TRPC4 aggravates hypoxic pulmonary hypertension by promoting pulmonary endothelial cell apoptosis.

Pulmonary hypertension (PH) is a devastating disease that lacks effective treatment options and is characterized by severe pulmonary vascular remodeling. Pulmonary arterial endothelial cell (PAEC) dysfunction drives the initiation and pathogenesis of pulmonary arterial hypertension. Canonical transient receptor potential (TRPC) channels, a family of Ca2+-permeable channels, play an important role in various diseases. However, the effect and mechanism of TRPCs on PH development have not been fully elucidated. Among the TRPC family members, TRPC4 expression was markedly upregulated in PAECs from hypoxia combined with SU5416 (HySu)-induced PH mice and monocrotaline (MCT)-treated PH rats, as well as in hypoxia-exposed PAECs, suggesting that TRPC4 in PAECs may participate in the occurrence and development of PH. In this study, we aimed to investigate whether TRPC4 in PAECs has an aggravating effect on PH and elucidate the molecular mechanisms. We observed that hypoxia treatment promoted PAEC apoptosis through a caspase-12/endoplasmic reticulum stress (ERS)-dependent pathway. Knockdown of TRPC4 attenuated hypoxia-induced apoptosis and caspase-3/caspase-12 activity in PAECs. Accordingly, adeno-associated virus (AAV) serotype 6-mediated pulmonary endothelial TRPC4 silencing (AAV6-Tie-shRNA-TRPC4) or TRPC4 antagonist suppressed PH progression as evidenced by reduced right ventricular systolic pressure (RVSP), pulmonary vascular remodeling, PAEC apoptosis and reactive oxygen species (ROS) production. Mechanistically, unbiased RNA sequencing (RNA-seq) suggested that TRPC4 deficiency suppressed the expression of the proapoptotic protein sushi domain containing 2 (Susd2) in hypoxia-exposed mouse PAECs. Moreover, TRPC4 activated hypoxia-induced PAEC apoptosis by promoting Susd2 expression. Therefore, inhibiting TRPC4 ameliorated PAEC apoptosis and hypoxic PH in animals by repressing Susd2 signaling, which may serve as a therapeutic target for the management of PH.

Therapeutic potential and protective role of GRK6 overexpression in pulmonary arterial hypertension.

Abnormal proliferation of pulmonary arterial smooth muscle cells (PASMCs) is a key mechanism in the development of pulmonary arterial hypertension (PAH). Signal transducer and activator of transcription 3 (STAT3) signalling plays a critical role in modulating PASMC proliferation, and G-protein-coupled receptor kinase 6 (GRK6) regulates the STAT3 pathway. However, the mechanism underlying the relationship between GRK6 and PAH remains unclear. In this study, we aimed to investigate the role of GRK6 in PAH and determine its potential as a therapeutic target. We utilised hypoxia- and SU5416-induced PAH mouse models and a monocrotaline-induced PAH rat model to analyse the involvement of GRK6. We conducted gain- and loss-of-function experiments using mouse PASMCs. Modulation of GRK6 expression was achieved via a lentiviral vector in vitro and an adeno-associated virus serotype 1 encoding GRK6 in vivo. GRK6 was significantly downregulated in the lung tissues of PAH mice and rats, predominantly in PASMCs. Knockout of GRK6 exacerbated PAH, while both therapeutic and prophylactic overexpression of GRK6 alleviated PAH, as evidenced by a reduction in right ventricular systolic pressure, right ventricular wall to left ventricular wall plus ventricular septum ratio, pulmonary vascular media thickness, and pulmonary vascular muscularisation. Mechanistically, GRK6 overexpression attenuated hypoxia-induced PASMC proliferation and STAT3 phosphorylation. Conversely, knockdown of GRK6 promoted hypoxia-induced proliferation, which was mitigated by a STAT3 inhibitor. Our findings highlight the potential protective and beneficial roles of GRK6 in PAH; we propose a lung-targeted GRK6 gene therapy utilizing adeno-associated virus serotype 1 as a potential treatment approach for patients with PAH.

Transcription factors and potential therapeutic targets for pulmonary hypertension.

Pulmonary hypertension (PH) is a refractory and fatal disease characterized by excessive pulmonary arterial cell remodeling. Uncontrolled proliferation and hypertrophy of pulmonary arterial smooth muscle cells (PASMCs), dysfunction of pulmonary arterial endothelial cells (PAECs), and abnormal perivascular infiltration of immune cells result in pulmonary arterial remodeling, followed by increased pulmonary vascular resistance and pulmonary pressure. Although various drugs targeting nitric oxide, endothelin-1 and prostacyclin pathways have been used in clinical settings, the mortality of pulmonary hypertension remains high. Multiple molecular abnormalities have been implicated in pulmonary hypertension, changes in numerous transcription factors have been identified as key regulators in pulmonary hypertension, and a role for pulmonary vascular remodeling has been highlighted. This review consolidates evidence linking transcription factors and their molecular mechanisms, from pulmonary vascular intima PAECs, vascular media PASMCs, and pulmonary arterial adventitia fibroblasts to pulmonary inflammatory cells. These findings will improve the understanding of particularly interactions between transcription factor-mediated cellular signaling pathways and identify novel therapies for pulmonary hypertension.

Environmental eustress improves postinfarction cardiac repair via enhancing cardiac macrophage survival.

Macrophages play a vital role in cardiac repair following myocardial infarction (MI). An enriched environment (EE) is involved in the regulation of macrophage-related activities and disease progression; however, whether EE affects the phenotype and function of macrophages to improve postinfarction cardiac repair remains unknown. In this study, we found that EE improved cardiac function, decreased mortality, and ameliorated adverse ventricular remodeling in mice after MI, with these outcomes closely related to the increased survival of Ly6Clow macrophages and their CCR2-MHCIIlow subsets. EE increased the expression of brain-derived neurotrophic factor (BDNF) in the hypothalamus, leading to higher circulating levels of BDNF, which, in turn, regulated the cardiac macrophages. BDNF bound to tropomyosin receptor kinase B to activate downstream ERK1/2 and AKT pathways, promoting macrophage survival. These findings demonstrate that EE optimizes postinfarction cardiac repair and highlights the significance of EE as a previously unidentified strategy for impeding adverse ventricular remodeling.

Caspase-8 Promotes Pulmonary Hypertension by Activating Macrophage-Associated Inflammation and IL-1ß (Interleukin 1ß) Production.

BACKGROUND: Macrophages are involved in the pathogenesis of pulmonary arterial hypertension (PAH). Caspase-8, an apical component of cell death pathways, is significantly upregulated in macrophages of PAH animal models. However, its role in PAH remains unclear. Caspase-8 plays a critical role in regulating inflammatory responses via inflammasome activation, cell death, and cytokine induction. This study investigated the mechanism of regulation of IL-1ß (interleukin 1ß) activation in macrophages by caspase-8. METHODS: A hypoxia + SU5416-induced PAH mouse model and monocrotaline-induced rat model of PAH were constructed and the role of caspase-8 was analyzed. RESULTS: Caspase-8 and cleaved-caspase-8 were significantly upregulated in the lung tissues of SU5416 and hypoxia-treated PAH mice and monocrotaline-treated rats. Pharmacological inhibition of caspase-8 alleviated PAH compared with wild-type mice, observed as a significant reduction in right ventricular systolic pressure, ratio of right ventricular wall to left ventricular wall plus ventricular septum, pulmonary vascular media thickness, and pulmonary vascular muscularization; caspase-8 ablated mice also showed significant remission. Mechanistically, increased proliferation of pulmonary arterial smooth muscle cellss is closely associated with activation of the NLRP3 (NOD [nucleotide oligomerization domain]-, LRR [leucine-rich repeat]-, and PYD [pyrin domain]-containing protein 3) inflammasome and the IL-1ß signaling pathway. Although caspase-8 did not affect extracellular matrix synthesis, it promoted inflammatory cell infiltration and pulmonary arterial smooth muscle cell proliferation via NLRP3/IL-1ß activation during the development stage of PAH. CONCLUSIONS: Taken together, our study suggests that macrophage-derived IL-1ß via caspase-8-dependent canonical inflammasome is required for macrophages to play a pathogenic role in pulmonary perivascular inflammation.

Resolvin E1 Attenuates Pulmonary Hypertension by Suppressing Wnt7a/ß-Catenin Signaling.

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Tregs-derived interleukin 35 attenuates endothelial proliferation through STAT1 in pulmonary hypertension.

BACKGROUND: To explore the source, the role and the specific mechanism of IL-35 and its downstream molecules in the development of pulmonary hypertension. METHODS: 8-10 weeks male mice were undergoing hypoxia combined with SU5416 (HySu) to establish a pulmonary hypertension (PH) model. The phenotype of PH mice was measured by immunohistochemistry and immunofluorescence staining. The levels of two subunits (EBI3 and p35 subunits) in lung tissue were measured by real-time PCR and western blotting. EBI3 monoclonal antibody was administrated as IL-35 neutralization to offset systemic IL-35 expression. Fludarabine, an inhibitor of STAT1 (signal transducer and activator of transcription 1) was used to clarify the role of STAT1 under IL-35 treatment. RESULTS: After pulmonary hypertension, the expression of IL-35 and its two subunits (EBI3 and p35 subunits) in lung tissue were significantly increased. And the two subunits of IL-35 are highly expressed in Treg cells. Compared with the controlled PH mice, the IL-35 neutralization PH mice showed aggravated pulmonary hypertension phenotype. The specific manifestations are the increase of right ventricular systolic pressure (RVSP), the growing proportion of right heart [RV/(LV+S)], and the remodeling of pulmonary blood vessels increases. The expression of pulmonary vascular endothelium (CD31) in PH mice increased, and the proliferation ability of vascular endothelium enhanced after IL-35 was inhibited. IL-35 phosphorylates STAT1 through the receptor GP130 on pulmonary vascular endothelial cells, which in turn inhibits endothelial cell proliferation. IL-35 recombinant protein can reduce the expression of CD31 in lung tissues of PH mice. But the administration of STAT1 inhibitor made it invalid from the IL-35 effect of reversing pulmonary hypertension. CONCLUSIONS: Tregs-derived IL-35 can reverse the remodeling of pulmonary blood vessels and alleviate the progression of pulmonary hypertension by reducing the proliferation of endothelial cells.

Impact of Long-Term Home Quarantine on Mental Health and Physical Activity of People in Shanghai During the COVID-19 Pandemic.

This study aimed to investigate the effects of long-term home quarantine on the mental health of people during the COVID-19 epidemic in Shanghai. We conducted an online questionnaire survey on March 26 2020 and collected data on demographics, level of physical activity (PA), and mental health status of the participants. We assessed the mental health status using the Patient Health Questionnaire (PHQ-9) and Generalized Anxiety Disorder Scale (GAD-7), whereas PA was assessed using International Physical Activity Questionnaire Short Form (IPAQ-SF). Of all 2,409 valid samples, participants reported performing a total of 2015.20 metabolic equivalent of task (MET)-minutes/week of total PA before the outbreak period and 1720.29 MET-minutes/week of total PA during the outbreak period (p < 0.001). Participants who spent a longer time at home reported to have a better performance on the PHQ-9 (p = 0.087) and GAD-7 (p < 0.001). A high level of PA was considered an protective factor against depression (OR = 0.755, 95% CI 0.603-0.944, p < 0.001). Additionally, a high level of PA had a preventative effect on anxiety (OR = 0.741, 95% CI 0.568-0.967, p < 0.001), and a longer working period during the outbreak was shown to be a risk factor for anxiety (11-29 days, OR 1.455, 95% CI 1.110-1.909; 30-60 days OR 1.619, 95% CI 1.227-2.316). Home confinement during the pandemic might not have a negative effect on mental health provided that people engage in more PA indoors. This study encourages interventions for mental health problems through physical exercise.

Niacin Attenuates Pulmonary Hypertension Through H-PGDS in Macrophages.

RATIONALE: Pulmonary arterial hypertension (PAH) is characterized by progressive pulmonary vascular remodeling, accompanied by varying degrees of perivascular inflammation. Niacin, a commonly used lipid-lowering drug, possesses vasodilating and proresolution effects by promoting the release of prostaglandin D2 (PGD2). However, whether or not niacin confers protection against PAH pathogenesis is still unknown. OBJECTIVE: This study aimed to determine whether or not niacin attenuates the development of PAH and, if so, to elucidate the molecular mechanisms underlying its effects. METHODS AND RESULTS: Vascular endothelial growth factor receptor inhibitor SU5416 and hypoxic exposure were used to induce pulmonary hypertension (PH) in rodents. We found that niacin attenuated the development of this hypoxia/SU5416-induced PH in mice and suppressed progression of monocrotaline-induced and hypoxia/SU5416-induced PH in rats through the reduction of pulmonary artery remodeling. Niacin boosted PGD2 generation in lung tissue, mainly through H-PGDS (hematopoietic PGD2 synthases). Deletion of H-PGDS, but not lipocalin-type PGDS, exacerbated the hypoxia/SU5416-induced PH in mice and abolished the protective effects of niacin against PAH. Moreover, H-PGDS was expressed dominantly in infiltrated macrophages in lungs of PH mice and patients with idiopathic PAH. Macrophage-specific deletion of H-PGDS markedly decreased PGD2 generation in lungs, aggravated hypoxia/SU5416-induced PH in mice, and attenuated the therapeutic effect of niacin on PAH. CONCLUSIONS: Niacin treatment ameliorates the progression of PAH through the suppression of vascular remodeling by stimulating H-PGDS-derived PGD2 release from macrophages.

Macrophage-Derived Legumain Promotes Pulmonary Hypertension by Activating the MMP (Matrix Metalloproteinase)-2/TGF (Transforming Growth Factor)-ß1 Signaling.

Objective- Macrophages participate in the pathogenesis of pulmonary arterial hypertension (PAH). Lgmn (Legumain), a newly discovered cysteine proteinase belonging to the C13 peptidase family, is primarily expressed in macrophages; however, its roles in PAH remain unknown. Approach and Results- Herein, Lgmn was upregulated in lung tissues of PAH mice subjected to hypoxia plus SU5416 and PAH rats challenged with monocrotaline. Global Lgmn ablation and macrophage-specific ablation alleviated PAH compared with wild-type mice, evident from a reduction in right ventricular systolic pressure, the ratio of the right ventricular wall to the left ventricular wall plus the septum, the pulmonary vascular media thickness, and pulmonary vascular muscularization. Increased expression of ECM (extracellular matrix) proteins was correlated with MMP (matrix metalloproteinase)-2 activation and TGF (transforming growth factor)-ß1 signaling in the PAs. Although Lgmn did not affect inflammatory cell infiltration and PA smooth muscle cell proliferation, it drove increased the synthesis of ECM proteins via MMP-2 activation. MMP-2 hydrolyzed the TGF-ß1 precursor to the active form. An Lgmn-specific inhibitor markedly ameliorated PAH. Clinically, serum Lgmn levels were closely associated with the severity of idiopathic PAH. Conclusions- Our results indicate that Lgmn inhibition could be an effective strategy for preventing or delaying PAH.