Structurally diverse peroxisome proliferator-activated receptor agonists induce apoptosis in human uro-epithelial cells by a receptor-independent mechanism involving store-operated calcium channels

B. Chopra, N. T. Georgopoulos, A. Nicholl, J. Hinley, M. B. Oleksiewicz, J. Southgate

Research output: Contribution to journalArticlepeer-review

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 languageEnglish
Pages (from-to)688-700
Number of pages13
JournalCell proliferation
Volume42
Issue number5
DOIs
Publication statusPublished - Oct 2009

Keywords

  • HUMAN UROTHELIAL CELLS
  • GAMMA LIGAND TROGLITAZONE
  • PPAR-GAMMA
  • TERMINAL DIFFERENTIATION
  • URINARY-BLADDER
  • IN-VITRO
  • DEATH
  • MITOCHONDRIA
  • EXPRESSION
  • GROWTH

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