Levodopa attenuates cellular apoptosis in steroid-associated necrosis of the femoral head

Xi, Hongbo; Tao, Weijian; Jian, Zhengguang; Sun, Xuefeng; Gong, Xiaohong; Huang, Lixin; Dong, Tianhua

L-3-(3,4-dihydroxyphenyl) alanine (LEV), which is the L-isomer of dopa, was absorbed inside the intestine after oral administration to subsequently peak at a plasma concentration of 1-2 h. When LEV enters the central nervous system, it may increase the concentration of dopamine at the median eminence, stimulating dopamine receptors to increase the level of norepinephrine inside the hypothalamus. The latter would then excite the α-receptor and promote the release of growth hormone releasing factor, leading to the increased secretion of growth hormone (GH). GH is able to promote the synchronic proliferation of proosteoblasts and osteoblasts in fractures and peri-periosteal cambium layer, thus accelerating the repair process of NFH (19) . In addition, GH promotes the secretion of IGF-1 and other factors; IGF-1 is able to promote the synthesis of DNA and RNA in cartilage cells and cell mitosis to accelerate the speed of cartilaginous ossification. Previous in vitro studies have shown that IGF-1 inhibits the apoptosis of bone cells and osteoblasts, inducing the growth and maturation of bones and cartilages, reducing subendosteal bone resorption, increasing the net increase of bone mass, and thereby reducing the incidence of NFH and accelerating the repair process (19) .