Dibenzoylmethane ameliorates adiposity-mediated neuroinflammatory response and inflammation-mediated neuronal cell death in mouse microglia and neuronal cells

Dibenzoylmethane (DBM), a licorice-derived component, has numerous health benefits. The current study aimed to investigate the effect of DBM on adiposity-induced neuroinflammatory/oxidative response and microglial activation-induced neuronal cell damage. For this research, BV2 and HT22 cells were cultured using adipcyte- and microglia-conditioned media, respectively. DBM effectively suppressed lipopolysaccharide-induced productions in inducible nitric oxide synthase and cyclooxygenase2. Interleukin (IL)-6, monocyte chemoattractant protein-1, IL-1β, and tumor necrosis factor-α levels were also downregulated by DBM. In adipocyte-conditioned medium (ACM)-cultured BV2 cells, DBM effectively decreased ACM-induced generation of nitric oxide, reactive oxygen species, and inflammatory cytokines by activating nuclear factor erythroid 2-related factor 2/heme oxygenase-1 signaling and reducing nuclear factor kappa-light-chain-enhancer of activated B cells. In BV2-conditioned medium (BVM)-cultured neuron cells, DBM recovered the BVM-induced reduction of neuronal cell viability, thereby regulating B-cell lymphoma 2 (BCL2), BCL2-associated X (BAX), and cleaved caspase-3 protein expression. Taken together, DBM suppressed adiposity-induced inflammation/oxidative responses and inflammation-induced neuronal cell death.

The pivotal role of Nrf2 activators in adipocyte biology

Adipose tissue is instrumental in maintaining metabolic homeostasis by regulating energy storage in the form of triglycerides. In the case of over-nutrition, adipocytes favorably regulate lipogenesis over lipolysis and accumulate excess triglycerides, resulting in increased adipose tissue mass. An abnormal increase in hypertrophic adipocytes is associated with chronic complications such as insulin resistance, obesity, diabetes, atherosclerosis and nonalcoholic fatty liver disease. Experimental studies indicate the occurrence of oxidative stress in the pathogenesis of obesity. A common underlying link between increasing adipose tissue mass and oxidative stress is the Nuclear Factor Erythroid 2-related factor 2 (Nrf2), Keap1-Nrf2-ARE signaling, which plays an indispensable role in metabolic homeostasis by regulating oxidative and inflammatory responses. Additionally, Nrf2 also activates CCAAT/enhancer-binding protein α, (C/EBP-α), C/EBP-β and peroxisome proliferator-activated receptor γ (PPARγ) the crucial pro-adipogenic factors that promote de novo adipogenesis. Hence, at the forefront of research is the quest for prospecting novel compounds to modulate Nrf2 activity in the context of adipogenesis and obesity. This review summarizes the molecular mechanism behind the activation of the Keap1-Nrf2-ARE signaling network and the role of Nrf2 activators in adipocyte pathophysiology.

Brassinin, a brassica-derived phytochemical, regulates monocyte-to-macrophage differentiation and inflammatory responses in human monocytes and murine macrophages

OBJECTIVES

The effects and molecular mechanisms of brassinin (BR), an indole phytoalexin from cruciferous vegetables, on monocyte-to-macrophage differentiation and inflammatory responses were investigated in this study.

METHODS

Inflammatory responses from RAW264.7 cells and THP-1 were stimulated by lipopolysaccharide (1 µg/ml), and monocyte-to-macrophage differentiation of THP-1 was induced by phorbol myristate acetate (50 ng/ml). The production of inflammatory mediators was determined by ELISA, Western blot or real-time PCR. Reactive oxygen species were examined by DCFH-DA assay.

KEY FINDINGS

Brassinin at 50 µm suppressed lipopolysaccharide-induced production of nitric oxide synthase, cyclooxygenase-2, prostaglandin E2 and reactive oxygen species by 90%, 69%, 52% and 41%, respectively, in RAW264.7 cells. In THP-1 cells, BR inhibited phorbol myristate acetate-induced monocyte-to-macrophage differentiation by suppressing cluster of differentiation molecule β and CD36. In addition, BR suppressed translocation of nuclear factor 'kappa-light-chain-enhancer' of activated B cells (NF-κB) into the nucleus. However, BR activated the nuclear factor erythroid-derived 2-like 2 (Nrf2) and its target molecules hemoxygenase-1 (HO-1) and NAD(P)H: quinone oxidoreductase 1 (NQO1), with an increase in nuclear translocation of Nrf2.

CONCLUSIONS

Brassinin suppressed monocyte-to-macrophage differentiation and inflammatory responses by differentially regulating Nrf2 and NF-κB signallings.

Punicalagin, a Pomegranate-Derived Ellagitannin, Suppresses Obesity and Obesity-Induced Inflammatory Responses Via the Nrf2/Keap1 Signaling Pathway

SCOPE

Punicalagin (PCG) is one of the most abundant phytochemicals found in pomegranates. The effects and mechanistic action of PCG on obesity and obesity-induced inflammatory and oxidant responses are investigated in vitro and in vivo.

METHODS AND RESULTS

The effect of PCG on adipogenesis is examined using Oil red O staining. The effects and mechanism of action of PCG on inflammatory responses are determined in adipocyte-conditioned medium (ACM)-cultured macrophages, a cell-to-cell contact system, and a transwell system. The effects of PCG on obesity and obesity-induced inflammatory/oxidant responses are examined in high-fat diet (HFD)-fed mice. PCG effectively suppresses lipid accumulation in adipocytes and adipocyte-induced inflammatory responses in adipocyte-macrophage co-culture systems. Small interfering RNA (siRNA) transfection indicates that the PCG-mediated anti-inflammatory effect is exerted via the nuclear factor erythroid 2-related factor 2/Kelch-like ECH-associated protein 1(Nrf2/Keap1) pathway. PCG administration results in a significant reduction in body and white adipose tissue (WAT) weights. PCG favorably regulates pro- and anti-inflammatory cytokines, downregulating nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). Immunohistochemical (IHC) analysis demonstrates that PCG differentially modulates the distribution of complement component 3 receptor 4 subunit (CD11c) and cluster of differentiation 206 (CD206). PCG regulates the level of antioxidant and oxidant molecules by activating Nrf2/Keap1 signaling.

CONCLUSIONS

PCG ameliorates obesity and obesity-induced inflammatory responses via activation of Nrf2/Keap1 signaling, suggesting that PCG has potential as an oral agent to control obesity-mediated diseases.

Red ginseng extract regulates differentiation of monocytes to macrophage and inflammatory signalings in human monocytes

This study was aimed to investigate the effect of red ginseng extract (RGE) on monocyte to macrophage differentiation and inflammatory signalings in THP-1 human monocytes. In HPLC analysis, RGE contained saponin level of 516 μg/mg (extract) with 14 ginsenosides. RGE effectively suppressed the monocyte-to-macrophage differentiation induced by phorbol 12-myristate 13-acetated (PMA) by inhibiting the THP-1 cell adhesion. This result is evidenced by the down-regulation of cluster of differentiation molecule β (CD11β) and CD36. RGE significantly reduced translocation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) (78%), while cytosolic NF-κB was increased (53%), compared with LPS group. In addition, RGE significantly increased the protein abundance of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and its target protein, hemoxygenase-1 (HO-1), but, Kelch-like ECH-associated protein 1 (KEAP1), a negative regulator of Nrf2, was greatly decreased by RGE. Furthermore, RGE effectively mediated the regulation of Nrf2 level in nucleus and cytoplasm of THP-1.