Proceedings from the metrics forum in heart transplantation for performance monitoring.

Regulatory oversight for heart transplant programs is currently under review by the United Network for Organ Sharing (UNOS). There is concern whether 1-year patient and graft survival truly represent heart transplant center performance. Thus, a forum was organized by the Thoracic and Critical Care Community of Practice (TCC COP) of the American Society of Transplantation (AST) for the heart transplant community to voice their opinions on matters involving program performance monitoring by UNOS. A TCC COP work group was formed to review outcome metrics for adult heart transplantation and culminated in a virtual community forum (72 participants representing 61 heart transplant programs) on November 12-13, 2020. One-year posttransplant survival is still considered an appropriate and important measure to assess program performance. Waitlist mortality and offer acceptance rate as pretransplant metrics could also be useful measures of program performance, recognizing that outside factors may influence these metrics. In depth discussion of these metrics and other issues including auditing thresholds, innovations to reduce risk-averse behavior and personally designed program scorecards are included in this meeting proceedings.

Intermittent Use of a Short-Course Glucagon-like Peptide-1 Receptor Agonist Therapy Limits Adverse Cardiac Remodeling via Parkin-dependent Mitochondrial Turnover.

Given that adverse remodeling is the leading cause of heart failure and death in the USA, there is an urgent unmet need to develop new methods in dealing with this devastating disease. Here we evaluated the efficacy of a short-course glucagon-like peptide-1 receptor agonist therapy-specifically 2-quinoxalinamine, 6,7-dichloro-N-(1,1-dimethylethyl)-3-(methylsulfonyl)-,6,7-dichloro-2-methylsulfonyl-3-N-tert-butylaminoquinoxaline (DMB; aka Compound 2) - in attenuating adverse LV remodeling. We also examined the role, if any, of mitochondrial turnover in this process. Wild-type, Parkin knockout and MitoTimer-expressing mice were subjected to permanent coronary artery ligation, then treated briefly with DMB. LV remodeling and cardiac function were assessed by histology and echocardiography. Autophagy and mitophagy markers were examined by western blot and mitochondrial biogenesis was inferred from MitoTimer protein fluorescence and qPCR. We found that DMB given post-infarction significantly reduced adverse LV remodeling and the decline of cardiac function. This paralleled an increase in autophagy, mitophagy and mitochondrial biogenesis. The salutary effects of the drug were lost in Parkin knockout mice, implicating Parkin-mediated mitophagy as part of its mechanism of action. Our findings suggest that enhancing Parkin-associated mitophagy and mitochondrial biogenesis after infarction is a viable target for therapeutic mitigation of adverse remodeling.

Antiviral Effects of Menthol on Coxsackievirus B.

Coxsackievirus B (CVB) is a common human enterovirus that causes systemic infection but specifically replicates to high titers in the pancreas. It was reported that certain viruses induce mitochondrial fission to support infection. We documented that CVB triggers mitochondrial fission and blocking mitochondrial fission limits infection. The transient receptor potential channels have been implicated in regulating mitochondrial dynamics; namely, the heat and capsaicin receptor transient receptor potential cation channel subfamily V member 1 (TRPV1) contributes to mitochondrial depolarization and fission. When we transiently warmed HeLa cells to 39 °C prior to CVB exposure, infection was heightened, whereas cooling cells to 25 °C reduced infection. Inducing "cold" by stimulating transient receptor potential cation channel subfamily M member 8 (TRPM8) with menthol led to reduced infection and also resulted in lower levels of mitochondrial fission during infection. Additionally, menthol stabilized levels of mitochondrial antiviral signaling (MAVS) which is known to be tied to mitochondrial dynamics. Taken together, this highlights a novel pathway wherein CVB relies on TRPV1 to initiate proviral mitochondrial fission, which may contribute to the disruption of antiviral immunity. TRPM8 has been shown to antagonize TRPV1, and thus we hypothesize that stimulating TRPM8 blocks TRPV1-mediated mitochondrial fragmentation following CVB exposure and attenuates infection.

Simvastatin induces autophagic flux to restore cerulein-impaired phagosome-lysosome fusion in acute pancreatitis.

BACKGROUND: During pancreatitis, autophagy is activated, but lysosomal degradation of dysfunctional organelles including mitochondria is impaired, resulting in acinar cell death. Retrospective cohort analyses demonstrated an association between simvastatin use and decreased acute pancreatitis incidence. METHODS: We examined whether simvastatin can protect cell death induced by cerulein and the mechanisms involved during acute pancreatitis. Mice were pretreated with DMSO or simvastatin (20 mg/kg) for 24 h followed by 7 hourly cerulein injections and sacrificed 1 h after last injection to harvest blood and tissue for analysis. RESULTS: Pancreatic histopathology revealed that simvastatin reduced necrotic cell death, inflammatory cell infiltration and edema. We found that cerulein triggered mitophagy with autophagosome formation in acinar cells. However, autophagosome-lysosome fusion was impaired due to altered levels of LAMP-1, AMPK and ULK-1, resulting in autophagosome accumulation (incomplete autophagy). Simvastatin abrogated these effects by upregulating LAMP-1 and activating AMPK which phosphorylated ULK-1, resulting in increased formation of functional autolysosomes. In contrast, autophagosomes accumulated in control group during pancreatitis. The effects of simvastatin to promote autophagic flux were inhibited by chloroquine. Mitochondria from simvastatin-treated mice were resistant to calcium overload compared to control, suggesting that simvastatin induced mitochondrial quality control to eliminate susceptible mitochondria. Clinical specimens showed a significant increase in cell-free mtDNA in plasma during pancreatitis compared to normal controls. Furthermore, genetic deletion of parkin abrogated the benefits of simvastatin. CONCLUSION: Our findings reveal the novel role of simvastatin in enhancing autophagic flux to prevent pancreatic cell injury and pancreatitis.

Mitophagy protects against statin-mediated skeletal muscle toxicity.

The deleterious effects of statins on skeletal muscle are well known, but the mechanism associated with these effects remains unresolved. Statins are associated with mitochondrial damage, which may contribute to muscle myopathy. Here we demonstrate that simvastatin induces mitophagy in skeletal muscle cells and hypothesized that attenuating this process by silencing the mitophagy adapter p62/sequestosome-1 (SQSTM1) might mitigate myotoxicity. Surprisingly, silencing p62/SQSTM1 in differentiated C2C12 muscle cells exacerbated rather than attenuated myotoxicity. This inhibition of mitophagy in the face of statin challenge correlated with increased release of cytochrome c to the cytosol, activation of caspase-3, and lactate dehydrogenase (LDH) release. Correspondingly, targeted knockdown of Parkin, a canonical E3 ubiquitin ligase important for mitophagy, mirrored the effects of p62/SQSTM1 silencing. To corroborate these findings in vivo, we treated Parkin knockout mice with simvastatin for 2 wk. In line with our findings in vitro, these mitophagy-compromised mice displayed reduced spontaneous activity, loss of grip strength, and increased circulating levels of muscle damage marker LDH. Our findings demonstrate that mitophagy is an important mechanism to resist statin-induced skeletal muscle damage.-Ramesh, M., Campos, J. C., Lee, P., Song, Y., Hernandez, G., Sin, J., Tucker, K. C., Saadaeijahromi, H., Gurney, M., Ferreira, J. C. B., Andres, A. M. Mitophagy protects against statin-mediated skeletal muscle toxicity.

Coxsackievirus B infection induces the extracellular release of miR-590-5p, a proviral microRNA.

Coxsackievirus B is a significant human pathogen and is a leading cause of myocarditis. We and others have observed that certain enteroviruses including coxsackievirus B cause infected cells to shed extracellular vesicles containing infectious virus. Recent reports have shown that vesicle-bound virus can infect more efficiently than free virus. Though microRNAs are differentially regulated in cells following infection, few have been associated with the vesicles shed from infected cells. Here we report exclusive trafficking of specific microRNAs into viral vesicles compared to vesicles from non-infected cells. We found that the most highly-expressed unique microRNA in viral vesicles was miR-590-5p, which facilitates prolonged viral replication by blocking apoptotic factors. Cells over-expressing this miR were significantly more susceptible to infection. This may be a mechanism by which coxsackievirus B boosts subsequent rounds of infection by co-packaging virus and a select set of pro-viral microRNAs in extracellular vesicles.