Methylmalonic acidaemia leads to increased production of reactive oxygen species and induction of apoptosis through the mitochondrial/caspase pathway

Abstract

Methylmalonic acidaemia (MMA) is a heterogeneous group of rare genetic metabolic disorders caused by defects related to intracellular cobalamin (vitamin B(12)) metabolism. Increasing evidence has emerged suggesting that free radical generation is involved in the pathophysiology of neurodegenerative diseases, including some inborn errors of metabolism. We have previously identified in MMA patients several differentially expressed proteins involved in oxidative stress [mitochondrial superoxide dismutase (MnSOD) and mitochondrial glycerophosphate dehydrogenase (mGPDH)] and apoptosis by a proteomic approach. We have now extensively evaluated various parameters related to oxidative stress and apoptosis in cultured fibroblasts from a spectrum of patients with methylmalonic acidaemia. Fibroblasts from several MMA patients showed a significant increase in intracellular reactive oxygen species (ROS) content and in MnSOD expression level with respect to controls, suggesting a cellular response to intrinsic ROS stress. Moreover, we have demonstrated, using siRNA, that mGPDH is an important ROS generator in MMA patients. Cells from patients with MMA had a higher rate of apoptosis than those of controls and there was evidence that this process primarily involves the mitochondrial/caspase-dependent pathway. ROS level-phenotype correlation revealed that patients with severe neonatal cblB disorder had elevated intracellular ROS content. These findings support the possible role of oxidative stress in the pathophysiology of methylmalonic acidaemia.

Inherited disorders affecting mitochondrial function are associated with glutathione deficiency and hypocitrullinemia

“…Nevertheless, studies in animal models have demonstrated a clear link between organic acid metabolites and oxidative stressinduced mitochondrial dysfunction (3,4,19). Our findings also lend support to evidence of increased ROS production and mitochondrial impairment found in animal studies and fibroblasts or liver samples obtained from organic acidemia patients (5,6,19).…”

“…Respiratory chain abnormalities have been documented in organic acidemia patients, such as methylmalonic acidemia (MMA) and propionic acidemia (PA), a knockout mouse model of MMA, and other animal models exposed to acids typically produced in excess in organic acidemias (3)(4)(5). The precise mechanism of respiratory chain impairment in organic acidemias is unknown, although impaired OXPHOS, generation of free radicals, and decreased iGSH are likely contributors to disease pathogenesis (3,4,6).…”

Multiple OXPHOS Deficiency in the Liver, Kidney, Heart, and Skeletal Muscle of Patients With Methylmalonic Aciduria and Propionic Aciduria

“…On the opposite, oxidative stress has been suggested as another pathogenic mechanism in patients with PA or MMA (26). Recently, in a large series of fibroblasts derived from patients with MMA, Richard et al (27) reported variable levels of both ROS and detoxification enzymes ranging from normal to clearly increased levels (8,28). Although the contribution of oxidative stress in PA and MMA remains unclear, our results indicate that it is not systematically increased and suggest that OXPHOS deficiency may develop independently of abnormal free radical generation.…”

Genetic and cellular studies of oxidative stress in methylmalonic aciduria (MMA) cobalamin deficiency type C (cblC) with homocystinuria (MMACHC)

“…For ROS and apoptosis assays skin fibroblasts from five controls (GM03348, GM08680, GM08429, GM05756, GM08333; Coriell cell Repositories, NJ) and 11 patients were cultured as previously described [Richard et al, 2007]. Assays were performed when the cultures reached 75 to 85% confluence.…”