Annexins-a family of proteins with distinctive tastes for cell signaling and membrane dynamics

Annexins are cytosolic proteins with conserved three-dimensional structures that bind acidic phospholipids in cellular membranes at elevated Ca2+ levels. Through this they act as Ca2+-regulated membrane binding modules that organize membrane lipids, facilitating cellular membrane transport but also displaying extracellular activities. Recent discoveries highlight annexins as sensors and regulators of cellular and organismal stress, controlling inflammatory reactions in mammals, environmental stress in plants, and cellular responses to plasma membrane rupture. Here, we describe the role of annexins as Ca2+-regulated membrane binding modules that sense and respond to cellular stress and share our view on future research directions in the field.

Regulating Neutrophil PAD4/NOX-Dependent Cerebrovasular Thromboinflammation

Background: Neutrophil extracellular trap (NET) production has been implicated in the pathogenesis of thromboinflammatory conditions such as Sickle Cell Disease (SCD), contributing to heightened risk for ischemic stroke. NETs are catalyzed by the enzyme Peptidyl Arginine Deiminase 4 (PAD4) and neutrophil derived reactive oxygen species (ROS), especially NADPH oxidase (NOX) which interacts with PAD4 and is therefore critical for neutrophil function. However, the role that NOX-dependent ROS and NETs play in the accelerated cerebral microvascular thrombosis associated with thromboinflammatory conditions, such as SCD, has not been fully elucidated and is the aim of this study. Methods: The in-vitro effects of targeting PAD4 and NOX were examined using physiologically relevant NET assays with neutrophils isolated from healthy volunteers (control) and SCD patients. In addition, in-vivo intravascular effects of targeting PAD4 and NOX in the cerebral microcirculation of C57BL/6 and sickle transgenic mice (STM) were assessed using a photoactivation thrombosis model (light/dye) coupled with real-time fluorescence intravital microscopy. Results: We found that targeting PAD4 and NOX in human neutrophils significantly inhibited ionomycin dependent H3cit⁺ neutrophils. Targeting PAD4 and NOX in-vivo resulted in prolonged blood flow cessation in cerebrovascular arterioles as well as venules. Moreover, we were able to replicate the effects of PAD4 and NOX targeting in a clinical model of accelerated thromboinflammation by increasing blood flow cessation times in cerebral microvessels in STM. These findings concurred with the clinical setting i.e. neutrophils isolated from SCD patients, which possessed an attenuation of H3cit⁺ neutrophil production on targeting PAD4 and NOX. Conclusions: Taken together, our compelling data suggests that PAD4 and NOX play a significant role in neutrophil driven thromboinflammation. Targeting PAD4 and NOX limits pathological H3cit⁺ neutrophils, which may further explain attenuation of cerebral thrombosis. Overall, this study presents a viable pre-clinical model of prevention and management of thromboinflammatory complications such as ischemic stroke.

Skeletal muscle angiogenic, regulatory, and heat shock protein responses to prolonged passive hyperthermia of the human lower limb

Passive hyperthermia induces a range of physiological responses including augmenting skeletal muscle mRNA expression. This experiment aimed to examine gene and protein responses to prolonged passive leg hyperthermia. Seven young participants underwent 3 h of resting unilateral leg heating (HEAT) followed by a further 3 h of rest, with the contralateral leg serving as an unheated control (CONT). Muscle biopsies were taken at baseline (0 h), and at 1.5, 3, 4, and 6 h in HEAT and 0 and 6 h in CONT to assess changes in selected mRNA expression via qRT-PCR, and HSP72 and VEGFα concentration via ELISA. Muscle temperature (T_m) increased in HEAT plateauing from 1.5 to 3 h (+3.5 ± 1.5°C from 34.2 ± 1.2°C baseline value; P < 0.001), returning to baseline at 6 h. No change occurred in CONT. Endothelial nitric oxide synthase (eNOS), Forkhead box O1 (FOXO-1), Hsp72, and VEGFα mRNA increased in HEAT (P < 0.05); however, post hoc analysis identified that only Hsp72 mRNA statistically increased (at 4 h vs. baseline). When peak change during HEAT was calculated angiopoietin 2 (ANGPT-2) decreased (-0.4 ± 0.2-fold), and C-C motif chemokine ligand 2 (CCL2) (+2.9 ± 1.6-fold), FOXO-1 (+6.2 ± 4.4-fold), Hsp27 (+2.9 ± 1.7-fold), Hsp72 (+8.5 ± 3.5-fold), Hsp90α (+4.6 ± 3.7-fold), and VEGFα (+5.9 ± 3.1-fold) increased from baseline (all P < 0.05). At 6 h T_m were not different between limbs (P = 0.582; CONT = 32.5 ± 1.6°C, HEAT = 34.3 ± 1.2°C), and only ANGPT-2 (P = 0.031; -1.3 ± 1.4-fold) and VEGFα (P = 0.030; 1.1 ± 1.2-fold) differed between HEAT and CONT. No change in VEGFα or HSP72 protein concentration were observed over time; however, peak change in VEGFα did increase (P < 0.05) in HEAT (+140 ± 184 pg·mL^-1) versus CONT (+7 ± 86 pg·mL^-1). Passive hyperthermia transiently augmented ANGPT-2, CCL2, eNOS, FOXO-1, Hsp27, Hsp72, Hsp90α and VEGFα mRNA, and VEGFα protein.

Bryostatin-1 Attenuates Ischemia-Elicited Neutrophil Transmigration and Ameliorates Graft Injury after Kidney Transplantation

Ischemia reperfusion injury (IRI) is a form of sterile inflammation whose severity determines short- and long-term graft fates in kidney transplantation. Neutrophils are now recognized as a key cell type mediating early graft injury, which activates further innate immune responses and intensifies acquired immunity and alloimmunity. Since the macrolide Bryostatin-1 has been shown to block neutrophil transmigration, we aimed to determine whether these findings could be translated to the field of kidney transplantation. To study the effects of Bryostatin-1 on ischemia-elicited neutrophil transmigration, an in vitro model of hypoxia and normoxia was equipped with human endothelial cells and neutrophils. To translate these findings, a porcine renal autotransplantation model with eight hours of reperfusion was used to study neutrophil infiltration in vivo. Graft-specific treatment using Bryostatin-1 (100 nM) was applied during static cold storage. Bryostatin-1 dose-dependently blocked neutrophil activation and transmigration over ischemically challenged endothelial cell monolayers. When applied to porcine renal autografts, Bryostatin-1 reduced neutrophil graft infiltration, attenuated histological and ultrastructural damage, and improved renal function. Our novel findings demonstrate that Bryostatin-1 is a promising pharmacological candidate for graft-specific treatment in kidney transplantation, as it provides protection by blocking neutrophil infiltration and attenuating functional graft injury.

COVID-19 through Adverse Outcome Pathways: Building networks to better understand the disease - 3rd CIAO AOP Design Workshop

On April 28-29, 2021, 50 scientists from different fields of expertise met for the 3rd online CIAO workshop. The CIAO project “Modelling the Pathogenesis of COVID-19 using the Adverse Outcome Pathway (AOP) framework” aims at building a holistic assembly of the available scientific knowledge on COVID-19 using the AOP framework. An individual AOP depicts the disease progression from the initial contact with the SARS-CoV-2 virus through biological key events (KE) toward an adverse outcome such as respiratory distress, anosmia or multiorgan failure. Assembling the individual AOPs into a network highlights shared KEs as central biological nodes involved in multiple outcomes observed in COVID-19 patients. During the workshop, the KEs and AOPs established so far by the CIAO members were presented and posi­tioned on a timeline of the disease course. Modulating factors influencing the progression and severity of the disease were also addressed as well as factors beyond purely biological phenomena. CIAO relies on an interdisciplinary crowd­sourcing effort, therefore, approaches to expand the CIAO network by widening the crowd and reaching stakeholders were also discussed. To conclude the workshop, it was decided that the AOPs/KEs will be further consolidated, inte­grating virus variants and long COVID when relevant, while an outreach campaign will be launched to broaden the CIAO scientific crowd.

Neutrophils and Platelets: Immune Soldiers Fighting Together in Stroke Pathophysiology

Neutrophils and platelets exhibit a diverse repertoire of functions in thromboinflammatory conditions such as stroke. Most cerebral ischemic events result from longstanding chronic inflammation secondary to underlying pathogenic conditions, e.g., hypertension, diabetes mellitus, obstructive sleep apnea, coronary artery disease, atrial fibrillation, morbid obesity, dyslipidemia, and sickle cell disease. Neutrophils can enable, as well as resolve, cerebrovascular inflammation via many effector functions including neutrophil extracellular traps, serine proteases and reactive oxygen species, and pro-resolving endogenous molecules such as Annexin A1. Like neutrophils, platelets also engage in pro- as well as anti-inflammatory roles in regulating cerebrovascular inflammation. These anucleated cells are at the core of stroke pathogenesis and can trigger an ischemic event via adherence to the hypoxic cerebral endothelial cells culminating in aggregation and clot formation. In this article, we review and highlight the evolving role of neutrophils and platelets in ischemic stroke and discuss ongoing preclinical and clinical strategies that may produce viable therapeutics for prevention and management of stroke.

Thromboinflammation in coronavirus disease 2019: The clot thickens

Since the start of the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) pandemic, a disease that has become one of the world's greatest global health challenges, the role of the immune system has been at the forefront of scientific studies. The pathophysiology of coronavirus disease 2019 (COVID‐19) is complex, which is evident in those at higher risk for poor outcome. Multiple systems contribute to thrombosis and inflammation seen in COVID‐19 patients, including neutrophil and platelet activation, and endothelial dysfunction. Understanding how the immune system functions in different patient cohorts (particularly given recent emerging events with the Oxford/AstraZeneca vaccine) is vital to understanding the pathophysiology of this devastating disease and for the subsequent development of novel therapeutic targets and to facilitate possible drug repurposing strategies that could benefit society on a global scale.

Long-lived lanthanide emission via a pH-sensitive and switchable LRET complex

Lanthanide-based luminescence resonance energy transfer (LRET) can be used as a tool to enhance lanthanide emission for time-resolved cellular imaging applications. By shortening lanthanide emission lifetimes whilst providing an alternative radiative pathway to the formally forbidden, weak lanthanide-only emission, the photon flux of such systems is increased. With this aim in mind, we investigated energy transfer in differently spaced donor–acceptor terbium–rhodamine pairs with the LRET “on” (low pH) and LRET “off” (high pH). Results informed the design, preparation and characterisation of a compound containing terbium, a spectrally-matched pH-responsive fluorophore and a receptor-targeting group. By combining these elements, we observed switchable LRET, where the targeting group sensitises lanthanide emission, resulting in an energy transfer to the rhodamine dye with an efficiency of E = 0.53. This strategy can be used to increase lanthanide emission rates for brighter optical probes.

A pH-sensitive luminescence resonance energy transfer (LRET) was explored as a method to increase photon flux in a terbium-rhodamine-receptor targeting group construct. At low pH, long-lived dye emission and shorter terbium lifetimes were observed.

The impact of thrombo-inflammation on the cerebral microcirculation

The intertwined processes of thrombosis and inflammation (termed "thrombo-inflammation") are significant drivers of cerebrovascular diseases, and as such, they represent prime targets for drug discovery programs focusing on treatment and management of cerebrovascular diseases. Most cerebrovascular events result from chronic systemic microcirculatory dysfunction due to underlying conditions, for example, hypertension, diabetes mellitus, coronary artery disease, dyslipidemia, and sickle cell disease. Immune cells especially neutrophils play a critical role in the onset and maintenance of neuroinflammatory responses in the microcirculation. Neutrophils have the ability to drive both inflammatory and anti-inflammatory/pro-resolution effects depending on the underlying vascular state (physiological vs. pathological). In this article, we highlight the pathophysiological role of neutrophils in stroke and discuss ongoing pharmacotherapeutic strategies that are focused on identifying potential therapeutic targets for enhancing neuroprotection, mitigating inflammatory pathways, and enabling resolution.

Targeting the AnxA1/Fpr2/ALX pathway regulates neutrophil function, promoting thromboinflammation resolution in sickle cell disease

Neutrophils play a crucial role in the intertwined processes of thrombosis and inflammation. An altered neutrophil phenotype may contribute to inadequate resolution, which is known to be a major pathophysiological contributor of thromboinflammatory conditions such as sickle cell disease (SCD). The endogenous protein annexin A1 (AnxA1) facilitates inflammation resolution via formyl peptide receptors (FPRs). We sought to comprehensively elucidate the functional significance of targeting the neutrophil-dependent AnxA1/FPR2/ALX pathway in SCD. Administration of AnxA1 mimetic peptide AnxA1Ac2-26 ameliorated cerebral thrombotic responses in Sickle transgenic mice via regulation of the FPR2/ALX (a fundamental receptor involved in resolution) pathway. We found direct evidence that neutrophils with SCD phenotype play a key role in contributing to thromboinflammation. In addition, AnxA1Ac2-26 regulated activated SCD neutrophils through protein kinase B (Akt) and extracellular signal-regulated kinases (ERK1/2) to enable resolution. We present compelling conceptual evidence that targeting the AnxA1/FPR2/ALX pathway may provide new therapeutic possibilities against thromboinflammatory conditions such as SCD.

Targeting AnxA1/Formyl Peptide Receptor 2 Pathway Affords Protection against Pathological Thrombo-Inflammation

Stroke is a leading cause of death and disability globally and is associated with a number of co-morbidities including sepsis and sickle cell disease (SCD). Despite thrombo-inflammation underlying these co-morbidities, its pathogenesis remains complicated and drug discovery programs aimed at reducing and resolving the detrimental effects remain a major therapeutic challenge. The objective of this study was to assess whether the anti-inflammatory pro-resolving protein Annexin A1 (AnxA1) was able to reduce inflammation-induced thrombosis and suppress platelet activation and thrombus formation in the cerebral microvasculature. Using two distinct models of pathological thrombo-inflammation (lipopolysaccharide (LPS) and sickle transgenic mice (STM)), thrombosis was induced in the murine brain using photoactivation (light/dye) coupled with intravital microscopy. The heightened inflammation-induced microvascular thrombosis present in these two distinct thrombo-inflammatory models was inhibited significantly by the administration of AnxA1 mimetic peptide AnxA1_Ac2-26 (an effect more pronounced in the SCD model vs. the endotoxin model) and mediated by the key resolution receptor, Fpr2/ALX. Furthermore, AnxA1_Ac2-26 treatment was able to hamper platelet aggregation by reducing platelet stimulation and aggregation (by moderating α_IIbβ₃ and P-selectin). These findings suggest that targeting the AnxA1/Fpr2/ALX pathway represents an attractive novel treatment strategy for resolving thrombo-inflammation, counteracting e.g., stroke in high-risk patient cohorts.

Bioinformatics Analysis of Gut Microbiota and CNS Transcriptome in Virus-Induced Acute Myelitis and Chronic Inflammatory Demyelination; Potential Association of Distinct Bacteria With CNS IgA Upregulation

Virus infections have been associated with acute and chronic inflammatory central nervous system (CNS) diseases, e.g., acute flaccid myelitis (AFM) and multiple sclerosis (MS), where animal models support the pathogenic roles of viruses. In the spinal cord, Theiler's murine encephalomyelitis virus (TMEV) induces an AFM-like disease with gray matter inflammation during the acute phase, 1 week post infection (p.i.), and an MS-like disease with white matter inflammation during the chronic phase, 1 month p.i. Although gut microbiota has been proposed to affect immune responses contributing to pathological conditions in remote organs, including the brain pathophysiology, its precise role in neuroinflammatory diseases is unclear. We infected SJL/J mice with TMEV; harvested feces and spinal cords on days 4 (before onset), 7 (acute phase), and 35 (chronic phase) p.i.; and examined fecal microbiota by 16S rRNA sequencing and CNS transcriptome by RNA sequencing. Although TMEV infection neither decreased microbial diversity nor changed overall microbiome patterns, it increased abundance of individual bacterial genera Marvinbryantia on days 7 and 35 p.i. and Coprococcus on day 35 p.i., whose pattern-matching with CNS transcriptome showed strong correlations: Marvinbryantia with eight T-cell receptor (TCR) genes on day 7 and with seven immunoglobulin (Ig) genes on day 35 p.i.; and Coprococcus with gene expressions of not only TCRs and IgG/IgA, but also major histocompatibility complex (MHC) and complements. The high gene expression of IgA, a component of mucosal immunity, in the CNS was unexpected. However, we observed substantial IgA positive cells and deposition in the CNS, as well as a strong correlation between CNS IgA gene expression and serum anti-TMEV IgA titers. Here, changes in a small number of distinct gut bacteria, but not overall gut microbiota, could affect acute and chronic immune responses, causing AFM- and MS-like lesions in the CNS. Alternatively, activated immune responses would alter the composition of gut microbiota.

Targeting of Formyl Peptide Receptor 2 for in vivo imaging of acute vascular inflammation

Inflammatory conditions are associated with a variety of diseases and can significantly contribute to their pathophysiology. Neutrophils are recognised as key players in driving vascular inflammation and promoting inflammation resolution. As a result, neutrophils, and specifically their surface formyl peptide receptors (FPRs), are attractive targets for non-invasive visualization of inflammatory disease states and studying mechanistic details of the process.

Methods: A small-molecule Formyl Peptide Receptor 2 (FPR2/ALX)-targeted compound was combined with two rhodamine-derived fluorescent tags to form firstly, a targeted probe (Rho-pip-C1) and secondly a targeted, pH-responsive probe (Rho-NH-C1) for in vivo applications. We tested internalization, toxicity and functional interactions with neutrophils in vitro for both compounds, as well as the fluorescence switching response of Rho-NH-C1 to neutrophil activation. Finally, in vivo imaging (fluorescent intravital microscopy [IVM]) and therapeutic efficacy studies were performed in an inflammatory mouse model.

Results: In vitro studies showed that the compounds bound to human neutrophils via FPR2/ALX without causing internalization at relevant concentrations. Additionally, the compounds did not cause toxicity or affect neutrophil functional responses (e.g. chemotaxis or transmigration). In vivo studies using IVM showed Rho-pip-C1 bound to activated neutrophils in a model of vascular inflammation. The pH-sensitive (“switchable”) version termed Rho-NH-C1 validated these findings, showing fluorescent activity only in inflammatory conditions.

Conclusions: These results indicate a viable design of fluorescent probes that have the ability to detect inflammatory events by targeting activated neutrophils.

Endogenous Specialized Proresolving Mediator Profiles in a Novel Experimental Model of Lymphatic Obstruction and Intestinal Inflammation in African Green Monkeys

Changes in the intestinal lymphatic vascular system, such as lymphatic obstruction, are characteristic features of inflammatory bowel diseases. The lymphatic vasculature forms a conduit to enable resolution of inflammation; this process is driven by specialized endogenous proresolving mediators (SPMs). To evaluate contributions of lymphatic obstruction to intestinal inflammation and to study profiles of SPMs, we generated a novel animal model of lymphatic obstruction using African green monkeys. Follow-up studies were performed at 7, 21, and 61 days. Inflammation was determined by histology. Luminex assays were performed to evaluate chemokine and cytokine levels. In addition, lipid mediator metabololipidomic profiling was performed to identify SPMs. After 7 days, lymphatic obstruction resulted in a localized inflammatory state, paralleled by an increase in inflammatory chemokines and cytokines, which were found to be up-regulated after 7 days but returned to baseline after 21 and 61 days. At the same time, a distinct pattern of SPMs was profiled, with an increase for D-series resolvins, protectins, maresins, and lipoxins at 61 days. These results indicate that intestinal lymphatic obstruction can lead to an acute inflammatory state, accompanied by an increase in proinflammatory mediators, followed by a phase of resolution, paralleled by an increase and decrease of respective SPMs.

In vivo delivery of a fluorescent FPR2/ALX-targeted probe using focused ultrasound and microbubbles to image activated microglia

Targeted imaging agent labels activated microglia when delivered into the brain with focused ultrasound and microbubbles – a tool to investigate inflammation in neurological disorders.

Ischemia-Reperfusion Injury in Sickle Cell Disease: From Basics to Therapeutics

Sickle cell disease (SCD) is one of the most common hereditary hemoglobinopathies worldwide, affecting almost 400,000 newborns globally each year. It is characterized by chronic hemolytic anemia and endothelial dysfunction, resulting in a constant state of disruption of the vascular system and leading to recurrent episodes of ischemia-reperfusion injury (I/RI) to multiple organ systems. I/RI is a fundamental vascular pathobiological paradigm and contributes to morbidity and mortality in a wide range of conditions, including myocardial infarction, stroke, acute kidney injury, and transplantation. I/RI is characterized by an initial restriction of blood supply to an organ, which can lead to ischemia, followed by the subsequent restoration of perfusion and concomitant reoxygenation. Recent advances in the pathophysiology of SCD have led to an understanding that many of the consequences of this disease can be explained by mechanisms associated with I/RI. The following review focuses on the evolving pathobiology of SCD, how various complications of SCD can be attributed to I/RI, and the role of timely therapeutic intervention(s) based on targeting mediators or pathways that influence I/R insult.

Development, characterisation and in vitro evaluation of lanthanide-based FPR2/ALX-targeted imaging probes

We report the design, preparation and characterisation of three small-molecule, Formyl Peptide Receptor (FPR)-targeted lanthanide complexes (Tb·14, Eu·14 and Gd·14). Long-lived, metal-based emission was observed from the terbium complex (τH2O = 1.9 ms), whereas only negligible lanthanide signals were detected in the europium analogue. Ligand-centred emission was investigated using Gd·14 at room temperature and 77 K, leading to the postulation that metal emission may be sensitised via a ligand-based charge transfer state of the targeting Quin C1 unit. Comparatively high longitudinal relaxivity values (r1) for octadentate metal complexes of Gd·14 were determined (6.9 mM-1 s-1 at 400 MHz and 294 K), which could be a result of a relative increase in twisted square antiprism (TSAP) isomer prevalence compared to typical DOTA constructs (as evidenced by NMR spectroscopy). In vitro validation of concentration responses of Tb·14via three key neutrophil functional assays demonstrated that the inflammatory responses of neutrophils (i.e. chemotaxis, transmigration and granular release) remained unchanged in the presence of specific concentrations of the compound. Using a time-resolved microscopy set-up we were able to observe binding of the Tb·14 probe to stimulated human neutrophils around the cell periphery, while in the same experiment with un-activated neutrophils, no metal-based signals were detected. Our results demonstrate the utility of Tb·14 for time-resolved microscopy with lifetimes several orders of magnitude longer than autofluorescent signals and a preferential uptake in stimulated neutrophils.

Novel Role for the AnxA1-Fpr2/ALX Signaling Axis as a Key Regulator of Platelet Function to Promote Resolution of Inflammation

Supplemental Digital Content is available in the text.

Background:

Ischemia reperfusion injury (I/RI) is a common complication of cardiovascular diseases. Resolution of detrimental I/RI-generated prothrombotic and proinflammatory responses is essential to restore homeostasis. Platelets play a crucial part in the integration of thrombosis and inflammation. Their role as participants in the resolution of thromboinflammation is underappreciated; therefore we used pharmacological and genetic approaches, coupled with murine and clinical samples, to uncover key concepts underlying this role.

Methods:

Middle cerebral artery occlusion with reperfusion was performed in wild-type or annexin A1 (AnxA1) knockout (AnxA1^−/−) mice. Fluorescence intravital microscopy was used to visualize cellular trafficking and to monitor light/dye–induced thrombosis. The mice were treated with vehicle, AnxA1 (3.3 mg/kg), WRW4 (1.8 mg/kg), or all 3, and the effect of AnxA1 was determined in vivo and in vitro.

Results:

Intravital microscopy revealed heightened platelet adherence and aggregate formation post I/RI, which were further exacerbated in AnxA1^−/− mice. AnxA1 administration regulated platelet function directly (eg, via reducing thromboxane B₂ and modulating phosphatidylserine expression) to promote cerebral protection post-I/RI and act as an effective preventative strategy for stroke by reducing platelet activation, aggregate formation, and cerebral thrombosis, a prerequisite for ischemic stroke. To translate these findings into a clinical setting, we show that AnxA1 plasma levels are reduced in human and murine stroke and that AnxA1 is able to act on human platelets, suppressing classic thrombin-induced inside-out signaling events (eg, Akt activation, intracellular calcium release, and Ras-associated protein 1 [Rap1] expression) to decrease α_IIbβ₃ activation without altering its surface expression. AnxA1 also selectively modifies cell surface determinants (eg, phosphatidylserine) to promote platelet phagocytosis by neutrophils, thereby driving active resolution. (n=5–13 mice/group or 7–10 humans/group.)

Conclusions:

AnxA1 affords protection by altering the platelet phenotype in cerebral I/RI from propathogenic to regulatory and reducing the propensity for platelets to aggregate and cause thrombosis by affecting integrin (α_IIbβ₃) activation, a previously unknown phenomenon. Thus, our data reveal a novel multifaceted role for AnxA1 to act both as a therapeutic and a prophylactic drug via its ability to promote endogenous proresolving, antithromboinflammatory circuits in cerebral I/RI. Collectively, these results further advance our knowledge and understanding in the field of platelet and resolution biology.

Novel Role of T Cells and IL-6 (Interleukin-6) in Angiotensin II-Induced Microvascular Dysfunction

Hypertension is an established risk factor for subsequent cardiovascular diseases, with Ang II (angiotensin II) playing a major role in mediating thrombotic and inflammatory abnormalities. Although T cells and IL-6 (interleukin-6) play an important role in adaptive immune responses, little is known about their role(s) in the thromboinflammatory responses associated with Ang II. Here we show using intravital microscopy coupled with the light/dye injury model that Rag-1 deficient (Rag-1-/-) and IL-6 deficient (IL-6-/-) mice are afforded protection against Ang II-induced thrombosis. Blocking IL-6 receptors (using CD126 and gp130 antibodies) significantly diminished Ang II-mediated thrombosis and inflammatory cell recruitment in mice. Furthermore, the adoptive transfer of IL-6-/--derived T cells into Rag-1-/- mice failed to accelerate Ang II-induced thrombosis compared with Rag-1-/- mice reconstituted with wild-type-derived T cells, suggesting T cell IL-6 mediates the thrombotic abnormalities associated Ang II hypertension. Interestingly, adoptive transfer of WT T cells into Rag-1-/-/Ang II mice resulted in increased numbers of immature platelets, which constitutes a more active platelet population, that is, prothrombotic and proinflammatory. To translate our in vivo findings, we used clinical samples to demonstrate that IL-6 also predisposes platelets to an interaction with collagen receptors, thereby increasing the propensity for platelets to aggregate and cause thrombosis. In summary, we provide compelling evidence for the involvement of IL-6, IL-6R, and T-cell-dependent IL-6 signaling in Ang II-induced thromboinflammation, which may provide new therapeutic possibilities for drug discovery programs for the management of hypertension.

Potential therapeutic roles of stem cells in ischemia-reperfusion injury

Ischemia-reperfusion injury (I/RI), produced by an initial interruption of organ blood flow and its subsequent restoration, contributes significantly to the pathophysiologies of stroke, myocardial infarction, renal I/RI, intestinal I/RI and liver I/RI, which are major causes of disability (including transplant failure) and even mortality. While the restoration of blood flow is required to restore oxygen and nutrient requirements, reperfusion often triggers local and systemic inflammatory responses and subsequently elevate the ischemic insult where the duration of ischemia determines the magnitude of I/RI damage. I/RI increases vascular leakage, changes transcriptional and cell death programs, drives leukocyte entrapment and inflammation and oxidative stress in tissues. Therapeutic approaches which reduce complications associated with I/RI are desperately needed to address the clinical and economic burden created by I/RI. Stem cells (SC) represent ubiquitous and uncommitted cell populations with the ability to self-renew and differentiate into one or more developmental 'fates'. Like immune cells, stem cells can home to and penetrate I/R-injured tissues, where they can differentiate into target tissues and induce trophic paracrine signaling which suppress injury and maintain tissue functions perturbed by ischemia-reperfusion. This review article summarizes the present use and possible protective mechanisms underlying stem cell protection in diverse forms of ischemia-reperfusion.

IL-1β reduces cardiac lymphatic muscle contraction via COX-2 and PGE2 induction: Potential role in myocarditis

The role of lymphatic vessels in myocarditis is largely unknown, while it has been shown to play a key role in other inflammatory diseases. We aimed to investigate the role of lymphatic vessels in myocarditis using in vivo model induced with Theiler's murine encephalomyelitis virus (TMEV) and in vitro model with rat cardiac lymphatic muscle cells (RCLMC). In the TMEV model, we found that upregulation of a set of inflammatory mediator genes, including interleukin (IL)-1β, tumor necrosis factor (TNF)-αand COX-2 were associated with disease activity. Thus, using in vitro collagen gel contraction assays, we decided to clarify the role(s) of these mediators by testing contractility of RCLMC in response to IL-1β and TNF-α individually and in combination, in the presence or absence of: IL-1 receptor antagonist (Anakinra); cyclooxygenase (COX) inhibitors inhibitors (TFAP, diclofenac and DuP-697). IL-1β impaired RCLMC contractility dose-dependently, while co-incubation with both IL-1β and TNF-α exhibited synergistic effects in decreasing RCLMC contractility with increased COX-2 expression. Anakinra maintained RCLMC contractility; Anakinra blocked the mobilization of COX-2 induced by IL-1β with or without TNF-α. COX-2 inhibition blocked the IL-1β-mediated decrease in RCLMC contractility. Mechanistically, we found that IL-1β increased prostaglandin (PG) E₂ release dose-dependently, while Anakinra blocked IL-1β mediated PGE₂ release. Using prostaglandin E receptor 4 (EP4) receptor antagonist, we demonstrated that EP4 receptor blockade maintained RCLMC contractility following IL-1β exposure. Our results indicate that IL-1β reduces RCLMC contractility via COX-2/PGE₂ signaling with synergistic cooperation by TNF-α. These pathways may help provoke inflammatory mediator accumulation within the heart, driving progression from acute myocarditis into dilated cardiomyopathy.

The isothiocyanate sulforaphane modulates platelet function and protects against cerebral thrombotic dysfunction

BACKGROUND AND PURPOSE

Platelet activation provides a critical link between inflammation and thrombosis. Sulforaphane (SFN), a naturally occurring isothiocyanate, has been shown to display both anti-inflammatory and anti-thrombotic actions in the systemic microvasculature. As inflammation promotes thrombosis and vice versa, in this study we investigated whether SFN is able to reduce inflammatory potentiation of thrombotic events, suppress platelet activation and thrombus formation in the cerebral microvasculature.

EXPERIMENTAL APPROACH

Thrombosis was induced in the murine brain using the light/dye-injury model, in conjunction with LPS treatment, with and without SFN treatment. In vitro and in vivo platelet assays (aggregation, flow and other functional tests) were also employed, using both human and murine platelets.

KEY RESULTS

SFN was found to reduce LPS-mediated enhancement of thrombus formation in the cerebral microcirculation. In tail-bleed experiments, LPS treatment prolonged bleeding time, and SFN treatment was found to protect against this LPS-induced derangement of platelet function. SFN inhibited collagen-mediated platelet aggregation in vitro and in vivo and the associated adhesion and impaired calcium signalling. Furthermore, glycoprotein VI was shown to be involved in the protective effects observed with SFN treatment.

CONCLUSIONS AND IMPLICATIONS

The data presented here provide evidence for the use of SFN in preventing stroke in selected high-risk patient cohorts.

Therapeutic Potential of Annexin A1 in Ischemia Reperfusion Injury

Cardiovascular disease (CVD) continues to be the leading cause of death in the world. Increased inflammation and an enhanced thrombotic milieu represent two major complications of CVD, which can culminate into an ischemic event. Treatment for these life-threatening complications remains reperfusion and restoration of blood flow. However, reperfusion strategies may result in ischemia-reperfusion injury (I/RI) secondary to various cardiovascular pathologies, including myocardial infarction and stroke, by furthering the inflammatory and thrombotic responses and delivering inflammatory mediators to the affected tissue. Annexin A1 (AnxA1) and its mimetic peptides are endogenous anti-inflammatory and pro-resolving mediators, known to have significant effects in resolving inflammation in a variety of disease models. Mounting evidence suggests that AnxA1, which interacts with the formyl peptide receptor (FPR) family, may have a significant role in mitigating I/RI associated complications. In this review article, we focus on how AnxA1 plays a protective role in the I/R based vascular pathologies.

A critical role for both CD40 and VLA5 in angiotensin II-mediated thrombosis and inflammation

Angiotensin II (Ang-II)-induced hypertension is associated with accelerated thrombus formation in arterioles and leukocyte recruitment in venules. The mechanisms that underlie the prothrombotic and proinflammatory responses to chronic Ang-II administration remain poorly understood. We evaluated the role of CD40/CD40 ligand (CD40L) signaling in Ang-II-mediated microvascular responses and assessed whether and how soluble CD40L (sCD40L) contributes to this response. Intravital video microscopy was performed to analyze leukocyte recruitment and dihydrorhodamine-123 oxidation in postcapillary venules. Thrombus formation in cremaster muscle arterioles was induced by using the light/dye endothelial cell injury model. Wild-type (WT), CD40^-/-, and CD40L^-/- mice received Ang-II for 14 d via osmotic minipumps. Some mice were treated with either recombinant sCD40L or the VLA5 (very late antigen 5; α5β1) antagonist, ATN-161. Our results demonstrate that CD40^-/-, CD40L^-/-, and WT mice that were treated with ATN-161 were protected against the thrombotic and inflammatory effects of Ang-II infusion. Infusion of sCD40L into CD40^-/- or CD40L^-/- mice restored the prothrombotic effect of Ang-II infusion. Mice that were treated with ATN-161 and infused with sCD40L were protected against accelerated thrombosis. Collectively, these novel findings suggest that the mechanisms that underlie Ang-II-dependent thrombotic and inflammatory responses link to the signaling of CD40L via both CD40 and VLA5.-Senchenkova, E. Y., Russell, J., Vital, S. A., Yildirim, A., Orr, A. W., Granger, D. N., Gavins, F. N. E. A critical role for both CD40 and VLA5 in angiotensin II-mediated thrombosis and inflammation.

Metallothionein I as a direct link between therapeutic hematopoietic stem/progenitor cells and cerebral protection in stroke

Stroke continues to be a leading cause of death and disability worldwide, yet effective treatments are lacking. Previous studies have indicated that stem-cell transplantation could be an effective treatment. However, little is known about the direct impact of transplanted cells on injured brain tissue. We wanted to help fill this knowledge gap and investigated effects of hematopoietic stem/progenitor cells (HSPCs) on the cerebral microcirculation after ischemia-reperfusion injury (I/RI). Treatment of HSPCs in I/RI for up to 2 wk after cerebral I/RI led to decreased mortality rate, decreased infarct volume, improved functional outcome, reduced microglial activation, and reduced cerebral leukocyte adhesion. Confocal microscopy and fluorescence-activated cell sorting analyses showed transplanted HSPCs emigrate preferentially into ischemic cortex brain parenchyma. We isolated migrated HSPCs from the brain; using RNA sequencing to investigate the transcriptome, we found metallothionein (MT, particularly MT-I) transcripts were dramatically up-regulated. Finally, to confirm the significance of MT, we exogenously administered MT-I after cerebral I/RI and found that it produced neuroprotection in a manner similar to HSPC treatment. These findings provide novel evidence that the mechanism through which HSPCs promote repair after stroke maybe via direct action of HSPC-derived MT-I and could therefore be exploited as a useful therapeutic strategy for stroke.-Smith, H. K., Omura, S., Vital, S. A., Becker, F., Senchenkova, E. Y., Kaur, G., Tsunoda, I., Peirce, S. M., Gavins, F. N. E. Metallothionein I as a direct link between therapeutic hematopoietic stem/progenitor cells and cerebral protection in stroke.

Sickle cell disease: a malady beyond a hemoglobin defect in cerebrovascular disease

INTRODUCTION

Sickle cell disease (SCD) is a devastating monogenic disorder that presents as a multisystem illness and affects approximately 100,000 individuals in the United States alone. SCD management largely focuses on primary prevention, symptomatic treatment and targeting of hemoglobin polymerization and red blood cell sickling. Areas covered: This review will discuss the progress of SCD over the last few decades, highlighting some of the clinical (mainly cerebrovascular) and psychosocial challenges of SCD in the United States. In addition, focus will also be made on the evolving science and management of this inherited disease. Expert commentary: Until recently hydroxyurea (HU) has been the only FDA approved therapy for SCD. However, advancing understanding of SCD pathophysiology has led to multiple clinical trials targeting SCD related thrombo-inflammation, abnormal endothelial biology, increased oxidant stress and sickle cell mutation. Yet, despite advancing understanding, available therapies are limited. SCD also imposes great psychosocial challenges for the individual and the affected community, which has previously been under-recognized. This has created a pressing need for complementary adjuvant therapies with repurposed and novel drugs, in addition to the establishment of comprehensive clinics focusing on both the medical treatment and the psychosocial issues associated with SCD.

Mast cells mediate early neutrophil recruitment and exhibit anti-inflammatory properties via the formyl peptide receptor 2/lipoxin A4 receptor

BACKGROUND AND PURPOSE

In recent years, studies have focused on the resolution of inflammation, which can be achieved by endogenous anti-inflammatory agonists such as Annexin A1 (AnxA1). Here, we investigated the effects of mast cells (MCs) on early LPS-induced neutrophil recruitment and the involvement of the AnxA1-formyl peptide receptor 2/ALX (FPR2/ALX or lipoxin A₄ receptor) pathway.

EXPERIMENTAL APPROACH

Intravital microscopy (IVM) was used to visualize and quantify the effects of LPS (10 μg per mouse i.p.) on murine mesenteric cellular interactions. Furthermore, the role that MCs play in these inflammatory responses was determined in vivo and in vitro, and effects of AnxA1 mimetic peptide Ac2-26 were assessed.

KEY RESULTS

LPS increased both neutrophil endothelial cell interactions within the mesenteric microcirculation and MC activation (determined by IVM and ruthenium red dye uptake), which in turn lead to the early stages of neutrophil recruitment. MC recruitment of neutrophils could be blocked by preventing the pro-inflammatory activation (using cromolyn sodium) or enhancing an anti-inflammatory phenotype (using Ac2-26) in MCs. Furthermore, MCs induced neutrophil migration in vitro, and MC stabilization enhanced the release of AnxA1 from neutrophils. Pharmacological approaches (such as the administration of FPR pan-antagonist Boc2, or the FPR2/ALX antagonist WRW4) revealed neutrophil FPR2/ALX to be important in this process.

CONCLUSIONS AND IMPLICATIONS

Data presented here provide evidence for a role of MCs, which are ideally positioned in close proximity to the vasculature, to act as sentinel cells in neutrophil extravasation and resolution of inflammation via the AnxA1-FPR2/ALX pathway.

Surgical Approach for Middle Cerebral Artery Occlusion and Reperfusion Induced Stroke in Mice

Stroke is a leading cause of death worldwide and continues to be one of the major causes of long-term adult disabilities. About 87% of strokes are ischemic in origin and occur in the territory of the middle cerebral artery (MCA). Currently the only Food and Drug Administration (FDA) approved drug for the treatment of this devastating disease is tissue plasminogen activator (tPA). However, tPA has a small therapeutic window for administration (3 - 6 hr), and is only effective in 4% of the patients who actually receive it. Current research focuses on understanding the pathophysiology of stroke in order to find potential therapeutic targets. Thus, reliable models are crucial, and the MCA occlusion (MCAo) model (also termed the intraluminal filament or suture model) is deemed to be the most clinically relevant surgical model of ischemic stroke, and is fairly non-invasive and easily reproducible. Typically the MCAo model is used with rodents, especially with mice due to all the genetic variations available for this species. Here we describe (and present in the video) how to successfully perform the MCAo model (with reperfusion) in mice to generate reliable and reproducible data.

Abstract 4816: Potent inhibition of the cell proliferation and induction of apoptosis in lymphoma cells by the anthelminthic drug niclosamide: in vitro data

Background: Niclosamide, an anthelminthic drug, has demonstrated anti-cancer potential in variety of malignancies. However only a limited number of studies have been performed in lymphoma models, therefore we hypothesized that niclosamide may also have anti-cancer potential on B-cell lymphomas.

Materials and Methods: Established B lymphoma cell lines were exposed to different concentrations of niclosamide and IC50 was calculated using GraphPad Prism 6.0 software. Cell viability and proliferation were assessed by CellTiter-Blue and trypan blue exclusion assays. Apoptosis was assessed by flow cytometry following Annexin-V/ propidium iodide staining. Gene expression changes were studied using GeneChip Human Transcriptome Array 2.0. Colony forming assays were performed in methylcellulose. Ultrastructural cellular changes were studied with electron microscopy. Peripheral blood mononuclear cells (PBMCs) from individuals without active cancer and from patients with different hematologic disorders, were also exposed with niclosamide.

Results: Treatment with niclosamide resulted in time-and dose- dependent apoptosis, cytotoxicity and inhibition of proliferation in different lymphoma cell lines including vincristine-refractory cell line. The IC50 of lymphoma cells lines is as follows: Daudi: 0.33 ìM; HBL-2: 0.57 ìM; KOPN-8: 0.72 ìM; Ramos: 0.53 ìM and SU-DHL4-VR: 0.45 ìM. Niclosamide also inhibited clonal growth in semi-solid media. Gene expression changes were studied in Daudi and KOPN-8 cells treated with 2.5 ìM Niclosamide for 3 and 6 hours. 96 genes were consistently overexpressed, 59 down-regulated. 10 genes involved in the tumor necrosis factor (TNF) pathway and 10 genes involving the DNA damage pathway were overexpressed. 13 out of the 59 down-regulated genes were involved in mitochondrial function. Electron microscopy showed that filopodia increased and lipid vacuoles developed whereas mitochondria were less numerous in KOPN-8 cells. The viability of PBMCs from 8 individuals without lymphoma was unchanged when incubated with niclosamide, whereas niclosamide showed significant cytotoxicity in a patient with mantle cell lymphoma (MCL).

Conclusion: Niclosamide effectively inhibits the proliferation of B lymphoma cell lines, including vincristine-refractory lymphoma cells, and induces apoptosis at concentrations non-toxic to PBMCs. Interestingly, niclosamide exhibited cytotoxic activity against MCL cells - a finding worth testing further in this difficult-to-treat disease. The mechanism of action of Niclosamide may involve the TNF receptor pathway, mitochondrial function and DNA damage response pathway. We plan to elucidate further specific mechanism(s) of action, and evaluate synergistic effects with other antineoplastic agents, and perform in vivo studies.

Citation Format: Junaid Ansari, Hazem El-Osta, Paula Polk, Jeffrey J. Aufman, Guillermo A. Herrera, James Cardelli, Rodney E. Shackelford, Glenn M. Mills, Magdalena L. Circu, Felicity N. E. Gavins, Reinhold Munker. Potent inhibition of the cell proliferation and induction of apoptosis in lymphoma cells by the anthelminthic drug niclosamide: in vitro data. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4816.

Sulforaphane induces neurovascular protection against a systemic inflammatory challenge via both Nrf2-dependent and independent pathways

Sepsis is often characterized by an acute brain inflammation and dysfunction, which is associated with increased morbidity and mortality worldwide. Preventing cerebral leukocyte recruitment may provide the key to halt progression of systemic inflammation to the brain. Here we investigated the influence of the anti-inflammatory and anti-oxidant compound, sulforaphane (SFN) on lipopolysaccharide (LPS)-induced cellular interactions in the brain. The inflammatory response elicited by LPS was blunted by SFN administration (5 and 50mg/kg i.p.) 24h prior to LPS treatment in WT animals, as visualized and quantified using intravital microscopy. This protective effect of SFN was lost in Nrf2-KO mice at the lower dose tested, however 50mg/kg SFN revealed a partial effect, suggesting SFN works in part independently of Nrf2 activity. In vitro, SFN reduced neutrophil recruitment to human brain endothelial cells via a down regulation of E-selectin and vascular cell adhesion molecule 1 (VCAM-1). Our data confirm a fundamental dose-dependent role of SFN in limiting cerebral inflammation. Furthermore, our data demonstrate that not only is Nrf2 in part essential in mediating these neuroprotective effects, but they occur via down-regulation of E-selectin and VCAM-1. In conclusion, SFN may provide a useful therapeutic drug to reduce cerebral inflammation in sepsis.

Formyl-Peptide Receptor 2/3/Lipoxin A4 Receptor Regulates Neutrophil-Platelet Aggregation and Attenuates Cerebral Inflammation: Impact for Therapy in Cardiovascular Disease

BACKGROUND

Platelet activation at sites of vascular injury is essential for hemostasis, but it is also a major pathomechanism underlying ischemic injury. Because anti-inflammatory therapies limit thrombosis and antithrombotic therapies reduce vascular inflammation, we tested the therapeutic potential of 2 proresolving endogenous mediators, annexin A1 N-terminal derived peptide (AnxA1Ac2-26) and aspirin-triggered lipoxin A4 (15-epi-lipoxin A4), on the cerebral microcirculation after ischemia/reperfusion injury. Furthermore, we tested whether the lipoxin A4 receptor formyl-peptide receptor 2/3 (Fpr2/3; ortholog to human FPR2/lipoxin A4 receptor) evoked neuroprotective functions after cerebral ischemia/reperfusion injury.

METHODS AND RESULTS

Using intravital microscopy, we found that cerebral ischemia/reperfusion injury was accompanied by neutrophil and platelet activation and neutrophil-platelet aggregate formation within cerebral microvessels. Moreover, aspirin-triggered lipoxin A4 activation of neutrophil Fpr2/3 regulated neutrophil-platelet aggregate formation in the brain and inhibited the reactivity of the cerebral microvasculature. The same results were obtained with AnxA1Ac2-26 administration. Blocking Fpr2/lipoxin A4 receptor with the antagonist Boc2 reversed this effect, and treatments were ineffective in Fpr2/3 knockout mice, which displayed an exacerbated disease severity, evidenced by increased infarct area, blood-brain barrier dysfunction, increased neurological score, and elevated levels of cytokines. Furthermore, aspirin treatment significantly reduced cerebral leukocyte recruitment and increased endogenous levels of aspirin-triggered lipoxin A4, effects again mediated by Fpr2/3.

CONCLUSION

Fpr2/lipoxin A4 receptor is a therapeutic target for initiating endogenous proresolving, anti-inflammatory pathways after cerebral ischemia/reperfusion injury.

(99m)Tc SPECT imaging agent based on cFLFLFK for the detection of FPR1 in inflammation

Non-invasive imaging of the inflammatory process can provide great insight into a wide variety of disease states, aiding diagnosis, evaluation and effective targeted treatment. During inflammation, blood borne leukocytes are recruited, through a series of activation and adhesion steps, to the site of injury or infection where they migrate across the blood vessel wall into the tissue. Thus, tracking leukocyte recruitment and accumulation provides a dynamic and localised read out of inflammatory events. Current leukocyte imaging techniques require ex vivo labelling of patient blood, involving laborious processing and potential risks to both patient and laboratory staff. Utilising high affinity ligands for leukocyte specific receptors may allow for injectable tracers that label leukocytes in situ, omitting potentially hazardous ex vivo handling. Formyl peptide receptors (FPRs) are a group of G-protein coupled receptors involved in the chemotaxis and inflammatory functioning of leukocytes. Highly expressed on leukocytes, and up-regulated during inflammation, these receptors provide a potential target for imaging inflammatory events. Herein we present the synthesis and initial in vitro testing of a potential Single Photon Emission Computed Tomography (SPECT) leukocyte tracer. The FPR1 antagonist cFLFLFK-NH2, which displays high affinity with little physiological effect, has been linked via a PEG motif to a (99m)Tc chelate. This tracer shows in vitro binding to human embryonic kidney cells expressing the FPR1 receptor, and functional in vitro tests reveal cFLFLFK-NH2 compounds to have no effect on inflammatory cell functioning. Overall, these data show that (99m)Tc.cFLFLFK-NH2 may be a useful tool for non-invasive imaging of leukocyte accumulation in inflammatory disease states.

IL-1β reduces tonic contraction of mesenteric lymphatic muscle cells, with the involvement of cycloxygenase-2 and prostaglandin E2

BACKGROUND AND PURPOSE

The lymphatic system maintains tissue homeostasis by unidirectional lymph flow, maintained by tonic and phasic contractions within subunits, 'lymphangions'. Here we have studied the effects of the inflammatory cytokine IL-1β on tonic contraction of rat mesenteric lymphatic muscle cells (RMLMC).

EXPERIMENTAL APPROACH

We measured IL-1β in colon-conditioned media (CM) from acute (AC-CM, dextran sodium sulfate) and chronic (CC-CM, T-cell transfer) colitis-induced mice and corresponding controls (Con-AC/CC-CM). We examined tonic contractility of RMLMC in response to CM, the cytokines h-IL-1β or h-TNF-α (5, 10, 20 ng·mL(-1) ), with or without COX inhibitors [TFAP (10(-5)  M), diclofenac (0.2 × 10(-5)  M)], PGE2 (10(-5)  M)], IL-1-receptor antagonist, Anakinra (5 μg·mL(-1) ), or a selective prostanoid EP4 receptor antagonist, GW627368X (10(-6) and 10(-7)  M).

KEY RESULTS

Tonic contractility of RMLMC was reduced by AC- and CC-CM compared with corresponding control culture media, Con-AC/CC-CM. IL-1β or TNF-α was not found in Con-AC/CC-CM, but detected in AC- and CC-CM. h-IL-1β concentration-dependently decreased RMLMC contractility, whereas h-TNF-α showed no effect. Anakinra blocked h-IL-1β-induced RMLMC relaxation, and with AC-CM, restored contractility to RMLMC. IL-1β increased COX-2 protein and PGE2 production in RMLMC.. PGE2 induced relaxations in RMLMC, comparable to h-IL-1β. Conversely, COX-2 and EP4 receptor inhibition reversed relaxation induced by IL-1β.

CONCLUSIONS AND IMPLICATIONS

The IL-1β-induced decrease in RMLMC tonic contraction was COX-2 dependent, and mediated by PGE2 . In experimental colitis, IL-1β and tonic lymphatic contractility were causally related, as this cytokine was critical for the relaxation induced by AC-CM and pharmacological blockade of IL-1β restored tonic contraction.

Both MC1 and MC3 Receptors Provide Protection From Cerebral Ischemia-Reperfusion-Induced Neutrophil Recruitment

OBJECTIVE

Neutrophil recruitment is a key process in the pathogenesis of stroke, and may provide a valuable therapeutic target. Targeting the melanocortin (MC) receptors has previously shown to inhibit leukocyte recruitment in peripheral inflammation, however, it is not known whether treatments are effective in the unique cerebral microvascular environment. Here, we provide novel research highlighting the effects of the MC peptides on cerebral neutrophil recruitment, demonstrating important yet discrete roles for both MC1 and MC3.

APPROACH AND RESULTS

Using intravital microscopy, in 2 distinct murine models of cerebral ischemia-reperfusion (I/R) injury, we have investigated MC control for neutrophil recruitment. After global I/R, pharmacological treatments suppressed pathological neutrophil recruitment. MC1 selective treatment rapidly inhibited neutrophil recruitment while a nonselective MC agonist provided protection even when coadministered with an MC3/4 antagonist, suggesting the importance of early MC1 signaling. However, by 2-hour reperfusion, MC1-mediated effects were reduced, and MC3 anti-inflammatory circuits predominated. Mice bearing a nonfunctional MC1 displayed a transient exacerbation of neutrophil recruitment after global I/R, which diminished by 2 hours. However importantly, enhanced inflammatory responses in both MC1 mutant and MC3 (-/-) mice resulted in increased infarct size and poor functional outcome after focal I/R. Furthermore, we used an in vitro model of leukocyte recruitment to demonstrate these anti-inflammatory actions are also effective in human cells.

CONCLUSIONS

These studies reveal for the first time MC control for neutrophil recruitment in the unique pathophysiological context of cerebral I/R, while also demonstrating the potential therapeutic value of targeting multiple MCs in developing effective therapeutics.

Targeting the annexin 1-formyl peptide receptor 2/ALX pathway affords protection against bacterial LPS-induced pathologic changes in the murine adrenal cortex

Hypothalamo-pituitary-adrenocortical dysfunction contributes to morbidity and mortality in a high proportion of patients with sepsis. Here, we provide new insights into the underlying adrenal pathology. Using a murine model of endotoxemia (LPS injection), we demonstrate that adrenal insufficiency is triggered early in the disease. LPS induced a local inflammatory response in the adrenal gland within 4 hours of administration, coupled with increased expression of mRNAs for annexin A1 (AnxA1) and the formyl peptide receptors [(Fprs) 1, 2, and 3], a loss of lipid droplets in cortical cells (index of availability of cholesterol, the substrate for steroidogenesis), and a failure to mount a steroidogenic response to ACTH. Deletion of AnxA1 or Fpr2/3 in mice prevented lipid droplet loss, but not leukocyte infiltration. LPS increased adrenal myeloid differentiation primary response gene 88 and TLR2 mRNA expression, but not lymphocyte antigen 96 or TLR4. By contrast, neutrophil depletion prevented leukocyte infiltration and increased AnxA1, Fpr1, and Fpr3 mRNAs but had no impact on lipid droplet loss. Our novel data demonstrate that AnxA1 and Fpr2 have a critical role in the manifestation of adrenal insufficiency in this model, through regulation of cholesterol ester storage, suggesting that pharmacologic interventions targeting the AnxA1/FPR/ALX pathway may provide a new approach for the maintenance of adrenal steroidogenesis in sepsis.

Targeting formyl peptide receptor 2 reduces leukocyte-endothelial interactions in a murine model of stroke

Ischemia/reperfusion (I/R) injury following stroke can worsen patient outcome through excess inflammation. This study investigated the pharmacologic potential of targeting an endogenous anti-inflammatory circuit via formyl peptide receptor (FPR) 2/lipoxin receptor (ALX) (Fpr2/3 in mouse) in global cerebral I/R. Mice (C57BL/6 and Fpr2/3(-/-)) were subjected to bilateral common carotid artery occlusion, followed by reperfusion and treatment with FPR agonists: AnxA1Ac2-26 [Annexin A1 mimetic peptide (Ac-AMVSEFLKQAWFIENEEQEYVQTVK), 2.5 μg/kg] and 15-epimer-lipoxin A4 (15-epi-LXA4; FPR2/ALX specific, 12.5 and 100 ng/kg). Leukocyte-endothelial (L-E) interactions in the cerebral microvasculature were then quantified in vivo using intravital fluorescence microscopy. 15-epi-LXA4 administration at the start of reperfusion reduced L-E interactions after 40 min (which was sustained at 2 h with high-dose 15-epi-LXA4) to levels seen in sham-operated animals. AnxA1Ac2-26 treatment decreased leukocyte adhesion at 40 min and all L-E interactions at 2 h (up to 95%). Combined treatment with AnxA1Ac2-26 plus FPR antagonists t-Boc-FLFLF (250 ng/kg) or WRW4 (FPR2/ALX selective, 1.4 μg/kg) abrogated the effects of AnxA1Ac2-26 fully at 40 min. Antagonists were less effective at 2 h, which we demonstrate is likely because of their impact on early L-E interactions. Our findings indicate that FPR2/ALX activity elicits considerable control over vascular inflammatory responses during cerebral I/R and, therefore, provide evidence that targeting FPR2/ALX may be beneficial for patients who suffered from stroke.

Phytochemicals: countering risk factors and pathological responses associated with ischaemia reperfusion injury

Plant derived non-nutritive molecules, known as phytochemicals, have been investigated for their ability to provide protection against inflammation. Emerging studies of several vasculopathies (e.g. atherosclerosis, hypertension) provide novel data to support these anti-inflammatory effects and offer evidence for involvement of host pathways. Fundamental mechanisms of action are common amongst these compounds, and furthermore, the administration of these phytochemicals activates host defence pathways innately present to protect cells from oxidative stress. This review will elucidate the real benefit of therapeutic intervention with these phytochemicals for vasculopathies, and associated ischaemia reperfusion injury in both the heart and brain.

Annexin A1 and the regulation of innate and adaptive immunity

Inflammation is the body’s way of defending itself against noxious stimuli and pathogens. Under normal circumstances, the body is able to eliminate the insult and subsequently promote the resolution of inflammation and the repair of damaged tissues. The concept of homeostasis is one that not only requires a fine balance between both pro-inflammatory mediators and pro-resolving/anti-inflammatory mediators, but also that this balance occurs in a time and space-specific manner. This review examines annexin A1, an anti-inflammatory protein that, when used as an exogenous therapeutic, has been shown to be very effective in limiting inflammation in a diverse range of experimental models, including myocardial ischemia/reperfusion injury, arthritis, stroke, multiple sclerosis, and sepsis. Notably, this glucocorticoid-inducible protein, along with another anti-inflammatory mediator, lipoxin A₄, is starting to help explain and shape our understanding of the resolution phase of inflammation. In so doing, these molecules are carving the way for innovative drug discovery, based on the stimulation of endogenous pro-resolving pathways.

Intravital microscopy: new insights into cellular interactions

Inflammation is the body's way of combating invading pathogens or noxious stimuli. Under normal conditions, the complex host response of rubor, dolor, calor, tumor, and functio laesa is essential for survival and the return to homeostasis. However, unregulated inflammation is all too often observed in diseases such as rheumatoid arthritis, stroke, and cancer. The host inflammatory response is governed by a number of tightly regulated processes that enable cellular trafficking to occur at the sites of damage to ultimately ensure the resolution of inflammation. Intravital microscopy (IVM) provides quantitative, qualitative, and dynamic insights into cell biology and these cellular interactions. This review highlights the pros and cons of this specialized technique and how it has evolved to help understand the physiology and pathophysiology of inflammatory events in a number of different disease states, leading to a number of potential therapeutic targets for drug discovery.

Leukocyte recruitment in the brain in sepsis: involvement of the annexin 1-FPR2/ALX anti-inflammatory system

Unregulated inflammation underlies many diseases, including sepsis. Much interest lies in targeting anti-inflammatory mechanisms to develop new treatments. One such target is the anti-inflammatory protein annexin A1 (AnxA1) and its receptor, FPR2/ALX. Using intravital videomicroscopy, we investigated the role of AnxA1 and FPR2/ALX in a murine model of endotoxin-induced cerebral inflammation [intraperitoneal injection of lipopolysaccharide (LPS)]. An inflammatory response was confirmed by elevations in proinflammatory serum cytokines, increased cerebrovascular permeability, elevation in brain myeloperoxidase, and increased leukocyte rolling and adhesion in cerebral venules of wild-type (WT) mice, which were further exacerbated in AnxA1-null mice. mRNA expression of TLR2, TLR4, MyD-88, and Ly96 was also assessed. The AnxA1-mimetic peptide, AnxA1(Ac2-26) (100 μg/mouse, ∼33 μmol) mitigated LPS-induced leukocyte adhesion in WT and AnxA1-null animals without affecting leukocyte rolling, in comparison to saline control. AnxA1(Ac2-26) effects were attenuated by Boc2 (pan-FPR antagonist, 10 μg/mouse, ∼12 nmol), and by minocycline (2.25 mg/mouse, ∼6.3 nmol). The nonselective Fpr agonists, fMLP (6 μg/mouse, ∼17 nmol) and AnxA1(Ac2-26), and the Fpr2-selective agonist ATLa (5 μg/mouse, ∼11 nmol) were without effect in Fpr2/3(-/-) mice. In summary, our novel results demonstrate that the AnxA1/FPR2 system has an important role in effecting the resolution of cerebral inflammation in sepsis and may, therefore, provide a novel therapeutic target.

The peritoneal tumour microenvironment of high-grade serous ovarian cancer

High-grade serous ovarian cancer (HGSC) disseminates early and extensively throughout the peritoneal space, causing multiple lesions that are a major clinical problem. The aim of this study was to investigate the cellular composition of peritoneal tumour deposits in patient biopsies and their evolution in mouse models using immunohistochemistry, intravital microscopy, confocal microscopy, and 3D modelling. Tumour deposits from the omentum of HGSC patients contained a prominent leukocyte infiltrate of CD3(+) T cells and CD68(+) macrophages, with occasional neutrophils. Alpha-smooth muscle actin(+) (α-SMA(+) ) pericytes and/or fibroblasts surrounded these well-vascularized tumour deposits. Using the murine bowel mesentery as an accessible mouse peritoneal tissue that could be easily imaged, and two different transplantable models, we found multiple microscopic tumour deposits after i.p. injection of malignant cells. Attachment to the peritoneal surface was rapid (6-48 h) with an extensive CD45(+) leukocyte infiltrate visible by 48 h. This infiltrate persisted until end point and in the syngeneic murine ID8 model, it primarily consisted of CD3(+) T lymphocytes and CD68(+) macrophages with α-SMA(+) cells also involved from the earliest stages. A majority of tumour deposits developed above existing mesenteric blood vessels, but in avascular spaces new blood vessels tracked towards the tumour deposits by 2-3 weeks in the IGROV-1 xenografts and 6 weeks in the ID8 syngeneic model; a vigorous convoluted blood supply was established by end point. Inhibition of tumour cell cytokine production by stable expression of shRNA to CXCR4 in IGROV-1 cells did not influence the attachment of cells to the mesentery but delayed neovascularization and reduced tumour deposit size. We conclude that the multiple peritoneal tumour deposits found in HGSC patients can be modelled in the mouse. The techniques described here may be useful for assessing treatments that target the disseminated stage of this disease.

The potential of stem cell therapy for stroke: is PISCES the sign?

Substantial developments in the field of stem cell research point toward novel therapies for the treatment of diseases such as stroke. This review covers the establishment of tissue damage in stroke and the status of current therapies. We evaluate stem cell therapy with respect to other treatments, including clinical, preclinical, and failed, and provide a comprehensive account of stem cell clinical trials for stroke therapy currently underway. Finally, we describe mechanisms through which stem cells improve outcome in experimental stroke as well as potential pitfalls this basic research has identified.

Modeling inflammation and microvascular dysfunction

We are using confocal intravital microscopy to understand the mechanisms behind leukocyte trafficking in the brain, thus providing potential therapeutic targets for neurovascular diseases, for example, stroke and multiple sclerosis.

Microvascular thrombosis and CD40/CD40L signaling

BACKGROUND

Although inflammation and thrombosis are now recognized to be interdependent processes that activate and perpetuate each other, the signaling molecules that link these two processes remain poorly understood.

OBJECTIVES

The objective of this study was to assess the contribution of the CD40/CD40L signaling system to the enhanced microvascular thrombosis that accompanies two distinct experimental models of inflammation, that is, endotoxemia (lipopolysaccharide [LPS]) and dextran sodium sulfate (DSS)-induced colitis.

METHODS

Thrombosis was induced in cerebral (LPS model) and cremaster muscle (DSS model) arterioles and venules of wild-type (WT) mice and mice deficient in either CD40 (CD40(-/-)) or CD40L (CD40L(-/-)), using the light/dye (photoactivation) method.

RESULTS AND CONCLUSIONS

A comparison of thrombus formation between WT and mutant mice revealed a role for CD40 and/or CD40L in the inflammation-enhanced thrombosis responses in both of the cerebral and muscle vasculatures. However, the relative contributions of CD40 and its ligand to thrombus formation differed between vascular beds (brain vs. muscle) and vessel types (arterioles vs. venules). The protective effect of CD40L deficiency in cerebral arterioles exposed to LPS was significantly blunted by administration of soluble CD40L. These findings implicate CD40 and its ligand in the enhanced thrombus formation that is associated with acute and chronic inflammation.