Pressure overload-induced mild cardiac hypertrophy reduces left ventricular transmural differences in mitochondrial respiratory chain activity and increases oxidative stress

Cumulative Deleterious Effects of Tetrahydrocannabinoid (THC) and Ethanol on Mitochondrial Respiration and Reactive Oxygen Species Production Are Enhanced in Old Isolated Cardiac Mitochondria

Delta 9 tetrahydrocannabinol (THC), the main component of cannabis, has adverse effects on the cardiovascular system, but whether concomitant ethanol (EtOH) and aging modulate its toxicity is unknown. We investigated dose responses of THC and its vehicle, EtOH, on mitochondrial respiration and reactive oxygen production in both young and old rat cardiac mitochondria (12 and 90 weeks). THC dose-dependently impaired mitochondrial respiration in both groups, and such impairment was enhanced in aged rats (-97.5 ± 1.4% vs. -75.6 ± 4.0% at 2 × 10-5 M, and IC50: 0.7 ± 0.05 vs. 1.3 ± 0.1 × 10-5 M, p < 0.01, for old and young rats, respectively). The EtOH-induced decrease in mitochondrial respiration was greater in old rats (-50.1 ± 2.4% vs. -19.8 ± 4.4% at 0.9 × 10-5 M, p < 0.0001). Further, mitochondrial hydrogen peroxide (H2O2) production was enhanced in old rats after THC injection (+46.6 ± 5.3 vs. + 17.9 ± 7.8%, p < 0.01, at 2 × 10-5 M). In conclusion, the deleterious cardiac effects of THC were enhanced with concomitant EtOH, particularly in old cardiac mitochondria, showing greater mitochondrial respiration impairment and ROS production. These data improve our knowledge of the mechanisms potentially involved in cannabis toxicity, and likely support additional caution when THC is used by elderly people who consume alcohol.

Adaptive and maladaptive roles of different angiotensin receptors in the development of cardiac hypertrophy and heart failure

Angiotensin II (Ang II) is formed by the action of angiotensin-converting enzyme (ACE) in the renin-angiotensin system. This hormone is known to induce cardiac hypertrophy and heart failure and its actions are mediated by the interaction of both pro- and antihypertrophic Ang II receptors (AT1R and AT2R). Ang II is also metabolized by ACE 2 to Ang-(1-7), which elicits the activation of Mas receptors (MasR) for inducing antihypertrophic actions. Since heart failure under different pathophysiological situations is preceded by adaptive and maladaptive cardiac hypertrophy, we have reviewed the existing literature to gain some information regarding the roles of AT1R, AT2R, and MasR in both acute and chronic conditions of cardiac hypertrophy. It appears that the activation of AT1R may be involved in the development of adaptive and maladaptive cardiac hypertrophy as well as subsequent heart failure because both ACE inhibitors and AT1R antagonists exert beneficial effects. On the other hand, the activation of both AT2R and MasR may prevent the occurrence of maladaptive cardiac hypertrophy and delay the progression of heart failure, and thus therapy with different activators of these antihypertrophic receptors under chronic pathological stages may prove beneficial. Accordingly, it is suggested that a great deal of effort should be made to develop appropriate activators of both AT2R and MasR for the treatment of heart failure subjects.

Extracellular vesicles DJ-1 derived from hypoxia-conditioned hMSCs alleviate cardiac hypertrophy by suppressing mitochondria dysfunction and preventing ATRAP degradation

BACKGROUND

As a pathological myocardial remodeling process in a variety of cardiovascular diseases, cardiac hypertrophy still has no effective treatment. Human mesenchymal stem cells (hMSCs) derived extracellular vesicles (EVs) has been recognized as a promising treatment strategy for cardiac disease.

METHODS

In this study, the inhibitory effects on cardiac hypertrophy are compared between normoxia-conditioned hMSC-derived EVs (Nor-EVs) and hypoxia-conditioned hMSC-derived EVs (Hypo-EVs) in neonatal rat cardiomyocytes (NRCMs) after angiotensin II (Ang II) stimulation and in a mouse model of transverse aortic constriction (TAC).

RESULTS

We demonstrate that Hypo-EVs exert an increased inhibitory effect on cardiac hypertrophy compared with Nor-EVs. Parkinson disease protein 7 (PARK7/DJ-1) is identify as a differential protein between Nor-EVs and Hypo-EVs by quantitative proteomics analysis. Results show that DJ-1, which is rich in Hypo-EVs, alleviates mitochondrial dysfunction and excessive mitochondrial reactive oxygen species (mtROS) production as an antioxidant. Mechanistic studies demonstrate for the first time that DJ-1 may suppress cardiac hypertrophy by inhibiting the activity of proteasome subunit beta type 10 (PSMB10) through a direct physical interaction. This interaction can inhibit angiotensin II type 1 receptor (AT1R)-mediated signaling pathways resulting in cardiac hypertrophy through alleviating ubiquitination degradation of AT1R-associated protein (ATRAP).

CONCLUSIONS

When taken together, our study suggests that Hypo-EVs have significant potential as a novel therapeutic agent for the treatment of cardiac hypertrophy.

BRD4 Silencing Protects Angiotensin II-Induced Cardiac Hypertrophy by Inhibiting TLR4/NF-κB and Activating Nrf2-HO-1 Pathways

Background

Heart failure is a critical health problem worldwide, and cardiac hypertrophy is an important characteristic of heart failure. Bromodomain-containing protein 4 (BRD4) is involved in various cellular processes, including cardiac hypertrophy. This study aimed to investigate the mechanism underlying the effects of BRD4 on cardiac hypertrophy.

Methods

Rat myoblast H9c2 cells were treated with angiotensin II (Ang II) to increase the mRNA and protein expressions of BRD4. BRD4 was silenced by small interfering RNA (siRNA) in H9c2 cells. Proteins involved in Nrf2-HO-1 pathway were determined by Western blot.

Results

Our data suggest that BRD4 silencing attenuated Ang II, increased the percentage of TUNEL + cells and caspase-3 activity, increased oxidative stress, and increased the expression and content of pro-inflammatory cytokines. Mechanistically, we found that BRD4 silencing enhanced the protein expressions of Nrf2 and HO-1 and inhibited the TLR4 and phosphorylation of NF-kappa B in Ang II-stimulated H9c2 cells. TLR4 overexpression attenuated cardioprotection against Ang II by BRD4 silencing, including cardiac hypertrophy, oxidative stress, and inflammatory cytokine production. Additionally, TLR4 overexpression attenuated an increase in Nrf2 and HO-1 proteins and decreased phosphorylated NF-kappa B in H9c2 cells.

Conclusion

Our results speculate that the BRD4/TLR4 axis might be a promising strategy for treating cardiovascular diseases with cardiac hypertrophy, including HF.

Adrenergic Receptor Regulation of Mitochondrial Function in Cardiomyocytes

ABSTRACT

Adrenergic receptors (ARs) are G protein-coupled receptors that are stimulated by catecholamines to induce a wide array of physiological effects across tissue types. Both α1- and β-ARs are found on cardiomyocytes and regulate cardiac contractility and hypertrophy through diverse molecular pathways. Acute activation of cardiomyocyte β-ARs increases heart rate and contractility as an adaptive stress response. However, chronic β-AR stimulation contributes to the pathobiology of heart failure. By contrast, mounting evidence suggests that α1-ARs serve protective functions that may mitigate the deleterious effects of chronic β-AR activation. Here, we will review recent studies demonstrating that α1- and β-ARs differentially regulate mitochondrial biogenesis and dynamics, mitochondrial calcium handling, and oxidative phosphorylation in cardiomyocytes. We will identify potential mechanisms of these actions and focus on the implications of these findings for the modulation of contractile function in the uninjured and failing heart. Collectively, we hope to elucidate important physiological processes through which these well-studied and clinically relevant receptors stimulate and fuel cardiac contraction to contribute to myocardial health and disease.

Cardioprotective effects of early intervention with sacubitril/valsartan on pressure overloaded rat hearts

Left ventricular remodeling due to pressure overload is associated with poor prognosis. Sacubitril/valsartan is the first-in-class Angiotensin Receptor Neprilysin Inhibitor and has been demonstrated to have superior beneficial effects in the settings of heart failure. The aim of this study was to determine whether sacubitril/valsartan has cardioprotective effect in the early intervention of pressure overloaded hearts and whether it is superior to valsartan alone. We induced persistent left ventricular pressure overload in rats by ascending aortic constriction surgery and orally administrated sacubitril/valsartan, valsartan, or vehicle one week post operation for 10 weeks. We also determined the effects of sacubitril/valsartan over valsartan on adult ventricular myocytes and fibroblasts that were isolated from healthy rats and treated in culture. We found that early intervention with sacubitril/valsartan is superior to valsartan in reducing pressure overload-induced ventricular fibrosis and in reducing angiotensin II-induced adult ventricular fibroblast activation. While neither sacubitril/valsartan nor valsartan changes cardiac hypertrophy development, early intervention with sacubitril/valsartan protects ventricular myocytes from mitochondrial dysfunction and is superior to valsartan in reducing mitochondrial oxidative stress in response to persistent left ventricular pressure overload. In conclusion, our findings demonstrate that sacubitril/valsartan has a superior cardioprotective effect over valsartan in the early intervention of pressure overloaded hearts, which is independent of the reduction of left ventricular afterload. Our study provides evidence in support of potential benefits of the use of sacubitril/valsartan in patients with resistant hypertension or in patients with severe aortic stenosis.

Mitochondrial redox and TCA cycle metabolite signaling in the heart

Mitochondria are essential signaling organelles that regulate a broad range of cellular processes and thereby heart function. Multiple mechanisms participate in the communication between mitochondria and the nucleus that maintain cardiomyocyte homeostasis, including mitochondrial reactive oxygen species (ROS) and metabolic shifts in TCA cycle metabolite availability. An increased rate of ROS generation can cause irreversible damage to the cell and proposed to be a leading cause of many pathologies, including accelerated aging and heart disease. Myocardial impairments are also characterised by specific coordinated metabolic changes and dysregulated inflammatory responses. Hence, the mitochondrial respiratory chain is an important mediator between health and disease in the heart. This review will first outline the sources of ROS in the heart, mitochondrial metabolite dynamics, and provide an overview of their implications for heart disease. In addition, we will concentrate our discussion around current cardioprotective strategies relevant to mitochondrial ROS. Thorough understanding of mitochondrial signaling and the complex interplay with vital signaling pathways in the heart might allow us to develop novel therapeutic approaches to cardiovascular disease.

Mitochondrial protective effects of PARP-inhibition in hypertension-induced myocardial remodeling and in stressed cardiomyocytes

AIMS

During oxidative stress mitochondria become the main source of endogenous reactive oxygen species (ROS) production. In the present study, we aimed to clarify the effects of pharmacological PARP-1 inhibition on mitochondrial function and quality control processes.

MAIN METHODS

L-2286, a quinazoline-derivative PARP inhibitor, protects against cardiovascular remodeling and heart failure by favorable modulation of signaling routes. We examined the effects of PARP-1 inhibition on mitochondrial quality control processes and function in vivo and in vitro. Spontaneously hypertensive rats (SHRs) were treated with L-2286 or placebo. In the in vitro model, 150 μM H2O2 stress was applied on neonatal rat cardiomyocytes (NRCM).

KEY FINDINGS

PARP-inhibition prevented the development of left ventricular hypertrophy in SHRs. The interfibrillar mitochondrial network were less fragmented, the average mitochondrial size was bigger and showed higher cristae density compared to untreated SHRs. Dynamin related protein 1 (Drp1) translocation and therefore the fission of mitochondria was inhibited by L-2286 treatment. Moreover, L-2286 treatment increased the amount of fusion proteins (Opa1, Mfn2), thus preserving structural stability. PARP-inhibition also preserved the mitochondrial genome integrity. In addition, the mitochondrial biogenesis was also enhanced due to L-2286 treatment, leading to an overall increase in the ATP production and improvement in survival of stressed cells.

SIGNIFICANCE

Our results suggest that the modulation of mitochondrial dynamics and biogenesis can be a promising therapeutical target in hypertension-induced myocardial remodeling and heart failure.

Elucidation of the mechanism of action of pinitol against pressure overload-induced cardiac hypertrophy and fibrosis in an animal model of aortic stenosis

The long-term imposition of pressure overload on the cardiac tissue causes left ventricular hypertrophy (LVH) and cardiac fibrosis. Pinitol has been reported to possess antioxidant potential. The aim was to evaluate the efficacy of pinitol against pressure overload-induced cardiac hypertrophy and fibrosis in the aortic stenosis (AS) rat model. Cardiac hypertrophy was produced in Sprague-Dawley rats by abdominal aortic constriction and treated with lisinopril (15 mg/kg) or pinitol (5, 10, and 20 mg/kg). Pressure overload-induced alterations in hemodynamic and left ventricular function tests, cardiac SOD, GSH, MDA, NO, Na-K-ATPase, and mitochondrial complex enzyme levels were significantly attenuated by pinitol. The upregulated mRNA expressions of cardiac ANP, BNP, cTn-I, TNF-α, IL-1β, IL-6, Bax, Caspase-3, collagen-I, and cardiac apoptosis were markedly downregulated by pinitol. In conclusion, pinitol ameliorated pressure overload-induced LVH and fibrosis via its anti-inflammatory, antioxidant, antifibrotic, and antiapoptotic potential in experimental AS.

Regional variations in ex-vivo diffusion tensor anisotropy are associated with cardiomyocyte remodeling in rats after left ventricular pressure overload

BACKGROUND

Pressure overload left ventricular (LV) hypertrophy is characterized by increased cardiomyocyte width and ventricle wall thickness, however the regional variation of this remodeling is unclear. Cardiovascular magnetic resonance (CMR) diffusion tensor imaging (DTI) may provide a non-invasive, comprehensive, and geometrically accurate method to detect regional differences in structural remodeling in hypertrophy. We hypothesized that DTI parameters, such as fractional and planar anisotropy, would reflect myocyte remodeling due to pressure overload in a regionally-dependent manner.

METHODS

We investigated the regional distributions of myocyte remodeling in rats with or without transverse aortic constriction (TAC) via direct measurement of myocyte dimensions with confocal imaging of thick tissue sections, and correlated myocyte cross-sectional area and other geometric features with parameters of diffusivity from ex-vivo DTI in the same regions of the same hearts.

RESULTS

We observed regional differences in several parameters from DTI between TAC hearts and SHAM controls. Consistent with previous studies, helix angles from DTI correlated strongly with those measured directly from histological sections (p < 0.001, R2 = 0.71). There was a transmural gradient in myocyte cross-sectional area in SHAM hearts that was diminished in the TAC group. We also found several regions of significantly altered DTI parameters in TAC LV compared to SHAM, especially in myocyte sheet angle dispersion and planar anisotropy. Among others, these parameters correlated significantly with directly measured myocyte aspect ratios.

CONCLUSIONS

These results show that structural remodeling in pressure overload LV hypertrophy is regionally heterogeneous, especially transmurally, with a greater degree of remodeling in the sub-endocardium compared to the sub-epicardium. Additionally, several parameters derived from DTI correlated significantly with measurements of myocyte geometry from direct measurement in histological sections. We suggest that DTI may provide a non-invasive, comprehensive method to detect regional structural myocyte LV remodeling during disease.

Study of respiratory chain dysfunction in heart disease

The relentlessly beating heart has the greatest oxygen consumption of any organ in the body at rest reflecting its huge metabolic turnover and energetic demands. The vast majority of its energy is produced and cycled in form of ATP which stems mainly from oxidative phosphorylation occurring at the respiratory chain in the mitochondria. A part from energy production, the respiratory chain is also the main source of reactive oxygen species and plays a pivotal role in the regulation of oxidative stress. Dysfunction of the respiratory chain is therefore found in most common heart conditions. The pathophysiology of mitochondrial respiratory chain dysfunction in hereditary cardiac mitochondrial disease, the aging heart, in LV hypertrophy and heart failure, and in ischaemia-reperfusion injury is reviewed. We introduce the practicing clinician to the complex physiology of the respiratory chain, highlight its impact on common cardiac disorders and review translational pharmacological and non-pharmacological treatment strategies.

Left ventricular hypertrophy does not prevent heart failure in experimental hypertension

BACKGROUND

Left ventricular hypertrophy (LVH) secondary to hypertension has been accepted to prevent heart failure (HF) while paradoxically increasing cardiovascular morbi-mortality.

OBJECTIVES

To evaluate whether antihypertensive treatment inhibits LVH, restores beta-adrenergic response and affects myocardial oxidative metabolism.

METHODS

Ninety spontaneously hypertensive rats (SHR) were distributed into groups and treated (mg/kg, p.o.) with: losartan 30 (L), hydralazine 11 (H), rosuvastatin 10 (R), carvedilol 20 (C). Hypertension control group comprised 18 normotensive rats (Wistar-Kyoto, WKY). Following euthanasia at 16months, contractility was measured in 50% of rats (Langendorff system) before and after isoproterenol (Iso) 10^-9M, 10^-7M and 10^-5M stimulation. Left ventricular weight (LVW) was measured in the remaining hearts, and normalized by BW. Expression of thioredoxin 1 (Trx-1), peroxyredoxin 2 (Prx-2), glutaredoxin 3 (Grx-3), caspase-3 and brain natriuretic peptide (BNP) was determined.

RESULTS

Systolic blood pressure (mmHg): 154±3 (L), 137±1 (H), 190±3 (R)*, 206±3 (SHR)*, 183±1 (C)**, and 141±1 (WKY) (*p<0.05 vs. L, H, WKY, **p<0.05 vs. L, H, WKY, SHR). LVW/BW was higher in SHR and R (p<0.05). Groups SHR, R and C evidenced baseline contractile depression. Response to Iso 10^-5M was similar in WKY and L. Expression of Trx-1, Prx-2 and Grx-3 increased in C, H, R and L (p<0.01).

CONCLUSIONS

Present findings argue against the traditional idea and support that LVH might not be required to prevent HF. Increased expression of thioredoxins by antihypertensive treatment might be involved in protection from HF.

Muscles Susceptibility to Ischemia-Reperfusion Injuries Depends on Fiber Type Specific Antioxidant Level

Muscle injury resulting from ischemia-reperfusion largely aggravates patient prognosis but whether and how muscle phenotype modulates ischemia-reperfusion-induced mitochondrial dysfunction remains to be investigated. We challenged the hypothesis that glycolytic muscles are more prone to ischemia-reperfusion-induced injury than oxidative skeletal muscles. We therefore determined simultaneously the effect of 3 h of ischemia induced by aortic clamping followed by 2 h of reperfusion (IR, n = 11) on both gastrocnemius and soleus muscles, as compared to control animals (C, n = 11). Further, we investigated whether tempol, an antioxidant mimicking superoxide dismutase, might compensate a reduced defense system, likely characterizing glycolytic muscles (IR-Tempol, n = 7). In the glycolytic gastrocnemius muscle, as compared to control, ischemia-reperfusion significantly decreased mitochondrial respiration (-30.28 ± 6.16%, p = 0.003), increased reactive oxygen species production (+79.15 ± 28.72%, p = 0.04), and decreased reduced glutathione (-28.19 ± 6.80%, p = 0.011). Less deleterious effects were observed in the oxidative soleus muscle (-6.44 ± 6.30%, +4.32 ± 16.84%, and -8.07 ± 10.84%, respectively), characterized by enhanced antioxidant defenses (0.63 ± 0.05 in gastrocnemius vs. 1.24 ± 0.08 μmol L^-1 g^-1 in soleus). Further, when previously treated with tempol, glycolytic muscle was largely protected against the deleterious effects of ischemia-reperfusion. Thus, oxidative skeletal muscles are more protected than glycolytic ones against ischemia-reperfusion, thanks to their antioxidant pool. Such pivotal data support that susceptibility to ischemia-reperfusion-induced injury differs between organs, depending on their metabolic phenotypes. This suggests a need to adapt therapeutic strategies to the specific antioxidant power of the target organ to be protected.

Low-Intensity Ultrasound Decreases α-Synuclein Aggregation via Attenuation of Mitochondrial Reactive Oxygen Species in MPP(+)-Treated PC12 Cells

Many studies have shown that mitochondrial dysfunction and the subsequent oxidative stress caused by excessive reactive oxygen species (ROS) generation play a central role in the pathogenesis of Parkinson's disease (PD). We have previously shown that low-intensity ultrasound (LIUS) could reduce ROS generation by L-buthionine-(S,R)-sulfoximine (BSO) in retinal pigment epithelial cells. In this study, we studied the effects of LIUS stimulation on the ROS-dependent α-synuclein aggregation in 1-methyl-4-phenylpyridinium ion (MPP⁺)-treated PC12 cells. We found that LIUS stimulation suppressed the MPP⁺-induced ROS generation and inhibition of mitochondrial complex I activity in PC12 cells in an intensity-dependent manner at 30, 50, and 100 mW/cm². Furthermore, LIUS stimulation at 100 mW/cm² suppressed inhibition of mitochondrial complex activity by MPP⁺ and actually resulted in a decrease of α-synuclein phosphorylation and aggregation induced by MMP⁺ treatment in PC12 cells. LIUS stimulation also inhibited expression of casein kinase 2 (CK2) that appears to mediate ROS-dependent α-synuclein aggregation. Finally, LIUS stimulation alleviated the death of PC12 cells by MPP⁺ treatment in an intensity-dependent manner. We, hence, suggest that LIUS stimulation inhibits ROS generation by MPP⁺ treatment, thereby suppressing α-synuclein aggregation in PC12 cells.

Left Ventricular Transmural Gradient in Mitochondrial Respiration Is Associated with Increased Sub-Endocardium Nitric Oxide and Reactive Oxygen Species Productions

OBJECTIVE

Left ventricle (LV) transmural gradient in mitochondrial respiration has been recently reported. However, to date, the physiological mechanisms involved in the lower endocardium mitochondrial respiration chain capacity still remain to be determined. Since, nitric oxide (NO) synthase expression in the heart has spatial heterogeneity and might impair mitochondrial function, we investigated a potential association between LV transmural NO and mitochondrial function gradient.

METHODS

Maximal oxidative capacity (VMax) and relative contributions of the respiratory chain complexes II, III, IV (VSucc) and IV (VTMPD), mitochondrial content (citrate synthase activity), coupling, NO (electron paramagnetic resonance), and reactive oxygen species (ROS) production (H2O2 and dihydroethidium (DHE) staining) were determined in rat sub-endocardium (Endo) and sub-epicardium (Epi). Further, the effect of a direct NO donor (MAHMA NONOate) on maximal mitochondrial respiratory rates (Vmax) was determined.

RESULTS

Mitochondrial respiratory chain activities were reduced in the Endo compared with the Epi (-16.92%; P = 0.04 for Vmax and -18.73%; P = 0.02, for Vsucc, respectively). NO production was two-fold higher in the Endo compared with the Epi (P = 0.002) and interestingly, increasing NO concentration reduced Vmax. Mitochondrial H2O2 and LV ROS productions were significantly increased in Endo compared to Epi, citrate synthase activity and mitochondrial coupling being similar in the two layers.

CONCLUSIONS

LV mitochondrial respiration transmural gradient is likely related to NO and possibly ROS increased production in the sub-endocardium.

Caffeic acid ethanolamide prevents cardiac dysfunction through sirtuin dependent cardiac bioenergetics preservation

BACKGROUND

Cardiac oxidative stress, bioenergetics and catecholamine play major roles in heart failure progression. However, the relationships between these three dominant heart failure factors are not fully elucidated. Caffeic acid ethanolamide (CAEA), a synthesized derivative from caffeic acid that exerted antioxidative properties, was thus applied in this study to explore its effects on the pathogenesis of heart failure.

RESULTS

In vitro studies in HL-1 cells exposed to isoproterenol showed an increase in cellular and mitochondria oxidative stress. Two-week isoproterenol injections into mice resulted in ventricular hypertrophy, myocardial fibrosis, elevated lipid peroxidation, cardiac adenosine triphosphate and left ventricular ejection fraction decline, suggesting oxidative stress and bioenergetics changes in catecholamine-induced heart failure. CAEA restored oxygen consumption rates and adenosine triphosphate contents. In addition, CAEA alleviated isoproterenol-induced cardiac remodeling, cardiac oxidative stress, cardiac bioenergetics and function insufficiency in mice. CAEA treatment recovered sirtuin 1 and sirtuin 3 activity, and attenuated the changes of proteins, including manganese superoxide dismutase and hypoxia-inducible factor 1-α, which are the most likely mechanisms responsible for the alleviation of isoproterenol-caused cardiac injury

CONCLUSION

CAEA prevents catecholamine-induced cardiac damage and is therefore a possible new therapeutic approach for preventing heart failure progression.

Tetrahydrocannabinol induces brain mitochondrial respiratory chain dysfunction and increases oxidative stress: a potential mechanism involved in cannabis-related stroke

Cannabis has potential therapeutic use but tetrahydrocannabinol (THC), its main psychoactive component, appears as a risk factor for ischemic stroke in young adults. We therefore evaluate the effects of THC on brain mitochondrial function and oxidative stress, key factors involved in stroke. Maximal oxidative capacities V_max (complexes I, III, and IV activities), V_succ (complexes II, III, and IV activities), V_tmpd (complex IV activity), together with mitochondrial coupling (V_max/V₀), were determined in control conditions and after exposure to THC in isolated mitochondria extracted from rat brain, using differential centrifugations. Oxidative stress was also assessed through hydrogen peroxide (H₂O₂) production, measured with Amplex Red. THC significantly decreased V_max (−71%; P < 0.0001), V_succ (−65%; P < 0.0001), and V_tmpd (−3.5%; P < 0.001). Mitochondrial coupling (V_max/V₀) was also significantly decreased after THC exposure (1.8±0.2 versus 6.3±0.7; P < 0.001). Furthermore, THC significantly enhanced H₂O₂ production by cerebral mitochondria (+171%; P < 0.05) and mitochondrial free radical leak was increased from 0.01±0.01 to 0.10±0.01% (P < 0.001). Thus, THC increases oxidative stress and induces cerebral mitochondrial dysfunction. This mechanism may be involved in young cannabis users who develop ischemic stroke since THC might increase patient's vulnerability to stroke.

Oxidative stress markers and C-reactive protein are related to severity of heart failure in patients with dilated cardiomyopathy

Background. The aim of study was to determine relationships between functional capacity (NYHA class), left ventricle ejection fraction (LVEF), hemodynamic parameters, and biomarkers of redox state and inflammation in patients with dilated cardiomyopathy (DCM). Methods. DCM patients (n = 109, aged 45.97 ± 10.82 years), NYHA class IIV, and LVEF 2.94 ± 7.1% were studied. Controls comprised age-matched healthy volunteers (n = 28). Echocardiography and right heart catheterization were performed. Serum activities of superoxide dismutase isoenzymes (MnSOD and CuZnSOD), concentrations of uric acid (UA), malondialdehyde (MDA), and C-reactive protein (hs-CRP) were measured. Results. MnSOD, UA, hs-CRP, and MDA were significantly higher in DCM patients compared to controls. Except MDA concentration, above parameters were higher in patients in III-IV NYHA class or with lower LVEF. hsCRP correlated with of MnSOD (P < 0.05) and CuZnSOD activity (P < 0.01). Both isoenzymes positively correlated with mPAP and pulmonary capillary wedge pressure (MnSOD, resp., P < 0.01 and P < 0.05 and CuZnSOD P < 0.05; P < 0.05). UA positively correlated with MnSOD (P < 0.05), mPAP (P < 0.05), and PVRI (P < 0.05). The negative correlation between LVEF and UA (P < 0.01) was detected. Conclusion. There are relationships among the severity of symptoms of heart failure, echocardiographic hemodynamic parameters, oxidative stress, and inflammatory activation. Increased MnSOD activity indicates the mitochondrial source of ROS in patients with advanced heart failure.

The breathing heart - mitochondrial respiratory chain dysfunction in cardiac disease

The relentlessly beating heart has the greatest oxygen consumption of any organ in the body at rest reflecting its huge metabolic turnover and energetic demands. The vast majority of its energy is produced and cycled in form of ATP which stems mainly from oxidative phosphorylation occurring at the respiratory chain in the mitochondria. Apart from energy production, the respiratory chain is also the main source of reactive oxygen species and plays a pivotal role in the regulation of oxidative stress. Dysfunction of the respiratory chain is therefore found in most common heart conditions. The pathophysiology of mitochondrial respiratory chain dysfunction in hereditary cardiac mitochondrial disease, the ageing heart, in LV hypertrophy and heart failure, and in ischaemia-reperfusion injury is reviewed. We introduce the practising clinician to the complex physiology of the respiratory chain, highlight its impact on common cardiac disorders and review translational pharmacological and non-pharmacological treatment strategies.

Impact of iron oxide nanoparticles on brain, heart, lung, liver and kidneys mitochondrial respiratory chain complexes activities and coupling

The present study evaluates the effects of iron oxide nanoparticles (ION) on mitochondrial respiratory chain complexes activities in five organs characterized by different oxidative capacities and strongly involved in body detoxification. Isolated mitochondria were extracted from brain, heart, lung, liver and kidneys in twelve Wistar rats (8 weeks) using differential centrifugations. Maximal oxidative capacities (Vmax), mitochondrial respiratory chain complexes activity using succinate (Vsucc, complexes II, III, and IV activities) or N, N, N', N'-tetramethyl-p-phenylenediaminedihydrochloride (tmpd)/ascorbate (Vtmpd, complex IV activity) and, mitochondrial coupling (Vmax/Vo) were determined in controls and after exposure to 100, 200, 300 and 500μg/ml Fe3O4. Data showed that baseline maximal oxidative capacities were 26.3±4.7, 48.9±4.6, 11.3±1.3, 27.0±2.5 and 13.4±1.7μmol O2/min/g protein in brain, heart, lung, liver, and kidneys mitochondria, respectively. Complexes II, III, and IV activities also significantly differed between the five organs. Interestingly, as compared to baseline values and in all tissues examined, exposure to ION did not alter mitochondrial respiratory chain complexes activities whatever the nanoparticles (NPs) concentration used. Thus, ION did not show any toxicity on mitochondrial coupling and respiratory chain complexes I, II, III, and IV activities in these five major organs.