Localization of transforming growth factor-beta 1, -beta 2 and -beta 3 gene expression in bovine mammary gland

Immune defenses of the mammary gland epithelium of dairy ruminants

The epithelium of the mammary gland (MG) fulfills three major functions: nutrition of progeny, transfer of immunity from mother to newborn, and its own defense against infection. The defense function of the epithelium requires the cooperation of mammary epithelial cells (MECs) with intraepithelial leucocytes, macrophages, DCs, and resident lymphocytes. The MG is characterized by the secretion of a large amount of a nutrient liquid in which certain bacteria can proliferate and reach a considerable bacterial load, which has conditioned how the udder reacts against bacterial invasions. This review presents how the mammary epithelium perceives bacteria, and how it responds to the main bacterial genera associated with mastitis. MECs are able to detect the presence of actively multiplying bacteria in the lumen of the gland: they express pattern recognition receptors (PRRs) that recognize microbe-associated molecular patterns (MAMPs) released by the growing bacteria. Interactions with intraepithelial leucocytes fine-tune MECs responses. Following the onset of inflammation, new interactions are established with lymphocytes and neutrophils recruited from the blood. The mammary epithelium also identifies and responds to antigens, which supposes an antigen-presenting capacity. Its responses can be manipulated with drugs, plant extracts, probiotics, and immune modifiers, in order to increase its defense capacities or reduce the damage related to inflammation. Numerous studies have established that the mammary epithelium is a genuine effector of both innate and adaptive immunity. However, knowledge gaps remain and newly available tools offer the prospect of exciting research to unravel and exploit the multiple capacities of this particular epithelium.

TGF-beta signalling in bovine mammary gland involution and a comparative assessment of MAC-T and BME-UV1 cells as in vitro models for its study

The goal of the dairy industry is ultimately to increase lactation persistency, which is the length of time during which peak milk yield is sustained. Lactation persistency is determined by the balance of cell apoptosis and cell proliferation; when the balance is skewed toward the latter, this results in greater persistency. Thus, we can potentially increase milk production in dairy cows through manipulating apoptogenic and antiproliferative cellular signaling that occurs in the bovine mammary gland. Transforming growth factor beta 1 (TGFβ1) is an antiproliferative and apoptogenic cytokine that is upregulated during bovine mammary gland involution. Here, we discuss possible applications of TGFβ1 signaling for the purposes of increasing lactation persistency. We also compare the features of mammary alveolar cells expressing SV-40 large T antigen (MAC-T) and bovine mammary epithelial cells-clone UV1 (BME-UV1) cells, two extensively used bovine mammary epithelial cell lines, to assess their appropriateness for the study of TGFβ1 signaling. TGFβ1 induces apoptosis and arrests cell growth in BME-UV1 cells, and this was reported to involve suppression of the somatotropic axis. Conversely, there is no proof that exogenous TGFβ1 induces apoptosis of MAC-T cells. In addition to TGFβ1's different effects on apoptosis in these cell lines, hormones and growth factors have distinct effects on TGFβ1 secretion and synthesis in MAC-T and BME-UV1 cells as well. MAC-T and BME-UV1 cells may behave differently in response to TGFβ1 due to their contrasting phenotypes; MAC-T cells have a profile indicative of both myoepithelial and luminal populations, while the BME-UV1 cells exclusively contain a luminal-like profile. Depending on the nature of the research question, the use of these cell lines as models to study TGFβ1 signaling should be carefully tailored to the questions asked.

[Aspects of the innate immune response to intramammary Staphylococcus aureus infections in cattle]

Staphylococcus aureus is the pathogen most frequently isolated from bovine mastitis worldwide, causing chronic intramammary infections that limit profitable dairying. The objective of this article is to characterize the mechanisms involved in S. aureus mammary gland infections considering two different aspects of the infectious process; on the one hand, the aspects involved in the host innate immune response and on the other hand, the capacity of this organism to evade the immune system and interact with different cell types. The exploration of S. aureus interactions with the immune response of bovine mammary gland will help identify targets to outline new preventive or curative alternatives for intramammary infections caused by this organism.

Short communication: opposing effects of lactoferrin on the proliferation of fibroblasts and epithelial cells from bovine mammary gland

Lactoferrin is present in several physiologic fluids, including milk and colostrum. Recently, evidence has accumulated that lactoferrin acts as a regulator of cell proliferation. Lactoferrin mRNA and protein levels in bovine mammary glands are known to markedly increase after cessation of milking. To clarify the role of bovine lactoferrin (bLF) in mammary involution and remodeling during dry periods, we investigated whether bLF affects the proliferation of cultured cells derived from bovine mammary gland and examined the mechanism underlying the proliferative response to bLF. Addition of bLF to the culture medium increased the proliferation of bovine mammary stromal fibroblasts (bMSF), but decreased that of bovine mammary epithelial cells (bMEC). Proliferation was significantly increased in the bMSF treated with bLF (100μg/mL or greater) as compared with unstimulated cells. The maximal proliferative effect of bLF on bMSF occurred at 1,000μg/mL, such that the proliferation of the bLF-stimulated bMSF was approximately 2.5 times that of unstimulated cells. The bLF increased the production of proliferating cell nuclear antigen and rapid phosphorylation of the p44/p42 mitogen-activated protein kinase in bMSF, but not in bMEC. The bLF-induced proliferation and production of proliferating cell nuclear antigen in bMSF was suppressed by U0126, a specific inhibitor of mitogen-activated protein kinase. Furthermore, treatment with bLF for 24h decreased the mRNA levels of the 3 isoforms of transforming growth factor β in bMSF (16-66%) but upregulated those in bMEC (122-157%). These opposite effects of bLF on the proliferation of epithelial and fibroblast cells and their expression of transforming growth factor β may play a crucial role in bovine mammary involution and remodeling.

TGF-β mediates suppression of adipogenesis by estradiol through connective tissue growth factor induction

In the bone marrow cavity, adipocyte numbers increase, whereas osteoblast progenitor numbers decrease with aging. Because adipocytes and osteoblasts share a common progenitor, it is possible that this shift is due to an increase in adipocyte-lineage cells at the expense of osteoblast-lineage commitment. Estrogens inhibit adipocyte differentiation, and in both men and women, circulating estrogens correlate with bone loss with aging. In bone cells, estrogens stimulate expression of TGF-β and suppress mesenchymal cell adipogenesis. Using a tripotential mesenchymal cell line, we have examined whether estradiol suppression of adipocyte differentiation is due to stimulation of TGF-β and the mechanism by which TGF-β suppresses adipogenesis. We observed that estradiol-mediated suppression of adipogenic gene expression required at least 48 h treatment. TGF-β expression increased within 24 h of estradiol treatment, and TGF-β inhibition reversed estradiol influences on adipogenesis and adipocyte gene expression. Connective tissue growth factor (CTGF) mediates TGF-β suppression of adipogenesis in mouse 3T3-L1 cells. CTGF expression was induced within 24 h of TGF-β treatment, whereas estradiol-mediated induction required 48 h treatment. Moreover, estradiol-mediated induction of CTGF was abrogated by TGF-β inhibition. These data support that estradiol effects on adipogenesis involves TGF-β induction, which then induces CTGF to suppress adipogenesis.

Host-response patterns of intramammary infections in dairy cows

Many different bacterial species have the ability to cause an infection of the bovine mammary gland and the host response to these infections is what we recognize as mastitis. In this review we evaluate the pathogen specific response to the three main bacterial species causing bovine mastitis: Escherichia coli, Streptococcus uberis and Staphylococcus aureus. In this paper we will review the bacterial growth patterns, host immune response and clinical response that results from the intramammary infections. Clear differences in bacterial growth pattern are shown between bacterial species. The dominant pattern in E. coli infections is a short duration high bacteria count infection, in S. aureus this is more commonly a persistent infection with relative low bacteria counts and in S. uberis a long duration high bacteria count infection is often observed. The host immune response differs significantly depending on the invading bacterial species. The underlying reasons for the differences and the resulting host response are described. Finally we discuss the clinical response pattern for each of the three bacterial species. The largest contrast is between E. coli and S. aureus where a larger proportion of E. coli infections cause potentially severe clinical symptoms, whereas the majority of S. aureus infections go clinically unnoticed. The relevance of fully understanding the bovine host response to intramammary infection is discussed, some major gaps in our knowledge are highlighted and directions for future research are indicated.

Interlobular and intralobular mammary stroma: genotype may not reflect phenotype

Background

The normal growth and function of mammary epithelial cells depend on interactions with the supportive stroma. Alterations in this communication can lead to the progression or expansion of malignant growth. The human mammary gland contains two distinctive types of fibroblasts within the stroma. The epithelial cells are surrounded by loosely connected intralobular fibroblasts, which are subsequently surrounded by the more compacted interlobular fibroblasts. The different proximity of these fibroblasts to the epithelial cells suggests distinctive functions for these two subtypes. In this report, we compared the gene expression profiles between the two stromal subtypes.

Methods

Fresh normal breast tissue was collected from reduction mammoplasty patients and immediately placed into embedding medium and frozen on dry ice. Tissue sections were subjected to laser capture microscopy to isolate the interlobular from the intralobular fibroblasts. RNA was prepared and subjected to microarray analysis using the Affymetrix Human Genome U133 GeneChip^®. Data was analyzed using the Affy and Limma packages available from Bioconductor. Findings from the microarray analysis were validated by RT-PCR and immunohistochemistry.

Results

No statistically significant difference was detected between the gene expression profiles of the interlobular and intralobular fibroblasts by microarray analysis and RT-PCR. However, for some of the genes tested, the protein expression patterns between the two subtypes of fibroblasts were significantly different.

Conclusion

This study is the first to report the gene expression profiles of the two distinct fibroblast populations within the human mammary gland. While there was no significant difference in the gene expression profiles between the groups, there was an obvious difference in the expression pattern of several proteins tested. This report also highlights the importance of studying gene regulation at both the transcriptional and post-translational level.

Pathogen-dependent induction of cytokines and other soluble inflammatory mediators during intramammary infection of dairy cows

Mastitis is a highly prevalent and costly disease of dairy cows that is commonly caused by intramammary bacterial infection. The innate immune response to bacterial penetration of the mammary gland is evoked within hours of infection, and the rapidity and magnitude of this response have been demonstrated to influence the resolution of this disease. Cytokines and other mediators of inflammation are known to play critical roles in the innate immune response to intramammary infection. The objectives of this review are to summarize the current understanding of the cytokine response to intramammary infection, highlight recent findings identifying differences in the cytokine response to various bacterial pathogens, and discuss future research directions that will increase our knowledge of the role of inflammatory mediators in predicting and governing the outcome of mastitis.

Increased Milk Levels of Transforming Growth Factor-α, β1, and β2 During Escherichia coli-Induced Mastitis

Among the gram-negative bacteria that cause mastitis, Escherichia coli are the most prevalent. The innate immune system provides initial protection against E. coli infection by detecting the presence of the foreign pathogens and by mounting an inflammatory response, the latter of which is mediated by cytokines such as IL-1beta, IL-8, and tumor necrosis factor (TNF)-alpha. Although changes in these cytokines during mastitis have been well-described, it is believed that other mediators moderate mammary gland inflammatory responses as well. The growth factors/cytokines transforming growth factor (TGF)-alpha, TGF-beta1, and TGF-beta2 are all expressed in the mammary gland and have been implicated in regulating mammary gland development. In other tissues, these growth factors/cytokines have been shown to moderate inflammation. The objective of the current study was to determine whether TGF-alpha, TGF-beta1, and TGF-beta2 milk concentrations were altered during the course of E. coli-induced mastitis. The contralateral quarters of 11 midlactating Holstein cows were challenged with either saline or 72 cfu of E. coli, and milk samples were collected. Basal milk levels of TGF-alpha, TGF-beta1, and TGF-beta2 were 98.81 +/- 22.69 pg/mL, 3.35 +/- 0.49 ng/mL, and 22.36 +/- 3.78 ng/mL, respectively. Analysis of whey samples derived from E. coli-infected quarters revealed an increase in milk levels of TGF-alpha within 16 h of challenge, and these increases persisted for an additional 56 h. Elevated TGF-beta1 and TGF-beta2 milk concentrations were detected in E. coli-infected quarters 32 h after challenge, and these elevations were sustained throughout the study. Because TGF-alpha, TGF-beta1, and TGF-beta2 have been implicated in mediating inflammatory processes, their induction during mastitis is consistent with a role for these molecules in mediating mammary gland host innate immune responses to infection.

Differential Gene Expression of Cytokine and Cell Surface Molecules in T cell Subpopulation Derived from Mammary Gland Secretion of Cows

PROBLEM

As T cell subpopulations in the mammary gland secretion (MGS) of cows dynamically vary through the lactation cycle, their functional analysis is important to understand the mammary immune responses.

METHOD OF STUDY

T cell subpopulations were positively selected from MGS during lactation period and non-lactation period (dry period) by a magnetic cell sorter. The messenger RNA (mRNA) expression of cytokine and cell surface molecules in the subpopulations stimulated with anti-CD3 was investigated using reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

CD4+ T cells from MGS significantly expressed mRNA of interferon (IFN)-gamma, interleukin (IL)-2, granulocyte-macrophage colony-stimulating factor (GM-CSF), transforming growth factor (TGF)-beta, tumor necrosis factor (TNF)-alpha, IL-4, CD40 ligand (CD40L), Fas ligand (FasL) and IL-2 receptor (IL-2R) during dry period, and mRNA of IFN-gamma, IL-2 and TGF-beta during lactation period. Their expression during lactation period was always less than that during dry period. CD8+ T cells from MGS substantially expressed mRNA of IFN-gamma, IL-2, GM-CSF, TGF-beta, TNF-alpha, FasL and IL-2R during dry period and mRNA of IFN-gamma, GM-CSF, TGF-beta, TNF-alpha and c-kit during lactation period. The TGF-beta, TNF-alpha, c-kit and IL-2R mRNA expression of T cells in MGS during lactation period mostly depended on gammadelta T cells. Interestingly, c-kit mRNA was exclusively expressed in gammadelta T cells.

CONCLUSIONS

The cytokine expression of T cells in MGS of cows depended on the T cell subpopulations. The present findings suggested that the activation of gammadelta T cells via c-kit receptor participated in the suppressed expression of cytokine mRNA in T cells during lactation period.

The insulin-like growth factor and epidermal growth factor families in mammary cell growth in ruminants: action and interaction with hormones

Selective breeding and improved management have had major effects in increasing peak milk yields but relatively little effect on lactation persistency. In ruminants, cell loss appears to be largely responsible for the decline in milk yield. Little is known about the longevity of individual cells, but, in lactating dairy cows, few epithelial cells are in the S phase (DNA synthesis) of the cell cycle. The IGF and epidermal growth factor families are direct mitogens, stimulating DNA synthesis in cultures of ruminant mammary epithelial cells. Receptors that mediate the effects of these growth factors, the type 1 IGF receptor and the epidermal growth factor receptor, respectively, are present at similar levels in membranes prepared from the mammary glands of nonpregnant and pregnant sheep. Binding capacity falls by parturition and remains low during lactation. These findings suggest that the drive to mammary development in pregnancy comes from control of growth factors, and, in the case of IGF, modulating binding proteins, a control exerted by hormones, which, in general, are not themselves mitogens. A paracrine or autocrine mode of action and, therefore, local growth factor synthesis, are more likely to be important than systemic concentrations of growth factor. Stimulatory growth factors produced locally by the mammary gland include IGF-I, IGF-II, transforming growth factor-alpha, and amphiregulin. More information is needed on the control of stimulatory and inhibitory growth factors and on how growth factors control the cell cycle. Knowledge of these processes could result in strategies to improve lactation persistency by increasing secretory cell renewal or reducing cell loss during lactation.

Transforming growth factor beta-1 and beta-2 in human tear fluid

PURPOSE

To evaluate human tear fluid for transforming growth factor beta isoforms 1 and 2 (TGF-beta1 and TGF-beta2).

METHODS

To accomplish this, human tears were evaluated for TGF-betas by quantitative antibody sandwich ELISA (sELISA), mink lung epithelial cell (MLEC) growth inhibition bioassay and western blotting. Various physical and chemical treatments were used to activate TGF-beta in these assays.

RESULTS

TGF-betas could not be detected in untreated or heated tears by sELISA; however, mean TGF-beta1 concentrations of 2.32 ng/ml were detected in acid-activated tears by sELISA. Furthermore, 10.54 ng/ml of TGF-beta1 and 2.98 ng/ml of TGF-beta2 were detected in tears treated with the mucolytic agent, acetylcysteine. Total TGF-beta bioactivity in human tears measured by the MLEC assay was found to be 13.04 ng/ml in untreated tears and 24.85 ng/ml in acid-activated tears. Approximately one-half TGF-beta in tear specimens was biologically active (mean = 52%, range 39-71%). Total tear TGF-beta bioactivity could be completely neutralized by recombinant human TGF-beta1 latency associated peptide (rh TGF-beta1 LAP). Mean neutralization of tear TF-beta bioactivity was 83% by TGF-beta1-specific antisera, and was 13% by TBF-beta2-specific antisera. Immunoreactive TBF-beta bands at approximately 12.5 and 95 kD were observed in immunoblots of reduced acidified tears. A high molecular weight (MW) TGF-beta band (>203 dD) was noted in untreated tears; however, this band disappeared following treatment with acetylcysteine.

CONCLUSIONS

The results of these studies indicate that TGF-beta1 and TGF-beta2 are present in human tear fluid, and TGF-beta1 is the predominant isoform. There appear to be factors in human tears capable of binding TGF-beta.

Production and secretion of transforming growth factor beta (TGF-beta) by the human lacrimal gland

PURPOSE

Transforming growth factor beta (TGF-beta) isoforms 1 and 2 have recently been detected in stimulated human tear fluid. The purpose of this study was to determine if these TGF-sbeta are produced and secreted by the lacrimal gland.

METHODS

To accomplish this, reverse transcriptase polymerase chain reaction (RT-PCR) was used to detect expression of TGF-beta1 and TGF-beta2 mRNAs in normal human and rabbit lacrimal gland biopsies. Northern blot analyses were used for comparing the relative levels of expression of these TGF-beta mRNAs in rabbit lacrimal glands. Human lacrimal gland biopsies were evaluated by immunohistochemistry for production of TGF-beta1, TGF-beta1 latency associated peptide (LAP), and TGF-beta2 proteins. Supernatants of unstimulated and carbachol-stimulated human lacrimal gland explant cultures were evaluated for secretion of TGF-beta1 and TGF-beta2 by ELISA:

RESULTS

TGF-beta1 and TGF-beta2 mRNA expression was found in all human and rabbit lacrimal gland specimens by RT-PCR. A greater level of expression of TGF-beta1 than TGF-beta2 mRNA in the rabbit lacrimal gland was noted by Northern blot. In human lacrimal gland biopsies, TGF-beta1 and TGF-beta1 LAP were detected in acinar and ductal epithelia by immunohistochemistry. TGF-beta2 specific antibodies stained a small percentage of acinar and ductal epithelia, as well as material within the lumens of tubulo-acinar complexes in one-third of these glands. TGF-beta1 was detected in supernatants of human lacrimal gland explants, and the concentration of TGF-beta1 increased by an average of 280% after carbachol-stimulation (p = 0.004). TGF-beta2 could not be detected in unstimulated or stimulated human lacrimal gland supernatants.

CONCLUSIONS

The results of these experiments indicate that TGF-beta1 and TGF-beta2 are produced by and TGF-beta1 is secreted by the human lacrimal gland. They also suggest that the lacrimal gland may be one source of TGF-beta in human tear fluid.

Two distinct phases of apoptosis in mammary gland involution: proteinase-independent and -dependent pathways

Postlactational involution of the mammary gland is characterized by two distinct physiological events: apoptosis of the secretory, epithelial cells undergoing programmed cell death, and proteolytic degradation of the mammary gland basement membrane. We examined the spatial and temporal patterns of apoptotic cells in relation to those of proteinases during involution of the BALB/c mouse mammary gland. Apoptosis was almost absent during lactation but became evident at day 2 of involution, when beta-casein gene expression was still high. Apoptotic cells were then seen at least up to day 8 of involution, when beta-casein gene expression was being extinguished. Expression of sulfated glycoprotein-2 (SGP-2), interleukin-1 beta converting enzyme (ICE) and tissue inhibitor of metalloproteinases-1 was upregulated at day 2, when apoptotic cells were seen initially. Expression of the matrix metalloproteinases gelatinase A and stromelysin-1 and the serine proteinase urokinase-type plasminogen activator, which was low during lactation, was strongly upregulated in parallel starting at day 4 after weaning, coinciding with start of the collapse of the lobulo-alveolar structures and the intensive tissue remodeling in involution. The major sites of mRNA synthesis for these proteinases were fibroblast-like cells in the periductal stroma and stromal cells surrounding the collapsed alveoli, suggesting that the degradative phase of involution is due to a specialized mesenchymal-epithelial interaction. To elucidate the functional role of these proteinases during involution, at the onset of weaning we treated mice systemically with the glucocorticoid hydrocortisone, which is known to inhibit mammary gland involution. Although the initial wave of apoptotic cells appeared in the lumina of the gland, the dramatic regression and tissue remodeling usually evident by day 5 was substantially inhibited by systemic treatment with hydrocortisone. mRNA and protein for gelatinase A, stromelysin-1 and uPA were weakly induced, if at all, in hydrocortisone-treated mice. Furthermore, mRNA for membrane-type matrix metalloproteinase decreased after hydrocortisone treatment and paralleled the almost complete inhibition of activation of latent gelatinase A. Concomitantly, the gland filled with an overabundance of milk. Our data support the hypothesis that there are at least two distinct phases of involution: an initial phase, characterized by induction of the apoptosis-associated genes SGP-2 and ICE and apoptosis of fully differentiated mammary epithelial cells without visible degradation of the extracellular matrix, and a second phase, characterized by extracellular matrix remodeling and altered mesenchymal-epithelial interactions, followed by apoptosis of cells that are losing differentiated functions.

Characterization of transforming growth factor-beta growth regulatory effects and receptors on bovine mammary cells

Transforming growth factor-beta (TGF-beta) has been shown to inhibit mammary morphogenesis, growth, and differentiation in murine studies. We have characterized TGF-beta receptors and their autoregulation, and the growth response to TGF-beta 1 and TGF-beta 2 in cultured bovine mammary epithelium (MAC-T) and fibroblasts. Affinity labelling studies revealed that fibroblast and epithelial cells contained type I, II, and III (betaglycan) receptors, with the type III receptor being the predominant binding component. On both fibroblasts and epithelial cells, TGF-beta 1 and TGF-beta 2 had equal binding affinities for the type I and II receptors, but TGF-beta 2 had a higher affinity for the type III receptor. Also, preincubation of MAC-T cells with 50 pM TGF-beta 1 or TGF-beta 2 markedly downregulated TGF-beta receptors. Proliferative response was measured using both total DNA and 3H-thymidine incorporation. Both TGF-beta isoforms were effective in inhibiting proliferation of MAC-T cells and fibroblasts. Inhibition of proliferation was not altered following immortalization of fibroblasts with SV-40 Large-T-antigen (LT), even when the cells acquired a transformed phenotype. Inhibition of proliferation was not a result of cytotoxicity, as TGF-beta at concentrations 1,000-fold higher than ED50 levels did not increase cell death. Moreover, the inhibition was reversible as shown by return of cellular proliferation to control levels following TGF-beta removal. Although growth inhibition was not transient as culture of MAC-T cells in TGF-beta resulted in sustained inhibition of proliferation for at least 144 h.

Tyrosine kinases are involved with the expression of inducible nitric oxide synthase in human articular chondrocytes

The present study characterizes mechanisms involved with the induction of nitric oxide (NO) production, nitric oxide synthase (NOS) enzymatic activity and mRNA expression in human articular chondrocytes. Activation of chondrocytes with lipopolysaccharide (LPS) or IL-1 resulted in time- and dose-dependent increases in iNOS mRNA followed by increased NOS enzymatic activity and NO release. The protein tyrosine kinase (PTK) inhibitors herbimycin A or genistein reduced IL-1 or LPS-induced NO release and NOS enzymatic activity. This was associated with inhibition of iNOS mRNA expression as determined by reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization. In contrast, inhibitors of protein kinase C (PKC) or protein kinase A (PKA) did not affect these responses. These results were confirmed in experiments with second messenger agonists where neither activation of PKC, nor increases in cyclic adenosine monophosphate (cAMP) or increased intracellular calcium levels were associated with the induction of iNOS mRNA or NO release. These results suggest that PKC, PKA and calcium-dependent signals are not required or sufficient for the stimulation of NO production. However, NO production is dependent on tyrosine kinases due to their role in the expression of iNOS mRNA.

Inducible nitric oxide synthase from human articular chondrocytes: cDNA cloning and analysis of mRNA expression

Human articular chondrocytes can be induced by IL-1 beta, TNF-alpha or LPS to release high levels of nitric oxide. Using degenerate PCR primers based on homologous regions from previously cloned NOS enzymes, a 1.9 kb cDNA fragment was amplified from IL-1 beta stimulated but not from resting chondrocytes. Screening of a lambda gt11 cDNA library, which was prepared from RNA of IL-1 beta activated chondrocytes, resulted in the isolation of the complete cDNA, encoding a protein of 1153 amino acids. Comparison of the cDNA sequence identified human chondrocyte iNOS to be almost identical to the sequence recently reported for the hepatocyte enzyme, differing in 12 amino acids. Northern blot analysis revealed, that stimulated chondrocytes express a single 4.5 kb iNOS mRNA species. IL-1 beta induction of iNOS mRNA was detectable by 6 h and continued to be elevated throughout a 72 h culture period. Screening of a human bone cDNA library identified this inducible NOS to be also expressed by bone cells.

Expression of transforming growth factor beta mRNA isoforms in human breast cancer

Using an RNAse protection assay, expression of messenger RNA for isoforms of TGF-beta was determined in a series of breast cancers. Of 50 tumours, 45 (90%) expressed TGF-beta 1 mRNA, 39 (78%) expressed TGF-beta 2, and 47 (94%) expressed TGF-beta 3. Patterns of expression varied between different tumours: 37 (74%) cancers expressed all three TGF-beta isoforms, ten (20%) expressed only two isoforms and two expressed TGF-beta 1 alone. One sample showed no evidence of TGF-beta mRNA expression. Although most breast cancers expressed mRNA for at least one isoform of TGF-beta, there were differences in patterns of mRNA expression between individual tumours. The relatively small number of tumours examined precluded detailed analysis between expression and other clinical parameters, but a significant association was identified between one aspect of isoform expression and lymph node status, in that the majority of tumours expressing all three isoforms were associated with lymph node involvement, whereas tumours without one or more isoform were usually lymph node negative (P = 0.025 by Fisher's exact test).

Enhanced translational efficiency of a novel transforming growth factor beta 3 mRNA in human breast cancer cells

The mRNA for transforming growth factor beta 3 (TGF-beta 3) includes a long (1.1-kb) 5' noncoding region which exerts a potent inhibitory effect on translational efficiency. We now report that many human breast cancer cell lines (T47-D, SK-BR-3, ZR-75-1, and BT-474) express two mRNA species for TGF-beta 3: the 3.5-kb transcript previously described as the only TGF-beta 3 mRNA species in cells and a novel 2.6-kb transcript which lacks approximately 870 nucleotides from the 5' noncoding region. The 5' end of the shorter transcript was sequenced, establishing it to be a 5' truncation of the full-length TGF-beta 3 transcript. Estradiol decreased mRNA levels of both TGF-beta 3 mRNA transcripts to an equivalent degree in estrogen receptor-positive cells. In contrast, the synthetic progestin gestodene altered the relative abundance of the two transcripts, preferentially diminishing the expression of the 2.6-kb transcript. The potential for enhanced mRNA translation attributable to the shorter 5' noncoding region was evaluated by transfection of cells with chimeric plasmid constructs in which the transcription unit consisted of coding sequence for chloramphenicol acetyltransferase downstream of the 5' noncoding sequence from TGF-beta 3. The translational efficiency of chloramphenicol acetyltransferase-encoding mRNA containing the shorter 5' noncoding region of the 2.6-kb TGF-beta 3 transcript was approximately seven times greater than with the full-length 5' noncoding region of TGF-beta 3. Polysome analysis of TGF-beta 3 mRNA in SK-BR-3 cells supported the hypothesis that the 2.6-kb transcript was more actively engaged in translation.

Enhanced translational efficiency of a novel transforming growth factor beta 3 mRNA in human breast cancer cells

The mRNA for transforming growth factor beta 3 (TGF-beta 3) includes a long (1.1-kb) 5' noncoding region which exerts a potent inhibitory effect on translational efficiency. We now report that many human breast cancer cell lines (T47-D, SK-BR-3, ZR-75-1, and BT-474) express two mRNA species for TGF-beta 3: the 3.5-kb transcript previously described as the only TGF-beta 3 mRNA species in cells and a novel 2.6-kb transcript which lacks approximately 870 nucleotides from the 5' noncoding region. The 5' end of the shorter transcript was sequenced, establishing it to be a 5' truncation of the full-length TGF-beta 3 transcript. Estradiol decreased mRNA levels of both TGF-beta 3 mRNA transcripts to an equivalent degree in estrogen receptor-positive cells. In contrast, the synthetic progestin gestodene altered the relative abundance of the two transcripts, preferentially diminishing the expression of the 2.6-kb transcript. The potential for enhanced mRNA translation attributable to the shorter 5' noncoding region was evaluated by transfection of cells with chimeric plasmid constructs in which the transcription unit consisted of coding sequence for chloramphenicol acetyltransferase downstream of the 5' noncoding sequence from TGF-beta 3. The translational efficiency of chloramphenicol acetyltransferase-encoding mRNA containing the shorter 5' noncoding region of the 2.6-kb TGF-beta 3 transcript was approximately seven times greater than with the full-length 5' noncoding region of TGF-beta 3. Polysome analysis of TGF-beta 3 mRNA in SK-BR-3 cells supported the hypothesis that the 2.6-kb transcript was more actively engaged in translation.

Role of epidermal growth factor and transforming growth factors in mammary development and lactation

Epidermal growth factor, transforming growth factor-alpha, and transforming growth factor-beta 1 are potent effectors of mammary growth that work in concert with endocrine hormones, such as estrogen, progesterone, corticosteroids, and prolactin. Estrogen and progesterone stimulate production of epidermal growth factor or transforming growth factor-alpha to stimulate mammary growth. Epidermal growth factor and prolactin synergize in whole organ culture to cause lobulo-alveolar development and to alter the profile of synthesized milk proteins. Transforming growth factor-beta 1 inhibits mammary development of prepubertal mice. However, once the gland is committed to differentiation, transforming growth factor-beta 1 no longer affects mammary morphogenesis. The role of transforming growth factor-beta 1 in milk protein synthesis is unknown. Transforming growth factor-alpha and -beta 1 mRNA have both been identified in the mammary gland of cows. The gland has epidermal growth factor receptors, and epidermal growth factor or transforming growth factor-alpha can stimulate proliferation of mammary epithelial cells in vitro. The role of transforming growth factor-beta 1 in bovine mammary tissue has not been studied. An understanding of the role of epidermal growth factor, the transforming growth factors, and their interactions with endocrine hormones will lead to a more complete understanding of how mammary development and lactation are regulated.