ABSTRACT
Di-2-ethyl hexyl phthalate (DEHP), an industrial plasticizer and a ubiquitous environmental contaminant, is an established endocrine disruptor (ED). Increasing evidences indicate that some EDs interfere with osteoblast differentiation and function. In the present study, we investigated the effects of DEHP on the expression of cell cycle proteins, differentiation markers, Runx2 and its co-activator TAZ in osteoblasts derived from neonatal rat calvaria. A significant decrease in protein levels of cyclin D1 and CDK-2 was found at high dosage of DEHP (100 µM) after 24h treatment. DEHP treatment caused a significant decrease in ALP mRNA. While DEHP treatment significantly decreased the TAZ at mRNA and protein levels, it decreased only the Runx2protein levels. Histochemical localization of ALP, collagen and mineralized nodules studied from cells treated with DEHP (10 and 100 µM) for 21 days revealed a drastic decrease in collagen, ALP and mineralization. In conclusion, DEHP affected differentiation of neonatal rat calvarial osteoblasts and mineralization of matrix secreted by these cells.
Subject(s)
Diethylhexyl Phthalate/toxicity , Environmental Pollutants/toxicity , Osteoblasts/drug effects , Plasticizers/toxicity , Acyltransferases , Alkaline Phosphatase/genetics , Alkaline Phosphatase/metabolism , Animals , Animals, Newborn , Calcification, Physiologic/drug effects , Cell Differentiation/drug effects , Cell Survival/drug effects , Cells, Cultured , Collagen/metabolism , Core Binding Factor Alpha 1 Subunit/genetics , Core Binding Factor Alpha 1 Subunit/metabolism , Cyclin D1/metabolism , Cyclin-Dependent Kinase 2/metabolism , Intracellular Signaling Peptides and Proteins/metabolism , Osteoblasts/cytology , Osteoblasts/metabolism , RNA, Messenger/metabolism , Rats , Skull/cytology , Transcription Factors/genetics , Transcription Factors/metabolismABSTRACT
Thyroid stimulating hormone (TSH) is shown to have definite anabolic effects on skeletal metabolism. Previous studies have demonstrated that Insulin-like growth factors (IGF-I and IGF-II) and their six high affinity binding proteins (IGFBPs 1-6) regulate proliferation and differentiation of bone-forming osteoblasts. The current study was intended to determine whether the anabolic effects of TSH on human osteoblastic (SaOS2) cells are mediated through insulin-like growth factor system components. TSH given at 0.01 ng to 10 ng/ml dose levels for 24 and 48 h significantly increased human osteoblastic (SaOS2) cell proliferation and alkaline phosphatase activity, the differentiation marker. TSH significantly increased IGFs (IGF-I and IGF-II) mRNA expression after 6 and 24 h and their protein levels after 24 and 48 h of treatment, respectively. Unlike the IGFs, the IGFBPs responded differently to TSH treatment. Though there were some inconsistencies in the regulation of stimulatory IGF binding protein-3 and -5 by TSH treatment, there was an overall increase at the mRNA abundance and protein levels. Again, the inconsistency persisted at the regulation of the inhibitory IGFBPs 2, 4, and 6 especially at the level of mRNA expression due to TSH treatment, there is an overall decrease in the levels of IGFBP-2, 4, and 6 in the conditioned media (CM) of SaOS2 cell cultures. The IGFBP proteases which control the availability of IGFs are also regulated by hormones. Pregnancy-Associated Plasma Protein-A (PAPP-A) is responsible for the proteolysis of IGFBP-4. TSH treatment significantly unregulated the expression of PAPP-A both at mRNA and protein levels. In conclusion, TSH promotes human osteoblastic (SaOS2) cell proliferation and differentiation by upregulating IGFs and their stimulatory IGF binding proteins and down regulating the inhibitory IGF binding proteins.
Subject(s)
Cell Differentiation/physiology , Cell Proliferation , Insulin-Like Growth Factor II/metabolism , Insulin-Like Growth Factor I/metabolism , Thyrotropin/metabolism , Alkaline Phosphatase/biosynthesis , Alkaline Phosphatase/genetics , Cell Differentiation/drug effects , Cell Line , Down-Regulation/drug effects , Down-Regulation/physiology , Female , Humans , Insulin-Like Growth Factor Binding Proteins/genetics , Insulin-Like Growth Factor Binding Proteins/metabolism , Insulin-Like Growth Factor I/genetics , Insulin-Like Growth Factor II/genetics , Osteoblasts , Pregnancy-Associated Plasma Protein-A/genetics , Pregnancy-Associated Plasma Protein-A/metabolism , Proteolysis/drug effects , RNA, Messenger/biosynthesis , RNA, Messenger/genetics , Thyrotropin/pharmacology , Time Factors , Up-Regulation/drug effects , Up-Regulation/physiologyABSTRACT
Environmental pollutants that disrupt endocrine system might also affect the modeling and remodeling of bone. Environmental factors, irrespective of age and sex contribute for the development of secondary osteoporosis. Polychlorinated biphenyls have adverse effects on various organs including bone. The present study was designed to investigate the effects of PCB (Aroclor 1254) on femur bone and the ameliorative role of vitamin C or E. In this regard, four groups of adult male albino rats were used as control, PCB (2mg/kgb.wt.), PCB+vitamin C (100mg/kgb.wt.) and PCB+vitamin E (50mg/kgb.wt.). The bone formation markers (ALP, Collagen), bone resorption marker (TRAP), antioxidant enzymes (SOD, GPX and GST) and lipid peroxidation in the femur were studied. Aroclor 1254 treatment decreased the ALP activity and collagen, but increased the TRAP activity and lipid peroxidation. While it decreased the SOD and GPX activity, GST was unaltered. Interestingly, simultaneous administration of vitamin C or E prevented the adverse effects of Aroclor 1254 in the femur. In conclusion, the present investigation suggests that Aroclor 1254 induced oxidative stress affects femoral bone metabolism. However, vitamin C or vitamin E protected the femur from the oxidative stress.