Introduction

Transient receptor potential melastatin 3 (TRPM3) is a calcium-permeable non-selective cation channel with broad sensory and metabolic functions, yet its role in renal and cardiovascular physiology remains poorly defined. Given the central role of the kidney in long-term blood pressure (BP) regulation, this study examined whether TRPM3 contributes to systemic haemodynamic control through renal tubular and vascular mechanisms.

Material and Methods

All animal procedures were in accordance with the EC guiding principles regarding the care and use of animals (Directive 2010/63/UE), with protocols approved by the institutional ethics committee. BP was measured in conscious wild-type (WT) and Trpm3 knockout (KO) mice under basal conditions and following angiotensin II (AngII) infusion or losartan treatment. Renal TRPM3 expression was assessed by RNAscope and reporter labelling, and renal function was evaluated in isolated perfused kidneys and by in vivo glomerular filtration rate (GFR) measurements.

Results

Trpm3-KO mice exhibited a mild hypotensive phenotype relative to WT animals (WT n=66 male, 31 female; KO n=61 male, 19 female; P<0.0001, Aligned Rank Transform-ANOVA), accompanied by increased urinary Na⁺ excretion, reduced plasma volume, and unchanged haematocrit, suggesting that enhanced natriuresis underlies hypotension. AngII infusion raised BP in WT (from 84±3 mmHg to 99±8 mmHg; P=0.00017) but not in Trpm3-KO mice (from 81±3 mmHg to 81±6 mmHg; P=0.95 ANOVA). By contrast, losartan lowered BP similarly in both genotypes, arguing against altered AT1 receptor responsiveness as the primary cause of the phenotype.

Within the kidney, TRPM3 was detected in the juxtaglomerular apparatus (macula densa), distal convoluted tubule, and collecting duct, but absent from proximal tubule, VSMCs, and renin-positive granular cells, consistent with a role in tubular sensing and distal Na⁺/water handling. Dapagliflozin, which increases Na⁺ delivery to the macula densa, reduced renal flow and GFR in WT, and both responses were significantly attenuated in Trpm3-KO mice, indicating impaired tubuloglomerular feedback (TGF) in the absence of TRPM3. Accordingly, the TRPM3 blocker Primidone similarly attenuated the dapagliflozin-evoked vasoconstrictor response in WT kidneys (WT n=6 vs. KO n=5, P=0.005; WT+primidone n=5, P=0.02; ANOVA), further supporting a functional role for TRPM3 in TGF.

TRPM3 activation by pregnenolone sulfate induced vasodilation in pre-constricted renal vessels. This response was abolished by calcitonin gene-related peptide receptor (CGRP) blockade or nitric oxide synthase inhibition and was absent in Trpm3-KO kidneys. Immunolabelling of renal arteries showed TRPM3 reporter signal colocalised with CGRP in perivascular sensory nerve fibres, with no detectable signal in VSMCs or endothelium. This sensory neurovascular component indicates that renal TRPM3 can also modulate vascular tone through CGRP- and nitric oxide-dependent signalling.

Conclusions

These findings identify renal TRPM3 as a regulator of Na⁺ and water balance that contributes to long-term BP homeostasis through TGF and distal nephron function, while also engaging a perivascular sensory pathway that shapes renal haemodynamics.