WITHDRAWN: Update in Critical Care 2021.

Ahead of Print article withdrawn by publisher.

Long-term comprehensive cardiopulmonary phenotyping of COVID-19.

BACKGROUND: Persistent symptoms after initial COVID-19 infection are common and are frequently referred to by the umbrella terms "post-COVID syndrome" and "long COVID". The sheer number of affected patients pose an increasing challenge to healthcare systems worldwide. To date, our understanding of the pathophysiology of the post-COVID syndrome remains poor and the extent to which persistent cardiopulmonary abnormalities contribute to the symptom complex is unclear. We sought to determine the presence and impact of cardiopulmonary sequelae after COVID-19 in longitudinal assessment. METHODS: We report on 71 patients who underwent comprehensive, longitudinal testing in regular intervals for up to 12 months after their initial COVID-19 diagnosis. Testing included pulmonary function testing, cardiopulmonary exercise testing, dedicated left and right heart echocardiography, lung ultrasonography, and cardiac MRI. RESULTS: Our results demonstrate that subjective quality of life after COVID-19 (EQ-5D visual acuity scale, VAS, 67.4 for patients treated as outpatient, 79.2 for patients admitted to the general floor, 71.8 for patients treated in an ICU) is not related to the severity of the initial infection. Maximal exercise capacity is also reduced (VO2max 79% predicted, SD ± 19%); however, this is driven in large parts by patients who had initially required ICU-level of care. The degree of objective reduction in exertion did not correlate with quality of life scores. Pulmonary function testing revealed mild and persistent reduction in DLCO over the first 12 months without significant restrictive or obstructive lung disease. Left and right heart function was intact with good RV function and intact RV/PA coupling, imaging findings suggestive of myocarditis were uncommon (7% of patients). CONCLUSION: A reduction in exercise capacity after COVID-19 is common, but is most prominent in patients previously treated in the ICU and more likely related to deconditioning or fatigue than to cardiopulmonary impairment. Subjective quality of life scores are independent of the severity of initial infection and do not correlate with objective measures of cardiopulmonary function. In our cohort, persistent cardiopulmonary impairment after COVID-19 was uncommon. The post-COVID syndrome is unlikely to be the result of cardiopulmonary sequalae and may reflect a post-ICU syndrome in some. Trial registration Registered on clinicaltrials.gov (NCT04442789), Date: June 23, 2020.

Identification of a Novel EIF2AK Variant and Genetics-Assisted Approach to Diagnosis of Pulmonary Capillary Hemangiomatosis.

Pulmonary capillary hemangiomatosis (PCH) is an uncommon type of pulmonary vascular disease characterized by capillary proliferation and very poor prognosis owing to misdiagnosis and lack of effective therapeutic options. Mutations in the eukaryotic translation initiation factor 2α kinase 4 (EIF2AK4) gene have been reported in pulmonary veno-occlusive disease and PCH. In this report, we present a patient whose diagnosis of PCH was delayed by 2 ½ years despite prior surgical lung biopsy and clinical and laboratory findings suggestive of pulmonary hypertension. Genotyping revealed a novel likely pathogenic variant in the EIF2AK4 gene. Review of surgical lung biopsy performed 2 ½ years prior confirmed PCH histology along with constrictive bronchiolitis.

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. Tissue-resident alveolar macrophages (TR-AMs) reside in an environment characterized by remarkably low glucose concentrations, making glycolysis-linked immunometabolism an inefficient and unlikely means of immune activation. In this study, we show that TR-AMs rely on oxidative phosphorylation to meet their energy demands and maintain extremely low levels of glycolysis under steady-state conditions. Unlike bone marrow-derived macrophages, TR-AMs did not experience enhanced glycolysis in response to LPS, and glycolytic inhibition had no effect on their proinflammatory cytokine production. Hypoxia-inducible factor 1α stabilization promoted glycolysis in TR-AMs and shifted energy production away from oxidative metabolism at baseline, but it was not sufficient for TR-AMs to mount further increases in glycolysis or enhance immune function in response to LPS. Importantly, we confirmed these findings in an in vivo influenza model in which infiltrating macrophages had significantly higher glycolytic and proinflammatory gene expression than TR-AMs. These findings demonstrate that glycolysis is dispensable for macrophage effector function in TR-AM and highlight the importance of macrophage tissue origin (tissue resident vs. recruited) in immunometabolism.

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

Idiopathic pulmonary fibrosis is a fatal interstitial lung disease characterized by the TGF-ß (transforming growth factor-ß)-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 de novo synthesis of glycine, the most abundant amino acid found in collagen protein. TGF-ß upregulates the expression of the enzymes of the de novo serine-glycine synthesis pathway in lung fibroblasts; however, the transcriptional and signaling regulators of this pathway remain incompletely understood. Here, we demonstrate that TGF-ß promotes accumulation of ATF4 (activating transcription factor 4), which is required for increased expression of the serine-glycine synthesis pathway enzymes in response to TGF-ß. We found that induction of the integrated stress response (ISR) contributes to TGF-ß-induced ATF4 activity; however, the primary driver of ATF4 downstream of TGF-ß is activation of mTORC1 (mTOR Complex 1). TGF-ß activates the PI3K-Akt-mTOR pathway, and inhibition of PI3K prevents activation of downstream signaling and induction of ATF4. Using a panel of mTOR inhibitors, we found that ATF4 activation is dependent on mTORC1, independent of mTORC2. Rapamycin, which incompletely and allosterically inhibits mTORC1, had no effect on TGF-ß-mediated induction of ATF4; however, Rapalink-1, which specifically targets the kinase domain of mTORC1, completely inhibited ATF4 induction and metabolic reprogramming downstream of TGF-ß. Our results provide insight into the mechanisms of metabolic reprogramming in myofibroblasts and clarify contradictory published findings on the role of mTOR inhibition in myofibroblast differentiation.

Ambulatory Transition from Parenteral Prostanoid to Inhaled Treprostinil in Patients with Pulmonary Arterial Hypertension.

PURPOSE: The intravenous or subcutaneous delivery of prostanoid drugs for moderate to severe pulmonary arterial hypertension has been fraught with complications and patient dissatisfaction. Combination therapy including inhaled treprostinil is an attractive alternative in clinically stable patients. Uncertainties exist about the patient characteristics and the optimal setting (inpatient versus office/home) for transition. METHODS: Sixteen stable patients with pulmonary arterial hypertension and favorable risk profile were transitioned from parenteral prostanoid to combination therapy including inhaled treprostinil in the home setting. Nine patients were using intravenous treprostinil, two patients were using subcutaneous treprostinil, and five patients were using intravenous epoprostenol at a median dose of 80 (interquartile range, IQR 72-90), 76.5 (68 and 85), and 28 (IQR 26-30) ng/kg/min respectively. Patients were followed up for a median of 732.5 days after transition (IQR 506.5-1294 days). RESULTS: Patients tolerated the transition to inhaled treprostinil well without significant change in functional class (81.25% FC I/II before transition vs. 87.5% after), 6-min walk distance [349 m (IQR 226-461 m) to 364 m (IQR 238-565 m), p = 0.09] or NT-proBNP [149 pg/ml (IQR 71.5-383 pg/ml) to 186.5 pg/ml (IQR 83.5-444 pg/ml), p = 0.38]. Hemodynamic data, where available, showed significant improvements in mean pulmonary artery pressure and pulmonary vascular resistance from 36 mmHg (IQR 27-46.5 mmHg) and 5.2 Wood Units (WU) (IQR 3.1-5.6 WU) to 28.5 mmHg (IQR 22-35.5 mmHg) and 3.2 WU (IQR 2.4-4.2 WU) (p-values 0.022 and 0.003). More patients were on triple therapy after transition, and side effects reported were less severe. CONCLUSION: For select patients, transition from a parenteral prostanoid-based therapy to a combination regimen including inhaled treprostinil in the home setting appears safe and well tolerated.

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. It is not known how changes in local oxygen concentration that occur during conditions such as acute respiratory distress syndrome (ARDS) might affect TR-AM metabolism and function; however, ARDS is associated with progressive loss of TR-AMs, which correlates with the severity of disease and mortality. Here, we demonstrate that hypoxia robustly stabilizes HIF-1α in TR-AMs to promote a glycolytic phenotype. Hypoxia altered TR-AM metabolite signatures, cytokine production, and decreased their sensitivity to the inhibition of mitochondrial function. By contrast, hypoxia had minimal effects on BMDM metabolism. The effects of hypoxia on TR-AMs were mimicked by FG-4592, a HIF-1α stabilizer. Treatment with FG-4592 decreased TR-AM death and attenuated acute lung injury in mice. These findings reveal the importance of microenvironment in determining macrophage metabolic phenotype and highlight the therapeutic potential in targeting cellular metabolism to improve outcomes in diseases characterized by acute inflammation.

IL-6 Inhibition in Critically Ill COVID-19 Patients Is Associated With Increased Secondary Infections.

Background: Anti-inflammatory therapies such as IL-6 inhibition have been proposed for COVID-19 in a vacuum of evidence-based treatment. However, abrogating the inflammatory response in infectious diseases may impair a desired host response and pre-dispose to secondary infections. Methods: We retrospectively reviewed the medical record of critically ill COVID-19 patients during an 8-week span and compared the prevalence of secondary infection and outcomes in patients who did and did not receive tocilizumab. Additionally, we included representative histopathologic post-mortem findings from several COVID-19 cases that underwent autopsy at our institution. Results: One hundred eleven patients were identified, of which 54 had received tocilizumab while 57 had not. Receiving tocilizumab was associated with a higher risk of secondary bacterial (48.1 vs. 28.1%; p = 0.029 and fungal (5.6 vs. 0%; p = 0.112) infections. Consistent with higher number of infections, patients who received tocilizumab had higher mortality (35.2 vs. 19.3%; p = 0.020). Seven cases underwent autopsy. In three cases who received tocilizumab, there was evidence of pneumonia on pathology. Of the four cases that had not been given tocilizumab, two showed evidence of aspiration pneumonia and two exhibited diffuse alveolar damage. Conclusions: Experimental therapies are currently being applied to COVID-19 outside of clinical trials. Anti-inflammatory therapies such as anti-IL-6 therapy have the potential to impair viral clearance, pre-dispose to secondary infection, and cause harm. We seek to raise physician awareness of these issues and highlight the need to better understand the immune response in COVID-19.

IL6 inhibition in critically ill COVID-19 patients is associated with increased secondary infections.

BACKGROUND: Anti-inflammatory therapies such as IL-6 inhibition have been proposed for COVID-19 in a vacuum of evidence-based treatment. However, abrogating the inflammatory response in infectious diseases may impair a desired host response and predispose to secondary infections. METHODS: We retrospectively reviewed the medical record of critically ill COVID-19 patients during an 8-week span and compared the prevalence of secondary infection and outcomes in patients who did and did not receive tocilizumab. Additionally, we included representative histopathologic post-mortem findings from several COVID-19 cases that underwent autopsy at our institution. RESULTS: 111 patients were identified, of which 54 had received tocilizumab while 57 had not. Receiving tocilizumab was associated with a higher risk of secondary bacterial (48.1% vs. 28.1%, p=0.029 and fungal (5.6% vs. 0%, p=0.112) infections. Consistent with higher number of infections, patients who received tocilizumab had higher mortality (35.2% vs. 19.3%, p=0.020). Seven cases underwent autopsy. In 3 cases who received tocilizumab, there was evidence of pneumonia on pathology. Of the 4 cases that had not been given tocilizumab, 2 showed evidence of aspiration pneumonia and 2 exhibited diffuse alveolar damage. CONCLUSIONS: Experimental therapies are currently being applied to COVID-19 outside of clinical trials. Anti-inflammatory therapies such as anti-IL-6 therapy have the potential to impair viral clearance, predispose to secondary infection, and cause harm. We seek to raise physician awareness of these issues and highlight the need to better understand the immune response in COVID-19.

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 Acod1 (Aconitate decarboxylase 1) as one of the top genes induced by PM in macrophages. Acod1 encodes a mitochondrial enzyme that produces itaconate, which has been shown to exert anti-inflammatory effects via NRF2 after LPS. Here, we demonstrate that PM induces Acod1 and itaconate, which reduced mitochondrial respiration via complex II inhibition. Using Acod1-/- mice, we found that Acod1/endogenous itaconate does not affect PM-induced inflammation or NRF2 activation in macrophages in vitro or in vivo. In contrast, exogenous cell permeable itaconate, 4-octyl itaconate (OI) attenuated PM-induced inflammation in macrophages. OI was sufficient to activate NRF2 in macrophages; however, NRF2 was not required for the anti-inflammatory effects of OI. We conclude that the effects of itaconate production on inflammation are stimulus-dependent, and that there are important differences between endogenous and exogenously-applied itaconate.

Air pollution is a major global health problem that causes around 4.2 million deaths each year. Once inhaled, pollution particles can remain in the lungs, where they cause inflammation, tissue damage, and ultimately chronic disease. Macrophages, a population of immune cells in the lungs, are involved in this inflammatory process. Itaconate is a molecule with potential anti-inflammatory effects, produced by mammalian cells including macrophages. Recent studies have shown that a modified form of the molecule, 4-octyl itaconate, reduces inflammation when applied to cells exposed to lipopolysaccharide, a component of infectious bacteria that is, usually, a strong trigger of inflammation. These experiments used the 4-octyl modification to ensure that itaconate could get into the cells. Itaconate's anti-inflammatory action is thought to work by activating a signaling process in cells called the NRF2 pathway. NRF2 is a protein made by 'active' macrophages, that is, macrophages already primed to respond to foreign particles. NRF2 in turn increases production of factors that 'damp down' inflammation, all of which are collectively termed the NRF2 anti-inflammatory pathway. Although macrophages in the lungs are linked with inflammation caused by air pollution, their role ­ and that of itaconate ­ is still not well-understood. Sun et al. therefore wanted to determine if itaconate helps macrophages control pollution-induced inflammation. Initial experiments treated mouse macrophage cells with pollution particles. Analyzing gene activity in these cells showed that exposure to pollution did indeed switch on the Acod1 gene, which encodes the enzyme that makes itaconate. It also turned on genes for other molecules involved in inflammation. Pre-treating macrophages with 4-octyl itaconate before pollution exposure reduced inflammation and also, as expected, turned on the NRF2 pathway. To determine whether cells' own production of itaconate affected lung inflammation, macrophages were isolated from mutant mice lacking Acod1. Comparing these cells, which could not make itaconate, with normal cells revealed that removing itaconate did not change the inflammatory response to pollution. Activity of the NRF2 pathway also remained similar in both types of cells. This showed that itaconate produced by macrophages likely has different effects on lung inflammation from other forms of the compound. These findings represent a step forward in understanding how pollution interacts with immune cells in the lungs. They reveal that the source of anti-inflammatory factors can be just as important in shaping immune responses as the type of factor. These results highlight the need for further, detailed work on the mechanisms underlying pollution-induced disease.

Review of the Association between Splenectomy and Chronic Thromboembolic Pulmonary Hypertension.

Recent evidence suggests that there may be a link between splenectomy and the later development of pulmonary hypertension, in particular World Health Organization group IV pulmonary hypertension (chronic thromboembolic pulmonary hypertension). Epidemiological studies have demonstrated an odds ratio as high as 18 for the development of chronic thromboembolic pulmonary hypertension after splenectomy in comparison with matched control subjects who have not undergone splenectomy. The mechanisms governing the association between removal of the spleen and the subsequent development of chronic thromboembolic pulmonary hypertension remain incompletely understood; however, recent advances in understanding of coagulation homeostasis have shed some light on this association. Splenectomy increases the risk of venous thromboembolic disease, a necessary precursor of chronic thromboembolic pulmonary hypertension, by generating a prothrombotic state. This prothrombotic state likely results from a reduction in the removal of circulating procoagulant factors from the bloodstream after splenectomy. Although much is to be learned, circulating microparticles have emerged as the most likely mediator for the development of thrombosis after splenectomy. Apparently because of a reduction in reticuloendothelial cell clearance, microparticle levels are elevated in patients after splenectomy. Elevated circulating microparticle levels have been linked to thromboembolism and pulmonary hypertension in a dose-dependent fashion. It is important for health care providers to be aware of the link between splenectomy and chronic thromboembolic pulmonary hypertension. We are optimistic that clarification of the exact mechanisms that govern this association will yield clinical guidelines and potential treatments.

Do omega-3 polyunsaturated Fatty acids prevent cardiovascular disease? A review of the randomized clinical trials.

Fish oil is rich in the omega-3 polyunsaturated fatty acids (PUFAs) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Numerous epidemiological studies and several large randomized clinical trials have shown that modest doses of omega-3 PUFAs significantly reduce the risk of unstable angina, myocardial infarction, and sudden cardiac death as well as death in coronary artery disease and heart failure patients. Based on the scientific evidence, the American Heart Association (AHA) has recommended all individuals eat fish at least twice a week to prevent cardiovascular disease. For individuals with coronary artery disease, the recommended dose of omega-3 PUFAs is 1 g of EPA and DHA daily. To lower triglyceride levels, much higher doses are needed. However, more recent randomized clinical trials have questioned the cardiovascular benefits of fish oil. These studies have contributed to the uncertainty health care providers face when recommending omega-3 PUFA supplementation according to clinical guidelines. The purpose of this review is to examine the randomized clinical trials and scientific evidence between omega-3 PUFAs and cardiovascular outcomes to better understand the current role of omega-3 PUFAs in improving cardiovascular health.