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Cryptococcus neoformans mitochondrial superoxide dismutase: an essential link between antioxidant function and high-temperature growth.

ABSTRACT: Manganese superoxide dismutase is an essential component of the mitochondrial antioxidant defense system of most eukaryotes. In the present study, we used a reverse-genetics approach to assess the contribution of the Cryptococcus neoformans manganese superoxide dismutase (Sod2) for antioxidant defense. Strains with mutations in the SOD2 gene exhibited increased susceptibility to oxidative stress as well as poor growth at elevated temperatures compared to isogenic wild-type strains. The sod2Delta mutants were also avirulent in a murine model of inhaled cryptococcosis. Reconstitution of a sod2Delta mutant restored Sod2 activity, eliminated the oxidative stress and temperature-sensitive (ts) phenotypes, and complemented the virulence phenotype. Characterization of the ts phenotype revealed a dependency between Sod2 antioxidant activity and the ability of C. neoformans cells to adapt to growth at elevated temperatures. The ts phenotype could be suppressed by the addition of either ascorbic acid (10 mM) or Mn salen (200 muM) at 30 degrees C, but not at 37 degrees C. Furthermore, sod2Delta mutant cells that were incubated for 24 h at 37 degrees C under anaerobic, but not aerobic, conditions were viable when shifted to the permissive conditions of 25 degrees C in the presence of air. These data suggest that the C. neoformans Sod2 is a major component of the antioxidant defense system in this human fungal pathogen and that adaptation to growth at elevated temperatures is also dependent on Sod2 activity.

SUBMITTER: Giles SS

PROVIDER: S-EPMC544162 | biostudies-literature | 2005 Jan

REPOSITORIES: biostudies-literature

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Cryptococcus neoformans mitochondrial superoxide dismutase: an essential link between antioxidant function and high-temperature growth.

Giles Steven S SS Batinic-Haberle Ines I Perfect John R JR Cox Gary M GM

Eukaryotic cell 20050101 1

Manganese superoxide dismutase is an essential component of the mitochondrial antioxidant defense system of most eukaryotes. In the present study, we used a reverse-genetics approach to assess the contribution of the Cryptococcus neoformans manganese superoxide dismutase (Sod2) for antioxidant defense. Strains with mutations in the SOD2 gene exhibited increased susceptibility to oxidative stress as well as poor growth at elevated temperatures compared to isogenic wild-type strains. The sod2Delta ...[more]

PMID: 15643059

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Project description:ImportanceX-linked adrenoleukodystrophy (ALD) may switch phenotype to the fatal cerebral form (ie, cerebral ALD [cALD]), the cause of which is unknown. Determining differences in antioxidant capacity and superoxide dismutase (SOD) levels between phenotypes may allow for the generation of a clinical biomarker for predicting the onset of cALD, as well as initiating a more timely lifesaving therapy.ObjectiveTo identify variations in the levels of antioxidant capacity and SOD activity between ALD phenotypes in patients with cALD or adrenomyeloneuropathy (AMN), heterozygote female carriers, and healthy controls and, in addition, correlate antioxidant levels with clinical outcome scores to determine a possible predictive value.Design, setting, and participantsSamples of monocytes and blood plasma were prospectively collected from healthy controls, heterozygote female carriers, and patients with AMN or cALD. We are counting each patient as 1 sample in our study. Because adrenoleukodystrophy is an X-linked disease, the affected group populations of cALD and AMN are all male. The heterozygote carriers are all female. The samples were assayed for total antioxidant capacity and SOD activity. The data were collected in an academic hospital setting. Eligibility criteria included patients who received a diagnosis of ALD and heterozygote female carriers, both of which groups were compared with age-matched controls. The prospective samples (n?=?30) were collected between January 2015 to January 2016, and existing samples were collected from tissue storage banks at the Kennedy Krieger Institute (n?=?30). The analyses were performed during the first 3 months of 2016.Main outcome and measuresCommercially available total antioxidant capacity and SOD assays were performed on samples of monocytes and blood plasma and correlated with magnetic resonance imaging severity score.ResultsA reduction in antioxidant capacity was shown between the healthy controls (0.225 mmol trolox equivalent) and heterozygote carriers (0.181 mmol trolox equivalent), and significant reductions were seen between healthy controls and patients with AMN (0.102 mmol trolox equivalent; P?<?.01), as well as healthy controls and patients with cALD (0.042 mmol trolox equivalent; P?<?.01). Superoxide dismutase activity in human blood plasma mirrored these reductions between prospectively collected samples from healthy controls (2.66 units/mg protein) and samples from heterozygote female carriers (1.91 units/mg protein), patients with AMN (1.39 units/mg protein; P?=?.01), and patients with cALD (0.8 units/mg protein; P?<?.01). Further analysis of SOD activity in biobank samples showed significant reductions between patients with AMN (0.89 units/mg protein) and patients with cALD (0.18 units/mg protein) (P?=?.03). Plasma SOD levels from patients with cALD demonstrated an inverse correlation to brain magnetic resonance imaging severity score (R2?=?0.75, P?<?.002). Longitudinal plasma SOD samples from the same patients (n?=?4) showed decreased activity prior to and at the time of cerebral diagnosis over a period of 13 to 42 months (mean period, 24 months).Conclusions and relevancePlasma SOD may serve as a potential biomarker for cerebral disease in ALD following future prospective studies.

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Cryptococcus neoformans mitochondrial superoxide dismutase: an essential link between antioxidant function and high-temperature growth.

Publications

Cryptococcus neoformans mitochondrial superoxide dismutase: an essential link between antioxidant function and high-temperature growth.

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