Abstract
The anti-inflammatory activity of licorice (LE) and roated licorice (rLE) extracts determined in the murine phorbol ester-induced acute inflammation model and collagen-induced arthritis (CIA) model of human rheumatoid arthritis. rLE possessed greater activity than LE in inhibiting phorbol ester-induced ear edema. Oral administration of LE or rLE reduced clinical arthritis score, paw swelling, and histopathological changes in a murine CIA. LE and rLE decreased the levels of proinflammatory cytokines in serum and matrix metalloproteinase-3 expression in the joints. Cell proliferation and cytokine secretion in response to type II collagen or lipopolysaccharide stimulation were suppressed in spleen cells from LE or rLE-treated CIA mice. Furthermore, LE and rLE treatment prevented oxidative damages in liver and kidney tissues of CIA mice. Taken together, LE and rLE have benefits in protecting against both acute inflammation and chronic inflammatory conditions including rheumatoid arthritis. rLE may inhibit the acute inflammation more potently than LE.
Highlights
Human rheumatoid arthritis (RA) is an autoimmune disease associated with painful joints that affects approximately 1% of the worldwide population, for which there is no effective cure available [1, 2]
We found that roasted licorice extract was more potent than unroasted licorice extract (LE) in inhibiting ear edema in mice treated with phorbol ester, which induces acute inflammation due to the increased activity of tumor necrosis factor (TNF)-α and IL-1β [17]
We investigated the antiarthritic effects of roated licorice (rLE) in a murine collagen-induced arthritis (CIA) model that has been widely accepted as an appropriate animal model of human rheumatoid arthritis [18]
Summary
Human rheumatoid arthritis (RA) is an autoimmune disease associated with painful joints that affects approximately 1% of the worldwide population, for which there is no effective cure available [1, 2]. Infiltrating immune cells produce and release a variety of cytokines, predominantly tumor necrosis factor (TNF)-α and interleukin (IL)-1β, which attract and activate other inflammatory cells, propagating a vicious inflammatory cycle that leads to bone damage [4]. These cytokines increase the production of matrix metalloproteinases (MMPs), enzymes that can degrade all components of the extracellular matrix, leading to destruction of cartilage [5]. It is necessary to develop preventive and therapeutic agents that have minimal toxicity, and oriental natural medicinal plants with antiinflammatory activities are a useful resource to obtain novel antiarthritic agents
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