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Biomedical subjects

S P Atamas

Publications and source records attributed to S P Atamas.

13 recordsLinked to original sources
PubMed1999

Antagonistic effects of an alternative splice variant of human IL-4, IL-4delta2, on IL-4 activities in human monocytes and B cells.

IL-4 is a pleiotropic cytokine which exerts its actions on various lineages of hematopoietic and nonhematopoietic cells. This cytokine is one of the central regulators of immunity in health and disease states. An alternative splice variant, in which the second of four exons is omitted, has been recently described and designated as IL-4delta2. The variant has been previously described as a potential naturally occurring antagonist of human IL-4 (hIL-4)-stimulated T cell proliferation. In this study, we investigated the effects of recombinant human (rh) IL-4delta2 on monocytes and B cells. In monocytes, rhIL-4delta2 blocked inhibitory action of hIL-4 on LPS-induced cyclooxygenase-2 expression and subsequent prostaglandin E2 secretion. In B cells, rhIL-4delta2 was an antagonist of the hIL-4-induced synthesis of IgE and expression of CD23. Our results broaden the spectrum of hIL-4-antagonistic activities of rhIL-4delta2, thus creating the background for the potential use of rhIL-4delta2 as a therapeutic anti-hIL-4 agent.

Alternative Splicing↗
PubMed1999

Vasculitis in the Palmerston North mouse model of lupus: phenotype and cytokine production profile of infiltrating cells.

OBJECTIVE: To define the phenotype of cells in the perivascular and vascular infiltrates of Palmerston North (PN) mice and the cytokines that those cells produce. METHODS: Immunohistologic analysis, flow cytometric analysis, and reverse transcriptase-polymerase chain reaction (RT-PCR) studies were performed on tissues and cells from female PN mice and age-matched and sex-matched DBA/2 mice. RESULTS: With aging, PN mice developed a female-predominant, lupus-like disease, with a severe systemic mononuclear cell perivasculitis and vasculitis. The perivasculitis involved arteries and veins in kidney, liver, brain, and lung; the vasculitis predominantly involved veins and venules. The perivascular and vascular infiltrates in female PN mice were composed mainly of an unusual cell type that expressed phenotypic markers characteristic of both T cells (Thy1+, CD3+, CD4+, T cell receptor + [TCR+]) and B cells (B220+). In addition, the infiltrates contained a smaller number of conventional CD4+,B220- T cells and macrophages. Very few CD8+ T cells or surface Ig+ B cells were seen. Unlike the Thy1+,B220+ T cells present in MRL/lpr mice, most of which were CD4-,CD8- and TCRalpha/beta+, the majority of the Thy1+,B220+ T cells in the perivascular/vascular infiltrates of PN mice were CD4+ and expressed either TCRalpha/beta or TCRgamma/delta. By immunohistologic staining, the cells in the perivascular and vascular infiltrates in the kidneys of older PN mice were shown to produce interleukin-4 (IL-4), IL-6, and IL-10, but not IL-2, interferon-gamma, transforming growth factor beta, tumor necrosis factor alpha, or IL-1beta. By RT-PCR, the kidneys of older PN mice were found to express high levels of IL-4, IL-6, and IL-10 messenger RNA. CONCLUSION: The vascular and perivascular infiltrates in PN mice are composed predominantly of an unusual subpopulation of T cells that are Thy1+,B220+,CD4+,CD8-, express either TCRalpha/beta or TCRgamma/delta, and produce mainly type 2 cytokines. The exact role of these cells in the immunopathogenesis of lupus-like disease in PN mice remains to be elucidated.

Animals↗
PubMed1999

Production of type 2 cytokines by CD8+ lung cells is associated with greater decline in pulmonary function in patients with systemic sclerosis.

OBJECTIVE: This study addresses the hypothesis that a profibrotic pattern of cytokines is produced in the lungs of patients with systemic sclerosis (SSc) and causes fibrosis. METHODS: Using a reverse transcriptase-polymerase chain reaction technique, interleukin-4 (IL-4), IL-5, and interferon-gamma (IFNgamma) messenger RNA (mRNA) were measured in unseparated CD8+ and CD4+ bronchoalveolar lavage (BAL) cells from SSc patients and healthy controls. To confirm the results, CD8+ T cells were cloned from BAL fluids, and the pattern of cytokine mRNA made by these cells was determined. Serial pulmonary function tests were done. RESULTS: BAL cells from healthy controls made IFNgamma mRNA, with no or little IL-4 or IL-5 mRNA. In contrast, BAL cells from the majority of SSc patients made IL-4 and/or IL-5 mRNA, with or without approximately equal amounts of IFNgamma mRNA. This pattern of cytokines was made by CD8+ T cells, which were increased in the lungs of these SSc patients. Patients whose BAL cells made this type 2 pattern of cytokine mRNA had a significant decline in forced vital capacity over time after the BAL, whereas patients whose BAL cells made IFNgamma mRNA alone did not. Both wild-type and an alternative splice variant of IL-4 mRNA were increased in BAL cells from SSc patients. Both forms of IL-4 stimulated alpha2(I) collagen mRNA in human dermal and lung fibroblasts. CONCLUSION: The type 2 pattern of cytokine mRNA produced by BAL cells from SSc patients differs from unopposed IFNgamma production found in healthy BAL cells. This production of type 2 cytokine mRNA by CD8+ T cells is associated with a significant decline in lung function over time, which suggests a pathologic role for these T cells in interstitial fibrosis in SSc.

Adolescent↗
PubMed1998

5'-degenerate 3'-dideoxy-terminated competitors of PCR primers increase specificity of amplification.

Amplification of a product in PCR with specific primers may be viewed as an artificial Darwinian-type "selection of the fittest". In other selective systems, such as general evolution, immune system and probably brain cortex, the stringency of selection is not absolute but rather degenerate, with selection of many highly fit units, not limited, however, to only the fittest. In PCR also, annealing of the primers is not absolutely specific. The subsequent amplification frequently leads to amplification of not only the desired product but also to less-specific sequences. Using theoretical analysis of the degenerate mode of selection, we predict theoretically and prove experimentally that 5'-degenerate, 3'-dideoxy-terminated competitors of PCR primers can be used to dramatically improve the specificity of PCR amplification without affecting the quantitation of the final specific product.

Animals↗
PubMed1997

Alternative splice variants of cytokines: making a list.

The cytokine network is an extremely complicated and redundant system of mutually interdependent pleiotropic cytokines that interacts with a variety of cells, tissues and organs producing various regulatory effects, both local and systemic. Recent studies have revealed a new source of complexity in the cytokine network--alternative splicing. This minireview attempts to summarize the available data on the alternative splicing of cytokines and its regulatory significance.

Alternative Splicing↗
PubMed1997

Molecular model of an alternative splice variant of human IL-4, IL-4 delta 2, a naturally occurring inhibitor of IL-4-stimulated T cell proliferation.

The molecular model of IL-4 delta 2, a naturally occurring splice variant of human IL-4 with exons 1, 3, and 4 in an open reading frame, is described. The second exon codes the main part of the long loop AB connected the helices A and B in parallel superposition. Therefore the hydrophobic core and the native fold of the rest part of IL-4 delta 2 molecule could be preserved without any significant changes only in the case of revolution of the helix A relative to other helices. In the result, the dominated a left-handed four-helix bundle structure of IL-4 with an up-up-down-down structural pattern is transformed to the IL-4 delta 2 structure with a down-up-down-down structural pattern.

Humans↗
PubMed1996

Identification and characterization of two alternative splice variants of human interleukin-2.

Our previous work showed that alternative splicing is used to make an inhibitory variant of human interleukin (IL)-4. Because of homology between IL-4 and IL-2 proteins and receptors, we tested whether alternative splicing is used to generate similar inhibitory variants of human IL-2. Messenger RNA from peripheral blood mononuclear cells was subjected to reverse transcription-polymerase chain reaction using IL-2 exon 1- and exon 4-specific primers. Two amplification products, named IL-2delta2 and IL-2delta3, were found in addition to the native IL-2 product. The IL-2delta2 cDNA sequence was identical to IL-2 cDNA throughout the entire coding region, except exon 2 was omitted by alternative splicing. In IL-2delta3 cDNA, the third exon of IL-2 was omitted by alternative splicing. Unlike IL-2, IL-2delta2 and IL-2delta3 did not stimulate T cell proliferation. However, both inhibited IL-2 costimulation of T cell proliferation, and both inhibited cellular binding of rhIL-2 to high affinity IL-2 receptors. Thus, IL-2 is the second cytokine that uses alternative splicing to generate variants that are competitive inhibitors.

Alternative Splicing↗
PubMed1996

An alternative splice variant of human IL-4, IL-4 delta 2, inhibits IL-4-stimulated T cell proliferation.

Alternative splicing of mRNA can generate protein isoforms that are preferentially expressed in different tissues or during different states of cell differentiation or activation. Protein isoforms may have different functions. In this study, we cloned, expressed, and tested functional effects of a naturally occurring splice variant of human IL-4, called IL-4 delta 2. In IL-4 delta 2, the second exon of IL-4 is omitted by alternative splicing, with exons 1, 3, and 4 joined in an open reading frame. We found that IL-4 delta 2 RNA is expressed in the PBMC of all donors tested, usually in lower amounts than IL-4 RNA. In contrast, IL-4 delta 2 RNA is expressed in much higher levels than IL-4 RNA in thymocytes and bronchoalveolar lavage cells, suggesting tissue specificity of expression. IL-4 delta 2 cDNA was expressed in yeast. Recombinant human (rh) IL-4 delta 2 was partially purified and found to be glycosylated, with a protein core of 13 to 15 kDa. Unlike rhIL-4, rhIL-4 delta 2 did not act as a costimulator for T cell proliferation. However, rhIL-4 delta 2 inhibited the ability of rhIL-4 to act as a T cell costimulator. Inhibition was independent of glycosylation and was not mediated by toxicity. Iodinated IL-4 delta 2 was found to bind specifically to human PBMC and tumor lines known to express IL-4 receptors. Excess unlabeled IL-4 inhibited cellular binding of labeled IL-4 delta 2. Thus, rhIL-4 delta 2 is a naturally occurring splice variant of IL-4 that is preferentially expressed in the thymus and airways and inhibits function of complete IL-4. The balance between IL-4 and IL-4 delta 2 may be important in the regulation of IL-4 effects.

Amino Acid Sequence↗
PubMed1996

Self-organization in computer simulated selective systems.

In certain biologic systems, the signal selects functional or numerical expansion of the recognizing elements. Examples of these systems include the immune system, brain cortex, and evolution. One common feature of these Darwinian-type systems is degenerate recognition, in which one signal can recognize several different elements, with different affinities and consequences. For example, T cell antigen receptors and antibodies demonstrate relative but not absolute specificity of recognition. Thus, the variables of dose of the signal and affinity of the recognizing element modulate the outcome. Another feature of these systems is the ability to create self-organized patterns, which do not mirror the incoming signals. The hypothesis of this study is that degenerate recognition with subsequent selection of recognizing elements can explain self-organization of these systems. An entirely numerical model was explored, using the cellular automata approach. Three intrinsic features of a common selective system were incorporated into this model: a large number of recognizing elements; degenerative recognition of stimuli by these elements; and subsequent selection. Different numerical patterns of incoming stimuli were tested. The model showed self-organizing dynamics. Usually, the population of recognizing elements demonstrated an initial period of equilibrium, then a chaotic transitional state, and, finally, the bifurcational appearance of a stable self-organized pattern. The final resolution into a stable pattern can be either gradual or quasi-saltational. I conclude that systems with a large number of recognizing elements, degenerative recognition, and selection of recognizing elements can self organize based upon the pattern of the incoming stimuli.

Computer Simulation↗
PubMed1996

Hemostatic changes after dietary coenzyme Q10 supplementation in swine.

Improved cardiovascular morbidity and mortality have been observed in several clinical studies of dietary supplementation with coenzyme Q10 (CoQ10). We elucidated the effect of CoQ10 on certain hemostatic parameters that may influence the progression of heart disease. Twelve Yorkshire swine were randomized to receive diet supplementation with either CoQ10 or placebo for 20 days. Blood samples were obtained at baseline and at the end of the feeding period. At the end of the protocol, there were no significant differences in hemostatic parameters in the placebo group. A significant increase in total serum CoQ10 level (from 0.39 +/- 0.06 to 0.96 +/- 0.04 microgram/ml, p < 0.001) was noted after the feeding period in the CoQ10-supplemented group. We observed significant inhibition of ADP-induced platelet aggregation (-9.9%) and a decrease in plasma fibronectin (-20.2%), thromboxane B2 (TXB2, -20.6%), prostacyclin (-23.2%), and endothelin-1 (ET-1, -17.9%) level. There were no changes in the plasma concentrations of the natural antithrombotics [antithrombin-III (AT-III), protein S, and protein C] after CoQ10 supplementation. CoQ10 supplementation in a dose of 200 mg daily is associated with mild antiaggregatory changes in the hemostatic profile. Clinical beneficial effects of CoQ10 may be related in part to a diminished incidence of thrombotic complications.

Angiotensin III↗
PubMedDate not supplied

Generation of a variant of human interleukin-4 by alternative splicing.

A second species of interleukin-4 (IL-4) mRNA was identified using both a reverse transcription-polymerase chain reaction and an RNase protection assay. This novel IL-4 mRNA was 48 base pairs smaller than IL-4 mRNA, which is the size of IL-4 exon 2. Sequence data of cloned cDNA demonstrated that this variant contained IL-4 exons 1,3 and 4, with exon 1 spliced directly to exon 3 in an open reading frame. The entire protein encoding region of this variant, named IL-4 delta 2, was identical to IL-4 except for the omission of exon 2. IL-4 delta 2 mRNA was detected in all human peripheral blood mononuclear cells tested and in purified CD3+ T cells. Amounts of both IL-4 and IL-4 delta 2 mRNAs increased upon T cell activation, although IL-4 mRNA increased to a greater extent than IL-4 delta 2 mRNA did. Human IL-3, IL-5, IL-13, and granulocyte macrophage-colony stimulating factor did not use alternative splicing to delete exon 2. We speculate that IL-4 delta 2 may regulate IL-4 function.

Alternative Splicing↗