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Biochemical Copyright Pharmacology, 0 1996 Elsevier Science Vol. 51, pp. 247-252, Inc. 1996. ELSEVIER ISSN 0006-2952/ 96/ $15.00 SSDI 0006-2952(96)02130-2 + 0.00 Liposomal Incorporation Effect of 1.25Dihydroxyvitamin Phospholipase C Signal Transduction and the Eicosanoid Kirsten Pn$er* and Gustav F. Jitikowski DEPARTMENT OF ANATOMY II, UNIVERSITY OF JENA, GERMANY Changes the D, on the Pathway Cascade on Keratinocytes in Vitro ABSTRACT. ability mediates its action via genomic and nongenomic of phospholipase C and the subsequent vitamin D, in liposomes of varying compositions The influence of empty liposomes (1 mM) and free and liposomally incorporated nM) on the rapid release of sulfidoleucotrien vitro. Free 10 nM 1.25-dihydroxyvitamin followed by a swift decrease in sulfidoleucotrien Empty liposomes and liposomal-incorporated results suggest the occurrence of specific binding sites for 1.25-dihydroxyvitamin are incapable of recognizing 1.25sdihydroxyvitamin MACOL 51;3:247-252, 1996. 1.25-dihydroxyvitamin to regulate the proliferation D, is of clinical and differentiation importance of human keratinocytes. pathways. The nongenomic rapid rise in calcium within the cells. We incorporated in an attempt to improve their effect/ negative (e.g. in the treatment of psoriasis) given its 1.25-Dihydroxyvitamin actions begin with the activation D, 1.25-dihydroxy- side effect ratio. 1.25-dihydroxyvitamin was examined in keratinocytes within 30 seconds, concentration D, did not show such a strong effect. These D, on the membrane level that D, trapped within liposomal D, (10 and inositole D, provoked and inositole I.25dihydroxyvitamin 1,4,5 triphosphate a rapid rise in sulfidoleucotriens 1,4,5_triphosphate in after 10 minutes. membrane. BIOCHEM PHAR- KEY leucotrien; WORDS. 1.25-dihydroxyvitamin keratinocytes D,; liposome, phospholipase C; inositole 1,4,5_triphosphate; sulfido- Liposomes have been widely used as drug carriers [l-3]. Lipo- somal encapsulation allows the improved specificity of drug effect while minimizing negative side effects. In dermatologi- cal applications this means that a drug will remain confined to the skin, 1.25-Dihydroxyvitamin thereby avoiding systemic D, is known effects. to regulate the prolif- eration it is used for the treatment marked by hyperproliferation, network, and inflammation nocytes follow an altered differentiation disturbed barrier functions of the skin. Vitamin D compounds have been proven to exert antipso- riatic effects, as shown by the decrease in the proliferative activity of epidermal keratinocytes, ferentiation program, and anti-inflammatory The mode of action of the steroid hormone vitamin D, can be subdivided into genomic and nongenomic and differentiation of human of psoriasis, a disease of the skin disregulation of the skin. The lesional kerati- pathway, leading to keratinocytes. Therefore, of the cytokine normalization of the dif- capacity [4-61. effects [7]. The * Corresponding author: Kirsten Priifer, Institut fiir Anatomie 11, Friedrich- Schiller Universitgt Jena D-07740 J ena, Teichgraben 7, Germany. Tel. Ger- many 3641 631299; FAX Germany 3641 631249. t Abbreviations: 1.25 D,, 1 alpha,25-dihydroxyvitamin D,; DMEM, Dulbec- co’s modified Eagle’s medium; DMPC, 1,2-dimyristoyl-sn-glycero-3-phospho- choline; eggPC, egg lecithin; DOPC, 1,2-dioleyl-sn-glycero-3-phosphocho- line. Received 1 June 1995; accepted 11 September 1995. former are mediated by a specific nuclear receptor which binds on promoter regions and regulates transcription of genes, thereby influencing proliferation [&lo]. A 1.25-dihydroxyvitamin tion of the VDR, probably by protein kinase C, is necessary for the transcriptional activity of the VDR [l 11. When the inosi- tole 1,4,5-triphosphate signal pathway is activated, calcium is delivered from intracellular depots [12]. In chicken myoblasts, 1.25-dihydroxyvitamin pendent arachidonic acid mobilization caused partially by ac- tivation of phospholipase A, [13]. As shown in our previous paper [14], the incorporation of different vitamin D, analogues in liposomes of various composition liferation-inhibiting effect of the free vitamin D, analogues on human keratinocytes. In some cases this effect was even di- minished. However, in no case was the liposomal incorpora- tion cytotoxic. We were able to provide evidence that the uptake of liposomes by keratinocytes probably by endocytosis. We suggested that the additional activation pase C and phospholipase A, by phospholipids, added as lipo- somes, may cause changes or cumulative effects in pathways responsible for proliferation and differentiation keratinocytes. In the present study we addressed the question whether liposomal incorporation causes changes in signal and metabolic pathways as compared to the free drug. (VDR), and differentiation Ds-dependent phosphoryla- embryo D, induces a calcium-de- did not enhance the pro- occurs within four hours, of phospholi- of human of 1.25-dihydroxyvitamin D,