Rationale: Acute lung injury (ALI) is an important cause of morbidity and mortality, with no currently effective pharmacological therapies. Neutrophils have been specifically implicated in the pathogenesis of ALI, and there has been significant research into the mechanisms of early neutrophil recruitment, but those controlling the later phases of neutrophil emigration that characterize disease are poorly understood. Objectives: To determine the influence of peripheral blood monocytes (PBMs) in established ALI. Methods: In a murine model of LPS-induced ALI, three separate models of conditional monocyte ablation were used: systemic liposomal clodronate (sLC), inducible depletion using CD11b diphtheria toxin receptor (CD11b DTR) transgenic mice, and antibodydependent ablation of CCR2 hi monocytes. Measurements and Main Results: PBMs play a critical role in regulating neutrophil emigration in established murine LPS-induced lung injury. Gr1 hi and Gr1 lo PBM subpopulations contribute to this process. PBM depletion is associated with a significant reduction in measures of lung injury. The specificity of PBM depletion was demonstrated by replenishment studies in which the effects were reversed by systemic PBM infusion but not by systemic or local pulmonary infusion of mature macrophages or lymphocytes. Conclusions: These results suggest that PBMs, or the mechanisms by which they influence pulmonary neutrophil emigration, could represent therapeutic targets in established ALI. Keywords: acute lung injury; LPS; monocytes; neutrophilsThe innate inflammatory response is geared to the clearance of pathogens, but excessive and persistent granulocyte accumulation is detrimental to the host (1). Acute lung injury (ALI) and its severe form, acute respiratory distress syndrome (ARDS), are characterized by neutrophil-mediated lung injury, the most common etiology being severe sepsis (2). Neutrophil-mediated lung injury of the epithelial/endothelial interface and consequent vascular leak are the hallmarks of ALI/ARDS (2-4). There are 200,000 cases per year of ALI in the United States, with a mortality of approximately 40% (2). No pharmacological agents have been shown convincingly to affect mortality. There is thus a pressing need to define critical mediators of neutrophil recruitment and to implement specific, mechanismbased therapeutic interventions.The neutrophilic response in ALI has been described as occurring in two distinct phases (5): an initial "recruitment phase" mediated by chemokines followed by a "persistent phase" of neutrophil recruitment, possibly mediated in part by stromal-derived factor-1 (SDF-1/CXCL12) (5). Patients often present with established lung inflammation, and interventions must therefore be guided toward this second phase of neutrophil recruitment to reduce lung injury and ventilator dependence. The underlying cellular mechanisms driving this second phase of neutrophil recruitment remain to be fully characterized.Peripheral blood monocytes (PBMs) are recruited alongside neutrophils in acute inflammati...

Respiratory infections in mechanically ventilated patients caused by Gram-negative bacteria are a major cause of morbidity. Rapid and unequivocal determination of the presence, localization, and abundance of bacteria is critical for positive resolution of the infections and could be used for patient stratification and for monitoring treatment efficacy. Here, we developed an in situ approach to visualize Gram-negative bacterial species and cellular infiltrates in distal human lungs in real time. We used optical endomicroscopy to visualize a water-soluble optical imaging probe based on the antimicrobial peptide polymyxin conjugated to an environmentally sensitive fluorophore. The probe was chemically stable and nontoxic and, after in-human intrapulmonary microdosing, enabled the specific detection of Gram-negative bacteria in distal human airways and alveoli within minutes. The results suggest that pulmonary molecular imaging using a topically administered fluorescent probe targeting bacterial lipid A is safe and practical, enabling rapid in situ identification of Gram-negative bacteria in humans.

A fluorescently labelled ubiquicidin peptide enables bacterial detection in human lung tissue in vitro.

BackgroundAcute respiratory distress syndrome (ARDS) is an often fatal neutrophil-dominant lung disease. Although influenced by multiple proinflammatory mediators, identification of suitable therapeutic candidates remains elusive. We aimed to delineate the presence of mitochondrial formylated peptides in ARDS and characterise the functional importance of formyl peptide receptor 1 (FPR1) signalling in sterile lung inflammation.MethodsMitochondrial formylated peptides were identified in bronchoalveolar lavage fluid (BALF) and serum of patients with ARDS by liquid chromatography–tandem mass spectrometry. In vitro, human neutrophils were stimulated with mitochondrial formylated peptides and their effects assessed by flow cytometry and chemotaxis assay. Mouse lung injury was induced by mitochondrial formylated peptides or hydrochloric acid. Bone marrow chimeras determined the contribution of myeloid and parenchymal FPR1 to sterile lung inflammation.ResultsMitochondrial formylated peptides were elevated in BALF and serum from patients with ARDS. These peptides drove neutrophil activation and chemotaxis through FPR1-dependent mechanisms in vitro and in vivo. In mouse lung injury, inflammation was attenuated in Fpr1−/− mice, effects recapitulated by a pharmacological FPR1 antagonist even when administered after the onset of injury. FPR1 expression was present in alveolar epithelium and chimeric mice demonstrated that both myeloid and parenchymal FPR1 contributed to lung inflammation.ConclusionsWe provide the first definitive evidence of mitochondrial formylated peptides in human disease and demonstrate them to be elevated in ARDS and important in a mouse model of lung injury. This work reveals mitochondrial formylated peptide FPR1 signalling as a key driver of sterile acute lung injury and a potential therapeutic target in ARDS.

Citation for published item:urstji¡ D xikol nd ekrmD ehsn F nd ghoudhryD ushr F nd whonldD xeil nd nnerD wihel qF nd edrettiD ittore nd hlgrnoD ul eF nd hole(eldD imm nd qirkinD tohn wF nd wooreD enne nd frdleyD wrk nd hhliwlD uevin @PHITA 9woEolor wide(eld )uoresene miroendosopy enles multiplexed moleulr imging in the lveolr spe of humn lung tissueF9D tournl of iomedil optisFD PI @RAF HRTHHWF Further information on publisher's website: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Abstract. We demonstrate a fast two-color widefield fluorescence microendoscopy system capable of simultaneously detecting several disease targets in intact human ex vivo lung tissue. We characterize the system for light throughput from the excitation light emitting diodes, fluorescence collection efficiency, and chromatic focal shifts. We demonstrate the effectiveness of the instrument by imaging bacteria (Pseudomonas aeruginosa) in ex vivo human lung tissue. We describe a mechanism of bacterial detection through the fiber bundle that uses blinking effects of bacteria as they move in front of the fiber core providing detection of objects smaller than the fiber core and cladding (∼3 μm). This effectively increases the measured spatial resolution of 4 μm. We show simultaneous imaging of neutrophils, monocytes, and fungus (Aspergillus fumigatus) in ex vivo human lung tissue. The instrument has 10 nM and 50 nM sensitivity for fluorescein and Cy5 solutions, respectively. Lung tissue autofluorescence remains visible at up to 200 fps camera acquisition rate. The optical system lends itself to clinical translation due to high-fluorescence sensitivity, simplicity, and the ability to multiplex several pathological molecular imaging targets simultaneously.

A SPAD-based line sensor fabricated in 130 nm CMOS technology capable of acquiring time-resolved fluorescence spectra (TRFS) in 8.3 milliseconds is presented. To the best of our knowledge, this is the fastest time correlated single photon counting (TCSPC) TRFS acquisition reported to date. The line sensor is an upgrade to our prior work and incorporates: i) parallelized interface from sensor to surrounding circuitry enabling high line rate to the PC (19,000 lines/s) and ii) novel time-gating architecture where detected photons in the OFF region are rejected digitally after the output stage of the SPAD. The time-gating architecture was chosen to avoid electrical transients on the SPAD high voltage supplies when gating is achieved by excess bias modulation. The time-gate has an adjustable location and time window width allowing the user to focus on time-events of interest. On-chip integrated center-of-mass (CMM) calculations provide efficient acquisition of photon arrivals and direct lifetime estimation of fluorescence decays. Furthermore, any of the SPC, TCSPC and on-chip CMM modes can be used in conjunction with the time-gating. The higher readout rate and versatile architecture greatly empower the user and will allow widespread applications across many techniques and disciplines. Here we focused on 3 examples of TRFS and time-gated Raman spectroscopy: i) kinetics of chlorophyll A fluorescence from an intact leaf; ii) kinetics of a thrombin biosensor FRET probe from quenched to fluorescence states; iii) ex vivo mouse lung tissue autofluorescence TRFS; iv) time-gated Raman spectroscopy of toluene at 3056 cm peak. To the best of our knowledge, we detect spectrally for the first time the fast rise in fluorescence lifetime of chlorophyll A in a measurement over single fluorescent transient.

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Rapid in situ detection of pathogens coupled with high resolution imaging in the distal human lung has the potential to provide new insights and diagnostic utility in patients in whom pneumonia is suspected. We have previously described an antimicrobial peptide (AMP) Ubiquicidin (fragment UBI 29–41 ) labelled with an environmentally sensitive fluorophore that optically detected bacteria in vitro but not ex vivo . Here, we describe further chemical development of this compound and demonstrate that altering the secondary structure of the AMP to generate a tri-branched dendrimeric scaffold provides enhanced signal in vitro and ex vivo and consequently allows the rapid detection of pathogens in situ in an explanted human lung. This compound (NBD-UBI dend ) demonstrates bacterial labelling specificity for a broad panel of pathogenic bacteria and Aspergillus fumigatus . NBD-UBI dend demonstrated high signal-to-noise fluorescence amplification upon target engagement, did not label host mammalian cells and was non-toxic and chemically robust within the inflamed biological environment. Intrapulmonary delivery of NBD-UBI dend , coupled with optical endomicroscopy demonstrated real-time, in situ detection of bacteria in explanted whole human Cystic Fibrosis lungs.