Differential expression of E-type prostanoid receptors 2 and 4 in microglia stimulated with lipopolysaccharide

Abstract

BackgroundCyclooxygenase-2 (COX-2) is induced under inflammatory conditions, and prostaglandin E2 (PGE2) is one of the products of COX activity. PGE2 has pleiotropic actions depending on the activation of specific E-type prostanoid EP1-4 receptors. We investigated the involvement of PGE2 and EP receptors in glial activation in response to an inflammatory challenge induced by LPS.MethodsCultures of mouse microglia or astroglia cells were treated with LPS in the presence or absence of COX-2 inhibitors, and the production of PGE2 was measured by ELISA. Cells were treated with PGE2, and the effect on LPS-induced expression of TNF-α messenger RNA (mRNA) and protein was studied in the presence or absence of drug antagonists of the four EP receptors. EP receptor expression and the effects of EP2 and EP4 agonists and antagonists were studied at different time points after LPS.ResultsPGE2 production after LPS was COX-2-dependent. PGE2 reduced the glial production of TNF-α after LPS. Microglia expressed higher levels of EP4 and EP2 mRNA than astroglia. Activation of EP4 or EP2 receptors with selective drug agonists attenuated LPS-induced TNF-α in microglia. However, only antagonizing EP4 prevented the PGE2 effect demonstrating that EP4 was the main target of PGE2 in naïve microglia. Moreover, the relative expression of EP receptors changed during the course of classical microglial activation since EP4 expression was strongly depressed while EP2 increased 24 h after LPS and was detected in nuclear/peri-nuclear locations. EP2 regulated the expression of iNOS, NADPH oxidase-2, and vascular endothelial growth factor. NADPH oxidase-2 and iNOS activities require the oxidation of NADPH, and the pentose phosphate pathway is a main source of NADPH. LPS increased the mRNA expression of the rate-limiting enzyme of the pentose pathway glucose-6-phosphate dehydrogenase, and EP2 activity was involved in this effect.ConclusionsThese results show that while selective activation of EP4 or EP2 exerts anti-inflammatory actions, EP4 is the main target of PGE2 in naïve microglia. The level of EP receptor expression changes from naïve to primed microglia where the COX-2/PGE2/EP2 axis modulates important adaptive metabolic changes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-016-0780-7) contains supplementary material, which is available to authorized users.

Activation of EP2 receptor suppresses poly(I: C) and LPS‐mediated inflammation in primary microglia and organotypic hippocampal slice cultures: Contributing role for MAPKs

“…In accordance to our work, anti‐inflammatory action following EP 2 activation has been shown in LPS‐induced microglia by reducing TNFα expression (Bonfill‐Teixidor, Otxoa‐de‐Amezaga, Font‐Nieves, Sans‐Fons, & Planas, ). In contrast, conditional deletion of EP 2 suppressed LPS inflammation in mouse myeloid lineage cells (Johansson et al, ).…”

Protective Effects of L-902,688, a Prostanoid EP4 Receptor Agonist, against Acute Blood-Brain Barrier Damage in Experimental Ischemic Stroke

“…The EP4 receptor is expressed in many cell types including endothelium, neurons, microglia, astrocytes, and peripheral immune cells (Sando et al, 1994 ; Hata and Breyer, 2004 ; Yokoyama et al, 2013 ; Bonfill-Teixidor et al, 2017 ). Permeability of the BBB after stroke can be altered by complex cellular and molecular interactions between cells of the neurovascular unit and the peripheral immune system.…”

CD69 Plays a Beneficial Role in Ischemic Stroke by Dampening Endothelial Activation

“…32 Cell cultures Primary microglial and astroglial cell cultures were obtained from newborn mice as reported. 33 Fluorescence activated cell sorting (FACS) of endothelial cells and gene expression CD45 -CD11b -CD31 + brain endothelial cells were sorted using Aria II cell sorter (BD Biosciences) with the following antibodies: CD31 (clone 390, PE-CY7, eBiosciences), and CD45 and CD11b (as above). Purity of the sorted endothelial cells was checked by flow cytometry (95±2%, mean±SD, n=4) ( Supplementary Fig.…”