TGF-β1 limits the onset of innate lung inflammation by promoting mast cell-derived IL-6

Unexpected Expression and Function of FcεRI in Immortalized Breast Cancer Cells: A Cautionary Null Study

The high-affinity IgE receptor, FcεRI, is typically associated with type 2 effectors such as mast cells (MC). The relatively unique expression profile of FcεRI and accumulating evidence from pre-clinical and clinical settings, such as MC interactions with tumors, have led us to study MCs as a potential therapeutic target in breast cancer. Our work identified MCs interacting with tumor cells at primary sites using the 4T1 (BALB/c) adenocarcinoma model in vivo. However, this analysis was complicated by a surprising finding that the tumor cells intrinsically and strongly expressed FcεRI. We further studied the expression and function of FcεRI in breast cancer cells in vitro. The 4T1 cells expressed FcεRI to a level similar to mouse bone marrow-derived MC (BMMC). Additionally, two established breast cancer cultures derived from human T-47D cells, one estrogen-dependent (E3) and the other estrogen-withdrawn (EWD8), also expressed FcεRI with EWD8 cells showing the greatest abundance. Functional analyses indicated that IgE-mediated antigen stimulation did not elicit classic Ca2+ flux in breast cancer cells as seen in the respective species' MCs; however, FcεRI crosslinking could stimulate IL-6 production from the T-47D derivatives. Preliminary analysis of primary breast cancer biopsy datasets using R2: Genomics Analysis and Visualization Platform was discordant with our in vivo model and in vitro observations. Indeed, FcεRI mRNA abundance declined in metastatic breast cancers compared to non-cancerous breast tissue. Altogether, we report a previously unidentified and immunologically substantive difference between breast cancer models and human primary tumors. Investigators pursuing FcεRI-relevant therapeutics in this context should be aware of this translational barrier.

Revisiting regulatory T cells as modulators of innate immune response and inflammatory diseases

Regulatory T cells (Treg) are known to be critical for the maintenance of immune homeostasis by suppressing the activation of auto- or allo-reactive effector T cells through a diverse repertoire of molecular mechanisms. Accordingly, therapeutic strategies aimed at enhancing Treg numbers or potency in the setting of autoimmunity and allogeneic transplants have been energetically pursued and are beginning to yield some encouraging outcomes in early phase clinical trials. Less well recognized from a translational perspective, however, has been the mounting body of evidence that Treg directly modulate most aspects of innate immune response under a range of different acute and chronic disease conditions. Recognizing this aspect of Treg immune modulatory function provides a bridge for the application of Treg-based therapies to common medical conditions in which organ and tissue damage is mediated primarily by inflammation involving myeloid cells (mononuclear phagocytes, granulocytes) and innate lymphocytes (NK cells, NKT cells, γδ T cells and ILCs). In this review, we comprehensively summarize pre-clinical and human research that has revealed diverse modulatory effects of Treg and specific Treg subpopulations on the range of innate immune cell types. In each case, we emphasize the key mechanistic insights and the evidence that Treg interactions with innate immune effectors can have significant impacts on disease severity or treatment. Finally, we discuss the opportunities and challenges that exist for the application of Treg-based therapeutic interventions to three globally impactful, inflammatory conditions: type 2 diabetes and its end-organ complications, ischemia reperfusion injury and atherosclerosis.

Low-dose radiation therapy suppresses viral pneumonia by enhancing broad-spectrum anti-inflammatory responses via transforming growth factor-β production

Low-dose radiation therapy (LDRT) can suppress intractable inflammation, such as that in rheumatoid arthritis, and is used for treating more than 10,000 rheumatoid arthritis patients annually in Europe. Several recent clinical trials have reported that LDRT can effectively reduce the severity of coronavirus disease (COVID-19) and other cases of viral pneumonia. However, the therapeutic mechanism of LDRT remains unelucidated. Therefore, in the current study, we aimed to investigate the molecular mechanism underlying immunological alterations in influenza pneumonia after LDRT. Mice were irradiated to the whole lung 1 day post-infection. The changes in levels of inflammatory mediators (cytokines and chemokines) and immune cell populations in the bronchoalveolar lavage (BALF), lungs, and serum were examined. LDRT-treated mice displayed markedly increased survival rates and reduced lung edema and airway and vascular inflammation in the lung; however, the viral titers in the lungs were unaffected. Levels of primary inflammatory cytokines were reduced after LDRT, and transforming growth factor-β (TGF-β) levels increased significantly on day 1 following LDRT. Levels of chemokines increased from day 3 following LDRT. Additionally, M2 macrophage polarization or recruitment was increased following LDRT. We found that LDRT-induced TGF-β reduced the levels of cytokines and polarized M2 cells and blocked immune cell infiltration, including neutrophils, in BALF. LDRT-induced early TGF-β production was shown to be a key regulator involved in broad-spectrum anti-inflammatory activity in virus-infected lungs. Therefore, LDRT or TGF-β may be an alternative therapy for viral pneumonia.

Physical exercise is associated with a reduction in plasma levels of fractalkine, TGF-β1, eotaxin-1 and IL-6 in younger adults with mobility disability

Mobility disability (MD) refers to substantial limitations in life activities that arise because of movement impairments. Although MD is most prevalent in older individuals, it can also affect younger adults. Increasing evidence suggests that inflammation can drive the development of MD and may need to be targeted for MD prevention. Physical exercise has anti-inflammatory properties and has been associated with MD prevention. However, no studies to date have examined whether exercise interventions affect the peripheral inflammatory status in younger adults with MD. To this end, we used blood samples from young and middle-aged adults with MD (N = 38; median age = 34 years) who participated in a 12-week intervention that included aerobic and resistance exercise training. A pre-post assessment of inflammatory biomarkers was conducted in plasma from two timepoints, i.e., before the exercise trial and at follow-up (3–7 days after the last exercise session). We successfully measured 15 inflammatory biomarkers and found that exercise was associated with a significant reduction in levels of soluble fractalkine, transforming growth factor beta 1 (TGF-β1), eotaxin-1 and interleukin (IL) 6 (corrected α = 0.004). We also found significant male-specific effects of exercise on (i) increasing IL-16 and (ii) decreasing vascular endothelial growth factor-A (VEGF-A). In line with our results, previous studies have also found that exercise can reduce levels of TGF-β1, eotaxin-1 and IL-6. However, our finding that exercise reduces plasma levels of fractalkine in younger adults with MD, as well as the sex-dependent findings, have not been previously reported and warrant replication in larger cohorts. Given the suggested role of inflammation in promoting MD development, our study provides additional support for the use of physical exercise as a treatment modality for MD.

25-Hydroxycholesterol metabolism is altered by lung inflammation, and its local administration modulates lung inflammation in mice

Inflammation is a critical component of many lung diseases including asthma and acute lung injury (ALI). Using high-performance liquid chromatography-mass spectrometry, we quantified the levels of oxysterols in two different murine models of lung diseases. These are lipid mediators derived from cholesterol and known to modulate immunity and inflammation. Interestingly, 25-hydroxycholesterol (25-OHC) was the only oxysterol with altered levels during lung inflammation, and its levels were differently affected according to the model. Therefore, we sought to assess how this oxysterol would affect lung inflammatory responses. In a model of lipopolysaccharide (LPS)-induced acute lung inflammation, 25-OHC levels were increased, and most of the hallmarks of the model (eg, leukocyte recruitment, mRNA expression, and secretion of inflammatory cytokines) were decreased following its intratracheal administration. We also found that, when administered in the lung, 25-OHC is metabolized locally into 25-hydroxycholesterol-3-sulfate and 7α,25-dihydroxycholesterol. Their administration in the lungs did not recapitulate all the effects of 25-OHC. Conversely, in a model of allergic asthma induced by intranasal administration of house dust mites (HDM), 25-OHC levels were decreased, and when intranasally administered, this oxysterol worsened the hallmarks of the model (eg, leukocyte recruitment, tissue remodeling [epithelium thickening and peribranchial fibrosis], and cytokine expression) and induced changes in leukotriene levels. Ex vivo, we found that 25-OHC decreases LPS-induced primary alveolar macrophage activation while having no effect on neutrophil activation. Its sulfated metabolite, 25-hydroxycholesterol-3-sulfate, decreased neutrophil, but not macrophage activation. Taken together, our data support a differential role of 25-OHC in ALI and allergic inflammation models.

ZFP36 protects lungs from intestinal I/R-induced injury and fibrosis through the CREBBP/p53/p21/Bax pathway

Acute lung injury induced by ischemia-reperfusion (I/R)-associated pulmonary inflammation is associated with high rates of morbidity. Despite advances in the clinical management of lung disease, molecular therapeutic options for I/R-associated lung injury are limited. Zinc finger protein 36 (ZFP36) is an AU-rich element-binding protein that is known to suppress the inflammatory response. A ZFP36 binding site occurs in the 3' UTR of the cAMP-response element-binding protein (CREB) binding protein (CREBBP) gene, which is known to interact with apoptotic proteins to promote apoptosis. In this study, we investigate the involvement of ZFP36 and CREBBP on I/R-induced lung injury in vivo and in vitro. Intestinal ischemia/reperfusion (I/R) activates inflammatory responses, resulting in injury to different organs including the lung. Lung tissues from ZFP36-knockdown mice and mouse lung epithelial (MLE)-2 cells were subjected to either Intestinal I/R or hypoxia/reperfusion, respectively, and then analyzed by Western blotting, immunohistochemistry, and real-time PCR. Silico analyses, pull down and RIP assays were used to analyze the relationship between ZFP36 and CREBBP. ZFP36 deficiency upregulated CREBBP, enhanced I/R-induced lung injury, apoptosis, and inflammation, and increased I/R-induced lung fibrosis. In silico analyses indicated that ZFP36 was a strong negative regulator of CREBBP mRNA stability. Results of pull down and RIP assays confirmed that ZFP36 direct interacted with CREBBP mRNA. Our results indicated that ZFP36 can mediate the level of inflammation-associated lung damage following I/R via interactions with the CREBBP/p53/p21/Bax pathway. The downregulation of ZFP36 increased the level of fibrosis.

Proteomic Characterization, Biodistribution, and Functional Studies of Immune-Therapeutic Exosomes: Implications for Inflammatory Lung Diseases

Dendritic cell (DC)-derived exosomes (DC EXO), natural nanoparticles of endosomal origin, are under intense scrutiny in clinical trials for various inflammatory diseases. DC EXO are eobiotic, meaning they are well-tolerated by the host; moreover, they can be custom-tailored for immune-regulatory or -stimulatory functions, thus presenting attractive opportunities for immune therapy. Previously we documented the efficacy of immunoregulatory DCs EXO (regDCs EXO) as immunotherapy for inflammatory bone disease, in an in-vivo model. We showed a key role for encapsulated TGFβ1 in promoting a bone sparing immune response. However, the on- and off-target effects of these therapeutic regDC EXO and how target signaling in acceptor cells is activated is unclear. In the present report, therapeutic regDC EXO were analyzed by high throughput proteomics, with non-therapeutic EXO from immature DCs and mature DCs as controls, to identify shared and distinct proteins and potential off-target proteins, as corroborated by immunoblot. The predominant expression in regDC EXO of immunoregulatory proteins as well as proteins involved in trafficking from the circulation to peripheral tissues, cell surface binding, and transmigration, prompted us to investigate how these DC EXO are biodistributed to major organs after intravenous injection. Live animal imaging showed preferential accumulation of regDCs EXO in the lungs, followed by spleen and liver tissue. In addition, TGFβ1 in regDCs EXO sustained downstream signaling in acceptor DCs. Blocking experiments suggested that sustaining TGFβ1 signaling require initial interaction of regDCs EXO with TGFβ1R followed by internalization of regDCs EXO with TGFβ1-TGFβ1R complex. Finally, these regDCs EXO that contain immunoregulatory cargo and showed biodistribution to lungs could downregulate the main severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) target receptor, ACE2 on recipient lung parenchymal cells via TGFβ1 in-vitro. In conclusion, these results in mice may have important immunotherapeutic implications for lung inflammatory disorders.

Potential Targets to Mitigate Trauma- or Sepsis-Induced Immune Suppression

In sepsis and trauma, pathogens and injured tissue provoke a systemic inflammatory reaction which can lead to overwhelming inflammation. Concurrent with the innate hyperinflammatory response is adaptive immune suppression that can become chronic. A current key issue today is that patients who undergo intensive medical care after sepsis or trauma have a high mortality rate after being discharged. This high mortality is thought to be associated with persistent immunosuppression. Knowledge about the pathophysiology leading to this state remains fragmented. Immunosuppressive cytokines play an essential role in mediating and upholding immunosuppression in these patients. Specifically, the cytokines Interleukin-10 (IL-10), Transforming Growth Factor-β (TGF-β) and Thymic stromal lymphopoietin (TSLP) are reported to have potent immunosuppressive capacities. Here, we review their ability to suppress inflammation, their dynamics in sepsis and trauma and what drives the pathologic release of these cytokines. They do exert paradoxical effects under certain conditions, which makes it necessary to evaluate their functions in the context of dynamic changes post-sepsis and trauma. Several drugs modulating their functions are currently in clinical trials in the treatment of other pathologies. We provide an overview of the current literature on the effects of IL-10, TGF-β and TSLP in sepsis and trauma and suggest therapeutic approaches for their modulation.

Divergent Mast Cell Responses Modulate Antiviral Immunity During Influenza Virus Infection

Influenza A virus (IAV) is a respiratory pathogen that infects millions of people each year. Both seasonal and pandemic strains of IAV are capable of causing severe respiratory disease with a high risk of respiratory failure and opportunistic secondary infection. A strong inflammatory cytokine response is a hallmark of severe IAV infection. The widespread tissue damage and edema in the lung during severe influenza is largely attributed to an overexuberant production of inflammatory cytokines and cell killing by resident and infiltrating leukocytes. Mast cells (MCs) are a sentinel hematopoietic cell type situated at mucosal sites, including the lung. Poised to react immediately upon detecting infection, MCs produce a vast array of immune modulating molecules, including inflammatory cytokines, chemokines, and proteases. As such, MCs have been implicated as a source of the immunopathology observed in severe influenza. However, a growing body of evidence indicates that MCs play an essential role not only in inducing an inflammatory response but in suppressing inflammation as well. MC-derived immune suppressive cytokines are essential to the resolution of a number of viral infections and other immune insults. Absence of MCs prolongs infection, exacerbates tissue damage, and contributes to dissemination of the pathogen to other tissues. Production of cytokines such as IL-10 and IL-6 by MCs is essential for mitigating the inflammation and tissue damage caused by innate and adaptive immune cells alike. The two opposing functions of MCs—one pro-inflammatory and one anti-inflammatory—distinguish MCs as master regulators of immunity at the site of infection. Amongst the first cells to respond to infection or injury, MCs persist for the duration of the infection, modulating the recruitment, activation, and eventual suppression of other immune cells. In this review, we will discuss the immune modulatory roles of MCs over the course of viral infection and propose that the immune suppressive mediators produced by MCs are vital to minimizing immunopathology during influenza infection.

Beyond IgE: Alternative Mast Cell Activation Across Different Disease States

Mast cells are often regarded through the lens of IgE-dependent reactions as a cell specialized only for anti-parasitic and type I hypersensitive responses. However, recently many researchers have begun to appreciate the expansive repertoire of stimuli that mast cells can respond to. After the characterization of the interleukin (IL)-33/suppression of tumorigenicity 2 (ST2) axis of mast cell activation-a pathway that is independent of the adaptive immune system-researchers are revisiting other stimuli to induce mast cell activation and/or subsequent degranulation independent of IgE. This discovery also underscores that mast cells act as important mediators in maintaining body wide homeostasis, especially through barrier defense, and can thus be the source of disease as well. Particularly in the gut, inflammatory bowel diseases (Crohn's disease, ulcerative colitis, etc.) are characterized with enhanced mast cell activity in the context of autoimmune disease. Mast cells show phenotypic differences based on tissue residency, which could manifest as different receptor expression profiles, allowing for unique mast cell responses (both IgE and non-IgE mediated) across varying tissues as well. This variety in receptor expression suggests mast cells respond differently, such as in the gut where immunosuppressive IL-10 stimulates the development of food allergy or in the lungs where transforming growth factor-β1 (TGF-β1) can enhance mast cell IL-6 production. Such differences in receptor expression illustrate the truly diverse effector capabilities of mast cells, and careful consideration must be given toward the phenotype of mast cells observed in vitro. Given mast cells' ubiquitous tissue presence and their capability to respond to a broad spectrum of non-IgE stimuli, it is expected that mast cells may also contribute to the progression of autoimmune disorders and other disease states such as metastatic cancer through promoting chronic inflammation in the local tissue microenvironment and ultimately polarizing toward a unique T_h17 immune response. Furthermore, these interconnected, atypical activation pathways may crosstalk with IgE-mediated signaling differently across disorders such as parasitism, food allergies, and autoimmune disorders of the gut. In this review, we summarize recent research into familiar and novel pathways of mast cells activation and draw connections to clinical human disease.

Allergic inflammation is initiated by IL-33-dependent crosstalk between mast cells and basophils

IgE-primed mast cells in peripheral tissues, including the skin, lung, and intestine, are key initiators of allergen-triggered edema and inflammation. Particularly in severe forms of allergy, this inflammation becomes strongly neutrophil dominated, and yet how mast cells coordinate this type of response is unknown. We and others have reported that activated mast cells--a hematopoietic cell type--can produce IL-33, a cytokine known to participate in allergic responses but generally considered as being of epithelial origin and driving Type 2 immune responses (e.g., ILC2 and eosinophil activation). Using models of skin anaphylaxis, our data reveal that mast cell-derived IL-33 also initiates neutrophilic inflammation. We demonstrate a cellular crosstalk mechanism whereby activated mast cells crosstalk to IL-33 receptor-bearing basophils, driving these basophils to adopt a unique response signature rich in neutrophil-associated molecules. We further establish that basophil expression of CXCL1 is necessary for IgE-driven neutrophilic inflammation. Our findings thus unearth a new mechanism by which mast cells initiate local inflammation after antigen triggering and might explain the complex inflammatory phenotypes observed in severe allergic diseases. Moreover, our findings (i) establish a functional link from IL-33 to neutrophilic inflammation that extends IL-33-mediated biology well beyond that of Type 2 immunity, and (ii) demonstrate the functional importance of hematopoietic cell-derived IL-33 in allergic pathogenesis.

Ameliorative effects of silymarin on HCl-induced acute lung injury in rats; role of the Nrf-2/HO-1 pathway

OBJECTIVES

Aspiration is a common cause of acute lung injury (ALI), which lacks an effective treatment. Inflammation and oxidative stress play key roles in ALI development. Silymarin is an active extract of Silybum marianum plant seeds (milk thistle). Silymarin has potent anti-inflammatory and antioxidant effects; however its role in aspiration induced ALI has not been investigated. The aim of this study is to investigate the role of silymarin in the treatment of hydrochloric acid (HCl) aspiration induced ALI and explores its mechanisms of action.

MATERIALS AND METHODS

The study included three groups of rats: Control non-treated group, ALI group (intra-tracheal HCl injected), and silymarin treated ALI group. White blood cells (WBCs) with differential count, oxidative stress parameters, B-cell lymphoma 2 (Bcl-2), transforming growth factor-beta (TGF-β), cyclooxygenase 2 (COX-2), nuclear factor erythroid 2-related factor-2 (Nrf-2), and heme oxygenase-1 (HO-1) were investigated. Lung tissue histopathology and immunohistochemical expression of survivin and proliferating cell nuclear antigen (PCNA) were also examined.

RESULTS

The results of the study showed that HCL caused histopathological changes in ALI with leukocytopenia and increased oxidative stress biomarkers. It increased TGF-β, up-regulated mRNA expression of COX-2, Nrf-2, and HO-1 and increased survivin and PCNA but decreased Bcl-2. Silymarin ameliorated the histopathological lung injury with further up-regulation of Nrf-2 and HO-1 mRNA and decreased the inflammatory and fibrotic parameters together with up-regulation of the anti-apoptotic and the proliferation parameters.

CONCLUSION

The protective effect of silymarin against ALI is mediated by Nrf-2/HO-1 pathway with subsequent antioxidant, anti-inflammatory, antiapoptotic, and proliferating activities.

Determining Immune and miRNA Biomarkers Related to Respiratory Syncytial Virus (RSV) Vaccine Types

Respiratory Syncytial Virus (RSV) causes serious respiratory tract illness and substantial morbidity and some mortality in populations at the extremes of age, i.e., infants, young children, and the elderly. To date, RSV vaccine development has been unsuccessful, a feature linked to the lack of biomarkers available to assess the safety and efficacy of RSV vaccine candidates. We examined microRNAs (miR) as potential biomarkers for different types of RSV vaccine candidates. In this study, mice were vaccinated with a live attenuated RSV candidate that lacks the small hydrophobic (SH) and attachment (G) proteins (CP52), an RSV G protein microparticle (GA2-MP) vaccine, a formalin-inactivated RSV (FI-RSV) vaccine or were mock-treated. Several immunological endpoints and miR expression profiles were determined in mouse serum and bronchoalveolar lavage (BAL) following vaccine priming, boost, and RSV challenge. We identified miRs that were linked with immunological parameters of disease and protection. We show that miRs are potential biomarkers providing valuable insights for vaccine development.

T-Regulatory Cells Confer Increased Myelination and Stem Cell Activity after Stroke-Induced White Matter Injury

Stroke-induced hypoxia causes oligodendrocyte death due to inflammation, lack of oxygen and exacerbation of cell death. Bone marrow-derived stem cells (BMSCs) possess an endogenous population of T-regulatory cells (T_regs) which reduce secretion of pro-inflammatory cytokines that lead to secondary cell death. Here, we hypothesize that oligodendrocyte progenitor cells (OPCs) cultured with BMSCs containing their native T_reg population show greater cell viability, less pro-inflammatory cytokine secretion and greater myelin production after exposure to oxygen-glucose deprivation and reoxygenation (OGD/R) than OPCs cultured without T_regs. OPCs were cultured and then exposed to OGD/R. BMSCs with or without T_regs were added to the co-culture immediately after ischemia. The T_regs were depleted by running the BMSCs through a column containing a magnetic substrate. Fibroblast growth factor beta (FGF-β) and interleukin 6 (IL-6) ELISAs determined BMSC activity levels. Immunohistochemistry assessed OPC differentiation. OPCs cultured with BMSCs containing their endogenous T_regs showed increased myelin production compared to the BMSCs with depleted T_regs. IL-6 and FGF-β were increased in the group cultured with T_regs. Collectively, these results suggest that BMSCs containing T_regs are more therapeutically active, and that T_regs have beneficial effects on OPCs subjected to ischemia. T_regs play an important role in stem cell therapy and can potentially treat white matter injury post-stroke.

Soluble transforming growth factor beta-1 enhances murine mast cell release of Interleukin 6 in IgE-independent and Interleukin 13 in IgE-dependent settings in vitro

INTRODUCTION

For immune cells transforming growth factor beta-1 (TGF-β1) can enhance or repress effector functions. Here, we characterize the effects of TGF-β1 on IgE-mediated and IL-33-mediated activation of primary murine mast cells derived from hematopoietic stem cells (bone marrow derived mast cells; BMMC). We also investigated potential interactions between TGF-β1 and stem cell factor (SCF). We conclude TGF-β1 plays a selectively stimulatory role for mast cell cultures in vitro.

METHODS

BMMCs from C57BL/6 mice were differentiated with IL-3 and then treated with TGF-β1. BMMCs were exposed to TGF-β1, primed with IgE, activated with antigen, and then IL-6 and IL-13 cytokine release was quantified using ELISA. Additionally, the effects of TGF-β1 on both IgE and IL-33-mediated short term activation were observed via flow cytometric analysis of both surface LAMP-1 expression and intracellular IL-6. Receptor colocalization was visualized using fluorescence confocal microscopy and individual receptor expression levels were also quantified.

RESULTS

Resting IL-6 production increased with TGF-β1 but significance was lost following BMMC activation via IgE receptor (FcεRI) crosslinking. This was similar to a comparison effect due to SCF treatment alone, which also enhanced resting levels of IL-6. TGF-β1 treatment enhanced release of IL-13 only with FcεRI-IgE-mediated activation. TGF-β1 suppressed mobilization of IL-6 with short-term BMMC activation when stimulated with IL-33. Lastly, colocalization patterns of the SCF receptor (CD117) and FcεRI with IgE crosslinking were unaffected by TGF-β1 treatment, but individual expression levels for FcεRI, CD117, and TGFβRII were all reduced following either IgE activation or TGF-β1 treatment; this reduction was partially recovered in BMMCs that were both activated by IgE and treated with TGF-β1.

DISCUSSION

These data reveal a novel positive effect of soluble TGF-β1 on mast cell activation in vitro, suggesting mast cells may be activated through a non-canonical pathway by TGF-β1. Understanding this interaction will provide insight into the potential role of mast cells in settings where TGF-β1 is produced in an aberrant manner, such as in and around high grade tumors.

Regulatory T Cells and Acute Lung Injury: Cytokines, Uncontrolled Inflammation, and Therapeutic Implications

Acute respiratory distress syndrome/acute lung injury (ALI) was described in 1967. The uncontrolled inflammation is a central issue of the syndrome. The regulatory T cells (Tregs), formerly known as suppressor T cells, are a subpopulation of T cells. Tregs indirectly limits immune inflammation-inflicted tissue damage by employing multiple mechanisms and creating the appropriate immune environment for successful tissue repair. And it plays a central role in the resolution of ALI. Accordingly, for this review, we will focus on Treg populations which are critical for inflammatory immunity of ALI, and the effect of interaction between Treg subsets and cytokines on ALI. And then explore the possibility of cytokines as beneficial factors in inflammation resolution of ALI.

Outcomes and prognostic factors for aggressive posterior retinopathy of prematurity following initial treatment with intravitreal ranibizumab

Background

This study sought to identify factors associated with retinal detachment and retreatment of aggressive posterior retinopathy of prematurity (APROP) initially treated with intravitreal ranibizumab (IVR) injection as well as the efficacy of IVR treatment.

Methods

This was a retrospective study. A total of 83 preterm infants (160 eyes) diagnosed with APROP who were primarily treated with IVR were included. The 160 eyes were divided into two groups based on the anatomic outcomes. Group A included 35 eyes that developed retinal detachment, and Group B included 125 eyes without retinal detachment. The following patient factors were retrospectively reviewed: gender, gestational age (GA), birth weight (BW), postmenstrual age (PMA) at first treatment, iris neovascularizations, retinal hemorrhage, neutrophil and lymphocyte counts before the first intravitreal injection, neutrophil-to-lymphocyte ratio (NLR), anatomical outcomes, additional treatment and follow-up time. Three dummy variables were created as dependent variables based on the methods of retreatment. The possible risk factors for APROP were evaluated, and statistical analyses included univariate and multivariate logistic regression.

Results

A total of 160 eyes from 83 preterm infants (56 males and 27 females) underwent initial IVR treatment with a follow-up time of 17.17 ± 10.54 months. Thirty-five of the 160 (21.9%) eyes progressed to retinal detachment, and 82 of the 125 (65.6%) non-retinal detachment eyes needed retreatment, with favorable anatomical outcomes. The disease improved approximately 1.5 ± 1.2 weeks after the first IVR treatment. The mean recurrence period of APROP was approximately 7.5 ± 6.9 weeks after the first IVR treatment. Multiple logistic regression analysis revealed postmenstrual age (P < 0.001) and neutrophil count (P = 0.009) as the most significant factors for retinal detachment in APROP. Retinal hemorrhage (P = 0.007) and BW (P = 0.04) were most significantly associated with APROP recurrence and retreatment.

Conclusions

IVR injection is an effective treatment for APROP. In this study, older postmenstrual age and low neutrophil count were identified as risk factors for retinal detachment in APROP. In addition, retinal hemorrhage and low BW were significantly associated with recurrence and retreatment in non-retinal detachment APROP. Thus, patients with a lower BW, older postmenstrual age, low neutrophil count and retinal hemorrhage should be reexamined in a timely and more frequent manner.

Surviving Deadly Lung Infections: Innate Host Tolerance Mechanisms in the Pulmonary System

Much research on infectious diseases focuses on clearing the pathogen through the use of antimicrobial drugs, the immune response, or a combination of both. Rapid clearance of pathogens allows for a quick return to a healthy state and increased survival. Pathogen-targeted approaches to combating infection have inherent limitations, including their pathogen-specific nature, the potential for antimicrobial resistance, and poor vaccine efficacy, among others. Another way to survive an infection is to tolerate the alterations to homeostasis that occur during a disease state through a process called host tolerance or resilience, which is independent from pathogen burden. Alterations in homeostasis during infection are numerous and include tissue damage, increased inflammation, metabolic changes, temperature changes, and changes in respiration. Given its importance and sensitivity, the lung is a good system for understanding host tolerance to infectious disease. Pneumonia is the leading cause of death for children under five worldwide. One reason for this is because when the pulmonary system is altered dramatically it greatly impacts the overall health and survival of a patient. Targeting host pathways involved in maintenance of pulmonary host tolerance during infection could provide an alternative therapeutic avenue that may be broadly applicable across a variety of pathologies. In this review, we will summarize recent findings on tolerance to host lung infection. We will focus on the involvement of innate immune responses in tolerance and how an initial viral lung infection may alter tolerance mechanisms in leukocytic, epithelial, and endothelial compartments to a subsequent bacterial infection. By understanding tolerance mechanisms in the lung we can better address treatment options for deadly pulmonary infections.

Controlling Mast Cell Activation and Homeostasis: Work Influenced by Bill Paul That Continues Today

Mast cells are tissue resident, innate immune cells with heterogenous phenotypes tuned by cytokines and other microenvironmental stimuli. Playing a protective role in parasitic, bacterial, and viral infections, mast cells are also known for their role in the pathogenesis of allergy, asthma, and autoimmune diseases. Here, we review factors controlling mast cell activation, with a focus on receptor signaling and potential therapies for allergic disease. Specifically, we will discuss our work with FcεRI and FγR signaling, IL-4, IL-10, and TGF-β1 treatment, and Stat5. We conclude with potential therapeutics for allergic disease. Much of these efforts have been influenced by the work of Bill Paul. With many mechanistic targets for mast cell activation and different classes of therapeutics being studied, there is reason to be hopeful for continued clinical progress in this area.

Fine chalk dust induces inflammatory response via p38 and ERK MAPK pathway in rat lung

Chalk teaching is widely used in the world due to low cost, especially in some developing countries. During teaching with chalks, a large amount of fine chalk dust is produced. Although exposure to chalk dust is associated with respiratory diseases, the mechanism underlying the correlation between chalk dust exposure and adverse effects has not fully been elucidated. In this study, inflammation and its signal pathway in rat lungs exposed to fine chalk dust were examined through histopathology analyses; pro-inflammatory gene transcription; and protein levels measured by HE staining, RT-PCR, and western blot analysis. The results demonstrated that fine chalk dust increased neutrophils and up-regulated inflammatory gene mRNA levels (TNF-α, IL-6, TGF-β1, iNOS, and ICAM-1), and oxidative stress marker (HO-1) level, leading to the increase of inflammatory cell infiltration and inflammatory injury on the lungs. These inflammation responses were mediated, at least in part, via p38 and extracellular regulated proteinase (ERK) mitogen-activated protein kinase (MAPK) signaling mechanisms. In contrast, N-acetyl-L-cysteine (NAC) supplement significantly ameliorated these changes in inflammatory responses. Our results support the hypothesis that fine chalk dust can damage rat lungs and the NAC supplement may attenuate fine chalk dust-associated lung inflammation.

Roles of TGF-β signaling pathway in endoplasmic reticulum stress in endothelial cells stimulated with cigarette smoke extract

To investigate the role of signaling pathway in the effect of endoplasmic reticulum stress (ER stress) in endothelial cells stimulated with cigarette smoke extract (CSE). Human umbilical vein endothelial cells (HUVECs) were cultured and divided into 3 groups: CSE-stimulated group, CSE-stimulated with 4-PBA group, and negative control group. HUVECs were cultured and stimulated with CSE at concentrations of 5%, 10% and 20%, respectively, mRNA of CXCL-8 and GRP78 was detected by real-time PCR. ELISA was performed to test the expression of CXCL-8 protein, and neutrophils migration was detected by Transwell board test. The NF-κB, ERK, p38MAPK and transforming growth factor beta (TGF-β) were detected by flow cytometry. The mRNA of CXCL-8 and GRP78 increased in CSE-stimulated HUVECs (P<0.05). Furthermore, it was concentration-dependent. 4-PBA significantly reduced the expression of CXCL-8 protein (P<0.05) and neutrophil migration (P<0.05). The TGF-β, rather than the NF-κB, ERK and P38MAPK pathway might be involved in ER stress stimulated by CSE. CSE induced neutrophils migration by increasing the expression of CXCL-8 in endothelial cells. ER stress might play a role in the effect of neutrophils migration stimulated with CSE, and TGF-β pathway may contribute to the ER stress in HUVECs.

Kaurenoic acid activates TGF-β signaling

BACKGROUND

Kaurenoic acid (ent-kaur-16-en-19-oic acid: KA) is a key constituent found in the roots of Aralia continentalis Kitagawa (Araliaceae) that has been used for treating rheumatism in traditional Asian medicine.

HYPOTHESIS

Although KA was reported to suppress inflammation by activating Nrf2, the anti-inflammatory function of KA is less characterized. Given the complex nature of the inflammatory response and the critical role of TGF-β in resolving inflammation, we hypothesized that KA suppresses inflammatory response by activating TGF-β signaling.

METHODS

Murine macrophage RAW 264.7, human lung epithelial cell MRC-5, and a TGFβRII defective cell HCT116 were treated with various amounts of KA. KA was also administered to mouse lung via intratracheal (i.t.) route. Phosphorylated Smad2 and Smad3 were analyzed by western blot. TGFβ-dependent gene expression was determined by immunoblotting of α-SMA and luciferase assay.

RESULTS

KA induced the phosphorylation of Smad2 and Smad3, key activator molecules in TGF-β signaling. EW7197, an inhibitor for activin receptor-like kinase 5/TGF-β receptor I (TGFβR1) suppressed KA-mediated phosphorylation of Smad2. Similarly, KA failed to phosphorylate Smad2 in HCT116, suggesting that KA acts through the prototypic TGFβR. KA treatment increased the transcriptional activity driven by a Smad-binding element in a luciferase reporter assay and induced the α-smooth muscle actin (α-SMA). Similarly, i.t. KA induced the phosphorylation of Smad2 and increased the expression ofα-SMA in mouse lungs.

CONCLUSION

KA activated TGF-β signaling, suggesting that TGFβ signaling is associated with KA suppressing inflammation.

Regulation of Innate and Adaptive Immunity by TGFβ

Immune regulation by cytokines is crucial in maintaining immune homeostasis, promoting responses to infection, resolving inflammation, and promoting immunological memory. Additionally, cytokine responses drive pathology in immune-mediated disease. A crucial cytokine in the regulation of all aspects of an immune response is transforming growth factor beta (TGFβ). Although best known as a crucial regulator of T cell responses, TGFβ plays a vital role in regulating responses mediated by virtually every innate and adaptive immune cell, including dendritic cells, B cells, NK cells, innate lymphoid cells, and granulocytes. Here, we review our current knowledge of how TGFβ regulates the immune system, highlighting the multifunctional nature of TGFβ and how its function can change depending on location and context of action.

Klf10 deficiency in mice exacerbates pulmonary inflammation by increasing expression of the proinflammatory molecule NPRA

KLF10 is a transforming growth factor (TGF)-β/Smad downstream regulated gene. KLF10 binds to the promoter of target genes and mimics the effects of TGF-β as a transcriptional factor. In our laboratory, we noted that Klf10 deficiency in mice is associated with significant inflammation of the lungs. However, the precise mechanism of this association remains unknown. We previously identified NPRA as a target gene potentially regulated by KLF10 through direct binding; NPRA knockout have known that prevented lung inflammation in a mouse model of allergic asthma. Here, we further explored the regulatory association between KLF10 and NPRA on the basis of the aforementioned findings. Our results demonstrated that KLF10 acts as a transcriptional repressor of NPRA and that KLF10 binding reduces NPRA expression in vitro. Compared with wild-type mice, Klf10-deficient mice were more sensitive to lipopolysaccharide or ovalbumin challenge and showed more severe inflammatory histological changes in the lungs. Moreover, Klf10-deficient mice showed pulmonary neutrophil accumulation. These findings collectively reveal the precise site where KLF10 signaling affects pulmonary inflammation by attenuating NPRA expression. They also verify the importance of KLF10 and atrial natriuretic peptide/NPRA in exerting influences on chronic pulmonary disease pathogenesis.

Muscle wound healing in rainbow trout (Oncorhynchus mykiss)

We followed the progression of healing of deep excisional biopsy punch wounds over the course of 365 days in rainbow trout (Oncorhynchus mykiss) by monitoring visual wound healing and gene expression in the healing muscle at regular intervals (1, 3, 7, 14, 38 and 100 days post-wounding). In addition, we performed muscle texture analysis one year after wound infliction. The selected genes have all previously been investigated in relation to vertebrate wound healing, but only few specifically in fish. The selected genes were interleukin (IL)-1β, IL-6, transforming growth factor (TGF)-β1 and -β3, matrix metalloproteinase (MMP) -9 and -13, inducible nitric oxide synthase (iNOS), fibronectin (FN), tenascin-C (TN-C), prolyl 4-hydroxylase α1-chain (P4Hα1), lysyl oxidase (LOX), collagen type I α1-chain (ColIα1), CD41 and CD163. Wound healing progressed slowly in the presented study, which is at least partially due to the low temperature of about 8.5 °C during the first 100 days. The inflammation phase lasted more than 14 days, and the genes relating to production and remodeling of new extracellular matrix (ECM) exhibited a delayed but prolonged upregulation starting 1-2 weeks post-wounding and lasting until at least 100 days post-wounding. The gene expression patterns and histology reveal limited capacity for muscle regeneration in rainbow trout, and muscle texture analyses one year after wound infliction confirm that wounds heal with fibrosis. At 100 dpw epidermis had fully regenerated, and dermis partially regenerated. Scales had not regenerated even after one year. CD163 is a marker of "wound healing"-type M2c macrophages in mammals. M2 macrophage markers are as yet poorly described in fish. The pattern of CD163 expression in the present study is consistent with the expected timing of presence of M2c macrophages in the wound. CD163 may thus potentially prove a valuable marker of M2 macrophages - or a subset hereof - in fish. We subjected a group of fish to bathing in an immunomodulatory β-glucan product during wound healing, but found this to have very limited effect on wound healing in contrast to a previously published study on common carp.

Neutrophilic Lung Inflammation Suppressed by Picroside II Is Associated with TGF-β Signaling

Although acute lung injury (ALI) is a leading cause of death in intensive care unit, effective pharmacologic means to treat ALI patients are lacking. The rhizome of Picrorhiza scrophulariiflora used in a traditional herbal medicine in Asian countries has been shown to have anti-inflammatory function, and picroside II (PIC II) is known as a major constituent in the plant. Here, we examined whether PIC II has an anti-inflammatory activity, which is applicable for treating ALI. We found that although it is not significantly effective in suppressing proinflammatory factor NF-κB or in activating anti-inflammatory factor Nrf2, PIC II induced the phosphorylation of Smad 2, with concomitant increase of luciferase activity from SBE luciferase reporter in RAW 264.7 cells. H&E staining of lung, differential counting of cells in bronchoalveolar lavage fluid, and semiquantitative RT-PCR analyses of lung tissues show that an intratracheal (i.t.) spraying of PIC II suppressed neutrophilic inflammation and the expression of proinflammatory cytokine genes in the lung, which were elicited by an i.t. LPS instillation to the lung. In addition, PIC II treatment increased the phosphorylation of Smad 2 in the lung tissue. Together, our results suggest that PIC II plays a role as an anti-inflammatory constituent in P. scrophulariiflora, whose activity is associated at least in part with TGF-β signaling.

Role of interleukin-6 in regulation of immune responses to remodeling after myocardial infarction

Myocardial remodeling following myocardial infarction (MI) is emerging as key causes of chronic infarct mortality. Interleukin-6 is a classic pro-inflammatory cytokine needed to mount an effective immune response. It seems that interleukin-6 acts as an important role in the dynamic and superbly orchestrated process of innate immunity after MI. Interleukin-6 timely suppresses of innate immune signals to prevent the catastrophic consequences of uncontrolled inflammation on cardiac geometry and function, and thus tunes myocardial remodeling. A comprehensive understanding of biological processes of interleukin-6 in innate immunity leading to inflammatory response and disease-related ventricular remodeling is helpful to find the solution of chronic heart failure. To accomplish this, we reviewed the articles of interleukin-6 regard to inflammation, innate immunity, and cardiac remodeling. This review focuses on the role of interleukin-6 that dominates cell-mediated immunity, especially on neutrophils, monocytes, macrophages, and fibroblasts. In addition, we will also briefly discuss other inflammatory cytokines involved in this process within the paper.

Activated mast cells synthesize and release soluble ST2-a decoy receptor for IL-33

IL-33 released from damaged cells plays a central role in allergic inflammation by acting through its membrane-bound receptor, ST2 receptor (ST2L). IL-33 activity can be neutralized by the soluble spliced variant of ST2 (sST2) that has been associated with allergic inflammation but its source is not well defined. We investigated whether mast cells (MCs) are a significant source of sST2 following activation through FcεRI or ST2. We find that antigen and IL-33 induce substantial production and release of sST2 from human and mouse MCs in culture and do so synergistically when added together or in combination with stem cell factor. Moreover, increases in circulating sST2 during anaphylaxis in mice were dependent on the presence of MCs. Human MCs activated via FcεRI failed to generate IL-33 and IL-33 produced by mouse bone marrow-derived MCs was retained within the cells. Therefore, FcεRI-mediated sST2 production is independent of MC-derived IL-33 acting in an autocrine manner. These results are consistent with the conclusion that both mouse and human MCs when activated are a significant inducible source of sST2 but not IL-33 and thus have the ability to modulate the biologic impact of IL-33 produced locally by other cell types during allergic inflammation.

Activation of LXRs using the synthetic agonist GW3965 represses the production of pro-inflammatory cytokines by murine mast cells

BACKGROUND

The activation of liver X receptor (LXR) α or LXRβ negatively regulates the expression of pro-inflammatory genes in mammalian cells. We recently reported that 25-hydroxycholesterol, a representative LXR-activating oxysterol, suppresses IL-6 production in mouse mast cells (MCs) following its engagement of the high-affinity IgE receptor (FcεRI). This finding suggests that murine MCs express functional LXRs; however, the mechanisms underlying the LXR-dependent repression of the MC-mediated production of pro-inflammatory cytokines, including IL-6, are poorly understood. Therefore, we employed the synthetic LXR ligand GW3965 to examine the functions of LXRα and LXRβ in the production of pro-inflammatory cytokines by murine bone marrow-derived MCs (BMMCs).

METHODS

We prepared BMMCs from wild-type (WT), LXRα(-/-), and LXRα/β(-/-) mice. Each group of BMMCs was pretreated with GW3965 and then stimulated with IgE+antigen (Ag) or lipopolysaccharide (LPS). Cytokine production was then analyzed using specific ELISA kits.

RESULTS

The activation of LXRs by GW3965 significantly attenuated the production of IL-1α and IL-1β, but not of IL-6, in the WT and LXRα(-/-) BMMCs stimulated with IgE+Ag. However, GW3965 treatment decreased the production of IL-1α, IL-1β, and IL-6 in WT and LXRα(-/-) BMMCs upon stimulation with LPS, while the GW3965-mediated suppression of cytokine production was nearly absent from the LXRα/β(-/-) BMMCs.

CONCLUSIONS

These findings demonstrate, for the first time, that the activation of LXRs by GW3965 attenuates the antigen- or LPS-induced production of pro-inflammatory cytokines, such as IL-1α and IL-1β, in murine MCs and that LXRβ plays an important role in the LXR-mediated repression of cytokine production.

Conditional overexpression of TGFβ1 promotes pulmonary inflammation, apoptosis and mortality via TGFβR2 in the developing mouse lung

Background

Earlier studies have reported that transforming growth factor beta 1(TGFβ1) is a critical mediator of hyperoxia-induced acute lung injury (HALI) in developing lungs, leading to impaired alveolarization and a pulmonary phenotype of bronchopulmonary dysplasia (BPD). However, the mechanisms responsible for the TGFβ1-induced inflammatory signals that lead to cell death and abnormal alveolarization are poorly understood. We hypothesized that TGFβ1 signaling via TGFβR2 is necessary for the pathogenesis of the BPD pulmonary phenotype resulting from HALI.

Methods

We utilized lung epithelial cell-specific TGFβ1 overexpressing transgenic and TGFβR2 null mutant mice to evaluate the effects on neonatal mortality as well as pulmonary inflammation and apoptosis in developing lungs. Lung morphometry was performed to determine the impaired alveolarization and multicolor flow cytometry studies were performed to detect inflammatory macrophages and monocytes in lungs. Apoptotic cell death was measured with TUNEL assay, immunohistochemistry and western blotting and protein expression of angiogenic mediators were also analyzed.

Results

Our data reveals that increased TGFβ1 expression in newborn mice lungs leads to increased mortality, macrophage and immature monocyte infiltration, apoptotic cell death specifically in Type II alveolar epithelial cells (AECs), impaired alveolarization, and dysregulated angiogenic molecular markers.

Conclusions

Our study has demonstrated the potential role of inhibition of TGFβ1 signaling via TGFβR2 for improved survival, reduced inflammation and apoptosis that may provide insights for the development of potential therapeutic strategies targeted against HALI and BPD.

Genistein inhibits pro‑inflammatory cytokines in human mast cell activation through the inhibition of the ERK pathway

Anaphylaxis is a rapidly occurring allergic reaction to any foreign substance, including venom from insects, foods and medications, which may cause fatalities. To prevent anaphylaxis, these triggers must be avoided. However, avoidance of numerous triggers is difficult. For this reason, the development of immunotherapeutic adjuvants that suppress the allergic response is important for anaphylaxis control. Mast cells are one of the major inflammatory cells involved in the inflammatory response, which secrete several inflammatory cytokines, including tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-1β, and recruits other immune cells. Mast cells are also involved in a number of diseases, such as sinusitis, rheumatoid arthritis and asthma. Genistein, a phytoestrogen, has been reported to have anti-oxidative and anti-inflammatory activities. However, the effects of genistein on the anti-inflammatory response of mast cells remain unknown. In the present study, the anti-inflammatory effects of genistein on mast cells were investigated. Genistein significantly decreased IL-6 and IL-1β mRNA levels, as well as IL-6 production in PMA/A23187-induced mast cells activation. In addition, genistein inhibited the phosphorylation of ERK 1/2 in PMA/A23187-induced mast cell activation. However, phosphorylation of p38 was not altered. Thus, these findings indicate that genistein inhibited the inflammatory status of mast cells through inhibition of the ERK pathway.

Density and duration of pneumococcal carriage is maintained by transforming growth factor β1 and T regulatory cells

RATIONALE

Nasopharyngeal carriage of Streptococcus pneumoniae is a prerequisite for invasive disease, but the majority of carriage episodes are asymptomatic and self-resolving. Interactions determining the development of carriage versus invasive disease are poorly understood but will influence the effectiveness of vaccines or therapeutics that disrupt nasal colonization.

OBJECTIVES

We sought to elucidate immunological mechanisms underlying noninvasive pneumococcal nasopharyngeal carriage.

METHODS

Pneumococcal interactions with human nasopharyngeal and bronchial fibroblasts and epithelial cells were investigated in vitro. A murine model of nasopharyngeal carriage and an experimental human pneumococcal challenge model were used to characterize immune responses in the airways during carriage.

MEASUREMENTS AND MAIN RESULTS

We describe the previously unknown immunological basis of noninvasive carriage and highlight mechanisms whose perturbation may lead to invasive disease. We identify the induction of active transforming growth factor (TGF)-β1 by S. pneumoniae in human host cells and highlight the key role for TGF-β1 and T regulatory cells in the establishment and maintenance of nasopharyngeal carriage in mice and humans. We identify the ability of pneumococci to drive TGF-β1 production from nasopharyngeal cells in vivo and show that an immune tolerance profile, characterized by elevated TGF-β1 and high nasopharyngeal T regulatory cell numbers, is crucial for prolonged carriage of pneumococci. Blockade of TGF-β1 signaling prevents prolonged carriage and leads to clearance of pneumococci from the nasopharynx.

CONCLUSIONS

These data explain the mechanisms by which S. pneumoniae colonize the human nasopharynx without inducing damaging host inflammation and provide insight into the role of bacterial and host constituents that allow and maintain carriage.

Downregulation of Mcl-1 has anti-inflammatory pro-resolution effects and enhances bacterial clearance from the lung

Phagocytes not only coordinate acute inflammation and host defense at mucosal sites, but also contribute to tissue damage. Respiratory infection causes a globally significant disease burden and frequently progresses to acute respiratory distress syndrome, a devastating inflammatory condition characterized by neutrophil recruitment and accumulation of protein-rich edema fluid causing impaired lung function. We hypothesized that targeting the intracellular protein myeloid cell leukemia 1 (Mcl-1) by a cyclin-dependent kinase inhibitor (AT7519) or a flavone (wogonin) would accelerate neutrophil apoptosis and resolution of established inflammation, but without detriment to bacterial clearance. Mcl-1 loss induced human neutrophil apoptosis, but did not induce macrophage apoptosis nor impair phagocytosis of apoptotic neutrophils. Neutrophil-dominant inflammation was modelled in mice by either endotoxin or bacteria (Escherichia coli). Downregulating inflammatory cell Mcl-1 had anti-inflammatory, pro-resolution effects, shortening the resolution interval (Ri) from 19 to 7 h and improved organ dysfunction with enhanced alveolar-capillary barrier integrity. Conversely, attenuating drug-induced Mcl-1 downregulation inhibited neutrophil apoptosis and delayed resolution of endotoxin-mediated lung inflammation. Importantly, manipulating lung inflammatory cell Mcl-1 also accelerated resolution of bacterial infection (Ri; 50 to 16 h) concurrent with enhanced bacterial clearance. Therefore, manipulating inflammatory cell Mcl-1 accelerates inflammation resolution without detriment to host defense against bacteria, and represents a target for treating infection-associated inflammation.