Necrotizing Fasciitis Within 72 hours After Presentation with Skin and Skin Structure Infection.

INTRODUCTION: A small percentage of patients with skin infections later develop necrotizing fasciitis (NF). Diagnostic testing is needed to identify patients with skin infections at low risk of NF who could be discharged from the emergency department (ED) after antibiotic initiation. Elevated lactate has been associated with NF; existing estimates of the frequency of NF are based on retrospective reviews, and cases often lack testing for lactate. We present the incidence of patients with skin infections who developed NF and their baseline lactates. METHODS: In four phase-3 trials, 2883 adults with complicated or acute bacterial skin and skin structure infections were randomized to dalbavancin or comparator, with early and late follow-up visits through Day 28. We prospectively collected baseline plasma lactates in one trial to assess an association with NF. RESULTS: NF was diagnosed in 3/2883 patients (0.1%); all three survived. In the study with prospectively collected baseline lactates (n = 622), 15/622 (2.4%) had a lactate ≥4 millimoles per liter (mmol/L), including 3/622 (0.5%) with a lactate ≥7 mmol/L. NF was not seen in patients with a lactate <4 mmol/L; NF was seen in 1/15 (6.7%) with a lactate ≥4 mmol/L, including 1/3 (33.3%) with lactate ≥7 mmol/L. CONCLUSIONS: NF incidence within 72 hours of antibiotic initiation in patients with complicated or acute bacterial skin and skin structure infections was extremely low (0.1%) and occurred in 6.7% with a lactate ≥4 mmol/L. Lactate <4 mmol/L can be used to identify patients at low risk of NF who could be safely discharged from the ED after antibiotic initiation.

Recurrent TERT promoter mutations in urothelial carcinoma and potential clinical applications.

Increased telomerase activity is associated with almost all types of advanced human cancers with unknown molecular mechanism(s). Two recurrent point mutations in the promoter region of telomerase reverse transcriptase (TERT)--the key subunit of telomerase--have recently been identified in melanoma as well as a small sample of bladder cancer cell lines. However, the incidence and clinical-pathological significance of these mutations in urothelial carcinoma have not been well established yet. We collected 86 specimens of urothelial carcinoma including upper and lower urinary tract: high grade and low grade, invasive and noninvasive, and primary and metastatic. We also included some matched benign urothelium and common benign bladder lesions: cystitis, nephrogenic adenoma, and inverted papilloma. In addition, we collected urine samples for urothelial carcinoma workup; blood samples from patients underwent cystectomy with extensive lymphovascular invasion. All specimens were subject to polymerase chain reaction amplification and bidirectional Sanger sequencing for the TERT promoter mutations: C228T and C250T. We found that 64 (74%) of 86 carcinoma samples harbored 1 of the 2 TERT promoter mutations (C228T, n = 54; C250T, n = 10); the incidences were roughly equal regardless of site of origin, histologic grade, and invasive status. All matched benign and benign lesion samples showed wild-type sequence. These TERT promoter mutations are the most common genetic alterations in urothelial carcinoma and are not associated with tumor locations, grade, or invasiveness. Importantly, the feasibility of detecting these mutations in urine samples may provide a novel method to detect urothelial carcinoma in urine.

Long-term methionine-diet induced mild hyperhomocysteinemia associated cardiac metabolic dysfunction in multiparous rats.

Mild hyperhomocysteinemia (HHcy, clinically defined as less than 30 µmol/L) is an independent cardiovascular disease (CVD) risk factor, and is associated with many complications during pregnancy, such as preeclampsia (PE). The aim of this study was to assess the effect of long-term mild HHcy on cardiac metabolic function of multiparous rats. Female rats were mated 3 to 4 times and were fed with methionine in drinking water to increase plasma Hcy (2.9 ± 0.3 to 10.5 ± 2.3 µmol/L) until termination. This caused significant increase of heart weight/body weight (0.24 ± 0.01 to 0.27 ± 0.01 g/100 g) and left ventricle weight (0.69 ± 0.03 to 0.78 ± 0.01 g). Superoxide production was increased by 2.5-fold in HHcy hearts using lucigenin chemiluminescence. The ability of bradykinin and carbachol to regulate myocardial oxygen consumption (MVO2) in vitro was impaired by 59% and 66% in HHcy heart, and it was restored by ascorbic acid (AA), tempol, or apocynin (Apo). Protein expression of p22(phox) subunit of NAD(P)H oxidase was increased by 2.6-fold, but there were no changes in other NAD(P)H oxidase subunits, NOSs or SODs. Microarray revealed 1518 genes to be differentially regulated (P < 0.05). The mRNA level of NAD(P)H oxidase subunits, NOSs or SODs remained unchanged. In conclusion, long-term mild HHcy increases cardiac superoxide mainly through regulation of p22(phox) component of the NAD(P)H oxidase and impairs the ability of NO to regulate MVO2 in heart of multiparous mothers.

Genome Sequence of Borrelia chilensis VA1, a South American Member of the Lyme Borreliosis Group.

Borrelia chilensis strain VA1 is a recently described South American member of the Borrelia burgdorferi sensu lato complex from Chile. Whole-genome sequencing analysis determined its linear chromosome and plasmids lp54 and cp26, confirmed its membership in the Lyme borreliosis group, and will open new research avenues regarding its pathogenic potential.

Identification of a novel clone, ST736, among Enterococcus faecium clinical isolates and its association with daptomycin nonsusceptibility.

Resistance to daptomycin in enterococcal clinical isolates remains rare but is being increasingly reported in the United States and worldwide. There are limited data on the genetic relatedness and microbiological and clinical characteristics of daptomycin-nonsusceptible enterococcal clinical isolates. In this study, we assessed the population genetics of daptomycin-nonsusceptible Enterococcus faecium (DNSE) clinical isolates by multilocus sequence typing (MLST) and whole-genome sequencing analysis. Forty-two nonduplicate DNSE isolates and 43 randomly selected daptomycin-susceptible E. faecium isolates were included in the analysis. All E. faecium isolates were recovered from patients at a tertiary care medical center in suburban New York City from May 2009 through December 2013. The daptomycin MICs of the DNSE isolates ranged from 6 to >256 µg/ml. Three major clones of E. faecium (ST18, ST412, and ST736) were identified among these clinical isolates by MLST and whole-genome sequence-based analysis. A newly recognized clone, ST736, was seen in 32 of 42 (76.2%) DNSE isolates and in only 14 of 43 (32.6%) daptomycin-susceptible E. faecium isolates (P < 0.0001). This report provides evidence of the association between E. faecium clone ST736 and daptomycin nonsusceptibility. The identification and potential spread of this novel E. faecium clone and its association with daptomycin nonsusceptibility constitute a challenge for patient management and infection control at our medical center.

CYP2C29 produces superoxide in response to shear stress.

OBJECTIVE: Activation of CYP2C29 releases superoxide during shear stress-induced dilation (SSID). METHODS: Mesenteric arteries isolated from female eNOS-KO and WT mice were cannulated and pressurized. Vasodilation and superoxide production in response to shear stress were assessed. RESULTS: Shear stress-induced dilation was significantly attenuated in vessels of eNOS-KO compared with WT mice, which was normalized by tempol and PEG-Catalase, in a PPOH (inhibitor of CYP2C29)-sensitive manner, but remained unaffected by VAS2870 and allopurinol, inhibitors of NADPH oxidase and xanthine oxidase, respectively. NaNO(2)-induced dilation was comparable in both strains of mice. Confocal microscopy shows that SS-stimulated superoxide was increased particularly in the endothelium of eNOS-KO mice. HPLC analysis of 2-EOH indicated an increase in SS-stimulated superoxide in vessels of eNOS-KO mice, a response that was sensitive to PPOH. Inhibition of soluble epoxide hydrolase significantly enhanced SSID without affecting SS-stimulated superoxide production. CYP2C29 and catalase were upregulated, and exogenous H(2)O(2) caused vasoconstriction in vessels of eNOS-KO mice. CONCLUSIONS: CYP2C29 synthesizes EETs to mediate SSID, and simultaneously releases superoxide and sequential H(2)O(2), which in turn impair SSID.

Oxidant-NO dependent gene regulation in dogs with type I diabetes: impact on cardiac function and metabolism.

BACKGROUND: The mechanisms responsible for the cardiovascular mortality in type I diabetes (DM) have not been defined completely. We have shown in conscious dogs with DM that: 1) baseline coronary blood flow (CBF) was significantly decreased, 2) endothelium-dependent (ACh) coronary vasodilation was impaired, and 3) reflex cholinergic NO-dependent coronary vasodilation was selectively depressed. The most likely mechanism responsible for the depressed reflex cholinergic NO-dependent coronary vasodilation was the decreased bioactivity of NO from the vascular endothelium. The goal of this study was to investigate changes in cardiac gene expression in a canine model of alloxan-induced type 1 diabetes. METHODS: Mongrel dogs were chronically instrumented and the dogs were divided into two groups: one normal and the other diabetic. In the diabetic group, the dogs were injected with alloxan monohydrate (40-60 mg/kg iv) over 1 min. The global changes in cardiac gene expression in dogs with alloxan-induced diabetes were studied using Affymetrix Canine Array. Cardiac RNA was extracted from the control and DM (n = 4). RESULTS: The array data revealed that 797 genes were differentially expressed (P < 0.01; fold change of at least ±2). 150 genes were expressed at significantly greater levels in diabetic dogs and 647 were significantly reduced. There was no change in eNOS mRNA. There was up regulation of some components of the NADPH oxidase subunits (gp91 by 2.2 fold, P < 0.03), and down-regulation of SOD1 (3 fold, P < 0.001) and decrease (4 - 40 fold) in a large number of genes encoding mitochondrial enzymes. In addition, there was down-regulation of Ca2+ cycling genes (ryanodine receptor; SERCA2 Calcium ATPase), structural proteins (actin alpha). Of particular interests are genes involved in glutathione metabolism (glutathione peroxidase 1, glutathione reductase and glutathione S-transferase), which were markedly down regulated. CONCLUSION: our findings suggest that type I diabetes might have a direct effect on the heart by impairing NO bioavailability through oxidative stress and perhaps lipid peroxidases.

Roles of CYP2C29 and RXR gamma in vascular EET synthesis of female mice.

We aimed to identify which cytochrome P-450 (CYP) family/subfamily, as well as related transcription factor(s), is responsible for the estrogen-dependent synthesis of epoxyeicosatrienoic acids (EETs) to initiate shear stress-induced vasodilation. Microarray analysis indicated a significant upregulation of CYP2C29 and retinoid X receptor gamma (RXRgamma) in isolated mesenteric arteries/arterioles of female endothelial nitric oxide synthase-knockout mice, a result that was validated by real-time RT-PCR. The cannulated vessels were then perfused with 2 and 10 dyn/cm(2) shear stress, followed by collection of the perfusate to determine EET concentrations and isoforms. Shear stress dose-dependently stimulated the release of EETs into the perfusate, associated with an EET-mediated vasodilation, in which predominantly 14,15-EET and 11,12-EET contributed to the responses ( approximately 87.4% of total EETs). Transfection of vessels with CYP2C29 siRNA eliminated the release of EETs into the perfusate, which was evidenced by an abolished vasodilation, and confirmed by RT-PCR and Western blot analyses. Knockdown of RXRgamma in these vessels significantly inhibited the production of EETs, parallel to a reduced vasodilation. RXRgamma siRNA not only silenced the vascular RXRgamma expression, but synchronously downregulated CYP2C29 expression, leading to a reduced EET synthesis. In conclusion, our data provide the first evidence for a specific signaling cascade, by which estrogen potentially activates the CYP2C29 gene in the absence of nitric oxide, to synthesize EETs in response to shear stress, via an RXRgamma-related regulatory mechanism.

Potential mechanisms of low-sodium diet-induced cardiac disease: superoxide-NO in the heart.

RATIONALE: Patients on a low salt (LS) diet have increased mortality. OBJECTIVE: To determine whether reduction in NO bioactivity may contribute to the LS-induced cardiac dysfunction and mortality. METHODS AND RESULTS: Adult male mongrel dogs were placed on LS (0.05% sodium chloride) for 2 weeks. Body weight (25.4 + or - 0.4 to 23.6 + or - 0.4 kg), left ventricular systolic pressure (137.0 + or - 3.4 to 124.0 + or - 6.7 mm Hg), and mean aortic pressure (111 + or - 3.1 to 98 + or - 4.3 mm Hg) decreased. Plasma angiotensin II concentration increased (4.4 + or - 0.7 to 14.8 + or - 3.7 pg/mL). Veratrine-induced (5 microg/kg) NO-mediated vasodilation was inhibited by 44% in LS; however, the simultaneous intravenous infusion of ascorbic acid or apocynin acutely and completely reversed this inhibition. In LS heart tissues, lucigenin chemiluminescence was increased 2.3-fold to angiotensin II (10(-8) mol/L), and bradykinin (10(-4) mol/L) induced reduction of myocardial oxygen consumption in vitro was decreased (40 + or - 1.3% to 16 + or - 6.3%) and completely restored by coincubation with tiron, tempol or apocynin. Switching of substrate uptake from free fatty acid to glucose by the heart was observed (free fatty acid: 8.97 + or - 1.39 to 4.53 + or - 1.12 micromol/min; glucose: 1.31 + or - 0.52 to 6.86 + or - 1.78 micromol/min). Western blotting indicated an increase in both p47(phox) (121%) and gp91(phox) (44%) as did RNA microarray analysis (433 genes changed) showed an increase in p47(phox) (1.6-fold) and gp91(phox) (2.0 fold) in the LS heart tissue. CONCLUSIONS: LS diet induces the activation of the renin-angiotensin system, which increases oxidative stress via the NADPH oxidase and attenuates NO bioavailability in the heart.

Identification of a coronary vascular progenitor cell in the human heart.

Primitive cells capable of generating small resistance arterioles and capillary structures in the injured myocardium have been identified repeatedly. However, these cells do not form large conductive coronary arteries that would have important implications in the management of the ischemic heart. In the current study, we determined whether the human heart possesses a class of progenitor cells that regulates the growth of endothelial cells (ECs) and smooth muscle cells (SMCs) and vasculogenesis. The expression of vascular endothelial growth-factor receptor 2 (KDR) was used, together with the stem cell antigen c-kit, to isolate and expand a resident coronary vascular progenitor cell (VPC) from human myocardial samples. Structurally, vascular niches composed of c-kit-KDR-positive VPCs were identified within the walls of coronary vessels. The VPCs were connected by gap junctions to ECs, SMCs, and fibroblasts that operate as supporting cells. In vitro, VPCs were self-renewing and clonogenic and differentiated predominantly into ECs and SMCs and partly into cardiomyocytes. To establish the functional import of VPCs, a critical stenosis was created in immunosuppressed dogs, and tagged human VPCs were injected in proximity to the constricted artery. One month later, there was an increase in coronary blood flow (CBF) distal to the stenotic artery, resulting in functional improvement of the ischemic myocardium. Regenerated large, intermediate, and small human coronary arteries and capillaries were found. In conclusion, the human heart contains a pool of VPCs that can be implemented clinically to form functionally competent coronary vessels and improve CBF in patients with ischemic cardiomyopathy.

Cardiac structure and function in humans: a new cardiovascular physiology laboratory.

As the traditional cardiovascular control laboratory has disappeared from the first-year medical school curriculum, we have recognized the need to develop another "hands-on" experience as a vehicle for wide-ranging discussions of cardiovascular control mechanisms. Using an echocardiograph, an automatic blood pressure cuff, and a reclining bicycle, we developed protocols to illustrate the changes in cardiac and vascular function that occur with changes in posture, venous return, and graded exercise. We use medical student volunteers and a professional echocardiographer to generate and acquire data, respectively. In small-group sessions, we developed an interactive approach to discuss the data and to make a large number of calculations from a limited number of measurements. The sequence of cardiac events and cardiac structure in vivo were illustrated with the volunteers lying down, standing, and then with their legs raised passively above the heart to increase venous return. Volunteers were then asked to peddle the bicycle to achieve steady-state heart rates of 110 and 150 beats/min. Data were collected in all these states, and calculations were performed and used as the basis of a small-group discussion to illustrate physiological principles. Information related to a surprisingly large number of cardiovascular control mechanisms was derived, and its relevance to cardiovascular dysfunction was explored. This communication describes our experience in developing a new cardiovascular control laboratory to reinforce didactic material presented in lectures and small-group sessions.

Notch1 regulates the fate of cardiac progenitor cells.

The Notch receptor mediates cell fate decision in multiple organs. In the current work we tested the hypothesis that Nkx2.5 is a target gene of Notch1 and raised the possibility that Notch1 regulates myocyte commitment in the adult heart. Cardiac progenitor cells (CPCs) in the niches express Notch1 receptor, and the supporting cells exhibit the Notch ligand Jagged1. The nuclear translocation of Notch1 intracellular domain (N1ICD) up-regulates Nkx2.5 in CPCs and promotes the formation of cycling myocytes in vitro. N1ICD and RBP-Jk form a protein complex, which in turn binds to the Nkx2.5 promoter initiating transcription and myocyte differentiation. In contrast, transcription factors of vascular cells are down-regulated by Jagged1 activation of the Notch1 pathway. Importantly, inhibition of Notch1 in infarcted mice impairs the commitment of resident CPCs to the myocyte lineage opposing cardiomyogenesis. These observations indicate that Notch1 favors the early specification of CPCs to the myocyte phenotype but maintains the newly formed cells in a highly proliferative state. Dividing Nkx2.5-positive myocytes correspond to transit amplifying cells, which condition the replicative capacity of the heart. In conclusion, Notch1 may have critical implications in the control of heart homeostasis and its adaptation to pathologic states.

Coronary nitric oxide production controls cardiac substrate metabolism during pregnancy in the dog.

The aim of this study was to examine the role of nitric oxide (NO) in the control of cardiac metabolism at 60 days of pregnancy (P60) in the dog. There was a basal increase in diastolic coronary blood flow during pregnancy and a statistically significant increase in cardiac output (55 +/- 4%) and in cardiac NOx production (44 +/- 4 to 59 +/- 3 nmol/min, P < 0.05). Immunohistochemistry of the left ventricle showed an increase in endothelial nitric oxide synthase staining in the endothelial cells at P60. NO-dependent coronary vasodilation (Bezold-Jarisch reflex) was increased by 20% and blocked by N(G)-nitro-l-arginine methyl ester (l-NAME). Isotopically labeled substrates were infused to measure oleate, glucose uptake, and oxidation. Glucose oxidation was not significantly different in P60 hearts (5.4 +/- 0.5 vs. 6.2 +/- 0.4 micromol/min) but greatly increased in response to l-NAME injection (to 19.9 +/- 0.9 micromol/min, P < 0.05). Free fatty acid (FFA) oxidation was increased in P60 (from 5.3 +/- 0.6 to 10.4 +/- 0.5 micromol/min, P < 0.05) and decreased in response to l-NAME (to 4.5 +/- 0.5 micromol/min, P < 0.05). There was an increased oxidation of FFA for ATP production but no change in the respiratory quotient during pregnancy. Genes associated with glucose and glycogen metabolism were downregulated, whereas genes involved in FFA oxidation were elevated. The acute inhibition of NO shifts the heart away from FFA and toward glucose metabolism despite the downregulation of the carbohydrate oxidative pathway. The increase in endothelium-derived NO during pregnancy results in a tonic inhibition of glucose oxidation and reliance on FFA uptake and oxidation to support ATP synthesis in conjunction with upregulation of FFA metabolic enzymes.

Activation of cardiac progenitor cells reverses the failing heart senescent phenotype and prolongs lifespan.

Heart failure is the leading cause of death in the elderly, but whether this is the result of a primary aging myopathy dictated by depletion of the cardiac progenitor cell (CPC) pool is unknown. Similarly, whether current lifespan reflects the ineluctable genetic clock or heart failure interferes with the genetically determined fate of the organ and organism is an important question. We have identified that chronological age leads to telomeric shortening in CPCs, which by necessity generate a differentiated progeny that rapidly acquires the senescent phenotype conditioning organ aging. CPC aging is mediated by attenuation of the insulin-like growth factor-1/insulin-like growth factor-1 receptor and hepatocyte growth factor/c-Met systems, which do not counteract any longer the CPC renin-angiotensin system, resulting in cellular senescence, growth arrest, and apoptosis. However, pulse-chase 5-bromodeoxyuridine-labeling assay revealed that the senescent heart contains functionally competent CPCs that have the properties of stem cells. This subset of telomerase-competent CPCs have long telomeres and, following activation, migrate to the regions of damage, where they generate a population of young cardiomyocytes, reversing partly the aging myopathy. The senescent heart phenotype and heart failure are corrected to some extent, leading to prolongation of maximum lifespan.

Hyperhomocysteinemia alters cardiac substrate metabolism by impairing nitric oxide bioavailability through oxidative stress.

BACKGROUND: Hyperhomocysteinemia (HHcy) has been considered a vascular disease associated with increased levels of oxidative stress that results in scavenging of NO. However, little is known of the impact of HHcy on cardiac function and especially myocardial metabolism. METHODS AND RESULTS: L-Homocysteine was intravenously infused into conscious dogs, and the dogs were fed methionine to increase plasma homocysteine to 10 micromol/L for acute and 24 micromol/L for chronic HHcy. There was no significant change in hemodynamics with HHcy. Veratrine-induced, NO-dependent, coronary vasodilation (Bezold-Jarisch reflex) was reduced by 32% but was restored by simultaneous intravenous infusion of ascorbic acid or apocynin. Acute and chronic HHcy significantly increased uptake of glucose and lactate and decreased uptake of free fatty acid by the heart. HHcy significantly decreased bradykinin- or carbachol-induced reduction of myocardial oxygen consumption in vitro, and this effect was completely restored by coincubation with ascorbic acid, Tempol, or apocynin. Western blot analysis indicated an increase in Nox2 (82%) and a reduction in endothelial nitric oxide synthase (39%), phospho-endothelial nitric oxide synthase (39%), and superoxide dismutase-1 (45%). Microarray analysis of gene expression in heart tissue from chronic HHcy indicated a switch in cardiac phenotype to enzymes that metabolize glucose. CONCLUSIONS: HHcy directly modulates substrate use by the heart independent of changes in hemodynamics or ventricular function by reducing NO bioavailability through the generation of superoxide. The progression of cardiac or coronary heart disease associated with HHcy should be evaluated in light of the impact of alterations in the regulation of cardiac metabolism and substrate use.

Altered expression of a limited number of genes contributes to cardiac decompensation during chronic ventricular tachypacing in dogs.

Our aim was to determine the changes in the gene expression profile occurring during the transition from compensated dysfunction (CD) to decompensated heart failure (HF) in pacing-induced dilated cardiomyopathy. Twelve chronically instrumented dogs underwent left ventricular pacing at 210 beats/min for 3 wk and at 240 beats thereafter, and four normal dogs were used as control. The transition from CD to HF occurred between the 3rd and 4th wk of pacing, with end-stage HF at 28 +/- 1 days. RNA was extracted from left ventricular tissue at control and 3 and 4 wk of pacing (n = 4) and tested with the Affymetrix Canine Array. We found 509 genes differentially expressed in CD vs. control (P < or = 0.05, fold change > or = +/-2), with 362 increasing and 147 decreasing; 526 genes were differentially expressed in HF vs. control (P < or = 0.05; fold change > or = +/-2), with 439 increasing and 87 decreasing. To better understand the transition, we compared gene alterations at 3 vs. 4 wk pacing and found that only 30 genes differed (P < or = 0.05; fold change of +/-2). We conclude that a number of processes including normalization of gene regulation during decompensation, appearance of new upregulated genes and maintenance of gene expression all contribute to the transition to overt heart failure with an unexpectedly small number of genes differentially regulated.

Glucose-6-phosphate dehydrogenase-derived NADPH fuels superoxide production in the failing heart.

In the failing heart, NADPH oxidase and uncoupled NO synthase utilize cytosolic NADPH to form superoxide. NADPH is supplied principally by the pentose phosphate pathway, whose rate-limiting enzyme is glucose 6-phosphate dehydrogenase (G6PD). Therefore, we hypothesized that cardiac G6PD activation drives part of the excessive superoxide production implicated in the pathogenesis of heart failure. Pacing-induced heart failure was performed in eight chronically instrumented dogs. Seven normal dogs served as control. End-stage failure occurred after 28 +/- 1 days of pacing, when left ventricular end-diastolic pressure reached 25 mm Hg. In left ventricular tissue homogenates, spontaneous superoxide generation measured by lucigenin (5 microM) chemiluminescence was markedly increased in heart failure (1338 +/- 419 vs. 419 +/- 102 AU/mg protein, P < 0.05), as were NADPH levels (15.4 +/- 1.5 vs. 7.5 +/- 1.5 micromol/gww, P < 0.05). Superoxide production was further stimulated by the addition of NADPH. The NADPH oxidase inhibitor gp91(ds-tat) (50 microM) and the NO synthase inhibitor L-NAME (1 mM) both significantly lowered superoxide generation in failing heart homogenates by 80% and 76%, respectively. G6PD was upregulated and its activity higher in heart failure compared to control (0.61 +/- 0.10 vs. 0.24 +/- 0.03 nmol/min/mg protein, P < 0.05), while superoxide production decreased to normal levels in the presence of the G6PD inhibitor 6-aminonicotinamide. We conclude that the activation of myocardial G6PD is a novel mechanism that enhances NADPH availability and fuels superoxide-generating enzymes in heart failure.

COX-2 contributes to the maintenance of flow-induced dilation in arterioles of eNOS-knockout mice.

Our previous studies demonstrated that, in gracilis muscle arterioles of male mice deficient in the gene for endothelial nitric oxide synthase (eNOS), flow-induced dilation (FID) is mediated by endothelial PGs. Thus the present study aimed to identify the specific isoform of cyclooxygenase (COX) responsible for the compensatory mediation of FID in arterioles of eNOS-knockout (KO) mice. Experiments were conducted on gracilis muscle arterioles of male eNOS-KO and wild-type (WT) mice. Basal tone and magnitude of FID of arterioles were comparable in the two strains of mice. A role for COX isoforms in the mediation of the responses was assessed by use of valeryl salicylate (3 mM) and NS-398 (10 microM), inhibitors of COX-1 and COX-2, respectively. In eNOS-KO arterioles, valeryl salicylate or NS-398 alone inhibited FID (at maximal flow rate) by approximately 51% and approximately 58%, respectively. Administration of both inhibitors eliminated the dilation. In WT arterioles, inhibition of COX-2 did not significantly affect FID, whereas inhibition of COX-1 decreased the dilation by approximately 57%. The residual portion of the response was abolished by additional administration of Nomega-nitro-L-arginine methyl ester. Western blot analysis indicated a comparable content of COX-1 protein in arterioles of WT and eNOS-KO mice. COX-2 protein, which was not detectable in arterioles of WT mice, was strongly expressed in arterioles of eNOS-KO mice, together with an upregulation of COX-2 gene expression. Immunohistochemical staining confirmed the presence of COX-2 in the endothelium of eNOS-KO arterioles. In conclusion, COX-2-derived PGs are the mediators responsible for maintenance of FID in arterioles of eNOS-deficient mice.

Comparative transcriptional profiling of Borrelia burgdorferi clinical isolates differing in capacities for hematogenous dissemination.

Borrelia burgdorferi, the etiologic agent of Lyme disease, is genetically heterogeneous. Previous studies have shown a significant association between the frequency of hematogenous dissemination in Lyme disease patients and the genotype of the infecting B. burgdorferi strain. Comparative transcriptional profiling of two representative clinical isolates with distinct genotypes (BL206 and B356) was undertaken. A total of 78 open reading frames (ORFs) had expression levels that differed significantly between the two isolates. A number of genes with potential involvement in nutrient uptake (BB0603, BBA74, BB0329, BB0330, and BBB29) have significantly higher expression levels in isolate B356. Moreover, nearly 25% of the differentially expressed genes are predicted to be localized on the cell surface, implying that these two isolates have cell surface properties that differ considerably. One of these genes, BBA74, encodes a protein of 257 amino acid residues that has been shown to possess porin activity. BBA74 transcript level was >20-fold higher in B356 than in BL206, and strain B356 contained three- to fivefold more BBA74 protein. BBA74 was disrupted by the insertion of a kanamycin resistance cassette into the coding region. The growth rates of both wild-type and mutant strains were essentially identical, and cultures reached the same final cell densities. However, the mutant strains consistently showed prolonged lags of 2 to 5 days prior to the induction of log-phase growth compared to wild-type strains. It is tempting to speculate that the absence of BBA74 interferes with the enhanced nutrient uptake that may be required for the entry of cells into log-phase growth. These studies demonstrate the value of comparative transcriptional profiling for identifying differences in the transcriptomes of B. burgdorferi clinical isolates that may provide clues to pathogenesis. The 78 ORFs identified here are a good starting point for the investigation of factors involved in the hematogenous dissemination of B. burgdorferi.

Transcriptional basis for exercise limitation in male eNOS-knockout mice with age: heart failure and the fetal phenotype.

Endothelium-derived nitric oxide (NO) is pivotal in regulating mitochondrial O(2) consumption (Vo(2)) and glucose uptake in mice. The aim of this study was to investigate the mechanism of age- and genotype-related exercise limitation in male endothelial NO synthase (eNOS)-knockout (KO, n = 16) and wild-type (WT, n = 19) mice. Treadmill testing was performed at 12, 14, 16, 18, and 21 mo of age. Vo(2), CO(2) production, respiratory exchange ratio, and maximal running distance were determined during treadmill running. There were good linear correlations for increase of speed with increase of Vo(2). The difference between KO and WT mice was not significant at 12 mo but was significant at 18 mo. Linear regression showed that KO mice consumed more O(2) at the same absolute and relative workloads, suggesting that Vo(2) was not inhibited by NO in KO mice. KO mice performed 30-50% less work than WT mice at each age (work = vertical distance x weight). In contrast to WT mice, the work performed by KO mice significantly decreased from 17 +/- 1.4 m.kg at 12 mo to 9.4 +/- 1.7 m.kg at 21 mo. Running distance was significantly decreased from 334 +/- 27 m at 12 mo to 178 +/- 38 m at 21 mo, and maximal Vo(2), CO(2) production, and respiratory exchange ratio per work unit were significantly higher in KO than in WT mice. Gene arrays showed evidence of a fetal phenotype in KO mice at 21 mo. In conclusion, age- and genotype-related exercise limitations in maximal work performed and maximal running distance in male eNOS-KO mice indicated that fetal phenotype and age were related to onset of heart failure.