# Outer membrane vesicles in macrophage inflammation and pyroptosis

> **NIH NIH R03** · UNIVERSITY OF COLORADO DENVER · 2021 · $77,750

## Abstract

PROJECT SUMMARY
Innate immune cells such as macrophages detect pathogens by recognizing pathogen-associated
molecular patterns (PAMPs) such as lipopolysaccharides (LPS, also known as endotoxin) displayed on the
surface of Gram-negative bacteria. Extracellular and endosomal LPS molecules are recognized by Toll-like
receptor 4. Cytosolic LPS, on the other hand, is detected by caspase-11 (in mice) and caspase-4/5
(in humans). Interestingly, it was recently found that outer membrane vesicles (OMVs) released by
extracellular Gram-negative bacteria can deliver LPS and other bacterial molecules to the cytosol of
macrophages. OMVs first enter macrophages through endocytosis, followed by the translocation of
bacterial molecules across the endosome membrane into the cytosol to trigger pyroptosis, an inflammatory
form of cell death. The molecular basis of OMV-triggered pyroptosis remains poorly understood. In
particular, it is unknown how OMVs bind and enter macrophages, and how OMVs crosses the
endosome membrane. The goal of this proposed research is to address these key questions by
genetically dissecting OMV-induced pyroptosis using an unbiased genome-wide CRISPR genetic
screen. In our preliminary studies, we established assays to measure OMV-induced pyroptosis in
macrophages. Moreover, we developed tools to genetically dissect complex mammalian pathways using
genome-wide CRISPR screens. Here, we will take strategic advantage of these systems to dissect OMV-
induced pyroptosis in macrophages using an unbiased genome-wide CRISPR genetic screen. We will
then validate the identified genes in pooled and targeted secondary screens. Finally, we will further
characterize selected genes identified in the screens in primary human macrophages. These studies will
provide a genome-scale view of OMV-induced pyroptosis and will expand our knowledge of inflammatory
responses in pathogen-host interactions. Insights gleaned from this pilot study will facilitate the
development of safer and more effective strategies to treat pathogen infection and inflammatory diseases.
Moreover, we anticipate that these findings will guide the engineering of drug delivery vehicles using OMVs.

## Key facts

- **NIH application ID:** 10129090
- **Project number:** 1R03AI151651-01A1
- **Recipient organization:** UNIVERSITY OF COLORADO DENVER
- **Principal Investigator:** Suzhao Li
- **Activity code:** R03 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $77,750
- **Award type:** 1
- **Project period:** 2021-03-05 → 2023-02-28

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10129090

## Citation

> US National Institutes of Health, RePORTER application 10129090, Outer membrane vesicles in macrophage inflammation and pyroptosis (1R03AI151651-01A1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10129090. Licensed CC0.

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