Abstract
Objectives:
Peroxisome proliferator-activated receptors (PPARs) are implicated in epithelial cell proliferation and differentiation, but investigation has been confounded by potential off-target effects of some synthetic PPAR ligands. Our aim was to determine mechanisms underlying the pro-apoptotic effect of synthetic PPAR agonists in normal human bladder uro-epithelial (urothelial) cells and to reconcile this with the role of PPARs in urothelial cytodifferentiation.
Materials and methods:
Normal human urothelial (NHU) cells were grown as non-immortal lines in vitro and exposed to structurally diverse agonists ciglitazone, troglitazone, rosiglitazone (PPAR gamma), ragaglitazar (PPAR alpha/gamma), fenofibrate (PPAR alpha) and L165041 (PPAR beta/delta).
Results:
NHU cells underwent apoptosis following acute exposure to ciglitazone, troglitazone or ragaglitazar, but not fenofibrate, L165041 or rosiglitazone, and this was independent of ERK or p38 MAP-kinase activation. Pro-apoptotic agonists induced sustained increases in intracellular calcium, whereas removal of extracellular calcium altered the kinetics of ciglitazone-mediated calcium release from sustained to transient. Cell death was accompanied by plasma-membrane disruption, loss of mitochondrial membrane-potential and caspase-9/caspase-3 activation. PPAR gamma-mediated apoptosis was unaffected following pre-treatment with PPAR gamma antagonist T0070907 and was strongly attenuated by store-operated calcium channel (SOC) inhibitors 2-APB and SKF-96365.
Conclusions:
Our results provide a mechanistic basis for the ability of some PPAR agonists to induce death in NHU cells and demonstrate that apoptosis is mediated via PPAR-independent mechanisms, involving intracellular calcium changes, activation of SOCs and induction of the mitochondrial apoptotic pathway.
Original language | English |
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Pages (from-to) | 688-700 |
Number of pages | 13 |
Journal | Cell proliferation |
Volume | 42 |
Issue number | 5 |
DOIs | |
Publication status | Published - Oct 2009 |
Keywords
- HUMAN UROTHELIAL CELLS
- GAMMA LIGAND TROGLITAZONE
- PPAR-GAMMA
- TERMINAL DIFFERENTIATION
- URINARY-BLADDER
- IN-VITRO
- DEATH
- MITOCHONDRIA
- EXPRESSION
- GROWTH