The common TMEM173 HAQ, AQ alleles rescue CD4 T cellpenia, restore T-regs, and prevent SAVI (N153S) inflammatory disease in mice

The significance of STING (encoded by the TMEM173 gene), in tissue inflammation and cancer immunotherapy has been increasingly recognized. Intriguingly, common human STING alleles R71H-G230A-R293Q (HAQ) and G230A-R293Q (AQ) are carried by ~60% of East Asians and ~40% of Africans, respectively. Here, we examine the modulatory effects of HAQ, AQ alleles on STING-associated vasculopathy with onset in infancy (SAVI), an autosomal dominant, fatal inflammatory disease caused by gain-of-function human STING mutations. CD4 T cellpenia is evident in SAVI patients and mouse models. Using STING knock-in mice expressing common human STING alleles HAQ, AQ, and Q293, we found that HAQ, AQ, and Q293 splenocytes resist STING-mediated cell death ex vivo, establishing a critical role of STING residue 293 in cell death. The HAQ/SAVI(N153S) and AQ/SAVI(N153S) mice did not have CD4 T cellpenia. The HAQ/SAVI(N153S), AQ/SAVI(N153S) mice have more (~10-fold, ~20-fold, respectively) T-regs than WT/SAVI(N153S) mice. Remarkably, while they have comparable TBK1, IRF3, and NFκB activation as the WT/SAVI, the AQ/SAVI mice have no tissue inflammation, regular body weight, and normal lifespan. We propose that STING activation promotes tissue inflammation by depleting T-regs cells in vivo. Billions of modern humans have the dominant HAQ, AQ alleles. STING research and STING-targeting immunotherapy should consider TMEM173 heterogeneity in humans.

Non-Interferon-Dependent Role of STING Signaling in Pulmonary Hypertension

BACKGROUND

Patients with constitutive activation of DNA-sensing pathway through stimulator of IFN (interferon) genes (STING), such as those with STING-associated vasculopathy with onset in infancy, develop pulmonary hypertension (PH). However, the role of STING signaling in general PH patients is heretofore undescribed. Here, we seek to investigate the role of STING in PH development.

METHODS

STING expression in patient lung samples was examined. PH was induced in global STING-deficient mice and global type I IFN receptor 1-deficient mice using bleomycin or chronic hypoxia exposure. PH development was evaluated by right ventricular systolic pressure and Fulton index, with additional histological and flow cytometric analysis. VEGF (vascular endothelial growth factor) expression on murine immune cells was quantified and evaluated with multiplex and flow cytometry. Human myeloid-derived cells were differentiated from peripheral blood mononuclear cells and treated with either STING agonist or STING antagonist for evaluation of VEGF secretion.

RESULTS

Global STING deficiency protects mice from PH development, and STING-associated PH seems independent of type I IFN signaling. Furthermore, a role for STING-VEGF signaling pathway in PH development was demonstrated, with altered VEGF secretion in murine pulmonary infiltrated myeloid cells in a STING-dependent manner. In addition, pharmacological manipulation of STING in human myeloid-derived cells supports in vivo findings. Finally, a potential role of STING-VEGF-mediated apoptosis in disease development and progression was illustrated, providing a roadmap toward potential therapeutic applications.

CONCLUSIONS

Overall, these data provide concrete evidence of STING involvement in PH, establishing biological plausibility for STING-related therapies in PH treatment.

ACE2 overexpression in corticotropin-releasing-hormone cells offers protection against pulmonary hypertension

Background

Pulmonary hypertension (PH), characterized by elevated pulmonary pressure and right heart failure, is a systemic disease involving inappropriate sympathetic activation and an impaired gut-brain-lung axis. Global overexpression of angiotensin converting enzyme 2 (ACE2), a cardiopulmonary protective enzyme of the renin-angiotensin system, attenuates PH induced by chronic hypoxia. Neurons within the paraventricular nucleus of the hypothalamus (PVN) that synthesize corticotropin-releasing hormone (CRH) are activated by stressors, like hypoxia, and this activation augments sympathetic outflow to cardiovascular tissues. These data coupled with our observations that ACE2 overexpression in CRH cells (CRH-ACE2KI mice) decreases anxiety-like behavior via suppression of hypothalamic-pituitary-adrenal (HPA) axis activity by decreasing CRH synthesis, led us to hypothesize that selective ACE2 overexpression in CRH neurons would protect against hypoxia-induced PH.

Methods

CRH-ACE2KI and WT male and female mice were exposed to chronic hypoxia (10%O2) or normoxia (21%O2) for 4 weeks in a ventilated chamber with continuous monitoring of oxygen and carbon dioxide concentrations (n = 7-10/group). Pulmonary hemodynamics were measured with Millar pressure catheters then tissues were collected for histological analyses.

Results

Chronic hypoxia induced a significant increase (36.4%) in right ventricular (RV) systolic pressure (RVSP) in WT mice, which was not observed in CRH-ACE2KI mice. No significant differences in RVSP were observed between male and female mice in any of the groups.

Conclusion

Overexpression of ACE2 in CRH cells was protective against hypoxia-induced PH. Since the majority of expression of CRH is in brain nuclei such as paraventricular nucleus of the hypothalamus (PVN) and/or central nucleus of the amygdala (CeA) these data indicate that the protective effects of ACE2 are, at least in part, centrally mediated. This contributes to the systemic nature of PH disease and that CRH neurons may play an important role in PH.

Defining the age-dependent and tissue-specific circadian transcriptome in male mice

Cellular circadian clocks direct a daily transcriptional program that supports homeostasis and resilience. Emerging evidence has demonstrated age-associated changes in circadian functions. To define age-dependent changes at the systems level, we profile the circadian transcriptome in the hypothalamus, lung, heart, kidney, skeletal muscle, and adrenal gland in three age groups. We find age-dependent and tissue-specific clock output changes. Aging reduces the number of rhythmically expressed genes (REGs), indicative of weakened circadian control. REGs are enriched for the hallmarks of aging, adding another dimension to our understanding of aging. Analyzing differential gene expression within a tissue at four different times of day identifies distinct clusters of differentially expressed genes (DEGs). Increased variability of gene expression across the day is a common feature of aged tissues. This analysis extends the landscape for understanding aging and highlights the impact of aging on circadian clock function and temporal changes in gene expression.

Cardiopulmonary disease as sequelae of long-term COVID-19: Current perspectives and challenges

COVID-19 infection primarily targets the lungs, which in severe cases progresses to cytokine storm, acute respiratory distress syndrome, multiorgan dysfunction, and shock. Survivors are now presenting evidence of cardiopulmonary sequelae such as persistent right ventricular dysfunction, chronic thrombosis, lung fibrosis, and pulmonary hypertension. This review will summarize the current knowledge on long-term cardiopulmonary sequelae of COVID-19 and provide a framework for approaching the diagnosis and management of these entities. We will also identify research priorities to address areas of uncertainty and improve the quality of care provided to these patients.

Apparent Absence of BMAL1-Dependent Skeletal Muscle-Kidney Cross Talk in Mice

BMAL1 is a core mammalian circadian clock transcription factor responsible for the regulation of the expression of thousands of genes. Previously, male skeletal-muscle-specific BMAL1-inducible-knockout (iMS-BMAL1 KO) mice have been described as a model that exhibits an aging-like phenotype with an altered gait, reduced mobility, muscle weakness, and impaired glucose uptake. Given this aging phenotype and that chronic kidney disease is a disease of aging, the goal of this study was to determine if iMS-BMAL1 KO mice exhibit a renal phenotype. Male iMS-BMAL1 KO and control mice were challenged with a low potassium diet for five days. Both genotypes responded appropriately by conserving urinary potassium. The iMS-BMAL1 KO mice excreted less potassium during the rest phase during the normal diet but there was no genotype difference during the active phase. Next, iMS-BMAL1 KO and control mice were used to compare markers of kidney injury and assess renal function before and after a phase advance protocol. Following phase advance, no differences were detected in renal mitochondrial function in iMS-BMAL1 KO mice compared to control mice. Additionally, the glomerular filtration rate and renal morphology were similar between groups in response to phase advance. Disruption of the clock in skeletal muscle tissue activates inflammatory pathways within the kidney of male mice, and there is evidence of this affecting other organs, such as the lungs. However, there were no signs of renal injury or altered function following clock disruption of skeletal muscle under the conditions tested.

A wrinkle in time: circadian biology in pulmonary vascular health and disease

An often overlooked element of pulmonary vascular disease is time. Cellular responses to time, which are regulated directly by the core circadian clock, have only recently been elucidated. Despite an extensive collection of data regarding the role of rhythmic contribution to disease pathogenesis (such as systemic hypertension, coronary artery, and renal disease), the roles of key circadian transcription factors in pulmonary hypertension remain understudied. This is despite a large degree of overlap in the pulmonary hypertension and circadian rhythm fields, not only including shared signaling pathways, but also cell-specific effects of the core clock that are known to result in both protective and adverse lung vessel changes. Therefore, the goal of this review is to summarize the current dialogue regarding common pathways in circadian biology, with a specific emphasis on its implications in the progression of pulmonary hypertension. In this work, we emphasize specific proteins involved in the regulation of the core molecular clock while noting the circadian cell-specific changes relevant to vascular remodeling. Finally, we apply this knowledge to the optimization of medical therapy, with a focus on sleep hygiene and the role of chronopharmacology in patients with this disease. In dissecting the unique relationship between time and cellular biology, we aim to provide valuable insight into the practical implications of considering time as a therapeutic variable. Armed with this information, physicians will be positioned to more efficiently use the full four dimensions of patient care, resulting in improved morbidity and mortality of pulmonary hypertension patients.

Fecal matter transplant from Ace2 overexpressing mice counteracts chronic hypoxia-induced pulmonary hypertension

Recent evidence suggests pulmonary hypertension (PH), a disease of the pulmonary vasculature actually has multiorgan pathophysiology and perhaps etiology. Herein, we demonstrated that fecal matter transplantation from angiotensin-converting enzyme 2 overexpressing mice counteracted the effects of chronic hypoxia to prevent pulmonary hypertension, neuroinflammation, and gut dysbiosis in wild type recipients.

Circadian Rhythm Effects on the Molecular Regulation of Physiological Systems

Nearly every system within the body contains an intrinsic cellular circadian clock. The circadian clock contributes to the regulation of a variety of homeostatic processes in mammals through the regulation of gene expression. Circadian disruption of physiological systems is associated with pathophysiological disorders. Here, we review the current understanding of the molecular mechanisms contributing to the known circadian rhythms in physiological function. This article focuses on what is known in humans, along with discoveries made with cell and rodent models. In particular, the impact of circadian clock components in metabolic, cardiovascular, endocrine, musculoskeletal, immune, and central nervous systems are discussed. © 2021 American Physiological Society. Compr Physiol 11:1-30, 2021.

Likelihood-based tests for detecting circadian rhythmicity and differential circadian patterns in transcriptomic applications

Circadian rhythmicity in transcriptomic profiles has been shown in many physiological processes, and the disruption of circadian patterns has been found to associate with several diseases. In this paper, we developed a series of likelihood-based methods to detect (i) circadian rhythmicity (denoted as LR_rhythmicity) and (ii) differential circadian patterns comparing two experimental conditions (denoted as LR_diff). In terms of circadian rhythmicity detection, we demonstrated that our proposed LR_rhythmicity could better control the type I error rate compared to existing methods under a wide variety of simulation settings. In terms of differential circadian patterns, we developed methods in detecting differential amplitude, differential phase, differential basal level and differential fit, which also successfully controlled the type I error rate. In addition, we demonstrated that the proposed LR_diff could achieve higher statistical power in detecting differential fit, compared to existing methods. The superior performance of LR_rhythmicity and LR_diff was demonstrated in four real data applications, including a brain aging data (gene expression microarray data of human postmortem brain), a time-restricted feeding data (RNA sequencing data of human skeletal muscles) and a scRNAseq data (single cell RNA sequencing data of mouse suprachiasmatic nucleus). An R package for our methods is publicly available on GitHub https://github.com/diffCircadian/diffCircadian.

The Third Man: DNA sensing as espionage in pulmonary vascular health and disease

For as long as nucleic acids have been utilized to vertically and horizontally transfer genetic material, living organisms have had to develop methods of recognizing cytosolic DNA as either pathogenic (microbial invasion) or physiologic (mitosis and cellular proliferation). Derangement in key signaling molecules involved in these pathways of DNA sensing result in a family of diseases labeled interferonopathies. An interferonopathy, characterized by constitutive expression of type I interferons, ultimately manifests as severe autoimmune disease at a young age. Afflicted patients present with a constellation of immune-mediated conditions, including primary lung manifestations such as pulmonary fibrosis and pulmonary hypertension. The latter condition is especially interesting in light of the known role that DNA damage plays in a variety of types of inherited and induced pulmonary hypertension, with free DNA detection elevated in the circulation of affected individuals. While little is known regarding the role of cytosolic DNA sensing in development of pulmonary vascular disease, exciting new research in the related fields of immunology and oncology potentially sheds light on future areas of fruitful exploration. As such, the goal of this review is to summarize the state of the field of nucleic acid sensing, extrapolating common shared pathways that parallel our knowledge of pulmonary hypertension, in a molecular and cell-specific manner. Principles of DNA sensing related to known pulmonary injury inducing stimuli are also evaluated, in addition to potential therapeutic targets. Finally, future directions in pulmonary hypertension research and treatments will be briefly discussed.

Idiopathic pulmonary fibrosis and pulmonary hypertension: Heracles meets the Hydra

Idiopathic pulmonary fibrosis (IPF) is a fatal lung disease where the additional presence of pulmonary hypertension (PH) reduces survival. In particular, the presence of coexistent pulmonary vascular disease in patients with advanced lung parenchymal disease results in worse outcomes than either diagnosis alone. This is true with respect to the natural histories of these diseases, outcomes with medical therapies, and even outcomes following lung transplantation. Consequently, there is a striking need for improved treatments for PH in the setting of IPF. In this review, we summarize existing therapies from the perspective of molecular mechanisms underlying lung fibrosis and vasoconstriction/vascular remodelling and discuss potential future targets for pharmacotherapy. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.1/issuetoc.

Gut Pathology and Its Rescue by ACE2 (Angiotensin-Converting Enzyme 2) in Hypoxia-Induced Pulmonary Hypertension

Therapeutic advances for pulmonary hypertension (PH) have been incremental because of the focus on the pulmonary vasculature in PH pathology. Here, we evaluate the concept that PH is, rather, a systemic disorder involving interplay among multiorgan systems, including brain, gut, and lungs. Therefore, the objective of this study was to evaluate the hypothesis that PH is associated with a dysfunctional brain-gut-lung axis and that global overexpression of ACE2 (angiotensin-converting enzyme 2) rebalances this axis and protects against PH. ACE2 knockin and wild-type (WT; C57BL/6) mice were subjected to chronic hypoxia (10% FIO2) or room air for 4 weeks. Cardiopulmonary hemodynamics, histology, immunohistochemistry, and fecal 16S rRNA microbial gene analyses were evaluated. Hypoxia significantly increased right ventricular systolic pressure, sympathetic activity as well as the number and activation of microglia in the paraventricular nucleus of the hypothalamus in WT mice. This was associated with a significant increase in muscularis layer thickening and decreases in both villi length and goblet cells and altered gut microbiota. Global overexpression of ACE2 prevented changes in hypoxia-induced pulmonary and gut pathophysiology and established distinct microbial communities from WT hypoxia mice. Furthermore, WT mice subjected to fecal matter transfer from ACE2 knockin mice were resistant to hypoxia-induced PH compared with their controls receiving WT fecal matter transfer. These observations demonstrate that ACE2 ameliorates these hypoxia-induced pathologies and attenuates PH. The data implicate dysfunctional brain-gut-lung communication in PH and provide novel avenues for therapeutic interventions.

Emergency myelopoiesis contributes to immune cell exhaustion and pulmonary vascular remodelling

BACKGROUND AND PURPOSE

Pulmonary hypertension (PH) secondary to chronic lung disease (World Health Organization Group 3 PH) is deadly, with lung transplant being the only available long-term treatment option. Myeloid-derived cells are known to affect progression of both pulmonary fibrosis and PH, although the mechanism of action is unknown. Therefore, we investigated the effect of myeloid cell proliferation induced by emergency myelopoiesis on development of PH and therapy directed against programmed death-ligand 1 (PD-L1), expressed by myeloid cells in prevention of pulmonary vascular remodelling.

EXPERIMENTAL APPROACH

LysM.Cre-DTR ("mDTR") mice were injected with bleomycin (0.018 U·g^-1 , i.p.) while receiving either vehicle or diphtheria toxin (DT; 100 ng, i.p.) to induce severe PH. Approximately 4 weeks after initiation of bleomycin protocol, right ventricular pressure measurements were performed and tissue samples collected for histologic assessment. In a separate experiment, DT-treated mice were given anti-PD-L1 antibody (αPD-L1; 500 μg, i.p.) preventive treatment before bleomycin administration.

KEY RESULTS

Mice undergoing induction of emergency myelopoiesis displayed more severe PH, right ventricular remodelling and pulmonary vascular muscularization compared to controls, without a change in lung fibrosis. This worsening of PH was associated with increased pulmonary myeloid-derived suppressor cell (MDSC), particularly polymorphonuclear MDSC (PMN-MDSC). Treatment with αPD-L1 normalized pulmonary pressures. PD-L1 expression was likewise found to be elevated on circulating PMN-MDSC from patients with interstitial lung disease and PH.

CONCLUSIONS AND IMPLICATIONS

PD-L1 is a viable therapeutic target in PH, acting through a signalling axis involving MDSC.

LINKED ARTICLES

This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.1/issuetoc.

Chemokine signaling axis between endothelial and myeloid cells regulates development of pulmonary hypertension associated with pulmonary fibrosis and hypoxia

Pulmonary hypertension complicates the care of many patients with chronic lung diseases (defined as Group 3 pulmonary hypertension), yet the mechanisms that mediate the development of pulmonary vascular disease are not clearly defined. Despite being the most prevalent form of pulmonary hypertension, to date there is no approved treatment for patients with disease. Myeloid-derived suppressor cells (MDSCs) and endothelial cells in the lung express the chemokine receptor CXCR2, implicated in the evolution of both neoplastic and pulmonary vascular remodeling. However, precise cellular contribution to lung disease is unknown. Therefore, we used mice with tissue-specific deletion of CXCR2 to investigate the role of this receptor in Group 3 pulmonary hypertension. Deletion of CXCR2 in myeloid cells attenuated the recruitment of polymorphonuclear MDSCs to the lungs, inhibited vascular remodeling, and protected against pulmonary hypertension. Conversely, loss of CXCR2 in endothelial cells resulted in worsened vascular remodeling, associated with increased MDSC migratory capacity attributable to increased ligand availability, consistent with analyzed patient sample data. Taken together, these data suggest that CXCR2 regulates MDSC activation, informing potential therapeutic application of MDSC-targeted treatments.

Abstract 037: Global ACE2 Over-Expression is Protective Against a Dysfunctional Brain-Gut-Lung Axis in Hypoxia-Induced Pulmonary Hypertension

Background and Objectives: Angiotensin converting enzyme 2 (ACE2), key enzyme of the vasoprotective axis of the renin angiotensin system, has been implicated in many pulmonary diseases including pulmonary hypertension (PH). Plasma levels of ACE2 in group-1 pulmonary hypertensive patients are decreased and activation of this enzyme by small molecule activators, overexpression or administration of recombinant ACE2, all have beneficial outcomes on PH. Furthermore, involvement of neuroinflammation and impaired brain-gut-lung axis have been proposed in PH. These observations have led us to propose that beneficial effect of ACE2 are, at least in part, due to attenuation of neuroinflammation and rebalancing of gut microbiota and improvement in pathology.

Methods: ACE2 knock-in (ACE2KI) and wild-type mice (WT; C57BL/6) were subjected to hypoxia (10% FIO2) or room air for 4 weeks (n=8-10/group). Right ventricular systolic pressure (RVSP), and electrocardiography were performed, tissues examined by standard histological techniques, and stool collected for 16S rRNA analysis at 4 weeks.

Results: Hypoxia-induced significantly increased RVSP in WT but not ACE2KI mice (20±1.6 vs 32±1.9, p<0.001 and 24.3±1.5 vs 21±1.3mmHg, respectively). This was accompanied in WT, but not ACEKI, by ~5-fold increase in sympathetic activation (LF/HF; p<0.001) and ~2-fold increase (p<0.01) in microglia activation in the paraventricular nucleus (PVN) of the hypothalamus. There was increased fibrotic area (p<0.01) and muscularis layer thickening (p<0.001) and decreased villi length (p<0.01) and goblet cells (p<0.001) in the small intestine of WT but not ACE2KI mice following hypoxia. Finally, beta diversity of gut microbiome of WT, but not ACE2KI, mice was significantly altered by hypoxia (ANOSIM P=0.001).

Conclusions: Microglial activation in PVN, sympathetic activation, gut pathology and altered gut microbiome are associated with hypoxia-induced PH. Global overexpression of ACE2 prevents all of these parameters. The involvement of organs other than lungs, and ACE2, present novel therapeutic potentials for PH.

Abstract P235: Altered Brain-Gut-Lung Axis in Hypoxia-Induced Pulmonary Hypertension

Background: Recent evidence indicate that gut microbiota plays important role in pathogenesis and progression of chronic lung diseases such as asthma, respiratory infections and COPD. However, implications of this gut-lung communication and involvement of peripheral and neural immune system in pulmonary hypertension (PH) remains unknown.

Objective: Investigate the hypothesis that increased activation of microglial cells, autonomic nervous system, altered gut pathology and gut microbiota are associated with PH suggesting a dysfunctional brain-gut-lung axis in PH pathology.

Methods: C57BL/6 (WT) male mice were exposed to chronic hypoxia (10%O2) or Normoxia for 4 weeks in a ventilated chamber (n=5-8/group). Millar pressure catheter was used to measure pulmonary hemodynamics, Iba1 specific antibody for immunohistochemical analysis of microglial cells and fecal 16S rDNA for gut microbiota analysis.

Results: Hypoxia induced a 77% increase in right ventricular (RV) systolic pressure (RVSP: N:19.5 ± 2 mmHg Vs H:33.7 ± 2, p<0.001) and RV hypertrophy (RVH: N: 0.139 ± 0.09 Vs H: 0.192± 0.008). This was associated with substantial enhancement in sympathetic activity (LF/HF: N:0.23 ± 0.8 mmHg Vs H: 1.19 ± 0.08, p<0.001) and increase in number of microglial cells in autonomic brain regions, predominantly the paraventricular nucleus of hypothalamus. Characteristics of gut pathology such as ~50% increase in fibrotic area and muscularis layer thickness and significantly decreased villi length and number of goblet cells in small intestine were also observed. Also, principal coordinate analysis of the bacterial composition profile showed a clear separation and clustering of bacterial genera of hypoxic and normoxic mice (ANOSIM p<0.001).

Conclusions: (I) Hypoxia-induced pulmonary and cardiac pathophysiology is associated with increased microglia in cardiorespiratory-relevant areas and enhanced sympathetic activity. (II) Fibrotic area and muscularis layer thickness increased while villi length and number of goblet cells decreased in gut (III) gut microbiota are altered. Together, these observations indicated an altered brain-gut-lung axis in PH.

Transforming growth factor beta1 targets estrogen receptor signaling in bronchial epithelial cells

Background

Sex differences in idiopathic pulmonary fibrosis (IPF) suggest a protective role for estrogen (E2); however, mechanistic studies in animal models have produced mixed results. Reports using cell lines have investigated molecular interactions between transforming growth factor beta1 (TGF-β1) and estrogen receptor (ESR) pathways in breast, prostate, and skin cells, but no such interactions have been described in human lung cells. To address this gap in the literature, we investigated a role for E2 in modulating TGF-β1-induced signaling mechanisms and identified novel pathways impacted by estrogen in bronchial epithelial cells.

Methods

We investigated a role for E2 in modulating TGF-β1-induced epithelial to mesenchymal transition (EMT) in bronchial epithelial cells (BEAS-2Bs) and characterized the effect of TGF-β1 on ESR mRNA and protein expression in BEAS-2Bs. We also quantified mRNA expression of ESRs in lung tissue from individuals with IPF and identified potential downstream targets of E2 signaling in BEAS-2Bs using RNA-Seq and gene set enrichment analysis.

Results

E2 negligibly modulated TGF-β1-induced EMT; however, we report the novel observation that TGF-β1 repressed ESR expression, most notably estrogen receptor alpha (ESR1). Results of the RNA-Seq analysis showed that TGF-β1 and E2 inversely modulated the expression of several genes involved in processes such as extracellular matrix (ECM) turnover, airway smooth muscle cell contraction, and calcium flux regulation. We also report that E2 specifically modulated the expression of genes involved in chromatin remodeling pathways and that this regulation was absent in the presence of TGF-β1.

Conclusions

Collectively, these results suggest that E2 influences unexplored pathways that may be relevant to pulmonary disease and highlights potential roles for E2 in the lung that may contribute to sex-specific differences.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0861-5) contains supplementary material, which is available to authorized users.

rhACE2 Therapy Modifies Bleomycin-Induced Pulmonary Hypertension via Rescue of Vascular Remodeling

Background: Pulmonary hypertension (PH) is a progressive cardiovascular disease, characterized by endothelial and smooth muscle dysfunction and vascular remodeling, followed by right heart failure. Group III PH develops secondarily to chronic lung disease such as idiopathic pulmonary fibrosis (IPF), and both hastens and predicts mortality despite of all known pharmacological interventions. Thus, there is urgent need for development of newer treatment strategies. Objective: Angiotensin converting enzyme 2 (ACE2), a member of the renin angiotensin family, is therapeutically beneficial in animal models of pulmonary vascular diseases and is currently in human clinical trials for primary PH. Although previous studies suggest that administration of ACE2 prevents PH secondary to bleomycin-induced murine IPF, it is unknown whether ACE2 can reverse or treat existing disease. Therefore, in the present study, we tested the efficacy of ACE2 in arresting the progression of group 3 PH. Methods: To establish pulmonary fibrosis, we administered 0.018 U/g bleomycin 2x/week for 4 weeks in adult FVB/N mice, and sacrificed 5 weeks following the first injection. ACE2 or vehicle was administered via osmotic pump for the final 2 weeks, beginning 3 weeks after bleomycin. Echocardiography and hemodynamic assessment was performed prior to sacrifice and tissue collection. Results: Administration of bleomycin significantly increased lung collagen expression, pulmonary vascular remodeling, and pulmonary arterial pressure, and led to mild right ventricular hypertrophy. Acute treatment with ACE2 significantly attenuated vascular remodeling and increased pulmonary SOD2 expression without measurable effects on pulmonary fibrosis. This was associated with nonsignificant positive effects on pulmonary arterial pressure and cardiac function. Conclusion: Collectively, our findings enumerate that ACE2 treatment improved pulmonary vascular muscularization following bleomycin exposure, concomitant with increased SOD2 expression. Although it may not alter the pulmonary disease course of IPF, ACE2 could be an effective therapeutic strategy for the treatment of group 3 PH.

Vascular Endothelial Cell-Specific Connective Tissue Growth Factor (CTGF) Is Necessary for Development of Chronic Hypoxia-Induced Pulmonary Hypertension

Chronic hypoxia frequently complicates the care of patients with interstitial lung disease, contributing to the development of pulmonary hypertension (PH), and premature death. Connective tissue growth factor (CTGF), a matricellular protein of the Cyr61/CTGF/Nov (CCN) family, is known to exacerbate vascular remodeling within the lung. We have previously demonstrated that vascular endothelial-cell specific down-regulation of CTGF is associated with protection against the development of PH associated with hypoxia, though the mechanism for this effect is unknown. In this study, we generated a transgenic mouse line in which the Ctgf gene was floxed and deleted in vascular endothelial cells that expressed Cre recombinase under the control of VE-Cadherin promoter (eCTGF KO mice). Lack of vascular endothelial-derived CTGF protected against the development of PH secondary to chronic hypoxia, as well as in another model of bleomycin-induced pulmonary hypertension. Importantly, attenuation of PH was associated with a decrease in infiltrating inflammatory cells expressing CD11b or integrin α_M (ITGAM), a known adhesion receptor for CTGF, in the lungs of hypoxia-exposed eCTGF KO mice. Moreover, these pathological changes were associated with activation of—Rho GTPase family member—cell division control protein 42 homolog (Cdc42) signaling, known to be associated with alteration in endothelial barrier function. These data indicate that endothelial-specific deletion of CTGF results in protection against development of chronic-hypoxia induced PH. This protection is conferred by both a decrease in inflammatory cell recruitment to the lung, and a reduction in lung Cdc42 activity. Based on our studies, CTGF inhibitor treatment should be investigated in patients with PH associated with chronic hypoxia secondary to chronic lung disease.

Myeloid-derived Suppressor Cells Are Necessary for Development of Pulmonary Hypertension

Pulmonary hypertension (PH) complicates the care of patients with chronic lung disease, such as idiopathic pulmonary fibrosis (IPF), resulting in a significant increase in morbidity and mortality. Disease pathogenesis is orchestrated by unidentified myeloid-derived cells. We used murine models of PH and pulmonary fibrosis to study the role of circulating myeloid cells in disease pathogenesis and prevention. We administered clodronate liposomes to bleomycin-treated wild-type mice to induce pulmonary fibrosis and PH with a resulting increase in circulating bone marrow-derived cells. We discovered that a population of C-X-C motif chemokine receptor (CXCR) 2⁺ myeloid-derived suppressor cells (MDSCs), granulocytic subset (G-MDSC), is associated with severe PH in mice. Pulmonary pressures worsened despite improvement in bleomycin-induced pulmonary fibrosis. PH was attenuated by CXCR2 inhibition, with antagonist SB 225002, through decreasing G-MDSC recruitment to the lung. Molecular and cellular analysis of clinical patient samples confirmed a role for elevated MDSCs in IPF and IPF with PH. These data show that MDSCs play a key role in PH pathogenesis and that G-MDSC trafficking to the lung, through chemokine receptor CXCR2, increases development of PH in multiple murine models. Furthermore, we demonstrate pathology similar to the preclinical models in IPF with lung and blood samples from patients with PH, suggesting a potential role for CXCR2 inhibitor use in this patient population. These findings are significant, as there are currently no approved disease-specific therapies for patients with PH complicating IPF.

"A small leak will sink a great ship": hypoxia-inducible factor and group III pulmonary hypertension

Pulmonary hypertension complicating idiopathic pulmonary fibrosis, also known as secondary pulmonary hypertension, represents a major source of morbidity and mortality in affected patients. While the study of primary pulmonary arterial hypertension has yielded several therapies, the same is not true for the treatment of pulmonary hypertension secondary to pulmonary fibrosis. Recent studies have indicated an important role of hypoxia-inducible factor (HIF) - a regulatory protein that is vital in adaptation to hypoxic conditions - in the development of secondary pulmonary hypertension. HIF influences development of hypoxia-induced pulmonary hypertension through alteration in voltage-gated potassium channels and homeostatic calcium regulation, resulting in disruption of endothelial cell-cell communication, and eventual vascular remodeling. This article summarizes salient literature related to HIF and secondary pulmonary hypertension, in addition to proposing a final common pathway in known mechanistic pathways that result in endothelial barrier integrity loss - vascular "leak" - primarily through a shared endothelial-epithelial signaling protein family, CCN.

Expression of mutant bone morphogenetic protein receptor II worsens pulmonary hypertension secondary to pulmonary fibrosis

Pulmonary fibrosis is often complicated by pulmonary hypertension (PH), and previous studies have shown a potential link between bone morphogenetic protein receptor II (BMPR2) and PH secondary to pulmonary fibrosis. We exposed transgenic mice expressing mutant BMPR2 and control mice to repetitive intraperitoneal injections of bleomycin for 4 weeks. The duration of transgene activation was too short for mutant BMPR2 mice to develop spontaneous PH. Mutant BMPR2 mice had increased right ventricular systolic pressure compared to control mice, without differences in pulmonary fibrosis. We found increased hypoxia-inducible factor (HIF)1-α stabilization in lungs of mutant-BMPR2-expressing mice compared to controls following bleomycin treatment. In addition, expression of the hypoxia response element protein connective tissue growth factor was increased in transgenic mice as well as in a human pulmonary microvascular endothelial cell line expressing mutant BMPR2. In mouse pulmonary vascular endothelial cells, mutant BMPR2 expression resulted in increased HIF1-α and reactive oxygen species production following exposure to hypoxia, both of which were attenuated with the antioxidant TEMPOL. These data suggest that expression of mutant BMPR2 worsens secondary PH through increased HIF activity in vascular endothelium. This pathway could be therapeutically targeted in patients with PH secondary to pulmonary fibrosis.

Endothelial HIF signaling regulates pulmonary fibrosis-associated pulmonary hypertension

Pulmonary hypertension (PH) complicating chronic parenchymal lung disease, such as idiopathic pulmonary fibrosis, results in significant morbidity and mortality. Since the hypoxia-inducible factor (HIF) signaling pathway is important for development of pulmonary hypertension in chronic hypoxia, we investigated whether HIF signaling in vascular endothelium regulates development of PH related to pulmonary fibrosis. We generated a transgenic model in which HIF is deleted within vascular endothelial cells and then exposed these mice to chronic intraperitoneal bleomycin to induce PH associated with lung fibrosis. Although no differences in the degree of fibrotic remodeling were observed, we found that endothelial HIF-deficient mice were protected against development of PH, including right ventricle and pulmonary vessel remodeling. Similarly, endothelial HIF-deficient mice were protected from PH after a 4-wk exposure to normobaric hypoxia. In vitro studies of pulmonary vascular endothelial cells isolated from the HIF-targeted mice and controls revealed that endothelial HIF signaling increases endothelial cell expression of connective tissue growth factor, enhances vascular permeability, and promotes pulmonary artery smooth muscle cell proliferation and wound healing ability, all of which have the potential to impact the development of PH in vivo. Taken together, these studies demonstrate that vascular endothelial cell HIF signaling is necessary for development of hypoxia and pulmonary fibrosis associated PH. As such, HIF and HIF-regulated targets represent a therapeutic target in these conditions.

β-catenin in the alveolar epithelium protects from lung fibrosis after intratracheal bleomycin

RATIONALE

Alveolar epithelial cells (AECs) play central roles in the response to lung injury and the pathogenesis of pulmonary fibrosis.

OBJECTIVES

We aimed to determine the role of β-catenin in alveolar epithelium during bleomycin-induced lung fibrosis.

METHODS

Genetically modified mice were developed to selectively delete β-catenin in AECs and were crossed to cell fate reporter mice that express β-galactosidase (βgal) in cells of AEC lineage. Mice were given intratracheal bleomycin (0.04 units) and assessed for AEC death, inflammation, lung injury, and fibrotic remodeling. Mouse lung epithelial cells (MLE12) with small interfering RNA knockdown of β-catenin underwent evaluation for wound closure, proliferation, and bleomycin-induced cytotoxicity.

MEASUREMENTS AND MAIN RESULTS

Increased β-catenin expression was noted in lung parenchyma after bleomycin. Mice with selective deletion of β-catenin in AECs had greater AEC death at 1 week after bleomycin, followed by increased numbers of fibroblasts and enhanced lung fibrosis as determined by semiquantitative histological scoring and total collagen content. However, no differences in lung inflammation or protein levels in bronchoalveolar lavage were noted. In vitro, β-catenin-deficient AECs showed increased bleomycin-induced cytotoxicity as well as reduced proliferation and impaired wound closure. Consistent with these findings, mice with AEC β-catenin deficiency showed delayed recovery after bleomycin.

CONCLUSIONS

β-Catenin in the alveolar epithelium protects against bleomycin-induced fibrosis. Our studies suggest that AEC survival and wound healing are enhanced through β-catenin-dependent mechanisms. Activation of the developmentally important β-catenin pathway in AECs appears to contribute to epithelial repair after epithelial injury.

Anesthetic Preconditioning with Sevoflurane Does Not Protect the Spinal Cord After an Ischemic-Reperfusion Injury in the Rat

Anesthetic preconditioning (APC) is a protective mechanism, whereby exposure to a volatile anesthetic renders a tissue resistant to a subsequent ischemic insult. We hypothesized that APC of the rat spinal cord with sevoflurane would reduce neurologic deficit after an ischemic-reperfusion injury. Rats were randomly assigned to 1 of 5 groups. The ischemic preconditioning (IPC) group (n = 14) had 3 min of IPC, 30 min of reperfusion, and 12 min of ischemia. The chronic APC (cSEVO) group (n = 14) had 1 h of APC with 3.5% sevoflurane on each of 2 days before ischemia. The acute APC (aSEVO) group (n = 14) had 1 h of APC with 3.5% sevoflurane followed by a 1-h washout period before the induction of ischemia. The controls (n = 14) underwent no preconditioning before ischemia. IPC attenuated the ischemia-reperfusion injury, whereas aSEVO and cSEVO groups were no better than control animals. Histologic evaluation of the spinal cord showed severe neurologic damage in all groups except for the IPC group and sham-operated rats. APC with sevoflurane did not reduce neurologic injury in a rat model of spinal cord ischemia. Traditional ischemic preconditioning had a strong protective benefit on neurologic outcome.

Cryptosporidiosis: an outbreak associated with drinking water despite state-of-the-art water treatment

OBJECTIVE

To determine the magnitude and source of an outbreak of cryptosporidiosis among persons with human immunodeficiency virus (HIV) infection and to determine whether the outbreak extended into the immunocompetent population.

DESIGN

Matched case-control study and environmental investigation.

SETTING

Clark County, Nevada.

PARTICIPANTS

Adults with HIV infection (36 case-patients with laboratory-confirmed Cryptosporidium parvum infection and 107 controls), matched by physician or clinic and by CD4+ cell count category.

MEASUREMENTS

Potential risk factors for infection, death rates, and data on water quality.

RESULTS

Review of surveillance and microbiology records identified 3 cases of cryptosporidiosis in 1992 (the first year that cryptosporidiosis was reportable in Nevada), 23 cases in 1993, and 78 cases in the first quarter of 1994. Of the 78 laboratory-confirmed cases in the first quarter of 1994, 61 (78.2%) were in HIV-infected adults. Of these 61 adults, 32 (52.5%) had died by 30 June 1994; at least 20 of the 32 (62.5%) had cryptosporidiosis listed on their death certificates. In the case-control study, persons who drank any unboiled tap water were four times more likely than persons who drank only bottled water to have had cryptosporidiosis (odds ratio, 4.22 [95% Cl, 1.22 to 14.65]; P = 0.02). For persons with CD4+ cell counts less than 100 cells/mm3, the association between tap water and cryptosporidiosis was even stronger (odds ratio, 13.52 [Cl, 1.78 to 102.92]; P = 0.01). Additional data indicate that this outbreak also affected persons who were not infected with HIV. No elevated turbidity values or coliform counts and no Cryptosporidium oocysts were found in testing of source (Lake Mead) or finished (treated) water during the study period, but so-called presumptive oocysts were intermittently found after the investigation in samples of source water, filter backwash, and finished water.

CONCLUSIONS

A cryptosporidiosis outbreak was associated with municipal drinking water, despite state-of-the-art water treatment and water quality better than that required by current federal standards. This outbreak highlights the importance of surveillance for cryptosporidiosis and the need for guidelines for the prevention of water-borne-Cryptosporidium infection among HIV-infected persons.

Prophylactic oophorectomy in operable instances of carcinoma of the breast

In 1964, a prospective study was initiated of prophylactic oophorectomy in operable instances of carcinoma of the breast, in patients who showed evidence of ovarian activity. Patients were randomized to a control group and a group treated by surgical castration. By December 1979, 359 patients were evaluable at five years and 240 patients at ten years. The over-all results of the oophorectomy series were superior to that for those of the control group. Patients who had cancer confined to the breast showed no significant benefit from oophorectomy. When one to three axillary nodes were involved, women less than 50 years of age were found to benefit significantly from prophylactic oophorectomy, in relapse-free status at five years, and in survival and relapse-free status at ten years. Patients 50 years of age and older showed no advantage from oophorectomy. It s suggested that there is a place for prophylactic oophorectomy in patients who are less than 50 years of age with operable carcinoma of the breast and with positive axillary nodes.