Lysophosphatidylcholine enhances I(Ks) currents in cardiac myocytes through activation of G protein, PKC and Rho signaling pathways

Lysophosphatidylcholine (LPC) is a bioactive phospholipid that accumulates rapidly in the ischemic myocardium. In recent years, it has been shown that some of the actions of LPC are mediated through the activation of the membrane G proteins. However, the precise mechanism(s) responsible for the LPC-related intracellular signaling in the regulation of cardiac ion channels are still poorly understood. The present study was undertaken to examine whether LPC regulates the slow component of the delayed rectifier K⁺ current (I_Ks) and, if so, what intracellular signals are important for this process. Isolated guinea pig cardiac myocytes were voltage-clamped using the whole-cell configuration of the patch-clamp method. The bath application of 1-palmitoyl-lysophosphatidylcholine (LPC-16) concentration-dependently (EC₅₀ = 0.7 μM) and reversibly increased I_Ks in atrial cells, but failed to potentiate I_Ks in ventricular myocytes. In contrast, 1-oleoyl-lysophosphatidylcholine (LPC-18:1) only produced a slight I_Ks increase, and 1-caproyl-lysophosphatidylcholine (LPC-6) or the LPC-16 precursor (phosphatidylcholine) had no effect on I_Ks. Pretreatment of atrial cells with an antibody against the N-terminus of the G2A receptor significantly reduced the LPC-16-induced potentiation of I_Ks. The inhibition of heterotrimeric G protein, phospholipase C (PLC) and protein kinase C (PKC) significantly reduced LPC-16-induced enhancement of I_Ks. Moreover, the blockade of Rho and Rho-kinase by specific inhibitors also inhibited the activity of LPC-16. Immunohistochemical studies demonstrated that G2A was densely distributed in the plasma membrane of atrial myocytes. Therefore, the present study suggests that the activation of a G protein (probably Gα_q) by LPC-16 potentiates I_Ks currents through the PLC-PKC and Rho-kinase pathways.     

Aeromonas hydrophila-induced alterations in cytosolic calcium activate pro-apoptotic cPKC-MEK1/2-TNFα axis in infected headkidney macrophages of Clarias gariepinus

Alterations in intracellular-calcium (Ca²⁺)_i homeostasis is critical to Aeromonas hydrophila-induced headkidney macrophages (HKM) apoptosis of Clarias gariepinus, though the implications are poorly understood. Here, we describe the role of intermediate molecules of Ca²⁺⁻signaling pathway that are involved in HKM apoptosis. We observed phosphoinositide-3-kinase/phospholipase C is critical for (Ca²⁺)_i release in infected HKM. Heightened protein kinase-C (PKC) activity and phosphorylation of MEK1/2-ERK1/2 was noted which declined in presence of 2-APB, Go6976 and PD98059, inhibitors to IP3-receptor, conventional PKC isoforms (cPKC) and MEK1/2 respectively implicating Ca²⁺/cPKC/MEK-ERK1/2 axis imperative in A. hydrophila-induced HKM apoptosis. Significant tumor necrosis factor-α (TNFα) production and its subsequent reduction in presence of MEK-ERK1/2 inhibitor U0126 suggested TNFα production downstream to cPKC-mediated signaling via MEK1/2-ERK1/2 pathway. RNAi and inhibitor studies established the role of TNFα in inducing caspase-8-mediated apoptosis of infected HKM. We conclude, alterations in A. hydrophila-induced (Ca²⁺)i alterations activate cPKC-MEK1/2-ERK1/2-TNFα signaling cascade triggering HKM apoptosis.     

DDX3和酪蛋白激酶1ε在肌萎缩侧索硬化症转基因鼠海马中的表达

目的检测DDX3和酪蛋白激酶1ε(CK1ε)在肌萎缩侧索硬化症(ALS)转基因鼠海马中的表达变化,揭示DDX3和CK1ε的表达改变与ALS发病的关系。方法 33只ALS转基因鼠和33只野生型鼠分别于发病不同时期取材,应用RT-PCR和Western blotting技术检测海马组织中DDX3和CK1ε的表达变化;通过免疫荧光双标染色技术观察DDX3和CK1ε阳性细胞的分布特点及其与神经元、星形胶质细胞等的共表达情况。结果与野生型鼠相比,ALS转基因鼠海马中DDX3 mRNA和蛋白在发病早期变化不明显,中期和晚期表达均明显降低;CK1εmRNA和蛋白则在发病早期、中期和晚期表达均降低。免疫荧光双标结果显示,在ALS鼠和野生型鼠海马齿状回区和CA区均可检测到DDX3和CK1ε阳性细胞。DDX3和CK1ε主要表达在神经元,在星形胶质细胞未见表达。与野生型鼠比较,ALS转基因鼠海马中DDX3和CK1ε免疫反应性明显降低。结论 DDX3和CK1εmRNA和蛋白在ALS转基因鼠海马中表达均降低,表明DDX3和CK1ε表达异常与ALS海马区病变密切相关。     

Aliskiren ameliorates pressure overload-induced heart hypertrophy and fibrosis in mice

Aim:

Aliskiren (ALK) is a renin inhibitor that has been used in the treatment of hypertension. The aim of this study was to determine whether ALK could ameliorate pressure overload-induced heart hypertrophy and fibrosis, and to elucidate the mechanisms of action.

Methods:

Transverse aortic constriction (TAC) was performed in mice to induce heart pressure overload. ALK (150 mg·kg⁻¹·d⁻¹, po), the autophagy inhibitor 3-methyladenine (10 mg·kg⁻¹ per week, ip) or the PKCβI inhibitor {"type":"entrez-nucleotide","attrs":{"text":"LY333531","term_id":"1257370768","term_text":"LY333531"}}LY333531 (1 mg·kg⁻¹·d-¹, po) was administered to the mice for 4 weeks. Heart hypertrophy, fibrosis and function were evaluated based on echocardiography, histological and biochemical measurements. Mechanically stretched cardiomyocytes of rats were used for in vitro experiments. The levels of signaling proteins were measured using Western blotting, while the expression of the relevant genes was analyzed using real-time QRT-PCR.

Results:

TAC induced marked heart hypertrophy and fibrosis, accompanied by high levels of Ang II in plasma and heart, and by PKCβI/α and ERK1/2 phosphorylation in heart. Meanwhile, TAC induced autophagic responses in heart, i.e. increases in autophagic structures, expression of Atg5 and Atg16 L1 mRNAs and LC3-II and Beclin-1 proteins. These pathological alterations in TAC-mice were significantly ameliorated or blocked by ALK administration. In TAC-mice, 3-methyladenine administration also ameliorated heart hypertrophy, fibrosis and dysfunction, while {"type":"entrez-nucleotide","attrs":{"text":"LY333531","term_id":"1257370768","term_text":"LY333531"}}LY333531 administration inhibited ERK phosphorylation and autophagy in heart. In mechanically stretched cardiomyocytes, {"type":"entrez-protein","attrs":{"text":"CGP53353","term_id":"875191971","term_text":"CGP53353"}}CGP53353 (a PKCβI inhibitor) prevented ERK phosphorylation and autophagic responses, while U0126 (an ERK inhibitor) blocked autophagic responses.

Conclusion:

ALK ameliorates heart hypertrophy, fibrosis and dysfunction in the mouse model in setting of chronic pressure overload, via suppressing Ang II-PKCβI-ERK1/2-regulated autophagy.     

Astragaloside IV inhibits PMA-induced EPCR shedding through MAPKs and PKC pathway

Astragaloside IV (AS-IV), a main active substance isolated from Astragalus membranaceus Bunge, has been shown to have multiple pharmacological effects. Endothelial cell protein C receptor (EPCR) is a marker of inflammation, and is also a major member of protein C (PC) anti-coagulation system. EPCR can be cut off from the cell surface by tumor necrosis factor-α converting enzyme (TACE), which is controlled through mitogen-activated protein kinase (MAPK) and protein kinase C (PKC) pathways. To develop novel therapeutic drug for EPCR shedding, the effect of AS-IV was studied in phorbol-12-myristate 13-acetate (PMA)-induced human umbilical vein endothelial cells (HUVECs) and the potential molecular mechanism of AS-IV action was investigated. The results showed that AS-IV could significantly inhibit PMA-induced EPCR shedding. In further study, AS-IV suppressed the expression and activity of TACE. In addition, AS-IV could decrease the phosphorylation of MAPK such as janus kinase (JNK) and p38, and inhibit activation of PKC through the prevention of non-phosphorylation and phosphorylation of specific PKC isoforms in PMA-stimulated HUVECs. These findings indicate that AS-IV may be used as a natural medicine to treat EPCR-related systemic inflammation and cardiovascular diseases by targeting MAPK and PKC pathway.     

The hinge region in androgen receptor control

The region between the DNA-binding domain and the ligand-binding domain of nuclear receptors is termed the hinge region. Although this flexible linker is poorly conserved, diverse functions have been ascribed to it. For the androgen receptor (AR), the hinge region and in particular the (629)RKLKKL(634) motif, plays a central role in controlling AR activity, not only because it acts as the main part of the nuclear translocation signal, but also because it regulates the transactivation potential and intranuclear mobility of the receptor. It is also a target site for acetylation, ubiquitylation and methylation. The interplay between these different modifications as well as the phosphorylation at serine 650 will be discussed here. The hinge also has an important function in AR binding to classical versus selective androgen response elements. In addition, the number of coactivators/corepressors that might act via interaction with the hinge region is still growing. The importance of the hinge region is further illustrated by the different somatic mutations described in patients with androgen insensitivity syndrome and prostate cancer. In conclusion, the hinge region serves as an integrator for signals coming from different pathways that provide feedback to the control of AR activity.     

Early pregnancy induced expression of prostaglandin E2 receptors EP2 and EP4 in the ovine endometrium and regulated by interferon tau through multiple cell signaling pathways

Prostaglandin E2 (PGE₂) plays pleiotropic roles at fetal-maternal interface during establishment of pregnancy. The objectives of the study were to: (i) determine regulation of PGE2 receptors EP1, EP2, EP3, and EP4 in the endometrium during the estrous cycle and early pregnancy; and (ii) understand endometrial epithelial and stromal cell-specific hormonal regulation of EP2 and EP4 in sheep. Results indicate that: (i) early pregnancy induces expression of EP2 and EP4 but not EP1 and EP3 proteins in the endometrium on days 12-16 compared to that of estrous cycle; (ii) intrauterine infusion of interferon tau (IFNT) increases expression of EP2 and EP4 proteins in endometrium; and (iii) IFNT activates distinct epithelial and stromal cell-specific JAK, EGFR, ERK1/2, AKT, or JNK signaling module to regulate expression of EP2 and EP4 proteins in the ovine endometrium. Our results indicate a role for EP2 and EP4-mediated PGE₂ signaling in endometrial functions and establishment of pregnancy in ruminants.     

慢性低氧所致肺动脉高压对大鼠肺动脉内蛋白激酶Cα的膜转位和蛋白表达量的影响

目的 通过观察慢性低氧所致肺动脉高压对大鼠肺动脉内蛋白激酶Cα(PKCα)的膜转位和蛋白表达量的影响,初步探讨PKCα在慢性低氧诱导大鼠肺动脉高压的发生和发展过程中所起的作用.方法 采用慢性常压低氧[氧浓度(10±0.1)％]大鼠肺动脉高压模型,将雄性SD大鼠随机分为正常对照组、低氧1d、3d、7d、14 d和21d组,检测大鼠右心室收缩压(RVSP)和右心室肥厚指数(RVHI),肺组织苏木精-伊红(HE)染色,应用蛋白免疫印迹和免疫组织化学的方法检测PKCα膜转位和蛋白表达水平的变化.结果 ①低氧1d、3d、7d、14 d和21d组与正常对照组相比,RVSP和RV/(LV+S)比值均明显增加(P＜0.05),低氧暴露3d、7d、14 d和21 d后大鼠肺动脉壁明显增厚;②PKCα的蛋白表达量在慢性低氧1d、3d、7d和14 d后比正常对照组明显下降(P＜0.05).结论 PKCα蛋白表达量的下调可能参与了慢性低氧诱导的大鼠肺动脉高压的发生和发展过程.     

AQP4与PKC在大鼠CIR后脑水肿模型中的变化及作用

目的通过研究大鼠局灶性脑缺血再灌注后水通道蛋白4（AQP4）、蛋白激酶C（PKC）表达水平的变化,来探讨两者与脑水肿之间的关系。方法通过线栓法复制大鼠大脑中动脉缺血（MCAO）再灌注模型,动物随机分为正常对照组（Norm）、假手术组（Sham）、缺血再灌注组（CIR）。参照Garcia JH法进行神经功能缺损评分、用Elliot法检测脑组织含水量、免疫组化法检测AQP4及PKC的表达。结果 CIR后6h即有神经功能缺损,脑含水量在CIR12h明显升高,1~3d时达到高峰;AQP4表达在早期水平降低,从12h逐渐升高,至CIR 24h明显升高,3d达高峰;PKC在CIR后6h开始持续性升高,至第5d仍保持较高水平。结论早期的细胞源性脑水肿可能和PKC的升高有关,后期的血管源性脑水肿可能和AQP4的升高相关。