Direct vagus nerve stimulation: A new tool to control allergic airway inflammation through α7 nicotinic acetylcholine receptor.

BACKGROUND AND PURPOSE: Asthma is characterized by airway inflammation, mucus hypersecretion, and airway hyperresponsiveness. The use of nicotinic agents to mimic the cholinergic anti-inflammatory pathway (CAP) controls experimental asthma. Yet, the effects of vagus nerve stimulation (VNS)-induced CAP on allergic inflammation remain unknown. EXPERIMENTAL APPROACH: BALB/c mice were sensitized and challenged with house dust mite (HDM) extract and treated with active VNS (5 Hz, 0.5 ms, 0.05-1 mA). Bronchoalveolar lavage (BAL) fluid was assessed for total and differential cell counts and cytokine levels. Lungs were examined by histopathology and electron microscopy. KEY RESULTS: In the HDM mouse asthma model, VNS at intensities equal to or above 0.1 mA (VNS 0.1) but not sham VNS reduced BAL fluid differential cell counts and alveolar macrophages expressing α7 nicotinic receptors (α7nAChR), goblet cell hyperplasia, and collagen deposition. Besides, VNS 0.1 also abated HDM-induced elevation of type 2 cytokines IL-4 and IL-5 and was found to block the phosphorylation of transcription factor STAT6 and expression level of IRF4 in total lung lysates. Finally, VNS 0.1 abrogated methacholine-induced hyperresponsiveness in asthma mice. Prior administration of α-bungarotoxin, a specific inhibitor of α7nAChR, but not propranolol, a specific inhibitor of ß2-adrenoceptors, abolished the therapeutic effects of VNS 0.1. CONCLUSION AND IMPLICATIONS: Our data revealed the protective effects of VNS on various clinical features in allergic airway inflammation model. VNS, a clinically approved therapy for depression and epilepsy, appears to be a promising new strategy for controlling allergic asthma.

Natural Products for the Management of Asthma and COPD.

Chronic airway inflammatory diseases like asthma, chronic obstructive pulmonary disease (COPD), and their associated exacerbations cause significant socioeconomic burden. There are still major obstacles to effective therapy for controlling severe asthma and COPD progression. Advances in understanding the pathogenesis of the two diseases at the cellular and molecular levels are essential for the development of novel therapies. In recent years, significant efforts have been made to identify natural products as potential drug leads for treatment of human diseases and to investigate their efficacy, safety, and underlying mechanisms of action. Many major active components from various natural products have been extracted, isolated, and evaluated for their pharmacological efficacy and safety. For the treatment of asthma and COPD, many promising natural products have been discovered and extensively investigated. In this chapter, we will review a range of natural compounds from different chemical classes, including terpenes, polyphenols, alkaloids, fatty acids, polyketides, and vitamin E, that have been demonstrated effective against asthma and/or COPD and their exacerbations in preclinical models and clinical trials. We will also elaborate in detail their underlying mechanisms of action unraveled by these studies and discuss new opportunities and potential challenges for these natural products in managing asthma and COPD.

Isthmin-1 attenuates allergic Asthma by stimulating adiponectin expression and alveolar macrophage efferocytosis in mice.

BACKGROUND: Allergic asthma is a common respiratory disease that significantly impacts human health. Through in silico analysis of human lung RNASeq, we found that asthmatic lungs display lower levels of Isthmin-1 (ISM1) expression than healthy lungs. ISM1 is an endogenous anti-inflammatory protein that is highly expressed in mouse lungs and bronchial epithelial cells, playing a crucial role in maintaining lung homeostasis. However, how ISM1 influences asthma remains unclear. This study aims to investigate the potential involvement of ISM1 in allergic airway inflammation and uncover the underlying mechanisms. METHODS: We investigated the pivotal role of ISM1 in airway inflammation using an ISM1 knockout mouse line (ISM1-/-) and challenged them with house dust mite (HDM) extract to induce allergic-like airway/lung inflammation. To examine the impact of ISM1 deficiency, we analyzed the infiltration of immune cells into the lungs and cytokine levels in bronchoalveolar lavage fluid (BALF) using flow cytometry and multiplex ELISA, respectively. Furthermore, we examined the therapeutic potential of ISM1 by administering recombinant ISM1 (rISM1) via the intratracheal route to rescue the effects of ISM1 reduction in HDM-challenged mice. RNA-Seq, western blot, and fluorescence microscopy techniques were subsequently used to elucidate the underlying mechanisms. RESULTS: ISM1-/- mice showed a pronounced worsening of allergic airway inflammation and hyperresponsiveness upon HDM challenge. The heightened inflammation in ISM1-/- mice correlated with enhanced lung cell necroptosis, as indicated by higher pMLKL expression. Intratracheal delivery of rISM1 significantly reduced the number of eosinophils in BALF and goblet cell hyperplasia. Mechanistically, ISM1 stimulates adiponectin secretion by type 2 alveolar epithelial cells partially through the GRP78 receptor and enhances adiponectin-facilitated apoptotic cell clearance via alveolar macrophage efferocytosis. Reduced adiponectin expression under ISM1 deficiency also contributed to intensified necroptosis, prolonged inflammation, and heightened severity of airway hyperresponsiveness. CONCLUSIONS: This study revealed for the first time that ISM1 functions to restrain airway hyperresponsiveness to HDM-triggered allergic-like airway/lung inflammation in mice, consistent with its persistent downregulation in human asthma. Direct administration of rISM1 into the airway alleviates airway inflammation and promotes immune cell clearance, likely by stimulating airway adiponectin production. These findings suggest that ISM1 has therapeutic potential for allergic asthma.

Dexamethasone protects against Aspergillus fumigatus-induced severe asthma via modulating pulmonary immunometabolism.

Severe asthma is a difficult-to-treat chronic airway inflammatory disease requiring systemic corticosteroids to achieve asthma control. It has recently been shown that drugs targeting immunometabolism have elicited anti-inflammatory effects. The purpose of this study was to investigate potential immunometabolic modulatory actions of systemic dexamethasone (Dex) in an Aspergillus fumigatus (Af)-induced severe asthma model. Mice were repeatedly exposed to the Af aeroallergen before systemic treatment with Dex. Simultaneous measurements of airway inflammation, real-time glycolytic and oxidative phosphorylation (OXPHOS) activities, expression levels of key metabolic enzymes, and amounts of metabolites were studied in lung tissues, and in primary alveolar macrophages (AMs) and eosinophils. Dex markedly reduced Af-induced eosinophilic airway inflammation, which was coupled with an overall reduction in lung glycolysis, glutaminolysis, and fatty acid synthesis. The anti-inflammatory effects of Dex may stem from its immunometabolic actions by downregulating key metabolic enzymes including pyruvate dehydrogenase kinase, glutaminase, and fatty acid synthase. Substantial suppression of eosinophilic airway inflammation by Dex coincided with a specific escalation of mitochondrial proton leak in primary lung eosinophils. Besides, while our findings confirmed that inflammation corresponds with an upregulation of glycolysis, it was accompanied with an unexpectedly stable or elevated OXPHOS in the lungs and activated immune cells, respectively. Our findings reveal that the anti-inflammatory effects of Dex in severe asthma are associated with downregulation of pyruvate dehydrogenase kinase, glutaminase, and fatty acid synthase, and the augmentation of mitochondrial proton leak in lung eosinophils. These enzymes and biological processes may be valuable targets for therapeutic interventions against severe asthma.

Degradation of MK2 with natural compound andrographolide: A new modality for anti-inflammatory therapy.

The p38MAPK-MK2 signaling axis functions as an initiator of inflammation. Targeting the p38MAPK-MK2 signaling axis represents a direct therapeutic intervention of inflammatory diseases. We described here a novel role of andrographolide (AG), a small-molecule ent-labdane natural compound, as an inhibitor of p38MAPK-MK2 axis via MK2 degradation. AG was found to bind to the activation loop of MK2, located at the interface of the p38MAPK-MK2 biomolecular complex. This interaction disrupted the complex formation and predisposed MK2 to proteasome-mediated degradation. We showed that AG induced MK2 degradation in a concentration- and time-dependent manner and exerted its anti-inflammatory effects by enhancing the mRNA-destabilizing activity of tristetraprolin, thereby inhibiting pro-inflammatory mediator production (e.g., TNF-α, MCP-1). Administration of AG via intratracheal (i.t.) route to mice induced MK2 downregulation in lung alveolar macrophages, but not lung tissues, and prevented macrophage activation. Our study also demonstrated that the anti-inflammatory effects achieved by AG via MK2 degradation were more durable and sustained than that achieved by the conventional MK2 kinase inhibitors (e.g., PF-3644022). Taken together, our findings illustrated a novel mode of action of AG by modulating the p38MAPK-MK2 signaling axis and would pave the way for the development of a novel class of anti-inflammatory agents targeting MK2 for degradation by harnessing the privileged scaffold of AG.

Multifunctional Antibacterial Nanonets Attenuate Inflammatory Responses through Selective Trapping of Endotoxins and Pro-Inflammatory Cytokines.

Extracellular lipopolysaccharide (LPS) released from bacteria cells can enter the bloodstream and cause septic complications with excessive host inflammatory responses. Target-specific strategies to inactivate inflammation mediators have largely failed to improve the prognosis of septic patients in clinical trials. By utilizing their high density of positive charges, de novo designed peptide nanonets are shown to selectively entrap the negatively charged LPS and pro-inflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). This in turn enables the nanonets to suppress LPS-induced cytokine production by murine macrophage cell line and rescue the antimicrobial activity of the last-resort antibiotic, colistin, from LPS binding. Using an acute lung injury model in mice, it is demonstrated that intratracheal administration of the fibrillating peptides is effective at lowering local release of TNF-α and IL-6. Together with previously shown ability to simultaneously trap and kill pathogenic bacteria, the peptide nanonets display remarkable potential as a holistic, multifunctional anti-infective, and anti-septic biomaterial.

Calcaratarin D, a labdane diterpenoid, attenuates mouse asthma via modulating alveolar macrophage function.

BACKGROUND AND PURPOSE: Alveolar macrophages (AMs) contribute to airway inflammation and remodelling in allergic asthma. Calcaratarin D (CalD), a labdane diterpenoid from rhizomes of the medicinal plant Alpinia calcarata, has recently been shown to possess anti-inflammatory properties. The present study evaluated protective effects of CalD in a house dust mite (HDM)-induced asthma mouse model. EXPERIMENTAL APPROACH: The effects of CalD on AMs in contributing to anti-inflammatory effects in asthma were investigated through in vivo, ex vivo, and in vitro experiments. KEY RESULTS: CalD reduced total bronchoalveolar lavage fluid and differential cell count, serum IgE levels, mucus hypersecretion, and airway hyperresponsiveness in HDM-challenged mice. Additionally, CalD affected a wide array of pro-inflammatory cytokines and chemokines and oxidative damage markers in isolated lung tissues. CalD suppressed the HDM-induced increase in Arg1 (M2 macrophage marker) in AMs from lung tissue and reduced lung polyamine levels. CalD weakened antigen presentation capability of AMs by reducing CD80 expression, reduced AM-derived CCL17 and CCL22 levels, and lessened Th2 cytokines from CD4+ T-cells from asthma lung digest. CalD blocked the HDM-induced FoxO1/IRF4 pathway and restored impaired the Nrf2/HO-1 antioxidant pathway in lung tissues. CalD inhibited IL-4/IL-13-stimulated JAK1/STAT6 pathway, FoxO1 protein expression, and chemokine production in primary AMs. Structure-activity relationship study revealed the α,ß-unsaturated γ-butyrolactone in CalD is capable of forming covalent bonds with cellular protein targets essential for its action. CONCLUSION AND IMPLICATIONS: Our results demonstrate for the first time that CalD is a novel anti-inflammatory natural compound for allergic asthma that modulates AM function.

Angiotensin II type-2 receptor activation in alveolar macrophages mediates protection against cigarette smoke-induced chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death globally. Cumulative evidence has implicated renin-angiotensin system (RAS) in the pathogenesis of COPD. Alveolar macrophages (AMs) are the first line immune defense in the respiratory system and play a critical role in the lung homeostasis. This study aimed to investigate the role of AMs in contributing to the protective effects of angiotensin II type-2 receptor (AT2R) activation in cigarette smoke (CS)-induced COPD. The AM polarization, phagocytosis and metabolism, and the underlying biochemical mechanisms of compound 21 (C21), a selective and potent non-peptide small molecule AT2R agonist, were evaluated in a two-week CS-induced COPD mouse model. C21 restored AM phagocytosis ability, reversing CS-induced AM phagocytosis impairment. CS exposure polarized AMs towards M1 phenotype, whereas, C21 skewed the CS-exposed AMs towards M2 phenotype. C21 reprogrammed CS-exposed AM metabolism from a high glycolysis-driven process to support inflammation energy demand to a high mitochondrial respiration process to limit inflammation. Besides, C21 upregulated AT2R and Mas receptor levels in CS-exposed AMs, favoring the anti-inflammatory Ang II/AT2R axis and Ang 1-7/Mas axis in the RAS. C21 restored the normal levels of sirtuin 1 (SIRT1) and MAPK phosphatase 1 (MKP1) in CS-exposed AMs, leading to the reduction of phospho-p38, phospho-ERK and p65 subunit of NF-κB levels in CS-exposed AMs. We report here for the first time that AT2R agonist C21 acts by boosting the protective functions of AMs against CS-induced COPD, and our results support the development of AT2R agonist for the treatment of COPD.

ISM1 suppresses LPS-induced acute lung injury and post-injury lung fibrosis in mice.

BACKGROUND: Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) are clinical syndromes characterized by acute lung inflammation, pulmonary edema and hypoxemia, with up to 50% mortality rate without effective pharmacological therapy. Following the acute inflammation, repair and remodeling occurs which in some cases resulting in lung fibrosis. The pathophysiology of ALI/ARDS remains incompletely understood. Lipopolysaccharide (LPS)-induced ALI in mice have been widely used as a model to study human ALI/ARDS. Isthmin 1 (ISM1) is a secreted protein highly abundant in mouse lung. We have previously reported that upon intratracheal LPS instillation, ISM1 expression in the lung is further upregulated. Recently, we also reported that ISM1 is an anti-inflammatory protein in the lung with Ism1-/- mice presenting spontaneous chronic low-grade lung inflammation and obvious emphysema at young adult stage. However, what role ISM1 plays in ALI/ARDS and lung fibrosis remain unclear. METHODS: Using Ism1-/- mice and intratracheal LPS-induced ALI, and local delivery of recombinant ISM1 (rISM1), we investigated the role ISM1 plays in ALI and post-ALI lung fibrosis using flow cytometry, Western blot, antibody array, immunohistochemistry (IHC), immunofluorescent and other histological staining. RESULTS: We reveal that ISM1 deficiency in mice led to an intensified acute lung inflammation upon intratracheal LPS challenge, with a heightened leukocyte infiltration including neutrophils and monocyte-derived alveolar macrophages, as well as upregulation of multiple pro-inflammatory cytokines/chemokines including tumor necrosis factor α (TNF-α). Although innate immune cells largely subsided to the baseline by day 7 post-LPS challenge in both wild-type and Ism1-/- mice, Ism1-/- lung showed increased post-ALI fibrosis from day 9 post-LPS treatment with increased myofibroblasts, excessive collagen accumulation and TGF-ß upregulation. The heightened lung fibrosis remained on day 28 post-LPS. Moreover, intranasal delivered recombinant ISM1 (rISM1) effectively suppressed LPS-induced acute lung inflammation and ALI, and rISM1 suppressed LPS-induced NF-κB activation in cultured mouse alveolar macrophages. CONCLUSION: Together with our previous report, this work further established ISM1 as an endogenous anti-inflammation protein in the lung, restraining excessive host inflammatory response to LPS-triggered ALI and suppressing post-ALI lung fibrosis likely through suppressing NF-κB activation and pro-inflammatory cytokine/chemokine production.

ISM1 protects lung homeostasis via cell-surface GRP78-mediated alveolar macrophage apoptosis.

Alveolar macrophages (AMs) are critical for lung immune defense and homeostasis. They are orchestrators of chronic obstructive pulmonary disease (COPD), with their number significantly increased and functions altered in COPD. However, it is unclear how AM number and function are controlled in a healthy lung and if changes in AMs without environmental assault are sufficient to trigger lung inflammation and COPD. We report here that absence of isthmin 1 (ISM1) in mice (Ism1-/- ) leads to increase in both AM number and functional heterogeneity, with enduring lung inflammation, progressive emphysema, and significant lung function decline, phenotypes similar to human COPD. We reveal that ISM1 is a lung resident anti-inflammatory protein that selectively triggers the apoptosis of AMs that harbor high levels of its receptor cell-surface GRP78 (csGRP78). csGRP78 is present at a heterogeneous level in the AMs of a healthy lung, but csGRP78high AMs are expanded in Ism1-/- mice, cigarette smoke (CS)-induced COPD mice, and human COPD lung, making these cells the prime targets of ISM1-mediated apoptosis. We show that csGRP78high AMs mostly express MMP-12, hence proinflammatory. Intratracheal delivery of recombinant ISM1 (rISM1) depleted csGRP78high AMs in both Ism1-/- and CS-induced COPD mice, blocked emphysema development, and preserved lung function. Consistently, ISM1 expression in human lungs positively correlates with AM apoptosis, suggesting similar function of ISM1-csGRP78 in human lungs. Our findings reveal that AM apoptosis regulation is an important physiological mechanism for maintaining lung homeostasis and demonstrate the potential of pulmonary-delivered rISM1 to target csGRP78 as a therapeutic strategy for COPD.

Activation of angiotensin II type-2 receptor protects against cigarette smoke-induced COPD.

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death globally. Cumulative evidence has implicated renin-angiotensin system (RAS) in the pathogenesis of COPD. This study aimed to investigate potential protective effects of angiotensin II type-2 receptor (AT2R) activation in cigarette smoke (CS)-induced COPD models. Compound 21 (C21), a selective and potent non-peptide small molecule AT2R agonist, was evaluated for anti-inflammatory, anti-oxidative and anti-remodeling activities in a two-week (acute) and an eight-week (chronic) CS-induced COPD models. C21 inhibited CS-induced increases in macrophage and neutrophil counts, pro-inflammatory cytokines and oxidative damage markers in bronchoalveolar lavage (BAL) fluid, and TGF-ß1 in lung tissues, from COPD models. C21 restored phosphatase activities and reduced phospho-p38 MAPK, phospho-ERK and p65 subunit of NF-κB levels in CS-exposed lung tissues. C21 also suppressed CS-induced increases in α-Sma, Mmp9, Mmp12 and hydroxyproline levels in lung tissues, and neutrophil elastase activity in BAL fluid. C21 modulated RAS in CS-exposed lungs by downregulating Ang II but upregulating Ang-(1-7) and Mas receptor levels. C21 prevented CS-induced emphysema and improved lung functions in chronic COPD model. We report here for the first time the protective effects of AT2R agonist C21 against CS-induced COPD, and provide strong evidence for further development of AT2R agonist for the treatment of COPD.

Restoration of HDAC2 and Nrf2 by andrographolide overcomes corticosteroid resistance in chronic obstructive pulmonary disease.

BACKGROUND AND PURPOSE: Corticosteroid resistance poses a major barrier to an effective anti-inflammatory therapy for chronic obstructive pulmonary disease (COPD). The present study aimed to investigate potential corticosteroid re-sensitization actions of andrographolide, a bioactive molecule from the herb Andrographis paniculata, in COPD models, particularly in peripheral blood mononuclear cells (PBMCs) from COPD patients. EXPERIMENTAL APPROACH: Corticosteroid sensitivity in PBMCs collected from COPD patients, or in human monocytic U937 cells exposed to cigarette smoke extract (CSE), was determined by measuring LPS-induced IL-8 production, in the presence and absence of andrographolide. The mechanisms of corticosteroid re-sensitization action of andrographolide were evaluated in a mouse cigarette smoke (CS)-induced acute lung injury model. KEY RESULTS: Impaired inhibition of IL-8 production by dexamethasone was detected in PBMCs from COPD patients and in CSE-exposed U937 cells, together with reduced levels of nuclear factor erythroid 2-related factor 2 (Nrf2) and histone deacetylase-2 (HDAC2). In both PBMCs and CSE-exposed U937 cells, andrographolide restored dexamethasone inhibition of IL-8 production, accompanied by the up-regulation of Nrf2 and HDAC2 levels. In the U937 cells, andrographolide was able to block CSE-induced Akt and reduce the level of c-Jun. Besides, andrographolide also augmented dexamethasone actions on lowering total and neutrophil counts, cytokine levels, and oxidative damage markers in bronchoalveolar lavage fluid from CS-exposed mice. CONCLUSION AND IMPLICATIONS: We report here for the first time a novel corticosteroid re-sensitization property of andrographolide in human PBMCs and provide mechanistic evidence to support clinical evaluation of andrographolide in reversing steroid resistance in COPD.

Gene silencing of receptor-interacting protein 2 protects against cigarette smoke-induced acute lung injury.

BACKGROUND AND PURPOSE: Chronic obstructive pulmonary disease (COPD) is characterized by progressive alveolar damage and generally irreversible airflow limitation. Nuclear factor-κB (NF-κB) plays a critical role in COPD pathogenesis. Receptor-interacting protein 2 (Rip2), a 60 kDa adaptor protein, is a positive regulator of NF-κB pathway and also an inducible transcriptional product of NF-κB activation. We sought to investigate if Rip2 gene silencing could protect against cigarette smoke (CS)-induced acute lung injury. EXPERIMENTAL APPROACH: Gene silencing efficacy of Rip2 siRNA was characterized in mouse macrophage and mouse lung epithelial cell lines, and in a CS-induced acute lung injury mouse model. Bronchoalveolar lavage (BAL) fluid cell counts, levels of pro-inflammatory and oxidative damage markers, lung section inflammatory and epithelium thickness scorings, and nuclear NF-κB translocation were measured. KEY RESULTS: CS was found to upregulate Rip2 level in mouse lungs. Rip2 siRNA was able to suppress Rip2 levels in both macrophage and lung epithelial cell lines and in mouse lungs, block CS extract (CSE)-induced mediator release by the cultured cells, and abate neutrophil counts in BAL fluid from CS-challenged mice. Rip2 siRNA suppressed CS-induced inflammatory and oxidative damage markers, and nuclear p65 accumulation and transcriptional activation in lung tissues. Besides, Rip2 siRNA was able to disrupt CSE-induced NF-κB activation in a NF-κB reporter gene assay. CONCLUSIONS AND IMPLICATIONS: Taken together, we report for the first time that Rip2 gene silencing ameliorated CS-induced acute lung injury probably via disruption of the NF-κB activity, postulating that Rip2 may be a novel therapeutic target for COPD.

Andrographolide simultaneously augments Nrf2 antioxidant defense and facilitates autophagic flux blockade in cigarette smoke-exposed human bronchial epithelial cells.

Cigarette smoking is the leading cause of chronic obstructive pulmonary disease (COPD). Cigarette smoke heightens oxidative stress and impairs autophagy, advancing COPD progression. Andrographolide is a bioactive diterpenoid lactone isolated from the plant Andrographis paniculata which has been a traditional medicinal herb for respiratory diseases. As airway epithelial cells form the first interface to be exposed to cigarette smoke, this study aimed to explore the modulatory effects of andrographolide on oxidative stress and autophagy in human bronchial epithelial BEAS-2B cells exposed to cigarette smoke extract (CSE). CSE (2%) exposure increased autophagic markers p62 and LC3B-II levels in BEAS-2B cells. Andrographolide alone increased p62 and p-p62 (S349) but not LC3B-II in BEAS-2B cells. However, in the presence of CSE, andrographolide was able to simultaneously increase LC3B-II level and enhance antioxidant defense by decreasing oxidative stress and increasing total antioxidant capacity, through upregulation of nuclear Nrf2 via the p62-Nrf2 positive feedback loop. Using RFP-GFP-LC3B transfected BEAS-2B cells exposed to CSE, andrographolide was found to impair autophagosome fusion with lysosome, which may account for the moderate increase in activated caspase 3/7 and annexin V levels. Our findings revealed for the first time that andrographolide simultaneously upregulated antioxidant defense through the p62-Nrf2 loop and moderately induced apoptosis through impairment of autophagic flux in CSE-exposed bronchial epithelium. Andrographolide facilitated cigarette smoke-induced apoptosis may be a potential toxicological outcome or may protect against chronic inflammation and aberrant DNA repair. Validation of these in-vitro findings in an experimental COPD model by andrographolide is warranted.

Ribosomal Protein S3 Gene Silencing Protects Against Cigarette Smoke-Induced Acute Lung Injury.

Chronic obstructive pulmonary disease (COPD) is estimated to be the third leading cause of death by 2030. Transcription factor NF-κB may play a critical role in COPD pathogenesis. Ribosomal protein S3 (RPS3), a 40S ribosomal protein essential for executing protein translation, has recently been found to interact with the NF-κB p65 subunit and promote p65 DNA-binding activity. We sought to study whether RPS3 gene silencing could protect against cigarette-smoke (CS)-induced acute lung injury in a mouse model. Effects of an intratracheal RPS3 siRNA in CS-induced lung injury were determined by measuring bronchoalveolar lavage (BAL) fluid cell counts, levels of inflammatory and oxidative damage markers, and NF-κB translocation. Lung RPS3 level was found to be upregulated for the first time with CS exposure, and RPS3 siRNA blocked CS-induced neutrophil counts in BAL fluid. RPS3 siRNA suppressed CS-induced lung inflammatory mediator and oxidative damage marker levels, as well as nuclear p65 accumulation and transcriptional activation. RPS3 siRNA was able to disrupt CS extract (CSE)-induced NF-κB activation in an NF-κB reporter gene assay. We report for the first time that RPS3 gene silencing ameliorated CS-induced acute lung injury, probably via interruption of the NF-κB activity, postulating that RPS3 is a novel therapeutic target for COPD.

Targeting the renin-angiotensin system as novel therapeutic strategy for pulmonary diseases.

The renin-angiotensin system (RAS) plays a major role in regulating electrolyte balance and blood pressure. RAS has also been implicated in the regulation of inflammation, proliferation and fibrosis in pulmonary diseases such as asthma, acute lung injury (ALI), chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF) and pulmonary arterial hypertension (PAH). Current therapeutics suffer from some drawbacks like steroid resistance, limited efficacies and side effects. Novel intervention is definitely needed to offer optimal therapeutic strategy and clinical outcome. This review compiles and analyses recent investigations targeting RAS for the treatment of inflammatory lung diseases. Inhibition of the upstream angiotensin (Ang) I/Ang II/angiotensin receptor type 1 (AT1R) pathway and activation of the downstream angiotensin-converting enzyme 2 (ACE2)/Ang (1-7)/Mas receptor pathway are two feasible strategies demonstrating efficacies in various pulmonary disease models. More recent studies favor the development of targeting the downstream ACE2/Ang (1-7)/Mas receptor pathway, in which diminazene aceturate, an ACE2 activator, GSK2586881, a recombinant ACE2, and AV0991, a Mas receptor agonist, showed much potential for further development. As the pathogenesis of pulmonary diseases is so complex that RAS modulation may be used alone or in combination with existing drugs like corticosteroids, pirfenidone/nintedanib or endothelin receptor antagonists for different pulmonary diseases. Personalized medicine through genetic screening and phenotyping for angiotensinogen or ACE would aid treatment especially for non-responsive patients. This review serves to provide an update on the latest development in the field of RAS targeting for pulmonary diseases, and offer some insights into future direction.

Is there a future for andrographolide to be an anti-inflammatory drug? Deciphering its major mechanisms of action.

Andrographis paniculata has long been part of the traditional herbal medicine system in Asia and in Scandinavia. Andrographolide was isolated as a major bioactive constituent of A. paniculata in 1951, and since 1984, andrographolide and its analogs have been scrutinized with modern drug discovery approach for anti-inflammatory properties. With this accumulated wealth of pre-clinical data, it is imperative to review and consolidate different sources of information, to decipher the major anti-inflammatory mechanisms of action in inflammatory diseases, and to provide direction for future studies. Andrographolide and its analogs have been shown to provide anti-inflammatory benefits in a variety of inflammatory disease models. Among the diverse signaling pathways investigated, inhibition of NF-κB activity is the prevailing anti-inflammatory mechanism elicited by andrographolide. There is also increasing evidence supporting endogenous antioxidant defense enhancement by andrographolide through Nrf2 activation. However, the exact pathway leading to NF-κB and Nrf2 activation by andrographolide has yet to be elucidated. Validation and consensus on the major mechanistic actions of andrographolide in different inflammatory conditions are required before translating current findings into clinical settings. There are a few clinical trials conducted using andrographolide in fixed combination formulation which have shown anti-inflammatory benefits and good safety profile. A concerted effort is definitely needed to identify potent andrographolide lead compounds with improved pharmacokinetics and toxicological properties. Taken together, andrographolide and its analogs have great potential to be the next new class of anti-inflammatory agents, and more andrographolide molecules are likely moving towards clinical study stage in the near future.

Radiation-Induced Dermatitis is Mediated by IL17-Expressing γδ T Cells.

Radiation dermatitis is a serious cutaneous injury caused by radiation therapy or upon accidental nuclear exposure. However, the pathogenic immune mechanisms underlying this injury are still poorly understood. We seek to discover how the dysregulated immune response after irradiation orchestrates skin inflammation. The skin on the left flank of C57BL/6J wild-type and C57BL/6J Tcrd-/- mice, which are deficit in γδ T cells, was exposed to a single X-ray dose of 25 Gy, and the right-flank skin was used as a sham-irradiated control. At 4 weeks postirradiation, the wild-type skin exhibited signs of depilation, erythema and desquamation. Histological analysis showed hyperproliferation of keratinocytes and acanthosis. Dramatic elevation of IL17-expressing T cells was identified from the irradiated skin, which was mainly contributed by γδ T cells and innate lymphoid cells, rather than Th17 cells. Furthermore, protein levels of critical cytokines for IL17-expressing γδ T cell activation, IL1ß and IL23 were found markedly upregulated. Lastly, radiation-induced dermatitis was significantly attenuated in γδ T cell knockout mice. In vitro, normal human epidermal keratinocytes (NHEKs) could be initiator cells of inflammation by providing a great number of pro-inflammatory mediators upon radiation, and as well as effector cells of epidermal hyperplasia in response to exogenous IL17 and/or IL22 treatment. Our findings implicate a novel role of IL17-expressing γδ T cells in mediating radiation-induced skin inflammation. This study reveals the innate immune response pathway as a potential therapeutic target for radiation skin injury.

Radiation-Induced Dermatitis is Mediated by IL17-Expressing γδ T Cells.

Radiation dermatitis is a serious cutaneous injury caused by radiation therapy or upon accidental nuclear exposure. However, the pathogenic immune mechanisms underlying this injury are still poorly understood. We seek to discover how the dysregulated immune response after irradiation orchestrates skin inflammation. The skin on the left flank of C57BL/6J wild-type and C57BL/6J Tcrd-/- mice, which are deficit in γδ T cells, was exposed to a single X-ray dose of 25 Gy, and the right-flank skin was used as a sham-irradiated control. At 4 weeks postirradiation, the wild-type skin exhibited signs of depilation, erythema and desquamation. Histological analysis showed hyperproliferation of keratinocytes and acanthosis. Dramatic elevation of IL17-expressing T cells was identified from the irradiated skin, which was mainly contributed by γδ T cells and innate lymphoid cells, rather than Th17 cells. Furthermore, protein levels of critical cytokines for IL17-expressing γδ T cell activation, IL1ß and IL23 were found markedly upregulated. Lastly, radiation-induced dermatitis was significantly attenuated in γδ T cell knockout mice. In vitro, normal human epidermal keratinocytes (NHEKs) could be initiator cells of inflammation by providing a great number of pro-inflammatory mediators upon radiation, and as well as effector cells of epidermal hyperplasia in response to exogenous IL17 and/or IL22 treatment. Our findings implicate a novel role of IL17-expressing γδ T cells in mediating radiation-induced skin inflammation. This study reveals the innate immune response pathway as a potential therapeutic target for radiation skin injury.