Segal Scott, Pancaro Carlo, Bonney Iwona, Marchand James E
From the Department of Anesthesiology, Wake Forest School of Medicine, Winston-Salem, North Carolina.
Department of Anesthesiology, Division of Obstetric Anesthesiology, University of Michigan Health Systems, Ann Arbor, Michigan.
Anesth Analg. 2017 Dec;125(6):2134-2140. doi: 10.1213/ANE.0000000000002479.
Women laboring with epidural analgesia experience fever much more frequently than do women who chose other forms of analgesia, and maternal intrapartum fever is associated with numerous adverse consequences, including brain injury in the fetus. We developed a model of noninfectious inflammatory fever in the near-term pregnant rat to simulate the pathophysiology of epidural-associated fever and hypothesized that it would produce fetal brain inflammation.
Twenty-four pregnant Sprague-Dawley rats were studied at 20 days gestation (term: 22 days). Dams were treated by injection of rat recombinant interleukin (IL)-6 or vehicle at 90-minute intervals, and temperature was monitored every 30 minutes. Eight hours after the first treatment, dams were delivered of fetuses and then killed. Maternal IL-6 was measured at delivery. Fetal brains (n = 24) were processed and stained for ED-1/CD68, a marker for activated microglia, and cell counts in the lateral septal and hippocampal brain regions were measured. Fetal brains were also stained for cyclooxygenase-2 (COX-2), a downstream marker of neuroinflammation. Eight fetal brains were further analyzed for quantitative forebrain COX-2 by Western blotting compared to a β-actin standard. Maternal temperature and IL-6 levels were compared between treatments, as were cell counts, COX-2 staining, and COX-2 levels by Mann-Whitney U test, repeated-measures analysis of variance, or Fisher exact test, as appropriate.
Injection of rat IL-6 at 90-minute intervals produced an elevation of maternal temperature compared to vehicle (P < .0001). IL-6 levels were elevated to clinically relevant levels at delivery in IL-6 compared to vehicle-treated animals (mean ± standard deviation: 923 ± 97 vs 143 ± 94 pg/mL, P = .0006). ED-1-stained cells were present in significantly higher numbers in fetal brains from IL-6 compared to saline-treated dams (median [interquartile range]: caudal hippocampus, 99 [94-104] and 64 [57-68], respectively, P = .002; lateral septum, 102 [96-111] and 68 [65-69], respectively, P = .002), as well as COX-2 immunostaining (lateral septum, 22 [20-26] and 17 [15-18], respectively, P = .005; dorsal hippocampus, 27 [22-32] and 16 [14-19], respectively, P = .013) and quantitative COX-2 Western blotting activity (mean ± standard error of the mean: vehicle, 0% of β-actin intensity versus IL-6, 41.5% ± 24%, P < .001).
Noninfectious inflammatory fever is inducible in the near-term pregnant rat by injection of IL-6 at levels comparable to those observed during human epidural labor analgesia. Maternal IL-6 injection causes neuroinflammation in the fetus.
与选择其他镇痛方式的女性相比，接受硬膜外镇痛分娩的女性发热更为频繁，且产妇分娩期发热会引发诸多不良后果，包括胎儿脑损伤。我们构建了一个近足月妊娠大鼠的非感染性炎性发热模型，以模拟硬膜外相关发热的病理生理学过程，并推测该模型会导致胎儿脑部炎症。
选取24只妊娠20天（足月为22天）的Sprague-Dawley大鼠进行研究。每隔90分钟给母鼠注射大鼠重组白细胞介素（IL）-6或赋形剂，并每30分钟监测一次体温。首次治疗8小时后，对母鼠进行剖宫产取出胎儿，随后处死母鼠。分娩时测定母鼠IL-6水平。对24个胎儿的大脑进行处理，用ED-1/CD68（一种活化小胶质细胞的标志物）染色，并测量侧隔区和海马区的细胞计数。胎儿大脑还用环氧合酶-2（COX-2，神经炎症的下游标志物）进行染色。与β-肌动蛋白标准品相比，对8个胎儿大脑进行Western印迹法进一步分析定量前脑COX-2。采用Mann-Whitney U检验、重复测量方差分析或Fisher精确检验，对不同处理组之间的母鼠体温和IL-6水平、细胞计数、COX-2染色及COX-2水平进行比较。
与注射赋形剂相比，每隔90分钟注射大鼠IL-6可使母鼠体温升高（P <.0001）。与赋形剂处理的动物相比，IL-6组母鼠分娩时IL-6水平升高至临床相关水平（均值±标准差：923±97 vs 143±94 pg/mL，P =.0006）。与生理盐水处理的母鼠相比，IL-6组胎儿大脑中ED-1染色细胞数量显著增多（中位数[四分位间距]：尾侧海马区分别为99[94 - 104]和64[57 - 68]，P =.002；侧隔区分别为102[96 - 111]和68[65 - 69]，P =.002），COX-2免疫染色也增多（侧隔区分别为22[20 - 26]和17[15 - 18]，P =.005；背侧海马区分别为27[22 - 32]和16[14 - 19]，P =.013），且定量COX-2 Western印迹活性增强（均值±平均标准误：赋形剂组为β-肌动蛋白强度的0%，而IL-6组为41.5%±24%，P <.001）。
通过注射与人类硬膜外分娩镇痛期间观察到的水平相当的IL-6，可在近足月妊娠大鼠中诱导非感染性炎性发热。母鼠注射IL-6会导致胎儿神经炎症。
