The NLRP3 inflammasome is a multiprotein complex that plays a pivotal role in regulating the innate immune system and inflammatory signaling. Upon activation by PAMPs and DAMPs, NLRP3 oligomerizes and activates caspase-1 which initiates the processing and release of pro-inflammatory cytokines IL-1β and IL-18. NLRP3 is the most extensively studied inflammasome to date due to its array of activators and aberrant activation in several inflammatory diseases. Studies using small molecules and biologics targeting the NLRP3 inflammasome pathway have shown positive outcomes in treating various disease pathologies by blocking chronic inflammation. In this review, we discuss the recent advances in understanding the NLRP3 mechanism, its role in disease pathology, and provide a broad review of therapeutics discovered to target the NLRP3 pathway and their challenges.
NLRP3 inflammasome has recently emerged as an attractive drug target for neurodegenerative disorders. In our continuing studies, a new chemical scaffold was designed as selective inhibitors of NLRP3 inflammasome. Initial characterization of the lead HL16 demonstrated improved however non-selective inhibition on the NLRP3 inflammasome. Structure-activity relationship studies of HL16 identified a new lead, 17 (YQ128), with an IC 50 of 0.30 ± 0.01 μM. Further studies from in vitro and in vivo models confirmed its selective inhibition on the NLRP3 inflammaome and its brain penetration. Furthermore, pharmacokinetic studies in rats at 20 mg/kg indicated extensive systemic clearance and tissue distribution, leading to a half-life of 6.6 hours. However, the oral bioavailability is estimated to be only 10%, which may reflect limited GI permeability and possibly high first-pass effects. Collectively, these findings strongly encourage development of more potent analogs with improved pharmacokinetic properties from this new chemical scaffold.
Background: Alzheimer’s disease (AD) is a progressive neurodegenerative disorder, and the most common type of dementia. A growing body of evidence has implicated neuroinflammation as an essential player in the etiology of AD. Inflammasomes are intracellular multiprotein complexes and essential components of innate immunity in response to pathogen- and danger-associated molecular patterns. Among the known inflammasomes, the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome plays a critical role in the pathogenesis of AD. Objective: We recently developed a novel class of small molecule inhibitors that selectively target the NLRP3 inflammasome. One of the lead compounds, JC124, has shown therapeutic efficacy in a transgenic animal model of AD. In this study we will test the preventative efficacy of JC124 in another strain of transgenic AD mice. Methods: In this study, 5-month-old female APP/PS1 and matched wild type mice were treated orally with JC124 for 3 months. After completion of treatment, cognitive functions and AD pathologies, as well as protein expression levels of synaptic proteins, were assessed. Results: We found that inhibition of NLRP3 inflammasome with JC124 significantly decreased multiple AD pathologies in APP/PS1 mice, including amyloid-β (Aβ) load, neuroinflammation, and neuronal cell cycle re-entry, accompanied by preserved synaptic plasticity with higher expression of pre- and post-synaptic proteins, increased hippocampal neurogenesis, and improved cognitive functions. Conclusion: Our study demonstrates the importance of the NLRP3 inflammasome in AD pathological development, and pharmacological inhibition of NLRP3 inflammasome with small molecule inhibitors represents a potential therapy for AD.
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