Extracellular ATP activates hyaluronan synthase 2 (HAS2) in epidermal keratinocytes via P2Y2, Ca2+ signaling, and MAPK pathways

Hyaluronan Tetrasaccharides Penetrate into the Skin by Passive Diffusion and Contribute to Skin Health

Hyaluronan (HA) is a commonly used material in cosmetics and pharmaceuticals because of its various pharmacological activities. However, because of its large molecular weight, HA penetrates the skin very poorly and most of it remains on the skin surface. Thus, topically applied HA could not be expected to function biologically in the skin. However, we have confirmed that HA tetrasaccharides (HA4), which is the smallest unit of HA, penetrate into the skin by passive diffusion and affect epidermal metabolism. Topical treatment of HA4 rescues the epidermal damage caused by long-term UVA irradiation. Furthermore, various biological functions of HA4 to maintain healthy skin was observed in cell culture studies. This review describes the skin permeability of HA4 and how it contributes to healthy skin.

G protein coupled P2Y2 receptor as a regulatory molecule in cancer progression

The occurrence and development of cancer involves the participation of many factors, its pathological mechanism is far more complicated than other diseases, and the treatment is also extremely difficult. Although the treatment of cancer adopts diversified methods to improve the survival rate and quality of life of patients, but the drug resistance, metastasis and recurrence of cancer cause most patients to fail in treatment. Therefore, exploring new molecular targets in cancer pathology is of great value for improving and preventing the treatment of cancer. Fortunately, the P2Y2 purinergic receptor (P2Y2 receptor) in the G protein-coupled receptor family has been recognized for regulating cancer progression. Agonist activated P2Y2 receptor has a certain contribution to the growth and metastasis of tumor cells. P2Y2 receptor activation participates in cancer progression by regulating calcium ion channels and classical signaling pathways (such as PLC-PKC and PI3K/AKT). It has the effect of anti-tumor therapy by inhibiting the activation of P2Y2 receptor (the use of antagonist) and reducing its expression. Therefore, in this article, we focus on the expression patterns of P2Y2 receptor in cancer and potential pharmacological targets as anti-cancer treatments.

Hyaluronic acid metabolism and chemotherapy resistance: recent advances and therapeutic potential

Hyaluronic acid (HA) is a major component of the extracellular matrix, providing essential mechanical scaffolding for cells and, at the same time, mediating essential biochemical signals required for tissue homeostasis. Many solid tumors are characterized by dysregulated HA metabolism, resulting in increased HA levels in cancer tissues. HA interacts with several cell surface receptors, such as cluster of differentiation 44 and receptor for hyaluronan-mediated motility, thus co-regulating important signaling pathways in cancer development and progression. In this review, we describe the enzymes controlling HA metabolism and its intracellular effectors emphasizing their impact on cancer chemotherapy resistance. We will also explore the current and future prospects of HA-based therapy, highlighting the opportunities and challenges in the field.

Epidermal keratinocytes regulate hyaluronan metabolism via extracellularly secreted hyaluronidase 1 and hyaluronan synthase 3

Hyaluronan (HA) is a high-molecular-weight (HMW) glycosaminoglycan, which is a fundamental component of the extracellular matrix that is involved in a variety of biological processes. We previously showed that the HYBID/KIAA1199/CEMIP axis plays a key role in the depolymerization of HMW-HA in normal human dermal fibroblasts (NHDFs). However, its roles in normal human epidermal keratinocytes (NHEKs) remained unclear. HYBID mRNA expression in NHEKs was lower than that in NHDFs, and NHEKs showed no depolymerization of extracellular HMW-HA in culture, indicating that HYBID does not contribute to extracellular HA degradation. In this study, we found that the cell-free conditioned medium of NHEKs degraded HMW-HA under weakly acidic conditions (pH 4.8). This degrading activity was abolished by hyaluronidase 1 (HYAL1) knockdown but not by HYAL2 knockdown. Newly synthesized HYAL1 was mainly secreted extracellularly, and the secretion of HYAL1 was increased during differentiation, suggesting that epidermal interspace HA is physiologically degraded by HYAL1 according to pH decrease during stratum corneum formation. In HA synthesis, hyaluronan synthase 3 (HAS3) knockdown reduced HA production by NHEKs, and interferon-γ-dependent HA synthesis was correlated with increased HAS3 expression. Furthermore, HA production was increased by TMEM2 knockdown through enhanced HAS3 expression. These results indicate that NHEKs regulate HA metabolism via HYAL1 and HAS3, and TMEM2 is a regulator of HAS3-dependent HA production.

Double-modified, thio and methylene ATP analogue facilitates wound healing in vitro and in vivo

Recent data indicate that extracellular ATP affects wound healing efficacy via P2Y2-dependent signaling pathway. In the current work, we propose double-modified ATP analogue-alpha-thio-beta,gamma-methylene-ATP as a potential therapeutic agent for a skin regeneration. For the better understanding of structure-activity relationship, beside tested ATP analogues, the appropriate single-modified derivatives of target compound, such as alpha-thio-ATP and beta,gamma-methylene-ATP, were also tested in the context of their involvement in the activation of ATP-dependent purinergic signaling pathway via the P2Y2 receptor. The diastereomerically pure alpha-thio-modified-ATP derivatives were obtained using the oxathiaphospholane method as separate SP and RP diastereomers. Both the single- and double- modified ATP analogues were then tested for their impact on the viability and migration of human keratinocytes. The involvement of P2Y2-dependent purinergic signaling was analyzed in silico by molecular docking of the tested compounds to the P2Y2 receptor and experimentally by studying intracellular calcium mobilization in the human keratinocytes HaCaT. The effects obtained for ATP analogues were compared with the results for ATP as a natural P2Y2 agonist. To confirm the contribution of the P2Y2 receptor to the observed effects, the tests were also performed in the presence of the selective P2Y2 antagonist-AR-C118925XX. The ability of the alpha-thio-beta,gamma-methylene-ATP to influence cell migration was analyzed in vitro on the model HaCaT and MDA-MB-231 cells by wound healing assay and transwell migration test as well as in vivo using zebrafish system. The impact on tissue regeneration was estimated based on the regrowth rate of cut zebrafish tails. The in vitro and in vivo studies have shown that the SP-alpha-thio-beta,gamma-methylene-ATP analogue promotes regeneration-related processes, making it a suitable agent for enhance wound healing. Performed studies indicated its impact on the cell migration, induction of epithelial-mesenchymal transition and intracellular calcium mobilization. The enhanced regeneration of cut zebrafish tails confirmed the pro-regenerative activity of this ATP analogue. Based on the performed studies, the SP-alpha-thio-beta,gamma-methylene-ATP is proposed as a potential therapeutic agent for wound healing and skin regeneration treatment.

Mesenchymal stromal cells confer breast cancer doxorubicin resistance by producing hyaluronan

Chemotherapy resistance represents a major cause of therapeutic failure and mortality in cancer patients. Mesenchymal stromal cells (MSCs), an integral component of tumor microenvironment, are known to promote drug resistance. However, the detailed mechanisms remain to be elucidated. Here, we found that MSCs confer breast cancer resistance to doxorubicin by diminishing its intratumoral accumulation. Hyaluronan (HA), a major extracellular matrix (ECM) product of MSCs, was found to mediate the chemoresistant effect. The chemoresistant effect of MSCs was abrogated when hyaluronic acid synthase 2 (HAS2) was depleted or inhibited. Exogenous HA also protected tumor grafts from doxorubicin. Molecular dynamics simulation analysis indicates that HA can bind with doxorubicin, mainly via hydrophobic and hydrogen bonds, and thus reduce its entry into breast cancer cells. This mechanism is distinct from the reported chemoresistant effect of HA via its receptor on cell surface. High HA serum levels were also found to be positively associated with chemoresistance in breast cancer patients. Our findings indicate that the HA-doxorubicin binding dynamics can confer cancer cells chemoresistance. Reducing HA may enhance chemotherapy efficacy.

Rosa gallica and its active compound, cyanidin-3,5-O-diglucoside, improve skin hydration via the GLK signaling pathway

Rosa gallica has been previously reported to display anti-inflammatory, anti-oxidative, and anti-skin wrinkle activities. However, the effect of Rosa gallica on skin hydration and its active components are largely unknown. Herein, we aimed to investigate the skin hydration effect of rose petal extract (RPE) in humans and elucidate the underlying molecular mechanism. A double-blinded clinical study was performed to investigate the effect of RPE on skin hydration. Stratum corneum moisture analysis demonstrated that RPE treatment significantly improved hydration levels in human skin. Furthermore, HAS2 and hyaluronic acid levels were notably increased by RPE in keratinocytes and 3D human skin equivalent model. By comparing the modulatory effect on HAS2 expression, cyanidin-3,5-O-diglucoside (CDG) was identified as the most potent compound in RPE likely responsible for skin hydration. The kinase activity of GLK, an upstream regulator of MAPK signaling, was increased by CDG in a dose-dependent manner. Importantly, silencing GLK reversed CDG-mediated HAS2 upregulation, further supporting the involvement of GLK in the CDG-mediated effects. Binding of CDG to GLK was confirmed by pull-down assay and computer modeling. These findings suggest that RPE and its active component CDG increases skin hydration by upregulating HAS2 expression through modulating the GLK-MAP2K-MAPK signaling pathway.

HAS2-Ezrin-ER axis plays a role in acquired antiestrogen resistance of ER-positive breast cancer

The development of endocrine resistance is a major clinical problem in estrogen receptor-positive (ER+) breast cancer (BrCa) treatment, in which how cancer cells acquire resistance remains obscure. Hyaluronan synthase 2 (HAS2) is the most critical synthase in producing hyaluronan and is well known for its involvement in cancer growth, metabolism and metastasis. Recent evidence has proved that HAS2 is involved in cellular acquired resistance to drug therapy in BrCa. In this work, we first observed that HAS2 expression was decreased in the endocrine-resistant ER+ BrCa cells. Further knocking-out experiments confirmed that the loss of HAS2 in parental ER+ BrCa cells resulted in a following antiestrogen resistance. Next, we found that the HAS2-loss could induce an upregulation of Ezrin, a member of the membrane cytoskeletal protein family who plays key roles in cellular signal transduction. Notably, we identified that the increase of Ezrin induced by HAS2-loss could inhibit the ERα expression and augment antiestrogen resistance, suggesting that a HAS2-Ezrin-ER axis may be associated with the acquirement of endocrine resistance in ER+ BrCa cells. Finally, knockdown or inhibition of Ezrin could restore the sensitivity of endocrine-resistant cells to antiestrogens treatment by activating ERα signaling. Taken together, our findings unraveled a novel HAS2-Ezrin-ER route in regulating the sensitivity of ER+ BrCa cells to antiestrogens, in which Ezrin may be a potential target in endocrine therapy.

In Vitro Anti-Photoaging and Skin Protective Effects of Licania macrocarpa Cuatrec Methanol Extract

The Licania genus has been used in the treatment of dysentery, diabetes, inflammation, and diarrhea in South America. Of these plants, the strong anti-inflammatory activity of Licania macrocarpa Cuatrec (Chrysobalanaceae) has been reported previously. However, the beneficial activities of this plant on skin health have remained unclear. This study explores the protective activity of a methanol extract (50-100 μg/mL) in the aerial parts of L. macrocarpa Cuatrec (Lm-ME) and its mechanism, in terms of its moisturizing/hydration factors, skin wrinkles, UV radiation-induced cell damage, and radical generation (using RT/real-time PCR, carbazole assays, flowcytometry, DPPH/ABTS, and immunoblotting analysis). The anti-pigmentation role of Lm-ME was also tested by measuring levels of melanin, melanogenesis-related genes, and pigmentation-regulatory proteins. Lm-ME decreased UVB-irradiated death in HaCaT cells by suppressing apoptosis and inhibited matrix metalloproteinases 1/2 (MMP1/2) expression by enhancing the activity of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38. It was confirmed that Lm-ME displayed strong antioxidative activity. Lm-ME upregulated the expression of hyaluronan synthases-2/3 (HAS-2/3) and transglutaminase-1 (TGM-1), as well as secreted levels of hyaluronic acid (HA) via p38 and JNK activation. This extract also significantly inhibited the production of hyaluronidase (Hyal)-1, -2, and -4. Lm-ME reduced the melanin expression of microphthalmia-associated transcription factor (MITF), tyrosinase, and tyrosinase-related protein-1/2 (TYRP-1/2) in α-melanocyte-stimulating hormone (α-MSH)-treated B16F10 cells via the reduction of cAMP response element-binding protein (CREB) and p38 activation. These results suggest that Lm-ME plays a role in skin protection through antioxidative, moisturizing, cytoprotective, and skin-lightening properties, and may become a new and promising cosmetic product beneficial for the skin.

Possible role of pannexin 1 channels and purinergic receptors in the pathogenesis and mechanism of action of SARS-CoV-2 and therapeutic potential of targeting them in COVID-19

Identifying signaling pathways and molecules involved in SARS-CoV-2 pathogenesis is pivotal for developing new effective therapeutic or preventive strategies for COVID-19. Pannexins (PANX) are ATP-release channels in the plasma membrane essential in many physiological and immune responses. Activation of pannexin channels and downstream purinergic receptors play dual roles in viral infection, either by facilitating viral replication and infection or inducing host antiviral defense. The current review provides a hypothesis demonstrating the possible contribution of the PANX1 channel and purinergic receptors in SARS-CoV-2 pathogenesis and mechanism of action. Moreover, we discuss whether targeting these signaling pathways may provide promising preventative therapies and treatments for patients with progressive COVID-19 resulting from excessive pro-inflammatory cytokines and chemokines production. Several inhibitors of this pathway have been developed for the treatment of other viral infections and pathological consequences. Specific PANX1 inhibitors could be potentially included as part of the COVID-19 treatment regimen if, in future, studies demonstrate the role of PANX1 in COVID-19 pathogenesis. Of note, any ATP therapeutic modulation for COVID-19 should be carefully designed and monitored because of the complex role of extracellular ATP in cellular physiology.

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.

Calcium Signaling in the Photodamaged Skin: In Vivo Experiments and Mathematical Modeling

The epidermis forms an essential barrier against a variety of insults. The overall goal of this study was to shed light not only on the effects of accidental epidermal injury, but also on the mechanisms that support laser skin resurfacing with intra-epidermal focal laser-induced photodamage, a widespread medical practice used to treat a range of skin conditions. To this end, we selectively photodamaged a single keratinocyte with intense, focused and pulsed laser radiation, triggering Ca2+ waves in the epidermis of live anesthetized mice with ubiquitous expression of a genetically encoded Ca2+ indicator. Waves expanded radially and rapidly, reaching up to eight orders of bystander cells that remained activated for tens of minutes, without displaying oscillations of the cytosolic free Ca2+ concentration ([Formula: see text]). By combining in vivo pharmacological dissection with mathematical modeling, we demonstrate that Ca2+ wave propagation depended primarily on the release of ATP, a prime damage-associated molecular patterns (DAMPs), from the hit cell. Increments of the [Formula: see text] in bystander cells were chiefly due to Ca2+ release from the endoplasmic reticulum (ER), downstream of ATP binding to P2Y purinoceptors. ATP-dependent ATP release though connexin hemichannels (HCs) affected wave propagation at larger distances, where the extracellular ATP concentration was reduced by the combined effect of passive diffusion and hydrolysis due to the action of ectonucleotidases, whereas pannexin channels had no role. Bifurcation analysis suggests basal keratinocytes have too few P2Y receptors (P2YRs) and/or phospholipase C (PLC) to transduce elevated extracellular ATP levels into inositol trisphosphate (IP3) production rates sufficiently large to sustain [Formula: see text] oscillations.

Matters of size: Roles of hyaluronan in CNS aging and disease

Involvement of extracellular matrix (ECM) components in aging and age-related neurodegeneration is not well understood. The role of hyaluronan (HA), a major extracellular matrix glycosaminoglycan, in malignancy and inflammation is gaining new understanding. In particular, the differential biological effects of high molecular weight (HMW-HA) and low molecular weight hyaluronan (LMW-HA), and the mechanism behind such differences are being uncovered. Tightly regulated in the brain, HA can have diverse effects on cellular development, growth and degeneration. In this review, we summarize the homeostasis and signaling of HA in healthy tissue, discuss its distribution and ontogeny in the central nervous system (CNS), summarize evidence for its involvement in age-related neurodegeneration and Alzheimer Disease (AD), and assess the potential of HA as a therapeutic target in the CNS.

Regulation of hyaluronan production by β2 adrenergic receptor signaling

BACKGROUND

Hyaluronan (HA), the main component of the extracellular matrix, is involved in tissue elasticity and cell scaffolding, and in progression of conditions such as cancer, inflammation and wound healing. Signaling by G protein coupled receptor (GPCR) activation increases expression of hyaluronan synthase (HAS) and HA production. The β2 adrenergic receptor (β2AR) is a catecholamine-liganded GPCR that is involved in cancer progression and wound healing. Since HA and β2AR are involved in a common pathology, we investigated whether β2AR signaling regulates HA production.

METHODS

After stimulating β2AR-expressing cells with a β agonist, the amount of HA in the culture medium was measured and HAS expression was examined by real-time PCR. A variety of signaling molecule inhibitors were used to identify signaling pathways that alter HAS expression.

RESULTS

β2AR activation increased HA production and enhanced HAS2 expression. The increase in HAS2 expression by β2AR activation occurred via the Gs - adenylyl cyclase - PKA - CREB signal transduction pathway.

CONCLUSIONS

Downstream signal transduction by β2AR activation increased HA production by enhancing transcription of the HAS2 gene. This study suggests that β2AR is a GPCR that regulates HA production, and that stimulation with a catecholamine (β2 agonist) can regulate HA production.

GENERAL SIGNIFICANCE

β2AR may function through regulation of HA production in cancer progression and wound healing.

Kahweol Exerts Skin Moisturizing Activities by Upregulating STAT1 Activity

Kahweol is a diterpene present in coffee. Until now, several studies have shown that kahweol has anti-inflammatory and anti-angiogenic functions. Due to the limited research available about skin protection, this study aims to discern the potential abilities of kahweol and the possible regulation targets. First, the cytotoxicity of kahweol was checked by 3-4-5-dimethylthiazol-2-yl)-2-5-diphenyltetrazolium bromide assay, while 2,20-azino-bis (3ethylbenzothiazoline-6-sulphonic acid) diammonium salt and 1-diphenyl-2-picryl-hydrazyl were used to examine the radical scavenging ability. Polymerase chain reaction analysis was performed to explore the proper time points and doses affecting skin hydration and barrier-related genes. Luciferase assay and Western blotting were used to explore the possible transcription factors. Finally, fludarabine (a STAT1 inhibitor) was chosen to discern the relationship between skin-moisturizing factors and STAT1. We found that HaCaT cells experienced no toxicity from kahweol, and kahweol displayed moderate radical scavenging ability. Moreover, kahweol increased the outcome of HAS1, HAS2, occludin, and TGM-1 from six hours in a dose-dependent manner as well as the activation of STAT1 from six hours. Additionally, kahweol recovered the suppression of HAS2, STAT1-mediated luciferase activity, and HA secretion, which was all downregulated by fludarabine. In this study, we demonstrated that kahweol promotes skin-moisturizing activities by upregulating STAT1.

Autocrine regulation of wound healing by ATP release and P2Y2 receptor activation

AIMS

Application of exogenous nucleotides can modulate wound healing via the activation of purinergic receptors. However, evidence for the release of endogenous nucleotides and the subsequent activation of purinergic receptors in this process has not been well defined. Therefore, the current study aimed to investigate wound-mediated nucleotide release and autocrine purinergic signalling during HaCaT keratinocyte wound closure following scratch injury.

MAIN METHODS

An in vitro scratch wound apparatus was employed to study wound healing over 24-h in the presence of modulators of ATP release, P2 receptors and pathways downstream of P2 receptor activation.

KEY FINDINGS

Adenosine 5'-triphosphate (ATP) was released from scratched cells. The ectonucleotidase apyrase and pharmacological inhibition of the nucleotide release hemichannel, pannexin-1, decreased wound closure over time. The non-selective P2Y receptor antagonist suramin and the selective P2Y₂ receptor antagonist AR-C118925XX, but not other P2 antagonists, decreased wound closure. AR-C118925XX decreased wound closure in a concentration-dependent fashion. However, exogenous P2Y₂ receptor agonists, ATP or uridine 5'-triphosphate, did not enhance wound closure. PCR and immunoblotting confirmed P2Y₂ receptor expression in HaCaT cells. U73122, a phospholipase C antagonist, and 2-aminoethoxydiphenylborate, an inositol 1,4,5-trisphosphate receptor-sensitive Ca²⁺-release channel antagonist, decreased wound closure consistent with P2Y₂ receptor activation. Absence of extracellular or intracellular Ca²⁺ or inhibition of intracellular Ca²⁺-release also impaired wound closure.

SIGNIFICANCE

These data describe a novel autocrine signalling mechanism in which wound-mediated release of endogenous ATP in response to mechanical scratching of HaCaT cells activates P2Y₂ receptors to facilitate wound closure.

Enhancement of skin barrier and hydration-related molecules by protopanaxatriol in human keratinocytes

Background

Protopanaxatriol (PPT) is a secondary intestinal metabolite of ginsenoside in ginseng. Although the effects of PPT have been reported in various diseases including cancer, diabetes and inflammatory diseases, the skin protective effects of PPT are poorly understood.

Methods

HaCaT cells were treated with PPT in a dose-dependent manner. mRNA and protein levels which related to skin barrier and hydration were detected compared with retinol. Luciferase assay was performed to explore the relative signaling pathway. Western blot was conducted to confirm these pathways and excavated further signals.

Results

PPT enhanced the expression of filaggrin (FLG), transglutaminase (TGM)-1, claudin, occludin and hyaluronic acid synthase (HAS) −1, −2 and −3. The mRNA expression levels of FLG, TGM-1, HAS-1 and HAS-2 were suppressed under NF-κB inhibition. PPT significantly augmented NF-κB-luc activity and upregulated Src/AKT/NF-κB signaling. In addition, PPT also increased phosphorylation of the mitogen-activated protein kinases (MAPKs) ERK, JNK and p38 and upstream MAPK activators (MEK and MKK). Furthermore, transcriptional activity of AP-1 and CREB, which are downstream signaling targets of MAPK, was enhanced by PPT.

Conclusion

PPT improves skin barrier function and hydration through Src/AKT/NF-κB and MAPK signaling. Therefore, PPT may be a valuable component for cosmetics or treating skin disorders.

Inhibition of glycolysis by targeting lactate dehydrogenase A facilitates hyaluronan synthase 2 synthesis in synovial fibroblasts of temporomandibular joint osteoarthritis

OBJECTIVE

Although associations between dysregulated glucose metabolism and human rheumatoid arthritis have been reported, the disturbance and influence of glycolytic metabolism on temporomandibular joint osteoarthritis remains unclear. This study aimed to investigate the expression level and metabolite profile of the critical glycolytic enzyme, lactate dehydrogenase A (LDHA) in synovial fibroblasts (SFs) of TMJOA, assess the effect of glycolytic inhibition on synthesis of hyaluronan synthase 2 (HAS2) and inflammation progression in these cells.

METHODS

Immunohistochemistry and western blotting were performed to detect the expression of LDHA in the lining and sub-lining layers of synovial tissue and SFs. MTT and EdU assays were used to measure the cell proliferation. The cell apoptosis were demonstrated by TUNEL staining and Annexin V/PI double staining. A potent and specific inhibitor of LDHA, GSK2837808A, was administrated to suppress the activity of LDHA and detect the potential efficacy on HAS2.

RESULTS

LDHA expression was dramatically higher in the synovial tissue and SFs from TMJOA patients compared to control groups. LDHA inhibition impaired active LDHA performance, suppressed the glucose uptake and decreased lactate concentration. Furthermore, GSK2837808A reversed the occurrence of low ratio of ATP/AMP, high level of Adenosine Monophosphate-activated Protein Kinase (AMPK) activation, disturbed HAS2 synthesis and hyaluronic acid (HA) production by inhibiting LDHA. The cellular viability and cell cycle were not affected by GSK2837808A at the working concentration.

CONCLUSIONS

Targeting LDHA using its specific suppressant GSK2837808A impeded lactate secretion and contributed to HAS2 and HA synthesis in TMJOA SFs, providing the vital role of LDHA associated with TMJOA pathogenesis and a novel therapeutic approach for TMJOA.

MSC-derived exosomes protect against oxidative stress-induced skin injury via adaptive regulation of the NRF2 defense system

Oxidative stress is a major cause of skin injury induced by damaging stimuli such as UV radiation. Currently, owing to their immunomodulatory properties, mesenchymal stem cell-derived exosomes (MSC-Exo), as a nanotherapeutic agent, have attracted considerable attention. Here, we investigated the therapeutic effects of MSC-Exo on oxidative injury in H₂O₂-stimulated epidermal keratinocytes and UV-irradiated wild type and nuclear factor-erythroid 2-related factor-2 (Nrf2) knocked down cell and animal models. Our findings showed that MSC-Exo treatment reduced reactive oxygen species generation, DNA damage, aberrant calcium signaling, and mitochondrial changes in H₂O₂-stimulated keratinocytes or UV-irradiated mice skin. Exosome therapy also improved antioxidant capacities shown by increased ferric ion reducing antioxidant power and glutathione peroxidase or superoxide dismutase activities in oxidative stress-induced cell and skin injury. In addition, it alleviated cellular and histological responses to inflammation and oxidation in cell or animal models. Furthermore, the NRF2 signaling pathway was involved in the antioxidation activity of MSC-Exo, while Nrf2 knockdown attenuated the antioxidant capacities of MSC-Exo in vitro and in vivo, suggesting that these effects are partially mediated by the NRF2 signaling pathway. These results indicate that MSC-Exo can repair oxidative stress-induced skin injury via adaptive regulation of the NRF2 defense system. Thus, MSC-Exo may be used as a potential dermatological nanotherapeutic agent for treating oxidative stress-induced skin diseases or disorders.

Mycosporine-like amino acids stimulate hyaluronan secretion by up-regulating hyaluronan synthase 2 via activation of the p38/MSK1/CREB/c-Fos/AP-1 axis

Hyaluronan (HA) is an extracellular matrix glycosaminoglycan that critically supports the physicochemical and mechanical properties of the skin. Here, we demonstrate that mycosporine-like amino acids (MAAs), which typically function as UV-absorbing compounds, can stimulate HA secretion from normal human fibroblasts. MAA-stimulated HA secretion was associated with significantly increased and decreased levels of mRNAs encoding HA synthase 2 (HAS2) and the HA-binding protein involved in HA depolymerization (designated HYBID), respectively. Using immunoblotting, we found that MAAs at 10 and at 25 μg/ml stimulate the phosphorylation of the mitogen-activated protein kinase (MAPK) p38, extracellular signal-regulated kinase (ERK)/c-Jun, and mitogen- and stress-activated protein kinase 1 (MSK1) (at Thr-581, Ser-360, and Ser-376, respectively) and activation of cAMP-responsive element-binding protein (CREB) and activating transcription factor 2 (ATF2), but not phosphorylation of JUN N-terminal kinase (JNK) or NF-κB (at Ser-276 or Ser-536, respectively), and increased c-Fos protein levels. Moreover, a p38-specific inhibitor, but not inhibitors of MAPK/ERK kinase (MEK), JNK, or NF-κB, significantly abrogated the increased expression of HAS2 mRNA, accompanied by significantly decreased MAA-stimulated HA secretion. These results suggested that the p38-MSK1-CREB-c-Fos-transcription factor AP-1 (AP-1) or the p38-ATF2 signaling cascade is responsible for the MAA-induced stimulation of HAS2 gene expression. Of note, siRNA-mediated ATF2 silencing failed to abrogate MAA-stimulated HAS2 expression, and c-Fos silencing abolished the increased expression of HAS2 mRNA. Our findings suggest that MAAs stimulate HA secretion by up-regulating HAS2 mRNA levels through activation of an intracellular signaling cascade consisting of p38, MSK1, CREB, c-Fos, and AP-1.

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.

Immunotherapy: breaching the barriers for cancer treatment

The great ambition to treat cancer through harnessing a patient's own immune responses has started to become reality. Clinical trials have shown impressive results and some patients reaching the end of existing treatment options have achieved full remission. Yet the response rate even within the most promising trials remain at just 30-40% of patients. To date, the focus of immunotherapy research has been to identify tumour antigens, and to enhance activation of effector lymphocytes. Yet this is only the first step to effective immunotherapy for a broader range of patients. Activated cytotoxic T cells can only act on their tumour cell targets if they have free and easy access to all tumour regions. Solid tumours are complex, heterogeneous environments which vary greatly in their physical properties. We must now focus our efforts on understanding how factors such as the composition, density and geometry of tumour extracellular matrix acts to impede or promote immune cell infiltration and activation, and work to design novel pharmacological interventions which restore and enhance leucocyte trafficking within solid tumours. This article is part of a discussion meeting issue 'Forces in cancer: interdisciplinary approaches in tumour mechanobiology'.

Effects of mutations in the post-translational modification sites on the trafficking of hyaluronan synthase 2 (HAS2)

Vesicular trafficking of hyaluronan synthases (HAS1-3) from endoplasmic reticulum (ER) through Golgi to plasma membrane (PM), and either back to endosomes and lysosomes, or out into extracellular vesicles, is important for their activities. We studied how post-translational modifications affect the trafficking of HAS2 by mutagenesis of the sites of ubiquitination (K190R), phosphorylation (T110A) and O-GlcNAcylation (S221A), using Dendra2- and EGFP-HAS2 transfected into COS1 cells. Confocal microscopy showed HAS2 wild type (wt) and its K190R and S221A mutants in ER, Golgi and extracellular vesicles, while the T110A mutant remained mostly in the ER. HA synthesis was reduced by S221A, while completely blocked by K190R and T110A. Cell-surface biotinylation indicated that T110A was absent from PM, while S221A was close to the level of wt, and K190R was increased in PM. TIRF microscopy analysis gave similar results. Rab10 silencing increased HA secretion by HAS2, likely by inhibiting endocytosis of the enzyme from PM, as reported before for HAS3. Green-to-red photo-conversion of Dendra2-HAS2 constructs suggested slower decay of K190R and S221A than HAS2 wt, while T110A was barely degraded at all. S221D and S221E, the phosphomimetic mutants of this site, decayed faster and blocked hyaluronan synthesis, suggesting alternative O-GlcNAc/-PO₄ substitution to regulate the stability of the enzyme. Probing the role of dynamic O-GlcNAcylation at S221 by adding glucosamine increased the half-life of only HAS2 wt. The Dendra2·HAS2 disappearance from Golgi was slower for K190R. Of the two inactive constructs, K190R co-transfected with HAS2 wt suppressed, whereas T110A had no effect on HA synthesis. Interestingly, the HAS2-stimulated shedding of extracellular vesicles was dependent on HAS residence in PM but independent of HA synthesis. The results indicate that post-translational modifications control the trafficking of HAS2, and that trafficking is an integral part of the post-translational regulation of HAS2 activity.