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Autophagy mediated CoCrMo particle-induced peri-implant osteolysis by promoting osteoblast apoptosis.

Wang Z, Liu N, Liu K, Zhou G, Gan J, Wang Z, Shi T, He W, Wang L, Guo T, Bao N, Wang R, Huang Z, Chen J, Dong L, Zhao J, Zhang J - Autophagy (2015)

Bottom Line: Both autophagy inhibitor 3-MA (3-methyladenine) and siRNA of Atg5 could dramatically reduce CoPs-induced apoptosis in osteoblasts.Further, inhibition of autophagy with 3-MA ameliorated the severity of osteolysis in PIO animal models.Moreover, 3-MA also prevented osteoblast apoptosis in an antiautophagic way when tested in PIO model.

View Article: PubMed Central - PubMed

Affiliation: a Jinling Hospital; Department of Orthopaedics; State Key Laboratory of Pharmaceutical Biotechnology; Nanjing University ; Nanjing , China.

ABSTRACT
Wear particle-induced osteolysis is the leading cause of aseptic loosening, which is the most common reason for THA (total hip arthroplasty) failure and revision surgery. Although existing studies suggest that osteoblast apoptosis induced by wear debris is involved in aseptic loosening, the underlying mechanism linking wear particles to osteoblast apoptosis remains almost totally unknown. In the present study, we investigated the effect of autophagy on osteoblast apoptosis induced by CoCrMo metal particles (CoPs) in vitro and in a calvarial resorption animal model. Our study demonstrated that CoPs stimulated autophagy in osteoblasts and PIO (particle-induced osteolysis) animal models. Both autophagy inhibitor 3-MA (3-methyladenine) and siRNA of Atg5 could dramatically reduce CoPs-induced apoptosis in osteoblasts. Further, inhibition of autophagy with 3-MA ameliorated the severity of osteolysis in PIO animal models. Moreover, 3-MA also prevented osteoblast apoptosis in an antiautophagic way when tested in PIO model. Collectively, these results suggest that autophagy plays a key role in CoPs-induced osteolysis and that targeting autophagy-related pathways may represent a potential therapeutic approach for treating particle-induced peri-implant osteolysis.

No MeSH data available.


Related in: MedlinePlus

Autophagy mediated the upregulation of BAX induced by CoPs. (A) Western blots performed after osteoblast cells were incubated with 3-MA (10 mM), siAtg5 and siCtrl before being stimulated with CoPs (50 µg/ml) for 24 h. (B, C) The density of the western blots bands shown in (A) was quantified using ImageJ software. siCtrl, siControl. Data are presented as means ± S.E.M. from 3 independent experiments. *, P < 0.05 and **, P < 0.01 vs. control; ##, P < 0.01 vs. CoPs group.
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f0004: Autophagy mediated the upregulation of BAX induced by CoPs. (A) Western blots performed after osteoblast cells were incubated with 3-MA (10 mM), siAtg5 and siCtrl before being stimulated with CoPs (50 µg/ml) for 24 h. (B, C) The density of the western blots bands shown in (A) was quantified using ImageJ software. siCtrl, siControl. Data are presented as means ± S.E.M. from 3 independent experiments. *, P < 0.05 and **, P < 0.01 vs. control; ##, P < 0.01 vs. CoPs group.

Mentions: Both the antiapoptotic protein BCL2 (B-cell CLL/lymphoma 2) and the pro-apoptotic protein BAX (BCL2-associated X protein) belong to the BCL2 family. Recently, studies have demonstrated that these BCL2 family proteins are involved in the crosstalk between autophagy and apoptosis.14 In the present study, we first investigated the expression of the BAX and BCL2 proteins in CoPs-stimulated osteoblasts. CoPs treatment increased the level of BAX protein but had no effect on the expression of BCL2, thereby raising the BAX/BCL2 ratio (Fig. 4A to C). To investigate whether autophagy was involved in the upregulation of BAX, we next performed western blot analysis in cells cotreated with CoPs and the autophagy inhibitor 3-MA. As shown in Figure 4A to C, the upregulation of BAX was significantly decreased when osteoblasts were treated with 3-MA. In addition, 3-MA treatment significantly inhibited the CoPs-induced upregulation of the BAX/BCL2 ratio (Fig. 4A and C). Autophagy is tightly regulated by a limited number of highly evolutionarily conserved molecules called ATGs, including ATG5.32 To further confirm that the upregulation of the BAX/BCL2 ratio was due to autophagy, we used siRNA against Atg5 to inhibit autophagy more specifically at the molecular level (Fig. 3F).33,34SiAtg5 markedly rescued the CoPs-induced upregulation of the BAX/BCL2 ratio (Fig. 4A and C).Figure 4.


Autophagy mediated CoCrMo particle-induced peri-implant osteolysis by promoting osteoblast apoptosis.

Wang Z, Liu N, Liu K, Zhou G, Gan J, Wang Z, Shi T, He W, Wang L, Guo T, Bao N, Wang R, Huang Z, Chen J, Dong L, Zhao J, Zhang J - Autophagy (2015)

Autophagy mediated the upregulation of BAX induced by CoPs. (A) Western blots performed after osteoblast cells were incubated with 3-MA (10 mM), siAtg5 and siCtrl before being stimulated with CoPs (50 µg/ml) for 24 h. (B, C) The density of the western blots bands shown in (A) was quantified using ImageJ software. siCtrl, siControl. Data are presented as means ± S.E.M. from 3 independent experiments. *, P < 0.05 and **, P < 0.01 vs. control; ##, P < 0.01 vs. CoPs group.
© Copyright Policy - open-access
Related In: Results  -  Collection

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f0004: Autophagy mediated the upregulation of BAX induced by CoPs. (A) Western blots performed after osteoblast cells were incubated with 3-MA (10 mM), siAtg5 and siCtrl before being stimulated with CoPs (50 µg/ml) for 24 h. (B, C) The density of the western blots bands shown in (A) was quantified using ImageJ software. siCtrl, siControl. Data are presented as means ± S.E.M. from 3 independent experiments. *, P < 0.05 and **, P < 0.01 vs. control; ##, P < 0.01 vs. CoPs group.
Mentions: Both the antiapoptotic protein BCL2 (B-cell CLL/lymphoma 2) and the pro-apoptotic protein BAX (BCL2-associated X protein) belong to the BCL2 family. Recently, studies have demonstrated that these BCL2 family proteins are involved in the crosstalk between autophagy and apoptosis.14 In the present study, we first investigated the expression of the BAX and BCL2 proteins in CoPs-stimulated osteoblasts. CoPs treatment increased the level of BAX protein but had no effect on the expression of BCL2, thereby raising the BAX/BCL2 ratio (Fig. 4A to C). To investigate whether autophagy was involved in the upregulation of BAX, we next performed western blot analysis in cells cotreated with CoPs and the autophagy inhibitor 3-MA. As shown in Figure 4A to C, the upregulation of BAX was significantly decreased when osteoblasts were treated with 3-MA. In addition, 3-MA treatment significantly inhibited the CoPs-induced upregulation of the BAX/BCL2 ratio (Fig. 4A and C). Autophagy is tightly regulated by a limited number of highly evolutionarily conserved molecules called ATGs, including ATG5.32 To further confirm that the upregulation of the BAX/BCL2 ratio was due to autophagy, we used siRNA against Atg5 to inhibit autophagy more specifically at the molecular level (Fig. 3F).33,34SiAtg5 markedly rescued the CoPs-induced upregulation of the BAX/BCL2 ratio (Fig. 4A and C).Figure 4.

Bottom Line: Both autophagy inhibitor 3-MA (3-methyladenine) and siRNA of Atg5 could dramatically reduce CoPs-induced apoptosis in osteoblasts.Further, inhibition of autophagy with 3-MA ameliorated the severity of osteolysis in PIO animal models.Moreover, 3-MA also prevented osteoblast apoptosis in an antiautophagic way when tested in PIO model.

View Article: PubMed Central - PubMed

Affiliation: a Jinling Hospital; Department of Orthopaedics; State Key Laboratory of Pharmaceutical Biotechnology; Nanjing University ; Nanjing , China.

ABSTRACT
Wear particle-induced osteolysis is the leading cause of aseptic loosening, which is the most common reason for THA (total hip arthroplasty) failure and revision surgery. Although existing studies suggest that osteoblast apoptosis induced by wear debris is involved in aseptic loosening, the underlying mechanism linking wear particles to osteoblast apoptosis remains almost totally unknown. In the present study, we investigated the effect of autophagy on osteoblast apoptosis induced by CoCrMo metal particles (CoPs) in vitro and in a calvarial resorption animal model. Our study demonstrated that CoPs stimulated autophagy in osteoblasts and PIO (particle-induced osteolysis) animal models. Both autophagy inhibitor 3-MA (3-methyladenine) and siRNA of Atg5 could dramatically reduce CoPs-induced apoptosis in osteoblasts. Further, inhibition of autophagy with 3-MA ameliorated the severity of osteolysis in PIO animal models. Moreover, 3-MA also prevented osteoblast apoptosis in an antiautophagic way when tested in PIO model. Collectively, these results suggest that autophagy plays a key role in CoPs-induced osteolysis and that targeting autophagy-related pathways may represent a potential therapeutic approach for treating particle-induced peri-implant osteolysis.

No MeSH data available.


Related in: MedlinePlus