Activation and overexpression of Sirt1 attenuates lung fibrosis via P300

The role of Sirtuin 1 in regulation of fibrotic genes expression in pre-adipocytes

Purpose

Considering inhibition of pre-adipocyte cells differentiation in adipose tissue fibrosis, we aimed to explore whether Sirt1 and Hif-1α in pre-adipocytes have a significant effect on fibrotic gene expression.

Methods

3T3-L1 pre-adipocytes were transfected with SIRT1-specific siRNA, confirmed by real-time polymerase chain reaction (RT-PCR) and western blotting. Additionally, cells were treated with varying concentrations of resveratrol and sirtinol as the activator and inhibitor of Sirt1, respectively. Involvement of Hif-1α was evaluated by treatment with echinomycin. Subsequently, we assessed the gene and protein expressions related to fibrosis in the extracellular matrix of adipose tissue, including collagen VI (Col VI), lysyl oxidase (Lox), matrix metalloproteinase-2 (Mmp-2), Mmp-9, and osteopontin (Opn) in pre-adipocytes through RT-PCR and western blot.

Results

The current study demonstrated that Sirt1 knockdown and reduced enzyme activity significantly increased the expression of Col VI, Lox, Mmp-2, Mmp-9, and Opn genes in the treated 3T3-L1 cells compared to the control group. Interestingly, resveratrol significantly decreased the gene expression related to the fibrosis pathway. Inhibition of Hif-1α by echinomycin led to a significant reduction in Col VI, Mmp-2, and Mmp-9 gene expression in the treated group compared to the control.

Conclusion

This study highlights that down-regulation of Sirt1 might be a predisposing factor in the emergence of adipose tissue fibrosis by enhancing the expression of extracellular matrix (ECM) components. Activation of Sirt1, similar to suppressing of Hif-1α in pre-adipocytes may be a beneficial approach for attenuating fibrotic gene expression.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-024-01389-4.

Sirtuins and Cellular Senescence in Patients with Idiopathic Pulmonary Fibrosis and Systemic Autoimmune Disorders

The sirtuin family is a heterogeneous group of proteins that play a critical role in many cellular activities. Several degenerative diseases have recently been linked to aberrant sirtuin expression and activity because of the involvement of sirtuins in maintaining cell longevity and their putative antiaging function. Idiopathic pulmonary fibrosis and progressive pulmonary fibrosis associated with systemic autoimmune disorders are severe diseases characterized by premature and accelerated exhaustion and failure of alveolar type II cells combined with aberrant activation of fibroblast proliferative pathways leading to dramatic destruction of lung architecture. The mechanisms underlying alveolar type II cell exhaustion in these disorders are not fully understood. In this review, we have focused on the role of sirtuins in the pathogenesis of idiopathic and secondary pulmonary fibrosis and their potential as biomarkers in the diagnosis and management of fibrotic interstitial lung diseases.

Mitochondrial network dynamics in pulmonary disease: Bridging the gap between inflammation, oxidative stress, and bioenergetics

Once thought of in terms of bioenergetics, mitochondria are now widely accepted as both the orchestrator of cellular health and the gatekeeper of cell death. The pulmonary disease field has performed extensive efforts to explore the role of mitochondria in regulating inflammation, cellular metabolism, apoptosis, and oxidative stress. However, a critical component of these processes needs to be more studied: mitochondrial network dynamics. Mitochondria morphologically change in response to their environment to regulate these processes through fusion, fission, and mitophagy. This allows mitochondria to adapt their function to respond to cellular requirements, a critical component in maintaining cellular homeostasis. For that reason, mitochondrial network dynamics can be considered a bridge that brings multiple cellular processes together, revealing a potential pathway for therapeutic intervention. In this review, we discuss the critical modulators of mitochondrial dynamics and how they are affected in pulmonary diseases, including chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), acute lung injury (ALI), and pulmonary arterial hypertension (PAH). A dysregulated mitochondrial network plays a crucial role in lung disease pathobiology, and aberrant fission/fusion/mitophagy pathways are druggable processes that warrant further exploration. Thus, we also discuss the candidates for lung disease therapeutics that regulate mitochondrial network dynamics.

Curculigoside Attenuates Endoplasmic Reticulum Stress-Induced Epithelial Cell and Fibroblast Senescence by Regulating the SIRT1-P300 Signaling Pathway

The senescence of alveolar epithelial cells (AECs) and fibroblasts plays a pivotal role in the pathogenesis of idiopathic pulmonary fibrosis (IPF), a condition lacking specific therapeutic interventions. Curculigoside (CCG), a prominent bioactive constituent of Curculigo, exhibits anti-osteoporotic and antioxidant activities. Our investigation aimed to elucidate the anti-senescence and anti-fibrotic effects of CCG in experimental pulmonary fibrosis and delineate its underlying molecular mechanisms. Our findings demonstrate that CCG attenuates bleomycin-induced pulmonary fibrosis and lung senescence in murine models, concomitantly ameliorating lung function impairment. Immunofluorescence staining for senescence marker p21, alongside SPC or α-SMA, suggested that CCG's mitigation of lung senescence correlates closely with the deceleration of senescence in AECs and fibroblasts. In vitro, CCG mitigated H2O2-induced senescence in AECs and the natural senescence of primary mouse fibroblasts. Mechanistically, CCG can upregulate SIRT1 expression, downregulating P300 expression, enhancing Trim72 expression to facilitate P300 ubiquitination and degradation, reducing the acetylation levels of antioxidant enzymes, and upregulating their expression levels. These actions collectively inhibited endoplasmic reticulum stress (ERS) and alleviated senescence. Furthermore, the anti-senescence effects and mechanisms of CCG were validated in a D-galactose (D-gal)-induced progeroid model. This study provides novel insights into the mechanisms underlying the action of CCG in cellular senescence and chronic diseases, offering potential avenues for the development of innovative drugs or therapeutic strategies.

MAPK phosphatase 1 inhibition of p38α within lung myofibroblasts is essential for spontaneous fibrosis resolution

Fibrosis following tissue injury is distinguished from normal repair by the accumulation of pathogenic and apoptosis-resistant myofibroblasts (MFs), which arise primarily by differentiation from resident fibroblasts. Endogenous molecular brakes that promote MF dedifferentiation and clearance during spontaneous resolution of experimental lung fibrosis may provide insights that could inform and improve the treatment of progressive pulmonary fibrosis in patients. MAPK phosphatase 1 (MKP1) influences the cellular phenotype and fate through precise and timely regulation of MAPK activity within various cell types and tissues, yet its role in lung fibroblasts and pulmonary fibrosis has not been explored. Using gain- and loss-of-function studies, we found that MKP1 promoted lung MF dedifferentiation and restored the sensitivity of these cells to apoptosis - effects determined to be mainly dependent on MKP1's dephosphorylation of p38α MAPK (p38α). Fibroblast-specific deletion of MKP1 following peak bleomycin-induced lung fibrosis largely abrogated its subsequent spontaneous resolution. Such resolution was restored by treating these transgenic mice with the p38α inhibitor VX-702. We conclude that MKP1 is a critical antifibrotic brake whose inhibition of pathogenic p38α in lung fibroblasts is necessary for fibrosis resolution following lung injury.

Particulate matter-mediated oxidative stress induces airway inflammation and pulmonary dysfunction through TXNIP/NF-κB and modulation of the SIRT1-mediated p53 and TGF-β/Smad3 pathways in mice

Exposure to particulate matter is currently recognized as a serious aggravating factor of respiratory diseases. In this study, we investigated the effects of particulate matter (PM) on the respiratory system in BALB/c mice and NCI-H292 cells. PM (0, 2.5, 5 and 20 mg/kg) was administered to mice by intra-tracheal instillation for 7 days. After a 7 day-repeated treatment of PM, we evaluated inflammatory cytokines/cell counts in bronchoalveolar lavage fluid (BALF) and conducted pulmonary histology and functional test. We also investigated the role of TXNIP/NF-κB and SIRT1-mediated p53 and TGF-β/Smad3 pathways in PM-induced airway inflammation and pulmonary dysfunction. PM caused a significant increase in pro-inflammatory cytokines, inflammatory cell counts in bronchoalveolar lavage fluid. PM-mediated oxidative stress down-regulated thioredoxin-1 and up-regulated thioredoxin-interacting protein and activation of nuclear factor-kappa B in the lung tissue and PM-treated NCI-H292 cells. PM suppressed sirtuin1 protein levels and increased p53 acetylation in PM-exposed mice and PM-treated NCI-H292 cells. In addition, PM caused inflammatory cell infiltration and the thickening of alveolar walls by exacerbating the inflammatory response in the lung tissue. PM increased levels of transforming growth factor-β, phosphorylation of Smad3 and activation of α-smooth muscle actin, and collagen type1A2 in PM-exposed mice and PM-treated NCI-H292 cells. In pulmonary function tests, PM exposure impaired pulmonary function resembling pulmonary fibrosis, characterized by increased resistance and elastance of the respiratory system, and resistance, elastance, and damping of lung tissues, whereas decreased compliance of the respiratory system, forced expired volume and forced vital capacity. Overall, PM-mediated oxidative stress caused airway inflammation and pulmonary dysfunction with pulmonary fibrosis via TXNIP pathway/NF-κB activation and modulation of the SIRT1-mediated TGF-β/Smad3 pathways. The results of this study can provide fundamental data on the potential adverse effects and underlying mechanism of pulmonary fibrosis caused by PM exposure as a public health concern. Due to the potential toxicity of PM, people with respiratory disease must be careful with PM exposure.

The molecular mechanisms of extracellular matrix-derived hydrogel therapy in idiopathic pulmonary fibrosis models

Idiopathic Pulmonary Fibrosis (IPF) is a progressively debilitating lung condition characterized by oxidative stress, cell phenotype shifts, and excessive extracellular matrix (ECM) deposition. Recent studies have shown promising results using decellularized ECM-derived hydrogels produced through pepsin digestion in various lung injury models and even a human clinical trial for myocardial infarction. This study aimed to characterize the composition of ECM-derived hydrogels, assess their potential to prevent fibrosis in bleomycin-induced IPF models, and unravel their underlying molecular mechanisms of action. Porcine lungs were decellularized and pepsin-digested for 48 h. The hydrogel production process, including visualization of protein molecular weight distribution and hydrogel gelation, was characterized. Peptidomics analysis of ECM-derived hydrogel contained peptides from 224 proteins. Probable bioactive and cell-penetrating peptides, including collagen IV, laminin beta 2, and actin alpha 1, were identified. ECM-derived hydrogel treatment was administered as an early intervention to prevent fibrosis advancement in rat models of bleomycin-induced pulmonary fibrosis. ECM-derived hydrogel concentrations of 1 mg/mL and 2 mg/mL showed subtle but noticeable effects on reducing lung inflammation, oxidative damage, and protein markers related to fibrosis (e.g., alpha-smooth muscle actin, collagen I). Moreover, distinct changes were observed in macroscopic appearance, alveolar structure, collagen deposition, and protein expression between lungs that received ECM-derived hydrogel and control fibrotic lungs. Proteomic analyses revealed significant protein and gene expression changes related to cellular processes, pathways, and components involved in tissue remodeling, inflammation, and cytoskeleton regulation. RNA sequencing highlighted differentially expressed genes associated with various cellular processes, such as tissue remodeling, hormone secretion, cell chemotaxis, and cytoskeleton engagement. This study suggests that ECM-derived hydrogel treatment influence pathways associated with tissue repair, inflammation regulation, cytoskeleton reorganization, and cellular response to injury, potentially offering therapeutic benefits in preventing or mitigating lung fibrosis.

Autocrine TGF-β-positive feedback in profibrotic AT2-lineage cells plays a crucial role in non-inflammatory lung fibrogenesis

The molecular etiology of idiopathic pulmonary fibrosis (IPF) has been extensively investigated to identify new therapeutic targets. Although anti-inflammatory treatments are not effective for patients with IPF, damaged alveolar epithelial cells play a critical role in lung fibrogenesis. Here, we establish an organoid-based lung fibrosis model using mouse and human lung tissues to assess the direct communication between damaged alveolar type II (AT2)-lineage cells and lung fibroblasts by excluding immune cells. Using this in vitro model and mouse genetics, we demonstrate that bleomycin causes DNA damage and activates p53 signaling in AT2-lineage cells, leading to AT2-to-AT1 transition-like state with a senescence-associated secretory phenotype (SASP). Among SASP-related factors, TGF-β plays an exclusive role in promoting lung fibroblast-to-myofibroblast differentiation. Moreover, the autocrine TGF-β-positive feedback loop in AT2-lineage cells is a critical cellular system in non-inflammatory lung fibrogenesis. These findings provide insights into the mechanism of IPF and potential therapeutic targets.

EP300 as a Molecular Integrator of Fibrotic Transcriptional Programs

Fibrosis is a condition characterized by the excessive accumulation of extracellular matrix proteins in tissues, leading to organ dysfunction and failure. Recent studies have identified EP300, a histone acetyltransferase, as a crucial regulator of the epigenetic changes that contribute to fibrosis. In fact, EP300-mediated acetylation of histones alters global chromatin structure and gene expression, promoting the development and progression of fibrosis. Here, we review the role of EP300-mediated epigenetic regulation in multi-organ fibrosis and its potential as a therapeutic target. We discuss the preclinical evidence that suggests that EP300 inhibition can attenuate fibrosis-related molecular processes, including extracellular matrix deposition, inflammation, and epithelial-to-mesenchymal transition. We also highlight the contributions of small molecule inhibitors and gene therapy approaches targeting EP300 as novel therapies against fibrosis.

Sirtuin family in autoimmune diseases

In recent years, epigenetic modifications have been widely researched. As humans age, environmental and genetic factors may drive inflammation and immune responses by influencing the epigenome, which can lead to abnormal autoimmune responses in the body. Currently, an increasing number of studies have emphasized the important role of epigenetic modification in the progression of autoimmune diseases. Sirtuins (SIRTs) are class III nicotinamide adenine dinucleotide (NAD)-dependent histone deacetylases and SIRT-mediated deacetylation is an important epigenetic alteration. The SIRT family comprises seven protein members (namely, SIRT1-7). While the catalytic core domain contains amino acid residues that have remained stable throughout the entire evolutionary process, the N- and C-terminal regions are structurally divergent and contribute to differences in subcellular localization, enzymatic activity and substrate specificity. SIRT1 and SIRT2 are localized in the nucleus and cytoplasm. SIRT3, SIRT4, and SIRT5 are mitochondrial, and SIRT6 and SIRT7 are predominantly found in the nucleus. SIRTs are key regulators of various physiological processes such as cellular differentiation, apoptosis, metabolism, ageing, immune response, oxidative stress, and mitochondrial function. We discuss the association between SIRTs and common autoimmune diseases to facilitate the development of more effective therapeutic strategies.

Customizable Resveratrol Spray-dried Micro-composites for Inhalation as a Promising Contender for Treatment of Idiopathic Pulmonary Fibrosis

The past decades have witnessed tremendous expansion in utilization of plant-derived medicines as resveratrol (RES) in treating several diseases like idiopathic pulmonary fibrosis (IPF). RES can exhibit its role in treating IPF via its outstanding antioxidant and anti-inflammatory activities. The goal of this work was to formulate RES-loaded spray-dried composite microparticles (SDCMs) suitable for pulmonary delivery via dry powder inhaler (DPI). They were prepared by spray drying of a previously prepared RES-loaded bovine serum albumin nanoparticles (BSA NPs) dispersion using different carriers. RES-loaded BSA NPs, prepared by the desolvation technique, acquired suitable particle size of 177.67±0.95 nm and entrapment efficiency of 98.7±0.35% with perfectly uniform size distribution and high stability. Considering the attributes of the pulmonary route, NPs were co-spray dried with compatible carriers viz. mannitol, dextran, trehalose, leucine, glycine, aspartic acid, and glutamic acid to fabricate SDCMs. All formulations showed suitable mass median aerodynamic diameter less than 5 µm; that is suitable for deep lung deposition. However, the best aerosolization behavior was attained from using leucine with fine particle fraction (FPF) of 75.74%, followed by glycine with FPF of 54.7%. Finally, a pharmacodynamic study was conducted on bleomycin-induced mice, and it strongly revealed the role of the optimized formulations in alleviating PF through suppressing the levels of hydroxyproline, tumor necrosis factor-α and matrix metalloproteinase-9 with obvious improvements in the treated lung histopathology. These findings indicate that in addition to leucine, the glycine amino acid, which is not commonly used yet, is very promising in the formulation of DPIs.

Relief of ovalbumin-induced airway remodeling by the glycyl-l-histidyl-l-lysine-Cu2+ tripeptide complex via activation of SIRT1 in airway epithelial cells

Fixed airflow limitation (FAO), prevalent in patients with severe or difficult-to-treat asthma, is mainly caused by airway remodeling. Airway remodeling is initiated by inflammation and involves subsequent pathological changes. Glycyl-l-histidyl-l-lysine (GHK) is a matrikine with anti-inflammatory and antioxidant effects, naturally existing in human tissue. At present, the GHK level in human plasma and whether it is related to airway remodeling of asthma remain unclear. This study was conducted to determine how GHK is involved in airway remodeling in asthma. Our result showed that the plasma GHK levels of patients with asthma were significantly lower than those of age-matched healthy controls. In asthma patients, plasma GHK levels display a moderate correlation with FEF_25-75%, and patients with FAO had significantly lower GHK levels. Ovalbumin-induced mice of asthma model treated with PBS or GHK-Cu (a form of GHK with higher bioavailability) were used to evaluate the effect of exogenous GHK supplement on airway remodeling. GHK-Cu administration alleviated airway remodeling, as reflected by decreased peribronchial collagen deposition and airway mucus secretion, and suppressed epithelial-mesenchymal transition. The therapeutical effect related to decreased TGF-β1 level. Successively, network pharmacology and the validation data of experiments in vivo and vitro demonstrated that GHK-Cu decreased TGF-β1 level by increasing SIRT1 expression and activating SIRT1 deacetylation in airway epithelial cells, thereby alleviating airway remodeling. Collectively, decreased plasma GHK levels were related to FAO in asthma patients. Through the direct binding and activation of SIRT1, exogenous GHK-Cu administration alleviated airway remodeling in asthmatic mice.

Sirt1 Overexpression Inhibits Fibrous Scar Formation and Improves Functional Recovery After Cerebral Ischemic Injury Through the Deacetylation of 14-3-3ζ

Cerebral ischemic stroke is one of the leading causes of human death. The fibrous scar is one of major factors influencing repair in central nervous system (CNS) injury. Silencing information regulator 2-related enzyme 1 (Sirt1) can regulate peripheral tissue and organ fibrosis. However, it is unclear how the fibrous scar forms and is regulated and it is unknown whether and how Sirt1 regulates the formation of the fibrous scar after cerebral ischemic stroke. Therefore, in the present study, we examined the effects of Sirt1 on the formation of the fibrotic scar after middle cerebral artery occlusion/reperfusion (MCAO/R) injury in vivo and on the transforming growth factor β1 (TGF-β1)-induced meningeal fibroblast fibrotic response in vitro, and we explored the molecular mechanisms underlying the Sirt1-regulated fibrosis process in vitro. We found that MCAO/R injury induced fibrotic scar formation in the ischemic area, which was accompanied by the downregulation of Sirt1 expression. The overexpression of Sirt1 reduced the infarct volume, improved Nissl body structure and reduced neurons injury, attenuated formation of fibrotic scar, upregulated growth associated protein43 (GAP43) and synaptophysin (SYP) expression, and promoted neurological function recovery. Similarly, Sirt1 expression was also downregulated in the TGF-β1-induced fibrosis model. Sirt1 overexpression inhibited fibroblast migration, proliferation, transdifferentiation into myofibroblasts, and secretion of extracellular matrix(ECM) by regulating the deacetylation of lysine at K49 and K120 sites of 14-3-3ζ in vitro. Therefore, we believe that Sirt1 could regulate fibrous scar formation and improve neurological function after cerebral ischemic stroke through regulating deacetylation of 14-3-3ζ.

Artesunate reduces sepsis-mediated acute lung injury in a SIRT1-dependent manner

Introduction

Sepsis-mediated acute lung injury (ALI) is a critical clinical condition. Artesunate (AS) is a sesquiterpene lactone endoperoxide that was discovered in Artemisia annua, which is a traditional Chinese herb. AS has a broad set of biological and pharmacological actions; however, its protective effect on lipopolysaccharide (LPS)-induced ALI remains unclear.

Methods

LPS-mediated ALI was induced in rats through bronchial LPS inhalation. Then NR8383 cells were treated with LPS to establish an in vitro model. Further, we administered different AS doses in vivo and in vitro.

Results

AS administration significantly decreased LPS-mediated pulmonary cell death and inhibited pulmonary neutrophil infiltration. Additionally, AS administration increased SIRT1 expression in pulmonary sections. Administration of a biological antagonist or shRNA-induced reduction of SIRT1 expression significantly inhibited the protective effect of AS against LPS-induced cellular injury, pulmonary dysfunction, neutrophil infiltration, and apoptosis. This demonstrates that enhanced SIRT1 expression is crucially involved in the observed protective effects.

Conclusion

Our findings could suggest the use of AS for treating lung disorders through a mechanism involving SIRT1 expression.

Epigenetics as a versatile regulator of fibrosis

Fibrosis, a process caused by excessive deposition of extracellular matrix (ECM), is a common cause and outcome of organ failure and even death. Researchers have made many efforts to understand the mechanism of fibrogenesis and to develop therapeutic strategies; yet, the outcome remains unsatisfactory. In recent years, advances in epigenetics, including chromatin remodeling, histone modification, DNA methylation, and noncoding RNA (ncRNA), have provided more insights into the fibrotic process and have suggested the possibility of novel therapy for organ fibrosis. In this review, we summarize the current research on the epigenetic mechanisms involved in organ fibrosis and their possible clinical applications.

Roles of lipid metabolism and its regulatory mechanism in idiopathic pulmonary fibrosis: A review

Idiopathic pulmonary fibrosis is a progressive lung disease of unknown etiology characterized by distorted distal lung architecture, inflammation, and fibrosis. Several lung cell types, including alveolar epithelial cells and fibroblasts, have been implicated in the development and progression of fibrosis. However, the pathogenesis of idiopathic pulmonary fibrosis is still incompletely understood. The latest research has found that dysregulation of lipid metabolism plays an important role in idiopathic pulmonary fibrosis. The changes in the synthesis and activity of fatty acids, cholesterol and other lipids seriously affect the regenerative function of alveolar epithelial cells and promote the transformation of fibroblasts into myofibroblasts. Mitochondrial function is the key to regulating the metabolic needs of a variety of cells, including alveolar epithelial cells. Sirtuins located in mitochondria are essential to maintain mitochondrial function and cellular metabolic homeostasis. Sirtuins can maintain normal lipid metabolism by regulating respiratory enzyme activity, resisting oxidative stress, and protecting mitochondrial function. In this review, we aimed to discuss the difference between normal and idiopathic pulmonary fibrosis lungs in terms of lipid metabolism. Additionally, we highlight recent breakthroughs on the effect of abnormal lipid metabolism on idiopathic pulmonary fibrosis, including the effects of sirtuins. Idiopathic pulmonary fibrosis has its high mortality and limited therapeutic options; therefore, we believe that this review will help to develop a new therapeutic direction from the aspect of lipid metabolism in idiopathic pulmonary fibrosis.

The sirtuin family in health and disease

Sirtuins (SIRTs) are nicotine adenine dinucleotide(+)-dependent histone deacetylases regulating critical signaling pathways in prokaryotes and eukaryotes, and are involved in numerous biological processes. Currently, seven mammalian homologs of yeast Sir2 named SIRT1 to SIRT7 have been identified. Increasing evidence has suggested the vital roles of seven members of the SIRT family in health and disease conditions. Notably, this protein family plays a variety of important roles in cellular biology such as inflammation, metabolism, oxidative stress, and apoptosis, etc., thus, it is considered a potential therapeutic target for different kinds of pathologies including cancer, cardiovascular disease, respiratory disease, and other conditions. Moreover, identification of SIRT modulators and exploring the functions of these different modulators have prompted increased efforts to discover new small molecules, which can modify SIRT activity. Furthermore, several randomized controlled trials have indicated that different interventions might affect the expression of SIRT protein in human samples, and supplementation of SIRT modulators might have diverse impact on physiological function in different participants. In this review, we introduce the history and structure of the SIRT protein family, discuss the molecular mechanisms and biological functions of seven members of the SIRT protein family, elaborate on the regulatory roles of SIRTs in human disease, summarize SIRT inhibitors and activators, and review related clinical studies.

Small ubiquitin-related modifier (SUMO)ylation of SIRT1 mediates (-)-epicatechin inhibited- differentiation of cardiac fibroblasts into myofibroblasts

CONTEXT

(-)-Epicatechin (EPI) is a crucial substance involved in the protective effects of flavanol-rich foods. Previous studies have indicated EPI has a cardioprotective effect, but the molecular mechanisms in inhibition of cardiac fibrosis are unclear.

OBJECTIVE

We evaluated the effect of EPI in preventing cardiac fibrosis and the underlying molecular mechanism related to the SIRT1-SUMO1/AKT/GSK3β pathway.

MATERIALS AND METHODS

Cardiac fibrosis mice model was established with transaortic constriction (TAC). Male C57BL/6 mice were randomly separated into 4 groups. Mice received 1 mg/kg/day of EPI or vehicle orally for 4 weeks. The acutely isolated cardiac fibroblasts were induced to myofibroblasts with 1 µM angiotensin II (Ang II). The cardiac function was measured with the ultrasonic instrument. Histological analysis of mice's hearts was determined with H&E or Masson method. The protein level of fibrosis markers, SUMOylation of SIRT1, and AKT/GSK3β pathway were quantified by immunofluorescence and western blot.

RESULTS

EPI treatment (1 mg/kg/day) could reverse the TAC-induced decline in LVEF (TAC, 61.28% ± 1.33% vs. TAC + EPI, 74.00% ± 1.64%), LVFS (TAC, 28.16% ± 0.89% vs. TAC + EPI, 37.18% ± 1.29%). Meantime, we found that 10 µM EPI blocks Ang II-induced transformation of cardiac fibroblasts into myofibroblasts. The underlying mechanism of EPI-inhibited myofibroblasts transformation involves activation of SUMOylation of SIRT1 through SP1. Furthermore, SUMOylation of SIRT1 inhibited Ang II-induced fibrogenic effect via the AKT/GSK3β pathway.

CONCLUSION

EPI plays a protective effect on cardiac fibrosis by regulating the SUMO1-dependent modulation of SIRT1, which provides a theoretical basis for use in clinical therapies.

Renalase Challenges the Oxidative Stress and Fibroproliferative Response in COVID-19

The hallmark of the coronavirus disease 2019 (COVID-19) pathophysiology was reported to be an inappropriate and uncontrolled immune response, evidenced by activated macrophages, and a robust surge of proinflammatory cytokines, followed by the release of reactive oxygen species, that synergistically result in acute respiratory distress syndrome, fibroproliferative lung response, and possibly even death. For these reasons, all identified risk factors and pathophysiological processes of COVID-19, which are feasible for the prevention and treatment, should be addressed in a timely manner. Accordingly, the evolving anti-inflammatory and antifibrotic therapy for severe COVID-19 and hindering post-COVID-19 fibrosis development should be comprehensively investigated. Experimental evidence indicates that renalase, a novel amino-oxidase, derived from the kidneys, exhibits remarkable organ protection, robustly addressing the most powerful pathways of cell trauma: inflammation and oxidative stress, necrosis, and apoptosis. As demonstrated, systemic renalase administration also significantly alleviates experimentally induced organ fibrosis and prevents adverse remodeling. The recognition that renalase exerts cytoprotection via sirtuins activation, by raising their NAD⁺ levels, provides a “proof of principle” for renalase being a biologically impressive molecule that favors cell protection and survival and maybe involved in the pathogenesis of COVID-19. This premise supports the rationale that renalase's timely supplementation may prove valuable for pathologic conditions, such as cytokine storm and related acute respiratory distress syndrome. Therefore, the aim for this review is to acknowledge the scientific rationale for renalase employment in the experimental model of COVID-19, targeting the acute phase mechanisms and halting fibrosis progression, based on its proposed molecular pathways. Novel therapies for COVID-19 seek to exploit renalase's multiple and distinctive cytoprotective mechanisms; therefore, this review should be acknowledged as the thorough groundwork for subsequent research of renalase's employment in the experimental models of COVID-19.

cBleomycin restricts the glycolysis of lymphatic endothelial cells by inhibiting dimeric PKM2 formation: A novel mechanism for lymphatic malformation treatment

Glycolysis is activated in lymphatic endothelial cells and contributes to the development of lymphatic malformations (LMs). Bleomycin (BLM) is the most wildly used sclerosant for LMs, but its mechanisms are unknown. Here, our data showed that BLM suppressed the glycolysis of human dermal lymphatic endothelial cells (HDLECs) via inhibiting the expression and nucleus translocation of pyruvate kinase M2 isoform (PKM2) and inhibited dimeric PKM2 formation. Furthermore, the proliferation of LM lesions was inhibited by BLM through the down-regulation of nuclear PKM2 in the rat model. Additionally, PKM2, especially the nuclear PKM2 along with Ki-67, was inhibited in the lymphatic vessels of BLM-treated LMs. Our findings provide a new molecular mechanism of BLM in LM sclerotherapy treatment.

Specific epigenetic regulators serve as potential therapeutic targets in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF), a disorder observed mostly in older human beings, is characterised by chronic and progressive lung scarring leading to an irreversible decline in lung function. This health condition has a dismal prognosis and the currently available drugs only delay but fail to reverse the progression of lung damage. Consequently, it becomes imperative to discover improved therapeutic compounds and their cellular targets to cure IPF. In this regard, a number of recent studies have targeted the epigenetic regulation by histone deacetylases (HDACs) to develop and categorise antifibrotic drugs for lungs. Therefore, this review focuses on how aberrant expression or activity of Classes I, II and III HDACs alter TGF-β signalling to promote events such as epithelial-mesenchymal transition, differentiation of activated fibroblasts into myofibroblasts, and excess deposition of the extracellular matrix to propel lung fibrosis. Further, this study describes how certain chemical compounds or dietary changes modulate dysregulated HDACs to attenuate five faulty TGF-β-dependent profibrotic processes, both in animal models and cell lines replicating IPF, thereby identifying promising means to treat this lung disorder.

Sirt1 overexpression improves senescence-associated pulmonary fibrosis induced by vitamin D deficiency through downregulating IL-11 transcription

Determining the mechanism of senescence-associated pulmonary fibrosis is crucial for designing more effective treatments for chronic lung diseases. This study aimed to determine the following: whether Sirt1 and serum vitamin D decreased with physiological aging, promoting senescence-associated pulmonary fibrosis by activating TGF-β1/IL-11/MEK/ERK signaling, whether Sirt1 overexpression prevented TGF-β1/IL-11/MEK/ERK signaling-mediated senescence-associated pulmonary fibrosis in vitamin D-deficient (Cyp27b1^-/- ) mice, and whether Sirt1 downregulated IL-11 expression transcribed by TGF-β1/Smad2 signaling through deacetylating histone at the IL-11 promoter in pulmonary fibroblasts. Bioinformatics analysis with RNA sequencing data from pulmonary fibroblasts of physiologically aged mice was conducted for correlation analysis. Lungs from young and physiologically aged wild-type (WT) mice were examined for cell senescence, fibrosis markers, and TGF-β1/IL-11/MEK/ERK signaling proteins, and 1,25(OH)₂ D₃ and IL-11 levels were detected in serum. Nine-week-old WT, Sirt1 mesenchymal transgene (Sirt1^Tg ), Cyp27b1^-/- , and Sirt1^Tg Cyp27b1^-/- mice were observed the pulmonary function, aging, and senescence-associated secretory phenotype and TGF-β1/IL-11/MEK/ERK signaling. We found that pulmonary Sirt1 and serum vitamin D decreased with physiological aging, activating TGF-β1/IL-11/MEK/ERK signaling, and promoting senescence-associated pulmonary fibrosis. Sirt1 overexpression improved pulmonary dysfunction, aging, DNA damage, senescence-associated secretory phenotype, and fibrosis through downregulating TGF-β1/IL-11/MEK/ERK signaling in Cyp27b1^-/- mice. Sirt1 negatively regulated IL-11 expression through deacetylating H3K9/14ac mainly at the region from -871 to -724 of IL-11 promoter, also the major binding region of Smad2 which regulated IL-11 expression at the transcriptional level, and subsequently inhibiting TGF-β1/IL-11/MEK/ERK signaling in pulmonary fibroblasts. This signaling in aging fibroblasts could be a therapeutic target for preventing senescence-associated pulmonary fibrosis induced by vitamin D deficiency.

Longevity-Promoting Pathways and Transcription Factors Respond to and Control Extracellular Matrix Dynamics During Aging and Disease

Aging is one of the largest risk factors for cancer, type 2 diabetes, osteoarthritis, cardiovascular diseases, and other age-related pathologies. Here, we give a detailed description of the interplay of chronic age-related pathologies with the remodeling of the extracellular matrix during disease development and progression. Longevity-promoting signaling pathways slow or prevent age-related diseases. In particular, we focus on the mTOR signaling pathway, sirtuins, and canonical longevity-promoting transcription factors, such as FOXO, NF-κB, and Nrf2. We extend our analysis using chromatin immunoprecipitation (ChIP) sequencing and transcriptomic data and report that many established and emerging longevity-promoting transcription factors, such as CREB1, FOXO1,3, GATA1,2,3,4, HIF1A, JUN, KLF4, MYC, NFE2L2/Nrf2, RELA/NF-κB, REST, STAT3,5A, and TP53/p53, directly regulate many extracellular matrix genes and remodelers. We propose that modulation of these pathways increases lifespan and protects from age-related diseases in part due to their effects on extracellular matrix remodeling. Therefore, to successfully treat age-related diseases, it is necessary to better understand the connection between extracellular matrix components and longevity pathways.

SIRT1 prevents cigarette smoking-induced lung fibroblasts activation by regulating mitochondrial oxidative stress and lipid metabolism

BACKGROUND

Cigarette smoking (CS) is a strong risk factor for idiopathic pulmonary fibrosis (IPF). It can activate lung fibroblasts (LF) by inducing redox imbalance. We previously showed that clearing mitochondrial reactive oxygen species (mtROS) protects against CS-induced pulmonary fibrosis. However, the precise mechanisms of mtROS in LF need further investigation. Here we focused on mtROS to elucidate how it was regulated by CS in LF and how it contributed to LF activation.

METHODS

We treated cells with 1% cigarette smoking extract (CSE) and examined mtROS level by MitoSOX™ indicator. And the effect of CSE on expression of SIRT1, SOD2, mitochondrial NOX4 (mtNOX4), fatty acid oxidation (FAO)-related protein PPARα and CPT1a and LF activation marker Collagen I and α-SMA were detected. Nile Red staining was performed to show cellular lipid content. Then, lipid droplets, autophagosome and lysosome were marked by Bodipy 493/503, LC3 and LAMP1, respectively. And lipophagy was evaluated by the colocalization of lipid droplets with LC3 and LAMP1. The role of autophagy on lipid metabolism and LF activation were explored. Additionally, the effect of mitochondria-targeted ROS scavenger mitoquinone and SIRT1 activator SRT1720 on mitochondrial oxidative stress, autophagy flux, lipid metabolism and LF activation were investigated in vitro and in vivo.

RESULTS

We found that CS promoted mtROS production by increasing mtNOX4 and decreasing SOD2. Next, we proved mtROS inhibited the expression of PPARα and CPT1a. It also reduced lipophagy and upregulated cellular lipid content, suggesting lipid metabolism was disturbed by CS. In addition, we showed both insufficient FAO and lipophagy resulted from blocked autophagy flux caused by mtROS. Moreover, we uncovered decreased SIRT1 was responsible for mitochondrial redox imbalance. Furthermore, we proved that both SRT1720 and mitoquinone counteracted the effect of CS on NOX4, SOD2, PPARα and CPT1a in vivo.

CONCLUSIONS

We demonstrated that CS decreased SIRT1 to activate LF through dysregulating lipid metabolism, which was due to increased mtROS and impaired autophagy flux. These events may serve as therapeutic targets for IPF patients.

Astaxanthin Ameliorates high-fat diet-induced cardiac damage and fibrosis by upregulating and activating SIRT1

This study evaluated the protective effect of astaxanthin (ASX) against high-fat diet (HFD)-induced cardiac damage and fibrosis in rats and examined if the mechanism of protection involves modulating SIRT1. Rat were divided into 5 groups (n = 10/group) as: 1) control: fed normal diet (3.82 kcal/g), 2) control + ASX (200 mg/kg/orally), 3) HFD: fed HFD (4.7 kcal/g), 4) HFD + ASX (200 mg/kg/orally), and HFD + ASX + EX-527 (1 mg/kg/i.p) (a selective SIRT1 inhibitor). All treatments were conducted for 14 weeks. Administration of ASX reduced cardiomyocyte damage, inhibited inflammatory cell infiltration, preserved cardiac fibers structure, prevented collagen deposition and protein levels of TGF-β 1 in the left ventricles (LVs) of HFD-fed rats. In the LVs of both the control and HFD-fed rat, ASX significantly reduced levels of reactive oxygen species (ROS), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and p-smad2/3 (Lys19) but increased the levels of glutathione (GSH), catalase, and manganese superoxide dismutase (MnSOD). Concomitantly, it increased the nuclear activity of Nrf2 and reduced that of NF-κB p65. Furthermore, administration of ASX to both the control and HFD-fed rats increased total and nuclear levels of SIRT1, stimulated the nuclear activity of SIRT1, and reduced the acetylation of Nrf2, NF-κB p65, and Smad3. All these cardiac beneficial effects of ASX in the HFD-fed rats were abolished by co-administration of EX-527. In conclusion, ASX stimulates antioxidants and inhibits markers of inflammation under basal and HFD conditions. The mechanism of protection involves, at least, activation SIRT1 signaling.

SFPQ rescues F508del-CFTR expression and function in cystic fibrosis bronchial epithelial cells

Cystic fibrosis (CF) occurs as a result of mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which lead to misfolding, trafficking defects, and impaired function of the CFTR protein. Splicing factor proline/glutamine-rich (SFPQ) is a multifunctional nuclear RNA-binding protein (RBP) implicated in the regulation of gene expression pathways and intracellular trafficking. Here, we investigated the role of SFPQ in the regulation of the expression and function of F508del-CFTR in CF lung epithelial cells. We find that the expression of SFPQ is reduced in F508del-CFTR CF epithelial cells compared to WT-CFTR control cells. Interestingly, the overexpression of SFPQ in CF cells increases the expression as well as rescues the function of F508del-CFTR. Further, comprehensive transcriptome analyses indicate that SFPQ plays a key role in activating the mutant F508del-CFTR by modulating several cellular signaling pathways. This is the first report on the role of SFPQ in the regulation of expression and function of F508del-CFTR in CF lung disease. Our findings provide new insights into SFPQ-mediated molecular mechanisms and point to possible novel epigenetic therapeutic targets for CF and related pulmonary diseases.

The emerging role of metabolism in fibrosis

The metabolic shift that cancer cells undergo towards aerobic glycolysis was identified as a defining feature in tumours almost 100 years ago; however, it has only recently become apparent that similar metabolic reprogramming is a key feature in other diseases - with fibrosis now entering the fray. In this perspective, an overview of the recent evidence implicating increased glycolysis and glutaminolysis as mediators of fibrosis is presented, with a particular emphasis on the novel therapeutic possibilities this introduces. Furthermore, the impact that metabolic reprogramming has on redox homeostasis is discussed, providing an insight into how this often-overlooked mechanism may drive the pathogenesis.

Apigenin Alleviates Oxidative Stress-Induced Cellular Senescence via Modulation of the SIRT1-NAD[Formula: see text]-CD38 Axis

Oxidative stress-induced cellular senescence is now regarded as an important driving mechanism in chronic lung diseases-particularly chronic obstructive pulmonary disease (COPD). 4[Formula: see text],5,7-trihydroxyflavone (Apigenin) is a natural flavonoid product abundantly present in fruits, vegetables, and Chinese medicinal herbs. It has been known that apigenin has anti-oxidant, anti-inflammatory and liver-protecting effects. The efficacy of apigenin for lung aging, however, has not been reported. In this study, we selected the hydrogen peroxide (H₂O[Formula: see text]- or doxorubicin (DOXO)-induced senescence model in WI-38 human embryonic lung fibroblast cells to determine the potential anti-aging effects of apigenin in vitro and associated molecular mechanisms. We found that apigenin reduced senescence-associated [Formula: see text]-galactosidase (SA-[Formula: see text]-gal) activity and promoted cell growth, concomitant with a decrease in levels of Acetyl (ac)-p53, p21[Formula: see text], and p16[Formula: see text] and an increase in phospho (p)-Rb. Apigenin also increased the activation ratio of silent information regulator 1 (SIRT1), nicotinamide adenine dinucleotide (NAD[Formula: see text], and NAD[Formula: see text]/NADH and inhibited cluster of differentiation 38 (CD38) activity in a concentration-dependent manner. SIRT1 inhibition by SIRT1 siRNA abolished the anti-aging effect of apigenin. In addition, CD38 inhibition by CD38 siRNA or apigenin increased the SIRT1 level and reduced H₂O₂-induced senescence. Our findings suggest that apigenin is a promising phytochemical for reducing the impact of senescent cells in age-related lung diseases such as COPD.

Spontaneous Lung Fibrosis Resolution Reveals Novel Antifibrotic Regulators

Fibroblast activation is transient in successful wound repair but persistent in fibrotic pathologies. Understanding fibroblast deactivation during successful wound healing may provide new approaches to therapeutically reverse fibroblast activation. To characterize the gene programs that accompany fibroblast activation and reversal during lung fibrosis resolution, we used RNA sequencing analysis of flow sorted Col1α1-GFP-positive and CD45-, CD31-, and CD326-negative cells isolated from the lungs of young mice exposed to bleomycin. We compared fibroblasts isolated from control mice with those isolated at Days 14 and 30 after bleomycin exposure, representing the peak of extracellular matrix deposition and an early stage of fibrosis resolution, respectively. Bleomycin exposure dramatically altered fibroblast gene programs at Day 14. Principal component and differential gene expression analyses demonstrated the predominant reversal of these trends at Day 30. Upstream regulator and pathway analyses of reversing "resolution" genes identified novel candidate antifibrotic genes and pathways. Two genes from these analyses that were decreased in expression at Day 14 and reversed at Day 30, Aldh2 and Nr3c1, were selected for further analysis. Enhancement of endogenous expression of either gene by CRISPR activation in cultured human idiopathic pulmonary fibrosis fibroblasts was sufficient to reduce profibrotic gene expression, fibronectin deposition, and collagen gel compaction, consistent with roles for these genes in fibroblast deactivation. This combination of RNA sequencing analysis of freshly sorted fibroblasts and hypothesis testing in cultured idiopathic pulmonary fibrosis fibroblasts offers a path toward identification of novel regulators of lung fibroblast deactivation, with potential relevance to understanding fibrosis resolution and its failure in human disease.

Nutraceutical, Dietary, and Lifestyle Options for Prevention and Treatment of Ventricular Hypertrophy and Heart Failure

Although well documented drug therapies are available for the management of ventricular hypertrophy (VH) and heart failure (HF), most patients nonetheless experience a downhill course, and further therapeutic measures are needed. Nutraceutical, dietary, and lifestyle measures may have particular merit in this regard, as they are currently available, relatively safe and inexpensive, and can lend themselves to primary prevention as well. A consideration of the pathogenic mechanisms underlying the VH/HF syndrome suggests that measures which control oxidative and endoplasmic reticulum (ER) stress, that support effective nitric oxide and hydrogen sulfide bioactivity, that prevent a reduction in cardiomyocyte pH, and that boost the production of protective hormones, such as fibroblast growth factor 21 (FGF21), while suppressing fibroblast growth factor 23 (FGF23) and marinobufagenin, may have utility for preventing and controlling this syndrome. Agents considered in this essay include phycocyanobilin, N-acetylcysteine, lipoic acid, ferulic acid, zinc, selenium, ubiquinol, astaxanthin, melatonin, tauroursodeoxycholic acid, berberine, citrulline, high-dose folate, cocoa flavanols, hawthorn extract, dietary nitrate, high-dose biotin, soy isoflavones, taurine, carnitine, magnesium orotate, EPA-rich fish oil, glycine, and copper. The potential advantages of whole-food plant-based diets, moderation in salt intake, avoidance of phosphate additives, and regular exercise training and sauna sessions are also discussed. There should be considerable scope for the development of functional foods and supplements which make it more convenient and affordable for patients to consume complementary combinations of the agents discussed here. Research Strategy: Key word searching of PubMed was employed to locate the research papers whose findings are cited in this essay.

PGC-1α regulates airway epithelial barrier dysfunction induced by house dust mite

Background

The airway epithelial barrier function is disrupted in the airways of asthmatic patients. Abnormal mitochondrial biogenesis is reportedly involved in the pathogenesis of asthma. However, the role of mitochondrial biogenesis in the airway barrier dysfunction has not been elucidated yet. This study aimed to clarify whether the peroxisome proliferator-activated receptor γ coactivator-1alpha (PGC-1α), a central regulator of mitochondrial biogenesis, is involved in the disruption of the airway barrier function induced by aeroallergens.

Methods

BEAS-2B cells were exposed to house dust mite (HDM) and the expressions of PGC-1α and E-cadherin, a junctional protein, were examined by immunoblotting. The effect of SRT1720, a PGC-1α activator, was investigated by immunoblotting, immunocytochemistry, and measuring the transepithelial electrical resistance (TEER) on the HDM-induced reduction in mitochondrial biogenesis markers and junctional proteins in airway bronchial epithelial cells. Furthermore,the effects of protease activated receptor 2 (PAR2) inhibitor, GB83, Toll-like receptor 4 (TLR4) inhibitor, lipopolysaccharide from Rhodobacter sphaeroides (LPS-RS), protease inhibitors including E64 and 4-(2-Aminoethyl) benzenesulfonyl fluoride hydrochloride (AEBSF) on the HDM-induced barrier dysfunction were investigated.

Results

The amounts of PGC-1α and E-cadherin in the HDM-treated cells were significantly decreased compared to the vehicle-treated cells. SRT1720 restored the expressions of PGC-1α and E-cadherin reduced by HDM in BEAS-2B cells. Treatment with SRT1720 also significantly ameliorated the HDM-induced reduction in TEER. In addition, GB83, LPS-RS, E64 and AEBSF prevented the HDM-induced reduction in the expression of PGC1α and E-cadherin.

Conclusions

The current study demonstrated that HDM disrupted the airway barrier function through the PAR2/TLR4/PGC-1α-dependent pathway. The modulation of this pathway could be a new approach for the treatment of asthma.

Modulation of bleomycin-induced oxidative stress and pulmonary fibrosis by N-acetylcysteine in rats via AMPK/SIRT1/NF-κβ

The efficacy of bleomycin (BLM) as an antineoplastic drug is limited to the development of dose and time-dependent pulmonary fibrosis. This study was intended to investigate the effect of N-acetylcysteine (NAC) on BLM-induced pulmonary fibrosis in rats. Twenty rats were randomly divided to the following four groups: Group one served as control; group two received BLM (15 mg/kg, intraperitoneal (ip)) for five consecutive days; group three received NAC (200 mg/kg, ip) for five consecutive days; and group four received NAC 1 hour before BLM for 5 days. The expression of connective tissue growth factor (CTGF), platelet-derived growth factor (PDGF), silent information regulator l (SIRT1), AMP-activated protein kinase (AMPK) were determined by qRT-PCR in lung tissues. The changes in transforming growth factor-beta1 (TGF-β1), tumour necrosis factor-α (TNF-α), interleukin-β1 (IL-β1) and nuclear factor kappa-β (NF-κβ) in serum were measured by ELISA. The tissue antioxidant status was determined biochemically. BLM administration caused pulmonary fibrosis as evidenced by increased levels of inflammatory mediators (TGF-β1, TNF-α, IL-β1 and NF-κβ) in serum (P < .05), elevated lipid peroxidation and nitric oxide and depleted endogenous antioxidants in lung tissue (P < .05). The expression levels of SIRT1 and AMPK were significantly decreased (P < .05), while the expression levels of CTGF and PDGF were increased significantly in the BLM group as compared to the control group (P < .05). These alterations were normalized by NAC intervention. NAC markedly attenuated the lung histopathological changes and reduced collagen deposition. These results suggest that NAC exerted an ameliorative effect against BLM-induced oxidative damage and pulmonary fibrosis via SIRT1/ AMPK/ NF-κβ pathways.

Caveolin-1 scaffolding domain peptide regulates glucose metabolism in lung fibrosis

Increased metabolism distinguishes myofibroblasts or fibrotic lung fibroblasts (fLfs) from the normal lung fibroblasts (nLfs). The mechanism of metabolic activation in fLfs has not been fully elucidated. Furthermore, the antifibrogenic effects of caveolin-1 scaffolding domain peptide CSP/CSP7 involving metabolic reprogramming in fLfs are unclear. We therefore analyzed lactate and succinate levels, as well as the expression of glycolytic enzymes and hypoxia inducible factor-1α (HIF-1α). Lactate and succinate levels, as well as the basal expression of glycolytic enzymes and HIF-1α, were increased in fLfs. These changes were reversed following restoration of p53 or its transcriptional target microRNA-34a (miR-34a) expression in fLfs. Conversely, inhibition of basal p53 or miR-34a increased glucose metabolism, glycolytic enzymes, and HIF-1α in nLfs. Treatment of fLfs or mice having bleomycin- or Ad-TGF-β1-induced lung fibrosis with CSP/CSP7 reduced the expression of glycolytic enzymes and HIF-1α. Furthermore, inhibition of p53 or miR-34a abrogated CSP/CSP7-mediated restoration of glycolytic flux in fLfs in vitro and in mice with pulmonary fibrosis and lacking p53 or miR-34a expression in fibroblasts in vivo. Our data indicate that dysregulation of glucose metabolism in fLfs is causally linked to loss of basal expression of p53 and miR-34a. Treatment with CSP/CSP7 constrains aberrant glucose metabolism through restoration of p53 and miR-34a.

Virus-Induced Asthma Exacerbations: SIRT1 Targeted Approach

The prevalence of asthma has increased worldwide. Asthma exacerbations triggered by upper respiratory tract viral infections remain a major clinical problem and account for hospital admissions and time lost from work. Virus-induced asthma exacerbations cause airway inflammation, resulting in worsening asthma and deterioration in the patients’ quality of life, which may require systemic corticosteroid therapy. Despite recent advances in understanding the cellular and molecular mechanisms underlying asthma exacerbations, current therapeutic modalities are inadequate for complete prevention and treatment of these episodes. The pathological role of cellular senescence, especially that involving the silent information regulator 2 homolog sirtuin (SIRT) protein family, has recently been demonstrated in stable and exacerbated chronic respiratory disease states. This review discusses the role of SIRT1 in the pathogenesis of bronchial asthma. It also discusses the role of SIRT1 in inflammatory cells that play an important role in virus-induced asthma exacerbations. Recent studies have hypothesized that SIRT1 is one of major contributors to cellular senescence. SIRT1 levels decrease in Th2 and non-Th2-related airway inflammation, indicating the role of SIRT1 in several endotypes and phenotypes of asthma. Moreover, several models have demonstrated relationships between viral infection and SIRT1. Therefore, targeting SIRT1 is a novel strategy that may be effective for treating virus-induced asthma exacerbations in the future.

Sirtuins as endogenous regulators of lung fibrosis: A current perspective

Fibrotic lung diseases qualify among the most dreaded irreversible interstitial pulmonary complications with progressive yet largely unpredictable clinical course. Idiopathic pulmonary fibrosis (IPF) is the most challenging prototype characterized by unknown and complex molecular etiology, severe dearth of non-invasive therapeutic options and average lifespan of 2-5 years in patients post diagnosis. Lung fibrosis (LF) is a leading cause of death in the industrialized world with the propensity to contract, significantly increasing with age. Approximately 45% deaths in US are attributed to fibrotic diseases while around 7% respiratory disease-associated deaths, annually in UK, are actually attributed to IPF. Recent developments in the field of LF have unambiguously pointed towards the pivotal role of Sirtuins (SIRTs) in regulating disease progression, thereby qualifying as potential anti-fibrotic drug targets. These NAD⁺-dependent lysine deacetylases, deacylases and ADP-ribosyltransferases are evolutionarily conserved proteins, regulated by diverse metabolic/environmental factors and implicated in age-related degenerative and inflammatory disorders. While SIRT1, SIRT6 and SIRT7 are predominantly nuclear, SIRT3, SIRT4, SIRT5 are mainly mitochondrial and SIRT2 is majorly cytosolic with occasional nuclear translocation. SIRT1, SIRT3, SIRT6 and SIRT7 are documented as cytoprotective sirtuins implicated in cardiovascular, pulmonary and metabolic diseases including fibrosis; however functional roles of remaining sirtuins in pulmonary pathologies are yet elusive. Here, we provide a comprehensive recent update on the regulatory role of sirtuins on LF along with discussion on potential therapeutic modulation of endogenous Sirtuin expression through synthetic/plant-derived compounds which can help synthetic chemists and ethnopharmacologists to design new-generation cheap, non-toxic Sirtuin-based drugs against LF.

p300 in Cardiac Development and Accelerated Cardiac Aging

The heart is the first functional organ that develops during embryonic development. While a heartbeat indicates life, cessation of a heartbeat signals the end of life. Heart disease, due either to congenital defects or to acquired dysfunctions in adulthood, remains the leading cause of death worldwide. Epigenetics plays a key role in both embryonic heart development and heart disease in adults. Stress-induced vascular injury activates pathways involved in pathogenesis of accelerated cardiac aging that includes cellular dysfunction, pathological cardiac hypertrophy, diabetic cardiomyopathy, cardiac matrix remodeling, cardiac dysfunction and heart failure. Acetyltransferase p300 (p300), a major epigenetic regulator, plays a pivotal role in heart development during embryogenesis, as deficiency or abnormal expression of p300 leads to embryonic death at early gestation periods due to deformation of the heart and neural tube. Acetyltransferase p300 controls heart development through histone acetylation-mediated chromatin remodeling and transcriptional regulation of genes required for cardiac development. In adult hearts, p300 is differentially expressed in different chambers and epigenetically controls cardiac gene expression. Deregulation of p300, in response to prohypertrophic and profibrogenic stress signals, is associated with increased recruitment of p300 to several genes including transcription factors, increased acetylation of specific lysines in histones and transcription factors, altered chromatin organization, and increased hypertrophic and fibrogenic gene expression. Cardiac hypertrophy and myocardial fibrogenesis are common pathological manifestations of several stress-induced accelerated cardiac aging-related pathologies, including high blood pressure-induced or environmentally induced cardiac hypertrophy, myocardial infarction, diabetes-induced cardiomyopathy, and heart failure. Numerous studies using cellular and animal models clearly indicate that pharmacologic or genetic normalization of p300 activity has the potential to prevent or halt the progression of cardiac aging pathologies. Based on these preclinical studies, development of safe, non-toxic, small molecule inhibitors/epidrugs targeting p300 is an ideal approach to control accelerated cardiac aging-related deaths worldwide.

Dual role of sirtuin 1 in inflammatory bowel disease

Silent information regulator-1 (SIRT-1), is a member of the class III group of histone deacetylases and is collectively called sirtuins. There have been preclinical and clinical studies indicating the downregulation and decreased activity of sirtuin 1 in various inflammatory bowel disease models. Furthermore, the downregulation of sirtuin 1 is responsible for the sustained production of proinflammatory cytokines and the generation of oxidative stress in colitis. Hyperacetylation of NF-κB and HSF-1 (heat shock factor-1) in the absence of sirtuin1 is responsible for the induction of colitis. Accordingly, exogenous administration of sirtuin1 activators has been shown to attenuate the colitis in various inflammatory bowel disease models. On the other hand, the knockdown of sirtuin 1 gene or pharmacologic inhibition of sirtuin 1 has also been shown to be protective in the colitis. The deletion of the sirtuin1 gene may be helpful in the improvement of the disease condition of colitis through the maintenance of gastrointestinal immune homeostasis. The current review highlights the dual role of sirtuin 1 in the different experimental models of IBD along with possible mechanisms.

CMH-Small Molecule Docks into SIRT1, Elicits Human IPF-Lung Fibroblast Cell Death, Inhibits Ku70-deacetylation, FLIP and Experimental Pulmonary Fibrosis

Regenerative capacity in vital organs is limited by fibrosis propensity. Idiopathic pulmonary fibrosis (IPF), a progressive lung disease linked with aging, is a classic example. In this study, we show that in flow cytometry, immunoblots (IB) and in lung sections, FLIP levels can be regulated, in vivo and in vitro, through SIRT1 activity inhibition by CMH (4-(4-Chloro-2-methylphenoxy)-N-hydroxybutanamide), a small molecule that, as we determined here by structural biology calculations, docked into its nonhistone substrate Ku70-binding site. Ku70 immunoprecipitations and immunoblots confirmed our theory that Ku70-deacetylation, Ku70/FLIP complex, myofibroblast resistance to apoptosis, cell survival, and lung fibrosis in bleomycin-treated mice, are reduced and regulated by CMH. Thus, small molecules associated with SIRT1-mediated regulation of Ku70 deacetylation, affecting FLIP stabilization in fibrotic-lung myofibroblasts, may be a useful strategy, enabling tissue regeneration.

SIRT1 Deficiency, Specifically in Fibroblasts, Decreases Apoptosis Resistance and Is Associated with Resolution of Lung-Fibrosis

In contrast to normal regenerating tissue, resistance to Fas- and FasL-positive T cell-induced apoptosis were detected in myofibroblasts from fibrotic-lungs of humans and mice following bleomycin (BLM) exposure. In this study we show, decreased FLIP expression in lung-tissues with resolution of BLM-induced fibrosis and in isolated-lung fibroblasts, with decreased resistance to apoptosis. Using a FLIP-expression vector or a shFLIP-RNA, we further confirmed the critical need for FLIP to regain/lose susceptibility of fibrotic-lung myofibroblast to Fas-induced apoptosis. Our study further show that FLIP is regulated by SIRT1 (Sirtuin 1) deacetylase. Chimeric mice, with SIRT1-deficiency in deacetylase domain (H355Y-Sirt1^y/y), specifically in mesenchymal cells, were not only protected from BLM-induced lung fibrosis but, as assessed following Ku70 immunoprecipitation, had also decreased Ku70-deacetylation, decreasedKu70/FLIP complex, and decreased FLIP levels in their lung myofibroblasts. In addition, myofibroblasts isolated from lungs of BLM-treated miR34a-knockout mice, exposed to a miR34a mimic, which we found here to downregulate SIRT1 in the luciferase assay, had a decreased Ku70-deacetylation indicating decrease in SIRT1 activity. Thus, SIRT1 may mediate, miR34a-regulated, persistent FLIP levels by deacetylation of Ku70 in lung myofibroblasts, promoting resistance to cell-death and lung fibrosis.

Regulation of left atrial fibrosis induced by mitral regurgitation by SIRT1

SIRT1 (silent information regulator 1) is a histone deacetylase. It can sense the energy level in cells and delay cell senescence, leading to resistance to external stress and improving metabolism. Mitral regurgitation (MR) is a common disease in cardiac surgery. However, there are no previous studies on SIRT1 and left atrial fibrosis caused by MR. In this study, we aimed to explore the regulatory effect of SIRT1 on left atrial fibrosis induced by MR. We used Guizhou miniature pigs to establish an MR model and a sham operation model after anaesthesia induction and respiratory intubation, and these model animals were followed for 30 months after the surgery. The differential distribution and expression of SIRT1 and collagen I in the left atrium was determined by immunofluorescence and Western blotting. Furthermore, we treated NIH3T3 fibroblasts (CFs) with resveratrol and Angiotensin II (Ang II) to analyse the specific mechanism involved in the development of myocardial fibrosis. The results showed that the MR model was successfully constructed. There were 8 pigs in the MR group and 6 pigs in the control group. In both the animal experiments and the cell experiments, the expression of collagen I in the MR group was increased significantly compared to that in the control group, while the expression of SIRT1 was decreased.

Cellular Senescence as a Mechanism and Target in Chronic Lung Diseases

Cellular senescence is now considered an important driving mechanism for chronic lung diseases, particularly chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis. Cellular senescence is due to replicative and stress-related senescence with activation of p53 and p16^INK4a, respectively, leading to activation of p21^CIP1 and cell cycle arrest. Senescent cells secrete multiple inflammatory proteins known as the senescence-associated secretory phenotype, leading to low-grade chronic inflammation, which further drives senescence. Loss of key antiaging molecules sirtuin-1 and sirtuin-6 may be important in acceleration of aging and arises from oxidative stress reducing phosphatase PTEN (phosphatase tensin homolog), thereby activating PI3K (phosphoinositide-3-kinase) and mTOR (mammalian target of rapamycin). MicroRNA-34a (miR-34a), which is regulated by PI3K-mTOR signaling, plays a pivotal role in reducing sirtuin-1/6, and its inhibition with an antagomir results in their restoration, reducing markers of senescence, reducing senescence-associated secretory phenotype, and reversing cell cycle arrest in epithelial cells from peripheral airways of patients with COPD. miR-570 is also involved in reduction of sirtuin-1 and cellular senescence and is activated by p38 mitogen-activated protein kinase. These miRNAs may be released from cells in extracellular vesicles that are taken up by other cells, thereby spreading senescence locally within the lung but also outside the lung through the circulation; this may account for comorbidities of COPD and other lung diseases. Understanding the mechanisms of cellular senescence may result in new treatments for chronic lung disease, either by inhibiting PI3K-mTOR signaling, by inhibiting specific miRNAs, or by deletion of senescent cells with senolytic therapies, already shown to be effective in experimental lung fibrosis.

Sirt1 antisense long non-coding RNA attenuates pulmonary fibrosis through sirt1-mediated epithelial-mesenchymal transition

Long noncoding RNAs sirt1 antisense (sirt1 AS) was reported to play crucial roles in the progression of organ fibrosis. However, the roles of sirt1 AS in idiopathic pulmonary fibrosis (IPF) are still unknown. In addition, we have previously demonstrated that astragaloside IV (ASV), a bioactive saponin extract of the Astragalus root, significantly alleviates IPF by inhibiting transforming growth factor β1 (TGF-β1) induced epithelial-mesenchymal transition (EMT). Further investigations into the influence of ASV on lncRNAs expression will be helpful to delineate the complex regulatory networks underlying the biological function of ASV. Here, we found sirt1 AS expression was significantly decreased in BLM-induced pulmonary fibrosis. We further found that sirt1 AS effectively inhibited TGF-β1-meidated EMT in vitro and alleviated the progression of IPF in vivo. Mechanistically, sirt1 AS was validate to enhance the stability of sirt1 and increased sirt1 expression, thereby to inhibit EMT in IPF. Furthermore, we demonstrated that ASV treatment increased sirt1 AS expression and silencing of sirt1 AS impaired anti-fibrosis effects of ASV on IPF. Collectively, sirt1 AS was critical for ASV-mediated inhibition of IPF progression and targeting of sirt1 AS by ASV could be a potential therapeutic approach for IPF.

Mesenchymal Stem Cells Attenuate Diabetic Lung Fibrosis via Adjusting Sirt3-Mediated Stress Responses in Rats

Diabetes affects a variety of organs such as the kidneys, eyes, and liver, and there is increasing evidence that the lung is also one of the target organs of diabetes and imbalance of Sirt3-mediated stress responses such as inflammation, oxidative stress, apoptosis, autophagy, and ER stress may contribute to diabetic lung fibrosis. Although previous studies have reported that mesenchymal stem cells (MSCs) have beneficial effects on various diabetic complications, the effect and mechanisms of MSCs on diabetes-induced lung injury are not clear. In this study, the STZ-induced diabetes model was constructed in rats, and the effect and potential mechanisms of bone marrow MSCs on diabetic lung fibrosis were investigated. The results revealed that fibrotic changes in the lung were successfully induced in the diabetic rats, while MSCs significantly inhibited or even reversed the changes. Specifically, MSCs upregulated the expression levels of Sirt3 and SOD2 and then activated the Nrf2/ARE signaling pathway, thereby controlling MDA, GSH content, and iNOS and NADPH oxidase subunit p22phox expression levels in the lung tissue. Meanwhile, high levels of Sirt3 and SOD2 induced by MSCs reduced the expression levels of IL-1β, TNF-α, ICAM-1, and MMP9 by suppressing the NF-κB/HMGB1/NLRP3/caspase-1 signaling pathway, as well as regulating the expression levels of cleaved caspasese-3, Bax, and Bcl2 by upregulating the expression level of P-Akt, thereby inhibiting the apoptosis of the lung tissue. In addition, MSCs also regulated the expression levels of LC3, P62, BiP, Chop, and PERK, thereby enhancing autophagy and attenuating endoplasmic reticulum stress. Taken together, our results suggest that MSCs effectively attenuate diabetic lung fibrosis via adjusting Sirt3-mediated responses, including inflammation, oxidative stress, apoptosis, autophagy, and endoplasmic reticulum stress, providing a theoretical foundation for further exploration of MSC-based diabetic therapeutics.

Mitochondrial dysfunction and chronic lung disease

The functions of body gradually decrease as the age increases, leading to a higher frequency of incidence of age-related diseases. Diseases associated with aging in the respiratory system include chronic obstructive pulmonary disease (COPD), IPF (idiopathic pulmonary fibrosis), asthma, lung cancer, and so on. The mitochondrial dysfunction is not only a sign of aging, but also is a disease trigger. This article aims to explain mitochondrial dysfunction as an aging marker, and its role in aging diseases of lung. We also discuss whether the mitochondria can be used as a target for the treatment of aging lung disease.

Inactivation of nuclear histone deacetylases by EP300 disrupts the MiCEE complex in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and highly lethal lung disease with unknown etiology and poor prognosis. IPF patients die within 2 years after diagnosis mostly due to respiratory failure. Current treatments against IPF aim to ameliorate patient symptoms and to delay disease progression. Unfortunately, therapies targeting the causes of or reverting IPF have not yet been developed. Here we show that reduced levels of miRNA lethal 7d (MIRLET7D) in IPF compromise epigenetic gene silencing mediated by the ribonucleoprotein complex MiCEE. In addition, we find that hyperactive EP300 reduces nuclear HDAC activity and interferes with MiCEE function in IPF. Remarkably, EP300 inhibition reduces fibrotic hallmarks of in vitro (patient-derived primary fibroblast), in vivo (bleomycin mouse model), and ex vivo (precision-cut lung slices, PCLS) IPF models. Our work provides the molecular basis for therapies against IPF using EP300 inhibition.

Idiopathic pulmonary fibrosis (IPF) is a lethal disease with insufficient treatment strategies. Here the authors show that reduction of the microRNA MIRLET7D and hyperactivation of EP300 contribute to impaired epigenetic silencing by the MiCEE complex in pulmonary fibroblasts of IPF patients, and demonstrate the benefit of inhibiting EP300 for the treatment of IPF.

Targeting anti-aging protein sirtuin (Sirt) in the diagnosis of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a severe, incurable, age-associated respiratory disorder that has gained significance because of its unknown etiology and lack of therapeutic approaches. IPF causes maximum damage to the alveolar epithelial cells, thereby leading to lung remodeling and initiating epithelial to mesenchymal transition (EMT). The actual molecular mechanisms underlying IPF still remain unclear, and knowledge about these mechanisms would be helpful in its diagnosis. Sirtuins (Sirt) are class of NAD+-dependent proteins, widely known to exert positive and protective effects on age-related diseases such as diabetes, cancer, and so on, and are also involved in regulating IPF. The sirtuin family comprises of seven members (Sirt1 to Sirt7), out of which Sirt1, Sirt3, Sirt6, and Sirt7 exert positive effects on IPF. Sirt1 is associated with aging and inhibits cellular senescence and fibrosis. Sirt1 is well recognized in controlling pulmonary fibrosis and is also considered as a prime positive mediator of EMT. The expressions of Sirt3 protein tend to decline in IPF patients; hence it is known as an anti-fibrotic protein. Sirt6 indeed has been proven to reduce EMT during IPF. Decreased levels of Sirt7 during IPF regulate lung fibroblasts. Hence, active levels of Sirt1, Sirt3, Sirt6, and Sirt7 can be attractive target models to elucidate a novel potential therapeutic approach for IPF. In this prospect, we have discussed the role of Sirtuins in pulmonary fibrosis by exploring the recent research evidence that highlight the role of sirtuins and also describes their protective effects.

Nicotinamide riboside protects against liver fibrosis induced by CCl4 via regulating the acetylation of Smads signaling pathway

AIMS

Increasing nicotinamide adenine dinucleotide (NAD⁺) by Nicotinamide riboside (NR) provides protective benefits in multiple disorders. However, the role of NR on liver fibrosis is unclear. We performed in vivo and in vitro experiments to test the hepatic protective effects of NR against liver fibrosis and the underlying mechanisms.

MATERIALS AND METHODS

Mice were injected with CCl₄ to establish liver fibrosis model. NR was given by gavage to explore the hepatic protection of NR. LX-2 cells were given a TGF-β stimulation ± NR, the activation of LX-2 cells and the acetylation of Smads were analyzed. To further confirm the role of Sirt1 on the protective pathway of NR, we knockdown Sirt1 in LX-2 cells.

KEY FINDINGS

We found NR could prevent liver fibrosis and reverse the existing liver fibrosis. NR inhibited the activation of LX-2 cells induced by TGF-β, activated Sirt1 and deacetylated Smad2/3. Sirt1 knockdown diminished the inhibiting effect of NR on LX-2 cells activation, and increased expressions of acetylated Smads. In conclusion, NR could prevent liver fibrosis via suppressing activation of hepatic stellate cells (HSCs). This protective effect was mediated by regulating the acetylation of Smads signaling pathway.

SIGNIFICANCE

NR protected mice against liver fibrosis induced by CCl₄. NR suppressed activation of hepatic stellate cells induced by TGF-β. NR protects liver fibrosis via increasing the activity of Sirt1 and decreasing the expression of P300, resulting in the deacetylation of Smads in stellate cells.

The Role of Epigenetic Modifications in Systemic Sclerosis: A Druggable Target

Systemic sclerosis (SSc) is a rare autoimmune disorder characterised by skin fibrosis that often also affects internal organs, eventually resulting in mortality. Although management of the symptoms has extended lifespan, patients still suffer from poor quality of life, hence the need for improved therapies. Development of efficacious treatments has been stymied by the unknown aetiology, although recent advancements suggest a potentially key role for epigenetics - the regulation of gene expression by noncoding RNAs and chemical modifications to DNA or DNA-associated proteins. Herein, the evidence implicating epigenetics in the pathogenesis of SSc is discussed with an emphasis on the therapeutic potential this introduces to the field - particularly the repurposing of epigenetic targeting cancer therapeutics and newly emerging miRNA-based strategies.