Characterization of cardiac effects of OPA1 protein promotion in transgenic animal model

Introduction

Mitochondria forms a dynamic network in cells, which is regulated by the balance between mitochondrial fusion and fission. The inhibition of mitochondrial fission could result in positive effects in acute ischemic/reperfusion injury models, due to prevention of mitochondrial membrane potential fall that goes along with fission processes. However, inhibition of fission in chronic models is disadvantageous because it obstructs the elimination of damaged mitochondrial fragments. OPA1 – in view of the previous results – a possible therapy target, as a fusion promoter and structure stabilizer protein.

Methods

We used transgenic mice in which OMA1 and YME1L cleavage spots of OPA1 were deleted. This resulted in higher representation of L-OPA1 compared to S-OPA1. After genotyping and model validation all animals were examined by echocardiograph and ECG on two occasions, at week 11 and 36. Histology samples were made from hearts, in case of mitochondrial morphology and structure remodelling examination. Cardiomyocytes were isolated from neonatal mice to determine the efficiency of mitochondrial respiration by SeaHorse assay method.

Results

Capillary Western immunoassay proved the presence and higher concentration of OPA1 in the TG animals. Echocardiographic examination showed a significant ejection fraction reduction in TG animals at week 36, but remodelling in histology samples could not be observed. The efficiency of mitochondrial respiration was decreased in TG animals compared to WT animals, according to the results of SeaHorse assay.

Conclusion

OPA1 protein promotion has a negative effect on systolic function during ageing. We confirmed that volume overload and ventricular remodeling did not manifested. The reason behind the loss of pump function might be at least partly the energy deficit due to the mitochondrial respiratory failure and the damage in mitochondrial quality control pathways.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): The research in Hungary was funded by NKFIH within the framework of the project TKP2021-EGA-17.

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.

P5994Role of BGP-15 treatment in hypertensive heart failure progression and mitochondrial protection

Introduction

The deterioration of mitochondrial quality control greatly contributes to the hypertension induced cardiac remodeling and progression of heart failure. Our previous in vitro results demonstrated the mitochondrial protective effect of antioxidant BGP-15 compound in the presence of cellular stress.

Purpose

In our recent study we investigated the effect of BGP-15 on cardiac remodeling in spontaneously hypertensive rats (SHR) with manifested heart failure and on mitochondrial dynamics and function in cell culture model.

Methods

15-month-old male SHR received 25 mg/kg/day BGP-15 (SHR-B) or placebo (SHR-C) for 18 weeks. Age matched Wistar rats (WKY) were used as normotensive control. The heart function was monitored by echocardiography. Histological preparations were made from cardiac tissue. Neonatal rat cardiomyocytes (NRCMs) were used as in vitro model. 150 μM H2O2 stress and 50 μM BGP-15 treatment was applied. Mitochondrial network was stained with MitoTracker Red. Mitochondrial membrane potential was detected using JC-1 dye, while mitochondrial function was monitored by the Agilent Seahorse XFp, Cell Mito Stress Test. In both model the cellular levels of mitochondrial dynamics proteins were measured in Western blot. To study the ultrastructure we used electron microscopy in our in vivo and in vitro model.

Results

Left ventricular (LV) mass and LV wall thickness were increased significantly in SHR-C group compared to the initial values (p<0.05). These parameters were decreased considerably in the SHR-B group. Ejection fraction (EF%) decreased in both SHR group although this downturn was minimal because of the treatment. Chronic high blood pressure caused higher collagen deposition in SHR-C rats that was significantly diminished in the SHR-B group. Regarding the mitochondrial function decrease in the levels of fusion proteins OPA1 and MFN2 was observed in the SHR-C group. These differences were significantly reduced by BGP-15 treatment (p<0.05). Mitigation of the level of fission protein DRP1 was however reduced by BGP-15 (p<0.05). In our cellular model, we observed that the H2O2-induced mitochondrial fragmentation was decreased by BGP-15 treatment (p<0.05). BGP-15 treatment prevented mitochondrial membrane potential fall in H2O2 stress (p<0.05). There was no significant difference in basal respiration among groups by monitoring the mitochondrial function. The maximal respiration capacity and ATP production were significantly higher in the BGP-15 treated group in comparison to the stressed group (p<0.05).

Conclusion

BGP-15 treatment has beneficial effects on mitochondrial dynamics and structure by promoting fusion processes. It also supports the maintenance of mitochondrial function through the preservation of the mitochondrial structure. The mitigation of remodeling processes and the preserved EF in the treated group are results at least partly of the comprehensible effects of BGP-15 on mitochondrial structure and function.

Acknowledgement/Funding

GINOP-2.3.2-15-2016-00049; GINOP-2.3.2-15-2016-00048; GINOP-2.3.3-15-2016-00025

P781Resveratrol improves cardiac function and exerts an anti-inflammatory effect in systolic heart failure patients

Introduction

The positive effects of resveratrol on heart failure have already been evaluated in several experimental animal models, however, in a human clinical trial it was not yet confirmed. The aim of our study was to assess the effect of resveratrol supplementation on left ventricular structure and function in patients with heart failure with reduced ejection fraction (HFrEF).

Methods and materials

60 HFrEF patients (age: 66.7±11.04 years, 17 women and 43 men) were enrolled into our study. They were randomized into two groups, in the first group (n=30) daily 2x50 mg resveratrol was administered orally and placebo was given in the other group (n=30). 56% of the enrolled patients had ischemic HFrEF. During the whole study period, patients were taken the optimal medical therapy of HFrEF (ACEI/ARB, BB, MRA) in the same dose as before the randomization. On the day of randomization and 3 months later echocardiography, six minutes walking test (6MWT) and quality of life questionnaire (QoL) test were performed. Besides the routine lab tests, the levels of biomarkers (NT-proBNP, galectin-3) and inflammatory cytokines (IL-1, IL-6) were also measured.

Results

After the 3-month-long follow-up period left ventricular ejection fraction improved significantly in the resveratrol group comparing to the placebo group (p<0.001). The function of the right ventricle (RV) improved (p<0.05), moreover the RV dimensions, as well as atrial volumes decreased significantly in the resveratrol group (p<0.05). In the case of 6MWT (p<0.05) and QoL test (p<0.05) a significant improvement could be observed in the resveratrol group versus the placebo group (p<0.05). Lab test analysis showed that resveratrol supplementation reduced significantly the total cholesterol level (p<0,05) and LDL-C level (p<0,05) and had no overt effect on other metabolic parameters. NT-proBNP level increased significantly in the placebo group (p<0.05) by the end of the trial, however, in the resveratrol group we could see a slight improving tendency (NS). In the case of Galectin-3, no significant changes could be seen.

Conclusions

Our results revealed that resveratrol supplementation in systolic heart failure patients adding to the standard medical therapy resulted in an improvement of echocardiographic parameters, functional status and decreased the level of inflammatory cytokines.

Acknowledgement/Funding

GINOP-2.3.2-15-2016-00048