Surfactant dysfunction and lung inflammation in the female mouse model of lymphangioleiomyomatosis

Heterogeneity and Cancer-Related Features in Lymphangioleiomyomatosis Cells and Tissue

Lymphangioleiomyomatosis (LAM) is a rare, low-grade metastasizing disease characterized by cystic lung destruction. LAM can exhibit extensive heterogeneity at the molecular, cellular, and tissue levels. However, the molecular similarities and differences among LAM cells and tissue, and their connection to cancer features are not fully understood. By integrating complementary gene and protein LAM signatures, and single-cell and bulk tissue transcriptome profiles, we show sources of disease heterogeneity, and how they correspond to cancer molecular portraits. Subsets of LAM diseased cells differ with respect to gene expression profiles related to hormones, metabolism, proliferation, and stemness. Phenotypic diseased cell differences are identified by evaluating lumican (LUM) proteoglycan and YB1 transcription factor expression in LAM lung lesions. The RUNX1 and IRF1 transcription factors are predicted to regulate LAM cell signatures, and both regulators are expressed in LAM lung lesions, with differences between spindle-like and epithelioid LAM cells. The cancer single-cell transcriptome profiles most similar to those of LAM cells include a breast cancer mesenchymal cell model and lines derived from pleural mesotheliomas. Heterogeneity is also found in LAM lung tissue, where it is mainly determined by immune system factors. Variable expression of the multifunctional innate immunity protein LCN2 is linked to disease heterogeneity. This protein is found to be more abundant in blood plasma from LAM patients than from healthy women. IMPLICATIONS: This study identifies LAM molecular and cellular features, master regulators, cancer similarities, and potential causes of disease heterogeneity.

Interleukin-6 mediates PSAT1 expression and serine metabolism in TSC2-deficient cells

Tuberous sclerosis complex (TSC) and lymphangioleiomyomatosis (LAM) are caused by aberrant mechanistic Target of Rapamycin Complex 1 (mTORC1) activation due to loss of either TSC1 or TSC2 Cytokine profiling of TSC2-deficient LAM patient-derived cells revealed striking up-regulation of Interleukin-6 (IL-6). LAM patient plasma contained increased circulating IL-6 compared with healthy controls, and TSC2-deficient cells showed up-regulation of IL-6 transcription and secretion compared to wild-type cells. IL-6 blockade repressed the proliferation and migration of TSC2-deficient cells and reduced oxygen consumption and extracellular acidification. U-¹³C glucose tracing revealed that IL-6 knockout reduced 3-phosphoserine and serine production in TSC2-deficient cells, implicating IL-6 in de novo serine metabolism. IL-6 knockout reduced expression of phosphoserine aminotransferase 1 (PSAT1), an essential enzyme in serine biosynthesis. Importantly, recombinant IL-6 treatment rescued PSAT1 expression in the TSC2-deficient, IL-6 knockout clones selectively and had no effect on wild-type cells. Treatment with anti-IL-6 (αIL-6) antibody similarly reduced cell proliferation and migration and reduced renal tumors in Tsc2 ^+/- mice while reducing PSAT1 expression. These data reveal a mechanism through which IL-6 regulates serine biosynthesis, with potential relevance to the therapy of tumors with mTORC1 hyperactivity.

Air particulate matter pollution and circulating surfactant protein: A systemic review and meta-analysis

OBJECTIVE

Air particulate matter (PM) pollution is associated with the alterations in circulating pulmonary damage proteins. But there are not consistent results among the epidemiological studies. The aim of this study is to investigate the alteration of surfactant protein (SP) from PM exposure.

METHODS

We conducted a comprehensive meta-analysis by searching the databases of PubMed, Medline, EMBASE, Web of Science and CNKI before October 2020 which reported PM pollutants and surfactant protein in the population. The sources of heterogeneity were assessed by subgroup (smoking, particulate matter with different aerodynamic diameter, exposure duration) analysis. We also used the publication bias tests for the comprehensive assessment.

RESULTS

This meta-analysis consisted of 10 studies with 1985 subjects. The results showed that the combined standardized mean difference (SMD) value was 0.05, 95% confidence interval (CI) was -0.07 to 0.17 for serum SP-A and -0.81 (95% CI: -1.41 to -0.21) for circulating SP-D. Among smokers, the combined SMD value of SP-A were 0.29 (95% CI: 0.05 to 0.52). We did not find the correlation between publication year of SP-A and SP-D and study heterogeneity.

CONCLUSIONS

Circulating SP-D was significantly decreased by air particulate matter. Serum SP-A was significantly increased by PM exposure among smokers. Circulating surfactant protein may be considered as a biomarker for respiratory injury caused by air particulate matter.

Zoledronic acid inhibits TSC2-null cell tumor growth via RhoA/YAP signaling pathway in mouse models of lymphangioleiomyomatosis

Background

This study is to investigate the effects of zoledronic acid (ZA) on TSC2-null cell proliferation and on the tumor progression and recurrence in mouse models of lymphangioleiomyomatosis (LAM).

Methods

Subcutaneous mouse models and LAM mouse models were established. Immunohistochemistry and immunofluorescence were performed to detect the protein expression levels. TUNEL assay was conducted to detect cell apoptosis. Immunoprecipitation was carried out to determine the interaction between proteins.

Results

ZA prevented the growth of TSC2-null cells both in culture and in LAM mouse models. Compared with rapamycin, ZA more effectively promoted the apoptosis of TSC2-null cells. Moreover, combined with the rapamycin, ZA effectively suppressed the tumor recurrence after drug withdrawal and ZA inhibited the activity of GTPase RhoA by decreasing protein geranylgeranylation, resulting in changes of Yap nucleus translocation.

Conclusion

ZA promotes cell apoptosis in TSC2-null cells through the RhoA/YAP signaling pathway. ZA may be used for the clinical treatment of LAM.

Review of the Application of Nanovesicles and the Human Interstitial Fluid in Gastrointestinal Premalignant Lesion Detection, Diagnosis, Prognosis and Therapy

Premalignant lesions arise from cells that abnormally proliferate and have a tendency to become cancerous. Developing methods to specifically target and remove these premalignant lesions is imperative to the prevention of malignant progression into gastrointestinal (GI) tumors. However, accurate detection and diagnosis of GI precancerous lesions is challenging, as these lesions show little or no structural change. Thus, this prevents early intervention and reduces the success rate of therapy. In this review, we performed a systematic analysis of the technological advancements in the combined application of nanovesicles (NVs) and the human interstitial fluid (HIF) to specifically target GI premalignant lesions. NVs, which include quantum dots (QDs), are small membranous vehicles of a nanometer diameter that are widely used as drug delivery vectors, therapeutic effectors and diagnostic sensors. HIF is the fluid that is present in human interstitial tissues (HITs) in which signaling molecules and agents travel and can be found throughout the body. HIF is exploited by tumor cells for their invasion, migration and spread. Because the HITs span the entire submucosa of the gastrointestinal tract, they have been increasingly targeted in GI tumor therapy. The challenges involved in the combined application of NVs and HIF in the detection, diagnosis, prognosis and therapy of GI premalignant lesions are also discussed.

S-Nitrosylation of α1-Antitrypsin Triggers Macrophages Toward Inflammatory Phenotype and Enhances Intra-Cellular Bacteria Elimination

Background: Human α1-antitrypsin (hAAT) is a circulating anti-inflammatory serine-protease inhibitor that rises during acute phase responses. in vivo, hAAT reduces bacterial load, without directly inhibiting bacterial growth. In conditions of excess nitric-oxide (NO), hAAT undergoes S-nitrosylation (S-NO-hAAT) and gains antibacterial capacity. The impact of S-NO-hAAT on immune cells has yet to be explored.

Aim: Study the effects of S-NO-hAAT on immune cells during bacterial infection.

Methods: Clinical-grade hAAT was S-nitrosylated and then compared to unmodified hAAT, functionally, and structurally. Intracellular bacterial clearance by THP-1 macrophages was assessed using live Salmonella typhi. Murine peritoneal macrophages were examined, and signaling pathways were evaluated. S-NO-hAAT was also investigated after blocking free mambranal cysteine residues on cells.

Results: S-NO-hAAT (27.5 uM) enhances intracellular bacteria elimination by immunocytes (up to 1-log reduction). S-NO-hAAT causes resting macrophages to exhibit a pro-inflammatory and antibacterial phenotype, including release of inflammatory cytokines and induction of inducible nitric oxide synthase (iNOS) and TLR2. These pro-inflammatory effects are dependent upon cell surface thiols and activation of MAPK pathways.

Conclusions: hAAT duality appears to be context-specific, involving S-nitrosylation in a nitric oxide rich environment. Our results suggest that S-nitrosylation facilitates the antibacterial activity of hAAT by promoting its ability to activate innate immune cells. This pro-inflammatory effect may involve transferring of nitric oxide from S-NO-hAAT to a free cysteine residue on cellular targets.

Serum endostatin levels are associated with diffusion capacity and with tuberous sclerosis- associated lymphangioleiomyomatosis

Endostatin is a naturally occurring collagen fragment with anti-angiogenic properties. We investigated the association between serum endostatin levels and DLCO in a cohort of patients with lymphangioleiomyomatosis (LAM). Associations of endostatin levels to clinical features of LAM were explored using logistic regression models. Endostatin levels were associated with DLCO and were higher in subjects with TSC-associated LAM compared to sporadic LAM. These data suggest that endostatin could be a predictive biomarker of decline in DLCO and that germline mutational inactivation of the TSC1 or TSC2 gene is associated with higher endostatin levels. These findings could offer novel insights into the pathogenesis of LAM.

Surfactant Protein D in Respiratory and Non-Respiratory Diseases

Surfactant protein D (SP-D) is a multimeric collectin that is involved in innate immune defense and expressed in pulmonary, as well as non-pulmonary, epithelia. SP-D exerts antimicrobial effects and dampens inflammation through direct microbial interactions and modulation of host cell responses via a series of cellular receptors. However, low protein concentrations, genetic variation, biochemical modification, and proteolytic breakdown can induce decomposition of multimeric SP-D into low-molecular weight forms, which may induce pro-inflammatory SP-D signaling. Multimeric SP-D can decompose into trimeric SP-D, and this process, and total SP-D levels, are partly determined by variation within the SP-D gene, SFTPD. SP-D has been implicated in the development of respiratory diseases including respiratory distress syndrome, bronchopulmonary dysplasia, allergic asthma, and chronic obstructive pulmonary disease. Disease-induced breakdown or modifications of SP-D facilitate its systemic leakage from the lung, and circulatory SP-D is a promising biomarker for lung injury. Moreover, studies in preclinical animal models have demonstrated that local pulmonary treatment with recombinant SP-D is beneficial in these diseases. In recent years, SP-D has been shown to exert antimicrobial and anti-inflammatory effects in various non-pulmonary organs and to have effects on lipid metabolism and pro-inflammatory effects in vessel walls, which enhance the risk of atherosclerosis. A common SFTPD polymorphism is associated with atherosclerosis and diabetes, and SP-D has been associated with metabolic disorders because of its effects in the endothelium and adipocytes and its obesity-dampening properties. This review summarizes and discusses the reported genetic associations of SP-D with disease and the clinical utility of circulating SP-D for respiratory disease prognosis. Moreover, basic research on the mechanistic links between SP-D and respiratory, cardiovascular, and metabolic diseases is summarized. Perspectives on the development of SP-D therapy are addressed.

Surfactant protein D multimerization and gene polymorphism in COPD and asthma

BACKGROUND AND OBJECTIVE

A structural single nucleotide polymorphism rs721917 in the surfactant protein D (SP-D) gene, known as Met11Thr, was reported to influence the circulating levels and degree of multimerization of SP-D and was associated with both COPD and atopy in asthma. Moreover, disease-related processes are known to degrade multimerized SP-D, however, the degree of the protein degradation in these diseases is not clarified. We aimed to determine the distribution of multimerized (high molecular weight (HMW)) and non-multimerized (low molecular weight (LMW)) species of serum SP-D and their correlation with genetic polymorphisms and presence of disease in Lebanese COPD and asthmatic patients.

METHODS

Serum SP-D levels were measured by ELISA in 88 COPD, 121 asthmatic patients and 223 controls. Randomly selected subjects were chosen for genotyping of rs721917 and multimerization studies. HMW and LMW SP-D were separated by gel permeation chromatography.

RESULTS

Serum SP-D levels were significantly increased in patients with COPD, but not in asthmatic patients, when compared to controls. Met11Thr variation strongly affected serum SP-D levels and the degree of multimerization, but was not associated with COPD and asthma in the study. Remarkably, HMW/LMW serum SP-D ratio was significantly lower in Met11/Met11 COPD and asthmatic patients compared to controls.

CONCLUSION

Collectively, non-multimerized species of serum SP-D were dominant in COPD and asthmatic patients suggesting that degradation of SP-D takes place to a significant degree in pulmonary disease. Assays that can separate SP-D proteolytic breakdown products or modified forms from naturally occurring SP-D trimers may result in optimal disease markers for pulmonary inflammatory diseases.

Cathepsin K in Lymphangioleiomyomatosis: LAM Cell-Fibroblast Interactions Enhance Protease Activity by Extracellular Acidification

Lymphangioleiomyomatosis (LAM) is a rare disease in which LAM cells and fibroblasts form lung nodules and it is hypothesized that LAM nodule-derived proteases cause cyst formation and tissue damage. On protease gene expression profiling in whole lung tissue, cathepsin K gene expression was 40-fold overexpressed in LAM compared with control lung tissue (P ≤ 0.0001). Immunohistochemistry confirmed cathepsin K protein was expressed in LAM but not control lungs. Cathepsin K gene expression and protein and protease activity were detected in LAM-associated fibroblasts but not the LAM cell line 621-101. In lung nodules, cathepsin K immunoreactivity predominantly co-localized with LAM-associated fibroblasts. In vitro, fibroblast extracellular cathepsin K activity was minimal at pH 7.5 but significantly enhanced at pH 7 and 6. 621-101 cells reduced extracellular pH with acidification dependent on 621-101 mechanistic target of rapamycin activity and net hydrogen ion exporters, particularly sodium bicarbonate co-transporters and carbonic anhydrases, which were also expressed in LAM lung tissue. In LAM cell-fibroblast co-cultures, acidification paralleled cathepsin K activity, and both were reduced by sodium bicarbonate co-transporter (P ≤ 0.0001) and carbonic anhydrase inhibitors (P = 0.0021). Our findings suggest that cathepsin K activity is dependent on LAM cell-fibroblast interactions, and inhibitors of extracellular acidification may be potential therapies for LAM.

Lymphangioleiomyomatosis

Lymphangioleiomyomatosis is a rare multisystem disease predominantly affecting women that can occur sporadically or in association with tuberous sclerosis. Lung cysts progressively replace the lung parenchyma, which leads to dyspnea, recurrent pneumothorax, and in some cases respiratory failure. Patients may also have lymphatic disease in the thorax, abdomen, and pelvis, and renal angiomyolipomas. Treatment includes supportive care, bronchodilators, and for those with progressive disease, mammalian target of rapamycin (mTOR) inhibitors.

Surfactant Protein-D Is Essential for Immunity to Helminth Infection

Pulmonary epithelial cell responses can enhance type 2 immunity and contribute to control of nematode infections. An important epithelial product is the collectin Surfactant Protein D (SP-D). We found that SP-D concentrations increased in the lung following Nippostrongylus brasiliensis infection; this increase was dependent on key components of the type 2 immune response. We carried out loss and gain of function studies of SP-D to establish if SP-D was required for optimal immunity to the parasite. N. brasiliensis infection of SP-D-/- mice resulted in profound impairment of host innate immunity and ability to resolve infection. Raising pulmonary SP-D levels prior to infection enhanced parasite expulsion and type 2 immune responses, including increased numbers of IL-13 producing type 2 innate lymphoid cells (ILC2), elevated expression of markers of alternative activation by alveolar macrophages (alvM) and increased production of the type 2 cytokines IL-4 and IL-13. Adoptive transfer of alvM from SP-D-treated parasite infected mice into naïve recipients enhanced immunity to N. brasiliensis. Protection was associated with selective binding by the SP-D carbohydrate recognition domain (CRD) to L4 parasites to enhance their killing by alvM. These findings are the first demonstration that the collectin SP-D is an essential component of host innate immunity to helminths.

Infections by parasitic worms are very common, and controlling them is a major medical and veterinary challenge. Very few drugs exist to treat them, and the parasites can develop resistance to these. In order to find new ways to control worm infections, understanding how our immune system responds to them is essential. Many important parasitic worm infections move through the host lung. In this study we show that a major secreted protein in the lung, Surfactant Protein D (SP-D), is essential for immunity to a parasitic worm infection. We found that this protein binds to worm larvae in the lung to help the immune system kill them. Infecting mice that do not express SP-D with worms demonstrates SP-D is important in this immune response. These mice are unable to launch an effective anti-worm immune response and have many more worms in their intestine compared to mice that do express SP-D. We also show that if we increase SP-D levels in the lung the mouse has better immunity to worms. Together this shows for the first time that SP-D is very important for immunity to worm infections.

Pharmacological targeting of VEGFR signaling with axitinib inhibits Tsc2-null lesion growth in the mouse model of lymphangioleiomyomatosis

Pulmonary lymphangioleiomyomatosis (LAM), a rare progressive lung disease associated with mutations of the tuberous sclerosis complex 2 (Tsc2) tumor suppressor gene, manifests by neoplastic growth of LAM cells, induction of cystic lung destruction, and respiratory failure. LAM severity correlates with upregulation in serum of the prolymphangiogenic vascular endothelial growth factor D (VEGF-D) that distinguishes LAM from other cystic diseases. The goals of our study was to determine whether Tsc2 deficiency upregulates VEGF-D, and whether axitinib, the Food and Drug Administration-approved small-molecule inhibitor of VEGF receptor (VEGFR) signaling, will reduce Tsc2-null lung lesion growth in a mouse model of LAM. Our data demonstrate upregulation of VEGF-D in the serum and lung lining in mice with Tsc2-null lesions. Progressive growth of Tsc2-null lesions induces recruitment and activation of inflammatory cells and increased nitric oxide production. Recruited cells isolated from the lung lining of mice with Tsc2-null lesions demonstrate upregulated expression of provasculogenic Vegfa, prolymphangiogenic Figf, and proinflammatory Nos2, Il6, and Ccl2 genes. Importantly, axitinib is an effective inhibitor of Tsc2-null lesion growth and inflammatory cell recruitment, which correlates with reduced VEGF-D levels in serum and lung lining. Our data demonstrate that pharmacological inhibition of VEGFR signaling with axitinib inhibits Tsc2-null lesion growth, attenuates recruitment and activation of inflammatory cells, and reduces VEGF-D levels systemically and in the lung lining. Our study suggests a potential therapeutic benefit of inhibition of VEGFR signaling for treatment of LAM.