Role of leukocytes, complement system and endothelium in rat renal ischaemia-reperfusion injury

Introduction: Renal Ischaemia-Reperfusion injury (IRI) is a complex mechanism involving the interplay between endothelium, leukocytes and the complement system. To evaluate the role of these three key mediators, a rat model was used to evaluate changes seen in renal IRI. Two interventional agents: Anti-Thymocyte Globulin (ATG) and Soluble Complement Receptor-1 (sCR1) were used to modulate leukocyte and complement response in this IRI model with a view to assess, and define IRI mechanism. Methods: The Ischaemia-Reperfusion (IR) model involved unilateral left renal ischemia (n=10) for 40 minutes, followed by 48 hours of reperfusion. ATG (n=8), ATG Isotype (n=8) and sCR1(n=8) were given IV prior to the laparotomy followed by IR model. The sham group (n=6) served as controls. Blood CD3 lymphocyte counts and CH50 complement assay were used to check efficacy of ATG and sCR1 respectively. The kidneys retrieved at 48 hours were analysed for histology, immunohistochemistry and RT-qPCR studies. Results: The IR group showed significant injury compared to the sham group. ATG treatment offered significant histological protection mainly via decreased leukocyte infiltrate and endothelial protection compared to the IR and Isotype controls. CH50 assay showed complete ablation of complement activity at the time of reperfusion, with return to normality at 24 hours. sCR1 treatment conferred protection from IRI predominantly via suppression of the complement cascade (C3, C9), reduced leukocyte infiltrates and V endothelial protection. RT-qPCR showed down-regulation of injury molecules – KIM-1 and NGAL in both the intervention groups. Conclusion: Modulation of leukocytes and complement system using single dose ATG and sCR1 led to significant endothelial protection, resulting in amelioration of renal ischaemia-reperfusion injury. The complement system was ablated at the time of reperfusion and was reconstituted by 24 hours, thus indicating that suppression of complement system during the phase of IR provides an avenue for mitigating IRI

Complement Activation Contributes to Severe Acute Respiratory Syndrome Coronavirus Pathogenesis

Acute respiratory distress syndrome (ARDS) is immune-driven pathologies that are observed in severe cases of severe acute respiratory syndrome coronavirus (SARS-CoV) infection. SARS-CoV emerged in 2002 to 2003 and led to a global outbreak of SARS. As with the outcome of human infection, intranasal infection of C57BL/6J mice with mouse-adapted SARS-CoV results in high-titer virus replication within the lung, induction of inflammatory cytokines and chemokines, and immune cell infiltration within the lung. Using this model, we investigated the role of the complement system during SARS-CoV infection. We observed activation of the complement cascade in the lung as early as day 1 following SARS-CoV infection. To test whether this activation contributed to protective or pathologic outcomes, we utilized mice deficient in C3 (C3–/–), the central component of the complement system. Relative to C57BL/6J control mice, SARS-CoV-infected C3–/– mice exhibited significantly less weight loss and less respiratory dysfunction despite equivalent viral loads in the lung. Significantly fewer neutrophils and inflammatory monocytes were present in the lungs of C3–/– mice than in C56BL/6J controls, and subsequent studies revealed reduced lung pathology and lower cytokine and chemokine levels in both the lungs and the sera of C3–/– mice than in controls. These studies identify the complement system as an important host mediator of SARS-CoV-induced disease and suggest that complement activation regulates a systemic proinflammatory response to SARS-CoV infection. Furthermore, these data suggest that SARS-CoV-mediated disease is largely immune driven and that inhibiting complement signaling after SARS-CoV infection might function as an effective immune therapeutic. IMPORTANCE The complement system is a critical part of host defense to many bacterial, viral, and fungal infections. It works alongside pattern recognition receptors to stimulate host defense systems in advance of activation of the adaptive immune response. In this study, we directly test the role of complement in SARS-CoV pathogenesis using a mouse model and show that respiratory disease is significantly reduced in the absence of complement even though viral load is unchanged. Complement-deficient mice have reduced neutrophilia in their lungs and reduced systemic inflammation, consistent with the observation that SARS-CoV pathogenesis is an immune-driven disease. These data suggest that inhibition of complement signaling might be an effective treatment option following coronavirus infection

Global Vascular Guidelines on the Management of Chronic Limb-Threatening Ischemia

Chronic limb-threatening ischemia (CLTI)is associated with mortality, amputation, and impaired quality of life. These Global Vascular Guidelines (GVG)are focused on definition, evaluation, and management of CLTI with the goals of improving evidence-based care and highlighting critical research needs. The term CLTI is preferred over critical limb ischemia, as the latter implies threshold values of impaired perfusion rather than a continuum. CLTI is a clinical syndrome defined by the presence of peripheral artery disease (PAD)in combination with rest pain, gangrene, or a lower limb ulceration >2 weeks duration. Venous, traumatic, embolic, and nonatherosclerotic etiologies are excluded. All patients with suspected CLTI should be referred urgently to a vascular specialist. Accurately staging the severity of limb threat is fundamental, and the Society for Vascular Surgery Threatened Limb Classification system, based on grading of Wounds, Ischemia, and foot Infection (WIfI)is endorsed. Objective hemodynamic testing, including toe pressures as the preferred measure, is required to assess CLTI. Evidence-based revascularization (EBR)hinges on three independent axes: Patient risk, Limb severity, and ANatomic complexity (PLAN). Average-risk and high-risk patients are defined by estimated procedural and 2-year all-cause mortality. The GVG proposes a new Global Anatomic Staging System (GLASS), which involves defining a preferred target artery path (TAP)and then estimating limb-based patency (LBP), resulting in three stages of complexity for intervention. The optimal revascularization strategy is also influenced by the availability of autogenous vein for open bypass surgery. Recommendations for EBR are based on best available data, pending level 1 evidence from ongoing trials. Vein bypass may be preferred for average-risk patients with advanced limb threat and high complexity disease, while those with less complex anatomy, intermediate severity limb threat, or high patient risk may be favored for endovascular intervention. All patients with CLTI should be afforded best medical therapy including the use of antithrombotic, lipid-lowering, antihypertensive, and glycemic control agents, as well as counseling on smoking cessation, diet, exercise, and preventive foot care. Following EBR, long-term limb surveillance is advised. The effectiveness of nonrevascularization therapies (eg, spinal stimulation, pneumatic compression, prostanoids, and hyperbaric oxygen)has not been established. Regenerative medicine approaches (eg, cell, gene therapies)for CLTI should be restricted to rigorously conducted randomizsed clinical trials. The GVG promotes standardization of study designs and end points for clinical trials in CLTI. The importance of multidisciplinary teams and centers of excellence for amputation prevention is stressed as a key health system initiative. © 2019 Society for Vascular Surgery and European Society for Vascular Surger