Exacerbation Of Acute Lung Injury Research Articles

Targeting the TRAF3-ULK1-NLRP3 regulatory axis to control alveolar macrophage pyroptosis in acute lung injury.

Acute lung injury (ALI) is a serious condition characterized by damage to the lungs. Recent research has revealed that activation of the NLRP3 inflammasome in alveolar macrophages, a type of immune cell in the lungs, plays a key role in the development of ALI. This process, known as pyroptosis, contributes significantly to ALI pathogenesis. Researchers have conducted comprehensive bioinformatics analyses and identified 15 key genes associated with alveolar macrophage pyroptosis in ALI. Among these, NLRP3 has emerged as a crucial regulator. This study further reveal that the ULK1 protein diminishes the expression of NLRP3, thereby reducing the immune response of alveolar macrophages and mitigating ALI. Conversely, TRAF3, another protein, is found to inhibit ULK1 through a process called ubiquitination, leading to increased activation of the NLRP3 inflammasome and exacerbation of ALI. This TRAF3-mediated suppression of ULK1 and subsequent activation of NLRP3 are confirmed through various in vitro and in vivo experiments. The presence of abundant M0 and M1 alveolar macrophages in the ALI tissue samples further support these findings. This research highlights the TRAF3-ULK1-NLRP3 regulatory axis as a pivotal pathway in ALI development and suggests that targeting this axis could be an effective therapeutic strategy for ALI treatment.

The features of the course of virus-associated acute lung injury in mice with induced immunosuppression

BACKGROUND: Among all groups of patients with virus-associated acute lung injury with influenza infection, the most severe course is observed in patients with immunosuppression. In this case, despite the studied mechanism of the course of combined pathology, the question of therapy in this group of patients remains unclear.
 AIM: To study the features of the course of acute lung injury in influenza infection with secondary immunosuppression in an experiment for the possibility of searching for experimental therapy for this combined pathology.
 MATERIALS AND METHODS: The study was performed on 115 outbred female mice. The mouse-adapted pandemic influenza virus A/California/7/09MA (H1N1)pdm09 was used for modeling viral acute lung injury. Experimental immunosuppression was reproduced by administration of methotrexate (1.25 mg/kg intraperitoneally, once every 3 days during 3 weeks before infection). During the experiment, mortality, blood oxygen saturation, the concentration of pro-inflammatory cytokines in the lungs, and the severity of lung injury were measured.
 RESULTS: The presence of experimental immunosuppression led to an exacerbation of acute lung injury in infected animals in terms of mortality and lung damage. Changes in the dynamics of proinflammatory cytokines (TNF-, IL-6, IL-1) in the lungs were observed during acute lung injury. Retarded recovery of the lungs functional activity was noted.
 CONCLUSIONS: The experimental immunosuppression contributed to the exacerbation of acute lung injury and to an increase in the duration of the pathology. These changes could be associated with an altered process of elimination of the pathogen. The reproduced model of combined pathology was used for searching a therapy for these complications.

Histone Deacetylase 6 Mediates Cigarette Smoke‐Induced Increase in Lung Endothelial Permeability and Susceptibility to Acute Lung Injury

Cigarette smoke (CS) is associated with the development of acute lung injury (ALI) in humans. We have shown that acute CS exposure increases susceptibility to lipopolysaccharide (LPS)-induced ALI in vivo and endothelial cell (EC) permeability in vitro. Here, we examined the effects of subacute CS exposure on ALI development, and underlying mechanism, using animal models of CS exposure and lung EC exposed to cigarette smoke extract (CSE). We found 3 wks of CS exposure exacerbated LPS-induced ALI. Histone deacetylase 6 (HDAC6) deacetylates proteins essential for endothelial barrier function. HDAC6 phosphorylation, which potentially activates its deacetylase activity, increased in lung of mice exposed to CS and EC exposed to CSE. CSE also decreased acetylation of α-tubulin, the major target of HDAC6, causing microtubule depolymerization. HDAC6 inhibition attenuated CS-induced increase in EC permeability and exacerbation of ALI. Similar protection was seen with taxol, which preserved α-tubulin acetylation. GSK-3β is activated by inhibiting Akt. In coordination with HDAC6 phosphorylation, CSE decreased phosphorylation of Akt and GSK-3β; effects were ameliorated by the antioxidant N-acetylcysteine. Our results suggest CS increases EC permeability, thereby enhancing susceptibility to ALI, by oxidative stress-dependent Akt inhibition and subsequent GSK-3β/HDAC6-mediated α-tubulin deacetylation. Specific inhibition of HDAC6 may help treatment of CS-associated ALI. PH-05-015 (QL), P20GM103652 (QL, SR), PULM-811-10S (SR), R25 HL088992 (SR), T32 ES007272 (EC), Brown SRA (MX).

Activation of pulmonary invariant NKT cells leads to exacerbation of acute lung injury caused by LPS through local production of IFN- and TNF- by Gr-1+ monocytes

Invariant NK T (iNKT) cells are known to play a critical role in the regulation of inflammatory responses in various clinical settings. In the present study, we assessed the contribution of iNKT cells to the development of acute lung injury (ALI), which was caused by intra-tracheal administration of LPS. Jα18 gene-disrupted mice lacking these cells underwent neutrophilic inflammatory responses in lungs at an equivalent level as control mice. Next, mice were sensitized intra-tracheally with α-galactosylceramide, an activator of iNKT cells, followed by challenge with LPS. In this model, mice showed severe lung injury, and all mice were killed within 72 h after LPS injection. IFN-γ and tumor necrosis factor (TNF)-α were strikingly elevated in the lungs of these mice. Administration of neutralizing mAb against IFN-γ and TNF-α attenuated lung injury in a histopathological analysis and improved their survival rate. Flow cytometric analysis revealed that IFN-γ was expressed in NK cells, iNKT cells and also Gr-1(dull+)Ly-6C(+) monocytes and TNF-α was detected mainly in Gr-1(bright+)Ly-6G(+) neutrophils and Gr-1(dull+)Ly-6C(+) monocytes. Otherwise, in mice treated with LPS alone, IFN-γ was not detected in the lungs and Gr-1(bright+)Ly-6G(+) neutrophil was a main cellular source of TNF-α production. Anti-Gr-1 mAb resulted in the attenuation of ALI and decrease in the level of these cytokines. These results indicated that activation of iNKT cells led to striking exacerbation of ALI caused by LPS and that Gr-1(+) monocytes were recruited in the lungs with expressing IFN-γ and TNF-α and played an important role in the development of these responses.

Pathogenesis of severe acute respiratory syndrome

Pathogenesis of severe acute respiratory syndrome

Oxygenation Inhibits the Physiological Tissue-Protecting Mechanism and Thereby Exacerbates Acute Inflammatory Lung Injury

Acute respiratory distress syndrome (ARDS) usually requires symptomatic supportive therapy by intubation and mechanical ventilation with the supplemental use of high oxygen concentrations. Although oxygen therapy represents a life-saving measure, the recent discovery of a critical tissue-protecting mechanism predicts that administration of oxygen to ARDS patients with uncontrolled pulmonary inflammation also may have dangerous side effects. Oxygenation may weaken the local tissue hypoxia-driven and adenosine A2A receptor (A2AR)-mediated anti-inflammatory mechanism and thereby further exacerbate lung injury. Here we report experiments with wild-type and adenosine A2AR-deficient mice that confirm the predicted effects of oxygen. These results also suggest the possibility of iatrogenic exacerbation of acute lung injury upon oxygen administration due to the oxygenation-associated elimination of A2AR-mediated lung tissue-protecting pathway. We show that this potential complication of clinically widely used oxygenation procedures could be completely prevented by intratracheal injection of a selective A2AR agonist to compensate for the oxygenation-related loss of the lung tissue-protecting endogenous adenosine. The identification of a major iatrogenic complication of oxygen therapy in conditions of acute lung inflammation attracts attention to the need for clinical and epidemiological studies of ARDS patients who require oxygen therapy. It is proposed that oxygen therapy in patients with ARDS and other causes of lung inflammation should be combined with anti-inflammatory measures, e.g., with inhalative application of A2AR agonists. The reported observations may also answer the long-standing question as to why the lungs are the most susceptible to inflammatory injury and why lung failure usually precedes multiple organ failure.

Effect of granulocyte colony-stimulating factor on bleomycin-induced acute lung injury and pulmonary fibrosis.

Potentially fatal pulmonary toxicity is a dreaded complication of bleomycin. Increased use of granulocyte colony-stimulating factor in patients receiving chemotherapy has been paralleled by an increased incidence of bleomycin-induced pulmonary toxicity. We investigated whether granulocyte colony-stimulating factor (25 microg x kg(-1) x day(-1), 4 days) enhanced endotracheal bleomycin-induced (5 mg/kg) acute lung injury and fibrosis in rats. University laboratory. Sprague-Dawley rats. We compared the effects of alveolar instillation of bleomycin in rats treated with either granulocyte colony-stimulating factor or saline. Mortality was 25% with bleomycin only and 50% with bleomycin + granulocyte colony-stimulating factor. Granulocyte colony-stimulating factor increased alveolar neutrophil recruitment, pulmonary edema, and lung myeloperoxidase activity on day 4. Lung static compliance on day 15 was severely decreased with bleomycin alone and showed a further significant decrease when granulocyte colony-stimulating factor was added (controls, 3.85 +/- 0.14 mL/kPa; bleomycin, 1.44 +/- 0.06 mL/kPa; and bleomycin + granulocyte colony-stimulating factor, 0.65 +/- 0.09 mL/kPa; control vs. bleomycin, p <.0001; and bleomycin vs. bleomycin + granulocyte colony-stimulating factor, p =.0003). Lung morphology with bleomycin + granulocyte colony-stimulating factor showed, in addition to the changes observed with bleomycin alone, four patterns indicating more severe disease: honeycomb foci, pleural thickening with hyaline fibrosis, interstitial granuloma with increased number of macrophages but not neutrophils, and established interstitial fibrosis. Lidocaine, which prevents neutrophil adhesion to endothelial cells, inhibited granulocyte colony-stimulating factor-related exacerbation of acute lung injury (bronchoalveolar lavage fluid cells and pulmonary edema) and pulmonary fibrosis (lung static compliance and morphologic changes). Granulocyte colony-stimulating factor enhances bleomycin-induced lung toxicity by a mechanism that probably involves neutrophils.

Intravascular membrane oxygenation and carbon dioxide removal--a new application for permissive hypercapnia?

Pressure limited ventilation or "lung rest" may prevent further exacerbation of acute lung injury from high airway pressures. A therapeutic goal of an intracorporeal oxygenation and carbon dioxide removal device (IVOX) is reduction of airway pressures. We noted increased IVOX CO2 removal as mixed venous CO2 increased in experimental animals. However, we recognize the limited clinical utility of removing approximately 30% of venous CO2. Therefore, intentional hypoventilation to limit airway pressures (mild permissive hypercapnia) was used in 5 patients with respiratory failure, and again we noted improved CO2 removal with increasing mixed venous CO2 concentrations. Preliminary calculations demonstrate that a CO2 gradient of approximately 70 mm Hg is needed to remove 100 ml CO2/min. The use of more aggressive permissive hypercapnia protocols with IVOX may permit further reduction in airway pressure without problems of severe respiratory acidosis.