Electroacupuncture promotes the gastrointestinal motility of diabetic mice by CNP/NPR-B-cGMP and PDE3A-cGMP signaling.

BACKGROUND: Electroacupuncture (EA) can promote gastrointestinal (GI) motility of diabetic mice, but the mechanism is not clearly elucidated. Natriuretic peptides (NPs) were related to the diabetes-induced gut dysfunction of mice, which may be associated with ICC (interstitial cells of cajal). Besides, EA could increase the ICC of diabetic mice. Our aim was to explore whether EA can promote the gut motility by CNP/NPR-B-cGMP and PDE3A-cGMP signaling in diabetic mice, and the relationship between NPs and ICC. METHODS: Wild C57BL/6 male mice were divided into five groups: control group, diabetic mellitus (DM group), diabetic mellitus plus sham EA group (SEA), diabetic mellitus plus low-frequency EA group (LEA), and diabetic mellitus plus high-frequency group (HEA). Gastrointestinal motility was assessed by gastric emptying and GI transit test. Immunofluorescence staining was applied to assess the expression level of CNP, NPR-B, and c-Kit. Western blot, PCR, and ELISA were used to detect the level of CNP, NPR-B, PDE2A, PDE3A, c-Kit, mSCF, and cGMP content. The correlativity between NPR-B and mSCF was evaluated by Pearson's correlation and linear regression analyses. KEY RESULTS: (a) EA could improve the GI dysfunction of diabetic mice. (b) CNP, NPR-B, and cGMP contents were decreased, but the level of PDE3A, c-Kit, and mSCF was increased in the EA groups. (c) There was a negative correlation between NPR-B and mSCF among the groups. CONCLUSIONS AND INFERENCES: Electroacupuncture promotes the GI function by CNP/NPR-B-cGMP and PDE3A-cGMP signaling in diabetic mice; up-regulated mSCF/c-Kit signaling by EA may be mediated partially via down-regulation of CNP/NPR-B signaling.

[Effects of acupuncture on ANP and CNP in adrenal gland and CORT in plasma in rats with chronic emotional stress anxiety].

OBJECTIVE: To analyze the effects of acupuncture on the level of atrial natriuretic peptide (ANP), C-type natriuretic peptide (CNP) in adrenal gland and the content of corticosterone (CORT) in plasma in rats withchronic emotional stress anxiety, and to explore the partial action mechanism of acupuncture on anxiety disorder. METHODS: Thirty-two healthy Sprague-Dawley (SD) rats, after 7 days of feeding and domestication, were randomly divided into a blank group (10 rats), a model group (11 rats) and an acupuncture group (11 rats). The rats inthe model group and acupuncture group were treated with unpredictable chronic emotional stress (CES) method toestablish the model of anxiety. Rats in the acupuncture group were treated with acupuncture at "Neiguan" (PC 6)and "Shenmen" (HT 7), once every other day, 30 minutes each time. The model establishment and treatment lasted 15 days. Rats in the blank group were treated with identical immobilization but no treatment was given. Theelevated plus maze was used to test the behavioral changes of rats with anxiety; the level of CORT in plasma wasdetected by ELISA, and the expression level of CNP and ANP in adrenal cortex and medulla was detected by immunohistochemical method. RESULTS: (1) The percentage of open-arms time in total time (OT%) in elevated plus maze in the model group was significantly lower than that in the blank group (P<0. 05); the OT% in the acupuncture group was significantly higher than that in the model group (P<0.01). (2) The content of CORT in plasma in the model group was higher than that in the blank group (P<0. 05), while that in the acupuncture group was significantly lower than that in the model group (P<0. 05). (3) The expression of ANP in adrenal medulla and cortex in the model group was lower than that in the blank group (P<0. 01), while the expression of CNP in adrenal medulla and cortex in the model group was higher than that in the blank group (P<0. 01). CONCLUSION: The effects of acupuncture against anxiety are likely to be related to the regulation on the expression of ANP and CNP in adrenal medulla, affecting the release of CORT and inhibition on the activity !f hypothalamic-pituitary-adrenal axis (HPA axis).

Brain-specific natriuretic peptide receptor-B deletion attenuates high-fat diet-induced visceral and hepatic lipid deposition in mice.

C-type natriuretic peptide (CNP) and its receptor, natriuretic peptide receptor-B (NPR-B), are abundantly distributed in the hypothalamus. To explore the role of central CNP/NPR-B signaling in energy regulation, we generated mice with brain-specific NPR-B deletion (BND mice) by crossing Nestin-Cre transgenic mice and mice with a loxP-flanked NPR-B locus. Brain-specific NPR-B deletion prevented body weight gain induced by a high-fat diet (HFD), and the mesenteric fat and liver weights were significantly decreased in BND mice fed an HFD. The decreased liver weight in BND mice was attributed to decreased lipid accumulation in the liver, which was confirmed by histologic findings and lipid content. Gene expression analysis revealed a significant decrease in the mRNA expression levels of CD36, Fsp27, and Mogat1 in the liver of BND mice, and uncoupling protein 2 mRNA expression was significantly lower in the mesenteric fat of BND mice fed an HFD than in that of control mice. This difference was not observed in the epididymal or subcutaneous fat. Although previous studies reported that CNP/NPR-B signaling inhibits SNS activity in rodents, SNS is unlikely to be the underlying mechanism of the metabolic phenotype observed in BND mice. Taken together, CNP/NPR-B signaling in the brain could be a central factor that regulates visceral lipid accumulation and hepatic steatosis under HFD conditions. Further analyses of the precise mechanisms will enhance our understanding of the contribution of the CNP/NPR-B system to energy regulation.

CNP signal pathway up-regulated in rectum of depressed rats and the interventional effect of Xiaoyaosan.

AIM: To investigate the distribution and expression of C-type natriuretic peptide (CNP)/natriuretic peptide receptor B (NPR-B) in the rectum of a rodent depression model and the interventional effect of Xiaoyaosan (XYS). METHODS: Male rats (n = 45) of clean grade (200 ± 20 g) were divided into five groups after one week of adaptive feeding: primary control, depression model, low dose XYS, middle dose XYS, and high dose XYS. The animal experiment continued for 3 wk. Primary controls were fed normally ad libitum. The rats of all other groups were raised in solitary and exposed to classic chronic mild unpredictable stimulation each day. XYS groups were perfused intragastrically with low dose, middle dose, and high dose XYS one hour before stimulation. Primary control and depression model groups were perfused intragastrically with normal saline under similar conditions as the XYS groups. Three weeks later, all rats were sacrificed, and the expression levels of CNP and NPR-B in rectum tissues were analyzed by immunohistochemistry, real-time polymerase chain reaction, and Western blotting. RESULTS: CNP and NPR-B were both expressed in the rectum tissues of all rats. However, the expression levels of CNP and NPR-B at both gene and protein levels in the depression model group were significantly higher when compared to the primary control group (n = 9; P < 0.01). XYS intervention markedly inhibited the expression levels of CNP and NPR-B in depressed rats. The expression levels of CNP and NPR-B in the high dose XYS group did not significantly differ from the expression levels in the primary control group. Additionally, the high and middle dose XYS groups (but not the low dose group) significantly exhibited lower CNP and NPR-B expression levels in the rectum tissues of the respectively treated rats compared to the untreated depression model cohort (n = 9; P < 0.01). CONCLUSION: The CNP/NPR-B pathway is upregulated in the rectum of depressed rats and may be one mechanism for depression-associated digestive disorders. XYS antagonizes this pathway at least partially.

Regulation of C-type natriuretic peptides and natriuretic peptide receptor-B expression in diabetic rats renal treated by Tongluo Recipe.

OBJECTIVE: To investigate the expression of C-type natriuretic peptides (CNP) and natriuretic peptide receptor-B (NPR-B) receptor in diabetic rats renal cortex, and the regulation by Tongluo Recipe (TLR). METHODS: Sixty male SD rats were divided into 3 groups: the normal control group, diabetic model group and diabetic TLR group. Each group was further divided into two subgroups of ten in each, according to 4-week or 12-week observation period. Streptozotocin (STZ)-induced diabetic rats were treated with TLR (1.0 g·kg(-1)·d(-1)) for 4 and 12 weeks, respectively. (1) The essential information was collected for comparing renal mass, serum creatinine and 24 h urine albumen on each group was calculated. (2) CNP mRNA and NPR-B mRNA were detected by realtime-polymerase chain reaction (PCR) on rats renal cortex. (3) Concentration of CNP on renal cortex or serum were analyzed by enzyme-linked immunosorbent assay (ELISA). (4) Pathological evaluation and NPR-B immunostaining for renal tissue were also performed. RESULTS: (1) CNP and NPR-B mRNA levels were detected in each treated or untreated group, with slight elevated in untreated diabetes rats administrated with STZ after 4-week and CNP mRNA level remarkable elevated at 39.21 times higher than normal control group after 12 weeks, but NPR-B mRNA level showed a remarkably down-regulation at 98.07% after 12 weeks. CNP mRNA of TLR-treated group was also elevated after 12-week treatment, but less than untreated group. (2) Concentrations of CNP in renal cortex were obviously increased in treated or untreated diabetes rats, within these groups the treatment of TLR was found more significantly on prompting CNP concentration. Comparing to normal group, serum concentrations of CNP were also increased in treated or untreated diabetic groups, but there was no difference between these diabetic groups. (3) Renal lesions like glomerular volume increased are observed mostly in the relative early stage after 4 weeks. Although TLR treated group had no significant difference in their glomerular volume, the degrees of injury of glomerulus were ameliorated, as well as the NPR-B immunostaining enhanced in glomerulus. Weakly positive immunostaining of NPR-B are observed in glomerulus of normal control, and negative in glomerulus of untreated diabetes rats administrated with STZ after 12 weeks, whereas TLR-treatment groups showed a little enhancement. CONCLUSION: CNP and NPR-B showed different characteristic on renal cortex at different pathological period in diabetes rats, and TLR regulated their expression.

Intracerebroventricular administration of C-type natriuretic peptide suppresses food intake via activation of the melanocortin system in mice.

C-type natriuretic peptide (CNP) and its receptor are abundantly distributed in the brain, especially in the arcuate nucleus (ARC) of the hypothalamus associated with regulating energy homeostasis. To elucidate the possible involvement of CNP in energy regulation, we examined the effects of intracerebroventricular administration of CNP on food intake in mice. The intracerebroventricular administration of CNP-22 and CNP-53 significantly suppressed food intake on 4-h refeeding after 48-h fasting. Next, intracerebroventricular administration of CNP-22 and CNP-53 significantly decreased nocturnal food intake. The increment of food intake induced by neuropeptide Y and ghrelin was markedly suppressed by intracerebroventricular administration of CNP-22 and CNP-53. When SHU9119, an antagonist for melanocortin-3 and melanocortin-4 receptors, was coadministered with CNP-53, the suppressive effect of CNP-53 on refeeding after 48-h fasting was significantly attenuated by SHU9119. Immunohistochemical analysis revealed that intracerebroventricular administration of CNP-53 markedly increased the number of c-Fos-positive cells in the ARC, paraventricular nucleus, dorsomedial hypothalamus, ventromedial hypothalamic nucleus, and lateral hypothalamus. In particular, c-Fos-positive cells in the ARC after intracerebroventricular administration of CNP-53 were coexpressed with α-melanocyte-stimulating hormone immunoreactivity. These results indicated that intracerebroventricular administration of CNP induces an anorexigenic action, in part, via activation of the melanocortin system.

Natriuretic peptide receptor-C regulates coronary blood flow and prevents myocardial ischemia/reperfusion injury: novel cardioprotective role for endothelium-derived C-type natriuretic peptide.

BACKGROUND: Ischemia/reperfusion (I/R) injury complicates myocardial infarction and stroke by exacerbating tissue damage and increasing risk of mortality. We have recently identified C-type natriuretic peptide (CNP) as an endothelium-derived hyperpolarizing factor in the mesenteric resistance vasculature and described a novel signaling pathway involving activation of natriuretic peptide receptor C (NPR-C), which plays a pivotal role in the regulation of local blood flow. We tested the hypothesis that CNP/NPR-C signaling is a novel regulatory pathway governing coronary blood flow and protecting against I/R injury. METHODS AND RESULTS: CNP and (Cys18)-atrial natriuretic factor (4-23) amide (cANF(4-23)) elicited dose-dependent decreases in coronary perfusion pressure (CPP) that were blocked by Ba(2+) and ouabain in the isolated Langendorff rat heart. The endothelium-dependent vasodilator acetylcholine elicited the release of CNP from the coronary endothelium. CNP and cANF(4-23) reduced infarct size after 25 minutes of global ischemia and 120 minutes of reperfusion, maintaining CPP and left ventricular pressure at preischemic values. The vasorelaxant and protective activity of CNP and cANF(4-23) were enhanced in the absence of endothelium-derived nitric oxide. CONCLUSIONS: Endothelium-derived CNP is involved in the regulation of the coronary circulation, and NPR-C activation underlies the vasorelaxant activity of this peptide. Moreover, this newly defined pathway represents a protective mechanism against I/R injury and a novel target for therapeutic intervention in ischemic cardiovascular disorders.

Postnatal ontogeny of natriuretic peptide systems in the rat hypothalamus.

Our study has attempted to clarify the developmental profile of atrial natriuretic peptide (ANP) and C-type natriuretic peptide (CNP) along with the expression of their receptors in the rat hypothalamus. Radioimmunoassay (RIA) of dissected hypothalamic tissue revealed that ANP rose from 167 +/- 50 pg/mg protein immediately after birth to 516 +/- 78 pg/mg protein in the next 24 h and to 928 +/- 100 pg/mg protein by postnatal day (PD) 5. A second increment of ANP in the hypothalamus was noted between PD 10 and PD 20 (from 780 +/- 110 to 2,650 +/- 136 pg/mg protein). These changes were not gender-related and consistent with a rise of ANP mRNA. Diethylstilbestrol treatment of immature rats increased hypothalamic ANP concentration from 2.11 +/- 0.24 to 2.97 +/- 0.44 ng/mg protein (P<0.001), but equine chorionic gonadotropin had no effect, indicating that estrogen is a potential stimulus of ANP only at supra-physiological concentrations. CNP, the most abundant natriuretic peptide in the brain, gradually increased in the developing hypothalamus, but did not plateau at PD 20. Reverse transcription-polymerase chain reaction analysis of ANP receptor mRNA demonstrated higher guanylyl cyclase (GC) A, no changes in GC-B, and lower C-receptor levels in adult compared to newborn rats. In conclusion, we have shown that hypothalamic ANP undergoes a dramatic rise after birth, and progresses further until the 3rd postnatal week. ANP and CNP changes in the developing hypothalamus can influence brain maturation.