Abstract
Heme-oxygenase-1 (HO-1), an important enzyme involved in vascular disease, transplantation, and inflammation, catalyzes the degradation of heme into carbon monoxide and biliverdin. It has been reported that overexpression of HO-1 inhibits osteoclastogenesis. However, the effect of HO-1 on osteoblast differentiation is still not clear. We here used adenoviral vector expressing recombinant human HO-1 and HO-1 inducer hemin to study the effects of HO-1 in primary cultured osteoblasts. The results showed that induction of HO-1 inhibited the maturation of osteoblasts including mineralized bone nodule formation, alkaline phosphatase activity and decreased mRNA expression of several differentiation markers such as alkaline phosphatase, osteocalcin, and RUNX2. Furthermore, downstream products of HO-1, bilirubin, carbon monoxide, and iron, are involved in the inhibitory action of HO-1. HO-1 can be induced by H(2)O(2), lipopolysaccharide and inflammatory cytokines such as TNF-alpha and IL-1beta in osteoblasts and also in STZ-induced diabetic mice. In addition, endogenous PPARgamma ligand, 15-deoxy-Delta(12,14)-prostaglandin-J2 (15d-PGJ2) markedly increased both mRNA and protein levels of HO-1 in osteoblasts via PI3K-Akt and MAPK pathways. Blockade of HO activity by ZnPP IX antagonized the inhibitory action on osteocalcin expression by hemin and 15d-PGJ2. Our results indicate that upregulation of HO-1 inhibits the maturation of osteoblasts and HO-1 may be involved in oxidative- or inflammation-induced bone loss.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Alkaline Phosphatase / metabolism
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Animals
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Bilirubin / metabolism
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Calcification, Physiologic* / drug effects
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Calcification, Physiologic* / genetics
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Carbon Dioxide / metabolism
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Cell Differentiation* / drug effects
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Cell Differentiation* / genetics
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Cells, Cultured
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Core Binding Factor Alpha 1 Subunit / metabolism
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Cytokines / metabolism
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Diabetes Mellitus, Experimental / enzymology
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Heme Oxygenase (Decyclizing) / metabolism
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Heme Oxygenase-1 / genetics
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Heme Oxygenase-1 / metabolism*
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Hemin / pharmacology
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Humans
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Hydrogen Peroxide / pharmacology
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Inflammation Mediators / metabolism
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Iron / metabolism
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Lipopolysaccharides / pharmacology
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Male
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Membrane Proteins / metabolism
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Mice
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Mice, Inbred ICR
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Mitogen-Activated Protein Kinases / metabolism
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Organometallic Compounds / pharmacology
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Osteoblasts / drug effects
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Osteoblasts / enzymology*
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Osteocalcin / metabolism
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Oxidative Stress
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Phosphatidylinositol 3-Kinases / metabolism
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Prostaglandin D2 / analogs & derivatives
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Prostaglandin D2 / metabolism
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Proto-Oncogene Proteins c-akt / metabolism
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RNA, Messenger / metabolism
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Rats
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Rats, Sprague-Dawley
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Signal Transduction
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Time Factors
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Transduction, Genetic
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Up-Regulation
Substances
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15-deoxyprostaglandin J2
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Core Binding Factor Alpha 1 Subunit
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Cytokines
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Inflammation Mediators
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Lipopolysaccharides
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Membrane Proteins
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Organometallic Compounds
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RNA, Messenger
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Runx2 protein, rat
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tricarbonyldichlororuthenium (II) dimer
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Osteocalcin
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Carbon Dioxide
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Hemin
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Hydrogen Peroxide
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Iron
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HMOX1 protein, human
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Heme Oxygenase (Decyclizing)
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Heme Oxygenase-1
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Hmox1 protein, mouse
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Hmox1 protein, rat
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Phosphatidylinositol 3-Kinases
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Proto-Oncogene Proteins c-akt
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Mitogen-Activated Protein Kinases
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Alkaline Phosphatase
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Bilirubin
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Prostaglandin D2