Endothelin and calciotropic hormones share regulatory pathways in multidrug resistance protein 2-mediated transport

Abstract

Wever KE, Masereeuw R, Miller DS, Hang XM, Flik G. Endothelin and calciotropic hormones share regulatory pathways in multidrug resistance protein 2-mediated transport. Am J Physiol Renal Physiol 292: F38 -F46, 2007. First published August 15, 2006; doi:10.1152/ajprenal.00479.2005.-The kidney of vertebrates plays a key role in excretion of endogenous waste products and xenobiotics. Active secretion in the proximal nephron is at the basis of this excretion, mediated by carrier proteins including multidrug resistance protein 2 (Mrp2). We previously showed that Mrp2 function is reduced by endothelin-1 (ET-1) through a basolateral B-type receptor, nitric oxide (NO), cGMP, and PKC (Notenboom S, Miller DS, Smits P, Russel FGM, Masereeuw R. Am J Physiol Renal Physiol 282: F458 -F464, 2002; Notenboom S, Miller DS, Smits P, Russel FG, Masereeuw R. Am J Physiol Renal Physiol 287: F33-F38, 2004). This pathway was rapidly activated by several nephrotoxicants and appeared to be calcium dependent. In the present study, we studied the effect of the calciotropic hormones parathyroid hormone (PTH), PTH-related protein (PTHrP), and stanniocalcin (STC) to interfere with ET-regulated Mrp2 transport. Like ET-1, PTH reduces Mrp2-mediated transport by 40% in killifish renal proximal tubules. When given in combination, an additive effect was seen, which is partially reversed by the PKC inhibitor calphostin C. Recombinant PTHrP shows a comparable inhibitory effect, which is concentration dependent and additive to the inhibition by ET. STC fully reverses PTHrPinhibited transport as does a guanylyl cyclase inhibitor. Finally, to confirm PTHrP bioactivity in a homologous assay, we performed immunolocalization and transport studies in sea bream kidney tubules. Mrp2 immunoreactivity was observed in ϳ40% of the tubules and is associated with the brush-border and apical plasma membrane of cells. Both proximal tubules and distal (collecting) tubules express the antigen. A highly significant 40% inhibition of Mrp2-mediated transport was observed with PTHrP in sea bream tubules. In conclusion, ET-regulated Mrp2 transport is influenced by calciotropic hormones and involves PKC and cGMP signaling. parathyroid hormone; parathyroid hormone-related protein; stanniocalcin; xenobiotic transport; fluorescein-methotrexate; Sparus auratus; gilthead sea bream; Fundulus heteroclitus; killifish THE KIDNEY OF VERTEBRATES plays a key role in excretion of endogenous waste products and xenobiotics. Active secretion in the proximal nephron is at the basis of this excretion. Secretion of xenobiotics in proximal tubules is mediated by carrier proteins, including members of the ATP-binding cassette (ABC) superfamily of transmembrane proteins (53). The multidrug resistance-associated protein 2 (Mrp2; ABCC2) belongs to this family. This transporter is found in liver canalicular membranes (6, 37), luminal membranes of the intestine (52), and luminal membranes of renal proximal tubule cells (42). Mrp2 transports a plethora of chemicals, from large lipophilic, organic ani...

Regulatory Pathways for ATP-binding Cassette Transport Proteins in Kidney Proximal Tubules

“…Signaling appeared to be Ca 2+ dependent, because ET release was blocked by the Ca 2+ -channel blocker, nifedipine, and it was activated (in the absence of nephrotoxicants) by elevated medium Ca 2+ . The calciotropic hormones, parathyroid hormone, PTH-related protein, and stanniocalcin, were also found to interfere with ET-regulated Mrp2 activity through PKC and cGMP signaling (58). Conversely, the results also pointed towards Ca 2+ -independent activation of NOS, suggesting involvement of iNOS that could be confirmed in rat studies (51).…”

Association of serum NO x level with clustering of metabolic syndrome components in middle-aged and elderly general populations in Japan

“…However, any evaluation of urinary cGMP as a substitute for NO bioavailability requires some caution. Since urinary cGMP excretion is likely to depend on the renal function [23,24], the renal dysfunction of cGMP and NO x excretion in urine may result in the increase of circulating NO x levels. Moreover, it has been reported that a creatinine adjustment of urinary biological indicators assayed in spot urine is not a reliable tool for conversion into 24-h urinary excretion [25].…”

Parathyroid hormone-related protein in teleost fish

“…These observations prompted the question whether calcemic factors, such as PTHrP, would interfere with this transport pathway. Indeed, PTHrP interferes with the endothelin regulated Mrp2 med iated transport (Wever et al, 2006). The inhibitory effect of recombinant PTHrP on Mrp2 mediated transport is con centration-dependent, with a maximal inhibition of 40% at 20-60 nmol l_1, a concentration that indicates a para crine action of PTHrP.…”

“…The endothelin-induced inhibition is additive to the PTHrP-induced effect, indicating that the inhibitions proceed at least partly through separate intracellular pathways. Another interesting observation was that the endogenous PTHrP antagonist stanniocalcin (Verbost et al, 1993), which exerts actions via intracellular calcium and PKC pathways, reverses the combined PTHrP/ET inhibition of Mrp2-transport completely (Wever et al, 2006). Clearly, PTHrP has the nephron as target and studies on PTHrP effects on calcium and phosphate handling by fish kidney are warranted.…”