AM404, paracetamol metabolite, prevents prostaglandin synthesis in activated microglia by inhibiting COX activity

Soraya Wilke Saliba,Ellen Fortwängler,Antônio Carlos Pinheiro de Oliveira,Ariel R. Marcotegui,Johannes Ditrich,Juan Carlos Perazzo,Eduardo Muñoz,Bernd L. Fiebich

doi:10.1186/s12974-017-1014-3

Abstract

BackgroundN-arachidonoylphenolamine (AM404), a paracetamol metabolite, is a potent agonist of the transient receptor potential vanilloid type 1 (TRPV1) and low-affinity ligand of the cannabinoid receptor type 1 (CB1). There is evidence that AM404 exerts its pharmacological effects in immune cells. However, the effect of AM404 on the production of inflammatory mediators of the arachidonic acid pathway in activated microglia is still not fully elucidated.MethodIn the present study, we investigated the effects of AM404 on the eicosanoid production induced by lipopolysaccharide (LPS) in organotypic hippocampal slices culture (OHSC) and primary microglia cultures using Western blot, immunohistochemistry, and ELISA.ResultsOur results show that AM404 inhibited LPS-mediated prostaglandin E2 (PGE2) production in OHSC, and LPS-stimulated PGE2 release was totally abolished in OHSC if microglial cells were removed. In primary microglia cultures, AM404 led to a significant dose-dependent decrease in the release of PGE2, independent of TRPV1 or CB1 receptors. Moreover, AM404 also inhibited the production of PGD2 and the formation of reactive oxygen species (8-iso-PGF2 alpha) with a reversible reduction of COX-1- and COX-2 activity. Also, it slightly decreased the levels of LPS-induced COX-2 protein, although no effect was observed on LPS-induced mPGES-1 protein synthesis.ConclusionsThis study provides new significant insights about the potential anti-inflammatory role of AM404 and new mechanisms of action of paracetamol on the modulation of prostaglandin production by activated microglia.

Highlights

N-arachidonoylphenolamine (AM404), a paracetamol metabolite, is a potent agonist of the transient receptor potential vanilloid type 1 (TRPV1) and low-affinity ligand of the cannabinoid receptor type 1 (CB1)
Our results show that AM404 inhibited LPS-mediated prostaglandin E2 (PGE2) production in organotypic hippocampal slice cultures (OHSC), and LPS-stimulated PGE2 release was totally abolished in OHSC if microglial cells were removed
It slightly decreased the levels of LPS-induced COX-2 protein, no effect was observed on LPS-induced Microsomal prostaglandin E synthase (mPGES)-1 protein synthesis

Summary

Introduction

N-arachidonoylphenolamine (AM404), a paracetamol metabolite, is a potent agonist of the transient receptor potential vanilloid type 1 (TRPV1) and low-affinity ligand of the cannabinoid receptor type 1 (CB1). The effect of AM404 on the production of inflammatory mediators of the arachidonic acid pathway in activated microglia is still not fully elucidated. Acetaminophen (N-acetyl-para-aminophenol or paracetamol) was introduced in the market more than a century ago. This compound is one of the most common prescribed and over-the-counter (OTC) drugs in the world, its mechanism of action is not fully understood. It has been shown that acetaminophen has good analgesic and antipyretic properties, but a weak anti-inflammatory activity, inhibiting the prostaglandin synthesis in the central nervous system (CNS) [1], but not peripherally [2]. In the CNS, p-aminophenol is conjugated with arachidonic acid by the fatty acid amide hydrolase (FAAH) to produce N-arachidonoylphenolamine (AM404) [3,4,5]. It has been suggested that AM404 may be responsible for the analgesic mechanism of paracetamol [3, 6, 7]

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