Introduction: Major trauma is any tissue injury that can lead to disability or death. Regardless of the site of trauma, patients suffer from acute lung failure and often require ventilation. Unfortunately, ventilator-dependence increased the risk of bacterial lung pneumonia. Using a mouse trauma model, in the form of skin burn injury, we revealed that the infiltration of granulocytes in the lungs, praticularly neutrophils, contribute to a loss of pulmonary function. Early post-injury, systemically upregulated transforming growth factor beta (TGFβ) drove neutrophil accumulation and clustering (cell-cell interactions) in the lung capillaries, and elevated expression of program death ligand-1 (PD-L1) and cluster of differentiation 80 (CD80) on neutrophils. However, the function of PD-L1 and CD80 on neutrophils is unclear. Neutrophils are known to be highly motile, allowing them to respond swiftly to infection. The mechanism by which injury-induced TGFβ affects neutrophil microbicidal ability, however, remains unkown. Hypothesis: We hypothesize that neutrophils cluster through PD-L1 and CD80 interaction, resulting in reduced motility and compromised microbicidal ability. Methods and Results: Using extracted mouse neutrophils, confocal microscopy revealed colocalization of PD-L1 and CD80 on clustered neutrophils following TGFβ treatment. To determine how TGFβ-induced clustering affects neutrophil motility, we generated mice with neutrophil-specific TGFβ receptor 2 (Tgfbr2) depletion (Tgfbr2fl/fl MRP8cre/+). Lung intravital microscopy revealed that, while injury reduced displacement and velocity of WT mice neutrophils, Tgfbr2KO neutrophils partially restored their migration ability. Conclusion and Impacts: Burn injured patients are acutely susceptible to bacterial pneumonia with no alternative treatment for multi-drug resistant pathogens. In this study, we revealved a TGFβ induced PD-L1-CD80 inetraction on neutrophils, causing clustering and restricted motility. Characterization of injury-induced phenotypic and functional changes of neutrophils insight into alternative treatments for antimicrobial bacterial pneumonia in not only burn-injured patients, but also other major trauma and infectious diseases.

The revascularisation of ischemic skeletal muscle is associated with remote organ injury including lungs. Mobilisation of activated polymorphonuclear neutrophils and monocyte to the lungs after the reperfusion of ischemic lower limb results mainly from the release of inflammatory mediators from the ischemic tissue and leukocyte trapping into the remote organ. The CD36 scavenger receptor (SR-B2) is widely expressed in many immune and non immune cells. In this study, we investigated the effect of a CD36 receptor ligand, EP 80317 (Haic-D-Trp(2-Me)-D-Lys-Trp-D-Phe-Lys-NH2), in lung inflammation after hind limb ischemia-reperfusion in wild-type C57BL/6J mice. All the experiment protocols have been approved by the Institutional Animal Ethics Committee under the guidelines of the Canadian Council for Animal Care. Male C57BL/6J mice (CD36+/+ and CD36-/-) were pretreated daily for 14 days with 300 μg/kg of EP 80317 or 0.9% vehicle subcutaneously. Mice, under isoflurane anaesthesia, were subjected to 30 minute occlusion of the right hind limb blood flow by the application of a rubber band upstream of the femoral muscle, followed by 3 hours of reperfusion. Mice were euthanized by an overdose of isoflurane and exsanguination, and tissues were collected. The results show a marked reduction of leukocytes in lung homogenates as assessed by the myeloperoxidase assay, by 39% in EP 80317-treated mice compared to vehicle treated mice (p<0.001). In contrast, no change was observed in CD36-/- mice. Interleukin-1beta levels were reduced by 29% (p<0.05) in the lung homogenate of mice treated with EP80317. Morover, leukotriene B4 (LTB4) and prostaglandin E2 (PGE2) levels were reduced by 22% (p<0.05) and 53% (p<0.05), respectively in lung homogenates whereas no change was observed in Cd36-deficient mice. A reduction in malonyldialdehyde concentrations of 49% (p < 0.05) was observed, but these levels remained unchanged in CD36-deficient mice. These results show, for the first time, that targeting the CD36 receptor reduces lung inflammation by attenuating the generation of the lipid mediators LTB4 and PGE2, in addition to reducing cytokine and systemic indices of oxidative stress. These results suggest that the CD36 receptor could be a target for the treatment of remote pulmonary inflammation.

Introduction: Stress influences the immune system according to the nature, intensity, and time during which stress is experienced. It is well established that the consequences of stress on developing brains and cortisol production are sex-specific. However, there is limited knowledge on the long-term impact of early life stress on immune responses. Given that immune programming occurs early in life and that immunity and stress both involve sexual dimorphisms, our hypothesis is that early life stress induces sex-specific immune alterations. Objective: Our objective is to evaluate the sex-specific impact of early life stress in adults on lung immune response. Methods: We used a well-established rat model of early life stress: neonatal maternal separation (NMS). Lung antimicrobial inflammatory responses to either Poly I:C or LPS were assessed in adult female and male control (CTRL) and NMS. Innate and adaptative immune cells from broncho-alveolar lavage (BAL) of adult rats were identified using flow cytometry. Results: We observed that activation of adaptative immune responses (including B and T cells) is stronger in female NMS compared to controls. Interestingly, NMS increased BAL cell recruitment after LPS exposure, especially in male NMS, whereas after Poly I:C exposure, we observed lower recruitment of cells in BAL, markedly in female NMS. Moreover, the proportion of alveolar macrophages was higher in female NMS compared to male NMS after LPS exposure only. On the other hand, we demonstrated that following LPS exposure, male NMS had an increased neutrophilic inflammation whereas following Poly I:C exposure, neutrophilic inflammation appears in female NMS. Conclusion: These results suggest that anti-viral and anti-bacterial responses are sex-specifically altered by NMS, even though corticosterone dysregulation after NMS is only observed in males. The impact of NMS on long-term immune response could originate from sex-specific alteration of bone-marrow immune progenitors.

Pulmonary hypertension (PH) is a severe disease that arises from multiple etiologies, leading to right ventricular failure and death. Pulmonary perivascular inflammation has gradually gained increased attention as an early common hallmark across different PH groups. Most of the used treatments target the pulmonary vasoconstriction (PGI2 analogus, ET-1 inhibitors and Phosphodiesterase inhibitors) that stimulate smooth muscle cell relaxation. However, pulmonary hypertension remains associated with significant morbidity.We therefore hypothesised that inflammation plays a crucial role in the severity of abnormal vasoconstriction in PH. Based on this hypothesis, we have selected a candidate family of bioactive lipids: omega-3 fatty acid (EPA, DHA and DPA) and their metabolits with high resolving potential, called the SPM for specialised proresolving mediators (resolvins, protectins and maresins). Human pulmonary arteries (HPA) derived from PH or non-PH patients were gathered at Bichat hospital. Using an isolated organ system, we have assessed the functional effects of EPA, DHA, and DPA alone and in combination with vasoactive compounds relevant to the pathology. Furthermore, we have examined the underlying mechanisms of the observed effects on each signalling pathway by using western blot and ELISA. We measured the endogenous SPM expressed in pulmonary vascular tissue (+/- PH) with LC/MS-MS after a stimulation with omega-3, and finally we describe the localization and transcript level of the enzymes involved in the SPM biosynthesis and their receptors in the human pulmonary vascular wall respectively with RT-qPCR and immunofluorescence. In summary, our findings indicate that omega-3 fatty acids, and their metabolites the SPM possess inherent vasorelaxant properties, especially in non-PH HPA. However, in the context of PH, these relaxing effects seem to diminish. Additionally, our investigations unveiled intriguing interactions between omega-3 fatty acids, notably DHA and DPA, with HPA responses to Iloprost (enhancement of vasorelaxation) and Prostaglandin E2 (reduction of vasoconstriction) for both non-PH and PH HPA.