The p38 Mitogen-Activated Protein Kinase Critically Regulates Human Keratinocyte Inflammasome Activation

Fenini, Gabriele; Grossi, Serena; Gehrke, Samuel; Satoh, Takashi; Contassot, Emmanuel; French, Lars E.

doi:10.1016/j.jid.2017.10.037

Cited by 34 publications

(31 citation statements)

References 54 publications

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“…Our data also showed no degradation of IkBa in response to nigericin, indicating that contribution of NF-kB to unprimed inflammasome is not mediated by the activating signal as previously shown for LLME (55). Despite the regulation of p38 activity downstream of TAK1 and the contribution of p38 activity to NLRP3 inflammasome activation (56,57), we observed no effect of p38 inhibition on unprimed NLRP3 inflammasome activation. Our data highlight an important role for TAK1 and basal NF-kB activity in unprimed inflammasome activation.…”

Section: Discussionsupporting

confidence: 79%

Priming Is Dispensable for NLRP3 Inflammasome Activation in Human Monocytes In Vitro

et al. 2020

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Interleukin (IL)-18 and IL-1b are potent pro-inflammatory cytokines that contribute to inflammatory conditions such as rheumatoid arthritis and Alzheimer's disease. They are produced as inactive precursors that are activated by large macromolecular complexes called inflammasomes upon sensing damage or pathogenic signals. NLRP3 inflammasome activation is regarded to require a priming step that causes NLRP3 and IL-1b gene upregulation, and also NLRP3 post-translational licencing. A subsequent activation step leads to the assembly of the complex and the cleavage of pro-IL-18 and pro-IL-1b by caspase-1 into their mature forms, allowing their release. Here we show that human monocytes, but not monocyte derived macrophages, are able to form canonical NLRP3 inflammasomes in the absence of priming. NLRP3 activator nigericin caused the processing and release of constitutively expressed IL-18 in an unprimed setting. This was mediated by the canonical NLRP3 inflammasome that was dependent on K + and Cl − efflux and led to ASC oligomerization, caspase-1 and Gasdermin-D (GSDMD) cleavage. IL-18 release was impaired by the NLRP3 inhibitor MCC950 and by the absence of NLRP3, but also by deficiency of GSDMD, suggesting that pyroptosis is the mechanism of release. This work highlights the readiness of the NLRP3 inflammasome to assemble in the absence of priming in human monocytes and hence contribute to the very early stages of the inflammatory response when IL-1b has not yet been produced. It is important to consider the unprimed setting when researching the mechanisms of NLRP3 activation, as to not overshadow the pathways that occur in the absence of priming stimuli, which might only enhance this response.

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Section: Discussionsupporting

confidence: 79%

Priming Is Dispensable for NLRP3 Inflammasome Activation in Human Monocytes In Vitro

et al. 2020

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“…Most important, in contrast to NLRP3 sgRNA CRISPR/Cas9-targetd HPKs, those with ablated ASC or NLRP1 expression secreted drastically reduced levels of IL-1b upon UVB irradiation and upon treatment with nigericin compared with the corresponding control cells. This shows that NLRP1 rather than NLRP3 is the main inflammasome sensor of HPKs, as also recently suggested (Fenini et al, 2018). The importance of NLRP1 in human skin is also supported by other reports showing a susceptibility to skin inflammation and autoimmunity, such as vitiligo and psoriasis, caused by variations in NLRP1 (Ekman et al, 2014;Jin et al, 2007aJin et al, , 2007bLevandowski et al, 2013).…”

Section: Discussionsupporting

confidence: 86%

“…An siRNA approach suggested that both NLRP1 and NLRP3 contribute to UVBinduced IL-1b secretion in HPKs (Feldmeyer et al, 2007). On the other hand, pharmacological inhibition of the NLRP3 inflammasome had no effect on IL-1b release by HPKs (Fenini et al, 2018). To address this inconsistency, we generated NLRP1 and NLRP3 sgRNA CRISPR/Cas9-targeted HPKs, using two different sgRNAs; ASC sgRNA CRISPR/Cas9-targeted cells served as control.…”

Section: Characterization Of Knockout Hpksmentioning

confidence: 99%

Genome Editing of Human Primary Keratinocytes by CRISPR/Cas9 Reveals an Essential Role of the NLRP1 Inflammasome in UVB Sensing

Fenini

Grossi

Contassot

et al. 2018

Journal of Investigative Dermatology

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By forming a protective barrier, epidermal keratinocytes represent the first line of defense against environmental insults. UVB radiation of the sun is a major challenge for the skin and can induce inflammation, aging, and eventually skin cancer. UVB induces an immune response in human keratinocytes resulting in activation and secretion of the proinflammatory cytokines proIL-1β and -18. This is mediated by an assembly of protein complexes, termed inflammasomes. However, the mechanisms underlying sensing of UVB by keratinocytes, and particularly the types of inflammasomes required for cytokine secretion, are a matter of debate. To address these questions, we established a protocol that allows the generation of CRISPR/Cas9-targeted human primary keratinocytes. Our experiments showed an essential role of the NLRP1 rather than the NLRP3 inflammasome in UVB sensing and subsequent IL-1β and -18 secretion by keratinocytes. Moreover, NLRP1 but not NLRP3 was required for inflammasome activation in response to nigericin, a potassium ionophore and well-established NLRP3 activator in immune cells. Because the CRISPR/Cas9-targeted cells retained their full differentiation capacity, genome editing of human primary keratinocytes might be useful for numerous research and medical applications.

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“…The role of p38 in the priming process has emerged recently. Fenini et al reported that in primary human keratinocytes, two p38 MAPK isoforms, p38α and p38δ, are required for UVB-induced inflammasome activation and IL-1β secretion ( 61 ). In addition, Wang et al showed that CDD-450, an inhibitor that selectively blocks p38α activation of downstream MAPKAPK2 (MK2), suppresses the activation of NLRP3 inflammasome without blockade of NLRP3 expression ( 62 ).…”

Section: Phosphorylation By Mapksmentioning

confidence: 99%

Regulation of NLRP3 Inflammasome by Phosphorylation

2018

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The cytosolic pattern recognition receptor (PRR) NOD-like receptor family, pyrin domain containing 3 (NLRP3) senses a wide range of pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs). Upon activation, NLRP3 triggers the assembly of inflammasome via the self-oligomerization and the recruitment of apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC) and pro-caspase-1, facilitating the robust immune responses including the secretion of proinflammatory cytokines and pyroptosis. The NLRP3 inflammasome must be well orchestrated to prevent the aberrant activations under physiological and pathological conditions, because uncontrolled activation of NLRP3 inflammasome is one of the major causes of a variety of autoimmune diseases and metabolic disorders. Therefore, understanding the molecular mechanisms for controlling NLRP3 inflammasome activation may provide novel strategies for the treatment of NLRP3-related diseases. Although NLRP3 inflammasome can be regulated at the transcriptional level, the post-translational modification (PTM) of NLRP3 as well as other inflammasome components has also been showed to be critical for the regulation of its activation. Several kinases and phosphatases have been shown to control NLRP3 inflammasome activation in response to either exogenous pathogen infections or endogenous molecules, such as bile acids. In this review, we summarize our current knowledge of phosphorylation patterns and their functional role in the regulation of NLRP3 inflammasome, and suggest interesting areas for future research.

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The p38 Mitogen-Activated Protein Kinase Critically Regulates Human Keratinocyte Inflammasome Activation

Cited by 34 publications

References 54 publications

Priming Is Dispensable for NLRP3 Inflammasome Activation in Human Monocytes In Vitro

Priming Is Dispensable for NLRP3 Inflammasome Activation in Human Monocytes In Vitro

Genome Editing of Human Primary Keratinocytes by CRISPR/Cas9 Reveals an Essential Role of the NLRP1 Inflammasome in UVB Sensing

Regulation of NLRP3 Inflammasome by Phosphorylation

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