Research articleLicochalcone E activates Nrf2/antioxidant response element signaling pathway in both neuronal and microglial cells: therapeutic relevance to neurodegenerative disease☆
Introduction
Parkinson's disease (PD) is a progressive neurodegenerative disease characterized by a selective loss of dopamine (DA)-producing neurons in the substantia nigra pars compacta (SNpc) and a reduction in their terminals within the striatum. Dopaminergic (DArgic) neurodegeneration in this nigrostriatal pathway causes typical motor deficits, such as resting tremor, rigidity, bradykinesia and postural instability. While the etiological link to DArgic neuronal loss remains unknown, evidences suggest crucial roles for oxidative stress, mitochondrial defects, protein aggregation and misfolding, and inflammation in the pathogenesis of PD [1], [2].
Oxidative stress has been largely associated with the development of PD due to the highly oxidative conditions in DArgic neurons. Oxidative stress activates death signaling, including mitochondria-dependent apoptosis, and finally triggers cellular demise [3]. Among various candidates that can generate oxidative stress in DArgic neurons, DA itself is a primary source of oxidative stress that causes cytotoxicity to DArgic neurons [4]. DA-induced oxidative stress can be induced by auto-oxidation forming reactive quinone species [5], [6], [7]. Quinones are unstable and highly reactive and can readily attack cellular nucleophiles and cause covalent modification of essential macromolecules.
In addition, neuroinflammatory processes play a significant role in the generation of oxidative stress and the pathogenesis of PD. Neuropathological evidence indicates that neuroinflammatory response is detectable and accompanied by neuronal loss in PD: for example, inflammatory mediators are present in the cerebrospinal fluid [8] and the brains of PD patients [9], and signs of microglial activation can be observed in the area of SNpc in Parkinson's brain [10]. Many toxic factors, including superoxide anions, nitric oxide (NO), arachidonic acid and its metabolites, chemokines, and proinflammatory cytokines, can be generated by microglial activation. Activated microglia causes increased generation of reactive oxygen species (ROS), and oxidative stress also has the potential to induce an inflammatory response. Thus, these two mechanisms — oxidative stress and inflammation — are not independent but rather work synergistically through complex interactions exacerbating neurodegeneration. Therefore, the mechanism directly implicated in controlling oxidative stress and inflammatory response could be an attractive target in preventing the onset and/or delaying the progression of PD.
The transcription factor nuclear factor-E2-related factor-2 (Nrf2) is a central protein that regulates the transcription of phase II enzymes and other enzymes that are important in the antioxidative response. Under normal conditions, Nrf2 is sequestered in the cytoplasm by binding to Kelch-like ECH-associated protein 1 (Keap1). Upon stimulation, Nrf2 dissociates from Keap1 and is translocated into the nucleus where it binds to antioxidant response element (ARE) and activates the expression of ARE-dependent genes. ARE is a cis-acting regulatory element in promoter regions of genes encoding antioxidant proteins and plays a crucial role in the transcriptional regulation of downstream genes important in the cellular response to oxidative stress, such as NAD(P)H:quinone oxidoreductase 1 (NQO1) and heme oxygenase-1 (HO-1). NQO1 catalyzes the two-electron reduction of quinone to the redox-stable hydroquinone and protects cells against oxidative damage [11], [12]. HO-1 is responsible for the conversion of heme to biliverdin and carbon monoxide and functions as an antioxidant enzyme [13], [14] and an anti-inflammatory stress protein [15].
The roots of Glycyrrhiza inflata B. (Leguminosae) are known to be a source for characteristic phenolic compounds that have various pharmacological activities, including anti-inflammatory [16], antioxidative [17] and anticarcinogenic activities [18]. Six retrochalcones or reversely constructed chalcones have been isolated: licochalcone A–E and echinatin [18], [19]. Licochalcone E (Lico-E) is a very recently characterized retrochalcone that exhibits potent cytotoxicity to human tumor cell lines and endothelial cells [20], as well as anti-inflammatory potential to reduce skin inflammation [21].
Because chalcones are powerful inducers of phase II detoxifying enzymes and cytoprotective HO-1 [22], [23], in the present study, we asked whether (a) Lico-E possesses anti-inflammatory activity in lipopolysaccharide (LPS)-induced microglial BV2 cells, and antioxidant and cytoprotective activities from 6-hydroxydopamine (6-OHDA)-induced DArgic SH-SY5Y cell death; (b) Lico-E activates Nrf2 signaling and induces NQO1 and HO-1, which mediate the cytoprotective and anti-inflammatory activities of Lico-E; and (3) Lico-E is cytoprotective against DArgic neurodegeneration in the in vivo experimental models of PD.
Section snippets
Materials
Lico-E was obtained from the roots of G. inflata B. [20]. Dulbecco's modified Eagle's medium (DMEM), fetal bovine serum (FBS), penicillin/streptomycin and trypsin/EDTA were from Hyclone (Logan, UT, USA). LPS (L4516), 6-OHDA, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), α-actin antibody and TRI reagent were purchased from Sigma-Aldrich (St. Louis, MO, USA). Antibodies against inducible nitric oxide synthase (iNOS) (sc-649), cyclooxygenase-2 (COX-2) (sc-1745), β-actin (sc-8432), anti-Nrf2
Lico-E attenuates LPS-induced inflammatory response in microglial BV2 cells
Microglia are resident macrophages in the central nervous system and are primarily responsible for the inflammatory response in the pathogenesis of various neurodegenerative diseases including PD. In the present study, we used the BV2 cell line, which is a well-known murine microglial cell line showing similar phenotypic and functional properties with reactive microglial cells [27].
Because a number of chalcone derivatives exhibit anti-inflammatory activity [28], we first asked whether Lico-E (
Discussion
The present study demonstrates that (a) Lico-E obtained from the roots of G. inflata B. attenuates LPS-induced inflammatory responses in microglial BV2 cells and protects DArgic SH-SY5Y cells from 6-OHDA cytotoxicity, (b) Lico-E has neuroprotective effects against MPTP-induced nigrostriatal DArgic neurodegeneration in mice and (c) Lico-E activates the Nrf2 pathway and up-regulates downstream antioxidant enzyme expressions both in vitro and in vivo.
Retrochalcones including licochalcone A–D (Lico
References (50)
- et al.
Involvement of induction and mitochondrial targeting of orphan nuclear receptor Nur77 in 6-OHDA-induced SH-SY5Y cell death
Neurochem Int
(2010) - et al.
Prevention of dopamine-induced cell death by thiol antioxidants: possible implications for treatment of Parkinson's disease
Exp Neurol
(1996) - et al.
Role of cyclooxygenase-2 in tetrahydrobiopterin-induced dopamine oxidation
Biochem Biophys Res Commun
(2007) - et al.
Inflammatory regulators in Parkinson's disease: iNOS, lipocortin-1, and cyclooxygenases-1 and -2
Mol Cell Neurosci
(2000) - et al.
Contribution of NAD(P)H:quinone oxidoreductase 1 to protection against carcinogenesis, and regulation of its gene by the Nrf2 basic-region leucine zipper and the arylhydrocarbon receptor basic helix–loop–helix transcription factors
Mutat Res
(2004) - et al.
Role of nicotinamide quinone oxidoreductase 1 (NQO1) in protection against toxicity of electrophiles and reactive oxygen intermediates
Methods Enzymol
(2004) - et al.
Antioxidants and oxidants regulated signal transduction pathways
Biochem Pharmacol
(2002) - et al.
Dimethylfumarate induces immunosuppression via glutathione depletion and subsequent induction of heme oxygenase 1
J Invest Dermatol
(2007) - et al.
Antioxidative and superoxide scavenging activities of retrochalcones in Glycyrrhiza inflata
Bioorg Med Chem
(1998) - et al.
New type chalcones from licorice root
Tetrahedron Lett
(1975)
Licochalcone E reduces chronic allergic contact dermatitis and inhibits IL-12p40 production through down-regulation of NF-kappaB
Int Immunopharmacol
Bromocriptine activates NQO1 via Nrf2-PI3K/Akt signaling: novel cytoprotective mechanism against oxidative damage
Pharmacol Res
Microglial reaction in MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) induced Parkinson's disease mice model
Neurodegeneration
Synthesis and anti-inflammatory activity of chalcone derivatives
Bioorg Med Chem Lett
Licochalcone A significantly suppresses LPS signaling pathway through the inhibition of NF-kappaB p65 phosphorylation at serine 276
Cell Signal
Glycyrrhiza inflata-derived chalcones, licochalcone A, licochalcone B and licochalcone D, inhibit phosphorylation of NF-kappaB p65 in LPS signaling pathway
Int Immunopharmacol
Upregulation of heme oxygenase-1 by Epigallocatechin-3-gallate via the phosphatidylinositol 3-kinase/Akt and ERK pathways
Life Sci
trans-Resveratrol, a natural antioxidant from grapes, increases sperm output in healthy rats
J Nutr
Chalcone inhibits the activation of NF-kappaB and STAT3 in endothelial cells via endogenous electrophile
Life Sci
In vivo modulation of the Parkinsonian phenotype by Nrf2
Neurotoxicology
Nrf2-mediated protection against 6-hydroxydopamine
Brain Res
Hydrophobicity and central nervous system agents: on the principle of minimal hydrophobicity in drug design
J Pharm Sci
Molecular pathways of neurodegeneration in Parkinson's disease
Science
Neuroinflammation in Parkinson's disease: is there sufficient evidence for mechanism-based interventional therapy?
Front Biosci
Reactive dopamine metabolites and neurotoxicity: implications for Parkinson's disease
Adv Exp Med Biol
Cited by (85)
Scutellarin attenuates oxidative stress and neuroinflammation in cerebral ischemia/reperfusion injury through PI3K/Akt-mediated Nrf2 signaling pathways
2023, European Journal of PharmacologyPrivileged chalcone scaffolds in drug discovery
2023, Privileged Scaffolds in Drug DiscoveryDiphenyl diselenide modulates antioxidant status, inflammatory and redox-sensitive genes in diesel exhaust particle-induced neurotoxicity
2022, Chemico-Biological InteractionsLicochalcone B attenuates neuronal injury through anti-oxidant effect and enhancement of Nrf2 pathway in MCAO rat model of stroke
2021, International ImmunopharmacologyCitation Excerpt :Moreover, by IHC staining and ELISA, we also found that Lico B suppressed the TNF-α and iNOS (proinflammatory cytokine), but increased the IL-4 (anti-inflammatory cytokine) [38], revealing its anti-inflammatory activity. Previously, the potential of Lico A in anti-oxidant therapies have been widely explored in various diseases, such as hepatotoxicity, skin damage, neurodegenerative diseases [39–43], nevertheless, the anti-oxidant activity of Lico B has not been illustrated yet. Actually, to the best of our knowledge, this is the first report that verify the anti-oxidant, and anti-inflammatory activities of Lico B in animal models.
- ☆
This research was supported by Technology Development Program for Agriculture and Forestry, Ministry for Food, Agriculture, Forestry and Fisheries, Republic of Korea (106073-1; to H.J. Choi).
- 1
S.S. Kim and J. Lim contributed equally to this work.