Blockage of the fractalkine pathway reduces hyperalgesia and prevents morphological glial alterations-Comparison between inflammatory and neuropathic orofacial pain in male rats

This study aimed to evaluate the effects of inhibitors of the fractalkine pathway in hyperalgesia in inflammatory and neuropathic orofacial pain in male rats and the morphological changes in microglia and satellite glial cells (SGCs). Rats were submitted to zymosan-induced arthritis of the temporomandibular joint or infraorbital nerve constriction, and treated intrathecally with a P2 X7 antagonist, a cathepsin S inhibitor or a p-38 mitogen-activated protein kinase (MAPK) inhibitor. Mechanical hyperalgesia was evaluated 4 and 6 h following arthritis induction or 7 and 14 days following nerve ligation. The expression of the receptor CX3 CR1 , phospho-p-38 MAPK, ionized calcium-binding adapter molecule-1 (Iba-1), and glutamine synthetase and the morphological changes in microglia and SGCs were evaluated by confocal microscopy. In both inflammatory and neuropathic models, untreated animals presented a higher expression of CX3 CR1 and developed hyperalgesia and up-regulation of phospho-p-38 MAPK, which was prevented by all drugs (p < .05). The number of microglial processes endpoints and the total branch length were lower in the untreated animals, but the overall immunolabeling of Iba-1 was altered only in neuropathic rats (p < .05). The mean area of SGCs per neuron was significantly altered only in the inflammatory model (p < .05). All morphological alterations were reverted by modulating the fractalkine pathway (p < .05). In conclusion, the blockage of the fractalkine pathway seemed to be a possible therapeutic strategy for inflammatory and neuropathic orofacial pain, reducing mechanical hyperalgesia by impairing the phosphorylation of p-38 MAPK and reverting morphological alterations in microglia and SGCs.

Electroacupuncture Reduces Inflammation but Not Bone Loss on Periodontitis in Arthritic Rats

Periodontitis and rheumatoid arthritis (RA) are inflammatory diseases characterized by chronic inflammation and bone erosion. Electroacupuncture (EA) shows anti-inflammatory and anti-resorptive effects in experimental periodontitis (EP) and in RA. It is important to investigate whether EA shows these effects in periodontal tissues in the presence of these two inflammatory diseases or not. For this, Wistar rats were divided into six groups: control (C); experimental rheumatoid arthritis (RA; bovine type II collagen-induced (CII)); experimental periodontitis (EP); RA/EP (RA + EP); EP/EA (EP treated with EA); RA/EP/EA (RA + EP treated with EA). EP was induced 21 days after RA induction and EA was performed previously and during the EP induction period, every 3 days until the 36th experimental day. The rats were euthanized on day 39. RA was evaluated by edema and the withdrawal threshold of hind paws. The maxillae were removed, and alveolar bone loss (ABL) and bone radiographic density (BRD) were evaluated. Immunohistochemical analyses for interleukins (IL)-6 and -17 and nuclear factor (NF)-κB were performed. Our results showed that EA reduced only the pain intensity in arthritic rats. Histomorphometric, macroscopic, and radiographic analyses did not show differences between the control and EP/EA groups. EA caused a reduction in ABL and BRD only in the presence of EP. EA caused a reduction in IL-6 and -17 in all groups, but NF-κB was only reduced in the arthritic rats with EP. In conclusion, EA reduced the inflammation related to periodontitis in arthritic rats but did not prevent ABL.

Involvement of Endothelin Receptors in Peripheral Sensory Neuropathy Induced by Oxaliplatin in Mice

The aim of this study was to evaluate the participation of the endothelin ET_A and ET_B receptors and the effects of bosentan in oxaliplatin-induced peripheral sensory neuropathy (OIN) in mice. Adult male Swiss mice received 1 mg/kg of oxaliplatin intravenously, twice a week for 5 weeks. Dorsal root ganglia (DRG) and spinal cords were removed for evaluation of the endothelin ET_A and ET_B receptor expression. Afterwards, selective (BQ-123 and BQ-788; 10 nmol in 30 μL, intraplantarly) and non-selective (bosentan, 100 mg/kg, orally) antagonists were administered in order to evaluate the involvement of the endothelin receptors in OIN. Mechanical and thermal nociception tests were performed once a week for 56 days. Oxaliplatin induced mechanical and thermal hypersensitivity and increased the endothelin ET_A receptor expression in both the DRG and spinal cord (P < 0.05). Endothelin ET_B receptor expression was increased in the DRG (P < 0.05) but not in the spinal cord. Both endothelin ET_A and ET_B receptor selective antagonists partially prevented mechanical hyperalgesia in mice with OIN (P < 0.05). Moreover, bosentan prevented mechanical and thermal hypersensitivity in oxaliplatin-treated mice (P < 0.05). In conclusion, both endothelin ET_A and ET_B receptors seem to be involved in the OIN in mice and they should be considered possible targets for the management of this clinical feature.