Onion (Allium cepa L.)-Derived Nanoparticles Inhibited LPS-Induced Nitrate Production, However, Their Intracellular Incorporation by Endocytosis Was Not Involved in This Effect on RAW264 Cells.

Masao Yamasaki,Hayaka Kimura,Ichiro Kamei,Kenjiro Ogawa,Rina Furusho,Masahiro Ikeda,Tatsuya Oshima,Kazuo Nishiyama,Yumi Yamasaki,Hiroko Sonoda

doi:10.3390/molecules26092763

Abstract

The aim of this study was to evaluate the involvement of nanoparticles prepared from Allium cepa L. as anti-inflammatory agents. In the present study, we identified nanoparticles from Allium cepa L. using the ultracentrifugation exosome purification method. The nanoparticles were referred to as 17,000× g and 200,000× g precipitates, and they contained quercetins, proteins, lipids, and small-sized RNA. The nanoparticles inhibited nitric oxide production from lipopolysaccharide (LPS)-stimulated RAW264 cells without cytotoxic properties. Cellular incorporation was confirmed by laser microscopic observation after PKH26 staining. The inhibition of caveolae-dependent endocytosis and macropinocytosis significantly prevented the incorporation of the nanoparticles but had no effect on the inhibition of nitric oxide in RAW264 cells. Collectively, the identified nanoparticles were capable of inhibiting the LPS response via extracellular mechanisms. Taken together, the way of consuming Allium cepa L. without collapsing the nanoparticles is expected to provide an efficient anti-inflammatory effect.

Highlights

The health-promoting effects of natural plant resources, especially vegetables and fruits, have attracted attention from researchers and among general consumers
We evaluated the anti-inflammatory properties of onion-derived nanoparticles on RAW264 cells
Dynamic light scattering analysis and electrophoresis data showed that both 17 Kp and 200 Kp were similar to the exosome, in that they were nano-sized and included proteins and small sized

Summary

Introduction

The health-promoting effects of natural plant resources, especially vegetables and fruits, have attracted attention from researchers and among general consumers. Numerous studies have focused on the identification and purification of active components in food, and these studies have certainly contributed to the development of functional foods These studies enabled depicting the detailed mechanisms of food function at the molecular level, we are interested in the difference between unpurified or unprocessed foods and purified compounds in terms of their health-promoting effects. The ingestion of plant cell structures may at least partly explain the health benefit of consuming raw and unprocessed foods. In this context, exosome-like nanoparticles found in various vegetables and fruit have health-promoting effects. Onion (Allium cepa L.) is one of the most popular vegetables in the world and is well known for its health benefits

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