Our current and previous studies have demonstrated that systemic EP2 antagonism, delayed for 2-4 h after pilocarpine SE, is neuroprotective (Jiang et al
Our current and previous studies have demonstrated that systemic EP2 antagonism, delayed for 2-4 h after pilocarpine SE, is neuroprotective (Jiang et al., 2013; Rojas et al., 2015). after SE in EP2-sufficient mice but not in EP2 conditional KOs. EP2 deficiency Diacetylkorseveriline in innate immune cells accelerated the recovery from sickness behaviors following SE. Surprisingly, neurodegeneration was not alleviated in myeloid conditional KOs. Systemic EP2 antagonism prevented monocyte brain infiltration and provided broader rescue of SE-induced effects than myeloid EP2 ablation, including neuroprotection and broader suppression of inflammatory mediators. Reporter expression indicated that this cellular target of CD11b-driven Cre was circulating myeloid cells but, unexpectedly, not microglia. These findings indicate that activation of EP2 receptors on immune myeloid cells drives substantial deficits in behavior and disrupts the BBB after SE. The benefits of systemic EP2 antagonism can Diacetylkorseveriline be attributed, in part, to blocking brain recruitment of blood-borne monocytes. SIGNIFICANCE STATEMENT Unabated seizures reduce quality of life, promote the development of epilepsy, and can be fatal. We previously identified activation of prostaglandin EP2 receptors as a driver of undesirable consequences of seizures. However, the relevant EP2-expressing cell types remain unclear. Here we identify peripheral innate immune cells as a driver of the EP2-related unfavorable consequences of seizures. Removal of EP2 from peripheral immune cells was beneficial, abolishing production of a key inflammatory cytokine, accelerating weight regain, and limiting behavioral deficits. These findings provide evidence that EP2 engagement on peripheral immune and brain endothelia contributes to the deleterious effects of SE, and will assist in the development of beneficial therapies to enhance quality of life in individuals who suffer prolonged seizures. KO mice display greatly reduced monocyte brain infiltration and reduced hippocampal levels of the proinflammatory cytokine IL-1. Notably, blocking monocyte recruitment to the brain enhances weight regain, reduces BBB erosion, and is neuroprotective in hippocampus, identifying brain-invading monocytes as an immune cell subtype that contributes to the deleterious consequences of SE (Varvel et al., 2016). Administration of a brain-permeable antagonist for the prostanoid EP2 receptor hours after pilocarpine- or diisopropyl fluorophosphate-induced SE produces Diacetylkorseveriline a broad range of beneficial effects, including reduction in delayed mortality, blunted neuroinflammation, prevention of BBB opening, neuroprotection, and accelerated weight regain (Jiang et al., 2013; Rojas et al., 2015), which together mimic the effect of conditional ablation of Cox-2 from those neurons in which it is rapidly induced after pilocarpine-induced SE (Serrano et al., 2011). Thus, activation of the prostanoid EP2 receptor is usually a strong driver of Cox-2-mediated deleterious effects following SE. However, in these studies, EP2 receptors were globally antagonized; thus, the relevant cell types involved in EP2-driven consequences of SE remain enigmatic. Moreover, it remains unclear whether the benefits attributed to systemic Diacetylkorseveriline EP2 antagonism also include reduced monocyte brain recruitment. In summary, EP2 receptors are widely expressed by neurons, microglia, and other cell types throughout the brain (see Results). To determine which of the deleterious effects of Cox-2 induction after SE can be attributed to EP2 receptor activation on innate immune myeloid cells, we examined the consequences of genetically ablating the EP2 gene from CD11b-expressing myeloid cells. We also decided whether systemic pharmacologic inhibition of EP2 could LCA5 antibody prevent monocyte infiltration into the brain after SE. We showed that CD11b-driven Cre was expressed in brain endothelial cells and most circulating monocytes but only sparely in microglia. Selective deletion of immune cell EP2 receptors enhanced weight gain after pilocarpine-induced SE, alleviated early neurobehavioral deficits, prevented opening of the BBB, and selectively blunted IL-6 induction in the hippocampus. However, neuronal damage was not attenuated in the EP2 conditional KO mice after SE. By contrast, systemic EP2 antagonism after kainate-induced SE provided neuronal protection, inhibited multiple inflammatory mediators, and blocked monocyte brain infiltration. Together, these findings indicate that EP2 activation on innate immune cells contributes selectively to the sickness behaviors observed after SE, and that the benefits of EP2 antagonism include blocking monocyte infiltration. Materials and Methods Mice All mice used in the current study were housed in the same rooms in Emory’s animal facility during the course of the experiment, with one room designated for animal breeding and maintenance and another room solely for SE experiments. The lights were on a 12 h on/off cycle, and mice were fed and watered (Boillee et al., 2006) and female (Johansson et al., 2013) mice from K. Andreasson (Stanford University), maintained around the C57BL/6 (Charles River) background. The mice were subsequently intercrossed to propagate the.