A New Frontier in Immunometabolism. Cholesterol in Lung Health and Disease

Polyhexamethylene guanidine aerosol causes irreversible changes in blood proteins that associated with the severity of lung injury

Polyhexamethylene guanidine (PHMG) is a positively charged polymer used as a disinfectant that kills microbes but can cause pulmonary fibrosis if inhaled. After the long-term risks were confirmed in South Korea, it became crucial to measure toxicity through diverse surrogate biomarkers, not only proteins, especially after these hazardous chemicals had cleared from the body. These biomarkers, identified by their biological functions rather than simple numerical calculations, effectively explained the imbalance of pulmonary surfactant caused by fibrosis from PHMG exposure. These long-term studies on children exposed to PHMG has shown that blood protein indicators, primarily related to apolipoproteins and extracellular matrix, can distinguish the degree of exposure to humidifier disinfectants (HDs). We defined the extreme gradient boosting models and computed reflection scores based on just ten selected proteins, which were also verified in adult women exposed to HD. The reflection scores successfully discriminated between the HD-exposed and unexposed groups in both children and adult females (AUROC: 0.957 and 0.974, respectively) and had a strong negative correlation with lung function indicators. Even after an average of more than 10 years, blood is still considered a meaningful specimen for assessing the impact of environmental exposure to toxic substances, with proteins providing in identifying the pathological severity of such conditions.

Cholesterol and Cholesterol-Lowering Medications in COVID-19-An Unresolved Matter

Infections with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) cause coronavirus disease 2019 (COVID-19), a disease with very heterogeneous symptoms. Dyslipidaemia is prevalent in at least 20% of Europeans, and dyslipidaemia before SARS-CoV-2 infection increases the risk for severe COVID-19 and mortality by 139%. Many reports described reduced serum cholesterol levels in virus-infected patients, in particular in those with severe disease. The liver is the major organ for lipid homeostasis and hepatic dysfunction appears to occur in one in five patients infected with SARS-CoV-2. Thus, SARS-CoV-2 infection, COVID-19 disease severity and liver injury may be related to impaired cholesterol homeostasis. These observations prompted efforts to assess the therapeutic opportunities of cholesterol-lowering medications to reduce COVID-19 severity. The majority of studies implicate statins to have beneficial effects on disease severity and outcome in COVID-19. Proprotein convertase subtilisin/kexin type 9 (PCSK9) antibodies have also shown potential to protect against COVID-19. This review describes the relationship between systemic cholesterol levels, liver injury and COVID-19 disease severity. The potential effects of statins and PCSK9 in COVID-19 are summarised. Finally, the relationship between cholesterol and lung function, the first organ to be affected by SARS-CoV-2, is described.

The relationship between cardiometabolic index and pulmonary function among U.S. adults: insights from the National Health and Nutrition Examination Survey (2007-2012)

BACKGROUND

Previous findings have revealed that disorders of lipid metabolism may be a risk factor for pulmonary function damage; however, the combined effect of dyslipidemia and central obesity on pulmonary function is unclear. The cardiometabolic index (CMI) is a composite of serum lipids (triglyceride (TG)/high-density lipoprotein cholesterol (HDL-C)) and visceral fat parameters (waist-to-height ratio (WHtR)). This research aimed to investigate the link between CMI and pulmonary function, employing large-scale demographic data sourced from the National Health and Nutrition Examination Survey (NHANES) database.

METHODS

This cross-sectional study used data involving 4125 adults aged 20 and above collected by NHANES between 2007 and 2012. We defined CMI as the exposure variable and measured outcomes using forced expiratory volume in one second (FEV1), forced vital capacity (FVC), and FEV1/FVC to evaluate pulmonary function. Weighted multiple linear regression models and subgroup analyses were employed to investigate separate relationships between CMI and pulmonary function. In addition, to investigate variations across different strata and evaluate the robustness of the findings, interaction tests and sensitivity analyses were conducted.

RESULTS

Results from the weighted multiple linear regression analysis indicated a unit increase in log2-CMI was associated with a reduction of 82.63 mL in FEV1 and 112.92 mL in FVC. The negative association remained significant after transforming log2-CMI by quartile (Q). When the log2-CMI level reached Q4, β coefficients (β) were -128.49 (95% CI: -205.85, -51.13), -169.01 (95% CI: -266.72, -71.30), respectively. According to the interaction test findings, the negative association linking log2-CMI with FEV1 and FVC persists regardless of confounding factors including age, gender, BMI, physical activity (PA), and smoking status. A subsequent sensitivity analysis provided additional confirmation of the stability and reliability of the results. For females, the inflection points for the nonlinear relationships between log2-CMI and FEV1, as well as log2-CMI and FVC, were identified at 2.33 and 2.11, respectively. While in males, a consistent negative association was observed.

CONCLUSIONS

Our findings suggest that higher CMI is associated with lower FEV1 and FVC. CMI may serve as a complementary consideration to the assessment and management of pulmonary function in clinical practice.

Lipoprotein(a) and Lung Function Are Associated in Older Adults: Longitudinal and Cross-Sectional Analyses

While numerous studies have confirmed a causal association between lipoprotein(a) [Lp(a)] and cardiovascular diseases, only a few studies have assessed the relationship between Lp(a) and pulmonary health, with inconsistent findings regarding this topic. This study's aim was to examine whether levels of serum Lp(a) are associated with lung function in a dataset of relatively healthy older adults. We used longitudinal data collected at two time points 7.4 ± 1.5 years apart from 679 participants (52% women, 68 [65-71] years old) from the Berlin Aging Study II (BASE-II). Multiple linear regression models adjusting for covariates were applied to examine the association between Lp(a) and lung function. The forced expiratory volume in one second (FEV1) and the forced vital capacity (FVC) were higher in both men and women with higher Lp(a) levels. However, since this association between lung function parameters and Lp(a) was not supported by Mendelian randomization analyses using recent genome-wide association study data, these relationships should be investigated in future work, as the observed differences are, in part, considerable and potentially clinically relevant.

Suppression of Lung Oxidative Stress, Inflammation, and Fibrosis following Nitrogen Mustard Exposure by the Selective Farnesoid X Receptor Agonist Obeticholic Acid

Nitrogen mustard (NM) is a cytotoxic vesicant known to cause pulmonary injury that can progress to fibrosis. NM toxicity is associated with an influx of inflammatory macrophages in the lung. Farnesoid X receptor (FXR) is a nuclear receptor involved in bile acid and lipid homeostasis that has anti-inflammatory activity. In these studies, we analyzed the effects of FXR activation on lung injury, oxidative stress, and fibrosis induced by NM. Male Wistar rats were exposed to phosphate-buffered saline (vehicle control) or NM (0.125 mg/kg) by intratracheal Penncentury-MicroSprayer aerosolization; this was followed by treatment with the FXR synthetic agonist, obeticholic acid (OCA, 15 mg/kg), or vehicle control (0.13-0.18 g peanut butter) 2 hours later and then once per day, 5 days per week thereafter for 28 days. NM caused histopathological changes in the lung, including epithelial thickening, alveolar circularization, and pulmonary edema. Picrosirius red staining and lung hydroxyproline content were increased, indicative of fibrosis; foamy lipid-laden macrophages were also identified in the lung. This was associated with aberrations in pulmonary function, including increases in resistance and hysteresis. Following NM exposure, lung expression of HO-1 and iNOS, and the ratio of nitrates/nitrites in bronchoalveolar lavage fluid (BAL), markers of oxidative stress increased, along with BAL levels of inflammatory proteins, fibrinogen, and sRAGE. Administration of OCA attenuated NM-induced histopathology, oxidative stress, inflammation, and altered lung function. These findings demonstrate that FXR plays a role in limiting NM-induced lung injury and chronic disease, suggesting that activating FXR may represent an effective approach to limiting NM-induced toxicity. SIGNIFICANCE STATEMENT: In this study, the role of farnesoid-X-receptor (FXR) in mustard vesicant-induced pulmonary toxicity was analyzed using nitrogen mustard (NM) as a model. This study's findings that administration of obeticholic acid, an FXR agonist, to rats reduces NM-induced pulmonary injury, oxidative stress, and fibrosis provide novel mechanistic insights into vesicant toxicity, which may be useful in the development of efficacious therapeutics.

Real-Time Exposure to 3D-Printing Emissions Elicits Metabolic and Pro-Inflammatory Responses in Human Airway Epithelial Cells

Three-dimensional (3D) printer usage in household and school settings has raised health concerns regarding chemical and particle emission exposures during operation. Although the composition of 3D printer emissions varies depending on printer settings and materials, little is known about the impact that emissions from different filament types may have on respiratory health and underlying cellular mechanisms. In this study, we used an in vitro exposure chamber system to deliver emissions from two popular 3D-printing filament types, acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA), directly to human small airway epithelial cells (SAEC) cultured in an air-liquid interface during 3D printer operation. Using a scanning mobility particle sizer (SMPS) and an optical particle sizer (OPS), we monitored 3D printer particulate matter (PM) emissions in terms of their particle size distribution, concentrations, and calculated deposited doses. Elemental composition of ABS and PLA emissions was assessed using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX). Finally, we compared the effects of emission exposure on cell viability, inflammation, and metabolism in SAEC. Our results reveal that, although ABS filaments emitted a higher total concentration of particles and PLA filaments emitted a higher concentration of smaller particles, SAEC were exposed to similar deposited doses of particles for each filament type. Conversely, ABS and PLA emissions had distinct elemental compositions, which were likely responsible for differential effects on SAEC viability, oxidative stress, release of inflammatory mediators, and changes in cellular metabolism. Specifically, while ABS- and PLA-emitted particles both reduced cellular viability and total glutathione levels in SAEC, ABS emissions had a significantly greater effect on glutathione relative to PLA emissions. Additionally, pro-inflammatory cytokines including IL-1β, MMP-9, and RANTES were significantly increased due to ABS emissions exposure. While IL-6 and IL-8 were stimulated in both exposure scenarios, VEGF was exclusively increased due to PLA emissions exposures. Notably, ABS emissions induced metabolic perturbation on amino acids and energy metabolism, as well as redox-regulated pathways including arginine, methionine, cysteine, and vitamin B3 metabolism, whereas PLA emissions exposures caused fatty acid and carnitine dysregulation. Taken together, these results advance our mechanistic understanding of 3D-printer-emissions-induced respiratory toxicity and highlight the role that filament emission properties may play in mediating different respiratory outcomes.

Independent effect of the triglyceride-glucose index on all-cause mortality in critically ill patients with chronic obstructive pulmonary disease and asthma: A retrospective cohort study

BACKGROUND

The triglyceride-glucose (TyG) index serves as a reliable proxy for insulin resistance (IR). IR has been linked to heightened incidence, prevalence, or severity of chronic obstructive pulmonary disease (COPD) and asthma. Prior research indicates that critically ill patients are prone to developing IR. Nevertheless, few studies have delved into the correlation between IR and all-cause mortality in critically ill patients with COPD and asthma. Therefore, the aim of this study is to explore the association between the TyG index and all-cause mortality in patients with COPD and asthma, with the goal of assessing the impact of IR on the prognosis of this patient population.

METHODS

This is a retrospective study, and all data are from the Medical Information Mart for Intensive Care IV (MIMIC-IV) critical care database. This study included 684 ICU patients with COPD and asthma and divided them into quartiles based on TyG index levels. The primary outcomes of this study were all-cause mortality during follow-up, encompassing mortality at 30 days, 90 days, and 180 days. The Kaplan-Meier analysis was used to compare all-cause mortality among the above four groups. Cox proportional hazards analyses were performed to examine the association between TyG index and all-cause mortality in critically ill patients with COPD and asthma. Restricted cubic spline analysis was used to assess potential nonlinear association between the TyG index and the primary outcome.

RESULTS

A total of 684 patients (53.9% female) were included. The 90-days all-cause mortality rate and 180-days all-cause mortality were 11.7% and 12.3%, respectively. Kaplan-Meier analysis revealed a significant association between the TyG index and both 90-days all-cause mortality (log-rank p = .039) and 180-days all-cause mortality (log-rank p = .017). Cox proportional hazards analysis revealed a significant association between the TyG index and 90-days all-cause mortality in both the unadjusted model (HR, 1.30 [95% CI 1.08-1.57] p = .005) and the model adjusted for age, gender, and diabetes (HR, 1.38 [95% CI 1.15-1.67] p < .001). Similarly, the TyG index was associated with 180-days all-cause mortality in the unadjusted model (HR, 1.30 [95% CI 1.09-1.56] p = .004) and the model adjusted for age, sex, and diabetes (HR, 1.38 [95% CI 1.15-1.66] p < .001). The restricted cubic splines (RCS) regression model indicated a significant nonlinear association between the TyG index and both 90-days and 180-days all-cause mortality. Specifically, TyG index >4.8 was associated with an increased risk of mortality at both 90 days and 180 days.

CONCLUSIONS

In summary, our results extend the utility of the TyG index to critically ill patients with COPD and asthma. Our study shows that the TyG index is a potential predictor of all-cause mortality in critically ill patients with COPD and asthma. In addition, in patients with a TyG index exceeding 4.8, there was a heightened risk of mortality. Measuring the TyG index may help with risk stratification and prognosis prediction in critically ill patients with COPD and asthma. Further prospective studies are needed to confirm our findings.

Oxysterols in Infectious Diseases

Oxysterols have emerged as important bioactive lipids in the immune response to infectious diseases. This chapter discusses our current knowledge of oxysterols and their receptors in bacterial and viral infections of the respiratory and gastrointestinal tracts. Oxysterols are produced in response to infections and have multiple roles including chemotaxis of immune cells to the site of infection and regulation of inflammation. Some oxysterols have been shown to possess antiviral or antibacterial activity.Lastly, we delve into the emerging mechanisms of action of oxysterols. Oxysterols can enhance host cell resistance via reduction of membrane accessible cholesterol, modulate membrane immune signalling, and impact inflammasome activation and efferocytosis.

Endogenous and Therapeutic 25-Hydroxycholesterols May Worsen Early SARS-CoV-2 Pathogenesis in Mice

Oxysterols (i.e., oxidized cholesterol species) have complex roles in biology. 25-Hydroxycholesterol (25HC), a product of the activity of cholesterol-25-hydroxylase (CH25H) on cholesterol, has recently been shown to be broadly antiviral, suggesting therapeutic potential against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, 25HC can also amplify inflammation and be converted by CYP7B1 (cytochrome P450 family 7 subfamily B member 1) to 7α,25-dihydroxycholesterol, a lipid with chemoattractant activity, via the G protein-coupled receptor EBI2 (Epstein-Barr virus-induced gene 2)/GPR183 (G protein-coupled receptor 183). Here, using in vitro studies and two different murine models of SARS-CoV-2 infection, we investigate the effects of these two oxysterols on SARS-CoV-2 pneumonia. We show that although 25HC and enantiomeric-25HC are antiviral in vitro against human endemic coronavirus-229E, they did not inhibit SARS-CoV-2; nor did supplemental 25HC reduce pulmonary SARS-CoV-2 titers in the K18-human ACE2 (angiotensin-converting enzyme 2) mouse model in vivo. Treatment with 25HC also did not alter immune cell influx into the airway, airspace cytokines, lung pathology, weight loss, symptoms, or survival but was associated with increased airspace albumin, an indicator of microvascular injury, and increased plasma proinflammatory cytokines. Conversely, mice treated with the EBI2/GPR183 inhibitor NIBR189 displayed a modest increase in lung viral load only at late time points but no change in weight loss. Consistent with these findings, although Ch25h and 25HC were upregulated in the lungs of SARS-CoV-2-infected wild-type mice, lung viral titers and weight loss in Ch25h-/- and Gpr183-/- mice infected with the β variant were similar to those in control animals. Taken together, endogenous 25HCs do not significantly regulate early SARS-CoV-2 replication or pathogenesis, and supplemental 25HC may have proinjury rather than therapeutic effects in SARS-CoV-2 pneumonia.

Analysis of tissue lipidomics and computed tomography pulmonary fat attenuation volume (CTPFAV ) in idiopathic pulmonary fibrosis

BACKGROUND AND OBJECTIVE

There is increasing interest in the role of lipids in processes that modulate lung fibrosis with evidence of lipid deposition in idiopathic pulmonary fibrosis (IPF) histological specimens. The aim of this study was to identify measurable markers of pulmonary lipid that may have utility as IPF biomarkers.

STUDY DESIGN AND METHODS

IPF and control lung biopsy specimens were analysed using a unbiased lipidomic approach. Pulmonary fat attenuation volume (PFAV) was assessed on chest CT images (CTPFAV ) with 3D semi-automated lung density software. Aerated lung was semi-automatically segmented and CTPFAV calculated using a Hounsfield-unit (-40 to -200HU) threshold range expressed as a percentage of total lung volume. CTPFAV was compared to pulmonary function, serum lipids and qualitative CT fibrosis scores.

RESULTS

There was a significant increase in total lipid content on histological analysis of IPF lung tissue (23.16 nmol/mg) compared to controls (18.66 mol/mg, p = 0.0317). The median CTPFAV in IPF was higher than controls (1.34% vs. 0.72%, p < 0.001) and CTPFAV correlated significantly with DLCO% predicted (R2  = 0.356, p < 0.0001) and FVC% predicted (R2  = 0.407, p < 0.0001) in patients with IPF. CTPFAV correlated with CT features of fibrosis; higher CTPFAV was associated with >10% reticulation (1.6% vs. 0.94%, p = 0.0017) and >10% honeycombing (1.87% vs. 1.12%, p = 0.0003). CTPFAV showed no correlation with serum lipids.

CONCLUSION

CTPFAV is an easily quantifiable non-invasive measure of pulmonary lipids. In this pilot study, CTPFAV correlates with pulmonary function and radiological features of IPF and could function as a potential biomarker for IPF disease severity assessment.

We need to talk about lung cancer's cholesterol-hoarding problem

Proliferative cells require excess cholesterol to support rapid membrane biogenesis. Using a mutant KRAS mouse model of non-small cell lung cancer, Guilbaud et al. show that lung cancers accumulate cholesterol by locally and distally reprogramming lipid trafficking and that cholesterol-removing interventions may hold promise as a therapeutic strategy.

Scavenger receptor BI attenuates oxidized phospholipid-induced pulmonary inflammation

Damage associated molecular patterns (DAMPs) are molecules released from dead/dying cells following toxicant and/or environmental exposures that activate the immune response through binding of pattern recognition receptors (PRRs). Excessive production of DAMPs or failed clearance leads to chronic inflammation and delayed inflammation resolution. One category of DAMPs are oxidized phospholipids (oxPLs) produced upon exposure to high levels of oxidative stress, such as following ozone (O3) induced inflammation. OxPLs are bound by multiple classes of PRRs that include scavenger receptors (SRs) such as SR class B-1 (SR-BI) and toll-like receptors (TLRs). Interactions between oxPLs and PRRs appear to regulate inflammation; however, the role of SR-BI in oxPL-induced lung inflammation has not been defined. Therefore, we hypothesize that SR-BI is critical in protecting the lung from oxPL-induced pulmonary inflammation/injury. To test this hypothesis, C57BL/6J (WT) female mice were dosed with oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphatidylcholine (oxPAPC) by oropharyngeal aspiration which increased pulmonary SR-BI expression. Following oxPAPC exposure, SR-BI deficient (SR-BI-/-) mice exhibited increased lung pathology and inflammatory cytokine/chemokine production. Lipidomic analysis revealed that SR-BI-/- mice had an altered pulmonary lipidome prior to and following oxPAPC exposure, which correlated with increased oxidized phosphatidylcholines (PCs). Finally, we characterized TLR4-mediated activation of NF-κB following oxPAPC exposure and discovered that SR-BI-/- mice had increased TLR4 mRNA expression in lung tissue and macrophages, increased nuclear p65, and decreased cytoplasmic IκBα. Overall, we conclude that SR-BI is required for limiting oxPAPC-induced lung pathology by maintaining lipid homeostasis, reducing oxidized PCs, and attenuating TLR4-NF-κB activation, thereby preventing excessive and persistent inflammation.

Integrated Proteomics and Metabolomics Analysis to Explore the Amelioration Mechanisms of Rosa roxburghii Tratt Fruit Polyphenols on Lipopolysaccharide-Induced Acute Lung Injury Mice

Acute lung injury (ALI) is the main cause of death for the elderly and children due to its high morbidity and mortality rates. Plant-derived functional foods are becoming increasingly important to the healthcare and food industries for adjunctive and alternative treatments of ALI. Polyphenols have been regarded to be beneficial to the prevention and amelioration of ALI. Rosa roxburghii Tratt fruit polyphenols (RRTP) has potential to prevent ALI, but mechanism remains unclear. This study was set up to systematically analyze the RRTP extract active ingredients, comprehensively evaluate its protective effects via lung histopathological examination, protein concentration, and cytokines production in ALI mice induced by lipopolysaccharide (LPS), and finally revealed alleviation mechanisms of the regulatory effects of RRTP by proteomics and metabolomics approach. The results demonstrated RRTP could synergistically exert significant preventive effects against ALI by notably ameliorating lung histopathological damage and pulmonary capillary permeability in ALI mice, inhibiting lung tissue inflammatory response and acute phase proteins and S-100 calcium binding proteins, suppressing excessive activation of complement and coagulation cascades, and regulating disordered lipids metabolism and amino acid metabolism. This study illustrated that RRTP has obvious advantages in ALI adjunctive therapy and revealed the complicated amelioration mechanisms, which provides a breakthrough for the development and demonstration of RRTP as a nutritional compound additive for complementary therapy of ALI.

Diverse functions of apolipoprotein A-I in lung fibrosis

Apolipoprotein A-I (apoA-I) mediates reverse cholesterol transport (RCT) out of cells. In addition to its important role in the RTC, apoA-I also possesses anti-inflammatory and antioxidative functions including the ability to activate inflammasome and signal via toll-like receptors. Dysfunctional apoA-I or its low abundance may cause accumulation of cholesterol mass in alveolar macrophages, leading to the formation of foam cells. Increased numbers of foam cells have been noted in the lungs of mice after experimental exposure to cigarette smoke, silica, or bleomycin and in the lungs of patients suffering from different types of lung fibrosis, including idiopathic pulmonary fibrosis (IPF). This suggests that dysregulation of lipid metabolism may be a common event in the pathogenesis of interstitial lung diseases. Recognition of the emerging role of cholesterol in the regulation of lung inflammation and remodeling provides a challenging concept for understanding lung diseases and offers novel and exciting avenues for therapeutic development. Accordingly, a number of preclinical studies demonstrated decreased expression of inflammatory and profibrotic mediators and preserved lung tissue structure following the administration of the apoA-I or its mimetic peptides. This review highlights the role of apoA-I in lung fibrosis and provides evidence for its potential use in the treatment of this pathological condition.

Surfactant protein D inhibits lipid-laden foamy macrophages and lung inflammation in chronic obstructive pulmonary disease

Increased levels of surfactant protein D (SP-D) and lipid-laden foamy macrophages (FMs) are frequently found under oxidative stress conditions and/or in patients with chronic obstructive pulmonary disease (COPD) who are also chronically exposed to cigarette smoke (CS). However, the roles and molecular mechanisms of SP-D and FMs in COPD have not yet been determined. In this study, increased levels of SP-D were found in the bronchoalveolar lavage fluid (BALF) and sera of ozone- and CS-exposed mice. Furthermore, SP-D-knockout mice showed increased lipid-laden FMs and airway inflammation caused by ozone and CS exposure, similar to that exhibited by our study cohort of chronic smokers and COPD patients. We also showed that an exogenous recombinant fragment of human SP-D (rfhSP-D) prevented the formation of oxidized low-density lipoprotein (oxLDL)-induced FMs in vitro and reversed the airway inflammation and emphysematous changes caused by oxidative stress and CS exposure in vivo. SP-D upregulated bone marrow-derived macrophage (BMDM) expression of genes involved in countering the oxidative stress and lipid metabolism perturbations induced by CS and oxLDL. Our study demonstrates the crucial roles of SP-D in the lipid homeostasis of dysfunctional alveolar macrophages caused by ozone and CS exposure in experimental mouse emphysema, which may provide a novel opportunity for the clinical application of SP-D in patients with COPD.

Evaluation of endogenous and therapeutic 25-hydroxycholesterols in murine models of pulmonary SARS-CoV-2 infection

Oxysterols (i.e., oxidized cholesterol species) have complex roles in biology. 25-hydroxycholesterol (25HC), a product of activity of cholesterol-25-hydroxylase (CH25H) upon cholesterol, has recently been shown to be broadly antiviral, suggesting therapeutic potential against SARS-CoV-2. However, 25HC can also amplify inflammation and tissue injury and be converted by CYP7B1 to 7α,25HC, a lipid with chemoattractant activity via the G protein-coupled receptor, EBI2/GPR183. Here, using in vitro studies and two different murine models of SARS-CoV-2 infection, we investigate the effects of these two oxysterols on SARS-CoV-2 pneumonia. We show that while 25HC and enantiomeric-25HC are antiviral in vitro against human endemic coronavirus-229E, they did not inhibit SARS-CoV-2; nor did supplemental 25HC reduce pulmonary SARS-CoV-2 titers in the K18-human ACE2 mouse model in vivo. 25HC treatment also did not alter immune cell influx into the airway, airspace cytokines, lung pathology, weight loss, symptoms, or survival but was associated with increased airspace albumin, an indicator of microvascular injury, and increased plasma pro-inflammatory cytokines. Conversely, mice treated with the EBI2/GPR183 inhibitor NIBR189 displayed a modest increase in lung viral load only at late time points, but no change in weight loss. Consistent with these findings, although Ch25h was upregulated in the lungs of SARS-CoV-2-infected WT mice, lung viral titers and weight loss in Ch25h-/- and Gpr183-/- mice infected with the beta variant were similar to control animals. Taken together, endogenous 25-hydroxycholesterols do not significantly regulate early SARS-CoV-2 replication or pathogenesis and supplemental 25HC may have pro-injury rather than therapeutic effects in SARS-CoV-2 pneumonia.

Effects of phytosterols' intake on systemic and tissue-specific lipid metabolism in C57BL/6J mice

This study aimed to investigate the long-term effects of phytosterols (PS) intake on systemic and tissue-specific lipid metabolism in C57BL/6J mice. Healthy male C57BL/6J mice were randomly divided into control diet group (CS) and PS diet group (2% PS). After 28 weeks of continuous feeding, serums, livers, and lungs were collected for targeted free sterols quantification, biochemical tests, lipid profile detection, and RNA-seq analysis. Compared with the CS group, 2% PS supplementation significantly increased campesterol concentrations and its ratio to cholesterol in the serum, liver, and lung of mice, with cholestanol concentrations and its ratio to cholesterol decreased. Total cholesterol (TC) levels were reduced in the serum of the PS group (p < 0.05), with the triglyceride (TG) levels unchanged. In response to the decreased circulating cholesterol concentration, the expression of endogenous cholesterol synthesis genes was upregulated in the liver, but caused no obvious lipid accumulation and inflammatory cell infiltration. However, for peripheral tissues, long-term PS-fed mice exhibited diminished cholesterol synthesis, fatty acid transport, and oxidation in the lung. The results provided clear indication that 2% PS diet effectively reduced circulating TC levels in the healthy mice, with tissue-specific lipid metabolic regulation in the liver and the lung.

Regulatory roles of external cholesterol in human airway epithelial mitochondrial function through STARD3 signalling

BACKGROUND

Hypercholesterolemia is found in patients with chronic lung inflammation, during which airway epithelial cells play important roles in maintenance of inflammatory responses to pathogens. The present study aims at molecular mechanisms by which cholesterol changes airway epithelial sensitivity in response to smoking.

METHODS

Human bronchial epithelial cells (HBEs) were stimulated with cigarette smoke extract (CSE) and mice were exposed to CS/lipopolysaccharide (LPS) as models in vitro and in vivo. Severe COPD patients and healthy volunteers were also enrolled and the level of cholesterol in plasma was detected by metabolomics. Filipin III and elisa kits were used to stain free cholesterol. Mitochondrial function was detected by mitotracker green, mitotracker green, and Seahorse. Mitochondrial morphology was detected by high content screening and electron microscopy. The mRNA and protein levels of mitochondrial dynamics-related proteins were detected by RT-qPCR and Western blot,respectively. BODIPY 493/503 was used to stain lipid droplets. Lipidomics was used to detect intracellular lipid components. The mRNA level of interleukin (IL)-6 and IL-8 were detected by RT-qPCR.

RESULTS

We found that the cholesterol overload was associated with chronic obstructive pulmonary disease (COPD) and airway epithelia-driven inflammation, evidenced by hypercholesterolemia in patients with COPD and preclinical models, alteration of lipid metabolism-associated genes in CSE-induced airway epithelia and production of ILs. External cholesterol altered airway epithelial sensitivity of inflammation in response to CSE, through the regulation of STARD3-MFN2 pathway, cholesterol re-distribution, altered transport and accumulation of cholesterol, activities of lipid transport regulators and disorder of mitochondrial function and dynamics. MFN2 down-regulation increased airway epithelial sensitivity and production of ILs after smoking, at least partially by injuring fatty acid oxidation and activating mTOR phosphorylation.

CONCLUSIONS

Our data provide new insights for understanding molecular mechanisms of cholesterol-altered airway epithelial inflammation and for developing diagnostic biomarkers and therapeutic targets to improve patient outcomes.

A 66-Year-Old Man With Subacute Cough and Worsening Dyspnea Previously Diagnosed With COVID-19 Pneumonia

A 66-year-old man presented with subacute cough and worsening dyspnea. Labs were notable for moderate peripheral eosinophilia, and computed tomography (CT) scan demonstrated extensive crazy-paving throughout bilateral upper lung fields. Bronchoalveolar lavage (BAL) revealed macrophages with lipid-filled vacuoles and negative periodic acid-Schiff (PAS) stain. Further history obtained from the patient and family was notable for daily application of commercially available vapor rub to nares and intentional deep inhalation of nebulized fluids containing scented oils. The patient was diagnosed with exogenous lipoid pneumonia through an unusual route of lipid administration.

Immunomodulation by heavy metals as a contributing factor to inflammatory diseases and autoimmune reactions: Cadmium as an example

Cadmium (Cd) represents a unique hazard because of the long biological half-life in humans (20-30 years). This metal accumulates in organs causing a continuum of responses, with organ disease/failure as extreme outcome. Some of the cellular and molecular alterations in target tissues can be related to immune-modulating potential of Cd. This metal may cause adverse responses in which components of the immune system function as both mediators and effectors of Cd tissue toxicity, which, in combination with Cd-induced alterations in homeostatic reparative activities may contribute to tissue dysfunction. In this work, current knowledge concerning inflammatory/autoimmune disease manifestations found to be related with cadmium exposure are summarized. Along with epidemiological evidence, animal and in vitro data are presented, with focus on cellular and molecular immune mechanisms potentially relevant for the disease susceptibility, disease promotion, or facilitating development of pre-existing pathologies.

Reduction and exhausted features of T lymphocytes under serological changes, and prognostic factors in COVID-19 progression

Aims

Coronavirus disease 2019 (COVID-19) is a novel viral infection threatening worldwide health as currently there exists no effective treatment strategy and vaccination programs are not publicly available yet. T lymphocytes play an important role in antiviral defenses. However, T cell frequency and functionality may be affected during the disease.

Material and methods

Total blood samples were collected from patients with mild and severe COVID-19, and the total lymphocyte number, as well as CD4+ and CD8 + T cells were assessed using flowcytometry. Besides, the expression of exhausted T cell markers was evaluated. The levels of proinflammatory cytokines were also investigated in the serum of all patients using enzyme-linked immunesorbent assay (ELISA). Finally, the obtained results were analyzed along with laboratory serological reports.

Results

COVID-19 patients showed lymphopenia and reduced CD4+ and CD8 + T cells, as well as high percentage of PD-1 expression by T cells, especially in severe cases. Serum secretion of TNF-α, IL-1β, and IL-2 receptor (IL-2R) were remarkably increased in patients with severe symptoms, as compared with healthy controls. Moreover, high levels of triglyceride (TG) and low density lipoprotein cholesterol (LDL-C), were correlated with the severity of the disease.

Conclusion

Reduced number and function of T cells were observed in COVID-19 patients, especially in severe patients. Meanwhile, the secretion of proinflammatory cytokines was increased as the disease developed. High level of serum IL-2R was also considered as a sign of lymphopenia. Additionally, hypercholesterolemia and hyperlipidemia could be important prognostic factors in determining the severity of the infection.

Genetic Susceptibility to Pneumonia: A GWAS Meta-Analysis Between the UK Biobank and FinnGen

Pneumonia is a respiratory condition with complex etiology. Host genetic variation is thought to contribute to individual differences in susceptibility and symptom manifestation. Here, we analyze pneumonia data from the UK Biobank (14,780 cases and 439,096 controls) and FinnGen (9980 cases and 86,519 controls) and perform a genomewide association study meta-analysis. We use gene-based tests, colocalization, genetic correlation, latent causal variable (LCV) and polygenic prediction in an independent Australian sample (N = 5595) to draw insights into the etiology of pneumonia risk. We identify two independent loci on chromosome 15 (lead single-nucleotide polymorphisms rs2009746 and rs76474922) to be associated with pneumonia (p < 5e-8). Gene-based tests revealed 18 genes in chromosomes 15, 16 and 9, including IL127, PBX3, ApoB receptor (APOBR) and smoking related genes CHRNA3/5, statistically associated with pneumonia. We observed genetic correlations between pneumonia and cardiorespiratory, psychiatric and inflammatory related traits. LCV analysis suggests a strong genetic causal relationship with cardiovascular health phenotypes. Polygenic risk scores for pneumonia significantly predicted self-reported pneumonia in an independent sample, albeit with a small effect size (OR = 1.11 95% CI [1.04, 1.19], p < .05). Sensitivity analyses suggested the associations in chromosome 15 are mediated by smoking history, but the associations in chromosomes 16 and 9, and polygenic prediction were robust to adjustment for smoking. Altogether, our results highlight common genetic variants, genes and potential pathways that contribute to individual differences in susceptibility to pneumonia, and advance our understanding of the genetic factors underlying heterogeneity in respiratory medical outcomes.

Serum levels of small HDL particles are negatively correlated with death or lung transplantation in an observational study of idiopathic pulmonary fibrosis

BACKGROUND

Serum lipoproteins, such as high density lipoproteins (HDL), may influence disease severity in idiopathic pulmonary fibrosis (IPF). Here, we investigated associations between serum lipids and lipoproteins and clinical endpoints in IPF.

METHODS

Clinical data and serum lipids were analyzed from a discovery cohort (59 IPF subjects, 56 healthy volunteers) and validated using an independent, multicenter cohort (207 IPF subjects) from the Pulmonary Fibrosis Foundation registry. Associations between lipids and clinical endpoints (FVC, forced vital capacity; 6MWD, 6 min walk distance; GAP (Gender Age Physiology) index; death or lung transplantation) were examined using Pearson's correlation and multivariable analyses.

RESULTS

Serum concentrations of small HDL particles (S-HDLP_NMR), measured by nuclear magnetic resonance (NMR) spectroscopy, correlated negatively with the GAP index in the discovery cohort of IPF subjects. The negative correlation of S-HDLP_NMR with GAP index was confirmed in the validation cohort of IPF subjects. Higher levels of S-HDLP_NMR were associated with lower odds of death or its competing outcome, lung transplantation (OR of 0.9 for each 1 μmol·L^-1 increase in S-HDLP_NMR, p<0.05), at 1, 2, and 3 years from study entry in a combined cohort of all IPF subjects.

CONCLUSIONS

Higher serum levels of S-HDLP_NMR are negatively correlated with the GAP index, as well as with lower observed mortality or lung transplantation in IPF subjects. These findings support the hypothesis that S-HDLP_NMR may modify mortality risk in patients with IPF.

Obesity and severe coronavirus disease 2019: molecular mechanisms, paths forward, and therapeutic opportunities

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) appears to have higher pathogenicity among patients with obesity. Obesity, termed as body mass index greater than 30 kg/m2, has now been demonstrated to be important comorbidity for disease severity during coronavirus disease 2019 (COVID-19) pandemic and associated with adverse events. Unraveling mechanisms behind this phenomenon can assist scientists, clinicians, and policymakers in responding appropriately to the COVID-19 pandemic. In this review, we systemically delineated the potential mechanistic links between obesity and worsening COVID-19 from altered physiology, underlying diseases, metabolism, immunity, cytokine storm, and thrombosis. Problematic ventilation caused by obesity and preexisting medical disorders exacerbate organ dysfunction for patients with obesity. Chronic metabolic disorders, including dyslipidemia, hyperglycemia, vitamin D deficiency, and polymorphisms of metabolism-related genes in obesity, probably aid SARS-CoV-2 intrusion and impair antiviral responses. Obesity-induced inadequate antiviral immunity (interferon, natural killer cells, invariant natural killer T cell, dendritic cell, T cells, B cell) at the early stage of SARS-CoV-2 infection leads to delayed viral elimination, increased viral load, and expedited viral mutation. Cytokine storm, with the defective antiviral immunity, probably contributes to tissue damage and pathological progression, resulting in severe symptoms and poor prognosis. The prothrombotic state, driven in large part by endothelial dysfunction, platelet hyperactivation, hypercoagulability, and impaired fibrinolysis in obesity, also increases the risk of severe COVID-19. These mechanisms in the susceptibility to severe condition also open the possibility for host-directed therapies in population with obesity. By bridging work done in these fields, researchers can gain a holistic view of the paths forward and therapeutic opportunities to break the vicious cycle of obesity and its devastating complications in the next emerging pandemic.

The role of high cholesterol in age-related COVID19 lethality

Coronavirus disease 2019 (COVID19) is a respiratory infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) originating in Wuhan, China in 2019. The disease is notably severe in elderly and those with underlying chronic conditions. A molecular mechanism that explains why the elderly are vulnerable and why children are resistant is largely unknown. Here we show loading cells with cholesterol from blood serum using the cholesterol transport protein apolipoprotein E (apoE) enhances the entry of pseudotyped SARS-CoV-2 and the infectivity of the virion. Super resolution imaging of the SARS-CoV-2 entry point with high cholesterol shows almost twice the total number of endocytic entry points. Cholesterol concomitantly traffics angiotensinogen converting enzyme (ACE2) to the endocytic entry site where SARS-CoV-2 presumably docks to efficiently exploit entry into the cell. Furthermore, in cells producing virus, cholesterol optimally positions furin for priming SARS-CoV-2, producing a more infectious virion with improved binding to the ACE2 receptor. In vivo, age and high fat diet induces cholesterol loading by up to 40% and trafficking of ACE2 to endocytic entry sites in lung tissue from mice. We propose a component of COVID19 severity based on tissue cholesterol level and the sensitivity of ACE2 and furin to cholesterol. Molecules that reduce cholesterol or disrupt ACE2 localization with viral entry points or furin localization in the producer cells, may reduce the severity of COVID19 in obese patients.

The Role of ABC Transporters in Lipid Metabolism and the Comorbid Course of Chronic Obstructive Pulmonary Disease and Atherosclerosis

Chronic obstructive pulmonary disease (COPD) ranks among the leading causes of morbidity and mortality worldwide. COPD rarely occurs in isolation and is often combined with various diseases. It is considered that systemic inflammation underlies the comorbid course of COPD. The data obtained in recent years have shown the importance of violations of the cross-links of lipid metabolism and the immune response, which are links in the pathogenesis of both COPD and atherosclerosis. The role of lipid metabolism disorders in the pathogenesis of the comorbid course of COPD and atherosclerosis and the participation of ATP-binding cassette (ABC) transporters in these processes is discussed in this article. It is known that about 20 representatives of a large family of ABC transporters provide lipid homeostasis of cells by moving lipids inside the cell and in its plasma membrane, as well as removing lipids from the cell. It was shown that some representatives of the ABC-transporter family are involved in various links of the pathogenesis of COPD and atherosclerosis, which can determine their comorbid course.

Oxysterols Modify NLRP2 in Epithelial Cells, Identifying a Mediator of Ozone-induced Inflammation

Ozone (O₃) is a prevalent air pollutant causing lung inflammation. Previous studies demonstrate that O₃ oxidizes lipids, such as cholesterol, in the airway to produce oxysterols, such as secosterol-A (SecoA), which are electrophiles capable of forming covalent linkages preferentially with lysine residues and consequently modify protein function. The breadth of proteins modified by this oxysterol as well as the biological consequences in the lung are unknown. Using an alkynyl-tagged form of SecoA and shotgun proteomics, we identified 135 proteins to be modified bronchial epithelial cells. Among them was NLR Family Pyrin Domain Containing 2 (NLRP2) forming a SecoA-protein adduct at lysine (K1019) in the terminal leucine-rich-repeat, a known regulatory region for NLR proteins. NLRP2 expression in airway epithelial cells was characterized and CRISPR-Cas9 knockout and shRNA knockdown of NLRP2 was used to determine its function in O₃-induced inflammation. No evidence for NLPR2 inflammasome formation or NLRP2-dependent increase in caspase-1 activity in response to O₃ was observed. O₃-induced pro-inflammatory gene expression for CXCL2 and CXCL8/IL8 was further enhanced in NLRP2 knockout cells, suggesting a negative regulatory role. Reconstitution of NLRP2 KO cells with K1019R mutant NLRP2 partially blocked SecoA adduction and enhanced O₃-induced IL-8 release as compared to wild type NLRP2. Together, our findings uncover NLRP2 as a highly abundant, key component of pro-inflammatory signaling pathways in airway epithelial cells and as a novel mediator of O₃-induced inflammation.

Inflammatory Pathways in Sarcoidosis

Concepts regarding etiology and pathophysiology of sarcoidosis have changed remarkably within the past 5 years. Sarcoidosis is now viewed as a complex multi-causation disease related to a diverse collection of external environmental or infectious signals. It is generally accepted that the cause of sarcoidosis is unknown. Moreover, concepts of the inflammatory pathway have been modified by the realization that intrinsic genetic factors and innate immunity may modify adaptive immune responses to external triggers. With those potential regulatory pathways in mind, we will attempt to discuss the current understanding of the inflammatory response in sarcoidosis with emphasis on development of pulmonary granulomatous pathology. In that context, we will emphasize that both macrophages and T lymphocytes play key roles, with sometimes overlapping cytokine production (i.e., TNFα and IFN-γ) but also with unique mediators that influence the pathologic picture. Numerous studies have shown that in a sizable number of sarcoidosis patients, granulomas spontaneously resolve, usually within 3 years. Other sarcoidosis patients, however, may develop a chronic granulomatous disease which may subsequently lead to fibrosis. This chapter will outline our current understanding of inflammatory pathways in sarcoidosis which initiate and mediate granulomatous changes or onset of pulmonary fibrosis.

Construction of Recombinant Human GM-CSF and GM-CSF-ApoA-I Fusion Protein and Evaluation of Their Biological Activity

In this study, two strains of the yeast P. pastoris were constructed, one of which produced authentic recombinant human granulocyte-macrophage colony-stimulating factor (ryGM-CSF), and the other was a chimera consisting of ryGM-CSF genetically fused with mature human apolipoprotein A-I (ApoA-I) (ryGM-CSF-ApoA-I). Both forms of the cytokine were secreted into the culture medium. The proteins’ yield during cultivation in flasks was 100 and 60 mg/L for ryGM-CSF and ryGM-CSF-ApoA-I, respectively. Both forms of recombinant GM-CSF stimulated the proliferation of human TF-1 erythroleukemia cells; however, the amount of chimera required was 10-fold that of authentic GM-CSF to induce a similar proliferative effect. RyGM-CSF exhibited a 2-fold proliferative effect on BFU-E (burst-forming units—erythroid) at a concentration 1.7 fold less than non-glycosylated E. coli-derived GM-CSF. The chimera together with authentic ryGM-CSF increased the number of both erythroid precursors and BMC granulocytes after 48 h of incubation of human bone marrow cells (BMCs). In addition, the chimeric form of ryGM-CSF was more effective at increasing the viability of the total amount of BMCs, decreasing apoptosis compared to the authentic form. ryGM-CSF-ApoA-I normalized the proliferation, maturation, and segmentation of neutrophils within the physiological norm, preserving the pool of blast cells under conditions of impaired granulopoiesis. The chimera form of GM-CSF exhibited the properties of a multilinear growth factor, modulating the activity of GM-CSF and, perhaps, it may be more suitable for the normalization of granulopoiesis.

Lung function decline is associated with serum uric acid in Korean health screening individuals

We performed a retrospective cohort study of 19,237 individuals who underwent at least three health screenings with follow-up periods of over 5 years to find a routinely checked serum marker that predicts lung function decline. Using linear regression models to analyze associations between the rate of decline in the forced expiratory volume in 1 s (FEV1) and the level of 10 serum markers (calcium, phosphorus, uric acid, total cholesterol, total protein, total bilirubin, alkaline phosphatase, aspartate aminotransferase, creatinine, and C-reactive protein) measured at two different times (at the first and third health screenings), we found that an increased uric acid level was significantly associated with an accelerated FEV1 decline (P = 0.0014 and P = 0.037, respectively) and reduced FEV1 predicted % (P = 0.0074 and P = 8.64 × 10^–7, respectively) at both visits only in non-smoking individuals. In addition, we confirmed that accelerated forced vital capacity (FVC) and FEV1/FVC ratio declines were observed in non-smoking individuals with increased serum uric acid levels using linear mixed models. The serum uric acid level thus potentially predicts an acceleration in lung function decline in a non-smoking general population.

Association of Triglyceride-Glucose Index and Lung Health: A Population-based Study

BACKGROUND

Metabolic syndrome and insulin resistance are associated with worsened outcomes of chronic lung disease. The triglyceride-glucose index (TyG), a measure of metabolic dysfunction, is associated with metabolic syndrome and insulin resistance, but its relationship to lung health is unknown.

RESEARCH QUESTION

What is the relationship of TyG to respiratory symptoms, chronic lung disease, and lung function?

STUDY DESIGN AND METHODS

This study analyzed data from the National Health and Nutrition Examination Survey from 1999 to 2012. Participants included fasting adults age ≥ 40 years (N = 6,893) with lung function measurements in a subset (n = 3,383). Associations of TyG with respiratory symptoms (cough, phlegm production, wheeze, and exertional dyspnea), chronic lung disease (diagnosed asthma, chronic bronchitis, and emphysema), and lung function (FEV₁, FVC, and obstructive or restrictive spirometry pattern) were evaluated, adjusting for sociodemographic variables, comorbidities, and smoking. TyG was compared vs insulin resistance, represented by the homeostatic model assessment of insulin resistance (HOMA-IR), and vs the metabolic syndrome.

RESULTS

TyG was moderately correlated with HOMA-IR (Spearman ρ = 0.51) and had good discrimination for metabolic syndrome (area under the receiver-operating characteristic curve, 0.80). A one-unit increase in TyG was associated with higher odds of cough (adjusted OR [aOR], 1.28; 95% CI, 1.06-1.54), phlegm production (aOR, 1.20; 95% CI, 1.01-1.43), wheeze (aOR, 1.18; 95% CI, 1.03-1.35), exertional dyspnea (aOR, 1.21; 95% CI, 1.07-1.38), and a diagnosis of chronic bronchitis (aOR, 1.21; 95% CI, 1.02-1.43). TyG was associated with higher relative risk of a restrictive spirometry pattern (adjusted relative risk ratio, 1.45; 95% CI, 1.11-1.90). Many associations were maintained with additional adjustment for HOMA-IR or metabolic syndrome.

INTERPRETATION

TyG was associated with respiratory symptoms, chronic bronchitis, and a restrictive spirometry pattern. Associations were not fully explained by insulin resistance or metabolic syndrome. TyG is a satisfactory measure of metabolic dysfunction with relevance to pulmonary outcomes. Prospective study to define TyG as a biomarker for impaired lung health is warranted.

Participation of ABCA1 Transporter in Pathogenesis of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is the important medical and social problem. According to modern concepts, COPD is a chronic inflammatory disease, macrophages play a key role in its pathogenesis. Macrophages are heterogeneous in their functions, which is largely determined by their immunometabolic profile, as well as the features of lipid homeostasis, in which the ATP binding cassette transporter A1 (ABCA1) plays an essential role. The objective of this work is the analysis of the ABCA1 protein participation and the function of reverse cholesterol transport in the pathogenesis of COPD. The expression of the ABCA1 gene in lung tissues takes the second place after the liver, which indicates the important role of the carrier in lung function. The participation of the transporter in the development of COPD consists in provision of lipid metabolism, regulation of inflammation, phagocytosis, and apoptosis. Violation of the processes in which ABCA1 is involved may be a part of the pathophysiological mechanisms, leading to the formation of a heterogeneous clinical course of the disease.

Novel Mechanisms of Ozone-Induced Pulmonary Inflammation and Resolution, and the Potential Protective Role of Scavenger Receptor BI

INTRODUCTION

Increases in ambient levels of ozone (O3), a criteria air pollutant, have been associated with increased susceptibility and exacerbations of chronic pulmonary diseases through lung injury and inflammation. O3 induces pulmonary inflammation, in part by generating damage-associated molecular patterns (DAMPs), which are recognized by pattern recognition receptors (PRRs), such as toll-like receptors (TLRs) and scavenger receptors (SRs). This inflammatory response is mediated in part by alveolar macrophages (AMs), which highly express PRRs, including scavenger receptor BI (SR-BI). Once pulmonary inflammation has been induced, an active process of resolution occurs in order to prevent secondary necrosis and to restore tissue homeostasis. The processes known to promote the resolution of inflammation include the clearance by macrophages of apoptotic cells, known as efferocytosis, and the production of specialized pro-resolving mediators (SPMs). Impaired efferocytosis and production of SPMs have been associated with the pathogenesis of chronic lung diseases; however, these impairments have yet to be linked with exposure to air pollutants.

SPECIFIC AIMS

The primary goals of this study were: Aim 1 - to define the role of SR-BI in O3-derived pulmonary inflammation and resolution of injury; and Aim 2 - to determine if O3 exposure alters pulmonary production of SPMs and processes known to promote the resolution of pulmonary inflammation and injury.

METHODS

To address Aim 1, female wild-type (WT) and SR-BI-deficient, or knock-out (SR-BI KO), mice were exposed to either O3 or filtered air. In one set of experiments mice were instilled with an oxidized phospholipid (oxPL). Bronchoalveolar lavage fluid (BALF) and lung tissue were collected for the analyses of inflammatory and injury markers and oxPL. To estimate efferocytosis, mice were administered apoptotic cells (derived from the Jurkat T cell line) after O3 or filtered air exposure.

To address Aim 2, male WT mice were exposed to either O3 or filtered air, and levels of SPMs were assessed in the lung, as well as markers of inflammation and injury in BALF. In some experiments SPMs were administered before exposure to O3or filtered air, to determine whether SPMs could mitigate inflammatory or resolution responses. Efferocytosis was measured as in Aim 1.

RESULTS

For Aim 1, SR-BI protein levels increased in the lung tissue of mice exposed to O3, compared with mice exposed to filtered air. Compared with WT controls, SR-BI KO mice had a significant increase in the number of neutrophils in their airspace 24 hours post O3 exposure. The oxPL levels increased in the airspace of both WT and SR-BI KO mice after O3 exposure, compared with filtered air controls. Four hours after instillation of an oxPL, SR-BI KO mice had an increase in BALF neutrophils and total protein, and a nonsignificant increase in macrophages compared with WT controls. O3 exposure decreased efferocytosis in both WT and SR-BI KO female mice.

For Aim 2, mice given SPM supplementation before O3 exposure showed significantly increased AM efferocytosis when compared with the O3exposure control mice and also showed some mitigation of the effects of O3 on inflammation and injury. Several SPMs and their precursors were measured in lung tissue using reverse-phase high performance liquid chromatography (HPLC) with tandem mass spectrometry (MS/MS). At 24 hours after O3 exposure 14R-hydroxydocosahexaenoic acid (HDHA) and 10,17-dihydroxydocosahexaenoic acid (diHDoHE) were significantly decreased in lung tissue, but at 6 hours after exposure, levels of these SPMs increased.

CONCLUSIONS

Our findings identify novel mechanisms by which O3 may induce pulmonary inflammation and also increase susceptibility to and exacerbations of chronic lung diseases.

Interactions between ABCC4/MRP4 and ABCC7/CFTR in human airway epithelial cells in lung health and disease

ATP binding cassette (ABC) transporters are present in all three domains of life - Archaea, Bacteria, and Eukarya. The conserved nature is a testament to the importance of these transporters in regulating endogenous and exogenous substrates required for life to exist. In humans, 49 ABC transporters have been identified to date with broad expression in different lung cell types with multiple transporter family members contributing to lung health and disease. The ABC transporter most commonly known to be linked to lung pathology is ABCC7, also known as cystic fibrosis transmembrane conductance regulator - CFTR. Closely related to the CFTR genomic sequence is ABCC4/multi-drug resistance protein-4. Genomic proximity is shared with physical proximity, with ABCC4 and CFTR physically coupled in cell membrane microenvironments of epithelial cells to orchestrate functional consequences of cyclic-adenosine monophosphate (cAMP)-dependent second messenger signaling and extracellular transport of endogenous and exogenous substrates. The present concise review summarizes the emerging data defining a role of the (ABCC7/CFTR)-ABCC4 macromolecular complex in human airway epithelial cells as a physiologically important pathway capable of impacting endogenous and exogenous mediator transport and ion transport in both lung health and disease.

Risk Factors in Patients with Diabetes Hospitalized for COVID-19: Findings from a Multicenter Retrospective Study

METHODS

In this multicenter retrospective study, patients with COVID-19 in China were included and classified into two groups according to whether they were complicated with diabetes or not. Demographic symptoms and laboratory data were extracted from medical records. Univariable and multivariable logistic regression methods were used to explore the risk factors.

RESULTS

538 COVID-19 patients were finally included in this study, of whom 492 were nondiabetes and 46 were diabetes. The median age was 47 years (IQR 35.0-56.0). And the elderly patients with diabetes were more likely to have dry cough, and the alanine aminotransferase, lactate dehydrogenase, Ca, and mean hemoglobin recovery rate were higher than the other groups. Furthermore, we also found the liver and kidney function of male patients was worse than that of female patients, while female cases should be paid more attention to the occurrence of bleeding and electrolyte disorders. Moreover, advance age, blood glucose, gender, prothrombin time, and total cholesterol could be considered as risk factors for COVID-19 patients with diabetes through the multivariable logistic regression model in our study.

CONCLUSION

The potential risk factors found in our study showed a major piece of the complex puzzle linking diabetes and COVID-19 infection. Meanwhile, focusing on gender and age factors in COVID-19 patients with or without diabetes, specific clinical characteristics, and risk factors should be paid more attention by clinicians to figure out a targeted intervention to improve clinical efficacy worldwide.

Spreading of a mycobacterial cell-surface lipid into host epithelial membranes promotes infectivity

Several virulence lipids populate the outer cell wall of pathogenic mycobacteria. Phthiocerol dimycocerosate (PDIM), one of the most abundant outer membrane lipids, plays important roles in both defending against host antimicrobial programs and in evading these programs altogether. Immediately following infection, mycobacteria rely on PDIM to evade Myd88-dependent recruitment of microbicidal monocytes which can clear infection. To circumvent the limitations in using genetics to understand virulence lipids, we developed a chemical approach to track PDIM during Mycobacterium marinum infection of zebrafish. We found that PDIM's methyl-branched lipid tails enabled it to spread into host epithelial membranes to prevent immune activation. Additionally, PDIM’s affinity for cholesterol promoted this phenotype; treatment of zebrafish with statins, cholesterol synthesis inhibitors, decreased spreading and provided protection from infection. This work establishes that interactions between host and pathogen lipids influence mycobacterial infectivity and suggests the use of statins as tuberculosis preventive therapy by inhibiting PDIM spread.

Lung transcriptome of a COVID-19 patient and systems biology predictions suggest impaired surfactant production which may be druggable by surfactant therapy

An incomplete understanding of the molecular mechanisms behind impairment of lung pathobiology by COVID-19 complicates its clinical management. In this study, we analyzed the gene expression pattern of cells obtained from biopsies of COVID-19-affected patient and compared to the effects observed in typical SARS-CoV-2 and SARS-CoV-infected cell-lines. We then compared gene expression patterns of COVID-19-affected lung tissues and SARS-CoV-2-infected cell-lines and mapped those to known lung-related molecular networks, including hypoxia induced responses, lung development, respiratory processes, cholesterol biosynthesis and surfactant metabolism; all of which are suspected to be downregulated following SARS-CoV-2 infection based on the observed symptomatic impairments. Network analyses suggest that SARS-CoV-2 infection might lead to acute lung injury in COVID-19 by affecting surfactant proteins and their regulators SPD, SPC, and TTF1 through NSP5 and NSP12; thrombosis regulators PLAT, and EGR1 by ORF8 and NSP12; and mitochondrial NDUFA10, NDUFAF5, and SAMM50 through NSP12. Furthermore, hypoxia response through HIF-1 signaling might also be targeted by SARS-CoV-2 proteins. Drug enrichment analysis of dysregulated genes has allowed us to propose novel therapies, including lung surfactants, respiratory stimulants, sargramostim, and oseltamivir. Our study presents a distinct mechanism of probable virus induced lung damage apart from cytokine storm.

Lipid laden macrophages and electronic cigarettes in healthy adults

Background

An outbreak of E-cigarette or Vaping Product Use-Associated Lung Injury (EVALI) with significant morbidity and mortality was reported in 2019. While most patients with EVALI report vaping tetrahydrocannabinol (THC) oils contaminated with vitamin E acetate, a subset report only vaping with nicotine-containing electronic cigarettes (e-cigs). Whether or not e-cigs cause EVALI, the outbreak highlights the need for identifying long term health effects of e-cigs. EVALI pathology includes alveolar damage, pneumonitis and/or organizing pneumonia, often with lipid-laden macrophages (LLM). We assessed LLM in the lungs of healthy smokers, e-cig users, and never-smokers as a potential marker of e-cig toxicity and EVALI.

Methods

A cross-sectional study using bronchoscopy was conducted in healthy smokers, e-cig users, and never-smokers (n = 64). LLM, inflammatory cell counts, and cytokines were determined in bronchial alveolar fluids (BAL). E-cig users included both never-smokers and former light smokers.

Findings

High LLM was found in the lungs of almost all smokers and half of the e-cig users, but not those of never-smokers. LLM were not related to THC exposure or smoking history. LLM were significantly associated with inflammatory cytokines IL-4 and IL-10 in e-cig users, but not smoking-related cytokines.

Interpretation

This is the first report of lung LLM comparing apparently healthy smokers, e-cig users, and never-smokers. LLM are not a specific marker for EVALI given the frequent positivity in smokers; whether LLMs are a marker of lung inflammation in some e-cig users requires further study.

Funding

The National Cancer Institute, the National Heart, Lung, and Blood Institute, the Food and Drug Administration Center for Tobacco Products, the National Center For Advancing Translational Sciences, and Pelotonia Intramural Research Funds

Bronchoalveolar lavage: role in the evaluation of pulmonary interstitial disease

INTRODUCTION

Bronchoalveolar lavage (BAL), a noninvasive, well-tolerated procedure is an important diagnostic tool that can facilitate the diagnosis of various lung diseases. This procedure allows the assessment of large alveolar compartments, by providing cells as well as non-cellular constituents from the lower respiratory tract. Alterations in BAL fluid and cells ratio reflects pathological changes in the lung parenchyma. In some cases, clinicians use BAL as a differential diagnosis guide for interstitial lung disease.

AREAS COVERED

In this review, we summarized the diagnostic criteria for BAL in interstitial lung diseases, pulmonary infections, lung cancer and other pathologies such as fat embolism, gastroesophageal reflux and collagen vascular disease. For this review, we have selected scientific papers published in the PubMed database in our area of interest. We aimed to highlight the usefulness of BAL in respiratory pathology.

EXPERT OPINION

Although BAL fluid analyzes has an essential role in the diagnostic work-up of many lung pathologies, it should be performed in selected patients. For accurate results, the BAL technique is very important to be standardized.

Transcriptional profiling of lung macrophages during pulmonary injury induced by nitrogen mustard

Nitrogen mustard (NM) and sulfur mustard are cytotoxic alkylating agents that cause severe and progressive damage to the respiratory tract. Evidence indicates that macrophages play a key role in the acute inflammatory phase and the later resolution/profibrotic phase of the pathogenic response. These diverse roles are mediated by inflammatory macrophages broadly classified as M1 proinflammatory and M2 anti-inflammatory that sequentially accumulate in the lung in response to injury. The goal of the present study was to identify signaling mechanisms contributing to macrophage activation in response to mustards. To accomplish this, we used RNA sequencing to analyze the gene expression profiles of lung macrophages isolated 1 and 28 days after intratracheal exposure of rats to NM (0.125 mg/kg) or phosphate-buffered saline control. We identified 641 and 792 differentially expressed genes 1 and 28 days post-NM exposure, respectively. These genes are primarily involved in processes related to cell movement and are regulated by cytokines, including tumor necrosis factor-α, interferon-γ, and interleukin-1β. Some of the most significantly enriched canonical pathways included STAT3 and NF-κB signaling. These cytokines and pathways may represent potential targets for therapeutic intervention to mitigate mustard-induced lung toxicity.

Air Space Distension Precedes Spontaneous Fibrotic Remodeling and Impaired Cholesterol Metabolism in the Absence of Surfactant Protein C

Surfactant protein (SP)-C deficiency is found in samples from patients with idiopathic pulmonary fibrosis, especially in familial forms of this disease. We hypothesized that SP-C may contribute to fibrotic remodeling in aging mice and alveolar lipid homeostasis. For this purpose, we analyzed lung function, alveolar dynamics, lung structure, collagen content, and expression of genes related to lipid and cholesterol metabolism of aging SP-C knockout mice. In addition, in vitro experiments with an alveolar macrophage cell line exposed to lipid vesicles with or without cholesterol and/or SP-C were performed. Alveolar dynamics showed progressive alveolar derecruitment with age and impaired oxygen saturation. Lung structure revealed that decreasing volume density of alveolar spaces was accompanied by increasing of the ductal counterparts. Simultaneously, septal wall thickness steadily increased, and fibrotic wounds appeared in lungs from the age of 50 weeks. This remarkable phenotype is unique to the 129Sv strain, which has an increased absorption of cholesterol, linking the accumulation of cholesterol and the absence of SP-C to a fibrotic remodeling process. The findings of this study suggest that overall loss of SP-C results in an age-dependent, complex, heterogeneous phenotype characterized by a combination of overdistended air spaces and fibrotic wounds that resembles combined emphysema and pulmonary fibrosis in patients with idiopathic pulmonary fibrosis. Addition of SP-C to cholesterol-laden lipid vesicles enhanced the expression of cholesterol metabolism and transport genes in an alveolar macrophage cell line, identifying a potential new lipid-protein axis involved in lung remodeling.

Cholesterol-modifying drugs in COVID-19

Infection with severe acute respiratory syndrom coronavirus 2 (SARS-CoV-2) is more likely to lead to poor outcomes in the elderly and those with cardiovascular disease, obesity or metabolic syndrome. Here, we consider mechanisms by which dyslipidaemia and the use of cholesterol-modifying drugs could influence the virus-host relationship. Cholesterol is essential for the assembly, replication and infectivity of enveloped virus particles; we highlight several cholesterol-modifying drugs with the potential to alter the SARS-CoV-2 life cycle that could be tested in in vitro and in vivo models. Although cholesterol is an essential component of immune cell membranes, excess levels can dysregulate protective immunity and promote exaggerated pulmonary and systemic inflammatory responses. Statins block the production of multiple sterols, oxysterols and isoprenoids, resulting in a pleiotropic range of context-dependent effects on virus infectivity, immunity and inflammation. We highlight antiviral, immunomodulatory and anti-inflammatory effects of cholesterol-modifying drugs that merit further consideration in the management of SARS-CoV-2 infection.

Involvement of ABC-transporters and acyltransferase 1 in intracellular cholesterol-mediated autophagy in bovine alveolar macrophages in response to the Bacillus Calmette-Guerin (BCG) infection

Background

Understanding pathogenic mechanisms is imperative for developing novel treatment to the tuberculosis, an important public health burden worldwide. Recent studies demonstrated that host cholesterol levels have implications in the establishment of Mycobacterium tuberculosis (M. tuberculosis, Mtb) infection in host cells, in which the intracellular cholesterol-mediated ATP-binding cassette transporters (ABC-transporters) and cholesterol acyltransferase1 (ACAT1) exhibited abilities to regulate macrophage autophagy induced by Mycobacterium bovis bacillus Calmette–Guérin (BCG).

Results

The results showed that a down-regulated expression of the ABC-transporters and ACAT1 in primary bovine alveolar macrophages (AMs) and murine RAW264.7 cells in response to a BCG infection. The inhibited expression of ABC-transporters and ACAT1 was associated with the reduction of intracellular free cholesterol, which in turn induced autophagy in macrophages upon to the Mycobacterial infection. These results strongly suggest an involvement of ABC-transporters and ACAT1 in intracellular cholesterol-mediated autophagy in AMs in response to BCG infection.

Conclusion

This study thus provides an insight into into a mechanism by which the cholesterol metabolism regulated the autophagy in macrophages in response to mycobacterial infections.

Alveolar Dynamics and Beyond - The Importance of Surfactant Protein C and Cholesterol in Lung Homeostasis and Fibrosis

Surfactant protein C (SP-C) is an important player in enhancing the interfacial adsorption of lung surfactant lipid films to the alveolar air-liquid interface. Doing so, surface tension drops down enough to stabilize alveoli and the lung, reducing the work of breathing. In addition, it has been shown that SP-C counteracts the deleterious effect of high amounts of cholesterol in the surfactant lipid films. On its side, cholesterol is a well-known modulator of the biophysical properties of biological membranes and it has been proven that it activates the inflammasome pathways in the lung. Even though the molecular mechanism is not known, there are evidences suggesting that these two molecules may interplay with each other in order to keep the proper function of the lung. This review focuses in the role of SP-C and cholesterol in the development of lung fibrosis and the potential pathways in which impairment of both molecules leads to aberrant lung repair, and therefore impaired alveolar dynamics. From molecular to cellular mechanisms to evidences in animal models and human diseases. The evidences revised here highlight a potential SP-C/cholesterol axis as target for the treatment of lung fibrosis.

Regulation of Macrophage Foam Cell Formation During Nitrogen Mustard (NM)-Induced Pulmonary Fibrosis by Lung Lipids

Nitrogen mustard (NM) is a vesicant known to target the lung, causing acute injury which progresses to fibrosis. Evidence suggests that activated macrophages contribute to the pathologic response to NM. In these studies, we analyzed the role of lung lipids generated following NM exposure on macrophage activation and phenotype. Treatment of rats with NM (0.125 mg/kg, i.t.) resulted in a time-related increase in enlarged vacuolated macrophages in the lung. At 28 days postexposure, macrophages stained positively for Oil Red O, a marker of neutral lipids. This was correlated with an accumulation of oxidized phospholipids in lung macrophages and epithelial cells and increases in bronchoalveolar lavage fluid (BAL) phospholipids and cholesterol. RNA-sequencing and immunohistochemical analysis revealed that lipid handling pathways under the control of the transcription factors liver-X receptor (LXR), farnesoid-X receptor (FXR), peroxisome proliferator-activated receptor (PPAR)-ɣ, and sterol regulatory element-binding protein (SREBP) were significantly altered following NM exposure. Whereas at 1-3 days post NM, FXR and the downstream oxidized low-density lipoprotein receptor, Cd36, were increased, Lxr and the lipid efflux transporters, Abca1 and Abcg1, were reduced. Treatment of naïve lung macrophages with phospholipid and cholesterol enriched large aggregate fractions of BAL prepared 3 days after NM exposure resulted in upregulation of Nos2 and Ptgs2, markers of proinflammatory activation, whereas large aggregate fractions prepared 28 days post NM upregulated expression of the anti-inflammatory markers, Il10, Cd163, and Cx3cr1, and induced the formation of lipid-laden foamy macrophages. These data suggest that NM-induced alterations in lipid handling and metabolism drive macrophage foam cell formation, potentially contributing to the development of pulmonary fibrosis.

DESE: estimating driver tissues by selective expression of genes associated with complex diseases or traits

The driver tissues or cell types in which susceptibility genes initiate diseases remain elusive. We develop a unified framework to detect the causal tissues of complex diseases or traits according to selective expression of disease-associated genes in genome-wide association studies (GWASs). This framework consists of three components which run iteratively to produce a converged prioritization list of driver tissues. Additionally, this framework also outputs a list of prioritized genes as a byproduct. We apply the framework to six representative complex diseases or traits with GWAS summary statistics, which leads to the estimation of the lung as an associated tissue of rheumatoid arthritis.

A risk factor for early wheezing in infants: rapid weight gain

Background

The aim of this study was to investigate the correlation between rapid weight gain and early wheezing.

Methods

This study screened 701 infants with lower respiratory tract infection who were no more than 4 months from Jan 1st to Dec 31st in 2018. According to weight-for-age Z-value (WAZ), these infants were divided into the considerably slow weight gain group (group I), the normal weight gain group (group II) and the excessively rapid weight gain group (group III), respectively. The clinical characteristics, weight growth speeds and serum lipid levels were analyzed, and multivariable Logistic model was conducted to select significant variables.

Results

Our results showed that male (OR = 1.841, 95%CI: 1.233–2.751), family wheezing (OR = 5.118, 95%CI: 2.118–12.365), age (OR = 1.273, 95%CI: 1.155–1.403), eczema (OR = 2.769, 95%CI: 1.793–4.275), respiratory syncytial virus (RSV) infection (OR = 1.790, 95%CI: 1.230–2.604), birth weight (OR = 1.746, 95%CI: 1.110–2.746) and total cholesterol (TC) (OR = 1.027, 95%CI: 1.019–1.036) and ΔWAZ (OR = 1.182, 95%CI: 1.022–1.368) were associated with early wheezing. Results indicated that serum TC (P = 0.018) and ΔWAZ (P = 0.023) were positive correlation with wheezing days.

Conclusion

Besides male, family wheezing, age, eczema, RSV infection, birth weight and TC, the rapid weight growth as a risk factor should be concerned in the early wheezing infants.