Kallikrein–Kinin System in Neovascularization

Tissue Kallikrein supplementation in ischemic phase protects the neurovascular unit and attenuates reperfusion-induced injury in ischemic stroke

Tissue kallikrein (TK) has emerged as a potential neuroprotective agent in ischemic stroke (IS), yet the optimal timing and mechanisms of TK therapy remain unclear. Here, we established a causal link between lower baseline TK levels and an increased risk of stroke through a retrospective, multicenter cohort study involving 2115 initially non-stroke subjects monitored for 5 years. Sequentially, we observed a notable increase in bradykinin receptor 2 (B2R) levels during the ischemic phase of the IS model, while levels of TK and bradykinin receptor 1 (B1R) remained stable. Intriguingly, both B1R and B2R exhibited a significant elevation 24 h after reperfusion. Further investigations in preclinical models demonstrated that TK supplementation activates the PI3K/AKT signaling pathway via enhanced B2R expression during the ischemic phase, leading to nuclear translocation of Hif-1α. This activation enhances the expression of VEGF and eNOS, thereby fortifying the neurovascular unit. Moreover, it suppresses the activation of the kallikrein-kinin system induced by reperfusion injury, effectively reducing inflammation, ROS production, apoptosis, and endothelial barrier dysfunction. Thus, our findings highlight the significance of TK supplementation during the ischemic phase in attenuating reperfusion-induced injury in IS, providing a mechanistic rationale for determining the optimal timing for TK supplementation therapy.

A comprehensive proteomic profiling of urinary exosomes and the identification of early non-invasive biomarker in patients with coronary artery disease

Urinary small extracellular vesicles or exosomes (uEVs) source could be an emerging trove of biomarkers in coronary artery disease (CAD). It is a chronic inflammatory disease having a long asymptomatic phase of fatty-fibrous development in arteries leading to angina, myocardial infarction, and death. Our study was aimed at identifying differential protein expression profiling of uEVs in CAD. We collected urine samples of CAD patients (n = 41) age 18-65 years and gender matched healthy controls (n = 41). We isolated uEVs using differential ultracentrifugation. Further, uEV samples were characterized by western blotting exosome markers (Flotillin, TSG, CD63, and CD9), nano tracking analysis, and transmission and scanning electron microscopy. A total of 508 proteins were identified by iTRAQ-based mass spectrometry. We observed protein expression levels of AZGP1, SEMG1/2, ORM1, IGL, SERPINA5, HSPG2, prosaposin, gelsolin, and CD59 were upregulated, and UMOD, KNG1, AMBP, prothrombin, and TF were downregulated. Protein-protein interactions, gene ontology and pathway analysis were performed to functionally annotate identified uEVs proteins. A novel uEVs differential protein signature is shown. On validating UMOD protein by ELISA in two clinically different CAD, stable-CAD patients had lower levels than healthy controls whereas recent myocardial infarction patients had lowest. Our findings suggest UMOD importance as early diagnostic biomarker. SIGNIFICANCE: Coronary artery disease is a chronic inflammatory disease caused by gradual deposition of cholesterol and fat along with other proteins to develop plaque inside arteries. This further leads to blockage of artery, heart attack and death. There are no identifiable early biomarkers to diagnose this. For the first time, we have identified the differentially expressed proteins isolated from non-invasive uEV of CAD patients compared to healthy controls by using MS Orbitrap and iTRAQ labelling of peptides. We have identified decreased levels of UMOD protein in CAD. These findings have been confirmed by ELISA. Furthermore, the levels of UMOD were observed as more highly decreased in recent myocardial infarction CAD patients, indicating the importance of this protein as an early diagnostic biomarker. Conclusively, our study represents a non-invasive urinary EVs trove of differentially expressed proteins in CAD. This will form a groundwork for understanding the pathophysiology of CAD and will help in future translational research utilizing uEVs.

Cortisol Dose-Dependently Impairs Migration and Tube-like Formation in a Trophoblast Cell Line and Modulates Inflammatory and Angiogenic Genes

Several stimuli can change maternal hormone levels during pregnancy. These changes may affect trophoblastic cells and modulate the development of the embryo and the placental tissue itself. Changes in cortisol levels are associated with impaired trophoblast implantation and function, in addition to other pregnancy complications. This study aims to analyze the effects of low and high doses of cortisol on an extravillous trophoblast cell line, and the effects of various exposures to this hormone. SGHPL-4 cells were treated with cortisol at five doses (0-1000 nM) and two exposures (continuous: 24 h/day; and intermittent: 2 h/day). In intermittent treatment, cortisol acted mainly as an anti-inflammatory hormone, repressing gene expression of kinin B1 receptors, interleukin-6, and interleukin-1β. Continuous treatment modulated inflammatory and angiogenic pathways, significantly repressing angiogenic factors and their receptors. Cortisol affected cell migration and tube-like structures formation. In conclusion, both continuous and intermittent exposure to cortisol repressed the expression of inflammatory genes, while only continuous exposure repressed the expression of angiogenic genes, suggesting that a sustained increase in the levels of this hormone is more harmful than a high short-term increase. Cortisol also impaired tube-like structures formation, and kinin receptors may be involved in this response.

Intermittent hypoxia changes the interaction of the kinin-VEGF system and impairs myocardial angiogenesis in the hypertrophic heart

Intermittent hypoxia (IH) is a feature of obstructive sleep apnea (OSA), a condition highly associated with hypertension-related cardiovascular diseases. Repeated episodes of IH contribute to imbalance of angiogenic growth factors in the hypertrophic heart, which is key in the progression of cardiovascular complications. In particular, the interaction between vascular endothelial growth factor (VEGF) and the kallikrein-kinin system (KKS) is essential for promoting angiogenesis. However, researchers have yet to investigate experimental models of IH that reproduce OSA, myocardial angiogenesis, and expression of KKS components. We examined temporal changes in cardiac angiogenesis in a mouse IH model. Adult male C57BI/6 J mice were implanted with Matrigel plugs and subjected to IH for 1-5 weeks with subsequent weekly histological evaluation of vascularization. Expression of VEGF and KKS components was also evaluated. After 3 weeks, in vivo myocardial angiogenesis and capillary density were decreased, accompanied by a late increase of VEGF and its type 2 receptor. Furthermore, IH increased left ventricular myocardium expression of the B2 bradykinin receptor, while reducing mRNA levels of B1 receptor. These results suggest that in IH, an unexpected response of the VEGF and KKS systems could explain the reduced capillary density and impaired angiogenesis in the hypoxic heart, with potential implications in hypertrophic heart malfunction.

Ts14 from Tityus serrulatus boosts angiogenesis and attenuates inflammation and collagen deposition in sponge-induced granulation tissue in mice

We have previously described a 25mer anti-hypertensive peptide, previously named TsHpt-I (Tityus serrulatus Hypotensin-I), now Ts14, as an agonist of B2 kinin receptor. Bradykinin is known to play physiological roles in angiogenic, inflammatory, and fibrogenic processes, mostly mediated by B2 receptor. Therefore, we investigated whether Ts14 could modulate key events (neovascularization, inflammatory cell recruitment, and extracellular matrix deposition) of the fibrovascular tissue, induced by polyether-polyurethane sponge implants in mice. Sponges were implanted in the dorsum of 7-week-old C57Bl/6 male mice that received daily intrasponge treatment with Ts14 (27.25μg/sponge/day in 10μL PBS) or vehicle (10μL PBS/sponge/day) and were assessed on day 7 after surgery. Hemoglobin content, blood flow (laser Doppler perfusion imaging), and VEGF levels in the implants, used as indices of vascularization, indicated that Ts14 enhanced angiogenesis in implants relative to the PBS-treated group. Interestingly, Ts14 reduced TNF-α levels and neutrophil infiltration, although stimulated macrophage infiltration into implants, as determined by myeloperoxidase (MPO) and N-acetyl-β-d-glucosaminidase (NAG) enzyme activities, respectively. Regarding the fibrogenic component (soluble collagen content and Sirius-red histological staining), we observed that Ts14 inhibited collagen deposition in the implants. Overall, our results suggest that Ts14 exerts proangiogenic, anti-inflammatory, and anti-fibrogenic activities. These effects may indicate a therapeutical potential of this peptide in conditions where angiogenesis, inflammation, and fibrogenesis contribute to disease progression and chronicity.

Moving Past Anti-VEGF: Novel Therapies for Treating Diabetic Retinopathy

Diabetic retinopathy is the leading cause of blindness in working age adults, and is projected to be a significant future health concern due to the rising incidence of diabetes. The recent advent of anti-vascular endothelial growth factor (VEGF) antibodies has revolutionized the treatment of diabetic retinopathy but a significant subset of patients fail to respond to treatment. Accumulating evidence indicates that inflammatory cytokines and chemokines other than VEGF may contribute to the disease process. The current review examines the presence of non-VEGF cytokines in the eyes of patients with diabetic retinopathy and highlights mechanistic pathways in relevant animal models. Finally, novel drug targets including components of the kinin-kallikrein system and emerging treatments such as anti-HPTP (human protein tyrosine phosphatase) β antibodies are discussed. Recognition of non-VEGF contributions to disease pathogenesis may lead to novel therapeutics to enhance existing treatments for patients who do not respond to anti-VEGF therapies.

Angiogenesis dysregulation in term asphyxiated newborns treated with hypothermia

BACKGROUND

Neonatal encephalopathy following birth asphyxia is a major predictor of long-term neurological impairment. Therapeutic hypothermia is currently the standard of care to prevent brain injury in asphyxiated newborns but is not protective in all cases. More robust and versatile treatment options are needed. Angiogenesis is a demonstrated therapeutic target in adult stroke. However, no systematic study examines the expression of angiogenesis-related markers following birth asphyxia in human newborns.

OBJECTIVE

This study aimed to evaluate the expression of angiogenesis-related protein markers in asphyxiated newborns developing and not developing brain injury compared to healthy control newborns.

DESIGN/METHODS

Twelve asphyxiated newborns treated with hypothermia were prospectively enrolled; six developed eventual brain injury and six did not. Four healthy control newborns were also included. We used Rules-Based Medicine multi-analyte profiling and protein array technologies to study the plasma concentration of 49 angiogenesis-related proteins. Mean protein concentrations were compared between each group of newborns.

RESULTS

Compared to healthy newborns, asphyxiated newborns not developing brain injury showed up-regulation of pro-angiogenic proteins, including fatty acid binding protein-4, glucose-6-phosphate isomerase, neuropilin-1, and receptor tyrosine-protein kinase erbB-3; this up-regulation was not evident in asphyxiated newborns eventually developing brain injury. Also, asphyxiated newborns developing brain injury showed a decreased expression of anti-angiogenic proteins, including insulin-growth factor binding proteins -1, -4, and -6, compared to healthy newborns.

CONCLUSIONS

These findings suggest that angiogenesis pathways are dysregulated following birth asphyxia and are putatively involved in brain injury pathology and recovery.

The kallikrein-kinin system in diabetic retinopathy

Diabetic retinopathy (DR) is a major microvascular complication associated with type 1 and type 2 diabetes mellitus, which can lead to visual impairment and blindness. Current treatment strategies for DR are mostly limited to laser therapies, steroids, and anti-VEGF agents, which are often associated with unwanted side effects leading to further complications. Recent evidence suggests that kinins play a primary role in the development of DR through enhanced vascular permeability, leukocytes infiltration, and other inflammatory mechanisms. These deleterious effects are mediated by kinin B1 and B2 receptors, which are expressed in diabetic human and rodent retina. Importantly, kinin B1 receptor is virtually absent in sane tissue, yet it is induced and upregulated in diabetic retina. These peptides belong to the kallikrein-kinin system (KKS), which contains two separate and independent pathways of regulated serine proteases, namely plasma kallikrein (PK) and tissue kallikrein (TK) that are involved in the biosynthesis of bradykinin (BK) and kallidin (Lys-BK), respectively. Hence, ocular inhibition of kallikreins or antagonism of kinin receptors offers new therapeutic avenues in the treatment and management of DR. Herein, we present an overview of the principal features and known inflammatory mechanisms associated with DR along with the current therapeutic approaches and put special emphasis on the KKS as a new and promising therapeutic target due to its link with key pathways directly associated with the development of DR.

Tissue kallikrein is related to the severity of coronary artery disease

BACKGROUND

The impairment of the tissue kallikrein (KLK1)-kinin system (KKS) may result in atheroma development. However, it remains unclear if the KKS correlates with coronary artery disease (CAD).

METHODS

KLK1, VEGF and hs-CRP plasma levels were measured in 100 patients newly diagnosed with CAD and 33 CAD-free controls. Patients were followed-up for the incidence of major adverse cardiovascular events (MACE) for 8months to 2y. Gene expression of KLK1, CD105 and CD68 was assessed in human coronary endarterectomy specimens.

RESULTS

Patients with CAD and acute coronary syndrome (ACS) had significantly elevated KLK1 levels. In addition, the concentration of hs-CRP was increased in ACS patients. A strong positive correlation between plasma KLK1 and the severity of CAD was also demonstrated, suggesting that high KLK1 levels are an independent predictor for CAD. MACE during follow-up significantly correlated with KLK1 levels in the ACS group. Unstable coronary plaques demonstrated markedly increased KLK1 levels, macrophage infiltration and high microvessel density. Additionally, KLK1 staining primarily colocalized with macrophages.

CONCLUSIONS

In the present study, plasma KLK1 levels were a useful predictor for the presence and extent of CAD. More extensive studies are, however, necessary in order to validate these findings.

iTRAQ-based quantitative proteomic analysis of submandibular glands from rats with STZ-induced hyperglycemia

The impairment of salivary glands activity is often connected to the complaints of dry-mouth and subsequent degradation of the periodontium of diabetic patients. In this context, submandibular glands (SMGs) play a central role in saliva production and so the understanding of the molecular pathways affected is of paramount importance. Using a streptozotocin-induced hyperglycemia rat model and two different time points (2 and 4 months), we applied mass spectrometry-based proteomic techniques, validated with standard western blot analysis, to identify and quantify the effect of chronic hyperglycemia on the proteome of SMGs. We observed significant variations of proteins such as kallikreins, protein S100A6 or annexins. After 2 months of hyperglycemia, we observed an early phase response characterized by a significant increase of protein S100A6, linked to the inflammatory response, together with the impairment of metabolic and energy production processes. On the other hand, vesicular transport appeared to be favoured in such conditions. Interestingly, in a long-term response to hyperglycemia after 4 months of exposure, we observed a general attenuation of the variations. In conclusion, we present data that support the existence of an adaptation of the gland to long-term stress.

New topics in bradykinin research

Bradykinin has been implicated to contribute to allergic inflammation and the pathogenesis of allergic conditions. It binds to endothelial B(1) and B(2) receptors and exerts potent pharmacological and physiological effects, notably, decreased blood pressure, increased vascular permeability and the promotion of classical symptoms of inflammation such as vasodilation, hyperthermia, oedema and pain. Towards potential clinical benefit, bradykinin has also been shown to exert potent antithrombogenic, antiproliferative and antifibrogenic effects. The development of pharmacologically active substances, such as bradykinin receptor blockers, opens up new therapeutic options that require further research into bradykinin. This review presents current understanding surrounding the role of bradykinin in nonallergic angioedema and other conditions seen by allergists and emergency physicians, and its potential role as a therapeutic target.

The many faces of the contact pathway and their role in thrombosis

Understanding inherent differences between thrombosis and hemostasis in the vascular system are critical to developing safe and effective anticoagulants. To this end, constituents of the contact activated and intrinsic pathway of coagulation appear to be involved in pathological thrombus formation, but are not required for normal hemostasis. In addition to coagulation, activation of the contact system is involved in fibrinolytic, inflammatory, and angiogenic processes that can also contribute to the thrombotic environment. This review discusses the role of the contact system in these processes, and highlights the potential of FXII and FXI as safer targets for antithrombotic therapy.

Arteriogenesis Is Modulated By Bradykinin Receptor Signaling

Rationale:

Positive outward remodeling of pre-existing collateral arteries into functional conductance arteries, arteriogenesis, is a major endogenous rescue mechanism to prevent cardiovascular ischemia. Collateral arterial growth is accompanied by expression of kinin precursor. However, the role of kinin signaling via the kinin receptors (B1R and B2R) in arteriogenesis is unclear.

Objective:

The purpose of this study was to elucidate the functional role and mechanism of bradykinin receptor signaling in arteriogenesis.

Methods and Results:

Bradykinin receptors positively affected arteriogenesis, with the contribution of B1R being more pronounced than B2R. In mice, arteriogenesis upon femoral artery occlusion was significantly reduced in B1R mutant mice as evidenced by reduced microspheres and laser Doppler flow perfusion measurements. Transplantation of wild-type bone marrow cells into irradiated B1R mutant mice restored arteriogenesis, whereas bone marrow chimeric mice generated by reconstituting wild-type mice with B1R mutant bone marrow showed reduced arteriogenesis after femoral artery occlusion. In the rat brain 3-vessel occlusion arteriogenesis model, pharmacological blockade of B1R inhibited arteriogenesis and stimulation of B1R enhanced arteriogenesis. In the rat, femoral artery ligation combined with arterial venous shunt model resulted in flow-driven arteriogenesis, and treatment with B1R antagonist R715 decreased vascular remodeling and leukocyte invasion (monocytes) into the perivascular tissue. In monocyte migration assays, in vitro B1R agonists enhanced migration of monocytes.

Conclusions:

Kinin receptors act as positive modulators of arteriogenesis in mice and rats. B1R can be blocked or therapeutically stimulated by B1R antagonists or agonists, respectively, involving a contribution of peripheral immune cells (monocytes) linking hemodynamic conditions with inflammatory pathways.