Lysosomal cathepsins have recently been reported to play crucial roles in the regulation of the mitochondrial death cascade by an unclear mechanism leading to mitochondrial membrane permeabilization. Glycosaminoglycans (GAG) are a family of ionic polysaccharides present at the lysosomal compartment and shown to inhibit lysosomal cathepsin activities. The implication of this family of polysaccharides in the regulation of the pre-mitochondrial death cascade has still not been considered. Here, we demonstrate in a model of skin fibroblasts submitted to oxidative stress that a GAG-mimetic protects the lysosome from membrane disruption, reduces intracellular ROS levels, and inhibits mitochondrial membrane potential collapse, cytochrome c release and caspases-9 and -3 activations without affecting the extrinsic pathway of apoptosis. Heparan sulfate and chondroitin sulfate, but not heparin, showed also protecting effects when assessing key points of the intrinsic pathway of apoptosis. We suggest the existence of molecular links between endogenous GAGs and the regulation of apoptosis.

Heparin affin regulatory peptide (HARP), also named pleiotropin, is a secreted polypeptide that belongs to a new family of heparin-binding growth/differentiation factors. In this study, we investigated the expression and distribution of HARP mRNA and protein in rat uterus. Semi-quantitative reverse transcriptase PCR experiments showed variations in HARP mRNA levels throughout the estrous cycle, with a maximum during diestrus, pointing to hormonal regulation of HARP mRNA expression. Uterine expression of HARP mRNA was studied in ovariectomized animals treated with 17 -estradiol, progesterone alone or progesterone and RU486. In these experiments, progesterone upregulated HARP mRNA expression. Induction was observed 6 h after progesterone injection and was inhibited by RU486 treatment. In contrast, after 17 -estradiol injection, a slight decrease in HARP mRNA expression was observed. In situ hybridization studies with digoxigenin-labeled DNA probe revealed that HARP mRNA was present in smooth muscle cells of both myometrium and blood vessels and also in endothelial cells from endometrium. Immunohistochemical studies showed that HARP expression was not limited to cells that expressed HARP mRNA, but also occurred in both the luminal and glandular epithelium even though its transcript was never detected. We conclude that HARP may mediate the effects of progesterone on the homeostasis and vascularization of uterine tissue.