N ε -(Carboxymethyl)lysine Depositions in Intramyocardial Blood Vessels in Human and Rat Acute Myocardial Infarction

Increased perivascular fibrosis and pro-fibrotic cellular transition in intramyocardial blood vessels in myocardial infarction patients

Background and objectives

Structural and functional changes in the intramyocardial microcirculation increase the risk of myocardial infarction (MI). This study investigated intramyocardial perivascular fibrosis and pro-fibrotic cellular transitions in deceased acute and subacute MI patients to explore their involvement in the pathogenesis of MI.

Methods

Left ventricular tissue (LV) was obtained from the infarction area of autopsied patients with acute-phase MI (3-6 h; n = 24), subacute-phase MI (5-14 days; n = 12), and noninfarcted controls (n = 14). Perivascular fibrosis and fibroblast activation protein (FAP) expression were quantified using (immuno)histochemistry. Fibroblast-like transitioning of vascular smooth muscle cells (VSMC) and endothelial cells (EC) was quantified using immunofluorescent microscopy.

Results

Perivascular fibrosis was elevated in acute-phase (77.69 %) and subacute-phase (72.19 %: border zone 95.18 %: infarct core) MI patients (p < 0.0001) compared to controls (61.03 %). FAP expression was higher in both acute-phase (1.46 %) and subacute-phase (18.01 %: border zone 5.67 %: infarct core) compared to controls (0.46 %) (p < 0.05). VSMC fibroblast-like cellular transition (SMA + S100A4+ vessels fraction) was higher in acute-phase (31.96 %) and subacute-phase (21.90 %: border zone; 37.25 %: infarct core) MI compared to controls (8.95 %) (p < 0.05). Similarly, EC fibroblast-like cellular transition (CD31 + S100A4+ area fraction) was increased in acute-phase MI (10.14 %) and subacute-phase MI (8.31 %: border zone 10.15 %: infarct core) compared to controls (2.67 %) (p < 0.05).

Conclusion

Increased perivascular fibrosis, fibroblast activation and vascular cellular transition in intramyocardial blood vessels of MI patients may contribute to MI development. Further increases of FAP expression and perivascular fibrosis, particularly in subacute-phase infarct cores, suggest MI itself exacerbates fibroblast activation and perivascular fibrosis, theoretically increasing reinfarction risk.

Increased accumulation of the advanced glycation endproduct Ne(carboxymethyl) lysine in the intramyocardial vasculature in patients with epicarditis

Advanced glycation end-products (AGEs) are implicated in the pathogenesis of vascular disease. In previous studies we have found increased deposition of N(e)-(carboxymethyl)lysine (CML) in intramyocardial vasculature in the heart in acute myocardial infarction and myocarditis. It is known that the process of inflammation plays a role in the formation of AGEs. In this study we have explored the presence of CML (a major AGE) in the heart of patients with epicarditis using a monoclonal anti-CML antibody. Nine patients with epicarditis (n = 9) died and their hearts were used for this study, control were hearts from patients who died from conditions unrelated to heart disease and without signs of myocarditis or epicarditis CML deposition and complement were significantly increased in patients with epicarditis compared to control hearts. Thus epicarditis increases CML depositions in the intramyocardial vasculature.

The AGE-RAGE Axis and the Pathophysiology of Multimorbidity in COPD

Chronic obstructive pulmonary disease (COPD) is a disease of the airways and lungs due to an enhanced inflammatory response, commonly caused by cigarette smoking. Patients with COPD are often multimorbid, as they commonly suffer from multiple chronic (inflammatory) conditions. This intensifies the burden of individual diseases, negatively affects quality of life, and complicates disease management. COPD and comorbidities share genetic and lifestyle-related risk factors and pathobiological mechanisms, including chronic inflammation and oxidative stress. The receptor for advanced glycation end products (RAGE) is an important driver of chronic inflammation. Advanced glycation end products (AGEs) are RAGE ligands that accumulate due to aging, inflammation, oxidative stress, and carbohydrate metabolism. AGEs cause further inflammation and oxidative stress through RAGE, but also through RAGE-independent mechanisms. This review describes the complexity of RAGE signaling and the causes of AGE accumulation, followed by a comprehensive overview of alterations reported on AGEs and RAGE in COPD and in important co-morbidities. Furthermore, it describes the mechanisms by which AGEs and RAGE contribute to the pathophysiology of individual disease conditions and how they execute crosstalk between organ systems. A section on therapeutic strategies that target AGEs and RAGE and could alleviate patients from multimorbid conditions using single therapeutics concludes this review.

Cardiac inflammation and microvascular procoagulant changes are decreased in second wave compared to first wave deceased COVID-19 patients

Background

Compelling evidence has shown cardiac involvement in COVID-19 patients. However, the overall majority of these studies use data obtained during the first wave of the pandemic, while recently differences have been reported in disease course and mortality between first- and second wave COVID-19 patients. The aim of this study was to analyze and compare cardiac pathology between first- and second wave COVID-19 patients.

Methods

Autopsied hearts from first- (n = 15) and second wave (n = 10) COVID-19 patients and from 18 non-COVID-19 control patients were (immuno)histochemically analyzed. CD45+ leukocyte, CD68+ macrophage and CD3+ T lymphocyte infiltration, cardiomyocyte necrosis and microvascular thrombosis were quantified. In addition, the procoagulant factors Tissue Factor (TF), Factor VII (FVII), Factor XII (FXII), the anticoagulant protein Dipeptidyl Peptidase 4 (DPP4) and the advanced glycation end-product N(^ε)-Carboxymethyllysine (CML), as markers of microvascular thrombogenicity and dysfunction, were quantified.

Results

Cardiac inflammation was significantly decreased in second wave compared to first wave COVID-19 patients, predominantly related to a decrease in infiltrated lymphocytes and the occurrence of lymphocytic myocarditis. This was accompanied by significant decreases in cardiomyocyte injury and microvascular thrombosis. Moreover, microvascular deposits of FVII and CML were significantly lower in second wave compared to first wave COVID-19 patients.

Conclusions

These results show that in our cohort of fatal COVID-19 cases cardiac inflammation, cardiomyocyte injury and microvascular thrombogenicity were markedly decreased in second wave compared to first wave patients. This may reflect advances in COVID-19 treatment related to an increased use of steroids in the second COVID-19 wave.

Myocardial infarction coincides with increased NOX2 and Nε-(carboxymethyl) lysine expression in the cerebral microvasculature

Background

Myocardial infarction (MI) is associated with mental health disorders, in which neuroinflammation and cerebral microvascular dysfunction may play a role. Previously, we have shown that the proinflammatory factors N^ε-(carboxymethyl)lysine (CML) and NADPH oxidase 2 (NOX2) are increased in the human infarcted heart microvasculature. The aim of this study was to analyse the presence of CML and NOX2 in the cerebral microvasculature of patients with MI.

Methods

Brain tissue was obtained at autopsy from 24 patients with MI and nine control patients. According to their infarct age, patients with MI were divided into three groups: 3–6 hours old (phase I), 6 hours–5 days old (phase II) and 5–14 days old (phase III). CML and NOX2 in the microvasculature were studied through immunohistochemical analysis.

Results

We observed a 2.5-fold increase in cerebral microvascular CML in patients with phase II and phase III MI (phase II: 21.39±7.91, p=0.004; phase III: 24.21±10.37, p=0.0007) compared with non-MI controls (8.55±2.98). NOX2 was increased in microvessels in patients with phase II MI (p=0.002) and phase III MI (p=0.04) compared with controls. No correlation was found between CML and NOX2 (r=0.58, p=0.13).

Conclusions

MI coincides with an increased presence of CML and NOX2 in the brain microvasculature. These data point to proinflammatory alterations in the brain microvasculature that may underlie MI-associated mental health disorders.

Comparison of metabolic fate, target organs, and microbiota interactions of free and bound dietary advanced glycation end products

Increased intake of Western diets and ultra-processed foods is accompanied by increased intake of advanced glycation end products (AGEs). AGEs can be generated exogenously in the thermal processing of food and endogenously in the human body, which associated with various chronic diseases. In food, AGEs can be divided into free and bound forms, which differ in their bioavailability, digestion, absorption, gut microbial interactions and untargeted metabolites. We summarized the measurements and contents of free and bound AGE in foods. Moreover, the ingestion, digestion, absorption, excretion, gut microbiota interactions, and metabolites and metabolic pathways between free and bound AGEs based on animal and human studies were compared. Bound AGEs were predominant in most of the selected foods, while beer and soy sauce were rich in free AGEs. Only 10%-30% of AGEs were absorbed into the systemic circulation when orally administered. The excretion of ingested free and bound AGEs was approximately 90% and 60%, respectively. Dietary free CML has a detrimental effect on gut microbiota composition, while bound AGEs have both detrimental and beneficial impacts. Free and bound dietary AGEs changed amino acid metabolism, energy metabolism and carbohydrate metabolism. And besides, bound dietary AGEs altered vitamin metabolism, and glycerolipid metabolism.

Basement membrane proteins in various arterial beds from individuals with and without type 2 diabetes mellitus: a proteome study

BACKGROUND

Basement membrane (BM) accumulation is a hallmark of micro-vessel disease in diabetes mellitus (DM). We previously reported marked upregulation of BM components in internal thoracic arteries (ITAs) from type 2 DM (T2DM) patients by mass spectrometry. Here, we first sought to determine if BM accumulation is a common feature of different arteries in T2DM, and second, to identify other effects of T2DM on the arterial proteome.

METHODS

Human arterial samples collected during heart and vascular surgery from well-characterized patients and stored in the Odense Artery Biobank were analysed by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). We included ascending thoracic aortas (ATA) (n = 10 (type 2 DM, T2DM) and n = 10 (non-DM)); laser capture micro-dissected plaque- and media compartments from carotid plaques (n = 10 (T2DM) and n = 9 (non-DM)); and media- and adventitia compartments from ITAs (n = 9 (T2DM) and n = 7 (non-DM)).

RESULTS

We first extended our previous finding of BM accumulation in arteries from T2DM patients, as 7 of 12 pre-defined BM proteins were significantly upregulated in bulk ATAs consisting of > 90% media. Although less pronounced, BM components tended to be upregulated in the media of ITAs from T2DM patients, but not in the neighbouring adventitia. Overall, we did not detect effects on BM proteins in carotid plaques or in the plaque-associated media. Instead, complement factors, an RNA-binding protein and fibrinogens appeared to be regulated in these tissues from T2DM patients.

CONCLUSION

Our results suggest that accumulation of BM proteins is a general phenomenon in the medial layer of non-atherosclerotic arteries in patients with T2DM. Moreover, we identify additional T2DM-associated effects on the arterial proteome, which requires validation in future studies.

Immunohistochemistry of advanced glycation end product Nε-(carboxymethyl)lysine in coronary arteries in relation to cardiac fibrosis and serum N-terminal-pro basic natriuretic peptide in forensic autopsy cases

Objective

Advanced glycation end products (AGEs) are known to play important roles in the development of diabetes mellitus and atherosclerosis.　N^ε-(carboxymethyl)lysine (CML) is the major AGE, and is found in the arterial walls in the heart. The CML involvement in myocardial ischemia has been reported. We studied the immunohistochemical localization of CML in the hearts from forensic autopsies in relation to the age, serum N-terminal-pro basic natriuretic peptide (NT-proBNP), heart weights, and the degree of peri-myocardial fibrous tissues reflecting coronary microvascular infarction and myocardial remodeling.

Results

The CML immunoreactivity in the endothelial cells and intima of arterial walls in the interstitium of ventricular muscles was significantly stronger in the aged group, compatible with the progression of atherosclerosis. The blood level of NT-proBNP, a known useful marker for heart failure, had the positive correlation with the CML immunoreactivity. The degree of fibrosis, heart weights and the histories of hypertension and hyperlipidemia showed positive correlations with the CML immunoreactivity. Our results show the novel positive correlation between the CML immunohistochemistry in the heart vessels and heart conditions, and its future usefulness in the cardiovascular evaluation in histopathology.

Infectious myocarditis: the role of the cardiac vasculature

Infectious myocarditis is the result of an immune response to a microbial infection of the heart. The blood vessels of the heart, both the intramyocardial microvasculature and the large epicardial coronary arteries, play an important role in the pathogenesis of infectious myocarditis. First of all, in addition to cardiomyocytes, endothelial cells of the cardiac (micro)vasculature are direct targets for infection. Moreover, through the expression of adhesion molecules and antigen presenting Major Histocompatibility Complex molecules, the blood vessels assist in shaping the cellular immune response in infectious myocarditis. In addition, damage and dysfunction of the cardiac (micro)vasculature are associated with thrombus formation as well as aberrant regulation of vascular tone including coronary vasospasm. These in turn can cause cardiac perfusion abnormalities and even myocardial infarction. In this review, we will discuss the role of the cardiac (micro)vasculature in the pathogenesis of infectious myocarditis.

Characterization of advanced glycation end products and their receptor (RAGE) in an animal model of myocardial infarction

Circulating advanced glycation end products (AGE) and their receptor, RAGE, are increased after a myocardial infarction (MI) episode and seem to be associated with worse prognosis in patients. Despite the increasing importance of these molecules in the course of cardiac diseases, they have never been characterized in an animal model of MI. Thus, the aim of this study was to characterize AGE formation and RAGE expression in plasma and cardiac tissue during cardiac remodeling after MI in rats. Adult male Wistar rats were randomized to receive sham surgery (n = 15) or MI induction (n = 14) by left anterior descending coronary artery ligation. The MI group was stratified into two subgroups based on postoperative left ventricular ejection fraction: low (MIlowEF) and intermediate (MIintermEF). Echocardiography findings and plasma levels of AGEs, protein carbonyl, and free amines were assessed at baseline and 2, 30, and 120 days postoperatively. At the end of follow-up, the heart was harvested for AGE and RAGE evaluation. No differences were observed in AGE formation in plasma, except for a decrease in absorbance in MIlowEF at the end of follow-up. A decrease in yellowish-brown AGEs in heart homogenate was found, which was confirmed by immunodetection of N-ε-carboxymethyl-lysine. No differences could be seen in plasma RAGE levels among the groups, despite an increase in MI groups over the time. However, MI animals presented an increase of 50% in heart RAGE at the end of the follow-up. Despite the inflammatory and oxidative profile of experimental MI in rats, there was no increase in plasma AGE or RAGE levels. However, AGE levels in cardiac tissue declined. Thus, we suggest that the rat MI model should be employed with caution when studying the AGE-RAGE signaling axis or anti-AGE drugs for not reflecting previous clinical findings.

Quantitative assessment of organ distribution of dietary protein-bound 13 C-labeled Nɛ -carboxymethyllysine after a chronic oral exposure in mice

SCOPE

N^ɛ -Carboxymethyl-lysine (CML) is a prominent advanced glycation end-product which is not only found in vivo but also in food. It is known that a percentage of the dietary CML (dCML) is absorbed into the circulation and only partly excreted in the urine. Several studies have tried to measure how much dCML remains in tissues. However obstacles to interpreting the data have been found.

METHODS AND RESULTS

A new protocol which discriminates dCML from native CML (nCML) has been developed. Three CML isotopes with different mass-to-charge ratios were used: nCML N^ε -carboxymethyl-L-lysine, dCML N^ε -[¹³ C]carboxy[¹³ C]methyl-L-lysine and internal standard N^ε -carboxymethyl-L-[4,4,5,5-² H₄ ]lysine. Wild-type (n = 7) and RAGE^-/- (n = 8) mice were fed for 30 days with either a control, or a BSA-bound dCML-enriched diet. Organs were analyzed for nCML and dCML using liquid chromatography-tandem mass spectrometry. Mice exposed to dCML showed an accumulation in all tissues tested except fat. The rate of deposition was high (81-320 μg_dCML /g dry matter) in kidneys, intestine, and lungs and low (<5 μg/g) in heart, muscle, and liver. This accumulation was not RAGE dependent.

CONCLUSION

The kidney is not the only organ affected by the accumulation of dCML. Its high accumulation in other tissues and organs may also, however, have important physiological consequences.

Atrial fibrillation coincides with the advanced glycation end product N(ε)-(carboxymethyl)lysine in the atrium

Presence of advanced glycation end products (AGEs) in the heart induces a proinflammatory phenotype. However, the presence of AGEs within atrial tissue of atrial fibrillation (AF) patients is unknown and was analyzed here. Left atrial appendage tissue from 33 AF patients and 9 controls was analyzed for the presence of the major AGEs N(ε)-(carboxymethyl)lysine (CML), VCAM-1, neutrophilic granulocytes, lymphocytes, and macrophages in both the fat tissue and myocardium separately. The total amount of fibrosis was also analyzed. Presence of CML was significantly higher in blood vessels of the left atrial appendage in AF patients as compared to controls, independent of diabetes mellitus. In AF patients, VCAM-1 expression in blood vessels and the numbers of infiltrated neutrophilic granulocytes, lymphocytes, and macrophages significantly increased compared to controls, and were highest in the fat tissue; there was no significant difference in fibrosis compared to controls. Interestingly, total amount of CML and fibrosis in AF and control patients correlated positively. Finally, there was no difference between AF patients based on AF type or surgical indication in the presence of CML, VCAM-1 expression, inflammatory cells, and fibrosis. Our results indicate that in AF the intramyocardial blood vessels of the left atrial appendage have an increased CML presence and proinflammatory status coinciding with a local increase in the number of inflammatory cells.

Myocardial infarction induces atrial inflammation that can be prevented by C1-esterase inhibitor

AIMS

Inflammation plays an important role in the pathogenesis of myocardial infarction (MI). Whether MI induces atrial inflammation is unknown however. Here, we analysed atrial inflammation in patients with MI and in rats with experimentally induced MI. The effect of the anti-inflammatory agent C1-esterase inhibitor (C1inh) on atrial inflammation in rats was also analysed.

METHODS

In the hearts of patients who died at different time points after MI (total n=24, mean age=60), neutrophils (myeloperoxidase-positive cells), lymphocytes (CD45-positive cells) and macrophages (CD68-positive cells) were quantified in the myocardium of the left and right atria and the infarcted left and non-infarcted right ventricles and compared with control patients (n=5, mean age=59). For the left and right atria, inflammatory cells were also quantified in the atrial adipose tissue. MI was induced in 17 rats, of which 10 were subsequently treated with C1inh for 6 days. Forty-two days post-MI, lymphocytes, macrophages and the endothelial inflammation marker N^ε-(carboxymethyl)lysine (CML) were analysed in the myocardium of both the atria and ventricles.

RESULTS

In all investigated areas of the human hearts increased lymphocytes and macrophages were observed to a varying extent, especially between 6 h and 5 days following MI. Similarly, in rats MI resulted in an increase of inflammatory cells and CML in the atria. C1inh treatment decreased atrial inflammation.

CONCLUSIONS

MI induces atrial inflammation in patients and in rats. C1inh treatment could counteract this MI-induced atrial inflammation in rats.

Prevention of age-induced N(ε)-(carboxymethyl)lysine accumulation in the microvasculature

OBJECTIVE

N(ε)-(carboxymethyl)lysine (CML) is one of the major advanced glycation end products in both diabetics and nondiabetics. CML depositions in the microvasculature have recently been linked to the aetiology of acute myocardial infarction and cognitive impairment in Alzheimer's disease, possibly related to local enhancement of inflammation and oxidative processes. We hypothesized that CML deposition in the microvasculature of the heart and brain is age-induced and that it could be inhibited by a diet intervention with docosahexaenoic acid (DHA), an omega-3 fatty acid known for its anti-inflammatory and antioxidative actions.

MATERIALS AND METHODS

ApoE(-/-) mice (n = 50) were fed a Western diet and were sacrificed after 40, 70 and 90 weeks. Part of these mice (n = 20) were fed a Western diet enriched with DHA from 40 weeks on. CML in cardiac and cerebral microvessels was quantified using immunohistochemistry.

RESULTS

Cardiac microvascular depositions of CML significantly increased with an immunohistochemical score of 11·85 [5·92-14·60] at 40 weeks, to 33·17 [17·60-47·15] at 70 weeks (P = 0·005). At the same time points, cerebral microvascular CML increased from 6·45; [4·78-7·30] to 12·99; [9·85-20·122] (P = 0·003). DHA decreased CML in the intramyocardial vasculature at both 70 and 90 weeks, significant at 70 weeks [33·17; (17·60-47·15) vs. 14·73; (4·44-28·16) P = 0·037]. No such effects were found in the brain.

CONCLUSIONS

Accumulation of N(ε)-(carboxymethyl)lysine in the cerebral and cardiac microvasculature is age-induced and is prevented by DHA in the intramyocardial vessels of ApoE(-/-) mice.

Impaired microcirculatory perfusion in a rat model of cardiopulmonary bypass: the role of hemodilution

Although hemodilution is attributed as the main cause of microcirculatory impairment during cardiopulmonary bypass (CPB), this relationship has never been investigated. We investigated the distinct effects of hemodilution with or without CPB on microvascular perfusion and subsequent renal tissue injury in a rat model. Male Wistar rats (375–425 g) were anesthetized, prepared for cremaster muscle intravital microscopy, and subjected to CPB ( n = 9), hemodilution alone ( n = 9), or a sham procedure ( n = 6). Microcirculatory recordings were performed at multiple time points and analyzed for perfusion characteristics. Kidney and lung tissue were investigated for mRNA expression for genes regulating inflammation and endothelial adhesion molecule expression. Renal injury was assessed with immunohistochemistry. Hematocrit levels dropped to 0.24 ± 0.03 l/l and 0.22 ± 0.02 l/l after onset of hemodilution with or without CPB. Microcirculatory perfusion remained unaltered in sham rats. Hemodilution alone induced a 13% decrease in perfused capillaries, after which recovery was observed. Onset of CPB reduced the perfused capillaries by 40% (9.2 ± 0.9 to 5.5 ± 1.5 perfused capillaries per microscope field; P < 0.001), and this reduction persisted throughout the experiment. Endothelial and inflammatory activation and renal histological injury were increased after CPB compared with hemodilution or sham procedure. Hemodilution leads to minor and transient disturbances in microcirculatory perfusion, which cannot fully explain impaired microcirculation following cardiopulmonary bypass. CPB led to increased renal injury and endothelial adhesion molecule expression in the kidney and lung compared with hemodilution. Our findings suggest that microcirculatory impairment during CPB may play a role in the development of kidney injury.

Clinical diabetic cardiomyopathy: a two-faced disease with restrictive and dilated phenotypes

Diabetes mellitus-related cardiomyopathy (DMCMP) was originally described as a dilated phenotype with eccentric left ventricular (LV) remodelling and systolic LV dysfunction. Recently however, clinical studies on DMCMP mainly describe a restrictive phenotype with concentric LV remodelling and diastolic LV dysfunction. Both phenotypes are not successive stages of DMCMP but evolve independently to respectively heart failure with preserved left ventricular ejection fraction (HFPEF) or reduced left ventricular ejection fraction (HFREF). Phenotype-specific pathophysiological mechanisms were recently proposed for LV remodelling and dysfunction in HFPEF and HFREF consisting of coronary microvascular endothelial dysfunction in HFPEF and cardiomyocyte cell death in HFREF. A similar preferential involvement of endothelial or cardiomyocyte cell compartments explains DMCMP development into distinct restrictive/HFPEF or dilated/HFREF phenotypes. Diabetes mellitus (DM)-related metabolic derangements such as hyperglycaemia, lipotoxicity, and hyperinsulinaemia favour development of DMCMP with restrictive/HFPEF phenotype, which is more prevalent in obese type 2 DM patients. In contrast, autoimmunity predisposes to a dilated/HFREF phenotype, which manifests itself more in autoimmune-prone type 1 DM patients. Finally, coronary microvascular rarefaction and advanced glycation end-products deposition are relevant to both phenotypes. Diagnosis of DMCMP requires impaired glucose metabolism and exclusion of coronary, valvular, hypertensive, or congenital heart disease and of viral, toxic, familial, or infiltrative cardiomyopathy. In addition, diagnosis of DMCMP with restrictive/HFPEF phenotype requires normal systolic LV function and diastolic LV dysfunction, whereas diagnosis of DMCMP with dilated/HFREF phenotype requires systolic LV dysfunction. Treatment of DMCMP with restrictive/HFPEF phenotype is limited to diuretics and lifestyle modification, whereas DMCMP with dilated/HFREF phenotype is treated in accordance to HF guidelines.

Advanced glycation end product Nε-carboxymethyllysine induces endothelial cell injury: the involvement of SHP-1-regulated VEGFR-2 dephosphorylation

N(ε)-carboxymethyllysine (CML), a major advanced glycation end product, plays a crucial role in diabetes-induced vascular injury. The roles of protein tyrosine phosphatases and vascular endothelial growth factor (VEGF) receptors in CML-related endothelial cell injury are still unclear. Human umbilical vein endothelial cells (HUVECs) are a commonly used human EC type. Here, we tested the hypothesis that NADPH oxidase/reactive oxygen species (ROS)-mediated SH2 domain-containing tyrosine phosphatase-1 (SHP-1) activation by CML inhibits the VEGF receptor-2 (VEGFR-2, KDR/Flk-1) activation, resulting in HUVEC injury. CML significantly inhibited cell proliferation and induced apoptosis and reduced VEGFR-2 activation in parallel with the increased SHP-1 protein expression and activity in HUVECs. Adding recombinant VEGF increased forward biological effects, which were attenuated by CML. The effects of CML on HUVECs were abolished by SHP-1 siRNA transfection. Exposure of HUVECs to CML also remarkably escalated the integration of SHP-1 with VEGFR-2. Consistently, SHP-1 siRNA transfection and pharmacological inhibitors could block this interaction and elevating [(3)H]thymidine incorporation. CML also markedly activated the NADPH oxidase and ROS production. The CML-increased SHP-1 activity in HUVECs was effectively attenuated by antioxidants. Moreover, the immunohistochemical staining of SHP-1 and CML was increased, but phospho-VEGFR-2 staining was decreased in the aortic endothelium of streptozotocin-induced and high-fat diet-induced diabetic mice. We conclude that a pathway of tyrosine phosphatase SHP-1-regulated VEGFR-2 dephosphorylation through NADPH oxidase-derived ROS is involved in the CML-triggered endothelial cell dysfunction/injury. These findings suggest new insights into the development of therapeutic approaches to reduce diabetic vascular complications.

NOX5 expression is increased in intramyocardial blood vessels and cardiomyocytes after acute myocardial infarction in humans

Reactive oxygen species producing NADPH oxidases play important roles under different (patho)physiological conditions. NOX1, NOX2, and NOX4 are important sources of reactive oxygen species in the heart, but knowledge of the calcium-dependent NOX5 in the heart is lacking. The presence of NOX5 was studied via RT-PCR in heart tissue from patients with end-stage heart failure; the tissue was obtained during cardiac transplantation surgery. NOX5 positivity and cellular localization were studied via IHC and digital-imaging microscopy in heart tissues of patients who did not have heart disease and in infarction areas of patients who died of myocardial infarctions of different durations. Furthermore, NOX5 expression was analyzed in vitro by using Western blot analysis. NOX5 RNA was found in the hearts of controls and patients with ischemic cardiomyopathy. In controls, NOX5 localized to the endothelium of a limited number of intramyocardial blood vessels and to a limited number of scattered cardiomyocytes. In infarcted hearts, NOX5 expression increased, especially in infarctions >12 hours, which manifested as an increase in NOX5-positive intramyocardial blood vessels, as well as in endothelium, smooth muscle, and cardiomyocytes. NOX5 was found in cardiomyocyte cytoplasm, plasma membrane, intercalated disks, and cross striations. Western blot analysis confirmed NOX5 expression in isolated human cardiomyocytes. For the first time to our knowledge, we demonstrate NOX5 expression in human intramyocardial blood vessels and cardiomyocytes, with significant increases in the affected myocardium after acute myocardial infarction.

Human platelet lysate as a fetal bovine serum substitute improves human adipose-derived stromal cell culture for future cardiac repair applications

Adipose-derived stromal cells (ASC) are promising candidates for cell therapy, for example to treat myocardial infarction. Commonly, fetal bovine serum (FBS) is used in ASC culturing. However, FBS has several disadvantages. Its effects differ between batches and, when applied clinically, transmission of pathogens and antibody development against FBS are possible. In this study, we investigated whether FBS can be substituted by human platelet lysate (PL) in ASC culture, without affecting functional capacities particularly important for cardiac repair application of ASC. We found that PL-cultured ASC had a significant 3-fold increased proliferation rate and a significantly higher attachment to tissue culture plastic as well as to endothelial cells compared with FBS-cultured ASC. PL-cultured ASC remained a significant 25% smaller than FBS-cultured ASC. Both showed a comparable surface marker profile, with the exception of significantly higher levels of CD73, CD90, and CD166 on PL-cultured ASC. PL-cultured ASC showed a significantly higher migration rate compared with FBS-cultured ASC in a transwell assay. Finally, FBS- and PL-cultured ASC had a similar high capacity to differentiate towards cardiomyocytes. In conclusion, this study showed that culturing ASC is more favorable in PL-supplemented medium compared with FBS-supplemented medium.

The presence of N(ε)-(Carboxymethyl) lysine in the human epidermis

It is well known that advanced glycation end products (AGEs) are formed in long-lived dermal proteins such as collagen, and that their formation is related to skin aging. To examine the distribution of AGEs in skin tissue, we performed immunofluorescence studies on the human skin using an anti-AGEs antibody. Interestingly, AGEs signals were observed not only in the dermis but also in the epidermis. The objectives of this study were to confirm the presence of N(ε)-(Carboxymethyl) lysine (CML), an AGE structure, in the epidermis and to characterize the CML-modified proteins. The presence of CML in the stratum corneum (SC) was examined using liquid chromatography-electrospray ionization time-of-flight mass spectrometry. Concordance between the retention times of a compound in the SC hydrolysate and authentic CML, as well as with the specific mass transition of CML, was detected. This result showed that CML is present in the epidermis. In order to characterize the CML-modified proteins in the epidermis, protein samples extracted from the SC were analyzed using two-dimensional electrophoresis followed by an amino acid sequence analysis. The clarified peptide sequences covered approximately 27% of the amino acid sequences of cytokeratin 10 (K10). In the immunoblotting experiment following the two-dimensional electrophoresis, where protein samples extracted from whole epidermis were used, the position of the major CML-positive spots corresponded to those of K10. Taken together these results showed that CML is present in the human epidermis, and suggest that K10 is one of the target molecules for CML modification in the epidermis.

Glucose degradation products result in cardiovascular toxicity in a rat model of renal failure

BACKGROUND

It has been shown that glucose degradation products (GDP) generated during heat sterilization of peritoneal dialysis (PD) fluids impair the peritoneal membrane locally, then enter the systemic circulation and cause damage to the remnant kidney. Here we examined in subtotally nephrectomized (SNX) rats whether GDP also affect the cardiovascular system.

MATERIALS AND METHODS

Standard 5/6 nephrectomy was carried out in Sprague-Dawley rats; other rats were sham operated and left untreated for 3 weeks. Through an osmotic mini-pump, SNX+GDP group received GDP intravenously for 4 weeks; the SNX and the sham-operated groups remained without GDP. The experiment was terminated for all groups 7 weeks postoperatively. We analyzed cardiovascular damage by serum analyses and immunohistochemical investigation.

RESULTS

In SNX+GDP animals, expression of the advanced glycation end product (AGE) marker carboxymethyllysine and receptor of AGE (RAGE) were significantly higher in the myocardium and the aorta compared to the SNX rats. We also found significantly higher levels of apoptosis measured by caspase 3 staining in the cardiovascular system in the SNX+GDP group. Moreover, we observed a more pronounced expression of oxidative stress in the SNX+GDP rats compared to the SNX rats. In serum analyses, advanced oxidation protein products and reactive oxygen species were increased, as was immunohistochemical endothelial nitric oxide synthase.

CONCLUSIONS

In addition to local toxic effects, GDP cause systemic toxicity. Here we showed that, in SNX rats, administration of GDP increased cardiovascular damage. In particular, we found increased levels of AGE, RAGE, oxidative stress, and apoptosis. Whether these findings are of clinical relevance has to be further investigated.

Molecular determinants of heart failure with normal left ventricular ejection fraction

In population-based studies, heart failure with normal left ventricular (LV) ejection fraction (HFNEF) is now increasingly recognized and referred to as diastolic heart failure. However, the pathogenic mechanisms underlying HFNEF are incompletely understood, mainly because of limited availability of human myocardial biopsy material. Nevertheless, recent studies have examined in vivo hemodynamics, in vitro cardiomyocyte function, myofilamentary protein composition, collagen content and deposition of advanced glycation end products from LV endomyocardial biopsies. These measures were compared between HFNEF patients, subjects without symptoms of heart failure (controls), patients with heart failure and reduced ejection function (HFREF), and patients with HFNEF and HFREF with diabetes mellitus. This article summarizes the various findings of these studies and focuses on the possible correlations among altered LV myocardial structure, cardiomyocyte function, myofilamentary proteins, and extracellular matrices. These findings revealed novel mechanisms responsible for diastolic LV dysfunction, and they have important therapeutic implications, particularly HFNEF, for which a specific heart failure treatment strategy is largely lacking.

Elevation of the glycoxidation product N(epsilon)-(carboxymethyl)lysine in patients presenting with acute myocardial infarction

BACKGROUND

An important role in the acceleration of vascular disease has been previously suggested for advanced glycation end products. N(epsilon)-(carboxymethyl)lysine (CML) is an advanced glycation end product formed on protein by combined non-enzymatic glycation and glycoxidation reactions. CML reacts with the receptor of advanced glycation end products inducing impairment of endothelium dependent relaxation and is a marker of oxidative stress.

METHODS

A total of 40 patients with acute myocardial infarction (17 patients with ST-elevation myocardial infarction, 23 patients with non-ST-elevation myocardial infarction) and 40 patients with stable coronary artery disease were included consecutively in this study. During coronary angiography, peripheral venous blood sample was taken for measuring CML.

RESULTS

Serum levels of CML were significantly increased in patients with acute myocardial infarction [17.9+/-10.7 vs. 6.6+/-3.1 arbitrary units (AU)/mg protein, p<0.001]. A cut-off value of CML>9.5 AU/mg protein was associated with an odds ratio of acute myocardial infarction of 39.7 [95% confidence interval (CI): 11.1-142, p<0.001], a sensitivity of 0.85 (95% CI: 0.70-0.94) and a specificity of 0.88 (95% CI: 0.73-0.96).

CONCLUSIONS

CML levels are significantly elevated in patients presenting with acute myocardial infarction. These results suggest the involvement of endothelial dysfunction (through receptor interaction) and oxidative stress in acute myocardial infarction.

Mechanical ventilation during experimental sepsis increases deposition of advanced glycation end products and myocardial inflammation

Introduction

Increasing evidence links advanced glycation end products (AGE) including N^ε-(carboxymethyl)lysine (CML) to the development of heart failure. Accumulation of AGE leads to myocardial inflammation, which is considered as one of the possible mechanisms underlying sepsis-induced cardiac dysfunction. We hypothesized that mechanical ventilation (MV) augmented sepsis-induced myocardial CML deposition and inflammation.

Methods

Sepsis was induced using a modified cecal ligation and perforation (CLP) technique in 36 male adult Sprague Dawley rats. Rats were randomized to four hours of MV with low tidal volume (LTV: 6 ml/kg, PEEP 5 cmH₂O, n = 10) or high tidal volume (HTV: 15 ml/kg, PEEP 3 cmH₂O, n = 10) 24 hours after the induction of sepsis. Eight rats served as septic, non-ventilated controls and eight as non-septic, non-ventilated controls. After 28 hours all rats were killed. The number of extravascular polymorphonuclear (PMN) leucocytes, macrophages, and lymphocytes was measured as the number of positive cells/mm². The number of CML positive endothelial cells were semi-quantified based upon an intensity score. The CML intensity score was correlated with the number of inflammatory cells to study the association between CML depositions and inflammation.

Results

Gas exchange was comparable between the ventilated groups. Sepsis induced a significant increase in CML deposition in both ventricles that was significantly augmented by MV compared with non-ventilated septic controls (left ventricle 1.1 ± 1.0 vs 0.7 ± 0.1, P = 0.030; right ventricle 2.5 ± 0.5 vs 0.6 ± 0.1, P = 0.037), irrespective of ventilatory strategy. In the right ventricle there was a non-significant tendency towards increased CML deposition in the HTV group compared with septic, non-ventilated controls (1.0 ± 0.1 vs 0.7 ± 0.09, P = 0.07). Sepsis induced a significant increase in the number of macrophages and PMNs compared with non-ventilated septic controls that was augmented by MV, irrespective of ventilatory strategy. CML deposition was significantly correlated with the number of macrophages and PMNs in the heart.

Conclusions

Sepsis induces CML deposition in the heart with a predominant right ventricular inflammation that is significantly augmented by MV, irrespective of the ventilatory strategy.

Advanced glycation end products accumulate in vascular smooth muscle and modify vascular but not ventricular properties in elderly hypertensive canines

BACKGROUND

Advanced glycation end products (AGEs) are believed to increase left ventricular (LV) and vascular stiffness, in part via cross-linking proteins. We determined whether and where AGEs were increased in elderly hypertensive nondiabetic dogs and whether an AGE cross-link breaker (ALT-711) improved vascular or ventricular function.

METHODS AND RESULTS

Elderly dogs with experimental hypertension (old hypertensives [OH]) were randomized to receive ALT-711 (OH+ALT group; n=11; 1 mg/kg PO) or not (OH group; n=11) for 8 weeks. Conscious blood pressure measurements (weekly), echocardiography (week 8), and anesthetized study (week 8) with LV pressure-volume analysis and aortic pressure-dimension and pressure-flow assessment over a range of preloads and afterloads were performed. In LV and aorta from OH, OH+ALT, and young normal dogs, AGE content (immunohistochemistry and Western analysis for N(epsilon)-(carboxymethyl)lysine [CML]) was assessed. Aortic CML content was markedly increased in OH and OH+ALT dogs compared with young normal dogs. CML was localized to aortic and aortic vasa vasorum smooth muscle but not to collagen or elastin. CML was essentially undetectable in young normal, OH, or OH+ALT myocardium but was visible in large vessels in the LV. ALT-711 therapy was associated with lower blood pressure and pulse pressure, decreased systemic vascular resistance, increased aortic distensibility and arterial compliance, and, notably, significant aortic dilatation. Neither LV systolic nor diastolic function was different in OH+ALT versus OH dogs.

CONCLUSIONS

In elderly hypertensive canines, AGE accumulation and AGE cross-link breaker effects were confined to the vasculature without evidence of myocardial accumulation or effects. The lack of AGE accumulation in collagen-rich areas suggests that the striking vascular effects may be mediated by mechanisms other than collagen cross-linking.

Advanced glycation end products and diabetic foot disease

Diabetic foot disease is an important complication of diabetes. The development and outcome of foot ulcers are related to the interplay between numerous diabetes-related factors such as nerve dysfunction, impaired wound healing and microvascular and/or macrovascular disease.The formation of advanced glycation end products (AGEs) has been recognized as an important pathophysiological mechanism in the development of diabetic complications. Several mechanisms have been proposed by which AGEs lead to diabetic complications such as the accumulation of AGEs in the extracellular matrix causing aberrant cross-linking, the binding of circulating AGEs to the receptor of AGEs (RAGE) on different cell types and activation of key cell signalling pathways with subsequent modulation of gene expression, and intracellular AGE formation leading to quenching of nitric oxide and impaired function of growth factors. In the last decade, many experimental studies have shown that these effects of AGE formation may play a role in the pathogenesis of micro- and macrovascular complications of diabetes, diabetic neuropathy and impaired wound healing. In recent years also, several clinical studies have shown that glycation is an important pathway in the pathophysiology of those complications that predispose to the development of foot ulcers. Currently, there are a number of ways to prevent or decrease glycation and glycation-induced tissue damage. Although not in the area of neuropathy or wound healing, recent clinical studies have shown that the AGE-breakers may be able to decrease adverse vascular effects of glycation with few side effects.

Diastolic stiffness of the failing diabetic heart: importance of fibrosis, advanced glycation end products, and myocyte resting tension

BACKGROUND

Excessive diastolic left ventricular stiffness is an important contributor to heart failure in patients with diabetes mellitus. Diabetes is presumed to increase stiffness through myocardial deposition of collagen and advanced glycation end products (AGEs). Cardiomyocyte resting tension also elevates stiffness, especially in heart failure with normal left ventricular ejection fraction (LVEF). The contribution to diastolic stiffness of fibrosis, AGEs, and cardiomyocyte resting tension was assessed in diabetic heart failure patients with normal or reduced LVEF.

METHODS AND RESULTS

Left ventricular endomyocardial biopsy samples were procured in 28 patients with normal LVEF and 36 patients with reduced LVEF, all without coronary artery disease. Sixteen patients with normal LVEF and 10 with reduced LVEF had diabetes mellitus. Biopsy samples were used for quantification of collagen and AGEs and for isolation of cardiomyocytes to measure resting tension. Diabetic heart failure patients had higher diastolic left ventricular stiffness irrespective of LVEF. Diabetes mellitus increased the myocardial collagen volume fraction only in patients with reduced LVEF (from 14.6+/-1.0% to 22.4+/-2.2%, P<0.001) and increased cardiomyocyte resting tension only in patients with normal LVEF (from 5.1+/-0.7 to 8.5+/-0.9 kN/m2, P=0.006). Diabetes increased myocardial AGE deposition in patients with reduced LVEF (from 8.8+/-2.5 to 24.1+/-3.8 score/mm2; P=0.005) and less so in patients with normal LVEF (from 8.2+/-2.5 to 15.7+/-2.7 score/mm2, P=NS).

CONCLUSIONS

Mechanisms responsible for the increased diastolic stiffness of the diabetic heart differ in heart failure with reduced and normal LVEF: Fibrosis and AGEs are more important when LVEF is reduced, whereas cardiomyocyte resting tension is more important when LVEF is normal.

Markers of endothelial activity are related to components of the metabolic syndrome, but not to circulating concentrations of the advanced glycation end-product Nɛ-carboxymethyl-lysine in healthy Swedish men

Endothelial function is considered important in the development of cardiovascular diseases and type 2 diabetes. Circulating advanced glycation end-products (AGEs) and dietary components have been shown to affect endothelial function in type 2 diabetics, but determinants of endothelial function in a non-diabetic population are more poorly investigated. Therefore, we investigated relationships between dietary habits, AGEs and endothelial activation in men with isolated metabolic disturbances. Circulating markers of endothelial activation (soluble forms of vascular cell adhesion molecule-1, intercellular adhesion molecule-1, E-selectin and von Willebrand factor) and plasma N epsilon-carboxymethyl-lysine (CML, the predominant AGE in human plasma) were analyzed in a cross-sectional study of 294 healthy men. Individuals completed a 7-day dietary record, and metabolic and inflammatory parameters were determined. NCEP/ATPIII-criteria were used to define the metabolic syndrome. Endothelial activation was higher in individuals with the metabolic syndrome, and was positively related to certain features of the syndrome (insulin, glucose, inflammation and obesity), but not to others (triacylglycerol and blood pressure). Dietary factors were related to endothelial activation, but CML was not. Multivariate analysis revealed energy and alcohol intake, along with insulin and markers of oxidative stress and inflammation, to be positive predictors of endothelial activation. In this cohort of otherwise healthy men, endothelial activation was increased in individuals with the full metabolic syndrome, but not in those with only some of the components of the metabolic syndrome. Insulin resistance, inflammation, oxidative stress, the dietary intake of energy and alcohol, but not plasma CML, predicted endothelial activation in these men.

Anti-inflammatory agents and monoHER protect against DOX-induced cardiotoxicity and accumulation of CML in mice

Cardiac damage is the major limiting factor for the clinical use of doxorubicin (DOX). Preclinical studies indicate that inflammatory effects may be involved in DOX-induced cardiotoxicity. N^ε-(carboxymethyl) lysine (CML) is suggested to be generated subsequent to oxidative stress, including inflammation. Therefore, the aim of this study was to investigate whether CML increased in the heart after DOX and whether anti-inflammatory agents reduced this effect in addition to their possible protection on DOX-induced cardiotoxicity. These effects were compared with those of the potential cardioprotector 7-monohydroxyethylrutoside (monoHER).

BALB/c mice were treated with saline, DOX alone or DOX preceded by ketoprofen (KP), dexamethasone (DEX) or monoHER. Cardiac damage was evaluated according to Billingham. N^ε-(carboxymethyl) lysine was quantified immunohistochemically.

Compared to saline, a 21.6-fold increase of damaged cardiomyocytes was observed in mice treated with DOX (P<0.001). Addition of KP, DEX or monoHER before DOX significantly reduced the mean ratio of abnormal cardiomyocytes in comparison to mice treated with DOX alone (P⩽0.02). In addition, DOX induced a significant increase in the number of CML-stained intramyocardial vessels per mm² (P=0.001) and also in the intensity of CML staining (P=0.001) compared with the saline-treated group. N^ε-(carboxymethyl) lysine positivity was significantly reduced (P⩽0.01) by DOX-DEX, DOX-KP and DOX-monoHER. These results confirm that inflammation plays a role in DOX-induced cardiotoxicity, which is strengthened by the observed DOX-induced accumulation of CML, which can be reduced by anti-inflammatory agents and monoHER.

The role of mitochondrial K(ATP) channels in cardioprotection

Pro-coagulant and pro-inflammatory intramyocardial (micro)vasculature plays an important role in acute myocardial infarction (AMI). Currently, inhibition of serine protease dipeptidyl peptidase 4 (DPP4) receives a lot of interest as an anti-hyperglycemic therapy in type 2 diabetes patients. However, DPP4 also possesses anti-thrombotic properties and may behave as an immobilized anti-coagulant on endothelial cells. Here, we studied the expression and activity of endothelial DPP4 in human myocardial infarction in relation to a prothrombogenic endothelial phenotype. Using (immuno)histochemistry, DPP4 expression and activity were found on the endothelium of intramyocardial blood vessels in autopsied control hearts (n = 9). Within the infarction area of AMI patients (n = 73), this DPP4 expression and activity were significantly decreased, coinciding with an increase in Tissue Factor expression. In primary human umbilical vein endothelial cells (HUVECs), Western blot analysis and digital imaging fluorescence microscopy revealed that DPP4 expression was strongly decreased after metabolic inhibition, also coinciding with Tissue Factor upregulation. Interestingly, inhibition of DPP4 activity with diprotin A also enhanced the amount of Tissue Factor encountered and induced the adherence of platelets under flow conditions. Ischemia induces loss of coronary microvascular endothelial DPP4 expression and increased Tissue Factor expression in AMI as well as in vitro in HUVECs. Our data suggest that the loss of DPP4 activity affects the anti-thrombogenic nature of the endothelium.