title: Carotenoid derivatives inhibit nuclear factor kappa B activity in bone and cancer cells by targeting key thiol groups.
abstract: Aberrant activation of the nuclear factor kappa B (NFkB) transcription system contributes to cancer progression, and has a harmful effect on bone health. Several major components of the NFkB pathway such as IkB Kinase (IKK) and the NFkB subunits contain cysteine residues that are critical for their activity. The interaction of electrophiles with these cysteine residues results in NFkB inhibition. Carotenoids, hydrophobic plant pigments, are devoid of electrophilic groups, and we have previously demonstrated that carotenoid derivatives, but not the native compounds activate the Nrf2 transcription system. The aim of the current study was to examine whether carotenoid derivatives inhibit NFkB, and, if so, to determine the molecular mechanism underpinning the inhibitory action. We report in the present study that a mixture of oxidized derivatives, prepared by ethanol extraction from partially oxidized lycopene preparation, inhibited NFkB reporter gene activity. In contrast, the intact carotenoid was inactive. A series of synthetic dialdehyde carotenoid derivatives inhibited reporter activity as well as several stages of the NFkB pathway in both cancer and bone cells. The activity of the carotenoid derivatives depended on the reactivity of the electrophilic groups in reactions such as Michael addition to sulfhydryl groups of proteins. Specifically, carotenoid derivatives directly interacted with two key proteins of the NFkB pathway: the IKKβ and the p65 subunit. Direct interaction with IKKβ was found in an in vitro kinase assay with a recombinant enzyme. The inhibition by carotenoid derivatives of p65 transcriptional activity was observed in a reporter gene assay performed in the presence of excess p65. This inhibition action resulted, at least in part, from direct interaction of the carotenoid derivative with p65 leading to reduced binding of the protein to DNA as evidenced by electrophoretic mobility shift assay (EMSA) experiments. Importantly, we found by using mutation in key cysteine residues of both p65 and IKK that specific thiol groups are essential for NFkB inhibition by carotenoid derivatives. In conclusion, we propose that electrophilic carotenoid derivatives contribute to cancer prevention as well as bone health maintenance via the inhibition of the NFkB transcription system. Pivotal thiol groups of both IKK and p65 play a key role in this process.
authors: Clinical Biochemistry and Pharmacology, Faculty of Health Sciences, Ben-Gurion University of the Negev and Soroka Medical Center, Beer Sheva, Israel. Electronic address: karinlin@post.bgu.ac.il.
authors: Karin
authors: K
authors: Linnewiel-Hermoni
authors: Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel; Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel.
authors: Yair
authors: Y
authors: Motro
authors: Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel; Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel.
authors: Yifat
authors: Y
authors: Miller
authors: Clinical Biochemistry and Pharmacology, Faculty of Health Sciences, Ben-Gurion University of the Negev and Soroka Medical Center, Beer Sheva, Israel.
authors: Joseph
authors: J
authors: Levy
authors: Clinical Biochemistry and Pharmacology, Faculty of Health Sciences, Ben-Gurion University of the Negev and Soroka Medical Center, Beer Sheva, Israel.
authors: Yoav
authors: Y
authors: Sharoni
mesh_terms: D001842:Bone and Bones / Q000166:cytology; D002338:Carotenoids / Q000737:chemistry / Q000494:pharmacology*; D045744:Cell Line, Tumor; D004247:DNA / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000737:chemistry; D024202:Electrophoretic Mobility Shift Assay; D017930:Genes, Reporter / Q000187:drug effects / Q000235:genetics; D006801:Humans; D051550:I-kappa B Kinase / Q000037:antagonists & inhibitors* / Q000235:genetics; D000077276:Lycopene; D051267:NF-E2-Related Factor 2 / Q000378:metabolism; D009369:Neoplasms / Q000188:drug therapy / Q000517:prevention & control; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D051996:Transcription Factor RelA / Q000037:antagonists & inhibitors* / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D004268:DNA-Binding Proteins; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; C498143:RELA protein, human; D013438:Sulfhydryl Compounds; D051996:Transcription Factor RelA; D002338:Carotenoids; D004247:DNA; D051550:I-kappa B Kinase; D000077276:Lycopene