Hippocampal Caspase-4 non-canonical inflammasome activation is associated with microglia-synapse crosstalk disruption and drives depression-like behaviors.

Authors

Chao Lu, Yanqing Wang, Guoliang Dai, Wenzheng Ju, Yan Sun, Hailou Zhang, Lei Wu

Published in

Brain, behavior, and immunity. Pages 107012. Sep 13, 2026. Epub Sep 13, 2026.

Abstract

The neuroinflammation hypothesis has reshaped our understanding of depression; however, most studies have focused on the canonical NLRP3 inflammasome, leaving the role of the non-canonical inflammasome, particularly Caspase-4, largely unexplored. This study aimed to investigate whether hippocampal non-canonical inflammasome activation drives microglial neuroinflammation and impairs synaptic plasticity to precipitate depression-like behavior.
Male C57BL/6J mice were subjected to chronic unpredictable mild stress (CUMS) for 4 weeks, followed by behavioral testing tail suspension test (TST), forced swimming test (FST), sucrose preference test (SPT), novelty-suppressed feeding test (NSF), and open field test (OFT) and hippocampal transcriptomic profiling. Because the murine genome lacks a Caspase-4 ortholog (its functional counterpart being Caspase-11), human Caspase-4 (hCasp4) was ectopically overexpressed in the mouse hippocampus via adeno-associated virus (AAV9-CMV-hCasp4-eGFP) stereotaxic injection, with AAV9-CMV-eGFP as the control. Reverse-transcription quantitative PCR (RT-qPCR) and western blot were used to detect Caspase-4 expression. Immunofluorescence was performed to detect NLRP3, nuclear factor-κB (NF-κB) p65, guanylate-binding protein 1 (GBP1), ionized calcium-binding adapter molecule 1 (IBA-1), Ca²⁺/calmodulin-dependent protein kinase II (CaMKII), postsynaptic density protein 95 (PSD95), and Synapsin1, with semi-quantitative and co-localization analyses using ImageJ.
CUMS induced depression-like behaviors and significantly upregulated hippocampal Caspase-4 expression, accompanied by with significant enrichment of the NOD-like receptor signaling pathway and activation of the NLRP3 inflammasome enrichment. Ectopic hippocampal expression of human Caspase-4 was sufficient to reduce sucrose preference and increase immobility time in the TST, without affecting locomotor activity. Mechanistically, Caspase-4 activation elevated overexpression was accompanied by elevated GBP1 and increased promoted IBA-1⁺ microglial immunoreactivity activation, enhanced NLRP3 expression and NF-κB p65 nuclear immunoreactivity, and ultimately suppressed hippocampal CaMKII expression while decreasing together with decreased PSD95 and Synapsin1 levels and their spatial co-localization area. These molecular associations are correlative; loss-of-function, rescue, and functional synaptic assays were not performed.
Hippocampal Caspase-4-associated non-canonical inflammasome activation via Caspase-4 serves as a critical upstream driver of depression-like behavior by orchestrating GBP1-dependent microglial inflammation and disrupting CaMKII-dependent synaptic plasticity signaling may contribute to depression-like behavior through a putative pathway involving GBP1-related microglial inflammation and downregulation of CaMKII and synaptic proteins. Because the evidence is partly correlative and the model relies on ectopic expression of human Caspase-4 in mice, these findings should be regarded as hypothesis-generating. Targeting the Caspase-4 non-canonical inflammasome warrants further investigation as a potential, may offer a novel immunotherapeutic strategy for depression.

PMID:
42732838
Bibliographic data and abstract were imported from PubMed on 14 Sep 2026.

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