The complement cascade in lung injury and disease

BACKGROUND

The complement system is an important arm of immune defense bringing innate and adaptive immunity. Although originally regarded as a major complementary defense mechanism against pathogens, continuously emerging evidence has uncovered a central role of this complex system in several diseases including lung pathologies.

MAIN BODY

Complement factors such as anaphylatoxins C3a and C5a, their receptors C3aR, C5aR and C5aR2 as well as complement inhibitory proteins CD55, CD46 and CD59 have been implicated in pathologies such as the acute respiratory distress syndrome, pneumonia, chronic obstructive pulmonary disease, asthma, interstitial lung diseases, and lung cancer. However, the exact mechanisms by which complement factors induce these diseases remain unclear. Several complement-targeting monoclonal antibodies are reported to treat lung diseases.

CONCLUSIONS

The complement system contributes to the progression of the acute and chronic lung diseases. Better understanding of the underlying mechanisms will provide groundwork to develop new strategy to target complement factors for treatment of lung diseases.

Aquaporin Expression and Regulation in Clinical and Experimental Sepsis

Sepsis is an inflammatory disorder caused by the host's dysfunctional response to infection. Septic patients present diverse clinical characteristics, and in the recent years, it has been the main cause of death in intensive care units (ICU). Aquaporins, membrane proteins with a role in water transportation, have been reported to participate in numerous biological processes. Their role in sepsis progression has been studied extensively. This review aims to examine recent literature on aquaporin expression and regulation in clinical sepsis, as well as established experimental models of sepsis. We will present how sepsis affects aquaporin expression at the molecular and protein level. Moreover, we will delve into the importance of aquaporin regulation at transcriptional, post-transcriptional, translational, and post-translational levels in sepsis by presenting data on aquaporin regulation by non-coding RNAs and selected chemical molecules. Finally, we will focus on the importance of aquaporin single-nucleotide polymorphisms in the setting of sepsis.

Increased Levels of Galectin-3 in Critical COVID-19

Severe COVID-19 is related to hyperinflammation and multiple organ injury, including respiratory failure, thus requiring intensive care unit (ICU) admission. Galectin-3, a carbohydrate-binding protein exhibiting pleiotropic effects, has been previously recognized to participate in inflammation, the immune response to infections and fibrosis. The aim of this study was to evaluate the relationship between galectin-3 and the clinical severity of COVID-19, as well as assess the prognostic accuracy of galectin-3 for the probability of ICU mortality. The study included 235 COVID-19 patients with active disease, treated in two different Greek hospitals in total. Our results showed that median galectin-3 serum levels on admission were significantly increased in critical COVID-19 patients (7.2 ng/mL), as compared to the median levels of patients with less severe disease (2.9 ng/mL, p = 0.003). Galectin-3 levels of the non-survivors hospitalized in the ICU were significantly higher than those of the survivors (median 9.1 ng/mL versus 5.8 ng/mL, p = 0.001). The prognostic accuracy of galectin-3 for the probability of ICU mortality was studied with a receiver operating characteristic (ROC) curve and a multivariate analysis further demonstrated that galectin-3 concentration at hospital admission could be assumed as an independent risk factor associated with ICU mortality. Our results were validated with galectin-3 measurements in a second patient cohort from a different Greek university hospital. Our results, apart from strongly confirming and advancing previous knowledge with two patient cohorts, explore the possibility of predicting ICU mortality, which could provide useful information to clinicians. Therefore, galectin-3 seems to establish its involvement in the prognosis of hospitalized COVID-19 patients, suggesting that it could serve as a promising biomarker in critical COVID-19.

Persistent Endothelial Lung Damage and Impaired Diffusion Capacity in Long COVID

Since the beginning of the pandemic, both COVID-19-associated coagulopathy biomarkers and a plethora of endothelial biomarkers have been proposed and tested as prognostic tools of severity and mortality prediction. As the pandemic is gradually being controlled, attention is now focusing on the long-term sequelae of COVID-19. In the present study, we investigated the role of endothelial activation/dysfunction in long COVID syndrome. This observational study included 68 consecutive long COVID patients and a healthy age and sex-matched control group. In both groups, we measured 13 endothelial biomarkers. Moreover, in the long COVID patients, we evaluated fatigue and dyspnea severity, lung diffusion capacity (DLCO), and the 6-min walk (6MWT) test as measures of functional capacity. Our results showed that markers of endothelial activation/dysfunction were higher in long COVID patients, and that soluble intracellular adhesion molecule 1 (sICAM-1) and soluble vascular adhesion molecule 1 (sVCAM-1) negatively correlated with lung diffusion and functional capacity (sICAM-1 vs. DLCO, r = -0.306, p = 0.018; vs. 6MWT, r = -0.263, p = 0.044; and sVCAM-1 vs. DLCO, r= -0.346, p = 0.008; vs. 6MWT, r = -0.504, p < 0.0001). In conclusion, evaluating endothelial biomarkers alongside clinical tests might yield more specific insights into the pathophysiological mechanisms of long COVID manifestations.

Investigation of Serum Endocan Levels and Age in Critical Inflammatory Conditions

Aging negatively affects the endothelium. Endocan (ESM-1), an endothelium-derived soluble proteoglycan, participates in fundamental biological processes of endothelial cells. We aimed to examine the role of endothelial dysfunction and age in poor outcomes in critical illness. ESM-1 levels were measured in the sera of mechanically ventilated critically ill patients, including COVID-19, non-septic, and septic patients. The 3 patient cohorts were divided based on age (≥65 and <65). Critically ill COVID-19 patients had statistically higher ESM-1 levels compared to critically ill septic and non-septic patients. Only in critically ill septic patients were ESM-1 levels higher in older compared to younger patients. Finally, the age-subgrouped patients were further subdivided based on intensive care unit (ICU) outcome. ESM-1 levels were similar in COVID-19 survivors and non-survivors, irrespective of age. Interestingly, only for the younger critically ill septic patients, non-survivors had higher ESM-1 levels compared to survivors. In the non-septic survivors and non-survivors, ESM-1 levels remained unaltered in the younger patients and tended to be higher in the elderly. Even though endocan has been recognized as an important prognostic biomarker in critically ill patients with sepsis, in our patient cohort, increased age, as well as the extent of endothelial dysfunction, seemed to affect its prognostic ability.

Prognostic Value of HIF-1α-Induced Genes in Sepsis/Septic Shock

Hypoxia is characterized as one of the main consequences of sepsis, which is recognized as the leading cause of death in intensive care unit (ICU) patients. In this study, we aimed to examine whether the expression levels of genes regulated under hypoxia could be utilized as novel biomarkers for sepsis prognosis in ICU patients. Whole blood expression levels of hypoxia-inducible factor-1α (HIF1A), interferon-stimulated gene 15 (ISG15), hexokinase 2 (HK2), lactate dehydrogenase (LDHA), heme oxygenase-1 (HMOX1), erythropoietin (EPO), and the vascular endothelial growth factor A (VEGFA) were measured on ICU admission in 46 critically ill, initially non-septic patients. The patients were subsequently divided into two groups, based on the development of sepsis and septic shock (n = 25) or lack thereof (n = 21). HMOX1 mRNA expression was increased in patients who developed sepsis/septic shock compared to the non-septic group (p < 0.0001). The ROC curve, multivariate logistic regression, and Kaplan-Meier analysis demonstrated that HMOX1 expression could be utilized for sepsis and septic shock development probability. Overall, our results indicate that HMOX1 mRNA levels have the potential to be a valuable predictive factor for the prognosis of sepsis and septic shock in ICU patients.

Endotheliopathy in Acute COVID-19 and Long COVID

The pulmonary endothelium is a highly regulated organ that performs a wide range of functions under physiological and pathological conditions. Since endothelial dysfunction has been demonstrated to play a direct role in sepsis and acute respiratory distress syndrome, its role in COVID-19 has also been extensively investigated. Indeed, apart from the COVID-19-associated coagulopathy biomarkers, new biomarkers were recognised early during the pandemic, including markers of endothelial cell activation or injury. We systematically searched the literature up to 10 March 2023 for studies examining the association between acute and long COVID-19 severity and outcomes and endothelial biomarkers.

NEW INSIGHTS INTO THE PATHOPHYSIOLOGY OF TRAUMA AND HEMORRHAGE

ABSTRACT

Circulatory shock from trauma and hemorrhage remains a clinical challenge with mortality still high within the first hours after impact. It represents a complex disease involving the impairment of a number of physiological systems and organs and the interaction of different pathological mechanisms. Multiple external and patient-specific factors may further modulate and complicate the clinical course. Recently, novel targets and models with complex multiscale interaction of data from different sources have been identified which offer new windows of opportunity. Future works needs to consider patient-specific conditions and outcomes to mount shock research onto the next higher level of precision and personalized medicine.

Acute Kidney Injury Predictors and Outcomes after Cardiac Surgery in Children with Congenital Heart Disease: An Observational Cohort Study

Acute Kidney Injury (AKI) commonly complicates cardiac surgery in children with congenital heart disease (CHD). In this study we assessed incidence, risk factors, and outcomes of postoperative AKI, while testing the hypothesis that, depending on the underlying diagnosis, there would be significant differences in AKI incidence among different diagnostic groups. We conducted an observational cohort study of children with CHD undergoing cardiac surgery in a single tertiary center between January 2019 and August 2021 (n = 362). Kidney Disease Improving Global Outcome (KDIGO) criteria were used to determine the incidence of postoperative AKI. Diagnosis was incorporated into multivariate models using an anatomic-based CHD classification system. Overall survival was estimated using Kaplan−Meier curves. Log-rank test and adjusted Cox proportional hazard modelling were used to test for differences in survival distributions and determine AKI effect on survival function, respectively. AKI occurred in 70 (19.3%), with 21.4% in-hospital mortality for AKI group. Younger age, lower weight, longer cardiopulmonary bypass time, preoperative mechanical ventilation and diagnostic category were associated with postoperative AKI. Resolution rate was 92.7% prior to hospital discharge for survivors. AKI was associated with longer duration of mechanical ventilation, ICU and hospital length of stay. AKI patients had significantly higher probability of all-cause mortality postoperatively when compared to the non-AKI group (log-rank test, p < 0.001). Adjusted hazard ratio for AKI versus non-AKI group was 11.08 (95% CI 2.45−50.01; p = 0.002). Diagnostic category was associated with cardiac surgery-related AKI in children with CHD, a finding supporting the development of lesion specific models for risk stratification. Postoperative AKI had detrimental impact on clinical outcomes and was associated with decreased survival to hospital discharge.

The Paradox of Pulmonary Vascular Resistance: Restoration of Pulmonary Capillary Recruitment as a Sine Qua Non for True Therapeutic Success in Pulmonary Arterial Hypertension

Exercise-induced increases in pulmonary blood flow normally increase pulmonary arterial pressure only minimally, largely due to a reserve of pulmonary capillaries that are available for recruitment to carry the flow. In pulmonary arterial hypertension, due to precapillary arteriolar obstruction, such recruitment is greatly reduced. In exercising pulmonary arterial hypertension patients, pulmonary arterial pressure remains high and may even increase further. Current pulmonary arterial hypertension therapies, acting principally as vasodilators, decrease calculated pulmonary vascular resistance by increasing pulmonary blood flow but have a minimal effect in lowering pulmonary arterial pressure and do not restore significant capillary recruitment. Novel pulmonary arterial hypertension therapies that have mainly antiproliferative properties are being developed to try and diminish proliferative cellular obstruction in precapillary arterioles. If effective, those agents should restore capillary recruitment and, during exercise testing, pulmonary arterial pressure should remain low despite increasing pulmonary blood flow. The effectiveness of every novel therapy for pulmonary arterial hypertension should be evaluated not only at rest, but with measurement of exercise pulmonary hemodynamics during clinical trials.

The Antifibrotic Effects of Inhaled Treprostinil: An Emerging Option for ILD

Interstitial lung diseases (ILD) encompasses a heterogeneous group of parenchymal lung diseases characterized by variable amounts of inflammation and fibrosis. The targeting of fibroblasts and myofibroblasts with antifibrotic treatments is a potential therapeutic target for these potentially fatal diseases. Treprostinil is unique among the prostacyclin mimetics in that it has distinct actions at additional prostaglandin receptors. Preclinical and clinical evidence suggests that treprostinil has antifibrotic effects through the activation of the prostaglandin E receptor 2 (EP₂), the prostaglandin D receptor 1 (DP₁), and peroxisome proliferator-activated receptors (PPAR). In vivo studies of EP₂ and the DP₁ have found that administration of treprostinil resulted in a reduction in cell proliferation, reduced collagen secretion and synthesis, and reduced lung inflammation and fibrosis. In vitro and in vivo studies of PPARβ and PPARγ demonstrated that treprostinil inhibited fibroblast proliferation in a dose-dependent manner. Clinical data from a post hoc analysis of the INCREASE trial found that inhaled treprostinil improved forced vital capacity in the overall population as well as in idiopathic interstitial pneumonia and idiopathic pulmonary fibrosis subgroups. These preclinical and clinical findings suggest a dual benefit of treprostinil through the amelioration of both lung fibrosis and pulmonary hypertension.

Pulmonary Vascular Research Institute GoDeep: A meta-registry merging deep phenotyping datafrom international PH reference centers

The Pulmonary Vascular Research Institute GoDeep meta-registry is a collaboration of pulmonary hypertension (PH) reference centers across the globe. Merging worldwide PH data in a central meta-registry to allow advanced analysis of the heterogeneity of PH and its groups/subgroups on a worldwide geographical, ethnical, and etiological landscape (ClinTrial. gov NCT05329714). Retrospective and prospective PH patient data (diagnosis based on catheterization; individuals with exclusion of PH are included as a comparator group) are mapped to a common clinical parameter set of more than 350 items, anonymized and electronically exported to a central server. Use and access is decided by the GoDeep steering board, where each center has one vote. As of April 2022, GoDeep comprised 15,742 individuals with 1.9 million data points from eight PH centers. Geographic distribution comprises 3990 enrollees (25%) from America and 11,752 (75%) from Europe. Eighty-nine perecent were diagnosed with PH and 11% were classified as not PH and provided a comparator group. The retrospective observation period is an average of 3.5 years (standard error of the mean 0.04), with 1159 PH patients followed for over 10 years. Pulmonary arterial hypertension represents the largest PH group (42.6%), followed by Group 2 (21.7%), Group 3 (17.3%), Group 4 (15.2%), and Group 5 (3.3%). The age distribution spans several decades, with patients 60 years or older comprising 60%. The majority of patients met an intermediate risk profile upon diagnosis. Data entry from a further six centers is ongoing, and negotiations with >10 centers worldwide have commenced. Using electronic interface-based automated retrospective and prospective data transfer, GoDeep aims to provide in-depth epidemiological and etiological understanding of PH and its various groups/subgroups on a global scale, offering insights for improved management.

Increase of HO-1 Expression in Critically Ill COVID-19 Patients Is Associated with Poor Prognosis and Outcome

Heme-oxygenase (HO)-1 is a cytoprotective enzyme with strong antioxidant and anti-apoptotic properties and previous reports have also emphasized the antiviral properties of HO-1, either directly or via induction of interferons. To investigate the potential role of HO-1 in patients with coronavirus disease 2019 (COVID-19), the present study assessed changes in HO-1 expression in whole blood and tissue samples. Upregulation of HO-1 protein was observed in lung, liver, and skin tissue independently of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) presence. A significant increase of blood HO-1 mRNA levels was observed in critically ill COVID-19 patients compared to those in severe COVID-19 patients and healthy controls. This increase was accompanied by significantly elevated levels of serum ferritin and bilirubin in critically ill compared to patients with severe disease. Further grouping of patients in survivors and non-survivors revealed a significant increase of blood HO-1 mRNA levels in the later. Receiver operating characteristic (ROC) analysis for prediction of ICU admission and mortality yielded an AUC of 0.705 (p = 0.016) and 0.789 (p = 0.007) respectively indicating that HO-1 increase is associated with poor COVID-19 progression and outcome. The increase in HO-1 expression observed in critically ill COVID-19 patients could serve as a mechanism to counteract increased heme levels driving coagulation and thrombosis or as an induced protective mechanism.

Mechanistic Understanding of Lung Inflammation: Recent Advances and Emerging Techniques

Acute respiratory distress syndrome (ARDS) is a life-threatening lung injury characterized by an acute inflammatory response in the lung parenchyma. Hence, it is considered as the most appropriate clinical syndrome to study pathogenic mechanisms of lung inflammation. ARDS is associated with increased morbidity and mortality in the intensive care unit (ICU), while no effective pharmacological treatment exists. It is very important therefore to fully characterize the underlying pathobiology and the related mechanisms, in order to develop novel therapeutic approaches. In vivo and in vitro models are important pre-clinical tools in biological and medical research in the mechanistic and pathological understanding of the majority of diseases. In this review, we will present data from selected experimental models of lung injury/acute lung inflammation, which have been based on clinical disorders that can lead to the development of ARDS and related inflammatory lung processes in humans, including ventilation-induced lung injury (VILI), sepsis, ischemia/reperfusion, smoke, acid aspiration, radiation, transfusion-related acute lung injury (TRALI), influenza, Streptococcus (S.) pneumoniae and coronaviruses infection. Data from the corresponding clinical conditions will also be presented. The mechanisms related to lung inflammation that will be covered are oxidative stress, neutrophil extracellular traps, mitogen-activated protein kinase (MAPK) pathways, surfactant, and water and ion channels. Finally, we will present a brief overview of emerging techniques in the field of omics research that have been applied to ARDS research, encompassing genomics, transcriptomics, proteomics, and metabolomics, which may recognize factors to help stratify ICU patients at risk, predict their prognosis, and possibly, serve as more specific therapeutic targets.

The impact of cardiovascular comorbidities associated with risk for left heart disease on idiopathic pulmonary arterial hypertension: Data from the Hellenic Pulmonary Hypertension Registry (HOPE)

Whereas younger female patients were diagnosed with idiopathic pulmonary arterial hypertension (IPAH) in 1980s, it is now frequently encountered in elderly patients with cardiovascular comorbidities (CVCs) associated with increased risk for left heart disease. We present data until November 2019 regarding specific features and clinical outcomes of IPAH population from the Hellenic Pulmonary Hypertension Registry (HOPE). Patients were divided into two groups based on the presence of ≥ or <3 CVCs, arterial hypertension, diabetes mellitus, obesity, presence of coronary artery disease, or atrial fibrillation. Overall, 77 patients with IPAH (55.1 [interquartile range, IQR: 24.1] years, 62.8% women) have been recorded. Fifteen patients (19.2%) had ≥3 CVCs, while 25 (32%) were over 65 years old. Patients with ≥3 CVCs were older, presented an almost equal female to male ratio, walked less in 6‐min walk test, and had lower mean arterial pulmonary pressure and pulmonary vascular resistance at baseline than patients with less CVCs. Fewer patients with ≥3 CVCs received PAH‐specific treatment compared to patients with less comorbidities (n = 11 [73.3%] versus n = 58 [95.5%], p = 0.02). During a median follow‐up period of 3.8 (IQR: 2.7) years, 18 patients died (all‐cause mortality 24.3%). Male sex and older age were independent predictors of mortality and/or lung transplantation, while CVCs did not have a significant impact on clinical outcomes. In this nationwide, register‐based study, the epidemiology of IPAH involves older patients with CVCs, who seem to have less hemodynamic compromise, but worse functional impairment and are treated less aggressively with PAH pharmacotherapy.

Aggressive Afterload Lowering to Improve the Right Ventricle: A New Target for Medical Therapy in Pulmonary Arterial Hypertension?

Despite numerous therapeutic advances in pulmonary arterial hypertension, patients continue to suffer high morbidity and mortality, particularly considering a median age of 50 years. This article explores whether early, robust reduction of right ventricular afterload would facilitate substantial improvement in right ventricular function and thus whether afterload reduction should be a treatment goal for pulmonary arterial hypertension. The earliest clinical studies of prostanoid treatment in pulmonary arterial hypertension demonstrated an important link between lowering mean pulmonary arterial pressure (or pulmonary vascular resistance) and improved survival. Subsequent studies of oral monotherapy or sequential combination therapy demonstrated smaller reductions in mean pulmonary arterial pressure and pulmonary vascular resistance. More recently, retrospective reports of initial aggressive prostanoid treatment or initial combination oral and parenteral therapy have shown marked afterload reduction along with significant improvements in right ventricular function. Some data suggest that reaching threshold levels for pressure or resistance (components of right ventricular afterload) may be key to interrupting the self-perpetuating injury of pulmonary vascular disease in pulmonary arterial hypertension and could translate into improved long-term clinical outcomes. Based on these clues, the authors postulate that improved clinical outcomes might be achieved by targeting significant afterload reduction with initial oral combination therapy and early parenteral prostanoids.

Pulmonary capillary recruitment and distention in mammalian lungs: species similarities

Pulmonary arterial pressure rises minimally during exercise. The pulmonary microcirculation accommodates increasing blood flow via recruitment of pulmonary capillaries and, at higher flows, by distention of already perfused capillaries. The flow transition range between recruitment and distention has not been studied or compared across mammalian species, including humans. We hypothesised that the range would be similar. Functional pulmonary capillary surface area (FCSA) can be estimated using validated metabolic techniques. We reviewed data from previous studies in three mammalian species (perfused rabbit lungs and dog lung lobes, and exercising humans) and generated blood flow–FCSA curves over a range of flows. We noted where the curves diverged from the theoretical line of pure recruitment (Recruitment) and determined the flow where the curve slope equalled 50% that of Recruitment, or equalled that of a theoretical curve representing full capillary distention (Distention). The three mammalian species have similar flow ranges for the transition from predominantly recruitment to predominantly distention, with dogs having the highest transition point. Within the physiological range of most daily activity, the species are similar and accommodate increasing blood flow mainly via recruitment, with progressive distention at higher flows. This is highly relevant to pulmonary physiology during exercise.

Lungs accept exercise blood flow by filling a larger fraction of their capillaries, then distending already filled capillaries as flow rises more. Our review shows the transition range is around 2.5 to 3.5 times resting flow in mammals, including humans.https://bit.ly/3JFWuG7

Lactate and Lactate-to-Pyruvate Ratio in Critically Ill COVID-19 Patients: A Pilot Study

A limited number of coronavirus disease-19 (COVID-19) cases may require treatment in an intensive care unit (ICU). Arterial blood lactate levels are routinely measured in the ICU to estimate disease severity, predict poor outcomes, and monitor therapeutic handlings. A number of studies have suggested that, simultaneously with lactate, pyruvate should also be measured, providing augmented prognostic ability, and a better understanding of the underlying metabolic alterations in ICU patients. Hence, the aim of the present study was to elucidate the relationship between lactate levels and the lactate-to-pyruvate (LP) ratio with the clinical outcome in mechanically ventilated COVID-19 patients. Lactate and pyruvate were serially measured during the first 24 h of ICU stay. A group of ICU non-COVID-19 patients was used as a comparison group. The majority of COVID-19 patients (82.5%) had normal lactate levels and a normal LP ratio on ICU admission (normal metabolic pattern). A small, yet significant, percentage of patients had either elevated lactate levels or a high LP ratio (abnormal metabolic pattern); these patients exhibited a significantly higher risk of ICU mortality compared to the patients with a normal metabolic pattern (72.7% vs. 34.6%, p = 0.04). In our critically ill COVID-19 patients, elevated lactate levels or high LP ratios on admission to the ICU could be associated with poor clinical outcome.

Post-Intensive Care Syndrome in Survivors from Critical Illness including COVID-19 Patients: A Narrative Review

Current achievements in medical science and technological advancements in intensive care medicine have allowed better support of critically ill patients in intensive care units (ICUs) and have increased survival probability. Post-intensive care syndrome (PICS) is a relatively new term introduced almost 10 years ago, defined as "new or worsening impairments in physical, cognitive, or mental health status arising after critical illness and persisting beyond acute care hospitalization". A significant percentage of critically ill patients suffer from PICS for a prolonged period of time, with physical problems being the most common. The exact prevalence of PICS is unknown, and many risk factors have been described well. Coronavirus disease 2019 (COVID-19) survivors seem to be at especially high risk for developing PICS. The families of ICU survivors can also be affected as a response to the stress suffered during the critical illness of their kin. This separate entity is described as PICS family (PICS-F). A multidisciplinary approach is warranted for the treatment of PICS, involving healthcare professionals, clinicians, and scientists from different areas. Improving outcomes is both challenging and imperative for the critical care community. The review of the relevant literature and the study of the physical, cognitive, and mental sequelae could lead to the prevention and timely management of PICS and the subsequent improvement of the quality of life for ICU survivors.

Serum Neutrophil Gelatinase-Associated Lipocalin (NGAL) Could Provide Better Accuracy Than Creatinine in Predicting Acute Kidney Injury Development in Critically Ill Patients

Acute kidney injury (AKI) is one of the most common complications in critically ill patients. In recent years, studies have focused on exploring new biomarkers for the early diagnosis and prognosis of AKI. The aim of this study was to investigate serum prognostic biomarkers (neutrophil gelatinase-associated lipocalin, NGAL, and creatinine) of AKI in critically ill patients. The study included 266 critically ill, initially nonseptic, patients admitted to a multidisciplinary ICU. Serum levels of NGAL and creatinine were measured at ICU admission. ROC curves were generated to estimate the prognostic value of the biomarkers, while a logistic regression analysis was performed to assess their association with an increased AKI risk. Patients were divided in two groups based on the development (n = 98) or not (n = 168) of AKI during their ICU stay. Serum NGAL levels at ICU admission were significantly higher in those who subsequently developed AKI compared to those who did not (p < 0.0001). NGAL was shown to be more accurate in predicting AKI development than creatinine; furthermore, NGAL levels were associated with an increased risk of AKI development (1.005 (1.002–1.008), p < 0.0001). In the present study, we were able to demonstrate that increased serum NGAL levels at ICU admission might be predictive of AKI development during ICU hospitalization. Further studies are needed to support NGAL as a prognostic marker of acute kidney injury.

Could Soluble Endothelial Protein C Receptor Levels Recognize SARS-CoV2-Positive Patients Requiring Hospitalization?

INTRODUCTION

The endothelial protein C receptor (EPCR) is a protein that regulates the protein C anticoagulant and anti-inflammatory pathways. A soluble form of EPCR (sEPCR) circulates in plasma and inhibits activated protein C (APC) activities. The clinical impact of sEPCR and its involvement in COVID-19 has not been explored. In this study, we investigated whether sEPCR levels were related to COVID-19 patients' requirement for hospitalization.

METHODS

Plasma sEPCR levels were measured on hospital admission in 84 COVID-19 patients, and in 11 non-hospitalized SARS-CoV2-positive patients approximately 6 days after reported manifestation of their symptoms. Multiple logistic regression analysis was performed to identify potential risk factors for hospitalization and receiver operating characteristic (ROC) curves were generated to assess their value.

RESULTS

In our cohort, hospitalized patients had considerably higher sEPCR levels upon admission compared with outpatients [107.5 (76.7-156.3) vs. 44.6 (12.1-84.4) ng/mL; P < 0.0001)]. The ROC curve using hospitalization as the classification variable and sEPCR levels as the prognostic variable generated an area under the curve at 0.845 (95% CI = 0.710-0.981, P < 0.001). Additionally, we investigated the predictive value of sEPCR combined with BMI, age, or D-dimers.

CONCLUSIONS

In our cohort, sEPCR levels in COVID-19 patients upon hospital admission appear considerably elevated compared with outpatients; this could lead to impaired APC activities and might contribute to the pro-coagulant phenotype reported in such patients. sEPCR measurement might be useful as a point-of-care test in SARS-CoV2-positive patients.

Combination of the CD8+:B-cell and Neutrophil-to-Lymphocyte Ratio as a Novel Prediction Model for Intubation Need and Disease Severity in COVID-19 Patients

BACKGROUND

The study provides a novel prediction model for COVID-19 progression and outcome by the combination of the CD8⁺: B-cells ratio with neutrophil-to-lymphocyte ratio (NLR).

PATIENTS AND METHODS

Immune phenotyping was performed in 120 COVID-19 patients.

RESULTS

A decrease in CD8⁺:B-cell (p<0.0001) and in lymphocyte-to-CRP (LCR) ratio (p<0.0001) was observed in intubated patients versus non-intubated with an increase for CD4⁺:CD8⁺ (p<0.01), NLR (p<0.0001) and CRP: Albumin (p<0.001). Receiving operating curve (ROC) analysis predicting requirement for mechanical ventilation revealed the highest AUC for CD8⁺:B-cells, (AUC=0.795, p<0.001) versus NLR (AUC=0.783, p<0.001), LCR (AUC=0.779, p<0.001), Albumin:CRP (AUC=0.750, p<0.001) and CD4⁺:CD8⁺ (AUC=0.779, p<0.001). Combination of the CD8⁺: B-cell ratio with the NLR increased the AUC (AUC=0.845, p<0.001). The combined ratios correlated with outcome defined as duration of hospital (r=0.435, p<0.001) or ICU stay (r=0.596, p<0.001).

CONCLUSION

Combination of the CD8⁺: B-cell ratio and NLR serves as a useful prognostic tool for COVID-19 patient progression.

Demographic, Clinical and Immunogenetic Profiles of a Greek Cohort of COVID-19 Patients

The present cross-sectional study consists of a comprehensive analysis of epidemiological, laboratory, and clinical characteristics of COVID-19 patients in relation to their immunogenetic profiles. We studied 125 COVID-19 patients comprising different stages of disease severity; non-hospitalized (mild n = 69) and hospitalized (n = 56). Analysis of disease characteristics revealed no major differences between males and females of each group of patients while hospitalized patients were older and presented with comorbidities. A positive allele association was observed for HLA-DRB1*01 in total COVID-19 patients versus healthy controls. Subgrouping of COVID-19 patients in mild and hospitalized further identified a statistically significant increase in HLA-DRB1*01 in mild COVID-19 patients versus controls. The frequency of A*11, A*23, and DRB1*09 alleles was higher, while the frequency of C*12 was lower, in hospitalized patients versus healthy controls albeit with uncorrected statistical significance. The identification of specific allele associations may provide useful future markers for disease susceptibility in order to allow successful clinical management of COVID-19 patients.

Evaluating the Role of the Interleukin-23/17 Axis in Critically Ill COVID-19 Patients

Studies have hypothesized a potential role of the interleukin (IL)-23/17 axis in coronavirus disease 2019 (COVID-19). However, to date, levels of IL-23 and 17 have not been compared between critically ill COVID-19 patients and critically ill non-COVID-19 patients. IL-23 and 17 were measured on admission to the intensive care unit (ICU) in critically ill COVID-19 (N = 38) and critically ill non-COVID-19 (N = 34) patients with an equal critical illness severity. Critically ill non-COVID-19 patients did not have sepsis or septic shock on ICU admission. None of the enrolled patients had previously received corticosteroids. In our study, circulating IL-17 levels were higher in the COVID-19 patients. More specifically, critically ill COVID-19 patients had levels of 0.78 (0.05-1.8) pg/mL compared to 0.11 (0.05-0.9) pg/mL in the critically ill non-COVID-19 patients (p = 0.04). In contrast, IL-23 levels were comparable between groups. A group of patients hospitalized in the specialized COVID-19 clinic (N = 16) was also used to evaluate IL-17 and IL-23 levels with respect to COVID-19 severity. Non-critically ill COVID-19 patients had undetectable levels of both cytokines. Our results support the notion of inhibiting IL-17 in critical COVID-19 infection.

Low-Dose Dobutamine Stress Echocardiography for the Early Detection of Pulmonary Arterial Hypertension in Selected Patients with Systemic Sclerosis Whose Resting Echocardiography Is Non-Diagnostic for Pulmonary Hypertension

BACKGROUND

Dobutamine stress echocardiography (DSE) has limited application in systemic sclerosis (SSc). We examined DSE usefulness in revealing pulmonary arterial hypertension (PAH) in selected SSc patients whose resting echocardiography for pulmonary hypertension (PH) was non-diagnostic.

METHODS

Forty SSc patients underwent right heart catheterization (RHC) and, simultaneously, low-dose DSE (incremental doses up to 20 μg/kg/min). Inclusion criteria were: preserved left and right ventricular (RV) function (tricuspid annulus plane systolic excursion [TAPSE] ≥ 16 mm and tissue Doppler imaging-derived systolic velocity of tricuspid annulus [RVS'] > 10 cm/s), normal pulmonary function tests, and baseline maximal tricuspid regurgitation (TR) velocity of 2.7-3.2 m/s.

RESULTS

Of 36 patients who completed DSE, resting RHC diagnosed PAH in 12 patients (33.3%). At 20 μg/kg/min, patients with PAH had higher TR velocity, higher pulmonary arterial pressure measured by RHC, and lower RV inotropic response compared with patients without PAH. A cut-off value of maximal TR velocity >3.1 m/s had a sensitivity of 80%, a specificity of 84.2%, and an accuracy of 82.4% for the detection of PAH.

CONCLUSIONS

Low-dose DSE has a satisfactory diagnostic accuracy for the early detection of PAH in highly selected SSc patients whose baseline echocardiographic measurements for PH lie in the gray zone.

Vitamin D in infectious complications in critically ill patients with or without COVID-19

25-hydroxyvitamin D [25(OH)D] is an important immunomodulator, whose deficiency may aggravate the incidence and outcome of infectious complications in patients admitted to the intensive care unit. The most recognized extra-skeletal action of vitamin D is the regulation of immune function. Host defense against intracellular pathogens depends upon both innate and adaptive immunity. It has been suggested that vitamin D regulates the pro-inflammatory endothelial response to lipopolysaccharide, rendering it a role in the sepsis cascade. Recent studies have indicated that vitamin D deficiency may be associated with worse outcomes in patients with coronavirus disease 2019 (COVID-19), such as more severe disease and higher mortality rates. To this end, clinical trials with vitamin D supplementation are being carried out in an effort to improve COVID-19 outcomes. In this review, we will discuss the role of vitamin D in the immune response, and more specifically its effect on immune cells. Subsequently, we will provide an overview of the studies that have investigated the predictive value of vitamin D in critical illness outcomes, and its therapeutic value as a supplement in critically ill patients. Finally, the emerging role of vitamin D deficiency in COVID-19 infection risk, and worse outcomes will be discussed.

Soluble Angiotensin Converting Enzyme 2 (ACE2) Is Upregulated and Soluble Endothelial Nitric Oxide Synthase (eNOS) Is Downregulated in COVID-19-induced Acute Respiratory Distress Syndrome (ARDS)

A damaged endothelium is an underlying condition of the many complications of COVID-19 patients. The increased mortality risk associated with diseases that have underlying endothelial dysfunction, such as acute respiratory distress syndrome (ARDS), suggests that endothelial (e) nitric oxide synthase (NOS)-derived nitric oxide could be an important defense mechanism. Additionally, intravenous recombinant angiotensin converting enzyme 2 (ACE2) was recently reported as an effective therapy in severe COVID-19, by blocking viral entry, and thus reducing lung injury. Very few studies exist on the prognostic value of endothelium-related protective molecules in severe COVID-19 disease. To this end, serum levels of eNOS, inducible (i) NOS, adrenomedullin (ADM), soluble (s) ACE2 levels, and serum (s) ACE activity were measured on hospital admission in 89 COVID-19 patients, hospitalized either in a ward or ICU, of whom 68 had ARDS, while 21 did not. In our cohort, the COVID-19-ARDS patients had considerably lower eNOS levels compared to the COVID-19 non-ARDS patients. On the other hand, sACE2 was significantly higher in the ARDS patients. iNOS, ADM and sACE activity did not differ. Our results might support the notion of two distinct defense mechanisms in COVID-19-derived ARDS; eNOS-derived nitric oxide could be one of them, while the dramatic rise in sACE2 may also represent an endogenous mechanism involved in severe COVID-19 complications, such as ARDS. These results could provide insight to therapeutical applications in COVID-19.

Endothelial, Immunothrombotic, and Inflammatory Biomarkers in the Risk of Mortality in Critically Ill COVID-19 Patients: The Role of Dexamethasone

Endothelial dysfunction, coagulation and inflammation biomarkers are increasingly emerging as prognostic markers of poor outcomes and mortality in severe and critical COVID-19. However, the effect of dexamethasone has not been investigated on these biomarkers. Hence, we studied potential prognostic biomarkers of mortality in critically ill COVID-19 patients who had either received or not dexamethasone. Biomarker serum levels were measured on intensive care unit (ICU) admission (within 24 h) in 37 dexamethasone-free and 29 COVID-19 patients who had received the first dose (6 mg) of dexamethasone. Receiver operating characteristic (ROC) curves were generated to assess their value in ICU mortality prediction, while Kaplan-Meier analysis was used to explore associations between biomarkers and survival. In the dexamethasone-free COVID-19 ICU patients, non-survivors had considerably higher levels of various endothelial, immunothrombotic and inflammatory biomarkers. In the cohort who had received one dexamethasone dose, non-survivors had higher ICU admission levels of only soluble (s) vascular cell adhesion molecule-1 (VCAM-1), soluble urokinase-type plasminogen activator receptor (suPAR) and presepsin. As determined from the generated ROC curves, sVCAM-1, suPAR and presepsin could still be reliable prognostic ICU mortality biomarkers, following dexamethasone administration (0.7 < AUC < 0.9). Moreover, the Kaplan-Meier survival analysis showed that patients with higher than the median values for sVCAM-1 or suPAR exhibited a greater mortality risk than patients with lower values (Log-Rank test, p < 0.01). In our single-center study, sVCAM-1, suPAR and presepsin appear to be valuable prognostic biomarkers in assessing ICU mortality risk in COVID-19 patients, even following dexamethasone administration.

The wide spectrum of β-thalassaemia intermedia-induced pulmonary hypertension: two case reports on the possible role of specific pulmonary arterial hypertension therapy

Pulmonary hypertension (PH) development remains a significant cardiovascular complication of haemoglobinopathies, severely affecting the morbidity and mortality of such patients. According to the 5th World Symposium on PH, PH related with chronic haemolytic anaemias is classified in group 5, mainly due to the multifactorial pathophysiology of PH in this patient population. There are no clear guidelines regarding the management of PH in patients with haemoglobinopathies; the use of specific pulmonary arterial hypertension (PAH) therapy in patients with β-thalassaemia and PH is based on data derived from other forms of PH, expert opinion and small series or case reports. The existing knowledge on the use of specific-PAH therapy in β-thalassaemia patients with PH is limited, and in most cases the diagnosis of PH is based on echocardiographic findings only. We herein report two patients with β-thalassaemia intermedia (TI) and PH, who got same initial approach but different outcome, to highlight the wide spectrum of TI-induced PH, the importance of optimal disease-directed therapy and the possible role of specific-PAH therapy. We also emphasize the central role of right heart catheterization in the diagnosis and follow-up of PH, since this information does facilitate the suitable use or withdrawal of specific PAH drugs in these patients.

Quality of Life, Depression, and Anxiety in Survivors of Critical Illness from a Greek ICU. A Prospective Observational Study

The physical and psychological consequences of critical illness may affect intensive care unit survivors for up to five years, and hence, health-related quality of life has emerged as an important measure of outcome in this population. We aimed at investigating the quality of life, the presence of anxiety and depression symptoms, and the correlations of clinical and psychological parameters with the quality of life scores in survivors of critical illness one year after discharge from intensive care. Widely used scales that have been validated for the Greek population were used. One thousand two hundred and seventy (1270) patients were assessed for eligibility. Inclusion criteria were age between 18 and 68 years and the presence of critical illness requiring endotracheal intubation and mechanical ventilation for more than three days. One hundred and four (104) patients were included in the final analysis; forty-nine age and sex-matched healthy volunteers were included for comparison. One year following intensive care unit discharge, survivors of critical illness had impaired quality of life scores, as measured with the WHOQOL-Bref, compared to healthy subjects (p < 0.001 for the physical and psychological domains, and p = 0.006 for the domain of social relationships). In addition, we found that quality of life scores were significantly lower in patients with comorbidities (p < 0.01), and correlated with the duration of ICU stay (r = −0.19, p = 0.04) and with the presence of symptoms suggestive of depression (r = −0.66, p < 0.0001) and post-traumatic stress disorder (r = −0.61, p < 0.0001). Approximately one-third of our patients scored high in the CES-D scale for depression, while the majority of them scored high in the STAI scale for anxiety symptoms.

May We Use Non-Invasive Indices of Aortic Stiffness and Endothelial Glycocalyx as Biomarkers for Idiopathic Pulmonary Artery Hypertension Follow-Up?

Idiopathic pulmonary arterial hypertension (IPAH) initial evaluation and follow-up, a rare and incurable disease if left untreated, is based on a multiparametric approach (functional status of the patient, biomarkers, hemodynamic parameters and imaging evaluation of right heart impairment). Arterial stiffness (AS) and endothelial glycocalyx are indices of systemic circulation. We present the 3-years follow-up of a female IPAH patient. We propose aortic stiffness and endothelial glycocalyx indices as non-invasive markers of either improvement or deterioration of IPAH disease.

A novel ratio of CD8+:B-cells as a prognostic marker of coronavirus disease 2019 patient progression and outcome

Infection with SARS-COV-2 may result in severe pneumonia potentially leading to mechanical ventilation and intensive care treatment. The aim of the present study was to analyze the immune responses in critically ill coronavirus 2019 (COVID-19) patients requiring mechanical ventilation and assess their potential use as markers of clinical progression and outcome. Confirmed COVID-19 patients were grouped into those requiring mechanical ventilation (intubated) and non-intubated. Immune phenotyping was performed and cytokine levels were determined. A novel ratio of CD8⁺:B cells was significantly lower in intubated versus non-intubated (p = 0.015) and intubated non-survivors (NSV) versus survivors (SV) (p = 0.015). The same ratio correlated with outcome, CRP, IL-6 levels and neutrophil count. Receiving operating curve (ROC) analysis for prediction of requirement of mechanical ventilation by the CD8⁺:B cells ratio revealed an AUC of 0.747 and a p = 0.007. The ratio of CD8⁺:B cells may serve as a useful prognostic marker for disease severity and outcome.

A role for bronchial epithelial autotaxin in ventilator-induced lung injury

Background

The pathophysiology of acute respiratory distress syndrome (ARDS) may eventually result in heterogeneous lung collapse and edema-flooded airways, predisposing the lung to progressive tissue damage known as ventilator-induced lung injury (VILI). Autotaxin (ATX; ENPP2), the enzyme largely responsible for extracellular lysophosphatidic acid (LPA) production, has been suggested to play a pathogenic role in, among others, pulmonary inflammation and fibrosis.

Methods

C57BL/6 mice were subjected to low and high tidal volume mechanical ventilation using a small animal ventilator: respiratory mechanics were evaluated, and plasma and bronchoalveolar lavage fluid (BALF) samples were obtained. Total protein concentration was determined, and lung histopathology was further performed

Results

Injurious ventilation resulted in increased BALF levels of ATX. Genetic deletion of ATX from bronchial epithelial cells attenuated VILI-induced pulmonary edema.

Conclusion

ATX participates in VILI pathogenesis.

Selection of the Appropriate Control Group Is Essential in Evaluating the Cytokine Storm in COVID-19

BACKGROUND/AIM

Lately, studies have reported contradicting results on the cytokine storm seen in critically-ill COVID-19 patients. Depending on the control group used, cytokines have been found to be higher, similar or even lower in COVID-19 compared to critical illnesses associated with elevated cytokine concentrations. However, most of these studies do not take into account critical illness severity. Hence, we decided to compare cytokine levels in critically-ill COVID-19 patients and critically-ill patients of a general intensive care unit (ICU), who did not have sepsis or septic shock, but had an equal disease severity.

PATIENTS AND METHODS

Interleukin (IL)-6, IL-8, IL-10 and tumour necrosis factor-α (TNF-α) were measured on ICU admission in mechanically ventilated, COVID-19 (N=36) and non-COVID-19 (N=30) patients, who had not received dexamethasone, and had equal critical illness severity. Non-COVID-19 patients did not have sepsis or septic shock.

RESULTS

In our case control study, circulating IL-6 and IL-10 were lower, while TNF-α and IL-8 levels were higher in critically-ill COVID-19 patients, compared to critically-ill non-COVID-19 patients.

CONCLUSION

It is difficult to infer whether the cytokine storm seen in COVID-19 differs from other critical conditions. It is important to recognize that the conclusions of related studies may depend on control group selection.

ICU Admission Levels of Endothelial Biomarkers as Predictors of Mortality in Critically Ill COVID-19 Patients

Endotheliopathy is suggested to be an important feature of COVID-19 in hospitalized patients. To determine whether endotheliopathy is involved in COVID-19-associated mortality, markers of endothelial damage were assessed in critically ill COVID-19 patients upon intensive care unit (ICU) admission. Thirty-eight critically ill COVID-19 patients were included in this observational study, 10 of whom died in the ICU. Endothelial biomarkers, including soluble (s)E-selectin, sP-selectin, angiopoietin 1 and 2 (Ang-1 and Ang-2, respectively), soluble intercellular adhesion molecule 1 (sICAM-1), vascular endothelial growth factor (VEGF), soluble vascular endothelial (VE)-cadherin, and von Willebrand factor (vWf), were measured upon ICU admission. The ICU cohort was subsequently divided into survivors and non-survivors; Kaplan-Meier analysis was used to explore associations between biomarkers and survival, while receiver operating characteristic (ROC) curves were generated to determine their potential prognostic value. sE-selectin, sP-selectin, Ang-2, and sICAM-1 were significantly elevated in ICU non-survivors compared to survivors, and also associated with a higher mortality probability in the Kaplan-Meier analysis. The prognostic values of sE-selectin, Ang-2, and sICAM-1 from the generated ROC curves were greater than 0.85. Hence, we conclude that in our cohort, ICU non-survivors had higher levels of specific endothelial markers compared to survivors. Elevated levels of these markers upon ICU admission could possibly predict mortality in COVID-19.

Study of inflammatory biomarkers in COPD and asthma exacerbations

INTRODUCTION

Exacerbations are critical events in the course of asthma and chronic obstructive pulmonary disease (COPD). These events are potentially life-threatening, and the studies have shown that they have tremendous implications on long-term disease control and the overall prognosis of the patients. The aim of this study was to examine adipokines, cytokines and C-reactive protein (CRP) as potential biomarkers in asthma and COPD.

MATERIAL AND METHODS

Prospective cohort study of COPD and asthma patients treated for acute exacerbations. Thirty-nine COPD patients and 15 asthmatic patients were included in the study. Leptin, adiponectin, resistin, interleukin (Il)-6, 8, 18, tumor necrosis factor-a (TNF-a), and CRP were measured at three time points: on admission, at resolution and at the stable phase. Pre- and post-bronchodilation spirometry was additionally performed at resolution and at the stable phase.

RESULTS

In COPD patients, leptin, leptin/adiponectin (L/A) ratio and resistin were elevated on admission compared to the stable phase. In asthmatic patients, leptin levels were raised on admission compared to the stable phase, and adiponectin was elevated at resolution compared to admission. In both diseases, CRP was significantly increased on admission compared to both resolution and stable disease. Finally, TNF-a could distinguish between asthma and COPD stable phase.

CONCLUSIONS

Leptin and CRP levels may be useful biomarkers in monitoring COPD and asthma response to treatment during an exacerbation episode. Hypoadiponectinemia was detected in asthma and COPD during all stages of the diseases. TNF-a could distinguish between asthma and COPD stable phase.

Low 25-Hydroxyvitamin D Levels on Admission to the Intensive Care Unit May Predispose COVID-19 Pneumonia Patients to a Higher 28-Day Mortality Risk: A Pilot Study on a Greek ICU Cohort

We aimed to examine whether low intensive care unit (ICU) admission 25-hydroxyvitamin D (25(OH)D) levels are associated with worse outcomes of COVID-19 pneumonia. This was a prospective observational study of SARS-CoV2 positive critically ill patients treated in a multidisciplinary ICU. Thirty (30) Greek patients were included, in whom 25(OH)D was measured on ICU admission. Eighty (80%) percent of patients had vitamin D deficiency, and the remaining insufficiency. Based on 25(OH)D levels, patients were stratified in two groups: higher and lower than the median value of the cohort (15.2 ng/mL). The two groups did not differ in their demographic or clinical characteristics. All patients who died within 28 days belonged to the low vitamin D group. Survival analysis showed that the low vitamin D group had a higher 28-day survival absence probability (log-rank test, p = 0.01). Critically ill COVID-19 patients who died in the ICU within 28 days appeared to have lower ICU admission 25(OH)D levels compared to survivors. When the cohort was divided at the median 25(OH)D value, the low vitamin D group had an increased risk of 28-day mortality. It seems plausible, therefore, that low 25(OH)D levels may predispose COVID-19 patients to an increased 28-day mortality risk.

Endothelial Damage in Acute Respiratory Distress Syndrome

The pulmonary endothelium is a metabolically active continuous monolayer of squamous endothelial cells that internally lines blood vessels and mediates key processes involved in lung homoeostasis. Many of these processes are disrupted in acute respiratory distress syndrome (ARDS), which is marked among others by diffuse endothelial injury, intense activation of the coagulation system and increased capillary permeability. Most commonly occurring in the setting of sepsis, ARDS is a devastating illness, associated with increased morbidity and mortality and no effective pharmacological treatment. Endothelial cell damage has an important role in the pathogenesis of ARDS and several biomarkers of endothelial damage have been tested in determining prognosis. By further understanding the endothelial pathobiology, development of endothelial-specific therapeutics might arise. In this review, we will discuss the underlying pathology of endothelial dysfunction leading to ARDS and emerging therapies. Furthermore, we will present a brief overview demonstrating that endotheliopathy is an important feature of hospitalised patients with coronavirus disease-19 (COVID-19).

Serum Coenzyme Q10 Levels are Decreased in Critically-Ill Septic Patients: Results From a Preliminary Study

BACKGROUND

The increased oxidative stress resulting from the inflammatory responses in sepsis initiates changes in mitochondrial function which may result in organ damage, the most common cause of death in the intensive care unit (ICU). Deficiency of coenzyme Q10 (CoQ10), a key cofactor in the mitochondrial respiratory chain, could potentially disturb mitochondrial bioenergetics and oxidative stress, and may serve as a biomarker of mitochondrial dysfunction. Hence, we aimed to investigate in initially non-septic patients whether CoQ10 levels are decreased in sepsis and septic shock compared to ICU admission, and to evaluate its associations with severity scores, inflammatory biomarkers, and ICU outcomes.

METHODS

Observational retrospective analysis on 86 mechanically-ventilated, initially non-septic, ICU patients. CoQ10 was sequentially measured on ICU admission, sepsis, septic shock or at ICU discharge. CoQ10 was additionally measured in 25 healthy controls. Inflammatory biomarkers were determined at baseline and sepsis.

RESULTS

On admission, ICU patients who developed sepsis had lower CoQ10 levels compared to healthy controls (0.89 vs. 1.04 µg/ml, p < 0.05), while at sepsis and septic shock CoQ10 levels decreased further (0.63 µg/ml; p < 0.001 and 0.42 µg/ml; p < 0.0001, respectively, from admission). In ICU patients who did not develop sepsis, admission CoQ10 levels were also lower than healthy subjects (0.81 µg/ml; p < 0.001) and were maintained at the same levels until discharge.

CONCLUSION

CoQ10 levels in critically-ill patients are low on ICU admission compared to healthy controls and exhibit a further decrease in sepsis and septic shock. These results suggest that sepsis severity leads to CoQ10 depletion.

Knockdown of bone morphogenetic protein type II receptor leads to decreased aquaporin 1 expression and function in human pulmonary microvascular endothelial cells

Bone morphogenetic proteins (BMPs) were once considered only to have a role in bone formation. It is now known that they have pivotal roles in other organ diseases, including heritable pulmonary arterial hypertension (PAH), where genetic mutations in the type II BMP receptor (BMPR2) are the commonest cause of receptor dysfunction. However, it has also recently been demonstrated that aquaporin 1 (Aqp1) dysfunction may contribute to PAH, highlighting that PAH development may involve more than one pathogenic pathway. Whether reduction in BMPR2 affects Aqp1 is unknown. We therefore studied Aqp1 in BMPR2-silenced human pulmonary microvascular endothelial cells (HPMECs). We demonstrated reduced Aqp1 mRNA, protein, and function in the BMPR2-silenced cells. Additionally, BMPR2-silenced cells exhibited lower expression of BMP-signaling molecules. In conclusion, decreased BMPR2 appears to affect Aqp1 at the mRNA, protein, and functional levels. This observation may identify a contributory mechanism for PAH.

Is pulmonary arterial hypertension associated with interferon-β therapy for multiple sclerosis reversible? A case study to explore the complexity

The possible causal relationship between interferon-β exposure and pulmonary arterial hypertension development requires close follow-up of patients on treatment with interferon-β http://bit.ly/2OPGSVP.

Longitudinal evaluation of glucocorticoid receptor alpha/beta expression and signalling, adrenocortical function and cytokines in critically ill steroid-free patients

PURPOSE

Glucocorticoid actions are mediated by the glucocorticoid receptor (GCR) whose dysfunction leads to glucocorticoid tissue resistance. Our objective was to evaluate GCR-α and GCR-β expression and key steps in the GCR signalling cascade in critical illness.

METHODS

Expression of GCR and major GCR-target genes, cortisol, adrenocorticotropin (ACTH) and cytokines was measured in 42 patients on ICU admission and on days 4, 8, and 13. Twenty-five age- and sex-matched subjects were used as controls.

RESULTS

Acutely, mRNA expression of GCR-α was 10-fold and of GCR-β 3-fold the expression of controls, while during the sub-acute phase expression of both isoforms was lower compared to controls. Expression of FKBP5 and GILZ decreased significantly. Cortisol levels remained elevated and ACTH increased during the 13-day period.

CONCLUSIONS

GCR expression and hypothalamic-pituitary-adrenal axis function undergo a biphasic response during critical illness. The dissociation between low GCR expression and high cortisol implies an abnormal stress response.

Cardiac Catheterization versus Echocardiography for Monitoring Pulmonary Pressure: A Prospective Study in Patients with Connective Tissue Disease-Associated Pulmonary Arterial Hypertension

Standard echocardiography is important for pulmonary arterial hypertension (PAH) screening in patients with connective tissue disease (CTD), but PAH diagnosis and monitoring require cardiac catheterization. Herein, using cardiac catheterization as reference, we tested the hypothesis that follow-up echocardiography is adequate for clinical decision-making in these patients. We prospectively studied 69 consecutive patients with CTD-associated PAH. Invasive baseline pulmonary artery systolic pressure (PASP) was 60.19 ± 16.33 mmHg (mean ± SD) and pulmonary vascular resistance (PVR) was 6.44 ± 2.95WU. All patients underwent hemodynamic and echocardiographic follow-up after 9.47 ± 7.29 months; 27 patients had a third follow-up after 17.2 ± 7.4 months from baseline. We examined whether clinically meaningful hemodynamic deterioration of follow-up catheterization-derived PASP (i.e., > 10% increase) could be predicted by simultaneous echocardiography. Echocardiography predicted hemodynamic PASP deterioration with 59% sensitivity, 85% specificity, and 63/83% positive/negative predictive value, respectively. In multivariate analysis, successful echocardiographic prediction correlated only with higher PVR in previous catheterization (p = 0.05, OR = 1.235). Notably, in patients having baseline PVR > 5.45 WU, echocardiography had both sensitivity and positive predictive values of 73%, and both specificity and negative predictive value of 91% for detecting hemodynamic PASP deterioration. In selected patients with CTD-PAH echocardiography can predict PASP deterioration with high specificity and negative predictive value. Additional prospective studies are needed to confirm that better patient selection can increase the ability of standard echocardiography to replace repeat catheterization.

Ghrelin alterations during experimental and human sepsis

BACKGROUND

Ghrelin is a hormone mainly produced by cells of the gastric mucosa, which has been shown to possess anti-inflammatory and immunomodulatory properties. The objective of the study was to investigate ghrelin levels during sepsis, as well as in an experimental sepsis model.

METHODS

All consecutive admissions to the ICU of a tertiary hospital in Athens, Greece were screened for eligibility during the study. Thirty four non-septic patients upon ICU admission who subsequently developed sepsis were enrolled. Clinical data and scores were recorded, and blood samples were obtained at baseline (upon ICU admission), and at sepsis development. Total and active ghrelin, leptin, and cytokines were measured. Moreover, lipopolysaccharide (LPS) was administered to mice in order to induce endotoxemia and at specified time points, blood and tissue samples were collected.

RESULTS

In patients, serum total and active ghrelin concentrations were significantly elevated in sepsis compared to baseline (553.8 ± 213.4 vs 193.5 ± 123.2, p < 0.001; 254.3 ± 70.6 vs 56.49 ± 16.3, p < 0.001). Active ghrelin levels at the sepsis stage were inversely correlated with SOFA score and length of stay in the ICU (p = 0.023 and p = 0.027 respectively). In the mouse endotoxemia model ghrelin levels were elevated following LPS treatment, and the same trend was observed for leptin, TNFα and IL-6. Ghrelin administration managed to reduce IL-6 levels in mouse serum and in BALF. Pulmonary expression of ghrelin and its receptor GHSR1a was found decreased in LPS-treated mice.

CONCLUSIONS

In a well-defined cohort of ICU patients, we have demonstrated that active and total ghrelin increase in sepsis. The same is true for the experimental sepsis model used in the study. The inverse correlation of active ghrelin levels with SOFA score and length of ICU stay among septic patients is indicative of a potential protective role of active ghrelin during the septic process.

Epidemiology and initial management of pulmonary arterial hypertension: real-world data from the Hellenic pulmOnary hyPertension rEgistry (HOPE)

Pulmonary arterial hypertension (PAH) is a heterogenous clinical entity with poor prognosis, despite recent major pharmacological advances. To increase awareness about the pathophysiology, epidemiology, and management of the disease, large national registries are required. The Hellenic pulmOnary hyPertension rEgistry (HOPE) was launched in early 2015 and enrolls patients from all pulmonary hypertension subgroups in Greece. Baseline epidemiologic, diagnostic, and initial treatment data of consecutive patients with PAH are presented in this article. In total, 231 patients with PAH were enrolled from January 2015 until April 2018. At baseline, about half of patients with PAH were in World Health Organization functional class II. The majority of patients with PAH (56.7%) were at intermediate 1-year mortality risk, while more than one-third were low-risk patients, according to an abbreviated risk stratification score. Half of patients with PAH were on monotherapy, 38.9% received combination therapy, while prostanoids were used only in 12.1% of patients. In conclusion, baseline data of the Greek PAH population share common characteristics, but also have some differences with other registries, the most prominent being a better functional capacity. This may reflect earlier diagnosis of PAH that in conjunction with the increased proportion of patients with atypical PAH could partially explain the preference for monotherapy and the limited use of prostanoids in Greece. Nevertheless, early, advanced specific therapy is strongly recommended.

Orotracheal treprostinil administration attenuates bleomycin-induced lung injury, vascular remodeling, and fibrosis in mice

Pulmonary fibrosis is a progressive disease characterized by disruption of lung architecture and deregulation of the pulmonary function. Prostacyclin, a metabolite of arachidonic acid, is a potential disease mediator since it exerts anti-inflammatory and anti-fibrotic actions. We investigated the effect of treprostinil, a prostacyclin analogue, in bleomycin-induced experimental pulmonary fibrosis. Bleomycin sulfate or saline was administrated intratracheally to mice (n = 9-10/group) at day 0. Orotracheal aspiration of treprostinil or vehicle was administered daily and started 24 h prior to bleomycin challenge. Evaluation of lung pathology was performed in tissue samples and bronchoalveolar lavage fluid collected 7, 14 and 21 days after bleomycin exposure. Lung injury was achieved due to bleomycin exposure at all time points as indicated by impaired lung mechanics, pathologic lung architecture (from day 14), and cellular and protein accumulation in the alveolar space accompanied by a minor decrease in lung tissue VE-cadherin at day 14. Treprostinil preserved lung mechanics, and reduced lung inflammation, fibrosis, and vascular remodeling (day 21); reduced cellularity and protein content of bronchoalveolar lavage fluid were additionally observed with no significant effect on VE-cadherin expression. Bleomycin-induced collagen deposition was attenuated by treprostinil from day 14, while treprostinil involvement in regulating inflammatory processes appears mediated by NF-κB signaling. Overall, prophylactic administration of treprostinil, a stable prostacyclin analogue, maintained lung function, and prevented bleomycin-induced lung injury, and fibrosis, as well as vascular remodeling, a hallmark of pulmonary hypertension. This suggests potential therapeutic efficacy of treprostinil in pulmonary fibrosis and possibly in pulmonary hypertension related to chronic lung diseases.

Pulmonary capillary surface area in supine exercising humans: demonstration of vascular recruitment

In exercising humans, cardiac output (CO) increases, with minor increases in pulmonary artery pressure (PAP). It is unknown if the CO is accommodated via distention of already perfused capillaries or via recruitment of nonconcomitantly perfused pulmonary capillaries. Ten subjects (9 female) performed symptom-limited exercise. Six had resting mean PAP (PAPm) <20 mmHg, and four had PAPm between 21 and 24 mmHg. The first-pass pulmonary circulatory metabolism of [³H]benzoyl-Phe-Ala-Pro (BPAP) was measured at rest and at peak exercise, and functional capillary surface area (FCSA) was calculated. Data are means ± SD. Mean pulmonary arterial pressure rose from 18.8 ± 3.3 SD mmHg to 28.5 ± 4.6 SD mmHg, CO from 6.4 ± 1.6 to 13.4 ± 2.9 L/min, and pulmonary artery wedge pressure from 14 ± 3.3 to 19.5 ± 5 mmHg (all P ≤ 0.001). Percent BPAP metabolism fell from 74.7 ± 0.1% to 67.1 ± 0.1%, and FCSA/body surface area (BSA) rose from 2,939 ± 640 to 5,018 ± 1,032 mL·min^-1·m^-2 (all P < 0.001). In nine subjects, the FCSA/BSA-to-CO relationship suggested principally capillary recruitment and not distention. In subject 10, a marathon runner, resting CO and FCSA/BSA were high, and increases with exercise suggested distention. Exercising humans demonstrate pulmonary capillary recruitment and distention. At moderate resting CO, increasing blood flow causes principally recruitment while, based on one subject, when exercise begins at high CO, further increases appear to cause distention. Our findings clarify an important physiologic question. The technique may provide a means for further understanding exercise physiology, its limitation in pulmonary hypertension, and responses to therapy.