Expression of nephronectin is inhibited by oncostatin M via both JAK/STAT and MAPK pathways

AbstractNephronectin (Npnt), also called POEM, is an extracellular matrix protein considered to play critical roles as an adhesion molecule in the development and functions of various tissues, such as the kidneys, liver, and bones. In the present study, we examined the molecular mechanism of Npnt gene expression and found that oncostatin M (OSM) strongly inhibited Npnt mRNA expression in MC3T3-E1 cells from a mouse osteoblastic cell line. OSM also induced a decrease in Npnt expression in both time- and dose-dependent manners via both the JAK/STAT and MAPK pathways. In addition, OSM-induced inhibition of osteoblast differentiation was recovered by over-expression of Npnt. These results suggest that OSM inhibits Npnt expression via the JAK/STAT and MAPK pathways, while down-regulation of Npnt by OSM influences inhibition of osteoblast differentiation

Shared and Distinct Functions of the Transcription Factors IRF4 and IRF8 in Myeloid Cell Development

Interferon regulatory factor (IRF) 8 and IRF4 are structurally-related, hematopoietic cell-specific transcription factors that cooperatively regulate the differentiation of dendritic cells and B cells. Whilst in myeloid cells IRF8 is known to modulate growth and differentiation, the role of IRF4 is poorly understood. In this study, we show that IRF4 has activities similar to IRF8 in regulating myeloid cell development. The ectopic expression of IRF4 in myeloid progenitor cells in vitro inhibits cell growth, promotes macrophages, but hinders granulocytic cell differentiation. We also show that IRF4 binds to and activates transcription through the IRF-Ets composite sequence (IECS). Furthermore, we demonstrate that Irf8-/-Irf4-/- mice exhibit a more severe chronic myeloid leukemia (CML)-like disease than Irf8-/- mice, involving a disproportionate expansion of granulocytes at the expense of monocytes/macrophages. Irf4-/- mice, however, display no obvious abnormality in myeloid cell development, presumably because IRF4 is expressed at a much lower level than IRF8 in granulocyte-macrophage progenitors. Our results also suggest that IRF8 and IRF4 have not only common but also specific activities in myeloid cells. Since the expression of both the IRF8 and IRF4 genes is downregulated in CML patients, these results may add to our understanding of CML pathogenesis

Lysine-specific gingipain promotes lipopolysaccharide- and active-vitamin D_{3}-induced osteoclast differentiation by degrading osteoprotegerin

Porphyromonas gingivalis is one of the major pathogens of periodontitis, a condition characterized by excessive alveolar bone resorption by osteoclasts. The bacterium produces cysteine proteases called gingipains, which are classified according to their cleavage-site specificity into lysine-specific (Kgp) and arginine-specific gingipains (Rgps). In this study, we examined the effects of gingipains on osteoclast differentiation. In co-cultures of mouse bone marrow cells and osteoblasts, formation of multinucleated osteoclasts induced by 1α,25-dihydroxyvitamin D(3) [1α,25(OH)(2)D(3)] was augmented by Kgp but not by RgpB. A physiological concentration (0.1 nM) of 1α,25(OH)(2)D(3) induced the osteoclast formation in the presence of 100 nM Kgp to the extent comparable to that induced by 10 nM 1α,25(OH)(2)D(3). Kgp also enhanced osteoclastogenesis induced by various microbial components including lipopolysaccharide. Combined use of Kgp and 1α,25(OH)(2)D(3) or lipopolysaccharide also increased the number of resorption pits developed on dentin slices, indicating the osteoclasts formed in the presence of Kgp possess bone-resorbing activity. The enhanced osteoclastogenesis by Kgp was correlated with a depletion of osteoprotegerin in co-culture media and proteolytic activity-dependent, since benzyloxycarbonyl-phenylalanyl-lysyl-acycloxyketone, an inhibitor of Kgp, completely abolished osteoclastogenesis induced by Kgp. Kgp digested osteoprotegerin, since its recombinant protein was susceptible to degradation by Kgp in the presence of serum. As a result, Kgp did not augment osteoclastogenesis in co-cultures of osteoprotegerin-deficient osteoblasts and bone marrow cells. In addition, enhanced osteoclastogenesis by Kgp was abolished by excess amount of recombinant osteoprotegerin. These findings suggest that degradation of osteoprotegerin is one of the mechanisms underlying promotion of osteoclastogenesis by Kgp

Lactate-induced histone lactylation by p300 promotes osteoblast differentiation.

Lactate, which is synthesized as an end product by lactate dehydrogenase A (LDHA) from pyruvate during anaerobic glycolysis, has attracted attention for its energy metabolism and oxidant effects. A novel histone modification-mediated gene regulation mechanism termed lactylation by lactate was recently discovered. The present study examined the involvement of histone lactylation in undifferentiated cells that underwent differentiation into osteoblasts. C2C12 cells cultured in medium with a high glucose content (4500 mg/L) showed increases in marker genes (Runx2, Sp7, Tnap) indicating BMP-2-induced osteoblast differentiation and ALP staining activity, as well as histone lactylation as compared to those cultured in medium with a low glucose content (900 mg/L). Furthermore, C2C12 cells stimulated with the LDH inhibitor oxamate had reduced levels of BMP-2-induced osteoblast differentiation and histone lactylation, while addition of lactate to C2C12 cells cultured in low glucose medium resulted in partial restoration of osteoblast differentiation and histone lactylation. These results indicate that lactate synthesized by LDHA during glucose metabolism is important for osteoblast differentiation of C2C12 cells induced by BMP-2. Additionally, silencing of p300, a possible modifier of histone lactylation, also inhibited osteoblast differentiation and reduced histone lactylation. Together, these findings suggest a role of histone lactylation in promotion of undifferentiated cells to undergo differentiation into osteoblasts

Association of aging with gene expression profiling in mouse submandibular glands

Aging, also called senescence, is thought to be a physiological phenomenon that commonly occurs in various organs and tissues (Enoki et al., 2007 [1]). Many older adults experience dysfunction in their salivary glands, for example xerostomia, which is defined as dry mouth resulting from reduced or absent saliva flow (Nagler et al., 2004 [2]). In the present study, we investigated gene expression in submandibular glands of young (8 weeks old) and adult (50 weeks old) mice to analyze association of aging with gene expression profiling in mouse submandibular glands. Whole-genome gene expression profiles were analyzed using an Illumina Sentrix system with Mouse-WG-6 v.2 Expression BeadChips (Illumina). Of the genes screened, 284 showed detection values at a significance level of P < 0.01. Among those, the expression of 94 genes (33%) showed a greater decrease in adult mice as compared to young mice. On the other hand, that of 190 genes (77%) was increased in the adults more than in young mice. The data obtained in this study are publicly available in the Gene Expression Omnibus (GEO) database (accession number GSE66857)