Antagonism of endogenous putative P2Y receptors reduces the growth of MDCK-derived cysts cultured in vitro

Epithelial Transport and Cell Biology Group, Centre for Nephrology and Dept. of Physiology, Royal Free and Univ. College Medical School, Rowland Hill St., London NW3 2PF, UK.
American journal of physiology. Renal physiology (Impact Factor: 3.25). 02/2007; 292(1):F15-25. DOI: 10.1152/ajprenal.00103.2006
Source: PubMed


P2Y receptors couple to G proteins and either mobilize intracellular Ca(2+) or alter cAMP levels to modulate the activity of Ca(2+)- and cAMP-sensitive ion channels. We hypothesize that increased ion transport into the lumen of MDCK cysts can osmotically drive fluid movement and increase cyst size. Furthermore, activation of the adenylate cyclase/cAMP pathway may trigger cell proliferation via an extracellular signal-related kinase cascade. To test this hypothesis, several P2Y receptor inhibitors were used on the MDCK in vitro model of renal cyst formation. The nonspecific P2 receptor inhibitors reactive blue 2 and suramin reduced cyst growth significantly, as did PPADS and, to a lesser extent, the P2Y(1)-specific antagonist MRS2179. Cyst growth was reduced by approximately 50% when ATP was removed from the culture medium with apyrase, although stable analogs of ATP failed to increase cyst size. The nonselective P2X receptor inhibitor Coomassie brilliant blue G was ineffective at reducing cyst growth, suggesting no involvement of P2X receptors. Finally, the presence of selective inhibitors of ERK activation (either PD98059 or U0126) greatly reduced cyst growth, whereas in untreated cysts ERK activity was observed to increase with time. We conclude that stimulation of endogenous P2Y receptors by extracellular ATP increases growth of MDCK cysts via cAMP-dependent activation of the ERK pathway. P2Y receptor antagonists may have therapeutic potential in reducing cyst size and slowing disease progression; although further studies in vitro and in vivo are needed to investigate the specificity and role of these P2Y receptors in renal cystic diseases.

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Available from: Brian Frederick King, Jan 02, 2016
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    • "Here authors agreed that ERK activation is an important factor in cyst growth. However, they found no evidence for the involvement of a P2XR, and concluded that a P2YR is responsible for cAMP-dependent activation of the ERK pathway and cyst growth (Turner et al., 2007). "
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    ABSTRACT: P2X ionotropic non-selective cation channels are expressed throughout the kidney and are activated in a paracrine or autocrine manner following the binding of extracellular ATP and related extracellular nucleotides. Whilst there is a wealth of literature describing a regulatory role of P2 receptors (P2R) in the kidney, there are significantly less data on the regulatory role of P2X receptors (P2XR) compared with that described for metabotropic P2Y. Much of the historical literature describing a role for P2XR in the kidney has focused heavily on the role of P2X1R in the autoregulation of renal blood flow. More recently, however, there has been a plethora of manuscripts providing compelling evidence for additional roles for P2XR in both kidney health and disease. This review summarizes the current evidence for the involvement of P2XR in the regulation of renal tubular and vascular function, and highlights the novel data describing their putative roles in regulating physiological and pathophysiological processes in the kidney.
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    • "In comparison to cpk mice CECs, in MDCK cell-derived cysts, treatment with non-specific P2 receptor antagonists (Reactive Blue 2, suramin) or removal of ATP from culture medium with apyrase (by 50%) attenuated the cAMP-ERK-dependant growth by ~50% (Turner et al., 2007). In this model, cyst growth was not affected by treatment with a non-selective P2X inhibitor, Coomassie Brilliant Blue G), suggesting a role for P2Y receptors (Turner et al., 2007). Similarly, in a separate report, in MDCK cysts derived from principal cells (Clone C7), ATP-dependent cyst growth was driven by fluid secretion rather than cell proliferation and was synergistic with cAMP (Buchholz et al., 2011). "
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    ABSTRACT: Polycystic kidney diseases (PKD) are a group of inherited ciliopathies in which the formation and growth of multiple cysts derived from the distal nephron and collecting duct leads to the disruption of normal kidney architecture, chronic interstitial inflammation/fibrosis and hypertension. Kidney failure is the most life-threatening complication of PKD, and is the consequence of cyst expansion, renal interstitial disease and loss of normal kidney tissue. Over the last decade, accumulating evidence suggests that the autocrine and paracrine effects of ATP (through its receptor family P2X and P2Y), could be detrimental for the progression of PKD. (2009). In vitro, ATP-P2 signaling promotes cystic epithelial cell proliferation, chloride-driven fluid secretion and apoptosis. Furthermore, dysfunction of the polycystin signal transduction pathways promotes the secretagogue activity of extracellular ATP by activating a calcium-activated chloride channel via purinergic receptors. Finally, ATP is a danger signal and could potentially contribute to interstitial inflammation associated with PKD. These data suggest that ATP-P2 signaling worsens the progression of cyst enlargement and interstitial inflammation in PKD.
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