Hypercapnia increases ACE2 expression and pseudo-SARS-CoV-2 entry in bronchial epithelial cells by augmenting cellular cholesterol

Patients with chronic lung disease, obesity, and other co-morbid conditions are at increased risk of severe illness and death when infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Hypercapnia, the elevation of CO2 in blood and tissue, commonly occurs in patients with severe acute and chronic lung disease, including those with pulmonary infections, and is also associated with high mortality risk. We previously reported that hypercapnia increases viral replication and mortality of influenza A virus infection in mice. We have also shown that culture in elevated CO2 upregulates expression of cholesterol synthesis genes in primary human bronchial epithelial cells. Interestingly, factors that increase the cholesterol content of lipid rafts and lipid droplets, platforms for viral entry and assembly, enhance SARS-CoV-2 infection. In the current study, we investigated the effects of hypercapnia on ACE2 expression and entry of SARS-CoV-2 pseudovirus (p-SARS-CoV-2) into airway epithelial cells. We found that hypercapnia increased ACE2 expression and p-SARS-CoV-2 uptake by airway epithelium in mice, and in cultured VERO and human bronchial epithelial cells. Hypercapnia also increased total cellular and lipid raft-associated cholesterol in epithelial cells. Moreover, reducing cholesterol synthesis with inhibitors of sterol regulatory element binding protein 2 (SREBP2) or statins, and depletion of cellular cholesterol, each blocked the hypercapnia-induced increases in ACE2 expression and p-SARS-CoV-2 entry into epithelial cells. Cigarette smoke extract (CSE) also increased ACE2 expression, p-SARS-CoV-2 entry and cholesterol accumulation in epithelial cells, an effect not additive to that of hypercapnia, but also inhibited by statins. These findings reveal a mechanism that may account, in part, for poor clinical outcomes of SARS-CoV-2 infection in patients with advanced lung disease and hypercapnia, and in those who smoke cigarettes. Further, our results suggest the possibility that cholesterol-lowering therapies may be of particular benefit in patients with hypercapnia when exposed to or infected with SARS-CoV-2

CD11b suppresses TLR activation of nonclassical monocytes to reduce primary graft dysfunction after lung transplantation

Primary graft dysfunction (PGD) is the leading cause of postoperative mortality in lung transplant recipients and the most important risk factor for development of chronic lung allograft dysfunction. The mechanistic basis for the variability in the incidence and severity of PGD between lung transplant recipients is not known. Using a murine orthotopic vascularized lung transplant model, we found that redundant activation of Toll-like receptors 2 and 4 (TLR2 and -4) on nonclassical monocytes activates MyD88, inducing the release of the neutrophil attractant chemokine CXCL2. Deletion of Itgam (encodes CD11b) in nonclassical monocytes enhanced their production of CXCL2 and worsened PGD, while a CD11b agonist, leukadherin-1, administered only to the donor lung prior to lung transplantation, abrogated CXCL2 production and PGD. The damage-associated molecular pattern molecule HMGB1 was increased in peripheral blood samples from patients undergoing lung transplantation after reperfusion and induced CXCL2 production in nonclassical monocytes via TLR4/MyD88. An inhibitor of HMGB1 administered to the donor and recipient prior to lung transplantation attenuated PGD. Our findings suggest that CD11b acts as a molecular brake to prevent neutrophil recruitment by nonclassical monocytes following lung transplantation, revealing an attractive therapeutic target in the donor lung to prevent PGD in lung transplant recipients

Tissue-resident, extravascular Ly6c- monocytes are critical for inflammation in the synovium

Monocytes are abundant immune cells that infiltrate inflamed organs. However, the majority of monocyte studies focus on circulating cells, rather than those in tissue. Here, we identify and characterize an intravascular synovial monocyte population resembling circulating non-classical monocytes and an extravascular tissue-resident monocyte-lineage cell (TR-MC) population distinct in surface marker and transcriptional profile from circulating monocytes, dendritic cells, and tissue macrophages that are conserved in rheumatoid arthritis (RA) patients. TR-MCs are independent of NR4A1 and CCR2, long lived, and embryonically derived. TR-MCs undergo increased proliferation and reverse diapedesis dependent on LFA1 in response to arthrogenic stimuli and are required for the development of RA-like disease. Moreover, pathways that are activated in TR-MCs at the peak of arthritis overlap with those that are downregulated in LFA1-/- TR-MCs. These findings show a facet of mononuclear cell biology that could be imperative to understanding tissue-resident myeloid cell function in RA.</p

Detecting small low emission radiating sources

The article addresses the possibility of robust detection of geometrically small, low emission sources on a significantly stronger background. This problem is important for homeland security. A technique of detecting such sources using Compton type cameras is developed, which is shown on numerical examples to have high sensitivity and specificity and also allows to assign confidence probabilities of the detection. 2D case is considered in detail

Nonclassical Ly6C(-) Monocytes Drive the Development of Inflammatory Arthritis in Mice

Different subsets and/or polarized phenotypes of monocytes and macrophages may play distinct roles during the development and resolution of inflammation. Here, we demonstrate in a murine model of rheumatoid arthritis that non-classical Ly6C(−) monocytes are required for the initiation and progression of sterile joint inflammation. Moreover, non-classical Ly6C(−) monocytes differentiate into inflammatory macrophages (M1), which drive disease pathogenesis and display plasticity during the resolution phase. During the development of arthritis, these cells polarize toward an alternatively activated phenotype (M2), promoting the resolution of joint inflammation. The influx of Ly6C(−) monocytes and their subsequent classical and then alternative activation occurs without changes in synovial tissue-resident macrophages, which express markers of M2 polarization throughout the course of the arthritis and attenuate joint inflammation during the initiation phase. These data suggest that circulating Ly6C(−) monocytes recruited to the joint upon injury orchestrate the development and resolution of autoimmune joint inflammation

Mangiferin Decreases Plasma Free Fatty Acids through Promoting Its Catabolism in Liver by Activation of AMPK

Mangiferin has been shown to have the effect of improving dyslipidemia. Plasma free fatty acids (FFA) are closely associated with blood lipid metabolism as well as many diseases including metabolic syndrome. This study is to investigate whether mangiferin has effects on FFA metabolism in hyperlipidemic rats. Wistar rats were fed a high-fat diet and administered mangiferin simultaneously for 6 weeks. Mangiferin (50, 100, 150 mg/kg BW) decreased dose-dependently FFA and triglycerides (TG) levels in plasma, and their accumulations in liver, but increased the β-hydroxybutyrate levels in both plasma and liver of hyperlipidemic rats. HepG2 cells were treated with oleic acid (OA, 0.2 mmol/L) to simulate the condition of high level of plasma FFA in vitro, and were treated with different concentrations of mangiferin simultaneously for 24 h. We found that mangiferin significantly increased FFA uptake, significantly decreased intracellular FFA and TG accumulations in HepG2 cells. Mangiferin significantly increased AMP-activated protein kinase (AMPK) phosphorylation and its downstream proteins involved in fatty acid translocase (CD36) and carnitine palmitoyltransferase 1 (CPT1), but significantly decreased acyl-CoA: diacylgycerol acyltransferase 2 (DGAT2) expression and acetyl-CoA carboxylase (ACC) activity by increasing its phosphorylation level in both in vivo and in vitro studies. Furthermore, these effects were reversed by Compound C, an AMPK inhibitor in HepG2 cells. For upstream of AMPK, mangiferin increased AMP/ATP ratio, but had no effect on LKB1 phosphorylation. In conclusion, mangiferin decreased plasma FFA levels through promoting FFA uptake and oxidation, inhibiting FFA and TG accumulations by regulating the key enzymes expression in liver through AMPK pathway. Therefore, mangiferin is a possible beneficial natural compound for metabolic syndrome by improving FFA metabolism

Mitochondria Regulate Proliferation in Adult Cardiac Myocytes

Newborn mammalian cardiomyocytes quickly transition from a fetal to an adult phenotype that utilizes mitochondrial oxidative phosphorylation but loses mitotic capacity. We tested whether forced reversal of adult cardiomyocytes back to a fetal glycolytic phenotype would restore proliferative capacity. We deleted Uqcrfs1 (mitochondrial Rieske iron-sulfur protein, RISP) in hearts of adult mice. As RISP protein decreased, heart mitochondrial function declined, and glucose utilization increased. Simultaneously, the hearts underwent hyperplastic remodeling during which cardiomyocyte number doubled without cellular hypertrophy. Cellular energy supply was preserved, AMPK activation was absent, and mTOR activation was evident. In ischemic hearts with RISP deletion, new cardiomyocytes migrated into the infarcted region, suggesting the potential for therapeutic cardiac regeneration. RNA sequencing revealed upregulation of genes associated with cardiac development and proliferation. Metabolomic analysis revealed a decrease in α-ketoglutarate (required for TET-mediated demethylation) and an increase in S-adenosylmethionine (required for methyltransferase activity). Analysis revealed an increase in methylated CpGs near gene transcriptional start sites. Genes that were both differentially expressed and differentially methylated were linked to upregulated cardiac developmental pathways. We conclude that decreased mitochondrial function and increased glucose utilization can restore mitotic capacity in adult cardiomyocytes, resulting in the generation of new heart cells, potentially through the modification of substrates that regulate epigenetic modification of genes required for proliferation