Suppression of sirtuin 1 alleviates airway inflammation through mTOR‑mediated autophagy

The role of deacetylase SIRT1 in allergic diseases

The silent information regulator sirtuin 1 (SIRT1) protein is an NAD+-dependent class-III lysine deacetylase that serves as an important post-transcriptional modifier targeting lysine acetylation sites to mediate deacetylation modifications of histones and non-histone proteins. SIRT1 has been reported to be involved in several physiological or pathological processes such as aging, inflammation, immune responses, oxidative stress and allergic diseases. In this review, we summarized the regulatory roles of SIRT1 during allergic disorder progression. Furthermore, we highlight the therapeutic effects of targeting SIRT1 in allergic diseases.

SIRT1: An Intermediator of Key Pathways Regulating Pulmonary Diseases

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

Investigating Forkhead Box O Transcription Factor 1 Gene's Relation to Immunoglobulin E in House Dust Mite-Allergic Asthma Patients

House dust mite (HDM)-allergic asthma is an abnormal immune response to extrinsic aeroallergens found in human vicinities. Studying the role of the associated immunity biomarkers and their interplay helps in discovering novel therapeutic strategies that can be used in adjunct with effective long-term immunotherapy. This study investigates the total serum IgE, FoxO1, and Sirtuin 1 (SIRT1) gene expressions in HDM-allergic asthma patients. We enrolled 40 patients for each of the following three groups: an HV group of healthy volunteers and HDM/AA and HDM/SCIT groups of HDM-allergic asthma patients who did not and who did receive immunotherapy before recruitment in this study, respectively. The results elucidated that total IgE was strikingly elevated in the HDM/AA group and showed little decline in the HDM/SCIT group. Both FoxO1 and SIRT1 gene expressions showed the highest levels in the HDM/SCIT group. There was a negative correlation between total IgE and both FoxO1 and SIRT1 in the HDM/AA group while there was a positive correlation with SIRT1 in the HDM/SCIT group. In conclusion, the interplay of the three immunity biomarkers related to HDM-allergic asthma after the course of immunotherapy treatment suggests further, broader studies on the feasibility of their role as immunity biomarkers in the control and remission of HDM-allergic asthma.

Identification of Hub Genes in the Pathogenesis of Bronchiolitis Obliterans via Bioinformatic Analysis and Experimental Verification

Background

Bronchiolitis obliterans (BO) is a chronic disease that can arise as a complication of severe childhood pneumonia and can also impact the long-term survival of patients after lung transplantation. However, the precise molecular mechanism underlying BO remains unclear. We aimed to identify BO-associated hub genes and their molecular mechanisms.

Methods

BO-associated transcriptome datasets (GSE52761, GSE137169, and GSE94557) were downloaded from the Gene Expression Omnibus (GEO) database to identify differentially expressed genes (DEGs). Additional bioinformatics analyses, such as Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Protein-Protein Interaction (PPI) analyses, were performed to determine functional roles and DEG-associated regulatory networks. Prediction of hub genes using the 12 algorithms available in the Cytohubba plugin of Cytoscape software was also performed. Verification was performed using the BO mouse model.

Results

Our results revealed 57 DEGs associated with BO, of which 18 were down-regulated and 39 were up-regulated. The Cytohubba plugin data further narrowed down the 57 DEGs into 9 prominent hub genes (CCR2, CD1D, GM2A, TFEC, MPEG1, CTSS, GPNMB, BIRC2, and CTSZ). Genes such as CCR2, TFEC, MPEG1, CTSS, and CTSZ were dysregulated in 2,3-butanedione-induced BO mice, whereas TFEC, CTSS, and CTSZ were dysregulated in nitric acid-induced BO mouse models.

Conclusion

Our study identified and validated four novel BO biomarkers, which may allow further investigation into the development of distinct BO diagnostic markers and novel therapeutic avenues.

Empagliflozin inhibits autophagy and mitigates airway inflammation and remodelling in mice with ovalbumin-induced allergic asthma

Empagliflozin, a selective inhibitor of Na⁺-glucose cotransporter-2, has been reported to exert anti-inflammatory and anti-fibrotic effects in addition to autophagy modulation. Addressing the role of autophagy in allergic asthma revealed controversial results. The potential effect of empagliflozin treatment on airway inflammation and remodelling as well as autophagy modulation in a murine model of allergic asthma was investigated. Over a 7-week period, male BALB/c mice were sensitized and challenged by intraperitoneal injection and inhalation of ovalbumin, respectively. Animals were treated with empagliflozin (10 mg/kg; orally) and/or rapamycin (an autophagy inducer; 4 mg/kg; intraperitoneally) before every challenge. Methacholine-induced airway hyperresponsiveness was evaluated one day after the last challenge. After euthanasia, serum, bronchoalveolar lavage fluid, and lung tissues were collected for biochemical, histopathological, and immunohistochemical assessment. Results revealed that empagliflozin decreased airway hyperresponsiveness, serum ovalbumin-specific immunoglobulin E, and bronchoalveolar lavage total and differential leukocytic counts. Levels of inflammatory and profibrotic cytokines (IL-4, IL-5, IL-13, IL-17, and transforming growth factor-β1) were all inhibited. Moreover, empagliflozin preserved pulmonary microscopic architecture and alleviated bronchiolar epithelial thickening, goblet cell hyperplasia, fibrosis and smooth muscle hypertrophy. These effects were associated with inhibition of ovalbumin-activated autophagic flux, as demonstrated by decreased LC3B expression and LC3BII/I ratio, as well as increased P62 expression. However, the therapeutic potential of empagliflozin was inhibited when rapamycin was co-administered. In conclusion, this study demonstrates that empagliflozin has immunomodulatory, anti-inflammatory, and anti-remodelling properties in ovalbumin-induced allergic asthma and suggests that autophagic flux inhibition may play a role in empagliflozin's anti-asthmatic effects.

Gut-Derived Metabolites from Dietary Tryptophan Supplementation Quench Intestinal Inflammation through the AMPK-SIRT1-Autophagy Pathway

Tryptophan has drawn wide attention due to its involvement in improving intestinal immune defense directly and indirectly by regulating metabolic pathways. The study aims to elucidate the potential modulating roles of tryptophan to protect against intestinal inflammation and elucidate the underlying molecular mechanisms. The protective effects of tryptophan against intestinal inflammation are examined in the lipopolysaccharide (LPS)-induced inflammatory model. We first found that tryptophan markedly (p < 0.01) inhibited proinflammatory cytokines production and nuclear factor κB (NF-κB) pathway activation upon LPS challenge. Next, we demonstrated that tryptophan (p < 0.05) attenuated LPS-caused intestinal mucosal barrier damage by increasing the number of goblet cells, mucins, and antimicrobial peptides (AMPs) in the ileum of mice. In addition, tryptophan (p < 0.05) inhibited LPS-induced autophagic flux through the AMP-activated protein kinase (AMPK)-sirtuin 1 (SIRT1) pathway in the intestinal systems to maintain autophagy homeostasis. Meanwhile, tryptophan also reshaped the gut microbiota composition in LPS-challenge mice by increasing the abundance of short-chain fatty acid (SCFA)-producing bacteria such as Acetivibrio (0.053 ± 0.017 to 0.21 ± 0.0041%). Notably, dietary tryptophan resulted in the activation of metabolic pathways during the inflammatory response. Furthermore, exogenous treatment of tryptophan metabolites kynurenine (Kyn) and 5-HT in porcine intestinal epithelial cells (IPEC-J2 cells) reproduced similar protective effects as tryptophan to attenuate LPS-induced intestinal inflammation through regulating the AMPK-SIRT1-autophagy. Taken together, the present study indicates that tryptophan exhibits intestinal protective and immunoregulatory effects resulting from the activation of metabolic pathways, maintenance of gut mucosal barrier integrity, microbiota composition, and AMPK-SIRT1-autophagy level.

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.

The Ameliorative Effect of Empagliflozin in Vigabatrin-Induced Cerebellar/Neurobehavioral Deficits: Targeting mTOR/AMPK/SIRT-1 Signaling Pathways

Introduction. Vigabatrin (VGB) is an antiepileptic drug that acts to irreversibly inhibit the γ-aminobutyric acid (GABA) transaminase enzyme, elevating GABA levels. Broad studies have established that long-term treatment and/or high doses of VGB lead to variable visual defects. However, little attention has been paid to its other side effects, especially those demonstrating cerebellar involvement. Sodium glucose-linked co-transporter 2 (SGLT2) inhibitors are antidiabetic agents with protective effects far greater than expected based on their anti-hyperglycemic effect. Method. Our study herein was designed to investigate the possible ameliorative effect of empagliflozin, the SGLT2 inhibitors, in VGB-induced cerebellar toxicity. A total of 40 male Wistar rats were allocated equally into 4 groups: Group I: control group; Group II: VGB group; Group III empagliflozin treated VGB group; and Group IV: empagliflozin treated group. All groups were subjected to the detection of cerebellar messenger RNA gene expression of silent mating type information regulation 2 homolog 1 (SIRT1) and Nucleoporin p62 (P62). Mammalian target of rapamycin (mTOR), adenosine monophosphate-activated protein kinase (AMPK), and beclin1 levels were assessed by the ELISA technique while malondialdehyde (MDA) level and superoxide dismutase (SOD) activity were detected spectrophotometrically. Immuno-histochemical studies, focusing on glial fibrillary acidic protein (GFAP) and S100 were performed, and the optical color density and the mean area percentage of GFAP positive astrocytes and the number of S 100 positive cells were also counted. Results. Following empagliflozin treatment, we documented significant upregulation of both SIRT1 and P62 mRNA gene expression. Additionally, AMPK, Beclin1 levels, and SOD activity were significantly improved, while both mTOR and MDA levels were significantly reduced. Conclusions. We concluded for the first time that empagliflozin efficiently ameliorated the VGB-induced disrupted mTOR/AMPK/SIRT-1 signaling axis with subsequent improvement of the autophagy machinery and mitigation of the oxidative and inflammatory cellular environment, paving the way for an innovative therapeutic potential in managing VGB-induced neurotoxicity.

Vitamin D Attenuates Airway Inflammation in Asthmatic Guinea Pigs Using Mammalian Target of Rapamycin-Mediated Autophagy

The purpose of this experiment is to find out the function of Vitamin D (VD) in airway inflammation in asthmatic guinea pigs by regulating mammalian target of rapamycin (mTOR)-mediated autophagy. A total of 40 male guinea pigs were randomly assigned into the Con group, the ovalbumin (OVA)-sensitized group, the VD group, the VD + dimethyl sulfoxide group, and the VD + rapamycin (mTOR inhibitor) group. Then, serum from all groups was harvested for the measurement of immunoglobulin E (IgE), interleukin (IL)-4, and IL-5 levels. Next, bronchoalveolar lavage fluid was collected for cell counting. Moreover, lung tissues were extracted to assess levels of p-mTOR and autophagy factors (LC3B, Beclin1, Atg5, and P62). Compared with the Con group, the OVA group showed elevated levels of IgE, IL-4, and IL-5, increased contents of eosinophils, neutrophil, and lymphocytes, and declined monocytes. And the VD group improved inflammatory reactions in the guinea pigs. Besides, the OVA group showed lower levels of p-mTOR and P62 and higher autophagy levels than the Con group, while the VD group had opposite results. Rapamycin annulled the suppressive role of VD to airway inflammation in asthmatic guinea pigs. VD might inhibit OVA-induced airway inflammation by inducing mTOR activation and downregulating autophagy in asthmatic guinea pigs.

Autophagy in ovary and polycystic ovary syndrome: role, dispute and future perspective

Polycystic ovary syndrome (PCOS) is a unification of endocrine and metabolic disorders and has become immensely prevalent among women of fertile age. The prime organ affected in PCOS is the ovary and its distressed functioning elicits disturbed reproductive outcomes. In the ovary, macroautophagy/autophagy performs a pivotal role in directing the chain of events starting from oocytes origin until its fertilization. Recent discoveries demonstrate a significant role of autophagy in the pathogenesis of PCOS. Defective autophagy in the follicular cells during different stages of follicles is observed in the PCOS ovary. Exploring different autophagy pathways provides a platform for predicting the possible cause of altered ovarian physiology in PCOS. In this review, we have emphasized autophagy's role in governing follicular development under normal circumstances and in PCOS, including significant abnormalities associated with PCOS such as anovulation, hyperandrogenemia, metabolic disturbances, and related abnormality. So far, few studies have linked autophagy and PCOS and propose its essential role in PCOS progression. However, detailed knowledge in this area is lacking. Here we have summarized the latest knowledge related to autophagy associated with PCOS. This review's main objective is to provide a background of autophagy in the ovary, its possible connection with PCOS and suggested a novel proposal for future studies to aid a better understanding of PCOS pathogenesis.Abbreviations: AE: androgen excess; AF: antral follicle; AKT/PKB: AKT serine/threonine kinase; AMH: anti-Mullerian hormone; AMPK: AMP-activated protein kinase; ATG: autophagy-related; BCL2: BCL2 apoptosis regulator; BECN1: beclin 1; BMP: bone morphogenetic protein; CASP3: caspase 3; CL: corpus luteum; CYP17A1/P450C17: cytochrome P450 family 17 subfamily A member 1; CYP19A1: cytochrome P450 family 19 subfamily A member 1; DHEA: dehydroepiandrosterone; EH: endometrial hyperplasia; FF: follicular fluid; FOXO: forkhead box O; FSH: follicle stimulating hormone; GC: granulosa cell; GDF: growth differentiation factor; HA: hyperandrogenemia; HMGB1: high mobility group box 1; IGF1: insulin like growth factor 1; INS: insulin; IR: insulin resistance; LHCGR/LHR: luteinizing hormone/choriogonadotropin receptor; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MAPK/ERK: mitogen-activated protein kinase; MAPK8/JNK: mitogen-activated protein kinase 8; MTOR: mechanistic target of rapamycin kinase; MTORC: mechanistic target of rapamycin complex; NAFLD: nonalcoholic fatty liver disease; NFKB: nuclear factor kappa B; OLR1/LOX-1: oxidized low density lipoprotein receptor 1; oxLDL: oxidized low-density lipoproteins; PA: palmitic acid; PCOS: polycystic ovary syndrome; PF: primary follicle; PGC: primordial germ cell; PI3K: phosphoinositide 3-kinase; PMF: primordial follicle; ROS: reactive oxygen species; RP: resting pool; SIRT1: sirtuin 1; SQSTM1/p62: sequestosome 1; T2DM: type 2 diabetes mellitus; TC: theca cell; TUG1: taurine up-regulated 1.

HDAC6 and CXCL13 Mediate Atopic Dermatitis by Regulating Cellular Interactions and Expression Levels of miR-9 and SIRT1

Histone deacetylase 6 (HDAC6) has been known to regulate inflammatory diseases. The role of HDAC6 in allergic skin inflammation has not been studied. We studied the role of HDAC6 in atopic dermatitis (AD) and the mechanisms associated with it. The decreased expression or chemical inhibition of HDAC6 suppressed AD by decreasing autophagic flux and cellular features of AD. AD increased expression levels of the Th1 and Th2 cytokines, but decreased expression levels of forkhead box P3 (FoxP3) and interleukin-10 (IL-10) in an HDAC6-dependent manner. CXC chemokine ligand 13 (CXCL13), which was increased in an HDAC6-depenednt manner, mediated AD. MiR-9, negatively regulated by HDAC6, suppressed AD by directly regulating the expression of sirtuin 1 (SIRT1). The downregulation or inhibition of SIRT1 suppressed AD. Experiments employing culture medium and transwell suggested that cellular interactions involving mast cells, keratinocytes, and dermal fibroblast cells could promote AD; HDAC6 and CXCL13 were found to be necessary for these cellular interactions. Mouse recombinant CXCL13 protein increased HDAC6 expression in skin mast cells and dermal fibroblast cells. CXCL13 protein was found to be present in the exosomes of DNCB-treated skin mast cells. Exosomes of DNCB-treated skin mast cells enhanced invasion potentials of keratinocytes and dermal fibroblast cells and increased expression levels of HDAC6, SIRT1 and CXCL13 in keratinocytes and dermal fibroblast cells. These results indicate that HDAC6 and CXCL13 may serve as targets for the developing anti-atopic drugs.

Rapamycin protects against aristolochic acid nephropathy in mice by potentiating mammalian target of rapamycin‑mediated autophagy

Autophagy serves a crucial role in the etiology of kidney diseases, including drug‑induced renal impairment, inherited kidney disease, diabetic nephropathy and aristolochic acid nephropathy (AAN) and is, therefore, a potential target for treatment. We previously demonstrated that rapamycin could attenuate AAN in mice; however, the underlying mechanism remains to be elucidated. Therefore, whether the renal protective effect of rapamycin (an autophagy activator) is related to autophagy in aristolochic acid (AA)‑treated mice was of particular interest. The pathophysiological roles of rapamycin were investigated in AA‑induced nephrotoxicity in mice and the mechanisms of rapamycin action were explored by evaluating the modulation of autophagy in rapamycin‑treated mice and cultured renal tubular epithelial cells. Supplementation with rapamycin reversed AA‑induced kidney injury in mice and improved AA‑induced autophagy damage in vivo and in vitro. Mechanistically, rapamycin inhibited the renal expression of phosphorylated (p‑)mammalian target of rapamycin (mTOR) and p‑ribosomal S6 protein kinase 1, which in turn activated renal autophagy and decreased apoptosis, probably by removing AA‑elicited damaged mitochondria and misfolded proteins. The findings of the present study demonstrated that rapamycin protects against AA‑induced nephropathy by activating the mTOR‑autophagy axis and suggested that rapamycin may be a promising pharmacological target for the treatment of AAN.

Autophagy: A Friend or Foe in Allergic Asthma?

Autophagy is a major self-degradative process through which cytoplasmic material, including damaged organelles and proteins, are delivered and degraded in the lysosome. Autophagy represents a dynamic recycling system that produces new building blocks and energy, essential for cellular renovation, physiology, and homeostasis. Principal autophagy triggers include starvation, pathogens, and stress. Autophagy plays also a pivotal role in immune response regulation, including immune cell differentiation, antigen presentation and the generation of T effector responses, the development of protective immunity against pathogens, and the coordination of immunometabolic signals. A plethora of studies propose that both impaired and overactive autophagic processes contribute to the pathogenesis of human disorders, including infections, cancer, atherosclerosis, autoimmune and neurodegenerative diseases. Autophagy has been also implicated in the development and progression of allergen-driven airway inflammation and remodeling. Here, we provide an overview of recent studies pertinent to the biology of autophagy and molecular pathways controlling its activation, we discuss autophagy-mediated beneficial and detrimental effects in animal models of allergic diseases and illuminate new advances on the role of autophagy in the pathogenesis of human asthma. We conclude contemplating the potential of targeting autophagy as a novel therapeutic approach for the management of allergic responses and linked asthmatic disease.

Rheostatic Balance of Circadian Rhythm and Autophagy in Metabolism and Disease

Circadian rhythms are physical, behavioral and environmental cycles that respond primarily to light and dark, with a period of time of approximately 24 h. The most essential physiological functions of mammals are manifested in circadian rhythm patterns, including the sleep-wake cycle and nutrient and energy metabolism. Autophagy is a conserved biological process contributing to nutrient and cellular homeostasis. The factors affecting autophagy are numerous, such as diet, drugs, and aging. Recent studies have indicated that autophagy is activated rhythmically in a clock-dependent manner whether the organism is healthy or has certain diseases. In addition, autophagy can affect circadian rhythm by degrading circadian proteins. This review discusses the interaction and mechanisms between autophagy and circadian rhythm. Moreover, we introduce the molecules influencing both autophagy and circadian rhythm. We then discuss the drugs affecting the circadian rhythm of autophagy. Finally, we present the role of rhythmic autophagy in nutrient and energy metabolism and its significance in physiology and metabolic disease.