Immunoglobulin genes and severity of COVID-19.

There is tremendous interindividual and interracial variability in the outcome of SARS-CoV-2 infection, suggesting the involvement of host genetic factors. Here, we investigated whether IgG allotypes GM (γ marker) 3 and GM 17, genetic markers of IgG1, contributed to the severity of COVID-19. IgG1 plays a pivotal role in response against SARS-CoV-2 infection. We also investigated whether these GM alleles synergistically/epistatically with IGHG3 and FCGR2A alleles-which have been previously implicated in COVID-19-modulated the extent of COVID-19 severity. The study population consisted of 316 COVID-19 patients who needed treatment in the intensive care unit of Hospital Universitario Central de Asturias. All individuals were genotyped for GM 3/17, IGHG3 hinge length, and FCGR2A rs1801274 A/G polymorphisms. Among the 316 critical patients, there were 86 deaths. The risk of death among critical patients was significantly higher in subjects with GM 17 (IgG1) and short hinge length (IgG3). GM 17-carriers were at almost three-fold higher risk of death than non-carriers (p < 0.001; OR = 2.86, CI 1.58-5.16). Subjects with short hinge length of IgG3 had a two-fold higher risk of death than those with medium hinge length (p = 0.01; OR = 2.16, CI 1.19-3.90). GM 3/3 and IGHG3 (MM) genotypes were less frequent among death vs. survivors (9% vs 36%, p < 0.001) and associated with protective effect (OR = 0.18, 95% CI = 0.08-0.39). This is the first report implicating IgG1 allotypes in COVID-19-spurred death. It needs to be replicated in an independent study population.

Chromosome-Y haplogroups in Asturias (Northern Spain) and their association with severe COVID-19.

The main objective of this study was to determine whether the common Y-haplogroups were be associated with the risk of developing severe COVID-19 in Spanish male. We studied 479 patients who required hospitalization due to COVID-19 and 285 population controls from the region of Asturias (northern Spain), They were genotyped for several polymorphisms that define the common European Y-haplogroups. We compared the frequencies between patients and controls aged ≤ 65 and >65 years. There were no different haplogroup frequencies between the two age groups of controls. Haplogroup R1b was less common in patients aged ≤65 years. Haplogroup I was more common in the two patient´s groups compared to controls (p = 0.02). Haplogroup R1b was significantly more frequent among hypertensive patients, without difference between the hypertensive and normotensive controls. This suggested that R1b could increase the risk for severe COVID-19 among male with pre-existing hypertension. In conclusion, we described the Y-haplogroup structure among Asturians. We found an increased risk of severe COVID-19 among haplogroup I carriers, and a significantly higher frequency of R1b among hypertensive patients. These results indicate that Y-chromosome variants could serve as markers to define the risk of developing a severe form of COVID-19.

Repair of Acute Respiratory Distress Syndrome in COVID-19 by Stromal Cells (REALIST-COVID Trial): A Multicenter, Randomized, Controlled Clinical Trial.

Rationale: Mesenchymal stromal cells (MSCs) may modulate inflammation, promoting repair in coronavirus disease (COVID-19)-related acute respiratory distress syndrome (ARDS). Objectives: We investigated the safety and efficacy of ORBCEL-C (CD362 [cluster of differentiation 362]-enriched, umbilical cord-derived MSCs) in COVID-19-related ARDS. Methods: In this multicenter, randomized, double-blind, allocation-concealed, placebo-controlled trial (NCT03042143), patients with moderate to severe COVID-19-related ARDS were randomized to receive ORBCEL-C (400 million cells) or placebo (Plasma-Lyte 148). The primary safety and efficacy outcomes were the incidence of serious adverse events and oxygenation index at Day 7, respectively. Secondary outcomes included respiratory compliance, driving pressure, PaO2:FiO2 ratio, and Sequential Organ Failure Assessment score. Clinical outcomes relating to duration of ventilation, lengths of ICU and hospital stays, and mortality were collected. Long-term follow-up included diagnosis of interstitial lung disease at 1 year and significant medical events and mortality at 2 years. Transcriptomic analysis was performed on whole blood at Days 0, 4, and 7. Measurements and Main Results: Sixty participants were recruited (final analysis: n = 30 received ORBCEL-C, n = 29 received placebo; 1 participant in the placebo group withdrew consent). Six serious adverse events occurred in the ORBCEL-C group and three in the placebo group (risk ratio, 2.9 [95% confidence interval, 0.6-13.2]; P = 0.25). Day 7 mean (SD) oxygenation index did not differ (ORBCEL-C, 98.3 [57.2] cm H2O/kPa; placebo, 96.6 [67.3] cm H2O/kPa). There were no differences in secondary surrogate outcomes or in mortality at Day 28, Day 90, 1 year, or 2 years. There was no difference in the prevalence of interstitial lung disease at 1 year or significant medical events up to 2 years. ORBCEL-C modulated the peripheral blood transcriptome. Conclusion: ORBCEL-C MSCs were safe in subjects with moderate to severe COVID-19-related ARDS but did not improve surrogates of pulmonary organ dysfunction.

Age-dependent effect of the IFIH1/MDA5 gene variants on the risk of critical COVID-19.

MDA5, encoded by the IFIH1gene, is a cytoplasmic sensor of viral RNAs that triggers interferon (IFN) antiviral responses. Common and rare IFIH1 variants have been associated with the risk of type 1 diabetes and other immune-mediated disorders, and with the outcome of viral diseases. Variants associated with reduced IFN expression would increase the risk for severe viral disease. The MDA5/IFN pathway would play a critical role in the response to SARS-CoV-2 infection mediating the extent and severity of COVID-19. Here, we genotyped a cohort of 477 patients with critical ICU COVID-19 (109 death) for three IFIH1 functional variants: rs1990760 (p.Ala946Thr), rs35337543 (splicing variant, intron 8 + 1G > C), and rs35744605 (p.Glu627Stop). The main finding of our study was a significant increased frequency of rs1990760 C-carriers in early-onset patients (< 65 years) (p = 0.01; OR = 1.64, 95%CI = 1.18-2.43). This variant was also increased in critical vs. no-ICU patients and in critical vs. asymptomatic controls. The rs35744605 C variant was associated with increased blood IL6 levels at ICU admission. The rare rs35337543 splicing variant showed a trend toward protection from early-onset critical COVID-19. In conclusion, IFIH1 variants associated with reduced gene expression and lower IFN response might contribute to develop critical COVID-19 with an age-dependent effect.

Transcriptomic clustering of critically ill COVID-19 patients.

BACKGROUND: Infections caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may cause a severe disease, termed coronavirus disease 2019 (COVID-19), with significant mortality. Host responses to this infection, mainly in terms of systemic inflammation, have emerged as key pathogenetic mechanisms and their modulation has shown a mortality benefit. METHODS: In a cohort of 56 critically ill COVID-19 patients, peripheral blood transcriptomes were obtained at admission to an intensive care unit (ICU) and clustered using an unsupervised algorithm. Differences in gene expression, circulating microRNAs (c-miRNAs) and clinical data between clusters were assessed, and circulating cell populations estimated from sequencing data. A transcriptomic signature was defined and applied to an external cohort to validate the findings. RESULTS: We identified two transcriptomic clusters characterised by expression of either interferon-related or immune checkpoint genes, respectively. Steroids have cluster-specific effects, decreasing lymphocyte activation in the former but promoting B-cell activation in the latter. These profiles have different ICU outcomes, despite no major clinical differences at ICU admission. A transcriptomic signature was used to identify these clusters in two external validation cohorts (with 50 and 60 patients), yielding similar results. CONCLUSIONS: These results reveal different underlying pathogenetic mechanisms and illustrate the potential of transcriptomics to identify patient endotypes in severe COVID-19 with the aim to ultimately personalise their therapies.

IGHG3 hinge length variation was associated with the risk of critical disease and death in a Spanish COVID-19 cohort.

IgG3 would play an important role in the immune adaptive response against SARS-CoV-2, and low plasma levels might increase the risk of COVID-19 severity and mortality. The IgG3 hinge sequence has a variable repeat of a 15 amino acid exon with common 4-repeats (M) and 3-repeats (S). This length IGHG3 polymorphism might affect the IgG3 effector functions. The short hinge length would reduce the IgG3 flexibility and impairs the neutralization and phagocytosis compared to larger length-isoforms. We genotyped the IGHG3 length polymorphism in patients with critical COVID-19 (N = 516; 107 death) and 152 moderate-severe but no-critical cases. Carriers of the S allele had an increased risk of critical ICU and mortality (p < 0.001, OR = 2.79, 95% CI = 1.66-4.65). This adverse effect might be explained by a less flexibility and reduced ability to induce phagocytosis or viral neutralization for the short length allele. We concluded that the IgG3 hinge length polymorphism could be a predictor of critical COVID-19 and the risk of death. This study was based on a limited number of patients from a single population, and requires validation in larger cohorts.

The FCGR2A rs1801274 polymorphism was associated with the risk of death among COVID-19 patients.

Polymorphisms of Fcγ receptors have been associated with variable responses to infections. We determined the association of functional polymorphisms rs1801274 in the FCGR2A and rs396991 in the FCGR3A with COVID-19 severity. This study involved 453 patients with severe COVID-19, in which the FCGR2A rs1801274 G-allele (131-Arg) was significantly associated with death (p = 0.02, OR = 1.47). This effect was independent of age and increased IL6 and D-Dimer levels. This study suggests that the FCGR2A gene might be associated with the risk of death among COVID-19 patients. Our study has several limitations, mainly the limited number of patients and the inclusion of a single population. It is thus necessary to confirm this result in larger cohorts from different populations.

Mechanical ventilation promotes lung tumour spread by modulation of cholesterol cell content.

BACKGROUND: Mechanical stretch of cancer cells can alter their invasiveness. During mechanical ventilation, lungs may be exposed to an increased amount of stretch, but the consequences on lung tumours have not been explored. METHODS: To characterise the influence of mechanical ventilation on the behaviour of lung tumours, invasiveness assays and transcriptomic analyses were performed in cancer cell lines cultured in static conditions or under cyclic stretch. Mice harbouring lung melanoma implants were submitted to mechanical ventilation and metastatic spread was assessed. Additional in vivo experiments were performed to determine the mechanodependent specificity of the response. Incidence of metastases was studied in a cohort of lung cancer patients that received mechanical ventilation compared with a matched group of nonventilated patients. RESULTS: Stretch increases invasiveness in melanoma B16F10luc2 and lung adenocarcinoma A549 cells. We identified a mechanosensitive upregulation of pathways involved in cholesterol processing in vitro, leading to an increase in pro-protein convertase subtilisin/kexin type 9 (PCSK9) and LDLR expression, a decrease in intracellular cholesterol and preservation of cell stiffness. A course of mechanical ventilation in mice harbouring melanoma implants increased brain and kidney metastases 2 weeks later. Blockade of PCSK9 using a monoclonal antibody increased cell cholesterol and stiffness and decreased cell invasiveness in vitro and metastasis in vivo. In patients, mechanical ventilation increased PCSK9 abundance in lung tumours and the incidence of metastasis, thus decreasing survival. CONCLUSIONS: Our results suggest that mechanical stretch promote invasiveness of cancer cells, which may have clinically relevant consequences. Pharmacological manipulation of cholesterol endocytosis could be a novel therapeutic target in this setting.

FURIN gene variants (rs6224/rs4702) as potential markers of death and cardiovascular traits in severe COVID-19.

Furin is a protease that plays a key role in the infection cycle of SARS-CoV-2 by cleaving the viral proteins during the virus particle assembly. In addition, Furin regulates several physiological processes related to cardio-metabolic traits. DNA variants in the FURIN gene are candidates to regulate the risk of developing these traits as well as the susceptibility to severe COVID-19. We genotyped two functional FURIN variants (rs6224/rs4702) in 428 COVID-19 patients in the intensive care unit. The association with death (N = 106) and hypertension, diabetes, and hyperlipidaemia was statistically evaluated. The risk of death was associated with age, hypertension, and hypercholesterolemia. The two FURIN alleles linked to higher expression (rs6224 T and rs4702 A) were significantly increased in the death cases (odds ratio= 1.40 and 1.43). Homozygosis for the two high expression genotypes (rs6224 TT and rs4702 AA) and for the T-A haplotype was associated with an increased risk of hypercholesterolemia. In the multiple logistic regression both, hypercholesterolemia and the TT + AA genotype were significantly associated with death. In conclusion, besides its association with hypercholesterolemia, FURIN variants might be independent risk factors for the risk of death among COVID-19 patients.

The Interferon-induced transmembrane protein 3 gene (IFITM3) rs12252 C variant is associated with COVID-19.

BACKGROUND AND AIMS: The interferon-induced transmembrane proteins play an important antiviral role by preventing viruses from traversing the cellular lipid bilayer. IFITM3 gene variants have been associated with the clinical response to influenza and other viruses. Our aim was to determine whether the IFITM3 rs12252 polymorphism was associated with the risk of developing severe symptoms of COVID-19 in our population. METHODS: A total of 288 COVID-19 patients who required hospitalization (81 in the intensive care unit) and 440 age matched controls were genotyped with a Taqman assay. Linear regression models were used to compare allele and genotype frequencies between the groups, correcting for age and sex. RESULTS: Carriers of the minor allele frequency (rs12252 C) were significantly more frequent in the patients compared to controls after correcting by age and sex (p = 0.01, OR = 2.02, 95%CI = 1.19-3.42). This genotype was non-significantly more common among patients who required ICU. CONCLUSIONS: The IFITM3 rs12252 C allele was a risk factor for COVID-19 hospitalization in our Caucasian population. The extent of the association was lower than the reported among Chinese, a population with a much higher frequency of the risk allele.

Alveolar CCN1 is associated with mechanical stretch and acute respiratory distress syndrome severity.

The cellular communication network factor 1 (CCN1) is a matricellular protein that can modulate multiple tissue responses, including inflammation and repair. We have previously shown that adenoviral overexpression of Ccn1 is sufficient to cause acute lung injury in mice. We hypothesized that CCN1 is present in the airspaces of lungs during the acute phase of lung injury, and higher concentrations are associated with acute respiratory distress syndrome (ARDS) severity. We tested this hypothesis by measuring 1) CCN1 in bronchoalveolar lavage fluid (BALF) and lung homogenates from mice subjected to ventilation-induced lung injury (VILI), 2) Ccn1 gene expression and protein levels in MLE-12 cells (alveolar epithelial cell line) subjected to mechanical stretch, and 3) CCN1 in BALF from mechanically ventilated humans with and without ARDS. BALF CCN1 concentrations and whole lung CCN1 protein levels were significantly increased in mice with VILI (n = 6) versus noninjured controls (n = 6). Ccn1 gene expression and CCN1 protein levels were increased in MLE-12 cells cultured under stretch conditions. Subjects with ARDS (n = 77) had higher BALF CCN1 levels compared with mechanically ventilated subjects without ARDS (n = 45) (P < 0.05). In subjects with ARDS, BALF CCN1 concentrations were associated with higher total protein, sRAGE, and worse [Formula: see text]/[Formula: see text] ratios (all P < 0.05). CCN1 is present in the lungs of mice and humans during the acute inflammatory phase of lung injury, and concentrations are higher in patients with increased markers of severity. Alveolar epithelial cells may be an important source of CCN1 under mechanical stretch conditions.

Lung Purinoceptor Activation Triggers Ventilator-Induced Brain Injury.

OBJECTIVES: Mechanical ventilation can cause ventilator-induced brain injury via afferent vagal signaling and hippocampal neurotransmitter imbalances. The triggering mechanisms for vagal signaling during mechanical ventilation are unknown. The objective of this study was to assess whether pulmonary transient receptor potential vanilloid type-4 (TRPV4) mechanoreceptors and vagal afferent purinergic receptors (P2X) act as triggers of ventilator-induced brain injury. DESIGN: Controlled, human in vitro and ex vivo studies, as well as murine in vivo laboratory studies. SETTING: Research laboratory. SUBJECTS: Wild-type, TRPV4-deficient C57BL/6J mice, 8-10 weeks old. Human postmortem lung tissue and human lung epithelial cell line BEAS-2B. INTERVENTION: Mice subjected to mechanical ventilation were studied using functional MRI to assess hippocampal activity. The effects of lidocaine (a nonselective ion-channel inhibitor), P2X-purinoceptor antagonist (iso-PPADS), or genetic TRPV4 deficiency on hippocampal dopamine-dependent pro-apoptotic signaling were studied in mechanically ventilated mice. Human lung epithelial cells (BEAS-2B) were used to study the effects of mechanical stretch on TRPV4 and P2X expression and activation. TRPV4 levels were measured in postmortem lung tissue from ventilated and nonventilated patients. MEASUREMENTS AND MAIN RESULTS: Hippocampus functional MRI analysis revealed considerable changes in response to the increase in tidal volume during mechanical ventilation. Intratracheal lidocaine, iso-PPADS, and TRPV4 genetic deficiency protected mice against ventilationinduced hippocampal pro-apoptotic signaling. Mechanical stretch in both, BEAS-2B cells and ventilated wild-type mice, resulted in TRPV4 activation and reduced Trpv4 and P2x expression. Intratracheal replenishment of adenosine triphosphate in Trpv4 mice abrogated the protective effect of TRPV4 deficiency. Autopsy lung tissue from ventilated patients showed decreased lung TRPV4 levels compared with nonventilated CONCLUSIONS:: TRPV4 mechanosensors and purinergic receptors are involved in the mechanisms of ventilator-induced brain injury. Inhibition of this neural signaling, either using nonspecific or specific inhibitors targeting the TRPV4/adenosine triphosphate/P2X signaling axis, may represent a novel strategy to prevent or treat ventilator-induced brain injury.

Lung Recruitability in Severe Acute Respiratory Distress Syndrome Requiring Extracorporeal Membrane Oxygenation.

OBJECTIVES: Quantification of potential for lung recruitment may guide the ventilatory strategy in acute respiratory distress syndrome. However, there are no quantitative data on recruitability in patients with severe acute respiratory distress syndrome who require extracorporeal membrane oxygenation. We sought to quantify potential for lung recruitment and its relationship with outcomes in this cohort of patients. DESIGN: A single-center, retrospective, observational cohort study. SETTING: Tertiary referral severe respiratory failure center in a university hospital in the United Kingdom. PATIENTS: Forty-seven adults with severe acute respiratory distress syndrome requiring extracorporeal membrane oxygenation. INTERVENTION: None. MEASUREMENTS AND MAIN RESULTS: In patients with severe acute respiratory distress syndrome-mainly of pulmonary origin (86%)-the potential for lung recruitment and the weight of nonaerated, poorly aerated, normally aerated, and hyperaerated lung tissue were assessed at low (5 cmH2O) and high (45 cmH2O) airway pressures. Patients were categorized as high or low potential for lung recruitment based on the median potential for lung recruitment value of the study population. The median potential for lung recruitment was 24.3% (interquartile range = 11.4-37%) ranging from -2% to 76.3% of the total lung weight. Patients with potential for lung recruitment above the median had significantly shorter extracorporeal membrane oxygenation duration (8 vs 13 d; p = 0.013) and shorter ICU stay (15 vs 22 d; p = 0.028), but mortality was not statistically different (24% vs 46%; p = 0.159). CONCLUSIONS: We observed significant variability in potential for lung recruitment in patients with severe acute respiratory distress syndrome requiring extracorporeal membrane oxygenation. Patients with high potential for lung recruitment had a shorter ICU stay and shorter extracorporeal membrane oxygenation duration.

Impaired lung repair during neutropenia can be reverted by matrix metalloproteinase-9.

BACKGROUND: Neutrophils may cause tissue disruption during migration and by releasing cytotoxic molecules. However, the benefits of neutrophil depletion observed in experimental models of lung injury do not correspond with the poor outcome of neutropenic patients. METHODS: To clarify the role of neutrophils during repair, mice with ventilator induced lung injury (VILI) were rendered neutropenic after damage, and followed for 48 hours of spontaneous breathing. Lungs were harvested and inflammatory mediators and matrix metalloproteinases measured. Bronchoalveolar lavage fluid (BALF) from ventilated patients with acute respiratory distress syndrome, with or without neutropenia, was collected, the same mediators measured and their effects in an ex vivo model of alveolar repair studied. Finally, neutropenic mice were treated after VILI with exogenous matrix metalloproteinase-9 (MMP-9). RESULTS: Lungs from neutropenic animals showed delayed repair and displayed higher levels of tumour necrosis factor α, interferon γ and macrophage inflammatory protein 2, and absence of MMP-9. BALF from ventilated neutropenic patients with acute respiratory distress syndrome showed similar results. BALFs from neutropenic patients yielded a delayed closure rate of epithelial wounds ex vivo, which was improved by removal of collagen or addition of exogenous MMP-9. Lastly, treatment of neutropenic mice with exogenous MMP-9 after VILI reduced tissue damage without modifying cytokine concentrations. CONCLUSION: Release of MMP-9 from neutrophils is required for adequate matrix processing and lung repair.

Impact of Initial Ventilatory Strategy in Hematological Patients With Acute Respiratory Failure: A Systematic Review and Meta-Analysis.

OBJECTIVE: Acute respiratory failure in hematological patients is related to a high mortality. Noninvasive mechanical ventilation may benefit a subset of these patients, but the overall effect on mortality and the risks derived from its failure are unclear. Our objective was to review the impact of initial ventilatory strategy on mortality and the risks related to noninvasive mechanical ventilation failure in this group of patients. DATA SOURCES: Data sources, including PubMed and conference proceedings, were searched from the year 2000 to January 2015. STUDY SELECTION: We selected studies reporting mortality and the need for mechanical ventilation in hematological patients with acute respiratory failure. DATA EXTRACTION: Two trained reviewers independently conducted study selection, abstracted data, and assessed the risk of bias. Discrepancies between reviewers were resolved through discussion and consensus. The outcomes explored were all-cause mortality after mechanical ventilation and incidence of noninvasive mechanical ventilation failure. DATA SYNTHESIS: A random-effects model was used in all the analysis. Thirteen studies, involving 2,380 patients, were included. Use of noninvasive mechanical ventilation was related to a better outcome than initial intubation (risk ratio, 0.74; 95% CI, 0.65-0.84). Failure of noninvasive mechanical ventilation did not increase the overall risk of death (risk ratio, 1.02; 95% CI, 0.93-1.13). There were signs of publication bias and substantial heterogeneity among the studies. Compensation of this bias by using the trim-and-fill method showed a significant risk of death after noninvasive mechanical ventilation failure (risk ratio, 1.07; 95% CI, 1.00-1.14). Meta-regression analysis showed that the predicted risk of death for the noninvasive mechanical ventilation group acted as a significant moderator, with a higher risk of death after noninvasive mechanical ventilation failure in those studies reporting lower predicted mortality. CONCLUSIONS: Noninvasive mechanical ventilation is associated with a lower risk of death in hematological patients with respiratory failure. Noninvasive mechanical ventilation failure may worsen the prognosis, mainly in less severe patients.

Impact of Recruitment on Static and Dynamic Lung Strain in Acute Respiratory Distress Syndrome.

BACKGROUND: Lung strain, defined as the ratio between end-inspiratory volume and functional residual capacity, is a marker of the mechanical load during ventilation. However, changes in lung volumes in response to pressures may occur in injured lungs and modify strain values. The objective of this study was to clarify the role of recruitment in strain measurements. METHODS: Six oleic acid-injured pigs were ventilated at positive end-expiratory pressure (PEEP) 0 and 10 cm H2O before and after a recruitment maneuver (PEEP = 20 cm H2O). Lung volumes were measured by helium dilution and inductance plethysmography. In addition, six patients with moderate-to-severe acute respiratory distress syndrome were ventilated with three strategies (peak inspiratory pressure/PEEP: 20/8, 32/8, and 32/20 cm H2O). Lung volumes were measured in computed tomography slices acquired at end-expiration and end-inspiration. From both series, recruited volume and lung strain (total, dynamic, and static) were computed. RESULTS: In the animal model, recruitment caused a significant decrease in dynamic strain (from [mean ± SD] 0.4 ± 0.12 to 0.25 ± 0.07, P < 0.01), while increasing the static component. In patients, total strain remained constant for the three ventilatory settings (0.35 ± 0.1, 0.37 ± 0.11, and 0.32 ± 0.1, respectively). Increases in tidal volume had no significant effects. Increasing PEEP constantly decreased dynamic strain (0.35 ± 0.1, 0.32 ± 0.1, and 0.04+0.03, P < 0.05) and increased static strain (0, 0.06 ± 0.06, and 0.28 ± 0.11, P < 0.05). The changes in dynamic and total strain among patients were correlated to the amount of recruited volume. An analysis restricted to the changes in normally aerated lung yielded similar results. CONCLUSION: Recruitment causes a shift from dynamic to static strain in early acute respiratory distress syndrome.

Exposure to mechanical ventilation promotes tolerance to ventilator-induced lung injury by Ccl3 downregulation.

Inflammation plays a key role in the development of ventilator-induced lung injury (VILI). Preconditioning with a previous exposure can damp the subsequent inflammatory response. Our objectives were to demonstrate that tolerance to VILI can be induced by previous low-pressure ventilation, and to identify the molecular mechanisms responsible for this phenomenon. Intact 8- to 12-wk-old male CD1 mice were preconditioned with 90 min of noninjurious ventilation [peak pressure 17 cmH2O, positive end-expiratory pressure (PEEP) 2 cmH2O] and extubated. Seven days later, preconditioned mice and intact controls were submitted to injurious ventilation (peak pressure 20 cmH2O, PEEP 0 cmH2O) for 2 h to induce VILI. Preconditioned mice showed lower histological lung injury scores, bronchoalveolar lavage albumin content, and lung neutrophilic infiltration after injurious ventilation, with no differences in Il6 or Il10 expression. Microarray analyses revealed a downregulation of Calcb, Hspa1b, and Ccl3, three genes related to tolerance phenomena, in preconditioned animals. Among the previously identified genes, only Ccl3, which encodes the macrophage inflammatory protein 1 alpha (MIP-1α), showed significant differences between intact and preconditioned mice after high-pressure ventilation. In separate, nonconditioned animals, treatment with BX471, a specific blocker of CCR1 (the main receptor for MIP-1α), decreased lung damage and neutrophilic infiltration caused by high-pressure ventilation. We conclude that previous exposure to noninjurious ventilation induces a state of tolerance to VILI. Downregulation of the chemokine gene Ccl3 could be the mechanism responsible for this effect.

Mechanical ventilation triggers hippocampal apoptosis by vagal and dopaminergic pathways.

RATIONALE: Critically ill patients frequently develop neuropsychological disturbances including acute delirium or memory impairment. The need for mechanical ventilation is a risk factor for these adverse events, but a mechanism that links lung stretch and brain injury has not been identified. OBJECTIVES: To identify the mechanisms that lead to brain dysfunction during mechanical ventilation. METHODS: Brains from mechanically ventilated mice were harvested, and signals of apoptosis and alterations in the Akt survival pathway were studied. These measurements were repeated in vagotomized or haloperidol-treated mice, and in animals intracerebroventricularly injected with selective dopamine-receptor blockers. Hippocampal slices were cultured and treated with micromolar concentrations of dopamine, with or without dopamine receptor blockers. Last, levels of dysbindin, a regulator of the membrane availability of dopamine receptors, were assessed in the experimental model and in brain samples from ventilated patients. MEASUREMENTS AND MAIN RESULTS: Mechanical ventilation triggers hippocampal apoptosis as a result of type 2 dopamine receptor activation in response to vagal signaling. Activation of these receptors blocks the Akt/GSK3ß prosurvival pathway and activates the apoptotic cascade, as demonstrated in vivo and in vitro. Vagotomy, systemic haloperidol, or intracerebroventricular raclopride (a type 2 dopamine receptor blocker) ameliorated this effect. Moreover, ventilation induced a concomitant change in the expression of dysbindin-1C. These results were confirmed in brain samples from ventilated patients. CONCLUSIONS: These results prove the existence of a pathogenic mechanism of lung stretch-induced hippocampal apoptosis that could explain the neurological changes in ventilated patients and may help to identify novel therapeutic approaches.

Exploring the translational landscape of the long noncoding RNA transcriptome in acute respiratory distress syndrome: it is a long way to the top.

Acute respiratory distress syndrome (ARDS) poses a significant and widespread public health challenge. Extensive research conducted in recent decades has considerably improved our understanding of the disease pathophysiology. Nevertheless, ARDS continues to rank among the leading causes of mortality in intensive care units and its management remains a formidable task, primarily due to its remarkable heterogeneity. As a consequence, the syndrome is underdiagnosed, prognostication has important gaps and selection of the appropriate therapeutic approach is laborious. In recent years, the noncoding transcriptome has emerged as a new area of attention for researchers interested in biomarker development. Numerous studies have confirmed the potential of long noncoding RNAs (lncRNAs), transcripts with little or no coding information, as noninvasive tools for diagnosis, prognosis and prediction of the therapeutic response across a broad spectrum of ailments, including respiratory conditions. This article aims to provide a comprehensive overview of lncRNAs with specific emphasis on their role as biomarkers. We review current knowledge on the circulating lncRNAs as potential markers that can be used to enhance decision making in ARDS management. Additionally, we address the primary limitations and outline the steps that will be essential for integration of the use of lncRNAs in clinical laboratories. Our ultimate objective is to provide a framework for the implementation of lncRNAs in the management of ARDS.