Impact of general anesthesia on postoperative complications in orthognathic surgery: a retrospective comparison of total intravenous anesthesia versus volatile anesthesia.

Orthognathic surgery has a high incidence of postoperative nausea (PON) and vomiting (POV), delaying mobility initiation and postoperative recovery. Bleeding is another risk associated with this surgical procedure. We aimed to compare total intravenous anesthesia (TIVA) and volatile anesthesia in patients undergoing orthognathic surgery in terms of postoperative nausea and vomiting (PONV) incidence and hemodynamic changes. This retrospective study included 82 patients who underwent bilateral sagittal split ramus osteotomies at Saga University Hospital between April 2016 and April 2021. We compared the effects of TIVA and volatile anesthesia on PONV onset after surgery, acute postoperative hemodynamic changes (blood pressure and heart rate), and factors contributing to PONV. PON was significantly lower in the TIVA group than in the volatile anesthesia group. The total dose of fentanyl contributed to the onset of POV, while the onset of PON was associated with low volumes of fluid infusion and urine in the TIVA and volatile anesthesia groups, respectively. Furthermore, post-extubation hemodynamic change was significantly smaller in the TIVA group than in the volatile anesthesia group. Therefore, TIVA could have a reduced risk of PONV and hemodynamic changes in patients undergoing orthognathic surgery. Employing TIVA could mitigate perioperative complications and enhance patient safety.

A novel role of helix-loop-helix transcriptional factor Bhlhe40 in osteoclast activation.

The basic helix-loop-helix transcriptional factor, Bhlhe40 has been shown as a crucial regulator of immune response, tumorigenesis, and circadian rhythms. We identified Bhlhe40 as a possible regulator of osteoclast differentiation and function by shRNA library screening and found that Bhlhe40 was required for osteoclast activation. Bhlhe40 expression was induced in bone marrow macrophages (BMMs) by RANKL, whereas the expression of its homolog Bhlhe41 was decreased in osteoclastogenesis. µCT analysis of tibias revealed that Bhlhe40 knockout (KO) mice exhibited increased bone volume phenotype. Bone morphometric analysis showed that osteoclast number and bone resorption were decreased in Bhlhe40 KO mice, whereas significant differences in the osteoblast parameters were not seen between wild-type (WT) and Bhlhe40 KO mice. In vitro culture of BMMs showed that Bhlhe40 deficiency did not cause difference in osteoclast formation. In contrast, bone resorption activity of Bhlhe40 KO osteoclasts was markedly reduced in comparison with that of WT osteoclasts. Analysis of potential target genes of Bhlhe40 using data-mining platform ChIP-Atlas (http://chip-atlas.org) revealed that predicted target genes of Bhlhe40 were related to proton transport and intracellular vesicle acidification. We then analyzed the expression of proton pump, the vacuolar (V)-ATPases which are responsible for bone resorption. The expression of V-ATPases V1c1 and V0a3 was suppressed in Bhlhe40 KO osteoclasts. In addition, Lysosensor yellow/blue DND 160 staining demonstrated that vesicular acidification was attenuated in vesicles of Bhlhe40 KO osteoclasts. Furthermore, analysis with pH-sensitive fluorescent probe showed that proton secretion was markedly suppressed in Bhlhe40 KO osteoclasts compared to that in WT osteoclasts. Our findings suggest that Bhlhe40 plays a novel important role in the regulation of acid production in osteoclastic bone resorption.

Leukemia/lymphoma-related factor (LRF) or osteoclast zinc finger protein (OCZF) overexpression promotes osteoclast survival by increasing Bcl-xl mRNA: A novel regulatory mechanism mediated by the RNA binding protein SAM68.

RANKL induces NFATc1, a key transcriptional factor to induce osteoclast-specific genes such as cathepsin K, whereas transcriptional control of osteoclast survival is not fully understood. Leukemia/lymphoma-related factor (LRF) in mouse and osteoclast zinc finger protein (OCZF) in rat are zinc finger and BTB domain-containing protein (zBTB) family of transcriptional regulators, and are critical regulators of hematopoiesis. We have previously shown that differentiation and survival were enhanced in osteoclasts from OCZF-Transgenic (Tg) mice. In the present study, we show a possible mechanism of osteoclast survival regulated by LRF/OCZF and the role of OCZF overexpression in pathological bone loss. In the in vitro cultures, LRF was highly colocalized with NFATc1 in cells of early stage in osteoclastogenesis, but only LRF expression persisted after differentiation into mature osteoclasts. LRF expression was further enhanced in resorbing osteoclasts formed on dentin slices. Osteoclast survival inhibitor such as alendronate, a bisphosphonate reduced LRF expression. Micro CT evaluation revealed that femurs of OCZF-Tg mice showed significantly lower bone volume compared to that of WT mice. Furthermore, OCZF overexpression markedly promoted bone loss in ovariectomy-induced osteolytic mouse model. The expression of anti-apoptotic Bcl-xl mRNA, which is formed by alternative splicing, was enhanced in the cultures in which osteoclasts are formed from OCZF-Tg mice. In contrast, the expression of pro-apoptotic Bcl-xs mRNA was lost in the culture derived from OCZF-Tg mice. We found that the expression levels of RNA binding splicing regulator, Src substrate associated in mitosis of 68 kDa (Sam68) protein were markedly decreased in OCZF-Tg mice-derived osteoclasts. In addition, shRNA-mediated knockdown of Sam68 expression increased the expression of Bcl-xl mRNA, suggesting that SAM68 regulates the expression of Bcl-xl. These results indicate that OCZF overexpression reduces protein levels of Sam68, thereby promotes osteoclast survival, and suggest that LRF/OCZF is a promising target for regulating pathological bone loss.

IgG immune complexes with Staphylococcus aureus protein A enhance osteoclast differentiation and bone resorption by stimulating Fc receptors and TLR2.

Staphylococcus aureus is a main pathogen of osteomyelitis and protein A is a virulence factor with high affinity for IgG. In this study, we investigated whether S. aureus affects the differentiation and bone resorption of osteoclasts through the IgG-binding capacity of protein A. Staphylococcus aureus pre-treated with serum or IgG showed marked enhancement in osteoclastogenesis and bone resorption compared to non-treated S. aureus or a protein A-deficient mutant. Blocking of the Fc receptor and deletion of the Fcγ receptor gene in osteoclast precursor cells showed that enhanced osteoclastogenesis stimulated by S. aureus IgG immune complexes (ICs) was mediated by the Fc receptor on osteoclast precursor cells. In addition, osteoclastogenesis stimulated by S. aureus ICs but not the protein A-deficient mutant was markedly reduced in osteoclast precursor cells of Myd88-knockout mice. Moreover, NFATc1, Syk and NF-κB signals were necessary for osteoclastogenesis stimulated by S. aureus ICs. The results suggest the contribution of a of Toll-like receptor 2 (TLR2)-Myd88 signal to the activity of S. aureus ICs. We further examined the expression of pro-inflammatory cytokines that is known to be enhanced by FcγR-TLR cross-talk. Osteoclasts induced by S. aureus ICs showed higher expression of TNF-α and IL-1ß, and marked stimulation of proton secretion of osteoclasts activated by pro-inflammatory cytokines. Finally, injection of S. aureus, but not the protein A-deficient mutant, exacerbated bone loss in implantation and intra-peritoneal administration mouse models. Our results provide a novel mechanistic aspect of bone loss induced by S. aureus in which ICs and both Fc receptors and TLR pathways are involved.

Deficiency of stress-associated gene Nupr1 increases bone volume by attenuating differentiation of osteoclasts and enhancing differentiation of osteoblasts.

Nuclear protein 1 (NUPR1) is a multifunctional stress-induced protein involved in regulating tumorigenesis, apoptosis, and autophagy. Bone homeostasis is maintained by bone-resorbing osteoclasts and bone-forming osteoblasts and osteocytes. We aimed to determine the role of NUPR1 in bone metabolism. Using microcomputed tomography, we found that mice lacking Nupr1 exhibited increased bone volume. Histologic analysis showed that Nupr1 deficiency decreased osteoclast numbers but increased osteoblast numbers and osteoid formation. In vitro culture of bone marrow macrophages showed that receptor activator of NF-κB ligand-induced osteoclastogenesis was down-regulated in Nupr1-deficient mice. In contrast, primary osteoblasts from Nupr1-deficient mice revealed that proliferation of osteoblasts and expression of bone matrix proteins were markedly enhanced. In addition, expression of autophagy-related genes, formation of autophagosomes, and cell survival were up-regulated in Nupr1-deficient osteoblasts. In contract, deletion of Nupr1 reduced the formation of osteocyte cellular projection, which is an indicator of mature osteocytes. Importantly, we found that the expression of sclerostin (Sost), an inhibitor of bone formation, was down-regulated in the osteoblasts and osteocytes of Nupr1-deficient mice. Conversely, Nupr1 overexpression enhanced Sost expression in primary osteoblasts. Collectively, these results indicate that Nupr1 deficiency increases bone volume by attenuating production of Sost and osteoclastogenesis and enhancing differentiation of osteoblasts.-Shiraki, M., Xu, X., Iovanna, J. L., Kukita, T., Hirata, H., Kamohara, A., Kubota, Y., Miyamoto, H., Mawatari, M., Kukita, A. Deficiency of stress-associated gene Nupr1 increases bone volume by attenuating differentiation of osteoclasts and enhancing differentiation of osteoblasts.

Prostate transmembrane protein androgen induced 1 is induced by activation of osteoclasts and regulates bone resorption.

Osteoclasts derived from hematopoietic cells are activated on bone surface. To resorb bone, osteoclasts release acid and lysosome acid hydrolase via membrane transport. Prostate transmembrane protein androgen induced 1 (Pmepa1) is a type I transmembrane protein that regulates proliferation, migration, and metastasis of cancer cells. Because recent reports showed that Pmepa1 is involved in membrane transport in cancer cells, we investigated the role of Pmepa1 in osteoclast function. Pmepa1 expression was barely detected in osteoclasts formed on plastic surfaces in vitro, but was markedly increased in activated osteoclasts formed on calcified matrix. Inhibitors of bone resorption, such as alendronate, bafilomycin A1, and the PI3K inhibitor LY294002, suppressed the expression of Pmepa1 in osteoclasts. Knockdown of Pmepa1 expression impaired bone resorption activity and inhibited formation of a ring-like, actin-rich podosome belt that is essential for osteoclast function. Pmepa1 protein localized to lysosomes in osteoclasts. In addition, in sites of bone destruction observed in rats with adjuvant-induced arthritis, a marked high level of Pmepa1 expression was associated with the osteoclasts' resorbing bone. Our results suggest that Pmepa1 is a critical regulator of bone resorption and is a promising marker for activated osteoclasts and a potential therapeutic target in pathologic bone destruction.-Xu, X., Hirata, H., Shiraki, M., Kamohara, A., Nishioka, K., Miyamoto, H., Kukita, T., Kukita, A. Prostate transmembrane protein androgen induced 1 is induced by activation of osteoclasts and regulates bone resorption.