Programa de Pós-Graduação em Ciências Biológicas: Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
Departamento de Medicina Interna, Faculdade de Medicina, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
Mol Cell Biochem. 2019 Aug;458(1-2):99-112. doi: 10.1007/s11010-019-03534-7. Epub 2019 Apr 29.
Maleic acid (MA), which has been reported to be highly excreted in propionic acidemia (PAcidemia), was demonstrated to cause nephropathy by bioenergetics impairment and oxidative stress, but the effects on kidney mitochondrial respiration has not yet been properly investigated. Therefore, the present study investigated the effects of MA (0.05-5 mM), as well as of propionic (PA) and 3-hydroxypropionic (3OHPA) acids (5 mM) that accumulate in PAcidemia, on mitochondrial respiration supported by glutamate, glutamate plus malate or succinate in mitochondrial fractions and homogenates from rat kidney, as well as in permeabilized kidney cells. MA markedly decreased oxygen consumption in state 3 (ADP-stimulated) and uncoupled (CCCP-stimulated) respiration in glutamate and glutamate plus malate-respiring mitochondria, with less prominent effects when using succinate. We also found that PA significantly decreased state 3 and uncoupled respiration in glutamate- and glutamate plus malate-supported mitochondria, whereas 3OHPA provoked milder or no changes. Furthermore, glutamate dehydrogenase and α-ketoglutarate dehydrogenase activities necessary for glutamate oxidation were significantly inhibited by MA in a dose-dependent and competitive fashion. The MA-induced decrease of state 3 and uncoupled respiration found in mitochondrial fractions were also observed in homogenates and permeabilized renal cells that better mimic the in vivo cellular milieu. Taken together, our data indicate that MA, and PA to a lesser extent, disturb mitochondrial-oxidative metabolism in the kidney with the involvement of critical enzymes for glutamate oxidation. It is postulated that our present findings may be possibly involved in the chronic renal failure observed in patients with PAcidemia.
顺丁烯二酸（MA）已被报道在丙酸血症（PAcidemia）中高度排泄，其通过生物能量损伤和氧化应激导致肾病，但对肾脏线粒体呼吸的影响尚未得到适当研究。因此，本研究调查了 MA（0.05-5 mM）以及在 PAcidemia 中积累的丙酸（PA）和 3-羟基丙酸（3OHPA）酸（5 mM）对谷氨酸、谷氨酸加苹果酸或琥珀酸支持的线粒体呼吸的影响在大鼠肾脏线粒体部分和匀浆中以及在通透的肾脏细胞中。MA 显著降低了谷氨酸和谷氨酸加苹果酸呼吸线粒体中状态 3（ADP 刺激）和去耦联（CCCP 刺激）呼吸的耗氧量，而使用琥珀酸时影响较小。我们还发现，PA 显著降低了谷氨酸和谷氨酸加苹果酸支持的线粒体中的状态 3 和去耦联呼吸，而 3OHPA 则引起较轻或无变化。此外，MA 以剂量依赖性和竞争性方式显著抑制谷氨酸氧化所需的谷氨酸脱氢酶和α-酮戊二酸脱氢酶活性。在线粒体部分中观察到的 MA 诱导的状态 3 和去耦联呼吸的降低也在匀浆和通透的肾细胞中观察到，这些细胞更好地模拟了体内细胞环境。总之，我们的数据表明，MA，以及程度较小的 PA，会干扰肾脏的线粒体氧化代谢，涉及到谷氨酸氧化的关键酶。据推测，我们目前的发现可能与 PAcidemia 患者中观察到的慢性肾衰竭有关。
