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D L Mann

Publications and source records attributed to D L Mann.

At least 73 records · Page 4Linked to original sources
PubMed1997

Comparison of HIV-1 envelope-specific CD4+ T cell lines simultaneously established from peripheral blood mononuclear cells and lymph node biopsy in HIV-1-infected individuals.

HIV-1 envelope-specific CD4+ T cell lines were established simultaneously from PBMC and lymph node mononuclear cells of two HIV-1-infected patients. Three recombinant envelope proteins were used to establish the CD4+ T cell lines: gp160NL4-3, gp120IIIB, and gp120MN. Six T cell lines were established from the first patient, one for each Ag from each compartment, and four T cell lines, two per compartment, were established from the second patient. Each line was challenged with a panel of overlapping peptides spanning the entire gp120 sequence to define its T cell epitope specificity. The pattern of recognition for all the lines from any given patient was similar between compartments. Each patient had a different pattern of peptide recognition. TCR analysis showed a heterogeneous usage of Vbeta between lines with same peptide specificity and established from different compartments. These data suggest that the cellular immune response does not phenotypically vary between the peripheral blood and lymph node compartments, but demonstrates genotypic heterogeneity, showing possible redundancy of the immune response to HIV-1 gp160.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Frequency of HLA allele-specific peptide motifs in HIV-1 proteins correlates with the allele's association with relative rates of disease progression after HIV-1 infection.

An HLA allele-specific cytotoxic T lymphocyte response is thought to influence the rate of disease progression in HIV-1-infected individuals. In a prior study of 139 HIV-1-infected homosexual men, we identified HLA class I alleles and observed an association of specific alleles with different relative hazards for progression to AIDS. Seeking an explanation for this association, we searched HIV-1 protein sequences to determine the number of peptides matching motifs defined by combinations of specific amino acids reported to bind 16 class I alleles. Analyzing complete sequences of 12 clade B HIV isolates, we determined the number of allele motifs that were conserved (occurring in all 12 isolates) and nonconserved (occurring in only one isolate), as well as the average number of allele motifs per isolate. We found significant correlations with an allele's association with disease progression for counts of conserved motifs in gag (R = 0.73; P = 0.002), pol (R = 0.58, P = 0.024), gp120 (R = 0.78, P = 0.00056), and total viral protein sequences (R = 0.67, P = 0.0058) and also for counts of nonconserved motifs in gag (R = 0.62, P = 0.013), pol (R = 0.74, P = 0.0017), gp41 (R = 0.52, P = 0.046), and total viral protein (R = 0.71, P = 0.0033). We also found significant correlations for the average number of motifs per isolate for gag, pol, gp120, and total viral protein. This study provides a plausible functional explanation for the observed association of different HLA alleles with variable rates of disease progression.

Alleles↗
PubMed1997

Circulating interleukin-6 in severe heart failure.

In a group of patients with New York Heart Association class IV heart failure, significant relations between interleukin-6 and tumor necrosis factor-alpha, and between levels of both interleukin-6 and tumor necrosis factor-alpha and plasma levels of norepinephrine were observed. The present study also demonstrates that in patients with heart failure, elevated levels of tumor necrosis factor-alpha and interleukin-6 may be present even without cachexia.

Adult↗
PubMed1997

Blocking the endogenous increase in HSP 72 increases susceptibility to hypoxia and reoxygenation in isolated adult feline cardiocytes.

BACKGROUND: Heat shock protein (HSP) 72 is a ubiquitous protein that is rapidly induced in response to stress and is thought to constitute an endogenous protective response. Previously, work has focused on the effect of overexpression of HSP 72 in various cell types. We were interested in testing the hypothesis that blocking the increase in HSP 72 that occurs in response to hypoxia or ischemia would be deleterious, thus showing that the endogenous response in cells, particularly cardiac cells, is an important line of defense against cell injury. METHODS AND RESULTS: Isolated adult feline cardiocytes were treated with a 14-mer phosphorothioate antisense (AS) to HSP 72 and then exposed to mild (8 hours) or severe (12 hours) hypoxia. With mild hypoxia, an increase in LDH release, a decrease in MTT uptake, and a decrease in live-to-dead ratios were seen in AS-treated cells compared with control cells and cells treated with the complementary sense sequence or with AS to major histocompatibility complex I. AS treatment converted mild hypoxic injury to a pattern of cell injury seen with severe injury. After severe hypoxia, all treatment groups showed an increase in LDH, a decrease in MTT uptake, and a decrease in live-to-dead ratios; AS-treated cells had the greatest increase in cell injury. AS treatment produced a 40% decrease in HSP 72 levels after hypoxia compared with control cells treated with hypoxia. A dose-response study showed inhibition of the increase in HSP 72 with as little as 5 micrograms (1.24 mumol/L) of AS. CONCLUSIONS: (1) Blocking an increase in HSP 72 with AS increases the susceptibility of adult cardiac myocytes to hypoxic injury. (2) HSP 72 is an important part of the normal cell response to stress and is important in protecting cardiac myocytes from hypoxia and reoxygenation.

Animals↗
PubMed1997

Tumor necrosis factor-alpha provokes a hypertrophic growth response in adult cardiac myocytes.

BACKGROUND: Tumor necrosis factor-alpha (TNF-alpha) is a pleiotropic cytokine with a broad range of concentration-dependent effects. The recent observation that TNF-alpha is expressed by the cardiac myocyte after certain forms of stress suggests that TNF-alpha might contribute to the maintenance of normal tissue homeostasis after environmental injury. Accordingly, the purpose of this study was to examine the effects of TNF-alpha on protein synthesis in cultured adult cardiac myocytes. METHODS AND RESULTS: Cultured adult feline cardiac myocytes were stimulated with 10 to 1000 U/mL TNF-alpha to examine the effects of this cytokine on the rate of protein synthesis and degradation. Stimulation with TNF-alpha led to an accelerated rate of general protein synthesis and a time-dependent decrease in protein degradation in adult cardiac myocytes. The specificity of these findings was demonstrated by studies in which the effects of TNF-alpha on protein synthesis were blocked by a neutralizing anti-TNF-alpha antibody as well as studies in which TNF-alpha-conditioned medium had no effect on protein synthesis in myocytes. In addition to the TNF-alpha-induced increase in the general protein synthesis, stimulation with TNF-alpha led to a 2.4-fold increase in net actin protein synthesis and a 3.3-fold increase in net myosin heavy chain synthesis. Finally, the effects of TNF-alpha on adult cardiac myocytes were shown to be dependent on cell-substrate interaction, suggesting that the cell signaling pathways used by TNF-alpha are dependent on a preserved interaction between cell integrins and the extracellular matrix. CONCLUSIONS: The observation that TNF-alpha provokes a hypertrophic growth response in cardiac myocytes suggests that TNF-alpha may play an important role in myocardial homeostasis after environmental stress.

Actins↗
PubMed1997

Sphingosine mediates the immediate negative inotropic effects of tumor necrosis factor-alpha in the adult mammalian cardiac myocyte.

To determine whether activation of the neutral sphingomyelinase pathway was responsible for the immediate (<30 min) negative inotropic effects of tumor necrosis factor-alpha (TNF-alpha), we examined sphingosine levels in diluent and TNF-alpha-stimulated cardiac myocytes. TNF-alpha stimulation of adult feline cardiac myocytes provoked a rapid (<15 min) increase in the hydrolysis of [14C]sphingomyelin in cell-free extracts, as well as an increase in ceramide mass, consistent with cytokine-induced activation of the neutral sphingomyelinase pathway. High performance liquid chromatographic analysis of lipid extracts from TNF-alpha-stimulated cardiac myocytes showed that TNF-alpha stimulation produced a rapid (<30 min) increase in free sphingosine levels. Moreover, exogenous D-sphingosine mimicked the effects of TNF-alpha on intracellular calcium homeostasis, as well as the negative inotropic effects of TNF-alpha in isolated contracting myocytes; time course studies showed that exogenous D-sphingosine produced abnormalities in cell shortening that were maximal at 5 min. Finally, blocking sphingosine production using an inhibitor of ceramidase, n-oleoylethanolamine, completely abrogated the negative inotropic effects of TNF-alpha in isolated contracting cardiac myocytes. Additional studies employing biologically active ceramide analogs and sphingosine 1-phosphate suggested that neither the immediate precursor of sphingosine nor the immediate metabolite of sphingosine, respectively, were likely to be responsible for the immediate negative inotropic effects of TNF-alpha. Thus, these studies suggest that sphingosine mediates the immediate negative inotropic effects of TNF-alpha in isolated cardiac myocytes.

Animals↗
PubMed1997

The role of cytokines in disease progression in heart failure.

Recent studies have identified the importance of biologically active molecules such as neurohormones as mediators of disease progression in heart failure. More recently it has become apparent that in addition to neurohormones, another portfolio of biologically active molecules, termed cytokines, are also expressed in the setting of heart failure. This article reviews recent clinical and experimental material that suggests that the cytokines, much like the neurohormones, may represent another class of biologically active molecules that are responsible for the development and progression of heart failure.

Animals↗
PubMed1997

Hemodynamic regulation of tumor necrosis factor-alpha gene and protein expression in adult feline myocardium.

Tumor necrosis factor-alpha (TNF-alpha) mRNA and protein biosynthesis were examined in adult feline myocardium in the presence and absence of superimposed hemodynamic pressure overloading. A brief period of hemodynamic pressure overloading ex vivo resulted in de novo TNF-alpha mRNA expression within 30 minutes and de novo TNF-alpha protein production within 60 minutes; neither TNF-alpha mRNA nor protein was detected in hearts perfused at normal perfusion pressures. Moreover, TNF-alpha mRNA and protein biosynthesis were observed in myocyte and nonmyocyte cell types in the pressure-overloaded hearts. To determine whether a simple passive stretch of the myocardium was a sufficient stimulus for TNF-alpha biosynthesis, we examined TNF-alpha mRNA expression in stretched and unstretched papillary muscles. This study showed that myocardial stretch was a sufficient stimulus for the induction of TNF-alpha mRNA biosynthesis. The functional significance of the intramyocardial production of TNF-alpha was determined by examining cell motion in isolated contracting cardiac myocytes treated with superfusates from pressure-overloaded and control hearts. These studies showed that cell motion was depressed in myocytes treated with superfusates from the pressure-overloaded hearts but was normal with the superfusates from the control hearts. Finally, hemodynamic pressure overloading in vivo under physiological conditions was also shown to result in de novo intramyocardial TNF-alpha mRNA biosynthesis. In conclusion, this study constitutes the initial demonstration that the adult mammalian myocardium elaborates biologically active TNF-alpha, both ex vivo and in vivo, in response to hemodynamic pressure overloading.

Animals↗
PubMed1996

Tumor necrosis factor-alpha and tumor necrosis factor receptors in the failing human heart.

BACKGROUND: Tumor necrosis factor-alpha (TNF-alpha) is a proinflammatory cytokine that produces negative inotropic effects in the heart. Recently, elevated levels of TNF-alpha have been reported in patients with advanced congestive heart failure. Although TNF-alpha is thought to exert its deleterious effects by binding to two cell surface receptors, TNFR1 and TNFR2, the level of expression and regulation of TNF receptors in the heart in cardiac disease states is not known. METHODS AND RESULTS: We examined mRNA and protein levels for TNFR1, TNFR2, and TNF-alpha in explanted hearts from organ donors as well as in patients with end-stage dilated cardiomyopathy (DCM) and ischemic heart disease (IHD). Northern blot analysis revealed that mRNA for TNFR1 and TNFR2 was present in nonfailing, DCM, and IHD hearts. TNFR1 and TNFR2 receptor protein levels, as measured by ELISA, were decreased 60% in DCM and IHD patients compared with nonfailing hearts (P < .005). To determine a potential mechanism for the decrease in TNF receptor expression, we measured levels of circulating soluble TNF receptors (sTNFRs) in DCM and IHD patients. This analysis showed that there was a significant one-and-a-half to threefold increase in sTNFRs in DCM (P < .03) and IHD patients (P < .001). Another important finding was that TNF-alpha mRNA and TNF-alpha protein were present in the explanted hearts from DCM and IHD patients but not in nonfailing hearts. CONCLUSIONS: In summary, the results of this study constitute the initial demonstration that TNF receptor proteins are dynamically regulated in patients with advanced congestive heart failure. Moreover, the observation that failing hearts express elevated levels of TNF-alpha suggests that overexpression of this cytokine may be one of several different maladaptive mechanisms responsible for the progressive cardiac decompensation that occurs in advanced heart failure.

Adult↗
PubMed1996

Expression of HLA class I molecules and the transporter associated with antigen processing in hepatocellular carcinoma.

The expression of the HLA class I molecules on the cell surface was investigated in hepatocellular carcinoma (HCC) cell lines using complement-mediated cytotoxicity (CMC) and flow cytometric analysis. Although HLA-A antigens were detected by CMC in all cell lines tested, HLA-B and -C antigens were not detectable in six of seven HCC cell lines. These results were also confirmed by flow cytometric analysis focusing on HLA-Bw4 and Bw6 public antigens. Furthermore, complementary DNA (cDNA) from each cell line was tested for the expression of HLA-A, -B, -C and the transporter associated with antigen processing genes (TAP1 and TAP2). Two cell lines showed a reduced level of one or both of the TAP messenger RNAs (mRNAs), and one of these showed a reduction of HLA-B and -C gene expression as well, but the others had detectable mRNA levels. These results demonstrate that hepatocellular carcinoma cell lines tested in the current study lose or decrease the expression of HLA-B and -C alleles on the cell surface, even though mRNA encoding these alleles is present, suggesting that the loss of the HLA molecules might be caused by posttranscriptional events or failure to transport and load peptides necessary for HLA expression. The selective loss of HLA-B and -C, but not -A, molecules (which also excludes a beta 2-microglobulin defect) is intriguing, and may be attributable to the ability of some of the HLA-A molecules to load signal peptides not requiring TAP transport, or to natural selection of HLA-B or -C locus-specific immune surveillance.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1996

Proinflammatory cytokine levels in patients with depressed left ventricular ejection fraction: a report from the Studies of Left Ventricular Dysfunction (SOLVD).

OBJECTIVES: This study sought to assess proinflammatory cytokine levels in patients in the studies of left ventricular dysfunction trial (SOLVD) in relation to both their New York Heart Association functional classification and their neurohormonal status before randomization. BACKGROUND: Elevated levels of tumor necrosis factor-alpha have been identified in 30% to 40% of patients with heart failure. However, it is unclear which subsets of patients with heart failure elaborate tumor necrosis factor-alpha. It is also unclear what the mechanism for the increased expression of proinflammatory cytokines is. METHODS: Tumor necrosis factor-alpha and interleukin-6 levels were analyzed by enzymes-linked immunoassay using randomly selected plasma samples from patients in functional classes I to III who were enrolled in neurohormonal substudies of the SOLVD trial; age-matched healthy subjects served as the control group. RESULTS: Plasma levels of tumor necrosis factor-alpha (p < 0.001) were elevated in patients in functional classes I to III ([mean +/- SD] 1.95 +/- 0.54, 2.63 +/- 0.48, 6.4 +/- 1.9 pg/ml, respectively) compared with age-matched control subjects (0.75 +/- 0.05 pg/ml) and were progressively elevated in relation to decreasing functional status of the patient. Plasma levels of interleukin-6 (p < 0.001) were elevated in patients in functional classes I to III (3.3 +/- 0.55, 6.2 +/- 1.1, 5.22 +/- 0.9 pg/ml, respectively) compared with age-matched control subjects (1.8 +/- 0.5 pg/ml and were progressively elevated in relation to decreasing functional status of the patient. Cox proportional-hazards analysis showed that there was a trend toward significance between plasma tumor necrosis factor-alpha (p < 0.07) and survival, whereas there was no significant relation for plasma interleukin-6 (p < 0.72). Except for atrial natriuretic factor, which correlated weakly (r = 0.23, p = 0.04) with circulating tumor necrosis factor-alpha levels, there was no significance correlation between neurohormonal and proinflammatory cytokine levels. CONCLUSIONS: Circulating levels of proinflammatory cytokines increase in patients as their functional heart failure classification deteriorates. Moreover, activation of the neurohumoral axis is unlikely to completely explain the elaboration of proinflammatory cytokines in heart failure.

Aged↗
PubMed1996

Basic mechanisms in heart failure: the cytokine hypothesis.

Although the development and progression of heart failure have traditionally been viewed as hemodynamic disorders, there is now an increasing awareness that the syndrome of heart failure cannot be simply and/or precisely defined solely in hemodynamic terms. The inability of the so-called hemodynamic hypothesis to explain the progression of heart failure has given rise to the notion that heart failure may progress as a result of the overexpression of an ensemble of biologically active molecules referred to generically as neurohormones. More recently, it has become apparent that in addition to neurohormones, another portfolio of biologically active molecules, termed cytokines, are also expressed in the setting of heart failure. This article reviews recent clinical and experimental material that suggests that the cytokines, much like the neurohormones, may represent another class of biologically active molecules that are responsible for the development and progression of heart failure.

Animals↗
PubMed1996

The effect of tumor necrosis factor-alpha on cardiac structure and function: a tale of two cytokines.

The ability of the myocardium to successfully compensate for and adapt to stress, ultimately determines whether the heart will decompensate and fail, or whether instead it will maintain preserved function. Despite the importance of the myocardial response to environmental stress, very little is known with respect to the biochemical mechanisms that are responsible for mediating and integrating the stress response in the heart. In the present review we will summarize recent experimental material which suggests that tumor necrosis factor-alpha (TNF-alpha), a pro-inflammatory cytokine that has been identified consistently in virtually all forms of cardiac injury, may play an important role in mediating and integrating the myocardial response to stress. The theme that will emerge from this discussion is that the short-term expression of TNF-alpha within the heart may provide the heart with an adaptive response to stress, whereas long-term expression of TNF-alpha may be frankly maladaptive by producing cardiac decompensation.

Adaptation, Physiological↗
PubMed1996

Stress activated cytokines and the heart.

The ability of myocardium to successfully compensate for, and adapt to, stress ultimately determines whether the heart will decompensate and fail, or whether it will instead maintain preserved function. Despite the importance of the myocardial response to environmental stress, very little is known with respect to the biochemical mechanisms that are responsible for mediating and integrating the stress response in the heart. In the present review we will summarize recent experimental material which suggests that cytokines that are expressed within the myocardium in response to a environment injury, namely tumor necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1) and interleukin-6 (IL-6), may play an important role in initiating and integrating homeostatic responses within the heart. However, these 'stress-activated' cytokines all have the potential to produce cardiac decompensation when expressed at sufficiently high concentrations. Accordingly, the theme that will emerge from this discussion is that the short-term expression of stress-activated cytokines within the heart may provide the heart with an adaptive response to stress, whereas long-term expression of these molecules may be frankly maladaptive by producing cardiac decompensation.

Cytokines↗
PubMed1996

Influence of combinations of human major histocompatibility complex genes on the course of HIV-1 infection.

Major histocompatibility complex (MHC) genes (HLA in humans) regulate the immune response to foreign antigens. Molecular and serologic techniques were used to identify products of HLA class I, class II and transporter (TAP) genes (also part of the MHC) in homosexual seroconverters to human immunodeficiency virus type 1 (HIV-1). Comprehensive statistical analysis produced an HLA profile that predicted time from HIV-1 infection to the onset of AIDS. The profile was developed in a cohort of 139 men and evaluated in a second unrelated cohort of 102 men. In the evaluation cohort, the profile discriminated a sixfold difference between groups with the shortest and longest times to AIDS (P = 0.001). These findings support current theory about control of antigen processing by HLA genes and have implications for immunopathogenesis of HIV-1 and other infections.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Tumor necrosis factor-alpha-induced expression of heat shock protein 72 in adult feline cardiac myocytes.

Tumor necrosis factor-alpha (TNF-alpha) is a proinflammatory cytokine that is elaborated in a myriad of cardiac disease states. Although the biological role for TNF-alpha in the adult heart is not known, a recent study in fetal myocardial cells has shown that this cytokine increases the synthesis of low-molecular-weight stress proteins. These findings suggested the interesting possibility that TNF-alpha might play a functional role in the adult heart by increasing the expression of stress proteins in cardiac myocytes. Accordingly, the purpose of this study was to determine whether TNF-alpha would modulate the expression of heat shock protein 72 (HSP 72), a stress protein that is thought to exert protective effects in the adult heart. Stimulation of adult feline cardiac myocytes with a range of TNF-alpha concentrations (10-1,000 U/ml) for 12 h showed that concentrations of TNF-alpha < or = 10 U/ml had no effect on HSP 72 expression: increased HSP 72 expression was detected 3 h following cytokine stimulation, peaked by approximately 12 h, and then returned toward baseline by 48 h. Additional studies indicated that stimulation of the type 1 TNF receptor was responsible for the increase in HSP 72 expression. In summary, these studies constitute the initial demonstration that TNF-alpha exerts concentration- and time-dependent effects on the expression of HSP 72 in the adult mammalian cardiac myocytes, thus suggesting the interesting possibility that the elaboration of TNF-alpha may enable the heart to better withstand certain forms of stress.

Animals↗
PubMed1995

Expression and functional significance of tumor necrosis factor receptors in human myocardium.

BACKGROUND: Tumor necrosis factor-alpha (TNF-alpha), a proinflammatory cytokine with potent negative inotropic properties, is elaborated in septic shock, acute myocarditis, reperfusion injury, and congestive heart failure. TNF-alpha acts by binding to two specific receptors: TNFR1 and TNFR2. However, neither the presence nor the significance of TNF receptors has been studied in the adult mammalian heart. METHODS AND RESULTS: In the present study, we showed that the adult heart expresses mRNA and receptor proteins for TNFR1 and TNFR2. Moreover, immunohistochemical staining studies localized TNFR1 and TNFR2 to the cardiac myocyte, providing a potential signaling pathway for the deleterious effects of TNF-alpha. The functional significance of the expression of TNFR1 and TNFR2 was explored with the use of a simple cell motion assay in which we assessed the effect(s) of TNF-alpha mutants known to bind selectively to human TNFR1 and TNFR2. We showed that the negative inotropic effect of wild-type TNF-alpha in isolated feline cardiac myocytes was mimicked by the TNF mutant that binds to TNFR1, whereas the TNF mutant that binds to TNFR2 had no significant effect on cell motion. CONCLUSIONS: Results of the present study show that the adult human heart expresses both mRNA and receptor proteins for TNFR1 and TNFR2; moreover, the negative inotropic effects of TNF-alpha in adult cardiac myocytes appear to be initiated by activation of TNFR1.

Adolescent↗