Pulmonary surfactant and COVID-19: A new synthesis

Chapter 1: COVID-19 pathogenesis poses paradoxes difficult to explain with traditional physiology. For instance, since type II pneumocytes are considered the primary cellular target of SARS-CoV-2;as these produce pulmonary surfactant (PS), the possibility that insufficient PS plays a role in COVID-19 pathogenesis has been raised. However, the opposite of predicted high alveolar surface tension is found in many early COVID-19 patients: paradoxically normal lung volumes and high compliance occur, with profound hypoxemia. That 'COVID anomaly' was quickly rationalised by invoking traditional vascular mechanisms-mainly because of surprisingly preserved alveolar surface in early hypoxemic cases. However, that quick rejection of alveolar damage only occurred because the actual mechanism of gas exchange has long been presumed to be non-problematic, due to diffusion through the alveolar surface. On the contrary, we provide physical chemical evidence that gas exchange occurs by an process of expansion and contraction of the three-dimensional structures of PS and its associated proteins. This view explains anomalous observations from the level of cryo-TEM to whole individuals. It encompasses results from premature infants to the deepest diving seals. Once understood, the COVID anomaly dissolves and is straightforwardly explained as covert viral damage to the 3D structure of PS, with direct treatment implications. As a natural experiment, the SARS-CoV-2 virus itself has helped us to simplify and clarify not only the nature of dyspnea and its relationship to pulmonary compliance, but also the fine detail of the PS including such features as water channels which had heretofore been entirely unexpected.Copyright ©

Surfactant Protein B Reduces Respiratory Viral Infectivity in Human Lungs

Purpose of Study: COVID pneumonia caused by SARS-CoV-2 can result in a depletion of surfactant & lung injury, which resembles neonatal respiratory distress syndrome. Exogenous surfactant has shown promise as a therapeutic option in intubated hospitalized patients. Our preliminary data in human lung organoids (LOs) with a deficiency of surfactant protein B (SP-B) showed an increased viral load compared to normal LOs. Single cell RNA sequencing (scRNAseq) revealed that SP-B-deficient cells showed increased viral entry genes (ACE2 receptor) & dysregulated inflammatory markers emanating from the lung cells themselves. Our objective was to determine: (1) cell-specific transcriptional differences between normal & SP-B deficient human lung cells after infection with SARS-CoV-2 and (2) a therapeutic role of SP-B protein & surfactant in COVID-19 pneumonia. Methods Used: We used normal and SP-B mutant (homozygous, frameshift, loss of function mutation p.Pro133GlnfsTer95, previously known as 121ins2) human induced pluripotent stem cells (hiPSC) and differentiated them into 3D proximal lung organoids. The organoids were infected with the delta variant of SARS-CoV-2 for 24 hours at an MOI of 1. Infected and uninfected organoids were fixed in trizol in triplicate and underwent processing for bulk RNA sequencing. We tested for differentially expressed genes using the program DEseq. We also plated normal iPSC derived lung organoids as a monolayer and pre-treated them with 1mg/ml of Poractant alfa or 5 uM of recombinant SP-B protein. The delta strain of SARS-CoV-2 was added to the 96 wells at an MOI of 0.1 for one hour with shaking, then an overlay with DMEM/CMC/FBS was added and left on for 23 hours. The plate was fixed and stained for nucleocapsid (NC) protein. Summary of Results: Bioinformatic analysis of the bulk RNA sequencing data showed an increase in the multiple cytokines and chemokines in the SP-B mutant LOs compared to control. We also saw differential gene expression patterns in the SP-B mutant LOs including a reduction in SFTPC, FOXA2, and NKX2-1 and an increase in IL1A, VEGFA, PPARG and SMAD3. In the exogenous surfactant experiments, there was a decrease in total expression of viral NC in the Poractant alfa & rSP-B-treated cells compared to SARS-CoV-2 infection alone (p<0.001). Conclusion(s): Surfactant modulates the viral load of SARS-CoV-2 infection in the human lung. Deficiency in SP-B results in the dysregulation of the lung epithelial inflammatory signaling pathways resulting in worsening infections.

Regional Oxygenation in Neonates with Anemia.

Purpose. Assessment of regional oxygenation in neonates with anemic syndrome and after its correction. Materials and methods. The study included 76 neonates. Depending on the fact of the presence or absence of anemia, which required its correction, all included in the study infants were divided into 2 groups: with anemia - 8 patients and without it - 68 patients. Multiregional monitoring of tissue oxygenation was performed with the help of INVOS 5100C cerebral/somatic oximeter (Covidien, Medtronic, USA). Results and discussion. In comparison with infants with anemia, the comparison group had higher level of minimal cerebral oxygenation (73 [66;80] versus 56 [39;70], p=0.0447), and lower cFTOE values (0.17 [0.11;0.23] versus 0.35 [0,30;0,48], p=0,0021). It was also found that a newborn with RDS and cFTOE> 0.22 is 3.5 times more likely to have anemia, which requires PRBC transfusion. Correction of anemia was accompanied by the increase of hemoglobin level by 51 [36;56] g/l and hematocrit - by 16 [15;17] %. Moreover, only crSO2 and cFTOE showed the differences before and after transfusion: crSO2 before - 60 [55;69] and after - 65 [61;71], p=0.0156;cFTOE before - 0.40 [0.30;0.45] and after 0.34 [0.27;0.38], p=0.0078. Conclusion. Monitoring of regional oxygenation in neonates can be used for early diagnosis of oxygen imbalance in tissues on the background of development of anemia, and assessment of the effectiveness of its correction as well.Copyright © 2020, Professionalnye Izdaniya. All rights reserved.

Polysaturated fatty acids and their derivatives regulate respiratory infections.

The regulation of inflammation is a complex pathophysiological process that depends on the production of oxygenated lipid derivatives essential polyunsaturated fatty acids, like omega-3 and omega-6, among which are the lipoxins resolvins and protectins, called specialized pro-resolving lipid mediators (SPM). Their activity is associated with the control of respiratory infection processes to modulate the production of proinflammatory cytokines, avoiding damage due to inflammation-associated necrosis, reducing microbial loads, and promoting tissue remodeling. Therefore, we review some of the biochemical, physiological and immunological aspects of SPM in the regulation of inflammation in respiratory infections.Copyright © 2022, Instituto Nacional de Enfermedades Respiratorias. All rights reserved.

COVID-19 Infection in Parturients: Comparative Neonatal and Maternal Outcomes in a Single-institute Regional Hospital in Thailand

Objective: Chonburi province is ranked fourth in Thailand in terms of COVID-19 cases. The objective was to compare neonatal and maternal outcomes among pregnant women with and without COVID-19 infection delivered in Chonburi hospital. Materials and Methods: The present study was a retrospective matched cohort study that included all pregnant women who delivered between January 1 and August 31, 2021, at Chonburi Hospital, Thailand. The exposure group comprised women with a current or previous positive COVID-19 PCR test, while the comparators were the PCR negative group. The matching ratio was 1:4, based on gestational and maternal age, parity, and the closest delivery date. Clinical data were obtained from medical records. Results: Forty-six pregnant women had a positive COVID-19 PCR, 24 (52.17%) were Thai and 22 (47.83%) were of other ethnicities. Most (60.87%) were asymptomatic or required no medical assistance. Three (6.52%) had severe pneumonia and required respiratory support. Neither maternal death nor vertical transmission was detected. Compared with 184 COVID-19-negative pregnant women, no significant differences in low APGAR score of less than 7, and preeclampsia in the 46 COVID-19-positive pregnant women were observed. However, COVID-19-positive pregnant women showed an increased rate of neonatal respiratory distress (RD) (relative risk [RR] 2.55;95% confidence interval [CI] 1.04 to 6.21] and clinical early-onset neonatal sepsis (RR 3.60;1.55 to 8.36). Additionally, a higher cesarean section rate was observed in the COVID-19 positive group (RR 1.45, 1.11 to 1.85). Conclusion: There were no significant differences in neonates with APGAR of less than 7 between the cohort of 46 pregnant women who tested positive for COVID-19 and those who tested negative. However, a higher rate of cesarean delivery, presumed early-onset neonatal septicemia, and RD in the COVID-19 positive group were noted and should be monitored.

Plasma and Airway Levels of Surfactant Protein D Degradation Reflect Progression of ARDS in Ventilated Patients with SARS-CoV-2

Background: Patients with COVID-19 present severe respiratory symptoms progressing to acute respiratory distress syndrome (ARDS). Upon infection, SARS-CoV-2 destroys cells expressing the ACE2 receptor including alveolar type II cells (AT2). These cells are found in the alveolar-capillary barrier which normally secrete pulmonary surfactant, a complex of lipid and surfactant proteins (SPA, SP-B, SP-C, SP-D). Exogenous surfactant therapy (mainly composed of phospholipids, SP-B, and SP-C) has been successful in treating neonatal respiratory distress syndrome (nRDS) caused by surfactant deficiency in preterm babies.Plasma SP-D has been proposed as a marker of lung injury in COVID-19 but so far, no reports have evaluated sequential SP-D levels in both airway and plasma. As part of a clinical trial repurposing surfactant therapy to treat adult ventilated COVID-19 patients, we hypothesized that plasma SP-D levels may reflect decreased lung integrity and that SP-D degradation in plasma and airway samples from COVID-19 patients may reflect disease progression and severity. Methods: Enzyme-linked immunosorbent assay (ELISA) was used to quantify SP-D concentration in patient plasma and tracheal aspirate samples. Western Blotting was used to identify any protein degradation. Sequential daily plasma and airway samples were analysed. Results: SP-D concentration in serum was 10-20 times higher in patients ventilated for COVID-19 than in healthy volunteers. Additionally, the concentration of SP-D in plasma has shown to be 10-100-fold higher than in tracheal aspirates. Furthermore, degraded fragments of SP-D were detected at a higher ratio than intact SP-D in plasma of ventilated patients. This ratio decreased with administration of surfactant therapy (containing phospholipids and SP-B and SP-C but no SPA or SP-D). Conclusions: Increased serum SP-D and decreased tracheal aspirate SP-D from ventilated COVID-19 patients suggested leakage of pulmonary surfactant into the bloodstream caused by damage to the alveolar-capillary barrier in diseased lungs. The ratio of degraded vs. intact SP-D found in the plasma was compared before and after therapeutic surfactant administration. The results indicated that levels of SP-D in plasma and tracheal aspirates together with the ratio of degraded and intact SP-D in the plasma may be useful indicators of the severity of COVID-19 lung disease progression.

Pneumopericardium in a Newborn with Respiratory Distress and COVID-19

BACKGROUND: Pneumopericardium (PPC) is one of the rarest pulmonary air leak syndromes, but the incidence is the highest in the neonatal period. Risk factors include premature infants with respiratory distress (RD) syndrome, receiving active resuscitation, meconium aspiration syndrome, and aggressive mechanical ventilation. Several cases have also been reported related to COVID-19. CASE PRESENTATION: We report a case of a female newborn with a birth weight of 3300 grams a COVID-19 confirmed 35-year-old G3P2A0 mother. The baby was not crying at born and the amniotic fluid was stained green. The baby experienced RD and was intubated. A babygram was performed at the age of 5 h with the impression of a too deep endotracheal tube, neonatal pneumonia, and PPC. COVID-19 RT-PCR examination of the baby was positive. There were no signs of cardiac tamponade, so it was decided to take conservative and supportive management. CONCLUSION: Resolution of PPC was found on repeated babygram 26 h later. The baby was then discharged after 19 days of treatment.

COVID-19 Infection in Pregnancy: Obstetrical Risk Factors and Neonatal Outcomes-A Monocentric, Single-Cohort Study.

The effects of coronavirus disease 2019 caused by severe acute respiratory syndrome coronavirus 2 on pregnant women and neonates are mainly unknown, since limited data are available in the literature. We conducted a monocentric and cross-sectional study enrolling 122 un-vaccinated pregnant women with COVID-19 infection tested by RT-PCR nasopharyngeal swab. Only 4.1% of the patients had severe COVID-19 symptoms together with major respiratory symptoms and intensive care unit admission, whereas 35.25% of women had comorbidities and two-thirds of them were overweight or obese. COVID-19 was detected mainly in the third trimester (98.36%) and multiparous women (59.02%). The mode of delivery was influenced by mild-severe COVID-19 symptoms, with a higher number of urgent or emergent cesarean sections than spontaneous or operative vaginal births. Preterm births were associated with high BMI, mode of delivery (higher among cesarean sections), nulliparity, and severe COVID-19 symptoms. In cases of severe COVID-19 symptoms, there was a higher rate of respiratory distress syndrome among newborns. In the end, only the presence of a severe COVID-19 infection worsened the obstetrical and neonatal outcomes, with higher rates of urgent or emergent cesarean section, preterm births, and neonatal respiratory distress syndrome.

Intravenous sulforhodamine B reduces alveolar surface tension, improves oxygenation, and reduces ventilation injury in a respiratory distress model.

In the neonatal respiratory distress syndrome (NRDS) and acute respiratory distress syndrome (ARDS), mechanical ventilation supports gas exchange but can cause ventilation-induced lung injury (VILI) that contributes to high mortality. Further, surface tension, T, should be elevated and VILI is proportional to T. Surfactant therapy is effective in NRDS but not ARDS. Sulforhodamine B (SRB) is a potential alternative T-lowering therapeutic. In anesthetized male rats, we injure the lungs with 15 min of 42 mL/kg tidal volume, VT, and zero end-expiratory pressure ventilation. Then, over 4 h, we support the rats with protective ventilation-VT of 6 mL/kg with positive end-expiratory pressure. At the start of the support period, we administer intravenous non-T-altering fluorescein (targeting 27 µM in plasma) without or with therapeutic SRB (10 nM). Throughout the support period, we increase inspired oxygen fraction, as necessary, to maintain >90% arterial oxygen saturation. At the end of the support period, we euthanize the rat; sample systemic venous blood for injury marker ELISAs; excise the lungs; combine confocal microscopy and servo-nulling pressure measurement to determine T in situ in the lungs; image fluorescein in alveolar liquid to assess local permeability; and determine lavage protein content and wet-to-dry ratio (W/D) to assess global permeability. Lungs exhibit focal injury. Surface tension is elevated 72% throughout control lungs and in uninjured regions of SRB-treated lungs, but normal in injured regions of treated lungs. SRB administration improves oxygenation, reduces W/D, and reduces plasma injury markers. Intravenous SRB holds promise as a therapy for respiratory distress.NEW & NOTEWORTHY Sulforhodmaine B lowers T in alveolar edema liquid. Given the problematic intratracheal delivery of surfactant therapy for ARDS, intravenous SRB might constitute an alternative therapeutic. In a lung injury model, we find that intravenously administered SRB crosses the injured alveolar-capillary barrier thus reduces T specifically in injured lung regions; improves oxygenation; and reduces the degree of further lung injury. Intravenous SRB administration might help respiratory distress patients, including those with the novel coronavirus, avoid mechanical ventilation or, once ventilated, survive.