# Brain-Derived Neurotrophic Factor Deficiency Exacerbates Innate Immune Responses by Enhancing NLRP3 Inflammasome Activation and GSDMD-Mediated Pyroptosis in Mice

## TL;DR

This study shows that low levels of BDNF in mice worsen inflammation by boosting NLRP3 inflammasome activity and cell death, suggesting BDNF could be a treatment target for inflammatory diseases.

## Contribution

The study reveals BDNF as a novel endogenous regulator of NLRP3 inflammasome activation and GSDMD-mediated pyroptosis through NF-κB inhibition and autophagy/membrane repair.

## Key findings

- BDNF deficiency in mice increases IL-1β and IL-18 levels after LPS/nigericin stimulation.
- BDNF deficiency enhances NLRP3 inflammasome activation and GSDMD-mediated pyroptosis.
- BDNF deficiency impairs autophagy and ESCRT-III-dependent membrane repair.

## Abstract

Background and Objectives: The NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome is a key innate immune complex, and its aberrant activation contributes to metabolic and neurodegenerative diseases. Brain-derived neurotrophic factor (BDNF) is a neurotrophin with anti-inflammatory and metabolic regulatory functions, but its role in NLRP3 inflammasome activation and gasdermin D (GSDMD)-mediated pyroptosis remains unclear. The aim of this study was to investigate the effects of BDNF deficiency on LPS- and nigericin-induced NLRP3 inflammasome activation and GSDMD-mediated pyroptosis in vivo, and to elucidate the involvement of NF-κB signaling, autophagy, and ESCRT-III-dependent plasma membrane repair in this process. Materials and Methods: In this in vivo study, male Bdnf +/+ and Bdnf +/− mice were subjected to lipopolysaccharide (LPS) plus nigericin-induced NLRP3 inflammasome activation. Serum and hippocampus, cortex, liver, epididymal adipose, and muscle tissues were collected 24 h after stimulation for analysis of inflammasome-related, autophagy-related, and membrane repair-related proteins by Western blotting and of serum BDNF, interleukin-1β (IL-1β), and interleukin-18 (IL-18) by ELISA. Results: Bdnf +/− mice displayed significantly reduced circulating BDNF levels and exhibited exaggerated LPS plus nigericin-induced increases in IL-1β and IL-18 compared with Bdnf +/+ mice. Across all tissues, BDNF deficiency enhanced NF-κB p65, NLRP3, active caspase-1 p20, and GSDMD expression, indicating amplified inflammasome activation and pyroptosis. Conversely, LC3B and SQSTM1/p62 levels were decreased, and VPS4A expression, a key component of the ESCRT-III membrane repair machinery, was suppressed in Bdnf +/− mice, suggesting impaired selective autophagy, autophagosome formation, and plasma membrane repair. Conclusions: Together, these findings indicate that BDNF restrains NLRP3 inflammasome activation and GSDMD-mediated pyroptosis through inhibition of NF-κB signaling and coordinated activation of autophagy and ESCRT-III-dependent membrane repair. BDNF thus emerges as an endogenous negative regulator of inflammasome activity and a potential therapeutic target for conditions characterized by aberrant NLRP3-driven inflammation.