Presence of immunoreactive salusin-alpha in human serum and urine

The relationship of salusins with Parkinson's Disease, Alzheimer's Disease, and acute ischemic stroke: A preliminary study

Neuroinflammation, oxidative stress, and apoptosis play important roles in the pathophysiology of Alzheimer's Disease (AD), Parkinson's Disease (PD), and Acute Ischemic Stroke (AIS). Salusin-α and salusin-β peptides, which were shown to be present in many tissues, including the central nervous system, were also shown to be associated with apoptosis, inflammation, and oxidative stress. In the present study, the relationship between Salusin-α and salusin-β peptides and AD, PD, and AIS were investigated. A total of 179 people were included in the present study, including 46 AD, 44 PD, 42 AIS, and 47 controls. Plasma Salusin-α and salusin-β levels were measured with the ELISA Method. The plasma salusin-β levels of AD, PD, and AIS patients were lower than the control group at significant levels (p < 0.05). It was also found that there were correlations between salusin-α and salusin-β levels and age, triglyceride, LDL-c, total cholesterol, and hemoglobin levels. In this study, we found that salusin- β, an endogenous neuropeptide, was associated with AD, PD and AIS. The low level of salusin-β in these diseases in which neuronal damage occurs may be related to the neuroprotective properties of this endogenous peptide. Further studies are needed to fully understand the relationship between salusin-β and the pathophysiology of these diseases.

Serum salusin-α and salusin-β levels in patients with psoriatic arthritis

INTRODUCTION

Psoriatic arthritis (PsA) is a chronic inflammatory disease characterized by skin lesions and joint involvement. Salusin-α and salusin-β are two new bioactive molecules. It is reported that salusins may have role in regulation of the immune system and inflammation. The aim of our study was to evaluate the serum salusin-α and salusin-β levels in PsA patients and to establish the possible relationship with the disease features.

MATERIAL AND METHODS

Our study included 40 PsA patients who fulfilled the CASPAR criteria and 40 healthy volunteers. Demographic, clinical, laboratory and radiological data and disease activity indices (PASI, BASDAI, BASFI, HAQ) were recorded in all patients. The enzyme-linked immunosorbent assay (ELISA) method was used to measure serum salusin-α and salusin-β levels.

RESULTS

The demographic data were as follows: 13 patients (32.5%) were males and 27 (67.5%) were female, mean age was 48.5 years and mean disease duration was 2.4 years. Patients' history was taken and clinical assessment was performed; 20 (50%) patients had a family history, 18 (45%) patients were smoker, 19 (47.5%) patients had HLA-B27 positivity, 33 (82.5%) had sacroiliitis, 36 (90%) had enthesitis, 23 (57.5%) had distal interphalangeal (DIP) joint and nail involvement, 26 (65%) had wrist involvement, and 11 (27.5%) had ankle involvement. Laboratory data of the patients were recorded; 20 (50%) patients had elevated CRP level and 25 (62.5%) patients had an elevated ESR level. The study results showed that PsA patients had an elevated serum salusin-α level when compared with the control group (p = 0.004). The association between serum salusin-α level and ankle arthritis was found (p = 0.04). Serum levels of salusin-β were similar in PsA patients and controls both (p = 0.285).

CONCLUSIONS

We found elevated serum salusin-α in PsA patients while the serum salusin-β levels were normal. Salusin-α may have a possible role in disease pathogenesis and it may be use as a reliable biomarker in PsA patients. Multicenter prospective studies are needed in this regard.

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.

Influence of irisin on diet-induced metabolic syndrome in experimental rat model

OBJECTIVE

To evaluate the influence of irisin on the experimental paradigm of non-alcoholic fatty liver (NAFL) as a part of MetS cluster.

METHODS

Forty male albino rats were divided into four groups; normal control, standard diet + irisin, high carbohydrate and fat diet (HCHF), and HCHF + irisin. After the experimental period, levels of fasting blood sugar (FBS), insulin, lipid profile, kidney functions, salusin-alpha (Sal-α), adropin, and retinol-binding protein-4 (RBP-4) were evaluated. Peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1α) expression in skeletal muscle was evaluated by quantitative real-time PCR. Aorta, liver, pancreas, and skeletal muscle tissue samples were prepared for histopathological examination.

RESULTS

Rats administrated HCHF showed elevated levels of FBS, lipid profile, kidney functions, RBP-4, and downregulation of PGC-1α expression along with a decline in levels of insulin, Sal-α, and adropin while administration of irisin significantly attenuated these levels.

CONCLUSIONS

Irisin as based therapy could emerge as a new line of treatment against MetS and its related diseases.

Salusin-β Mediates High Glucose-Induced Inflammation and Apoptosis in Retinal Capillary Endothelial Cells via a ROS-Dependent Pathway in Diabetic Retinopathy

BACKGROUND

Diabetic retinopathy (DR) is characterized by retinal vascular endothelial cell death and vascular inflammation, which are microvascular complications of diabetes mellitus (DM). Salusin-β, a newly identified peptide, is closely associated with hypertension, atherosclerosis and diabetic cardiomyopathy. However, the exact role of salusin-β in high glucose (HG)-induced retinal capillary endothelial cell (REC) inflammation and apoptosis remains unclear.

PATIENTS AND METHODS

A total of 60 patients with type 2 diabetes and 20 healthy controls were included in this study. Based on fundus fluorescein angiography findings, the diabetic patients were divided into three subgroups: diabetes without retinopathy (DWR), non-proliferative DR (NPDR) and proliferative DR (PDR). Serum salusin-β levels were measured by enzyme-linked immunosorbent assay. Human RECs (HRECs) were cultured in normal glucose (NG) and HG medium with or without salusin-β. Salusin-β expression was analysed by Western blotting and immunofluorescence staining. Expression of the pro-inflammatory cytokines MCP-1, IL-1β, TNF-α, and VCAM-1 was analysed by Western blotting. Reactive oxygen species (ROS) production was measured with 2',7'-dichlorofluorescein diacetate (DCFH-DA). Cell apoptosis rates were determined by flow cytometry. The levels of p38, JNK, p-p38, and p-JNK and the apoptosis-related proteins cleaved caspase-3, Bax, and cl2 were analysed by Western blotting.

RESULTS

Serum salusin-β levels were higher in diabetic patients than in healthy controls (p = 0.0027), especially in patients with NPDR and PDR (both p<0.01). HG upregulated salusin-β expression in HRECs in a time-dependent manner. Salusin-β exacerbated inflammation and apoptosis, upregulated intracellular ROS production in HG-induced HRECs, and activated ROS-dependent JNK and p38 MAPK signalling, while knockdown of salusin-β suppressed these effects.

CONCLUSION

Our findings indicate that salusin-β can promote inflammation and apoptosis via ROS-dependent JNK and p38 MAPK signalling in HG-induced HRECs and could be a therapeutic target for DR.

Salusin- is superior to salusin- as a marker for evaluating coronary atherosclerosis

Objective

This study was performed to evaluate the interaction effect of salusin-α and salusin-β on coronary artery injury or stenosis.

Methods

The salusin-α and salusin-β concentrations were measured by enzyme-linked immunosorbent assay in 256 patients who underwent coronary angiography for chest pain, and coronary artery stenosis was assessed by the SYNTAX scoring system. Multivariate logistic regression was used to analyze the correlation between variables and coronary artery stenosis. The interaction of salusin-α and salusin-β on coronary artery stenosis was further explored by multiple linear regression.

Results

The model goodness of fit (R) for the interaction effect of salusin-α and salusin-β on coronary artery stenosis was 0.863, and the adjusted R value revealed that the interaction could explain 74.3% of the variation in SYNTAX scores. The F-statistic exceeded F_0.05 (3.031485935) and P < 0.001, further showing that salusin-α and salusin-β had a significant interaction effect on coronary artery stenosis. The standard coefficient for salusin-β (0.797) was higher than that for salusin-α (−0.367, indicating an inhibitory effect), showing that salusin-β had a greater effect on coronary artery stenosis.

Conclusions

Salusin-β, a potential marker for assessing coronary atherosclerosis, was superior to salusin-α, contributing to our understanding of the etiology of coronary artery stenosis.

The importance of circulating levels of salusin-α, salusin-β, and heregulin-β1 in atherosclerotic coronary arterial disease

OBJECTIVE

The relationship between the severity of atherosclerotic coronary artery disease (CAD) and circulating levels of salusin-α, salusin-β and heregulin-β1 has been investigated. In addition, the relationship with these peptides and high sensitive C-reactive protein (hsCRP) has been investigated.

METHODS

The study was conducted on 55 volunteers who had normal coronary angiography (CAG) as the control group, 35 volunteers with the degree of coronary artery stenosis below 50% in CA as the non-critical stenosis group, 37 volunteers with narrowing of one coronary artery above 50% as single vessel group and 41 volunteers with narrowing of more than one coronary artery above 50% as multi-vessel group. One hundred and thirteen volunteers have been included to CAD group.

RESULTS

There was no statistically significant difference in serum salusin-α levels between groups. Serum salusin-β ve hsCRP levels were significantly lower in control group compared to other groups and CAD group. There was no statistically significant difference in salusin-β and salusin-α levels in reciprocal comparison of other groups other than heregulin-β1 levels. Heregulin-β1 levels were significantly lower in 'non-critical occlusion' and 'multiple artery occlusion' groups compared to control group. Heregulin-β1 levels in 'single artery occlusion' group were significantly higher than control, 'non-critical occlusion' and 'multiple artery occlusion' groups.

CONCLUSION

Salusin-α levels does not indicate any significant differences between any groups in our study however the relationship of salusin-α with salusin- β and heregulin-β1 levels drives to cogitate that these peptides can be used as biomarkers and therapeutic approaches in CAD. We think that these peptides will be used in laboratories routinely in future in addition to hsCRP for CAD.

Potent Antibacterial Activity of Synthetic Peptides Designed from Salusin-β and HIV-1 Tat(49-57)

Salusin-β is an endogenous bioactive peptide that was identified in a human full-length enriched cDNA library using bioinformatics analyses. In our previous study, we found that synthetic salusin-β exhibits antibacterial activity against only Gram-positive microorganisms such as Staphylococcus aureus NBRC 12732. Salusin-β has an ability to depolarize the cytoplasmic membrane of this bacterium, and this phenomenon may be linked to the antibacterial activity of this peptide. A cell-penetrating peptide (CPP), human immunodeficiency virus (HIV)-1 transactivator of transcription (Tat) (49-57) is a short cationic peptide that can traverse cell membranes. In this report, synthetic peptide conjugates of salusin-β and HIV-1 Tat(49-57) showed potent antibacterial activities against both Gram-positive Staphylococcus aureus NBRC 12732 and Gram-negative Escherichia coli NBRC 12734. The synthetic peptides also depolarized the cytoplasmic membrane of Escherichia coli NBRC 12734 as well as Staphylococcus aureus NBRC 12732. These results suggested that HIV-1 Tat(49-57) is a protein transduction domain or CPP that changes the interaction mode between salusin-β and the cell membrane of Escherichia coli NBRC 12734. By binding to HIV-1 Tat(49-57), salusin-β showed a broad antibacterial spectrum regardless of whether the target was a Gram-positive or Gram-negative bacterium.

Salusin-β Is Involved in Diabetes Mellitus-Induced Endothelial Dysfunction via Degradation of Peroxisome Proliferator-Activated Receptor Gamma

The pathophysiological mechanisms for vascular lesions in diabetes mellitus (DM) are complex, among which endothelial dysfunction plays a vital role. Therapeutic target against endothelial injury may provide critical venues for treatment of diabetic vascular diseases. We recently identified that salusin-β contributed to high glucose-induced endothelial cell apoptosis. However, the roles of salusin-β in DM-induced endothelial dysfunction remain largely elusive. Male C57BL/6J mice were used to induce type 2 diabetes mellitus (T2DM) model. Human umbilical vein endothelial cells (HUVECs) were cultured in high glucose/high fat (HG/HF) medium. We demonstrated increased expression of salusin-β in diabetic aortic tissues and high-glucose/high-fat- (HG/HF-) incubated HUVECs. Disruption of salusin-β by shRNA abrogated the reactive oxygen species (ROS) production, inflammation, and nitrotyrosine content of HUVECs cultured in HG/HF medium. The HG/HF-mediated decrease in peroxisome proliferator-activated receptor γ (PPARγ) expression was restored by salusin-β shRNA, and PPARγ inhibitor T0070907 abolished the protective actions of salusin-β shRNA on endothelial injury in HG/HF-treated HUVECs. Salusin-β silencing obviously improved endothelium-dependent vasorelaxation, oxidative stress, inflammatory response, and nitrative stress in diabetic aorta. Taken together, our results highlighted the essential role of salusin-β in pathological endothelial dysfunction, and salusin-β may be a promising target in treatment of vascular complications of DM.

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.

Salusins and adropin: New peptides potentially involved in lipid metabolism and atherosclerosis

Dyslipidemia is one of the most potent risk factors for the development of atherosclerosis. The high atherosclerotic risk in dyslipidemic patients is associated with endothelial dysfunction. During the last two decades, novel bioactive peptides have emerged as potential biomarkers of endothelial dysfunction and dyslipidemia-salusins and adropin. Salusin-alpha is likely to prevent atherosclerosis, while salusin-beta may act as a potential proatherogenic factor. Adropin was recently identified as important for energy homeostasis and lipid metabolism. Adropin is closely related to the inhibition of atherosclerosis by up-regulation of the endothelial nitric oxide synthase expression through the vascular endothelial growth factor receptor-2. These peptides represent a novel target to limit diseases characterized by endothelial dysfunction and may form the basis for the development of new therapeutic agents for treating metabolic disorders associated with atherosclerosis.

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.

Physiological fluctuations of human plasma total salusin-β, an endogenous parasympathomimetic/proatherosclerotic peptide

Salusin-β is an endogenous bioactive peptide that systemically exerts acute parasympathomimetic hemodynamic actions and locally induces atherogenesis. Due to its unique physicochemical characteristics to immediately adhere to all types of plastic and glassware, its plasma concentrations have only been successfully determined very recently. Using a total of 50 healthy adults (median age 28 years, range 24-57 years), we evaluated whether circulating salusin-β levels are affected by the autonomic nervous functions. Plasma total salusin-β levels obtained during daytime ambulatory monitoring of heart rate variability showed strong negative correlations with variables reflecting parasympathetic nervous activity, high frequency amplitude (HF; r=-0.27, p=0.0018) and the square root of the mean squared differences of successive normal-to-normal intervals (RMSSD; r=-0.19, p=0.0292), but did not with low frequency amplitude (LF) or LF/HF, variables influenced by sympathetic nervous activity. Because early morning nadir in the diurnal variation of plasma total salusin-β levels appeared to follow the nighttime parasympathetic nervous activity peak as quantified by HF and RMSSD, we determined whether parasympathetic stimulation reduces plasma salusin-β levels. Both Valsalva maneuver (p<0.05) and urination (p<0.05) significantly reduced plasma total salusin-β levels. Despite the fact that salusin-β is the sole endogenous parasympathomimetic peptide identified to date, the current results argue against the contention that physiological parasympathetic augmentation is the consequences of upregulated circulating salusin-β. Rather, circulating salusin-β levels are suppressed following physiological parasympathetic stimulation and appear to constitute a negative feedback relationship with the parasympathetic nervous system.

Salusin-β, an antimicrobially active peptide against Gram-positive bacteria

Salusin-β has been detected in numerous mammalian tissues and has been shown to have various effects on the cardiovascular system. In this study, we showed that salusin-β exhibited potent antibacterial activity against Gram-positive microorganisms such as Bacillus subtilis NBRC 3513, Bacillus megaterium ATCC 19213, Staphylococcus aureus NBRC 12732, and Staphylococcus epidermidis NBRC 12933. A cytoplasmic membrane-depolarizing assay using the DiSC3(5) dye revealed that the addition of 4 nmol/mL of salusin-β caused the leakage of fluorescence dye from Staphylococcus aureus NBRC 12732. The antimicrobial potency and circular dichroism (CD) spectroscopy of five analogs related to salusin-β were examined to determine structure-function relationships in its N- and C-terminal regions. The results obtained suggest that the N-terminal sequences of the salusin-β molecule are important for the expression of the potent antimicrobial activity of this peptide. A profile corresponding to that of the α-helix conformation was observed in the salusin-β solution.

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.

Salusins: potential use as a biomarker for atherosclerotic cardiovascular diseases

Human salusin- α and salusin- β are related peptides produced from prosalusin. Bolus injection of salusin- β into rats induces more profound hypotension and bradycardia than salusin- α . Central administration of salusin- β increases blood pressure via release of norepinephrine and arginine-vasopressin. Circulating levels of salusin- α and salusin- β are lower in patients with essential hypertension. Salusin- β exerts more potent mitogenic effects on human vascular smooth muscle cells (VSMCs) and fibroblasts than salusin- α . Salusin- β accelerates inflammatory responses in human endothelial cells and monocyte-endothelial adhesion. Human macrophage foam cell formation is stimulated by salusin- β but suppressed by salusin- α . Chronic salusin- β infusion into apolipoprotein E-deficient mice enhances atherosclerotic lesions; salusin- α infusion reduces lesions. Salusin- β is expressed in proliferative neointimal lesions of porcine coronary arteries after stenting. Salusin- α and salusin- β immunoreactivity have been detected in human coronary atherosclerotic plaques, with dominance of salusin- β in macrophage foam cells, VSMCs, and fibroblasts. Circulating salusin- β levels increase and salusin- α levels decrease in patients with coronary artery disease. These findings suggest that salusin- β and salusin- α may contribute to proatherogenesis and antiatherogenesis, respectively. Increased salusin- β and/or decreased salusin- α levels in circulating blood and vascular tissue are closely linked with atherosclerosis. Salusin- α and salusin- β could be candidate biomarkers and therapeutic targets for atherosclerotic cardiovascular diseases.

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.

Serum salusin-α levels are inversely correlated with the presence and severity of coronary artery disease

We sought to measure serum salusin-α levels in patients with coronary artery disease (CAD) and to assess their correlation with the severity of the disease. We enrolled 172 patients with CAD and 91 controls. We assessed the angiographic severity of CAD by coronary atherosclerosis index (CAI) and detected serum salusin-α levels by enzyme-linked immunosorbent assay (ELISA). We demonstrated that CAD patients had significantly lower serum salusin-α levels compared to controls. Moreover, serum salusin-α levels were independently and negatively correlated with the presence and severity of CAD. These findings indicated that salusin-α might serve as a potential biomarker for predicting the development and progression of CAD.

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.

Salusins protect myocardium against ischemic injury by alleviating endoplasmic reticulum stress

Salusins are regulatory peptides that affect cardiovascular function. We previously reported that salusin-α and -β protected cultured cardiomyocytes from serum deprivation-induced cell death through upregulating glucose-regulated protein 78 (GRP78), an endoplasmic reticulum (ER) resident protein whose overexpression acts as a marker and suppressor of ER stress. The present study examined whether salusin-α and -β inhibit ER stress in ischemic myocardium. In a rat model of myocardial infarction created by ligating the left anterior descending coronary artery (LAD), salusin-α or -β was intravenously injected at 5 or 15 nmol kg(-1) 15 min prior to 2 h of LAD occlusion. The high dose of salusin-α and -β significantly improved heart function and hemodynamics in LAD-occluded rats, but had no effects in sham-operated rats. The arrhythmias caused by LAD occlusion were markedly attenuated by salusin-α and -β. The apoptotic rate in ischemic myocardium was reduced from 31.5%±3.7% to 19.8%±2.2% and 12.3%±2.2%, and the infarct size was reduced from 53.4%±4.0% of the risk area to 26.5%±9.7% and 23.7%±8.9% by 15 nmol kg(-1) salusin-α and -β, respectively. Furthermore, salusin-α and -β prevented the activation of GRP78 and ER stress-specific apoptotic effectors caspase-12 and CHOP (C/EBP homologous protein), and attenuated the reduction of an ER stress-associated antiapoptotic protein Bcl-2 in ischemic cardiac tissue. The salusins also inhibited the ER stress induced by tunicamycin in cultured rat H9c2 cardiomyocytes. These results indicate that salusins protect myocardium against ischemic injury by inhibiting ER stress and ER stress-associated apoptosis.

Endogenous bioactive peptides as potential biomarkers for atherosclerotic coronary heart disease

Cardiovascular disease is the leading cause of death worldwide, with high medical costs and rates of disability. It is therefore important to evaluate the use of cardiovascular biomarkers in the early diagnosis of coronary artery disease (CAD). We have screened a variety of recently identified bioactive peptides candidates in anticipation that they would allow detection of atherosclerotic CAD. Especially, we have focused on novel anti-atherogenic peptides as indicators and negative risk factors for CAD. In vitro, in vivo and clinical studies indicated that human adiponectin, heregulin-β₁, glucagon-like peptide-1 (GLP-1), and salusin-α, peptides of 244, 71, 30, and 28 amino acids, respectively, attenuate the development and progression of atherosclerotic lesions by suppressing macrophage foam cell formation via down-regulation of acyl-coenzyme A: cholesterol acyltransferase-1. Circulating levels of these peptides in the blood are significantly decreased in patients with CAD compared to patients without CAD. Receiver operating characteristic analyses showed that salusin-α is a more useful biomarker, with better sensitivity and specificity, compared with the others for detecting CAD. Therefore, salusin-α, heregulin-β₁, adiponectin, and/or GLP-1, alone or in various combinations, may be useful as biomarkers for atherosclerotic CAD.

Enhanced expression of salusin-β contributes to progression of atherosclerosis in LDL receptor deficient mice

Atherosclerosis is an important underlying pathology of cardiovascular diseases. The aim of this study was to observe the expression of salusin-β, a new vasoactive peptide, in vascular tissues of low-density lipoprotein receptor deficient (LDLR–/–) mice, and to evaluate the effect of salusin-β on the development of atherosclerosis in LDLR–/– mice. Six-week-old, male LDLR–/– mice were subcutaneously injected with salusin-β or the vehicle, once a day for 12 weeks. The expressions of salusin-β in both mRNA and peptide levels were determined by reverse transcription – polymerase chain reaction, Western blot, and immunohistochemistry. Atherosclerotic lesions were analyzed by staining with hematoxylin and eosin or oil red O. Our results showed that expression of salusin-β in mRNA and salusin-β peptide levels were enhanced in LDLR–/– mice. Subcutaneous injection of salusin-β significantly aggravated the atherosclerotic lesions, and increased lipid deposits in the arteries of LDLR–/– mice. Moreover, salusin-β significantly increased the serum level of low-density lipoprotein cholesterol, but not total cholesterol, triglycerides, or high-density lipoprotein cholesterol. These results suggest that the enhanced expression of salusin-β contributes to progression of atherosclerosis in LDLR–/– mice by up-regulating the serum low-density lipoprotein cholesterol level. This study provides a potential therapeutic target for the prevention and treatment of atherosclerosis.

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.

Release of salusin-beta from human monocytes/macrophages

Salusin-alpha and salusin-beta are related bioactive peptides biosynthesized from the same precursor, prosalusin. Despite the potent hemodynamic and proatherosclerotic activities of salusin-beta, its exact distribution and biological functions remain largely undetermined because of technical difficulties associated with its unique physicochemical characteristics, such as marked adhesiveness to polypropylene and polystyrene. By circumventing these problems, we recently established a specific radioimmunoassay for detecting immunoreactive human salusin-beta. In the current study, we demonstrated the release of salusin-beta from the human monoblastic leukemia cell lines, THP-1 and U937. Dilution curves of extracted conditioned media from both cells were parallel with those of standard human salusin-beta by radioimmunoassay. Reverse-phase high performance liquid chromatography coupled with radioimmunoassay detection of the culture supernatants revealed a major immunoreactive component that co-eluted with authentic salusin-beta. Both cell lines secreted salusin-beta-like immunoreactivity (LI) into serum-free media as a function of time (1234.3 + or - 122.7 and 186.7 + or - 9.1 fmol/10(5) cells per 24h). When THP-1 and U937 cells differentiated into macrophages after incubation with 2-O-tetradecanoylphorbol-13-acetate (TPA), they secreted far greater amounts of salusin-beta-LI into the culture supernatant (3351.9 + or - 899.3 and 1545.8 + or - 183.3 fmol/10(5) cells per 24h). TPA treatment accelerated the processing of prosalusin into its cleaved fragments, suggesting that the increased secretion of salusin-beta-LI in THP-1-derived macrophages was caused by the enhanced intracellular processing of prosalusin. Stimulation with the inflammatory cytokines, tumor necrosis factor alpha (TNF-alpha) and lipopolysaccharide (LPS), resulted in increased secretion of salusin-beta without inducing expression of the gene for preprosalusin, suggesting that TNF-alpha and LPS stimulated the release of salusin-beta. These data demonstrate that salusin-beta, which induces macrophage foam cell formation, is secreted in its authentic form from human monocytes/macrophages.

Expression of prosalusin in human neuroblastoma cells

Salusins, which are derived from the prosalusin precursor molecule, regulate hemodynamics, mitogenesis and atherogenesis. The preprosalusin gene is ubiquitously expressed, while the salusin-beta peptide is present in systemic endocrine cells and the neuroendocrine system. However, the regulatory mechanisms for the preprosalusin gene and prosalusin expression remain to be investigated. Real-time quantitative RT-PCR and salusin-alpha radioimmunoassay revealed that the neuroblastoma cell line, SK-N-SH, exhibited marked upregulation of preprosalusin mRNA and salusin-alpha-like immunoreactivity (LI) when incubated under 2% serum condition. However, SK-N-SH cells released a limited amount of salusin-alpha-LI into the culture supernatant. Reverse-phase high performance liquid chromatography coupled with radioimmunoassay after extraction of proteins from the conditioned media using an octyl-silica column did not reveal a component that co-eluted with authentic salusin-alpha. Western blotting of the nuclear extracts from SK-N-SH showed the expression of prosalusin and its cleaved fragments, but not authentic salusin-alpha. Addition of Jak-2 inhibitors to growing SK-N-SH cells cultured under 10% serum condition resulted in increased salusin-alpha-LI expression. Suppression of Jak-2 mRNA using siRNAs upregulated intracellular salusin-alpha-LI, as detected by immunofluorescence. In summary, the preprosalusin gene and prosalusin protein are expressed in a neuroblastoma cell line and upregulated by reduced serum. The Jak-2 pathway may be involved in the regulation of salusin expression.

Biosynthesis and secretion of salusin-alpha from human cells

Salusins originally identified using bioinformatics analyses have been shown to act on the cardiovascular and endocrine systems. Although the hypotensive activity of salusin-alpha is limited, it exerts a significant anti-atherosclerotic effect via suppression of foam cell formation in human monocyte-derived macrophages by down-regulating acyl-CoA:cholesterol acyltransferase-1. Furthermore, serum salusin-alpha levels show a close negative correlation with the severity of atherosclerotic diseases. However, biosynthesis and secretion of salusin-alpha peptide from cultured mammalian cells have not been demonstrated to date. We examined the expression, synthesis and release of salusin-alpha in human-derived cell lines. Preprosalusin mRNA and protein were detected ubiquitously in all cells tested, whereas the processing of preprosalusin into salusin-alpha peptide is dependent upon each cell type. Immunohistochemical study revealed the most abundant salusin-alpha-like immunoreactivity to be present in HeLa cells which released salusin-alpha-like immunoreactivity into the culture supernatant. Analysis of extracted conditioned media from HeLa cells by reverse-phase high performance liquid chromatography coupled with radioimmunoassay detection revealed a single immunoreactive component that co-eluted with authentic salusin-alpha. These results present the first evidence that salusin-alpha is biosynthesized and released from human-derived cells.

Serum salusin-alpha levels are decreased and correlated negatively with carotid atherosclerosis in essential hypertensive patients

Salusin-alpha is a new bioactive peptide with mild hypotensive and bradycardic effects. Our recent study showed that salusin-alpha suppresses foam cell formation in human monocyte-derived macrophages by down-regulating acyl-CoA:cholesterol acyltransferase-1, contributing to its anti-atherosclerotic effect. To clarify the clinical implications of salusin-alpha in hypertension and its complications, we examined the relationship between serum salusin-alpha levels and carotid atherosclerosis in hypertensive patients. The intima-media thickness (IMT) and plaque score in the carotid artery, blood pressure, serum levels of salusin-alpha, and atherosclerotic parameters were determined in 70 patients with essential hypertension and in 20 normotensive controls. There were no significant differences in age, gender, body mass index, fasting plasma glucose level, or serum levels of high-sensitive C-reactive protein, high- or low-density lipoprotein (LDL) cholesterol, small dense LDL, triglycerides, lipoprotein(a), or insulin between the two groups. Serum salusin-alpha levels were significantly lower in hypertensive patients than in normotensive controls. The plasma urotensin-II level, maximal IMT, plaque score, systolic and diastolic blood pressure, and homeostasis model assessment for insulin resistance (HOMA-IR) were significantly greater in hypertensive patients than in normotensive controls. In all subjects, maximal IMT was significantly correlated with age, systolic blood pressure, LDL cholesterol, urotensin-II, salusin-alpha, and HOMA-IR. Forward stepwise multiple linear regression analysis revealed that salusin-alpha levels had a significantly independent and negative association with maximal IMT. Serum salusin-alpha levels were significantly lower in accordance with the severity of plaque score. Our results suggest that the decrease in serum salusin-alpha, an anti-atherogenic peptide, may be associated with carotid atherosclerosis in hypertensive patients.