Department of Physiology and Pharmacology, Pasteur institute of Iran, Tehran, Iran.
Department of Physiology and Pharmacology, Pasteur institute of Iran, Tehran, Iran.
Exp Neurol. 2022 Nov;357:114202. doi: 10.1016/j.expneurol.2022.114202. Epub 2022 Aug 13.
Toll-like receptor 4 (TLR4) signaling plays a detrimental role in traumatic brain injury (TBI) pathology. Pharmacologic or genetic inactivating TLR4 diminish TBI inflammation and neurological complications. Nonetheless, TLR4 priming alleviates TBI inflammation and seizure susceptibility. We investigated impact of postconditioning with TLR4 agonist monophosphoryl lipid A (MPL) on TBI neuroinflammation and epileptogenesis in rats. TBI was induced in temporo-parietal cortex of rats by Controlled Cortical Impact device. Then rats received a single dose (0.1 μg/rat) of MPL by intracerebroventricular injection. After 24 h, CCI-injured rats received intraperitoneal injection of pentylenetetrazole 35 mg/kg once every other day until acquisition of generalized seizures. The injury size, number of survived neurons, and brain protein level of TNF-α, TGF-β, IL-10, and arginase1 (Arg1) were determined. Astrocytes and macrophage/microglia activation/polarization was assessed by double immunostaining with anti GFAP/Arg1 or anti Iba1/Arg1 antibodies. The CCI-injured rats developed generalized seizures after 5.9 ± 1.3 pentylenetetrazole injections (p < 0.001, compared to 12.3 ± 1.4 injections for sham-operated rats). MPL treatment returned the accelerated rate of epileptogenesis in TBI state to the sham-operated level. MPL did not change damage volume but attenuated number of dead neurons (p < 0.01). MPL decreased TNF-α overexpression (6 h post-TBI p < 0.0001), upregulated expression of TGF-β (48 h post-TBI, p < 0.0001), and IL-10 (48 h post-TBI, p < 0.0001) but did not change Arg1 expression. GFAP/Arg1 and Iba1/Arg1 positive cells were detected in TBI area with no significant change following MPL administration. MPL administration after TBI reduces vulnerability to seizure acquisition through down regulating neural death and inflammation, and up-regulating anti-inflammatory cytokines. This capacity along with the clinical safety, makes MPL a potential candidate for development of drugs against neurological deficits of TBI.
Toll 样受体 4（TLR4）信号在创伤性脑损伤（TBI）病理中起着有害的作用。药理学或遗传学上失活 TLR4 可减轻 TBI 炎症和神经并发症。尽管如此，TLR4 引发可减轻 TBI 炎症和癫痫易感性。我们研究了 TLR4 激动剂单磷酰脂质 A（MPL）后处理对大鼠 TBI 神经炎症和癫痫发生的影响。通过控制性皮质撞击装置在大鼠颞顶叶皮层诱导 TBI。然后，大鼠通过侧脑室注射接受单剂量（0.1μg/rat）MPL。24 小时后，CCI 损伤大鼠每两天腹腔注射戊四氮 35mg/kg 一次，直到获得全身性癫痫发作。通过免疫荧光双重染色用抗 GFAP/Arg1 或抗 Iba1/Arg1 抗体测定损伤大小、存活神经元数量以及 TNF-α、TGF-β、IL-10 和精氨酸酶 1（Arg1）的脑蛋白水平。通过用抗 GFAP/Arg1 或抗 Iba1/Arg1 抗体进行双重免疫染色评估星形胶质细胞和巨噬细胞/小胶质细胞激活/极化。CCI 损伤大鼠在 5.9±1.3 次戊四氮注射后发展为全身性癫痫发作（p<0.001，与 sham 手术大鼠的 12.3±1.4 次注射相比）。MPL 治疗将 TBI 状态下加速的癫痫发生速度恢复到 sham 手术水平。MPL 不改变损伤体积，但减少了死亡神经元的数量（p<0.01）。MPL 降低了 TNF-α的过表达（伤后 6 小时，p<0.0001），上调了 TGF-β的表达（伤后 48 小时，p<0.0001）和 IL-10（伤后 48 小时，p<0.0001），但不改变 Arg1 的表达。在 TBI 区域检测到 GFAP/Arg1 和 Iba1/Arg1 阳性细胞，但 MPL 给药后无明显变化。TBI 后给予 MPL 可通过下调神经死亡和炎症以及上调抗炎细胞因子来降低获得癫痫发作的易感性。这种能力以及临床安全性使 MPL 成为开发治疗 TBI 神经功能障碍药物的潜在候选药物。
