Interfacial Approach to Polyaromatic Hydrocarbon Toxicity: Phosphoglyceride and Cholesterol Monolayer Response to Phenantrene, Anthracene, Pyrene, Chrysene, and Benzo[a]pyrene

Interactions of phenantrene, anthracene, pyrene, chrysene and benzo[a]pyrene (polyaromatic hydrocarbons) with model phospholipid membranes were probed using the Langmuir technique. The lipid monolayers were prepared using 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 1,2-dipalmitoylsn-glycero-3-ethanolamine, 1,2-dipalmitoyl-sn-glycero-3-glycerol, 1,2-dipalmitoyl-sn-glycero-3-serine, 1,2-myristoyl-sn-glycero-3-phosphoethanolamine, 1,2-dilauroyl-sn-glycero-3-phosphocholine and cholesterol. Surface pressure and electrical surface potential were measured on mixed phospholipid/PAHs monolayers spread on a pure water subphase. The morphology of the mixed monolayers was followed with Brewster angle microscopy. Polarization-modulation infrared reflectionabsorption spectroscopy spectra obtained on DPPE/benzo[a]pyrene showed that the latter interacts with the carbonyl groups of the phospholipid. On the other hand, the activity of phospholipase A2 towards DLPC used as a probe to locate benzo[a]pyrene in the monolayers indicate that the polyaromatic hydrocarbons are not accessible to the enzyme. The results obtained show that all PAHs studied affect the properties of the pure lipid, albeit in different way. The most notable effects, namely film fluidization and morpholy changes, were observed with benzo[a]pyrene. In contrast, the complexity of mixed lipid monolayers makes the effect of PAHs difficult to detect. It can be assumed that the differences observed between PAHs in monolayers correlate with their toxicity.