Abstract
Harnessing melanins to scavenge free radicals in vivo may yield treatment methods for inflammatory disorders. Furthermore, elucidation of the mechanism underlying melanin-mediated suppression of free radicals, which is yet unclear, is warranted. Herein, we chemically synthesized melanin-mimetic nanoparticles (MeNPs) and investigated the mechanism underlying their use. MeNPs efficiently suppressed hydroxyl radicals by converting some MeNP hydroxyl groups to ketone groups. Furthermore, they suppressed hydroxyl radicals produced by lipopolysaccharide-treated Kupffer cells involved in hepatic cirrhosis pathogenesis, without causing significant cytotoxicity. The present results indicate the suitability of MeNPs to treat hepatic cirrhosis; however, further in vivo studies are warranted to determine their treatment efficacy.
Highlights
Melanins are biopolymers produced by melanocytes and are widely distributed many organisms [1]
Treatments involving the use of organic-inorganic hybrid nanoparticles and erythrocyte-like polymer microparticles have reportedly been used to repair most fibrotic tissues and restore hepatic function to physiological levels in cases of hepatic cirrhosis [4,5]
We verified that mimetic nanoparticles (MeNPs) suppressed hydroxyl radicals produced by Kupffer cells (KCs), which are involved in hepatic cirrhosis pathogenesis
Summary
Melanins are biopolymers produced by melanocytes and are widely distributed many organisms [1] One of their important functions is quenching of free radicals. Among the brown-black eumelanins and yellowish-redpheomelanins, which have different precursors, and the former can suppress free radicals [2]. Free radicals such as hydroxyl radicals have the greatest oxidative power and cause various disorders [3]. Various types of nano- or micron-sized particles such as organic-inorganic hybrids [4], erythrocyte-like polymers [5], lipids [6,7,8], and proteins [9], which can suppress free radicals have been developed. We verified that MeNPs suppressed hydroxyl radicals produced by Kupffer cells (KCs), which are involved in hepatic cirrhosis pathogenesis
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