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Amiprilose hydrochloride has been shown to inhibit the proliferation of a number of hyperproliferative cell types including psoriatic skin cells. In the present study, the effects of amiprilose hydrochloride on human tissue equivalents were examined by incubating a) dermal equivalents, b) skin equivalents in the process of epidermalization, and c) mature skin equivalents, with varying concentrations of the drug. In all three models amiprilose hydrochloride concentrations of 0.1% (wt/vol) and lower were not toxic to fibroblasts and keratinocytes and did not interfere with the differentiation of the skin equivalent and the developing skin equivalent. When tested in dermal equivalents, concentrations of amiprilose hydrochloride between 0.1 and 0.5% resulted in changes in fibroblast morphology with development of large intracellular vacuoles, and concentrations greater than 5% were toxic. In mature skin equivalents, in addition to changes in fibroblast morphology, amiprilose hydrochloride in concentrations of 1 to 10% affected the epidermis. When 0.5% amiprilose hydrochloride was present in the developing skin equivalent during differentiation, the epidermal keratinocytes were also affected. Thus the morphology of basal keratinocytes was modified, the differentiation was incomplete, and the dermal-epidermal attachment was compromised. These studies suggest the possibility of an extracellular mechanism of action of amiprilose hydrochloride and delineate acceptable dosage ranges for the potential drug.

The accumulation of modified proteins in aging is well documented in many aging models. For example, the deamidated isoforms of triosephosphate isomerase accumulate in: (a) old erythrocytes, (b) fibroblasts from old donors, (c) fibroblasts aged in vitro, (d) premature-aging syndromes and (e) old cells in the eye lens. However, a fundamental remaining question is: 'Do such modified proteins interfere with cellular function?' It has been difficult to assess this question at the molecular level using whole-organism models and equally frustrating to evaluate the physiological significance of such changes using classical cellular models. Tissue equivalent systems (TES) provide an opportunity for examining the molecular basis and physiological consequences of modified proteins during aging. TES are composed of differentiating and proliferating heterogeneous cell types with symbiotic cell-cell and cell-matrix interactions. They closely resemble, both morphologically and functionally, the tissues from which they were derived. Aging studies utilizing TES can provide information on modifications of protein structures, isozyme patterns, enzymes of the cellular environmental protection system and metabolic parameters which may regulate protein synthesis and degradation.

Amiprilose hydrochloride, a 3-substituted glucose derivative, was found to inhibit the proliferation of human fibroblasts and keratinocytes originating from psoriatic lesions. Fibroblasts and keratinocytes were obtained from skin biopsies of normal donors, and from the biopsies of active/involved and uninvolved sites of psoriatic donors. The cells were cultured as monolayers or as components of tissue equivalent models. Keratinocytes and fibroblasts originating from biopsies of psoriatically involved areas were shown to proliferate at a significantly higher rate than those derived from uninvolved areas. The antiproliferative effect of amiprilose hydrochloride was not observed with normal keratinocytes or fibroblasts from the skin of healthy donors or from uninvolved areas of psoriatic donors. Amiprilose hydrochloride was not cytotoxic to any of these cells at levels below 0.1%. The combination of the low cytotoxicity and the selective antiproliferative effect indicates that this compound may be a useful antipsoriatic agent. The use of monolayer cultures and tissue equivalent models in this study illustrates the utility of such a progressive strategy in the evaluation of potential topical pharmaceuticals.