Effects of renal denervation on monocrotaline induced pulmonary remodeling

Current Overview of the Biology and Pharmacology in Sugen/Hypoxia-Induced Pulmonary Hypertension in Rats

The Sugen 5416/hypoxia (Su/Hx) rat model of pulmonary arterial hypertension (PAH) demonstrates most of the distinguishing features of PAH in humans, including increased wall thickness and obstruction of the small pulmonary arteries along with plexiform lesion formation. Recently, significant advancement has been made describing the epidemiology, genomics, biochemistry, physiology, and pharmacology in Su/Hx challenge in rats. For example, there are differences in the overall reactivity to Su/Hx challenge in different rat strains and only female rats respond to estrogen treatments. These conditions are also encountered in human subjects with PAH. Also, there is a good translation in both the biochemical and metabolic pathways in the pulmonary vasculature and right heart between Su/Hx rats and humans, particularly during the transition from the adaptive to the nonadaptive phase of right heart failure. Noninvasive techniques such as echocardiography and magnetic resonance imaging have recently been used to evaluate the progression of the pulmonary vascular and cardiac hemodynamics, which are important parameters to monitor the efficacy of drug treatment over time. From a pharmacological perspective, most of the compounds approved clinically for the treatment of PAH are efficacious in Su/Hx rats. Several compounds that show efficacy in Su/Hx rats have advanced into phase II/phase III studies in humans with positive results. Results from these drug trials, if successful, will provide additional treatment options for patients with PAH and will also further validate the excellent translation that currently exists between Su/Hx rats and the human PAH condition.

Carotid Baroreceptor Stimulation Ameliorates Pulmonary Arterial Remodeling in Rats With Hypoxia-Induced Pulmonary Hypertension

BACKGROUND

Sympathetic hyperactivity plays an important role in the initiation and maintenance of pulmonary hypertension. Carotid baroreceptor stimulation (CBS) is an effective autonomic neuromodulation therapy. We aim to investigate the effects of CBS on hypoxia-induced pulmonary hypertension and its underlying mechanisms.

METHODS AND RESULTS

Rats were randomly assigned into 4 groups, including a Control-sham group (n=7), a Control-CBS group (n=7), a Hypoxia-sham group (n=10) and a Hypoxia-CBS group (n=10). Echocardiography, ECG, and hemodynamics examination were performed. Samples of blood, lung tissue, pulmonary arteries, and right ventricle were collected for the further analysis. In the in vivo study, CBS reduced wall thickness and muscularization degree in pulmonary arterioles, thereby improving pulmonary hemodynamics. Right ventricle hypertrophy, fibrosis and dysfunction were all improved. CBS rebalanced autonomic tone and reduced the density of sympathetic nerves around pulmonary artery trunks and bifurcations. RNA-seq analysis identified BDNF and periostin (POSTN) as key genes involved in hypoxia-induced pulmonary hypertension, and CBS downregulated the mRNA expression of BDNF and POSTN in rat pulmonary arteries. In the in vitro study, norepinephrine was found to promote pulmonary artery smooth muscle cell proliferation while upregulating BDNF and POSTN expression. The proliferative effect was alleviated by silence BDNF or POSTN.

CONCLUSIONS

Our results showed that CBS could rebalance autonomic tone, inhibit pulmonary arterial remodeling, and improve pulmonary hemodynamics and right ventricle function, thus delaying hypoxia-induced pulmonary hypertension progression. There may be a reciprocal interaction between POSTN and BDNF that is responsible for the underlying mechanism.

Autonomic nervous modulation: early treatment for pulmonary artery hypertension

Pulmonary artery hypertension (PAH) is a chronic vascular disease defined by the elevation of pulmonary vascular resistance and mean pulmonary artery pressure, which arises due to pulmonary vascular remodelling. Prior research has already established a link between the autonomic nervous system (ANS) and PAH. Therefore, the rebalancing of the ANS offers a promising approach for the treatment of PAH. The process of rebalancing involves two key aspects: inhibiting an overactive sympathetic nervous system and fortifying the impaired parasympathetic nervous system through pharmacological or interventional procedures. However, the understanding of the precise mechanisms involved in neuromodulation, whether achieved through medication or intervention, remains insufficient. This limited understanding hinders our ability to determine the appropriate timing and scope of such treatment. This review aims to integrate the findings from clinical and mechanistic studies on ANS rebalancing as a treatment approach for PAH, with the ultimate goal of identifying a path to enhance the safety and efficacy of neuromodulation therapy and improve the prognosis of PAH.

Pulmonary and Systemic Hemodynamics following Multielectrode Radiofrequency Catheter Renal Denervation in Acutely Induced Pulmonary Arterial Hypertension in Swine

Objective

We aimed to assess the effects of renal denervation (RDN) on systemic and pulmonary hemodynamics in a swine model of thromboxane A2- (TXA2-) induced pulmonary arterial hypertension (PAH).

Methods

The study protocol comprised two PAH inductions with a target mean pulmonary artery pressure (PAP) of 40 mmHg at baseline and following either the RDN or sham procedure. Ten Landrace pigs underwent the first PAH induction; then, nine animals were randomly allocated in 1 : 1 ratio to RDN or sham procedure; the second PAH induction was performed in eight animals (one animal died of pulmonary embolism during the first PAH induction, and one animal died after RDN). In the RDN group, ablation was performed in all available renal arteries, and balloon inflation within artery branches was performed in controls. An autopsy study of the renal arteries was performed.

Results

At baseline, the target mean PAP was achieved in all animals with 25.0 [20.1; 25.2] mcg of TXA2. The second PAH induction required the same mean TXA2 dose and infusion time. There was no statistically significant difference in the mean PAP at second PAH induction between the groups (39.0 ± 5.3 vs. 39.75 ± 0.5 mmHg, P > 0.05). In the RDN group, the second PAH induction resulted in a numerical but insignificant trend toward a decrease in the mean systemic blood pressure and systemic vascular resistance, when compared with the baseline induction (74 ± 18.7 vs. 90.25 ± 28.1 mmHg and 1995.3 ± 494.3 vs. 2433.7 ± 1176.7 dyn∗sec∗cm⁻⁵, P > 0.05, respectively). No difference in hemodynamic parameters was noted in the sham group between the first and second PAH induction. Autopsy demonstrated artery damage in both groups, but RDN resulted in more severe lesions.

Conclusions

According to our results, RDN does not result in significant acute pulmonary or systemic hemodynamic changes in the TXA2-induced PAH model. The potential chronic effects of RDN on PAH require further research.

Mineralocorticoid receptors in pulmonary hypertension and right heart failure: From molecular biology to therapeutic targeting

Pulmonary hypertension (PH) is a devastating condition characterized by pulmonary vascular remodelling, leading to progressive increase in pulmonary artery pressure and subsequent right ventricular failure. Aldosterone and the mineralocorticoid receptor (MR), a nuclear transcription factor, are key drivers of cardiovascular disease and MR antagonists are well-established in heart failure. Now, a growing body of evidence points at a detrimental role of MR in PH. Pharmacological MR blockade attenuated PH and prevented RV failure in experimental models. Mouse models with cell selective MR deletion suggest that this effect is mediated by MR in endothelial cells. While the evidence from experimental studies appears convincing, the available clinical data on MR antagonist use in patients with PH is more controversial. Integrated analysis of clinical data together with MR-dependent molecular alterations may provide insights why some patients respond to MRA treatment while others do not. Potential ways to identify MRA 'responders' include the analysis of underlying PH causes, stage of disease, or sex, as well as new biomarkers.

Effect of Renal Denervation on Cardiac Function and Inflammatory Factors in Heart Failure After Myocardial Infarction

Supplemental Digital Content is Available in the Text.

Heart failure (HF) affects around 100 million people and is a staggering burden for health care system worldwide. Rapid and sustained activation of inflammatory response is an important feature of HF after myocardial infarction. Sympathetic overactivation is also an important factor in the occurrence and progression of HF. The beneficial effect of renal denervation (RDN) has been demonstrated in HF. In the current study, we hypothesized that RDN improves cardiac function in HF canine models due to acute myocardial infarction (AMI) and reduced inflammation might be involved. Twenty-four beagles were randomized into the control (n = 8), HF (n = 8), and HF + RDN group (n = 8). The HF model after AMI was established by embolization the anterior descending distal artery with anhydrous ethanol in the HF and HF + RDN group. Bilateral renal artery ablation was performed in the HF + RDN group. Cardiac function, serum creatine kinase, creatine kinase-MB and NT-Pro BNP level, and expression of inflammation-related proteins in myocardial were examined. Because the paraventricular nucleus of the hypothalamus might be involved in inflammation-induced central neural excitation in HF and plays an important role in regulating extracellular fluid volume and sympathetic activity, expression of inflammation-related proteins in hypothalamus was also examined. AMI and post-AMI HF model was created successfully. Compared with the HF group, dogs in the HF + RDN group showed better cardiac function 4 weeks after AMI: lower left ventricular end-diastolic pressure, left ventricular end-diastolic dimension, and left ventricular end-systolic dimension and higher LEVF and left ventricular systolic pressure (P < 0.05 for all) were observed in the HF + RDN group. In addition, dogs in the HF + RDN group had slightly less ventricular fibrosis. Interestingly, RDN had lower expression of inflammation-related proteins including interleukin-6, tumor necrosis factors-α, nuclear factor κB, and monocyte chemotactic protein 1 (P < 0.05 for all) in both myocardial tissue and hypothalamus. RDN can improve cardiac function in dogs with HF after myocardial infarction. Our results suggested that RDN might affect cytokine-induced central neural excitation in HF and later affect sympathetic activity. Our results suggested a potential beneficial mechanism of RDN independent of mechanism involving renal afferent and efferent sympathetic nerves.

Histopathological changes of pulmonary vascular remodeling in dogs affected with pulmonary hypertension secondary to degenerative mitral valve disease

INTRODUCTION/OBJECTIVES

Pulmonary hypertension (PH) can cause pulmonary arterial remodeling. Medial remodeling is a structural change of the pulmonary artery seen with PH. Hyperplasia and hypertrophy of pulmonary arterial smooth muscle cells (SMCs) are suggested as causes of medial remodeling. To demonstrate the histopathological changes of the pulmonary artery in dogs affected with PH secondary to degenerative mitral valve disease (DMVD) compared with DMVD without PH and control dogs.

ANIMALS

Lung samples obtained from the carcasses of 19 older small-breed dogs (Control, n = 5; DMVD, n = 7; DMVD + PH, n = 7).

MATERIALS AND METHODS

Lung tissue sections were stained with hematoxylin and eosin, Masson's trichrome, and proliferating cell nuclear antigen (PCNA) immunohistochemistry.

RESULTS

The internal diameters of the pulmonary artery in the three groups were not different. Masson's trichrome staining revealed no collagen deposition in the intimal layer of the pulmonary artery in all dogs. The external diameter, percentage of medial thickness (%MT), percentage of SMC layer and collagen deposition areas, average number of SMCs, and the percentage of PCNA positive cells (%PCNA) of the pulmonary artery were increased in the DMVD and DMVD + PH groups compared with the control group. The %PCNA in the DMVD + PH group was significantly decreased when compared with the DMVD group.

CONCLUSIONS

Medial remodeling was found in left-sided heart failure DMVD dogs with and without PH. The medial remodeling in DMVD dogs with and without PH is related to SMC hyperplasia, hypertrophy, and collagen deposition, leading to an increased medial layer thickness of the pulmonary artery.

Neurohormonal modulation in pulmonary arterial hypertension

Pulmonary hypertension is a fatal condition of elevated pulmonary pressures, complicated by right heart failure. Pulmonary hypertension appears in various forms; one of those is pulmonary arterial hypertension (PAH) and is particularly characterised by progressive remodelling and obstruction of the smaller pulmonary vessels. Neurohormonal imbalance in PAH patients is associated with worse prognosis and survival. In this back-to-basics article on neurohormonal modulation in PAH, we provide an overview of the pharmacological and nonpharmacological strategies that have been tested pre-clinically and clinically. The benefit of neurohormonal modulation strategies in PAH patients has been limited by lack of insight into how the neurohormonal system is changed throughout the disease and difficulties in translation from animal models to human trials. We propose that longitudinal and individual assessments of neurohormonal status are required to improve the timing and specificity of neurohormonal modulation strategies. Ongoing developments in imaging techniques such as positron emission tomography may become helpful to determine neurohormonal status in PAH patients in different disease stages and optimise individual treatment responses.

The Expression of Proteins Related to Serotonin Pathway in Pulmonary Arteries of Dogs Affected With Pulmonary Hypertension Secondary to Degenerative Mitral Valve Disease

Background: Pulmonary hypertension (PH) can cause medial thickening, a hallmark of pulmonary arterial remodeling. The serotonin (5HT) pathway has been suggested as a factor associated with PH by inducing pulmonary arterial smooth muscle cells (SMCs) proliferation, a major cause of medial thickening. This study aims to demonstrate the expression of molecules in the 5HT pathway in the pulmonary artery of dogs affected with PH secondary to degenerative mitral valve disease (DMVD) compared to DMVD and healthy control dogs. Materials and Methods: The study included lung samples from the carcasses of 19 older small-breed dogs (Control n = 5, DMVD n = 7, DMVD+PH n = 7). Lung tissue sections were performed Hematoxylin and Eosin staining for measuring the percentage of medial thickness and immunohistochemistry for evaluating the expression of proteins in the 5HT pathway including serotonin transporter (SERT), serotonin 2A receptor (5HT2A), tryptophan hydroxylase 1 (TPH1), extracellular regulated kinase 1/2 (ERK1/2), and phosphorylated ERK1/2 (pERK1/2). Results: Medial thickening of the pulmonary arteries was found in the DMVD and DMVD+PH groups compared to the control. The medial thickening of the DMVD+PH group was increased significantly compared to that in the DMVD group. Intracytoplasmic expression of proteins related to the 5HT pathway was mainly presented in the medial layer of the pulmonary arteries. The control group showed a low expression of proteins related to the 5HT pathway. An intensive expression of SERT, 5HT2A, TPH1, and ERK1/2 protein was seen in the DMVD and DMVD+PH groups. Interestingly, pERK1/2 was strongly represented only in the DMVD+PH group. Conclusions: Overexpression of proteins related to the 5HT pathway including SERT, 5HT2A, TPH1, ERK1/2, and pERK1/2 was associated with medial remodeling in dogs affected with secondary to DMVD.

Neurohormonal Modulation as a Therapeutic Target in Pulmonary Hypertension

The autonomic nervous system (ANS) and renin-angiotensin-aldosterone system (RAAS) are involved in many cardiovascular disorders, including pulmonary hypertension (PH). The current review focuses on the role of the ANS and RAAS activation in PH and updated evidence of potential therapies targeting both systems in this condition, particularly in Groups 1 and 2. State of the art knowledge in preclinical and clinical use of pharmacologic drugs (beta-blockers, beta-three adrenoceptor agonists, or renin-angiotensin-aldosterone signaling drugs) and invasive procedures, such as pulmonary artery denervation, is provided.

Pulmonary artery denervation for pulmonary arterial hypertension

Pulmonary arterial hypertension remains a progressive, life-limiting disease despite optimal medical therapy. Pulmonary artery denervation has arisen as a novel intervention in the treatment of pulmonary arterial hypertension, and other forms of pulmonary hypertension, with the aim of reducing the sympathetic activity of the pulmonary circulation. Pre-clinical studies and initial clinical trials have demonstrated that the technique can be performed safely with some positive effects on clinical, haemodynamic and echocardiographic markers of disease. The scope of the technique in current practice remains limited given the absence of well-designed, large-scale, international randomised controlled clinical trials. This review provides an overview of this exciting new treatment modality, including pathophysiology, technical innovations and recent trial results.

Pulmonary arterial hypertension: the case for a bioelectronic treatment

Pulmonary arterial hypertension (PAH) is a rare disease of unknown etiology that progresses to right ventricular failure. It has a complex pathophysiology, which involves an imbalance between vasoconstrictive and vasodilative processes in the pulmonary circulation, pulmonary vasoconstriction, vascular and right ventricular remodeling, systemic inflammation, and autonomic imbalance, with a reduced parasympathetic and increased sympathetic tone. Current pharmacological treatments for PAH include several classes of drugs that target signaling pathways in vascular biology and cardiovascular physiology, but they can have severe unwanted effects and they do not typically stop the progression of the disease. Pulmonary artery denervation has been tested clinically as a method to suppress sympathetic overactivation, however it is a nonspecific and irreversible intervention. Bioelectronic medicine, in particular vagus nerve stimulation (VNS), has been used in cardiovascular disorders like arrhythmias, heart failure and arterial hypertension and could, in principle, be tested as a treatment in PAH. VNS can produce pulmonary vasodilation and renormalize right ventricular function, via activation of pulmonary and cardiac vagal fibers. It can suppress systemic inflammation, via activation of fibers that innervate the spleen. Finally, VNS can gradually restore the balance between parasympathetic and sympathetic tone by regulating autonomic reflexes. Preclinical studies support the feasibility of using VNS in PAH. However, there are challenges with such an approach, arising from the need to affect a relatively small number of relevant vagal fibers, and the potential for unwanted cardiac and noncardiac effects of VNS in this sensitive patient population.

Renal Denervation Reduced Ventricular Arrhythmia After Myocardial Infarction by Inhibiting Sympathetic Activity and Remodeling

Background Ventricular arrhythmia after myocardial infarction is the most important risk factor for sudden cardiac death, which poses a serious threat to human health. As the correlation between autonomic nervous systemic dysfunction and heart rhythm abnormality has been gradually revealed, remedies targeting autonomic nervous system dysfunction, especially the sympathetic nerve, have emerged. Among them, renal denervation is noted for its powerful effect on the inhibition of sympathetic nerve activity. We aim to investigate whether renal denervation can reduce ventricular arrhythmia after myocardial infarction and thus decrease the risk of sudden cardiac death. In addition, we explore the potential mechanism with respect to nerve activity and remodeling. Methods and Results Twenty-four beagles were randomized into the control (n=4), renal denervation (n=10), and sham (n=10) groups. Permanent left anterior descending artery ligation was performed to establish myocardial infarction in the latter 2 groups. Animals in the renal denervation group underwent both surgical and chemical renal denervation. Compared with dogs in the sham group, dogs in the renal denervation group demonstrated attenuated effective refractory period shortening and inhomogeneity, flattened restitution curve, increased ventricular threshold, and decreased ventricular arrhythmia. Heart rate variability assessment, catecholamine measurement, and nerve discharge recordings all indicated that renal denervation could reduce whole-body and local tissue sympathetic tone. Tissue analysis revealed a significant decrease in neural remodeling in both the heart and stellate ganglion. Conclusions Surgical and chemical renal denervation decreased whole-body and local tissue sympathetic activity and reversed neural remodeling in the heart and stellate ganglion. Consequently, renal denervation led to beneficial remodeling of the electrophysiological characteristics in the infarction border zone, translating to a decrease in ventricular arrhythmia after myocardial infarction.

Potential Contribution of Carotid Body-Induced Sympathetic and Renin-Angiotensin System Overflow to Pulmonary Hypertension in Intermittent Hypoxia

PURPOSE OF REVIEW

Obstructive sleep apnea (OSA), featured by chronic intermittent hypoxia (CIH), is an independent risk for systemic hypertension (HTN) and is associated with pulmonary hypertension (PH). The precise mechanisms underlying pulmonary vascular remodeling and PH in OSA are not fully understood. However, it has been suggested that lung tissue hypoxia, oxidative stress, and pro-inflammatory mediators following CIH exposure may contribute to PH.

RECENT FINDINGS

New evidences obtained in preclinical OSA models support that an enhanced carotid body (CB) chemosensory reactiveness to oxygen elicits sympathetic and renin-angiotensin system (RAS) overflow, which contributes to HTN. Moreover, the ablation of the CBs abolished the sympathetic hyperactivity and HTN in rodents exposed to CIH. Accordingly, it is plausible that the enhanced CB chemosensory reactivity may contribute to the pulmonary vascular remodeling and PH through the overactivation of the sympathetic-RAS axis. This hypothesis is supported by the facts that (i) CB stimulation increases pulmonary arterial pressure, (ii) denervation of sympathetic fibers in pulmonary arteries reduces pulmonary remodeling and pulmonary arterial hypertension (PAH) in humans, and (iii) administration of angiotensin-converting enzyme (ACE) or blockers of Ang II type 1 receptor (ATR1) ameliorates pulmonary remodeling and PH in animal models. In this review, we will discuss the supporting evidence for a plausible contribution of the CB-induced sympathetic-RAS axis overflow on pulmonary vascular remodeling and PH induced by CIH, the main characteristic of OSA.

alpha1A-adrenoceptor is involved in norepinephrine-induced proliferation of pulmonary artery smooth muscle cells via CaMKII signaling

Pulmonary arterial hypertension (PAH) is a progressive disease of the pulmonary vasculature characterized by excessive proliferation of pulmonary artery smooth muscle cells (PASMCs). Some studies have demonstrated the sympathetic nervous system is activated in PAH and norepinephrine (NE) released is closely linked with its activation. However, the subtypes of adrenoreceptor (AR) and the downstream molecular cascades which are involved in the proliferation of PASMCs are still unclear. In this study, adult male Wistar rats were exposed to chronic hypoxia and PASMCs were cultured in hypoxic condition. Significant upregulation of α_1A -AR was identified by Western blot analysis or immunofluorescence in all of the pulmonary arteries, lung tissues, and cell hypoxic models. Western blot analysis, flow cytometry, and immunofluorescence were applied to detect the roles of α_1A -AR in NE mediated proliferation of PASMCs. We revealed 5-methylurapidil (5-MU) reversed NE-induced upregulation of PCNA, CyclinA and CyclinE, more cells from G₀ /G₁ phase to G₂ /M+S phase, enhancement of the microtubule formation. In addition, we found calcium/calmodulin(CaM)-dependent protein kinase type II (CaMKII) pathway was involved in α_1A -AR-mediated cell proliferation. [Ca²⁺ ]_i measurements showed that an increase of [Ca²⁺ ]_i caused by NE or/and hypoxia could be blocked by 5-MU in PASMCs. Western blot analysis results demonstrated the augmentation of CaMKII phosphorylation level was caused by hypoxia or NE in pulmonary arteries, lung tissues, and PASMCs. KN62 attenuated NE-induced proliferation of PASMCs under normoxia and hypoxia. In conclusion, those results suggested NE which stimulated α_1A -AR-mediated the proliferation of PASMCs, which may be via the CaMKII pathway, and it could be used as a novel treatment strategy in PAH.

Autonomic nervous system involvement in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a chronic pulmonary vascular disease characterized by increased pulmonary vascular resistance (PVR) leading to right ventricular (RV) failure. Autonomic nervous system involvement in the pathogenesis of PAH has been demonstrated several years ago, however the extent of this involvement is not fully understood. PAH is associated with increased sympathetic nervous system (SNS) activation, decreased heart rate variability, and presence of cardiac arrhythmias. There is also evidence for increased renin-angiotensin-aldosterone system (RAAS) activation in PAH patients associated with clinical worsening. Reduction of neurohormonal activation could be an effective therapeutic strategy for PAH. Although therapies targeting adrenergic receptors or RAAS signaling pathways have been shown to reverse cardiac remodeling and improve outcomes in experimental pulmonary hypertension (PH)-models, the effectiveness and safety of such treatments in clinical settings have been uncertain. Recently, novel direct methods such as cervical ganglion block, pulmonary artery denervation (PADN), and renal denervation have been employed to attenuate SNS activation in PAH. In this review, we intend to summarize the multiple aspects of autonomic nervous system involvement in PAH and overview the different pharmacological and invasive strategies used to target autonomic nervous system for the treatment of PAH.