase (ODC) is the first rate-limiting enzyme in polyamine biosynthesis, which is essential for cell survival. We hypothesized that the ODC/polyamine system is involved in ischemic preconditioning (IPC)-mediated cardioprotection through the activation of Erk1/2 and Akt and through the inhibition of the mitochondrial permeability transition (mPT). Isolated rat hearts were subjected to 40 min of ischemia either with or without IPC (3 cycles of 5-min global ischemia), and ODC protein expression, polyamine content, and Akt and Erk1/2 phosphorylation were evaluated after 30 min of reperfusion. IPC significantly upregulated the ODC/polyamine pathway, promoted Erk1/2 and Akt phosphorylation, and reduced the infarct size and heart dysfunction after reperfusion. An inhibitor of ODC, α-difluoromethylornithine (DFMO), abolished the IPC-induced cardioprotection. Moreover, the inhibition of the IPC-induced activation of Erk1/2 and Akt using PD98059 or wortmannin downregulated the ODC/polyamine system. In separate studies, the Ca(2+) load required to open the mPT pore was significantly lower in DFMO-treated cardiac mitochondria than in mitochondria from IPC hearts. Furthermore, spermine or spermidine significantly inhibited the mPT induced by CaCl2. These results suggest that IPC upregulates the ODC/polyamine system and mediates preconditioning cardioprotection, which may depend on the phosphorylation/activation of Erk1/2 and Akt and on the inhibition of the mPT during reperfusion.

The effect of deep hypothermia on the human pulmonary circulation

OBJECTIVE

Acute rises in pulmonary artery pressures following complex cardiac surgery are associated with high morbidity and mortality. We hypothesised that periods of deep hypothermia predispose to elevated pulmonary pressures upon rewarming. We investigated the effect of this hypothermic preconditioning on isolated human pulmonary arteries and isolated perfused lungs.

METHODS

Isometric tension was measured in human pulmonary artery rings (n=24). We assessed the constriction and dilation of these arteries at 37 °C and 17 °C. Isolated perfused human lung models consisted of lobes ventilated via a bronchial cannula and perfused with Krebs via a pulmonary artery cannula. Bronchial and pulmonary artery pressures were recorded. We investigated the effect of temperature using a heat exchanger.

RESULTS

Rewarming from 17 °C to 37 °C caused a 1.3 fold increase in resting tension (p<0.05). Arteries constricted 8.6 times greater to 30 nM KCl, constricted 17 times greater to 1 nM Endothelin-1 and dilated 30.3 times greater to 100 μM SNP at 37 °C than at 17 °C (p<0.005). No difference was observed in the responses of arteries originally maintained at 37 °C compared to those arteries maintained at 17 °C and rewarmed to 37 °C. Hypothermia blunted the increase in pulmonary artery pressures to stimulants such as potassium chloride as well as to H-R but did not precondition arteries to higher pulmonary artery pressures upon re-warming.

CONCLUSIONS

Deep hypothermia reduces the responsiveness of human pulmonary arteries but does not, however, precondition an exaggerated response to vasoactive agents upon re-warming.

Positive oxidative stress in aging and aging-related disease tolerance

It is now well established that reactive oxygen species (ROS), reactive nitrogen species (RNS), and a basal level of oxidative stress are essential for cell survival. It is also well known that while severe oxidative stress often leads to widespread oxidative damage and cell death, a moderate level of oxidative stress, induced by a variety of stressors, can yield great beneficial effects on adaptive cellular responses to pathological challenges in aging and aging-associated disease tolerance such as ischemia tolerance. Here in this review, I term this moderate level of oxidative stress as positive oxidative stress, which usually involves imprinting molecular signatures on lipids and proteins via formation of lipid peroxidation by-products and protein oxidation adducts. As ROS/RNS are short-lived molecules, these molecular signatures can thus execute the ultimate function of ROS/RNS. Representative examples of lipid peroxidation products and protein oxidation adducts are presented to illustrate the role of positive oxidative stress in a variety of pathological settings, demonstrating that positive oxidative stress could be a valuable prophylactic and/or therapeutic approach targeting aging and aging-associated diseases.

Global and ocular hypothermic preconditioning protect the rat retina from ischemic damage

Retinal ischemia could provoke blindness. At present, there is no effective treatment against retinal ischemic damage. Strong evidence supports that glutamate is implicated in retinal ischemic damage. We investigated whether a brief period of global or ocular hypothermia applied 24 h before ischemia (i.e. hypothermic preconditioning, HPC) protects the retina from ischemia/reperfusion damage, and the involvement of glutamate in the retinal protection induced by HPC. For this purpose, ischemia was induced by increasing intraocular pressure to 120 mm Hg for 40 min. One day before ischemia, animals were submitted to global or ocular hypothermia (33°C and 32°C for 20 min, respectively) and fourteen days after ischemia, animals were subjected to electroretinography and histological analysis. Global or ocular HPC afforded significant functional (electroretinographic) protection in eyes exposed to ischemia/reperfusion injury. A marked alteration of the retinal structure and a decrease in retinal ganglion cell number were observed in ischemic retinas, whereas global or ocular HPC significantly preserved retinal structure and ganglion cell count. Three days after ischemia, a significant decrease in retinal glutamate uptake and glutamine synthetase activity was observed, whereas ocular HPC prevented the effect of ischemia on these parameters. The intravitreal injection of supraphysiological levels of glutamate induced alterations in retinal function and histology which were significantly prevented by ocular HPC. These results support that global or ocular HPC significantly protected retinal function and histology from ischemia/reperfusion injury, probably through a glutamate-dependent mechanism.

Protein Oxidative Modifications: Beneficial Roles in Disease and Health

Protein oxidative modifications, also known as protein oxidation, are a major class of protein posttranslational modifications. They are caused by reactions between protein amino acid residues and reactive oxygen species (ROS) or reactive nitrogen species (RNS) and can be classified into two categories: irreversible modifications and reversible modifications. Protein oxidation has been often associated with functional decline of the target proteins, which are thought to contribute to normal aging and age-related pathogenesis. However, it has now been recognized that protein oxidative modifications can also play beneficial roles in disease and health. This review summarizes and highlights certain positive roles of protein oxidative modifications that have been documented in the literature. Covered oxidatively modified protein adducts include carbonylation, 3-nitrotyrosine, s-sulfenation, s-nitrosylation, s-glutathionylation, and disulfide formation. All of which have been widely analyzed in numerous experimental systems associated with redox stress conditions. The authors believe that selected protein targets, when modified in a reversible manner in prophylactic approaches such as preconditioning or ischemic tolerance, may provide potential promise in maintaining health and fighting disease.