Release of salusin-beta from human monocytes/macrophages

Serum salusin-β levels in patients with systemic lupus erythematosus

OBJECTIVE

Endothelial dysfunction (ED) has an important role in the pathogenesis of systemic lupus erythematosus (SLE). Studies on other inflammatory diseases show that salusin-β with various mechanisms may play a role in the promotion of ED and inflammation. The aim of this study was to measure serum salusin-β levels in SLE patients and evaluate it as a potential biomarker in assessing SLE activity and predicting organ involvement.

METHODS

In a cross-sectional study, 60 patients diagnosed with SLE and 30 age- and sex-matched healthy controls were enrolled. Disease activity of SLE patients was assessed by the systemic lupus erythematosus disease activity index 2000 (SLEDAI-2 K). Serum levels of salusin-ß were measured using a human salusin-ß enzyme-linked immunosorbent assay kit.

RESULTS

Serum salusin-β levels in SLE and control groups were 474.2 ± 117.1 pg/ml and 157.7 ± 88.7 pg/ml, respectively. The difference was significant (P = 0.001). There was no significant correlation between serum salusin-β levels with age (r =  - 0.06, P = 0.632) and SLEDAI (r =  - 0.185, P = 0.158). In patients with nephritis and thrombosis, serum salusin-β was significantly higher. In addition, in patients with serositis, serum salusin-β was significantly lower. Multiple linear regression analysis showed that serum salusin-β levels retained a significant association with nephritis and thrombosis after model adjustment for serositis, nephritis, and thrombosis.

CONCLUSIONS

Our findings showed that salusin-β might have a possible role in the pathogenesis of SLE. Salusin-β may be a potential biomarker for nephritis and thrombosis in SLE. Key Points • Serum salusin-β levels were significantly higher in SLE patients than the control group. • There was no significant correlation between serum salusin-β levels with age and SLEDAI. • Serum salusin-β levels retained a significant association with nephritis and thrombosis.

Salusins: advance in cardiovascular disease research

Salusins are discovered in 2003 and divided into salusin-α and salusin-β, which are bioactive peptides with hemodynamic and mitotic activity and mainly distributed in plasma, urine, endocrine glands and kidneys. A large number of studies have shown that salusins can regulate lipid metabolism, inflammatory response and vascular proliferation. Despite the profound and diverse physiological properties of salusins, the exact mechanism of their cardiovascular effects remains to be determined. The potential mechanisms of action of salusins in cardiovascular-related diseases such as atherosclerosis, hypertension, heart failure, myocardial infarction and myocarditis, and their use as biomarkers of cardiovascular disease are discussed. This review aims to provide a new strategy for the diagnosis and prevention of clinical cardiovascular diseases.

Association Between Dermcidin, Salusin-α, Salusin-β Molecules and Diabetic Foot Infections

Dermcidin, salusin-α, and salusin-β are three recently discovered molecules that confer antimicrobial properties. The present study aims to investigate the association between dermcidin, salusin-α, and salusin-β in the etiopathology of patients with diabetic foot infection. The study included three groups: Group 1 - diabetic foot infection; Group 2 - diabetes without history of diabetic foot; and Group 3 - the control group. Plasma dermcidin, salusin-α, and salusin-β levels were compared across the groups. Median (Q1-Q3) values of plasma dermcidin levels in Groups 1, 2, and 3 were 3.45 (0.8-4.4), 5.2 (3.7-6.4), and 5.8 (3.1-10) ng/mL, respectively. Diabetic foot infection group had significantly lower plasma dermcidin levels compared to diabetes only group and control group (P = .000, ANOVA), whereas there was no statistically significant difference between the Group 2 and Group 3 (P = .163, ANOVA). Salusin-α and salusin-β levels were significantly higher in the Group 3 compared to the other groups. Based on our findings, diabetic foot infection group had significantly lower plasma dermcidin levels and salusin-α and salusin-β levels were significantly higher in the control group. These molecules (dermcidin specifically) can be researched as an adjuvant therapeutic agent in addition to conventional treatments in diabetic foot diabetic foot infections. Also, it can be searched this may prevent many complications including amputation.

Intracerebroventricular salusin-β infusion to rats increases hypothalamus-pituitary-testicular axis hormones

Salusin-β (Sal-β), which originates from preprosalusin, is a multifunctional hormone with a peptide structure. Sal-β exists in the hypothalamus and can stimulate the pituitary gland. The present study was conducted to determine the effects of Sal-β on hormones that play roles in the male reproductive system. Forty male Wistar Albino rats were used in the study. No infusions were performed on the control group, and infusions were applied to the infusion groups (artificial cerebrospinal fluid to the sham group, 2 and 20 nM Sal-β to the experimental group) through intracerebroventricular infusion for 7 days at 10 μl/hour rate. The animals were decapitated after 7 days of infusion; and the hypothalamus, testicles, and blood tissue samples were collected. The gonadotropin-releasing hormone (GnRH) mRNA levels were determined from the hypothalamus tissues by using the Real Time-PCR Method, and the serum luteinizing hormone (LH), follicle-stimulating hormone (FSH) and testosterone levels were determined using the ELISA method. Also, Hematoxylin-Eosin Staining Method was used for histopathological evaluations in the testicle tissues. As a result, Sal-β infusion increased GnRH mRNA levels in hypothalamus tissues (p < 0.05) besides, serum LH, FSH, and testosterone levels of the rats were higher at significant levels following Sal-β infusion compared to the control and sham group (p < 0.05). In the histological examination of the testicle tissues, Sal-β application was found to decrease the seminiferous tubule diameter and germinal epithelial thickness (p < 0.05). This evidence is the first, indicating that Sal-β, which is administered to male rats with central infusion, stimulates hypothalamus and pituitary tissues, and causes increased secretion of male reproductive hormones.

Knockdown of Salusin-β Improves Cardiovascular Function in Myocardial Infarction-Induced Chronic Heart Failure Rats

Salusin-β is a biologically active peptide with 20 amino acids that exerts several cardiovascular activity-regulating effects, such as regulating vascular endothelial function and the proliferation of vascular smooth muscle cells. However, the regulatory effects of salusin-β in myocardial infarction-induced chronic heart failure (CHF) are still unknown. The current study is aimed at investigating the effects of silencing salusin-β on endothelial function, cardiac function, vascular and myocardial remodeling, and its underlying signaling pathways in CHF rats induced by coronary artery ligation. CHF and sham-operated (Sham) rats were subjected to tail vein injection of adenoviral vectors encoding salusin-β shRNA or a control-shRNA. The coronary artery (CA), pulmonary artery (PA), and mesenteric artery (MA) were isolated from rats, and isometric tension measurements of arteries were performed. Compared with Sham rats, the plasma salusin-β, leptin and visfatin levels and the salusin-β protein expression levels of CA, PA, and MA were increased, while the acetylcholine- (ACh-) induced endothelium-dependent vascular relaxation of CA, PA, and MA was attenuated significantly in CHF rats and was improved significantly by salusin-β gene knockdown. Salusin-β knockdown also improved cardiac function and vascular and myocardial remodeling, increased endothelial nitric oxide synthase (eNOS) activity and nitric oxide (NO) levels, and decreased NAD(P)H oxidase activity, NOX-2 and NOX-4 expression, and reactive oxygen species (ROS) levels in arteries in CHF rats. The effects of salusin-β knockdown in CHF rats were attenuated significantly by pretreatment with the NOS inhibitor L-NAME. These results indicate that silencing salusin-β contributes to the improvement of endothelial function, cardiac function, and cardiovascular remodeling in CHF by inhibiting NAD(P)H oxidase-ROS generation and activating eNOS-NO production.

A TOR2A Gene Product: Salusin-β Contributes to Attenuated Vasodilatation of Spontaneously Hypertensive Rats

PURPOSE

Attenuated vasodilatation of small arteries is a hallmark feature of hypertension. Salusin-β, which is a TOR2A gene product and an important vasoactive peptide, has a close relationship with cardiovascular disease. This study aimed to determinate the roles of salusin-β in vasodilatation, and its signal pathways in Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR).

METHODS

Isometric tension experiments were performed. Vasodilatation was induced by acetylcholine (ACh) or sodium nitroprusside (SNP).

RESULTS

Plasma salusin-β levels and their protein expressions in coronary artery (CA), mesenteric artery (MA), and pulmonary artery (PA) of SHR were much higher than that of WKY. Intravenous injection of salusin-β increased arterial blood pressure in SHR, while anti-salusin-β IgG decreased it. Salusin-β further deteriorated, while anti-salusin-β IgG improved, the attenuated ACh-induced relaxation, the decreased nitric oxide (NO) level, and endothelial nitric oxide synthase (eNOS) activity in arteries of SHR, and salusin-β had no significant effect on SNP-induced relaxation. The NAD(P)H oxidase activity and reactive oxygen species (ROS) level in arteries of SHR were much higher than that of WKY, which was further increased by salusin-β but reduced by anti-salusin-β IgG. ROS scavenger NAC or antioxidant apocynin significantly inhibited, while SOD inhibitor DETC aggravated, the effects of salusin-β, and the eNOS inhibitor L-NAME inhibited the effects of anti-salusin-β IgG.

CONCLUSIONS

These results indicated that enhanced salusin-β activity is involved in attenuated endothelium-dependent vasodilatation pathogenesis in SHR by activating NAD(P)H oxidase derived ROS generation and inhibiting eNOS activation and NO release.

Identification and quantification of plasma free salusin-β, an endogenous parasympathomimetic peptide

Salusin-β is an endogenous parasympathomimetic proatherosclerotic peptide. Salusin-β was initially predicted from bioinformatic analyses and later immunologically detected in human biofluids. However, elucidation of salusin-β bioactivity has faced enormous challenges because of its unique physicochemical characteristics that cause it to strongly adhere to laboratory apparatus materials. In the strictest sense, the discovery of bioactive peptides is not complete until their exact native sequences have been confirmed in the peripheral circulation. In this study, we determined the plasma molecular form and levels of free salusin-β to determine its pathophysiological significance. Ultra-high-yield enrichment and preseparation of non-tryptic human plasma was followed by LC-MS/MS, and full-length salusin-β and seven different endogenous fragment sequences were identified. We established a new ELISA that specifically detects plasma free salusin-β without cross-reacting with any of its identified endogenous fragments. Free salusin-β levels exhibited a profound early morning nadir and rapidly decreased in response to parasympathetic nervous augmentation. Our technical advance in plasma native peptide analysis successfully identified a hard-to-detect bioactive peptide, salusin-β, together with its formerly unrecognized fragments, and further suggests that conventional immunological measurements of target peptides may not be fully representative.

The time changes of endogenous salusin-β in septic rats

Salusin-α and salusin-β are newly found bioactive peptides of 28 and 20 amino acids, respectively, which are widely distributed in the hematopoietic system, endocrine system, and central nervous system. Salusins exert cardiovascular effects, including hypotension and bradycardia; promote vascular inflammation; and so on. However, little information is available yet on the relationships of salusin-β with sepsis. In this study, we investigated the distribution and content of endogenous salusin-β in septic rats. A total of 72 specified pathogen-free (SPF) male Sprague-Dawley (SD) rats were randomly divided into control group (sham operation, n = 36) and experimental group (n = 36) with sepsis rat model by cecal ligation and puncture (CLP). The model group rats were sacrificed after 6, 12, and 24 h of treatment. The concentration of salusin-β in spleen, stomach, small intestine, hypothalamus, and serum specimens was detected by enzyme-linked immunosorbent assay (ELISA). It showed that salusin-β was endogenously generated in rat tissues, including spleen, stomach, small intestine, hypothalamus, and serum. The content of salusin-β in the spleen was higher than that in other tissues. The content of salusin-β in the spleen, stomach, and small intestine, together with the serum level of salusin-β, increased significantly at 6 h after CLP compared with the control group ( P < 0.05). The content of salusin-β in spleen and serum peaked at 12 h, and in small intestine, it reached the summit at 24 h. Meanwhile, no significant fluctuations in salusin-β content were observed in the stomach. The content of salusin-β in hypothalamus began to increase at 6 h, and a significant increase appeared 12 h after CLP ( P < 0.05). In conclusion, this study shows that the time-dependent alterations of salusin-β in septic rats suggest that salusin-β might be involved in the pathogenesis of sepsis.

IS SALUSIN-ALPHA A NEW MARKER OF CARDIOVASCULAR DISEASE RISK IN HYPOTHYROIDISM?

Introduction

Salusins are multifunctional endogenous peptides shown in human and rat tissues. Serum salusin α level is decreased in coronary artery disease and lack of salusin α enhances coronary atherosclerosis. Hypothyroidism is a chronic inflammatory disease that has a high risk of developing cardiovascular disease. Here we aimed to search the relationship of overt hypothyroidism and subclinical hypothyroidism with salusin α and other inflammatory markers, also the effect of L-thyroxine treatment on these findings.

Material and Methods

32 patients with overt hypothyroidism taking L-thyroxine treatment, 18 patients with subclinical hypothyroidism without treatment and 25 healthy patients as control group were included in the study. Serum salusin α, TNF α, sCRP, glucose, insulin and lipid levels were tested for all groups and results were evaluated with SPSS statistical analysis method.

Results

HDL, sCRP, salusin mean values were statistically significantly different in all 3 groups. HDL level was statistically significantly higher in control group compared to treatment group. sCRP level was higher and salusin level was lower in both treatment and non-treatment hypothyroidism groups compared to control group. When treatment and non-treatment hypothyroidism groups were compared, there was no statistically significant difference for salusin α, but HDL level was high and insulin level was low statistically significant in treatment group.

Conclusions

Salusin α that is shown to be protective for coronary artery disease and hypertension, is found to be significantly low in hypothyroidism, thus it is a marker that increases the cardiovascular disease risk in this specific patient group.

Salusin-β contributes to vascular inflammation associated with pulmonary arterial hypertension in rats

OBJECTIVE

Inflammation is closely linked to pulmonary arterial hypertension (PAH). Salusin-β, a bioactive peptide, has been reported to participate in vascular inflammation. We therefore hypothesized that salusin-β contributes to monocrotaline (MCT)-induced PAH in rats.

METHODS

Male Sprague-Dawley rats were treated with MCT (60 mg kg(-1), single intraperitoneal injection). Salusin-β expression in the lungs of the MCT-treated rats was evaluated using immunofluorescence staining, western blot, and real-time PCR. For salusin-β blockade assay, rats injected with MCT were given a chronic infusion of anti-salusin-β immunoglobulin G (IgG) (salusin-β blocker, 1.0 μg kg(-1) h(-1)) or isotype-matched control IgG. Four weeks after MCT+anti-salusin-β treatment, the effects of salusin-β blockade were determined using hemodynamics, western blot, real-time PCR, and immunohistochemical detection. The effect of salusin-β on human pulmonary arterial endothelial cell (HPAEC) function was detected by adhesion and tube formation experiments in vitro.

RESULTS

Salusin-β expression was significantly increased in the lungs of the MCT-treated rats, and immunofluorescence results showed that salusin-β was predominantly expressed in pulmonary macrophages and vascular endothelial cells. Salusin-β blockade significantly ameliorated PAH by acting against pulmonary vascular remodeling, decreasing macrophage infiltration, and reducing pro-inflammatory cytokine expression and nuclear factor-kappa B (NF-κB) activity in the lungs of the MCT-treated rats. In addition, salusin-β could induce cell adhesion and accelerate angiogenesis by activating the NF-κB pathway and promoting pro-inflammatory cytokine expression in the cultured HPAECs. This effect was suppressed by addition of the NF-κB inhibitor, N-acetyl-L-cysteine.

CONCLUSIONS

Salusin-β plays a crucial role in the development of MCT-induced PAH models.

Salusin-β as a powerful endogenous antidipsogenic neuropeptide

Salusin-β is an endogenous parasympathomimetic peptide, predominantly localized to the hypothalamus and posterior pituitary. Subcutaneously administered salusin-β (50 nmol/mouse) significantly increased water intake but did not affect locomotor activity or food intake. The salusin-β-induced increase in water intake was completely abrogated by pretreatment with muscarinic antagonist, atropine sulphate. In contrast, intracerebroventricular injection of salusin-β, at lower doses (10–100 fmol/mouse) caused a long-lasting decrease in water intake and locomotor activity throughout the entire dark phase of the diurnal cycle. Pre-injection of intracerebroventricular anti-salusin-β IgG completely abrogated the central salusin-β mediated suppression of water intake and locomotor activity. These results demonstrate contrasting actions of salusin-β in the control of water intake via the central and peripheral systems and highlight it as a potent endogenous antidipsogenic neuropeptide.

A short history, principles, and types of ELISA, and our laboratory experience with peptide/protein analyses using ELISA

Playing a critical role in the metabolic homeostasis of living systems, the circulating concentrations of peptides/proteins are influenced by a variety of patho-physiological events. These peptide/protein concentrations in biological fluids are measured using various methods, the most common of which is enzymatic immunoassay EIA/ELISA and which guide the clinicians in diagnosing and monitoring diseases that inflict biological systems. All the techniques where enzymes are employed to show antigen-antibody reactions are generally referred to as enzymatic immunoassay EIA/ELISA method. Since the basic principles of EIA and ELISA are the same. The main objective of this review is to present an overview of the historical journey that had led to the invention of EIA/ELISA, an indispensible method for medical and research laboratories, types of ELISA developed after its invention [direct (the first ELISA method invented), indirect, sandwich and competitive methods], problems encountered during peptide/protein analyses (pre-analytical, analytical and post-analytical), rules to be followed to prevent these problems, and our laboratory experience of more than 15 years.

Is the serum level of salusin-β associated with hypertension and atherosclerosis in the pediatric population?

BACKGROUND

Salusins are recently identified endogenous bioactive peptides that have hypotensive and bradycardiac effects. Salusin-β is involved in the pathogenesis of human atherosclerosis.

METHODS

This was a prospective cohort study of a young patient population with hypertension (HTN). Based on ambulatory blood pressure monitoring (ABPM), the adolescents were categorized into two groups, namely, a hypertensive group consisting of patients with essential (primary) HTN (HTN group) and a group consisting of patients with white-coat HTN [reference (R) group]. Correlations between serum salusin-β level and clinical, laboratory and ambulatory blood pressure (BP) variables were assessed.

RESULTS

The median salusin-β concentration was significantly higher in patients with essential HTN than in those with white-coat HTN (R group). Salusin-β was positively correlated with the body mass index Z-score, systolic and diastolic blood pressure (BP) from three independent measurements, mean systolic BP during the daytime, triglyceride (TG) level, and atherogenic index (TG/high-density lipoprotein-cholesterol ratio).

CONCLUSIONS

The results of this preliminary study suggest that salusin-β may play an important role in the pathogenesis of HTN in a young population. Further research should focus on the role of salusin-β in the mechanism of essential HTN and the assessment of possible correlations between salusin-β and other well-known markers of atherosclerosis in both teenagers and adults. This research should serve as a base for future studies in this field.

Salusin-β not salusin-α promotes vascular inflammation in ApoE-deficient mice via the I-κBα/NF-κB pathway

Objective

Vascular inflammation plays an important role in the development and progression of atherosclerosis. Recently, salusins (salusin-α and salusin-β) have been reported to be associated wtih atherosclerosis. However, its underlying mechanism remains incompletely known. In this study, we observed the effects of salusins on vascular inflammation in apoE-deficient (apoE-/-) mice.

Methods and Results

Six-week old male apoE-/- mice were infused with salusin-α, salusin-β or vehicle for 8 weeks via osmotic mini-pumps. Our results showed that apoE-/- mice receiving vehicle alone developed severe atherosclerotic lesions and dyslipidemia, with significantly up-regulated levels of IL-6, TNF-α, VCAM-1 and MCP-1. For apoE-/- mice receiving 8 weeks of salusin-β infusion, the atherosclerotic lesions were markedly aggravated, and the levels of IL-6, TNF-α, VCAM-1 and MCP-1 were substantially increased, despite a similar plasma lipid concentration with that of apoE-/- mice. However, after 8 week-infusion of salusin-α, apoE-/- mice presented significant amelioration in atherosclerotic lesions, along with remarkably up-regulated level of high-density lipoprotein-cholesterol (HDL-C) and down-regulated levels of IL-6 and TNF-α, but without any effect on the expressions of VCAM-1 and MCP-1. Furthermore, the activation of nuclear factor-κB (NF-κB), an important transcription factor essential for inflammatory molecules, and the degradation of I-κBα, an inhibitor of NF-κB, were markedly increased in apoE-/- mice receiving vehicle alone. Treatment with salusin-β not salusin-α could remarkably accelerate the process of NF-κB nuclear translocation and I-κBα degradation.

Conclusion

Salusin-β, but not salusin-α, promotes vascular inflammation in apoE-deficient mice via the I-κBα/NF-κB pathway. These findings provide further insight into the mechanism of salusins in atherosclerosis and potential targets for the prevention and treatment of atherosclerosis.

Serum salusin-α levels in systemic lupus erythematosus and systemic sclerosis

OBJECTIVE

Systemic lupus erythematosus (SLE) and systemic sclerosis (SSc), chronic inflammatory diseases, demonstrate an increased incidence of cardiovascular manifestations and subclinical atherosclerotic disease. Salusin-α is a novel bioactive peptide that suppresses the formation of macrophage foam cells, and its serum level is significantly lower in patients with angiographically proven coronary artery disease. The aims of the study were to assess serum salusin-α level and its potential association with the predictors of atherosclerosis in SLE and SSc.

MATERIAL AND METHODS

The study included 20 SLE and 22 SSc patients and 23 healthy controls (HC). All of the participants were female. Tumour necrosis factor-α (TNF-α), IL-6 and salusin-α levels, homeostasis model assessment for insulin resistance (HOMA-IR) index and common carotid intima-media thickness (IMT) were determined.

RESULTS

Salusin-α levels were lower and the IMTs were higher in the SLE and SSc groups than in the HC group. The salusin-α level was correlated with neither the disease activity scores nor cytokine levels and IMT in the SLE and SSc groups, although it was correlated with triglyceride level in the SLE group (r=-0.564, p=0.012), and with HOMA-IR index in the HC group (r=0.485, p=0.019).

CONCLUSION

The present preliminary study may support the idea that SSc leads to subclinical atherosclerosis, as in SLE. Moreover, it can be concluded that the decreased salusin-α levels in SLE and SSc may contribute to subclinical atherosclerosis. However, further studies with larger sample size are needed to demonstrate this contribution in SLE and SSc.

Concentrations of preptin, salusins and hepcidins in plasma and milk of lactating women with or without gestational diabetes mellitus

This study was undertaken to ascertain whether human milk contains preptin, salusin-alpha (salusin-α) and -beta (salusin-β) and pro-hepcidin and hepcidin-25, and whether there are relationships between plasma and milk preptin, salusin-α and -β and pro-hepcidin and hepcidin-25 concentrations in lactating mothers with and without gestational diabetes mellitus (GDM). Blood was obtained from non-lactating women (n = 12), non-diabetic lactating women (n = 12), and GDM lactating women (n = 12). Colostrum, transitional milk, and mature milk samples were collected just before suckling from healthy and GDM lactating women. Peptides concentrations were determined by ELISA and EIA. Mammary gland tissues were screened immunohistochemically for these peptides. Women with GDM had significantly higher plasma and colostum preptin concentrations than healthy lactating women during the colostral and transitional milk period. Salusin-alpha and -beta levels in milk and plasma were lower in women with GDM. Salusin-α and -β were significantly lower in both plasma and colostrums of GDM than of healthy lactating women. Women with GDM had significantly higher colostum prohepcidin and hepcidin-25 concentrations than healthy lactating women during the colostral period. Plasma prohepcidin was also higher in women with GDM than in healthy lactating women during the colostral period, but plasma prohepcidin and hepcidin-25 levels decreased during mature milk period. Transitional milk pro-hepcidin and hepcidin-25 levels in women with GDM were higher than in healthy lactating women. All these results revealed that the mammary gland produces those peptides, which were present in milk at levels correlating with plasma concentrations.

Circulating levels of human salusin-β, a potent hemodynamic and atherogenesis regulator

Using bioinformatics analysis, we previously identified salusin-β, an endogenous bioactive peptide with diverse physiological activities. Salusin-β is abundantly expressed in the neuroendocrine system and in systemic endocrine cells/macrophages. Salusin-β acutely regulates hemodynamics and chronically induces atherosclerosis, but its unique physicochemical characteristics to tightly adhere to all types of plastic and glassware have prevented elucidation of its precise pathophysiological role. To quantitate plasma total salusin-β concentrations, we produced rabbit and chicken polyclonal antibodies against the C- and N-terminal end sequences, circumvented its sticky nature, and successfully established a sandwich enzyme-linked immunosorbent assay (ELISA). Salusin-β was abundantly present in the plasma of healthy volunteers, ranging from 1.9 to 6.6 nmol/L. Reverse phase-high performance liquid chromatography analysis showed that a single immunoreactive salusin-β peak coincided with synthetic authentic salusin-β. Plasma salusin-β concentrations were unaffected by postural changes and by potent vasopressin release stimuli, such as hypertonic saline infusion or smoking. However, salusin-β concentrations showed significant circadian variation; concentrations were high during the daytime and reached the lowest concentrations in the early morning. Plasma salusin-β levels in subjects with diabetes mellitus, coronary artery disease, and cerebrovascular disease showed distinctly higher levels than healthy controls. Patients with panhypopituitarism combined with complete central diabetes insipidus also showed significantly higher plasma salusin-β levels. Therefore, the ELISA system developed in this study will be useful for evaluating circulating total salusin-β levels and for confirming the presence of authentic salusin-β in human plasma. The obtained results suggest a limited contribution of the neuroendocrine system to peripheral total salusin-β concentrations and a role for plasma total salusin-β concentrations as an indicator of systemic vascular diseases.

Effects of Salusin-β on action potential and ionic currents in ventricular myocytes of rats

AIM

Salusin-β is a regulatory peptide that exerts negative inotropic effect on ventricular muscle, but its electrophysiological effects on ventricular myocytes are still unknown.

METHODS

Action potential and channel currents such as sodium current (I(N) (a) ), transient outward potassium current (I(to) ), steady-state potassium current (I(sus) ), sodium-calcium exchange current (I(N) (aCa) ) and inward rectifier potassium current (I(K) (1) ) were measured in ventricular myocytes isolated from 12 to 16 weeks rats by whole-cell voltage-clamp techniques.

RESULTS

Salusin-β dose-dependently shortened the duration of action potential in rat ventricular myocytes. Furthermore, salusin-β significantly inhibited I(N) (aCa) and increased I(to) , but did not affect I(N) (a) , I(sus) and I(K) (1) .

CONCLUSION

These results suggest that the effect of salusin-β on action potential may be partly attributed to a decrease in inward currents and an increase in outward currents.

Serum concentration and kidney expression of salusin-α and salusin-β in rats with metabolic syndrome induced by fructose

Salusins expressed in a variety of tissues exert a hypotensive effect owing to their vasodilator action. They are found in serum and tissues in two different forms: salusin-α and salusin-β. Metabolic syndrome (MetS) is an important public health problem characterized by diabetes, obesity, abnormal blood lipid levels and high blood pressure. We investigated how salusins in the circulation and in kidney tissues change in relation to MetS. Experiments were conducted on 5-week-old Sprague-Dawley male rats assigned to either a control group or a MetS group. Controls were fed standard rat food and water ad libitum, while the MetS group was fed standard food with 10% fructose solution added to their drinking water for three months. After three months, all animals were sacrificed after a one night fast. Blood and tissues were collected and stored appropriately. Biochemical parameters were analyzed using the Konelab 60 auto-analyzer. Salusin-α and salusin-β levels in the blood and kidneys were studied using the ELISA method. The salusin expression in the renal tissue was shown by immunohistochemical staining. Compared to the control group, the MetS group showed elevated uric acid and other lipid parameters for high-density lipoprotein cholesterol. Serum salusin-α and salusin-β levels were decreased; however, salusin levels/mg kidney tissue were elevated. Immunohistochemical analysis of salusins in kidney tissue revealed their presence in the epithelium cells of the glomeruli, and proximal and distal tubule cells. The expression of both peptides in renal tissues was greater in the MetS group than in the control group. We believe that salusins are critical mediators in the etiopathology of MetS. Altered salusin levels are thought to regulate hypertension, which is a component of MetS.

The bioactive peptides salusins and apelin-36 are produced in human arterial and venous tissues and the changes of their levels during cardiopulmonary bypass

This study aimed to examine the effects of CPB on salusin-α, salusin-β and apelin-36 bioactive peptides in people who are planned to undergo coronary artery bypass graft (CABG) operation due to coronary artery disease and to explore whether these peptides are produced in human aortic, saphenous and arterial tissues. The study included age and BMI matched 15 patients who underwent CABG operation by CPB. In order to determine salusin-α, salusin-β and apelin-36 levels, venous blood samples were collected before induction of anesthesia (T1), before CPB (T2), 5 min before the removal of cross-clamp (T3), 5 min after the removal of cross-clamp (T4), upon arrival in the intensive care (T5), at postoperative 24th hour (T6) and 72nd hour (T7). Salusin and apelin expressions of the tissues were shown by immunohistochemical method. Peptide amounts of sera and tissues were measured using ELISA. Salusins production by vessels occurs in fibroblast cells of the media in the aorta and smooth muscle cells of the media in the LIMA and saphena. Apelin is produced by endothelial cells of the intima and fibroblast cells of the media in the aorta and by smooth muscle cells of the media in the LIMA and saphena. Changes in the levels of salusin-β and apelin-36 were significant during CPB. Salusin-α, salusin-β and apelin-36 are locally synthesized in the arteries and veins. Salusins and apelin-36 might be important markers in the CPB, and also that salusin-β was more specific in comparison to salusin-α.

Distinct systemic distribution of salusin-α and salusin-β in the rat

Salusin-α and salusin-β are multifunctional bioactive peptides that were initially predicted using in silico analyses. These peptides should be concomitantly biosynthesized from prosalusin in humans. However, little information is available yet on the biosynthesis and mode of presence of salusin-α and salusin-β in non-human species. In the present study, we examined whether salusin-α and salusin-β are conserved in the rat and whether salusin-α and salusin-β show distinct systemic distributions. Immunohistochemical analysis of rat tissues using a specific anti-rat salusin-α antibody detected immunoreactivity extensively in neuronal cells and fibers, and abundantly in the epithelial tissues throughout the organs. This distribution contrasts sharply with that of salusin-β, which is mainly localized to the neuroendocrine and hematopoietic systems. Western blot analysis of rat spleen extracts showed the presence of cleaved fragments corresponding to putative rat salusin-α. Reverse-phase and gel filtration high performance liquid chromatography analyses coupled with radioimmunoassay detection of rat urine extracts revealed a major immunoreactive component that co-eluted with synthetic putative rat salusin-β. These data support the processing of rat prosalusin into salusin-α and salusin-β despite absent dibasic amino acids between the two.

Serum levels and urinary excretion of salusin-alpha in renal insufficiency

Salusin-alpha was recently shown to exert anti-atherosclerotic effects and its potential role as a clinical marker for atherosclerosis has been proposed. We determined serum salusin-alpha concentrations in 99 patients across a diverse range of renal functions and urinary salusin-alpha excretions in 12 patients with non-dialyzed renal failure using a highly sensitive and specific radioimmunoassay. Serum salusin-alpha concentrations in patients with moderate to advanced renal insufficiency (eGFR < 30 ml/min/1.73 m(2)) were significantly lower than those with preserved renal function (eGFR > 60 ml/min/1.73 m(2)) (6.1 + or - 2.4 pmol/l vs. 11.8 + or - 1.1 pmol/l, p < 0.05). Since renal failure is frequently associated with atherosclerosis, we analyzed the relationship between serum salusin-alpha and eGFR after excluding patients with advanced atherosclerotic diseases. The serum salusin-alpha level was correlated with eGFR values (n = 94, p < 0.005). Patients with renal insufficiency showed reduced urinary salusin-alpha excretion, but the magnitude of the reduction was less than that for the decrease in serum salusin-alpha. Consequently, their salusin-alpha clearance often exceeded endogenous creatinine clearance levels. In conclusion, the decreased serum concentrations of salusin-alpha, an anti-atherosclerotic peptide, may be associated with impaired renal function, suggesting a potential role of decreased salusin-alpha in the acceleration of atherosclerosis in chronic kidney diseases. Urinary salusin-alpha may originate from the renal tubules, and may not necessarily represent the peptides filtered at the glomerulus.