Intermedin alleviates diabetic vascular calcification by inhibiting GLUT1 through activation of the cAMP/PKA signaling pathway

BACKGROUND AND AIMS

Vascular calcification (VC) is regarded as an independent risk factor for cardiovascular events in type 2 diabetic patients. Glucose transporter 1 (GLUT1) involves VC. Intermedin/Adrenomedullin-2 (IMD/ADM2) is a cardiovascular protective peptide that can inhibit multiple disease-associated VC. However, the role and mechanism of IMD in diabetic VC remain unclear. Here, we investigated whether IMD inhibits diabetic VC by inhibiting GLUT1.

METHODS AND RESULTS

It was found that plasma IMD concentration was significantly decreased in type 2 diabetic patients and in fructose-induced diabetic rats compared with that in controls. Plasma IMD content was inversely correlated with fasting blood glucose level and VC severity. IMD alleviated VC in fructose-induced diabetic rats. Deficiency of Adm2 aggravated and Adm2 overexpression attenuated VC in high-fat diet-induced diabetic mice. In vitro, IMD mitigated high glucose-induced calcification of vascular smooth muscle cells (VSMCs). Mechanistically, IMD reduced advanced glycation end products (AGEs) content and the level of receptor for AGEs (RAGE). IMD decreased glucose transporter 1 (GLUT1) levels. The inhibitory effect of IMD on RAGE protein level was blocked by GLUT1 knockdown. GLUT1 knockdown abolished the effect of IMD on alleviating VSMC calcification. IMD receptor antagonist IMD17-47 and cyclic adenosine monophosphate/protein kinase A (cAMP/PKA) inhibitor H89 abolished the inhibitory effects of IMD on GLUT1 and VSMC calcification.

CONCLUSIONS

These findings revealed that IMD exerted its anti-calcification effect by inhibiting GLUT1, providing a novel therapeutic target for diabetic VC.

Promising novel therapeutic targets for kidney disease: Emphasis on kidney-specific proteins

Worldwide, around 850 million people are diagnosed with kidney disease but the available treatment options are still limited. Preclinical studies propose a plethora of druggable targets that can attenuate kidney disease and could qualify as novel therapeutic strategies, although most of these targets still await clinical testing. Here, we review some promising candidate targets for chronic kidney disease: intermedin, periostin, sirtuin, the cannabinoid receptor, Klotho, and uromodulin. For acute kidney injury, we discuss Apelin, Elabela, growth differentiation factor-15, Fyn kinase, and Klotho. Target selection for further clinical development should consider redundancies with the standard of care, potential synergistic effects with existing treatments, as well as the potential of additional effects on the cardiovascular system as a common comorbidity in patients with kidney disease.

THE INCREASED PLASMA LEVELS OF INTERMEDIN IN PATIENTS WITH TYPE 2 DIABETES MELLITUS

Context

Intermedin (IMD) is the member of calcitonin gene-related peptide family, and tightly associated with type 2 diabetes mellitus (T2DM). The change of plasma IMD levels in T2DM is still unknown.

Objective

We aimed to investigate the plasma levels of IMD in patients with T2DM.

Design

Fortyone patients with T2DM who were hospitalized in the endocrinology department of Civil Aviation General Hospital from January 2012 to June 2015 were enrolled, and 44 volunteers were selected as the control group.

Subjects and Methods

Plasma level of IMD was detected by ELISA. Diagnostic value of IMD was analyzed by area under the receiver operating characteristic (ROC) curve (AUC).

Results

The plasma level of IMD in T2DM group was higher than that in the healthy control group, whereas smoking or cardiovascular complications did no influence the IMD levels. IMD levels were correlated with BMI, DBP, triglyceride, uric acid, urea nitrogen, fasting and 2 hours postprandial blood glucose, and HbA1C. The greatest value of AUC for IMD was only 58.73%.

Conclusions

Although plasma levels of IMD were increased in patients with T2DM, the very low diagnostic value of IMD for T2DM might not be used for the disease diagnosis.

Compensatory elevated serum intermedin levels are associated with increased vascular calcification in hemodialysis patients

INTRODUCTION

Vascular calcification (VC), which is a pathological process of abnormal calcium and phosphorus deposition in blood vessels, valves, heart and other tissues, is highly prevalent and predicts mortality in dialysis patients. Its mechanisms are complex and unclear. We presume that intermedin (IMD), a kind of small molecule active peptide, may play roles in VC in hemodialysis (HD) patients. This study aims to evaluate serum IMD levels and establish their relation to VC and other parameters in HD patients.

METHODS

A total of 116 patients on maintenance HD treatment and 52 age- and sex-matched healthy controls were enrolled in this study. Serum IMD levels were measured by radioimmunoassay (RIA). VC was evaluated by abdominal aortic calcification scores.

RESULTS

Serum IMD levels were significantly lower in HD patients than in controls [24.89 (13.55, 50.24) pg/ml vs. 137.79 (93.21, 201.64) pg/ml, P < 0.0001]. In addition, IMD was negatively correlated with the serum phosphate level (P = 0.036) in HD patients. However, compared with the group whose IMD levels were above the median, patients with IMD levels less than the median had a lower incidence of VC (P = 0.031). Multivariate logistic regression analyses revealed that serum IMD levels more than 24.89 pg/ml (P = 0.014, OR = 0.285), higher serum iPTH levels (P < 0.0001, OR = 1.093) and older age (P = 0.009, OR = 1.003) were significant independent determinant factors for VC in HD patients.

CONCLUSION

The serum IMD levels were significantly lower in HD patients than that in healthy group. In addition to higher PTH levels and older age, compensatory elevated IMD levels may be an independently determinant factor for VC in HD patients. This was the first study about IMD and VC in dialysis patients.

Intermedin1-53 Inhibits NLRP3 Inflammasome Activation by Targeting IRE1α in Cardiac Fibrosis

Intermedin (IMD), a paracrine/autocrine peptide, protects against cardiac fibrosis. However, the underlying mechanism remains poorly understood. Previous study reports that activation of nucleotide-binding oligomerization domain (NOD)-like receptor family pyrin domain containing 3 (NLRP3) inflammasome contributes to cardiac fibrosis. In this study, we aimed to investigate whether IMD mitigated cardiac fibrosis by inhibiting NLRP3. Cardiac fibrosis was induced by angiotensin II (Ang II) infusion for 2 weeks in rats. Western blot, real-time PCR, histological staining, immunofluorescence assay, RNA sequencing, echocardiography, and hemodynamics were used to detect the role and the mechanism of IMD in cardiac fibrosis. Ang II infusion resulted in rat cardiac fibrosis, shown as over-deposition of myocardial interstitial collagen and cardiac dysfunction. Importantly, NLRP3 activation and endoplasmic reticulum stress (ERS) were found in Ang II-treated rat myocardium. Ang II infusion decreased the expression of IMD and increased the expression of the receptor system of IMD in the fibrotic rat myocardium. IMD treatment attenuated the cardiac fibrosis and improved cardiac function. In addition, IMD inhibited the upregulation of NLRP3 markers and ERS markers induced by Ang II. In vitro, IMD knockdown by small interfering RNA significantly promoted the Ang II-induced cardiac fibroblast and NLRP3 activation. Moreover, silencing of inositol requiring enzyme 1 α (IRE1α) blocked the effects of IMD inhibiting fibroblast and NLRP3 activation. Pre-incubation with PKA pathway inhibitor H89 blocked the effects of IMD on the anti-ERS, anti-NLRP3, and anti-fibrotic response. In conclusion, IMD alleviated cardiac fibrosis by inhibiting NLRP3 inflammasome activation through suppressing IRE1α via the cAMP/PKA pathway.

Intermedin attenuates macrophage phagocytosis via regulation of the long noncoding RNA Dnm3os/miR-27b-3p/SLAMF7 axis in a mouse model of atherosclerosis in diabetes

Atherosclerosis in diabetes is a leading cause of cardiovascular complications. Intermedin (IMD) is a calcitonin peptide that is known to inhibit macrophage phagocytosis in atherosclerosis, but the exact mechanism is unclear. We investigate genes that are differentially expressed in response to IMD in hyperglycemic conditions and determine whether they delay the progression of atherosclerosis. An atherosclerotic and diabetic-murine model was generated in 8-week-old male ApoE-/- mice receiving streptozotocin and a high-fat diet. The mouse model was treated with IMD and the expression levels of NF-κB, Dnm3os, miR-27b-3p, and SLAMF7 were detected in plaque tissue and macrophages cultured with high glucose concentrations. Phagocytosis was determined by oxidized-low-density lipoprotein (Ox-LDL) uptake and the interactions among Dnm3os, SLAMF7 and miR-27b-3p were assessed by dual-luciferase reporter assays. The expression of NF-κB, Dnm3os, and SLAMF7 was enhanced in atherosclerotic plaques but decreased by IMD. The suppression of Dnm3os reduced plaque formation in IMD-treated mice even further whereas increased by miR-27b-3p. Dnm3os and SLAMF7 were competitively bind to miR-27b-3p in vivo. In vitro, ox-LDL uptake is elevated in macrophages cultured in hyperglycemic conditions but reduced by IMD. Dual-luciferase assays indicate that Dnm3os positively regulates SLAMF7 through miR-27b-3p expression. In conclusion, Dnm3os is involved in macrophage phagocytosis through the competitive binding of SLAMF7 with miR-27b-3p. IMD induces the suppression of Dnm3os to inhibit macrophage phagocytosis and alleviate atherosclerosis in diabetes.

Experimental study on renoprotective effect of intermedin on diabetic nephropathy

Intermedin(IMD) is a novel member of the calcitonin/calcitonin gene-related peptide (CT/CGRP) family that has anti-inflammatory, antioxidant and anti-apoptosis properties. This study aimed to evaluate the renoprotective effects of IMD on podocyte apoptotic loss and slit diaphragm protein deficiency the kidneys of rats with in streptozotocin (STZ) induced diabetes in high glucose-exposed podocytes. Our results showed that IMD significantly attenuated proteinuria, and alleviated the abnormal alterations in glomerular ultrastructure in vivo. IMD also improved the induction of slit diaphragm proteins, and restored the decreased Bcl-2 expression and suppressed Bax and caspase-3 induction in the diabetic glomeruli. In addition, IMD attenuated podocyte apoptosis and filamentous actin (F-actin) rearrangement in high glucose-exposed podocytes. Exposure to high glucose elevated the unfolded protein response (UPR) to endoplasmic reticulum (ER) stress in renal podocytes, and IMD treatment blocked such ER stress responses pertinent to podocyte apoptosis and reduced synthesis of slit diaphragm proteins in vivo and in vitro. These observations demonstrate that targeting ER stress is an underlying mechanism of IMD-mediated amelioration of diabetes-associated podocyte injury and dysfunction.

Neuroprotection of Intermedin Against Cerebral Ischemia/Reperfusion Injury Through Cerebral Microcirculation Improvement and Apoptosis Inhibition

Ischemic stroke is the primary cause of disability and mortality worldwide. Ischemia/reperfusion (I/R)-induced microcirculatory dysfunction and organ injury generally occur after ischemic stroke. Several studies have shown that intermedin (IMD) has a regulating function on cerebral microcirculation and blood-brain barrier via relaxing cerebral vessels and improving the local blood supply after cerebral ischemia. However, a unified conclusion has not been reached, and the underlying mechanism remains unclear. To observe and analyze the changes of cerebral microcirculation perfusion of cerebral IRI by IMD post-treatment in the rats and further explore the mechanism underlying the beneficial effect of IMD on cerebral IRI. Thirty-nine rats were divided into three groups: sham, I/R, and I/R + IMD groups. After IMD ischemia post-treatment, the rat cerebral infarction rate and the degree of neurological deficit were evaluated by TTC staining and neurological function score; the changes in the amount of cerebral microcirculation implantation on the injured side of the rats were observed by laser Doppler; the pathological changes and cell ultrastructure of rat cortex and hippocampus were observed by HE staining and transmission electron microscopy; the neuron apoptosis in the rat cortex and hippocampus was detected by TUNEL staining and immunohistochemical staining. Impaired neurological function, abnormal cortical/hippocampal neuron morphology, and the proportion of cerebral infarction were significantly improved in the IMD group compared with the I/R group, which suggested a possible neuroprotective role of IMD. IMD treatment also increased the average perfusion of cerebral surface microcirculation in rats by astonished 42.7 times. Finally, IMD administration decreased the caspase-3- and Bax-positive cell numbers and apoptotic cell ratio. IMD has a significant protective effect on neuronal damage caused by cerebral I/R in rats by improving cerebral microcirculation and inhibiting apoptosis.

Endogenous intermedin protects against intimal hyperplasia by inhibiting endoplasmic reticulum stress

Extensive proliferation of vascular smooth muscle cell (VSMC) contributes to intimal hyperplasia following vascular injury, in which endoplasmic reticulum stress (ERS) plays a critical role. Intermedin (IMD) is a vascular paracrine/autocrine peptide exerting numerous beneficial effects in cardiovascular diseases. IMD overexpression could alleviate intimal hyperplasia. Here, we investigated whether endogenous IMD protects against intimal hyperplasia by inhibiting endoplasmic reticulum stress. The mouse left common carotid-artery ligation-injury model was established to induce intimal hyperplasia using IMD^-/-mice and C57BL/6 J wild-type (WT) mice. Platelet-derived growth factor-BB (PDGF-BB) was used to stimulate the proliferation of VSMC. IMD^-/- mice displayed exacerbated intimal hyperplasia induced by complete ligation of the left carotid artery at 14 d and 28 d compared to WT mice. However, IMD-deficiency had no effect on blood pressure, plasma triglyceride, and fasting blood glucose levels in mice. Furthermore, VSMCs derived from IMD^-/- mice showed increased cell proliferation and dramatically elevated levels of glucose regulated protein 78 (GRP78), activating transcription factor 4 (ATF4), ATF6 mRNA under PDGF-BB treatment compared to WT mice-derived VSMCs. In addition, exogenous administration of IMD significantly attenuated PDGF-BB-induced cell proliferation and GRP78, phosphorylase-inositol requiring enzyme 1α, ATF4, and ATF6 protein levels. Thus, endogenous IMD may counteract ERS to exert protective role in response to vascular injury and IMD is expected to be a therapeutic target for the prevention and treatment of restenosis.

Inhibition of endoplasmic reticulum stress by intermedin1-53 attenuates angiotensin II-induced abdominal aortic aneurysm in ApoE KO Mice

Endoplasmic reticulum stress (ERS) is involved in the development of abdominal aortic aneurysm (AAA). Since bioactive peptide intermedin (IMD)1-53 protects against AAA formation, here we investigated whether IMD1-53 attenuates AAA by inhibiting ERS. AAA model was induced by angiotensin II (AngII) in ApoE KO mouse background. AngII-treated mouse aortas showed increased ERS gene transcription of caspase12, eukaryotic translation initiation factor 2a (eIf2a) and activating transcription factor 4(ATF4).The protein level of ERS marker glucose regulated protein 94(GRP94), ATF4 and C/EBP homologous protein 10(CHOP) was also up-regulated by AngII. Increased ERS levels were accompanied by severe VSMC apoptosis in human AAA aorta. In vivo administration of IMD1-53 greatly reduced AngII-induced AAA and abrogated the activation of ERS. To determine whether IMD inhibited AAA by ameliorating ERS, we used 2 non-selective ERS inhibitors phenyl butyrate (4-PBA) and taurine (TAU). Similar to IMD, PBA, and TAU significantly reduced the incidence of AAA and AAA-related pathological disorders. In vitro, AngII infusion up-regulated CHOP, caspase12 expression and led to VSMC apoptosis. IMD siRNA aggravated the CHOP, caspase12-mediated VSMC apoptosis, which was abolished by ATF4 silencing. IMD infusion promoted the phosphorylation of adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) in aortas in ApoE KO mice, and the AMPK inhibitor compound C abolished the protective effect of IMD on VSMC ERS and apoptosis induced by AngII. In conclusion, IMD may protect against AAA formation by inhibiting ERS via activating AMPK phosphorylation.

Intermedin in Paraventricular Nucleus Attenuates Sympathoexcitation and Decreases TLR4-Mediated Sympathetic Activation via Adrenomedullin Receptors in Rats with Obesity-Related Hypertension

Intermedin/adrenomedullin-2 (IMD/AM2), a member of the calcitonin gene-related peptide/AM family, plays an important role in protecting the cardiovascular system. However, its role in the enhanced sympathoexcitation in obesity-related hypertension is unknown. In this study, we investigated the effects of IMD in the paraventricular nucleus (PVN) of the hypothalamus on sympathetic nerve activity (SNA), and lipopolysaccharide (LPS)-induced sympathetic activation in obesity-related hypertensive (OH) rats induced by a high-fat diet for 12 weeks. Acute experiments were performed under anesthesia. The dynamic alterations of sympathetic outflow were evaluated as changes in renal SNA and mean arterial pressure (MAP) in response to specific drugs. Male rats were fed a control diet (12% kcal as fat) or a high-fat diet (42% kcal as fat) for 12 weeks to induce OH. The results showed that IMD protein in the PVN was downregulated, but Toll-like receptor 4 (TLR4) and plasma norepinephrine (NE, indicating sympathetic hyperactivity) levels, and systolic blood pressure were increased in OH rats. LPS (0.5 µg/50 nL)-induced enhancement of renal SNA and MAP was greater in OH rats than in obese or control rats. Bilateral PVN microinjection of IMD (50 pmol) caused greater decreases in renal SNA and MAP in OH rats than in control rats, and inhibited LPS-induced sympathetic activation, and these were effectively prevented in OH rats by pretreatment with the AM receptor antagonist AM22-52. The mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) inhibitor U0126 in the PVN partially reversed the LPS-induced enhancement of SNA. However, IMD in the PVN decreased the LPS-induced ERK activation, which was also effectively prevented by AM22-52. Chronic IMD administration resulted in significant reductions in the plasma NE level and blood pressure in OH rats. Moreover, IMD lowered the TLR4 protein expression and ERK activation in the PVN, and decreased the LPS-induced sympathetic overactivity. These results indicate that IMD in the PVN attenuates SNA and hypertension, and decreases the ERK activation implicated in the LPS-induced enhancement of SNA in OH rats, and this is mediated by AM receptors.

Intermedin promotes hepatic carcinoma cell proliferation through upregulation of miR-155

OBJECTIVE

MicroRNAs (miRNAs) plays an important role in the development of malignant carcinoma. The small peptide intermedin (IMD) can promote hepatic carcinoma cell proliferation. The aim of the present study is to examine the effect of miR-155 on IMD-stimulated hepatic carcinoma cell proliferation.

METHODS

Proliferation of hepatic carcinoma SMMC7721 cells was detected by CCK-8, expression of proliferating cell nuclear antigen (PCNA) and miR-155 was detected by real-time PCR.

RESULTS

We found that IMD promotes the proliferation of SMMC7721 cells in a time and dose-dependent manner. IMD can upregulate the expression of miR-155, and blocking of miR-155 can inhibit the IMD-induced SMMC7721 cell proliferation to some extent.

CONCLUSION

This study demonstrated that IMD can promote the proliferation of human hepatic carcinoma cell line SMMC7721 cells through upregulation of miR-155. This study may contribute to hepatic cancer prevention and therapy.

Intermedin inhibits unilateral ureteral obstruction-induced oxidative stress via NADPH oxidase Nox4 and cAMP-dependent mechanisms

NADPH oxidase Nox4-derived reactive oxygen species (ROS) play important roles in renal fibrosis. Our previous study demonstrated that intermedin (IMD) alleviated unilateral ureteral obstruction (UUO)-induced renal fibrosis by inhibition of ROS. However, the precise mechanisms remain unclear. Herein, we investigated the effect of IMD on Nox4 expression and NADPH oxidase activity in rat UUO model, and explored if these effect were achieved through cAMP-PKA pathway, the important post-receptor signal transduction pathway of IMD, in TGF-β1-stimulated rat proximal tubular cell (NRK-52E). Renal fibrosis was induced by UUO. NRK-52E was exposed to rhTGF-β1 to establish an in vitro model of fibrosis. IMD was overexpressed in the kidney and in NRK-52E by IMD gene transfer. We studied UUO-induced ROS by measuring dihydroethidium levels and lipid peroxidation end-product 4-hydroxynonenal expression. Nox4 expression in the obstructed kidney of UUO rat or in TGF-β1-stimulated NRK-52E was measured by quantitative RT-PCR and Western blotting. We analyzed NADPH oxidase activity using a lucigenin-enhanced chemiluminescence system. We showed that UUO-stimulated ROS production was remarkably attenuated by IMD gene transfer. IMD overexpression inhibited UUO-induced up-regulation of Nox4 and activation of NADPH oxidase. Consistent with in vivo results, TGF-β1-stimulated increase in Nox4 expression and NADPH oxidase activity was blocked by IMD. In NRK-52E, these beneficial effects of IMD were abolished by pretreatment with N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide hydrochloride (H-89), a PKA inhibitor, and mimicked by a cell-permeable cAMP analog dibutyl-cAMP. Our results indicate that IMD exerts anti-oxidant effects by inhibition of Nox4, and the effect can be mediated by cAMP-PKA pathway.

Intermedin reduces neointima formation by regulating vascular smooth muscle cell phenotype via cAMP/PKA pathway

BACKGROUND AND AIMS

Vascular smooth muscle cell (VSMC) dedifferentiation contributes to neointima formation, which results in various vascular disorders. Intermedin (IMD), a cardiovascular paracrine/autocrine polypeptide, is involved in maintaining circulatory homeostasis. However, whether IMD protects against neointima formation remains largely unknown. The purpose of this study is to investigate the role of IMD in neointima formation and the possible mechanism.

METHODS

IMD_1-53 (100ng/kg/h) or saline water was used on rat carotid-artery balloon-injury model. The mouse left common carotid-artery ligation-injury model was established using IMD-transgenic and C57BL/6J mice. Immunohistochemistry and immunofluorescence staining was used to detect the protein expression in rat carotid arteries. Radioimmunoassay was used to determine the serum IMD level. The hematoxylin andeosin staining was used for carotid arteries morphological testing. In vitro, for rat primary cultured VSMC phenotype transition, proliferation and migration assays, platelet-derived growth factor-BB (PDGF-BB) reagent and IMD_1-53 peptide were added to the culture media at the final concentration of 20 ng/mL and 10^-7mol/L respectively. Quantification of VSMC proliferation involved MTT and BrdU assay and migration was detected by wound-healing assay. Western blot and realtime PCR were used to detect the protein and mRNA levels of tissues or cells.

RESULTS

With the rat carotid-artery balloon-injury model, IMD was significantly downregulated in injured arteries and plasma. Exogenous IMD_1-53 greatly inhibited neointima formation and prevented VSMC from switching to a synthetic phenotype. With the left common carotid-artery ligation-injury model, IMD-transgenic mice showed less neointima formation than C57BL/6J mice. PDGF-BB reduced IMD mRNA expression in rat primary cultured VSMCs but increased that of its receptors, calcitonin receptor-like receptor or receptor activity-modifying proteins. Furthermore, PDGF-BB promoted VSMC proliferation and migration and transformed VSMCs to the synthetic phenotype, which was reversed with IMD_1-53 treatment. Mechanistically, IMD_1-53 maintained the contractile VSMC phenotype via the cyclic adenosine monophosphate/protein kinase A (cAMP/PKA) pathway.

CONCLUSIONS

IMD attenuated neointima formation both in the rat model of carotid-artery balloon injury and mouse model of common carotid-artery ligation injury. IMD protection may be mediated by maintaining a VSMC contractile phenotype via the cAMP/PKA pathway.

Intermedin attenuates renal fibrosis by induction of heme oxygenase-1 in rats with unilateral ureteral obstruction

BACKGROUND

Intermedin [IMD, adrenomedullin-2 (ADM-2)] attenuates renal fibrosis by inhibition of oxidative stress. However, the precise mechanisms remain unknown. Heme oxygenase-1 (HO-1), an antioxidant agent, is associated with antifibrogenic effects. ADM is known to induce HO-1. Whether IMD has any effect on HO-1 is unclear. Herein, we determined whether the antifibrotic properties of IMD are mediated by induction of HO-1.

METHODS

Renal fibrosis was induced by unilateral ureteral obstruction (UUO) performed on male Wistar rats. Rat proximal tubular epithelial cell line (NRK-52E) was exposed to rhTGF-β1 (10 ng/ml) to establish an in vitro model of epithelial-mesenchymal transition (EMT). IMD was over-expressed in vivo and in vitro using the vector pcDNA3.1-IMD. Zinc protoporphyrin (ZnPP) was used to block HO-1 enzymatic activity. IMD effects on HO-1 expression in the obstructed kidney of UUO rat and in TGF-β1-stimulated NRK-52E were analyzed by real-time RT-PCR, Western blotting or immunohistochemistry. HO activity in the obstructed kidney, contralateral kidney of UUO rat and NRK-52E was examined by measuring bilirubin production. Renal fibrosis was determined by Masson trichrome staining and collagen I expression. Macrophage infiltration and IL-6 expression were evaluated using immunohistochemical analysis. In vivo and in vitro EMT was assessed by measuring α-smooth muscle actin (α-SMA) and E-cadherin expression using Western blotting or immunofluorescence, respectively.

RESULTS

HO-1 expression and HO activity were increased in IMD-treated UUO kidneys or NRK-52E. The obstructed kidneys of UUO rats demonstrated significant interstitial fibrosis on day 7 after operation. In contrast, kidneys that were treated with IMD gene transfer exhibited minimal interstitial fibrosis. The obstructed kidneys of UUO rats also had greater macrophage infiltration and IL-6 expression. IMD restrained infiltration of macrophages and expression of IL-6 in UUO kidneys. The degree of EMT was extensive in obstructed kidneys of UUO rats as indicated by decreased expression of E-cadherin and increased expression of α-SMA. In vitro studies using NRK-52E confirmed these observations. EMT was suppressed by IMD gene delivery. However, all of the above beneficial effects of IMD were eliminated by ZnPP, an inhibitor of HO enzyme activity.

CONCLUSION

This study demonstrates that IMD attenuates renal fibrosis by induction of HO-1.

Hypercholesterolemia Up-Regulates the Expression of Intermedin and Its Receptor Components in the Aorta of Rats via Inducing the Oxidative Stress

OBJECTIVE

Hypercholesterolemia can cause damage to the artery. Intermedin (IMD) is a novel member of the calcitonin gene-related peptide family. This study aims to investigate the aortic expression of IMD and its receptors in hypercholesterolemia without atherosclerosis.

METHODS

Male Wistar rats were fed with high cholesterol diet, with or without simvastatin and vitamin C. Both the malondialdehyde (MDA) and superoxide dismutase (SOD) in plasma and aorta were determined as the oxidative stress biomarkers. The plasma IMD was assessed by radioimmunoassay. Within the aorta, the mRNA expression of IMD along with its receptor components was determined, and the corresponding protein level of the CRLR/RAMPs was also assessed.

RESULTS

The hypercholesterolemia rats without atherosclerotic lesion manifested a higher level of MDA and SOD and the plasma IMD elevated. Increased expression of IMD and all its receptor components (CRLR, RAMP1, RAMP2, and RAMP3) were displayed within the aorta. The simvastatin indirectly attenuated oxidative stress by improving lipid profiles, while the vitamin C directly reduced oxidative stress without interfering with the serum lipids. Both simvastatin and vitamin C ameliorated the aortic injury, decreased the plasma IMD level, and recovered the expression of IMD and its receptors within the aorta.

CONCLUSIONS

The up-regulated expression of IMD is observed within the aorta of the hypercholesterolemia rats. In addition, the oxidative stress participates in the up-regulation.

Intermedin attenuates myocardial infarction through activation of autophagy in a rat model of ischemic heart failure via both cAMP and MAPK/ERK1/2 pathways

Intermedin is a proopiomelanocortin-derived peptide before opioid promoting cortical hormone, its main function embodies in mononuclear macrophages and neutrophilic granulocytes to inhibit the proinflammatory cytokines. The aim of this study is to determine intermedin attenuates myocardial infarction and its related mechanisms in a rat model of ischemic heart failure. After rat model of ischemic heart failure was set up, myocardial infarction, blood levels of activities of creatine kinase (CK), the MB isoenzyme of creatine kinase (CK-MB), lactate dehydrogenase (LDH) and cardiac troponin T (cTnT) were effectively reduced by treatment with intermedin. Tumor necrosis factor (TNF-α) and interleukin-6 (IL-6) in a rat model of ischemic heart failure were recovered by pretreatment with intermedin. Administrate of intermedin availably promoted cAMP contents and suppressed caspase-3 protein in ischemic heart failure rat. ERK1/2 and LC3 protein expression were significantly activated and autophagy was significantly promoted by intermedin in a rat model of ischemic heart failure. These results indicate that intermedin protected rat heart, attenuates myocardial infarction from ischemic heart failure in the rat model. The underlying mechanisms may include upregulation of cAMP, ERK1/2 and LC3 protein expression and activating of autophagy.

Intermedin ameliorates IgA nephropathy by inhibition of oxidative stress and inflammation

IgA nephropathy (IgAN) is the most frequent form of glomerulonephritis worldwide. The role of oxidative stress and inflammation in the pathogenesis of IgAN has been reported. Intermedin (IMD) is a newly discovered peptide that is closely related to adrenomedullin. We have recently reported that IMD can significantly reduce renal ischemia/reperfusion injury by diminishing oxidative stress and suppressing inflammation. The present study was designed to explore whether IMD ameliorates IgAN via oxidative stress- and inflammation-dependent mechanisms. Our results showed that IMD administration resulted in the prevention of albuminuria and ameliorated renal pathomorphological changes. These findings were associated with (1) decreased renal TGF-β1 and collagen IV expression, (2) an increased SOD level and reduced MDA level, (3) the inhibition of the renal activation of NF-κB p65 and (4) the downregulation of the expression of inflammatory factors (TNF-α, MCP-1 and MMP-9) in the kidney. These results indicate that IMD in the kidney protects against IgAN by reducing oxidative stress and suppressing inflammation.

The novel tumor angiogenic factor, adrenomedullin-2, predicts survival in pancreatic adenocarcinoma

BACKGROUND

Tumor angiogenesis has been demonstrated to have an important role in the development, progression, and metastasis of pancreas cancer. Adrenomedullin-2 (ADM2) is a calcitonin gene-related peptide that has recently been shown to be a novel tumor angiogenesis factor, acting via mitogen-activated protein kinase/extracellular signal-regulated kinase, phosphoinositide 3-kinase/Akt, and vascular endothelial growth factor/vascular endothelial growth factor-2 signaling pathways. Through the use of tissue microarray (TMA) technology, we hypothesize that ADM2 is an important tumor angiogenesis factor in pancreatic cancer.

METHODS

Multiple TMAs were created using tissue from pancreatic cancer patients resected between January 1996 and December 2006. Core tissue samples of formalin-fixed, paraffin-embedded blocks of pancreatic cancer tissue were collected through an institutional review board-approved protocol and linked to available clinicopathologic data. Two TMAs consisting of 112 and 60 patients with pancreatic adenocarcinoma were studied for ADM2 protein expression using a quantitative, automated immunofluorescent microscopy system, a technology that removes potential observer bias in TMA analysis. The results were analyzed using independent Student t-test, chi-square, log-rank regression, and Kaplan-Meier methods.

RESULTS

One hundred sixteen patients were identified for complete analysis, and 56 patients had complete survival data. Median follow-up for survivors was 14.5 mo. Total cellular levels of ADM2 were found to be a predictor of survival in pancreatic cancer. Low ADM2 levels were associated with a higher 5-y survival compared with high ADM2 levels (18% versus 6%, P = 0.05). Median survival was also worse in high ADM2 expressers (18.7 versus 8.6 mo). In accordance with prior-published pancreatic cancer data, a worse histologic grade (P = 0.001), tumor (T) stage (P = 0.009), and overall disease stage (P = 0.004), all portended a worse survival.

CONCLUSIONS

For the first time, we have demonstrated that high levels of ADM2 expression predict a poorer survival in patients with pancreatic adenocarcinoma. This suggests a possible role of ADM2 in pancreas cancer and as a novel biomarker that predicts poorer survival. Additional study of ADM2 in pancreatic cancer will help reveal its true angiogenic role in pancreas cancer and its potential role as a novel therapeutic target.

Intermedin restricts vessel sprouting by inhibiting the loosening of endothelial junction

Vessel sprouting from pre-existing vasculature is a key step for the formation of a functional vasculature. The low level of vascular endothelial growth factor (VEGF) induces normal and stable angiogenesis, whereas high level of VEGF causes irregular and over sprouted vasculature. Intermedin (IMD) is a novel member of calcitonin family, and was found to be able to restrict the excessive vessel sprouting. However, the underlying mechanism had not been elucidated. In this study, using in vitro and in vivo angiogenic models, we found that the loosening of endothelial junction could significantly increase the ability of low-dose VEGF to induce vessel sprouting. IMD inhibited the junction dissociation-induced vessel sprouting by re-establishing the complex of vascular endothelial cadherin on the cell-cell contact. Our findings suggested a novel mechanism through which IMD could restrict the excessive vessel sprouting by preventing the endothelial junction from dissociation, and provide new insight into the understanding of the regulation of sprouting angiogenesis.

Low-dose adrenomedullin-2/intermedin(8-47) reduces pulmonary ischemia/reperfusion injury

Adrenomedullin-2/intermedin stabilizes the pulmonary microvascular barrier challenged by application of thrombin ex vivo and by experimental ventilation in vivo. Here, we test the hypothesis that adrenomedullin-2/intermedin(8-47) protects mouse lungs from ischemia/reperfusion injury in vivo. C57BL/6 mice were anesthetized, intubated, ventilated, and heparinized. Blood vessels and the main bronchus of the left lung were clamped for 90min. Thereafter, lungs were reperfused for 120min. Five min before clamping and before reperfusion, mice obtained intravenous injections of adrenomedullin-2/intermedin(8-47). After reperfusion, mice were sacrificed and bronchoalveolar lavage of the left and the right lung was performed separately. The integrity of the blood-air barrier was investigated by electron microscopy using stereological methods. In response to ischemia/reperfusion injury, intraalveolar leukocytes accumulated in the ischemic lung. Two applications of 10ng/kg body weight adrenomedullin-2/intermedin(8-47) dramatically reduced leukocyte infiltration to about 15% (p≤0.001). Also the proportion of the subpopulation of neutrophil granulocytes decreased (12% vs 5%, p=0.013). Electron microscopy revealed a protection of the blood-air barrier by adrenomedullin-2/intermedin(8-47). Adrenomedullin-2/intermedin(8-47) ameliorates early ischemia/reperfusion injury in mouse lungs by protecting the integrity of the blood-air barrier and by potently reducing leukocyte influx into the alveolar space. Adrenomedullin-2/intermedin(8-47) might be of therapeutic interest in lung transplantation and cardiopulmonary bypass.

Induction of adrenomedullin 2/intermedin expression by thyroid stimulating hormone in thyroid

TSH is the important regulator of thyroid function but detailed molecular mechanisms have not been clarified. We first generated the iodine deficient (ID) rat in which goiter is induced by accelerated endogenous TSH secretion. The result of microarray analysis demonstrated markedly increased levels of adrenomedullin 2/intermedin (AM2/IMD) expression in the ID rat thyroid. AM2/IMD is a potent vasodilator. AM2/IMD mRNA expression was induced by TSH in a rat thyroid follicular cell line FRTL-5. Immunohistochemical analysis in human normal and Graves' disease thyroid revealed that AM2/IMD immunoreactivity was detected in follicular cells and more pronounced in Graves' disease. These results indicated that TSH induced AM2/IMD expression in the rat thyroid gland and it could locally work as a potent vasodilator, resulting in the expansion of thyroid inter-follicular capillaries. AM2/IMD could also contribute to facilitate thyroid hormone synthesis possibly via vasodilation effects and/or cAMP stimulating effects in the human thyroid gland.

Intermedin as a prognostic factor for major adverse cardiovascular events in patients with ST-segment elevation acute myocardial infarction

Intermedin functions systemically as a potent vasodilator and its plasma levels have been shown to be elevated in patients with acute myocardial infarction. This study aimed to evaluate the prognostic value of plasma intermedin level in the patients with ST-segment elevation acute myocardial infarction. Plasma intermedin concentrations of 128 patients and 128 healthy controls were determined using a radioimmunoassay. Patients were followed up for 6 months for major adverse cardiovascular events (MACE) consisting of cardiovascular mortality, reinfarction, hospitalization for decompensated heart failure, and lift-threatening arrhythmia. The association of plasma intermedin levels with MACE was investigated by univariate and multivariate analyses. Plasma intermedin levels were significantly higher in patients than in healthy subjects. Elevated plasma level of intermedin was identified as an independent predictor of MACE. Receiver operating characteristic curve analysis showed that plasma intermedin levels had high predictive value for MACE. Moreover, its predictive value was similar to Global Registry of Acute Coronary Events scores' based on area under curve. Meantime, it obviously improved Global Registry of Acute Coronary Events scores' predictive value in a combined logistic-regression model. In multivariate Cox's proportional hazard analysis, plasma intermedin level emerged as an independent predictor of MACE-free survival. Thus, our results suggest that high plasma intermedin level is associated with poor outcomes of patients and may be a useful prognostic biomarker in ST-segment elevation acute myocardial infarction.

Adrenomedullin and intermedin gene transcription is increased in leukocytes of patients with chronic heart failure at different stages of the disease

Adrenomedullin (ADM) is a vasodilatory peptide expressed in many tissues. Its levels are elevated in various diseases including chronic heart failure (CHF) and it has been suggested that the up-regulation of ADM in cardiac disease represents a protective mechanism. Similarly, intermedin (IMD), a novel member of the calcitonin/calcitonin gene-related peptide family, is considered a potential endogenous protector of the heart. Previous studies demonstrated that in CHF patients, elevated plasma concentrations of ADM and IMD reflect the patient's disease severity and prognosis, while the behavior of mRNA expression is not known. The aim of this study was to evaluate ADM/IDM transcriptomic profiling in human leukocytes of CHF patients as a function of clinical severity, assessing possible changes with respect to healthy subjects (C). mRNA expression was evaluated by Real-Time PCR and total RNA was extracted from leukocytes of C (n=8) and from CHF patients (NYHA I-II n=10; NYHA III-IV n=14) with PAXgene Blood RNA Kit. Significantly higher levels of ADM and IMD mRNA were found in CHF as a function of clinical severity (ADM: C=0.03 ± 0.013, NYHA I-II=0.11 ± 0.084, NYHA III-IV=11.46 ± 4.72, p=0.037 C vs NYHA III-IV, p=0.028 NYHA I-II vs NYHA III-IV; IMD: C=0.158 ± 0.041, NYHA I-II=0.93 ± 0.40, NYHA III-IV=2.6 ± 0.67, p=0.014 C vs NYHA III-IV, p=0.014 NYHA I-II vs NYHA III-IV). This study highlights, for the first time, the possibility of evaluating ADM and IMD mRNA expression in human whole blood samples by Real-Time PCR study providing further relevant information and providing a more complete interpretation of the pathophysiology of the disease.

Intermedin enhances sympathetic outflow via receptor-mediated cAMP/PKA signaling pathway in nucleus tractus solitarii of rats

Direct administration of intermedin (IMD) into the brain elicits cardiovascular effects different from the systemic administration. Nucleus tractus solitarii (NTS) is an important region for the cardiovascular regulation. The present study was designed to determine the effect of IMD on modulating the sympathetic outflow and its related molecular mechanism in the NTS. Renal sympathetic nerve activity (RSNA) and mean arterial pressure (MAP) were recorded in anesthetized rats. Site-specific microinjection of IMD (20pmol) bilaterally into the NTS significantly increased RSNA and MAP. IMD-evoked increases of RSNA and MAP were almost abolished by pretreatment with receptor antagonist ADM22-52, an adenylyl cyclase (AC) inhibitor SQ22536, or a protein kinase A (PKA) inhibitor Rp-cAMP. However, pretreatment with another receptor antagonist calcitonin gene-related peptide (CGRP)8-37 did not suppress the increases of RSNA and MAP induced by IMD. Furthermore, IMD increased the cyclic adenosine monophosphate (cAMP) level, which was inhibited by ADM22-52 pretreatment in the NTS. These results suggest that IMD participates in the sympathetic nerve activity and central regulation of the cardiovascular system and a receptor-mediated cAMP/PKA signaling pathway is involved in IMD-induced effects in the NTS.

Intermedin modulates hypoxic pulmonary vascular remodeling by inhibiting pulmonary artery smooth muscle cell proliferation

BACKGROUND

Hypoxic pulmonary arterial hypertension (PAH) is a disabling disease with limited treatment options. Hypoxic pulmonary vascular remodeling is a major cause of hypoxic PAH. Pharmacological agents that can inhibit the remodeling process may have great therapeutic value.

OBJECTIVE

To examine the effect of intermedin (IMD), a new calcitonin gene-related peptide family of peptide, on hypoxic pulmonary vascular remodeling.

METHODS

Rats were exposed to normoxia or hypoxia (∼10% O(2)), or exposed to hypoxia and treated with IMD, administered by an implanted mini-osmotic pump (6.5 μg/rat/day), for 4 weeks. The effects of IMD infusion on the development of hypoxic PAH and right ventricle (RV) hypertrophy, on pulmonary vascular remodeling, on pulmonary artery smooth muscle cell (PASMC) proliferation and apoptosis, and on the activations of l-arginine nitric oxide (NO) pathway and endoplasmic reticulum stress apoptotic pathway were examined.

RESULTS

Rats exposed to hypoxia developed PAH and RV hypertrophy. IMD treatment alleviated PAH and prevented RV hypertrophy. IMD inhibited hypoxic pulmonary vascular remodeling as indicated by reduced wall thickness and increased lumen diameter of pulmonary arterioles, and decreased muscularization of distal pulmonary vasculature in hypoxia-exposed rats. IMD treatment inhibited PASMC proliferation and promoted PASMC apoptosis. IMD treatment increased tissue level of constitutive NO synthase activity and tissue NO content in lungs, and enhanced l-arginine uptake into pulmonary vascular tissues. IMD treatment increased cellular levels of glucose-regulated protein (GRP) 78 and GRP94, two major markers of endoplasmic reticulum (ER) stress, and increased caspase-12 expression, the ER stress-specific caspase, in lungs and cultured PASMCs.

CONCLUSIONS

These results demonstrate that IMD treatment attenuates hypoxic pulmonary vascular remodeling, and thereby hypoxic PAH mainly by inhibiting PASMC proliferation. Promotion of PASMC apoptosis may also contribute to the inhibitory effect of IMD. Activations l-arginine-NO pathway and of ER stress-specific apoptosis pathway could be the mechanisms mediating the anti-proliferative and pro-apoptotic effects of IMD.

Effects of continuous intermedin infusion on blood pressure and hemodynamic function in spontaneously hypertensive rats

OBJECTIVE

To examine the effects of exogenously administered intermedin (IMD, adrenomedullin-2) on arterial blood pressure, cardiac function and the cardiovascular IMD receptor system in spontaneously hypertensive rats (SHRs) as well as to investigate the associated mechanisms.

METHODS

Thirteen week-old male rats were divided in Wistar Kyoto (WKY) group (n = 12), SHR group (n = 12), IMD group (SHRs infused with IMD 1-47 500 ng/kg per hour, n = 12), and ADM group (SHRs infused with adrenomedullin 500 ng/kg per hour, n = 12).

RESULTS

A two-week continuous administration of low dose IMD 1-47 via mini-osmotic pumps markedly reduced blood pressure, the maximal rates of increase and decrease of left-ventricle pressure development (LV ± dp/dt(max)), left ventricular systolic pressure and heart rate in SHRs. Furthermore, IMD also inhibited protein over-expression of cardiovascular IMD receptors, myocardial Receptor Activity-Modifying Proteins (RAMP1 and RAMP2), aortic RAMP1, RAMP2, RAMP3, and calcitonin receptor-like receptor (CRLR); suppressed up-regulation of aortic RAMP1, RAMP2, RAMP3 and CRLR gene expression; and markedly elevated the mRNA abundance of myocardial atrial natriuretic peptide (ANP) and myocardial brain natriuretic peptide (BNP). Additionally, IMD 1-47 administration in SHRs increased aortic cAMP concentration and reduced myocardial cAMP concentration.

CONCLUSION

These findings support the speculation that IMD, as a cardiovascular active peptide, is involved in blood pressure reduction and cardiac function amelioration during hypertension. The mechanism underlying this effect may involve IMD binding of a receptor complex formed by RAMPs and CRLR, and consequential regulation of cAMP levels and other cardiovascular active factors, such as ANP and BNP.