Sargaquinoic acid attenuates inflammatory responses by regulating NF-κB and Nrf2 pathways in lipopolysaccharide-stimulated RAW 264.7 cells

Exploring the pathophysiological influence of heme oxygenase-1 on neuroinflammation and depression: A study of phytotherapeutic-based modulation

BACKGROUND

The heme oxygenase (HO) system plays a significant role in neuroprotection and reduction of neuroinflammation and neurodegeneration. The system, via isoforms HO-1 and HO-2, regulates cellular redox balance. HO-1, an antioxidant defense enzyme, is highlighted due to its association with depression, characterized by heightened neuroinflammation and impaired oxidative stress responses.

METHODOLOGY

We observed the pathophysiology of HO-1 and phytochemicals as its modulator. We explored Science Direct, Scopus, and PubMed for a comprehensive literature review. Bibliometric and temporal trend analysis were done using VOSviewer.

RESULTS

Several phytochemicals can potentially alleviate neuroinflammation and oxidative stress-induced depressive symptoms. These effects result from inhibiting the MAPK and NK-κB pathways - both implicated in the overproduction of pro-inflammatory factors - and from the upregulation of HO-1 expression mediated by Nrf2. Bibliometric and temporal trend analysis further validates these associations.

CONCLUSION

In summary, our findings suggest that antidepressant agents can mitigate neuroinflammation and depressive disorder pathogenesis via the upregulation of HO-1 expression. These agents suppress pro-inflammatory mediators and depressive-like symptoms, demonstrating that HO-1 plays a significant role in the neuroinflammatory process and the development of depression.

QM/MM Study of the Catalytic Mechanism and Substrate Specificity of the Aromatic Substrate C-Methyltransferase Fur6

In the field of medical chemistry and other organic chemistry, introducing a methyl group into a designed position has been difficult to achieve. However, owing to the vigorous developments in the field of enzymology, methyltransferases are considered potential tools for addressing this problem. Within the methyltransferase family, Fur6 catalyzes the methylation of C3 of 1,2,4,5,7-pentahydroxynaphthalene (PHN) using S-adenosyl-l-methionine (SAM) as the methyl donor. Here, we report the catalytic mechanism and substrate specificity of Fur6 based on computational studies. Our molecular dynamics (MD) simulation studies reveal the reactive form of PHN and its interactions with the enzyme. Our hybrid quantum mechanics/molecular mechanics (QM/MM) calculations suggest the reaction pathway of the methyl transfer step in which the energy barrier is 8.6 kcal mol-1. Our free-energy calculations with a polarizable continuum model (PCM) indicate that the final deprotonation step of the methylated intermediate occurs after it is ejected into the water solvent from the active center pocket of Fur6. Additionally, our studies on the protonation states, the highest occupied molecular orbital (HOMOs), and the energy barriers of the methylation reaction for the analogs of PHN demonstrate the mechanism of the specificity to PHN. Our study provides valuable insights into Fur6 chemistry, contributing to a deeper understanding of molecular mechanisms and offering an opportunity to engineer the enzyme to achieve high yields of the desired product(s).

Sargachromenol Attenuates Inflammatory Responses by Regulating NF-κB and Nrf2 Pathways in RAW 264.7 Cells and LPS-treated Mice

This study aims to explore the anti-inflammatory mechanisms of sargachromenol in both RAW 264.7 cells and lipopolysaccharide (LPS)-treated mice, as previous reports have suggested that sargachromenol possesses anti-aging, anti-inflammatory, antioxidant, and neuroprotective properties. Although the precise mechanism behind its anti-inflammatory activity remains unclear, pretreatment with sargachromenol effectively reduced the production of nitric oxide, prostaglandin E2, and interleukin (IL)-1β in LPS-stimulated RAW 264.7 cells by inhibiting cyclooxygenase-2. Moreover, sargachromenol inhibited the activation of nuclear factor-κB (NF-κB) by preventing the degradation of the inhibitor of κB-α (IκB-α) and inhibiting protein kinase B (Akt) phosphorylation in LPS-stimulated cells. We also found that sargachromenol induced the production of heme oxygenase-1 (HO-1) by activating the nuclear transcription factor erythroid-2-related factor 2 (Nrf2). In LPS-treated mice, oral administration of sargachromenol effectively reduced the levels of IL-1β, IL-6, and tumor necrosis factor-α (TNF-α) in the serum, suggesting its ability to suppress the production of inflammatory mediators by inhibiting the Akt/NF-κB pathway and upregulating the Nrf2/HO-1 pathway.

Chlorogenic Acid Alleviates LPS-Induced Inflammation and Oxidative Stress by Modulating CD36/AMPK/PGC-1α in RAW264.7 Macrophages

Chlorogenic acid (CGA) is a bioactive substance with anti-inflammatory activities. Clusters of CD36 have been suggested to be widely involved in inflammatory damage. However, the mechanism of CGA protecting against LPS-induced inflammation involving the CD36 regulation is unclear. Here, we demonstrated that CGA protected against LPS-induced cell death and decreased the production of ROS. Moreover, the SOD, CAT, and GSH-Px activities were also upregulated in CGA-treated cells during LPS stimulation. CGA reduced COX-2 and iNOS expression and IL-1β, IL-6, and TNF-α secretion in LPS-stimulated RAW264.7 macrophages. In addition, CGA treatment widely involved in immune-related signaling pathways, including NF-κB signaling, NOD-like receptor signaling, and IL-17 signaling using transcriptomic analysis and CD36 also markedly reduced during CGA pretreatment in LPS-induced RAW264.7 cells. Furthermore, the CD36 inhibitor SSO attenuated inflammation and oxidative stress by enabling activation of the AMPK/PGC-1α cascade. These results indicate that CGA might provide benefits for the regulation of inflammatory diseases by modulating CD36/AMPK/PGC-1α to alleviate oxidative stress.

Structural diversity, biosynthesis, and health-promoting properties of brown algal meroditerpenoids

Marine algae that constitute hundreds of millions of tons of biomass are the oldest representatives of the plant kingdom. Recently, there has been growing interest in the utilization of algae as sustainable feedstocks for natural products with an economic value. Among these natural products are the meroditerpenoids, which are renowned for their protective effects against oxidative stress, inflammation, cancer, obesity, diabetes, and neurodegenerative disorders. Meroditerpenoids have a mixed biosynthetic origin and display a wide range of structural diversity. Their basic structure consists of a ring system bearing a diterpenoid side chain. Structural variations are observed in terms of the functional groups and saturation/cyclization of the diterpenoid side chain. This review classifies algal meroditerpenoids as plastoquinones, chromanols, chromenes, chromones, cyclic meroditerpenoids, nahocols, and isonahocols and examines their potential applications in functional foods and biopharmacology. Their lipid solubility, low molecular weight, and propensity to cross the blood-brain barrier places meroditerpenoids as potential drug candidates. There is growing interest in the study of algal meroterpenoids, and recent research has reported the structure of several new meroterpenoids and their biological activities. Further research is needed to extend the use of algal meroditerpenoids in preclinical trials. Understanding the mechanism of their biosynthesis will allow the development of de novo biosynthesis and biomimetic synthesis strategies for the industrial-scale production of meroditerpenoids and their synthetic derivatives to aid pharmaceutical research. This review is the first to summarize up-to-date information on all brown algae-derived meroditerpenoids.

Potential Beneficial Effects of Sargassum spp. in Skin Aging

Seaweeds are receiving much attention as a rich source of bioactive compounds with cosmeceutical potential. Recent studies have revealed that Sargassum spp., a genus of brown algae in the family Sargassaceae, has multiple functions in preventing and improving skin aging. Sargassum spp. contains many bioactive compounds, such as fucoidan, fucoxanthin, terpenoids, flavonoids, and meroterpenoids. These Sargassum spp. extracts and derivative compounds have excellent potential for skincare, as they exhibit skin health-promoting properties, including antioxidants, anti-inflammation, whitening, skin barrier repair, and moisturizing. Therefore, searching for bioactive compounds in marine resources such as Sargassum spp. could be an attractive approach to preventing and improving skin aging. The current review focused on the various biological abilities of Sargassum extracts or derived compounds for anti-skin aging.

Meroterpenoid-Rich Ethanoic Extract of Sargassum macrocarpum Ameliorates Dextran Sulfate Sodium-Induced Colitis in Mice

Colitis is a colon mucosal disorder characterized by intestinal damage and inflammation. This current study aimed to evaluate the effect of meroterpenoid-rich ethanoic extract of a brown algae, Sargassum macrocarpum (MES) on dextran sulfate sodium (DSS)-induced colitis in mice and explore the possible mechanisms. Mice were given 4% DSS in drinking water for 7 days to induce colitis, followed by 3 days of regular water. MES (12 mg/kg body weight) or celecoxib (10 mg/kg body weight) was administrated orally to mice on a daily basis during these 10 days. Both MES and celecoxib supplementations significantly attenuated DSS-induced weight loss, shortening of colon length, elevated myeloperoxidase activity as well as histomorphological changes of colon. MES and celecoxib reduced the inflammation level of colon tissue, as indicated by its suppression on a panel of pro-inflammatory cytokines, including interleukin (IL)-1β, IL-17, tumor necrosis factor α, and interferon γ, and a group of inflammatory proteins, including intracellular adhesion molecule 1, vascular adhesion molecule 1, matrix metalloproteinase (MMP)-2, MMP-9, MMP-13, and inducible nitric oxidase. In addition, their administration down-regulated pro-inflammatory cytokines in serum. Moreover, the supplementation of MES suppressed the DSS-induced hyperactivation of Akt, JNK, and NF-κB signaling pathways. Taken together, our results demonstrate that MES ameliorates DSS-induced colitis in mice, suggesting that MES may have therapeutic implications for the treatment of colitis.

Sargahydroquinoic Acid, a Cyclooxygenase-2 Inhibitor, Attenuates Inflammatory Responses by Regulating NF-κB Inactivation and Nrf2 Activation in Lipopolysaccharide-Stimulated Cells

Sargahydroquinoic acid (SHQA) is a major plastoquinone in Sargassum macrocarpum and has shown the capacity to prevent inflammation and oxidative stress. However, the protective mechanisms were unclear. The molecular mechanisms of SHQA on ameliorating inflammation and oxidative stress have been investigated, using lipopolysaccharide (LPS)-stimulated macrophages. SHQA was isolated and purified from S. macrocarpum and the anti-inflammatory mechanisms were explored using LPS-stimulated murine macrophage RAW 264.7 cells. SHQA did not change the expression of cyclooxygenase-2 (COX-2) but inhibited the activity of COX-2. As a result, SHQA significantly diminished the secretions of nitric oxide (NO), prostaglandin E2 (PGE2), and multiple pro-inflammatory cytokines. LPS-induced activation of nuclear factor-κB (NF-κB) was inhibited by SHQA by preventing the degradation of inhibitor κB-α (IκBα). NF-κB activation was also downregulated by the inhibition of Akt phosphorylation in LPS-stimulated cells. Furthermore, SHQA induced the expression of heme oxygenase 1 via Nrf2 activation. These results indicated that SHQA inhibited LPS-induced expressions of inflammatory mediators via suppressing the Akt-mediated NF-κB pathway as well as upregulating the Nrf2/HO-1 pathway. Our findings suggest that SHQA might be a potential therapeutic agent in various inflammatory diseases.

Rhoifolin Alleviates Inflammation of Acute Inflammation Animal Models and LPS-Induced RAW264.7 Cells via IKKβ/NF-κB Signaling Pathway

Rhoifolin (ROF) is a main effective component in Citrus grandis 'Tomentosa'. ROF has a potential anti-inflammatory activity, but its specific effects and mechanisms have not been studied. This study investigated the anti-inflammatory activity of ROF and searched for its possible molecular mechanisms. A mouse model of acute inflammation was induced by lipopolysaccharide, and the effects of ROF on pathological damages of the lung and liver were observed. Carrageenan-induced paw edema rat model was used to evaluate the effect of ROF on the volume of swelling paw. In LPS-induced RAW264.7 macrophages, the expression levels of pro-inflammatory cytokines IL-1β, IL-6, and TNF-α were measured using ELISA. Real-time PCR was used to measure the mRNA levels of iNOS and CCL2. Western blot was used to detect the activation of IκBα and IKKβ in NF-κB signaling pathways. The results showed that ROF accelerated the recoveries of liver and lung tissue damages in acute inflammation mice and inhibited carrageenan-induced paw edema in rats; in addition, ROF significantly suppressed the secretion of TNF-α, IL-1β, and IL-6 in the serum of rats and mouse model. In LPS-induced RAW264.7 cells, 100 μmol/L ROF enhanced cell viability and suppressed the production of TNF-α, IL-6, and IL-1β significantly. ROF also decreased the mRNA expression of iNOS and CCL2 and inhibited IκBα and IKKβ phosphorylation. In summary, ROF had a potential therapeutic value for inflammation. Our research provided experimental basis for the further development of ROF as an anti-inflammatory drug and for clarifying the anti-inflammatory substance basis of Citrus grandis 'Tomentosa'. Graphical Abstract.

Diterpenoids Isolated from Podocarpus macrophyllus Inhibited the Inflammatory Mediators in LPS-Induced HT-29 and RAW 264.7 Cells

Species of Podocarpus are used traditionally in their native areas for the treatment of fevers, asthma, coughs, cholera, chest pain, arthritis, rheumatism, and sexually transmitted diseases. To identify natural products having efficacy against inflammatory bowel disease (IBD), we identified a new, 16-hydroxy-4β-carboxy-O-β-D-glucopyranosyl-19-nor-totarol (4) together with three known diterpenoids from P. macrophyllus. Furthermore, all the extracts, fractions, and isolates 1–4 were investigated for their anti-inflammatory effects by assessing the expression on nitric oxide (NO) production and proinflammatory cytokines in lipopolysaccharide (LPS)-stimulated RAW 264.7 and HT-29 cells. Among them, nagilactone B (2) exhibited a potent anti-inflammatory effect against NO production on RAW 264.7 cells; therefore, nagilactone B was further assessed for anti-inflammatory activity. Western blot analysis revealed that nagilactone B significantly decreased the expression of LPS-stimulated protein, inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2, and phosphorylated extracellular regulated kinase (pERK)1/2. In addition, nagilactone B downregulated tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-8 levels in LPS-induced macrophages and colonic epithelial cells. To our best knowledge, this is the first report on the inhibitory effect of nagilactone B (pure state) and rakanmakilactone G against NO production in LPS-stimulated RAW 264.7 cells. Thus, diterpenoids isolated from P. macrophyllus could be employed as potential therapeutic phytochemicals for IBD.

Meroterpenoids: A Comprehensive Update Insight on Structural Diversity and Biology

Meroterpenoids are secondary metabolites formed due to mixed biosynthetic pathways which are produced in part from a terpenoid co-substrate. These mixed biosynthetically hybrid compounds are widely produced by bacteria, algae, plants, and animals. Notably amazing chemical diversity is generated among meroterpenoids via a combination of terpenoid scaffolds with polyketides, alkaloids, phenols, and amino acids. This review deals with the isolation, chemical diversity, and biological effects of 452 new meroterpenoids reported from natural sources from January 2016 to December 2020. Most of the meroterpenoids possess antimicrobial, cytotoxic, antioxidant, anti-inflammatory, antiviral, enzyme inhibitory, and immunosupressive effects.

Glaucocalyxin A Attenuates Allergic Responses by Inhibiting Mast Cell Degranulation through p38MAPK/NrF2/HO-1 and HMGB1/TLR4/NF-κB Signaling Pathways

Glaucocalyxin A (GLA) has various pharmacological effects like antioxidation, immune regulation, and antiatherosclerosis. Here, in this study, the effect and mechanism of GLA on mast cell degranulation were studied. The results of the anti-DNP IgE-mediated passive cutaneous anaphylaxis (PCA) showed that GLA dramatically inhibited PCA in vivo, as evidenced by reduced Evans blue extravasation and decreased ear thickness. In addition, GLA significantly reduced the release of histamine and β-hexosaminidase, calcium influx, cytokine (IL-4, TNF-α, IL-1β, IL-13, and IL-8) production in the RBL-2H3 (rat basophilic leukemia cells), and RPMCs (peritoneal mast cells) in vitro. Moreover, we further investigated the regulatory mechanism of GLA on antigen-induced mast cells by Western blot, which showed that GLA inhibited FcεRI-mediated signal transduction and invalidated the phosphorylation of Syk, Fyn, Lyn, Gab2, and PLC-γ1. In addition, GLA inhibited the recombinant mouse high mobility group protein B1- (HMGB1-) induced mast cell degranulation through limiting nuclear translocation of NF-κBp65. Treatment of mast cells with siRNA-HMGB1 significantly inhibited HMGB1 levels, as well as MyD88 and TLR4, decreased intracellular calcium levels, and suppressed the release of β-hexosaminidase. Meanwhile, GLA increased NrF2 and HO-1 levels by activating p38MAPK phosphorylation. Consequently, these data suggest that GLA regulates the NrF2/HO-1 signaling pathway through p38MAPK phosphorylation and inhibits HMGB1/TLR4/NF-κB signaling pathway to reduce mast cell degranulation and allergic inflammation. Our findings could be used as a promising therapeutic drug against allergic inflammatory disease.

Potential Anti-Aging Substances Derived from Seaweeds

Aging is a major risk factor for many chronic diseases, such as cancer, cardiovascular disease, and diabetes. The exact mechanisms underlying the aging process are not fully elucidated. However, a growing body of evidence suggests that several pathways, such as sirtuin, AMP-activated protein kinase, insulin-like growth factor, autophagy, and nuclear factor erythroid 2-related factor 2 play critical roles in regulating aging. Furthermore, genetic or dietary interventions of these pathways can extend lifespan by delaying the aging process. Seaweeds are a food source rich in many nutrients, including fibers, polyunsaturated fatty acids, vitamins, minerals, and other bioactive compounds. The health benefits of seaweeds include, but are not limited to, antioxidant, anti-inflammatory, and anti-obese activities. Interestingly, a body of studies shows that some seaweed-derived extracts or isolated compounds, can modulate these aging-regulating pathways or even extend lifespans of various animal models. However, few such studies have been conducted on higher animals or even humans. In this review, we focused on potential anti-aging bioactive substances in seaweeds that have been studied in cells and animals mainly based on their anti-aging cellular and molecular mechanisms.

Pterostilbene Inhibits FcεRI Signaling through Activation of the LKB1/AMPK Pathway in Allergic Response

In this study, the role and mechanism of pterostilbene (Pts) in mast cell degranulation in vitro and in vivo were investigated. The results showed that Pts inhibited mast cell-mediated local passive allergic reactions in mice. In addition, treatment with Pts reduced both histamine release and calcium influx in rat peritoneal mast cells and RBL-2H3 cells and reduced IgE-mediated mast cell activation. Furthermore, the mechanism underlying Pts inhibition of mast cell signaling was probed via studying the effects of Pts on liver kinase B1 (LKB1), including the use of the LKB1 activator metformin and siRNA knockdown of LKB1. The data showed that Pts reduced the release of inflammatory mediators such as tumor necrosis factor-α, interleukin-6, leukotriene C4, and prostaglandin D2 in mast cells by activating the LKB1/adenosine monophosphate (AMP)-activated protein kinase (AMPK) signaling pathway. Furthermore, Pts inhibited phosphorylation of FcεRI and FcεRI-mediated degranulation in RBL-2H3 cells. These effects were attenuated after LKB1 knockdown. Taken together, Pts could inhibit FcεRI signaling through activation of the LKB1/AMPK signaling pathway in IgE-mediated mast cell activation. Thus, Pts might be an effective therapeutic agent for mast cell-mediated allergic diseases.

Evaluation of antioxidant activities of various solvent extract from Sargassum serratifolium and its major antioxidant components

Sargassum serratifolium has been known to contain a high level of meroterpenoids as antioxidant components. We investigated antioxidant activities and active components in various solvent extracts from S. serratifolium. Ethyl acetate, ethanol, and methanol extracts showed relatively strong DPPH, ABTs, and superoxide radical scavenging activities. Hexane and ethyl acetate extract showed the strongest hydroxyl radical and reactive oxygen species (ROS), respectively, scavenging activities. Sargahydroquinoic acid (SHQA), sargachromanol (SCM) and sargaquinoic acid (SQA) were main antioxidant components in S. serratifolium. Ethanol extract showed the highest levels of SHQA, SCM, and SQA which comprised to be 227 ± 6.31 mg/g. SHQA and SCM exhibited stronger antioxidant capacities than SQA based on lower IC50 values in ROS, DPPH, ABTs, and superoxide radical scavenging assays. The result showed that ethanol is the most efficient extracting solvent for the active components from S. serratifolium and the plant has the potential as a natural antioxidant.

Imperatorin Suppresses Anaphylactic Reaction and IgE-Mediated Allergic Responses by Inhibiting Multiple Steps of FceRI Signaling in Mast Cells: IMP Alleviates Allergic Responses in PCA

This study is to investigate the effects of imperatorin (IMP) on allergic responses mediated by mast cells, both in vitro and in vivo. Passive cutaneous anaphylaxis (PCA) model was established. Histological detection was performed to assess the ear histology. ELISA and Western blot analysis were used to detect the levels of corresponding cytokines and signalling pathway proteins. IMP decreased the leakage of Evans blue and the ear thickness in the PCA models, in a dose-dependent manner, and alleviated the degranulation of mast cells. Moreover, IMP reduced the expression of TNF-α, IL-4, IL-1β, IL-8, and IL-13. Furthermore, IMP inhibited the phosphorylation levels of Syk, Lyn, PLC-γ1, and Gab2, as well as the downstream MAPK, PI3K/AKT, and NF-κB signaling pathways. In addition, IMP inhibited the mast cell-mediated allergic responses through the Nrf2/HO-1 pathway. IMP attenuates the allergic responses through inhibiting the degranulation and decreasing the expression levels of proinflammatory cytokines in the mast cells, involving the PI3K/Akt, MAPK, NF-κB, and Nrf2/HO-1 pathways.

Anti-Arthritis Effect through the Anti-Inflammatory Effect of Sargassum muticum Extract in Collagen-Induced Arthritic (CIA) Mice

(1) Background: Rheumatoid arthritis is a chronic autoimmune disease that causes progressive articular damage and functional loss. It is characterized by synovial inflammation that leads to progressive cartilage destruction. For this reason, research on functional foods that reduce the inflammatory response are under progress. (2) Methods: We focused on the anti-inflammatory effects of Sargassum muticum, and confirmed the effect of the extract on the collagen-induced arthritis (CIA) DBA/1J mice model. (3) Results: The extract was given at concentrations of 50, 100, and 200 mg/kg, and the arthritis score and edema volume of the experimental group were significantly different from the CIA group. The level of interleukin (IL)-6, tumor necrosis factor (TNF)-α, and interferon (IFN)-γ were determined in serum and lymphocytes. The expression of these cytokines in the serum remarkably decreased from S. muticum extract (SME)100 mg/kg, and decreased from SME 200 mg/kg in lymphocytes. Also, immunohistochemical analysis of IL-6 and TNF-α in the joints revealed that the inflammatory response was noticeably lower when treated with S. muticum extract. (4) Conclusions: This study provides results of the experiment of S. muticum extract treatment in a mouse model. The treatment was found to contribute to the alleviation of edema and symptoms by reducing the expression of inflammatory cytokines. It was concluded that it may be a useful substance to help in the mitigation of arthritis symptoms.

Sargaquinoic acid ameliorates hyperpigmentation through cAMP and ERK-mediated downregulation of MITF in α-MSH-stimulated B16F10 cells

Hyperpigmentation disorders of the skin adversely influence the quality of life. We previously demonstrated the hypopigmenting properties of the ethanolic extract from Sargassum serratifolium and identified sargaquinoic acid (SQA) as an active component. The current study aims to investigate the hypopigmenting action of SQA in α-melanocyte stimulating hormone (α-MSH)-stimulated B16F10 cells. SQA attenuated cellular melanin synthesis by inhibiting the expression of the melanogenic enzymes, including tyrosinase (TYR), tyrosinase-related protein 1 (TRP1), and TRP2. SQA also inhibited cellular TYR activity in a dose-dependent manner. Reduced intracellular cAMP accumulation by SQA treatment resulted in the suppressed phosphorylation of cAMP-responsive element-binding protein (CREB), leading to the downregulation of microphthalmia-associated transcription factor (MITF) in α-MSH-stimulated B16F10 cells. SQA increased the phosphorylation of extracellular signal-regulated kinase (ERK)1/2 and MITF (Ser73), inducing proteasomal degradation of MITF. SQA showed high binding affinity to the cAMP binding domain of PKA; the direct binding of SQA to PKA may exert an additional inhibitory effect on the PKA-dependent CREB activation. Our data demonstrated that SQA suppressed melanin production through the cAMP/CREB- and ERK1/2-mediated downregulation of MITF in α-MSH-stimulated B16F10 cells and SQA has a potential therapeutic agent for the treatment of skin hyperpigmentation disorders.

Biflavonoids Isolated from Selaginella tamariscina and Their Anti-Inflammatory Activities via ERK 1/2 Signaling

Selaginella tamariscina (S. tamariscina) (Beauv.) Spring (Selaginellaceae) has been used in oriental medicine for the treatment of dysmenorrhea, chronic hepatitis, hyperglycemia, amenorrhea, hematuria, prolapse of the anus and metrorrhagia. In the present study, we isolated two strong anti-inflammatory compounds, the biflavonoids hinokiflavone (H) and 7′-O-methyl hinokiflavone (mH), from S. tamariscina and examined their anti-inflammatory activities in lipopolysaccharide (LPS)-mediated murine macrophages (RAW 264.7) and colon epithelial cells (HT-29). H and mH suppressed the production of the inflammatory mediators nitric oxide (NO), interleukin (IL)-6, IL-8, and tumor-necrosis factor (TNF)-α, which are most highly activated in inflammatory bowel disease (IBD). In addition, Western blot analysis revealed that H and mH suppressed the LPS-induced expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2, and the activation of nuclear factor-κB (NF-κB) and extracellular regulated kinases (ERK) 1/2. These results suggest that H and mH are compounds having potent anti-inflammatory effects that could be used to treat such diseases as IBD.

Anti-inflammatory activity of mulberrofuran K isolated from the bark of Morus bombycis

Morus bombycis Koidzumi, commonly known as silkworm mulberry, is a plant belonging to family Moraceae. It has been used in Asian countries as a traditional medicine for treating hypertension, diabetes, and inflammatory disorders. In this study, we isolated eleven compounds from the cortex of M. bombycis and evaluated their inhibitory effects on nitric oxide (NO) production as an indicator of their anti-inflammatory activities using lipopolysaccharide (LPS)-stimulated murine macrophages. Compound 4 showed the most potent inhibitory activity on NO production. It was identified as mulberrofuran K (MFK). Anti-inflammatory activity of MFK was then carried out using LPS-stimulated RAW264.7 cells. MFK suppressed the production of NO, reactive oxygen species (ROS), and proinflammatory cytokines (interleukin (IL)-1β, IL-6 and tumor necrosis factor alpha (TNF-α)) in a concentration-dependent manner. Western blot analysis revealed that MFK treatment inhibited expression levels of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). MFK also inhibited transcriptional activation of nuclear factor-κB (NF-κB) and extracellular-regulated kinases (ERK) 1/2 in LPS-stimulated murine macrophages. These results suggest that MFK, an anti-inflammatory constituents of M. bombycis cortex, has potential as a therapeutic candidates for preventing and treating inflammatory diseases.

Hypopigmenting Effects of Brown Algae-Derived Phytochemicals: A Review on Molecular Mechanisms

There is a rapid increase in the demand for natural hypopigmenting agents from marine sources for cosmeceutical and pharmaceutical applications. Currently, marine macroalgae are considered as a safe and effective source of diverse bioactive compounds. Many research groups are exploring marine macroalgae to discover and characterize novel compounds for cosmeceutical, nutraceutical, and pharmaceutical applications. Many types of bioactive secondary metabolites from marine algae, including phlorotannins, sulfated polysaccharides, carotenoids, and meroterpenoids, have already been documented for their potential applications in the pharmaceutical industry. Among these metabolites, phlorotannins from brown algae have been widely screened for their pharmaceutical and hypopigmenting effects. Unfortunately, the majority of these articles did not have detailed investigations on molecular targets, which is critical to fulfilling the criteria for their cosmeceutical and pharmaceutical use. Very recently, a few meroterpenoids have been discovered from Sargassum sp., with the examination of their anti-melanogenic properties and mechanisms. Despite the scarcity of in vivo and clinical investigations of molecular mechanistic events of marine algae-derived hypopigmenting agents, identifying the therapeutic targets and their validation in humans has been a major challenge for future studies. In this review, we focused on available data representing molecular mechanisms underlying hypopigmenting properties of potential marine brown alga-derived compounds.

Asiaticoside Mitigates the Allergic Inflammation by Abrogating the Degranulation of Mast Cells

The effects of asiaticoside (AS) on allergic responses mediated by mast cells were investigated. AS showed no obvious cytotoxicity on RPMCs (rat peritoneal mast cells). AS reduced the intracellular calcium in RPMCs and deprived the histamine release and degranulation. AS also decreased the generation of antigen-induced tumor necrosis factor α, interleukin (IL)-4, IL-8, and IL-1β in RBL-2H3 cells sensitized by IgE. The suppression of AS on pro-inflammatory cytokines was related with the activation of the intracellular FcεRI and the inhibition of the nuclear factor-κB signaling pathway. In addition, AS disabled the phosphorylation of antigen-induced Syk, Lyn, Gab2, and PLCγ1, thus suppressing the downstream Akt phosphorylation and MAPKs pathways. It also increased HO-1 and Nrf2 expression time dependently. In summary, we demonstrate that AS suppresses the allergic inflammation mediated by mast cells and this effect might be mediated by FcεRI-dependent signaling pathways.

Polydatin inhibits mast cell-mediated allergic inflammation by targeting PI3K/Akt, MAPK, NF-κB and Nrf2/HO-1 pathways

Polydatin(PD) shows anti-allergic inflammatory effect, and this study investigated its underlying mechanisms in in vitro and in vivo models. IgE-mediated passive cutaneous anaphylaxis (PCA) and passive systemic anaphylaxis (PSA) models were used to confirm PD effect in vivo. Various signaling pathway proteins in mast cell were examined. RT-PCR, ELISA and western blotting were applied when appropriate. Activity of Lyn and Fyn kinases in vitro was measured using the Kinase Enzyme System. PD dose-dependently reduced the pigmentation of Evans blue in the PCA model and decreased the concentration of serum histamine in PSA model, and attenuated the degranulation of mast cells without generating cytotoxicity. PD decreased pro-inflammatory cytokine expression (TNF-α, IL-4, IL-1β, and IL-8). PD directly inhibited activity of Lyn and Syk kinases and down-regulated downstream signaling pathway including MAPK, PI3K/AKT and NF-kB. In addition, PD also targets Nrf2/HO-1 pathway to inhibit mast cell-derived allergic inflammatory reactions. In conclusion, the study demonstrates that PD is a possible therapeutic candidate for allergic inflammatory diseases. It directly inhibited activity of Lyn and Syk kinases and down-regulates the signaling pathway of MAPK, PI3K/AKT and NF-κB, and up-regulates the signaling pathway of Nrf2/HO-1 to inhibit the degranulation of mast cells.

Sargachromenol protects against vascular inflammation by preventing TNF-α-induced monocyte adhesion to primary endothelial cells via inhibition of NF-κB activation

Vascular inflammation is a key factor in the pathogenesis of atherosclerosis. The purpose of this study was to investigate the protective effects of sargachromenol (SCM) against tumor necrosis factor (TNF)-α-induced vascular inflammation. SCM decreased the expression of cell adhesion molecules, including intracellular adhesion molecule-1 and vascular cell adhesion molecule-1, in TNF-α-stimulated human umbilical vein endothelial cells (HUVECs), resulted in reduced adhesion of monocytes to HUVECs. SCM also decreased the production of monocyte chemoattractant protein-1 and matrix metalloproteinase-9 in TNF-α-induced HUVECs. Additionally, SCM inhibited activation of nuclear factor kappa B (NF-κB) induced by TNF-α through preventing the degradation of inhibitor kappa B. Moreover, SCM reduced the production of reactive oxygen species in TNF-α-treated HUVECs. Overall, SCM alleviated vascular inflammation through the regulation of NF-κB activation and through its intrinsic antioxidant activity in TNF-α-induced HUVECs. These results indicate that SCM may have potential application as a therapeutic agent against vascular inflammation.

Anti-Inflammatory Effect of Ethanolic Extract of Sargassum serratifolium in Lipopolysaccharide-Stimulated BV2 Microglial Cells

Sargassum serratifolium was found to contain high concentrations of meroterpenoids, having strong antioxidant, anti-inflammatory, and neuroprotective activities. This study aims to investigate the anti-inflammatory mechanisms of an ethanolic extract of S. serratifolium (ESS) using lipopolysaccharide (LPS)-stimulated BV2 microglial cells and to identify the anti-inflammatory components in ESS. The level of proinflammatory cytokines was measured by enzyme-linked immunosorbent assay. The expression of inflammation-related proteins and mRNA was evaluated by Western blot and reverse transcription-polymerase chain reaction analysis, respectively. Anti-inflammatory activities of isolated components from ESS were analyzed in LPS-stimulated BV2 cells. ESS inhibited LPS-induced nitric oxide (NO) and prostaglandin E2 and the expression of inducible NO synthase and cyclooxygenase-2. ESS also decreased the release of proinflammatory cytokines in a dose-dependent manner. LPS-induced nuclear factor-kappa B (κB) transcriptional activity and translocation into the nucleus were remarkably suppressed by ESS through the prevention of inhibitor κB-α degradation. The main anti-inflammatory components in ESS were identified as sargahydroquinoic acid, sargachromenol, and sargaquinoic acid based on the inhibition of NO production using LPS-stimulated BV2 cells. Furthermore, treatment with ESS significantly reduced levels of tumor necrosis factor-α and interleukin-1β stimulated with LPS in mouse hippocampus. Our results indicate that ESS can be used as a functional food or therapeutic agent for the treatment of neuroinflammatory diseases.