Integrated analysis of single-cell RNA sequencing and bulk RNA data reveals gene regulatory networks and targets in dilated cardiomyopathy.

Dilated cardiomyopathy (DCM) is a common cause of heart failure, thromboembolism, arrhythmias, and sudden cardiac death. The quality of life and long-term survival rates of patients with dilated DCM have greatly improved in recent decades. Nevertheless, the clinical prognosis for DCM patients remains unfavorable. The primary driving factors underlying the pathogenesis of DCM remain incompletely understood. The present study aimed to identify driving factors underlying the pathogenesis of DCM from the perspective of gene regulatory networks. Single-cell RNA sequencing data and bulk RNA data were obtained from the Gene Expression Omnibus (GEO) database. Differential gene analysis, single-cell genomics analysis, and functional enrichment analysis were conducted using R software. The construction of Gene Regulatory Networks was performed using Python. We used the pySCENIC method to analyze the single-cell data and identified 401 regulons. Through variance decomposition, we selected 19 regulons that showed significant responsiveness to DCM. Next, we employed the ssGSEA method to assess regulons in two bulk RNA datasets. Significant statistical differences were observed in 9 and 13 regulons in each dataset. By intersecting these differentiated regulons and identifying shared targets that appeared at least twice, we successfully pinpointed three differentially expressed targets across both datasets. In this study, we assessed and identified 19 gene regulatory networks that were responsive to the disease. Furthermore, we validated these networks using two bulk RNA datasets of DCM. The elucidation of dysregulated regulons and targets (CDKN1A, SAT1, ZFP36) enhances the molecular understanding of DCM, aiding in the development of tailored therapies for patients.

Low-normal free triiodothyronine as a predictor of post-operative atrial fibrillation after surgical coronary revascularization.

Background: Recent studies have focused on the association between thyroid function within normal range and cardiovascular diseases, especially on free triiodothyronine (FT3) levels. This study aims to evaluate the effects of normal FT3 level on new-onset atrial fibrillation (AF) in patients with surgical coronary revascularization. Methods: The patients who underwent surgical coronary revascularization were enrolled in the retrospective study. Thyroid function was tested after an overnight fast on the first morning of hospitalization. Serum FT3 level was divided into quartile groups within the normal range. Hazards ratios (HRs) of FT3 level for AF were analyzed by COX proportional hazard model. Results: This study included 503 patients with a mean [standard deviation (SD)] age of 63 (±9) years, and 396 (78.73%) were male. Post-operative AF (POAF) occurred in 120 (23.86%) patients at a median of two days after surgical coronary revascularization. The cumulating incidence of AF was significantly higher in the FT3 quartile 1 (Q1) group especially in older patients as evidenced by Kaplan-Meier analysis. Additionally, the patients who experienced AF had longer hospital stays, the same result was also found in the FT3 Q1 group. Further study demonstrated that low-normal FT3 was an independent predictor of POAF [HR =1.52, 95% confidence interval (CI): 1.01, 2.28, P=0.045]. Conclusions: Low-normal FT3 is associated with an increased risk of POAF and is an independent predictor of POAF. Patients who experienced AF have longer hospital stays. The findings may help to identify patients with surgical coronary revascularization at a higher risk for the development of AF.

Research progress on predicting atrial fibrillation recurrence after radiofrequency ablation based on electrocardiogram-related parameters.

Atrial fibrillation (AF) is the most common arrhythmia. It is associated with increased stroke risks, thromboembolism, and other complications, which are great life and economic burdens for patients. In recent years, with the maturity of percutaneous catheter radiofrequency ablation (RFA) technology, it has become a first-line therapy for AF. However, some patients still experience AF recurrence (AFR) after RFA, which can cause serious consequences. Therefore, it is critical to identify appropriate parameters that are predictive of prognosis and to be able to translate the parameters easily into the clinical setting. Here, we reviewed possible predicting indicators for AFR, focusing on all the electrocardiogram indicators, such as P wave duration, PR interval and so on. It may provide valuable information for guiding clinical works.

Exploring an immune cells-related molecule in STEMI by bioinformatics analysis.

BACKGROUND: ST-elevated myocardial infarction (STEMI) is the leading cause of mortality worldwide. The mortality rate of heart attacks has decreased due to various preventive factors and the development of early diagnostic resuscitation measures, but the long-term prognosis remains poor. The present study aimed to identify novel serum biomarkers in STEMI patients and explored a possible new mechanism of STEMI from an immune molecular angle with bioinformatics analysis. METHODS: Gene expression profiles were obtained from Gene Expression Omnibus (GEO) database. Differential gene analysis, machine learning algorithms, gene set enrichment analysis, and immune cell infiltration analysis were conducted using R software. RESULTS: We identified 146 DEGs (differentially expressed genes) in the integrated dataset between the STEMI and CAD (coronary artery disease) groups. Immune infiltration analysis indicated that eleven cell types were differentially infiltrated. Through correlation analysis, we further screened 25 DEGs that showed a high correlation with monocytes and neutrophils. Afterwards, five genes consistently selected by all three machine learning algorithms were considered candidate genes. Finally, we identified a hub gene (ADM) as a biomarker of STEMI. AUC curves showed that ADM had more than 80% high accuracy in all datasets. CONCLUSIONS: In this study, we explored a potentially new mechanism of STEMI from an immune molecular perspective, which might provide insights into the pathogenesis of STEMI. ADM positively correlated with monocytes and neutrophils, suggesting its potential role in the immune response during STEMI. Additionally, we validated the diagnostic performance of ADM in two external datasets, which could help to develop new diagnostic tools or therapeutic strategies.

MiRNA-122-5p inhibitor abolishes angiotensin II-mediated loss of autophagy and promotion of apoptosis in rat cardiofibroblasts by modulation of the apelin-AMPK-mTOR signaling.

MicroRNAs (miRNAs) have emerged as essential regulators that could have pivotal roles in cardiac homeostasis and pathological remodeling of various cardiovascular diseases. We previously demonstrated that miRNA-122-5p overexpression exacerbated the process of vascular hypertrophy, fibrosis, and dysfunction in hypertensive rats and rat aortic adventitial fibroblasts. However, the exact roles and underlying mechanisms of miRNA-122-5p in myocardial fibroblasts remain largely unknown. In this work, neonatal rat cardiofibroblasts (CFs) were isolated and primarily cultured from the hearts of 2- to 3-d-old Sprague-Dawley rats. Stimulation of angiotensin II (Ang II) resulted in marked increases in cellular proliferation and migration and levels of collagen I, collagen III, CTGF, and TGF-ß1 in cultured CFs. Furthermore, Ang II led to promoted expression of P62, Bax, and phosphorylated mTOR as well as downregulation of LC3II, beclin-1, and AMPK-phosphorylated levels, thereby contributing to imbalance of autophagy and apoptosis, and cellular injury in CFs, which were significantly ameliorated by treatment with miRNA-122-5p inhibitor. These changes were associated with decreased levels of collagen I, collagen III, CTGF, and TGF-ß1. Furthermore, Ang II-induced loss of autophagy and promotion of apoptosis in CFs were prevented by the treatment with Pyr1-apelin-13 or AMPK agonist AICAR or mTOR inhibitor rapamycin, respectively. In contrast, administration of miRNA-122-5p mimics and autophagy inhibitor 3-methylademine reversed beneficial roles of Pyr1-apelin-13. Collectively, these data indicated that miRNA-122-5p is an essential regulator of autophagy and apoptosis in rat CFs via the apelin/AMPK/mTOR signaling pathway, which may be potentially used as a therapeutic target in myocardial fibrosis and related diseases.

Use of serum albumin and activities of daily living to predict mortality in long-lived individuals over 95 years of age: a population-based study.

Both activities of daily living (ADL) and some blood biomarkers (such as albumin) have been associated with mortality in very elderly people, but scarce data is available on the predictive performance of them in isolation or in combination, which is important for clinicians in decision making. Here, based on prospective mortality data over a 6-year follow-up period from 433 long-lived individuals (LLIs) aged 95+ years in the Rugao longevity cohort, we aimed to evaluate Cox proportional hazard ratios (HRs) and discriminative power (ROC curve) of 14 biomarkers and ADL for all-cause mortality. We found that six biomarkers (total triglyceride, albumin, low-density lipoprotein cholesterol, platelet count, lymphocyte count, and neutrophil count) were associated with mortality with a p < .10 in the univariate model. Significant associations of albumin and neutrophil count with mortality were observed when they were simultaneously included in a multivariate model, with HRs of 0.97 (95 % CI 0.94, 0.99; p = .005) and 1.09 (95 % CI 1.00, 1.18; p = .043). With respect to ADL, the corresponding HR was 1.10 (95 % CI 1.07, 1.14; p < .001). Low albumin (<40 g/L) combined with ADL dependent had a significantly increased mortality risk (HR = 2.19; 95 % CI 1.63, 2.95). Albumin and ADL separately showed good discriminative accuracies (area under the curve [AUC] = 0.68 and 0.66, respectively), and their combination had an increased predictive utility (AUC = 0.73). In conclusion, both albumin and ADL are efficient predictors of all-cause mortality in long-lived populations and their combination further increases discriminative power. The preliminary findings, if validated and translated, would help clinicians to identify the elderly people at varying mortality risk.

Vascular endothelial function of patients with stable coronary artery disease.

OBJECTIVES: To evaluate vascular endothelial function and contributing factors in coronary heart disease (CHD) patients. METHODS: One hundred twenty six CHD outpatients were randomly recruited. Reactive hyperemia index (RHI) <1.67 indicates endothelial dysfunction. Correlation between RHI and different biochemical parameters was evaluated. RESULTS: RHI in patients receiving statins treatment was significantly higher than patients without statins treatment (P<0.05). RHI in patients with more than 3 risk factors for CHD was also markedly lower than that in patients with ≤2 risk factors (P<0.05). Patients with lesions at several branches of coronary artery had a markedly lower RHI when compared with those with coronary lesions at a single branch (P<0.05). For patients without statins treatment, RHI increased significantly after statins treatment for 1 month (P=0.01). In patients with endothelial dysfunction, FBG, HbA1C, hs-CRP and Hcy were significantly higher than those in patients with normal endothelial function (P<0.05 for all). Smokers with CHD had a remarkably lower RHI when compared with non-smokers (P<0.05). CONCLUSIONS: Smoking, FBG, HbA1C, Hcy and hs-CRP are significantly associated with endothelial dysfunction. Endothelial dysfunction is also related to the numbers of risk factors for CHD, degree of coronary lesions and statins. Statins treatment may significantly improve the endothelial function of CHD patients.

Relationships between Depressive Symptoms and Endothelial Function Among Outpatients of a General Hospital in China.

BACKGROUND: This study aimed to investigate the endothelial function by reactive hyperemia index (RHI) in patients with depression, subjects recovering from depression, and subjects without a history of depression. MATERIAL AND METHODS: Outpatients were recruited from a general hospital in China; 62 patients diagnosed with depression and the 17-item Hamilton Rating Scale for Depression (HAMD17) total scores ≥17 were enrolled as the depression group, 62 patients with a history of depression, discontinuation of antidepressants therapy at least 3 months ago, and HAMD17 ≤7 were recruited as remission group, and 62 subjects without a history of depression served as the control group (HAMD17 ≤7). RESULTS: The mean RHI was 1.93, 2.34, and 2.19 in depression, control, and remission groups, respectively, showing a significant difference among the 3 groups (P=0.0004). In addition, a marked difference in RHI was found between depression and control groups (P=0.0003) and between depression and remission groups (P=0.0270). However, there was no significant difference between remission and control groups (P=0.3363). CONCLUSIONS: There is a relationship between depression and endothelial dysfunction in outpatients from a general hospital in China. The improvement of depression is synchronous with the improvement of endothelial function.

NINJ2 polymorphism is associated with ischemic stroke in Chinese Han population.

Recently, a genome-wide association study reported an association between two single nucleotide polymorphisms (SNPs) rs11833579 and rs12425791 near NINJ2 gene and ischemic stroke in Caucasians. Therefore, NINJ2 gene is an important candidate locus in the prevalence of ischemic stroke. We performed a hospital based genetic association study in Chinese Han subjects to investigate the relationship between NINJ2 gene and ischemic stroke. We genotyped 14 tagging single nucleotide polymorphisms (tSNP) in 749 ischemic stroke subjects and 924 control subjects and conducted the association between these tSNPs and ischemic stroke. We detected a tSNP rs10849373 in the first intron of the NINJ2 gene significantly associated with ischemic stroke (both genotype and allelic p=0.0001). The minor A allele increased the risk of ischemic stroke with a per-allele OR of 1.37 for the additive genetic model in univariate analysis (p=0.0001). The significance remained after adjustment for the covariates of age, gender, BMI, cigarette smoking, alcohol drinking, hypertension, and diabetes. Therefore, we report a new genetic variant, rs10849373, located in the first intron of the NINJ2 gene, conferring risk of ischemic stroke in Chinese Han subjects. Further genetic association and functional studies are required to search the causal functional variant in linkage disequilibrium with this polymorphism.

Hydrogen Sulfide-a potent multichannel anti-arrhythmic drug.

-Arrhythmia is a big headache for cardiologist for a long time. A new antiarrythmic drug with good effects and few side effects should be explored. Hydrogen sulfide, a newly found gaseous transmitter, was found to have multi-effects on a variety of ion channels. It may be a promising antiarrythmic drug. This article reviews the different effects of hydrogen sulfide on different ion channels.

Hydrogen sulfide opens the KATP channel on rat atrial and ventricular myocytes.

OBJECTIVE: Hydrogen sulfide (H(2)S), an endogenous gaseous transmitter, was found to protect the heart from various forms of injury, but the underlying mechanism is not known. H(2)S can open the K(ATP) channel on vascular smooth muscle cells, and the objective of this study was to determine whether H(2)S can open the K(ATP) channel on myocardiocytes. METHODS: The whole-cell patch-clamp technique was used to record I(K,ATP) and action potentials of atrial and ventricular myocytes isolated from the hearts of male Wistar rats. Sodium hydrogen sulfide (NaHS) was used as a donor of H(2)S to observe the effect of exogenous H(2)S on I(K,ATP). DL-propargylglycine (PPG), an inhibitor of the synthesis of H(2)S, was used at a concentration of 200 microM to observe the effect of endogenous H(2)S on I(K,ATP). RESULTS: NaHS at concentrations (in microM) of 9.375, 18.75, 37.5, 75 and 150 increased I(K,ATP) by 12.8% (p > 0.05), 28.4% (p < 0.05), 38.8% (p < 0.01), 51.2% (p < 0.01) and 58.6% (p< 0.01) on ventricular myocytes, respectively, and by 6.8% (p > 0.05), 10.4% (p > 0.05), 18.9% (p < 0.01), 24.8% (p < 0.01) and 37.2% (p < 0.01) on atrial myocytes, respectively. The H(2)S-induced decrease in the duration of action potentials (APD(90)) of ventricular myocytes was concentration-dependent, although only NaHS at a concentration of 150 microM decreased the APD(90) significantly (15%, p < 0.05). The H(2)S-induced decrease in APD(90) on atrial myocytes was concentration dependent, but the statistical difference was not significant. Inhibition of I(K,ATP) by PPG was time dependent and the level of inhibition was: ventricular myocytes, 7% (p > 0.05), 10% (p < 0.05), 15.3% (p < 0.01), 24.0% (p < 0.01) and 28.9% (p < 0.01); atrial myocytes, 15.8% (p > 0.05), 21.3% (p > 0.05), 26.5% (p < 0.01), 34.0% (p < 0.01) and 43.2% (p < 0.01) measured at 5, 10, 15, 20 and 25 min, respectively. The increase in the APD(90), by PPG was time dependent for ventricular myocytes [increased by 12.8% (p < 0.05) at 25 min]. The same was true for atrial myocytes, although only the value at 25 min was significant (15%, p < 0.05). CONCLUSIONS: H(2)S decreased the APD(90),and both the endogenous and exogenous H(2)S-induced increase in I(K,ATP) on both atrial and ventricular myocytes was concentration dependent. These results may help to explain, at least in part, how H(2)S protects heart cells from various forms of injury.

[Effects of hydrogen sulfide on the K ATP current in isolated rat ventricular myocytes].

OBJECTIVE: To investigate the effects of endogenous and exogenous hydrogen sulfide (H(2)S) on the K(ATP) current in isolated rat ventricular myocytes. METHODS: Ventricular myocytes were isolated from rat heart by modified Langendorff perfusion with collagenase. K(ATP) current of single rat ventricular myocytes was recorded by whole-cell patch-clamp technique. RESULTS: The density of K(ATP) current was significantly reduced by 200 micromol/L DL-propargylglycine (PPG, an irreversible inhibitor of the H(2)S) [(5.3258 +/- 0.7556) pA/pF vs. (3.7856 +/- 0.4312) pA/pF, P < 0.01] in a time-dependent way. The density of K(ATP) current could be significantly increased by NaHS (a H(2)S donor, 9.375, 18.75, 37.5, 75, 150 micromol/L) in a concentration-dependent manner [(6.6310 +/- 0.6092) pA/pF vs. (9.0949 +/- 1.0259) pA/pF at 150 micromol/L, P < 0.01]. CONCLUSION: Both endogenous and exogenous H(2)S could open K(ATP) channels and enhance the K(ATP) current in rat ventricular myocytes.

Inhibition of the cystathionine-gamma-lyase/hydrogen sulfide pathway in rat vascular smooth muscle cells by cobalt-60 gamma radiation.

BACKGROUND: Radiation is a promising treatment for in stent restenosis and restenosis following percutaneous transluminal coronary angioplasty, which has troubled interventional cardiologists for a long time. It inhibits neointima hyperplasia, vascular remodeling, and increases the mean luminal diameter. The mechanism of intracoronary brachytherapy for restenosis is not well understood. Endogenous gaseous transmitters including nitric oxide and carbon monoxide are closely related to restenosis. Hydrogen sulfide, a new endogenous gaseous transmitter, is able to inhibit the proliferation of vascular smooth muscle cells and vascular remodeling. This study aimed to clarify the effect of radiation on cystathionine-gamma-lyase/hydrogen sulfide pathway in rat smooth muscle cells. METHODS: We studied the effect of radiation on the cystathionine-gamma-lyase/hydrogen sulfide pathway. Rat vascular smooth muscle cells were radiated with (60)Co gamma at doses of 14 Gy and 25 Gy respectively. Then the mRNA level of cystathionine-gamma-lyase was studied by quantitative reverse-transcription competitive polymerase chain reaction. Hydrogen sulfide concentration in culture medium was determined by methylene blue spectrophotometry. Cystathionine-gamma-lyase activity in vascular smooth muscle cells was also studied. RESULTS: (60)Co gamma radiation at a dose of 1 Gy did not affect the cystathionine-gamma-lyase/hydrogen sulfide pathway significantly. However, (60)Co gamma radiation at doses of 14 Gy and 25 Gy decreased the hydrogen sulfide synthesis by 21.9% (P<0.05) and 26.8% (P<0.01) respectively. At the same time, they decreased the cystathionine-gamma-lyase activity by 15.1% (P<0.05) and 20.5% (P<0.01) respectively, and cystathionine-gamma-lyase mRNA expression by 29.3% (P<0.01) and 38.2% (P<0.01) respectively. CONCLUSION: Appropriate (60)Co gamma radiation inhibits the H(2)S synthesis by inhibiting the gene expression of cystathionine-gamma-lyase and the cystathionine-gamma-lyase activity.

[Hydrogen sulfide: a novel cardiovascular functional regulatory gas factor].

Hydrogen sulfide (H(2)S) may be endogenously produced by cystathionine beta-lyase (CBS) and cystathionine gamma-lyase (CSE) as a cardiovascular physiological functional factor. On the hypoxic pulmonary hypertension (HPH) animal model, the plasma H(2)S concentration, the gene expression and the activity (CSE) were decreased in lung tissues In L-NAME induced hypertension and spontaneous hypertension rats (SHR) models, the plasma H(2)S concentration, vascular CSE activity and mRNA expression were obviously decreased. When H(2)S was exogenously supplied, systolic pressure obviously decrease. These studies suggested that CSE/H(2)S pathway participated in the pathophysiological development of hypertension. The endogenous level of H(2)S produced by some arterial tissues increased in both septic and endotoxic shock rats. The level of H(2)S highly correlated with the endogenous level of NO. These results suggest that H(2)S may be a novel cardiovascular functional regulator.

Effects of cobalt-60 gamma-radiation on the synthesis of adrenomedullin and endothelin in rat vascular smooth muscle cells.

We studied the effects of cobalt-60 Gamma-radiation on the gene expression and secretion of adrenomedullin (Adm) and endothelin (ET) in cultured rat vascular smooth muscle cells (VSMCs). Rat VSMCs cultured in Dulbecoo's modified Eagle's medium containing 10% FBS were radiated with cobalt-60 Gamma-radiation at doses of 1, 14, and 25 Gy, respectively. Then the mRNA of Adm and ET in VSMCs were detected by the reverse-transcriptative competitive polymerase chain reaction. Adm and ET levels in rat VSMCs were measured by radioimmunoassay. As compared with that of the control, the secretions of Adm in rat VSMCs radiated at doses of 14 and 25 Gy were increased by 270% (P < 0.05) and 233% (P < 0.05), respectively. The mRNA levels of Adm were increased by 82.4% (P < 0.01) and 101% (P <0.01), respectively. Meanwhile, the secretions of ET were decreased by 27.3% (P < 0.01) and 58.0% (P < 0.01) in VSMCs radiated at doses of 14 and 25 Gy, respectively. In parallel, the mRNA levels of ET were decreased by 47.1% (P < 0.01) and 40.2% (P < 0.01), respectively. Radiation at a dose of 1 Gy had no significant effect on Adm and ET at the gene and protein levels. As compared with the control, the Adm/ET ratios in VSMCs increased by 65% (P > 0.05), 409% (P < 0.01), and 693% (P < 0.01), respectively, with radiation at doses of 1,14 and 25 Gy, respectively. The balance of Adm/ET in VSMCs could be changed by cobalt-60 Gamma-radiation, which might play an important role in the use of radiotherapy for restenosis.

The role of hydrogen sulfide generation in the pathogenesis of hypertension in rats induced by inhibition of nitric oxide synthase.

OBJECTIVE: The present study intended to investigate whether the impaired H2S synthase/H2S pathway is associated with hypertension. METHODS: Hypertension in Wistar rats was induced by the oral administration of the l-arginine analog, NG-nitro-l-arginine methyl ester (l-NAME) in their drinking water for a period of 6 weeks. The control rats were given plain tap water only. Sodium hydrosulfide (NaHS) was given by intraperitoneal injection to both the control group and the l-NAME-treated group. The systolic BP (blood pressure) was measured by a tail-cuff method using a pulse transducer. Plasma hydrogen sulfide (H2S), and H2S generation by thoracic aorta and superior mesenteric artery, were determined. In addition, the activity of cystathionine-gamma-lyase (CSE) in thoracic aorta and superior mesenteric artery, most responsible for H2S production, was also measured. Competitive reverse transcriptase-polymerase chain reaction (RT-PCR) was used to determine CSE mRNA in thoracic aorta. RESULTS: l-NAME caused a time-dependent elevation of systolic BP. The heart-to-body weight ratio of l-NAME-treated rats was 27% higher than that of controls. The systolic BP in the NaHS-treated l-NAME group was significantly decreased, by 19% (P < 0.01), in comparison with the l-NAME group. The heart-to-body weight ratio decreased significantly by 12%. l-NAME inhibited CSE gene expression significantly. The inhibition of H2S generation and CSE activity by l-NAME was greatly attenuated in the NaHS-treated l-NAME group. However, there was no significant difference in nitric oxide (NO) generation between the l-NAME group and the NaHS-treated l-NAME group. CONCLUSION: In summary, dysfunction of the vascular H2S synthase/H2S pathway was found in l-NAME-induced hypertensive rats. Exogenous H2S effectively prevented the development of hypertension induced by l-NAME. These findings suggest that the H2S synthase/H2S pathway participates in hypertension.

[Effects of peptides originated from the proadrenomedullin on the production of nitric oxide in rat aorta].

OBJECTIVE: To observe the effect of adrenomedullin (ADM) on the production of nitric oxide (NO) in rat aorta and the effect of Proadrenomedullin N-terminal 20 peptide (PAMP) and adrenotensin (ADT) on the ADM-induced NO production. METHODS: Isolated aortic tissues were exposed to ADM, PAMP and ADT for 2 h. The NO production, indicated by nitrite content in the incubated media, and the nitric oxide synthase (NOS) activity in the incubated tissues were assayed. RESULTS: Nitrite productions and NOS activities of the aortic tissues were significantly increased by ADM in a concentration-dependent manner. The nitrite production and NOS activity of the aortic tissues stimulated by ADM (10(-8) mol.L-1) incubation were (0.282 +/- 0.046) mumol per mg protein and (0.323 +/- 0.056) pmol.min-1 per mg protein, respectively, which were greater than those of the control (0.173 +/- 0.026) mumol per mg protein and (0.110 +/- 0.028) pmol.min-1 per mg protein (P < 0.01), respectively. The nitrite production and NOS activity were (0.204 +/- 0.049) mumol per mg protein and(0.178 +/- 0.023) pmol.min-1 per mg protein when the tissues were treated with ADM (10(-8) mol.L-1) and PAMP (10(-8) mol.L-1) in combination, and were (0.150 +/- 0.036) mumol per mg protein and (0.123 +/- 0.031) pmol.min-1 per mg protein when ADM (10(-8) mol.L-1) and ADT (10(-8) mol.L-1) were used in combination, which were significantly less than those in ADM (10(-8) mol.L-1) group. After incubation of the aortic tissues with the same concentrations(10(-8) mol.L-1) of ADM, PAMP and ADT in combination, the nitrite production and NOS activity were (0.162 +/- 0.029) mumol per mg protein and (0.110 +/- 0.024) pmol.min-1 per mg protein, which were also greatly reduced as compared with those of the ADM group (10(-8) mol.L-1, P < 0.01). However, neither PAMP nor ADT had effect on the production of nitrite and NOS activity in the aortic tissues. CONCLUSION: ADM enhanced the NO production in rat aorta, which was antagonized by PAMP and ADT alone or in combination through influencing the NOS activity.

Roles of different peptide fragments derived from proadrenomedullin in the regulation of vascular tone in isolated rat aorta.

The effects of proadrenomedullin N-terminal 20 peptide (PAMP) and adrenotensin (ADT) on adrenomedullin (ADM)-induced vasodilation were investigated in aortic rings from rat. ADM (10(-9) to 10(-7)M) relaxed the aorta preconstricted with phenylephrine in a concentration-dependent manner. Denudation of endothelium or pretreatment with nitric oxide synthase (NOS) inhibitor, L-NAME, attenuated the vasodilatory action of ADM. ADM-induced vasorelaxation in the aortic rings with endothelium was converted to contraction by PAMP, but not by ADT. The ADM-induced vasodilation was not affected by PAMP in aorta rings without endothelium or in intact aortic rings pretreated with L-NAME. ADM-stimulated nitrite production and NOS activity of the aortas, which was inhibited by PAMP, ADT or PAMP plus ADT. ADM, PAMP, and ADT increased the cyclic adenosine monophosphate (cAMP) contents in vascular tissue. The combination of ADM with PAMP or ADT caused a smaller increase in cAMP level as compared with that of PAMP or ADT alone. These results show that ADM-induced endothelium-dependent vasodilation could be converted to vasoconstriction in the presence of PAMP, probably through a NO-dependent pathway. There was no indication that cAMP was involved in the converting effect of PAMP on ADM vasodilator action.