α-Pyrrolidinooctanophenone facilitates activation of human microglial cells via ROS/STAT3-dependent pathway

Pyrrolidinophenone derivatives (PPs) are amphetamine-like designer drugs containing a pyrrolidine ring, and their adverse effects resemble those of methamphetamine (METH). Microglial activation has been recently suggested as a key event in eliciting the adverse effects against dysfunction of the central nervous system. The aim of this study is to clarify the mechanisms of microglial activation induced by PPs.

We employed the human microglial cell line HMC3 to assess microglial activation induced by PPs and evaluated the capacities for proliferation and interleukin-6 (IL-6) production that are characteristic features of the activation events.

The WST-1 assay indicated that viability of HMC3 cells was increased by treatment with sublethal concentrations (5-20 µM) of α-pyrrolidinooctanophenone (α-POP), a highly lipophilic PP, whereas it was decreased by treatment with concentrations above 40 µM. Treatment with sublethal α-POP concentrations up-regulated the expression and secretion of IL-6. Additionally, α-POP-induced increase in cell viability was restored by pretreating with N-acetyl-L-cysteine, a reactive oxygen species (ROS) scavenger, and stattic, an inhibitor of signal transducer and activator of transcription 3 (STAT3), respectively, suggesting that activation of the ROS/STAT3 pathway is involved in the α-POP-induced activation of HMC3 cells. The increases in cell viability were also observed in HMC3 cells treated with other α-POP derivatives and METH.

These results suggest that enhanced productions of ROS and IL-6 are also involved in microglial activation by drug treatment and that HMC3 cell-based system is available to evaluate accurately the microglial activation induced by abused drugs.