Interdependent regulation of afferent renal nerve activity and renal function: role of transient receptor potential vanilloid type 1, neurokinin 1, and calcitonin gene-related peptide receptors

Abstract

Our previous studies have shown that the activation of the transient receptor potential vanilloid type 1 (TRPV1) expressed in the renal pelvis leads to an increase in ipsilateral afferent renal nerve activity (ARNA) and contralateral renal excretory function, but the molecular mechanisms of TRPV1 action are largely unknown. This study tests the hypothesis that activation of receptors of neurokinin 1 (NK1) or calcitonin gene-related peptide (CGRP) by endogenously released substance P (SP) or CGRP following TRPV1 activation, respectively, governs TRPV1-induced increases in ARNA and renal excretory function. Capsaicin (CAP; 0.04, 0.4, and 4 nM), a selective TRPV1 agonist, administered into the renal pelvis dose-dependently increased ARNA. CAP (4 nM)-induced increases in ipsilateral ARNA or contralateral urine flow rate (Uflow) and urinary sodium excretion (UNa) were abolished by capsazepine (CAPZ), a selective TRPV1 antagonist, or 2-[1-imino-2-(2-methoxyphenyl)ethyl]-7,7-diphenyl-4-perhydroisoindolone (3aR,7aR) (RP67580) or cis-2-(diphenylmethyl)-N-[(2-iodophenyl)-methyl]-1 azabicyclo[2.2.2]octan-3-amine (L703,606), selective NK1 antagonists, but not by CGRP8-37, a selective CGRP receptor antagonist. Both SP (7.4 nM) and CGRP (0.13 muM) increased ARNA, Uflow, or UNa, and increases in these parameters induced by CGRP but not SP were abolished by CAPZ. CAP at 4 nM perfused into the renal pelvis caused the release of SP and CGRP, which was blocked by CAPZ but not by RP67580, L703,606, or CGRP8-37. Immunofluorescence results showed that NK1 receptors were expressed in sensory neurons in dorsal root ganglion and sensory nerve fibers innervating the renal pelvis. Taken together, our data indicate that NK1 activation induced by SP release upon TRPV1 activation governs TRPV1 function and that a TRPV1-dependent mechanism is operant in CGRP action.

Figure 1

Ipsilateral afferent renal nerve activity (ARNA) induced by capsaicin (CAP) perfused into the left renal pelvis (n=5–6 in each group). CAP was given at 0.04nM, 0.4nM and 4nM into the left renal pelvis, and reprehensive recording at each dose is shown. ** vs basal value and ## vs 0.04nM CAP-treated group, ** p<0.01, ## p<0.01.

Figure 2

Ipsilateral ARNA induced by different concentration of substance P (SP) given via left renal pelvis perfusion (n=5–6 in each group). SP was given at 3.7nM, 7.4nM and 14.8nM into the left renal pelvis. ** vs basal value and ## vs 0.04nM CAP-treated group, ** p<0.01, ## p<0.01.

Figure 3

Effect of CAP without or with capsazepine (CAPZ) given into the left renal pelvis on contralateral urine flow rate (Uflow, Fig. 3A), contralateral urine sodium excretion (UNa, Fig. 3B) and ipsilateral ARNA (Fig. 3C, n=5–6 in each group). ** vs basal value of each group, ** p<0.01.

Figure 4

Effect of RP67580, L703, 606 and CGRP8-37 on contralateral urine flow rate (Uflow, Fig. 4A), contralateral urine sodium excretion (UNa, Fig. 4B) and ipsilateral ARNA (Fig. 4C) induced by CAP given into the left renal pelvis (n=5–6 in each group). ** vs basal value of each group, ** p<0.01.

Figure 5

Effect of calcitonin gene-related peptide (CGRP) with or without CAPZ on contralateral urine flow rate (Uflow, Fig. 6A), contralateral urine sodium excretion (UNa, Fig. 6B) and ipsilateral ARNA (Fig. 6C) induced by CAP given into the left renal pelvis (n=5–6 in each group). ** vs basal value of each group, ** p<0.01.

Figure 6

Effect of SP with or without CAPZ on contralateral urine flow rate (Uflow, Fig. 5A), contralateral urine sodium excretion (UNa, Fig. 5B) and ipsilateral ARNA (Fig. 5C) induced by CAP given into the left renal pelvis (n=5–7 in each group). ** vs basal value of each group, ** p<0.01.

Figure 7

Level of SP and CGRP released into urine from left kidney before, during and after treatment. ** vs basal value of each group, ** p<0.01. ## vs 4nM CAP-treated group, ## p<0.01

Figure 8

Immunofluorscence staining of neurokinin 1 (NK1) receptor in DRG and the renal pelvis. Staining of NK1 receptors (arrows) in DRG (Fig. 8A) and in the renal pelvis in green (Fig. 8C) is shown. The negative controls in which no anti-NK1 receptor antiserum was used for DRG (Fig. 8B) and the renal pelvis (Fig. 8D) are also shown.

Figure 9

The figure shows a putative scheme for the possible pathways studies in the present study. Activation of TRPV1 causes the release of the neuropeptides, including CGRP and SP. SP subsequently activates NK1 receptors located in sensory nerves and evokes ARNA. In contrast, CGRP-induced increases in ARNA depend on TRPV1 activation. It is unknown whether all the components are expressed in the same cell, and the scheme is a simplified version that intends to depict possible crosstalk between TRPV1, CGRP and NK1 receptors.