Cysteamine prevents inhibition of thiol-containing enzymes caused by cystine or cystine dimethylester loading in rat brain cortex

Abstract

Cystinosis is a systemic genetic disease caused by a lysosomal transport deficiency accumulating cystine in the lysosomes of all tissues. Although tissue damage might depend on cystine accumulation, the mechanisms of tissue damage are still obscures. Considering that thiol-containing enzymes are critical for several metabolic pathways, our main objective was to investigate the effects of cystine or cystine dimethylester load on the thiol-containing enzymes creatine kinase and pyruvate kinase, in the brain cortex of young Wistar rats. The animals were injected twice a day with 1.6 micromol/g body weight of cystine dimethylester or 1 micromol/g body weight of cystine and/or 0.46 micromol/g body weight of cysteamine from the 16th to the 20th postpartum day and sacrificed after 12 h. Cystine or cystine dimethylester administration inhibited the two enzyme activities. Co-administration of cysteamine, the drug used to treat cystinotic patients, normalized the two enzyme activities. Lactate dehydrogenase activity, a nonthiol-containing enzyme was not affected by cystine dimethylester administration. Cystine inhibits creatine kinase and pyruvate activities possibly by oxidation of the sulfhydryl groups of the enzymes. Considering that creatine kinase and pyruvate kinase, like other thiol-containing enzymes, are crucial for energy homeostasis and antioxidant defenses, the enzymes inhibition caused by cystine released from lysosomes could be one of the mechanisms of tissue damage in patients with cystinosis.

Endogenous neuroprotection in chronic neurodegenerative disorders: with particular regard to the kynurenines

“…Cysteamine, an antioxidant, is capable of the prevention of lipid peroxidation and can exert beneficial effects through its action on enzymes responsible for the maintenance of an antioxidant milieu or energy preservation [204, 205]. Its oxidized form, cystamine, exerts a transglutaminase inhibitory effect (reviewed in [206]).…”

Generation of the oxidized form protects human brain type creatine kinase against cystine-induced inactivation

“…Without treatment, most children with cystinosis develop renal failure, visuospatial difficulties, and increasing discrepancy in a progressive cognitive impairment due to cystine accumulation in the brain [4,5]. Accumulated data indicated that at the molecule level, the high concentration of intracellular cystine affected the activity and functions of many thiol-containing enzymes, such as pyruvate kinase and creatine kinase [6][7][8][9].…”

“…Previous studies have indicated that BBCK is one of the targets of oxidative stresses induced by dis- eases or toxins. Particularly, BBCK inactivation by cystine and cystine dimethyl ester (CDME) has been observed by in vivo studies [6][7][8][9]21,22], while the other CK isoforms seem not to be affected during the pathogenesis of cystinosis [23]. The in vivo studies suggest that cystine or CDME may affect enzyme activity by the induction of free radicals and lipoperoxidation production, the increase of carbonylation of proteins and the decrease of thiol/disulfide ratio [24].…”

Cysteamine revisited: repair of arginine to cysteine mutations

“…In addition to reducing cystine, cysteamine is considered to play a crucial role in antioxidant defense and energy homeostasis in cystinosis. Cysteamine prevents lipid peroxidation and protein carbonylation thus protecting the activities of superoxide dismutase and glutathione peroxidase (Dubinsky and Gray 2006, Kessler et al 2008), normalizes the activities of creatine kinase and pyruvate kinase, and maintains the GSH pool (Rech et al 2008, Wilmer et al 2011). The recommended cysteamine bitartrate (Cystagon®) dose for cystinosis patients over 12 years of age and over 50 kg is a total of 2 g/day, divided in four doses daily.…”