Immune-enhancing effects of gamma-irradiated sericin

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Immune-enhancing effects of gamma-irradiated sericin In-Bong Song1 • Hye-Ju Han2 • Jungkee Kwon1,2

Received: 23 April 2019 / Revised: 19 January 2020 / Accepted: 21 January 2020 Ó The Korean Society of Food Science and Technology 2020

Abstract Gamma radiation changes the molecular structure and activity of proteins, which in turn changes their physiological effects. Sericin, one of the silk peptides, has beneficial effects to humans such as inducing apoptosis, acting as an anti-oxidant. The effects of gamma irradiation on the physiological activity of fibroin have been studied, but its effects on sericin alone have not yet been established. In this study, we assessed the effects of gamma irradiation on sericin (I-sericin) in regard to its inflammatory effects in vitro and in vivo. Our results showed that I-sericin (5 kGy) significantly increased nitric oxide production, proliferation of immune cells, and effectively attenuated lipopolysaccharide (LPS)-induced inflammation. The mice were fed I-sericin for 4 weeks and treated with LPS; they exhibited significantly increased proliferation of lymphocytes, activation of NK cells and decreased secretion of inflammatory cytokines These results suggest gamma-irradiated I-sericin as a valuable functional food supplement by immune-enhancing and anti-inflammation effects.

& Jungkee Kwon [email protected] In-Bong Song [email protected] Hye-Ju Han [email protected] 1

Central Research and Development, Between Inc, Iksan, Republic of Korea

2

Department of Laboratory Animal Medicine, College of Veterinary Medicine, Chonbuk National University, 79 Gobongro, Jeonbuk, Iksan 54596, Republic of Korea

Keywords Sericin  Gamma irradiation  Immune enhancement  Anti-inflammation

Introduction Food irradiation kills microbes and insects and is a highly effective conservation technique that reduces dependence on chemical fumigants and preservatives. It reduces food losses due to microbial spoilage and insect damage (Roberts, 2014; Verde et al., 2013). Specifically, irradiation with gamma rays is known to be safe and effective in food storage by reducing microorganisms and viruses and preventing addition of biological hazards and toxic substances such as N-nitrosamine and biologically active amines (Lafortune et al., 2005). In addition, gamma irradiation has been reported to change physiological properties of proteins by altering their structure (Valdes-Diaz et al., 2007). Gamma irradiation results in changes in physiological properties through fragmentation, cross-linking, aggregation, and oxidation by oxygen radicals (Davies, 1987; Dogbevi et al., 1999). Therefore, there are efforts to exploit these irradiation-induced changes in physiological properties of organic compounds to develop various therapeutic agents (Brandstetter et al., 2009; Lee et al., 2012; Pereira et al., 2017). The immune system is a biological defense from various external factors such as pathogenic bacteria, toxins, and viruses. The immune system is mainly divided into innate immunity and adaptive immunity. T