# NF-kappaB and Mitochondrial Signals as Positive and Negative Regulators of Inflammation

> **NIH NIH R37** · UNIVERSITY OF CALIFORNIA, SAN DIEGO · 2020 · $590,745

## Abstract

PROJECT SUMMARY
 This renewal application of our long-term effort to understand how IKK-dependent NF-κB signaling
controls inflammation and immunity is focused on positive and negative regulation of the NLRP3 inflammasome
by NF-κB and mitochondrial (mt) metabolism. Our effort will be placed on complete elucidation of a novel
signaling mechanism, identified in our laboratory, through which engagement of Toll-like receptors (TLR) renders
macrophages (M) responsive to stress, damage signals and microparticles that trigger NLRP3 inflammasome
activation and induce IL-1β and IL-18 production. Persistent NLRP3 inflammasome activation is involved in
several neurodegenerative, metabolic and inflammatory diseases, e.g. Alzheimer’s disease, type II diabetes and
osteoarthritis (OA), but its poor understanding has prevented development of novel NLRP3-specific anti-
inflammatory drugs. Furthermore, previous attempts to alleviate inflammation by targeting IKK-dependent NF-
κB signaling have failed due to enhanced NLRP3 inflammasome activation. By studying how NF-κB negatively
regulates the NLRP3 inflammasome, we identified a critical role for mitochondria in control of inflammasome
activity. Whereas, NF-κB- and p62-dependent mitophagy terminates NLRP3 inflammasome activation in
stimulated M, TLR4 or TLR3 engagement triggers mtDNA replication via a novel, pathway based on activation
of IRF-1 and induction of the nucleotide kinase CMPK2. This pathway is essential for production of oxidized (Ox)
mtDNA in TLR-activated M that were exposed to diverse NLRP3 inflammasome activators, e.g. ATP, nigericin,
alum and DOTAP liposomes. Our results suggest that Ox-mtDNA is the ultimate NLRP3 ligand responsible for
inflammasome assembly and activation. We will continue to study this pathway and investigate the suitability of
its targeting for treatment of currently incurable inflammatory diseases, such as OA. Accordingly, we will
determine whether CMPK2 knockout and knockin mice exhibit defective NLRP3 inflammasome activation and
are therefore resistant to hydroxyapatite-induced joint inflammation. We will also determine how CMPK2-
dependent mtDNA replication supports Ox-mtDNA production and examine whether the latter binds NLRP3
directly, map the binding site and conduct biochemical and structural studies to determine how Ox-mtDNA
binding induces the association of NLRP3 with the inflammasome scaffold protein ASC. We will investigate how
other mt signals and metabolites, reactive oxygen species (ROS) and itaconic acid (IA), modulate synthesis of
pro-IL-1β, pro-IL-18 and other cytokines. These studies will focus on the role of the oxidant-responsive
transcription factor NRF2 in cytokine gene expression and will also explore how mtROS and IA affect NF-κB
activity and its crosstalk with NRF2. These studies will expand our basic understanding of the fundamental
mechanisms that control inflammation and will lay the foundation for developing novel anti-inflammatory drugs
that in...

## Key facts

- **NIH application ID:** 9976418
- **Project number:** 5R37AI043477-23
- **Recipient organization:** UNIVERSITY OF CALIFORNIA, SAN DIEGO
- **Principal Investigator:** Michael Karin
- **Activity code:** R37 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $590,745
- **Award type:** 5
- **Project period:** 1998-07-01 → 2023-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9976418

## Citation

> US National Institutes of Health, RePORTER application 9976418, NF-kappaB and Mitochondrial Signals as Positive and Negative Regulators of Inflammation (5R37AI043477-23). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9976418. Licensed CC0.

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