Role of Transient Receptor Potential Ankyrin 1 Ion Channel and Somatostatin sst4 Receptor in the Antinociceptive and Anti-inflammatory Effects of Sodium Polysulfide and Dimethyl Trisulfide

Abstract

Transient receptor potential ankyrin 1 (TRPA1) non-selective ligand-gated cation channels are mostly expressed in primary sensory neurons. Polysulfides (POLYs) are Janus-faced substances interacting with numerous target proteins and associated with both protective and detrimental processes. Activation of TRPA1 in sensory neurons, consequent somatostatin (SOM) liberation and action on sst4 receptors have recently emerged as mediators of the antinociceptive effect of organic trisulfide dimethyl trisulfide (DMTS). In the frame of the present study, we set out to compare the participation of this mechanism in antinociceptive and anti-inflammatory effects of inorganic sodium POLY and DMTS in carrageenan-evoked hind-paw inflammation. Inflammation of murine hind paws was induced by intraplantar injection of carrageenan (3% in 30 µL saline). Animals were treated intraperitoneally with POLY (17 µmol/kg) or DMTS (250 µmol/kg) or their respective vehicles 30 min prior paw challenge and six times afterward every 60 min. Mechanical pain threshold and swelling of the paws were measured by dynamic plantar aesthesiometry and plethysmometry at 2, 4, and 6 h after initiation of inflammation. Myeloperoxidase (MPO) activity in the hind paws were detected 6 h after challenge by luminescent imaging. Mice genetically lacking TRPA1 ion channels, sst4 receptors and their wild-type counterparts were used to examine the participation of these proteins in POLY and DMTS effects. POLY counteracted carrageenan-evoked mechanical hyperalgesia in a TRPA1 and sst4 receptor-dependent manner. POLY did not influence paw swelling and MPO activity. DMTS ameliorated all examined inflammatory parameters. Mitigation of mechanical hyperalgesia and paw swelling by DMTS were mediated through sst4 receptors. These effects were present in TRPA1 knockout animals, too. DMTS inhibited MPO activity with no participation of the sensory neuron-SOM axis. While antinociceptive effects of POLY are transmitted by activation of peptidergic nerves via TRPA1, release of SOM and its effect on sst4 receptors, those of DMTS partially rely on SOM release triggered by other routes. SOM is responsible for the inhibition of paw swelling by DMTS, but TRPA1 does not contribute to its release. Modulation of MPO activity by DMTS is independent of TRPA1 and sst4.

Keywords: IR-676; carrageenan; dimethyl trisulfide; luminol; polysulfide; somatostatin; sst4; transient receptor potential ankyrin 1.

Figure 1

Antinociceptive effect of sodium polysulfide (POLY, 17 µmol/kg) in carrageenan-induced paw inflammation is mediated by transient receptor potential ankyrin 1 (TRPA1) and sst4 receptors. Mechanical pain threshold of saline or carrageenan-injected (3% in 20 µL saline) hind paws of (A) TRPA1 WT, (B) TRPA1 KO, (C) sst4 receptor WT, and (D) sst4 receptor KO animals in response to POLY or vehicle treatment. Data are shown as mean ± SEM. n = 6–8. ^cp < 0.05 vs. saline-injected paws. ^pp < 0.05 vs. vehicle of POLY. ^gp < 0.05 vs. TRPA1 WT animals. Two-way repeated-measure ANOVA followed by Bonferroni’s multiple comparison test.

Figure 2

Antinociceptive effect of dimethyl trisulfide (DMTS, 250 µmol/kg) in carrageenan-evoked paw inflammation is independent of the transient receptor potential ankyrin 1 (TRPA1) ion channel, but is mediated by somatostatin (SOM) sst4 receptors. Effect of DMTS or vehicle treatment on mechanical pain threshold of either saline or carrageenan-treated (3% in 20 µL saline) hind paws of (A) TRPA1 WT, (B) TRPA1 KO, (C) sst4 receptor WT, and (D) sst4 receptor KO mice. Data are shown as mean ± SEM. n = 6–8. ^cp < 0.05 vs. saline-injected paws. ^dp < 0.05 vs. vehicle of DMTS. ^gp < 0.05 vs. TRPA1 WT animals. Two-way repeated-measure ANOVA followed by Bonferroni’s multiple comparison test.

Figure 3

Sodium polysulfide (POLY; 17 µmol/kg, i.p.) does not affect paw swelling detected by plethysmometry in carrageenan-induced hind paw inflammation. Effect of POLY or vehicle treatment on paw swelling of either saline or carrageenan-treated (3% in 20 µL saline) hind paws of (A) transient receptor potential ankyrin 1 (TRPA1) WT, (B) TRPA1 KO, (C) sst4 receptor WT, and (D) sst4 receptor KO mice. Data are shown as mean ± SEM. n = 6–8. ^cp < 0.05 vs. saline-injected paws. Two-way repeated-measure ANOVA followed by Bonferroni’s multiple comparison test.

Figure 4

Alleviating effect of dimethyl trisulfide (DMTS, 250 µmol/kg, i.p.) on edema formation in carrageenan-induced hind paw inflammation is independent of the transient receptor potential ankyrin 1 (TRPA1) ion channel, but is mediated by somatostatin (SOM) sst4 receptors. Effect of DMTS or vehicle treatment on hind paw edema detected by plethysmometry in saline or carrageenan-treated (3% in 20 µL saline) feet of (A) TRPA1 WT, (B) TRPA1 KO, (C) sst4 receptor WT, and (D) sst4 receptor KO mice. Data are shown as mean ± SEM. n = 6–8. ^cp < 0.05 vs. saline-injected paws. ^dp < 0.05 vs. vehicle of DMTS. ^gp < 0.05 vs. TRPA1 WT animals. Two-way repeated-measure ANOVA followed by Bonferroni’s multiple comparison test.

Figure 5

Polysulfide (POLY) treatment (17 µmol/kg, i.p.) does not alter myeloperoxidase (MPO) activity shown by luminol bioluminescence in murine hind paws with carrageenan-induced inflammation. (A) Bioluminescence in saline and carrageenan-injected (3% in 20 µL saline) hind feet of transient receptor potential ankyrin 1 (TRPA1) WT and KO animals. (B) Representative bioluminescent images of saline and carrageenan-treated (3% in 20 µL saline) hind paws of TRPA1 WT and KO mice illustrating MPO activity. (C) Luminol bioluminescence in saline and carrageenan-treated (3% in 20 µL saline) hind feet of sst4 receptor WT and KO mice. (D) Representative bioluminescent images of saline and carrageenan-treated (3% in 20 µL saline) hind paws of sst4 WT and KO animals. Data are shown as mean ± SEM. n = 7–8. ^cp < 0.05 vs. saline-injected paws. One-way ANOVA followed by Bonferroni’s multiple comparison test.

Figure 6

Dimethyl trisulfide (DMTS) administration (250 µmol/kg, i.p.) decreases myeloperoxidase (MPO) activity indicated by luminol bioluminescence in sst4 receptor WT and KO mice undergoing carrageenan-induced inflammation of the hind foot. (A) Bioluminescence in saline and carrageenan-treated (3% in 20 µL saline) hind paws of transient receptor potential ankyrin 1 (TRPA1) WT and KO animals. (B) Representative bioluminescent images of saline and carrageenan-treated (3% in 20 µL saline) hind paws of TRPA1 WT and KO mice depicting MPO activity. (C) Luminol bioluminescence in saline and carrageenan-treated (3% in 20 µL saline) hind paws of sst4 receptor WT and KO mice. (D) Representative bioluminescent images of saline and carrageenan-injected (3% in 20 µL saline) hind paws of sst4 WT and KO animals. Data are shown as mean ± SEM. n = 6–9. ^cp < 0.05 vs. saline-injected paws. ^dp < 0.05 vs. carrageenan-injected paws of mice treated with the vehicle of DMTS. One-way ANOVA followed by Bonferroni’s multiple comparison test.