Depletion of microRNA-451 in response to allergen exposure accentuates asthmatic inflammation by regulating Sirtuin2

Context-dependent role of sirtuin 2 in inflammation

Sirtuin 2 is a member of the sirtuin family nicotinamide adenine dinucleotide (NAD+)-dependent deacetylases, known for its regulatory role in different processes, including inflammation. In this context, sirtuin 2 has been involved in the modulation of key inflammatory signaling pathways and transcription factors by deacetylating specific targets, such as nuclear factor κB and nucleotide-binding oligomerization domain-leucine-rich-repeat and pyrin domain-containing protein 3 (NLRP3). However, whether sirtuin 2-mediated pathways induce a pro- or an anti-inflammatory response remains controversial. Sirtuin 2 has been implicated in promoting inflammation in conditions such as asthma and neurodegenerative diseases, suggesting that its inhibition in these conditions could be a potential therapeutic strategy. Conversely, arthritis and type 2 diabetes mellitus studies suggest that sirtuin 2 is essential at the peripheral level and, thus, its inhibition in these pathologies would not be recommended. Overall, the precise role of sirtuin 2 in inflammation appears to be context-dependent, and further investigation is needed to determine the specific molecular mechanisms and downstream targets through which sirtuin 2 influences inflammatory processes in various tissues and pathological conditions. The present review explores the involvement of sirtuin 2 in the inflammation associated with different pathologies to elucidate whether its pharmacological modulation could serve as an effective strategy for treating this prevalent symptom across various diseases.

Regulation of immune cells by miR-451 and its potential as a biomarker in immune-related disorders: a mini review

In 2005, Altuvia and colleagues were the first to identify the gene that encodes miR-451 in the human pituitary gland, located in chromosome region 17q11.2. Subsequent studies have confirmed that miR-451 regulates various immune cells, including T cells, B cells, microglia, macrophages, and neutrophils, thereby influencing disease progression. The range of immune-related diseases affected encompasses various cancers, lymphoblastic leukemia, and injuries to the lungs and spinal cord, among others. Moreover, miR-451 is produced by immune cells and can regulate both their own functions and those of other immune cells, thus creating a regulatory feedback loop. This article aims to comprehensively review the interactions between miR-451 and immune cells, clarify the regulatory roles of miR-451 within the immune system, and assess its potential as both a therapeutic target and a biomarker for immune-related diseases.

Regulation of Macrophage Polarization in Allergy by Noncoding RNAs

Allergy is a type 2 immune reaction triggered by antigens known as allergens, including food and environmental substances such as peanuts, plant pollen, fungal spores, and the feces and debris of mites and insects. Macrophages are myeloid immune cells with phagocytic abilities that process exogenous and endogenous antigens. Upon activation, they can produce effector molecules such as cytokines as well as anti-inflammatory molecules. The dysregulation of macrophage function can lead to excessive type 1 inflammation as well as type 2 inflammation, which includes allergic reactions. Thus, it is important to better understand how macrophages are regulated in the pathogenesis of allergies. Emerging evidence highlights the role of noncoding RNAs (ncRNAs) in macrophage polarization, which in turn can modify the pathogenesis of various immune-mediated diseases, including allergies. This review summarizes the current knowledge regarding this topic and considers three classes of ncRNAs: microRNAs, long ncRNAs, and circular ncRNAs. Understanding the roles of these ncRNAs in macrophage polarization will provide new insights into the pathogenesis of allergies and identify potential novel therapeutic targets.

Sex-specific lung inflammation and mitochondrial damage in a model of electronic cigarette exposure in asthma

The prevalence of electronic cigarette (EC) use among adult with asthma has continued to increase over time, in part due to the belief of being less harmful than smoking. However, the extent of their toxicity and the involved mechanisms contributing to the deleterious impact of EC exposure on patients with preexisting asthma have not been delineated. In the present project, we tested the hypothesis that EC use contributes to respiratory damage and worsening inflammation in the lungs of patients with asthma. To define the consequences of EC exposure in established asthma, we used a mouse model with/without preexisting asthma for short-term exposure to EC aerosols. C57/BL6J mice were sensitized and challenged with a DRA (dust mite, ragweed, Aspergillus fumigates, 200 µg/mL) mixture and exposed daily to EC with nicotine (2% nicotine in 30:70 propylene glycol: vegetable glycerin) or filtered air for 2 wk. The mice were evaluated at 24 h after the final EC exposure. After EC exposure in asthmatic mice, lung inflammatory cell infiltration and goblet cell hyperplasia were increased, whereas EC alone did not cause airway inflammation. Our data also show that mitochondrial DNA (mtDNA) content and a key mtDNA regulator, mitochondrial transcription factor A (TFAM), are reduced in asthmatic EC-exposed mice in a sex-dependent manner. Together, these results indicate that TFAM loss in lung epithelium following EC contributes to male-predominant sex pathological differences, including mitochondrial damage, inflammation, and remodeling in asthmatic airways.NEW & NOTEWORTHY Respiratory immunity is dysregulated in preexisting asthma, and further perturbations by EC use could exacerbate asthma severity. However, the extent of their toxicity and the involved mechanisms contributing to the deleterious impact of EC exposure on patients with preexisting asthma have not been delineated. We found that EC has unique biological impacts in lungs and potential sex differences with loss of TFAM, a key mtDNA regulator, in lung epithelial region from our animal EC study.

Advances in respiratory physiology in mouse models of experimental asthma

Recent advances in mouse models of experimental asthma coupled with vast improvements in systems that assess respiratory physiology have considerably increased the accuracy and human relevance of the outputs from these studies. In fact, these models have become important pre-clinical testing platforms with proven value and their capacity to be rapidly adapted to interrogate emerging clinical concepts, including the recent discovery of different asthma phenotypes and endotypes, has accelerated the discovery of disease-causing mechanisms and increased our understanding of asthma pathogenesis and the associated effects on lung physiology. In this review, we discuss key distinctions in respiratory physiology between asthma and severe asthma, including the magnitude of airway hyperresponsiveness and recently discovered disease drivers that underpin this phenomenon such as structural changes, airway remodeling, airway smooth muscle hypertrophy, altered airway smooth muscle calcium signaling, and inflammation. We also explore state-of-the-art mouse lung function measurement techniques that accurately recapitulate the human scenario as well as recent advances in precision cut lung slices and cell culture systems. Furthermore, we consider how these techniques have been applied to recently developed mouse models of asthma, severe asthma, and asthma-chronic obstructive pulmonary disease overlap, to examine the effects of clinically relevant exposures (including ovalbumin, house dust mite antigen in the absence or presence of cigarette smoke, cockroach allergen, pollen, and respiratory microbes) and to increase our understanding of lung physiology in these diseases and identify new therapeutic targets. Lastly, we focus on recent studies that examine the effects of diet on asthma outcomes, including high fat diet and asthma, low iron diet during pregnancy and predisposition to asthma development in offspring, and environmental exposures on asthma outcomes. We conclude our review with a discussion of new clinical concepts in asthma and severe asthma that warrant investigation and how we could utilize mouse models and advanced lung physiology measurement systems to identify factors and mechanisms with potential for therapeutic targeting.

Roles of sirtuins in asthma

Sirtuins are nicotinamide adenine dinucleotide (NAD⁺)-dependent lysine deacylases and deacetylases that participate in a variety of cellular processes, including transcriptional activity, energy metabolism, DNA damage response, inflammation, apoptosis, autophagy, and oxidative stress. As a result, sirtuins are linked to multiple pathophysiological processes, such as cardiovascular diseases, metabolic diseases, autoimmune diseases, infectious diseases, and respiratory diseases. Asthma is the most common respiratory disease, which is characterized by airway inflammation and airway remodeling. Accumulating evidence has indicated that sirtuins are involved in the pathogenesis of asthma. Furthermore, some studies have suggested that sirtuin modulators are potential agents for the treatment of asthma via alteration of the expression or activity of sirtuins. In this review, we illustrate the role of sirtuins in asthma, discuss related molecular mechanisms, and evaluate the sirtuins-targeted therapy for asthma.

Targeting ETosis by miR-155 inhibition mitigates mixed granulocytic asthmatic lung inflammation

Asthma is phenotypically heterogeneous with several distinctive pathological mechanistic pathways. Previous studies indicate that neutrophilic asthma has a poor response to standard asthma treatments comprising inhaled corticosteroids. Therefore, it is important to identify critical factors that contribute to increased numbers of neutrophils in asthma patients whose symptoms are poorly controlled by conventional therapy. Leukocytes release chromatin fibers, referred to as extracellular traps (ETs) consisting of double-stranded (ds) DNA, histones, and granule contents. Excessive components of ETs contribute to the pathophysiology of asthma; however, it is unclear how ETs drive asthma phenotypes and whether they could be a potential therapeutic target. We employed a mouse model of severe asthma that recapitulates the intricate immune responses of neutrophilic and eosinophilic airway inflammation identified in patients with severe asthma. We used both a pharmacologic approach using miR-155 inhibitor-laden exosomes and genetic approaches using miR-155 knockout mice. Our data show that ETs are present in the bronchoalveolar lavage fluid of patients with mild asthma subjected to experimental subsegmental bronchoprovocation to an allergen and a severe asthma mouse model, which resembles the complex immune responses identified in severe human asthma. Furthermore, we show that miR-155 contributes to the extracellular release of dsDNA, which exacerbates allergic lung inflammation, and the inhibition of miR-155 results in therapeutic benefit in severe asthma mice. Our findings show that targeting dsDNA release represents an attractive therapeutic target for mitigating neutrophilic asthma phenotype, which is clinically refractory to standard care.

Deciphering the role of miRNA in reprogramming plant responses to drought stress

Drought is the most prevalent environmental stress that affects plants' growth, development, and crop productivity. However, plants have evolved adaptive mechanisms to respond to the harmful effects of drought. They reprogram their: transcriptome, proteome, and metabolome that alter their cellular and physiological processes and establish cellular homeostasis. One of the crucial regulatory processes that govern this reprogramming is post-transcriptional regulation by microRNAs (miRNAs). miRNAs are small non-coding RNAs, involved in the downregulation of the target mRNA via translation inhibition/mRNA degradation/miRNA-mediated mRNA decay/ribosome drop off/DNA methylation. Many drought-inducible miRNAs have been identified and characterized in plants. Their main targets are regulatory genes that influence growth, development, osmotic stress tolerance, antioxidant defense, phytohormone-mediated signaling, and delayed senescence during drought stress. Overexpression of drought-responsive miRNAs (Osa-miR535, miR160, miR408, Osa-miR393, Osa-miR319, and Gma-miR394) in certain plants has led to tolerance against drought stress indicating their vital role in stress mitigation. Similarly, knock down (miR166/miR398c) or deletion (miR169 and miR827) of miRNAs has also resulted in tolerance to drought stress. Likewise, engineered Arabidopsis plants with miR165, miR166 using short tandem target mimic strategy, exhibited drought tolerance. Since miRNAs regulate the expression of an array of drought-responsive genes, they can act as prospective targets for genetic manipulations to enhance drought tolerance in crops and achieve sustainable agriculture. Further investigations toward functional characterization of diverse miRNAs, and understanding stress-responses regulated by these miRNAs and their utilization in biotechnological applications is highly recommended.

Overexpressing long non-coding RNA OIP5-AS1 ameliorates sepsis-induced lung injury in a rat model via regulating the miR-128-3p/Sirtuin-1 pathway

Sepsis, resulting from infections, is a systemic inflammatory response syndrome with a high fatality rate. The present study revolves around probing into the function and molecular mechanism of long non-coding RNA OIP5 antisense RNA 1 (lncRNA OIP5-AS1) in modulating acute lung injury (ALI) mediated by sepsis. Here, a sepsis model was constructed using cecal ligation and puncture (CLP) surgery in vivo. The alveolar macrophage cell line NR8383 and the alveolar type II cell line RLE-6TN were dealt with lipopolysaccharide (LPS) for in-vitro experiments. We discovered that OIP5-AS1 and Sirtuin1 (SIRT1) were markedly down-regulated in sepsis models elicited by CLP or LPS, while miR-128-3p experienced a dramatic up-regulation. OIP5-AS1 overexpression attenuated NR8383 and RLE-6TN cell apoptosis triggered by LPS and suppressed the expressions of nuclear factor kappa B (NF-κB), inducible nitric oxide synthase (iNOS), interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in NR8383 and RLE-6TN cells, whereas miR-128-3p overexpression resulted in the opposite phenomenon. Moreover, OIP5-AS1 overexpression relieved lung edema, lung epithelial cell apoptosis, infiltration of myeloperoxidase (MPO)-labeled polymorphonuclear neutrophils (PMN), inflammatory responses triggered by CLP in vivo. Mechanistically, miR-128-3p, which targeted SIRT1, was hobbled by OIP5-AS1. All in all, OIP5-AS1 overexpression enhanced sepsis-induced ALI by modulating the miR-128-3p/SIRT1 pathway, which helps create new insights into sepsis treatment.

Role of Epigenetics in the Pathogenesis, Treatment, Prediction, and Cellular Transformation of Asthma

Asthma is a mysterious disease with heterogeneity in etiology, pathogenesis, and clinical phenotypes. Although ongoing studies have provided a better understanding of asthma, its natural history, progression, pathogenesis, diversified phenotypes, and even the exact epigenetic linkage between childhood asthma and adult-onset/old age asthma remain elusive in many aspects. Asthma heritability has been established through genetic studies, but genetics is not the only influencing factor in asthma. The increasing incidence and some unsolved queries suggest that there may be other elements related to asthma heredity. Epigenetic mechanisms link genetic and environmental factors with developmental trajectories in asthma. This review provides an overview of asthma epigenetics and its components, including several epigenetic studies on asthma, and discusses the epigenetic linkage between childhood asthma and adult-onset/old age asthma. Studies involving asthma epigenetics present valuable novel approaches to solve issues related to asthma. Asthma epigenetic research guides us towards gene therapy and personalized T cell therapy, directs the discovery of new therapeutic agents, predicts long-term outcomes in severe cases, and is also involved in the cellular transformation of childhood asthma to adult-onset/old age asthma.

MiR-154-5p-MCP1 Axis Regulates Allergic Inflammation by Mediating Cellular Interactions

In a previous study, we have demonstrated that p62, a selective receptor of autophagy, can regulate allergic inflammation. In the present study, microRNA array analysis showed that miR-154-5p was increased by antigen (DNP-HSA) in a p62-dependent manner in rat basophilic leukemia cells (RBL2H3). NF-kB directly increased the expression of miR-154-5p. miR-154-5p mediated in vivo allergic reactions, including passive cutaneous anaphylaxis and passive systemic anaphylaxis. Cytokine array analysis showed that antigen stimulation increased the expression of MCP1 in RBL2H3 cells in an miR-154-5p-dependent manner. Reactive oxygen species (ROS)-ERK-NF-kB signaling increased the expression of MCP1 in antigen-stimulated RBL2H3 cells. Recombinant MCP1 protein induced molecular features of allergic reactions both in vitro and in vivo. Anaphylaxis-promoted tumorigenic potential has been known to be accompanied by cellular interactions involving mast cells, and macrophages, and cancer cells. Our experiments employing culture medium, co-cultures, and recombinant MCP1 protein showed that miR-154 and MCP1 mediated these cellular interactions. MiR-154-5p and MCP1 were found to be present in exosomes of RBL2H3 cells. Exosomes from PSA-activated BALB/C mouse induced molecular features of passive cutaneous anaphylaxis in an miR-154-5p-dependent manner. Exosomes from antigen-stimulated RBL2H3 cells enhanced both tumorigenic and metastatic potentials of B16F1 melanoma cells in an miR-154-5p-dependent manner. Exosomes regulated both ROS level and ROS mediated cellular interactions during allergic inflammation. Our results indicate that the miR-154-5p-MCP1 axis might serve as a valuable target for the development of anti-allergy therapeutics.

Deletion of MicroRNA-144/451 Cluster Aggravated Brain Injury in Intracerebral Hemorrhage Mice by Targeting 14-3-3ζ

This study aims at evaluating the importance and its underlying mechanism of the cluster of microRNA-144/451 (miR-144/451) in the models with intracerebral hemorrhage (ICH). A model of collagenase-induced mice with ICH and a model of mice with simple miR-144/451 gene knockout (KO) were used in this study. Neurodeficits and the water content of the brain of the mice in each group were detected 3 days after collagenase injection. The secretion of proinflammatory cytokines, such as tumor necrosis factor α (TNF-α) and interleukin 1β (IL-1β), as well as certain biomarkers of oxidative stress, was determined in this study. The results revealed that the expression of miR-451 significantly decreased in the mice with ICH, whereas miR-144 showed no significant changes. KO of the cluster of miR-144/451 exacerbated the neurological deficits and brain edema in the mice with ICH. Further analyses demonstrated that the KO of the cluster of miR-144/451 significantly promoted the secretion of TNF-α and IL-1β and the oxidative stress in the perihematomal region of the mice with ICH. In addition, the miR-144/451's depletion inhibited the regulatory axis' activities of miR-451-14-3-3ζ-FoxO3 in the mice with ICH. In conclusion, these data demonstrated that miR-144/451 might protect the mice with ICH against neuroinflammation and oxidative stress by targeting the pathway of miR-451-14-3-3ζ-FoxO3.

AGK2 ameliorates mast cell-mediated allergic airway inflammation and fibrosis by inhibiting FcεRI/TGF-β signaling pathway

Asthma is characterized by airway hyperresponsiveness and allergic inflammation, detrimentally affecting the patients' quality of life. The development of new drugs for the treatment of asthma is warranted to alleviate these issues. Recent studies have demonstrated that sirtuin2 (SIRT2) aggravates asthmatic inflammation by up-regulation of T-helper type 2 responses and macrophage polarization. However, effects of SIRT2 on mast cell activation remain obscure. In this study, we investigated the effects of AGK2, an inhibitor for SIRT2, on mast cell-mediated allergic airway inflammation. Pre-treatment with AGK2 inhibited degranulation of mast cells by suppressing the FcεRI signaling pathway and intracellular calcium influx. The expression of pro-inflammatory cytokines, such as tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-4, IL-5, IL-6, and IL-8, was inhibited via regulation of transcription factors such as NF-κB and NRF2. These effects of AGK2 were verified in passive cutaneous anaphylaxis and acute lung injury animal models. AGK2 attenuated Evans blue pigmentation by inhibiting mast cell activation and lung barrier dysfunction by inhibiting inflammatory responses in these animal models. In the ovalbumin (OVA)-induced allergic airway inflammation murine model, AGK2 alleviated allergic asthma symptoms such as lung histological changes (immune cell and mast cell infiltration, collagen deposition, and α-smooth muscle actin expression) and serum immunoglobulins (Ig) levels (IgE, OVA-specific IgE, IgG1, and IgG2a). Moreover, AGK2 reduced the levels of pro-inflammatory cytokines (TNF-α, IL-1β, IL-4, IL-5, and IL-6) and inflammatory mediators (myeloperoxidase, eosinophil peroxidase, and tumor growth factor-α) in the bronchoalveolar lavage fluid and lung tissues. In addition, the anti-fibrotic effects of AGK2 were verified using lung epithelial cells and TGF-β/Smad reporter stable cells. In conclusion, our findings suggest that SIRT2 plays a role in mast cell-mediated airway inflammatory disease. Therefore, AGK2 is a good potential candidate for treating allergic asthma and lung inflammation.