A Critical Role of the mTOR/eIF2α Pathway in Hypoxia-Induced Pulmonary Hypertension

Emerging insights into pulmonary hypertension: the potential role of mitochondrial dysfunction and redox homeostasis

Pulmonary hypertension (PH) is heterogeneous diseases that can lead to death due to progressive right heart failure. Emerging evidence suggests that, in addition to its role in ATP production, changes in mitochondrial play a central role in their pathogenesis, regulating integrated metabolic and signal transduction pathways. This review focuses on the basic principles of mitochondrial redox status in pulmonary vascular and right ventricular disorders, a series of dysfunctional processes including mitochondrial quality control (mitochondrial biogenesis, mitophagy, mitochondrial dynamics, mitochondrial unfolded protein response) and mitochondrial redox homeostasis. In addition, we will summarize how mitochondrial renewal and dynamic changes provide innovative insights for studying and evaluating PH. This will provide us with a clearer understanding of the initial signal transmission of mitochondria in PH, which would further improve our understanding of the pathogenesis of PH.

Characteristics and outcomes of patients developing pulmonary hypertension associated with proteasome inhibitors

BACKGROUND

Pulmonary arterial hypertension (PAH) has been described in patients treated with proteasome inhibitors (PIs). Our objective was to evaluate the association between PIs and PAH.

METHODS

Characteristics of incident PAH cases previously treated with carfilzomib or bortezomib were analysed from the French pulmonary hypertension registry and the VIGIAPATH programme from 2004 to 2023, concurrently with a pharmacovigilance disproportionality analysis using the World Health Organization (WHO) global database (VigiBase) and a meta-analysis of randomised controlled trials.

RESULTS

11 incident cases of PI-associated PAH were identified (six with carfilzomib and five with bortezomib) with a female:male ratio of 2.7:1, a median age of 61 years, and a median delay between PI first exposure and PAH of 6 months. Four patients died (two from right heart failure, one from respiratory distress and one from an unknown cause). At diagnosis, six were in New York Heart Association Functional Class III/IV with severe haemodynamic impairment (median mean pulmonary arterial pressure 39 mmHg, cardiac index 2.45 L·min-1·m-2 and pulmonary vascular resistance 7.2 WU). In the WHO pharmacovigilance database, 169 cases of PH associated with PI were reported since 2013 with significant signals of disproportionate reporting (SDR) for carfilzomib, regardless of the definition of cases or control group. However, SDR for bortezomib were inconsistent. The systematic review identified 17 clinical trials, and carfilzomib was associated with a significantly higher risk of dyspnoea, severe dyspnoea and PH compared with bortezomib.

CONCLUSION

PIs may induce PAH in patients undergoing treatment, with carfilzomib emitting a stronger signal than bortezomib, and these patients should be monitored closely.

Upregulation of eIF2α by m6A modification accelerates the proliferation of pulmonary artery smooth muscle cells in MCT-induced pulmonary arterial hypertension rats

Pulmonary arterial hypertension (PAH) is a malignant cardiovascular disease. Eukaryotic initiation factor 2α (eIF2α) plays an important role in the proliferation of pulmonary artery smooth muscle cells (PASMCs) in hypoxia-induced pulmonary hypertension (HPH) rats. However, the regulatory mechanism of eIF2α remains poorly understood in PAH rats. Here, we discover eIF2α is markedly upregulated in monocrotaline (MCT)-induced PAH rats, eIF2α can be upregulated by mRNA methylation, and upregulated eIF2α can promote PASMC proliferation in MCT-PAH rats. GSK2606414, eIF2α inhibitor, can downregulate the expression of eIF2α and alleviate PASMC proliferation in MCT-PAH rats. And we further discover the mRNA of eIF2α has a common sequence with N 6-methyladenosine (m6A) modification by bioinformatics analysis, and the expression of METTL3, WTAP, and YTHDF1 is upregulated in MCT-PAH rats. These findings suggest a potentially novel mechanism by which eIF2α is upregulated by m6A modification in MCT-PAH rats, which is involved in the pathogenesis of PAH.

Atorvastatin rescues pulmonary artery hypertension by inhibiting the AKT/ERK-dependent PDGF-BB/HIF-1α axis

BACKGROUND

The aim of this study is to explore the role of atorvastatin in rescuing pulmonary artery hypertension (PAH) by inhibiting the AKT/ERK-dependent PDGF-BB/HIF-1α axis.

METHODS

PAH model in rats was established by MCT induction, followed by Atorvastatin intervention. Pulmonary hemodynamic measurement and pulmonary morphological evaluation in rats were conducted. Human pulmonary artery smooth muscle cells (hPASMCs) were subjected to hypoxic exposure or PDGF-BB treatment, followed by atorvastatin induction. Relative levels of HIF-1α, p-ERK and p-Akt were detected. Viability and apoptosis were respectively determined by cell counting kit-8 (CCK-8) assay and flow cytometry.

RESULTS

Atorvastatin protected PAH-induced increases in RVSP and Fulton's index in rats. Meanwhile, it inhibited vascular remodeling following PAH by downregulating HIF-1α and PDGF-BB. Hypoxia or PDGF-BB treatment in hPASMCs resulted in upregulation of p-ERK and p-Akt, and viability increase, which were partially abolished by Atorvastatin intervention. In addition, atorvastatin triggered apoptosis in hypoxia or PDGF-BB-induced hPASMCs.

CONCLUSIONS

Atorvastatin inhibits the activation of HIF-1α and proliferative ability, and triggers apoptosis in hPASMCs exposed to hypoxia or PDGF-BB treatment through inactivating the AKT/ERK pathway.

Mammalian Target of Rapamycin as the Therapeutic Target of Vascular Proliferative Diseases: Past, Present, and Future

ABSTRACT

The abnormal proliferation of vascular smooth muscle cells (VSMCs) is a key pathological characteristic of vascular proliferative diseases. Mammalian target of rapamycin (mTOR) is an evolutionarily conserved serine/threonine kinase that plays an important role in regulating cell growth, motility, proliferation, and survival, as well as gene expression in response to hypoxia, growth factors, and nutrients. Increasing evidence shows that mTOR also regulates VSMC proliferation in vascular proliferative diseases and that mTOR inhibitors, such as rapamycin, effectively restrain VSMC proliferation. However, the molecular mechanisms linking mTOR to vascular proliferative diseases remain elusive. In our review, we summarize the key roles of the mTOR and the recent discoveries in vascular proliferative diseases, focusing on the therapeutic potential of mTOR inhibitors to target the mTOR signaling pathway for the treatment of vascular proliferative diseases. In this study, we discuss mTOR inhibitors as promising candidates to prevent VSMC-associated vascular proliferative diseases.

The Isoquinoline-Sulfonamide Compound H-1337 Attenuates SU5416/Hypoxia-Induced Pulmonary Arterial Hypertension in Rats

Pulmonary arterial hypertension (PAH) is characterized by elevated pulmonary arterial pressure and right heart failure. Selective pulmonary vasodilators have improved the prognosis of PAH; however, they are not able to reverse pulmonary vascular remodeling. Therefore, a search for new treatment agents is required. H-1337 is an isoquinoline-sulfonamide compound that inhibits multiple serine/threonine kinases, including Rho-associated protein kinase (ROCK) and mammalian target of rapamycin (mTOR). Here, we investigated the effects of H-1337 on pulmonary hypertension and remodeling in the pulmonary vasculature and right ventricle in experimental PAH induced by SU5416 and hypoxia exposure. H-1337 and H-1337M1 exerted inhibitory effects on ROCK and Akt. H-1337 inhibited the phosphorylation of myosin light chain and mTOR and suppressed the proliferation of smooth muscle cells in vitro. H-1337 treatment also suppressed the phosphorylation of myosin light chain and mTOR in the pulmonary vasculature and decreased right ventricular systolic pressure and the extent of occlusive pulmonary vascular lesions. Furthermore, H-1337 suppressed aggravation of right ventricle hypertrophy. In conclusion, our data demonstrated that inhibition of ROCK and mTOR pathways with H-1337 suppressed the progression of pulmonary vascular remodeling, pulmonary hypertension, and right ventricular remodeling.

Hypoxia and the integrated stress response promote pulmonary hypertension and preeclampsia: Implications in drug development

Chronic hypoxia is a common cause of pulmonary hypertension, preeclampsia, and intrauterine growth restriction (IUGR). The molecular mechanisms underlying these diseases are not completely understood. Chronic hypoxia may induce the generation of reactive oxygen species (ROS) in mitochondria, promote endoplasmic reticulum (ER) stress, and result in the integrated stress response (ISR) in the pulmonary artery and uteroplacental tissues. Numerous studies have implicated hypoxia-inducible factors (HIFs), oxidative stress, and ER stress/unfolded protein response (UPR) in the development of pulmonary hypertension, preeclampsia and IUGR. This review highlights the roles of HIFs, mitochondria-derived ROS and UPR, as well as their interplay, in the pathogenesis of pulmonary hypertension and preeclampsia, and their implications in drug development.

Single-cell transcriptomic profile of human pulmonary artery endothelial cells in health and pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is an insidious disease characterized by severe remodeling of the pulmonary vasculature caused in part by pathologic changes of endothelial cell functions. Although heterogeneity of endothelial cells across various vascular beds is well known, the diversity among endothelial cells in the healthy pulmonary vascular bed and the pathologic diversity among pulmonary arterial endothelial cells (PAEC) in PAH is unknown and previously unexplored. Here single-cell RNA sequencing technology was used to decipher the cellular heterogeneity among PAEC in the human pulmonary arteries isolated from explanted lungs from three patients with PAH undergoing lung transplantation and three healthy donor lungs not utilized for transplantation. Datasets of 36,368 PAH individual endothelial cells and 36,086 healthy cells were analyzed using the SeqGeq bioinformatics program. Total population differential gene expression analyses identified 629 differentially expressed genes between PAH and controls. Gene Ontology and Canonical Ingenuity analysis revealed pathways that are known to be involved in pathogenesis, as well as unique new pathways. At the individual cell level, dimensionality reduction followed by density based clustering revealed the presence of eight unique PAEC clusters that were typified by proliferative, angiogenic or quiescent phenotypes. While control and PAH harbored many similar subgroups of endothelial cells, PAH had greater proportions of angiogenic and proliferative subsets. These findings identify that only specific subgroups of PAH PAEC have gene expression different than healthy PAEC, and suggest these subpopulations lead to the pathologic functions leading to remodeling.

mTOR Signaling in Pulmonary Vascular Disease: Pathogenic Role and Therapeutic Target

Pulmonary arterial hypertension (PAH) is a progressive and fatal disease without a cure. The exact pathogenic mechanisms of PAH are complex and poorly understood, yet a number of abnormally expressed genes and regulatory pathways contribute to sustained vasoconstriction and vascular remodeling of the distal pulmonary arteries. Mammalian target of rapamycin (mTOR) is one of the major signaling pathways implicated in regulating cell proliferation, migration, differentiation, and protein synthesis. Here we will describe the canonical mTOR pathway, structural and functional differences between mTOR complexes 1 and 2, as well as the crosstalk with other important signaling cascades in the development of PAH. The pathogenic role of mTOR in pulmonary vascular remodeling and sustained vasoconstriction due to its contribution to proliferation, migration, phenotypic transition, and gene regulation in pulmonary artery smooth muscle and endothelial cells will be discussed. Despite the progress in our elucidation of the etiology and pathogenesis of PAH over the two last decades, there is a lack of effective therapeutic agents to treat PAH patients representing a significant unmet clinical need. In this review, we will explore the possibility and therapeutic potential to use inhibitors of mTOR signaling cascade to treat PAH.

PDGF/MEK/ERK axis represses Ca2+ clearance via decreasing the abundance of plasma membrane Ca2+ pump PMCA4 in pulmonary arterial smooth muscle cells

Pulmonary arterial hypertension (PAH) is a rare and lethal disease characterized by vascular remodeling and vasoconstriction, which is associated with increased intracellular calcium ion concentration ([Ca2+]i). Platelet-derived growth factor-BB (PDGF-BB) is the most potent mitogen for pulmonary arterial smooth muscle cells (PASMCs) and is involved in vascular remodeling during PAH development. PDGF signaling has been proved to participate in maintaining Ca2+ homeostasis of PASMCs; however, the mechanism needs to be further elucidated. Here, we illuminate that the expression of plasma membrane calcium-transporting ATPase 4 (PMCA4) was downregulated in PASMCs after PDGF-BB stimulation, which could be abolished by restraining the mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK/ERK). Functionally, suppression of PMCA4 attenuated the [Ca2+]i clearance in PASMCs after Ca2+ entry, promoting cell proliferation and elevating cell locomotion through mediating formation of focal adhesion. Additionally, the expression of PMCA4 was decreased in the pulmonary artery of monocrotaline (MCT)- or hypoxia-induced PAH rats. Moreover, knockdown of PMCA4 could increase the right ventricular systolic pressure (RVSP) and wall thickness (WT) of pulmonary artery in rats raised under normal conditions. Taken together, our findings demonstrate the importance of the PDGF/MEK/ERK/PMCA4 axis in intracellular Ca2+ homeostasis in PASMCs, indicating a functional role of PMCA4 in pulmonary arterial remodeling and PAH development.

Autophagy, Unfolded Protein Response and Lung Disease

Acute Respiratory Distress Syndrome is a severe disorder affecting thousands of individuals worldwide. The available medical countermeasures do not sufficiently suppress the unacceptable high mortality rates associated with those in need. Thus, intense efforts aim to delineate the function of the lung endothelium, so to deliver new therapeutic approaches against this disease. The present manuscript attempts to shed light on the interrelations between the unfolded protein response and autophagy towards lung disease, to deliver a new line of possible therapeutic approaches against the ferocious Acute Respiratory Distress Syndrome.

Proteomic Analysis of KCNK3 Loss of Expression Identified Dysregulated Pathways in Pulmonary Vascular Cells

The physiopathology of pulmonary arterial hypertension (PAH) is characterized by pulmonary artery smooth muscle cell (PASMC) and endothelial cell (PAEC) dysfunction, contributing to pulmonary arterial obstruction and PAH progression. KCNK3 loss of function mutations are responsible for the first channelopathy identified in PAH. Loss of KCNK3 function/expression is a hallmark of PAH. However, the molecular mechanisms involved in KCNK3 dysfunction are mostly unknown. To identify the pathological molecular mechanisms downstream of KCNK3 in human PASMCs (hPASMCs) and human PAECs (hPAECs), we used a Liquid Chromatography-Tandem Mass Spectrometry-based proteomic approach to identify the molecular pathways regulated by KCNK3. KCNK3 loss of expression was induced in control hPASMCs or hPAECs by specific siRNA targeting KCNK3. We found that the loss of KCNK3 expression in hPAECs and hPASMCs leads to 326 and 222 proteins differentially expressed, respectively. Among them, 53 proteins were common to hPAECs and hPASMCs. The specific proteome remodeling in hPAECs in absence of KCNK3 was mostly related to the activation of glycolysis, the superpathway of methionine degradation, and the mTOR signaling pathways, and to a reduction in EIF2 signaling pathways. In hPASMCs, we found an activation of the PI3K/AKT signaling pathways and a reduction in EIF2 signaling and the Purine Nucleotides De Novo Biosynthesis II and IL-8 signaling pathways. Common to hPAECs and hPASMCs, we found that the loss of KCNK3 expression leads to the activation of the NRF2-mediated oxidative stress response and a reduction in the interferon pathway. In the hPAECs and hPASMCs, we found an increased expression of HO-1 (heme oxygenase-1) and a decreased IFIT3 (interferon-induced proteins with tetratricopeptide repeats 3) (confirmed by Western blotting), allowing us to identify these axes to understand the consequences of KCNK3 dysfunction. Our experiments, based on the loss of KCNK3 expression by a specific siRNA strategy in control hPAECs and hPASMCs, allow us to identify differences in the activation of several signaling pathways, indicating the key role played by KCNK3 dysfunction in the development of PAH. Altogether, these results allow us to better understand the consequences of KCNK3 dysfunction and suggest that KCNK3 loss of expression acts in favor of the proliferation and migration of hPASMCs and promotes the metabolic shift and apoptosis resistance of hPAECs.

Endoplasmic reticulum stress and pulmonary hypertension

Pulmonary hypertension is a fatal disease of which pulmonary vasculopathy is the main pathological feature resulting in the mean pulmonary arterial pressure higher than 25 mmHg. Moreover, pulmonary hypertension remains a tough problem with unclear molecular mechanisms. There have been dozens of studies about endoplasmic reticulum stress during the onset of pulmonary hypertension in patients, suggesting that endoplasmic reticulum stress may have a critical effect on the pathogenesis of pulmonary hypertension. The review aims to summarize the rationale to elucidate the role of endoplasmic reticulum stress in pulmonary hypertension. Started by reviewing the mechanisms responsible for the unfolded protein response following endoplasmic reticulum stress, the potential link between endoplasmic reticulum stress and pulmonary hypertension were introduced, and the contributions of endoplasmic reticulum stress to different vascular cells, mitochondria, and inflammation were described, and finally the potential therapies of attenuating endoplasmic reticulum stress for pulmonary hypertension were discussed.

Effects of Starvation on Antioxidant-Related Signaling Molecules, Oxidative Stress, and Autophagy in Juvenile Chinese Perch Skeletal Muscle

The autophagic lysosomal protein degradation pathway is an evolutionarily conserved pathway, which utilizes lysosomes to degrade and to circulate cell components. Autophagy has been observed in many different types of cells, but its role in skeletal muscle protein degradation has not been thoroughly studied, especially in aquatic species. This study assessed the expression of antioxidant-related signaling genes and the effects of starvation on antioxidant capacity, reactive oxygen species (ROS) content, autophagy-related gene, and autophagosome formation in the skeletal muscle of juvenile Chinese perch after short-term starvation. The results indicated that after starvation for 2 days, the expression of antioxidant-related signaling genes, such as Nrf2 and S6K, was upregulated, while Keap1 was downregulated in the muscle of juvenile Chinese perch. The amounts of antioxidant enzymes ROS, MDA, AHRFR, and ASA and the activities of SOD, CAT, GPx, and GST were increased, and the mRNA levels of GPx, GSTA, GST4A, GSTT1, MnSOD, ZnSOD, and CAT were upregulated. Meanwhile, there was no significant change in the level of LC3-II protein. When starvation was prolonged to 5 days, Nrf2 and S6K1 continued to increase and mTOR and Keap1 significantly decreased; ROS and ASA content continued to be significantly increased, but the MDA and AHRFR content and the SOD, CAT GR, and GPx activities all decreased. The expression of MnSOD, ZnSOD, and GR decreased significantly, and GST4A, GSTT1, and CAT tended to decrease to levels consistent with normal feeding. The expression of all autophagy-related genes except Ulk1 significantly increased, the formation of autophagosomes and autolysosomes was enhanced in muscle, and LC3 protein levels in muscle increased significantly. Our data suggested that the autophagy that occurs in the skeletal muscle tissue of Chinese perch due to dietary deprivation is involved in a series of molecular and physiological responses, including changes in antioxidant signaling molecules, in antioxidant capacity and in autophagy and autophagy-related gene expression.

PIM1 (Moloney Murine Leukemia Provirus Integration Site) Inhibition Decreases the Nonhomologous End-Joining DNA Damage Repair Signaling Pathway in Pulmonary Hypertension

OBJECTIVE

Pulmonary arterial hypertension (PAH) is a fatal disease characterized by the narrowing of pulmonary arteries (PAs). It is now established that this phenotype is associated with enhanced PA smooth muscle cells (PASMCs) proliferation and suppressed apoptosis. This phenotype is sustained in part by the activation of several DNA repair pathways allowing PASMCs to survive despite the unfavorable environmental conditions. PIM1 (Moloney murine leukemia provirus integration site) is an oncoprotein upregulated in PAH and involved in many prosurvival pathways, including DNA repair. The objective of this study was to demonstrate the implication of PIM1 in the DNA damage response and the beneficial effect of its inhibition by pharmacological inhibitors in human PAH-PASMCs and in rat PAH models. Approach and Results: We found in vitro that PIM1 inhibition by either SGI-1776, TP-3654, siRNA (silencer RNA) decreased the phosphorylation of its newly identified direct target KU70 (lupus Ku autoantigen protein p70) resulting in the inhibition of double-strand break repair (Comet Assay) by the nonhomologous end-joining as well as reduction of PAH-PASMCs proliferation (Ki67-positive cells) and resistance to apoptosis (Annexin V positive cells) of PAH-PASMCs. In vivo, SGI-1776 and TP-3654 given 3× a week, improved significantly pulmonary hemodynamics (right heart catheterization) and vascular remodeling (Elastica van Gieson) in monocrotaline and Fawn-Hooded rat models of PAH.

CONCLUSIONS

We demonstrated that PIM1 phosphorylates KU70 and initiates DNA repair signaling in PAH-PASMCs and that PIM1 inhibitors represent a therapeutic option for patients with PAH.

Crosstalk between the Akt/mTORC1 and NF-κB signaling pathways promotes hypoxia-induced pulmonary hypertension by increasing DPP4 expression in PASMCs

Abnormal wound healing by pulmonary artery smooth muscle cells (PASMCs) promotes vascular remodeling in hypoxia-induced pulmonary hypertension (HPH). Increasing evidence shows that both the mammalian target of rapamycin complex 1 (mTORC1) and nuclear factor-kappa B (NF-κB) are involved in the development of HPH. In this study, we explored the crosstalk between mTORC1 and NF-κB in PASMCs cultured under hypoxic condition and in a rat model of hypoxia-induced pulmonary hypertension (HPH). We showed that hypoxia promoted wound healing of PASMCs, which was dose-dependently blocked by the mTORC1 inhibitor rapamycin (5-20 nM). In PASMCs, hypoxia activated mTORC1, which in turn promoted the phosphorylation of NF-κB. Molecular docking revealed that mTOR interacted with IκB kinases (IKKs) and that was validated by immunoprecipitation. In vitro kinase assays and mass spectrometry demonstrated that mTOR phosphorylated IKKα and IKKβ separately. Inhibition of mTORC1 decreased the level of phosphorylated IKKα/β, thus reducing the phosphorylation and transcriptional activity of NF-κB. Bioinformatics study revealed that dipeptidyl peptidase-4 (DPP4) was a target gene of NF-κB; DPP4 inhibitor, sitagliptin (10-500 μM) effectively inhibited the abnormal wound healing of PASMCs under hypoxic condition. In the rat model of HPH, we showed that NF-κB activation (at 3 weeks) was preceded by mTOR signaling activation (after 1 or 2 weeks) in lungs, and administration of sitagliptin (1-5 mg/kg every day, ig) produced preventive effects against the development of HPH. In conclusion, hypoxia activates the crosstalk between mTORC1 and NF-κB, and increased DPP4 expression in PASMCs that leads to vascular remodeling. Sitagliptin, a DPP4 inhibitor, exerts preventive effect against HPH.

eIF2α promotes vascular remodeling via autophagy in monocrotaline-induced pulmonary arterial hypertension rats

PURPOSE

Eukaryotic initiation factor 2α (eIF2α) plays important roles in the proliferation and survival of pulmonary artery smooth muscle cells (PASMCs) in animal hypoxia-induced pulmonary hypertension models. However, the underlying mechanism remains unknown at large. Autophagy has been reported to play a key role in the vascular remodeling in pulmonary arterial hypertension (PAH). The purposes of this study are to determine the functions of eIF2α and autophagy in the vascular remodeling of the monocrotaline-induced PAH rats and to clarify the correlation between eIF2α and autophagy.

METHODS

We established a rat model of monocrotaline-induced PAH, and we established a cell model of platelet derived growth factor (PDGF)-induced PASMCs proliferation. The vascular morphology and the expression of eIF2α, LC3B, and p62 were assessed in the pulmonary arterial tissue of Sprague-Dawleyrats and PDGF-induced PASMCs.

RESULTS

Autophagy was significantly active in monocrotaline model group (MCT)-induced PAH rats, which obviously promotes vascular remodeling in MCT-induced PAH rats. Furthermore, the proliferation of PASMCs was induced by PDGF in vitro. The expression of LC3B, eIF2α was increased in the PDGF-induced PASMCs proliferation, and the expression of p62 was reduced in the PDGF-induced PASMCs proliferation. Moreover, eIF2α siRNA downregulated the expression of eIF2α and LC3B, and upregulated the expression of p62 in PDGF-induced PASMCs proliferation. eIF2α siRNA inhibited the PDGF-induced PASMCs proliferation. Finally, chloroquine can upregulate the protein expression of LC3B and p62, it also can inhibit proliferation in PDGF-induced PASMCs.

CONCLUSION

Based on these observations, we conclude that eIF2α promotes the proliferation of PASMCs and vascular remodeling in monocrotaline-induced PAH rats through accelerating autophagy pathway.

Autophagy in pulmonary hypertension: Emerging roles and therapeutic implications

Autophagy is an important mechanism for cellular self-digestion and basal homeostasis. This gene- and modulator-regulated pathway is conserved in cells. Recently, several studies have shown that autophagic dysfunction is associated with pulmonary hypertension (PH). However, the relationship between autophagy and PH remains controversial. In this review, we mainly introduce the effects of autophagy-related genes and some regulatory molecules on PH and the relationship between autophagy and PH under the conditions of hypoxia, monocrotaline injection, thromboembolic stress, oxidative stress, and other drugs and toxins. The effects of other autophagy-related drugs, such as chloroquine, 3-methyladenine, rapamycin, and other potential therapeutic drugs and targets, in PH are also described.

Sulfur dioxide attenuates hypoxia-induced pulmonary arteriolar remodeling via Dkk1/Wnt signaling pathway

OBJECTIVE

This study investigated the impact of SO₂ on rats with hypoxic pulmonary vascular structural remodeling and its possible mechanisms.

MATERIALS AND METHODS

Pulmonary vascular morphological change was examined by HE staining. RNA-based high-throughput sequencing (RNA-seq) was performed to detect differential expression of mRNAs in Normal and Hypoxia-induced Pulmonary hypertension (HPH) rats. The Real-time quantitative RT-PCR (q RT-PCR) was used for validation of wnt7b, sfrp2, cacna1f, DKK1, CaSR and vimentin mRNA expression levels. Protein levels of CaSR, Vimentin, Caspase3, E-cadherin and P-Akt1/2/3 were detected by Western blot and immunohistochemistry.

RESULTS

This study showed that SO₂ significantly attenuated the interstitial thickening and prominent media hypertrophy of pulmonary arteries. SO₂ downregulated p-Akt1/2/3 protein level and upregulated E-cadherin protein level in lung tissues, which inhibited the proliferation and epithelial-to-mesenchymal transition (EMT) in HPH rats. RNA-seq and PCR validation results showed that levels of Wnt7b, Sfrp2 and Cacna1f mRNAs decreased and Dkk1 mRNA level increased obviously in HPH rats. Moreover, SO₂ attenuated the mRNA and protein level of CaSR, which was activated in HPH rats and resulted in the proliferation of PASMCs. Besides, the mRNA and protein expression of vimentin in PASMCs significantly reduced after SO₂ treatment.

CONCLUSION

Together, these findings indicate that SO₂ could attenuate hypoxia-induced pulmonary arteriolar remodeling and may suppress the proliferation and migration of PASMCs at least in part through the Dkk1/Wnt signaling pathway.

Clinical characteristics in lymphangioleiomyomatosis-related pulmonary hypertension: an observation on 50 patients

Lymphangioleiomyomatosis (LAM) is a rare diffuse cystic lung disease. Knowledge on LAM-related pulmonary hypertension (PH) is limited. This study aimed to analyze the clinical characteristics of LAM with elevated pulmonary artery pressure (PAP) and evaluate the potential efficacy of sirolimus. The study involved 50 LAM patients who underwent echocardiography. According to the tricuspid regurgitation velocity (TRV), these patients were divided into the TRV ⩽ 2.8 m/s group and TRV > 2.8 m/s group. Both groups comprised 25 females with an average age of 38.6 ± 8.1 and 41.5 ± 8.9 years. In the TRV > 2.8 m/s group, the estimated systolic PAP (SPAP) was significantly elevated (52.08 ± 12.45 mmHg vs. 30.24 ± 5.25 mmHg, P < 0.01). Linear analysis showed that SPAP was correlated with forced expiratory volume in 1 s (FEV₁), diffusing capacity of the lungs for carbon monoxide, alveolar arterial oxygen gradient (P_A-aO₂), and 6 min walking distance (r =-0.392, -0.351, 0.450, and -0.591, respectively; P < 0.05), in which P_A-aO₂ was a risk factor for SPAP elevation (β = 0.064, OR = 1.066, P < 0.05). Moreover, in 10 patients who received sirolimus therapy, SPAP decreased from 57.0 12.6 mmHg to 35.2 ± 11.1 mmHg. The study showed that LAM patients with PH exhibit poor pulmonary function and hypoxemia and may benefit from sirolimus treatment.

Comprehensive Map and Functional Annotation of Human Pituitary and Thyroid Proteome

Knowledge about human tissue proteome will provide insights into health organ physiology. To construct a comprehensive data set of human pituitary and thyroid proteins, post-mortem pituitaries and thyroids from 10 normal individuals were used. The pooled samples were prepared using two methods. One part of the sample was processed using 14 high-abundance proteins immunoaffinity column. The other part was directly subjected to digestion. Finally, a total of 7596 proteins in pituitary and 5602 proteins in thyroid with high confidence were identified, with 6623 and 4368 quantified, respectively. A total of 5781 of pituitary and 3178 of thyroid proteins have not been previously reported in the normal pituitary and thyroid proteome. Comparison of pituitary and thyroid proteome indicated that thyroid prefers to be involved in nerve system regeneration and metabolic regulation, while pituitary mainly performs functions of signal transduction and cancer modulation. Our results, for the first time, comprehensively profiled and functionally annotated the largest high-confidence data set of proteome of two important endocrine glands, pituitary and thyroid, which is important for further studies on biomarker identification and molecular mechanisms of pituitary and thyroid disorders. The mapping results can be freely downloaded at http://www.urimarker.com/pituitary/ and http://www.urimarker.com/thyroid/ . The raw data are available via ProteomeXchange with identifier PXD006471.

Mapping differential cellular protein response of mouse alveolar epithelial cells to multi-walled carbon nanotubes as a function of atomic layer deposition coating

Carbon nanotubes (CNTs), a prototypical engineered nanomaterial, have been increasingly manufactured for a variety of novel applications over the past two decades. However, since CNTs possess fiber-like shape and cause pulmonary fibrosis in rodents, there is concern that mass production of CNTs will lead to occupational exposure and associated pulmonary diseases. The aim of this study was to use contemporary proteomics to investigate the mechanisms of cellular response in E10 mouse alveolar epithelial cells in vitro after exposure to multi-walled CNTs (MWCNTs) that were functionalized by atomic layer deposition (ALD). ALD is a method used to generate highly uniform and conformal nanoscale thin-film coatings of metals to enhance novel conductive properties of CNTs. We hypothesized that specific types of metal oxide coatings applied to the surface of MWCNTs by ALD would determine distinct proteomic profiles in mouse alveolar epithelial cells in vitro that could be used to predict oxidative stress and pulmonary inflammation. Uncoated (U)-MWCNTs were functionalized by ALD with zinc oxide (ZnO) to yield Z-MWCNTs or aluminum oxide (Al₂O₃) to yield A-MWCNTs. Significant differential protein expression was found in the following critical pathways: mTOR/eIF4/p70S6K signaling and Nrf-2 mediated oxidative stress response increased following exposure to Z-MWCNTs, interleukin-1 signaling increased following U-MWCNT exposure, and inhibition of angiogenesis by thrombospondin-1, oxidative phosphorylation, and mitochondrial dysfunction increased following A-MWCNT exposure. This study demonstrates that specific types of metal oxide thin film coatings applied by ALD produce distinct cellular and biochemical responses related to lung inflammation and fibrosis compared to uncoated MWCNT exposure in vitro.

The Triangle of Death in Alzheimer's Disease Brain: The Aberrant Cross-Talk Among Energy Metabolism, Mammalian Target of Rapamycin Signaling, and Protein Homeostasis Revealed by Redox Proteomics

SIGNIFICANCE

Alzheimer's disease (AD) is a multifactorial neurodegenerative disorder and represents one of the most disabling conditions. AD shares many features in common with systemic insulin resistance diseases, suggesting that it can be considered as a metabolic disease, characterized by reduced insulin-stimulated growth and survival signaling, increased oxidative stress (OS), proinflammatory cytokine activation, mitochondrial dysfunction, impaired energy metabolism, and altered protein homeostasis. Recent Advances: Reduced glucose utilization and energy metabolism in AD have been associated with the buildup of amyloid-β peptide and hyperphosphorylated tau, increased OS, and the accumulation of unfolded/misfolded proteins. Mammalian target of rapamycin (mTOR), which is aberrantly activated in AD since early stages, plays a key role during AD neurodegeneration by, on one side, inhibiting insulin signaling as a negative feedback mechanism and, on the other side, regulating protein homeostasis (synthesis/clearance).

CRITICAL ISSUES

It is likely that the concomitant and mutual alterations of energy metabolism-mTOR signaling-protein homeostasis might represent a self-sustaining triangle of harmful events that trigger the degeneration and death of neurons and the development and progression of AD. Intriguingly, the altered cross-talk between the components of such a triangle of death, beyond altering the redox homeostasis of the neuron, is further exacerbated by increased levels of OS that target and impair key components of the pathways involved. Redox proteomic studies in human samples and animal models of AD-like dementia led to identification of oxidatively modified components of the pathways composing the triangle of death, therefore revealing the crucial role of OS in fueling this aberrant vicious cycle.

FUTURE DIRECTIONS

The identification of compounds able to restore the function of the pathways targeted by oxidative damage might represent a valuable therapeutic approach to slow or delay AD. Antioxid. Redox Signal. 26, 364-387.

Activation of the mTOR dependent signaling pathway underlies ketamine-induced uropathy

AIMS

To investigate the pathogenic role of activation of the mammalian target of the rapamycin (mTOR) in the ketamine induced microvascular injury.

METHODS

Twenty-three patients with ketamine-induced cystitis (KC) and 16 control volunteers were recruited. Bladder tissues were obtained from both groups by cystoscopic biopsies. Phospho-S6 ribosomal protein (p-S6RP), an end product of the mTOR pathway, was stained in the urinary bladder from both groups. Endothelial cells of the urinary bladder (HBdMECs) were examined to investigate the in vitro activation of the mTOR pathway and the co-expression of the endothelial marker (cluster of differentiation 31 [CD31]) and the mesenchymal marker (fibroblast-specific protein 1 [FSP-1]).

RESULTS

Expression of p-S6RP increased significantly after ketamine exposure, especially in the vesical microvessels of KC patients. In HBdMECs treated with 100 µM Ketamine, time-dependent activation of the mTOR pathway occurred, with significantly increased levels of the phosphorylated forms of mTOR at 30 min and of S6RP and p70S6 kinase (p70S6K) at 6 h. The increased level of p-S6RP returned to baseline within 2 days after ketamine exposure. The co-expression of CD31 and FSP-1 implied that EndMT was present in HBdMECs at 7 days after ketamine treatment, while TGF-β1 facilitated significant up-regulation of FSP-1 at 1 day after treatment. Furthermore, when the mTOR inhibitor rapamycin was administered with ketamine to the HBdMECs, the expression of FSP-1 decreased significantly.

CONCLUSIONS

Ketamine induces activation of the mTOR pathway and subsequent mesenchymal phenotypic expression (FSP1) in HBdMECs.