Protoporphyrin photosensitivity cannot be attenuated by oral N-acetylcysteine

Area of Science:

• Biochemistry
• Dermatology
• Genetics

Background:

• Erythropoietic protoporphyria (EPP) causes skin photodermatosis due to protoporphyrin (PP) accumulation.
• Oxidative stress, including hydroxyl radical generation, is implicated in EPP pathogenesis.
• Antioxidants like beta-carotene have shown potential benefits in managing EPP.

Purpose of the Study:

• To investigate the efficacy of N-acetylcysteine (NAC) in treating photodermatosis in EPP patients.
• To assess NAC's impact on oxidative stress markers and PP levels in EPP.
• To evaluate NAC's potential to activate ferrochelatase and support the glutathione system.

Main Methods:

• A double-blind, crossover, placebo-controlled study involving 6 EPP patients.
• Patients received N-acetylcysteine (NAC) at 1800 mg/day.
• Evaluated photosensitivity, patient-reported hypersensitivity, reduced glutathione levels, red blood cell PP content, and fecal PP excretion.

Main Results:

• N-acetylcysteine (NAC) did not significantly alter photosensitivity test results or patient-reported light hypersensitivity.
• NAC administration did not increase reduced glutathione levels or affect protoporphyrin (PP) levels in red blood cells or feces.
• No adverse effects were observed during the study period.

Conclusions:

• Oral N-acetylcysteine (NAC), at the dose of 1800 mg/day, is not effective for treating photodermatosis in erythropoietic protoporphyria (EPP).
• The proposed mechanisms of action for NAC, including H2O2 scavenging and ferrochelatase activation, did not translate to clinical benefit in this EPP cohort.
• Further research may be needed to explore alternative or higher doses of NAC, or different therapeutic strategies for EPP.