Salusin-β contributes to vascular inflammation associated with pulmonary arterial hypertension in rats

Novel insights and new therapeutic potentials for macrophages in pulmonary hypertension

Inflammation and immune processes underlie pulmonary hypertension progression. Two main different activated phenotypes of macrophages, classically activated M1 macrophages and alternatively activated M2 macrophages, are both involved in inflammatory processes related to pulmonary hypertension. Recent advances suggest that macrophages coordinate interactions among different proinflammatory and anti-inflammatory mediators, and other cellular components such as smooth muscle cells and fibroblasts. In this review, we summarize the current literature on the role of macrophages in the pathogenesis of pulmonary hypertension, including the origin of pulmonary macrophages and their response to triggers of pulmonary hypertension. We then discuss the interactions among macrophages, cytokines, and vascular adventitial fibroblasts in pulmonary hypertension, as well as the potential therapeutic benefits of macrophages in this disease. Identifying the critical role of macrophages in pulmonary hypertension will contribute to a comprehensive understanding of this pathophysiological abnormality, and may provide new perspectives for pulmonary hypertension management.

The relationship of salusins with Parkinson's Disease, Alzheimer's Disease, and acute ischemic stroke: A preliminary study

Neuroinflammation, oxidative stress, and apoptosis play important roles in the pathophysiology of Alzheimer's Disease (AD), Parkinson's Disease (PD), and Acute Ischemic Stroke (AIS). Salusin-α and salusin-β peptides, which were shown to be present in many tissues, including the central nervous system, were also shown to be associated with apoptosis, inflammation, and oxidative stress. In the present study, the relationship between Salusin-α and salusin-β peptides and AD, PD, and AIS were investigated. A total of 179 people were included in the present study, including 46 AD, 44 PD, 42 AIS, and 47 controls. Plasma Salusin-α and salusin-β levels were measured with the ELISA Method. The plasma salusin-β levels of AD, PD, and AIS patients were lower than the control group at significant levels (p < 0.05). It was also found that there were correlations between salusin-α and salusin-β levels and age, triglyceride, LDL-c, total cholesterol, and hemoglobin levels. In this study, we found that salusin- β, an endogenous neuropeptide, was associated with AD, PD and AIS. The low level of salusin-β in these diseases in which neuronal damage occurs may be related to the neuroprotective properties of this endogenous peptide. Further studies are needed to fully understand the relationship between salusin-β and the pathophysiology of these diseases.

Downregulation of salusins alleviates hypertrophic cardiomyopathy via attenuating oxidative stress and autophagy

INTRODUCTION

Salusins, which are translated from the alternatively spliced mRNA of torsin family 2 member A (TOR2A), play a vital role in regulation of various cardiovascular diseases. However, it remains unclear precisely regarding their roles in hypertrophic cardiomyopathy (HCM). Therefore, this study was conducted to explore therapeutic effect and the underlying mechanisms of salusins on HCM.

MATERIAL AND METHODS

In vivo experiments, Sprague-Dawley rats were used to induce HCM model by angiotensin (Ang) II infusion for 4 weeks. The rats were randomly divided into four groups, namely, Saline + Control shRNA (n = 7), Ang II + Control shRNA (n = 8), Saline + TOR2A shRNA (n = 7), and Ang II + TOR2A shRNA groups (n = 8). After HCM induction, doppler echocardiography is recommended to evaluate heart function. In vitro experiments, primary neonatal rat cardiomyocytes (NRCMs) and cardiac fibroblasts (NRCFs) were obtained from newborn rats, and were treated with Ang II (10-6 M) for 24 h.

RESULTS

After treatment with Ang II, levels of salusin-α and salusin-β were elevated in serum and cardiac tissues of rats and in the neonatal rat cardiomyocytes and cardiac fibroblasts. Downregulation of salusins alleviated the Ang II-induced cardiac hypertrophy by suppressing the increased atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and beta-myosin heavy chain (β-MHC) and cardiac fibrosis by blocking collagen I, collagen III and transforming growth factor-beta (TGF-β), and it also attenuated oxidative stress by suppressing the increased reactive oxygen species (ROS) and malondialdehyde (MDA) levels and reversing the decreased superoxide dismutase (SOD) activity and autophagy by inhibiting the increased microtubule-associated protein light chain 3B (LC3B), Beclin1, autophagy related gene (Atg) 3 and Atg5 in the cardiac tissues of Ang II-infused rats and in the Ang II-treated NRCMs.

CONCLUSIONS

All these findings suggest that the levels of salusins were elevated in the HCM, and targeting of salusins contributes to alleviation of cardiac hypertrophy and fibrosis probably via attenuating oxidative stress and autophagy. Accordingly, targeting of salusins may be a strategy for HCM therapy.

Serum salusin-α and -β levels in patients with parkinson's disease

BACKGROUND

The etiology of Parkinson's disease (PD) is not well known and there is increasing evidence that oxidative stress also plays an important role in its pathogenesis. Salusins alpha (salusin-α) and beta (salusin-β) affect the central nervous system, vasculature, and kidneys to increase the inflammatory response in endothelial cells, stimulate oxidative stress, and increase monocyte-endothelial adhesion. Neuroinflammation and oxidative stress play roles in the etiopathogenesis of PD.

PURPOSE

To investigate whether salusin-α and -β are related to PD and whether they are correlated with the development of atherosclerosis, body mass index, disease duration, and the Parkinson's Hoehn and Yahr stage.

RESULTS

The low-density lipoprotein cholesterol (LDL-C), total cholesterol, and salusin-β levels were significantly lower and age was significantly higher in Parkinson patients compared to healthy controls (ρ < 0.005). We found a negative linear correlation between salusin-β and the Hoehn and Yahr stage (ρ < 0.001, r = -0.515) in the patients.

CONCLUSIONS

There was a relationship between salusin-β and PD and a correlation between the salusin-β levels and Parkinson's stage. A possible underlying disease mechanism is an increase in oxidative stress and decrease in neuroprotective effects due to low salusin-β levels. Therefore, the effects of salusin-β in treating Parkinson disease should be evaluated. Further studies are needed to understand the effects of salusin-β treatment on preventing or slowing the course of PD.

Upregulated expression of a TOR2A gene product-salusin-β in the paraventricular nucleus enhances sympathetic activity and cardiac sympathetic afferent reflex in rats with chronic heart failure induced by coronary artery ligation

AIM

Enhanced cardiac sympathetic afferent reflex (CSAR) promotes sympathetic hyperactivation in chronic heart failure (CHF). Salusin-β is a torsin family 2 member A (TOR2A) gene product and a cardiovascular active peptide closely associated with cardiovascular diseases. We aimed to determine the roles of salusin-β in the paraventricular nucleus (PVN) in modulating enhanced CSAR and sympathetic hyperactivation in rats with CHF induced by coronary artery ligation and elucidate the underlying molecular mechanisms.

METHODS

CSAR was evaluated based on the responses of mean arterial pressure (MAP) and renal sympathetic nerve activity (RSNA) to the epicardial administration of capsaicin in rats under anesthesia.

RESULTS

Salusin-β protein expression was upregulated in the PVN of the CHF compared with sham-operated rats. Salusin-β microinjection into the PVN dose-dependently increased MAP and RSNA and enhanced CSAR, while anti-salusin-β IgG exerted opposite effects. The effect of salusin-β was inhibited by reactive oxygen species (ROS) scavenger or NAD(P)H oxidase inhibitor but promoted by superoxide dismutase inhibitor. The effect of anti-salusin-β IgG was interdicted by nitric oxide (NO) synthase inhibitor. Furthermore, chronic salusin-β gene knockdown in PVN attenuated CSAR, reduced sympathetic output, improved myocardial remodeling and cardiac function, decreased NAD(P)H oxidase activity and ROS levels, and increased NO levels in the CHF rats.

CONCLUSION

Increased salusin-β activity in the PVN contributes to sympathetic hyperactivation and CSAR in CHF by inhibiting NO release and stimulating NAD(P)H oxidase-ROS production. Reducing endogenous central salusin-β expression might be a novel strategy for preventing and treating CHF in the future.

The Clinical Significance of Salusins in Systemic Sclerosis-A Cross-Sectional Study

Background: Systemic sclerosis (SSc) is a connective tissue disease manifesting with progressive fibrosis of the skin and internal organs. Its pathogenesis is strictly associated with vascular disfunction and damage. Salusin-α and salusin-β, endogenous peptides regulating secretion of pro-inflammatory cytokines and vascular smooth muscle proliferation, may potentially play a role in SSc pathogenesis. Objectives: The aim of this study was to assess the concentration of salusins in sera of patients with SSc and healthy controls and to evaluate correlations between the salusins levels and selected clinical parameters within the study group. Materials and methods: 48 patients with SSc (44 women; mean age, 56.4, standard deviation, 11.4) and 25 adult healthy volunteers (25 women; mean age, 55.2, standard deviation, 11.2) were enrolled. All patients with SSc were treated with vasodilators and twenty-seven of them (56%) also received immunosuppressive therapy. Results: Circulating salusin-α was significantly elevated in patients with SSc in comparison to healthy controls (U = 350.5, p = 0.004). Patients with SSc receiving immunosuppression had higher serum salusin-α concentrations compared with those without immunosuppressive therapy (U = 176.0, p = 0.026). No correlation was observed between salusins concentrations and skin or internal organ involvement parameters. Conclusions: Salusin-α, a bioactive peptide mitigating the endothelial disfunction, was elevated in patients with systemic sclerosis receiving vasodilators and immunosuppressants. Increased salusin-α concertation may be associated with the initiation of atheroprotective processes in patients with SSc managed pharmacologically, which requires verification in future studies.

Salusin-β, a TOR2A gene product, promotes proliferation, migration, fibrosis, and calcification of smooth muscle cells and accelerates the imbalance of vasomotor function and vascular remodeling in monocrotaline-induced pulmonary hypertensive rats

Purpose: The hyper-proliferation, promoted migration, fibrosis, and calcification of pulmonary arterial smooth muscle cells (PASMCs) play critical roles in pulmonary artery (PA) continuous contraction and vascular remodeling, leading to elevated pulmonary arterial resistance and pulmonary hypertension (PH). In this study, we sought to ascertain the effects of a TOR2A gene product, salusin-β, on PASMCs’ proliferation, migration, fibrosis, calcification, and the imbalance of vasomotor function as well as pulmonary vascular remodeling in monocrotaline (MCT)-induced PH rats and their underlying mechanisms.

Methods: Knockdown or overexpression of salusin-β in rats or PASMCs was performed through tail vein injection or cell transfection of virus. The right ventricular systolic pressure (RVSP) of the rat was measured by right ventricle catheterization. Sodium nitroprusside (SNP) or acetylcholine (ACh)-induced dose-dependent relaxation was used to evaluate the vasodilatation function. Primary PASMCs were isolated from the PAs of control and PH rats.

Results: The salusin-β protein expressions were significantly increased in PAs and PASMCs isolated from PH rats compared with control rats. Knockdown of salusin-β in rats decreased high K⁺ solution-induced contraction, RVSP and RV hypertrophy index, improved SNP or ACh-induced vascular relaxation of PAs, and relieved vascular remodeling and calcification of PAs from PH rats. Silencing salusin-β in PASMCs isolated from PH rats alleviated the proliferation, migration, fibrosis, and calcification, as well as the NAD(P)H oxidase activity and reactive oxygen species (ROS) level. Overexpression of salusin-β exerted the opposite effects on vasomotor function and vascular remodeling, and PASMCs proliferation, migration, fibrosis and calcification.

Conclusion: Increased salusin-β activity in PAs from PH rats contributes to PASMCs proliferation, migration, fibrosis, and calcification, leading to the imbalance of vascular contraction and relaxation and vascular remodeling through stimulating the production of NAD(P)H oxidase derived ROS.

Saluisn-β contributes to endothelial dysfunction in monocrotaline-induced pulmonary arterial hypertensive rats

BACKGROUND

The endothelial dysfunction and the consequent attenuated pulmonary vasodilatation are the major causes of elevated pulmonary arterial resistance and pressure in pulmonary arterial hypertension (PAH). Current study aimed to explore the effects of a TOR2A gene product, salusin-β, on endothelium-dependent vascular relaxation and the progression of PAH in monocrotaline (MCT)-induced PAH rats as well as the relevant signaling pathway.

METHODS

Acetylcholine (ACh)-induced dose-dependent relaxation was used to evaluate the endothelium-dependent vasodilatation function.

RESULTS

The salusin-β level in plasma and pulmonary artery (PA) in MCT-PAH rats were significantly increased, while the ACh-induced endothelium-dependent vasodilatation was attenuated. After salusin-β incubation or overexpression of salusin-β gene, the endothelium-dependent relaxation was further deteriorated, while anti-salusin-β IgG incubation or knockdown of salusin-β improved it in PAH rats. The superoxide anions scavenger NAC or the antioxidant apocynin inhibited the effect of salusin-β, while the SOD inhibitor DETC further enhanced it. The nitric oxide (NO) synthase inhibitor L-NAME almost blocked the effect of anti-salusin-β IgG. Silencing of salusin-β in PAH rats decreased right ventricular (RV) systolic pressure, RV hypertrophy index, NAD(P)H oxidase activity and ROS level, and increased the eNOS activity and NO level of PA. Overexpression of salusin-β played opposite roles.

CONCLUSIONS

The elevated saluisn-β level in PAH rats plays important roles in the reduction of endothelium-dependent vasodilatation and participates in the progression of PAH through stimulating NAD(P)H oxidase-ROS production and inhibiting eNOS-NO release.

Intracerebroventricular salusin-β infusion to rats increases hypothalamus-pituitary-testicular axis hormones

Salusin-β (Sal-β), which originates from preprosalusin, is a multifunctional hormone with a peptide structure. Sal-β exists in the hypothalamus and can stimulate the pituitary gland. The present study was conducted to determine the effects of Sal-β on hormones that play roles in the male reproductive system. Forty male Wistar Albino rats were used in the study. No infusions were performed on the control group, and infusions were applied to the infusion groups (artificial cerebrospinal fluid to the sham group, 2 and 20 nM Sal-β to the experimental group) through intracerebroventricular infusion for 7 days at 10 μl/hour rate. The animals were decapitated after 7 days of infusion; and the hypothalamus, testicles, and blood tissue samples were collected. The gonadotropin-releasing hormone (GnRH) mRNA levels were determined from the hypothalamus tissues by using the Real Time-PCR Method, and the serum luteinizing hormone (LH), follicle-stimulating hormone (FSH) and testosterone levels were determined using the ELISA method. Also, Hematoxylin-Eosin Staining Method was used for histopathological evaluations in the testicle tissues. As a result, Sal-β infusion increased GnRH mRNA levels in hypothalamus tissues (p < 0.05) besides, serum LH, FSH, and testosterone levels of the rats were higher at significant levels following Sal-β infusion compared to the control and sham group (p < 0.05). In the histological examination of the testicle tissues, Sal-β application was found to decrease the seminiferous tubule diameter and germinal epithelial thickness (p < 0.05). This evidence is the first, indicating that Sal-β, which is administered to male rats with central infusion, stimulates hypothalamus and pituitary tissues, and causes increased secretion of male reproductive hormones.

Evaluation of salusin-α and salusin-β levels in patients with type 2 diabetes mellitus and determination of the impact of severity of hyperglycemia on salusin levels

AIMS

To investigate the usefulness of salusin-α and salusin-β as biomarkers in patients with type 2 diabetes mellitus (T2DM) and to determine whether diabetes severity and obesity have an effect on the salusin levels in diabetic patients.

METHODS

The study included a total of 90 patients, comprising 55 diagnosed with T2DM and 35 healthy volunteers with similar demographic characteristics. Salusins were assayed by a commercially available ELISA kit.

RESULTS

The salusin-β levels were found to be significantly higher in T2DM group compared to control group, while the salusin-α levels were lower (p < 0.05, for both). Furthermore, in patient group, Spearman analysis showed a statistically significant negative correlation between salusin-α and fasting glucose and glycated hemoglobin (HbA1c), whereas salusin-β had a statistically significant positive correlation with fasting glucose and HbA1c (p < 0.05, for both). When analyzed according to the HbA1c groups, the patients with HbA1c > 9% had significantly lower salusin-α and higher salusin-β levels levels compared to those with HbA1c < 9% (p < 0.05, for both). When examined according to body-mass-index groups, there was no significant difference in the salusin levels of the patient and control groups (p > 0.05).

CONCLUSION

We demonstrated that the serum salusin-α level was decreased whereas the salusin-β level was increased in patients with T2DM compared to healthy subjects, and this was more pronounced as T2DM-deteriorated. We also showed that obesity had no effect on salusin levels among diabetics. This study may provide a basis for the availability of salusin-targeted therapies, especially in uncontrolled T2DM.

Salusin-β Mediates High Glucose-Induced Inflammation and Apoptosis in Retinal Capillary Endothelial Cells via a ROS-Dependent Pathway in Diabetic Retinopathy

BACKGROUND

Diabetic retinopathy (DR) is characterized by retinal vascular endothelial cell death and vascular inflammation, which are microvascular complications of diabetes mellitus (DM). Salusin-β, a newly identified peptide, is closely associated with hypertension, atherosclerosis and diabetic cardiomyopathy. However, the exact role of salusin-β in high glucose (HG)-induced retinal capillary endothelial cell (REC) inflammation and apoptosis remains unclear.

PATIENTS AND METHODS

A total of 60 patients with type 2 diabetes and 20 healthy controls were included in this study. Based on fundus fluorescein angiography findings, the diabetic patients were divided into three subgroups: diabetes without retinopathy (DWR), non-proliferative DR (NPDR) and proliferative DR (PDR). Serum salusin-β levels were measured by enzyme-linked immunosorbent assay. Human RECs (HRECs) were cultured in normal glucose (NG) and HG medium with or without salusin-β. Salusin-β expression was analysed by Western blotting and immunofluorescence staining. Expression of the pro-inflammatory cytokines MCP-1, IL-1β, TNF-α, and VCAM-1 was analysed by Western blotting. Reactive oxygen species (ROS) production was measured with 2',7'-dichlorofluorescein diacetate (DCFH-DA). Cell apoptosis rates were determined by flow cytometry. The levels of p38, JNK, p-p38, and p-JNK and the apoptosis-related proteins cleaved caspase-3, Bax, and cl2 were analysed by Western blotting.

RESULTS

Serum salusin-β levels were higher in diabetic patients than in healthy controls (p = 0.0027), especially in patients with NPDR and PDR (both p<0.01). HG upregulated salusin-β expression in HRECs in a time-dependent manner. Salusin-β exacerbated inflammation and apoptosis, upregulated intracellular ROS production in HG-induced HRECs, and activated ROS-dependent JNK and p38 MAPK signalling, while knockdown of salusin-β suppressed these effects.

CONCLUSION

Our findings indicate that salusin-β can promote inflammation and apoptosis via ROS-dependent JNK and p38 MAPK signalling in HG-induced HRECs and could be a therapeutic target for DR.

Anti‑inflammatory effect of salusin‑β knockdown on LPS‑activated alveolar macrophages via NF‑κB inhibition and HO‑1 activation

Inflammation of alveolar macrophages is the primary pathological factor leading to acute lung injury (ALI), and NF-κB activation and HO-1 inhibition are widely involved in inflammation. Salusin-β has been reported to contribute to the progression of the inflammatory response, but whether salusin-β could regulate inflammation in lipopolysaccharide (LPS)-induced ALI remains unknown. The present study aimed to investigate the role of salusin-β in LPS-induced ALI and to uncover the potential underlying mechanisms. Sprague-Dawley rats were subjected to LPS administration, and then pathological manifestations of lung tissues, inflammatory cytokines levels in bronchoalveolar lavage fluid (BALF) and expression of salusin-β in macrophages of lung tissues were assessed. NR8383 cells with or without salusin-β knockdown were treated with LPS, and then the concentration of inflammatory cytokines, and the expression of high mobility group box-1 (HMGB1), NF-κB signaling molecules and heme oxygenase-1 (HO-1) levels were detected. The results showed that LPS caused injury of lung tissues, increased the levels of proinflammatory cytokines in BALF, and led to higher expression of salusin-β or macrophages in lung tissues of rats. In vitro experiments, LPS also upregulated salusin-β expression in NR8383 cells. Knockdown of salusin-β using short hairpin (sh)RNA inhibited the LPS-induced generation of inflammatory cytokines. LPS also enhanced HMGB1, phosphorylated (p)-IκB and p-p65 expression, but reduced HO-1 expression in both lung tissues and NR8383 cells, which were instead inhibited by the transfection of sh-salusin-β. In addition, knockdown of HO-1 using shRNA reversed the inhibitory effect of sh-salusin-β on the LPS-induced generation of inflammatory cytokines, activation of NF-κB signaling and inactivation of HO-1. In conclusion, this study suggested that knockdown of salusin-β may inhibit LPS-induced inflammation in alveolar macrophages by blocking NF-κB signaling and upregulating HO-1 expression.

A TOR2A Gene Product: Salusin-β Contributes to Attenuated Vasodilatation of Spontaneously Hypertensive Rats

PURPOSE

Attenuated vasodilatation of small arteries is a hallmark feature of hypertension. Salusin-β, which is a TOR2A gene product and an important vasoactive peptide, has a close relationship with cardiovascular disease. This study aimed to determinate the roles of salusin-β in vasodilatation, and its signal pathways in Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR).

METHODS

Isometric tension experiments were performed. Vasodilatation was induced by acetylcholine (ACh) or sodium nitroprusside (SNP).

RESULTS

Plasma salusin-β levels and their protein expressions in coronary artery (CA), mesenteric artery (MA), and pulmonary artery (PA) of SHR were much higher than that of WKY. Intravenous injection of salusin-β increased arterial blood pressure in SHR, while anti-salusin-β IgG decreased it. Salusin-β further deteriorated, while anti-salusin-β IgG improved, the attenuated ACh-induced relaxation, the decreased nitric oxide (NO) level, and endothelial nitric oxide synthase (eNOS) activity in arteries of SHR, and salusin-β had no significant effect on SNP-induced relaxation. The NAD(P)H oxidase activity and reactive oxygen species (ROS) level in arteries of SHR were much higher than that of WKY, which was further increased by salusin-β but reduced by anti-salusin-β IgG. ROS scavenger NAC or antioxidant apocynin significantly inhibited, while SOD inhibitor DETC aggravated, the effects of salusin-β, and the eNOS inhibitor L-NAME inhibited the effects of anti-salusin-β IgG.

CONCLUSIONS

These results indicated that enhanced salusin-β activity is involved in attenuated endothelium-dependent vasodilatation pathogenesis in SHR by activating NAD(P)H oxidase derived ROS generation and inhibiting eNOS activation and NO release.

Salusin-β mediates tubular cell apoptosis in acute kidney injury: Involvement of the PKC/ROS signaling pathway

Salusin-β is abundantly expressed in many organs and tissues including heart, blood vessels, brain and kidneys. Recent studies have identified salusin-β as a bioactive peptide that contributes to various diseases, such as atherosclerosis, hypertension, diabetes and metabolic syndrome. However, the role of salusin-β in the pathogenesis of acute kidney injury (AKI) is largely unclear. In the present study, we investigated the roles of salusin-β in cisplatin or lipopolysaccharide (LPS)-induced renal injury. Herein, we found that salusin-β expression was upregulated in both renal tubular cells and kidney tissues induced by both cisplatin and LPS. In vitro, silencing of salusin-β diminished, whereas overexpression of salusin-β exaggerated the increased PKC phosphorylation, oxidative stress, histone γH2AX expression, p53 activation and apoptosis in either cisplatin or LPS-challenged renal tubular cells. More importantly, salusin-β overexpression-induced tubular cell apoptosis were abolished by using the PKC inhibitor Go 6976, reactive oxygen species (ROS) scavenger NAC, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor apocynin (Apo) or p53 inhibitor Pifithrin-α. In animals, blockade of salusin-β alleviated PKC phosphorylation, ROS accumulation, DNA damage, and p53 activation as well as renal dysfunction in mice after administration of cisplatin or LPS. Taken together, these results suggest that overexpressed salusin-β is deleterious in AKI by activation of the PKC/ROS signaling pathway, thereby priming renal tubular cells for apoptosis and death.

Targeting IL-17 attenuates hypoxia-induced pulmonary hypertension through downregulation of β-catenin

BACKGROUND

The role of interleukin 17 (IL-17) in hypoxic pulmonary hypertension (HPH) remains unclear. This study is designed to explore whether IL-17 is a potential target for HPH treatment.

METHODS

Clinic samples from the lung tissue and serum were obtained from qualified patients. Western blotting, immunohistochemistry and/or ELISA were used to measure the expression of relevant proteins. HPH models were established in C57BL/6 wild-type (WT) and IL-17 ^-/- mice and were treated with exogenous recombinant mouse IL-17 (rmIL-17) or an IL-17 neutralising antibody. Assays for cell proliferation, angiogenesis and adhesion were employed to analyse the behaviours of human pulmonary arterial endothelial cells (HPAECs). A non-contact Transwell coculture model was used to evaluate intercellular interactions.

RESULTS

Expression of IL-17 was increased in lung tissue of both patients with bronchiectasis/COPD-associated PH and HPH mouse model. Compared with WT mice, IL-17 ^-/- mice had attenuated HPH, whereas administration of rmIL-17 aggravated HPH. In vitro, recombinant human IL-17 (rhIL-17) promoted proliferation, angiogenesis and adhesion in HPAECs through upregulation of Wnt3a/β-catenin/CyclinD1 pathway, and siRNA-mediated knockdown of β-catenin almost completely reversed this IL-17-mediated phenomena. IL-17 promoted the proliferation but not the migration of human pulmonary arterial smooth muscle cells (HPASMCs) cocultured with HPAECs under both normoxia and hypoxia, but IL-17 had no direct effect on proliferation and migration of HPASMCs. Blockade of IL-17 with a neutralising antibody attenuated HPH in WT mice.

CONCLUSIONS

IL-17 contributes to the pathogenesis of HPH through upregulation of β-catenin expression. Targeting IL-17 might provide potential benefits for alternative therapeutic strategies for HPH.

IL-33 Initiates Vascular Remodelling in Hypoxic Pulmonary Hypertension by up-Regulating HIF-1α and VEGF Expression in Vascular Endothelial Cells

IL-33 may play a role in the vascular remodelling of hypoxic pulmonary hypertension (PH) but the precise mechanisms are still unclear. We hypothesized that hypoxia promotes expression of IL-33 and its receptor ST2 on vascular endothelial cells, which in turn leads to dysfunction of vascular endothelial cells and smooth muscle cells contributing to PH. Immunohistochemistry showed that immunoreactivity for IL-33 and ST2 was significantly increased in lung tissue of murine model of hypoxia-induced PH (HPH) and of subjects with bronchiectasis-PH. trans-Thoracic echocardiography showed that haemodynamic changes and right ventricular hypertrophy associated with HPH were significantly abrogated in St2^−/− compared with WT mice. Administration of IL-33 further exacerbated these changes in the hypoxia-exposed WT mice. In vitro, hypoxia significantly increased IL-33/ST2 expression by human pulmonary arterial endothelial cells (HPAECs), while exogenous IL-33 enhanced proliferation, adhesiveness and spontaneous angiogenesis of HPAECs. Knockdown of endogenous Il33 or St2 using siRNA transfection significantly suppressed these effects in both normoxic and hypoxic culture-conditions. Deletion of the St2 gene attenuated hypoxia-induced, elevated lung expression of HIF-1α/VEGFA/VEGFR-2/ICAM-1, while administration of exogenous VEGFA partially reversed the attenuation of the haemodynamic indices of PH. Correspondingly, knockdown of the St2 or Hif1α genes almost completely abrogated IL-33-induced expression of HIF-1α/VEGFA/VEGFR-2 by HPAECs in vitro. Further, IL-33-induced angiogenesis by HPAECs was extensively abrogated by knockdown of the Hif1α/Vegfa or Vegfr2 genes. These data suggest that hypoxia induces elevated expression of IL-33/ST2 by HPAECs which, at least partly by increasing downstream expression of HIF-1α and VEGF initiates vascular remodelling resulting in HPH.

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Evidence before this study

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We have been focusing on the role of cytokines in the pathogenesis of chronic pulmonary diseases for a long time, including asthma, COPD, fibrosis and bronchiectasis. We and others found that IL-33 might contribute to the occurrence and prognosis of many other diseases through binding its receptor ST2. Based on these findings, we were very eager to know whether IL-33/ST2 axis also exerts a role in hypoxia-induced pulmonary hypertension (HPH), a complication of many chronic respiratory diseases. Although it is well known that HIF-1α and VEGF play critical role in this complication, it is still unclear what the upstream of HIF-1α and VEGF is. Therefore, we first tested immunoreactivity for IL-33 and its receptor ST2 in the lung tissue sections derived from surgical specimens and from our established murine models of HPH. Surprisingly, we noted the increased immunoreactivity for both targets in these tissue sections. These findings inspired us to further explore the details of IL-33/ST2 in the pathogenesis of HPH.

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Added value of this study

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HPH is a life-threatening complication because there is lack of effective treatment. Although pulmonary arteries and ventricular remodelling might be mainly involved in the pathogenesis of the disease, the precise mechanisms are largely unknown. In the present study, we showed that hypoxia is a critical driver which induced expression of IL-33 and ST2 by endothelial cells. These factors, in turn triggered expression of HIF-1α and VEGF by endothelial cells and led to proliferation, adhesion and tube formation of these cells. We also showed that in the presence of IL-33, endothelial cells were able to affect proliferation and migration of artery smooth muscle cells, although IL-33 alone did not have such effects. These findings suggest that hypoxia and IL-33/ST2 might be initiators for HPH, through regulating downstream factors HIF-1α and VEGF.

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Implications of all the available evidence

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Our data suggest that IL-33/ST2 axis plays critical role in the pathogenesis of hypoxia-induced pulmonary hypertension because depletion of these molecules much remitted the phenomenon of complication. These observations might provide alternative therapeutic strategy for clinical treatment of HPH.

Betaine Attenuates Monocrotaline-Induced Pulmonary Arterial Hypertension in Rats via Inhibiting Inflammatory Response

Background: Pulmonary arterial hypertension (PAH) is characterized by increased pulmonary vascular resistance, leading to right ventricular failure and death. Recent studies have suggested that chronic inflammatory processes are involved in the pathogenesis of PAH. Several studies have demonstrated that betaine possesses outstanding anti-inflammatory effects. However, whether betaine exerts protective effects on PAH by inhibiting inflammatory responses in the lungs needs to be explored. To test our hypothesis, we aimed to investigate the effects of betaine on monocrotaline-induced PAH in rats and attempted to further clarify the possible mechanisms. Methods: PAH was induced by monocrotaline (50 mg/kg) and oral administration of betaine (100, 200, and 400 mg/kg/day). The mean pulmonary arterial pressure, right ventricular systolic pressure, and right ventricle hypertrophy index were used to evaluate the development of PAH. Hematoxylin and eosin staining and Masson staining were performed to measure the extents of vascular remodeling and proliferation in fibrous tissue. Monocyte chemoattractant protein-1 (MCP-1) and endothelin-1 (ET-1) were also detected by immunohistochemical staining. Nuclear factor-κB (NF-κB), tumor necrosis factor alpha (TNF-α), and interleukin-1β (IL-1β) were assessed by Western blot. Results: This study showed that betaine improved the abnormalities in right ventricular systolic pressure, mean pulmonary arterial pressure, right ventricle hypertrophy index, and pulmonary arterial remodeling induced by monocrotaline compared with the PAH group. The levels of MCP-1 and ET-1 also decreased. Western blot indicated that the protein expression levels of NF-κB, TNF-α, and IL-1β significantly decreased (p < 0.01). Conclusion: Our study demonstrated that betaine attenuated PAH through its anti-inflammatory effects. Hence, the present data may offer novel targets and promising pharmacological perspectives for treating monocrotaline-induced PAH.

Salusin-β Is Involved in Diabetes Mellitus-Induced Endothelial Dysfunction via Degradation of Peroxisome Proliferator-Activated Receptor Gamma

The pathophysiological mechanisms for vascular lesions in diabetes mellitus (DM) are complex, among which endothelial dysfunction plays a vital role. Therapeutic target against endothelial injury may provide critical venues for treatment of diabetic vascular diseases. We recently identified that salusin-β contributed to high glucose-induced endothelial cell apoptosis. However, the roles of salusin-β in DM-induced endothelial dysfunction remain largely elusive. Male C57BL/6J mice were used to induce type 2 diabetes mellitus (T2DM) model. Human umbilical vein endothelial cells (HUVECs) were cultured in high glucose/high fat (HG/HF) medium. We demonstrated increased expression of salusin-β in diabetic aortic tissues and high-glucose/high-fat- (HG/HF-) incubated HUVECs. Disruption of salusin-β by shRNA abrogated the reactive oxygen species (ROS) production, inflammation, and nitrotyrosine content of HUVECs cultured in HG/HF medium. The HG/HF-mediated decrease in peroxisome proliferator-activated receptor γ (PPARγ) expression was restored by salusin-β shRNA, and PPARγ inhibitor T0070907 abolished the protective actions of salusin-β shRNA on endothelial injury in HG/HF-treated HUVECs. Salusin-β silencing obviously improved endothelium-dependent vasorelaxation, oxidative stress, inflammatory response, and nitrative stress in diabetic aorta. Taken together, our results highlighted the essential role of salusin-β in pathological endothelial dysfunction, and salusin-β may be a promising target in treatment of vascular complications of DM.

Overexpression of salusin-β is associated with poor prognosis in ovarian cancer

Ovarian cancer is recognized as one of the worst gynecologic malignancies associated with rapid metastasis and poor overall survival rate. The identified valuable molecular biomarkers criticize importance of timely diagnosis for ovarian cancer. Salusin-β levels are dramatically increased in women with polycystic ovarian syndrome. However, the roles of salusin-β in ovarian cancer have yet to be fully elucidated. A total of 57 paired ovarian cancer specimens and matched adjacent normal tissues were used to measure the salusin-β levels. The prognostic value of salusin-β for tumor progression and survival rate was investigated. The effects of salusin-β on ovarian cancer cell proliferation and epithelial-mesenchymal transition were also explored. The expression of salusin-β was significantly increased in ovarian cancer tissue specimens compared with matched normal adjacent tissue (P<0.05). The high salusin-β level was closely related with FIGO stage and lymph node metastases. The ovarian cancer patients with high salusin-β had a shorter overall survival (P<0.05). Salusin-β obviously enhanced the proliferation and epithelial mesenchymal-transition of SKOV3 cells. Furthermore, salusin-β substantially decreased the expression of p-GSK-3β and GSK-3β, but stimulated the β-catenin expression and downstream genes of wnt/β-catenin including cyclin D1 and C-myc. Our data demonstrated for the first time that upregulated salusin-β may be a novel independent prognostic biomarker for overall survival of ovarian cancer. Salusin-β accelerated the proliferation and epithelial mesenchymal transition of ovarian cancer cells at least partly via activation of Wnt/β-catenin signaling pathway. Salusin-β may be an important target for therapeutic intervention in ovarian cancer.

Aldehyde dehydrogenase 2 protects against oxidative stress associated with pulmonary arterial hypertension

The cardioprotective benefits of aldehyde dehydrogenase 2 (ALDH2) are well established, although the regulatory role of ALDH2 in vascular remodeling in pulmonary arterial hypertension (PAH) is largely unknown. ALDH2 potently regulates the metabolism of aldehydes such as 4-hydroxynonenal (4-HNE), the endogenous product of lipid peroxidation. Thus, we hypothesized that ALDH2 ameliorates the proliferation and migration of human pulmonary artery smooth muscle cells (HPASMCs) by inhibiting 4-HNE accumulation and regulating downstream signaling pathways, thereby ameliorating pulmonary vascular remodeling. We found that low concentrations of 4-HNE (0.1 and 1μM) stimulated cell proliferation by enhancing cyclin D1 and c-Myc expression in primary HPASMCs. Low 4-HNE concentrations also enhanced cell migration by activating the nuclear factor kappa B (NF-κB) signaling pathway, thereby regulating matrix metalloprotein (MMP)-9 and MMP2 expression in vitro. In vivo, Alda-1, an ALDH2 agonist, significantly stimulated ALDH2 activity, reducing elevated 4-HNE and malondialdehyde levels and right ventricular systolic pressure in a monocrotaline-induced PAH animal model to the level of control animals. Our findings indicate that 4-HNE plays an important role in the abnormal proliferation and migration of HPASMCs, and that ALDH2 activation can attenuate 4-HNE-induced PASMC proliferation and migration, possibly by regulating NF-κB activation, in turn ameliorating vascular remodeling in PAH. This mechanism might reflect a new molecular target for treating PAH.