Heme oxygenase-1/p21WAF1 mediates peroxisome proliferator-activated receptor-gamma signaling inhibition of proliferation of rat pulmonary artery smooth muscle cells

The Antimicrobial Activity of Human Defensins at Physiological Non-Permeabilizing Concentrations Is Caused by the Inhibition of the Plasma Membrane H+-ATPases

Human defensins are cysteine-rich peptides (Cys-rich peptides) of the innate immune system. Defensins contain an ancestral structural motif (i.e., γ-core motif) associated with the antimicrobial activity of natural Cys-rich peptides. In this study, low concentrations of human α- and β-defensins showed microbicidal activity that was not associated with cell membrane permeabilization. The cell death pathway was similar to that previously described for human lactoferrin, also an immunoprotein containing a γ-core motif. The common features were (1) cell death not related to plasma membrane (PM) disruption, (2) the inhibition of microbicidal activity via extracellular potassium, (3) the influence of cellular respiration on microbicidal activity, and (4) the influence of intracellular pH on bactericidal activity. In addition, in yeast, we also observed (1) partial K+-efflux mediated via Tok1p K+-channels, (2) the essential role of mitochondrial ATP synthase in cell death, (3) the increment of intracellular ATP, (4) plasma membrane depolarization, and (5) the inhibition of external acidification mediated via PM Pma1p H+-ATPase. Similar features were also observed with BM2, an antifungal peptide that inhibits Pma1p H+-ATPase, showing that the above coincident characteristics were a consequence of PM H+-ATPase inhibition. These findings suggest, for the first time, that human defensins inhibit PM H+-ATPases at physiological concentrations, and that the subsequent cytosolic acidification is responsible for the in vitro microbicidal activity. This mechanism of action is shared with human lactoferrin and probably other antimicrobial peptides containing γ-core motifs.

Vincamine alleviates intrahepatic cholestasis in rats through modulation of NF-kB/PDGF/klf6/PPARγ and PI3K/Akt pathways

The defect in the hepatobiliary transport system results in an impairment of bile flow, leading to accumulation of toxic compounds with subsequent liver disorders. Vincamine, a plant indole alkaloid that is utilized as a dietary supplement, has been known for its promising pharmacological activities. For the first time, the present study was planned to estimate, at the molecular level, the potentiality of vincamine against alfa-naphthyl isothiocyanate (ANIT)-induced hepatic cholestasis. Liver function tests were analyzed. Hepatic activity of SOD and levels of GSH and MDA were assessed. Hepatic contents of bax, bcl2, NF-kB, PPARγ, catalase, heme-oxygenase-1, NTCP, and BSEP were evaluated using ELISA. mRNA levels of NF-kB, IL-1β, IL-6, TNFα, PDGF, klf6, PPARγ, and P53 were examined using qRT-PCR. PI3K, Akt and cleaved caspase-3 proteins were assessed using western blotting. Histopathological analyses were performed using hematoxylin & eosin staining. ANIT-induced hepatic cholestasis elevated liver function tests, including AST, ALT, GGT, ALP, and total bilirubin. ANIT reduced the protein expression of NTCP and BSEP hepatic transporters. It induced the expression of the inflammatory genes, TNFα, IL-6, IL-1β, and PDGF, and the expression of NF-kB at the genetic and protein level and suppressed the anti-inflammatory genes, klf6 and PPARγ. Also, antioxidant markers were reduced during ANIT induction such as GSH, SOD, catalase, heme-oxygenase-1 and PI3K/Akt pathway, while MDA levels were elevated. Furthermore, the expression of P53 gene, bax and cleaved caspase 3 proteins were activated, while bcl2 was inhibited. Also, the histopathological analysis showed degeneration of hepatocytes and inflammatory cellular infiltrates. However, vincamine treatment modulated all these markers. It improved liver function tests. It inhibited the expression of NF-kB, TNFα, IL-6, IL-1β and PDGF and activated the expression of klf6 and PPARγ. Furthermore, vincamine reduced MDA levels and induced GSH, SOD, catalase, heme-oxygenase-1 and PI3K/Akt pathway. Additionally, it inhibited expression of P53 gene, bax and cleaved caspase 3 proteins. More interestingly, vincamine showed better outcomes on the hepatic histopathological analysis and improved the alterations induced by ANIT. Vincamine alleviated hepatic dysfunction during ANIT-induced intrahepatic cholestasis through its anti-inflammatory and antioxidant efficacies by the modulation of NF-kB/PDGF/klf6/PPARγ and PI3K/Akt pathways.

Harnessing peroxisome proliferator-activated receptor γ agonists to induce Heme Oxygenase-1: a promising approach for pulmonary inflammatory disorders

The activation of peroxisome proliferator-activated receptor (PPAR)-γ has been extensively shown to attenuate inflammatory responses in conditions such as asthma, acute lung injury, and acute respiratory distress syndrome, as demonstrated in animal studies. However, the precise molecular mechanisms underlying these inhibitory effects remain largely unknown. The upregulation of heme oxygenase-1 (HO-1) has been shown to confer protective effects, including antioxidant, antiapoptotic, and immunomodulatory effects in vitro and in vivo. PPARγ is highly expressed not only in adipose tissues but also in various other tissues, including the pulmonary system. Thiazolidinediones (TZDs) are highly selective agonists for PPARγ and are used as antihyperglycemic medications. These observations suggest that PPARγ agonists could modulate metabolism and inflammation. Several studies have indicated that PPARγ agonists may serve as potential therapeutic candidates in inflammation-related diseases by upregulating HO-1, which in turn modulates inflammatory responses. In the respiratory system, exposure to external insults triggers the expression of inflammatory molecules, such as cytokines, chemokines, adhesion molecules, matrix metalloproteinases, and reactive oxygen species, leading to the development of pulmonary inflammatory diseases. Previous studies have demonstrated that the upregulation of HO-1 protects tissues and cells from external insults, indicating that the induction of HO-1 by PPARγ agonists could exert protective effects by inhibiting inflammatory signaling pathways and attenuating the development of pulmonary inflammatory diseases. However, the mechanisms underlying TZD-induced HO-1 expression are not well understood. This review aimed to elucidate the molecular mechanisms through which PPARγ agonists induce the expression of HO-1 and explore how they protect against inflammatory and oxidative responses.

Peptide-Based Biomaterials for Bone and Cartilage Regeneration

The healing of osteochondral defects (OCDs) that result from injury, osteochondritis, or osteoarthritis and bear lesions in the cartilage and bone, pain, and loss of joint function in middle- and old-age individuals presents challenges to clinical practitioners because of non-regenerative cartilage and the limitations of current therapies. Bioactive peptide-based osteochondral (OC) tissue regeneration is becoming more popular because it does not have the immunogenicity, misfolding, or denaturation problems associated with original proteins. Periodically, reviews are published on the regeneration of bone and cartilage separately; however, none of them addressed the simultaneous healing of these tissues in the complicated heterogeneous environment of the osteochondral (OC) interface. As regulators of cell adhesion, proliferation, differentiation, angiogenesis, immunomodulation, and antibacterial activity, potential therapeutic strategies for OCDs utilizing bone and cartilage-specific peptides should be examined and investigated. The main goal of this review was to study how they contribute to the healing of OCDs, either alone or in conjunction with other peptides and biomaterials.

Specific Cationic Antimicrobial Peptides Enhance the Recovery of Low-Load Quiescent Mycobacterium tuberculosis in Routine Diagnostics

The culture confirmation of Mycobacterium tuberculosis (MTB) remains the gold standard for the diagnosis of Tuberculosis (TB) with culture conversion representing proof of cure. However, over 40% of TB samples fail to isolate MTB even though many patients remain infectious due to the presence of viable non-culturable forms. Previously, we have shown that two short cationic peptides, T14D and TB08L, induce a hormetic response at low concentrations, leading to a stimulation of growth in MTB and the related animal pathogen Mycobacterium bovis (bTB). Here, we examine these peptides showing they can influence the mycobacterial membrane integrity and function through membrane potential reduction. We also show this disruption is associated with an abnormal reduction in transcriptomic signalling from specific mycobacterial membrane sensors that normally monitor the immediate cellular environment and maintain the non-growing phenotype. We observe that exposing MTB or bTB to these peptides at optimal concentrations rapidly represses signalling mechanisms maintaining dormancy phenotypes, which leads to the promotion of aerobic metabolism and conversion into a replicative phenotype. We further show a practical application of these peptides as reagents able to enhance conventional routine culture methods by stimulating mycobacterial growth. We evaluated the ability of a peptide-supplemented sample preparation and culture protocol to isolate the MTB against a gold standard routine method tested in parallel on 255 samples from 155 patients with suspected TB. The peptide enhancement increased the sample positivity rate by 46% and decreased the average time to sample positivity of respiratory/faecal sampling by seven days. The most significant improvements in isolation rates were from sputum smear-negative low-load samples and faeces. The peptide enhancement increased sampling test sensitivity by 19%, recovery in samples from patients with a previously culture-confirmed TB by 20%, and those empirically treated for TB by 21%. We conclude that sample decontamination and culture enhancement with D-enantiomer peptides offer good potential for the much-needed improvement of the culture confirmation of TB.

The Combination of Antibiotic and Non-Antibiotic Compounds Improves Antibiotic Efficacy against Multidrug-Resistant Bacteria

Bacterial antibiotic resistance, especially the emergence of multidrug-resistant (MDR) strains, urgently requires the development of effective treatment strategies. It is always of interest to delve into the mechanisms of resistance to current antibiotics and target them to promote the efficacy of existing antibiotics. In recent years, non-antibiotic compounds have played an important auxiliary role in improving the efficacy of antibiotics and promoting the treatment of drug-resistant bacteria. The combination of non-antibiotic compounds with antibiotics is considered a promising strategy against MDR bacteria. In this review, we first briefly summarize the main resistance mechanisms of current antibiotics. In addition, we propose several strategies to enhance antibiotic action based on resistance mechanisms. Then, the research progress of non-antibiotic compounds that can promote antibiotic-resistant bacteria through different mechanisms in recent years is also summarized. Finally, the development prospects and challenges of these non-antibiotic compounds in combination with antibiotics are discussed.

Biological Function of Antimicrobial Peptides on Suppressing Pathogens and Improving Host Immunity

The emergence of drug-resistant genes and concerns about food safety caused by the overuse of antibiotics are becoming increasingly prominent. There is an urgent need for effective alternatives to antibiotics in the fields of livestock production and human medicine. Antimicrobial peptides can effectively replace antibiotics to kill pathogens and enhance the immune functions of the host, and pathogens cannot easily produce genes that are resistant to them. The ability of antimicrobial peptides (AMPs) to kill pathogens is associated with their structure and physicochemical properties, such as their conformation, electrical charges, hydrophilicity, and hydrophobicity. AMPs regulate the activity of immunological cells and stimulate the secretion of inflammatory cytokines via the activation of the NF-κB and MAPK signaling pathways. However, there are still some limitations to the application of AMPs in the fields of livestock production and human medicine, including a restricted source base, high costs of purification and expression, and the instability of the intestines of animals and humans. This review summarizes the information on AMPs as effective antibiotic substitutes to improve the immunological functions of the host through suppressing pathogens and regulating inflammatory responses. Potential challenges for the commercial application of AMPs in animal husbandry and human medicine are discussed.

Myopia Control Efficacy and Long-Term Safety of a Novel Orthokeratology Lens (MESOK Study)-A Randomized Controlled Clinical Trial Combining Clinical and Tear Proteomics Data

Myopia control efficacy and long-term safety of the Breath-O-Correct orthokeratology (OK) lens was evaluated in a 2-year randomized, single vision (SV) spectacle lens-controlled, single-blind clinical trial combining clinical and tear proteomics data. A total of 71 children (43 OK, 9.8 ± 1.3 years; 28 SV, 9.5 ± 1.4 years) completed the 2-year study. Axial length (AL), cycloplegic refraction, clinical safety parameters (best-corrected visual acuity, central cornea thickness, corneal endothelial health, ocular surface disease index), and quantitative tear proteomics were evaluated by masked examiners. Mean 2-year-normalized AL elongations in the OK and SV groups differed significantly (p = 0.03) and were 0.37 ± 0.37 mm and 0.60 ± 0.41 mm, respectively. OK-mediated myopia control efficacy was 37.1%. No significant difference was found in clinical safety parameters of both groups (p > 0.10), except for a thinner central corneal thickness in the OK group (p = 0.01). Proteomics revealed modest OK lens-mediated effects on immune response proteins, including an increased abundance of haptoglobin at 6 and 12 months and a decreased abundance of two proteins (neutrophil defensin 3 and histone 4) at 6 months. The changes were further validated using a high-resolution multiple-reaction monitoring (MRM^HR) mass spectrometry. In summary, the Breath-O-Correct OK lens significantly reduced AL elongation in schoolchildren without adverse clinical effects or subclinical inflammatory responses.

Pulmonary artery smooth muscle cell phenotypic switching: A key event in the early stage of pulmonary artery hypertension

Pulmonary arterial hypertension (PAH) is a currently incurable pulmonary vascular disease. Since current research on PAH is mainly aimed at the middle and late stages of disease progression, no satisfactory results have been achieved. This has led researchers to focus on the early stages of PAH. This review highlights for the first time a key event in the early stages of PAH progression, namely, the occurrence of pulmonary arterial smooth muscle cell (PASMC) phenotypic switching. Summarizing the related reports of performance conversion provides new perspectives and directions for the early pathological progression and treatment strategies for PAH.

Antimicrobial Proteins: Structure, Molecular Action, and Therapeutic Potential

Second- and third-line treatments of patients with antibiotic-resistant infections can have serious side effects, such as organ failure with prolonged care and recovery. As clinical practices such as cancer therapies, chronic disease treatment, and organ transplantation rely on the ability of available antibiotics to fight infection, the increased resistance of microbial pathogens presents a multifaceted, serious public health concern worldwide. The pipeline of traditional antibiotics is exhausted and unable to overcome the continuously developing multi-drug resistance. To that end, the widely observed limitation of clinically utilized antibiotics has prompted researchers to find a clinically relevant alternate antimicrobial strategy. In recent decades, the discovery of antimicrobial peptides (AMPs) as an excellent candidate to overcome antibiotic resistance has received further attention, particularly from scientists, health professionals, and the pharmaceutical industry. Effective AMPs are characterized by a broad spectrum of antimicrobial activities, high pathogen specificity, and low toxicity. In addition to their antimicrobial activity, AMPs have been found to be involved in a variety of biological functions, including immune regulation, angiogenesis, wound healing, and antitumor activity. This review provides a current overview of the structure, molecular action, and therapeutic potential of AMPs.

α‑lipoic acid inhibits cerulein/resistin‑induced expression of interleukin‑6 by activating peroxisome proliferator‑activated receptor‑γ in pancreatic acinar cells

Cerulein‑induced pancreatitis resembles human acute pancreatitis in terms of pathological events, such as enzymatic activation and inflammatory cell infiltration in the pancreas. Cerulein is a cholecystokinin analog that increases levels of reactive oxygen species (ROS) and interleukin‑6 (IL‑6) expression level in pancreatic acinar cells. Serum levels of resistin, which is secreted from adipocytes, are reportedly higher in patients with acute pancreatitis than in healthy individuals. Previously, it was shown that the adipokine resistin can aggravate the cerulein‑induced increase in ROS levels and IL‑6 expression level in pancreatic acinar cells. Peroxisome proliferator‑activated receptor‑gamma (PPAR‑γ) is a key regulator of the transcription and expression of antioxidant enzymes, including heme oxygenase 1 (HO‑1) and catalase. α‑lipoic acid, a naturally occurring dithiol antioxidant, can prevent cerulein‑induced pancreatic damage in rats. In the present study, it was aimed to investigate whether α‑lipoic acid can attenuate the cerulein/resistin‑induced increase in IL‑6 expression and ROS levels via PPAR‑γ activation in pancreatic acinar AR42J cells. The anti‑inflammatory mechanism of α‑lipoic acid was determined using reverse transcription‑quantitative PCR, western blot analysis, enzyme‑linked immunosorbent assay, immunofluorescence staining and fluorometry. Treatment with cerulein and resistin increased ROS levels and IL‑6 expression level, which were inhibited by α‑lipoic acid in pancreatic acinar cells. α‑lipoic acid increased the nuclear translocation and expression level of PPAR‑γ and the expression levels of its target genes: HO‑1 and catalase. The PPAR‑γ antagonist GW9662 and HO‑1 inhibitor zinc protoporphyrin reversed the inhibitory effect of α‑lipoic acid on cerulein/resistin‑induced increase in ROS and IL‑6 levels. In conclusion, α‑lipoic acid inhibits the cerulein/resistin‑induced increase in ROS production and IL‑6 expression levels by activating PPAR‑γ and inducing the expression of HO‑1 and catalase in pancreatic acinar cells.

Heme Oxygenase-1 Inhibits the Proliferation of Hepatic Stellate Cells by Activating PPARγ and Suppressing NF-κB

Background

Hepatic stellate cells (HSCs) are reported to play significant roles in the development of liver fibrosis. Heme oxygenase-1 (HO-1) is a key rate-limiting enzyme, which could decrease collagen synthesis and liver damage. Nevertheless, it was yet elusive towards the function and mechanism of HO-1.

Methods

An HO-1 inducer Hemin or an HO-1 inhibitor ZnPP-IX was used to treat the activated HSC-T6, respectively. MTT assay was adopted to detect cell proliferation. Immunocytochemical staining was employed to test the levels of alpha-smooth muscle actin (α-SMA), peroxisome proliferator-activated receptor-γ (PPARγ), and nuclear factor-kappa B (NF-kappa B) levels in HSC-T6. HO-1, PPARγ, and NF-κB expression levels were measured by qRT-PCR and Western blotting. ELISA was then used to detect the levels of transforming growth factor- (TGF-) beta 1 (TGF-β1), interleukin-6 (IL-6), serum hyaluronic acid (HA), and serum type III procollagen aminopeptide (PIIIP).

Results

HSC-T6 proliferation was inhibited in Hemin-treated HSCs. The levels of α-SMA, HA, and PIIIP and the production of ECM were lower in Hemin-treated HSCs, whereas those could be rescued by ZnPP-IX. NF-κB activation was decreased, but PPARγ expression was increased after HO-1 upregulation. Furthermore, the levels of TGF-β1 and IL-6, which were downstream of activated NF-κB in HSC-T6, were reduced. The PPAR-specific inhibitor GW9662 could block those mentioned effects.

Conclusions

Our data demonstrated that HO-1 induction could inhibit HSC proliferation and activation by regulating PPARγ expression and NF-κB activation directly or indirectly, which makes it a promising therapeutic target for liver fibrosis.

Peroxisome Proliferator-Activated Receptors (PPARs) and Oxidative Stress in Physiological Conditions and in Cancer

Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear hormone receptor superfamily. Originally described as “orphan nuclear receptors”, they can bind both natural and synthetic ligands acting as agonists or antagonists. In humans three subtypes, PPARα, β/δ, γ, are encoded by different genes, show tissue-specific expression patterns, and contribute to the regulation of lipid and carbohydrate metabolisms, of different cell functions, including proliferation, death, differentiation, and of processes, as inflammation, angiogenesis, immune response. The PPAR ability in increasing the expression of various antioxidant genes and decreasing the synthesis of pro-inflammatory mediators, makes them be considered among the most important regulators of the cellular response to oxidative stress conditions. Based on the multiplicity of physiological effects, PPAR involvement in cancer development and progression has attracted great scientific interest with the aim to describe changes occurring in their expression in cancer cells, and to investigate the correlation with some characteristics of cancer phenotype, including increased proliferation, decreased susceptibility to apoptosis, malignancy degree and onset of resistance to anticancer drugs. This review focuses on mechanisms underlying the antioxidant and anti-inflammatory properties of PPARs in physiological conditions, and on the reported beneficial effects of PPAR activation in cancer.

Peroxisome Proliferator-Activated Receptor-Gamma (PPAR-ɣ): Molecular Effects and Its Importance as a Novel Therapeutic Target for Cerebral Ischemic Injury

Cerebral ischemic injury is a leading cause of death and long-term disability throughout the world. Peroxisome proliferator-activated receptor gamma (PPAR-ɣ) is a ligand-activated nuclear transcription factor that is a member of the PPAR family. PPAR-ɣ has been shown in several in vitro and in vivo models to prevent post-ischemic inflammation and neuronal damage by negatively controlling the expression of genes modulated by cerebral ischemic injury, indicating a neuroprotective effect during cerebral ischemic injury. A extensive literature review of PubMed, Medline, Bentham, Scopus, and EMBASE (Elsevier) databases was carried out to understand the nature of the extensive work done on the mechanistic role of Peroxisome proliferator activated receptor gamma and its modulation in Cerebral ischemic injury. PPAR-ɣ can interact with specific DNA response elements to control gene transcription and expression when triggered by its ligand. It regulates lipid metabolism, improves insulin sensitivity, modulates antitumor mechanisms, reduces oxidative stress, and inhibits inflammation. This review article provides insights on the current state of research into the neuroprotective effects of PPAR-ɣ in cerebral ischemic injury, as well as the cellular and molecular mechanisms by which these effects are modulated, such as inhibition of inflammation, reduction of oxidative stress, suppression of pro-apoptotic production, modulation of transcription factors, and restoration of injured tissue through neurogenesis and angiogenesis.

RNA-Seq Expression Analysis of Chronic Asthmatic Mice with Bu-Shen-Yi-Qi Formula Treatment and Prediction of Regulated Gene Targets of Anti-Airway Remodeling

Airway remodeling is one of the typical pathological characteristics of asthma, while the structural changes of the airways in asthma are complex, which impedes the development of novel asthma targeted therapy. Our previous study had shown that Bu-Shen-Yi-Qi formula (BSYQF) could ameliorate airway remodeling in chronic asthmatic mice by modulating airway inflammation and oxidative stress in the lung. In this study, we analysed the lung transcriptome of control mice and asthmatic mouse model with/without BSYQF treatment. Using RNA-sequencing (RNA-seq) analysis, we found that 264/1746 (15.1%) of transcripts showing abnormal expression in asthmatic mice were reverted back to completely or partially normal levels by BSYQF treatment. Additionally, based on previous results, we identified 21 differential expression genes (DEGs) with fold changes (FC) > (±) 2.0 related to inflammatory, oxidative stress, mitochondria, PI3K/AKT, and MAPK signal pathways which may play important roles in the mechanism of the anti-remodeling effect of BSYQF treatment. Through inputting 21 DEGs into the IPA database to construct a gene network, we inferred Adipoq, SPP1, and TNC which were located at critical nodes in the network may be key regulators of BSYQF's anti-remodeling effect. In addition, the quantitative real-time polymerase chain reaction (qRT-PCR) result for the selected four DEGs matched those of the RNA-seq analysis. Our results provide a preliminary clue to the molecular mechanism of the anti-remodeling effect of BSYQF in asthma.

Redox Biology of Peroxisome Proliferator-Activated Receptor-γ in Pulmonary Hypertension

Significance: Peroxisome proliferator-activated receptor-gamma (PPARγ) maintains pulmonary vascular health through coordination of antioxidant defense systems, inflammation, and cellular metabolism. Insufficient PPARγ contributes to pulmonary hypertension (PH) pathogenesis, whereas therapeutic restoration of PPARγ activity attenuates PH in preclinical models. Recent Advances: Numerous studies in the past decade have elucidated the complex mechanisms by which PPARγ in the pulmonary vasculature and right ventricle (RV) protects against PH. The scope of PPARγ-interconnected pathways continues to expand and includes induction of antioxidant genes, transrepression of inflammatory signaling, regulation of mitochondrial biogenesis and bioenergetic integrity, control of cell cycle and proliferation, and regulation of vascular tone through interactions with nitric oxide and endogenous vasoactive molecules. Furthermore, PPARγ interacts with an extensive regulatory network of transcription factors and microRNAs leading to broad impact on cell signaling. Critical Issues: Abundant evidence suggests that targeting PPARγ exerts diverse salutary effects in PH and represents a novel and potentially translatable therapeutic strategy. However, progress has been slowed by an incomplete understanding of how specific PPARγ pathways are critically disrupted across PH disease subtypes and lack of optimal pharmacological ligands. Future Directions: Recent studies indicate that ligand-induced post-translational modifications of the PPARγ receptor differentially induce therapeutic benefits versus adverse side effects of PPARγ receptor activation. Strategies to selectively target PPARγ activity in diseased cells of pulmonary circulation and RV, coupled with development of ligands designed to specifically regulate post-translational PPARγ modifications, may unlock the full therapeutic potential of this versatile master transcriptional and metabolic regulator in PH.

S1P induces pulmonary artery smooth muscle cell proliferation by activating calcineurin/NFAT/OPN signaling pathway

The upregulation of osteopontin(OPN) has been found to contribute to the proliferation of pulmonary artery smooth muscle cells(PASMCs), and activation of PPARγ has been shown to suppress OPN expression in THP-1 cells. However, the molecular mechanisms underlying the upregulation of OPN expression and PPARγ agonist modulation of OPN expression in PASMCs remain largely unclear. Here we found that S1P stimulated PASMCs proliferation and up-regulated OPN expression in rat PASMCs, which was accompanied with the activation of phospholipase C(PLC), calcineurin and translocation of NFATc3 to nucleus. Further study showed that inhibition of PLC by U73122, suppression of calcineurin activity by cyclosporine A(CsA) or knockdown of NFATc3 using small interfering RNA suppressed S1P-induced OPN up-regulation. Activation of PPARγ by pioglitazone suppressed S1P-induced activation of calcineurin/NFATc3 signaling pathway and followed OPN up-regulation. Taken together, our study indicates that S1P stimulates OPN expression by activation of PLC/calcineurin/NFATc3 signaling pathway, and activation of PPARγ suppresses calcineurin/NFATc3-mediated OPN expression in PASMCs.

Role of Gender in Regulation of Redox Homeostasis in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is one of the diseases with a well-established gender dimorphism. The prevalence of PAH is increased in females with a ratio of 4:1, while poor survival prognosis is associated with the male gender. Nevertheless, the specific contribution of gender in disease development and progression is unclear due to the complex nature of the PAH. Oxidative and nitrosative stresses are important contributors in PAH pathogenesis; however, the role of gender in redox homeostasis has been understudied. This review is aimed to overview the possible sex-specific mechanisms responsible for the regulation of the balance between oxidants and antioxidants in relation to PAH pathobiology.

Agonist of PPAR-γ Reduced Epithelial-Mesenchymal Transition in Eosinophilic Chronic Rhinosinusitis with Nasal Polyps via Inhibition of High Mobility Group Box1

Epithelial-mesenchymal transition (EMT) has been reported to occur in eosinophilic chronic rhinosinusitis with nasal polyps (ECRSwNP). Among the cytokines that cause EMT, high mobility group box 1 (HMGB1) has been shown to give rise to EMT in airway epithelial cells. However, the mechanism of HMGB1-induced EMT in ECRSwNP is unknown. We explored the mechanism and possible inhibitor. Immunohistochemistry (IHC), immunofluorescence (IF), and western blot assay were used to detect the expression and location of HMGB1, peroxisome proliferator-activated receptor-γ (PPAR-γ), and EMT markers in eighteen ECRSwNP and twelve normal nasal mucosa tissues. Epithelial cells isolated from ECRSwNP were cultured with various doses of recombinant human HMGB1 (rhHMGB1) to study the expression of PPAR-γ, and EMT markers. Additionally, the ligand of PPAR-γ was incubated with epithelial cells to interfere with the effects of lipopolysaccharide (LPS) or rhHMGB1 to explore the effect on expression of HMGB1 and EMT markers. These results suggest that HMGB1 was highly expressed in ECRSwNP compared with its expression in control tissues, and EMT was also found highly in ECRSwNP compared with control tissues. Moreover, the cytoplasmic accumulation of HMGB1 in ECRSwNP was obvious compared with normal tissues. We also found dose-dependent induction by rhHMGB1 of up-regulation of N-cadherin and vimentin and down-regulation of ZO-1 and E-cadherin in epithelial cells isolated from ECRSwNP. The agonist of PPAR-γ not only reduced release of HMGB1 induced by LPS, but also reversed the EMT. The protective role of PPAR-γ also appeared in cells that had been incubated with rhHMGB1. In the current study, we discovered that the agonist of PPAR-γ has a potential role in inhibited HMGB1-induced EMT in ECRSwNP. The agonist of PPAR-γ may contribute to inhabit epithelial cells to become mesenchymal-like cells which play an important role in the pathogenesis of ECRSwNP.

Haem oxygenase-1 up-regulation by rosiglitazone via ROS-dependent Nrf2-antioxidant response elements axis or PPARγ attenuates LPS-mediated lung inflammation

BACKGROUND AND PURPOSE

Haem oxygenase-1 (HO-1) is induced by thiazolidinediones including rosiglitazone and exerts anti-inflammatory effects in various models. However, the molecular mechanisms underlying rosiglitazone-induced HO-1 expression remain largely unknown in human pulmonary alveolar epithelial cells (HPAEpiCs).

EXPERIMENTAL APPROACH

HO-1 expression was determined by real time-PCR, Western blotting and promoter reporter analyses. Signalling pathways were investigated using pharmacological inhibitors or specific siRNAs. Interactions between nuclear factor erythroid-2-related factor (Nrf2) and antioxidant response elements (ARE) binding site of the HO-1 promoter were investigated with chromatin immunoprecipitation assays.

KEY RESULTS

Up-regulation of HO-1 in HPAEpiCs or in mice by rosiglitazone blunted ICAM-1 expression and monocyte adhesion to HPAEpiCs challenged with LPS. Rosiglitazone-induced HO-1 expression was significantly attenuated by NADPH oxidase (NOX) inhibitors (apocynin and diphenyleneiodonium) or ROS scavenger (N-acetyl cysteine). The involvement of NOX activity and ROS generation in rosiglitazone-induced HO-1 expression was confirmed by transfection with p47phox or NOX2 siRNA. Moreover, pretreatment with the inhibitors of c-Src (c-Srci II), proline-rich tyrosine kinase 2 (Pyk2) (PF431396), Akt (Akti VIII) or PPARγ (GW9662) and transfection with siRNA of c-Src, Pyk2, Akt or PPARγ abolished the rosiglitazone-induced HO-1 expression in HPAEpiCs. Subsequently, Nrf2 was activated by phosphorylation of c-Src, Pyk2 and Akt, which turned on transcription of HO-1 gene by binding to AREs binding site and enhancing ARE promoter activity.

CONCLUSIONS AND IMPLICATIONS

Rosiglitazone induces HO-1 expression via either NOX/ROS/c-Src/Pyk2/Akt-dependent Nrf2 activation or PPARγ in HPAEpiCs and suppresses LPS-mediated inflammatory responses, suggesting that PPARγ agonists may be useful for protection against pulmonary inflammation.

Curcumin Attenuates Pulmonary Inflammation in Lipopolysaccharide Induced Acute Lung Injury in Neonatal Rat Model by Activating Peroxisome Proliferator-Activated Receptor γ (PPARγ) Pathway

Background

This study aimed to investigate the therapeutic effect of curcumin in lipopolysaccharide (LPS) induced neonatal acute lung injury (ALI) and the possibly associated molecular mechanisms.

Material/Methods

ALI neonatal animal model was established by using LPS. Curcumin and/or peroxisome proliferator-activated receptor γ (PPARγ) inhibitor BADGE (bisphenol A diglycidyl ether) were administrated to animals. Lung edema was evaluated by PaO₂ and lung wet/dry weight ratio (W/D) measurements. EMSA was used to determine the PPARγ activity. Levels of high-mobility group box 1 (HMGB1), secretory receptor for advanced glycation end products (RAGE), tumor necrosis factor α (TNFα), interleukin 6 (IL6), and transforming growth factor β1 (TGFβ1) in bronchoalveolar lavage fluid (BALF) were examined by ELISA. Western blotting was used to evaluate the expression levels of HMGB1, RAGE, heme oxygenase 1 (HO1), TNFα, IL6, and TGFβ1 in lung tissue.

Results

Curcumin administration significantly improved lung function by increasing PaO₂ and decreasing W/D in neonatal ALI rats. Curcumin treatment upregulated the PPARγ activity and expression level of HO1 which were suppressed in lung tissue of neonatal ALI rats. Elevated levels of HMGB1, RAGE, TNFα, IL6, and TGFβ1 in both lung tissue and BALF from neonatal ALI rats were decreased dramatically by curcumin treatment. PPARγ inhibitor BADGE administration impaired curcumin’s alleviation on lung edema, inhibitory effects on inflammatory cytokine expression and recovery of PPARγ/HO1 signaling activation.

Conclusions

Curcumin alleviated lung edema in LPS-induced ALI by inhibiting inflammation which was induced by PPARγ/HO1 regulated-HMGB1/RAGE pro-inflammatory pathway.

Novel candidate genes important for asthma and hypertension comorbidity revealed from associative gene networks

BACKGROUND

Hypertension and bronchial asthma are a major issue for people's health. As of 2014, approximately one billion adults, or ~ 22% of the world population, have had hypertension. As of 2011, 235-330 million people globally have been affected by asthma and approximately 250,000-345,000 people have died each year from the disease. The development of the effective treatment therapies against these diseases is complicated by their comorbidity features. This is often a major problem in diagnosis and their treatment. Hence, in this study the bioinformatical methodology for the analysis of the comorbidity of these two diseases have been developed. As such, the search for candidate genes related to the comorbid conditions of asthma and hypertension can help in elucidating the molecular mechanisms underlying the comorbid condition of these two diseases, and can also be useful for genotyping and identifying new drug targets.

RESULTS

Using ANDSystem, the reconstruction and analysis of gene networks associated with asthma and hypertension was carried out. The gene network of asthma included 755 genes/proteins and 62,603 interactions, while the gene network of hypertension - 713 genes/proteins and 45,479 interactions. Two hundred and five genes/proteins and 9638 interactions were shared between asthma and hypertension. An approach for ranking genes implicated in the comorbid condition of two diseases was proposed. The approach is based on nine criteria for ranking genes by their importance, including standard methods of gene prioritization (Endeavor, ToppGene) as well as original criteria that take into account the characteristics of an associative gene network and the presence of known polymorphisms in the analysed genes. According to the proposed approach, the genes IL10, TLR4, and CAT had the highest priority in the development of comorbidity of these two diseases. Additionally, it was revealed that the list of top genes is enriched with apoptotic genes and genes involved in biological processes related to the functioning of central nervous system.

CONCLUSIONS

The application of methods of reconstruction and analysis of gene networks is a productive tool for studying the molecular mechanisms of comorbid conditions. The method put forth to rank genes by their importance to the comorbid condition of asthma and hypertension was employed that resulted in prediction of 10 genes, playing the key role in the development of the comorbid condition. The results can be utilised to plan experiments for identification of novel candidate genes along with searching for novel pharmacological targets.

Egr-1 mediates leptin-induced PPARγ reduction and proliferation of pulmonary artery smooth muscle cells

Loss of peroxisome proliferator-activated receptor γ (PPARγ) has been found to contribute to pulmonary artery smooth muscle cell (PASMC) proliferation and pulmonary arterial remodeling therefore the development of pulmonary hypertension (PH). Yet, the molecular mechanisms underlying PPARγ reduction in PASMC remain poorly understood. Here, we demonstrated that leptin dose- and time-dependently inducued PPARγ down-regulation and proliferation of primary cultured rat PASMC, this was accompanied with the activation of extracellular regulated kinase1/2 (ERK1/2) signaling pathway and subsequent induction of early growth response-1 (Egr-1) expression. The presence of MEK inhibitors U0126 or PD98059, or prior silencing Egr-1 with small interfering RNA suppressed leptin-induced PPARγ reduction. In addition, activation of PPARγ by pioglitazone or targeting ERK1/2/Egr-1 suppressed leptin-induced PASMC proliferation. Taken together, our study indicates that ERK1/2 signaling pathway-mediated leptin-induced PPARγ reduction and PASMC proliferation through up-regulation of Egr-1 and suggests that targeting leptin/ERK1/2/Egr-1 pathway might have potential value in ameliorating vascular remodeling and benefit PH.

Effects of FHL1 and P21 on hypoxia-induced pulmonary vascular remodeling in neonatal rats

Numerous studies have demonstrated that altered expression levels of four and a half LIM domains 1 (FHL1) and P21 are necessary for hypoxia-induced pulmonary vascular remodeling in both adult rats and human patients with idiopathic pulmonary arterial hypertension. However, whether FHL1 and P21 are present in the pulmonary artery and whether these proteins affect pulmonary vascular remodeling in hypoxia-induced pulmonary hypertension (HPH) in neonatal rats remain unknown. The present study investigated the effects of altered FHL1 and P21 expression on pulmonary vascular remodeling in neonatal rats with HPH. A total of 32 newborn Sprague-Dawley rats were exposed to hypoxia or room air for 7 or 14 days (n=8/subgroup). Parameters including the percentage of medial wall thickness (WT%), the percentage of medial wall area (WA%), right ventricular (RV) mean pressure, RV hypertrophy index (RVHI) and RV systolic pressure (RVSP) were measured to evaluate the development of HPH. Additionally, the expressions of FHL1 and P21 in the pulmonary artery smooth muscle cells (PASMCs) were measured by reverse transcription-quantitative polymerase chain reaction, western blot analysis and immunohistochemical staining. WA%, WT%, RV mean pressure, RVHI and RVSP were significantly increased in the HPH model group when compared with the control group (P<0.01). The protein expression levels of FHL1 were significantly increased in the HPH group (P<0.05), while the mRNA and protein expression levels of P21 were significantly reduced (P<0.05). Pearson correlation analysis indicated that the protein expressions of FHL1 and P21 were correlated with WA% and WT% (all P<0.001), and that the protein expression of P21 was negatively correlated with that of FHL1 (P<0.01). The results indicated that the expressions of FHL1 and P21 were altered in the PASMCs of newborn rats with HPH. Furthermore, FHL1 and P21 may serve important roles in pulmonary vascular remodeling.

5-HT induces PPAR γ reduction and proliferation of pulmonary artery smooth muscle cells via modulating GSK-3β/β-catenin pathway

Studies have shown that peroxisome proliferator-activated receptor γ (PPAR γ) is down-regulated in pulmonary vascular lesions of patients with pulmonary hypertension (PH) and animal models of PH. Yet, the detailed molecular mechanisms underlying this alteration are not fully defined; the aim of this study is to address this issue. 5-HT dose- and time-dependently reduced PPAR γ expression and promoted pulmonary artery smooth muscle cells (PASMCs) proliferation; this was accompanied with the phosphorylation of Akt, inactivation of GSK-3β and up-regulation of β-catenin. Importantly, pre-treatment of cells with PI3K inhibitor (Ly294002) or prior silencing of β-catenin with siRNA blocked 5-HT-induced PPAR γ reduction and PASMCs proliferation. In addition, inactivation or lack of GSK-3β or inhibition of proteasome function up-regulated β-catenin protein without affecting its mRNA level and reduced PPAR γ protein expression. Taken together, our study indicates that 5-HT suppresses PPAR γ expression and stimulates PASMCs proliferation by modulating GSK-3β/β-catenin axis, and suggests that targeting this pathway might have potential value in the management of PH.

MicroRNA-27a/b mediates endothelin-1-induced PPARγ reduction and proliferation of pulmonary artery smooth muscle cells

The down-regulation of peroxisome proliferator-activated receptor γ (PPARγ) expression has been found to correlate with the proliferation of pulmonary artery smooth muscle cells (PASMC), pulmonary vascular remodeling and pulmonary hypertension, while the molecular mechanisms underlying PPARγ reduction in PASMC remain largely unclear. The aim of the current study is to address this issue. Endothelin-1 (ET-1) dose- and time-dependently resulted in PPARγ reduction and proliferation of primary cultured rat PASMC, which was accompanied by the activation of nuclear factor-kappaB (NF-κB) and subsequent induction of microRNA-27a/b (miR-27a/b) expression. Chromatin immunoprecipitation assay revealed that NF-κB directly bound to the promoter regions of miR-27a/b. Luciferase reporter assay identified that miR-27a/b directly regulates the expression of PPARγ in PASMC. Further study indicated that the presence of either NF-κB inhibitor pyrrolidinedithiocarbamate or prior silencing miR-27a/b with anti-miRNA oligonucleotides suppressed ET-1-induced PPARγ reduction and proliferation of PASMC, while overexpression of miR-27a/b reduced PPARγ expression and enhanced PASMC proliferation. Taken together, our study demonstrates that ET-1 stimulates miR-27a/b expression by activation of the NF-κB pathway, which in turn results in PPARγ reduction and contributes to ET-1-induced PASMC proliferation.

Activation of PPARγ by baicalin attenuates pulmonary hypertension in an infant rat model by suppressing HMGB1/RAGE signaling

Pulmonary hypertension (PH) is a vascular disease, and proinflammatory factors are strongly implicated in its pathogenesis, causing right ventricular (RV) hypertrophy and heart failure. Baicalin exhibits potent anti‐inflammation activity. This study aimed to investigate the curative effects of baicalin in an infant rodent model of PH and to further explore the underlying mechanisms. A PH model in infant rats was induced by hypoxia and the resulting rats were administered baicalin in incremental dosages. Invasive hemodynamic methods were used to measure mean pulmonary arterial pressure (mPAP) and RV end‐diastolic pressure (RVEDP). RV hypertrophy was assessed by mass pathology and histology. ELISAs were used to determine concentrations of high‐mobility group box 1 (HMGB1), secretory receptor for advanced glycation end products (sRAGE), interleukin 6 (IL6) and transforming growth factor β (TGFβ1) in bronchoalveolar lavage fluid (BALF). Electrophoretic mobility shift and phosphorylation in nuclear extracts were used to evaluate the activation of peroxisome proliferator‐activated receptor γ (PPARγ). Western blotting was used to detect the expression levels of heme oxygenase 1 (HO1), HMGB1, RAGE, IL6 and TGFβ1 in lung tissue. Baicalin administration significantly attenuated mPAP, RVEDP and RV hypertrophy in infant rats with PH. HMGB1, sRAGE, IL6 and TGFβ1 levels in BALF were also reduced by baicalin treatment. Baicalin activated PPARγ, which promoted expression of HO1. Furthermore, expression levels of HMGB1, RAGE, IL6 and TGFβ1 in lung tissue were dramatically decreased by baicalin in a dosage‐dependent manner. Baicalin showed curative effects in infant rats with PH. Activation of PPARγ that inhibited HMGB1/RAGE inflammatory signaling was involved.

Butein induction of HO-1 by p38 MAPK/Nrf2 pathway in adipocytes attenuates high-fat diet induced adipose hypertrophy in mice

Adipose tissue inflammation and oxidative stress are key components in the development of obesity and insulin resistance. Heme oxygenase (HO)-1 in adipocytes protects against obesity and adipose dysfunction. In this study, we report the identification of butein, a flavonoid chalcone, as a novel inducer of HO-1 expression in adipocytes in vitro and in vivo. Butein upregulated HO-1 mRNA and protein expression in 3T3-L1 adipocytes, accompanied by Kelch-Like ECH-Associated Protein (Keap) 1 degradation and increase in the nuclear level of nuclear factor erythroid 2-related factor 2 (Nrf2). Butein modulation of Keap1 and Nrf2 as well as HO-1 upregulation was reversed by pretreatment with p38 MAPK inhibitor SB203580, indicating the involvement of p38 MAPK in butein activation of Nrf2 in adipocytes. In addition, HO-1 activation by butein led to the inhibitions of reactive oxygen species and adipocyte differentiation, as evidenced by the fact that butein repression of reactive oxygen species and adipogenesis was reversed by pretreatment with HO-1 inhibitor SnPP. Induction of HO-1 expression by butein was also demonstrated in the adipose tissue of C57BL/6 mice fed a high-fat diet administered along with butein for three weeks, and correlated with the inhibitions of adiposity and adipose tissue inflammation, which were reversed by co-administration of SnPP. Altogether, our results demonstrate that butein activates the p38 MAPK/Nrf2/HO-1 pathway to act as a potent inhibitor of adipose hypertrophy and inflammation in a diet-induced obesity model and thus has potential for suppressing obesity-linked metabolic syndrome.

Sodium tanshinone IIA sulfonate inhibits hypoxia-induced enhancement of SOCE in pulmonary arterial smooth muscle cells via the PKG-PPAR-γ signaling axis

Our laboratory previously showed that sodium tanshinone IIA sulfonate (STS) inhibited store-operated Ca(2+) entry (SOCE) through store-operated Ca(2+) channels (SOCC) via downregulating the expression of transient receptor potential canonical proteins (TRPC), which contribute to the formation of SOCC (Wang J, Jiang Q, Wan L, Yang K, Zhang Y, Chen Y, Wang E, Lai N, Zhao L, Jiang H, Sun Y, Zhong N, Ran P, Lu W. Am J Respir Cell Mol Biol 48: 125-134, 2013). The detailed molecular mechanisms by which STS inhibits SOCE and downregulates TRPC, however, remain largely unknown. We have previously shown that, under hypoxic conditions, inhibition of protein kinase G (PKG) and peroxisome proliferator-activated receptor-γ (PPAR-γ) signaling axis results in the upregulation of TRPC (Wang J, Yang K, Xu L, Zhang Y, Lai N, Jiang H, Zhang Y, Zhong N, Ran P, Lu W. Am J Respir Cell Mol Biol 49: 231-240, 2013). This suggests that strategies targeting the restoration of this signaling pathway may be an effective treatment strategy for pulmonary hypertension. In this study, our results demonstrated that STS treatment can effectively prevent the hypoxia-mediated inhibition of the PKG-PPAR-γ signaling axis in rat distal pulmonary arterial smooth muscle cells (PASMCs) and distal pulmonary arteries. These effects of STS treatment were blocked by pharmacological inhibition or specific small interfering RNA knockdown of either PKG or PPAR-γ. Moreover, targeted PPAR-γ agonist markedly enhanced the beneficial effects of STS. These results comprehensively suggest that STS treatment can prevent hypoxia-mediated increases in intracellular calcium homeostasis and cell proliferation, by targeting and restoring the hypoxia-inhibited PKG-PPAR-γ signaling pathway in PASMCs.

Bromodomain-Containing Protein 4

Rationale:

Pulmonary arterial hypertension (PAH) is a vasculopathy characterized by enhanced pulmonary artery (PA) smooth muscle cell (PASMC) proliferation and suppressed apoptosis. Decreased expression of microRNA-204 has been associated to this phenotype. By a still elusive mechanism, microRNA-204 downregulation promotes the expression of oncogenes, including nuclear factor of activated T cells, B-cell lymphoma 2, and Survivin. In cancer, increased expression of the epigenetic reader bromodomain-containing protein 4 (BRD4) sustains cell survival and proliferation. Interestingly, BRD4 is a predicted target of microRNA-204 and has binding sites on the nuclear factor of activated T cells promoter region.

Objective:

To investigate the role of BRD4 in PAH pathogenesis.

Methods and Results:

BRD4 is upregulated in lungs, distal PAs, and PASMCs of patients with PAH compared with controls. With mechanistic in vitro experiments, we demonstrated that BRD4 expression in PAH is microRNA-204 dependent. We further studied the molecular downstream targets of BRD4 by inhibiting its activity in PAH–PASMCs using a clinically available inhibitor JQ1. JQ1 treatment in PAH–PASMCs increased p21 expression, thus triggering cell cycle arrest. Furthermore, BRD4 inhibition, by JQ1 or siBRD4, decreased the expression of 3 major oncogenes, which are overexpressed in PAH: nuclear factor of activated T cells, B-cell lymphoma 2, and Survivin. Blocking this oncogenic signature led to decreased PAH-PASMC proliferation and increased apoptosis in a BRD4-dependent manner. Indeed, pharmacological JQ1 or molecular (siRNA) inhibition of BRD4 reversed this pathological phenotype in addition to restoring mitochondrial membrane potential and to increasing cells spare respiratory capacity. Moreover, BRD4 inhibition in vivo reversed established PAH in the Sugen/hypoxia rat model.

Conclusions:

BRD4 plays a key role in the pathological phenotype in PAH, which could offer new therapeutic perspectives for patients with PAH.

Regulation of Cell Cycle Regulators by SIRT1 Contributes to Resveratrol-Mediated Prevention of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a major cause of morbidity and mortality in rheumatic diseases. Vascular remodeling due to the proliferation of pulmonary arterial smooth muscle cells (PASMCs) is central to the development of PAH. To date, it is still unclear if Silence Information Regulator 1 (SIRT1) regulates cell cycle regulators in the proliferation of PASMCs and contributes to prevention of PAH by resveratrol. In this study, we found that a significant decrease of SIRT1 expression levels in platelet-derived growth factor BB (PDGF-BB) treated human PASMCs (HPASMCs) and in monocrotaline (MCT) induced PAH rat. Overexpression of SIRT1 induced G1 phase arrest and increased p21 expression but decreased cyclin D1 expression in PDGF-BB treated HPASMCs. Moreover, resveratrol attenuated pulmonary arterial remodeling, decreased pulmonary arterial pressure, and upregulated SIRT1 and p21 expression but downregulated cyclin D1 expression in MCT induced PAH rat. Notably, knockdown of SIRT1 eliminated the regulation of resveratrol on p21 and cyclin D1 expression in PDGF-BB treated HPASMCs. These results demonstrated that SIRT1 mediated the regulation of resveratrol on the expression of cell cycle regulatory molecules. It suggests that SIRT1 exerts a protective role in PAH associated with rheumatic diseases and can be a potential treatment target.

The PPARγ agonist, rosiglitazone, attenuates airway inflammation and remodeling via heme oxygenase-1 in murine model of asthma

AIM

Rosiglitazone is one of the specific PPARγ agonists showing potential therapeutic effects in asthma. Though PPARγ activation was considered protective in inhibiting airway inflammation and remodeling in asthma, the specific mechanisms are still unclear. This study was aimed to investigate whether heme oxygenase-1 (HO-1) related pathways were involved in rosiglitazone-activated PPARγ signaling in asthma treatment.

METHODS

Asthma was induced in mice by multiple exposures to ovalbumin (OVA) in 8 weeks. Prior to every OVA challenge, the mice received rosiglitazone (5 mg/kg, p.o.). After the mice were sacrificed, the bronchoalveolar lavage fluid (BALF), blood samples and lungs were collected for analyses. The activities of HO-1, MMP-2 and MMP-9 in airway tissue were assessed, and the expression of PPARγ, HO-1 and p21 proteins was also examined.

RESULTS

Rosiglitazone administration significantly attenuated airway inflammation and remodeling in mice with OVA-induced asthma, which were evidenced by decreased counts of total cells, eosinophils and neutrophils, and decreased levels of IL-5 and IL-13 in BALF, and by decreased airway smooth muscle layer thickness and reduced airway collagen deposition. Furthermore, rosiglitazone administration significantly increased PPARγ, HO-1 and p21 expression and HO-1 activity, decreased MMP-2 and MMP-9 activities in airway tissue. All the therapeutic effects of rosiglitazone were significantly impaired by co-administration of the HO-1 inhibitor ZnPP.

CONCLUSION

Rosiglitazone effectively attenuates airway inflammation and remodeling in OVA-induced asthma of mice by activating PPARγ/HO-1 signaling pathway.

Systems-level regulation of microRNA networks by miR-130/301 promotes pulmonary hypertension

Development of the vascular disease pulmonary hypertension (PH) involves disparate molecular pathways that span multiple cell types. MicroRNAs (miRNAs) may coordinately regulate PH progression, but the integrative functions of miRNAs in this process have been challenging to define with conventional approaches. Here, analysis of the molecular network architecture specific to PH predicted that the miR-130/301 family is a master regulator of cellular proliferation in PH via regulation of subordinate miRNA pathways with unexpected connections to one another. In validation of this model, diseased pulmonary vessels and plasma from mammalian models and human PH subjects exhibited upregulation of miR-130/301 expression. Evaluation of pulmonary arterial endothelial cells and smooth muscle cells revealed that miR-130/301 targeted PPARγ with distinct consequences. In endothelial cells, miR-130/301 modulated apelin-miR-424/503-FGF2 signaling, while in smooth muscle cells, miR-130/301 modulated STAT3-miR-204 signaling to promote PH-associated phenotypes. In murine models, induction of miR-130/301 promoted pathogenic PH-associated effects, while miR-130/301 inhibition prevented PH pathogenesis. Together, these results provide insight into the systems-level regulation of miRNA-disease gene networks in PH with broad implications for miRNA-based therapeutics in this disease. Furthermore, these findings provide critical validation for the evolving application of network theory to the discovery of the miRNA-based origins of PH and other diseases.

PPAR-γ inhibits IL-13-induced collagen production in mouse airway fibroblasts

Interleukin-13 (IL-13) plays an important role in extracellular matrix production of airway remodeling in asthma. Activation of PPAR-γ has been shown to inhibit the occurrence of airway fibrosis in asthma, yet it remains unknown whether the effect of PPAR-γ on suppression of airway fibrosis is associated with the inhibition of IL-13 signaling. In the present study, primary cultured airway fibroblasts were stimulated with IL-13, and JAK inhibitor, PDGF receptor blocker and MEK inhibitor were applied to investigate the involvement of these pathways in IL-13-induced collagen production. Our results demonstrate that IL-13 dose- and time-dependently induced collagen production in primary cultured mouse airway fibroblasts; this effect was blocked by inhibition of JAK/STAT6 signal pathway. IL-13 also stimulated JAK/STAT6-dependent PDGF production, elevation of PDGF in turn activated ERK1/2 MAPK and caused collagen production. Activation of PPAR-γ by rosiglitazone reduced IL-13-induced collagen expression by suppression of STAT6-driven PDGF production. Our results indicate that activation of JAK/STAT6 signal and subsequent PDGF generation and ERK1/2 MAPK activation mediate IL-13-induced collagen production in airway fibroblasts. This study suggests that activation of PPAR-γ might be a novel strategy for the treatment of asthma partially by inhibition of airway fibrosis.

A novel hypothesis: up-regulation of HO-1 by activation of PPARγ inhibits HMGB1-RAGE signaling pathway and ameliorates the development of ALI/ARDS

Suppression of inflammation in acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) by activation of peroxisome proliferator-activated receptor (PPAR)-γ has been well demonstrated in animal model studies. However, the molecular mechanisms underlying this effect remain largely unknown. The induction of heme oxygenase-1 (HO-1) exerts antioxidant, anti-apoptotic, and immunomodulatory functions in various situations. Recent studies have indicated that activation of PPARγ induces expression of HO-1, suggesting that HO-1 is a downstream target of PPARγ. Meanwhile, study has shown that activation of PPARγ ameliorates inflammatory response of cells by inhibiting high mobility group box 1 (HMGB1) release. In pulmonary system, binding of HMGB1 to its receptor for advanced glycation end-products (RAGE) triggers the production of pro-inflammatory cytokines, chemokines, adhesion molecules and reactive oxygen species, promoting the development of ALI/ARDS. Based on the recent findings that induction of HO-1 protects tissues and cells from extracellular stress by reducing HMGB1 production, we propose the hypothesis that HO-1 may mediate the protective effects of PPARγ on inhibition of HMGB1-RAGE signaling pathway to attenuate the development of ALI/ARDS.

Relaxation of human pulmonary arteries by PPARγ agonists

It has been suggested that activation of nuclear peroxisome proliferator-activated receptors γ (PPARγ) may represent a new strategy for the treatment of pulmonary arterial hypertension. It has been demonstrated that PPARγ activation relaxed the isolated mouse pulmonary artery. The aims of the present study were to examine whether and to which extent the two PPARγ agonists rosiglitazone and pioglitazone relax the isolated human pulmonary artery and to investigate the underlying mechanism(s). Isolated human pulmonary arteries were obtained from patients without clinical evidence of pulmonary hypertension during resection of lung carcinoma. Vasodilatory effects of PPARγ agonists were examined on endothelium-intact or endothelium-denuded vessels preconstricted with the thromboxane prostanoid receptor agonist U-46619. Rosiglitazone and pioglitazone (0.01–100 μM) caused a concentration- and/or time-dependent full relaxation of U-46619-preconstricted vessels. The rosiglitazone-induced relaxation was attenuated by the PPARγ antagonist GW9662 1 μM, endothelium denudation, the nitric oxide synthase inhibitor L-NAME 300 μM, the cyclooxygenase inhibitor indomethacin 10 μM, and the K_ATP channel blocker glibenclamide 10 μM. The prostacyclin IP receptor antagonist RO1138452 1 μM shifted the concentration–response curve for rosiglitazone to the right. The PPARγ agonists pioglitazone and rosiglitazone relax human pulmonary arteries. The rosiglitazone-induced vasorelaxation is partially endothelium-dependent and involves PPARγ receptors, arachidonic acid degradation products, nitric oxide, and K_ATP channels. Thus, the relaxant effect of PPARγ agonists in human pulmonary arteries may represent a new therapeutic target in pulmonary arterial hypertension.

Statins inhibit pulmonary artery smooth muscle cell proliferation by upregulation of HO-1 and p21WAF1

Simvastatin is a 3-hydroxy-3-methylglutaryl-CoA reductase inhibitor, which has been shown to ameliorate the development of pulmonary hypertension in animal model by suppression of pulmonary artery smooth muscle cells (PASMCs) proliferation, yet its underlying molecular mechanisms are not completely understood. In this study, we show that simvastatin dose-dependently inhibited serotonin-stimulated PASMCs proliferation. This was accompanied with the parallel induction of heme oxyganase-1 (HO-1) and upregulation of p21(WAF1). More importantly, we found that Tin-protoporphyrin (SnPP), a selective inhibitor of HO-1, could block the effect of simvastatin on inhibition of cell proliferation in response to serotonin and abolish simvastatin-induced p21(WAF1) expression. The inhibitive effect of simvastatin on cell proliferation was also significantly suppressed by silencing p21(WAF1) with siRNA transfection. The extent of effect of SnPP on inhibition of cell proliferation was similar to that of lack of p21(WAF1) by siRNA transfection. Taken together, our study suggests that simvastatin inhibits PASMCs proliferation by sequential upregulation of HO-1 and p21(WAF1) to benefit pulmonary hypertension.

Reactive oxygen and nitrogen species in pulmonary hypertension

Pulmonary vascular disease can be defined as either a disease affecting the pulmonary capillaries and pulmonary arterioles, termed pulmonary arterial hypertension, or a disease affecting the left ventricle, called pulmonary venous hypertension. Pulmonary arterial hypertension (PAH) is a disorder of the pulmonary circulation characterized by endothelial dysfunction, as well as intimal and smooth muscle proliferation. Progressive increases in pulmonary vascular resistance and pressure impair the performance of the right ventricle, resulting in declining cardiac output, reduced exercise capacity, right-heart failure, and ultimately death. While the primary and heritable forms of the disease are thought to affect over 5000 patients in the United States, the disease can occur secondary to congenital heart disease, most advanced lung diseases, and many systemic diseases. Multiple studies implicate oxidative stress in the development of PAH. Further, this oxidative stress has been shown to be associated with alterations in reactive oxygen species (ROS), reactive nitrogen species (RNS), and nitric oxide (NO) signaling pathways, whereby bioavailable NO is decreased and ROS and RNS production are increased. Many canonical ROS and NO signaling pathways are simultaneously disrupted in PAH, with increased expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases and xanthine oxidoreductase, uncoupling of endothelial NO synthase (eNOS), and reduction in mitochondrial number, as well as impaired mitochondrial function. Upstream dysregulation of ROS/NO redox homeostasis impairs vascular tone and contributes to the pathological activation of antiapoptotic and mitogenic pathways, leading to cell proliferation and obliteration of the vasculature. This paper will review the available data regarding the role of oxidative and nitrosative stress and endothelial dysfunction in the pathophysiology of pulmonary hypertension, and provide a description of targeted therapies for this disease.

Heme oxygenase-1 prevents liver fibrosis in rats by regulating the expression of PPARγ and NF-κB

AIM: To investigate the effects of heme oxygenase (HO)-1 on liver fibrosis and the expression of peroxisome proliferator-activated receptor gamma (PPARγ) and nuclear factor-kappa B (NF-κB) in rats.

METHODS: Sixty Wistar rats were used to construct liver fibrosis models and were randomly divided into 5 groups: group A (normal, untreated), group B (model for 4 wk, untreated), group C (model for 6 wk, untreated), group D [model for 6 wk, treated with zinc protoporphyrin IX (ZnPP-IX) from week 4 to week 6], group E (model for 6 wk, treated with hemin from week 4 to week 6). Next, liver injury was assessed by measuring serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and albumin levels. The degree of hepatic fibrosis was evaluated by measuring serum hyaluronate acid (HA), type IV collagen (IV-C) and by histological examination. Hydroxyproline (Hyp) content in the liver homogenate was determined. The expression levels of alpha-smooth muscle actin (α-SMA) in liver tissue were measured by real-time quantitative polymerase chain reaction (RT-PCR). The expression levels of PPARγ and NF-κB were determined by RT-PCR and Western blotting.

RESULTS: The expression of HO-1 increased with the development of fibrosis. Induction of HO-1 by hemin significantly attenuated the severity of liver injury and the levels of liver fibrosis as compared with inhibition of HO-1 by ZnPP-IX. The concentrations of serum ALT, AST, HA and IV-C in group E decreased compared with group C and group D (P < 0.01). Amount of Hyp and α-SMA in the liver tissues in group E decreased compared with group C (0.62 ± 0.14 vs 0.84 ± 0.07, 1.42 ± 0.17 vs 1.84 ± 0.17, respectively, P < 0.01) and group D (0.62 ± 0.14 vs 1.11 ± 0.16, 1.42 ± 0.17 vs 2.56 ± 0.37, respectively, P < 0.01). The expression of PPARγ at levels of transcription and translation decreased with the development of fibrosis especially in group D; and it increased in group E compared with groups C and D (0.88 ± 0.15 vs 0.56 ± 0.19, 0.88 ± 0.15 vs 0.41 ± 0.11, respectively, P < 0.01). The expression of NF-κB increased with the development of fibrosis especially in group D; and it decreased in group E compared with groups C and D (1.43 ± 0.31 vs 1.89 ± 0.29, 1.43 ± 0.31 vs 2.53 ± 0.54, respectively, P < 0.01).

CONCLUSION: Our data demonstrate a potential mechanism that HO-1 can prevent liver fibrosis by enhancing the expression of PPARγ and decreasing the expression of NF-κB in liver tissues.

Inhibition of ubiquitin proteasome function suppresses proliferation of pulmonary artery smooth muscle cells

Inhibition of proteasome function has been shown to suppress several types of cells proliferation; this study investigates whether this also occurs in pulmonary artery smooth muscle cells (PASMCs) and its potential mechanisms. Serotonin induced 4.27-fold increase in DNA synthesis in PASMCs, and this effect was dose-dependently blocked by prior incubation of cells with MG132, a specific proteasome inhibitor. Inhibition of proteasome function did not modulate serotonin-triggered pro-proliferation signaling pathways, such as extracellular signal-regulated mitogen-activated protein kinase (ERK1/2 MAPK) and Ras homolog gene family member A (RhoA). Further study indicated that treatment of PASMCs with serotonin reduced p21(WAF1) protein level but not its transcription; this was reversed by inhibiting ERK1/2 MAPK or RhoA cascade equally. In addition, MG132 increased the protein level of p21(WAF1) in a dose-dependent manner in the presence of serotonin, 10 μM MG132 led to a 4.2-fold increase in p21(WAF1) protein level, and this effect was not mediated by increasing p21(WAF1) mRNA level. More importantly, cell lacking p21(WAF1) by siRNA transfection abolished the inhibitive effect of MG132 on cells proliferation. Our study suggests that accumulation of p21(WAF1) protein level caused by proteasome inhibition particularly mediated its inhibitive effect on PASMCs proliferation, and inhibition of proteasome function might have potential value in the treatment of pulmonary hypertension.

Mechanisms of disease: pulmonary arterial hypertension

Our understanding of, and approach to, pulmonary arterial hypertension has undergone a paradigm shift in the past decade. Once a condition thought to be dominated by increased vasoconstrictor tone and thrombosis, pulmonary arterial hypertension is now seen as a vasculopathy in which structural changes driven by excessive vascular cell growth and inflammation, with recruitment and infiltration of circulating cells, play a major role. Perturbations of a number of molecular mechanisms have been described, including pathways involving growth factors, cytokines, metabolic signaling, elastases, and proteases, that may underlie the pathogenesis of the disease. Elucidating their contribution to the pathophysiology of pulmonary arterial hypertension could offer new drug targets. The role of progenitor cells in vascular repair is also under active investigation. The right ventricular response to increased pressure load is recognized as critical to survival and the molecular mechanisms involved are attracting increasing interest. The challenge now is to integrate this new knowledge and explore how it can be used to categorize patients by molecular phenotype and tailor treatment more effectively.

Adenovirus-mediated peroxisome proliferator activated receptor gamma overexpression prevents nutritional fibrotic steatohepatitis in mice

OBJECTIVE

The pathogenesis of non-alcoholic steatohepatitis is still unclear. We have demonstrated previously that peroxisome proliferator activated receptor gamma (PPARγ) ligand protects against inflammation and fibrogenesis in experimental non-alcoholic steatohepatitis. We aim to elucidate the effect and the mechanism of PPARγ itself on nutritional fibrotic steatohepatitis in mice.

METHODS

C57BL/6J mice were fed with methionine-choline deficient (MCD) diet for 8 weeks to induce fibrotic steatohepatitis. Mice fed the MCD diet were treated with adenovirus carrying PPARγ (Ad-PPARγ), Ad-PPARγ plus PPARγ agonist rosiglitazone, or PPARγ antagonist 2-chloro-5-nitrobenzaniliden (GW9662), respectively. The effects of up-regulation of PPARγ in the presence or absence of its agonist/or antagonist were assessed by comparing the severity of hepatic injury, activation of hepatic stellate cells and the expression of adiponectin, heme oxygenase-1, and fibrogenic related genes.

RESULTS

Mice fed with MCD diet for 8 weeks showed severe hepatic injury including hepatic steatosis, inflammatory infiltration, and fibrosis. Administration of Ad-PPARγ significantly lowered serum alanine aminotransferase level and ameliorated hepatic steatosis, necroinflammation, and fibrosis. These effects were associated with enhanced expression of PPARγ, up-regulated expression of adiponectin and heme oxygenase-1, and down-regulated expression of tumor necrosis factor alpha, interleukin-6, α-smooth muscle actin, transforming growth factor beta 1, matrix metallopeptidase-2, and -9. Administration of GW9662 promoted the severity of liver histology.

CONCLUSIONS

The present study provided evidences for the protective role of overexpressing PPARγ in ameliorating hepatic fibrosing steatohepatitis in mice. Modulation of PPARγ expression might serve as a therapeutic approach for fibrotic steatohepatitis.

Heterogeneous activation of p19Arf in pulmonary artery smooth muscle cells

p19(ARF) is a tumor suppressor that leads to cell cycle arrest or apoptosis by stabilizing p53. p19(ARF) is not critical for cell cycle regulation under normal conditions, but loss of p19(ARF) is seen in many human cancers, and a murine p19(Arf) knockout model leads to malignant proliferation and tumor formation; its role in controlling nonmalignant proliferation is less defined. To examine this question, pulmonary artery smooth muscle cells (PASMC) were expanded in culture from a transgenic mouse in which the coding sequence of the p19(Arf) gene was replaced with a cDNA encoding green fluorescent protein (GFP), leaving the promoter intact. During the first 10 days in culture, wild-type, heterozygous, and knockout PASMC grew similarly, but, by day 14, p19(Arf)-deficient PASMC proliferated faster than p19(Arf) heterozygous or wild-type cells; reexpression of p19(Arf) prevented the increased proliferation. This time course correlated with activation of the p19(Arf) promoter, as indicated by the appearance of GFP positivity in p19(Arf)-deficient PASMC. By day 42, ∼80% of p19(Arf)-deficient cells were GFP-positive. When GFP-positive, p19(Arf)-deficient cells were sorted and subcultured separately, they remained GFP-positive, indicating that once cells had activated the p19(Arf) promoter, the promoter remained active in those and all subsequent daughter cells. In contrast, GFP-negative p19(Arf)-deficient cells gave rise to a combination of GFP-positive and -negative daughter cells over time. These results suggest that a subpopulation of PASMC are resistant to the signals that activate the p19(Arf) promoter, an event that would normally target these cells for arrest or cell death.