Abstract: Objective To investigate the role of ΔFosB as a transcription factor in the reduction of lipopolysaccharide (LPS)-induced neuroinflammation by minocycline. Methods Adult C57BL/6 mice at 10 weeks of age received intraperitoneal (i.p.) injections of saline or minocycline (50 mg/kg) for three consecutive days. On the third day, mice were also injected via i.p. with saline or Escherichia coli LPS (0.83 mg/kg). The morphology of microglia indicating the state of neuroinflammation and ΔFosB as a transcription factor were examined by immunohistochemistry. Images of the staining were analyzed with Image-Pro Premier 3D. Statistical analysis was performed with GraphPad Prism. Results Minocycline alleviated LPS-induced neuroinflammation as evidenced by the reduced activation of microglia in locus coeruleus (LC). Minocycline significantly increased the number of ΔFosB-positive neurons in LC, the lateral parabrachial nucleus (LPB) and paraventricular nucleus of the hypothalamus (PVN). Conclusions Minocycline alleviates LPS-induced neuroinflammation possibly by increasing the expression of ΔFosB in emotion-regulating brain regions including LC, LPB and PVN.

Key words: depression, ΔFosB, minocycline, microglia