Background: Naloxone, an opioid receptor antagonist, possesses potent anti-inflammation effects. We previously confirmed the effects of naloxone on inhibiting upregulation of inflammatory cytokine interleukin-1β (IL-1β). Production of mature form IL-1β is mediated by the nod-like receptor protein 3 (NLRP3) inflammasome, a multiprotein complex composed of NLRP3, and the adaptor protein apoptosis-associated speck-like protein contains a caspase recruitment domain (ASC). We elucidated whether naloxone could inhibit the activation of NLRP3 inflammasome.
Material and methods: To induce IL-1β production and NLRP3 inflammasome activation, the human monocytic leukemia cell line THP-1 cells were first primed with lipopolysaccharide (LPS, 1 μg/mL) and then activated with adenosine triphosphate (ATP, 1 mM). For NLRP3 transcription, THP-1 cells were only treated with LPS priming.
Results: Enzyme-link immunosorbent assay data revealed that the concentration of IL-1β in THP-1 cells treated with LPS plus ATP was significantly higher than that in THP-1 cells treated with LPS plus ATP plus naloxone (0.1 μM) (P < 0.001). Real-time quantitative reverse transcription and polymerase chain reaction data also revealed that NLRP3 mRNA concentration in THP-1 cells treated with LPS was significantly higher than that in THP-1 cells treated with LPS plus naloxone (P = 0.001). ASC speck formation, that is, ASC assembles into a large protein complex, is an indicator for NLRP3 inflammasome activation. Our data revealed that the percentage of cells containing ASC specks in THP-1 cells treated with LPS plus ATP was also significantly higher than that in THP-1 cells treated with LPS plus ATP plus naloxone (P < 0.001).
Conclusions: Naloxone inhibits NLRP3 inflammasome activation.
Keywords: ASC; IL-1β; Inflammasome; NLRP3; Naloxone; THP-1 cell.
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