E-cig vapor condensate alters proteome and lipid profiles of membrane rafts: impact on inflammatory responses in a549 cells.

Introduction:
This article investigates the molecular mechanisms associated with tobacco-flavored electronic cigarette (e-cig) vapor condensate (TF-ECVC) induced inflammation in human alveolar lung epithelial cells (a549). The study focuses on the effect of TF-ECVC on cell viability, inflammatory signaling pathways, and the expression of membrane-bound/cytosolic pattern recognition receptors (PRRs), lipid raft proteins, and transcription factors.

Key Points:

* The study used tobacco-flavored e-cig vapor condensate (TF-ECVC) with and without nicotine and exposed a549 cells to different concentrations of TF-ECVC for 24 and 48 hours.
* The results showed that high concentration TF-ECVC treatment induces cytotoxicity in a549 cells and treatment with TF-ECVC (w/wo nicotine) elicits the production of inflammatory cytokines/chemokines at both the mRNa and protein levels.
* The study also found that TF-ECVC (w/wo nicotine) promotes the expression of pattern recognition receptors (TLR-4 and NOD-1) and lipid raft-associated protein caveolin-1 in a549 cells.
* The researchers performed proximity ligation assay (PLa) and found proximity between caveolin-1 and NOD-1 in TF-ECVC-challenged a549 cells, indicating that NOD-1 localizes to caveolae following TF-ECVC challenge.
* Proteomic analysis of purified lipid raft fractions from TF-ECVC-challenged a549 cells revealed that the protein profile in the lipid rafts was distinct in TF-ECVC±Nic-exposed cells, and 8 out of 1680 proteins were found to be differentially localized in the lipid raft fractions isolated from a549 cells exposed to TF-ECVC condensates (w/o nicotine) compared to the fractions isolated from air-exposed controls.
* Lipidomic profiling of isolated rafts revealed a significant increase in the levels of cholesterol, cardiolipin, and phosphatidylglycerol in TF-ECVC (±Nic)-challenged a549 cells, and the presence of nicotine in TF-ECVC resulted in a pronounced accumulation of various classes of lipids in the raft entities of a549 cells.
* The study found that caveolin-1 knockdown reverses TF-ECVC (w/wo nicotine)-induced inflammation in a549 cells, indicating that caveolae play a crucial role in modulating downstream inflammation in TF-ECVC-challenged lung epithelial cells.

Main Message:
The study provides important insights into the molecular mechanisms associated with TF-ECVC-induced inflammation in a549 cells. The results suggest that TF-ECVC (w/wo nicotine) elicits inflammatory responses through lipid raft entities, and caveolin-1 plays a crucial role in modulating downstream inflammation in TF-ECVC-challenged lung epithelial cells. The study highlights the need for further studies to identify biomarkers/intervention targets to mitigate short- and long-term health effects of vaping.

Singh DP, Begum R, Kaur G, et al. E-cig vapor condensate alters proteome and lipid profiles of membrane rafts: impact on inflammatory responses in a549 cells. Cell biology and toxicology. 2021;37(5):773-793. doi:10.1007/s10565-020-09573-x