Inhibition of CaMKII in mitochondria preserves endothelial barrier function after irradiation
Authors: Stephen J Roy
Bryan G Allen
Isabella M Grumbach
Douglas R Spitz
Olha M Koval
Karima Ait-Aissa
Sara C Sebag
Journal: Free Radical Biology and Medicine (2020)
Discipline: BIOLOGY & BIOCHEMISTRY
Keywords: Calmodulin-dependent kinase II; Endotheliopathy; Endothelium; Mitochondria/mitochondrial Ca(2+) uniporter; Radiation.
Affiliations: Abboud Cardiovascular Research Center, Division of Cardiovascular Medicine, Department of Internal Medicine, 169 Newton Rd, 4336 PBDB, University of Iowa, Iowa City, IA, 52242, USA., Free Radical and Radiation Biology Program, Department of Radiation Oncology, Holden Comprehensive Cancer Center, B180 Medical Laboratories, University of Iowa, Iowa City, IA, 52242, USA., Abboud Cardiovascular Research Center, Division of Cardiovascular Medicine, Department of Internal Medicine, 169 Newton Rd, 4336 PBDB, University of Iowa, Iowa City, IA, 52242, USA; Free Radical and Radiation Biology Program, Department of Radiation Oncology, Holden Comprehensive Cancer Center, B180 Medical Laboratories, University of Iowa, Iowa City, IA, 52242, USA; Veterans Affairs Health Care System, 601 Hwy 6 West Iowa City, IA, 52246, USA. Electronic address: .

Abstract:  Damage to the microvascular endothelium is an important part of normal tissue injury after radiation exposure and driven by the production of pro-oxidants. The Ca2+/calmodulin-dependent protein kinase II is present in the mitochondrial matrix (mitoCaMKII) where it regulates Ca2+ uptake via the mitochondrial Ca2+ uniporter (MCU) and pro-oxidant production. Here, we demonstrate that radiation exposure disrupts endothelial cell barrier integrity in vitro, but can be abrogated by inhibition of mitoCaMKII, MCU, or opening of the mitochondrial transition pore. Scavenging of mitochondrial pro-oxidants with mitoTEMPO before, but not after irradiation, protected barrier function. Furthermore, markers of apoptosis and mitochondrial pro-oxidant production were elevated at 24 h following irradiation and abolished by mitoCaMKII inhibition. Endothelial barrier dysfunction was detected as early as 2 h after irradiation. Despite only mildly impaired mitochondrial respiration, the intracellular ATP levels were significantly reduced 4 h after irradiation and correlated with barrier function. MitoCaMKII inhibition improved intracellular ATP concentrations by increasing glycolysis. Finally, DNA double strand break repair and non-homologous end joining, two major drivers of ATP consumption after irradiation, were greatly increased but not significantly affected by mitoCaMKII inhibition. These findings support the hypothesis that mitoCaMKII activity is linked to mitochondrial pro-oxidant production, reduced ATP production, and loss of endothelial barrier function following irradiation. The inhibition of mitoCaMKII is a promising approach to limiting radiation-induced endothelial injury. 

Retracted: No

PubPeer comments:
 Fig 6F say it shows  quantification of ECAR at baseline . How this value calculated? Is baseline ECAR value just ECAR with no oligomycin or FCCP or rotenone antimycin? , 
 There is huge error bar in figure 6E but much more small error bar in figure 6F which is suppose to be baseline value taken from figure 6E. How this possible? Look mitoCAMKIIN + IR condition. In figure 6E it having error bar at baseline more than 0.01, but in figure 6F this error bar much much smaller. Same in other experiment condition also. Absolute value also not match between figure 6E and 6F. MitoCAMKII + IR mean in figure 6E look at least more than 0.03 but clear much less than 0.03 in figure 6F. How this also possible? Can author show raw data that making these figures? ![file] , 
 Thank you very much for bringing this to our attention. We will investigate. , 
 Corrigendum: https: www.sciencedirect.com science article pii S0891584921007231 Corrigendum not explain big difference of error bar between Fig 6E and 6F of baseline ECAR for mitoCMAKIIN + IR condition. Adding one experiment not change this. If Fig 6F analysing data from same independent experiments shown Fig 6E than there cannot be such big change from 6E to 6F. Because of very small error bar of Fig 6F you can get statistical significance . If using values shown in Fig 6E there will be no statistical significance even if n=5. Fig legend say statistical analysis use 5 independent experiment but maybe Fig 6F using replicate reading from same experiment and not from independent experiment. Will authors give raw value for 6E and F so peers do analysis? ,