Tirilazad does not protect rat brain from brachytherapy-induced injury

Neuroprotective effect of resveratrol against radiation after surgically induced brain injury by reducing oxidative stress, inflammation, and apoptosis through NRf2/HO-1/NF-κB signaling pathway

The impact of resveratrol (RSV) on radiation (RAD)-induced brain injury in rats' brains was investigated. A total of 40 male Wistar Albino rats were randomly divided into four groups (control, RAD, RAD + RSV, and RSV groups, with 10 rats in each group). The results revealed a significant decrease in catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase activities, as well as glutathione (GSH) content. Further, a significant elevation in malondialdehyde, nitric oxide, interleukin-1-beta (IL-1β), IL-6, and transforming growth factor-β1 levels were observed. Furthermore, decreased B-cell lymphoma 2 (Bcl-2), increased Bcl-2-associated X, and tumor necrosis factor-α genes expression, decreased nuclear factor erythroid-related factor 2, heme oxygenase-1, and increased nuclear factor-κB protein levels were noticed. Also, an apoptosis marker, caspase-3-positive cells, was seen in the hippocampus. Those effects were observed in the RAD group of rats. The treatment of RSV displayed a significant amendment of the studied parameters in the brain tissues of the RAD group of animals. This effect is interrelated to the ability of RSV to scavenge the free radicals, enhance the activity of the antioxidant enzymes, increase GSH contents, and downregulate the inflammatory responses and apoptosis markers in the brain tissues of RAD animals. In conclusion, this study demonstrated that the potent antioxidant, anti-inflammatory, and antiapoptotic activities of RSV can improve the antioxidant status and suppress the inflammatory responses and apoptosis in the brain tissues of RAD animals.

Histone deacetylase inhibitor, valproic acid, radiosensitizes the C6 glioma cell line in vitro

Valproic acid (VPA) is a well-tolerated drug that is used to treat seizure disorders and that has recently been shown to inhibit histone deacetylase. The present study investigated the effects of VPA on the radiosensitization of the rat C6 glioma cell line in vitro. To select an appropriate treatment concentration and time, MTT and flow cytometry assays were performed to measure the inhibitory effects of VPA at various concentrations and incubation time-points. The radiosensitizing effect of VPA was determined using clonogenic experiments. VPA- and radiation-induced C6 apoptosis was analyzed using quantitative polymerase chain reaction and western blot analysis. Cell proliferation was significantly inhibited by VPA in a time- and dose-dependent manner (P<0.05). VPA enhanced radiation-induced C6 cell death and there was clear inhibition of clonogenic formation [sensitizer enhancement ratio (SER), 1.30]. This effect was closely associated with the concentration of VPA. VPA treatment decreased the mRNA and protein levels of Bcl-2, whereas increased changes were detected with Bax. At a concentration of 0.5 mmol/l, VPA had a low toxicity and enhanced the radiosensitization of the C6 cells. VPA may radiosensitize glioma cells by inhibiting cellular proliferation and inducing apoptosis by regulating apoptosis-related molecular changes.

Intravitreal triamcinolone acetonide for acute radiation papillopathy

OBJECTIVE

To evaluate intravitreal triamcinolone acetonide for patients with visually symptomatic acute radiation-induced papillopathy.

METHODS

In a prospective, nonrandomized, single-center case series, intravitreal triamcinolone acetonide (4 mg/0.1 mL) was injected through the pars plana using sterile technique in 9 patients with radiation papillopathy after plaque radiotherapy for choroidal melanoma. Status of radiation papillopathy and final visual acuity were the main outcome measures.

RESULTS

At the time of diagnosis of the choroidal melanoma, visual acuity was 20/20 to 20/40 (n = 6), 20/60 (n = 2), and 20/100 (n = 1). The mean radiation dose to the optic disk was 6,175 cGy (median, 5,994 cGy; range, 3,571-12,760 cGy). Radiation papillopathy developed a mean of 18 months (median, 17 months; range, 6-33 months) after plaque radiotherapy. In all cases, the choroidal melanoma was regressed, and there was no retinal detachment or neovascularization of the retina, optic disk, or iris. Concomitant radiation maculopathy was found in 8 eyes manifesting as macular edema (n = 8), intraretinal dot hemorrhages (n = 6), intraretinal exudation (n = 6), or nerve fiber layer infarction (n = 3). The radiation papillopathy findings included optic disk hyperemia (n = 9), edema (n = 9), and circumpapillary hemorrhage (n = 8). At the time of diagnosis of radiation papillopathy, visual acuity was 20/70 (n = 1), 20/100 (n = 4), 20/200 (n = 1), and counting fingers (n = 3). At 1 week after injection of triamcinolone acetonide, visual acuity improvement was found in seven patients, and resolution of optic disk hyperemia and edema was noted for four and three patients, respectively. At a mean follow-up of 11 months (median, 9 months; range, 6-19 months), visual acuity was stable or improved in 7 patients, and resolution of optic disk hyperemia and edema was found in all 9 patients. The mean time to improvement in visual acuity by > or =2 lines was 3 weeks (median, 1 week; range, 1-12 weeks). The mean time to complete resolution of radiation papillopathy was 4 months. The two patients with worse final visual acuity also had macular hole and central retinal vein obstruction. The only complication of this therapy was possibly related cataract in three patients.

CONCLUSION

During short-term follow-up, acute radiation-induced papillopathy appears to respond rapidly to intravitreal triamcinolone acetonide injection with resolution of optic disk hyperemia and edema and modest return of visual acuity. The long-term effects remain unknown.

Beneficial effects of the radioprotectant 21-aminosteroid U-74389G in a radiosurgery rat malignant glioma model

PURPOSE

To evaluate the radioprotectant effects of the 21-aminosteroid U-74389G on the rat C6 glioma model after stereotactic radiosurgery. Because radiosurgery causes both tumor cytotoxicity, as well as regional brain edema, we hypothesized that this drug might exhibit advantageous or deleterious effects on healthy and neoplastic tissue.

METHODS

Rats were implanted with 10(6) C6 glioma cells into the right frontal brain and randomized to a Control Group (n = 18), radiosurgery on Day 14 (50% isodose = 35 Gy) (n = 15), or radiosurgery preceded by a single 15 mg/kg intravenous dose of 21-aminosteroid (n = 27). All animals were killed by 90 days and evaluated for survival, tumor size, the presence or absence of regional parenchymal edema, or radiation-induced vasculopathy.

RESULTS

After tumor implantation, median survival in the Control Group was 23 days. Significant improvements in median survival were noted after RS alone (median, 31 days; p = 0.02), and RS plus 21-aminosteroid (median, 59 days; p < 0.0001). In the Control Group, mean tumor diameter was 5.4 mm. After RS alone, the mean diameter was 3.2 mm (p = 0.002), and after RS plus 21-aminosteroid, 2.9 mm (p = 0.0002). In the Control Group, the tumor grew as a hypercellular, compact mass. Only 3 of 18 animals had peritumoral edema. In contrast, 7 of 15 animals in the RS group had evidence of edema (p = 0.006), but rats that received 21-aminosteroid showed no increase compared to controls (p = 0.38). Similarly, 6 of 15 animals that had radiosurgery alone showed evidence of vasculopathy (p = 0.005) compared to no animals in the control group and only 2 of 27 aminosteroid-treated animals.

CONCLUSIONS

The 21-aminosteroid U-74389G exhibits a radioprotectant effect on normal brain tissue, but does not appear to protect the tumor in an in vivo rat radiosurgery model. We believe that the observed beneficial effects on healthy brain led to significant prolongation of animal survival; perhaps, by limiting the adverse effects of high-dose radiosurgery. This radioprotectant should now be evaluated in randomized clinical trials in patients with malignant brain tumors.

Radioprotective effects of the 21-aminosteroid U-74389G for stereotactic radiosurgery

OBJECTIVE

Future improvements in the results of stereotactic radiosurgery will be related to better patient selection, dose planning, radiosensitization of the target, and, possibly, protection of the brain surrounding the target. 21-Aminosteroids may provide protection against brain radiation injury by inhibition of lipid peroxidation and a selective action on vascular endothelium. We hypothesized that the 21-aminosteroid U-74389G would reduce radiosurgery-related brain injury without attenuating the target volume response.

METHODS

One hundred and forty-five rats were divided into four experimental groups before undergoing radiosurgery: control (n = 47); low-dose U-74389G (5 mg/kg of body weight, n = 30); high-dose U-74389G (15 mg/kg, n = 20); and methylprednisolone (2 mg/kg, n = 48). The drug was administered 1 hour before radiosurgery (4-mm gamma knife collimator) of the normal rat frontal lobe (single-fraction maximum doses of 50, 100, or 150 Gy) was performed. All brains underwent histological examination at 90 or 150 days to evaluate the diameters of necrosis and the findings of radiation-induced vasculopathy, brain edema, and gliosis.

RESULTS

None of the animals that received 50-Gy radiation developed histological changes, whereas all of the animals that received 150-Gy radiation developed radiation necrosis without drug-induced protection from vascular changes or edema. In animals receiving 100-Gy radiation, high-dose aminosteroid reduced radiation-induced vasculopathy at 90 days (P = 0.06) and at 150 days (P = 0.02) and prevented regional edema at 90 days (P = 0.01) and at 150 days (P = 0.03). Low-dose aminosteroid and corticosteroid provided no protection.

CONCLUSION

The 21-aminosteroid U-74389G provided protection after a single intravenously administered dose of 15 mg/kg against radiation-induced vasculopathy and edema. High-dose 21-aminosteroids seem to have optimal properties for radiosurgery, surrounding brain protection without reducing the therapeutic effect desired within the target volume.