Department of Medical Research, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung, Taiwan.
Bone. 2011 Nov;49(5):1080-9. doi: 10.1016/j.bone.2011.08.006. Epub 2011 Aug 11.
Excessive glucocorticoid administration accelerates osteoblast apoptosis and skeletal deterioration. Heat shock proteins (HSPs) regulate metabolic activities in osteoblastic cells. This study characterized the biological significance of HSP60 in glucocorticoid-induced bone loss. Rats were treated with glucocorticoid, HSP60 antisense oligonucleotides, or adenovirus-mediated HSP60 gene transfer. Bone mineral density, metaphyseal trabecular micro-architecture, and fragility were analyzed by dual X-ray absorptiometry, micro-computed tomography, and material testing, respectively. Differential proteomic profiles of bone tissue extracts were detected by bi-dimensional electrophoresis and mass spectrometry. Survival and proapoptotic signal transduction were quantified by immunoblotting. Glucocorticoid-treated rats had low bone mineral density and metaphyseal trabecular microstructure in association with downregulation of collagen 1α1 and HSP60 expressions in bone tissue. Gain of HSP60 function by adenovirus-mediated HSP60 gene transfer abrogated the deleterious effects of glucocorticoid treatment on bone mass, trabecular microstructure, and mechanical strength. Enhancement of HSP60 signaling attenuated the glucocorticoid-induced loss of trabecular bone volume, mineral acquisition reactions and osteoblast surface. HSP60 gene transfer activated ERK and Akt and reduced Bax and cytochrome c release, as well as caspase-3 cleavage, which attenuated the inhibitory effects of glucocorticoid treatment on osteoblast survival. Loss of HSP60 function by HSP60 antisense oligonucleotides accelerated mitochondrial apoptotic programs and osteoblast apoptosis. Knockdown of HSP60 induced loss of bone mass, micro-architecture integrity, and mechanical property. Taken together, loss of HSP60 signaling contributes to the glucocorticoid-induced enhancement of pro-apoptotic reactions, thereby accelerating osteoblast apoptosis and bone mass loss. Enhancement of HSP60 function is beneficial for protecting bone tissue against the glucocorticoid-induced inhibition of bone cell viability and bone formation.
过量的糖皮质激素给药会加速成骨细胞凋亡和骨骼恶化。热休克蛋白 (HSPs) 调节成骨细胞的代谢活动。本研究探讨了 HSP60 在糖皮质激素诱导的骨丢失中的生物学意义。通过给予糖皮质激素、HSP60 反义寡核苷酸或腺病毒介导的 HSP60 基因转移处理大鼠。采用双能 X 线吸收仪、微计算机断层扫描和材料测试分别分析骨矿物质密度、骺板小梁微观结构和脆性。通过二维电泳和质谱检测骨组织提取物的差异蛋白质组谱。通过免疫印迹定量检测细胞存活和促凋亡信号转导。糖皮质激素处理的大鼠骨矿物质密度和骺板小梁微观结构降低，同时伴有骨组织中胶原 1α1 和 HSP60 表达下调。腺病毒介导的 HSP60 基因转移增强 HSP60 功能可消除糖皮质激素处理对骨量、小梁微观结构和机械强度的有害影响。增强 HSP60 信号转导可减弱糖皮质激素诱导的小梁骨体积、矿物质获取反应和成骨细胞表面的丢失。HSP60 基因转移可激活 ERK 和 Akt，减少 Bax 和细胞色素 c 的释放以及 caspase-3 的切割，从而减弱糖皮质激素处理对成骨细胞存活的抑制作用。HSP60 反义寡核苷酸降低 HSP60 功能可加速线粒体凋亡程序和成骨细胞凋亡。HSP60 敲低会导致骨量、微结构完整性和机械性能丧失。综上所述，HSP60 信号的丧失导致促凋亡反应增强，从而加速成骨细胞凋亡和骨量丢失。增强 HSP60 功能有利于保护骨组织免受糖皮质激素抑制骨细胞活力和骨形成的影响。
