Biomedical subjects

F Bühling

Publications and source records attributed to F Bühling.

45 records · Page 3Linked to original sources

PubMed1996

CD26 mediates the action of HIV-1 Tat protein on DNA synthesis and cytokine production in U937 cells.

The human immunodeficiency virus 1 (HIV-1) Tat protein is known to be capable of suppressing antigen- and CD3-induced activation of human T cells. Previously, it was shown that Tat can bind to the dipeptidyl peptidase IV (DP IV, CD26) and inhibit the degradation of the chromogenic substrate Gly-Pro-p-nitroanilide. Using the method of free zone capillary electrophoresis, here we have shown that the DP IV-catalyzed hydrolysis of the NH2-X-Pro-containing cytokine peptides IL-2(1-12), IL-1 beta(1-6), and IL-6(1-12) was also significantly inhibited by the Tat protein. Moreover, HIV-1 Tat at a concentration of 10 micrograms/ml was found to have a strong suppressive effect on DNA synthesis and IL-1 beta production, but stimulates secretion of IL-1 receptor antagonist (IL-1RA) and TNF-alpha of CD26-expressing U937-H cells. It did not impair neither DNA synthesis nor cytokine production of low CD26-expressing U937-L cells. Similar results have been found with synthetic DP IV/CD26 inhibitors (Immunobiol., 1994, vol. 192, pp. 121-136). These data strongly suggest that Tat protein is a potent "natural" inhibitor of DP IV/CD26, and they support the hypothesis that DPIV plays a role in Tat's immunosuppressive activity.

Cytokines↗

PubMed1995

Functional role of CD26 on human B lymphocytes.

CD26 is a well-known activation marker on T cells and natural killer (NK) cells [1]. It is identical with the ectopeptidase dipeptidyl peptidase IV (DP IV). The expression of CD26 on B cells has been discussed controversially [2,3]. We have studied the expression of this enzyme on B cells from the peripheral blood of healthy donors and of CVID patients, on cells of the Daudi Burkitt line and the EBV-transformed B-cell lines Jojo and Laz509. DP IV was detected by using anti-CD26 monoclonal antibodies and with help of specific enzyme substrates. Further the influence of specific synthetic DP IV inhibitors on mitogenic activation of purified B cells and DNA synthesis of cell lines was studied. We could show that in both groups 0-5% of freshly isolated CD20-positive B cells do express the CD26 antigen. After stimulation with pokeweed mitogen or St. aureus protein, the fraction of CD26-positive cells was enhanced up to 51% and 36%, respectively. Interestingly, induction of CD26 expression on B cells from CVID patients occurs in a manner similar to the B cells from healthy donors. Treatment of peripheral blood B cells and B-cell lines with highly specific competitive DP IV inhibitors leads to a significant inhibition of DNA synthesis in a dose-dependent manner. These data show that CD26 can be considered to be an activation marker not only of T- and NK cells but also of a main population of B cells, suggesting an involvement of CD26 in B-cell activation.

B-Lymphocytes↗

PubMed1995

Transforming growth factor beta 1 inhibits interleukin-10 mRNA expression and production in pokeweed mitogen-stimulated peripheral blood mononuclear cells and T cells.

The multifunctional cytokine transforming growth factor-beta 1 (TGF-beta 1) is known to inhibit the proliferation of lymphocytes. Whether this effect is a result of a direct action of TGF-beta 1 or an involvement of other "immunoinhibitory" cytokines is not yet clear. Here we have analyzed the effects of TGF-beta 1 on IL-10 and IL-1RA production in pokeweed mitogen-stimulated peripheral blood mononuclear cells (PBMC) and purified T lymphocytes. We show in these systems that TGF-beta 1 at a concentration of 10 ng/ml significantly suppresses both IL-10 mRNA expression and IL-10 production. IL-2 and IL-6 were capable of abolishing the effect of TGF-beta 1 on DNA synthesis and production of IL-10 by T lymphocytes in an additive manner. However, TGF-beta 1 did not influence IL-1RA production in PWM-stimulated PBMC. The present data show that the inhibitory effect of TGF-beta 1 on mitogen-activated immune cells is not the consequence of induction of the inhibitory cytokines IL-10 or IL-1RA but rather an inhibitory action on the production of IL-2 and/or IL-6.

DNA↗

PubMed1994

Prenylated proteins and lymphocyte proliferation: inhibition by d-limonene related monoterpenes.

The aim of the present study was to explore the role of post-translational isoprenoid modification of cellular proteins in the proliferation of human lymphocytes. We here report that treatment of phytohemagglutinin-stimulated peripheral blood mononuclear cells with monoterpenes including d-limonene, perillic acid and perillyl alcohol (0.5-5 mM) which selectively inhibit the isoprenylation of 21-26-kDa proteins resulted in a dose-dependent inhibition of DNA synthesis. Cell cycle analysis revealed that perillic acid arrested cells in G1 and prevented cells from entering S phase in a manner similar to that induced by the specific 3-hydroxy-3-methylglutaryl-CoA reductase inhibitor, compactin. However, unlike compactin, the perillic acid-induced effects on lymphocyte proliferation were not prevented by addition of mevalonate. We also examined the incorporation of [3H]mevalonate into proteins in resting and phytohemagglutinin-stimulated lymphocytes during the first 30 h of culture. While in unstimulated lymphocytes radioactivity was predominantly incorporated into a cluster of 21-26-kDa proteins, mitogenic stimulation was associated with a striking increase in [3H]mevalonate incorporation into a protein (approximately 68 kDa) with migration characteristics similar to that of nuclear lamin B. Treatment of phytohemagglutinin-stimulated lymphocytes with 5 mM d-limonene, 2.5 mM perillic acid or 1.25 mM perillyl alcohol strongly suppressed [3H]mevalonate-labeling of proteins to a degree that correlated with the level of DNA synthesis inhibition. These findings suggest that those mevalonate-derived products required for lymphocyte proliferation may include one or more isoprenylated proteins and that the isoprenylation of these proteins is required for cell cycle progression.

Cell Cycle↗

PubMed1994

Transforming growth factor-beta 1 (TGF-beta 1) inhibits DNA synthesis of PWM-stimulated PBMC via suppression of IL-2 and IL-6 production.

The multifunctional cytokine transforming growth factor-beta 1 (TGF-beta 1) is known to inhibit the proliferation of lymphocytes. However, the role of TGF-beta 1 in the production and secretion of various interleukins is not yet clear. In this study we have analysed in parallel the effects of TGF-beta 1 on both DNA synthesis and production of the cytokines IL-1, IL-2, IL-6, and TNF-alpha by pokeweed mitogen-stimulated peripheral blood mononuclear cells. With this stimulation system we show that TGF-beta 1 at a concentration of 15 ng/ml significantly suppresses IL-2 and IL-6 production. The release of IL-1 and TNF-alpha, however, was not influenced under these conditions. Under similar conditions DNA synthesis of PWM-stimulated PBMC was found to be inhibited by 50 +/- 10%. Using flow cytometric methods we could demonstrate that TGF-beta 1 arrested the cells in the G0/G1 phase of the cell cycle. Taken together, these results suggest that TGF-beta 1 may suppress immune responses by inhibiting the endogenous production of IL-2 and IL-6.

DNA↗

PubMed1994

Inhibitors of dipeptidyl peptidase IV (DP IV, CD26) specifically suppress proliferation and modulate cytokine production of strongly CD26 expressing U937 cells.

Various studies from different laboratories have shown that the membrane ectoenzyme dipeptidyl peptidase IV (DP IV, CD26) expressed in T and NK cells is involved in the regulation of DNA synthesis and cytokine production. In this paper, we performed a biochemical and functional characterization of dipeptidyl peptidase IV on the human histiocytic lymphoma cell line U937. Using U937 clones expressing low to high levels of membrane localized CD26, we found that the synthetic reversible inhibitors of DP IV, Lys-[Z(NO2)]-thiazolidide and Lys-[Z(NO2)]-piperidide, have different effects on all functions. In U937-H cells that strongly express high levels of CD26, DP IV inhibitors were shown to suppress DNA synthesis and production of IL-1 beta, but stimulate the secretion of the IL-1 receptor antagonist (IL-1RA) and of TNF-alpha. In contrast, both inhibitors did not influence the cytokine production and DNA synthesis in U937-L cells exhibiting low level CD26 expression. These data support the hypothesis that CD26 plays a crucial role in proliferation and cytokine production, not only in T cells, but also in other cell systems, and that enzymatic activity is essential for its function.

Blotting, Western↗

PubMed1993

Dipeptidyl peptidase IV (CD26) on human lymphocytes. Synthetic inhibitors of and antibodies against dipeptidyl peptidase IV suppress the proliferation of pokeweed mitogen-stimulated peripheral blood mononuclear cells, and IL-2 and IL-6 production.

In the present report, we describe that synthetic inhibitors of and polyclonal and monoclonal antibodies against the membrane ectoenzyme dipeptidyl peptidase IV (DP IV, CD26) inhibit the production of IL-2 and IL-6 and, concomitantly, DNA synthesis of pokeweed mitogen-stimulated peripheral blood mononuclear cells (PBMC). The release of IL-1 and TNF-alpha, was not influenced under these conditions. The data support the hypothesis that DP IV, possibly in conjunction with other peptidase, is involved in the regulation of activation and proliferation of T lymphocytes.

Antibodies, Monoclonal↗

PubMed1993

Aminopeptidase N (CD13, EC 3.3.4.11.2) occurs on the surface of resting and concanavalin A-stimulated lymphocytes.

Using different approaches evidence is provided that aminopeptidase N (APN, EC 3.4.11.2, CD13) is expressed on the surface of resting and stimulated human lymphocytes. 1) 50% of total Ala-pNA hydrolysis of viable cells was found to be due to the ectoenzyme APN as revealed by titration with the new inhibitor probestin in comparison to purified APN from human kidney (Ki value 6.5 nM). After stimulation with ConA an increase of Ala-pNA hydrolysis was observed from 8 pkat up to 15 pkat/10(6) cells. 2) This correlated with an increase of APN (CD13) surface expression as detected by antibody surface labeling of unstimulated (5-12% CD13 positive cells) and stimulated lymphocytes (28-36% CD13 positive lymphocytes) using polyclonal and monoclonal antibodies. 3) In vivo APN was found to be expressed on the surface of up to 50% lymphocytes isolated from the synovial fluid of rheumatoid patients.

Aminopeptidases↗

PubMedDate not supplied

Expression and functional role of dipeptidyl peptidase IV (CD26) on human natural killer cells.

The expression and functional role of dipeptidyl peptidase IV (DP IV, CD26, EC 3.4.14.5) was studied on human natural killer (NK) cells. Here we show that freshly isolated NK cells do express only low amounts of DP IV. However, after IL-2 stimulation of NK cells (70% purity) surface DP IV expression was significantly increased in a subpopulation (30%) of these cells. Specific DP IV inhibitors (Lys-[Z-(NO2)]-piperidide, Lys-[Z(NO2)]-thiazolidide) and polyclonal antibodies directed against the ectopeptidase suppressed DNA synthesis and cell cycle progression of NK cells. The natural cytotoxic activity of DP IV+ CD56+ cells was found unchanged in comparison to those of DP IV- CD56+ cells. DP IV inhibitors had no effect on the natural cytotoxicity of mononuclear cells. From these data we conclude that DP IV is involved in the regulation of proliferation of NK cells, whereas natural cytotoxicity seems to be regulated independently.

Cell Cycle↗