Serum surfactant protein D in COVID-19 is elevated and correlated with disease severity

Update prognostic potency of surfactant protein D (SP-D) in the COVID-19 landscape: an In-depth meta-analytical exploration

INTRODUCTION

Surfactant Protein D (SP-D), a key component of the innate immune system, has attracted significant interest for its potential role in the pathophysiology and prognosis of COVID-19. This systematic review and meta-analysis aim to clarify the prognostic importance of SP-D levels in COVID-19 patients.

METHODS

A comprehensive literature search was conducted using PubMed, Web of Science, Cochrane Library, Scopus, EMBASE, and Google Scholar, covering studies published from January 2000 to January 2024. The inclusion criteria focused on studies measuring SP-D levels in the serum or plasma of COVID-19 patients, comparing severe and non-severe cases. Standardized mean differences (SMD) with 95% confidence intervals (CI) were calculated using a random-effects model to assess overall effect sizes. Meta-regressions and subgroup analyses were performed to identify potential sources of heterogeneity, including patient age, assay techniques, and gender ratio.

RESULTS

The meta-analysis incorporated data from nine studies involving 5,410 COVID-19 patients. Elevated SP-D levels were significantly correlated with increased disease severity, yielding an SMD of 0.642 (95% CI: 0.314 to 0.870; p = 0.012).

CONCLUSION

This meta-analysis confirms the prognostic significance of SP-D in the context of COVID-19. Elevated SP-D levels are associated with severe disease outcomes, highlighting its potential as a prognostic biomarker.

Surfactant-derived protein type B: a new biomarker linked to respiratory failure and lung damage in mild to moderate SARS-CoV-2 pneumonia

Background

The COVID-19 pandemic has led to significant concern due to its impact on human health, particularly through pneumonia-induced lung damage. Surfactant proteins A and D (SP-A and SP-D) are implicated in COVID-19 lung damage, but the role of surfactant protein B (SP-B) remains unclear.

Methods

We conducted a single-centre, prospective observational study involving 73 hospitalised COVID-19 pneumonia patients. SP-B levels were measured within 48 h of admission, alongside SP-A and SP-D in a subset. Clinical data were collected, and follow-up visits were conducted after 6 months.

Results

At hospitalisation, circulating immature SP-B levels measured in 73 patients (median 26.31 arbitrary units (AU) (interquartile range 14.27-41.31)) correlated significantly with lung involvement (r=0.447, p<0.001) and oxygen support requirement (p=0.005). SP-B levels did not predict mechanical ventilation or intensive care unit admission. SP-B decreased significantly (p<0.001) from 25.53 AU (14.36-41.46) at the acute hospitalisation to 12.73 AU (9.12-20.23) at the 6-month follow-up, whereas SP-A and SP-D did not change significantly. Immature SP-B (but not SP-A and SP-D) was confirmed to be significantly associated with the need for oxygen support (n=26, 58%) during the hospitalisation (p<0.05).

Conclusion

Immature SP-B emerges as a potential biomarker for COVID-19 pneumonia severity and prognosis. Its dynamic changes suggest utility in monitoring disease progression and long-term outcomes, despite limitations in predicting hard end-points. Larger studies are needed to validate these findings and understand the underlying mechanisms of surfactant protein dysregulation in COVID-19 pathogenesis.

Process-Specific Blood Biomarkers and Outcomes in COVID-19 Versus Non-COVID-19 ARDS (APEL-COVID Study): A Prospective, Observational Cohort Study

Background: Severe acute respiratory syndrome (SARS) and acute respiratory distress syndrome (ARDS) are often considered separate clinico-radiological entities. Whether these conditions also present a single process-specific systemic biomolecular phenotype and how this relates to patient outcomes remains unknown. A prospective cohort study was conducted, including adult patients admitted to the ICU and general floors for COVID-19-related (COVID+) or non-COVID-19-related (COVID-) acute respiratory failure during the main phase of the pandemic. The primary objective was to study blood biomarkers and outcomes among different groups and severity subsets. Results: A total of 132 patients were included, as follows: 67 COVID+, 54 COVID- (with 11 matched control subjects for biomarker reference), and 58 of these patients allowed for further pre- and post-analysis. The baseline apelin (APL) levels were higher in COVID+ patients (p < 0.0001 vs. COVID- patients) and in SARS COVID+ patients (p ≤ 0.02 vs. ARDS), while the IL-6 levels were higher in ARDS COVID- patients (p ≤ 0.0001 vs. SARS). Multivariable logistic regression analyses with cohort biomarkers and outcome parameters revealed the following: (i) log-transformed neprilysin (NEP) activity was significantly higher in COVID+ patients (1.11 [95% CI: 0.4-1.9] vs. 0.37 [95% CI: 0.1-0.8], fold change (FC): 1.43 [95% CI: 1.04-1.97], p = 0.029) and in SARS patients (FC: 1.65 [95% CI: 1.05-2.6], p = 0.032 vs. non-SARS COVID+ patients, and 1.73 [95% CI: 1.19-2.5], p = 0.005 vs. ARDS COVID- patients) and (ii) higher lysyl oxidase (LOX) activity and APL levels were respectively associated with death and a shorter length of hospital stay in SARS COVID+ patients (Odds Ratios (OR): 1.01 [1.00-1.02], p = 0.05, and OR: -0.007 [-0.013-0.0001], p = 0.048). Conclusion: Process-specific blood biomarkers exhibited distinct profiles between COVID+ and COVID- patients, and across stages of severity. NEP and LOX activities, as well as APL levels, are particularly linked to COVID+ patients and their outcomes (ClinicalTrials.gov Identifier: NCT04632732).

Unraveling the enigma: The emerging significance of pulmonary surfactant proteins in predicting, diagnosing, and managing COVID-19

BACKGROUND

Severe cases of COVID-19 often lead to the development of acute respiratory syndrome, a critical condition believed to be caused by the harmful effects of SARS-CoV-2 on type II alveolar cells. These cells play a crucial role in producing pulmonary surfactants, which are essential for proper lung function. Specifically focusing on surfactant proteins, including Surfactant protein A (SP-A), Surfactant protein B, Surfactant protein C, and Surfactant protein D (SP-D), changes in the levels of pulmonary surfactants may be a significant factor in the pathological changes seen in COVID-19 infection.

OBJECTIVE

This study aims to gain insights into surfactants, particularly their impacts and changes during COVID-19 infection, through a comprehensive review of current literature. The study focuses on the function of surfactants as prognostic markers, diagnostic factors, and essential components in the management and treatment of COVID-19.

FINDING

In general, pulmonary surfactants serve to reduce the surface tension at the gas-liquid interface, thereby significantly contributing to the regulation of respiratory mechanics. Additionally, these surfactants play a crucial role in the innate immune system within the pulmonary microenvironment. Within the spectrum of COVID-19 infections, a compelling association is observed, characterized by elevated levels of SP-D and SP-A across a range of manifestations from mild to severe pneumonia. The sudden decline in respiratory function observed in COVID-19 patients may be attributed to the decreased synthesis of surfactants by type II alveolar cells.

CONCLUSION

Collectin proteins such as SP-A and SP-D show promise as biomarkers, offering potential avenues for predicting and monitoring pulmonary alveolar injury in the context of COVID-19. This clarification enhances our understanding of the molecular complexities contributing to respiratory complications in severe COVID-19 cases, providing a foundation for targeted therapeutic approaches using surfactants and refined clinical management strategies.

Could SP-A and SP-D Serum Levels Predict COVID-19 Severity?

Given the various clinical manifestations that characterize Coronavirus Disease 2019 (COVID-19), the scientific community is constantly searching for biomarkers with prognostic value. Surfactant proteins A (SP-A) and D (SP-D) are collectins that play a crucial role in ensuring proper alveolar function and an alteration of their serum levels was reported in several pulmonary diseases characterized by Acute Respiratory Distress Syndrome (ARDS) and pulmonary fibrosis. Considering that such clinical manifestations can also occur during Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection, we wondered if these collectins could act as prognostic markers. In this regard, serum levels of SP-A and SP-D were measured by enzyme immunoassay in patients with SARS-CoV-2 infection (n = 51) at admission (T0) and after seven days (T1) and compared with healthy donors (n = 11). SP-D increased in COVID-19 patients compared to healthy controls during the early phases of infection, while a significant reduction was observed at T1. Stratifying SARS-CoV-2 patients according to disease severity, increased serum SP-D levels were observed in severe compared to mild patients. In light of these results, SP-D, but not SP-A, seems to be an eligible marker of COVID-19 pneumonia, and the early detection of SP-D serum levels could be crucial for preventive clinical management.

Human surfactant protein A inhibits SARS-CoV-2 infectivity and alleviates lung injury in a mouse infection model

Introduction

SARS coronavirus 2 (SARS-CoV-2) infects human angiotensin-converting enzyme 2 (hACE2)-expressing lung epithelial cells through its spike (S) protein. The S protein is highly glycosylated and could be a target for lectins. Surfactant protein A (SP-A) is a collagen-containing C-type lectin, expressed by mucosal epithelial cells and mediates its antiviral activities by binding to viral glycoproteins.

Objective

This study examined the mechanistic role of human SP-A in SARS-CoV-2 infectivity and lung injury in vitro and in vivo.

Results

Human SP-A can bind both SARS-CoV-2 S protein and hACE2 in a dose-dependent manner (p<0.01). Pre-incubation of SARS-CoV-2 (Delta) with human SP-A inhibited virus binding and entry and reduced viral load in human lung epithelial cells, evidenced by the dose-dependent decrease in viral RNA, nucleocapsid protein (NP), and titer (p<0.01). We observed significant weight loss, increased viral burden, and mortality rate, and more severe lung injury in SARS-CoV-2 infected hACE2/SP-A KO mice (SP-A deficient mice with hACE2 transgene) compared to infected hACE2/mSP-A (K18) and hACE2/hSP-A1 (6A2) mice (with both hACE2 and human SP-A1 transgenes) 6 Days Post-infection (DPI). Furthermore, increased SP-A level was observed in the saliva of COVID-19 patients compared to healthy controls (p<0.05), but severe COVID-19 patients had relatively lower SP-A levels than moderate COVID-19 patients (p<0.05).

Discussion

Collectively, human SP-A attenuates SARS-CoV-2-induced acute lung injury (ALI) by directly binding to the S protein and hACE2, and inhibiting its infectivity; and SP-A level in the saliva of COVID-19 patients might serve as a biomarker for COVID-19 severity.

[Lung-protective effect of esketamine combined with distal limb ischemic preconditioning in elderly patients undergoing thoracoscopic radical surgery for lung cancer: a randomized controlled trial in 160 cases]

OBJECTIVE

To evaluate the effect of esketamine combined with distal limb ischemic preconditioning (LIP) for lung protection in elderly patients undergoing thoracoscopic radical surgery for lung cancer.

METHODS

This randomized trial was conducted in 160 patients undergoing elective thoracoscopic surgery for lung cancer, who were randomized into control group (with saline injection and sham LIP), esketamine group, LIP group, and esketamine + LIP group (n=40). Before anesthesia induction, according to the grouping, the patients received an intravenous injection with 0.5 mg/kg esketamine or 10 ml saline (in control group). LIP was induced by applying a tourniquet 1-2 cm above the popliteal fossa in the left lower limb to block the blood flow for 5 min for 3 times at the interval of 5 min, and sham LIP was performed by applying the tourniquet without pressurization for 30 min. Oxygenation index (OI) and alveolar-arterial PO2 difference (A-aDO2) were calculated before induction (T0), at 30 min (T0.5) and 1 h (T1) of one-lung ventilation (OLV), and at 1 h after two-lung ventilation (T3). Serum levels of SP-D, CC-16 and TNF-α were measured by ELISA at T0, T1, T2 (2 h of OLV), T3, and 24 h after the operation (T4). The length of hospital stay and postoperative pulmonary complications of the patients were recorded.

RESULTS

Compared with those in the control group, the patients in the other 3 groups had significantly lower CC-16, SP-D and TNF-α levels, shorter hospital stay, and lower incidences of lung infection and lung atelectasis (all P < 0.05). Serum CC-16, SP-D and TNF-α levels, hospital stay, incidences of complications were significantly lower or shorter in the combined treatment group than in esketamine group and LIP group (all P < 0.05).

CONCLUSION

In elderly patients undergoing thoracoscopic radical surgery for lung cancer, treatment with esketamine combined with LIP can alleviate acute lung injury by enhancing anti-inflammatory response to shorten postoperative hospital stay, reduce lung complications and promote the patients' recovery.

In-vivo studies of targeted and localized cancer drug release from microporous poly-di-methyl-siloxane (PDMS) devices for the treatment of triple negative breast cancer

Triple-negative breast cancer (TNBC) treatment is challenging and frequently characterized by an aggressive phenotype and low prognosis in comparison to other subtypes. This paper presents fabricated implantable drug-loaded microporous poly-di-methyl-siloxane (PDMS) devices for the delivery of targeted therapeutic agents [Luteinizing Hormone-Releasing Hormone conjugated paclitaxel (PTX-LHRH) and Luteinizing Hormone-Releasing Hormone conjugated prodigiosin (PG-LHRH)] for the treatment and possible prevention of triple-negative cancer recurrence. In vitro assessment using the Alamar blue assay demonstrated a significant reduction (p < 0.05) in percentage of cell growth in a time-dependent manner in the groups treated with PG, PG-LHRH, PTX, and PTX-LHRH. Subcutaneous triple-negative xenograft breast tumors were then induced in athymic female nude mice that were four weeks old. Two weeks later, the tumors were surgically but partially removed, and the device implanted. Mice were observed for tumor regrowth and organ toxicity. The animal study revealed that there was no tumor regrowth, six weeks post-treatment, when the LHRH targeted drugs (LHRH-PTX and LHRH-PGS) were used for the treatment. The possible cytotoxic effects of the released drugs on the liver, kidney, and lung are assessed using quantitative biochemical assay from blood samples of the treatment groups. Ex vivo histopathological results from organ tissues showed that the targeted cancer drugs released from the implantable drug-loaded device did not induce any adverse effect on the liver, kidneys, or lungs, based on the results of qualitative toxicity studies. The implications of the results are discussed for the targeted and localized treatment of triple negative breast cancer.

Molecular Impact of Conventional and Electronic Cigarettes on Pulmonary Surfactant

The alveolar epithelium is covered by a non-cellular layer consisting of an aqueous hypophase topped by pulmonary surfactant, a lipo-protein mixture with surface-active properties. Exposure to cigarette smoke (CS) affects lung physiology and is linked to the development of several diseases. The macroscopic effects of CS are determined by several types of cell and molecular dysfunction, which, among other consequences, lead to surfactant alterations. The purpose of this review is to summarize the published studies aimed at uncovering the effects of CS on both the lipid and protein constituents of surfactant, discussing the molecular mechanisms involved in surfactant homeostasis that are altered by CS. Although surfactant homeostasis has been the topic of several studies and some molecular pathways can be deduced from an analysis of the literature, it remains evident that many aspects of the mechanisms of action of CS on surfactant homeostasis deserve further investigation.

Risk factors for clinically significant diffuse parenchymal lung abnormalities persisting after severe COVID-19 pneumonia

Background & objectives

The risk factors for clinically significant diffuse parenchymal lung abnormalities (CS-DPLA) persisting after severe coronavirus disease 2019 (COVID-19) pneumonia remain unclear. The present study was conducted to assess whether COVID-19 severity and other parameters are associated with CS-DPLA.

Methods

The study participants included patients who recovered after acute severe COVID-19 and presented with CS-DPLA at two or six month follow up and control group (without CS-DPLA). Adults volunteers without any acute illness, chronic respiratory illness and without a history of severe COVID-19 were included as healthy controls for the biomarker study. The CS-DPLA was identified as a multidimensional entity involving clinical, radiological and physiological pulmonary abnormalities. The primary exposure was the neutrophil-lymphocyte ratio (NLR). Recorded confounders included age, sex, peak lactate dehydrogenase (LDH), advanced respiratory support (ARS), length of hospital stay (LOS) and others; associations were analyzed using logistic regression. The baseline serum levels of surfactant protein D, cancer antigen 15-3 and transforming growth factor-β (TGF-β) were also compared among cases, controls and healthy volunteers.

Results

We identified 91/160 (56.9%) and 42/144 (29.2%) participants with CS-DPLA at two and six months, respectively. Univariate analyses revealed associations of NLR, peak LDH, ARS and LOS with CS-DPLA at two months and of NLR and LOS at six months. The NLR was not independently associated with CS-DPLA at either visit. Only LOS independently predicted CS-DPLA at two months [adjusted odds ratios (aOR) (95% confidence interval [CI]), 1.16 (1.07-1.25); P<0.001] and six months [aOR (95% CI) and 1.07 (1.01-1.12); P=0.01]. Participants with CS-DPLA at six months had higher baseline serum TGF-β levels than healthy volunteers.

Interpretation and conclusions

Longer hospital stay was observed to be the only independent predictor of CS-DPLA six months after severe COVID-19. Serum TGF-β should be evaluated further as a biomarker.

Human Surfactant Protein A Alleviates SARS-CoV-2 Infectivity in Human Lung Epithelial Cells

SARS coronavirus 2 (SARS-CoV-2) infects human angiotensin-converting enzyme 2 (hACE2)-expressing lung epithelial cells through its spike (S) protein. The S protein is highly glycosylated and could be a target for lectins. Surfactant protein A (SP-A) is a collagen-containing C-type lectin, expressed by mucosal epithelial cells and mediates its antiviral activities by binding to viral glycoproteins. This study examined the mechanistic role of human SP-A in SARS-CoV-2 infectivity. The interactions between human SP-A and SARS-CoV-2 S protein and hACE2 receptor, and SP-A level in COVID-19 patients were assessed by ELISA. The effect of SP-A on SARS-CoV-2 infectivity was analyzed by infecting human lung epithelial cells (A549-ACE2) with pseudoviral particles and infectious SARS-CoV-2 (Delta variant) pre-incubated with SP-A. Virus binding, entry, and infectivity were assessed by RT-qPCR, immunoblotting, and plaque assay. The results showed that human SP-A can bind SARS-CoV-2 S protein/RBD and hACE2 in a dose-dependent manner (p<0.01). Human SP-A inhibited virus binding and entry, and reduce viral load in lung epithelial cells, evidenced by the dose-dependent decrease in viral RNA, nucleocapsid protein, and titer (p<0.01). Increased SP-A level was observed in the saliva of COVID-19 patients compared to healthy controls (p<0.05), but severe COVID-19 patients had relatively lower SP-A levels than moderate COVID-19 patients (p<0.05). Therefore, SP-A plays an important role in mucosal innate immunity against SARS-CoV-2 infectivity by directly binding to the S protein and inhibiting its infectivity in host cells. SP-A level in the saliva of COVID-19 patients might serve as a biomarker for COVID-19 severity.

Cellular and molecular features of COVID-19 associated ARDS: therapeutic relevance

The severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection can be asymptomatic or cause a disease (COVID-19) characterized by different levels of severity. The main cause of severe COVID-19 and death is represented by acute (or acute on chronic) respiratory failure and acute respiratory distress syndrome (ARDS), often requiring hospital admission and ventilator support.The molecular pathogenesis of COVID-19-related ARDS (by now termed c-ARDS) is still poorly understood. In this review we will discuss the genetic susceptibility to COVID-19, the pathogenesis and the local and systemic biomarkers correlated with c-ARDS and the therapeutic options that target the cell signalling pathways of c-ARDS.

Drug-Induced Interstitial Lung Diseases

Drug-induced interstitial lung disease (DI-ILD) is an increasingly common cause of morbidity and mortality as the list of culprit drugs continues to grow. Unfortunately, DI-ILD is difficult to study, diagnose, prove, and manage. This article attempts to raise awareness of the challenges in DI-ILD and discusses the current clinical landscape.

Multi-omics of NET formation and correlations with CNDP1, PSPB, and L-cystine levels in severe and mild COVID-19 infections

The detailed mechanisms of COVID-19 infection pathology remain poorly understood. To improve our understanding of SARS-CoV-2 pathology, we performed a multi-omics and correlative analysis of an immunologically naïve SARS-CoV-2 clinical cohort from blood plasma of uninfected controls, mild, and severe infections. Consistent with previous observations, severe patient populations showed an elevation of pulmonary surfactant levels. Intriguingly, mild patients showed a statistically significant elevation in the carnosine dipeptidase modifying enzyme (CNDP1). Mild and severe patient populations showed a strong elevation in the metabolite L-cystine (oxidized form of the amino acid cysteine) and enzymes with roles in glutathione metabolism. Neutrophil extracellular traps (NETs) were observed in both mild and severe populations, and NET formation was higher in severe vs. mild samples. Our correlative analysis suggests a potential protective role for CNDP1 in suppressing PSPB release from the pulmonary space whereas NET formation correlates with increased PSPB levels and disease severity. In our discussion we put forward a possible model where NET formation drives pulmonary occlusions and CNDP1 promotes antioxidation, pleiotropic immune responses, and vasodilation by accelerating histamine synthesis.

Severe COVID-19 patients show a dysregulation of the NLRP3 inflammasome in circulating neutrophils

SARS-CoV-2 triggers inflammasome-dependent release of pro-inflammatory cytokine IL-1β and pyroptosis, therefore, contributes to the huge inflammatory response observed in severe COVID-19 patients. Less is known about the engagement of inflammasome in neutrophils, main players in tissue injury and severe infection. We studied the activation of the inflammasome in neutrophils from severe COVID-19 patients and assessed its consequence in term of cells contribution to disease pathogenesis. We demonstrated that NLRP3 inflammasome is dramatically activated in neutrophils from severe COVID-19 patients and that the specific inhibition of NLRP3 reverts neutrophils' activation. Next, the stimulation of severe patients' neutrophils with common NLRP3 stimuli was not able to further activate the inflammasome, possibly due to exhaustion or increased percentage of circulating immature neutrophils. Collectively, our results demonstrate that the NLRP3 inflammasome is hyperactivated in severe COVID-19 neutrophils and its exhaustion may be responsible for the increased susceptibility to subsequent (and possibly lethal) infections. Our findings thus include a novel piece in the complex puzzle of COVID-19 pathogenesis.

Surfactant protein D (SP-D) as a biomarker of SARS-CoV-2 infection

Background

Surfactant protein-D (SP-D) is a lung-resident protein that has emerged as a potential biomarker for COVID-19. Previous investigations on acute respiratory distress syndrome patients demonstrated a significant increment of SP-D serum levels in pathological conditions. Since SP-D is not physiologically permeable to alveoli-capillary membrane and poorly expressed by other tissues, this enhancement is likely due to an impairment of the pulmonary barrier caused by prolonged inflammation.

Methods

A retrospective study on a relatively large cohort of patients of Hospital Pio XI of Desio was conducted to assess differences of the hematic SP-D concentrations among COVID-19 patients and healthy donors and if SP-D levels resulted a risk factor for disease severity and mortality.

Results

The first analysis, using an ANOVA-model, showed a significant difference in the mean of log SP-D levels between COVID-19 patients and healthy donors. Significant variations were also found between dead vs survived patients. Results confirm that SP-D concentrations were significantly higher for both hospitalized COVID-19 and dead patients, with threshold values of 150 and 250 ng/mL, respectively. Further analysis conducted with Logistic Mixed models, highlighted that higher SP-D levels at admission and increasing differences among follow-up and admission values resulted the strongest significant risk factors of mortality (model predictive accuracy, AUC = 0.844).

Conclusions

The results indicate that SP-D can be a predictive marker of COVID-19 disease and its outcome. Considering its prognostic value in terms of mortality, the early detection of SP-D levels and its follow-up in hospitalized patients should be considered to direct the therapeutic intervention.

Pulmonary Fibrosis as a Result of Acute Lung Inflammation: Molecular Mechanisms, Relevant In Vivo Models, Prognostic and Therapeutic Approaches

Pulmonary fibrosis is a chronic progressive lung disease that steadily leads to lung architecture disruption and respiratory failure. The development of pulmonary fibrosis is mostly the result of previous acute lung inflammation, caused by a wide variety of etiological factors, not resolved over time and causing the deposition of fibrotic tissue in the lungs. Despite a long history of study and good coverage of the problem in the scientific literature, the effective therapeutic approaches for pulmonary fibrosis treatment are currently lacking. Thus, the study of the molecular mechanisms underlying the transition from acute lung inflammation to pulmonary fibrosis, and the search for new molecular markers and promising therapeutic targets to prevent pulmonary fibrosis development, remain highly relevant tasks. This review focuses on the etiology, pathogenesis, morphological characteristics and outcomes of acute lung inflammation as a precursor of pulmonary fibrosis; the pathomorphological changes in the lungs during fibrosis development; the known molecular mechanisms and key players of the signaling pathways mediating acute lung inflammation and pulmonary fibrosis, as well as the characteristics of the most common in vivo models of these processes. Moreover, the prognostic markers of acute lung injury severity and pulmonary fibrosis development as well as approved and potential therapeutic approaches suppressing the transition from acute lung inflammation to fibrosis are discussed.

Correlation between serum surfactant protein-D level with respiratory compliance and acute respiratory distress syndrome in critically ill COVID-19 Patients: A retrospective observational study

Background

Acute respiratory distress syndrome (ARDS) is one of the manifestations of severe coronavirus disease 2019 (COVID-19) with low respiratory compliance and poor oxygenation as main characteristics and mortality rate of 50%-94%. Surfactants, including surfactant protein D (SP-D), have a role in maintaining respiratory compliance. This study aimed to analyze the relationship between serum SP-D levels with respiratory compliance and ARDS in patients with critically ill COVID-19 pneumonia.

Methods

This study was a cross-sectional study. Subjects were adult reverse transcription-polymerase chain reaction-confirmed COVID-19 patients who had ARDS treated with invasive mechanical ventilation. All data were obtained from medical records. Statistical analysis was done using Spearman test, Mann-Whitney test, and receiver operating characteristic curve.

Results

Serum level of SP-D was significantly correlated with static respiratory compliance (P = 0.009; correlation coefficient [rs] = 0.467). Serum SP-D levels correlated with ARDS severity (P < 0.001). SP-D levels had a very strong diagnostic value for ARDS severity, with an optimal cutoff value of 44.24 ng/mL (sensitivity 92.3%; specificity 94.1%). ARDS severity also correlated significantly with respiratory compliance (P = 0.005; correlation coefficient 0.496).

Conclusion

Higher serum SP-D levels were associated with lower respiratory compliance, ARDS severity, and may be utilized diagnostically to identify patients with severe ARDS.

Clinical Utility of Circulating Pneumoproteins as Diagnostic and Prognostic Biomarkers in COVID-19: A Systematic Review and Meta-analysis

INTRODUCTION

This study explored circulating pneumoproteins in the diagnosis, severity, and prognosis of COVID-19 by meta-analysis.

METHODS

We searched five databases and other sources until December 16, 2021. Standardized mean difference (SMD) and 95% confidence interval (CI) were the overall outcomes. RevMan 5.3, Stata 16, and Meta-DiSc 1.4 were utilized for pooled analysis.

RESULTS

A total of 2432 subjects from 26 studies were included. Patients with COVID-19 had higher circulating KL-6, SP-D, and SP-A levels (SMD 1.34, 95% CI [0.60, 2.08]; SMD 1.74, 95% CI [0.64, 2.84]; SMD 3.42, 95% CI [1.31, 5.53], respectively) than healthy individuals. Circulating SP-D levels were not significantly different in survivors and non-survivors (SMD - 0.19, 95% CI [- 0.78, 0.40]). Circulating KL-6, SP-D, and RAGE levels in patients with mild to moderate COVID-19 were significantly lower (SMD - 0.93, 95% CI [- 1.22, - 0.65]; SMD - 1.32, 95% CI [- 2.34, - 0.29]; SMD - 1.17, 95% CI [- 2.06, - 0.28], respectively) than in patients with severe COVID-19. Subgroup analysis suggested that country and total number may be related to the heterogeneity when analyzing SP-D in patients with mild to moderate vs. severe COVID-19. The meta-analysis of diagnostic accuracy including KL-6 for severity, KL-6 for mortality, and SP-D for severity demonstrated that they all had limited diagnostic value.

CONCLUSION

Therefore, circulating pneumoproteins (KL-6, SP-D, and RAGEs) reflect the diagnosis, severity, and prognosis of COVID-19, and follow-up studies are still needed.

The Characteristics of Patients with Severe COVID-19 Pneumonia Treated with Direct Hemoperfusion Using Polymyxin B-Immobilized Fiber Column (PMX-DHP)

Purpose

The characteristics of patients with severe COVID-19 pneumonia who underwent direct hemoperfusion using polymyxin B-immobilized fiber column (PMX-DHP), in addition to steroids and immunomodulators, remain unclear.

Patients and Methods

We conducted a retrospective observational study on 31 patients with severe COVID-19 pneumonia treated with PMX-DHP in an intensive care unit (ICU) from December 2020 to September 2021.

Results

Outcomes 28 days after admission to the ICU were 20 in the survival group and 11 in the death group. Parameters significantly different between the survival and death group before PMX-DHP were percentage of invasive mechanical ventilation (25% vs 72.7%, P = 0.0209), PaO₂/F_IO₂ (P/F) ratio (104.5 vs 75, P = 0.0317), and sequential organ failure assessment (SOFA) score (2 vs 3, P = 0.0356). Invasive mechanical ventilation avoidance rate was significantly different between the survival (100%) and death group (0%) (P = 0.0012). P/F ratio, respiratory ratio (RR), and lymphocyte counts improved significantly after PMX-DHP for all patients. The lymphocyte counts changed significantly in the survival (P < 0.0001), but not the death group (P = 0.7927).

Conclusion

PMX-DHP, in addition to steroids and immunomodulators, may improve oxygenation and alleviate tachypnea by modulating the lymphocyte numbers and levels of various mediator against severe COVID-19 pneumonia. It may be better to perform PMX-DHP before multi organ dysfunction and lung injury has progressed. Furthermore, the early increase in lymphocyte counts after PMX-DHP might be an indicate a positive outcome.

Serum stratifin and presepsin as candidate biomarkers for early detection of COVID-19 disease progression

The prognosis of patients with severe cases of COVID-19 is poor; thus, biomarkers for earlier prediction of COVID-19 progression are vital. We measured levels of five lung injury-related biomarkers, SP-D, KL-6, presepsin, kallistatin and stratifin, in serum samples collected serially during hospitalization from 31 patients with mild/moderate or severe/critical COVID-19 pneumonia, and their predictive performances were compared. Like the previously reported presepsin, a new biomarker candidate, stratifin, was significantly elevated with the onset of severe or critical symptoms in COVID-19 patients and decreased with symptom improvement. Notably, changes in stratifin and presepsin levels were distinctly earlier than those in SP-D, KL-6 and even SpO₂/FiO₂ values. Furthermore, serum levels of these biomarkers were significantly higher at the pre-severe stage (before the start of oxygen support) of patients who eventually advanced to severe/critical stages than in the patients who remained at the mild/moderate stage. These results were confirmed in an independent cohort, including 71 mild/moderate and 14 severe/critical patients, for whom the performance of stratifin and presepsin in discriminating between mild/moderate and pre-severe conditions of COVID-19 patients was superior to that of the SpO₂/FiO₂ ratio. Therefore, we concluded that stratifin and presepsin could be used as prognostic biomarkers for severe COVID-19 progression.

CAN PULMONARY SURFACTANT PROTEINS BE RELIABLE INDICATORS OF COVID-19-ASSOCIATED PULMONARY INJURY?

The COVID-19 pandemic is still raging all over the world. New variants of the coronavirus emerge and infect recovered from previous infections, vaccinated, and unvaccinated subjects. One aspect remains unchanged that is the lungs are the main targets of the pandemic coronavirus. This challenging situation requires the search for reliable predictive markers of severe and complicated course of the disease. Serum surfactant proteins are known to correlate with pulmonary injury severity in numerous diseases. Measurement of such protein levels may help timely predict the risk. Surfactant proteins can also be helpful diagnostic purposes in COVID-19.

Comparing the Cytokine Storms of COVID-19 and Pandemic Influenza

Emerging respiratory viruses are major health threats due to their potential to cause massive outbreaks. Over the past 2 years, the coronavirus disease 2019 (COVID-19) pandemic has caused millions of cases of severe infection and deaths worldwide. Although natural and vaccine-induced protective immune mechanisms against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been increasingly identified, the factors that determine morbimortality are less clear. Comparing the immune signatures of COVID-19 and other severe respiratory infections such as the pandemic influenza might help dissipate current controversies about the origin of their severe manifestations. As such, identifying homologies in the immunopathology of both diseases could provide targets for immunotherapy directed to block shared pathogenic mechanisms. Meanwhile, finding unique characteristics that differentiate each infection could shed light on specific immune alterations exploitable for diagnostic and individualized therapeutics for each case. In this study, we summarize immunopathological aspects of COVID-19 and pandemic influenza from the perspective of cytokine storms as the driving force underlying morbidity. Thereby, we analyze similarities and differences in the cytokine profiles of both infections, aiming to bring forward those molecules more attractive for translational medicine and drug development.

Hydrophilic But Not Hydrophobic Surfactant Protein Genetic Variants Are Associated With Severe Acute Respiratory Syncytial Virus Infection in Children

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infection-related hospitalization in the first year of life. Surfactant dysfunction is central to pathophysiologic mechanisms of various pulmonary diseases including RSV. We hypothesized that RSV severity is associated with single nucleotide polymorphisms (SNPs) of surfactant proteins (SPs). We prospectively enrolled 405 RSV-positive children and divided them into moderate and severe RSV disease. DNA was extracted and genotyped for sixteen specific SP gene SNPs. SP-A1 and A2 haplotypes were assigned. The association of RSV severity with SP gene SNPs was investigated by multivariate logistic regression. A likelihood ratio test was used to test the goodness of fit between two models (one with clinical and demographic data alone and another that included genetic variants). p ≤ 0.05 denotes statistical significance. A molecular dynamics simulation was done to determine the impact of the SFTPA2 rs1965708 on the SP-A behavior under various conditions. Infants with severe disease were more likely to be younger, of lower weight, and exposed to household pets and smoking, as well as having co-infection on admission. A decreased risk of severe RSV was associated with the rs17886395_C of the SFTPA2 and rs2243639_A of the SFTPD, whereas an increased risk was associated with the rs1059047_C of the SFTPA1. RSV severity was not associated with SNPs of SFTPB and SFTPC. An increased risk of severe RSV was associated with the 1A0 genotype of SFTPA2 in its homozygous or heterozygous form with 1A3. A molecular dynamic simulation study of SP-A variants that differ in amino acid 223, an important amino acid change (Q223K) between 1A0 and 1A3, showed no major impact on the behavior of these two variants except for higher thermodynamic stability of the K223 variant. The likelihood ratio test showed that the model with multi-allelic variants along with clinical and demographic data was a better fit to predict RSV severity. In summary, RSV severity was associated with hydrophilic (but not with hydrophobic) SPs gene variants. Collectively, our findings show that SP gene variants may play a key role in RSV infection and have a potential role in prognostication.

The Wildland Firefighter Exposure and Health Effect (WFFEHE) Study: Rationale, Design, and Methods of a Repeated-Measures Study

The wildland firefighter exposure and health effect (WFFEHE) study was a 2-year repeated-measures study to investigate occupational exposures and acute and subacute health effects among wildland firefighters. This manuscript describes the study rationale, design, methods, limitations, challenges, and lessons learned. The WFFEHE cohort included fire personnel ages 18-57 from six federal wildland firefighting crews in Colorado and Idaho during the 2018 and 2019 fire seasons. All wildland firefighters employed by the recruited crews were invited to participate in the study at preseason and postseason study intervals. In 2019, one of the crews also participated in a 3-day midseason study interval where workplace exposures and pre/postshift measurements were collected while at a wildland fire incident. Study components assessed cardiovascular health, pulmonary function and inflammation, kidney function, workplace exposures, and noise-induced hearing loss. Measurements included self-reported risk factors and symptoms collected through questionnaires; serum and urine biomarkers of exposure, effect, and inflammation; pulmonary function; platelet function and arterial stiffness; and audiometric testing. Throughout the study, 154 wildland firefighters participated in at least one study interval, while 144 participated in two or more study interval. This study was completed by the Centers for Disease Control and Prevention's National Institute for Occupational Safety and Health through a collaborative effort with the U.S. Department of Agriculture Forest Service, Department of the Interior National Park Service, and Skidmore College. Conducting research in the wildfire environment came with many challenges including collecting study data with study participants with changing work schedules and conducting study protocols safely and operating laboratory equipment in remote field locations. Forthcoming WFFEHE study results will contribute to the scientific evidence regarding occupational risk factors and exposures that can impact wildland firefighter health over a season and across two wildland fire seasons. This research is anticipated to lead to the development of preventive measures and policies aimed at reducing risk for wildland firefighters and aid in identifying future research needs for the wildland fire community.

Human Cell Organelles in SARS-CoV-2 Infection: An Up-to-Date Overview

Since the end of 2019, the whole world has been struggling with the life-threatening pandemic amongst all age groups and geographic areas caused by Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV-2). The Coronavirus Disease 2019 (COVID-19) pandemic, which has led to more than 468 million cases and over 6 million deaths reported worldwide (as of 20 March 2022), is one of the greatest threats to human health in history. Meanwhile, the lack of specific and irresistible treatment modalities provoked concentrated efforts in scientists around the world. Various mechanisms of cell entry and cellular dysfunction were initially proclaimed. Especially, mitochondria and cell membrane are crucial for the course of infection. The SARS-CoV-2 invasion depends on angiotensin converting enzyme 2 (ACE2), transmembrane serine protease 2 (TMPRSS2), and cluster of differentiation 147 (CD147), expressed on host cells. Moreover, in this narrative review, we aim to discuss other cell organelles targeted by SARS-CoV-2. Lastly, we briefly summarize the studies on various drugs.

SP-D and CC-16 Pneumoproteins' Kinetics and Their Predictive Role During SARS-CoV-2 Infection

Background

Surfactant protein D (SP-D) and pulmonary club cell protein 16 (CC-16) are called “pneumoproteins” and are involved in host defense against oxidative stress, inflammation, and viral outbreak. This study aimed to determine the predictive value of these pneumoproteins on the incidence of acute respiratory distress syndrome (ARDS) or death in patients with coronavirus disease-2019 (COVID-19).

Methods

This retrospective study included 87 patients admitted to an emergency department. Blood samples were collected on three time points (days 1, 5, and 14 from hospital admission). SP-D and CC-16 serum levels were determined, and univariate and multivariate analyses considering confounding variables (age, body mass index, tobacco use, dyspnea, hypertension, diabetes mellitus, neutrophil-to-lymphocyte ratio) were performed.

Results

Based on the multivariate analysis, SP-D level on D1 was positively and slightly correlated with subsequent development of ARDS, independent of body mass index, dyspnea, and diabetes mellitus. CC-16 level on D1 was modestly and positively correlated with fatal outcome. A rise in SP-D between D1 and D5 and D1 and D14 had a strong negative association with incidence of ARDS. These associations were independent of tobacco use and neutrophil-to-lymphocyte ratio.

Conclusions

Overall, our data reveal that increase in SP-D levels is a good prognostic factor for patients with COVID-19, and that initial CC-16 levels correlated with slightly higher risk of death. SP-D and CC-16 may prove useful to predict outcomes in patients with COVID-19.

Pulmonary surfactant as a versatile biomaterial to fight COVID-19

The COVID-19 pandemic has wielded an enormous pressure on global health care systems, economics and politics. Ongoing vaccination campaigns effectively attenuate viral spreading, leading to a reduction of infected individuals, hospitalizations and mortality. Nevertheless, the development of safe and effective vaccines as well as their global deployment is time-consuming and challenging. In addition, such preventive measures have no effect on already infected individuals and can show reduced efficacy against SARS-CoV-2 variants that escape vaccine-induced host immune responses. Therefore, it is crucial to continue the development of specific COVID-19 targeting therapeutics, including small molecular drugs, antibodies and nucleic acids. However, despite clear advantages of local drug delivery to the lung, inhalation therapy of such antivirals remains difficult. This review aims to highlight the potential of pulmonary surfactant (PS) in the treatment of COVID-19. Since SARS-CoV-2 infection can progress to COVID-19-related acute respiratory distress syndrome (CARDS), which is associated with PS deficiency and inflammation, replacement therapy with exogenous surfactant can be considered to counter lung dysfunction. In addition, due to its surface-active properties and membrane-interacting potential, PS can be repurposed to enhance drug spreading along the respiratory epithelium and to promote intracellular drug delivery. By merging these beneficial features, PS can be regarded as a versatile biomaterial to combat respiratory infections, in particular COVID-19.

Host cell entry mediators implicated in the cellular tropism of SARS‑CoV‑2, the pathophysiology of COVID‑19 and the identification of microRNAs that can modulate the expression of these mediators (Review)

The pathophysiology of coronavirus disease 2019 (COVID-19) is mainly dependent on the underlying mechanisms that mediate the entry of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) into the host cells of the various human tissues/organs. Recent studies have indicated a higher order of complexity of the mechanisms of infectivity, given that there is a wide-repertoire of possible cell entry mediators that appear to co-localise in a cell- and tissue-specific manner. The present study provides an over-view of the 'canonical' SARS-CoV-2 mediators, namely angiotensin converting enzyme 2, transmembrane protease serine 2 and 4, and neuropilin-1, expanding on the involvement of novel candidates, including glucose-regulated protein 78, basigin, kidney injury molecule-1, metabotropic glutamate receptor subtype 2, ADAM metallopeptidase domain 17 (also termed tumour necrosis factor-α convertase) and Toll-like receptor 4. Furthermore, emerging data indicate that changes in microRNA (miRNA/miR) expression levels in patients with COVID-19 are suggestive of further complexity in the regulation of these viral mediators. An in silico analysis revealed 160 candidate miRNAs with potential strong binding capacity in the aforementioned genes. Future studies should concentrate on elucidating the association between the cellular tropism of the SARS-CoV-2 cell entry mediators and the mechanisms through which they might affect the clinical outcome. Finally, the clinical utility as a biomarker or therapeutic target of miRNAs in the context of COVID-19 warrants further investigation.

A case of xenon inhalation therapy for respiratory failure and neuropsychiatric disorders associated with COVID-19

Acute respiratory distress syndrome (ARDS) is the main danger to the life of patients with pneumonia caused by SARS-CoV-2. At the same time, respiratory failure (RF) after ARDS can persist for a long time despite intensive therapy. Therefore, it is important to develop new effective approaches for restoring the ventilation function of the lungs after COVID-19. Here, we present a case report of effective application of short-term inhalations of xenon-oxygen (Xe/O₂) gas mixture for treatment of RF and neuropsychiatric disorders (NPD) associated with COVID-19. The patient inhaled a gas mixture of 70 % Xe and 30 % O₂. We used multispiral computed tomography, evaluated psychometry, studied hematological and biochemical blood parameters, and applied some other methods of clinical studies to assess the therapeutic effectiveness of Xe inhalation. Also, we studied the mechanism of action of xenon with computer modeling. The clinical case showed the high efficacy of Xe/O₂ mixture for treating severe RF and NPD after SARS-CoV-2 infection. Xenon inhalations dramatically increased oxygen saturation and the degree of pneumatization of the lungs. We found out that in coronavirus pneumonia, saturated phospholipids of surfactant are transferred to the solid-ordered phase, which disrupts the surface tension of the alveoli and alveolar gas exchange. Using molecular modeling methods, we demonstrated that the xenon atom increases the distance between the acyl chains of phospholipids due to the van der Waals dispersion interaction. These changes allow for the phase transition of phospholipids from the solid-ordered phase to the liquid phase and restore the functional activity of the surfactant. The findings suggest the feasibility of conducting studies on the effectiveness of Xe/O₂ inhalations for treating ARDS in SARS-CoV-2 infection.