Balloon Angioplasty - The Legacy of Andreas Grüntzig, M.D. (1939-1985)

In 1974, at the Medical Policlinic of the University of Zürich, German-born physician-scientist Andreas Grüntzig (1939-1985) for the first time applied a balloon-tipped catheter to re-open a severely stenosed femoral artery, a procedure, which he initially called "percutaneous transluminal dilatation". Balloon angioplasty as a therapy of atherosclerotic vascular disease, for which Grüntzig and Charles T. Dotter (1920-1985) received a nomination for the Nobel Prize in Physiology or Medicine in 1978, became one of the most successful examples of translational medicine in the twentieth century. Known today as percutaneous transluminal angioplasty (PTA) in peripheral arteries or percutaneous transluminal coronary angioplasty (PTCA) or percutaneous coronary intervention (PCI) in coronary arteries, balloon angioplasty has become the method of choice to treat patients with acute myocardial infarction or occluded leg arteries. On the occasion of the 40(th) anniversary of balloon angioplasty, we summarize Grüntzig's life and career in Germany, Switzerland, and the United States and also review the developments in vascular medicine from the 1890s to the 1980s, including Dotter's first accidental angioplasty in 1963. The work of pioneers of catheterization, including Pedro L. Fariñas in Cuba, André F. Cournand in France, Werner Forssmann, Werner Porstmann and Eberhard Zeitler in Germany, António Egas Moniz and Reynaldo dos Santos in Portugal, Sven-Ivar Seldinger in Sweden, and Barney Brooks, Thomas J. Fogarty, Melvin P. Judkins, Richard K. Myler, Dickinson W. Richards, and F. Mason Sones in the United States, is discussed. We also present quotes by Grüntzig and excerpts from his unfinished autobiography, statements of Grüntzig's former colleagues and contemporary witnesses, and have included hitherto unpublished historic photographs and links to archive recordings and historic materials. This year, on June 25, 2014, Andreas Grüntzig would have celebrated his 75(th) birthday. This article is dedicated to his memory.

G protein-coupled estrogen receptor protects from atherosclerosis

Coronary atherosclerosis and myocardial infarction in postmenopausal women have been linked to inflammation and reduced nitric oxide (NO) formation. Natural estrogen exerts protective effects on both processes, yet also displays uterotrophic activity. Here, we used genetic and pharmacologic approaches to investigate the role of the G protein-coupled estrogen receptor (GPER) in atherosclerosis. In ovary-intact mice, deletion of gper increased atherosclerosis progression, total and LDL cholesterol levels and inflammation while reducing vascular NO bioactivity, effects that were in some cases aggravated by surgical menopause. In human endothelial cells, GPER was expressed on intracellular membranes and mediated eNOS activation and NO formation, partially accounting for estrogen-mediated effects. Chronic treatment with G-1, a synthetic, highly selective small molecule agonist of GPER, reduced postmenopausal atherosclerosis and inflammation without uterotrophic effects. In summary, this study reveals an atheroprotective function of GPER and introduces selective GPER activation as a novel therapeutic approach to inhibit postmenopausal atherosclerosis and inflammation in the absence of uterotrophic activity.

Endothelin and endothelin antagonists in chronic kidney disease

The incidence and prevalence of chronic kidney disease (CKD), with diabetes and hypertension accounting for the majority of cases, is on the rise, with up to 160 million individuals worldwide predicted to be affected by 2020. Given that current treatment options, primarily targeted at the renin-angiotensin system, only modestly slow down progression to end-stage renal disease, the urgent need for additional effective therapeutics is evident. Endothelin-1 (ET-1), largely through activation of endothelin A receptors, has been strongly implicated in renal cell injury, proteinuria, inflammation, and fibrosis leading to CKD. Endothelin receptor antagonists (ERAs) have been demonstrated to ameliorate or even reverse renal injury and/or fibrosis in experimental models of CKD, whereas clinical trials indicate a substantial antiproteinuric effect of ERAs in diabetic and nondiabetic CKD patients even on top of maximal renin-angiotensin system blockade. This review summarizes the role of ET in CKD pathogenesis and discusses the potential therapeutic benefit of targeting the ET system in CKD, with attention to the risks and benefits of such an approach.

Advancing and Translating Knowledge in Vascular Medicine

For centuries, physicians have depended on the use of written information to gain knowledge. Book printing and binding introduced by Gutenberg in the fifteenth century revolutionized and accelerated the distribution of information. Advancing medical knowledge and progress is not only linked to the scientific quality of a discovery determining it will be accepted by the peers but also by its communication and sharing of new findings with the medical community. All these factors determine whether new knowledge will advance and improve clinical practice, medical education, and ultimately, patient care, and human health. In the past decade medical publishing has witnessed a revolution with regard to the instant, online availability of published "open access" information, which can be accessed and printed from any computer connected to the internet. As an example, how language and availability of printed information may affect distribution of knowledge, we discuss the publication of the first results of balloon angioplasty in patients with peripheral vascular disease 40 years ago by Andreas Grüntzig, M.D. at the University of Zürich. Vascular Medicine, as part of Frontiers in Cardiovascular Medicine, will provide open access provided to all published content for sharing and distributing new and most up-to-date information on clinical practice and medical knowledge in vascular medicine. We anticipate that the ongoing transformation of scientific publishing through open access will further accelerate this process and make new knowledge available even faster. Immediate, unrestricted, and rapid access to the most current knowledge published will play a role in maintaining and advancing human vascular health across the globe.

Estrogen biology: new insights into GPER function and clinical opportunities

Estrogens play an important role in the regulation of normal physiology, aging and many disease states. Although the nuclear estrogen receptors have classically been described to function as ligand-activated transcription factors mediating genomic effects in hormonally regulated tissues, more recent studies reveal that estrogens also mediate rapid signaling events traditionally associated with G protein-coupled receptors. The G protein-coupled estrogen receptor GPER (formerly GPR30) has now become recognized as a major mediator of estrogen's rapid cellular effects throughout the body. With the discovery of selective synthetic ligands for GPER, both agonists and antagonists, as well as the use of GPER knockout mice, significant advances have been made in our understanding of GPER function at the cellular, tissue and organismal levels. In many instances, the protective/beneficial effects of estrogen are mimicked by selective GPER agonism and are absent or reduced in GPER knockout mice, suggesting an essential or at least parallel role for GPER in the actions of estrogen. In this review, we will discuss recent advances and our current understanding of the role of GPER and the activity of clinically used drugs, such as SERMs and SERDs, in physiology and disease. We will also highlight novel opportunities for clinical development towards GPER-targeted therapeutics, for molecular imaging, as well as for theranostic approaches and personalized medicine.

Endothelin-1 but not angiotensin II contributes to functional aging in murine carotid arteries

AIMS

Aging is a major risk factor for carotid artery disease and stroke. Endothelin-1 (ET-1) and angiotensin II (Ang II) are important modifiers of vascular disease, partly through increased activity of NADPH oxidase and vasoconstrictor prostanoids. Since the renin-angiotensin and endothelin systems become activated with age, we hypothesized that aging affects NADPH oxidase- and prostanoid-dependent contractions to ET-1 and Ang II.

MAIN METHODS

Carotid artery rings of young (4 month-old) and old (24 month-old) C57BL6 mice were pretreated with the NO synthase inhibitor L-NAME to exclude differential effects of NO. Contractions to ET-1 and Ang II were determined in the presence and absence of the NADPH oxidase-selective inhibitor gp91ds-tat or the thromboxane-prostanoid receptor antagonist SQ 29,548. Gene expression of endothelin and angiotensin receptors was measured by qPCR.

KEY FINDINGS

Aging reduced ET-1-induced contractions and diminished ETA but increased ETB receptor gene expression levels. Gp91ds-tat inhibited contractions to ET-1 in young and to a greater extent in old animals, whereas SQ 29,548 had no effect. Ang II-induced contractions were weak compared to ET-1 and unaffected by aging, gp91ds-tat, and SQ 29,548. Aging had also no effect on AT1A and AT1B receptor gene expression levels.

SIGNIFICANCE

Aging in carotid arteries decreases ETA receptor gene expression and responsiveness to ET-1, which nevertheless becomes increasingly dependent upon NAPDH oxidase activity with age; responses to Ang II and gene expression of its receptors are however unaffected. These findings suggest that physiological aging differentially regulates functional responses to G protein-coupled receptor agonists and the signaling pathways associated with their activation.

Obesity and heterozygous endothelial overexpression of prepro-endothelin-1 modulate responsiveness of mouse main and segmental renal arteries to vasoconstrictor agents

AIMS

Levels of the endothelium-derived peptide endothelin-1 (ET-1) are elevated in obese humans, and ET-1 mediated vascular tone is increased. Renal arterial smooth muscle is highly responsive to ET-1. Whether or not endothelium-derived ET-1 affects contractions of the renal artery under normal conditions or in obesity is unknown. The present study was designed to investigate whether or not overexpression of endogenous ET-1 in the endothelium affects the responsiveness of the main and segmental renal arteries differently in obesity.

MAIN METHODS

Mice with tie-1 promoter-driven endothelium-restricted heterozygous overexpression of preproendothelin-1 were used (TET(het)). Obesity was induced in TET(het) mice and wild-type (WT) littermates by feeding a high fat diet for 30 weeks; lean controls were kept on standard chow. The renal arteries were studied in wire myographs testing contractions (in the presence of l-NAME) to ET-1, serotonin, and U46619.

KEY FINDINGS

Contractions to ET-1 were comparable between groups in main renal arteries, but augmented in segmental preparations from obese mice. Serotonin-induced responses were enhanced in obese TET(het) mice renal arteries compared to lean controls. Concentration-contraction curves to U46619 were shifted significantly to the left in main renal arteries of obese animals, and the maximal response was significantly increased between lean and obese TET(het) mice.

SIGNIFICANCE

These results indicate an augmented responsiveness of main renal arteries in obesity particularly to TP receptor activation. When combined with endothelial ET-1 overexpression this effect is even more pronounced, which may help to gain further insights into the mechanisms of hypertension in obesity.

Regulation of vascular smooth muscle tone by adipose-derived contracting factor

Obesity and arterial hypertension, important risk factors for atherosclerosis and coronary artery disease, are characterized by an increase in vascular tone. While obesity is known to augment vasoconstrictor prostanoid activity in endothelial cells, less is known about factors released from fat tissue surrounding arteries (perivascular adipose). Using lean controls and mice with either monogenic or diet-induced obesity, we set out to determine whether and through which pathways perivascular adipose affects vascular tone. We unexpectedly found that in the aorta of obese mice, perivascular adipose potentiates vascular contractility to serotonin and phenylephrine, indicating activity of a factor generated by perivascular adipose, which we designated “adipose-derived contracting factor” (ADCF). Inhibition of cyclooxygenase (COX) fully prevented ADCF-mediated contractions, whereas COX-1 or COX-2-selective inhibition was only partially effective. By contrast, inhibition of superoxide anions, NO synthase, or endothelin receptors had no effect on ADCF activity. Perivascular adipose as a source of COX-derived ADCF was further confirmed by detecting increased thromboxane A₂ formation from perivascular adipose-replete aortae from obese mice. Taken together, this study identifies perivascular adipose as a novel regulator of arterial vasoconstriction through the release of COX-derived ADCF. Excessive ADCF activity in perivascular fat under obese conditions likely contributes to increased vascular tone by antagonizing vasodilation. ADCF may thus propagate obesity-dependent hypertension and the associated increased risk in coronary artery disease, potentially representing a novel therapeutic target.

Hypernatraemic dehydration in Jamaican breastfed neonates: a 12-year review in a baby-friendly hospital

A 12-year retrospective review of neonates admitted with hypernatraemic dehydration to the neonatal unit of the University Hospital of the West Indies was conducted between 1 January 1990 and 31 December 2001. Twenty-four infants fulfilled the criteria for hypernatraemic dehydration. Nineteen (79%) women were either nulliparous or primiparous with a mean (SD) age of 26.9 (4.4) yrs. Modal length of hospital stay for mothers was 24 hrs. Twenty (83.3%) infants were exclusively breastfed. Mean (SD) age at presentation was 7.4 (3.8) days. Mean (SD) percentage weight loss between birth and presentation was 18.9% (6.3). Mean (SD) serum sodium at presentation was 164.8 (13.9) mmol/L. Babies visited at home by nurses had a lower mean serum sodium, were less dehydrated and were significantly less acidiotic. Their mean (SD) length of hospital stay was also significantly less [4.2 (1.4) days] than those who were not visited [7.9 (3.8) days] (p < 0.05). Complications occurred in 19 (79%) of infants and included renal failure (19, 79%), seizures (3, 13%) and intraventricular haemorrhage (1, 4%), and one died (4%). Hypernatraemic dehydration is an uncommon complication of failure to establish breastfeeding but is associated with severe morbidity and mortality. Education programmes are needed to increase awareness amongst health-care workers and mothers in order to prevent the problem.

Invasive pneumococcal disease in Jamaican children

A 5-year retrospective review of cases of invasive pneumococcal disease admitted to the Bustamante Hospital for Children, Jamaica was conducted. A total of 111 cases were identified. The estimated incidence of invasive pneumococcal disease in Kingston and St Andrew was 21/100,000 children under the age of 10 years. The majority of cases (76%) were in the under-2-years age group. All four deaths were of infants. Pre-existing medical conditions included sickle cell disease, HIV and undernutrition. The rate of resistance to penicillin was 13.8%. Meningitis accounted for three of the four deaths identified and poor outcome was identified in 28% of cases of meningitis. We conclude that invasive pneumococcal disease causes significant morbidity and mortality in young Jamaican children. Strategies directed at preventing HIV infection and malnutrition and improving the care of children with sickle cell disease and HIV infection would significantly reduce disease incidence.

Themed section: endothelin

This themed section of the British Journal of Pharmacology contains reviews on recent developments in endothelin research arising from the Twelfth International Conference on Endothelin (ET-12). It includes the emerging role for endothelin-2 in the cardiovascular system, ovarian development, immunology and cancer. The action of endothelin on two key targets is discussed: the paracrine or autocrine regulation of contractility and growth in the heart and the role of endothelin in renal disease. Epidemiological studies have demonstrated cardiovascular disease and circulating levels of endothelin-1 are lower in premenopausal women than in men and evidence is presented for the contribution of sex differences in responses to the peptide. Transcription is the primary level of regulation of the endothelin gene; and current research on the epigenetic regulation of the endothelin pathway, including the silencing of the EDNRB gene encoding the ET(B) receptor during tumourigenesis, is reviewed.

LINKED ARTICLES

This article is part of a themed section on Endothelin. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2013.168.issue-1. To view the previously published paper by Dhaun et al. visit http://dx.doi.org/10.1111/j.1476-5381.2012.02070.x.

Prevention and endothelial therapy of coronary artery disease

Functional integrity of endothelial cells is an indicator and a prerequisite for vascular health and counteracts the development of atherosclerosis. This concept of 'endothelial therapy' was developed in the late 1990s as an approach to preserve or restore endothelial cell health given that 'the knowledge of the mechanisms involved in 'endothelial dysfunction' allows us to interfere specifically with pathogenic pathways at very early time points and to slow down the progression of disease'. In the present review, the principles underlying endothelial cell health will be discussed as well as the role of endothelial therapy as a preventive measure to reduce the prevalence of coronary artery disease or to delay disease progression in patients with chronic coronary artery disease. This article also highlights the importance of active participation, the need to reduce the number of future patients in view of the rising prevalence of childhood obesity, and the potential of endothelial therapy to improve survival, reduce disability and health costs, and to improve overall quality of life in patients at risk for or already diagnosed with coronary artery disease. The preventive and therapeutic approaches and considerations described herein can be applied by physicians, patients, parents, educators, health agencies, and political decision makers to help reducing the global cardiovascular disease burden in the decades to come.

Cholesterol and atherosclerosis: modulation by oestrogen

PURPOSE OF REVIEW

Oestrogens are important modulators of lipid metabolism, inflammation and vascular homeostasis. Endogenous oestrogens contribute to the low prevalence of atherosclerotic vascular disease in premenopausal women with intact ovarian function, and cessation of oestrogen production following menopause increases cardiovascular risk. Orally administered oestrogens such as postmenopausal hormone therapy increase HDL and reduce LDL cholesterol levels, and they increase triglyceride levels. Current guidelines do not recommend postmenopausal hormone therapy for cardiovascular prevention.

RECENT FINDINGS

Recent clinical studies have suggested potential benefits of natural oestrogen or selective oestrogen receptor modulators on cardiovascular outcomes, effects that are associated with lipid profile improvements. In contrast to earlier studies such as the Women's Health Initiative, the Heart and Estrogen/Progestin Replacement Study or the Estrogen Replacement and Atherosclerosis trial, in which investigators used hormone mixtures derived from horse urine (misleadingly named 'conjugated oestrogens' with unknown activity on oestrogen receptors), triphasic oestrogen therapy started early after menopause as primary prevention study protocol improved outcome. New studies suggest therapeutic potential of natural oestrogens and certain selective oestrogen receptor modulators to reduce coronary artery disease risk in postmenopausal women.

SUMMARY

Endogenous oestrogens are important regulators of lipid metabolism and inhibit inflammation, vascular cell growth and plaque progression in premenopausal women. The recent trials warrant further studies, which should also determine how much of the potential benefits are due to improvements of lipid metabolism.

The potential for an enhanced role for MRI in radiation-therapy treatment planning

The exquisite soft-tissue contrast of magnetic resonance imaging (MRI) has meant that the technique is having an increasing role in contouring the gross tumor volume (GTV) and organs at risk (OAR) in radiation therapy treatment planning systems (TPS). MRI-planning scans from diagnostic MRI scanners are currently incorporated into the planning process by being registered to CT data. The soft-tissue data from the MRI provides target outline guidance and the CT provides a solid geometric and electron density map for accurate dose calculation on the TPS computer. There is increasing interest in MRI machine placement in radiotherapy clinics as an adjunct to CT simulators. Most vendors now offer 70 cm bores with flat couch inserts and specialised RF coil designs. We would refer to these devices as MR-simulators. There is also research into the future application of MR-simulators independent of CT and as in-room image-guidance devices. It is within the background of this increased interest in the utility of MRI in radiotherapy treatment planning that this paper is couched. The paper outlines publications that deal with standard MRI sequences used in current clinical practice. It then discusses the potential for using processed functional diffusion maps (fDM) derived from diffusion weighted image sequences in tracking tumor activity and tumor recurrence. Next, this paper reviews publications that describe the use of MRI in patient-management applications that may, in turn, be relevant to radiotherapy treatment planning. The review briefly discusses the concepts behind functional techniques such as dynamic contrast enhanced (DCE), diffusion-weighted (DW) MRI sequences and magnetic resonance spectroscopic imaging (MRSI). Significant applications of MR are discussed in terms of the following treatment sites: brain, head and neck, breast, lung, prostate and cervix. While not yet routine, the use of apparent diffusion coefficient (ADC) map analysis indicates an exciting future application for functional MRI. Although DW-MRI has not yet been routinely used in boost adaptive techniques, it is being assessed in cohort studies for sub-volume boosting in prostate tumors.

Clinical trials with endothelin receptor antagonists: what went wrong and where can we improve?

In the early 1990s, within three years of cloning of endothelin receptors, orally active endothelin receptor antagonists (ERAs) were tested in humans and the first clinical trial of ERA therapy in humans was published in 1995. ERAs were subsequently tested in clinical trials involving heart failure, pulmonary arterial hypertension, resistant arterial hypertension, stroke/subarachnoid hemorrhage and various forms of cancer. The results of most of these trials - except those for pulmonary arterial hypertension and scleroderma-related digital ulcers - were either negative or neutral. Problems with study design, patient selection, drug toxicity, and drug dosing have been used to explain or excuse failures. Currently, a number of pharmaceutical companies who had developed ERAs as drug candidates have discontinued clinical trials or further drug development. Given the problems with using ERAs in clinical medicine, at the Twelfth International Conference on Endothelin in Cambridge, UK, a panel discussion was held by clinicians actively involved in clinical development of ERA therapy in renal disease, systemic and pulmonary arterial hypertension, heart failure, and cancer. This article provides summaries from the panel discussion as well as personal perspectives of the panelists on how to proceed with further clinical testing of ERAs and guidance for researchers and decision makers in clinical drug development on where future research efforts might best be focused.