Abstract
Although previous studies suggested an anti-inflammatory property of Brazilian red propolis (BRP), the mechanisms involved in the anti-inflammatory effects of BRP and its activity on macrophages were still not elucidated. This study aimed to evaluate whether BRP attenuates the inflammatory effect of LPS on macrophages and to investigate its underlying mechanisms. BRP was added to RAW 264.7 murine macrophages after activation with LPS. NO production, cell viability, cytokines profile were evaluated. Activation of inflammatory signaling pathways and macrophage polarization were determined by RT-qPCR and Western blot. BRP at 50 μg/ml inhibited NO production by 78% without affecting cell viability. Cd80 and Cd86 were upregulated whereas mrc1 was down regulated by BRP indicating macrophage polarization at M1. BRP attenuated the production of pro-inflammatory mediators IL-12, GM-CSF, IFN-Ɣ, IL-1β in cell supernatants although levels of TNF- α and IL-6 were slightly increased after BRP treatment. Levels of IL-4, IL-10 and TGF-β were also reduced by BRP. BRP significantly reduced the up-regulation promoted by LPS of transcription of genes in inflammatory signaling (Pdk1, Pak1, Nfkb1, Mtcp1, Gsk3b, Fos and Elk1) and of Il1β and Il1f9 (fold-change rate > 5), which were further confirmed by the inhibition of NF-κB and MAPK signaling pathways. Furthermore, the upstream adaptor MyD88 adaptor-like (Mal), also known as TIRAP, involved in TLR2 and TLR4 signaling, was down- regulated in BRP treated LPS-activated macrophages. Given that BRP inhibited multiple signaling pathways in macrophages involved in the inflammatory process activated by LPS, our data indicated that BRP is a noteworthy food-source for the discovery of new bioactive compounds and a potential candidate to attenuate exhacerbated inflammatory diseases.
Highlights
Inflammation provides protection against pathogens, and modulates repair and healing after cellular damage
Inflammation may be controlled by non-steroidal anti-inflammatory drugs, but other treatment strategies include the administration of inhibitors of pro-inflammatory cytokines, such as anti- tumor necrosis factor alpha (TNF-α) [2], anti-interleukin (IL)-6 [3], and anti-IL-1 [1]
nitric oxide (NO) production was reduced in LPS (500 ng/ml) treated cells even at the lower tested Brazilian red propolis (BRP) concentration (Fig 2)
Summary
Inflammation provides protection against pathogens, and modulates repair and healing after cellular damage. Inflammation may be controlled by non-steroidal anti-inflammatory drugs, but other treatment strategies include the administration of inhibitors of pro-inflammatory cytokines, such as anti- tumor necrosis factor alpha (TNF-α) [2], anti-interleukin (IL)-6 [3], and anti-IL-1 [1]. Macrophages can be activated by a wide range of substances, including cytokines derived from T and natural killer (NK) cells and direct recognition by binding to microbial components such as the lipopolysaccharide (LPS) from the Gram negative bacteria cell wall. These highly plastic cells differentiate with substantial shifts in gene expression depending on specific stimuli, giving rise to at least two phenotypes with specialized functions[6]
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