Abstract
The NOD-, LRR-, and pyrin-domain-containing protein 3 (NLRP3) inflammasome is a node of intracellular stress pathways and a druggable target which integrates mitochondrial stress and inflammatory cascades. While a body of evidence suggests the involvement of the NLRP3 inflammasome in numerous diseases, a lack of reliable measurement techniques highlights the need for a robust assay using small quantities of biological samples. We present a literature overview on peripheral activation of the NLRP3 inflammasome in mood disorders, then outline a process to develop and validate a robust assay to measure baseline and activated intracellular levels of “apoptosis-associated speck-like protein containing a CARD” (ASC) as a key component of an inflammatory profile in peripheral blood mononuclear cells (PBMC). A consistent association between high NLRP3 mRNA levels and relevant cytokines was seen in the literature. Using our method to measure ASC, stimulation of PBMC with lipopolysaccharide and nigericin or adenosine triphosphate resulted in microscopic identification of intracellular ASC specks, as well as interleukin 1 (IL-1) beta and caspase-1 p10 in the periphery. This was abolished by dose-dependent pre-treatment with 100 nM MCC950. We also report the use of this technique in a small pilot sample from patients with bipolar disorder and depressive disorders. The results show that levels of intracellular ASC and IL-1 beta are sensitive to change upon activation and maintained over time, which may be used to improve the detection of NLRP3 activation and guide personalized therapeutic strategy in the treatment of patients.
Highlights
Inflammasomes are multiprotein complexes which are activated via infectious microbes and other molecules derived from host proteins [1]
In NLRP3, this occurs through its pyrin domain, which associates with a protein known as apoptosisassociated speck-like protein containing a CARD (ASC) [5]
We identified seven articles investigated NLRP3 inflammasome activation in neuropsychiatric patients suffering from mood disorders, including major depressive disorder (MDD) and bipolar disorder [24,25,26,27,28,29,30]
Summary
Inflammasomes are multiprotein complexes which are activated via infectious microbes and other molecules derived from host proteins [1]. The inflammasomes regulate the activation of caspase-1 and induce inflammation [2]. An example is the nucleotide binding domain (NOD)-, leucine-rich repeat (LRR)-, and pyrin domain (PYD)-containing protein 3 (NLRP3) [3]. There are significant differences in how each individual inflammasome complex assembles after recognition of its specific stimuli [4]. In NLRP3, this occurs through its pyrin domain, which associates with a protein known as apoptosisassociated speck-like protein containing a CARD (ASC) [5]. Procaspase-1 is believed to be activated by dimerization, and through autoproteolytic processing, activates important pro-inflammatory cytokines including interleukin 1 (IL-1) beta and IL-18 [6]
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