PIEZOs mediate neuronal sensing of blood pressure and the baroreceptor reflex

Abstract

Activation of stretch-sensitive baroreceptor neurons exerts acute control over heart rate and blood pressure. Although this homeostatic baroreflex has been described for more than 80 years, the molecular identity of baroreceptor mechanosensitivity remains unknown. We discovered that mechanically activated ion channels PIEZO1 and PIEZO2 are together required for baroreception. Genetic ablation of both Piezo1 and Piezo2 in the nodose and petrosal sensory ganglia of mice abolished drug-induced baroreflex and aortic depressor nerve activity. Awake, behaving animals that lack Piezos had labile hypertension and increased blood pressure variability, consistent with phenotypes in baroreceptor-denervated animals and humans with baroreflex failure. Optogenetic activation of Piezo2-positive sensory afferents was sufficient to initiate baroreflex in mice. These findings suggest that PIEZO1 and PIEZO2 are the long-sought baroreceptor mechanosensors critical for acute blood pressure control.

Fig. 1.. Expression of Piezo1 and Piezo2 transcript in NPJc.

A, Z-projection of NPJc tissue after fluorescent in-situ hybridization with probes targeting Piezo1 (red) and Piezo2 (cyan). Nuclei labeled with DAPI (blue). Arrows mark double-positive cells. B, Quantification of transcript labeling area as a fraction of total cell area (n = 290 cells, 6 mice). Each dot represents one cell. C-F, NPJc cell bodies back-labeled by carotid sinus CTB injections (green) and Piezo transcript (below) shows a Piezo2⁺ (C, E) and Piezo1⁺ (D, F) cell (arrows). G, Quantification of Piezo transcript labeling area in CTB⁺ cells (n = 95 cells, 8 mice). Piezo-negative cells not shown.

Fig. 2.. Baroreflex is abolished in nodose/petrosal ganglia-specific dKO mice.

A, Cardiovascular recordings show PE-induced baroreflex in WT mice, but no baroreflex in dKO littermates. BP, raw blood pressure signal. SYS, systolic blood pressure derived from raw BP. HR, heart rate. Changes of B, systolic blood pressure C, heart rate and D, baroreflex (10 s after i.v. injection of PE) in knock-out mice. Number of animals shown in bars (B) also apply for C-D. Piezo1: Phox2bCre⁺;Piezo1^f/f (KO) mice. Piezo2: Phox2bCre⁺;Piezo2^f/f (KO) mice. Piezo1 Piezo2: Phox2bCre⁺;Piezo1^f/fPiezo2^f/f (KO) mice. All WT are littermates. E, Traces show BP and ADN activity induced by PE and sodium nitroprusside injection in a WT and a dKO mouse. F, Statistical analysis of drug-induced ADN activity in WT and dKO mice. G, Raw BP and ADN activity example before and after PE injection. Expanded time scale showed bursts of ADN activity in phase with individual arterial pulses in WT. No integrated activity is observed in dKO mice. *p < 0.05, ***p < 0.001 and n.s., statistically not significant, unpaired Student’s t-test, means ± s.e.m.

Fig. 3.. Increased BP variability in conscious nodose/petrosal ganglia-specific dKO mice.

A, Continuous measurements of mean arterial pressure (MAP) and HR over 72 h, binned by hour. The differences between groups were significant during night (gray shading, two-way ANOVA, means ± s.e.m). B, Average MAP and HR during day (6am-6pm) and night (6pm-6am). C, sBRS, expressed as change in PI (ms) per change in systolic BP (mmHg), was significantly reduced in dKO mice (n = 17) compared to WT (n = 15). D, Frequency distribution histogram of the systolic blood pressure from 72 h. Red arrows indicate wider distribution of BP in dKO mice. E, BP variability reported as standard deviation from 72-h period. F, Maximum and minimum BP values. P values are indicated in the bars. *p < 0.05, **p < 0.01 and ***p < 0.001, n.s. is not significant. Unpaired Student’s t-test unless indicated otherwise, means ± s.e.m. n = 7–17.

Fig. 4.. Piezo2-positive sensory neurons acutely control blood pressure.

A, Schematic depiction of the optogenetic strategy. The carotid sinus and vagus nerve is illuminated to activate ChR2-expressing Piezo2-sensory neurons. The optical fiber was placed on area 1) vagus nerve trunk, 2) superior laryngeal branch and 3) carotid sinus. B, Traces of cardiovascular effects following focal vagus nerve illumination (blue shading) in anesthetized Piezo2Cre^-;ChR2-eYFP (WT, black trace) and Piezo2Cre⁺;ChR2-eYFP mice (Piezo2Cre⁺, grey, blue, and pink traces). Numbers on left (–3) correspond to locations in A. Blood pressure was measured by a pressure transducer cannulated in the left carotid artery. BP, carotid arterial pressure. HR, heart rate. C, Light-induced changes in BP and HR were calculated over the 10 s (n = 7–18 as indicated. ***p < 0.001, n.s., statistically not significant, unpaired Student’s t-test, means ± s.e.m.).