Stanozolol activates the cross-talk of estrogen receptor alpha-insulin-like growth factor-1 receptor-extracellular-signal regulated kinase 1/2 in the growth plate chondrocytes of estrogen-inhibited adolescent rats in vitro / 中华儿科杂志

ABSTRACT

<p><b>OBJECTIVE</b>To investigate the effects and the mechanisms of stanozolol (ST) on the proliferation, maturation and differentiation of in vitro cultured growth plate chondrocyte isolated from gonadotropin releasing hormone analogue (GnRHa)-treated adolescent rats, to study if ST mediates the proliferation of chondrocytes via the estrogen receptor alpha (ERalpha), androgen receptor (AR) and/or insulin-like growth factor-1 receptor (IGF-1R) and interactions of the two receptor and IGF-1R receptor signaling pathway, to investigate the mechanism of the biological effects in ST promoting bone growth/maturity at molecular level.</p><p><b>METHOD</b>The rats were weaned at the end of 3 weeks and intramuscular injection of triptorelin of GnRHa preparations, qow x 2 was started. The rats were sacrificed at the end of 7 weeks, and then the tibiae growth plates were taken out with sterile procedure. The chondrocytes were obtained by two-time enzyme digestion method, and the experiments were carried out with the primary chondrocytes. Immunohistochemical staining of proliferating cell nuclear antigen (PCNA) and Western blot analysis were applied.</p><p><b>RESULT</b>The results of PCNA demonstrated that stanozolol enhanced the proliferation of the chondrocytes, time-course studies showed that the proliferation were maximally stimulated by stanozolol after 2 days of incubation and decreased again after longer periods of incubation. The expression of p-ERalpha, p-IGF-1R and p-extracellular-signal regulated kinase 1/2 (ERK1/2) increased with the incubation period of ST treatment, and reached the peak value at a certain time, and then gradually decreased. The expression of p-ERalpha, p-IGF-1R and p-ERK1/2 increased with the elevation of ST concentration, and reached the peak value at 10(-9) - 10(-8) mol/L, then gradually decreased. ST induced-p-ERalpha expression was partially blocked by ERalpha and mitogen-activated protein kinase kinase inhibitors. ST induced-p-IGF-1R expression was partially blocked by ERalpha and IGF-1R inhibitors. ST induced-p-ERK1/2 expression was partially blocked by mitogen-activated protein kinase kinase and IGF-1R inhibitors.</p><p><b>CONCLUSION</b>As an androgen derivation, ST exerts its biological effects of promoting proliferation of the long bone growth plate chondrocytes via activating the classic ERalpha receptor pathway and mitogen-activated protein kinase pathway, and at the same time, by activation of IGF-1R. Both IGF-1R and ERalpha can promote "cross-talk" of two systems' receptor signal through mitogen-activated protein kinase signal pathway.</p>