Acute respiratory distress syndrome

NO in Viral Infections: Role and Development of Antiviral Therapies

Nitric oxide is a ubiquitous signaling radical that influences critical body functions. Its importance in the cardiovascular system and the innate immune response to bacterial and viral infections has been extensively investigated. The overproduction of NO is an early component of viral infections, including those affecting the respiratory tract. The production of high levels of NO is due to the overexpression of NO biosynthesis by inducible NO synthase (iNOS), which is involved in viral clearance. The development of NO-based antiviral therapies, particularly gaseous NO inhalation and NO-donors, has proven to be an excellent antiviral therapeutic strategy. The aim of this review is to systematically examine the multiple research studies that have been carried out to elucidate the role of NO in viral infections and to comprehensively describe the NO-based antiviral strategies that have been developed thus far. Particular attention has been paid to the potential mechanisms of NO and its clinical use in the prevention and therapy of COVID-19.

Wheat and chaffs in the interpretation of the current COVID19 outbreak in Italy

The COVID19 outbreak in Italy is still a big concern. The Italian Government has recommended citizens to respect faithfully any compulsory legal disposition in order to stay home and so contributing in escaping viral contacts and slowing down epidemic. Emergency has raised a widely animated debate about how to read and comprehend the daily case numbers, the medical and caregivers availability, the needs to swab asymptomatic subjects. In this review the authors discuss about the many wheat and chaffs of how this virus disease is addressed .

VEGF mediates fat embolism-induced acute lung injury via VEGF receptor 2 and the MAPK cascade

Fat embolism (FE) is a lethal medical emergency often caused by fracture of long bones and amputation of limbs. Vascular endothelial growth factor (VEGF) promotes angiogenesis and increases vascular permeability. We tested the hypothesis that VEGF plays a critical role in FE-induced acute respiratory distress syndrome (ARDS) and acute lung injury (ALI). Fat tissues were collected from male Sprague-Dawley rats, and animal oil was extracted and mixed with water to form fatty micelles. The micelles were then injected into the tail vein to produce FE and ALI in rats. Lung weight gain was measured as the index of pulmonary edema. The expression of pulmonary VEGF was evaluated by real-time PCR and western blot analysis. Inducible nitric oxide synthase (iNOS) and phosphorylation of mitogen-activated protein kinase (MAPK) were determined by western blot analyses. Interleukin-1β (IL-1β) was quantified by ELISAs. Hematoxylin and eosin staining was used to evaluate the pathological damage of ALI. In this study, we found that animal oil-induced FE significantly increased pulmonary VEGF expression and MAPK phosphorylation. We also evaluated the inflammatory response after FE and found that iNOS and IL-1β significantly increased after FE. Systemic administration of SU-1498, an antagonist of VEGF receptor 2 (VEGFR-2), significantly attenuated the FE-induced inflammatory response and histological damage. This study suggested that VEGF is involved in FE-induced ARDS via the VEGFR-2 and MAPK cascades, which induce IL-1β release and iNOS upregulation. Blockade of could be used to treat FE-induced pulmonary damage.

Attenuation of lipopolysaccharide-induced lung inflammation by ascorbic acid in rats: Histopathological and ultrastructural study

Introduction:

Lipopolysaccharide is a bacterial endotoxin that induces acute lung injury in experimental animals, which is similar to acute respiratory distress syndrome in humans. The induced tissue trauma ends in fibrosis. Understanding the pathogenesis is important in the prevention and treatment of the complications. This study was assigned to investigate the long-term lipopolysaccharide-induced lung injury and the postulated protective effect of ascorbic acid on these changes.

Materials and methods:

Twenty-four adult male albino rats were divided into three groups. Group I was the controls, group II received lipopolysaccharide and group III received lipopolysaccharide and ascorbic acid. After 30 days of starting treatment, lung tissue samples were obtained.

Results:

Group II lung tissues showed marked thickening of the alveolar septa with collapsed alveolar sacs, detached bronchial epithelium, inflammatory cell infiltration and excessive deposition of collagen. Group III showed mild thickening of the alveolar walls, scanty inflammatory cell infiltration, mild parabronchial fibrosis and less marked collagen deposition. α-Smooth muscle actin staining of group II showed marked expression of the actin-positive cells. Less potential expression of the dye was found in group III. Ultrastructural examination of group II showed evident structural changes in pneumocytes with capillary basement membrane irregularity and interruption compared to uniform basement membrane in group III with less prominent intracellular changes in pneumocytes.

Conclusion:

Ascorbic acid attenuated the inflammatory response and fibrosis in the lungs of rats treated with lipopolysaccharide as evidenced by the histological, immunohistochemical and ultrastructural studies.

A review of genetic methods and models for analysis of coronavirus-induced severe pneumonitis

Coronaviruses (CoVs) have been studied for over 60 years, but have only recently gained notoriety as deadly human pathogens with the emergence of severe respiratory syndrome CoV and Middle East respiratory syndrome virus. The rapid emergence of these viruses has demonstrated the need for good models to study severe CoV respiratory infection and pathogenesis. There are, currently, different methods and models for the study of CoV disease. The available genetic methods for the study and evaluation of CoV genetics are reviewed here. There are several animal models, both mouse and alternative animals, for the study of severe CoV respiratory disease that have been examined, each with different pros and cons relative to the actual pathogenesis of the disease in humans. A current limitation of these models is that no animal model perfectly recapitulates the disease seen in humans. Through the review and analysis of the available disease models, investigators can employ the most appropriate available model to study various aspects of CoV pathogenesis and evaluate possible antiviral treatments that may potentially be successful in future treatment and prevention of severe CoV respiratory infections.

Oroxylin-A rescues LPS-induced acute lung injury via regulation of NF-κB signaling pathway in rodents

BACKGROUND AND PURPOSE

Successful drug treatment for sepsis-related acute lung injury (ALI) remains a major clinical problem. This study was designed to assess the beneficial effects of post-treatment of oroxylin A (OroA), a flavonoid, in ameliorating lipopolysaccharides (LPS)-induced lung inflammation and fatality.

EXPERIMENTAL APPROACH

Rats were injected with LPS (10 mg/kg, iv) to induce ALI, and OroA was given (15 mg/kg, iv) 1 hr or 6 hrs after LPS challenge. Twenty four hrs after LPS challenge, biochemical changes in the blood and lung tissues, and morphological/histological alterations in the lung associated with inflammation and injury were examined. Therapeutic effect of OroA was assessed by measuring the survival rate in endotoxemic mice.

KEY RESULTS

LPS (10 mg/kg, iv) significantly altered WBC counts, elevated plasma tumor necrosis factor (TNF)-α and nitric oxide (NO), increased pulmonary edema, thickened alveolar septa, and decreased survival rate. These changes were ameliorated by OroA (15 mg/kg, iv) administered 1 hr or 6 hrs after LPS challenge. This post-treatment also significantly attenuated LPS-induced activation of nuclear factor-κB (NF-κB) and the release of high mobility group box 1 (HMGB1) in lung tissues. Furthermore, post-treatment with OroA (60 mg/kg, ip) administered 1 hr or 6 hrs after LPS challenge in mice significantly increased survival rate.

CONCLUSION AND IMPLICATION

OroA administered after induction of ALI by LPS significantly prevent and revere lung tissues injuries with increased survival rate. Positive post-treatment effects of OroA suggest that OroA is a potentially useful candidate for managing lung inflammation in LPS-induced endotoxemia and septic shock.

Acute lung injury and acute respiratory distress syndrome: experimental and clinical investigations

Acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) can be associated with various disorders. Recent investigation has involved clinical studies in collaboration with clinical investigators and pathologists on the pathogenetic mechanisms of ALI or ARDS caused by various disorders. This literature review includes a brief historical retrospective of ALI/ARDS, the neurogenic pulmonary edema due to head injury, the long-term experimental studies and clinical investigations from our laboratory, the detrimental role of NO, the risk factors, and the possible pathogenetic mechanisms as well as therapeutic regimen for ALI/ARDS.

Acute respiratory distress syndrome and lung injury: Pathogenetic mechanism and therapeutic implication

To review possible mechanisms and therapeutics for acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). ALI/ARDS causes high mortality. The risk factors include head injury, intracranial disorders, sepsis, infections and others. Investigations have indicated the detrimental role of nitric oxide (NO) through the inducible NO synthase (iNOS). The possible therapeutic regimen includes extracorporeal membrane oxygenation, prone position, fluid and hemodynamic management and permissive hypercapnic acidosis etc. Other pharmacological treatments are anti-inflammatory and/or antimicrobial agents, inhalation of NO, glucocorticoids, surfactant therapy and agents facilitating lung water resolution and ion transports. β-adrenergic agonists are able to accelerate lung fluid and ion removal and to stimulate surfactant secretion. In conscious rats, regular exercise training alleviates the endotoxin-induced ALI. Propofol and N-acetylcysteine exert protective effect on the ALI induced by endotoxin. Insulin possesses anti-inflammatory effect. Pentobarbital is capable of reducing the endotoxin-induced ALI. In addition, nicotinamide or niacinamide abrogates the ALI caused by ischemia/reperfusion or endotoxemia. This review includes historical retrospective of ALI/ARDS, the neurogenic pulmonary edema due to head injury, the detrimental role of NO, the risk factors, and the possible pathogenetic mechanisms as well as therapeutic regimen for ALI/ARDS.

Regulation of ENaC-mediated alveolar fluid clearance by insulin via PI3K/Akt pathway in LPS-induced acute lung injury

BACKGROUND

Stimulation of epithelial sodium channel (ENaC) increases Na(+) transport, a driving force of alveolar fluid clearance (AFC) to keep alveolar spaces free of edema fluid that is beneficial for acute lung injury (ALI). It is well recognized that regulation of ENaC by insulin via PI3K pathway, but the mechanism of this signaling pathway to regulate AFC and ENaC in ALI remains unclear. The aim of this study was to investigate the effect of insulin on AFC in ALI and clarify the pathway in which insulin regulates the expression of ENaC in vitro and in vivo.

METHODS

A model of ALI (LPS at a dose of 5.0 mg/kg) with non-hyperglycemia was established in Sprague-Dawley rats receiving continuous exogenous insulin by micro-osmotic pumps and wortmannin. The lungs were isolated for measurement of bronchoalveolar lavage fluid(BALF), total lung water content(TLW), and AFC after ALI for 8 hours. Alveolar epithelial type II cells were pre-incubated with LY294002, Akt inhibitor and SGK1 inhibitor 30 minutes before insulin treatment for 2 hours. The expressions of α-,β-, and γ-ENaC were detected by immunocytochemistry, reverse transcriptase polymerase chain reaction (RT-PCR) and western blotting.

RESULTS

In vivo, insulin decreased TLW, enchanced AFC, increased the expressions of α-,β-, and γ-ENaC and the level of phosphorylated Akt, attenuated lung injury and improved the survival rate in LPS-induced ALI, the effects of which were blocked by wortmannin. Amiloride, a sodium channel inhibitor, significantly reduced insulin-induced increase in AFC. In vitro, insulin increased the expressions of α-,β-, and γ-ENaC as well as the level of phosphorylated Akt but LY294002 and Akt inhibitor significantly prevented insulin-induced increase in the expression of ENaC and the level of phosphorylated Akt respectively. Immunoprecipitation studies showed that levels of Nedd4-2 binding to ENaC were decreased by insulin via PI3K/Akt pathway.

CONCLUSIONS

Our study demonstrated that insulin alleviated pulmonary edema and enhanced AFC by increasing the expression of ENaC that dependent upon PI3K/Akt pathway by inhibition of Nedd4-2.

Niacinamide mitigated the acute lung injury induced by phorbol myristate acetate in isolated rat's lungs

BACKGROUND

Phorbol myristate acetate (PMA) is a strong neutrophil activator and has been used to induce acute lung injury (ALI). Niacinamide (NAC) is a compound of B complex. It exerts protective effects on the ALI caused by various challenges. The purpose was to evaluate the protective effects of niacinamide (NAC) on the PMA-induced ALI and associated changes.

METHODS

The rat's lungs were isolated in situ and perfused with constant flow. A total of 60 isolated lungs were randomized into 6 groups to received Vehicle (DMSO 100 μg/g), PMA 4 μg/g (lung weight), cotreated with NAC 0, 100, 200 and 400 mg/g (lung weight). There were 10 isolated lungs in each group. We measured the lung weight and parameters related to ALI. The pulmonary arterial pressure and capillary filtration coefficient (Kfc) were determined in isolated lungs. ATP (adenotriphosphate) and PARP [poly(adenosine diphophate-ribose) polymerase] contents in lung tissues were detected. Real-time PCR was employed to display the expression of inducible and endothelial NO synthases (iNOS and eNOS). The neutrophil-derived mediators in lung perfusate were determined.

RESULTS

PMA caused increases in lung weight parameters. This agent produced pulmonary hypertension and increased microvascular permeability. It resulted in decrease in ATP and increase in PARP. The expression of iNOS and eNOS was upregulated following PMA. PMA increased the neutrophil-derived mediators. Pathological examination revealed lung edema and hemorrhage with inflammatory cell infiltration. Immunohistochemical stain disclosed the presence of iNOS-positive cells in macrophages and endothelial cells. These pathophysiological and biochemical changes were diminished by NAC treatment. The NAC effects were dose-dependent.

CONCLUSIONS

Our results suggest that neutrophil activation and release of neutrophil-derived mediators by PMA cause ALI and associated changes. NO production through the iNOS-producing cells plays a detrimental role in the PMA-induced lung injury. ATP is beneficial, while PARP plays a deteriorative effect on the PMA-induced ALI. NAC exerts protective effects on the inflammatory cascade leading to pulmonary injury. This B complex compound may be applied for clinical usage and therapeutic regimen.

Urokinase-type plasminogen activator (uPA) induces pulmonary microvascular endothelial permeability through low density lipoprotein receptor-related protein (LRP)-dependent activation of endothelial nitric-oxide synthase

Urokinase plasminogen activator (uPA) and PA inhibitor type 1 (PAI-1) are elevated in acute lung injury, which is characterized by a loss of endothelial barrier function and the development of pulmonary edema. Two-chain uPA and uPA-PAI-1 complexes (1-20 nM) increased the permeability of monolayers of human pulmonary microvascular endothelial cells (PMVECs) in vitro and lung permeability in vivo. The effects of uPA-PAI-1 were abrogated by the nitric-oxide synthase (NOS) inhibitor L-NAME (N(D)-nitro-L-arginine methyl ester). Two-chain uPA (1-20 nM) and uPA-PAI-1 induced phosphorylation of endothelial NOS-Ser(1177) in PMVECs, which was followed by generation of NO and the nitrosylation and dissociation of β-catenin from VE-cadherin. uPA-induced phosphorylation of eNOS was decreased by anti-low density lipoprotein receptor-related protein-1 (LRP) antibody and an LRP antagonist, receptor-associated protein (RAP), and when binding to the uPA receptor was blocked by the isolated growth factor-like domain of uPA. uPA-induced phosphorylation of eNOS was also inhibited by the protein kinase A (PKA) inhibitor, myristoylated PKI, but was not dependent on PI3K-Akt signaling. LRP blockade and inhibition of PKA prevented uPA- and uPA-PAI-1-induced permeability of PMVEC monolayers in vitro and uPA-induced lung permeability in vivo. These studies identify a novel pathway involved in regulating PMVEC permeability and suggest the utility of uPA-based approaches that attenuate untoward permeability following acute lung injury while preserving its salutary effects on fibrinolysis and airway remodeling.

Diabetes, insulin, and development of acute lung injury

OBJECTIVES

Recently, many studies have investigated the immunomodulatory effects of insulin and glucose control in critical illness. This review examines evidence regarding the relationship between diabetes and the development of acute lung injury/acute respiratory distress syndrome (ALI/ARDS), reviews studies of lung injury related to glycemic and nonglycemic metabolic features of diabetes, and examines the effect of diabetic therapies.

DATA SOURCES AND STUDY SELECTION

A MEDLINE/PubMed search from inception to August 1, 2008, was conducted using the search terms acute lung injury, acute respiratory distress syndrome, hyperglycemia, diabetes mellitus, insulin, hydroxymethylglutaryl-CoA reductase inhibitors (statins), angiotensin-converting enzyme inhibitor, and peroxisome proliferator-activated receptors, including combinations of these terms. Bibliographies of retrieved articles were manually reviewed.

DATA EXTRACTION AND SYNTHESIS

Available studies were critically reviewed, and data were extracted with special attention to the human and animal studies that explored a) diabetes and ALI; b) hyperglycemia and ALI; c) metabolic nonhyperglycemic features of diabetes and ALI; and d) diabetic therapies and ALI.

CONCLUSIONS

Clinical and experimental data indicate that diabetes is protective against the development of ALI/ARDS. The pathways involved are complex and likely include effects of hyperglycemia on the inflammatory response, metabolic abnormalities in diabetes, and the interactions of therapeutic agents given to diabetic patients. Multidisciplinary, multifaceted studies, involving both animal models and clinical and molecular epidemiology techniques, are essential.

Mechanism of fulminant pulmonary edema caused by enterovirus 71

Pulmonary edema (PE) may occur with enterovirus 71 (EV71) infection. We monitored arterial pressure (AP) and heart rate (HR) in patients with EV71 infection and analyzed the variability of AP and HR. Sympathetic activity, AP, and HR increased with respiratory stress. Thereafter, parasympathetic activity increased with decreases in AP and HR. The lungs showed edema with inducible nitric oxide synthase (iNOS) expression. Destruction of the medial, ventral, and caudal medulla may lead to sympathetic overactivation, causing blood to shift to the lungs. The pathogenesis of PE may also involve iNOS and nitric oxide.