Adrenergic and cholinergic plasticity in heart failure

Cholinesterase inhibitors associated with lower rate of mortality in dementia patients with heart failure: a nationwide propensity weighting study

PURPOSE

This study investigates the potential impact of cholinesterase inhibitors (ChEIs) on patients with heart failure (HF) and dementia. ChEIs are known to boost acetylcholine levels and benefit cognition in patients with dementia; however, their effect on patients with HF is uncertain. This study aimed to assess whether cardiovascular events and mortality among patients with HF and dementia are altered by ChEI therapy.

METHODS

Data from the National Health Insurance Research Database in Taiwan were retrospectively analyzed. Dementia patients diagnosed with HF were followed for 5 years until all-cause mortality, cardiovascular mortality, hospitalization for worsening HF, or the end of the study. Multivariable Cox models and inverse probability of treatment weighting (IPTW) were employed.

RESULTS

Out of 20,848 patients with dementia, 5138 had HF. Among them, 726 were ChEI users and 4412 were non-users. Based on IPTW, the ChEI users had significantly lower estimated risks of all-cause mortality [hazard ratio (HR) 0.43; 95% confidence interval (CI) 0.38-0.49, p < 0.001] and cardiovascular mortality (HR 0.41; 95% CI 0.33-0.53, p < 0.001) compared with the non-users, but there was no significant difference in hospitalization for worsening HF (HR 0.73; 95% CI 0.51-1.05, p = 0.091) after 5 years. The survival benefits of ChEIs were consistent across subgroups.

CONCLUSIONS

The results of this retrospective cohort study suggest that ChEIs may be beneficial in reducing all-cause and cardiovascular mortality in patients with dementia with HF. Further research is needed to validate these findings and explore the potential benefits of ChEIs in all patients with HF, including those without dementia.

RGS3L allows for an M2 muscarinic receptor-mediated RhoA-dependent inotropy in cardiomyocytes

The role and outcome of the muscarinic M₂ acetylcholine receptor (M₂R) signaling in healthy and diseased cardiomyocytes is still a matter of debate. Here, we report that the long isoform of the regulator of G protein signaling 3 (RGS3L) functions as a switch in the muscarinic signaling, most likely of the M₂R, in primary cardiomyocytes. High levels of RGS3L, as found in heart failure, redirect the G_i-mediated Rac1 activation into a G_i-mediated RhoA/ROCK activation. Functionally, this switch resulted in a reduced production of reactive oxygen species (- 50%) in cardiomyocytes and an inotropic response (+ 18%) in transduced engineered heart tissues. Importantly, we could show that an adeno-associated virus 9-mediated overexpression of RGS3L in rats in vivo, increased the contractility of ventricular strips by maximally about twofold. Mechanistically, we demonstrate that this switch is mediated by a complex formation of RGS3L with the GTPase-activating protein p190RhoGAP, which balances the activity of RhoA and Rac1 by altering its substrate preference in cardiomyocytes. Enhancement of this complex formation could open new possibilities in the regulation of the contractility of the diseased heart.

Acute Detubulation of Ventricular Myocytes Amplifies the Inhibitory Effect of Cholinergic Agonist on Intracellular Ca2+ Transients

Muscarinic receptors expressed in cardiac myocytes play a critical role in the regulation of heart function by the parasympathetic nervous system. How the structural organization of cardiac myocytes affects the regulation of Ca²⁺ handling by muscarinic receptors is not well-defined. Using confocal Ca²⁺ imaging, patch-clamp techniques, and immunocytochemistry, the relationship between t-tubule density and cholinergic regulation of intracellular Ca²⁺ in normal murine ventricular myocytes and myocytes with acute disruption of the t-tubule system caused by formamide treatment was studied. The inhibitory effect of muscarinic receptor agonist carbachol (CCh, 10 μM) on the amplitude of Ca²⁺ transients, evoked by field-stimulation in the presence of 100 nM isoproterenol (Iso), a β-adrenergic agonist, was directly proportional to the level of myocyte detubulation. The timing of the maximal rate of fluorescence increase of fluo-4, a Ca²⁺-sensitive dye, was used to classify image pixels into the regions functionally coupled or uncoupled to the sarcolemmal Ca²⁺ influx (I_Ca). CCh decreased the fraction of coupled regions and suppressed Ca²⁺ propagation from sarcolemma inside the cell. Formamide treatment reduced I_Ca density and decreased sarcoplasmic reticulum (SR) Ca²⁺ content. CCh did not change SR Ca²⁺ content in Iso-stimulated control and formamide-treated myocytes. CCh inhibited peak I_Ca recorded in the presence of Iso by ∼20% in both the control and detubulated myocytes. Reducing I_Ca amplitude up to 40% by changing the voltage step levels from 0 to –25 mV decreased Ca²⁺ transients in formamide-treated but not in control myocytes in the presence of Iso. CCh inhibited CaMKII activity, whereas CaMKII inhibition with KN93 mimicked the effect of CCh on Ca²⁺ transients in formamide-treated myocytes. It was concluded that the downregulation of t-tubules coupled with the diminished efficiency of excitation–contraction coupling, increases the sensitivity of Ca²⁺ release and propagation to muscarinic receptor-mediated inhibition of both I_Ca and CaMKII activity.

Role of neuronal nitric oxide synthase on cardiovascular functions in physiological and pathophysiological states

This review describes and summarizes the role of neuronal nitric oxide synthase (nNOS) on the central nervous system, particularly on brain regions such as the ventrolateral medulla (VLM) and the periaqueductal gray matter (PAG), and on blood vessels and the heart that are involved in the regulation and control of the cardiovascular system (CVS). Furthermore, we shall also review the functional aspects of nNOS during several physiological, pathophysiological, and clinical conditions such as exercise, pain, cerebral vascular accidents or stroke and hypertension. For example, during stroke, a cascade of molecular, neurochemical, and cellular changes occur that affect the nervous system as elicited by generation of free radicals and nitric oxide (NO) from vulnerable neurons, peroxide formation, superoxides, apoptosis, and the differential activation of three isoforms of nitric oxide synthases (NOSs), and can exert profound effects on the CVS. Neuronal NOS is one of the three isoforms of NOSs, the others being endothelial (eNOS) and inducible (iNOS) enzymes. Neuronal NOS is a critical homeostatic component of the CVS and plays an important role in regulation of different systems and disease process including nociception. The functional and physiological roles of NO and nNOS are described at the beginning of this review. We also elaborate the structure, gene, domain, and regulation of the nNOS protein. Both inhibitory and excitatory role of nNOS on the sympathetic autonomic nervous system (SANS) and parasympathetic autonomic nervous system (PANS) as mediated via different neurotransmitters/signal transduction processes will be explored, particularly its effects on the CVS. Because the VLM plays a crucial function in cardiovascular homeostatic mechanisms, the neuroanatomy and cardiovascular regulation of the VLM will be discussed in conjunction with the actions of nNOS. Thereafter, we shall discuss the up-to-date developments that are related to the interaction between nNOS and cardiovascular diseases such as hypertension and stroke. Finally, we shall focus on the role of nNOS, particularly within the PAG in cardiovascular regulation and neurotransmission during different types of pain stimulus. Overall, this review focuses on our current understanding of the nNOS protein, and provides further insights on how nNOS modulates, regulates, and controls cardiovascular function during both physiological activity such as exercise, and pathophysiological conditions such as stroke and hypertension.

Guizhi Decoction () Inhibits Cholinergic Transdifferentiation by Regulating Imbalance of NGF and LIF in Salt-Sensitive Hypertensive Heart Failure Rats

OBJECTIVE

To observe the imbalance of anatomical and functional innervation factors of sympathetic nerves, nerve growth factor (NGF) and leukemia inhibitory factor (LIF), in salt-sensitive hypertensive heart failure rats and to explore the effects of treatment with Guizhi Decoction () on sympathetic remodeling by inhibiting cholinergic transdifferentiation.

METHODS

SS-13^BN and Dahl salt-sensitive (DS) rats were divided into 3 groups: SS-13^BN group (control group, n=9), DS group (model group, n=9) and GS group (Guizhi Decoction, n=9). After 10 weeks of a high-salt diet, the GS group rats were given Guizhi Decoction and other two groups were given saline at an equal volume as a vehicle. After 4 weeks' intragastric administration, rats were executed to detect the relevant indicators. Echocardiography and plasma n-terminal pro-B type natriuretic peptide (NT-proBNP) levels were used to assess cardiac function. Noradrenaline (NA) levels in the plasma and myocardium were detected to evaluate the sympathetic function. NGF and LIF expression were detected in the myocardium by Western blot or quantitative real-time PCR. Double immunofluorescence or Western blot was used to detect tyrosine hydroxylase (TH), choline acetyltransferase (CHAT) and growth associated protein 43 (GAP43) in order to reflect anatomical and functional changes of sympathetic nerves.

RESULTS

DS group had anatomical and functional deterioration of sympathetic nerves in the decompensation period of heart failure compared with SS-13^BN group. Compared with the DS group, Guizhi Decoction significantly decreased the expression of LIF mRNA/protein (P<0.01), increased the expression of NGF (P<0.05 or P<0.01), enhanced the levels of TH+/GAP43+ and TH+/CHAT+ positive nerve fibers (P<0.01), and improved the protein expression of TH and GAP43 in left ventricle, but had no effect on CHAT (P>0.05). Guizhi Decoction inhibited inflammatory infiltration and collagen deposition of myocardial injury, increased the content of myocardial NA (P<0.05), reduced the plasma NA level (P<0.01), improved cardiac function (P<0.01), and improved weight and blood pressure to some extent (P<0.05), compared with DS group.

CONCLUSIONS

Guizhi Decoction could inhibit cholinergic transdifferentiation of sympathetic nerves, improve the anatomical and functional denervation of sympathetic nerves, and delay the progression of decompensated heart failure. The mechanism may be associated with the correction of the imbalance of NGF and LIF.

The Effect of Autoantibody against M2-Muscarinic Acetylcholine Receptor in Heart Failure Patients on Digoxin Treatment

Background: Autoantibody against M2-muscarinic acetylcholine receptor (anti-M2AChR) has a biological effect similar to a vagus agonist. Digoxin has a function of vagus nervous system stimulation. We hypothesized that anti-M2AChR is highly correlated with digoxin in patients with chronic heart failure (CHF). Methods: Synthetic M2AChR peptides served as the target antigen in an ELISA were used to screen the sera of 80 CHF patients, who were separated into a negative (–) or positive (+) anti-M2AChR group according to their anti-M2AChR reactivity. Echocardiography and serum digoxin concentration (SDC) were performed at baseline and after 1 year of digoxin in combination with the standard treatment regime. The end-point events were compared over 1 year of follow-up. Results: Seventy-two CHF patients completed the final data analysis, including 32 (+)anti-M2AChR and 40 (–)anti-M2AChR patients. The resting heart rate of the positive group was higher than that of the negative group at baseline (p < 0.05; 89.0 ± 1.6 vs. 83.8 ± 1.1 bpm). Both groups showed improvement in the left ventricular end-diastolic and end-systolic dimensions and ejection fraction with digoxin in combination with the standard treatment regime for 1 year (all p < 0.01). However, the 32 patients with (–)anti-M2AChR had greater improvements than the 40 patients with (+)anti-M2AChR, and this was accompanied by a marked decrease of rehospitalization (all p < 0.01) but not of cardiovascular mortality after 1 year. The SDC of patients with (–)anti-M2AChR was significantly lower than that of patients with (+)anti-M2AChR (p < 0.05; 0.63 ± 0.05 vs.1.16 ± 0.06 ng/mL) and had a positive correlation with anti-M2AChR (r = 0.81, p < 0.001). Conclusion: These results suggested that anti-M2AChR could be a useful biomarker of vagus nerve overactivation and is associated with a poor response to digoxin treatment in CHF patients.