Activation of AMPK prevents monocrotaline-induced pulmonary arterial hypertension by suppression of NF-κB-mediated autophagy activation

Pulmonary artery-targeted low-dose metformin-loaded nanocapsules safely improve pulmonary arterial hypertension in rats

Introduction

Pulmonary arterial hypertension (PAH) remains a challenge to tackle despite various available medications. Metformin, although promising, has major adverse effects; the use of an appropriate drug delivery method may improve its efficacy and safety. The aim of this study was to develop a novel treatment for PAH using metformin. We developed a novel approach of using low-dose metformin encapsulated in pulmonary artery-targeted nanocapsules to alleviate PAH while avoiding adverse effects.

Methods

Metformin-loaded lung-targeted nanocapsules (MET nanocapsules) were created using a specific lipid composition, including cationic lipids. Their uptake and effects on cell viability were assessed in human pulmonary arterial smooth muscle cells (hPASMCs) from healthy individuals and patients with PAH. Their therapeutic effects were assessed in a PAH rat model. The safety of MET nanocapsules was confirmed using rat serum biochemical tests.

Results

We successfully prepared MET nanocapsules and demonstrated their effectiveness in inhibiting PASMC proliferation. In PAH model rats, MET nanocapsule treatment led to improved hemodynamics, right ventricular hypertrophy, and pulmonary arterial medial thickening. The nanocapsules effectively accumulated in the lungs of PAH model rats.

Conclusion

Intravenous administration of MET nanocapsules is a safe and innovative therapeutic approach for PAH. This method could improve PAH treatment outcomes while minimizing adverse effects, with potential applications in other types of pulmonary hypertension.

Evaluation of metformin's effect on the adult and juvenile stages of Schistosoma mansoni: an in-vitro study

Metformin (Met), a well-known anti-diabetic drug with a potent autophagy induction property, has been proven to be effective against several parasitic diseases. In the present in vitro study, the effect of Met on the viability and ultrastructure of Schistosoma mansoni adults and juveniles in comparison with the standard anti-schistosomal drug, praziquantel (PZQ), was investigated. Adults and juveniles were treated in vitro with 5 µM PZQ and/or 10 mM Met. The viability of the treated worms was screened over a three-day period by light microscopy and recorded as mortality rates (MR). The alterations in the ultrastructure were verified using scanning and transmission electron microscopy. Met showed significant anti-schistosomal activity against both adults and juveniles and resulted in severe tegumental damage in the form of loss of integrity and architecture, with evident vacuolation suggestive of increased autophagy. Met might be a potential drug either alone or as an adjuvant to PZQ for the treatment of schistosomiasis mansoni and warrant its further assessment in animal models of disease.

Pulmonary Hypertension and Right Ventricle: A Pathophysiological Insight

Background

Pulmonary hypertension (PH) is a pulmonary vascular disease characterized by elevated pulmonary vascular pressure. Long-term PH, irrespective of its etiology, leads to increased right ventricular (RV) pressure, RV hypertrophy, and ultimately, RV failure.

Main body

Research indicates that RV failure secondary to hypertrophy remains the primary cause of mortality in pulmonary arterial hypertension (PAH). However, the impact of PH on RV structure and function under increased overload remains incompletely understood. Several mechanisms have been proposed, including extracellular remodeling, RV hypertrophy, metabolic disturbances, inflammation, apoptosis, autophagy, endothelial-to-mesenchymal transition, neurohormonal dysregulation, capillary rarefaction, and ischemia.

Conclusions

Studies have demonstrated the significant role of oxidative stress in the development of RV failure. Understanding the interplay among these mechanisms is crucial for the prevention and management of RV failure in patients with PH.

CC chemokines Modulate Immune responses in Pulmonary Hypertension

BACKGROUND

Pulmonary hypertension (PH) represents a progressive condition characterized by the remodeling of pulmonary arteries, ultimately culminating in right heart failure and increased mortality rates. Substantial evidence has elucidated the pivotal role of perivascular inflammatory factors and immune dysregulation in the pathogenesis of PH. Chemokines, a class of small secreted proteins, exert precise control over immune cell recruitment and functionality, particularly with respect to their migration to sites of inflammation. Consequently, chemokines emerge as critical drivers facilitating immune cell infiltration into the pulmonary tissue during inflammatory responses. This review comprehensively examines the significant contributions of CC chemokines in the maintenance of immune cell homeostasis and their pivotal role in regulating inflammatory responses. The central focus of this discussion is directed towards elucidating the precise immunoregulatory actions of CC chemokines concerning various immune cell types, including neutrophils, monocytes, macrophages, lymphocytes, dendritic cells, mast cells, eosinophils, and basophils, particularly in the context of pH processes. Furthermore, this paper delves into an exploration of the underlying pathogenic mechanisms that underpin the development of PH. Specifically, it investigates processes such as cellular pyroptosis, examines the intricate crosstalk between bone morphogenetic protein receptor type 2 (BMPR2) mutations and the immune response, and sheds light on key signaling pathways involved in the inflammatory response. These aspects are deemed critical in enhancing our understanding of the complex pathophysiology of PH. Moreover, this review provides a comprehensive synthesis of findings from experimental investigations targeting immune cells and CC chemokines.

AIM OF REVIEW

In summary, the inquiry into the inflammatory responses mediated by CC chemokines and their corresponding receptors, and their potential in modulating immune reactions, holds promise as a prospective avenue for addressing PH. The potential inhibition of CC chemokines and their receptors stands as a viable strategy to attenuate the inflammatory cascade and ameliorate the pathological manifestations of PH. Nonetheless, it is essential to acknowledge the current state of clinical trials and the ensuing progress, which regrettably appears to be less than encouraging. Substantial hurdles exist in the successful translation of research findings into clinical applications. The intention is that such emphasis could potentially foster the advancement of potent therapeutic agents presently in the process of clinical evaluation. This, in turn, may further bolster the potential for effective management of PH.

Emerging connectivity of programmed cell death pathways and pulmonary vascular remodelling during pulmonary hypertension

Pulmonary hypertension (PH) is a chronic progressive vascular disease characterized by abnormal pulmonary vascular resistance and pulmonary artery pressure. The major structural alteration during PH is pulmonary vascular remodelling, which is mainly caused by the imbalance between proliferation and apoptosis of pulmonary vascular cells. Previously, it was thought that apoptosis was the only type of programmed cell death (PCD). Soon afterward, other types of PCD have been identified, including autophagy, pyroptosis, ferroptosis and necroptosis. In this review, we summarize the role of the above five forms of PCD in mediating pulmonary vascular remodelling, and discuss their guiding significance for PH treatment. The current review could provide a better understanding of the correlation between PCD and pulmonary vascular remodelling, contributing to identify new PCD-associated drug targets for PH.

Inhibition of NF-κB signaling unveils novel strategies to overcome drug resistance in cancers

Drug resistance in cancer remains a major challenge in oncology, impeding the effectiveness of various treatment modalities. The nuclear factor-kappa B (NF-κB) signaling pathway has emerged as a critical player in the development of drug resistance in cancer cells. This comprehensive review explores the intricate relationship between NF-κB and drug resistance in cancer. We delve into the molecular mechanisms through which NF-κB activation contributes to resistance against chemotherapeutic agents, targeted therapies, and immunotherapies. Additionally, we discuss potential strategies to overcome this resistance by targeting NF-κB signaling, such as small molecule inhibitors and combination therapies. Understanding the multifaceted interactions between NF-κB and drug resistance is crucial for the development of more effective cancer treatment strategies. By dissecting the complex signaling network of NF-κB, we hope to shed light on novel therapeutic approaches that can enhance treatment outcomes, ultimately improving the prognosis for cancer patients. This review aims to provide a comprehensive overview of the current state of knowledge on NF-κB and its role in drug resistance, offering insights that may guide future research and therapeutic interventions in the fight against cancer.

The interaction between lncRNAs and transcription factors regulating autophagy in human cancers: A comprehensive and therapeutical survey

Autophagy, as a highly conserved cellular process, participates in cellular homeostasis by degradation and recycling of damaged organelles and proteins. Besides, autophagy has been evidenced to play a dual role through cancer initiation and progression. In the early stage, it may have a tumor-suppressive function through inducing apoptosis and removing damaged cells and organelles. However, late stages promote tumor progression by maintaining stemness features and induction of chemoresistance. Therefore, identifying and targeting molecular mechanisms involved in autophagy is a potential therapeutic strategy for human cancers. Multiple transcription factors (TFs) are involved in the regulation of autophagy by modulating the expression of autophagy-related genes (ATGs). In addition, a wide array of long noncoding RNAs (lncRNAs), a group of regulatory ncRNAs, have been evidenced to regulate the function of these autophagy-related TFs through tumorigenesis. Subsequently, the lncRNAs/TFs/ATGs axis shows great potential as a therapeutic target for human cancers. Therefore, this review aimed to summarize new findings about the role of lncRNAs in regulating autophagy-related TFs with therapeutic perspectives.

The role and mechanism of AMPK in pulmonary hypertension

Pulmonary hypertension (PH) is a chronic progressive disease with high mortality. There has been more and more research focusing on the role of AMPK in PH. AMPK consists of three subunits-α, β, and γ. The crosstalk among these subunits ultimately leads to a delicate balance to affect PH, which results in conflicting conclusions about the role of AMPK in PH. It is still unclear how these subunits interfere with each other and achieve balance to improve or deteriorate PH. Several signaling pathways are related to AMPK in the treatment of PH, including AMPK/eNOS/NO pathway, Nox4/mTORC2/AMPK pathway, AMPK/BMP/Smad pathway, and SIRT3-AMPK pathway. Among these pathways, the role and mechanism of AMPK/eNOS/NO and Nox4/mTORC2/AMPK pathways are clearer than others, while the SIRT3-AMPK pathway remains still unclear in the treatment of PH. There are drugs targeting AMPK to improve PH, such as metformin (MET), MET combination, and rhodiola extract. In addition, several novel factors target AMPK for improving PH, such as ADAMTS8, TUFM, and Salt-inducible kinases. However, more researches are needed to explore the specific AMPK signaling pathways involved in these novel factors in the future. In conclusion, AMPK plays an important role in PH.

Downregulation of PDCD4 through STAT3/ATF6/autophagy mediates MIF-induced PASMCs proliferation/migration and vascular remodeling

To address the molecular mechanisms underlying macrophage migration inhibitory factor (MIF) induced pulmonary artery smooth muscle cells (PASMCs) proliferation, migration and vascular remodeling in pulmonary hypertension (PH), primary cultured rat PASMCs and monocrotaline (MCT)-induced rats with PH were applied in the present study. The results showed that MIF increased signal transducer and activator of transcription 3 (STAT3) phosphorylation, and then stimulated activating transcription factor 6 (ATF6) activation, subsequently triggered autophagy activation, which further led to programmed cell death factor 4 (PDCD4) lysosomal degradation, and eventually promoted PASMCs proliferation/migration. In lung tissues of MCT rats, MIF protein expression was elevated, phosphorylation of STAT3 and activation of ATF6 were increased, activation of autophagy was evident, and reduction of PDCD4 was observed. Intervention with MIF inhibitor 4-Iodo-6-phenylpyrimidine (4-IPP), ATF6 blocker melatonin or autophagy inhibitor chloroquine, confirmed the in vitro interaction among MIF, STAT3, ATF6, autophagy and PDCD4 in MCT induced rats with PH. Targeting MIF/STAT3/ATF6/autophagy/PDCD4 axis effectively prevented the development of PH by suppressing PASMCs proliferation and vascular remodeling. In conclusions, we demonstrate that MIF activates the STAT3/ATF6/autophagy cascade and then degrades PDCD4 leading to PASMCs proliferation/migration and pulmonary vascular remodeling, suggesting that intervention this axis might have potential value in management of PH.

Metformin may be a viable adjunctive therapeutic option to potentially enhance immune reconstitution in HIV-positive immunological non-responders

ABSTRACT

Incomplete immune reconstitution remains a global challenge for human immunodeficiency virus (HIV) treatment in the present era of potent antiretroviral therapy (ART), especially for those individuals referred to as immunological non-responders (INRs), who exhibit dramatically low CD4 + T-cell counts despite the use of effective antiretroviral therapy, with long-term inhibition of viral replication. In this review, we provide a critical overview of the concept of ART-treated HIV-positive immunological non-response, and also explain the known mechanisms which could potentially account for the emergence of immunological non-response in some HIV-infected individuals treated with appropriate and effective ART. We found that immune cell exhaustion, combined with chronic inflammation and the HIV-associated dysbiosis syndrome, may represent strategic aspects of the immune response that may be fundamental to incomplete immune recovery. Interestingly, we noted from the literature that metformin exhibits properties and characteristics that may potentially be useful to specifically target immune cell exhaustion, chronic inflammation, and HIV-associated gut dysbiosis syndrome, mechanisms which are now recognized for their critically important complicity in HIV disease-related incomplete immune recovery. In light of evidence discussed in this review, it can be seen that metformin may be of particularly favorable use if utilized as adjunctive treatment in INRs to potentially enhance immune reconstitution. The approach described herein may represent a promising area of therapeutic intervention, aiding in significantly reducing the risk of HIV disease progression and mortality in a particularly vulnerable subgroup of HIV-positive individuals.

Epigenetic regulation of programmed cell death in hypoxia-induced pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a severe progressive disease that may cause early right ventricular failure and eventual cardiac failure. The pathogenesis of PAH involves endothelial dysfunction, aberrant proliferation of pulmonary artery smooth muscle cells (PASMCs), and vascular fibrosis. Hypoxia has been shown to induce elevated secretion of vascular endothelial growth factor (VEGF), leading to the development of hypoxic PAH. However, the molecular mechanisms underlying hypoxic PAH remain incompletely understood. Programmed cell death (PCD) is a natural cell death and regulated by certain genes. Emerging evidence suggests that apoptotic resistance contributes to the development of PAH. Moreover, several novel types of PCD, such as autophagy, pyroptosis, and ferroptosis, have been reported to be involved in the development of PAH. Additionally, multiple diverse epigenetic mechanisms including RNA methylation, DNA methylation, histone modification, and the non-coding RNA molecule-mediated processes have been strongly linked to the development of PAH. These epigenetic modifications affect the expression of genes, which produce important changes in cellular biological processes, including PCD. Consequently, a better understanding of the PCD processes and epigenetic modification involved in PAH will provide novel, specific therapeutic strategies for diagnosis and treatment. In this review, we aim to discuss recent advances in epigenetic mechanisms and elucidate the role of epigenetic modifications in regulating PCD in hypoxia-induced PAH.

The brief overview, antivirus and anti-SARS-CoV-2 activity, quantitative methods, and pharmacokinetics of cepharanthine: a potential small-molecule drug against COVID-19

To effectively respond to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), an increasing number of researchers are focusing on the antiviral activity of cepharanthine (CEP), which is a clinically approved drug being used for over 70 years. This review aims to provide a brief overview of CEP and summarize its recent findings in quantitative analysis, pharmacokinetics, therapeutic potential, and mechanism in antiviral and anti-SARS-CoV-2 activity. Given its remarkable capacity against SARS-CoV-2 infection in vitro and in vivo, with its primary target organ being the lungs, and its good pharmacokinetic profile; mature and stable manufacturing technique; and its advantages of safety, effectiveness, and accessibility, CEP has become a promising drug candidate for treating COVID-19 despite being an old drug.

The AMPK-dependent inhibition of autophagy plays a crucial role in protecting photoreceptor from photooxidative injury

Excessive light exposure can potentially cause irreversible damage to the various photoreceptor cells, and this aspect has been considered as an important factor leading to the progression of the different retinal diseases. AMP-activated protein kinase (AMPK) and the mammalian target of rapamycin (mTOR) are crucial intracellular signaling hubs involved in the regulation of cellular metabolism, energy homeostasis, cellular growth and autophagy. A number of previous studies have indicated that either AMPK activation or mTOR inhibition can promote autophagy in most cases. In the current study, we have established an in vitro as well as in vivo photooxidation-damaged photoreceptor model and investigated the possible influence of visible light exposure in the AMPK/mTOR/autophagy signaling pathway. We have also explored the potential regulatory effects of AMPK/mTOR on light-induced autophagy and protection achieved by suppressing autophagy in photooxidation-damaged photoreceptors. We observed that light exposure led to a significant activation of mTOR and autophagy in the photoreceptor cells. However, intriguingly, AMPK activation or mTOR inhibition significantly inhibited rather than promoting autophagy, which was termed as AMPK-dependent inhibition of autophagy. In addition, either indirectly suppressing autophagy by AMPK activation/ mTOR inhibition or directly blocking autophagy with an inhibitor exerted a significant protective effect on the photoreceptor cells against the photooxidative damage. Neuroprotective effects caused by the AMPK-dependent inhibition of autophagy were also verified with a retinal light injured mouse model in vivo. Overall, our findings demonstrated that AMPK / mTOR pathway could inhibit autophagy through AMPK-dependent inhibition of autophagy to significantly protect the photoreceptors from photooxidative injury, which may aid to further develop novel targeted retinal neuroprotective drugs.

Exosomal miR-663b from "M1" macrophages promotes pulmonary artery vascular smooth muscle cell dysfunction through inhibiting the AMPK/Sirt1 axis

BACKGROUND

Inflammatory mediators from macrophages are proven to be involved in pulmonary vascular remodeling in pulmonary hypertension (PH). Here, this study intends to explore the mechanism of "M1" macrophage-derived exosomal miR-663b in pulmonary artery smooth muscle cells (PASMCs) dysfunctions and pulmonary hypertension.

METHODS

Hypoxia-treated PASMCs were utilized for constructing an in-vitro pulmonary hypertension model. THP-1 cells were treated with PMA (320 nM) and LPS (10 μg/mL) + IFN-γ (20 ng/ml) for eliciting macrophage "M1" polarization. Exosomes derived from "M1" macrophages were isolated and added into PASMCs. The proliferation, inflammation, oxidative stress, and migration of PASMCs were evaluated. RT-PCR or Western blot examined the levels of miR-663b and the AMPK/Sirt1 pathway. Dual luciferase activity assay and RNA pull-down assay were carried out for confirming the targeted association between miR-663b and AMPK. An in-vivo PH model was built. Macrophage-derived exosomes with miR-663b inhibition were used for treating the rats, and alterations of pulmonary histopathology were monitored.

RESULTS

miR-663b was obviously up-regulated in hypoxia-elicited PASMCs and M1 macrophages. miR-663b overexpression boosted hypoxia-induced proliferation, inflammation, oxidative stress, and migration in PASMCs, whereas miR-663b low expression resulted in the opposite situation. AMPK was identified as a target of miR-663b, and miR-663b overexpression curbed the AMPK/Sirt1 pathway. AMPK activation ameliorated the damaging impact of miR-663b overexpression and "M1" macrophage exosomes on PASMCs. In vivo, "M1" macrophage exosomes with miR-663b low expression alleviated pulmonary vascular remodeling in pulmonary hypertension rats.

CONCLUSION

Exosomal miR-663b from "M1" macrophage facilitates PASMC dysfunctions and PH development by dampening the AMPK/Sirt1 axis.

AMPK activation by metformin protects against pulmonary hypertension in rats and relaxes isolated human pulmonary artery

Pulmonary hypertension (PH) is associated with pulmonary vasoconstriction and endothelial dysfunction leading to impaired nitric oxide (NO) and prostacyclin (PGI₂) pathways. Metformin, the first line treatment for type 2 diabetes and AMP-activated protein kinase (AMPK) activator, has been recently highlighted as a potential PH treatment. AMPK activation has been reported to improve endothelial function by enhancing endothelial NO synthase (eNOS) activity and to have relaxant effects in blood vessels. In this study, we examined the effect of metformin treatment on PH as well as on NO and PGI₂ pathways in monocrotaline (MCT)-injected rats with established PH. Moreover, we investigated the anti-contractile effects of AMPK activators on endothelium-denuded human pulmonary arteries (HPA) from Non-PH and Group 3 PH patients (due to lung diseases and/or hypoxia). Furthermore, we explored the interaction between treprostinil and the AMPK/eNOS pathway. Our results showed that metformin protected against PH progression in MCT rats where it reduced the mean pulmonary artery pressure, pulmonary vascular remodeling and right ventricular hypertrophy and fibrosis compared to vehicle-treated MCT rats. The protective effects on rat lungs were mediated in part by increasing eNOS activity and protein kinase G-1 expression but not through the PGI₂ pathway. In addition, incubation with AMPK activators reduced the phenylephrine-induced contraction of endothelium-denuded HPA from Non-PH and PH patients. Finally, treprostinil also augmented eNOS activity in HPA smooth muscle cells. In conclusion, we found that AMPK activation can enhance the NO pathway, attenuate vasoconstriction by direct effects on smooth muscles, and reverse established MCT-induced PH in rats.

The Novel Lysosomal Autophagy Inhibitor (ROC-325) Ameliorates Experimental Pulmonary Hypertension

BACKGROUND

Autophagy plays an important role in the pathogenesis of pulmonary hypertension (PH). ROC-325 is a novel small molecule lysosomal autophagy inhibitor that has more potent anticancer activity than the antimalarial drug hydroxychloroquine, the latter has been prevalently used to inhibit autophagy. Here, we sought to determine the therapeutic benefit and mechanism of action of ROC-325 in experimental PH models.

METHODS AND RESULTS

Hemodynamics, echocardiography, and histology measurement showed that ROC-325 treatment prevented the development of PH, right ventricular hypertrophy, fibrosis, dysfunction, and vascular remodeling after monocrotaline and Sugen5416/hypoxia administration. ROC-325 attenuated high K⁺ or alveolar hypoxia-induced pulmonary vasoconstriction and enhanced endothelial-dependent relaxation in isolated pulmonary artery rings. ROC-325 treatment inhibited autophagy and enhanced endothelial nitric oxide synthase activity in lung tissues of monocrotaline-PH rats. In cultured human and rat pulmonary arterial smooth muscle cell and pulmonary arterial endothelial cell under hypoxia exposure, ROC-325 increased LC3B (light chain 3 beta) and p62 accumulation, endothelial cell nitric oxide production via phosphorylation of endothelial nitric oxide synthase (Ser1177) and dephosphorylation of endothelial nitric oxide synthase (Thr495) as well as decreased HIF (hypoxia-inducible factor)-1α and HIF-2α stabilization.

CONCLUSIONS

These data indicate that ROC-325 is a promising novel agent for the treatment of PH that inhibits autophagy, downregulates HIF levels, and increases nitric oxide production.

Activation of Autophagy Induces Monocrotaline-Induced Pulmonary Arterial Hypertension by FOXM1-Mediated FAK Phosphorylation

PURPOSE

It has been shown that activation of autophagy promotes the development of pulmonary arterial hypertension (PAH). Meanwhile, forkhead box M1 (FOXM1) has been found to induce autophagy in several types of cancer. However, it is still unclear whether FOXM1 mediates autophagy activation in PAH, and detailed mechanisms responsible for these processes are indefinite.

METHOD

PAH was induced by a single intraperitoneal injection of monocrotaline (MCT) to rats. The right ventricle systolic pressure (RVSP), right ventricular hypertrophy index (RVHI), percentage of medial wall thickness (%MT), α-smooth muscle actin (α-SMA) staining, and Ki67 staining were performed to evaluate the development of PAH. The protein levels of FOXM1, phospho-focal adhesion kinase (p-FAK), FAK, and LC3B were determined by immunoblotting or immunohistochemistry.

RESULTS

FOXM1 protein level and FAK activity were significantly increased in MCT-induced PAH rats, this was accompanied with the activation of autophagy. Pharmacological inhibition of FOXM1 or FAK suppressed MCT-induced autophagy activation, decreased RVSP, RVHI and %MT in MCT-induced PAH rats, and inhibited the proliferation of pulmonary arterial smooth muscle cells and pulmonary vessel muscularization in MCT-induced PAH rats.

CONCLUSION

FOXM1 promotes the development of PAH by inducing FAK phosphorylation and subsequent activation of autophagy in MCT-treated rats.

Protective effects of metformin in various cardiovascular diseases: Clinical evidence and AMPK-dependent mechanisms

Metformin, a well-known AMPK agonist, has been widely used as the first-line drug for treating type 2 diabetes. There had been a significant concern regarding the use of metformin in people with cardiovascular diseases (CVDs) due to its potential lactic acidosis side effect. Currently growing clinical and preclinical evidence indicates that metformin can lower the incidence of cardiovascular events in diabetic patients or even non-diabetic patients beyond its hypoglycaemic effects. The underlying mechanisms of cardiovascular benefits of metformin largely involve the cellular energy sensor, AMPK, of which activation corrects endothelial dysfunction, reduces oxidative stress and improves inflammatory response. In this minireview, we summarized the clinical evidence of metformin benefits in several widely studied cardiovascular diseases, such as atherosclerosis, ischaemic/reperfusion injury and arrhythmia, both in patients with or without diabetes. Meanwhile, we highlighted the potential AMPK-dependent mechanisms in in vitro and/or in vivo models.

Effects of the peripheral CB1 receptor antagonist JD5037 in mono— and polytherapy with the AMPK activator metformin in a monocrotaline-induced rat model of pulmonary hypertension

Pulmonary hypertension (PH) is a disease leading to increased pressure in the pulmonary artery and right heart failure. The adenosine monophosphate-activated protein kinase (AMPK) activator, metformin, has a protective effect against PH. CB₁ receptor blockade reduces the number of pathological alterations in experimental lung fibrosis. The current study evaluates the effect of the peripheral cannabinoid CB₁ receptor antagonist JD5037 in mono- and polytherapy with metformin in rat monocrotaline-induced mild PH. Animals received metformin (100 mg/kg), JD5037 (3 mg/kg), or a combination of both once daily for 21 days. Monocrotaline (60 mg/kg) increased right ventricular (RV) systolic pressure (RVSP), led to RV and lung hypertrophy and remodeling, and decreased oxygen saturation. Metformin partially restored the monocrotaline-induced effects, i.e., decreased RVSP, increased oxygen saturation, and counteracted cardiac fibrotic, hypertrophic, and inflammatory changes. JD5037 modified parameters related to inflammation and/or fibrosis. Only polytherapy with metformin and JD5037 improved Fulton’s index and coronary artery hypertrophy and tended to be more effective than monotherapy against alterations in RVSP, oxygen saturation and coronary artery tunica media vacuolization. In conclusion, monotherapy with JD5037 does not markedly influence the PH-related changes. However, polytherapy with metformin tends to be more efficient than any of these compounds alone.

The phytochemical and pharmacological profile of taraxasterol

Taraxasterol is one of the bioactive triterpenoids found in dandelion, a member of the family Asteraceae. In the animal or cellular models of several ailments, including liver damage, gastritis, colitis, arthritis, pneumonia, tumors, and immune system diseases, taraxasterol has been shown to have significant preventive and therapeutic effects. This review aims to evaluate the current state of research and provide an overview of the possible applications of taraxasterol in various diseases. The reported phytochemical properties and pharmacological actions of taraxasterol, including anti-inflammatory, anti-oxidative, and anti-carcinogenic properties, and its potential molecular mechanisms in developing these diseases are highlighted. Finally, we further explored whether taraxasterol has protective effects on neuronal death in neurodegenerative diseases. In addition, more animal and clinical studies are also required on the metabolism, bioavailability, and safety of taraxasterol to support its applications in pharmaceuticals and medicine.

Identification of autophagy-related biomarkers in patients with pulmonary arterial hypertension based on bioinformatics analysis

Autophagy participates in the regulation of pulmonary arterial hypertension (PAH). However, the role of autophagy-related genes (ARGs) in the pathogenesis of the PAH is still unclear. This study aimed to identify the ARGs in PAH via bioinformatics analysis. A microarray dataset (GSE113439) was downloaded from the Gene Expression Omnibus database to identify differentially expressed ARGs (DEARGs). Protein–protein interactions network, gene ontology, and Kyoto Encyclopedia of Genes and Genomes enrichment analyses were performed to screen hub genes and the underlying molecular mechanisms of PAH. Finally, the mRNA expression of the hub genes was validated using the GSE53408 dataset. Twenty-six DEARGs were identified, all of which were upregulated. Enrichment analyses revealed that these DEARGs were mainly enriched in the nucleotide-binding oligomerization domain (NOD)-like receptor signaling pathway, PI3K-Akt signaling pathway, response to hypoxia, response to nutrient levels, and autophagy. Among these hub genes, the mRNA expression levels of HSP90AA1, HIF1A, MET, IGF1, LRRK2, CLTC, DNM1L, MDM2, RICTOR, and ROCK2 were significantly upregulated in PAH patients than in healthy individuals. Ten hub DEARGs were identified and may participate in the pathogenesis of the PAH via the regulation of autophagy. The present study may provide novel therapeutic targets for PAH prevention and treatment and expand our understanding of PAH.

AMPK and the Challenge of Treating Hypoxic Pulmonary Hypertension

Hypoxic pulmonary hypertension (HPH) is characterized by sustained elevation of pulmonary artery pressure produced by vasoconstriction and hyperproliferative remodeling of the pulmonary artery and subsequent right ventricular hypertrophy (RVH). The search for therapeutic targets for cardiovascular pathophysiology has extended in many directions. However, studies focused on mitigating high-altitude pulmonary hypertension (HAPH) have been rare. Because AMP-activated protein kinase (AMPK) is involved in cardiovascular and metabolic pathology, AMPK is often studied as a potential therapeutic target. AMPK is best characterized as a sensor of cellular energy that can also restore cellular metabolic homeostasis. However, AMPK has been implicated in other pathways with vasculoprotective effects. Notably, cellular metabolic stress increases the intracellular ADP/ATP or AMP/ATP ratio, and AMPK activation restores ATP levels by activating energy-producing catabolic pathways and inhibiting energy-consuming anabolic pathways, such as cell growth and proliferation pathways, promoting cardiovascular protection. Thus, AMPK activation plays an important role in antiproliferative, antihypertrophic and antioxidant pathways in the pulmonary artery in HPH. However, AMPK plays contradictory roles in promoting HPH development. This review describes the main findings related to AMPK participation in HPH and its potential as a therapeutic target. It also extrapolates known AMPK functions to discuss the less-studied HAPH context.

Differential Expression Profile of microRNAs and Tight Junction in the Lung Tissues of Rat With Mitomycin-C-Induced Pulmonary Veno-Occlusive Disease

Background

Pulmonary veno-occlusive disease (PVOD) is characterized by increased pulmonary vascular resistance. Currently, there is a lack of effective treatment. It is of great significance to explore molecular targets for treatment. This study investigated the differential expression profile of miRNAs and tight junction in the lung tissues of rats with mitomycin-C (MMC)-induced PVOD.

Methods

A total of 14 rats were divided into the control group and he PVOD group. We measured mean pulmonary arterial pressure (mPAP) and right ventricular hypertrophy index (RVHI). Pathological changes including those in lung tissues, pulmonary venules, and capillary were detected by H&E and orcein staining. Western blot was used to detect GCN2, ZO-1, occludin, and claudin-5 expression. We analyzed the miRNAs profile in the rat lung tissues by high-throughput sequencing. The top differentially expressed miRNAs were validated by using real-time polymerase chain reaction (RT-PCR).

Results

There were severe pulmonary artery hypertrophy/hyperplasia, thickening, and occlusion in the small pulmonary veins, pulmonary edema, and dilated capillaries in MMC-induced rats with PVOD. In addition, mPAP and RVHI were significantly increased (P < 0.05). The expression of GCN2 was significantly decreased (P < 0.05). A total of 106 differentially expressed miRNAs were identified. According to the fold changes, the top ten upregulated miRNAs were miRNA-543-3p, miRNA-802-5p, miRNA-493-3p, miRNA-539-3p, miRNA-495, miRNA-380-5p, miRNA-214-5p, miRNA-539-5p, miRNA-190a-3p, and miRNA-431. The top 10 downregulated miRNAs were miRNA-201-3p, miRNA-141-3p, miRNA-1912-3p, miRNA-500-5p, miRNA-3585-5p, miRNA-448-3p, miRNA-509-5p, miRNA-3585-3p, miRNA-449c-5p, and miRNA-509-3p. RT-PCR confirmed that miRNA-214-5p was upregulated, while miRNA-141-3p was downregulated (P < 0.05). Functional analysis showed various signaling pathways and metabolic processes, such as fatty acid biosynthesis, tight junction, and the mTOR signaling pathway. In addition, the expression of the tight junction-related protein of ZO-1, occludin, and claudin-5 was significantly decreased in rats with PVOD (P < 0.05).

Conclusion

miRNAs may be involved in the pathogenesis of PVOD. Furthermore, ZO-1, occludin, and claudin-5 verification confirmed that the tight junction may be involved in the development of the disease.

Metformin inhibits pulmonary artery smooth muscle cell proliferation by upregulating p21 via NONRATT015587.2

Pulmonary artery hypertension (PAH) is a complex and progressive disease characterized by pulmonary vascular remodeling. Our previous study confirmed that NONRATT015587.2 could promote the proliferation of PASMCs and pulmonary vascular remodeling. However, the exact mechanism by which NONRATT015587.2 promotes PASMC proliferation is unclear. Bioinformatics analysis revealed that p21 is located at the downstream target of NONRATT015587.2. NONRATT015587.2 expression and localization were analyzed by PCR and fluorescence in situ hybridization. Proliferation was detected by Cell Counting Kit-8, flow cytometry and western blotting. In the current study, a monocrotaline (MCT)-induced PAH rat model and cultured pulmonary artery smooth muscle cells (PASMCs) were used in vitro to elucidate the exact mechanism of NONRATT015587.2 in pulmonary vascular remodeling, alongside the effect following metformin (MET) treatment on vascular remodeling and smooth muscle cell proliferation. The results demonstrated that NONRATT015587.2 expression was upregulated in the MCT group and reduced in the MET + MCT group. In addition, NONRATT015587.2 could promote the proliferation of PASMCs. The expression levels of p21 were reduced in the MCT group, but increased in the MCT + MET group. Additionally, the expression of NONRATT015587.2 was upregulated in platelet-derived growth factor-BB (PDGF-BB)-induced PASMCs, whereas that of p21 was downregulated. Following MET treatment, the expression of NONRATT015587.2 was downregulated and that of p21 was upregulated, which inhibited the proliferation of PASMCs. After overexpression of NONRATT015587.2 in vitro, the proliferation effect of PASMCs was consistent with exogenous PDGF-BB treatment, and MET reversed this effect. NONRATT015587.2 silencing inhibited the proliferation of PASMCs. In addition, p21 silencing reversed the inhibitory effect of NONRATT015587.2 silencing on the proliferation of PASMCs. However, the proliferation of PASMCs was inhibited following MET treatment when NONRATT015587.2 and p21 were silenced at the same time. Thus, NONRATT015587.2 promoted the proliferation of PASMCs by targeting p21, and MET inhibited the proliferation of PASMCs by upregulating p21 mediated via NONRATT015587.2.

The therapeutic effect and mechanism of Rapamycin combined with HO-3867 on monocrotaline-induced pulmonary hypertension in rats

This study test was designed to investigate the possible modulatory effect of rapamycin combined with HO-3867 in monocrotaline(MCT)-induced pulmonary arterial hypertension in rats. We hypothesized that combined treatment with rapamycin and HO-3867 is superior to either alone in attenuating MCT-induced rat pulmonary arterial hypertension (PAH). Pulmonary arterial hypertension was induced by a single intraperitoneal injection of monocrotaline (60 mg/kg). 2 weeks later, rapamycin (2 mg/kg i.p.) and HO3867 (10 mg/kg i.h.) were administered daily, alone and in combination, for 2 weeks. Right ventricular systolic pressure, echocardiography were recorded and then rats were sacrificed. Histological analysis of pulmonary arteries medial wall thickness, right ventricular hypertrophy index (RVHI), the ratio of right ventricular to body weight, and collagen volume fraction (CVF) of right ventricular were performed. Moreover, the expression of t-STAT3, p-STAT3, t-Akt, p-Akt in lung and t-STAT3, p-STAT3, t-S6, p-S6 in right ventricular were examined. The result showed that combined treatment provided a considerable improvement toward maintaining hemodynamic changes, lung vascular remodeling as well as amending RV remodeling and function. Furthermore, Combined treatment can normalize the protein levels of two signal pathways in lung and heart tissue, where p-S6 or p-Akt significantly decreased compared to HO-3867 alone, or p-STAT3 significantly reduced compared to rapamycin alone. In conclusion, combined treatment with rapamycin and HO-3867 is superior to either alone in attenuating MCT-induced PAH in rats.

NF-κB/p65 Competes With Peroxisome Proliferator-Activated Receptor Gamma for Transient Receptor Potential Channel 6 in Hypoxia-Induced Human Pulmonary Arterial Smooth Muscle Cells

Objective: Peroxisome proliferator-activated receptor gamma (PPARγ) has an anti-proliferation effect on pulmonary arterial smooth muscle cells (PASMCs) via the transient receptor potential channel (TRPC) and protects against pulmonary artery hypertension (PAH), whereas nuclear factor-kappa B (NF-κB) has pro-proliferation and pro-inflammation effects, which contributes to PAH. However, the association between them in PAH pathology remains unclear. Therefore, this study aimed to investigate this association and the mechanisms underlying TRPC1/6 signaling-mediated PAH.

Methods: Human pulmonary arterial smooth muscle cells (hPASMCs) were transfected with p65 overexpressing (pcDNA-p65) and interfering plasmids (shp65) and incubated in normal and hypoxic conditions (4% O₂ and 72 h). The effects of hypoxia and p65 expression on cell proliferation, invasion, apoptosis, [Ca²⁺]i, PPARγ, and TRPC1/6 expression were determined using Cell Counting Kit-8 (CCK-8), Transwell, Annexin V/PI, Fura-2/AM, and western blotting, respectively. In addition, the binding of p65 or PPARγ proteins to the TRPC6 promoter was validated using a dual-luciferase report assay, chromatin-immunoprecipitation-polymerase chain reaction (ChIP-PCR), and electrophoretic mobility shift assay (EMSA).

Results: Hypoxia inhibited hPASMC apoptosis and promoted cell proliferation and invasion. Furthermore, it increased [Ca²⁺]i and the expression of TRPC1/6, p65, and Bcl-2 proteins. Moreover, pcDNA-p65 had similar effects on hypoxia treatment by increasing TRPC1/6 expression, [Ca²⁺]i, hPASMC proliferation, and invasion. The dual-luciferase report and ChIP-PCR assays revealed three p65 binding sites and two PPARγ binding sites on the promoter region of TRPC6. In addition, hypoxia treatment and shPPARγ promoted the binding of p65 to the TRPC6 promoter, whereas shp65 promoted the binding of PPARγ to the TRPC6 promoter.

Conclusion: Competitive binding of NF-κB p65 and PPARγ to TRPC6 produced an anti-PAH effect.

Ferulic Acid Ameliorates Hepatic Inflammation and Fibrotic Liver Injury by Inhibiting PTP1B Activity and Subsequent Promoting AMPK Phosphorylation

Chronic inflammation in response to persistent exogenous stimuli or damage results in liver fibrosis, which subsequently progresses into malignant liver diseases with high morbidity and mortality. Ferulic acid (FA) is a phenolic acid widely isolated from abundant plants and exhibits multiple biological activities including anti-oxidant, anti-inflammation and enhancement of immune responses. Adenosine monophosphate-activated protein kinase (AMPK) functions as a critical energy sensor and is regulated through the phosphorylation of liver kinases like LKB1 or dephosphorylation by protein tyrosine phosphatases (PTPs). However, the role of FA in carbon tetrachloride (CCl₄)-induced chronic inflammation and liver fibrosis and AMPK activation has not been elucidated. Here we reported that FA ameliorated CCl₄-induced inflammation and fibrotic liver damage in mice as indicated by reduced levels of serum liver function enzyme activities and decreased expression of genes and proteins associated with fibrogenesis. Additionally, FA inhibited hepatic oxidative stress, macrophage activation and HSC activation via AMPK phosphorylation in different liver cells. Mechanically, without the participation of LKB1, FA-induced anti-inflammatory and anti-fibrotic effects were abrogated by a specific AMPK inhibitor, compound C. Combining with the results of molecular docking, surface plasmon resonance and co-immunoprecipitation assays, we further demonstrated that FA directly bound to and inhibited PTP1B, an enzyme responsible for dephosphorylating key protein kinases, and eventually leading to the phosphorylation of AMPK. In summary, our results indicated that FA alleviated oxidative stress, hepatic inflammation and fibrotic response in livers through PTP1B-AMPK signaling pathways. Taken together, we provide novel insights into the potential of FA as a natural product-derived therapeutic agent for the treatment of fibrotic liver injury.

Lessons from Cancer Metabolism for Pulmonary Arterial Hypertension and Fibrosis

Metabolism is essential for a living organism to sustain life. It provides energy to a cell by breaking down compounds (catabolism) and supplies building blocks for the synthesis of macromolecules (anabolism). Signal transduction pathways tightly regulate mammalian cellular metabolism. Simultaneously, metabolism itself serves as a signaling pathway to control many cellular processes, such as proliferation, differentiation, cell death, gene expression, and adaptation to stress. Considerable progress in the metabolism field has come from understanding how cancer cells co-opt metabolic pathways for growth and survival. Recent data also show that several metabolic pathways may participate in the pathogenesis of lung diseases, some of which could be promising therapeutic targets. In this translational review, we will outline the basic metabolic principles learned from the cancer metabolism field as they apply to the pathogenesis of pulmonary arterial hypertension and fibrosis and will place an emphasis on therapeutic potential.

Novel Treatment Pathways in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a severe and progressive vascular disease characterized by pulmonary vascular remodeling, proliferation, and inflammation. Despite the availability of effective treatments, PAH may culminate in right ventricular failure and death. Currently approved medications act through three well-characterized pathways: the nitric oxide, endothelin, and prostacyclin pathways. Ongoing research efforts continue to expand our understanding of the molecular pathogenesis of this complex and multifactorial disease. Based on recent discoveries in the pathobiology of PAH, several new treatments are being developed and tested with the goal of modifying the disease process and ultimately improving the long-term prognosis.

AMPK and Pulmonary Hypertension: Crossroads Between Vasoconstriction and Vascular Remodeling

Pulmonary hypertension (PH) is a debilitating and life-threatening disease characterized by increased blood pressure within the pulmonary arteries. Adenosine monophosphate-activated protein kinase (AMPK) is a heterotrimeric serine-threonine kinase that contributes to the regulation of metabolic and redox signaling pathways. It has key roles in the regulation of cell survival and proliferation. The role of AMPK in PH is controversial because both inhibition and activation of AMPK are preventive against PH development. Some clinical studies found that metformin, the first-line antidiabetic drug and the canonical AMPK activator, has therapeutic efficacy during treatment of early-stage PH. Other study findings suggest the use of metformin is preferentially beneficial for treatment of PH associated with heart failure with preserved ejection fraction (PH-HFpEF). In this review, we discuss the "AMPK paradox" and highlight the differential effects of AMPK on pulmonary vasoconstriction and pulmonary vascular remodeling. We also review the effects of AMPK activators and inhibitors on rescue of preexisting PH in animals and include a discussion of gender differences in the response to metformin in PH.

ERK/Drp1-dependent mitochondrial fission contributes to HMGB1-induced autophagy in pulmonary arterial hypertension

OBJECTIVES

High-mobility group box-1 (HMGB1) and aberrant mitochondrial fission mediated by excessive activation of GTPase dynamin-related protein 1 (Drp1) have been found to be elevated in patients with pulmonary arterial hypertension (PAH) and critically implicated in PAH pathogenesis. However, it remains unknown whether Drp1-mediated mitochondrial fission and which downstream targets of mitochondrial fission mediate HMGB1-induced pulmonary arterial smooth muscle cells (PASMCs) proliferation and migration leading to vascular remodelling in PAH. This study aims to address these issues.

METHODS

Primary cultured PASMCs were obtained from male Sprague-Dawley (SD) rats. We detected RNA levels by qRT-PCR, protein levels by Western blotting, cell proliferation by Cell Counting Kit-8 (CCK-8) and EdU incorporation assays, migration by wound healing and transwell assays. SD rats were injected with monocrotaline (MCT) to establish PAH. Hemodynamic parameters were measured by closed-chest right heart catheterization.

RESULTS

HMGB1 increased Drp1 phosphorylation and Drp1-dependent mitochondrial fragmentation through extracellular signal-regulated kinases 1/2 (ERK1/2) signalling activation, and subsequently triggered autophagy activation, which further led to bone morphogenetic protein receptor 2 (BMPR2) lysosomal degradation and inhibitor of DNA binding 1 (Id1) downregulation, and eventually promoted PASMCs proliferation/migration. Inhibition of ERK1/2 cascade, knockdown of Drp1 or suppression of autophagy restored HMGB1-induced reductions of BMPR2 and Id1, and diminished HMGB1-induced PASMCs proliferation/migration. In addition, pharmacological inhibition of HMGB1 by glycyrrhizin, suppression of mitochondrial fission by Mdivi-1 or blockage of autophagy by chloroquine prevented PAH development in MCT-induced rats PAH model.

CONCLUSIONS

HMGB1 promotes PASMCs proliferation/migration and pulmonary vascular remodelling by activating ERK1/2/Drp1/Autophagy/BMPR2/Id1 axis, suggesting that this cascade might be a potential novel target for management of PAH.

Novel Targets of Metformin in Cardioprotection: Beyond the Effects Mediated by AMPK

Ischemic heart disease is the main cause of death globally. In the heart, the ischemia/reperfusion injury gives rise to a complex cascade of molecular signals, called cardiac remodeling, which generates harmful consequences for the contractile function of the myocardium and consequently heart failure. Metformin is the drug of choice in the treatment of type 2 diabetes mellitus. Clinical data suggest the direct effects of this drug on cardiac metabolism and studies in animal models showed that metformin activates the classical pathway of AMP-activated protein kinase (AMPK), generating cardioprotective effects during cardiac remodeling, hypertrophy and fibrosis. Furthermore, new studies have emerged about other targets of metformin with a potential role in cardioprotection. This state of the art review shows the available scientific evidence of the cardioprotective potential of metformin and its possible effects beyond AMPK. Targeting of autophagy, mitochondrial function and miRNAs are also explored as cardioprotective approaches along with a therapeutic potential. Further advances related to the biological effects of metformin and cardioprotective approaches may provide new therapies to protect the heart and prevent cardiac remodeling and heart failure.

Apelin receptor upregulation in spontaneously hypertensive rat contributes to the enhanced vascular smooth muscle cell proliferation by activating autophagy

Background

Proliferation of vascular smooth muscle cells (VSMCs) plays a vital role in the progression of vascular remodeling and hypertension. Apelin-13 promotes VSMC proliferation of normal rats. This study was designed to investigate the roles of apelin receptor (APJ) and apelin-13 in VSMC proliferation of hypertension rats and underlying mechanisms.

Methods

Primary VSMCs were obtained from aorta of Wistar-Kyoto rat (WKY) and spontaneously hypertensive rat (SHR). The expressions of apelin and APJ were detected by Western bolt and PCR, as well as immunohistochemistry. VSMC proliferation was evaluated with CCK-8 kit, PCNA protein expression and percentage of EdU-positive cells. Autophagy was determined by the ratio of LC3BII to LC3BI, ATG5 and p62 protein expressions, as well as LC3B immunofluorescence.

Results

APJ expression was increased while apelin expression was reduced in aorta and VSMCs of SHR compared with those of WKY. Exogenous apelin-13 promoted VSMC proliferation and autophagy of both WKY and SHR, which were prevented by APJ antagonist F13A. Blockade of APJ had no significant effects on VSMC proliferation and autophagy of WKY, but attenuated VSMC proliferation and autophagy of SHR. Administration of autophagy inhibitor 3-methyladenine (3-MA) not only attenuated VSMC proliferation of SHR, but prevented apelin-13-induced VSMC proliferation of both WKY and SHR.

Conclusions

Apelin-13 stimulates VSMC proliferation via APJ-mediated enhancement in autophagy. APJ upregulation in SHR contributes to the enhanced VSMC proliferation.

The effects of metformin on autophagy

Metformin is the first-line option for treating newly diagnosed diabetic patients and also involved in other pharmacological actions, including antitumor effect, anti-aging effect, polycystic ovarian syndrome prevention, cardiovascular action, and neuroprotective effect, etc. However, the mechanisms of metformin actions were not fully illuminated. Recently, increasing researches showed that autophagy is a vital medium of metformin playing pharmacological actions. Nevertheless, results on the effects of metformin on autophagy were inconsistent. Apart from few clinical evidences, more data focused on kinds of no-clinical models. First, many studies showed that metformin could induce autophagy via a number of signaling pathways, including AMPK-related signaling pathways (e.g. AMPK/mTOR, AMPK/CEBPD, MiTF/TFE, AMPK/ULK1, and AMPK/miR-221), Redd1/mTOR, STAT, SIRT, Na⁺/H⁺ exchangers, MAPK/ERK, PK2/PKR/AKT/ GSK3β, and TRIB3. Secondly, some signaling pathways were involved in the process of metformin inhibiting autophagy, such as AMPK-related signaling pathways (AMPK/NF-κB and other undetermined AMPK-related signaling pathways), Hedgehog, miR-570-3p, miR-142-3p, and MiR-3127-5p. Thirdly, two types of signaling pathways including PI3K/AKT/mTOR and endoplasmic reticulum (ER) stress could bidirectionally impact the effectiveness of metformin on autophagy. Finally, multiple signal pathways were reviewed collectively in terms of affecting the effectiveness of metformin on autophagy. The pharmacological effects of metformin combining its actions on autophagy were also discussed. It would help better apply metformin to treat diseases in term of mediating autophagy.

Glucose-6-phosphate dehydrogenase deficiency contributes to metabolic abnormality and pulmonary hypertension

We have previously reported that several patients with idiopathic pulmonary hypertension (PH) had different types of G6PD deficiency. However, the role of G6PD in PH is multifactorial because G6PD is involved in controlling oxidative stress, metabolic switch, and red blood cell fragility. To delineate the contribution of G6PD to PH pathogenesis, we utilized a mouse line with decreased expression of G6PD (10% from wild-type level). We confirmed that mice with G6PD deficiency develop spontaneous pulmonary hypertension with pulmonary artery and right heart remodeling. G6PD deficiency resulted in increased free hemoglobin and activation of the p38 pathway, which we recently reported induces the development of PH in the sugen/hypoxia model via endothelial barrier dysfunction. Metabolomics analysis of G6PD deficient mice indicates the switch to alternative metabolic fluxes that feed into the pentose phosphate pathway (PPP), resulting in the upregulation of oxidative stress, fatty acid pathway, and reduction in pyruvate production. Thus, G6PD deficiency did not reduce PPP flux that is important for proliferation but activated collateral pathways at the cost of increased oxidative stress. Indeed, we found the upregulation of myo-inositol oxidase, reduction in GSH/GSSG ratio, and increased nitration in the lungs of G6PD-deficient mice. Increased oxidative stress also results in the activation of PI3K, ERK1/2, and AMPK that contribute to the proliferation of pulmonary vasculature. Therefore, G6PD deficiency has a multimodal effect, including hemolysis, metabolic reprogramming, and oxidative stress leading to the PH phenotype in mice.

Activation of AMPK suppresses S1P-induced airway smooth muscle cells proliferation and its potential mechanisms

The aims of the present study were to investigate the signaling mechanisms for sphingosine-1-phosphate (S1P)-induced airway smooth muscle cells (ASMCs) proliferation and to explore the effect of activation of adenosine monophosphate-activated protein kinase (AMPK) on S1P-induced ASMCs proliferation and its underlying mechanisms. S1P phosphorylated signal transducer and activator of transcription 3 (STAT3) through binding to S1PR_2/3, and this further sequentially up-regulated polo-like kinase 1 (PLK1) and inhibitor of differentiation 2 (ID2) protein expression. Pretreatment of cells with S1PR₂ antagonist JTE-013, S1PR₃ antagonist CAY-10444, knockdown of STAT3, PLK1 and ID2 attenuated S1P-triggered ASMCs proliferation. In addition, activation of AMPK by metformin inhibited S1P-induced ASMCs proliferation by suppressing STAT3 phosphorylation and therefore suppression of PLK1 and ID2 protein expression. Our study suggests that S1P promotes ASMCs proliferation by stimulating S1PR_2/3/STAT3/PLK1/ID2 axis, and activation of AMPK suppresses ASMCs proliferation by targeting on STAT3 signaling pathway. Activation of AMPK might benefit asthma by inhibiting airway remodeling.

Metformin prevents the development of monocrotaline-induced pulmonary hypertension by decreasing serum levels of big endothelin-1

Pulmonary hypertension (PH) is a disease with poor prognosis, and it is characterized by the progressive elevation of pulmonary vascular resistance and pressure. Various factors are associated with the pathology of PH, including AMP-activated protein kinase (AMPK) deficiency. The present study aimed to evaluate the therapeutic effect of metformin, an AMPK activator, in a monocrotaline (MCT)-induced PH rat model. Rats were randomly divided into the following three groups: i) Saline-injected group (sham group); ii) monocrotaline (MCT)-injected group (PH group); iii) MCT-injected and metformin-treated group (MT group). Four weeks following MCT injection, cardiac ultrasonography, invasive hemodynamic measurements, measurement of serum levels of big endothelin-1 (big ET-1) and histological analysis were performed to evaluate the effect of metformin treatment in PH. Pulmonary arterial pressure and serum big ET-1 concentrations were reduced in the MT group compared with the PH group. Medial wall thickness and wall area of the pulmonary arterioles in the MT group were decreased compared with the PH group. Comparing the right heart functional parameters among groups revealed that the acceleration time/ejection time ratio improved in the MT group compared with the PH group. Thus, the present study demonstrated the efficacy of metformin in an MCT-induced PH rat model and suggested that metformin may be a valuable, potential novel therapeutic for the treatment of PH.

Sphingosine-1-phosphate promotes pulmonary artery smooth muscle cells proliferation by stimulating autophagy-mediated E-cadherin/CDH1 down-regulation

It has been shown that sphingosine-1-phosphate (S1P) is elevated in patients with pulmonary arterial hypertension (PAH) and promotes the proliferation of pulmonary artery smooth muscle cells (PASMCs). Meanwhile, S1P has been found to induce the activation of autophagy in several types of human diseases including cancers. However, it is still unclear whether activation of autophagy mediates S1P-induced PASMCs proliferation, and detailed mechanisms responsible for these processes are indefinite. The aims of this study are to address these issues. S1P dose- and time-dependently reduced the expression of E-cadherin/CDH1 and stimulated PASMCs proliferation; this was accompanied with the elevation of TNF receptor-associated factor 2 (TRAF2), up-regulation and ubiquitination of BECN1 and the activation of autophagy. Prior silencing TRAF2 or BECN1 using siRNA or pre-incubation of cells with autophagy inhibitor chloroquine phosphate (CQ) suppressed S1P-induced autophagy activation and subsequent CDH1 degradation and further PASMCs proliferation. Taken together, our study indicates that S1P promotes the activation of autophagy by accelerating TRAF2-mediated BECN1 up-regulation and ubiquitination, which in turn results in CDH1 reduction and contributes to PASMCs proliferation.

UL16-Binding Protein 1 Induced HTR-8/SVneo Autophagy via NF-κB Suppression Mediated by TNF-α Secreted through uNK Cells

UL16-binding protein 1(ULBP1) has been reported to inhibit trophoblast invasion through the modification of secretion functions of uNK cells in the previous study, but its mechanisms remain unclear. In this study, we investigated the related mechanism by which upregulated ULBP1 expression impaired trophoblast invasion. We found that conditioned media with ULBP1 increased autophagy in HTR-8/SVneo, and anti-TNF-α-neutralizing antibody rescued the autophagy caused by the conditioned medium. We further found TNF-α induced autophagy in trophoblast cells in a dose-dependent way and accompanied by a decreased activity of nuclear factor-kappa B (NF-κB). Inhibition of NF-κB activation by chemical inhibitor augmented these autophagic responses to TNF-α in the cells. In addition, interruption NF-κB caused a significant decrease in HTR-8/SVneo invasion and enhanced the inhibition effect of TNF-α on HTR-8/SVneo invasion. Taken together, these findings suggest that TNF-α is able to regulate autophagic activity via suppressing NF-κB, which might be the mechanism related to ULBP1 in preeclampsia pathogenesis.

Emerging roles of let‑7d in attenuating pulmonary arterial hypertension via suppression of pulmonary artery endothelial cell autophagy and endothelin synthesis through ATG16L1 downregulation

Pulmonary arterial hypertension (PAH) is a severe disease characterized by elevated pulmonary arterial pressure and pulmonary vascular resistance, resulting in right ventricular failure and death. Compelling evidence has suggested the roles of microRNAs (miRNAs/miRs) in PAH. The present study investigated the possible effects of miR-let-7d on PAH through autophagy-related 16-like 1 (ATG16L1). Initially, the serum levels of let-7d in PAH patients were detected. Rats were then treated with monocrotaline to induce a rat model of PAH, after which the right ventricular systolic pressure (RVSP) and right ventricular hypertrophy index (RVHI) were determined. Next, the putative binding sites between let-7d and ATG16L1 were detected. The expression of let-7d and ATG16L1 in PAH rat models and cells was upregulated or downregulated to assess the effects of these molecules on autophagy in pulmonary artery vascular endothelial cells (PAECs) and on endothelin synthesis. In addition, the levels of p62, LC3-I, LC3-II, LC3B and endothelin-1 (ET-1) were assessed. The results obtained revealed that let-7d was downregulated in the serum of PAH patients and rats with PAH. Importantly, ATG16L1 was found to be a target gene of let-7d and let-7d could suppress the expression of ATG16L1. Overexpression of let-7d was found to reduce RVSP and RVHI values. Additionally, upregulation of let-7d or depletion of ATG16L1 led to suppression of PAEC autophagy and endothelin synthesis, corresponding to decreased ratios of LC3-II to LC3-I and reduced levels of LC3B but elevated levels of p62 in PAECs and ET-1 in plasma and lung tissues. In summary, let-7d upregulation alleviates PAH by inhibiting autophagy in PAECs and suppressing endothelin synthesis through negative regulation of ATG16L1.

Cardioprotection in right heart failure

Ischaemic and pharmacological conditioning of the left ventricle is mediated by the activation of signalling cascades, which finally converge at the mitochondria and reduce ischaemia/reperfusion (I/R) injury. Whereas the molecular mechanisms of conditioning in the left ventricle are well characterized, cardioprotection of the right ventricle is principally feasible but less established. Similar to what is known for the left ventricle, a dysregulation in signalling pathways seems to play a role in I/R injury of the healthy and failing right ventricle and in the ability/inability of the right ventricle to respond to a conditioning stimulus. The maintenance of mitochondrial function seems to be crucial in both ventricles to reduce I/R injury. As far as currently known, similar molecular mechanisms mediate ischaemic and pharmacological preconditioning in the left and right ventricles. However, the two ventricles seem to respond differently towards exercise‐induced preconditioning.

LINKED ARTICLES

This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.23/issuetoc

Inhibition of ROS-NF-κB-dependent autophagy enhances Hypocrellin A united LED red light-induced apoptosis in squamous carcinoma A431 cells

Cutaneous squamous cell carcinoma (cSCC) is a type of malignant skin tumor derived from epidermal Malpighian cells. Photodynamic therapy is regarded as a crucial method in oncology. Hypocrellin A (HA), an efficient natural photosensitizer, has been reported to exert excellent light induced antiviral, antimicrobial and anticancer activity through mediating multiple signaling pathways. The purpose of the present study is to examine the effects of HA united red light irradiation on human squamous carcinoma A431 cells and further reveal the underlying regulatory mechanisms. The results showed that synergistic treatment of HA and red light irradiation inhibited cell proliferation and induced cell apoptosis and autophagy. Moreover, HA united red light irradiation caused a significant accumulation of reactive oxygen species (ROS), and induced the activation of c-Jun NH 2 terminal kinases (JNKs) which was inhibited by the antioxidant N-Acetyl-cysteine (NAC). Furthermore, HA united red light irradiation activated the nuclear factor-kappa B (NF-κB) pathway, and inhibition of NF-κB activity exacerbated HA united red light irradiation-induced apoptosis but suppressed cell autophagy. In addition, the inhibition of autophagy promoted HA united red light irradiation-induced apoptosis and facilitated the NF-κB activity. Over all, our results revealed that HA united red light irradiation could inhibit A431 cell proliferation by inducing apoptosis and autophagy via the activation of the ROS mediated JNK and NF-κB pathways, providing prospective for HA as a potential therapeutic for the treatment of cSCC.

Metformin as a protective agent against natural or chemical toxicities: a comprehensive review on drug repositioning

BACKGROUND

Metformin is the first prescribed drug for hyperglycemia in type 2 diabetes mellitus. Mainly by activating AMPK pathway, this drug exerts various functions that among them protective effects are of the interest.

PURPOSE

Herein, we aimed to gather data about the protective impacts of metformin against various natural or chemical toxicities.

RESULTS

An extensive search among PubMed, Scopus, and Google Scholar was conducted by keywords related to protection, toxicity, natural and chemical toxins and, metformin. Our literature review showed metformin alongside its anti-hyperglycemic effect has a wide range of anti-toxic effects against anti-tumour and routine drugs, natural and chemical toxins, herbicides and, heavy metals.

CONCLUSION

It is evident that metformin is a potent drug against the toxicity of a broad spectrum of natural, chemical toxic agents which is proved by a vast number of studies. Metformin mainly through AMPK axis can protect different organs against toxicities. Moreover, metformin preserves DNA integrity and can be an option for adjuvant therapy to ameliorate side effect of other therapeutics.

Redox Regulation of Ion Channels and Receptors in Pulmonary Hypertension

Significance: Pulmonary hypertension (PH) is characterized by elevated vascular resistance due to vasoconstriction and remodeling of the normally low-pressure pulmonary vasculature. Redox stress contributes to the pathophysiology of this disease by altering the regulation and activity of membrane receptors, K+ channels, and intracellular Ca2+ homeostasis. Recent Advances: Antioxidant therapies have had limited success in treating PH, leading to a growing appreciation that reductive stress, in addition to oxidative stress, plays a role in metabolic and cell signaling dysfunction in pulmonary vascular cells. Reactive oxygen species generation from mitochondria and NADPH oxidases has substantial effects on K+ conductance and membrane potential, and both receptor-operated and store-operated Ca2+ entry. Critical Issues: Some specific redox changes resulting from oxidation, S-nitrosylation, and S-glutathionylation are known to modulate membrane receptor and ion channel activity in PH. However, many sites of regulation that have been elucidated in nonpulmonary cell types have not been tested in the pulmonary vasculature, and context-specific molecular mechanisms are lacking. Future Directions: Here, we review what is known about redox regulation of membrane receptors and ion channels in PH. Further investigation of the mechanisms involved is needed to better understand the etiology of PH and develop better targeted treatment strategies.

Interaction among inflammasome, autophagy and non-coding RNAs: new horizons for drug

Autophagy and inflammasomes are shown to interact in various situations including infectious disease, cancer, diabetes and neurodegeneration. Since multiple layers of molecular regulators contribute to the interplay between autophagy and inflammasome activation, the detail of such interplay remains largely unknown. Non-coding RNAs (ncRNAs), which have been implicated in regulating an expanding list of cellular processes including immune defense against pathogens and inflammatory response in cancer and metabolic diseases, may join in the crosstalk between inflammasomes and autophagy in physiological or disease conditions. In this review, we summarize the latest research on the interlink among ncRNAs, inflammasomes and autophagy and discuss the emerging role of these three in multiple signaling transduction pathways involved in clinical conditions. By analyzing these intriguing interconnections, we hope to unveil the mechanism inter-regulating these multiple processes and ultimately discover potential drug targets for some refractory diseases.

Cepharanthine: An update of its mode of action, pharmacological properties and medical applications

BACKGROUND

Cepharanthine (CEP) is a drug used in Japan since the 1950s to treat a number of acute and chronic diseases, including treatment of leukopenia, snake bites, xerostomia and alopecia. It is the only approved drug for Human use in the large class of bisbenzylisoquinoline alkaloids. This natural product, mainly isolated from the plant Stephania cephalantha Hayata, exhibits multiple pharmacological properties including anti-oxidative, anti-inflammatory, immuno-regulatory, anti-cancer, anti-viral and anti-parasitic properties.

PURPOSE

The mechanism of action of CEP is multifactorial. The drug exerts membrane effects (modulation of efflux pumps, membrane rigidification) as well as different intracellular and nuclear effects. CEP interferes with several metabolic axes, primarily with the AMP-activated protein kinase (AMPK) and NFκB signaling pathways. In particular, the anti-inflammatory effects of CEP rely on AMPK activation and NFκB inhibition.

CONCLUSION

In this review, the historical discovery and development of CEP are retraced, and the key mediators involved in its mode of action are presented. The past, present, and future of CEP are recapitulated. This review also suggests new opportunities to extend the clinical applications of this well-tolerated old Japanese drug.

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.

Small GTPase RHOE/RND3, a new critical regulator of NF-κB signalling in glioblastoma multiforme?

Objectives

Abnormal activation of NF‐κB signalling is a major mechanism of apoptosis resistance in glioblastoma multiforme (GBM). Therefore, better understanding of the regulation of NF‐κB signalling has a significant impact for GBM therapy. Here, we uncovered a critical role of the small GTPase RND3 in regulating the p65 subunit of NF‐κB and NF‐κB signalling in GBM.

Materials and methods

Human GBM samples, GBM cells and a human orthotopic GBM‐xenografted animal model were used. The mechanisms of RND3 in regulation of NF‐κB signalling and GBM cell apoptosis were examined by luciferase assay, quantitative PCR, immunostaining, immunoblotting, immunofluorescence, coimmunoprecipitation, TUNEL staining, JC‐1 analysis and flow cytometry.

Results

Overexpression of RND3 led to reduced p65 activity in GBM‐cultured cells and a GBM animal model, indicating that the NF‐κB pathway is negatively regulated by RND3 in GBM. Mechanistically, we found that RND3 bound p65 and promoted p65 ubiquitination, leading to decreased p65 protein levels. Furthermore, RND3 enhanced cleaved caspase 3 levels and promoted apoptosis in GBM cells, and RND3 expression was positively correlated with cleaved caspase 3 and IL‐8 in human GBM samples. The effect of RND3 on promoting apoptosis disappeared when p65 ubiquitination was blocked by protease inhibitor carfilzomib or upon co‐expression of ectopic p65.

Conclusions

RND3 binds p65 protein and promotes its ubiquitination, resulting in reduced p65 protein expression and inhibition of NF‐κB signalling to induce GBM cell apoptosis.

Lipopolysaccharide-Induced Autophagy Mediates Retinal Pigment Epithelium Cells Survival. Modulation by the Phospholipase D Pathway

Inflammation and oxidative stress are common factors involved in the pathogenesis of retinal diseases, such as aged-related macular degeneration (AMD) and diabetic retinopathy (DR). Autophagy is a catabolic process essential to cell survival in response to stress. This process is highly active in retinal pigment epithelium (RPE) cells. Our previous findings demonstrated that lipopolysaccharide (LPS) induces an inflammatory response of RPE cells that implies classical phospholipases D (PLD1 and 2) activation, cyclooxygenase-2 (COX-2) expression, prostaglandin E₂ (PGE₂) production and reduced cell viability. In this work, we studied the autophagic process and its modulation by the PLD pathway in D407 and ARPE-19 RPE cells exposed to LPS. LPS (10 μg/ml or 25 μg/ml) exposure for 24 h increased light chain 3B-II (LC3B-II) content (an autophagy marker) and LC3B-positive punctate structures in both RPE cell lines studied. Next, the drug bafilomycin A₁ (BAF, 50 nM) was used to block the autophagic flux. In cells pre-incubated with BAF, LC3B-II and sequestosome 1 (SQSTM1/p62) levels and autophagosome-like structures were increased by LPS, demonstrating that the inflammatory injury increases the autophagic process in RPE cells. To study the role of the PLD pathway, cells were pre-incubated for 1 h with selective PLD1 (VU0359595) or PLD2 (VU0285655-1) inhibitors prior to LPS addition. Under control condition, LC3B-positive punctate structures were increased in cells pre-incubated with PLD2 inhibitor while with PLD1 inhibitor were increased in cells exposed to LPS. MTT reduction assays showed that early autophagy inhibitors, 3-methyladenin (3-MA) or LY294002, enhanced the loss in cell viability induced by LPS exposure for 48 h. On the contrary, the inhibition of PLD1 and PLD2 prevented the loss in cell viability induced by LPS. In conclusion, our results show that even though LPS treatment promotes an inflammatory response in RPE cells, it also triggers the activation of the autophagic process which in turn may serve as a protective mechanism for the cells. In addition, we demonstrate that the PLD pathway modulates the autophagic process in RPE cells. Our findings contribute to the knowledge of the molecular basis of retinal inflammatory and degenerative diseases and open new avenues for potential therapeutic exploration.