Introduction Both primary and secondary mitochondrial respiratory chain dysfunction result in generation of abnormal levels of free radicals that deplete intracellular stores of glutathione. The glutathione system is the main natural defense mechanism that helps to combat oxidative damage. We report the intracellular reduced glutathione (iGSH) levels in patients with either primary mitochondrial disease or organic acidemias.
Methods Thirty-five subjects, classified as having either known electron transport chain defects (eg, specific complex deficiencies, pathogenic mtDNA mutations) (n = 17), unknown mitochondrial disease (n = 9), or organic acidemias (n = 9) were studied. Peripheral blood buffy coats were treated with monochlorobimane (MCB), then stained for leukocyte subset markers and subjected to Hi-D fluorescence activated cell sorting (FACS).
Results Primary mitochondrial disorders: When compared to normal controls (n = 20), iGSH levels in CD4 T cells (MCB ratio 1.38 ± 0.32 v. 1.66 ± 0.27 in controls, p = .004), CD8 T cells (MCB ratio 1.29 ± 0.29 v. 1.52 ± 0.21 in controls, p = .001), B cells (MCB ratio 0.65 ± 0.2 v 0.98 ± 0.2 in controls, p = .03), and monocytes (MCB ratio 0.96 ± 0.18 v 1.25 ± 0.2 in controls, p = .04) were significantly lower in mitochondrial disease subjects who were not on antioxidants. No significant difference in either T cell subtype was seen in those taking antioxidants when compared to normal controls. iGSH levels in neutrophils tended to be lower in patients that were not on antioxidants (p = .057). Organic acidemias: When compared to normal controls (n = 20), iGSH levels in CD4 T cells (MCB ratio 1.12 ± 0.15 v. 1.69 ± 0.27 in controls, p = .002), CD8 T cells (MCB ratio 1.04 ± 0.20 v. 1.52 ± 0.21 in controls, p = .003), neutrophils (MCB ratio 0.69 ± 0.24 v. 1.00 ± 0.24, p = .044), and monocytes (MCB ratio 0.90 ± 0.28 v 1.22 ± 0.25, p = .045) were significantly lower in subjects with organic acidemias. No significant difference in iGSH levels was observed in B cells.
Conclusions T cells (CD4 and CD8 subsets), neutrophils, and monocytes may have lower iGSH levels in mitochondrial disorders and organic acidemias. In subjects taking antioxidants, there appears to be sparing of iGSH levels. The significance of the selective low iGSH levels in T cell subsets when compared to B cells is unclear. Given that T cell iGSH levels tend to be low in mitochondrial disorders and organic acidemias, it is reasonable to explore the therapeutic effect of N-acetylcysteine in these disorders.