Development of pulmonary hypertension remains a major hurdle to corrective surgery in Down syndrome

Down syndrome is the most common chromosomal abnormality encountered in clinical practice with 50%of them having associated congenital heart disease(CHD).Shunt lesions account for around 75%of all CHDs in Down syndrome.Down syndrome patients,especially with large shunts are particularly predisposed to early development of severe pulmonary hypertension(PH)compared with shunt lesions in general population.This necessitates timely surgical correction which remains the only viable option to prevent long term morbidity and mortality.However,despite clear recommendations,there is wide gap between actual practice and fear of underlying PH which often leads to surgical refusals in Down syndrome even when the shunt is reversible.Another peculiarity is that Down syndrome patients can develop PH even after successful correction of shunt.It is not uncommon to come across Down syndrome patients with uncorrected shunts in adulthood with irreversible PH at which stage intracardiac repair is contraindicated and the only option available is a combined heartlung transplant.However,despite the guidelines laid by authorities,the rates of cardiac transplant in adult Down syndrome remain dismal largely attributable to the high prevalence of intellectual disability in them.The index case presents a real-world scenario highlighting the impact of severe PH on treatment strategies and discrimination driven by the fear of worse outcomes in these patients.

Risk Stratification and Prognosis of Pulmonary Arterial Hypertension Associated with Congenital Heart Disease

Background:Current guidelines for managing pulmonary arterial hypertension(PAH)recommend a risk strati-fication approach.However,the applicability and accuracy of these strategies for PAH associated with congenital heart disease(PAH-CHD)require further validation.This study aims to validate the reliability and predictive accuracy of a simplified stratification strategy for PAH-CHD patients over a three-year follow-up.Additionally,new prognostic variables are identified and novel risk stratification methods are developed for assessing and managing PAH-CHD patients.Methods:This retrospective study included 126 PAH-CHD patients.Clinical and biochemical variables across risk groups were assessed using Kruskal-Wallis and Fisher’s exact tests.Indepen-dent risk factors were identified using ordered logistic regression,while Kaplan-Meier and Cox proportional hazards regression analyses evaluated their impact on all-cause mortality.A new stratification model for the PAH-CHD population was constructed based on these analyses.Results:Significant survival differences across stratified risk groups were observed(p<0.001),validating the effectiveness of the simplified risk stratification method in PAH-CHD patients.Prothrombin activity was a strong independent predictor of adverse outcomes of PAH-CHD patients(Hazard ratio 0.95,p<0.001,C-index 0.70).A model combining N-terminal pro-brain natriuretic peptide,prothrombin activity,albumin,and right atrial area achieved an area under the curve of 0.89 and a C-index of 0.85.Conclusions:The simplified risk stratification method is applicable to PAH-CHD patients.Prothrombin activity is a strong independent predictor of adverse outcomes.A comprehensive risk stratification approach,incorporating both established and novel biomarkers,enhances accessibility and offers predictive efficacy during follow-up for PAH-CHD patients,comparable to established models.

Treatment and Clinical Management of Chronic Thromboembolic Pulmonary Hypertension:An Update of Literature Review

Chronic thromboembolic pulmonary hypertension(CTEPH)is a chronic,progressive,debilitating,and life-threa-tening complication of pulmonary embolism(PE).Recent technological advances have permitted various treat-ment options for the treatment of CTEPH,including surgery,angioplasty,and medical treatment,depending on the location and characteristics of lesions.Pulmonary endarterectomy(PEA)is the treatment of choice for CTEPH,as it offers excellent long-term outcomes and a high probability of recovery.Moreover,various medical and interventional therapies are currently being developed for patients with inoperable CTEPH.This review mainly summarizes the current treatment approaches of CTEPH,offering more options for specialist physicians to,thus,better manage chronic thromboembolic syndromes.

Mufangji tang ameliorates pulmonary arterial hypertension through improving vascular remodeling,inhibiting inflammatory response and oxidative stress,and inducing apoptosis

Background:Mufangji tang(MFJT)is composed of Ramulus Cinnamomi,Radix Ginseng,Cocculus orbiculatus(Linn.)DC.,and Gypsum.In clinical settings,MFJT has been effectively employed in addressing a range of respiratory disorders,notably including pulmonary arterial hypertension(PAH).However,the mechanism of action of MFJT on PAH remains unknown.Methods:In this study,a monocrotaline-induced PAH rat model was established and treated with MFJT.The therapeutic effects of MFJT on PAH rat model were evaluated.Network pharmacology was conducted to screen the possible targets for MFJT on PAH,and the molecular docking between the main active components and the core targets was carried out.The key targets identified from network pharmacology were tested.Results:Results showed significant therapeutic effects of MFJT on PAH rat model.Analysis of network pharmacology revealed several potential targets related to apoptosis,inflammation,oxidative stress,and vascular remodeling.Molecular docking showed that the key components were well docked with the core targets.Further experimental validation results that MFJT treatment induced apoptosis(downregulated Bcl-2 levels and upregulated Bax levels in lung tissue),inhibited inflammatory response and oxdative stress(decreased the levels of IL-1β,TNF-α,inducible NOS,and malondialdehyde,and increased the levels of endothelial nitric oxide synthase,nitric oxide,glutathione and superoxide dismutase),reduced the proliferation of pulmonary arterial smooth muscle cells(downregulated ET-1 andβ-catenin levels and ERK1/2 phosphorylation,increased GSK3βlevels).Conclusion:Our study revealed MFJT treatment could alleviate PAH in rats via induction of apoptosis,inhibition of inflammation and oxidative stress,and the prevention of vascular remodeling.

Intervention control of aerobic exercise in maintaining quality of life and pulmonary hypertension in hemodialysis patients

BACKGROUND Pulmonary hypertension is a serious complication in the treatment of maintenance hemodialysis patients,which seriously affects the quality of life of patients and threatens their life safety.Prevention,treatment and improvement of pulmonary hypertension are of great significance to improve the quality of life of patients.AIM To investigate the intervention and control of pedal-powered bicycle in maintaining quality of life and pulmonary hypertension in hemodialysis patients.METHODS 73 patients with maintenance hemadialysis combined with pulmonary arterial hypertension at a hemodialysis center in a certain hospital from May 2021 to May 2022 are selected.Patients are divided into two groups,37 cases in the control group(group C)and 36 cases in the intervention group(group I).Patients are divided into two groups,group C is treated with oral administration of betaglandin sodium combined with routine nursing care.Based on group C,group I conducts power cycling exercises.RESULTS After treatment,group I patients had higher muscle strength,36-Item Short Form Health Survey scores,and Kidney Disease Targets Areas scores;The 6-minute walk distance test index level was higher and the Borg score was lower;The group I had lower systolic blood pressure,greater vital capacity,higher positive emotion,lower systolic pulmonary artery pressure index level,higher arterial partial oxygen pressure level,lower pulmonary vascular resistance index level,and higher blood oxygen saturation level[158.91±11.89 vs 152.56±12.81,1795.01±603.18 vs 1907.20±574.15,24.00(22.00,29.00)vs 24.00(22.00,28.00),P<0.001].CONCLUSION Aerobic exercise combined with Western medicine treatment can effectively improve patients'pulmonary hypertension,alleviate their negative emotions,and enable them to achieve a higher level of quality of life.

Impact of diabetes mellitus on mortality in pulmonary hypertension:A systematic review and meta-analysis

BACKGROUND Pulmonary hypertension(PH)is a progressive disease characterized by endothelial dysfunction and vascular remodeling and is a leading cause of mortality worldwide.Although it is independently associated with multiple comorbidities,the impact of diabetes mellitus(DM)on mortality in patients with PH remains uncertain.To address this issue,we conducted a systematic review and meta-analysis to investigate the effect of DM on survival in patients with pulmonary hypertension.AIM To investigate the impact of diabetes mellitus on mortality in pulmonary hypertension patients.METHODS We conducted a comprehensive search of four major electronic bibliographic databases like PubMed,Google Scholar,Scopus,and Embase,and identified 106 relevant studies,out of 1561 articles,published since the year 2000 for full-text review.Fourteen retrospective and prospective cohort studies that compared survival between patients with DM and those without DM in the context of PH were deemed eligible for inclusion in our meta-analysis.The study was registered on PROSPERO with the identifier CRD42023390232.RESULTS A total of 116455 patients with PH were included in the meta-analysis,of whom 41228 suffered from DM and 75227 did not.The results of our meta-analysis indicate an elevated mortality rate among PH patients with diabetes mellitus in comparison to those without DM[odds ratio(OR)=1.40,95%CI:1.15–1.70,P=0.0006].The metaregression analysis unveiled a statistically significant negative association between mean age and effect size(coefficient=-0.036,P value=0.018).Conversely,a statistically significant positive association was detected between female proportion and effect size(coefficient=0.000,P value<0.001).CONCLUSION Our meta-analysis,which included approximately 116500 PH patients,revealed that the presence of diabetes mellitus was associated with increased odds of mortality when compared to non-diabetic patients.The metaregression analysis indicates that studies with older participants and lower proportions of females tend to exhibit smaller effect sizes.Clinically,these findings underscore the importance of incorporating diabetes status into the risk stratification of patients with PH with more aggressive monitoring and early intervention to improve prognosis potentially.

Effects of combined aerobic,resistance and inspiratory training in patients with pulmonary hypertension:A systematic review

BACKGROUND Pulmonary hypertension(PH)is a serious progressive disorder of the modern world,characterized by endothelial dysfunction and impaired vasoreactivity.Patients with PH usually present exercise intolerance from the very early stages and reduced exercise capacity.Exercise training has been shown to have beneficial effects in patients with cardiovascular comorbidities.However,data regarding the effects of combined exercise training programs in patients with PH still remains limited.AIM To investigate the effects of combined exercise training programs on exercise capacity and quality of life in patients with PH.METHODS Our search included all available randomized controlled trials(RCTs)regarding combined aerobic,resistance and inspiratory training programs in patients with PH in 4 databases(Pubmed,PEDro,Embase,CINAHL)from 2012 to 2022.Five RCTs were included in the final analysis.Functional capacity,assessed by peak VO_(2)or 6-min walking test(6MWT),as well as quality of life,assessed by the SF-36 questionnaire,were set as the primary outcomes in our study.RESULTS Peak VO_(2)was measured in 4 out of the 5 RCTs while 6MWT was measured in all RCTs.Both indices of functional capacity were significantly increased in patients with PH who underwent combined exercise training compared to the controls in all of the included RCTs(P<0.05).Quality of life was measured in 4 out of 5 RCTs.Although patients improved their quality of life in each group,however,only 2 RCTs demonstrated further improvement in patients performing combined training compared to controls.CONCLUSION By this systematic review,we have demonstrated that combined aerobic,resistance and inspiratory exercise training is safe and has beneficial effects on aerobic capacity and quality of life in patients with PH.Such exercise training regimen may be part of the therapeutic strategy of the syndrome.

Combined Sciatic, Femoral, and Obturator Nerve Blocks for Ankle Surgery in a Patient with Severe Pulmonary Hypertension—A Case Report

We report a patient with severe pulmonary arterial hypertension (PAH) undergoing tibio-talo-calcaneal fusion due to Charcot joint. Despite the advancement in the management of PAH, the risks of anesthesia, surgery, and postoperative morbidity and mortality still remain high. A 46-year-old female was presented with severe PAH and end stage renal disease requiring hemodialysis three times a week. Ultrasound-guided sciatic, femoral, and obturator nerve blocks were performed with 0.5% levobupivacaine 15 ml, 10 ml, and 5 ml, respectively. All the blocks were successful, and the patient underwent uneventful anesthesia and surgery. In addition, the postoperative pain control lasted for 15 h and the patient was discharged on POD 5 without any complications. Therefore, ultrasound-guided sciatic, femoral, and obturator nerve blocks are valuable alternative to the general or neuraxial anesthesia in patients with severe pulmonary hypertension.

Pulmonary arterial hypertension confirmed by right heart catheterization following COVID-19 pneumonia: A case report and review of literature

BACKGROUND Pulmonary arterial hypertension(PAH)is a disease of the arterioles resulting in an increased resistance in pulmonary circulation with associated high pressures in the pulmonary arteries,causing irreversible remodeling of the pulmonary arterial walls.Coronavirus disease 2019(COVID-19)has been associated with development of new onset PAH in the literature leading to symptoms of dyspnea,cough and fatigue that persist in spite of resolution of acute COVID-19 infection.However,the majority of these cases of COVID related PAH were diagnosed using echocardiographic data or via right heart catheterization in mechanically ventilated patients.CASE SUMMARY Our case is the first reported case of COVID related PAH diagnosed by right heart catheterization in a non-mechanically ventilated patient.Right heart catheterization has been the gold standard for diagnosis of pulmonary hypertension.Our patient had right heart catheterization four months after her initial COVID-19 infection due to persistent dyspnea.CONCLUSION This revealed new onset PAH that developed following her infection with COVID-19,an emerging sequela of the infection.

Intraoperative pulmonary hypertension occurred in an asymptomatic patient with pre-existent liver cirrhotic and portal hypertension

Portopulmonary hypertension(PPH) is clinically defined as the development of pulmonary arterial hypertension complicated by portal hypertension,with or without advanced hepatic disease.Physical signs may be absent in mild to moderate PPH and only appear in a hyperdynamic circulatory state.Similar signs of advanced liver disease can be observed in severe PPH,with ascites and lower extremity edema.Pulmonary hypertension is usually diagnosed after anesthetic induction during liver transplantation(LT).We present intraoperative pulmonary hypertension in a 41-year-old male patient with hepatic cirrhosis.Since this patient had no preoperation laboratory data supporting the diagnosises of pulmonary hypertension and was asymptomatic for a number of years,it was necessary to send him to the intensive care unit after operation.Further study should be focued on the diagnosis and treatment of pulmonary arterial hypertension in order to reduce its mortality.

Pulmonary hypertension secondary to seronegative rheumatoid arthritis overlapping antisynthetase syndrome:A case report

BACKGROUND Polyarthritis is the most frequent clinical manifestation in antisynthetase syndrome(ASS)forms of idiopathic inflammatory myositis and may be misdiagnosed as rheumatoid arthritis(RA),particularly in patients with seronegative RA(SNRA).It is unclear whether there is an overlap between ASS and RA,or if ASS sometimes mimics RA.Pulmonary hypertension(PAH)is common in connective tissue diseases(CTDs).However,published reports on CTD-PAH do not include overlapping CTDs,and its incidence and impact on patient prognosis are unclear.CASE SUMMARY We report the case of a 63-year-old woman who presented with a 3-mo history of symptom aggravation of recurrent symmetrical joint swelling and pain that had persisted for over 10 years.The patient was diagnosed with RA and interstitial lung disease.The patient repeatedly presented to the hospital’s respiratory and rhe-umatology departments with arthralgia,plus shortness of breath after activity.Relevant tests indicated that anti-CCP and RF remained negative,while anti-J0-1 and anti-Ro-52 were strongly positive.It was not until recently that we recognized that this could be an unusual case of SNRA with concurrent ASS.Joint pain was relieved after regular anti-rheumatic treatment.Chest computed tomography scans showed that pulmonary interstitial changes did not progress significantly over several years;however,they showed gradual widening of the pulmonary artery,and cardiac ultrasound indicated elevated pulmonary artery systolic pressure.The prescribed treatment of PAH was not effective in improving shortness of breath.CONCLUSION Overlap of RA and ASS may be missed.Further research is necessary to facilitate early diagnosis,effective evaluation,and prognosis.

Fathal pulmonary hypertension after distal splenorenal shunt in schistosomal portal hypertension

Mansonic schistosomiasis is the main cause of portal hypertension in Brazil. Hepatosplenic (HS) form is manifested by hepatomegaly mainly on the left hepatic lobe associated with large splenomegaly and bleeding due to esophageal varices with high mortality rates.

Prevalence of pulmonary hypertension among children with Down syndrome:A systematic review and meta-analysis

BACKGROUND Pulmonary hypertension(PH)has serious short-and long-term consequences.PH is gaining increasing importance in high risk groups such as Down syndrome(DS)as it influences their overall survival and prognosis.Hence,there is a dire need to collate the prevalence rates of PH in order to undertake definitive measures for early diagnosis and management.AIM To determine the prevalence of PH in children with DS.METHODS The authors individually conducted a search of electronic databases manually(Cochrane library,PubMed,EMBASE,Scopus,Web of Science).Data extraction and quality control were independently performed by two reviewers and a third reviewer resolved any conflicts of opinion.The words used in the literature search were“pulmonary hypertension”and“pulmonary arterial hypertension”;“Down syndrome”and“trisomy 21”and“prevalence”.The data were analyzed by Comprehensive Meta-Analysis Software Version 2.Risk of bias assessment and STROBE checklist were used for quality assessment.RESULTS Of 1578 articles identified,17 were selected for final analysis.The pooled prevalence of PH in these studies was 25.5%.Subgroup analysis was carried out for age,gender,region,year of publication,risk of bias and etiology of PH.CONCLUSION This review highlights the increasing prevalence of PH in children with DS.It is crucial for pediatricians to be aware of this morbid disease and channel their efforts towards earlier diagnosis and successful management.Community-based studies with a larger sample size of children with DS should be carried out to better characterize the epidemiology and underlying etiology of PH in DS.

Role of pulmonary perfusion magnetic resonance imaging for the diagnosis of pulmonary hypertension:A review

Among five types of pulmonary hypertension,chronic thromboembolic pulmonary hypertension(CTEPH)is the only curable form,but prompt and accurate diagnosis can be challenging.Computed tomography and nuclear medicine-based techniques are standard imaging modalities to non-invasively diagnose CTEPH,however these are limited by radiation exposure,subjective qualitative bias,and lack of cardiac functional assessment.This review aims to assess the methodology,diagnostic accuracy of pulmonary perfusion imaging in the current literature and discuss its advantages,limitations and future research scope.

Contribution of oxidative stress to pulmonary arterial hypertension

Recent data implicate oxidative stress as a mediator of pulmonary hypertension (PH) and of the associated pathological changes to the pulmonary vasculature and right ventricle (RV). Increases in reactive oxygen species (ROS), altered redox state, and elevated oxidant stress have been demonstrated in the lungs and RV of several animal models of PH, including chronic hypoxia, monocrotaline toxicity, caveolin-1 knock-out mouse, and the transgenic Ren2 rat which overexpresses the mouse renin gene. Generation of ROS in these models is derived mostly from the activities of the nicotinamide adenine dinucleotide phosphate oxidases, xanthine oxidase, and uncoupled endothelial nitric oxide synthase. As disease progresses circulating monocytes and bone marrow-derived monocytic progenitor cells are attracted to and accumulate in the pulmonary vasculature. Once established, these inflammatory cells generate ROS and secrete mitogenic and fibrogenic cytokines that induce cell proliferation and fibrosis in the vascular wall resulting in progressive vascular remodeling. Deficiencies in antioxidant enzymes also contribute to pulmonary hypertensive states. Current therapies were developed to improve endothelial function, reduce pulmonary artery pressure, and slow the progression of vascular remodeling in the pulmonary vasculature by targeting deficiencies in either NO (PDE-type 5 inhibition) or PGI 2 (prostacyclin analogs), or excessive synthesis of ET-1 (ET receptor blockers) with the intent to improve patient clinical status and survival. New therapies may slow disease progression to some extent, but long term management has not been achieved and mortality is still high. Although little is known concerning the effects of current pulmonary arterial hypertension treatments on RV structure and function, interest in this area is increasing. Development of therapeutic strategies that simultaneously target pathology in the pulmonary vasculature and RV may be beneficial in reducing mortality associated with RV failure.

Pulmonary hypertension in hereditary haemorrhagic telangiectasia

Hereditary haemorrhagic telangiectasia(HHT) is an autosomal dominant inherited disorder characterised by vascular malformations in predominantly the brain,liverand lungs.Pulmonary hypertension(PH) is increasingly recognised as a severe complication of HHT.PH may be categorised into two distinct types in patients with HHT.Post-capillary PH most often results from a high pulmonary blood flow that accompanies the high cardiac output state associated with liver arteriovenous malformations.Less frequently,the HHT-related gene mutations in ENG or ACVRL1 appear to predispose patients with HHT to develop pre-capillary pulmonary arterial hypertension.Differentiation between both forms of PH by right heart catheterisation is essential,since both entities are associated with severe morbidity and mortality with different treatment options.Therefore all HHT patients should be referred to an HHT centre.

Hemodynamic assessment of pulmonary hypertension

There has been significant progress in our understanding of the pathobiology, epidemiology and prognosis of pulmonary vascular disease and, over the past few years, there has been an explosion of clinical therapeutic trials for pulmonary arterial hypertension (PAH). The increasing number of different conditions now associated with PAH and the appearance of new diagnostic techniques have led to a need for a systematic diagnostic approaches and a new disease classification, which has resulted in notable improvements in the quality and efficacy of clinical care. We appreciate traditional resting right heart catheterization techniques (which still remain the gold standard for diagnosing PAH and managing patients on therapy) and look forward to novel invasive techniques (e.g. intravascular ultrasound) that add greatly to our understanding of right ventricle and pulmonary circulation, and for the interpretation of data from clinical trials as well.

Pulmonary hypertension and metabolic syndrome: Possible connection, PPARγ and Caveolin-1

A number of disparate diseases can lead to pulmonary hypertension(PH), a serious disorder with a high morbidity and mortality rate. Recent studies suggest that the associated metabolic dysregulation may be an important factor adversely impacting the prognosis of PH. Furthermore, metabolic syndrome is associated with vascular diseases including PH. Inflammation plays a significant role both in PH and metabolic syndrome. Adipose tissue modulates lipid and glucose metabolism, and also produces pro-and anti-inflammatory adipokines that modulate vascular function and angiogenesis, suggesting a close functional relationship between the adipose tissue and the vasculature. Both caveolin-1, a cell membrane scaffolding protein and peroxisome proliferator-activated receptor(PPAR) γ, a ligandactivated transcription factor are abundantly expressed in the endothelial cells and adipocytes. Both caveolin-1 and PPARγ modulate proliferative and anti-apoptotic pathways, cell migration, inflammation, vascular homeostasis, and participate in lipid transport, triacylglyceride synthesis and glucose metabolism. Caveolin-1 and PPARγ regulate the production of adipokines and in turn are modulated by them. This review article summarizes the roles and inter-relationships of caveolin-1,PPARγ and adipokines in PH and metabolic syndrome.

The Role of Endogenous Carbon Monoxide in the Hypoxic Vascular Remodeling of Rat Model of Hypoxic Pulmonary Hypertension

We investigated the expression of heme oxygenase 1 (HO 1) gene and production of endogenous carbon monoxide (CO) in the rat lung tissue at different time points of chronic hypoxic pulmonary hypertension and the effect of hemin on the expression of HO 1 gene and pulmonary hypertension. A rat model of hypoxic pulmonary hypertension was recreated by exposure to intermittent normobaric hypoxic environment (10 % O 2). Reverse transcriptase polymerase chain reaction (RT PCR) was performed to determine the level of HO 1 mRNA in the rat lung tissue and double wave length spectrophotometry was used to evaluate the quantity of COHb in arterial blood. Cardiac catheterization was employed to measure the right ventricular systolic pressure (RVSP) and HE staining was performed in dissected lung tissue to observe the pathological changes of the intra acinar pulmonary arteries (IAPA). It was found that (1) There was a low level of HO 1 mRNA in normal rat lung tissue, but the level of HO 1 mRNA increased by 2-4 times in the lung tissue of hypoxic rats ( P <0.01). The quantity of COHb was 2-3 times those of control group ( P <0.01 or P <0.05). These were accompanied by the increased of RVSP and the thickened IAPA; (2) Hemin could keep the HO 1 mRNA and COHb in the hypoxic rat lung tissue at a high level, and partially suppressed the increase of rat RVSP, thereby ameliorating the pathological changes of IAPA. In conclusion, the upregulation of the expression of HO 1 gene and production of CO in the rat lung of hypoxic pulmonary hypertension plays a role of inhibition in the development of hypoxic pulmonary hypertension. Hemin has a therapeutic effect on hypoxic pulmonary hypertension.

Role of ROS/Kv/HIF Axis in the Development of Hypoxia-Induced Pulmonary Hypertension

Hypoxic pulmonary hypertension (HPH) is a common complication in patients with chronic obstructive pulmonary disease (COPD), sleep-disordered breathing, or dwellers in high altitude. The exact mechanisms underlying the development of HPH still remain unclear. Reactive oxygen species (ROS),hypoxia inducible factors (HIF), and potassium channels (KV) are believed as the main factors during the development of HPH. We propose that the “ROS/Kv/HIF axis” may play an important initiating role in the development of HPH. Being formed under a hypoxic condition, ROS affects the expression and function of HIFs or KV, and consequently triggers multiple downstream signaling pathways and genes expression that participate in promoting pulmonary vasoconstriction and arterial remodeling. Thus, further study determining the initiating role of “ROS/Kv/HIF axis” in the development of HPH could provide theoretic evidences to better understand the underlying mechanisms of HPH, and help identify new potential targets in the treatment of HPH.