Glycosaminoglycans and glucose prevent apoptosis in 4-methylumbelliferone-treated human aortic smooth muscle cells

Interaction of Hyaluronan Acid with Some Proteins in Aqueous Solution as Studied by NMR

According to actual literature data, hyaluronic acid (HA) that is presented in the extracellular matrix can interact with proteins and thereby affect several important functions of the cell membrane. The purpose of this work was to reveal the features of the interaction of HA with proteins using the PFG NMR method by sampling two systems: aqueous solutions of HA with bovine serum albumin (BSA) and aqueous solutions of HA with hen egg-white lysozyme (HEWL). It was found that the presence of BSA in the HA aqueous solution initiates a certain additional mechanism; as a result, the population of HA molecules in the gel structure increases to almost 100%. At the same time, for an aqueous solution of HA/HEWL, even in the range of low (0.01-0.2%) HEWL contents, strong signs of degradation (depolymerization) of some HA macromolecules were observed such that they lost the ability to form a gel. Moreover, lysozyme molecules form a strong complex with degraded HA molecules and lose their enzymatic function. Thus, the presence of HA molecules in the intercellular matrix, as well as in the state associated with the surface of the cell membrane, can, in addition to the known ones, perform one more important function: the function of protecting the cell membrane from the destructive action of lysozymes. The obtained results are important for understanding the mechanism and features of the interaction of extracellular matrix glycosaminoglycan with cell membrane proteins.

Hyaluronan in the Cancer Cells Microenvironment

The presence of the glycosaminoglycan hyaluronan in the extracellular matrix of tissues is the result of the cooperative synthesis of several resident cells, that is, macrophages and tumor and stromal cells. Any change in hyaluronan concentration or dimension leads to a modification in stiffness and cellular response through receptors on the plasma membrane. Hyaluronan has an effect on all cancer cell behaviors, such as evasion of apoptosis, limitless replicative potential, sustained angiogenesis, and metastasis. It is noteworthy that hyaluronan metabolism can be dramatically altered by growth factors and matrikines during inflammation, as well as by the metabolic homeostasis of cells. The regulation of HA deposition and its dimensions are pivotal for tumor progression and cancer patient prognosis. Nevertheless, because of all the factors involved, modulating hyaluronan metabolism could be tough. Several commercial drugs have already been described as potential or effective modulators; however, deeper investigations are needed to study their possible side effects. Moreover, other matrix molecules could be identified and targeted as upstream regulators of synthetic or degrading enzymes. Finally, co-cultures of cancer, fibroblasts, and immune cells could reveal potential new targets among secreted factors.

Long non-coding RNAs at the crossroad of vascular smooth muscle cell phenotypic modulation in atherosclerosis and neointimal formation

Despite extraordinary advances in the comprehension of the pathophysiology of atherosclerosis and the employment of very effective treatments, cardiovascular diseases are still a major cause of mortality and represent a large share of health expenditure worldwide. Atherosclerosis is a disease affecting the medium and large arteries, which consists of a progressive accumulation of fatty substances, cellular waste products and fibrous elements, which culminates in the buildup of a plaque obstructing the blood flow. Endothelial dysfunction represents an early pathological event, favoring immune cells recruitment and triggering local inflammation. The release of inflammatory cytokines and other signaling molecules stimulates phenotypic modifications in the underlying vascular smooth muscle cells, which, in physiological conditions, are responsible for the maintenance of vessels architecture while regulating vascular tone. Vascular smooth muscle cells are highly plastic and may respond to disease stimuli by de-differentiating and losing their contractility, while increasing their synthetic, proliferative, and migratory capacity. This phenotypic switching is considered a pathological hallmark of atherogenesis and is ruled by the activation of selective gene programs. The advent of genomics and the improvement of sequencing technologies deepened our knowledge of the complex gene expression regulatory networks mediated by non-coding RNAs, and favored the rise of innovative therapeutic approaches targeting the non-coding transcriptome. In the context of atherosclerosis, long non-coding RNAs have received increasing attention as potential translational targets, due to their contribution to the molecular dynamics modulating the expression of vascular smooth muscle cells contractile/synthetic gene programs. In this review, we will focus on the most well-characterized long non-coding RNAs contributing to atherosclerosis by controlling expression of the contractile apparatus and genes activated in perturbed vascular smooth muscle cells.

ROLE OF HYALURONAN IN PATHOPHYSIOLOGY OF VASCULAR1 ENDOTHELIAL AND SMOOTH MUSCLE CELLS

One of the main components of the extracellular matrix (ECM) of the blood vessel is hyaluronic acid or hyaluronan (HA). It is a ubiquitous polysaccharide belonging to the family of glycosaminoglycans, but, differently from other proteoglycan-associated glycosaminoglycans, it is synthesized on the plasma membrane by a family of three HA synthases (HAS). HA can be released as a free polymer in the extracellular space or remain associated with the membrane in the pericellular space via HAS or via binding proteins. In fact, several cell surface proteins can interact with HA working as HA receptors like CD44, RHAMM, and LYVE-1. In physiological conditions, HA is localized in the glycocalyx and in the adventitia and is responsible for the loose and hydrated vascular structure favoring flexibility and allowing the stretching of vessels in response to mechanical forces. During atherogenesis, ECM undergoes dramatic alterations which have a crucial role in lipoprotein retention and in triggering multiple signaling cascades that wake up cells from their quiescent status. HA becomes highly present in the media and neointima favoring smooth muscle cells dedifferentiation, migration, and proliferation that strongly contribute to vessel wall thickening. Further, HA is able to modulate immune cell recruitment both within the vessel wall and on the endothelial cell layer. This review is focused on the effects of HA on vascular cell behavior.

A Connecting Link between Hyaluronan Synthase 3-Mediated Hyaluronan Production and Epidermal Function

Hyaluronan (HA), an essential component of the extracellular matrix of the skin, is synthesized by HA synthases (HAS1-3). To date, epidermal HA has been considered a major player in regulating cell proliferation and differentiation. However, a previous study reported that depletion of epidermal HA by Streptomyces hyaluronidase (St-HAase) has no influence on epidermal structure and function. In the present study, to further explore roles of epidermal HA, we examined effects of siRNA-mediated knockdown of HAS3, as well as conventional HA-depletion methods using St-HAase and 4-methylumbelliferone (4MU), on epidermal turnover and architecture in reconstructed skin or epidermal equivalents. Consistent with previous findings, HA depletion by St-HAase did not have a substantial influence on the epidermal architecture and turnover in skin equivalents. 4MU treatment resulted in reduced keratinocyte proliferation and epidermal thinning but did not seem to substantially decrease the abundance of extracellular HA. In contrast, siRNA-mediated knockdown of HAS3 in epidermal equivalents resulted in a significant reduction in epidermal HA content and thickness, accompanied by decreased keratinocyte proliferation and differentiation. These results suggest that HAS3-mediated HA production, rather than extracellularly deposited HA, may play a role in keratinocyte proliferation and differentiation, at least in the developing epidermis in reconstructed epidermal equivalents.

Hyaluronan: A Neuroimmune Modulator in the Microbiota-Gut Axis

The commensal microbiota plays a fundamental role in maintaining host gut homeostasis by controlling several metabolic, neuronal and immune functions. Conversely, changes in the gut microenvironment may alter the saprophytic microbial community and function, hampering the positive relationship with the host. In this bidirectional interplay between the gut microbiota and the host, hyaluronan (HA), an unbranched glycosaminoglycan component of the extracellular matrix, has a multifaceted role. HA is fundamental for bacterial metabolism and influences bacterial adhesiveness to the mucosal layer and diffusion across the epithelial barrier. In the host, HA may be produced and distributed in different cellular components within the gut microenvironment, playing a role in the modulation of immune and neuronal responses. This review covers the more recent studies highlighting the relevance of HA as a putative modulator of the communication between luminal bacteria and the host gut neuro-immune axis both in health and disease conditions, such as inflammatory bowel disease and ischemia/reperfusion injury.

HA and HS Changes in Endothelial Inflammatory Activation

Cardiovascular diseases are a group of disorders caused by the presence of a combination of risk factors, such as tobacco use, unhealthy diet and obesity, physical inactivity, etc., which cause the modification of the composition of the vessel’s matrix and lead to the alteration of blood flow, matched with an inflammation condition. Nevertheless, it is not clear if the inflammation is a permissive condition or a consequent one. In order to investigate the effect of inflammation on the onset of vascular disease, we treated endothelial cells with the cytokine TNF-α that is increased in obese patients and is reported to induce cardiometabolic diseases. The inflammation induced a large change in the extracellular matrix, increasing the pericellular hyaluronan and altering the heparan sulfate Syndecans sets, which seems to be related to layer permeability but does not influence cell proliferation or migration nor induce blood cell recruitment or activation.

A guide to the composition and functions of the extracellular matrix

Extracellular matrix (ECM) is a dynamic 3-dimensional network of macromolecules that provides structural support for the cells and tissues. Accumulated knowledge clearly demonstrated over the last decade that ECM plays key regulatory roles since it orchestrates cell signaling, functions, properties and morphology. Extracellularly secreted as well as cell-bound factors are among the major members of the ECM family. Proteins/glycoproteins, such as collagens, elastin, laminins and tenascins, proteoglycans and glycosaminoglycans, hyaluronan, and their cell receptors such as CD44 and integrins, responsible for cell adhesion, comprise a well-organized functional network with significant roles in health and disease. On the other hand, enzymes such as matrix metalloproteinases and specific glycosidases including heparanase and hyaluronidases contribute to matrix remodeling and affect human health. Several cell processes and functions, among them cell proliferation and survival, migration, differentiation, autophagy, angiogenesis, and immunity regulation are affected by certain matrix components. Structural alterations have been also well associated with disease progression. This guide on the composition and functions of the ECM gives a broad overview of the matrisome, the major ECM macromolecules, and their interaction networks within the ECM and with the cell surface, summarizes their main structural features and their roles in tissue organization and cell functions, and emphasizes the importance of specific ECM constituents in disease development and progression as well as the advances in molecular targeting of ECM to design new therapeutic strategies.

4-Methylumbelliferone as a potent and selective antitumor drug on a glioblastoma model

Glioblastoma (GBM), the most frequent primary tumor of the central nervous system, has a median survival of 14.6 months. 4-Methylumbelliferone (4MU) is a coumarin derivative widely used as a hyaluronan synthesis inhibitor with proven antitumor activity and without toxic effects reported. We aim to evaluate the antitumor effect of 4MU alone or combined with temozolomide (TMZ) on a GBM cell line, its absence of toxicity on brain cells and its selectivity for tumor cells. The antitumor effect of 4MU alone or combined with TMZ was evaluated on GL26 cells by assessing the metabolic activity through the XTT assay, cell proliferation by BrdU incorporation assay, migration by the wound healing assay, cell death by fluorescein diacetate/propidium iodide (FDA/PI) staining, apoptosis by membrane asymmetry and DNA fragmentation and metalloproteinase activity by zymography. The levels of hyaluronan and its capacity to counteract the effects of 4MU and the expression of RHAMM and CD44 were also determined. The toxicity and selectivity of 4MU were determined by XTT assay and PI staining on normal brain primary cell culture (NBPC-GFP) and GL26/NBPC-GFP cocultures. The GL26 cells expressed RHAMM but not CD44 while synthetized hyaluronan. 4MU decreased hyaluronan synthesis, diminished proliferation and induced apoptosis while reducing cell migration and the activity of metalloproteinases, which was restored by addition of hyaluronic acid. Furthermore, 4MU sensitized GL26 cells to the TMZ effect and showed selective toxicity on tumor cells without exhibiting neurotoxic effects. We demonstrated for the first time the cytotoxic effect of 4MU on GBM cells, highlighting its potential usefulness to improve GBM treatment.

Sirtuin 1 reduces hyaluronan synthase 2 expression by inhibiting nuclear translocation of NF-κB and expression of the long-noncoding RNA HAS2-AS1

Hyaluronan (HA) is one of the most prevalent glycosaminoglycans of the vascular extracellular matrix (ECM). Abnormal HA accumulation within blood vessel walls is associated with tissue inflammation and is prominent in most vascular pathological conditions such as atherosclerosis and restenosis. Hyaluronan synthase 2 (HAS2) is the main hyaluronan synthase enzyme involved in HA synthesis and uses cytosolic UDP-glucuronic acid and UDP-GlcNAc as substrates. The synthesis of UDP-glucuronic acid can alter the NAD⁺/NADH ratio via the enzyme UDP-glucose dehydrogenase, which oxidizes the alcohol group at C6 to the COO^- group. Here, we show that HAS2 expression can be modulated by sirtuin 1 (SIRT1), the master metabolic sensor of the cell, belonging to the class of NAD⁺-dependent deacetylases. Our results revealed the following. 1) Treatments of human aortic smooth muscle cells (AoSMCs) with SIRT1 activators (SRT1720 and resveratrol) inhibit both HAS2 expression and accumulation of pericellular HA coats. 2) Tumor necrosis factor α (TNFα) induced HA-mediated monocyte adhesion and AoSMC migration, whereas SIRT1 activation prevented immune cell recruitment and cell motility by reducing the expression levels of the receptor for HA-mediated motility, RHAMM, and the HA-binding protein TNF-stimulated gene 6 protein (TSG6). 3) SIRT1 activation prevented nuclear translocation of NF-κB (p65), which, in turn, reduced the levels of HAS2-AS1, a long-noncoding RNA that epigenetically controls HAS2 mRNA expression. In conclusion, we demonstrate that both HAS2 expression and HA accumulation by AoSMCs are down-regulated by the metabolic sensor SIRT1.

3,6-Anhydro-L-galactose increases hyaluronic acid production via the EGFR and AMPKα signaling pathway in HaCaT keratinocytes

BACKGROUND

Hyaluronic acid (HA) is an important factor in skin hydration maintenance. In mammalian keratinocytes, hyaluronan synthase 2 (HAS2) is a critical enzyme in HA production. Therefore, the promotion of HAS2 expression in keratinocytes may be a strategy for maintaining skin moisture.

OBJECTIVE

The aim was to determine the skin hydration effect and regulatory mechanisms of 3,6-anhydro-L-galactose (L-AHG), a main component of red macroalgal carbohydrates in human keratinocytes.

METHODS

L-AHG was applied to an immortalized human epidermal keratinocyte cell line (HaCaT cells). HA production, HAS2 protein and mRNA levels, and the activation of the signaling pathways involved in HAS2 expression were measured. HA levels were also evaluated for three dimensional (3D) reconstructed human skin.

RESULTS

Our results suggest that L-AHG upregulates HA production and may enhance HAS2 expression by activating EGFR-mediated ERK, PI3K/Akt, and STAT3 signaling pathways. We confirmed that L-AHG activated the AMPKα signaling pathway which in turn could regulate HAS2 expression in HaCaT cells. The effects of L-AHG on HA production were observed in the 3D reconstructed human skin model.

CONCLUSION

Our results suggest that L-AHG may enhance skin moisture retention by increasing HA synthesis in human epidermal keratinocytes.

Revisiting the hallmarks of cancer: The role of hyaluronan

Extracellular matrix (ECM) is a complex network of macromolecules such as proteoglycans (PGs), glycosaminoglycans (GAGs) and fibrous proteins present within all tissues and organs. The main role of ECM is not only to provide an essential mechanical scaffold for the cells but also to mediate crucial biochemical cues that are required for tissue homeostasis. Dysregulations in ECM deposition alter cell microenvironment, triggering the onset or the rapid progression of several diseases, including cancer. Hyaluronan (HA) is a ubiquitous component of ECM considered as one of the main players of cancer initiation and progression. This review discusses how HA participate in and regulate several aspects of tumorigenesis, with particular attention to the hallmarks of cancer proposed by Hanahan and Weinberg such as sustaining of the proliferative signaling, evasion of apoptosis, angiogenesis, activation of invasion and metastases, reprogramming of energy metabolism and evasion of immune response.

Hyaluronan as tunable drug delivery system

The hyaluronan (HA) polymer is an important macromolecule of extracellular matrix with remarkable structure and functions: it is a linear and unbranched polymer without sulphate or phosphate groups and has key role in several biological processes in mammals. It is ubiquitous in mammalian tissues with several and specific functions, influencing cell proliferation and migration as well as angiogenesis and inflammation. To exert these important functions in tissues HA modifies the concentration and size. Considering this HA content in tissues is carefully controlled by different mechanisms including covalent modification of the synthetic enzymes and epigenetic control of their gene expression. The function of HA is also critical in several pathologies including cancer, diabetes and chronic inflammation. Among these biological roles, the structural properties of HA allow to use this polymer in regenerative medicine including cosmetics and drug delivery. HA takes advantage from its capacity to form gels even at concentration of 1% producing scaffolds with very intriguing mechanical properties. These hydrogels are useful in regenerative medicine as biocompatible material for advanced therapeutic uses. In this review we highlight the biological aspects of HA addressing the mechanisms controlling the HA content in tissues and its role as drug delivery system.

Stiffness of Aligned Fibers Regulates the Phenotypic Expression of Vascular Smooth Muscle Cells

Electrospun uniaxially aligned ultrafine fibers show great promise in constructing vascular grafts mimicking the anisotropic architecture of native blood vessels. However, understanding how the stiffness of aligned fibers would impose influences on the functionality of vascular cells has yet to be explored. The present study aimed to explore the stiffness effects of electrospun aligned fibrous substrates (AFSs) on phenotypic modulation in vascular smooth muscle cells (SMCs). A stable jet coaxial electrospinning (SJCES) method was employed to generate highly aligned ultrafine fibers of poly(l-lactide- co-caprolactone)/poly(l-lactic acid) (PLCL/PLLA) in shell-core configuration with a remarkably varying stiffness region from 0.09 to 13.18 N/mm. We found that increasing AFS stiffness had no significant influence on the cellular shape and orientation along the fiber direction with the cultured human umbilical artery SMCs (huaSMCs) but inhibited the cell adhesion rate, promoted cell proliferation and migration, and especially enhanced the F-actin fiber assembly in the huaSMCs. Notably, higher fiber stiffness resulted in significant downregulation of contractile markers like alpha-smooth muscle actin (α-SMA), smooth muscle myosin heavy chain, calponin, and desmin, whereas upregulated the gene expression of pathosis-associated osteopontin ( OPN) in the huaSMCs. These results allude to the phenotype of huaSMCs on stiffer AFSs being miserably modulated into a proliferative and pathological state. Consequently, it adversely affected the proliferation and migration behavior of human umbilical vein endothelial cells as well. Moreover, stiffer AFSs also revealed to incur significant upregulation of inflammatory gene expression, such as interleukin-6 ( IL-6), monocyte chemoattractant protein-1 ( MCP-1), and intercellular adhesion molecule-1 ( ICAM-1), in the huaSMCs. This study stresses that although electrospun aligned fibers are capable of modulating native-like oriented cell morphology and even desired phenotype realization or transition, they might not always direct cells into correct functionality. The integrated fiber stiffness underlying is thereby a critical parameter to consider in engineering structurally anisotropic tissue-engineered vascular grafts to ultimately achieve long-term patency.

The Complex Interplay Between Extracellular Matrix and Cells in Tissues

Extracellular matrix (ECM) maintains the structural integrity of tissues and regulates cell and tissue functions. ECM is comprised of fibrillar proteins, proteoglycans (PGs), glycosaminoglycans, and glycoproteins, creating a heterogeneous but well-orchestrated network. This network communicates with resident cells via cell-surface receptors. In particular, integrins, CD44, discoidin domain receptors, and cell-surface PGs and additionally voltage-gated ion channels can interact with ECM components, regulating signaling cascades as well as cytoskeleton configuration. The interplay of ECM with recipient cells is enriched by the extracellular vesicles, as they accommodate ECM, signaling, and cytoskeleton molecules in their cargo. Along with the numerous biological properties that ECM can modify, autophagy and angiogenesis, which are critical for tissue homeostasis, are included. Throughout development and disease onset and progression, ECM endures rearrangement to fulfill cellular requirements. The main responsible molecules for tissue remodeling are ECM-degrading enzymes including matrix metalloproteinases, plasminogen activators, cathepsins, and hyaluronidases, which can modify the ECM structure and function in a dynamic mode. A brief summary of the complex interplay between ECM macromolecules and cells in tissues and the contribution of ECM in tissue homeostasis and diseases is given.

The CD44-HA axis and inflammation in atherosclerosis: A temporal perspective

Cardiovascular disease (CVD) due to atherosclerosis is a disease of chronic inflammation at both the systemic and the tissue level. CD44 has previously been implicated in atherosclerosis in both humans and mice. This multi-faceted receptor plays a critical part in the inflammatory response during the onset of CVD, though little is known of CD44's role during the latter stages of the disease. This review focuses on the role of CD44-dependent HA-dependent effects on inflammatory cells in several key processes, from disease initiation throughout the progression of atherosclerosis. Understanding how CD44 and HA regulate inflammation in atherogenesis is key in determining the utility of the CD44-HA axis as a therapeutic target to halt disease and potentially promote disease regression.

Role of hyaluronan in atherosclerosis: Current knowledge and open questions

Hyaluronan (HA), HA synthases (HAS) and HA receptors are expressed during the progression of atherosclerotic plaques. HA is thought to promote the activated phenotype of local vascular smooth muscle cells characterized by increased migration, proliferation and matrix synthesis. Furthermore, HA may modulate the immune response by increasing macrophage retention and by promoting the polarization of Th1 cells that enhance macrophage driven inflammation as well. The pro-atherosclerotic functions of HA are opposed by the presence of HA in the glycocalyx where it critically contributes to anti-thrombotic and anti-inflammatory function of the glycocalyx. Patients with atherosclerosis often are affected by comorbidities among them diabetes mellitus type 2 and inflammatory comorbidities. Diabetes mellitus type 2 likely has close interrelations to HA synthesis in atherosclerosis because the activity and transcription of HA synthases are sensitive to the intracellular glucose metabolism, which determines the substrate availability and the posttranslational modifications of HA synthases. The pro-inflammatory comorbidities aggravate the course of atherosclerosis and will affect the expression of the genes related to HA biosynthesis, -degradation, HA-matrix assembly or signaling. One example being the induction of HAS3 by interleukin-1β and other cytokines. Furthermore complications of atherosclerosis such as the healing after myocardial infarction also involve HA responses.

Changes in hyaluronan deposition in the rat myenteric plexus after experimentally-induced colitis

Myenteric plexus alterations hamper gastrointestinal motor function during intestinal inflammation. Hyaluronan (HA), an extracellular matrix glycosaminoglycan involved in inflammatory responses, may play a role in this process. In the colon of control rats, HA-binding protein (HABP), was detected in myenteric neuron soma, perineuronal space and ganglia surfaces. Prominent hyaluronan synthase 2 (HAS2) staining was found in myenteric neuron cytoplasm, suggesting that myenteric neurons produce HA. In the myenteric plexus of rats with 2, 4-dinitrobenzene sulfonic (DNBS)-induced colitis HABP staining was altered in the perineuronal space, while both HABP staining and HA levels increased in the muscularis propria. HAS2 immunopositive myenteric neurons and HAS2 mRNA and protein levels also increased. Overall, these observations suggest that inflammation alters HA distribution and levels in the gut neuromuscular compartment. Such changes may contribute to alterations in the myenteric plexus.

Roles and targeting of the HAS/hyaluronan/CD44 molecular system in cancer

Synthesis, deposition, and interactions of hyaluronan (HA) with its cellular receptor CD44 are crucial events that regulate the onset and progression of tumors. The intracellular signaling pathways initiated by HA interactions with CD44 leading to tumorigenic responses are complex. Moreover, HA molecules may perform dual functions depending on their concentration and size. Overexpression of variant isoforms of CD44 (CD44v) is most commonly linked to cancer progression, whereas their loss is associated with inhibition of tumor growth. In this review, we highlight that the regulation of HA synthases (HASes) by post-translational modifications, such as O-GlcNAcylation and ubiquitination, environmental factors and the action of microRNAs is important for HA synthesis and secretion in the tumor microenvironment. Moreover, we focus on the roles and interactions of CD44 with various proteins that reside extra- and intracellularly, as well as on cellular membranes with particular reference to the CD44-HA axis in cancer stem cell functions, and the importance of CD44/CD44v6 targeting to inhibit tumorigenesis.

UDP-sugar substrates of HAS3 regulate its O-GlcNAcylation, intracellular traffic, extracellular shedding and correlate with melanoma progression

Hyaluronan content is a powerful prognostic factor in many cancer types, but the molecular basis of its synthesis in cancer still remains unclear. Hyaluronan synthesis requires the transport of hyaluronan synthases (HAS1-3) from Golgi to plasma membrane (PM), where the enzymes are activated. For the very first time, the present study demonstrated a rapid recycling of HAS3 between PM and endosomes, controlled by the cytosolic levels of the HAS substrates UDP-GlcUA and UDP-GlcNAc. Depletion of UDP-GlcNAc or UDP-GlcUA shifted the balance towards HAS3 endocytosis, and inhibition of hyaluronan synthesis. In contrast, UDP-GlcNAc surplus suppressed endocytosis and lysosomal decay of HAS3, favoring its retention in PM, stimulating hyaluronan synthesis, and HAS3 shedding in extracellular vesicles. The concentration of UDP-GlcNAc also controlled the level of O-GlcNAc modification of HAS3. Increasing O-GlcNAcylation reproduced the effects of UDP-GlcNAc surplus on HAS3 trafficking, while its suppression showed the opposite effects, indicating that O-GlcNAc signaling is associated to UDP-GlcNAc supply. Importantly, a similar correlation existed between the expression of GFAT1 (the rate limiting enzyme in UDP-GlcNAc synthesis) and hyaluronan content in early and deep human melanomas, suggesting the association of UDP-sugar metabolism in initiation of melanomagenesis. In general, changes in glucose metabolism, realized through UDP-sugar contents and O-GlcNAc signaling, are important in HAS3 trafficking, hyaluronan synthesis, and correlates with melanoma progression.

Conserved miR-26b enhances ovarian granulosa cell apoptosis through HAS2-HA-CD44-Caspase-3 pathway by targeting HAS2

The hyaluronan synthase 2 (HAS2)-hyaluronic acid (HA)-CD44-Caspase-3 pathway is involved in ovarian granulosa cell (GC) functions in mammals. HAS2 is a key enzyme required for HA synthesis and is the key factor in this pathway. However, the regulation of HAS2 and the HAS2-mediated pathway by microRNAs in GCs is poorly understood. Here, we report that miR-26b regulates porcine GC (pGC) apoptosis through the HAS2-HA-CD44-Caspase-3 pathway by binding directly to the 3′- untranslated region of HAS2 mRNA. Knockdown of miR-26b reduced pGC apoptosis. Luciferase reporter assays demonstrated that HAS2 is a direct target of miR-26b in pGCs. Knockdown and overexpression of miR-26b increased and decreased, respectively, HA content, and HAS2 and CD44 expression in pGCs. At the same time, inhibition and overexpression of miR-26b decreased and increased the expression of Caspase-3, a downstream factor in the HAS2-HA-CD44 pathway. Moreover, knockdown of HAS2 enhanced pGC apoptosis, reduced the inhibitory effects of a miR-26b inhibitor on pGC apoptosis, repressed HA content and CD44 expression, and promoted Caspase-3 expression. In addition, overexpression of HAS2 has a opposite effect. Collectively, miR-26b positively regulates pGC apoptosis via a novel HAS2-HA-CD44-Caspase-3 pathway by targeting the HAS2 gene.

Cyclic AMP-elevating Agents Promote Cumulus Cell Survival and Hyaluronan Matrix Stability, Thereby Prolonging the Time of Mouse Oocyte Fertilizability

Cumulus cells sustain the development and fertilization of the mammalian oocyte. These cells are retained around the oocyte by a hyaluronan-rich extracellular matrix synthesized before ovulation, a process called cumulus cell-oocyte complex (COC) expansion. Hyaluronan release and dispersion of the cumulus cells progressively occur after ovulation, paralleling the decline of oocyte fertilization. We show here that, in mice, postovulatory changes of matrix are temporally correlated to cumulus cell death. Cumulus cell apoptosis and matrix disassembly also occurred in ovulated COCs cultured in vitro. COCs expanded in vitro with FSH or EGF underwent the same changes, whereas those expanded with 8-bromo-adenosine-3',5'-cyclic monophosphate (8-Br-cAMP) maintained integrity for a longer time. It is noteworthy that 8-Br-cAMP treatment was also effective on ovulated COCs cultured in vitro, prolonging the vitality of the cumulus cells and the stability of the matrix from a few hours to >2 days. Stimulation of endogenous adenylate cyclase with forskolin or inhibition of phosphodiesterase with rolipram produced similar effects. The treatment with selective cAMP analogues suggests that the effects of cAMP elevation are exerted through an EPAC-independent, PKA type II-dependent signaling pathway, probably acting at the post-transcriptional level. Finally, overnight culture of ovulated COCs with 8-Br-cAMP significantly counteracted the decrease of fertilization rate, doubling the number of fertilized oocytes compared with control conditions. In conclusion, these studies suggest that cAMP-elevating agents prevent cumulus cell senescence and allow them to continue to exert beneficial effects on oocyte and sperm, thereby extending in vitro the time frame of oocyte fertilizability.

Hyaluronan Does Not Regulate Human Epidermal Keratinocyte Proliferation and Differentiation

Hyaluronan (HA) is synthesized by three HA synthases (HAS1, HAS2, and HAS3) and secreted in the extracellular matrix. In human skin, large amounts of HA are found in the dermis. HA is also synthesized by keratinocytes in the epidermis, although its epidermal functions are not clearly identified yet. To investigate HA functions, we studied the effects of HA depletion on human keratinocyte physiology within in vitro reconstructed human epidermis. Inhibition of HA synthesis with 4-methylumbelliferone (4MU) did not modify the expression profile of the epidermal differentiation markers involucrin, keratin 10, and filaggrin during tissue reconstruction. In contrast, when keratinocytes were incubated with 4MU, cell proliferation was decreased. In an attempt to rescue the proliferation function, HA samples of various mean molecular masses were added to keratinocyte cultures treated with 4MU. These samples were unable to rescue the initial proliferation rate. Furthermore, treatments with HA-specific hyaluronidase, although removing almost all HA from keratinocyte cultures, did not alter the differentiation or proliferation processes. The differences between 4MU and hyaluronidase effects did not result from differences in intracellular HA, sulfated glycosaminoglycan concentration, apoptosis, or levels of HA receptors, all of which remained unchanged. Similarly, knockdown of UDP-glucose 6-dehydrogenase (UGDH) using lentiviral shRNA effectively decreased HA production but did not affect proliferation rate. Overall, these data suggest that HA levels in the human epidermis are not directly correlated with keratinocyte proliferation and differentiation and that incubation of cells with 4MU cannot equate with HA removal.

Hyperglycemia-Induced Changes in Hyaluronan Contribute to Impaired Skin Wound Healing in Diabetes: Review and Perspective

Ulcers and chronic wounds are a particularly common problem in diabetics and are associated with hyperglycemia. In this targeted review, we summarize evidence suggesting that defective wound healing in diabetics is causally linked, at least in part, to hyperglycemia-induced changes in the status of hyaluronan (HA) that resides in the pericellular coat (glycocalyx) of endothelial cells of small cutaneous blood vessels. Potential mechanisms through which exposure to high glucose levels causes a loss of the glycocalyx on the endothelium and accelerates the recruitment of leukocytes, creating a proinflammatory environment, are discussed in detail. Hyperglycemia also affects other cells in the immediate perivascular area, including pericytes and smooth muscle cells, through exposure to increased cytokine levels and through glucose elevations in the interstitial fluid. Possible roles of newly recognized, cross-linked forms of HA, and interactions of a major HA receptor (CD44) with cytokine/growth factor receptors during hyperglycemia, are also discussed.

Hyaluronan - a functional and structural sweet spot in the tissue microenvironment

Transition from homeostatic to reactive matrix remodeling is a fundamental adaptive tissue response to injury, inflammatory disease, fibrosis, and cancer. Alterations in architecture, physical properties, and matrix composition result in changes in biomechanical and biochemical cellular signaling. The dynamics of pericellular and extracellular matrices, including matrix protein, proteoglycan, and glycosaminoglycan modification are continually emerging as essential regulatory mechanisms underlying cellular and tissue function. Nevertheless, the impact of matrix organization on inflammation and immunity in particular and the consequent effects on tissue healing and disease outcome are arguably under-studied aspects of adaptive stress responses. Herein, we review how the predominant glycosaminoglycan hyaluronan (HA) contributes to the structure and function of the tissue microenvironment. Specifically, we examine the evidence of HA degradation and the generation of biologically active smaller HA fragments in pathological settings in vivo. We discuss how HA fragments versus nascent HA via alternate receptor-mediated signaling influence inflammatory cell recruitment and differentiation, resident cell activation, as well as tumor growth, survival, and metastasis. Finally, we discuss how HA fragmentation impacts restoration of normal tissue function and pathological outcomes in disease.

Biology and biotechnology of hyaluronan

The hyaluronan (HA) polymer is a critical component of extracellular matrix with a remarkable structure: is a linear and unbranched polymer without sulphate or phosphate groups. It is ubiquitous in mammals showing several biological functions, ranging from cell proliferation and migration to angiogenesis and inflammation. For its critical biological functions the amount of HA in tissues is carefully controlled by different mechanisms including covalent modification of the synthetic enzymes and epigenetic control of their gene expression. The concentration of HA is also critical in several pathologies including cancer, diabetes and inflammation. Beside these biological roles, the structural properties of HA allow it to take advantage of its capacity to form gels even at concentration of 1 % producing scaffolds with very promising applications in regenerative medicine as biocompatible material for advanced therapeutic uses. In this review we highlight the biological aspects of HA addressing the mechanisms controlling the HA content in tissues as well as its role in important human pathologies. In the second part of the review we highlight the different use of HA polymers in the modern biotechnology.

Hyaluronan synthases posttranslational regulation in cancer

Hyaluronan (HA) is a critical component of cancer microenvironment that is known to increase tumor progression and aggressiveness. The synthesis of HA starts from the cytosolic precursors UDP-N-acetylglucosamine and UDP-glucuronic acid. These two sugar nucleotides have several functions in addition to glycoconjugate synthesis and glucuronidation reactions, each of which can have a critical role in cancer. HA is synthesized by a family of three HA synthase (HAS) enzymes and, in this review, we described the main posttranslational modifications that are known to regulate HA metabolism. In particular, as the main HAS in adult tissues is HAS2, we focused on the role of AMPK-mediated phosphorylation and glycosylation by O-linked N-acetylglucosamine (O-GlcNAcylation) of HAS2 which mediate HAS2 inactivation and activation, respectively. HA catabolism, furnishing glucuronic acid and N-acetylglucosamine, can represent for a cancer cell a valid source of substrates to sustain complex tumor metabolism, and we highlight a presumable metabolic fate of such sugars in tumor cells.

4-methylumbelliferone treatment and hyaluronan inhibition as a therapeutic strategy in inflammation, autoimmunity, and cancer

Hyaluronan (HA) is a prominent component of the extracellular matrix at many sites of chronic inflammation, including type 1 diabetes (T1D), multiple sclerosis, and numerous malignancies. Recent publications have demonstrated that when HA synthesis is inhibited using 4-methylumbelliferone (4-MU), beneficial effects are observed in several animal models of these diseases. Notably, 4-MU is an already approved drug in Europe and Asia called "hymecromone" where it is used to treat biliary spasm. However, there is uncertainty regarding how 4-MU treatment provides benefit in these animal models and the potential long-term consequences of HA inhibition. Here, we review what is known about how HA contributes to immune dysregulation and tumor progression. Then, we review what is known about 4-MU and hymecromone in terms of mechanism of action, pharmacokinetics, and safety. Finally, we review recent studies detailing the use of 4-MU to treat animal models of cancer and autoimmunity.

Regulation of hyaluronan synthesis in vascular diseases and diabetes

Cell microenvironment has a critical role determining cell fate and modulating cell responses to injuries. Hyaluronan (HA) is a ubiquitous extracellular matrix glycosaminoglycan that can be considered a signaling molecule. In fact, interacting with several cell surface receptors can deeply shape cell behavior. In vascular biology, HA triggers smooth muscle cells (SMCs) dedifferentiation which contributes to vessel wall thickening. Furthermore, HA is able to modulate inflammation by altering the adhesive properties of endothelial cells. In hyperglycemic conditions, HA accumulates in vessels and can contribute to the diabetic complications at micro- and macrovasculature. Due to the pivotal role in favoring atherogenesis and neointima formation after injuries, HA could be a new target for cardiovascular pathologies. This review will focus on the recent findings regarding the regulation of HA synthesis in human vascular SMCs. In particular, the effects of the intracellular HA substrates availability, adenosine monophosphate-activated protein kinase (AMPK), and protein O-GlcNAcylation on the main HA synthetic enzyme (i.e., HAS2) will be discussed.

Hyaluronan synthase 2 protects skin fibroblasts against apoptosis induced by environmental stress

A balanced turnover of dermal fibroblasts is crucial for structural integrity and normal function of the skin. During recovery from environmental injury (such as UV exposure and physical wounding), apoptosis is an important mechanism regulating fibroblast turnover. We are interested in the role that hyaluronan (HA), an extracellular matrix molecule synthesized by HA synthase enzymes (Has), plays in regulating apoptosis in fibroblasts. We previously reported that Has1 and Has3 double knock-out (Has1/3 null) mice show accelerated wound closure and increased numbers of fibroblasts in the dermis. In the present study, we report that HA levels and Has2 mRNA expression are higher in cultured Has1/3 null primary skin fibroblasts than in wild type (WT) cells. Apoptosis induced by two different environmental stressors, UV exposure and serum starvation (SS), was reduced in the Has1/3 null cells. Hyaluronidase, added to cultures to remove extracellular HA, surprisingly had no effect upon apoptotic susceptibility to UVB or SS. However, cells treated with 4-methylumbelliferone to inhibit HA synthesis were sensitized to apoptosis induced by SS or UVB. When fibroblasts were transfected with Has2-specific siRNA that lowered Has2 mRNA and HA levels by 90%, both Has1/3 null and WT cells became significantly more sensitive to apoptosis. The exogenous addition of high molecular weight HA failed to reverse this effect. We conclude that Has1/3 null skin fibroblasts (which have higher levels of Has2 gene expression) are resistant to stress-induced apoptosis.

Natural antisense transcript for hyaluronan synthase 2 (HAS2-AS1) induces transcription of HAS2 via protein O-GlcNAcylation

Changes in the microenvironment organization within vascular walls are critical events in the pathogenesis of vascular pathologies, including atherosclerosis and restenosis. Hyaluronan (HA) accumulation into artery walls supports vessel thickening and is involved in many cardiocirculatory diseases. Excessive cytosolic glucose can enter the hexosamine biosynthetic pathway, increase UDP-N-acetylglucosamine (UDP-GlcNAc) availability, and lead to modification of cytosolic proteins via O-linked attachment of the monosaccharide β-N-GlcNAc (O-GlcNAcylation) from UDP-GlcNAc by the enzyme O-GlcNAc transferase. As many cytoplasmic and nuclear proteins can be glycosylated by O-GlcNAc, we studied whether the expression of the HA synthases that synthesize HA could be controlled by O-GlcNAcylation in human aortic smooth muscle cells. Among the three HAS isoenzymes, only HAS2 mRNA increased after O-GlcNAcylation induced by glucosamine treatments or by inhibiting O-GlcNAc transferase with PUGNAC (O-(2-acetamido-2-deoxy-d-glucopyranosylidene)amino-N-phenylcarbamate). We found that the natural antisense transcript of HAS2 (HAS2-AS1) was absolutely necessary to induce the transcription of the HAS2 gene. Moreover, we found that O-GlcNAcylation modulated HAS2-AS1 promoter activation by recruiting the NF-κB subunit p65, but not the HAS2 promoter, whereas HAS2-AS1 natural antisense transcript, working in cis, regulated HAS2 transcription by altering the chromatin structure around the HAS2 proximal promoter via O-GlcNAcylation and acetylation. These results indicate that HAS2 transcription can be finely regulated not only by recruiting transcription factors to the promoter as previously described but also by modulating chromatin accessibility by epigenetic modifications.

Isothiocyanate analogs targeting CD44 receptor as an effective strategy against colon cancer

Inflammatory pathway plays an important role in tumor cell progression of colorectal cancers. Although colon cancer is considered as one of the leading causes of death worldwide, very few drugs are available for its effective treatment. Many studies have examined the effects of specific COX-2 and 5-LOX inhibitors on human colorectal cancer, but the role of isothiocyanates (ITSCs) as COX-LOX dual inhibitors engaged in hyaluronan-CD44 interaction has not been studied. In the present work, we report series of ITSC analogs incorporating bioisosteric thiosemicarbazone moiety. These inhibitors are effective against panel of human colon cancer cell lines including COX-2 positive HCA-7, HT-29 cells lines, and hyaluronan synthase-2 (Has2) enzyme over-expressing transformed intestinal epithelial Apc10.1Has2 cells. Specifically, our findings indicate that HA-CD44v6-mediated COX-2/5-LOX signaling mediate survivin production, which in turn, supports anti-apoptosis and chemo-resistance leading to colon cancer cell survival. The over-expression of CD44v6shRNA as well as ITSC treatment significantly decreases the survival of colon cancer cells. The present results thus offer an opportunity to evolve potent inhibitors of HA synthesis and CD44v6 pathway and thus underscoring the importance of the ITSC analogs as chemopreventive agents for targeting HA/CD44v6 pathway.

Metabolic control of hyaluronan synthases

Hyaluronan (HA) is a glycosaminoglycan composed by repeating units of D-glucuronic acid (GlcUA) and N-acetylglucosamine (GlcNAc) that is ubiquitously present in the extracellular matrix (ECM) where it has a critical role in the physiology and pathology of several mammalian tissues. HA represents a perfect environment in which cells can migrate and proliferate. Moreover, several receptors can interact with HA at cellular level triggering multiple signal transduction responses. The control of the HA synthesis is therefore critical in ECM assembly and cell biology; in this review we address the metabolic regulation of HA synthesis. In contrast with other glycosaminoglycans, which are synthesized in the Golgi apparatus, HA is produced at the plasma membrane by HA synthases (HAS1-3), which use cytoplasmic UDP-glucuronic acid and UDP-N-acetylglucosamine as substrates. UDP-GlcUA and UDP-hexosamine availability is critical for the synthesis of GAGs, which is an energy consuming process. AMP activated protein kinase (AMPK), which is considered a sensor of the energy status of the cell and is activated by low ATP:AMP ratio, leads to the inhibition of HA secretion by HAS2 phosphorylation at threonine 110. However, the most general sensor of cellular nutritional status is the hexosamine biosynthetic pathway that brings to the formation of UDP-GlcNAc and intracellular protein glycosylation by O-linked attachment of the monosaccharide β-N-acetylglucosamine (O-GlcNAcylation) to specific aminoacid residues. Such highly dynamic and ubiquitous protein modification affects serine 221 residue of HAS2 that lead to a dramatic stabilization of the enzyme in the membranes.

Oxidized low density lipoprotein (LDL) affects hyaluronan synthesis in human aortic smooth muscle cells

Thickening of the vessel in response to high low density lipoprotein(s) (LDL) levels is a hallmark of atherosclerosis, characterized by increased hyaluronan (HA) deposition in the neointima. Human native LDL trapped within the arterial wall undergoes modifications such as oxidation (oxLDL). The aim of our study is to elucidate the link between internalization of oxLDL and HA production in vitro, using human aortic smooth muscle cells. LDL were used at an effective protein concentration of 20-50 μg/ml, which allowed 80% cell viability. HA content in the medium of untreated cells was 28.9 ± 3.7 nmol HA-disaccharide/cell and increased after oxLDL treatment to 53.9 ± 5.6. OxLDL treatments doubled the transcripts of HA synthase HAS2 and HAS3. Accumulated HA stimulated migration of aortic smooth muscle cells and monocyte adhesiveness to extracellular matrix. The effects induced by oxLDL were inhibited by blocking LOX-1 scavenger receptor with a specific antibody (10 μg/ml). The cholesterol moiety of LDL has an important role in HA accumulation because cholesterol-free oxLDL failed to induce HA synthesis. Nevertheless, cholesterol-free oxLDL and unmodified cholesterol (20 μg/ml) induce only HAS3 transcription, whereas 22,oxysterol affects both HAS2 and HAS3. Moreover, HA deposition was associated with higher expression of endoplasmic reticulum stress markers (CHOP and GRP78). Our data suggest that HA synthesis can be induced in response to specific oxidized sterol-related species delivered through oxLDL.

4-methylumbelliferone inhibits angiogenesis in vitro and in vivo

4-Methylumbelliferone (4-MU) is a hyaluronic acid biosynthesis inhibitor with antitumoral and antimetastatic effects. The objective of the present study was to determine the potential of 4-MU as an antiangiogenic compound. To fulfill this aim, cultured endothelial cells were used to perform an array of in vitro assays, as well as two different in vivo angiogenesis assays. This study demonstrates that, in fact, 4-MU behaves as a new inhibitor of both in vitro and in vivo angiogenesis. In vitro, 4-MU affects several key steps of angiogenesis, including endothelial cell proliferation, adhesion, tube formation, and extracellular matrix remodeling. Half-maximal inhibitory concentrations (IC50) values in the proliferation assay were 0.65 ± 0.04 and 0.37 ± 0.03 mM for HMEC and RF-24 endothelial cells, respectively. 4-MU (2 mM) treatment for 24 h induced apoptosis in 13% of HMEC and 5% of RF-24 cells. The number of adherent endothelial cells decreased by >20% after 24 h of treatment with 1 mM 4-MU. Minimal inhibitory concentrations in the tube formation assay were 2 and 0.5 mM 4-MU for HMEC and RF-24, respectively. Matrix metalloproteinase-2 expression was differentially altered upon 4-MU treatment in both tested endothelial cell lines. Taken together, the results suggest that 4-MU may have potential as a new candidate multitargeted bioactive compound for antiangiogenic therapy.

Role of UDP-N-acetylglucosamine (GlcNAc) and O-GlcNAcylation of hyaluronan synthase 2 in the control of chondroitin sulfate and hyaluronan synthesis

Hyaluronan (HA) is a glycosaminoglycan present in most tissue microenvironments that can modulate many cell behaviors, including proliferation, migration, and adhesive proprieties. In contrast with other glycosaminoglycans, which are synthesized in the Golgi, HA is synthesized at the plasma membrane by one or more of the three HA synthases (HAS1-3), which use cytoplasmic UDP-glucuronic acid and UDP-N-acetylglucosamine as substrates. Previous studies revealed the importance of UDP-sugars for regulating HA synthesis. Therefore, we analyzed the effect of UDP-GlcNAc availability and protein glycosylation with O-linked N-acetylglucosamine (O-GlcNAcylation) on HA and chondroitin sulfate synthesis in primary human aortic smooth muscle cells. Glucosamine treatment, which increases UDP-GlcNAc availability and protein O-GlcNAcylation, increased synthesis of both HA and chondroitin sulfate. However, increasing O-GlcNAcylation by stimulation with O-(2-acetamido-2-deoxy-d-glucopyranosylidene)amino-N-phenylcarbamate without a concomitant increase of UDP-GlcNAc increased only HA synthesis. We found that HAS2, the main synthase in aortic smooth muscle cells, can be O-GlcNAcylated on serine 221, which strongly increased its activity and its stability (t(½) >5 h versus ∼17 min without O-GlcNAcylation). S221A mutation prevented HAS2 O-GlcNAcylation, which maintained the rapid turnover rate even in the presence of GlcN and increased UDP-GlcNAc. These findings could explain the elevated matrix HA observed in diabetic vessels that, in turn, could mediate cell dedifferentiation processes critical in vascular pathologies.

Hyaluronan expressed by the hematopoietic microenvironment is required for bone marrow hematopoiesis

The contribution of hyaluronan (HA) to the regulatory network of the hematopoietic microenvironment was studied using knock-out mice of three hyaluronan synthase genes (Has1, Has2, and Has3). The number of hematopoietic progenitors was decreased in bone marrow and increased in extramedullary sites of Prx1-Cre;Has2(flox/flox);Has1(-/-);Has3(-/-) triple knock-out (tKO) mice as compared with wild type (WT) and Has1(-/-);Has3(-/-) double knock-out (dKO) mice. In line with this observation, decreased hematopoietic activity was observed in long term bone marrow cultures (LTBMC) from tKO mice, whereas the formation of the adherent layer and generation of hematopoietic cells in WT and dKO cultures was not different. 4-Methylumbelliferone (4MU) was used to pharmacologically inhibit the production of HA in LTBMC. Treatment with 4MU inhibited HA synthesis, decreased expression of HAS2 and HAS3, and eliminated hematopoiesis in LTBMC, and this effect was alleviated by the addition of exogenous HA. Exogenous HA also augmented the cell motility in LTBMC, which correlated with the HA-stimulated production of chemokines and growth factors. Conditioned media from HA-induced LTBMC enhanced the chemotaxis of hematopoietic stem/progenitor cells (HSPC) in response to SDF-1. Exposure of endothelial cells to 4MU decreased their ability to support HSPC rolling and adhesion. In addition, migration of transplanted HSPC into the marrow of 4MU-pretreated mice was lower than in untreated mice. Collectively, the results suggest that HA depletion reduces the ability of the microenvironment to support HSPC, and confirm a role for HA as a necessary regulatory element in the structure of the hematopoietic microenvironment.