Disruption of Sirtuin 1-Mediated Control of Circadian Molecular Clock and Inflammation in Chronic Obstructive Pulmonary Disease

SIRT1: An Intermediator of Key Pathways Regulating Pulmonary Diseases

Silent information regulator type-1 (SIRT1), a nicotinamide adenine dinucleotide+-dependent deacetylase, is a member of the sirtuins family and has unique protein deacetylase activity. SIRT1 participates in physiological as well as pathophysiological processes by targeting a wide range of protein substrates and signalings. In this review, we described the latest progress of SIRT1 in pulmonary diseases. We have introduced the basic information and summarized the prominent role of SIRT1 in several lung diseases, such as acute lung injury, acute respiratory distress syndrome, chronic obstructive pulmonary disease, lung cancer, and aging-related diseases.

Telomerase: a nexus between cancer nanotherapy and circadian rhythm

Cancer represents a complex disease category defined by the unregulated proliferation and dissemination of anomalous cells within the human body. According to the GLOBOCAN 2020 report, the year 2020 witnessed the diagnosis of approximately 19.3 million new cases of cancer and 10.0 million individuals succumbed to the disease. A typical cell eventually becomes cancerous because of a long-term buildup of genetic instability and replicative immortality. Telomerase is a crucial regulator of cancer progression as it induces replicative immortality. In cancer cells, telomerase inhibits apoptosis by elongating the length of the telomeric region, which usually protects the genome from shortening. Many nanoparticles are documented as being available for detecting the presence of telomerase, and many were used as delivery systems to transport drugs. Furthermore, telomere homeostasis is regulated by the circadian time-keeping machinery, leading to 24-hour rhythms in telomerase activity and TERT mRNA expression in mammals. This review provides a comprehensive discussion of various kinds of nanoparticles used in telomerase detection, inhibition, and multiple drug-related pathways, as well as enlightens an imperative association between circadian rhythm and telomerase activity from the perspective of nanoparticle-based anticancer therapeutics.

Analysis of Key Genes and miRNA-mRNA Networks Associated with Glucocorticoids Treatment in Chronic Obstructive Pulmonary Disease

Background

Some patients with chronic obstructive pulmonary disease (COPD) benefit from glucocorticoid (GC) treatment, but its mechanism is unclear.

Objective

With the help of the Gene Expression Omnibus (GEO) database, the key genes and miRNA-mRNA related to the treatment of COPD by GCs were discussed, and the potential mechanism was explained.

Methods

The miRNA microarray dataset (GSE76774) and mRNA microarray dataset (GSE36221) were downloaded, and differential expression analysis were performed. Gene Ontology (GO) function and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed on the differentially expressed genes (DEGs). The protein interaction network of the DEGs in the regulatory network was constructed with the STRING database, and the key genes were screened through Cytoscape. Potential downstream target genes regulated by differentially expressed miRNAs (DEMs) were predicted by the miRWalk3.0 database, and miRNA-mRNA regulatory networks were constructed. Finally, some research results were validated.

Results

① Four DEMs and 83 DEGs were screened; ② GO and KEGG enrichment analysis mainly focused on the PI3K/Akt signalling pathway, ECM receptor interaction, etc.; ③ CD2, SLAMF7, etc. may be the key targets of GC in the treatment of COPD; ④ 18 intersection genes were predicted by the mirwalk 3.0 database, and 9 pairs of miRNA-mRNA regulatory networks were identified; ⑤ The expression of miR-320d-2 and TFCP2L1 were upregulated by dexamethasone in the COPD cell model, while the expression of miR-181a-2-3p and SLAMF7 were downregulated.

Conclusion

In COPD, GC may mediate the expression of the PI3K/Akt signalling pathway through miR-181a-2-3p, miR-320d-2, miR-650, and miR-155-5p, targeting its downstream signal factors. The research results provide new ideas for RNA therapy strategies of COPD, and also lay a foundation for further research.

Hypoxia Induces Alterations in the Circadian Rhythm in Patients with Chronic Respiratory Diseases

The function of the circadian cycle is to determine the natural 24 h biological rhythm, which includes physiological, metabolic, and hormonal changes that occur daily in the body. This cycle is controlled by an internal biological clock that is present in the body's tissues and helps regulate various processes such as sleeping, eating, and others. Interestingly, animal models have provided enough evidence to assume that the alteration in the circadian system leads to the appearance of numerous diseases. Alterations in breathing patterns in lung diseases can modify oxygenation and the circadian cycles; however, the response mechanisms to hypoxia and their relationship with the clock genes are not fully understood. Hypoxia is a condition in which the lack of adequate oxygenation promotes adaptation mechanisms and is related to several genes that regulate the circadian cycles, the latter because hypoxia alters the production of melatonin and brain physiology. Additionally, the lack of oxygen alters the expression of clock genes, leading to an alteration in the regularity and precision of the circadian cycle. In this sense, hypoxia is a hallmark of a wide variety of lung diseases. In the present work, we intended to review the functional repercussions of hypoxia in the presence of asthma, chronic obstructive sleep apnea, lung cancer, idiopathic pulmonary fibrosis, obstructive sleep apnea, influenza, and COVID-19 and its repercussions on the circadian cycles.

Acute and Repeated Ozone Exposures Differentially Affect Circadian Clock Gene Expression in Mice

Circadian rhythms have an established role in regulating physiological processes, such as inflammation, immunity, and metabolism. Ozone, a common environmental pollutant with strong oxidative potential, is implicated in lung inflammation/injury in asthmatics. However, whether O3 exposure affects the expression of circadian clock genes in the lungs is not known. In this study, changes in the expression of core clock genes are analyzed in the lungs of adult female and male mice exposed to filtered air (FA) or O3 using qRT-PCR. The findings are confirmed using an existing RNA-sequencing dataset from repeated FA- and O3 -exposed mouse lungs and validated by qRT-PCR. Acute O3 exposure significantly alters the expression of clock genes in the lungs of females (Per1, Cry1, and Rora) and males (Per1). RNA-seq data revealing sex-based differences in clock gene expression in the airway of males (decreased Nr1d1/Rev-erbα) and females (increased Skp1), parenchyma of females and males (decreased Nr1d1 and Fbxl3 and increased Bhlhe40 and Skp1), and alveolar macrophages of males (decreased Arntl/Bmal1, Per1, Per2, Prkab1, and Prkab2) and females (increased Cry2, Per1, Per2, Csnk1d, Csnk1e, Prkab2, and Fbxl3). These findings suggest that lung inflammation caused by O3 exposure affects clock genes which may regulate key signaling pathways.

Targeting Rev-Erbα to protect against ischemia-reperfusion-induced acute lung injury in rats

BACKGROUND

The dysregulation of local circadian clock has been implicated in the pathogenesis of a broad spectrum of diseases. However, the pathophysiological role of intrinsic circadian clocks Rev-Erbα in ischemia-reperfusion (IR)-induced acute lung injury (ALI) remains unclear.

METHODS

The IR-ALI model was established by subjecting isolated perfused rat lungs to 40 min of ischemia followed by 60 min of reperfusion. Rats were randomly assigned to one of six groups: control, control + SR9009 (Rev-Erbα agonist, 50 mg/kg), IR, and IR + SR9009 at one of three dosages (12.5, 25, 50 mg/kg). Bronchoalveolar lavage fluids (BALF) and lung tissues were obtained and analyzed. In vitro experiments utilized mouse lung epithelial cells (MLE-12) exposed to hypoxia-reoxygenation (HR) and pretreated with SR9009 (10 µM/L) and Rev-Erbα siRNA.

RESULTS

SR9009 exhibited a dose-dependent reduction in lung edema in IR-ALI. It significantly inhibited the production of TNF-α, IL-6, and CINC-1 in BALF. Moreover, SR9009 treatment restored suppressed IκB-α levels and reduced nuclear NF-κB p65 levels in lung tissues. In addition, a SR9009 mitigated IR-induced apoptosis and mitogen-activated protein kinase (MAPK) activation in injured lung tissue. Finally, treatment with Rev-Erbα antagonist SR8278 abolished the protective action of SR9009. In vitro analyses showed that SR9009 attenuated NF-κB activation and KC/CXCL-1 levels in MLE-12 cells exposed to HR, and these effects were significantly abrogated by Rev-Erbα siRNA.

CONCLUSIONS

The findings suggest that SR9009 exerts protective effects against IR-ALI in a Rev-Erbα-dependent manner. SR9009 may provide a novel adjuvant therapeutic approach for IR-ALI.

Involvement of the SIRT1-NLRP3 pathway in the inflammatory response

The silent information regulator 2 homolog 1-NACHT, LRR and PYD domains-containing protein 3 (SIRT1-NLRP3) pathway has a crucial role in regulation of the inflammatory response, and is closely related to the occurrence and development of several inflammation-related diseases. NLRP3 is activated to produce the NLRP3 inflammasome, which leads to activation of caspase-1 and cleavage of pro-interleukin (IL)-1β and pro-IL-18 to their active forms: IL-1β and IL-18, respectively. They are proinflammatory cytokines which then cause an inflammatory response.SIRT1 can inhibit this inflammatory response through nuclear factor erythroid 2-related factor 2 and nuclear factor-kappa B pathways. This review article focuses mainly on how the SIRT1-NLRP3 pathway influences the inflammatory response and its relationship with melatonin, traumatic brain injury, neuroinflammation, depression, atherosclerosis, and liver damage. Video Abstract.

Association of rest-activity circadian rhythm with chronic respiratory diseases, a cross-section survey from NHANES 2011-2014

OBJECTIVE

A growing number of studies have examined the 24-h rest-activity characteristics in relation to health outcomes. Up to now, few studies have paid attention to the role of rest-activity circadian rhythm in chronic respiratory diseases (CRDs); therefore, to fill this gap, our study innovatively explored the association of rest-activity circadian rhythm indices with CRDs.

METHODS

A total of 7412 participants from the National Health and Nutrition Examination Survey (NHANES) 2011-2014 were included in this study. The rest-activity circadian rhythm indices were calculated using accelerometer data and were divided into quartiles to perform logistic regression.

RESULTS

Participants in the highest quartile of Relative amplitude (RA) had a lower prevalence of emphysema, chronic bronchitis and asthma, compared to those in the lowest quartile. Participants in the highest quartile of Intradaily variability (IV) was associated with a higher prevalence of emphysema relative to those in the lowest quartile. Compared to those in the lowest quartile, participants in the highest quartile of the average activity of the most active continuous 10-h period (M10) had a lower prevalence of emphysema. Additionally, compared to those in the lowest quartile of the average activity of the least active continuous 5-h period (L5) and L5 start time, participants in the highest quartile had a higher prevalence of asthma.

CONCLUSIONS

This study demonstrated that in general US adult population, disrupted rest-activity circadian rhythm was associated with a higher prevalence of CRDs.

Current Perspective on the Role of the Circadian Clock and Extracellular Matrix in Chronic Lung Diseases

The circadian clock is a biochemical oscillator that rhythmically regulates physiological and behavioral processes such as inflammation, immunity, and metabolism in mammals. Circadian clock disruption is a key driver for chronic inflammatory as well as fibrotic lung diseases. While the mechanism of circadian clock regulation in the lung has been minimally explored, some evidence suggests that the transforming growth factor β (TGFβ) signaling pathway and subsequent extracellular matrix (ECM) accumulation in the lung may be controlled via a clock-dependent mechanism. Recent advancements in this area led us to believe that pharmacologically targeting the circadian clock molecules may be a novel therapeutic approach for treating chronic inflammatory lung diseases such as asthma, chronic obstructive pulmonary disease (COPD), and idiopathic pulmonary fibrosis (IPF). Here, we update the current perspective on the circadian clock role in TGFβ1 signaling and extracellular matrix production during chronic lung diseases.

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.

Role of Circadian Transcription Factor Rev-Erb in Metabolism and Tissue Fibrosis

Circadian rhythms significantly affect metabolism, and their disruption leads to cardiometabolic diseases and fibrosis. The clock repressor Rev-Erb is mainly expressed in the liver, heart, lung, adipose tissue, skeletal muscles, and brain, recognized as a master regulator of metabolism, mitochondrial biogenesis, inflammatory response, and fibrosis. Fibrosis is the response of the body to injuries and chronic inflammation with the accumulation of extracellular matrix in tissues. Activation of myofibroblasts is a key factor in the development of organ fibrosis, initiated by hormones, growth factors, inflammatory cytokines, and mechanical stress. This review summarizes the importance of Rev-Erb in ECM remodeling and tissue fibrosis. In the heart, Rev-Erb activation has been shown to alleviate hypertrophy and increase exercise capacity. In the lung, Rev-Erb agonist reduced pulmonary fibrosis by suppressing fibroblast differentiation. In the liver, Rev-Erb inhibited inflammation and fibrosis by diminishing NF-κB activity. In adipose tissue, Rev- Erb agonists reduced fat mass. In summary, the results of multiple studies in preclinical models demonstrate that Rev-Erb is an attractive target for positively influencing dysregulated metabolism, inflammation, and fibrosis, but more specific tools and studies would be needed to increase the information base for the therapeutic potential of these substances interfering with the molecular clock.

Common Ground between Biological Rhythms and Forensics

Simple Summary

Biological clocks regulate the timing of numerous body functions in adaption to daily repeating cycles in the environment, such as the sleep–wake phases that are trained by the cycling changes of night and day light. The identification of a deceased victim is a critical component in a forensic investigation, but it can be significantly hampered by the condition of the dead body and the lack of personal records and documents. This review links current knowledge on the molecular mechanisms of biological rhythms to forensically relevant aspects, including the time period since death, cause of death, the use of insects for forensics, sex and age of a person, ethnic background and development. Putting these findings in context demonstrates how the analysis of molecular clock analysis could be used as tool for future personal identification in forensic investigations.

Abstract

Biological clocks set the timing for a large number of essential processes in the living human organism. After death, scientific evidence is required in forensic investigations in order to collect as much information as possible on the death circumstances and personal identifiers of the deceased victim. We summarize the associations between the molecular mechanisms of biological rhythms and forensically relevant aspects, including post-mortem interval and cause of death, entomological findings, sex, age, ethnicity and development. Given their importance during lifetime, biological rhythms could be potential tools to draw conclusions on the death circumstances and the identity of a deceased person by mechanistic investigations of the different biological clocks in a forensic context. This review puts the known effects of biological rhythms on the functions of the human organism in context with potential applications in forensic fields of interest, such as personal identification, entomology as well as the determination of the post-mortem interval and cause of death.

Monoterpenes as Sirtuin-1 Activators: Therapeutic Potential in Aging and Related Diseases

Sirtuin 1 (SIRT) is a class III, NAD+-dependent histone deacetylase that also modulates the activity of numerous non-histone proteins through deacylation. SIRT1 plays critical roles in regulating and integrating cellular energy metabolism, response to stress, and circadian rhythm by modulating epigenetic and transcriptional regulation, mitochondrial homeostasis, proteostasis, telomere maintenance, inflammation, and the response to hypoxia. SIRT1 expression and activity decrease with aging, and enhancing its activity extends life span in various organisms, including mammals, and improves many age-related diseases, including cancer, metabolic, cardiovascular, neurodegenerative, respiratory, musculoskeletal, and renal diseases, but the opposite, that is, aggravation of various diseases, such as some cancers and neurodegenerative diseases, has also been reported. Accordingly, many natural and synthetic SIRT1 activators and inhibitors have been developed. Known SIRT1 activators of natural origin are mainly polyphenols. Nonetheless, various classes of non-polyphenolic monoterpenoids have been identified as inducers of SIRT1 expression and/or activity. This narrative review discusses current information on the evidence that supports the role of those compounds as SIRT1 activators and their potential both as tools for research and as pharmaceuticals for therapeutic application in age-related diseases.

A wrinkle in time: circadian biology in pulmonary vascular health and disease

An often overlooked element of pulmonary vascular disease is time. Cellular responses to time, which are regulated directly by the core circadian clock, have only recently been elucidated. Despite an extensive collection of data regarding the role of rhythmic contribution to disease pathogenesis (such as systemic hypertension, coronary artery, and renal disease), the roles of key circadian transcription factors in pulmonary hypertension remain understudied. This is despite a large degree of overlap in the pulmonary hypertension and circadian rhythm fields, not only including shared signaling pathways, but also cell-specific effects of the core clock that are known to result in both protective and adverse lung vessel changes. Therefore, the goal of this review is to summarize the current dialogue regarding common pathways in circadian biology, with a specific emphasis on its implications in the progression of pulmonary hypertension. In this work, we emphasize specific proteins involved in the regulation of the core molecular clock while noting the circadian cell-specific changes relevant to vascular remodeling. Finally, we apply this knowledge to the optimization of medical therapy, with a focus on sleep hygiene and the role of chronopharmacology in patients with this disease. In dissecting the unique relationship between time and cellular biology, we aim to provide valuable insight into the practical implications of considering time as a therapeutic variable. Armed with this information, physicians will be positioned to more efficiently use the full four dimensions of patient care, resulting in improved morbidity and mortality of pulmonary hypertension patients.

Circadian clock dysfunction of epithelial cells in pulmonary diseases

Highly-differentiated pulmonary epithelial cells are essential for maintaining lung homeostasis by exerting various physiological functions, which are regulated by circadian clock consisted of an autoregulatory feedback loop of clock genes, including Brain-Muscle Aryl-hydrocarbon Receptor Nuclear Translocator-Like 1 (BMAL1) and Nuclear Heme Receptor Reverse Erythroblastosis Virus α (REV-ERB-α). The circadian clock dysfunction of epithelial cells has been increasingly associated with the pulmonary diseases: BMAL1 and REV-ERB-α regulates inflammatory response of club cells induced by lipopolysaccharide and cigarette smoke (CS) respectively; the clock disfunction in alveolar epithelial type2 cells (AEC-II) has been implicated in CS-induced airway inflammation and early-life hyperoxia-related susceptibility to influenza infection; the ciliary beat frequency of ciliated cells also shows circadian rhythms. Here, we review the current knowledge on the circadian regulation of different epithelial-cell subtypes, attempting to provide insights into how clock dysfunction contributes to pulmonary diseases, and explore possible pharmacological therapies and future directions for fundamental studies.

Melatonin ameliorates cerebral ischemia-reperfusion injury in diabetic mice by enhancing autophagy via the SIRT1-BMAL1 pathway

Diabetic brains are more vulnerable to ischemia-reperfusion injury. Previous studies have proved that melatonin could protect against cerebral ischemia-reperfusion (CIR) injury in non-diabetic stroke models; however, its roles and the underlying mechanisms against CIR injury in diabetic mice remain unknown. Streptozotocin-induced diabetic mice and high-glucose-cultured HT22 cells were exposed to melatonin, with or without administration of the autophagy inhibitor 3-methyladenine (3-MA) and the specifically silent information regulator 1 (SIRT1) inhibitor EX527, and then subjected to CIR or oxygen-glucose deprivation/reperfusion operation. We found that diabetic mice showed aggravated brain damage, increased apoptosis and oxidative stress, and deficient autophagy following CIR compared with non-diabetic counterparts. Melatonin treatment exhibited improved histological damage, neurological outcomes, and cerebral infarct size. Intriguingly, melatonin markedly increased cell survival, anti-oxidative and anti-apoptosis effects, and significantly enhanced autophagy. However, these effects were largely attenuated by 3-MA or EX527. Additionally, our cellular experiments demonstrated that melatonin increased the SIRT1-BMAL1 pathway-related proteins' expression in a dose-dependent manner. In conclusion, these results indicate that melatonin treatment can protect against CIR-induced brain damage in diabetic mice, which may be achieved by the autophagy enhancement mediated by the SIRT1-BMAL1 pathway.

Recent Advances in Chronotherapy Targeting Respiratory Diseases

Respiratory diseases contribute to a significant percentage of mortality and morbidity worldwide. The circadian rhythm is a natural biological process where our bodily functions align with the 24 h oscillation (sleep-wake cycle) process and are controlled by the circadian clock protein/gene. Disruption of the circadian rhythm could alter normal lung function. Chronotherapy is a type of therapy provided at specific time intervals based on an individual's circadian rhythm. This would allow the drug to show optimum action, and thereby modulate its pharmacokinetics to lessen unwanted or unintended effects. In this review, we deliberated on the recent advances employed in chrono-targeted therapeutics for chronic respiratory diseases.

The Link between Circadian Clock Genes and Autophagy in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD), a progressive respiratory disease, is characterized by the alveolar epithelium injury and persistent airway inflammation. It is documented that oscillation and dysregulated expression of circadian clock genes, like Bmal1, Per1, and Per2, involved in COPD pathogenies, including chronic inflammation and imbalanced autophagy level, and targeting the associations of circadian rhythm and autophagy is promising strategies in the management and treatment of COPD. Herein, we reviewed the mechanisms of the circadian clock and the unbalance of the autophagic level in COPD, as well as the link between the two, so as to provide further theoretical bases for the study on the pathogenesis of COPD.

Molecular clock REV-ERBα regulates cigarette smoke-induced pulmonary inflammation and epithelial-mesenchymal transition

Cigarette smoke (CS) is the main etiological factor in the pathogenesis of emphysema/chronic obstructive pulmonary disease (COPD), which is associated with abnormal epithelial-mesenchymal transition (EMT). Previously, we have shown an association among circadian rhythms, CS-induced lung inflammation, and nuclear heme receptor α (REV-ERBα), acting as an antiinflammatory target in both pulmonary epithelial cells and fibroblasts. We hypothesized that molecular clock REV-ERBα plays an important role in CS-induced circadian dysfunction and EMT alteration. C57BL/6J WT and REV-ERBα heterozygous (Het) and –KO mice were exposed to CS for 30 days (subchronic) and 4 months (chronic), and WT mice were exposed to CS for 10 days with or without REV-ERBα agonist (SR9009) administration. Subchronic/chronic CS exposure caused circadian disruption and dysregulated EMT in the lungs of WT and REV-ERBα–KO mice; both circadian and EMT dysregulation were exaggerated in the REV-ERBα–KO condition. REV-ERBα agonist, SR9009 treatment reduced acute CS-induced inflammatory response and abnormal EMT in the lungs. Moreover, REV-ERBα agonist (GSK4112) inhibited TGF-β/CS–induced fibroblast differentiation in human fetal lung fibroblast 1 (HFL-1). Thus, CS-induced circadian gene alterations and EMT activation are mediated through a Rev-erbα–dependent mechanism, which suggests activation of REV-ERBα as a novel therapeutic approach for smoking-induced chronic inflammatory lung diseases.

Lymphocyte senescence in COPD is associated with decreased sirtuin 1 expression in steroid resistant pro-inflammatory lymphocytes

BACKGROUND

The class III NAD-dependent histone deacetylase (HDAC) sirtuin 1 (SIRT1) is an important regulator of senescence, aging, and inflammation. SIRT1de-acetylates chromatin histones, thereby silencing inflammatory gene transcription. We have reported increased steroid-resistant senescent pro-inflammatory CD28nullCD8+ T cells in patients with chronic obstructive pulmonary disease (COPD). We hypothesized that SIRT1 is reduced in these cells in COPD, and that treatment with SIRT1 activators (resveratrol, curcumin) and agents preventing NAD depletion (theophylline) would upregulate SIRT1 and reduce pro-inflammatory cytokine expression in these steroid-resistant cells.

METHODS

Blood was collected from n = 10 COPD and n = 10 aged-matched controls. Expression of CD28, SIRT1, and pro-inflammatory cytokines was determined in CD8+ and CD8- T and natural killer T (NKT)-like cells cultured in the presence of ±1 µM prednisolone, ±5 mg/L theophylline, ±1 µM curcumin, ±25 µM resveratrol, using flow cytometry and immunofluorescence.

RESULTS

There was an increase in the percentage of CD28nullCD8+ T and NKT-like cells in COPD patients compared with controls. Decreased SIRT1 expression was identified in CD28nullCD8+T and NKT-like cells compared with CD28+ counterparts from both patients and controls (e.g. CD28null 11 ± 3% versus CD28+ 57 ± 9%). Loss of SIRT1 was associated with increased production of IFNγ and TNFα, steroid resistance, and disease severity. SIRT1 expression was upregulated in the presence of all drugs and was associated with a decrease in steroid resistance and IFNγ and TNFα production by CD28nullCD8+T and NKT-like cells. The presence of the SIRT1 inhibitor, EX-527 negated [by 92 ± 12% (median ± SEM)] the effect of the SIRT1 activator SRT720 on the percentage of CD8+ T cells producing IFNγ and TNFα.

CONCLUSIONS

Steroid resistance in pro-inflammatory CD28nullCD8+ T and NKT-like cells is associated with decreased SIRT1 expression. Treatment with prednisolone, in combination with theophylline, curcumin or resveratrol increases SIRT1 expression, restores steroid sensitivity, and inhibits pro-inflammatory cytokine production from these cells and may reduce systemic inflammation in COPD. The reviews of this paper are available via the supplemental material section.

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.

Proinflammatory Cytokine Interleukin 1β Disrupts β-cell Circadian Clock Function and Regulation of Insulin Secretion

Intrinsic β-cell circadian clocks are important regulators of insulin secretion and overall glucose homeostasis. Whether the circadian clock in β-cells is perturbed following exposure to prodiabetogenic stressors such as proinflammatory cytokines, and whether these perturbations are featured during the development of diabetes, remains unknown. To address this, we examined the effects of cytokine-mediated inflammation common to the pathophysiology of diabetes, on the physiological and molecular regulation of the β-cell circadian clock. Specifically, we provide evidence that the key diabetogenic cytokine IL-1β disrupts functionality of the β-cell circadian clock and impairs circadian regulation of glucose-stimulated insulin secretion. The deleterious effects of IL-1β on the circadian clock were attributed to impaired expression of key circadian transcription factor Bmal1, and its regulator, the NAD-dependent deacetylase, Sirtuin 1 (SIRT1). Moreover, we also identified that Type 2 diabetes in humans is associated with reduced immunoreactivity of β-cell BMAL1 and SIRT1, suggestive of a potential causative link between islet inflammation, circadian clock disruption, and β-cell failure. These data suggest that the circadian clock in β-cells is perturbed following exposure to proinflammatory stressors and highlights the potential for therapeutic targeting of the circadian system for treatment for β-cell failure in diabetes.

Integrative Analysis Reveals Common and Unique Roles of Tetraspanins in Fibrosis and Emphysema

While both chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF) are multifactorial disorders characterized by distinct clinical and pathological features, their commonalities and differences have not been fully elucidated. We sought to investigate the preventive roles of tetraspanins Cd151 and Cd9 -that are involved in diverse cellular processes in lung pathophysiology- in pulmonary fibrosis and emphysema, respectively, and to obtain a deeper understanding of their underlying molecular mechanisms toward facilitating improved therapeutic outcomes. Using an integrative approach, we examined the transcriptomic changes in the lungs of Cd151- and Cd9-deficient mice using functional-enrichment-analysis, pathway-perturbation-analysis and protein-protein-interaction (PPI) network analysis. Circadian-rhythm, extracellular-matrix (ECM), cell-adhesion and inflammatory responses and associated factors were prominently influenced by Cd151-deletion. Conversely, cellular-junctions, focal-adhesion, vascular-remodeling, and TNF-signaling were deeply impacted by Cd9-deletion. We also highlighted a “common core” of factors and signaling cascades that underlie the functions of both Cd151 and Cd9 in lung pathology. Circadian dysregulation following Cd151-deletion seemingly facilitated progressive fibrotic lung phenotype. Conversely, TGF-β signaling attenuation and TNF-signaling activation emerged as potentially novel functionaries of Cd9-deletion-induced emphysema. Our findings offer promising avenues for developing novel therapeutic treatments for pulmonary fibrosis and emphysema.

Decreased Expression of Sirt1 Contributes to Ocular Behçet's Disease Progression via Th17 and Th22 Response

BACKGROUND

Previous studies have indicated that Sirtuin 1 (Sirt1) plays an important role in suppressing inflammatory responses in many diseases. However, the Sirt1 levels and role of Sirt1 in ocular Behçet's disease (OBD) have not been fully elucidated.

OBJECTIVE

The objective of this study was to investigate the role of Sirt1 in the pathogenesis of OBD.

METHODS

Sirt1 and cytokine levels were measured using ELISA. Cell viability was determined using the Cell Counting Kit-8. The frequencies of Th17 and Th22 cells were detected using flow cytometry.

RESULTS

We found decreased expression of Sirt1 in CD4+ T cells obtained from patients with active OBD. SRT1720, an agonist of Sirt1, significantly upregulated Sirt1 expression in CD4+ T cells from patients with active OBD. Sirt1 activation by SRT1720 significantly suppressed the production of interleukin (IL)-17 and IL-22 by CD4+ T cells and inhibited the expansion of Th17 and Th22 cells.

CONCLUSION

Our results suggest that decreased Sirt1 expression might be involved in the pathogenesis of OBD and that activation of Sirt1 might be considered a potential target for OBD.

Disruption of Physiological Rhythms Persist Following Cessation of Cigarette Smoke Exposure in Mice

Background

Physiological rhythms in mammals are essential for maintaining health, whereas disruptions may cause or exacerbate disease pathogenesis. As such, our objective was to characterize how cigarette smoke exposure affects physiological rhythms of otherwise healthy mice using telemetry and cosinor analysis.

Methods

Female BALB/c mice were implanted with telemetry devices to measure body temperature, heart rate, systolic blood pressure (SBP), and activity. Following baseline measurements, mice were exposed to cigarette smoke for approximately 50 min twice daily during weekdays over 24 weeks. Physiological parameters were recorded after 1, 4, 8, and 24 weeks of exposure or after 4 weeks cessation following 4 weeks of cigarette smoke exposure.

Results

Acute cigarette smoke exposure resulted in anapyrexia, and bradycardia, with divergent effects on SBP. Long term, cigarette smoke exposure disrupted physiological rhythms after just 1 week, which persisted across 24 weeks of exposure (as shown by mixed effects on mesor, amplitude, acrophase, and goodness-of-fit using cosinor analysis). Four weeks of cessation was insufficient to allow full recovery of rhythms.

Conclusion

Our characterization of the pathophysiology of cigarette smoke exposure on physiological rhythms of mice suggests that rhythm disruption may precede and contribute to disease pathogenesis. These findings provide a clear rationale and guide for the future use of chronotherapeutics.

Applications of a novel radiotelemetry method for the measurement of intrathoracic pressures and physiological rhythms in freely behaving mice

Techniques to comprehensively evaluate pulmonary function carry a variety of limitations, including the ability to continuously record intrathoracic pressures (ITP), acutely and chronically, in a natural state of freely behaving animals. Measurement of ITP can be used to derive other respiratory parameters, which provide insight to lung health. Our aim was to develop a surgical approach for the placement of a telemetry pressure sensor to measure ITP, providing the ability to chronically measure peak pressure, breath frequency, and timing of the respiratory cycle to facilitate circadian analyses related to breathing patterns. Applications of this technique are shown using a moderate hypoxic challenge. Male C57Bl/6 mice were implanted with radiotelemetry devices to record heart rate, temperature, activity, and ITP during 24-h normoxia, 24-h hypoxia ([Formula: see text] = 0.15), and return to 48-h normoxia. Radiotelemetry of ITP permitted the detection of hypoxia-induced increases in "the ITP equivalent" of ventilation, which were driven by increases in breathing frequency and ITP on a short-term time scale. Respiratory frequency, derived from pressure waveforms, was increased by a decrease in expiratory time without changes in inspiratory time. Chronically, telemetric recording allowed for circadian analyses of respiratory drive, as assessed by inspiratory pressure divided by inspiratory time, which was increased by hypoxia and remained elevated for 48 h of recovery. Furthermore, respiratory frequency demonstrated a circadian rhythm, which was disrupted through the recovery period. In conclusion, radiotelemetry of ITP is a viable, long-term, chronic methodology that extends traditional methods to evaluate respiratory function in mice.NEW & NOTEWORTHY We have demonstrated for the first time in mice that radiotelemetry is an effective tool for the continuous and chronic recording of intrathoracic pressure (ITP) to facilitate circadian rhythm analyses. We show that continuous 24-h hypoxic stress alters the circadian rhythms of heart rate, body temperature, activity, and respiratory parameters, acutely and perpetually, through normoxic recovery. Radiotelemetry of ITP can complement traditional methods for evaluating respiratory function and better our understanding of respiratory pathophysiology.

Therapeutics on the clock: Circadian medicine in the treatment of chronic inflammatory diseases

The circadian clock is a collection of endogenous oscillators with a periodicity of ~ 24 h. Recently, our understanding of circadian rhythms and their regulation at genomic and physiologic scales has grown significantly. Knowledge of the circadian influence on biological processes has provided new possibilities for novel pharmacological strategies. Directly targeting the biological clock or its downstream targets, and/or using timing as a variable in drug therapy are now important pharmacological considerations. The circadian machinery mediates many aspects of the inflammatory response and, reciprocally, an inflammatory environment can disrupt circadian rhythms. Therefore, intense interest exists in leveraging circadian biology as a means to treat chronic inflammatory diseases such as sepsis, asthma, rheumatoid arthritis, osteoarthritis, and cardiovascular disease, which all display some type of circadian signature. The purpose of this review is to evaluate the crosstalk between circadian rhythms, inflammatory diseases, and their pharmacological treatment. Evidence suggests that carefully rationalized application of chronotherapy strategies - alone or in combination with small molecule modulators of circadian clock components - can improve efficacy and reduce toxicity, thus warranting further investigation and use.

Impact of circadian disruption on health; SIRT1 and Telomeres

Circadian clock is a biochemical oscillator in organisms that regulates the circadian rhythm of numerous genes over 24 h. The circadian clock is involved in telomere homeostasis by regulating the diurnal rhythms of telomerase activity, TERT mRNA level, TERRA expression, and telomeric heterochromatin formation. Particularly, CLOCK and BMAL1 deficiency contribute to telomere shortening by preventing rhythmic telomerase activity and TERRA expression, respectively. Telomere shortening increases the number of senescent cells with impaired circadian rhythms. In return, telomerase reconstitution improves impaired circadian rhythms of senescent cells. SIRT1 that is an NAD+-dependent deacetylase positively regulates circadian clock and telomere homeostasis. SIRT1 contributes to the circadian clock by mediating CLOCK/BMAL1 complex formation, BMAL1 transcription and PER2 disruption. On the other hand, SIRT1 ensures telomere homeostasis by inducing telomerase and shelterin protein expression and regulating telomere heterochromatin formation. SIRT1 inhibition leads to both circadian clock and telomeres dysfunction that inhibit its activity. In light of this current evidence, we could suggest that the BMAL1/CLOCK complex regulates the telomere homeostasis in SIRT1 dependent manner, and also telomere dysfunction inhibits circadian clock function by suppressing SIRT1 activity to induce age-related diseases. We consider that increasing SIRT1 activity can prevent age-related diseases and help healthy aging by protecting telomere integrity and circadian clock function for individuals subjected to circadian rhythm disruption such as shift works, individuals with sleep disorders, and in the elderly population.

Exposure to Cigarette Smoke Enhances the Stemness of Alveolar Type 2 Cells

Chronic exposure to cigarette smoke (CS) causes chronic inflammation, oxidative stress, and apoptosis of epithelial cells, which results in destruction of the lung matrix. However, the mechanism by which the lung fails to repair the CS-induced damage, thereby succumbing to emphysema, remains unclear. Alveolar type 2 (AT2) cells comprise the stem cells of the alveolar compartments and are responsible for repairing and maintaining lung tissues. In this study, we examined the effect of chronic CS on AT2 stem cells. Adult mice expressing GFP in their AT2 cells were exposed to CS for > 3 months. Histological assessment showed that CS not only induced emphysematous changes but also increased the number of AT2 cells compared with that of air-exposed lungs. Assessment of sorted GFP+/AT2 cells via the stem cell three-dimensional organoid/colony-forming assay revealed that the number and size of the colonies formed by the CS-exposed AT2 stem cells were significantly higher than those of air-exposed control AT2 cells. Although CS-exposed lungs had more apoptotic cells, examination of the surviving AT2 stem cells in two-dimensional in vitro culture revealed that they developed a higher ability to resist apoptosis. Microarray analysis of CS-exposed AT2 stem cells revealed the upregulation of genes related to circadian rhythm and inflammatory pathways. In conclusion, we provide evidence that AT2 stem cells respond to chronic CS exposure by activating their stem cell function, thereby proliferating and differentiating faster and becoming more resistant to apoptosis. Disturbances in expression levels of several circadian rhythm-related genes might be involved in these changes.

Association analysis between chronic obstructive pulmonary disease and polymorphisms in circadian genes

Background

Circadian genes have been suggested to play an important role in lung pathology. However, it remains unknown whether polymorphisms of these genes are associated with chronic obstructive pulmonary disease (COPD). Here, we aimed to investigate the association of circadian genes polymorphisms with COPD in a case-control study of 477 COPD patient and 323 control Han Chinese persons.

Methods

Genotyping assays were carried out for nine single nucleotide polymorphisms (SNPs) from five circadian genes (PER3, CLOCK, RORB, BMAL1 and CRY2) that were previously identified in lung pathology. Age, sex, BMI and smoking status and comorbidities were recorded for all subjects.

Results

No significant association was found in all SNP sites in overall subjects and no significant difference was found in age, sex, smoking status stratification analysis.

Discussion

The findings of this investigation indicated the effect of circadian genes polymorphisms on COPD susceptibility may only be small and possibly dependent on the subject factors, such as age and sex.

Circadian Clock and Complement Immune System-Complementary Control of Physiology and Pathology?

Mammalian species contain an internal circadian (i.e., 24-h) clock that is synchronized to the day and night cycles. Large epidemiological studies, which are supported by carefully controlled studies in numerous species, support the idea that chronic disruption of our circadian cycles results in a number of health issues, including obesity and diabetes, defective immune response, and cancer. Here we focus specifically on the role of the complement immune system and its relationship to the internal circadian clock system. While still an incompletely understood area, there is evidence that dysregulated proinflammatory cytokines, complement factors, and oxidative stress can be induced by circadian disruption and that these may feed back into the oscillator at the level of circadian gene regulation. Such a feedback cycle may contribute to impaired host immune response against pathogenic insults. The complement immune system including its activated anaphylatoxins, C3a and C5a, not only facilitate innate and adaptive immune response in chemotaxis and phagocytosis, but they can also amplify chronic inflammation in the host organism. Consequent development of autoimmune disorders, and metabolic diseases associated with additional environmental insults that activate complement can in severe cases, lead to accelerated tissue dysfunction, fibrosis, and ultimately organ failure. Because several promising complement-targeted therapeutics to block uncontrolled complement activation and treat autoimmune diseases are in various phases of clinical trials, understanding fully the circadian properties of the complement system, and the reciprocal regulation by these two systems could greatly improve patient treatment in the long term.

Significant Unresolved Questions and Opportunities for Bioengineering in Understanding and Treating COVID-19 Disease Progression

COVID-19 is a disease that manifests itself in a multitude of ways across a wide range of tissues. Many factors are involved, and though impressive strides have been made in studying this novel disease in a very short time, there is still a great deal that is unknown about how the virus functions. Clinical data has been crucial for providing information on COVID-19 progression and determining risk factors. However, the mechanisms leading to the multi-tissue pathology are yet to be fully established. Although insights from SARS-CoV-1 and MERS-CoV have been valuable, it is clear that SARS-CoV-2 is different and merits its own extensive studies. In this review, we highlight unresolved questions surrounding this virus including the temporal immune dynamics, infection of non-pulmonary tissue, early life exposure, and the role of circadian rhythms. Risk factors such as sex and exposure to pollutants are also explored followed by a discussion of ways in which bioengineering approaches can be employed to help understand COVID-19. The use of sophisticated in vitro models can be employed to interrogate intercellular interactions and also to tease apart effects of the virus itself from the resulting immune response. Additionally, spatiotemporal information can be gleaned from these models to learn more about the dynamics of the virus and COVID-19 progression. Application of advanced tissue and organ system models into COVID-19 research can result in more nuanced insight into the mechanisms underlying this condition and elucidate strategies to combat its effects.

Cellular stress responses and dysfunctional Mitochondrial-cellular senescence, and therapeutics in chronic respiratory diseases

The abnormal inflammatory responses due to the lung tissue damage and ineffective repair/resolution in response to the inhaled toxicants result in the pathological changes associated with chronic respiratory diseases. Investigation of such pathophysiological mechanisms provides the opportunity to develop the molecular phenotype-specific diagnostic assays and could help in designing the personalized medicine-based therapeutic approaches against these prevalent diseases. As the central hubs of cell metabolism and energetics, mitochondria integrate cellular responses and interorganellar signaling pathways to maintain cellular and extracellular redox status and the cellular senescence that dictate the lung tissue responses. Specifically, as observed in chronic obstructive pulmonary disease (COPD) and pulmonary fibrosis, the mitochondria-endoplasmic reticulum (ER) crosstalk is disrupted by the inhaled toxicants such as the combustible and emerging electronic nicotine-delivery system (ENDS) tobacco products. Thus, the recent research efforts have focused on understanding how the mitochondria-ER dysfunctions and oxidative stress responses can be targeted to improve inflammatory and cellular dysfunctions associated with these pathologic illnesses that are exacerbated by viral infections. The present review assesses the importance of these redox signaling and cellular senescence pathways that describe the role of mitochondria and ER on the development and function of lung epithelial responses, highlighting the cause and effect associations that reflect the disease pathogenesis and possible intervention strategies.

Role of Non-Coding RNAs in Lung Circadian Clock Related Diseases

Circadian oscillations are regulated at both central and peripheral levels to maintain physiological homeostasis. The central circadian clock consists of a central pacemaker in the suprachiasmatic nucleus that is entrained by light dark cycles and this, in turn, synchronizes the peripheral clock inherent in other organs. Circadian dysregulation has been attributed to dysregulation of peripheral clock and also associated with several diseases. Components of the molecular clock are disrupted in lung diseases like chronic obstructive pulmonary disease (COPD), asthma and IPF. Airway epithelial cells play an important role in temporally organizing magnitude of immune response, DNA damage response and acute airway inflammation. Non-coding RNAs play an important role in regulation of molecular clock and in turn are also regulated by clock components. Dysregulation of these non-coding RNAs have been shown to impact the expression of core clock genes as well as clock output genes in many organs. However, no studies have currently looked at the potential impact of these non-coding RNAs on lung molecular clock. This review focuses on the ways how these non-coding RNAs regulate and in turn are regulated by the lung molecular clock and its potential impact on lung diseases.

Circadian Clock and Sirtuins in Diabetic Lung: A Mechanistic Perspective

Diabetes-induced tissue injuries in target organs such as the kidney, heart, eye, liver, skin, and nervous system contribute significantly to the morbidity and mortality of diabetes. However, whether the lung should be considered a diabetic target organ has been discussed for decades. Accumulating evidence shows that both pulmonary histological changes and functional abnormalities have been observed in diabetic patients, suggesting that the lung is a diabetic target organ. Mechanisms underlying diabetic lung are unclear, however, oxidative stress, systemic inflammation, and premature aging convincingly contribute to them. Circadian system and Sirtuins have been well-documented to play important roles in above mechanisms. Circadian rhythms are intrinsic mammalian biological oscillations with a period of near 24 h driven by the circadian clock system. This system plays an important role in the regulation of energy metabolism, oxidative stress, inflammation, cellular proliferation and senescence, thus impacting metabolism-related diseases, chronic airway diseases and cancers. Sirtuins, a family of adenine dinucleotide (NAD⁺)-dependent histone deacetylases, have been demonstrated to regulate a series of physiological processes and affect diseases such as obesity, insulin resistance, type 2 diabetes (T2DM), heart disease, cancer, and aging. In this review, we summarize recent advances in the understanding of the roles of the circadian clock and Sirtuins in regulating cellular processes and highlight the potential interactions of the circadian clock and Sirtuins in the context of diabetic lung.

Resetting the Aging Clock: Implications for Managing Age-Related Diseases

Worldwide, individuals are living longer due to medical and scientific advances, increased availability of medical care and changes in public health policies. Consequently, increasing attention has been focused on managing chronic conditions and age-related diseases to ensure healthy aging. The endogenous circadian system regulates molecular, physiological and behavioral rhythms orchestrating functional coordination and processes across tissues and organs. Circadian disruption or desynchronization of circadian oscillators increases disease risk and appears to accelerate aging. Reciprocally, aging weakens circadian function aggravating age-related diseases and pathologies. In this review, we summarize the molecular composition and structural organization of the circadian system in mammals and humans, and evaluate the technological and societal factors contributing to the increasing incidence of circadian disorders. Furthermore, we discuss the adverse effects of circadian dysfunction on aging and longevity and the bidirectional interactions through which aging affects circadian function using examples from mammalian research models and humans. Additionally, we review promising methods for managing healthy aging through behavioral and pharmacological reinforcement of the circadian system. Understanding age-related changes in the circadian clock and minimizing circadian dysfunction may be crucial components to promote healthy aging.

Sirtuins as novel targets in the pathogenesis of airway inflammation in bronchial asthma

Sirtuins are NAD-dependent class III histone deacetylase, which modulate the epigenetic changes to influence the functions in normal and diseased conditions. Preclinical studies have described an increase in the levels of sirtuin 2 and decrease in the levels of sirtuin 6 in the lungs. Sirtuin 2 exerts proinflammatory actions and hence, its blockers reduce the airway inflammation and symptoms of asthma. On the other hand, sirtuin 6 is anti-inflammatory and its activators produce beneficial actions in asthma. The beneficial effects of sirtuin 6 have been attributed to decrease in acetylation of transcriptional factor GATA3 in the T cells, which is associated with decrease in the T_H2 immune response. However, there seems to be dual role of sirtuin 1 in airway inflammation as its proinflammatory as well as anti-inflammatory actions have been described in asthma. The anti-inflammatory actions of sirtuin 1 have been attributed to decrease in acetylation of GATA3 and inhibition of Akt/NF-kappaB signaling. On the other hand, proinflammatory actions of sirtuin 1 have been attributed to increase in the expression of HIF-1α and VEGF along with repression of PPAR-γ activity. The present review discusses the role of different sirtuins in the pathogenesis of bronchial asthma. Moreover, it also discusses sirtuin-triggered signaling pathways that may contribute in modulating the disease state of bronchial asthma.

Resveratrol Prevents Acrylamide-Induced Mitochondrial Dysfunction and Inflammatory Responses via Targeting Circadian Regulator Bmal1 and Cry1 in Hepatocytes

Acrylamide, mainly formed in Maillard browning reaction during food processing, causes defects in liver circadian clock and mitochondrial function by inducing oxidative stress. Resveratrol is a polyphenol that has powerful antioxidant and anti-inflammatory activity. However, the preventive effects of resveratrol on acrylamide-triggered oxidative damage and circadian rhythm disorders are unclear at the current stage. The present research revealed that resveratrol pretreatment prevented acrylamide-induced cell death, mitochondrial dysfunction, and inflammatory responses in HepG2 liver cells. Acrylamide significantly triggered disorders of circadian genes transcription and protein expressions including Bmal1 and Cry 1 in primary hepatocytes, which were prevented by resveratrol pretreatment. Moreover, we found that the beneficial effects of resveratrol on stimulating Nrf2/NQO-1 pathway and mitochondrial respiration complex expressions in acrylamide-treated cells were Bmal1-dependent. Similarly, the inhibitory effects of resveratrol on inflammation signaling NF-κB were Cry1-dependent. In conclusion, these results demonstrated resveratrol could be a promising compound in suppressing acrylamide-induced hepatotoxicity and balancing the circadian clock.

The role of different SIRT1-mediated signaling pathways in toxic injury

Common environmental pollutants and drugs encountered in everyday life can cause toxic damage to the body through oxidative stress, inflammatory stimulation, induction of apoptosis, and inhibition of energy metabolism. Silent information regulator 1 (SIRT1), a nicotinamide adenine dinucleotide-dependent deacetylase, is a member of the evolutionarily highly conserved Sir2 (silent information regulator 2) superprotein family, which is located in the nucleus and cytoplasm. It can deacetylate protein substrates in various signal transduction pathways to regulate gene expression, cell apoptosis and senescence, participate in the process of neuroprotection, energy metabolism, inflammation and the oxidative stress response in living organisms, and plays an important role in toxic damage caused by toxicants and in the process of SIRT1 activator/inhibitor antagonized toxic damage. This review summarizes the role that SIRT1 plays in toxic damage caused by toxicants via its interactions with protein substrates in certain signaling pathways.

Waterpipe smoke and e-cigarette vapor differentially affect circadian molecular clock gene expression in mouse lungs

The use of emerging tobacco products, such as waterpipe or hookah and electronic cigarettes (e-cigs), has gained significant popularity and are promoted as safer alternatives to conventional cigarettes. Circadian systems are internal biological oscillations that are considered important regulators of immune functions in mammals. Tobacco induced inflammatory lung diseases frequently exhibit time-of-day/night variation in lung function and symptom severity. We investigated the impact of inhaled e-cig vapor and waterpipe smoke (WPS) on pulmonary circadian molecular clock disruption by determining the changes in expression levels and abundance of core clock component genes (BMAL1, CLOCK) and clock-controlled output genes (Rev-erbα, Per2, Rev-erbβ, Cry2, Rorα) in mouse lungs. We showed that the expression levels of these pulmonary core clock genes and clock-controlled output genes were altered significantly following exposure to WPS (Bmal1, Clock, and Rev-erbα). We further showed a significant yet differential effect on expression levels of core clock and clock-controlled genes (Bmal1, Per2) in the lungs of mice exposed to e-cig vapor containing nicotine. Thus, acute exposure to WPS and e-cig vapor containing nicotine contributes to altered expression of circadian molecular clock genes in mouse lungs, which may have repercussions on lung cellular and biological functions.

H. pylori infection induced BMAL1 expression and rhythm disorder aggravate gastric inflammation

BACKGROUND

Rhythm abnormalities are crucial for diverse diseases. However, their role in disease progression induced by Helicobacter pylori (H. pylori) remains elusive.

METHODS

H. pylori infection was used in in vivo and in vitro experiments to examine its effect on rhythmic genes. The GEO database was used to screen H. pylori affecting rhythm genes, and the effect of rhythm genes on inflammatory factors. Chromatin immunoprecipitation and dual luciferase assays were used to further find out the regulation between molecules. Animal models were used to confirm the relationship between rhythm genes and H. pylori-induced inflammation.

FINDINGS

BMAL1 disorders aggravate inflammation induced by H. pylori. Specifically, H. pylori induce BMAL1 expression in vitro and in vivo through transcriptional activation of LIN28A, breaking the circadian rhythm. Mechanistically, LIN28A binds to the promoter region of BMAL1 and directly activates its transcription under H. pylori infection. BMAL1 in turn functions as a transcription factor and enhances the expression of proinflammatory cytokine TNF-α, thereby promoting inflammation. Of note, BMAL1 dysfunction in the rhythm disorder animal model aggravates inflammatory response induced by H. pylori infection in vivo.

INTERPRETATION

These findings in this study imply the pathogenic relationship between BMAL1 and H. pylori. BMAL1 may serve as a potential diagnostic marker and therapeutic target for the early diagnosis and treatment of diseases related to H. pylori infection. FUND: National Natural Science Foundation of China.

Redox regulation of circadian molecular clock in chronic airway diseases

At the cellular level, circadian timing is maintained by the molecular clock, a family of interacting clock gene transcription factors, nuclear receptors and kinases called clock genes. Daily rhythms in pulmonary function are dictated by the circadian timing system, including rhythmic susceptibility to the harmful effects of airborne pollutants, exacerbations in patients with chronic airway disease and the immune-inflammatory response to infection. Further, evidence strongly suggests that the circadian molecular clock has a robust reciprocal interaction with redox signaling and plays a considerable role in the response to oxidative/carbonyl stress. Disruption of the circadian timing system, particularly in airway cells, impairs pulmonary rhythms and lung function, enhances oxidative stress due to airway inhaled pollutants like cigarette smoke and airborne particulate matter and leads to enhanced inflammosenescence, inflammasome activation, DNA damage and fibrosis. Herein, we briefly review recent evidence supporting the role of the lung molecular clock and redox signaling in regulating inflammation, oxidative stress, and DNA damage responses in lung diseases and their exacerbations. We further describe the potential for clock genes as novel biomarkers and therapeutic targets for the treatment of chronic lung diseases.

Asymmetric expression level of clock genes in left vs. right nasal mucosa in humans with and without allergies and in rats: Circadian characteristics and possible contribution to nasal cycle

Numerous peripheral tissues possess self-sustaining daily biologic rhythms that are regulated at the molecular level by clock genes such as PER1, PER2, CLOCK, and BMAL1. Physiological function of nasal mucosa exhibits rhythmic variability to a day-night environmental cycle. Nevertheless, little is known of the expression and distribution pattern of clock genes in nasal mucosa. The present study investigates the expression level and distribution pattern of PER1, PER2, CLOCK, and BMAL1 genes in nasal mucosa of healthy controls, allergic rhinitis patients, and normal rats. In human and rat nasal mucosa, the levels of these genes are asymmetrically expressed in nasal mucosa derived from right and left cavities in normal controls, allergic patients, and rat. In human nasal mucosa, the expression levels of these genes were higher in the decongested side than the congested mucosa. In rat nasal mucosa, these clock genes are expressed in a rhythmic circadian manner under the regular light/dark cycles. The expression levels of MUC5AC, a key mucin genes produced in superficial epithelium, are higher in decongested side than that congested side in human nasal mucosa. In rat nasal mucosa, MUC5AC levels showed a circadian rhythm which was associated with different expression levels in nasal mucosa derived from the right and left nasal cavities. Taken together with these results, the present study shows that the clock genes such as PER1, PER2, CLOCK, and BMAL1 are present in human and rat nasal mucosa, and suggest that these clock genes may control the pathophysiological function of nasal mucosa as circadian oscillators and affect the maintenance of the nasal cycle.

Timing Matters: Circadian Rhythm in Sepsis, Obstructive Lung Disease, Obstructive Sleep Apnea, and Cancer

Physiological and cellular functions operate in a 24-hour cyclical pattern orchestrated by an endogenous process known as the circadian rhythm. Circadian rhythms represent intrinsic oscillations of biological functions that allow for adaptation to cyclic environmental changes. Key clock genes that affect the persistence and periodicity of circadian rhythms include BMAL1/CLOCK, Period 1, Period 2, and Cryptochrome. Remarkable progress has been made in our understanding of circadian rhythms and their role in common medical conditions. A critical review of the literature supports the association between circadian misalignment and adverse health consequences in sepsis, obstructive lung disease, obstructive sleep apnea, and malignancy. Circadian misalignment plays an important role in these disease processes and can affect disease severity, treatment response, and survivorship. Normal inflammatory response to acute infections, airway resistance, upper airway collapsibility, and mitosis regulation follows a robust circadian pattern. Disruption of normal circadian rhythm at the molecular level affects severity of inflammation in sepsis, contributes to inflammatory responses in obstructive lung diseases, affects apnea length in obstructive sleep apnea, and increases risk for cancer. Chronotherapy is an underused practice of delivering therapy at optimal times to maximize efficacy and minimize toxicity. This approach has been shown to be advantageous in asthma and cancer management. In asthma, appropriate timing of medication administration improves treatment effectiveness. Properly timed chemotherapy may reduce treatment toxicities and maximize efficacy. Future research should focus on circadian rhythm disorders, role of circadian rhythm in other diseases, and modalities to restore and prevent circadian disruption.

Development and Therapeutic Potential of Small-Molecule Modulators of Circadian Systems

Circadian timekeeping systems drive oscillatory gene expression to regulate essential cellular and physiological processes. When the systems are perturbed, pathological consequences ensue and disease risks rise. A growing number of small-molecule modulators have been reported to target circadian systems. Such small molecules, identified via high-throughput screening or derivatized from known scaffolds, have shown promise as drug candidates to improve biological timing and physiological outputs in disease models. In this review, we first briefly describe the circadian system, including the core oscillator and the cellular networks. Research progress on clock-modulating small molecules is presented, focusing on development strategies and biological efficacies. We highlight the therapeutic potential of small molecules in clock-related pathologies, including jet lag and shiftwork; various chronic diseases, particularly metabolic disease; and aging. Emerging opportunities to identify and exploit clock modulators as novel therapeutic agents are discussed.

The nuclear receptor and clock gene REV-ERBα regulates cigarette smoke-induced lung inflammation

REV-ERBα is a nuclear heme receptor, transcriptional repressor and critical component of the molecular clock that drives daily rhythms of metabolism. Evidence reveals that REV-ERBα also plays an important regulatory role in clock-dependent lung physiology and inflammatory responses. We hypothesize that cigarette smoke (CS) exposure influences REV-ERBα abundance in the lungs, facilitating a pro-inflammatory phenotype. To determine the impact of REV-ERBα activation in the CS-induced inflammatory response we treated primary human small airway epithelial cells (SAECs) with CS extract (CSE) or lipopolysaccharide (LPS) in the absence or presence of pre-treatment with the REV-ERBα agonist GSK 4112. We also exposed adult C57BL/6J (WT) and Rev-erbα global KO mice to CS (10 and 30 days) and measured pro-inflammatory cytokine release. Our data reveal that pre-treatment with GSK 4112 reduced CSE/LPS induced pro-inflammatory cytokines release from both SAECs and mouse lung fibroblasts (MLFs). Furthermore, REV-ERBα KO mice show a greater inflammatory response to 10 and 30 days of CS, including increased neutrophil lung influx, pro-inflammatory cytokine (IL-6, MCP-1 and KC) release, and pro-senescence marker (p16) when compared to WT mice. These data demonstrate that REV-ERBα is a critical regulator of CS-induced lung inflammatory responses.