title: Flavokawains A and B from kava (Piper methysticum) activate heat shock and antioxidant responses and protect against hydrogen peroxide-induced cell death in HepG2 hepatocytes.
abstract: Context Flavokawains are secondary metabolites from the kava plant (Piper methysticum Forst. f., Piperaceae) that have anticancer properties and demonstrated oral efficacy in murine cancer models. However, flavokawains also have suspected roles in rare cases of kava-induced hepatotoxicity. Objective To compare the toxicity flavokawains A and B (FKA, FKB) and monitor the resulting transcriptional responses and cellular adaptation in the human hepatocyte cell line, HepG2. Materials and methods HepG2 were treated with 2-100 μM FKA or FKB for 24-48 h. Cellular viability was measured with calcein-AM and changes in signalling and gene expression were monitored by luciferase reporter assay, real-time PCR and Western blot of both total and nuclear protein extracts. To test for subsequent resistance to oxidative stress, cells were pretreated with 50 μM FKA, 10 μM FKB or 10 μM sulphoraphane (SFN) for 24 h, followed by 0.4-2.8 mM H2O2 for 48 h, and then viability was assessed. Results FKA (≤100 μM) was not toxic to HepG2, whereas FKB caused significant cell death (IC50=23.2 ± 0.8 μM). Both flavokawains activated Nrf2, increasing HMOX1 and GCLC expression and enhancing total glutathione levels over 2-fold (p < 0.05). FKA and FKB also activated HSF1, increasing HSPA1A and DNAJA4 expression. Also, flavokawain pretreatment mitigated cell death after a subsequent challenge with H2O2, with FKA being more effective than FKB, and similar to SFN. Conclusions Flavokawains promote an adaptive cellular response that protects hepatocytes against oxidative stress. We propose that FKA has potential as a chemopreventative or chemotherapeutic agent.
authors.affiliation: a Department of Pharmaceutical Sciences , Daniel K. Inouye College of Pharmacy, University of Hawaii at Hilo , Hilo , HI , USA ;
authors.forename: Keanu D
authors.initials: KD
authors.lastname: Pinner
authors.affiliation: a Department of Pharmaceutical Sciences , Daniel K. Inouye College of Pharmacy, University of Hawaii at Hilo , Hilo , HI , USA ;
authors.forename: Christina T K
authors.initials: CT
authors.lastname: Wales
authors.affiliation: a Department of Pharmaceutical Sciences , Daniel K. Inouye College of Pharmacy, University of Hawaii at Hilo , Hilo , HI , USA ;
authors.forename: Rachel A
authors.initials: RA
authors.lastname: Gristock
authors.affiliation: a Department of Pharmaceutical Sciences , Daniel K. Inouye College of Pharmacy, University of Hawaii at Hilo , Hilo , HI , USA ;
authors.forename: Hoa T
authors.initials: HT
authors.lastname: Vo
authors.affiliation: a Department of Pharmaceutical Sciences , Daniel K. Inouye College of Pharmacy, University of Hawaii at Hilo , Hilo , HI , USA ;
authors.forename: Nadine
authors.initials: N
authors.lastname: So
authors.affiliation: a Department of Pharmaceutical Sciences , Daniel K. Inouye College of Pharmacy, University of Hawaii at Hilo , Hilo , HI , USA ;|b Cancer Biology Program, University of Hawaii Cancer Center , Honolulu , HI , USA.
authors.forename: Aaron T
authors.initials: AT
authors.lastname: Jacobs
mesh_terms: D000975:Antioxidants / Q000302:isolation & purification / Q000494:pharmacology* / Q000633:toxicity; D002470:Cell Survival / Q000187:drug effects; D002599:Chalcone / Q000031:analogs & derivatives* / Q000302:isolation & purification / Q000494:pharmacology / Q000633:toxicity; D019610:Cytoprotection; D004305:Dose-Response Relationship, Drug; D005419:Flavonoids / Q000302:isolation & purification / Q000494:pharmacology* / Q000633:toxicity; D005721:Glutamate-Cysteine Ligase / Q000235:genetics / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D050956:HSP40 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D018869:Heat-Shock Response / Q000187:drug effects*; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D006801:Humans; D006861:Hydrogen Peroxide / Q000633:toxicity*; D020901:Kava / Q000737:chemistry; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects*; D008517:Phytotherapy; D010936:Plant Extracts / Q000302:isolation & purification / Q000494:pharmacology* / Q000633:toxicity; D010946:Plants, Medicinal; D013997:Time Factors; D015854:Up-Regulation
chemical_list: D000975:Antioxidants; C494646:DNAJA4 protein, human; D005419:Flavonoids; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; C490786:HSPA1A protein, human; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D010936:Plant Extracts; C500809:flavokawain A; C452039:flavokawain B; D002599:Chalcone; D006861:Hydrogen Peroxide; C496541:HMOX1 protein, human; D051547:Heme Oxygenase-1; C000609392:GCLC protein, human; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione
keywords: Cell stress; HSF1; Nrf2; hepatotoxic; viability