4-Octyl itaconate (4-OI) attenuates lipopolysaccharide-induced acute lung injury by suppressing PI3K/Akt/NF-κB signaling pathways in mice

Ameliorative effect of pedunculoside on sepsis-induced acute lung injury, inflammation and pulmonary fibrosis in mice model via suppressing AKT/NF-κB pathway

BACKGROUND/OBJECTIVES

Sepsis-induced acute lung injury (ALI) is the typical complications of sepsis with a high global incidence and mortality. Inhibition of inflammatory response is a crucial and effective strategy for sepsis-induced ALI. Pedunculoside (PE) has been shown to have an anti-inflammatory effect on various diseases. However, the effect and mechanism of PE on sepsis-induced ALI remain unknown.

MATERIALS/METHODS

A mice model of sepsis-induced ALI was constructed by cecal ligation and puncture (CLP). The effect of PE on the CLP-induced mice were assessed using pathological staining, terminal deoxynucleotidyl transferase deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL), reverse transcription quantitative polymerase chain reaction (RT-qPCR), enzyme-linked immunosorbent assay (ELISA) and western blot assays.

RESULTS

PE reduced pathological symptoms and scores, apoptosis and the W/D ratio of lung tissues in CLP-induced mice. Besides, PE decreased the level of interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α), pulmonary fibrosis and the expression of fibrosis markers. Mechanically, PE inhibited AKT/NF-κB signaling in CLP-induced mice. Activation of AKT/NF-κB pathway abolished the ameliorative effect of PE on the pathological symptoms, the release of inflammatory factors and pulmonary fibrosis of CLP-induced mice.

CONCLUSION

PE improved inflammation and pulmonary fibrosis by inhibiting AKT/NF-κB pathway in CLP-induced mice.

Itaconate in host inflammation and defense

Immune cells undergo rapid and extensive metabolic changes during inflammation. In addition to contributing to energetic and biosynthetic demands, metabolites can also function as signaling molecules. Itaconate (ITA) rapidly accumulates to high levels in myeloid cells under infectious and sterile inflammatory conditions. This metabolite binds to and regulates the function of diverse proteins intracellularly to influence metabolism, oxidative response, epigenetic modification, and gene expression and to signal extracellularly through binding the G protein-coupled receptor (GPCR). Administration of ITA protects against inflammatory diseases and blockade of ITA production enhances antitumor immunity in preclinical models. In this article, we review ITA metabolism and its regulation, discuss its target proteins and mechanisms, and conjecture a rationale for developing ITA-based therapeutics to treat inflammatory diseases and cancer.

4-Octyl itaconate promotes alveolar ridge preservation following tooth extraction

The search for medications that can effectively reduce alveolar bone loss following tooth extraction is of great interest. This study aimed to observe the roles of 4-octyl itaconate (4-OI) in RANKL-induced osteoclastogenesis of bone marrow macrophages (BMMs) in vitro. Mandibular second molars were extracted to evaluate whether 4-OI could alleviate alveolar bone loss. 4-OI inhibited RANKL-induced osteoclastogenesis and promoted Nrf2 expression in bone marrow macrophages in vitro. Positive Nrf2 expressions were observed in inflammatory cells and osteoclasts in vivo. Treatment with 4-octyl itaconate increased Nrf2 expression, resulting in reduced inflammatory infiltration and osteoclastic activity after tooth extraction. Furthermore, increased expression of OCN and enhanced-alveolar bone healing of extraction socket were observed in the 4-OI group compared to the control group. Our results suggested that 4-OI could serve as a promising pharmacologic candidate for alveolar ridge preservation by alleviating alveolar bone loss following tooth extraction in rats.

Signaling pathways and potential therapeutic targets in acute respiratory distress syndrome (ARDS)

Acute respiratory distress syndrome (ARDS) is a common condition associated with critically ill patients, characterized by bilateral chest radiographical opacities with refractory hypoxemia due to noncardiogenic pulmonary edema. Despite significant advances, the mortality of ARDS remains unacceptably high, and there are still no effective targeted pharmacotherapeutic agents. With the outbreak of coronavirus disease 19 worldwide, the mortality of ARDS has increased correspondingly. Comprehending the pathophysiology and the underlying molecular mechanisms of ARDS may thus be essential to developing effective therapeutic strategies and reducing mortality. To facilitate further understanding of its pathogenesis and exploring novel therapeutics, this review provides comprehensive information of ARDS from pathophysiology to molecular mechanisms and presents targeted therapeutics. We first describe the pathogenesis and pathophysiology of ARDS that involve dysregulated inflammation, alveolar-capillary barrier dysfunction, impaired alveolar fluid clearance and oxidative stress. Next, we summarize the molecular mechanisms and signaling pathways related to the above four aspects of ARDS pathophysiology, along with the latest research progress. Finally, we discuss the emerging therapeutic strategies that show exciting promise in ARDS, including several pharmacologic therapies, microRNA-based therapies and mesenchymal stromal cell therapies, highlighting the pathophysiological basis and the influences on signal transduction pathways for their use.

Metabolite itaconate in host immunoregulation and defense

Metabolic states greatly influence functioning and differentiation of immune cells. Regulating the metabolism of immune cells can effectively modulate the host immune response. Itaconate, an intermediate metabolite derived from the tricarboxylic acid (TCA) cycle of immune cells, is produced through the decarboxylation of cis-aconitate by cis-aconitate decarboxylase in the mitochondria. The gene encoding cis-aconitate decarboxylase is known as immune response gene 1 (IRG1). In response to external proinflammatory stimulation, macrophages exhibit high IRG1 expression. IRG1/itaconate inhibits succinate dehydrogenase activity, thus influencing the metabolic status of macrophages. Therefore, itaconate serves as a link between macrophage metabolism, oxidative stress, and immune response, ultimately regulating macrophage function. Studies have demonstrated that itaconate acts on various signaling pathways, including Keap1-nuclear factor E2-related factor 2-ARE pathways, ATF3-IκBζ axis, and the stimulator of interferon genes (STING) pathway to exert antiinflammatory and antioxidant effects. Furthermore, several studies have reported that itaconate affects cancer occurrence and development through diverse signaling pathways. In this paper, we provide a comprehensive review of the role IRG1/itaconate and its derivatives in the regulation of macrophage metabolism and functions. By furthering our understanding of itaconate, we intend to shed light on its potential for treating inflammatory diseases and offer new insights in this field.

The impacts of SphK1 on inflammatory response and oxidative stress in LPS-induced ALI/ARDS

As severe conditions, acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) threaten human health. Inflammation and oxidative stress play a vital role in the pathogenesis of ALI/ARDS. Sphingosine kinase 1 (SphK1) significantly contributes to mediating inflammatory responses. Nevertheless, the impact of SphK1 on lipopolysaccharide (LPS)-triggered ALI/ARDS remains largely undetermined. In our current work, we explored the impact of SphK1 on ALI/ARDS using a mouse model. We studied whether it could reduce LPS-triggered inflammatory response and oxidative stress by suppressing SphK1 in ALI/ARDS. The mice were treated with the inhibitor of SphK1 (N,N-dimethylsphingosine, DMS) before intraperitoneal injection of LPS. Moreover, we assessed the survival rate, and several parameters, such as the lung wet/dry (W/D) ratio, myeloperoxidase (MPO) activity, superoxide dismutase (SOD) activity, malondialdehyde (MDA) content, and the release of inflammatory cytokines. Western blotting analysis was adopted to evaluate the levels of phosphoinositide 3-kinase (PI3K)/serine/threonine kinase (AKT) pathways. We showed that the inhibitor of SphK1 not only ameliorated LPS-stimulated lung histopathological changes and W/D ratio of lung tissue but also elevated the survival rate, the SOD activity and decreased the MDA content, MPO activity, interleukin-6 (IL-6) and tumor necrosis factor-ɑ (TNF-ɑ) production by regulating the PI3K/AKT signaling pathway in lung tissue. Taken together, SphK1 played an essential role in inflammatory responses and oxidative stress. The underlying mechanism might be linked to the activation and up-regulation of the PI3K/AKT signaling pathway in LPS-triggered ALI/ARDS.

4-Octyl itaconate attenuates glycemic deterioration by regulating macrophage polarization in mouse models of type 1 diabetes

BACKGROUND

Pancreatic beta cell dysfunction and activated macrophage infiltration are early features in type 1 diabetes pathogenesis. A tricarboxylic acid cycle metabolite that can strongly activate NF-E2-related factor 2 (Nrf2) in macrophages, itaconate is important in a series of inflammatory-associated diseases via anti-inflammatory and antioxidant properties. However, its role in type 1 diabetes is unclear. We used 4-octyl itaconate (OI), the cell-permeable itaconate derivate, to explore its preventative and therapeutic effects in mouse models of type 1 diabetes and the potential mechanism of macrophage phenotype reprogramming.

METHODS

The mouse models of streptozotocin (STZ)-induced type 1 diabetes and spontaneous autoimmune diabetes were used to evaluate the preventative and therapeutic effects of OI, which were performed by measuring blood glucose, insulin level, pro- and anti-inflammatory cytokine secretion, histopathology examination, flow cytometry, and islet proteomics. The protective effect and mechanism of OI were examined via peritoneal macrophages isolated from STZ-induced diabetic mice and co-cultured MIN6 cells with OI-pre-treated inflammatory macrophages in vitro. Moreover, the inflammatory status of peripheral blood mononuclear cells (PBMCs) from type 1 diabetes patients was evaluated after OI treatment.

RESULTS

OI ameliorated glycemic deterioration, increased systemic insulin level, and improved glucose metabolism in STZ-induced diabetic mice and non-obese diabetic (NOD) mice. OI intervention significantly restored the islet insulitis and beta cell function. OI did not alter the macrophage count but significantly downregulated the proportion of M1 macrophages. Additionally, OI significantly inhibited MAPK activation in macrophages to attenuate the macrophage inflammatory response, eventually improving beta cell dysfunction in vitro. Furthermore, we detected higher IL-1β production upon lipopolysaccharide stimulation in the PBMCs from type 1 diabetes patients, which was attenuated by OI treatment.

CONCLUSIONS

These results provided the first evidence to date that OI can prevent the progression of glycemic deterioration, excessive inflammation, and beta cell dysfunction predominantly mediated by restricting macrophage M1 polarization in mouse models of type 1 diabetes.

Serum metabolomics reveal pathways associated with protective effect of ginsenoside Rg3 on immune stress

Our previous study has demonstrated that administration of ginsenoside Rg3 ameliorates immune stress by inhibiting inflammatory responses, reducing oxidative damage and upregulating mRNA expression of mTOR, SOD-1, and HO-1. However, the specific mechanism in relation to the protective effect of ginsenoside Rg3 on stressed broilers especially the metabolites alteration remains obscure. The present study aimed to investigate the underlined mechanism in relation to the pathogenesis and protective effect of ginsenoside Rg3 on stressed broilers using liquid chromatograph-mass spectrometry profiling. Eighteen broiler chicks were randomly allocated to 3 treatments: Control, Model and Rg3. Chickens in Rg3 group received intraperitoneally administered 1 mg/kg Rg3 2 h before LPS challenge. Then the broilers were intraperitoneally injection of 250 µg/kg LPS at the age of 12, 14, 33, and 35 d to induce immune stress. Control group was injected with an equivalent amount of sterile saline. At the end of the experiment, the serum was obtained for metabolomics analysis. The changes in serum metabolic profiles were investigated with the application of metabolomics approach. Distinct changes in metabolite patterns in serum were observed by orthogonal partial least square-discriminate analysis. In total, 35 metabolites were identified, among which 17 differential metabolites were found between Control and Model group, and 18 differential metabolites were identified between Model and Rg3 group. Metabolic pathway analysis revealed potential serum metabolites involved in oxidative stress and inflammation, degradation of lipid and protein in broiler chicks with immune stress. In addition, the protective effect of Rg3 on the stressed chicks may be largely mediated by BCAA metabolism, apoptosis and mTOR signaling pathway. These results suggested the potential biomarkers involved in pathogenesis and prevention of stress induced by Escherichia coli lipopolysaccharide.

Aconitate decarboxylase 1 regulates glucose homeostasis and obesity in mice

OBJECTIVE

The intersection between immunology and metabolism contributes to the pathogenesis of obesity-associated metabolic diseases as well as molecular control of inflammatory responses. The metabolite itaconate and the cell-permeable derivatives have robust anti-inflammatory effects; therefore, it is hypothesized that cis-aconitate decarboxylase (Acod1)-produced itaconate has a protective, anti-inflammatory effect during diet-induced obesity and metabolic disease.

METHODS

Wild-type and Acod1-/- mice were subjected to diet-induced obesity. Glucose metabolism was analyzed by glucose tolerance tests, insulin tolerance tests, and indirect calorimetry. Gene expression and transcriptome analysis was performed using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and RNA sequencing.

RESULTS

Wild-type and Acod1-/- mice on high-fat diet had equivalent weight gain, but Acod1-/- mice had impaired glucose metabolism. Insulin tolerance tests and glucose tolerance tests after 12 weeks on high-fat diet revealed significantly higher blood glucose levels in Acod1-/- mice. This was associated with significant enrichment of inflammatory gene sets and a reduction in genes related to adipogenesis and fatty acid metabolism. Analysis of naive Acod1-/- mice showed a significant increase in fat deposition at 3 and 6 months of age and obesity and insulin resistance by 12 months.

CONCLUSIONS

The data show that Acod1 has an important role in the regulation of glucose homeostasis and obesity under normal and high-fat diet conditions.

4-Octyl itaconate suppresses the osteogenic response in aortic valvular interstitial cells via the Nrf2 pathway and alleviates aortic stenosis in mice with direct wire injury

Calcific aortic valve disease (CAVD) is the most prevalent valvular heart disease in older individuals, but there is a lack of drug treatment. The cellular biological mechanisms of CAVD are still unclear. Oxidative stress and endoplasmic reticulum stress (ER stress) have been suggested to be involved in the progression of CAVD. Many studies have demonstrated that 4-octyl itaconate (OI) plays beneficial roles in limiting inflammation and oxidative injury. However, the potential role of OI in CAVD has not been thoroughly explored. Thus, we investigated OI-mediated modulation of ROS generation and endoplasmic reticulum stress to inhibit osteogenic differentiation in aortic valve interstitial cells (VICs). In our study, calcified aortic valves showed increased levels of ER stress and superoxide anion, as well as abnormal expression of Hmox1 and NQO1. In VICs, OI activated the Nrf2 signaling cascade and contributed to Nrf2 stabilization and nuclear translocation, thus augmenting the expression of genes downstream of Nrf2 (Hmox1 and NQO1). Moreover, OI ameliorated osteogenic medium (OM)-induced ROS production, mitochondrial ROS levels and the loss of mitochondrial membrane potential in VICs. Furthermore, OI attenuated the OM-induced upregulation of ER stress markers, osteogenic markers and calcium deposition, which were blocked by the Nrf2-specific inhibitor ML385. Interestingly, we found that OM-induced ER stress and osteogenic differentiation were ROS-dependent and that Hmox1 silencing triggered ROS production, ER stress and elevated osteogenic activity, which were inhibited by NAC. Overexpression of NQO1 mediated by adenovirus vectors significantly suppressed OM-induced ER stress and osteogenic markers. Collectively, these results showed the anti-osteogenic effects of OI on AVICs by regulating the generation of ROS and ER stress by activating the Nrf2 signaling pathway. Furthermore, OI alleviated aortic stenosis in a mouse model with direct wire injury. Due to its antioxidant properties, OI could be a potential drug for the prevention and/or treatment of CAVD.

Four-Octyl itaconate ameliorates periodontal destruction via Nrf2-dependent antioxidant system

Periodontitis is a widespread oral disease characterized by continuous inflammation of the periodontal tissue and an irreversible alveolar bone loss, which eventually leads to tooth loss. Four-octyl itaconate (4-OI) is a cell-permeable itaconate derivative and has been recognized as a promising therapeutic target for the treatment of inflammatory diseases. Here, we explored, for the first time, the protective effect of 4-OI on inhibiting periodontal destruction, ameliorating local inflammation, and the underlying mechanism in periodontitis. Here we showed that 4-OI treatment ameliorates inflammation induced by lipopolysaccharide in the periodontal microenvironment. 4-OI can also significantly alleviate inflammation and alveolar bone loss via Nrf2 activation as observed on samples from experimental periodontitis in the C57BL/6 mice. This was further confirmed as silencing Nrf2 blocked the antioxidant effect of 4-OI by downregulating the expression of downstream antioxidant enzymes. Additionally, molecular docking simulation indicated the possible mechanism under Nrf2 activation. Also, in Nrf2^−/− mice, 4-OI treatment did not protect against alveolar bone dysfunction due to induced periodontitis, which underlined the importance of the Nrf2 in 4-OI mediated periodontitis treatment. Our results indicated that 4-OI attenuates inflammation and oxidative stress via disassociation of KEAP1-Nrf2 and activation of Nrf2 signaling cascade. Taken together, local administration of 4-OI offers clinical potential to inhibit periodontal destruction, ameliorate local inflammation for more predictable periodontitis.

Aconitate Decarboxylase 1 Deficiency Exacerbates Mouse Colitis Induced by Dextran Sodium Sulfate

Ulcerative colitis is a complex inflammatory bowel disorder disease that can induce rectal and colonic dysfunction. Although the prevalence of IBD in Western countries is almost 0.5% of the general population, genetic causes are still not fully understood. In a recent discovery, itaconate was found to function as an immune-modulating metabolite in mammalian immune cells, wherein it is synthesized as an antimicrobial compound from the citric acid cycle intermediate cis-aconitic acid. However, the association between the Acod1 (Aconitate decarboxylase 1)-itaconate axis and ulcerative colitis has rarely been studied. To elucidate this, we established a DSS-induced colitis model with Acod1-deficient mice and then measured the mouse body weights, colon lengths, histological changes, and cytokines/chemokines in the colon. We first confirmed the upregulation of Acod1 RNA and protein expression levels in DSS-induced colitis. Then, we found that colitis symptoms, including weight loss, the disease activity index, and colon shortening, were worsened by the depletion of Acod1. In addition, the extent of intestinal epithelial barrier breakdown, the extent of immune cell infiltration, and the expression of proinflammatory cytokines and chemokines in Acod1-deficient mice were higher than those in wild-type mice. Finally, we confirmed that 4-octyl itaconate (4-OI) alleviated DSS-induced colitis in Acod1-deficient mice and decreased the expression of inflammatory cytokines and chemokines. To our knowledge, this study is the first to elucidate the role of the Acod1-itaconate axis in colitis. Our data clearly showed that Acod1 deletion resulted in severe DSS-induced colitis and substantial increases in inflammatory cytokine and chemokine levels. Our results suggest that Acod1 may normally play an important regulatory role in the pathogenesis of colitis, demonstrating the potential for novel therapies using 4-OI.

Bioinspired Multifunctional Black Phosphorus Hydrogel with Antibacterial and Antioxidant Properties: A Stepwise Countermeasure for Diabetic Skin Wound Healing

Cutaneous wound healing, especially diabetic wound healing, is a common clinical challenge. Reactive oxygen species (ROS) and bacterial infection are two major detrimental states that induce oxidative stress and inflammatory responses and impede angiogenesis and wound healing. A derivative of the metabolite itaconate, 4-octyl itaconate (4OI) has attracted increasing research interest in recent years due to its antioxidant and anti-inflammatory properties. In this study, 4OI-modified black phosphorus (BP) nanosheets are incorporated into a photosensitive, multifunctional gelatin methacrylamide hydrogel to produce a new photothermal therapy (PTT) and photodynamic therapy (PDT) system with antibacterial and antioxidant properties for diabetic wound regeneration. Under laser irradiation, the 4OI-BP-entrapped hydrogel enables rapid gelation, forming a membrane on wounds, and offers high PTT and PDT efficacy to eliminate bacterial infection. Without laser irradiation, BP acts as a carrier and controls the release of 4OI, with which it synergistically enhances antioxidant activity, thus alleviating excessive ROS damage to endothelial cells, promoting neovascularization, and facilitating faster diabetic wound closure. These findings indicate that 4OI-BP-entrapped multifunctional hydrogel provides a stepwise countermeasure with antibacterial and antioxidant properties for enhanced diabetic wound healing and may lead to novel therapeutic interventions for diabetic ulcers.

Physalin B ameliorates inflammatory responses in lipopolysaccharide-induced acute lung injury mice by inhibiting NF-κB and NLRP3 via the activation of the PI3K/Akt pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Physalin B (PB) is an active constituent of Physalis alkekengi L. var. Franchetii, which is a traditional medicine for clearing heat and detoxification, resolving phlegm, and diuresis. It has been commonly applied to treat sore throat, phlegm-heat, cough, dysuria, pemphigus, and eczema.

AIM OF STUDY

Physalin B has shown efficacy as an anti-acute lung injury (ALI) agent previously; however, its mechanisms of action remain unclear. In the present study, we established a lipopolysaccharide-induced septic ALI model using BALB/c mice to further confirm the therapeutic potential of PB and to assess the underlying molecular mechanisms.

MATERIALS AND METHODS

We used 75% ethanol and macroporous resin for extraction, separation, and enrichment of PB. The LPS-induced ALI mouse model was used to determine anti-inflammatory effects of PB. The severity of acute lung injury was evaluated by hematoxylin and eosin staining, wet/dry lung ratio, and myeloperoxidase (MPO) activity in lung tissue. An automatic analyzer was used to measure the arterial blood gas index. Protein levels of pro-inflammatory cytokines in serum, bronchoalveolar lavage fluid (BALF), and lung tissue was measured using an ELISA. Quantitative RT-PCR was used to measure changes in RNA levels of pro-inflammatory cytokines in the lungs. A fluorometric assay kit was used for determination of apoptosis-related factors to assess anti-apoptotic effects of PB. Western blotting was used to assess levels of key pathway proteins and apoptosis-related proteins. Connections between the pathways were tested through inhibitor experiments.

RESULTS

Pretreatment with PB (15 mg kg^-1 d^-1, i.g.) significantly reduced lung wet/dry weight ratios and MPO activity in blood and BALF of ALI mice, and it alleviated LPS-induced inflammatory cell infiltration in lung tissue. The levels of pro-inflammatory factors TNF-α, IL-6, and IL-1β and their mRNA levels in blood, BALF, and lung tissue were reduced following PB pretreatment. PB pretreatment also downregulated the apoptotic factors caspase-3, caspase-9, and apoptotic protein Bax, and it upregulated apoptotic protein Bcl-2. The NF-κB and NLRP3 pathways were inhibited through activation of the PI3K/Akt pathway due to PB pretreatment, whereas administration of PI3K inhibitors increased activation of these pathways.

CONCLUSIONS

Taken together, our results suggest that the anti-ALI properties of PB are closely associated with the inactivation of NF-κB and NLRP3 by altering the PI3K/Akt pathway. Furthermore, our findings provide a novel strategy for application of PB as a potential agent for treating patients with ALI. To the best of our knowledge, this is the first study to elucidate the underlying mechanism of action of PB against ALI.

Irg1/itaconate metabolic pathway is a crucial determinant of dendritic cells immune-priming function and contributes to resolute allergen-induced airway inflammation

Itaconate is produced from the mitochondrial TCA cycle enzyme aconitase decarboxylase (encoded by immune responsive gene1; Irg1) that exerts immunomodulatory function in myeloid cells. However, the role of the Irg1/itaconate pathway in dendritic cells (DC)-mediated airway inflammation and adaptive immunity to inhaled allergens, which are the primary antigen-presenting cells in allergic asthma, remains largely unknown. House dust mite (HDM)-challenged Irg1^-/- mice displayed increases in eosinophilic airway inflammation, mucous cell metaplasia, and Th2 cytokine production with a mechanism involving impaired mite antigen presentations by DC. Adoptive transfer of HDM-pulsed DC from Irg1-deficient mice into naïve WT mice induced a similar phenotype of elevated type 2 airway inflammation and allergic sensitization. Untargeted metabolite analysis of HDM-pulsed DC revealed itaconate as one of the most abundant polar metabolites that potentially suppress mitochondrial oxidative damage. Furthermore, the immunomodulatory effect of itaconate was translated in vivo, where intranasal administration of 4-octyl itaconate 4-OI following antigen priming attenuated the manifestations of HDM-induced airway disease and Th2 immune response. Taken together, these data demonstrated for the first time a direct regulatory role of the Irg1/itaconate pathway in DC for the development of type 2 airway inflammation and suggest a possible therapeutic target in modulating allergic asthma.