Studies found that sympathetic nerves showed germination growth and increased density in the tissues of some disease animal models and old mouse models. These studies suggest that sympathetic nerves are closely related to aging. In this study, the expression of tyrosine hydroxylase (TH), marker for sympathetic nerve was detected by immunohistochemistry in liver, lung, spleen tissues of older mice and human colorectal adenoma tissues. The results confirmed that the density of sympathetic nerve fibers increased significantly in aging tissues. However, the mechanism of this biological change in aging tissues is not yet clear. In this paper, the human fibroblast lines 2BS were used as the experimental materials, through transcriptome sequencing we found that the Netrin-1, a secretory axon guidance protein, was significantly upregulated in senescent cells. ELISA and Real-time PCR results showed that the level of Netrin-1 proteins and mRNAs were higher in premature senescence induced by bleomycin, ionizing radiation, cancer protein RasV12 overexpression and replicative senescence of 2BS cells than that of young control groups. DNA damage response (DDR) is an important regulatory pathway for senescent cell secretion proteins. To determine whether up-regulated expression of Netrin-1 in senescent cells is related to DDR, small molecule compounds were used to inhibit the activity of ataxia telangiectasia mutated (ATM) and checkpoint kinase (CHK2), which are important effector molecules of DDR, in bleomycin-induced senescent 2BS cells. ELISA and Real-time quantitative PCR results showed that: blocking DDR activity in senescent cells did not change the level of Netrin-1 compared with the bleomycin-induced senescence group, suggesting that Netrin-1 in senescent cells is not dependent on the DDR pathway. Western blotting revealed that histone methyltransferase EZH2 was significantly less expressed in senescent cells than in younger cells. Real-time PCR results showed that inhibition of EZH2 activity in young cells by small molecule compounds resulted in increased expression of Netrin-1. CHIP assays showed that EZH2 significantly enriched the DNA fragments in the promoter region of Netrin-1 in young cells, but not in senescent cells. The results above suggest that the down-regulated expression of EZH2 in senescent cells is an important reason for the increased expression of Netrin-1. The co-culture results of DRG in rats and senescent cells confirmed that senescent cells have a guiding effect on sympathetic nerves and this phenomenon is dependent on the secretion of Netrin-1. Based on the results above, this paper concluded that the up-regulated expression of Netrin-1 in senescent cells is independent of DDR pathway and related to the down-regulated expression of EZH2. Senescent cells promote sympathetic axonal directional growth by secreting Netrin-1. This provides a new clue for the in-depth study about the mechanism and prevention and treatment of senile diseases, which could be of potential application value.
周晓佳,于爱清,毛泽斌. EZH2在衰老细胞中表达下调引起Netrin-1表达增加进而促进交感神经轴突生长[J]. 中国生物化学与分子生物学报, 2019, 35(5): 517-527.
ZHOU Xiao-Jia, YU Ai-Qing, Mao Ze-Bin. Down-regulated Expression of EZH2 in Senescent Cells Leads to Increased Netrin-1 and thereby Promotes Sympathetic Axon Growth. Chinese Journal of Biochemistry and Molecular Biol, 2019, 35(5): 517-527.
[1] Niccoli T, Partridge L. Ageing as a risk factor for disease[J]. Curr Biol, 2012, 22(17): R741-752
[2] McHugh D, Gil J. Senescence and aging: Causes, consequences, and therapeutic avenues[J]. J Cell Biol, 2018, 217(1): 65-77
[3] Nelson G, Wordsworth J, Wang C, et al. A senescent cell bystander effect: senescence-induced senescence [J]. Aging Cell, 2012, 11(2): 345-349
[4] Xu M, Tchkonia T, Ding H, et al. JAK inhibition alleviates the cellular senescence-associated secretory phenotype and frailty in old age[J]. Proc Natl Acad Sci U S A, 2015, 112(46): E6301-6310
[5] Xu M, Bradley EW, Weivoda MM, et al. Transplanted senescent cells induce an osteoarthritis-like condition in mice[J]. J Gerontol A Biol Sci Med Sci, 2017, 72(6): 780-785
[6] Burton DG. Cellular senescence, ageing and disease[J]. Age (Dordr), 2009, 31(1): 1-9
[7] Sikora E, Bielak-Zmijewska A, Mosieniak G. Cellular senescence in ageing, age-related disease and longevity[J]. Curr Vasc Pharmacol, 2014, 12(5): 698-706
[8] Childs BG, Gluscevic M, Baker DJ, et al. Senescent cells: an emerging target for diseases of ageing[J]. Nat Rev Drug Discov, 2017, 16(10): 718-735
[9] Crutcher KA. Aging and neuronal plasticity: lessons from a model[J]. Auton Neurosci, 2002, 96(1): 25-32
[10] Hart EC, Wallin BG, Barnes JN, et al. Sympathetic nerve activity and peripheral vasodilator capacity in young and older men[J]. Am J Physiol Heart Circ Physiol, 2014, 306(6): H904-909
[11] Bakovic M, Filipovic N, Ferhatovic Hamzic L, et al. Changes in neurofilament 200 and tyrosine hydroxylase expression in the cardiac innervation of diabetic rats during aging[J]. Cardiovasc Pathol, 2018, 32: 38-43
[12] Jimenez-Andrade JM, Mantyh PW. Sensory and sympathetic nerve fibers undergo sprouting and neuroma formation in the painful arthritic joint of geriatric mice[J]. Arthritis Res Ther, 2012, 14(3): R101
[13] Tessier-Lavigne M, Goodman CS. The molecular biology of axon guidance[J]. Science, 1996, 274(5290): 1123-1133
[14] Bashaw GJ, Klein R. Signaling from axon guidance receptors[J]. Cold Spring Harb Perspect Biol, 2010, 2(5): a001941
[15] Kennedy TE, Serafini T, De La Torre JR, et al. Netrins are diffusible chemotropic factors for commissural axons in the embryonic spinal cord[J]. Cell, 1994, 78(3): 425-435
[16] Serafini T, Kennedy TE, Galko MJ, et al. The netrins define a family of axon outgrowth-promoting proteins homologous to C. elegans UNC-6[J]. Cell, 1994, 78(3): 409-424
[17] Lai Wing Sun K, Correia JP, Kennedy TE. Netrins: versatile extracellular cues with diverse functions[J]. Development, 2011, 138(11): 2153-2169
[18] Di Meglio T, Kratochwil CF, Vilain N, et al. Ezh2 orchestrates topographic migration and connectivity of mouse precerebellar neurons[J]. Science, 2013, 339(6116): 204-207
[19] Baker DJ, Childs BG, Durik M, et al. Naturally occurring p16(Ink4a)-positive cells shorten healthy lifespan[J]. Nature, 2016, 530(7589): 184-189
[20] Baker DJ, Wijshake T, Tchkonia T, et al. Clearance of p16(Ink4a)-positive senescent cells delays ageing-associated disorders[J]. Nature, 2011, 479(7372): 232-236
[21] Kirkland JL, Tchkonia T. Cellular senescence: A translational perspective[J]. EBioMedicine, 2017, 21: 21-28
[22] Zhu Y, Tchkonia T, Pirtskhalava T, et al. The Achilles' heel of senescent cells: from transcriptome to senolytic drugs[J]. Aging Cell, 2015, 14(4): 644-658
[23] Tchkonia T, Zhu Y, van Deursen J, et al. Cellular senescence and the senescent secretory phenotype: therapeutic opportunities[J]. J Clin Invest, 2013, 123(3): 966-972
[24] Layne K, Ferro A, Passacquale G. Netrin-1 as a novel therapeutic target in cardiovascular disease: to activate or inhibit?[J]. Cardiovasc Res, 2015, 107(4): 410-419
[25] Mehlen P, Guenebeaud C. Netrin-1 and its dependence receptors as original targets for cancer therapy[J]. Curr Opin Oncol, 2010, 22(1): 46-54
[26] Ramesh G. Role of Netrin-1 beyond the brain: from biomarker of tissue injury to therapy for inflammatory diseases[J]. Recent Pat Biomark, 2012, 2(3): 202-208