Mecanismos envolvidos na síndrome da dor aguda induzida por paclitaxel em camundongos: Participação de mastócitos e células satélites gliais

Abstract

Paclitaxel is an antineoplastic drug used as a first line in the treatment of several solid tumors, particularly in breast, ovarian, lung, head and neck carcinomas. However, patients receiving paclitaxel treatment often develop a painful condition that occurs immediately after the treatment with this drug, known as acute pain syndrome associated with paclitaxel. Nevertheless, the mechanisms by which paclitaxel induces this painful condition is not yet known. The aim of this study was to investigate the involvement of mast cells and satellite glial cells in the acute pain syndrome induced by paclitaxel. Adult male wild-type mice (C57BL/6), SH mutant mice and TNFR1/R2, TLR4, IL-1R, IL-6 and CCR2 knockout mice were used. Acute pain syndrome was induced by intravenous paclitaxel (4 mg / kg, single dose). After administration of paclitaxel, mechanical and thermal sensitivity (cold) were assessed. The mechanical sensitivity was evaluated using von Frey filaments, measuring pressure in grams. The sensitivity to cold was evaluated with a stimulus of 10 °C (acetone) applied to the right hind paw, leading to agitation and paw elevation behaviors, as well as licking, measured in seconds. The heat sensitivity was assessed by the Hargreaves test, where an infrared light source is positioned under the animal's hind paw for 20s or until the animal exhibits a positive response (flinch or paw withdrawal), then the light source stop automatically. In addition, mast cell line culture and satellite glial cells (dorsal root ganglia primary culture) were stimulated with paclitaxel. Samples (plasma, sciatic nerve, dorsal root ganglia and spinal cord) were collected for determination of gene expression and cytokine levels (IL-1β, TNF-α, IL-6, MCP-1 and KC / CXCL1). Immunofluorescence (c-Fos, IL-6 and tryptase) was also performed. The concentration of cytokines/chemokines (IL-1β, TNF-α e IL-6, MCP-1 e KC/CXCL1) was also evaluated in the supernatant of mast cells and satellite glial cells. The results demonstrated that intravenous injection of paclitaxel significantly reduced (p < 0.05) the nociceptive threshold, inducing mechanical and thermal hyperalgesic responses following administration of paclitaxel. However, when assessing the thermal response to heat, it was found that paw withdrawal latency was not altered with paclitaxel treatment when compared to the control group. Immunofluorescence reaction for c-Fos in the dorsal root and spinal cord ganglia, demonstrated cell activation evidenced by an increased immunoexpression was observed in the groups treated with paclitaxel. Administration of paclitaxel caused a significant (p<0.05) increase in IL-1β, TNF-α, IL-6, MCP-1 and KC / CXCL1 levels. Mechanical and thermal cold hyperalgesia were significantly reduced (p <0.05) in SH animals (no mast cells) when compared to wild animals, and treatment with sodium cromoglycate (mast cell membrane stabilizer) was effective (p <0.05) in inhibiting mechanical and thermal hyperalgesia after the chemotherapic treatment. Pretreatment with sodium cromoglycate significantly (p<0.05) prevented the increase of cytokines and chemokines in mice treated with paclitaxel. In the SH mice treated with paclitaxel, no significant increase (p<0.05) of cytokines was observed. Paclitaxel stimulation resulted in a significant (p<0.05) increase in cytokines (TNF-α, IL-6) and chemokines (MCP-1) concentration in mast cell culture. In addition, immunofluorescence of the dorsal root ganglion demonstrated increased immunoexpression of tryptase and IL-6 after administration of paclitaxel. The results also showed that the TLR4 receptor was involved in the development of paclitaxel-induced hyperalgesia, since knockout animals to TLR4 receptor treated with this chemotherapic did not develop mechanical and thermal hyperalgesia. The results also demonstrated that, in the TLR4 knockout mice treated with paclitaxel, there was no significant increase (p <0.05) in cytokines and chemokines; and when compared to the group of WT mice, a significant reduction (p <0.05) in cytokine and chemokine levels was observed. In addition, paclitaxel caused a significant (p <0.05) increase of cytokines (TNF-α and IL-6) and chemokines (MCP-1 and KC/CXCL) in satellite glial cell culture and the deletion of the TLR4 receptor gene was able to prevent this increase in cytokine/chemokine levels. The study showed for the first time that mast cells and satellite glial cells are involved in the development of acute pain induced by paclitaxel in mice. In addition, the study revealed that the activation of mast cells and satellite glial cells is possibly due to the binding of paclitaxel to TLR4, inducing the release of cytokines/chemokines that contribute to the development of acute pain induced by paclitaxel.