生长抑素对肝星状细胞的影响机制
发布时间:2008-01-15 作者:路人乙 来源:网络资源
2 结果
2.1 SST对HSC增生的影响 MTT结果显示，SST浓度在10-6-10-9 mol/L范围内均可剂量依赖性地抑制活化的HSC增生，10-6 mol/L及10-7 mol/L组的抑制率分别达30.5 %和15.8 %（P %26lt;0.01）．
2.2 SST对HSC凋亡及细胞周期的影响 AO/EB荧光染色法：部分HSC变为圆形，核缩小，碎裂，呈颗粒状、块状致密浓染，黄绿色荧光显著增强（图1）．计数结果表明，各浓度SST均可促进活化的HSC凋亡，且有明显量效关系，尤以10-6 mol/L及10-7 mol/L组作用最明显（P%26lt;0.05）．流式细胞术：10-6,10-7,10-8,10-9,10-10mol/L SST处理组及对照组的HSC凋亡率分别为16.6±4.6 %、6.1±1.8%、2.8±0.7%、2.3±1.0 %、1.6±0.6 %及1.5±1.2 %．10-6 mol/L及10-7 mol/L组与对照组相比，凋亡率存在显著性差异（P %26lt;0.01）．同时，各SST处理组中G0/G1期细胞比例增高，S期细胞比例降低.10-6 mol/L及10-7 mol/L组与对照组比较，G0/G1期细胞由78.5±4.4 %分别提高至93.1±9.7 % (P %26lt;0.01)及90.7%±8.0 %(P %26lt;0.05)，S期细胞则由12.5±2.9 %分别减低至1.8±0.4 % (P %26lt;0.01) 及 3.9±0.9 % (P %26lt;0.05)．TUNEL法：10-6，10-7，10-8，10-9及10-10 mol/L SST处理组的凋亡指数分别为14.7±3.9 %、6.0±1.0 %、2.3±0.6 %、2.0±0.8 %及1.7±0.9 %，其中10-6 mol/L及10-7 mol/L组的凋亡指数明显高于对照组的2.2±0.7 %(P %26lt;0.01)．加SST 72 h后透射电镜下出现凋亡的形态特征[26]:细胞皱缩，空泡增多，线粒体轻度增多，肿胀，内质网扩张．胞核收缩，染色质凝聚成块，或呈环状致密带，沿核膜内侧排列．并见少量凋亡小体．
图1 SST对活化HSC凋亡的影响 （×400倍）
3 讨论
SST是重要的细胞增生及分化调节肽,通过阻断生长因子及激素的合成、分泌或由受体(SSTR1、SSTR2A、SSTR2B 及SSTR3-SSTR5)介导,可抑制各种细胞增生[5-9]，具有广泛的生理作用．SST有SST-14、SST-28等多种分子形式，其中以SST-14最为重要．HSC在肝硬化的发生、发展过程中起关键作用[10-13]．近年来发现，肝小叶内的神经纤维含SST，且与肝窦内皮细胞及HSC密切接触[14]．2001年Reynaert et al [15]提出，HSC在活化过程中开始表达SSTR1、SSTR2及SSTR3．由此推测，SST可能通过旁泌方式在HSC的活化过程中发挥负调节作用．此外，以自泌和/或旁泌方式释放IGF、EGF及TGF-a等有丝分裂原[10]，对HSC的持续激活及肝硬化形成十分重要，而SST可抑制这些细胞因子的分泌，并可逆转EGF对受体的作用．同样提示SST可能具有抗肝硬化作用．
本研究显示，SST浓度在10-6-10-9 mol/L范围内，均可通过剂量依赖方式抑制活化的HSC增生，当浓度达10-6 mol/L或10-7 mol/L时，抑制作用具有统计学意义．SST的增生抑制作用主要由SSTR1、2、4、5介导．通过与G蛋白藕合，SSTR可抑制腺苷酸环化酶活性，使细胞内cAMP水平降低，进而激活PTP，调节MAPK活性，影响c-fos，c-jun，c-myc的转录，最终阻碍细胞增生，并致细胞周期阻滞[16，17]．我们发现，经SST处理后G0/G1期细胞比例增高，S期细胞比例降低，这与Sharma et al [16]的报道一致．表明G0/G1期阻滞是SST发挥抗增生作用的重要机制．
活化的HSC主要通过凋亡方式减少[18-22]．SST则通过SSTR2、SSTR3诱导细胞凋亡[23-25]，其机制与选择性激活酸性核酸内切酶有关．细胞内酸化及酸性核酸内切酶的激活，引起DNA断裂，激活野生型p53．激活的PTP也可使p53丝氨酸残基去磷酸化而活化，从而引起凋亡[27-35]．我们运用荧光染色、流式细胞术、TUNEL、透射电镜等方法，从形态及生化角度均证实SST可促进体外原代培养的大鼠HSC凋亡，且SST浓度与HSC凋亡率呈正相关．SST浓度达10-6 mol/L及10-7 mol/L时，凋亡率的改变可达显著性水平．
总之,低剂量SST即可有效抑制活化的HSC增生,提高其凋亡率,因而可能在肝硬化的防治中发挥重要作用,值得进一步深入探讨．
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