Cardiac kinin level in experimental diabetes mellitus: role of kininases

Accelerated ageing and coronary microvascular dysfunction in chronic heart failure in Tgαq*44 mice

Age represents a major risk factor in heart failure (HF). However, the mechanisms linking ageing and HF are not clear. We aimed to identify the functional, morphological and transcriptomic changes that could be attributed to cardiac ageing in a model of slowly progressing HF in Tgαq*44 mice in reference to the cardiac ageing process in FVB mice. In FVB mice, ageing resulted in the impairment of diastolic cardiac function and in basal coronary flow (CF), perivascular and interstitial fibrosis without changes in the cardiac activity of angiotensin-converting enzyme (ACE) or aldosterone plasma concentration. In Tgαq*44 mice, HF progression was featured by the impairment of systolic and diastolic cardiac function and in basal CF that was associated with a distinct rearrangement of the capillary architecture, pronounced perivascular and interstitial fibrosis, progressive activation of cardiac ACE and systemic angiotensin-aldosterone-dependent pathways. Interestingly, cardiac ageing genes and processes were represented in Tgαq*44 mice not only in late but also in early phases of HF, as evidenced by cardiac transcriptome analysis. Thirty-four genes and 8 biological processes, identified as being ageing related, occurred early and persisted along HF progression in Tgαq*44 mice and were mostly associated with extracellular matrix remodelling and fibrosis compatible with perivascular fibrosis resulting in coronary microvascular dysfunction (CMD) in Tgαq*44 mice. In conclusion, accelerated and persistent cardiac ageing contributes to the pathophysiology of chronic HF in Tgαq*44 mice. In particular, prominent perivascular fibrosis of microcirculation resulting in CMD represents an accelerated cardiac ageing phenotype that requires targeted treatment in chronic HF.

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) and Comorbidities: Linked by Vascular Pathomechanisms and Vasoactive Mediators?

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is often associated with various other syndromes or conditions including mast cell activation (MCA), dysmenorrhea and endometriosis, postural tachycardia (POTS) and small fiber neuropathy (SFN). The causes of these syndromes and the reason for their frequent association are not yet fully understood. We previously published a comprehensive hypothesis of the ME/CFS pathophysiology that explains the majority of symptoms, findings and chronicity of the disease. We wondered whether some of the identified key pathomechanisms in ME/CFS are also operative in MCA, endometriosis and dysmenorrhea, POTS, decreased cerebral blood flow and SFN, and possibly may provide clues on their causes and frequent co-occurrence. Our analysis indeed provides strong arguments in favor of this assumption, and we conclude that the main pathomechanisms responsible for this association are excessive generation and spillover into the systemic circulation of inflammatory and vasoactive tissue mediators, dysfunctional β2AdR, and the mutual triggering of symptomatology and disease initiation. Overall, vascular dysfunction appears to be a strong common denominator in these linkages.

A Unifying Hypothesis of the Pathophysiology of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): Recognitions from the finding of autoantibodies against ß2-adrenergic receptors

Myalgic Encephalomyelitis or Chronic Fatigue Syndrome (CFS/ME) is a complex and severely disabling disease with a prevalence of 0.3% and no approved treatment and therefore a very high medical need. Following an infectious onset patients suffer from severe central and muscle fatigue, chronic pain, cognitive impairment, and immune and autonomic dysfunction. Although the etiology of CFS/ME is not solved yet, there is numerous evidence for an autoantibody mediated dysregulation of the immune and autonomic nervous system. We found elevated ß2 adrenergic receptor (ß2AdR) and M3 acetylcholine receptor antibodies in a subset of CFS/ME patients. As both ß2AdR and M3 acetylcholine receptor are important vasodilators, we would expect their functional disturbance to result in vasoconstriction and hypoxemia. An impaired circulation and oxygen supply could result in many symptoms of ME/CFS. There are consistent reports of vascular dysfunction in ME/CFS. Muscular and cerebral hypoperfusion has been shown in ME/CFS in various studies and correlated with fatigue. Metabolic changes in ME/CFS are also in line with a concept of hypoxia and ischemia. Here we try to develop a unifying working concept for the complex pathomechanism of ME/CFS based on the presence of dysfunctional autoantibodies against ß2AdR and M3 acetylcholine receptor and extrapolate it to the pathophysiology of ME/CFS without an autoimmune pathogenesis.

Neprilysin Inhibitors and Bradykinin

Bradykinin has important physiological actions related to the regulation of blood vessel tone and renal function, and protection from ischemia reperfusion injury. However, bradykinin also contributes to pathological states such as angioedema and inflammation. Bradykinin is metabolized by many different peptidases that play a major role in the control of bradykinin levels. Peptidase inhibitor therapies such as angiotensin converting enzyme (ACE) and neprilysin inhibitors increase bradykinin levels, and the challenge for such therapies is to achieve the beneficial cardiovascular and renal effects without the adverse consequences such as angioedema that may result from increased bradykinin levels. Neprilysin also metabolizes natriuretic peptides. However, despite the potential therapeutic benefit of increased natriuretic peptide and bradykinin levels, neprilysin inhibitor therapy has only modest efficacy in essential hypertension and heart failure. Initial attempts to combine neprilysin inhibition with inhibition of the renin angiotensin system led to the development of omapatrilat, a drug that combines ACE and neprilysin inhibition. However, omapatrilat produced an unacceptably high incidence of angioedema in patients with hypertension (2.17%) in comparison with the ACE inhibitor enalapril (0.68%), although angioedema incidence was less in patients with heart failure with reduced ejection fraction (HFrEF) treated with omapatrilat (0.8%), and not different from that for enalapril therapy (0.5%). More recently, LCZ696, a drug that combines angiotensin receptor blockade and neprilysin inhibition, was approved for the treatment of HFrEF. The approval of LCZ696 therapy for HFrEF represents the first approval of long-term neprilysin inhibitor administration. While angioedema incidence was acceptably low in HFrEF patients receiving LCZ696 therapy (0.45%), it remains to be seen whether LCZ696 therapy for other conditions such as hypertension is also accompanied by an acceptable incidence of angioedema.

Identification and Validation of a Salivary Protein Panel to Detect Heart Failure Early

BACKGROUND

Over 26 million people suffer from heart failure (HF) globally. Current diagnosis of HF relies on clinical evaluation, blood assays and imaging techniques. Our aim is to develop a diagnostic assay to detect HF in at risk individuals within the community using human saliva as a medium, potentially leading to a simple, safe early warning system.

METHODS

Saliva samples were collected from healthy controls (n=36) and HF patients (n=75). Salivary proteome profiles were analysed by Sequential Window Acquisition of All Theoretical fragment ion spectra - Mass Spectrometry (SWATH-MS). A total of 738 proteins were quantified and 177 proteins demonstrated significant differences between HF patients and healthy controls. Candidate biomarkers were chosen based on their abundance and difference between the two cohorts. A multi-protein panel was developed using logistic regression analysis. The diagnostic performance of the multi-protein panel was assessed using receiver operative characteristic curves. The candidate proteins were further confirmed, using western blot analysis, and validated technically, using an independent biological cohort.

RESULTS

A group of six proteins were chosen in the discovery phase as potential candidates based on their differences in the abundance between the two cohorts. During the validation phase, two of the proteins were not detected with western blotting and as such were removed. The final panel consists of four proteins with sensitivity of 83.3%, specificity of 62.5% with an area under ROC curve of 0.78 in discriminating healthy controls from NYHA class I/II HF patients, and was validated in a second independent cohort study.

CONCLUSION

Analysis of salivary proteome using SWATH-MS revealed novel HF-specific protein candidates yielding high diagnostic performance. A multi-centre longitudinal clinical trial will be the next step before clinical implementation of this panel.

Angiotensin type 1a receptor-deficient mice develop diabetes-induced cardiac dysfunction, which is prevented by renin-angiotensin system inhibitors

Background

Diabetes-induced organ damage is significantly associated with the activation of the renin-angiotensin system (RAS). Recently, several studies have demonstrated a change in the RAS from an extracellular to an intracellular system, in several cell types, in response to high ambient glucose levels. In cardiac myocytes, intracellular angiotensin (ANG) II synthesis and actions are ACE and AT₁ independent, respectively. However, a role of this system in diabetes-induced organ damage is not clear.

Methods

To determine a role of the intracellular ANG II in diabetic cardiomyopathy, we induced diabetes using streptozotocin in AT_1a receptor deficient (AT_1a-KO) mice to exclude any effects of extracellular ANG II. Further, diabetic animals were treated with a renin inhibitor aliskiren, an ACE inhibitor benazeprilat, and an AT₁ receptor blocker valsartan.

Results

AT_1a-KO mice developed significant diastolic and systolic dysfunction following 10 wks of diabetes, as determined by echocardiography. All three drugs prevented the development of cardiac dysfunction in these animals, without affecting blood pressure or glucose levels. A significant down regulation of components of the kallikrein-kinin system (KKS) was observed in diabetic animals, which was largely prevented by benazeprilat and valsartan, while aliskiren normalized kininogen expression.

Conclusions

These data indicated that the AT_1a receptor, thus extracellular ANG II, are not required for the development of diabetic cardiomyopathy. The KKS might contribute to the beneficial effects of benazeprilat and valsartan in diabetic cardiomyopathy. A role of intracellular ANG II is suggested by the inhibitory effects of aliskiren, which needs confirmation in future studies.

Cobalt-Protoporphyrin Improves Heart Function by Blunting Oxidative Stress and Restoring NO Synthase Equilibrium in an Animal Model of Experimental Diabetes

Myocardial dysfunction and coronary macro/microvascular alterations are the hallmarks of diabetic cardiomyopathy and are ascribed to increased oxidative stress and altered nitric oxide synthase (NOS) activity. We hypothesize that pre-treatment by cobalt-protoporphyrin IX (CoPP) ameliorates both myocardial function and coronary circulation in streptozotocin (STZ)-induced diabetic rats. Isolated hearts from diabetic rats in Langendorff configuration displayed lower left ventricular function and higher coronary resistance (CR) compared to hearts from control animals. CoPP treatment of diabetic animals (0.3 mg/100 g body weight i.p., once a week for 3 weeks) significantly increased all the contractile/relaxation indexes (p < 0.01), while decreasing CR (p < 0.01). CoPP enhanced HO-1 protein levels and reduced oxidative stress in diabetic animals, as indicated by the significant (p < 0.05) decrease in heart % GSSG, [Formula: see text] and malondialdehyde (MDA) levels. CoPP increased adiponectin levels and phosphorylation of AKT and AMPK and reversed the eNOS/iNOS expression imbalance observed in the untreated diabetic heart. Furthermore, after CoPP treatment, a rise in malonyl-CoA as well as a decrease in acetyl-CoA was observed in diabetic hearts. In this experimental model of diabetic cardiomyopathy, CoPP treatment improved both cardiac function and coronary flow by blunting oxidative stress, restoring eNOS/iNOS expression balance and increasing HO-1 levels, thereby favoring improvement in both endothelial function and insulin sensitivity.

Kinins in cardiac inflammation and regeneration: insights from ischemic and diabetic cardiomyopathy

The kallikrein-kinin system (KKS) is a system of vasoactive peptides, the kinins, involved in different aspects of remodeling, inflammation and angiogenesis. Kinins mediate their actions through two receptors, B1R and B2R. It is increasingly recognized that the KKS is involved in the inflammatory processes of the heart. Evidence shows that the B2R is beneficial in myocardial diseases, protecting from inflammation, fibrosis and apoptosis, while B1R shows a proinflammatory character contributing to the disease progression by increasing the production of cytokines and stimulating the migration of immune cells. Furthermore, novel important actions of the KKS and its receptors contribute to neovascularization and recruitment of endothelial progenitor cells in ischemic areas and endothelial dysfunction. The kinin receptors could therefore constitute potential therapeutic targets in the treatment of myocardial ischemia and diabetic cardiomyopathy.

Development of diabetic cardiomyopathy and the kallikrein-kinin system--new insights from B1 and B2 receptor signaling

Diabetic cardiomyopathy is a specific cardiomyopathy which develops in patients with diabetes mellitus in the absence of coronary atherosclerosis and hypertension. Despite the potential importance of this disease entity, the underlying mechanisms are only incompletely understood. Changes in calcium handling, disruption of the extracellular matrix regulation with accumulation of cardiac collagen, and furthermore cardiac inflammation may be an important mediator of this disease. This brief review focuses on the current aspects of the kallikrein-kinin system and its influence on the development of diabetic cardiomyopathy with particular regard to the kinin receptors B1 and B2, as their role in the development of this disease is still under discussion. Whether the role of the B1 receptor is similar to the well-described beneficial role of the B2 receptor or whether its function is opposed to the B2 receptor is controversial. Some recent findings suggest that the B1 receptor mediates cardiac inflammation and therefore may be detrimental for cardiac function in the setting of diabetic cardiomyopathy.

Attenuation of left ventricular dysfunction by an ACE inhibitor after myocardial infarction in a kininogen-deficient rat model

Bradykinin (BK) coronary outflow and left ventricular (LV) performance of kininogen-deficient Brown Norway Katholiek (BNK) rats and Brown Norway Hannover (BNH) controls were investigated. We analyzed whether the angiotensin-converting enzyme (ACE) inhibitor ramipril is able to attenuate LV dysfunction after induction of myocardial infarction (MI) in this animal model. Ex vivo, the basal BK content in the coronary outflow of buffer-perfused, isolated hearts was measured by specific radioimmunoassay. In vivo, left ventricular pressure (LVP), the maximal rate of LVP increase, LV end-diastolic pressure, the maximal rate of LVP decrease and heart rate were determined using a tip catheter 3 weeks after induction of MI. Compared to BNK rats, basal BK outflow was increased 30-fold in controls (p<0.01). In vivo, we found no significant differences between sham-ligated BNK and BNH rats in basal LV function. After MI, the impairment of LV function was significantly worse in BNK rats when compared to BNH rats. ACE inhibition significantly attenuated this LV dysfunction in both groups, when compared to untreated animals. Reduced basal BK level resulting from kininogen deficiency has no effect on basal LV function, but remains to be a risk factor for the ischemic heart. However, ACE inhibition is sufficient to improve LV function despite kininogen deficiency.

Anti-inflammatory effects of atorvastatin improve left ventricular function in experimental diabetic cardiomyopathy

AIMS/HYPOTHESIS

Emerging evidence suggests that statins exert beneficial effects beyond those predicted by their cholesterol-lowering actions. We investigated whether atorvastatin influences the development of left ventricular (LV) dysfunction, independently of cholesterol-lowering, in an experimental model of type 1 diabetes mellitus cardiomyopathy.

METHODS

Streptozotocin-induced diabetic rats were treated with atorvastatin (50 mg/kg daily, orally) or with vehicle for 6 weeks. LV function was analysed using tip-catheter measurements. Cardiac stainings of TNF-alpha, IL-1beta, intercellular adhesion molecule-1, vascular cellular adhesion molecule-1, CD11a/lymphocyte-associated antigen-1, CD11b/macrophage antigen alpha, CD18/beta2-integrin, ED1/CD68, collagen I and III, and Sirius Red were assessed by digital image analysis. Ras-related C3 botulinum toxin substrate (RAC1) and ras homologue gene family, member A (RHOA) activities were determined by RAC1 glutathione-S-transferase-p21-activated kinase and rhotekin pull-down assays, respectively. Cardiac lipid peroxides were measured by a colorimetric assay. The phosphorylation state of p38 mitogen-activated protein kinase (MAPK) and endothelial nitric oxide synthase (eNOS) protein production were analysed by western blot.

RESULTS

Diabetes was associated with induced cardiac stainings of TNF-alpha, IL-1beta, cellular adhesion molecules, increased leucocyte infiltration, macrophage residence and cardiac collagen content. In contrast, atorvastatin reduced both intramyocardial inflammation and myocardial fibrosis, resulting in improved LV function. This effect was paralleled with a normalisation of diabetes-induced RAC1 and RHOA activity, in the absence of LDL-cholesterol lowering. In addition, atorvastatin decreased diabetes-induced cardiac lipid peroxide levels and p38 MAPK phosphorylation by 1.3-fold (p < 0.05) and 3.2-fold (p < 0.0005), respectively, and normalised the reduced eNOS production caused by diabetes.

CONCLUSIONS/INTERPRETATION

These data indicate that atorvastatin, independently of its LDL-cholesterol-lowering capacity, reduces intramyocardial inflammation and myocardial fibrosis, resulting in improved LV function in an experimental model of diabetic cardiomyopathy.

The role of the renal kallikrein-kinin system in diabetic nephropathy

PURPOSE OF REVIEW

Diabetic nephropathy is one of the most common complications in diabetes mellitus. Multiple pathogenic mechanisms are now believed to contribute to this disease, including inflammatory cytokines, autacoids and oxidative stress. Numerous studies have shown that the kallikrein-kinin system may be involved in these mechanisms. This review focuses on recent research advance on the potential role of the kallikrein-kinin system in the development of diabetic nephropathy, and its clinical relevance.

RECENT FINDINGS

A collection of recent studies has shown that angiotensin-converting enzyme inhibitors, which inhibit angiotensin II formation and degradation of bradykinin, and vasopeptidase inhibitors attenuated the development of diabetic nephropathy in experimental animals and clinical settings. The role of the kallikrein-kinin system in diabetes is further supported by findings that diabetic nephropathy is worsened in diabetic mice lacking bradykinin B2 receptors. Although long-acting bradykinin B2 receptor agonists have been shown to have renal protective effects, their therapeutic benefits have not been well studied.

SUMMARY

Current experimental investigations demonstrated that pharmacological intervention of the kallikrein-kinin system improved renal conditions in diabetes mellitus. These findings suggest that the kallikrein-kinin system may be a therapeutic target in preventing and treating diabetic nephropathy.

Cardiac function and remodeling is attenuated in transgenic rats expressing the human kallikrein-1 gene after myocardial infarction

Bradykinin coronary outflow, left ventricular performance and left ventricular dimensions of transgenic rats harboring the human tissue kallikrein-1 gene TGR(hKLK1) were investigated under basal and ischemic conditions. Bradykinin content in the coronary outflow of buffer-perfused, isolated hearts of controls and TGR(hKLK1) was measured by specific radioimmunoassay before and after global ischemia. Left ventricular function and left ventricular dimensions were determined in vivo using a tip catheter and echocardiography 6 days and 3 weeks after induction of myocardial infarction. Left ventricular type I collagen mRNA expression was analyzed by RNase protection assay. Compared to controls, basal bradykinin outflow was 3.5 fold increased in TGR(hKLK1). Ischemia induced an increase of bradykinin coronary outflow in controls but did not induce a further increase in TGR(hKLK1). However, despite similar unchanged infarction sizes, left ventricular function and remodeling improved in TGR(hKLK1) after myocardial infarction, indicated by an increase in left ventricular pressure (+34%; P<0.05), contractility (dp/dt max. +25%; P<0.05), and in ejection fraction (+20%; P<0.05) as well as by a reduction in left ventricular enddiastolic pressure (-49%, P<0.05), left ventricular enddiastolic diameter (-20%, P<0.05), and collagen mRNA expression (-15%, P<0.05) compared to controls. A chronically activated transgenic kallikrein kinin system with expression of human kallikrein-1 gene counteracts the progression of left ventricular contractile dysfunction after experimental myocardial infarction. Further studies have to show whether these results can be caused by other therapeutically options. Long acting bradykinin receptor agonists might be an alternative option to improve ischemic heart disease.

Improvement of defective sarcoplasmic reticulum Ca2+transport in diabetic heart of transgenic rats expressing the human kallikrein‐1 gene

The bradykinin-forming enzyme kallikrein-1 is expressed in the heart. To examine whether contractile performance and sarcoplasmic reticulum Ca2+ transport of the diabetic heart can be rescued by targeting the kallikrein-kinin system, we studied left ventricular function and sarcoplasmic reticular Ca2+ uptake after induction of streptozotocin-induced diabetes mellitus in transgenic rats expressing the human tissue kallikrein-1 gene. Six weeks after a single injection of either streptozotocin (70 mg/kg ip) or vehicle, left ventricular performance was determined using a Millar-Tip catheter system. The Ca2+-transporting activity of reticulum-derived membrane vesicles was determined in left ventricular homogenates as oxalate-supported 45Ca2+ uptake. Western blot analysis was used to quantify the reticular Ca2+-ATPase SERCA2a, phospholamban, and the phosphorylation status of the latter. Contractile performance and Ca2+ uptake activity were similar in nondiabetic wild-type and transgenic rats. Severely diabetic wild-type animals exhibited impaired left ventricular performance and decreased reticular Ca2+ uptake (-39% vs. wild-type rats, P<0.05, respectively). These changes were attenuated in diabetic transgenic rats that, in addition, exhibited a markedly increased phospholamban phosphorylation at the Ca2+/calmodulin kinase-specific site threonine17 (2.2-fold vs. diabetic wild-type rats, P<0.05). These transgene-related effects were abolished after treatment with the bradykinin B2 receptor antagonist icatibant (Hoe 140). The SERCA2-to-phospholamban ratio, phosphoserine16-phospholamban levels, and the apparent affinity for Ca2+ of the uptake reaction did not differ between the groups. Increasing the activity of the kallikrein-kinin system by expressing a human kallikrein-1 transgene protects rat heart against diabetes-induced contractile and reticular Ca2+ transport dysfunctions. An increased phosphorylation of the SERCA2 regulatory protein phospholamban at threonine17 via a B2 receptor-mediated mechanism is thereby involved.