





DOI:10.3969/j.issn.2095-1191.2025.01.028
摘要:【目的】探究N-乙酰半胱氨酸(N-acetylcysteine,NAC)緩解小鼠代謝綜合征膀胱纖維化的分子機制,為深入理解膀胱纖維化的病理學過程及開發新的治療策略提供理論參考。【方法】選擇8周齡C57BL/6雄性小鼠和ob/ob(B6.V-Lepob/J)雄性小鼠(代謝綜合征模型),試驗持續20周,試驗結束后處死小鼠,采集膀胱組織。以C57BL/6雄性小鼠為對照組(Con),ob/ob(B6.V-Lepob/J)雄性小鼠為代謝綜合征模型組(ob/ob),利用Western blotting檢測小鼠膀胱組織中TGF-β1、SMAD、p38、p-ERK、p-JNK、α-SMA、3-Nitrotyrosine(NT)等蛋白相對表達量,采用免疫組織化學染色檢測小鼠膀胱組織中NF-κB與TGF-β1表達情況及分布特點。分離小鼠膀胱平滑肌細胞(BSMCs),篩選葡萄糖濃度并繪制BSMCs生長曲線。設對照組(Con)、高糖組(HG)、高糖+NAC組(HG+NAC)和高滲組(HO),檢測CRP、IL-6、IL-1β、NLRP3、TGF-β1、BK-β1、SKCa3蛋白相對表達量。使用MCC950和PDTC抑制NLRP3和NF-κB信號通路,檢測ROCK1、NLRP3、NF-κB、TGF-β1蛋白相對表達量。【結果】與Con組相比,ob/ob組小鼠膀胱組織中NT、TGF-β1和α-SMA蛋白相對表達量顯著升高(Plt;0.05,下同),SMAD、p38、p-ERK和p-JNK蛋白相對表達量無顯著差異(Pgt;0.05,下同)。葡萄糖濃度篩選結果表明,45 mmol/L的葡萄糖為最佳干預濃度。Western blotting檢測結果顯示,與Con組相比,HG組BSMCs中CRP、IL-6、TGF-β1、IL-1β和NLRP3蛋白相對表達量顯著升高,BK-β1和SKCa3蛋白相對表達量顯著降低。與HG組相比,HG+NAC組BSMCs中CRP、IL-6、TGF-β1、IL-1β和NLRP3蛋白相對表達量顯著降低,BK-β1和SKCa3蛋白相對表達量顯著升高。抑制NLRP3和NF-κB信號通路后,與HG組相比,HG+MCC950和HG+PTCD組BSMCs中TGF-β1蛋白相對表達量顯著降低,NF-κB蛋白相對表達量顯著升高,HG+MCC950組BSMCs中ROCK1和NLRP3蛋白相對表達量顯著降低,HG+PTCD組BSMCs中ROCK1和NLRP3蛋白相對表達量無顯著差異。【結論】高糖因素誘發的小鼠膀胱功能損傷涉及氧化應激—炎癥反應—組織纖維化相關分子機制通路,NAC主要通過抑制ROS/NLRP3/NF-κB/TGF-β1信號通路阻斷功能損傷中氧化應激、炎癥反應和纖維化的發展進程。與抗炎治療相比,NAC抗氧化治療對組織纖維化的治療效果可能更顯著。
關鍵詞:N-乙酰半胱氨酸;代謝綜合征;膀胱功能損害;氧化應激;炎癥反應
中圖分類號:S865.13文獻標志碼:A文章編號:2095-1191(2025)01-0314-10
Molecular mechanism of N-acetylcysteine alleviating bladder fibrosis in mice with metabolic syndrome
RENYa-lin1,2,SU Bo-yan2,HE Qi-qi2*
(1College of Animal Sciences and Technology,Guangxi University,Nanning,Guangxi 530004,China;2Department of Urology,Lanzhou University Second Hospital,Lanzhou,Gansu 730030,China)
Abstract:【Objective】To explore the molecular mechanism by which N-acetylcysteine(NAC)alleviated bladder fi-brosis in metabolic syndrome mice,which could provide theoretical reference for a deeper understanding of the pathologi-cal process of bladder fibrosis and the development of new treatment strategies.【Method】C57BL/6 male mice and ob/ob(B6.V-Lepob/J)male mice(metabolic syndrome model)at 8 weeks of age were selected.The experiment lasted for 20 weeks.After the end of the experiment,the mice were killed and the bladder tissues were collected.C57BL/6 male mice were used as the control group(Con),and ob/ob(B6.V-Lepob/J)male mice were used as the metabolic syndrome model group(ob/ob).The relative expression levelsofTGF-β1,SMAD,p38,p-ERK,p-JNK,α-SMA,3-Nitrotyrosine(NT)and other proteins in the bladder tissues of mice were detected by Western blotting.Immunohistochemical staining was used to detect the expression and distribution characteristics of NF-κB and TGF-β1 in the bladder tissues of mice.Mouse bladder smooth muscle cells(BSMCs)were isolated,the glucose concentration was screened and the growth curve of BSMCs was drawn.The control group(Con),high glucose group(HG),high glucose+NAC group(HG+NAC)and hyperos-motic group(HO)were set up to detect the relative expression levels of CRP,IL-6,IL-1β,NLRP3,TGF-β1,BK-β1 and SKCa3 proteins.MCC950 and PDTC were used to inhibit the NLRP3 and NF-κB signaling pathways,and the relative ex-pression levels of ROCK1,NLRP3,NF-κB and TGF-β1 proteins were detected.【Result】Compared with the Con group,the relative expression of NT,TGF-β1 andα-SMA proteins in the bladder tissue of the ob/ob group mice was signifi-cantly increased(rlt;0.05,the same below),and there was no significant difference in the relative expression of SMAD,p38,p-ERK and p-JNK proteins(rgt;0.05,the same below).The results of glucose concentration screening showed that 45 mmol/L glucose was the optimal intervention concentration.Western blotting results showed that compared with the Con group,the relative expression of CRP,IL-6,TGF-β1,IL-1βand NLRP3 proteins in BSMCs of the HG group was signifi-cantly increased,and the relative expression of BK-β1 and SKCa3 proteins was significantly decreased.Compared with the HG group,the relative expression of CRP,IL-6,TGF-β1,IL-1βand NLRP3 proteins in BSMCs of the HG+NAC group was significantly decreased,and the relative expression of BK-β1 and SKCa3 proteins was significantly increased.After in-hibiting the NLRP3 and NF-κB signaling pathways,compared with the HG group,the relative expression of TGF-β1 pro-tein in BSMCs of HG+MCC950 and HG+PTCD groups was significantly decreased,and the relative expression of NF-κB protein was significantly increased;the relative expression of ROCK1 and NLRP3 proteins in BSMCs of HG+MCC950 group was significantly decreased,and there was no significant difference in the relative expression of ROCK1 and NLRP3 proteins in BSMCs of HG+PTCD group.【Conclusion】High glucose-induced bladder function damage in mice involves molecular mechanism pathways related to oxidative stress-inflammatory response-tissue fibrosis.NAC mainly blocks the development of oxidative stress,inflammatory response and fibrosis in functional damage by inhibiting the ROS/NLRP3/NF-κB/TGF-β1 signaling pathway.Compared with anti-inflammatory treatment,NAC antioxidant treat-ment may have a more significant therapeutic effect on tissue fibrosis.
Key words:N-acetylcysteine;metabolic syndrome;bladder function damage;oxidative stress;inflammatory re- sponse
Foundation items:National Natural Science Foundation of China(81800671,82360156);Gansu Health Care In-dustry Research Management Project(GSWSKY2021-070);Lanzhou University Cuiying Talent Top Project(CY2021-MS-A02)
0引言
【研究意義】近年來,肥胖問題在全球范圍內日益嚴峻,尤其是在人類和動物群體中,肥胖發生率逐年上升。Courcier等(2010)、Cave等(2012)研究表明,約63%的貓和59%的狗存在超重或肥胖問題。肥胖所引發的代謝綜合征(Metabolic syndrome,MS)已被證實與下尿路疾病密切相關,如膀胱出口梗阻、膀胱過度活動癥及尿潴溜等,并能導致MS型膀胱功能損傷(Metabolic syndrome bladder dysfunc-tion,MBD)(Lee et al.,2008;Zhang et al.,2018;Fu et al.,2024)。N-乙酰半胱氨酸(N-acetylcysteine,NAC)是一種廣泛應用的抗氧化劑和抗炎劑,是內源性氨基酸L-半胱氨酸的衍生物,也是三肽谷胱甘肽(GSH)的前體物質(王海云等,2023)。Samuni等(2013)研究表明,NAC不僅能調節氧化應激反應,還能影響多種疾病的病理進程,包括線粒體功能障礙、細胞凋亡及炎癥反應等。探究NAC緩解小鼠代謝綜合征膀胱纖維化的潛在分子機制,對深入理解膀胱纖維化的病理學過程及開發新的治療策略具有重要意義。【前人研究進展】Tanaka等(2005)對糖脂代謝的研究表明,貓肝臟中葡萄糖激酶的活性缺乏,且糖異生速率的限制酶活性顯著高于犬,使得貓更易形成肥胖,并發生胰島素抵抗,最終發展為MS;Tvarijonaviciute等(2012)研究發現,約20%的超重或肥胖犬存在代謝紊亂,且符合MS的診斷標準。肥胖相關的代謝綜合征是動物泌尿系統疾病的重要危險因素。Lekcharoensuk等(2000)研究發現,肥胖引起的代謝綜合征還會增加犬只罹患尿道括約肌功能不全、草酸鈣結石癥及膀胱移行細胞癌等疾病的風險;Henegar等(2001)研究表明,肥胖癥與犬類腎臟組織學變化密切相關,表現為腎小囊、系膜基質、腎小球和腎小管基底膜的增厚,及腎小球的分裂細胞數增加;He等(2016)對B6.V-Lepob/J小鼠肥胖模型的研究表明,肥胖引發的代謝綜合征會導致排尿功能障礙,且ob/ob小鼠和高脂飼料喂養的SD大鼠均是研究MS相關疾病的理想動物模型;章文靜等(2017)研究發現,果糖誘導的代謝綜合征動物模型表現出高水平的逼尿肌細胞凋亡及膀胱逼尿肌肥厚,同時膀胱壁M2、M3型毒蕈堿受體的表達也顯著上調;Rodríguez等(2020)研究發現,肥胖的伊比利亞母豬表現出腎小球腫大、系膜擴張、結節性腎小球硬化及脂質沉積等病理特征。NAC能通過清除活性氧(Reactive oxygen species,ROS)來調節氧化還原平衡,在多種疾病模型中展現出顯著的抗氧化與抗炎作用(雷少青等,2018;Yang et al.,2019;Yuan et al.,2019;楊欣榮等,2020;Li etal.,2022)。氧化應激涉及自由基積累與抗氧化防御系統失衡,是多種病理過程的核心驅動因素。雷少青等(2018)研究表明,NAC可通過直接中和ROS、增強GSH合成酶活性及恢復線粒體功能等途徑有效減輕氧化應激誘導的組織損傷,在2型糖尿病模型中,NAC顯著降低了肝臟脂質過氧化產物丙二醛(MDA)水平,并抑制了FoxO1信號通路過度活化,進而改善了代謝紊亂引起的器官損傷。在泌尿系統疾病領域,氧化應激與膀胱過度活動癥的發病機制密切相關。唐陽國等(2022)研究表明,MS型SD大鼠膀胱平滑肌含量減少,黏膜下炎癥細胞增多,并伴有較多的粗大纖維條索,使用NAC治療后,病理變化有所緩解;武冠宇等(2023)研究發現,膀胱組織中ROS的異常積累可導致尿路上皮敏感性增強與逼尿肌功能失調,表明NAC可能通過抑制炎癥因子的釋放及調節相關信號通路來發揮抗氧化作用。【本研究切入點】NAC能有效緩解高脂飼料誘導的肥胖大鼠膀胱纖維化(He et al.,2016),但其具體分子機制尚未見報道。【擬解決的關鍵問題】采用Western blotting、免疫組織化學染色等方法,解析NAC抑制代謝綜合征膀胱纖維化進程的分子機制,闡明抗氧化治療與經典抗炎信號通路間的交叉對話機制,為開發基于多靶點協同干預的MBD精準治療策略提供理論依據。
1材料與方法
1.1試驗材料
1.1.1試驗動物供試20只SPF級6周齡C57BL/6雄性小鼠購自廣西醫科大學實驗動物中心,20只瘦素缺陷型ob/ob(B6.VLepob/J)雄性小鼠(代謝綜合征模型)購自鼠來寶(武漢)生物科技有限公司。動物試驗由蘭州大學第二醫院倫理委員會批準,批準號2021A-006。
1.1.2細胞株來源小鼠膀胱平滑肌細胞(BSMCs)由C57BL/6雄性小鼠膀胱組織分離獲得。取5只雄性小鼠,經安樂死后,通過腹部正中切口切取膀胱組織;膀胱組織在生理鹽水和PBS中反復洗滌,去除黏膜、黏膜下層及漿膜層,剪成肉糜,使用II型膠原酶消化1 h;消化后的組織通過細胞篩網過濾并離心,接種于含10%胎牛血清(FBS)和1%雙抗的DMEM細胞培養基中;培養48 h后換液,繼續培養7 d,直至細胞鋪板并進行傳代。
1.1.3主要儀器設備及試劑主要儀器設備:熒光顯微鏡(寧波舜宇儀器有限公司)、渦旋振蕩器(武漢賽維爾生物科技有限公司)、實時熒光定量PCR儀(上海楓嶺生物技術有限公司)、超微量分光光度計[鼎昊源(天津)生物科技有限公司]、垂直板電泳轉移裝置(北京六一生物科技有限公司)、化學發光儀(上海天能生命科學有限公司)、酶標儀[帝肯(上海)實驗器材有限公司]、脫水機(濟南丹吉爾電子有限公司)、包埋機和冷凍臺(武漢俊杰電子有限公司)、病理切片機(上海徠卡儀器有限公司)、掃描儀(山東斯瑞締醫療科技有限公司)。供試試劑:高脂飼料(蛋白20%,碳水化合物20%,脂肪60%)和常規飼料(蛋白20%,碳水化合物76%,脂肪4%)(沈陽茂華生物科技有限公司)、葡萄糖和NAC(合肥凱米克生化科技有限公司)、D-甘露醇(大連美侖生物技術有限公司)、抗熒光淬滅劑和DAPI(武漢賽維爾生物科技有限公司)、IL-6抗體、TGF-β抗體和TGF-β1抗體[賽信通(上海)生物試劑有限公司]、BK-β1抗體、p-ERK抗體和p-JNK抗體[艾博抗(上海)貿易有限公司]、SKCa3抗體(亞諾法生技股份有限公司)、NF-κB抗體、IL-1β抗體、GAPDH抗體、β-Actin抗體和ROCK1抗體(武漢三鷹生物技術有限公司)、MCC950和PDTC(上海皓元生物醫藥科技有限公司)。
1.2動物飼養
實驗小鼠飼養在溫度(23±2)℃、濕度(50±10)%、12 h光照/12 h黑暗交替的動物房內2周,自由采食,以適應環境。選擇8周齡C57BL/6雄性小鼠和ob/ob(B6.V-Lepob/J)雄性小鼠,試驗持續20周,試驗結束后處死小鼠,采集膀胱組織。
1.3免疫組織化學染色
C57BL/6雄性小鼠為對照組(Con),ob/ob(B6.V-Lepob/J)雄性小鼠為代謝綜合征模型組(ob/ob)。小鼠膀胱組織在4%多聚甲醛中固定,隨后進行脫水、石蠟包埋、切片和抗原修復處理。切片完成后,使用3%BSA封閉30min,加入一抗在4℃下孵育過夜。使用PBS洗滌3次,每次5min,加入二抗,在避光條件下孵育50min。使用DAPI復染細胞核,滴加抗熒光淬滅劑封片。
1.4葡萄糖濃度篩選
BSMCs在37℃培養箱中于含10%FBS的DMEM細胞培養基中培養。以正常培養的BSMCs為對照(Con),在0、25、50和100 mmol/L葡萄糖中培養7 d進行初步篩選,隨后在25~50 mmol/L間增設35、40和45 mmol/L濃度,進一步篩選。使用超微量分光光度計檢測OD450 nm,繪制細胞生長曲線,確定最佳干預濃度。
1.5試驗分組
在確定葡萄糖最佳干預濃度后,試驗設對照組(Con)、高糖組(HG)、高糖+NAC組(HG+NAC)和高滲組(HO),分別于DMEM細胞培養基、45 mmol/L葡萄糖、45 mmol/L葡萄糖和5 mmol/L NAC、50 mmol/L甘露醇中培養48 h。為進一步探究NAC干預對細胞纖維化的作用機制,使用0.01μmol/L MCC950和0.01μmol/L PDTC處理細胞,試驗設對照組(Con)、高糖組(HG)、高糖+MCC950組(HG+MCC950)、高糖+PDTC組(HG+PDTC)和高滲組(HO)。
1.6 Western blotting檢測
向組織和細胞樣品加入蛋白裂解液,按照試劑盒說明提取蛋白。取100μL上清液,在4°C下12000 r/min離心10 min,通過BCA法測定蛋白濃度;蛋白樣品經10%SDS-PAGE分析后,將蛋白轉移至PVDF膜,使用5%脫脂奶粉封閉1.5 h;PVDF膜與一抗在4℃下孵育過夜;使用1×TBST洗膜3次,每次5min;加入二抗置于搖床中室溫孵育2~3 h;使用1×TBST洗膜3次,每次10 min;加入適量ELC發光顯影液,在凝膠顯影儀下曝光觀察。
1.7統計分析
試驗數據采用GraphPad Prism 9.0進行單因素方差分析(One-way ANOVA)及制圖。
2結果與分析
2.1小鼠膀胱組織中炎癥因子、氧化應激與重構因子相關蛋白相對表達量
收集C57BL/6雄性小鼠和ob/ob(B6.V-Lepob/J)雄性小鼠膀胱組織,進行Western blotting檢測。結果如圖1-A所示,ob/ob組小鼠膀胱組織中3-Nitroty‐rosine(NT)、TGF-β1及α-SMA蛋白相對表達量顯著高于Con組(rlt;0.05,下同),提示ob/ob組小鼠膀胱存在明顯的氧化應激及纖維化現象。對膀胱組織中多個炎癥標志物進行Western blotting檢測,以明確氧化應激與纖維化的炎癥通路。結果(圖1-B)顯示,與Con組相比,ob/ob組小鼠膀胱組織中SMAD、p38、p-ERK和p-JNK蛋白相對表達量無顯著差異(rgt;0.05,下同),提示TGF-β1和α-SMA蛋白的激活由其他信號通路介導。
2.2小鼠膀胱組織中NF-κB和TGF-β1免疫組織化學染色結果
免疫組織化學染色結果(圖2)顯示,Con組小鼠膀胱組織中NF-κB和TGF-β1的熒光信號較分散且強度較低,ob/ob組小鼠膀胱組織中NF-κB與TGF-β1的熒光信號較集中且強度較高,此外,還在小鼠膀胱組織觀察到大量細胞碎片,表明細胞發生損傷甚至凋亡。提示高糖環境中NF-κB和TGF-β1在膀胱組織中的活化程度更高。
2.3葡萄糖濃度篩選結果
在篩選高糖培養條件時,發現25 mmol/L葡萄糖能明顯促進BSMCs生長(圖3),通過進一步篩選葡萄糖濃度,最終確定45 mmol/L為最佳干預濃度,細胞生長曲線如圖4所示,與Con組相比,45 mmol/L的葡萄糖組BSMCs OD450 nm在第4 d顯著升高,第5~7 d極顯著升高(rlt;0.01)。
2.4 NAC對BSMCs中炎癥因子、重構因子與鉀離子通道相關蛋白相對表達量的影響
Western blotting檢測結果(圖5)顯示,與Con組相比,HG組BSMCs中CRP、IL-6、TGF-β1、IL-1β和NLRP3蛋白相對表達量顯著升高,鉀離子通道蛋白BK-β1和SKCa3相對表達量顯著降低;與HG組相比,HG+NAC組BSMCs中CRP、IL-6、TGF-β1、IL-1β和NLRP3蛋白相對表達量顯著降低,BK-β1和SKCa3蛋白相對表達量顯著升高。上述結果表明,高糖環境下BSMCs中炎癥因子及重構因子蛋白相對表達量升高,誘導細胞纖維化加劇,同時細胞內鉀離子通道功能受到抑制,NAC則降低了高糖環境下BSMCs中炎癥因子及重構因子蛋白相對表達量,緩解了高糖環境造成的BSMCs鉀離子通道功能抑制。
2.5抑制NLRP3和NF-κB信號通路對BSMCs中重構因子、炎癥因子與氧化應激相關蛋白相對表達量的影響
結果(圖6)顯示,與HG組相比,HG+MCC950和HG+PTCD組BSMCs中TGF-β1蛋白相對表達量顯著降低,提示NLRP3和NF-κB信號通路在高糖誘導的TGF-β1活化過程中發揮了重要作用,NF-κB蛋白相對表達量顯著升高,HG+MCC950組BSMCs中ROCK1和NLRP3蛋白相對表達量顯著降低,HG+PTCD組BSMCs中ROCK1和NLRP3蛋白相對表達量無顯著差異。提示MBD的發展為氧化應激誘導的炎癥反應和纖維化表現,且與抗氧化治療相比,抗炎治療對纖維化抑制的效果較為有限。
3討論
MBD與糖尿病膀胱的病理過程具有相似性,高血糖引起的氧化應激所誘發的炎癥反應,能導致膀胱環形肌出現纖維化及神經調節紊亂,進而改變膀胱的收縮頻率與力量,最終發展為糖尿病并引發尿潴留和尿毒癥。唐陽國等(2022)研究表明,高脂飼料飼喂的大鼠膀胱組織抗氧化能力降低,且發生組織纖維化,而NAC治療能有效緩解MBD的癥狀。本研究發現,NAC的干預有效緩解了MBD的氧化應激,抑制了膀胱纖維化,但具體的分子機制尚未明確。ob/ob組小鼠膀胱組織中NT蛋白相對表達量顯著高于Con組,提示ob/ob組小鼠膀胱組織氧化應激水平升高。此外,ob/ob組小鼠膀胱組織中TGF-β1和α-SMA蛋白相對表達量顯著高于Con組,表明其膀胱組織纖維化加劇。研究表明,低濃度的ROS可調節細胞信號轉導和血管張力等生理過程,而高濃度的ROS則會誘導細胞凋亡并造成組織損傷(Birder,2020),進而導致TGF-β1過度激活,促進細胞外基質(ECM)過度沉積,成纖維細胞過度增殖和分化,最終加劇膠原沉積和纖維增生(Yan et al.,2018)。
在MBD的病理過程中,氧化應激與纖維化的發生可能是通過炎癥反應介導的。高糖和肥胖等因素引發的胰島素抵抗會導致慢性氧化應激,產生大量ROS,而過量的ROS會導致脂質、蛋白質、碳水化合物和DNA發生氧化損傷,進而影響細胞生存(Rich‐ter et al.,1988;Cadenas and Davies,2000;Pacher et al.,2007)。與核DNA相比,線粒體DNA(mtDNA)更易受到ROS的影響(Herrero and Barja,2001),mtDNA損傷不僅引發炎癥反應,還會導致線粒體形態改變與功能損傷(Krysko et al.,2011;Chen et al.,2018),進一步產生線粒體活性氧(mtROS),加劇氧化應激反應。研究表明,ROS能增強T淋巴細胞活化,誘導白細胞和內皮細胞的黏附與趨化,進而滲透到炎癥反應區域(Dr?ge,2002;Valko et al.,2007)。此外,脂質過氧化物可間接激活2型環氧合酶(COX-2),從而激活巨噬細胞的炎癥潛能(Kumagai et al.,2004)。研究表明,MS患者機體存在與炎癥相關性較高的組織重塑過程,肥胖癥患者機體普遍處于慢性低級炎癥狀態,體內炎癥因子CRP、TNF-α、IL-6、IL-1β水平普遍高出正常范圍(陳曉可等,2024)。本研究發現,相較于Con組,HG組BSMCs中CRP、IL-6、TGF-β1、IL-1β、NLRP3蛋白相對表達量顯著升高,提示細胞炎癥反應加劇。IL-6不僅參與免疫與炎癥反應,還能通過誘導趨化因子和黏附因子激活巨噬細胞等炎癥細胞發生分化與遷移,促進組織重塑(王信光等,2024)。NAC干預后,BSMCs中CRP、IL-6、TGF-β1、IL-1β、NLRP3蛋白相對表達量顯著降低,表明NAC抑制了小鼠膀胱組織炎癥反應和纖維化。NAC是一種經典的天然抗氧化劑,乙酰化合物的結構特點使其具有明顯的還原性,分子內游離的巰基能清除機體內的自由基,此外,NAC進入細胞后其含有的半胱氨酸能通過消除自由基減少氧化損
傷并促進GSH合成,而GSH能直接清除OH-和O-,進而增強機體抗氧化能力(Tenório et al.,2021)。NAC的巰基在清除自由基的同時,還能減輕DNA損傷,調整信號轉導與基因表達,抵抗細胞凋亡(Kumar etal.,2021)。本研究中,ob/ob組小鼠膀胱組織中p38、p-ERK與p-JNK蛋白相對表達量與Con組差異不顯著,提示活化TGF-β1及誘導α-SMA介導的組織再生可能由其他信號通路完成。
本研究發現,HG組BSMCs中NLRP3異常升高,推測NLRP3可能是抑制膀胱纖維化的重要干預因子。NLRP3在動脈粥樣硬化、糖尿病、肝纖維化、肺纖維化及各種急性、慢性腎臟疾病中廣泛存在,并通過調節炎癥反應參與線粒體自噬與凋亡(Shahzad et al.,2015;Gong et al.,2016;Ludwig-Portugall et al.,2016)。NLRP3能促使IL-1β和IL-18的分泌,進而引發炎癥反應(姜昊瑋和吳照球,2022)。研究發現,NLRP3激活可能受到線粒體損傷、mtROS刺激、K+外流與溶酶體損傷釋放組織蛋白酶等因素的影響(Santoro et al.,1992;Unger et al.,1992;齊士勇和徐勇,2021)。本研究發現,與Con組相比,HG組BSMCs離子通道蛋白BK-β1和SKCa3相對表達量顯著降低,與HG組相比,HG+NAC組BSMCs中BK-β1和SKCa3蛋白相對表達量顯著升高,提示NLRP3可能參與了MBD的病理發展進程。研究表明,給予高脂飲食的NLRP3缺陷小鼠對胰島素高度敏感(Zhou et al.,2010);NLRP3在大鼠膀胱中定位于尿路上皮(Hughes et al.,2015),能誘導膀胱出口梗阻、出血性膀胱炎及糖尿病并發癥等膀胱病理性疾病發生(Hughes et al.,2014,2016);缺乏NLRP3的糖尿病小鼠不會出現糖尿病性膀胱功能障礙,NLRP3的缺失不僅不影響血糖水平,還能消除炎癥癥狀(Hughes et al.,2019)。本研究發現,與Con組相比,HG組BSMCs中NLRP3和IL-1β蛋白相對表達量顯著升高,與HG組相比,HG+NAC組BSMCs中NLRP3和IL-1β蛋白相對表達量顯著降低。研究表明,在NF-κB激活信號下,NLRP3能與ASC、caspase-1組裝形成NLRP3炎癥小體,而NLRP3炎癥小體可釋放caspase-1,并分泌IL-1β、IL-18和Gasdermin D等細胞因子,進而激活細胞焦亡(孫瑋等,2024;陶懷祥等,2024)。此外,低濃度的過氧化氫能激活NF-κB以調節促炎細胞因子水平,進而引發炎癥反應并激活NADPH氧化酶,刺激并增加ROS的產生,最終加重氧化應激反應(Prieto et al.,2014)。NF-κB參與許多炎癥性疾病的發生,是TLR4信號通路下游的核轉錄激活因子,能激活大量炎癥細胞因子的轉錄和表達,是調控炎癥反應進程的主要轉導信號(Luo et al.,2022)。NAC能通過清除ROS而抑制NF-κB的信號轉導,進而減少炎癥因子的表達并抑制NLRP3炎癥小體的形成,最終減輕炎癥反應。
Ruiz-Ortega等(2020)研究表明,NF-κB/TGF-β1信號通路在有關纖維化的疾病進展過程中發揮重要作用。本研究發現,與Con組相比,ob/ob組小鼠膀胱組織中大量細胞發生損傷,可觀察到許多細胞碎片,NF-κB與TGF-β1分布不均,集中在細胞核周圍,提示ob/ob組小鼠膀胱組織可能發生NLRP3/NF-κB信號通路引發的細胞焦亡。抑制NLRP3和NF-κB信號通路后,與HG組相比,HG+MCC950和HG+PDTC組BSMCs中TGF-β1蛋白相對表達量顯著降低,表明抑制NF-κB和NLRP3信號通路有利于減輕纖維化,而介導氧化應激反應的ROCK1蛋白相對表達量受NF-κB抑制的影響較小,且與HG組相比,HG+NAC組BSMCs中TGF-β1、IL-1β和NLRP3蛋白相對表達量顯著降低,進一步證實了NLRP3/NF-κB信號通路是ROS的下游產物,三者共同介導纖維化的發生。此外,相較于通過NLRP3/NF-κB信號通路抑制炎癥反應,NAC的抗氧化治療可能更有利于MBD轉歸。
4結論
高糖因素誘發的小鼠膀胱功能損傷涉及氧化應激—炎癥反應—組織纖維化相關分子機制通路,NAC主要通過抑制ROS/NLRP3/NF-κB/TGF-β1信號通路阻斷功能損傷中氧化應激、炎癥反應和纖維化的發展進程。與抗炎治療相比,NAC抗氧化治療對組織纖維化的治療效果可能更顯著。
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