Immunostimulatory activity of the aqueous extract from the leaves of <em>Sambucus racemosa</em> subsp. <em>pendula</em> through TLR4‑dependent JNK activation in RAW264.7 cells

Choi,Hyeok Jin; Park,Gwang Hun; Choi,Jeong Won; Park,So Jung; Hwang,Jin Hyuk; Lee,Sang Hun; Kwon,Hae-Yun; Choi,Min Yeong; Jeong,Jin Boo

doi:10.3892/br.2024.1821

Immunostimulatory activity of the aqueous extract from the leaves of Sambucus racemosa subsp. pendula through TLR4‑dependent JNK activation in RAW264.7 cells

Authors:
- Hyeok Jin Choi
- Gwang Hun Park
- Jeong Won Choi
- So Jung Park
- Jin Hyuk Hwang
- Sang Hun Lee
- Hae-Yun Kwon
- Min Yeong Choi
- Jin Boo Jeong
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Affiliations: Department of Forest Science, Andong National University, Andong, Gyeongsangbuk 36729, Republic of Korea, Forest Medicinal Resources Research Center, National Institute of Forest Science, Yeongju, Gyeongsangbuk 36040, Republic of Korea
Published online on: July 19, 2024 https://doi.org/10.3892/br.2024.1821
Article Number: 133
Copyright: © Choi et al. This is an open access article distributed under the terms of Creative Commons Attribution License.

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Abstract

Sambucus racemosa subsp. pendula (SRP) is an endemic plant of Korea, exclusively found on Ulleungdo Island. SRP is widely used as both a traditional medicine and food source. However, there is a lack of research on the pharmacological activities of SRP. Therefore, the present study aimed to explore the potential use of SRP leaves (SRPL) as a natural immunostimulant by analyzing its macrophage activation properties and the underlying mechanisms of action. Among the various extraction conditions, SRPL (AE20‑SRPL) extracted with 100% distilled water at 20˚C induced the highest nitric oxide (NO) production in RAW264.7 cells. Thus, the further studies were performed using AE20‑SRPL. AE20‑SRPL increased the production of immunostimulatory factors such as NO, prostaglandin E2, inducible nitric oxide synthase, cyclooxygenase‑2, IL‑1β and TNF‑α and phagocytosis in a dose‑dependent manner in RAW264.7 cells without exhibiting cytotoxicity. Among Toll‑like receptor (TLR)2 and TLR4, inhibition of TLR4 significantly reduced AE20‑SRPL‑mediated increases in the production of immunostimulatory factors and phagocytosis in RAW264.7 cells. Furthermore, in RAW264.7 cells, inhibition of JNK, one of the components of MAPK signaling along with ERK1/2 and p38, attenuated the AE20‑SRPL‑mediated increases in the production of immunostimulatory factors and phagocytosis. Additionally, AE20‑SRPL induced the phosphorylation of JNK and inhibition of TLR4 reduced AE20‑SRPL‑mediated JNK phosphorylation. These results suggested that AE20‑SRPL may enhance the production of immunostimulatory factors and phagocytosis through TLR4‑dependent activation of JNK in macrophages. Although the present study is limited to in vitro research using a cell model, AE20‑SRPL demonstrated potential as a natural material capable of inducing macrophage activation for immune enhancement.

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