Efficacy and Mechanism of Lutongning Granules in Treatment of Trigeminal Neuralgia Induced by Injection of Talc into Infraorbital Foramen of Model Rats Based on P2X7R-mediated Neuroinflammation / 中国实验方剂学杂志

ABSTRACT

ObjectiveTo evaluate the effectiveness of Lutongning granules in the treatment of trigeminal neuralgia in animal models and study its mechanism of action， so as to provide laboratory data support for the clinical application of Lutongning granules and precise treatment. MethodMale SD rats were randomly divided into normal group， model group， carbamazepine group （0.06 g·kg-1·d-1）， high-dose Lutongning group （2.70 g·kg-1·d-1）， and low-dose Lutongning group （1.35 g·kg-1·d-1） according to the stratified basic mechanical pain thresholds， with 10 rats in each group. A trigeminal neuralgia model of rats was prepared by injecting 30% talc suspension into the infraorbital foramen area of the rat. The drug groups were administered 10 mL·kg-1 of drugs by gavage after 2 h of modeling. The normal group and the model group were administered distilled water by gavage under the same conditions once a day for 10 consecutive days. Von Frey brushes were used to determine the mechanical pain threshold of rats. A fully automated blood and body fluid analyzer was employed to detect the blood routine of rats. Hematoxylin and eosin （HE） staining was utilized to detect the pathological changes in the trigeminal ganglion and medulla oblongata tissue. Transmission electron microscopy was used to scan the ultrastructure of the medulla oblongata tissue. Enzyme-linked immunosorbent assay （ELISA） was used to detect the levels of inflammatory factors interleukin （IL）-1， IL-6， IL-8， tumor necrosis factor （TNF）-α， neuropeptide substance P， and β-endorphins （β-EP） in the serum of rats， and Western blot was used to detect the protein expression levels of IL-1β， purinergic receptor P2X7 （P2X7R）， and phosphorylated p38 mitogen-activated protein kinase （p-p38 MAPK）. ResultCompared with that in the normal group， the pain threshold of rats in the model group was significantly lower （P<0.01）. The absolute value of neutrophils （NEUT#） and the percentage of neutrophils （NEUT） were significantly improved， and the percentage of lymphocytes （LYMPH） was significantly reduced （P<0.01）. The serum levels of IL-1， IL-6， IL-8， and TNF-α were significantly increased （P<0.01）. SP content in brain tissue was significantly increased， and β-EP content was significantly decreased （P<0.01）. The relative protein expression of IL-1β， P2X7R， and p-p38 MAPK was significantly increased （P<0.05）. HE staining and transmission electron microscopy results of medulla oblongata tissue revealed neuronal degeneration， mild proliferation of microglial cells， reduction in the number of myelinated nerves， and obvious demyelination. The trigeminal nerve fibers of rats were disarranged， and some nerve fibers showed vacuolization. Axons were swollen， and Schwann cells proliferated. Demyelination was observed. Compared with the model group， each administration group significantly increased the pain threshold of rats （P<0.05， P<0.01）， reduced NEUT# and NEUT， and elevated LYMPH （P<0.05， P<0.01）. The administration group significantly decreased the levels of IL-1， IL-6， IL-8， and TNF-α in serum and SP in brain tissue （P<0.01） and increased the level of β-EP （P<0.01）. They significantly down-regulated the protein expression of IL-1β， P2X7R， and p-p38 MAPK（P<0.05， P<0.01） and significantly ameliorated the pathological changes in medulla oblongata tissue and trigeminal nerves of rats. ConclusionLutongning Granules had significant therapeutic effects on trigeminal neuralgia induced by injection of talc into the infraorbital foramen of model rats， and the mechanism may be related to amelioration of P2X7R-mediated neuroinflammation and inhibition of demyelination of myelinated nerves.