Role of Arginine and its Metabolism in TGF-β-Induced Activation of Lung Fibroblasts.

Arginine is a conditionally essential amino acid with known roles in protein production, nitric oxide synthesis, biosynthesis of proline and polyamines, and regulation of intracellular signaling pathways. Arginine biosynthesis and catabolism have been linked to TGF-β-induced activation of fibroblasts in the context of pulmonary fibrosis; however, a thorough study on the metabolic and signaling roles of arginine in the process of fibroblast activation has not been conducted. Here, we used metabolic dropouts and labeling strategies to determine how activated fibroblasts utilize arginine.

Sustained hypoxia but not intermittent hypoxia induces HIF-1α transcriptional response in human aortic endothelial cells.

Obstructive sleep apnea (OSA) is characterized by intermittent hypoxic environments at the cellular level and is an independent risk factor for the development of cardiovascular disease. Endothelial cell (EC) dysfunction precedes the development of cardiovascular disease; however, the mechanisms by which ECs respond to these intermittent hypoxic events are poorly understood. To better understand EC responses to hypoxia, we examined the effects of sustained hypoxia (SH) and intermittent hypoxia (IH) on the activation of HIF-1α in ECs.

HIF-1α regulates mitochondrial function in bone marrow-derived macrophages, but not in tissue-resident alveolar macrophages.

HIF-1α plays a critical role in shaping macrophage phenotype and effector function. We have previously shown that tissue-resident alveolar macrophages (TR-AMs) have extremely low glycolytic capacity at steady-state, but can shift toward glycolysis under hypoxic conditions. Here, using inducible HIF-1α knockout ( ) TR-AMs and bone marrow-derived macrophages (BMDMs) and show that TR-AM HIF-1α is required for the glycolytic shift under prolyl hydroxylase inhibition, but is dispensable at steady-state for inflammatory effector function.

ATF4 and mTOR regulate metabolic reprogramming in TGF-β-treated lung fibroblasts.

Idiopathic pulmonary fibrosis is a fatal disease characterized by the TGF-β-dependent activation of lung fibroblasts, leading to excessive deposition of collagen proteins and progressive replacement of healthy lung with scar tissue. We and others have shown that fibroblast activation is supported by metabolic reprogramming, including the upregulation of the synthesis of glycine, the most abundant amino acid found in collagen protein. How fibroblast metabolic reprogramming is regulated downstream of TGF-β is incompletely understood.

Loss of heme oxygenase 2 causes reduced expression of genes in cardiac muscle development and contractility and leads to cardiomyopathy in mice.

Obstructive sleep apnea (OSA) is a common breathing disorder that affects a significant portion of the adult population. In addition to causing excessive daytime sleepiness and neurocognitive effects, OSA is an independent risk factor for cardiovascular disease; however, the underlying mechanisms are not completely understood. Using exposure to intermittent hypoxia (IH) to mimic OSA, we have recently reported that mice exposed to IH exhibit endothelial cell (EC) activation, which is an early process preceding the development of cardiovascular disease.

Intermittent hypoxia inhibits epinephrine-induced transcriptional changes in human aortic endothelial cells.

Obstructive sleep apnea (OSA) is an independent risk factor for cardiovascular disease. While intermittent hypoxia (IH) and catecholamine release play an important role in this increased risk, the mechanisms are incompletely understood. We have recently reported that IH causes endothelial cell (EC) activation, an early phenomenon in the development of cardiovascular disease, via IH-induced catecholamine release.

HIF-1α induces glycolytic reprograming in tissue-resident alveolar macrophages to promote cell survival during acute lung injury.

Cellular metabolism is a critical regulator of macrophage effector function. Tissue-resident alveolar macrophages (TR-AMs) inhabit a unique niche marked by high oxygen and low glucose. We have recently shown that in contrast to bone marrow-derived macrophages (BMDMs), TR-AMs do not utilize glycolysis and instead predominantly rely on mitochondrial function for their effector response.

Intermittent Hypoxia-Induced Activation of Endothelial Cells Is Mediated Sympathetic Activation-Dependent Catecholamine Release.

Obstructive sleep apnea (OSA) is a common breathing disorder affecting a significant percentage of the adult population. OSA is an independent risk factor for cardiovascular disease (CVD); however, the underlying mechanisms are not completely understood. Since the severity of hypoxia correlates with some of the cardiovascular effects, intermittent hypoxia (IH) is thought to be one of the mechanisms by which OSA may cause CVD.

Single-cell metabolic imaging reveals a SLC2A3-dependent glycolytic burst in motile endothelial cells.

Single-cell motility is spatially heterogeneous and driven by metabolic energy. Directly linking cell motility to cell metabolism is technically challenging but biologically important. Here, we use single-cell metabolic imaging to measure glycolysis in individual endothelial cells with genetically encoded biosensors capable of deciphering metabolic heterogeneity at subcellular resolution.

The lung microenvironment shapes a dysfunctional response of alveolar macrophages in aging.

Alveolar macrophages orchestrate the response to viral infections. Age-related changes in these cells may underlie the differential severity of pneumonia in older patients. We performed an integrated analysis of single-cell RNA-Seq data that revealed homogenous age-related changes in the alveolar macrophage transcriptome in humans and mice.

TGF-β Promotes Metabolic Reprogramming in Lung Fibroblasts via mTORC1-dependent ATF4 Activation.

Idiopathic pulmonary fibrosis is a fatal interstitial lung disease characterized by the TGF-β (transforming growth factor-β)-dependent differentiation of lung fibroblasts into myofibroblasts, which leads to excessive deposition of collagen proteins and progressive scarring. We have previously shown that synthesis of collagen by myofibroblasts requires synthesis of glycine, the most abundant amino acid found in collagen protein. TGF-β upregulates the expression of the enzymes of the serine-glycine synthesis pathway in lung fibroblasts; however, the transcriptional and signaling regulators of this pathway remain incompletely understood.

Endogenous itaconate is not required for particulate matter-induced NRF2 expression or inflammatory response.

Particulate matter (PM) air pollution causes cardiopulmonary mortality via macrophage-driven lung inflammation; however, the mechanisms are incompletely understood. RNA-sequencing demonstrated () as one of the top genes induced by PM in macrophages. encodes a mitochondrial enzyme that produces itaconate, which has been shown to exert anti-inflammatory effects via NRF2 after LPS.

Tissue-Resident Alveolar Macrophages Do Not Rely on Glycolysis for LPS-induced Inflammation.

Macrophage effector function is dynamic in nature and largely dependent on not only the type of immunological challenge but also the tissue-specific environment and developmental origin of a given macrophage population. Recent research has highlighted the importance of glycolytic metabolism in the regulation of effector function as a common feature associated with macrophage activation. Yet, most research has used macrophage cell lines and bone marrow-derived macrophages, which do not account for the diversity of macrophage populations and the role of tissue specificity in macrophage immunometabolism.

Glutamine Metabolism Is Required for Collagen Protein Synthesis in Lung Fibroblasts.

Idiopathic pulmonary fibrosis (IPF) is characterized by the transforming growth factor (TGF)-β-dependent differentiation of lung fibroblasts into myofibroblasts, leading to excessive deposition of extracellular matrix proteins, which distort lung architecture and function. Metabolic reprogramming in myofibroblasts is emerging as an important mechanism in the pathogenesis of IPF, and recent evidence suggests that glutamine metabolism is required in myofibroblasts, although the exact role of glutamine in myofibroblasts is unclear. In the present study, we demonstrate that glutamine and its conversion to glutamate by glutaminase are required for TGF-β-induced collagen protein production in lung fibroblasts.

Role of truncated oxidized phospholipids in acute endothelial barrier dysfunction caused by particulate matter.

Particulate matter (PM) air pollution is a global environmental health problem contributing to more severe lung inflammation and injury. However, the molecular and cellular mechanisms of PM-induced exacerbation of lung barrier dysfunction and injury are not well understood. In the current study, we tested a hypothesis that PM exacerbates vascular barrier dysfunction via ROS-induced generation of truncated oxidized phospholipids (Tr-OxPLs).

Microtubule destabilization caused by particulate matter contributes to lung endothelial barrier dysfunction and inflammation.

Exposure to particulate matter (PM) associated with air pollution remains a major public health concern, as it has been linked to significant increase in cardiopulmonary morbidity and mortality. Lung endothelial cell (EC) dysfunction is one of the hallmarks of cardiovascular events of lung exposure to PM. However, the role of PM in acute lung injury (ALI) exacerbation and delayed recovery remains incompletely understood.

Metformin Targets Mitochondrial Electron Transport to Reduce Air-Pollution-Induced Thrombosis.

Urban particulate matter air pollution induces the release of pro-inflammatory cytokines including interleukin-6 (IL-6) from alveolar macrophages, resulting in an increase in thrombosis. Here, we report that metformin provides protection in this murine model. Treatment of mice with metformin or exposure of murine or human alveolar macrophages to metformin prevented the particulate matter-induced generation of complex III mitochondrial reactive oxygen species, which were necessary for the opening of calcium release-activated channels (CRAC) and release of IL-6.

P311 Promotes Lung Fibrosis via Stimulation of Transforming Growth Factor-β1, -β2, and -β3 Translation.

Interstitial lung fibrosis, a frequently idiopathic and fatal disease, has been linked to the increased expression of profibrotic transforming growth factor (TGF)-βs. P311 is an RNA-binding protein that stimulates TGF-β1, -β2, and -β3 translation in several cell types through its interaction with the eukaryotic translation initiation factor 3b. We report that P311 is switched on in the lungs of patients with idiopathic pulmonary fibrosis (IPF) and in the mouse model of bleomycin (BLM)-induced pulmonary fibrosis.

Inhalational exposure to particulate matter air pollution alters the composition of the gut microbiome.

Recent studies suggest an association between particulate matter (PM) air pollution and gastrointestinal (GI) disease. In addition to direct deposition, PM can be indirectly deposited in oropharynx via mucociliary clearance and upon swallowing of saliva and mucus. Within the GI tract, PM may alter the GI epithelium and gut microbiome.

Baicalein Rescues Delayed Cooling via Preservation of Akt Activation and Akt-Mediated Phospholamban Phosphorylation.

Cooling reduces the ischemia/reperfusion (I/R) injury seen in sudden cardiac arrest (SCA) by decreasing the burst of reactive oxygen species (ROS). Its cardioprotection is diminished when delay in reaching the target temperature occurs. Baicalein, a flavonoid derived from the root of , possesses antioxidant properties.

Inhibition of Phosphoglycerate Dehydrogenase Attenuates Bleomycin-induced Pulmonary Fibrosis.

Organ fibrosis, including idiopathic pulmonary fibrosis, is associated with significant morbidity and mortality. Because currently available therapies have limited effect, there is a need to better understand the mechanisms by which organ fibrosis occurs. We have recently reported that transforming growth factor (TGF)-β, a key cytokine that promotes fibrogenesis, induces the expression of the enzymes of the de novo serine and glycine synthesis pathway in human lung fibroblasts, and that phosphoglycerate dehydrogenase (PHGDH; the first and rate-limiting enzyme of the pathway) is required to promote collagen protein synthesis downstream of TGF-β.

is required for disturbed flow-induced metabolic reprogramming in human and porcine vascular endothelium.

Hemodynamic forces regulate vascular functions. Disturbed flow (DF) occurs in arterial bifurcations and curvatures, activates endothelial cells (ECs), and results in vascular inflammation and ultimately atherosclerosis. However, how DF alters EC metabolism, and whether resulting metabolic changes induce EC activation, is unknown.

Regulation of lung endothelial permeability and inflammatory responses by prostaglandin A2: role of EP4 receptor.

The role of prostaglandin A2 (PGA2) in modulation of vascular endothelial function is unknown. We investigated effects of PGA2 on pulmonary endothelial cell (EC) permeability and inflammatory activation and identified a receptor mediating these effects. PGA2 enhanced the EC barrier and protected against barrier dysfunction caused by vasoactive peptide thrombin and proinflammatory bacterial wall lipopolysaccharide (LPS).