Small Extracellular Vesicle Signaling and Mitochondrial Transfer Reprograms T Helper Cell Function in Human Asthma.

RATIONALE: Asthma is a chronic inflammatory disease of the airways that involves crosstalk between myeloid-derived regulatory cells (MDRCs) and CD4+ T cells. Although small extracellular vesicles (sEVs) are known to mediate cell-cell communication, the role of sEV signaling via mitochondria in perpetuating asthmatic airway inflammation is unknown. OBJECTIVES: We investigated the effects of MDRC-derived exosomes on dysregulated T cell responses in asthmatics. METHODS: Small extracellular vesicles isolated from bronchoalveolar lavage fluid or airway MDRCs of mild to moderate asthmatics or healthy controls were co-cultured with autologous peripheral and airway CD4+ T lymphocytes. sEV internalization, sEV-mediated transfer of mitochondria targeted GFP to T cells, sEV mitochondrial signaling, and subsequent activation, proliferation and polarization of CD4+ T lymphocytes to Th1, Th2 and Th17 subsets were assessed. MEASUREMENTS AND MAIN RESULTS: Airway MDRC-derived sEVs from asthmatics mediated T cell receptor engagement and transfer of mitochondria that induced antigen-specific activation and polarization into Th17 and Th2 cells, drivers of chronic airway inflammation in asthma. CD4+ T cells internalized sEVs containing mitochondria predominantly by membrane fusion, and blocking mitochondrial oxidant signaling in MDRC-derived exosomes mitigated T cell activation. Reactive oxygen species-mediated signaling that elicited T cell activation in asthmatics was sEV-dependent. A Drp1-dependent mitochondrial fission in pro-inflammatory MDRCs promoted mitochondrial packaging within sEVs, which then co-localized with the polarized actin cytoskeleton and mitochondrial networks in the organized immune synapse of recipient T cells. CONCLUSIONS: Our studies indicate a previously unrecognized role for mitochondrial fission and exosomal mitochondrial transfer in dysregulated T cell activation and Th cell differentiation in asthma which could constitute a novel therapeutic target.

A Novel Translational PET Imaging Approach to Quantifying Distal Tumor Immune Activation After Targeted Radiation Therapy and Checkpoint Blockade.

PURPOSE: This study aimed to provide a novel noninvasive method to quantify abscopal immune activation and predict combinational treatment response using [68Ga]-NOTA-GZP positron emission tomography (PET) imaging. METHODS AND MATERIALS: 4T1 breast cancer cells were implanted bilaterally in the mammary fat pad of Balb/c mice and Lewis's lung cancer cells (LLC) were implanted bilaterally on the shoulders of C57/Bl6 mice. One of the tumors received a single fraction of 12 Gy irradiation followed by combination of concurrent PD-1 and CTLA-4 inhibitors or controls. Tumor growth of the irradiated and nonirradiated tumors was measured and compared with 12 Gy irradiation only, checkpoint inhibitor only, and no treatment control group. Changes in granzyme B activity were assessed with [68Ga]-NOTA-GZP PET imaging from baseline and every 3 days until day 9. RESULTS: In the 4T1 model, concurrent treatment with dual checkpoint inhibitors and radiation resulted in reduction of the irradiated tumor volume at day 30. At this same time point, the nonirradiated tumor volume for combination treatment decreased significantly, consistent with abscopal immune activation. Similarly, in the LLC model, concurrent treatment inhibited tumor growth on the nonirradiated tumor at day 15. On day 9, granzyme B PET signal in both 4T1 and LLC models was significantly higher in the nonirradiated tumors that responded to concurrent treatment compared with subsequent nonresponding tumors. A similar lack of granzyme B signal was observed in the nonirradiated tumors from mice that received radiation or checkpoint inhibitors only and control tumors. Receiver operating characteristic analysis identified a PET threshold of 1.505 and 1.233 on day 9 that predicted treatment response in 4T1 and LLC models, respectively. CONCLUSIONS: [68Ga]-NOTA-GZP PET imaging was able to noninvasively predict abscopal immune activation before subsequent tumor volume changes after combination treatment. It provides a potential translational paradigm for investigating distal immune activation postradiation in a clinical setting.

NK and NKT cells in the pathogenesis of Hidradenitis suppurativa: Novel therapeutic strategy through targeting of CD2.

Hidradenitis suppurativa (HS) is a chronic debilitating inflammatory skin disease with poorly understood pathogenesis. Single-cell RNAseq analysis of HS lesional and healthy individual skins revealed that NKT and NK cell populations were greatly expanded in HS, and they expressed elevated CD2, an activation receptor. Immunohistochemistry analyses confirmed significantly expanded numbers of CD2+ cells distributed throughout HS lesional tissue, and many co-expressed the NK marker, CD56. While CD4+ T cells were expanded in HS, CD8 T cells were rare. CD20+ B cells in HS were localized within tertiary follicle like structures. Immunofluorescence microscopy showed that NK cells (CD2 + CD56 dim ) expressing perforin, granzymes A and B were enriched within the hyperplastic follicular epidermis and tunnels of HS and juxtaposed with apoptotic cells. In contrast, NKT cells (CD2 + CD3 + CD56 bright ) primarily expressed granzyme A and were associated with α-SMA expressing fibroblasts within the fibrotic regions of the hypodermis. Keratinocytes and fibroblasts expressed high levels of CD58 (CD2 ligand) and they interacted with CD2 expressing NKT and NK cells. The NKT/NK maturation and activating cytokines, IL-12, IL-15 and IL-18, were significantly elevated in HS. Inhibition of cognate CD2-CD58 interaction with blocking anti-CD2 mAb in HS skin organotypic cultures resulted in a profound reduction of the inflammatory gene signature and secretion of inflammatory cytokines and chemokines in the culture supernate. In summary, we show that a cellular network of heterogenous NKT and NK cell populations drives inflammation, tunnel formation and fibrosis in the pathogenesis of HS. Furthermore, CD2 blockade is a viable immunotherapeutic approach for the management of HS.

Epigenetic switch reshapes epithelial progenitor cell signatures and drives inflammatory pathogenesis in hidradenitis suppurativa.

Hidradenitis suppurativa (HS) is a complex inflammatory skin disease with undefined mechanistic underpinnings. Here, we investigated HS epithelial cells and demonstrated that HS basal progenitors modulate their lineage restriction and give rise to pathogenic keratinocyte clones, resulting in epidermal hyperproliferation and dysregulated inflammation in HS. When comparing to healthy epithelial stem/progenitor cells, in HS, we identified changes in gene signatures that revolve around the mitotic cell cycle, DNA damage response and repair, as well as cell-cell adhesion and chromatin remodeling. By reconstructing cell differentiation trajectory and CellChat modeling, we identified a keratinocyte population specific to HS. This population is marked by S100A7/8/9 and KRT6 family members, triggering IL1, IL10, and complement inflammatory cascades. These signals, along with HS-specific proinflammatory cytokines and chemokines, contribute to the recruitment of certain immune cells during the disease progression. Furthermore, we revealed a previously uncharacterized role of S100A8 in regulating the local chromatin environment of target loci in HS keratinocytes. Through the integration of genomic and epigenomic datasets, we identified genome-wide chromatin rewiring alongside the switch of transcription factors (TFs), which mediated HS transcriptional profiles. Importantly, we identified numerous clinically relevant inflammatory enhancers and their coordinated TFs in HS basal CD49fhigh cells. The disruption of the S100A enhancer using the CRISPR/Cas9-mediated approach or the pharmacological inhibition of the interferon regulatory transcription factor 3 (IRF3) efficiently reduced the production of HS-associated inflammatory regulators. Our study not only uncovers the plasticity of epidermal progenitor cells in HS but also elucidates the epigenetic mechanisms underlying HS pathogenesis.

Altered sphingolipid pathway in SARS-CoV-2 infected human lung tissue.

Introduction: The SARS-CoV-2 mediated COVID-19 pandemic has impacted millions worldwide. Hyper-inflammatory processes, including cytokine storm, contribute to long-standing tissue injury and damage in COVID-19. The metabolism of sphingolipids as regulators of cell survival, differentiation, and proliferation has been implicated in inflammatory signaling and cytokine responses. Sphingosine-kinase-1 (SK1) and ceramide-synthase-2 (CERS2) generate metabolites that regulate the anti- and pro-apoptotic processes, respectively. Alterations in SK1 and CERS2 expression may contribute to the inflammation and tissue damage during COVID-19. The central objective of this study is to evaluate structural changes in the lung post-SARS-CoV-2 infection and to investigate whether the sphingolipid rheostat is altered in response to SARS-CoV-2 infection. Methods: Central and peripheral lung tissues from COVID-19+ or control autopsies and resected lung tissue from COVID-19 convalescents were subjected to histologic evaluation of airspace and collagen deposisiton, and immunohistochemical evaluation of SK1 and CERS2. Results: Here, we report significant reduction in air space and increase in collagen deposition in lung autopsy tissues from patients who died from COVID-19 (COVID-19+) and COVID-19 convalescent individuals. SK1 expression increased in the lungs of COVID-19+ autopsies and COVID-19 convalescent lung tissue compared to controls and was mostly associated with Type II pneumocytes and alveolar macrophages. No significant difference in CERS2 expression was noted. SARS-CoV-2 infection upregulates SK1 and increases the ratio of SK1 to CERS2 expression in lung tissues of COVID-19 autopsies and COVID-19 convalescents. Discussion: These data suggest an alteration in the sphingolipid rheostat in lung tissue during COVID-19, suggesting a potential contribution to the inflammation and tissue damage associated with viral infection.

Mechanism underlying follicular hyperproliferation and oncogenesis in hidradenitis suppurativa.

Hidradenitis suppurativa (HS) is a skin disorder that causes chronic painful inflammation and hyperproliferation, often with the comorbidity of invasive keratoacanthoma (KA). Our research, employing high-resolution immunofluorescence and data science approaches together with confirmatory molecular analysis, has identified that the 5'-cap-dependent protein translation regulatory complex eIF4F is a key factor in the development of HS and is responsible for regulating follicular hyperproliferation. Specifically, eIF4F translational targets, Cyclin D1 and c-MYC, orchestrate the development of HS-associated KA. Although eIF4F and p-eIF4E are contiguous throughout HS lesions, Cyclin D1 and c-MYC have unique spatial localization and functions. The keratin-filled crater of KA is formed by nuclear c-MYC-induced differentiation of epithelial cells, whereas the co-localization of c-MYC and Cyclin D1 provides oncogenic transformation by activating RAS, PI3K, and ERK pathways. In sum, we have revealed a novel mechanism underlying HS pathogenesis of follicular hyperproliferation and the development of HS-associated invasive KA.

The Association of Periconception Asthma Medication Discontinuation with Adverse Obstetric Outcomes.

OBJECTIVE: This study aimed to investigate asthma medication reduction in the periconceptional period as it relates to asthma status and adverse outcomes in pregnancy. STUDY DESIGN: In a prospective cohort study, self-reported current and past asthma medications were collected and analyzes compared measures of asthma status in women who discontinued asthma medication in the 6 months prior to enrollment ("step-down") versus those who did not ("no change"). Evaluation of asthma was done at three study visits (one per trimester) and by daily diaries, including measures of lung function (percent predicted forced expiratory volume in 1 and 6 s [%FEV1, %FEV6], peak expiratory flow [%PEF], forced vital capacity [%FVC], FEV1 to FVC ratio [FEV1/FVC]), lung inflammation (fractional exhaled nitric oxide [FeNO], ppb), rate of asthma symptoms (activity limitation, night symptoms, rescue inhaler use, wheeze, shortness of breath, cough, chest tightness, chest pain), and rate of asthma exacerbations. Adverse pregnancy outcomes were also evaluated. Adjusted regression analyses examined whether adverse outcomes differed by periconceptional asthma medication changes. RESULTS: Of 279 participants included in analyses, 135 (48.4%) did not change asthma medication in the periconceptional period, whereas 144 (51.6%) reported a step down in medication. Those in the step-down group were more likely to have milder disease (88 [61.1%] in the step-down vs. 74 [54.8%] in the no change group), exhibited less activity limitation (rate ratio [RR]: 0.68, 95% confidence interval [CI]: 0.47-0.98), and experienced fewer asthma attacks (RR: 0.53, 95% CI: 0.34-0.84) during pregnancy. The step-down group had a nonsignificant increase in overall odds of experiencing an adverse pregnancy outcome (odds ratio: 1.62, 95% CI: 0.97-2.72). CONCLUSION: Over half of women with asthma reduce asthma medication in the periconceptional period. Although these women typically have milder disease, a step down in medication may be associated with an increased risk of adverse pregnancy outcomes. KEY POINTS: · Many women reduce their asthma medication in pregnancy.. · Reduction is more common among those with mild disease.. · Medication reduction may lead to adverse pregnancy outcomes..

Dysbiotic lung microbial communities of neonates from allergic mothers confer neonate responsiveness to suboptimal allergen.

In humans and animals, offspring of allergic mothers have increased responsiveness to allergens. This is blocked in mice by maternal supplementation with α-tocopherol (αT). Also, adults and children with allergic asthma have airway microbiome dysbiosis with increased Proteobacteria and may have decreased Bacteroidota. It is not known whether αT alters neonate development of lung microbiome dysbiosis or whether neonate lung dysbiosis modifies development of allergy. To address this, the bronchoalveolar lavage was analyzed by 16S rRNA gene analysis (bacterial microbiome) from pups of allergic and non-allergic mothers with a basal diet or αT-supplemented diet. Before and after allergen challenge, pups of allergic mothers had dysbiosis in lung microbial composition with increased Proteobacteria and decreased Bacteroidota and this was blocked by αT supplementation. We determined whether intratracheal transfer of pup lung dysbiotic microbial communities modifies the development of allergy in recipient pups early in life. Interestingly, transfer of dysbiotic lung microbial communities from neonates of allergic mothers to neonates of non-allergic mothers was sufficient to confer responsiveness to allergen in the recipient pups. In contrast, neonates of allergic mothers were not protected from development of allergy by transfer of donor lung microbial communities from either neonates of non-allergic mothers or neonates of αT-supplemented allergic mothers. These data suggest that the dysbiotic lung microbiota is dominant and sufficient for enhanced neonate responsiveness to allergen. Importantly, infants within the INHANCE cohort with an anti-inflammatory profile of tocopherol isoforms had an altered microbiome composition compared to infants with a pro-inflammatory profile of tocopherol isoforms. These data may inform design of future studies for approaches in the prevention or intervention in asthma and allergic disease early in life.

Clinical Outcomes in COVID-19 Patients Treated with Immunotherapy.

Introduction: The full impact of COVID-19 infections on patients with cancer who are actively being treated with chemotherapy or immune checkpoint inhibitors (ICIs) has not been fully defined. Our goal was to track clinical outcomes in this specific patient population. Methods: We performed a retrospective chart review of 121 patients (age > 18 years) at the University of Alabama at Birmingham from January 2020 to December 2021 with an advanced solid malignancy that were eligible to be treated with ICIs or on current therapy within 12 months of their COVID-19 diagnosis. Results: A total of 121 patients were examined in this study, and 61 (50.4%) received immunotherapy treatment within 12 months. One quarter of the patients on ICIs passed away, compared to 13% of the post-chemotherapy cohort. Patients who were vaccinated for COVID-19 had lower mortality compared to unvaccinated patients (X2 = 15.19, p < 0.001), and patients with lower ECOG (0.98) were associated with lower mortality compared to patients with worse functional status (0.98 vs. 1.52; t = 3.20; p < 0.01). Conclusions: COVID-19-related ICI mortality was higher compared to patients receiving chemotherapy. However, ICI cessation or delay is unwarranted as long there has been a risk−benefit assessment undertaken with the patient.

Mitochondrial uncoupling protein-2 reprograms metabolism to induce oxidative stress and myofibroblast senescence in age-associated lung fibrosis.

Mitochondrial dysfunction has been associated with age-related diseases, including idiopathic pulmonary fibrosis (IPF). We provide evidence that implicates chronic elevation of the mitochondrial anion carrier protein, uncoupling protein-2 (UCP2), in increased generation of reactive oxygen species, altered redox state and cellular bioenergetics, impaired fatty acid oxidation, and induction of myofibroblast senescence. This pro-oxidant senescence reprogramming occurs in concert with conventional actions of UCP2 as an uncoupler of oxidative phosphorylation with dissipation of the mitochondrial membrane potential. UCP2 is highly expressed in human IPF lung myofibroblasts and in aged fibroblasts. In an aging murine model of lung fibrosis, the in vivo silencing of UCP2 induces fibrosis regression. These studies indicate a pro-fibrotic function of UCP2 in chronic lung disease and support its therapeutic targeting in age-related diseases associated with impaired tissue regeneration and organ fibrosis.

Systemic Checkpoint Blockade by PD-L1 Single-Chain Antibody Confers Potent Antitumor Immunity and Long-term Survival.

Immune checkpoint inhibitors (ICI) are promising in adjuvant settings for solid tumors and hematologic malignancies. They are currently used in the treatment as mAbs in high concentrations, raising concerns of toxicity and adverse side effects. Among various checkpoint molecules, targeting the programmed cell death protein-1 (PD-1)-programmed death-ligand 1 (PD-L1) axis has garnered more clinical utility than others have. To develop a physiologically relevant and systemically stable level of ICIs from a one-time application by genetic antibody engineering, we endeavored using a nonpathogenic, replication-deficient recombinant adeno-associated vector (rAAV) expressing single-chain variable fragments (scFv) of PD-L1 antibody and tested in syngeneic mouse therapy models of MC38 colorectal and EMT6 breast tumors. Results of this study indicated a significant protection against PD-L1-mediated inhibition of CD8+ T-cell function, against the growth of primary and secondary tumors, and durable antitumor CTLs activity by adoptive CD8+ T-cell transfer. Stable maintenance of PD-L1 scFv in vivo resulted in an increase in PD-1- CD8+ T cells and a concomitant decrease in regulatory T cells, M2 macrophages, and myeloid-derived suppressor cells in the tumor microenvironment. Overall, these data demonstrate the potential of rAAV-PD-L1-scFv as an alternative to mAb targeting of PD-L1 for tumor therapy.

Role of hair follicles in the pathogenesis of arsenical-induced cutaneous damage.

Arsenical vesicants cause skin inflammation, blistering, and pain. The lack of appropriate animal models causes difficulty in defining their molecular pathogenesis. Here, Ptch1+/- /C57BL/6 mice were employed to investigate the pathobiology of the arsenicals lewisite and phenylarsine oxide (PAO). Following lewisite or PAO challenge (24 h), the skin of animals becomes grayish-white, thick, leathery, and wrinkled with increased bi-fold thickness, Draize score, and necrotic patches. In histopathology, infiltrating leukocytes (macrophages and neutrophils), epidermal-dermal separation, edema, apoptotic cells, and disruption of tight and adherens junction proteins can be visualized. PCR arrays and nanoString analyses showed significant increases in cytokines/chemokines and other proinflammatory mediators. As hair follicles (HFs), which provide an immune-privileged environment, may affect immune cell trafficking and consequent inflammatory responses, we compared the pathogenesis of these chemicals in this model to that in Ptch1+/- /SKH-1 hairless mice. Ptch1+/- /SKH-1 mice have rudimentary, whereas Ptch1+/- /C57BL/6 mice have well-developed HFs. Although no significant differences were observed in qualitative inflammatory responses between the two strains, levels of cytokines/chemokines differed. Importantly, the mechanism of inflammation was identical; both reactive oxygen species induction and consequent activation of unfolded protein response signaling were similar. These data reveal that the acute molecular pathogenesis of arsenicals in these two murine models is similar.

Ex Vivo Culture Models of Hidradenitis Suppurativa for Defining Molecular Pathogenesis and Treatment Efficacy of Novel Drugs.

Hidradenitis suppurativa (HS) is a complex and debilitating inflammatory skin disease for which no effective treatment is available currently. This is partly because of the lack of adequate human or animal models for defining the pathobiology of the disease. Here, we describe the development of air-liquid (A-L) interface, liquid-submersion (L-S), and bioreactor (Bio) ex vivo skin culture models. All three ex vivo platforms were effective for culturing skin samples for up to 14 days. Tissue architecture and integrity remained intact for at least 3 days for healthy skin and 14 days for HS skin. Up to day 3, no significant differences were observed in % early apoptotic cells among all three platforms. However, late apoptotic/necrotic cell death was increased in HS skin at day 3 in A-L and Bio culture. These cultures efficiently support the growth of various cells populations, including keratinocytes and immune cells. Profiling inflammatory gene signatures in HS skin from these ex vivo cultures showed dynamic changes in expression at day 3 and day 14. All three culture platforms were necessary to represent the inflammatory gene status of HS skin at day 0, suggesting that not all gene clusters were identically altered in each culture method. Similarly, cytokine/chemokine profiling of the supernatants from vehicle- and drug-treated ex vivo HS cultures again showed a better prediction of drug efficacy against HS. Overall, development of these three culture systems collectively provides a powerful tool to uncover the pathobiology of HS progression and screen various drugs against HS.

Advances in molecular pathogenesis of hidradenitis suppurativa: Dysregulated keratins and ECM signaling.

Hidradenitis suppurativa (HS) is characterized by deep-seated, highly inflamed, and painful lumps/abscesses, fistulae, and sinus tracts that grow extensively deep in the dermis and are highly immunogenic in nature. In about one-third of the HS patients there is strong evidence for the role of γ-secretase mutations along with dysregulated Notch signaling. However, the contribution of dysregulated Notch signaling in HS pathogenesis in relation to hair follicle alterations and hyper-activation of the immune system remains undefined. A genome-wide association study (GWAS), proteomic data and functional investigations of identified sequence variants in HS pathology are not fully revealing. The disease initiation or progression may involve bacterial infection besides intrinsic functional defects in keratinocytes, which may be key to further exacerbate immune cell infiltration and cytokine production in and around the lesional tissue. The absence of a suitable animal model that could fully recapitulate the pathogenesis of HS is a major impediment for proper understanding the underlying mechanisms and development of effective treatments. The presence of extracellular matrix (ECM) degradation products along with dysregulation in keratinocytes and, dermal fibroblasts ultimately affect immune regulation and are various components of HS pathogenesis. Bacterial infection further exacerbates the complexity of the disease progression. While anti-TNFα therapy shows partial efficacy, treatment to cure HS is absent. Multiple clinical trials targeting various cytokines, complement C5a and ECM products are in progress. This review provides state-of-the-art information on these aspects with a focus on dysregulated keratinocyte and immune cells; and role of ECM, and Keratin functions in this regard.

Local SARS-CoV-2 Peptide-Specific Immune Responses in Lungs of Convalescent and Uninfected Human Subjects.

Multi-specific and long-lasting T cell immunity have been recognized as indicators for long term protection against pathogens including the novel coronavirus SARS-CoV-2, the causative agent of the COVID-19 pandemic. Functional significance of peripheral memory T cells in individuals recovering from COVID-19 (COVID-19 + ) are beginning to be appreciated; but little is known about lung resident memory T cells (lung TRM) in SARS-CoV-2 infection. Here, we utilize a perfused three dimensional (3D) human lung tissue model and identify pre-existing local T cell immunity against SARS-CoV-2 proteins in lung tissues. We report ex vivo maintenance of functional multi-specific IFN-γ secreting lung TRM in COVID-19 + and their induction in lung tissues of vaccinated COVID-19 + . Importantly, we identify SARS-CoV-2 peptide-responding B cells and IgA + plasma cells in lung tissues of COVID-19 + in ex vivo 3D-tissue models. Our study highlights the importance of balanced and local anti-viral immune response in the lung with persistent induction of TRM and IgA + plasma cells for future protection against SARS-CoV-2 infection. Further, our data suggest that inclusion of multiple viral antigens in vaccine approaches may broaden the functional profile of memory T cells to combat the severity of coronavirus infection.

Indoleamine 2, 3-Dioxygenase Promotes Aryl Hydrocarbon Receptor-Dependent Differentiation Of Regulatory B Cells in Lung Cancer.

Regulatory B cells (Breg) are IL-10 producing subsets of B cells that contribute to immunosuppression in the tumor microenvironment (TME). Breg are elevated in patients with lung cancer; however, the mechanisms underlying Breg development and their function in lung cancer have not been adequately elucidated. Herein, we report a novel role for Indoleamine 2, 3- dioxygenase (IDO), a metabolic enzyme that degrades tryptophan (Trp) and the Trp metabolite L-kynurenine (L-Kyn) in the regulation of Breg differentiation in the lung TME. Using a syngeneic mouse model of lung cancer, we report that Breg frequencies significantly increased during tumor progression in the lung TME and secondary lymphoid organs, while Breg were reduced in tumor-bearing IDO deficient mice (IDO-/-). Trp metabolite L-Kyn promoted Breg differentiation in-vitro in an aryl hydrocarbon receptor (AhR), toll-like receptor-4-myeloid differentiation primary response 88, (TLR4-MyD88) dependent manner. Importantly, using mouse models with conditional deletion of IDO in myeloid-lineage cells, we identified a significant role for immunosuppressive myeloid-derived suppressor cell (MDSC)-associated IDO in modulating in-vivo and ex-vivo differentiation of Breg. Our studies thus identify Trp metabolism as a therapeutic target to modulate regulatory B cell function during lung cancer progression.

Sphingolipids in Lung Pathology in the Coronavirus Disease Era: A Review of Sphingolipid Involvement in the Pathogenesis of Lung Damage.

Sphingolipids are bioactive lipids involved in the regulation of cell survival, proliferation, and the inflammatory response. The SphK/S1P/S1PR pathway (S1P pathway) is a driver of many anti-apoptotic and proliferative processes. Pro-survival sphingolipid sphingosine-1-phosphate (S1P) initiates its signaling cascade by interacting with various sphingosine-1-phosphate receptors (S1PR) through which it is able to exert its pro-survival or inflammatory effects. Whereas sphingolipids, including ceramides and sphingosines are pro-apoptotic. The pro-apoptotic lipid, ceramide, can be produced de novo by ceramide synthases and converted to sphingosine by way of ceramidases. The balance of these antagonistic lipids and how this balance manifests is the essence of the sphingolipid rheostat. Recent studies on SARS-CoV-2 have implicated the S1P pathway in the pathogenesis of novel coronavirus disease COVID-19-related lung damage. Accumulating evidence indicates that an aberrant inflammatory process, known as "cytokine storm" causes lung injury in COVID-19, and studies have shown that the S1P pathway is involved in signaling this hyperinflammatory response. Beyond the influence of this pathway on cytokine storm, over the last decade the S1P pathway has been investigated for its role in a wide array of lung pathologies, including pulmonary fibrosis, pulmonary arterial hypertension (PAH), and lung cancer. Various studies have used S1P pathway modulators in models of lung disease; many of these efforts have yielded results that point to the potential efficacy of targeting this pathway for future treatment options. Additionally, they have emphasized S1P pathway's significant role in inflammation, fibrosis, and a number of other endothelial and epithelial changes that contribute to lung damage. This review summarizes the S1P pathway's involvement in COVID-19 and chronic lung diseases and discusses the potential for targeting S1P pathway as a therapeutic option for these diseases.

Mesenchymal stromal cell aging impairs the self-organizing capacity of lung alveolar epithelial stem cells.

Multicellular organisms maintain structure and function of tissues/organs through emergent, self-organizing behavior. In this report, we demonstrate a critical role for lung mesenchymal stromal cell (L-MSC) aging in determining the capacity to form three-dimensional organoids or 'alveolospheres' with type 2 alveolar epithelial cells (AEC2s). In contrast to L-MSCs from aged mice, young L-MSCs support the efficient formation of alveolospheres when co-cultured with young or aged AEC2s. Aged L-MSCs demonstrated features of cellular senescence, altered bioenergetics, and a senescence-associated secretory profile (SASP). The reactive oxygen species generating enzyme, NADPH oxidase 4 (Nox4), was highly activated in aged L-MSCs and Nox4 downregulation was sufficient to, at least partially, reverse this age-related energy deficit, while restoring the self-organizing capacity of alveolospheres. Together, these data indicate a critical role for cellular bioenergetics and redox homeostasis in an organoid model of self-organization and support the concept of thermodynamic entropy in aging biology.

Many tissues in the body are capable of regenerating by replacing defective or worn-out cells with new ones. This process relies heavily on stem cells, which are precursor cells that lack a set role in the body and can develop into different types of cells under the right conditions. Tissues often have their own pool of stem cells that they use to replenish damaged cells. But as we age, this regeneration process becomes less effective. Many of our organs, such as the lungs, are lined with epithelial cells. These cells form a protective barrier, controlling what substances get in and out of the tissue. Alveoli are parts of the lungs that allow oxygen and carbon dioxide to move between the blood and the air in the lungs. And alveoli rely on an effective epithelial cell lining to work properly. To replenish these epithelial cells, alveoli have pockets, in which a type of epithelial cell, known as AEC2, lives. These cells can serve as stem cells, developing into a different type of cell under the right conditions. To work properly, AEC2 cells require close interactions with another type of cell called L-MSC, which supports the maintenance of other cells and also has the ability to differentiate into several other cell types. Both cell types can be found close together in these stem cell pockets. So far, it has been unclear how aging affects how these cells work together to replenish the epithelial lining of the alveoli. To investigate, Chanda et al. probed AEC2s and L-MSCs in the alveoli of young and old mice. The researchers collected both cell types from young (2-3 months) and aged (22-24 months) mice. Various combinations of these cells were grown to form 3D structures, mimicking how the cells grow in the lungs. Young L-MSCs formed normal 3D structures with both young and aged AEC2 cells. But aged L-MSCs developed abnormal, loose structures with AEC2 cells (both young and old cells). Aged L-MSCs were found to have higher levels of an enzyme (called Nox4) that produces oxidants and other 'pro-aging' factors, compared to young L-MSCs. However, reducing Nox4 levels in aged L-MSCs allowed these cells to form normal 3D structures with young AEC2 cells, but not aged AEC2 cells. These findings highlight the varying effects specific stem cells have, and how their behaviour is affected by pro-aging factors. Moreover, the pro-aging enzyme Nox4 shows potential as a therapeutic target ­ downregulating its activity may reverse critical effects of aging in cells.