Advances in cardiovascular research. 15th Annual Meeting of the European Council for Cardiovascular Research (ECCR). La Colle sur Loup, France, 8-10 October 2010

The 15th Annual Meeting of the European Council of Cardiovascular Research brought together basic and clinical scientists working in the cardiovascular field in La Colle sur Loup, France. Upfront basic and clinical research addressing the mechanisms of disease, identification of biomarkers or development of new treatments was communicated in 101 presentations, 35 of them as a part of five on-topic oral sessions and three workshops. Three keynote lectures reviewed current knowledge and the latest data about mechanosensitive channels in pressure regulation, cell therapy in cardiovascular disease and mechanisms of cardiovascular risk associated with diabetic nephropathy. This article summarizes highlights of the oral sessions, workshops and keynote lectures

Emerging drugs which target the renin-angiotensin-aldosterone system

Introduction: The renin-angiotensin-aldosterone system (RAAS) is already the most important target for drugs in the cardiovascular system. However, still new developments are underway to interfere with the system on different levels. Areas covered: The novel strategies to interfere with RAAS aim to reduce the synthesis of the two major RAAS effector hormones, angiotensin (Ang) II and aldosterone, or interfere with their receptors, AT1 and mineralocorticoid receptor, respectively. Moreover, novel targets have been identified in RAAS, such as the (pro)renin receptor, and molecules, which counteract the classical actions of Ang II and are therefore beneficial in cardiovascular diseases. These include the AT2 receptor and the ACE2/Ang-(1-7)/Mas axis. The search for drugs activating these tissue-protective arms of RAAS is therefore the most innovative field in RAAS pharmacology. Expert opinion: Most of the novel pharmacological strategies to inhibit the classical RAAS need to prove their superiority above the existing treatment in clinical trials and then have to compete against these now quite cheap drugs in a competitive market. The newly discovered targets have functions beyond the cardiovascular system opening up novel therapeutic areas for drugs interfering with RAAS components

Angiotensin AT(2) Receptor Stimulation Alleviates Collagen-Induced Arthritis by Upregulation of Regulatory T Cell Numbers

The angiotensin AT(2) receptor (AT(2)R) is a main receptor of the protective arm of the renin-angiotensin system and exerts for instance anti-inflammatory effects. The impact of AT(2)R stimulation on autoimmune diseases such as rheumatoid arthritis (RA) is not yet known. We investigated the therapeutic potential of AT(2)R-stimulation with the selective non-peptide AT(2)R agonist Compound 21 (C21) in collagen-induced arthritis (CIA), an animal model for inflammatory arthritis. Arthritis was induced by immunization of DBA/1J mice with collagen type II (CII). Prophylactic and therapeutic C21 treatment alleviates arthritis severity and incidence in CIA. Joint histology revealed significantly less infiltrates of IL-1 beta and IL-17A expressing cells and a well-preserved articular cartilage in C21- treated mice. In CIA, the number of CD4(+)CD25(+)FoxP3(+) regulatory T (Treg) cells significantly increased upon C21 treatment compared to vehicle. T cell differentiation experiments demonstrated increased expression of FoxP3 mRNA, whereas IL-17A, STAT3 and IFN-gamma mRNA expression were reduced upon C21 treatment. In accordance with the mRNA data, C21 upregulated the percentage of CD4(+)FoxP3(+) cells in Treg polarizing cultures compared to medium-treated controls, whereas the percentage of CD4(+)IL-17A(+) and CD4(+)IFN-gamma(+) T cells was suppressed. To conclude, C21 exerts beneficial effects on T cell-mediated experimental arthritis. We found that C21-induced AT(2)R-stimulation promotes the expansion of CD4(+) regulatory T cells and suppresses IL-17A production. Thus, AT(2)R-stimulation may represent an attractive treatment strategy for arthritis

The renin-angiotensin system: going beyond the classical paradigms

Thirty years ago a novel axis of the renin-angiotensin system (RAS) was unveiled by the discovery of angiotensin (Ang)-(1-7) generation in-vivo. Later angiotensin-converting enzyme 2 (ACE2) was shown to be the main mediator of this reaction and Mas was found to be the receptor for the heptapeptide. The functional analysis of this novel axis of the RAS which followed its discovery revealed numerous protective actions in particular for cardiovascular diseases. In parallel, similar protective actions were also described for one of the two receptors of Ang II, AT2R, in contrast to the other, AT1R, which mediates deleterious actions of this peptide e.g. in the setting of cardiovascular disease. Very recently, another branch of the RAS was discovered, based on Ang peptides in which the aminoterminal aspartate is replaced by alanine, the alatensins. Ala-Ang-(1-7) or alamandine was shown to interact with the Mas-related receptor (MrgD) and first functional data indicate that this peptide also exerts protective effects in the cardiovascular system. This review summarizes the presentations given at the International Union of Physiological Sciences Congress in Rio de Janeiro, 2017, during the symposium "The renin-angiotensin system: going beyond the classical paradigms", in which the signaling and the physiological actions of Ang-(1-7), ACE2, AT2R and the alatensins were reported (with a focus on non-CNS tissues) and the therapeutic opportunities based on these findings were discussed

Angiotensin AT(2) Receptor Stimulation Alleviates Collagen-Induced Arthritis by Upregulation of Regulatory T Cell Numbers

The angiotensin AT(2) receptor (AT(2)R) is a main receptor of the protective arm of the renin-angiotensin system and exerts for instance anti-inflammatory effects. The impact of AT(2)R stimulation on autoimmune diseases such as rheumatoid arthritis (RA) is not yet known. We investigated the therapeutic potential of AT(2)R-stimulation with the selective non-peptide AT(2)R agonist Compound 21 (C21) in collagen-induced arthritis (CIA), an animal model for inflammatory arthritis. Arthritis was induced by immunization of DBA/1J mice with collagen type II (CII). Prophylactic and therapeutic C21 treatment alleviates arthritis severity and incidence in CIA. Joint histology revealed significantly less infiltrates of IL-1 beta and IL-17A expressing cells and a well-preserved articular cartilage in C21- treated mice. In CIA, the number of CD4(+)CD25(+)FoxP3(+) regulatory T (Treg) cells significantly increased upon C21 treatment compared to vehicle. T cell differentiation experiments demonstrated increased expression of FoxP3 mRNA, whereas IL-17A, STAT3 and IFN-gamma mRNA expression were reduced upon C21 treatment. In accordance with the mRNA data, C21 upregulated the percentage of CD4(+)FoxP3(+) cells in Treg polarizing cultures compared to medium-treated controls, whereas the percentage of CD4(+)IL-17A(+) and CD4(+)IFN-gamma(+) T cells was suppressed. To conclude, C21 exerts beneficial effects on T cell-mediated experimental arthritis. We found that C21-induced AT(2)R-stimulation promotes the expansion of CD4(+) regulatory T cells and suppresses IL-17A production. Thus, AT(2)R-stimulation may represent an attractive treatment strategy for arthritis

The past, present and future of angiotensin II type 2 receptor stimulation

Studying the angiotensin type 2 receptor (AT2) has been problematic in the past because a pharmacological tool for direct, specific in vitro and in vivo stimulation of the receptor has been lacking. Consequently, current knowledge about AT2 receptor signalling and function had to be obtained by indirect approaches, like studying animals or cells with genetically altered AT2 receptor expression levels, inhibitory experiments using specific AT2 receptor antagonists, stimulation with angiotensin II under concomitant angiotensin II type 1 receptor blockade or stimulation with the peptide agonist CGP42112A, which has additional AT2 receptor antagonistic properties. The recently developed non-peptide AT2 receptor agonist Compound 21 now, for the first time, allows direct, selective and specific AT2 receptor stimulation in vitro and in vivo. This new tool will certainly revolutionise AT2 receptor research, enable many new insights into AT2 receptor function and may also have the potential to become a future medical drug. This article reviews milestone findings about AT2 receptor functional properties obtained by 'conventional' experimental approaches within the last 20 years. Moreover, it provides an overview of the first results obtained by direct AT2 receptor stimulation with Compound 21, comprising effects on alkaline secretion, neurite outgrowth, blood pressure and post-infarct cardiac function

Identification of protein phosphatase involvement in the AT(2)-receptor induced activation of endothelial nitric oxide synthase

The angiotensin AT2 receptor (AT(2)R) promotes vasodilation by nitric oxide (NO) release from endothelial cells. However, the mechanisms underlying the AT(2)R-induced stimulation of endothelial NO synthase (eNOS) is still not completely understood. Therefore, we investigated whether in addition to the known AT(2)R-mediated phosphorylation of eNOS at Ser1177, activation of phosphatases and dephosphorylation of eNOS at Tyr657 and Thr495 are also involved. Human Aortic Endothelial Cells (HAEC) were stimulated with the AT(2)R-agonist C21 (1µM) in the presence or absence of either PD123319 (10µM; AT(2)R-antagonist), L-NAME (10µM; eNOS inhibitor), MK-2206 (100nM; Akt-inhibitor) sodium fluoride (1nM; serine/threonine-phosphatase inhibitor) or sodium orthovanadate (10nM; tyrosine-phosphatase inhibitor). NO release was estimated by quantifying DAF-FM fluorescence. The phosphorylation status of activating (eNOS-Ser1177) or inhibitory eNOS residues (eNOS-Tyr657, eNOS-Thr495) was determined by Western blotting. Phosphorylation of Akt at Ser473 was measured to estimate Akt activity. AT(2)R-stimulation significantly increased NO release from HAEC, which was blocked by PD123319, L-NAME and both phosphatase inhibitors. Intracellular calcium transients were not changed by C21. AT(2)R-stimulation resulted in phosphorylation of eNOS-Ser1177 and dephosphorylation of eNOS-Tyr657 and eNOS-Thr495. Phosphorylation at eNOS-Ser1177 was prevented by inhibition of Akt with MK-2206. From these data we conclude that AT2R-stimulation in human endothelial cells increases eNOS activity through phosphorylation of activating eNOS residues (eNOS-Ser1177) by Akt, and through dephosphorylation of inactivating eNOS residues (eNOS-Tyr657, eNOS-Thr495) by serine/threonine and tyrosine phosphatases, thus increasing NO release