No abstract

Primary coenzyme Q 10 (CoQ 10 ) deficiency includes a group of rare autosomal recessive disorders primarily characterized by neurological and muscular symptoms. Rarely, glomerular involvement has been reported. The COQ2 gene encodes the para-hydroxybenzoate-polyprenyl-transferase enzyme of the CoQ 10 synthesis pathway. We identified two patients with early-onset glomerular lesions that harbored mutations in the COQ2 gene. The first patient presented with steroid-resistant nephrotic syndrome at the age of 18 months as a result of collapsing glomerulopathy, with no extrarenal symptoms. The second patient presented at five days of life with oliguria, had severe extracapillary proliferation on renal biopsy, rapidly developed end-stage renal disease, and died at the age of 6 months after a course complicated by progressive epileptic encephalopathy. Ultrastructural examination of renal specimens from these cases, as well as from two previously reported patients, showed an increased number of dysmorphic mitochondria in glomerular cells. Biochemical analyses demonstrated decreased activities of respiratory chain complexes [IIϩIII] and decreased CoQ 10 concentrations in skeletal muscle and renal cortex. In conclusion, we suggest that inherited COQ2 mutations cause a primary glomerular disease with renal lesions that vary in severity and are not necessarily associated with neurological signs. COQ2 nephropathy should be suspected when electron microscopy shows an increased number of abnormal mitochondria in podocytes and other glomerular cells.

We have recently shown that dinitrosyl diglutathionyl iron complex, a possible in vivo nitric oxide (NO) donor, binds with extraordinary affinity to one of the active sites of human glutathione transferase (GST) P1-1 and triggers negative cooperativity in the neighboring subunit of the dimer. This strong interaction has also been observed in the human Mu, Alpha, and Theta GST classes, suggesting a common mechanism by which GSTs may act as intracellular NO carriers or scavengers. We present here the crystal structure of GST P1-1 in complex with the dinitrosyl diglutathionyl iron ligand at high resolution. In this complex the active site Tyr-7 coordinates to the iron atom through its phenolate group by displacing one of the GSH ligands. The crucial importance of this catalytic residue in binding the nitric oxide donor is demonstrated by site-directed mutagenesis of this residue with His, Cys, or Phe residues. The relative binding affinity for the complex is strongly reduced in all three mutants by about 3 orders of magnitude with respect to the wild type. Electron paramagnetic resonance spectroscopy studies on intact Escherichia coli cells expressing the recombinant GST P1-1 enzyme indicate that bacterial cells, in response to NO treatment, are able to form the dinitrosyl diglutathionyl iron complex using intracellular iron and GSH. We hypothesize the complex is stabilized in vivo through binding to GST P1-1.

Increasing evidence suggests that iron-mediated oxidative stress might underlie the development of neurodegeneration in Friedreich's ataxia (FRDA), an autosomal recessive ataxia caused by decreased expression of frataxin, a protein implicated in iron metabolism. In this study, we demonstrate that, in fibroblasts of patients with FRDA, the cellular redox equilibrium is shifted toward more protein-bound glutathione. Furthermore, we found that actin is glutathionylated, probably as a result of the accumulation of reactive oxygen species, generated by iron overload in the disease. Indeed, highpressure liquid chromatography analysis of control fibroblasts in vivo treated with FeSO 4 showed a significant increase in the protein-bound/free GSH ratio, and Western blot analysis indicated a relevant rise in glutathionylation. Actin glutathionylation contributes to impaired microfilament organization in FRDA fibroblasts. Rhodamine phalloidin staining revealed a disarray of actin filaments and a reduced signal of F-actin fluorescence. The same hematoxylin/eosin-stained cells showed abnormalities in size and shape. When we treated FRDA fibroblasts with reduced glutathione, we obtained a complete rescue of cytoskeletal abnormalities and cell viability. Thus, we conclude that oxidative stress may induce actin glutathionylation and impairment of cytoskeletal functions in FRDA fibroblasts.Oxidative stress has been proposed to underlie neurodegeneration in Friedreich's ataxia (FRDA), 1 the most common of the hereditary ataxias, caused by severely reduced levels of frataxin, a protein implicated in iron metabolism. FRDA is characterized by degeneration of the large sensory neurons and spinocerebellar tracts, cardiomyopathy, and increased incidence of diabetes. Most patients (95%) are homozygous for the hyperexpansion of a GAA repeat sequence in the first intron of the frataxin gene; a few are heterozygous for a GAA expansion and a point mutation (1-3). Data from yeast suggest that frataxin deficiency results in iron accumulation within mitochondria and increased sensitivity to oxidative stress (4, 5). Mouse models for FRDA exhibit cardiomyopathy, sensory nerve defects, and Fe-S enzyme deficiency followed by intramitochondrial iron deposits (6). Patients with FRDA have iron deposits in the heart, increased mitochondrial iron in fibroblasts, and greater sensitivity to oxidative stress by pro-oxidants such as FeCl 3 and hydrogen peroxide (3,7,8). Furthermore, a defective mitochondrial respiratory chain has been found in FRDA tissues, in association with iron accumulation and moderate decreases in mtDNA levels (9, 10).Iron is a crucial reagent in the Fenton reaction, as it can react with mitochondrially generated superoxide anion (O 2 . ) to produce the toxic hydroxyl radical (OH ⅐ ), and iron-mediated oxidative stress has been hypothesized to underlie the pathophysiology of the disease. Increased levels of oxidative stress markers such as plasma malondialdehyde and urine 8-hydroxy-2-deoxyguanosine have been found in patients with F...

We investigated the prognostic indicators in ten hyperammonemic neonates: four treated by continuous arteriovenous hemodialysis (CAVHD), four with continuous venovenous hemodialysis (CVVHD), and two with hemodialysis (HD). Plasma ammonium levels decreased significantly within the first 24 h irrespective of dialysis modality (from 1419 to 114 micromol/l, median values; P<0.0001). CVVHD achieved the highest ammonium clearance. HD provided highest ammonium extraction but clearance was hampered by severe hemodynamic instability. Five patients had a good outcome (normal at follow-up of 9-59 months), five had poor outcome (four died and one has severe neurological damage). Total coma duration was shorter in patients who had a good outcome (47+/-11 vs 78+/-13 h; P=0.02). Remarkably, only coma duration before dialysis determined this difference (22.2+/-10.1 vs 48.8+/-11.2 h; P=0.02). In cases with good outcome, coma duration was <33 h, whereas the others exceeded this limit. The prognosis was not related to dialysis modality, rapidity in reducing ammonium levels or to the underlying metabolic defect. In conclusion, results showed CVVHD to be the optimal modality for extracorporeal ammonium detoxification. However, the most relevant indicator for prognosis was coma duration before the start of dialysis. Therefore, major efforts should be made to refer patients quickly to highly specialized centers.

No abstract

Hemophagocytic lymphohistiocytosis (HLH) is characterized by immune dysregulation due to inadequate restraint of overactivated immune cells and is associated with a variable clinical spectrum having overlap with more common pathophysiologies. HLH is difficult to diagnose and can be part of inflammatory syndromes. Here, we identify a novel hematological/autoinflammatory condition (NOCARH syndrome) in four unrelated patients with superimposable features, including neonatal-onset cytopenia with dyshematopoiesis, autoinflammation, rash, and HLH. Patients shared the same de novo CDC42 mutation (Chr1:22417990CT, p.R186C) and altered hematopoietic compartment, immune dysregulation, and inflammation. CDC42 mutations had been associated with syndromic neurodevelopmental disorders. In vitro and in vivo assays documented unique effects of p.R186C on CDC42 localization and function, correlating with the distinctiveness of the trait. Emapalumab was critical to the survival of one patient, who underwent successful bone marrow transplantation. Early recognition of the disorder and establishment of treatment followed by bone marrow transplant are important to survival.

No abstract