Hypoxia-Inducible Factor-1α in SM22α-Expressing Cells Modulates Alveolarization.

Worldwide, the incidence of both preterm births and chronic lung disease of infancy, or bronchopulmonary dysplasia, remains high. Infants with bronchopulmonary dysplasia have larger and fewer alveoli, a lung pathology that can persist into adulthood. Although recent data point to a role for hypoxia-inducible factor-1α (HIF-1α) in mediating pulmonary angiogenesis and alveolarization, the cell-specific role of HIF-1α remains incompletely understood. Thus, we hypothesized that HIF-1α, in a distinct subset of mesenchymal cells, mediates postnatal alveolarization. To test the hypothesis, we generated mice with a cell-specific deletion of HIF-1α by crossing SM22α promoter-driven Cre mice with HIF-1αflox/flox mice (SM22α-HIF-1α-/-), determined SM-22α-expressing cell identity using single-cell RNA sequencing, and interrogated samples from preterm infants. Deletion of HIF-1α in SM22α-expressing cells had no effect on lung structure at day 3 of life. However, at 8 days, there were fewer and larger alveoli, a difference that persisted into adulthood. Microvascular density, elastin organization, and peripheral branching of the lung vasculature were decreased in SM22α-HIF-1α-/- mice, compared with control mice. Single-cell RNA sequencing demonstrated that three mesenchymal cell subtypes express SM22α: myofibroblasts, airway smooth muscle cells, and vascular smooth muscle cells. Pulmonary vascular smooth muscle cells from SM22α-HIF-1α-/- mice had decreased angiopoietin-2 expression and, in coculture experiments, a diminished capacity to promote angiogenesis that was rescued by angiopoietin-2. Angiopoietin-2 expression in tracheal aspirates of preterm infants was inversely correlated with overall mechanical ventilation time, a marker of disease severity. We conclude that SM22α-specific HIF-1α expression drives peripheral angiogenesis and alveolarization in the lung, perhaps by promoting angiopoietin-2 expression.

Prenatal vitamin D supplementation mitigates inflammation-related alveolar remodeling in neonatal mice.

The development of chronic lung disease in the neonate, also known as bronchopulmonary dysplasia (BPD), is the most common long-term complication in prematurely born infants. In BPD, the disease-characteristic inflammatory response culminates in nonreversible remodeling of the developing gas exchange area, provoked by the impact of postnatal treatments such as mechanical ventilation (MV) and oxygen treatment. To evaluate the potential of prenatal treatment regimens to modulate this inflammatory response and thereby impact the vulnerability of the lung toward postnatal injury, we designed a multilayered preclinical mouse model. After administration of either prenatal vitamin D-enriched (VitD+; 1,500 IU/g food) or -deprived (VitD-; <10 IU/kg) food during gestation in C57B6 mice (the onset of mating until birth), neonatal mice were exposed to hyperoxia (FiO2 = 0.4) with or without MV for 8 h at days 5-7 of life, whereas controls spontaneously breathed room air. Prenatal vitamin D supplementation resulted in a decreased number of monocytes/macrophages in the neonatal lung undergoing postnatal injury together with reduced TGF-ß pathway activation. In consequence, neonatal mice that received a VitD+ diet during gestation demonstrated less extracellular matrix (ECM) remodeling upon lung injury, reflected by the reduction of pulmonary α-smooth muscle actin-positive fibroblasts, decreased collagen and elastin deposition, and lower amounts of interstitial tissue in the lung periphery. In conclusion, our findings support strategies that attempt to prevent vitamin D insufficiency during pregnancy as they could impact lung health in the offspring by mitigating inflammatory changes in neonatal lung injury and ameliorating subsequent remodeling of the developing gas exchange area.NEW & NOTEWORTHY Vitamin D-enriched diet during gestation resulted in reduced lung inflammation and matrix remodeling in neonatal mice exposed to clinically relevant, postnatal injury. The results underscore the need to monitor the subclinical effects of vitamin D insufficiency that impact health in the offspring when other risk factors come into play.

Corrigendum: Monocyte signature as a predictor of chronic lung disease in the preterm infant.

[This corrects the article DOI: 10.3389/fimmu.2023.1112608.].

Monocyte signature as a predictor of chronic lung disease in the preterm infant.

Introduction: Inflammation is a key driver of morbidity in the vulnerable preterm infant exposed to pre- and postnatal hazards and significantly contributes to chronic lung disease, i.e. bronchopulmonary dysplasia (BPD). However, the early changes in innate immunity associated with BPD development are incompletely understood. Methods: In very immature preterm infants below 32 weeks gestational age (GA; n=30 infants), monocyte subtypes were identified by Flow Cytometry at birth and throughout the postnatal course including intracellular TNF expression upon LPS stimulation. Complementing these measurements, cytokine end growth factor expression profiles (Luminex® xMAP®; n=110 infants) as well as gene expression profiles (CodeLinkTM Human I Bioarray; n=22) were characterized at birth. Results: The abundance of monocyte subtypes differed between preterm and term neonates at birth. Specifically, CD14++CD16+ (intermediate) monocytes demonstrated a dependency on PMA and elevated levels of nonclassical (CD14+CD16++) monocytes characterized preterm infants with developing BPD. Postnatally, lung injury was associated with an increase in intermediate monocytes, while high levels of nonclassical monocytes persisted. Both subtypes were revealed as the main source of intracellular TNF-α expression in the preterm infant. We identified a cytokine and growth factor expression profile in cord blood specimen of preterm infants with developing BPD that corresponded to the disease-dependent regulation of monocyte abundances. Multivariate modeling of protein profiles revealed FGF2, sIL-2 Rα, MCP-1, MIP1a, and TNF-α as predictors of BPD when considering GA. Transcriptome analysis demonstrated genes predicting BPD to be overrepresented in inflammatory pathways with increased disease severity characterized by the regulation of immune and defense response pathways and upstream regulator analysis confirmed TNF-α, interleukin (IL) -6, and interferon α as the highest activated cytokines in more severe disease. Whereas all BPD cases showed downstream activation of chemotaxis and activation of inflammatory response pathways, more severe cases were characterized by an additional activation of reactive oxygen species (ROS) synthesis. Discussion: In the present study, we identified the early postnatal presence of nonclassical (CD14+CD16++) and intermediate (CD14++CD16+) monocytes as a critical characteristic of BPD development including a specific response pattern of monocyte subtypes to lung injury. Pathophysiological insight was provided by the protein and transcriptome signature identified at birth, centered around monocyte and corresponding granulocyte activation and highlighting TNFα as a critical regulator in infants with developing BPD. The disease severity-dependent expression patterns could inform future diagnostic and treatment strategies targeting the monocytic cell and its progeny.

Relationship between impaired BMP signalling and clinical risk factors at early-stage vascular injury in the preterm infant.

INTRODUCTION: Chronic lung disease, that is, bronchopulmonary dysplasia (BPD) is the most common complication in preterm infants and develops as a consequence of the misguided formation of the gas-exchange area undergoing prenatal and postnatal injury. Subsequent vascular disease and its progression into pulmonary arterial hypertension critically determines long-term outcome in the BPD infant but lacks identification of early, disease-defining changes. METHODS: We link impaired bone morphogenetic protein (BMP) signalling to the earliest onset of vascular pathology in the human preterm lung and delineate the specific effects of the most prevalent prenatal and postnatal clinical risk factors for lung injury mimicking clinically relevant conditions in a multilayered animal model using wild-type and transgenic neonatal mice. RESULTS: We demonstrate (1) the significant reduction in BMP receptor 2 (BMPR2) expression at the onset of vascular pathology in the lung of preterm infants, later mirrored by reduced plasma BMP protein levels in infants with developing BPD, (2) the rapid impairment (and persistent change) of BMPR2 signalling on postnatal exposure to hyperoxia and mechanical ventilation, aggravated by prenatal cigarette smoke in a preclinical mouse model and (3) a link to defective alveolar septation and matrix remodelling through platelet derived growth factor-receptor alpha deficiency. In a treatment approach, we partially reversed vascular pathology by BMPR2-targeted treatment with FK506 in vitro and in vivo. CONCLUSION: We identified impaired BMP signalling as a hallmark of early vascular disease in the injured neonatal lung while outlining its promising potential as a future biomarker or therapeutic target in this growing, high-risk patient population.

Pharmacokinetic Engineering of OX40-Blocking Anticalin Proteins Using Monomeric Plasma Half-Life Extension Domains.

Anticalin® proteins have been proven as versatile clinical stage biotherapeutics. Due to their small size (∼20 kDa), they harbor a short intrinsic plasma half-life which can be extended, e.g., by fusion with IgG or Fc. However, for antagonism of co-immunostimulatory Tumor Necrosis Factor Receptor Superfamily (TNFRSF) members in therapy of autoimmune and inflammatory diseases, a monovalent, pharmacokinetically optimized Anticalin protein format that avoids receptor clustering and therefore potential activation is favored. We investigated the suitability of an affinity-improved streptococcal Albumin-Binding Domain (ABD) and the engineered Fab-selective Immunoglobulin-Binding Domain (IgBD) SpGC3Fab for plasma Half-Life Extension (HLE) of an OX40-specific Anticalin and bispecific Duocalin proteins, neutralizing OX40 and a second co-immunostimulatory TNFRSF member. The higher affinity of ABD fusion proteins to human serum albumin (HSA) and Mouse Serum Albumin (MSA), with a 4 to 5-order of magnitude lower KD compared with the binding affinity of IgBD fusions to human/mouse IgG, translated into longer terminal plasma half-lives (t 1/2). Hence, the anti-OX40 Anticalin-ABD protein reached t 1/2 values of ∼40 h in wild-type mice and 110 h in hSA/hFcRn double humanized mice, in contrast to ∼7 h observed for anti-OX40 Anticalin-IgBD in wild-type mice. The pharmacokinetics of an anti-OX40 Anticalin-Fc fusion protein was the longest in both models (t 1/2 of 130 h and 146 h, respectively). Protein formats composed of two ABDs or IgBDs instead of one single HLE domain clearly showed longer presence in the circulation. Importantly, Anticalin-ABD and -IgBD fusions showed OX40 receptor binding and functional competition with OX40L-induced cellular reactivity in the presence of albumin or IgG, respectively. Our results suggest that fusion to ABD or IgBD can be a versatile platform to tune the plasma half-life of Anticalin proteins in response to therapeutic needs.

The BPD trio? Interaction of dysregulated PDGF, VEGF, and TGF signaling in neonatal chronic lung disease.

The development of neonatal chronic lung disease (nCLD), i.e., bronchopulmonary dysplasia (BPD) in preterm infants, significantly determines long-term outcome in this patient population. Risk factors include mechanical ventilation and oxygen toxicity impacting on the immature lung resulting in impaired alveolarization and vascularization. Disease development is characterized by inflammation, extracellular matrix remodeling, and apoptosis, closely intertwined with the dysregulation of growth factor signaling. This review focuses on the causes and consequences of altered signaling in central pathways like transforming growth factor (TGF), platelet-derived growth factor (PDGF), and vascular endothelial growth factor (VEGF) driving these above indicated processes, i.e., inflammation, matrix remodeling, and vascular development. We emphasize the shared and distinct role of these pathways as well as their interconnection in disease initiation and progression, generating important knowledge for the development of future treatment strategies.

Attenuated PDGF signaling drives alveolar and microvascular defects in neonatal chronic lung disease.

Neonatal chronic lung disease (nCLD) affects a significant number of neonates receiving mechanical ventilation with oxygen-rich gas (MV-O2). Regardless, the primary molecular driver of the disease remains elusive. We discover significant enrichment for SNPs in the PDGF-Rα gene in preterms with nCLD and directly test the effect of PDGF-Rα haploinsufficiency on the development of nCLD using a preclinical mouse model of MV-O2 In the context of MV-O2, attenuated PDGF signaling independently contributes to defective septation and endothelial cell apoptosis stemming from a PDGF-Rα-dependent reduction in lung VEGF-A. TGF-ß contributes to the PDGF-Rα-dependent decrease in myofibroblast function. Remarkably, endotracheal treatment with exogenous PDGF-A rescues both the lung defects in haploinsufficient mice undergoing MV-O2 Overall, our results establish attenuated PDGF signaling as an important driver of nCLD pathology with provision of PDGF-A as a protective strategy for newborns undergoing MV-O2.

Translation of Angiotensin-Converting Enzyme 2 upon Liver- and Lung-Targeted Delivery of Optimized Chemically Modified mRNA.

Changes in lifestyle and environmental conditions give rise to an increasing prevalence of liver and lung fibrosis, and both have a poor prognosis. Promising results have been reported for recombinant angiotensin-converting enzyme 2 (ACE2) protein administration in experimental liver and lung fibrosis. However, the full potential of ACE2 may be achieved by localized translation of a membrane-anchored form. For this purpose, we advanced the latest RNA technology for liver- and lung-targeted ACE2 translation. We demonstrated in vitro that transfection with ACE2 chemically modified messenger RNA (cmRNA) leads to robust translation of fully matured, membrane-anchored ACE2 protein. In a second step, we designed eight modified ACE2 cmRNA sequences and identified a lead sequence for in vivo application. Finally, formulation of this ACE2 cmRNA in tailor-made lipidoid nanoparticles and in lipid nanoparticles led to liver- and lung-targeted translation of significant amounts of ACE2 protein, respectively. In summary, we provide evidence that RNA transcript therapy (RTT) is a promising approach for ACE2-based treatment of liver and lung fibrosis to be tested in fibrotic disease models.

Absence of TNF-α enhances inflammatory response in the newborn lung undergoing mechanical ventilation.

Bronchopulmonary dysplasia (BPD), characterized by impaired alveolarization and vascularization in association with lung inflammation and apoptosis, often occurs after mechanical ventilation with oxygen-rich gas (MV-O2). As heightened expression of the proinflammatory cytokine TNF-α has been described in infants with BPD, we hypothesized that absence of TNF-α would reduce pulmonary inflammation, and attenuate structural changes in newborn mice undergoing MV-O2 Neonatal TNF-α null (TNF-α(-/-)) and wild type (TNF-α(+/+)) mice received MV-O2 for 8 h; controls spontaneously breathed 40% O2 Histologic, mRNA, and protein analysis in vivo were complemented by in vitro studies subjecting primary pulmonary myofibroblasts to mechanical stretch. Finally, TNF-α level in tracheal aspirates from preterm infants were determined by ELISA. Although MV-O2 induced larger and fewer alveoli in both, TNF-α(-/-) and TNF-α(+/+) mice, it caused enhanced lung apoptosis (TUNEL, caspase-3/-6/-8), infiltration of macrophages and neutrophils, and proinflammatory mediator expression (IL-1ß, CXCL-1, MCP-1) in TNF-α(-/-) mice. These differences were associated with increased pulmonary transforming growth factor-ß (TGF-ß) signaling, decreased TGF-ß inhibitor SMAD-7 expression, and reduced pulmonary NF-κB activity in ventilated TNF-α(-/-) mice. Preterm infants who went on to develop BPD showed significantly lower TNF-α levels at birth. Our results suggest a critical balance between TNF-α and TGF-ß signaling in the developing lung, and underscore the critical importance of these key pathways in the pathogenesis of BPD. Future treatment strategies need to weigh the potential benefits of inhibiting pathologic cytokine expression against the potential of altering key developmental pathways.

Sequential Salinomycin Treatment Results in Resistance Formation through Clonal Selection of Epithelial-Like Tumor Cells.

Acquiring therapy resistance is one of the major obstacles in the treatment of patients with cancer. The discovery of the cancer stem cell (CSC)-specific drug salinomycin raised hope for improved treatment options by targeting therapy-refractory CSCs and mesenchymal cancer cells. However, the occurrence of an acquired salinomycin resistance in tumor cells remains elusive. To study the formation of salinomycin resistance, mesenchymal breast cancer cells were sequentially treated with salinomycin in an in vitro cell culture assay, and the resulting differences in gene expression and salinomycin susceptibility were analyzed. We demonstrated that long-term salinomycin treatment of mesenchymal cancer cells resulted in salinomycin-resistant cells with elevated levels of epithelial markers, such as E-cadherin and miR-200c, a decreased migratory capability, and a higher susceptibility to the classic chemotherapeutic drug doxorubicin. The formation of salinomycin resistance through the acquisition of epithelial traits was further validated by inducing mesenchymal-epithelial transition through an overexpression of miR-200c. The transition from a mesenchymal to a more epithelial-like phenotype of salinomycin-treated tumor cells was moreover confirmed in vivo, using syngeneic and, for the first time, transgenic mouse tumor models. These results suggest that the acquisition of salinomycin resistance through the clonal selection of epithelial-like cancer cells could become exploited for improved cancer therapies by antagonizing the tumor-progressive effects of epithelial-mesenchymal transition.

Salinomycin treatment reduces metastatic tumor burden by hampering cancer cell migration.

BACKGROUND: Tumor spreading is the major threat for cancer patients. The recently published anti-cancer drug salinomycin raised hope for an improved treatment by targeting therapy-refractory cancer stem cells. However, an unambiguous role of salinomycin against cancer cell migration and metastasis formation remains elusive. FINDINGS: We report that salinomycin effectively inhibits cancer cell migration in a variety of cancer types as determined by Boyden chamber assays. Additionally, cells were treated with doxorubicin at a concentration causing a comparable low cytotoxicity, emphasizing the anti-migratory potential of salinomycin. Moreover, single-cell tracking by time-lapse microscopy demonstrated a remarkable effect of salinomycin on breast cancer cell motility. Ultimately, salinomycin treatment significantly reduced the metastatic tumor burden in a syngenic mouse tumor model. CONCLUSIONS: Our findings clearly show that salinomycin can strongly inhibit cancer cell migration independent of the induction of cell death. We furthermore demonstrate for the first time that salinomycin treatment reduces metastasis formation in vivo, strengthening its role as promising anti-cancer therapeutic.

Mode of cell death induction by pharmacological vacuolar H+-ATPase (V-ATPase) inhibition.

The vacuolar H(+)-ATPase (V-ATPase), a multisubunit proton pump, has come into focus as an attractive target in cancer invasion. However, little is known about the role of V-ATPase in cell death, and especially the underlying mechanisms remain mostly unknown. We used the myxobacterial macrolide archazolid B, a potent inhibitor of the V-ATPase, as an experimental drug as well as a chemical tool to decipher V-ATPase-related cell death signaling. We found that archazolid induced apoptosis in highly invasive tumor cells at nanomolar concentrations which was executed by the mitochondrial pathway. Prior to apoptosis induction archazolid led to the activation of a cellular stress response including activation of the hypoxia-inducible factor-1α (HIF1α) and autophagy. Autophagy, which was demonstrated by degradation of p62 or fusion of autophagosomes with lysosomes, was induced at low concentrations of archazolid that not yet increase pH in lysosomes. HIF1α was induced due to energy stress shown by a decline of the ATP level and followed by a shutdown of energy-consuming processes. As silencing HIF1α increases apoptosis, the cellular stress response was suggested to be a survival mechanism. We conclude that archazolid leads to energy stress which activates adaptive mechanisms like autophagy mediated by HIF1α and finally leads to apoptosis. We propose V-ATPase as a promising drugable target in cancer therapy caught up at the interplay of apoptosis, autophagy, and cellular/metabolic stress.

miR-200c sensitizes breast cancer cells to doxorubicin treatment by decreasing TrkB and Bmi1 expression.

Acquired resistance to classical chemotherapeutics is a major obstacle in cancer treatment. Doxorubicin is frequently used in breast cancer therapy either as single-agent or in combination with other drugs like docetaxel and cyclophosphamide. All these chemotherapies have in common that they are administered sequentially and often result in chemoresistance. Here, we mimicked this pulse therapy of breast cancer patients in an in vitro cell culture model, where the epithelial breast cancer cell line BT474 was sequentially treated with doxorubicin for several treatment cycles. In consequence, we obtained chemoresistant cells displaying a mesenchymal-like phenotype with decreased levels of miR-200c. To investigate the involvement of miR-200c in resistance formation, we inhibited and overexpressed miR-200c in different cell lines. Thereby, the cells were rendered more resistant or susceptible to doxorubicin treatment. Moreover, the receptor tyrosine kinase TrkB and the transcriptional repressor Bmi1 were identified as miR-200c targets mediating the drug resistance. Hence, we provide a mechanism of acquired resistance to doxorubicin that is caused by the loss of miR-200c. Along with this, our study demonstrates the complex network of microRNA mediated chemoresistance highlighting the challenges in cancer therapy and the importance of novel microRNA-modulating anticancer agents.

Combinatorial treatment of mammospheres with trastuzumab and salinomycin efficiently targets HER2-positive cancer cells and cancer stem cells.

A major obstacle in the successful treatment of cancer is the occurrence of chemoresistance. Cancer cells surviving chemotherapy and giving rise to a recurrence of the tumor are termed cancer stem cells and can be identified by elevated levels of certain stem cell markers. Eradication of this cell population is a priority objective in cancer therapy. Here, we report elevated levels of stem cell markers in MCF-7 mammospheres. Likewise, an upregulation of HER2 and its differential expression within individual cells of mammospheres was observed. Sorting for HER2(high) and HER2(low) cells revealed an upregulation of stem cell markers NANOG, OCT4 and SOX2 in the HER2(low) cell fraction. Accordingly, HER2(low) cells also showed reduced proliferation, ductal-like outgrowths and an increased number of colonies in matrigel. Xenografts from subcutaneously injected HER2(low) sorted cells exihibited earlier onset but slower growth of tumors and an increase in stem cell markers compared to tumors developed from the HER2(high) fraction. Treatment of mammospheres with salinomycin reduced the expression of SOX2 indicating a selective targeting of cancer stem cells. Trastuzumab however, did not reduce the expression of SOX2 in mammospheres. Furthermore, a combinatorial treatment of mammospheres with trastuzumab and salinomycin was superior to single treatment with each drug. Thus, targeting HER2 expressing tumors with anti-HER2 therapies will not necessarily eliminate cancer stem cells and may lead to a more aggressive cancer cell phenotype. Our study demonstrates efficient killing of both HER2 positive cells and cancer stem cells, hence opening a possibility for a new combinatorial treatment strategy.