title: The amelioration of phagocytic ability in microglial cells by curcumin through the inhibition of EMF-induced pro-inflammatory responses.
abstract: BACKGROUND
  Insufficient clearance by microglial cells, prevalent in several neurological conditions and diseases, is intricately intertwined with MFG-E8 expression and inflammatory responses. Electromagnetic field (EMF) exposure can elicit the pro-inflammatory activation and may also trigger an alteration of the clearance function in microglial cells. Curcumin has important roles in the anti-inflammatory and phagocytic process. Here, we evaluated the ability of curcumin to ameliorate the phagocytic ability of EMF-exposed microglial cells (N9 cells) and documented relative pathways.
  
  
  METHODS
  N9 cells were pretreated with or without recombinant murine MFG-E8 (rmMFG-E8), curcumin and an antibody of toll-like receptor 4 (anti-TLR4), and subsequently treated with EMF or a sham exposure. Their phagocytic ability was evaluated using phosphatidylserine-containing fluorescent bioparticles. The pro-inflammatory activation of microglia was assessed via CD11b immunoreactivity and the production of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β) and nitric oxide (NO) via the enzyme-linked immunosorbent assay or the Griess test. We evaluated the ability of curcumin to ameliorate the phagocytic ability of EMF-exposed N9 cells, including checking the expression of MFG-E8, αvβ3 integrin, TLR4, nuclear factor-κB (NF-κB) and signal transducer and activator of transcription 3 (STAT3) using Western blotting.
  
  
  RESULTS
  EMF exposure dramatically enhanced the expression of CD11b and depressed the phagocytic ability of N9 cells. rmMFG-E8 could clearly ameliorate the phagocytic ability of N9 cells after EMF exposure. We also found that EMF exposure significantly increased the secretion of pro-inflammatory cytokines (TNF-α, IL-6 and IL-1β) and the production of NO; however, these increases were efficiently chilled by the addition of curcumin to the culture medium. This reduction led to the amelioration of the phagocytic ability of EMF-exposed N9 cells. Western blot analysis revealed that curcumin and naloxone restored the expression of MFG-E8 but had no effect on TLR4 and cytosolic STAT3. Moreover, curcumin significantly reduced the expression of NF-κB p65 in nuclei and phospho-STAT3 (p-STAT3) in cytosols and nuclei.
  
  
  CONCLUSIONS
  This study indicates that curcumin ameliorates the depressed MFG-E8 expression and the attenuated phagocytic ability of EMF-exposed N9 cells, which is attributable to the inhibition of the pro-inflammatory response through the NF-κB and STAT3 pathways.
authors.forename: Gen-Lin
authors.initials: GL
authors.lastname: He
authors.forename: Yong
authors.initials: Y
authors.lastname: Liu
authors.forename: Min
authors.initials: M
authors.lastname: Li
authors.forename: Chun-Hai
authors.initials: CH
authors.lastname: Chen
authors.forename: Peng
authors.initials: P
authors.lastname: Gao
authors.forename: Zheng-Ping
authors.initials: ZP
authors.lastname: Yu
authors.affiliation: Key Laboratory of Medical Protection for Electromagnetic Radiation Ministry of Education, Third Military Medical University, 30 Gaotanyan Street, Chongqing 400038, PR China. xuesenyyy@gmail.com.
authors.forename: Xue-Sen
authors.initials: XS
authors.lastname: Yang
mesh_terms: D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D039481:CD11b Antigen / Q000378:metabolism; D002461:Cell Line, Transformed; D003474:Curcumin / Q000494:pharmacology*; D016207:Cytokines / Q000378:metabolism; D004307:Dose-Response Relationship, Radiation; D015536:Down-Regulation / Q000187:drug effects; D004574:Electromagnetic Fields / Q000009:adverse effects*; D005434:Flow Cytometry; D007249:Inflammation / Q000209:etiology*; D051379:Mice; D017628:Microglia / Q000187:drug effects / Q000473:pathology / Q000528:radiation effects; D016328:NF-kappa B / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D010586:Phagocytes / Q000187:drug effects / Q000502:physiology*; D010587:Phagocytosis; D050796:STAT3 Transcription Factor / Q000378:metabolism; D013997:Time Factors
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D039481:CD11b Antigen; D016207:Cytokines; D016328:NF-kappa B; D050796:STAT3 Transcription Factor; D009569:Nitric Oxide; D003474:Curcumin