Abnormal Cyclic Nucleotide Signaling at the Outer Mitochondrial Membrane In Sympathetic Neurons During the Early Stages of Hypertension

Abstract

Background: Disruption of cyclic nucleotide signaling in sympathetic postganglionic neurons contributes to impaired intracellular calcium handling (Ca 2+ ) and the development of dysautonomia during the early stages of hypertension, although how this occurs is poorly understood. Emerging evidence supports the uncoupling of signalosomes in distinct cellular compartments involving cyclic nucleotide–sensitive PDEs (phosphodiesterases), which may underpin the autonomic phenotype in stellate neurons. Methods: Using a combination of single-cell RNA sequencing together with Forster resonance energy transfer–based sensors to monitor cyclic adenosine 3’,5’-monophosphate, PKA (protein kinase A)-dependent phosphorylation and cGMP (cyclic guanosine 3’,5’-monophosphate), we tested the hypothesis that dysregulation occurs in a sub-family of PDEs in the cytosol and outer mitochondrial membrane of neurons from the stellate ganglion. Results: PDE2A, 6D, 7A, 9A genes were highly expressed in young Wistar neurons and also conserved in neurons from spontaneously hypertensive rats (SHRs). In stellate neurons from prehypertensive SHRs, we found the levels of cyclic adenosine 3’,5’-monophosphate and cGMP at the outer mitochondrial membrane were decreased compared with normal neurons. The reduced cyclic adenosine 3’,5’-monophosphate response was due to the hydrolytic activity of overexpressed PDE2A2 located at the mitochondria. Normal cyclic adenosine 3’,5’-monophosphate levels were re-established by inhibition of PDE2A. There was also a greater PKA-dependent phosphorylation in the cytosol and at the outer mitochondrial membrane in spontaneously hypertensive rat neurons, where this response was regulated by protein phosphatases. The cGMP response was only restored by inhibition of PDE6. Conclusions: When taken together, these results suggest that site-specific inhibition of PDE2A and PDE6D at the outer mitochondrial membrane may provide a therapeutic target to ameliorate cardiac sympathetic impairment during the onset of hypertension.

Genotypes of Stim1 and the proximal region on chromosome 1 exert opposite effects on stroke susceptibility in stroke-prone spontaneously hypertensive rat

“…Among the candidate genes identified above, Pde2a and Folr1 were good candidate genes from the standpoint of gene function [16,18–20].…”

“…PDE2A is a cGMP-dependent phosphodiesterase that hydrolyzes both cAMP and cGMP to terminate their biological effects [31]. PDE2A activity was shown to be higher in SHR than in WKY, and this was associated with sympathetic hyperactivity in this model [18–20]. FOLR1 is mainly expressed in renal tubular cells and is required for the uptake of 5-methyltetrahydrofolate from filtrated primitive urine [32].…”

“…Functional and physiological analyses related to candidate genes Among the candidate genes identified above, Pde2a and Folr1 were good candidate genes from the standpoint of gene function [16,[18][19][20].…”

Healthy cardiac myocytes can decrease sympathetic hyperexcitability in the early stages of hypertension

“…TrkA receptors are essential for the survival of sympathetic neurons and their distal targets in vivo (Fagan et al, 1996) as well as regulating the synaptic properties of the neuron (Luther and Birren, 2009). Supporting a key role for NGF, Dokshokova et al (2022) observed that sympathetic innervated NGF-silenced cardiac myocytes appeared fragmented and had smaller TH-marked varicosities, compared with controls, which would reinforce the idea of a structural underpinning for impaired neuronal signaling from the heart itself if it is diseased. This may be particular pertinent in models of heart failure and post myocardial infarction where the primary disease is cardiac in origin (Habecker et al, 2016).…”

“…In the early stages of hypertension in the SHR, the heightened sympathetic responsiveness may result from down-regulation of M-current that restricts neural firing ( Davis et al, 2020 ), local inflammation associated with macrophages ( Neely et al, 2022 ), increased activity of Cav 2.2 ( Larsen et al, 2016a ), impaired NO-cGMP signaling ( Li et al, 2007 ), and abnormal regulation of mitochondrial phosphodiesterases ( Li et al, 2022 ). These responses are linked to greater intracellular calcium (Ca 2+ ) transients ( Li et al, 2012 ; Neely et al, 2022 ) and facilitated exocytosis of classical transmitters ( Lu et al, 2015 ) and neuropeptides ( Herring et al, 2008 ).…”