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  • Obesity is associated with chronic low grade inflammation re

    2024-03-04

    Obesity is associated with chronic low-grade netarsudil resulting from increased M1 macrophage infiltration into adipose tissue, which can subsequently lead to the development of insulin resistance. Previously, we reported that LFE and FSB both reduced body weight gain in high fat diet-induced obese mice and ob/ob mice, and these anti-obesity effects of LFE and FSB were shown to be due to PPARγ antagonism, resulting in the inhibition of adipocyte differentiation (Kwak et al., 2016). We speculated that FSB might also have anti-inflammatory effects. Accordingly, we investigated the anti-inflammatory effects of FSB and the underlying molecular mechanisms responsible in murine macrophages using LPS as an inflammatory stimulator.
    Material and methods <br> Results
    Discussion Prolonged and excessive activation of macrophages has been implicated in various inflammatory and immune diseases. Furthermore, obesity-induced chronic low-grade inflammation is believed to contribute to the developments of insulin resistance and type 2 diabetes mellitus, and it appears that macrophage infiltration, particularly infiltration of the M1 phenotype, into adipose tissue contributes to systemic inflammatory conditions. Accordingly, it is widely held that anti-inflammatory agents may retard the progress of inflammatory and metabolic diseases. In the present study, we sought to investigate the pharmacological activity of FSB against LPS-induced inflammatory response in macrophages and to elucidate the molecular signaling mechanisms involved. A proposed molecular mechanism for the FSB action is presented in Fig. 8. Previously, we reported that LFE and its active component FSB inhibited 3T3-L1 preadipocyte differentiation via PPARγ antagonism, and that the in vivo application of LFE reduced body weight gain in ob/ob and diet-induced obese mice (Kwak et al., 2016). In the present study, we examined whether FSB possesses anti-inflammatory effects in macrophages, and to determine the mechanism responsible for its action. Our findings provide first evidence that FSB is able to inhibit LPS-induced inflammatory responses in vitro and in vivo. FSB significantly and concentration-dependently inhibited LPS-induced NO production at non-toxic concentrations and reduced iNOS mRNA and protein expression in RAW264.7 and primary macrophages. PGE2, another pro-inflammatory mediator, was also induced by LPS, and this induction was also suppressed concentration dependently by FSB along the reduced mRNA and protein expressions of COX-2. Furthermore, pretreating macrophages with FSB significantly reduced the LPS-induced expressions of TNF-α, IL-1β, and IL-6 proteins and mRNAs, all indicates that FSB has potent anti-inflammatory effects against LPS-induced inflammatory responses in murine macrophages. Interestingly, LFE was shown to inhibit mycelia growth of Magnaporthe oryzae, suggesting its possible use as a biopesticide (Lee, 2016). NF-κB is a master regulator of the expressions of several inflammatory mediators, including iNOS, COX-2, and various cytokines. Upon activation, NF-κB is translocated from cytoplasm to the nucleus (Remick, 1995), where it binds to specific DNA nucleotide sequences to initiate the transcriptions of its downstream elements. Several reports have shown the suppression of NF-κB by a natural or a synthetic inhibitor ameliorates endotoxin-induced sepsis by inhibiting inflammatory mediators (Park et al., 2015). In the present study, FSB pre-treatment strongly and concentration-dependently reduced nuclear p65 levels after LPS treatment, indicating the nuclear translocation of NF-κB was suppressed by FSB. To confirm the involvement of NF-κB in the action mechanism of FSB, we used a NF-κB promoter luciferase activity assay. It was found that FSB pretreatment markedly inhibited LPS-induced NF-κB promoter activity, indicating the anti-inflammatory effects of FSB were at least partly mediated by suppression of the transcriptional activity of NF-κB.