CD4+CD25+Foxp3+ Tregs resolve experimental lung injury in mice and are present in humans with acute lung injury

Soluble interleukin 2 receptor is risk for sarcopenia in Men with high fracture risk

Background & aims

Sarcopenia is an age-related disease that increases the risk of falls and fractures in older adults. However, there is no blood biochemical marker to help to predict or diagnose sarcopenia in clinical practice. Soluble interleukin 2 receptor (sIL-2R) was reported to be associated with muscle satellite cell dysfunction which played an important role in the pathogenesis of sarcopenia. Thereby, we aimed to explore the association between serum sIL-2R and sarcopenia in older adults at high risk of fractures.

Methods

A total of 429 hospitalized older adults (age ≥55 years) were enrolled in this cross-sectional study (mean age ​= ​66.62 ​± ​6.59 years; 62.7% female). Logistic regression analysis was performed to assess the association of sIL-2R with sarcopenia, muscle mass, muscle strength, and physical performance, respectively. The optimal models for the diagnosis of sarcopenia and low hand grip strength (HGS) were established by multivariable binary logistic regression analysis with backward selection, and further were evaluated for the diagnostic values by receiver operating characteristic (ROC) curve.

Results

Higher sIL-2R levels were found in sarcopenia than no-sarcopenia group in male (median 421 U/mL (interquartile range [IQR] 217 U/mL) vs median 362 U/mL (IQR 157 U/mL); n ​= ​77 vs 83; p ​< ​0.01). Compared to the lowest sIL-2R tertile, the highest tertile of sIL-2R was independently associated with the risk of low HGS (odds ratio [OR] 4.608, 95% confidence interval [CI] 1.673–12.695) and the risk of sarcopenia (OR 3.306, 95% CI 1.496–7.302) in men. ROC curves revealed that the Area Under the Curve (AUC) of the optimal models for diagnosing sarcopenia and low HGS was 0.752 and 0.846.

Conclusion

Our results suggest that serum sIL-2R is the independent risk factor for sarcopenia and low muscle strength only in men. sIL-2R may be developed to be a biochemical marker for sarcopenia and low muscle strength diagnoses in older men at high risk of fractures, but more prospective studies are needed to prove it.

The translational potential of this article

Our results showed that the highest tertile of sIL-2R was independent of low risk of HGS and sarcopenia in men, compared to the lowest tertile. As the population ages, sIL-2R may become a potential diagnostic tool for predicting low HGS and sarcopenia among men at high risk of fractures.

COVID-19 immunopathology: From acute diseases to chronic sequelae

The clinical manifestation of coronavirus disease 2019 (COVID-19) mainly targets the lung as a primary affected organ, which is also a critical site of immune cell activation by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, recent reports also suggest the involvement of extrapulmonary tissues in COVID-19 pathology. The interplay of both innate and adaptive immune responses is key to COVID-19 management. As a result, a robust innate immune response provides the first line of defense, concomitantly, adaptive immunity neutralizes the infection and builds memory for long-term protection. However, dysregulated immunity, both innate and adaptive, can skew towards immunopathology both in acute and chronic cases. Here we have summarized some of the recent findings that provide critical insight into the immunopathology caused by SARS-CoV-2, in acute and post-acute cases. Finally, we further discuss some of the immunomodulatory drugs in preclinical and clinical trials for dampening the immunopathology caused by COVID-19.

Immunotherapy strategies and prospects for acute lung injury: Focus on immune cells and cytokines

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) is a disastrous condition, which can be caused by a wide range of diseases, such as pneumonia, sepsis, traumas, and the most recent, COVID-19. Even though we have gained an improved understanding of acute lung injury/acute respiratory distress syndrome pathogenesis and treatment mechanism, there is still no effective treatment for acute lung injury/acute respiratory distress syndrome, which is partly responsible for the unacceptable mortality rate. In the pathogenesis of acute lung injury, the inflammatory storm is the main pathological feature. More and more evidences show that immune cells and cytokines secreted by immune cells play an irreplaceable role in the pathogenesis of acute lung injury. Therefore, here we mainly reviewed the role of various immune cells in acute lung injury from the perspective of immunotherapy, and elaborated the crosstalk of immune cells and cytokines, aiming to provide novel ideas and targets for the treatment of acute lung injury.

IL-33 Deficiency Attenuates Lung Inflammation by Inducing Th17 Response and Impacting the Th17/Treg Balance in LPS-Induced ARDS Mice via Dendritic Cells

Objectives

The characteristic pathophysiological feature of acute respiratory distress syndrome (ARDS) is a dysregulated inflammatory response. T helper 17 (Th17) cells in the lung are inflammatory cells that contribute to pulmonary inflammatory cascades. In addition, Th17/regulatory T cells (Treg cells) also play an important role in the inflammatory process. Dendritic cells (DCs) can regulate the differentiation of CD4+ T cells, including Th17 and Treg cells. Recent evidence revealed that interleukin-33 (IL-33) signaling could activate and mature DCs. Therefore, the aim of this study was to investigate the effects of IL-33 on inflammation and immunoregulation by inducing the Th17 response and influencing the Th17/Treg balance in LPS-induced ARDS.

Methods

IL-33 gene knockout mice and the administration of recombinant mouse IL-33 (rmIL-33) were used to investigate the role of IL-33 and the underlying mechanisms in an LPS-induced ARDS model. Hematoxylin and eosin (H&E) staining, wet/dry (W/D) weight ratios, cell counts, and the levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-17 (IL-17), and interleukin-10 (IL-10) in bronchoalveolar lavage fluid (BALF) were investigated. The levels of IL-33, orphan nuclear receptor gamma t (RORγt), and forkhead transcription factor protein 3 (FOXP3) protein in lung tissue were evaluated by Western blotting. The mRNA expression levels of IL-33 and RORγt were measured by quantitative real-time polymerase chain reaction (qRT-PCR). Th17 and Treg cell frequencies were determined by flow cytometry. The levels of IL-6 in the supernatant in a dendritic cell culture system were examined by ELISA.

Results

Increased expression of IL-33 was observed in mice with LPS-induced ARDS. IL-33 deficiency significantly inhibited inflammation and attenuated LPS-induced ARDS, whereas pretreatment with rmIL-33 aggravated pulmonary inflammatory response. Furthermore, depletion of IL-33 inhibited Th17 cells, significantly decreased RORγt mRNA and protein expression and IL-17 levels in BALF, and led to less differentiation of T cells into Th17 cells than Treg cells. Moreover, IL-33^-/- DCs secreted less IL-6 and IL-23 than normal control DCs.

Conclusion

IL-33 deficiency alleviated lung injury in the LPS-induced ARDS model, which was closely related to suppressing Th17 responses and regulating the Th17/Treg balance. The expansion of Th17 cells and imbalance in Th17/Treg cells may be associated with IL-6 and IL-23 secreted from IL-33-activated DCs.

Stepwise acquisition of unique epigenetic signatures during differentiation of tissue Treg cells

Regulatory T cells in non-lymphoid tissues are not only critical for maintaining self-tolerance, but are also important for promoting organ homeostasis and tissue repair. It is proposed that the generation of tissue Treg cells is a stepwise, multi-site process, accompanied by extensive epigenome remodeling, finally leading to the acquisition of unique tissue-specific epigenetic signatures. This process is initiated in the thymus, where Treg cells acquire core phenotypic and functional properties, followed by a priming step in secondary lymphoid organs that permits Treg cells to exit the lymphoid organs and seed into non-lymphoid tissues. There, a final specialization process takes place in response to unique microenvironmental cues in the respective tissue. In this review, we will summarize recent findings on this multi-site tissue Treg cell differentiation and highlight the importance of epigenetic remodeling during these stepwise events.

Antigen-Specific T Cells and SARS-CoV-2 Infection: Current Approaches and Future Possibilities

COVID-19, a significant global health threat, appears to be an immune-related disease. Failure of effective immune responses in initial stages of infection may contribute to development of cytokine storm and systemic inflammation with organ damage, leading to poor clinical outcomes. Disease severity and the emergence of new SARS-CoV-2 variants highlight the need for new preventative and therapeutic strategies to protect the immunocompromised population. Available data indicate that these people may benefit from adoptive transfer of allogeneic SARS-CoV-2-specific T cells isolated from convalescent individuals. This review first provides an insight into the mechanism of cytokine storm development, as it is directly related to the exhaustion of T cell population, essential for viral clearance and long-term antiviral immunity. Next, we describe virus-specific T lymphocytes as a promising and efficient approach for the treatment and prevention of severe COVID-19. Furthermore, other potential cell-based therapies, including natural killer cells, regulatory T cells and mesenchymal stem cells are mentioned. Additionally, we discuss fast and effective ways of producing clinical-grade antigen-specific T cells which can be cryopreserved and serve as an effective "off-the-shelf" approach for rapid treatment of SARS-CoV-2 infection in case of sudden patient deterioration.

Role of CD8+ T cell exhaustion in the progression and prognosis of acute respiratory distress syndrome induced by sepsis: a prospective observational study

Background

CD8⁺ T cells are important for protective immunity against intracellular pathogens. Excessive amounts of antigen and/or inflammatory signals often lead to the gradual deterioration of CD8⁺ T cell function, a state called “exhaustion”. However, the association between CD8⁺ T cell exhaustion and acute respiratory distress syndrome (ARDS) has not been studied. This study was conducted to elucidate how CD8⁺ T cells and inhibitory receptors were related to the clinical prognosis of ARDS.

Methods

A prospective observational study in an emergency department enrolled patients who were diagnosed with sepsis-associated ARDS according to the sepsis-3 criteria and Berlin definition. Peripheral blood samples were collected within 24 h post recruitment. CD8⁺ T cell count, proliferation ratio, cytokine secretion, and the expression of coinhibitory receptors were assayed.

Results

Sixty-two patients with ARDS met the inclusion criteria. CD8⁺ T cell counts and proliferation rates were dramatically decreased in non-surviving ARDS patients. Increasing programmed cell death 1 (PD-1) expression on the CD8⁺ T cell surface was seen in patients with worse organ function, while an increasing level of T cell immunoglobulin mucin-3 (Tim-3) was associated with a longer duration of the shock. Kaplan–Meier analysis showed that low CD8⁺ T cell percentages and increased inhibitory molecule expression were significantly associated with a worse survival rate.

Conclusions

CD8⁺ T cells and coinhibitory receptors are promising independent prognostic markers of sepsis-induced ARDS, and increased CD8⁺ T cell exhaustion is significantly correlated with poor prognosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12873-022-00733-2.

Peribronchial Inflammation Resulting from Regulatory T Cell Deficiency Damages the Respiratory Epithelium and Disturbs Barrier Function

Regulatory T cells (Tregs) that express the transcription factor Foxp3 have a critical role in limiting inflammatory processes and tissue damage. Whether Tregs are functional in maintaining epithelial barriers and in control of tight junction expression has not yet been explored. In this study, we investigated the effect of Treg deficiency on the airway epithelial barrier in an experimental murine model in which diphtheria toxin was repeatedly injected in Foxp3-diphtheria toxin receptor (DTR) mice to deplete Tregs. This resulted in spontaneous peribronchial inflammation and led to a systemic and local increase of IL-4, IL-5, CCL3, IFN-γ, and IL-10 and a local (lung) increase of IL-6 and IL-33 and decreased amphiregulin levels. Moreover, Treg depletion increased airway permeability and decreased epithelial tight junction (protein and mRNA) expression. CTLA4-Ig treatment of Treg-depleted mice almost completely prevented barrier dysfunction together with suppression of lung inflammation and cytokine secretion. Treatment with anti–IL-4 partly reversed the effects of Treg depletion on tight junction expression, whereas neutralization of IL-6 of IFN-γ had either no effect or only a limited effect. We conclude that Tregs are essential to protect the epithelial barrier at the level of tight junctions by restricting spontaneous T cell activation and uncontrolled secretion of cytokines, in particular IL-4, in the bronchi.

Lung Regeneration: Cells, Models, and Mechanisms

Lung epithelium, the lining that covers the inner surface of the respiratory tract, is directly exposed to the environment and thus susceptible to airborne toxins, irritants, and pathogen-induced damages. In adult mammalian lungs, epithelial cells are generally quiescent but can respond rapidly to repair of damaged tissues. Evidence from experimental injury models in rodents and human clinical samples has led to the identification of these regenerative cells, as well as pathological metaplastic states specifically associated with different forms of damages. Here, we provide a compendium of cells and cell states that exist during homeostasis in normal lungs and the lineage relationships between them. Additionally, we discuss various experimental injury models currently being used to probe the cellular sources-both resident and recruited-that contribute to repair, regeneration, and remodeling following acute and chronic injuries. Finally, we discuss certain maladaptive regeneration-associated cell states and their role in disease pathogenesis.

Cigarette Smoke and Morphine Promote Treg Plasticity to Th17 via Enhancing Trained Immunity

CD4+ regulatory T cells (Tregs) respond to environmental cues to permit or suppress inflammation, and atherosclerosis weakens Treg suppression and promotes plasticity. However, the effects of smoking plus morphine (SM + M) on Treg plasticity remain unknown. To determine whether SM + M promotes Treg plasticity to T helper 17 (Th17) cells, we analyzed the RNA sequencing data from SM, M, and SM + M treated Tregs and performed knowledge-based and IPA analysis. We demonstrated that (1) SM + M, M, and SM upregulated the transcripts of cytokines, chemokines, and clusters of differentiation (CDs) and modulated the transcripts of kinases and phosphatases in Tregs; (2) SM + M, M, and SM upregulated the transcripts of immunometabolism genes, trained immunity genes, and histone modification enzymes; (3) SM + M increased the transcripts of Th17 transcription factor (TF) RORC and Tfh factor CXCR5 in Tregs; M increased the transcripts of T helper cell 1 (Th1) TF RUNX3 and Th1-Th9 receptor CXCR3; and SM inhibited Treg TGIF1 transcript; (4) six genes upregulated in SM + M Tregs were matched with the top-ranked Th17 pathogenic genes; and 57, 39 genes upregulated in SM + M Tregs were matched with groups II and group III Th17 pathogenic genes, respectively; (5) SM + M upregulated the transcripts of 70 IPA-TFs, 11 iTregs-specific TFs, and 4 iTregs-Th17 shared TFs; and (6) SM + M, M, and SM downregulated Treg suppression TF Rel (c-Rel); and 35 SM + M downregulated genes were overlapped with Rel-/- Treg downregulated genes. These results provide novel insights on the roles of SM + M in reprogramming Treg transcriptomes and Treg plasticity to Th17 cells and novel targets for future therapeutic interventions involving immunosuppression in atherosclerotic cardiovascular diseases, autoimmune diseases, transplantation, and cancers.

Regulatory T cells in inflammation and resolution of acute lung injury

Introduction

Acute respiratory distress syndrome (ARDS) is characterized by hypoxemia and increased lung permeability and would result in acute respiratory failure and with high mortality. In patients who survive from acute lung injury (ALI)/ARDS, it is an active process of the transition from injury to resolution depending on the coordinated immune system. The roles of regulatory CD4⁺T cells (Tregs) are now gradually being clarified during inflammation and resolution of ARDS. However, clear conclusions about roles of Tregs in ALI/ARDS are only a few.

Objective

This review provides an overview of phenotype, differentiation, and suppressive mechanisms of Tregs and focuses on keys of biology of Tregs in alveolar space during the inflammatory response and resolution of ALI/ARDS.

Data Source

Literature search of Web of Science, PubMed, and EMBASE was made to find relative articles about Tregs in ALI/ARDS. We used the following search terms: Tregs, ALI, ARDS, inflammation, and resolution.

Conclusion

More and more studies have indicated Tregs involved in the processes of inflammation and resolution of ALI/ARDS. A deep understanding of the roles of Tregs may indicate new treatments for patients of ARDS. Therapies aimed at expansion or adaptive transfer of Tregs could be an effective therapy to ARDS patients.

A randomised, double-blind, placebo-controlled, multicentre clinical trial of AZD1656 in diabetic patients hospitalised with COVID-19: The ARCADIA Trial - implications for therapeutic immune modulation

BACKGROUND

A potential immunotherapeutic role for AZD1656 (a glucokinase activator) in the treatment of COVID-19 was hypothesized. The ARCADIA trial investigated the safety and efficacy of AZD1656 in diabetic patients admitted to hospital with COVID-19.

METHODS

The ARCADIA trial was a Phase II randomised, double-blind, placebo-controlled clinical trial. Adult diabetic patients, admitted with COVID-19, were recruited at 28 hospitals in the UK, Romania and Czech Republic and randomly assigned (1:1) to receive AZD1656 tablets (100mg twice a day), or matched placebo, for up to 21 days, in addition to usual care. All involved were masked to treatment allocation. The primary endpoint was clinical improvement measured at Day 14. The Full Analysis Set (FAS) included all patients who received at least one dose of assigned treatment. ARCADIA is complete and registered with ClinicalTrials.gov (NCT04516759).

FINDINGS

Between 29 September 2020 to 16 April 2021, 170 patients were screened and 156 patients were randomised, three of whom did not commence treatment. Of the remaining 153, 80 were assigned to AZD1656 and 73 were assigned to placebo and included in the Full Analysis Set (FAS). The primary analysis showed no statistically significant difference between groups (AZD1656: 76·3%; Placebo: 69·9%, p=0·19). There was no difference in the number of adverse events between groups (AZD1656: 35·7%; Placebo: 33·3%). Mortality was lower in the AZD1656 group compared to the placebo group (AZD1656: four (5%); Placebo: nine (12·3%), p=0·090)). At Day 7 there were zero deaths in the AZD1656 group compared to six deaths in the placebo group (p=0·011, post hoc). A difference between groups in time to hospital discharge was also seen (p=0·16). Immunophenotyping data suggested that AZD1656-treated patients had a less pro-inflammatory immune response and a better adaptive immune response than those treated with placebo.

INTERPRETATION

Although the trial did not achieve its primary endpoint, AZD1656 was associated with a decrease in deaths and a reduction in the duration of hospitalisation, as compared to Placebo. Immunophenotyping and immunochemistry indicated an immunomodulatory effect of AZD1656. The trial suggests a beneficial therapeutic effect of AZD1656 and identifies a new therapeutic concept: small molecule activation of endogenous homeostatic immune cells which themselves become the therapeutic agent within the body. Phase 2 trials of this size carry the risk of false positive results and confirmation of these results in a larger clinical trial is now required.

FUNDING

UK Research and Innovation (UKRI) 'Innovate UK' programme and Excalibur Medicines Ltd.

Promises and Challenges of Cell-Based Therapies to Promote Lung Regeneration in Idiopathic Pulmonary Fibrosis

The lung epithelium is constantly exposed to harmful agents present in the air that we breathe making it highly susceptible to damage. However, in instances of injury to the lung, it exhibits a remarkable capacity to regenerate injured tissue thanks to the presence of distinct stem and progenitor cell populations along the airway and alveolar epithelium. Mechanisms of repair are affected in chronic lung diseases such as idiopathic pulmonary fibrosis (IPF), a progressive life-threatening disorder characterized by the loss of alveolar structures, wherein excessive deposition of extracellular matrix components cause the distortion of tissue architecture that limits lung function and impairs tissue repair. Here, we review the most recent findings of a study of epithelial cells with progenitor behavior that contribute to tissue repair as well as the mechanisms involved in mouse and human lung regeneration. In addition, we describe therapeutic strategies to promote or induce lung regeneration and the cell-based strategies tested in clinical trials for the treatment of IPF. Finally, we discuss the challenges, concerns and limitations of applying these therapies of cell transplantation in IPF patients. Further research is still required to develop successful strategies focused on cell-based therapies to promote lung regeneration to restore lung architecture and function.

Regulatory T cells regulate blastemal proliferation during zebrafish caudal fin regeneration

The role of T cells in appendage regeneration remains unclear. In this study, we revealed an important role for regulatory T cells (Tregs), a subset of T cells that regulate tolerance and tissue repair, in the epimorphic regeneration of zebrafish caudal fin tissue. Upon amputation, fin tissue-resident Tregs infiltrate into the blastema, a population of progenitor cells that produce new fin tissues. Conditional genetic ablation of Tregs attenuates blastemal cell proliferation during fin regeneration. Blastema-infiltrating Tregs upregulate the expression of igf2a and igf2b, and pharmacological activation of IGF signaling restores blastemal proliferation in Treg-ablated zebrafish. These findings further extend our understandings of Treg function in tissue regeneration and repair.

The dark side of Tregs during aging

In the last century, we have seen a dramatic rise in the number of older persons globally, a trend known as the grey (or silver) tsunami. People live markedly longer than their predecessors worldwide, due to remarkable changes in their lifestyle and in progresses made by modern medicine. However, the older we become, the more susceptible we are to a series of age-related pathologies, including infections, cancers, autoimmune diseases, and multi-morbidities. Therefore, a key challenge for our modern societies is how to cope with this fragile portion of the population, so that everybody could have the opportunity to live a long and healthy life. From a holistic point of view, aging results from the progressive decline of various systems. Among them, the distinctive age-dependent changes in the immune system contribute to the enhanced frailty of the elderly. One of these affects a population of lymphocytes, known as regulatory T cells (Tregs), as accumulating evidence suggest that there is a significant increase in the frequency of these cells in secondary lymphoid organs (SLOs) of aged animals. Although there are still discrepancies in the literature about modifications to their functional properties during aging, mounting evidence suggests a detrimental role for Tregs in the elderly in the context of bacterial and viral infections by suppressing immune responses against non-self-antigens. Interestingly, Tregs seem to also contribute to the reduced effectiveness of immunizations against many pathogens by limiting the production of vaccine-induced protective antibodies. In this review, we will analyze the current state of understandings about the role of Tregs in acute and chronic infections as well as in vaccination response in both humans and mice. Lastly, we provide an overview of current strategies for Treg modulation with potential future applications to improve the effectiveness of vaccines in older individuals.

Recent advances in passive immunotherapies for COVID-19: The Evidence-Based approaches and clinical trials

In late 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged, causing a global pandemic called COVID-19. Currently, there is no definitive treatment for this emerging disease. Global efforts resulted in developing multiple platforms of COVID-19 vaccines, but their efficacy in humans should be wholly investigated in the long-term clinical and epidemiological follow-ups. Despite the international efforts, COVID-19 vaccination accompanies challenges, including financial and political obstacles, serious adverse effects (AEs), the impossibility of using vaccines in certain groups of people in the community, and viral evasion due to emerging novel variants of SARS-CoV-2 in many countries. For these reasons, passive immunotherapy has been considered a complementary remedy and a promising way to manage COVID-19. These approaches arebased on reduced inflammation due to inhibiting cytokine storm phenomena, immunomodulation,preventing acute respiratory distress syndrome (ARDS), viral neutralization, anddecreased viral load. This article highlights passive immunotherapy and immunomodulation approaches in managing and treating COVID-19 patients and discusses relevant clinical trials (CTs).

Implications of regulatory T cells in non-lymphoid tissue physiology and pathophysiology

Treg cells have been initially described as gatekeepers for the control of autoimmunity, as they can actively suppress the activity of other immune cells. However, their role goes beyond this as Treg cells further control immune responses during infections and tumor development. Furthermore, Treg cells can acquire additional properties for e.g., the control of tissue homeostasis. This is instructed by a specific differentiation program and the acquisition of effector properties unique to Treg cells in non-lymphoid tissues. These tissue Treg cells can further adapt to their tissue environment and acquire distinct functional properties through specific transcription factors activated by a combination of tissue derived factors, including tissue-specific antigens and cytokines. In this review, we will focus on recent findings extending our current understanding of the role and differentiation of these tissue Treg cells. As such we will highlight the importance of tissue Treg cells for tissue maintenance, regeneration, and repair in adipose tissue, muscle, CNS, liver, kidney, reproductive organs, and the lung.

Protective role of tissue-resident regulatory T cells in a murine model of beryllium-induced disease

CD4+ T cells drive the immunopathogenesis of chronic beryllium disease (CBD), and their recruitment to the lung heralds the onset of granulomatous inflammation. We have shown that regulatory CD4+ T cells (Tregs) control granuloma formation in an HLA-DP2 transgenic (Tg) model of CBD. In these mice, Be oxide (BeO) exposure resulted in the accumulation of three distinct CD4+ T cell subsets in the lung with the majority of tissue-resident memory cells expressing FoxP3. The amount of Be regulated the number of total and antigen-specific CD4+ T cells and Tregs in the lungs of HLA-DP2 Tg mice. Depletion of Tregs increased the number of IFN-γ-producing CD4+ T cells and enhanced lung injury while mice treated with IL2/αIL-2 complexes had increased Tregs and reduced inflammation and Be-responsive T cells in the lung. BeO-experienced resident Tregs suppressed anti-CD3-induced proliferation of CD4+ T cells in a contact-dependent manner. CLTLA-4 and ICOS blockade as well as addition of LPS to BeO-exposed mice increased the Teff/Treg ratio and enhanced lung injury. Collectively, these data show that the protective role of tissue-resident Tregs is dependent on quantity of Be exposure and is overcome by blocking immune regulatory molecules or additional environmental insults.

The Dynamic Role of FOXP3+ Tregs and Their Potential Therapeutic Applications During SARS-CoV-2 Infection

Coronavirus disease 2019 (COVID-19) has been raging all around the world since the beginning of 2020, and leads to acute respiratory distress syndrome (ARDS) with strong cytokine storm which contributes to widespread tissue damage and even death in severe patients. Over-activated immune response becomes one of the characteristics of severe COVID-19 patients. Regulatory T cells (Treg) play an essential role in maintaining the immune homeostasis, which restrain excessive inflammation response. So FOXP3+ Tregs might participate in the suppression of inflammation caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Besides suppressive function, tissue resident Tregs are also responsible for tissue repair. In this review, we mainly summarize the latest research focusing on the change of FOXP3+ Tregs in the COVID-19 patients, discuss the relationship between disease severity and number change of Tregs and speculate the potential role of FOXP3+ Tregs during SARS-CoV-2 infection. Furthermore, we introduce some potential Treg-based therapies to improve patients’ outcomes, which include small molecular drugs, antibody drugs, CAR-Treg and cytokine treatment. We hope to reduce tissue damage of severe COVID-19 patients and offer better prognosis through Treg-based therapy.

Modulation of T Cell Responses by Fucoidan to Inhibit Osteogenesis

Fucoidan has sparked considerable interest in biomedical applications because of its inherent (bio)physicochemical characteristics, particularly immunomodulatory effects on macrophages, neutrophils, and natural killer cells. However, the effect of fucoidan on T cells and the following regulatory interaction on cellular function has not been reported. In this work, the effect of sterile fucoidan on the T-cell response and the subsequent modulation of osteogenesis is investigated. The physicochemical features of fucoidan treated by high-temperature autoclave sterilization are characterized by UV–visible spectroscopy, X-ray diffraction, Fourier transform infrared and nuclear magnetic resonance analysis. It is demonstrated that high-temperature autoclave treatment resulted in fucoidan depolymerization, with no change in its key bioactive groups. Further, sterile fucoidan promotes T cells proliferation and the proportion of differentiated T cells decreases with increasing concentration of fucoidan. In addition, the supernatant of T cells co-cultured with fucoidan greatly suppresses the osteogenic differentiation of MC3T3-E1 by downregulating the formation of alkaline phosphatase and calcium nodule compared with fucoidan. Therefore, our work offers new insight into the fucoidan-mediated T cell and osteoblast interplay.

Comprehensive Analysis of Potential ceRNA Network and Different Degrees of Immune Cell Infiltration in Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a leading cause of death in critically ill patients due to hypoxemic respiratory failure. The specific pathogenesis underlying ARDS has not been fully elucidated. In this study, we constructed a triple regulatory network involving competing endogenous RNA (ceRNA) to investigate the potential mechanism of ARDS and evaluated the immune cell infiltration patterns in ARDS patients. Overall, we downloaded three microarray datasets that included 60 patients with sepsis-induced ARDS and 79 patients with sepsis alone from the public Gene Expression Omnibus (GEO) database and identified differentially expressed genes (DEGs, including 9 DElncRNAs, 9 DEmiRNAs, and 269 DEmRNAs) by R software. The DEGs were subjected to the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) for functional enrichment analysis, and a protein–protein interaction (PPI) network was generated for uncovering interactive relationships among DEmRNAs. Then, a ceRNA network that contained 5 DElncRNAs, 7 DEmiRNAs, and 71 DEmRNAs was established according to the overlapping genes in both DEGs and predicted genes by public databases. Finally, we identified the TUG1/miR-140-5p/NFE2L2 pathway as the hub pathway in the whole network through Cytoscape. In addition, we evaluated the distribution of 22 subtypes of immune cells and recognized three differentially expressed immune cells in patients with sepsis-induced ARDS by “Cell Type Identification by Estimating Relative Subsets of Known RNA Transcripts (CIBERSORT)” algorithm, namely, naive B cells, regulatory T cells, and eosinophils. Correlations between differentially expressed immune cells and hub genes in the ceRNA network were also performed. In conclusion, we demonstrated a new potential regulatory mechanism underlying ARDS (the TUG1/miR-140-5p/NFE2L2 ceRNA regulatory pathway), which may help in further exploring the pathogenesis of ARDS.

ROS-responsive polymer nanoparticles with enhanced loading of dexamethasone effectively modulate the lung injury microenvironment

The acute lung injury (ALI) is an inflammatory disorder associated with cytokine storm, which activates various reactive oxygen species (ROS) signaling pathways and causes severe complications in patients as currently seen in coronavirus disease 2019 (COVID-19). There is an urgent need for medication of the inflammatory lung environment and effective delivery of drugs to lung to reduce the burden of high doses of medications and attenuate inflammatory cells and pathways. Herein, we prepared dexamethasone-loaded ROS-responsive polymer nanoparticles (PFTU@DEX NPs) by a modified emulsion approach, which achieved high loading content of DEX (11.61 %). DEX was released faster from the PFTU@DEX NPs in a ROS environment, which could scavenge excessive ROS efficiently both in vitro and in vivo. The PFTU NPs and PFTU@DEX NPs showed no hemolysis and cytotoxicity. Free DEX, PFTU NPs and PFTU@DEX NPs shifted M1 macrophages to M2 macrophages in RAW264.7 cells, and showed anti-inflammatory modulation to A549 cells in vitro. The PFTU@DEX NPs treatment significantly reduced the increased total protein concentration in BALF of ALI mice. The delivery of PFTU@DEX NPs decreased the proportion of neutrophils significantly, mitigated the cell apoptosis remarkably compared to the other groups, reduced M1 macrophages and increased M2 macrophages in vivo. Moreover, the PFTU@DEX NPs had the strongest ability to suppress the expression of NLRP3, Caspase1, and IL-1β. Therefore, the PFTU@DEX NPs could efficiently suppress inflammatory cells, ROS signaling pathways, and cell apoptosis to ameliorate LPS-induced ALI. STATEMENT OF SIGNIFICANCE: The acute lung injury (ALI) is an inflammatory disorder associated with cytokine storm, which activates various reactive oxygen species (ROS) signaling pathways and causes severe complications in patients. There is an urgent need for medication of the inflammatory lung environment and effective delivery of drugs to modulate the inflammatory disorder and suppress the expression of ROS and inflammatory cytokines. The inhaled PFTU@DEX NPs prepared through a modified nanoemulsification method suppressed the activation of NLRP3, induced the polarization of macrophage phenotype from M1 to M2, and thereby reduced the neutrophil infiltration, inhibited the release of proteins and inflammatory mediators, and thus decreased the acute lung injury in vivo.

A diminished immune response underlies age-related SARS-CoV-2 pathologies

Morbidity and mortality in response to SARS-CoV-2 infection are significantly elevated in people of advanced age. To understand the underlying biology of this phenotype, we utilize the golden hamster model to compare how the innate and adaptive immune responses to SARS-CoV-2 infection differed between younger and older animals. We find that while both hamster cohorts showed similar virus kinetics in the lungs, the host response in older animals was dampened, with diminished tissue repair in the respiratory tract post-infection. Characterization of the adaptive immune response also revealed age-related differences, including fewer germinal center B cells in older hamsters, resulting in reduced potency of neutralizing antibodies. Moreover, older animals demonstrate elevated suppressor T cells and neutrophils in the respiratory tract, correlating with an increase in TGF-β and IL-17 induction. Together, these data support that diminished immunity is one of the underlying causes of age-related morbidity.

SARS-CoV-2: A Master of Immune Evasion

Viruses and their hosts have coevolved for a long time. This coevolution places both the pathogen and the human immune system under selective pressure; on the one hand, the immune system has evolved to combat viruses and virally infected cells, while viruses have developed sophisticated mechanisms to escape recognition and destruction by the immune system. SARS-CoV-2, the pathogen that is causing the current COVID-19 pandemic, has shown a remarkable ability to escape antibody neutralization, putting vaccine efficacy at risk. One of the virus's immune evasion strategies is mitochondrial sabotage: by causing reactive oxygen species (ROS) production, mitochondrial physiology is impaired, and the interferon antiviral response is suppressed. Seminal studies have identified an intra-cytoplasmatic pathway for viral infection, which occurs through the construction of tunneling nanotubes (TNTs), hence enhancing infection and avoiding immune surveillance. Another method of evading immune monitoring is the disruption of the antigen presentation. In this scenario, SARS-CoV-2 infection reduces MHC-I molecule expression: SARS-CoV-2's open reading frames (ORF 6 and ORF 8) produce viral proteins that specifically downregulate MHC-I molecules. All of these strategies are also exploited by other viruses to elude immune detection and should be studied in depth to improve the effectiveness of future antiviral treatments. Compared to the Wuhan strain or the Delta variant, Omicron has developed mutations that have impaired its ability to generate syncytia, thus reducing its pathogenicity. Conversely, other mutations have allowed it to escape antibody neutralization and preventing cellular immune recognition, making it the most contagious and evasive variant to date.

COVID-19 immunotherapy: Treatment based on the immune cell-mediated approaches

Multiple efforts are currently underway to control and treat severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), causing coronavirus disease 2019 (COVID-19) worldwide. Despite all efforts, the virus that emerged in Wuhan city has rapidly spread globally and led to a public health emergency of international concern (PHEIC) due to the lack of approved antiviral therapy. Nevertheless, SARS-CoV-2 has had a significant influence on the evolution of cellular therapeutic approaches. Adoptive immune cell therapy is innovative and offers either promising prophylactic or therapy for patients with moderate-to-severe COVID-19. This approach is aimed at developing safety and providing secure and effective therapy in combination with standard therapy for all COVID-19 infected individuals. Based on the effective results of previous studies on both inflammatory and autoimmune diseases, various immune cell therapies against COVID-19 have been reviewed and discussed. It must be considered that the application of cell therapy for treatment and to eliminate infected respiratory cells could result in excessive inflammation, so this treatment must be used in combination with other treatments, despite its many beneficial efforts.

Mucosal immune responses to infection and vaccination in the respiratory tract

The lungs are constantly exposed to inhaled debris, allergens, pollutants, commensal or pathogenic microorganisms, and respiratory viruses. As a result, innate and adaptive immune responses in the respiratory tract are tightly regulated and are in continual flux between states of enhanced pathogen clearance, immune-modulation, and tissue repair. New single-cell-sequencing techniques are expanding our knowledge of airway cellular complexity and the nuanced connections between structural and immune cell compartments. Understanding these varied interactions is critical in treatment of human pulmonary disease and infections and in next-generation vaccine design. Here, we review the innate and adaptive immune responses in the lung and airways following infection and vaccination, with particular focus on influenza virus and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The ongoing SARS-CoV-2 pandemic has put pulmonary research firmly into the global spotlight, challenging previously held notions of respiratory immunity and helping identify new populations at high risk for respiratory distress.

Moving to the Outskirts: Interplay Between Regulatory T Cells and Peripheral Tissues

Regulatory T cells (Tregs) restrain excessive immune responses and dampen inflammation. In addition to this classical immune suppressive role, Tregs in non-lymphoid tissues also promote tissue homeostasis, regeneration and repair. In this review, we outline our current understanding of how Tregs migrate to peripheral tissues and the factors required for their maintenance at these sites. We discuss the tissue-specific adaptations of Tregs at barrier and immuno-privileged sites and the mechanisms that regulate their function within these organs. Furthermore, we outline what is known about the interactions of Tregs with non-immune cells in the different peripheral tissues at steady state and upon challenge or tissue damage. A thorough understanding of the tissue-specific adaptations and functions of Tregs will potentially pave the way for therapeutic approaches targeting their regenerative role.

Cellular therapies for the treatment and prevention of SARS-CoV-2 infection

Patients with blood disorders who are immune suppressed are at increased risk for infection with severe acute respiratory syndrome coronavirus 2. Sequelae of infection can include severe respiratory disease and/or prolonged duration of viral shedding. Cellular therapies may protect these vulnerable patients by providing antiviral cellular immunity and/or immune modulation. In this recent review of the field, phase 1/2 trials evaluating adoptive cellular therapies with virus-specific T cells or natural killer cells are described along with trials evaluating the safety, feasibility, and preliminary efficacy of immune modulating cellular therapies including regulatory T cells and mesenchymal stromal cells. In addition, the immunologic basis for these therapies is discussed.

Epigenetic Control of Regulatory T Cell Stability and Function: Implications for Translation

FoxP3+ regulatory T (Treg) cells maintain immune homeostasis, promote self-tolerance, and have an emerging role in resolving acute inflammation, providing tissue protection, and repairing tissue damage. Some data suggest that FoxP3+ T cells are plastic, exhibiting susceptibility to losing their function in inflammatory cytokine-rich microenvironments and paradoxically contributing to inflammatory pathology. As a result, plasticity may represent a barrier to Treg cell immunotherapy. Here, we discuss controversies surrounding Treg cell plasticity and explore determinants of Treg cell stability in inflammatory microenvironments, focusing on epigenetic mechanisms that clinical protocols could leverage to enhance efficacy and limit toxicity of Treg cell-based therapeutics.

Mucosal tissue regulatory T cells are integral in balancing immunity and tolerance at portals of antigen entry

Foxp3+ regulatory T cells (Tregs) are a subset of CD4+ T cells that exert suppressive control over other immune cells. Tregs are critical for preventing systemic autoimmunity and maintaining peripheral tolerance, and yet they also assist in orchestration of immunity to pathogenic insult, wherein they limit collateral immunopathology and assist in facilitating a fine balance between immune tolerance and effector activity. Tregs have been extensively studied in lymphoid tissues, and a growing body of work has characterized phenotypically distinct Tregs localized in various nonlymphoid tissue compartments. These tissue Tregs can perform location-specific, alternative functions, highlighting their dynamic, context-dependent roles. Tregs have also been identified in mucosal tissues where specialized physiological functions are paramount, including helping the host to respond appropriately to pathogenic versus innocuous antigens that are abundant at mucosal portals of antigen entry. As in other tissue Treg compartments, mucosal Tregs in the respiratory, gastrointestinal, and genitourinary tracts are distinct from circulating counterparts and can carry out mucosa-specific functions as well as classic suppressive functions that are the hallmark of Tregs. In this review, we summarize current knowledge regarding mucosal Tregs in both health and disease.

Regulatory T Cells: Angels or Demons in the Pathophysiology of Sepsis?

Sepsis is a syndrome characterized by life-threatening organ dysfunction caused by the dysregulated host response to an infection. Sepsis, especially septic shock and multiple organ dysfunction is a medical emergency associated with high morbidity, high mortality, and prolonged after-effects. Over the past 20 years, regulatory T cells (Tregs) have been a key topic of focus in all stages of sepsis research. Tregs play a controversial role in sepsis based on their heterogeneous characteristics, complex organ/tissue-specific patterns in the host, the multi-dimensional heterogeneous syndrome of sepsis, the different types of pathogenic microbiology, and even different types of laboratory research models and clinical research methods. In the context of sepsis, Tregs may be considered both angels and demons. We propose that the symptoms and signs of sepsis can be attenuated by regulating Tregs. This review summarizes the controversial roles and Treg checkpoints in sepsis.

A Focused Review on Primary Graft Dysfunction after Clinical Lung Transplantation: A Multilevel Syndrome

Primary graft dysfunction (PGD) is the clinical syndrome of acute lung injury after lung transplantation (LTx). However, PGD is an umbrella term that encompasses the ongoing pathophysiological and -biological mechanisms occurring in the lung grafts. Therefore, we aim to provide a focused review on the clinical, physiological, radiological, histological and cellular level of PGD. PGD is graded based on hypoxemia and chest X-ray (CXR) infiltrates. High-grade PGD is associated with inferior outcome after LTx. Lung edema is the main characteristic of PGD and alters pulmonary compliance, gas exchange and circulation. A conventional CXR provides a rough estimate of lung edema, while a chest computed tomography (CT) results in a more in-depth analysis. Macroscopically, interstitial and alveolar edema can be distinguished below the visceral lung surface. On the histological level, PGD correlates to a pattern of diffuse alveolar damage (DAD). At the cellular level, ischemia-reperfusion injury (IRI) is the main trigger for the disruption of the endothelial-epithelial alveolar barrier and inflammatory cascade. The multilevel approach integrating all PGD-related aspects results in a better understanding of acute lung failure after LTx, providing novel insights for future therapies.

Update on the Features and Measurements of Experimental Acute Lung Injury in Animals: An Official American Thoracic Society Workshop Report

Advancements in methods, technology, and our understanding of the pathobiology of lung injury have created the need to update the definition of experimental acute lung injury (ALI). We queried 50 participants with expertise in ALI and acute respiratory distress syndrome using a Delphi method composed of a series of electronic surveys and a virtual workshop. We propose that ALI presents as a "multidimensional entity" characterized by four "domains" that reflect the key pathophysiologic features and underlying biology of human acute respiratory distress syndrome. These domains are 1) histological evidence of tissue injury, 2) alteration of the alveolar-capillary barrier, 3) presence of an inflammatory response, and 4) physiologic dysfunction. For each domain, we present "relevant measurements," defined as those proposed by at least 30% of respondents. We propose that experimental ALI encompasses a continuum of models ranging from those focusing on gaining specific mechanistic insights to those primarily concerned with preclinical testing of novel therapeutics or interventions. We suggest that mechanistic studies may justifiably focus on a single domain of lung injury, but models must document alterations of at least three of the four domains to qualify as "experimental ALI." Finally, we propose that a time criterion defining "acute" in ALI remains relevant, but the actual time may vary based on the specific model and the aspect of injury being modeled. The continuum concept of ALI increases the flexibility and applicability of the definition to multiple models while increasing the likelihood of translating preclinical findings to critically ill patients.

Lacticaseibacillus rhamnosus modulates the inflammatory response and the subsequent lung damage in a murine model of acute lung inflammation

OBJECTIVE

The present study investigated the anti-inflammatory effect of the probiotic Lacticaseibacillus rhamnosus (Lr) on lung inflammation induced by Lipopolysaccharide (LPS) of Escherichia coli in C57BL/6 mice.

METHODS

C57BL/6 mice were divided into four groups: control, LPS, Lr (1 day) + LPS, and Lr (14 days) + LPS. Total and differential cells from Bronchoalveolar Lavage Fluid (BALF) were counted in a Neubauer 40X chamber, and pro-and anti-inflammatory cytokines (IL-1β, IL-6, CXCL-1, TNF-α, TGF-β, and IL-10) were measured by ELISA assay. The analysis of whole leukocytes in blood was performed using the automated system Sysmex 800i. Morphometry of pulmonary tissue evaluated alveolar hemorrhage, alveolar collapse, and inflammatory cells. Pulmonary vascular permeability was assessed by Evans blue dye extravasation, and bronchoconstriction was evaluated in a tissue bath station. The transcription factor NF-kB was evaluated by ELISA, and its gene expression and TLR-2, TLR-4, MMP-9, MMP-12, and TIMP by PCR.

RESULTS

The probiotic Lr had a protective effect against the inflammatory responses induced by LPS. Lr significantly reduced pro-inflammatory cells in the airways, lung parenchyma, and blood leukocytes. Furthermore, Lr reduced the production of pro-inflammatory cytokines and chemokines in BALF and the expression of TLRs, MMPs, and NF-kB in lung tissue and maintained the expression of TIMP in treated animals promoting a protective effect on lung tissue.

CONCLUSIONS

The results of the study indicate that pre-treatment with the probiotic Lr may be a promising way to mitigate lung inflammation in endotoxemia.

The fellowship of regulatory and tissue-resident memory cells

T cells located in non-lymphoid tissues have come to prominence in recent years. CD8+ tissue-resident memory (Trm) cells are important for tissue immune surveillance, provide an important line of defence against invading pathogens and show promise in cancer therapies. These cells differ in phenotype from other memory populations, are adapted to the tissue they home to where they found their cognate antigen and have different metabolic requirements for survival and activation. CD4+ Foxp3+ regulatory T (Treg) cells also consist of specialised populations, found in non-lymphoid tissues, with distinct transcriptional programmes. These cells have equally adapted to function in the tissue they made their home. Both Trm and Treg cells have functions beyond immune defence, involving tissue homeostasis, repair and turnover. They are part of a multicellular communication network. Intriguingly, occupying the same niche, Treg cells are important in the establishment of Trm cells, which may have implications to harness the immune surveillance and tissue homeostasis properties of Trm cells for future therapies.

Exogenous and Endogenous Dendritic Cell-Derived Exosomes: Lessons Learned for Immunotherapy and Disease Pathogenesis

Immune therapeutic exosomes, derived exogenously from dendritic cells (DCs), the 'directors' of the immune response, are receiving favorable safety and tolerance profiles in phase I and II clinical trials for a growing number of inflammatory and neoplastic diseases. DC-derived exosomes (EXO), the focus of this review, can be custom tailored with immunoregulatory or immunostimulatory molecules for specific immune cell targeting. Moreover, the relative stability, small size and rapid uptake of EXO by recipient immune cells offer intriguing options for therapeutic purposes. This necessitates an in-depth understanding of mechanisms of EXO biogenesis, uptake and routing by recipient immune cells, as well as their in vivo biodistribution. Against this backdrop is recognition of endogenous exosomes, secreted by all cells, the molecular content of which is reflective of the metabolic state of these cells. In this regard, exosome biogenesis and secretion is regulated by cell stressors of chronic inflammation and tumorigenesis, including dysbiotic microbes, reactive oxygen species and DNA damage. Such cell stressors can promote premature senescence in young cells through the senescence associated secretory phenotype (SASP). Pathological exosomes of the SASP amplify inflammatory signaling in stressed cells in an autocrine fashion or promote inflammatory signaling to normal neighboring cells in paracrine, without the requirement of cell-to-cell contact. In summary, we review relevant lessons learned from the use of exogenous DC exosomes for immune therapy, as well as the pathogenic potential of endogenous DC exosomes.

Toward a Paradigm to Distinguish Distinct Functions of FOXP3+ Regulatory T Cells

FOXP3⁺ regulatory T (Treg) cells are a unique subset of CD4⁺ T cells that classically function as master regulators of immune homeostasis. Besides this canonical suppressive role, which is required to maintain self-tolerance, a growing body of literature has identified Treg cells as critical orchestrators of tissue protection during acute stress and as effector cells that drive repair following tissue injury. Despite substantial interest in these distinct roles, the field has struggled to disentangle Treg cell suppressive functions from those that promote tissue defense and repair. In this article, we will examine the literature in the context of specific physiologic settings, contrasting the suppressive function of Treg cells with their emerging roles in promoting tissue homeostasis and tissue repair. Further, we will discuss a new paradigm differentiating tissue defense from tissue repair-a paradigm needed to translate Treg cell-based therapies to the clinic.

Protective role of (5R)-5-hydroxytriptolide in lipopolysaccharide-induced acute lung injury by suppressing dendritic cell activation

(5R)-5-hydroxytriptolide (LLDT-8) is a triptolide derivative with potent immunosuppressive property. This study aimed to investigate whether LLDT-8 manifests anti-inflammatory effects and influences dendritic cell function in early phase of lipopolysaccharide (LPS)-induced acute lung injury (ALI). C57BL/6 mice were administrated with LPS (6 mg/kg) to induce ALI and LLDT-8 were administrated at different doses (0.125 mg, 0.25 mg, 0.5 mg/kg). Histological changes were demonstrated by hematoxylin and eosin staining. Activation of dendritic cells were measured by flow cytometry. The concentrations of cytokines were measured by enzyme-linked immunosorbent assay. Bone marrow-derived dendritic cells (BMDCs) were acquired to explore immunosuppressive effects of LLDT-8 in vitro. Expression of Toll-like receptor 4 (TLR4), phosphorylation of inhibitor kappa B alpha (IκBα) and nuclear translocation of nuclear factor kappa B (NF-κB) were explored by immunoblot. Immunosuppressive property of LLDT-8-treated BMDCs were measured by adoptive transfer. The survival rate of ALI mice was significantly improved by LLDT-8 at the dose of 0.25 mg/kg. Moreover, systemic inflammatory response was suppressed and lung injury was relieved. LLDT-8 inhibited the activation of dendritic cells in vivo and influenced maturation, apoptosis and cytokine secretion capacity of BMDCs in vitro. Additionally, LLDT-8-treated BMDCs manifested reduced expression of TLR4, phosphorylation of IκBα and nuclear translocation of NF-κB. Adoptive transfer of LLDT-8-treated BMDCs alleviated LPS-induced lung injury. LLDT-8 also had protective effects on Pseudomonas aeruginosa-induced ALI. In conclusion, LLDT-8 played a protective role against ALI and suppressed dendritic cell activation potentially through affecting TLR4 expression and NF-κB signaling.

ARCADIA study protocol: a phase II, randomised, double-blind, placebo-controlled clinical trial to assess the safety and efficacy of AZD1656 in patients with diabetes hospitalised with suspected or confirmed COVID-19

INTRODUCTION

COVID-19, caused by SARS-CoV-2, remains a global pandemic that has affected more than 100 million people worldwide with over 4.8 million deaths as of October 2021. Patients with diabetes have both an increased susceptibility to SARS-CoV-2 infection, enhanced disease severity and increased risk of mortality. The challenge presented in these patients is both to improve glycaemic control-which itself may confer a survival advantage-and to help maintain or restore immunological homeostasis. The specific glucokinase activator AZD1656 may address both of these challenges via its glucose-lowering effect and its immunological mechanism of action. The aim of the Alleviation of cardioRespiratory complications in patients with COVID-19 And DIAbetes (ARCADIA) trial is to investigate this hypothesis and determine whether AZD1656 can improve clinical outcomes for these patients.

METHODS AND ANALYSIS

ARCADIA is a double-blind, placebo-controlled, interventional study of AZD1656 in 150 patients with either type 1 or type 2 diabetes who have been admitted to hospital with COVID-19. Eligible, consented patients will be randomised in a 1:1 manner to receive either active drug or matched placebo tablets while they are in hospital. All patients will receive the usual and current standard of care for patients with COVID-19 in that hospital. Clinical and laboratory data will be collected and assessed at baseline and throughout their participation in the study. Data will be captured in the case report form, which will be electronically archived at the end of the trial in the trial master file. The WHO 8-point Ordinal Scale for Clinical Improvement will be used to measure clinical outcome for the primary endpoint of the trial.

ETHICS AND DISSEMINATION

Ethical approval has been obtained from the East Midlands-Leicester South Ethics Committee (REC 20/EM/0198) in the UK, from the National Bioethics Committee of Medicines and Medical Devices in Bucharest, Romania, and from the Ethics Committee IKEM a TN in Prague, Czech Republic. All study-related data will be used by the sponsor in accordance with local data protection law. In the UK, all patient identifiable data will be stored on a password-protected National Health Service N3 network with full audit trail. Anonymised data will be stored in an ISO27001 certificated data warehouse.

TRIAL REGISTRATION NUMBER

EudraCT 2020-002211-21, NCT04516759.

Disease Tolerance during Viral-Bacterial Co-Infections

Disease tolerance has emerged as an alternative way, in addition to host resistance, to survive viral-bacterial co-infections. Disease tolerance plays an important role not in reducing pathogen burden, but in maintaining tissue integrity and controlling organ damage. A common co-infection is the synergy observed between influenza virus and Streptococcus pneumoniae that results in superinfection and lethality. Several host cytokines and cells have shown promise in promoting tissue protection and damage control while others induce severe immunopathology leading to high levels of morbidity and mortality. The focus of this review is to describe the host cytokines and innate immune cells that mediate disease tolerance and lead to a return to host homeostasis and ultimately, survival during viral-bacterial co-infection.

Baicalein suppresses lipopolysaccharide-induced acute lung injury by regulating Drp1-dependent mitochondrial fission of macrophages

Acute lung injury (ALI) and its serious form, the acute respiratory distress syndrome (ARDS) are devastating diseases without effective chemotherapy. Exuberant or uncontrolled proinflammation responses in the lung, also known as "cytokine storms", is one of the main culprits in the pathogenesis of organ failure, and anti-inflammatory therapy is essential to alleviate ALI/ARDS-associated injuries. Emerging evidence suggests that baicalein has potent anti-inflammatory and antioxidant properties. However, the underlined mechanism of baicalein to mitigate inflammation in ALI remains unclear. Herein, we demonstrated a critical role for baicalein in suppressing the inflammatory response of LPS-activated macrophages. We found that mitochondria function was restored in the condition of baicalein. Interestingly, results showed that mitochondrial dysfunction positively correlates with inflammatory cytokine generation at each corresponding baicalein concentration. Further mRNA analysis revealed that baicalein mitigates mitochondrial defects via attenuation of dynamin-related protein 1 (Drp1) expression. These reprogrammed mitochondria prevent their function shift from the ATP synthesis to reactive oxygen species (ROS) production after the LPS challenge, thereby dampening NF-κB-dependent inflammatory cytokine transcription. Baicalein reduces the production of inflammatory mediators TNF-α, MIP-1, IL-6, and diminishes neutrophil influx and severity of endotoxin-mediated ALI. Taken together, our results show that baicalein may serve as a new clinical therapeutic strategy in ALI by modulating Drp1-induced mitochondrial impairment, restraining inflammatory responses, and reducing the severity of lung injury.

Airway Basal Cells, Protectors of Epithelial Walls in Health and Respiratory Diseases

The airway epithelium provides a critical barrier to the outside environment. When its integrity is impaired, epithelial cells and residing immune cells collaborate to exclude pathogens and to heal tissue damage. Healing is achieved through tissue-specific stem cells: the airway basal cells. Positioned near the basal membrane, airway basal cells sense and respond to changes in tissue health by initiating a pro-inflammatory response and tissue repair via complex crosstalks with nearby fibroblasts and specialized immune cells. In addition, basal cells have the capacity to learn from previous encounters with the environment. Inflammation can indeed imprint a certain memory on basal cells by epigenetic changes so that sensitized tissues may respond differently to future assaults and the epithelium becomes better equipped to respond faster and more robustly to barrier defects. This memory can, however, be lost in diseased states. In this review, we discuss airway basal cells in respiratory diseases, the communication network between airway basal cells and tissue-resident and/or recruited immune cells, and how basal cell adaptation to environmental triggers occurs.

Interrelation Between Fibroblasts and T Cells in Fibrosing Interstitial Lung Diseases

Interstitial lung diseases (ILDs) are a heterogeneous group of diseases characterized by varying degrees of inflammation and fibrosis of the pulmonary interstitium. The interrelations between multiple immune cells and stromal cells participate in the pathogenesis of ILDs. While fibroblasts contribute to the development of ILDs through secreting extracellular matrix and proinflammatory cytokines upon activation, T cells are major mediators of adaptive immunity, as well as inflammation and autoimmune tissue destruction in the lung of ILDs patients. Fibroblasts play important roles in modulating T cell recruitment, differentiation and function and conversely, T cells can balance fibrotic sequelae with protective immunity in the lung. A more precise understanding of the interrelation between fibroblasts and T cells will enable a better future therapeutic design by targeting this interrelationship. Here we highlight recent work on the interactions between fibroblasts and T cells in ILDs, and consider the implications of these interactions in the future development of therapies for ILDs.

Research progress in immune microenvironment regulation of muscle atrophy induced by peripheral nerve injury

Denervated skeletal muscular atrophy is primarily characterized by loss of muscle strength and mass and an unideal functional recovery of the muscle after extended denervation. This review emphasizes the interaction between the immune system and the denervated skeletal muscle. Immune cells such as neutrophils, macrophages and T-cells are activated and migrate to denervated muscle, where they release a high concentration of cytokines and chemokines. The migration of these immune cells, the transformation of different functional immune cell subtypes, and the cytokine network in the immune microenvironment may be involved in the regulatory process of muscle atrophy or repair. However, the exact mechanisms of the interaction between these immune cells and immune molecules in skeletal muscles are unclear. In this paper, the immune microenvironment regulation of muscle atrophy induced by peripheral nerve injury is reviewed.

In Vivo Measurement of Granzyme Proteolysis from Activated Immune Cells with PET

The biology of human granzymes remains enigmatic in part due to our inability to probe their functions outside of in vitro assays or animal models with divergent granzyme species. We hypothesize that the biology of human granzymes could be better elaborated with a translational imaging technology to reveal the contexts in which granzymes are secreted and biochemically active in vivo. Here, we advance toward this goal by engineering a Granzyme targeting Restricted Interaction Peptide specific to family member B (GRIP B) to measure secreted granzyme B (GZMB) biochemistry with positron emission tomography. A proteolytic cleavage of 64Cu-labeled GRIP B liberates a radiolabeled form of Temporin L, which sequesters the radioisotope by binding to adjacent phospholipid bilayers. Thus, at extended time points postinjection (i.e., hours, not seconds), tissue biodistribution of the radioisotope in vivo reflects relative units of the GZMB activity. As a proof of concept, we show in three syngeneic mouse cancer models that 64Cu-GRIP B detects GZMB from T cells activated with immune checkpoint inhibitors (CPI). Remarkably, the radiotracer detects the proteolysis within tumors but also in lymphoid tissue, where immune cells are activated by a systemic CPI. Control experiments with an uncleavable analogue of 64Cu-GRIP B and tumor imaging studies in germline GZMB knockout mice were applied to show that 64Cu-GRIP B is specific for GZMB proteolysis. Furthermore, we explored a potential noncytotoxic function for GZMB by applying 64Cu-GRIP B to a model of pulmonary inflammation. In summary, we demonstrate that granzyme biochemistry can be assessed in vivo using an imaging modality that can be scaled vertically into human subjects.

The β3/5 Integrin-MMP9 Axis Regulates Pulmonary Inflammatory Response and Endothelial Leakage in Acute Lung Injury

Background

Acute lung injury (ALI) is a severe respiratory disease with high rates of morbidity and mortality. Many mediators regarding endogenous or exogenous are involved in the pathophysiology of ALI. Here, we have uncovered the involvement of integrins and matrix metalloproteinases, as critical determinants of excessive inflammation and endothelial permeability, in the regulation of ALI.

Methods

Inflammatory cytokines were measured by quantitative real-time PCR for mRNA levels and ELISA for secretion levels. Endothelial permeability assay was detected by the passage of rhodamine B isothiocyanate-dextran. Mice lung permeability was assayed by Evans blue albumin (EBA). Western blot was used for protein level measurements. The intracellular reactive oxygen species (ROS) were evaluated using a cell-permeable probe, DCFH-DA. Intratracheal injection of lipopolysaccharide (LPS) into mice was conducted to establish the lung injury model.

Results

Exogenous MMP-9 significantly aggravated the inflammatory response and permeability in mouse pulmonary microvascular endothelial cells (PMVECs) treated by LPS, whereas knockdown of MMP-9 exhibited the opposite phenotypes. Knockdown of integrin β3 or β5 in LPS-treated PMVECs significantly downregulated MMP-9 expression and decreased inflammatory response and permeability in the presence or absence of exogenous MMP-9. Additionally, the interaction of MMP-9 and integrin β5 was impaired by a ROS scavenger, which further decreased the pro-inflammatory cytokines production and endothelial leakage in PMVECs subjected to co-treatment (LPS with exogenous MMP-9). In vivo studies, exogenous MMP-9 treatment or knockdown β3 integrin significantly decreased survival in ALI mice. Notably, knockdown of β5 integrin alone had no remarkable effect on survival, but which combined with anti-MMP-9 treatment significantly improved the survival by ameliorating excessive lung inflammation and permeability in ALI mice.

Conclusion

These findings support the β3/5 integrin-MMP-9 axis as an endogenous signal that could play a pivotal role in regulating inflammatory response and alveolar-capillary permeability in ALI.

T lymphocytes as critical mediators in tissue regeneration, fibrosis, and the foreign body response

Research on the foreign body response (FBR) to biomaterial implants has been focused on the roles that the innate immune system has on mediating tolerance or rejection of implants. However, the immune system also involves the adaptive immune response and it must be included in order to form a complete picture of the response to biomaterials and medical implants. In this review, we explore recent understanding about the roles of adaptive immune cells, specifically T cells, in modulating the immune response to biomaterial implants. The immune response to implants elicits a delicate balance between tissue repair and fibrosis that is mainly regulated by three types of T helper cell responses -T helper type 1, T helper type 2, and T helper type 17- and their crosstalk with innate immune cells. Interestingly, many T cell response mechanisms to implants overlap with the process of fibrosis or repair in different tissues. This review explores the fibrotic and regenerative T cell biology and draws parallels to T cell responses to biomaterials. Additionally, we also explore the biomedical engineering advancements in biomaterial applications in designing particle and scaffold systems to modulate T cell activity for therapeutics and devices. Not only do the deliberate engineering design of physical and chemical material properties and the direct genetic modulation of T cells not only offer insights to T cell biology, but they also present different platforms to develop immunomodulatory biomaterials. Thus, an in-depth understanding of T cells' roles can help to navigate the biomaterial-immune interactions and reconsider the long-lasting adaptive immune response to implants, which, in the end, contribute to the design of immunomodulatory medical implants that can advance the next generation of regenerative therapy. STATEMENT OF SIGNIFICANCE: This review article integrates knowledge of adaptive immune responses in tissue damage, wound healing, and medical device implantation. These three fields, often not discussed in conjunction, are important to consider when evaluating and designing biomaterials. Through incorporation of basic biological research alongside engineering research, we provide an important lens through which to evaluate adaptive immune contributions to regenerative medicine and medical device development.

Luteolin activates Tregs to promote IL-10 expression and alleviating caspase-11-dependent pyroptosis in sepsis-induced lung injury

OBJECTIVES

Acute respiratory distress syndrome (ARDS) is characterized by an excessive pulmonary inflammatory response. Pyroptosis is a newly form of programmed inflammatory cell death that is triggered by inflammatory caspases. Studies have shown that Luteolin has powerful anti-inflammation effects through activating the function of regulatory T cells (Tregs). The study aimed at investigating the effects of Luteolin on CLP-induced ALI.

METHODS

In our study, we employed the mouse cecal ligation and puncture (CLP) model to explore whether Luteolin contributed to alleviated lung injury in vivo. H&E staining and wet/dry (W/D) weight ratios were used to evaluate the severity of lung injury. The serum and BALF of cytokines were assessed by ELISA. The number of neutrophils in the BALF was counted. Immunohistochemistry of IL-10 and MPO in lung tissue was detected. The ROS level in lung was tested by ROS Assay Kit and expression of Gpx4 in lung tissue was detected by qRT-PCR and Western blotting. The regulatory T cells (Treg) population was analyzed in spleen and Peripheral blood mononuclear cells (PBMCs). The levels of caspase-11 protein, caspase-1 protein, GSDMD protein, IL-1α and IL-1β protein in the lung tissue was evaluated by Western blotting.

RESULTS

We found Luteolin significantly inhibits inflammation and attenuated CLP-induced lung injury in vivo, and the levels of, caspase-11, caspase-1, GSDMD, IL-1α and IL-1β protein in the lungs of CLP mice decreased significantly after pretreatment with Luteolin. Furthermore, the results showed that Luteolin could increase Treg frequencies and IL-10 levels in serum and BALF of CLP mice. It is noteworthy that depleting Tregs reverse Luteolin ameliorated lung injury, and IL-10 neutralizing antibodies treatment aggravated lung pyroptosis.

CONCLUSIONS

Our study illustrated that Luteolin contributed to alleviated lung injury, and attenuated caspase-11-dependent pyroptosis in the lung tissue of the CLP-induced ALI mouse model. The mechanisms could be related to regulating the frequency of Tregs and the levels of Treg derived IL-10. Treg cells were show to produce IL-10 and could alleviating caspase-11-dependent lung pyroptosis.