Abstract
Prasiola japonica possesses several biological activities. However, reports on the anti-inflammatory activities and molecular mechanisms of its different solvent fractions remain limited. In this study, we investigated the potential anti-inflammatory activities of P. japonica ethanol extract (Pj-EE) and four solvent fractions of Pj-EE made with hexane (Pj-EE-HF), chloroform (Pj-EE-CF), butanol (Pj-EE-BF), or water (Pj-EE-WF) in both in vitro (LPS-induced macrophage-like RAW264.7 cells) and in vivo (carrageenan-induced acute paw edema mouse models) experiments. The most active solvent fraction was selected for further analysis. Various in vitro and in vivo assessments, including nitric oxide (NO), cytokines, luciferase assays, real-time polymerase chain reactions, and immunoblotting analyses were performed to evaluate the underlying mechanisms. In addition, the phytochemical constituents were characterized by Liquid chromatography-tandem mass spectrometry. In in vitro studies, the highest inhibition of NO production was observed in Pj-EE-CF. Further examination revealed that Pj-EE-CF decreased the expression of inflammation-related cytokines in LPS-induced RAW264.7 cells and suppressed subsequent AP-1-luciferase activity by inhibition of phosphorylation events in the AP-1 signaling pathway. Pj-EE-CF treatment also demonstrated the strongest reduction in thickness and volume of carrageenan-induced paw edema, while Pj-EE-BF showed the lowest activity. Furthermore, Pj-EE-CF also reduced gene expression and cytokines production in tissue lysates of carrageenan-induced paw edema. These findings support and validate the evidence that Pj-EE, and especially Pj-EE-CF, could be a good natural source for an anti-inflammatory agent that targets the AP1 pathway.
Highlights
Inflammation is the protective response of the immune system against various pathogens and cellular danger signals, mediated primarily by immune cells such as macrophages
Three major mitogen-activated protein kinases (MAPKs), c-Jun N-terminal kinase (JNK), p38, and extracellular signal-regulated kinase (ERK), mediate nuclear translocation and activate transcription factors in the activator protein-1 (AP-1) pathway [3,7]. Activation of this transcription factor induces the expression of numerous inflammatory genes, such as inducible nitric oxide synthase, cyclooxygenase-2 (COX-2), interleukin (IL)-6, IL-1β, and tumor necrosis factor-alpha (TNF-α), which will stimulate matrix metalloproteinase (MMP) expression, subsequently releasing the production of the inflammatory mediator, nitric oxide (NO), and various cytokines [4,8,9,10,11]
P. japonica ethanol extract (Pj-EE)-CF (100 μg/mL) had the strongest effect (p = 0.0071) on the secretion of NO and up to 80% inhibition on LPS-induced RAW264.7 cells
Summary
Inflammation is the protective response of the immune system against various pathogens and cellular danger signals, mediated primarily by immune cells such as macrophages. Three major mitogen-activated protein kinases (MAPKs), c-Jun N-terminal kinase (JNK), p38, and extracellular signal-regulated kinase (ERK), mediate nuclear translocation and activate transcription factors in the AP-1 pathway [3,7]. The freshwater green algae P. japonica has been shown to possess medicinal benefits including antioxidant, antiapoptotic, anti-melanogenic, and anti-inflammatory effects. Most of those studies were limited to identifying such effects of the crude ethanolic extract of P. japonica in the NF-κB pathway and mainly focused on the skin cell lines [13,18,19,20]. In in vivo studies in carrageenan-induced acute paw edema mouse models, the molecular targets and phytochemical constituents of Pj-EE-CF are evaluated
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