Proinflammatory and proliferative responses of human proximal tubule cells to PAR-2 activation

Abstract

Despite the abundant expression of protease-activated receptor (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 nonrenal 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 proinflammatory 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 800 μM), a control peptide, VKGILS-NH2 (200 μM), or trypsin (0.01–100 nM). PAR-2 expression (RT-PCR), intracellular Ca2+ mobilization (fura-2 fluorimetry), DNA synthesis (thymidine incorporation), fibronectin production (ELISA, Western blotting), and monocyte chemotactic protein (MCP)-1 secretion (ELISA) were measured. Trypsinogen expression in kidney and PTC cultures was determined by immunohistochemistry and Western blotting. In the kidney PTC were the predominant cell type expressing PAR-2. SLIGKV-NH2, but not VKGILS-NH2, stimulated a rapid concentration-dependent mobilization of intracellular Ca2+ and ERK1/2 phosphorylation and, by 24 h, 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 expression in the human kidney. In PTC cultures SLIGKV-NH2 initiates proinflammatory and proliferative responses. Trypsinogen expressed within the kidney has the potential to contribute to PAR-2 activation in certain circumstances.

Proteinase-activated Receptor-2 Transactivation of Epidermal Growth Factor Receptor and Transforming Growth Factor-β Receptor Signaling Pathways Contributes to Renal Fibrosis

“…Phosphorylated Smad2/3 forms an oligomeric complex with Smad4, which then translocates to the nucleus to initiate the transcription of genes that regulate fibrosis, cell proliferation, differentiation, and apoptosis (42). Previous observations in isolated cultured human tubular epithelial cells have demonstrated that functional epithelial PAR2 activation stimulates the production of monocyte chemotactic protein-1 and TGF␤ (11). In addition to a proinflammatory role of PAR2, our data shows that PAR2 contributes to profibrotic pathways by acting synergistically with TGF␤ to induce Smad2 activation and CTGF expression consistent with the in vivo studies.…”

“…In the kidney, PAR2 is abundantly expressed in the proximal tubular cells of renal cortex, and renal PAR2 activation is associated with changes in renal hemodynamics, ion secretion, and inflammation (9,10). Studies have also indicated a proinflammatory role for PAR2 in the kidney, as receptor stimulation with PAR2-AP was found to augment MCP-1 production in human proximal tubular cell cultures (11).…”

Neutrophil Elastase Acts as a Biased Agonist for Proteinase-activated Receptor-2 (PAR2)

“…That Endogenously Express PAR2-In order to confirm the existence of NE-dependent biased signaling in cells that endogenously express PAR2, we have examined the effect of NE on calcium and MAPK signaling in HPT cells that naturally express high levels of PAR2 (24). Treatment of HPT cells with NE did not stimulate a calcium signal but significantly attenuated subsequent trypsin-stimulated calcium transients (Fig.…”

PAR2-induced inflammatory responses in human kidney tubular epithelial cells

“…Within the human kidney, PAR2 is especially prominent in the proximal tubule cells of the renal cortex and renal vasculature (21,48,49). Studies have shown PAR2 involvement in the control of renal blood flow, ion transport, inflammation, and fibrosis (5,17,18,21).…”