Abstract
Triptolide (T10) is a common anti-inflammatory and analgesic drug. However, the activation of microglia and elimination of the corresponding inflammatory response are new targets for the treatment of neuropathic pain. Chemokine CCL (CCL2) is a key mediator for activating microglia. In this study, the effects of triptolide on the activation and polarization of microglia cells and CCL2 and its corresponding receptor, chemokine receptor 2 (CCR2), were mainly discussed. Microglia were stimulated with 1 μg/mL lipopolysaccharide (LPS) and pretreated with 10, 20, and 40 nM T10 and CCR2 antagonist (RS102895), respectively. The quantitative polymerase chain reaction (QPCR) and western blot results showed that T10 could obviously inhibit the upregulation of CCL2 and CCR2 induced by LPS stimulation in microglia cells, inhibit the fluorescence intensity of glial fibrillary acidic protein (GFAP) and inducible nitric oxide synthase (iNOS) antibody immunostaining in cells, and upregulate the fluorescence intensity of arginase 1 antibody in cells. The expression of interleukin-6 (IL-6), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α) was inhibited in a dose-dependent manner. RS102895 can significantly reverse the activation and M2 polarization of microglia pretreated with 40 nM T10 and weaken the anti-inflammatory effect of T10. The addition of CCL2 did not extremely affect the function of RS102895. T10 may inhibit microglia activation and M1 polarization by inhibiting the expression of CCL2 and CCR2, promoting M2 polarization, reducing the level of inflammatory factors in cells, and exerting its analgesic effect, which is worthy of clinical promotion as a drug for neuropathic pain.
Highlights
Neuropathic pain refers to the changes and confusion in the process of sensory nerve signals when entering the spinal cord and brain caused by lesions or diseases of the somatosensory system in the absence of nociceptive stimulation, as a result of the body’s pathological adaptive response [1, 2]
After microglia were treated with 1 μg/mL LPS for 24 h, quantitative polymerase chain reaction (QPCR) detected the expressions of CCL2 mRNA and chemokine receptor 2 (CCR2) mRNA in cells
Microglia were pretreated with different concentrations of T10 before adding the LPS, and the results showed that T10 could obviously inhibit the upregulated mRNA and protein expressions of CCL2 and CCR2 in
Summary
Neuropathic pain refers to the changes and confusion in the process of sensory nerve signals when entering the spinal cord and brain caused by lesions or diseases of the somatosensory system in the absence of nociceptive stimulation, as a result of the body’s pathological adaptive response [1, 2]. Plastic changes and sensory responses of somatosensory neurons were the main research directions for rational treatment of pain after neuropathy injury, but in recent years, studies have found that glial cells may be the key cells of neuropathic pain. Under the pathological state of glial cells, they can release a large number of cytokines and chemokines. It forms a close interaction with neurons to regulate the transmission of pain [4, 5]. Microglia, as the main macrophages and immune response cells in the central nervous system, is a necessary condition for synaptic changes and pain allergy after nerve injury [4,5,6,7]. Microglia cells have become a powerful target in the targeted therapy of neuropathic pain [4, 8]
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