Oxidative stress regulates cardiomyocyte energy metabolism through the IGF2BP2-dynamin2 signaling pathway.

BACKGROUND: Over the past few decades, numerous clinical and experimental studies have confirmed that oxidative stress is enhanced in heart failure (HF). We recently found that inhibition of highly expressed dynamin2 can protect myocardial ischemia-reperfusion injury in mice and inhibit oxidative stress in ischemic cardiomyocytes. However, the specific mechanisms are still not fully understood. In this study, we hypothesized that oxidative stress induces cardiomyocyte apoptosis through IGF2BP2 regulation, which is regulated through the dynamin2 expression. METHODS: H2O2-treated cardiomyocytes were observed for the regulatory effect of reactive oxygen species (ROS) on IGF2BP2 and the effect of IGF2BP2 on dynamin2 gene expression was determined by lentiviral-mediated IGF2BP2 overexpression. Then, siRNA knockdown of dynamin2 was used to observe whether it can alter the effect of IGF2BP2 on myocardial cells. Finally, IGF2BP2 was knocked down in ischemic rats using shRNA to determine the effects of IGF2BP2 on myocardial ischemia. RESULTS: ROS can promote dynamin2 expression by inducing IGF2BP2 expression and dynamin2 knockdown could reduce the injury of IGF2BP2 to cardiomyocytes. Inhibition of IGF2BP2 expression in myocardial ischemic rats ameliorated cardiac fibrosis in ischemic myocardium. CONCLUSION: Oxidative stress can induce cardiomyocyte apoptosis through the IGF2BP2-dynamin2 pathway. Inhibition of IGF2BP2 expression significantly improves the fibrosis and remodeling that occurs in ischemic myocardium.

The association of metabolic syndrome components and chronic kidney disease in patients with hypertension.

BACKGROUND: Hypertension is a highly prevalent disease and the leading cause of chronic kidney disease (CKD). Metabolic syndrome could also be the risk factor for CKD. We sought to study the association between metabolic syndrome components and the prevalence of CKD in patients with hypertension. METHODS: We carried out a multi-center cross-sectional study from Apr. 2017- Apr. 2018 in 15 cities in China. RESULTS: A total of 2484 patients with hypertension were enrolled. Among them, 56% were male and the average age was 65.12 ± 12.71 years. The systolic BP/diastolic BP was 142 ± 18/83 ± 12 mmHg. Metabolic syndrome components turned out to be highly prevalent in patients with hypertension, ranging from 40 to 58%. The prevalence of chronic kidney disease reached 22.0%. Multi-variate logistic analysis revealed that elevated triglyceride (TG) (OR = 1.81, 95% CI 1.28-2.57, p < 0.01), elevated fasting blood glucose (FBG) (OR = 1.43, 95% CI 1.00-2.07, p = 0.05) and hypertension grades (OR = 1.20, 95% CI 1.00-1.44, p = 0.05) were associated with the prevalence of CKD. In sub-group analysis, elevated TG remained strongly associated with CKD in both diabetes (OR = 2.10, 95%CI 1.22-3.61, p < 0.01) and non-diabetes (OR = 1.53, 95% CI 1.09-2.16, p = 0.01). In sub-group analysis of hypertension grades, there was also a graded trend between elevated TG and CKD from controlled blood pressure (BP) to hypertension grade 2 (OR = 1.81, 95%CI 1.06-3.11, p = 0.03; OR = 1.85, 95%CI 1.00-3.43, p = 0.05; OR = 2.81, 95% CI 1.09-7.28, p = 0.03, respectively). CONCLUSION: Elevated TG, elevated FBG and hypertension grades were significantly associated with the prevalence of CKD in patients with hypertension. Particularly, elevated TG was strongly associated with CKD, independent of diabetes and hypertension grades.

Targeting Dynamin 2 as a Novel Pathway to Inhibit Cardiomyocyte Apoptosis Following Oxidative Stress.

BACKGROUND/AIMS: Inhibition of Drp-1-mediated mitochondrial fission limits reactive oxygen species (ROS) production and apoptosis in cardiomyocytes subjected to ischemia/reperfusion injury. It remains unknown if Dynamin 2 inhibition results in similar protective effects. Here we studied the role of Dynamin 2 in cardiomyocyte oxidative stress-induced apoptosis and ROS production. METHODS: The effect of lentiviral shRNA (lv5-shRNA) mediated Dynamin 2 knockdown on apopotosis, mitochondria, and ROS production were studied in neonatal mouse cardiomycytes, which were further treated with either selective Drp1 inhibitor mdivi-1 or the Dynamin 2/Drp1 inhibitor Dynasore. Apoptosis was evaluated by flow cytometry. Mitochondrial morphology and transmembrane potential (ΔΨm) were studied by confocal microscopy, and ROS production was detected by dichlorofluorescein diacetate. RESULTS: Inhibition of Drp1 and Dynamin 2 protected against mitochondrial fragmentation, maintained ΔΨm, attenuated cellular ROS production and limited apoptosis. Moreover, Lv5-shRNA mediated knockdown of Dynamin 2 alleviated mitochondrial fragmentation, and reduced both ROS production and oxidative stress-induced apoptosis. The protective effects of Dynamin 2 knockdown were enhanced by Dynasore, indicating an added benefit. CONCLUSIONS: Oxidative stress-induced apoptosis and ROS production are attenuated by not only Drp1 inhibition but also Dynamin 2 inhibition, implicating Dynamin 2 as a mediator of oxidative stress in cardiomyocytes.

[Effect of atorvastatin on exercise tolerance in patients with diastolic dysfunction and exercise-induced hypertension].

OBJECTIVE: To investigate the effect of atorvastatin on exercise tolerance in patients with diastolic dysfunction and exercise-induced hypertension. METHODS: A randomized, double-blind, placebo-controlled prospective study was performed. Sixty patients with diastolic dysfunction (mitral flow velocity E/A <1) and exercise-induced hypertension (SBP>200 mm Hg) treated with atorvastatin (20 mg q.d) or placebo for 1 year. Cardiopulmonary exercise test and exercise blood pressure measurement were performed. Plasma B-natriuretic peptide (BNP) concentration at rest and at peak exercise, plasma high sensitive-C reaction protein (hs-CRP) and endothelin (ET) concentration were determined at baseline and after treatment. RESULTS: After treatment by atorvastatin, the resting SBP, pulse pressure, the peak exercise SBP and BNP were significantly decreased; and the exercise time, metabolic equivalent, maximal oxygen uptake and anaerobic threshold were increased. All of these parameters had significant differences with baseline levels (P<0.05) and the rest pulse pressure, the peak exercise SBP and BNP, and the exercise time had significant differences compared with placebo treatment (P<0.05). Plasma concentrations of hs-CRP and ET were markedly reduced by atorvastatin treatment compared with baseline and placebo (P<0.05). No difference in above parameters was found before and after placebo treatment (P>0.05). CONCLUSION: In patients with diastolic dysfunction at rest and exercise-induced hypertension, atorvastatin can effectively reduce plasma hs-CRP and ET level, lower blood pressure and peak exercise SBP, decrease peak exercise plasma BNP concentration, and ultimately improve exercise tolerance.

BIN1 localizes the L-type calcium channel to cardiac T-tubules.

The BAR domain protein superfamily is involved in membrane invagination and endocytosis, but its role in organizing membrane proteins has not been explored. In particular, the membrane scaffolding protein BIN1 functions to initiate T-tubule genesis in skeletal muscle cells. Constitutive knockdown of BIN1 in mice is perinatal lethal, which is associated with an induced dilated hypertrophic cardiomyopathy. However, the functional role of BIN1 in cardiomyocytes is not known. An important function of cardiac T-tubules is to allow L-type calcium channels (Cav1.2) to be in close proximity to sarcoplasmic reticulum-based ryanodine receptors to initiate the intracellular calcium transient. Efficient excitation-contraction (EC) coupling and normal cardiac contractility depend upon Cav1.2 localization to T-tubules. We hypothesized that BIN1 not only exists at cardiac T-tubules, but it also localizes Cav1.2 to these membrane structures. We report that BIN1 localizes to cardiac T-tubules and clusters there with Cav1.2. Studies involve freshly acquired human and mouse adult cardiomyocytes using complementary immunocytochemistry, electron microscopy with dual immunogold labeling, and co-immunoprecipitation. Furthermore, we use surface biotinylation and live cell confocal and total internal fluorescence microscopy imaging in cardiomyocytes and cell lines to explore delivery of Cav1.2 to BIN1 structures. We find visually and quantitatively that dynamic microtubules are tethered to membrane scaffolded by BIN1, allowing targeted delivery of Cav1.2 from the microtubules to the associated membrane. Since Cav1.2 delivery to BIN1 occurs in reductionist non-myocyte cell lines, we find that other myocyte-specific structures are not essential and there is an intrinsic relationship between microtubule-based Cav1.2 delivery and its BIN1 scaffold. In differentiated mouse cardiomyocytes, knockdown of BIN1 reduces surface Cav1.2 and delays development of the calcium transient, indicating that Cav1.2 targeting to BIN1 is functionally important to cardiac calcium signaling. We have identified that membrane-associated BIN1 not only induces membrane curvature but can direct specific antegrade delivery of microtubule-transported membrane proteins. Furthermore, this paradigm provides a microtubule and BIN1-dependent mechanism of Cav1.2 delivery to T-tubules. This novel Cav1.2 trafficking pathway should serve as an important regulatory aspect of EC coupling, affecting cardiac contractility in mammalian hearts.

Non-viral Vectors in Gene Therapy: Recent Development, Challenges, and Prospects.

Gene therapy has been experiencing a breakthrough in recent years, targeting various specific cell groups in numerous therapeutic areas. However, most recent clinical studies maintain the use of traditional viral vector systems, which are challenging to manufacture cost-effectively at a commercial scale. Non-viral vectors have been a fast-paced research topic in gene delivery, such as polymers, lipids, inorganic particles, and combinations of different types. Although non-viral vectors are low in their cytotoxicity, immunogenicity, and mutagenesis, attracting more and more researchers to explore the promising delivery system, they do not carry ideal characteristics and have faced critical challenges, including gene transfer efficiency, specificity, gene expression duration, and safety. This review covers the recent advancement in non-viral vectors research and formulation aspects, the challenges, and future perspectives.

Stable drug encapsulation in micelles and microemulsions.

Oral absorption of hydrophobic drugs can be significantly improved using lipid-based non-particulate drug delivery systems, which avoid the dissolution step. Micellar and microemulsion systems, being the most dispersed of all, appear the most promising. While these systems show high drug entrapment and release under sink conditions, the improvement in oral drug bioavailability is often unpredictable. The formulation and drug-related biopharmaceutical aspects of these systems that govern oral absorption have been widely studied. Among these, preventing drug precipitation upon aqueous dilution could play a predominant role in many cases. Predictive ability and quick methods for assessment of such problems could be very useful to the formulators in selecting lead formulations. This review will attempt to summarize the research work that could be useful in developing these tools.

[Relationship of collagen content, intimal thickening and angiotensin II level of iliac arteries after balloon injury in rabbits]

OBJECTIVE: To investigate the relationship of collagen content intimal thickening and angiotensin II level of iliac arteries after balloon injury in rabbits. METHODS Fifty male New Zealand white rabbits were randomly devided into 6 groups: losartan groups, benazapril groups and control groups for 4 weeks or 8 weeks. Every rabbit underwent endothelial debridement of the right iliac artery. lorsartan (15 mg/kg/d) and benazapril (5 mg/kg/d) were orally administrated respectively in losartan groups and benazepril groups from 5 days before until 4 weeks or 8 weeks after balloon injury. RESULTS: Collagen content and intimal area of rabbit iliac arteries were increased after balloon injury. After intervention for 4 weeks with losartan and benazapril, collagen content was decreased in losartan and benazapril groups than in control group 23.58+/-6.16 % and 22.67+/-10.20 % compared with 35.20+/-7.25 % respectively, P<0.05. After intervention for 8 weeks, collagen content was significantly decreased (20.69+/-11.16)% and 25.41+/-11.00 % compared with 42.69+/-13.99 % respectively, P<0.05; Intimal area and intimal to medial area ratio were also decreased in losartan and benazapril groups than in control group; Lumen area was increased in losartan and benazapril groups than in control group(0.79+/-0.25)mm2 and (0.76+/-0.28)mm2 compared with (0.62+/-0.27)mm2 P<0.05; Tissue angiotensin II level was increased in losartan group (516.31+/-70.79)pg/mg.pro compared with (410.72+/-100.11)pg/mg.pro, P<0.05, and decreased in benazapril group than in control group (340.62+/-67.69)pg/mg.pro compared with (410.72+/-100.11)pg/mg.pro, P<0.05. There were close correlation between tissue angiotensin II level and intimal area, or between tissue angiotensin II level and intimal to medial area ratio, or and collagen content in benazapril group, respectively, P<0.05. Conclusion (1) Collagen protein is a dynamic participant in vascular injury. (2) Tissue renin angiotensin system may play an important role in collagen accumulation, intimal thickening and vascular injury after angioplasty. (3) Losartan and benazapril reduce vascular collagen content and inhibit intimal thickening after balloon injury.

Dynasore protects mitochondria and improves cardiac lusitropy in Langendorff perfused mouse heart.

BACKGROUND: Heart failure due to diastolic dysfunction exacts a major economic, morbidity and mortality burden in the United States. Therapeutic agents to improve diastolic dysfunction are limited. It was recently found that Dynamin related protein 1 (Drp1) mediates mitochondrial fission during ischemia/reperfusion (I/R) injury, whereas inhibition of Drp1 decreases myocardial infarct size. We hypothesized that Dynasore, a small noncompetitive dynamin GTPase inhibitor, could have beneficial effects on cardiac physiology during I/R injury. METHODS AND RESULTS: In Langendorff perfused mouse hearts subjected to I/R (30 minutes of global ischemia followed by 1 hour of reperfusion), pretreatment with 1 µM Dynasore prevented I/R induced elevation of left ventricular end diastolic pressure (LVEDP), indicating a significant and specific lusitropic effect. Dynasore also decreased cardiac troponin I efflux during reperfusion and reduced infarct size. In cultured adult mouse cardiomyocytes subjected to oxidative stress, Dynasore increased cardiomyocyte survival and viability identified by trypan blue exclusion assay and reduced cellular Adenosine triphosphate(ATP) depletion. Moreover, in cultured cells, Dynasore pretreatment protected mitochondrial fragmentation induced by oxidative stress. CONCLUSION: Dynasore protects cardiac lusitropy and limits cell damage through a mechanism that maintains mitochondrial morphology and intracellular ATP in stressed cells. Mitochondrial protection through an agent such as Dynasore can have clinical benefit by positively influencing the energetics of diastolic dysfunction.

Limited forward trafficking of connexin 43 reduces cell-cell coupling in stressed human and mouse myocardium.

Gap junctions form electrical conduits between adjacent myocardial cells, permitting rapid spatial passage of the excitation current essential to each heartbeat. Arrhythmogenic decreases in gap junction coupling are a characteristic of stressed, failing, and aging myocardium, but the mechanisms of decreased coupling are poorly understood. We previously found that microtubules bearing gap junction hemichannels (connexons) can deliver their cargo directly to adherens junctions. The specificity of this delivery requires the microtubule plus-end tracking protein EB1. We performed this study to investigate the hypothesis that the oxidative stress that accompanies acute and chronic ischemic disease perturbs connexon forward trafficking. We found that EB1 was displaced in ischemic human hearts, stressed mouse hearts, and isolated cells subjected to oxidative stress. As a result, we observed limited microtubule interaction with adherens junctions at intercalated discs and reduced connexon delivery and gap junction coupling. A point mutation within the tubulin-binding domain of EB1 reproduced EB1 displacement and diminished connexon delivery, confirming that EB1 displacement can limit gap junction coupling. In zebrafish hearts, oxidative stress also reduced the membrane localization of connexin and slowed the spatial spread of excitation. We anticipate that protecting the microtubule-based forward delivery apparatus of connexons could improve cell-cell coupling and reduce ischemia-related cardiac arrhythmias.

Pulmonary hypertension associated with autoimmune hemolytic anemia: a case report.

We reported a case of a 68-year-old male who had pulmonary hypertension associated with autoimmune hemolytic anemia.