The Role of Sargahydroquinoic Acid and Sargachromenol in the Anti-Inflammatory Effect of Sargassum yezoense.

The anti-inflammatory effect of the ethanol extract of Sargassum yezoense and its fractions were investigated in this study. The ethanol extract exhibited a strong anti-inflammatory effect on lipopolysaccharide-stimulated RAW 264.7 macrophages and effectively suppressed the M1 polarization of murine bone-marrow-derived macrophages stimulated by lipopolysaccharides and IFN-γ (interferon-gamma). Through a liquid-liquid extraction process, five fractions (n-hexane, chloroform, ethyl acetate, butanol, and aqueous) were acquired. Among these fractions, the chloroform fraction (SYCF) was found to contain the highest concentration of phenolic compounds, along with two primary meroterpenoids, sargahydroquinoic acid (SHQA) and sargachromenol (SCM), and exhibit significant antioxidant capacity. It also demonstrated a robust anti-inflammatory effect. A direct comparison was conducted to assess the relative contribution of SHQA and SCM to the anti-inflammatory properties of SYCF. The concentrations of SHQA and SCM tested were determined based on their relative abundance in SYCF. SHQA contributed to a significant portion of the anti-inflammatory property of SYCF, while SCM played a limited role. These findings not only highlight the potential of the chloroform-ethanol fractionation approach for concentrating meroterpenoids in S. yezoense but also demonstrate that SHQA and other bioactive compounds work additively or synergistically to produce the potent anti-inflammatory effect of SYCF.

Sargahydroquinoic acid inhibits TNFα-induced AP-1 and NF-κB signaling in HaCaT cells through PPARα activation.

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily of ligand-activated transcription factors and expressed in various cell types in the skin, including keratinocytes, fibroblasts and infiltrating immune cells. Thus, their ligands are targets for the treatment of various skin disorders, such as photo-aging and chronological aging of skin. Intensive studies have revealed that PPARα/γ functions in photo-aging and age-related inflammation by regulating matrix metalloproteinases (MMPs) via activator protein-1 (AP-1) and nuclear factor kappa B (NF-κB). However, the detailed mechanism of PPARα/γ's role in skin aging has not yet been elucidated. In this study, we confirmed that sargahydroquinoic acid (SHQA) as a PPARα/γ ligand significantly decreased Tumor Necrosis Factor-alpha (TNFα)-induced MMP-2/-9 expression by downregulating TNFα-induced transcription factors, subsequently reducing IκBα degradation and blocking NF-κB p65 nuclear translocation in HaCaT human epidermal keratinocyte cells. Treatment of cells with SHQA and GW6471 (PPARα antagonist) not bisphenol A diglycidyl ether (PPARγ antagonists), reversed the effect on TNFα-induced inflammatory signaling pathway activation. Taken together, our data suggest that SHQA inhibit TNFα-induced MMP-2/-9 expression and age-related inflammation by suppressing AP-1 and NF-κB pathway via PPARα.

Sargahydroquinoic acid isolated from Sargassum serratifolium as inhibitor of cellular basophils activation and passive cutaneous anaphylaxis in mice.

Basophils and mast cells are characteristic effector cells in allergic reactions. Sargahydorquinoic acid (SHQA), a compound isolated from Sargassum serratifolium (marine alga), possesses various biochemical properties, including potent antioxidant activities. The objective of the present study was to investigate inhibitory effects of SHQA on the activation of human basophilic KU812F cells induced by phorbol myristate acetate and A23187 (PMACI), a calcium ionophore. Furthermore, we confirmed the inhibitory effects of SHQA on the activation of rat basophilic leukemia (RBL)-2H3 cells induced by compound 48/80 (com 48/80), bone marrow-derived mast cells (BMCMCs) induced by anti-dinitrophenyl(DNP)-immunoglobulin E (IgE)/DNP-bovine serum albumin (BSA), DNP/IgE and on the reaction of passive cutaneous anaphylaxis (PCA) mediated by IgE. SHQA reduced PMACI-induced intracellular reactive oxygen species (ROS) and calcium levels. Western blot analysis revealed that SHQA downregulated the activation of ERK, p38, and NF-κB in a dose-dependent manner. Moreover, SHQA suppressed the production and gene expression of various cytokines, including interleukin (IL)-1 ß, IL-4, IL-6, and IL-8 in PMACI-induced KU812F cells and IL-4 and tumor necrosis factor (TNF)- α in com 48/80-induced RBL-2H3 cells. It also determined the inhibition of PMACI, com 48/80- and IgE/DNP-induced degranulation by reducing the release of ß -hexosaminidase. Furthermore, it attenuated the IgE/DNP-induced PCA reaction in the ears of BALB/c mice. These results suggest that SHQA isolated from S. serratifolium is a potential therapeutic functional food material for inhibiting effector cell activation in allergic reactions and anaphylaxis in animal model.

Sargahydroquinoic Acid Suppresses Hyperpigmentation by cAMP and ERK1/2-Mediated Downregulation of MITF in α-MSH-Stimulated B16F10 Cells.

Hyperpigmentation diseases of the skin require topical treatment with depigmenting agents. We investigated the hypopigmented mechanisms of sargahydroquinoic acid (SHQA) in alpha-melanocyte-stimulating hormone (α-MSH)-stimulated B16F10 cells. SHQA reduced cellular tyrosinase (TYR) activity and melanin content in a concentration-dependent manner and attenuated the expression of TYR and tyrosinase-related protein 1 (TRP1), along with their transcriptional regulator, microphthalmia-associated transcription factor (MITF). SHQA also suppressed α-MSH-induced cellular production of cyclic adenosine monophosphate (cAMP), which inhibited protein kinase A (PKA)-dependent cAMP-responsive element-binding protein (CREB) activation. Docking simulation data showed a potential binding affinity of SHQA to the regulatory subunit RIIß of PKA, which may also adversely affect PKA and CREB activation. Moreover, SHQA activated ERK1/2 signaling in B16F10 cells, stimulating the proteasomal degradation of MITF. These data suggest that SHQA ameliorated hyperpigmentation in α-MSH-stimulated B16F10 cells by downregulating MITF via PKA inactivation and ERK1/2 phosphorylation, indicating that SHQA is a potent therapeutic agent against skin hyperpigmentation disorders.

Sargahydroquinoic acid (SHQA) suppresses cellular senescence through Akt/mTOR signaling pathway.

AIM: The effects of sargahydroquinoic acid (SHQA) on cellular senescence and the underlying mechanisms were investigated using human umbilical vascular endothelial cells (HUVECs). METHODS: SHQA or DMSO was supplemented into the medium. Low dose of H2O2 was used to induce premature senescence. Replicative senescence was achieved by continuously culturing cells until they reached a plateau phase. Senescence biomarkers, including p53, p21, and p16 proteins, and SA-ß-Gal activity were measured. RESULTS: Pretreatment of SHQA significantly suppressed the oxidative stress-induced protein expression of p53, p21, and p16, as well as the activity of SA-ß-Gal. Additionally, SHQA also delayed the replicative senescence as indicated by an increased population doubling number, reduced protein expression of p53, p21, and p16, as well as a decreased SA-ß-Gal activity. SHQA inhibited the phosphorylation of Akt, mTOR, and downstream targets of mTOR, such as p-S6K, which was elevated by premature senescence and replicative senescence. In the absence of senescence stimuli, SHQA also inhibited the Akt/mTOR signaling pathway and promoted autophagy. CONCLUSIONS: SHQA suppressed senescence induced by oxidative stress and replication through inhibiting the Akt/mTOR pathway. With the potential of acting as an Akt/mTOR inhibitor, SHQA might be useful for developing anti-ageing therapy.

Protective effect of sargahydroquinoic acid against Aß25-35-evoked damage via PI3K/Akt mediated Nrf2 antioxidant defense system.

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by memory loss and cognitive impairment. ß-Amyloid (Aß) is widely accepted as the main neurotoxin that triggers mitochondrial-associated oxidative stress, leading to neuronal death in AD. Following our preliminary research on the neuroprotective effects of the brown alga Sargassum serratifolium, its major compounds, including sargaquinoic acid, sargahydroquinoic acid (SHQA), and sargachromenol, were investigated to elucidate the antioxidant and anti-apoptotic properties of Aß25-35-stimulated PC12 cells. SHQA exhibited the most potent effect on Aß-induced mitochondrial-associated oxidative stress and apoptosis. In addition, the compound enhanced the expression and translocation of nuclear factor-E2-related factor 2 (Nrf2), while reducing the expression of cytoplasmic Kelch-like ECH-associated protein 1 (Keap1). Furthermore, the compound upregulated the expression of Nrf2-regulated antioxidant enzymes, including HO-1, NQO1, GCLc, GCLm, and TrxR1. Co-treatment with SHQA and LY294002, a specific PI3K inhibitor, inhibited nuclear Nrf2 expression and Akt phosphorylation, demonstrating that SHQA-mediated Nrf2 activation was directly associated with the PI3K/Akt signaling pathway. Mechanistic studies indicate that activation of the PI3K/Akt/Nrf2 pathway is the molecular basis for the neuroprotective effects of SHQA. In silico docking simulation revealed that SHQA established specific interactions with the key amino acid residues of PI3K, Akt, and Nrf2-Keap1 via hydrogen bonding and van der Waals interactions, which may affect the biological capacities of target markers. Overall, this is the first report of this novel mechanism of SHQA as a Nrf2 activator against Aß-mediated oxidative damage, suggesting that the compound might be a potential agent for the prevention of AD.

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.

In Vitro Evaluation of the Phytopharmacological Potential of Sargassum incisifolium for the Treatment of Inflammatory Bowel Diseases.

Background: Comprised of Crohn's disease and ulcerative colitis, inflammatory bowel diseases (IBD) are characterized by chronic inflammation of the gastro-intestinal tract, which often results in severe damage to the intestinal mucosa. This study investigated metabolites from the South African endemic alga, Sargassum incisifolium, as potential treatments for IBD. Phytochemical evaluation of S. incisifolium yielded prenylated toluhydroquinones and toluquinones, from which semi-synthetic analogs were derived, and a carotenoid metabolite. The bioactivities of S. incisifolium fractions, natural products, and semi-synthetic derivatives were evaluated using various in vitro assays. Methods: Sargahydroquinoic acid isolated from S. incisifolium was converted to several structural derivatives by semi-synthetic modification. Potential modulation of IBD by S. incisifolium crude fractions, natural compounds, and sargahydroquinoic acid analogs was evaluated through in vitro anti-inflammatory activity, anti-oxidant activity, cytotoxicity against HT-29 and Caco-2 colorectal cancer cells, and PPAR-γ activation. Results: Sargahydroquinoic acid acts on various therapeutic targets relevant to IBD treatment. Conclusions: Conversion of sargahydroquinoic acid to sarganaphthoquinoic acid increases peroxisome proliferator activated receptor gamma (PPAR-γ) activity, compromises anti-oxidant activity, and has no effect on cytotoxicity against the tested cell lines.

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-1ß 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.