Dilation of epicardial coronary arteries by the G protein-coupled estrogen receptor agonists G-1 and ICI 182,780

Endogenous estrogens protect from coronary artery disease in premenopausal women, but the mechanisms involved are only partly understood. This study investigated whether activation of the novel G protein-coupled estrogen receptor (GPER, formerly known as GPR30) affects coronary artery tone, and whether this is affected by concomitant blockade of estrogen receptors (ER) alpha and beta. Rings of epicardial porcine coronary arteries suspended in organ chambers were precontracted with prostaglandin F(2)alpha, and direct effects of G-1 (GPER agonist) and ICI 182,780 (GPER agonist and ERalpha/ERbeta antagonist) were determined. In addition, indirect effects on contractility to endothelin-1 and serotonin (a vasoconstrictor released from aggregating platelets during acute myocardial infarction) were assessed. ICI 182,780 and G-1 caused acute dilation of coronary arteries to a comparable degree (p < 0.05 vs. solvent control). Both GPER agonists attenuated contractions to endothelin-1 (p < 0.05 vs. ethanol), but not to serotonin (n.s.). In summary, these findings provide evidence for direct and indirect coronary artery dilator effects of GPER independent of ERalpha and ERbeta, and are the first demonstration of arterial vasodilation in response to ICI 182,780.

Therapeutic potential of endothelin receptor antagonists for chronic proteinuric renal disease in humans

Diabetes and arterial hypertension continue to be the main causes of chronic renal failure in 2010, with a rising prevalence in part due to the worldwide obesity epidemic. Proteinuria is a main feature of chronic renal disease and mediated by defects in the glomerular filtration barrier and is as a good predictor of cardiovascular events. Indeed, chronic renal disease due to glomerulosclerosis is one of the important risk factors for the development of coronary artery disease and stroke. Glomerulosclerosis develops in response to inflammatory activation and increased growth factor production. Preclinical and first preliminary clinical studies provide strong evidence that endogenous endothelin-1 (ET-1), a 21-amino-acid peptide with strong growth-promoting and vasoconstricting properties, plays a central role in the pathogenesis of proteinuria and glomerulosclerosis via activation of its ET(A) subtype receptor involving podocyte injury. These studies have not only shown that endothelin participates in the disease processes of hypertension and glomerulosclerosis but also that features of chronic renal disease such as proteinuria and glomerulosclerosis are reversible processes. Remarkably, the protective effects of endothelin receptors antagonists (ERAs) are present even on top of concomitant treatments with inhibitors of the renin-angiotensin system. This review discusses current evidence for a role of endothelin for proteinuric renal disease and podocyte injury in diabetes and arterial hypertension and reviews the current status of endothelin receptor antagonists as a potential new treatment option in renal medicine.

Pneumococcal meningitis in Jamaican children

OBJECTIVE

To describe the clinical features and outcome of pneumococcal meningitis in Jamaican children.

METHODS

All patients admitted to the Bustamante Hospital for Children, during the period 1995-1999, who had pneumococcus isolated from cerebrospinal fluid (CSF) or pleocytosis in association with a blood culture isolate of pneumococcus were selected. Demographic, clinical and laboratory data were collected.

RESULTS

Twenty-five (23%) of 111 patients with pneumococcal infections satisfied criteria for meningitis. The median age was 8 months (range 0.5-60 months). There were 4 (16%) cases of sickle cell disease, 2 (50%) of whom were first diagnosed during the current illness. This represents a 53-fold increased risk of pneumoccocal meningitis in patients with Sickle-cell disease based on population prevalence rates. Oxacillin resistance occurred in 3 (12%) patients, one of whom died. Mortality rate was 12% (3) with all deaths occurring in infants < 1 year. Poor outcome occurred in 36% (9) of the patients. Of the (35%) 8 survivors who had follow-up evaluation, (38%) 3 had documented hearing loss.

CONCLUSIONS

Meningitis is a common clinical syndrome of invasive pneumococcal disease, occurring in 23% of cases resulting in mortality and high morbidity among Jamaican children. Local seroepidemiological studies are urgently needed to inform national vaccine decisions. As an interim plan, policymakers should consider a risk-based strategy to vaccine prophylaxis that will ensure that high risk groups such as children with sickle cell disease are offered currently available conjugate pneumococcal vaccines.

Non-genomic regulation of vascular cell function and growth by estrogen

Estrogens exert rapid, non-genomic effects, which are mediated by plasma membrane-associated estrogen receptors (mER) mERalpha and mERbeta, and the intracellular transmembrane G protein-coupled estrogen receptor (GPER). Membrane-initiated responses contribute to transcriptional activation, resulting in a complex interplay of nuclear and extra-nuclear mechanisms that mediate the acute physiological responses to estrogens. Non-genomic estrogen signaling also activates a variety of intracellular estrogen signaling pathways that regulate vascular function and cell growth involving rapid but also long-term effects. This review discusses recent advances in understanding of the mechanisms of non-genomic estrogen receptor signaling in the vascular wall.

Signaling, physiological functions and clinical relevance of the G protein-coupled estrogen receptor GPER

GPR30, now named GPER1 (G protein-coupled estrogen receptor1) or GPER here, was first identified as an orphan 7-transmembrane G protein-coupled receptor by multiple laboratories using either homology cloning or differential expression and subsequently shown to be required for estrogen-mediated signaling in certain cancer cells. The actions of estrogen are extensive in the body and are thought to be mediated predominantly by classical nuclear estrogen receptors that act as transcription factors/regulators. Nevertheless, certain aspects of estrogen function remain incompatible with the generally accepted mechanisms of classical estrogen receptor action. Many recent studies have revealed that GPER contributes to some of the actions of estrogen, including rapid signaling events and rapid transcriptional activation. With the introduction of GPER-selective ligands and GPER knockout mice, the functions of GPER are becoming more clearly defined. In many cases, there appears to be a complex interplay between the two receptor systems, suggesting that estrogen-mediated physiological responses may be mediated by either receptor or a combination of both receptor types, with important medical implications.

Regulatory role of G protein-coupled estrogen receptor for vascular function and obesity

We found that the selective stimulation of the intracellular, transmembrane G protein-coupled estrogen receptor (GPER), also known as GPR30, acutely lowers blood pressure after infusion in normotensive rats and dilates both rodent and human arterial blood vessels. Stimulation of GPER blocks vasoconstrictor-induced changes in intracellular calcium concentrations and vascular tone, as well as serum-stimulated cell proliferation of human vascular smooth muscle cells. Deletion of the GPER gene in mice abrogates vascular effects of GPER activation and is associated with visceral obesity. These findings suggest novel roles for GPER in protecting from cardiovascular disease and obesity.

Endothelin: 20 years from discovery to therapy

Since its identification as an endothelial cell-derived vasoconstrictor peptide in 1988, endothelin-1, the predominant member of the endothelin peptide family, has received considerable interest in basic medical science and in clinical medicine, which is reflected by more than 20 000 scientific publications on endothelin research in the past 20 years. The story of endothelin is unique as the gene sequences of endothelin receptors and the first receptor antagonists became available within only 4 years of the identification of the peptide sequence. The first clinical study in patients with congestive heart failure was published only 3 years thereafter. Yet, despite convincing experimental evidence of a pathogenetic role for endothelin in development, cell function, and disease, many initial clinical studies on endothelin antagonism were negative. In many of these studies, study designs or patient selection were inadequate. Today, for diseases such as pulmonary hypertension, endothelin antagonist treatment has become reality in clinical medicine, and ongoing clinical studies are evaluating additional indications, such as renal disease and cancer. Twenty years after the discovery of endothelin, its inhibitors have finally arrived in the clinical arena and are now providing us with new options to treat disease and prolong the lives of patients. Possible future indications include resistant arterial hypertension, proteinuric renal disease, cancer, and connective tissue diseases.

Upregulation of vascular ET(B) receptor gene expression after chronic ET(A) receptor blockade in prediabetic NOD mice

In the aorta of prediabetic non-obese diabetic mice, a model of human type 1 diabetes, we investigated gene expression of the endothelin receptors and contractility to big endothelin-1 and endothelin-1 at the ages of 10 and 16 weeks. A subgroup of 10- week-old animals was treated with the endothelin ETA receptor antagonist LU461314 (30 mg/kg per day for 6 weeks). Blood glucose levels were normal in all animals. Real-time polymerase chain reaction analysis revealed that vascular ETB receptor expression was higher in 10-week-old non-obese diabetic (NOD) mice compared with controls. In 16-week-old NOD mice, but not in control mice, ETB receptor mRNA was twofold lower (P < 0.05 vs 10-week-old NOD mice). In all groups ETA receptor expression was unaffected by age or treatment. Contractions to big endothelin-1 and endothelin-1 were lower in 10-week-old NOD mice compared with controls. Treatment with LU461314 increased ETB receptor expression in 16-week-old NOD mice, but had no effect on vascular contractility. These data indicate that dysregulation of ETB receptor expression and a decreased contractile response to big endothelin-1 and endothelin-1 are present in the prediabetic state of a model of human type 1 diabetes. These alterations occur independent of glucose levels. Furthermore, ETA receptor blockade is effective in increasing ETB receptor gene expression, suggesting a potential role for endothelin ETA antagonists in the treatment of type 1 diabetes.

Routine laboratory investigations in infants and children presenting with fever and seizures at the University Hospital of the West Indies

A retrospective chart review of the case notes of all children aged 6 months to 8 years presenting with fever and seizures to the University Hospital of the West Indies (UHWI) between January 2000 and December 2004 was conducted. Descriptive analyses were performed. Fifty-nine children (median age 1.58 years, range 0.58 to 6.83 years) were entered into the study. The main laboratory abnormalities were metabolic acidosis (23%), anaemia (10%), leukocytosis (35%) and hypomagnesaemia (3%). These were not significantly associated with meningitis or an underlying bacterial infection. There were no significant episodes of hyponatraemia, hypocalcaemia or hypoglycaemia. Meningitis was uncommon and occurred in only two (3.4%) children both younger than 16 months of age and who had other abnormal clinical signs. This study demonstrated that routine performance of haematological and biochemical investigations in children presenting with seizures and fever were of limited value. Lumbar punctures in children older than age 18 months with no other abnormal clinical signs were also found to be of low yield Current American Academy of Paediatrics (AAP) recommendations that serum electrolytes, calcium, phosphate, magnesium, complete blood count and blood glucose should not be performed routinely in a child with a first simple febrile seizure can be safely applied to this study population.

Reversal of proteinuric renal disease and the emerging role of endothelin

Proteinuria is a major long-term clinical consequence of diabetes and hypertension, conditions that lead to progressive loss of functional renal tissue and, ultimately, end-stage renal disease. Proteinuria is also a strong predictor of cardiovascular events. Convincing preclinical and clinical evidence exists that proteinuria and the underlying glomerulosclerosis are reversible processes. This Review outlines the mechanisms involved in the development of glomerulosclerosis--particularly those responsible for podocyte injury--with an emphasis on the potential capacity of endothelin receptor blockade to reverse this process. There is strong evidence that endothelin-1, a peptide with growth-promoting and vasoconstricting properties, has a central role in the pathogenesis of proteinuria and glomerulosclerosis, which is mediated via activation of the ET(A) receptor. Several antiproteinuric drugs, including angiotensin-converting-enzyme inhibitors, angiotensin receptor antagonists, statins and certain calcium channel blockers, inhibit the formation of endothelin-1. Preclinical studies have demonstrated that endothelin receptor antagonists can reverse proteinuric renal disease and glomerulosclerosis, and preliminary studies in humans with renal disease have shown that these drugs have remarkable antiproteinuric effects that are additive to those of standard antiproteinuric therapy. Additional clinical studies are needed.

Regional heterogeneity of functional changes in conduit arteries after high-fat diet

OBJECTIVE

To determine effects of dietary fat content on vascular responses in different conduit arteries in mice.

METHODS AND PROCEDURES

Vascular responses to reactive oxygen species (ROS)/hydroxyl radical (.OH), acetylcholine (ACh), endothelin-1 (ET-1), and angiotensin II (Ang II) were determined in carotid and femoral arteries of C57BL/6J mice fed with diets varying in fat content (low fat (LF), 12.3%; high fat (HF), 41%; and very high fat (VHF), 58% (kcal from fat)) for 15 weeks, beginning at 4 weeks of age.

RESULTS

In precontracted rings of carotid and femoral artery, ROS/.OH-induced a rapid, transient vasodilation. In the carotid, but not in femoral artery, ROS/.OH-induced dilation increased with increasing dietary fat intake (P < 0.05 vs. LF diet), while contractile responses to ROS/.OH remained unaffected. In femoral arteries, ROS/.OH-induced contractions were reversed into relaxations after both HF and VHF diet (P < 0.05 vs. LF diet). Both ET-1 and Ang II induced strong contractions in the femoral artery that were unaffected by dietary fat intake. In contrast, in the carotid artery Ang II-induced contraction was attenuated after HF and VHF diets (P < 0.005 vs. LF diet), whereas ET-1-induced vasoconstriction was significantly increased (P < 0.05 VHF vs. LF and HF). Treatment with VHF diet enhanced ACh-mediated endothelium-dependent relaxation only in the femoral artery (P < 0.05 vs. HF).

DISCUSSION

These findings demonstrate that dietary fat content has regional and distinct effects on vascular function in different vascular beds. The data also suggest the possibility that in selected conduit arteries ROS-dependent vasodilator mechanisms become activated in response to increased dietary fat intake.

Urinary tract infection in neonates with serious bacterial infections admitted to the University Hospital of the West Indies

OBJECTIVE

The aim of this study was to describe the epidemiology of urinary tract infection in neonates, with serious bacterial infections, admitted to the University Hospital of the West Indies.

METHODS

Admission records of all neonates admitted to the neonatal unit of the University Hospital of the West Indies between January 1995 and December 2000 for sepsis evaluation were reviewed. Infants who had positive bacterial cultures were identified using laboratory records. Those satisfying the criteria for urinary tract infection were selected for detailed analysis. Demographic, clinical and laboratory data were collected using a pre-coded questionnaire. Descriptive analyses were performed.

RESULTS

Fifty-one (38%) of 135 babies with positive bacterial isolates had confirmed urinary tract infection. Male:female ratio was 6:1. Common presenting features included fever (32%), poor feeding (30%) and irritability (22%). The mean white cell count was 14 +/- 6.26. E coli and Klebsiella species were most frequently identified. Factors associated with a diagnosis of urinary tract infection included male gender (p < 0.001), age > 48 hours (p < 0.05) and a presenting complaint of poor feeding (p < 0.003). Imaging studies of the renal tract detected abnormalities in 5 (10.4%) neonates.

CONCLUSIONS

Urinary tract infection is an important cause of serious bacterial infection in neonates affecting 1 in 3 babies with proven bacterial infection and may be the first indicator of underlying structural abnormalities. The absence of specific distinguishing clinical features makes it necessary to include urine cultures in the sepsis evaluation of neonates presenting with symptoms suggestive of sepsis.

Knowledge, perception and practices of healthcare professionals at tertiary level hospitals in Kingston, Jamaica, regarding neonatal pain management

OBJECTIVE

To determine knowledge, perception and practices of healthcare professionals at tertiary level hospitals in Kingston, Jamaica, regarding neonatal pain management.

DESIGN AND METHODS

Physicians and nurses actively involved in providing neonatal care at three tertiary level hospitals were invited to participate. A 21-item self-administered questionnaire was used to obtain information on knowledge, perception and practice of neonatal pain management. Descriptive analyses were performed.

RESULTS

A total of 147 healthcare workers participated giving a response rate of 85%. Male to female ratio was 1: 4.4. Nurses accounted for 76 (52%) of the respondents while 70 (48%) were physicians. Seventy-three (50%) individuals were unaware of the degree of pain neonates were capable of experiencing and only 38 (27%) knew that premature infants were capable of feeling pain. One hundred and four (71%) respondents were able to identify physiological markers of pain and most respondents were able to discriminate between painful and non-painful procedures. However, 100 (68%) respondents rarely prescribed analgesia for procedures previously rated as painful. Seventy-one (51%) respondents admitted to not using analgesia for alleviating procedural pain in neonates. Twenty-five (18%) individuals thought that the procedure was too short to require analgesic support while 41 (30%) stated that medication was not usually prescribed for procedural pain. Physician scores were significantly higher than those attained by nurses for knowledge (p = 0.003) and for pain perception (p = 0.001) but no significant differences were noted for practice (p = 0.18).

CONCLUSION

There is an overwhelming deficiency in the knowledge, perception and practice of neonatal pain management at tertiary level institutions in Kingston, Jamaica. There is the urgent need for the education of health professionals on neonatal pain management. This will in turn facilitate change in perception and eventually, along with the institution of local policies and protocols, influence practice.

Endothelin stimulates vascular hydroxyl radical formation: effect of obesity

Reactive oxygen species (ROS) and endothelin-1 (ET-1) contribute to vascular pathophysiology in obesity. In this context, whether ET-1 modulates hydroxyl radical (•OH) formation and the function of ROS/•OH in obesity is not known. In the present study, formation and function of ROS, including •OH, were investigated in the aorta of lean and leptin-deficient obese ob/ob mice. Hydroxyl radical formation was detected ex vivo using terephthalic acid in intact aortic rings and the involvement of ROS in ET-1-mediated vasoreactivity was analyzed using the antioxidant EPC-K1, a combination of α-tocopherol and ascorbic acid. Generation of either •OH, •O2−, and H2O2was strongly inhibited by EPC-K1 (all P < 0.05). In obese mice, basal vascular •OH formation and ROS activity were reduced by 3-fold and 5-fold, respectively ( P < 0.05 vs. lean). ET-1 markedly enhanced •OH formation in lean (6-fold, P < 0.05 vs. untreated) but not in obese mice. Obesity increased ET-1-induced contractions ( P < 0.05 vs. lean), and ROS scavenging further enhanced the response ( P < 0.05 vs. untreated). Exogenous ROS, including •OH caused stronger vasodilation in obese animals ( P < 0.05 vs. lean), whereas endothelium-dependent relaxation was similar between lean and obese animals. In conclusion, we present a sensitive method allowing ex vivo measurement of vascular •OH generation and provide evidence that ET-1 regulates vascular •OH formation. The data indicate that in obesity, vascular formation of ROS, including •OH is lower, whereas the sensitivity to ROS is increased, suggesting a novel and important role of ROS, including •OH in the regulation of vascular tone in disease status associated with increased body weight.