Citations

Background— Recent studies in animals suggest that circulating recipient endothelial precursors may participate in the biology of transplant vasculopathy. It is currently unknown whether a similar interaction between recipient endothelial cells and the vessel wall occurs in human subjects undergoing allogeneic cardiac transplantation. Methods and Results— Circulating endothelial cells and endothelial progenitor cells (EPCs) were quantified in 15 cardiac transplantation subjects with and without angiographic evidence of vasculopathy. In a separate series of experiments, the origin (donor or recipient) of transplant plaque endothelial cells was assessed in subjects who had undergone a gender-mismatched cardiac transplantation and had histological evidence of severe vasculopathy at the time of heart explantation. Circulating EPC outgrowth colonies in peripheral blood were significantly reduced in subjects with transplant vasculopathy compared with those without angiographic evidence of disease (EPC colony-forming units [CFU EPC ]: 4.5±1.9 versus 15.1±3.7, P <0.05). There was no significant difference in circulating endothelial cell numbers as defined by day 4 culture acetylated LDL/lectin assay in either of these patient groups. In a separate group of 5 subjects who underwent gender-mismatched cardiac transplantation, there was a significant seeding of recipient endothelial cells (range: 1% to 24% of all luminal endothelial cells) in large-vessel lumen and adventitial microvessel lumen of arteriopathic vessels. No opposite-sex chimeric cells were observed in control gender-matched transplantation scenarios. Conclusions— These data suggest that the human cardiac transplant arteriopathy is associated with reduction in circulating endothelial precursors and with seeding of recipient-derived endothelial cells at the site of plaque development.

Purpose: To assess the neurocognitive effects of cranial radiotherapy on patients with low-grade gliomas, we analyzed cognitive performance data collected in a prospective, intergroup clinical trial. Methods: Patients included 203 adults with supratentorial low-grade gliomas randomly assigned to a lower dose (50.4 Gy in 28 fractions) or a higher dose (64.8 Gy in 36 fractions) of localized radiotherapy. Folstein Mini-Mental State Examination (MMSE) scores and neurologic function scores (NFS) at baseline and key evaluations were analyzed. Median follow-up was 7.4 years in 101 patients still alive. A change of more than three MMSE points was considered clinically significant. Results: In patients without tumor progression, significant deterioration from baseline occurred at years 1, 2, and 5 in 8.2%, 4.6%, and 5.3% of patients, respectively. Most patients with an abnormal baseline MMSE score (< 27) experienced significant increases. Baseline variables such as radiation dose, conformal versus conventional radiotherapy, number of radiation fields, age, sex, tumor size, NFS, seizures, and seizure medications did not predict cognitive function changes. Conclusion: In this population, most low-grade glioma patients maintained a stable neurocognitive status after focal radiotherapy as measured by the MMSE. Patients with an abnormal baseline MMSE were more likely to have an improvement in cognitive abilities than deterioration after receiving radiotherapy. Only a small percentage of patients had cognitive deterioration after radiotherapy. However, more discriminating neurocognitive assessment tools may identify cognitive decline not apparent with the use of the MMSE.

Protein kinase C (PKC) activation in human eosinophils increases NADPH oxidase activity, which is associated with plasma membrane depolarization. In this study, membrane potential measurements of eosinophils stimulated with phorbol ester (phorbol 12-myristate 13-acetate; PMA) were made using a cell-permeable oxonol membrane potential indicator, diBAC4(3). Within 10 minutes after PMA stimulation, eosinophils depolarized from–32.9±5.7 mV to +17.3±1.8 mV. The time courses of depolarization and proton channel activation were virtually identical. Blocking the proton conductance with 250 μM ZnCl2(+43.0±4.2 mV) or increasing the proton channel activation threshold by reducing the extracellular pH to 6.5 (+44.4±1.4 mV) increased depolarization compared with PMA alone. Additionally, the protein kinase C(PKC) δ-selective blocker, rottlerin, inhibited PMA-stimulated depolarization, indicating that PKCδ was involved in regulating depolarization associated with eosinophil NADPH oxidase activity. Thus, the membrane depolarization that is associated with NADPH oxidase activation in eosinophils is sufficient to produce marked proton channel activation under physiological conditions.

Mitochondria are the primary site of skeletal muscle fuel metabolism and ATP production. Although insulin is a major regulator of fuel metabolism, its effect on mitochondrial ATP production is not known. Here we report increases in vastus lateralis muscle mitochondrial ATP production capacity (32–42%) in healthy humans ( P < 0.01) i.v. infused with insulin (1.5 milliunits/kg of fat-free mass per min) while clamping glucose, amino acids, glucagon, and growth hormone. Increased ATP production occurred in association with increased mRNA levels from both mitochondrial (NADH dehydrogenase subunit IV) and nuclear [cytochrome c oxidase (COX) subunit IV] genes (164–180%) encoding mitochondrial proteins ( P < 0.05). In addition, muscle mitochondrial protein synthesis, and COX and citrate synthase enzyme activities were increased by insulin ( P < 0.05). Further studies demonstrated no effect of low to high insulin levels on muscle mitochondrial ATP production for people with type 2 diabetes mellitus, whereas matched nondiabetic controls increased 16–26% ( P < 0.02) when four different substrate combinations were used. In conclusion, insulin stimulates mitochondrial oxidative phosphorylation in skeletal muscle along with synthesis of gene transcripts and mitochondrial protein in human subjects. Skeletal muscle of type 2 diabetic patients has a reduced capacity to increase ATP production with high insulin levels.

Background— Caveolin-1 is a regulator of signaling events originating from plasma membrane microdomains termed caveolae. This study was performed to determine the regulatory role of caveolin-1 on the proliferative events induced by platelet-derived growth factor (PDGF) in vascular smooth muscle cells (VSMCs). Methods and Results— Treatment of VSMCs with PDGF for 24 hours resulted in a loss of caveolin-1 protein expression and plasma membrane–associated caveolae, despite a 3-fold increase in caveolin-1 mRNA. Pretreatment of VSMCs with chloroquine, an inhibitor of lysosomal function, inhibited the PDGF-induced loss of caveolin-1. These studies demonstrated that caveolin-1 was a target of PDGF signaling events. Adenoviral overexpression of caveolin-1 was associated with a switch in PDGF-induced signaling events from a proliferative response to an apoptotic response. This overexpression inhibited PDGF-induced expression of cyclin D1 in the presence of unaffected mitogen-activated protein kinase activation. Conclusions— Taken together, these studies suggest that caveolin-1 is an inhibitor of PDGF proliferative responses and might be capable of transforming PDGF-induced proliferative signals into death signals.

Background and Purpose— The magnitude of inherited risk of stroke may lessen with age, and this would have implications for optimizing genomic approaches to identifying genetic risk factors for stroke. We investigated the relationship between age and inherited risk of stroke. Methods— Family histories of stroke were obtained in systematic interviews with 310 adult men and women with recent CT- or MR-confirmed ischemic stroke. Probability of stroke in first-degree relatives was analyzed by logistic regression, adjusting for sibship size. Results— The probability of having a sibling with stroke increased as proband age at stroke presentation increased. Per decade increase in proband age, the odds ratio was 1.65 (95% confidence interval [CI], 1.20 to 2.28; P =0.002) for a concordant sibling and 1.69 (95% CI, 1.15 to 2.49; P =0.008) for ≥2 first-degree relatives with a history of stroke. Conclusions— Clustering of stroke was not greater in families with probands manifesting symptoms of stroke in earlier than later adulthood. The relationship between proband age and positive family history of stroke does not suggest an upper age-limit cutoff for genomewide linkage studies.

The inflammatory infiltrate in atherosclerotic plaque is composed of T cells and macrophages. CD4 + T cells with a unique phenotype, CD4 + CD28 null , are preferentially recruited into culprit lesions. These T cells are distinct from classic CD4 + CD28 + T cells in gene expression and function, including their ability to mediate cytolysis. In this study, we have investigated the regulation of CD4 + CD28 null T-cell cytolytic function. In patients with acute coronary syndromes (ACS), CD4 + CD28 null T cells express killer immunoglobulin-like receptors (KIRs). KIRs encompass a polymorphic family of receptors that recognize HLA class I molecules and have been implicated in self-tolerance. CD4 + CD28 null T-cell clones from patients with ACS and age-matched controls were compared for their KIR-expression profile. T-cell clones derived from the patients expressed a broader spectrum of KIRs ( P <0.001) with preference for the stimulatory variant, CD158j. Additionally, CD4 + T-cell clones from patients but not those from controls acquired de novo expression of the DAP12 molecule, an adapter chain that transmits CD158j-derived signals. Cumulative expression of CD158j and DAP12 endowed cytolytic competence on CD4 + CD28 null T cells, allowing them to kill in the absence of T-cell receptor triggering. Our data demonstrate that CD4 + CD28 null T cells in ACS are characterized by a unique gene expression profile. Consequently, these T cells acquire cytolytic capability that can bypass the need for T-cell receptor triggering and, thus, impose a threat to self-tolerance.