Differential inhibitory effects of methylmalonic acid on respiratory chain complex activities in rat tissues

Abstract

Methylmalonic acidemia is an inherited metabolic disorder biochemically characterized by tissue accumulation of methylmalonic acid (MMA) and clinically by progressive neurological deterioration and kidney failure, whose pathophysiology is so far poorly established. Previous studies have shown that MMA inhibits complex II of the respiratory chain in rat cerebral cortex, although no inhibition of complexes I-V was found in bovine heart. Therefore, in the present study we investigated the in vitro effect of 2.5mM MMA on the activity of complexes I-III, II, II-III and IV in striatum, hippocampus, heart, liver and kidney homogenates from young rats. We observed that MMA caused a significant inhibition of complex II activity in striatum and hippocampus (15-20%) at low concentrations of succinate in the medium, but not in the peripheral tissues. We also verified that the inhibitory property of MMA only occurred after exposing brain homogenates for at least 10 min with the acid, suggesting that this inhibition was mediated by indirect mechanisms. Simultaneous preincubation with the nitric oxide synthase inhibitor Nomega-nitro-L-arginine methyl ester (L-NAME) and catalase (CAT) plus superoxide dismutase (SOD) did not prevent MMA-induced inhibition of complex II, suggesting that common reactive oxygen (superoxide, hydrogen peroxide and hydroxyl radical) and nitric (nitric oxide) species were not involved in this effect. In addition, complex II-III (20-35%) was also inhibited by MMA in all tissues tested, and complex I-III only in the kidney (53%) and liver (38%). In contrast, complex IV activity was not changed by MMA in all tissues studied. These results indicate that MMA differentially affects the activity of the respiratory chain pending on the tissues studied, being striatum and hippocampus more vulnerable to its effect. In case our in vitro data are confirmed in vivo in tissues from methylmalonic acidemic patients, it is feasible that that the present findings may be related to the pathophysiology of the tissue damage characteristic of these patients.

Renal transplant in methylmalonic acidemia: could it be the best option?

“…Histological changes are detected in the basal ganglia in the central nervous system [23] and in the renal tubuli [15], tissues both requiring high amounts of energy [24]. The cellular insult is believed to stem from an altered energy metabolism: the high concentrations of MMA and its metabolites (malonate and methyl citrate) [25] in the brain (at striatum and hippocampus) [26] inhibit complexes II and III of the respiratory chain and in the renal tubular cells inhibit complexes I and III [7]. The resulting cellular damage is similar to that observed in cellular pathology of mitochondrial origin [27,28].…”

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

“…Moreover, mitochondrial reactive oxygen species (ROS) play an important role in cellular damage in several neurodegenerative disorders [Andersen, 2004]. Several in vitro studies have reported that one of the metabolic consequences of the mitochondrial dysfunction in MMA patients is ROS production in several tissues such as liver, kidney, and brain [Chandler et al, 2009;Pettenuzzo et al, 2006]. On the other hand, homocysteine (Hcys) has been associated with ROS production and apoptosis induction through the mitochondrial/caspase pathway in several tissues such as bone and vascular endothelium Koh et al, 2006;Perna et al, 2003].…”

Methylmalonate inhibits succinate‐supported oxygen consumption by interfering with mitochondrial succinate uptake

“…There is a great deal of evidence suggesting that MMA compromises mitochondrial function, since it competes with malate transport (Halperin et al 1971), increases lactate production ex vivo and in vitro Saad et al 2006;Wajner and Coelho 1997;Wajner et al 1992) and decreases ATP levels (McLaughlin et al 1998), CO 2 production (Wajner et al 1992) and succinate-supported O 2 consumption (Kowaltowski et al 2006;Maciel et al 2004;Toyoshima et al 1995). It has also been proposed that MMA is a weak competitive inhibitor of succinate dehydrogenase (SDH) in rat brain and liver, an effect that has been attributed to the structural similarity between MMA, malonate (MA), the classical SDH inhibitor, and succinate, the substrate of SDH (Brusque et al 2002;Dutra et al 1993;Fleck et al 2004;Marisco et al 2003;Pettenuzzo et al 2006;Toyoshima et al 1995). However, the inhibitory effect of MMA on SDH activity has not been detected in purified submitochondial particles from bovine heart (Kolker et al 2003;Okun et al 2002) and when high concentrations of succinate were used in the medium to measure this enzymatic activity (Brusque et al 2002;Pettenuzzo et al 2006).…”