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

LRRK2 Attenuates Antioxidant Response in Familial Parkinson's Disease Derived Neural Stem Cells

Parkinson's disease (PD) is the second most prevalent neurodegenerative disease, characterized by the loss of midbrain dopaminergic neurons which leads to impaired motor and cognitive functions. PD is predominantly an idiopathic disease; however, about 5% of cases are linked to hereditary mutations. The most common mutation in both familial and sporadic PD is the G2019S mutation of leucine-rich repeat kinase 2 (LRRK2). Currently, it is not fully understood how this mutation leads to PD pathology. In this study, we isolated self-renewable, multipotent neural stem cells (NSCs) from induced pluripotent stem cells (iPSCs) harboring the G2019S LRRK2 mutation and compared them with their isogenic gene corrected counterparts using single-cell RNA-sequencing. Unbiased single-cell transcriptomic analysis revealed perturbations in many canonical pathways, specifically NRF2-mediated oxidative stress response, and glutathione redox reactions. Through various functional assays, we observed that G2019S iPSCs and NSCs exhibit increased basal levels of reactive oxygen species (ROS). We demonstrated that mutant cells show significant increase in the expression for KEAP1 and decrease in NRF2 associated with a reduced antioxidant response. The decreased viability of mutant NSCs in the H2O2-induced oxidative stress assay was rescued by two potent antioxidant drugs, PrC-210 at concentrations of 500 µM and 1 mM and Edaravone at concentrations 50 µM and 100 µM. Our data suggest that the hyperactive LRRK2 G2019S kinase activity leads to increase in KEAP1, which binds NRF2 and leads to its degradation, reduction in the antioxidant response, increased ROS, mitochondria dysfunction and cell death observed in the PD phenotype.

Significant Reduction of Total-Body Irradiation-Induced Death in Mice Treated with PrC-210 24 Hours Postirradiation

The search for radiation countermeasures that can serve as: i. a pre-exposure agent to protect against subsequent irradiation, and/or ii. a post-exposure agent to mitigate the development of Acute Radiation Syndrome after radiation exposure, remains a prominent goal of the U.S. Government. This study was undertaken to determine whether PrC-210, when administered once, 24 h postirradiation, would provide a survival benefit and would mitigate Acute Radiation Syndrome in mice that had received an otherwise 95-100% lethal radiation dose. Our results show that a single intraperitoneal dose of PrC-210 (0.3-0.4 MTD, 151-201 ug/gm body weight) administered 24 h postirradiation, conferred: i. a 45% survival advantage (P = 0.002) in outbred ICR mice and a 25% survival advantage (P = 0.037) in inbred C57Bl/6 mice, ii. a significant increase in body weight in surviving mice (P = 0.012), iii. a discernible protection of intestinal structure by MRI imaging of live mice, iv. visibly denser jejunal villi and surface epithelium and v. visible bone marrow population in PrC-210-treated mice versus saline controls. The ability of PrC-210 to suppress 100% of radiation-induced death when administered minutes before irradiation, or roughly half of this effect (45%) when administered 24 h postirradiation is noteworthy. Determining the multiple paths by which PrC-210 protection is conferred is a process; the results in this report showing protection of two of the major systems central to Acute Radiation Syndrome damage, is a good first step. This was the first study of PrC-210 administered postirradiation; it conferred substantial survival benefit and suppression of Acute Radiation Syndrome. This outcome supports the continued development of PrC-210 to protect humans exposed to ionizing radiation.

Suppression of Inflammation-Associated Kidney Damage Post-Transplant Using the New PrC-210 Free Radical Scavenger in Rats

Allograft kidney transplantation, which triggers host cellular- and antibody-mediated rejection of the kidney, is a major contributor to kidney damage during transplant. Here, we asked whether PrC-210 would suppress damage seen in allograft kidney transplant. Brown Norway (BN) rat kidneys were perfused in situ (UW Solution) with or without added 30 mM PrC-210, and then immediately transplanted into Lewis (LEW) rats. 20 h later, the transplanted BN kidneys and LEW rat plasma were analyzed. Kidney histology, and kidney/serum levels of several inflammation-associated cytokines, were measured to assess mismatch-related kidney pathology, and PrC-210 protective efficacy. Twenty hours after the allograft transplants: (i) significant histologic kidney tubule damage and mononuclear inflammatory cell infiltration were seen in allograft kidneys; (ii) kidney function metrics (creatinine and BUN) were significantly elevated; (iii) significant changes in key cytokines, i.e., TIMP-1, TNF-alpha and MIP-3A/CCL20, and kidney activated caspase levels were seen. In PrC-210-treated kidneys and recipient rats, (i) kidney histologic damage (Banff Scores) and mononuclear infiltration were reduced to untreated background levels; (ii) creatinine and BUN were significantly reduced; and (iii) activated caspase and cytokine changes were significantly reduced, some to background. In conclusion, the results suggest that PrC-210 could provide broadly applicable organ protection for many allograft transplantation conditions; it could protect transplanted kidneys during and after all stages of the transplantation process-from organ donation, through transportation, re-implantation and the post-operative inflammation-to minimize acute and chronic rejection.

Determination of plasma levels of the active thiol form of the direct-acting PrC-210 ROS-scavenger using a fluorescence-based assay

PrC-210 is a direct-acting ROS-scavenger. It's active when administered orally, IV, or topically; it has none of the nausea/emesis nor hypotension side effects that have precluded human amifostine use. PrC-210 confers 100% survival to mice and rats that received an otherwise 100% lethal radiation dose and 36% reduction of ischemia-reperfusion-induced mouse myocardial infarct damage, and thus is a viable candidate to prevent human ROS-induced ischemia-reperfusion and ionizing radiation toxicities. We report the first assay for the pharmacologically active PrC-210 thiol in blood. PrC-210 has no double-bonds nor light absorption, so derivatizing the thiol with a UV-absorbing fluorochrome enables quantification. This assay: i) is done on the benchtop; it's read with a fluorescence plate reader, ii) provides linear product formation through 60 min, iii) quantifies μM to low mM rodent blood levels of PrC-210 that confer complete radioprotection, iv) accurately reflects PrC-210 thiol formation of mixed disulfides with other thiols in blood, and v) shows excellent between-day assay outcome with very low standard deviation and coefficient of variation. A fluorescence assay quantifying formation of a PrC-210 thiol-bimane adduct enables measurement of blood PrC-210 thiol. A blood assay will help in the development of PrC-210 for use in the human clinical setting.

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

Ischemia-reperfusion injury, including injury from warm- and cold-ischemia (CI) organ storage, remains a significant problem for all solid organ transplants. Suppressing CI damage would reduce delayed graft function and increase the donor organ pool size. PrC-210 has demonstrated superior prevention of damage in several preclinical studies as an immediate-acting free-radical scavenger. Here, we describe its profound efficacy in suppressing CI injury in a rat kidney model.

Impact of the PrC-210 Radioprotector Molecule on Cancer Deaths in p53-Deficient Mice

Radiation-induced cancer is an ongoing and significant problem, with sources that include clinics worldwide in which 3.1 billion radiology exams are performed each year, as well as a variety of other scenarios such as space travel and nuclear cleanup. These radiation exposures are typically anticipated, and the exposure is typically well below 1 Gy. When radiation-induced (actually ROS-induced) DNA mutation is prevented, then so too are downstream radiation-induced cancers. Currently, there is no protection available against the effects of such <1 Gy radiation exposures. In this study, we address whether the new PrC-210 ROS-scavenger is effective in protecting p53-deficient (p53^-/-) mice against X-ray-induced accelerated tumor mortality; this is the most sensitive radiation tumorigenesis model currently known. Six-day-old p53^-/- pups received a single intraperitoneal PrC-210 dose [0.5 maximum tolerated dose (MTD)] or vehicle, and 25 min later, pups received 4.0 Gy X-ray irradiation. At 5 min postirradiation, blood was collected to quantify white blood cell c-H2AX foci. Over the next 250 days, tumor-associated deaths were recorded. Findings revealed that when administered 25 min before 4 Gy X-ray irradiation, PrC-210 reduced DNA damage (c-H2AX foci) by 40%, and in a notable coincidence, caused a 40% shift in tumor latency/incidence, and the 0.5 MTD PrC210 dose had no discernible toxicities in these p53^-/- mice. Essentially, the moles of PrC-210 thiol within a single 0.5 MTD PrC-210 dose suppressed the moles of ROS generated by 40% of the 4 Gy X-ray dose administered to p53^-/- pups, and in doing so, eliminated the lifetime leukemia/lymphoma risk normally residing "downstream" of that 40% of the 4 Gy dose. In conclusion: 1. PrC-210 is readily tolerated by the 6-day-old p53^-/- mice, with no discernible lifetime toxicities; 2. PrC-210 does not cause the nausea, emesis or hypotension that preclude clinical use of earlier aminothiols; and 3. PrC-210 significantly increased survival after 4 Gy irradiation in the p53^-/- mouse model.

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

Background.

Ischemia-reperfusion (IR) injury remains a significant problem for all solid organ transplants; thus, an important unmet need in transplantation is the prevention of IR injury. PrC-210 has demonstrated superior prevention of reactive oxygen species damage in several preclinical studies as a free radical scavenger. Here, we describe its profound efficacy in suppressing IR injury in a murine model of kidney IR injury.

Methods.

C57/B6 mice underwent laparotomy with the left renal pedicle occluded for 30 minutes to induce IR injury. Right nephrectomy was performed at the time of surgery. Mice received a single systemic dose of the PrC-210, PrC-211, or PrC-252 aminothiols 20 minutes before IR injury. Twenty-four hours following IR injury, blood and kidney tissue were collected for analysis. Kidney caspase-3 level (a marker of cell death), direct histological analysis of kidneys, and serum blood urea nitrogen (BUN) were measured in animals to assess reactive oxygen species scavenger protective efficacies.

Results.

A single systemic PrC-210 dose 20 minutes before IR injury resulted in significant reductions in (1) IR-induced kidney caspase level (P < 0.0001); caspase was reduced to levels not significantly different than control caspase levels seen in unperturbed kidneys, (2) IR-induced renal tubular injury scores (P < 0.0001); brush border loss and tubular dilation were markedly reduced, and (3) serum BUN compared with control IR injury kidneys (P < 0.0001). The ranked protective efficacies of PrC-210 > PrC-211 >> PrC-252 paralleled previous radioprotection studies of the molecules.

Conclusions.

A single PrC-210 dose, minutes before the IR insult, profoundly reduced caspase, renal tubular injury, and serum BUN in mice exposed to standard kidney IR injury. These findings support further development of the PrC-210 molecule to suppress or prevent IR injury in organ transplant and other IR injury settings.