Practical guidelines for rigor and reproducibility in preclinical and clinical studies on cardioprotection

The potential for ischemic preconditioning to reduce infarct size was first recognized more than 30 years ago. Despite extension of the concept to ischemic postconditioning and remote ischemic conditioning and literally thousands of experimental studies in various species and models which identified a multitude of signaling steps, so far there is only a single and very recent study, which has unequivocally translated cardioprotection to improved clinical outcome as the primary endpoint in patients. Many potential reasons for this disappointing lack of clinical translation of cardioprotection have been proposed, including lack of rigor and reproducibility in preclinical studies, and poor design and conduct of clinical trials. There is, however, universal agreement that robust preclinical data are a mandatory prerequisite to initiate a meaningful clinical trial. In this context, it is disconcerting that the CAESAR consortium (Consortium for preclinicAl assESsment of cARdioprotective therapies) in a highly standardized multi-center approach of preclinical studies identified only ischemic preconditioning, but not nitrite or sildenafil, when given as adjunct to reperfusion, to reduce infarct size. However, ischemic preconditioning—due to its very nature—can only be used in elective interventions, and not in acute myocardial infarction. Therefore, better strategies to identify robust and reproducible strategies of cardioprotection, which can subsequently be tested in clinical trials must be developed. We refer to the recent guidelines for experimental models of myocardial ischemia and infarction, and aim to provide now practical guidelines to ensure rigor and reproducibility in preclinical and clinical studies on cardioprotection. In line with the above guideline, we define rigor as standardized state-of-the-art design, conduct and reporting of a study, which is then a prerequisite for reproducibility, i.e. replication of results by another laboratory when performing exactly the same experiment

Amphotericin forms an extramembranous and fungicidal sterol sponge

Amphotericin has remained the powerful but highly toxic last line of defense in treating life-threatening fungal infections in humans for over 50 years with minimal development of microbial resistance. Understanding how this small molecule kills yeast is thus critical for guiding development of derivatives with an improved therapeutic index and other resistance-refractory antimicrobial agents. In the widely accepted ion channel model for its mechanism of cytocidal action, amphotericin forms aggregates inside lipid bilayers that permeabilize and kill cells. In contrast, we report that amphotericin exists primarily in the form of large, extramembranous aggregates that kill yeast by extracting ergosterol from lipid bilayers. These findings reveal that extraction of a polyfunctional lipid underlies the resistance-refractory antimicrobial action of amphotericin and suggests a roadmap for separating its cytocidal and membrane-permeabilizing activities. This new mechanistic understanding is also guiding development of the first derivatives of amphotericin that kill yeast but not human cells

Extracellular Vesicles As miRNA Nano-Shuttles: Dual Role in Tumor Progression

[EN] Tumor-derived extracellular vesicles (EVs) have a pleiotropic role in cancer, interacting with target cells of the tumor microenvironment, such as fibroblasts, immune and endothelial cells. EVs can modulate tumor progression, angiogenic switch, metastasis, and immune escape. These vesicles are nano-shuttles containing a wide spectrum of miRNAs that contribute to tumor progression. MiRNAs contained in extracellular vesicles (EV-miRNAs) are disseminated in the extracellular space and are able to influence the expression of target genes with either tumor suppressor or oncogenic functions, depending on both parental and target cells. Metastatic cancer cells can balance their oncogenic potential by expressing miRNAs with oncogenic function, whilst exporting miRNAs with tumor suppressor roles out of the cells. 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Mitochondrial ‘kiss-and-run': interplay between mitochondrial motility and fusion–fission dynamics

Visualizing mitochondrial fusion in real time, we identified two classes of fusion events in mammalian cells. In addition to complete fusion, we observed transient fusion events, wherein two mitochondria came into close apposition, exchanged soluble inter-membrane space and matrix proteins, and re-separated, preserving the original morphology. Transient fusion exhibited rapid kinetics of the sequential and separable mergers of the outer and inner membranes, but allowed only partial exchange of integral membrane proteins. When the inner membrane fusion protein Opa1 level was lowered or was greatly elevated, transient fusions could occur, whereas complete fusions disappeared. Furthermore, transient fusions began from oblique or lateral interactions of mitochondria associated with separate microtubules, whereas complete fusions resulted from longitudinal merging of organelles travelling along a single microtubule. In contrast to complete fusion, transient fusions both required and promoted mitochondrial motility. Transient fusions were also necessary and sufficient to support mitochondrial metabolism. Thus, Opa1 expression and cytoskeletal anchorage govern a novel form of fusion that has a distinct function in mitochondrial maintenance