Differential effects of mechanical ventilatory strategy on lung injury and systemic organ inflammation in mice

Hemodynamic effects of positive end-expiratory pressure

PURPOSE OF REVIEW

Positive end-expiratory pressure (PEEP) is required in the Berlin definition of acute respiratory distress syndrome and is a cornerstone of its treatment. Application of PEEP increases airway pressure and modifies pleural and transpulmonary pressures according to respiratory mechanics, resulting in blood volume alteration into the pulmonary circulation. This can in turn affect right ventricular preload, afterload and function. At the opposite, PEEP may improve left ventricular function, providing no deleterious effect occurs on the right ventricle.

RECENT FINDINGS

This review examines the impact of PEEP on cardiac function with regards to heart-lung interactions, and describes its consequences on organs perfusion and function, including the kidney, gut, liver and the brain. PEEP in itself is not beneficious nor detrimental on end-organ hemodynamics, but its hemodynamic effects vary according to both respiratory mechanics and association with other hemodynamic variables such as central venous or mean arterial pressure. There are parallels in the means of preventing deleterious impact of PEEP on the lungs, heart, kidney, liver and central nervous system.

SUMMARY

The quest for optimal PEEP settings has been a prominent goal in ARDS research for the last decades. Intensive care physician must maintain a high degree of vigilance towards hemodynamic effects of PEEP on cardiac function and end-organs circulation.

Interorgan communication networks in the kidney-lung axis

The homeostasis and health of an organism depend on the coordinated interaction of specialized organs, which is regulated by interorgan communication networks of circulating soluble molecules and neuronal connections. Many diseases that seemingly affect one primary organ are really multiorgan diseases, with substantial secondary remote organ complications that underlie a large part of their morbidity and mortality. Acute kidney injury (AKI) frequently occurs in critically ill patients with multiorgan failure and is associated with high mortality, particularly when it occurs together with respiratory failure. Inflammatory lung lesions in patients with kidney failure that could be distinguished from pulmonary oedema due to volume overload were first reported in the 1930s, but have been largely overlooked in clinical settings. A series of studies over the past two decades have elucidated acute and chronic kidney-lung and lung-kidney interorgan communication networks involving various circulating inflammatory cytokines and chemokines, metabolites, uraemic toxins, immune cells and neuro-immune pathways. Further investigations are warranted to understand these clinical entities of high morbidity and mortality, and to develop effective treatments.

The impact of acute kidney injury stages on the outcomes of veno-arterial extracorporeal membrane oxygenation

BACKGROUND

Although acute kidney injury (AKI) has been established as an independent risk factor for in-hospital mortality for patients on veno-arterial (V-A) extracorporeal membranous oxygenation (ECMO), the impact of Kidney Disease Improving Global Outcomes (KDIGO) stages of AKI has yet to be elucidated as a risk factor.

METHODS

We conducted a retrospective analysis of patient outcomes based on KDIGO stages of AKI at a single institution. The analysis was a cohort of 179 patients; 66 without AKI, 19 with stage 1 AKI, 18 with stage 2 AKI, and 76 with stage 3 AKI.

RESULTS

Every 1-year increase in age was associated with 4% increased odds of mortality at 30 days (95% confidence interval [CI] 1.01, 1.07; p = 0.004). The presence of AKI at any stage was associated with 59% increased odds of 30-day mortality (95% CI 0.81, 3.10; p = 0.176). The presence of stage 1 AKI was associated with a 5% decreased odds of 30-day mortality (95% CI 0.32, 2.89). The presence of stage 2 AKI (odds ratio [OR] 2.29, 95% CI 0.69, 7.55; p = 0.173) and stage 3 AKI (OR 1.68, 95% CI 0.81, 3.46; p = 0.164) was associated with increased odds of 30-day mortality.

CONCLUSION

Based on our single-center study, higher KDIGO stages of AKI likely have increased odds of mortality at 30 days. Larger studies are needed to confirm these findings.

Diesel exhaust PM2.5 greatly deteriorates fibrosis process in pre-existing pulmonary fibrosis via ferroptosis

Fine particulate matter (PM2.5) has been widely reported to contribute to the pathogenesis of pulmonary diseases. The direct hazardous effect of PM2.5 on the respiratory system at high concentrations in vitro and in vivo have been well identified. However, its effect on the pre-existing respiratory diseases of patients at environment-related concentrations remains unclear. Diesel exhaust PM2.5 as a primary representative of ambient PM2.5 fine particles were used to investigated the effect of PM2.5 on the fibrosis progression of existing pulmonary fibrosis disease models. This study reported that PM2.5 could result in the enhanced sensitivity to fibrotic response, which may be ascribed to ferroptosis induced by PM2.5 in damaged lung areas. Proteomic analysis revealed that the upregulation of HO-1 as a key mechanism in the ferroptosis and exacerbation of pulmonary fibrosis induced by PM2.5. As a result, HO-1 degraded heme-containing protein and released iron in fibrotic cells, leading to generation of mitochondrial ROS and impaired mitochondrial function. Transmission electron microscopic assay verified that PM2.5 entered the mitochondria of fibrotic cells and was accompanied by significant mitochondrial morphological changes characterized by increased mitochondrial membrane density and reduced mitochondrial size. The HO-1 inhibitor zinc protoporphyrin and mitochondrion-targeted antioxidant Mito-TEMPO significantly attenuated PM2.5-induced ferroptosis and exacerbation of fibrosis. In addition, AMPK-ULK1 axis-triggered autophagy activation and NCOA4-mediated degradation of ferritin by autophagy were found to be related to the PM2.5-induced ferroptosis of fibrotic cells. As evidenced by the inhibition of autophagy with 3-methyladenine or AMPK inhibitor, NCOA4 knockdown decreased intracellular iron accumulation and lipid peroxidation, thereby relieving PM2.5-induced epithelial-mesenchymal transition and cell death in fibrotic cells. Overall, this study provided experimental support for the idea that PM2.5 greatly deteriorates fibrosis process in pre-existing pulmonary fibrosis, and HO-1-mediated mitochondrial dysfunction and NCOA4-mediated ferritinophagy are jointly required for the PM2.5-induced ferroptosis and enhanced fibrosis effects.

Prenatal PM2.5 exposure contributes to neuronal tau lesion in male offspring mice through mitochondrial dysfunction-mediated insulin resistance

The epidemiological evidence has linked prenatal exposure to fine particulate matter (PM_2.5) pollution with neurological diseases in offspring. However, the biological process and toxicological mechanisms remain unclear. Tau protein is a neuronal microtubule-associated protein expressed in fetal brain and plays a critical role in mediating neuronal development. Aberrant expression of tau is associated with adverse neurodevelopmental outcomes. To study whether prenatal exposure to PM_2.5 pollution induce tau lesion in mice offspring and elucidate the underlying pathogenic mechanism, we exposed pregnant mice to PM_2.5 (3 mg/kg b.w.) by oropharyngeal aspiration every other day. The results indicate that prenatal PM_2.5 exposure induced hyperphosphorylation of tau in the cortex of postnatal male offspring, which was accompanied by insulin resistance through the IRS-1/PI3K/AKT signaling pathway. Importantly, we further found that prenatal PM_2.5 exposure induced mitochondrial dysfunction by disrupting mitochondrial ultrastructure and decreasing the expression of rate-limiting enzymes (CS, IDH2 and FH) in the Krebs cycle and the subunits of mitochondrial complex IV and V (CO1, CO4, ATP6, and ATP8) during postnatal neurodevelopment. The findings suggest that prenatal PM_2.5 exposure could induce tauopathy-like changes in male offspring, in which mitochondrial dysfunction-induced insulin resistance might play an important role.

When the Renal (Function) Begins to Fall: A Mini-Review of Acute Kidney Injury Related to Acute Respiratory Distress Syndrome in Critically Ill Patients

Acute kidney injury (AKI) is one of the most frequent causes of organ failure encountered in patients in the intensive care unit (ICU). Because of its predisposition to occur in the most critically ill patients, it is not surprising to observe a high frequency of AKI in patients with acute respiratory distress syndrome (ARDS). However, few studies have been carried out to assess the epidemiology of AKI in subgroups of ARDS patients using recommended KDIGO criteria. Moreover, the mechanisms involved in the physio-pathogenesis of AKI are still poorly understood, in particular the impact of mechanical ventilation on the kidneys. We carried out a review of the literature, focusing on the epidemiology and physiopathology of AKI in patients with ARDS admitted to the ICU. We addressed the importance of clinical management, focusing on mechanical ventilation for improving outcomes, on AKI. Finally, we also propose candidate treatment strategies and management perspectives. Our literature search showed that AKI is particularly common in ICU patients with ARDS. In association with the classic risk factors for AKI, such as comorbidities and iatrogeny, changes in mechanical ventilation parameters, which have been exclusively evaluated for their outcomes on respiratory function and death, must be considered carefully in terms of their impact on the short-term renal prognosis.

Physiological and Pathophysiological Consequences of Mechanical Ventilation

Mechanical ventilation is a life-support system used to ensure blood gas exchange and to assist the respiratory muscles in ventilating the lung during the acute phase of lung disease or following surgery. Positive-pressure mechanical ventilation differs considerably from normal physiologic breathing. This may lead to several negative physiological consequences, both on the lungs and on peripheral organs. First, hemodynamic changes can affect cardiovascular performance, cerebral perfusion pressure (CPP), and drainage of renal veins. Second, the negative effect of mechanical ventilation (compression stress) on the alveolar-capillary membrane and extracellular matrix may cause local and systemic inflammation, promoting lung and peripheral-organ injury. Third, intra-abdominal hypertension may further impair lung and peripheral-organ function during controlled and assisted ventilation. Mechanical ventilation should be optimized and personalized in each patient according to individual clinical needs. Multiple parameters must be adjusted appropriately to minimize ventilator-induced lung injury (VILI), including: inspiratory stress (the respiratory system inspiratory plateau pressure); dynamic strain (the ratio between tidal volume and the end-expiratory lung volume, or inspiratory capacity); static strain (the end-expiratory lung volume determined by positive end-expiratory pressure [PEEP]); driving pressure (the difference between the respiratory system inspiratory plateau pressure and PEEP); and mechanical power (the amount of mechanical energy imparted as a function of respiratory rate). More recently, patient self-inflicted lung injury (P-SILI) has been proposed as a potential mechanism promoting VILI. In the present chapter, we will discuss the physiological and pathophysiological consequences of mechanical ventilation and how to personalize mechanical ventilation parameters.

Outcome-Stratified Analysis of Biomarker Trajectories for Patients Infected With Severe Acute Respiratory Syndrome Coronavirus 2

Longitudinal trajectories of vital signs and biomarkers during admission remain poorly characterized for COVID-19 patients despite their potential to provide critical insights about disease progression. We studied 1884 patients with SARS-CoV2 infection from 3/4/2020-6/25/2020 within one Maryland hospital system and used a retrospective longitudinal framework with linear mixed-effects models to investigate relevant biomarker trajectories leading up to three critical outcomes: mechanical ventilation, discharge, and death. Trajectories of four vital signs (respiratory rate, SpO₂/FiO₂, pulse, and temperature) and four lab values (C-reactive protein (CRP), absolute lymphocyte count (ALC), estimated glomerular filtration rate (eGFR), and D-dimer) clearly distinguished the trajectories of COVID-19 patients. Prior to any ventilation, log-CRP, log-ALC, respiratory rate, and SpO₂/FiO₂ trajectories diverge approximately 8-10 days before discharge or death. Following ventilation, log-CRP, log-ALC, respiratory rate, SpO₂/FiO₂, and eGFR trajectories again diverge 10-20 days prior to death or discharge. Trajectories improved until discharge and remained unchanged or worsened until death. Our approach characterizes the distribution of biomarker trajectories leading up to competing outcomes of discharge versus death. Moving forward, this model can contribute to quantifying the joint probability of future biomarkers and outcomes provided clinical data up to a given moment.

Acute kidney injury in ECMO patients

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2021. Other selected articles can be found online at  https://www.biomedcentral.com/collections/annualupdate2021 . Further information about the Annual Update in Intensive Care and Emergency Medicine is available from  https://link.springer.com/bookseries/8901 .

D-Limonene Is a Potential Monoterpene to Inhibit PI3K/Akt/IKK-α/NF-κB p65 Signaling Pathway in Coronavirus Disease 2019 Pulmonary Fibrosis

At the time of the prevalence of coronavirus disease 2019 (COVID-19), pulmonary fibrosis (PF) related to COVID-19 has become the main sequela. However, the mechanism of PF related to COVID (COVID-PF) is unknown. This study aimed to explore the key targets in the development of COVID-PF and the mechanism of d-limonene in the COVID-PF treatment. The differentially expressed genes of COVID-PF were downloaded from the GeneCards database, and their pathways were analyzed. d-Limonene was molecularly docked with related proteins to screen its pharmacological targets, and a rat lung fibrosis model was established to verify d-limonene's effect on COVID-PF-related targets. The results showed that the imbalance between collagen breakdown and metabolism, inflammatory response, and angiogenesis are the core processes of COVID-PF; and PI3K/AKT signaling pathways are the key targets of the treatment of COVID-PF. The ability of d-limonene to protect against PF induced by bleomycin in rats was reported. The mechanism is related to the binding of PI3K and NF-κB p65, and the inhibition of PI3K/Akt/IKK-α/NF-κB p65 signaling pathway expression and phosphorylation. These results confirmed the relationship between the PI3K–Akt signaling pathway and COVID-PF, showing that d-limonene has a potential therapeutic value for COVID-PF.

Focus on renal blood flow in mechanically ventilated patients with SARS-CoV-2: a prospective pilot study

Mechanically ventilated patients with ARDS due to the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) seem particularly susceptible to AKI. Our hypothesis was that the renal blood flow could be more compromised in SARS-CoV-2 patients than in patients with “classical” ARDS. We compared the renal resistivity index (RRI) and the renal venous flow (RVF) in ARDS patients with SARS-CoV-2 and in ARDS patients due to other etiologies. Prospective, observational pilot study performed on 30 mechanically ventilated patients (15 with SARS-COV-2 ARDS and 15 with ARDS). Mechanical ventilation settings included constant-flow controlled ventilation, a tidal volume of 6 ml/kg of ideal body weight and the PEEP level titrated to the lowest driving pressure. Ultrasound Doppler measurements of RRI and RVF pattern were performed in each patient. Patients with SARS-COV-2 ARDS had higher RRI than patients with ARDS (0.71[0.67–0.78] vs 0.64[0.60–0.74], p = 0.04). RVF was not-continuous in 9/15 patients (71%) in the SARS-COV-2 ARDS group and in and 5/15 (33%) in the ARDS group (p = 0.27). A linear correlation was found between PEEP and RRI in patients with SARS-COV-2 ARDS (r² = 0.31; p = 0.03) but not in patients with ARDS. Occurrence of AKI was 53% in patients with SARS-COV-2 ARDS and 33% in patients with ARDS (p = 0.46). We found a more pronounced impairment in renal blood flow in mechanically ventilated patients with SARS-COV-2 ARDS, compared with patients with “classical” ARDS.

A Potential Bioelectromagnetic Method to Slow Down the Progression and Prevent the Development of Ultimate Pulmonary Fibrosis by COVID-19

Introduction

Right now, we are facing a global pandemic caused by the coronavirus SARS-CoV-2 that causes the highly contagious human disease COVID-19. The number of COVID-19 cases is increasing at an alarming rate, more and more people suffer from it, and the death toll is on the rise since December 2019, when COVID-19 has presumably appeared. We need an urgent solution for the prevention, treatment, and recovery of the involved patients.

Methods

Modulated electro-hyperthermia (mEHT) is known as an immuno-supportive therapy in oncology. Our proposal is to apply this method to prevent the progression of the disease after its identification, to provide treatment when necessary, and deliver rehabilitation to diminish the fibrotic-often fatal-consequences of the infection.

Hypothesis

The effects of mEHT, which are proven for oncological applications, could be utilized for the inactivation of the virus or for treating the fibrotic consequences. The hypothesized mEHT effects, which could have a role in the antiviral treatment, it could be applied for viral-specific immune-activation and for anti-fibrotic treatments.

Prophylactic administration of carnosine and melatonin abates the incidence of apoptosis, inflammation, and DNA damage induced by titanium dioxide nanoparticles in rat livers

Although titanium dioxide nanoparticles (TDO-ns) are extensively used in the food, medicine, and cosmetic industries, discussions about the possible hazards of nanomaterials are just beginning to emerge. This study aimed to detect the inflammatory stress, oxidative stress, and apoptotic cell death induced in the livers of rats exposed to TDO-ns (600 mg/kg, particle size ≤ 100 nm). Furthermore, the modulation of these toxic effects by two potent naturally occurring antioxidants, carnosine (Carno) or melatonin (Melato), was evaluated. The co-administration of carnosine or melatonin to rats intoxicated with TDO-ns significantly attenuated the increases in serum tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), C-reactive protein (CRP), immunoglobulin G (IgG), vascular endothelial growth factor (VEGF), nitric oxide (NO), and alanine aminotransferase (ALT) levels. The two agents markedly ameliorated hepatic DNA damage and the alterations in hepatic malondialdehyde (MDA), glutathione (GSH), cytochrome P450, caspase-3, total phospholipid, phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, sphingomyelin, and triglyceride (TG) levels. These results support the use of Carno or Melato as prophylactic agents against TDO-ns-induced liver damage.

Incidence, Risk Factors, and Prognostic Implications of Acute Kidney Injury in Patients with Acute Exacerbation of COPD

Purpose

Little is known about the incidence, risk factors, and prognostic implications of acute kidney injury (AKI) in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD) in China. In this study, we investigated the incidence, risk factors, and short-term outcomes of AKI in these patients.

Patients and Methods

We analyzed the records of 1768 patients admitted to Nanjing First Hospital with a principal diagnosis of AECOPD. Of these, 377 patients had AKI.

Results

AKI occurred in 377 patients (21%). Independent risk factors for AKI in patients with AECOPD were advanced age, coronary artery disease, anemia, cancer, chronic kidney disease, hypercapnic encephalopathy, acute respiratory failure, and mechanical ventilation. Patients with AKI had worse prognostic implications and were more likely to require mechanical ventilation (38.7% vs 19.1%, P<0.001); non-invasive mechanical ventilation (38.2% vs 18.9%, P<0.001); invasive mechanical ventilation (18.3% vs 3.1%, P<0.001); intensive care unit (ICU) admission (33.7% vs 12.9%, P<0.001); had a longer ICU stay (9 days vs 8 days, P=0.033) and longer hospitalization (13 days vs 10 days, P<0.001); and higher in-hospital mortality (18.0% vs 2.7%, P<0.001) than those without AKI. Multivariable analysis indicated that compared to patients without AKI, those with stage 1, 2, or 3 AKI had a 1.9-fold, 2.1-fold, or 6.0-fold increased risk of in-hospital death, respectively.

Conclusion

AKI is common in patients with AECOPD requiring hospitalization. Patients with AKI have worse short-term outcomes. Thus, AKI may be a prognostic predictor of patient survival.

Sex difference in bronchopulmonary dysplasia of offspring in response to maternal PM2.5 exposure

The adverse effects of fine particulate matters (PM_2.5) on respiratory diseases start in utero. In order to investigate whether maternal PM_2.5 exposure could lead to bronchopulmonary dysplasia (BPD) in offspring, PM_2.5 was collected in Taiyuan, Shanxi, China during the annual heating period. Mice were mated and gestation day 0 (GD0) was considered the day on which a vaginal plug was observed. The plug-positive mice received 3 mg/kg b.w. PM_2.5 by oropharyngeal aspiration every other day starting on GD0 and throughout the gestation period. Offspring were sacrificed at postnatal days (PNDs) 1, 7, 14 and 21. We assessed some typical BPD-like symptoms in offspring. The results showed that maternal PM_2.5 exposure caused low birth weight, hypoalveolarization, decreased angiogenesis, suppressed production of secretory and surfactant proteins, and increased inflammation in the lungs of male offspring. However, maternal PM_2.5 exposure induced only hypoalveolarization and inflammation in the lungs of female offspring. Furthermore, these alterations were reversed during postnatal development. Our results demonstrated that maternal exposure to PM_2.5 caused reversible BPD-related consequences in offspring, and male offspring were more sensitive than females. However, these alterations were reversed during postnatal development.

Risk factors and outcomes of acute kidney injury in ventilated newborns

Purpose: This study aimed to investigate the occurrence and risk factors of acute kidney injury (AKI) in ventilated newborns.

Methods: In total, 139 newborns receiving mechanical ventilation (MV) were reviewed in this retrospective study. The demographic and clinical data were collected. Then, the independent risk factors for AKI were evaluated using univariate and multivariate logistic regression analyses.

Results: The incidence rate of AKI was 15.11% (21/139) in ventilated newborns. Univariate analysis showed significant differences in gestational age, birth weight, Apagar scores, the highest oxygen concentration, serum creatinine levels at admission and 48 h after MV, history of asphyxia, urine output at 48 h after MV, invasive MV, noninvasive MV, and outcomes between AKI and non-AKI groups (all p < .05). The lower gestational age (odd ratio (OR): 1.194, 95% confidence interval (CI): 1.013–1.407, p = .035), the increased use of invasive mechanical ventilation (IMV) (OR: 4.790, 95% CI: 1.115–20.575, p = .035), and lower birth weight (OR: 0.377, 95% CI: 0.178–0.801, p = .011) were independent risk factors for the occurrence of AKI. Additionally, higher stage of AKI was significantly associated with poor prognosis of AKI (p = .018).

Conclusion: In this retrospective study, it was found that lower gestational age, birth weight, and increased use of IMV were independent risk factors for AKI in ventilated newborns. The poor prognosis might be indicated by the higher AKI stage.

Can melatonin reduce the severity of COVID-19 pandemic?

The current COVID-19 pandemic is one of the most devastating events in recent history. The virus causes relatively minor damage to young, healthy populations, imposing life-threatening danger to the elderly and people with diseases of chronic inflammation. Therefore, if we could reduce the risk for vulnerable populations, it would make the COVID-19 pandemic more similar to other typical outbreaks. Children don't suffer from COVID-19 as much as their grandparents and have a much higher melatonin level. Bats are nocturnal animals possessing high levels of melatonin, which may contribute to their high anti-viral resistance. Viruses induce an explosion of inflammatory cytokines and reactive oxygen species, and melatonin is the best natural antioxidant that is lost with age. The programmed cell death coronaviruses cause, which can result in significant lung damage, is also inhibited by melatonin. Coronavirus causes inflammation in the lungs which requires inflammasome activity. Melatonin blocks these inflammasomes. General immunity is impaired by anxiety and sleep deprivation. Melatonin improves sleep habits, reduces anxiety and stimulates immunity. Fibrosis may be the most dangerous complication after COVID-19. Melatonin is known to prevent fibrosis. Mechanical ventilation may be necessary but yet imposes risks due to oxidative stress, which can be reduced by melatonin. Thus, by using the safe over-the-counter drug melatonin, we may be immediately able to prevent the development of severe disease symptoms in coronavirus patients, reduce the severity of their symptoms, and/or reduce the immuno-pathology of coronavirus infection on patients' health after the active phase of the infection is over.

Effects of lung protective ventilation on postoperative pulmonary outcomes for prolonged oral cancer combined with free flap surgery

The intraoperative lung protective ventilation with low tidal volume, positive end expiratory pressure (PEEP) and intermittent lungs recruitment was found to decrease postoperative pulmonary complications. In this retrospective medical records study, we investigated the effects of lung protective ventilation on postoperative pulmonary outcomes among the patients received prolonged oral cancer combined with free flap surgery.We collected the medical records of the patients received oral cancer surgery with the operation time more than 12 hours from January 2011 to December 2015. We recordedFifty nine cases were included. Thirty cases received the lung protective ventilation and 29 cases received conventional ventilation. Compared to the patients received conventional ventilation, the patients received intraoperative lung protective ventilation showedIn conclusion, for the prolonged oral cancer combined with free flap surgery, the intraoperative lung protective ventilation improves postoperative pulmonary outcomes and decreases the duration of ICU stay.

Relation between Respiratory Mechanics, Inflammation, and Survival in Experimental Mechanical Ventilation

Low-tidal volume (Vt) ventilation might protect healthy lungs from volutrauma but lead to inflammation resulting from other mechanisms, namely alveolar derecruitment and the ensuing alveolar collapse and tidal reexpansion. We hypothesized that the different mechanisms of low- and high-volume injury would be reflected in different mechanical properties being associated with development of pulmonary inflammation and mortality: an increase of hysteresis, reflecting progressive alveolar derecruitment, at low Vt; an increase of elastance, as a result of overdistension, at higher Vt. Mice were allocated to "protective" (6 ml/kg) or "injurious" (15-20 ml/kg) Vt groups and ventilated for 16 hours or until death. We measured elastance and hysteresis; pulmonary IL-6, IL-1β, and MIP-2 (macrophage inflammatory protein 2); wet-to-dry ratio; and blood gases. Survival was greater in the protective group (60%) than in the injurious group (25%). Nonsurvivors showed increased pulmonary cytokines, particularly in the injurious group, with the increase of elastance reflecting IL-6 concentration. Survivors instead showed only modest increases of cytokines, independent of Vt and unrelated to the increase of elastance. No single lung strain threshold could discriminate survivors from nonsurvivors. Hysteresis increased faster in the protective group, but, contrary to our hypothesis, its change was inversely related to the concentration of cytokines. In this model, significant mortality associated with pulmonary inflammation occurred even for strain values as low as about 0.8. Low Vt improved survival. The accompanying increase of hysteresis was not associated with greater inflammation.

Lung-kidney interactions in critically ill patients: consensus report of the Acute Disease Quality Initiative (ADQI) 21 Workgroup

BACKGROUND

Multi-organ dysfunction in critical illness is common and frequently involves the lungs and kidneys, often requiring organ support such as invasive mechanical ventilation (IMV), renal replacement therapy (RRT) and/or extracorporeal membrane oxygenation (ECMO).

METHODS

A consensus conference on the spectrum of lung-kidney interactions in critical illness was held under the auspices of the Acute Disease Quality Initiative (ADQI) in Innsbruck, Austria, in June 2018. Through review and critical appraisal of the available evidence, the current state of research, and both clinical and research recommendations were described on the following topics: epidemiology, pathophysiology and strategies to mitigate pulmonary dysfunction among patients with acute kidney injury and/or kidney dysfunction among patients with acute respiratory failure/acute respiratory distress syndrome. Furthermore, emphasis was put on patients receiving organ support (RRT, IMV and/or ECMO) and its impact on lung and kidney function.

CONCLUSION

The ADQI 21 conference found significant knowledge gaps about organ crosstalk between lung and kidney and its relevance for critically ill patients. Lung protective ventilation, conservative fluid management and early recognition and treatment of pulmonary infections were the only clinical recommendations with higher quality of evidence. Recommendations for research were formulated, targeting lung-kidney interactions to improve care processes and outcomes in critical illness.

The Importance of Tyrosine Phosphorylation Control of Cellular Signaling Pathways in Respiratory Disease: pY and pY Not

Reversible phosphorylation of proteins on tyrosine residues is an essential signaling mechanism by which diverse cellular processes are closely regulated. The tight temporal and spatial control of the tyrosine phosphorylation status of proteins by protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs) is critical to cellular homeostasis as well as to adaptations to the external environment. Via regulation of cellular signaling cascades involving other protein kinases and phosphatases, receptors, adaptor proteins, and transcription factors, PTKs and PTPs closely control diverse cellular processes such as proliferation, differentiation, migration, inflammation, and maintenance of cellular barrier function. Given these key regulatory roles, it is not surprising that dysfunction of PTKs and PTPs is important in the pathogenesis of human disease, including many pulmonary diseases. The roles of various PTKs and PTPs in acute lung injury and repair, pulmonary fibrosis, pulmonary vascular disease, and inflammatory airway disease are discussed in this review. It is important to note that although there is overlap among many of these proteins in various disease states, the mechanisms by which they influence the pathogenesis of these conditions differ, suggesting wide-ranging roles for these enzymes and their potential as therapeutic targets.

Mechanosensing and Mechanoregulation of Endothelial Cell Functions

Vascular endothelial cells (ECs) form a semiselective barrier for macromolecules and cell elements regulated by dynamic interactions between cytoskeletal elements and cell adhesion complexes. ECs also participate in many other vital processes including innate immune reactions, vascular repair, secretion, and metabolism of bioactive molecules. Moreover, vascular ECs represent a unique cell type exposed to continuous, time-dependent mechanical forces: different patterns of shear stress imposed by blood flow in macrovasculature and by rolling blood cells in the microvasculature; circumferential cyclic stretch experienced by the arterial vascular bed caused by heart propulsions; mechanical stretch of lung microvascular endothelium at different magnitudes due to spontaneous respiration or mechanical ventilation in critically ill patients. Accumulating evidence suggests that vascular ECs contain mechanosensory complexes, which rapidly react to changes in mechanical loading, process the signal, and develop context-specific adaptive responses to rebalance the cell homeostatic state. The significance of the interactions between specific mechanical forces in the EC microenvironment together with circulating bioactive molecules in the progression and resolution of vascular pathologies including vascular injury, atherosclerosis, pulmonary edema, and acute respiratory distress syndrome has been only recently recognized. This review will summarize the current understanding of EC mechanosensory mechanisms, modulation of EC responses to humoral factors by surrounding mechanical forces (particularly the cyclic stretch), and discuss recent findings of magnitude-specific regulation of EC functions by transcriptional, posttranscriptional and epigenetic mechanisms using -omics approaches. We also discuss ongoing challenges and future opportunities in developing new therapies targeting dysregulated mechanosensing mechanisms to treat vascular diseases. © 2019 American Physiological Society. Compr Physiol 9:873-904, 2019.

Quercetin and Idebenone Ameliorate Oxidative Stress, Inflammation, DNA damage, and Apoptosis Induced by Titanium Dioxide Nanoparticles in Rat Liver

Titanium dioxide nanoparticles (TiO₂-NPs) are extensively used in a wide range of applications; however, many reports have investigated their nanotoxicological effect at the molecular level either in vitro or in vivo systems. The defensive roles of quercetin (Qur) or idebenone (Id) against the hepatotoxicity induced by TiO₂-NPs were evaluated in the current study. The results showed that the coadministration of Qur or Id to rats intoxicated with TiO₂-NPs markedly ameliorated the elevation in hepatic malondialdehyde (MDA), serum alanine amino-transferase (ALT), glucose, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), immunoglobin G (IgG), and C-reactive protein (CRP) levels compared to their levels in TiO₂-NPs-treated rats. The aforementioned antioxidants also effectively modulated the changes in the levels of serum vascular endothelial growth factor (VEGF), nitric oxide (NO), hepatic DNA breakage, caspase-3, and inhibition of drug metabolizing enzymes (cytochrome P450s; CYP4502E12E1) in rat livers induced by TiO₂-NPs toxicity. The histopathological examination of the liver section showed that TiO₂-NPs caused severe degeneration of most hepatocytes with an increase in collagen in the portal region, while treatment with the antioxidants in question improved liver architecture. These outcomes supported the use of Qur and Id as protective agents against the hepatotoxicity induced by TiO₂-NPs and other hepatotoxic drugs.

Community-acquired versus hospital-acquired acute kidney injury in patients with acute exacerbation of COPD requiring hospitalization in China

Purpose

Previous studies have described the incidence, risk factors, and outcomes for patients with acute exacerbations of COPD (AECOPD) developing acute kidney injury (AKI). However, little is known about the differences between community-acquired AKI (CA-AKI) and hospital-acquired AKI (HA-AKI) in patients with AECOPD. Thus, in this study, we compared prevalence, risk factors, and outcomes for these patients with CA-AKI and HA-AKI.

Patients and methods

This study was conducted from January 2014 to January 2017, and data from adult inpatients with AECOPD were analyzed retrospectively. A total of 1,768 patients were included, 280 patients were identified with CA-AKI and 97 patients were with HA-AKI.

Results

Prevalence of CA-AKI was 15.8% and that of HA-AKI was 5.5%, giving an overall AKI prevalence of 21.3%. Patients with CA-AKI had a higher prevalence of chronic kidney disease (CKD) and lower prevalence of chronic cor pulmonale than patients with HA-AKI. Risk factors for developing HA-AKI and CA-AKI were similar, such as being elderly, requirement for mechanical ventilation, and a history of coronary artery disease and CKD. Patients with HA-AKI were more likely to have stage 3 AKI and worse short-term outcomes. In comparison with patients with CA-AKI, those with HA-AKI were more likely to require non-invasive mechanical ventilation (31.3% versus 16.8%; P = 0.003) and had a longer duration of mechanical ventilation (11 days versus 8 days; P = 0.020), longer hospitalization (14 days versus 12 days; P = 0.038), and higher inpatient mortality (32.0% versus 13.2%; P < 0.001). Patients with HA-AKI had worse (multivariate-adjusted) inpatient survival than those with CA-AKI (hazard ratio, 1.7 [95% confidence interval, 1.03-2.81; P = 0.038] for the HA-AKI group).

Conclusion

AKI was common in patients with AECOPD requiring hospitalization. CA-AKI was more common than HA-AKI but otherwise demonstrated similar demographics and risk factors. Nevertheless, patients with HA-AKI had worse short-term outcomes.

Ambient fine particulate matter exposure induces reversible cardiac dysfunction and fibrosis in juvenile and older female mice

BACKGROUND

Cardiovascular disease is the leading cause of mortality in the advanced world, and age is an important determinant of cardiac function. The purpose of the study is to determine whether the PM2.5-induced cardiac dysfunction is age-dependent and whether the adverse effects can be restored after PM2.5 exposure withdrawal.

METHODS

Female C57BL/6 mice at different ages (4-week-old, 4-month-old, and 10-month-old) received oropharyngeal aspiration of 3 mg/kg b.w. PM2.5 every other day for 4 weeks. Then, 10-month-old and 4-week-old mice were exposed to PM2.5 for 4 weeks and withdrawal PM2.5 1 or 2 weeks. Heart rate and systolic blood pressure were measured using a tail-cuff system. Cardiac function was assessed by echocardiography. Left ventricles were processed for histology to assess myocardial fibrosis. ROS generation was detected by photocatalysis using 2',7'-dichlorodihydrofluorescein diacetate (DCFHDA). The expression of cardiac fibrosis markers (Col1a1, Col3a1) and possible signaling molecules, including NADPH oxidase 4 (NOX-4), transforming growth factor β1 (TGFβ1), and Smad3, were detected by qPCR and/ or Western blot.

RESULTS

PM2.5 exposure induced cardiac diastolic dysfunction of mice, elevated the heart rate and blood pressure, developed cardiac systolic dysfunction of 10-month-old mice, and caused fibrosis in both 4-week-old and 10-month-old mice. PM2.5 exposure increased the expression of Col1a1, Col3a1, NOX-4, and TGFβ1, activated Smad3, and generated more reactive oxygen species in the myocardium of 4-week-old and 10-month-old mice. The withdrawal from PM2.5 exposure restored blood pressure, heart rate, cardiac function, expression of collagens, and malonaldehyde (MDA) levels in hearts of both 10-month-old and 4-week-old mice.

CONCLUSION

Juvenile and older mice are more sensitive to PM2.5 than adults and suffer from cardiac dysfunction. PM2.5 exposure reversibly elevated heart rate and blood pressure, induced cardiac systolic dysfunction of older mice, and reversibly induced fibrosis in juvenile and older mice. The mechanism by which PM2.5 exposure resulted in cardiac lesions might involve oxidative stress, NADPH oxidase, TGFβ1, and Smad-dependent pathways.

Prophylactic administration of carnosine and melatonin abates the incidence of renal toxicity induced by an over dose of titanium dioxide nanoparticles

The alleviative effects of two antioxidants, carnosine (Car) and melatonin (Mel), against titanium dioxide nanoparticles (TiO₂ -NPs) toxicity-induced oxidative and inflammatory renal damage were examined in rats. Administration of these antioxidants along with TiO₂ -NPs effectively reduced serum urea, uric acid, creatinine, glucose, tumor necrosis factor-α, interleukin-6, C-reactive protein, immunoglobulin G, vascular endothelial growth factor, and nitric oxide, as well as a significant amelioration of the decrease in glutathione levels in renal tissue was observed, compared to those in rats treated with TiO₂ -NPs alone. The renoprotective properties of the antioxidants were confirmed by reduced intensity of renal damage as demonstrated by histological findings. In conclusion, Car and Mel play protective roles against TiO₂ -NPs-induced renal inflammation and oxidative injury, likely due to their antioxidant and anti-inflammatory properties.

The effect of an intraoperative, lung-protective ventilation strategy in neurosurgical patients undergoing craniotomy: study protocol for a randomized controlled trial

BACKGROUND

Ventilator-induced lung injury is a major cause of postoperative pulmonary complications (PPCs) in patients undergoing neurosurgery after general anesthesia. However, there is no study on the effect of a lung-protective ventilation strategy in patients undergoing neurosurgery.

METHODS

This is a single-center, randomized, parallel-group controlled trial which will be carried out at Beijing Tiantan Hospital, Capital Medical University. Three hundred and thirty-four patients undergoing intracranial tumor surgery will be randomly allocated to the control group and the protective-ventilation strategy group. In the control group, tidal volume (VT) will be set at 10-12 ml/kg of predicted body weight but PEEP and recruitment maneuvers will not be used. In the protective group, VT will be set at 6-8 ml/kg of predicted body weight, PEEP at 6-8 cmH₂O, and a recruitment maneuver will be used intermittently. The primary outcome is pulmonary complications within 7 days postoperatively. Secondary outcomes include intraoperative brain relaxation, the postoperative complications within 30 days and the cost analysis.

DISCUSSION

This study aims to determine if the protective, pulmonary-ventilation strategy decreases the incidence of PPCs in patients undergoing neurosurgical anesthesia. If our results are positive, the study will indicate whether the protective, pulmonary-ventilation strategy is efficiently and safely used in neurosurgical patients undergoing the craniotomy.

TRIAL REGISTRATION

ClinicalTrials.gov, ID: NCT02386683 . Registered on 18 October 2014.

PM2.5-bound metal metabolic distribution and coupled lipid abnormality at different developmental windows

Atmospheric fine particulate matter (PM_2.5) is a serious threat to human health. As a toxicant constituent, metal leads to significant health risks in a population, but exposure to PM_2.5-bound metals and their biological impacts are not fully understood. In this study, we determined the metal contents of PM_2.5 samples collected from a typical coal-burning city and then investigated the metabolic distributions of six metals (Zn, Pb, Mn, As, Cu, and Cd) following PM_2.5 inhalation in mice in different developmental windows. The results indicate that fine particles were mainly deposited in the lung, but PM_2.5-bound metals could reach and gather in secondary off-target tissues (the lung, liver, heart and brain) with a developmental window-dependent property. Furthermore, elevations in triglycerides and cholesterol levels in sensitive developmental windows (the young and elderly stages) occurred, and significant associations between metals (Pb, Mn, As and Cd) and cholesterol in the heart, brain, liver and lung were observed. These findings suggest that PM_2.5 inhalation caused selective metal metabolic distribution in tissues with a developmental window-dependent property and that the effects were associated with lipid alterations. This provides a foundation for the underlying systemic toxicity following PM_2.5 exposure based on metal components.

Spontaneously Breathing Extracorporeal Membrane Oxygenation Support Provides the Optimal Bridge to Lung Transplantation

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is being increasingly used as a bridge to lung transplantation. Small, single-institution series have described increased success using ECMO in spontaneously breathing patients compared with patients on ECMO with mechanical ventilation, but this strategy has not been evaluated on a large scale.

METHODS

Using the United Network for Organ Sharing database, all adult patients undergoing isolated lung transplantation from May 2005 through September 2013 were identified. Patients were categorized by their type of pretransplant support: no support, ECMO only, invasive mechanical ventilation (iMV) only, and ECMO + iMV. Kaplan-Meier survival analysis with log-rank testing was performed to compare survival based on type of preoperative support. A Cox regression model was used to determine whether type of preoperative support was independently associated with survival, using previously established predictors of survival as covariates.

RESULTS

Approximately 12,403 primary adult pulmonary transplantations were included in this analysis. Sixty-five patients (0.52%) were on ECMO only, 612 (4.93%) required only iMV, 119 (0.96%) were on ECMO + iMV, and the remaining 11,607 (94.6%) required no invasive support before transplantation. One-year survival was decreased in all patients requiring support, regardless of type. However, mid-term survival was similar between patients on ECMO alone and those not on support but significantly worse with patients requiring iMV only or ECMO + iMV. In multivariable analysis, ECMO + iMV and iMV alone were independently associated with decreased survival compared with nonsupport patients, whereas ECMO alone was not significant.

CONCLUSIONS

In patients with worsening pulmonary disease awaiting lung transplantation, those supported via ECMO with spontaneous breathing demonstrated improved survival compared with other bridging strategies.

Partial extracorporeal carbon dioxide removal using a standard continuous renal replacement therapy device: a preliminary study

To test the feasibility, safety, and efficacy of partial extracorporeal CO2 removal (PECCO2R) using a standard continuous renal replacement (CRRT) device with a pediatric oxygenation membrane introduced into the circuit in a serial manner. In this retrospective single-center study, we have studied mechanically ventilated patients with persistent significant respiratory acidosis and acute renal failure requiring ongoing CRRT. Sixteen patients were treated with our PECCO2R device. PaCO2 and arterial pH were measured before as well as at 6 and 12 hours after PECCO2R implementation. Hemodynamic parameters were continuously monitored. Our PECCO2R system was efficient to significantly reduce PaCO2 and increase arterial pH. The median PaCO2 before treatment was 77 mm Hg (59-112) with a median reduction of 24 mm Hg after 6 hours and 30 mm Hg after 12 hours (31% and 39%, respectively). The median pH increase was 0.16 at 6 hours and 0.23 at 12 hours. Partial extracorporeal CO2 removal treatment had no effect on oxygenation. No complication was observed. Our PECCO2R approach based on the simple introduction of a pediatric extracorporeal membrane oxygenation membrane into the circuit of a standard CRRT device is easy to implement, safe, and efficient to improve respiratory acidosis.

Kidney-Organ Interaction

The practice of critical care nephrology demands an intimate understanding of the interactions and “crosstalk” that occurs between the kidney and multiple organ systems, in particular the heart, lung, gut, and brain. Accumulating evidence suggests that acute injury and dysfunction to the kidney can incite and propagate cardiac, pulmonary, gastrointestinal, and neurologic injury and dysfunction through a host of mechanisms.

Injurious mechanical ventilation causes kidney apoptosis and dysfunction during sepsis but not after intra-tracheal acid instillation: an experimental study

Background

Intratracheal aspiration and sepsis are leading causes of acute lung injury that frequently necessitate mechanical ventilation (MV), which may aggravate lung injury thereby potentially increasing the risk of acute kidney injury (AKI). We compared the effects of ventilation strategies and underlying conditions on the development of AKI.

Methods

Spraque Dawley rats were challenged by intratracheal acid instillation or 24 h of abdominal sepsis, followed by MV with a low tidal volume (LV_T) and 5 cm H₂O positive end-expiratory pressure (PEEP) or a high tidal volume (HV_T) and no PEEP, which is known to cause more lung injury after acid instillation than in sepsis. Rats were ventilated for 4 hrs and kidney function and plasma mediator levels were measured. Kidney injury was assessed by microscopy; apoptosis was quantified by TUNEL staining.

Results

During sepsis, but not after acid instillation, MV with HV_T caused more renal apoptosis than MV with LV_T. Increased plasma active plasminogen activator inhibitor-1 correlated to kidney apoptosis in the cortex and medulla. Increased apoptosis after HV_T ventilation during sepsis was associated with a 40% decrease in creatinine clearance.

Conclusions

AKI is more likely to develop after MV induced lung injury during an indirect (as in sepsis) than after a direct (as after intra-tracheal instillation) insult to the lungs, since it induces kidney apoptosis during sepsis but not after acid instillation, opposite to the lung injury it caused. Our findings thus suggest using protective ventilatory strategies in human sepsis, even in the absence of overt lung injury, to protect the kidney.

Effect of protective ventilation on postoperative pulmonary complications in patients undergoing general anaesthesia: a meta-analysis of randomised controlled trials

OBJECTIVE

To determine whether anaesthetised patients undergoing surgery could benefit from intraoperative protective ventilation strategies.

METHODS

MEDLINE, EMBASE and Cochrane Central Register of Controlled Trials (CENTRAL) were searched up to February 2014. Eligible studies evaluated protective ventilation versus conventional ventilation in anaesthetised patients without lung injury at the onset of mechanical ventilation. The primary outcome was the incidence of postoperative pulmonary complications. Included studies must report at least one of the following end points: the incidence of atelectasis or acute lung injury or pulmonary infections.

RESULTS

Four studies (594 patients) were included. Meta-analysis using a random effects model showed a significant decrease in the incidence of atelectasis (OR=0.36; 95% CI 0.22 to 0.60; p<0.0001; I(2)=0%) and pulmonary infections (OR=0.30; 95% CI 0.14 to 0.68; p=0.004; I(2)=20%) in patients receiving protective ventilation. Ventilation with protective strategies did not reduce the incidence of acute lung injury (OR=0.40; 95% CI 0.07 to 2.15; p=0.28; I(2)=12%), all-cause mortality (OR=0.77; 95% CI 0.33 to 1.79; p=0.54; I(2)=0%), length of hospital stay (weighted mean difference (WMD)=-0.52 day, 95% CI -4.53 to 3.48 day; p=0.80; I(2)=63%) or length of intensive care unit stay (WMD=-0.55 day, 95% CI -2.19 to 1.09 day; p=0.51; I(2)=39%).

CONCLUSIONS

Intraoperative use of protective ventilation strategies has the potential to reduce the incidence of postoperative pulmonary complications in patients undergoing general anaesthesia. Prospective, well-designed clinical trials are warranted to confirm the beneficial effects of protective ventilation strategies in surgical patients.

Potential impact of quercetin and idebenone against immuno- inflammatory and oxidative renal damage induced in rats by titanium dioxide nanoparticles toxicity

The aim of this study was to investigate the toxic impacts of titanium dioxide nanoparticles (TiO₂-NPs) on rat kidneys and the possible prophylactic role of either quercetin or idebenone. TiO₂-NPs were administered orally at either 600 mg or 1 g/kg body weight for 5 consecutive days to evaluate dose-dependent toxicity referred to the OECD guidelines for testing of chemicals. The results showed that administration of either low or high repeated doses of TiO₂-NPs to rats significantly increases serum kideney function biomarkers (urea, creatinine and uric acid) as well as increases in serum glucose and serum immuno- inflammatory biomarkers including tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), C-reactive protein (CRP), immunoglobin g (IGg), vascular endothelial growth factor (VEGF, angiogenic factor) and nitric oxide (NO) with a concomitant decrease in renal GSH content versus normal control values. The increase in these biomarkers was more evident in rats intoxicated with high TiO₂-NPs repeated doses. Oral co- administration of either quercetin or idebenone (each 200mg/Kg body weight) daily for three weeks to rats intoxicated by either of the two doses markedly ameliorated TiO₂-NPs induced alteration in the above biomarkers. The prophylactic impacts of both agents on biochemical markers were more pronounced in rats received low TiO₂-NPs repeated doses. The biochemical investigation was supported by histological examination. In conclusion, The data showed the severity in renotoxicity of TiO₂-NPs was dose-dependent and the protective effect of quercetin and idebenone may be related to their antioxidant and anti-inflammatory properties.

The effects of exogenous surfactant administration on ventilation-induced inflammation in mouse models of lung injury

Background

Mechanical ventilation (MV) is an essential supportive therapy for acute lung injury (ALI); however it can also contribute to systemic inflammation. Since pulmonary surfactant has anti-inflammatory properties, the aim of the study was to investigate the effect of exogenous surfactant administration on ventilation-induced systemic inflammation.

Methods

Mice were randomized to receive an intra-tracheal instillation of a natural exogenous surfactant preparation (bLES, 50 mg/kg) or no treatment as a control. MV was then performed using the isolated and perfused mouse lung (IPML) set up. This model allowed for lung perfusion during MV. In experiment 1, mice were exposed to mechanical ventilation only (tidal volume =20 mL/kg, 2 hours). In experiment 2, hydrochloric acid or air was instilled intra-tracheally four hours before applying exogenous surfactant and ventilation (tidal volume =5 mL/kg, 2 hours).

Results

For both experiments, exogenous surfactant administration led to increased total and functional surfactant in the treated groups compared to the controls. Exogenous surfactant administration in mice exposed to MV only did not affect peak inspiratory pressure (PIP), lung IL-6 levels and the development of perfusate inflammation compared to non-treated controls. Acid injured mice exposed to conventional MV showed elevated PIP, lung IL-6 and protein levels and greater perfusate inflammation compared to air instilled controls. Instillation of exogenous surfactant did not influence the development of lung injury. Moreover, exogenous surfactant was not effective in reducing the concentration of inflammatory cytokines in the perfusate.

Conclusions

The data indicates that exogenous surfactant did not mitigate ventilation-induced systemic inflammation in our models. Future studies will focus on altering surfactant composition to improve its immuno-modulating activity.

Mechanical ventilation enhances HMGB1 expression in an LPS-induced lung injury model

Background

Mechanical ventilation (MV) can augment inflammatory response in lipopolysaccharide (LPS) challenged lungs. High mobility group box 1 protein (HMGB1) is a pro-inflammatory mediator in ventilator-induced lung injury, but its mechanisms are not well defined. This study investigated the role of HMGB1 in lung inflammation in response to the combination of MV and LPS treatment.

Methods

Forty-eight male Sprague-Dawley rats were randomized to one of four groups: sham control; LPS treatment; mechanical ventilation; mechanical ventilation with LPS treatment. Mechanically ventilated animals received 10 ml/kg tidal volumes at a rate of 40 breaths/min for 4 h. In the HMGB1-blockade study, sixteen rats were randomly assigned to HMGB1 antibody group or control antibody group and animals were subjected to MV+LPS as described above. A549 cells were pre-incubated with different signal inhibitors before subjected to 4 h of cyclic stretch. Lung wet/dry weight (W/D) ratio, total protein and IgG concentration, number of neutrophils in bronchoalveolar lavage fluid (BALF), and lung histological changes were examined. The levels of interleukin-1β (IL-1β), IL-6, tumor necrosis factor-α (TNF-α), macrophage inflammatory protein-2 (MIP-2) and HMGB1 in BALF were measured using ELISA. Real-time quantitative PCR and Western blot were used to analyze mRNA and protein expression of HMGB1. Western blot were employed to analyze the activation of IκB-α, NF-κB, JNK, ERK, and p38.

Results

MV significantly augmented LPS-induced lung injury and HMGB1 expression, which was correlated with the increase in IL-1β, IL-6 and MIP-2 levels in BALF. In vivo, intratracheally administration of HMGB1 antibody significantly attenuated pulmonary inflammatory injury. In vitro experiments showed cyclic stretch induced HMGB1 expression through signaling pathways including p38 and NF-κB.

Conclusions

The findings indicated that moderate tidal volume MV augmented LPS induced lung injury by up-regulating HMGB1. The mechanism of HMGB1-mediated lung injury is likely to be signaling through p38 and NF-κB pathways.

Invasive mechanical ventilation as a risk factor for acute kidney injury in the critically ill: a systematic review and meta-analysis

Introduction

Mechanical ventilation (MV) is commonly regarded as a risk factor for acute kidney injury (AKI) in the critically ill. We investigated the strength of this association and whether settings of tidal volume (Vt) and positive end-expiratory pressure (PEEP) affect the risk for AKI.

Methods

We performed a systematic review and meta-analysis using studies found by searching MEDLINE, EMBASE, and references in relevant reviews and articles. We included studies reporting on a relation between the use of invasive MV and subsequent onset of AKI, or comparing higher with lower Vt or PEEP and subsequent onset of AKI. All studies clearly stating that MV was initiated after onset of AKI were excluded. We extracted the proportion with and without MV and AKI. We included 31 studies on invasive MV.

Results

The pooled odds ratio (OR) for the overall effect of MV on AKI was 3.16 (95% CI 2.32 to 4.28, P <0.001). Nearly all subgroups showed that MV increases the risk for AKI. The pooled OR for studies with a multivariate analysis including MV as a risk factor for AKI was 3.58 (95% CI 1.85 to 6.92; P <0.001). Different settings of Vt and PEEP showed no effect.

Conclusions

Invasive MV is associated with a threefold increase in the odds of developing AKI and various Vt or PEEP settings do not modify this risk. The latter argues in favour of a haemodynamic origin of AKI during MV.

Acute kidney injury increases mortality after lung transplantation

BACKGROUND

Acute kidney injury requiring renal replacement therapy (RRT) is associated with increased mortality after cardiac surgery. Studies examining the impact of RRT after lung transplantation (LTx) are limited. We evaluated risk factors and outcomes associated with RRT after LTx.

METHODS

We retrospectively reviewed all LTx recipients in the United Network for Organ Sharing database. Preoperative renal function was stratified by glomerular filtration rate (GFR) as determined by the Modification of Diet in Renal Disease formula (strata: ≥90, 60 to 90, and <60 mL · min(-1) · 1.73 m(-2)). Primary outcomes were 30-day, 1-year, and 5-year survival and need for post-LTx RRT. Risk adjusted multivariable Cox proportional hazards regression examined mortality. A multivariable logistic regression model evaluated risk factors for RRT.

RESULTS

From 2001 to 2011, 12,108 patients underwent LTx. After LTx, 655 patients (5.51%) required RRT. Patients requiring post-LTx RRT had decreased survival at 30 days (96.7% versus 76.0%, p < 0.001), 1 year (85.5% versus 35.8%, p < 0.001), and 5 years (56.4% versus 20.0%, p < 0.001). These differences persisted on multivariable analysis at 30 days (hazard ratio [HR] 7.98 [6.16 to 10.33], p < 0.001), 1 year (HR 7.93 [6.84 to 9.19], p < 0.001), and 5 years (HR 5.39 [4.75 to 6.11], p < 0.001). Preoperative kidney function was an important predictor of post-LTx RRT for a GFR of 60 to 90 (odds ratio 1.42 [1.16 to 1.75], p = 0.001) and a GFR less than 60 (odds ratio 2.68 [2.07 to 3.46], p < 0.001]. High center volume was protective.

CONCLUSIONS

In the largest study to evaluate acute kidney injury after LTx, the incidence of RRT is 5.51%. The need for post-LTx RRT dramatically increases both short- and long-term mortality. Several variables, including preoperative renal function, are predictors of post-LTx RRT and could be used to identify transplant candidates at risk for acute kidney injury.

Mechanical ventilation with high tidal volumes attenuates myocardial dysfunction by decreasing cardiac edema in a rat model of LPS-induced peritonitis

Background

Injurious mechanical ventilation (MV) may augment organ injury remote from the lungs. During sepsis, myocardial dysfunction is common and increased endothelial activation and permeability can cause myocardial edema, which may, among other factors, hamper myocardial function. We investigated the effects of MV with injuriously high tidal volumes on the myocardium in an animal model of sepsis.

Methods

Normal rats and intraperitoneal (i.p.) lipopolysaccharide (LPS)-treated rats were ventilated with low (6 ml/kg) and high (19 ml/kg) tidal volumes (Vt) under general anesthesia. Non-ventilated animals served as controls. Mean arterial pressure (MAP), central venous pressure (CVP), cardiac output (CO) and pulmonary plateau pressure (P_plat) were measured. Ex vivo myocardial function was measured in isolated Langendorff-perfused hearts. Cardiac expression of endothelial vascular cell adhesion molecule (VCAM)-1 and edema were measured to evaluate endothelial inflammation and leakage.

Results

MAP decreased after LPS-treatment and Vt-dependently, both independent of each other and with interaction. MV Vt-dependently increased CVP and Pplat and decreased CO. LPS-induced peritonitis decreased myocardial function ex vivo but MV attenuated systolic dysfunction Vt-dependently. Cardiac endothelial VCAM-1 expression was increased by LPS treatment independent of MV. Cardiac edema was lowered Vt-dependently by MV, particularly after LPS, and correlated inversely with systolic myocardial function parameters ex vivo.

Conclusion

MV attenuated LPS-induced systolic myocardial dysfunction in a Vt-dependent manner. This was associated with a reduction in cardiac edema following a lower transmural coronary venous outflow pressure during LPS-induced coronary inflammation.

High tidal volume mechanical ventilation-induced lung injury in rats is greater after acid instillation than after sepsis-induced acute lung injury, but does not increase systemic inflammation: an experimental study

BACKGROUND

To examine whether acute lung injury from direct and indirect origins differ in susceptibility to ventilator-induced lung injury (VILI) and resultant systemic inflammatory responses.

METHODS

Rats were challenged by acid instillation or 24 h of sepsis induced by cecal ligation and puncture, followed by mechanical ventilation (MV) with either a low tidal volume (Vt) of 6 mL/kg and 5 cm H2O positive end-expiratory pressure (PEEP; LVt acid, LVt sepsis) or with a high Vt of 15 mL/kg and no PEEP (HVt acid, HVt sepsis). Rats sacrificed immediately after acid instillation and non-ventilated septic animals served as controls. Hemodynamic and respiratory variables were monitored. After 4 h, lung wet to dry (W/D) weight ratios, histological lung injury and plasma mediator concentrations were measured.

RESULTS

Oxygenation and lung compliance decreased after acid instillation as compared to sepsis. Additionally, W/D weight ratios and histological lung injury scores increased after acid instillation as compared to sepsis. MV increased W/D weight ratio and lung injury score, however this effect was mainly attributable to HVt ventilation after acid instillation. Similarly, effects of HVt on oxygenation were only observed after acid instillation. HVt during sepsis did not further affect oxygenation, compliance, W/D weight ratio or lung injury score. Plasma interleukin-6 and tumour necrosis factor-α concentrations were increased after acid instillation as compared to sepsis, but plasma intercellular adhesion molecule-1 concentration increased during sepsis only. In contrast to lung injury parameters, no additional effects of HVt MV after acid instillation on plasma mediator concentrations were observed.

CONCLUSIONS

During MV more severe lung injury develops after acid instillation as compared to sepsis. HVt causes VILI after acid instillation, but not during sepsis. However, this differential effect was not observed in the systemic release of mediators.

Protective and Detrimental Effects of Sodium Sulfide and Hydrogen Sulfide in Murine Ventilator-induced Lung Injury

BACKGROUND

The antiinflammatory effects of hydrogen sulfide (H2S) and sodium sulfide (Na2S) treatment may prevent acute lung injury induced by high tidal volume (HVT) ventilation. However, lung protection may be limited by direct pulmonary toxicity associated with H2S inhalation. Therefore, the authors tested whether the inhalation of H2S or intravascular Na2S treatment can protect against ventilator-induced lung injury in mice.

METHODS

Anesthetized mice continuously inhaled 0, 1, 5, or 60 ppm H2S or received a single bolus infusion of Na2S (0.55 mg/kg) or vehicle and were then subjected to HVT (40 ml/kg) ventilation lasting 4 h (n = 4-8 per group).

RESULTS

HVT ventilation increased the concentrations of protein and interleukin-6 in bronchoalveolar lavage fluid, contributing to reduced respiratory compliance and impaired arterial oxygenation, and caused death from lung injury and pulmonary edema. Inhalation of 1 or 5 ppm H2S during HVT ventilation did not alter lung injury, but inhalation of 60 ppm H2S accelerated the development of ventilator-induced lung injury and enhanced the pulmonary expression of the chemoattractant CXCL-2 and the leukocyte adhesion molecules CD11b and L-selectin. In contrast, pretreatment with Na2S attenuated the expression of CXCL-2 and CD11b during HVT ventilation and reduced pulmonary edema. Moreover, Na2S enhanced the pulmonary expression of Nrf2-dependent antioxidant genes (NQO1, GPX2, and GST-A4) and prevented oxidative stress-induced depletion of glutathione in lung tissue.

CONCLUSIONS

The data suggest that systemic intravascular treatment with Na2S represents a novel therapeutic strategy to prevent both ventilator-induced lung injury and pulmonary glutathione depletion by activating Nrf2-dependent antioxidant gene transcription.

Interleukin-6 mediates pulmonary vascular permeability in a two-hit model of ventilator-associated lung injury

To test the hypothesis that interleukin-6 (IL-6) contributes to the development of ventilator-associated lung injury (VALI), IL-6-deficient (IL6(-/-)) and wild-type control (WT) mice received intratracheal hydrochloric acid followed by randomization to mechanical ventilation (MV + IT HCl) or spontaneous ventilation (IT HCl). After 4 hours, injury was assessed by estimation of lung lavage protein concentration and total and differential cell counts, wet/dry lung weight ratio, pulmonary cell death, histologic inflammation score (LIS), and parenchymal myeloperoxidase (MPO) concentration. Vascular endothelial growth factor (VEGF) concentration was measured in lung lavage and homogenate, as IL-6 and stretch both regulate expression of this potent mediator of permeability. MV-induced increases in alveolar barrier dysfunction and lavage VEGF were attenuated in IL6(-/-) mice as compared with WT controls, whereas tissue VEGF concentration increased. The effects of IL-6 deletion on alveolar permeability and VEGF concentration were inflammation independent, as parenchymal MPO concentration, LIS, and lavage total and differential cell counts did not differ between WT and IL6(-/-) mice following MV + IT HCl. These data support a role for IL-6 in promoting VALI in this two-hit model. Strategies to interfere with IL-6 expression or signaling may represent important therapeutic targets to limit the injurious effects of MV in inflamed lungs.

Dopamine inhibits pulmonary edema through the VEGF-VEGFR2 axis in a murine model of acute lung injury

The neurotransmitter dopamine and its dopamine receptor D2 (D2DR) agonists are known to inhibit vascular permeability factor/vascular endothelial growth factor (VEGF)-mediated angiogenesis and vascular permeability. Lung injury is a clinical syndrome associated with increased microvascular permeability. However, the effects of dopamine on pulmonary edema, a phenomenon critical to the pathophysiology of both acute and chronic lung injuries, have yet to be established. Therefore, we sought to determine the potential therapeutic effects of dopamine in a murine model of lipopolysaccharide (LPS)-induced acute lung injury (ALI). Compared with sham-treated controls, pretreatment with dopamine (50 mg/kg body wt) ameliorated LPS-mediated edema formation and lowered myeloperoxidase activity, a measure of neutrophil infiltration. Moreover, dopamine significantly increased survival rates of LPS-treated mice, from 0-75%. Mechanistically, we found that dopamine acts through the VEGF-VEGFR2 axis to reduce pulmonary edema, as dopamine pretreatment in LPS-treated mice resulted in decreased serum VEGF, VEGFR2 phosphorylation, and endothelial nitric oxide synthase phosphorylation. We used D2DR knockout mice to confirm that dopamine acts through D2DR to block vascular permeability in our lung injury model. As expected, a D2DR agonist failed to reduce pulmonary edema in D2DR(-/-) mice. Taken together, our results suggest that dopamine acts through D2DR to inhibit pulmonary edema-associated vascular permeability, which is mediated through VEGF-VEGFR2 signaling and conveys protective effects in an ALI model.

Bench-to-bedside review: Ventilation-induced renal injury through systemic mediator release--just theory or a causal relationship?

We review the current literature on the molecular mechanisms involved in the pathogenesis of acute kidney injury induced by plasma mediators released by mechanical ventilation. A comprehensive literature search in the PubMed database was performed and articles were identified that showed increased plasma levels of mediators where the increase was solely attributable to mechanical ventilation. A subsequent search revealed articles delineating the potential effects of each mediator on the kidney or kidney cells. Limited research has focused specifically on the relationship between mechanical ventilation and acute kidney injury. Only a limited number of plasma mediators has been implicated in mechanical ventilation-associated acute kidney injury. The number of mediators released during mechanical ventilation is far greater and includes pro- and anti-inflammatory mediators, but also mediators involved in coagulation, fibrinolysis, cell adhesion, apoptosis and cell growth. The potential effects of these mediators is pleiotropic and include effects on inflammation, cell recruitment, adhesion and infiltration, apoptosis and necrosis, vasoactivity, cell proliferation, coagulation and fibrinolysis, transporter regulation, lipid metabolism and cell signaling. Most research has focused on inflammatory and chemotactic mediators. There is a great disparity of knowledge of potential effects on the kidney between different mediators. From a theoretical point of view, the systemic release of several mediators induced by mechanical ventilation may play an important role in the pathophysiology of acute kidney injury. However, evidence supporting a causal relationship is lacking for the studied mediators.