The paradox of the neutrophil's role in tissue injury

Neutrophils in tissue injury and repair

As one of the first defenders of innate immune response, neutrophils make a rapid and robust response against infection or harmful agents. While traditionally regarded as suicidal killers that cause collateral tissue damage, recent findings on neutrophil extracellular trap formation, heterogeneity and plasticity and novel reparative functions have expanded our understanding of their diverse roles in health and disease. This review summarizes our current understanding of neutrophil-associated tissue injury, highlighting the emerging roles of neutrophil extracellular traps. This review will also focus on scrutinizing the roles of neutrophils in tissue repair and regeneration and will examine data on unexpected aspects of involvement of neutrophils in regulating normal tissue homeostasis.

Anti-inflammatory effect of stem bark of Paulownia tomentosa Steud. in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages and LPS-induced murine model of acute lung injury

ETHNOPHARMACOLOGICAL RELEVANCE

The leaves, bark, and flowers of Paulownia tomentosa Steud. have been widely used as a traditional medicine in East Asia to treat inflammatory and infectious diseases.

AIM OF THE STUDY

We investigated the protective effect of the methanol stem bark extract of P. tomentosa using an animal model of lipopolysaccharide (LPS)-induced acute lung injury (ALI).

MATERIALS AND METHODS

The UPLC Q-TOF-MS profiles for the methanol extract of P. tomentosa stem bark showed that verbascoside and isoverbascoside were the predominant compounds. Raw 264.7 cells were used for inhibitory effects of cytokine production in vitro. C57BL/6N mice were administered intranasally with LPS (10μg/per mouse) to induce ALI. H&E staining was used to evaluate histological changes in the lung.

RESULTS

Treatment with P. tomentosa stem bark extract (PTBE) suppressed the production of IL-6 and TNF-α in LPS-stimulated RAW 264.7 macrophages, and the recruitment of neutrophils and macrophages in the BALF of mice with LPS-induced ALI. PTBE also decreased the levels of reactive oxygen species (ROS) and pro-inflammatory cytokines in the BALF. PTBE reduced the levels of nitric oxide (NO) in the serum and of inducible nitric oxide synthase (iNOS) in the lung of ALI mice. PTBE also attenuated the infiltration of inflammatory cells and the expression of monocyte chemoattractant protein-1 (MCP-1) in the lung. In addition, PTBE suppressed the activation of NF-κB and the reduced expression of superoxide dismutase 3 (SOD3) in the lung.

CONCLUSION

The results suggest that PTBE has a protective effect on LPS-induced ALI.

Fracture initiates systemic inflammatory response syndrome through recruiting polymorphonuclear leucocytes

Fracture, a common type injury in trauma patients, often results in the development of the systemic inflammatory response syndrome (SIRS). Though the mechanism of the fracture-initiated SIRS still remains not well characterized, it is well documented that the polymorphonuclear leucocytes (PMN) play an important role in the inflammatory process. We hypothesize that fractures recruit PMN to the local tissue, which is followed by an increase in the number of peripheral PMN and initiation of SIRS. In the current study, we established a closed femoral fracture rat model. We evaluated the levels of MPO, IL-1β and CINC-1 in fractured tissue homogenate, and we measured the levels of IL-6 and IL-10, the biomarkers for systemic inflammatory response, in the rat sera. In clinical part of the study, we collected blood from patients with isolated closed femoral fractures and evaluated PMN-related chemoattractants (IL-8, IL-1β and G-CSF) and the number of peripheral PMN. We further evaluated the level of mitochondrial DNA in the local haematoma of fracture and the circulating plasma of the patients with fracture. In the animal model of closed femoral fracture, we found a significant recruitment of PMN to the local tissue after fracture, which correlates with the elevated MPO level. We also showed that the concentration of IL-1β and CINC-1 in local tissue is significantly increased and might be responsible for the PMN recruitment. Recruitment of PMN to the local tissue was accompanied with a significant increase in the systemic levels of IL-6 and IL-10 in serum. In the patients with closed femoral fracture, we observed an increase in the number of peripheral PMN and PMN-related chemoattractants, including IL-8, IL-1β and G-CSF. The level of mitochondrial DNA in the local haematoma of fracture and the circulating plasma of patients were significantly higher compared to the healthy volunteers. Our data suggest that fracture released mitochondrial DNA into the local haematoma of fracture, which recruited the PMN into the local tissue via chemokines (IL-1β and CINC-1), then increased the numbers of peripheral PMN and SIRS related cytokines in serum (IL-6 and IL-10). This might be the mechanism of the fracture-initiated SIRS.

Neutrophil-Lymphocyte Ratio: Prognostic Impact in Heart Surgery. Early Outcomes and Late Survival

BACKGROUND

The neutrophil-lymphocyte ratio (NLR) is a recognized marker of inflammation associated with poor outcomes in various clinical situations. We analyzed the prognostic significance of preoperative elevated NLR in patients undergoing cardiac surgery.

METHODS

We performed a retrospective review of 3,027 consecutive patients undergoing cardiac surgery. Receiver-operating-characteristic was used to determine the cutoff value for elevated NLR. Multivariate regression was used to determine the predictive value of preoperative NLR on clinical outcomes. Cox proportional hazards functions were used to determine predictors of late events. Late survival data to 16 years was obtained from the Ministry of Interior.

RESULTS

The cutoff value for elevated NLR was 2.6. Patients with elevated NLR were older (p < 0.0001), had a higher incidence of cardiac comorbidity (p < 0.0001), and higher European System for Cardiac Operative Risk Evaluation score (p < 0.0001). An elevated NLR emerged as an independent predictor of operative mortality (hazard ratio [HR] 2.15, 95% confidence interval [CI]: 1.51 to 3.08, p < 0.0001); pleural effusion (HR 1.42, 95% CI: 1.13 to 1.80, p = 0.003); low output syndrome (HR 1.54, 95% CI: 1.23 to 1.93, p = 0.0002); prolonged ventilation (HR 1.49, 95% CI: 1.23 to 1.82, p = 0.0001); or composite outcomes (HR 1.61, 95% CI: 1.36 to 1.91, p < 0.0001). The NLR emerged as an independent predictor of late mortality (HR 1.19, 95% CI: 1.11 to 1.28; p < 0.0001).

CONCLUSIONS

Elevated NLR is associated with a higher incidence of adverse outcomes after cardiac surgery. It is a predictor of operative as well as late mortality. Further studies are warranted to determine whether prophylactic treatment with antiinflammatory agents can prevent such outcomes. It may be warranted to include the baseline NLR as another variable in risk stratification of patients about to undergo cardiac surgery.

Contribution of In Vivo and Organotypic 3D Models to Understanding the Role of Macrophages and Neutrophils in the Pathogenesis of Psoriasis

Psoriasis, a common chronic immune-mediated skin disease, is histologically characterized by a rapid keratinocyte turnover and differentiation defects. Key insights favor the idea that T cells are not the only key actors involved in the inflammatory process. Innate immune cells, more precisely neutrophils and macrophages, provide specific signals involved in the initiation and the maintenance of the pathogenesis. Current data from animal models and, to a lesser extent, three-dimensional in vitro models have confirmed the interest in leaning towards other immune cell types as a potential new cellular target for the treatment of the disease. Although these models do not mimic the complex phenotype nor all human features of psoriasis, their development is necessary and essential to better understand reciprocal interactions between skin cells and innate immune cells and to emphasize the crucial importance of the local lesional microenvironment. In this review, through the use of in vivo and 3D organotypic models, we aim to shed light on the crosstalk between epithelial and immune components and to discuss the role of secreted inflammatory molecules in the development of this chronic skin disease.

Interleukin-17A Aggravates Middle Ear Injury Induced by Streptococcus pneumoniae through the p38 Mitogen-Activated Protein Kinase Signaling Pathway

Acute otitis media (AOM) is one of the most common bacterial infectious diseases in children aged 2 to 7 years worldwide. We previously demonstrated that interleukin-17A (IL-17A) promotes an acute inflammatory response characterized by the influx of neutrophils into the middle ear cavity during Streptococcus pneumoniae-induced AOM. In general, the inflammatory response is viewed as an effector that frequently causes local tissue damage. However, little is known about the pathogenic effects of IL-17A in AOM. Here, we investigated the pathogenic effects of IL-17A by using wild-type (WT) and IL-17A knockout (KO) mouse models. The results showed that the pathogenic effects of AOM, including weight loss, histopathological changes, and proinflammatory cytokine production, were more severe in WT mice than in IL-17A KO mice, suggesting that IL-17A aggravates tissue damage in AOM. Furthermore, these pathogenic effects were found to be dependent on p38 mitogen-activated protein kinase (MAPK) and could be reversed in the presence of a p38 MAPK-specific inhibitor. It was also demonstrated that IL-17A promoted the production of neutrophil myeloperoxidase (MPO) through the p38 MAPK signaling pathway, which was responsible for the middle ear tissue injury. These data support the conclusion that IL-17A contributes to middle ear injury through the p38 MAPK signaling pathway.

Total Body Irradiation Mitigates Inflammation and Extends the Therapeutic Time Window for Anti-Ricin Antibody Treatment against Pulmonary Ricinosis in Mice

Ricin, a highly toxic plant-derived toxin, is considered a potential weapon in biowarfare and bioterrorism due to its pronounced toxicity, high availability, and ease of preparation. Pulmonary exposure to ricin results in the generation of an acute edematous inflammation followed by respiratory insufficiency and death. Massive neutrophil recruitment to the lungs may contribute significantly to ricin-mediated morbidity. In this study, total body irradiation (TBI) served as a non-pharmacological tool to decrease the potential neutrophil-induced lung injury. TBI significantly postponed the time to death of intranasally ricin-intoxicated mice, given that leukopenia remained stable following intoxication. This increase in time to death coincided with a significant reduction in pro-inflammatory marker levels, and led to marked extension of the therapeutic time window for anti-ricin antibody treatment.

Stingray venom activates IL-33 producing cardiomyocytes, but not mast cell, to promote acute neutrophil-mediated injury

One of the hallmarks of acute inflammation is neutrophil infiltration of tissues. We investigated molecular mechanisms implicated in acute neutrophilic inflammation induced by the venom of a freshwater stingray (Potamotrygon cf. henlei) in mice. Ray venom induced early mobilization of neutrophil in the microvasculature of cremaster mice and infiltration of the peritoneal cavity 2 hours after injury, in a dose-response manner. IL-1β, IL-6, TNF-α, and KC were produced. The neutrophilic infiltration did not occur in mice with ST2 receptor and MyD88 adapters neutralized, or in those with PI3K and p38 MAPK signaling blocked. Drastic reduction of neutrophil infiltration to peritoneal cavities was observed in ST2^−/−, TLR2/TLR4^−/−, MyD88^−/−, TRIF^−/− and IL-17A^−/− mice, and a partial reduction was observed in IL-18R^−/− mice. Mast cell Kit W(sh)/W(sh)-, AHR-, NLRP3-, ICE-, IL-1β-, P2RX7-, CD39-, IL-17RA-, and TBX21 KO mice retain the ability to induce neutrophilia in peritoneal cavity after ray venom injection. IL-6 and TNF-α alone were insufficient for promote neutrophilia in the absence of ST2 signaling. Finally, abundant production of IL-33 by cardiomyocytes was observed. These results refine our understanding of the importance of the IL-33/ST2 axis and IL-33-producing cardiomyocytes in the early acute neutrophilia induced by freshwater stingray venoms.

Anti-inflammatory effects of rosmarinic acid-4-O-β-D-glucoside in reducing acute lung injury in mice infected with influenza virus

Rosmarinic acid-4-O-β-D-glucoside (RAG) is a dicaffeoyl phenolic compound isolated from Sarcandra glabra (Thunb.) Nakai. Preliminary studies show that RAG has significant anti-inflammatory properties and can alleviate ear swelling in mice and the paw swelling in rats. Here, the anti-influenza effects of RAG were investigated in mice infected with A/FM/1/47 H1N1 virus. The survival rate and body weight were observed, the lung edema, virus copies, inflammatory cytokines (including IL-4, IL-5, TNF-α and IFN-γ) and oxidative damage indexes (including SOD, MDA, NO, and CAT) were measured. Moreover, immune cell recruitment in alveoli was measured with white blood cells and differential counts. Therapeutic RAG concentrations substantially improve the symptoms, mitigate body weight loss and alleviate lung edema induced by virus, thus improve survival protection effects. Furthermore, RAG was shown to regulate influenza virus-induced inflammatory cytokine expression, specifically by downregulating the Th1 cell cytokines IFN-γ, TNF-α and upregulating the Th2 cell cytokines IL-4, IL-5. Cell migration and infiltration were also diminished after RAG administration.

The blood-borne sialyltransferase ST6Gal-1 is a negative systemic regulator of granulopoiesis

Responding to systemic demands in producing and replenishing end-effector blood cells is predicated on the appropriate delivery and interpretation of extrinsic signals to the HSPCs. The data presented herein implicate the systemic, extracellular form of the glycosyltransferase ST6Gal-1 in the regulation of late-stage neutrophil development. ST6Gal-1 is typically a membrane-bound enzyme sequestered within the intracellular secretory apparatus, but an extracellular form is released into the blood from the liver. Both human and murine HSPCs, upon exposure to extracellular ST6Gal-1 ex vivo, exhibited decreased proliferation, diminished expression of the neutrophilic primary granule protein MPO, and decreased appearance of CD11b+ cells. HSPC suppression was preceded by decreased STAT-3 phosphorylation and diminished C/EBPα expression, without increased apoptosis, indicating attenuated G-CSF receptor signaling. A murine model to raise systemic ST6Gal-1 level was developed to examine the role of the circulatory enzyme in vivo. Our results show that systemic ST6Gal-1 modified the cell surface of the GMP subset of HSPCs and decreased marrow neutrophil reserves. Acute airway neutrophilic inflammation by LPS challenge was used to drive demand for new neutrophil production. Reduced neutrophil infiltration into the airway was observed in mice with elevated circulatory ST6Gal-1 levels. The blunted transition of GMPs into GPs in vitro is consistent with ST6Gal-1-attenuated granulopoiesis. The data confirm that circulatory ST6Gal-1 is a negative systemic regulator of granulopoiesis and moreover suggest a clinical potential to limit the number of inflammatory cells by manipulating blood ST6Gal-1 levels.

Luminol-amplified chemiluminescence detects mainly superoxide anion produced by human neutrophils

Reactive oxygen species (ROS) are produced by numerous biological systems and by several phagocytes such as neutrophils and macrophages. ROS include mostly superoxide anion, hydrogen peroxide, singlet oxygen and hydroxyl radical, which are involved in a variety of biological processes such as immunity, inflammation, apoptosis and cell signaling. Thus, there is a need for a sensitive and reliable method to measure ROS. The luminol-amplified chemiluminescence technique is widely used to measure ROS production by neutrophils; however, it is unclear which ROS species are detected by this technique. In this study, we show that Xanthine/Xanthine oxidase (XXO), a known superoxide-producing system, stimulated a luminol-amplified chemiluminescence in the absence of horseradish peroxidase (HRPO), while the presence of HRPO enhanced the response. Both reactions were inhibited by superoxide dismutase (SOD), but not by catalase, confirming that superoxide anion, and not hydrogen peroxide, is the species oxidizing luminol to produce chemiluminescence. Glucose/Glucose oxidase (GGO), a known hydrogen peroxide-producing system, did not induce luminol-amplified chemiluminescence in the absence of HRPO; however, addition of HRPO resulted in a chemiluminescence response, which was inhibited by catalase, but not by SOD. Myeloperoxidase (MPO), isolated from human neutrophils, was also able to enhance the superoxide- and hydrogen peroxide-dependent luminol-amplified chemiluminescence. The production of ROS by stimulated human neutrophils was detected by luminol-amplified chemiluminescence, which was only partially inhibited by SOD and catalase. Interestingly, adding HRPO to stimulated neutrophils increased the luminol-amplified chemiluminescence, which was strongly inhibited by SOD, but not by catalase. These results show that (a) luminol-amplified chemiluminescence is able to detect superoxide anion in the absence of peroxidases, but not hydrogen peroxide; (b) in the presence of peroxidases, luminol-amplified chemiluminescence is able to detect both superoxide anion and hydrogen peroxide; and

Priming of the neutrophil respiratory burst: role in host defense and inflammation

Neutrophils are the major circulating white blood cells in humans. They play an essential role in host defense against pathogens. In healthy individuals, circulating neutrophils are in a dormant state with very low efficiency of capture and arrest on the quiescent endothelium. Upon infection and subsequent release of pro-inflammatory mediators, the vascular endothelium signals to circulating neutrophils to roll, adhere, and cross the endothelial barrier. Neutrophils migrate toward the infection site along a gradient of chemo-attractants, then recognize and engulf the pathogen. To kill this pathogen entrapped inside the vacuole, neutrophils produce and release high quantities of antibacterial peptides, proteases, and reactive oxygen species (ROS). The robust ROS production is also called 'the respiratory burst', and the NADPH oxidase or NOX2 is the enzyme responsible for the production of superoxide anion, leading to other ROS. In vitro, several soluble and particulate agonists induce neutrophil ROS production. This process can be enhanced by prior neutrophil treatment with 'priming' agents, which alone do not induce a respiratory burst. In this review, we will describe the priming process and discuss the beneficial role of controlled neutrophil priming in host defense and the detrimental effect of excessive neutrophil priming in inflammatory diseases.

Underlying chronic inflammation alters the profile and mechanisms of acute neutrophil recruitment

Chronically inflamed tissues show altered characteristics that include persistent populations of inflammatory leukocytes and remodelling of the vascular network. As the majority of studies on leukocyte recruitment have been carried out in normal healthy tissues, the impact of underlying chronic inflammation on ongoing leukocyte recruitment is largely unknown. Here, we investigate the profile and mechanisms of acute inflammatory responses in chronically inflamed and angiogenic tissues, and consider the implications for chronic inflammatory disorders. We have developed a novel model of chronic ischaemia of the mouse cremaster muscle that is characterized by a persistent population of monocyte‐derived cells (MDCs), and capillary angiogenesis. These tissues also show elevated acute neutrophil recruitment in response to locally administered inflammatory stimuli. We determined that Gr1^lowMDCs, which are widely considered to have anti‐inflammatory and reparative functions, amplified acute inflammatory reactions via the generation of additional proinflammatory signals, changing both the profile and magnitude of the tissue response. Similar vascular and inflammatory responses, including activation of MDCs by transient ischaemia–reperfusion, were observed in mouse hindlimbs subjected to chronic ischaemia. This response demonstrates the relevance of the findings to peripheral arterial disease, in which patients experience transient exercise‐induced ischaemia known as claudication.These findings demonstrate that chronically inflamed tissues show an altered profile and altered mechanisms of acute inflammatory responses, and identify tissue‐resident MDCs as potential therapeutic targets. © 2016 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Dipeptide HCH6-1 inhibits neutrophil activation and protects against acute lung injury by blocking FPR1

Formyl peptide receptor 1 (FPR1) is an emerging therapeutic target for the discovery of drugs to treat neutrophilic inflammatory diseases. However, development of FPR1 antagonists for clinical use is still inadequate. The purpose of this study was to identify a synthetic dipeptide N-(N-benzoyl-L-tryptophanyl)-D-phenylanlanine methyl ester (HCH6-1) as a FPR1 inhibitor and to investigate its protective effects against acute lung injury (ALI). HCH6-1 inhibited superoxide anion generation, elastase release, and chemotaxis in human neutrophils specifically activated by formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLF), an FPR1 agonist. HCH6-1 produced right shifts in the concentration-response curves of fMLF, suggesting that HCH6-1 was a competitive antagonist of FPR1. Indeed, HCH6-1 bound to FPR1 in human neutrophils and neutrophil-like THP-1 as well as hFPR1-transfected HEK293 cells. Also, the FPR1 downstream signaling pathways were competitively inhibited by HCH6-1. Furthermore, HCH6-1 prevented pulmonary neutrophil infiltration and edema along with alveolar damage in LPS-induced ALI in mice. Our findings suggest that HCH6-1, a FPR1 antagonist, may have potential as a new therapeutic agent for treating FPR1-involved inflammatory lung diseases.

Erythrocyte sialoglycoproteins engage Siglec-9 on neutrophils to suppress activation

Healthy blood neutrophils are functionally quiescent in the bloodstream, have a short lifespan, and exit the circulation to carry out innate immune functions, or undergo rapid apoptosis and macrophage-mediated clearance to mitigate host tissue damage. Limitation of unnecessary intravascular neutrophil activation is also important to prevent serious inflammatory pathologies. Because neutrophils become easily activated after purification, we carried out ex vivo comparisons with neutrophils maintained in whole blood. We found a difference in activation state, with purified neutrophils showing signs of increased reactivity: shedding of l-selectin, CD11b upregulation, increased oxidative burst, and faster progression to apoptosis. We discovered that erythrocytes suppressed neutrophil activation ex vivo and in vitro, including reduced l-selectin shedding, oxidative burst, chemotaxis, neutrophil extracellular trap formation, bacterial killing, and induction of apoptosis. Selective and specific modification of sialic acid side chains on erythrocyte surfaces with mild sodium metaperiodate oxidation followed by aldehyde quenching with 4-methyl-3-thiosemicarbazide reduced neutrophil binding to erythrocytes and restored neutrophil activation. By enzyme-linked immunosorbent assay and immunofluorescence, we found that glycophorin A, the most abundant sialoglycoprotein on erythrocytes, engaged neutrophil Siglec-9, a sialic acid-recognizing receptor known to dampen innate immune cell activation. These studies demonstrate a previously unsuspected role for erythrocytes in suppressing neutrophils ex vivo and in vitro and help explain why neutrophils become easily activated after separation from whole blood. We propose that a sialic acid-based "self-associated molecular pattern" on erythrocytes also helps maintain neutrophil quiescence in the bloodstream. Our findings may be relevant to some prior experimental and clinical studies of neutrophils.

Porcine reproductive and respiratory syndrome virus (PRRSV) up-regulates IL-8 expression through TAK-1/JNK/AP-1 pathways

The acute phase of respiratory distress caused by porcine reproductive and respiratory syndrome virus (PRRSV) is likely a consequence of the release of inflammatory cytokines in the lung. IL-8, the main chemokine and activator of neutrophils, might be related to the lung injury upon PRRSV infection. In this study, we showed that PRRSV induced IL-8 expression in vivo and in vitro. Subsequently, we demonstrated that JNK and NF-κB pathways were activated upon PRRSV infection and required for the enhancement of IL-8 expression. We further verified that PRRSV-activated TAK-1 was essential for the activation of JNK and NF-κB pathways and IL-8 expression. Moreover, we revealed an AP-1 binding motif in the cloned porcine IL-8 (pIL-8) promoter, and deletion of this motif abolished the pIL-8 promoter activity. Finally, we found that the JNK-activated AP-1 subunit c-Jun was critical for the up-regulation of IL-8 expression by PRRSV. These data suggest that PRRSV-induced IL-8 production is likely through the TAK-1/JNK/AP-1 pathways.

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PRRSV infection induces IL-8 expression in vitro and in vivo.

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PRRSV up-regulates IL-8 expression through TAK-1/JNK/AP-1 pathways.

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AP-1 element in porcine IL-8 promoter is essential for PRRSV induced IL-8 expression.

Anti-inflammatory and anti-excitoxic effects of diethyl oxopropanamide, an ethyl pyruvate bioisoster, exert robust neuroprotective effects in the postischemic brain

Ethyl pyruvate (EP) is a simple aliphatic ester of pyruvic acid and has been shown to have robust neuroprotective effects via its anti-inflammatory, anti-oxidative, and anti-apoptotic functions. In an effort to develop novel EP derivatives with greater protective potencies than EP, we generated four EP isosteres, among them the neuroprotective potency of N,N-diethyl-2-oxopropanamide (DEOPA), in which the ethoxy group of EP was replaced with diethylamine, was far greater than that of EP. When DEOPA was administered intravenously (5 mg/kg) to rat middle cerebral artery occlusion (MCAO) model at 6 hrs post-surgery, it suppressed infarct formation, ameliorated neurological and sensory/motor deficits, and inhibited microglial activation and neutrophil infiltrations in the postischemic brain more effectively than EP. In particular, DEOPA markedly suppressed LPS-induced nitrite production and cytokine/chemokine inductions in microglia, neutrophils, and endothelial cells and these effects are attributable to inhibition of the activity of NF-κB by suppressing IκB-α degradation and p65 to DNA binding. In addition, DEOPA suppressed NMDA-induced neuronal cell death in primary cortical neuron cultures by NAD replenishment and suppression of NF-κB activity. Together, these results indicate DEOPA has multi-modal protective effects against ischemic brain damage targeting numerous cell types in the brain and also against other inflammation-related diseases.

Temporal gradients limit the accumulation of neutrophils towards sources of chemoattractant

Neutrophil trafficking during inflammation is a highly orchestrated process, coordinating neutrophil recruitment, sterilization of the wound, and inflammation resolution. Although the chemotactic signals guiding neutrophil recruitment to sites of inflammation are relatively well understood, mechanisms controlling cessation of neutrophil recruitment and return to normal tissue physiology remain undefined. To gain insights into these processes, we designed a microfluidic device with an array of chemoattractant reservoirs, which mimics the microenvironment in infected tissues, when multiple clusters of microbes are present. We monitored the temporal dynamics of neutrophil recruitment towards the chemoattractant reservoirs at single cell resolution, for 3 hours. We observed robust neutrophil recruitment that reached a plateau after 1.5 hours, despite the continuous presence of robust chemoattractant gradients around the reservoirs. The timing of the plateau was dependent on the geometry of the devices and was independent from the number of neutrophils. Based on these observations, we ruled out sub-population sensitivity, chemoattractant scavenging, and production of a self-limiting stop signal as potential mechanisms underpinning the plateau in neutrophil recruitment. We found a strong correlation between the temporal stabilization of concentration changes and the plateau in neutrophils recruitment. These results suggest that dynamic aspects of chemoattractant gradients are key for maximizing recruitment during the acute phase of infections and limiting the accumulation of neutrophils as soon as the infection is contained.

Human neutrophil peptide-1 decreases during ageing in selected Mexican population

Antimicrobial peptide innate immunity plays a central role in the susceptibility to infectious diseases, as has been described extensively in different settings. However, the role that these molecules play in the immunity mediated by polymorphonuclear phagocytes as part of the innate immunity of ageing individuals has not been described. In the present study, we addressed the question whether antimicrobial activity in polymorphonuclear cells from elderly individuals was altered in comparison with young adults. We compared phagocytosis index, bacterial killing efficiency, myeloperoxidase activity and cathelicidin expression. Results showed that there were no statistical differences among groups. However, human neutrophil peptide-1 (HNP-1) was decreased in the elderly individuals group. Results suggest that the decreased HNP-1 production in the polymorphonuclear phagocytes form elderly individuals might have an important participation in the increased susceptibility to infectious diseases.

Critical Role of the CXCL10/C-X-C Chemokine Receptor 3 Axis in Promoting Leukocyte Recruitment and Neuronal Injury during Traumatic Optic Neuropathy Induced by Optic Nerve Crush

Traumatic optic neuropathy (TON) is an acute injury of the optic nerve secondary to trauma. Loss of retinal ganglion cells (RGCs) is a key pathological process in TON, yet mechanisms responsible for RGC death remain unclear. In a mouse model of TON, real-time noninvasive imaging revealed a dramatic increase in leukocyte rolling and adhesion in veins near the optic nerve (ON) head at 9 hours after ON injury. Although RGC dysfunction and loss were not detected at 24 hours after injury, massive leukocyte infiltration was observed in the superficial retina. These cells were identified as T cells, microglia/monocytes, and neutrophils but not B cells. CXCL10 is a chemokine that recruits leukocytes after binding to its receptor C-X-C chemokine receptor (CXCR) 3. The levels of CXCL10 and CXCR3 were markedly elevated in TON, and up-regulation of CXCL10 was mediated by STAT1/3. Deleting CXCR3 in leukocytes significantly reduced leukocyte recruitment, and prevented RGC death at 7 days after ON injury. Treatment with CXCR3 antagonist attenuated TON-induced RGC dysfunction and cell loss. In vitro co-culture of primary RGCs with leukocytes resulted in increased RGC apoptosis, which was exaggerated in the presence of CXCL10. These results indicate that leukocyte recruitment in retinal vessels near the ON head is an early event in TON and the CXCL10/CXCR3 axis has a critical role in recruiting leukocytes and inducing RGC death.

Update on Inflammatory Biomarkers and Treatments in Ischemic Stroke

After an acute ischemic stroke (AIS), inflammatory processes are able to concomitantly induce both beneficial and detrimental effects. In this narrative review, we updated evidence on the inflammatory pathways and mediators that are investigated as promising therapeutic targets. We searched for papers on PubMed and MEDLINE up to August 2016. The terms searched alone or in combination were: ischemic stroke, inflammation, oxidative stress, ischemia reperfusion, innate immunity, adaptive immunity, autoimmunity. Inflammation in AIS is characterized by a storm of cytokines, chemokines, and Damage-Associated Molecular Patterns (DAMPs) released by several cells contributing to exacerbate the tissue injury both in the acute and reparative phases. Interestingly, many biomarkers have been studied, but none of these reflected the complexity of systemic immune response. Reperfusion therapies showed a good efficacy in the recovery after an AIS. New therapies appear promising both in pre-clinical and clinical studies, but still need more detailed studies to be translated in the ordinary clinical practice. In spite of clinical progresses, no beneficial long-term interventions targeting inflammation are currently available. Our knowledge about cells, biomarkers, and inflammatory markers is growing and is hoped to better evaluate the impact of new treatments, such as monoclonal antibodies and cell-based therapies.

Potent Antiedematous and Protective Effects of Ciprofloxacin in Pulmonary Ricinosis

The plant toxin ricin is considered a biological threat agent of concern and is most toxic when inhaled. Pulmonary exposure to a lethal dose of ricin can be redressed by treatment with antiricin antibodies; however, late antitoxin intervention is of limited efficacy. This limitation is associated with overt lung damage, clinically manifested as severe pulmonary inflammation, which develops over time. Increased evidence indicates that ciprofloxacin, a broad-spectrum antimicrobial agent, possesses immunomodulatory properties. Here we demonstrate that while antiricin antibody administration at late hours after intranasal exposure to ricin confers limited protection to mice, highly efficient protection can be achieved by adding ciprofloxacin to the antibody treatment. We further demonstrate that parameters associated with lung injury, in particular, pulmonary proinflammatory cytokine production, neutrophil migration, and edema, are sharply reduced in ricin-intoxicated mice that were treated with ciprofloxacin. The presented data highlight the potential clinical application of ciprofloxacin as a beneficial immunomodulatory agent in the course of ricin intoxication.

Comparison of immunohematological profile between endurance- and power-oriented elite athletes

There is general perception that elite athletes are highly susceptible to changes in immunohematological profile. The objective of this study was to compare immunohematological parameters of elite athletes of different aerobic and muscular strength sports and analyze changes over 2 months. Sixteen judoists and 14 swimmers were evaluated 2 months before (M1) and immediately prior to competition (M2). Hemogram and lymphocytes subpopulations were assessed with automatic counter and flow cytometry, respectively. Judoists had higher neutrophils and lower monocytes and eosinophils percentages than swimmers at M1 and M2. At M2 judoists had lower red blood cells (RBC), hemoglobin, and hematocrit than swimmers. At M2 judoists' hematocrit and CD16 decreased while swimmers' hemoglobin and hematocrit increased. In conclusion, neither sports characteristics nor intense training seem to displace the athletes' immunohematological profile out of the clinical range, despite the possibility of occurrence of microlesions that may stimulate production of leukocytes and reduction of RBC in judoists.

Pathology of diacetyl and 2,3-pentanedione airway lesions in a rat model of obliterative bronchiolitis

Inhalation of diacetyl vapors by workers has been associated with obliterative bronchiolitis (OB), a poorly understood fibroproliferative disease of the small airways. Significant insights into the pathogenesis of OB have been obtained through the use of a rat model. Inhalation exposure of rats to diacetyl or 2,3-pentanedione, a related flavoring agent, can cause severe injury to the airway epithelium and underlying basement membrane. Repeated exposure to diacetyl or 2,3-pentanedione leads to aberrant repair, fibroproliferation and partial to complete occlusion of the airway lumen. Fibroproliferative lesions in rat airways were found to include both intraluminal polyps and circumferential intramural lesions. Intraluminal polyps have been observed to form secondary attachments spanning the airway lumen causing increasing obstruction. These airway lesions in rats are accompanied by inflammation in the form of peribronchial and perivascular infiltrates of lymphocytes, eosinophils and neutrophils. Diacetyl-induced OB lesions in the rat are similar to OB lesions in humans and provide a good model for studying the pathogenesis of this disease.

Immunity and stroke, the hurdles of stroke research translation

Immunomodulatory therapies after stroke have the potential to provide clinical benefit to a subset of patients, but risk subverting the protective, healing aspects of the innate immune response. Neutrophils clear necrotic cerebral tissue and are important in immunomodulation, but can also contribute to tissue injury. Human trials for immunomodulatory stroke treatments in the sub-acute time frame have attempted to prevent peripheral neutrophil infiltration, but none have been successful and one trial demonstrated harm. These unselected trials had broad inclusion criteria and appear to not have had a specific treatment target. Unfortunately, due to the heterogeneous nature of brain ischemia in humans resulting in variation in clinical severity, the negative effect of thrombolytic drugs on the blood-brain barrier, and the heterogeneity of immune response, it may only be a subset of stroke patients who can realistically benefit from immunomodulation therapies. Translational research strategies require both an understanding of lab practices which create highly controlled environments in contrast to clinical practice where the diagnosis of stroke does not require the identification of a vessel occlusion. These differences between lab and clinical practices can be resolved through the integration of appropriate patient selection criteria and use of advanced imaging and ridged patient selection practices in clinical trials which will be an important part to the success of any future trials of translational research such as immunomodulation.

Alpha1-Antitrypsin Attenuates Renal Fibrosis by Inhibiting TGF-β1-Induced Epithelial Mesenchymal Transition

Alpha1-antitrypsin (AAT) exerts its anti-inflammatory effect through regulating the activity of serine proteinases. This study evaluated the inhibitory effects of AAT against the transforming growth factor (TGF)-β1 induced epithelial-to-mesenchymal transition (EMT) in unilateral ureter obstruction (UUO) mice and Madin-Darby canine kidney (MDCK) cells. C57BL/6 mice with induced UUO were injected intraperitoneally with AAT (80 mg/Kg) or vehicle for 7 days. MDCK cells were treated with TGF-β1 (2 ng/mL) for 48 hours to induce EMT, and co-treated with AAT (10 mg/mL) to inhibit the EMT. Masson’s trichrome and Sirius red staining was used to estimate the extent of renal fibrosis in UUO mice. The expression of alpha-smooth muscle actin (α-SMA), vimentin, fibronectin, collagen I, and E-cadherin in MDCK cells and kidney tissue were evaluated. Masson’s and Sirius red staining revealed that the area of renal fibrosis was significantly smaller in AAT treated UUO group compared with that of UUO and vehicle treated UUO groups. AAT treatment attenuated upregulation of Smad2/3 phosphorylation in UUO mouse model. Co-treatment of MDCK cells with TGF-β1 and AAT significantly attenuated the changes in the expression of α-SMA, vimentin, fibronectin, collagen I, and E-cadherin. AAT also decreased the phosphorylated Smad3 expression and the phosphorylated Smad3/Smad3 ratio in MDCK cells. AAT treatment inhibited EMT induced by TGF-β1 in MDCK cells and attenuated renal fibrosis in the UUO mouse model. The results of this work suggest that AAT could inhibit the process of EMT through the suppression of TGF-β/Smad3 signaling.

Anti-Inflammation of Natural Components from Medicinal Plants at Low Concentrations in Brain via Inhibiting Neutrophil Infiltration after Stroke

Inflammation after stroke consists of activation of microglia/astrocytes in situ and infiltration of blood-borne leukocytes, resulting in brain damage and neurological deficits. Mounting data demonstrated that most natural components from medicinal plants had anti-inflammatory effects after ischemic stroke through inhibiting activation of resident microglia/astrocytes within ischemic area. However, it is speculated that this classical activity cannot account for the anti-inflammatory function of these natural components in the cerebral parenchyma, where they are detected at very low concentrations due to their poor membrane permeability and slight leakage of BBB. Could these drugs exert anti-inflammatory effects peripherally without being delivered across the BBB? Factually, ameliorating blood-borne neutrophil recruitment in peripheral circulatory system has been proved to reduce ischemic damage and improve outcomes. Thus, it is concluded that if drugs could achieve effective concentrations in the cerebral parenchyma, they can function via crippling resident microglia/astrocytes activation and inhibiting neutrophil infiltration, whereas the latter will be dominating when these drugs localize in the brain at a low concentration. In this review, the availability of some natural components crossing the BBB in stroke will be discussed, and how these drugs lead to improvements in stroke through inhibition of neutrophil rolling, adhesion, and transmigration will be illustrated.

Curcumin suppresses NTHi-induced CXCL5 expression via inhibition of positive IKKβ pathway and up-regulation of negative MKP-1 pathway

Otitis media (OM) is the most common childhood bacterial infection, and leading cause of conductive hearing loss. Nontypeable Haemophilus influenzae (NTHi) is a major bacterial pathogen for OM. OM characterized by the presence of overactive inflammatory responses is due to the aberrant production of inflammatory mediators including C-X-C motif chemokine ligand 5 (CXCL5). The molecular mechanism underlying induction of CXCL5 by NTHi is unknown. Here we show that NTHi up-regulates CXCL5 expression by activating IKKβ-IκBα and p38 MAPK pathways via NF-κB nuclear translocation-dependent and -independent mechanism in middle ear epithelial cells. Current therapies for OM are ineffective due to the emergence of antibiotic-resistant NTHi strains and risk of side effects with prolonged use of immunosuppressant drugs. In this study, we show that curcumin, derived from Curcuma longa plant, long known for its medicinal properties, inhibited NTHi-induced CXCL5 expression in vitro and in vivo. Curcumin suppressed CXCL5 expression by direct inhibition of IKKβ phosphorylation, and inhibition of p38 MAPK via induction of negative regulator MKP-1. Thus, identification of curcumin as a potential therapeutic for treating OM is of particular translational significance due to the attractiveness of targeting overactive inflammation without significant adverse effects.

Patrolling monocytes promote intravascular neutrophil activation and glomerular injury in the acutely inflamed glomerulus

Nonclassical monocytes undergo intravascular patrolling in blood vessels, positioning them ideally to coordinate responses to inflammatory stimuli. Under some circumstances, the actions of monocytes have been shown to involve promotion of neutrophil recruitment. However, the mechanisms whereby patrolling monocytes control the actions of neutrophils in the circulation are unclear. Here, we examined the contributions of monocytes to antibody- and neutrophil-dependent inflammation in a model of in situ immune complex-mediated glomerulonephritis. Multiphoton and spinning disk confocal intravital microscopy revealed that monocytes patrol both uninflamed and inflamed glomeruli using β2 and α4 integrins and CX3CR1. Monocyte depletion reduced glomerular injury, demonstrating that these cells promote inappropriate inflammation in this setting. Monocyte depletion also resulted in reductions in neutrophil recruitment and dwell time in glomerular capillaries and in reactive oxygen species (ROS) generation by neutrophils, suggesting a role for cross-talk between monocytes and neutrophils in induction of glomerulonephritis. Consistent with this hypothesis, patrolling monocytes and neutrophils underwent prolonged interactions in glomerular capillaries, with the duration of these interactions increasing during inflammation. Moreover, neutrophils that interacted with monocytes showed increased retention and a greater propensity for ROS generation in the glomerulus. Also, renal patrolling monocytes, but not neutrophils, produced TNF during inflammation, and TNF inhibition reduced neutrophil dwell time and ROS production, as well as renal injury. These findings show that monocytes and neutrophils undergo interactions within the glomerular microvasculature. Moreover, evidence indicates that, in response to an inflammatory stimulus, these interactions allow monocytes to promote neutrophil recruitment and activation within the glomerular microvasculature, leading to neutrophil-dependent tissue injury.

Protease inhibition as new therapeutic strategy for GI diseases

The GI tract is the most exposed organ to proteases, both in physiological and pathophysiological conditions. For digestive purposes, the lumen of the upper GI tract contains large amounts of pancreatic proteases, but studies have also demonstrated increased proteolytic activity into mucosal tissues (both in the upper and lower GI tract), associated with pathological conditions. This review aims at outlining the evidences for dysregulated proteolytic homeostasis in GI diseases and the pathogenic mechanisms of increased proteolytic activity. The therapeutic potential of protease inhibition in GI diseases is discussed, with a particular focus on IBDs, functional GI disorders and colorectal cancer.

Cell death and inflammation: the case for IL-1 family cytokines as the canonical DAMPs of the immune system

It is well known that necrotic cells are capable of promoting inflammation through releasing so-called endogenous 'danger signals' that can promote activation of macrophages, dendritic cells, and other sentinel cells of the innate immune system. However, the identity of these endogenous proinflammatory molecules, also called damage-associated molecular patterns (DAMPs), has been debated since the 'danger model' was first advanced 20 years ago. While a relatively large number of molecules have been proposed to act as DAMPs, little consensus has emerged concerning which of these represent the key activators of sterile inflammation. Here I argue that the canonical DAMPs have long been hiding in plain sight, in the form of members of the extended IL-1 cytokine family (IL-1α, IL-1β, IL-18, IL-33, IL-36α, IL-36β, and IL-36γ). The latter cytokines possess all of the characteristics expected of endogenous DAMPs and initiate inflammation in a manner strikingly similar to that utilized by the other major category of inflammatory triggers, pathogen-associated molecular patterns (PAMPs). Furthermore, many PAMPs upregulate the expression of IL-1 family DAMPs, enabling robust synergy between these distinct classes of inflammatory triggers. Thus, multiple lines of evidence now suggest that IL-1 family cytokines represent the key initiators of necrosis-initiated sterile inflammation, as well as amplifiers of inflammation in response to infection-associated tissue injury.

Fine-tuning neutrophil activation: Strategies and consequences

In spite of their important role in host defense, neutrophils can also cause severe morbidity and mortality. Neutrophils have an extensive armory necessary to eradicate pathogens, but neutrophil infiltration and activation also induces major tissue injury associated with acute and chronic inflammatory disorders. Here, we review neutrophil anti-microbial functions and discuss their individual contribution to disease pathogenesis. Furthermore, we provide an overview of the anti-inflammatory drugs that can dampen neutrophil transmigration, elastase activity, and the production of reactive oxygen species which are already in clinical trials. The discovery of potential inhibitors of the release of neutrophil extracellular trap is still in its infancy. Here, we discuss small molecule inhibitors and inhibitory receptors that show promising results in reducing neutrophil extracellular trap formation in vitro and in vivo and discuss the advantages and drawbacks of inhibiting the release of neutrophil extracellular traps as a therapeutic treatment. Specific suppression of neutrophil extracellular trap formation, preferably while other antimicrobial functions are preserved, would be an ideal approach to treat neutrophilic inflammation, since it prevents acute as well as chronic neutrophil-associated pathology.

Big insights from small volumes: deciphering complex leukocyte behaviors using microfluidics

Inflammation is an indispensable component of the immune response, and leukocytes provide the first line of defense against infection. Although the major stereotypic leukocyte behaviors in response to infection are well known, the complexities and idiosyncrasies of these phenotypes in conditions of disease are still emerging. Novel tools are indispensable for gaining insights into leukocyte behavior, and in the past decade, microfluidic technologies have emerged as an exciting development in the field. Microfluidic devices are readily customizable, provide tight control of experimental conditions, enable high precision of ex vivo measurements of individual as well as integrated leukocyte functions, and have facilitated the discovery of novel leukocyte phenotypes. Here, we review some of the most interesting insights resulting from the application of microfluidic approaches to the study of the inflammatory response. The aim is to encourage leukocyte biologists to integrate these new tools into increasingly more sophisticated experimental designs for probing complex leukocyte functions.

Induction of Nerve Injury-Induced Protein 1 (Ninjurin 1) in Myeloid Cells in Rat Brain after Transient Focal Cerebral Ischemia

Nerve injury-induced protein-1 (Ninjurin-1, Ninj1) was initially identified as a novel adhesion molecule in rat sciatic nerve and to be up-regulated in neurons and Schwann cells of distal nerve segments after nerve transection or crush injury. Recently, Ninj1 was found to act as a modulator of cell migration, angiogenesis, and apoptosis. Accumulating evidence indicates that innate immune response plays beneficial and deleterious roles in brain ischemia, and the trans-endothelial migration of blood-derived immune cells is key initiator of this response. In the present study, we examined the expression profile and cellular distribution of Ninj1 in rat brain after transient focal cerebral ischemia. Ninj1 expression was found to be significantly induced in cortical penumbras 1 day after 60 min of middle cerebral artery occlusion (MCAO) and to increase gradually for 8 days and then declined. In infarction cores of cortices, patterns of Ninj1 expression were similar to those observed in cortical penumbras, except induction was maintained for 10 days. At 1 day post-MCAO, Ninj1 inductions were detected mainly in neutrophils and endothelial cells in both infarction cores and penumbras, but reactive macrophages were the major cellular expressers of Ninj1 at 4 days post-MCAO. Expressional induction in reactive macrophages was maintained in infarction cores after 12 days post-MCAO but not in penumbras. These dynamic expressions of Ninj1 in different immune cells at different times suggest that this protein performs various, critical roles in the modulation of acute and delayed immune responses in the postischemic brain.

Intermediate-Risk Chronic Stable Angina: Neutrophil-Lymphocyte Ratio and Fibrinogen Levels Improved Predicting Angiographically-Detected Coronary Artery Disease

BACKGROUND

Coronary heart disease (CHD) is the leading cause of death worldwide. Research indicates that coronary atherosclerosis is the most frequent cause of CHD. Evidence is scarce concerning the clinical efficacy of fibrinogen or neutrophil-lymphocyte ratio (NLR) measurement in risk-stratifying patients with chronic stable angina.

OBJECTIVES

To examine the independent and incremental prognostic value of fibrinogen and neutrophil-lymphocyte ratio (NLR) for angiographically-detected coronary artery disease (CAD).

PATIENTS AND METHODS

In this cross-sectional study, angiography was performed for 183 Iranian patients with chronic stable angina with exercise ECG-determined intermediate risk. Generalized estimated equations were used to obtain the odd ratio (OR) of CAD for a 1-unit increase in log-NLR and a 1-SD increase in plasma fibrinogen. Models were adjusted for established CAD risk factors. Integrated discriminatory improvement index (IDI) and net reclassification improvement index (NRI) were used as measures of predictive ability for CAD, combined with traditional risk factors by NLR and fibrinogen.

RESULTS

The mean age of the participants was 57.5, with 51.9% being male. Only 12% of participants had angiographically-determined patent coronary arteries. The number of participants with one, two, and three-vessel stenosis were 76, 31, 31, respectively, while 45 did not have stenosed vessels. NLR and fibrinogen levels were significantly higher in patients with stenosis in two (2.4 and 512 mg.dL^-1) or three (2.6 and 517 mg.dL^-1) coronary arteries, as compared to the group of patients with no significant involvement (2 and 430 mg.dL^-1) (all P < 0.01). Patients with a higher NLR and a higher fibrinogen levels were more likely to have higher grades of CAD. OR log-NLR = 1.36 (95% CI: 1.05 - 1.94) and OR Z-Fibrinogen = 1.61 (95% CI: 1.18 - 2.22). When NLR and fibrinogen were added to the traditional risk factors separately, the NRIs were 0.170 (0.023 - 0.324) and 0.380 (0.214 - 0.543), respectively. The NRI was 0.460 (0.303 - 0.620) when both NLR and fibrinogen added to traditional risk factors simultaneously.

CONCLUSIONS

NLR and fibrinogen predicted CAD, independent of traditional CAD risk factors. Both measures (whether separately or together) substantially enhanced the predictive performance of traditional risk factors for identifying patients with CAD.

In Vitro Neutrophil Migration Requires Protein Kinase C-Delta (δ-PKC)-Mediated Myristoylated Alanine-Rich C-Kinase Substrate (MARCKS) Phosphorylation

Dysregulated release of neutrophil reactive oxygen species and proteolytic enzymes contributes to both acute and chronic inflammatory diseases. Therefore, molecular regulators of these processes are potential targets for new anti-inflammatory therapies. We have shown previously that myristoylated alanine-rich C-kinase substrate (MARCKS), a well-known actin binding protein and protein kinase C (PKC) substrate, is a key regulator of neutrophil functions. In the current study, we investigate the role of PKC-mediated MARCKS phosphorylation in neutrophil migration and adhesion in vitro. We report that treatment of human neutrophils with the δ-PKC inhibitor rottlerin significantly attenuates f-Met-Leu-Phe (fMLF)-induced MARCKS phosphorylation (IC50=5.709 μM), adhesion (IC50=8.4 μM), and migration (IC50=6.7 μM), while α-, β-, and ζ-PKC inhibitors had no significant effect. We conclude that δ-PKC-mediated MARCKS phosphorylation is essential for human neutrophil migration and adhesion in vitro. These results implicate δ-PKC-mediated MARCKS phosphorylation as a key step in the inflammatory response of neutrophils.

Antipseudomonal Bacteriophage Reduces Infective Burden and Inflammatory Response in Murine Lung

As antibiotic resistance increases, there is a need for new therapies to treat infection, particularly in cystic fibrosis (CF), where Pseudomonas aeruginosa is a ubiquitous pathogen associated with increased morbidity and mortality. Bacteriophages are an attractive alternative treatment, as they are specific to the target bacteria and have no documented side effects. The efficacy of phage cocktails was established in vitro. Two P. aeruginosa strains were taken forward into an acute murine infection model with bacteriophage administered either prophylactically, simultaneously, or postinfection. The infective burden and inflammation in bronchoalveolar lavage fluid (BALF) were assessed at various times. With low infective doses, both control mice and those undergoing simultaneous phage treatment cleared P. aeruginosa infection at 48 h, but there were fewer neutrophils in BALF of phage-treated mice (median, 73.2 × 10(4)/ml [range, 35.2 to 102.1 × 10(4)/ml] versus 174 × 10(4)/ml [112.1 to 266.8 × 10(4)/ml], P < 0.01 for the clinical strain; median, 122.1 × 10(4)/ml [105.4 to 187.4 × 10(4)/ml] versus 206 × 10(4)/ml [160.1 to 331.6 × 10(4)/ml], P < 0.01 for PAO1). With higher infective doses of PAO1, all phage-treated mice cleared P. aeruginosa infection at 24 h, whereas infection persisted in all control mice (median, 1,305 CFU/ml [range, 190 to 4,700 CFU/ml], P < 0.01). Bacteriophage also reduced CFU/ml in BALF when administered postinfection (24 h) and both CFU/ml and inflammatory cells in BALF when administered prophylactically. A reduction in soluble inflammatory cytokine levels in BALF was also demonstrated under different conditions. Bacteriophages are efficacious in reducing both the bacterial load and inflammation in a murine model of P. aeruginosa lung infection. This study provides proof of concept for future clinical trials in patients with CF.

Peripheral Immune Cell Counts and Advanced Imaging as Biomarkers of Stroke Outcome

Introduction

Circulating neutrophil and lymphocyte levels may be modifiable outcome predictors of ischemic stroke. We sought to compare these immune cell parameters with advanced imaging assessment and the 90-day clinical outcome.

Methods

We used a retrospectively collected cohort of consecutive ischemic stroke patients presenting within 4.5 h of symptom onset who had acute CT perfusion and routine blood collection before treatment with intravenous thrombolysis and 24-hour MRI scanning at the John Hunter Hospital. Full blood counts were performed acutely at 24 h and 7 days. Patient outcomes were assed at 90 days after stroke with the modified Rankin Scale (mRS).

Results

Overall, 142 patients were assessed during the study period. Patients with a poor outcome (mRS 3-6) had increased neutrophils (44% increase, p = 0.016), decreased lymphocytes (7% decrease, p = 0.491) and an increased lymphocyte-to-neutrophil ratio (196% increase, p < 0.001). Patients with good outcomes (mRS 0-2) did not have significant changes in their full blood counts. There was no relationship between the neutrophil count at 24 h and penumbral volume (r² = 0.217, p = 0.212), reperfusion (r² = 0.111, p = 0.085), or core growth (r² = 0.297, p = 0.107). A backward multivariate analysis containing the 24-hour core volume and 24-hour neutrophil count was strongly related to the 3-month outcome (r² = 0.477, area under the curve = 0.902, p < 0.001).

Conclusions

Peripheral neutrophils have potential as a biomarker of outcome when used in conjunction with advanced imaging. Peripherally measured neutrophil counts change significantly over time after stroke and may be potential targets for immunomodulatory therapy in patients with a severe stroke or a large infarct volume.

Rapid Detection of Neutrophil Oxidative Burst Capacity is Predictive of Whole Blood Cytokine Responses

BACKGROUND

Maladaptive immune responses, particularly cytokine and chemokine-driven, are a significant contributor to the deleterious inflammation present in many types of injury and infection. Widely available applications to rapidly assess individual inflammatory capacity could permit identification of patients at risk for exacerbated immune responses and guide therapy. Here we evaluate neutrophil oxidative burst (NOX) capacity measured by plate reader to immuno-type Rhesus Macaques as an acute strategy to rapidly detect inflammatory capacity and predict maladaptive immune responses as assayed by cytokine array.

METHODS

Whole blood was collected from anesthetized Rhesus Macaques (n = 25) and analyzed for plasma cytokine secretion (23-plex Luminex assay) and NOX capacity. For cytokine secretion, paired samples were either unstimulated or ex-vivo lipopolysaccharide (LPS)-stimulated (100μg/mL/24h). NOX capacity was measured in dihydrorhodamine-123 loaded samples following phorbol 12-myristate 13-acetate (PMA)/ionomycin treatment. Pearson's test was utilized to correlate NOX capacity with cytokine secretion, p<0.05 considered significant.

RESULTS

LPS stimulation induced secretion of the inflammatory molecules G-CSF, IL-1β, IL-1RA, IL-6, IL-10, IL-12/23(p40), IL-18, MIP-1α, MIP-1β, and TNFα. Although values were variable, several cytokines correlated with NOX capacity, p-values≤0.0001. Specifically, IL-1β (r = 0.66), IL-6 (r = 0.74), the Th1-polarizing cytokine IL-12/23(p40) (r = 0.78), and TNFα (r = 0.76) were strongly associated with NOX.

CONCLUSION

NOX capacity correlated with Th1-polarizing cytokine secretion, indicating its ability to rapidly predict inflammatory responses. These data suggest that NOX capacity may quickly identify patients at risk for maladaptive immune responses and who may benefit from immuno-modulatory therapies. Future studies will assess the in-vivo predictive value of NOX in animal models of immune-mediated pathologies.

Partial MHC Constructs Treat Thromboembolic Ischemic Stroke Characterized by Early Immune Expansion

Inflammation and thrombosis are tightly linked, with inflammation contributing to thromboembolism and to stroke outcome. Thromboembolism is a frequent cause of ischemic stroke; yet, the most used occlusion mouse models of experimental stroke do not effectively replicate thromboembolism. Our group recently described a novel thromboembolic mouse model of stroke that successfully occludes the middle cerebral artery with high reproducibility. In the current study, we characterize the peripheral and local immune outcomes as well as the ischemic response to immune therapy in a clinically relevant mouse model of thromboembolic stroke. Brain and spleen tissues were harvested 24 h after thromboembolic stroke and cells immunophenotyped by flow cytometry. We observed a significant increase in neutrophils and early activated T cells in the spleen and an increase in neutrophils and activated monocytes/microglia in the ischemic cortex after thromboembolic stroke. Moreover, as was shown previously for transient MCAO models, treatment of thromboembolic stroke with partial MHC constructs significantly reduced ischemic damage indicating an equivalent effect of this immune-based therapy in the thromboembolic model that better mimics the pathophysiology of human stroke.

Cardiac Arrest Disrupts Caspase-1 and Patterns of Inflammatory Mediators Differently in Skin and Muscle Following Localized Tissue Injury in Rats: Insights from Data-Driven Modeling

BACKGROUND

Trauma often cooccurs with cardiac arrest and hemorrhagic shock. Skin and muscle injuries often lead to significant inflammation in the affected tissue. The primary mechanism by which inflammation is initiated, sustained, and terminated is cytokine-mediated immune signaling, but this signaling can be altered by cardiac arrest. The complexity and context sensitivity of immune signaling in general has stymied a clear understanding of these signaling dynamics.

METHODOLOGY/PRINCIPAL FINDINGS

We hypothesized that advanced numerical and biological function analysis methods would help elucidate the inflammatory response to skin and muscle wounds in rats, both with and without concomitant shock. Based on the multiplexed analysis of inflammatory mediators, we discerned a differential interleukin (IL)-1α and IL-18 signature in skin vs. muscle, which was suggestive of inflammasome activation in the skin. Immunoblotting revealed caspase-1 activation in skin but not muscle. Notably, IL-1α and IL-18, along with caspase-1, were greatly elevated in the skin following cardiac arrest, consistent with differential inflammasome activation.

CONCLUSION/SIGNIFICANCE

Tissue-specific activation of caspase-1 and the NLRP3 inflammasome appear to be key factors in determining the type and severity of the inflammatory response to tissue injury, especially in the presence of severe shock, as suggested via data-driven modeling.

Mouse models of human TB pathology: roles in the analysis of necrosis and the development of host-directed therapies

A key aspect of TB pathogenesis that maintains Mycobacterium tuberculosis in the human population is the ability to cause necrosis in pulmonary lesions. As co-evolution shaped M. tuberculosis (M.tb) and human responses, the complete TB disease profile and lesion manifestation are not fully reproduced by any animal model. However, animal models are absolutely critical to understand how infection with virulent M.tb generates outcomes necessary for the pathogen transmission and evolutionary success. In humans, a wide spectrum of TB outcomes has been recognized based on clinical and epidemiological data. In mice, there is clear genetic basis for susceptibility. Although the spectra of human and mouse TB do not completely overlap, comparison of human TB with mouse lesions across genetically diverse strains firmly establishes points of convergence. By embracing the genetic heterogeneity of the mouse population, we gain tremendous advantage in the quest for suitable in vivo models. Below, we review genetically defined mouse models that recapitulate a key element of M.tb pathogenesis—induction of necrotic TB lesions in the lungs—and discuss how these models may reflect TB stratification and pathogenesis in humans. The approach ensures that roles that mouse models play in basic and translational TB research will continue to increase allowing researchers to address fundamental questions of TB pathogenesis and bacterial physiology in vivo using this well-defined, reproducible, and cost-efficient system. Combination of the new generation mouse models with advanced imaging technologies will also allow rapid and inexpensive assessment of experimental vaccines and therapies prior to testing in larger animals and clinical trials.

Intravital autofluorescence 2-photon microscopy of murine intestinal mucosa with ultra-broadband femtosecond laser pulse excitation: image quality, photodamage, and inflammation

Ultra-broadband excitation with ultrashort pulses may enable simultaneous excitation of multiple endogenous fluorophores in vital tissue. Imaging living gut mucosa by autofluorescence 2-photon microscopy with more than 150 nm broad excitation at an 800-nm central wavelength from a sub-10 fs titanium-sapphire (Ti:sapphire) laser with a dielectric mirror based prechirp was compared to the excitation with 220 fs pulses of a tunable Ti:sapphire laser at 730 and 800 nm wavelengths. Excitation efficiency, image quality, and photochemical damage were evaluated. At similar excitation fluxes, the same image brightness was achieved with both lasers. As expected, with ultra-broadband pulses, fluorescence from NAD(P)H, flavines, and lipoproteins was observed simultaneously. However, nonlinear photodamage apparent as hyperfluorescence with functional and structural alterations of the tissue occurred earlier when the laser power was adjusted to the same image brightness. After only a few minutes, the immigration of polymorphonuclear leucocytes into the epithelium and degranulation of these cells, a sign of inflammation, was observed. Photodamage is promoted by the higher peak irradiances and/or by nonoptimal excitation of autofluorescence at the longer wavelength. We conclude that excitation with a tunable narrow bandwidth laser is preferable to ultra-broadband excitation for autofluorescence-based 2-photon microscopy, unless the spectral phase can be controlled to optimize excitation conditions.