Bypassing the compromised mitochondrial electron transport with methylene blue alleviates efavirenz/isoniazid-induced oxidant stress and mitochondria-mediated cell death in mouse hepatocytes.
Level 5 - mechanism / opinion, no new human data
In vitro laboratory study using isolated mouse mitochondria and cultured mouse hepatocytes.
PubMed 25460728 · doi:10.1016/j.redox.2014.03.003
What was done
Researchers evaluated the mechanisms of synergistic liver toxicity from efavirenz (EFV) and isoniazid (INH) using isolated mouse liver mitochondria and cultured mouse hepatocytes. They measured mitochondrial electron transport chain complex I and II inhibition, superoxide and peroxynitrite formation, mitochondrial permeability transition (mPT) pore opening, and necrotic cell death under exposure to EFV, INH, or their combination. They also tested rescue interventions with the peroxynitrite scavengers CBA and Fe-TMPyP, the acylamidase inhibitor bis-p-nitrophenyl phosphate, and the electron carrier bypass agent methylene blue.
What was found
In isolated mouse mitochondria, EFV inhibited complex I with an IC50 of ~30 µM, while hydrazine (an INH metabolite) inhibited complex II with an IC50 of ~30 µM. In cultured hepatocytes, neither INH alone (≤1000 µM) nor EFV alone (≤30 µM) caused cellular injury. Combined EFV/INH exposure stimulated superoxide and peroxynitrite production, opened the cyclosporine A-insensitive mPT, and caused necrosis. Injury was prevented by peroxynitrite scavengers, by blocking hydrazine generation with bis-p-nitrophenyl phosphate, and by bypassing complexes I and II with methylene blue.
Why it matters
This study provides a mechanistic explanation for why combined antiretroviral and anti-tuberculosis therapy increases drug-induced liver injury risk, pointing to dual-complex electron transport chain disruption as a driver of idiosyncratic toxicity.
Limits
The study was conducted exclusively in isolated mouse organelles and in vitro cell cultures, without in vivo confirmation or human tissue validation. The abstract does not report sample sizes, replication numbers, variance metrics, or exact cell death quantification.
Cited by
- supports Methylene blue donates electrons directly to the mitochondrial electron transport chain.