P2X purinergic receptors, activated by extracellular ATP, mediate a number of cardiac cellular effects and may be important under pathophysiological conditions. The objective of the present study was to characterize the P2X receptor-mediated ionic current and determine its role in heart failure using the calsequestrin (CSQ) model of cardiomyopathy. Membrane currents under voltage clamp were determined in myocytes from both wild-type (WT) and CSQ mice. The P2X agonist 2-methylthio-ATP (2-meSATP) induced an inward current that was greater in magnitude in CSQ than in WT ventricular cells. The novel agonist, MRS-2339, an N-methanocarba derivative of 2-chloro-AMP relatively resistant to nucleotidase, induced a current in the CSQ myocyte similar to that by 2-meSATP. When administered via a miniosmotic pump (Alzet), it significantly increased longevity compared with vehicle-injected mice (log rank test, P = 0.02). The improvement in survival was associated with decreases in the heart weight-to-body weight ratio and in cardiac myocyte cross-sectional area [MRS-2339-treated mice: 281 ± 15.4 (SE) μm2, n = 6 mice vs. vehicle-treated mice: 358 ± 27.8 μm2, n = 6 mice, P < 0.05]. MRS-2339 had no vasodilator effect in mouse aorta ring preparations, indicating that its salutary effect in heart failure is not because of any vascular unloading. The cardiac P2X current is upregulated in the CSQ heart failure myocytes. Chronic administration of a nucleotidase-resistant agonist confers a beneficial effect in the CSQ model of heart failure, apparently via an activation of the cardiac P2X receptor. Cardiac P2X receptors represent a novel and potentially important therapeutic target for the treatment of heart failure.
by
Emelia J Benjamin;
Josée Dupuis;
Martin G Larson;
Kathryn L Lunetta;
Sarah L Booth;
Diddahally R Govindaraju;
Sekar Kathiresan;
John F Keaney, Jr;
Michelle J Keyes;
Jing-Ping Lin;
James B Meigs;
Sander J Robins;
Jian Rong;
Renate Schnabel;
Joseph A Vita;
Thomas J Wang;
Peter W Wilson;
Philip A Wolf;
Ramachandran S Vasan
Background
Systemic biomarkers provide insights into disease pathogenesis, diagnosis, and risk stratification. Many systemic biomarker concentrations are heritable phenotypes. Genome-wide association studies (GWAS) provide mechanisms to investigate the genetic contributions to biomarker variability unconstrained by current knowledge of physiological relations.
Methods
We examined the association of Affymetrix 100K GeneChip single nucleotide polymorphisms (SNPs) to 22 systemic biomarker concentrations in 4 biological domains: inflammation/oxidative stress; natriuretic peptides; liver function; and vitamins. Related members of the Framingham Offspring cohort (n = 1012; mean age 59 ± 10 years, 51% women) had both phenotype and genotype data (minimum-maximum per phenotype n = 507–1008). We used Generalized Estimating Equations (GEE), Family Based Association Tests (FBAT) and variance components linkage to relate SNPs to multivariable-adjusted biomarker residuals. Autosomal SNPs (n = 70,987) meeting the following criteria were studied: minor allele frequency ≥ 10%, call rate ≥ 80% and Hardy-Weinberg equilibrium p ≥ 0.001.
Results
With GEE, 58 SNPs had p < 10-6: the top SNPs were rs2494250 (p = 1.00*10-14) and rs4128725 (p = 3.68*10-12) for monocyte chemoattractant protein-1 (MCP1), and rs2794520 (p = 2.83*10-8) and rs2808629 (p = 3.19*10-8) for C-reactive protein (CRP) averaged from 3 examinations (over about 20 years). With FBAT, 11 SNPs had p < 10-6: the top SNPs were the same for MCP1 (rs4128725, p = 3.28*10-8, and rs2494250, p = 3.55*10-8), and also included B-type natriuretic peptide (rs437021, p = 1.01*10-6) and Vitamin K percent undercarboxylated osteocalcin (rs2052028, p = 1.07*10-6). The peak LOD (logarithm of the odds) scores were for MCP1 (4.38, chromosome 1) and CRP (3.28, chromosome 1; previously described) concentrations; of note the 1.5 support interval included the MCP1 and CRP SNPs reported above (GEE model). Previous candidate SNP associations with circulating CRP concentrations were replicated at p < 0.05; the SNPs rs2794520 and rs2808629 are in linkage disequilibrium with previously reported SNPs. GEE, FBAT and linkage results are posted at http://www.ncbi.nlm.nih.gov/projects/gap/cgi-bin/study.cgi?id=phs000007 webcite.
Conclusion
The Framingham GWAS represents a resource to describe potentially novel genetic influences on systemic biomarker variability. The newly described associations will need to be replicated in other studies.
Background
Early arteriovenous fistula (AVF) creation is necessary to curb the use of central venous catheters (CVCs) and reduce their complications. We sought to examine patient characteristics that may influence persistent CVC use 90 days after dialysis therapy initiation among patients using a CVC.
Methods
Data from the 1999 to 2003 Clinical Performance Measures Project was linked to the Centers for Medicare & Medicaid Services Medical Evidence (2728) form.
Results
Most patients (59.4%) starting dialysis with a CVC failed to transition to permanent access within 90 days, whereas 25.4% received a graft and only 15.2% received an AVF. Older patients (>75 years) were more than 2-fold more likely to remain CVC dependent at 90 days (P = 0.0.001) compared with those younger than 50 years. In addition, race and sex were highly predictive of CVC dependence at 90 days; black females, white females, and black males were 75% (P < 0.001), 61% (P < 0.001), and 35% (P = 0.023) more likely than white males to maintain CVC use, whereas patients with ischemic heart disease and peripheral vascular disease were 35% (P = 0.023) and 39% (P = 0.007) more likely to remain CVC dependent at 90 days, respectively.
Conclusion
Prolonged CVC dependence is more likely to occur among patients of older age, females, blacks, and those with cardiovascular comorbidity, suggesting inadequate or late access referral or greater primary access failure. Our findings suggest possible missed opportunities for early conversion of patients to permanent vascular access that may vary by race and sex.
Diabetes is associated with several changes in gastrointestinal (GI) motility and associated symptoms such as nausea, bloating, abdominal pain, diarrhoea and constipation. The pathogenesis of altered GI functions in diabetes is multifactorial and the role of the enteric nervous system (ENS) in this respect has gained significant importance. In this review, we summarize the research carried out on diabetes-related changes in the ENS. Changes in the inhibitory and excitatory enteric neurons are described highlighting the role of loss of inhibitory neurons in early diabetic enteric neuropathy. The functional consequences of these neuronal changes result in altered gastric emptying, diarrhoea or constipation. Diabetes can also affect GI motility through changes in intestinal smooth muscle or alterations in extrinsic neuronal control. Hyperglycaemia and oxidative stress play an important role in the pathophysiology of these ENS changes. Antioxidants to prevent or treat diabetic GI motility problems have therapeutic potential. Recent research on the nerve–immune interactions demonstrates inflammation-associated neurodegeneration which can lead to motility related problems in diabetes.
Background
Little is known about the HIV/AIDS epidemic in the Indian Ocean region, including Mauritius. National records suggest a prevalence of HIV in Mauritius of < 1% in the general population, which is one of the lowest prevalence rates in southern Africa. However, HIV-positive cases have been increasing recently in Mauritius. We conducted a cross-sectional survey in January 2003 to assess the prevalence of HIVrelated sexual behaviors and their correlates among young people aged 15–24 years in Mauritius.
Methods
We identified 1200 participants using two-stage cluster sampling. Demographic, social, sexual, and knowledge of HIV/AIDS data were obtained in face-to-face interviews using a structured questionnaire administered by trained interviewers. The prevalence of sexual behaviors was described in relation to gender, and the correlates of ever having had sex and nonuse of condom at last sex were analyzed using logistic regression.
Results
In the target population, 30.9% of males and 9.7% of females reported a history of sexual intercourse. Of the currently sexually active participants, 50.6% of men and 71.2% of women did not use condoms at their last sexual encounter. Logistic regression revealed that work experience and marijuana use were significantly associated with men's sexual experience, whereas being out of school and drinking experience were significantly associated with women's sexual experience. For both men and women, being Christian and visiting nightclubs were associated with having ever had sexual intercourse (P < 0.05). In addition, not using a condom at the first sexual encounter and lack of exposure to a nongovernmental organization (NGO) dealing with HIV/AIDS were associated with the nonuse of condoms at the last sexual encounter (P < 0.05).
Conclusion
Young people in Mauritius are at risk of a future HIV epidemic because behaviors predisposing to HIV infection are prevalent among sexually experienced youth. A focused prevention program targeting young people should be reinforced as part of the National AIDS Control Program, taking into account the predictors of sexual behaviors identified here.
Background. Evidence suggests that attendance at medical grand rounds at academic medical centers is waning. The present study examined whether attendance at medical grand rounds increased after providing complimentary food to attendees and also assessed attendee attitudes about complimentary food. Methods. In this prospective, before-and-after study, attendance at medical grand rounds was monitored from September 25, 2002, to June 2, 2004, using head counts. With unrestricted industry (eg, pharmaceutical) financial support, complimentary food was provided to medical grand rounds attendees beginning June 4, 2003. Attendance was compared during the pre-complimentary food and complimentary food periods. Attitudes about the complimentary food were assessed with use of a survey administered to attendees at the conclusion of the study period. Results. The mean (± SD) overall attendance by head counts increased 38.4% from 184.1 ± 90.4 during the pre-complimentary food period to 254.8 ± 60.5 during the complimentary food period (P <.001). At the end of the study period, 70.1% of the attendee survey respondents indicated that they were more likely to attend grand rounds because of complimentary food, 53.6% indicated that their attendance increased as a result of complimentary food, and 53.1% indicated that their attendance would decrease if complimentary food was no longer provided. Notably, 80.3% indicated that food was not a distraction, and 81.7% disagreed that industry representatives had influence over medical grand rounds because of their financial support for the food. Conclusion. Providing free food may be an effective strategy for increasing attendance at medical grand rounds.
Background
Cystic fibrosis (CF) and short bowel syndrome (SBS) patients are unable to absorb vitamin D from the diet and thus are frequently found to be severely vitamin D deficient. We evaluated whether a commercial portable ultraviolet (UV) indoor tanning lamp that has a spectral output that mimics natural sunlight could raise circulating 25-hydroxyvitamin D [25(OH)D] levels in subjects with CF and SBS.
Methods
In initial pilot studies, two SBS subjects came to the outpatient clinic twice weekly for 8 weeks for UV light sessions of 6 min each. In a follow-up study, five CF subjects exposed their lower backs in a seated position to the sunlamp at a distance of 14 cm for 5–10 min depending on the skin type five times a week for 8 weeks. Blood samples for 25(OH)D and parathyroid hormone (PTH) measurements were performed at baseline and at the end of the study.
Results
In our study, with two SBS subjects, the indoor lamp increased or maintained circulating 25(OH)D levels during the winter months. We increased the UV lamp frequency and found an improved response in the CF patients. Serum 25(OH)D levels in CF subjects at baseline were 21 ± 3 ng/ml, which increased to 27 ± 4 ng/ml at the end of 8 weeks (P = 0.05). PTH concentration remained largely unchanged in both population groups.
Conclusion
A UV lamp that emits ultraviolet radiation similar to sunlight and thus produces vitamin D3 in the skin is an excellent alternative for CF, and SBS patients who suffer from vitamin D deficiency due to fat malabsorption, especially during the winter months when natural sunlight is unable to produce vitamin D3 in the skin. This UV lamp is widely available for commercial home use and could potentially be prescribed to patients with CF or SBS.
We have previously discovered the naturally occurring antitussive alkaloid noscapine as a tubulin-binding agent that attenuates microtubule dynamics and arrests mammalian cells at mitosis via activation of the c-Jun NH2-terminal kinase pathway. It is well established that the p53 protein plays a crucial role in the control of tumor cell response to chemotherapeutic agents and DNA-damaging agents; however, the relationship between p53-driven genes and drug sensitivity remains controversial. In this study, we compared chemosensitivity, cell cycle distribution, and apoptosis on noscapine treatment in four cell lines derived from the colorectal carcinoma HCT116 cells: p53+/+ (p53-wt), p53−/− (p53-null), p21−/− (p21-null), and BAX−/− (BAX-null). Using these isogenic variants, we investigated the roles of p53, BAX, and p21 in the cellular response to treatment with noscapine. Our results show that noscapine treatment increases the expression of p53 over time in cells with wild-type p53 status. This increase in p53 is associated with an increased apoptotic BAX/Bcl-2 ratio consistent with increased sensitivity of these cells to apoptotic stimuli. Conversely, loss of p53 and p21 alleles had a counter effect on both BAX and Bcl-2 expression and the p53-null and p21-null cells were significantly resistant to the antiproliferative and apoptotic effects of noscapine. All but the p53-null cells displayed p53 protein accumulation in a time-dependent manner on noscapine treatment. Interestingly, despite increased levels of p53, p21-null cells were resistant to apoptosis, suggesting a proapoptotic role of p21 and implying that p53 is a necessary but not sufficient condition for noscapine-mediated apoptosis.
The electrogenic Na+–HCO3− cotransporter (NBCe1) plays a central role in intracellular pH (pHi) regulation as well as HCO3− secretion by pancreatic ducts and HCO3− reabsorption by renal proximal tubules. To understand the structural requirements for the electrogenicity of NBCe1, we constructed chimeras of NBCe1-A and the electroneutral NBCn1-B, and used two-electrode voltage clamp to measure electrogenic transporter current in Xenopus oocytes exposed to 5% CO2–26 mm HCO3−(pH 7.40). The chimera consisting of NBCe1-A (i.e. NBCe1-A ‘background’) with the cytoplasmic N-terminal domain (Nt) of NBCn1-B had a reversal potential of −156.3 mV (compared with a membrane potential Vm of −43.1 mV in a HCO3−-free solution) and a slope conductance of 3.0 μS (compared with 12.5 μS for NBCe1-A). Also electrogenic were chimeras with an NBCe1-A background but with NBCn1-B contributing the extracellular loop (L) between transmembrane segment (TM) 5 and 6 (−140.9 mV/11.1 μS), the cytoplasmic C-terminal domain (Ct; −123.8 mV/9.7 μS) or Nt + L + Ct (−120.9 mV/3.7 μS). Reciprocal chimeras (with an NBCn1 background but with NBCe1 contributing Nt, L, Ct or Nt + L + Ct) produced no measurable electrogenic transporter currents in the presence of CO2–HCO3−. pHi recovered from an acid load, but without the negative shift of Vm that is characteristic of electrogenic Na+–HCO3− cotransporters. Thus, these chimeras were electroneutral, as were two others consisting of NBCe1(Nt–L)/NBCn1(TM6–Ct) and NBCn1(Nt–L)/NBCe1(TM6–Ct). We propose that the electrogenicity of NBCe1 requires interactions between TM1–5 and TM6–13.
Acute lung injury affects close to 200,000 people in the U.S. annually and leads to death in 40–50% of affected patients. Chronic ethanol abuse is thought to contribute to up to 40–50% of subjects who develop acute lung injury. We previously demonstrated in a rat model that chronic ethanol ingestion promoted acute lung injury and associated with chronic oxidant stress, activated matrix metalloproteinases, increased release of transforming growth factor-β, as well as increased expression and deposition of fibronectin, a matrix glycoprotein implicated in lung injury and repair. Since fibronectin can activate monocytes to increase proinflammatory cytokine expression, we hypothesized that generation of fibronectin-enriched matrices during chronic ethanol ingestion might contribute to the development of acute lung injury by stimulating unopposed inflammation. To test this hypothesis, we harvested alveolar type II cells from rats fed the Lieber DiCarli diet (6 wk; 36% of calories from ethanol). After 96 hours of culture, the matrices deposited ex vivo by the type II cells derived from ethanol-fed rats showed increased amounts of fibronectin protein as demonstrated by ELISA. When monocytic U937 cells were plated atop these matrices, there was increased expression of interleukin-1β. This stimulation was inhibited by antibodies against α5β1, a receptor that mediates many of the biological effects of fibronectin. We then tested whether antioxidants ameliorated these effects. Dietary supplements of the antioxidants N-acetylcysteine and Procysteine normalized matrix production by type II cells. Furthermore, the newly derived matrices did not stimulate interleukin-1β expression over control cells. These studies suggest that chronic ethanol exposure induces oxidant stress and activates lung tissue remodeling characterized by increased expression of fibronectin by alveolar type II cells. The newly deposited fibronectin-enriched matrices may stimulate the expression of proinflammatory cytokines in monocytic cells recruited to the lung after injury thereby explaining the priming effects of ethanol.