Quin-C1: a selective Fpr2 agonist that shifts microglial phenotype following LPS and Aβ1-42 exposure

Abstract

Oxidative stress and inflammation are both central contributors to Alzheimer’s disease (AD) pathology [1,2]. Microglia, the resident immune cells of the brain and spinal cord, are primary contributors the chronic oxidative and inflammatory brain environment seen in AD. Through their persistent and inappropriate activation, they consequentially contribute to neuronal damage [3]. Dampening this microglial state may provide neurons protection from this ever increasing chronic environment and is thus a potential therapeutic strategy for AD. Formyl peptide receptor 2 (Fpr2) is known to play a key role in peripheral inflammation resolution [4,5], and is expressed in microglia [6]. We have hypothesised that activation of this receptor with the agonist Quin-C1 can reduce both LPS and Aβ1-42 induced reactive oxygen species (ROS), and promote a pro-resolving microglial phenotype. Immortalised murine microglia (BV2 cells) were stimulated with LPS (50ng/ml) for 1h prior to treatment with 100nM Quin-C1. Cytokine (TNFα and IL-10) and nitric oxide (NO) production was detected at 24 and 48h. ROS were monitored with carboxy-H2DCFDA. LPS (50ng/ml) or Aβ1-42 (100nM) was administered for 10 minutes prior to Quin-C1 (100nM). ROS production was detected every 5 minutes for up to 2h. Primary murine microglia were treated with Aβ1-42 for 24h prior to Quin-C1. Expression of CD38 and CD206 were detected by flow cytometry 48h post-Aβ1-42 administration. Quin-C1 significantly suppressed LPS-induced production of TNFα and NO at both 24 and 48h. Further, Quin-C1 significantly enhanced the production of IL-10 48h post-exposure. Strikingly, Quin-C1 reduced LPS and Aβ1-42-induced ROS production back to baseline levels. This was then blocked when the Fpr2 antagonist, WRW4 (10μM), was added 5 minutes prior to Quin-C1. Finally, Quin-C1 successfully increased CD206 and reduced CD38 expression in primary murine microglia, following Aβ1-42 exposure. Together, these data highlight selective targeting of Fpr2 as a potential therapeutic target to dampen oxidative stress and neuroinflammation in AD. 1. Heneka et al. (2015). Lancet Neurol 14: 388-405. 2. Kamat et al. (2016). Mol Neurobiol 53: 648-661. 3. Cunningham C (2013). Glia 61: 71-90. 4. Vital et al. (2016). Circulation 133: 2169-79. 5. McArthur et al. (2015). J Immunol 195: 1139-51. 6. Zhu et al. (2015). J Alzheimers Dis 43: 1237-50