T3 Regulates a Human Macrophage-Derived TSH-β Splice Variant: Implications for Human Bone Biology.
TSH and thyroid hormones (T3 and T4) are intimately involved in bone biology. We have previously reported the presence of a murine TSH-β splice variant (TSH-βv) expressed specifically in bone marrow-derived macrophages and that exerted an osteoprotective effect by inducing osteoblastogenesis. To extend this observation and its relevance to human bone biology, we set out to identify and characterize a TSH-β variant in human macrophages. Real-time PCR analyses using human TSH-β-specific primers identified a 364-bp product in macrophages, bone marrow, and peripheral blood mononuclear cells that was sequence verified and was homologous to a human TSH-βv previously reported. We then examined TSH-βv regulation using the THP-1 human monocyte cell line matured into macrophages. After 4 days, 46.1% of the THP-1 cells expressed the macrophage markers CD-14 and macrophage colony-stimulating factor and exhibited typical morphological characteristics of macrophages. Real-time PCR analyses of these cells treated in a dose-dependent manner with T3 showed a 14-fold induction of human TSH-βv mRNA and variant protein. Furthermore, these human TSH-βv-positive cells, induced by T3 exposure, had categorized into both M1 and M2 macrophage phenotypes as evidenced by the expression of macrophage colony-stimulating factor for M1 and CCL-22 for M2. These data indicate that in hyperthyroidism, bone marrow resident macrophages have the potential to exert enhanced osteoprotective effects by oversecreting human TSH-βv, which may exert its local osteoprotective role via osteoblast and osteoclast TSH receptors.
Thyroid Research Unit (R.B., R.L., S.A.M., T.F.D.) and Mt Sinai Bone Program (R.B., R.L., M.Z., T.F.D.), Icahn School of Medicine at Mt Sinai, Mt Sinai Beth Israel Medical Center, New York, New York 10029; and James J. Peters Veterans Affairs Medical Center, New York, New York 10468.
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Baliram
Thyroid Research Unit (R.B., R.L., S.A.M., T.F.D.) and Mt Sinai Bone Program (R.B., R.L., M.Z., T.F.D.), Icahn School of Medicine at Mt Sinai, Mt Sinai Beth Israel Medical Center, New York, New York 10029; and James J. Peters Veterans Affairs Medical Center, New York, New York 10468.
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Latif
Thyroid Research Unit (R.B., R.L., S.A.M., T.F.D.) and Mt Sinai Bone Program (R.B., R.L., M.Z., T.F.D.), Icahn School of Medicine at Mt Sinai, Mt Sinai Beth Israel Medical Center, New York, New York 10029; and James J. Peters Veterans Affairs Medical Center, New York, New York 10468.
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Morshed
Thyroid Research Unit (R.B., R.L., S.A.M., T.F.D.) and Mt Sinai Bone Program (R.B., R.L., M.Z., T.F.D.), Icahn School of Medicine at Mt Sinai, Mt Sinai Beth Israel Medical Center, New York, New York 10029; and James J. Peters Veterans Affairs Medical Center, New York, New York 10468.
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Zaidi
Thyroid Research Unit (R.B., R.L., S.A.M., T.F.D.) and Mt Sinai Bone Program (R.B., R.L., M.Z., T.F.D.), Icahn School of Medicine at Mt Sinai, Mt Sinai Beth Israel Medical Center, New York, New York 10029; and James J. Peters Veterans Affairs Medical Center, New York, New York 10468.
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TF
Davies
D000818:Animals; D001842:Bone and Bones / Q000378:metabolism*; D016466:CHO Cells; D002460:Cell Line; D003412:Cricetulus; D006801:Humans; D008264:Macrophages / Q000378:metabolism*; D008297:Male; D008810:Mice, Inbred C57BL; D020033:Protein Isoforms; D037322:Thyrotropin, beta Subunit / Q000378:metabolism*; D014284:Triiodothyronine / Q000378:metabolism*
D020033:Protein Isoforms; D037322:Thyrotropin, beta Subunit; D014284:Triiodothyronine