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Figure 2 | BMC Medicine

Figure 2

From: Friedreich's ataxia: the vicious circle hypothesis revisited

Figure 2

The vicious circle hypothesis revisited in Friedreich's ataxia. (A) According to the vicious circle hypothesis, frataxin depletion results in impaired iron-sulphur cluster synthesis and/or stability with intramitochondrial accumulation of reactive iron. Reactive iron promotes Fenton chemistry, producing superoxide and hydrogen peroxide, which in turn destroys more iron-sulphur clusters. ISC, iron-sulphur cluster. (B) In frataxin-depleted cells, deficient signalling of antioxidant defences sensitises the frataxin-free iron-sulphur clusters to reactive oxygen species. This antioxidant sensitisation process results in intramitochondrial iron accumulation, mostly as amorphous nonreactive precipitates. ROS, reactive oxygen species.

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