TGF-beta receptor-binding proteins: complex interactions

Cloning and primary immunological study of TGF-β1 and its receptors TβR I /TβR II in tilapia(Oreochromis niloticus)

The transforming growth factor β (TGF-β) superfamily plays critical roles in tumor suppression, cell proliferation and differentiation, tissue morphogenesis, lineage determination, cell migration and apoptosis. Recently, TGF-β1, one important member of TGF-β superfamily, is suggested as an immune regulator in the teleost. In this study, we cloned the cDNAs of TGF-β1 and its receptors, TβR I and TβR II (including three isoforms) from tilapia (Genbank accession numbers: KP754231- KP754235). A tissue distribution profile analysis indicated that TGF-β1 was highly expressed in the head kidney, gill, spleen, kidney and PBLs (peripheral blood leukocytes); TβR I only showed considerable expression in the liver; and TβR II-2 was highly expressed in the kidney, gill, liver, head kidney and heart. We determined that the mRNA expressions of TGF-β and TβR I /TβR II-2 were significantly increased in tilapia head kidney and spleen leukocytes by the stimulation of Lipopolysaccharide (LPS) or Poly I: C. We also examined their expressions in the spleen and head kidney of tilapia after IP injection of streptococcus agalactiae. The results showed that the mRNA expressions of these three genes all increased in the head kidney as early as 6 h post infection, and in the spleen 3 d post infection. In addition, the protein level of TGF-β1 was also up-regulated in the head kidney and the spleen after infection. Taken together, our data indicate that the TGF-β1-TβR I /TβR II-2 system functions potentially in tilapia immune system.

Effects of Fufang Biejia Ruangan Pills on hepatic fibrosis in vivo and in vitro

AIM: To explore the protective effect and the relevant mechanisms of Fufang Biejia Ruangan Pills (FFBJRGP) on hepatic fibrosis in vivo and in vitro.

METHODS: Hepatic fibrosis was induced by carbon tetrachloride composite factors. Adult Wistar rats were randomly divided into four groups: normal control group; hepatic fibrosis model group; FFBJRGP-treated group at a daily dose of 0.55 g/kg; and colchicine-treated group at a daily dose of 0.1 g/kg. The effects of FFBJRGP on liver function, serum levels of hyaluronic acid (HA), type IV collagen (CIV), type III procollagen (PC III), laminin (LN), histopathology, and expression of transforming growth factor (TGF-β1) and Smad3 in hepatic fibrosis were evaluated in vivo. The effects of FFBJRGP on survival rate, hydroxyproline content and cell cycle distribution were further detected in vitro.

RESULTS: Compared with the hepatic fibrosis model group, rats treated with FFBJRGP showed a reduction in hepatic collagen deposition and improvement in hepatic lesions. Compared with those of the model group, the activities of alanine aminotransferase (62.0 ± 23.7 U/L) and aspartate aminotransferase (98.8 ± 40.0 U/L) in the FFBJRGP-treated group were decreased (50.02 ± 3.7 U/L and 57.2 ± 30.0 U/L, respectively, P < 0.01). Compared with those in the model group, the levels of PCIII (35.73 ± 17.90 μg/mL), HA (563.82 ± 335.54 ng/mL), LN (89.57 ± 7.59 ng/mL) and CIV (29.20 ± 6.17 ng/mL) were decreased to 30.18 ± 9.41, 456.18 ± 410.83, 85.46 ± 7.51 and 28.02 ± 9.45 ng/mL, respectively. Reverse-transcriptase polymerase chain reaction and Western blotting also revealed that expression of TGF-β1 and Smad3 were down-regulated in vivo. Cell proliferation was inhibited, the level of hydroxyproline was decreased compared with the control group (P < 0.01), and the cell cycle was redistributed when exposed to FFBJRGP in vitro.

CONCLUSION: FFBJRGP inhibits hepatic fibrosis in vivo and in vitro, which is probably associated with downregulation of fibrogenic signal transduction of the TGF-β-Smad pathway.

Effects of SARA on oxygen-glucose deprivation in PC12 cell line

Ischemic stroke is a major composition of cerebrovascular disease, seriously threatening to human health in the world. Activin A (ActA), belonging to transforming growth factor-beta (TGF-β) super family, plays an important role in the hypoxic-ischemic brain injury through ActA/Smads pathway. While as an essential phosphorylation assistor in TGF-β signaling, the functions and mechanisms of smad anchor for receptor activation (SARA) in ischemic brain injury remain poorly understood. To solve this problem and explore the pathological processes of ischemic stroke, we used an Oxygen-Glucose deprivation (OGD) model in nerve growth factor-induced differentiated rattus PC12 pheochromocytoma cells and down regulated the expressions of SARA by RNA interference technology. Our results showed that the repression of SARA before OGD exposure reduced the expressions of Smad2, 3, 4 mRNA and the phosphorylation rate of Smad2 protein, but it did not affect the mRNA expressions of Smad7. After OGD treatment, ActA/Smads pathway was activated and the expression of SARA in the SARA pre-repression group was significantly up-regulated. The pre-repression of SARA increased the sensitivities of nerve-like cells to OGD damage. Moreover, the mRNA expression of Smad7 which was supposed to participate in the negative feedback of ActA/Smads pathway was also elevated due to OGD injury. Taken together, these results suggest a positive role of SARA in assisting the phosphorylation of Smad2 and maintaining the neuron protective effect of ActA/Smads pathway.

Effect and mechanism of methyl helicterate isolated from Helicteres angustifolia (Sterculiaceae) on hepatic fibrosis induced by carbon tetrachloride in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Methyl helicterate is a triterpenoid isolated from Helicteres angustifolia (Sterculiaceae), one of the valuable traditional Chinese herbs. Antifibrotic activities of H. angustifolia have been extensively proved.

AIM OF THE STUDY

The purpose of this study was to investigate the effect of methyl helicterate (MH) on liver fibrosis in rats induced by carbon tetrachloride (CCl(4)) and to explore its underlying mechanism.

MATERIALS AND METHODS

Hepatic fibrosis was induced in male Sprague-Dawley (SD) rats by intragastric administration with 2 ml/kg CCl(4) (mixed 1:1 in peanut oil) twice a week for 12 weeks. To evaluate the effect of MH (16.72, 33.45, 66.90 mg/kg) on hepatic fibrosis, liver function, histological study and hepatic fibrosis evaluation were performed. Liver function was assessed by determining the serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), albumin (Alb) and total protein (TP). The biomarkers such as hydroxyproline (Hyp), hyaluronic acid (HA), type III precollagen (PCIII) and laminin (LN) were examined for the evaluation of hepatic fibrosis. The underlying mechanism was investigated by measuring oxidative stress level and detecting the expression of TGF-β1 mRNA and Smad3 protein.

RESULTS

MH (33.45, 66.90 mg/kg) treatment significantly inhibited the loss of body weight and the increase of liver index in rats induced by CCl(4). MH also improved the liver function as indicated by decreasing serum enzymatic activities of ALT, AST, TP and Alb (P<0.05). Histological results indicated that MH alleviated liver damage and reduced the formation of fibrous septa. Moreover, MH significantly decreased liver Hyp, HA, LN and PCIII (P<0.05). Research on mechanism showed that MH could markedly reduce liver malondialdehyde (MDA) concentration, increase activities of liver superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and inhibit the expression of TGF-β1 mRNA and Smad3 protein (P<0.05).

CONCLUSIONS

Our findings indicated that MH can inhibit CCl(4)-induced hepatic fibrosis, which may be ascribed to its radical scavenging action, antioxidant activity, and modulation of TGF-β-Smad3 signaling pathway.

Quantitative phosphoproteomics of transforming growth factor-β signaling in colon cancer cells

The transforming growth factor-β (TGF-β) signaling pathway progresses through a series of protein phosphorylation regulated steps. Smad4 is a key mediator of the classical TGF-β signaling pathway; however, reports suggest that TGF-β can activate other cellular pathways independent of Smad4. By investigating the TGF-β-regulated phosphoproteome, we aimed to uncover new functions controlled by TGF-β. We applied titanium dioxide to enrich phosphopeptides from stable isotope labeling with amino acids in cell culture (SILAC)-labeled SW480 cells stably expressing Smad4 and profiled them by mass spectrometry. TGF-β stimulation for 30 min resulted in the induction of 17 phosphopeptides and the repression of 8 from a total of 149 unique phosphopeptides. Proteins previously not known to be phosphorylated by TGF-β including programmed cell death protein 4, nuclear ubiquitous casein and cyclin-dependent kinases substrate, hepatoma-derived growth factor and cell division kinases amongst others were induced following TGF-β stimulation, while the phosphorylation of TRAF2 and NCK-interacting protein kinase are examples of proteins whose phosphorylation status was repressed. This phosphoproteomic screen has identified new TGF-β-modulated phosphorylation responses in colon carcinoma cells.

Protective effect of oxymatrine on myocardial fibrosis induced by acute myocardial infarction in rats involved in TGF-β₁-Smads signal pathway

Oxymatrine (1), a component extracted from a traditional Chinese herb Sophora japonica (Sophora flavescens Ait.), has been demonstrated to have a variety of pharmacological actions. Abundant experimental evidence indicates that 1 may exert a protective effect on the cardiovascular system. This study was designed to explore the possible role of 1 against myocardial fibrosis induced by acute myocardial infarction (AMI) and its modulation on transforming growth factor beta 1 (TGF-β(1))-Smads signaling pathways. Rats with AMI induced by ligation of left anterior descending branch were randomly assigned to receive 1 50 and 25 mg/kg intragastrically, and model group which were further compared with sham-operated group, and positive group treated with captopril. The effects of 4-week therapy with 1 starting 24 h after infarction had been investigated based on (1) hemodynamics, (2) tissue weights, (3) biochemical indicator (hydroxyproline contents in left ventricle), and (4) TGF-β(1), TGF-β(1) receptor (TβR(1)), Smad3, Smad4, Smad7, Col1, and Col3 expression by semi-quantitative reverse transcription PCR. Treatment with 1 significantly ameliorated hemodynamics, inhibited the expression of TβR(1) mRNA and Smad3 mRNA, and reduced the left ventricle weight/body weight. The results of this research indicated that 1 might protect against myocardial fibrosis and the mechanism may be involved in modulating TGF-β(1)-Smads signal pathway.

Proteomics of Smad4 regulated transforming growth factor-beta signalling in colon cancer cells

TGF-β signalling can play a paradoxical cell type specific role in cancer progression. Smad4 is a key mediator of the TGF-β pathway, and is mutated and/or deleted in many cancers. To investigate Smad4 regulated TGF-β signalling in colon cancer we conducted an iTRAQ mass spectrometry quantitative screen using wild type SW480 (Smad4 negative) colon carcinoma cells and stably restored Smad4 positive SW480 cells. In cells possessing a restored canonical TGF-β signalling pathway, 48 h TGF-β stimulation induced the expression of 15 proteins and repressed 1 protein, while in Smad4 wild type cells, TGF-β induced 7 proteins and repressed 2 proteins. The expression of several S100 protein family members (A2, A4, A10, and A11), transgelin-2 and AKAP12, amongst others, were shown to be regulated by TGF-β in a Smad4 dependent manner. We observed that S100 A4 could be repressed by TGF-β, independently of Smad4 expression, while other Smad4 independent TGF-β responses were restricted to induction of ribosomes and cytoskeletal proteins. Our proteomic screen has identified new Smad4 dependent and independent TGF-β responses in colon carcinoma cells.

Gfi-1B controls human erythroid and megakaryocytic differentiation by regulating TGF-β signaling at the bipotent erythro-megakaryocytic progenitor stage

Growth factor independence-1B (Gfi-1B) is a transcriptional repressor essential for erythropoiesis and megakaryopoiesis. Targeted gene disruption of GFI1B in mice leads to embryonic lethality resulting from failure to produce definitive erythrocytes, hindering the study of Gfi-1B function in adult hematopoiesis. We here show that, in humans, Gfi-1B controls the development of erythrocytes and megakaryocytes by regulating the proliferation and differentiation of bipotent erythro-megakaryocytic progenitors. We further identify in this cell population the type III transforming growth factor-β receptor gene, TGFBR3, as a direct target of Gfi-1B. Knockdown of Gfi-1B results in altered transforming growth factor-β (TGF-β) signaling as shown by the increase in Smad2 phosphorylation and its inability to associate to the transcription intermediary factor 1-γ (TIF1-γ). Because the Smad2/TIF1-γ complex is known to specifically regulate erythroid differentiation, we propose that, by repressing TGF-β type III receptor (TβRΙII) expression, Gfi-1B favors the Smad2/TIF1-γ interaction downstream of TGF-β signaling, allowing immature progenitors to differentiate toward the erythroid lineage.

Effects of Haobie Yangyin Ruanjian decoction on hepatic fibrosis induced by carbon tetrachloride in rats

AIM

To explore the anti-fibrotic effect of Haobie Yangyin Ruanjian decoction (HYRD) on CCl(4)-induced hepatic fibrosis in rats and its modulation on the transforming growth factor (TGF) beta-Smad signaling pathway.

METHODS

Fifty-six healthy Wistar rats were randomly divided into five groups: normal control group (n = 6), CCl(4)-induced hepatic fibrosis group (n = 14) and three treatment groups (the treated rats received HYRD via oral administration at daily dosages of 8.2, 2.5 and 0.82 g/kg, respectively) of HYRD (n = 12, respectively). Experimental hepatic fibrosis was induced by subcutaneous injection of carbon tetrachloride solution (CCl(4) dissolved in peanut oil, 4:6, V/V) with 0.5 mL/100 g body weight for the first time, and then 0.3 mL/100 g body weight twice a week for 8 wk. In the former 2 wk, rats were raised by feedstuff I (80% corn meal, 20% lard, 0.5% cholesterol). After 2 wk, they were raised by feedstuff II (corn meal and 0.5% cholesterol). Except for the control group, 30% alcohol solution was given orally to each rat every other day from the beginning, 1 mL for each rat. Liver function parameters and hepatic hydroxyproline content were detected by chromatometry. Serum levels of hyaluronic acid (HA), type IV collagen (CIV), type III precollagen (PCIII) and laminin (LN) were assayed with radioimmunoassay. Deposition of collagen was observed with hematoxylin-eosin staining and collagen staining. Gene expression of TGFbeta1 and Smad3 were detected with real-time reverse transcriptase-polymerase chain reaction and Western blotting, respectively.

RESULTS

The serum levels of alanine transaminase and aspartate transaminase were increased in the model group compared with the control group (P < 0.01), and they were decreased in the three treatment groups compared with the model group. The serum levels of total protein and albumin were decreased in the model group and increased in the three treatment groups. The hepatic hydroxyproline content and serum levels of PCIII, HA, LN and CIV were markedly increased in the model group compared with the control group, and decreased in the treatment groups. The gene expression of TGFbeta1 and Smad3 was enhanced in the model group compared with the control group, and HYRD could down regulate their expression.

CONCLUSION

HYRD can inhibit hepatic fibrosis induced by CCl(4) in rats, which is probably associated with its down-regulation on fibrogenic signal transduction of TGFbeta-Smad pathway.

Signal transduction and metabolism in chondrocytes is modulated by lactoferrin

OBJECTIVE

Activation of granulocytes causes a considerable rise in the concentration of lactoferrin (Lf) in synovial fluid (SF). We here investigate consequences thereof on signal transduction and the balance between catabolic and anabolic metabolism in chondrocytes.

METHODS

Signal transduction was analysed in cultured chondrocytes by immunodetection of mitogen activated protein kinases (MAPK) and analysis of Smad2 translocation to the nucleus. Expression levels of matrix metalloproteinases (MMPs) and of aggrecan were measured by reverse-transcription-PCR. The proteolytic activity of MMPs was ascertained by zymography. Expression of the low-density-lipoprotein-receptor-related-protein-1 (LRP-1), a Lf receptor for signalling, was assayed by immunohistochemistry in cartilage and in cultured chondrocytes by immunoblotting.

RESULTS

We found LRP-1 expressed in dedifferentiated chondrocytes in culture and in cartilage tissue preferentially on the articular surface where it can encounter Lf within SF. Lf stimulated proliferation of chondrocytes, comparable to transforming growth factor-beta1 (TGFbeta1) and activated p38 and the extracellular-signal regulated-kinases 1/2 (ERK1/2) within minutes. Surprisingly, Lf induced nuclear Smad2 translocation, a signal pathway ascribed to TGFbeta receptor activation. Lf significantly increased the levels of catabolic indicators such as MMP1, MMP2, MMP3 and MMP13 and inhibited aggrecan synthesis.

CONCLUSION

Lf is a robust regulator of chondrocyte metabolism, comparable to TGFbeta1. The catabolic influence together with the proliferative stimulus indicates a function as an early phase cytokine, enhancing MMPs, necessary for degradation of damaged tissue and stimulating proliferation of chondrocytes, necessary for reconstruction.

Bladder stromal loss of transforming growth factor receptor II decreases fibrosis after bladder obstruction

PURPOSE

Transforming growth factor-beta is a potent stimulator of extracellular matrix production. Several studies show that loss of transforming growth factor-beta signaling decreases kidney, liver and lung fibrosis. However, the role of transforming growth factor-beta signaling in bladder fibrosis is not entirely understood. We investigated the effect of stromal loss of such signaling in mice after partial bladder outlet obstruction.

MATERIALS AND METHODS

We performed partial bladder outlet obstruction by urethral ligation in 5-week-old female Tgfbr2(colTKO) mice. These mice were compared to WT mice with partial bladder outlet obstruction and to WT nonobstructed controls. After 4 weeks and before sacrifice urodynamics were performed. Bladder tissue was harvested, and p-Smad2 and collagen (Masson's trichrome) staining were performed.

RESULTS

Bladder compliance was increased in partially obstructed Tgfbr2(colTKO) mice and decreased in partially obstructed WT mice. The latter had increased smooth muscle hypertrophy and increased collagen deposition between smooth muscle bundles compared to those in Tgfbr2(colTKO) mice and nonobstructed controls. Transforming growth factor-beta responsive collagen promoter activity was significantly decreased in Tgfbr2 knockout bladder stromal cells vs WT stromal cells.

CONCLUSIONS

Stromal loss of transforming growth factor-beta signaling decreased collagen deposition after partial bladder outlet obstruction. In contrast to collagen production by recruited macrophages, stromal transforming growth factor-beta signaling appears to be the primary source of fibrosis after partial bladder outlet obstruction. These findings further support the hypothesis that manipulating transforming growth factor-beta signaling in bladder stromal cells would provide a future avenue for neuropathic bladder and bladder fibrosis treatment.

Role of SARA (SMAD anchor for receptor activation) in maintenance of epithelial cell phenotype

By inducing epithelial-to-mesenchymal transition (EMT), transforming growth factor-beta (TGF-beta) promotes cancer progression and fibrosis. Here we show that expression of the TGF-beta receptor-associated protein, SARA (Smad anchor for receptor activation), decreases within 72 h of exposure to TGF-beta and that this decline is both required and sufficient for the induction of several markers of EMT. It has been suggested recently that expression of the TGF-beta signaling mediators, Smad2 and Smad3, may have different functional effects, with Smad2 loss being more permissive for EMT progression. We find that the loss of SARA expression leads to a concomitant decrease in Smad2 expression and a disruption of Smad2-specific transcriptional activity, with no effect on Smad3 signaling or expression. Further, the effects of inducing the loss of Smad2 mimic those of the loss of SARA, enhancing expression of the EMT marker, smooth muscle alpha-actin. Smad2 mRNA levels are not affected by the loss of SARA. However, the ubiquitination of Smad2 is increased in SARA-deficient cells. We therefore examined the E3 ubiquitin ligase Smurf2 and found that although Smurf2 expression was unaltered in SARA-deficient cells, the interaction of Smad2 and Smurf2 was enhanced. These results describe a significant role for SARA in regulating cell phenotype and suggest that its effects are mediated through modification of the balance between Smad2 and Smad3 signaling. In part, this is achieved by enhancing the association of Smad2 with Smurf2, leading to Smad2 degradation.

The monocyte chemoattractant protein-1/CCR2 loop, inducible by TGF-beta, increases podocyte motility and albumin permeability

The role of monocyte chemoattractant protein-1 (MCP-1) in diabetic nephropathy is typically viewed through the lens of inflammation, but MCP-1 might exert noninflammatory effects on the kidney cells directly. Glomerular podocytes in culture, verified to express the marker nephrin, were exposed to diabetic mediators such as high glucose or angiotensin II and assayed for MCP-1. Only transforming growth factor-beta (TGF-beta) significantly increased MCP-1 production, which was prevented by SB431542 and LY294002, indicating that signaling proceeded through the TGF-beta type I receptor kinase and the phosphatidylinositol 3-kinase pathway. The TGF-beta-induced MCP-1 was found to activate the podocyte's cysteine-cysteine chemokine receptor 2 (CCR2) and, as a result, enhance the cellular motility, cause rearrangement of the actin cytoskeleton, and increase podocyte permeability to albumin in a Transwell assay. The preceding effects of TGF-beta were replicated by treatment with recombinant MCP-1 and blocked by a neutralizing anti-MCP-1 antibody or a specific CCR2 inhibitor, RS102895. In conclusion, this is the first description that TGF-beta signaling through PI3K induces the podocyte expression of MCP-1 that can then operate via CCR2 to increase cellular migration and alter albumin permeability characteristics. The pleiotropic effects of MCP-1 on the resident kidney cells such as the podocyte may exacerbate the disease process of diabetic albuminuria.

TGF-beta signal transduction in chronic kidney disease

Transforming growth factor (TGF)-beta is a central stimulus of the events leading to chronic progressive kidney disease, having been implicated in the regulation of cell proliferation, hypertrophy, apoptosis and fibrogenesis. The fact that it mediates these varied events suggests that multiple mechanisms play a role in determining the outcome of TGF-beta signaling. Regulation begins with the availability and activation of TGF-beta and continues through receptor expression and localization, control of the TGF-beta family-specific Smad signaling proteins, and interaction of the Smads with multiple signaling pathways extending into the nucleus. Studies of these mechanisms in kidney cells and in whole-animal experimental models, reviewed here, are beginning to provide insight into the role of TGF-beta in the pathogenesis of renal dysfunction and its potential treatment.

TGFbeta-induced RhoA activation and fibronectin production in mesangial cells require caveolae

Glomerular sclerosis of diverse etiologies is characterized by mesangial matrix accumulation, with transforming growth factor-beta (TGFbeta) an important pathogenic factor. The GTPase RhoA mediates TGFbeta-induced matrix accumulation in some settings. Here we study the role of the membrane microdomain caveolae in TGFbeta-induced RhoA activation and fibronectin upregulation in mesangial cells (MC). In primary rat MC, TGFbeta1 time dependently increased RhoA and downstream Rho kinase activation. Rho pathway inhibition blocked TGFbeta1-induced upregulation of fibronectin transcript and protein. TGFbeta1-induced RhoA activation was prevented by disrupting caveolae with cholesterol depletion and rescued by cholesterol repletion. Compared with wild types, RhoA/Rho kinase activation was absent in MC lacking caveolae. Reexpression of caveolin-1 (and caveolae) restored these responses. Phosphorylation of caveolin-1 on Y14, effected by Src kinases, has been implicated in signaling responses. Overexpression of nonphosphorylatable caveolin-1 Y14A prevented TGFbeta1-induced RhoA activation. TGFbeta1 also activated Src, and its inhibition blocked RhoA activation. Furthermore, TGFbeta1 led to association of RhoA and caveolin-1. This was prevented by Src or TGFbeta receptor I inhibition, and by caveolin-1 Y14A overexpression. Last, fibronectin upregulation by TGFbeta1 was blocked by Src inhibition, not seen in caveolin-1 knockout MC, and restored by caveolin-1 reexpression in the latter. TGFbeta1-induced collagen I accumulation also required caveolae. TGFbeta1-mediated Smad2/3 activation, however, did not require caveolae. We conclude that RhoA/Rho kinase mediates TGFbeta-induced fibronectin upregulation. This requires caveolae and caveolin-1 interaction with RhoA. Interference with caveolin/caveolae or RhoA signaling thus represents a potential target for the treatment of fibrotic renal disease.

Effect of Oxymatrine on the TGFbeta-Smad signaling pathway in rats with CCl4-induced hepatic fibrosis

AIM: To explore the anti-fibrotic effect of Oxymatrine on CCl₄-induced liver fibrosis in rats and its modulation on the TGFbeta-Smad signaling pathway.

METHODS: One hundred healthy male SD rats were randomly divided into three groups: normal group (n = 20), treatment group of Oxymatrine (n = 40) and CCl₄-induced fibrosis group (n = 40). Experimental hepatic fibrosis was induced by subcutaneous injection of carbon tetrachloride (CCl₄ soluted in liquid paraffin with the concentration of 300 g/L, the dosage of injection was 3 mL/kg, twice per week for 8 wk). The treated rats received Oxymatrine via celiac injection at a dosage of 10 mg/kg twice a week at the same time. The deposition of collagen was observed with H&E and Masson staining. The concentration of serum TGF-β1 was assayed with ELISA. The gene expression of Smads and CBP (CREB binding protein) was detected with in situ hybridization (ISH) and immunohistochemistry (IH), respectively. All the experimental figures were scanned and analyzed with special figure-analysis software.

RESULTS: A significant reduction of collagen deposition and rearrangement of the parenchyma was noted in the liver tissue of Oxymatrine-treated rats. The semi-quantitative histological scores (2.43 ± 0.47 &mgr;m²vs 3.76 ± 0.68 &mgr;m², P < 0.05) and average area of collagen in those rats were significantly decreased when compared with hepatic cirrhosis model rats (94.41 ± 37.26 &mgr;m²vs 290.86 ± 89.37 &mgr;m², P < 0.05). The gene expression of Smad 3 mRNA was considerably decreased in the treated animals. The A value of Smad 3 mRNA was lower in the treated rats than the model rats (0.034 ± 0.090 vs 0.167 ± 0.092, P < 0.05). Contrarily, the A value of Smad 7 mRNA was increased considerably in the treated animals (0.175 ± 0.065 vs 0.074 ± 0.012, P < 0.05). There was an obvious decrease in the expression of CBP mRNA in treated rats as illuminated by a reduction of its A value when compared with model rats (0.065 ± 0.049 vs 0.235 ± 0.025, P < 0.001).

CONCLUSION: Oxymatrine is effective in reducing the production and deposition of collagen in the liver tissue of experimental rats. Oxymatrine could promote the expression of Smad 7 and inhibit the expression of Smad 3 and CBP in CCl₄-induced hepatic fibrosis in SD rats, could modulate the fibrogenic signal transduction of TGFβ-Smad pathway.

Smad and p38 MAP kinase-mediated signaling of proteoglycan synthesis in vascular smooth muscle

Atherosclerosis is the underlying pathological process of most cardiovascular disease. A critical component of the "response to retention" hypothesis of atherogenesis is proteoglycan/low density lipoprotein (LDL) binding. Transforming growth factor beta (TGF-beta) is present in atherosclerotic lesions, regulates vascular smooth muscle cell (VSMC) proteoglycan synthesis via an unknown signaling pathway, and increases proteoglycan/LDL binding. This pathway was investigated using the activin receptor-like kinase 5 (ALK5) inhibitor SB431542 and inhibitors of p38 MAP kinase as a possible downstream or alternative mediator. TGF-beta stimulated and SB431542 inhibited the phosphorylation of Smad2/3. In human VSMC, TGF-beta increased [(35)S]sulfate incorporation into proteoglycans associated with a 19% increase in glycosaminoglycan (GAG) chain size by size exclusion chromatography. SB431542 caused a concentration-dependent decrease in TGF-beta-mediated [(35)S]sulfate incorporation with 92% inhibition at 3 mum. Two different p38 MAP kinase inhibitors, SB203580 and SB202190, but not the inactive analogue SB202474, concentration-dependently blocked TGF-beta-mediated [(35)S]sulfate incorporation. TGF-beta increased [(3)H]glucosamine incorporation into glycosaminoglycans by 180% and [(35)S]Met/Cys incorporation into proteoglycan core proteins by 35% with both effects completely inhibited by SB431542. Blocking both Smad2/3 and p38 MAP kinase pathways prevented the effect of TGF-beta to increase proteoglycan to LDL binding. TGF-beta mediates its effects on proteoglycan synthesis in VSMCs via the ALK5/Smad2/3 phosphorylation pathway as well as via the p38 MAP kinase signaling cascade. Further studies of downstream pathways controlling proteoglycan synthesis may identify potential therapeutic targets for the prevention of atherosclerosis and cardiovascular disease.

Increased serum levels of TGFbeta1 in children with localized scleroderma

BACKGROUND

There are neither sensitive nor specific laboratory tests for measuring disease activity in localized scleroderma (LS). Monitoring is done almost exclusively by clinical assessment. Our aim was to determine whether serum concentrations of TGFbeta1 are a good biomarker of disease activity in children with LS.

METHODS

55 pediatric patients with LS were divided into sub-types according to their main lesion; morphea, generalized morphea, linear scleoderma affecting a limb or the face. The lesions were further categorized by overall clinical assessment into active, inactive, and indeterminate groups according to disease activity. Serum TGFbeta1 concentration levels were measured by enzyme linked immunosorbent assay (ELISA), analyzed and correlated with disease subtypes and disease activity.

RESULTS

The mean TGFbeta1 concentration were significantly higher in the patient group (51393 +/- 33953 pg/ml) than in the control group (9825 +/- 5287 pg/ml) (P < 0.001). The mean concentration were elevated in all the disease subtypes, and did not correlate with disease duration or activity.

CONCLUSION

Serum concentration of TGFbeta1 were elevated in patients with all subtypes of LS irrespective of clinical disease activity. Although TGFbeta1 may play an important role in the pathogenesis of local skin fibrosis, circulating blood levels of molecules known to act locally may not be useful biomarkers of disease activity.

Requirement for the dynein light chain km23-1 in a Smad2-dependent transforming growth factor-beta signaling pathway

We have identified km23-1 as a novel transforming growth factor-beta (TGFbeta) receptor (TbetaR)-interacting protein that is also a light chain of the motor protein dynein (dynein light chain). Herein, we demonstrate by sucrose gradient analyses that, in the presence of TGFbeta but not in the absence, km23-1 was present in early endosomes with the TbetaRs. Further, confocal microscopy studies indicate that endogenous km23-1 was co-localized with endogenous Smad2 at early times after TGFbeta treatment, prior to Smad2 translocation to the nucleus. In addition, immunoprecipitation/blot analyses showed that TGFbeta regulated the interaction between endogenous km23-1 and endogenous Smad2 in vivo. Blockade of km23-1 using a small interfering RNA approach resulted in a reduction in both total intracellular Smad2 levels and in nuclear levels of phosphorylated Smad2 after TGFbeta treatment. This decrease was reversed by lactacystin, a specific inhibitor of the 26 S proteasome, suggesting that knockdown of km23-1 causes proteasomal degradation of phosphorylated (i.e. activated) Smad2. Blockade of km23-1 also resulted in a reduction in TGFbeta/Smad2-dependent ARE-Lux transcriptional activity, which was rescued by a km23-1 small interfering RNA-resistant construct. In contrast, a reduction in TGFbeta/Smad3-dependent SBE2-Luc transcriptional activity did not occur under similar conditions. Furthermore, overexpression of the dynactin subunit dynamitin, which is known to disrupt dynein-mediated intracellular transport, blocked TGFbeta-stimulated nuclear translocation of Smad2. Collectively, our findings indicate for the first time that a dynein light chain is required for a Smad2-dependent TGFbeta signaling pathway.

Mechanoregulation of gene expression in fibroblasts

Mechanical loads placed on connective tissues alter gene expression in fibroblasts through mechanotransduction mechanisms by which cells convert mechanical signals into cellular biological events, such as gene expression of extracellular matrix components (e.g., collagen). This mechanical regulation of ECM gene expression affords maintenance of connective tissue homeostasis. However, mechanical loads can also interfere with homeostatic cellular gene expression and consequently cause the pathogenesis of connective tissue diseases such as tendinopathy and osteoarthritis. Therefore, the regulation of gene expression by mechanical loads is closely related to connective tissue physiology and pathology. This article reviews the effects of various mechanical loading conditions on gene regulation in fibroblasts and discusses several mechanotransduction mechanisms. Future research directions in mechanoregulation of gene expression are also suggested.