Cardiac overexpression of catalase antagonizes ADH-associated contractile depression and stress signaling after acute ethanol exposure in murine myocytes

In-vivo hemodynamic imaging of acute prenatal ethanol exposure in fetal brain by photoacoustic tomography

Prenatal ethanol exposure (PEE) can lead to structural and functional abnormalities in fetal brain. Although neural developmental deficits due to PEE have been recognized, the immediate effects of PEE on fetal brain vasculature and hemodynamics remain poorly understood. One of the major obstacles that preclude the rapid advancement of studies on fetal vascular dynamics is the limitation of the imaging techniques. Thus, a technique for noninvasive in-vivo imaging of fetal vasculature and hemodynamics is desirable. In this study, we explored the dynamic changes of the vessel dimeter, density and oxygen saturation in fetal brain after acute maternal ethanol exposure in the second-trimester equivalent murine model using a real-time photoacoustic tomography system we developed for imaging embryo of small animals. The results indicate a significant decrease in fetal brain vessel diameter, perfusion and oxygen saturation. This work demonstrated that PAT can provide high-resolution noninvasive imaging ability to monitor fetal vascular dynamics.

Role of Stress Kinase JNK in Binge Alcohol-Evoked Atrial Arrhythmia

BACKGROUND

Excessive binge alcohol drinking has acute cardiac arrhythmogenic effects, including promotion of atrial fibrillation (AF), which underlies "Holiday Heart Syndrome." The mechanism that couples binge alcohol abuse with AF susceptibility remains unclear. We previously reported stress-activated c-Jun N-terminal kinase (JNK) signaling contributes to AF development. This is interesting because JNK is implicated in alcohol-caused organ malfunction beyond the heart.

OBJECTIVES

The purpose of this study was to detail how JNK promotes binge alcohol-evoked susceptibility to AF.

METHODS

The authors found binge alcohol-exposure leads to activated JNK, specifically JNK2. Furthermore, binge alcohol induces AF (24- vs. 1.8-Hz burst pacing-induced episodes per attempt per animal), higher incidence of diastolic intracellular Ca2+ activity (Ca2+ waves, sarcoplasmic reticulum [SR] Ca2+ leakage), and membrane voltage (Vm) and systolic Ca2+ release spatiotemporal heterogeneity (ΔtVm-Ca). These changes were completely eliminated by JNK inhibition both in vivo and in vitro. calmodulin kinase II (CaMKII) is a proarrhythmic molecule known to drive SR Ca2+ mishandling.

RESULTS

The authors report for the first time that binge alcohol activates JNK2, which subsequently phosphorylates the CaMKII protein, enhancing CaMKII-driven SR Ca2+ mishandling. CaMKII inhibition eliminates binge alcohol-evoked arrhythmic activities.

CONCLUSIONS

Our studies demonstrate that binge alcohol exposure activates JNK2 in atria, which then drives CaMKII activation, prompting aberrant Ca2+ waves and, thus, enhanced susceptibility to atrial arrhythmia. Our results reveal a previously unrecognized form of alcohol-driven kinase-on-kinase proarrhythmic crosstalk. Atrial JNK2 function represents a potential novel therapeutic target to treat and/or prevent AF.

Paradoxical Roles of Antioxidant Enzymes: Basic Mechanisms and Health Implications

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated from aerobic metabolism, as a result of accidental electron leakage as well as regulated enzymatic processes. Because ROS/RNS can induce oxidative injury and act in redox signaling, enzymes metabolizing them will inherently promote either health or disease, depending on the physiological context. It is thus misleading to consider conventionally called antioxidant enzymes to be largely, if not exclusively, health protective. Because such a notion is nonetheless common, we herein attempt to rationalize why this simplistic view should be avoided. First we give an updated summary of physiological phenotypes triggered in mouse models of overexpression or knockout of major antioxidant enzymes. Subsequently, we focus on a series of striking cases that demonstrate "paradoxical" outcomes, i.e., increased fitness upon deletion of antioxidant enzymes or disease triggered by their overexpression. We elaborate mechanisms by which these phenotypes are mediated via chemical, biological, and metabolic interactions of the antioxidant enzymes with their substrates, downstream events, and cellular context. Furthermore, we propose that novel treatments of antioxidant enzyme-related human diseases may be enabled by deliberate targeting of dual roles of the pertaining enzymes. We also discuss the potential of "antioxidant" nutrients and phytochemicals, via regulating the expression or function of antioxidant enzymes, in preventing, treating, or aggravating chronic diseases. We conclude that "paradoxical" roles of antioxidant enzymes in physiology, health, and disease derive from sophisticated molecular mechanisms of redox biology and metabolic homeostasis. Simply viewing antioxidant enzymes as always being beneficial is not only conceptually misleading but also clinically hazardous if such notions underpin medical treatment protocols based on modulation of redox pathways.

Nongenomic effects of estrogen mediate the dose-related myocardial oxidative stress and dysfunction caused by acute ethanol in female rats

Acute ethanol lowers blood pressure (BP) and cardiac output in proestrus and after chronic estrogen (E2) replacement in ovariectomized (OVX) female rats. However, whether rapid nongenomic effects of estrogen mediate these hemodynamic effects of ethanol remains unanswered. To test this hypothesis, we investigated the effect of ethanol (0.5 or 1.5 g/kg iv) on left ventricular (LV) function and oxidative markers in OVX rats pretreated 30 min earlier with 1 μg/kg E2 (OVXE2) or vehicle (OVX) and in proestrus sham-operated (SO) rats. In SO rats, ethanol caused significant and dose-related reductions in BP, rate of rise in LV pressure (LV dP/dtmax), and LV developed pressure (LVDP). These effects of ethanol disappeared in OVX rats and were restored in OVXE2 rats, suggesting rapid estrogen receptor signaling mediates the detrimental effects of ethanol on LV function. Ex vivo studies revealed that the estrogen-dependent myocardial dysfunction caused by ethanol was coupled with higher LV 1) generation of reactive oxygen species (ROS), 2) expression of malondialdehyde and 4-hydroxynonenal protein adducts, 3) phosphorylation of protein kinase B (Akt) and extracellular signal-regulated kinases (ERK1/2), and 4) catalase activity. ERK1/2 inhibition by PD-98059 (1 mg/kg iv) abrogated the myocardial dysfunction, hypotension, and the elevation in myocardial ROS generation caused by ethanol. We conclude that rapid estrogen receptor signaling is implicated in cellular events that lead to the generation of aldehyde protein adducts and Akt/ERK1/2 phosphorylation, which ultimately mediate the estrogen-dependent LV oxidative stress and dysfunction caused by ethanol in female rats.

The herbal formula CGX ameliorates the expression of vascular endothelial growth factor in alcoholic liver fibrosis

ETHNOPHARMACOLOGIC RELEVANCE

The Chunggan extract (CGX) is a traditional herbal formula prescribed for patients suffering from various liver diseases, including alcoholic liver disease, in which the mechanism of CGX action remains unclear. This study aimed to investigate the anti-hepatic fibrosis effects of CGX and its underlying mechanisms in alcohol-induced rat livers.

MATERIALS AND METHODS

To elucidate the mechanism of action of CGX, we evaluated gene expression profiles in the livers of rats treated with 30% alcohol and anti-fibrotic doses of CGX of 100 and 200 mg/kg/day at 1 day, and 2 and 4 weeks using microarrays. The mRNA and protein expression levels of vascular endothelial growth factor (VEGF), one of the candidate genes selected in this study, in alcohol-induced rat livers were measured by real-time PCR and enzyme-linked immunosorbent assays, respectively.

RESULTS

We identified 4128 genes as differentially expressed by at least twofold between alcohol-only- and alcohol-CGX-fed rats at various doses and time points, compared to naïve control animals. Twenty-three of these genes were associated with liver fibrosis and oxidative stress based on the GeneCards database, resulting in p<0.05 by ANOVA between the alcohol-only and alcohol-CGX groups. Especially, Vegf was decreased in CGX 200 mg/kg/day-fed rat livers at all time points evaluated, and mRNA and protein levels at the 4-week time point were validated.

CONCLUSION

These gene expression profiles provide a better understanding of the mechanisms underlying the anti-fibrotic effects of CGX. Suppression of VEGF may play a critical role in anti-fibrotic action of CGX in alcoholic liver injury.

Facilitated ethanol metabolism promotes cardiomyocyte contractile dysfunction through autophagy in murine hearts

Chronic drinking leads to myocardial contractile dysfunction where ethanol metabolism plays an essential role. Acetaldehyde, the main ethanol metabolite, mediates alcohol-induced cell injury although the underlying mechanism is still elusive. This study was designed to examine the mechanism involved in accelerated ethanol metabolism-induced cardiac defect with a focus on autophagy. Wild-type FVB and cardiac-specific overexpression of alcohol dehydrogenase mice were placed on a 4% nutrition-balanced alcohol diet for 8 weeks. Myocardial histology, immunohistochemistry, autophagy markers and signal molecules were examined. Expression of micro RNA miR-30a, a potential target of Beclin 1, was evaluated by real-time PCR. Chronic alcohol intake led to cardiac acetaldehyde accumulation, hypertrophy and overt autophagosome accumulation (LC3-II and Atg7), the effect of which was accentuated by ADH. Signaling molecules governing autophagy initiation including class III PtdIns3K, phosphorylation of mTOR and p70S6K were enhanced and dampened, respectively, following alcohol intake. These alcohol-induced signaling responses were augmented by ADH. ADH accentuated or unmasked alcohol-induced downregulation of Bcl-2, Bcl-xL and MiR-30a. Interestingly, ADH aggravated alcohol-induced p62 accumulation. Autophagy inhibition using 3-MA abolished alcohol-induced cardiomyocyte contractile anomalies. Moreover, acetaldehyde led to cardiomyocyte contractile dysfunction and autophagy induction, which was ablated by 3-MA. Ethanol or acetaldehyde increased GFP-LC3 puncta in H9c2 cells, the effect of which was ablated by 3-MA but unaffected by lysosomal inhibition using bafilomycin A(1), E64D and pepstatin A. In summary, these data suggested that facilitated acetaldehyde production via ADH following alcohol intake triggered cardiac autophagosome formation along with impaired lysosomal degradation, en route to myocardial defect.

Systems-scale analysis reveals pathways involved in cellular response to methamphetamine

Background

Methamphetamine (METH), an abused illicit drug, disrupts many cellular processes, including energy metabolism, spermatogenesis, and maintenance of oxidative status. However, many components of the molecular underpinnings of METH toxicity have yet to be established. Network analyses of integrated proteomic, transcriptomic and metabolomic data are particularly well suited for identifying cellular responses to toxins, such as METH, which might otherwise be obscured by the numerous and dynamic changes that are induced.

Methodology/Results

We used network analyses of proteomic and transcriptomic data to evaluate pathways in Drosophila melanogaster that are affected by acute METH toxicity. METH exposure caused changes in the expression of genes involved with energy metabolism, suggesting a Warburg-like effect (aerobic glycolysis), which is normally associated with cancerous cells. Therefore, we tested the hypothesis that carbohydrate metabolism plays an important role in METH toxicity. In agreement with our hypothesis, we observed that increased dietary sugars partially alleviated the toxic effects of METH. Our systems analysis also showed that METH impacted genes and proteins known to be associated with muscular homeostasis/contraction, maintenance of oxidative status, oxidative phosphorylation, spermatogenesis, iron and calcium homeostasis. Our results also provide numerous candidate genes for the METH-induced dysfunction of spermatogenesis, which have not been previously characterized at the molecular level.

Conclusion

Our results support our overall hypothesis that METH causes a toxic syndrome that is characterized by the altered carbohydrate metabolism, dysregulation of calcium and iron homeostasis, increased oxidative stress, and disruption of mitochondrial functions.

Aldehyde dehydrogenase 2 knockout accentuates ethanol-induced cardiac depression: role of protein phosphatases

Alcohol consumption leads to myocardial contractile dysfunction possibly due to the toxicity of ethanol and its major metabolite acetaldehyde. This study was designed to examine the influence of mitochondrial aldehyde dehydrogenase-2 (ALDH2) knockout (KO) on acute ethanol exposure-induced cardiomyocyte dysfunction. Wild-type (WT) and ALDH2 KO mice were subjected to acute ethanol (3g/kg, i.p.) challenge and cardiomyocyte contractile function was assessed 24h later using an IonOptix edge detection system. Western blot analysis was performed to evaluate ALDH2, protein phosphatase 2A (PP2A), phosphorylation of Akt, and glycogen synthase kinase-3beta (GSK-3beta). ALDH2 KO accentuated ethanol-induced elevation in cardiac acetaldehyde levels. Ethanol exposure depressed cardiomyocyte contractile function including decreased cell shortening amplitude and maximal velocity of shortening/relengthening as well as prolonged relengthening duration and a greater decline in peak shortening in response to increasing stimulus frequency, the effect of which was significantly exaggerated by ALDH2 KO. ALDH2 KO also unmasked an ethanol-induced prolongation of shortening duration. In addition, short-term in vitro incubation of ethanol-induced cardiomyocyte mechanical defects was exacerbated by the ALDH inhibitor cyanamide. Ethanol treatment dampened phosphorylation of Akt and GSK-3beta associated with upregulated PP2A, which was accentuated by ALDH2 KO. ALDH2 KO aggravated ethanol-induced decrease in mitochondrial membrane potential. These results suggested that ALDH2 deficiency led to worsened ethanol-induced cardiomyocyte function, possibly due to upregulated expression of protein phosphatase, depressed Akt activation, and subsequently impaired mitochondrial function. These findings depict a critical role of ALDH2 in the pathogenesis of alcoholic cardiomyopathy.

Cellular redox state protects acetaldehyde-induced alteration in cardiomyocyte function by modifying Ca2+ release from sarcoplasmic reticulum

Recent studies indicate that low concentrations of acetaldehyde may function as the primary factor in alcoholic cardiomyopathy by disrupting Ca2+ handling or disturbing cardiac excitation-contraction coupling. By producing reactive oxygen species, acetaldehyde shifts the intracellular redox potential from a reduced state to an oxidized state. We examined whether the redox state modulates acetaldehyde-induced Ca2+ handling by measuring Ca2+ transient using a confocal imaging system and single ryanodine receptor type 2 (RyR2) channel activity using the planar lipid bilayer method. Ca2+ transient was recorded in isolated rat ventricular myocytes with incorporated fluo 3. Intracellular reduced glutathione level was estimated using the monochlorobimane fluorometric method. Acetaldehyde at 1 and 10 μM increased Ca2+ transient amplitude and its relative area in intact myocytes, but acetaldehyde at 100 μM decreased Ca2+ transient area significantly. Acetaldehyde showed a minor effect on Ca2+ transient in myocytes in which intracellular reduced glutathione content had been decreased against challenge of diethylmaleate to a level comparable to that induced by exposure to ∼50 μM acetaldehyde. Channel activity of the RyR2 with slightly reduced cytoplasmic redox potential from near resting state (−213 mV) or without redox fixation was augmented by all concentrations of acetaldehyde (1–100 μM) used here. However, acetaldehyde failed to activate the RyR2 channel, when the cytoplasmic redox potential was kept with a reduced (−230 mV) or markedly oxidized (−180 mV) state. This result was similar to effects of acetaldehyde on Ca2+ transient in diethylmaleate-treated myocytes, probably being in oxidized redox potential. The present results suggest that acetaldehyde acts as an RyR2 activator to disturb cardiac muscle function, and redox potential protects the heart from acetaldehyde-induced alterations in myocytes.

Catalase alleviates cardiomyocyte dysfunction in diabetes: role of Akt, Forkhead transcriptional factor and silent information regulator 2

Oxidative stress has been speculated to play an essential role in diabetic cardiomyopathy. This study was designed to examine the effect of the antioxidant catalase on diabetes-induced cardiomyocyte dysfunction and the cellular mechanisms involved. Adult wild-type (FVB) and transgenic mice with cardiac-specific overexpression of catalase were made diabetic by a single injection of streptozotocin (STZ, 220 mg/kg; i.p., maintained for two weeks). Cardiomyocyte contractile properties were evaluated including peak shortening (PS), time-to-PS (TPS), time-to-relengthening (TR(90)), maximal velocity of shortening/relengthening (+/-dL/dt), intracellular Ca(2+) level and decay rate. STZ depressed -dL/dt, prolonged TPS and TR(90), elevated resting intracellular Ca(2+) level and reduced intracellular Ca(2+) decay in FVB myocytes. While catalase exhibited little effect on contractile and intracellular Ca(2+) properties in control myocytes, it negated diabetes-induced cardiomyocyte mechanical abnormalities. Diabetic myocytes exhibited enhanced levels of reactive oxygen species and apoptosis, which were alleviated by catalase. Western blot analysis revealed that diabetes reduced Akt phosphorylation, enhanced the silent information regulator 2 (Sirt2), and upregulated Forkhead transcriptional factor Foxo3a as well as glycogen synthase kinase-3beta (GSK-3beta) and pGSK-3beta. While catalase itself exhibited little effect on these proteins or their phosphorylation (with the exception of Sirt2), it significantly attenuated diabetes-induced alteration in pAkt, Foxo3a and Sirt2 without affecting GSK-3beta. Inhibition of Sirt2 using splitomicin impaired cardiomyocyte contractile function (reduced PS, +/-dL/dt, prolonged TPS and TR(90)). In summary, our data suggest potential roles of Akt, Foxo3a and Sirt2 in the onset of diabetic cardiomyopathy and the therapeutic potential of catalase.

Cardiac overexpression of alcohol dehydrogenase (ADH) alleviates aging-associated cardiomyocyte contractile dysfunction: role of intracellular Ca2+ cycling proteins

Aging is a complex biological process with contributions from a wide variety of genes including insulin-like growth factor I and alcohol dehydrogenase (ADH), which decline with advanced age. The goal of this study was to examine if ADH enzyme plays any role in cardiac aging. Ventricular myocytes were isolated from young (2-3 months old) or aged (26-28 months old) male FVB wild-type and cardiac-specific ADH (class I, isozyme type 1) transgenic mice. Mechanical properties were measured using an IonOptix system. Aged FVB myocytes displayed significantly reduced ADH activity compared with young ones, which was restored by the ADH transgene. Compared with young cardiomyocytes, aged FVB myocytes exhibited prolonged relengthening duration and a steaper decline in peak shortening amplitude in response to elevated electrical stimuli. Although ADH transgene itself did not alter mechanical properties in young mice, it rescued aging-associated diastolic dysfunction without affecting dampened contractile response to high stimulus frequency. Immunoblot analysis revealed reduced sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA2a) and Na(+)-Ca(2+) exchanger (NCX) levels in conjunction with enhanced phospholamban expression in aged FVB hearts. ADH transgene prevented aging-induced reduction in SERCA2a and NCX without affecting up-regulated phospholamban. Our data suggest that aging is associated with a reduced ADH enzymatic activity and diastolic dysfunction, which may be corrected with cardiac overexpression of the ADH enzyme. Alteration in cardiac Ca(2+) cycling proteins including SERCA2a and NCX may play a role in both pathogenesis of cardiac aging and the beneficial effect of ADH enzyme.