Middle age exacerbates acute respiratory distress syndrome in a double hit murine model

Lymphatic Flow: A Potential Target in Sepsis-Associated Acute Lung Injury

Sepsis is life-threatening organ dysfunction caused by an imbalance in the body’s response to infection and acute lung injury (ALI) related to sepsis is a common complication. The rapid morbidity and high mortality associated with sepsis is a significant clinical problem facing critical care medicine. Inflammation plays a vital role in the occurrence of sepsis. Notably, the body produces different immune cells and pro-inflammatory factors to clear pathogens. However, excessive inflammation can damage multiple tissues and organs when it fails to resolve in time. Additionally, lymphatic vessels could effectively transfer inflammatory cells and factors away from tissues and into blood circulation, thereby reducing damage, and promoting the resolution of inflammation. Therefore, any dysfunction and/or destruction of the lymphatic system may result in lymphedema followed by inflammatory storms and eventual sepsis. Consequently, the present study aimed to review and highlight the role of lymphatic vessels in related body tissues and organs during sepsis and other associated diseases.

Oxycodone attenuates vascular leak and lung inflammation in a clinically relevant two-hit rat model of acute lung injury

BACKGROUND

Oxycodone is a synthetic opioid receptor agonist that exerts antinociceptive activity via κ-, μ- and δ-opioid receptors (KOR, MOR and DOR, respectively). Activation of MOR has been reported to provide protection against acute lung injury (ALI). We hypothesized that pretreatment with oxycodone would attenuate lung injury at the level of alveolar tight junctions (TJs) and aquaporins (AQPs) and investigated this possibility in a two-hit model of ALI induced by lipopolysaccharide (LPS) and mechanical ventilation (MV).

METHOD

Male Sprague Dawley rats and A59 cells were divided into 6 groups: the control group, ALI group, oxycodone-pretreated group, and oxycodone/κ-, μ-, or δ-opioid receptor antagonist-pretreated groups. The rats were pretreated with oxycodone 30 min before intravenous injection of LPS and then allowed to recover for 24 h prior to MV, establishing a two-hit model of ALI. The cells were similarly treated with oxycodone (with or without antagonists) 30 min after exposure to lipopolysaccharide. The cells were cyclically stretched 24 h later to mirror the in vivo MV protocol.

RESULTS

Oxycodone alleviated the histological lung changes in the rats with ALI and decreased pulmonary microvascular permeability both in vivo and in vitro. Oxycodone upregulated the expression of claudin-5, ZO-1, AQP1, and AQP5 but downregulated the expression of TNF-α, IL-1β, TLR4, NF-κB, MMP9, and caspase-3 and suppressed endothelial apoptosis in vivo and in vitro. These protective effects of oxycodone were partly eliminated by KOR and MOR antagonists but not by DOR antagonists.

CONCLUSION

Oxycodone pretreatment appears to act via κ- and μ-opioid receptors to ameliorate LPS- and MV-induced lung injury by suppressing inflammation and apoptosis, and this protective effect might be mediated through the inhibition of the TLR4/NF-κB pathways.

Distal lung epithelial progenitor cell function declines with age

Tissue stem cell exhaustion is a key hallmark of aging, and in this study, we characterised its manifestation in the distal lung. We compared the lungs of 3- and 22-month old mice. We examined the gross morphological changes in these lungs, the density and function of epithelial progenitor populations and the epithelial gene expression profile. Bronchioles became smaller in their cross-sectional area and diameter. Using long-term EdU incorporation analysis and immunohistochemistry, we found that bronchiolar cell density remained stable with aging, but inferred rates of bronchiolar club progenitor cell self-renewal and differentiation were reduced, indicative of an overall slowdown in cellular turnover. Alveolar Type II progenitor cell density and self-renewal were maintained per unit tissue area with aging, but rates of inferred differentiation into Type I cells, and indeed overall density of Type I cells was reduced. Microarray analysis revealed age-related changes in multiple genes, including some with roles in proliferation and differentiation, and in IGF and TGFβ signalling pathways. By characterising how lung stem cell dynamics change with aging, this study will elucidate how they contribute to age-related loss of pulmonary function, and pathogenesis of common age-related pulmonary diseases.

Pulmonary Effects of Adjusting Tidal Volume to Actual or Ideal Body Weight in Ventilated Obese Mice

Obese patients could be more susceptible to mechanical ventilation (MV)-induced lung injury than non-obese patients due to weight-dependent changes in lung properties. The aim of this study was therefore to evaluate the pulmonary effects of 2 hours low V_T MV in a diet-induced obese mice model, with V_T calculated on either the actual body weight (V_Taw) or the ideal body weight (V_Tiw) . First, we hypothesized that a MV with V_Taw would be associated with altered lung mechanics and an increased lung inflammation. Second, we hypothesised that a MV with a V_Tiw would preserve lung mechanics and limit lung inflammation. We analyzed lung mechanics and inflammation using bronchoalveolar lavage (BAL) cell counts, flow cytometry tissue analysis and histology. Lung mechanics and inflammation were comparable in control and obese mice receiving V_Tiw. By contrast, obese mice receiving V_Taw had significantly more alterations in lung mechanics, BAL cellularity and lung influx of monocytes as compared to control mice. Their monocyte expression of Gr1 and CD62L was also increased. Alveolar neutrophil infiltration was significantly increased in all obese mice as compared to controls. In conclusion, our findings suggest that protective MV with a V_Taw is deleterious, with a marked alteration in lung mechanics and associated lung inflammation as compared to lean mice. With V_Tiw, lung mechanics and inflammation were close to that of control mice, except for an increased alveolar infiltrate of polymorphonuclear neutrophils. This inflammation might be attenuated by a blunted recruitment of inflammatory cells associated with obesity.