Investigação do efeito de uma nanopartícula da donepezila sobre a dor neuropática via receptores colinérgicos espinhais em camundongos

Abstract

Neuropathic pain comes from an injury to the somatosensory system, which can occur due to illness or another type of injury. This pain can manifest itself through various symptoms, including hyperalgesia and allodynia, impairing the quality of life, and may even cause disability in the affected individuals. Therefore, numerous studies have investigated different treatment strategies for neuropathic pain. The present study aimed to evaluate the effect of nasal administration of a nanostructured lipid carrier (CLN) loaded with donepezil, which is an anticholinesterase, on neuropathic pain; as well as evaluating the involvement of type 2 muscarinic receptors (mAChR M2) and type α7 nicotinic receptors (α7 nAChR), and microglia in this process. For this, male mice of the C57BL/6 lineage were used, subjected to the sciatic nerve constriction (CCI) model. The nociceptive threshold was assessed by von Frey filament tests, on the 21st day after CCI. To verify the influence of treatment with CLN-donepezil on motor activity, the rotarod test was also performed on the 21st day after CCI. The involvement of mAChR M2 and nAChR α7 receptors at the spinal level was investigated through intrathecal (i.t.) administration of the respective specific antagonists dimetindene and methylacaconitine, 10 minutes before nasal administration of CLN-donepezil. The expression of mRNA referring to nAChR α7 and mAChR M2 and microglia were evaluated in the spinal cord and thalamus using the RT-PCR technique. And the levels of the cytokines IL-10, IL-1β and TNF-α were evaluated, both in the spinal cord and in the thalamus, using the ELISA technique. The administration of CLN-donezepil reversed mechanical allodynia on the 21st day after CCI and did not influence the animals’ motor activity. The i.t. administrations of the antagonists prevented the antiallodynic effect of CLN-donepezil. An increase in gene expression of the α7 nAChR was observed in the thalamus, but not in the spinal cord. The gene expression of the microglial marker, TMEM119, was increased in the spinal cord only in the CCI group treated with CLN-donepezil, and in the thalamus in the untreated CCI and CCI groups treated with CLN-donepezil. Finally, the levels of the cytokines IL-10, IL-1β and TNF-α were evaluated using the ELISA technique, and there was no difference in the levels of cytokines in the spinal cord between the groups, and in the thalamus, the levels of TNF-α were shown to be higher in the CCI group, in the CCI group treated with CLN-donepezil these levels were reduced. Based on these results, we conclude that CLN-donepezil is effective in reducing mechanical allodynia induced by CCI, and that the mechanisms of this effect may involve the nAChR α7 and mAChR M2 receptors and the regulation of TNF-α at the thalamic level.