Submitted on February 20, 2007
Accepted on August 13, 2007
Pro-inflammatory and proliferative responses of human proximal tubule cells to PAR-2 activation
David Alan Vesey1*, Wade Kruger2, Philip Poronnik2, Glenda C Gobe3, and David W Johnson1
1 Renal Medicine, Princess Alexandra Hospital, Brisbane, Queensland, Australia
2 School of Biomedical Sciences, University of Queensland, Brisbane, Queensland, Australia
3 Molecular and Cellular Pathology, University of Queensland, Brisbane, Queensland, Australia
* To whom correspondence should be addressed. E-mail: David_Vesey{at}health.qld.gov.au.
Despite the abundant expression of protease-activated receptor-2 (PAR-2) in the kidney, its relevance to renal physiology is not well understood. A role for this receptor in inflammation and cell proliferation has recently been suggested in non-renal tissues. The aims of this study were to demonstrate that human proximal tubule cells (PTC) express functional PAR-2 and to investigate whether its activation can mediate pro-inflammatory and proliferative responses in these cells. Primary human PTC were cultured under serum free conditions with or without the PAR-2 activating peptide SLIGKV-NH2 (up to 800µM), a control peptide VKGILS-NH2 (200µM) or trypsin (0.01-100nM). PAR-2 expression, (RT-PCR), intracellular Ca2+ mobilisation (fura-2 fluorimetry), DNA synthesis (thymidine incorporation), fibronectin production (ELISA, Western blotting), and MCP-1 secretion (ELISA) were measured. Trypsinogen expression in the kidney and PTC cultures was determined by immunohistochemistry and Western blotting. In the kidney PTCs were the predominant cell type expressing PAR-2. SLIGKV-NH2, but not VKGILS-NH2, stimulated a rapid concentration-dependent mobilisation of intracellular Ca2+ and ERK1/2 phosphorylation and, by 24h, increases in DNA synthesis, fibronectin secretion and MCP-1 secretion. These delayed responses appeared to be independent of ERK1/2. Trypsin produced similar rapid but not delayed responses. Trypsinogen was weakly expressed by PTC in the kidney and in culture. In summary PTC are the main site of PAR-2 is expression in the human kidney. In PTC cultures SLIGKV-NH2 initiates pro-inflammatory and proliferative responses. Trypsinogen expressed within the kidney has the potential to contribute to PAR-2 activation in certain circumstances.
