OBJECTIVE: The NLRP3 (NALP3, cryopyrin) inflammasome, a key component of the 
innate immune system, facilitates caspase-1 and interleukin (IL)-1β processing, 
which amplifies the inflammatory response. Here, we investigated whether NLRP3 
knockdown decreases neutrophil infiltration, reduces brain edema, and improves 
neurological function in an intracerebral hemorrhage (ICH) mouse model. We also 
determined whether mitochondrial reactive oxygen species (ROS) governed by 
mitochondrial permeability transition pores (mPTPs) would trigger NLRP3 
inflammasome activation following ICH.
METHODS: ICH was induced by injecting autologous arterial blood (30μl) into a 
mouse brain. NLRP3 small interfering RNAs were administered 24 hours before ICH. 
A mPTP inhibitor (TRO-19622) or a specific mitochondria ROS scavenger 
(Mito-TEMPO) was coinjected with the blood. In naive animals, rotenone, which is 
a respiration chain complex I inhibitor, was applied to induce mitochondrial ROS 
production, and followed by TRO-19622 or Mito-TEMPO treatment. Neurological 
deficits, brain edema, enzyme-linked immunosorbent assay, Western blot, in vivo 
chemical cross-linking, ROS assay, and immunofluorescence were evaluated.
RESULTS: ICH activated the NLRP3 inflammasome. NLRP3 knockdown reduced brain 
edema and decreased myeloperoxidase (MPO) levels at 24 hours, and improved 
neurological functions from 24 to 72 hours following ICH. TRO-19622 or 
Mito-TEMPO reduced ROS, NLRP3 inflammasome components, and MPO levels following 
ICH. In naive animals, rotenone administration induced mPTP formation, ROS 
generation, and NLRP3 inflammasome activation, which were then reduced by 
TRO-19622 or Mito-TEMPO.
INTERPRETATION: The NLRP3 inflammasome amplified the inflammatory response by 
releasing IL-1β and promoting neutrophil infiltration following ICH. 
Mitochondria ROS may be a major trigger of NLRP3 inflammasome activation. The 
results of our study suggest that the inhibition of the NLRP3 inflammasome may 
effectively reduce the inflammatory response following ICH.ANN NEUROL 
2014;75:209-219.