메뉴 건너뛰기




Volumn 134, Issue 1, 2011, Pages 220-234

Oestrogens ameliorate mitochondrial dysfunction in Leber's hereditary optic neuropathy

Author keywords

LHON; mitochondrial disorders; oestrogen; oestrogen receptors; oxidative stress

Indexed keywords

ESTRADIOL; ESTROGEN RECEPTOR; ESTROGEN RECEPTOR BETA; FULVESTRANT; GALACTOSE; GLUCOSE; MANGANESE SUPEROXIDE DISMUTASE; MITOCHONDRIAL DNA; REACTIVE OXYGEN METABOLITE;

EID: 78650693389     PISSN: 00068950     EISSN: 14602156     Source Type: Journal    
DOI: 10.1093/brain/awq276     Document Type: Article
Times cited : (205)

References (49)
  • 1
    • 18544384889 scopus 로고    scopus 로고
    • Severe impairment of complex I-driven adenosine triphosphate synthesis in Leber hereditary optic neuropathy cybrids
    • Baracca A, Solaini G, Sgarbi G, Lenaz G, Baruzzi A, Schapira AH, et al. Severe impairment of complex I-driven adenosine triphosphate synthesis in Leber hereditary optic neuropathy cybrids. Arch Neurol 2005; 62: 730-6.
    • (2005) Arch Neurol , vol.62 , pp. 730-6
    • Baracca, A.1    Solaini, G.2    Sgarbi, G.3    Lenaz, G.4    Baruzzi, A.5    Schapira, A.H.6
  • 3
    • 4944263224 scopus 로고    scopus 로고
    • Leber hereditary optic neuropathy mtDNA mutations disrupt glutamate transport in cybrid cell lines
    • Beretta S, Mattavelli L, Sala G, Tremolizzo L, Schapira AH, Martinuzzi A, et al. Leber hereditary optic neuropathy mtDNA mutations disrupt glutamate transport in cybrid cell lines. Brain 2004; 127: 2183-92.
    • (2004) Brain , vol.127 , pp. 2183-92
    • Beretta, S.1    Mattavelli, L.2    Sala, G.3    Tremolizzo, L.4    Schapira, A.H.5    Martinuzzi, A.6
  • 4
    • 23844445847 scopus 로고    scopus 로고
    • 17beta-oestradiol up-regulates longevity-related anti-oxidant enzyme expression via the ERK1 and ERK2[MAPK]/ NFkappaB cascade
    • Borrás C, Gambini J, Gó mez-Cabrera MC, Sastre J, Pallardó FV, Mann GE, et al. 17beta-oestradiol up-regulates longevity-related anti-oxidant enzyme expression via the ERK1 and ERK2[MAPK]/NFkappaB cascade. Aging Cell 2005; 4: 113-18.
    • (2005) Aging Cell , vol.4 , pp. 113-18
    • Borrás, C.1    Gambini, J.2    Gómez-Cabrera, M.C.3    Sastre, J.4    Pallardó, F.V.5    Mann, G.E.6
  • 5
    • 0025820109 scopus 로고
    • X chromosome-linked and mitochondrial gene control of Leber hereditary optic neuropathy: Evidence from segregation analysis for dependence on X chromosome inactivation
    • Bu XD, Rotter JI. X chromosome-linked and mitochondrial gene control of Leber hereditary optic neuropathy: evidence from segregation analysis for dependence on X chromosome inactivation. Proc Natl Acad Sci USA 1991; 88: 8198-202.
    • (1991) Proc Natl Acad Sci USA , vol.88 , pp. 8198-202
    • Bu, X.D.1    Rotter, J.I.2
  • 6
    • 33645344999 scopus 로고    scopus 로고
    • Haplogroup effects and recombination of mitochondrial DNA: Novel clues from the analysis of Leber hereditary optic neuropathy pedigrees
    • Carelli V, Achilli A, Valentino ML, Rengo C, Semino O, Pala M, et al. Haplogroup effects and recombination of mitochondrial DNA: novel clues from the analysis of Leber hereditary optic neuropathy pedigrees. Am J Hum Genet 2006; 78: 564-74.
    • (2006) Am J Hum Genet , vol.78 , pp. 564-74
    • Carelli, V.1    Achilli, A.2    Valentino, M.L.3    Rengo, C.4    Semino, O.5    Pala, M.6
  • 7
    • 0037406049 scopus 로고    scopus 로고
    • Pathogenic expression of homoplasmic mtDNA mutations needs a complex nuclear-mitochondrial interaction
    • Carelli V, Giordano C, d'Amati G. Pathogenic expression of homoplasmic mtDNA mutations needs a complex nuclear-mitochondrial interaction. Trends Genet 2003; 19: 257-62.
    • (2003) Trends Genet , vol.19 , pp. 257-62
    • Carelli, V.1    Giordano, C.2    D'Amati, G.3
  • 10
    • 0037048622 scopus 로고    scopus 로고
    • Respiratory function in cybrid cell lines carrying European mtDNA haplogroups: Implications for Leber's hereditary optic neuropathy
    • Carelli V, Vergani L, Bernazzi B, Zampieron C, Bucchi L, Valentino M, et al. Respiratory function in cybrid cell lines carrying European mtDNA haplogroups: implications for Leber's hereditary optic neuropathy. Biochim Biophys Acta 2002; 1588: 7-14.
    • (2002) Biochim Biophys Acta , vol.1588 , pp. 7-14
    • Carelli, V.1    Vergani, L.2    Bernazzi, B.3    Zampieron, C.4    Bucchi, L.5    Valentino, M.6
  • 11
    • 0029981001 scopus 로고    scopus 로고
    • Evidence against an X-linked visual loss susceptibility locus in Leber hereditary optic neuropathy
    • Chalmers RM, Davis MB, Sweeney MG, Wood NW, Harding AE. Evidence against an X-linked visual loss susceptibility locus in Leber hereditary optic neuropathy. Am J Hum Genet 1996; 59: 103-8.
    • (1996) Am J Hum Genet , vol.59 , pp. 103-8
    • Chalmers, R.M.1    Davis, M.B.2    Sweeney, M.G.3    Wood, N.W.4    Harding, A.E.5
  • 12
    • 69949092670 scopus 로고    scopus 로고
    • Regulation of mitochon-drial respiratory chain biogenesis by estrogens/estrogen receptors and physiological pathological and pharmacological implications
    • Chen JQ, Cammarata PR, Baines CP, Yager JD. Regulation of mitochon-drial respiratory chain biogenesis by estrogens/estrogen receptors and physiological pathological and pharmacological implications. Biochim Biophys Acta 2009; 1793: 1540-70.
    • (2009) Biochim Biophys Acta , vol.1793 , pp. 1540-70
    • Chen, J.Q.1    Cammarata, P.R.2    Baines, C.P.3    Yager, J.D.4
  • 14
    • 9644267549 scopus 로고    scopus 로고
    • Binding of MCF-7 cell mito-chondrial proteins and recombinant human estrogen receptors alpha and beta to human mitochondrial DNA estrogen response elements
    • Chen JQ, Eshete M, Alworth WL, Yager JD. Binding of MCF-7 cell mito-chondrial proteins and recombinant human estrogen receptors alpha and beta to human mitochondrial DNA estrogen response elements. J Cell Biochem 2004b; 93: 358-73.
    • (2004) J Cell Biochem , vol.93 , pp. 358-73
    • Chen, J.Q.1    Eshete, M.2    Alworth, W.L.3    Yager, J.D.4
  • 15
    • 39149095963 scopus 로고    scopus 로고
    • Assay for apoptosis using the mitochondrial probes, Rhodamine123 and 10-N-nonyl acridine orange
    • Ferlini C, Scambia G. Assay for apoptosis using the mitochondrial probes, Rhodamine123 and 10-N-nonyl acridine orange. Nat Protoc 2007; 2: 3111-14.
    • (2007) Nat Protoc , vol.2 , pp. 3111-14
    • Ferlini, C.1    Scambia, G.2
  • 16
    • 20044381305 scopus 로고    scopus 로고
    • Antioxidant defences in cybrids harboring mtDNA mutations associated with Leber's hereditary optic neuropathy
    • Floreani M, Napoli E, Martinuzzi A, Pantano G, De Riva V, Trevisan R, et al. Antioxidant defences in cybrids harboring mtDNA mutations associated with Leber's hereditary optic neuropathy. FEBS J 2005; 272: 1124-35.
    • (2005) FEBS J , vol.272 , pp. 1124-35
    • Floreani, M.1    Napoli, E.2    Martinuzzi, A.3    Pantano, G.4    De Riva, V.5    Trevisan, R.6
  • 17
    • 70949088600 scopus 로고    scopus 로고
    • The background of mitochondrial DNA haplogroup J increases the sensitivity of Leber's hereditary optic neuropathy cells to 2,5-hexanedione toxicity
    • Ghelli A, Porcelli AM, Zanna C, Vidoni S, Mattioli S, Barbieri A, et al. The background of mitochondrial DNA haplogroup J increases the sensitivity of Leber's hereditary optic neuropathy cells to 2,5-hexanedione toxicity. PLoS One 2009; 4: e7922.
    • (2009) PLoS One , vol.4
    • Ghelli, A.1    Porcelli, A.M.2    Zanna, C.3    Vidoni, S.4    Mattioli, S.5    Barbieri, A.6
  • 18
    • 0037423202 scopus 로고    scopus 로고
    • Leber's hereditary optic neuropathy (LHON) pathogenic mutations induce mitochondrial-dependent apoptotic death in transmito-chondrial cells incubated with galactose medium
    • Ghelli A, Zanna C, Porcelli AM, Schapira AH, Martinuzzi A, Carelli V, et al. Leber's hereditary optic neuropathy (LHON) pathogenic mutations induce mitochondrial-dependent apoptotic death in transmito-chondrial cells incubated with galactose medium. J Biol Chem 2003; 278: 4145-50.
    • (2003) J Biol Chem , vol.278 , pp. 4145-50
    • Ghelli, A.1    Zanna, C.2    Porcelli, A.M.3    Schapira, A.H.4    Martinuzzi, A.5    Carelli, V.6
  • 19
    • 44149113049 scopus 로고    scopus 로고
    • Mitochondrial superoxide dismutase activation with 17 beta-estradiol-treated human lens epithelial cells
    • Gottipati S, Cammarata PR. Mitochondrial superoxide dismutase activation with 17 beta-estradiol-treated human lens epithelial cells. Mol Vis 2008; 14: 898-905.
    • (2008) Mol Vis , vol.14 , pp. 898-905
    • Gottipati, S.1    Cammarata, P.R.2
  • 20
    • 37548999745 scopus 로고    scopus 로고
    • X-Inactivation patterns in females harboring mtDNA mutations that cause Leber hereditary optic neuropathy
    • Hudson G, Carelli V, Horvath R, Zeviani M, Smeets HJ, Chinnery PF. X-Inactivation patterns in females harboring mtDNA mutations that cause Leber hereditary optic neuropathy. Mol Vis 2007a; 13: 2339-43.
    • (2007) Mol Vis , vol.13 , pp. 2339-43
    • Hudson, G.1    Carelli, V.2    Horvath, R.3    Zeviani, M.4    Smeets, H.J.5    Chinnery, P.F.6
  • 21
    • 34547796899 scopus 로고    scopus 로고
    • Clinical expression of Leber hereditary optic neuropathy is affected by the mitochondrial DNA-haplogroup background
    • Hudson G, Carelli V, Spruijt L, Gerards M, Mowbray C, Achilli A, et al. Clinical expression of Leber hereditary optic neuropathy is affected by the mitochondrial DNA-haplogroup background. Am J Hum Genet 2007b; 81: 228-33.
    • (2007) Am J Hum Genet , vol.81 , pp. 228-33
    • Hudson, G.1    Carelli, V.2    Spruijt, L.3    Gerards, M.4    Mowbray, C.5    Achilli, A.6
  • 22
    • 28144454984 scopus 로고    scopus 로고
    • Identification of an X-chromosomal locus and haplotype modulating the phenotype of a mitochondrial DNA disorder
    • Hudson G, Keers S, Yu-Wai Man P, Griffiths P, Huoponen K, Savontaus ML, et al. Identification of an X-chromosomal locus and haplotype modulating the phenotype of a mitochondrial DNA disorder. Am J Hum Genet 2005; 77: 1086-91.
    • (2005) Am J Hum Genet , vol.77 , pp. 1086-91
    • Hudson, G.1    Keers, S.2    Yu-Wai Man, P.3    Griffiths, P.4    Huoponen, K.5    Savontaus, M.L.6
  • 24
    • 0031039888 scopus 로고    scopus 로고
    • Comparison of the ligand binding specificity and transcript tissue distribution of estrogen receptors alpha and beta
    • Kuiper GG, Carlsson B, Grandien K, Enmark E, Haggblad J, Nilsson S, et al. Comparison of the ligand binding specificity and transcript tissue distribution of estrogen receptors alpha and beta. Endocrinology 1997; 138: 863-70.
    • (1997) Endocrinology , vol.138 , pp. 863-70
    • Kuiper, G.G.1    Carlsson, B.2    Grandien, K.3    Enmark, E.4    Haggblad, J.5    Nilsson, S.6
  • 28
    • 27144527399 scopus 로고    scopus 로고
    • Effect of CD4-monitored treatment interruption on mitochondrial DNA content in HIV-infected patients: A prospective study
    • Mussini C, Pinti M, Bugarini R, Borghi V, Nasi M, Nemes E, et al. Effect of CD4-monitored treatment interruption on mitochondrial DNA content in HIV-infected patients: a prospective study. AIDS 2005; 19: 1627-33.
    • (2005) AIDS , vol.19 , pp. 1627-33
    • Mussini, C.1    Pinti, M.2    Bugarini, R.3    Borghi, V.4    Nasi, M.5    Nemes, E.6
  • 29
    • 0021288861 scopus 로고
    • Assay of superoxide dismutase activity in tumor tissue
    • Oberley LW, Spitz DR. Assay of superoxide dismutase activity in tumor tissue. Methods Enzymol 1984; 105: 457-64.
    • (1984) Methods Enzymol , vol.105 , pp. 457-64
    • Oberley, L.W.1    Spitz, D.R.2
  • 31
    • 33744514462 scopus 로고    scopus 로고
    • Functional estrogen receptors in the mitochondria of breast cancer cells
    • Pedram A, Razandi M, Wallace DC, Levin ER. Functional estrogen receptors in the mitochondria of breast cancer cells. Mol Biol Cell 2006; 17: 2125-37.
    • (2006) Mol Biol Cell , vol.17 , pp. 2125-37
    • Pedram, A.1    Razandi, M.2    Wallace, D.C.3    Levin, E.R.4
  • 32
    • 57049107271 scopus 로고    scopus 로고
    • Mitochondrial DNA background modulates the assembly kinetics of OXPHOS complexes in a cellular model of mitochondrial disease
    • Pello R, Mart́n MA, Carelli V, Nijtmans LG, Achilli A, Pala M, et al. Mitochondrial DNA background modulates the assembly kinetics of OXPHOS complexes in a cellular model of mitochondrial disease. Hum Mol Genet 2008; 17: 4001-11.
    • (2008) Hum Mol Genet , vol.17 , pp. 4001-11
    • Pello, R.1    Mart́n, M.A.2    Carelli, V.3    Nijtmans, L.G.4    Achilli, A.5    Pala, M.6
  • 33
    • 0026457218 scopus 로고
    • Nonviability of cells with oxidative defects in galactose medium: A screening test for affected patient fibroblasts
    • Robinson BH, Petrova-Benedict R, Buncic JR, Wallace DC. Nonviability of cells with oxidative defects in galactose medium: a screening test for affected patient fibroblasts. Biochem Med Metab Biol 1992; 48: 122-6.
    • (1992) Biochem Med Metab Biol , vol.48 , pp. 122-6
    • Robinson, B.H.1    Petrova-Benedict, R.2    Buncic, J.R.3    Wallace, D.C.4
  • 34
    • 0042850443 scopus 로고    scopus 로고
    • Extensive investigation of a large Brazilian pedigree of 11778/ haplogroup J Leber hereditary optic neuropathy
    • Sadun AA, Carelli V, Salomao SR, Berezovsky A, Quiros PA, Sadun F, et al. Extensive investigation of a large Brazilian pedigree of 11778/ haplogroup J Leber hereditary optic neuropathy. Am J Ophthalmol 2003; 136: 231-8.
    • (2003) Am J Ophthalmol , vol.136 , pp. 231-8
    • Sadun, A.A.1    Carelli, V.2    Salomao, S.R.3    Berezovsky, A.4    Quiros, P.A.5    Sadun, F.6
  • 35
    • 19944426426 scopus 로고    scopus 로고
    • Retinal nerve fiber layer evaluation by optical coherence tomography in unaffected carriers with Leber'shereditary optic neuropathy mutations
    • Savini G, Barboni P, Valentino ML, Montagna P, Cortelli P, De Negri AM, et al. Retinal nerve fiber layer evaluation by optical coherence tomography in unaffected carriers with Leber'shereditary optic neuropathy mutations. Ophthalmology 2005; 112: 127-31.
    • (2005) Ophthalmology , vol.112 , pp. 127-31
    • Savini, G.1    Barboni, P.2    Valentino, M.L.3    Montagna, P.4    Cortelli, P.5    De Negri, A.M.6
  • 36
    • 34648837687 scopus 로고    scopus 로고
    • Induction of mitochondrial biogenesis is a maladaptive mechanism in mitochondrial cardiomyopathies
    • Sebastiani M, Giordano C, Nediani C, Travaglini C, Borchi E, Zani M, et al. Induction of mitochondrial biogenesis is a maladaptive mechanism in mitochondrial cardiomyopathies. J Am Coll Cardiol 2007; 50: 1362-9.
    • (2007) J Am Coll Cardiol , vol.50 , pp. 1362-9
    • Sebastiani, M.1    Giordano, C.2    Nediani, C.3    Travaglini, C.4    Borchi, E.5    Zani, M.6
  • 38
    • 47849092592 scopus 로고    scopus 로고
    • Estrogen actions on mitochondria-physiological and pathological implications
    • Simpkins JW, Yang SH, Sarkar SN, Pearce V. Estrogen actions on mitochondria-physiological and pathological implications. Cell Endocrinol 2008; 290: 51-9.
    • (2008) Cell Endocrinol , vol.290 , pp. 51-9
    • Simpkins, J.W.1    Yang, S.H.2    Sarkar, S.N.3    Pearce, V.4
  • 39
    • 24944498888 scopus 로고    scopus 로고
    • Differential subcellular distribution of estrogen receptor isoforms: Localization of ERalpha in the nucleoli and ERbeta in the mitochondria of human osteosarcoma SaOS-2 and hepatocarcinoma HepG2 cell lines
    • Solakidi S, Psarra AM, Sekeris CE. Differential subcellular distribution of estrogen receptor isoforms: localization of ERalpha in the nucleoli and ERbeta in the mitochondria of human osteosarcoma SaOS-2 and hepatocarcinoma HepG2 cell lines. Biochim Biophys Acta 2005; 1745: 382-92.
    • (2005) Biochim Biophys Acta , vol.1745 , pp. 382-92
    • Solakidi, S.1    Psarra, A.M.2    Sekeris, C.E.3
  • 40
    • 0033941791 scopus 로고    scopus 로고
    • Detection of apoptosis in tissue sections
    • Stadelmann C, Lassmann H. Detection of apoptosis in tissue sections. Cell Tissue Res 2000; 301: 19-31.
    • (2000) Cell Tissue Res , vol.301 , pp. 19-31
    • Stadelmann, C.1    Lassmann, H.2
  • 41
    • 33749999530 scopus 로고    scopus 로고
    • Suppression of reactive oxygen species and neurodegeneration by the PGC-1 transcriptional coactivators
    • St-Pierre J, Drori S, Uldry M, Silvaggi JM, Rhee J, Jager S, et al. Suppression of reactive oxygen species and neurodegeneration by the PGC-1 transcriptional coactivators. Cell 2006; 127: 379-408.
    • (2006) Cell , vol.127 , pp. 379-408
    • St-Pierre, J.1    Drori, S.2    Uldry, M.3    Silvaggi, J.M.4    Rhee, J.5    Jager, S.6
  • 42
    • 34250175807 scopus 로고    scopus 로고
    • Male prevalence of acquired color vision defects in asymptomatic carriers of Leber's hereditary optic neuropathy
    • Ventura DF, Gualtieri M, Oliveira AG, Costa MF, Quiros P, Sadun F, et al. Male prevalence of acquired color vision defects in asymptomatic carriers of Leber's hereditary optic neuropathy. Invest Ophthalmol Vis Sci 2007; 48: 2362-70.
    • (2007) Invest Ophthalmol Vis Sci , vol.48 , pp. 2362-70
    • Ventura, D.F.1    Gualtieri, M.2    Oliveira, A.G.3    Costa, M.F.4    Quiros, P.5    Sadun, F.6
  • 43
    • 0026034238 scopus 로고
    • Optic atrophy in Leber hereditary optic neuroretinopathy is probably determined by an X-chromosomal gene closely linked to DXS7
    • Vilkki J, Ott J, Savontaus ML, Aula P, Nikoskelainen EK. Optic atrophy in Leber hereditary optic neuroretinopathy is probably determined by an X-chromosomal gene closely linked to DXS7. Am J Hum Genet 1991; 48: 486-91.
    • (1991) Am J Hum Genet , vol.48 , pp. 486-91
    • Vilkki, J.1    Ott, J.2    Savontaus, M.L.3    Aula, P.4    Nikoskelainen, E.K.5
  • 44
    • 33750737290 scopus 로고    scopus 로고
    • Role of mitochondrial oxidative stress to explain the different longevity between genders: Protective effect of estrogens
    • Viña J, Sastre J, Pallardó FV, Gambini J, Borrás C. Role of mitochondrial oxidative stress to explain the different longevity between genders: protective effect of estrogens. Free Radic Res 2006; 40: 1359-65.
    • (2006) Free Radic Res , vol.40 , pp. 1359-65
    • Viña, J.1    Sastre, J.2    Pallardó, F.V.3    Gambini, J.4    Borrás, C.5
  • 45
    • 0024242545 scopus 로고
    • Mitochondrial DNA mutation associated with Leber's hereditary optic neuropathy
    • Wallace DC, Singh G, Lott MT, Hodge JA, Schurr TG, Lezza AM, et al. Mitochondrial DNA mutation associated with Leber's hereditary optic neuropathy. Science 1988; 242: 1427-30.
    • (1988) Science , vol.242 , pp. 1427-30
    • Wallace, D.C.1    Singh, G.2    Lott, M.T.3    Hodge, J.A.4    Schurr, T.G.5    Lezza, A.M.6
  • 46
    • 34247211016 scopus 로고    scopus 로고
    • Enhanced oxidative stress and aberrant mitochondrial biogenesis in human neuroblastoma SH-SY5Y cells during methamphetamine induced apoptosis
    • Wu CW, Ping YH, Yen JC, Chang CY, Wang SF, Yeh CL, et al. Enhanced oxidative stress and aberrant mitochondrial biogenesis in human neuroblastoma SH-SY5Y cells during methamphetamine induced apoptosis. Toxicol Appl Pharmacol 2007; 220: 243-51.
    • (2007) Toxicol Appl Pharmacol , vol.220 , pp. 243-51
    • Wu, C.W.1    Ping, Y.H.2    Yen, J.C.3    Chang, C.Y.4    Wang, S.F.5    Yeh, C.L.6
  • 48
    • 24644461049 scopus 로고    scopus 로고
    • Caspase-independent death of Leber's hereditary optic neuropathy cybrids is driven by energetic failure and mediated by AIF and Endonuclease G
    • Zanna C, Ghelli A, Porcelli AM, Martinuzzi A, Carelli V, Rugolo M. Caspase-independent death of Leber's hereditary optic neuropathy cybrids is driven by energetic failure and mediated by AIF and Endonuclease G. Apoptosis 2005; 10: 997-1007.
    • (2005) Apoptosis , vol.10 , pp. 997-1007
    • Zanna, C.1    Ghelli, A.2    Porcelli, A.M.3    Martinuzzi, A.4    Carelli, V.5    Rugolo, M.6
  • 49
    • 38849190029 scopus 로고    scopus 로고
    • OPA1 mutations associated with dominant optic atrophy impair oxidative phosphorylation and mitochondrial fusion
    • Zanna C, Ghelli A, Porcelli AM, Karbowski M, Youle RJ, Schimpf S, et al. OPA1 mutations associated with dominant optic atrophy impair oxidative phosphorylation and mitochondrial fusion. Brain 2008; 131: 352-67.
    • (2008) Brain , vol.131 , pp. 352-67
    • Zanna, C.1    Ghelli, A.2    Porcelli, A.M.3    Karbowski, M.4    Youle, R.J.5    Schimpf, S.6


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.