Melatonin against acute ischaemic stroke dependently via suppressing both inflammatory and oxidative stress downstream signallings
Kuan‐Hung Chen, Kun‐Chen Lin, Sheung‐Fat Ko, John Y. Chiang, Jun Guo, Hon‐Kan Yip
Abstract
Abstract This study tested the hypothesis that melatonin (Mel) therapy preserved the brain architectural and functional integrity against ischaemic stroke (IS) dependently through suppressing the inflammatory/oxidative stress downstream signalling pathways. Adult male B6 (n = 6 per each B6 group) and TLR4 knockout (ie TLR4 −/− ) (n = 6 per each TLR4 −/− group) mice were categorized into sham control (SC B6 ), SC TLR4−/− , IS B6 , IS TLR4−/− , IS B6 + Mel (i.p. daily administration) and IS TLR4−/− + Mel (i.p. daily administration). By day 28 after IS, the protein expressions of inflammatory (HMBG1/TLR2/TLR4/MAL/MyD88/RAM TRIF/TRAF6/IKK‐α/p‐NF‐κB/nuclear‐NF‐κB/nuclear‐IRF‐3&7/IL‐1β/IL‐6/TNF‐α/IFN‐γ) and oxidative stress (NOX‐1/NOX‐2/ASK1/p‐MKK4&7/p‐JNK/p‐c‐JUN) downstream pathways as well as mitochondrial‐damaged markers (cytosolic cytochrome C/cyclophilin D/SRP1/autophagy) were highest in group IS B6 , lowest in groups SC B6 and SC TLR4−/− , lower in group IS TLR4−/− + Mel than in groups IS TLR4−/− and IS B6 + Mel and lower in group IS B6 + Mel than in group IS TLR4−/− (all P < .0001). The brain infarct volume, brain infarct area and the number of inflammatory cells in brain (CD14/F4‐88) and in circulation (MPO+//Ly6C+/CD11b+//Ly6G+/CD11b+) exhibited an identical pattern, whereas the neurological function displayed an opposite pattern of inflammatory protein expression among the six groups (all P < .0001). In conclusion, TLR inflammatory and oxidative stress signallings played crucial roles for brain damage and impaired neurological function after IS that were significantly reversed by Mel therapy.