Very-long-chain fatty acids activate lysosomal hydrolases in neonatal human skin tissue

The aim of this study was to examine the in vitro effect of peroxisomal dysfunction on lysosomal enzymes, the autophagic machinery in the cell, in order to understand the mechanisms of pathogenesis of peroxisomal disorders.

Foreskin samples were obtained immediately after circumcision of 1- to 2-day-old infants at the Maternity Hospital, Kuwait. Skin tissues were cleaned, cut into slices of 1-2 mm2 in size and treated with lignoceric acid (1-20 microg/ml), a very-long-chain fatty acid (VLCFA), in the presence or absence of 1-5 mM aminotriazole (ATZ). A battery of lysosomal enzymes were assayed following treatment of dermal tissue with VLCFA or ATZ.

Treatment of skin slices with lignoceric acid significantly increased (p < 0.001) the enzymic activities of acid lipase, acid phosphatase, alpha-glucosidase, alpha-galactosidase, N-acetyl-alpha-D-glucosaminidase (NAGA) and N-acetyl-alpha-D-galactosaminidase (NAGTA). ATZ (1-5 mM), an inhibitor of key peroxi somal enzyme catalase, also markedly increased the enzymic activities of acid phosphatase, alpha-glucosidase (23%) and alpha-galactosidase (18%) without any significant effect on NAGA or NAGTA. Western blot analysis further revealed that both VLCFA and ATZ significantly increased the protein expression of lysosomal enzymes, beta-galactosidase and beta-glucuronidase.

Experimen tal dysfunction of peroxisomes mimicked by elevated VLCFA or ATZ-mediated catalase inhibition significantly increased the activities of lysosomal hydrolases in human dermal tissue, suggesting that activation of the lysosomal system could be one of the factors responsible for cellular damage during pathogenesis of peroxisomal diseases.