Molecular classification of cutaneous malignant melanoma by gene expression profiling

The most common human cancers are malignant neoplasms of the skin. Incidence of cutaneous melanoma is rising especially steeply, with minimal progress in non-surgical treatment of advanced disease. Despite significant effort to identify independent predictors of melanoma outcome, no accepted histopathological, molecular or immunohistochemical marker defines subsets of this neoplasm. Accordingly, though melanoma is thought to present with different 'taxonomic' forms, these are considered part of a continuous spectrum rather than discrete entities. Here we report the discovery of a subset of melanomas identified by mathematical analysis of gene expression in a series of samples. Remarkably, many genes underlying the classification of this subset are differentially regulated in invasive melanomas that form primitive tubular networks in vitro, a feature of some highly aggressive metastatic melanomas. Global transcript analysis can identify unrecognized subtypes of cutaneous melanoma and predict experimentally verifiable phenotypic characteristics that may be of importance to disease progression.

High-fidelity mRNA amplification for gene profiling

The completion of the Human Genome Project has made possible the comprehensive analysis of gene expression, and cDNA microarrays are now being employed for expression analysis in cancer cell lines or excised surgical specimens. However, broader application of cDNA microarrays is limited by the amount of RNA required: 50-200 microg of total RNA (T-RNA) and 2-5 microg poly(A) RNA. To broaden the use of cDNA microarrays, some methods aiming at intensifying fluorescence signal have resulted in modest improvement. Methods devoted to amplifying starting poly(A) RNA or cDNA show promise, in that detection can be increased by orders of magnitude. However, despite the common use of these amplification procedures, no systematic assessment of their limits and biases has been documented. We devised a procedure that optimizes amplification of low-abundance RNA samples by combining antisense RNA (aRNA) amplification with a template-switching effect (Clonetech, Palo Alto, CA). The fidelity of aRNA amplified from 1:10,000 to 1:100,000 of commonly used input RNA was comparable to expression profiles observed with conventional poly(A) RNA- or T-RNA-based arrays.

Altered urinary bladder function in mice lacking the vanilloid receptor TRPV1

In the urinary bladder, the capsaicin-gated ion channel TRPV1 is expressed both within afferent nerve terminals and within the epithelial cells that line the bladder lumen. To determine the significance of this expression pattern, we analyzed bladder function in mice lacking TRPV1. Compared with wild-type littermates, trpv1(-/-) mice had a higher frequency of low-amplitude, non-voiding bladder contractions. This alteration was accompanied by reductions in both spinal cord signaling and reflex voiding during bladder filling (under anesthesia). In vitro, stretch-evoked ATP release and membrane capacitance changes were diminished in bladders excised from trpv1(-/-) mice, as was hypoosmolality-evoked ATP release from cultured trpv1(-/-) urothelial cells. These findings indicate that TRPV1 participates in normal bladder function and is essential for normal mechanically evoked purinergic signaling by the urothelium.

Sphingolipids--the enigmatic lipid class: biochemistry, physiology, and pathophysiology

The "sphingosin" backbone of sphingolipids was so named by J. L. W. Thudichum in 1884 for its enigmatic ("Sphinx-like") properties. Although still an elusive class of lipids, research on the involvement of sphingolipids in the signal transduction pathways that mediate cell growth, differentiation, multiple cell functions, and cell death has been rapidly expanding our understanding of these compounds. In addition to the newly discovered role of ceramide as an intracellular second messenger for tumor necrosis factor-alpha, IL-1beta, and other cytokines, sphingosine, sphingosine-1-phosphate, and other sphingolipid metabolites have recently been demonstrated to modulate cellular calcium homeostasis and cell proliferation. Perturbation of sphingolipid metabolism using synthetic and naturally occurring inhibitors of key enzymes of the biosynthetic pathways is aiding the characterization of these processes; for examples, inhibition of cerebroside synthase has indicated a role for ceramide in cellular stress responses including heat shock, and inhibition of ceramide synthase (by fumonisins) has revealed the role of disruption of sphingolipid metabolism in several animal diseases. Fumonisins are currently the focus of a FDA long-term tumor study. This review summarizes recent research on (i) the role of sphingolipids as important components of the diet, (ii) the role of sphingoid base metabolites and the ceramide cycle in expression of genes regulating cell growth, differentiation, and apoptosis, (iii) the use of cerebroside synthase inhibitors as tools for understanding the role of sphingolipids as mediators of cell cycle progression, renal disease, and stress responses, and (iv) the involvement of disrupted sphingolipid metabolism in animal disease and cellular deregulation associated with exposure to inhibitors of ceramide synthase and serine palmitoyltransferase, key enzymes in de novo sphingolipid biosynthesis. These findings illustrate how an understanding of the function of sphingolipids can help solve questions in toxicology and this is undoubtedly only the beginning of this story.

Bcl-2 potentiates the maximal calcium uptake capacity of neural cell mitochondria

Expression of the human protooncogene bcl-2 protects neural cells from death induced by many forms of stress, including conditions that greatly elevate intracellular Ca2+. Considering that Bcl-2 is partially localized to mitochondrial membranes and that excessive mitochondrial Ca2+ uptake can impair electron transport and oxidative phosphorylation, the present study tested the hypothesis that mitochondria from Bcl-2-expressing cells have a higher capacity for energy-dependent Ca2+ uptake and a greater resistance to Ca(2+)-induced respiratory injury than mitochondria from cells that do not express this protein. The overexpression of bcl-2 enhanced the mitochondrial Ca2+ uptake capacity using either digitonin-permeabilized GT1-7 neural cells or isolated GT1-7 mitochondria by 1.7 and 3.9 fold, respectively, when glutamate and malate were used as respiratory substrates. This difference was less apparent when respiration was driven by the oxidation of succinate in the presence of the respiratory complex I inhibitor rotenone. Mitochondria from Bcl-2 expressors were also much more resistant to inhibition of NADH-dependent respiration caused by sequestration of large Ca2+ loads. The enhanced ability of mitochondria within Bcl-2-expressing cells to sequester large quantities of Ca2+ without undergoing profound respiratory impairment provides a plausible mechanism by which Bcl-2 inhibits certain forms of delayed cell death, including neuronal death associated with ischemia and excitotoxicity.

New approaches for studying and exploiting an old protuberance, the plant trichome

BACKGROUND AND AIMS

Much recent study of plant trichomes has focused on various aspects of glandular secreting trichomes (GSTs) and differentiation of simple trichomes. This Botanical Briefing will highlight: research on various aspects of, and manipulation of glandular secreting trichomes; molecular aspects of the differentiation and development of simple trichomes of arabidopsis and cotton; how methods for manipulation of model systems used in the above work can be applied to expand our understanding of less studied surface structures of plants.

SCOPE

The Briefing will cover: established and suggested roles of simple and glandular secreting trichomes; recent results regarding solute and ion movement in trichomes; methods for isolating trichomes; recent studies of trichome differentiation and development; attempts to modify metabolism in secreting trichomes; efforts to exploit trichomes for commercial and agronomic purposes.

Cytokine production at the site of disease in human tuberculosis

Clinical and immunologic evidence suggests that tuberculous pleuritis provides a model to understand protective immune mechanisms against Mycobacterium tuberculosis. We therefore evaluated the pattern of cytokine mRNA expression and cytokine production in pleural fluid and blood of patients with tuberculous pleuritis. RNA was extracted from mononuclear cells, reverse transcribed to cDNA, and amplified by polymerase chain reaction (PCR). After normalization for T-cell cDNA, cDNA from pleural fluid cells and peripheral blood mononuclear cells (PBMC) was amplified with cytokine-specific primers. PCR product was quantified by Southern blot. For the Th1 cytokines gamma interferon (IFN-gamma) and interleukin-2 (IL-2), PCR product was greater in pleural fluid than in blood, whereas PCR product for the Th2 cytokine IL-4 was decreased in pleural fluid compared with blood. Concentrations of IFN-gamma were elevated in pleural fluid compared with serum, but IL-2, IL-4, and IL-5 were not detectable. Mean concentrations of IFN-gamma and IL-2 in supernatants of M. tuberculosis-stimulated pleural fluid cells were significantly greater than corresponding concentrations in supernatants of stimulated PBMC. In situ hybridization showed that increased IFN-gamma production by pleural fluid cells was associated with a 20- to 60-fold increase in the frequency of antigen-reactive IFN-gamma-mRNA-expressing cells. Because IL-10 can be produced by T cells and macrophages, pleural fluid cells and PBMC were normalized for beta-actin cDNA content and then amplified by PCR with IL-10-specific primers. IL-10 mRNA was greater in pleural fluid cells than in PBMC and was expressed predominantly by macrophages. IL-10 concentrations were elevated in pleural fluid versus serum. These data provide strong evidence for compartmentalization of Th1 cytokines and IL-10 at the site of disease in humans with a resistant immune response to mycobacterial infection.

Quantitation of free sphingosine in liver by high-performance liquid chromatography

Conditions were established for the extraction of free sphingosine from liver and the separation and quantitation of this and other long-chain (sphingoid) bases (e.g., sphingosine, sphinganine, phytosphingosine, and homologs) by reverse-phase high-performance liquid chromatography (HPLC). The long-chain bases were extracted with chloroform and methanol and then treated with base to remove interfering lipids. After preparation of the o-phthalaldehyde derivatives, the long-chain bases could be separated using C18 columns eluted isocratically with methanol:5 mM potassium phosphate, pH 7.0 (90:10). The HPLC analyses took 15 to 20 min per sample and had lower limits of detection in the picomole range. Quantitation was facilitated by using a 20-carbon long-chain base homolog as an internal standard. The utility of the method was demonstrated with rat liver, providing the first quantitation of free sphingosine in this tissue of approximately 7 nmol/g wet wt.

Evolutionary relationships of endemic/epidemic and sylvatic dengue viruses

Endemic/epidemic dengue viruses (DEN) that are transmitted among humans by the mosquito vectors Aedes aegypti and Aedes albopictus are hypothesized to have evolved from sylvatic DEN strains that are transmitted among nonhuman primates in West Africa and Malaysia by other Aedes mosquitoes. We tested this hypothesis with phylogenetic studies using envelope protein gene sequences of both endemic/epidemic and sylvatic strains. The basal position of sylvatic lineages of DEN-1, -2, and -4 suggested that the endemic/epidemic lineages of these three DEN serotypes evolved independently from sylvatic progenitors. Time estimates for evolution of the endemic/epidemic forms ranged from 100 to 1,500 years ago, and the evolution of endemic/epidemic forms represents relatively recent events in the history of DEN evolution. Analysis of envelope protein amino acid changes predicted to have accompanied endemic/epidemic emergence suggested a role for domain III in adaptation to new mosquito and/or human hosts.

Characterization of ceramide synthesis. A dihydroceramide desaturase introduces the 4,5-trans-double bond of sphingosine at the level of dihydroceramide

Ceramide (N-acylsphingosine) biosynthesis has been proposed to involve introduction of the 4,5-trans-double bond of sphingosine after synthesis of dihydroceramide (i.e. N-acylsphinganine). For the first time, the in vitro conversion of dihydroceramide to ceramide has been demonstrated using rat liver microsomes and N-[1-14C]octanoyl-D-erythro-sphinganine (st-H2Cer) and either NADH or NADPH as co-substrate; the apparent Km values for st-H2Cer and NADH were 340 and 120 microM, respectively. Molecular oxygen is required for enzymatic activity, and cyanide, divalent copper, as well as antibodies raised against cytochrome b5 are inhibitory, which suggests that this enzyme should be named dihydroceramide desaturase based on these similarities with the mechanism of delta9-desaturase (stearoyl-CoA desaturase). Factors that influenced the activity of dihydroceramide desaturase include the alkyl chain length of the sphingoid base (in the order C18 > C12 > C8) and fatty acid (C8 > C18); the stereochemistry of the sphingoid base (D-erythro- > L-threo-dihydroceramides); the nature of the headgroup, with the highest activity with dihydroceramide, but some (approximately 20%) activity with dihydroglucosylceramide, however); and the ability to utilize alternative reductants (ascorbic acid could substitute for a reduced pyridine nucleotide, but was inhibitory at higher concentrations). Dihydroceramide desaturase was inhibited by dithiothreitol, which suggests that it might be possible to alter ceramide synthesis by varying the thiol status of hepatocytes. Consistent with this hypothesis, when rat hepatocytes were cultured in varying concentrations of N-acetylcysteine (5 and 10 mM), there was a decrease in the relative incorporation of [14C]serine into [14C]ceramide. These studies have conclusively established the pathway of ceramide synthesis via desaturation of dihydroceramide and have uncovered several properties of this reaction that warrant further consideration for their relevance to both sphingolipid metabolism and signaling.

The genetic architecture of selection at the human dopamine receptor D4 (DRD4) gene locus

Associations of the seven-repeat (7R) allele of the human dopamine receptor D4 (DRD4) gene with both the personality trait of novelty seeking and attention deficit/hyperactivity disorder have been reported. Recently, on the basis of the unusual DNA sequence organization of the DRD4 7R 48-bp tandem repeat (VNTR), we proposed that the 7R allele originated as a rare mutational event that increased to high frequency by positive selection. We now have resequenced the entire DRD4 locus from 103 individuals homozygous for 2R, 4R, or 7R variants of the VNTR, a method developed to directly estimate haplotype diversity. DNA from individuals of African, European, Asian, North and South American, and Pacific Island ancestry were used. 4R/4R homozygotes exhibit little linkage disequilibrium (LD) over the region examined, with more polymorphisms observed in DNA samples from African individuals. In contrast, the evidence for strong LD surrounding the 7R allele is dramatic, with all 7R/7R individuals (including those from Africa) exhibiting the same alleles at most polymorphic sites. By intra-allelic comparison at 18 high-heterozygosity sites spanning the locus, we estimate that the 7R allele arose prior to the upper Paleolithic era (approximately 40000-50000 years ago). Further, the pattern of recombination at these polymorphic sites is the pattern expected for selection acting at the 7R VNTR itself, rather than at an adjacent site. We propose a model for selection at the DRD4 locus consistent with these observed LD patterns and with the known biochemical and physiological differences between receptor variants.

Improved outcome of respiratory syncytial virus infection in a high-risk hospitalized population of Canadian children. Pediatric Investigators Collaborative Network on Infections in Canada

PURPOSE

To determine the outcomes in children at high risk for death or complications from respiratory disease who are hospitalized with respiratory syncytial virus (RSV) infection.

DESIGN

Retrospective chart review.

SETTING

Twelve pediatric tertiary care centers.

PATIENTS

All hospitalized children with an RSV infection diagnosed by a positive antigen detection test result or viral isolation during the study period from 1988 to 1991, encompassing three winter seasons. Charts from patients in the following high-risk groups were reviewed in detail: (1) congenital heart disease, (2) chronic lung disease, (3) immunodeficiency, (4) age less than 6 weeks, (5) gestational age less than 36 weeks, and (6) hypoxia (defined as oxygen saturation less than 90% or arterial oxygen pressure less than 60 mm Hg).

MEASUREMENTS

The age of all children, the date of RSV identification, and the use of oxygen supplementation, intensive care, and ventilatory support. In addition, the duration of these treatments and the duration of hospitalization were noted. Left-to-right shunting and pulmonary hypertension before RSV infection were determined in those children with congenital heart disease. The nature of the chronic lung disease was noted. Death within 2 weeks of RSV identification was recorded, and the use of ribavirin, bronchodilators, and corticosteroids was determined.

RESULTS

Significant year-to-year variation in the frequency of RSV infection was confirmed, with a peak during the 1989-1990 winter noted by the majority of centers (p = 0.0001). Of the 1584 patients in the study, 260 had underlying cardiac disease, 200 had chronic lung disease, 35 had compromised immune function, 378 had been premature, 373 were less than 6 weeks of age, and 338 had hypoxia. Seventeen patients died within 2 weeks (mortality rate 1%); significantly more patients with underlying cardiac disease (3.4%) or lung disease (3.5%) died. Immunocompromised patients had the longest hospital stay (median 39 days), followed by those patients with underlying cardiac or pulmonary disease (11 days); patients less than 6 weeks of age (5 days) and those with hypoxia (6 days) had the shortest hospital stays. Patients with underlying cardiac and pulmonary disease also required oxygen supplementation for a significantly longer period.

CONCLUSION

The year-to-year variation in frequency of RSV infection was confirmed in this study. Morbidity and mortality rates associated with RSV infection in a high-risk population in Canada were significantly lower than previously reported.

Obesity and obesity-related secondary conditions in adolescents with intellectual/developmental disabilities

BACKGROUND

To explore the prevalence of obesity and related secondary conditions associated with obesity in adolescents with intellectual/developmental disabilities (IDD).

METHODS

In total, 461 parents of adolescents with IDD (M = 14.9 year, SD = 1.9) across 49 US states completed a web-based survey containing questions related to their child's health status, including body weight and existing health conditions. Results were compared with published data for youth without disabilities.

RESULTS

Adolescents with autism and Down syndrome were two to three times more likely to be obese than adolescents in the general population. Secondary health conditions were higher in obese adolescents with IDD compared with healthy weight adolescents with IDD including high blood pressure, high blood cholesterol, diabetes, depression, fatigue, liver or gallbladder problems, low self-esteem, preoccupation with weight, early maturation and pressure sores.

CONCLUSION

Obesity is as much of a health problem in youth with IDD as it is among youth without disabilities and, in certain disability groups, is a significantly greater health problem. Obese youth with IDD have a high number of obesity-related secondary conditions predisposing them to greater health problems as they transition into adulthood. Federal and local initiatives to reduce obesity among youth in the general population must recognise the need for interventions that are also relevant (i.e. accessible and effective) for youth with IDD.

Randomised trial of intravenous immunoglobulin G, intravenous anti-D, and oral prednisone in childhood acute immune thrombocytopenic purpura

The most serious complication of childhood acute immune thrombocytopenic purpura (ITP), intracranial haemorrhage, occurs in about 1% of children with platelet counts below 20 x 10(9)/L. We conducted a randomised study to explore three treatment options in this high-risk group. 146 children (> 6 months and < 18 years old) with typical acute ITP and platelet counts of 20 x 10(9)/L or lower were randomised to receive high-dose intravenous immunoglobulin G (IVIgG) 1 g/kg on 2 consecutive days (n = 34), 0.8 g/kg once (n = 35), intravenous anti-D 25 micrograms/kg on 2 consecutive days (n = 38), or oral prednisone 4 mg/kg per day with tapering and discontinuation of prednisone by day 21 (n = 39). The rate of response as reflected by the number of days with platelet counts at 20 x 10(9)/L or lower and the time taken to achieve a platelet count 50 x 10(9)/L or more was significantly faster for both IVIgG groups than for the anti-D group (p < 0.05); the difference between prednisone and IVIgG was significant (p < 0.05) only for the IVIgG 0.8 g/kg group, and responses to the two IgG groups were similar. These differences in response rates were reflected in the percentages of children with platelet counts of 20 x 10(9)/L or lower at 72 hours following the start of treatment: 3% (IVIgG 0.8 g/kg x 1), 6% (IVIgG 1 g/kg x 2), 18% (anti-D), and 21% (oral prednisone 4 mg/kg/day). Treatment-associated toxicities included a fall in haemoglobin with anti-D (to less than 100 g/L in 24% of cases); weight gain with oral prednisone; and fever, nausea, vomiting, and headache with IVIgG. On the basis of these results, intravenous anti-D cannot be recommended as initial therapy for children with acute ITP and platelet counts of 20 x 10(9)/L or lower. A single dose of 0.8 g/kg IVIgG offers the fastest recovery for the least treatment; additional IgG or oral prednisone can be reserved for the one-third of children who continue to have platelet counts of 20 x 10(9)/L or less at 48-72 hours after the start of treatment.

Engineered pluripotent mesenchymal cells integrate and differentiate in regenerating bone: a novel cell-mediated gene therapy

BACKGROUND

Among the approximately 6.5 million fractures suffered in the United States every year, about 15% are difficult to heal. As yet, for most of these difficult cases there is no effective therapy. We have developed a mouse radial segmental defect as a model experimental system for testing the capacity of Genetically Engineered Pluripotent Mesenchymal Cells (GEPMC, C3H10T1/2 clone expressing rhBMP-2), for gene delivery, engraftment, and induction of bone growth in regenerating bone.

METHODS

Transfected GEPMC expressing rhBMP-2 were further infected with a vector carrying the lacZ gene, that encodes for beta-galactosidase (beta-gal). In vitro levels of rhBMP-2 expression and function were confirmed by immunohistochemistry, and bioassay. Differentiation was assayed using alkaline phosphatase staining. GEPMC were transplanted in vivo into a radial segmental defect. The main control groups included lacZ clones of WT-C3H10T1/2-LacZ, and CHO-rhBMP-2 cells. New bone formation was measured quantitatively via fluorescent labeling, X-ray analysis and histomorphometry. Engrafted mesenchymal cells were localized in vivo by beta-gal expression, and double immunofluorescence.

RESULTS

In vitro, GEPMC expressed rhBMP-2, beta-gal and spontaneously differentiated into osteogenic cells expressing alkaline phosphatase. Detection of transplanted cells revealed engrafted cells that had differentiated into osteoblasts and co-expressed beta-gal and rhBMP-2. Analysis of new bone formation revealed that at four to eight week post-transplantation, GEPMS significantly enhanced segmental defect repair.

CONCLUSIONS

Our study shows that cell-mediated gene transfer can be utilized for growth factor delivery to signaling receptors of transplanted cells (autocrine effect) and host mesenchymal cells (paracrine effect) suggesting the ability of GEPMC to engraft, differentiate, and stimulate bone growth. We suggest that our approach should lead to the designing of mesenchymal stem cell based gene therapy strategies for bone lesions as well as other tissues.

BMP-2 and BMP-9 promotes chondrogenic differentiation of human multipotential mesenchymal cells and overcomes the inhibitory effect of IL-1

Bone morphogenetic proteins play important roles in connective tissue morphogenesis. In this study, we used human multipotential mesenchymal cells as a target to analyze the effect of bone morphogenetic proteins on chondrogenesis. We also analyzed the effect of proinflammatory cytokine interleukin-1 on chondrogenic-differentiated cells and the interaction of IL-1beta with bone morphogenetic proteins. Cells placed in a 3-dimensional matrix of alginate beads and cultured in a serum-free media with bone morphogenetic protein-2 and -9 induced expression of type II collagen (Col2A1) mRNA and increased expression of aggrecan and cartilage oligomeric matrix protein suggesting chondrogenic differentiation of the cells. The transcription factor Sox-9 that regulates both Col2A1 and aggrecan gene expression showed increased expression with BMP treatment. Chondrogenic differentiated cells treated with interleukin-1 decreased Sox-9, Col2A1 and aggrecan gene expression. Removal of interleukin-1 and further addition of bone morphogenetic proteins resulted in returned expression of chondrogenic markers. Chondrogenic differentiated cells cultured in the presence of different concentrations of bone morphogenetic proteins and interleukin-1 showed that bone morphogenetic proteins were able to partially block the suppressive effect of interleukin-1. This study shows that bone morphogenetic proteins play an important role in chondrogenesis and may prove to be potential therapeutics in cartilage repair.

Selective modulation of human natural killer cells in vivo after prolonged infusion of low dose recombinant interleukin 2

The immunologic consequences of prolonged infusions of rIL-2 in doses that produce physiologic serum concentrations of this cytokine were investigated. rIL-2 in doses of 0.5-6.0 x 10(6) U/m2 per d (3.3-40 micrograms/m2 per d) was administered by continuous intravenous infusion for 90 consecutive days to patients with advanced cancer. IL-2 concentrations (25 +/- 25 and 77 +/- 64 pM, respectively) that selectively saturate high-affinity IL-2 receptors (IL-2R) were achieved in the serum of patients receiving rIL-2 infusions of 10 micrograms/m2 per d and 30 micrograms/m2 per d. A gradual, progressive expansion of natural killer (NK) cells was seen in the peripheral blood of these patients with no evidence of a plateau effect during the 3 mo of therapy. A preferential expansion of CD56bright NK cells was consistently evident. NK cytotoxicity against tumor targets was only slightly enhanced at these dose levels. However, brief incubation of these expanded NK cells with IL-2 in vitro induced potent lysis of NK-sensitive, NK-resistant, and antibody-coated targets. Infusions of rIL-2 at 40 micrograms/m2 per d produced serum IL-2 levels (345 +/- 381 pM) sufficient to engage intermediate affinity IL-2R p75, which is constitutively expressed by human NK cells. This did not result in greater NK cell expansion compared to the lower dose levels, but did produce in vivo activation of NK cytotoxicity, as evidenced by lysis of NK-resistant targets. There was no consistent change in the numbers of CD56- CD3+ T cells, CD56+ CD3+ MHC-unrestricted T cells, or B cells during infusions of rIL-2 at any of the dosages used. This study demonstrates that prolonged infusions of rIL-2 in doses that saturate only high affinity IL-2R can selectively expand human NK cells for an extended period of time with only minimal toxicity. Further activation of NK cytolytic activity can also be achieved in vivo, but it requires concentrations of IL-2 that bind intermediate affinity IL-2R p75. Clinical trials are underway attempting to exploit the differing effects of various concentrations of IL-2 on human NK cells in vivo.

Alteration of tissue and serum sphinganine to sphingosine ratio: an early biomarker of exposure to fumonisin-containing feeds in pigs

Fumonisins are a group of naturally occurring compounds produced by the fungus Fusarium moniliforme. They are believed to be the etiologic agent of several animal diseases associated with consumption of corn-based feeds including porcine pulmonary edema. Recently it was shown in vitro that fumonisins are specific inhibitors of sphingosine and sphinganine N-acyltransferases. Inhibition of these enzymes in cultured cells results in the accumulation of free long chain sphingoid bases, specifically sphingosine and sphinganine, and the depletion of complex sphingolipids. In this study, tissues and serum from male SPF pigs fed a nutritionally balanced diet containing corn or corn screenings naturally contaminated with fumonisins for up to 14 days were analyzed for free sphingoid bases and complex sphingolipids. Total fumonisins (B1 and B2) in the diets were analyzed at 0 (< 1), 5, 23, 39, 101, and 175 ppm. Pulmonary edema only occurred at 175 ppm, while histologic liver damage was present at > or = 23 ppm, and serum liver enzymes were significantly elevated at > or = 101 ppm. The results of this study show that free sphinganine is elevated in liver, lung, and kidney, from pigs consuming feeds containing fumonisins at total fumonisin concentrations of 23 ppm or greater. Sphingosine is also elevated in a dose-dependent manner, but to a lesser extent than sphinganine. The consequence of this differential inhibition is that the ratio of sphinganine to sphingosine increases, suggesting that sphinganine N-acyltransferase is the preferred target for fumonisins. Elevation of free sphinganine and free sphingosine in serum paralleled the increases in tissues. Statistically significant increases in the ratio were observed at feed concentrations as low as 5 ppm total fumonisins and in pigs (at higher concentrations) in which other serum biochemistry parameters and tissue morphology were not altered. Elevated ratios were also observed in serum from pigs fed pure fumonisin B1. The sensitivity of the ratio indicates that it could serve as an effective biomarker for consumption of fumonisin-containing feeds. In addition, the data supports the hypothesis that inhibition of sphingosine and sphinganine N-acyltransferase plays an important role in the pathogenesis of animal diseases associated with consumption of feed containing fumonisins.

Simultaneous genotyping and species identification using hybridization pattern recognition analysis of generic Mycobacterium DNA arrays

High-density oligonucleotide arrays can be used to rapidly examine large amounts of DNA sequence in a high throughput manner. An array designed to determine the specific nucleotide sequence of 705 bp of the rpoB gene of Mycobacterium tuberculosis accurately detected rifampin resistance associated with mutations of 44 clinical isolates of M. tuberculosis. The nucleotide sequence diversity in 121 Mycobacterial isolates (comprised of 10 species) was examined by both conventional dideoxynucleotide sequencing of the rpoB and 16S genes and by analysis of the rpoB oligonucleotide array hybridization patterns. Species identification for each of the isolates was similar irrespective of whether 16S sequence, rpoB sequence, or the pattern of rpoB hybridization was used. However, for several species, the number of alleles in the 16S and rpoB gene sequences provided discordant estimates of the genetic diversity within a species. In addition to confirming the array's intended utility for sequencing the region of M. tuberculosis that confers rifampin resistance, this work demonstrates that this array can identify the species of nontuberculous Mycobacteria. This demonstrates the general point that DNA microarrays that sequence important genomic regions (such as drug resistance or pathogenicity islands) can simultaneously identify species and provide some insight into the organism's population structure.

Fumonisin- and AAL-Toxin-Induced Disruption of Sphingolipid Metabolism with Accumulation of Free Sphingoid Bases

Fumonisins (FB) and AAL-toxin are sphingoid-like compounds produced by several species of fungi associated with plant diseases. In animal cells, both fumonisins produced by Fusarium moniliforme and AAL-toxin produced by Alternaria alternata f. sp. lycopersici inhibit ceramide synthesis, an early biochemical event in the animal diseases associated with consumption of F. moniliforme-contaminated corn. In duckweed (Lemna pausicostata Heglem. 6746), tomato plants (Lycopersicon esculentum Mill), and tobacco callus (Nicotiana tabacum cv Wisconsin), pure FB1 or AAL-toxin caused a marked elevation of phytosphingosine and sphinganine, sphingoid bases normally present in low concentrations. The relative increases were quite different in the three plant systems. Nonetheless, disruption of sphingolipid metabolism was clearly a common feature in plants exposed to FB1 or AAL-toxin. Resistant varieties of tomato (Asc/Asc) were much less sensitive to toxin-induced increases in free sphinganine. Because free sphingoid bases are precursors to plant "ceramides," their accumulation suggests that the primary biochemical lesion is inhibition of de novo ceramide synthesis and reacylation of free sphingoid bases. Thus, in plants the disease symptoms associated with A. alternata and F. moniliforme infection may be due to disruption of sphingolipid metabolism.

Sphingolipid metabolism: roles in signal transduction and disruption by fumonisins

Sphingolipids have important roles in membrane and lipoprotein structure and in cell regulation as second messengers for growth factors, differentiation factors, cytokines, and a growing list of agonists. Bioactive sphingolipids are formed both by the turnover of complex sphingolipids and as intermediates of sphingolipid biosynthesis. Usually, the amounts are highly regulated; however, by inhibiting ceramide synthase, fumonisins block the biosynthesis of complex sphingolipids and cause sphinganine (and sometimes sphingosine) to accumulate. Where the mechanism has been studied most thoroughly, the accumulation of sphingoid bases is a primary cause of the toxicity of fumonisin B (FB). Nonetheless, the full effects of fumonisins probably involve many biochemical events. The elevations in sphingoid bases also affect the amounts of other lipids, including the 1-phosphates and N-acetyl derivatives of sphinganine. Furthermore, the aminopentol backbone of FB1 (AP1) is both an inhibitor and a substrate for ceramide synthase, and the resultant N-palmitoyl-AP1 (PAP1) is an even more potent inhibitor of ceramide synthase (presumably as a product analog). PAP1 is 10 times more toxic than FB1 or AP1 for HT-29 cells in culture, and hence may play a role in the toxicity of nixtamalized fumonisins. All these processes--the effects of fumonisins on sphingolipid metabolism, the pathways altered by perturbation of sphingolipid metabolism, and the complex cellular behaviors regulated by sphingolipids--must be borne in mind when evaluating the pathologic effects of fumonisins.