Suppression of peripheral sympathetic activity underlies protease-activated receptor 2-mediated hypotension

Naps and cardiovascular disease risk in different age and sex groups: evidence from a large community cohort

STUDY OBJECTIVES

This study examined the relationship between naps and cardiovascular disease (CVD) events or death in different age and sex groups.

METHODS

A total of 3,069 participants stratified by age (< 65, 65-74, and ≥ 75 years old) and sex, underwent Cox regression analysis to assess nap's impact on CVD risk. Restricted cubic spline plots were used for dose-response relationships.

RESULTS

Significant age-stratified interactions were found when exploring the associations between nap frequency or duration and CVD events (Pinteraction = .001, .036, respectively). Individuals younger than 65 years with higher nap frequency or longer nap duration had a significantly increased risk of CVD events (P < .001, P = .001, respectively). The age group of 65-74 years showed significant associations between CVD events and nap frequency or nap duration (P = .017, .016, respectively), together with nap duration and CVD deaths (P = .008). In the subgroup of females aged 65-74, significant associations were found between nap frequency or duration and CVD events (P = .006, .002, respectively). Nap frequency or duration was also significantly associated with CVD deaths (P = .005, .010 respectively).

CONCLUSIONS

This study underscores a noteworthy correlation between a higher frequency or longer duration of daytime nap and an increased susceptibility to CVD among individuals aged 65-74 years, particularly in females. However, further research is needed to better understand the underlying mechanisms.

CLINICAL TRIAL REGISTRATION

Registry: ClinicalTrials.gov; Name: Sleep Heart Health Study; URL: https://clinicaltrials.gov/ct2/show/study/NCT00005275; Identifier: NCT00005275.

CITATION

Chen C, Guo Q, Cheng Y, Lan Y, Cheng D, Huang J. Naps and cardiovascular disease risk in different age and sex groups: evidence from a large community cohort. J Clin Sleep Med. 2024;20(8):1339-1348.

The independent and combined association of napping and night sleep duration with stroke in Chinese rural adults

BACKGROUND

Inappropriate sleep duration is a potential cause of stroke. But the effect of napping on stroke risk remains controversial and the interaction between night sleep and napping duration remains unclear. The objective of this study was to examine the independent and combined effects of napping and nocturnal sleep duration on stroke.

METHODS

Subjects were derived from a rural cohort study in Henan. The Pittsburgh Sleep Quality Index (PSQI) was applied to identify nap duration and nocturnal sleep duration. Binary logistic regression was employed to indicate the dose-response relationships between naps, nocturnal sleep, total 24-h sleep duration, and stroke.

RESULTS

Among the 37,341 participants (14,485 men), 2600 suffered from a stroke. The odds ratios (ORs) and 95% confidence level (CI) for stroke in the fully adjusted model were 1.37 (1.13-1.65) for men nappers compared to non-nappers. Compared to 7-8 h of sleep per day, night sleep durations < 6 h and ≥ 9 h and 24-h sleep duration ≥ 10 h were linked to increased odds of stroke in men. The ORs (95%CI) were 1.34 (1.06-1.69) in nocturnal sleep duration < 6 h, 1.30 (1.06-1.59) in nocturnal sleep duration ≥ 9 h, and 1.40 (1.15-1.71) in 24-h sleep duration ≥ 10 h in men. In addition, long naps and prolonged nocturnal sleep duration have a joint effect on stroke in the fully adjusted model.

CONCLUSION

The napping duration and nocturnal sleep duration have independently and jointly effects on stroke in rural populations. More research is required to explore the underlying mechanisms for this relationship.

CLINICAL TRIAL REGISTRATION

The Henan Rural Cohort Study has been registered on the Chinese Clinical Trial Register (Registration number: ChiCTR-OOC-15006699) ( http://www.chictr.org.cn/showproj.aspx?proj=11375 ).

The signaling of protease-activated receptor-2 activating peptide-induced contraction in cat esophageal smooth muscle cells

Protease-activated receptors (PARs) are a family of G protein-coupled receptors with a unique activation mechanism involving proteolytic cleavage of the extracellular N-terminal domain of the receptor. PAR2 has a contractile effect on esophageal smooth muscle. We investigate the signaling pathways of the PAR2-activating peptide (PAR2-AP) induced contraction in cat esophageal smooth muscle cells. The length of freshly isolated smooth muscle cells and permeabilized cells from feline esophagus were measured by scanning micrometry, and by confirming molecular basis via western blot analysis. The responses to PAR2-AP were initial and sustained contractions, depending on time. The maximum contraction of the initial phase occurred at 60 s. The PAR2-AP-induced contraction was mediated by Gαi1, Gαi3, and Gαq protein activation, leading to phospholipase-c (PLC) and myosin light chain kinase (MLCK) activation. 20 kDa myosin light chain (MLC20) was phosphorylated by PAR2-AP. Rho kinase-2 (ROCK-2), an activator of 17 kDa C-kinase potentiated Protein phosphatase-1 Inhibitor (CPI-17), was increased by PAR2 receptor activation. In conclusion, PAR2-AP produced an initial contraction mediated by Gαi1, Gαi3, and Gαq protein activation, resulting in PLC and MLCK activation. The sustained contraction by PAR2-AP was mediated by the Rho/Rho kinase-dependent pathway.

Phospholipase C-dependent hydrolysis of phosphatidylinositol 4,5-bisphosphate underlies agmatine-induced suppression of N-type Ca2+ channel in rat celiac ganglion neurons

Agmatine suppresses peripheral sympathetic tone by modulating Cav2.2 channels in peripheral sympathetic neurons. However, the detailed cellular signaling mechanism underlying the agmatine-induced Cav2.2 inhibition remains unclear. Therefore, in the present study, we investigated the electrophysiological mechanism for the agmatine-induced inhibition of Cav2.2 current (I_Cav2.2) in rat celiac ganglion (CG) neurons. Consistent with previous reports, agmatine inhibited I_Cav2.2 in a VI manner. The agmatine-induced inhibition of the I_Cav2.2 current was also almost completely hindered by the blockade of the imidazoline I₂ receptor (IR₂), and an IR₂ agonist mimicked the inhibitory effect of agmatine on I_Cav2.2, implying involvement of IR₂. The agmatine-induced I_Cav2.2 inhibition was significantly hampered by the blockade of G protein or phospholipase C (PLC), but not by the pretreatment with pertussis toxin. In addition, diC8-phosphatidylinositol 4,5-bisphosphate (PIP₂) dialysis nearly completely hampered agmatine-induced inhibition, which became irreversible when PIP₂ resynthesis was blocked. These results suggest that in rat peripheral sympathetic neurons, agmatine-induced IR₂ activation suppresses Cav2.2 channel voltage-independently, and that the PLC-dependent PIP₂ hydrolysis is responsible for the agmatine-induced suppression of the Cav2.2 channel.

Facilitation of serotonin-induced contraction of rat mesenteric artery by ketamine

Ketamine is an anesthetic with hypertensive effects, which make it useful for patients at risk of shock. However, previous ex vivo studies reported vasodilatory actions of ketamine in isolated arteries. In this study, we reexamined the effects of ketamine on arterial tones in the presence and absence of physiological concentrations of 5-hydroxytryptamine (5-HT) and norepinephrine (NE) by measuring the isometric tension of endothelium-denuded rat mesenteric arterial rings. Ketamine little affected the resting tone of control mesenteric arterial rings, but, in the presence of 5-HT (100~200 nM), ketamine (10~100 µM) markedly contracted the arterial rings. Ketamine did not contract arterial rings in the presence of NE (10 nM), indicating that the vasoconstrictive action of ketamine is 5-HT-dependent. The concentration-response curves (CRCs) of 5-HT were clearly shifted to the left in the presence of ketamine (30 µM), whereas the CRCs of NE were little affected by ketamine. The left shift of the 5-HT CRCs caused by ketamine was reversed with ketanserin, a competitive 5-HT_2A receptor inhibitor, indicating that ketamine facilitated the activation of 5-HT_2A receptors. Anpirtoline and BW723C86, selective agonists of 5-HT_1B and 5-HT_2B receptors, respectively, did not contract arterial rings in the absence or presence of ketamine. These results indicate that ketamine specifically enhances 5-HT_2A receptor-mediated vasoconstriction and that it is vasoconstrictive in a clinical setting. The facilitative action of ketamine on 5-HT_2A receptors should be considered in ketamine-induced hypertension as well as in the pathogenesis of diseases such as schizophrenia, wherein experimental animal models are frequently generated using ketamine.

Agmatine suppresses peripheral sympathetic tone by inhibiting N-type Ca(2+) channel activity via imidazoline I2 receptor activation

Agmatine, a putative endogenous ligand of imidazoline receptors, suppresses cardiovascular function by inhibiting peripheral sympathetic tone. However, the molecular identity of imidazoline receptor subtypes and its cellular mechanism underlying the agmatine-induced sympathetic suppression remains unknown. Meanwhile, N-type Ca(2+) channels are important for the regulation of NA release in the peripheral sympathetic nervous system. Therefore, it is possible that agmatine suppresses NA release in peripheral sympathetic nerve terminals by inhibiting Ca(2+) influx through N-type Ca(2+) channels. We tested this hypothesis by investigating agmatine effect on electrical field stimulation (EFS)-evoked contraction and NA release in endothelium-denuded rat superior mesenteric arterial strips. We also investigated the effect of agmatine on the N-type Ca(2+) current in superior cervical ganglion (SCG) neurons in rats. Our study demonstrates that agmatine suppresses peripheral sympathetic outflow via the imidazoline I2 receptor in rat mesenteric arteries. In addition, the agmatine-induced suppression of peripheral vascular sympathetic tone is mediated by modulating voltage-dependent N-type Ca(2+) channels in sympathetic nerve terminals. These results suggest a potential cellular mechanism for the agmatine-induced suppression of peripheral sympathetic tone. Furthermore, they provide basic and theoretical information regarding the development of new agents to treat hypertension.