The Effects of Fenoterol Inhalation After Acid Aspiration-Induced Lung Injury

Small molecule inhibitor CRT0066101 inhibits cytokine storm syndrome in a mouse model of lung injury

Pneumonia is an acute inflammation of the lungs induced by pathogenic microorganisms, immune damage, physical and chemical factors, and other factors, and the latest outbreak of novel coronavirus pneumonia is also an acute lung injury (ALI) induced by viral infection. However, there are currently no effective treatments for inflammatory cytokine storms in patients with ALI/acute respiratory distress syndrome (ARDS). Protein kinase D (PKD) is a highly active kinase that has been shown to be associated with the production of inflammatory cytokines. Therefore, small-molecule compounds that inhibit PKD may be potential drugs for the treatment of ALI/ARDS. In the present study, we evaluated the ability of the small-molecule inhibitor CRT0066101 to attenuate lipopolysaccharide (LPS)-induced inflammatory cytokine production through in vitro cell experiments and a mouse pneumonia model. We found that CRT0066101 significantly reduced the protein and mRNA levels of LPS-induced cytokines (e.g., IL-6, TNF-α, and IL-1β). CRT0066101 inhibited MyD88 and TLR4 expression and reduced NF-κB, ERK, and JNK phosphorylation. CRT0066101 also reduced NLRP3 activation, inhibited the assembly of the inflammasome complex, and attenuated inflammatory cell infiltration and lung tissue damage. Taken together, our data indicate that CRT0066101 exerts anti-inflammatory effects on LPS-induced inflammation through the TLR4/MyD88 signaling pathway, suggesting that CRT0066101 may have therapeutic value in acute lung injury and other MyD88-dependent inflammatory diseases.

Synergy between acid and endotoxin in an experimental model of aspiration-related lung injury progression

Aspiration is a common cause of lung injury, but it is unclear why some cases are self-limited while others progress to acute respiratory distress syndrome (ARDS). Sporadic exposure to more than one insult could account for this variable progression. We investigated whether synergy between airway acid and endotoxin (LPS) amplifies injury severity in mice and whether LPS levels in human patients could corroborate our experimental findings. C57BL/6 mice aspirated acid (pH 1.3) or normal saline (NS), followed by LPS aerosol or nothing. Bronchoalveolar lavage fluid (BALF) was obtained 2 to 49 h later. Mice were injected with FITC-dextran 25 h after aspiration and connected to a ventilator, and lung elastance (H) measured periodically following deep inflation (DI). Endotracheal and gastric aspirates were also collected from patients in the intensive care unit and assayed for pH and LPS. Lung instability (ΔH following DI) and pressure-volume hysteresis in acid- or LPS-exposed mice was greater than in controls but markedly greater in the combined acid/LPS group. BALF neutrophils, cytokines, protein, and FITC-dextran in the acid/LPS mice were geometrically higher than all other groups. BALF from acid-only mice markedly amplified LPS-induced TNF-α production in cultured macrophages. Human subjects had variable endotracheal LPS levels with the highest burden in those at higher risk of aspiration. Acid aspiration amplifies LPS signaling in mice to disrupt barrier function and lung mechanics in synergy. High variation in airway LPS and greater airway LPS burden in patients at higher risk of aspiration could help explain the sporadic progression of aspiration to ARDS.

Time course of metabolic activity and cellular infiltration in a murine model of acid-induced lung injury

PURPOSE

This study investigates whether positron emission tomography (PET) can be used to monitor the inflammatory response and its correlation with the later fibroproliferative phase in an experimental model of acute lung injury.

METHODS

Hydrochloric acid (0.1 N, pH 1, 1.5 ml/kg) was instilled into the right bronchus of mice. A group of mice underwent a micro-computed tomography (CT) scan 1 h after lung injury and a series of 2-[(18)F]fluorine-2-deoxy-D: -glucose (FDG)-PET scans (6, 24 and 48 h and 7 days after surgery). After 21 days respiratory static compliance was assessed and lung tissue was collected in order to measure the hydroxy (OH)-proline content. Other groups of mice underwent micro-CT and micro-PET scans at the same time points, and then were immediately killed to assess arterial blood gases and histology.

RESULTS

Histological analysis showed the recruitment of neutrophils and macrophages into the damaged lung, reaching the peak at 24 and 48 h, respectively. The time course of the [(18)F]FDG signal, used as a marker of inflammation, correlated with that of recruited inflammatory cells. In mice killed 21 days after the surgery, a correlation was found between reduced respiratory static compliance and high PET signal 7 days after lung injury. The PET signal also correlated with the OH-proline content.

CONCLUSIONS

This study demonstrated that PET imaging is a valid means of tracking the inflammatory response, also in longitudinal studies. Moreover, a correlation was found between persistence of the inflammatory response and fibrotic evolution of the injury.

Contribution of α - and β -Adrenergic Mechanisms to the Development of Pulmonary Edema

Endogenous or exogenous catecholamines can induce pulmonary edema (PE). This may occur in human pathologic conditions such as in pheochromocytoma or in neurogenic pulmonary edema (NPE) but can also be provoked after experimental administration of adrenergic agonists. PE can result from stimulation with different types of adrenergic stimulation. With α-adrenergic treatment, it develops more rapidly, is more severe with abundant protein-rich fluid in the alveolar space, and is accompanied by strong generalized inflammation in the lung. Similar detrimental effects of α-adrenergic stimulation have repeatedly been described and are considered to play a pivotal role in NPE or in PE in patients with pheochromocytoma. Although β-adrenergic agonists have often been reported to prevent or attenuate PE by enhancing alveolar fluid clearance, PE may also be induced by β-adrenergic treatment as can be observed in tocolysis. In experimental models, infusion of β-adrenergic agonists induces less severe PE than α-adrenergic stimulation. The present paper addresses the current understanding of the possible contribution of α- and β-adrenergic pathways to the development of PE.

A porcine model of acute lung injury by instillation of gastric fluid

BACKGROUND

About 15% of donor lungs are declined because of aspiration contributing to current organ shortage. The aim was to develop a porcine lung injury model by gastric juice (GJ) instillation to study different pretransplant treatment strategies.

MATERIALS AND METHODS

Pigs (n = 6/group) were anesthetized and monitored. At T0 bronchoalveolar lavage (BAL) was performed followed by instillation of 4 mL/kg GJ or saline solution (SAL). Hemodynamics, aerodynamics and oxygenation were recorded for two hours. Serum samples were collected. At T120 a second BAL was performed. CT scans of explanted, inflated lungs were taken, tissue samples were collected and wet/dry weight ratio (W/D) was calculated. Pepsin and bile acids were measured in BAL. IL-8, CRP and MMP-9 were measured in serum and in BAL.

RESULT

Oxygenation and lung compliance was lower in [GJ] versus [SAL] (P < 0.01 and P < 0.001, respectively). More consolidation areas were noticed on CT in GJ versus SAL (P < 0.01). Hemorrhage, edema and neutrophil inflammation were seen on histology in [GJ] (P < 0.01, P < 0.001, P < 0.001, respectively). BAL neutrophils, pepsin, bile acids, and IL-8 (P < 0.05) increased in [GJ]. W/D was higher in [GJ] versus SAL (P < 0.001).

CONCLUSION

Instillation of GJ in pig lungs caused acute lung injury with impaired oxygenation and increased inflammation in BAL, on histology, and on imaging. This model holds promise to assess the efficacy of a broad range of treatment strategies including ex vivo lung perfusion (EVLP).

Aspiration syndromes: aspiration pneumonia and pneumonitis

Aspiration pneumonia and pneumonitis are common clinical syndromes that occur in hospitalized patients. Aspiration pneumonia occurs in patients with dysphagia and usually presents as a community-acquired pneumonia with a focal infiltrate in a dependent bronchopulmonary segment. Patients with aspiration pneumonia require treatment with broad-spectrum antibiotics and management of the underlying dysphagia. Aspiration pneumonitis follows the aspiration of gastric contents, usually in patients with a marked decreased level of consciousness. Treatment of aspiration pneumonitis is essentially supportive; however, corticosteroids and other immunomodulating agents may have a role in these patients.