NLRP3 gene knockout blocks NF-κB and MAPK signaling pathway in CUMS-induced depression mouse model

Background: Abundant researches indicate that neuroinflammation has important roles in the pathophysiology of depression. Our previous study found that the NLRP3 inflammasome mediated stress-induced depression-like behavior in mice via regulating neuroinflammation. However, it still remains unclear that how the NLRP3 inflammasome influences related inflammatory signaling pathway to contribute to neuroinflammation in depression. Methods: We used wild-type mice and NLRP3 gene knockout mice to explore the role of NLRP3 inflammasome and related inflammatory signaling pathways in chronic unpredictable mild stress (CUMS) induced depression mouse model. Results: Both wild-type and NLRP3 knockout stress group mice gained less weight than control group mice after 4 weeks CUMS exposure. The wild-type mice subjected to 4 weeks CUMS displayed depression-like behaviors, including decreased sucrose preference and increased immobility time in the tail suspension test. The NLRP3 knockout stress group mice didn't demonstrate depression-like behaviors. The levels of interleukin-1 beta protein in serum and hippocampi of CUMS exposed wild-type mice were significantly higher, while the NLRP3 knockout stress group mice didn't show an elevation of interleukin-1 beta levels. Similarly to early researches, we found that CUMS led to promoted NLRP3 expression in hippocampi. In addition, the hippocampi in CUMS exposed wild-type mice had higher p-JNK and p-p38 protein expression, which indicated activation of the mitogen-activated protein kinases (MAPK) pathway. The knockout of NLRP3 gene inhibited CUMS-induced activation of the MAPK pathway. The nuclear factor kappa-light chain -enhancer of activated B cells (NF-kappa B) protein complex was activated in the hippocampi of wild-type mice after CUMS exposure, while knockout of NLRP3 gene hindered its activation. Conclusions: These data further proved that the NLRP3 inflammasome mediated CUMS-induced depression-like behavior. The NLRP3 inflammasome regulated CUMS-induced MAPK pathway and NF-kappa B protein complex activation in depression mouse model. Further researches targeting the NLRP3 inflammasome-signaling pathway might be under a promising future in the prevention and treatment of depression. (C) 2017 Elsevier B.V. All rights reserved.