Sirtuin 6 inhibits MWCNTs-induced epithelial-mesenchymal transition in human bronchial epithelial cells via inactivating TGF-β1/Smad2 signaling pathway

Autophagy aggravates multi-walled carbon nanotube-induced ferroptosis by suppressing PGC-1 dependent-mitochondrial biogenesis in lung epithelial cells

Multi-walled carbon nanotube (MWCNT) induced respiratory toxicity has become a growing concern, with ferroptosis emerging as a novel mechanism implicated in various respiratory diseases. However, whether ferroptosis is involved in MWCNT-elicited lung injury and the underlying molecular mechanisms warrant further exploration. In this study, we found that MWCNT-induced ferroptosis is autophagy-dependent, contributing to its cellular toxicity. Inhibiting of autophagy by pharmacological inhibitors 3-MA or ATG5 gene knockdown significantly attenuated MWCNT-induced ferroptosis, concomitant with rescued mitochondrial biogenesis. Rapamycin, the autophagy agonist, exacerbated the mitochondrial damage and MWCNT-induced ferroptosis. Moreover, lentivirus-mediated overexpression of PGC-1α inhibited ferroptosis, while inhibition of PGC-1α aggravated ferroptosis. In summary, our study unveils ferroptosis as a novel mechanism underlying MWCNT-induced respiratory toxicity, with autophagy promoting MWCNT-induced ferroptosis by hindering PGC-1α-dependent mitochondrial biogenesis.

Lung Toxicity and Molecular Mechanisms of Lead-Based Perovskite Nanoparticles in the Respiratory System

Lead-based perovskite nanoparticles (Pb-PNPs) have found extensive applications across diverse fields. However, because of poor stability and relatively strong water solubility, the potential toxicity of Pb-PNPs released into the environment during their manufacture, usage, and disposal has attracted significant attention. Inhalation is a primary route through which human exposure to Pb-PNPs occurs. Herein, the toxic effects and underlying molecular mechanisms of Pb-PNPs in the respiratory system are investigated. The in vitro cytotoxicity of CsPbBr3 nanoparticles in BEAS-2B cells is studied using multiple bioassays and electron microscopy. CsPbBr3 nanoparticles of different concentrations induce excessive oxidative stress and cell apoptosis. Furthermore, CsPbBr3 nanoparticles specifically recruit the TGF-β1, which subsequently induces epithelial-mesenchymal transition. In addition, the biodistribution and lung toxicity of representative CsPbBr3 nanoparticles in ICR mice are investigated following intranasal administration. These findings indicate that CsPbBr3 nanoparticles significantly induce pulmonary inflammation and epithelial-mesenchymal transition and can even lead to pulmonary fibrosis in mouse models. Above findings expose the adverse effects and molecular mechanisms of Pb-PNPs in the lung, which broadens the safety data of Pb-PNPs.

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.

Spatial distribution, sources and health risk assessment of heavy metals in topsoil around oil and natural gas drilling sites, Andhra Pradesh, India

Soils are usually the interface between human activity and environmental components that must be conserved and protected. As a result of rising industrialization and urbanization, activities such as exploration and extraction operations lead to the release of heavy metals into the environment. This study presents distribution of six heavy metals (As, Cr, Cu, Ni, Pb and Zn) in 139 top soil samples collected in and around oil and natural gas drilling sites at a sampling density of 1 site/12 km2. The results indicated the concentration ranged from 0.1 to 16 mg/kg for As, 3-707 mg/kg for Cr, 7-2324 mg/kg for Cu, 14-234 mg/kg for Ni, 9-1664 mg/kg for Pb, and 60-962 mg/kg for Zn. The contamination of soil was estimated on the basis of Index of geo accumulation (Igeo), enrichment factor (Ef), and contamination factor (Cf). Further, spatial distribution pattern maps indicated that the pollution levels for Cu, Cr, Zn, and Ni were higher around drilling sites of the study area relative to other regions. Using exposure factors for the local population and references from the USEPA's integrated database, potential ecological risk indices (PERI) and health risk assessments were made. The hazard index (HI) values of Pb (in adults) and Cr, Pb (in children) exceeded the recommended limit of HI = 1, indicating the non-carcinogenic risks. Total carcinogenic risk (TCR) calculations revealed Cr (in adults) and As, Cr (in children) levels in soils exceeded the threshold value of 1.0E - 04, indicating significant carcinogenic risk due to high metal concentrations in the study area. These results may assist in determining the soil's present state and its effect due to extraction strategies used during drilling process and initiate few remedial techniques, particularly for proper management strategies in farming activities to decrease point and non-point source of contamination.

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.

Insights into the antioxidative mechanisms of melatonin in ameliorating chromium-induced oxidative stress-mediated hepatic and renal tissue injuries in male Wistar rats

Chromium (Cr), a hazardous heavy metal, is toxic to human health and the environment. Severe detrimental effects of Cr on different physiological systems involve oxidative stress. In the current study, sodium dichromate di-hydrate was subcutaneously injected to male Wistar rats at a dose of 5 mg/kg b.w. and experimented up to 14 days to induce alterations in hepatic and renal tissues. Another group of rats was pre-treated with melatonin at three different doses (5, 10, and 20 mg/kg b.w.; orally) and 20 mg/kg b.w. dose was evidenced to provide maximal protection against Cr-induced alterations. The study demonstrated that melatonin efficiently preserved body weight, organ weight, intracellular antioxidant enzymes, and tissue morphology. Furthermore, melatonin was also found to protect organ damage markers, oxidative stress-biomarkers, activities of pro-oxidant enzymes, levels of reactive oxygen species (ROS), nitric oxide (NO), and collagen content through its antioxidative mechanisms. Moreover, melatonin effectively decreased tissue Cr content through its metal-chelating activity. Hence, the present study has established melatonin as a promising antioxidant for conserving the liver and kidney tissues from Cr-induced oxidative damage thereby strengthening the notion that this small indoleamine can act as a future therapeutic against Cr-induced oxidative stress-mediated tissue damage.

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.

The Promising Therapeutic Approaches for Radiation-Induced Pulmonary Fibrosis: Targeting Radiation-Induced Mesenchymal Transition of Alveolar Type II Epithelial Cells

Radiation-induced pulmonary fibrosis (RIPF) is a common consequence of radiation for thoracic tumors, and is accompanied by gradual and irreversible organ failure. This severely reduces the survival rate of cancer patients, due to the serious side effects and lack of clinically effective drugs and methods. Radiation-induced pulmonary fibrosis is a dynamic process involving many complicated and varied mechanisms, of which alveolar type II epithelial (AT2) cells are one of the primary target cells, and the epithelial-mesenchymal transition (EMT) of AT2 cells is very relevant in the clinical search for effective targets. Therefore, this review summarizes several important signaling pathways that can induce EMT in AT2 cells, and searches for molecular targets with potential effects on RIPF among them, in order to provide effective therapeutic tools for the clinical prevention and treatment of RIPF.

SIRT6 overexpression retards renal interstitial fibrosis through targeting HIPK2 in chronic kidney disease

Introduction: Renal interstitial fibrosis is a common pathophysiological change in the chronic kidney disease (CKD). Nicotinamide adenine dinucleotide (NAD)-dependent deacetylase sirtuin 6 (SIRT6) is demonstrated to protect against kidney injury. Vitamin B3 is the mostly used form of NAD precursors. However, the role of SIRT6 overexpression in renal interstitial fibrosis of CKD and the association between dietary vitamin B3 intake and renal function remain to be elucidated.

Methods: Wild-type (WT) and SIRT6-transgene (SIRT6-Tg) mice were given with high-adenine diets to establish CKD model. HK2 cells were exposed to transforming growth factor β1 (TGF-β1) in vitro to explore related mechanism. Population data from Multi-Ethnic Study of Atherosclerosis (MESA) was used to examine the association between dietary vitamin B3 intake and renal function decline.

Results: Compared to WT mice, SIRT6-Tg mice exhibited alleviated renal interstitial fibrosis as evidenced by reduced collagen deposit, collagen I and α-smooth muscle actin expression. Renal function was also improved in SIRT6-Tg mice. Homeodomain interacting protein kinase 2 (HIPK2) was induced during the fibrogenesis in CKD, while HIPK2 was downregulated after SIRT6 overexpression. Further assay in vitro confirmed that SIRT6 depletion exacerbated epithelial-to-mesenchymal transition of HK2 cells, which might be linked with HIPK2 upregulation. HIPK2 was inhibited by SIRT6 in the post-transcriptional level. Population study indicated that higher dietary vitamin B3 intake was independently correlated with a lower risk of estimate glomerular filtration rate decline in those ≥65 years old during follow-up.

Conclusion: SIRT6/HIPK2 axis serves as a promising target of renal interstitial fibrosis in CKD. Dietary vitamin B3 intake is beneficial for renal function in the old people.

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.

Epigenetic regulation in radiation-induced pulmonary fibrosis

PURPOSE

Radiation-induced pulmonary fibrosis (RIPF) is a common and serious adverse effect of radiotherapy for thoracic tumors, which occurs in the irreversible stage of radiation-induced lung injury (RILI) >6 months after irradiation. It is characterized by progressive and irreversible destruction of lung tissue and deterioration of lung function, which may impair quality of life and lead to respiratory failure and death. We hope this will draw attention to the involvement of epigenetics in the regulation of RIPF.

CONCLUSIONS

This review summarizes research progress on the role and mechanism of DNA methylation, noncoding RNA and RNA methylation in RIPF or RILI, and the possible role and mechanism of histone modification in RIPF. We have noticed that in tissue fibrosis, the epigenetic regulation mechanisms inside and outside the nucleus can influence each other. We speculate that RIPF may be regulated by an epigenetic regulatory network during its development, and believe that TGF-β, SNAIL, PTEN and EZH2 are four targets worthy of in-depth study.

Association of sirtuins (SIRT1-7) with lung and intestinal diseases

"Exterior-interior correlation between the lung and large intestine" is one of the important contents of traditional Chinese medicine. This theory describes the role of the lung and the intestine in association with disease treatment. The "lung-gut" axis is a modern extension of the "exterior-interior correlation between lung and large intestine" theory in TCM. Sirtuin (SIRT) is a nicotinamide adenine dinucleotide (NAD⁺)-dependent enzyme family with deacetylase properties, which is highly conserved from bacteria to humans. The sirtuin defines seven silencing regulatory proteins (SIRT1-7) in human cells. It can regulate aging, metabolism, and certain diseases. Current studies have shown that sirtuins have dual characteristics, acting as both tumor promoters and tumor inhibitors in cancers. This paper provides a comparative summary of the roles of SIRT1-7 in the intestine and lung (both inflammatory diseases and tumors), and the promoter/suppressor effects of targeting SIRT family microRNAs and modulators of inflammation or tumors. Sirtuins have great potential as drug targets for the treatment of intestinal and respiratory diseases. Meanwhile, it may provide new ideas of future drug target research.

Circ-SHPRH suppresses cadmium-induced transformation of human bronchial epithelial cells by regulating QKI expression via miR-224-5p

Circular RNAs (circRNAs) have been demonstrated to play critical roles in the pathogenesis of human cancers and carcinogenesis of several environmental pollutants. Nevertheless, the function of circRNAs in cadmium carcinogenesis is unclear. circ-SHPRH is down-regulated in many cancers including non-small cell lung cancer. In our present study, during cadmium-induced transformation of human bronchial epithelial BEAS-2B cells, epithelial-mesenchymal transition (EMT) was induced. Meanwhile, at the middle and late stages of cell transformation, cadmium down-regulated the expression of circ-SHPRH, as well as QKI, a tumor suppressor protein known to prevent the proliferation and EMT during progression of human cancers, compared with passage-matched control BEAS-2B cells. Overexpression of circ-SHPRH in cadmium-transformed BEAS-2B cells promoted the expression of QKI and significantly inhibited proliferation, EMT, invasion, migration and anchorage-independent growth in soft agar of the cells. Mechanistic studies showed that circ-SHPRH functioned as a sponge of miR-224-5p to regulate QKI expression. Interestingly, QKI and circ-SHPRH could form a positive-feedback loop that perpetuated circ-SHPRH/miR-224-5p/QKI axis. Collectively, our results demonstrated that circ-SHPRH inhibited cadmium-induced transformation of BEAS-2B cells through sponging miR-224-5p to regulate QKI expression under cadmium treatment. Our study uncovered a novel molecular mechanism involved in circRNAs in the development of lung cancer due to cadmium exposure.

ALKBH5 promotes cadmium-induced transformation of human bronchial epithelial cells by regulating PTEN expression in an m6A-dependent manner

Cadmium is a carcinogenic heavy metal that poses a severe threat to human beings. The underlying mechanism, however, remains elusive. N6-methyladenosine (m6A) is the most abundant post-transcriptional modification in mRNA that regulates RNA metabolism. Emerging evidence shows that m6A is involved in the pathogenesis of various cancers. In this study, human bronchial epithelial BEAS-2B cells were transformed by exposing to 2 μM of cadmium for 20 weeks to investigate the role of m6A in cadmium carcinogenesis. We found the level of m6A in mRNA was significantly decreased in cadmium-transformed BEAS-2B cells, and this change was regulated by m6A demethylase ALKBH5. ALKBH5 was significantly upregulated in the middle and late stages of cell transformation at week 8, 12, 16 and 20. Knockdown of ALKBH5 in cadmium-transformed cells alleviated cell proliferation, migration, invasion, and anchorage-independent growth, but co-transfection with ALKBH5 siRNA and PTEN siRNA restored the inhibitory effects of ALKBH5 knockdown on those transformation properties. ALKBH5 decreased the m6A level of PTEN mRNA, resulting in its instability and reduction of PTEN protein expression. These results indicate that ALKBH5-mediated demethylation m6A at PTEN mRNA is involved in cadmium-induced cell transformation. Our study provides a new perspective for the involvement of m6A modification in cadmium carcinogenesis.

FOXO3a Protects against Kidney Injury in Type II Diabetic Nephropathy by Promoting Sirt6 Expression and Inhibiting Smad3 Acetylation

Diabetic nephropathy (DN) is the most common cause of end-stage renal disease. Although numerous reports have demonstrated a correlation between epithelial-mesenchymal transition (EMT) and renal fibrosis, how these processes lead to tubular dysfunction remains unclear. Here, we show that FOXO3a protects kidneys from injury in type II DN by increasing Sirt6 expression, which deacetylates Smad3 and inhibits its transcriptional activity. The results showed that progressive EMT in the kidneys from db/db mice is associated with Sirt6 downregulation and involved in tubular injury and dysfunction. The reduction of Sirt6 levels in db/db mice resulted in progressive kidney injury, indicating the protective role of Sirt6. Furthermore, Sirt6 was shown to directly bind to Smad3, a key downstream mediator of TGF-β, and could deacetylate it to inhibit its nuclear accumulation and transcriptional activity in HK2 cells. Besides, we demonstrate that FOXO3a activates Sirt6 expression by binding to its promoter. shRNA-induced FOXO3a knockdown in the kidneys of db/db mice exacerbated tubular injury and renal function loss. Mechanistically, FOXO3a protects against kidney injury in type II DN through the Sirt6/Smad3 axis. Thus, the pharmacological targeting of FOXO3a-mediated Sirt6/Smad3 signaling pathways may provide a novel strategy for treating type II DN.

Understanding the Function of Mammalian Sirtuins and Protein Lysine Acylation

Protein lysine acetylation is an important posttranslational modification that regulates numerous biological processes. Targeting lysine acetylation regulatory factors, such as acetyltransferases, deacetylases, and acetyl-lysine recognition domains, has been shown to have potential for treating human diseases, including cancer and neurological diseases. Over the past decade, many other acyl-lysine modifications, such as succinylation, crotonylation, and long-chain fatty acylation, have also been investigated and shown to have interesting biological functions. Here, we provide an overview of the functions of different acyl-lysine modifications in mammals. We focus on lysine acetylation as it is well characterized, and principles learned from acetylation are useful for understanding the functions of other lysine acylations. We pay special attention to the sirtuins, given that the study of sirtuins has provided a great deal of information about the functions of lysine acylation. We emphasize the regulation of sirtuins to illustrate that their regulation enables cells to respond to various signals and stresses.

Andrographolide attenuates epithelial-mesenchymal transition induced by TGF-β1 in alveolar epithelial cells

Andrographolide (Andro), a component from Chinese medicinal herb Andrographis paniculata, could alleviate pulmonary fibrosis in rodents. Yet, whether and how Andro mitigates epithelial-mesenchymal transition (EMT) induced by TGF-β1 remain unknown. This study aimed to explore the effect of Andro on TGF-β1-induced EMT in human alveolar epithelial cells (AECs) and the mechanisms involved. We illustrated that Andro inhibited TGF-β1-induced EMT and EMT-related transcription factors in alveolar epithelial A549 cells. Andro also reduced TGF-β1-induced cell migration and synthesis of pro-fibrotic factors (ie CCN-2, TGF-β1), matrix metalloproteinases (ie MMP-2, MMP-9) and extracellular matrix (ECM) components (ie collagen 1), implying the inhibiting effect of Andro on TGF-β1-induced EMT-like cell behaviours. Mechanistically, Andro treatment not only repressed TGF-β1-induced Smad2/3 phosphorylation and Smad4 nuclear translocation, but also suppressed TGF-β1-induced Erk1/2 phosphorylation and nuclear translocation in A549 cells. And treatment with ALK5 inhibitor (SB431542) or Erk1/2 inhibitors (SCH772984 and PD98059) remarkably reduced EMT evoked by TGF-β1. In addition, Andro also reduced TGF-β1-induced intracellular ROS generation and NOX4 expression, and elevated antioxidant superoxide dismutase 2 (SOD2) expression, demonstrating the inhibiting effect of Andro on TGF-β1-induced oxidative stress, which is closely linked to EMT. Furthermore, Andro remarkably attenuated TGF-β1-induced down-regulation of sirtuin1 (Sirt1) and forkhead box O3 (FOXO3), implying that Andro protects AECs from EMT partially by activating Sirt1/FOXO3-mediated anti-oxidative stress pathway. In conclusion, Andro represses TGF-β1-induced EMT in AECs by suppressing Smad2/3 and Erk1/2 signalling pathways and is also closely linked to the activation of sirt1/FOXO3-mediated anti-oxidative stress pathway.