Investigation of the effect of soluble epoxide hydrolase inhibition in relation to NLRC4 inflammasome and antiinflammatory NLRC3 in lipopolysaccharide-induced inflammatory hyperalgesia model in mice

In this thesis, the mechanism of the effect of soluble epoxide hydolase (sEH) inhibition in relation to pro-inflammatory canonical nucleotide-binding oligomerization domain-like receptor C (NLRC) 4/apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC)/pro-caspase-1 inflammasome and noncanonical caspase-11 inflammasome in addition to antiinflammatory NLRC3 was investigated in lipopolysaccharide (LPS)-induced inflammatory hyperalgesia model in mice. Mice were divided into 9 groups: (1) saline, (2) LPS, (3) saline+dimethyl sulfoxide, (4) LPS+triflorometoksifenil-3-(1-propiyonilpiperidin-4-il)üre (trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl)urea; TPPU) (0.3 mg/kg), (5) saline+TPPU (0.5 mg/kg), (6) LPS+TPPU (0.5 mg/kg), and (7) LPS+TPPU (1 mg/kg). TPPU (4 ml/kg) was administered simultaneously with saline (10 ml/kg) or LPS (10 mg/kg) intraperitoneally. Reaction time to thermal stimuli within 30 seconds was evaluated in mice that received either saline or LPS after 6 hours. At the end of the experiments, the brains and spinal cords of the mice were removed after they were killed. In tissue homogenate supernatants prepared from brains and spinal cords, expression of β-tubulin, NLRC4, ASC, caspase-1 p20, caspase-11 p20, interleukin (IL)-1β, and NLRC3 proteins was measured by using the immunoblotting method in addition to 14,15-dihydroxyeicosatrienoic acid (14,15-DHET) and IL-1β levels by using suitable enzyme-linked immunosorbent assay kits. It was observed that LPS-induced decrease in the response time of mice to thermal stimulation was prevented with sEH inhibitor TPPU only at doses of 0.5 and 1 mg/kg. When TPPU was injected at the lowest effective dose (0.5 mg/kg), it prevented the increase induced by LPS in 14,15-DHET and IL-1β levels in addition to the expression of NLRC4, ASC, caspase-1 p20, caspase-11 p20, and IL-1β as well as decreased expression of NLRC3. These results suggested that a decrease in the formation/activation of pro-inflammatory canonical NLRC4/ASC/pro-caspase-1 and noncanonical caspase-11 inflammasome in addition to increased expression of NLRC3 in the central nervous system contributes to the preventive effect of inhibition of sEH with TPPU on inflammatory hyperalgesia induced by LPS.