Description: Auto-antibodies against to angiotensin II type 1 receptor (AT 1 R-AA) have been discovered in patients with hypertension and they have a close relationship with inflammatory factors. However, auto-antibodies to angiotensin II type 2 receptor (AT 2 R-AA) are seldom investigated in hypertension. Subjects ( n = 138) were enrolled and divided into three groups according to their blood pressure levels by using the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC-7) criteria: normotensive (≤120/80 mmHg, n = 31), pre-hypertensive (120–139/80–89 mmHg, n = 39), and hypertensive (≥140/90 mmHg, n = 68) groups. Plasma AT 1 R-AAs and AT 2 R-AAs were detected by enzyme-linked immunosorbent assay. Plasma tumour necrosis factor-α (TNF-α), endothelin-1 (ET-1), and angiotensin II (Ang II) were measured by radioimmunity assay. (i) Plasma AT 1 R-AAs were positively correlated with systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), TNF-α, ET-1, and Ang II. (ii) AT 2 R-AAs were negatively correlated with SBP, DBP, MAP, TNF-α, ET-1, Ang II, as well as uric acid and serum creatinine. (iii) TNF-α, ET-1, Ang II (all P 〈 0.01, when compared with the normotensive group), blood uric acid, and serum creatinine (both P 〈 0.05, when compared with the normotensive group) increased with BP level. (iv) Multiple linear regression analyses showed that age, AT 1 R-AAs, AT 2 R-AAs, and ET-1 were independent predictors for SBP. AT 1 R-AAs, AT 2 R-AAs, and ET-1 were independent predictors for DBP. AT 1 R-AAs, AT 2 R-AAs, ET-1, and Ang II were independent predictors for MAP. Plasma AT 1 R-AAs and AT 2 R-AAs play an important role in hypertension progression. AT 2 R-AAs are inversely related to renal dysfunction.

Description: Objective— We explored the role of endoplasmic reticulum (ER)–mitochondria Ca 2+ cross talk involving voltage-dependent anion channel-1 (VDAC1)/glucose-regulated protein 75/inositol 1,4,5-trisphosphate receptor 1 complex and mitofusin 2 in endothelial cells during hypoxia/reoxygenation (H/R), and investigated the protective effects of acetylcholine. Approach and Results— Acetylcholine treatment during reoxygenation prevented intracellular and mitochondrial Ca 2+ increases and alleviated ER Ca 2+ depletion during H/R in human umbilical vein endothelial cells. Consequently, acetylcholine enhanced mitochondrial membrane potential and inhibited proapoptotic cascades, thereby reducing cell death and preserving endothelial ultrastructure. This effect was likely mediated by the type-3 muscarinic acetylcholine receptor and the phosphatidylinositol 3-kinase/Akt pathway. In addition, interactions among members of the VDAC1/glucose-regulated protein 75/inositol 1,4,5-trisphosphate receptor 1 complex were increased after H/R and were associated with mitochondrial Ca 2+ overload and cell death. Inhibition of the partner of the Ca 2+ channeling complex (VDAC1 siRNA) or a reduction in ER–mitochondria tethering (mitofusin 2 siRNA) prevented the increased protein interaction within the complex and reduced mitochondrial Ca 2+ accumulation and subsequent endothelial cell death after H/R. Intriguingly, acetylcholine could modulate ER–mitochondria Ca 2+ cross talk by inhibiting the VDAC1/glucose-regulated protein 75/inositol 1,4,5-trisphosphate receptor 1 complex and mitofusin 2 expression. Phosphatidylinositol 3-kinase siRNA diminished acetylcholine-mediated inhibition of mitochondrial Ca 2+ overload and VDAC1/glucose-regulated protein 75/inositol 1,4,5-trisphosphate receptor 1 complex formation induced by H/R. Conclusions— Our data suggest that ER–mitochondria interplay plays an important role in reperfusion injury in the endothelium and may be a novel molecular target for endothelial protection. Acetylcholine attenuates both intracellular and mitochondrial Ca 2+ overload and protects endothelial cells from H/R injury, presumably by disrupting the ER–mitochondria interaction.

Description: This study aimed to explore the changes in calcium transient in the development of heart failure and the effects of levosimendan (LeV) on intracellular calcium dynamics. Cultured neonatal rat ventricular myocytes were divided into four groups: normal, norepinephrine (NE) only (10 µmol/L), NE + LeV1 (0.1 µmol/L), and NE + LeV2 (1 µmol/L). The calcium transients of the myocytes loaded with Fluo-3/AM were observed using a laser scanning confocal microscope. Compared with the control group, the calcium wave in the NE group dispersed, propagated slowly, and exhibited dyssynchrony of Ca 2+ release. Norepinephrine accelerated the beating rate of the cultured myocytes, decreased the systolic peak Ca 2+ , and increased the time to peak (Ttp) and decay time (Tau) of calcium transient. Levosimendan increased the synchrony of calcium transient, and reduced Ttp and Tau. In contrast, LeV did not affect the beating rate and systolic peak Ca 2+ . Both NE-only- and LeV-treated groups did not affect resting Ca 2+ and calcium transient amplitude of the myocytes. The currents from L-type calcium channel currents did not differ among the groups. Both NE and LeV shortened the action potential duration, but the effect of the latter was more serious than that of the former. Western blot results showed that the sarco/endoplasmic reticulum Ca 2+ -ATPase 2 (SERCA2) expression decreased in the NE group but increased in the LeV groups. The sodium–calcium exchanger 1 (NCX1) expression increased in the NE group but decreased in the LeV groups. Long-term exposure to NE decreased myocardial contractility by reducing the peak Ca 2+ of calcium transient and by prolonging and disrupting the conduction of calcium waves. Levosimendan elicits a positive inotropic effect by accelerating the velocity of calcium signal propagation and synchronizing calcium release without increasing calcium influx.