謝席勝,高 薇,馮勝剛,張 菊
(1.川北醫(yī)學(xué)院第二臨床醫(yī)學(xué)院·南充市中心醫(yī)院 腎內(nèi)科,四川 南充637000;2.川北醫(yī)學(xué)院,四川 南充637000)
狼瘡腎炎(lupus nephritis,LN),是系統(tǒng)性紅斑狼瘡(systemic lupus erythematosus,SLE)最常見的并發(fā)癥之一,已成為終末期腎?。╡nd stage renal disease,ESRD)主要病因之一[1]。LN 的發(fā)病機(jī)制主要涉及腎小球免疫復(fù)合物沉積導(dǎo)致的免疫損傷。因此,臨床上通常使用糖皮質(zhì)激素聯(lián)合環(huán)磷酰胺、嗎替麥考酚酯、鈣調(diào)磷酸酶抑制劑等進(jìn)行治療。這些方案在一定程度上可緩解LN進(jìn)程,但高復(fù)發(fā)率和嚴(yán)重的不良反應(yīng)是不容忽視的問題。SLE是在遺傳、環(huán)境等因素作用下,導(dǎo)致T淋巴細(xì)胞減少,B淋巴細(xì)胞過度增生,產(chǎn)生大量自身抗體,引發(fā)免疫反應(yīng),導(dǎo)致包括腎臟在內(nèi)的多系統(tǒng)損傷。腎臟損傷是免疫復(fù)合物沉積、自身抗體形成、促炎性細(xì)胞因子表達(dá),以及T細(xì)胞、B細(xì)胞、單核細(xì)胞、樹突狀細(xì)胞和腎臟實(shí)質(zhì)細(xì)胞在腎臟的相互作用的結(jié)果[2]。因此,目前靶向治療SLE及LN主要集中在包括影響B(tài)淋巴細(xì)胞活化、T淋巴細(xì)胞與B淋巴細(xì)胞相互作用及細(xì)胞因子等環(huán)節(jié)。
目前針對(duì)B細(xì)胞環(huán)節(jié)的靶向治療,包括抗CD20單克隆抗體利妥昔單體、抗CD22單克隆抗體依帕珠單抗、抗B淋巴細(xì)胞刺激因子貝利木單抗及組織蛋白酶S阻滯劑和蛋白酶抑制劑硼替佐米等。
1.1 利妥昔單抗 利妥昔單抗是一種抗CD20的單克隆抗體,大多存在于B細(xì)胞內(nèi)。普遍認(rèn)為利妥昔單抗治療SLE和LN的機(jī)制在于特異性拮抗人類CD20,選擇性誘導(dǎo)CD20﹢B細(xì)胞短暫性耗竭,消耗自身反應(yīng)性B細(xì)胞,減少引起疾病的自身抗體。B細(xì)胞耗盡后,利妥昔單抗促使BAFF水平升高,B細(xì)胞重建,從而增加新的自身反應(yīng)性B細(xì)胞的產(chǎn)生,即B調(diào)節(jié)細(xì)胞(Bregs)。由于不影響漿細(xì)胞,故不引起致病自身抗體水平的立即減少。另外,利妥昔單抗可通過IL-10依賴的機(jī)制來衰減炎癥反應(yīng)[3]。在ANCA相關(guān)性血管炎的研究中,兩種方案雖短期療效相似,但在維持治療階段,利妥昔單抗組未使用免疫抑制劑,環(huán)磷酰胺組卻接受了硫唑嘌呤的維持治療。由此初步證實(shí),通過B細(xì)胞耗竭來衰減自身免疫的方法可能有效地預(yù)防LN的復(fù)發(fā)[4~6]。然而,在有關(guān)利妥昔單抗治療LN的兩個(gè)大型前瞻性、安慰劑、隨機(jī)雙盲對(duì)照研究中卻發(fā)現(xiàn),利妥昔單抗聯(lián)合標(biāo)準(zhǔn)治療與安慰劑聯(lián)合標(biāo)準(zhǔn)治療對(duì)SLE或LN的療效和安全性未顯示出明顯差異[7,8]。但利妥昔單抗對(duì)LN有其優(yōu)勢(shì),可進(jìn)一步證明其療效,這對(duì)LN的治療將具有里程碑意義[9]。
1.2 依帕珠單抗 依帕珠單抗是針對(duì)CD22分子的IgG單克隆抗體。CD22系成熟B淋巴細(xì)胞表面標(biāo)記,參與B淋巴細(xì)胞表面受體信號(hào)傳導(dǎo),但在漿細(xì)胞不表達(dá)。依帕珠單抗可以通過抗體依賴的細(xì)胞介導(dǎo)細(xì)胞毒性作用 (ADCC)造成B細(xì)胞中度耗竭。與RTX不同的是,依帕珠單抗對(duì)B細(xì)胞不表現(xiàn)出補(bǔ)體依賴的細(xì)胞毒效應(yīng) (CDC)或直接的凋亡效應(yīng)[10]。
一項(xiàng)Ⅱb期臨床隨機(jī)、雙盲、安慰劑對(duì)照研究了依帕珠單抗治療中~重度活動(dòng)性SLE的療效。結(jié)果發(fā)現(xiàn),疾病活動(dòng)指數(shù)的控制及不良反應(yīng)的發(fā)生與臨床應(yīng)用劑量密切相關(guān)[11]。
1.3 貝利木單抗 抗B淋巴細(xì)胞刺激因子BAFF屬于腫瘤壞死因子超家族,其能與B淋巴細(xì)胞特異性結(jié)合,誘導(dǎo)其增殖、分化和分泌免疫球蛋白,在體液免疫中發(fā)揮重要作用。而作為抗BAFF的貝利木單抗是人源化IgG型單克隆抗體,可以與B淋巴細(xì)胞表面BAFF結(jié)合,阻止B淋巴細(xì)胞發(fā)育成熟,促進(jìn)其凋亡,并能中和BAFF,降低自身免疫反應(yīng)[12]。最近在非腎型SLE 3期臨床研究中發(fā)現(xiàn)[13],貝利木單抗治療的患者往往有更少的腎臟損害。此研究為LN維持階段中使用B細(xì)胞靶向療法提供了新的支持。
這個(gè)研究評(píng)估了其治療SLE的療效和安全性。研究結(jié)果顯示,貝利木單抗1mg/kg或10mg/kg加標(biāo)準(zhǔn)治療(MMF聯(lián)合激素)較安慰劑加標(biāo)準(zhǔn)治療能更顯著地改善狼瘡反應(yīng)指數(shù),能更快降低SLE疾病活動(dòng),且耐受性好,未出現(xiàn)嚴(yán)重的不良反應(yīng)[14~15]。另一項(xiàng)隨機(jī)對(duì)照研究顯示,使用貝利木單抗聯(lián)合MMF治療LN的療效較標(biāo)準(zhǔn)治療更有優(yōu)勢(shì),此研究證實(shí)了貝利木單抗對(duì)SLE患者腎臟損害具有改善作用。這為LN維持階段中使用B細(xì)胞靶向療法提供了循證依據(jù)[13]。
1.4 組織蛋白酶S阻滯劑 免疫細(xì)胞介導(dǎo)的主要相容性復(fù)合物Ⅱ是誘導(dǎo)SLE和LN的核心環(huán)節(jié)。研究證實(shí)蛋白酶S通過驅(qū)動(dòng)MHCⅡ介導(dǎo)T、B細(xì)胞活化、生發(fā)中心形成和誘導(dǎo)B細(xì)胞成熟為漿細(xì)胞。而組織蛋白酶S抑制劑可降低抗原提呈細(xì)胞中MHC II組件和抗原肽間的肽鏈的穩(wěn)定性,抑制免疫途徑,防止LN的進(jìn)展,成為治療LN的一種新策略[16]。
1.5 硼替佐米 作為另一種蛋白酶體抑制劑的硼替佐米可誘導(dǎo)漿細(xì)胞凋亡,在SLE和LN小鼠模型中證實(shí),硼替佐米可以防止LN的進(jìn)展和改善預(yù)后。更重要的是蛋白酶可激活NF-kB的轉(zhuǎn)錄因子,故硼替佐米也可阻止某些NF-kB依賴性促炎細(xì)胞因子的產(chǎn)生[17~19]。但硼替佐米的抗中性粒細(xì)胞胞漿抗體的實(shí)驗(yàn)?zāi)P脱芯勘砻?,硼替佐米只有在病程早期有效,其單?dú)作用不足以治療臨床LN[20],且由于它的神經(jīng)毒性[21],臨床使用更需謹(jǐn)慎。
2.1 阿巴西普 阿巴西普是CTLA-4和IgG重鏈部件之間融合形成的可溶性蛋白,可以與樹突細(xì)胞或B細(xì)胞的表面的B7分子特異性結(jié)合,阻斷B7.1/B7.2與T細(xì)胞上CD28之間的相互刺激作用,從而抑制T細(xì)胞活化[22]。動(dòng)物實(shí)驗(yàn)結(jié)果表明,阿巴西普與低劑量環(huán)磷酰胺聯(lián)合能完全誘導(dǎo)緩解大鼠的狼瘡腎炎[23]。然而在阿巴西普在改善腎功能、提高緩解率方面收獲甚微,這可能與CTLA4-Ig在人體內(nèi)對(duì)IL-6,血管內(nèi)皮 生 長 因 子 (vascular endothelial growth factor,VEGF),TNF-a和循環(huán)樹突細(xì)胞影響不大有關(guān)[24]。
2.2 共刺激因子阻斷劑 誘導(dǎo)性共刺激分子(Inducible co-stimulator,ICOS)屬于CD28/CTLA4家族,可促進(jìn)T細(xì)胞增殖和活化。這種膜糖蛋白在活化T細(xì)胞表面表達(dá),對(duì)T細(xì)胞增殖的共刺激和細(xì)胞因子的產(chǎn)生具有增強(qiáng)效應(yīng)[25]。ICOS可在活動(dòng)期SLE患者外周血CD4+T細(xì)胞中過度表達(dá),還可以提高外周血中的T細(xì)胞生成干擾素(IFN)-γ。此外,ICOS擴(kuò)增外周血T細(xì)胞的自體外周血B細(xì)胞,以產(chǎn)生抗dsDNA抗體的能力[26]。作為共刺激因子阻斷劑的B7相關(guān)蛋白-1是一種表達(dá)于B細(xì)胞和單核細(xì)胞的B7樣分子,可特異性結(jié)合ICOS[27],而ICOS和B7RP-1的這種通信的阻斷可能對(duì)治療SLE有一定影響力。
3.1 托珠單抗 IL-6是由白細(xì)胞和內(nèi)在腎細(xì)胞產(chǎn)生的多功能細(xì)胞因子,主要影響炎癥反應(yīng),可增加腎小球系膜細(xì)胞的增殖,還可刺激終端B細(xì)胞分化,產(chǎn)生免疫球蛋白,并促進(jìn)T細(xì)胞增殖生長。研究證實(shí)IL-6可增加狼瘡患者的疾病活動(dòng)性和抗dsDNA抗體水平[28]。此外,IL-6可以與IL-1和 TNF-α產(chǎn)生協(xié)同作用促進(jìn)炎癥[29]。托珠單抗是阻斷白細(xì)胞介素(IL)-6與其受體結(jié)合的單克隆抗體。一項(xiàng)開放性劑量遞增研究評(píng)估了托珠單抗對(duì)SLE的臨床療效和安全性。結(jié)果表明了托珠單抗對(duì)自身抗體細(xì)胞的特定效果[30]。
3.2 抗干擾素生物制劑 腎特異性自身免疫時(shí),SLE患者外周血干擾素(IFN-α)誘導(dǎo)基因明顯上調(diào)。IFN-α又驅(qū)使普通樹突狀細(xì)胞轉(zhuǎn)化為有效的抗原呈遞細(xì)胞,誘導(dǎo)B細(xì)胞分化為漿細(xì)胞,并促進(jìn)CD4+輔助性T(TH)細(xì)胞和CD8中央記憶T細(xì)胞成熟,從而增加自身免疫反應(yīng)。因此認(rèn)為針對(duì)IFN-α的人源化單克隆抗體蘭尼單抗和西法木單抗,可中和IFN-α活性,控制炎癥的同時(shí)防止腎臟的進(jìn)一步損傷[31]。
4.1 拉喹莫德 拉喹莫德是喹諾酮-3-甲酰胺的一種小分子衍生物??梢詼p少單核細(xì)胞對(duì)中樞神經(jīng)系統(tǒng)的浸潤、抑制促炎細(xì)胞因子和轉(zhuǎn)錄因子的表達(dá),如單核 細(xì) 胞 蛋 白-1 核 因 子-κB(nuclear factor-κB,NF-κkB)。拉喹莫德還可以通過趨向調(diào)節(jié)性T細(xì)胞(Tregs)和遠(yuǎn)離TH1和TH17細(xì)胞表型來調(diào)節(jié)炎癥環(huán)境[32,33]。無論拉喹莫德直接處理,或拉喹莫德治療后的多發(fā)性硬化患者體內(nèi)提取的白細(xì)胞或樹突細(xì)胞都顯示出炎性細(xì)胞因子和趨化因子基因的抑制和NF-kB表達(dá)的減少。此外,由于拉喹莫德可以減少參與抗原呈遞基因的表達(dá),減少pDCs。因此還具有調(diào)節(jié)自身免疫性疾病的作用[34]。在拉喹莫德(0.5mg/day或1mg/day)聯(lián)合標(biāo)準(zhǔn)治療與安慰劑聯(lián)合標(biāo)準(zhǔn)治療的多中心雙盲臨床二期研究中發(fā)現(xiàn),拉喹莫德與標(biāo)準(zhǔn)治療的組合在改善活動(dòng)性LN腎功能與單獨(dú)的標(biāo)準(zhǔn)治療相比,在改善腎功能方面表現(xiàn)出了累加效應(yīng),且上述兩種劑量均能很好耐受[35]。
4.2 在健康成人的腎臟中,TWEAK和其受體成纖維生長因子誘導(dǎo)14(FN14)表達(dá)水平較低。而狼瘡性腎炎免疫受損時(shí),腎臟中TWEAK和FN14被上調(diào),且在腎小管細(xì)胞中TWEAK與FN14結(jié)合,激活NF-kB。在LN的動(dòng)物模型中證實(shí),消耗TWEAK可減少腎臟的炎癥和損傷[36]。目前,Anti-Tweak的多中心隨機(jī)雙盲對(duì)照臨床研究正在進(jìn)行中,正在對(duì)有效性、安全性和耐受性進(jìn)行臨床三期評(píng)估。
4.3 依庫珠單抗 依庫珠單抗是一種完全重組人源化IgG2/IgG4單克隆抗體,可抑制C5轉(zhuǎn)化為毒素C5a和C5b,防止膜攻擊復(fù)合物(C5b-9)和趨化片段C5a的形成。依庫珠單抗作為經(jīng)典途徑的組件,可作用于補(bǔ)體系統(tǒng)的遠(yuǎn)端,且不干擾經(jīng)典途徑。對(duì)狼瘡性腎炎的治療,依庫珠單抗可以防止補(bǔ)體介導(dǎo)對(duì)腎小球細(xì)胞的直接損傷,并通過減少腎臟內(nèi)白細(xì)胞聚集來緩解腎臟炎癥反應(yīng)[37]。
針對(duì)SLE及LN免疫應(yīng)答不同環(huán)節(jié)靶向治療生物制劑的不斷涌現(xiàn),SLE及LN治療有了更多的選擇。目前大多數(shù)尚處于研究和臨床應(yīng)用初級(jí)階段,其有效性、安全性有待進(jìn)一步觀察和大規(guī)模隨機(jī)雙盲對(duì)照研究證實(shí)。盡管如此,各種新型生物制劑的開發(fā)和應(yīng)用,無疑為SLE及LN開拓了新的治療前景。
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