BackgroundObesity is frequently complicated by comorbid conditions, yet how excess adipose contributes is poorly understood. Although adipocytes in obese individuals induce systemic inflammation via secreted cytokines, another potential mediator has recently been identified (i.e. adipocyte-derived exosomes). We hypothesized that adipocyte-derived exosomes contain mediators capable of activating end-organ inflammatory and fibrotic signaling pathways.MethodsWe developed techniques to quantify and characterize exosomes shed by adipocytes from 7 obese (age: 12–17.5 years, BMI: 33–50 kg/m2) and 5 lean (age: 11–19 years, BMI: 22–25 kg/m2) subjects.ResultsAbundant exosomal miRNAs, but no mRNAs, were detected. Comparison of obese vs. lean visceral adipose donors detected 55 differentially-expressed miRNAs (p<0.05; fold change≥|1.2|). qRT-PCR confirmed downregulation of miR-148b (ratio = 0.2 [95% confidence interval = 0.1, 0.6]) and miR-4269 (0.3 [0.1, 0.8]), and upregulation of miR-23b (6.2 [2.2, 17.8]) and miR-4429 (3.8 [1.1 to 13.4]). Pathways analysis identified TGF-β signaling and Wnt/ β-catenin signaling among the top canonical pathways expected to be altered with visceral adiposity based on projected mRNA targets for the 55 differentially expressed miRNAs. A select mRNA target was validated in vitro.ConclusionThese data show that visceral adipocytes shed exosomal-mediators predicted to regulate key end-organ inflammatory and fibrotic signaling pathways.

Rationale: Sepsis-related mortality results in part from immunodeficiency secondary to profound lymphoid apoptosis. The biological mechanisms responsible are not understood.Objectives: Because recent evidence shows that platelets are involved in microvascular inflammation and that they accumulate in lymphoid microvasculature in sepsis, we hypothesized a direct role for platelets in sepsis-related lymphoid apoptosis. Methods: We studied megakaryocytes and platelets from a murineinduced sepsis model, with validation in septic children, which showed induction of the cytotoxic serine protease granzyme B. Measurements and Main Results: Platelets from septic mice induced marked apoptosis of healthy splenocytes ex vivo. Platelets from septic granzyme B null (2/2) mice showed no lymphotoxicity. Conclusions: Our findings establish a conceptual advance in sepsis: Septic megakaryocytes produce platelets with acutely altered mRNA profiles, and these platelets mediate lymphotoxicity via granzyme B. Given the contribution of lymphoid apoptosis to sepsis-related mortality, modulation of platelet granzyme B becomes an important new target for investigation and therapy.

PurposeEnd-organ apoptosis is well-described in progressive sepsis and Multiple Organ Dysfunction Syndrome (MODS), especially where platelets accumulate (e.g. spleen and lung). We previously reported an acute sepsis-induced cytotoxic platelet phenotype expressing serine protease granzyme B. We now aim to define the site(s) of and mechanism(s) by which platelet granzyme B induces end-organ apoptosis in sepsis.MethodsEnd-organ apoptosis in murine sepsis (i.e. polymicrobial peritonitis) was analyzed by immunohistochemistry. Platelet cytotoxicity was measured by flow cytometry following 90 minute ex vivo co-incubation with healthy murine splenocytes. Sepsis progression was measured via validated preclinical murine sepsis score.Measurements and Main ResultsThere was evident apoptosis in spleen, lung, and kidney sections from septic wild type mice. In contrast, there was a lack of TUNEL staining in spleens and lungs from septic granzyme B null mice and these mice survived longer following induction of sepsis than wild type mice. In co-incubation experiments, physical separation of septic platelets from splenocytes by a semi-permeable membrane reduced splenocyte apoptosis to a rate indistinguishable from negative controls. Chemical separation by the platelet GPIIb/IIIa receptor inhibitor eptifibatide decreased apoptosis by 66.6±10.6% (p = 0.008). Mice treated with eptifibatide in vivo survived longer following induction of sepsis than vehicle control mice.ConclusionsIn sepsis, platelet granzyme B-mediated apoptosis occurs in spleen and lung, and absence of granzyme B slows sepsis progression. This process proceeds in a contact-dependent manner that is inhibited ex vivo and in vivo by the platelet GPIIb/IIIa receptor inhibitor eptifibatide. The GPIIb/IIIa inhibitors and other classes of anti-platelet drugs may be protective in sepsis.

Objective A state-of-the-art centrifugal pump combined with hollow-fiber oxygenator for extracorporeal membrane oxygenation has potential advantages such as smaller priming volumes and decreased potential to cause tubing rupture as compared with the traditional roller head/silicone membrane systems. Adoption of these state-of-the-art systems has been slow in neonates as a result of past evidence of severe hemolysis that may lead to renal failure and increased mortality. Extracorporeal systems have also been linked to platelet dysfunction, a contributing factor toward intracranial hemorrhage, a leading cause of infant morbidity. Little data exist comparing the centrifugal systems with the roller systems in terms of hemolysis and platelet aggregation at low flow rates commonly used in neonatal extracorporeal membrane oxygenation. Design Prospective, comparative laboratory study. Setting University research laboratory. Subjects Centrifugal pump, roller pump, hollow-fiber oxygenator, and silicone membrane oxygenator. Interventions Comparative study using two pumps, the centrifugal Jostra Rotaflow (Maquet, Wayne, NJ) and the roller-head (Jostra, Maquet, Wayne, NJ), and two oxygenators, polymethly-pentene Quadrox-D (Maquet) and silicone membrane (Medtronic, Minneapolis, MN). Five test runs of four circuit combinations were examined for hemolysis and platelet aggregation during 6 hrs of continuous use in a simulated in vitro extracorporeal membrane oxygenation circuit circulating whole swine blood at 300 mL/min. Measurements and Main Results Hemolysis was assessed by spectrophometric measurement of plasma-free hemoglobin. Platelet aggregation was evaluated using monoclonal CD61 antibody fluorescent flow cytometry profiles. All of the extracorporeal membrane oxygenation systems created plasma-free hemoglobin at a similar rate compared with static blood control. There was no difference in the mean normalized index of hemolysis of the centrifugal/hollow-fiber oxygenator system as compared with the roller-head/silicone membrane systems (0.0032 g/100 L vs. 0.0058 g/100 L, p ≥ .7). None of the extracorporeal membrane oxygenation systems had a significant increase in platelet aggregation above baseline. Conclusions In a low-flow neonatal environment, a state-of-the-art centrifugal pump combined with new fiber-type oxygenators appear to be safe in regard to hemolysis and platelet aggregation.