Downregulation of miR-122 attenuates hypoxia/reoxygenation (H/R)-induced myocardial cell apoptosis by upregulating GATA-4

MicroRNA-122 has been reported to play a potential role in the apoptosis of myocardial cells. However, the effect of miR-122 in regulating myocardial ischemic injury has not been previously addressed. This study aimed to investigate the effect and the molecular basis of miR-122 on myocardial ischemic injury. Using the hypoxia/reoxygenation (H/R) model of rat cardiomyocytes H9C2 in vitro, we found that miR-122 was highly expressed in H9C2 cells after H/R treatment. Overexpression of miR-122 by recombinant adeno-associated viral vector infection markedly promoted the apoptosis of H9C2 cells induced by H/R treatment, whereas miR-122 inhibition significantly decreased cell apoptosis. Dual-luciferase reporter assay and western blot assay revealed that GATA-4 was a direct target gene of miR-122, and miR-122 suppressed the expression of GATA-4 via binding to its 3'-UTR. We further identified that overexpression of miR-122 inhibited the expression of GATA-4 at the mRNA and protein levels, whereas the inhibition of miR-122 upregulated the expression of GATA-4. Moreover, GATA-4 was poorly expressed in H/R H9C2 cells and the apoptosis induced by H/R was associated with the decrease in GATA-4 expression. Importantly, silencing of GATA-4 apparently abrogated the inhibitory effect of anti-miR-122 on H/R-induced cell apoptosis. In conclusion, these findings indicate that downregulation of miR-122 alleviates cardiomyocyte H/R injury through upregulation of GATA-4 expression, supplying a novel molecular target for myocardial ischemic injury.

Effects of albumin binding on photocytotoxicity of extracellular photosensitization reaction using talaporfin sodium to rat myocardial cells

BACKGROUND

We previously proposed a new treatment for tachyarrhythmia using an extracellular photosensitization reaction occurring in the interstitial space of myocardia shortly after the injection of talaporfin sodium. Using myocardial cells, we studied the photocytotoxicity of this extracellular photosensitization reaction between talaporfin sodium and albumin.

METHODS

The albumin concentrations tested spanned the physiological range found in the interstitial space (0-15 mg/ml) while the talaporfin sodium concentration were varied from 0 to 40 μg/ml. The reactions were conducted in 96-well plates. To obtain the binding ratio and the amount of energy deposited into the photosensitizer, we measured the change in the absorbance spectra of talaporfin sodium solutions containing different concentrations of albumin.

RESULTS

Photocytotoxicity to myocardial cell due to the reaction decreased when physiological concentrations of albumin were added to the reaction mix, and decreased sharply when the molar concentration ratio of albumin to talaporfin sodium was between 0.3 and 1.2. A monotonic binding ratio was obtained, ranging from 10 to 80%, at albumin concentrations of 0.1-1.0 mg/ml. We found that the lethality of the extracellular photosensitization reaction towards myocardial cells had a threshold albumin concentration, even though the energy deposited into the talaporfin sodium solution was calculated to be almost constant (4.23 ± 0.19 J/well) in the presence of 0-15 mg/ml albumin.

CONCLUSIONS

Based on the likely concentration of albumin in the interstitial space, we conclude that the photodynamic efficacy of talaporfin, under conditions used here, will markedly decrease if the albumin level exceeds 0.65 mg/ml.

Aspirin-induced heat stress resistance in chicken myocardial cells can be suppressed by BAPTA-AM in vitro

Our recent studies have displayed the protective functions of aspirin against heat stress (HS) in chicken myocardial cells, and it may be associated with heat shock proteins (HSPs). In this study, we further investigated the potential role of HSPs in the aspirin-induced heat stress resistance. Four of the most important HSPs including HspB1 (Hsp27), Hsp60, Hsp70, and Hsp90 were induced by aspirin pretreatment and were suppressed by BAPTA-AM. When HSPs were induced by aspirin, much slighter HS injury was detected. But more serious damages were observed when HSPs were suppressed by BAPTA-AM than those cells exposed to HS without BAPTA-AM, even the myocardial cells have been treated with aspirin in prior. Comparing to other HSPs, HspB1 presented the largest increase after aspirin treatments, 86-fold higher than the baseline (the level before HS). These findings suggested that multiple HSPs participated in aspirin's anti-heat stress function but HspB1 may contribute the most. Interestingly, during the experiments, we also found that apoptosis rate as well as the oxidative stress indicators (T-SOD and MDA) was not consistently responding to heat stress injury as expected. By selecting from a series of candidates, myocardial cell damage-related enzymes (CK-MB and LDH), cytopathological tests, and necrosis rate (measured by flow cytometry assays) are believed to be reliable indicators to evaluate heat stress injury in chicken's myocardial cells and they will be used in our further investigations.

Effect of down-regulated miR-15b-5p expression on arrhythmia and myocardial apoptosis after myocardial ischemia reperfusion injury in mice

In this study, the regulation of miR-15b-5p on myocardial ischemia reperfusion (I/R) injury-induced arrhythmia and myocardial apoptosis was investigated in mice. We observed the change in miR-15b-5p expression after mice suffered from myocardial I/R injury and the change in myocardial injury, infarct size, apoptosis, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), superoxide dismutase (SOD) and malondialdehyde (MDA) after down-regulation of miR-15b-5p expression. The negative regulation of miR-15b-5p to KCNJ2 as well as whether cardioprotective effect formed by miR-15b-5p down-regulation relied on the increase of KNCJ2 expression were measured by dual-luciferase reporter assay system. miR-15b-5p expression increased and KCNJ2 mRNA and protein expressions decreased after myocardial ischemia reperfusion (all P < 0.05). miR-15b-5p negatively regulated KCNJ2 in a targeted way. Down-regulating miR-15b-5p expression or increasing KCNJ2 expression significantly decreased the incidence of arrhythmia, infarct size and apoptosis after myocardial I/R and lowered MDA content in the myocardial tissue as well as IL-6 and TNF-α content in the blood (all P < 0.05). KCNJ2 gene knockout reversed the above cardioprotective effect formed by miR-15b-5p down-regulation (P < 0.05). Down-regulating miR-15b-5p expression or up-regulating KCNJ2 expression improves arrhythmia after mice suffered from myocardial I/R injury and inhibits myocardial apoptosis.

Protective effect of flavonoids from Rosa roxburghii Tratt on myocardial cells via autophagy

The aim of this study is to explore the effect of flavonoids from Rosa roxburghii Tratt (FRRT) on doxorubicin (DOX)-induced autophagy of myocardial cells. Primary isolation and culture of myocardial cells and H9C2 myocardial cell lines from 1 to 3-day-old rats were performed, myocardial cells were incubated using 5 μmol/L DOX and a cardiotoxicity model was established, intervention was conducted via FRRT, and the ultrastructure of myocardial cells was observed under a transmission electron microscope. The expressions of LC3-II and P62 proteins were detected through immunofluorescence and Western blotting. The ultrastructure showed a large quantity of autophagic vacuoles of the cells in DOX group with poor cell state. After the FRRT intervention, only a small quantity of autophagic vacuoles appeared in the myocardial cells, and there were many coarse microvilli on the cell surface. The expression of P62 protein was reduced in DOX group, while that in FRRT group was increased (p < 0.01). In conclusion, FRRT exerts a protective effect in the DOX-induced cardiotoxicity by down-regulating DOX-induced autophagy of myocardial cells.

Protective effect of lncRNA CRNDE on myocardial cell apoptosis in heart failure by regulating HMGB1 cytoplasm translocation through PARP-1

Long non-coding RNAs (lncRNAs) are bound up with the regulation of various diseases. Here, we probed into the effect of lncRNA colorectal neoplasia differentially expressed (CRNDE) on heart failure (HF). The pathological alterations and cell apoptosis of heart tissues were observed by hematoxylin-eosin and TUNEL staining. The viability or apoptosis of mouse myocardial cells HL-1 was tested by XTT or flow cytometry. The interaction between lncRNA CRNDE and poly-ADP-ribose polymerase 1 (PARP-1) was verified by RNA immunoprecipitation and RNA pull-down. The stability of the PARP-1 protein and the acetylation level of high mobility group box-1 (HMGB1) were determined by cycloheximide-chase and immunoprecipitation, respectively. LncRNA CRNDE expression was decreased in HF mice tissues and doxorubicin (Dox)-treated HL-1 cells, whereas PARP-1 and HMGB1 were increased. The overexpression of lncRNA CRNDE restrained HL-1 cell apoptosis induced by Dox. Moreover, the interaction between CRNDE and PARP-1 was corroborated, CRNDE negatively regulated PARP-1 expression, and the overexpression of CRNDE reduced PARP-1 protein stability. In HL-1 cells, PARP-1 positively regulated the acetylation level and cytoplasm translocation of HMGB1. CRNDE restrained Dox-induced apoptosis in mouse myocardial cells via the PARP-1/HMGB1 pathway.

Dependence of damage within 10min to myocardial cells by a photodynamic reaction with a high concentration of talaporfin sodium outside cells in vitro on parameters of laser irradiation

BACKGROUND

To investigate the immediate occurrence of irreparable severe damage to myocardial cells up to 10min after a photodynamic reaction with a high concentration of photosensitizer outside cells, we measured the damage response time and the parameters that govern the response time via rat myocardial Ca(2+) concentration. In our proposed method for catheter ablation of tachyarrhythmia by photodynamic reaction, there are two components to the electrical conduction block: an immediate electrical conduction block of several tens of seconds to several minutes, and a permanent electrical conduction block.

METHODS

Rat myocardial intracellular Ca(2+) concentration changes before, during and after the photodynamic reaction with a high concentration of photosensitizer outside myocardial cells were continuously observed using a Fluo-4 AM Ca(2+) probe. Talaporfin sodium with 663-nm excitation was used to induce the photodynamic reaction. Talaporfin concentration was 10-30μg/ml, radiant exposure was 10-40J/cm(2), and irradiance was 30-290mW/cm(2). We evaluated the response time of irreparable severe damage to myocardial cells, according to Ca(2+) concentration.

RESULTS

The response time of the defined severe damage occurrence to myocardial cells ranged from 200 to 500s. The response time decreased with increasing irradiance and photosensitizer concentration, but exhibited no significant change with total radiant exposure.

CONCLUSIONS

We found that severe myocardial cell damage caused by a photodynamic reaction with a high concentration of photosensitizer outside cells occurred within a few minutes, which might be useful for catheter ablation for tachyarrhythmia that needs immediate response during the ablation procedure.

Maternal exposure to a high-fat diet showed unfavorable effects on the body weight, apoptosis and morphology of cardiac myocytes in offspring

OBJECTIVE

The study intends to explore the functions of maternal high-fat diet exposure on progeny weight and heart.

METHODS

Sprague-Dawley (SD) rats, fed on a high-fat diet, were used to establish a model of weight gain before and during pregnancy. The body and cardiac weight of neonatal, 1-month- and 3-month-old rats were measured. The morphology of myocardial cells was observed by hemotoxylin and eosin (H&E) staining. The expression of caspase-3, 8, 9 was measured by qRT-PCR and western blot.

RESULTS

Normal pregnant rats, fed on a high-fat diet throughout pregnancy, had a significant increase in body and cardiac weight of their neonates, and more fat deposition in myocardial cells and an increased expression of caspase-3, 8, 9, compared with that of the normal pregnant rats + normal diet group. These phenomena were relieved through later diet control. Pregnant rats, which fed on a high-fat diet throughout pregnancy, showed more adverse effects on neonatal body and cardiac weight, myocardial cell fat deposition, and the expression of caspase-3, 8, 9, compared with pregnant rats exposed to high-fat diet + normal diet and pregnant rats exposed to high-fat diet + normal diet + exercise. These phenomena cannot be fully restored via controlling later diet.

CONCLUSIONS

Our results stated that a proper diet before and during pregnancy was important for the cardiac health of offspring.

Irradiance dependence of the conduction block of an in vitro cardiomyocyte wire

BACKGROUND

To obtain therapeutic condition precisely by in vitro experiment, we studied the irradiance dependence of the electrical conduction blockage caused by a photodynamic reaction using a high extracellular concentration of talaporfin sodium on a novel in vitro cardiomyocyte electrical conduction wire.

METHODS

The cardiomyocyte wires were constructed on patterned cultivation cover glass, which had cultivation areas 60μm in width, and a maximum length of 10mm. The talaporfin sodium concentration was set to 20μg/mL. The photodynamic reaction with a high extracellular photosensitizer concentration was performed with a short time interval (approximately 15min) between photosensitizer exposure and irradiation. A 663-nm laser was applied to the cardiomyocyte wire, and the irradiance was varied between 3 and 120mW/cm². The cardiomyocyte electrical conduction was evaluated using the cross-correlation function of intracellular Ca²⁺ probe fluorescence brightness from an upper and lower section outside the laser irradiation area of a wire every 10s, which lasted up to 600s.

RESULTS

The onset of electrical conduction blockage was defined by an 85% decrease in the cross-correlation function, compared with its initial value. The time for the electrical conduction blockage decreased from 600 to 300s as the irradiance was increased. Also, the probability of electrical conduction blockage was found to increase with increasing irradiance.

CONCLUSIONS

We found a strong dependence on the irradiance for the time and probability of electrical conduction blockage.

Comparison of myocardial cell survival 2 h and 24 h after extracellular talaporfin sodium-induced photodynamic reaction

BACKGROUND

We have proposed an application of photodynamic reaction for less-heated myocardial ablation which employs talaporfin sodium. Intracellular photodynamic reactions with ongoing uptake have the ability to induce apoptosis over time, raising the possibility of extending the lesion depth. The objective of this study was to understand how, in myocardial cells, the late cell survival levels change by incubation time with talaporfin sodium, and what dependence talaporfin sodium uptake has on the duration of incubation with talaporfin sodium in vitro.

METHODS

Rat myocardial cells were incubated with talaporfin sodium for 5-360 min and intracellular concentrations measured using a fluorescence micro-plate reader after wash. Cell survival was measured using a water-soluble tetrazolium assay at 2 and 24 h after a photodynamic reaction using a red diode laser of 660 nm, following 15-180 min of incubation with talaporfin sodium. Cells were stained with Hoechst 33342 to observe nuclear changes.

RESULTS

Intracellular talaporfin sodium concentration increased with incubation time, with a marked increase between 0 and 60 min. Cell survival at 24 h decreased by 20% when the duration of incubation with talaporfin sodium was extended from 15 to 30 min. Following incubation time of 30-180 min with talaporfin sodium, cell survival was decreased by approximately 30% between measurements at 2 and 24 h. The intracellular talaporfin sodium concentration that induced higher levels of late cell death with cell nuclei fragmentation in these cells was approximately 0.2 μg/mL.

CONCLUSION

We obtained the characteristics of late cell death occurrence and talaporfin sodium uptake to myocardial cell with various incubation times with talaporfin sodium.

Accuracy of electromagnetic models to estimate cardiomyocyte membrane polarization

External electric fields (E) induce a spatially heterogeneous variation in the membrane potential (ΔV_m) of cardiomyocytes that, if sufficiently large, results in an action potential and contraction. Insights into the phenomenon of ΔV_m induction by E have been classically gained with electromagnetic models due to the lack of adequate experimental approaches. However, it is not clear yet how reliable these models are. To assess the accuracy of commonly used models, a reference 3D numerical model for cardiomyocytes (NMReal) was developed, consisting of the cell membrane shell reconstructed from rendered confocal microscopy images of freshly isolated ventricular myocytes. NMReal was used to estimate the E-induced maximum ΔV_m values (ΔV_max), which were compared with estimates from seven other electromagnetic models. Accurate ΔV_max estimates (average error < 2%) were obtained with a less complex 3D model (NM3D) based on the extruded 2D image of the cell longitudinal section. Acceptable ΔV_max estimates (average error < 5%) were obtained with the prolate spheroid analytical model (PSAM) when the angle of E incidence and the cell major axis was < 30°. In this case, PSAM, a much simpler model requiring only the measurement of the longitudinal and transversal cell dimensions, can be a suitable alternative for ΔV_max calculation. Graphical abstract (A) Confocal images of the cell were used to reconstruct the realistic geometry of cardiomyocytes (NMReal). (B) NMReal was used to estimate the maximum variation in the transmembrane potential (ΔV_max) induced by an external electric field (E) applied at different angles with respect to the cell major axis. Plus (anode) and minus (cathode) signs indicate electrode position (E direction is from minus to plus). (C) Relative error (vs. NMReal) of ΔV_max estimation with simplified electromagnetic models, presented in descending order of accuracy (left-to-right, top-to-bottom). NM2D: 2D numerical model based on the longitudinal cell image; NM3D: numerical model based on the z extrusion of NM2D; EAM, PSAM, and CAM: ellipsoidal, prolate spheroidal, and cylindrical analytical models, respectively; PNM and CNM: parallelepipedal and cylindrical numerical models, respectively.

Effect of a photosensitization reaction performed during the first 3 min after exposure of rat myocardial cells to talaporfin sodium in vitro

To better understand the mechanism of photodynamic cardiac ablation, we studied the effects of a photosensitization reaction (PR) performed during the first 3 min after rat myocardial cells were exposed to talaporfin sodium. A 3-mm-square microelectrode array with 64 electrodes was used to continuously measure the action potentials of the myocardial cells. A 30 μg/mL talaporfin sodium solution, a chlorine photosensitizer, was used, along with a 663-nm red diode laser (86 mW/cm² for up to 600 s). The first trough of the measured action potential waveform corresponding to Na⁺ dynamics decreased exponentially with increasing PR duration. The average decay time of the exponential function from PR onset was 20.1 s. Marked morphological changes in the myocardial cells was observed after the PR. These results indicated that the behavior of the action potential waveform measured by the microelectrode array might be used as a less invasive method to evaluate the electrophysiological effects of a PR on myocardial cells.

THAP11 down-regulation may contribute to cardio-protective effects of sevoflurane anesthesia: Evidence from clinical and molecular evidence

This study aimed to explore the potential target of the cardio-protective effect induced by sevoflurane anesthesia based on evidence from clinical samples and in vitro model. Forty patients undergoing mitral valve replacement were randomly allocated to receive sevoflurane or propofol-based anesthesia. Atrial muscle specimens were collected from all patients, of which 5 were used to perform transcriptomics analysis. The cTn-I concentration was tested before, at the end of, and 24 h after surgery. In in vitro study, the expression level of the identified target gene, i.e., THAP11, was studied in H9C2 cells treated with sevoflurane or propofol. Then, we studied cell viability using CCK-8 staining, apoptosis by using flow cytometry, and cell death by lactic acid dehydrogenase (LDH) detection in H9C2 cells exposed to oxygen glucose deprivation/reoxygenation (OGD/R) injury. THAP11 was the most significantly down-regulated gene in the transcriptomics analysis (P < 0.001), as confirmed in validation samples (P = 0.006). THAP11 mRNA levels in atrial muscle specimens were positively associated with cTn-I levels at 24-h postoperatively (determination coefficient = 0.564; P < 0.001). Sevoflurane treatment down-regulated THAP11 in H9C2 cell models, which promoted cell viability, inhibited cell apoptosis, and death in the OGD/R injury cell model. Up-regulation of THAP11 reduced the protective effect of sevoflurane treatment against OGD/R injury. Sevoflurane anesthesia down-regulates the expression of THAP11, which contributes to a cardio-protective effect. THAP11 down-regulation promotes cell viability, and inhibits cell apoptosis and death, thereby protecting again myocardial injury; it may therefore be a novel target for perioperative cardio-protection.