Targeting mitochondria with methylene blue protects mice against acetaminophen-induced liver injury.
Level 5 - mechanism / opinion, no new human data
Preclinical in vitro and animal experimental study
PubMed 25142022 · doi:10.1002/hep.27385
What was done
Researchers evaluated the mechanism of acetaminophen (APAP) mitochondrial toxicity and the protective effect of methylene blue (MB) using isolated mouse hepatic mitochondria, yeast-derived reconstituted complex II model membranes, cultured mouse hepatocytes, and male C57BL/6J mice. Mice received 450 mg/kg APAP intraperitoneally, followed 90 minutes later by 10 mg/kg MB intraperitoneally, with subsequent assessment of complex II activity, serum alanine aminotransferase (ALT), and liver histology.
What was found
The APAP toxic metabolite N-acetyl-p-benzoquinoneimine (NAPQI) selectively inhibited mitochondrial complex II activity by >90% and decreased succinate-driven ATP biosynthesis. Methylene blue at concentrations <3 µM transferred electrons from NAPQI-altered complex II to cytochrome c, restoring ATP production in vitro. In cultured hepatocytes, MB prevented mitochondrial permeability transition and ATP depletion. In mice, 10 mg/kg MB administered 90 minutes post-APAP protected against massive centrilobular necrosis and elevated serum ALT, without altering SdhA or SdhC subunit protein levels after 4 hours.
Why it matters
This study identifies mitochondrial complex II inhibition by NAPQI as a key mediator of APAP hepatotoxicity and demonstrates that methylene blue acts as an alternative electron carrier to preserve hepatic ATP generation.
Limits
The study was conducted entirely in cell models and mice; human efficacy, safety, and pharmacokinetics in APAP overdose were not tested. Specific animal group sample sizes, precise serum ALT values, and therapeutic windows beyond 90 minutes post-overdose were not detailed in the abstract.
Cited by
- supports Methylene blue donates electrons directly to the mitochondrial electron transport chain.