Potential antipsoriatic effect of chondroitin sulfate through inhibition of NF-κB and STAT3 in human keratinocytes

Molecular mechanisms and potential applications of chondroitin sulphate in managing post-traumatic osteoarthritis

Post-traumatic osteoarthritis (PTOA), a disorder of the synovium, subchondral bone, and cartilage that affects the entire joint, constitutes approximately 12% of all cases of symptomatic osteoarthritis. This review summarizes the pathogenetic mechanisms that underlie the positive influence of chondroitin sulphates (CSs) on PTOA as means of preventive and therapeutic treatment. Mechanisms of PTOA development involve chondrocytes undergoing various forms of cell death (apoptosis, pyroptosis, necroptosis, ferroptosis and/or necrosis). Chondroitin sulphates are a class of glycosaminoglycans that improve the structure and function of cartilage and subchondral bone, which is associated with their ability to decrease the activation of NF-κB and p38 MAPK, and up-regulate Nrf2. Standardized small fish extract (SSFE) is an example of the drugs that can attenuate NF-κB-mediated systemic inflammation, potentially helping to reduce joint inflammation and cartilage degradation, improve joint function, and alleviate pain and disability in patients with these conditions.

Dual targeting of mTOR/IL-17A and autophagy by fisetin alleviates psoriasis-like skin inflammation

Psoriasis is a chronic autoimmune inflammatory skin disorder characterized by epidermal hyperplasia and aberrant immune response. In addition to aberrant cytokine production, psoriasis is associated with activation of the Akt/mTOR pathway. mTOR/S6K1 regulates T-lymphocyte activation and migration, keratinocytes proliferation and is upregulated in psoriatic lesions. Several drugs that target Th1/Th17 cytokines or their receptors have been approved for treating psoriasis in humans with variable results necessitating improved therapies. Fisetin, a natural dietary polyphenol with anti-oxidant and anti-proliferative properties, covalently binds mTOR/S6K1. The effects of fisetin on psoriasis and its underlying mechanisms have not been clearly defined. Here, we evaluated the immunomodulatory effects of fisetin on Th1/Th17-cytokine-activated adult human epidermal keratinocytes (HEKa) and anti-CD3/CD28-stimulated inflammatory CD4+ T cells and compared these activities with those of rapamycin (an mTOR inhibitor). Transcriptomic analysis of HEKa revealed 12,713 differentially expressed genes (DEGs) in the fisetin-treated group compared to 7,374 DEGs in the rapamycin-treated group, both individually compared to a cytokine treated group. Gene ontology analysis revealed enriched functional groups related to PI3K/Akt/mTOR signaling pathways, psoriasis, and epidermal development. Using in silico molecular modeling, we observed a high binding affinity of fisetin to IL-17A. In vitro, fisetin significantly inhibited mTOR activity, increased the expression of autophagy markers LC3A/B and Atg5 in HEKa cells and suppressed the secretion of IL-17A by activated CD4+ T lymphocytes or T lymphocytes co-cultured with HEKa. Topical administration of fisetin in an imiquimod (IMQ)-induced mouse psoriasis model exhibited a better effect than rapamycin in reducing psoriasis-like inflammation and Akt/mTOR phosphorylation and promoting keratinocyte differentiation and autophagy in mice skin lesions. Fisetin also significantly inhibited T-lymphocytes and F4/80+ macrophage infiltration into skin. We conclude that fisetin potently inhibits IL-17A and the Akt/mTOR pathway and promotes keratinocyte differentiation and autophagy to alleviate IMQ-induced psoriasis-like disease in mice. Altogether, our findings suggest fisetin as a potential treatment for psoriasis and possibly other inflammatory skin diseases.

Effects of alginate/chondroitin sulfate-based hydrogels on bone defects healing

Repairing bone defects remains challenging in orthopedics. Here, strontium (Sr) alginate hydrogels containing chondroitin sulfate (CS) were fabricated for enhancing bone defects repair. The effects of CS incorporation ratio on the morphology, structure, thermal stability, water uptake and mechanical performance of Sr-CS/alginate hydrogels were also evaluated. Increasing CS incorporation ratio, Sr-CS/alginate hydrogels exhibit decreasing mechanical properties and lower water retention capacity. In vitro results suggest that Sr-CS/alginate hydrogels with higher CS ratio facilitate the proliferation of osteoblasts. Additionally, the osteogenic genes expressions were investigated by real-time quantitative polymerase chain reaction (RT-qPCR). The results reveal that Sr-CS/alginate hydrogels should have positive effects on modulating the osteogenic factors. Moreover, by employing repair femoral cylindrical defects rabbit model, the efficiency of as-fabricated Sr-CS/alginate hydrogels in bone regeneration was evaluated. The animal study suggests that Sr-CS/alginate hydrogel could significantly facilitate bone defects repair and therefore should potentially be useful for osteochondral tissue engineering.

STAT3 speeds up progression of osteoarthritis through NF-κB signaling pathway

Osteoarthritis (OA) is the most common motor system disease in the elderly, with a high incidence and a huge social and economic burden. Therefore, it is urgent to study its potential pathogenesis to improve the therapeutic effect of the disease. In this study, we constructed a number of regulator-mediated OA dysfunction modules, and carried out in-depth analysis in order to examine the disease development process. Differential expression analysis, co-expression analysis and enrichment analysis were combined to screen genes related to disease progression. Subsequently, key regulatory factors in the process of OA were identified based on the pivotal regulators that may manipulate important parts of the module subnetwork. A total of 16 OA dysfunction modules were obtained, involving the aggregation of 3,239 module genes. Then, enrichment analysis showed that module genes were significantly involved in apoptosis, inflammation-related functions and signaling pathways. Finally, we revealed a series of regulators, including 842 ncRNA (miR-132-3p, miR-130a-3p and miR-590-3p), 59 transcription factors (NFKB1, RELA and STAT3). We consider that STAT3 is the core transcription factor and promotes the development of OA through the signal of NF-κB. Overall, our results provide biologists and pharmacists with a new way of thinking to reveal the disease process of OA, and provide a wider range of candidate targets for follow-up research.

The dual role of the glycosaminoglycan chondroitin-6-sulfate in the development, progression and metastasis of cancer

The remarkable structural heterogeneity of chondroitin sulfate (CS) and dermatan sulfate (DS) generates biological information that can be unique to each of these glycosaminoglycans (GAGs), and changes in their composition are translated into alterations in the binding profiles of these molecules. CS/DS can bind to various cytokines and growth factors, cell surface receptors, adhesion molecules, enzymes and fibrillar glycoproteins of the extracellular matrix, thereby influencing both cell behavior and the biomechanical and biochemical properties of the matrix. In this review, we summarize the current knowledge concerning CS/DS metabolism in the human cancer stroma. The remodeling of the GAG profile in the tumor niche is manifested as a substantial increase in the CS content and a gradual decrease in the proportion between DS and CS. Furthermore, the composition of CS and DS is also affected, which results in a substantial increase in the 6‐O‐sulfated and/or unsulfated disaccharide content, which is concomitant with a decrease in the 4‐O‐sulfation level. Here, we discuss the possible impact of alterations in the CS/DS sulfation pattern on the binding capacity and specificity of these GAGs. Moreover, we propose potential consequences of the stromal accumulation of chondroitin‐6‐sulfate for the progression and metastasis of cancer.

Chondroitin sulfate inhibits secretion of TNF and CXCL8 from human mast cells stimulated by IL-33

Glycosaminoglycans (GAGs) are linear, highly negatively charged carbohydrate chains present in connective tissues. Chondroitin sulfate (CS) and heparin (Hep) are also found in the numerous secretory granules of mast cells (MC), tissue immune cells involved in allergic and inflammatory reactions. CS and Hep may inhibit secretion of histamine from rat connective tissue MC, but their effect on human MC remains unknown. Human LAD2 MC were pre-incubated with CS, Hep, or dermatan sulfate (DS) before being stimulated by either the peptide substance P (SP, 2 μM) or the cytokine IL-33 (10 ng/mL). Preincubation with CS had no effect on MC degranulation stimulated by SP, but inhibited TNF (60%) and CXCL8 (45%) secretion from LAD2 cells stimulated by IL-33. Fluorescein-conjugated CS (CS-F) was internalized by LAD2 cells only at 37 °C, but not 4 °C, indicating it occurred by endocytosis. DS and Hep inhibited IL-33-stimulated secretion of TNF and CXCL8 to a similar extent as CS. None of the GAGs tested inhibited IL-33-stimulated gene expression of either TNF or CXCL8. There was no effect of CS on ionomycin-stimulated calcium influx. There was also no effect of CS on surface expression of the IL-33 receptor, ST2. Neutralization of the hyaluronan receptor CD44 did not affect the internalization of CS-F. The findings in this article show that CS inhibits secretion of TNF and CXCL8 from human cultured MC stimulated by IL-33. CS could be formulated for systemic or topical treatment of allergic or inflammatory diseases, such as atopic dermatitis, cutaneous mastocytosis, and psoriasis. © 2018 BioFactors, 45(1):49-61, 2019.

Glucosamine and Chondroitin Sulfate: What Has Been Learned Since the Glucosamine/chondroitin Arthritis Intervention Trial

Glucosamine and chondroitin sulfate, alone or in combination, are used worldwide by individuals suffering from osteoarthritis pain. They are by prescription in some countries but are available as over-the-counter dietary supplements in other countries, such as the United States. The inconclusive results of the National Institutes of Health-sponsored Glucosamine/chondroitin Arthritis Intervention Trial (GAIT) did little to clarify the efficacy of these agents. However, some newer studies have provided a better perspective on the potential benefits that they can offer. Because the 2 in combination showed a significant level of efficacy in the moderate-to-severe knee osteoarthritis subgroup of the GAIT, this review examines the randomized, controlled trials published from that time to the present. The findings of these studies are mixed, owing in some cases to the high rate of placebo response added to by the ethical incorporation of rescue analgesics into protocols designed to evaluate the slow-acting, subtle effects of glucosamine and chondroitin sulfate in combination. The strong influence of the placebo effect and confounding of results by rescue analgesics point to the importance of objective measurement tools such as osteoarthritis biomarker panels in long-term glucosamine/chondroitin sulfate clinical trials with less reliance on the subjective measurement tools commonly used in osteoarthritis trials of pharmaceuticals. [Orthopedics. 2018; 41(4):200-207.].

ITK and RLK Inhibitor PRN694 Improves Skin Disease in Two Mouse Models of Psoriasis

The chronic and highly prevalent skin disorder psoriasis vulgaris is characterized by a hyperproliferative epidermis and aberrant immune activity. Many studies have highlighted the role of differentiated T lymphocytes in psoriasis progression. Several biologics are currently available that target proinflammatory cytokines produced by T lymphocytes, but the need for improved therapies persists. The small molecule PRN694 covalently binds ITK and RLK, two Tec kinases activated downstream of T-lymphocyte activation, both of which are up-regulated in psoriatic skin. These Tec kinases are involved in signaling cascades mediating T-lymphocyte proliferation, differentiation, and migration and proinflammatory cytokine production. In vitro analysis showed that PRN694 effectively inhibited IL-17A production from murine T helper type 17-differentiated T lymphocytes. Additionally, PRN694 effectively reduced the psoriasis-like phenotype severity and reduced epidermal proliferation and thickness in both the Rac1^V12 and imiquimod mouse models of psoriasis. PRN694 also inhibited CD3⁺ T-cell and γδ T-cell infiltration into skin regions. Inhibition of ITK and RLK attenuated psoriasis-associated signaling pathways, indicating that PRN694 is an effective psoriasis therapeutic.

Chondroitin sulphate inhibits NF-κB activity induced by interaction of pathogenic and damage associated molecules

OBJECTIVE

To evaluate the anti-inflammatory mechanism of action of Chondroitin Sulphate (CS).

DESIGN

THP-1 macrophages were cultured with a range of sizes and concentrations of HA fragments with TLR4 (LPS in a physiologically relevant concentration determined by analyses of sera of a community clinic ascertained knee osteoarthritis (OA) cohort) or TLR2 (heat killed listeria bacteria) agonists and varying concentrations of CS in a physiologically relevant range (10-200 μg/ml). We measured IL-1β release, intracellular IL-1β, proIL-1β, caspase-1 and NF-κB activity and DNA binding activity of NF-κB transcription factors from nuclear and cytoplasmic extracts.

RESULTS

Serum LPS was significantly associated with radiographic knee joint space narrowing (JSN) (P = 0.02) in the OA cohort (n = 40). The priming dose of LPS used for these experiments (10 ng/ml) was below the lowest serum concentration of the OA cohort (median 47.09, range 14.43-81.36 ng/ml). Priming doses of LPS and HA fragments alone did not elicit an inflammatory response. However, primed with LPS, HA fragments produced large dose-dependent increases in IL-1β that were inhibitable by CS. CS did not inhibit caspase-1 activity but in physiologically achievable concentrations, attenuated NF-κB activity induced by either the TLR4 (LPS 1000 ng/ml) or TLR2 agonists alone or in combination with HA fragments. LPS induced and CS significantly reduced activity of canonical NF-κB transcription factors, p65, p50, c-Rel and RelB.

CONCLUSIONS

Subinflammatory concentrations of pathogenic (LPS, listeria) and damage associated (HA) molecules interact to induce macrophage-related inflammation. CS works upstream of the inflammasome by inhibiting activation of NF-κB transcription factors.

Intermolecular disulfide bond influences unphosphorylated STAT3 dimerization and function

Signal transducer and activator of transcription 3 (STAT3) is a transcription factor activated by the phosphorylation of tyrosine 705 in response to many cytokines and growth factors. Recently, the roles for unphosphorylated STAT3 (U-STAT3) have been described in response to cytokine stimulation, in cancers, and in the maintenance of heterochromatin stability. It has been reported that U-STAT3 dimerizes, shuttles between the cytoplasm and nucleus, and binds to DNA, thereby driving genes transcription. Although many reports describe the active role of U-STAT3 in oncogenesis in addition to phosphorylated STAT3, the U-STAT3 functional pathway remains elusive.In this report, we describe the molecular mechanism of U-STAT3 dimerization, and we identify the presence of two intermolecular disulfide bridges between Cys367 and Cys542 and Cys418 and Cys426, respectively. Recently, we reported that the same cysteines contribute to the redox regulation of STAT3 signaling pathway both in vitro and in vivo The presence of these disulfides is here demonstrated to largely contribute to the structure and the stability of U-STAT3 dimer as the dimeric form rapidly dissociates upon reduction in the S-S bonds. In particular, the Cys367-Cys542 disulfide bridge is shown to be critical for U-STAT3 DNA-binding activity. Mutation of the two Cys residues completely abolishes the DNA-binding capability of U-STAT3. Spectroscopic investigations confirm that the noncovalent interactions are sufficient for proper folding and dimer formation, but that the interchain disulfide bonds are crucial to preserve the functional dimer. Finally, we propose a reaction scheme of U-STAT3 dimerization with a first common step followed by stabilization through the formation of interchain disulfide bonds.

Portulaca oleracea L. aids calcipotriol in reversing keratinocyte differentiation and skin barrier dysfunction in psoriasis through inhibition of the nuclear factor κB signaling pathway

Psoriasis affects 2-4% of the population worldwide and its treatment is currently far from satisfactory. Calcipotriol and Portulaca oleracea have been reported to exhibit the capacity to inhibit inflammation in psoriatic patients and improve their clinical condition. However, the efficacy of a combination regimen of these two components remains unknown. The aim of the present study was to explore the therapeutic efficacy of P. oleracea extract combined with calcipotriol on plaque psoriasis and its potential mechanism. Eleven patients with plaque psoriasis were treated with humectant containing the active ingredients of P. oleracea extract, with or without 0.005% calcipotriol ointment in a right-left bilateral lesion self-control study. Differences were evaluated by investigation of the clinical efficacy, adverse effects, skin barrier function, histological structure, expression and proliferation of keratinocytes, differentiation markers (cytokeratin 10, filaggrin and loricrin), inflammatory factors [tumor necrosis factor (TNF)-α and interleukin (IL)-8], as well as the status of the nuclear factor κB (NF-κB) pathway. The combination of P. oleracea and calcipotriol was revealed to decrease adverse effects, reduce transepidermal water loss, potently reverse keratinocyte differentiation dysfunction, and inhibit the expression of TNF-α and IL-8 and the phosphorylation of the NF-κB inhibitor IκBα. This treatment is therefore anticipated to be suitable for use as a novel adjuvant therapy for psoriatic patients.

S-Glutathionylation at Cys328 and Cys542 impairs STAT3 phosphorylation

STAT3 is a latent transcription factor that promotes cell survival and proliferation and is often constitutively active in cancers. Although many reports provide evidence that STAT3 is a direct target of oxidative stress, its redox regulation is poorly understood. Under oxidative conditions STAT3 activity can be modulated by S-glutathionylation, a reversible redox modification of cysteine residues. This suggests the possible cross-talk between phosphorylation and glutathionylation and points out that STAT3 is susceptible to redox regulation. Recently, we reported that decreasing the GSH content in different cell lines induces inhibition of STAT3 activity through the reversible oxidation of thiol groups. In the present work, we demonstrate that GSH/diamide treatment induces S-glutathionylation of STAT3 in the recombinant purified form. This effect was completely reversed by treatment with the reducing agent dithiothreitol, indicating that S-glutathionylation of STAT3 was related to formation of protein-mixed disulfides. Moreover, addition of the bulky negatively charged GSH moiety impairs JAK2-mediated STAT3 phosphorylation, very likely interfering with tyrosine accessibility and thus affecting protein structure and function. Mass mapping analysis identifies two glutathionylated cysteine residues, Cys328 and Cys542, within the DNA-binding domain and the linker domain, respectively. Site direct mutagenesis and in vitro kinase assay confirm the importance of both cysteine residues in the complex redox regulatory mechanism of STAT3. Cells expressing mutant were resistant in this regard. The data presented herein confirmed the occurrence of a redox-dependent regulation of STAT3, identified the more redox-sensitive cysteines within STAT3 structure, and may have important implications for development of new drugs.

NF-κB and STAT3 inhibition as a therapeutic strategy in psoriasis: in vitro and in vivo effects of BTH

Benzo[b]thiophen-2-yl-3-bromo-5-hydroxy-5H-furan-2-one (BTH) is a simple and interesting synthetic derivative of petrosaspongiolide M, a natural compound isolated from a sea sponge with demonstrated potent anti-inflammatory activity through inhibition of the NF-κB signaling pathway. In the present study, we report the in vitro and in vivo pharmacological effect of BTH on some parameters related to the innate and adaptive response in the pathogenesis of psoriasis. BTH inhibited the release of some of the key psoriatic cytokines such as tumor necrosis factor α, IL-8, IL-6, and CCL27 through the downregulation of NF-κB in normal human keratinocytes. Moreover, it impaired signal transducers and activators of transcription 3 (STAT3) phosphorylation and translocation to the nucleus, which resulted in decreased keratinocyte proliferation. These results were confirmed in vivo in two murine models of psoriasis: the epidermal hyperplasia induced by 12-O-tetradecanoylphorbol-13-acetate and the imiquimod-induced skin inflammation model. In both cases, topical administration of BTH prevented skin infiltration and hyperplasia through suppression of NF-κB and STAT3 phosphorylation. Our results confirm the pivotal role of both transcriptional factors in skin inflammation, as occurs in psoriasis, and highlight the potential of small molecules as therapeutic agents for the treatment of this skin disease, with BTH being a potential candidate for future drug research.