Inflammation and CB2 signaling drive novel changes in the ocular lipidome and regulate immune cell activity in the eye

• Published in: Prostaglandins & other lipid mediators 2018-11, Vol.139, p.54-62
• Main Authors: Toguri, J.T., Leishman, E., Szczesniak, A.M., Laprairie, R.B., Oehler, O., Straiker, A.J., Kelly, M.E.M., Bradshaw, H.B.
• Format: Article
• Language: English
• Subjects: Cannabinoid; Cannabinoid receptor 2 (CB2); Endocannabinoid system; Eye; Inflammation; Lipidomics; Lipoamine; Ocular
• ISSN: 1098-8823
• DOI: 10.1016/j.prostaglandins.2018.09.004

•HU308 reduced leukocyte adhesion in WT and CB2 KO animals with EIU and reduced neutrophil recruitment in WT but not CB2 KO.•EIU increased 6 non-ECS lipids in WT. HU308 reduced these, while increasing 2-acyl glycerols and decreasing N-acyl glycines.•Saline-injected CB2 KO had elevated 2-acyl glycerols, reduced N-stearoyl and N-oleoyl ethanolamine, and PGE2 compared to WT.•CB2 KOs with EIU had 13 lipids that were significantly lower than WT with EIU including 4 N-acyl glycines.•HU308 had no effect on lipid levels in CB2 KOs with EIU, but further reduced 3 additional lipids compared to saline controls. Uveitis is inflammation of the uvea which consists of the iris, ciliary body and the choroid of the eye. Uveitis can lead to impaired vision and is responsible for 10% of all cases of blindness globally. Using an endotoxin-induced uveitis (EIU) rodent model, our previous data implicated the endogenous cannabinoid system (ECS) in the amelioration of many of the components of the inflammatory response. Here, we test the hypothesis that the reduction in inflammatory mediators in the EIU model by the CB2 agonist, HU308, is associated with changes in ECS endogenous ligands as well as related lipids, prostaglandins (PGs), 2-acyl glycerols, and lipoamines. Analysis of leukocytes and neutrophils, CB2 mRNA, and 26 lipids in the eye of WT mice after EIU induction and HU308 treatment were compared to the same analyses in the CB2 knock-out (CB2 KO) mouse. Endothelial leukocyte adhesion and neutrophil migration were significantly increased in both WT and CB2 KO after EIU. HU308 significantly reduced the leukocyte adhesion and neutrophil recruitment in the WT animals. HU308 also significantly reduced leukocyte adhesion in the CB2 KO mouse, yet, had no effect on neutrophil infiltration suggesting an important off-target effect of HU308. Lipidomics profiles revealed significant increases in 6 non-ECS lipids after EIU in the WT and that HU308 effectively reduced these back to control levels; in addition, HU308 increased levels of 2-acyl glycerols and decreased all N-acyl glycines. CB2 KOs with saline-injection compared to WT had significantly elevated levels of 2-acyl glycerols, whereas levels of N-oleoyl ethanolamine (OEA), N-stearoyl ethanolamine (SEA), and PGE2 were reduced. CB2 KOs with EIU had 13 lipids that were significantly lower than WT with EIU including 4 N-acyl glycines. HU308 had no effect on lipid concentrations in the CB2 KOs with EIU, however, it did cause furt