Perirenal adipose afferent nerves sustain pathological high blood pressure in rats

Abstract

Hypertension is a pathological condition of persistent high blood pressure (BP) of which the underlying neural mechanisms remain obscure. Here, we show that the afferent nerves in perirenal adipose tissue (PRAT) contribute to maintain pathological high BP, without affecting physiological BP. Bilateral PRAT ablation or denervation leads to a long-term reduction of high BP in spontaneous hypertensive rats (SHR), but has no effect on normal BP in control rats. Further, gain- and loss-of-function and neuron transcriptomics studies show that augmented activities and remodeling of L1-L2 dorsal root ganglia neurons are responsible for hypertension in SHR. Moreover, we went on to show that calcitonin gene-related peptide (CGRP) is a key endogenous suppressor of hypertension that is sequestered by pro-hypertensive PRAT in SHRs. Taken together, we identify PRAT afferent nerves as a pro-hypertensive node that sustains high BP via suppressing CGRP, thereby providing a therapeutic target to tackle primary hypertension.

Conflict of interest statement

The authors declare no competing financial interests.

© 2022. The Author(s).

Figures

Fig. 1. Acute effects of PRATA on blood pressure and peripheral vasomotion.

a Surgical diagram of PRATA. b Acute changes of the intracarotid arterial MAP post PRATA, n = 6 per group; Data are mean ± SEM. **P < 0.01, ***P < 0.001, ****P < 0.0001. Analysis of variance (ANOVA), Bonferroni post-hoc test, two-sided. c–f Changes of intracarotid arterial MAP post unilateral and half-volume PRATA (c), pararenal adipose tissue ablation (d), epididymal adipose tissue ablation (e) and inguinal adipose tissue ablation (f), n = 6 per group; Data are mean ± SEM. P > 0.05. ANOVA, Bonferroni post-hoc test, two-sided. g–l Laser speckle contrast imaging of the blood flow of mesenteric artery (g), carotid artery (h) and renal cortex (i), and quantification (j–l). n = 5 per group for all the imaging of the blood flow experiments in (j) and (l). n = 7 for WKY-PRATA group, n = 5 for SHR-PRATA group in (k). Data are mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. ANOVA, Bonferroni post-hoc test, two-sided.

Fig. 2. Effects of PRATA on hypertension of different causes and sympathetic output.

a, b Weekly measurement of arterial mean BP post PRATA in SHRs using radiotelemetry in the daytime (a) and at night (b), n = 6 per group; Data are mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. ANOVA, Bonferroni post-hoc test, two-sided. c, d Weekly measurement of tail arterial BP post PRATA in SHR (c) and WKY rats (d), n = 7 per group; Data are mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. ANOVA, Bonferroni post-hoc test, two-sided. e, f weekly measurement of tail arterial BP post PRATA in high fat diet (HFD) induced hypertensive rats (e) and high salt diet (HSD) induced hypertensive rats (f), n = 7 per group; Data are mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. ANOVA, Bonferroni post-hoc test, two-sided. g, h Changes of renal sympathetic and cervical vagal nerve discharge (g) and quantification (h), n = 6 per group; Data are mean ± SEM. *P < 0.05, ***P < 0.001, ****P < 0.0001. ANOVA, Bonferroni post-hoc test, two-sided.

Fig. 3. Enhanced L1-L2 DRG neuron activity as a regulator for high BP.

a, b Changes of intracarotid arterial MAP under L1-L2 DRG injection with capsaicin post PRATA, n = 5 for WKY-Sham + Cap and WKY-PRATA-4wk + Cap groups, n = 10 for SHR-Sham + Cap group, n = 8 for SHR-PRATA-4wk + Cap group, n = 6 for SHR-PRATA-12wk + Cap group; Data are mean ± SEM. *P < 0.05. ANOVA, Bonferroni post-hoc test, two-sided. c, d Changes of the intracarotid arterial MAP after selective inhibition of neuronal activity of L1-L2 DRGs using Gi-DREADDs in SHR, n = 5 for Saline-DREADD and CNO-DREADD group, n = 6 for Saline-mCherry and CNO-mCherry group; Data are mean ± SEM. *P < 0.05, ***P < 0.001, ****P < 0.0001 compared with Saline-DREADD group. ANOVA, Bonferroni post-hoc test, two-sided. e Changes of the intracarotid arterial MAP post PRATA with or without T12 spinal cord mutilation, n = 6 for SHR-PRATA group, n = 5 for SHR-PRATA + T12 mutilation group; Data are mean ± SEM. ***P < 0.001, ****P < 0.0001. ANOVA, Bonferroni post-hoc test, two-sided. f Changes of the intracarotid arterial MAP post PRAT denervation by RTX in SHRs, n = 6 per group; Data are mean ± SEM. *P < 0.05, **P < 0.01. ANOVA, Bonferroni post-hoc test, two-sided. g Weekly measurement of tail arterial BP post three repeated PRATD by RTX in SHRs, n = 6 per group; Data are mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. ANOVA, Bonferroni post-hoc test, two-sided. h, i Weekly measurement of tail arterial BP post PRATD in HFD induced hypertensive rats (h) and HSD induced hypertensive rats (i), n = 8 for HFD-HTN-Saline→PRAT group, n = 7 for HFD-HTN-RTX → PRAT group in (h); n = 7 per group in (i); Data are mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. ANOVA, Bonferroni post-hoc test, two-sided. Saline→PRAT: injection of saline into perirenal adipose tissue, RTX → PRAT: injection of resiniferatoxin into perirenal adipose tissue.

Fig. 4. Whole-transcriptome sequencing of isolated L1-L2 DRG neurons in SHRs.

a, b Differential gene expression in L1-L2 DRG neurons 4 weeks post PRATA. Hierarchical cluster and volcano analysis of 433 genes expressed differentially between sham and PRATA groups. The expression levels are indicated by the increased gradient of dark blue to light blue to red intensity. c, d GO enrichment analysis shows most of those upregulated genes are associated with neuron plasticity and development, and those downregulated genes are prone to RNA processing and would healing. e, f Test of differential expressed gene abundances using g:Profile showed that up-regulated genes mainly involved in neuron activities, while the downregulated genes enriched for RNA activities in post-PRATA SHRs compared with sham-operated SHRs.

Fig. 5. PRATA promotes L1-L2 DRG neuron remodeling.

a–e Imaging of central and peripheral axons by immunostaining of MAP2 and SMI-312 in L1-L2 DRG (a), scale bar = 50 μm; and quantification (b–e). n = 10 per group, Data are mean ± SEM. Non-significant (ns) P > 0.05, *P < 0.05, **P < 0.01, ***P < 0.001. ANOVA, Bonferroni post-hoc test, two-sided.

Fig. 6. CGRP as a mediator for BP-lowering effects of PRATA.

a, b Serum or plasma levels of CGRP assessed by ELISA post PRATA in chronic (a) or acute (b) experiments. n = 11 for WKY-PRATA-4wk group, n = 14 for other groups in (a). n = 10 per group in (b); Data are mean ± SEM. P > 0.05 non-significant (ns), *P < 0.05, **P < 0.01, ***P < 0.001. ANOVA, Bonferroni post-hoc test, two-sided. c mRNA levels of CGRP assessed by qPCR in L1 and L2 DRGs post PRATA, n = 6 per group; Data are mean ± SEM, P > 0.05 non-significant (ns), *P < 0.05, **P < 0.01. ANOVA, Bonferroni post-hoc test, two-sided. d Changes of the intracarotid arterial MAP post PRATA combined with CGRP8-37 (1 mg/kg) treatment, n = 5 for WKY-Saline, WKY-CGRP8-37, SHR-PRATA-Saline groups, n = 6 for SHR-Saline, SHR-CGRP8-37, SHR-PRATA-CGRP8-37 groups; Data are mean ± SEM. *P < 0.05, WKY-Saline vs. WKY-CGRP8-37; #P < 0.05, SHR-PRATA-Saline vs. SHR-PRATA-CGRP8-37; P > 0.05 non-significant (ns), SHR-Saline vs. SHR-CGRP8-37. ANOVA, Bonferroni post-hoc test, two-sided. e Weekly measurement of tail arterial BP post PRATA combined with CGRP8-37 (10 μg/kg/d) treatment, n = 8 for WKY-CGRP8-37 group, n = 7 for other groups; Data are mean ± SEM. *P < 0.05, WKY-Saline vs. WKY-CGRP8-37; #P < 0.05, SHR-PRATA-Saline vs. SHR-PRATA-CGRP8-37; &P < 0.05, SHR-Saline vs. SHR-PRATA-CGRP8-37. ANOVA, Bonferroni post-hoc test, two-sided.

Fig. 7. Schematic illustration of this study.

PRAT afferent nerves serve as a pathological node of hypertension that sustains high BP via suppressing CGRP, thereby being a potential therapeutic target to tackle primary hypertension.