Signal transduction and TGF-beta superfamily receptors

Proteome Analysis of Alpine Merino Sheep Skin Reveals New Insights into the Mechanisms Involved in Regulating Wool Fiber Diameter

Wool fiber is a textile material that is highly valued based on its diameter, which is crucial in determining its economic value. To analyze the molecular mechanisms regulating wool fiber diameter, we used a Data-independent acquisition-based quantitative proteomics approach to analyze the skin proteome of Alpine Merino sheep with four fiber diameter ranges. From three contrasts of defined groups, we identified 275, 229, and 190 differentially expressed proteins (DEPs). Further analysis using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways revealed that pathways associated with cyclic adenosine monophosphate and peroxisome proliferator-activated receptor signaling are relevant to wool fiber diameter. Using the K-means method, we investigated the DEP expression patterns across wool diameter ranges. Using weighted gene co-expression network analysis, we identified seven key proteins (CIDEA, CRYM, MLX, TPST2, GPD1, GOPC, and CAMK2G) that may be involved in regulating wool fiber diameter. Our findings provide a theoretical foundation for identifying DEPs and pathways associated with wool fiber diameter in Alpine Merino sheep to enable a better understanding of the molecular mechanisms underlying the genetic regulation of wool fiber quality.

Knockdown of HIPK2 attenuates angiotensin II-induced cardiac fibrosis in cardiac fibroblasts

ABSTRACT

Homeodomain-interacting protein kinase-2 (HIPK2), a member of an evolutionary conserved family of serine/threonine kinases, has been observed to be involved in the pathogenesis of fibrotic diseases. However, its role in cardiac fibrosis remains unclear. In the current study, we assessed the effect of HIPK2 on cardiac fibroblasts (CFs) in response to angiotensin II (Ang II) stimulation. The results indicated that HIPK2 expression was significantly increased in Ang II-induced CFs in a dose-dependent manner. Then, HIPK2 was knocked down in CFs to evaluate the roles of HIPK2. Knockdown of HIPK2 suppressed cell proliferation and migration in Ang II-induced CFs. The Ang II-caused increase in expression of α-SMA, a hallmark of myofibroblast differentiation, was decreased by knockdown of HIPK2. HIPK2 knockdown also reduced ECM production including type I collagen (Col I) and connective tissue growth factor (CTGF). Furthermore, knockdown of HIPK2 blocked the activation of TGF-β1/Smad pathway in Ang II-induced CFs. These data suggested that HIPK2 knockdown prevented the Ang II-induced activation of CFs via inhibiting TGF-β1/Smad pathway, indicating HIPK2 might be an anti-fibrosis target for the treatment of cardiac fibrosis.

Discovery of single nucleotide polymorphisms in bone morphogenetic protein (BMP) genes of goats by double digest restriction-site associated DNA sequencing

Context Two native goat breeds from Kerala, Malabari and Attappady Black, differ significantly in prolificacy (i.e. no. of kids born/kidding). Prolificacy is an important economic trait and the subject of genetic research showing that bone morphogenetic protein (BMP) genes have a significant effect. Double digest restriction-site associated DNA sequencing (ddRADseq) is a highly efficient and low cost technology for high density discovery of single nucleotide polymorphisms (SNPs), which could serve as predictive markers for animal breeding programs. Aims The study was aimed at discovering SNPs in BMP genes that affect prolificacy, using ddRADseq followed by validation of selected SNP. Methods Blood DNA samples of 10 highly prolific Malabari and 10 less prolific Attappady Black goats were pooled by group and subjected to ddRADseq. SNPs observed in BMP genes were investigated and compared between groups. A validation study was done for the c.614–32789C>T variant in 100 Malabari and 50 Attappady Black goats by using PCR-RFLP. Key results In total, 6333 variants were identified by ddRADseq. Three variants were identified in BMP genes, which included two intronic variants c.614–32789C>T and c.490+6793T>C, in genes BMP6 and BMP5 and a downstream gene variant near the BMPR1B gene. According to ddRADseq data, variants in BMP5 and BMP6 differed in allelic distribution between Malabari and Attappady Black goats. For c.490+6793T>C in BMP5, the CC genotype was predominant in the highly prolific Malabari whereas TC was present in the Attappady Black group. The variant c.614–32789C>T in BMP6 was genotyped as TC in Malabari and CC in Attappady Black goats by ddRADseq. This variant was predicted to have an effect on splicing, according to the tool SplicePort. On the basis of bioinformatics analysis and the role of BMP6 gene in follicular dynamics, the variant in BMP6 was selected for further validation studies. All three genotypes were identified by PCR-RFLP; the C allele was the rare allele in the population with an allele frequency of 0.36. Presence of both alleles C and T and the three genotypes CC, TC and TT in this larger population substantiated the robustness of ddRADseq technique. Conclusions The technique discovered high confidence SNPs, which could be used for further validation and association studies to develop markers for selection of animals and for genetic improvement of this complex trait. Implications Techniques such as ddRADseq provide a large number of SNPs, and investigation of those polymorphisms found across the genome will help to identify new loci affecting traits of interest. This, in turn, will aid in exploring genetically complex traits in a faster and cheaper manner.

NIM811 downregulates transforming growth factor‑β signal transduction in vivo and in vitro

Liver fibrosis is the common histological feature of a number of chronic liver diseases, and leads to cirrhosis and hepatocellular carcinoma (HCC). It has been demonstrated that N‑methyl‑4‑isoleucine cyclosporine (NIM811) attenuates CCl4‑induced liver fibrosis and inflammation in rats. The present study investigated whether NIM811 downregulated transforming growth factor (TGF)‑β signaling in rats with CCl4‑induced liver fibrosis and in HSC‑T6 cells. Liver tissues were obtained from rats with CCl4‑induced liver fibrosis, with or without NIM811 treatment. HSC‑T6 cells were cultured with or without NIM811 for 18 h under serum‑free conditions. Expression of collagen I, α‑smooth muscle actin (α‑SMA), TGF‑β1, TGF‑β receptor I (TβR‑I) and TGF‑β pathway downstream signaling molecules were measured by reverse transcription‑quantitative polymerase chain reaction and/or western blotting. Collagen I and TGF‑β1 content in the cell supernatant was measured by ELISA. NIM811 profoundly inhibited collagen I, α‑SMA, TGF‑β1 and TβR‑I expression in the liver of CCl4‑treated rats. Phosphorylation of Smad2, 3 and 1/5/8 was decreased in the liver of NIM811‑treated groups, accompanied by increased In addition, Smad7 expression compared with the CCl4‑treated rats. NIM811 inhibited collagen I, TGF‑β1 and TβR‑I expression in HSC‑T6 cells. Smad1 mRNA and phospho‑Smad1/5/8 protein levels decreased following NIM811 treatment, accompanied by increased Smad7 expression in HSC‑T6 cells compared with normal controls. Furthermore, NIM811 also inhibited collagen I mRNA expression in the liver of rats with CCl4‑induced liver fibrosis and in HSC‑T6 cells. The results suggest that the antifibrotic effect of NIM811 was due to the inhibition of TGF‑β1 and its downstream signaling molecules.

In vivo effects of adjunctive tetracycline treatment on refractory corneal ulcers in dogs

OBJECTIVE

To evaluate effect of adjunctive treatment with tetracycline analogues on time to complete corneal reepithelialization in dogs with nonhealing (ie, refractory) corneal ulcers.

DESIGN

Randomized controlled clinical trial.

ANIMALS

89 dogs with refractory corneal ulcers.

PROCEDURES

Corneal ulcers were treated via debridement and grid keratotomy. Dogs were assigned to receive 1 of 3 treatment regimens for up to 6 weeks: doxycycline (5 mg/kg [2.27 mg/lb], PO, q 12 h) with topically applied ophthalmic ointment containing neomycin, polymyxin B, and bacitracin (ie, triple antibiotic ointment; q 8 h); cephalexin (22 mg/kg [10 mg/lb], PO, q 12 h) with topically applied oxytetracycline ophthalmic ointment (q 8 h); or a control treatment of cephalexin (22 mg/kg, PO, q 12 h) with topically applied triple antibiotic ointment (q 8 h). Healing was monitored via measurements of the wound with calipers and evaluation of photographs obtained every 2 weeks. Treatment effectiveness was evaluated by wound healing and decreased signs of pain.

RESULTS

The Boxer breed was overrepresented in all groups. At the 2-week time point, wound healing was significantly more common in small-breed dogs, compared with large-breed dogs. Dogs treated with oxytetracycline ophthalmic ointment had a significantly shorter healing time than did dogs receiving the control treatment. Corneal ulcers in dogs that received doxycycline PO healed more rapidly than did ulcers in dogs in the control treatment group; however, this difference was not significant.

CONCLUSIONS AND CLINICAL RELEVANCE

Topical tetracycline ophthalmic ointment was a safe, inexpensive, and effective adjunctive treatment for refractory corneal ulcers in dogs.

The role of the slug transcription factor in cell migration during corneal re-epithelialization in the dog

Epithelial cell migration during corneal wound re-epithelialization shares features with the developmental process of epithelial-mesenchymal transition (EMT) modulated by Snail family transcription factors, including Slug. Our studies demonstrated that Slug expression was enhanced at sites of epithelial cell migration at the margins of normally healing corneal wounds in dogs, but significantly decreased at the margins of non-healing canine corneal erosions. Increased Slug expression was associated with internalization of E-cadherin and beta-catenin from the cell membrane and with enhanced expression of smooth-muscle-specific alpha-actin, tropomyosin, and matrix metalloproteinases at wound margins. Enhanced Slug expression in corneal explants due to an adenoviral expression construct or to oxytetracycline treatment resulted in significantly higher rates of corneal epithelial cell migration. Oxytetracycline appeared to act by stimulating transforming growth factor-beta activity, thus increasing Slug expression and enhancing corneal epithelial migration. These findings highlight the similarities between epithelial migration during EMT and during successful corneal wound healing, support an important role for the Snail family in the process, and indicate that modulating Slug expression may be clinically useful in treating non-healing corneal wounds.

Growth factors and their relationship to neoplastic and paraneoplastic disease

Growth factors are extracellular signaling molecules that act in an autocrine and paracrine fashion to regulate growth, proliferation, differentiation, and survival of cells. Dysregulation of the growth factor networks is intimately related to the molecular pathogenesis of neoplastic and paraneoplastic disease. Increasing knowledge of the molecular mechanisms underlying growth factors and their actions on cell cycling, cell division, and cell death is shedding light on new therapeutic avenues for molecular targeting of tumors. Epidermal growth factor and vascular endothelial growth factor both offer examples of how growth factor biology and its relationship to cancer can be harnessed to create effective clinical therapeutic tools such as monoclonal antibodies. This approach heralds a future in which rational molecular oncological therapy may increasingly become the norm.

Effects of TGF-beta s on the growth, collagen synthesis and collagen lattice contraction of human dental pulp fibroblasts in vitro

Transforming growth factor-beta (TGF-beta) is important in regulating the repair and regeneration of damaged dental pulp. For further elucidating the roles of different isoforms of TGF-beta in the healing and inflammatory processes of human dental pulp, we found that TGF-beta1, TGF-beta2 and TGF-beta3 inhibited the growth of two human dental pulp cell strains in vitro by 19-29, 18-25 and 23-26%, respectively, at a concentration of 0.5 ng/ml. TGF-beta also differentially stimulated the collagen synthesis of pulp cells. Collagen synthesis increased by 1 ng/ml of TGF-beta1 and TGF-beta2 by 42 and 51%, respectively. TGF-beta3 (0.1-1 ng/ml) lacked of stimulatory effect on collagen synthesis of pulp cells. Pulp cells have the intrinsic capacity to contract collagen lattice, leading to decreasing of lattice diameter. An 8 h exposure to TGF-beta1 and TGF-beta2 enhanced the pulp cell-populated collagen lattice contraction at concentrations ranging from 0.2 to 3 ng/ml. At similar concentrations, TGF-beta3 lacked of this stimulatory effect. When collagen lattice were detached after 24 h of exposure, TGF-beta1 and TGF-beta2 (0.6-3 ng/ml) induced the pulp cells-populated collagen lattice contraction within 4-8h of gel detachment. These results indicate that TGF-beta-induced collagen lattice contraction is a late cellular event. These in vitro results indicate that effects of TGF-beta isoforms on the growth, collagen synthesis and collagen lattice contraction of pulp cells may play crucial roles in the pathobiological processes of dental pulp.

Clinical implications of growth factors in flexor tendon wound healing

Recent research has focused on the role of growth factors in flexor tendon wound healing. These basic science reports have described the identification and quantification of various growth factors in in vitro and in vivo models. Although these reports have begun to piece together the cascade of events involved in flexor tendon wound healing, the clinical relevance for the practicing hand surgeon is unclear. Growth factors are cell-secreted proteins that regulate cellular functions. These growth factors are involved in cell differentiation and growth, including the normal processes of development and tissue repair. Several growth factors recently have been identified as playing roles in tendon healing including vascular endothelial growth factor (VEGF), insulin-like growth factor (IGF), platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF), and transforming growth factor beta (TGF-beta). In addition, the transcription factor NF-kappaB has been implicated in the signaling pathways of these growth factors. The purpose of this article is to describe what is known about the molecular basis of flexor tendon wound healing, to review the most commonly studied growth factors, and to summarize likely clinical applications of these growth factors to flexor tendon repair.

What is transforming growth factor-beta (TGF-β)?

The TGF-beta superfamily of proteins produces a wide range of frequently opposing effects in different cells and tissues in the body. However, its activation and mode of action are only partially understood because of its complexity in structure and functions and the variability in its downstream targets. Current work on these cytokines focuses on their receptors and the intercellular signalling pathways, comparing bioactivities between cell types and tracking their physiological and immunological effects in vivo. Future research will yield important therapeutic applications and the ability to manipulate these proteins in vivo.

Flexor tendon wound healing in vitro: lactate up-regulation of TGF-beta expression and functional activity

Flexor tendon wound healing in zone II is complicated by adhesions to the surrounding fibro-osseous sheath. These adhesions can significantly alter tendon gliding and ultimately hand function. Lactate and transforming growth factor-beta (TGF-beta) are two important mediators of wound healing that have been demonstrated to independently increase collagen production by cells of the tendon sheath, epitenon, and endotenon. This study examined the effects of lactate on TGF-beta peptide and receptor production by flexor tendon cells. Tendon sheath fibroblasts, epitenon tenocytes, and endotenon tenocytes were isolated from rabbit flexor tendons and cultured separately. Cell cultures were supplemented with 50 mM lactate, and the expression of three TGF-beta peptide isoforms (beta1, beta2, and beta3) and three receptor isoforms (R1, R2, and R3) was quantified with enzyme-linked immunosorbent assays. TGF-beta functional activity was also assessed with the addition of tendon cell conditioned media to mink lung epithelial cells transfected with a luciferase reporter gene expression construct responsive to TGF-beta. Supplementation of the cell culture medium with lactate significantly (p < 0.05) increased the expression of all TGF-beta peptide and receptor isoforms in all three cell lines. Tendon sheath fibroblasts exhibited the greatest increases in beta1 and beta2 peptide isoform expression (30 and 23 percent, respectively), whereas endotenon tenocytes demonstrated the greatest increase in beta3 peptide expression (32 percent). Epitenon tenocytes exhibited the greatest increases in receptor isoform R1 and R2 expression (17 and 19 percent, respectively). All three tendon cell types demonstrated significant (p < 0.05) increases in TGF-beta functional activity when exposed to lactate. Epitenon tenocytes demonstrated the greatest increase in activity (>4 times control values), whereas tendon sheath fibroblasts demonstrated the highest overall levels of total TGF-beta functional activity. Lactate significantly increased TGF-beta peptide (beta1, beta2, and beta3) expression, receptor (R1, R2, and R3) expression, and functional activity, suggesting a common pathway regulating tendon cell collagen production. Modulation of lactate and TGF-beta levels may provide a means of modulating the effects of TGF-beta on adhesion formation in flexor tendon wound healing.

Abnormal mucosal extracellular matrix deposition is associated with increased TGF-beta receptor-expressing mesenchymal cells in a mouse model of colitis

Transforming growth factor-beta (TGF-beta) depresses mucosal inflammation and upregulates extracellular matrix (ECM) deposition. We analyzed TGF-beta receptors RI and RII as well as ECM components using the CD4(+) T-cell-transplanted SCID mouse model of colitis. The principal change in colitis was an increased proportion of TGF-beta RII(+) mucosal mesenchymal cells, predominantly alpha-smooth muscle actin (SMA)(+) myofibroblasts, co-expressing vimentin and basement membrane proteins, but not type I collagen. TGF-beta RII(+) SMA(-) fibroblasts producing type I collagen were also increased, particularly in areas of infiltration and in ulcers. Type IV collagen and laminin were distributed throughout the gut lamina propria in disease but were restricted to the basement membrane in controls. In areas of severe epithelial damage, type IV collagen was lost and increased type I collagen was observed. To examine ECM production by these cells, mucosal mesenchymal cells were isolated. Cultured cells exhibited a similar phenotype and matrix profile to those of in vivo cells. The data suggested that there were at least two populations of mesenchymal cells responsible for ECM synthesis in the mucosa and that ligation of TGF-beta receptors on these cells resulted in the disordered and increased ECM production observed in colitic mucosa.

Effect of age and hypoxia on TGFbeta1 receptor expression and signal transduction in human dermal fibroblasts: impact on cell migration

Wound healing is critically affected by age, ischemia, and growth factors such as TGFbeta1. The combined effect of these factors on fibroblast migration, an essential component of wound healing, is poorly understood. To address this deficiency, we examined expression of TGFbeta receptor type I and II (TGFbetaRI and RII) under normoxia or hypoxia (1% O(2)) in cultured human dermal fibroblasts (HDFs) from young (ages 24-33) and aged (ages 61-73) adults. TGFbetaRI and RII expression was similar in both groups under normoxia. Hypoxia did not alter receptor levels in young HDFs but significantly decreased TGFbetaRI in aged cells (12 and 43%, respectively). Additionally, young cells displayed a 50% increase in activation of p42/p44 mitogen-activated kinase by TGFbeta1 (2-200 pg/ml) under hypoxia while aged cell levels of active p42/p44 decreased up to 24%. To determine functional outcomes of these findings, we measured the migratory capacity of the cells on type I collagen using a gold salt migration assay. Hypoxia increased the migratory index (MI) of young HDFs over normoxia by 30% but had no effect on aged cells. Under normoxia, TGFbeta1 (1-1000 pg/ml) increased young HDF migration in a concentration-dependent manner up to 109% over controls but minimally increased aged HDF migration (37%). Under hypoxia, TGFbeta1 significantly increased young cell MI at all concentrations but was without effect on the aged HDF response. These data demonstrate that aged fibroblasts have an impaired migratory capacity with complete loss of responsiveness to hypoxia and deficits in the migratory and signal transduction responsiveness to TGFbeta1 that may partly explain diminished healing capabilities often observed in aged patients.

Differential expression of transforming growth factor-beta receptors in a rabbit zone II flexor tendon wound healing model

Flexor tendon repair in zone II is complicated by adhesions that impair normal postoperative gliding. Transforming growth factor-beta (TGF-beta) is a family of growth factors that has been implicated in scar formation. The TGF-beta family of proteins binds to three distinct classes of membrane receptors, termed RI, RII, and RIII. In this study, we analyzed the temporal and spatial distribution of TGF-beta receptor isoforms (RI, RII, and RIII) in a rabbit zone II flexor tendon wound healing model.Twenty-eight adult New Zealand White rabbit forepaws underwent isolation of the middle digit flexor digitorum profundus tendon in zone II. The tendons underwent transection in zone II and immediate repair. The tendons were harvested at increasing time points: 1, 3, 7, 14, 28, and 56 days postoperatively (n = 4 at each time point). The control flexor tendons were harvested without transection and repair (n = 4). Immunohistochemical analysis was used to detect the expression patterns for TGF-beta receptors RI, RII, and RIII. Immunohistochemical staining of the transected and repaired tendons demonstrated up-regulation of TGF-beta RI, RII, and RIII protein levels. TGF-beta receptor production in the experimental group (transection and repair) was concentrated in the epitenon and along the repair site. Furthermore, the TGF-beta receptor expression levels peaked at day 14 and decreased by day 56 postoperatively. In contrast, minimal receptor expression was observed in the untransected and unrepaired control tendons. These data provide evidence that (1) TGF-beta receptors are up-regulated after injury and repair; (2) peak levels of TGF-beta receptor expression occurred at day 14 and decreased by day 56 after wounding and repair; and (3) both the tendon sheath and epitenon have the highest receptor expression, and both may play critical roles in flexor tendon wound healing. Understanding the up-regulation of TGF-beta isoforms and the up-regulation of their corresponding receptors during flexor tendon wound healing provides new targets for biomolecular modulation of postoperative scar formation.

Regulation of transforming growth factor-beta-receptor type I and type II messenger ribonucleic acid expression in the hamster ovary by gonadotropins and steroid hormones

The hormonal regulation of ovarian transforming growth factor-beta (TGF-beta) type I receptor (TbetaRI) and TbetaRII messenger (mRNA) expression was evaluated using cyclic and hypophysectomized hamsters. Northern blot analysis revealed that three TbetaRI and one TbetaRII gene transcripts were expressed in the hamster ovary. Reverse transcription-polymerase chain reaction quantitation revealed that receptor mRNA was differentially expressed during the estrous cycle. Although, mRNA levels for both receptor types increased steadily up to Day 4:0900 h, a sharp decline occurred following the gonadotropin surge. In fact, receptor mRNA started declining by Day 4:1200 h, long before the gonadotropin surge; however, only TbetaRI mRNA levels recovered partially by 1500 h to fall again by 1600 h. Although hypophysectomy preferentially reduced TbetaRII mRNA levels, gonadotropins as well as ovarian steroids significantly induced TbetaRI and TbetaRII mRNA expression within 48 h and 24 h, respectively; 5alpha-dihydrotesterone (DHT) induced only TbetaRII mRNA. The induction of ovarian TbetaRI and TbetaRII mRNA by estradiol-17beta() or progesterone was severely attenuated by dexamethasone. A marked increase in serum cortisol coincided with the periovulatory rise in serum gonadotropins. These results suggest that the increase in TGF-beta receptor mRNA expression correlates with gonadotropin-induced ovarian follicular development during the estrous cycle. Moreover, receptor mRNA expression is critically and differentially regulated by gonadotropins as well as ovarian steroids. Most importantly, glucocorticoid appears to play a critical modulatory role in the temporal expression of receptor mRNA in the ovary, hence, controlling folliculogenesis.

Differential gene expression in male and female rat lenses undergoing cataract induction by transforming growth factor-beta (TGF-beta)

Epidemiologic studies in humans as well as immunohistologic studies in animals have demonstrated significant sex differences in the propensity to develop cataract. Several studies suggest that estrogen may play a protective role against cataractogenesis. Indeed, male and ovariectomized female rat lenses have a greater susceptibility to cataract induced by transforming growth factor-beta (TGF-beta) than do normal female lenses. However, in spite of the current evidence that estrogen may play a pivotal role in cataractogenesis, the molecular mechanisms behind this phenomenon are largely undetermined. Our study utilized the differential display procedure to examine gene up- and down-regulation in male, normal female and ovariectomized female rat lenses exposed to TGF-beta. Male and normal female rat lenses were cultured with or without 0.15 ng ml(-1)TGF-beta. Lenses were then harvested, and total RNA was isolated for analysis by reverse-transcriptase differential display. Differentially expressed mRNAs were subcloned, sequenced and identified through GenBank database searches. The original experiment was repeated with the addition of ovariectomized female TGF-beta(+/-) conditions, and all differential patterns of gene expression were verified using Northern blot and RT-PCR analysis. Screening of approximately 12% of the mRNA population led to the identification of 27 differentially expressed cDNAs. Notably, strong gender differences were found in expression levels of gammaB-crystallin. In addition, proteasome Z subunit was up-regulated in TGF-beta-treated male and ovariectomized female lenses, but was down-regulated in TGF-beta-treated normal female lenses. This pattern of expression is consistent with the increased susceptibility of male and ovariectomized lenses to TGF-beta-induced cataract. We conclude that differential display is a useful and expedient method for analysing changes in gene expression in the lens. Structural and functional studies of the genes identified in this study may further elucidate mechanisms underlying the TGF-beta-induced cataract formation and differential rates of cataractogenesis in males vs females. In particular, our data suggest that the role of proteasome Z subunit in TGF-beta-induced anterior subcapsular cataract warrants further investigation.

Activin A exerts both pro- and anti-inflammatory effects on human term gestational tissues

There is a growing appreciation of the importance of activin as a modulator of immune function. The aim of the present study was to determine whether activin A exerts any effects on cytokine and prostaglandin (PG) production by the tissues of pregnancy. Explant cultures were established for amnion, choriodecidual and placental tissues derived from pregnancies delivered at term by Caesarean section (n=5 placentae). Explants were treated with activin A (0.5, 5 and 50 ng/ml) in serum-free Ham's F12/DME media for 24 h (n=3-4 replicates). Production rates of interleukin (IL)-1beta, IL-6, IL-8, tumour necrosis factor-alpha (TNF-alpha) and PGE(2)were determined using immunoassay. Differences between treatment groups were analysed by ANOVA followed by Dunnett's test;P< 0.05 was considered to be significant. Amnion IL-6 production exhibited biphasic responses to activin A: at 5 ng/ml activin A, IL-6 production was significantly stimulated (to 246+/-74.6 per cent of control (mean+/-sem), while at 50 ng/ml it was significantly inhibited (to 46+/-7.4 per cent of control). IL-8 and PGE(2)production by amnion showed significant responses to activin A that were similar to those of IL-6. No significant effects of activin A were observed on choriodecidual and placental IL-6, IL-8 and PGE(2)production. However, TNF-alpha production was significantly inhibited by 50 ng/ml activin A in both choriodecidual and placental explants (to 43+/-9.7 per cent and 51+/-6.7 per cent of control, respectively). Placental IL-1beta production was not altered by treatment with activin A at any concentration. These findings support the concept of activin as an immune modulator in tissues of pregnancy.

Transforming growth factor beta1-regulated cell proliferation and expression of neural cell adhesion molecule in B104 neuroblastoma cells: differential effects of ethanol

The expression and activity of factors influencing early neuronal development are altered by ethanol. Such factors include growth factors, for example, platelet-derived growth factor and basic fibroblast growth factor (for cell proliferation), and cell adhesion molecules (for neuronal migration). One agent, transforming growth factor beta1 (TGFbeta1), may affect both events. We tested the hypothesis that ethanol alters myriad TGFbeta1-mediated activities [i.e., cell proliferation and neural cell adhesion molecule (N-CAM) expression] using B104 neuroblastoma cells. TGFbeta1 inhibited the proliferation of B104 cells as evidenced by decreases in cell number and [3H]thymidine ([3H]dT) incorporation. TGFbeta1 induced sustained activation of extracellular signal-regulated kinases (ERKs), which are part of the family of mitogen-activated protein kinases (MAPKs). Treatment with PD98059 (a MAPK kinase blocker) abolished TGFbeta1-regulated inhibition of [3H]dT incorporation. TGFbeta1-mediated growth inhibition was potentiated by ethanol exposure. Ethanol also produced prolonged activation of ERK, an effect that was partially eliminated by treatment with PD98059. On the other hand, TGFbeta1 up-regulated N-CAM expression, and this up-regulation was not affected by treatment with PD98059. Ethanol inhibited the TGFbeta1-induced up-regulation of N-CAM expression in a concentration-dependent manner. Thus, TGFbeta1 affects ERK-dependent cell proliferation and ERK-independent N-CAM expression in B104 cells. Both activities are sensitive to ethanol and may underlie the ethanol-induced alterations in the proliferation and migration of CNS neurons.

The levels of leukemia inhibitory factor mRNA in a Schwann cell line are regulated by multiple second messenger pathways

Axotomy of sympathetic and sensory neurons leads to changes in their neuropeptide phenotypes. These changes are mediated in part by the induction of leukemia inhibitory factor (LIF) by nonneuronal cells. In the present study, we identified satellite/Schwann cells as a possible source of the injury-induced LIF. Using a Schwann cell line, SC-1 cells, we examined mechanisms of LIF induction. LIF mRNA levels increased rapidly when the cells were treated with 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate, phorbol 12-myristate 13-acetate (PMA), or A23187. Among these reagents, PMA was the most efficacious. Inhibition of protein kinase C (PKC) by GF-1 09203X significantly reduced the PMA-induced LIF mRNA levels. As PKC is known to activate the extracellular signal-regulated kinase (ERK) signaling pathway, the involvement of this pathway in the PMA-stimulated induction of LIF mRNA was examined. Phosphorylation of ERKs was increased following PMA treatment in SC-1 cells. Moreover, inhibition of ERK kinase activity by PD98059 dramatically reduced PMA-stimulated phosphorylation of ERKs and induction of LIF mRNA. These results indicate that LIF mRNA levels can be regulated by ERK activation via stimulation of PKC in Schwann cells.

Expression of transforming growth factor-beta receptors types II and III within various cells in the rat periodontium

This study reports the immunohistochemical localization of TGF-beta receptor type II (T beta R-II) and type III (T beta R-III) in cells of the forming periodontal ligament (PDL) in rat first molar roots. Mandibular periodontium was obtained from 3, 6 and 12-wk-old rats. This represented tissue from the initial, pre-mature and post-mature stages of root and periodontal development, respectively. Mandibular bone chips and molar roots were used to isolate osteoblasts, fibroblasts and cementoblasts. Cells were obtained using a 2-step trypsinization and explant technique, and cultured in Dulbecco's modification of Eagle's medium (DMEM) under routine cell culture conditions. Cells were cultured on coverslips for the purpose of detecting TGF-beta receptors, and compared with whole tissue sections using the same detection method. Cells which stained positively for T beta R-II and T beta R-III on both paraffin sections and cultured cell slides were counted. Both receptors were expressed in the various periodontal tissue compartments. PDL fibroblasts, cementoblasts and osteoblasts were stained positively for T beta R-II and T beta R-III. Endothelial cells were noted to be positive for T beta R-II only. T beta R-II was more widely distributed in cells than T beta R-III, but T beta R-III was extensively localized in the extracellular matrix. Both receptors were expressed on the cell membrane and also localized in the cytoplasm. The findings for paraffin sections were consistent with the immunohistochemical staining of cultured cells. The percentage of cells which stained positively for T beta R-II was greater (approximately 85%) than that for T beta R-III (approximately 60%) in all major types of the PDL cells on both paraffin sections and cultured cell slides. Extensive location of TGF-beta receptors in both cells and extracellular matrix suggests that several binding sites are available for TGF-beta s to interact with target cells during development and following maturation of the periodontium.

Neurofibromin modulation of ras activity is required for normal endocardial-mesenchymal transformation in the developing heart

Endocardial cushions are the precursors of the cardiac valves and form by a process of epithelial-mesenchymal transformation. Secreted growth factors from myocardium induce endocardial cells to transform into mesenchyme and invade the overlying extracellular matrix. Here, we show that the product of the Nf1 neurofibromatosis gene is required to regulate this event. In the absence of neurofibromin, mouse embryo hearts develop overabundant endocardial cushions due to hyperproliferation and lack of normal apoptosis. Neurofibromin deficiency in explant cultures is reproduced by activation of ras signaling pathways, and the Nf1(−/−) mutant phenotype is prevented by inhibiting ras in vitro. These results indicate that neurofibromin normally acts to modulate epithelial-mesenchymal transformation and proliferation in the developing heart by down regulating ras activity.

Production of the transforming growth factor-beta binding protein endoglin is regulated during chick heart development

The early embryonic heart consists of two cell types. The cells form an inner epithelial tube of endocardium within an outer tube of myocardium separated by a cell-free extracellular matrix. A crucial process in heart development is the production of cushion mesenchyme in the atrioventricular (AV) canal and outflow tract (OT). Cushion mesenchyme differentiates from the endocardium in response to signaling molecules produced by the adjacent myocardium. In chicken hearts, both transforming growth factor-beta3 (TGF-beta3) and TGF-beta2 are present and have been identified as being important in the production of cushion mesenchyme. We were interested in how the signals from these two similar molecules may be differentiated during early heart development. To this end, we examined the expression of endoglin, a TGF-beta receptor molecule, in the developing chick heart. Endoglin is typically located on endothelial cell layers and binds tightly to TGF-beta1 and TGF-beta3 but not well to TGF-beta2. We show that during the formation of the primitive heart tube, endoglin is found at relatively high levels in both presumptive myocardium and endocardium. However, as myocardium differentiates and development proceeds, endoglin expression is progressively reduced. At stage 20 in the heart, endoglin expression is most readily seen in the AV canal and the OT. This pattern of expression is similar to the reported TGF-beta3 expression patterns in the heart.

Oncostatin M Up-Regulates Tissue Inhibitor of Metalloproteinases-3 Gene Expression in Articular Chondrocytes via De Novo Transcription, Protein Synthesis, and Tyrosine Kinase- and Mitogen-Activated Protein Kinase-Dependent Mechanisms

Cytokines and growth factors regulate physiologic and pathologic turn-over of cartilage extracellular matrix (ECM) by altering the balance between tissue inhibitors of metalloproteinases (TIMPs) and matrix metalloproteinases (MMPs). Oncostatin M (OSM) is a cytokine of the IL-6 family whose levels are increased in the serum and synovial fluids of patients with rheumatoid arthritis. We examined responsiveness of the TIMP-3 gene to OSM in articular chondrocytes and studied the regulatory and signaling mechanisms of this response. OSM induced TIMP-3 mRNA and protein expression in a dose- and time-dependent fashion. Concomitantly, stromelysin-1 and collagenase-1 RNA and activities were also induced. A cartilage matrix growth factor, TGF-β, induced TIMP-3, but combined OSM and TGF-β did not further increase the extent of induction, suggesting a lack of synergy between the two. OSM induction of TIMP-3 gene expression was dependent upon de novo protein synthesis and transcription. RNA decay time-courses suggested that the OSM-mediated increase of TIMP-3 RNA was not due to enhanced message stability and, along with inhibition by actinomycin-D, suggested a transcriptional control. The antiinflammatory glucocorticoid, dexamethasone, down-regulated this augmentation. Investigation of the signaling mechanisms revealed that protein tyrosine kinase inhibitors genistein and herbimycin A, as well as the specific mitogen-activated protein kinase (MAPK) kinase inhibitor PD98059, suppressed OSM-induced TIMP-3 message expression, suggesting the involvement of tyrosine kinases and mitogen-activated protein kinase cascades in the signaling of OSM leading to TIMP-3 RNA enhancement. Thus OSM can potentially alter the cartilage matrix metabolism by regulating genes like TIMP-3 and matrix metalloproteinases.