Significant Suppression of CT Radiation-Induced DNA Damage in Normal Human Cells by the PrC-210 Radioprotector

Abstract

While computed tomography (CT) is now commonly used and considered to be clinically valuable, significant DNA double-strand breaks (γ-H2AX foci) in white blood cells from adult and pediatric CT patients have been frequently reported. In this study to determine whether γ-H2AX foci and X-ray-induced naked DNA damage are suppressed by administration of the PrC-210 radioprotector, human blood samples were irradiated in a CT scanner at 50-150 mGy with or without PrC-210, and γ-H2AX foci were scored. X-ray-induced naked DNA damage was also studied, and the DNA protective efficacy of PrC-210 was compared against 12 other common "antioxidants." PrC-210 reduced CT radiation-induced γ-H2AX foci in white blood cells to near background ( P < 0.0001) at radiation doses of 50-150 mGy. PrC-210 was most effective among the 13 "antioxidants" in reducing naked DNA X-ray damage, and its addition at 30 s before an OH pulse reduced to background theOH insult that otherwise induced >95% DNA damage. A systemic PrC-210 dose known to confer 100% survival in irradiated mice had no discernible effect on micro-CT image signal-to-noise ratio and CT image integrity. PrC-210 suppressed DNA damage to background or near background in each of these assay systems, thus supporting its development as a radioprotector for humans in multiple radiation exposure settings.

Significant Reduction of Murine Renal Ischemia-Reperfusion Cell Death Using the Immediate-Acting PrC-210 Reactive Oxygen Species Scavenger

“…In a recent head-to-head comparison of PrC-210 against 13 other commonly studied antioxidants and ROS scavengers, PrC-210 clearly demonstrated its superiority as a ROS scavenger. 17 N-acetylcysteine actually increased ROS-induced damage, and other molecules, including glutathione and vitamin E, were without effect or showed only a small effect over hours to days due to indirect mechanisms of action. One exception was WR-1065, the active form of amifostine, which though effective, is clinically precluded due to severe side effects.…”

Significant Improvement in Rat Kidney Cold Storage Using UW Organ Preservation Solution Supplemented With the Immediate-Acting PrC-210 Free Radical Scavenger

“…The gel-based assay of ·OH-induced plasmid DNA breaks, in which a 90-second pulse of ·OH was generated by x -ray, demonstrated that PrC-210 provided 100% suppression of the ·OH insult that otherwise induced >95% damage to the naked plasmid DNA. 23 Because several of the comparison molecules absorb UV light, the H 2 O 2 + UV light ·OH generator used in an earlier report 24 was replaced here with 90-second x-irradiation to produce the ·OH insult. In a previous titration comparison of antioxidants, 23 6 mmol/L PrC-210 was found to confer complete protection (Figure 3 A), so the molecules were compared here by addition at 6 mmol/L to DNA 10 minutes before the 90 seconds ·OH insult (Figure 3 B).…”

“… 23 Because several of the comparison molecules absorb UV light, the H 2 O 2 + UV light ·OH generator used in an earlier report 24 was replaced here with 90-second x-irradiation to produce the ·OH insult. In a previous titration comparison of antioxidants, 23 6 mmol/L PrC-210 was found to confer complete protection (Figure 3 A), so the molecules were compared here by addition at 6 mmol/L to DNA 10 minutes before the 90 seconds ·OH insult (Figure 3 B). Under these comparison conditions, none of the current UW solution antioxidants (ie, glutathione, adenosine, and allopurinol) 28 or proposed antioxidants in the new BUPS Solution 28 (ie, taurine, N-acetylcysteine, and ascorbic acid) showed any protection, while PrC-210 showed 100% protection of the at-risk plasmid DNA.…”

“…The active PrC-210 thiol form half-life at pH 7.2 is 3.5 hours. 23 Perfusion at 0 hour with 30 mmol/L PrC-210 in UW solution (Figure 5 A) confers complete kidney protection over 30 hours of 4°C storage. This indicates that ≈4 half-lives at pH ≈7.2 (30 → 1.9 mmol/L PrC-210 thiol) still provides a PrC-210 thiol concentration >1.5 to 2 mmol/L PrC-210 thiol seen in the plasma of mice that received 100% protection against an otherwise 100% lethal dose of whole-body irradiation.…”

“…Unlike traditional antioxidants that act indirectly over hours to days via NrF-2 to activate expression of protective genes, 22 PrC-210 directly scavenges ROS to confer 100% protection in seconds to minutes. 23 , 24 PrC-210 is the most effective, direct-acting, ROS scavenger in existence today. 23 , 25 To determine if PrC-210 can suppress the kidney cell death that occurs during the extended CI required in human kidney transplant, we measured the ability of PrC-210, administered in situ as a single perfusion of a rat donor kidney and also present during the 30 hour 4°C cold storage, to reduce the degree of kidney caspase and kidney tissue destruction over a 30-hour period of kidney CI storage.…”