Abstract
Bromelain is a mixture of proteolytic enzymes derived from pineapple (Ananas comosus) fruit and stem possessing several beneficial properties, particularly anti-inflammatory activity. However, the molecular mechanisms underlying the anti-inflammatory effects of bromelain are unclear. This study investigated the anti-inflammatory effects and inhibitory molecular mechanisms of crude and purified rhizome bromelains on lipopolysaccharide (LPS)-induced inflammation in RAW 264.7 macrophage cells. RAW264.7 cells were pre-treated with various concentrations of crude bromelain (CB) or purified bromelain (PB), and then treated with LPS. The production levels of pro-inflammatory cytokines and mediators, including nitric oxide (NO), interleukin (IL)-6, and tumor necrosis factor (TNF)-α were determined by Griess and ELISA assays. The expressions of inducible nitric oxide synthetase (iNOS), cyclooxygenase (COX)-2, nuclear factor kappa B (NF-κB), and mitogen-activated protein kinases (MAPKs)-signaling pathway-related proteins were examined by western blot analysis. The pre-treatment of bromelain dose-dependently reduced LPS-induced pro-inflammatory cytokines and mediators, which correlated with downregulation of iNOS and COX-2 expressions. The inhibitory potency of PB was stronger than that of CB. PB also suppressed phosphorylated NF-κB (p65), nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor alpha, extracellular signal-regulated kinases, c-Jun amino-terminal kinases, and p38 proteins in LPS-treated cells. PB then exhibited potent anti-inflammatory effects on LPS-induced inflammatory responses in RAW264.7 cells by inhibiting the NF-κB and MAPKs-signaling pathways.
Highlights
Bromelainis a mixture of proteolytic enzymes obtained from the fruit and stem of pineapple (Ananas comosus) [1,2] and is composed of different thiol endopeptidases and other components, such as phosphatases, glucosidases, peroxidase, cellulase, glycoprotein, and several protease inhibitors [3,4,5,6]]
We examined the inflammatory effects of crude bromelain (CB) and purified bromelain (PB) extracted from pineapple rhizomes, and the molecular mechanisms underlying the anti-inflammatory effect of bromelain on LPS-stimulated RAW264.7 cells were determined
We showed that LPS significantly increased production of nitric oxide (NO), IL-6, and tumor necrosis factor (TNF)-α in RAW264.7 macrophage cells
Summary
Bromelainis a mixture of proteolytic enzymes obtained from the fruit and stem of pineapple (Ananas comosus) [1,2] and is composed of different thiol endopeptidases and other components, such as phosphatases, glucosidases, peroxidase, cellulase, glycoprotein, and several protease inhibitors [3,4,5,6]]. The biological properties of bromelain include antimicrobial, antithrombotic, anticancer, and anti-inflammatory effects [3,6]. Several studies have revealed that bromelain reduced the secretion of inflammatory cytokines, including interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α in mouse macrophage cells [6,7]. Bromelain inhibits nuclear factorκB (NF-κB) translocation via G2/M arrest to apoptosis in human epidermoid carcinoma and melanoma cells [10]. Treatment of bromelain decreased the levels of cyclooxygenase-2 (COX-2) and vascular endothelial growth factor in hepatocellular carcinoma cells, resulting in reduced tumor neo-capillary density relative to that of untreated cells [11]. It has been reported that bromelain exhibited anti-inflammatory effects in lipopolysaccharide (LPS) on human U937 macrophages by suppressing pro-inflammatory cytokines, chemokines, and the cyclooxygenase pathway [12]
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