Variable Effects of Irritants (Methylmethacrylate, Terphenyls, Dithranol and Methylglyoxal-bis-Guanylhydrazone) on the Fine Structure of the Epidermis
The mechanism of delayed type hypersensitivity is identical for different allergens, but the targets of toxic substances vary. The effect of toxic substances on the fine structure of the skin is poorly understood. In this study the effects of methylmethacrylate (MMA), terphenyls, dithranol, and methylglyoxal-bis (guanylhydrazone) (MGBG) on rodent and human skin was compared. Conventional electron microscopy was performed.
MMA and terphenyls caused spongiosis of the epidermis without specific effects.
Dithranol (DIT) occlusion for 24 h caused the appearance of moderate to massive amounts of lipid droplets in basal keratinocytes and keratinocytes at the stratum granulosum/stratum corneum interface. Langerhans’ cells (LCs) displayed odd circular and branched Birbeck granules. DIT occlusion for 3 h showed that mitochondria of LCs are more susceptible than mitochondria of keratinocytes.
MGBG is an antiproliferative agent and a competitive inhibitor of an enzyme involved in polyamine biosynthesis (AMDC). MGBG treatment resulted in remarkable swelling of mitochondria of basal keratinocytes. The outer and inner mitochondrial membranes were distended and the christae were distorted. The mitochondria of the LCs were unaffected, suggesting that MGBG is especially taken up by proliferative cells.
The present study showed the fine structural dissimilarity caused by different topical substances on the skin: DIT had a specific effect on the mitochondria of the LCs and MGBG on the keratinocytes, while MMA and terphenyls had a classical irritant action on the epidermal cells. More basic science in the field is needed.