Mechanism of Acrolein Toxicity
Acrolein is a colorless, acrid-smelling chemical commonly produced by tobacco smoke, cooking grease, and the dehydration of glycerol to form other compounds such as biocides. Exposure to acrolein can cause negative health effects such as nose, skin, and respiratory irritation. Toxic effects due to acrolein can vary depending on the dose and duration of exposure. Acrolein is the simplest beta-unsaturated aldehyde, with an electrophilic-alpha carbon and carbonyl group making it highly reactive. Due to its chemical composition, acrolein is known to interact with nucleophiles and important proteins and enzymes involved with immune response. Previous studies suggested that acrolein interacts with two important proteins, transient receptor potential cation channel (TRPA1) and protein tyrosine phosphatases (PTP1B), involved in signaling lung macrophages. PTP1B binds to the enzyme src kinase, allowing it to activate NF-B, a regulator of inflammation. Modification of PTP1B (a negative regulator of M2 macrophages) due to acrolein, could result in increased M2 macrophage phenotype and produce toxic health effects after exposure. The hypothesis of this study is PTP1B in alveolar macrophages (AM) is a key target of acrolein exposure resulting in inhibited cytokine release in response to LPS. Experiments were carried out in vivo and in vitro to detect levels of PTP1B and src kinase in mouse AM and bone marrow derived macrophages (BMdM). Mice used in vivo were exposed to 4 mg/kg of acrolein, and AMs were lavaged following exposure. BMdM and AM cells used in vitro were cultured and exposed to acrolein one hour before assays were performed. Western blots and BCA assays were used to determine protein concentrations and detect PTP1B and src kinase in exposed cells. AM and BMdM were exposed to LPS, and ELISA assays were run to record the level of cytokines TNF- and IL-6. Results of the in vivo study confirmed that src kinase disappears when exposed to varying doses of acrolein. Western blots showed no decrease in PTP1B or detected acrolein adducts on proteins, suggesting that acrolein may target src kinase specifically. Results of the in vitro study suggest that AM were a more sensitive model over BMdM, assay detection of src kinase and cytokines was more sensitive in AM model. Additional work could be beneficial to understanding exact mechanism of acrolein toxicity involving PTP1B and src kinase in macrophages.
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