Enhanced Mitochondrial DNA Repair Resuscitates Transplantable Lungs Donated After Circulatory Death

Abstract

Lung IR injury mtDNA damage Lung transplant mtDNA DAMPs a b s t r a c t Background: Transplantation of lungs procured after donation after circulatory death (DCD)is challenging because postmortem metabolic degradation may engender susceptibility to ischemiaereperfusion (IR) injury. Because oxidative mitochondrial DNA (mtDNA) damage has been linked to endothelial barrier disruption in other models of IR injury, here we used a fusion protein construct targeting the DNA repair 8-oxoguanine DNA glycosylase-1 (OGG1) to mitochondria (mtOGG1) to determine if enhanced repair of mtDNA damage attenuates endothelial barrier dysfunction after IR injury in a rat model of lung procurement after DCD.Materials and methods: Lungs excised from donor rats 1 h after cardiac death were cold stored for 2 h after which they were perfused ex vivo in the absence and presence of mt-OGG1 or an inactive mt-OGG1 mutant. Lung endothelial barrier function and mtDNA integrity were determined during and at the end of perfusion, respectively. Results and Conclusions:Mitochondria-targeted OGG1 attenuated indices of lung endothelial dysfunction incurred after a 1h post-mortem period. Oxidative lung tissue mtDNA damage as well as accumulation of proinflammatory mtDNA fragments in lung perfusate, but not nuclear DNA fragments, also were reduced by mitochondria-targeted OGG1. A repairdeficient mt-OGG1 mutant failed to protect lungs from the adverse effects of DCD procurement.Conclusions: These findings suggest that endothelial barrier dysfunction in lungs procured after DCD is driven by mtDNA damage and point to strategies to enhance mtDNA repair in concert with EVLP as a means of alleviating DCD-related lung IR injury. ª

Effects of cold or warm ischemia and ex-vivo lung perfusion on the release of damage associated molecular patterns and inflammatory cytokines in experimental lung transplantation

“…A possible interpretation could be that DAMPs unrelated to those measured here trigger inflammation during EVLP. A candidate might be mitochondrial DNA, which has been detected in the EVLP perfusate of rat lungs (35), and in the BAL and plasma following LTx (36,37). Another possibility is that inflammation arises during EVLP independently from DAMP release, for example through the activation of the enzyme poly(ADP-ribose) polymerase (PARP), as recently proposed by our group (5,38), or could simply reflect the presence of endogenous inflammatory cells in the graft (39).…”

Does acute and persistent metabolic dysregulation in COVID-19 point to novel biomarkers and future therapeutic strategies?

“…Other therapies that target the kynurenine pathway and the NAD+/NADH ratio may mitigate the bioenergetic crisis and NAD-regulated immune responses [ 8 , 25 ]. Finally, strategies to suppress mitochondrial oxidant stress or repair oxidative mtDNA damage also have the potential to emerge as therapeutic strategies guided by targeted metabolomics monitoring [ 23 , 33 , 34 ].…”

Mitochondrial Damage-associated Molecular Patterns as Potential Biomarkers in DCD Heart Transplantation: Lessons From Myocardial Infarction and Cardiac Arrest

“…This concept is supported by preclinical findings in DCD hearts 18 and lungs. 19 This reperfusion-related specificity may confer an advantage to mtDAMPs as biomarkers over other markers of cell death (ie, cardiac troponins). Furthermore, since access to DCD hearts is often only possible at reperfusion after procurement, ESHP constitutes the perfect platform for the collection of perfusate samples at different time points enabling the monitoring of mtDAMP profiles.…”

“… 18 Likewise, another preclinical study using a DCD rat model reported elevated extracellular mtDNA concentration during lung reperfusion. 19 …”