Angiotensin II-superoxide-NFκB signaling and aortic baroreceptor dysfunction in chronic heart failure

Chronic heart failure: a disease of the brain

The underlying mechanism for clinical and biochemical manifestations of chronic heart failure (HF) may be due in part to neurohumoral adaptations, such as activation of the renin-angiotensin-aldosterone and sympathetic nervous systems in the periphery and the brain. Internet search and discussion with colleagues are the methods for this study. Since chronic HF is associated with autonomic imbalance with increased sympathetic nerve activity and a withdrawal of parasympathetic activity, it may be considered a brain disease. This phenomenon may be the result of an increased systemic and cerebral angiotensin II signaling because plasma angiotensin II is increased in humans and animals with chronic HF. The increase in angiotensin II signaling enhances sympathetic nerve activity through actions on both central and peripheral sites during chronic HF. Activation of angiotensin II signaling in different brain sites such as the paraventricular nucleus (PVN), rostral ventrolateral medulla (RVLM), and area postrema (AP) may increase the release of norepinephrine, oxidative stress, and inflammation leading to increased cardiac contractility. It is possible that blocking angiotensin II type 1 receptors decreases sympathetic nerve activity and cardiac sympathetic afferent reflex when therapy is administered to the PVN. The administration of an angiotensin receptor blocker by injection into the AP activates the sympatho-inhibitory baroreflex indicating that receptor blockers act by increasing parasympathetic activity. In chronic HF, in peripheral regions, angiotensin II elevates both norepinephrine release and synthesis and inhibits norepinephrine uptake at nerve endings, which may contribute to the increase in sympathetic nerve activity. Increased circulating angiotensin II during chronic HF may enhance the sympatho-excitatory chemoreflex and inhibit the sympatho-inhibitory baroreflex resulting in worsening of HF. Increased circulating angiotensin II signaling can directly act on the central nervous system via the subfornical organ and the AP to increase sympathetic outflow resulting in to neurohumoral dysfunction, resulting in to heart failure.

Cellular and Molecular Mechanisms Underlying Arterial Baroreceptor Remodeling in Cardiovascular Diseases and Diabetes

Clinical trials and animal experimental studies have demonstrated an association of arterial baroreflex impairment with the prognosis and mortality of cardiovascular diseases and diabetes. As a primary part of the arterial baroreflex arc, the pressure sensitivity of arterial baroreceptors is blunted and involved in arterial baroreflex dysfunction in cardiovascular diseases and diabetes. Changes in the arterial vascular walls, mechanosensitive ion channels, and voltage-gated ion channels contribute to the attenuation of arterial baroreceptor sensitivity. Some endogenous substances (such as angiotensin II and superoxide anion) can modulate these morphological and functional alterations through intracellular signaling pathways in impaired arterial baroreceptors. Arterial baroreceptors can be considered as a potential therapeutic target to improve the prognosis of patients with cardiovascular diseases and diabetes.

Research on Q-markers of Qiliqiangxin capsule for chronic heart failure treatment based on pharmacokinetics and pharmacodynamics association

BACKGROUND

Qiliqiangxin capsule (QLQX), composed of 11 herbs, is an effective traditional Chinese medicine (TCM) that has been widely used for treatment of chronic heart failure (CHF) in China. In the Chinese pharmacopoeia (Ch.P.) only astragaloside was described as the marker component to control the quality of QLQX, which could not reflect the overall effectiveness.

PURPOSE

The aim of this work was to investigate the quality markers (Q-markers) of QLQX based on the association of the pharmacodynamics (PD) of inhibitory effect on activated renin-angiotensin-aldosterone system (RAAS) and the pharmacokinetics (PK) of bioactive compounds according to the Q-marker theory.

METHODS

The contents of astragaloside, calycosin-7-glucoside, sinapine, ginsenoside Rb1, ginsenoside Rb2, ginsenoside Rg1, salvianolic acid A, salvianolic acid B, danshensu, rosmarinic acid, formononetin, aconitine, mesaconitine, hypaconitine, benzoylaconine, benzoylmesaconine and benzoylhypacoitine were determined by an HPLC-MS/MS method both in QLQX preparation and in the plasma of CHF rats administered intragastrically with QLQX. The effect of lowering angiotensin II (Ang II) production by QLQX was assayed by ELISA. The association between PK and PD was explored and the bioactive compounds with higher content in vitro and better exposure in vivo, which were closely related to the inhibitory effect on the activated RAAS, were identified as Q-markers of QLQX for CHF treatment.

RESULTS

The contents of 17 constituents were in the order of salvianolic acid B > danshensu > ginsenoside Rb1 > sinapine > benzoylmesaconine > astragaloside > benzoylhypacoitine > ginsenoside Rb2 > salvianolic acid A > ginsenoside Rg1 > calycosin-7-glucoside > rosmarinic acid > formononetin > benzoylaconine > hypaconitine > aconitine > mesaconitine in QLQX preparation. PK and PD association study of 14 bioactive compounds of QLQX showed the maximum effect (E_max) of astragaloside, calycosin-7-glucoside, sinapine and ginsenoside Rg1 and their peak concentration (C_max) appeared at the same time; while the time of E_max of ginsenoside Rb1, ginsenoside Rb2, salvianolic acid A, salvianolic acid B, danshensu, rosmarinic acid, formononetin, benzoylaconine, benzoylmesaconine and benzoylhypacoitine was delayed from the time of their C_max.

CONCLUSIONS

Astragaloside, calycosin-7-glucoside, sinapine and ginsenoside Rg1 are suitable as the Q-markers of QLQX for CHF treatment, which have higher content in vitro, finer exposure in vivo and a direct correlation with the inhibitory effect on activated RAAS.

Effect of captopril on radiation-induced TGF-β1 secretion in EA.Hy926 human umbilical vein endothelial cells

The pathophysiological mechanism involved in the sustained endothelial secretion of cytokines that leads to fibrosis 6–16 months after radiotherapy remains unclear. Angiotensin II (Ang II) is produced by the endothelium in response to stressing stimuli, like radiation, and may induce the synthesis of TGF-β, a profibrotic cytokine. In this study we tested the hypothesis that captopril, an angiotensin-converting enzyme (ACE) inhibitor, inhibits or attenuates radiation-induced endothelial TGF-β1 secretion. The human endothelial hybrid cell line EA.HY926 was irradiated with split doses of x-rays (28 Gy delivered in 14 fractions of 2 Gy). TGF-β1 mRNA, TNF-α mRNA and TGF-β1 protein levels were evaluated by RT-PCR and western blotting each month until the fifth month post radiation. Ang II was detected using radioimmunoassays, NF-κB activity was examined using EMSA, and western blotting was used to detect the expression of Iκ-Bα. To explore the role of Ang II on radiation-induced TGF-β1 release and Iκ-Bα expression, captopril was added to cultured cells before, during, or after irradiation. Sustained strong expression of TGF-β1 was observed after conventional fractionated irradiation. TNF-α, Ang II, and NF-κB activity were also increased in EA.Hy926 cells after radiation. Captopril decreased Ang II expression, inhibited the NF-κB pathway and reduced TGF-β1 expression. These data suggest that captopril might protect the endothelium from radiation-induced injury.

Hydrogen Sulfide Facilitates the Impaired Sensitivity of Carotid Sinus Baroreflex in Rats with Vascular Calcification

Arterial baroreflex is a general mechanism maintaining cardiovascular homeostasis; its sensitivity is reduced in vascular calcification (VC). Hydrogen sulfide (H₂S) treatment facilitates baroreflexive sensitivity in normal and hypertensive rats. Here, we aimed to detect the effect of H₂S on baroreflexive sensitivity in rats with VC. The rat VC model was induced by vitamin D₃ plus nicotine for 4 weeks. The sensitivity of baroreflex was detected by perfusing the isolated carotid sinus. VC was assessed by hematoxylin and eosin (H&E) staining, Ca²⁺ content and alkaline phosphatase (ALP) activity. Protein levels were detected by western blot analysis. Vitamin D₃ plus nicotine induced structural disorder and elevated Ca²⁺ content in the aortic and carotid arterial wall and increased plasma ALP activity. In the calcified aorta and carotid artery, protein levels of contractile phenotype markers of vascular smooth muscle cells (VSMCs) were downregulated and that of osteoblast-like phenotype markers and endoplasmic reticulum stress (ERS) markers were upregulated. NaHS treatment ameliorated the histologic disorder and Ca²⁺ content in the calcified aorta and carotid artery, inhibited the elevated plasma ALP activity, and prevented the transformation of the VSMC phenotype and activation of ERS in rats with VC. Chronic NaHS treatment prevented the impairment of the baroreflex sensitivity and acute NaHS treatment dose-dependently improved the sensitivity in rats with VC. Our results suggested that H₂S could directly facilitate the impairment of baroreflex in rats with VC and ameliorate VC, which might provide new target and strategy for regulation of the baroreflex and therapy of VC.