Patchouli alcohol inhibits the NLRP3 inflammasome in microglia to
enhance neurogenesis in male mice exposed to chronic mild stress
Abstract
Abstract Background and Purpose: Microglia-mediated neuroinflammation
contributes to major depressive disorder (MDD). Targeting microglia is a
promising strategy for treating MDD. Patchouli alcohol (PA), a active
component of Pogostemon cablin, has anti-inflammatory and
neuroprotective effects. Here, we investigate the microglia-mediated
neurogenesis pathway in which PA ameliorates depressive-like behaviors
in stress-induced animal model of depression. Experimental Approach:
C57BL/6 male mice were exposed to chronic mild stress (CMS) for 4 weeks,
then administered PA intraperitoneally at 10, 20 or 40 mg/kg once per
day for 3 weeks. The antidepressant effects of PA were evaluated in the
sucrose preference test, forced swimming test, and tail suspension test.
Microglial phenotypes and activation of the NLRP3 inflammation were
analyzed using RT-PCR, western blotting and immunofluorescence staining.
Effects of PA on neurogenesis were analyzed in vitro and in vivo using
immunofluorescence staining. Key Results: Behavioral assessments showed
that PA alleviated depressive-like behaviors in CMS-exposed mice. CMS
induced microglial activation and pro-inflammatory profiles, which were
blocked by PA treatment. PA attenuated the activation of NLRP3
inflammasome, leading to decreases in the levels of caspase-1, ASC,
IL-1β, and IL-18 in the hippocampus of CMS-exposed mice. In primary
microglia cultures, PA inhibited LPS-induced NLRP3 inflammasome
activation. PA rescued inflammation-inhibited neurogenesis in vivo and
in vitro. Conclusion and implications: Our results suggest that PA
inhibits the NLRP3 inflammasome and promotes microglia-mediated
neurogenesis, leading to antidepressant effects. Thus, PA may be a novel
treatment for inflammation-driven mental disorders.