Moira Clerici

Hyaluronan-CD44-ERK1/2 Regulate Human Aortic Smooth Muscle Cell Motility during Aging

The glycosaminoglycan hyaluronan (HA) modulates cell proliferation and migration, and it is involved in several human vascular pathologies including atherosclerosis and vascular restenosis. During intima layer thickening, HA increases dramatically in the neointima extracellular matrix. Aging is one of the major risk factors for the insurgence of vascular diseases, in which smooth muscle cells (SMCs) play a role by determining neointima formation through their migration and proliferation. Therefore, we established an in vitro aging model consisting of sequential passages of human aortic smooth muscle cells (AoSMCs). Comparing young and aged cells, we found that, during the aging process in vitro,HA synthesis significantly increases, as do HA synthetic enzymes (i.e. HAS2 and HAS3), the precursor synthetic enzyme (UDP-glucose dehydrogenase), and the HA receptor CD44. In aged cells, we also observed increased CD44 signaling that consisted of higher levels of phosphorylated MAP kinase ERK1/2. Further, aged AoSMCs migrated faster than young cells, and such migration could be modulated by HA, which alters the ERK1/2 phosphorylation. HA oligosaccharides of 6.8 kDa and an anti-CD44 blocking antibody prevented ERK1/2 phosphorylation and inhibited AoSMCs migration. These results indicate that, during aging, HA can modulate cell migration involving CD44-mediated signaling through ERK1/2. These data suggest that age-related HA accumulation could promote SMC migration and intima thickening during vascular neointima formation.

Proinflammatory Cytokines Induce Hyaluronan Synthesis and Monocyte Adhesion in Human Endothelial Cells through Hyaluronan Synthase 2 (HAS2) and the Nuclear Factor-κB (NF-κB) Pathway

Chronic inflammation is now accepted to have a critical role in the onset of several diseases as well as in vascular pathology, where macrophage transformation into foam cells contributes in atherosclerotic plaque formation. Endothelial cells (EC) have a critical function in recruitment of immune cells, and proinflammatory cytokines drive the specific expression of several adhesion proteins. During inflammatory responses several cells produce hyaluronan matrices that promote monocyte/macrophage adhesion through interactions with the hyaluronan receptor CD44 present on inflammatory cell surfaces. In this study, we used human umbilical chord vein endothelial cells (HUVECs) as a model to study the mechanism that regulates hyaluronan synthesis after treatment with proinflammatory cytokines. We found that interleukin 1β and tumor necrosis factors α and β, but not transforming growth factors α and β, strongly induced HA synthesis by NF-κB pathway. This signaling pathway mediated hyaluronan synthase 2 (HAS2) mRNA expression without altering other glycosaminoglycan metabolism. Moreover, we verified that U937 monocyte adhesion on stimulated HUVECs depends strongly on hyaluronan, and transfection with short interference RNA of HAS2 abrogates hyaluronan synthesis revealing the critical role of HAS2 in this process.

Hyaluronan synthesis is inhibited by adenosine monophosphate-activated protein kinase through the regulation of HAS2 activity in human aortic smooth muscle cells.

Hyaluronan (HA) is an extracellular matrix glycosaminoglycan (GAG) involved in cell motility, proliferation, tissue remodeling, development, differentiation, inflammation, tumor progression, and invasion and controls vessel thickening in cardiovascular diseases. Therefore, the control of HA synthesis could permit the fine-tuning of cell behavior, but the mechanisms that regulate HA synthesis are largely unknown. Recent studies suggest that the availability of the nucleotide-sugar precursors has a critical role. Because the formation of UDP-sugars is a highly energetically demanding process, we have analyzed whether the energy status of the cell could control GAG production. AMP-activated protein kinase (AMPK) is the main ATP/AMP sensor of mammalian cells, and we mimicked an energy stress by treating human aortic smooth muscle cells (AoSMCs) with the AMPK activators 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside and metformin. Under these conditions, HA synthesis, but not that of the other GAGs, was greatly reduced. We confirmed the inhibitory effect of AMPK using a specific inhibitor and knock-out cell lines. We found that AMPK phosphorylated Thr-110 of human HAS2, which inhibits its enzymatic activity. In contrast, the other two HAS isoenzymes (HAS1 and HAS3) were not modified by the kinase. The reduction of HA decreased the ability of AoSMCs to proliferate, migrate, and recruit immune cells, thereby reducing the pro-atherosclerotic AoSMC phenotype. Interestingly, such effects were not recovered by treatment with exogenous HA, suggesting that AMPK can block the pro-atherosclerotic signals driven by HA by interaction with its receptors.

The effects of 4-methylumbelliferone on hyaluronan synthesis, MMP2 activity, proliferation, and motility of human aortic smooth muscle cells

Extracellular matrix remodeling after proatherosclerotic injury involves an increase in hyaluronan (HA) that is coupled with vascular smooth muscle cell (SMC) migration, proliferation, and with neointima formation. As such events are dependent on HA, in this study we assessed the effects on SMC behavior of 4-methylumbelliferone (4-MU). As previously described in other cell types, 4-MU reduced HA in cultures of primary human aortic SMCs (AoSMCs) as well as the cellular content of the HA precursor UDP-glucuronic acid. We found that SMCs increased UDP-glucuronyl transferase 1 enzymes, which can reduce the cellular content of UDP-glucuronic acid confirming that the availability of the UDP-sugar substrates can regulate HA synthesis. Interestingly, we reported that 4-MU reduced the transcripts coding for the three HA synthases as well as UDP glucose pyrophosphorylase and dehydrogenase. As HA synthase transcript reduction is common to other cell types, the 4-MU effect on gene expression may be considered a mechanism for HA synthesis inhibition. Moreover, we showed that 4-MU strongly inhibits AoSMCs migration, which was restored by the addition of exogenous HA indicating that the rescuing depends on the interaction of HA with its receptor CD44. Besides the decrease in HA synthesis and cell migration, 4-MU reduced AoSMCs proliferation, indicating that 4-MU may exert a vasoprotective effect.

Hyaluronan and Human Endothelial Cell Behavior

Hyaluronan (HA) is the only nonsulphated glycosaminoglycan of extracellular matrix. In mammals HA is synthesised by three homologues HA synthases: HAS1, HAS2, and HAS3. The HA is daily catabolized by the hyaluronidase enzymes to either oligosaccharides or larger polymer. Despite its simple structure, HA is involved in a great number of biological functions, such as cell proliferation and migration, morphogenesis, wound healing, inflammation, angiogenesis, and tumor growth. Moreover, an important biological role is related to HA oligosaccharides that stimulate cytokine secretion and endothelial cell proliferation. Nevertheless no data about HA presence in endothelium are reported in literature. Several studies underline HA involvement in endothelial cell proliferation, migration, new vessels formation, and leucocytes recruitment. We review the role of HA in endothelial cell in normal condition and during vascular injury.

Modulation of hyaluronan synthase activity in cellular membrane fractions

Hyaluronan (HA), the only non-sulfated glycosaminoglycan, is involved in morphogenesis, wound healing, inflammation, angiogenesis, and cancer. In mammals, HA is synthesized by three homologous HA synthases, HAS1, HAS2, and HAS3, that polymerize the HA chain using UDP-glucuronic acid and UDP-N-acetylglucosamine as precursors. Since the amount of HA is critical in several pathophysiological conditions, we developed a non-radioactive assay for measuring the activity of HA synthases (HASs) in eukaryotic cells and addressed the question of HAS activity during intracellular protein trafficking. We prepared three cellular fractions: plasma membrane, cytosol (containing membrane proteins mainly from the endoplasmic reticulum and Golgi), and nuclei. After incubation with UDP-sugar precursors, newly synthesized HA was quantified by polyacrylamide gel electrophoresis of fluorophore-labeled saccharides and high performance liquid chromatography. This new method measured HAS activity not only in the plasma membrane fraction but also in the cytosolic membranes. This new technique was used to evaluate the effects of 4-methylumbeliferone, phorbol 12-myristate 13-acetate, interleukin 1β, platelet-derived growth factor BB, and tunicamycin on HAS activities. We found that HAS activity can be modulated by post-translational modification, such as phosphorylation and N-glycosylation. Interestingly, we detected a significant increase in HAS activity in the cytosolic membrane fraction after tunicamycin treatment. Since this compound is known to induce HA cable structures, this result links HAS activity alteration with the capability of the cell to promote HA cable formation.

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.

The monoclonal anti-BCL10 antibody (clone 331.1) is a sensitive and specific marker of pancreatic acinar cell carcinoma and pancreatic metaplasia

Acinar cell carcinoma (ACC) is a rare pancreatic cancer which may be difficult to distinguish from other solid nonadenocarcinoma tumors. The diagnosis depends on the demonstration of acinar differentiation, obtained with antibodies recognizing various pancreatic enzymes that, although specific, show different sensitivity. The C-terminal portion of the BCL10 protein shows homology with carboxyl ester hydrolase (CEH), an enzyme produced by pancreatic acinar cells. We investigated the usefulness of a C-terminal BCL10 monoclonal antibody in the diagnosis of ACCs. We examined normal pancreases and different pancreatic tumors including ACCs, mixed acinar–endocrine carcinomas, ductal adenocarcinomas, mucinous, serous, solid pseudopapillary, and endocrine neoplasms. In addition, various normal tissues and cases of pancreatic metaplasia of the gastroesophageal mucosa, cases of ectopic pancreas, gastrointestinal endocrine tumors, salivary and breast acinic cell carcinomas, gastric adenocarcinomas with and without acinar differentiation, and hepatocellular carcinomas were studied. BCL10 immunoreactivity paralleled that of CEH and was restricted to acinar cells of normal and ectopic pancreas, of pancreatic metaplasia, and of ACCs. The anti-BCL10 antibody was more sensitive in detecting ACCs and pancreatic metaplasia than antibodies directed against other pancreatic enzymes. We suggest using BCL10 antibody for diagnosing pancreatic tumors and whenever an acinar differentiation is suspected in gastrointestinal neoplastic and metaplastic lesions.

Molecular Control of the Hyaluronan Biosynthesis

Hyaluronan (HA) is the only unsulfated glycosaminoglycan (GAG) composed of repeating units of D-glucuronic acid and N-acetylglucosamine. The amount and the molecular weight of HA are important factors that regulate the physiology and pathology in several mammalian tissues. In fact hydrated HA makes ECM an ideal environment in which cells can move and proliferate. HA interacting with several receptors at the cellular level plays a critical role in signal transduction responses. The control of the HA synthesis is therefore a critical aspect in ECM and cells biology, but so far the information about this question is scanty. The synthesis of HA is due to several enzymes activities which not only involves its synthetic enzymes on the membranes of the cells (HA synthases 1, 2, 3, isoforms) but also the cytoplasmatic enzymes producing the UDP-sugar precursors. The UDP-sugars availability in cytoplasm is a critical point for the GAG synthesis and it seems to affect particularly the HA production. Eventually, the activity control of the enzymes involved in HA metabolism is obtained throughout both enzyme amount and their postsynthetic covalent modification, as phosphorylation. In fact, it was recently reported that HA synthase 3 may be phosphorylated after specific stimuli, and an increasing body of evidence supports the idea that the synthetic pathway of HA may be carefully regulated in all steps.

Ghrelin-Producing Well-Differentiated Neuroendocrine Tumor (Carcinoid) of Tailgut Cyst. Morphological, Immunohistochemical, Ultrastructural, and RT-PCR Study of a Case and Review of the Literature

Well-differentiated neuroendocrine tumors (carcinoids) arising in the presacral space are rare neoplasms that can arise in association with either sacrococcygeal teratomas or tailgut cysts. Although tumors arising in tailgut cysts are more frequent than those associated with teratomas, they are still very rare, and only 13 cases have been reported in the literature. We describe the first case of a carcinoid composed of ghrelin-producing cells arising in a tailgut cyst. Ghrelin production was demonstrated using immunohistochemistry, electron microscopy, and reverse transcription-polymerase chain reaction methods. A 73-year-old woman with back and pelvic pain was found to have a presacral mass histologically diagnosed, on needle biopsy, as a well-differentiated neuroendocrine tumor. Workup did not show another primary tumor or metastatic disease. The patient underwent laparoscopic resection of the mass, and the pathological diagnosis of the surgical specimen was of a tailgut cyst-associated carcinoid composed of ghrelin-producing cells. In addition, we have accurately reviewed the literature on presacral carcinoids, associated or unassociated with tailgut cysts, to give the reader a comprehensive overview of these very rare tumor types.