Minimal contribution of IP3R2 in cardiac differentiation and derived ventricular-like myocytes from human embryonic stem cells

Type 2 inositol 1,4,5-trisphosphate receptor (IP₃R2) regulates the intracellular Ca²⁺ release from endoplasmic reticulum in human embryonic stem cells (hESCs), cardiovascular progenitor cells (CVPCs), and mammalian cardiomyocytes. However, the role of IP₃R2 in human cardiac development is unknown and its function in mammalian cardiomyocytes is controversial. hESC-derived cardiomyocytes have unique merits in disease modeling, cell therapy, and drug screening. Therefore, understanding the role of IP₃R2 in the generation and function of human cardiomyocytes would be valuable for the application of hESC-derived cardiomyocytes. In the current study, we investigated the role of IP₃R2 in the differentiation of hESCs to cardiomyocytes and in the hESC-derived cardiomyocytes. By using IP₃R2 knockout (IP₃R2KO) hESCs, we showed that IP₃R2KO did not affect the self-renewal of hESCs as well as the differentiation ability of hESCs into CVPCs and cardiomyocytes. Furthermore, we demonstrated the ventricular-like myocyte characteristics of hESC-derived cardiomyocytes. Under the α₁-adrenergic stimulation by phenylephrine (10 μmol/L), the amplitude and maximum rate of depolarization of action potential (AP) were slightly affected in the IP₃R2KO hESC-derived cardiomyocytes at differentiation day 90, whereas the other parameters of APs and the Ca²⁺ transients did not show significant changes compared with these in the wide-type ones. These results demonstrate that IP₃R2 has minimal contribution to the differentiation and function of human cardiomyocytes derived from hESCs, thus provide the new knowledge to the function of IP₃R2 in the generation of human cardiac lineage cells and in the early cardiomyocytes.     

内皮素-1对缺氧/复氧所致心肌细胞凋亡的影响

目的探讨在缺氧/复氧过程中不同时期给予内皮素-1（ET-1）对缺氧/复氧所致心肌损伤与凋亡的影响。方法乳鼠心肌细胞缺氧/复氧模型,流式细胞仪检测心肌细胞凋亡,Hoechst 33258染色计算凋亡率,试剂盒检测乳酸脱氢酶（LDH）的活性。结果ET-1预处理组（EP）细胞生存率较缺氧复氧组（HR）提高,凋亡率下降,LDH活性下降;ET-1缺氧即刻处理组（EH）细胞生存率较HR组降低,凋亡率升高,LDH释放量增加;ET-1复氧处理组（ER）的细胞生存率、凋亡率及LDH活性与HR组均无统计学差异。结论ET-1预处理有心肌细胞保护作用,ET-1缺氧时有促进心肌细胞损伤和凋亡的作用。     

Increased expression of 78 kD glucose-regulated protein promotes cardiomyocyte apoptosis in a rat model of liver cirrhosis

Aims: This study was to investigate the role and underlying mechanism of 78 kD glucose-regulated protein (GRP78) in cardiomyocyte apoptosis in a rat model of liver cirrhosis. Methods: A rat model of liver cirrhosis was established with multiple pathogenic factors. A total of 42 male SD rats were randomly divided into the liver cirrhosis group and control group. Cardiac structure analysis was performed to assess alterations in cardiac structure. Cardiomyocytes apoptosis was detected by TdT-mediated dUTP nick end labeling method. Expression of GRP78, CCAAT/enhancer-binding protein homologous protein (CHOP), caspase-12, nuclear factor kappa-light-chain-enhancer of activated B cells p65 subunit (NF-κB p65) and B cell lymphoma-2 (Bcl-2) was detected by immunohistochemical staining. Results: The ratios of left ventricular wall thickness to heart weight and heart weight to body weight were significantly increased with the progression of liver cirrhosis (P < 0.05). Apoptosis index of cardiomyocytes was significantly increased with the progression of liver cirrhosis (P < 0.05). The expression levels of GRP78, CHOP and caspase-12 were significantly increased in the progression of liver cirrhosis (P < 0.05). The expression levels of NF-κB p65 and Bcl-2 were highest in the 4-wk liver cirrhosis, and they were decreased in the 6-wk and 8-wk in the progression of liver cirrhosis. GRP78 expression levels were positively correlated with apoptosis index, CHOP and caspase-12 expression levels (P < 0.05). CHOP expression levels were negatively correlated with NF-κB p65 and Bcl-2 expression levels (P < 0.05). Conclusion: Increased expression of GRP78 promotes cardiomyocyte apoptosis in rats with cirrhotic cardiomyopathy.     

4,4’-二异硫氰基茋-2,2’-二磺酸对高糖诱导心肌细胞损伤的保护作用

目的：探讨高糖诱导心肌细胞损伤过程中氯离子浓度的变化以及氯离子通道阻断剂4,4’-二异硫氰基茋-2,2’-二磺酸（DIDS）对受损心肌细胞的作用。方法原代培养乳鼠心肌细胞,应用葡萄糖浓度为33mmol/L DMEM培养基,作用72h,构建心肌细胞损伤模型。实验分为对照组、高糖组、高糖＋DIDS组和DIDS组。用MTT法检测细胞存活率,流式细胞仪检测细胞凋亡率,氯离子荧光探针（MQAE）检测细胞内氯离子浓度。结果高糖作用下的心肌细胞存活率呈浓度及时间依赖性降低（P＜0.05）,流式细胞仪检测显示受损心肌细胞以凋亡性损伤为主。MQAE检测结果显示,与对照组比较,高糖组细胞内氯离子浓度显著下降（P＜0.05）。心肌细胞存活率及细胞内氯离子浓度,DIDS组与对照组比较差异均无统计学意义（P＞0.05）。与高糖组比较,高糖＋DIDS组心肌细胞存活率显著升高,细胞内氯离子浓度下降明显减少,差异均有统计学意义（P＜0.05）。结论氯离子通道参与了高糖诱导的心肌细胞损伤过程,DIDS可在一定程度上减轻以凋亡为主的心肌细胞损伤。     

FTY720 attenuates hypoxia–reoxygenation-induced apoptosis in cardiomyocytes

FTY720, sphingosine 1 phosphate (S1P) receptor agonist, is a potent immunosuppressive agent. Numerous studies have documented a relationship between S1P and cardioprotection. We therefore hypothesized that a S1P analogue FTY720 would attenuate hypoxia/reoxygenation (H/R) induced cadiomyocyte apoptosis. H9C2 cardiomyocytes were employed to establish an in vitro model of H/R. Cells were treated or not with different doses of FTY720. Cell viability was measured by flow cytometry and TUNEL staining. Western blot was used to analyze downstream signaling pathway. We observed that FTY720 inhibits the expression of cleaved caspase-3 and activates both AKT and ERK1/2 pathways. AKT pathway can be blocked by MEK kinase inhibitor PD98059. ERK1/2 pathway can be blocked by the phosphoinositide-3 kinase inhibitor wortmannin. AKT and ERK1/2 activation can also be inhibited by S1P1/3 receptor antagonist VPC23019, Gi antagonist PTX. The protein levels of TNF-α and IL1ß were upregulated during hypoxia/reoxygenation and were attenuated by FTY720. We conclude that FTY720, via its cargo of S1P, can protect cardiomyocytes against hypoxia/reoxygenation injury. This effect is achieved by inhibiting caspase-3 expression, inflammatory cytokine levels and activating AKT and ERK1/2 signaling pathways. The prosurvival signal activation is dependent on S1P1, 3 subtype receptors and Gi protein.     

The effects of water immersion and restraint stress on the expressions of apelin,apelin receptor (APJR) and apoptosis rate in the rat heart

Apelin has been identified as an endogenous ligand of the orphan G-protein-coupled apelin receptor (APJR). These receptors are widely expressed in the central nervous system and periphery and play a role in the regulation of fluid and glucose homeostasis, feeding behavior, vessel formation, cell proliferation and immunity. We aimed to investigate whether water immersion and restraint stress have effects on apelin and APJR expression and apoptosis in heart tissue of male Wistar rats. The cardiac tissues were obtained from control, water immersion and restraint stress (WIRS) and apelin antagonist (F13A) + WIRS groups of rats and embedded in paraffin wax. Immunohistochemical staining methods were used to localize apelin, APJR and TUNEL immunopositive cells. H-SCORE was used for semi-quantitative determinations. Apelin protein levels were determined by Western blot in the cardiac tissues and plasma corticosteroid levels were measured by enzyme immunoassay (EIA). Apelin immunolocalization was found especially in endothelial cells and mast cells and faintly in cardiomyocytes, APJR immunostaining was shown in endothelial cells and cardiomyocytes, and TUNEL reaction was observed in endothelial cells and in some fibroblasts. Apelin expression was significantly increased in the WIRS and F13A + WIRS groups compared to the control group. The APJR reaction was similar in all groups. The number of TUNEL-positive cells was significantly higher in the F13A + WIRS group than that of the control group. Our study showed that WIRS for 6 h increased plasma corticosterone levels and cardiac apelin expression in rats. The increased levels of apelin inhibited stress-induced apoptosis in heart. These results may be important for the therapeutic approach to a variety of stress-related heart disease.     

Regenerative responses after mild heart injuries for cardiomyocyte proliferation in zebrafish

Background: The zebrafish heart regenerates after various severe injuries. Common processes of heart regeneration are cardiomyocyte proliferation, activation of epicardial tissue, and neovascularization. In order to further characterize heart regeneration processes, we introduced milder injuries and compared responses to those induced by ventricular apex resection, a widely used injury method. We used scratching of the ventricular surface and puncturing of the ventricle with a fine tungsten needle as injury‐inducing techniques. Results: Scratching the ventricular surface induced subtle cardiomyocyte proliferation and responses of the epicardium. Endothelial cell accumulation was limited to the surface of the heart. Ventricular puncture induced cardiomyocyte proliferation, endocardial and epicardial activation, and neo‐vascularization, similar to the resection method. However, the degree of the responses was milder, correlating with milder injury. Sham operation induced epicardial aldh1a2 expression but not tbx18 and WT1. Conclusions: Puncturing the ventricle induces responses equivalent to resection at milder degrees in a shorter time frame and can be used as a simple injury model. Scratching the ventricle did not induce heart regeneration and can be used for studying wound responses to epicardium. Developmental Dynamics 243:1477–1486, 2014. © 2014 Wiley Periodicals, Inc.     

脂联素受体在正常SD大鼠乳鼠心肌细胞的分布和表达

目的通过体外培养SD大鼠乳鼠心肌细胞,研究脂联素受体1(AdipoR1)、脂联素受体2(AdipoR2)及T-钙黏蛋白(T-cadherin)三种脂联素受体在大鼠乳鼠心肌细胞上的分布和表达。方法采用酶消化法原代培养乳鼠心肌细胞,通过α-肌动蛋白免疫荧光法对原代培养的心肌细胞进行鉴定,并在倒置相差显微镜下观察细胞生长状态。选用原代培养96h的单层心肌细胞进行实验,使用RT-PCR和细胞免疫组织化学方法检测AdipoR1、AdipoR2、T-cadherin的mRNA和蛋白在心肌细胞中的表达情况。结果在SD大鼠乳鼠心肌细胞上均检测到了AdipoR1、AdipoR2、T-cadherin的mRNA和蛋白表达,其中以AdipoR1和T-cad-herin的mRNA和蛋白表达量高,与AdipoR2的表达量相比差异有统计学意义(P<0.01)。结论脂联素受体1、脂联素受体2和T-钙黏蛋白,三种脂联素受体在SD大鼠乳鼠心肌细胞上均有表达,并以脂联素受体1和T-钙黏蛋白的表达为主,脂联素受体2表达量较少。     

Proteinase-activated receptor agonists stimulate the increase in intracellular Ca<Superscript>2+</Superscript> in cardiomyocytes and proliferation of cardiac fibroblasts from chick embryos

We studied activation of cultured cardiomyocytes and cardiac fibroblasts from chick embryos induced by agonists of PAR1 (thrombin and PAR1 peptide agonist) and PAR2 (trypsin, factor Xa, and peptide SLIGRL) by analyzing changes in intracellular Ca²⁺ concentration ([Ca²⁺]_i) and cardiac fibroblast proliferation. Exposure of cardiomyocytes with thrombin induced immediate permanent dose-dependent increase in [Ca²⁺]_i. Ca²⁺ response decreased in a calcium-free medium. Peptide agonists of PAR1 and PAR2 also stimulated the increase in [Ca²⁺]_i in cardiomyocytes. Thrombin induced a short-term increase in [Ca²⁺]_i in cardiac fibroblasts and potentiated cell proliferation. PAR2 agonists trypsin and peptide SLIGRL stimulated proliferation of cardiac fibroblasts. Our results indicate that cardiomyocytes and cardiac fibroblasts from chick embryos have at least two types of PAR (types 1 and 2). __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 144, No. 12, pp. 609–612, December, 2007     

哌唑嗪对去甲肾上腺素诱导心肌细胞凋亡的影响

目的：研究α受体拮抗剂哌唑嗪对去甲肾上腺素诱导的原代培养心肌细胞凋亡的影响。方法：采用噻唑蓝（MTT）法分析原代培养心肌细胞存活率;乳酸脱氢酶（LDH）外漏实验和吉姆萨染色实验观察原代心肌细胞损伤;JC-1免疫荧光实验检测线粒体膜电位变化;Annexin V-FITC/PI双染,流式细胞仪检测细胞凋亡。结果：NE（100 μmol·L^-1）作用于原代培养心肌细胞48 h,细胞存活率降低;LDH外漏增加;细胞形态改变,细胞数减少、胞体膨大、胞核居中、胞间间隙增大,呈明显病理学特征;线粒体膜电位降低;心肌细胞凋亡率增加。哌唑嗪明显改善去甲肾上腺素诱导的原代培养心肌细胞损伤,增加MTT值、降低LDH外漏量、改善心肌细胞病理形态、增加心肌细胞线粒体膜电位、降低心肌细胞凋亡率（P<0.05或P<0.01）。结论：哌唑嗪能显著抑制去甲肾上腺素诱导的心肌细胞凋亡,本实验为α受体阻断剂改善高交感诱导心肌细胞凋亡提供实验基础与理论指导。