In neurodegenerative diseases, debris of dead neurons are thought to trigger glia-mediated neuroinflammation, thus increasing neuronal death. Here, we show that expression of neurotoxic proteins associated with these diseases in microglia alone is sufficient to trigger death of naïve neurons directly and to propagate neuronal death through activation of naïve astrocytes to A1 state. Injury propagation is mediated, in great part, by the release of fragmented and dysfunctional microglial mitochondria to the neuronal milieu. The amount of damaged mitochondria released from microglia relative to functional mitochondria and the consequent neuronal injury are determined by Fis1-mediated mitochondrial fragmentation within the glia cells. The propagation of inflammatory response and neuronal cell death by extracellular dysfunctional mitochondria Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:

Mitochondrial dysfunction is a key contributor to septic cardiomyopathy. Although recent literature implicates dynamin related protein 1 (Drp1) and its mitochondrial adaptor fission 1 (Fis1) in the development of pathologic fission and mitochondrial failure in neurodegenerative disease, little is known about the role of Drp1/Fis1 interaction in the context of sepsis-induced cardiomyopathy. Our study tests the hypothesis that Drp1/Fis1 interaction is a major driver of sepsis-mediated pathologic fission, leading to mitochondrial dysfunction in the heart. Methods: H9C2 cardiomyocytes were treated with lipopolysaccharide (LPS) to evaluate changes in mitochondrial membrane potential, oxidative stress, cellular respiration, and mitochondrial morphology. Balb/c mice were treated with LPS, cardiac function was measured by echocardiogaphy, and mitochondrial morphology determined by electron microscopy (EM). Drp1/ Fis1 interaction was inhibited by P110 to determine whether limiting mitochondrial fission can reduce LPS-induced oxidative stress and cardiac dysfunction.Results: LPS-treated H9C2 cardiomyocytes demonstrated a decrease in mitochondrial respiration followed by an increase in mitochondrial oxidative stress and a reduction in membrane potential. Inhibition of Drp1/Fis1 interaction with P110 attenuated LPS-mediated cellular oxidative stress and preserved membrane potential. In vivo, cardiac dysfunction in LPS-treated mice was associated with increased mitochondrial fragmentation. Treatment with P110 reduced cardiac mitochondrial fragmentation, prevented decline in cardiac function, and reduced mortality.

Sepsis remains a major public health problem with no major therapeutic advances over the last several decades. The clinical and biological heterogeneity of sepsis have limited success of potential new therapies. Accordingly, there is considerable interest in developing a precision medicine approach to inform more rational development, testing, and targeting of new therapies. We previously developed the Pediatric Sepsis Biomarker Risk Model (PERSEVERE) to estimate mortality risk and proposed its use as a prognostic enrichment tool in sepsis clinical trials; prognostic enrichment selects patients based on mortality risk independent of treatment. Here, we show that PERSEVERE has excellent performance in a diverse cohort of children with septic shock with potential for use as a predictive enrichment strategy; predictive enrichment selects patients based on likely response to treatment. We demonstrate that the PERSEVERE biomarkers are reliably associated with mortality in mice challenged with experimental sepsis, thus providing an opportunity to test precision medicine strategies in the preclinical setting. Using this model, we tested two clinically feasible therapeutic strategies, guided by the PERSEVERE-based enrichment, and found that mice identified as high risk for mortality had a greater bacterial burden and could be rescued by higher doses of antibiotics. The association between higher pathogen burden and higher mortality risk was corroborated among critically ill children with septic shock. This bedside to bench to bedside approach provides proof of principle for PERSEVERE-guided application of precision medicine in sepsis.

Background Out of the myriad of complications associated with septic shock, septic-associated encephalopathy (SAE) carries a significant risk of morbidity and mortality. Blood-brain-barrier (BBB) impairment, which subsequently leads to increased vascular permeability, has been associated with neuronal injury in sepsis. Thus, preventing BBB damage is an attractive therapeutic target. Mitochondrial dysfunction is an important contributor of sepsis-induced multi-organ system failure. More recently, mitochondrial dysfunction in endothelial cells has been implicated in mediating BBB failure in stroke, multiple sclerosis and in other neuroinflammatory disorders. Here, we focused on Drp1-mediated mitochondrial dysfunction in endothelial cells as a potential target to prevent BBB failure in sepsis. Methods We used lipopolysaccharide (LPS) to induce inflammation and BBB disruption in a cell culture as well as in murine model of sepsis. BBB disruption was assessed by measuring levels of key tight-junction proteins. Brain cytokines levels, oxidative stress markers, and activity of mitochondrial complexes were measured using biochemical assays. Astrocyte and microglial activation were measured using immunoblotting and qPCR. Transwell cultures of brain microvascular endothelial cells co-cultured with astrocytes were used to assess the effect of LPS on expression of tight-junction proteins, mitochondrial function, and permeability to fluorescein isothiocyanate (FITC) dextran. Finally, primary neuronal cultures exposed to LPS were assessed for mitochondrial dysfunction. Results LPS induced a strong brain inflammatory response and oxidative stress in mice which was associated with increased Drp1 activation and mitochondrial localization. Particularly, Drp1-(Fission 1) Fis1-mediated oxidative stress also led to an increase in expression of vascular permeability regulators in the septic mice. Similarly, mitochondrial defects mediated via Drp1-Fis1 interaction in primary microvascular endothelial cells were associated with increased BBB permeability and loss of tight-junctions after acute LPS injury. P110, an inhibitor of Drp1-Fis1 interaction, abrogated these defects, thus indicating a critical role for this interaction in mediating sepsis-induced brain dysfunction. Finally, LPS mediated a direct toxic effect on primary cortical neurons, which was abolished by P110 treatment. Conclusions LPS-induced impairment of BBB appears to be dependent on Drp1-Fis1-mediated mitochondrial dysfunction. Inhibition of mitochondrial dysfunction with P110 may have potential therapeutic significance in septic encephalopathy.

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Sepsis is a deleterious immune response to infection that leads to organ failure and is the 11th most common cause of death worldwide. Despite plaguing humanity for thousands of years, the host factors that regulate this immunological response and subsequent sepsis severity and outcome are not fully understood. Here we describe how the Western diet (WD), a diet high in fat and sucrose and low in fiber, found rampant in industrialized countries, leads to worse disease and poorer outcomes in an LPS-driven sepsis model in WD-fed mice compared with mice fed standard fiber-rich chow (SC). We find that WD-fed mice have higher baseline inflammation (metaflammation) and signs of sepsis-associated immunoparalysis compared with SC-fed mice. WD mice also have an increased frequency of neutrophils, some with an “aged” phenotype, in the blood during sepsis compared with SC mice. Importantly, we found that the WD-dependent increase in sepsis severity and higher mortality is independent of the microbiome, suggesting that the diet may be directly regulating the innate immune system through an unknown mechanism. Strikingly, we could predict LPS-driven sepsis outcome by tracking specific WD-dependent disease factors (e.g., hypothermia and frequency of neutrophils in the blood) during disease progression and recovery. We conclude that the WD is reprogramming the basal immune status and acute response to LPS-driven sepsis and that this correlates with alternative disease paths that lead to more severe disease and poorer outcomes.

Mitochondria form a dynamic network governed by a balance between opposing fission and fusion processes. Because excessive mitochondrial fission correlates with numerous pathologies, including neurodegeneration, the mechanism governing fission has become an attractive therapeutic strategy. However, targeting fission is a double-edged sword as physiological fission is necessary for mitochondrial function. Fission is trigged by Drp1 anchoring to adaptors tethered to the outer mitochondrial membrane. We designed peptide P259 that distinguishes physiological from pathological fission by specifically inhibiting Drp1′s interaction with the Mff adaptor. Treatment of cells with P259 elongated mitochondria and disrupted mitochondrial function and motility. Sustained in vivo treatment caused a decline in ATP levels and altered mitochondrial structure in the brain, resulting in behavioral deficits in wild-type mice and a shorter lifespan in a mouse model of Huntington’s disease. Therefore, the Mff-Drp1 interaction is critical for physiological mitochondrial fission, motility, and function in vitro and in vivo. Tools, such as P259, that differentiate physiological from pathological fission will enable the examination of context-dependent roles of Drp1 and the suitability of mitochondrial fission as a target for drug development.

BackgroundHypertrophic cardiomyopathy (HCM) is a common inherited cardiac disease characterized by varying degrees of left ventricular outflow tract obstruction. In a large cohort, we compare the outcomes among 3 different hemodynamic groups.Methods and ResultsWe prospectively enrolled patients fulfilling standard diagnostic criteria for HCM from January 2005 to June 2015. Detailed phenotypic characterization, including peak left ventricular outflow tract pressure gradients at rest and after provocation, was measured by echocardiography. The primary outcome was a composite cardiovascular end point, which included new‐onset atrial fibrillation, new sustained ventricular tachycardia/ventricular fibrillation, new or worsening heart failure, and death. The mean follow‐up was 3.4±2.8 years. Among the 705 patients with HCM (mean age, 52±15 years; 62% men), 230 with obstructive HCM were older and had a higher body mass index and New York Heart Association class. The 214 patients with nonobstructive HCM were more likely to have a history of sustained ventricular tachycardia/ventricular fibrillation and implantable cardioverter defibrillator implantation. During follow‐up, 121 patients experienced a composite cardiovascular end point. Atrial fibrillation occurred most frequently in the obstructive group. Patients with nonobstructive HCM had more frequent sustained ventricular tachycardia/ventricular fibrillation events. In multivariate analysis, obstructive (hazard ratio, 2.80; 95% confidence interval, 1.64–4.80) and nonobstructive (hazard ratio, 1.94; 95% confidence interval, 1.09–3.45) HCM were associated with more adverse events compared with labile HCM.ConclusionsNonobstructive HCM carries notable morbidity, including a higher arrhythmic risk than the other HCM groups. Patients with labile HCM have a relatively benign clinical course. Our data suggest detailed sudden cardiac death risk stratification in nonobstructive HCM and monitoring with less aggressive management in labile HCM.