Role of Elevated Thrombospondin-1 in Kainic Acid-Induced Status Epilepticus.

Previous studies have suggested that thrombospondin-1 (TSP-1) regulates the transforming growth factor beta 1 (TGF-ß1)/phosphorylated Smad2/3 (pSmad2/3) pathway. Moreover, TSP-1 is closely associated with epilepsy. However, the role of the TSP-1-regulated TGF-ß1/pSmad2/3 pathway in seizures remains unclear. In this study, changes in this pathway were assessed following kainic acid (KA)-induced status epilepticus (SE) in rats. The results showed that increases in the TSP-1/TGF-ß1/pSmad2/3 levels spatially and temporally matched the increases in glial fibrillary acidic protein (GFAP)/chondroitin sulfate (CS56) levels following KA administration. Inhibition of TSP-1 expression by small interfering RNA or inhibition of TGF-ß1 activation with a Leu-Ser-Lys-Leu peptide significantly reduced the severity of KA-induced acute seizures. These anti-seizure effects were accompanied by decreased GFAP/CS56 expression and Smad2/3 phosphorylation. Moreover, inhibiting Smad2/3 phosphorylation with ponatinib or SIS3 also significantly reduced seizure severity, alongside reducing GFAP/CS56 immunoreactivity. These results suggest that the TSP-1-regulated TGF-ß1/pSmad2/3 pathway plays a key role in KA-induced SE and astrogliosis, and that inhibiting this pathway may be a potential anti-seizure strategy.

Inhibition of Transforming Growth Factor-ß Activation Diminishes Tumor Progression and Osteolytic Bone Disease in Mouse Models of Multiple Myeloma.

Transforming growth factor (TGF)-ß supports multiple myeloma progression and associated osteolytic bone disease. Conversion of latent TGF-ß to its biologically active form is a major regulatory node controlling its activity. Thrombospondin1 (TSP1) binds and activates TGF-ß. TSP1 is increased in myeloma, and TSP1-TGF-ß activation inhibits osteoblast differentiation. We hypothesized that TSP1 regulates TGF-ß activity in myeloma and that antagonism of the TSP1-TGF-ß axis inhibits myeloma progression. Antagonists (LSKL peptide, SRI31277) derived from the LSKL sequence of latent TGF-ß that block TSP1-TGF-ß activation were used to determine the role of the TSP1-TGF-ß pathway in mouse models of myeloma. TSP1 binds to human myeloma cells and activates TGF-ß produced by cultured human and mouse myeloma cell lines. Antagonists delivered via osmotic pump in an intratibial severe combined immunodeficiency CAG myeloma model or in a systemic severe combined immunodeficiency CAG-heparanase model of aggressive myeloma reduced TGF-ß signaling (phospho-Smad 2) in bone sections, tumor burden, mouse IL-6, and osteoclasts, increased osteoblast number, and inhibited bone destruction as measured by microcomputed tomography. SRI31277 reduced tumor burden in the immune competent 5TGM1 myeloma model. SRI31277 was as effective as dexamethasone or bortezomib, and SRI31277 combined with bortezomib showed greater tumor reduction than either agent alone. These studies validate TSP1-regulated TGF-ß activation as a therapeutic strategy for targeted inhibition of TGF-ß in myeloma.

Thrombospondin-1 is a glucocorticoid responsive protein in humans.

OBJECTIVE: Thrombospondin-1 (TSP1) is a matricellular protein whose gene expression has previously been shown to increase acutely after exposure to dexamethasone in vitro. The aim of this study was to determine if TSP1 is altered by acute and chronic states of glucocorticoid excess in human subjects. DESIGN AND METHODS: Three studies have been undertaken to assess the difference or change in TSP1 in response to altered glucocorticoid activity: i) an acute interventional study assessed the effects of a single 4 mg dose of dexamethasone in 20 healthy volunteers; ii) a cross-sectional study compared plasma TSP1 in 20 healthy volunteers and eight patients with Cushing's syndrome; iii) an interventional study assessed the effect on plasma TSP1 of an increase in hydrocortisone dose from ≤20 mg/day to 30 mg/day for 7 days in 16 patients with secondary adrenal insufficiency. RESULTS: In healthy volunteers, 4 mg dexamethasone significantly increased peripheral blood mononuclear cell (PBMC) TSP1 mRNA levels (P<0.0001) and plasma TSP1 concentrations (P<0.0001), peaking at 12 h. Median (interquartile range) plasma TSP1 was higher in Cushing's, 638 (535-756) ng/ml, than in healthy volunteers, 272 (237-336) ng/ml (P<0.0001). Plasma TSP1 >400 ng/ml diagnosed Cushing's syndrome with sensitivity of 100% and specificity of 85%. The higher hydrocortisone dose increased plasma TSP1 from 139 (86-199) to 256 (133-516) ng/ml, (P<0.01) in patients with secondary adrenal insufficiency. CONCLUSIONS: TSP1 is a glucocorticoid responsive protein in humans. Further research is required to determine if plasma TSP1 has a role as a glucocorticoid biomarker.

Effect of LSKL peptide on thrombospondin 1-mediated transforming growth factor ß signal activation and liver regeneration after hepatectomy in an experimental model.

BACKGROUND: A strategy for accelerating liver regeneration after hepatectomy would offer great benefits in preventing postoperative liver failure and improving surgical outcomes. Transforming growth factor (TGF) ß is a potent inhibitor of hepatocyte proliferation. Recently, thrombospondin (TSP) 1 has been identified as a negative regulator of liver regeneration by activation of local TGF-ß signals. This study aimed to clarify whether the LSKL (leucine-serine-lysine-leucine) peptide, which inhibits TSP-1-mediated TGF-ß activation, promotes liver regeneration after hepatectomy in mice. METHODS: Mice were operated on with a 70 per cent hepatectomy or sham procedure. Operated mice received either LSKL peptide or normal saline intraperitoneally at abdominal closure and 6 h after hepatectomy. Perioperative plasma TSP-1 levels were measured by enzyme-linked immunosorbent assay in patients undergoing hepatectomy. RESULTS: Administration of LSKL peptide attenuated Smad2 phosphorylation at 6 h. S-phase entry of hepatocytes was accelerated at 24 and 48 h by LSKL peptide, which resulted in faster recovery of the residual liver and bodyweight. Haematoxylin and eosin tissue staining and blood biochemical examinations revealed no significant adverse effects following the two LSKL peptide administrations. In the clinical setting, plasma TSP-1 levels were lowest on the first day after hepatectomy. However, plasma TSP-1 levels at this stage were significantly higher in patients with subsequent liver dysfunction compared with levels in those without liver dysfunction following hepatectomy. CONCLUSION: Only two doses of LSKL peptide during the early period after hepatectomy can promote liver regeneration. The transient inhibition of TSP-1/TGF-ß signal activation using LSKL peptide soon after hepatectomy may be a promising strategy to promote subsequent liver regeneration. Surgical relevance Although the mechanisms of liver regeneration after hepatectomy have been explored intensively in vivo, no therapeutic tools are thus far available to accelerate liver regeneration after hepatectomy in the clinical setting. Recently, the matricellular protein thrombospondin (TSP) 1, a major activator of latent transforming growth factor (TGF) ß1, has been identified as a negative regulator of liver regeneration after hepatectomy. In this study, the inhibition of TSP-1-mediated TGF-ß signal activation by LSKL (leucine-serine-lysine-leucine) peptide in the early period after hepatectomy accelerated liver regeneration without any adverse effects. In addition, continuous high plasma TSP-1 levels after hepatectomy were associated with liver damage in humans. The transient inhibition of TSP-1/TGF-ß signal activation using LSKL peptide in the early period after hepatectomy could be a novel therapeutic strategy to accelerate liver regeneration after hepatectomy.

Electroconvulsive seizure induces thrombospondin-1 in the adult rat hippocampus.

Synaptic dysfunction has recently gained attention for its involvement in mood disorders. Electroconvulsive therapy (ECT) possibly plays a role in synaptic repair. However, the underlying mechanisms remain uncertain. Thrombospondin-1 (TSP-1), a member of the TSP family, is reported to be secreted by astrocytes and to regulate synaptogenesis. We investigated the effects of electroconvulsive seizure (ECS) on the expression of TSPs in the adult rat hippocampus. Single and repeated ECS significantly increased TSP-1 mRNA expression after 2h and returned to sham levels at 24h. Conversely, the TSP-2 and -4 mRNA levels did not change. Only repeated ECS induced TSP-1 proteins. ECS also induced glial fibrillary acidic protein (GFAP) expression. The GFAP expression occurred later than the TSP-1 mRNA expression following single ECS; however, it occurred earlier and was more persistent following repeated ECS. ECS had no effect on the α2δ-1 or neuroligin-1 expressions, both of which are TSP-1 receptors. Furthermore, chronic treatment with antidepressants did not induce the expression of TSP-1 or GFAP. These findings suggest that repeated ECS, but not chronic treatment with antidepressants, induces TSP-1 expression partially via the activation of astrocytes. Therefore, TSP-1 is possibly involved in the synaptogenic effects of ECS.

Acute and chronic mu opioids differentially regulate thrombospondins 1 and 2 isoforms in astrocytes.

Chronic opioids induce synaptic plasticity, a major neuronal adaptation. Astrocyte activation in synaptogenesis may play a critical role in opioid tolerance, withdrawal, and dependence. Thrombospondins 1 and 2 (TSP1/2) are astrocyte-secreted matricellular glycoproteins that promote neurite outgrowth as well as dendritic spine and synapse formation, all of which are inhibited by chronic µ opioids. In prior studies, we discovered that the mechanism of TSP1 regulation by µ opioids in astrocytes involves crosstalk between three different classes of receptors, µ opioid receptor, EGFR and TGFßR. Moreover, TGFß1 stimulated TSP1 expression via EGFR and ERK/MAPK activation, indicating that EGFR is a signaling hub for opioid and TGFß1 actions. Using various selective antagonists, and inhibitors, here we compared the mechanisms of chronic opioid regulation of TSP1/2 isoform expression in vivo and in immortalized rat cortical astrocytes. TSP1/2 release from astrocytes was also monitored. Acute and chronic µ opioids, morphine, and the prototypic µ ligand, DAMGO, modulated TSP2 protein levels. TSP2 but not TSP1 protein content was up-regulated by acute (3 h) morphine or DAMGO by an ERK/MAPK dependent mechanism. Paradoxically, TSP2 protein levels were altered neither by TGFß1 nor by astrocytic neurotrophic factors, EGF, CNTF, and BMP4. TSP1/2 immunofluorescence was increased in astrocytes subjected to scratch-wounding, suggesting TSPs may be useful markers for the "reactive" state of these cells and potentially for different types of injury. Previously, we determined that chronic morphine attenuated both neurite outgrowth and synapse formation in cocultures of primary astrocytes and neurons under similar temporal conditions that µ opioids reduced TSP1 protein levels in astrocytes. Here we found that, after the same 8 day treatment, morphine or DAMGO diminished TSP2 protein levels in astrocytes. Therefore, µ opioids may deter synaptogenesis via both TSP1/2 isoforms, but by distinct mechanisms.

An autologous platelet-rich plasma stimulates periodontal ligament regeneration.

BACKGROUND: Regeneration of periodontal tissues is one of the most important goals for the treatment of periodontal disease. The technology of plasma rich in growth factors provides a biologic approach for the stimulation and acceleration of tissue healing. The purpose of this study is to evaluate the biologic effects of this technology on primary human periodontal ligament fibroblasts. METHODS: The authors studied the response of periodontal ligament cells to this pool of growth factors on cell proliferation, cell migration, secretion of several biomolecules, cell adhesion, and expression of α2 integrin. Cell proliferation and adhesion were evaluated by means of a fluorescence-based method. Cell migration was performed on culture inserts. The release of different biomolecules by periodontal ligament fibroblasts was quantified through enzyme-linked immunosorbent assay. The α2 integrin expression was assessed through Western blot. RESULTS: This autologous technology significantly stimulated cell proliferation, migration, adhesion, and synthesis of many growth factors from cells including vascular endothelial growth factor, thrombospondin 1, connective tissue growth factor, hepatocyte growth factor, and procollagen type I. The α2 integrin expression was lower in plasma rich in growth factor-treated cells compared to non-stimulated cells, although no statistically significant differences were observed. CONCLUSION: This plasma rich in growth factors exerts positive effects on periodontal ligament fibroblasts, which could be positive for periodontal regeneration.

Gene expression profiling concerning mineralization in human dental pulp cells treated with mineral trioxide aggregate.

INTRODUCTION: This study investigated changes in gene expressions related to mineralization when mineral trioxide aggregate (MTA) is applied in vitro to human dental pulp cells (HDPCs). METHODS: MTA in a Teflon tube (diameter 10 mm, height 2 mm) was applied to HDPCs. Empty tube-applied HDPCs were used as negative control. Total RNA was extracted at 6, 24, and 72 hours after MTA application for microarray analysis. The results were confirmed selectively by performing reverse transcriptase-polymerase chain reaction for genes that showed changes of more than 2-fold or less than half. RESULTS: Of the 24,546 genes, 109 genes were up-regulated more than 2-fold (eg, THBS1, VCAN, BHLHB2, FN1, COL10A1, TUFT1, and HMOX1), and 69 genes were down-regulated below 50% (eg, DCN, SOCS2, and IL8). CONCLUSIONS: These results suggest that rather than being a bio-inert material, MTA affects pulp cells in various ways. MTA appears to affect mineralization and induces slight inflammation and protective role against slight inflammation.

The ubiquitin ligase Nedd4-1 is required for heart development and is a suppressor of thrombospondin-1.

Nedd4 (Nedd4-1) is a Hect domain E3 ubiquitin ligase that also contains a C2 domain and three WW domains. Despite numerous in vitro studies, its biological function in vivo is not well understood. Here we show that disruption of Nedd4-1 in mice (leaving Nedd4-2 intact) caused embryonic lethality at mid gestation, with pronounced heart defects (double-outlet right ventricle and atrioventricular cushion defects) and vasculature abnormalities. Quantitative mass spectrometry and immunoblot analyses of lysates from the wild type and knock-out mouse embryonic fibroblasts to identify Nedd4-1 in vivo targets revealed dramatically increased amounts of thrombospondin-1 (Tsp-1) in the knock-out mouse embryonic fibroblasts and embryos. Tsp-1 is an inhibitor of angiogenesis, and its elevated level was mediated primarily by enhanced transcription. Interestingly, the administration of aspirin (an inhibitor of Tsp-1) to the pregnant heterozygote mothers led to a reduction in Tsp-1 levels and a substantial rescue of the embryonic lethality. These results suggest that Nedd4-1 is a suppressor of Tsp1 and that increased levels of Tsp-1 in the Nedd4-1 knock-out mice may have contributed to the developmental defect observed in the embryos.

Clinical and pharmacodynamic evaluation of metronomic cyclophosphamide, celecoxib, and dexamethasone in advanced hormone-refractory prostate cancer.

PURPOSE: The aims of the present study were to evaluate the clinical activity and the pharmacodynamic profile of the novel schedule of a single i.v. standard dose of cyclophosphamide (CTX) immediately followed by an oral metronomic CTX regimen with celecoxib (CXB) and dexamethasone (DEX) in advanced hormone-refractory prostate cancer patients. EXPERIMENTAL DESIGN: Twenty-eight patients (68% docetaxel-resistant) received 500 mg/m2 CTX i.v. bolus on day 1 and, from day 2, 50 mg/day CTX p.o. plus 200 mg/twice a day CXB p.o. and 1 mg/day DEX p.o. until disease progression. Plasma vascular endothelial growth factor (VEGF) and thrombospondin-1 were detected by ELISA, and real-time reverse transcription-PCR of VEGF and thrombospondin-1 gene expression on peripheral blood mononuclear cell and of VE-cadherin (VE-C) in blood samples was done. RESULTS: A confirmed prostate-specific antigen decrease of > or =50% from baseline was observed in 9 of 28 patients (32%). Median progression-free survival and overall survival were 3 months (95% confidence interval, 2.2-4.2 months) and 21 months (95% confidence interval, 12.4-29.4 months), respectively. Toxicity was mild and no grade 3 to 4 toxicities occurred. A significant relationship was found between plasma VEGF and prostate-specific antigen values (r = 0.4223; P < 0.001). VEGF levels significantly increased in nonresponders, whereas the responder patients maintained significantly lower levels of VE-C gene expression after the beginning of the treatment if compared with nonresponder ones. CONCLUSION: Metronomic CTX plus CXB and DEX showed favorable toxicity and activity profile in patients. VE-C gene expression and VEGF levels represent potentially useful pharmacodynamic markers for the clinical response.

Lowering blood pressure blocks mesangiolysis and mesangial nodules, but not tubulointerstitial injury, in diabetic eNOS knockout mice.

Recently, we and others reported that diabetic endothelial nitric oxide synthase knockout (eNOSKO) mice develop advanced glomerular lesions that include mesangiolysis and nodular lesions. Interestingly, insulin treatment lowered blood pressure and prevented renal lesions, raising the question as to whether these beneficial effects of insulin were due to its ability to lower either high glucose levels or high blood pressure. We, therefore, examined the effect of lowering blood pressure using hydralazine in this diabetic eNOSKO mouse model. Hydralazine treatment significantly blocked the development of mesangiolysis and microaneurysms, whereas tubulointerstitial injury was not prevented in these mice. Additionally, hydralazine did not reduce expression levels of either tubulointerstitial thrombospondin-1 or transforming growth factor-beta despite controlling blood pressure. On the other hand, the critical role of high glucose levels on the development of tubulointerstitial injury was suggested by the observation that serum glucose levels were correlated with tubulointerstitial injury, as well as with the expression levels of both transforming growth factor-beta and thrombospondin-1. Importantly, controlling blood glucose with insulin completely blocked tubulointerstitial injury in diabetic eNOSKO mice. These data suggest that glomerular injury is dependent on systemic blood pressure, whereas hyperglycemia may have a more important role in tubulointerstitial injury, possibly due to the stimulation of the thrombospondin-1-transforming growth factor-beta pathway in diabetic eNOSKO mice. This study could provide insights into the pathogenesis of advanced diabetic nephropathy in the presence of endothelial dysfunction.

Neoadjuvant treatment of colorectal cancer with bevacizumab: the perioperative angiogenic balance is sensitive to systemic thrombospondin-1 levels.

PURPOSE: Colorectal cancer patients receiving neoadjuvant treatment with bevacizumab, a monoclonal antibody neutralizing vascular endothelial growth factor (VEGF), may suffer from wound healing complications after surgery as the antibody persists in patient blood. We characterized the systemic angiogenic balance in the perioperative period to evaluate its effect on physiologic angiogenesis. EXPERIMENTAL DESIGN: Nineteen patients receiving combination chemotherapy and bevacizumab for six neoadjuvant cycles were compared with 14 patients receiving chemotherapy without bevacizumab. Plasma from perioperative days -1, +1, +7, and +21 was analyzed for VEGF, thrombospondin-1 (TSP-1), and PD-ECGF concentrations. The angiogenic capacity was further tested in an in vitro assay of endothelial cell proliferation and migration. RESULTS: On day +1, the onset of wound healing was reflected in a change of balance, i.e., an increase of proangiogenic factors VEGF and platelet-derived endothelial cell growth factor compared with low TSP-1 inhibitor levels in both treatment groups. Patients with bevacizumab therapy showed significantly higher blood levels of total VEGF throughout the evaluation period. However, most VEGF molecules were inactive, i.e., complexed with antibody. Nevertheless, the capacity to stimulate endothelial growth was higher for these plasma samples and was reflected in low TSP-1 levels and an altered TSP-1 sensitivity. When purified TSP-1 protein was added, plasma samples of the bevacizumab but not the chemotherapy group showed reduced endothelial growth. CONCLUSIONS: Feedback mechanisms of bevacizumab therapy are not restricted to VEGF expression but seem to involve additional factors, such as TSP-1, which influences the systemic angiogenic balance and permits endothelial growth.

Antiangiogenic and anticolorectal cancer effects of metronomic irinotecan chemotherapy alone and in combination with semaxinib.

Metronomic chemotherapy refers to the administration of chemotherapy at low, nontoxic doses on a frequent schedule with no prolonged breaks. The aim of the study is to rationally develop a CPT-11 metronomic regimen in preclinical settings of colon cancer. In vitro cell proliferation, apoptosis and thrombospondin-1/vascular endothelial growth factor (TSP-1/VEGF) expression analyses were performed on endothelial (HUVEC, HMVEC-d) and colorectal cancer (HT-29, SW620) cells exposed for 144 h to metronomic concentrations of SN-38, the active metabolite of CPT-11. HT-29 human colorectal cancer xenograft model was used, and tumour growth, microvessel density and VEGF/TSP-1 quantification was performed in tumours. In vitro and in vivo combination studies with the tyrosine inhibitor semaxinib were also performed. SN-38 preferentially inhibited endothelial cell proliferation alone and interacted synergistically with semaxinib; it induced apoptosis and increased the expression and secretion of TSP-1. Metronomic CPT-11 alone and combined with semaxinib significantly inhibits tumour growth in the absence of toxicity, which was accompanied by decreases in microvessel density and increases in TSP-1 gene expression in tumour tissues. In vitro results show the antiangiogenic properties of low-concentration SN-38, suggesting a key role of TSP-1 in this effect. In vivo, the CPT-11 metronomic schedule is effective against tumour and microvessel growth without toxic effect on mice.

Effect of maximum-tolerated doses and low-dose metronomic chemotherapy on serum vascular endothelial growth factor and thrombospondin-1 levels in patients with advanced nonsmall cell lung cancer.

BACKGROUND: Angiogenesis is regulated by a balance of both angiogenic inducers and inhibitors. This study was designed to evaluate the effect of both maximum-tolerated doses (MTD) and low-dose metronomic chemotherapy (LDM) on serum vascular endothelial growth factor (VEGF), thrombospondin-1 (TSP1) and VEGFR1 concentrations in patients with advanced nonsmall cell lung cancer. PATIENTS AND METHODS: Forty consecutive patients with advanced stage nonsmall cell lung cancer were included in this prospective study. Twenty patients received MTD chemotherapy including 75 mg/m2 of cisplatin and 75 mg/m2 of docetaxel on day 1. The LDM treatment consisted of cisplatin 25 mg/m2 and docetaxel 25 mg/m2 were given to other 20 patients on weeks 1, 2 and 3. Serum levels were prospectively measured in serum by ELISA at four times; before chemotherapy and at 1, 2 and 3 weeks following initiation of chemotherapy. RESULTS: The major finding in this study that MTD chemotherapy but not LDM chemotherapy resulted in significant changes in VEGFR1 and TSP1 serum levels. Due to the effect of LDM chemotherapy, we showed no statistically significant change in patients for all serum VEGF, TSP1 and VEGFR1 levels. Similarly, serum VEGF levels did not also change under MTD chemotherapy. The MTD chemotherapy induced significant and long-lasting increase of TSP1 levels and decrease of VEGFR1 levels that persisted for at least 3 weeks after the chemotherapy initiation. No significant correlations were found between serum VEGF and TSP1 levels in cancer patients treated with both LDM and MTD chemotherapy. The circulating angiogenic balance (TSP1/VEGF) is decreased in cancer patients (P=0.039). CONCLUSIONS: The continuous/metronomic chemotherapy may not achieve a more pronounced antiangiogenic effect than MTD-scheduling chemotherapy. Future studies involving a larger number of patients are needed to confirm the present findings.

Androgen and fibroblast growth factor 8 (FGF8) downregulation of thrombospondin 1 (TSP1) in mouse breast cancer cells.

In the search for androgen target genes responsible for malignant growth in S115 mouse mammary tumor cells we found that thrombospondin 1 (TSP1) expression was strongly downregulated by testosterone (Te). Experiments with cycloheximide suggested that Te repression of TSP1 was dependent on de novo protein synthesis. TSP1 repression by Te was preceded by the induction of fibroblast growth factor 8 (FGF8) expression. FGF8 has previously been shown to mediate androgen effects on proliferation of S115 cells by autocrine/paracrine mechanisms. It has also been shown to increase breast cancer cell growth as tumors in nude mice and to stimulate tumor angiogenesis. We studied here the possibility that FGF8 belonged to the Te-induced de novo synthesized proteins that mediate the effect of Te on TSP1 expression in these cells. We found that addition of FGF8b to in vitro cultures or ectopic expression of FGF8b in S115 cells repressed TSP1 expression at mRNA and protein levels even in the absence of Te. FGF2, another angiogenic member of FGF family, also downregulated TSP1 mRNA level in the in vitro cultures of S115 cells. The antisense oligonucleotides for FGF8 did not, however, prevent Te-repression of TSP1 mRNA expression and a neutralizing anti-FGF8b antibody only partially opposed Te induced downregulation of TSP1. These results suggest that both androgen and FGF8 inhibit TSP1 expression independently. They also suggest that opposite to many other androgen-induced responses in S115 cells, the effect of Te on the expression TSP1 is not mediated by FGF8.

Elevated glucose induction of thrombospondin-1 up-regulates fibronectin synthesis in proximal renal tubular epithelial cells through TGF-beta1 dependent and TGF-beta1 independent pathways.

BACKGROUND: TGF-beta1 bioactivation, consequent to the interaction of latent TGF-beta1 with thrombospondin-1 (TSP-1), correlates with matrix accumulation in mesangial cells. Tubulointerstitial damage predicts poor renal survival. There is little data on TGF-beta1 bioactivation and matrix synthesis in human proximal renal tubular epithelial cells under the influence of high glucose concentrations. This study thus investigates the role of TSP-1 in mediating elevated glucose-induction of TGF-beta1 bioactivation and fibronectin (FN) synthesis in human proximal tubular epithelial cells. METHODS: Human proximal renal tubular epithelial cells (HK-2 cells) were incubated with 5, 10, 20 or 30 mM D-glucose for up to 3 weeks either in the presence or absence of TSP-1 blocking peptide. In separate studies HK-2 cells were incubated with exogenous TSP-1 (0-10 ng/ml) or TGF-beta1 (0-10 ng/ml) for 24 h. Cell proliferation was assessed by [(3)H]-thymidine incorporation. TGF-beta1 transcript, secretion and bioactivity were investigated by quantitative real-time PCR, ELISA and the MLEC bioassay respectively. TSP-1 and FN synthesis were assessed by quantitative real-time PCR, ELISAs and Western blot analysis. RESULTS: Elevated glucose concentrations increased TSP-1 synthesis, which was associated with reduced cell proliferation, increased TGF-beta1 bioactivity, and stimulation of FN synthesis. The inclusion of TSP-1 blocking peptide to cells stimulated with elevated glucose concentration abrogated activation of TGF-beta1 and induction of FN secretion. Exogenous TSP-1 increased bioactive TGF-beta1 in HK-2 cells to initiate FN accumulation. Of interest is our observation that TSP-1 also increased matrix synthesis through a mechanism independent of TGF-beta1. TGF-beta1 in turn modulated TSP-1 synthesis, indicative of an autocrine loop between TSP-1 and TGF-beta1. CONCLUSIONS: TSP-1 plays an important role in the induction of matrix synthesis by high glucose concentrations in human proximal renal tubular epithelial cells, through TGF-beta1 dependent and TGF-beta1 independent pathways. Pharmacological intervention targeting increased TSP-1 expression may interrupt the pathogenesis of diabetic nephropathy.

Imiquimod as an antiangiogenic agent.

Imiquimod (imidazoquinoline 5%) is a topical immune response modifier agent that inhibits angiogenesis, the growth of new blood vessels. In addition to its stimulation of cell-mediated immunity, imiquimod's antiangiogenic activity contributes to its clinical efficacy by interfering with pathological neovascularization that promotes disease progression. The antiangiogenic mechanisms of imiquimod are due to its: 1) induction of cytokines that themselves inhibit angiogenesis (interferons, IL-10, IL-12); 2) local up-regulation of endogenous angiogenesis inhibitors (TIMP, TSP-1); 3) local down-regulation of pro-angiogenic factors (bFGF, MMP-9); and 4) promotion of endothelial cell apoptosis. This report discusses these mechanisms and the rationale for imiquimod's use as an antiangiogenic agent. Key principles of antiangiogenic therapy are presented to describe how imiquimod may be applied in a well-tolerated fashion to treat a broad range of angiogenesis-dependent dermatological conditions, including actinic keratosis (AK), basal cell carcinoma (BCC), squamous cell carcinoma (SCC), lentigo maligna, hemangiomas, Kaposi's sarcoma, pyogenic granuloma, and external genital warts.

Kinetics of biglycan, decorin and thrombospondin-1 in mercuric chloride-induced renal tubulointerstitial fibrosis.

We investigated the kinetics of decorin, biglycan and thrombospondin-1 in mercuric chloride-treated Brown Norway (BN) rats. BN rats were injected subcutaneously with 1 mg/kg b.w. of mercuric chloride one or three times. The kidney was examined histopathologically and the kinetics of decorin, biglycan and thrombospondin-1 was also examined using immunohistochemistry and real time RT-PCR. As a result, mercuric chloride induced tubular injury and subsequent tubulointerstitial fibrosis. In this lesion, the expression of thrombospondin-1 mRNA was most prominently elevated. The expression of decorin mRNA was next, but biglycan mRNA expression was not elevated. Moreover, decorin and thrombospondin-1 proteins were localized in tubular epithelial cells and peritubular interstitium. Moreover, kinetics of their mRNA expressions was relatively similar to the kinetics of TGF-beta1 mRNA expression previously reported. The present findings suggest that decorin and thrombospondin-1 may participate in the development of tubulointerstitial fibrosis and may have some relation with TGF-beta1 in mercuric chloride-treated BN rats.

Androgens repress the expression of the angiogenesis inhibitor thrombospondin-1 in normal and neoplastic prostate.

In order to understand why the angiogenesis inhibitor thrombospondin-1 (TSP1) is often, although not always, associated with prostatic tumors, we have investigated its relationship with the testosterone and the vasculature on which both normal and tumorigenic prostatic epithelia depend. In vivo, androgen withdrawal led to increased TSP1 production and decreased vascularization in the normal rat prostate which was reversed by androgen replacement. Androgen repression of TSP1 production occurred at the transcriptional level and was dependent on the presence of the first intron of the TSP1 gene. In an experimental model of prostate tumorigenesis, TSP1, when delivered by admixed stromal fibroblasts, markedly delayed LNCaP tumor growth and limited tumor vascularization. However, prolonged exposure to TSP1 resulted in the growth of tumors secreting high levels of vascular endothelial growth factor in the bloodstream of tumor-bearing animals and tumor growth was no longer sensitive to TSP1 inhibitory effects. Clinical evidence also suggested that prostate carcinomas are able to adapt to escape the antiangiogenic effects of TSP1. In human androgen-dependent localized prostate carcinomas, TSP1 expression was inversely correlated with blood vessel density. Androgen deprivation in patients with hormone-responsive tumors led to increased TSP1 expression and vascular regression. In contrast, despite a sustained expression in the tumor bed, TSP1 was no longer associated with decreased vascularization in hormone-refractory prostate tumors. Overall, these results suggest that the high in situ TSP1 exposure triggered by androgen deprivation in patients with prostate cancer could lead to early tumor resistance. Such patients could benefit from a combination of androgen deprivation and antiangiogenic therapy in order to minimize the induction of such tumor escape.

Vesnarinone-mediated alterations of gene expression in cardiac fibroblasts from aortic regurgitant hearts.

Pathologic fibrosis precedes heart failure (CHF) and death in experimental aortic regurgitation (AR). Vesnarinone, a positively inotropic quinolone derivative, suppresses survival of fibroblasts (CF) from hearts with chronic experimental AR. To explore further the potential effects of vesnarinone on cardiac fibrosis in AR, we tested the hypothesis that vesnarinone suppresses gene expression induced by AR in CF. Differentially expressed genes were isolated by suppression subtractive hybridization (SSH) in CF from hearts of 2 New Zealand White rabbits with surgically induced AR compared with 2 normal rabbits. In cultured AR-CF treated with and without vesnarinone (4 doses, including the dose that had caused maximal survival suppression in cultured AR-CF), drug effect was assessed on expression of genes found to be up-regulated by AR. SSH, reverse Northern analysis, and Northern analysis indicated that at doses several orders of magnitude lower than those used for treatment in CHF vesnarinone significantly down-regulated 2 genes (thrombospondin 1, annexin II) up-regulated by AR. The study confirmed earlier findings of AR-mediated alteration in expression of genes that code for noncollagen extracellular matrix (ECM) proteins. Thus, in CF conditioned by exposure to AR, vesnarinone at relatively low doses suppresses genes coding for 2 noncollagen ECM proteins up-regulated by AR. These pharmacologic effects may underlie potentially therapeutic mitigation of fibrosis by vesnarinone.