Pro-inflammatory GPR75 and anti-apoptotic phospholipase signaling pathways contribute to the ameliorating effect of soluble epoxide hydrolase inhibition on chronic experimental autoimmune encephalomyelitis in mice.

Soluble epoxide hydrolase (sEH) inhibition has currently emerged as a therapeutic target in the treatment of various neuroinflammatory neurodegenerative diseases, including multiple sclerosis. Previously, we reported that treatment of mice with a sEH-selective inhibitor, 1-(1-propanoylpiperidin-4-yl)-3-[4-(trifluoromethoxy)phenyl]urea; TPPU), ameliorated chronic experimental autoimmune encephalomyelitis (EAE) induced by myelin oligodendrocyte glycoprotein 35-55 peptide immunization followed by injection of pertussis toxin to mice via regulating pro-inflammatory and anti-inflammatory pathways in the central nervous system. This study tested the hypothesis that the pro-inflammatory G protein-coupled receptor (GPR) 75 and anti-apoptotic phospholipase C (PLC) signaling pathways also contribute to the ameliorating effect of TPPU on chronic EAE. Brains and spinal cords of phosphate-buffered saline-, dimethyl sulfoxide-, or TPPU (3 mg/kg)-treated mice were used for the measurement of sEH, GPR75, Gaq/11, activator protein (AP)-1, PLC ß4, phosphoinositide 3-kinase (PI3K) p85a, Akt1, mitogen-activated protein kinase kinase (MEK) 1/2, extracellular signal-regulated kinase (ERK) 1/2, cyclic adenosine monophosphate-response element-binding protein (CREB) 1, B-cell lymphoma (Bcl)-2, semaphorin (SEMA) 3A, and myelin proteolipid protein (PLP) expression and/or activity by using the immunoblotting method. Expression of sEH, GPR75, Gaq/11, c-jun, phosphorylated c-Jun, and SEMA3A was lower, while PLCß4, phosphorylated PI3K p85a, phosphorylated Akt1, phosphorylated MEK1/2, phosphorylated ERK1/2, phosphorylated CREB1, Bcl-2, and myelin PLP expression was higher in the tissues of TPPU (3 mg/kg)-treated mice as compared with the EAE and vehicle control groups. Inhibition of sEH by TPPU ameliorates chronic EAE through suppressing pro-inflammatory GPR75/Gaq/11/AP-1 pathway and reducing expression of the remyelination inhibitor, SEMA3A, as well as increasing anti-apoptotic PLC/PI3K/Akt1/MEK1/2/ERK1/2/CREB1/Bcl-2 pathway activity and myelin PLP expression.

Activation of GPR75 Signaling Pathway Contributes to the Effect of a 20-HETE Mimetic, 5,14-HEDGE, to Prevent Hypotensive and Tachycardic Responses to Lipopolysaccharide in a Rat Model of Septic Shock.

ABSTRACT: The orphan receptor, G protein-coupled receptor (GPR) 75, which has been shown to mediate various effects of 20-hydroxyeicosatetraenoic acid (20-HETE), is considered as a therapeutic target in the treatment of cardiovascular diseases in which changes in the production of 20-HETE play a key role in their pathogenesis. Our previous studies showed that 20-HETE mimetic, N -(20-hydroxyeicosa-5[Z],14[Z]-dienoyl)glycine (5,14-HEDGE), protects against vascular hyporeactivity, hypotension, tachycardia, and arterial inflammation induced by lipopolysaccharide (LPS) in rats. This study tested the hypothesis that the GPR75 signaling pathway mediates these effects of 5,14-HEDGE in response to systemic exposure to LPS. Mean arterial pressure reduced by 33 mm Hg, and heart rate increased by 102 beats/min at 4 hours following LPS injection. Coimmunoprecipitation studies demonstrated that (1) the dissociation of GPR75/Gα q/11 and GPR kinase interactor 1 (GIT1)/protein kinase C (PKC) α, the association of GPR75/GIT1, large conductance voltage and calcium-activated potassium subunit ß (MaxiKß)/PKCα, MaxiKß/proto-oncogene tyrosine-protein kinase (c-Src), and epidermal growth factor receptor (EGFR)/c-Src, MaxiKß, and EGFR tyrosine phosphorylation were decreased, and (2) the association of GIT1/c-Src was increased in the arterial tissues of rats treated with LPS. The LPS-induced changes were prevented by 5,14-HEDGE. N -[20-Hydroxyeicosa-6( Z ),15( Z )-dienoyl]glycine, a 20-HETE antagonist, reversed the effects of 5,14-HEDGE in the arterial tissues of LPS-treated rats. Thus, similar to 20-HETE, by binding to GPR75 and activating the Gα q/11 /PKCα/MaxiKß, GIT1/PKCα/MaxiKß, GIT1/c-Src/MaxiKß, and GIT1/c-Src/EGFR signaling pathways, 5,14-HEDGE may exert its protective effects against LPS-induced hypotension and tachycardia associated with vascular hyporeactivity and arterial inflammation.

Pharmacological inhibition of soluble epoxide hydrolase attenuates chronic experimental autoimmune encephalomyelitis by modulating inflammatory and anti-inflammatory pathways in an inflammasome-dependent and -independent manner.

We aimed to determine the effect of soluble epoxide hydrolase (sEH) inhibition on chronic experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis (MS), associated with changes in inflammasome-dependent and -independent inflammatory and anti-inflammatory pathways in the CNS of mice. C57BL/6 mice were used to induce chronic EAE by using an injection of MOG35-55 peptide/PT. Animals were observed daily and scored for EAE signs for 25 days after immunization. Following the induction of EAE, the scores were increased after 9 days and reached peak value as determined by ≥ 2 or ≤ 3 with 8% mortality rate on day 17. On day 17, mice were administered daily PBS, DMSO, or TPPU (a potent sEH inhibitor) (1, 3, or 10 mg/kg) until the end of the study. TPPU only at 3 mg/kg dose decreased the AUC values calculated from EAE scores obtained during the disease compared to EAE and vehicle control groups. On day 25, TPPU also caused an increase in the PPARα/ß/γ and NLRC3 proteins and a decrease in the proteins of TLR4, MyD88, NF-κB p65, p-NF-κB p65, iNOS/nNOS, COX-2, NLRC4, ASC, caspase-1 p20, IL-1ß, caspase-11 p20, NOX subunits (gp91phox and p47phox), and nitrotyrosine in addition to 14,15-DHET and IL-1ß levels compared to EAE and vehicle control groups. Our findings suggest that pharmacological inhibition of sEH attenuates chronic EAE likely because of enhanced levels of anti-inflammatory EETs in addition to PPARα/ß/γ and NLRC3 expression associated with suppressed inflammatory TLR4/MyD88/NF-κB signalling pathway, NLRC4/ASC/pro-caspase-1 inflammasome, caspase-11 inflammasome, and NOX activity that are responsible for inflammatory mediator formation in the CNS of mice.