It is perhaps not surprising that PG species with VPS34-IN1 different acyl groups have different signaling functions since in the lung saturated PG cannot block the anti-inflammatory effects of surfactant protein A on lipopolysaccharide -treated macrophages while unsaturated PG can. Nevertheless, to our knowledge, ours represents the first report of opposite effects of two species within the same phospholipid class on a particular cellular response. Our previous studies suggested that PG liposomes might be an ideal treatment to normalize skin function under both pathological and physiological conditions. The discovery reported here suggests that specific PG species might be used under different conditions. The efficacy of linoleic acid-containing PGs is intriguing considering the fact that this fatty acid is the predominant species in the epidermis. Thus, Marcello and colleagues found that linoleic acid represents over 20% of the fatty acid species in the epidermis. Interestingly, linoleic acid percentage was higher in the suprabasal layers of the epidermis in comparison with the basal layer. In addition, polyunsaturated fatty acids compose 37% of the fatty acids of suprabasal epidermis. This result suggests the possibility that PGs containing polyunsaturated fatty acids are ONO-4059 hydrochloride physiologically relevant in terms of regulating keratinocyte proliferation. Furthermore, it would suggest that PG formed from the action of PLD2 on phosphatidylcholine in the presence of glycerol may contain a high proportion of polyunsaturated fatty acids. For each PG species we tested, we also tested at the same time within the same cell preparation the effects of egg PG as a comparator. By performing an egg PG dose response in all experiments, a later assessment among experiments could be accomplished. As demonstrated previously, we observed both inhibitory and stimulatory effects of this phospholipid on keratinocyte proliferation. Egg PG exhibited an inhibitory effect on proliferation in rapidly proliferating cells, while in slowly proliferating keratinocytes, egg PG showed stimulatory effects on cell proliferation.