Comparative Study of Trans-Oral and Trans-Tracheal Intratracheal Instillations in a Murine Model of Acute Lung Injury

Intravital Microscopy of Lipopolysaccharide-Induced Inflammatory Changes in Different Organ Systems-A Scoping Review

Intravital microscopy (IVM) is a powerful imaging tool that captures biological processes in real-time. IVM facilitates the observation of complex cellular interactions in vivo, where ex vivo and in vitro experiments lack the physiological environment. IVM has been used in a multitude of studies under healthy and pathological conditions in different organ systems. IVM has become essential in the characterization of the immune response through visualization of leukocyte-endothelial interactions and subsequent changes within the microcirculation. Lipopolysaccharide (LPS), a common inflammatory trigger, has been used to induce inflammatory changes in various studies utilizing IVM. In this review, we provide an overview of IVM imaging of LPS-induced inflammation in different models, such as the brain, intestines, bladder, and lungs.

Lung and general health effects of Toll-like receptor-4 (TLR4)-interacting SPA4 peptide

Background

A surfactant protein-A-derived peptide, which we call SPA4 peptide (amino acids: GDFRYSDGTPVNYTNWYRGE), alleviates lung infection and inflammation. This study investigated the effects of intratracheally administered SPA4 peptide on systemic, lung, and health parameters in an outbred mouse strain, and in an intratracheal lipopolysaccharide (LPS) challenge model.

Methods

The outbred CD-1 mice were intratracheally administered with incremental doses of SPA4 peptide (0.625–10 μg/g body weight) once every 24 h, for 3 days. Mice left untreated and those treated with vehicle were included as controls. Mice were euthanized after 24 h of last administration of SPA4 peptide. In order to assess the biological activity of SPA4 peptide, C57BL6 mice were intratracheally challenged with 5 μg LPS/g body weight and treated with 50 μg SPA4 peptide via intratracheal route 1 h post LPS-challenge. Mice were euthanized after 4 h of LPS challenge. Signs of sickness and body weights were regularly monitored. At the time of necropsy, blood and major organs were harvested. Blood gas and electrolytes, serum biochemical profiles and SPA4 peptide-specific immunoglobulin G (IgG) antibody levels, and common lung injury markers (levels of total protein, albumin, and lactate, lactate dehydrogenase activity, and lung wet/dry weight ratios) were determined. Lung, liver, spleen, kidney, heart, and intestine were examined histologically. Differences in measured parameters were analyzed among study groups by analysis of variance test.

Results

The results demonstrated no signs of sickness or changes in body weight over 3 days of treatment with various doses of SPA4 peptide. It did not induce any major toxicity or IgG antibody response to SPA4 peptide. The SPA4 peptide treatment also did not affect blood gas, electrolytes, or serum biochemistry. There was no evidence of injury to the tissues and organs. However, the SPA4 peptide suppressed the LPS-induced lung inflammation.

Conclusions

These findings provide an initial toxicity profile of SPA4 peptide. Intratracheal administration of escalating doses of SPA4 peptide does not induce any significant toxicity at tissue and organ levels. However, treatment with a dose of 50 μg SPA4 peptide, comparable to 2.5 μg/g body weight, alleviates LPS-induced lung inflammation.

Gut-lung axis: The microbial contributions and clinical implications

Gut microbiota interacts with host immune system in ways that influence the development of disease. Advances in respiratory immune system also broaden our knowledge of the interaction between host and microbiome in the lung. Increasing evidence indicated the intimate relationship between the gastrointestinal tract and respiratory tract. Exacerbations of chronic gut and lung disease have been shown to share key conceptual features with the disorder and dysregulation of the microbial ecosystem. In this review, we discuss the impact of gut and lung microbiota on disease exacerbation and progression, and the recent understanding of the immunological link between the gut and the lung, the gut-lung axis.

Baicalin exerts protective effects against lipopolysaccharide-induced acute lung injury by regulating the crosstalk between the CX3CL1-CX3CR1 axis and NF-κB pathway in CX3CL1-knockout mice

Acute lung injury (ALI) as a serious diseases with high mortality and is considered a threat to human health and life. A number of studies have focused on the treatment and prevention of lung injury. However, the molecular mechanisms responsible for the development of lung injury are not yet fully understood, and this has impeded the development of effective drugs and treatment strategies. Hence, in the present study, mice with lipopolysaccharide (LPS)-induced ALI were used as a model to investigate the crosstalk between the CX3CL1-CX3CR1 axis and the nuclear factor (NF)-κB signaling pathway in the process of lung injury. CX3CL1-knockout (CX3CL1-KO or CX3CL1^−/−) mice were used to examine the role of the CX3CL1-CX3CR1 axis in LPS-induced lung injury. We used baicalin, a natural product, to investigate its anti-inflammatory effects and its protective effects against lung injury. Western blot analysis, reverse transcription-quantitavie PCR (RT-qPCR), immunohistochemistry, enzyme-linked immunosorbent assay (ELISA) and the analysis of biochemical indicators were used to determine the key signaling pathway involved in the development of lung injury. The results indicated that, on the one hand, baicalin exerted potent anti-inflammatory effects by inhibiting the activation of the CX3CL1-CX3CR1 axis and NF-κB, thus preventing the the crosstalk between the CX3CL1-CX3CR1 axis and NF-κB pathway. In addition, the phosphorylation of AKT, which was significantly induced by LPS-induced ALI through the CX3CL1-CX3CR1 axis, was inhibited by treatment with baicalin. On the other hand, we further investigated the role of the CX3CL1-CX3CR1 axis in lung injury. We determined the diffrences in the expression levels of CX3CR1 between wild-type (WT) and CX3CL1^−/− mice in order to establish its association with lung injury. Our results indicated that CX3CL1 may be the central and major indicator in the process of lung injury, which mediates the CX3CR1 receptor to activate AKT and further promote NF-κB activation. These findings demonstrate that the crosstalk between the CX3CL1-CX3CR1 axis and NF-κB signaling pathway plays a direct role in LPS-induced lung injury. The inhibition of the activation of the CX3CL1-CX3CR1 axis may thus suppress the development of ALI. In addition, baicalin inhibited the crosstalk between the CX3CL1-CX3CR1 axis and NF-κB pathway in mice with LPS-induced ALI. Thus, treatment with baicalin may be a potential therapeutic strategy for ALI.

Mouse Models of Acute Respiratory Distress Syndrome: A Review of Analytical Approaches, Pathologic Features, and Common Measurements

Acute respiratory distress syndrome (ARDS) is a severe pulmonary reaction requiring hospitalization, which is incited by many causes, including bacterial and viral pneumonia as well as near drowning, aspiration of gastric contents, pancreatitis, intravenous drug use, and abdominal trauma. In humans, ARDS is very well defined by a list of clinical parameters. However, until recently no consensus was available regarding the criteria of ARDS that should be evident in an experimental animal model. This lack was rectified by a 2011 workshop report by the American Thoracic Society, which defined the main features proposed to delineate the presence of ARDS in laboratory animals. These should include histological changes in parenchymal tissue, altered integrity of the alveolar capillary barrier, inflammation, and abnormal pulmonary function. Murine ARDS models typically are defined by such features as pulmonary edema and leukocyte infiltration in cytological preparations of bronchoalveolar lavage fluid and/or lung sections. Common pathophysiological indicators of ARDS in mice include impaired pulmonary gas exchange and histological evidence of inflammatory infiltrates into the lung. Thus, morphological endpoints remain a vital component of data sets assembled from animal ARDS models.

Instilled air promotes lipopolysaccharide-induced acute lung injury

Optimization of intratracheal instillation is necessary to establish an ideal animal model of acute lung injury (ALI) in order to further reveal the cellular and molecular pathogenesis of ALI. It is possible that instilling air from a prefilled syringe may promote the delivery of reagents into the alveolar spaces, resulting in different pulmonary responses. In the present study, the influence of instilling air by trans-tracheal intratracheal instillation in a lipopolysaccharide (LPS)-induced mouse model of ALI was investigated. The bronchoalveolar lavage (BAL) fluid biochemical index, BAL fluid differential cell counts, lung wet/dry weight ratio, lung histology and BAL fluid interleukin-8 (IL-8) levels were assessed 24 h subsequent to intratracheal instillation. Instilled air promoted LPS-induced ALI, as indicated by the severity of acute pulmonary inflammation and increased IL-8 release. In conclusion, this study indicates that instilled air may be used to improve the intratracheal instillation procedure and to establish a more reliable animal model of ALI.