Innate immunity in diabetes mellitus. Complement components C4BP and C3 promote survival of β cells under metabolic challenges.

The Complement system is a main effector mechanism of the innate immune system, acting to enhance clearance of pathogens, but also aids removal of biological debris from the body, including immunocomplexes, apoptotic/necrotic cells and protein aggregates. Complement regulators serve to prevent excessive inflammation and their interaction with the same materials targeted by the complement system results in ‘silent’ cleaning of wastes. Type 2 diabetes (T2D) is characterized by insulin resistance in peripheral tissues resulting in an initial compensatory upregulation of insulin production but ultimately leading to failure of blood glucose homeostasis and death of insulinsecreting pancreatic β-cells. T2D is now understood to have several components, which drives pancreatic islet dysfunction: high glucose concentration, proinflammatory cytokines, long chain free fatty acids, increased insulin synthesis demand and increased exposure to islet amyloid polypeptide (IAPP). IAPP a hormone co-secreted with insulin from pancreatic β-cells is capable to form amyloid and intermediate species; oligomers that are highly cytotoxic for β-cells. IAPP oligomers have been also shown to activate the NOD-like receptor pyrin domain containing-3 (NLRP3) inflammasome leading to production of the pro-inflammatory cytokine IL-1β, which in high concretions is a driver of β-cell pathology. Previously we described binding of complement regulator C4-binding protein (C4BP) to IAPP amyloid that affected transition of IAPP monomers and oligomers to mature IAPP fibrils.Therefore, we hypothesized that C4BP might inhibit IAPP oligomer-induced death of β-cells, and limit inflammasome activation and IL-1β secretion secondary to β-cell failure. Presence of C4BP with IAPP monomers, which tend to assemble into oligomers and amyloid, resulted in better survival of cultured rat insulinoma INS-1 β-cells compared to cells treated with IAPP alone. Similarly, addition of C4BP with IAPP to macrophages limited IAPP-dependent inflammasome activation and IL-1β release, ensuring protection of β-cells against IL-1β-driven toxicity. Dysregulated autophagy in β-cells coincides with failure of β-cells as well. Autophagy, a housekeeping activity,necessary for elimination and recycling of unwanted cellular components, supports β-cell health under metabolic challenges. A hub of the complement protein cascade, complement component 3 (C3) has been found to be highly expressed in human pancreatic islets with increased expression after exposure to β-cell specific stressors: IL-1β, palmitic acid (PA) and IAPP. We found that C3 regulates the process of autophagy and improves viability of INS-1 cells under IAPP and PA treatments. Furthermore, we found C3 to be cytoprotective against IL-1β induced death of β-cells. IL-1β driven upregulation of proapoptotic signalling does not seem to be dependent on canonical autophagy, but surprisingly intracellular/cytosolic C3 conferred protection to β-cells exposed to IL-1β

Resuscitation of the patient with suspected/confirmed COVID-19 when wearing personal protective equipment: A randomized multicenter crossover simulation trial

Background: The aim of the study was to evaluate various methods of chest compressions in patients with suspected/confirmed SARS-CoV-2 infection conducted by medical students wearing full personal protective equipment (PPE) for aerosol generating procedures (AGP).Methods: This was prospective, randomized, multicenter, single-blinded, crossover simulation trial. Thirty-five medical students after an advanced cardiovascular life support course, which included performing 2-min continuous chest compression scenarios using three methods: (A) manual chest compression (CC), (B) compression with CPRMeter, (C) compression with LifeLine ARM device. During resuscitation they are wearing full personal protective equipment for aerosol generating procedures.Results: The median chest compression depth using manual CC, CPRMeter and LifeLine ARM varied and amounted to 40 (38–45) vs. 45 (40–50) vs. 51 (50–52) mm, respectively (p = 0.002). The median chest compression rate was 109 (IQR; 102–131) compressions per minute (CPM) for manual CC, 107 (105–127) CPM for CPRMeter, and 102 (101–102) CPM for LifeLine ARM (p = 0.027). The percentage of correct chest recoil was the highest for LifeLine ARM — 100% (95–100), 80% (60–90) in CPRMeter group, and the lowest for manual CC — 29% (26–48).Conclusions: According to the results of this simulation trial, automated chest compression devices (ACCD) should be used for chest compression of patients with suspected/confirmed COVID-19. In the absence of ACCD, it seems reasonable to change the cardiopulmonary resuscitation algorithm (in the context of patients with suspected/confirmed COVID-19) by reducing the duration of the cardiopulmonary resuscitation cycle from the current 2-min to 1-min cycles due to a statistically significant reduction in the quality of chest compressions among rescuers wearing PPE AGP

Outside in : Roles of complement in autophagy

The complement system is a well-characterized cascade of extracellular serum proteins that is activated by pathogens and unwanted waste material. Products of activated complement signal to the host cells via cell surface receptors, eliciting responses such as removal of the stimulus by phagocytosis. The complement system therefore functions as a warning system, resulting in removal of unwanted material. This review describes how extracellular activation of the complement system can also trigger autophagic responses within cells, up-regulating protective homeostatic autophagy in response to perceived stress, but also initiating targeted anti-microbial autophagy in order to kill intracellular cytoinvasive pathogens. In particular, we will focus on recent discoveries that indicate that complement may also have roles in detection and autophagy-mediated disposal of unwanted materials within the intracellular environment. We therefore summarize the current evidence for complement involvement in autophagy, both by transducing signals across the cell membrane, as well as roles within the cellular environment

The human serum protein C4b-binding protein inhibits pancreatic IAPP-induced inflammasome activation

Aims/hypothesis: Inflammasome activation and subsequent IL-1 beta production is a driver of islet pathology in type 2 diabetes. Oligomers, but not mature amyloid fibrils, of human islet amyloid polypeptide (IAPP), which is co-secreted with insulin, trigger NOD-like receptor pyrin domain containing-3 (NLRP3) inflammasome activation. C4b-binding protein (C4BP), present in serum, binds to IAPP and affects transition of IAPP monomers and oligomers to amyloid fibrils. We therefore hypothesised that C4BP inhibits IAPP-mediated inflammasome activation and IL-1 beta production. Methods: Macrophages were exposed to IAPP in the presence or absence of plasma-purified human C4BP, and inflammasome activation was assessed by IL-1 beta secretion as detected by ELISA and reporter cell lines. IAPP fibrillation was assessed by thioflavin T assay. Uptake of IAPP-C4BP complexes and their effects on phagolysosomal stability were assessed by flow cytometry and confocal microscopy. The effect of C4BP regulation of IAPP-mediated inflammasome activation on beta cell function was assessed using a clonal rat beta cell line. Immunohistochemistry was used to examine the association of IAPP amyloid deposits and macrophage infiltration in isolated human and mouse pancreatic islets, and expression of C4BP from isolated human pancreatic islets was assessed by quantitative PCR, immunohistochemistry and western blot. Results: C4BP significantly inhibited IAPP-mediated IL-1 beta secretion from primed macrophages at physiological concentrations in a dose-dependent manner. C4BP bound to and was internalised together with IAPP. C4BP did not affect IAPP uptake into phagolysosomal compartments, although it did inhibit its formation into amyloid fibrils. The loss of macrophage phagolysosomal integrity induced by IAPP incubation was inhibited by co-incubation with C4BP. Supernatant fractions from macrophages activated with IAPP inhibited both insulin secretion and viability of clonal beta cells in an IL-1 beta-dependent manner but the presence of C4BP during macrophage IAPP incubation rescued beta cell function and viability. In human and mouse islets, the presence of amyloid deposits correlated with higher numbers of infiltrating macrophages. Isolated human islets expressed and secreted C4BP, which increased with addition of IL-1 beta. Conclusions/interpretation: IAPP deposition is associated with inflammatory cell infiltrates in pancreatic islets. C4BP blocks IAPP-induced inflammasome activation by preventing the loss of macrophage phagolysosomal integrity required for NLRP3 activation. The consequence of this is the preservation of beta cell function and viability. C4BP is secreted directly from human pancreatic islets and this increases in response to inflammatory cytokines. We therefore propose that C4BP acts as an extracellular chaperone protein that limits the proinflammatory effects of IAPP

Resuscitation of the patient with suspected//confirmed COVID-19 when wearing personal protective equipment: A randomized multicenter crossover simulation trial

Background: The aim of the study was to evaluate various methods of chest compressions in patients with suspected/confirmed SARS-CoV-2 infection conducted by medical students wearing full personal protective equipment (PPE) for aerosol generating procedures (AGP). Methods: This was prospective, randomized, multicenter, single-blinded, crossover simulation trial. Thirty-five medical students after an advanced cardiovascular life support course, which included performing 2-min continuous chest compression scenarios using three methods: (A) manual chest compression (CC), (B) compression with CPRMeter, (C) compression with LifeLine ARM device. During resuscitation they are wearing full personal protective equipment for aerosol generating procedures. Results: The median chest compression depth using manual CC, CPRMeter and LifeLine ARM varied and amounted to 40 (38-45) vs. 45 (40-50) vs. 51 (50-52) mm, respectively (p = 0.002). The median chest compression rate was 109 (IQR; 102-131) compressions per minute (CPM) for manual CC, 107 (105-127) CPM for CPRMeter, and 102 (101-102) CPM for LifeLine ARM (p = 0.027). The percentage of correct chest recoil was the highest for LifeLine ARM - 100% (95-100), 80% (60-90) in CPRMeter group, and the lowest for manual CC - 29% (26-48). Conclusions: According to the results of this simulation trial, automated chest compression devices (ACCD) should be used for chest compression of patients with suspected/confirmed COVID-19. In the absence of ACCD, it seems reasonable to change the cardiopulmonary resuscitation algorithm (in the context of patients with suspected/confirmed COVID-19) by reducing the duration of the cardiopulmonary resuscitation cycle from the current 2-min to 1-min cycles due to a statistically significant reduction in the quality of chest compressions among rescuers wearing PPE AGP