Rev-erbα can regulate the NF-κB/NALP3 pathway to modulate lipopolysaccharide-induced acute lung injury and inflammation

A New Frontier in Cystic Fibrosis Pathophysiology: How and When Clock Genes Can Affect the Inflammatory/Immune Response in a Genetic Disease Model

Cystic fibrosis (CF) is a monogenic syndrome caused by variants in the CF Transmembrane Conductance Regulator (CFTR) gene, affecting various organ and systems, in particular the lung, pancreas, sweat glands, liver, gastrointestinal tract, vas deferens, and vascular system. While for some organs, e.g., the pancreas, a strict genotype-phenotype occurs, others, such as the lung, display a different pathophysiologic outcome in the presence of the same mutational asset, arguing for genetic and environmental modifiers influencing severity and clinical trajectory. CFTR variants trigger a pathophysiological cascade of events responsible for chronic inflammatory responses, many aspects of which, especially related to immunity, are not ascertained yet. Although clock genes expression and function are known modulators of the innate and adaptive immunity, their involvement in CF has been only observed in relation to sleep abnormalities. The aim of this review is to present current evidence on the clock genes role in immune-inflammatory responses at the lung level. While information on this topic is known in other chronic airway diseases (chronic obstructive pulmonary disease and asthma), CF lung disease (CFLD) is lacking in this knowledge. We will present the bidirectional effect between clock genes and inflammatory factors that could possibly be implicated in the CFLD. It must be stressed that besides sleep disturbance and its mechanisms, there are not studies directly addressing the exact nature of clock genes' involvement in inflammation and immunity in CF, pointing out the directions of new and deepened studies in this monogenic affection. Importantly, clock genes have been found to be druggable by means of genetic tools or pharmacological agents, and this could have therapeutic implications in CFLD.

Electrochemiluminescence aptasensing method for ultrasensitive determination of lipopolysaccharide based on CRISPR-Cas12a accessory cleavage activity

In this study, an ultrasensitive electrochemiluminescence (ECL) aptasensing method was developed for lipopolysaccharide (LPS) determination based on CRISPR-Cas12a accessory cleavage activity. Tris (2,2'-bipyridine) dichlororuthenium (II) (Ru(bpy)32+) was adsorbed on the surface of a glassy carbon electrode (GCE) coated with a mixture of gold nanoparticles (AuNPs) and Nafion film via electrostatic interaction. The obtained ECL platform (Ru(bpy)32+/AuNP/Nafion/GCE) exhibited strong ECL emission. Thiol-functionalized single-stranded DNA (ssDNA) was modified with a ferrocenyl (Fc) group and autonomously assembled on the ECL platform of Ru(bpy)32+/AuNP/Nafion/GCE via thiol-gold bonding, resulting in the quenching of ECL emission. After hybridization of the LPS aptamer strand (AS) with its partial complementary strand (CS), the formed double-stranded DNA (dsDNA) could activate CRISPR-Cas12a to indiscriminately cleave ssDNA-Fc on the surface of Ru(bpy)32+/AuNP/Nafion/GCE, resulting in recovery of the ECL intensity of Ru(bpy)32+ due to the increasing distance between Fc and the electrode surface. The combination of LPS and AS suppressed the formation of dsDNA, inhibited the activation of CRISPR-Cas12a, and prevented further cleavage of ssDNA-Fc. This mechanism aided in upholding the integrity of ssDNA-Fc on the surface of the electrode and was combined with ECL quenching induced by the target. The ECL intensity decreased linearly as the concentration of LPS increased from 1 to 50,000 pg/mL and followed a logarithmic relationship. This method exhibited a remarkably low detection limit of 0.24 pg/mL, which meets the requirement for low-concentration detection of LPS in the human body. The proposed method demonstrates the capacity of CRISPR-Cas12a to perform non-specific cutting of single-stranded DNA and transform the resultant cutting substances into changes in the ECL signal. By amalgamating this approach with the distinct identification abilities of LPS and its aptamers, a simple, responsive, and discriminatory LPS assay was established that holds immense significance for clinical diagnosis.

Therapeutic potential of proteases in acute lung injury and respiratory distress syndrome via TLR4/Nrf2/NF-kB signaling modulation

The COVID-19 pandemic has drawn attention to acute lung injury and respiratory distress syndrome as major causes of death, underscoring the urgent need for effective treatments. Protease enzymes possess a wide range of beneficial effects, including antioxidant, anti-inflammatory, antifibrotic, and fibrinolytic effects. This study aimed to evaluate the potential therapeutic effects of bacterial protease and chymotrypsin in rats in mitigating acute lung injury induced by lipopolysaccharide. Molecular docking was employed to investigate the inhibitory effect of bacterial protease and chymotrypsin on TLR-4, the receptor for lipopolysaccharide. Bacterial protease restored TLR-4, Nrf2, p38 MAPK, NF-kB, and IKK-β levels to normal levels, while chymotrypsin normalized TLR-4, IKK-β, IL-6, and IL-17 levels. The expression of TGF-β, caspase-3, and VEGF in the bacterial protease- and chymotrypsin-treated groups was markedly reduced. Our results suggest that both therapies ameliorate LPS-induced acute lung injury and modulate the TLR4/Nrf2/NF-k signaling pathway. Each protease exhibited distinct mechanisms, with bacterial protease showing a better response to oxidative stress, edema, and fibrosis, whereas chymotrypsin provided a better response in the acute phase and innate immunity. These findings highlight the potential of each protease as a promising therapeutic option for acute lung injury and respiratory distress syndrome.

Circadian rhythm regulates the function of immune cells and participates in the development of tumors

Circadian rhythms are present in almost all cells and play a crucial role in regulating various biological processes. Maintaining a stable circadian rhythm is essential for overall health. Disruption of this rhythm can alter the expression of clock genes and cancer-related genes, and affect many metabolic pathways and factors, thereby affecting the function of the immune system and contributing to the occurrence and progression of tumors. This paper aims to elucidate the regulatory effects of BMAL1, clock and other clock genes on immune cells, and reveal the molecular mechanism of circadian rhythm's involvement in tumor and its microenvironment regulation. A deeper understanding of circadian rhythms has the potential to provide new strategies for the treatment of cancer and other immune-related diseases.

Mesenchymal stem cell conditioned medium alleviates acute lung injury through KGF-mediated regulation of epithelial sodium channels

Acute lung injury (ALI) is a progressive inflammatory injury, and mesenchymal stem cells (MSCs) can be used to treat ALI. MSC-conditioned medium (MSC-CM) contains many cytokines, in which keratinocyte growth factor (KGF) is a soluble factor that plays a role in lung development. We aim to explore the protective effects of MSCs secreted KGF on ALI, and investigate the involvement of epithelial sodium channel (ENaC), which are important in alveolar fluid reabsorption. Both lipopolysaccharides (LPS)-induced mouse and alveolar organoid ALI models were established to confirm the potential therapeutic effect of MSCs secreted KGF. Meanwhile, the expression and regulation of ENaC were determined in alveolar type II epithelial (ATII) cells. The results demonstrated that MSC-CM and KGF could alleviate the extent of inflammation-related pulmonary edema in ALI mice, which was abrogated by a KGF neutralizing antibody. In an alveolar organoid ALI model, KGF in MSC-CM could improve the proliferation and decrease the differentiation of ATII cells. At the cellular level, the LPS-inhibited protein expression of ENaC could be reversed by KGF in MSC-CM. In addition, bioinformatics analysis and our experimental data provided the evidence that the NF-κB signaling pathway may be involved in the regulation of ENaC. Our research confirmed that the therapeutic effect of MSC-CM on edematous ALI was closely related to KGF, which may be involved in the proliferation and differentiation of ATII cells, as well as the upregulation of ENaC expression by the inhibition of NF-κB signaling pathway.

Targeting NR1D1 in organ injury: challenges and prospects

Nuclear receptor subfamily 1, group D, member 1 (NR1D1, also known as REV-ERBα) belongs to the nuclear receptor (NR) family, and is a heme-binding component of the circadian clock that consolidates circadian oscillators. In addition to repressing the transcription of multiple clock genes associated with circadian rhythms, NR1D1 has a wide range of downstream target genes that are intimately involved in many physiopathological processes, including autophagy, immunity, inflammation, metabolism and aging in multiple organs. This review focuses on the pivotal role of NR1D1 as a key transcription factor in the gene regulatory network, with particular emphasis on the milestones of the latest discoveries of NR1D1 ligands. NR1D1 is considered as a promising drug target for treating diverse diseases and may contribute to research on innovative biomarkers and therapeutic targets for organ injury-related diseases. Further research on NR1D1 ligands in prospective human trials may pave the way for their clinical application in many organ injury-related disorders.

SerpinB1 is required for Rev-erbα-mediated protection against acute lung injury induced by lipopolysaccharide-in mice

BACKGROUND AND PURPOSE

Acute lung injury (ALI) is a serious, life-threatening inflammation of the lungs that still lacks effective treatment. We previously showed that serine protease inhibitor B1 (SerpinB1) protects against ALI induced by orthotopic autologous liver transplantation. However, the role of SerpinB1 in lipopolysaccharide (LPS)-induced ALI and its regulatory mechanisms are not known.

EXPERIMENTAL APPROACH

Wild-type (WT) and SerpinB1 knockout (KO) mice were treated with intratracheal LPS stimulation to induce ALI. Some of the WT and KO mice were injected i.p. with melatonin, a rhythm-related protein Rev-erbα agonist. The circadian rhythm in WT mice was disrupted by exposing mice to 24 h of continuous dark or light conditions after intratracheal LPS. Neutrophils were isolated from alveolar lavage fluid of WT and KO mice, and from human peripheral blood. Neutrophils were treated with LPS and melatonin.

KEY RESULTS

Disruption of circadian rhythm by either 24-h dark or light conditions exacerbated LPS-induced ALI and decreased expression of Rev-erbα and SerpinB1 protein in lung, whereas melatonin treatment increased SerpinB1 expression and attenuated LPS-induced ALI in WT mice, but not in KO mice. In isolated neutrophils, Rev-erbα was co-localized with SerpinB1 and bound to its promoter to trigger SerpinB1 transcription. Furthermore, LPS stimulation increased formation of neutrophil extracellular traps, which was reversed by melatonin treatment in neutrophils from WT mice, but not from KO mice.

CONCLUSION AND IMPLICATIONS

In mice, SerpinB1 is rhythmically regulated by Rev-erbα, and its down-regulation exacerbates LPS-induced ALI by inducing formation of neutrophil extracellular traps.

Crosstalk of NLRP3 inflammasome and noncoding RNAs in cardiomyopathies

Cardiovascular diseases (CVDs) identified as a serious public health problem. Although there is a lot of evidence that inflammatory processes play a significant role in the progression of CVDs, however, the precise mechanism is not fully understood. Nevertheless, recent studies have focused on inflammation and its related agents. Nucleotide oligomerization domain-, leucine-rich repeat-, and pyrin domain-containing protein 3 (NLRP3) is a type of pattern recognition receptor (PRR) that can recognize pathogen-associated molecular patterns and trigger innate immune response. NLRP3 is a component of the NOD-like receptor (NLR) family and have a pivotal role in detecting damage to cardiovascular tissue. It is suggested that activation of NLRP3 inflammasome leads to initiating and propagating the inflammatory response in cardiomyopathy. So, late investigations have highlighted the NLRP3 inflammasome activation in various forms of cardiomyopathy. On the other side, it was shown that noncoding RNAs (ncRNAs), particularly, microRNAs, lncRNAs, and circRNAs possess a regulatory function in the immune system's inflammatory response, implicating their involvement in various inflammatory disorders. In addition, their role in different cardiomyopathies was indicated in recent studies. This review article provides a summary of recent advancements focusing on the function of the NLRP3 inflammasome in common CVDs, especially cardiomyopathy, while also discussing the therapeutic potential of inhibiting the NLRP3 inflammasome regulated by ncRNAs.

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.

NLRP3 inflammasome: The rising star in cardiovascular diseases

Cardiovascular diseases (CVDs) are the prevalent cause of mortality around the world. Activation of inflammasome contributes to the pathological progression of cardiovascular diseases, including atherosclerosis, abdominal aortic aneurysm, myocardial infarction, dilated cardiomyopathy, diabetic cardiomyopathy, heart failure, and calcific aortic valve disease. The nucleotide oligomerization domain-, leucine-rich repeat-, and pyrin domain-containing protein 3 (NLRP3) inflammasome plays a critical role in the innate immune response, requiring priming and activation signals to provoke the inflammation. Evidence shows that NLRP3 inflammasome not only boosts the cleavage and release of IL-1 family cytokines, but also leads to a distinct cell programmed death: pyroptosis. The significance of NLRP3 inflammasome in the CVDs-related inflammation has been extensively explored. In this review, we summarized current understandings of the function of NLRP3 inflammasome in CVDs and discussed possible therapeutic options targeting the NLRP3 inflammasome.

Salvianolic Acid A Protects against Lipopolysaccharide-Induced Acute Lung Injury by Inhibiting Neutrophil NETosis

Salvianolic acid A (SAA) is one of bioactive polyphenol extracted from a Salvia miltiorrhiza (Danshen), which was widely used to treat cardiovascular disease in traditional Chinese medicine. SAA has been reported to be protective in cardiovascular disease and ischemia injury, with anti-inflammatory and antioxidative effect, but its role in acute lung injury (ALI) is still unknown. In this study, we sought to investigate the therapeutic effects of SAA in a murine model of lipopolysaccharide- (LPS-) induced ALI. The optimal dose of SAA was determined by comparing the attenuation of lung injury score after administration of SAA at three different doses (low, 5 mg/kg; medium, 10 mg/kg; and, high 15 mg/kg). Dexamethasone (DEX) was used as a positive control for SAA. Here, we showed that the therapeutic effect of SAA (10 mg/kg) against LPS-induced pathologic injury in the lungs was comparable to DEX. SAA and DEX attenuated the increased W/D ratio and the protein level, counts of total cells and neutrophils, and cytokine levels in the BALF of ALI mice similarly. The oxidative stress was also relieved by SAA and DEX according to the superoxide dismutase and malondialdehyde. NET level in the lungs was elevated in the injured lung while SAA and DEX reduced it significantly. LPS induced phosphorylation of Src, Raf, MEK, and ERK in the lungs, which was inhibited by SAA and DEX. NET level and phosphorylation level of Src/Raf/MEK/ERK pathway in the neutrophils from acute respiratory distress syndrome (ARDS) patients were also inhibited by SAA and DEX in vitro, but the YEEI peptide reversed the protective effect of SAA completely. The inhibition of NET release by SAA was also reversed by YEEI peptide in LPS-challenged neutrophils from healthy volunteers. Our data demonstrated that SAA ameliorated ALI via attenuating inflammation, oxidative stress, and neutrophil NETosis. The mechanism of such protective effect might involve the inhibition of Src activation.

The circadian immune system

The immune system is highly time-of-day dependent. Pioneering studies in the 1960s were the first to identify immune responses to be under a circadian control. Only in the last decade, however, have the molecular factors governing circadian immune rhythms been identified. These studies have revealed a highly complex picture of the interconnectivity of rhythmicity within immune cells with that of their environment. Here, we provide a global overview of the circadian immune system, focusing on recent advances in the rapidly expanding field of circadian immunology.

miR‑223 ameliorates thalamus hemorrhage‑induced central poststroke pain via targeting NLRP3 in a mouse model

Central poststroke pain (CPSP) is a central neuropathic pain syndrome that occurs following a stroke and mainly manifests as pain and paresthesia in the body region corresponding to the brain injury area. At present, due to the lack of clinical attention given to CPSP, patients suffer from long-term pain that seriously affects their quality of life. Current literature indicates that microRNA (miR)-223 can impede inflammation and prevent collateral damage. The NLR family pyrin domain containing 3 (NLRP3) inflammasome induces IL-18 and IL-1β secretion and maturation and participates in the inflammatory response. Previous evidence has confirmed that miR-223 can negatively regulate NLRP3 in the development of inflammatory responses. However, whether the miR-223 targeting of NLRP3 is involved in CPSP remains unclear. In the present study, the expression of miR-223 was detected by reverse transcription-quantitative PCR analysis. The expression levels of NLRP3, caspase-1, ASC, IL-18, IL-1β, ERK1/2, p-ERK1/2 and GFAP were detected by western blot analysis. The results demonstrated that thalamic hemorrhagic stroke triggered by microinjection of collagenase Ⅳ (Coll IV) into the ventral posterior lateral (VPL) nucleus results in pain hypersensitivity. miR-223 expression level were significantly reduced in the CPSP model. The expression levels of NLRP3, caspase-1, ASC, IL-18 and IL-1β were significantly increased in the CPSP model. The expression level of GFAP was detected to determine astrocyte activation. The results demonstrated that astrocyte activation induced by Coll IV produced a CPSP model. The p-ERK1/2 expression level was demonstrated to be significantly increased in the CPSP model. The introduction of an miR-223 agomir significantly attenuated thalamic pain and significantly decreased the levels of NLRP3, caspase-1, ASC and proinflammatory cytokines (IL-18 and IL-1β). Furthermore, introducing a miR-223 antagomir into the VPL nucleus of naïve mice mimicked thalamic pain and significantly increased the levels of NLRP3, caspase-1, ASC and proinflammatory cytokine levels (IL-18 and IL-1β). These results indicated that miR-223 inhibited NLRP3 inflammasome activity (caspase-1, NLRP3 and ASC), which ameliorated thalamus hemorrhage-induced CPSP in mice via NLRP3 downregulation. In conclusion, these results may determine the mechanisms underlying CPSP and facilitate development of targeted therapy for CPSP.

A transcriptomics-guided drug target discovery strategy identifies receptor ligands for lung regeneration

Currently, there is no pharmacological treatment targeting defective tissue repair in chronic disease. Here, we used a transcriptomics-guided drug target discovery strategy using gene signatures of smoking-associated chronic obstructive pulmonary disease (COPD) and from mice chronically exposed to cigarette smoke, identifying druggable targets expressed in alveolar epithelial progenitors, of which we screened the function in lung organoids. We found several drug targets with regenerative potential, of which EP and IP prostanoid receptor ligands had the most profound therapeutic potential in restoring cigarette smoke-induced defects in alveolar epithelial progenitors in vitro and in vivo. Mechanistically, we found, using single-cell RNA sequencing analysis, that circadian clock and cell cycle/apoptosis signaling pathways were differentially expressed in alveolar epithelial progenitor cells in patients with COPD and in a relevant model of COPD, which was prevented by prostaglandin E2 or prostacyclin mimetics. We conclude that specific targeting of EP and IP receptors offers therapeutic potential for injury to repair in COPD.

OUP accepted manuscript

Aims

Adverse cardiovascular events have day/night patterns with peaks in the morning, potentially related to endogenous circadian clock control of platelet activation. Circadian nuclear receptor Rev-erbα is an essential and negative component of the circadian clock. To date, the expression profile and biological function of Rev-erbα in platelets have never been reported.

Methods and results

Here, we report the presence and functions of circadian nuclear receptor Rev-erbα in human and mouse platelets. Both human and mouse platelet Rev-erbα showed a circadian rhythm that positively correlated with platelet aggregation. Global Rev-erbα knockout and platelet-specific Rev-erbα knockout mice exhibited defective in haemostasis as assessed by prolonged tail-bleeding times. Rev-erbα deletion also reduced ferric chloride-induced carotid arterial occlusive thrombosis, prevented collagen/epinephrine-induced pulmonary thromboembolism, and protected against microvascular microthrombi obstruction and infarct expansion in an acute myocardial infarction model. In vitro thrombus formation assessed by CD41-labelled platelet fluorescence intensity was significantly reduced in Rev-erbα knockout mouse blood. Platelets from Rev-erbα knockout mice exhibited impaired agonist-induced aggregation responses, integrin αIIbβ3 activation, and α-granule release. Consistently, pharmacological inhibition of Rev-erbα by specific antagonists decreased platelet activation markers in both mouse and human platelets. Mechanistically, mass spectrometry and co-immunoprecipitation analyses revealed that Rev-erbα potentiated platelet activation via oligophrenin-1-mediated RhoA/ERM (ezrin/radixin/moesin) pathway.

Conclusion

We provided the first evidence that circadian protein Rev-erbα is functionally expressed in platelets and potentiates platelet activation and thrombus formation. Rev-erbα may serve as a novel therapeutic target for managing thrombosis-based cardiovascular disease.

Key question

Adverse cardiovascular events have day/night patterns with peaks in the morning, potentially related to endogenous circadian clock control of platelet activation. Whether circadian nuclear receptor Rev-erba is present in platelets and regulates platelet function remains unknown.

Key finding

We provide the first evidence that Rev-erba is functionally expressed in platelets and acts as a positive regulator of platelet activation/thrombus formation through the oligophrenin-1-mediated RhoA/ERM signalling pathway.

Take home message

Our observations highlight the importance of circadian clock machinery in platelet physiology and support the notion that Rev-erba may serve as a novel therapeutic target for managing thrombosis-based cardiovascular 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.

The Potential Roles of Dec1 and Dec2 in Periodontal Inflammation

Periodontal inflammation is a common inflammatory disease associated with chronic inflammation that can ultimately lead to alveolar attachment loss and bone destruction. Understanding autophagy and pyroptosis has suggested their significant roles in inflammation. In recent years, studies of differentiated embryo-chondrocyte expressed genes 1 and 2 (Dec1 and Dec2) have shown that they play important functions in autophagy and in pyroptosis, which contribute to the onset of periodontal inflammation. In this review, we summarize recent studies on the roles of clock genes, including Dec1 and Dec2, that are related to periodontal inflammation and other diseases.

Nuclear Receptors and Clock Components in Cardiovascular Diseases

Cardiovascular diseases (CVD) are still the first cause of death worldwide. Their main origin is the development of atherosclerotic plaque, which consists in the accumulation of lipids and inflammatory leucocytes within the vascular wall of large vessels. Beyond dyslipidemia, diabetes, obesity, hypertension and smoking, the alteration of circadian rhythms, in shift workers for instance, has recently been recognized as an additional risk factor. Accordingly, targeting a pro-atherogenic pathway at the right time window, namely chronotherapy, has proven its efficiency in reducing plaque progression without affecting healthy tissues in mice, thus providing the rationale of such an approach to treat CVD and to reduce drug side effects. Nuclear receptors are transcriptional factors involved in the control of many physiological processes. Among them, Rev-erbs and RORs control metabolic homeostasis, inflammatory processes and the biological clock. In this review, we discuss the opportunity to dampen atherosclerosis progression by targeting such ligand-activated core clock components in a (chrono-)therapeutic approach in order to treat CVD.

Protectin D1 protects against lipopolysaccharide-induced acute lung injury through inhibition of neutrophil infiltration and the formation of neutrophil extracellular traps in lung tissue

Protectin D1 (PD1), a DHA-derived lipid mediator, has recently been shown to possess anti-inflammatory and pro-resolving properties. To date, little is known about the effect of PD1 on lipopolysaccharide (LPS)-induced acute lung injury (ALI) in mice. The aim of the present study was to investigate the therapeutic effects of PD1 on LPS-induced ALI and its potential mechanisms of action. ALI was induced via an intraperitoneal injection of LPS, where PD1 (2 ng/mouse) was administered intravenously 30 min after LPS challenge. Mice were sacrificed 24 h after modeling. Lung histopathological changes were assessed using hematoxylin and eosin staining and myeloperoxidase (MPO) activity was tested using immunohistochemistry. Tumor necrosis-α and interleukin-6 levels in the bronchoalveolar lavage fluid (BALF) and serum were measured using ELISA. To detect neutrophil extracellular traps produced by infiltrated neutrophils in the lung tissue, immunofluorescence staining was performed using anti-MPO and anti-histone H3 antibodies. The results indicated that PD1 significantly attenuated histological damage and neutrophil infiltration in lung tissue, reduced the lung wet/dry weight ratio, protein concentration and proinflammatory cytokine levels in BALF and decreased proinflammatory cytokine levels in serum. Moreover, neutrophil citrullinated histone H3 (CitH3) expression was also reduced after PD1 administration. In conclusion, PD1 attenuated LPS-induced ALI in mice via inhibition of neutrophil extracellular trap formation in lung tissue. Therefore, PD1 administration may serve to be a new strategy for treating ALI.

Systems and Circuits Linking Chronic Pain and Circadian Rhythms

Research over the last 20 years regarding the link between circadian rhythms and chronic pain pathology has suggested interconnected mechanisms that are not fully understood. Strong evidence for a bidirectional relationship between circadian function and pain has been revealed through inflammatory and immune studies as well as neuropathic ones. However, one limitation of many of these studies is a focus on only a few molecules or cell types, often within only one region of the brain or spinal cord, rather than systems-level interactions. To address this, our review will examine the circadian system as a whole, from the intracellular genetic machinery that controls its timing mechanism to its input and output circuits, and how chronic pain, whether inflammatory or neuropathic, may mediate or be driven by changes in these processes. We will investigate how rhythms of circadian clock gene expression and behavior, immune cells, cytokines, chemokines, intracellular signaling, and glial cells affect and are affected by chronic pain in animal models and human pathologies. We will also discuss key areas in both circadian rhythms and chronic pain that are sexually dimorphic. Understanding the overlapping mechanisms and complex interplay between pain and circadian mediators, the various nuclei they affect, and how they differ between sexes, will be crucial to move forward in developing treatments for chronic pain and for determining how and when they will achieve their maximum efficacy.

Mitochondrial-Targeting Antioxidant SS-31 Suppresses Airway Inflammation and Oxidative Stress Induced by Cigarette Smoke

This study investigated whether the mitochondrial-targeted peptide SS-31 can protect against cigarette smoke- (CS-) induced airway inflammation and oxidative stress in vitro and in vivo. Mice were exposed to CS for 4 weeks to establish a CS-induced airway inflammation model, and those in the experimental group were pretreated with SS-31 1 h before CS exposure. Pathologic changes and oxidative stress in lung tissue, inflammatory cell counts, and proinflammatory cytokine levels in bronchoalveolar lavage fluid (BALF) were examined. The mechanistic basis for the effects of SS-31 on CS extract- (CSE-) induced airway inflammation and oxidative stress was investigated using BEAS-2B bronchial epithelial cells and by RNA sequencing and western blot analysis of lung tissues. SS-31 attenuated CS-induced inflammatory injury of the airway and reduced total cell, neutrophil, and macrophage counts and tumor necrosis factor- (TNF-) α, interleukin- (IL-) 6, and matrix metalloproteinase (MMP) 9 levels in BALF. SS-31 also attenuated CS-induced oxidative stress by decreasing malondialdehyde (MDA) and myeloperoxidase (MPO) activities and increasing that of superoxide dismutase (SOD). It also reversed CS-induced changes in the expression of mitochondrial fission protein (MFF) and optic atrophy (OPA) 1 and reduced the amount of cytochrome c released into the cytosol. Pretreatment with SS-31 normalized TNF-α, IL-6, and MMP9 expression, MDA and SOD activities, and ROS generation in CSE-treated BEAS-2B cells and reversed the changes in MFF and OPA1 expression. RNA sequencing and western blot analysis showed that SS-31 inhibited CS-induced activation of the mitogen-activated protein kinase (MAPK) signaling pathway in vitro and in vivo. Thus, SS-31 alleviates CS-induced airway inflammation and oxidative stress via modulation of mitochondrial function and regulation of MAPK signaling and thus has therapeutic potential for the treatment of airway disorders caused by smoking.

Isorhapontigenin alleviates lipopolysaccharide-induced acute lung injury via modulating Nrf2 signaling

Nuclear factor erythroid-2 related factor 2 (Nrf2) is involved in mitigating various oxidative stress- and inflammation-induced diseases, including acute lung injury/acute respiratory distress syndrome (ALI/ARDS). Isorhapontigenin (ISO), from the Chinese herb Gnetum cleistostachyum, exhibits antioxidant and anti-inflammatory properties. In this study, we explored the protective effects of ISO in ALI and its underlying molecular mechanisms. ISO significantly mitigated ALI by reducing the lung wet/dry weight ratio, protein concentration in the bronchoalveolar lavage fluid (BALF), and the levels of myeloperoxidase and malondialdehyde. ISO also improved the superoxide dismutase and glutathione activity in vivo. Moreover, ISO effectively ameliorated the changes in IL-1β, IL-6, and TNF-α concentrations in BALF, prevented IκB degradation, and inhibited the phosphorylation of NF-κB p65 subunit in lung tissues; furthermore, it enhanced the nuclear translocation of Nrf2 and inhibited IL-1β, IL-6, TNF-α, iNOS, COX-2, and ROS production in lipopolysaccharide-treated RAW264.7 cells. The protective effects of ISO in ALI were significantly reversed in ML385-treated RAW264.7 cells and the mouse model, indicating its role in Nrf2-activation. In conclusion, ISO effectively ameliorated lipopolysaccharide-induced ALI by reducing inflammation and oxidative stress, primarily through activation of Nrf2 signaling.

Effect of gut microbiota on LPS-induced acute lung injury by regulating the TLR4/NF-kB signaling pathway

Acute lung injury (ALI) is a common acute respiratory disease treated in the clinic. Intestinal microflora disorder affect lung diseases through the gut-lung axis. In this study, we explored the regulatory mechanism of the gut flora in the host defense against lipopolysaccharide (LPS)-induced ALI through the TLR4/NF-kB pathway by constructing a gut microflora dysbiosis-model with antibiotic administration and reconstruction of the intestinal microecology. Then, high-throughput sequencing was performed, and the levels of secreted IgA (sIgA), β-defensins, and Muc2 were measured to assess the gut flora and mucosal barrier. The expression of TLR4, NF-kB, TNF-α, IL-1β, oxidative stress and the lung wet/dry (W/D) ratio were evaluated to assess lung damage. Hematoxylin and eosin (HE) staining was performed to evaluate the damage to the gut and lung tissues. Accordingly, gut microbiota imbalance may regulate the TLR4/NF-kB signaling pathway in the lung immune system, activating oxidative stress in the lung and mediating lung injury through the regulation of the gut barrier. However, fecal microbiota transplantation (FMT) impairs the activity of the TLR4/NF-kB signaling pathway in the lung and decreases oxidative stress in animals with ALI by restoring the gut microecology. CONCLUSIONS: Our results indicated the protective effect of gut flora in regulating immunity of LPS-induced ALI by modulating the TLR4/NF-kB signaling pathway which may induce inflammation and oxidative stress.

Nuclear Receptors in the Control of the NLRP3 Inflammasome Pathway

The innate immune system is the first line of defense specialized in the clearing of invaders whether foreign elements like microbes or self-elements that accumulate abnormally including cellular debris. Inflammasomes are master regulators of the innate immune system, especially in macrophages, and are key sensors involved in maintaining cellular health in response to cytolytic pathogens or stress signals. Inflammasomes are cytoplasmic complexes typically composed of a sensor molecule such as NOD-Like Receptors (NLRs), an adaptor protein including ASC and an effector protein such as caspase 1. Upon stimulation, inflammasome complex components associate to promote the cleavage of the pro-caspase 1 into active caspase-1 and the subsequent activation of pro-inflammatory cytokines including IL-18 and IL-1β. Deficiency or overactivation of such important sensors leads to critical diseases including Alzheimer diseases, chronic inflammatory diseases, cancers, acute liver diseases, and cardiometabolic diseases. Inflammasomes are tightly controlled by a two-step activation regulatory process consisting in a priming step, which activates the transcription of inflammasome components, and an activation step which leads to the inflammasome complex formation and the subsequent cleavage of pro-IL1 cytokines. Apart from the NF-κB pathway, nuclear receptors have recently been proposed as additional regulators of this pathway. This review will discuss the role of nuclear receptors in the control of the NLRP3 inflammasome and the putative beneficial effect of new modulators of inflammasomes in the treatment of inflammatory diseases including colitis, fulminant hepatitis, cardiac ischemia-reperfusion and brain diseases.

Recent advances in modulators of circadian rhythms: an update and perspective

Circadian rhythm is a universal life phenomenon that plays an important role in maintaining the multiple physiological functions and regulating the adaptability to internal and external environments of flora and fauna. Circadian alignment in humans has the greatest effect on human health, and circadian misalignment is closely associated with increased risk for metabolic syndrome, cardiovascular diseases, neurological diseases, immune diseases, cancer, sleep disorders, and ophthalmic diseases. The recent description of clock proteins and related post-modification targets was involved in several diseases, and numerous lines of evidence are emerging that small molecule modulators of circadian rhythms can be used to rectify circadian disorder. Herein, we attempt to update the disclosures about the modulators targeting core clock proteins and related post-modification targets, as well as the relationship between circadian rhythm disorders and human health as well as the therapeutic role and prospect of these small molecule modulators in circadian rhythm related disease.

Circadian Control of Inflammasome Pathways: Implications for Circadian Medicine

The innate immune system senses “non-self” molecules derived from pathogens (PAMPs) as well as endogenous damage-associated molecular patterns (DAMPs) and promotes sterile inflammation that is necessary for injury resolution, tissue repair/regeneration, and homeostasis. The NOD-, LRR- and pyrin domain containing protein 3 (NLRP3) is an innate immune signaling complex whose assembly and activation can be triggered by various signals ranging from microbial molecules to ATP or the abnormal accumulation of crystals, thus leading to IL-1β and IL-18 maturation and secretion. Deregulation of the NLRP3 signaling cascade is associated with numerous inflammatory and metabolic diseases including rheumatoid arthritis, gout, atherosclerosis or type 2 diabetes. Interestingly, the circadian clock controls numerous inflammatory processes while clock disruption leads to or exacerbates inflammation. Recently, the biological clock was demonstrated to control NLRP3 expression and activation, thereby controlling IL-1β and IL-18 secretion in diverse tissues and immune cells, particularly macrophages. Circadian oscillations of NLRP3 signaling is lost in models of clock disruption, contributing to the development of peritonitis, hepatitis, or colitis. Sterile inflammation is also an important driver of atherosclerosis, and targeting the production of IL-1β has proven to be a promising approach for atherosclerosis management in humans. Interestingly, the extent of injury after fulminant hepatitis or myocardial infarction is time-of-day dependent under the control of the clock, and chronotherapy represents a promising approach for the management of pathologies involving deregulation of NLRP3 signaling.

Inflammasome and Mitophagy Connection in Health and Disease

The inflammasome is a large intracellular protein complex that activates inflammatory caspase-1 and induces the maturation of interleukin (IL)-1β and IL-18. Mitophagy plays an essential role in the maintenance of mitochondrial homeostasis during stress. Previous studies have indicated compelling evidence of the crosstalk between inflammasome and mitophagy. Mitophagy regulation of the inflammasome, or vice versa, is crucial for various biological functions, such as controlling inflammation and metabolism, immune and anti-tumor responses, and pyroptotic cell death. Uncontrolled regulation of the inflammasome often results in pathological inflammation and pyroptosis, and causes a variety of human diseases, including metabolic and inflammatory diseases, infection, and cancer. Here, we discuss how improved understanding of the interactions between inflammasome and mitophagy can lead to novel therapies against various disease pathologies, and how the inflammasome-mitophagy connection is currently being targeted pharmacologically by diverse agents and small molecules. A deeper understanding of the inflammasome-mitophagy connection will provide new insights into human health and disease through the balance between mitochondrial clearance and pathology.

Protective Effect of Piceatannol Against Acute Lung Injury Through Protecting the Integrity of Air-Blood Barrier and Modulating the TLR4/NF-κB Signaling Pathway Activation

Acute lung injury (ALI) is a common and complex inflammatory lung syndrome with higher morbidity and mortality rate. Piceatannol (PIC) has anti-inflammation and anti-oxidant properties. The study was designed to explore the effect and the action mechanisms of PIC on lipopolysaccharide (LPS)-induced ALI. Twenty-four hours after LPS challenge, mice from different treatment groups were euthanized, and the bronchoalveolar lavage fluid (BALF) and lung tissue samples were collected. Then the degree of pulmonary edema, lung pathological changes, myeloperoxidase (MPO) activity, and the production of pro-inflammatory cytokines were detected. Additionally, the messenger RNA (mRNA) expressions associated with cell adhesion molecules and tight junction were analyzed through quantitative real-time (qRT)-PCR, and the TLR4/NF-κB activation was examined by western blot. The results showed that PIC significantly inhibited LPS-induced lung edema, histopathological damage, MPO activity, cell infiltration, and pro-inflammatory cytokines production. Moreover, PIC notably suppressed mRNA expressions associated with inflammation and cell adhesion molecules. Furthermore, PIC also alleviated LPS-induced damage of air-blood barrier through reducing the levels of total proteins in BALF and recovering the expression of occludin and ZO-1 in the lung tissues. We also found that PIC remarkably restrained the LPS-induced TLR4/NF-κB pathway activation in lung tissues. In conclusion, PIC may be potential to treat LPS-induced acute lung injury (ALI) via regulating air-blood barrier and TLR4/NF-κB signaling pathway activation.

Circadian pharmacological effects of berberine on chronic colitis in mice: Role of the clock component Rev-erbα

Berberine, initially isolated from Rhizoma Coptidis (Huanglian in Chinese), is a drug used to treat gastrointestinal disorders such as colitis. Here we uncovered a time-varying berberine effect on chronic colitis in mice, and investigated a potential role of the clock protein Rev-erbα in this timing effect. Berberine activity toward Rev-erbα was determined by luciferase reporter, Gal4-cotransfection assay and target gene expression analyses. Chronic colitis was induced by feeding mice with dextran sulfate sodium in drinking water. Colitis severity and pharmacological effects of berberine were assessed by measuring myeloperoxidase and malondialdehyde activities as well as the levels of inflammatory factors (IL-1β, IL-6, IL-18 and Ccl2). Berberine significantly inhibited Bmal1 (-2000/+100 bp)- and Nlrp3 (-1310/+100 bp)-Luc reporter activities, and dose-dependently decreased cellular expressions of both Bmal1 and Nlrp3. Also, it enhanced the transcriptional repressor activity of Rev-erbα in the Gal4 chimeric assay. These data indicated berberine as a Rev-erbα agonist. As expected, berberine attenuated inflammatory responses in BMDMs (bone marrow-derived macrophages) and in colitis mice. However, the anti-inflammatory effects of berberine were lost in BMDMs derived from Rev-erbα-deficient mice. Furthermore, chronic colitis displayed a diurnal rhythmicity in disease severity and its diurnal pattern was in an opposite phase to that of Rev-erbα expression, supporting a direct control of colitis by Rev-erbα. Moreover, berberine effects on chronic colitis were dosing time-dependent. ZT10 dosing generated a better treatment outcome compared to ZT2. This was because colitis was less severe and Rev-erbα expression was much higher at ZT10 than at ZT2. In conclusion, circadian pharmacological effects of berberine on chronic colitis were mainly contributed by diurnal rhythms of both disease severity and Rev-erbα (as a drug target). The findings may have implications for chronotherapeutic practice on colitis or related diseases.