Location
Philadelphia, PA
Start Date
17-4-2026 1:30 PM
End Date
17-4-2026 2:30 PM
Description
Introduction:
Coxiella burnetii is an obligate intracellular bacterium that infects alveolar macrophages and causes Q fever. The bacterium survives within a specialized intracellular compartment known as the Coxiella-containing vacuole (CCV). The bacterium manipulates host lipid metabolism using its type 4 secretion system (T4SS) to support intracellular survival and replication. Our laboratory has shown that Coxiella infection promotes lipid droplet (LD) breakdown, releasing precursors for immunosuppressive lipid mediators such as prostaglandin E2 (PGE2). However, the host transcriptional mechanisms regulating LD metabolism during infection remain unclear. Peroxisome proliferator-activated receptors (PPARs) are nuclear transcription factors that regulate lipid metabolism and immune responses in macrophages. In particular, PPARα plays an important role in lipid utilization and LD dynamics.
Objective:
Our objective was to determine whether modulation of PPARα signaling alters the expression of lipid metabolism and inflammatory genes in Coxiella-infected alveolar macrophages.
Methods:
Mouse alveolar macrophages were infected with wild-type Coxiella and a type IV secretion system mutant (dotA) Coxiella strain. Infected and uninfected (UI) cells were treated with either a PPARα agonist or antagonist to investigate the role of PPARα signaling during infection. Total RNA was isolated from macrophages and reverse-transcribed into cDNA. Quantitative real-time PCR (qRT-PCR) was performed to measure expression of plin2, a protein associated with cytoplasmic lipid droplet formation, stability, and intracellular lipid storage, and ptgs2, a gene encoding cyclooxygenase-2 (COX-2), an enzyme involved in prostaglandin synthesis. GAPDH served as the endogenous control, and relative gene expression was calculated using the ΔΔCt method. Experiments were conducted with technical replicates (triplicates) for each condition, and amplification was performed on a StepOnePlus real-time PCR system.
Results:
Our preliminary data indicates changes to plin2 and ptgs2 gene expression in PPARα agonist and antagonist-treated Coxiella-infected cells compared to the uninfected cells. We are currently analyzing the data to identify PPARα activity-mediated differential regulation of macrophage lipid droplet-associated genes and inflammatory pathways during Coxiella infection.
Conclusion:
Our preliminary findings demonstrate that PPARα signaling influences ptgs2 and plin2 transcription in Coxiella-infected macrophages. Increased PLIN2 expression following PPARα modulation would suggest increased lipid droplet formation whereas analyzing changes to ptgs2 would allow us to identify PPARα-mediated changes to the inflammatory environment in Coxiella-infected cells. Together, these results will support the role for PPARα in the metabolic reprogramming of macrophages during Coxiella infection to support bacterial intracellular growth.
Embargo Period
6-2-2028
Role of PPARα in Altering Macrophage Lipid Droplet Breakdown and PGE2 Production During Coxiella Infection
Philadelphia, PA
Introduction:
Coxiella burnetii is an obligate intracellular bacterium that infects alveolar macrophages and causes Q fever. The bacterium survives within a specialized intracellular compartment known as the Coxiella-containing vacuole (CCV). The bacterium manipulates host lipid metabolism using its type 4 secretion system (T4SS) to support intracellular survival and replication. Our laboratory has shown that Coxiella infection promotes lipid droplet (LD) breakdown, releasing precursors for immunosuppressive lipid mediators such as prostaglandin E2 (PGE2). However, the host transcriptional mechanisms regulating LD metabolism during infection remain unclear. Peroxisome proliferator-activated receptors (PPARs) are nuclear transcription factors that regulate lipid metabolism and immune responses in macrophages. In particular, PPARα plays an important role in lipid utilization and LD dynamics.
Objective:
Our objective was to determine whether modulation of PPARα signaling alters the expression of lipid metabolism and inflammatory genes in Coxiella-infected alveolar macrophages.
Methods:
Mouse alveolar macrophages were infected with wild-type Coxiella and a type IV secretion system mutant (dotA) Coxiella strain. Infected and uninfected (UI) cells were treated with either a PPARα agonist or antagonist to investigate the role of PPARα signaling during infection. Total RNA was isolated from macrophages and reverse-transcribed into cDNA. Quantitative real-time PCR (qRT-PCR) was performed to measure expression of plin2, a protein associated with cytoplasmic lipid droplet formation, stability, and intracellular lipid storage, and ptgs2, a gene encoding cyclooxygenase-2 (COX-2), an enzyme involved in prostaglandin synthesis. GAPDH served as the endogenous control, and relative gene expression was calculated using the ΔΔCt method. Experiments were conducted with technical replicates (triplicates) for each condition, and amplification was performed on a StepOnePlus real-time PCR system.
Results:
Our preliminary data indicates changes to plin2 and ptgs2 gene expression in PPARα agonist and antagonist-treated Coxiella-infected cells compared to the uninfected cells. We are currently analyzing the data to identify PPARα activity-mediated differential regulation of macrophage lipid droplet-associated genes and inflammatory pathways during Coxiella infection.
Conclusion:
Our preliminary findings demonstrate that PPARα signaling influences ptgs2 and plin2 transcription in Coxiella-infected macrophages. Increased PLIN2 expression following PPARα modulation would suggest increased lipid droplet formation whereas analyzing changes to ptgs2 would allow us to identify PPARα-mediated changes to the inflammatory environment in Coxiella-infected cells. Together, these results will support the role for PPARα in the metabolic reprogramming of macrophages during Coxiella infection to support bacterial intracellular growth.