Cutaneous Inflammation and Proliferation in vitro: Differential Effects and Mode of Action of Topical Glucocorticoids

Abstract

The nonhalogenated double ester of prednisolone, prednicarbate (PC), is the first topical glucocorticoid with an improved benefit/risk ratio verified clinically and in vitro. To evaluate if this is due to unique characteristics of this steroid, a new compound created according to an identical concept, prednisolone 17-ethylcarbonate, 21-phenylacetate (PEP), and the new halogenated monoester desoximetasone 21-cinnamate (DCE) were tested and compared to PC, desoximetasone (DM) and betamethasone 17-valerate (BMV). Isolated foreskin keratinocytes served for in vitro investigations of anti-inflammatory processes in the epidermis, fibroblasts of the same origin were used to investigate the atrophogenic potential. Inflammation was induced by TNFα, resulting in an increased interleukin 1α (Il-1α) synthesis. As quantified by ELISA, all drugs significantly reduced Il-1α production. But PC and BMV appeared particularly potent, followed by DM and the two new congeners, which revealed minor anti-inflammatory activity. Glucocorticoid esters including PEP are rapidly degraded in keratinocytes (85% within 12 h). Hence, a ribonuclease protection assay of Il-1α mRNA was performed allowing short incubation times and thus minimizing biodegradation. This assay confirmed the anti-inflammatory potency of native PC and BMV. In contrary DCE and PEP did not reduce Il-1α mRNA to a significant extent. Therefore PEP acts as a prodrug only. In fibroblasts, Il-1α and Il-6 syntheses indicate proliferation and inflammation, respectively. Whereas PC and PEP inhibited Il-1α and Il-6 production in fibroblasts only to a minor extent, cytokine synthesis was strongly affected by the conventional glucocorticoids BMV and DM, but also by DCE. The minor unwanted effect of PC and PEP on fibroblasts was also reflected by their low influence on cell proliferation as derived from ³H-thymidine incorporation. Again, more pronounced antiproliferative features were seen with the halogenated glucocorticoids. In the following, the correlation between antiphlogistic effects in keratinocytes (suppression of Il-1α) and antiproliferative effects in fibroblasts (suppression of Il-1α and Il-6; ³H-thymidine incorporation) was analyzed. Here, PC is revealed as the only glucocorticoid with an improved benefit/risk ratio. Native PEP is shown to be almost ineffective and DCE presents exactly the opposite features of PC. It is tempting to speculate if this is due to different glucocorticoid receptor subtypes or different signaling pathways in keratinocytes and fibroblasts.

Different Skin Thinning Potential of Equipotent Medium-Strength Glucocorticoids

“…Prednicarbate and prednisolone 17-ethylcarbonate primarily exert their anti-inflammatory activity by inhibiting the synthesis of IL-1· and IL-6 in keratinocytes [3,7,28]. Due to its high activity, native prednicarbate cannot be regarded as a prodrug anymore [28].…”

Non-animal models of epithelial barriers (skin, intestine and lung) in research, industrial applications and regulatory toxicology

“…Studies describing the effects of long-term use of glucocorticoids in HSEs, which were found to be as suitable models, have been described (Gysler et al, 1999;Lange et al, 2000;Lombardi Borgia et al, 2008). As another example, specific HSEs have been developed to simulate the disease conditions of psoriasis and skin cancer (Tab.…”

Test systems for the determination of glucocorticoid receptor ligand induced skin atrophy

“…Discrepancies observed between in vitro experiments might be due to indirect effects of GCs on fibroblasts by affecting the synthesis or actions of various factors produced by other cell types. Yet, more recent studies show anti-proliferative effects of GCs on primary human fibroblasts 20,26 and HaCaT cells, a human keratinocyte cell line, 20 only. Beside their anti-proliferative effects in cutaneous cells, GCs also affect collagen metabolism.…”