title: Pinocembrin protects hemorrhagic brain primarily by inhibiting toll-like receptor 4 and reducing M1 phenotype microglia.
abstract: Neuroinflammation is a major contributor to intracerebral hemorrhage (ICH) progression, but no drug is currently available to reduce this response and protect against ICH-induced injury. Recently, the natural product pinocembrin has been shown to ameliorate neuroinflammation and is undergoing a phase II clinical trial for ischemic stroke treatment. In this study, we examined the efficacy of pinocembrin in an ICH model, and further examined its effect on microglial activation and polarization. In vivo, pinocembrin dose-dependently reduced lesion volume by ∼47.5% and reduced neurologic deficits of mice at 72h after collagenase-induced ICH. The optimal dose of pinocembrin (5mg/kg) suppressed microglial activation as evidenced by decreases in CD68-positive microglia and reduced proinflammatory cytokines tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6. Pinocembrin also reduced the number of classically activated M1-like microglia without affecting M2-like microglia in the perilesional region. Additionally, pinocembrin decreased the expression of toll-like receptor (TLR)4 and its downstream target proteins TRIF and MyD88. The protection by pinocembrin was lost in microglia-depleted mice and in TLR4lps-delmice, and pinocembrin failed to decrease the number of M1-like microglia in TLR4lps-delmice. In lipopolysaccharide-stimulated BV-2 cells or primary microglia, pinocembrin decreased M1-related cytokines and markers (IL-1β, IL-6, TNF-α, and iNOS), NF-κB activation, and TLR4 expression, but it did not interfere with TLR4/MyD88 and TLR4/TRIF interactions or affect microglial phagocytosis of red blood cells. Inhibition of the TLR4 signaling pathway and reduction in M1-like microglial polarization might be the major mechanism by which pinocembrin protects hemorrhagic brain. With anti-inflammatory properties, pinocembrin could be a promising new drug candidate for treating ICH and other acute brain injuries.
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, the Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
authors.forename: Xi
authors.initials: X
authors.lastname: Lan
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, the Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
authors.forename: Xiaoning
authors.initials: X
authors.lastname: Han
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, the Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
authors.forename: Qian
authors.initials: Q
authors.lastname: Li
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, the Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Li
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, the Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
authors.forename: Yufeng
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, the Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
authors.forename: Tian
authors.initials: T
authors.lastname: Cheng
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, the Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
authors.forename: Jieru
authors.initials: J
authors.lastname: Wan
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, the Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhu
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, the Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA. Electronic address: jwang79@jhmi.edu.
authors.forename: Jian
authors.initials: J
authors.lastname: Wang
mesh_terms: D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology* / Q000627:therapeutic use; D016207:Cytokines / Q000378:metabolism; D044950:Flavanones / Q000494:pharmacology* / Q000627:therapeutic use; D020300:Intracranial Hemorrhages / Q000188:drug therapy* / Q000378:metabolism; D008297:Male; D051379:Mice; D017628:Microglia / Q000187:drug effects* / Q000378:metabolism; D018696:Neuroprotective Agents / Q000494:pharmacology* / Q000627:therapeutic use; D051197:Toll-Like Receptor 4 / Q000037:antagonists & inhibitors*
chemical_list: D000893:Anti-Inflammatory Agents; D016207:Cytokines; D044950:Flavanones; D018696:Neuroprotective Agents; D051197:Toll-Like Receptor 4; C016063:pinocembrin
keywords: Intracerebral hemorrhage; Microglial polarization; Pinocembrin; Toll-like receptor 4