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- PublicationGremlin 1 is required for macrophage M2 polarizationPro-proliferative, M2-like polarization of macrophages is a critical step in the development of fibrosis and remodeling in chronic lung diseases such as pulmonary fibrosis and pulmonary hypertension. Macrophages in healthy and diseased lungs express gremlin 1 (Grem1), a secreted glycoprotein that acts in both paracrine and autocrine manners to modulate cellular function. Increased Grem1 expression plays a central role in pulmonary fibrosis and remodeling, however, the role of Grem1 in M2-like polarization of macrophages has not previously been explored. The results reported here show that recombinant Grem1 potentiated M2-like polarization of mouse macrophages and bone marrow-derived macrophages (BMDMs) in response to the Th2 cytokines IL4 and IL13. Genetic depletion of Grem1 in BMDMs inhibited M2 polarization while exogenous gremlin 1 could partially rescue this effect. Taken together, these findings reveal that gremlin 1 is required for M2-like polarization of macrophages. We show here that gremlin 1 potentiated M2 polarization of mouse bone marrow-derived macrophages (BMDMs) in response to the Th2 cytokines IL4 and IL13. Genetic depletion of Grem1 in BMDMs inhibited M2 polarization while exogenous gremlin 1 partially rescued this effect. Taken together, these findings reveal a previously unknown requirement for gremlin 1 in M2 polarization of macrophages and suggest a novel cellular mechanism promoting fibrosis and remodeling in lung diseases.
- PublicationShear Stress Markedly Alters the Proteomic Response to Hypoxia in Human Pulmonary Endothelial CellsBlood flow produces shear stress that homeostatically regulates the phenotype of pulmonary endothelial cells, exerting antiinflammatory and antithrombotic actions and maintaining normal barrier function. Hypoxia due to diseases, such as chronic obstructive pulmonary disease (COPD), causes vasoconstriction, increased vascular resistance, and pulmonary hypertension. Hypoxia-induced changes in endothelial function play a central role in the development of pulmonary hypertension. However, the interactive effects of hypoxia and shear stress on the pulmonary endothelial phenotype have not been studied. Human pulmonary microvascular endothelial cells were cultured in normoxia or hypoxia while subjected to physiological shear stress or in static conditions. Unbiased proteomics was used to identify hypoxia-induced changes in protein expression. Using publicly available single-cell RNA sequencing datasets, differences in gene expression between the alveolar endothelial cells from COPD and healthy lungs were identified. Sixty proteins were identified whose expression changed in response to hypoxia in conditions of physiological shear stress but not in static conditions. These included proteins that are crucial for endothelial homeostasis (e.g., JAM-A [junctional adhesion molecule A], ERG [ETS transcription factor ERG]) or implicated in pulmonary hypertension (e.g., thrombospondin-1). Fifty-five of these 60 have not been previously implicated in the development of hypoxic lung diseases. mRNA for 5 of the 60 (ERG, MCRIP1 [MAPK regulated corepressor interacting protein 1], EIF4A2 [eukaryotic translation initiation factor 4A2], HSP90AA1 [heat shock protein 90 alpha family class A member 1], and DNAJA1 [DnaJ Hsp40 (heat shock protein family) member A1]) showed similar changes in the alveolar endothelial cells of COPD compared with healthy lungs in females but not in males. These data show that the proteomic responses of the pulmonary microvascular endothelium to hypoxia are significantly altered by shear stress and suggest that these shear-hypoxia interactions are important in the development of hypoxic pulmonary vascular disease.
22Scopus© Citations 3
- PublicationSex differences in the pulmonary microvascular endothelial responses to hypoxia under physiological shear stress(University College Dublin. School of Medicine, 2022)
;0000-0003-0842-2526Chronic respiratory diseases, such as chronic obstructive pulmonary disease (COPD), are commonly complicated by the development of pulmonary hypertension (PH), which significantly increases the morbidity and mortality. Sexual dimorphism exists in PH. Females with PH due to lung diseases and/or hypoxia have higher pulmonary vascular resistance than males. However, females have better survival with PH than males. Recent studies suggest that sex hormone independent mechanisms contribute to the protection of males from the development of pulmonary arterial hypertension. However, it remains unknown whether sex hormone independent mechanisms contribute to the sex bias in PH due to lung diseases and/or hypoxia. Pulmonary endothelial cells play a crucial role in the pulmonary vascular remodelling and vasoconstriction in the response to hypoxia. Commonly, endothelial cell responses are studied in vitro in static conditions, i.e., without flow-induced shear stress. However, in vivo endothelial cells constantly experience shear stress, which regulates endothelial cell phenotype and function. The aim of the studies reported in this thesis was to examine the sex differences in the responses of human pulmonary microvascular endothelial cells (HPMEC) to hypoxia, cultured under physiological shear stress, that are independent of the sex hormone environment. In order to expose HPMEC to the hypoxic environment in the conditions of physiological shear stress a novel approach was established. In these conditions sex differences between male and female HPMEC were identified on the RNA and protein levels. Endothelial to mesenchymal transition was higher in female cells and proliferation rate was higher in male cells. The identified sex different pathways might contribute to the sex bias in pulmonary hypertension. 62
- PublicationTranscriptomics and proteomics revealed sex differences in human pulmonary microvascular endothelial cellsMarked sexual dimorphism is displayed in the onset and progression of pulmonary hypertension (PH). Females more commonly develop pulmonary arterial hypertension (PAH), yet females with PAH and other types of PH have better survival than males. Pulmonary microvascular endothelial cells play a crucial role in the pulmonary vascular remodelling and increased pulmonary vascular resistance in PH. Given this background, we hypothesized that there are sex differences in the pulmonary microvascular endothelium basally and in response to hypoxia that are independent of the sex hormone environment. Human pulmonary microvascular endothelial cells (HPMECs) from healthy male and female donors, cultured under physiological shear stress, were analysed using RNA sequencing and label-free quantitative proteomics. Gene set enrichment analysis identified a number of sex different pathways both in normoxia and hypoxia, including pathways that regulate cell proliferation. In vitro, rate of proliferation in female HPMECs was lower than in male HPMECs, a finding that supports the omics results. Interestingly, thrombospondin1, an inhibitor of proliferation, was more highly expressed in female than in male cells. These results demonstrate for the first time important differences between female and male HPMECs that persist in the absence of sex hormone differences and identify novel pathways for further investigation that may contribute to sexual dimorphism in pulmonary hypertensive diseases.