DPP8/DPP9 inhibition elicits canonical Nlrp1b inflammasome hallmarks in murine macrophages.

Nathalia M De Vasconcelos,Ruth Geiss-Friedlander,Amanda Gonçalves,Koen Augustyns,Nina Van Opdenbosch,Anne-Marie Lambeir,Anvesh Jallapally,Rosa Martín-Pérez,Ingrid De Meester,Pieter Van Der Veken,Gwendolyn Vliegen,Emilie De Hert,Mohamed Lamkanfi

doi:10.26508/lsa.201900313

Nathalia M De Vasconcelos, Ruth Geiss-Friedlander + Show 11 more

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https://doi.org/10.26508/lsa.201900313

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Abstract

Activating germline mutations in the human inflammasome sensor NLRP1 causes palmoplantar dyskeratosis and susceptibility to Mendelian autoinflammatory diseases. Recent studies have shown that the cytosolic serine dipeptidyl peptidases DPP8 and DPP9 suppress inflammasome activation upstream of NLRP1 and CARD8 in human keratinocytes and peripheral blood mononuclear cells. Moreover, pharmacological inhibition of DPP8/DPP9 protease activity was shown to induce pyroptosis in murine C57BL/6 macrophages without eliciting other inflammasome hallmark responses. Here, we show that DPP8/DPP9 inhibition in macrophages that express a Bacillus anthracis lethal toxin (LeTx)-sensitive Nlrp1b allele triggered significantly accelerated pyroptosis concomitant with caspase-1 maturation, ASC speck assembly, and secretion of mature IL-1β and IL-18. Genetic ablation of ASC prevented DPP8/DPP9 inhibition-induced caspase-1 maturation and partially hampered pyroptosis and inflammasome-dependent cytokine release, whereas deletion of caspase-1 or gasdermin D triggered apoptosis in the absence of IL-1β and IL-18 secretion. In conclusion, blockade of DPP8/DPP9 protease activity triggers rapid pyroptosis and canonical inflammasome hallmarks in primary macrophages that express a LeTx-responsive Nlrp1b allele.

Highlights

Inflammasomes play critical roles in the host response against pathogenic invasion and in inflammatory responses elicited by a diversity of host-derived and environmental stressors (Lamkanfi & Dixit, 2012, 2014)
Our results demonstrate that DPP8/DPP9 inhibition significantly sensitizes macrophages that express a lethal toxin (LeTx)-responsive Nlrp1b allele to rapid pyroptosis induction concomitant with caspase-1 maturation, ASC speck assembly, and secretion of mature IL-1β and IL-18
To examine whether a LeTxresponsive Nlrp1b allele impacts cell death induction by the pan-dipeptidyl peptidases (DPP) inhibitor VBP (Fig S1A), we monitored the induction of pyroptotic cell lysis over time in B6 and B6Nlrp1b+ BMDMs in function of the number of nuclei stained with the membrane-impermeant DNA-intercalating dye Sytox Green (SG)

Summary

Introduction

Inflammasomes play critical roles in the host response against pathogenic invasion and in inflammatory responses elicited by a diversity of host-derived and environmental stressors (Lamkanfi & Dixit, 2012, 2014). Canonical inflammasomes are assembled when the germline-encoded intracellular pattern recognition receptors nucleotide-binding oligomerization domain, leucine rich repeat and pyrin domain containing (NLRP), NLRP3, NLRC4, absent in melanoma (AIM2), and Pyrin detect so-called pathogen-associated molecular patterns and damage-associated molecular patterns. These cytosolic multi-protein platforms promote proximity-induced autoactivation of the cysteine protease caspase-1, which in turn cleaves the cytosolic precursor forms of interleukin (IL)-1β and IL-18 into mature inflammatory cytokines. The latter inflammatory caspases elicit pyroptosis autonomously, while engaging the NLRP3 inflammasome downstream of GSDMD for caspase-1–mediated secretion of IL-1β and IL-18 (Kayagaki et al, 2011)

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