ノウナイ シュッケツ ビョウタイ シンテン キコウ ノ カイメイ オヨビ チリョウヤク タンサク ニ カンスル シンケイ ヤクリガク テキ ケンキュウ

熊本大

Lipoxin A4 Receptor Stimulation Attenuates Neuroinflammation in a Mouse Model of Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is caused by the rupture of blood vessels in the brain. The excessive activation of glial cells and the infiltration of numerous inflammatory cells are observed during bleeding. Thrombin is a key molecule that triggers neuroinflammation in the ICH brain. In this study, we focused on lipoxin A4 (LXA4), an arachidonic acid metabolite that has been reported to suppress inflammation and cell migration. LXA4 and BML-111, an agonist of the LXA4 receptor/formyl peptide receptor 2 (ALX/FPR2), suppressed microglial activation; LXA4 strongly inhibited the migration of neutrophil-like cells in vitro. ALX/FPR2 was expressed on neutrophils in the ICH mouse brain and the daily administration of BML-111 attenuated the motor coordination dysfunction and suppressed the production of proinflammatory cytokines in the ICH mouse brain. On the other hand, BML-111 did not show a significant reduction in the number of microglia and neutrophils. These results suggest that systemic administration of ALX/FPR2 agonists may suppress the neuroinflammatory response of microglia and neutrophils without a change in cell numbers. Additionally, their combination with molecules that reduce cell numbers, such as modulators of leukotriene B4 signaling, may be required in future studies

MRI-based analysis of intracerebral hemorrhage in mice reveals relationship between hematoma expansion and the severity of symptoms.

Intracerebral hemorrhage (ICH) is featured by poor prognosis such as high mortality rate and severe neurological dysfunction. In humans, several valuables including hematoma volume and ventricular expansion of hemorrhage are known to correlate with the extent of mortality and neurological dysfunction. However, relationship between hematoma conditions and the severity of symptoms in animal ICH models has not been clarified. Here we addressed this issue by using 7-tesla magnetic resonance imaging (MRI) on collagenase-induced ICH model in mice. We found that the mortality rate and the performance in behavioral tests did not correlate well with the volume of hematoma. In contrast, when hemorrhage invaded the internal capsule, mice exhibited high mortality and showed poor sensorimotor performance. High mortality rate and poor performance in behavioral tests were also observed when hemorrhage invaded the lateral ventricle, although worsened symptoms associated with ventricular hemorrhage were apparent only during early phase of the disease. These results clearly indicate that invasion of the internal capsule or the lateral ventricle by hematoma is a critical determinant of poor prognosis in experimental ICH model in mice as well as in human ICH patients. MRI assessment may be a powerful tool to refine investigations of pathogenic mechanisms and evaluations of drug effects in animal models of ICH

Relationship of hematoma volume with mortality and neurological dysfunctions in mouse ICH model.

<p>(A) Representative images of T2-MRI scans (+1.1 mm to −2.9 mm relative to bregma) in a mouse with small hematoma and a mouse with large hematoma at 6 h after induction of ICH. Boundary between hematoma and surrounding tissues is indicated by solid white line. (B) Time-dependent changes of hematoma volume in four groups of mice categorized by the initial volume of hematoma at 6 h after induction of ICH; <5 mm³ (<i>n</i> = 20 at 6 h), 5–10 mm³ (<i>n</i> = 18 at 6 h), 10–15 mm³ (<i>n</i> = 38 at 6 h) and >15 mm³ (<i>n</i> = 37 at 6 h). (C) Survival rate of mice after ICH. (D) Performance of mice in the beam-walking test evaluated by hindlimb fault rate. (E) Performance scores in the modified limb-placing test. Data sets consist of values derived from all mice surviving at each time point. *<i>P</i><0.05, **<i>P</i><0.01, ***<i>P</i><0.001, 5–10 mm³ group versus <5 mm³ group; ^#<i>P</i><0.05, ^##<i>P</i><0.01, ^###<i>P</i><0.001, 10–15 mm³ group versus <5 mm³ group; ^$$<i>P</i><0.01, ^$$$<i>P</i><0.001, 10–15 mm³ group versus <5 mm³ group.</p

Relationship between the degree of initial neurological dysfunction and mortality of mice after ICH.

<p>Surviving mice (<i>n</i> = 78) and dead mice (<i>n</i> = 35) as of 4 weeks after induction of ICH were compared by behavioral parameters assessed at 6 h after ICH; hindlimb fault rate (A), performance score (B) and walking distance (C) in the beam-walking test, and performance score in the modified limb-placing test (D). ***<i>P</i><0.001 versus dead group.</p

Invasion of hematoma into IC worsens mortality and neurological dysfunction.

<p>(A) Representative images of T2-MRI scans (+1.1, +0.1, −0.9 and −1.9 mm relative to bregma) in a non-IC ICH mouse and an IC ICH mouse at 6 h after induction of ICH. Boundary between hematoma and surrounding tissues is indicated by solid white line. (B) Close-up view of MRI images showing invasion of hematoma into IC in an IC ICH mouse. Arrows indicate the position of IC. (C–F) IC ICH mice (<i>n</i> = 26 at 6 h) and non-IC ICH mice (<i>n</i> = 27 at 6 h) were compared by hematoma volume (C), survival rate (D), hindlimb fault rate in the beam-walking test (E) and performance scores in the modified limb-placing test (F). Data sets consist of values derived from all mice surviving at each time point. *<i>P</i><0.05, **<i>P</i><0.01, ***<i>P</i><0.001 versus non-IC ICH group.</p

Induction of hemorrhage near IC resulted in high mortality rate and severe neurological dysfunctions.

<p>Group 1 mice (<i>n</i> = 56) received collagenase injection near IC, whereas group 2 mice (<i>n</i> = 55) received collagenase injection at a distant site from IC. (A) Time-dependent changes of hematoma volume. (B) Survival rate of mice after ICH. (C) Performance of mice in the beam-walking test evaluated by hindlimb fault rate. (D) Performance scores in modified limb-placing test. Data sets consist of values derived from all mice surviving at each time point. **<i>P</i><0.01, ***<i>P</i><0.001 versus group 2.</p