Citations

Objective— There is increasing evidence of an association between leptin and increased cardiovascular risk. Higher leptin levels are associated with increased levels of C-reactive protein (CRP), which itself elicits proatherogenic effects in the vascular endothelium. We tested the hypothesis that leptin induces CRP expression in human coronary artery endothelial cells (HCAECs). Methods and Results— We confirmed the presence of both long and short isoforms of the leptin receptor in cultured HCAECs. Leptin but not IFNαA/D nor tumor necrosis factor (TNF) α, induced expression of CRP. A dose dependent increase of CRP mRNA and protein was observed with increasing concentration of leptin (0 to 400 ng/mL). This increased CRP expression was attenuated in the presence of anti-leptin receptor antibodies and also by inhibition of ERK1/2 by PD98059 (20 to 40 μmol/L). Time (0 to 60 minutes) and leptin concentration (0 to 200 ng/mL)-dependence of ERK1/2 phosphorylation were evident in response to leptin treatment. Leptin also elicited ROS generation. Inhibition of ROS by catalase (200 μg/mL) prevented ERK1/2 phosphorylation and CRP mRNA transcription. Conclusion— Leptin induces CRP expression in HCAECs via activation of the leptin receptor, increased ROS production, and phosphorylation of ERK1/2. These studies suggest a mechanism for the proatherogenic effects of leptin.

AbstractSphingolipids (SLs), including glycosphingolipids, are found on the plasma membrane where they play important roles in a wide variety of cell functions, including cell‐cell communication, cell growth and differentiation, host‐pathogen interactions, and cell‐signaling events. This unit illustrates the use of fluorescent SL analogs to identify the mechanisms underlying SL endocytosis and subsequent intracellular trafficking. Techniques used to study SL domain formation at the plasma membrane, endocytic mechanisms and intracellular transport steps are highlighted. The use of biochemical treatments and dominant‐negative protein expression to block specific steps in lipid trafficking are also discussed.

Abstract MUC1 is a heterodimeric transmembrane glycoprotein that is overexpressed and aberrantly glycosylated in ductal adenocarcinomas. Differential phosphorylation of the MUC1 cytoplasmic tail (MUC1CT) has been associated with signaling events that influence the proliferation and metastasis of cancer cells. We identified a novel tyrosine phosphorylation site (HGRYVPP) in the MUC1CT by mass spectrometric analysis of MUC1 from human pancreatic adenocarcinoma cell lines. Analyses in vitro and in vivo showed that platelet-derived growth factor receptor β (PDGFRβ) catalyzed phosphorylation of this site and of tyrosine in the RDTYHPM site. Stimulation of S2-013.MUC1F cells with PDGF-BB increased nuclear colocalization of MUC1CT and β-catenin. PDGF-BB stimulation had no significant effect on cell proliferation rate; however, it enhanced invasion in vitro through Matrigel and in vivo tumor growth and metastases. Invasive properties of the cells were significantly altered on expression of phosphorylation-abrogating or phosphorylation-mimicking mutations at these sites. We propose that interactions of MUC1 and PDGFRβ induce signal transduction events that influence the metastatic properties of pancreatic adenocarcinoma. [Cancer Res 2007;67(11):5201–10]

Background— Little is known about the impact of technological and pharmacological advances on long-term outcome after percutaneous coronary intervention in general clinical practice. Methods and Results— We analyzed in-hospital and long-term outcome of 24 410 percutaneous coronary interventions among 18 575 unique patients who underwent percutaneous coronary intervention at Mayo Clinic over 25 years. The study population was divided into group 1 (n=3708), coronary interventions from 1979 to 1989; group 2 (n=7020), interventions from 1990 to 1996; group 3 (n=10 952), interventions from 1996 to 2003; and group 4 (n=2730), interventions from 2003 to 2004. Despite the fact that patients in groups 3 and 4 were significantly older, sicker, and had greater prevalence of comorbid conditions, heart failure, and previous revascularization than those in groups 1 and 2, procedural success in groups 3 and 4 improved significantly (94%) versus groups 2 (89%) and 1 (78%) ( P <0.001). Significant reduction in in-hospital mortality (groups 4 to 1: 1.8%, 1.7%, 2.6%, 3.0%; P <0.001) and need for emergency bypass surgery (groups 4 to 1: 0.4%, 0.5%, 1.6%, 5%; P <0.001) was noted in groups 3 and 4 compared with groups 1 and 2. Better adherence to currently recommended evidence-based medications for secondary prevention was seen in the recent time periods. After adjustment, significant reduction in follow-up mortality (hazard ratio, 0.81 and 0.74 for groups 3 and 4, respectively); death or myocardial infarction (hazard ratio, 0.80 and 0.75 for groups 3 and 4, respectively); death, myocardial infarction, or revascularization (hazard ratio, 0.76 and 0.58 for groups 3 and 4, respectively) was noted in recent time periods. Conclusions— Despite higher-risk profiles of patients who underwent percutaneous coronary intervention in recent time periods, procedural success as well as in-hospital and long-term outcomes improved significantly over the last 25 years.

Caveolar endocytosis is an important mechanism for the uptake of certain pathogens and toxins and also plays a role in the internalization of some plasma membrane (PM) lipids and proteins. However, the regulation of caveolar endocytosis is not well understood. We previously demonstrated that caveolar endocytosis and β1-integrin signaling are stimulated by exogenous glycosphingolipids (GSLs). In this study, we show that a synthetic GSL with nonnatural stereochemistry, β-d-lactosyl-N-octanoyl-l-threo-sphingosine, (1) selectively inhibits caveolar endocytosis and SV40 virus infection, (2) blocks the clustering of lipids and proteins into GSLs and cholesterol-enriched microdomains (rafts) at the PM, and (3) inhibits β1-integrin activation and downstream signaling. Finally, we show that small interfering RNA knockdown of β1 integrin in human skin fibroblasts blocks caveolar endocytosis and the stimulation of signaling by a GSL with natural stereochemistry. These experiments identify a new compound that can interfere with biological processes by inhibiting microdomain formation and also identify β1 integrin as a potential mediator of signaling by GSLs.

Glucocorticoids are potent regulators of protein, fat, and carbohydrate metabolism. To determine if cortisol production occurs within the splanchnic bed in humans, 11 nondiabetic subjects were studied using the hepatic/leg catheterization method along with an infusion of [9,11,12,12-2H4] cortisol (D4-cortisol) as proposed by Andrews et al. In the fasting state, there was net release (P &lt; 0.05) of cortisol from the splanchnic bed (6.1 ± 2.6 μg/min) and net uptake (P &lt; 0.05) by the leg (1.7 ± 0.7 μg/min). This, along with cortisol production by other tissues (e.g., the adrenals), resulted in a total-body cortisol appearance rate of 18.1 ± 1.9 μg/min. Fractional splanchnic D4-cortisol extraction averaged 12.9 ± 1.3% (P &lt; 0.001), splanchnic cortisol uptake 14.8 ± 2.0 μg/min (P &lt; 0.001), and splanchnic cortisol production 22.2 ± 3.3 μg/min (P &lt; 0.001). On the other hand, fractional leg D4-cortisol extraction averaged 5.6 ± 1.8% (P &lt; 0.02), leg cortisol uptake 2.3 ± 0.7 μg/min (P &lt; 0.01), and leg cortisol production 0.4 ± 0.4 μg/min, which did not differ from zero. Because D4-cortisol loses a deuterium during conversion to [9,12,12-2H3] cortisone (D3-cortisone), which in turn generates [9,12,122H3] cortisol (D3-cortisol) via 11-β hydroxysteroid dehydrogenase (11β-HSD) type 1, D3-cortisol production can be used as an index of 11β-HSD type 1 activity. Net splanchnic D3-cortisol release (3.9 ± 0.4 μg/min) and splanchnic D3-cortisol production (7.1 ± 0.7 μg/min) occurred (P &lt; 0.01) in all subjects. In contrast, there was minimal leg D3-cortisol production (0.04 ± 0.01 μg/min), resulting in a strong correlation between splanchnic D3-cortisol production and total-body 3D-cortisol production in both the fasting state (r = 0.84; P &lt; 0.02) and during an infusion of insulin (r = 0.97; P &lt; 0.01). Thus, splanchnic production of cortisol occurs in nondiabetic humans at rates approximating that which occurs in the remainder of the body. These data support the possibility that alterations in splanchnic cortisol production contribute to visceral fat accumulation and the hepatic insulin resistance of obesity or type 2 diabetes.

ABSTRACT Infective endocarditis due to vancomycin-resistant (VR) Enterococcus faecalis has only rarely been reported. We report a case of VR E. faecalis endocarditis that failed to respond to linezolid therapy, outline the virulence traits of the isolate, and review previously published cases of VR E. faecalis endocarditis.