Glucose and angiotensin II-derived endothelial extracellular vesicles regulate endothelial dysfunction via ERK1/2 activation

Molecular Mechanisms Underlying Heart Failure and Their Therapeutic Potential

Heart failure (HF) is a prominent fatal cardiovascular disorder afflicting 3.4% of the adult population despite the advancement of treatment options. Therefore, a better understanding of the pathogenesis of HF is essential for exploring novel therapeutic strategies. Hypertrophy and fibrosis are significant characteristics of pathological cardiac remodeling, contributing to HF. The mechanisms involved in the development of cardiac remodeling and consequent HF are multifactorial, and in this review, the key underlying mechanisms are discussed. These have been divided into the following categories thusly: (i) mitochondrial dysfunction, including defective dynamics, energy production, and oxidative stress; (ii) cardiac lipotoxicity; (iii) maladaptive endoplasmic reticulum (ER) stress; (iv) impaired autophagy; (v) cardiac inflammatory responses; (vi) programmed cell death, including apoptosis, pyroptosis, and ferroptosis; (vii) endothelial dysfunction; and (viii) defective cardiac contractility. Preclinical data suggest that there is merit in targeting the identified pathways; however, their clinical implications and outcomes regarding treating HF need further investigation in the future. Herein, we introduce the molecular mechanisms pivotal in the onset and progression of HF, as well as compounds targeting the related mechanisms and their therapeutic potential in preventing or rescuing HF. This, therefore, offers an avenue for the design and discovery of novel therapies for the treatment of HF.

Characteristic changes in the mRNA expression profile of plasma exosomes from patients with MPO-ANCA-associated vasculitis and its possible correlations with pathogenesis

To explore the expression patterns and potential roles of mRNAs in exosomes from patients with myeloperoxidase-specific anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (MPO-AAV). Plasma exosomes were isolated from MPO-AAV patients and healthy controls (HCs) to screen for differential mRNA expression via exosomal mRNA sequencing. The differentially expressed mRNAs in exosomes from the 2 groups were comparatively explored by bioinformatics analysis. The six most differentially expressed mRNAs were selected and validated in larger groups of MPO-AAV patients and HCs by real-time quantitative polymerase chain reaction (RT‒qPCR). The relationships between these selected mRNAs and patient characteristics were statistically analyzed. Compared with HCs, a total of 1077 mRNAs in exosomes from MPO-AAV patients were found to be significantly upregulated, including DEPDC1B and TPST1, while NSUN4 and AK4 were significantly downregulated. Statistical analysis did not reveal any correlation between the six selected mRNAs and clinical indicators, including disease activity. GO enrichment analysis revealed that these differentially expressed genes participate in various enzyme activities, protein synthesis, etc. KEGG pathway analysis revealed that metabolic pathways, cell adhesion molecules, epithelial signaling, and mitogen-activated protein kinase (MAPK) signaling pathways were significantly enriched in the exosomal mRNAs. There were significant differences in the expression of exosomal mRNAs between MPO-AAV patients and HCs, which may be related to the occurrence and development of MPO-AAV. These findings provide clues for further investigations of MPO-AAV pathogenesis and the identification of new potential therapeutic targets.

Insight into endothelial cell-derived extracellular vesicles in cardiovascular disease: Molecular mechanisms and clinical implications

The endothelium is crucial in regulating vascular function. Extracellular vesicles (EVs) serve as membranous structures released by cells to facilitate intercellular communication through the delivery of nucleic acids, lipids, and proteins to recipient cells in an paracrine or endocrine manner. Endothelial cell-derived EVs (EndoEVs) have been identified as both biomarkers and significant contributors to the occurrence and progression of cardiovascular disease (CVD). The impact of EndoEVs on CVD is complex and contingent upon the condition of donor cells, the molecular cargo within EVs, and the characteristics of recipient cells. Consequently, elucidating the underlying molecular mechanisms of EndoEVs is crucial for comprehending their contributions to CVD. Moreover, a thorough understanding of the composition and function of EndoEVs is imperative for their potential clinical utility. This review aims provide an up-to-date overview of EndoEVs in the context of physiology and pathophysiology, as well as to discuss their prospective clinical applications.

Extracellular vesicles in venous thromboembolism and pulmonary hypertension

Venous thromboembolism (VTE) is a multifactorial disease, and pulmonary hypertension (PH) is a serious condition characterized by pulmonary vascular remodeling leading with increased pulmonary vascular resistance, ultimately leading to right heart failure and death. Although VTE and PH have distinct primary etiologies, they share some pathophysiologic similarities such as dysfunctional vasculature and thrombosis. In both conditions there is solid evidence that EVs derived from a variety of cell types including platelets, monocytes, endothelial cells and smooth muscle cells contribute to vascular endothelial dysfunction, inflammation, thrombosis, cellular activation and communications. However, the roles and importance of EVs substantially differ between studies depending on experimental conditions and parent cell origins of EVs that modify the nature of their cargo. Numerous studies have confirmed that EVs contribute to the pathophysiology of VTE and PH and increased levels of various EVs in relation with the severity of VTE and PH, confirming its potential pathophysiological role and its utility as a biomarker of disease severity and as potential therapeutic targets.

Ginkgolide B caused the activation of the Akt/eNOS pathway through the antioxidant effect of SOD1 in the diabetic aorta

Ginkgo biloba extract (GBE) helps lower cardiovascular disease risk. Diabetes mellitus (DM)-induced endothelial dysfunction is a critical and initiating factor in the beginning of diabetic vascular complications. It was reported that GBE causes an endothelial-dependent relaxation. This study was designed to figure out the molecular basis on which GBE protects from endothelial dysfunction in diabetes because the underlying mechanisms are unclear. Studies were performed in a normal control group and streptozotocin/nicotinamide-induced DM group. In aortas, notably diabetic aortas, GBE, and ginkgolide B (GB), a constituent of GBE, produced a dose-dependent relaxation. The relaxation by GB was abolished by prior incubation with L-NNA (an endothelial nitric oxide synthase (NOS) inhibitor), LY294002 (a phosphoinositide 3-kinase (PI3K) inhibitor), and Akt inhibitor, confirming the essential role of PI3K/Akt/eNOS signaling pathway. We also demonstrated that GB induced the phosphorylation of Akt and eNOS in aortas. The superoxide dismutase1 (SOD1) expression level decreased in DM aortas, but GB stimulation increased SOD activity and SOD1 expression in DM aortas. Our novel findings suggest that in DM aortas, endothelial-dependent relaxation induced by GB was mediated by activation of SOD1, resulting in activation of the Akt/eNOS signaling pathway.

Extracellular vesicles in vascular remodeling

Vascular remodeling contributes to the development of a variety of vascular diseases including hypertension and atherosclerosis. Phenotypic transformation of vascular cells, oxidative stress, inflammation and vascular calcification are closely associated with vascular remodeling. Extracellular vesicles (EVs) are naturally released from almost all types of cells and can be detected in nearly all body fluids including blood and urine. EVs affect vascular oxidative stress, inflammation, calcification, and lipid plaque formation; and thereby impact vascular remodeling in a variety of cardiovascular diseases. EVs may be used as biomarkers for diagnosis and prognosis, and therapeutic strategies for vascular remodeling and cardiovascular diseases. This review includes a comprehensive analysis of the roles of EVs in the vascular remodeling in vascular diseases, and the prospects of EVs in the diagnosis and treatment of vascular diseases.

Role of Extracellular Vesicles in the Pathogenesis of Vascular Damage

Extracellular vesicles (EVs) are nanosized membrane-bound structures released by cells that are able to transfer nucleic acids, protein cargos, and metabolites to specific recipient cells, allowing cell-to-cell communications in an endocrine and paracrine manner. Endothelial, leukocyte, and platelet-derived EVs have emerged both as biomarkers and key effectors in the development and progression of different stages of vascular damage, from earliest alteration of endothelial function, to advanced atherosclerotic lesions and cardiovascular calcification. Under pathological conditions, circulating EVs promote endothelial dysfunction by impairing vasorelaxation and instigate vascular inflammation by increasing levels of adhesion molecules, reactive oxygen species, and proinflammatory cytokines. Platelets, endothelial cells, macrophages, and foam cells secrete EVs that regulate macrophage polarization and contribute to atherosclerotic plaque progression. Finally, under pathological stimuli, smooth muscle cells and macrophages secrete EVs that aggregate between collagen fibers and serve as nucleation sites for ectopic mineralization in the vessel wall, leading to formation of micro- and macrocalcification. In this review, we summarize the emerging evidence of the pathological role of EVs in vascular damage, highlighting the major findings from the most recent studies and discussing future perspectives in this research field.

Factor VIIa suppresses inflammation and barrier disruption through the release of EEVs and transfer of microRNA 10a

Coagulation protease, factor VIIa (FVIIa), binds to endothelial cell protein C receptor (EPCR) and induces anti-inflammatory and endothelial barrier protective responses via protease-activated receptor-1 (PAR1)-mediated, biased signaling. Our recent studies had shown that the FVIIa-EPCR-PAR1 axis induces the release of extracellular vesicles (EVs) from endothelial cells. In the present study, we investigated the mechanism of FVIIa release of endothelial EVs (EEVs) and the contribution of FVIIa-released EEVs to anti-inflammatory and vascular barrier protective effects, in both in vitro and in vivo models. Multiple signaling pathways regulated FVIIa release of EVs from endothelial cells, but the ROCK-dependent pathway appeared to be a major mechanism. FVIIa-released EEVs were enriched with anti-inflammatory microRNAs (miRs), mostly miR10a. FVIIa-released EEVs were taken up readily by monocytes/macrophages and endothelial cells. The uptake of FVIIa-released EEVs by monocytes conferred anti-inflammatory phenotype to monocytes, whereas EEV uptake by endothelial cells resulted in barrier protection. In additional experiments, EEV-mediated delivery of miR10a to monocytes downregulated the expression of TAK1 and activation of the NF-κB-mediated inflammatory pathway. In in vivo experiments, administration of FVIIa-released EEVs to wild-type mice attenuated LPS-induced increased inflammatory cytokines in plasma and vascular leakage into vital tissues. The incorporation of anti-miR10a into FVIIa-released EEVs diminished the ability of FVIIa-released EEVs to confer cytoprotective effects. Administration of the ROCK inhibitor Y27632, which significantly inhibits FVIIa release of EEVs into the circulation, to mice attenuated the cytoprotective effects of FVIIa. Overall, our study revealed novel insights into how FVIIa induces cytoprotective effects and communicates with various cell types.

Endothelial dysfunction caused by circulating microparticles from diabetic mice is reduced by PD98059 through ERK and ICAM-1

Endothelial dysfunction contributes to the development of diabetic complications and the production of circulating microparticles (MPs). Our previous study showed that diabetic mice-derived MPs (DM MPs) had increased levels of extracellular regulated protein kinase 1/2 (ERK1/2) and impaired endothelial-dependent relaxation in aortas when compared with control mice-derived MPs. This study was designed to investigate whether PD98059, an ERK1/2 inhibitor, affects the function of aortas and DM MPs. MPs were obtained from streptozotocin-induced DM, DM after PD98059 treatment, and ICR mice as control. The mice and MPs were then analyzed on the basis of their vascular function and enzyme expressions. Compared with the controls, platelet-derived MPs and ERK1/2 levels in the MPs were significantly elevated in the DM but showed little change in PD98059-treated DM. PD98059 mainly decreased ERK1/2 phosphorylation in the MPs. In the aortas of DM and DM MPs the endothelium-dependent vascular function was impaired, and there was a significantly greater improvement in the vascular function in the PD98059-treated DM aortas and the aortas treated with PD98059-treated DM MPs than in DM aortas and the aortas treated with DM MPs. Furthermore, DM MPs increased ERK1/2 and intracellular adhesion molecule-1 (ICAM-1) expressions in the aortas, but PD98059-treated DM MPs did not show these effects. For the first time, these results indicate that PD98059 treatment improves endothelial dysfunction in DM, and adhesion properties of DM MPs can be partly blocked by PD98059 via ERK and ICAM-1. These effects may explain some of the vascular complications in diabetes.

High-density lipoprotein's vascular protective functions in metabolic and cardiovascular disease - could extracellular vesicles be at play?

High-density lipoprotein (HDL) is a circulating complex of lipids and proteins known primarily for its role in reverse cholesterol transport and consequent protection from atheroma. In spite of this, therapies aimed at increasing HDL concentration do not reduce the risk of cardiovascular disease (CVD), and as such focus has shifted towards other HDL functions protective of vascular health - including vasodilatory, anti-inflammatory, antioxidant and anti-thrombotic actions. It has been demonstrated that in disease states such as CVD and conditions of insulin resistance such as Type 2 diabetes mellitus (T2DM), HDL function is impaired owing to changes in the abundance and function of HDL-associated lipids and proteins, resulting in reduced vascular protection. However, the gold standard density ultracentrifugation technique used in the isolation of HDL also co-isolates extracellular vesicles (EVs). EVs are ubiquitous cell-derived particles with lipid bilayers that carry a number of lipids, proteins and DNA/RNA/miRNAs involved in cell-to-cell communication. EVs transfer their bioactive load through interaction with cell surface receptors, membrane fusion and endocytic pathways, and have been implicated in both cardiovascular and metabolic diseases - both as protective and pathogenic mediators. Given that studies using density ultracentrifugation to isolate HDL also co-isolate EVs, biological effects attributed to HDL may be confounded by EVs. We hypothesise that some of HDL's vascular protective functions in cardiovascular and metabolic disease may be mediated by EVs. Elucidating the contribution of EVs to HDL functions will provide better understanding of vascular protection and function in conditions of insulin resistance and potentially provide novel therapeutic targets for such diseases.

Endothelial response to glucose: dysfunction, metabolism, and transport

The endothelial cell response to glucose plays an important role in both health and disease. Endothelial glucose-induced dysfunction was first studied in diabetic animal models and in cells cultured in hyperglycemia. Four classical dysfunction pathways were identified, which were later shown to result from the common mechanism of mitochondrial superoxide overproduction. More recently, non-coding RNA, extracellular vesicles, and sodium-glucose cotransporter-2 inhibitors were shown to affect glucose-induced endothelial dysfunction. Endothelial cells also metabolize glucose for their own energetic needs. Research over the past decade highlighted how manipulation of endothelial glycolysis can be used to control angiogenesis and microvascular permeability in diseases such as cancer. Finally, endothelial cells transport glucose to the cells of the blood vessel wall and to the parenchymal tissue. Increasing evidence from the blood-brain barrier and peripheral vasculature suggests that endothelial cells regulate glucose transport through glucose transporters that move glucose from the apical to the basolateral side of the cell. Future studies of endothelial glucose response should begin to integrate dysfunction, metabolism and transport into experimental and computational approaches that also consider endothelial heterogeneity, metabolic diversity, and parenchymal tissue interactions.

Apoptotic exosome-like vesicles regulate endothelial gene expression, inflammatory signaling, and function through the NF-κB signaling pathway

Persistent endothelial injury promotes maladaptive responses by favoring the release of factors leading to perturbation in vascular homeostasis and tissue architecture. Caspase-3 dependent death of microvascular endothelial cells leads to the release of unique apoptotic exosome-like vesicles (ApoExo). Here, we evaluate the impact of ApoExo on endothelial gene expression and function in the context of a pro-apoptotic stimulus. Endothelial cells exposed to ApoExo differentially express genes involved in cell death, inflammation, differentiation, and cell movement. Endothelial cells exposed to ApoExo showed inhibition of apoptosis, improved wound closure along with reduced angiogenic activity and reduced expression of endothelial markers consistent with the first phase of endothelial-to-mesenchymal transition (endoMT). ApoExo interaction with endothelial cells also led to NF-κB activation. NF-κB is known to participate in endothelial dysfunction in numerous diseases. Silencing NF-κB reversed the anti-apoptotic effect and the pro-migratory state and prevented angiostatic properties and CD31 downregulation in endothelial cells exposed to ApoExo. This study identifies vascular injury-derived extracellular vesicles (ApoExo) as novel drivers of NF-κB activation in endothelial cells and demonstrates the pivotal role of this signaling pathway in coordinating ApoExo-induced functional changes in endothelial cells. Hence, targeting ApoExo-mediated NF-κB activation in endothelial cells opens new avenues to prevent endothelial dysfunction.

Extracellular Vesicles and Insulin Resistance: A Potential Interaction in Vascular Dysfunction

Insulin resistance plays a key role in cardiovascular complications associated with diabetes mellitus and hypertensive disorders. In states of insulin resistance several circulating factors may contribute to a defective insulin sensitivity in different tissues, including the vasculature. One of these factors influencing the vascular insulin resistance are the extracellular vesicles. The extracellular vesicles include exosomes, microvesicles, and apoptotic bodies which are released to the circulation by different vascular cells. Since the cargo of extracellular vesicles seems to be altered in metabolic complications associated with insulin resistance, these vesicles may be candidates contributing to vascular insulin resistance. Despite the studies linking insulin resistance signalling pathways with the vascular effect of extracellular vesicles, the involvement of these structures in vascular insulin resistance is a phenomenon that remains unclear.

Different Calcium and Src Family Kinase Signaling in Mac-1 Dependent Phagocytosis and Extracellular Vesicle Generation

Encountering opsonized particles by neutrophils results in phagocytosis of the particle and generation of extracellular vesicles with antibacterial property (aEV). The aim of the present study is to compare the involvement of different receptors and receptor-proximal signaling pathways in these two parallel processes. Investigating human neutrophils from peripheral blood, we show that complement receptors are decisive for both processes whereas immunoglobulin binding Fc receptors (FcR) only participate moderately in phagocytosis and pattern recognition receptors induce mild EV production but only minimal phagocytosis. Studying bone marrow derived neutrophils of genetically modified animals we verify that the involved complement receptor is CR3, also known as the β₂ integrin Mac-1. We show that genetic deletion of the adaptor molecules FcRγ chain or DAP12 does not influence either process, suggesting potential redundant function. Combined absence of the Src family kinases Hck, Fgr, and Lyn drastically impairs phagocytosis but does not influence aEV production. In contrast, deletion of PLCγ2 has no influence on phagocytosis, but reduces aEV formation. In accord with the essential role of PLCγ2, aEV biogenesis both from murine and from human neutrophils is dependent on presence of extracellular calcium. Absence of external calcium prevented the generation of antibacterial EVs, whereas the spontaneous EV formation was not influenced. We thus show that phagocytosis and biogenesis of antibacterial EVs are independent processes and proceed on different signaling pathways although the same receptor plays the critical role in both. Our data reveal the possibility in neutrophilic granulocytes to modulate aEV production without disturbing the phagocytic process.

Role of Mac-1 integrin in generation of extracellular vesicles with antibacterial capacity from neutrophilic granulocytes

Production of extracellular vesicles (EVs) involved in intercellular communication is a common capacity of most cell types. Upon encountering opsonized microorganisms, neutrophilic granulocytes release EVs that compromise bacterial growth. We carried out a systematic investigation of the involvement of potential opsonin receptors in EV-generation from human and murine neutrophils. Applying flow cytometric, proteomic and functional analysis as well as using genetically modified mice, we demonstrate that formation of antibacterial EVs depends upon stimulation of the multifunctional Mac-1 integrin complex, also called as complement receptor 3 (CR3), whereas activation of immunoglobulin binding Fc receptors or pattern recognition receptors alone or in combination is ineffective. Mac-1/CR3 stimulation and downstream tyrosine kinase signalling affect both the numbers, the cargo content and the antibacterial capacity of the produced vesicles. In contrast, Mac-1/CR3 signalling is not required for spontaneous EV formation, clearly indicating the existence of separate molecular pathways in EV biogenesis. We propose that EVs are “tailor-made” with different composition and functional properties depending on the environmental circumstances.

Angiotensin II receptor blocker LCZ696 attenuates cardiac remodeling through the inhibition of the ERK signaling pathway in mice with pregnancy-associated cardiomyopathy

Pregnancy-associated cardiomyopathy (PAH) represents a pregnancy-associated myocardial disease that is characterized by the progression of heart failure due to marked left ventricular systolic dysfunction. Compelling evidence has highlighted the potential of angiotensin (Ang) receptor inhibitors as therapeutic targets in PAH treatment. The present study aims to elucidate the molecular mechanisms underlying Ang II receptor inhibitor LCZ696 treatment in PAH. Initially, a PAH mouse model was induced, followed by intraperitoneal injection of LCZ696. Subsequently, cardiomyocytes and fibroblasts were isolated, cultured, and treated with Ang II and LCZ696, followed by detection of the total survival rate, cardiac injury, cardiac fibrosis and apoptosis. Moreover, in order to quantify the cardiac hypertrophy and fibrosis degree of cardiac fibroblasts, the expression levels of markers of cardiac hypertrophy (ANP, βMHC and TIMP2) and markers of fibrosis (collagen I, collagen III and TGF-β) were evaluated. Furthermore, the potential effect of LCZ696 on the extracellular signal-regulated kinase (ERK) signaling pathway was examined. The acquired findings revealed that LCZ696 increased the total survival rate of PAH mice, but decreased cardiac injury, cardiac fibrosis, and apoptosis in vitro. LCZ696 attenuated cardiac injury induced by Ang II through the inhibition the expression of markers of cardiac hypertrophy, fibrosis and apoptosis by inhibiting ERK phosphorylation in vivo and in vitro. Altogether, LCZ676 could potentially alleviate cardiac remodeling in mice with PAH via blockade of the ERK signaling pathway activation. Our findings suggest that LCZ696 could be a potential target for PAH therapy.

ERK-containing microparticles from a diabetic mouse induce endothelial dysfunction

Endothelial dysfunction is a hallmark of diabetic vascular complications. Microparticles (MPs) are small vesicles shed from the surface of blood and vascular cells that act as stimuli and during apoptosis. Circulating MPs of diabetic rats have been shown to induce endothelial dysfunction. However, the underlying mechanisms require further study. In this study, we investigated how MPs from diabetic mice affect endothelial function. MPs were collected from streptozotocin-induced diabetic mice and Institute of Cancer Research (ICR) mice as controls. The levels of MPs were assessed and characterized by flow cytometry, enzyme-linked immunosorbent assay and dot blotting. Normal mice aortas were incubated with MPs and expressions of enzymes and vascular relaxation were analyzed. We found that (1) circulating MPs level increased in diabetic mice; (2) MPs impaired endothelial-dependent relaxation in mice aorta, but diabetic mice-derived MPs (diabetes mellitus (DM) MPs) were easier to attach to the endothelial cells than were control MPs; (3) DM MPs had more extracellular signal-regulated kinase (ERK)1/2 than did control mice-derived MPs, and they induced ERK1/2 activation in mice aortas; (4) DM MPs decreased endothelial nitric oxide synthase (eNOS) in mice aortas, and eNOS was emitted from endothelial cells to blood in the shape of endothelial MPs. DM MPs significantly altered endothelial function by activation of ERK1/2, which might provide a therapeutic target for diabetic vascular complications.

Extracellular vesicles in autoimmune vasculitis - Little dirts light the fire in blood vessels

Systemic vasculitis is diverse group of autoimmune disorders which are characterized by inflammation of blood vessel walls with deep aching and burning pain. Their underlying etiology and pathophysiology still remain poorly understood. Extracellular vesicles (EVs), including exosomes, microvesicles (MVs), and apoptotic bodies, are membrane vesicular structures that are released either during cell activation, or when cells undergo programmed cell death, including apoptosis, necroptosis, and pyroptosis. Although EVs were thought as cell dusts, but now they have been found to be potently active since they harbor bioactive molecules, such as proteins, lipids, nucleic acids, or multi-molecular complexes. EVs can serve as novel mediators for cell-to-cell communications by delivery bioactive molecules from their parental cells to the recipient cells. Earlier studies mainly focused on MVs budding from membrane surface. Recent studies demonstrated that EVs may also carry molecules from cytoplasm or even from nucleus of their parental cells, and these EVs may carry autoantigens and are important in vasculitis. EVs may play important roles in vasculitis through their potential pathogenic involvements in inflammation, autoimmune responses, procoagulation, endothelial dysfunction/damage, angiogenesis, and intimal hyperplasia. EVs have also been used as specific biomarkers for diagnostic use or disease severity monitoring. In this review, we have focused on the aspects of EV biology most relevant to the pathogenesis of vasculitis, discussed their perspective insights, and summarized the exist literature on EV relevant studies in vasculitis, therefore provides an integration of current knowledge regarding the novel role of EVs in systemic vasculitis.

Angiotensin II Signal Transduction: An Update on Mechanisms of Physiology and Pathophysiology

The renin-angiotensin-aldosterone system plays crucial roles in cardiovascular physiology and pathophysiology. However, many of the signaling mechanisms have been unclear. The angiotensin II (ANG II) type 1 receptor (AT₁R) is believed to mediate most functions of ANG II in the system. AT₁R utilizes various signal transduction cascades causing hypertension, cardiovascular remodeling, and end organ damage. Moreover, functional cross-talk between AT₁R signaling pathways and other signaling pathways have been recognized. Accumulating evidence reveals the complexity of ANG II signal transduction in pathophysiology of the vasculature, heart, kidney, and brain, as well as several pathophysiological features, including inflammation, metabolic dysfunction, and aging. In this review, we provide a comprehensive update of the ANG II receptor signaling events and their functional significances for potential translation into therapeutic strategies. AT₁R remains central to the system in mediating physiological and pathophysiological functions of ANG II, and participation of specific signaling pathways becomes much clearer. There are still certain limitations and many controversies, and several noteworthy new concepts require further support. However, it is expected that rigorous translational research of the ANG II signaling pathways including those in large animals and humans will contribute to establishing effective new therapies against various diseases.

Alteration of Vascular Responsiveness to Uridine Adenosine Tetraphosphate in Aortas Isolated from Male Diabetic Otsuka Long-Evans Tokushima Fatty Rats: The Involvement of Prostanoids

We investigated whether responsiveness to dinucleotide uridine adenosine tetraphosphate (Up₄A) was altered in aortas from type 2 diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats compared with those from age-matched control Long-Evans Tokushima Otsuka (LETO) rats at the chronic stage of disease. In OLETF aortas, we observed the following: (1) Up₄A-induced contractions were lower than those in the LETO aortas under basal conditions, (2) slight relaxation occurred due to Up₄A, but this was not observed in phenylephrine-precontracted LETO aortas, (3) acetylcholine-induced relaxation was reduced (vs. LETO), and (4) prostanoid release (prostaglandin (PG)F_2α, thromboxane (Tx)A₂ metabolite, and PGE₂) due to Up₄A was decreased (vs. LETO). Endothelial denudation suppressed Up₄A-induced contractions in the LETO group, but increased the contractions in the OLETF group. Under nitric oxide synthase (NOS) inhibition, Up₄A induced contractions in phenylephrine-precontracted aortas; this effect was greater in the LETO group (vs. the OLETF group). The relaxation response induced by Up₄A was unmasked by cyclooxygenase inhibitors, especially in the LETO group, but this effect was abolished by NOS inhibition. These results suggest that the relaxant component of the Up₄A-mediated response was masked by prostanoids in the LETO aortas and that the LETO and OLETF rats presented different contributions of the endothelium to the response.