Iron overload induces apoptosis of murine preosteoblast cells via ROS and inhibition of AKT pathway.

OBJECTIVE: This study investigates the inhibitory effect of iron overload on MC3T3-E1 cells and its molecular mechanism. METHODS: MC3T3-E1 cells were grown under different concentrations of FAC (ferric ammonium citrate), and the WST-8 assay was used to investigate the proliferation of cells following FAC with or without deferasirox. DCFH-DA fluorescence probe was applied to detect the cellular reactive oxygen species (ROS) level. The apoptotic cells were analyzed with Annexin V-FITC/PI and the Hoechst 33258 nuclear staining assay. The JC-1 staining assay was applied to observe the change in the mitochondrial transmembrane potential. The expression levels of caspase-3, PARP, Bcl-2 family proteins, and AKT kinase were detected with the Western blot assay. RESULTS: Iron overload had a cytotoxic effect on MC3T3-E1 cells in a dosage-dependent way and resulted in increasing level of intracellular ROS. Iron overload induced apoptosis in MC3T3-E1 cells via a caspase-dependent mechanism that is accompanied by mitochondria dysfunction and decreased expression of anti-apoptotic proteins. The expression levels of cleaved-caspase-3 and cleaved-PARP were upregulated, while the expression levels of caspase-9, caspase-7, caspase-3, and PARP were downregulated. Phosphorylation of AKT kinase decreased. CONCLUSION: Iron overload can generate ROS in cells, inhibit AKT kinase and its downstream proteins activity, and subsequently initiate apoptotic events.

Relationships of muscle strength and bone mineral density in ambulatory children with cerebral palsy.

SUMMARY: This work explores the relationships of muscle strength and areal bone mineral density (aBMD) in ambulatory children with cerebral palsy (CP). The knee extensor strength, but not motor function, was related to aBMD. Thus, muscle strength, especially antigravity muscle strength, was more associated with aBMD in these children than motor function. INTRODUCTION: Muscle strength is related to bone density in normal children. However, no studies have examined these relationships in ambulatory children with CP. This work explores the relationships of muscle strength and aBMD in ambulatory children with CP. METHODS: Forty-eight ambulatory children with spastic CP, aged 5-15 years, were classified into two groups based on Gross Motor Function Classification System levels: I (n = 28) and II (n = 20). Another 31 normal development (ND) children were recruited as the comparison group for the aBMD. Children with CP underwent assessments of growth, lumbar and distal femur aBMD, Gross Motor Function Measure-66 (GMFM-66), and muscle strength of knee extensor and flexor by isokinetic dynamometer. RESULTS: The distal femur aBMD, but not lumbar aBMD, was lower in children with CP than in ND children (p < 0.05). Children with level I had greater knee flexor strength and GMFM-66 scores than those with level II (p < 0.001). However, the knee extensor strength and distal femur and lumbar aBMD did not differ between two groups. Regression analysis revealed the weight and knee extensor strength, but not GMFM-66 scores, were related positively to the distal femur and lumbar aBMD (adjusted r (2) = 0.56-0.65, p < 0.001). CONCLUSIONS: These results suggest the muscle strength, especially antigravity muscle strength, were more associated with the bone density of ambulatory children with CP than motor function. The data may allow clinicians for early identifying the ambulatory CP children of potential low bone density.