Production of transforming growth factor beta by human T lymphocytes and its potential role in the regulation of T cell growth

The glioblastoma-derived T-cell suppressor factor/transforming growth factor beta 2 inhibits the generation of lymphokine-activated killer (LAK) cells

Glioblastoma cells release factors (G-TsF) which inhibit T-cell proliferation. The G-TsF is a novel member of the transforming growth factor beta family and is identical to TGF beta 2. The effect of G-TsF and TGF beta 2 on the induction of LAK cell activity was investigated by culturing PBL obtained from normal blood donors and brain tumour patients in varying concentrations (50-500 U/ml) of interleukin 2 (IL2) alone or IL2 plus G-TsF/TGF beta 2 (1 ng/ml) for 4 days. Subsequent cytolytic activity was measured against autologous and allogeneic glioblastoma targets, fresh NK-resistant melanoma cells and K562 cells. G-TsF/TGF beta 2 purified from glioblastoma cell cultures and TGF beta 2 isolated from porcine platelets significantly suppressed the generation of LAK cell activity, and the inhibitory effect could be reduced by higher concentrations of IL2. The suppressive effect of TGF beta 2 was most significant during the early stages of LAK cell generation and no inhibitory effect was seen when TGF beta 2 was added directly to the cytotoxicity assay. These results suggest that human glioblastomas may exert an inhibitory influence on the generation of an immune response in vivo through the production of G-TsF/TGF beta 2, and that the inhibitory effect may be modified by IL2.

Bacterial cell wall-induced immunosuppression. Role of transforming growth factor beta

Group A streptococcal cell wall (SCW)-injected rats exhibit a profound immunosuppression that persists for months after the initial intraperitoneal injection of SCW. The goal of this study was to determine the mechanisms for the suppressed T lymphocyte proliferative responses in this experimental model of chronic inflammation. When spleen cell preparations were depleted of adherent cells, restoration of T cell proliferative responses to Con A and PHA occurred, implicating adherent macrophages in the regulation of immunosuppression. Furthermore, macrophages from SCW-treated animals, when cocultured with normal spleen cells in the presence of Con A or PHA, effectively inhibited the proliferative response. Supernatants from suppressed spleen cell cultures were found to inhibit normal T cell mitogenesis. Taken together, these results implicated a soluble macrophage-derived suppressor factor in the down regulation of T cell proliferation after exposure to SCW in vivo. Subsequent in vitro studies to identify this suppressor molecule(s) revealed the activity to be indistinguishable from the polypeptide transforming growth factor beta (TGF-beta). Furthermore, TGF-beta was identified by immunolocalization within the spleens of SCW-injected animals. The cells within the spleen that stained positively for TGF-beta were phagocytic cells that had ingested, and were presumably activated by, the SCW. These studies document that TGF-beta, previously shown to be a potent immunosuppressive agent in vitro, also effectively inhibits immune function in chronic inflammatory lesions in vivo.

Transforming growth factor-beta 2 down-regulates HLA-DR antigen expression on human malignant glioma cells

Transforming growth factor-beta (TGF-beta) is known to have a potent inhibitory influence on several immune functions. It has recently been demonstrated that TGF-beta 2 is identical to the glioblastoma-derived T cell suppressor factor (G-TsF). In the present study, human malignant glioma cell lines were incubated with various concentrations of TGF-beta 2. An optimal concentration of 1 ng/ml TGF-beta 2 produced a partial but significant decrease of HLA-DR (class II) surface antigen expression on glioma cells expressing this antigen, as well as decreased levels of HLA-DR-specific mRNA. The surface expression of other HLA-related molecules, such as HLA-ABC (class I) and beta 2-microglobulin, was not influenced by TGF-beta 2. The suppressive effect of TGF-beta 2 on HLA-DR expression, both at the surface antigenic and cytoplasmic mRNA levels, could be completely overcome by adding relatively high concentrations (500 U/ml) of interferon (IFN)-gamma to the culture system. However, TGF-beta 2 inhibited the enhancement of HLA-DR surface expression produced by low concentrations of IFN-gamma on some cells which initially did not express these antigens. These results show that TGF-beta 2 can act as a regulator of HLA-DR antigen expression on human glioma cells.

Effects of type beta transforming growth factors on haematopoietic progenitor cells

The effects of type beta transforming growth factors (TGF-beta s) on normal human and murine haematopoietic progenitor cells were examined using bone marrow colony assays. In erythroid colony assays, TGF-beta 1 inhibited human CFU-E derived colony formation, BFU-E derived burst formation, and murine BFU-E derived burst formation in a dose dependent manner between 0.1 and 5.0 ng/ml. However, murine CFU-E derived colony formation was unaffected even at a concentration of 5.0 ng/ml TGF-beta 1. In myeloid colony assays, different sensitivity of progenitor cells to the inhibitory effects of TGF-beta s was observed between both species. TGF-beta 1 inhibited murine granulocyte-macrophage colony (GM-colony) formation and granulocyte colony (G-colony) formation in a dose dependent manner between 0.1 and 5.0 ng/ml, but had no remarkable effects on human GM-colony and G-colony formation. TGF-beta 2 also had similar inhibitory effects on haematopoietic progenitor cells, while its inhibitory effect was less potent than that of TGF-beta 1. Thus our data suggest that TGF-beta may be involved in negative regulation of haematopoiesis and that its inhibitory action may be restricted in lineage and/or species specific manner.

Resistance of tumor cells to tumor necrosis factor

TNF-alpha is clearly an important mediator of in vitro tumor cell cytotoxicity induced by the activated macrophage. There are a number of other nonspecific mediators of tumor cell cytotoxicity. These include natural killer cells (51, 52), lymphokine-activated killer cells (53), and natural cytotoxic cells (54). The role that TNF-alpha may play in the cytotoxicity induced by these cell types has not been completely elucidated. Neither is it known what role, if any, TNF-alpha may play in major histocompatibility-restricted (T cell)-mediated tumor cell cytotoxicity. Just as in the case of the activated macrophage, activated cytotoxic T cells produce a number of mediators that inhibit the growth of tumor cells or that induce tumor cell cytotoxicity (55). The role that TNF-alpha plays in the whole process of the regulation of tumorigenesis will not become completely defined until an appropriate set of genetic experiments is completed which utilizes transplantable tumor cell lines selected specifically for resistance to this cytokine in in vivo tumor models. The prominance of TNF-alpha as a mediator of macrophage-induced tumor cell cytotoxicity makes it a candidate for analysis in studies of the early stages of tumorigenesis. We have chosen to study mechanisms of resistance to this monokine. Our results have shown that there are multiple pathways leading to resistance to TNF-alpha-induced tumor cell cytotoxicity. These pathways include the production of transforming growth factors by tumor cells and the amplified expression of certain oncogenes. Other pathways will undoubtedly become elucidated as we begin to define the molecular mechanisms giving rise to the resistant phenotype.

Transforming growth factor beta inhibits formation of osteoclast-like cells in long-term human marrow cultures

Transforming growth factor beta (TGF-beta), a polypeptide present in abundant amounts in bone matrix, was examined for its effects on osteoclast formation by using a human bone marrow culture system in which multinucleated cells (MNCs) with osteoclast characteristics form. TGF-beta strongly inhibited MNC formation at concentrations as low as 1 ng/ml. TGF-beta also completely suppressed the effects of osteotropic factors known to stimulate MNC formation. The inhibitory effect of TGF-beta on osteoclast-like cell formation was more pronounced during the first week of culture, which corresponds to the period of proliferation of mononuclear osteoclast precursors. To examine whether the inhibitory effects of TGF-beta on MNC formation could be due to inhibition of the granulocyte/macrophage progenitor cell [colony-forming unit granulocyte/macrophage (CFU-GM)], the probable precursor for MNC, we tested the effects of TGF-beta on CFU-GM formation in presence of a source of colony-stimulating factor. Unexpectedly, TGF-beta at concentrations (0.1-1 ng/ml) that were inhibitory for MNC formation enhanced day 7 CFU-GM colony formation. This increase in CFU-GM colony formation seen in cultures containing TGF-beta resulted from significantly more granulocytic colonies being formed in the cultures, suggesting that TGF-beta may induce CFU-GM to differentiate preferentially to cells of the granulocytic lineage. Differentiation of CFU-GM to granulocytes rather than osteoclast precursors in response to TGF-beta would result in inhibition of MNC formation by depleting the precursor pool for MNC. These data suggest that inhibition of osteoclast-like cell formation by TGF-beta may be an important mechanism of control of local bone resorption.

Developmental expression of transforming growth factors alpha and beta in mouse fetus

Expression of mRNA for transforming growth factor alpha (TGF-alpha) and TGF-beta 1 during the fetal development of mice was evaluated by in situ hybridization. TGF-alpha mRNA was detected in 9- and 10-day fetuses but was absent in older fetuses. TGF-alpha mRNA-containing cells were found in the placenta, otic vesicle, oral cavity, pharyngeal pouch, first and second branchial arches, and developing kidneys. mRNA for TGF-beta 1 was present in hematopoietic cells of blood islands and capillaries and in the liver as it began to bud off on day 10 and function as a hematopoietic organ.

Transforming growth factor beta 1 selectively regulates early murine hematopoietic progenitors and inhibits the growth of IL-3-dependent myeloid leukemia cell lines

Transforming growth factor beta 1 (TGF-beta 1) has been shown to be associated with active centers of hematopoiesis and lymphopoiesis in the developing fetus. Therefore, the effects of TGF-beta 1 on mouse hematopoiesis were studied. TGF-beta 1 is a potent inhibitor of IL-3-induced bone marrow proliferation, but it does not inhibit the proliferation induced by granulocyte/macrophage, colony-stimulating factor (CSF), granulocyte CSF, and erythropoietin (Epo). TGF-beta 1 also inhibits IL-3-induced multipotential colony formation of bone marrow cells in soft agar, which includes early erythroid differentiation, while Epo-induced terminal differentiation is unaffected. In addition, IL-3-induced granulocyte/macrophage colonies were inhibited; however, small clusters of differentiated myeloid cells were consistently seen in cultures containing IL-3 and TGF-beta 1. Thus, TGF-beta 1 selectively inhibits early hematopoietic progenitor growth and differentiation but not more mature progenitors. TGF-beta 1 is also a potent inhibitor of IL-3-dependent and -independent myelomonocytic leukemic cell growth, while the more mature erythroid and macrophage leukemias are insensitive. Therefore, TGF-beta 1 functions as a selective regulator of differentiating normal hematopoietic cells, and suppresses myeloid leukemic cell growth.

Transforming growth factor beta inhibits bone resorption in fetal rat long bone cultures

TGF-beta 1 is a polypeptide that is abundant in bone matrix, is produced by bone cells, and modulates proliferation and differentiated functions of osteoblastic cells in vitro. TGF-beta 2 is a closely related polypeptide that was originally isolated from bone matrix. TGF-beta 1 has been shown previously to stimulate prostaglandin production in cultures of neonatal mouse calvariae, which causes these bones to resorb. We found similar effects with TGF-beta 2. In comparison, TGF-beta 1 and TGF-beta 2 failed to stimulate bone resorption in fetal rat long bone cultures during a 3-d incubation period in concentrations up to 50-100 times greater than those capable of inducing bone resorption in calvariae. Incubation with TGF-beta 1 for a further 3 d decreased bone resorption up to 30%. Moreover, bone resorption induced by the bone-resorbing agents IL 1 and 1,25-dihydroxyvitamin D3 was partially or completely inhibited by TGF-beta 1 and TGF-beta 2 during the second half of the 6-d incubation period. Inhibition of DNA synthesis with hydroxyurea inhibited bone resorption in long bones in a similar pattern to that seen with TGF-beta 1. The inhibitory effects of TGF-beta 1 and TGF-beta 2 on bone resorption in long bone cultures may therefore be due to inhibition of osteoclast precursor proliferation.

Deactivation of macrophages by transforming growth factor-beta

Macrophage activation--enhanced capacity to kill, in a cell that otherwise mostly scavenges--is essential for host survival from infection and contributes to containment of tumours. Both microbes and tumour cells, therefore, may be under pressure to inhibit or reverse the activation of macrophages. This reasoning led to the demonstration of macrophage deactivating factors from both microbes and tumour cells. In some circumstances the host itself probably requires the ability to deactivate macrophages. Macrophages are essential to the healing of wounds and repair of tissues damaged by inflammation. Yet the cytotoxic products of the activated macrophages can damage endothelium, fibroblasts, smooth muscle and parenchymal cells (reviewed in ref. 6). Thus, after an inflammatory site has been sterilized, the impact of macrophage activation on the host might shift from benefit to detriment. These concepts led us to search for macrophage deactivating effects among polypeptide growth factors that regulate angiogenesis, fibrogenesis and other aspects of tissue repair. Among 11 such factors, two proteins that are 71% similar proved to be potent macrophage deactivators: these are transforming growth factor-beta 1 (TGF-beta 1) and TGF-beta 2.

Transforming growth factor beta stimulates collagen and glycosaminoglycan biosynthesis in cultured rabbit articular chondrocytes

The effect of transforming growth factor beta (TGF-beta) on the production of matrix macromolecules was studied in cultures of rabbit articular chondrocytes. A 24 h exposure to TGF-beta at concentrations of 0.1, 1 and 10 ng/ml markedly stimulated the synthesis of collagen and non-collagen protein. Similar increases of glycosaminoglycan production was observed in the same experimental conditions. The distribution of these newly synthesized macromolecules between cell layer and medium was not altered by treatment with TGF-beta. The factor slightly enhanced the proliferation of chondrocytes in these experiments but its potent effect on matrix synthesis was independent of this growth stimulation. These results indicate that articular chondrocytes are target cells for TGF-beta and suggest that this growth factor could play a role in the repair process of cartilage during osteoarticular diseases.

Bifunctional activity of transforming growth factor type beta on the growth of NRK-49F cells, normal and transformed by Kirsten murine sarcoma virus

Transformation of rat NRK-49F cells (49F) by Kirsten murine sarcoma virus (Ki-MSV) renders these cells (Ki-49F cells) capable of autonomous anchorage independent (AI) growth. As compared to nontransformed 49F cells, the transformation by Ki-MSV does not modify the cell response to transforming growth factor-beta (TGF-beta) in monolayer conditions, but alters it in A I growth conditions. The growth of nontransformed or Ki-MSV-transformed adherent 49F cells is slowed down by porcine TGF-beta, and this effect is reversed by epidermal growth factor (EGF). This decrease in the cell growth rate, induced by TGF-beta, does not affect the cloning efficiency of untransformed and transformed adherent 49F cells. Contrarily, porcine TGF-beta decreases the A I cloning efficiency of Ki-49F cells in agar-gelled medium; this effect is only partly reversed by EGF, which does not synergise with TGF-beta to enhance the A I growth as in the case of untransformed 49F cells. Media conditioned by 49F cells, Ki-49F cells, and chicken embryo fibroblasts contain a latent TGF-beta whose capacity to promote the A I growth of 49F cells and to inhibit that of Ki-49F cells is unmasked by acidification. The same situation exists concerning TGF-beta from human platelets. Neutral extracts are inefficient in both tests of promotion and inhibition of A I growth and contain an acid-activable component with an apparent molecular weight of 600 kd. In acid extracts, a 5-9 kd apparent molecular weight component is responsible for the A I growth enhancement of 49F cells and the A I growth inhibition of Ki-49F cells. Further purification by reverse phase chromatography shows that both activities strictly coelute at the same point (32%) of an acetonitrile gradient. These results indicate that TGF-beta is present in physiological conditions as a latent form which requires activation for inhibiting the A I growth of transformed cells as well as for enhancing that of 49F cells.

Transforming growth factor beta (TGF-beta) induces fibrosis in a fetal wound model

The adult cellular response to tissue injury is characterized by acute inflammation followed eventually by fibroblast proliferation and collagen synthesis. Fetal tissue responses to injury differ markedly from those of the adult; an early acute inflammatory response is absent, few fibroblasts participate, and no collagen is deposited. The object of the present study was to analyze the effects of transforming growth factor beta (TGF-beta), an important regulatory molecule in adult healing events, on the fetal tissue response following wounding. Fetal cellular and extracellular matrix responses to injury were evaluated by placing subcutaneous wound implants containing TGF-beta (0.01 to 10 ng) in fetal rabbits at 24 days gestation (term = 31 days). Histologic responses one to seven days later were compared with fetal and adult control implants without TGF-beta. The histology of the adult implant was characterized by an early acute inflammatory response: by day 7 fibroblasts and collagen were predominant. In contrast, control implants removed from fetal rabbits had no histologic evidence of acute inflammation or fibroblast penetration and no collagen was deposited. When implants containing 1.0 ng TGF-beta were removed from fetal rabbits at seven days, a grossly fibrotic reaction was observed: histology confirmed marked fibroblast penetration with collagen deposition. Fetal implants containing 0.01 ng or 10 ng TGF-beta showed few fibroblasts but had increased numbers of inflammatory cells compared with controls. These observations demonstrate that the fetal response becomes adultlike with fibroblast proliferation and collagen accumulation when TGF-beta is added, thus documenting the responsiveness of the fetal system to adult repair signals.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of Nb2 T-lymphoma cell growth by transforming growth factor-beta

Transforming growth factor-beta (TGF-beta) inhibits proliferation of Nb2 cells, a rat T lymphoma, in response to lactogens and interleukin-2. Prostaglandins may play an important role in the pathway through which TGF-beta exerts its inhibitory actions, because prostaglandin E2 also inhibits proliferation of Nb2 cells, and indomethacin, an inhibitor of prostaglandin synthesis, reverses the inhibitory effects of TGF-beta on Nb2 cell proliferation.

Type beta transforming growth factor reversibly inhibits the early proliferative response to partial hepatectomy in the rat

Type beta transforming growth factor (TGF-beta), a factor produced by many cell types, is a potent inhibitor of hepatocyte DNA synthesis in vitro. To determine whether TGF-beta can influence hepatocyte proliferation in vivo, its effects were examined on the regenerative response of liver to partial hepatectomy (PH) in the rat. Porcine platelet-derived TGF-beta 1 (0.5 micrograms), administered intravenously at the time of PH and 11 hr later, reduced the fraction of hepatocytes engaged in DNA synthesis 22 hr after PH by 67% and inhibited the rate of hepatic [3H]thymidine incorporation by 50%. TGF-beta 2 produced a similar effect. A single dose of 0.5 micrograms of TGF-beta 1 given 11 hr after PH reduced liver [3H]thymidine incorporation by 32%; 4.5 micrograms of TGF-beta 1 or TGF-beta 2 inhibited DNA synthesis by 88% and the labeling index by 86%. Although sensitive to TGF-beta administered 11 hr after PH, late in the G1 phase of the cell cycle, a single dose of 0.5 micrograms given at the time of PH did not significantly influence DNA synthesis 22 hr after PH. The inhibitory effects of TGF-beta were transient; rats treated with two 0.5-microgram doses of TGF-beta at 0 and 11 hr had completely restored their original liver DNA mass 8 days after PH. Administration of 0.5 microgram of either TGF-beta 1 or TGF-beta 2 every 12 hr for 5 days failed to suppress the recovery of hepatic DNA mass. However, the nuclear labeling index of the TGF-beta-treated animals was significantly higher than that of the controls. There was no evidence of cytotoxicity from TGF-beta, as determined by liver histology and plasma concentrations of glucose, insulin-like growth factor I, and two hepatic enzymes. Thus, TGF-beta 1 and TGF-beta 2 reversibly inhibit the proliferative response of liver to PH and may be important in the modulation of normal liver growth and repair.

Transforming growth factor beta stimulates collagen-matrix contraction by fibroblasts: implications for wound healing

An important event during wound healing is the contraction of newly formed connective tissue (granulation tissue) by fibroblasts. The role of polypeptide growth factors in the process of wound contraction was investigated by analyzing the influence of transforming growth factor beta (TGF-beta), platelet-derived growth factor on the ability of fibroblasts to contract a collagen matrix in an in vitro system. TGF-beta, but not the other growth factors tested, markedly enhanced the ability of BHK-21,3T3-L1, and human foreskin fibroblasts to contract collagen gels. These results suggest that TGF-beta released from platelets and inflammatory cells at sites of tissue injury stimulates fibroblasts to contract the provisional wound matrix and that this effect contributes to the ability of TGF-beta to accelerate wound healing.

Growth factor expression in normal, benign, and malignant breast tissue

Several oncogenes seem to encode certain growth factors that may play a part in regulating cell growth in tumours. To assess whether such factors are synthesised endogenously by tumour cells the amounts of messenger RNA for several growth factors known to be synthesised by cancer cells of the breast in vitro were examined in biopsy specimens from 52 malignant and 15 non-malignant tumours of the breast and four samples of normal breast. Transforming growth factor beta messenger RNA was significantly more abundant in breast cancers (32 of 42 (76%) having appreciable amounts) than non-malignant breast tissue (five of 13 (38%) having similar amounts). Transcripts for both transforming growth factor alpha and its receptor, epidermal growth factor receptor, were found more commonly in carcinomas that were negative for oestrogen receptor (64% and 87%, respectively) than in those that were positive (27% and 30%, respectively). Insulin-like growth factor II messenger RNA was present in all 15 samples of non-malignant tissue but was found (in considerably lower amounts) in only 11 of 21 (52%) carcinomas. Epidermal growth factor receptor was also found in all non-malignant breast tissues, compared with 19 of 45 (42%) carcinomas. Platelet derived growth factor A and B chain transcripts coexisted in all normal and benign tissue and most carcinomas. This differing pattern of expression growth factors in tissue from malignant tumours compared with benign tumours and normal breast tissue suggests that some growth factors, particularly transforming growth factors alpha and beta, may have an important role in controlling growth of human breast cancers, particularly those that are hormone independent.

Production of transforming growth factor-beta activity by Ki-1 positive lymphoma cells and analysis of its role in the regulation of Ki-1 positive lymphoma growth

The growth of activated human T lymphocytes in response to interleukin-2 (IL-2) is suppressed by transforming growth factor-beta (TGF-beta). This study presents data that show a diminished response of two human lymphoma cell lines to physiologic regulation by TGF-beta. Cell line L-428 was derived from the malignant pleural effusion of a patient with far advanced nodular sclerosing Hodgkin's disease and has been shown to have clonal gene rearrangements characteristic of both B and T lymphocytes. Cell line Mac-1 was derived from the blood of a patient with clinically indolent cutaneous T-cell lymphoma. Both cell lines express the Hodgkin's disease associated antigen, Ki-1. These Ki-1 positive lymphomas are shown to secrete TGF-beta into serum-free culture media. The addition of picogram quantities of exogenous TGF-beta to cell cultures of indolent Ki-1 lymphoma (Mac-1) suppresses IL-2-dependent mitosis; however, the suppression is less than 45%. This suppression correlates with a decrease in the number of IL-2 receptors. No inhibition of Ki-1 positive Hodgkin's cells (L-428) was observed, and proliferation dependent on polyclonal IL-2 was either not affected or was slightly potentiated by TGF-beta. Receptor analysis indicates the absence of IL-2 and TGF-beta receptors on L-428 cells. Thus, these Ki-1 lymphomas derived from activated lymphocytes appear to secrete TGF-beta activity but continue to proliferate because of defective suppression of IL-2 (and related lymphokine)-dependent DNA synthesis.

Transforming growth factor-beta s are equipotent growth inhibitors of interleukin-1-induced thymocyte proliferation

The effects of two forms of transforming growth factor-beta, TGF-beta 1 and TGF-beta 2, upon the proliferative response of murine thymocytes were investigated in this study. TGF-beta 1 and TGF-beta 2 were found to be equipotent growth inhibitors of interleukin-1 (IL-1)- and phytohemagglutinin (PHA)-stimulated thymocytes when added at the initiation of the cultures. These factors suppressed the proliferative response in a dose-dependent fashion between 0.4 and 100 pM. The proliferative response was maximally inhibited (90% inhibition) at 100 pM. The half-maximal inhibitory dose (ID50) was 6 and 4 pM for TGF-beta 1 and TGF-beta 2, respectively. These factors were less effective or ineffective at suppressing the proliferation of thymocytes which had been prestimulated for 24 to 48 hr by IL-1 and PHA. Neither factor inhibited interleukin-2 (IL-2)-dependent thymocyte proliferation or the proliferation of an IL-2-dependent cytotoxic T cell line (CTL-L), suggesting that the anti-proliferative actions of these factors was by inhibition of cellular events triggered by IL-1. Furthermore, anti-TGF-beta 1 antibodies did neutralize the biological actions of TGF-beta 1 and these antibodies did block the binding of 125I-labeled TGF-beta 1 to cell surface receptors showing that the inhibitory action is mediated through specific receptors for TGF-beta 1 on thymocytes. These antibodies, however, did not neutralize the anti-proliferative action of TGF-beta 2. Although TGF-beta 1 and TGF-beta 2 exhibit very similar biological activities, these molecules are antigenically different and, therefore, have different tertiary structures.

Effects of transforming growth factor type beta upon bone cell populations grown either in monolayer or semisolid medium

Bone has been shown to store large amounts of transforming growth factor type beta (TGF beta) and this has recently been found to be synthesized by bone-forming cells. We report on studies undertaken to examine the effects of platelet-derived TGF beta on different bone cell populations, isolated from 1-day postnatal rat calvaria by sequential enzymatic digestion. In addition, we tried to determine which of these cell populations synthesize TGF beta. In this regard, evidence was collected to indicate that cell populations which were shown to be enriched with osteoblast-like cells synthesize TGF beta. Although the production of the factor appeared to be limited to a particular cell type, its action was found to be of a more general character, as all cell populations were found to respond to TGF beta. Contrary to earlier reports, TGF beta was shown to be inhibitory upon cell proliferation. In this context, growth of cells released during early digestions was reduced considerably more than growth of those released during late digestions. Studies on the effect upon protein synthesis revealed that TGF beta specifically inhibited collagen but not the synthesis of noncollagenous proteins. The synthesis of collagen was altered to a greater extent in cells isolated during late digestions than in cells of the early populations. Further information on the TGF beta-mediated effects on bone cell biology was provided by data showing that both alkaline phosphatase and cAMP production in response to PTH was greatly reduced by TGF beta. Finally, experiments performed to determine whether TGF beta induces any of the bone cell populations to acquire the transformed phenotype revealed that only populations previously shown to be enriched with osteoblast-like cells formed colonies in soft agarose.(ABSTRACT TRUNCATED AT 400 WORDS)

Transforming growth factor-beta: possible roles in carcinogenesis

TGF-beta is the prototype of a large family of multifunctional regulatory proteins. The principal sources of the peptide, platelets and bone, suggest that it plays a role in healing and remodeling processes. In vitro, TGF-beta is chemotactic for monocytes and fibroblasts and can greatly enhance accumulation of extracellular matrix components by fibroblasts. Its ability to stimulate the formation of granulation tissue locally and the demonstration of specific time- and tissue-dependent expression in embryogenesis suggest that similar mechanisms are operative in vivo. By analogy to its effects in wound healing and embryogenesis, it is proposed that TGF-beta, secreted by tumour cells, can augment tumour growth indirectly by effects on the stromal elements. These effects include suppression of the immune response, and enhancement of both angiogenesis and formation of connective tissue. Many tumour cells have escaped from direct growth inhibitory effects of TGF-beta by a variety of mechanisms including inability to activate the latent form of the peptide, loss of cellular receptors for TGF-beta, and loss of functional intracellular signal transduction pathways.

Transforming growth factor-beta-like activity in tumors of the central nervous system

Transforming growth factor type beta (TGF-beta) is a ubiquitous peptide with wide-ranging regulatory functions. This paper reports the initial isolation of TGF-beta activity from human glial and mesenchymally derived tumors and a human glial tumor cell line. While its physiological function at the molecular level is not yet defined, it is believed that this peptide plays a central role in the control of growth and transformation, with the exact role it plays being a function of the entire set of growth factors present in a given cell.

Depletion of protein kinase C induced by an anti HLA class I monoclonal antibody in phytohemagglutinin activated human T cells

Anti HLA Class I Monoclonal Antibody depletes Protein Kinase C (PKC) to 20% of control value in PHA activated human T cells. The effect is reversible: in 24 hours the enzymatic activity returns to 58% of control value. Removal of antibody from the culture medium increases the rate of recovery. Implications of this finding for the modulation by HLA Class I antigens of the proliferative response of T cells to lectins are discussed.

Effect of glucocorticoids, monokines and growth factors on the spontaneously developing responses of the rabbit isolated aorta to des-Arg9-bradykinin

1. The mechanisms modulating the spontaneous induction of contractile responses to agonists of the B1-receptors for kinins have been studied by submitting the rabbit isolated aorta preparation to various in vitro treatments. Des-Arg9-bradykinin (Des-Arg9-BK), applied after 6 h of in vitro incubation was the standard stimulus to monitor this up-regulation process. 2. Specific inhibition of the development of the contractile response to des-Arg9-BK was obtained by exposing tissues continuously to dexamethasone, dexamethasone sodium phosphate (DSP) or cortisol, but not to oestradiol. The maximal extent of the inhibition obtained at high concentrations of glucocorticoids was 86%. 3. No gross inhibition of protein synthesis was observed in the presence of DSP as monitored by [35S]-methionine incorporation into incubated pieces of rabbit aorta. 4. In vivo pretreatment of rabbits with DSP did not reduce further the development of the responses in vitro. DSP applied 15 min before the 6 h recording did not antagonize the contractile effect of the BK fragment. 5. Interleukin 1 (IL-1) and interleukin 2 (IL-2) applied in vitro for the first 3 h of incubation increased the development of the contractile response to des-Arg9-BK. 6. Arachidonic acid (AA), nordihydroguaiaretic acid, tumour necrosis factor-alpha (TNF) and transforming growth factor-beta (TGF-beta) failed to influence the spontaneous development of the response to kinins. 7. Continuous exposure to DSP (100 microM) markedly inhibited the action of stimulants in this system: IL-1, IL-2, epidermal growth factor and muramyl dipeptide. Moreover, the presence of AA (30 microM) did not prevent the inhibitory effect of DSP (100 microM). 8. None of the treatments applied singly or in combination modified the contractile response of the rabbit aorta to noradrenaline. 9. The results are discussed in terms of the possible involvement of immunocompetent cells in the up-regulation of vascular responsiveness to B, receptor agonists.

The glioblastoma-derived T cell suppressor factor/transforming growth factor-beta 2 inhibits T cell growth without affecting the interaction of interleukin 2 with its receptor

Human glioblastoma cells secrete a peptide termed glioblastoma-derived T cell suppressor factor (G-TsF) which inhibits T cell activation. Recently, purification and cloning of G-TsF revealed that G-TsF is identical to transforming growth factor-beta 2. As shown here, G-TsF suppresses the growth of an ovalbumin-specific mouse T helper cell clone (OVA-7T) independently of the stimulus used being either (a) antigen in the presence of antigen-presenting cells, or (b) interleukin 2 (IL2) or (c) phorbol ester and calcium ionophore. Furthermore, in the presence of antibodies against IL2 receptors, G-TsF was able to suppress the residual proliferation still observed when OVA-7T were stimulated with phorbol ester/ionophore. G-TsF failed to inhibit the release of IL3 from OVA-7T activated with IL2. Taken together, the data provide evidence that G-TsF does not directly interfere with interactions of IL2 with its receptor but rather inhibits T cell activation by interfering with an as yet unidentified pathway used by both IL2 and phorbol ester/ionophore. When analyzing different monokines and lymphokines for its effect on G-TsF-induced suppression of T cell growth the only factor found to partially neutralize the effect of G-TsF was tumor necrosis factor-alpha.

Suppression of immune cell function in vitro by recombinant human transforming growth factor-beta

The influence of recombinant human transforming growth factor-beta (rHuTGF-beta) on B-cell function and antigen-specific T-cell responses in vitro was investigated. The addition of 0.1 ng/ml of rHuTGF-beta to cultures of peripheral blood mononuclear cells (PBMC) stimulated with tetanus toxoid resulted in a 50% inhibition of the PBMC proliferative response as determined by [3H]thymidine incorporation. Further, rHuTGF-beta at 0.37 ng/ml caused a greater than 50% reduction in the number of immunoglobulin G-secreting cells among PBMC induced by pokeweed mitogen. rHuTGF-beta also inhibited the generation of allospecific cytotoxic T lymphocytes (CTL) in the mixed-lymphocyte reaction but had no effect on the cytolytic function of CTL generated in the absence of exogenous HuTGF-beta. The results indicate additional immunoregulatory activities for HuTGF-beta and suggest that this factor may play an important role in the regulation of the antigen-dependent immune response.

TGF-beta inhibits growth factor-induced DNA synthesis in hamster fibroblasts without affecting the early mitogenic events

Transforming growth factor beta (TGF-beta) was found to inhibit (IC50 = 0.1 ng/ml) alpha-thrombin or FGF-induced mitogenicity in G0-arrested Chinese hamster lung fibroblasts. Growth factor-stimulated cells became rapidly insensitive to TGF-beta addition during their progression through G0/G1 suggesting that an early step of the mitogenic response was the target of TGF-beta action. Surprisingly, none of the well characterized early mitogenic events commonly triggered by growth factors was found to be affected by TGF-beta addition. These responses included: phosphoinositide breakdown, activation of protein kinase C as determined by EGF receptor down-modulation, subsequent rises in pHi, c-fos, and c-myc mRNA levels, ribosomal protein S6 phosphorylation, the increase in RNA and protein synthesis, induction of ornithine decarboxylase. Only the induction of thymidine kinase, a marker of entry in the S phase, was found to be repressed by TGF-beta, with maximal inhibition when TGF-beta was added early in G1. These results indicate that the inhibitory action of TGF-beta does not affect the growth factors signalling pathways but touches an early event different from those so far analyzed.

Peptide growth factors are multifunctional

The actions of many peptide growth factors include both stimulation and inhibition of cell proliferation, as well as effects unrelated to the control of cell growth. One peptide can have both stimulatory and inhibitory activity in a single cell, depending on the context of the other signal molecules present.

Transforming growth factor-beta modulates the expression of osteoblast and chondroblast phenotypes in vitro

Transforming growth factor beta (TGF-beta) has been shown to induce chondrogenesis by embryonic rat mesenchymal cells (Seyedin et al., J. Biol. Chem., 261: 5693, 1986). Here we report the effects of bovine TGF-beta on the phenotypic expression of differentiated primary rat osteoblastic and chondroblastic cells. Culture of rat calvarial osteoblasts with TGF-beta resulted in a dose and time-dependent decrease in alkaline phosphatase activity. Levels of alkaline phosphatase were reduced to less than 10% of control values by 0.4 nM TGF-beta. The decrease became apparent after 24 hours and reached a maximum by 72 hours. Similarly, treatment of chondroblasts with 0.4 nM TGF-beta resulted in decreased production of cartilage-specific macromolecules: type II collagen and cartilage proteoglycan. Both cell types exhibited dramatic changes in cell shape after treatment with TGF-beta. Modulation of these differentiated markers by TGF-beta could be mimicked, in part, by addition of fibronectin. Addition of dihydrocytochalasin B blocked the inhibition of phenotypic expression by TGF-beta. These results indicate that TGF-beta inhibits phenotypic expression by osteoblasts and chondroblasts in vitro and suggest that this activity of TGF-beta may be mediated through interactions between the extracellular matrix and cytoskeletal elements.

Transforming growth factor beta mRNA increases during liver regeneration: a possible paracrine mechanism of growth regulation

Transforming growth factor beta (TGF-beta) is a growth factor with multiple biological properties including stimulation and inhibition of cell proliferation. To determine whether TGF-beta is involved in hepatocyte growth responses in vivo, we measured the levels of TGF-beta mRNA in normal liver and during liver regeneration after partial hepatectomy in rats. TGF-beta mRNA increases in the regenerating liver and reaches a peak (about 8 times higher than basal levels) after the major wave of hepatocyte cell division and mitosis have taken place and after the peak expression of the ras protooncogenes. Although hepatocytes from normal and regenerating liver respond to TGF-beta, they do not synthesize TGF-beta mRNA. Instead, the message is present in liver nonparenchymal cells and is particularly abundant in cell fractions enriched for endothelial cells. TGF-beta inhibits epidermal growth factor-induced DNA synthesis in vitro in hepatocytes from normal or regenerating liver, although the dose-response curves vary according to the culture medium used. We conclude that TGF-beta may function as the effector of an inhibitory paracrine loop that is activated during liver regeneration, perhaps to prevent uncontrolled hepatocyte proliferation.

A nuclear factor 1 binding site mediates the transcriptional activation of a type I collagen promoter by transforming growth factor-beta

Transforming growth factor-beta (TGF-beta) increases the steady-state RNA levels of several fibroblast extracellular matrix proteins. Using DNA transfection, we show that TGF-beta stimulates the activity of the mouse alpha 2(l) collagen promoter 5- to 10-fold in mouse NIH 3T3 and rat osteosarcoma cells. Deletion analysis indicates that a segment of this promoter between -350 and -300, overlapping a nuclear factor 1 (NF1) binding site, is needed for TGF-beta stimulation. A 3 bp substitution mutation abolishing NF1 binding to this site inhibits TGF-beta activation. Insertion of this NF1 binding site 5' to the SV40 early promoter makes the promoter TGF-beta inducible, but the 3 bp substitution does not. Similarly, when the NF1 binding site at the replication origin of adenovirus 2 and 5 is inserted 5' to the SV40 promoter, the promoter responds to TGF-beta. Therefore an NF1 binding site mediates the transcriptional activation of the mouse alpha 2(l) collagen promoter by TGF-beta.

Partial characterization of a fibroblast-stimulating factor produced by cloned murine T lymphocytes

T cells may regulate tissue fibrosis through the elaboration of soluble factors that stimulate fibroblast growth. The authors previously identified a factor produced by cloned Schistosoma mansoni antigen-specific T cells which served as a competence factor for murine fibroblasts. In the present report, they further characterize this fibroblast-stimulating factor (FsF) and differentiate it from a number of other T-cell-derived lymphokine activities. Crude supernatants from concanavalin-activated cloned T cells were fractionated by gel filtration, ion exchange, or reversed-phase high-pressure liquid chromatography. FsF has an apparent molecular weight of 17,000 and could be differentiated from colony-stimulating factor (CSF), interleukin-3 (IL-3), and interferon (IFN) on the basis of chromatographic characteristics. Highly purified or recombinant IL-2, IL-3, CSF, and IFN had no significant effect on fibroblast proliferation. Furthermore, a monoclonal anti-B-cell-stimulating factor-1 antibody only partially blocked the fibroblast proliferation induced by T-cell supernatants.

Characterization of a T-cell subset prevalent in immunoregulatory disorders in humans

T cells from individuals with certain autoimmune diseases (rheumatoid arthritis, graft-versus-host disease, acquired immunodeficiency syndrome) express high levels of a cell surface sialoglycoprotein with a molecular weight of 140 kDa (gp140). Although a low frequency of gp 140+ T cells was detected in the blood of normal individuals, upon stimulation with autologous EBV-transformed B cells (AMLR), the frequency of expression of gp140 was increased threefold. To further characterize gp 140+ T cells, rosetting techniques with ox erythrocytes coated with monoclonal anti-gp 140 antibody were used to isolate T-cell subsets for phenotypic, cell cycle, and functional analysis. The majority of gp140+ T cells expressed cytotoxic/suppressor (CD8+) phenotype in both normal and AMLR-activated states. Unstimulated gp140+ T cells had significantly greater nucleic acid content, as measured by acridine orange and flow cytometry, than gp140- T cells. Surprisingly, the gp140+ T-cell subset had a less proliferative response in vitro to pokeweed or phytohemaglutinin mitogens. These results suggest that gp140+ T cells in normal individuals and in patients with autoimmune diseases may have been activated previously in vivo and that they are relatively resistant to reactivation in vitro.

Type 1 transforming growth factor beta: amplified expression and secretion of mature and precursor polypeptides in Chinese hamster ovary cells

Recombinant type 1 transforming growth factor beta (TGF-beta) was expressed to high levels in CHO cells by using dihydrofolate reductase (dhfr) gene amplification. The expression plasmid was derived from the pSV2 vectors and contained, in tandem, the simian TGF-beta and mouse dhfr cDNAs. Transcription of both cDNAs was controlled by the simian virus 40 early promoter. Stepwise selection of transfected CHO cells in increasing concentrations of methotrexate yielded cell lines that expressed amplified TGF-beta nucleic acid sequences. The expression plasmid DNA was amplified greater than 35-fold in one of the methotrexate-selected transfectants. The major proteins secreted by these cells consisted of latent TGF-beta and TGF-beta precursor polypeptides, as judged by immunoblots by using site-specific anti-peptide antibodies derived from various regions of the TGF-beta precursor. Levels of recombinant TGF-beta protein secreted by these cells approached 30 micrograms/24 h per 10(7) cells and required prior acidification for optimal activity; nonacidified supernatants were approximately 1% as active as acidified material. Antibodies directed toward sequences present in the mature growth factor readily identified a proteolytically processed recombinant TGF-beta which, on sodium dodecyl sulfate-polyacrylamide gels, comigrated with highly purified natural TGF-beta. In addition to mature recombinant TGF-beta, site-specific antibodies demonstrated the existence of larger TGF-beta precursor polypeptides. The availability of biologically active recombinant type 1 TGF-beta and precursor forms should provide a means to examine the structure, function, and potential in vivo therapeutic use of this growth factor.

Regulation of platelet-derived growth factor gene expression by transforming growth factor beta and phorbol ester in human leukemia cell lines

We studied the expression of the genes encoding the A and B chains of platelet-derived growth factor (PDGF) in a number of human leukemia cell lines. Steady-state expression of the A-chain RNA was seen only in the promonocytic leukemia cell line U937 and in the T-cell leukemia cell line MOLT-4. It has previously been reported that both PDGF A and PDGF B genes are induced during megakaryoblastic differentiation of the K562 erythroleukemia cells and transiently during monocytic differentiation of the promyelocytic leukemia cell line HL-60 and U937 cells. In this study we show that PDGF A RNA expression was induced in HL-60 and Jurkat T-cell leukemia cells and increased in U937 and MOLT-4 cells after a 1- to 2-h stimulation with an 8 pM concentration of transforming growth factor beta (TGF-beta). PDGF A RNA remained at a constant, elevated level for at least 24 h in U937 cells, but returned to undetectable levels within 12 h in HL-60 cells. No PDGF A expression was induced by TGF-beta in K562 cells or in lung carcinoma cells (A549). Interestingly, essentially no PDGF B-chain (c-sis proto-oncogene) RNA was expressed simultaneously with PDGF A. In the presence of TGF-beta and protein synthesis inhibitors, PDGF A RNA was superinduced at least 20-fold in the U937 and HL-60 cells. PDGF A expression was accompanied by secretion of immunoprecipitable PDGF to the culture medium of HL-60 and U937 cells. The phorbol ester tumor promoter tetradecanoyl phorbol acetate also increased PDGF A expression with similar kinetics, but with a mechanism distinct from that of TGF-beta. These results suggest a role for TGF-beta in the differential regulation of expression of the PDGF genes.

Human platelet alpha granules contain a nonspecific inhibitor of megakaryocyte colony formation: its relationship to type beta transforming growth factor (TGF-beta)

Whole blood serum (WBS) and platelet-poor plasma-derived serum (PDS) from the same normal subject were compared for their abilities to support human megakaryocyte (MK) colony formation. In all cases, PDS promoted the growth of a higher number (20-50%) of MK colonies than did WBS. Increasing amounts of WBS decreased the number of colonies, whereas increasing concentration of PDS had no marked effects. Crude platelet extracts or platelet secretory products from thrombin-activated platelets also elicited an inhibition of MK colony formation in a dose-dependent manner. A complete inhibition was found for a dose equivalent to 1.10(9) platelets/ml and a 50% inhibition in a range of 1.10(7)-1.10(8) platelets/ml. These platelet products were also inhibitory for erythroid progenitor growth. Platelets from two patients with gray platelet syndrome elicited only a minor inhibition of MK growth, suggesting that the platelet alpha granule is the origin of this inhibition. When platelet extracts were acid-treated, the biological activity of the inhibitor on CFU-MK and CFU-E growth was 20-50-fold higher. In addition, a potent stimulatory activity on the growth of day 7 CFU-GM was observed. The enhancement of biological activities by acid treatment suggests that type beta transforming growth factor (TGF-beta) could be involved in this platelet inhibitory activity. The homogeneous native TGF-beta (from 1 pg to 1 ng/ml) produced the same effects previously induced by platelet products. It totally inhibited CFU-MK growth (at a 500 pg/ml), it inhibited CFU-E growth, and it stimulated growth of day 7 CFU-GM in the presence of a colony-stimulating factor. The inhibition of CFU-MK growth was also observed on purified progenitors. In conclusion, these results suggest that TGF-beta may be implicated in negative autocrine regulation of megakaryopoiesis. However, since this molecule has ubiquitous biological activities, its physiologic relevance as a normal regulator of megakaryopoiesis requires further investigation.

TGF-beta inhibits the in vitro induction of lymphokine-activated killing activity

Employing serum-free media, human peripheral blood mononuclear cells, and purified recombinant interleukin-2 (IL-2), conditions were observed in which the development of IL-2-driven cytotoxic activity was suppressed. The cytotoxic activity of such IL-2-generated lymphokine activated killing (LAK) was tested against natural killer-resistant cultured tumor cells (Daudi, Raji, and a glioma). LAK generation was inhibited by addition of some normal sera, normal platelets, or some tumor cells. Because recent reports have indicated that transforming growth factor-beta (TGF-beta)-like factors are often secreted by tumors and the acidic alpha granules of platelets and can be present in sera, we tested the effect of purified human TGF-beta on the activation of LAK. Our results indicated that TGF-beta is very suppressive for LAK induction, and can completely prevent both the IL-2-driven proliferation and cytotoxicity at concentrations as low as 5 ng/ml. Titrations of IL-2 and of TGF-beta indicated that the suppression is dose-dependent and can be avoided by employing higher levels of IL-2. It was also found that the suppressive effect of TGF-beta can be overcome by washing suppressed cell populations and further culture in low levels of IL-2. Collectively, these data indicate that TGF-beta can be a potent inhibitor of LAK generation under standard activation conditions, but that this effect is regulated by the relative level of IL-2 and may be overcome and/or reversed in vitro.

Density-dependent inhibition of cell growth by transforming growth factor-beta 1 in normal human fibroblasts

We report here that transforming growth factor-beta 1 (TGF-beta 1) inhibits platelet-derived growth factor (PDGF)-induced DNA synthesis in normal human fibroblasts in a cell density-dependent manner; no inhibition was seen in sparse cultures, approximately 50% inhibition in confluent cell cultures, and an almost total inhibition in dense cultures. The PDGF-inducible genes c-myc and c-fos were induced also by TGF-beta 1. Simultaneous addition of TGF-beta 1 and PDGF resulted in sustained, rather than transient, expression of c-fos mRNA; c-fos mRNA was detected as long as 24 hr after addition of PDGF and TFG-beta 1. TGF-beta 1 also induced mRNA for the A chain, but not the B chain, of PDGF. Conversely, PDGF induced TGF-beta 1 mRNA in sparse but not in dense cultures. These data indicate the existence of a complex interdependent regulation of PDGF and TGF-beta mRNA expression which is influenced by the cell density.

Transforming growth factor beta and inhibition of hepatocellular proliferation

Transforming growth factor beta (TGF beta) is a recently characterized polypeptide that elicits diverse biologic actions in a wide range of cell types in vitro. TGF beta is a bifunctional growth regulator of fibroblasts with either growth stimulation or growth inhibition but inhibits the growth of most epithelial cells. In addition, TGF beta can either block or induce the differentiation of certain cells. TGF beta reversibly inhibits DNA synthesis in normal adult rat hepatocytes and in cells isolated from regenerating liver 12 h and 18 h after partial hepatectomy. However, at 3 h and 6 h after hepatectomy there is a decrease in sensitivity of hepatocytes to growth inhibition by TGF beta. Recent data from other laboratories indicate that TGF beta expression increases substantially in liver after partial hepatectomy and that administration of purified TGF beta in vivo inhibits DNA synthesis in regenerating rat liver. Together with our observations, these findings suggest that TGF beta may play a central role as a negative paracrine growth regulator in adult rat liver.

Transforming growth factor-beta inhibits the in vitro generation of lymphokine-activated killer cells and cytotoxic T cells

The effect(s) of purified transforming growth factor-beta (TGF-beta) and platelet-derived growth factor (PDGF) on the induction and function of lymphokine-activated killer (LAK) cells and cytotoxic T lymphocytes (CTL) was examined. The addition of TGF-beta, but not PDGF, to cultures containing fresh C57BL/6 mouse splenocytes or human peripheral blood lymphocytes plus recombinant interleukin-2 markedly inhibited the development of mouse and human LAK cell activity (measured after 3 days for cytotoxicity against cultured or fresh tumor targets in 4-h 51Cr release assays). The addition of TGF-beta, but not PDGF, to a one-way, C57BL/6 anti-DBA/2, mixed lymphocyte reaction effectively blocked the generation of allospecific CTL as well. However, TGF-beta did not inhibit the effector function of LAK cells or of allospecific CTL when added directly to the short-term cytolytic assay. A second form of homodimeric TGF-beta, type 2, was also found to be suppressive on the development of murine LAK cells and allospecific CTL. Collectively, these data demonstrate that the peptide TGF-beta is a potent inhibitor of LAK cell and CTL generation in vitro.

Chemotactic response of embryonic limb bud mesenchymal cells and muscle-derived fibroblasts to transforming growth factor-beta

Transforming growth factor beta (TGF-beta) was tested for its ability to stimulate a chemotactic response in Stage 24 embryonic chick limb bud mesenchymal cells and muscle-derived fibroblasts. TGF-beta stimulated dose-dependent chemotaxis in both cell populations. Maximal chemotaxis was achieved with a concentration of 5 ng/ml for limb bud cells and as low as 15 pg/ml for muscle-derived fibroblasts. TGF-beta was not chemokinetic at these levels. Several other proteins found in bone, namely fibronectin, type I collagen, and osteonectin, were not chemotactic. However, both Bone Gla-protein and basic-FGF were found to be chemotactic but less effective than TGF-beta. Comparison with extracts of adult bone indicates that while TGF-beta is a potent chemoattractant, it does not account for all the chemotactic activity found in adult bone.

Cytokines: molecular and biological characteristics

Cytokines are soluble molecules with many cells as the source of their origin and as targets for their actions. They are pleiotropic in their biological functions. Some cytokines are distinct with respect to their molecular structure yet they have overlapping biological properties (Interleukin 1 and tumor necrosis factors). Others are structurally distinct and often have contrasting biological activities (e.g. tumor necrosis factors and transforming growth factor-beta). In this article I have briefly reviewed the molecular and biological properties of four cytokines that appears to play an important role in the pathogenesis of certain immunoinflammatory disorders. It is also to be stressed that there are additional cytokines (e.g. granulocyte-monocyte colony stimulating factors, interleukin 2, interferons etc.) that could also play a role in the pathogenesis of immunoinflammatory disorders.

Transforming growth factor beta-1 in acute myocardial infarction in rats

TGF-beta 1 has been examined in the heart during myocardial infarction caused by ligation of the left coronary artery. Infarcted and uninfarcted myocardium have been compared by immunohistochemical staining of TGF-beta 1 and by Northern blot analysis of mRNA. Normal ventricular myocytes are strongly stained by an antibody to TGF-beta 1. Progressive loss of staining of these myocytes begins within 1 hr after coronary ligation. However, by 24-48 hr after ligation, intense staining of myocytes at the margin of infarcted areas is seen. Northern blots of infarcted myocardium 48 hr after ligation show a 3- to 4-fold increase in the principal 2.4 kb TGF-beta 1 mRNA; there is also a marked increase in a minor 1.9 kb transcript. In the same tissue samples, there is a 2-fold decrease in the mRNA for the glycolytic enzyme, glyceraldehyde-3-phosphate dehydrogenase. The results indicate a significant role for TGF-beta in the response of the heart to injury.

Inhibition of the proliferative response of human B lymphocytes to B cell growth factor by transforming growth factor-beta

The effects of transforming growth factor-beta (TGF-beta) on the proliferative response of human B cells to the low molecular weight B cell growth factor (BCGF) have been investigated in this study. It was found that TGF-beta, at picomolar concentrations, strongly inhibited the BCGF-induced proliferation of anti-mu chain or Staphylococcus aureus Cowan I-activated human B cells and also of a BCGF-dependent cell line derived from a human lymphocytic nodular lymphoma. This inhibitory effect was detected in normal and serum-free culture conditions. The suppression was greatly reduced when TGF-beta was added to the culture one day after BCGF and could be reverted by removing TGF-beta from the culture medium. Since TGF-beta has been detected in supernatants from activated T cells, this factor may represent an important regulatory molecule in the feedback control of B cell activation.