Hyaluronan Synthesis Inhibitor 4-methylumbelliferone Research Articles

A hyaluronan synthesis inhibitor delays the progression of diabetic kidney disease in a mouse experimental model.

The role of hyaluronan (HA) in the development and progression of diabetic kidney disease (DKD), as well as the precise mechanisms and consequences of HA involvement in this pathology are still to be clarified. In this study, we assayed the effects of the HA synthesis inhibitor 4-methylumbelliferone (4-MU) on the development of DKD. Diabetic type 2 model mice (eNOS-/- C57BLKS/Jdb) were fed artificial diets containing 5% 4-MU or not for 9 weeks. Plasma glucose, glomerular filtration rate (GFR), albumin to creatinine ratio (ACR), and biomarkers of kidney function and systemic inflammation were measured at baseline and after treatment. Diabetic nephropathy was further characterized in treated and control mice by histopathology. Treated animals consumed a daily dose of approximately 6.2 g of 4-MU per kg of body weight. At the end of the experimental period, the 4-MU supplemented diet resulted in a significant decrease in non-fasting plasma glucose (516 [interquartile range 378-1170] vs. 1149 [875.8-1287] mg/dL, P=0.050) and a trend toward lower HA kidney content (5.6 ± 1.5 vs. 8.8 ± 3.1 ng/mg of kidney weight, P=0.070) compared to the control diet, respectively. Diabetic animals treated with 4-MU showed significantly higher GFR and lower urine ACR and plasma cystatin C levels than diabetic controls. Independent histological assessment of DKD also demonstrated a significant decrease in mesangial expansion score and glomerular injury index in 4-MU-treated mice compared to controls. Plasma glucose showed a strong correlation with kidney HA levels (r=0.66, P=0.0098). Both total hyaluronan (r=0.76, P=0.0071) and low-molecular-weight hyaluronan content (r=0.64, P=0.036) in the kidneys correlated with urine ACR in mice. These results show that the hyaluronan synthesis inhibitor 4-MU effectively slowed the progression of DKD and constitutes a potential new therapeutic approach to treat DKD.

4-Methylumbelliferone administration enhances radiosensitivity of human fibrosarcoma by intercellular communication

Hyaluronan synthesis inhibitor 4-methylumbelliferone (4-MU) is a candidate of radiosensitizers which enables both anti-tumour and anti-metastasis effects in X-ray therapy. The curative effects under such 4-MU administration have been investigated in vitro; however, the radiosensitizing mechanisms remain unclear. Here, we investigated the radiosensitizing effects under 4-MU treatment from cell experiments and model estimations. We generated experimental surviving fractions of human fibrosarcoma cells (HT1080) after 4-MU treatment combined with X-ray irradiation. Meanwhilst, we also modelled the pharmacological effects of 4-MU treatment and theoretically analyzed the synergetic effects between 4-MU treatment and X-ray irradiation. The results show that the enhancement of cell killing by 4-MU treatment is the greatest in the intermediate dose range of around 4 Gy, which can be reproduced by considering intercellular communication (so called non-targeted effects) through the model analysis. As supposed to be the involvement of intercellular communication in radiosensitization, the oxidative stress level associated with reactive oxygen species (ROS), which leads to DNA damage induction, is significantly higher by the combination of 4-MU treatment and irradiation than only by X-ray irradiation, and the radiosensitization by 4-MU can be suppressed by the ROS inhibitors. These findings suggest that the synergetic effects between 4-MU treatment and irradiation are predominantly attributed to intercellular communication and provide more efficient tumour control than conventional X-ray therapy.

Modulation of hyaluronan synthases and involvement of T cell-derived hyaluronan in autoimmune responses to transplanted islets

The extracellular matrix glycosaminoglycan hyaluronan (HA) accumulates in human and mouse islets during the onset of autoimmune type 1 diabetes (T1D). HA plays a critical role in T1D pathogenesis, as spontaneous disease is blocked in mice fed the HA synthesis inhibitor 4-methylumbelliferone (4MU). The present study demonstrates the involvement of HA in T cell-mediated autoimmune responses to transplanted islets and in in vivo and in vitro T cell activation. Scaffolded islet implants (SIs) loaded with RIP-mOVA mouse islets expressing chicken ovalbumin (OVA) on their β cells were grafted into T and B cell-deficient RIP-mOVA mice, which subsequently received CD4+ T cells from DO11.10 transgenic mice bearing OVA peptide-specific T cell receptors (TcRs), followed by injection of OVA peptide to induce an immune response to the OVA-expressing islets. By affinity histochemistry (AHC), HA was greatly increased in grafted islets with T cell infiltrates (compared to islets grafted into mice lacking T cells) and a portion of this HA co-localized with the infiltrating T cells. Transferred T cells underwent HA synthase (HAS) isoform switching – T cells isolated from the SI grafts strongly upregulated HAS1 and HAS2 mRNAs and downregulated HAS3 mRNA, in contrast to T cells from graft-draining mesenteric lymph nodes, which expressed HAS3 mRNA only. Expression of HAS1 and HAS2 proteins by T cells in SI infiltrates was confirmed by immunohistochemistry (IHC). DO11.10 mice fed 4MU had suppressed in vivo T cell immune priming (measured as a reduced recall response to OVA peptide) compared to T cells from control mice fed a normal diet. In co-cultures of naïve DO11.10 T cells and OVA peptide-loaded antigen-presenting cells (APCs), pre-exposure of the T cells (but not pre-exposure of APCs) to 4MU inhibited early T cell activation (CD69 expression). In addition, T cells exposed to 4MU during activation in vitro with anti-CD3/CD28 antibodies had inhibited phosphorylation of the CD3ζ subunit of the TcR, a very early event in TcR signaling. Collectively, our results demonstrate that T cell-derived HA plays a significant role in T cell immune responses, and that expression of T cell HAS isoforms changes in a locale-specific manner during in vivo priming and functional phases of the T cell response.

Hyaluronan synthesis inhibitor ４-methylumbelliferone affects extracellular matrix components in cultured human skin fibroblasts

Hyaluronan synthesis inhibitor ４-methylumbelliferone affects extracellular matrix components in cultured human skin fibroblasts

Inhibition of the hyaluronan matrix enhances metabolic anticancer therapy by dichloroacetate in vitro and in vivo.

Background and PurposeAerobic glycolysis is a unique feature of tumour cells that entails several advantages for cancer progression such as resistance to apoptosis. The low MW compound, dichloroacetate, is a pyruvate dehydrogenase kinase inhibitor, which restores oxidative phosphorylation and induces apoptosis in a variety of cancer entities. However, its therapeutic effectiveness is limited by resistance mechanisms. This study aimed to examine the role of the anti‐apoptotic hyaluronan (HA) matrix in this context and to identify a potential add‐on treatment option to overcome this limitation.Experimental ApproachThe metabolic connection between dichloroacetate treatment and HA matrix augmentation was analysed in vitro by quantitative PCR and affinity cytochemistry. Metabolic pathways were analysed using Seahorse, HPLC, fluorophore‐assisted carbohydrate electrophoresis, colourimetry, immunoblots, and immunochemistry. The effects of combining dichloroacetate with the HA synthesis inhibitor 4‐methylumbelliferone was evaluated in 2D and 3D cell cultures and in a nude mouse tumour xenograft regression model by immunoblot, immunochemistry, and FACS analysis.Key ResultsMitochondrial reactivation induced by dichloroacetate metabolically activated HA synthesis by augmenting precursors as well as O‐GlcNAcylation. This process was blocked by 4‐methylumbelliferone, resulting in enhanced anti‐tumour efficacy in 2D and 3D cell culture and in a nude mouse tumour xenograft regression model.Conclusions and ImplicationsThe HA rich tumour micro‐environment represents a metabolic factor contributing to chemotherapy resistance. HA synthesis inhibition exhibited pronounced synergistic actions with dichloroacetate treatment on oesophageal tumour cell proliferation and survival in vitro and in vivo suggesting the combination of these two strategies is an effective anticancer therapy.

The hyaluronan synthesis inhibitor 4-methylumbelliferone inhibits cell proliferation and wound healing on in vitro endometriosis models.

Laser-assisted MAL-PDT has been reported to increase the effectiveness of conventional PDT. Nonetheless, clinical effects of this association when reducing MAL incubation time is poorly discussed. Furthermore, the association of acoustic pressure wave ultrasound with laser-assisted MAL-PDT with short incubation time for field cancerization had not been reported before.To compare clinical effects of ablative fractional laser-assisted MAL-PDT associated with acoustic pressure wave ultrasound (IMPACT US) with 1-hour incubation time and conventional MAL-PDT for skin field cancerization on the forearms, as well as the impact on safety and tolerability.Fifteen patients with 638 AK (grade I-III) with field cancerized-skin on the forearms were enrolled in this left-right trial. Two protocols were randomly chosen. One side was treated with conventional MAL-PDT, whereas the other with laser-assisted MAL-PDT associated with acoustic pressure wave ultrasound with 1-hour incubation time. Actinic keratoses were quantitively measured, and the other signs of sun-damaged skin, like pigmentation and texture, in field cancerized skin were qualitatively evaluated before and after six months. Side effects were assessed subjectively during the procedure and one week after.All patients completed the study. At six months after treatment, both protocols reduced the number of AK (72%; CO2 + PDT, and 65%; MAL-PDT). The difference between these two protocols was not statistically significant (p = 0.77). The improvement of pigmentation and texture of field cancerized skin was more significant on the side treated with laser-assisted MAL-PDT associated with acoustic pressure wave ultrasound. Both protocols were well tolerated and without significant difference in adverse events.Laser-assisted MAL-PDT using CO2 laser and acoustic pressure wave ultrasound with short incubation time of 1 h was as effective as conventional MAL-PDT for field-cancerized skin with actinic keratosis in forearms with better cosmetic outcome.

Regulation of radiosensitivity by 4-methylumbelliferone via the suppression of interleukin-1 in fibrosarcoma cells.

Tumor recurrence and distant metastasis following radiotherapy, which can lead to poor prognosis, are caused by residual cancer cells that acquire radioresistance. Chemotherapy or a combination of targeted inhibitors can potentially enhance radiation sensitivity and prevent metastasis. It was previously reported that co-administration of the hyaluronan synthesis inhibitor 4-methylumbelliferone (4-MU) enhanced the lethality of X-ray irradiation in HT1080 human fibrosarcoma cells and decreased their invasiveness to a greater extent than either treatment alone. To clarify the molecular basis of these effects, the present study conducted mRNA expression profiling by cDNA microarray to identify the signaling pathways that are altered under this combination treatment. The activation state of the signaling pathways was classified by z-scores in the Ingenuity Pathway Analysis. The results revealed that the pro-inflammatory cytokines interleukin (IL)-6 and IL-8 were activated by 2 Gy X-ray irradiation, an effect that was abolished by co-administration of 4-MU. Similar trends were observed for the upstream signaling component IL-1. These results indicate that the radiosensitivity of fibrosarcoma cells is improved by suppressing inflammation through the administration of 4-MU.

4Mu Decreases CD47 Expression on Hepatic Cancer Stem Cells and Primes a Potent Antitumor T Cell Response Induced by Interleukin-12.

The tumor microenvironment (TME) represents a complex interplay between different cellular components, including tumor cells and cancer stem cells (CSCs), with the associated stroma; such interaction promotes tumor immune escape and sustains tumor growth. Several experimental approaches for cancer therapy are focused on TME remodeling, resulting in increased antitumor effects. We previously demonstrated that the hyaluronan synthesis inhibitor 4-methylumbelliferone (4Mu) decreases liver fibrosis and induces antitumor activity in hepatocellular carcinoma (HCC). In this work, 4Mu, in combination with an adenovirus encoding interleukin-12 genes (AdIL-12), elicited a potent antitumor effect and significantly prolonged animal survival (p< 0.05) in an orthotopic HCC model established in fibrotic livers. In assessing the presence of CSCs, we found reduced mRNA levels of CD133+, CD90+, EpCAM+, CD44+, and CD13+ CSC markers within HCC tumors (p< 0.01). Additionally, 4Mu downregulated the expression of the CSC marker CD47+ on HCC cells, promoted phagocytosis by antigen-presenting cells, and, combined with Ad-IL12, elicited a potent cytotoxic-specific Tcell response. Finally, animal survival was increased when CD133low HCC cells, generated upon 4Mu treatment, were injected in a metastatic HCC model. In conclusion, the combined strategy ameliorates HCC aggressiveness by targeting CSCs and as a result of the induction of anticancer immunity.

Abstract 2581: Antitumor effect of Trametinib, a selective MEK inhibitor, in combination with 4-methylumbelliferone, a hyaluronic acid synthesis inhibitor, in Malignant pleural mesothelioma cell lines

Abstract Introduction: Malignant pleural mesothelioma (MPM) is a highly aggressive malignancy for which no targeted therapy exists. The mitogen-activated protein kinase (MAPK) pathway plays critical roles in the regulation of tumorigenesis in multiple solid tumors, including MPM. Trametinib, a selective MEK inhibitor, have a survival benefit in patients with V600 BRAF-mutant metastatic melanoma. The effect of trametinib on MPM cells has not been well studied. Hyaluronan (HA) is one of the major components of the extracellular matrix. MPM is in most cases associated with elevated amounts of HA, which has increased the malignant properties of MPM cells. The HA synthesis inhibitor 4-methylumbelliferone (4-MU) has antitumor effects in various malignant tumors, but its effect on MPM cells has not been well studied. Purpose: We evaluated the effects of trametinib, 4-MU and their combination on MPM cells in vitro and in vivo. Experimental Design: The effects of trametinib, 4-MU, and their combination on MPM cells were evaluated using cell viability assay, western blot analysis, and mouse xenograft model. Results: Trametinib exhibited an antiproliferative activity in all four MPM cell lines, NCI-H226, NCI-H2452, NCI-H2052, and MSTO-211H, with IC50 values ranging from 0.15 μM to 12.7 μM. Trametinib blocked the phosphorylation of ERK until 72 hours and decreased the expression of CD44 in a dose-dependent manner. In addition, the expression of CD44 was inhibited (48-72 hours) after the suppression of ERK phosphorylation by trametinib. 4-MU exhibited an antiproliferative activity in MPM cells. 4-MU inhibited ERK phosphorylation but not CD44 expression. In mouse xenograft model, trametinib and 4-MU suppressed tumor growth (trametinib vs. control, P &amp;lt; 0.0001; 4-MU vs. control, P &amp;lt; 0.01), and their combination suppressed more strongly (combination vs. trametinib, P &amp;lt; 0.01; combination vs. 4-MU, P &amp;lt; 0.0001; combination vs. control, P &amp;lt; 0.0001). Conclusions: Trametinib and 4-MU exhibited antitumor activities in MPM cell lines. Furthermore, their combination exhibited more potent antitumor activities. These results suggests that Trametinib and 4-MU are promising therapeutic agents in MPM, and these combination therapies may be effective for the treatment of MPM. Citation Format: Hiroyuki Cho, Seiji Matsumoto, Yoshiko Fujita, Ayumi Kuroda, Masaki Hashimoto, Teruhisa Takuwa, Toshi Menju, Makoto Sonobe, Nobuyuki Kondo, Hiroshi Date, Seiki Hasegawa. Antitumor effect of Trametinib, a selective MEK inhibitor, in combination with 4-methylumbelliferone, a hyaluronic acid synthesis inhibitor, in Malignant pleural mesothelioma cell lines. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2581. doi:10.1158/1538-7445.AM2015-2581

Hyaluronan Metabolism in Human Keratinocytes and Atopic Dermatitis Skin Is Driven by a Balance of Hyaluronan Synthases 1 and 3

Hyaluronan (HA) is a glycosaminoglycan synthesized directly into the extracellular matrix by three hyaluronan synthases (HAS1, HAS2, and HAS3). HA is abundantly synthesized by keratinocytes but its epidermal functions remain unclear. We used culture models to grow human keratinocytes as autocrine monolayers or as reconstructed human epidermis (RHE) to assess HA synthesis and HAS expression levels during the course of keratinocyte differentiation. In both the models, epidermal differentiation downregulates HAS3 mRNA expression while increasing HAS1 without significant changes in hyaluronidase expression. HA production correlates with HAS1 mRNA expression level during normal differentiation. To investigate the regulation of HAS gene expression during inflammatory conditions linked to perturbed differentiation, lesional and non-lesional skin biopsies of atopic dermatitis (AD) patients were analyzed. HAS3 mRNA expression level increases in AD lesions compared with healthy and non-lesional skin. Simultaneously, HAS1 expression decreases. Heparin-binding EGF-like growth factor (HB-EGF) is upregulated in AD epidermis. An AD-like HAS expression pattern is observed in RHE incubated with HB-EGF. These results indicate that HAS1 is the main enzyme responsible for HA production by normal keratinocytes and thus, must be considered as an actor of normal keratinocyte differentiation. In contrast, HAS3 can be induced by HB-EGF and seems mainly involved in AD epidermis.

Hyaluronan Synthesis and Myogenesis: A REQUIREMENT FOR HYALURONAN SYNTHESIS DURING MYOGENIC DIFFERENTIATION INDEPENDENT OF PERICELLULAR MATRIX FORMATION

Exogenous hyaluronan is known to alter muscle precursor cell proliferation, migration, and differentiation, ultimately inhibiting myogenesis in vitro. The aim of the current study was to investigate the role of endogenous hyaluronan synthesis during myogenesis. In quantitative PCR studies, the genes responsible for synthesizing hyaluronan were found to be differentially regulated during muscle growth, repair, and pathology. Although all Has genes (Has1, Has2, and Has3) were differentially regulated in these models, only Has2 gene expression consistently associated with myogenic differentiation. During myogenic differentiation in vitro, Has2 was the most highly expressed of the synthases and increased after induction of differentiation. To test whether this association between Has2 expression and myogenesis relates to a role for Has2 in myoblast differentiation and fusion, C2C12 myoblasts were depleted of Has2 by siRNA and induced to differentiate. Depletion of Has2 inhibited differentiation and caused a loss of cell-associated hyaluronan and the hyaluronan-dependent pericellular matrix. The inhibition of differentiation caused by loss of hyaluronan was confirmed with the hyaluronan synthesis inhibitor 4-methylumbelliferone. In hyaluronan synthesis-blocked cultures, restoration of the pericellular matrix could be achieved through the addition of exogenous hyaluronan and the proteoglycan versican, but this was not sufficient to restore differentiation to control levels. These data indicate that intrinsic hyaluronan synthesis is necessary for myoblasts to differentiate and form syncytial muscle cells, but the hyaluronan-dependent pericellular matrix is not sufficient to support differentiation alone; additional hyaluronan-dependent cell functions that are yet unknown may be required for myogenic differentiation.

The hyaluronan synthesis inhibitor 4-methylumbelliferone exhibits antitumor effects against mesenchymal-like canine mammary tumor cells

Hyaluronan (HA), a principal constituent of the extracellular matrix (ECM), mediates growth and metastasis of tumor cells. The role of HA in the epithelial-mesenchymal transition (EMT) is well known, and increased ECM remodeling is observed in mesenchymal-like cells. The HA synthesis inhibitor 4-methylumbelliferone (4-MU) is anti-tumorigenic for various malignant tumors. However, the antitumor effect of 4-MU against canine mammary tumor cells that possess a mesenchymal-like phenotype is unclear. We examined the antitumor effect of 4-MU on CF41.Mg mesenchymal-like canine mammary tumor cells. We investigated the influence of 4-MU on the expression of HA synthase (HAS) 1-3 mRNA and observed dose-dependent downregulation of HAS2 mRNA at 24-72 h; in contrast, HAS3 expression was elevated at 24 h. Thus, 4-MU inhibited HA synthesis via HAS2 repression. 4-MU also inhibited cell proliferation and induced apoptosis in the CF41.Mg cells. Our experiments showed that 4-MU-induced apoptosis in CF41.Mg cells involved induction of the pro-apoptotic gene BAX. We also assessed motility and found that 4-MU reduced chemokinesis and chemotaxis in CF41.Mg cells. Our data suggest that 4-MU may serve as a candidate therapeutic agent for the treatment of canine mammary tumors. Since 4-MU exhibits antitumor activity in mesenchymal-like cells, it may also be a useful inhibitor of canine mammary tumor invasion and metastasis.

4-Methylumbelliferone leads to growth arrest and apoptosis in canine mammary tumor cells

Hyaluronan (HA), a major component of the extracellular matrix (ECM), is synthesized by HA synthase (HAS) 1, HAS2 and HAS3 and is intricately involved in cell growth and metastasis. The HA synthesis inhibitor 4-methylumbelliferone (4-MU) has been reported to exhibit anticancer properties in various types of malignant tumors. However, the underlying mechanisms at the molecular and cellular levels remain unclear. In this study, to establish an animal model for studying the function of HA in human breast cancer, we investigated the antitumor effects of 4-MU using canine mammary tumor (CF33) cells. First, we investigated the effects of 4-MU on HA production in CF33 cells. Quantitative analysis of HA in culture media showed that 4-MU inhibited HA synthesis, accompanied by downregulation of HAS2 mRNA levels, in a dose-dependent manner at 24-72 h. Additionally, we observed a 4-MU-mediated decrease in the extent of the cell-associated HA matrix. We examined the effect of 4-MU on cell growth and apoptosis in CF33 cells. 4-MU markedly inhibited cell proliferation and induced apoptosis in CF33 cells. In particular, our experiments showed that the mechanism of 4-MU-induced apoptosis in CF33 cells involved increased levels of expression of pro-apoptotic BAX mRNA and protein molecules. These data suggest that 4-MU may be a candidate therapeutic agent for the treatment of canine mammary tumors. Furthermore, this study provides the first indication that the canine mammary tumor may be a suitable model for comparative study of the function of HA in human breast cancer.

Glycosaminoglycans and Glucose Prevent Apoptosis in 4-Methylumbelliferone-treated Human Aortic Smooth Muscle Cells

Smooth muscle cells (SMCs) have a pivotal role in cardiovascular diseases and are responsible for hyaluronan (HA) deposition in thickening vessel walls. HA regulates SMC proliferation, migration, and inflammation, which accelerates neointima formation. We used the HA synthesis inhibitor 4-methylumbelliferone (4-MU) to reduce HA production in human aortic SMCs and found a significant increase of apoptotic cells. Interestingly, the exogenous addition of HA together with 4-MU reduced apoptosis. A similar anti-apoptotic effect was observed also by adding other glycosaminoglycans and glucose to 4-MU-treated cells. Furthermore, the anti-apoptotic effect of HA was mediated by Toll-like receptor 4, CD44, and PI3K but not by ERK1/2.

Hyaluronan Synthesis Mediates the Fibrotic Response of Keratocytes to Transforming Growth Factor β

TGFβ induces fibrosis in healing corneal wounds, and in vitro corneal keratocytes up-regulate expression of several fibrosis-related genes in response to TGFβ. Hyaluronan (HA) accumulates in healing corneas, and HA synthesis is induced by TGFβ by up-regulation of HA synthase 2. This study tested the hypothesis that HA acts as an extracellular messenger, enhancing specific fibrotic responses of keratocytes to TGFβ. HA synthesis inhibitor 4-methylumbelliferone (4MU) blocked TGFβ induction of HA synthesis in a concentration-dependent manner. 4MU also inhibited TGFβ-induced up-regulation of α-smooth muscle actin, collagen type III, and extra domain A-fibronectin. Chemical analogs of 4MU also inhibited fibrogenic responses in proportion to their inhibition of HA synthesis. 4MU, however, showed no effect on TGFβ induction of luciferase by the 3TP-Lux reporter plasmid. Inhibition of HA using siRNA to HA synthase 2 reduced TGFβ up-regulation of smooth muscle actin, fibronectin, and cell division. Similarly, brief treatment of keratocytes with hyaluronidase reduced TGFβ responses. These results suggest that newly synthesized cell-associated HA acts as an extracellular enhancer of wound healing and fibrosis in keratocytes by augmenting a limited subset of the cellular responses to TGFβ.

4-Methylumbelliferone inhibits tumour cell growth and the activation of stromal hyaluronan synthesis by melanoma cell-derived factors

There is a close correlation between tumour progression and hyaluronan production, either by tumour cells or by stromal cells that are stimulated by tumour-derived factors. Inhibition of tumour stimulation of fibroblast hyaluronan may suppress tumour growth and invasion. To examine the effect of the hyaluronan synthesis inhibitor 4-methylumbelliferone (4-MU) on the growth of and hyaluronan synthesis by fibroblasts and C8161 and MV3 melanoma cell lines, invasion, and inhibition of tumour cell-derived factor activation of fibroblasts. Effects of 4-MU on growth and hyaluronan synthesis by fibroblasts and melanoma cells were examined in monolayer culture and fibroblast-contracted collagen lattices, and their effects on the growth and invasion of tumour cells into collagen lattices were also studied. 4-MU caused a dose-dependent growth inhibition of fibroblast and melanoma cells with maximum inhibition at 0·5 mmol L(-1) 4-MU. At this dose, 4-MU inhibited (3) H-glucosamine incorporation into fibroblast glycosaminoglycans by 52%, and hyaluronan synthesis by 64%. The relative inhibition was more pronounced when fibroblasts were stimulated with C8161 melanoma cell-conditioned medium. 4-MU reduced the level of hyaluronan in fibroblast-contracted collagen lattices, and inhibited both the growth on and invasion into the lattices by melanoma cells. This growth inhibition appears to be predominantly independent of inhibition of hyaluronan synthesis. The effect on growth inhibition was reversible, and 4-MU had no effect on apoptosis. 4-MU is a potent inhibitor of hyaluronan synthesis, induction of stromal hyaluronan accumulation by tumour cells, and fibroblast and melanoma cell proliferation, and results suggest that 4-MU may have potential as a tumour cell anti-invasive and antiproliferative agent.

Involvement of Hyaluronan and Its Receptor CD44 with Choroidal Neovascularization

CD44 is a cell-surface adhesion molecule and receptor for hyaluronan (HA), one of the major extracellular matrix components. The purpose of the present study was to clarify a role of HA and CD44 in the development of choroidal neovascularization (CNV). Laser photocoagulation was used to induce CNV in C57BL/6 mice or CD44-deficient mice. The mRNA expression of CD44 and HA synthase (HAS)-2 in the retinal pigment epithelium (RPE)-choroid complex was evaluated by DNA microarray and real-time RT-PCR analyses 3 days after laser treatment. HA synthesis and CD44 expression were examined by immunohistochemistry 1 week after photocoagulation. Mice with laser-induced CNV were systemically administered the HA synthesis inhibitor 4-methylumbelliferone (MU) or an anti-CD44-neutralizing antibody. The response of CNV was analyzed by volumetric measurements 1 week after photocoagulation. Macrophage infiltration into CNV lesions was evaluated by real-time RT-PCR for F4/80 3 days after laser-induced injury. The induction of CNV led to a significant increase in expression of CD44 and HAS2 mRNA. HA and CD44 were immunopositive in the CNV lesions. Compared with vehicle treatment, the systemic application of MU significantly attenuated CNV volume in a dose-dependent fashion, together with macrophage infiltration into the lesions. Consistently, antibody-based blockade of CD44 resulted in a significant reduction of CNV volume, compared with the isotype control. In contrast, genetic ablation of CD44 significantly augmented CNV formation together with HA accumulation and macrophage infiltration, compared with wild-type mice. These results indicate a significant role of HA and its receptor CD44 in the development of CNV.

Stimulation of Small Proteoglycan Synthesis by the Hyaluronan Synthesis Inhibitor 4-Methylumbelliferone in Human Skin Fibroblasts

Human skin fibroblasts cultured with 4-methylumbelliferone (MU), a hyaluronan synthesis inhibitor, produce a hyaluronan-deficient extracellular matrix (See []). Our present study investigated the effects of MU on proteoglycan, which is the other main component of the extracellular matrix, and interacts with hyaluronan. Proteoglycans isolated from culture medium in the presence or absence of MU were characterized by gel-filtration chromatography, ion-exchange HPLC, electrophoresis, and immunoblotting. We found that MU had only a negligible effect on the synthesis of large proteoglycan but increased the production of small proteoglycan in comparison with cultures lacking MU. This small proteoglycan was identified by immunoblotting as decorin. The structures of decorin synthesized in the presence and absence of MU were compared by gel-filtration chromatography, and the data indicated that cells incubated with MU produced a larger decorin molecule than cells incubated without MU. Furthermore, the two decorins had galactosaminoglycan chains of different sizes. These results suggest that MU inhibits the synthesis of hyaluronan and accelerates production of the larger decorin in the extracellular matrix.

The Hyaluronan Synthesis Inhibitor 4-Methylumbelliferone Prevents Keratinocyte Activation and Epidermal Hyperproliferation Induced by Epidermal Growth Factor

Since excessive epidermal hyaluronan is associated with hyperproliferative states and disturbed terminal differentiation of the keratinocytes, we hypothesized that 4-methylumbelliferone (4-MU), an inhibitor of hyaluronan synthesis, could counteract these phenotypic features. Cultured epidermal keratinocytes showed a concentration dependent, maximum 83% reduction of hyaluronan in the presence of 0.2-1.0 mM 4-MU, whereas less decline was seen in the synthesis of chondroitin and heparan sulfate. The reduced hyaluronan was associated with no apparent change in its molecular mass. The 4-MU-treated keratinocytes showed an accentuated epithelial morphology with a flat, round cell shape, increased stress fibers and large vinculin-positive adhesion plaques, cytoskeletal changes consistent with the markedly reduced migration rate observed in scratched monolayer cultures. High concentrations of 4-MU also caused a block in keratinocyte proliferation, reversible upon 4-MU withdrawal. In the epidermis of organotypic cultures, 4-MU prevented the hyaluronan accumulation and epidermal hypertrophy induced by epidermal growth factor. The present results concur with earlier data indicating that enhanced cell locomotion and proliferation are associated with hyaluronan synthesis in activated keratinocytes. Cell proliferation, however, was blocked more strongly than expected on the basis of the incomplete hyaluronan synthesis inhibition, and may represent a novel target of 4-MU. At any rate, 4-MU and equivalent hyaluronan synthesis inhibitors might be considered for situations where suppression of epidermal activation and hyperproliferation is warranted.