Tissue-specific renin-angiotensin system in pulmonary lymphangioleiomyomatosis

Lymphangioleiomyomatosis: a metastatic lung disease

Lymphangioleiomyomatosis (LAM) is a rare disease affecting women, caused by somatic mutations in the TSC1 or TSC2 genes, and driven by estrogen. Similar to many cancers, it is metastatic, primarily to the lung. Despite its monogenetic nature, like many cancers, LAM is a heterogeneous disease. The cellular constituents of LAM are very diverse, including mesenchymal, epithelial, endothelial, and immune cells. LAM is characterized by dysregulation of many cell signaling pathways, distinct populations of LAM cells, and a rich microenvironment, in which the immune system appears to play an important role. This review delineates the heterogeneity of LAM and focuses on the metastatic features of LAM, the deregulated signaling mechanisms and the tumor microenvironment. Understanding the tumor-host interaction in LAM may provide insights into the development of new therapeutic strategies, which could be combinatorial or superlative to Sirolimus, the current U.S. Food and Drug Administration-approved treatment.

Lymphangioleiomyomatosis: pathogenesis, clinical features, diagnosis, and management

Lymphangioleiomyomatosis (LAM) is a slowly progressive, low-grade, metastasising neoplasm of women, characterised by infiltration of the lung parenchyma with abnormal smooth muscle-like cells, resulting in cystic lung destruction. The invading cell in LAM arises from an unknown source and harbours mutations in tuberous sclerosis complex (TSC) genes that result in constitutive activation of the mechanistic target of rapamycin (mTOR) pathway, dysregulated cellular proliferation, and a programme of frustrated lymphangiogenesis, culminating in disordered lung remodelling and respiratory failure. Over the past two decades, all facets of LAM basic and clinical science have seen important advances, including improved understanding of molecular mechanisms, novel diagnostic and prognostic biomarkers, effective treatment strategies, and comprehensive clinical practice guidelines. Further research is needed to better understand the natural history of LAM; develop more powerful diagnostic, prognostic, and predictive biomarkers; optimise the use of inhibitors of mTOR complex 1 in the treatment of LAM; and explore novel approaches to the development of remission-inducing therapies.

Histamine signaling and metabolism identify potential biomarkers and therapies for lymphangioleiomyomatosis

Inhibition of mTOR is the standard of care for lymphangioleiomyomatosis (LAM). However, this therapy has variable tolerability and some patients show progressive decline of lung function despite treatment. LAM diagnosis and monitoring can also be challenging due to the heterogeneity of symptoms and insufficiency of non-invasive tests. Here, we propose monoamine-derived biomarkers that provide preclinical evidence for novel therapeutic approaches. The major histamine-derived metabolite methylimidazoleacetic acid (MIAA) is relatively more abundant in LAM plasma, and MIAA values are independent of VEGF-D. Higher levels of histamine are associated with poorer lung function and greater disease burden. Molecular and cellular analyses, and metabolic profiling confirmed active histamine signaling and metabolism. LAM tumorigenesis is reduced using approved drugs targeting monoamine oxidases A/B (clorgyline and rasagiline) or histamine H1 receptor (loratadine), and loratadine synergizes with rapamycin. Depletion of Maoa or Hrh1 expression, and administration of an L-histidine analog, or a low L-histidine diet, also reduce LAM tumorigenesis. These findings extend our knowledge of LAM biology and suggest possible ways of improving disease management.

Mast-Cell Tryptase Release Contributes to Disease Progression in Lymphangioleiomyomatosis

Rationale: Lymphangioleiomyomatosis (LAM) is a multisystem disease that causes lung cysts and respiratory failure. Loss of TSC (tuberous sclerosis complex) gene function results in a clone of "LAM cells" with dysregulated mTOR (mechanistic target of rapamycin) activity. LAM cells and fibroblasts form lung nodules that also contain mast cells, although their significance is unknown. Objectives: To understand the mechanism of mast-cell accumulation and the role of mast cells in the pathogenesis of LAM. Methods: Gene expression was examined using transcriptional profiling and qRT-PCR. Mast cell/LAM nodule interactions were examined in vitro using spheroid TSC2-null cell/fibroblast cocultures and in vivo using an immunocompetent Tsc2-null murine homograft model. Measurements and Main Results: LAM-derived cell/fibroblast cocultures induced multiple CXC chemokines in fibroblasts. LAM lungs had increased tryptase-positive mast cells expressing CXCRs (CXC chemokine receptors) (P < 0.05). Mast cells located around the periphery of LAM nodules were positively associated with the rate of lung function loss (P = 0.016). LAM spheroids attracted mast cells, and this process was inhibited by pharmacologic and CRISPR/cas9 inhibition of CXCR1 and CXCR2. LAM spheroids caused mast-cell tryptase release, which induced fibroblast proliferation and increased LAM-spheroid size (1.36 ± 0.24-fold; P = 0.0019). The tryptase inhibitor APC366 and sodium cromoglycate (SCG) inhibited mast cell-induced spheroid growth. In vivo, SCG reduced mast-cell activation and Tsc2-null lung tumor burden (vehicle: 32.5.3% ± 23.6%; SCG: 5.5% ± 4.3%; P = 0.0035). Conclusions: LAM-cell/fibroblast interactions attract mast cells where tryptase release contributes to disease progression. Repurposing SCG for use in LAM should be studied as an alternative or adjunct to mTOR inhibitor therapy.

Downregulation of Membrane-bound Angiotensin Converting Enzyme 2 (ACE2) Receptor has a Pivotal Role in COVID-19 Immunopathology

BACKGROUND

The Coronavirus Disease 2019 (COVID-19) is becoming the major health issue in recent human history with thousands of deaths and millions of cases worldwide. Newer research and old experience with other coronaviruses highlighted a probable underlying mechanism of disturbance of the renin-angiotensin system (RAS) that is associated with the intrinsic effects of SARS-CoV-2 infection.

OBJECTIVE

In this review, we aimed to describe the intimate connections between the RAS components, the immune system and COVID-19 pathophysiology.

METHODS

This non-systematic review article summarizes recent evidence on the relationship between COVID-19 and the RAS.

RESULTS

Several studies have indicated that the downregulation of membrane-bound ACE2 may exert a key role for the impairment of immune functions and for COVID-19 patients' outcomes. The downregulation may occur by distinct mechanisms, particularly: (1) the shedding process induced by the SARS-CoV-2 fusion pathway, which reduces the amount of membrane-bound ACE2, stimulating more shedding by the high levels of Angiotensin II; (2) the endocytosis of ACE2 receptor with the virus itself and (3) by the interferon inhibition caused by SARS-CoV-2 effects on the immune system, which leads to a reduction of ACE2 receptor expression.

CONCLUSION

Recent research provides evidence of a reduction of the components of the alternative RAS axis, including ACE2 and Angiotensin-(1-7). In contrast, increased levels of Angiotensin II can activate the AT1 receptor in several organs. Consequently, increased inflammation, thrombosis and angiogenesis occur in patients infected with SARS-COV-2. Attention should be paid to the interactions of the RAS and COVID-19, mainly in the context of novel vaccines and proposed medications.

Lung Adenocarcinoma Syndecan-2 Potentiates Cell Invasiveness

Altered expression of syndecan-2 (SDC2), a heparan sulfate proteoglycan, has been associated with diverse types of human cancers. However, the mechanisms by which SDC2 may contribute to the pathobiology of lung adenocarcinoma have not been previously explored. SDC2 levels were measured in human lung adenocarcinoma samples and lung cancer tissue microarrays using immunohistochemistry and real-time PCR. To understand the role of SDC2 in vitro, SDC2 was silenced or overexpressed in A549 lung adenocarcinoma cells. The invasive capacity of cells was assessed using Matrigel invasion assays and measuring matrix metalloproteinase (MMP) 9 expression. Finally, we assessed tumor growth and metastasis of SDC2-deficient A549 cells in a xenograft tumor model. SDC2 expression was upregulated in malignant epithelial cells and macrophages obtained from human lung adenocarcinomas. Silencing of SDC2 decreased MMP9 expression and attenuated the invasive capacity of A549 lung adenocarcinoma cells. The inhibitory effect of SDC2 silencing on MMP9 expression and cell invasion was reversed by overexpression of MMP9 and syntenin-1. SDC2 silencing attenuated NF-κB p65 subunit nuclear translocation and its binding to the MMP9 promoter, which were restored by overexpression of syntenin-1. SDC2 silencing in vivo reduced tumor mass volume and metastasis. These findings suggest that SDC2 plays an important role in the invasive properties of lung adenocarcinoma cells and that its effects are mediated by syntenin-1. Thus, inhibiting SDC2 expression or activity could serve as a potential therapeutic target to treat lung adenocarcinoma.

Angiotensin-converting enzyme inhibitors may affect pulmonary function in lymphangioleiomyomatosis

INTRODUCTION

A local renin-angiotensin system exists in the pulmonary nodules of lymphangioleiomyomatosis patients. Sirolimus, the standard treatment for lymphangioleiomyomatosis, stabilizes lung function, but all patients do not respond to or tolerate sirolimus. As renin-angiotensin systems may affect tumor growth and metastasis, we questioned if angiotensin-converting enzyme inhibitors affected lymphangioleiomyomatosis disease progression.

METHODS

Retrospective study of 426 patients was performed, examining angiotensin-converting enzyme levels, pulmonary function data, and angiotensin-converting enzyme inhibitor treatment.

RESULTS

Serum angiotensin-converting enzyme levels were elevated in approximately 33% of patients, increased with duration of disease, and were inversely correlated with pulmonary function. Levels decreased significantly over time with sirolimus treatment. Treatment with angiotensin-converting enzyme inhibitors was reported by approximately 15% of patients and was significantly associated with a slower rate of decline in percentage predicted forced expiratory volume (FEV1) and diffusing capacity of the lungs for carbon monoxide (DLCO) in patients not treated with sirolimus. No significant differences in rates of decline of FEV1 or DLCO were seen in patients treated with both inhibitors and sirolimus versus sirolimus alone.

CONCLUSIONS

Angiotensin-converting enzyme inhibitors may slow decline of pulmonary function in patients with lymphangioleiomyomatosis not treated with sirolimus. These inhibitors may be an option or adjunct in the treatment of lymphangioleiomyomatosis. A clinical trial may be warranted to examine this possibility.

FUNDING

NIH.

The Lymphangioleiomyomatosis Lung Cell and Its Human Cell Models

Lymphangioleiomyomatosis (LAM) is a multisystem disease of women, affecting lungs, kidneys, and lymphatics. It is caused by the proliferation of abnormal smooth muscle-like LAM cells, with mutations and loss of heterozygosity in the TSC1 or, more frequently, TSC2 genes. Isolated pulmonary LAM cells have been difficult to maintain in culture, and most studies of LAM lung cells involve mixtures of TSC2 wild-type and TSC2-null cells. A clonal population of LAM lung cells has not been established, making analysis of the cells challenging. Cell lines have been established from angiomyolipomas, a common manifestation of LAM, and from tumors from patients with TSC. Circulating LAM cells have also been isolated from blood and other body fluids. LAM cells may also be identified in clusters apparently derived from lymphatic vessels. Genetics, patterns of antigen expression, and signaling pathways have been studied in LAM lung tissue and in LAM cell models, although rarely all in the same study. We show here that LAM cells manifest differences in these characteristics, depending on the source investigated, suggesting further studies.

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.

Roles of the Angiotensin System in Neonatal Lung Injury and Disease

The renin-angiotensin system (RAS) has long been known as a regulator of blood pressure and fluid homeostasis. In past several decades, local renin-angiotensin systems have been discovered in various tissues and novel actions of angiotensin II (ANGII) have emerged as an immunomodulator and profibrotic molecule. The enzyme responsible for its synthesis, angiotensin-converting-enzyme (ACE), is present in high concentrations in lung tissue. ACE cleaves angiotensin I (ANG I) to generate angiotensin II (ANGII), whereas ACE2 inactivates ANGII and is a negative regulator of the system. The RAS has been implicated in the pathogenesis of pulmonary hypertension, acute lung injury and experimental lung fibrosis. Recent studies in animal and humans indicate that the RAS also plays a critical role in fetal and neonatal lung diseases. Further investigations are needed to better understand the role of RAS, ACE and ACE-2 in neonatal lung injury. With more clarity and understanding, the RAS and/or ACE-2 may ultimately prove to constitute potential therapeutic targets for the treatment of neonatal lung diseases. This manuscript reviews the evidence supporting a role for RAS in neonatal lung injury and discusses new possibilities for therapeutic approaches.

[Pulmonary lymphangioleiomyomatosis: From pathogenesis to management]

INTRODUCTION

Pulmonary lymphangioleiomyomatosis (LAM) is a rare disease affecting mainly young women.

BACKGROUND

The respiratory manifestations are characterized by a progressive cystic destruction of the lung parenchyma. Extrapulmonary involvement includes benign renal tumours called angiomyolipomas and abdominal lymphatic masses called lymphangioleiomyomas. At the pathological level, the cellular proliferation found in LAM is in part due to the presence of mutations in the tumour suppressor genes TSC1 and TSC2 (Tuberous Sclerosis Complex). These mutations lead to the activation of the mTOR pathway, which is currently the main therapeutic target. mTOR inhibitors such as sirolimus or everolimus have shown a beneficial effect on the decline in pulmonary function and a reduction of angiomyolipoma size, but are necessary in only some patients.

PERSPECTIVES

LAM cells have migratory properties mediated by the formation of new lymphatic vessels. They are also able to secrete metalloproteases, which enhance their invasiveness. Moreover, the expression of estrogen and progesterone receptors by LAM cells suggests a possible role for sex hormones in the pathogenesis of the disease.

CONCLUSION

A better understanding of mTOR-independent mechanisms would allow the development of novel therapeutic approaches.

Antibody αPEP13h reacts with lymphangioleiomyomatosis cells in lung nodules

BACKGROUND

Lymphangioleiomyomatosis (LAM) is characterized by the proliferation in the lung, axial lymphatics (eg, lymphangioleiomyomas), and kidney (eg, angiomyolipomas) of abnormal smooth muscle-like LAM cells, which express melanoma antigens such as Pmel17/gp100 and have dysfunctional tumor suppressor tuberous sclerosis complex (TSC) genes TSC2 or TSC1. Histopathologic diagnosis of LAM in lung specimens is based on identification of the Pmel17 protein with the monoclonal antibody HMB-45.

METHODS

We compared the sensitivity of HMB-45 to that of antipeptide antibody αPEP13h, which reacts with a C-terminal peptide of Pmel17. LAM lung nodules were laser-capture microdissected to identify proteins by Western blotting.

RESULTS

HMB-45 recognized approximately 25% of LAM cells within the LAM lung nodules, whereas αPEP13h identified > 82% of LAM cells within these structures in approximately 90% of patients. Whereas HMB-45 reacted with epithelioid but not with spindle-shaped LAM cells, αPEP13h identified both spindle-shaped and epithelioid LAM cells, providing greater sensitivity for detection of all types of LAM cells. HMB-45 recognized Pmel17 in premelanosomal organelles; αPEP13h recognized proteins in the cytoplasm as well as in premelanosomal organelles. Both antibodies recognized a Pmel17 variant of approximately 50 kDa.

CONCLUSIONS

Based on its sensitivity and specificity, αPEP13h may be useful in the diagnosis of LAM and more sensitive than HMB-45.

Microscopic validation of macroscopic in vivo images enabled by same-slide optical and nuclear fusion

It is currently difficult to determine the molecular and cellular basis for radioscintigraphic signals obtained during macroscopic in vivo imaging. The field is in need of technology that helps bridge the macroscopic and microscopic regimes. To solve this problem, we developed a fiducial marker (FM) simultaneously compatible with 2-color near-infrared (NIR) fluorescence (700 and 800 nm), autoradiography, and conventional hematoxylin-eosin (HE) histology.

METHODS

The FM was constructed from an optimized concentration of commercially available human serum albumin, 700- and 800-nm NIR fluorophores, (99m)Tc-pertechnetate, dimethyl sulfoxide, and glutaraldehyde. Lymphangioleiomyomatosis cells coexpressing the sodium iodide symporter and green fluorescent protein were labeled with 700-nm fluorophore and (99m)Tc-pertechnatate and then administered intratracheally into CD-1 mice. After in vivo SPECT imaging and ex vivo SPECT and NIR fluorescence imaging of the lungs, 30-μm frozen sections were prepared and processed for 800-nm NIR fluorophore costaining, autoradiography, and HE staining on the same slide using the FMs to coregister all datasets.

RESULTS

Optimized FMs, composed of 100 μM unlabeled human serum albumin, 1 μM NIR fluorescent human serum albumin, 15% dimethyl sulfoxide, and 3% glutaraldehyde in phosphate-buffered saline (pH 7.4), were prepared within 15 min, displayed homogeneity and stability, and were visible by all imaging modalities, including HE staining. Using these FMs, tissue displaying high signal by SPECT could be dissected and analyzed on the same slide and at the microscopic level for 700-nm NIR fluorescence, 800-nm NIR fluorescence, autoradiography, and HE histopathologic staining.

CONCLUSION

When multimodal FMs are combined with a new technique for simultaneous same-slide NIR fluorescence imaging, autoradiography, and HE staining, macroscopic in vivo images can now be studied unambiguously at the microscopic level.

Evidence for pericyte origin of TSC-associated renal angiomyolipomas and implications for angiotensin receptor inhibition therapy

Nearly all patients with tuberous sclerosis complex (TSC) develop renal angiomyolipomas, although the tumor cell of origin is unknown. We observed decreased renal angiomyolipoma development in patients with TSC2- polycystic kidney disease 1 deletion syndrome and hypertension that were treated from an early age with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers compared with patients who did not receive this therapy. TSC-associated renal angiomyolipomas expressed ANG II type 1 receptors, platelet-derived growth factor receptor-β, desmin, α-smooth muscle actin, and VEGF receptor 2 but did not express the adipocyte marker S100 or the endothelial marker CD31. Sera of TSC patients exhibited increased vascular mural cell-secreted peptides, such as VEGF-A, VEGF-D, soluble VEGF receptor 2, and collagen type IV. These findings suggest that angiomyolipomas may arise from renal pericytes. ANG II treatment of angiomyolipoma cells in vitro resulted in an exaggerated intracellular Ca(2+) response and increased proliferation, which were blocked by the ANG II type 2 receptor antagonist valsartan. Blockade of ANG II signaling may have preventative therapeutic potential for angiomyolipomas.

Osteoprotegerin contributes to the metastatic potential of cells with a dysfunctional TSC2 tumor-suppressor gene

In addition to its effects on bone metabolism, osteoprotegerin (OPG), a soluble member of the tumor necrosis factor family of receptors, promotes smooth muscle cell proliferation and migration and may act as a survival factor for tumor cells. We hypothesized that these cellular mechanisms of OPG may be involved in the growth and proliferation of lymphangioleiomyomatosis (LAM) cells, abnormal smooth muscle-like cells with mutations in one of the tuberous sclerosis complex tumor-suppressor genes (TSC1/TSC2) that cause LAM, a multisystem disease characterized by cystic lung destruction, lymphatic infiltration, and abdominal tumors. Herein, we show that OPG stimulated proliferation of cells cultured from explanted LAM lungs, and selectively induced migration of LAM cells identified by the loss of heterozygosity for TSC2. Consistent with these observations, cells with TSC2 loss of heterozygosity expressed the OPG receptors, receptor activator of NF-κB ligand, syndecan-1, and syndecan-2. LAM lung nodules showed reactivities to antibodies to tumor necrosis factor-related apoptosis-inducing ligand, receptor activator of NF-κB ligand, syndecan-1, and syndecan-2. LAM lung nodules also produced OPG, as shown by expression of OPG mRNA and colocalization of reactivities to anti-OPG and anti-gp100 (HMB45) antibodies in LAM lung nodules. Serum OPG was significantly higher in LAM patients than in normal volunteers. Based on these data, it appears that OPG may have tumor-promoting roles in the pathogenesis of lymphangioleiomyomatosis, perhaps acting as both autocrine and paracrine factors.

Antenatal maternal protein deprivation: sexually dimorphic programming of the pancreatic renin-angiotensin system

As an underlying mechanism of antenatal maternal malnutrition-induced type 2 diabetes mellitus (T2DM), alterations in the local pancreatic renin-angiotensin system (RAS) may play a significant role. We tested the hypothesis that antenatal maternal protein deprivation (AMPD) leads to increased activity of the local pancreatic RAS, with associated hyperglycemia in the adult progeny. Mice dams were fed either control or 50% protein restricted diet (AMPD) starting one week before conception and maintained during complete gestation. Our results demonstrate low birth weight (control 1.5 ± 0.03 and AMPD 1.3 ± 0.03) and sexually dimorphic programming of the pancreatic RAS, with development of hyperglycemia only in the female mice offspring as a consequence of AMPD. No significant difference in serum insulin concentration was observed; however, AMPD was associated with increased mRNA and protein expression of angiotensinogen, renin and angiotensin-converting enzyme (ACE)-1 in male and female offspring. Of importance, mRNA and protein expression of ACE 2 and angiotensin II receptors was up-regulated only in the male offspring, as a consequence of AMPD. We conclude that sexually dimorphic programming of the pancreatic RAS expression is associated with AMPD diet-mediated development of hyperglycemia.

Optimizing treatments for lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM), a multisystem disease predominantly affecting premenopausal women, is associated with cystic lung destruction and lymphatic and kidney tumors. LAM results from the proliferation of a neoplastic cell that has mutations in the tuberous sclerosis complex 1 or 2 genes, leading to activation of a critical regulatory protein, mammalian target of rapamycin. In this report, we discuss the molecular mechanisms regulating LAM cell growth and report the results of therapeutic trials employing new targeted agents. At present, inhibitors of mammalian target of rapamycin such as sirolimus appear to be the most promising therapeutic agents, although drug toxicity and development of resistance are potential problems. As the pathogenesis of LAM is being further recognized, other therapeutic agents such as matrix metalloproteinase inhibitors, statins, interferon, VEGF inhibitors, chloroquine analogs and cyclin-dependent kinase inhibitors, along with sirolimus or a combination of several of these agents, may offer the best hope for effective therapy.

Clinical utility of diagnostic guidelines and putative biomarkers in lymphangioleiomyomatosis

Background

Lymphangioleiomyomatosis is a rare disease occurring almost exclusively in women. Diagnosis often requires surgical biopsy and the clinical course varies between patients with no predictors of progression. We evaluated recent diagnostic guidelines, clinical features and serum biomarkers as diagnostic and prognostic tools.

Methods

Serum vascular endothelial growth factor-D (VEGF-D), angiotensin converting enzyme (ACE), matrix metalloproteinases (MMP) -2 and -9, clinical phenotype, thoracic and abdominal computerised tomography, lung function and quality of life were examined in a cohort of 58 patients. 32 healthy female controls had serum biomarkers measured.

Results

Serum VEGF-D, ACE and total MMP-2 levels were elevated in patients. VEGF-D was the strongest discriminator between patients and controls (median = 1174 vs. 332 pg/ml p < 0.0001 with an area under the receiver operating characteristic curve of 0.967, 95% CI 0.93-1.01). Application of European Respiratory Society criteria allowed a definite diagnosis without biopsy in 69%. Adding VEGF-D measurement to ERS criteria further reduced the need for biopsy by 10%. VEGF-D was associated with lymphatic involvement (p = 0.017) but not the presence of angiomyolipomas.

Conclusions

Combining ERS criteria and serum VEGF-D reduces the need for lung biopsy in LAM. VEGF-D was associated with lymphatic disease but not lung function.

Antenatal maternal hypoxic stress: adaptations of the placental renin-angiotensin system in the mouse

The stress of Antenatal Maternal Hypoxia (AMH) can lead to a number of physiological and pathological changes in both mother and fetus, changes which can be linked to alterations in placental morphology and gene regulation. Recently, in the Brown Norway rat "model" of placental insufficiency, we reported alterations in placental renin-angiotensin system (RAS) genes. Moreover, AMH can lead to reduced oxygen availability to the fetus, similar to a state of placental insufficiency. Thus, in pregnant mice dams we tested the hypothesis that antenatal maternal hypoxic stress leads to alterations in the placental RAS. These alterations may, in part, account for the phenotypic changes in both pregnant mice dams as well as fetus and adult offspring.

METHODS

Pregnant FVB/NJ mice dams were either maintained as controls, or exposed to 10.5% O(2) for 48 h from 15.5 to 17.5 day post coitum. We then measured placental mRNA and protein expression of several RAS genes (n = 4 to 5; P < 0.05 was considered significant).

RESULT

In murine placenta: (1) angiotensinogen (AGT) mRNA was undetectable; however, AGT protein was detectable and increased significantly with AMH. (2) In AMH, although renin mRNA was reduced protein expression increased, in association with decreased microRNA (miRNA) 199b, which can lead to increased renin translation. (3) Also in AMH placenta, angiotensin converting enzyme (ACE) -1 mRNA was unaltered; however, protein expression increased significantly, in association with decreased miRNA 27a, which can result in increased ACE-1 translation. (4) In AMH placenta, ACE-2 mRNA was reduced significantly, whereas protein expression was significantly greater, in association with reduced miRNA 429. (5) In AMH placenta, angiotensin II type (AT) -1a receptor mRNA expression was unaltered while AT-1b receptor mRNA was undetectable in both groups. Moreover, AT-1 receptor protein expression was unchanged in response to AMH. (6) AT-2 receptor mRNA and proteins were undetectable in both groups.

CONCLUSION

The normal murine placenta possesses several components of RAS, and in response to AMH several of these elements undergo important changes. In addition, differential expression of RAS mRNA, miRNA and protein, indicate post-transcriptional regulatory mechanisms involved with hypoxic stress, and necessitate further investigation.

Erythropoietin-driven proliferation of cells with mutations in the tumor suppressor gene TSC2

Lymphangioleiomyomatosis (LAM) is characterized by cystic lung destruction, resulting from proliferation of smooth-muscle-like cells, which have mutations in the tumor suppressor genes TSC1 or TSC2. Among 277 LAM patients, severe disease was associated with hypoxia and elevated red blood cell indexes that accompanied reduced pulmonary function. Because high red cell indexes could result from hypoxemia-induced erythropoietin (EPO) production, and EPO is a smooth muscle cell mitogen, we investigated effects of EPO in human cells with genetic loss of tuberin function, and we found that EPO increased proliferation of human TSC2-/-, but not of TSC2+/-, cells. A discrete population of cells grown from explanted lungs was characterized by the presence of EPO receptor and loss of heterozygosity for TSC2, consistent with EPO involvement. In LAM cells from lung nodules, EPO was localized to the extracellular matrix, supporting evidence for activation of an EPO-driven signaling pathway. Although the high red cell mass of LAM patients could be related to advanced disease, we propose that EPO, synthesized in response to episodic hypoxia, may increase disease progression by enhancing the proliferation of LAM cells.

Antenatal maternal hypoxic stress: adaptations in fetal lung Renin-Angiotensin system

Antenatal maternal hypoxia (AMH) can lead to intrauterine growth restriction (IUGR), as well as idiopathic pulmonary hypertension of newborn and adult, the latter of which may be a consequence of alterations in the local pulmonary renin-angiotensin system (RAS). Little is known of these adaptations, however. Thus, we tested the hypothesis that antenatal maternal hypoxia is associated with alterations in gene and protein expression of the pulmonary renin-angiotensin system, which may play an important role in pulmonary disorders in the offspring. In FVB/NJ mice, we studied messenger RNA (mRNA) and protein expression, as well as promoter DNA methylation and microRNA (miRNA) levels in response to 48 hours hypoxia (10.5% O(2)) at 15.5 day post coitum (DPC). In response to AMH, the pulmonary mRNA levels of angiotensin-converting enzyme (ACE) 1.2, ACE-2, and angiotensin II type 1b (AT-1b) receptors were increased significantly, as compared to controls (N = 4). In response to antenatal hypoxia, pulmonary protein levels of renin and ACE-2 also were increased significantly, whereas ACE-1 protein expression was reduced. In fetal lungs, we also observed reduced expression of the miRNAs: mmu-mir -199b, -27b, -200b, and -468 that putatively increase the translation of renin, ACE-1, ACE-2, and AT-1 receptors, respectively. In response to AMH, promoter methylation of ACE was unchanged. We conclude that AMH leads to changes in expression of pulmonary RAS of fetal mice. The possible implications of these changes for the regulation of pulmonary vascular contractility in later life remain to be explored.

The natural history of lymphangioleiomyomatosis: markers of severity, rate of progression and prognosis

Lymphangioleiomyomatosis (LAM) is a multisystem disease of women, characterized by proliferation of abnormal smooth muscle-like cells (LAM cells) that can metastasize, leading to the formation of lung cysts, fluid-filled cystic structures in the axial lymphatics (e.g., lymphangioleiomyomas), and angiomyolipomas, benign tumors usually involving the kidneys, comprising LAM cells and adipocytes, intermixed with incompletely developed vascular structures. LAM occurs sporadically or in association with tuberous sclerosis complex, an autosomal dominant syndrome characterized by hamartoma-like tumor growths. LAM may present with progressive dyspnea, recurrent pneumothorax, chylothorax, or abdominal hemorrhage. Computed tomography scans show thin-walled cysts scattered throughout the lungs, abdominal angiomyolipomas, and lymphangioleiomyomas. Pulmonary function tests show reduced flow rates (FEV(1)) and diffusion capacity (DL(CO)). Exercise testing may reveal gas exchange abnormalities, ventilatory limitation, and hypoxemia, which can occur with near-normal lung function. Methods used to grade the severity of disease are the LAM histology score, semiquantitative and quantitative computer tomography, pulmonary function testing, and cardiopulmonary exercise testing. Currently, progression of disease is best assessed by serial measurements of FEV(1), DL(CO), and exercise performance. New quantitative radiographic techniques that may offer advantages over physiologic testing are now available. Several potential biomarkers, such as LAM cells in peripheral blood, urine, and chyle and chemokines, vascular endothelial growth factors, and matrix metalloproteinases, may be useful as diagnostic tools or markers of organ involvement, disease severity, and progression.

Lymphangioleiomyomatosis and TSC2-/- cells

The cells comprising pulmonary lymphangioleiomyomatosis (LAM) and renal angiomyolipomas (AMLs) are heterogeneous, with variable mixtures of cells exhibiting differentiation towards smooth muscle, fat, and vessels. Cells grown from LAM and AMLs have likewise tended to be heterogeneous. The discovery that LAM and AMLs contain cells with mutations in the TSC1 or TSC2 genes is allowing investigators to discriminate between "two-hit" cells and neighboring cells, providing insights into disease pathogenesis. In rare cases, it has been possible to derive cells from human tumors, including AMLs and TSC skin tumors that are highly enriched for TSC2(-/-) cells. Cells derived from an Eker rat uterine leiomyoma (ELT3 cells) are Tsc2-null and these have been used in a rodent cell models for LAM. Further improvements in the ability to reliably grow well-characterized TSC2(-/-) cells from human tumors are critical to developing in vitro and in vivo model systems for studies of LAM pathogenesis and treatment.

Involvement of lymphatics in lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM), a rare multisystem disease, occurs primarily in women, with cystic destruction of the lungs, abdominal tumors, and involvement of the axial lymphatics in the thorax and abdomen. To understand the pathogenesis of LAM, we initiated a longitudinal study of patients with LAM; over 500 patients have been enrolled. LAM results from the proliferation of a neoplastic cell (LAM cell), which has mutations in the tuberous sclerosis complex (TSC) genes, TSC1 or TSC2. Consistent with their metastatic behavior, LAM cells were isolated from blood, urine, and chylous effusions. Surface proteins on LAM cells include those found on metastatic cells and those involved in cell migration. In the lung, LAM cells are found clustered in nodules, which appear in the walls of the cysts, and in the interstitium. LAM lung nodules are traversed by slit-like vascular structures, with lining cells showing reactivity with antibodies against components of lymphatic endothelial cells. The axial lymphatics appear to be infiltrated by LAM cells, which may result in obstruction and formation of chyle-filled lymphangioleiomyomas. LAM cell clusters have been isolated from chylous pleural effusions, and it is hypothesized that these clusters may be responsible for metastatic spread of LAM cells via lymphatic vessels. Consistent with a lymphangiogenic process, levels of VEGF-D, a lymphangiogenic factor, were higher in sera of patients with LAM and lymphatic involvement (i.e., lymphangioleiomyoma, adenopathy) than in healthy volunteers or LAM patients with cystic disease limited to the lung. These findings are consistent with an important function for lymphangiogenesis in LAM.

Reversible airflow obstruction in lymphangioleiomyomatosis

BACKGROUND

We previously reported that approximately one-fourth of patients with lymphangioleiomyomatosis (LAM) may respond to therapy with bronchodilators. However, the validity of those observations has been questioned. The aims of the present study were to determine the prevalence of reversible airflow obstruction in patients with LAM and to identify associated clinical and physiologic parameters.

METHODS

First, the clinical and physiologic characteristics of 235 patients were analyzed to determine the frequency of the response to albuterol during a total of 2,307 visits. Second, we prospectively evaluated the response to albuterol (2.5 mg) and ipratropium (500 mug) in 130 patients, and correlated their responses with their clinical and physiologic characteristics.

RESULTS

In the retrospective study, 51% of the patients responded at least once to bronchodilators; of these, 12% responded >/= 50% of the time. A higher frequency of positive bronchodilator responses was associated with greater rates of decline in FEV(1) and diffusing capacity of the lung for carbon monoxide (Dlco). In the prospective study, 39 patients (30%) responded to bronchodilators, including 12 to ipratropium, 9 to albuterol, and 18 to both. The prevalence of asthma and smoking in the 39 responders was not different from that seen in the 91 nonresponders. Patients who responded to ipratropium, albuterol, or both had significantly (p < 0.02) lower FEV(1) and Dlco, and a greater rate of FEV(1) decline (p = 0.044) and Dlco decline (p = 0.039) than patients who did not respond to these bronchodilators. After adjusting for FEV(1)/FVC ratio, Dlco decline also was greater in responders than in nonresponders (p = 0.009).

CONCLUSIONS

Patients with LAM may have partially reversible airflow obstruction. A positive response to bronchodilators is associated with an accelerated rate of decline in pulmonary function.

Lymphatic involvement in lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a rare, multisystem disease affecting primarily premenopausal women. The disease is characterized by cystic lung disease, at times leading to respiratory compromise, abdominal tumors (in particular, renal angiomyolipomas), and involvement of the axial lymphatics (e.g., adenopathy, lymphangioleiomyomas). Disease results from the proliferation of neoplastic cells (LAM cells), which, in many cases, have a smooth muscle cell phenotype, express melanoma antigens, and have mutations in one of the tuberous sclerosis complex genes (TSC1 or TSC2). In the lung, LAM cells found in the vicinity of cysts are, at times, localized in nodules and may be responsible for cyst formation through the production of proteases. Lymphatic channels, expressing characteristic lymphatic endothelial cell markers, are found within the LAM lung nodules. LAM cells may also be localized within the walls of the axial lymphatics, and, in some cases, penetrate the wall and proliferate in the surrounding adipose tissue. Consistent with extensive lymphatic involvement in LAM, the serum concentration of VEGF-D, a lymphangiogenic factor, is higher in LAM patients than in healthy volunteers.

Oxidative stress contributes to pulmonary hypertension in the transgenic (mRen2)27 rat

The transgenic (mRen2)27 (Ren2) rat overexpresses mouse renin in extrarenal tissues, causing increased local synthesis of ANG II, oxidative stress, and hypertension. However, little is known about the role of oxidative stress induced by the tissue renin-angiotensin system (RAS) as a contributing factor in pulmonary hypertension (PH). Using male Ren2 rats, we test the hypothesis that lung tissue RAS overexpression and resultant oxidative stress contribute to PH and pulmonary vascular remodeling. Mean arterial pressure (MAP), right ventricular systolic pressure (RVSP), and wall thickness of small pulmonary arteries (PA), as well as intrapulmonary NADPH oxidase activity and subunit protein expression and reactive oxygen species (ROS), were compared in age-matched Ren2 and Sprague-Dawley (SD) rats pretreated with the SOD/catalase mimetic tempol for 21 days. In placebo-treated Ren2 rats, MAP and RVSP, as well as intrapulmonary NADPH oxidase activity and subunits (Nox2, p22phox, and Rac-1) and ROS, were elevated compared with placebo-treated SD rats (P < 0.05). Tempol decreased RVSP (P < 0.05), but not MAP, in Ren2 rats. Tempol also reduced intrapulmonary NADPH oxidase activity, Nox2, p22phox, and Rac-1 protein expression, and ROS in Ren2 rats (P < 0.05). Compared with SD rats, the cross-sectional surface area of small PA was 38% greater (P < 0.001) and luminal surface area was 54% less (P < 0.001) in Ren2 rats. Wall surface area was reduced and luminal area was increased in tempol-treated SD and Ren2 rats compared with untreated controls (P < 0.05). Collectively, the results of this investigation support a seminal role for enhanced tissue RAS/oxidative stress as factors in development of PH and pulmonary vascular remodeling.

Lymphangioleiomyomatosis and tuberous sclerosis complex

Lymphangioleiomyomatosis (LAM) is a rare multisystemic disease of women of child-bearing age and affects mainly the lungs, promoting cystic destruction of lung parenchyma or leading to abdominal tumor formation (e.g., angiomyolipomas, lymphangioleiomyomas). LAM can arise sporadically or in association with tuberous sclerosis complex (TSC), an autosomal inherited syndrome characterized by hamartoma-like tumor growth and pathologic features that are distinct from manifestations of pulmonary LAM. A substantial body of evidence has now been gathered suggesting that the two diseases share a common genetic origin. TSC is caused by mutations in two genes, TSC1 on chromosome 9q34 and TSC2 on 16p13. Both of these genes are tumor suppressor genes encoding hamartin (TSC1) and tuberin (TSC2). Sporadic LAM is correlated with a mutation in the TSC2 gene and tuberin appears to play a central role in the pathogenesis of the disease. A TSC2 loss or mutation leads to disruption of the tuberin-hamartin heteromer and dysregulation of S6K1 activation leading to aberrant cell proliferation seen in LAM disease. The extremely diverse clinical and radiologic features of the disease and the complex therapeutic approach are reviewed in detail. Although new therapeutic agents have been tested, to date no effective treatment has been proposed and the prognosis of patients with LAM remains poor. As long as newer therapeutic agents do not change this picture, lung transplantation remains the last hope for patients with respiratory failure at the advanced stage of the disease.