Measurement of Cardiac Angiotensin II by Immunoassays, HPLC-Chip/Mass Spectrometry, and Functional Assays

Evaluation of pathophysiological relationships between renin-angiotensin and ACE-ACE2 systems in cardiovascular disorders: from theory to routine clinical practice in patients with heart failure

Despite the progressive improvements in diagnosis and therapy during the first 20 years of this century, the morbidity and mortality of patients with heart failure (HF) remain high, resulting in an enormous health and economic burden. Only a further improvement in understanding the pathophysiological mechanisms related to the development of cardiac injury and dysfunction can allow more innovative and personalized approaches to HF management. The renin-angiotensin system (RAS) has a critical role in cardiovascular physiology by regulating blood pressure and electrolyte balance. The RAS is mainly regulated by both angiotensin converting enzyme (ACE) and type 2 angiotensin converting enzyme (ACE2). However, the balance between the various peptides and peptidases constituting the RAS/ACE pathway remains in great part unraveled in patients with HF. This review summarizes the role of the RAS/ACE axis in cardiac physiology and HF pathophysiology as well as some analytical issues relevant to the clinical and laboratory assessment of inter-relationships between these two systems. There is evidence that RAS peptides represent a dynamic network of peptides, which are altered in different HF states and influenced by medical therapy. However, the mechanisms of signal transduction have not been fully elucidated under physiological and pathophysiological conditions. Further investigations are necessary to explore novel molecular mechanisms related to the RAS, which will provide alternative therapeutic agents. Moreover, monitoring the circulating levels of active RAS peptides in HF patients may enable a personalized approach by facilitating assessment of the pathophysiological status of several cardiovascular diseases and thus better selection of therapies for HF patients.

Losartan counteracts the effects of cardiomyocyte swelling on glucose uptake and insulin receptor substrate-1 levels

A growing body of evidence demonstrates an association between Angiotensin II (Ang II) receptor blockers (ARBs) and enhanced glucose metabolism during ischemic heart disease. Despite these encouraging results, the mechanisms responsible for these effects during ischemia remain poorly understood. In this study we investigated the influence of losartan, an AT1 receptor blocker, and secreted Ang II (sAng II) on glucose uptake and insulin receptor substrate (IRS-1) levels during cardiomyocyte swelling. H9c2 cells were differentiated to cardiac muscle and the levels of myogenin, Myosin Light Chain (MLC), and membrane AT1 receptors were measured using flow cytometry. Intracellular Ang II (iAng II) was overexpressed in differentiated cardiomyocytes and swelling was induced after incubation with hypotonic solution for 40min. Glucose uptake and IRS-1 levels were monitored by flow cytometry using 2-NBDG fluorescent glucose (10μM) or an anti-IRS-1 monoclonal antibody in the presence or absence of losartan (10^-7M). Secreted Angiotensin II was quantified from the medium using a specific Ang II-EIA kit. To evaluate the relationship between sAng II and losartan effects on glucose uptake, transfected cells were pretreated with the drug for 24h and then exposed to hypotonic solution in the presence or absence of the secreted peptide. The results indicate that: (1) swelling of transfected cardiomyocytes decreased glucose uptake and induced the secretion of Ang II to the extracellular medium; (2) losartan antagonized the effects of swelling on glucose uptake and IRS-1 levels in transfected cardiomyocytes; (3) the effects of losartan on glucose uptake were observed during swelling only in the presence of sAng II in the culture medium. Our study demonstrates that both losartan and sAng II have essential roles in glucose metabolism during cardiomyocyte swelling.