CAN THIlPARN VOI CUOC SONG
• Nguyen Dirong Tuf
1. Can thifp ARN Id gi?
Can thifp ARN (RNA inteference - RNA can thifp) la mdt trong nhflng dgt phd cdng nghf quan trgng nhdt trong sinh hgc hifn dai. Trong nhung nam 90 thl ky XX, mgt sd nhd khoa hpc dd nghidn ciiu ve khd ndng uc che sy bieu hifn cua mRNA d thuc vdt vd ndm. Mac du hifn tupng nay dugc xdc dinh nhung chua dugc hidu vl bdn chat, CO che vd tac dung quan trpng cua nd. Nam 1998, hai nhd khoa hgc My la Andrew Fire va Craig Mello da cdng bd phdt hifn cua hp vd mdt co che cd the ldm suy bien ARN thdng tin (mRNA) dugc sao ma to mdt gene xac dinh vd hp gpi do Id "can thifp ARN". Co chl nay dugc kich hoat khi cac phdn tO ARN kep (dsRNA) xult hifn trong tl bdo. Khi do chuoi dsRNA kich hogt "co mdy" sinh hod, iam suy biln cdc phan tO mRNA dugc sao ma di truyen to ADN khdng bilu hifn dugc chuc nang gidi ma, cho ra chuoi protein tuong iing.
Dac bift, can thifp ARN vdi chudi dsRNA ngdn tryc tiejs cd thl thuc hien trong cac tl bao ddng vgt cd vii ma khdng gdy nen cac hifu Ong khdng dgc hieu. Vdi vifc khdm phd
ra ca che can thifp RNA (cdch vd hifu hod hoat dgng cua cdc gen xac djnh), hai nlid khoa hgc Andrew Z. Fire (Vifn Cdng nghf Massachusetts, Trudng Y Dgi hpc Stanford) vd Craig C.
Mel lo (Dgi hpc Harvard, Trudng Y Dgi hgc Massachusetts) da gidnh Gidi Nobel Y hgc 2006. TO dd, cac ling dung cua cdng nghf iRNA cd the dugc su dung de xac dinh vd danh gid chuc ndng cua hdng ngdn gene trong hf gene cd tiem nang tham gia vdo cdc kieu hinh cua benh. Mat khac, cdng nghf iRNA se cung cdp mdt phuong tien hieu qua de ngan chdn bieu hifn cua mdt gene cu the cd lien quan den bfnh tat.
2. Ca che can thifp ARN
Theo Fire A et al (1998), can thifp ARN (iRNA) Id mdt CO che dugc ddnh gia cao. Td ARN kep (dsRNA) dugc "cat" bdi enzyme Dicer Rnase III tgo ra doan ngdn (siRNA). Sau khi dugc ngp vdo trong tl bao, siRNA se gay ra suy thoai trinh ty cua chudi mRNA tuang ddng ciia nd. Can thifp RNA da dupc thyc hien Ian dau tien vdo nam 1998 bdi Andrew Fire va Craig Mello d giun trdn Caenorhabditis elegans, sau va sau do dugc tim thay trong mdt logt cac sinh vat khac, bao gdm cd ddng vgt cd vu.
Co che can thiep RNA cd the thay nhu sau:
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Thdng tin KH-CN Nghf An [21]
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Khi vdo cdc tl bdo, sao chep npi sinh ho^c ngoai sinh RNA mgch kdp ddi (IdsRNA) dupc bieu hifn nliu Id mpt ldc nhan kich hogt cua qud trinh can thiep RNA (HI-A), tilp dd dugc xu ly bdi enzyme Dicer RNase III trong m^t phan dng phy thugc vdo ATP (Hl-B). Dicer cdt IdsRNA thanh nhflng dogn ngSn cd kich thudc khodng 21-23 nucleotit (siRNA). Cdc dogn siRNA cung cd the dugc tdng hgp ben ngodi te bdo vd sau dd dugc dua vdo tc bdo thdng qua qud trinh khuech tdn hodc chuyen nhd xung dien (electroporation (Hl-C).
siRNA dugc tich hgp vdo phuc hgp RISC hieu img can thiep ARN trong dd bao gdm mdt protein Argonaute (Ago) la mpt trong nhflng thdnh phan chinh cua phOc hgp ndy, to do dan den mgt phOc hgp
RISC hogl dfng (HI-D).
Nhd dd, sgi siRNA Idm dilu ngugc lgi, hudng dSn RISC mRNA luong dong cua nd, phdn tdch phdn td mRNA md khdng gidi md, ndn khdng c6 protein ndo dugc t6ng hgp (Hl-E va F). Vifc khdm phd CO chl can thifp ARN cd y ldn lao dli vdi cu^c sing cda con ngudi vd cd d^ng thyc vdt.
3. Quii trlnh can t h i f p ARN vd khd ndng chong lai cdc viru.s
Sy can thifp RNA ddng vai Ird rat quan trpng trong vice chdng lgi sy xdm nhiem cua cdc virus vdo co thl vat chu, ddc bift Id cdc sinh vdt bac thap. Vdi nhflng virus cd thdng tin di truyen dugc chOa tren chuoi ARN kdp (dsRNA), khi xam nhiem vao te bao, chiing bam thdng tin di truyin (phdn tu dsRNA)
vdo te bdo vdt chu, dsRNA I4p tOc gSn vdo Dicer, phirc hgp RISC dugc kich hogt, RNA virus bj phdn buy vd tl bdo v^t chu thodt khdi sy xdm nhiem ndy (H2-A). Hay sy long hgp cua nhieu logi protein do cdc gene ma hoa cho doan nhd RNA (siRNA) kilm sodt. Sau khi xO 1^, siRNA ngdn cdn sy djch md to mRNA Ihdnh protein (H2- B). Hay trong phdng thf nghifm, cdc phan td RNA mgch don (ssRNA) dugc bien doi dl hogt hod phiic hgp RISC vd dl phan buy mRNA cua mgt gene chuyen bift ndo do (H2-C). Ben canh khd ndng bdo vf, cdc sinh vat bdc cao nhu con ngudi cdn phdt trien mdt hf thdng mien djch hifu qud Hen quan den khdng the, te bdo diet ty nhien (le bdo NK) va interferon.
4. Nhung CO* hoi mdi trong nghien cihi sinh hgc y dwffCy ky thu|t gene vd cham sdc siic khoe
Sy can thifp ARN dua ra nhieu iing dung thu vj trong ky thuat gene. Phan tO
dsRNA dugc thiet ke de gay
• bat boat cho cac gene ddc thu d ngudi, dgng vat hodc thyc v^t. Cdc phdn tu ARN cd khd ndng gay bat hogt dugc dua vdo te bdo vd kich hoat bg may can thifp ARN de phd
buy cdc mRNA cd md di truyin tucmg ddng. K^ thuat ndy da trd thdnh mgt dung cu nghien ciru quan trgng trong ngdnh smh hpc vd y dupc hgc. Trong tuong lai, mpi ngudi hy vpng ky thudt ndy se
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dugc sO dyng trong cd ITnh vuc y hpc lam sdng lan ngdnh ndng nghiep. Mft val cdng bd gan day cho thdy sy bdt hoat gene da dugc tien hdnli thanh cdng d cac te bdo ngudi va cdc ddng vat thi nghifm.
4.1. iRNA v&i ung thu Trong nhiing nam gan day, ARN can thifp (iRNA) da ndi len nhu la mdt co che quan ly ldn trong bilu hifn gene d sinh vgt cd nhan dien hinh. Ngudi ta hieu rang thay ddi d cac cap dp trong qua khO lien quan tryc tilp den benh ung thu vd cdc gene dot bien gdy ung thu (oncogene).
Hon nua, can thiep RNA dd dugc bien thdnh mgt cong cy mgnh cho bieu hifn gene nhan tao dieu chinh thdng qua sy bieu hien cua RNA can thifp cd kfeh thudc nhd (siRNA). Nhiing cdng cu ndy giup phdn dinh vai trd cua cac yeu td di ddng trong oncogenesis va dc che khdi u, dat nen mdng cho cdc phuong phdp tiep can mdi trong phat hifn gene. Hon nua, thdnh cdng dc che sy phdt trien ciia te bdo ung thu bdng each can thiep ARN nham tdi oncogene in vitro va in vivo hd trg nhiet tinh tilm nang cho cac dng dung dilu Iri cua ky thuat ndy.
Theo Pai SI, Lin YY, Macaes B, Meneshian A, Hung CF, Wu TC - Bd mdn Tai Miii Hgng vd Phdu thuat cd - Dai hgc Y khoa Johns Hopkins, Baltimore, My (2006), can thifp ARN (iRNA) la mdt qud trinh manh me ddy hua hen trong ITnh vuc dilu tri
ung thu. Vifc phdt hien ra can thifp ARN da tao ra ddng lyc trong cdng ddng khoa hpc, khdng chi vi nd dd dugc sO dung de nhanh chdng xdc dinh cdc phan tu quan trpng tham gia vdo nhieu qud trlnh mdc bfnh, bao gdm ung thu, ma cdn vi can thifp RNA cd tiem ndng dugc trd thanh mpt cdng nghf vdi cdc Ong dyng ldn trong dieu tri. Nhilu sdn pham gene lien quan den ung thu dd dugc khdm phd nhu Id myc tieu cho ARN can thifp.
Trong hdu bet cdc nghien cini, sy im lang cua sdn phdm gene quan trpng nhd cdng nghf IRNA da tao ra dnh hudng ddng ke chdng lai sy sinh sdi ndy nd (antiproliferative), su tang len nhanh chdng cua te bao nudi cdy trong mdi trudng hodc trong cdc md ddng vdt tien lam sdng. Tuy nhien, nhiing trd ngai nhu trong vifc Oc che khdng ddy du cua cdc gene myc tieu, dap iing miln dich khdng dgc hieu va cdi gpi la hifu ung myc tieu, cdn phdi vugt qua trudc khi cdng nghe nay cd the dupc dich sang ITnh vyc ldm sang thdnh cdng. Nhung tien bg dang kl da dugc thuc hien trong viec gidi quydt mdt sd vdn dd va dy dodn nhung thd nghifm lam sdng giai doan dau se dugc bdt dau trong tuang lai gdn.
4.2. Dung hgt nano "gdi"
iRNA di tim diit ti bdo ung thu
Cudc thO nghifm ldm sdng- ddu tien trdn co the
ngudi da chung td cac hat nano tim den dung nhung te bdo ung thu de bdt hoat sy gidi ma gene cdn thill. Theo ket qua nhflng lan thu nghifm lam sdng trudc day, hat nano chuyen dung "gdi"
"chat tri ung thu" dilu chl lu siRNA dd thdnh cdng trong vifc tim den myc lieu Id cdc td bao ung thu trong ca the ngudi va vd hifu hda tao ra san pham tO gene cdn thiet.
Cdc nha nghien ciiu van chua tilt Ip tdc dyng lam sdng ciia lifu phap nhung theo GS Phillip Sharp d Hpc vifn Cdng nghf Massachusetts, ngudi dugc nhan gidi thudng Nobel Y hgc nam 1993 nhd cdng nghien cdu ve qua trinh phan chia ARN, nhgn xet:
"Day Id mpt thdnh tuu rat phan khich, dieu ndy chiing td ITnh vyc nay dang trudng thdnh vd bat dau dugc ap dung de tri lifu cho benh nhan". Ke tO khi phat minh (nam 2000), nhung ddi kep ARN cd the vd hieu hda nhung gene can thiet. Cdc nhd nghien cOu da xem ky thudt ndy Id mdt cdch tiep can hihi dung de tao ra nhung dupc pham mdi vd cdng hifu. Dieu khd khdn Id viec dua "thudc ARN can thifp" den nhung te bdo muc tieu. Khi nap vdo md khdng bao bgc bao vf, nhiing phan tu CO nhd (siRNAs) nhanh chdng hi than lgc ra khdi co the. Cac nha nghien cuu da gang sue de thiet ke ra nhflng hat chua thudc tim den nhung te bao muc tieu cd du dp khac biet, khdng gay ra
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NGHIEN CUU - TRAO 001
dgc hgi ho^c khdng gdy ra phdn img mien djch cua co the. Cho den nay. mpt vdi cupc thu nghifm Idm sdng da dupc thyc hifn Jc kiC-ni Ira kha ndng ciia siRNA khi cung cap tryc tilp vdo mdt ho$c phdi dl chiia bfnh thodi hda vdng mge ho$c vidni phdi do virus. Da\ Id nhthig CO quan de tiep can. nen thuoc dd dugc iriiyOn tryc tiep ldi nhOng md dd vdi ARN can thifp khdng bgc.
Tuy nhien, d cugc thO nghifm mdi ddy, lan ddu lien ARN can thifp dugc dua mgt cdch he thong vao trong co the, tren ca sd sO dynjj nhiing hgt chuyen dyng de bao vf ARN can thiep. Khi di chuyen lan thu nghifm dau lien vifc dua IRNA ldi cdc te bao de tri ung thu, Mark Davis - Gido su Hda hgc d Caltech ndi: "Chiing tdi mudn chpn mdt gene Id thu pham gdy ra mdt logt cdc bfnh ung thu de tdng kha nang thay dupc cdng hifu ciia lifu phap mdi". Cdc nhd nghien cinj da phdn tfeh mau sinh thiet ciia 3 benh nhan bj u hde td trong thu nghifm lam sang sau khi hg dugc tiem 3 lieu thudc khac nhau. Hg Idn tim cac hat d nhiing mau dd vd phdl hifn thdy lugng hgt d nhiing te bdo khdi u cd lien quan den lieu lugng thudc dd tiem. Hp cflng dua nhung mdu mRNA (ARN thdng tin) dugc dinh chinh xdc vdo nhung noi ma siRNA dd dugc thiet ke de cdt bd, dl chOng td iRNA da thyc hien nhifm vy dung theo yeu cau. Cupc thd
nghifm ndy dugc tdi trg bdi Calando Pharmaceuticals, mpl cdng ly mdi khdi sy d California do Davis sdng l§p de phdt tricn nhOng lifu phdp trj ung thu bdng siRNA "gdi"
trong hgi nano. CuOc thd nghifm Id mOl budc khdi d^u day hda hijn, tuy nhidn vlln cdn nhilu vifc phdi ldm trudc khi lifu phdp dugc dp dyng rgng iHi lgi cdc bfnh vifn.
4.3. "Than du(rc" tit ARN can ttii^p
Theo Vifn sT Hdn Idm Vifn Khoa hgc Phdp Jean Paul Behr (2012), trong luong lai, ARN can thifp s6 Id trung tam ciia ngdnh dugc.
Nghien cuu cua cdc Gido su Fire va Mello cho thay cd rat nhieu phdn tO iRNA ldn tgi to giai dogn phdi thai cho den luc chet d cac sinh vat da bdo vdi nhifm vy dieu hda sy
"van hdnh" cua tl bdo. Co che cua iRNA Id phdn huy cac ARN thdng tin (mRNA) cua cdc gene nhdy (transposon) cd the gay dpi bien, cua vi nit hodc cdc ky sinh trung khdc tiem nhiem vao. Cdc gene "xdm luge"
nay bj phdl hifn vd vd hifu hda do cd md di truyen gidn^
vdi iRNA. Hieu dugc co che boat dgng, rdt nhieu nhdm nghien cOu tren thl gidi da Ihu nghifm nhflng lifu phdp gene nhdm dieu tn cdc bfnh do vi nit gay ra, bfnh Iy ve tim mach, ung thu, rdi logn ngi tiet. Cdc phdn tu iRNA mang ma di truydn chpn Ipc luong ddng vdi gene gdy hgi dugc dua vdo co thl nhdm
"tim dift" nhOng gene dd.
Ddy se Id mgt cugc cdch mgng thgt sy ciia ngdnh dugc trong xu thl dng dyng cdng nghf sinh hpc dang ngdy cdng tao dugc ch5 dirng beri cgnh phuong phdp dilu chl lhu6c truyin thong bdng cdch long hgp cdc hogt chat hda hpc.
Tuy nhidn, de iRNA c6 thl trd thdnh dugc pham thgt sy, cdc nhd khoa hgc phdi vugt qua khdng it trd ngai.
Trudc tidn, nhflng phan tii ndy trong ty nhien rat mdng manh vd l^n tai trong mpt thdi gian ngdn. Gidi phdp dugc dua ra la "khda" cdc nguyen td dxy cua iRNA, tac nhan khien cdu true nay khdng ben virng. Sau do, iRNA sd dugc xO Iy de lam chdm qud trinh dao thdi bdi than. Sy lien bd cua nganh hda hpc da giup phdt trien cdc ARN can thifp kich thudc nhd (siRNA) ben viing gap 100 Ian so vdi iRNA tu nhien, ddng thdi cd the de ddng dugc ldng hgp vdi so lugng Idn. Nhieu cdng ly hda sinh dd thu nghifm dua siRNA vao cdc bg phan cua CO the de chO^ bfnh, chdng ban mgt sd bfnh Iy vl mat nhu thodi hda hodng dilm lien quan den tudi gia. Kho khdn tilp theo la lam thl nao dua dugc siRNA vdo tl bdo ngudi, vdn dugc bdo vf rat k5f ludng. Cdc nhd khoa hoc dang nghien cdu phucmg phdp "ngya thanh Troy": cdy siRNA vdo cdc hgt nano.
Nhflng hat nano se dl tl bao
"nu6t" Idy m^t each ty nhien
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va chi giai phdng siRNA khi da vdo dugc phfa trong.
Phuong phdp ndy giup siRNA tieu dift tryc tidp cac te bao ung thu mang gene dot bien md khdng dnh hudng den cac te bdo Idnh trong ca thd.
4.4. Rdi logn m& mdu cd the chita dugfc?
Rdi loan mo mdu (Dyslipidemia) Id tdn ggi mpt sd benh do xdo trdn cdc ch4t md trong mau: hodc qud nhieu hoac qud it cdc chat lipoprotein. Bfnh thudng bieu hifn qua dp tdng cholesterol, tang logi lipoprotein "xau" (LDL), tdng logi triglyceride hoac thieu logi lipoprotein "tdt"
(HDL). Theo Crooke (2010), Lipoprotein dugc chia lam nhieu logl tuy theo ty trpng (density), HDL-c (ty trpng cao) - khoang 1/3 tdng sd cholesterol dugc mang trong HDL. Gidi y hgc cho rdng HDL thudng dem cholesterol ra khdi ddng mgch trd ve gan va sau dd bdi tiet ra khdi ca the. Mdt sd khac cdn cho rdng HDL "hdt" cholesterol 0
Tai lieu tham khao
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3. Science Daily (June 26, 2012), New Role for RNAi Discovered: Epigenetic Memory May Pass RNA Silencing from One Generation to the Next.
4. Harper P (2002), "The epidemiology of Huntington's disease".
5. Hyukjin Lee and Ung Hee Lee (2012), Researchers successfiilly used this 5 nanoparticle, made from several strands of DNA and RNA, to turn off a gene in tumor cells.
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thda trong cdc mdng xo vfla vd lam chdm sy phat triln ciia nhflng mdng ndy. Vi thl, HDL thudng cd mfnh danh Id logi "cholesterol cd ich".
HDL cdng thdp Ihi ca hgi bi bfnh tim mach cang cao, vd ngugc lai, HDL cao cd thl lam gidm co hgi bj bfnh tim mach. IDL-c (ty trgng trung binh) LDL-c (ly trgng thap) - ngugc lai vdi HDL, LDL cd mfnh danh Id "cholesterol xau". Khi cd qud nhilu LDL, cholesterol bi dua vdo cdc mdng cua ddng mach, dan dan lam hep dudng kinh ciia mach. Sau dd, ket hgp vdi cac chat khac trong mdng cua thanh dpng mgch tgo thdnh nhflng mdng xa vfla (atherosclerosis). Nhflng mang nay cd the bi rgn mil Idm cho thanh dgng mgch khdng dugc tron tru. Khi chay qua nhflng chd "gd ghe" nay, ddng mau dc bj hdn Ipan khdng deu, tri trf vd dl ddng lgi thdnh cyc mdu ddng (thrombus). Cyc mau ddng nay cd the phat trien theo kieu "phu sa bdi dap", Idp Idp chdng len
nhau, cd luc dii dk Idm nghen dpng mgch. Nlu trudng hgp ndy xdy ra trong dpng mach vanh tim thi kit qud la nghdn mach tim, gdy chiing nhoi mdu ca lim.
Trong trudng hgp cyc mau ddng hi sut ra khdi Ihdnh ddng mgch, trdi theo ddng mau cho den khi ket vdo mdt mgch cd dudng kinh nhd hon Idm nghdn mach dy.
Neu chdng may day la mach dan mdu ciia ndo thi ket qud Id chung tai biln mach mdu nao. Tdng mOc cholesterol, hay dung ban, tdng LDL- choleslerol (LDL-c) la nguyen nhdn chfnb cua chOng XO vfla Idm nghen mgch vanh tim dem den chiing dau that ngyc, nhdi mdu CO tim, chet bdt ngd vd suy tim. Hien nay, khoa hpc khang dinh hoan toan rdng giam lugng LDL-c trong mau se dem den gidm co hdi benh mach vdnh tim. Ngodi ra, neu sd Triglycerides cao va HDL-c thdp se lam tang dp nguy hai cua LDL-c, do do hai chat nay can phai dugc luu y./.
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