Nutr Res Pract.  2020 Dec;14(6):593-605. 10.4162/nrp.2020.14.6.593.

Paeoniflorin ameliorates Aβ-stimulated neuroinflammation via regulation of NF-κB signaling pathway and Aβ degradation in C6 glial cells

• Cho EJ
• Kim HY
• Lee AY

• KMID: 2508793
• DOI: http://doi.org/10.4162/nrp.2020.14.6.593

Abstract

BACKGROUND/OBJECTIVES
Alzheimer's disease is common age-related neurodegenerative condition characterized by amyloid beta (Aβ) accumulation that leads cognitive impairment. In the present study, we investigated the protective effect of paeoniflorin (PF) against Aβ-induced neuroinflammation and the underlying mechanism in C6 glial cells.
MATERIALS/METHODS
C6 glial cells were treated with PF and Aβ_25–35, and cell viability, nitric oxide (NO) production, and pro-inflammatory cytokine release were measured. Furthermore, the mechanism underlying the effect of PF on inflammatory responses and Aβ degradation was determined by Western blot.
RESULTS
Aβ_25–35 significantly reduced cell viability, but this reduction was prevented by the pretreatment with PF. In addition, PF significantly inhibited Aβ_25–35 -induced NO production in C6 glial cells. The secretion of interleukin (IL)-6, IL-1β, and tumor necrosis factor-alpha was also significantly reduced by PF. Further mechanistic studies indicated that PF suppressed the production of these pro-inflammatory cytokines by regulating the nuclear factor-kappa B (NF-κB) pathway. The protein levels of inducible NO synthase and cyclooxygenase-2 were downregulated and phosphorylation of NF-κB was blocked by PF. However, PF elevated the protein expression of inhibitor kappa B-alpha and those of Aβ degrading enzymes, insulin degrading enzyme and neprilysin.
CONCLUSIONS
These findings indicate that PF exerts protective effects against Aβ-mediated neuroinflammation by inhibiting NF-κB signaling, and these effects were associated with the enhanced activity of Aβ degradation enzymes.

Keyword

Paeonia; neurodegenerative diseases; amyloid; NF-kappaB; glial cells

Figure

• 

  Fig. 1 Effect of PF on the viability in Aβ25–35-treated C6 glial cells. ‘Control’ represents non-treated cells, ‘Aβ’ represents Aβ25–35-treated cells, ‘PF1’, ‘PF5’, or ‘PF10’ represent the 3 concentrations of PF treatment (1, 5, and 10 μg/mL, respectively) in Aβ25–35-treated cells. Values are mean ± SD.Aβ, amyloid beta; PF, paeoniflorin.a-cMeans with different letters are significantly different (P < 0.05) as determined by Duncan's multiple range test.

• 

  Fig. 2 Effect of PF on NO production in Aβ25–35-treated C6 glial cells. ‘Control’ represents non-treated cells, ‘Aβ’ represents Aβ25–35-treated cells, ‘PF1’, ‘PF5’, or ‘PF10’ represent the 3 concentrations of paeoniflorin treatment (1, 5, and 10 μg/mL, respectively) in Aβ25–35-treated cells. Values are mean ± SD.NO, nitric oxide; Aβ, amyloid beta; PF, paeoniflorin.a-cMeans with different letters are significantly different (P < 0.05) as determined by Duncan's multiple range test.

• 

  Fig. 3 Effect of PF on the production of IL-6 (A), IL-1β (B), and TNF-α (C) in Aβ25–35-treated C6 glial cells. ‘Control’ represents non-treated cells, ‘Aβ’ represents Aβ25–35-treated cells, ‘PF1’, ‘PF5’, or ‘PF10’ represent the 3 concentrations of paeoniflorin treatment (1, 5, and 10 μg/mL, respectively) in Aβ25–35-treated cells. Values are mean ± SD.IL, interleukin; Aβ, amyloid beta; PF, paeoniflorin; TNF-α, tumor necrosis factor-alpha.a-cMeans with different letters are significantly different (P < 0.05) as determined by Duncan's multiple range test.

• 

  Fig. 4 Effect of PF on the protein expression of iNOS, COX-2, pNF-κB, and IκB-α in Aβ25–35-treated C6 glial cells. ‘Control’ represents non-treated cells, ‘Aβ’ represents Aβ25–35-treated cells, ‘PF1’, ‘PF5’, or ‘PF10’ represent the 3 concentrations of paeoniflorin treatment (1, 5, and 10 μg/mL, respectively) in Aβ25–35-treated cells. Values are mean ± SD.iNOS, inducible NO synthase; Aβ, amyloid beta; PF, paeoniflorin; COX-2, cyclooxygenase-2; pNF-κB, phospho nuclear factor-kappa B; IκB-α, inhibitor kappa B-alpha.a-dMeans with different letters are significantly different (P < 0.05) as determined by Duncan's multiple range test.

• 

  Fig. 5 Effect of PF on the protein expression of IDE and NEP in Aβ25–35-treated C6 glial cells. ‘Control’ represents non-treated cells, ‘Aβ’ represents Aβ25–35-treated cells, ‘PF1’, ‘PF5’, or ‘PF10’ represent the 3 concentrations of paeoniflorin treatment (1, 5, and 10 μg/mL, respectively) in Aβ25–35-treated cells. Values are mean ± SD.IDE, insulin degrading enzyme; Aβ, amyloid beta; PF, paeoniflorin; NEP, neprilysin.a-cMeans with different letters are significantly different (P < 0.05) as determined by Duncan's multiple range test.

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