Contribution of Impaired Parasympathetic Activity to Right Ventricular Dysfunction and Pulmonary Vascular Remodeling in Pulmonary Arterial Hypertension

Research progress in myocardial function and diseases related to muscarinic acetylcholine receptor (Review)

Muscarinic acetylcholine (ACh) receptors (also known as M receptors) are widely distributed in all organs and tissues of the body, mainly playing a role in cholinergic nerve conduction. There are five known subtypes of muscarinic ACh receptors, but their pharmacological mechanisms of action on myocardial function have remained to be clearly defined. Functional myocardial diseases and myocardial injuries, such as arrhythmia, myocardial ischemia, myocarditis and myocardial fibrosis, may be affected by muscarinic ACh receptors. This article reviews the research progress of the regulation of myocardial function by muscarinic ACh receptors and related diseases, with the aim of developing better strategies and providing references for further revealing and clarifying the signal transduction and mechanisms of muscarinic ACh receptors in cardiomyocytes, and finding potential myocardial protective drugs that act on muscarinic ACh receptors.

A new approach to interpreting the LF/HF ratio: a study in hypertensive patients

Resistant arterial hypertension (RHTN) has been associated with sympathetic hyperactivity, which represents a significant challenge in the management and treatment of arterial hypertension. In the present study, autonomic modulation was analysed in hypertensive, resistant hypertensive, and refractory hypertensive patients, compared to a group of apparently healthy normotensive individuals. Participants with resistant hypertension were included only after the exclusion of secondary hypertension and pseudo-resistance diagnoses. Heart rate variability (HRV) analysis included parameters from the time domain, frequency domain, and nonlinear methods, providing a comprehensive assessment of global autonomic modulation. The results demonstrated a significant reduction in global HRV across all three hypertensive groups, evidenced by decreases in parameters from the time domain, frequency domain and nonlinear methods. Furthermore, a concomitant reduction in the low- and high-frequency components was observed, with the decrease in the high-frequency component being more pronounced. These findings challenge the traditional view of isolated sympathetic hyperactivity in hypertension. Instead, the results reveal a relative predominance of sympathetic function due to the more marked attenuation of parasympathetic activity. These results underscore the need to reinterpret autonomic dysfunction in arterial hypertension, particularly in its more severe forms, as a global loss of autonomic modulation.

α7nAChR on B cells directs T cell differentiation to prevent viral myocarditis

Patients with viral myocarditis (VMC) exhibit evident autonomic nervous system imbalance, and adverse cardiac remodeling is involved in impaired cholinergic function. The α7 nicotinic acetylcholine receptor (α7nAChR), which is a neurotransmitter receptor, exerts immunoregulatory effects. Recent advances have illuminated the evolution and functions of peripheral and cardiac B cells in heart disease. However, the role of α7nAChR expressed by B cells in the progression of VMC has not been established. We revealed the neuroimmune communication landscape in the heart and found that the phenotypes of cardiac and splenic B cells and their α7nAChR expression changed dynamically during the progression of VMC to dilated cardiomyopathy. α7nAChR on B cells serves as a negative regulator by inhibiting their proinflammatory functions and signaling pathways. B cell-specific α7nAChR deficiency exacerbated myocardial inflammation, fibrosis, and cardiac dysfunction. However, these effects were abrogated in non-B cells from mice with IL-17A knockdown. Enhanced degradation of acetylcholine leads to an imbalance in cholinergic signaling, resulting in impaired neurotransmission. The acetylcholinesterase inhibitor pyridostigmine bromide could improve cardiac remodeling and prevent the progression of VMC to the chronic phase, which was partly dependent on the α7nAChR on B cells. Our findings provide notable insights into cardiac-neural-immune communication during myocardial injury.

F. Oliveira R, Hilton JF, Graham BB. Morbidity and Mortality Associated With Pulmonary Arterial Hypertension in a Schistosomiasis-Endemic Region of Brazil

Data about pulmonary arterial hypertension (PAH) patients living in low- and middle-income countries remain scarce. This study assessed prognostic factors associated with time to clinical worsening (CW) or death of a cohort of PAH patients in Minas Gerais, Brazil. This retrospective cohort study describes baseline clinical variables by PAH etiology and estimates time from diagnosis to CW [all-cause death, any-cause hospitalization, or disease progression (decrease of ≥ 15% in 6MWD and need for additional PAH therapy or worsening of functional class (FC)] and time to death. 79 out of 102 participants developed CW and 38 died while under follow-up. The most prevalent etiologies were PAH associated with schistosomiasis (PAH-Sch), idiopathic (IPAH), with congenital heart disease (PAH-CHD), and with connective tissue disease (PAH-CTD). The overall median event-free time to CW was 3.3 (95% CI, 2.3-4.6) years, which was similar across etiologies (log-rank test: p = 0.12). WHO FC III-IV, DLCO < 70%, heart rate recovery in 1 min after the 6-min walk test (HRR1) < 18 beats/minute, and baseline mPAP ≥ 50 mmHg were predictive of CW-free time. The median time to all-cause mortality was 10.2 (95% CI, 6.8 - > 10) years and varied among etiologies (log-rank test: p < 0.001). Time to CW was statistically independent of PAH etiology but depended on baseline WHO FC, DLCO, HRR, and mPAP. After CW events, PAH-Sch and PAH-CTD survived less on average than IPAH and PAH-CHD participants.

Pulmonary Arterial Hypertension Induces Compensatory Increase of Left Ventricular Contractility Indexes in Rats in Response to Its Filling Insufficiency

Pulmonary arterial hypertension (PAH) is accompanied by changes in the pulmonary and systemic circulation. We studied the effect of PAH on the function of the left ventricle (LV). Left ventricular pressure and volume were simultaneously recorded in vivo in rats with monocrotaline-induced PAH (60 mg/kg). LV contractility and mechanical indexes were calculated. In addition, the relationships between LV maximum rate of contraction (dP/dtmax) or relaxation (dP/dtmin) and left ventricular end-diastolic volume (EDV) were assessed. PAH leads to a significant decrease in cardiac output at a constant HR as well as to a decrease in stroke volume at unchanged LV ejection fraction. In rats with PAH, the slopes of the dP/dtmax-EDV and dP/dtmin-EDV curves were greater than in control animals by 1.93 and 2.5 times, respectively. Thus, PAH leads to a compensatory increase in the dependence of LV contractility and "intensity" of LV relaxation on EDV.

Toll-like receptor 4 inhibition by pyridostigmine is associated with a reduction in hypertension and inflammation in rat models of preeclampsia

BACKGROUND

Preeclampsia (PE) is marked by hypertension and detrimental sterile inflammatory response. Despite the reported anti-inflammatory effect of pyridostigmine bromide (PYR) in different models, its anti-inflammatory mechanism in PE is unclear. This study assessed whether such an anti-inflammatory effect involves inhibition of placental Toll-like receptor 4 (TLR4) signaling.

METHODS

Placental TLR4 expression and its signaling were assessed respectively in PE women and Sprague-Dawley rats with reduced uterine perfusion pressure (RUPP) induced on gestational day14 (GD14). RUPP and lipopolysaccharides (LPS, 5 μg/kg)-induced PE rats were treated with a selective TLR4 signaling inhibitor (TAK-242, 2.5 mg/kg/day). The effect of PYR (20 mg/kg/day) on TLR4 expression and signaling was also assessed in RUPP or LPS-infused rats. On GD19, rats' mean arterial pressure (MAP) and samples were collected and processed. At the cellular level, the effect of acetylcholine (ACh), the indirect by-product of PYR activity, on LPS-stimulated HTR-8/SVneo cells was assessed.

RESULTS

Both PE women and RUPP rats had increased (P  < 0.05) placental TLR4 expression and elevated (P  < 0.05) MAP. Selective inhibition of TLR4 signaling with TAK-242 blunted (P < 0.05) RUPP-elevated MAP. Activation of TLR4 induced PE-like symptoms in dams, which were prevented by TAK-242. PYR reduced (P < 0.05) MAP and downregulated placental TLR4 expression and TLR4/TRAF6/NF-κB signaling-mediated inflammation in RUPP and in response to TLR4 selective activation. ACh inhibited the same signaling pathway in LPS-stimulated HTR-8 in vitro.

CONCLUSION

Our data support that PYR attenuates placental TLR4 expression and inhibits TLR4/TRAF6/NF-κB signaling pathway-mediated inflammation in RUPP, clarifying the anti-inflammatory mechanisms of PYR in the PE rat model.

Autonomic control of the pulmonary circulation: Implications for pulmonary hypertension

The autonomic regulation of the pulmonary vasculature has been under-appreciated despite the presence of sympathetic and parasympathetic neural innervation and adrenergic and cholinergic receptors on pulmonary vessels. Recent clinical trials targeting this innervation have demonstrated promising effects in pulmonary hypertension, and in this context of reignited interest, we review autonomic pulmonary vascular regulation, its integration with other pulmonary vascular regulatory mechanisms, systemic homeostatic reflexes and their clinical relevance in pulmonary hypertension. The sympathetic and parasympathetic nervous systems can affect pulmonary vascular tone and pulmonary vascular stiffness. Local afferents in the pulmonary vasculature are activated by elevations in pressure and distension and lead to distinct pulmonary baroreflex responses, including pulmonary vasoconstriction, increased sympathetic outflow, systemic vasoconstriction and increased respiratory drive. Autonomic pulmonary vascular control interacts with, and potentially makes a functional contribution to, systemic homeostatic reflexes, such as the arterial baroreflex. New experimental therapeutic applications, including pulmonary artery denervation, pharmacological cholinergic potentiation, vagal nerve stimulation and carotid baroreflex stimulation, have shown some promise in the treatment of pulmonary hypertension.

Autonomic Dysregulation in Pulmonary Hypertension: Role of Physical Exercise

Pulmonary hypertension (PH) is a rare and severe condition characterized by increased pressure in the pulmonary circulation, often resulting in right ventricular failure and death. The autonomic nervous system (ANS) plays a crucial role in the cardiovascular and pulmonary controls. Dysfunction of ANS has been implicated in the pathogenesis of cardiopulmonary diseases. Conversely, dysfunctions in ANS can arise from these diseases, impacting cardiac and pulmonary autonomic functions and contributing to disease progression. The complex interaction between ANS dysfunction and PH plays a crucial role in the disease progression, making it essential to explore interventions that modulate ANS, such as physical exercise, to improve the treatment and prognosis of patients with PH. This review addresses autonomic dysfunctions found in PH and their implications for the cardiopulmonary system. Furthermore, we discuss how physical exercise, a significant modulator of ANS, may contribute to the prognosis of PH. Drawing from evidence of aerobic and resistance exercise training in patients and experimental models of PH, potential cardiovascular benefits of exercise are presented. Finally, we highlight emerging therapeutic targets and perspectives to better cope with the complex condition. A comprehensive understanding of the interaction between ANS and PH, coupled with targeted physical exercise interventions, may pave the way for innovative therapeutic strategies and significantly improve the treatment and prognosis of vulnerable patients.

Respiratory, cardiovascular and musculoskeletal mechanisms involved in the pathophysiology of pulmonary hypertension: An updated systematic review of preclinical and clinical studies

BACKGROUND

Progressive exercise intolerance is a hallmark of pulmonary hypertension (pH), severely impacting patients' independence and quality of life (QoL). Accumulating evidence over the last decade shows that combined abnormalities in peripheral reflexes and target organs contribute to disease progression and exercise intolerance.

OBJECTIVE

The aim of this study was to review the literature of the last decade on the contribution of the cardiovascular, respiratory, and musculoskeletal systems to pathophysiology and exercise intolerance in pH.

METHODS

A systematic literature search was conducted using specific terms in PubMed, SciELO, and the Cochrane Library databases for original pre-clinical or clinical studies published between 2013 and 2023. Studies followed randomized controlled/non-randomized controlled and pre-post designs.

RESULTS

The systematic review identified 25 articles reporting functional or structural changes in the respiratory, cardiovascular, and musculoskeletal systems in pH. Moreover, altered biomarkers in these systems, lower cardiac baroreflex, and heightened peripheral chemoreflex activity seemed to contribute to functional changes associated with poor prognosis and exercise intolerance in pH. Potential therapeutic strategies acutely explored involved manipulating the baroreflex and peripheral chemoreflex, improving cardiovascular autonomic control via cardiac vagal control, and targeting specific pathways such as GPER1, GDF-15, miR-126, and the JMJD1C gene.

CONCLUSION

Information published in the last 10 years advances the notion that pH pathophysiology involves functional and structural changes in the respiratory, cardiovascular, and musculoskeletal systems and their integration with peripheral reflexes. These findings suggest potential therapeutic targets, yet unexplored in clinical trials, that could assist in improving exercise tolerance and QoL in patients with pH.

Dapagliflozin alleviates right heart failure by promoting collagen degradation by reducing ROS levels

BACKGROUND

Right ventricular (RV) fibrosis is an important pathological change that occurs during the development of right heart failure (RHF) induced by pulmonary hypertension (PH). Dapagliflozin (DAPA), a sodium-glucose cotransporter 2 (SGLT2) inhibitor, has been shown to play a major role in left heart failure, but it is unclear whether it has a positive effect on RHF. This study aimed to clarify the effect of DAPA on PH-induced RHF and investigate the underlying mechanisms.

METHODS

We conducted experiments on two rat models with PH-induced RHF and cardiac fibroblasts (CFs) exposed to pathological mechanical stretch or transforming growth factor-beta (TGF-β) to investigate the effect of DAPA.

RESULTS

In vivo, DAPA could improve pulmonary hemodynamics and RV function. It also attenuated right heart hypertrophy and RV fibrosis. In vitro, DAPA reduced collagen expression by increasing the production of matrix metalloproteinase 2 (MMP2) and matrix metalloproteinase 9 (MMP9). Additionally, DAPA was found to reduce reactive oxygen species (ROS) levels in CFs and the right heart in rats. Similar to DAPA, the ROS scavenger N-acetylcysteine (NAC) exerted antifibrotic effects on CFs. Therefore, we further investigated the mechanism by which DAPA promoted collagen degradation by reducing ROS levels.

CONCLUSIONS

In summary, we concluded that DAPA ameliorated PH-induced structural and functional changes in the right heart by increasing collagen degradation. Our study provides new ideas for the possibility of using DAPA to treat RHF.

Pulmonary Hypertension: Pharmacological and Non-Pharmacological Therapies

Pulmonary hypertension (PH) is a severe and chronic disease characterized by increased pulmonary vascular resistance and remodeling, often precipitating right-sided heart dysfunction and death. Although the condition is progressive and incurable, current therapies for the disease focus on multiple different drugs and general supportive therapies to manage symptoms and prolong survival, ranging from medications more specific to pulmonary arterial hypertension (PAH) to exercise training. Moreover, there are multiple studies exploring novel experimental drugs and therapies including unique neurostimulation, to help better manage the disease. Here, we provide a narrative review focusing on current PH treatments that target multiple underlying biochemical mechanisms, including imbalances in vasoconstrictor-vasodilator and autonomic nervous system function, inflammation, and bone morphogenic protein (BMP) signaling. We also focus on the potential of novel therapies for managing PH, focusing on multiple types of neurostimulation including acupuncture. Lastly, we also touch upon the disease's different subgroups, clinical presentations and prognosis, diagnostics, demographics, and cost.

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.

Beta-adrenergic blockade increases pulmonary vascular resistance and causes exaggerated hypoxic pulmonary vasoconstriction at high altitude: a physiological study

BACKGROUND

An increasing number of hypertensive persons travel to high altitude (HA) while using antihypertensive medications such as beta-blockers. Nevertheless, while hypoxic exposure initiates an increase in pulmonary artery pressure (Ppa) and pulmonary vascular resistance (PVR), the contribution of the autonomic nervous system is unclear. In animals, beta-adrenergic blockade has induced pulmonary vasoconstriction in normoxia and exaggerated hypoxic pulmonary vasoconstriction (HPV) and both effects were abolished by muscarinic blockade. We thus hypothesized that in humans, propranolol (PROP) increases Ppa and PVR in normoxia and exaggerates HPV, and that these effects of PROP are abolished by glycopyrrolate (GLYC).

METHODS

In seven healthy male lowlanders, Ppa was invasively measured without medication, with PROP and PROP + GLYC, both at sea level (SL, 488 m) and after a 3-week sojourn at 3454 m altitude (HA). Bilateral thigh-cuff release manoeuvres were performed to derive pulmonary pressure-flow relationships and pulmonary vessel distensibility.

RESULTS

At SL, PROP increased Ppa and PVR from (mean ± SEM) 14 ± 1 to 17 ± 1 mmHg and from 69 ± 8 to 108 ± 11 dyn s cm-5 (21% and 57% increase, P = 0.01 and P < 0.0001). The PVR response to PROP was amplified at HA to 76% (P < 0.0001, P[interaction] = 0.05). At both altitudes, PROP + GLYC abolished the effect of PROP on Ppa and PVR. Pulmonary vessel distensibility decreased from 2.9 ± 0.5 to 1.7 ± 0.2 at HA (P < 0.0001) and to 1.2 ± 0.2 with PROP, and further decreased to 0.9 ± 0.2% mmHg-1 with PROP + GLYC (P = 0.01).

CONCLUSIONS

Our data show that beta-adrenergic blockade increases, and muscarinic blockade decreases PVR, whereas both increase pulmonary artery elastance. Future studies may confirm potential implications from the finding that beta-adrenergic blockade exaggerates HPV for the management of mountaineers using beta-blockers for prevention or treatment of cardiovascular conditions.

Ultrasound Neuromodulation of an Anti-Inflammatory Pathway at the Spleen Improves Experimental Pulmonary Hypertension

BACKGROUND

Inflammation is pathogenically implicated in pulmonary arterial hypertension; however, it has not been adequately targeted therapeutically. We investigated whether neuromodulation of an anti-inflammatory neuroimmune pathway involving the splenic nerve using noninvasive, focused ultrasound stimulation of the spleen (sFUS) can improve experimental pulmonary hypertension.

METHODS

Pulmonary hypertension was induced in rats either by Sugen 5416 (20 mg/kg SQ) injection, followed by 21 (or 35) days of hypoxia (sugen/hypoxia model), or by monocrotaline (60 mg/kg IP) injection (monocrotaline model). Animals were randomized to receive either 12-minute-long sessions of sFUS daily or sham stimulation for 14 days. Catheterizations, echocardiography, indices of autonomic function, lung and heart histology and immunohistochemistry, spleen flow cytometry, and lung single-cell RNA sequencing were performed after treatment to assess the effects of sFUS.

RESULTS

Splenic denervation right before induction of pulmonary hypertension results in a more severe disease phenotype. In both sugen/hypoxia and monocrotaline models, sFUS treatment reduces right ventricular systolic pressure by 25% to 30% compared with sham treatment, without affecting systemic pressure, and improves right ventricular function and autonomic indices. sFUS reduces wall thickness, apoptosis, and proliferation in small pulmonary arterioles, suppresses CD3+ and CD68+ cell infiltration in lungs and right ventricular fibrosis and hypertrophy and lowers BNP (brain natriuretic peptide). Beneficial effects persist for weeks after sFUS discontinuation and are more robust with early and longer treatment. Splenic denervation abolishes sFUS therapeutic benefits. sFUS partially normalizes CD68+ and CD8+ T-cell counts in the spleen and downregulates several inflammatory genes and pathways in nonclassical and classical monocytes and macrophages in the lung. Differentially expressed genes in those cell types are significantly enriched for human pulmonary arterial hypertension-associated genes.

CONCLUSIONS

sFUS causes dose-dependent, sustained improvement of hemodynamic, autonomic, laboratory, and pathological manifestations in 2 models of experimental pulmonary hypertension. Mechanistically, sFUS normalizes immune cell populations in the spleen and downregulates inflammatory genes and pathways in the lung, many of which are relevant in human disease.

Clinical effect of perioperative stellate ganglion block on mechanical ventilation and respiratory function of elderly patients with septic shock

BACKGROUND

Here we investigated the effect of a stellate ganglion block on the perioperative mechanical ventilation and postoperative recovery of respiratory function of elderly patients with infectious shock.

METHODS

Thirty-six elderly patients with septic shock who underwent emergency general anesthesia at our hospital were randomly divided into treatment (T) and control (C) groups (n = 18 each). Group T received a preoperative stellate ganglion block, whereas group C received normal saline. Procalcitonin and C-reactive protein levels were compared preoperatively and at 1 and 7 days postoperative. Mean arterial pressure, oxygen saturation, and mean pulmonary artery pressure were measured preoperative and postoperative as well as at 1 and 7 days later. A blood gas analysis was performed preoperatively, at the end of the operation, during extubation, and at 1 and 7 days postoperative. Intubation under general anesthesia, the completion of anesthesia, and spontaneous respiratory recovery involve pulmonary dynamic compliance, plateau pressure, and mechanical ventilation.

RESULTS

General condition did not differ significantly between groups (P > .05). However, mean arterial pressure at the end of surgery and at 1 and 7 days postoperative were significantly higher in group T versus C (P < .05). Furthermore, mean oxygen saturation at the end of surgery and at 1 and 7 days postoperative was significantly lower in group T versus C (P < .05), while procalcitonin and C-reactive protein levels were significantly lower at 1 and 7 days postoperative. Group T had significantly better arterial partial pressure of carbon dioxide, partial pressure of oxygen, and partial pressure of oxygen/fraction of inspired oxygen than group C at the end of surgery, during extubation, and at 1 and 7 days postoperative (P < .05).

CONCLUSION

Group T exhibited superior inflammatory responses and respiratory function. Stellate ganglion block in elderly patients with septic shock reduces inflammation, improves mechanical ventilation perioperatively, and promotes postoperative recovery and respiratory function.

Donepezil attenuates progression of cardiovascular remodeling and improves prognosis in spontaneously hypertensive rats with chronic myocardial infarction

The acetylcholinesterase inhibitor donepezil restores autonomic balance, reduces inflammation, and improves long-term survival in rats with chronic heart failure (CHF) following myocardial infarction (MI). As arterial hypertension is associated with a significant risk of cardiovascular death, we investigated the effectiveness of donepezil in treating CHF in spontaneously hypertensive rats (SHR). CHF was induced in SHR by inducing permanent MI. After 2 weeks, the surviving SHR were randomly assigned to sham-operated (SO), untreated (UT), or oral donepezil-treated (DT, 5 mg/kg/day) groups, and various vitals and parameters were monitored. After 7 weeks of treatment, heart rate and arterial hypertension reduced significantly in DT rats than in UT rats. Donepezil treatment improved 50-day survival (41% to 80%, P = 0.004); suppressed progression of cardiac hypertrophy, cardiac dysfunction (cardiac index: 133 ± 5 vs. 112 ± 5 ml/min/kg, P < 0.05; left ventricular end-diastolic pressure: 12 ± 3 vs. 22 ± 2 mmHg, P < 0.05; left ventricular +dp/dtmax: 5348 ± 338 vs. 4267 ± 114 mmHg/s, P < 0.05), systemic inflammation, and coronary artery remodeling (wall thickness: 26.3 ± 1.4 vs. 34.7 ± 0.7 μm, P < 0.01; media-to-lumen ratio: 3.70 ± 0.73 vs. 8.59 ± 0.84, P < 0.001); increased capillary density; and decreased plasma catecholamine, B-type natriuretic peptide, arginine vasopressin, and angiotensin II levels. Donepezil treatment attenuated cardiac and coronary artery remodeling, mitigated cardiac dysfunction, and significantly improved the prognosis of SHR with CHF.

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.

Carotid Baroreceptor Stimulation Improves Pulmonary Arterial Remodeling and Right Ventricular Dysfunction in Pulmonary Arterial Hypertension

Autonomic nervous system imbalance is intricately associated with the severity and prognosis of pulmonary arterial hypertension (PAH). Carotid baroreceptor stimulation (CBS) is a nonpharmaceutical intervention for autonomic neuromodulation. The effects of CBS on monocrotaline-induced PAH were investigated in this study, and its underlying mechanisms were elucidated. The results indicated that CBS improved pulmonary hemodynamic status and alleviated right ventricular dysfunction, improving pulmonary arterial remodeling and right ventricular remodeling, thus enhancing the survival rate of monocrotaline-induced PAH rats. The beneficial effects of CBS treatment on PAH might be mediated through the inhibition of sympathetic overactivation and inflammatory immune signaling pathways.

Circulating acetylcholine serves as a potential biomarker role in pulmonary hypertension

BACKGROUND

An increased acetylcholine (ACh) level in the right ventricle tissue of pulmonary hypertension (PH) was revealed, which indicated the important role of ACh in disease pathogenesis. However, the relationship between plasma ACh levels and disease conditions and patients' prognosis has not been investigated. We aimed to explore the association between plasma ACh levels and the prognosis of patients with PH. We also discussed the feasibility of plasma ACh as a biomarker, which may contribute to the management of PH patients in the future.

METHODS

Patients with confirmed PH in Fuwai Hospital from April 2019 to August 2020 were enrolled. The primary clinical outcome in this study was defined as a composite outcome, including death/lung transplantation, heart failure, and worsening of symptoms. Fasting plasma was collected to detect the ACh levels. The association between ACh levels and patients' prognosis was explored.

RESULTS

Finally, four hundred and eight patients with PH were enrolled and followed for a mean period of 2.5 years. Patients in the high ACh group had worse World Health Organization Functional Class (WHO-FC), lower 6-minute walk distance (6 MWD), and higher N-terminal pro-brain natriuretic peptide (NT-proBNP). Notably, echocardiographic and hemodynamic parameters in the high metabolite group also suggested a worse disease condition compared with the low ACh group. After adjusting for confounders, compared with low ACh patients, those with high metabolite levels still have worse prognoses characterized as elevated risk of mortality, heart failure, and symptoms worsening.

CONCLUSION

High circulating ACh levels were associated with severe PH conditions and poor prognosis, which might serve as a potential biomarker in PH.

Sleep-disordered breathing patterns and prognosis in pulmonary arterial hypertension: A cluster analysis of nocturnal cardiorespiratory signals

BACKGROUND

Sleep-disordered breathing (SDB) is common among pulmonary arterial hypertension (PAH) patients and has been associated with unfavorable outcomes. This study aims to cluster overnight cardiorespiratory signals to investigate PAH phenotypes and examining their prognostic implications.

METHODS

In this retrospective cohort study, we recruited consecutive PAH patients who underwent right heart catheterization and nocturnal cardiorespiratory polygraphy to evaluate SDB. Cluster analysis was employed to classify patients based on their SDB patterns. Cox regression analysis and Kaplan-Meier curves were utilized to assess the association between cluster membership and clinical outcomes. Logistic regression was used to identify risk factors associated with the cluster at higher risk of adverse outcomes.

RESULTS

The study comprised 386 PAH patients, with a mean age of 44.7 ± 17.0 years, of which 46.6 % were male. Three distinct clusters of PAH patients were identified: Cluster 1 (N = 182) presented with minimal SDB, Cluster 2 (N = 125) displayed obstructive sleep apnea (OSA) without significant hypoxemia, and Cluster 3 (N = 79) exhibited predominantly severe hypoxemic burden along with comorbid OSA. Notably, patients in Cluster 3 had an independent association with an increased risk of clinical worsening (hazard ratio 1.96, 95 % confidence interval [CI] 1.08-3.56, P = 0.027) compared to those in Clusters 1, even after adjusting for common confounders. The rate of clinical worsening for PAH-related events and mortality was higher in Cluster 3 than in Clusters 1 and 2 (26.6 % vs. 12.6 % and 19.2 %, respectively, log-rank P = 0.024). Moreover, the left ventricular mass index was identified as an independent risk factor for Cluster 3 (odds ratios 1.01, 95 % CI 1.00-1.02, P = 0.004).

CONCLUSIONS

Patients with PAH who have nocturnal hypoxemia and OSA had worse clinical outcomes compared to those with only minimal SDB. Tailored management strategies that address both PAH and nocturnal hypoxemia may be effective in improving clinical outcomes.

Exploring the involvement of TASK-1 in the control of isolated rat right atrium function from healthy animals and an experimental model of monocrotaline-induced pulmonary hypertension

The TASK-1 channel belongs to the two-pore domain potassium channel family. It is expressed in several cells of the heart, including the right atrial (RA) cardiomyocytes and the sinus node, and TASK-1 channel has been implicated in the pathogenesis of atrial arrhythmias (AA). Thus, using the rat model of monocrotaline-induced pulmonary hypertension (MCT-PH), we explored the involvement of TASK-1 in AA. Four-week-old male Wistar rats were injected with 50 mg/kg of MCT to induce MCT-PH and isolated RA function was studied 14 days later. Additionally, isolated RA from six-week-old male Wistar rats were used to explore the ability of ML365, a selective blocker of TASK-1, to modulate RA function. The hearts developed right atrial and ventricular hypertrophy, inflammatory infiltrate and the surface ECG demonstrated increased P wave duration and QT interval, which are markers of MCT-PH. The isolated RA from the MCT animals showed enhanced chronotropism, faster contraction and relaxation kinetics, and a higher sensibility to extracellular acidification. However, the addition of ML365 to extracellular media was not able to restore the phenotype. Using a burst pacing protocol, the RA from MCT animals were more susceptible to develop AA, and simultaneous administration of carbachol and ML365 enhanced AA, suggesting the involvement of TASK-1 in AA induced by MCT. TASK-1 does not play a key role in the chronotropism and inotropism of healthy and diseased RA; however, it may play a role in AA in the MCT-PH model.

Geranylgeranylacetone reduces cardiomyocyte stiffness and attenuates diastolic dysfunction in a rat model of cardiometabolic syndrome

Titin-dependent stiffening of cardiomyocytes is a significant contributor to left ventricular (LV) diastolic dysfunction in heart failure with preserved LV ejection fraction (HFpEF). Small heat shock proteins (HSPs), such as HSPB5 and HSPB1, protect titin and administration of HSPB5 in vitro lowers cardiomyocyte stiffness in pressure-overload hypertrophy. In humans, oral treatment with geranylgeranylacetone (GGA) increases myocardial HSP expression, but the functional implications are unknown. Our objective was to investigate whether oral GGA treatment lowers cardiomyocyte stiffness and attenuates LV diastolic dysfunction in a rat model of the cardiometabolic syndrome. Twenty-one-week-old male lean (n = 10) and obese (n = 20) ZSF1 rats were studied, and obese rats were randomized to receive GGA (200 mg/kg/day) or vehicle by oral gavage for 4 weeks. Echocardiography and cardiac catheterization were performed before sacrifice at 25 weeks of age. Titin-based stiffness (Fpassive ) was determined by force measurements in relaxing solution with 100 nM [Ca2+ ] in permeabilized cardiomyocytes at sarcomere lengths (SL) ranging from 1.8 to 2.4 μm. In obese ZSF1 rats, GGA reduced isovolumic relaxation time of the LV without affecting blood pressure, EF or LV weight. In cardiomyocytes, GGA increased myofilament-bound HSPB5 and HSPB1 expression. Vehicle-treated obese rats exhibited higher cardiomyocyte stiffness at all SLs compared to lean rats, while GGA reduced stiffness at SL 2.0 μm. In obese ZSF1 rats, oral GGA treatment improves cardiomyocyte stiffness by increasing myofilament-bound HSPB1 and HSPB5. GGA could represent a potential novel therapy for the early stage of diastolic dysfunction in the cardiometabolic syndrome.

Cooling Down Inflammation in the Cardiovascular System via the Nicotinic Acetylcholine Receptor

ABSTRACT

Inflammation is a major player in many cardiovascular diseases including hypertension, atherosclerosis, myocardial infarction, and heart failure. In many individuals, these conditions coexist and mutually exacerbate each other's progression. The pathophysiology of these diseases entails the active involvement of both innate and adaptive immune cells. Immune cells that possess the α7 subunit of the nicotinic acetylcholine receptor on their surface have the potential to be targeted through both pharmacological and electrical stimulation of the cholinergic system. The cholinergic system regulates the inflammatory response to various stressors in different organ systems by systematically suppressing spleen-derived monocytes and chemokines and locally improving immune cell function. Research on the cardiovascular system has demonstrated the potential for atheroma plaque stabilization and regression as favorable outcomes. Smaller infarct size and reduced fibrosis have been associated with improved cardiac function and a decrease in adverse cardiac remodeling. Furthermore, enhanced electrical stability of the myocardium can lead to a reduction in the incidence of ventricular tachyarrhythmia. In addition, improving mitochondrial dysfunction and decreasing oxidative stress can result in less myocardial tissue damage caused by reperfusion injury. Restoring baroreflex activity and reduction in renal damage can promote blood pressure regulation and help counteract hypertension. Thus, the present review highlights the potential of nicotinic acetylcholine receptor activation as a natural approach to alleviate the adverse consequences of inflammation in the cardiovascular system.

Isolated Left Atrium Morphofunctional Study of an Experimental Pulmonary Hypertension Model in Rats

BACKGROUND

The high incidence of atrial arrhythmias in pulmonary hypertension (PH) might be associated with poor prognosis, and the left atrium (LA) may play a role in this. An important finding in PH studies is that LA remodeling is underestimated.

OBJECTIVE

This study investigated LA morphology and mechanical function, as well as the susceptibility to develop arrhythmias in a monocrotaline-induced PH (MCT-PH) model.

METHODS

Wistar rats aged 4 weeks received 50 mg/kg of MCT. Electrocardiography and histology analysis were performed to evaluate the establishment of the MCT-PH model. The tissue was mounted in an isolated organ bath to characterize the LA mechanical function.

RESULTS

Compared with the control group (CTRL), the MCT-PH model presented LA hypertrophy and changes in cardiac electrical activity, as evidenced by increased P wave duration, PR and QT interval in MCT-PH rats. In LA isolated from MCT-PH rats, no alteration in inotropism was observed; however, the time to peak contraction was delayed in the experimental MCT-PH group. Finally, there was no difference in arrhythmia susceptibility of LA from MCT-PH animals after the burst pacing protocol.

CONCLUSION

The morphofunctional remodeling of the LA did not lead to increased susceptibility to ex vivo arrhythmia after application of the burst pacing protocol.

Pathophysiology of the right ventricle in health and disease: an update

The contribution of the right ventricle (RV) to cardiac output is negligible in normal resting conditions when pressures in the pulmonary circulation are low. However, the RV becomes relevant in healthy subjects during exercise and definitely so in patients with increased pulmonary artery pressures both at rest and during exercise. The adaptation of RV function to loading rests basically on an increased contractility. This is assessed by RV end-systolic elastance (Ees) to match afterload assessed by arterial elastance (Ea). The system has reserve as the Ees/Ea ratio or its imaging surrogate ejection fraction has to decrease by more than half, before the RV undergoes an increase in dimensions with eventual increase in filling pressures and systemic congestion. RV-arterial uncoupling is accompanied by an increase in diastolic elastance. Measurements of RV systolic function but also of diastolic function predict outcome in any cause pulmonary hypertension and heart failure with or without preserved left ventricular ejection fraction. Pathobiological changes in the overloaded RV include a combination of myocardial fibre hypertrophy, fibrosis and capillary rarefaction, a titin phosphorylation-related displacement of myofibril tension-length relationships to higher pressures, a metabolic shift from mitochondrial free fatty acid oxidation to cytoplasmic glycolysis, toxic lipid accumulation, and activation of apoptotic and inflammatory signalling pathways. Treatment of RV failure rests on the relief of excessive loading.

Continuous long-term heart rate variability and risk assessment in pulmonary hypertension

OBJECTIVE

Current multimodal risk assessment for pulmonary hypertension (PH) has been redefined with a simplified assessment for follow-up in the new European Society of Cardiology/European Respiratory Society (ESC/ERS) guidelines. Follow-up risk assessment parameters include WHO functional class, 6 min walk test and N-terminal pro-brain natriuretic peptide. Although these parameters have prognostic implications assessment reflect data relating to specific time points.

METHODS

Patients diagnosed with PH received an implantable loop recorder (ILR) to monitor daytime and night-time heart rate (HR), HR variability (HRV) and daily physical activity. Associations between the ILR measurements and established risk parameters were analysed using correlations, linear mixed models as well as logistical mixed models for addressing the ESC/ERS risk-score.

RESULTS

41 patients (median age: 56 years, range: 44-61.5 years) were included. Continuous monitoring had a median duration of 755 days (range: 343-1138 days), totalling 96 patient-years. In the linear mixed models, HRV and physical activity indexed by daytime HR (PAiHR) were significantly associated with the ERS/ERC risk parameters. In a logistical mixed model, HRV revealed a significant difference between 1-year mortality (<5% vs >5%) (p=0.027) with an OR of 0.82 for being in the group with 1-year mortality >5% for every increase by one HRV unit.

CONCLUSIONS

Risk assessment in PH can be refined with continuous monitoring of HRV and PAiHR. These markers were associated with the ESC/ERC parameters. Our study with continuous risk stratification in PH demonstrated that a lower HRV predict worse prognosis.

Sympathetic Denervation and Pharmacological Stimulation of Parasympathetic Nervous System Prevent Pulmonary Vascular Bed Remodeling in Rat Model of Chronic Thromboembolic Pulmonary Hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) develops in 1.5-2.0% of patients experiencing pulmonary embolism (PE) and is characterized by stable pulmonary artery obstruction, heart failure, and poor prognosis. Little is known about involvement of autonomic nervous system (ANS) in the mechanisms of CTEPH. This study was aimed at evaluation of the effect of vagal and sympathetic denervation, as well as stimulation of the parasympathetic nervous system, on the outcomes of CTEPH in rats. CTEPH was induced by multiple intravenous injections of alginate microspheres. Sympathetic and vagal denervation was performed using unilateral surgical ablation of the stellate ganglion and vagotomy, respectively. Stimulation of the parasympathetic nervous system was carried out by administering pyridostigmine. The effect of neuromodulatory effects was assessed in terms of hemodynamics, histology, and gene expression. The results demonstrated the key role of ANS in the development of CTEPH. Sympathetic denervation as well as parasympathetic stimulation resulted in attenuated pulmonary vascular remodeling. These salutary changes were associated with altered MMP2 and TIMP1 expression in the lung and decreased FGFb level in the blood. Unilateral vagotomy had no effect on physiological and morphological outcomes of the study. The data obtained contribute to the identification of new therapeutic targets for CTEPH treatment.

Computational modelling of multi-temporal ventricular-vascular interactions during the progression of pulmonary arterial hypertension

A computational framework is developed to consider the concurrent growth and remodelling (G&R) processes occurring in the large pulmonary artery (PA) and right ventricle (RV), as well as ventricular-vascular interactions during the progression of pulmonary arterial hypertension (PAH). This computational framework couples the RV and the proximal PA in a closed-loop circulatory system that operates in a short timescale of a cardiac cycle, and evolves over a long timescale due to G&R processes in the PA and RV. The framework predicts changes in haemodynamics (e.g. 68.2% increase in mean PA pressure), RV geometry (e.g. 38% increase in RV end-diastolic volume) and PA tissue microstructure (e.g. 90% increase in collagen mass) that are consistent with clinical and experimental measurements of PAH. The framework also predicts that a reduction in RV contractility is associated with long-term RV chamber dilation, a common biomarker observed in the late-stage PAH. Sensitivity analyses on the G&R rate constants show that large PA stiffening (both short and long term) is affected by RV remodelling more than the reverse. This framework can serve as a foundation for the future development of a more predictive and comprehensive cardiovascular G&R model with realistic heart and vascular geometries.

Vagal nerve stimulation preserves right ventricular function in a rat model of right ventricular pressure overload

Vagal nerve stimulation (VNS) ameliorates pulmonary vascular remodeling and improves survival in a rat model of pulmonary hypertension (PH). However, the direct impact of VNS on right ventricular (RV) function, which is the key predictor of PH patients, remains unknown. We evaluated the effect of VNS among the three groups: pulmonary artery banding (PAB) with sham stimulation (SS), PAB with VNS, and control (no PAB). We stimulated the right cervical vagal nerve with an implantable pulse generator, initiated VNS 2 weeks after PAB, and stimulated for 2 weeks. Compared to SS, VNS increased cardiac index (VNS: 130 ± 10 vs. SS: 93 ± 7 ml/min/kg; p < 0.05) and end-systolic elastance assessed by RV pressure-volume analysis (VNS: 1.1 ± 0.1 vs. SS: 0.7 ± 0.1 mmHg/μl; p < 0.01), but decreased RV end-diastolic pressure (VNS: 4.5 ± 0.7 vs. SS: 7.7 ± 1.0 mmHg; p < 0.05). Furthermore, VNS significantly attenuated RV fibrosis and CD68-positive cell migration. In PAB rats, VNS improved RV function, and attenuated fibrosis, and migration of inflammatory cells. These results provide a rationale for VNS therapy as a novel approach for RV dysfunction in PH patients.

Enhancement of airway ciliary beating mediated via voltage-gated Ca2+ channels/α7-nicotinic receptors in mice

Acetylcholine (ACh), which activates muscarinic ACh receptors (mAChRs) and nicotinic ACh receptors (nAChRs), enhances airway ciliary beating by increasing the intracellular Ca²⁺ concentration ([Ca²⁺]_i). The mechanisms enhancing airway ciliary beating by nAChRs have remained largely unknown, although those by mAChRs are well understood. In this study, we focused on the effects of α7-nAChRs and voltage-gated Ca²⁺ channels (Ca_Vs) on the airway ciliary beating. The activities of ciliary beating were assessed by frequency (CBF, ciliary beat frequency) and amplitude (CBD, ciliary bend distance) measured by high-speed video microscopy. ACh enhanced CBF and CBD by 25% mediated by an [Ca²⁺]_i increase stimulated by mAChRs and α7-nAChRs (a subunit of nAChR) in airway ciliary cells of mice. Experiments using PNU282987 (an agonist of α7-nAChR) and MLA (an inhibitor of α7-nAChR) revealed that CBF and CBD enhanced by α7-nAChR are approximately 50% of those enhanced by ACh. CBF, CBD, and [Ca²⁺]_i enhanced by α7-nAChRs were inhibited by nifedipine, suggesting activation of Ca_Vs by α7-nAChRs. Experiments using a high K⁺ solution with/without nifedipine (155.5 mM K⁺) showed that the activation of Ca_Vs enhances CBF and CBD via an [Ca²⁺]_i increase. Immunofluorescence and immunoblotting studies demonstrated that Cav1.2 and α7-nAChR are expressed in airway cilia. Moreover, IL-13 stimulated MLA-sensitive increases in CBF and CBD in airway ciliary cells, suggesting an autocrine regulation of ciliary beating by Ca_V1.2/α7-nAChR/ACh. In conclusion, a novel Ca²⁺ signalling pathway in airway cilia, Ca_V1.2/α7-nAChR, enhances CBF and CBD and activates mucociliary clearance maintaining healthy airways.

Alpha7 nicotinic acetylcholine receptor mediates chronic nicotine inhalation-induced cardiopulmonary dysfunction

Cigarette smoking remains the leading modifiable risk factor for cardiopulmonary diseases; however, the effects of nicotine alone on cardiopulmonary function remain largely unknown. Previously, we have shown that chronic nicotine vapor inhalation in mice leads to the development of pulmonary hypertension (PH) with right ventricular (RV) remodeling. The present study aims to further examine the cardiopulmonary effects of nicotine and the role of the α7 nicotinic acetylcholine receptor (α7-nAChR), which is widely expressed in the cardiovascular system. Wild-type (WT) and α7-nAChR knockout (α7-nAChR-/-) mice were exposed to room air (control) or nicotine vapor daily for 12 weeks. Consistent with our previous study, echocardiography and RV catheterization reveal that male WT mice developed increased RV systolic pressure with RV hypertrophy and dilatation following 12-week nicotine vapor exposure; in contrast, these changes were not observed in male α7-nAChR-/- mice. In addition, chronic nicotine inhalation failed to induce PH and RV remodeling in female mice regardless of genotype. The effects of nicotine on the vasculature were further examined in male mice. Our results show that chronic nicotine inhalation led to impaired acetylcholine-mediated vasodilatory response in both thoracic aortas and pulmonary arteries, and these effects were accompanied by altered endothelial nitric oxide synthase phosphorylation (enhanced inhibitory phosphorylation at threonine 495) and reduced plasma nitrite levels in WT but not α7-nAChR-/- mice. Finally, RNA sequencing revealed up-regulation of multiple inflammatory pathways in thoracic aortas from WT but not α7-nAChR-/- mice. We conclude that the α7-nAChR mediates chronic nicotine inhalation-induced PH, RV remodeling and vascular dysfunction.

Heart rate recovery in 1 minute after the 6-minute walk test predicts adverse outcomes in pulmonary arterial hypertension

Heart rate recovery in 1 minute (HRR1) after the end of the 6-minute walk test (6MWT) is a non-invasive method of determining autonomic dysfunction. This parameter remains largely unexplored in pulmonary arterial hypertension (PAH) registries. We aimed to define the cut-off value and accuracy for abnormal HRR1 after the 6MWT and to investigate the association between HRR1 and clinical worsening in patients with PAH. This composite outcome was defined as first occurrence of all-cause death OR hospitalization from any cause OR disease progression characterized by decreased ≥ 15% in six-minute walking distance from baseline AND start of new specific PAH treatment or persistent worsening of World Health Organization functional class (WHO-FC). We performed a prospective cohort study that included 102 consecutive patients with PAH confirmed by right heart catheterization that underwent an 6MWT upon the diagnosis, recruited from September 2004 to April 2020 and followed up until April 2021 or death. The median HRR1 was 18 beats (IQR: 10–22), 50 and 52 PAH patients with <18 beats and ≥18 beats, respectively. The best cut-off for HRR1 to discriminate clinical worsening was 17 beats, with area under the curve (AUC) of 0.704 (95%CI: 0.584–0.824). The internal validation model by bootstrap showed an AUC of 0.676 (95%CI: 0.566–0.786) and the most accurate value was obtained in the seventh year of follow-up (AUC = 0.711; 95%CI: 0.596–0.844). Patients with an HRR1 <18 beats at baseline had a median event-free time of 2.17 years (95%CI: 1.82 to 2.52) versus 4.75 years (95%CI: 1.43 to 8.07) from those with ≥18 beats. In conclusion, a HRR1 value of less than 18 beats may be a reliable indicator of poor prognosis in patients with PAH.

Research Opportunities in Autonomic Neural Mechanisms of Cardiopulmonary Regulation: A Report From the National Heart, Lung, and Blood Institute and the National Institutes of Health Office of the Director Workshop

This virtual workshop was convened by the National Heart, Lung, and Blood Institute, in partnership with the Office of Strategic Coordination of the Office of the National Institutes of Health Director, and held September 2 to 3, 2020. The intent was to assemble a multidisciplinary group of experts in basic, translational, and clinical research in neuroscience and cardiopulmonary disorders to identify knowledge gaps, guide future research efforts, and foster multidisciplinary collaborations pertaining to autonomic neural mechanisms of cardiopulmonary regulation. The group critically evaluated the current state of knowledge of the roles that the autonomic nervous system plays in regulation of cardiopulmonary function in health and in pathophysiology of arrhythmias, heart failure, sleep and circadian dysfunction, and breathing disorders. Opportunities to leverage the Common Fund's SPARC (Stimulating Peripheral Activity to Relieve Conditions) program were characterized as related to nonpharmacologic neuromodulation and device-based therapies. Common themes discussed include knowledge gaps, research priorities, and approaches to develop novel predictive markers of autonomic dysfunction. Approaches to precisely target neural pathophysiological mechanisms to herald new therapies for arrhythmias, heart failure, sleep and circadian rhythm physiology, and breathing disorders were also detailed.

Heart-Rate Recovery at 1 Min After Exercise Predicts Response to Balloon Pulmonary Angioplasty in Patients With Inoperable Chronic Thromboembolic Pulmonary Hypertension

Background

Dysfunction of autonomic nervous system plays an important role in the development of pulmonary hypertension. The present study aimed to investigate the interaction between balloon pulmonary angioplasty (BPA) and cardiac autonomic function by using heart-rate recovery at 1 min (HRR1) after exercise as a surrogate marker.

Methods and Results

We retrospectively enrolled 89 consecutive patients with inoperable chronic thromboembolic pulmonary hypertension who underwent BPA from May, 2018 to Jan, 2021. According to hemodynamics at follow-up, patients were categorized as BPA responders if they met one or both of the following criteria: (1) mean pulmonary arterial pressure ≤ 30 mmHg and (2) a reduction of pulmonary vascular resistance ≥ 30%. Compared with baseline, HRR1 tended to increase within 7 days after the first BPA session, and this improvement persisted at follow-up. HRR1 at baseline and at follow-up were associated with well-validated markers of CTEPH severity, including N-terminal pro-brain natriuretic peptide, mean pulmonary arterial pressure and pulmonary vascular resistance. Furthermore, the change of HRR1 from baseline to follow-up was also associated with the change of those variables. After adjustment for confounders, baseline HRR1 was still a strong independent predictor of BPA outcome. Receiver operator characteristic curve analysis showed that the cutoff value for HRR1 in predicting BPA outcome was 19 beats.

Conclusions

BPA could significantly improve HRR1, suggesting the alleviation of sympathovagal imbalance. Easily available and non-invasive HRR1 seems to be a useful tool in predicting outcome of BPA and dynamically monitoring the efficacy of BPA.

A Meta-analysis of the efficacy of pulmonary artery denervation in the treatment of pulmonary hypertension

BACKGROUND

Pulmonary hypertension (pH) is a progressive and fatal disease with poor long-term prognosis and high mortality. Although great progress has been made in current treatment methods, the survival rate is still poor. Therefore, we need to find an effective treatment for pH.

OBJECTIVE

pH is a type of refractory, progressive, and fatal pulmonary vascular disease which involves a variety of clinical conditions and may complicate most cardiovascular and respiratory diseases. Pulmonary artery denervation (PADN) therapy for pH has become the current trend, but its clinical application still faces a series of problems, and its efficacy remains controversial. The purpose of the study is to evaluate the literature on the effects of PADN for pH.

METHOD

The PubMed, Embase, and Web of Science databases were searched by two researchers until April 9th, 2021. The literature was read and screened, and effective data(6-minute walking distance, cardiac output, mPAP, PVR,Left ventricular end-systolic diameter,Cardiac output,Readmission rate,Mortality,Cardiac function,and so on) was extracted, collated, and analyzed. The literature was managed by Endnote 9.3 software and evaluated by RevMan 5.3 software.

RESULTS

The meta-analysis included five controlled experiments with a total of 339 patients. The literature quality evaluations were all Level B. The meta-analysis results showed that compared with the control group, PADN treatment could improve the 6-minute walking distance of pH patients [WMD = 103.72, 95%CI (49.63, 157.82), P < 0.05], reduce mean pulmonary artery pressure (mPAP) [WMD = -7.26, 95%CI (-10.86, -3.66), P < 0.05], reduce pulmonary vascular resistance (PVR) [WMD = -4.53, 95%CI (-8.23, -0.83), P < 0.05], and improve cardiac output [WMD = 0.48, 95%CI (0.23, 0.73), P < 0.05]. There was no significant effect on the left ventricular end-systolic diameter [WMD = -0.13, 95%CI (-0.49, 0.24), P > 0.05], readmission rate [OR = 0.14, 95%CI (0.01, 1.87), P > 0.05], mortality rate [OR = 0.77, 95%CI (0.22, 2.69), P > 0.05], or cardiac function [OR = 0.32, 95%CI (0.05, 2.10), P > 0.05].

CONCLUSION

PADN is an effective method for the treatment of pH which is worthy of clinical promotion.

Increased Lung Uric Acid Deteriorates Pulmonary Arterial Hypertension

Background

Recent studies have demonstrated that uric acid (UA) enhances arginase activity, resulting in decreased NO in endothelial cells. However, the role of lung UA in pulmonary arterial hypertension (PAH) remains uncertain. We hypothesized that increased lung UA level contributes to the progression of PAH.

Methods and Results

In cultured human pulmonary arterial endothelial cells, voltage‐driven urate transporter 1 (URATv1) gene expression was detected, and treatment with UA increased arginase activity. In perfused lung preparations of VEGF receptor blocker (SU5416)/hypoxia/normoxia‐induced PAH model rats, addition of UA induced a greater pressure response than that seen in the control and decreased lung cGMP level. UA‐induced pressor responses were abolished by benzbromarone, a UA transporter inhibitor, or L‐norvaline, an arginase inhibitor. In PAH model rats, induction of hyperuricemia by administering 2% oxonic acid significantly increased lung UA level and induced greater elevation of right ventricular systolic pressure with exacerbation of occlusive neointimal lesions in small pulmonary arteries, compared with nonhyperuricemic PAH rats. Administration of benzbromarone to hyperuricemic PAH rats significantly reduced lung UA levels without changing XOR (xanthine oxidoreductase) activity, and attenuated right ventricular systolic pressure increase and occlusive lesion development. Topiroxostat, a XOR inhibitor, significantly reduced lung XOR activity in PAH rats, with no effects on increase in right ventricular systolic pressure, arterial elastance, and occlusive lesions. XOR‐knockout had no effects on right ventricular systolic pressure increase and arteriolar muscularization in hypoxia‐exposed mice.

Conclusions

Increased lung UA per se deteriorated PAH, whereas XOR had little impact. The mechanism of increased lung UA may be a novel therapeutic target for PAH complicated with hyperuricemia.

Acetylcholinesterase inhibition with Pyridostigmine attenuates hypertension and neuroinflammation in the paraventricular nucleus in rat model for Preeclampsia

Preeclampsia (PE) is characterized by hypertension, autonomic imbalance and inflammation. The subfornical organ (SFO) reportedly relays peripheral inflammatory mediator's signals to the paraventricular nucleus (PVN), a brain autonomic center shown to mediate hypertension in hypertensive rat but not yet in PE rat models. Additionally, we previously showed that Pyridostigmine (PYR), an acetylcholinesterase inhibitor, attenuated placental inflammation and hypertension in PE models. In this study, we investigated the effect of PYR on the activities of these brain regions in PE model. PYR (20 mg/kg/day) was administered to reduced uterine perfusion pressure (RUPP) Sprague-Dawley rat from gestational day (GD) 14 to GD19. On GD19, the mean arterial pressure (MAP) was recorded and samples were collected for analysis. RUPP rats exhibited increased MAP (P = 0.0025), elevated circulating tumor necrosis factor-α (TNF-α, P = 0.0075), reduced baroreflex sensitivity (BRS), increased neuroinflammatory markers including TNF-α, interleukin-1β (IL-1β), microglial activation (P = 0.0039), oxidative stress and neuronal excitation within the PVN and the SFO. Changes in MAP, in molecular and cellular expression induced by RUPP intervention were improved by PYR. The ability of PYR to attenuate TNF-α mediated central effect was evaluated in TNF-α-infused pregnant rats. TNF-α infusion-promoted neuroinflammation in the PVN and SFO in dams was abolished by PYR. Collectively, our data suggest that PYR improves PE-like symptoms in rat by dampening placental ischemia and TNF-α-promoted inflammation and pro-hypertensive activity in the PVN. This broadens the therapeutical potential of PYR in PE.

Mechanisms, Pathophysiology and Currently Proposed Treatments of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is one of the leading global causes of morbidity and mortality. A hallmark of COPD is progressive airflow obstruction primarily caused by cigarette smoke (CS). CS exposure causes an imbalance favoring pro- over antioxidants (oxidative stress), leading to transcription factor activation and increased expression of inflammatory mediators and proteases. Different cell types, including macrophages, epithelial cells, neutrophils, and T lymphocytes, contribute to COPD pathophysiology. Alteration in cell functions results in the generation of an oxidative and inflammatory microenvironment, which contributes to disease progression. Current treatments include inhaled corticosteroids and bronchodilator therapy. However, these therapies do not effectively halt disease progression. Due to the complexity of its pathophysiology, and the risk of exacerbating symptoms with existing therapies, other specific and effective treatment options are required. Therapies directly or indirectly targeting the oxidative imbalance may be promising alternatives. This review briefly discusses COPD pathophysiology, and provides an update on the development and clinical testing of novel COPD treatments.

Pyridostigmine ameliorates preeclamptic features in pregnant rats by inhibiting tumour necrosis factor-α synthetsis and antagonizing tumour necrosis factor-α-related effects

OBJECTIVE

Preeclampsia is a hypertensive disorder of pregnancy marked by an excessive inflammatory response. The anti-inflammatory effect of pyridostigmine (PYR) was previously reported; however, its role in hypertensive pregnancies remains unclear. We hypothesized that PYR could attenuate increased blood pressure and other pathological features in preeclampsia models.

METHODS

The expression of tumour necrosis factor (TNF)-α was evaluated in normal and preeclampsia pregnant women. PYR (20 mg/kg) was administered daily to reduced uterine perfusion pressure (RUPP) and TNF-α (150 ng/day) infused rats from gestation day 14 to GD19. In a cell culture experiment, the effect of acetylcholine (ACh) on TNF-α-stimulated primary human umbilical endothelial cells (HUVEC) was assessed.

RESULTS

Preeclampsia women had higher placental TNF-α expression than normal pregnant women. Mean arterial pressure (MAP) in the RUPP group was higher than in the Sham group. PYR inhibited serum and placental acetylcholinesterase activity in rats, and reduced MAP, placental oxidative stress, apoptosis and inflammation in the RUPP group but not in the Sham group. In addition, PYR significantly attenuated the TNF-α-induced increase in MAP, placental oxidative stress and apoptosis. Moreover, TNF-α decreased cell viability and increased the number of TUNEL-positive nuclei of HUVEC, which could largely be abolished by ACh treatment.

CONCLUSION

Collectively, PYR ameliorated hypertension and other preeclampsia-like symptoms in rat models of preeclampsia not only by inhibiting the synthesis of TNF-α but also by acting against TNF-α-induced detrimental effects directly, which is worthy of further investigation and may be used as a potential agent for preeclampsia management.

Promising therapeutic approaches in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a debilitating multifactorial disease characterized by progressive pulmonary vascular remodeling, elevated pulmonary arterial pressure, and pulmonary vascular resistance, resulting in right ventricular failure and subsequent death. Current available therapies do not reverse the disease, resulting in a persistent high morbidity and mortality. Thus, there is an urgent unmet medical need for novel effective therapies to better treat patients with PAH. Over the past few years, enthusiastic attempts have been made to identify novel effective therapies that address the essential roots of PAH with targeting key signaling pathways in both preclinical models and patients with PAH. This review aims to discuss the most emerging and promising therapeutic interventions in PAH pathogenesis.

α7 Nicotinic acetylcholine receptor mediates right ventricular fibrosis and diastolic dysfunction in pulmonary hypertension

Right ventricular (RV) fibrosis is a key feature of maladaptive RV hypertrophy and dysfunction and is associated with poor outcomes in pulmonary hypertension (PH). However, mechanisms and therapeutic strategies to mitigate RV fibrosis remain unrealized. Previously, we identified that cardiac fibroblast α7 nicotinic acetylcholine receptor (α7 nAChR) drives smoking-induced RV fibrosis. Here, we sought to define the role of α7 nAChR in RV dysfunction and fibrosis in the settings of RV pressure overload as seen in PH. We show that RV tissue from PH patients has increased collagen content and ACh expression. Using an experimental rat model of PH, we demonstrate that RV fibrosis and dysfunction are associated with increases in ACh and α7 nAChR expression in the RV but not in the left ventricle (LV). In vitro studies show that α7 nAChR activation leads to an increase in adult ventricular fibroblast proliferation and collagen content mediated by a Ca2+/epidermal growth factor receptor (EGFR) signaling mechanism. Pharmacological antagonism of nAChR decreases RV collagen content and improves RV function in the PH model. Furthermore, mice lacking α7 nAChR exhibit improved RV diastolic function and have lower RV collagen content in response to persistently increased RV afterload, compared with WT controls. These finding indicate that enhanced α7 nAChR signaling is an important mechanism underlying RV fibrosis and dysfunction, and targeted inhibition of α7 nAChR is a potentially novel therapeutic strategy in the setting of increased RV afterload.

Acetazolamide Improves Right Ventricular Function and Metabolic Gene Dysregulation in Experimental Pulmonary Arterial Hypertension

Background: Right ventricular (RV) performance is a key determinant of mortality in pulmonary arterial hypertension (PAH). RV failure is characterized by metabolic dysregulation with unbalanced anaerobic glycolysis, oxidative phosphorylation, and fatty acid oxidation (FAO). We previously found that acetazolamide (ACTZ) treatment modulates the pulmonary inflammatory response and ameliorates experimental PAH.

Objective: To evaluate the effect of ACTZ treatment on RV function and metabolic profile in experimental PAH.

Design/Methods: In the Sugen 5416/hypoxia (SuHx) rat model of severe PAH, RV transcriptomic analysis was performed by RNA-seq, and top metabolic targets were validated by RT-PCR. We assessed the effect of therapeutic administration of ACTZ in the drinking water on hemodynamics by catheterization [right and left ventricular systolic pressure (RVSP and LVSP, respectively)] and echocardiography [pulmonary artery acceleration time (PAAT), RV wall thickness in diastole (RVWT), RV end-diastolic diameter (RVEDD), tricuspid annular plane systolic excursion (TAPSE)] and on RV hypertrophy (RVH) by Fulton's index (FI) and RV-to-body weight (BW) ratio (RV/BW). We also examined myocardial histopathology and expression of metabolic markers in RV tissues.

Results: There was a distinct transcriptomic signature of RVH in the SuHx model of PAH, with significant downregulation of metabolic enzymes involved in fatty acid transport, beta oxidation, and glucose oxidation compared to controls. Treatment with ACTZ led to a pattern of gene expression suggestive of restored metabolic balance in the RV with significantly increased beta oxidation transcripts. In addition, the FAO transcription factor peroxisome proliferator-activated receptor gamma coactivator 1-alpha (Pgc-1α) was significantly downregulated in untreated SuHx rats compared to controls, and ACTZ treatment restored its expression levels. These metabolic changes were associated with amelioration of the hemodynamic and echocardiographic markers of RVH in the ACTZ-treated SuHx animals and attenuation of cardiomyocyte hypertrophy and RV fibrosis.

Conclusion: Acetazolamide treatment prevents the development of PAH, RVH, and fibrosis in the SuHx rat model of severe PAH, improves RV function, and restores the RV metabolic profile.

Effects of nasal high flow on sympathovagal balance, sleep, and sleep-related breathing in patients with precapillary pulmonary hypertension

BACKGROUND

In precapillary pulmonary hypertension (PH), nasal high flow therapy (NHF) may favorably alter sympathovagal balance (SVB) and sleep-related breathing through washout of anatomical dead space and alleviation of obstructive sleep apnea (OSA) due to generation of positive airway pressure.

OBJECTIVES

To investigate the effects of NHF on SVB, sleep, and OSA in patients with PH, and compare them with those of positive airway pressure therapy (PAP).

METHODS

Twelve patients with PH (Nice class I or IV) and confirmed OSA underwent full polysomnography, and noninvasive monitoring of SVB parameters (spectral analysis of heart rate, diastolic blood pressure variability). Study nights were randomly split into four 2-h segments with no treatment, PAP, NHF 20 L/min, or NHF 50 L/min. In-depth SVB analysis was conducted on 10-min epochs during daytime and stable N2 sleep at nighttime.

RESULTS

At daytime and compared with no treatment, NHF20 and NHF50 were associated with a flow-dependent increase in peripheral oxygen saturation but a shift in SVB towards increased sympathetic drive. At nighttime, NHF20 was associated with increased parasympathetic drive and improvements in sleep efficiency, but did not alter OSA severity. NHF50 was poorly tolerated. PAP therapy improved OSA but had heterogenous effects on SVB and neutral effects on sleep outcomes. Hemodynamic effects were neutral for all interventions.

CONCLUSIONS

In sleeping PH patients with OSA NHF20 but not NHF50 leads to decreased sympathetic drive likely due to washout of anatomical dead space. NHF was not effective in lowering the apnea-hypopnoea index and NHF50 was poorly tolerated.

The Cholinergic Drug Pyridostigmine Alleviates Inflammation During LPS-Induced Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a critical illness complication that is associated with high mortality. ARDS is documented in severe cases of COVID-19. No effective pharmacological treatments for ARDS are currently available. Dysfunctional immune responses and pulmonary and systemic inflammation are characteristic features of ARDS pathogenesis. Recent advances in our understanding of the regulation of inflammation point to an important role of the vagus-nerve-mediated inflammatory reflex and neural cholinergic signaling. We examined whether pharmacological cholinergic activation using a clinically approved (for myasthenia gravis) cholinergic drug, the acetylcholinesterase inhibitor pyridostigmine alters pulmonary and systemic inflammation in mice with lipopolysaccharide (LPS)-induced ARDS. Male C57Bl/6 mice received one intratracheal instillation of LPS or were sham manipulated (control). Both groups were treated with either vehicle or pyridostigmine (1.5 mg/kg twice daily, 3 mg/day) administered by oral gavage starting at 1 h post-LPS and euthanized 24 h after LPS administration. Other groups were either sham manipulated or received LPS for 3 days and were treated with vehicle or pyridostigmine and euthanized at 72 h. Pyridostigmine treatment reduced the increased total number of cells and neutrophils in the bronchoalveolar lavage fluid (BALF) in mice with ARDS at 24 and 72 h. Pyridostigmine also reduced the number of macrophages and lymphocytes at 72 h. In addition, pyridostigmine suppressed the levels of TNF, IL-1β, IL-6, and IFN-γ in BALF and plasma at 24 and 72 h. However, this cholinergic agent did not significantly altered BALF and plasma levels of the anti-inflammatory cytokine IL-10. Neither LPS nor pyridostigmine affected BALF IFN-γ and IL-10 levels at 24 h post-LPS. In conclusion, treatments with the cholinergic agent pyridostigmine ameliorate pulmonary and systemic inflammatory responses in mice with endotoxin-induced ARDS. Considering that pyridostigmine is a clinically approved drug, these findings are of substantial interest for implementing pyridostigmine in therapeutic strategies for ARDS.

Differences in the microcirculation disturbance in the right and left ventricles of neonatal rats with hypoxic pulmonary hypertension

Microcirculation disturbance is a crucial pathological basis of heart damage; however, microcirculation alterations induced by hypoxic pulmonary hypertension (HPH) remain unknown, and the left ventricle (LV) in HPH is conventionally ignored. Herein, we investigated the changes in the cardiac structure, function and microcirculation after HPH and further compared the differences between the right ventricle (RV) and LV. Using a neonatal rat model of HPH, we found RV myocardial hypertrophy, dysfunction and poor myocardial perfusion in HPH rats. Additionally, RV microcirculation disturbance manifested as the abnormal expression of endothelin-1/eNOS and increased expression of intercellular cell adhesion molecule-1 (ICAM-1) or E-selectin 3 days after hypoxia, followed by vascular inflammation, coronary arterial remodeling and microvascular sparseness. Impairment in LV vasodilation was detected in rats after 3 days of hypoxia; however, no obvious microvascular rarefaction or inflammatory reaction was observed in the LV. In conclusion, our results suggest that HPH mainly triggers RV microcirculation disturbances, causing low myocardial perfusion damage and cardiac dysfunction. Despite the differences in the RV and LV, their impaired microvascular function, mediated by endothelial cells, occurs almost simultaneously after HPH, earlier than cardiac functional or structural abnormalities.

Assessment of cardiac arrhythmias using long-term continuous monitoring in patients with pulmonary hypertension

BACKGROUND

Cardiac arrhythmias are considered a prominent phenomenon in patients with pulmonary hypertension (PH). Older studies reported that 8% to 35% of patients with PH had supraventricular tachycardia (SVT), associated with adverse outcomes. Still, these arrhythmias have only been investigated via short-term monitoring or limited electrocardiogram recordings.

METHODS

Patients without previous arrhythmias diagnosed with PH at a tertiary facility received an insertable cardiac monitor as part of a prospective cohort study. Baseline assessments included World Health Organization functional class, six-minute walk test, echocardiography, and cardiac magnetic resonance imaging.

RESULTS

Thirty-four patients with PH were included. Twenty-four patients had pulmonary arterial hypertension (PAH) and 10 had chronic thromboembolic PH (CTEPH). During 46 patient-years of continuous monitoring (median: 594 (range: 334-654) days per patient), 70 arrhythmia episodes were recorded in 13 patients (38%), with a median of two (range: 1-3) episodes and an arrhythmic burden median of 1.6 (range: 0.1-228) minutes per patient. SVTs were the most common arrhythmias, with 16% of episodes being atrial fibrillation and 84% being other types of SVTs. Additionally, three patients experienced bradycardias, including one resulting in syncope and subsequent pacemaker implantation. None of the patients had sustained ventricular arrhythmias.

CONCLUSIONS

Arrhythmias were seen in 38% of contemporary patients with PH during long-term continuous monitoring; however, the vast majority of episodes were short and self-limiting. Modern therapy may alleviate the development of arrhythmias in stable patients with PH. This study is the first study to deploy long-term continuous monitoring in patients with PH.