Microarray analysis of mRNA expression profiles in liver of ob/ob mice with real-time atmospheric PM2.5 exposure

Epidemiological studies have demonstrated the association between exposure to fine particulate matter (PM_2.5) and the onset of non-alcoholic fatty liver disease (NAFLD). However, the potential biological mechanism is largely unknown. Our study was aimed to explore the impact of PM_2.5 on the transcriptome level in the liver of ob/ob mice by atmosphere PM_2.5 whole-body dynamic exposure system, and meanwhile preliminarily investigated the effects of metformin intervention in this process. More than three thousand differentially expressed genes (DEGs) was screened out by microarray analysis (p < 0.05, |FC|> 1.5). KEGG pathway enrichment analysis showed that these DEGs were mainly enriched in cancers, infectious diseases, and signal transduction, and the most significant pathways were thyroid hormone signaling pathway, chronic myeloid leukemia and metabolic pathways. Then, 12 hub genes were gained through weighted gene correlation network analysis (WGCNA) and verified by qRT-PCR. The expression of 5 genes in darkslateblue module (cd53, fcer1g, cd68, ctss, laptm5) increased after PM_2.5 exposure and decreased after metformin intervention. They were related to insulin resistance, glucose and lipid metabolism and other liver metabolism, and also neurodegenerative diseases. This study provided valuable clues and possible protective measures to the liver damage in ob/ob mice caused by PM_2.5 exposure, and further research is needed to explore the related mechanism in detail.

The miR-146b-5p promotes Ewing's sarcoma cells progression via suppressing the expression of BTG2

Ewing sarcoma (ES) is a malignant tumor that occurs mostly in children. However, the underlying mechanisms of ES are still unknown. Analyzing the results of two previous miRNA array reports, we found that miR-146b-5p might be an onco-miRNA in ES progression. To test this hypothesis, we detected the expression levels of miR-146b-5p by real-time PCR and observed the effects of miR-146b-5p on the progression of ES cells by CCK8 and transwell assays. Bioinformatics and luciferase assays were used to identify the target genes of miR-146b-5p. It showed that the expression levels of miR-146b-5p were upregulated in ES cell lines compared with human mesenchymal stem cells (MSCs). Up- or downregulation of miR-146b-5p in ES cell lines could effectively promote or block the proliferation, migration, and invasion of ES cells, respectively. Furthermore, we demonstrated that BTG2 was one of the target genes and mediated the effects of miR-146b-5p in ES cells. Interestingly, we also found that miR-146b-5p was partly involved in the anticancer effects of pemetrexed in ES cells. Our study revealed that miR-146b-5p affected the progression of ES by suppressing BTG2, which might shed light on anticancer drug development and ES treatment in the future.

Serum- and glucocorticoid-inducible kinase 3 is a potential oncogene in nasopharyngeal carcinoma

INTRODUCTION

Serum- and glucocorticoid-inducible kinase 3, a serine/threonine kinase that functions downstream of the PI3K signaling pathway, plays a critical role in neoplastic processes. It is expressed by various tumors and contributes to carcinogenesis.

OBJECTIVE

The objective was to investigate serum- and glucocorticoid-inducible kinase 3 expression in nasopharyngeal carcinoma, to study the anti-tumor effects of serum- and glucocorticoid-inducible kinase 3 shRNA by inhibiting its expression in nasopharyngeal carcinoma cells and to discuss the potential implications of our findings.

METHODS

Serum- and glucocorticoid-inducible kinase 3 protein expression in nasopharyngeal carcinoma cell lines (CNE-1, CNE-2, HNE-1, HONE-1, and SUNE-1) and the human immortalized nasopharyngeal epithelium cell line NP69 were assayed by western blotting. Serum- and glucocorticoid-inducible kinase 3 expression in 42 paraffin-embedded nasopharyngeal carcinoma tissues were performed by immunohistochemistry. MTT assay, flow cytometry, and scratch tests were performed after CNE-2 cells were transfected with the best serum- and glucocorticoid-inducible kinase 3 shRNA plasmid selected by western blotting using lipofectamine to study its effect on cell proliferation, apoptosis, and migration.

RESULTS

Serum- and glucocorticoid-inducible kinase 3 was overexpressed in human nasopharyngeal carcinoma tissues and cells. Serum- and glucocorticoid-inducible kinase 3 expression decreased markedly after CNE-2 cells were transfected with the serum- and glucocorticoid-inducible kinase 3 shRNA, leading to strong inhibition of cell proliferation and migration. In addition, the apoptosis rate increased in CNE-2 cells after serum- and glucocorticoid-inducible kinase 3 knockdown.

CONCLUSION

Serum- and glucocorticoid-inducible kinase 3 expression was more frequently observed as the nasopharyngeal epithelium progresses from normal tissue to carcinoma. This suggests that serum- and glucocorticoid-inducible kinase 3 contributes to the multistep process of NPC carcinogenesis. Serum- and glucocorticoid-inducible kinase 3 represents a target for nasopharyngeal carcinoma therapy, and a basis exists for the further investigation of this adjuvant treatment modality for nasopharyngeal carcinoma.

B-cell translocation gene 2 regulates hepatic glucose homeostasis via induction of orphan nuclear receptor Nur77 in diabetic mouse model

B-cell translocation gene 2 (BTG2) is a member of an emerging gene family that is involved in cellular functions. In this study, we demonstrate that BTG2 regulates glucose homeostasis via upregulation of Nur77 in diabetic mice. Hepatic BTG2 gene expression was elevated by fasting and forskolin. Overexpression of Btg2 increased the expression of hepatic gluconeogenic genes and blood glucose output and subsequently impaired glucose and insulin tolerance. Upregulation of the transcriptional activity of Nur77, gluconeogenic genes, and glucose production by forskolin was observed by Btg2 transduction, but not in Btg2 knockdown. BTG2-stimulated glucose production and glucose-6-phosphatase promoter activity were attenuated by dominant-negative Nur77. Coimmunoprecipitation and chromatin immunoprecipitation assays showed that BTG2 induced Nur77 occupancy on the glucose-6-phosphatase promoter via a physical interaction. Btg2 gene expression was increased in streptozotocin-treated and db/db mice. Finally, impairment of glucose homeostasis, such as the increase of blood glucose, glucose intolerance, and insulin intolerance, was elevated in diabetic mice, whereas this phenomenon was abolished in knockdown of Btg2. Together, these data suggest that BTG2 participates in the regulation of hepatic glucose homeostasis, which means that BTG2 might serve as a potential therapeutic target for combating metabolic dysfunction.

Role of connective tissue growth factor in extracellular matrix degradation in renal tubular epithelial cells

In order to investigate the effects of connective tissue growth factor (CTGF) antisense oligodeoxynucleotide (ODN) on plasminogen activator inhibitor-1 (PAI-1) expression in renal tubular cells induced by transforming growth factor beta1 (TGF-beta1) and to explore the role of CTGF in the degradation of renal extracellular matrix (ECM), a human proximal tubular epithelial cell line (HKC) was cultured in vitro. Cationic lipid-mediated CTGF antisense ODN was transfected into HKC. After HKC were stimulated with TGF-beta1 (5 microg/L), the mRNA level of PAI-1 was detected by RT-PCR. Intracellular PAI-1 protein synthesis was assessed by flow cytometry. The secreted PAI-1 in the media was determined by Western blot. The results showed that TGF-beta1 could induce tubular CTGF and PAI-1 mRNA expression. The PAI-1 mRNA expression induced by TGF-beta1 was significantly inhibited by CTGF antisense ODN. CTGF antisense ODN also inhibited intracellular PAI-1 protein synthesis and lowered the levels of PAI-1 protein secreted into the media. It was concluded that CTGF might play a crucial role in the degradation of excessive ECM during tubulointerstitial fibrosis, and blocking the biological effect of CTGF may be a novel way in preventing renal fibrosis.

CD137-guided isolation and expansion of antigen-specific CD8 cells for potential use in adoptive immunotherapy

The efficient isolation and ex vivo expansion of antigen-specific T cells are crucial for successful adoptive immunotherapy against uncontrollable infections and cancers. Several methods have been reported for this purpose, for example, employing MHC-multimeric complexes, interferon-gamma secretion, and antibodies specific for molecules expressed on T-cell surfaces, including CD25, CD69, CD107a, CD137, and CD154. Of the latter, CD137 has been shown to be one of the most promising targets since it is only expressed on CD8(+) T cells early after encountering antigen, while being almost undetectable on resting cells. However, detailed comparisons between CD137-based and other methods have not yet been conducted. In this study, we therefore compared three approaches (with CD137, CD107a, and tetramers) using HLA-A24-restricted CMV pp65 and EBV BRLF1 epitopes as model antigens. We found that the CD137-based isolation of antigen-stimulated CD8(+) T cells was comparable to tetramer-based sorting in terms of purity and superior to the other two methods in terms of subsequent cell expansion. The method was less applicable to CD4(+) T cells since their CD137 upregulation is not sufficiently high. Collectively, this approach is most likely to be optimal among the methods tested for the isolation and expansion of antigen-specific CD8(+) cells.

Clinical significance and pathogenic function of connective tissue growth factor (CTGF/CCN2) in osteolytic mandibular squamous cell carcinoma

BACKGROUND

Mandibular bone destruction is a frequent occurrence in oral squamous cell carcinoma. However, the relationship between the bone destruction and associated factors is unclear. Here, the role and diagnostic utility of connective tissue growth factor (CCN2) in bone destruction of the mandible was investigated.

PATIENTS AND METHODS

The production of CCN2 was explored by using immunohistochemistry on paraffin-embedded tissues from 20 cases of mandibular squamous cell carcinoma. The effect of CCN2 on osteoclastogenesis was examined in vitro by using total bone marrow cell populations from male mice.

RESULTS

Immunohistochemical analysis showed that CCN2-positive signals were closely associated with destructive invasion of the mandible by oral squamous cell carcinomas. Consistent with these results, recombinant human CCN2 (rCCN2) stimulated tartrate-resistant acid phosphatase (TRAP)-positive osteoclast-like cell formation in vitro.

CONCLUSION

CCN2 can be considered a diagnostic marker and target for treatment in oral osteolytic mandibular squamous cell carcinoma.

[Effects of exogenous connective tissue growth factor on collagen III synthesis of human renal tubular epithelial cells]

OBJECTIVE

To explore the role of exogenous connective tissue growth factor (CTGF) in the collagen III synthesis of human renal tubular epithelial cell line HK2 in vitro.

METHODS

Cultured HK2 cells were randomly assigned to three groups: placebo-control, low-dose CTGF-treated (2.5 ng/mL) and high-dose CTGF-treated groups (20 ng/mL). Cell morphological changes were observed under an inverted microscope. Collagen III alpha mRNA expression was detected using RT-PCR. Immunohistochemistry staining was used to assess the levels of intracellular collagen III alpha protein.

RESULTS

After 48 hrs of low- or high- dose CTGF treatment, the appearances of HK2 cells were changed from oval to fusiform. High-dose CTGF treatment increased collagen III alpha mRNA expression (0.4461+/-0.0274 vs 0.2999+/-0.0115; P<0.05) as well as the protein expression of collagen III alpha (0.4075+/-0.0071 vs 0.3503+/-0.0136; P<0.05) compared with the placebo-control group.

CONCLUSIONS

CTGF can induce morphological changes of human renal tubular epithelial cells in vitro. High concentration of CTGF may increase the synthesis of collagen III alpha.

The impact of multiple splice sites in human L1 elements

LINE-1 elements represent a significant proportion of mammalian genomes. The impact of their activity on the structure and function of the host genomes has been recognized from the time of their discovery as an endogenous source of insertional mutagenesis. L1 elements contain numerous functional internal polyadenylation signals and splice sites that generate a variety of processed L1 transcripts. These sites are also reported to contribute to the generation of hybrid transcripts between L1 elements and host genes. Using northern blot analysis we demonstrate that L1 splicing, but not L1 polyadenylation, is delayed during the course of L1 expression. L1 splicing can also be negatively regulated by EBV SM protein known to alter this process. These results suggest a potential for L1 mRNA processing to be regulated in a tissue- and/or development-specific manner. The delay in L1 splicing may also serve to protect host genes from the excessive burden of L1 interference with their normal expression via aberrant splicing.

The matricellular protein CYR61 inhibits osteoclastogenesis by a mechanism independent of alphavbeta3 and alphavbeta5

Cysteine-rich protein 61 (CYR61/CCN1) belongs to the family of CCN matricellular proteins. Most of the known effects of CCN proteins appear to be due to binding to extracellular growth factors or integrins, including alpha(v)beta(3) and alpha(v)beta(5). Although CYR61 can stimulate osteoblast differentiation, until now the effect of CYR61 on osteoclasts was unknown. We demonstrate that recombinant human CYR61 inhibits the formation of multinucleated, alpha(v)beta(3)-positive, or tartrate-resistant acid phosphatase-positive human, mouse, and rabbit osteoclasts in vitro. CYR61 markedly reduced the expression of the osteoclast phenotypic markers tartrate-resistant acid phosphatase, matrix metalloproteinase-9, calcitonin receptor, and cathepsin K. However, CYR61 did not affect the formation of multinucleated osteoclasts when added to osteoclast precursors prior to fusion or affect the number or resorptive activity of osteoclasts cultured on dentine discs, indicating that CYR61 affects early osteoclast precursors but not mature osteoclasts. CYR61 did not affect receptor activator of nuclear factor-kappaB (RANK) ligand-induced phosphorylation of p38 or ERK1/2 in human macrophages and did not affect RANK ligand-induced activation of nuclear factor-kappaB, indicating that CYR61 does not appear to inhibit osteoclastogenesis by affecting RANK signaling. Furthermore, a mutant form of CYR61 defective in binding to alpha(v)beta(3) also inhibited osteoclastogenesis, and CYR61 inhibited osteoclastogenesis similarly in cultures of mouse wild-type or beta(5)(-/-) macrophages. Thus, CYR61 does not appear to inhibit osteoclast formation by interacting with alpha(v)beta(3) or alpha(v)beta(5). These observations demonstrate that CYR61 is a hitherto unrecognized inhibitor of osteoclast formation, although the exact mechanism of inhibition remains to be determined. Given that CYR61 also stimulates osteoblasts, CYR61 could represent an important bifunctional local regulator of bone remodeling.

Connective tissue growth factor increases matrix metalloproteinase-2 and suppresses tissue inhibitor of matrix metalloproteinase-2 production by cultured renal interstitial fibroblasts

The involvement of gelatinase (matrix metalloproteinase-2 [MMP-2] and MMP-9) in the matrix remodeling and development of tubulointerstitial fibrosis has been studied recently, but relatively little is known about the regulators and the mechanisms controlling the activation and expression of gelatinase in renal fibroblasts. In these studies, the production and underlying signaling pathway for gelatinase by exogenous connective tissue growth factor (CTGF) treatment were investigated. Here, we show that CTGF acts as a potent promoter of the activation and expression of MMP-2, but not MMP-9 in normal rat kidney fibroblasts cell line (NRK-49F). We found that CTGF significantly increased the activity of MMP-2, as well as MMP-2 protein in conditioned medium and MMP-2 mRNA levels in cells. In studies to address the mechanisms involved in the regulation of MMP-2 activity, we found that the tissue inhibitor of matrix metalloproteinase-2 (TIMP-2), the inhibitor of MMP-2, decreased significantly when cells were treated with CTGF. Further studies showed that extracellular signal-regulated kinase (ERK) signaling is responsible for most of the CTGF-induced MMP-2 expression and TIMP-2 suppression. When NRK-49F fibroblasts were incubated with CTGF, activation of ERK1/2 signaling was observed. Suppression of ERK1/2 activation with nontoxic concentrations of PD98059, a specific inhibitor of ERK activation, was associated with a reduction of CTGF-stimulated MMP-2 activity and protein expression. In addition, the CTGF-mediated reduction of TIMP-2 activity and protein expression was prevented when ERK1/2 activation was inhibited by PD98059. These results provide evidence that CTGF augments activation of MMP-2 through an effect on MMP-2 protein expression and TIMP-2 suppression, and that these effects are dependent on the activation of the ERK1/2 pathway.

Inhibition of integrin-linked kinase via a siRNA expression plasmid attenuates connective tissue growth factor-induced human proximal tubular epithelial cells to mesenchymal transition

BACKGROUND

Increasing evidence suggests that connective tissue growth factor (CTGF) is involved in the epithelial-to-mesenchymal transition (EMT). The exact intracellular events that drive this process, however, are not fully understood. In this study, we investigated the role of integrin-linked kinase (ILK) in mediating CTGF-induced EMT.

METHODS

The expression of alpha-smooth muscle actin (alpha-SMA) and E-cadherin upon the stimulation by recombinant human CTGF (rhCTGF) in cultured human tubular epithelial cell line (HK-2) was detected by real-time RT-PCR and Western blot. Subsequently, the role of ILK was determined by using ILK siRNA.

RESULTS

rhCTGF increased the mRNA expression of alpha-SMA significantly in a dose- and time-dependent manner, while E-cadherin mRNA decreased in a dose- and time-dependent manner. alpha-SMA protein was up-regulated after stimulation by 5 ng/ml CTGF for 96 h, and increased further after stimulation by 50 ng/ml. An immunocytochemical study showed that alpha-SMA was initially detectable at 48 h, and increased further at 72 h, while there was almost no alpha-SMA immunostaining observed in the control group at the same time point. E-cadherin protein was also down-regulated in a dose-dependent manner. Transfection of HK-2 cells with ILK-siRNA significantly attenuated rhCTGF-induced alpha-SMA induction and E-cadherin repression.

CONCLUSION

Our study suggested that ILK mediated the effect of EMT in proximal tubular epithelial cells stimulated by CTGF.

Connective tissue growth factor is an indicator of bone involvement in multiple myeloma, but matrix metalloproteinase-9 is not

Bone disease (BD) in multiple myeloma (MM) is because of the activation of osteoclasts and impairment of osteoblast differentiation. Connective tissue growth factor (CTGF) is known to participate in the differentiation of mesenchymal stem cells to committed osteoprogenitor cells. We analysed the concentration of circulating CTGF in 35 MM patients and 22 malignant lymphoma (ML) patients and 14 normal individuals. CTGF is protease-sensitive and thus is found as both an N-terminal half fragment (N-half CTGF) and whole (W-CTGF). Serum levels of W-CTGF and N-half CTGF + W-CTGF were determined by separate sandwich enzyme-linked immunosorbent assays. The level of W-CTGF was significantly lower (P < 0.005) in MM patients compared with ML patients and normal individuals, while N-half + W-CTGF was similar in all groups. Furthermore, W-CTGF was significantly lower in MM patients with BD compared with those without BD (P < 0.005) and this was independent of previous treatment. Matrix metalloproteinase (MMP)-9 is produced by myeloma cells and is thought to be related to BD in MM. However, MMP-9 does not cleave CTGF and serum MMP-9 level was not related to BD in MM. Thus, CTGF is an indicator of BD in MM; its metabolism and function in MM should be clarified.

Analysis of HSV-I ICP22 effects on HCMV major immediate-early promoter structure

The human cytomegalovirus (HCMV) major immediate-early (MIE) promoter has strong transcriptional promoting capability. Its cis-acting regulatory elements form a special structure in this region that is repeated multiple times; the biological significance of these elements and their different compositions in the transcriptional promoting process remain unclear. Our results demonstrate that the HSV-I MIE protein ICP22 can generate strong repression of many viral and cellular promoters and enhancers. We further studied the transcriptional effects of ICP22 on structural elements and mutations in various HCMV MIE promoters by using a CAT assay. In spite of different transcriptional effects of all the elements in the presence of ICP22, the transcriptional efficiencies exhibited by mutations generated by different compositions and an entire HCMV promoter, are not the simple sum of the functions of these elements. Furthermore, the transcriptional activities of specific sequences were not affected by the presence of ICP22. Therefore, it is assumed that the HCMV MIE promoter co-regulates expression of downstream genes by using viral and cellular specific factors via a specific pathway.

An activation-defective mutant of the human cytomegalovirus IE2p86 protein inhibits NF-κB-mediated stimulation of the human interleukin-6 promoter

The IE2p86 protein of human cytomegalovirus is an essential activator of early- and late-phase viral gene expression. Whilst IE2p86 activates expression of a number of cellular genes, it also represses certain cellular genes, particularly those activated by nuclear factor κB (NF-κB). As the interleukin-6 (IL-6) promoter can be activated by both NF-κB and IE2p86, it was examined whether there is competition between these two factors. Here, it is reported that both wild-type and mutant IE2p86 can block activation of the IL-6 promoter in response to interleukin-1β. By using an artificial activator in which the activation domain of NF-κB is directed to the promoter by the GAL4 DNA-binding domain, it is shown that the mutant form of IE2p86 can inhibit NF-κB-mediated activation at a step subsequent to promoter recruitment. These data therefore suggest a novel mechanism for inhibition of NF-κB by IE2p86.

Connective tissue growth factor (CTGF) promotes activated mesangial cell survival via up-regulation of mitogen-activated protein kinase phosphatase-1 (MKP-1)

Activated mesangial cells are thought to play a pivotal role in the development of kidney fibrosis under chronic pathological conditions, including DN (diabetic nephropathy). Their prolonged survival may enhance the development of the disease since they express increased amounts of growth factors and extracellular matrix proteins. CTGF (connective tissue growth factor) is one of the growth factors produced by activated mesangial cells and is reported to play a key role in the pathogenesis of DN. Previous studies have shown that addition of exogenous CTGF to HMCs (human mesangial cells) rapidly activates ERK1/2 (extracellular-signal-regulated kinase 1/2) MAPK (mitogen-activated protein kinase) and JNK (c-Jun N-terminal kinase) MAPK, but not the p38 MAPK, despite the activation of the upstream kinases, MKK3/6 (MAPK kinase 3/6). The aim of the present study was to investigate whether the lack of phosphorylated p38 MAPK by CTGF has an anti-apoptotic effect on activated HMCs. We show that in HMC CTGF induces the rapid transcriptional activation and synthesis of MKP-1 (MAPK phosphatase-1), a dual specificity phosphatase that dephosphorylates p38 MAPK. This in turn prevents the anti-apoptotic protein, Bcl-2, from being phosphorylated and losing its function, leading to the survival of the cells. Knockout of MKP-1 protein in mesangial cells treated with CTGF, using siRNA (small interfering RNA) or antisense oligonucleotides, allows p38 MAPK activation and induces mesangial cell death.

Expression of CCN1 (CYR61) in developing, normal, and diseased human kidney

CCN1 (cysteine-rich protein 61; Cyr61) is an extracellular matrix-associated signaling molecule that functions in cell migration, adhesion, and differentiation. We previously reported that CCN1 is induced at podocytes in rat anti-Thy-1 glomerulonephritis, a well-known model of reversible glomerular injury, but its expression and significance in the human kidney remain totally unknown (Sawai K, Mori K, Mukoyama M, Sugawara A, Suganami T, Koshikawa M, Yahata K, Makino H, Nagae T, Fujinaga Y, Yokoi H, Yoshioka T, Yoshimoto A, Tanaka I, Nakao K. J Am Soc Nephrol 14: 1154-1163, 2003). Here we report that, in the human kidney, CCN1 expression was confined to podocytes in normal adult and embryonic glomeruli from the capillary loop stage. Podocyte CCN1 expression was decreased in IgA nephropathy, diabetic nephropathy, and membranous nephropathy, whereas it remained unchanged in minimal change disease and focal segmental glomerulosclerosis. Downregulation of CCN1 was significantly greater in diseased kidneys with severe mesangial expansion. CCN1 protein was also localized in the thick ascending limb of Henle's loop, distal and proximal tubules, and collecting ducts, which was not altered in diseased kidneys. In vitro, recombinant CCN1 protein enhanced endothelial cell adhesion, whereas it prominently inhibited mesangial cell adhesion. CCN1 also completely suppressed mesangial cell migration, suggesting its role as a mesangial-repellent factor. In cultured podocytes, CCN1 markedly induced the expression of cyclin-dependent kinase inhibitor p27(Kip1) as well as synaptopodin in a dose-dependent manner and suppressed podocyte migration. These data indicate that CCN1 is expressed in podocytes, can act on glomerular cells to modulate glomerular remodeling, and is downregulated in diseased kidneys, suggesting that impairment of CCN1 expression in podocytes may contribute to the progression of glomerular disease with mesangial expansion.

Functional characteristics of connective tissue growth factor on vitreoretinal cells

Connective tissue growth factor (CTGF) level is elevated in eyes with proliferative vitreoretinal diseases, such as proliferative diabetic retinopathy and proliferative vitreoretinopathy (PVR), as we previously reported, but its functional characteristics on vitreoretinal cells are yet to be clarified. In this study, we demonstrated a growth-promoting effect of CTGF on cultured hyalocytes and bovine retinal pigment epithelial cells (BRPEs) with the induction of p44/p42 mitogen-activated protein kinase phosphorylation and [(3)H]thymidine incorporation. CTGF also stimulated the synthesis of fibronectin by hyalocytes and BRPEs without significant effect on collagen gel contraction by these cells. On the other hand, CTGF had no direct effects on the proliferation, migration, or in vitro tube formation by vascular endothelial cells. Nevertheless, CTGF promoted vascular endothelial growth factor (VEGF) gene expression by hyalocytes and BRPEs. Although the concentrations of both CTGF and VEGF in the human vitreous samples with proliferative vitreoretinal diseases were elevated, there was no significant correlation between these concentrations. These findings indicate that CTGF appears to be involved in the formation of proliferative membranes without direct regulation of their cicatricial contraction in the pathogenesis of proliferative vitreoretinal diseases. Whereas CTGF might have no direct effects or minimal effects, if any, on retinal neovascularization, it is possible that CTGF has indirect effects by modulating the expression of VEGF.

The angiogenic factor CCN1 promotes adhesion and migration of circulating CD34+ progenitor cells: potential role in angiogenesis and endothelial regeneration

Tissue regeneration involves the formation of new blood vessels regulated by angiogenic factors. We reported recently that the expression of the angiogenic factor CCN1 is up-regulated under various pathophysiologic conditions within the cardiovascular system. Because CD34+ progenitor cells participate in cardiovascular tissue regeneration, we investigated whether CCN1-detected for the first time in human plasma-promotes the recruitment of CD34+ progenitor cells to endothelial cells, thereby enhancing endothelial proliferation and neovascularization. In this study, we demonstrated that CCN1 and supernatants from CCN1-stimulated human CD34+ progenitor cells promoted proliferation of endothelial cells and angiogenesis in vitro and in vivo. In addition, CCN1 induced migration and transendothelial migration of CD34+ cells and the release of multiple growth factors, chemokines, and matrix metalloproteinase-9 (MMP-9) from these cells. Moreover, the CCN1-specific integrins alpha(M)beta(2) and alpha(V)beta(3) are expressed on CD34+ cells and CCN1 stimulated integrin-dependent signaling. Furthermore, integrin antagonists (RGD-peptides) suppressed both binding of CCN1 to CD34+ cells and CCN1-induced adhesion of CD34+ cells to endothelial cells. These data suggest that CCN1 promotes integrin-dependent recruitment of CD34+ progenitor cells to endothelial cells, which may contribute to paracrine effects on angiogenesis and tissue regeneration.

CCN1 protects cardiac myocytes from oxidative stress via β1 integrin–Akt pathway

CCN1 (Cyr61) is a secreted matricellular protein, mediating angiogenesis and cell survival through interaction with integrins. Although CCN1 expression is induced in the heart during ischemia and pressure overload, its function in cardiac myocytes remains to be elucidated. We hypothesized that CCN1 may not only induce angiogenesis but may also have a direct effect on cardiac myocytes during ischemia. In this study, we investigated the effect of CCN1 on survival of cardiac myocytes under oxidative stress and examined a signal transduction pathway downstream of CCN1. A solid-phase binding assay demonstrated that CCN1 was bound to cardiac myocytes in a dose-dependent, saturable manner. Inactivation of beta1 integrin in cardiac myocytes inhibited binding with CCN1, indicating that CCN1 was bound to cardiac myocytes via beta1 integrin. Knockdown of endogenous CCN1 decreased the number of surviving cells under oxidative stress, while pretreatment of cardiac myocytes with recombinant CCN1 significantly increased the number of surviving cells. Moreover, TUNEL staining showed that CCN1 significantly decreased apoptotic cells. Furthermore, treatment of cardiac myocytes with CCN1 induced phosphorylation of Akt and extracellular signal-regulated kinase (ERK). Inactivation of beta1 integrin inhibited CCN1-induced phosphorylation of these kinases and abolished the protective effect of CCN1. Moreover, pretreatment of cells with wortmannin completely blocked the protective effect of CCN1 on cardiac myocytes under oxidative stress, indicating that the protective effect of CCN1 was mainly mediated by activation of Akt. The antiapoptotic effect of CCN1 on cardiac myocytes together with its proangiogenic property could be beneficial in the treatment of ischemic heart disease.

Diverse activation states of RhoA in human lung cancer cells: contribution of G protein coupled receptors

Rho GTPases play an essential role in the control of various cellular functions. Accumulating evidence suggests that RhoA overexpression contributes to human cancer development. However, the activation states of RhoA are poorly defined in cancer cells. In this study, we examined both the expression levels and the activation states of RhoA in various lung cancer cells by quantitative real-time reverse transcriptase-polymerase chain reaction and in vivo Rho guanine nucleotide exchange assay, respectively. Moreover, we dissected the signaling pathway from the cell surface receptors to RhoA using a broad-spectrum G protein coupled receptor (GPCR) antagonist, [D-Arg1,D-Trp5,7,9,Leu11]Substance P (SP), and a recently reported Galphaq/11-selective inhibitor, YM-254890. We found that RhoA was expressed highly in large cell carcinoma cells but only weakly in adenocarcinoma cells. The activation states of RhoA are considerably different from its expression profiles. We found that four of six small cell lung carcinoma (SCLC) cell lines exhibited a moderate to high activation rate of RhoA. The addition of [D-Arg1,D-Trp5,7,9,Leu11]SP reduced RhoA activity by almost 60% in H69 SCLC cells. The addition of YM-254890 had no effect on RhoA activity in H69 cells. Our results suggest that RhoA is activated in various lung cancer cells independent of its expression levels, and the high activation state of RhoA in SCLC cells mainly depends on a neuroendocrine peptide autocrine system which signals through Galpha12 coupled GPCR to RhoA. This study provides new insights into RhoA signaling in lung cancer cells and may help in developing novel therapeutic strategies against lung cancer.

Dysregulated intracellular signaling impairs CTGF-stimulated responses in human mesangial cells exposed to high extracellular glucose

High ambient glucose activates intracellular signaling pathways to induce the expression of extracellular matrix and cytokines such as connective tissue growth factor (CTGF). Cell responses to CTGF in already glucose-stressed cells may act to transform the mesangial cell phenotype leading to the development of glomerulosclerosis. We analyzed cell signaling downstream of CTGF in high glucose-stressed mesangial cells to model signaling in the diabetic milieu. The addition of CTGF to primary human mesangial cells activates cell migration which is associated with a PKC-zeta-GSK3beta signaling axis. In high ambient glucose basal PKC-zeta and GSK3beta phosphorylation levels are selectively increased and CTGF-stimulated PKC-zeta and GSK3beta phosphorylation was impaired. These effects were not induced by osmotic changes. CTGF-driven profibrotic cell signaling as determined by p42/44 MAPK and Akt phosphorylation was unaffected by high glucose. Nonresponsiveness of the PKC-zeta-GSK3beta signaling axis suppressed effective remodeling of the microtubule network necessary to support cell migration. However, interestingly the cells remain plastic: modulation of glucose-induced PKC-beta activity in human mesangial cells reversed some of the pathological effects of glucose damage in these cells. We show that inhibition of PKC-beta with LY379196 and PKC-beta siRNA reduced basal PKC-zeta and GSK3beta phosphorylation in human mesangial cells exposed to high glucose. CTGF stimulation under these conditions again resulted in PKC-zeta phosphorylation and human mesangial cell migration. Regulation of PKC-zeta by PKC-beta in this instance may establish PKC-zeta as a target for constraining the progression of mesangial cell dysfunction in the pathogenesis of diabetic nephropathy.

Regulation of elastin promoter by lysyl oxidase and growth factors: cross control of lysyl oxidase on TGF-beta1 effects

Lysyl oxidase (LOX) plays a key role in the maturation of the extra-cellular matrix, by inducing the formation of lysyl cross-links in collagen and elastin molecules. Beside its enzymic activity, LOX is able to regulate the promoter of collagen III, one of its natural substrates. In this paper we demonstrated that LOX regulates also the promoter of elastin, inducing an important activation of its activity. In order to define the pathways used by LOX to achieve its effect, we activated some of the main fibrogenic signal pathways and studied the consequences on LOX effects on the promoter. TGF-beta1 activated most of the elastin promoter constructs that we studied, except for an inhibitory region contained in the region between -1500 and -1000 bp. The treatment with TGF-beta1 abolished completely the activation induced by LOX. LOX-over-expression coupled with TGF treatment abolished both effects in the -500 bp region. The treatment with CTGF also inhibited LOX effect, although to a lesser extent. However, CTGF behaved quite differently from TGF-beta1 suggesting that it is not necessarily the mediator of TGF effects. Basic FGF, the other fibrogenic factor that we tested, again abolished LOX-dependent activation, but by itself did not affect elastin promoter activity. Because TGF-beta1 activating effects, we used EMSA to examine the transcription factor binding patterns in presence of LOX, TGF-beta1 or both. The study showed that LOX reverted the patterns of several DNA-protein complexes along the 1.5 kb of the studied promoter region. Most were affected by both LOX and TGF-beta1, while on some only TGF-beta1 was effective. LOX presence mostly inhibited the TGF-regulated complexes. Many of those included SMAD transcription factors. Two more restricted regions binding AP1 and SMAD were identified as mediators of LOX effects and of LOX and TGF-beta1 cross-inhibition.

Homologous peptide of connective tissue growth factor ameliorates epithelial to mesenchymal transition of tubular epithelial cells

The hallmark of failing renal transplants is tubular atrophy and interstitial fibrosis. The cytokine connective tissue growth factor (CTGF or CCN2) plays an important role in epithelial-mesenchymal transition (EMT) of tubular epithelial cells (TECs). A unique domain within CTGF (IRTPKISKPIKFELSG) which binds to its potential receptor integrin alpha v beta3 has been identified. This study was carried out to further characterize a synthetic hexadeca-peptide (P2) homologous to this domain and to determine its effect on CTGF-mediated solid phase cell adhesion, EMT induction and fibrogenesis in rat renal NRK-52E cells. Results showed that both P2 and recombinant CTGF bound to NRK-52E cells. Unlike CTGF, P2 had little effect on EMT induction including cytoskeleton remodeling and expression of alpha-smooth muscle actin (alpha-SMA) and E-cadherin, nor did it have effect on fibrogenic induction including alternation of extracellular matrix (ECM) proteins, collagen type I and IV at gene and protein levels. All data showed that P2 bound preferably on the surface of NRK-52E cells and inhibited the effect of CTGF on EMT induction and cell fibrogenesis, probably by occupying the binding sites of CTGF within its potential receptors. Therefore, P2 may be used as a potential anti-fibrotic agent.

The C-terminal peptide of connective tissue growth factor blocks the full molecule binding to tubular epithelial cell

OBJECTIVES

Interstitial fibrosis is a critical pathologic change in chronic allograft nephropathy. The cytokine connective tissue growth factor (CTGF, also CCN2) plays an important role in epithelial-mesenchymal transformation (EMT) of tubular epithelial cells to renal interstitial fibrosis. The hexadeca-peptide within the C-terminal of CTGF (named P2) contains the unique binding domain of CTGF to its potential receptor, integrin alphavbeta3. This study examined whether P2 bound preferentially to the receptor and served as an inhibitor of CTGF.

METHODS

All studies used an established rat kidney tubular epithelial cell line NRK-52E. Chemically synthesized P2 was purified, and some of it labeled with FITC. The affinity of CTGF or P2 to NRK-52E cells was examined by a solid-phase cell adhesion assay. Competitive binding between P2 and CTGF to NRK-52E cells was examined with flow cytometric analysis.

RESULTS

Both P2 and CTGF bound to the NRK-52E cells, mediating cell adhesion. When the cells were incubated in the mixture of P2 and CTGF, P2 bound to the cells preferentially. Furthermore, when cells were preincubated with excessive CTGF, it became difficult for subsequent P2 binding to occur.

CONCLUSIONS

P2 and CTGF seemed to bind to cell membranes at the same binding domain. P2 competitively blocked CTGF binding, acting as a CTGF inhibitor.

Multiple activation of mitogen-activated protein kinases by purified independent CCN2 modules in vascular endothelial cells and chondrocytes in culture

CCN2 consists of 4 distinct modules that are conserved among various CCN family protein members. From the N-terminus, insulin-like growth factor binding protein (IGFBP), von Willebrand factor type C repeat (VWC), thrombospondin type 1 repeat (TSP1) and C-terminal cysteine-knot (CT) modules are all aligned tandem therein. The multiple functionality of CCN2 is thought to be enabled by the differential use of these modules when interacting with other molecules. In this study, we independently prepared all 4 purified module proteins of human CCN2, utilizing a secretory production system with Brevibacillus choshinensis and thus evaluated the cell biological effects of such single modules. In human umbilical vascular endothelial cells (HUVECs), VWC, TSP and CT modules, as well as a full-length CCN2, were capable of efficiently activating the ERK signal transduction cascade, whereas IGFBP was not. In contrast, the IGFBP module was found to prominently activate JNK in human chondrocytic HCS-2/8 cells, while the others showed similar effects at lower levels. In addition, ERK1/2 was modestly, but significantly activated by IGFBP and VWC in those cells. No single module, but a mixture of the 4 modules provoked a significant activation of p38 MAPK in HCS-2/8 cells, which was activated by the full-length CCN2. Therefore, the signals emitted by CCN2 can be highly differential, depending upon the cell types, which are thus enabled by the tetramodular structure. Furthermore, the cell biological effects of each module on these cells were also evaluated to clarify the relationship among the modules, the signaling pathways and biological outcomes. Our present results not only demonstrate that single CCN2 modules were potent activators of the intracellular signaling cascade to yield a biological response per se, while also providing new insight into the module-wise structural and functional relationship of a prototypic CCN family member, CCN2.

Connective tissue growth factor binds to fibronectin through the type I repeat modules and enhances the affinity of fibronectin to fibrin

Connective tissue growth factor (CTGF) is a member of the CCN family of the cysteine-rich proteins and involved in wound healing and fibrosis. We have previously shown a biochemical interaction between the CTGF and fibronectin (FN) using the yeast two-hybrid system. In this study, we confirmed the interaction between the CTGF and FN using the surface plasmon resonance (SPR) and solid-phase binding analysis. Our results show that the regions containing the FN type I repeat modules (the N-terminal fibrin, the gelatin-collagen and the C-terminal fibrin binding domains) of FN and the C-terminal domain of CTGF are required for the interaction. We also demonstrated that CTGF enhances the affinity of FN to fibrin. It appears that CTGF contributes to the extracellular matrix accumulation in wound healing and tissue fibrosis by enhancing the affinity of FN to fibrin. Because CTGF is up-regulated during the tissue repair and in coagulation cascade-associated fibrotic disorders, the new function of CTGF found in this study is consistent with its physiological role.

Role of connective tissue growth factor (CTGF) module 4 in regulating epithelial mesenchymal transition (EMT) in HK-2 cells

BACKGROUND

Recent studies have suggested that connective tissue growth factor (CTGF) plays a key role in tissue fibrosis including renal scarring. While studies showed several forms of CTGF with 10-38 kDa in the body fluids, little is known about these small molecule species. We investigated the effect of a 10 kDa CTGF molecule consisting of module 4, on the epithelial mesenchymal transition (EMT) in human proximal tubular cell line (HK-2).

METHODS

HK2 cells were cultured in DMEM medium. The response of cytokeratin (CK) and vimentin (VIM) mRNA and protein expression to the stimulation of rhCTGF(C) were observed by real-time PCR and immunocytochemistry. At the same time, the morphologic changes were observed by microscopy, and expression of alpha-smooth muscle actin (alpha-SMA) and fibronectin (FN) was detected by laser confocal microscope. These effects were compared with CTGF N-terminal [rhCTGF(N)], consisting of module 1-3, and observed in a condition with the addition of anti-CTGF antibody.

RESULTS

RhCTGF(C) induced striking changes in epithelial cells, including changes in cellular morphology, loss of CK, gain VIM and alpha-SMA, and increased levels of fibronectin. Cocultured with anti-CTGF antibody could abrogate most of these effects, while cells treated with rhCTGF(N) showed no significant phenotypic changes comparing to control group.

CONCLUSIONS

Our results suggest that module 4 could induce HK-2 cells EMT, whereas the residual fragment has no similar effect in spite of consisting of 3 modules of CTGF molecule.

A role for the endoplasmic reticulum protein retrotranslocation machinery during crosspresentation by dendritic cells

Crosspresentation of exogenous antigens (Ags) to CD8(+) T cells by dendritic cells generally requires their entry into the cytosol. Here we show that both soluble and phagocytosed extracellular Ags accessed the cytosol via molecular components required for endoplasmic reticulum (ER)-associated degradation (ERAD). Exogenous Pseudomonas aeruginosa Exotoxin A, which inhibits protein translocation from the ER to the cytosol, abrogated crosspresentation. Exotoxin A also prevented the transporter associated with antigen processing (TAP) inhibitor, ICP47, from entering the cytosol and blocking TAP-mediated peptide transport. In an in vitro model of retrotranslocation, the AAA ATPase p97, an enzyme critical for ERAD, was the only cytosolic cofactor required for protein export from isolated phagosomes. Functional p97 was also required for crosspresentation but not conventional presentation. Thus, crosspresentation appears to result from an adaptation of the retrotranslocation mechanisms involved in the degradation of misfolded ER proteins.

Increased collagen deposition and elevated expression of connective tissue growth factor in human thoracic aortic dissection

BACKGROUND

Thoracic aortic dissection (TAD) is characterized by dysregulated extracellular matrix. Little is known about the alterations of collagen and stimulators of collagen synthesis, eg, connective tissue growth factor (CTGF), in patients with TAD. In this study, we examined their roles in TAD.

METHODS AND RESULTS

Surgical specimens of the aortic wall of TAD patients (n=10) and controls (n=10) were tested for collagen types I and III and CTGF expression. When compared with controls, protein levels of type I and III collagen and CTGF were significantly increased by 3.2-, 3.7-, and 5.3-fold, respectively (P<0.05 for all). Similar patterns were shown in mRNA levels of type Ialpha and Ialpha2 collagen and CTGF. Using immunohistochemistry and trichrome staining, we also observed elevated levels of collagen in the aortic media and adventitia. Treatment with recombinant human CTGF increased collagen synthesis in cultured aortic smooth muscle cells in a dose- and time-dependent fashion, in which expression of collagens increased from 506+/-108 counts per minute to 2764+/-240 cpm by 50 ng/mL CTGF, and from 30+/-43 cpm to 429+/-102 cpm at 48 hours.

CONCLUSIONS

TAD patients exhibited significantly increased expression of aortic collagen types I and III as well as CTGF, which is likely to be responsible for the compromised aortic distensibility and systemic compliance. Because CTGF can increase collagen expression, CTGF may be a new target molecule in the pathogenesis and progression of TAD.

The antifibrogenic effect of (-)-epigallocatechin gallate results from the induction of de novo synthesis of glutathione in passaged rat hepatic stellate cells

Hepatic stellate cells (HSC) are the major players during hepatic fibrogenesis. Overproduction of extracellular matrix (ECM) is a characteristic of activated HSC. Transforming growth factor-beta (TGF-beta) is the most potent fibrogenic cytokine while connective tissue growth factor (CTGF) mediates the production of TGF-beta-induced ECM in activated HSC. HSC activation and hepatic fibrogenesis are stimulated by oxidative stress. Glutathione (GSH) is the most important intracellular antioxidant. The aim of this study is to explore the mechanisms of (-)-epigallocatechin-3-gallate (EGCG), the major and most active component in green tea extracts, in the inhibition of ECM gene expression in activated HSC. It is hypothesized that EGCG inhibits ECM gene expression in activated HSC by interrupting TGF-beta signaling through attenuating oxidative stress. It is found that EGCG interrupts TGF-beta signaling in activated HSC by suppressing gene expression of type I and II TGF-beta receptors. EGCG inhibits CTGF gene expression, leading to the reduction in the abundance of ECM, including alphaI(I) procollagen. Exogenous CTGF dose dependently eliminates the antifibrogenic effect. EGCG attenuates oxidative stress in passaged HSC by scavenging reactive oxygen species and reducing lipid peroxidation. De novo synthesis of GSH is a prerequisite for EGCG to interrupt TGF-beta signaling and to reduce the abundance of alphaI(I) procollagen in activated HSC in vitro. Taken together, our results demonstrate that the interruption of TGF-beta signaling by EGCG results in the suppression of gene expression of CTGF and ECM in activated HSC in vitro. In addition, our results, for the first time, demonstrate that the antioxidant property of EGCG derived from de novo synthesis of intracellular GSH plays a critical role in its antifibrogenic effect. These results provide novel insights into the mechanisms of EGCG as an antifibrogenic candidate in the prevention and treatment of liver fibrosis.

Mechanosensitive synoviocytes: A Ca2+–PKCα–MAP kinase pathway contributes to stretch-induced hyaluronan synthesis in vitro

Hyaluronan (HA) is central to joint function, contributing to synovial fluid retention, lubrication, matrix organisation and joint embryogenesis. HA synthesis by intimal synoviocytes is stimulated by stretch (SSHA), linking HA production to joint usage; but the signal transduction paths are unknown. Low passage rabbit synoviocytes (RS), cultured from micro dissected synovial intima, were subjected to 10min of 10% static stretch followed by 170-min relaxation, or to sustained stretch for 180min in a Flexcell 2000 apparatus. Medium HA content was analysed by a HA-binding assay. The roles of protein kinase C (PKC) isoforms, extracellular signal-regulated kinases (ERK1/2) and Ca(2+) signalling in SSHA were tested using kinase inhibitors, Ca(2+) chelators and Ca(2+) channel activators combined with Western blots for activated kinases. Stretch increased HA secretion by 57%, independently of stretch duration. PKCalpha translocated from cytosol to membrane and triggered the phosphorylation of ERK1/2. The PKC inhibitor bisindolylmaleimide (BIM) blocked both SSHA and ERK phosphorylation, as did Gö 6976, a specific inhibitor of Ca(2+)-dependent PKC. The Ca(2+) channel activator Bay K stimulated HA secretion and ERK phosphorylation. Extra- and intra-cellular Ca(2+) chelation by EGTA and BAPTA-AM (respectively) inhibited SSHA. SSHA was also blocked by the partially selective protein kinase A inhibitor, H-89. Connective tissue growth factor, CTGF, was not involved in SSHA. Thus, stimulation of synoviocyte HA secretion by static stretch is due at least in part the o activation of a Ca(2+) influx-dependent activation of the PKCalpha-MEK-ERK1/2 cascade. This is functionally important because it links joint lubrication to joint use.

Connective tissue growth factor/CCN2 stimulates actin disassembly through Akt/protein kinase B-mediated phosphorylation and cytoplasmic translocation of p27(Kip-1)

Connective tissue growth factor (CTGF/CCN2) is a 38-kDa secreted protein, a prototypic member of the CCN family, which is up-regulated in many diseases, including atherosclerosis, pulmonary fibrosis, and diabetic nephropathy. We previously showed that CTGF can cause actin disassembly with concurrent down-regulation of the small GTPase Rho A and proposed an integrated signaling network connecting focal adhesion dissolution and actin disassembly with cell polarization and migration. Here, we further delineate the role of CTGF in cell migration and actin disassembly in human mesangial cells, a primary target in the development of renal glomerulosclerosis. The functional response of mesangial cells to treatment with CTGF was associated with the phosphorylation of Akt/protein kinase B (PKB) and resultant phosphorylation of a number of Akt/PKB substrates. Two of these substrates were identified as FKHR and p27(Kip-1). CTGF stimulated the phosphorylation and cytoplasmic translocation of p27(Kip-1) on serine 10. Addition of the PI-3 kinase inhibitor LY294002 abrogated this response; moreover, addition of the Akt/PKB inhibitor interleukin (IL)-6-hydroxymethyl-chiro-inositol-2(R)-2-methyl-3-O-octadecylcarbonate prevented p27(Kip-1) phosphorylation in response to CTGF. Immunocytochemistry revealed that serine 10 phosphorylated p27(Kip-1) colocalized with the ends of actin filaments in cells treated with CTGF. Further investigation of other Akt/PKB sites on p27(Kip-1), revealed that phosphorylation on threonine 157 was necessary for CTGF mediated p27(Kip-1) cytoplasmic localization; mutation of the threonine 157 site prevented cytoplasmic localization, protected against actin disassembly and inhibited cell migration. CTGF also stimulated an increased association between Rho A and p27(Kip-1). Interestingly, this resulted in an increase in phosphorylation of LIM kinase and subsequent phosphorylation of cofilin, suggesting that CTGF mediated p27(Kip-1) activation results in uncoupling of the Rho A/LIM kinase/cofilin pathway. Confirming the central role of Akt/PKB, CTGF-stimulated actin depolymerization only in wild-type mouse embryonic fibroblasts (MEFs) compared to Akt-1/3 (PKB alpha/gamma) knockout MEFs. These data reveal important mechanistic insights into how CTGF may contribute to mesangial cell dysfunction in the diabetic milieu and sheds new light on the proposed role of p27(Kip-1) as a mediator of actin rearrangement.

A novel integrin alpha5beta1 binding domain in module 4 of connective tissue growth factor (CCN2/CTGF) promotes adhesion and migration of activated pancreatic stellate cells

BACKGROUND

Connective tissue growth factor (CCN2) is upregulated in pancreatic fibrosis and desmoplastic pancreatic tumours. CCN2 interacts with integrin alpha5beta1 on pancreatic stellate cells (PSC) in which it stimulates fibrogenesis, adhesion, migration, and proliferation.

AIM

To determine the structural domain(s) in CCN2 that interact with integrin alpha5beta1 to regulation PSC functions.

METHODS

Primary activated rat PSC were tested for their adherence to isoforms of CCN2 comprising modules 1-4 (CCN2(1-4)), modules 3-4 (CCN2(3-4)), module 3 alone (CCN2(3)), or module 4 alone (CCN2(4)). Adhesion studies were performed in the presence of EDTA, divalent cations, anti-integrin alpha5beta1 antibodies, CCN2 synthetic peptides, or heparin, or after pretreatment of the cells with heparinase, chondroitinase, or sodium chlorate. CCN2 integrin alpha5beta1 binding was analysed in cell free systems. The ability of CCN2(1-4), CCN2(3-4), or CCN2(4) to stimulate PSC migration was evaluated in the presence of anti-integrin alpha5beta1 or heparin.

RESULTS

PSC adhesion was stimulated by CCN2(1-4), CCN2(3-4), or CCN2(4) and supported by Mg2+ but not Ca2+. CCN2(4) supported PSC adhesion or migration were blocked by anti-integrin alpha5beta1 antibodies or by treatment of cells with heparinase or sodium chlorate. A direct interaction between CCN2(4) and integrin alpha5beta1 was demonstrated in cell free assays. The sequence GVCTDGR in module 4 mediated the binding between CCN2(4) and integrin alpha5beta1 as well as CCN2(4) mediated PSC adhesion and migration.

CONCLUSIONS

A GVCTDGR sequence in module 4 of CCN2 is a novel integrin alpha5beta1 binding site that is essential for CCN2 stimulated functions in PSC and which represents a new therapeutic target in PSC mediated fibrogenesis.

[Transdifferentiation and collagen-synthesis effects of exogenous connective tissue growth factor on renal tubular epithelial cells in vitro]

OBJECTIVE

To investigate the effects of recombinal human connective tissue growth factor (rhCTGF) stimulation on epithelial-myofibroblast transdifferentiation (EMT) and collagen-synthesis in human renal tubular epithelial cell line (HK2) in vitro.

METHODS

The cultured HK2 cells were stimulated with rhCTGF of 5 ng/mL. The morphological changes were observed under an inverted microscope. The cells were collected at 0, 3, 6, 12, 24 and 48 hrs after rhCTGF stimulation. The expression of E-cadherin,alpha-smooth muscle actin (alpha-SMA), collagen Ialpha1 (Col Ialpha1) and collagen IValpha1 (Col IValpha1) mRNAs were detected by RT-PCR.

RESULTS

rhCTGF stimulation changed the HK2 cell appearance from oval to fusiformdown-regulated the E-cadherin mRNA expression and up-regulated alpha-SMA mRNA expression, but had no effects the Col Ialpha1 and Col IValpha1 mRNA expression.

CONCLUSIONS

Exogenous CTGF can mediate the EMT but has no collagen-synthesis effects on HK2 cells.

New target genes for NOV/CCN3 in chondrocytes: TGF-beta2 and type X collagen

We studied the involvement of NOV/CCN3, whose function is poorly understood, in chondrocyte differentiation. NOV was found to upregulate TGF-beta2 and type X collagen and to act as a downstream effector of TGF-beta1 in ATDC5 and primary chondrocytes. Thus, NOV is a positive modulator of chondrogenesis.

INTRODUCTION

NOV/CCN3 is a matricellular protein that belongs to the CCN family. A growing body of evidence indicates that NOV could play a role in cell differentiation, particularly in chondrogenesis. During chick embryo development, NOV expression is tightly regulated in cartilage, and a high expression of NOV has been associated with cartilage differentiation in Wilms' tumors. However, a precise role for NOV and potential target genes of NOV in chondrogenesis are unknown.

MATERIALS AND METHODS

ATDC5 cells and primary chondrocytes were either treated with NOV recombinant protein or transfected with a NOV-specific siRNA to determine, using quantitative RT-PCR, the effect of NOV on the expression of several molecules involved in chondrocyte differentiation. Stable ATDC5 clones expressing NOV were also established to show that NOV was a downstream effector of TGF-beta1.

RESULTS

We established that NOV/CCN3 expression increases in ATDC5 cells at early stages of chondrogenic differentiation and precedes the appearance of TGF-beta2 and of several chondrocytic markers such as SOX9 or type X collagen. When exogenously administered, NOV recombinant protein up-regulates TGF-beta2 and type X collagen mRNA levels both in ATDC5 cells and in primary mouse chondrocytes but does not influence SOX9 expression. This regulation also occurs at the endogenous level because downregulation of NOV expression is correlated with an inhibition of TGF-beta2 and type X collagen in primary chondrocytes. Furthermore, we found that NOV expression is downregulated when chondrocytes are exposed to TGF-beta1-dedifferentiating treatment in chondrocytes, further providing evidence that NOV may counteract TGF-beta1 effects on chondrocytes.

CONCLUSIONS

This study provides the first characterization of two new targets of NOV involved in chondrocyte differentiation, shows that NOV acts with TGF-beta1 in a cascade of gene regulation, and indicates that NOV is a positive modulator of chondrogenesis.

Advanced glycation end-product-induced mitogenesis and collagen production are dependent on angiotensin II and connective tissue growth factor in NRK-49F cells

Diabetic nephropathy (DN) is characterized by glomerulopathy and tubulointerstitial expansion followed by renal fibrosis. Angiotensin II (Ang II) and connective tissue growth factor (CTGF) are involved in the pathogenesis of DN, while Janus kinase 2 (JAK2) is important in advanced glycation end-product (AGE)-induced effects in renal interstitial (NRK-49F) fibroblasts. Thus, we studied the role of Ang II, CTGF, and JAK2 in AGE-induced effects in NRK-49F cells. We found that AGE (150 microg/ml) increased mitogenesis and type I collagen production at 7 days while Ang II (10(-7)M) increased mitogenesis and type I collagen production at 3 days. We also found that AGE (150 microg/ml) increased angiotensinogen protein at 2 days, which was attenuated by AG-490 (a JAK2 inhibitor). AGE (150 microg/ml) increased CTGF mRNA and protein expression at 3 and 5 days, respectively. Ang II (10(-7)M) increased CTGF mRNA and protein expression at 1 and 2 days, respectively, which were attenuated by AG-490. Moreover, losartan (a type I angiotensin receptor blocker) and captopril (an angiotensin converting enzyme inhibitor) attenuated AGE-induced CTGF mRNA/protein expression while attenuating AGE-induced mitogenesis and type I collagen production. AG-490 and CTGF antisense (but not sense) oligodeoxynucleotide (ODN) attenuated Ang II (10(-7)M) and AGE-induced mitogenesis and type I collagen production at 3 and 7 days, respectively. We concluded that AGE (150 microg/ml)-induced mitogenesis and type I collagen production are dependent on the Ang II-JAK2-CTGF pathway in NRK-49F cells. Moreover, Ang II-induced mitogenesis and type I collagen production are dependent on the JAK2-CTGF pathway.

Characterization of antiproliferative and cytotoxic properties of the HSV-1 immediate-early ICPo protein

BACKGROUND

The identification of novel proteins displaying cytostatic and/or cytotoxic actions that could eventually be used for gene therapy is a major issue in cancer research. Data from the literature suggested that the immediate-early ICP0 protein from herpes simplex virus type 1 (HSV-1) could fulfill these properties as it had been observed that this protein is involved in arrest of cell growth at the G1/S and G2/M phases of the cell cycle and that deletion of ICP0 from HSV-1 or HSV-1-recombinant vectors significantly reduced their cytotoxicity. The molecular basis of its action is likely related to the ability of ICP0, which possesses E3-ubiquitin ligase activity, to target destruction of key cellular proteins, including centromeric proteins, resulting in abnormal chromosome segregation, unusual cytokinesis, and emergence of nuclear morphological aberrations. However, neither the gene therapy potential of ICP0 on its own nor its action on primary quiescent cells has been assessed to date. The aim of this work was therefore to evaluate the antiproliferative and cytotoxic properties of ICP0 on a human glioblastoma cell line and on quiescent primary cells, and to explore whether this protein has a potential for gene therapy of cancer.

METHODS

HSV-1-based amplicon particles were generated following a recently described method that produces relatively high titers of vector stocks that are essentially free of helper virus. These vectors express either wild-type ICP0 or FXE, a RING finger mutated inactive form of ICP0, together with reporter green fluorescent protein (GFP). The vectors were used to infect Gli36 cells, which derive from a human glioblastome, and cultured rat primary cardiomyocytes and brain cells, two well-established models of non-dividing cells. Expression and localization of ICP0 and FXE, as well as their action on centromeres and nuclear morphology, were evaluated by Western blotting, indirect immune fluorescence, and confocal microscopy using specific antibodies and DAPI labeling. The impact of ICP0 on cell growth, toxicity, and viability was evaluated in the different cells using a variety of methods, including FACS analysis after propidium iodide and AnnexinV staining, crystal violet staining, clonogenic capability, caspase 3 activation, MTT tests, and release of lactate dehydrogenase, after infection with the different vectors.

RESULTS

The three cell types under study showed high levels of transduction by amplicons and strong expression of GFP, ICP0, and FXE transgenic proteins. Wild-type ICP0, but not FXE, induced centromeric disruption, appearance of micronuclei, arrest of proliferation, and significant cell death in glioblastoma Gli36 cells. In contrast, neither micronuclei formation nor any other sign of cell toxicity could be observed in cultured primary cardiomyocytes or brain cells, as evaluated by MTT tests and crystal violet staining. Furthermore, in the case of cardiomyocytes, expression of ICP0 did not interfere with beating as cells continued to beat at the same frequency as non-infected cells for several days post-infection. Neither AnnexinV early staining nor caspase 3 activation was observed in dying infected Gli36 cells, suggesting that these cells were not entering apoptosis. In contrast, release of lactate dehydrogenase by infected Gli36 cells suggested a necrotic way of death.

CONCLUSIONS

ICP0 induced a strong cytostatic action followed by significant cell death on the glioblastoma Gli36 cell line. In contrast, neither cell death nor any other evidence of ICP0-induced toxicity affecting major physiological parameters was observed in primary cultured cardiomyoctes and brain cells, two models of primary non-cycling cells. These results suggest that ICP0 has gene therapy potential and could represent the first member of a novel family of directly acting proteins that could be used to treat cancers.

[Role of connective tissue growth factor in human renal tubular epithelial cell transdifferentiation in vitro]

OBJECTIVE

To observe the effect of connective tissue growth factor (CTGF) on the transdifferentiation of human renal tubular epithelial cells and to explore the influence of CTGF antisense oligodeoxynucleotide (ASODN) transfection on the transdifferentiation process induced by transforming growth factor-beta1 (TGF-beta1).

METHODS

Human renal tubular epithelial cells of the strain HKC were cultured and divided into 3 groups: (1) negative control group, (2) low dose CTGF group, treated with recombinant human CTGF (rhCTGF) with the terminal concentration of 2.5 microg/L, and (3) high dose CTGF group, treated with rhCTGF with the terminal concentration of 5.0 microg/L). To evaluate the contribution of CTGF to the transdifferentiation induced by TGF-beta1, Another HKC cells were divided into 4 groups: (1) untreated control group (Group C), (2) Group T, stimulated by TGF-beta1 (10.0 microg/L), (3) Group S, stimulated by sense ODN transfection + TGF-beta1 (10.0 microg/L), and (4) Group A, stimulated by antisense ODN transfection + TGF-beta1 (10.0 microg/L). RT-PCR was used to detect the mRNA expression of alpha-smooth muscle actin (alpha-SMA) and collagen type IV (col IV) mRNA. Indirect immunofluorescence assay and flow cytometry were used to assess the level of intracellular alpha-SMA protein. ELISA was used to determine the concentration of col IV in the media.

RESULTS

The normal HKC cells were round and the HKC cells stimulated with rhCTGF became elongated. Upon the stimulation of different concentrations of rhCTGF, the expression of alpha-SMA mRNA increased markedly (both P < 0.01), while the mRNA expression of collagen type IV gene was down-regulated significantly (both P < 0.01). The percentage of alpha-SMA positive cells was significantly higher in the stimulated groups than that in negative control with significant difference among any 2 groups (38.9%, 65.5% vs. 2.4% respectively, all P < 0.01). Under this condition, collagen type IV secreted into the culture medium was lowered markedly upon the induction of CTGF (P < 0.01). RT-PCR analysis showed that the CTGF gene expression was upregulated by TGF-beta1 stimulation and peaked in 3 hours, and the alpha-SMA expression was upregulated by TGF-beta1 stimulation, however, peaked in 6 hours. The CTGF mRNA expression of the HKC cells transfected with CTGF ASODN that was stimulated by TGF-beta1 10 microg/L was significantly suppressed (P < 0.01) and the alpha-SMA mRNA expression induced by TGF-beta1 10 microg/L was significantly inhibited by CTGF ASODN transfection (P < 0.01). Indirect immunofluorescence assay showed that normal HKC cells did not express alpha-SMA, 48 hours after stimulation of TGF-beta1 10 microg/L the HKC cells showed expression of alpha-SMA in the cytoplasm, and the intracytoplasmic alpha-SMA expression was significantly down-regulated by the transfection of CTGF ASODN (P < 0.01).

CONCLUSION

CTGF can promote the transdifferentiation of human renal tubular epithelial cells towards myofibroblast (MyoF) in vitro, and CTGF blockade results in a dramatic inhibition of TGF-beta-induced transdifferentiation of renal tubular cells. So CTGF may be a crucial factor in promoting tubular-epithelial myofibroblast transdifferentiation.

TGF-beta1 induces IL-8 and MCP-1 through a connective tissue growth factor-independent pathway

Transforming growth factor-beta(1) (TGF-beta(1)) functions as an important immunomodulatory cytokine in human kidney. Evidence suggests that connective tissue growth factor (CTGF) is an important downstream mediator of the profibrotic effects of TGF-beta(1). However, the role of CTGF in TGF-beta(1)-induced chemokine production remains unknown. This study was undertaken to determine whether CTGF is involved in mediating TGF-beta(1)-induced chemokine production in renal proximal tubular (HK-2) cells. Interleukin-8 (IL-8) and macrophage chemoattractant protein-1 (MCP-1) were measured. TGF-beta(1) induced an increase in IL-8 and MCP-1 (both P < 0.05) compared with control levels. CTGF was effectively silenced using small interference RNA (siRNA) in HK-2 cells. RT-PCR and real-time PCR confirmed a 94% reduction in CTGF mRNA. In the CTGF-silenced cells, TGF-beta(1)-stimulated IL-8 and MCP-1 secretion was not altered compared with control cells. Similarly, basal secretion of IL-8 and MCP-1 was not changed in CTGF-silenced cells. The direct effect of CTGF (20, 200, and 400 ng/ml) on IL-8 and MCP-1 was assessed at 24-, 48-, and 72-h time points and no stimulation was observed. Our studies further demonstrate that in the CTGF gene-silenced cells, CTGF partially mediates TGF-beta(1)-induced fibronectin and collagen IV secretion. These data suggest that TGF-beta(1) induced IL-8 and MCP-1 via CTGF-independent pathway. TGF-beta mediates both fibrosis and chemokine production in the proximal tubule of the kidney. However, CTGF plays a more specific role as a downstream mediator of TGF-beta(1)-induced fibrosis.

Connective tissue growth factor induces extracellular matrix in asthmatic airway smooth muscle

Transforming growth factor (TGF)-beta and connective tissue growth factor may be implicated in extracellular matrix protein deposition in asthma. We have recently reported that TGF-beta increased connective tissue growth factor expression in airway smooth muscle cells isolated from patients with asthma. In this study, we examined fibronectin and collagen production and signal transduction pathways after stimulation with TGF-beta and connective tissue growth factor. In both asthmatic and nonasthmatic airway smooth muscle cells, TGF-beta and connective tissue growth factor led to the production of fibronectin and collagen I. Fibronectin and collagen expression was extracellular regulated kinase-dependent in both cell types but phosphoinositide-3 kinase-dependent only in asthmatic airway smooth muscle cells. p38 was implicated in fibronectin but not collagen expression in both cell types. TGF-beta induction of fibronectin and collagen was in part mediated by an autocrine action of connective tissue growth factor. Phosphorylation of SMAD-2 may represent an additional pathway because this was increased in asthmatic cells. Our results suggest that these two cytokines may be important in the deposition of extracellular matrix proteins and that the signal transduction pathways may be different in asthmatic and nonasthmatic cells.

Inhibition of cell division by the human cytomegalovirus IE86 protein: role of the p53 pathway or cyclin-dependent kinase 1/cyclin B1

The human cytomegalovirus (HCMV) IE86 protein induces the human fibroblast cell cycle from G(0)/G(1) to G(1)/S, where cell cycle progression stops. Cells with a wild-type, mutated, or null p53 or cells with null p21 protein were transduced with replication-deficient adenoviruses expressing HCMV IE86 protein or cellular p53 or p21. Even though S-phase genes were activated in a p53 wild-type cell, IE86 protein also induced phospho-Ser(15) p53 and p21 independent of p14ARF but dependent on ATM kinase. These cells did not enter the S phase. In human p53 mutant, p53 null, or p21 null cells, IE86 protein did not up-regulate p21, cellular DNA synthesis was not inhibited, but cell division was inhibited. Cells accumulated in the G(2)/M phase, and there was increased cyclin-dependent kinase 1/cyclin B1 activity. Although the HCMV IE86 protein increases cellular E2F activity, it also blocks cell division in both p53(+/+) and p53(-/-) cells.

Downregulation of GFAP, TSP-1, and p53 in human glioblastoma cell line, U373MG, by IE1 protein from human cytomegalovirus

Human cytomegalovirus (HCMV) is a member of the beta-herpesvirus family, which has tropism for glial cells. It was recently reported that HCMV might play important roles in the pathogenesis of malignant glioma. In this study, we investigated the effects of the HCMV IE1 protein on the gene expression profile in the human glioblastoma cell line, U373MG by employing cDNA microarray technology. Using DNA chips containing approximately 1,000 human cDNAs, RNA samples from U373MG cells stably expressing IE1 were compared with those from the control cells lacking IE1 cDNA. Fluorescence intensities of 13 genes were significantly decreased in IE1-expressing cells, while one gene was found to be upregulated. Among these 14 genes, we chose to work further on glial fibrillary acidic protein (GFAP), thrombospondin-1 (TSP-1), and p53, because of their previously known involvement in tumorigenesis. The mRNA levels of all these genes were found to be decreased in IE1-expressing glioblastoma cells by real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) as well as Northern blot analysis. The decreased expression of these genes was also observed at protein levels as measured by immunocytochemistry or fluorescence-activated cell sorting (FACS) analysis. Our data strongly suggested that HCMV IE1 could modulate the expression of cellular genes that might play important roles in the pathogenesis of glial tumors.

Connective tissue growth factor causes persistent proalpha2(I) collagen gene expression induced by transforming growth factor-beta in a mouse fibrosis model

Skin fibrotic disorders such as systemic sclerosis (SSc) are characterized by an excessive production of extracellular matrix (ECM) and understood to develop under the influence of certain growth factors. Connective tissue growth factor (CTGF) is a cysteine-rich mitogenic peptide that is implicated in various fibrotic disorders and induced in fibroblasts after activation with transforming growth factor-beta (TGF-beta). To better understand the mechanisms of persistent fibrosis seen in SSc, we previously established an animal model of skin fibrosis induced by exogenous application of growth factors. In this model, TGF-beta transiently induced subcutaneous fibrosis and serial injections of CTGF after TGF-beta caused persistent fibrosis. To further define the mechanisms of skin fibrosis induced by TGF-beta and CTGF in vivo, we investigated in this study, the effects of growth factors on the promoter activity of the proalpha2 (I) collagen (COL1A2) gene in skin fibrosis. For this purpose, we utilized transgenic reporter mice harboring the -17 kb promoter sequence of the mouse COL1A2 linked to either a firefly luciferase gene or a bacterial beta-galactosidase gene. Serial injections of CTGF after TGF-beta resulted in a sustained elevation of COL1A2 mRNA expression and promoter activity compared with consecutive injection of TGF-beta alone on day 8. We also demonstrated that the number of fibroblasts with activated COL1A2 transcription was increased by serial injections of CTGF after TGF-beta in comparison with the injection of TGF-beta alone. Furthermore, the serial injections recruited mast cells and macrophages. The number of mast cells reached a maximum on day 4 and remained relatively high up to day 8. In contrast to the kinetics of mast cells, the number of macrophages was increased on day 4 and continued to rise during the subsequent consecutive CTGF injections until day 8. These results suggested that CTGF maintains TGF-beta-induced skin fibrosis by sustaining COL1A2 promoter activation and increasing the number of activated fibroblasts. The infiltrated mast cells and macrophages may also contribute to the maintenance of fibrosis.

[Connective tissue growth factor promotes the proliferation of myofibroblast through Erk-1/2 signaling pathway]

OBJECTIVE

To investigate the mechanism by which connective tissue growth factor (CTGF) enhances transforming growth factor-beta(1) (TGF-beta(1))-mediated myofibroblastic activation in renal interstitial fibroblast NRK-49F.

METHODS

NRK-49F cells were pretreated by TGF-beta(1) so that some cells transform into myofibroblasts, and then the cells were devided into vechile, CTGF treated group, TGF-beta(1) treated group, and PD98059 intervene group. The hallmark of myofibroblast, alpha-SMA immunostaining and marker of cellular proliferation, BrdU incorporation were determined by immunocytochemistry doublestaining. The protein level of alpha-SMA was determined by Western blot analysis.

RESULTS

CTGF induced a proliferative response in myofibroblast initiated by TGF-beta(1), whereas TGF-beta(1) had no action on proliferation. Although CTGF could not induce myofibroblastic activation in renal interstitial fibroblast, it upregulated the protein level of alpha-smooth muscle actin significantly in cells pretreated by TGF-beta1 (P < 0.05). Significant phosphorylation of Erk-1/2 was detected after incubation with CTGF for 30 min in the cells pretreated by TGF-beta(1), while TGF-beta(1) did not have this ability. Inhibition of Erk-1/2 activation by Mek kinase inhibitor PD98059 suppressed CTGF-mediated myofibroblasts proliferation and significantly down-regulated expression of alpha-SMA protein in cells pretreated by TGF-beta(1) (P < 0.05).

CONCLUSION

CTGF induced a proliferative response in TGF-beta(1)-initiated myofibroblasts, and this action is likely dependent on the activation of Erk-1/2 signaling pathway.

Modulation of the TGFbeta/Smad signaling pathway in mesangial cells by CTGF/CCN2

Transforming growth factor-beta (TGFbeta) drives fibrosis in diseases such as diabetic nephropathy (DN). Connective tissue growth factor (CTGF; CCN2) has also been implicated in this, but the molecular mechanism is unknown. We show that CTGF enhances the TGFbeta/Smad signaling pathway by transcriptional suppression of Smad 7 following rapid and sustained induction of the transcription factor TIEG-1. Smad 7 is a known antagonist of TGFbeta signaling and TIEG-1 is a known repressor of Smad 7 transcription. CTGF enhanced TGFbeta-induced phosphorylation and nuclear translocation of Smad 2 and Smad 3 in mesangial cells. Antisense oligonucleotides directed against TIEG-1 prevented CTGF-induced downregulation of Smad 7. CTGF enhanced TGFbeta-stimulated transcription of the SBE4-Luc reporter gene and this was markedly reduced by TIEG-1 antisense oligonucleotides. Expression of the TGFbeta-responsive genes PAI-1 and Col III over 48 h was maximally stimulated by TGFbeta+CTGF compared to TGFbeta alone, while CTGF alone had no significant effect. TGFbeta-stimulated expression of these genes was markedly reduced by both CTGF and TIEG-1 antisense oligonucleotides, consistent with the endogenous induction of CTGF by TGFbeta. We propose that under pathological conditions, where CTGF expression is elevated, CTGF blocks the negative feedback loop provided by Smad 7, allowing continued activation of the TGFbeta signaling pathway.

Module-specific antibodies against human connective tissue growth factor: utility for structural and functional analysis of the factor as related to chondrocytes

Connective tissue growth factor/hypertrophic chondrocyte specific gene product 24 (CTGF/Hcs24/CCN2) shows diverse functions in the process of endochondral ossification. It promotes not only the proliferation and differentiation of chondrocytes and osteoblasts in vitro, but also angiogenesis in vivo. The ctgf gene is a member of the gene family called CCN, and it encodes the characteristic 4-module structure of this family, with the protein containing IGFBP, VWC, TSP and CT modules. We raised several monoclonal antibodies and polyclonal antisera against CTGF, and located the epitopes in the modules by Western blotting. For mapping the epitopes, Brevibacillus-produced independent modules were utilized. As a result, at least 1 antibody or antiserum was prepared for the detection of each module in CTGF. Western blotting with these antibodies is expected to be useful for the analysis of CTGF fragmentation. Moreover, we examined the effects of these monoclonal antibodies on the biological functions of CTGF. One out of 3 humanized monoclonal antibodies was found to neutralize efficiently the stimulatory effect of CTGF on chondrocytic cell proliferation. This particular antibody bound to the CT module. In contrast, surprisingly, all of the 3 antibodies recognizing IGFBP, VWC and CT modules stimulated proteoglycan synthesis in chondrocytic cells. Together with previous findings, these results provide insight into the structural-functional relationships of CTGF in executing multiple functions.

Processing and presentation of HLA class I and II epitopes by dendritic cells after transfection with in vitro-transcribed MUC1 RNA

RNA transfection of dendritic cells (DCs) was shown to be highly efficient in eliciting CD8+ and CD4+ T-cell responses. However, antigen presentation pathways involved in generation of human leukocyte antigen (HLA) class I and class II peptides have remained elusive. To analyze this we incubated mucin 1 (MUC1) RNA-transfected DCs with compounds known to inhibit HLA class I presentation and used these cells in chromium 51 (51Cr)-release assays. As effectors, we used cytotoxic T lymphocyte (CTL) lines specific for the MUC1 peptides M1.1 and M1.2. We observed that the presentation of HLA-A*02 epitopes is inhibited by brefeldin A and lactacystin. To determine the requirement of a functional transporter associated with antigen processing (TAP), we cotransfected DCs with MUC1 and infected cell peptide 47 (ICP47) RNA. ICP47 could only inhibit the presentation of the M1.1 but not the M1.2 peptide, indicating that this epitope derived from the signal sequence is presented independently of TAP. Cocultivation of MUC1 RNA-transfected DCs with MUC1-specific CD4+ T lymphocytes revealed that the presentation of HLA class II peptides is sensitive to proteasomal inhibitors and brefeldin A. Furthermore, the presentation pathway requires lysosomal and endosomal processing and is mediated by autophagy. Our results demonstrate that the efficient presentation of cytosolic proteins on major histocompatibility complex (MHC) class II combines the proteolytic and lysosomal pathways.

Connective tissue growth factor CCN2 interacts with and activates the tyrosine kinase receptor TrkA

Connective tissue growth factor (CTGF) is implicated as a factor promoting tissue fibrosis in several disorders, including diabetic nephropathy. However, the molecular mechanism(s) by which it functions is not known. CTGF rapidly activates several intracellular signaling molecules in human mesangial cells (HMC), including extracellular signal-related kinase 1/2, Jun NH(2)-terminal kinase, protein kinase B, CaMK II, protein kinase Calpha, and protein kinase Cdelta, suggesting that it functions via a signaling receptor. Treating HMC with CTGF stimulated tyrosine phosphorylation of proteins 75 to 80 and 140 to 180 kD within 10 min, and Western blot analysis of anti-phosphotyrosine immunoprecipitates identified the neurotrophin receptor TrkA (molecular weight approximately 140 kD). Cross-linking rCTGF to cell surface proteins with 3,3'-dithiobis(sulfosuccinimidylpropionate) revealed that complexes formed with TrkA and with the general neurotrophin co-receptor p75(NTR). rCTGF stimulated phosphorylation of TrkA (tyr 490, 674/675). K252a, a known selective inhibitor of Trk, blocked this phosphorylation, CTGF-induced activation of signaling proteins, and CTGF-dependent induction of the transcription factor TGF-beta-inducible early gene in HMC. It is concluded that TrkA serves as a tyrosine kinase receptor for CTGF.