The effect of irradiation on sub-cellular particles--destruction of sulphydryl groups

Ferroptosis, a key to unravel the enigma of the FLASH effect?

Ferroptosis is a non-apoptotic form of cell death dependent on iron and lipid peroxides. It has been recently described to have a role on cell death after radiation (RT) through a DNA damage independent mechanism. While the modification of ferroptosis pathways is suggested to enhance radiosensitisation, normal tissue toxicity may limit the combined treatment of RT and ferroptosis inducers. FLASH RT is given at ultra-high dose rates to reduce normal tissue toxicities, which contributes to the RT effect on the tumour. Although several hypotheses including oxygen depletion, reduced ROS, and immune responses are suggested to explain the FLASH effect, the underlying mechanisms of normal tissue sparing effects are still not well understood. Previous studies highlighting the inverse effect of RT dose rates and lipid peroxidation, along with the hypothesis by Spitz et al, suggest that oxygen depletion from the chain reaction of lipid peroxidation and differences in labile pool between normal and tumour tissues may be related to the normal tissue sparing effect of FLASH. Therefore, the role of ferroptosis in ultra-high dose rate FLASH RT needs to be investigated further as it might be the key to increase the therapeutic window of FLASH RT.

Lead-induced regional lipid peroxidation in brain

Rats exposed to lead (2% lead acetate in drinking water for a period of 10 days) showed altered levels of phospholipids, lipid peroxide and lead ions. Lead ion concentrations were significantly increased in all brain regions with a maximum retention in the spinal cord and cerebellum. The cerebral cortex showed a higher percent elevation of lead ions as compared to the other areas of the brain. The phospholipid contents were significantly depressed in the cerebral cortex, cerebellum and spinal cord. Subsequently, the rate of lipid peroxidation has been enhanced in all brain regions following toxicosis. Increased rate of lipid peroxidation and decreased levels of phospholipids followed the similar rank order as that of increasing lead concentration was spinal cord, cerebellum, cerebral cortex and brain stem after lead intoxication.

Beneficial effects of penicillamine treatment on hereditary avian muscular dystrophy

Hereditary muscular dystrophy in chickens of the New Hampshire strain was treated with penicillamine from the 9th day after hatching to the 425th day. The adult maintenance dose for males was 50 mg/kg per day and for females, 13-65 mg/kg per day. In avian dystrophy, deterioration of the muscle fibers is evidenced in the 2nd mo by an inability of the birds to rise after falling on their backs and by a progressive rigidity of the wings. The drug delayed the onset of symptoms and partially alleviated the debilitating aspects of the disease. Penicillamine produced three major improvements: (a) better righting ability when birds were placed on their backs; (b) greater wing flexibility; (c) and suppression of plasma creatine phosphokinase activity. The results are statistically analyzed and discussed in relationship to Duchenne dystrophy. Normal birds were not affected by penicillamine as judged by these parameters. The rationale for using penicillamine, a sulfhydryl compound with reducing properties, was (a) to attempt to protect essential thiol enzymes in the anabolic and glycolytic pathways against inactivation and (b) to prevent collagen cross-linking and deposition in muscle. Although the precise mechanism of drug action has not been determined. the possible role of penicillamine in mitigating the symptoms of genetic dystrophy in man is under consideration. Further, penicillamine may have a more generalized application i the prevention of contractures in a variety of neuromuscular disorders.