Irisin Attenuates β-Amyloid–Induced Microglial Inflammation via the miR-451a/TLR4/NLRP3 Axis

23 Apr 20264 min read0 viewsJournal Feed

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IntroductionNeuroinflammation, which is driven by microglial activation, contributes to neurodegeneration. The myokine irisin exerts anti-inflammatory effects, potentially through microRNA-mediated regulation of inflammasome components.

However, the underlying molecular mechanisms remain incompletely defined. In this in vitro study we investigated whether irisin attenuates the β-amyloid (Aβ)-induced activation of human microglia via miR-451a-, miR-223-3p-, and miR-7-5p-dependent modulation of NLRP3-related genes.MethodsFor this aim, human immortalized microglia (hTERT) were LPS primed and Aβ1-42, stimulated in the presence or absence of irisin.

The expression of NLRP3, TLR4, caspase-1, IL-1β, IL-18, PYCARD, and selected microRNAs (miR-451a, miR-223-3p, and miR-7-5p) was quantified by digital droplet PCR. TLR4 expression in hTERT cells was analyzed by flow cytometry and intracellular ASC speck formation with NLRP3 colocalization and NF-κB nuclear translocation was measured by imaging flow cytometry.

Cytokine release was measured in the supernatants using ELISA.

Clinical Editorial

Summary

Irisin and microglial inflammasome signaling: mechanistic insights from an in vitro model

Study design and objective

An in vitro examination used human immortalized microglia (hTERT) to assess whether irisin can dampen β-amyloid (Aβ1-42)-induced microglial activation.
The analysis focused on miR-451a, miR-223-3p, and miR-7-5p regulatory control of NLRP3-related genes, with emphasis on TLR4 and inflammasome components.

Experimental approach and measurements

Cells were primed with LPS and stimulated with Aβ1-42, in the presence or absence of irisin.
Expression quantification employed digital droplet PCR for NLRP3, TLR4, caspase-1, IL-1β, IL-18, PYCARD, and selected microRNAs.
TLR4 surface expression was evaluated by flow cytometry; inflammasome assembly was assessed via ASC speck formation, NLRP3 colocalization, and NF-κB nuclear translocation using imaging flow cytometry.
Cytokine release into culture supernatants was measured by ELISA.
Functional disruption used loss-of-function transfections with miR-451a inhibitors or scrambled controls.

Key findings and interpretations

Irisin diminished Aβ1-42–induced microglial activation, evidenced by lower TLR4 expression and reduced NLRP3 inflammasome markers (including ASC speck formation and related gene/protein expression) as well as decreased NF-κB nuclear translocation.
MicroRNA changes accompanying irisin treatment included upregulation of miR-451a and miR-7-5p, with downregulation of miR-223-3p.
Inhibition of miR-451a partially reversed the anti-inflammatory effects of irisin, implicating miR-451a as a contributor to the modulation of the TLR4/NLRP3 axis in this in vitro context.

Context and limitations

The study highlights a potential link between exercise-related factors and microglial inflammatory responses through a miRNA-TLR4/NLRP3 axis, within an Aβ1-42 microglial activation framework.
The authors note that relevance to in vivo conditions and disease contexts remains to be established and requires further investigation.
The report explicitly limits conclusions to the in vitro model used and avoids extrapolation to clinical outcomes.

Gaps and open questions

It remains unclear how the observed miRNA changes translate to in vivo microglial behavior in neurodegenerative settings.
The relative contributions of miR-451a versus miR-7-5p and miR-223-3p require further dissection in more complex systems.