Effects of Remifentanil Preconditioning on Osteoblasts under Hypoxia-Reoxygenation Condition

Hypoxia inducible factor-1α related mechanism and TCM intervention in process of early fracture healing

As a common clinical disease, fracture is often accompanied by pain, swelling, bleeding as well as other symptoms and has a high disability rate, even threatening life, seriously endangering patients' physical and psychological health and quality of life. Medical practitioners take many strategies for the treatment of fracture healing, including Traditional Chinese Medicine (TCM). In the early stage of fracture healing, the local fracture is often in a state of hypoxia, accompanied by the expression of hypoxia inducible factor-1α (HIF-1α), which is beneficial to wound healing. Through literature mining, we thought that hypoxia, HIF-1α and downstream factors affected the mechanism of fracture healing, as well as dominated this process. Therefore, we reviewed the local characteristics and related signaling pathways involved in the fracture healing process and summarized the intervention of TCM on these mechanisms, in order to inspirit the new strategy for fracture healing, as well as elaborate on the possible principles of TCM in treating fractures based on the HIF molecular mechanism.

Targeting the opioid remifentanil: Protective effects and molecular mechanisms against organ ischemia-reperfusion injury

Opioids are widely used in clinical practice by activating opioid receptors (OPRs), but their clinical application is limited by a series of side effects. Researchers have been making tremendous efforts to promote the development and application of opioids. Fortunately, recent studies have identified the additional effects of opioids in addition to anesthesia and analgesia, particularly in terms of organ protection against ischemia-reperfusion (I/R) injury, with unique advantages. I/R injury in vital organs not only leads to cell dysfunction and structural damage but also induces acute and chronic organ failure, even death. Early prevention and appropriate therapeutic targets for I/R injury are crucial for organ protection. Opioids have shown cardioprotective effects for over 20 years, especially remifentanil, a derivative of fentanyl, which is a new ultra-short-acting opioid analgesic widely used in clinical anesthesia induction and maintenance. In this review, we provide current knowledge about the physiological effects related to OPR-mediated organ protection, focusing on the protective effect and mechanism of remifentanil on I/R injury in the heart and other vital organs. Herein, we also explored the potential application of remifentanil in clinical I/R injury. These findings provide a theoretical basis for the use of remifentanil to inhibit or alleviate organ I/R injury during the perioperative period and provide insights for opioid-induced human organ protection and drug development.

Remifentanil repairs cartilage damage and reduces the degradation of cartilage matrix in post-traumatic osteoarthritis, and inhibits IL-1β-induced apoptosis of articular chondrocytes via inhibition of PI3K/AKT/NF-κB phosphorylation

Background

Remifentanil (RFT) is an opioid analgesic with a unique pharmacokinetic profile, and plays an important role in the intra- and post-operative periods. Post-traumatic osteoarthritis (PTO) is a particular type of osteoarthritis (OA) that occurs secondary to a traumatic injury. In the present study, we investigated the effects of RFT both in vivo and in vitro.

Methods

In vivo, 50 Sprague Dawley (SD) rats (7 weeks old) were randomly divided into five groups. Four groups of rats received RFT (0.2, 0.5, and 1 µg) or vehicle (PTO group), while the remaining group served as the control. A PTO model in rats was established using the Hulth method. The cartilage damage, articular cartilage formation, and the degradation of cartilage matrix were evaluated. The effects of RFT on cell proliferation, apoptosis, and nuclear factor (NF)-κB phosphorylation were also examined.

Results

The results indicated that RFT improved cartilage damage, enhanced articular cartilage formation, and inhibited the degradation of cartilage matrix in PTO model rats. Compared with the control group, the protein levels of Osterix (OSX), Collagen type I alpha 1 (COL1A1), and osteocalcin (OC) were down-regulated in PTO model rats. RFT also inhibited the interleukin-1β (IL-1β)-induced apoptosis of chondrocytes in vitro. Furthermore, the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/NF-κB pathway was inhibited both in vitro and in vitro.

Conclusions

RFT has significant potential as a therapeutic intervention to ameliorate PTO and provides a foundation for further clinical studies.

The Effect of Opiates on Bone Formation and Bone Healing

PURPOSE OF REVIEW

Opioids have been shown to be associated with an increased risk of fracture. The purpose of this paper is to review recent research into the effects of opioids on bone formation and bone healing in animal models and in human studies.

RECENT FINDINGS

Most opioids, such as morphine and fentanyl, negatively affected bone remodeling and bone healing in animal models. Conversely, remifentanil has been recently shown to promote in vitro osteoblast differentiation and to inhibit differentiation and maturation of osteoclasts, therefore reducing bone resorption. According to the possible negative role of opioids in bone healing, opioid antagonists have been shown to enhance bone mineralization, suggesting a possible therapeutic role in the future for osteoporosis. Other neuropeptides, such as the vasoactive intestinal peptide (VIP) and the neuropeptide Y (NPY), have been proved to promote osteogenesis. The increased risk of fractures among opioid users may be related to their central nervous system side effects or to the reduced bone density, partly due to their endocrine effects, and partly to their direct activity on bone cells. Clinical data strongly suggested a potential negative effect of opioids in bone healing. The risk of nonunion fracture is significantly increased in opioid users, and bone mass density was reduced in patients under long-term opioid treatment. The direct effects of opioids on bone remodeling appears evident from these reports. Not all opioids have the same potential for negatively impacting bone healing. Opioid antagonists may increase bone density and could represent a possible future treatment for low bone mass density pathologies. However, further trials are warranted to clarify the clinical relevance of these emerging findings from animal studies.

Hyperglycemia-Induced Oxidative Stress Abrogates Remifentanil Preconditioning-Mediated Cardioprotection in Diabetic Rats by Impairing Caveolin-3-Modulated PI3K/Akt and JAK2/STAT3 Signaling

Diabetic hearts are more vulnerable to ischemia/reperfusion (I/R) injury and less responsive to remifentanil preconditioning (RPC), but the underlying mechanisms are incompletely understood. Caveolin-3 (Cav-3), the dominant isoform of cardiomyocyte caveolae, is reduced in diabetic hearts in which oxidative stress is increased. This study determined whether the compromised RPC in diabetes was an independent manifestation of hyperglycemia-induced oxidative stress or linked to impaired Cav-3 expression with associated signaling abnormality. RPC significantly attenuated postischemic infarction, cardiac dysfunction, myocardial apoptosis, and 15-F2t-isoprostane production (a specific marker of oxidative stress), accompanied with increased Cav-3 expression and enhanced Akt and STAT3 activation in control but not in diabetic rats. Pretreatment with the antioxidant N-acetylcysteine (NAC) attenuated hyperglycemia-induced reduction of Cav-3 expression and Akt and STAT3 activation and restored RPC-mediated cardioprotection in diabetes, which was abolished by cardiac-specific knockdown of Cav-3 by AAV9-shRNA-Cav-3, PI3K/Akt inhibitor wortmannin, or JAK2/STAT3 inhibitor AG490, respectively. Similarly, NAC could restore RPC protection from high glucose and hypoxia/reoxygenation-induced injury evidenced by decreased levels of LDH release, 15-F2t-isoprostane, O₂ ^-, and JC-1 monomeric cells, which were reversed by caveolae disrupter methyl-β-cyclodextrin, wortmannin, or AG490 in isolated primary cardiomyocytes or siRNAs of Cav-3, Akt, or STAT3 in H9C2 cells. Either methyl-β-cyclodextrin or Cav-3 knockdown reduced Akt and STAT3 activation. Further, the inhibition of Akt activation by a selective inhibitor or siRNA reduced STAT3 activation and vice versa, but they had no effects on Cav-3 expression. Thus, hyperglycemia-induced oxidative stress abrogates RPC cardioprotection by impairing Cav-3-modulated PI3K/Akt and JAK2/STAT3 signaling. Antioxidant treatment with NAC could restore RPC-induced cardioprotection in diabetes by improving Cav-3-dependent Akt and STAT3 activation and by facilitating the cross talk between PI3K/Akt and JAK2/STAT3 signaling pathways.

Remifentanil promotes osteoblastogenesis by upregulating Runx2/osterix expression in preosteoblastic C2C12 cells

Background

The imbalance between osteoblasts and osteoclasts can lead to pathological conditions such as osteoporosis. It has been reported that opioid adversely affect the skeletal system, but it is inconsistent. Remifentanil is currently used as an adjuvant analgesic drug in general anesthesia and sedation. The aim of the present study was to investigate the effect of remifentanil on the osteoblast differentiation and mechanism involved in this effect.

Methods

The C2C12 cells (mouse pluripotent mesenchymal cell line) were used as preosteoblast. Osteoblastic differentiation potency was determined by alkaline phosphatase (ALP) staining. C2C12 cell migration by remifentanil was evaluated using Boyden chamber migration assay. The expression of Runx2 and osterix was evaluated by RT-PCT and western blot analysis to investigate the mechanism involved in remifentanil-mediated osteoblast differentiation.

Results

ALP staining showed that remifentanil increased significantly osteoblast differentiation. In Boyden chamber migration assay, C2C12 cell migration was increased by remifentanil. RT-PCR and western blot analysis showed that the expression of Runx2 and osterix was upregulated by remifentanil.

Conclusions

We demonstrated that remifentanil increased osteoblast differentiation in vitro by upregulation of Runx2 and osterix expression. Therefore, remifentanil has the potential for assisting with bone formation and bone healing.

Remifentanil Negatively Regulates RANKL-Induced Osteoclast Differentiation and Bone Resorption by Inhibiting c-Fos/NFATc1 Expression

Remifentanil is commonly used in operating rooms and intensive care units for the purpose of anesthesia and sedation or analgesia. Although remifentanil may significantly affect the bone regeneration process in patients, there have been few studies to date on the effects of remifentanil on bone physiology. The purpose of this study was to investigate the effects of remifentanil on osteoclast differentiation and bone resorption. Bone marrow-derived macrophages (BMMs) were cultured for 4 days in remifentanil concentrations ranging from 0 to 100 ng/ml, macrophage colony-stimulating factor (M-CSF) alone, or in osteoclastogenic medium to induce the production of mature osteoclasts. To determine the degree of osteoclast maturity, tartrate-resistant acid phosphatase (TRAP) staining was performed. RT-PCR and western blotting analyses were used to determine the effect of remifentanil on the signaling pathways involved in osteoclast differentiation and maturation. Bone resorption and migration of BMMs were analyzed to determine the osteoclastic activity. Remifentanil reduced the number and size of osteoclasts and the formation of TRAP-positive multinuclear osteoclasts in a dose-dependent manner. Expression of c-Fos and NFATC1 was most strongly decreased in the presence of RANKL and remifentanil, and the activity of ERK was also inhibited by remifentanil. In the bone resorption assay, remifentanil reduced bone resorption and did not significantly affect cell migration. This study shows that remifentanil inhibits the differentiation and maturation of osteoclasts and reduces bone resorption.

Effect of remifentanil on pre-osteoclast cell differentiation in vitro

BACKGROUND

The structure and function of bone tissue is maintained through a constant remodeling process, which is maintained by the balance between osteoblasts and osteoclasts. The failure of bone remodeling can lead to pathological conditions of bone structure and function. Remifentanil is currently used as a narcotic analgesic agent in general anesthesia and sedation. However, the effect of remifentanil on osteoclasts has not been studied. Therefore, we investigated the effect of remifentanil on pre-osteoclast (pre-OCs) differentiation and the mechanism of osteoclast differentiation in the absence of specific stimulus.

METHODS

Pre-OCs were obtained by culturing bone marrow-derived macrophages (BMMs) in osteoclastogenic medium for 2 days and then treated with various concentration of remifentanil. The mRNA expression of NFATc1 and c-fos was examined by using real-time PCR. We also examined the effect of remifentanil on the osteoclast-specific genes TRAP, cathepsin K, calcitonin receptor, and DC-STAMP. Finally, we examined the influence of remifentanil on the migration of pre-OCs by using the Boyden chamber assay.

RESULTS

Remifentanil increased pre-OC differentiation and osteoclast size, but did not affect the mRNA expression of NFATc1 and c-fos or significantly affect the expression of TRAP, cathepsin K, calcitonin receptor, and DC-STAMP. However, remifentanil increased the migration of pre-OCs.

CONCLUSIONS

This study suggested that remifentanil promotes the differentiation of pre-OCs and induces maturation, such as increasing osteoclast size. In addition, the increase in osteoclast size was mediated by the enhancement of pre-OC migration and cell fusion.

Effects of remote ischemic post‑conditioning on fracture healing in rats

Remote ischemic post‑conditioning (RIPC) is an established method to activate the hypoxia‑inducible factor‑1α (HIF‑1α) pathway, which is involved in the impairment of fracture healing. However, the role of RIPC in fracture healing remains to be fully elucidated. In the present study, rats received fractures and were divided into two groups: Control and RIPC, in which hind limb occlusion was performed. Rats were sacrificed at 7, 14, 28 and 42 days subsequent to tibial fracture. Micro‑computed tomography was performed to measure healing of the bone tissue and biomechanical testing was used to test mechanical strength. In addition, the effects of hind limb occlusion on the expression of two primary angiogenic mediators, HIF‑1α and vascular endothelial growth factor (VEGF), as well as the osteoblast markers runt‑related transcription factor 2 (Runx2), alkaline phosphatase (ALP) and osteocalcin (OCN), were determined at the mRNA and protein levels by reverse transcription‑quantitative polymerase chain reaction, western blot analysis and immunohistochemistry. Systemic administration of hind limb occlusion (3 cycles/day, with each occlusion or release phase lasting 10 min) significantly promoted fracture healing and mechanical strength. The present study demonstrated that in rats treated with hind limb occlusion, the expression of HIF‑1α, VEGF, Runx2, ALP and OCN was significantly increased at the mRNA and protein levels, and that RIPC enhances fracture repair in vivo.

Endogenous Opiates and Behavior: 2015

This paper is the thirty-eighth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2015 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.

Protective effects of remifentanil against H2O2-induced oxidative stress in human osteoblasts

BACKGROUND

Bone injury is common in many clinical situations, such as surgery or trauma. During surgery, excessive reactive oxygen species (ROS) production decreases the quality and quantity of osteoblasts. Remifentanil decreases ROS production, reducing oxidative stress and the inflammatory response. We investigated remifentanil's protective effects against H₂O₂-induced oxidative stress in osteoblasts.

METHODS

To investigate the effect of remifentanil on human fetal osteoblast (hFOB) cells, the cells were incubated with 1 ng/ml of remifentanil for 2 h before exposure to H₂O₂. For induction of oxidative stress, hFOB cells were then treated with 200 µM H₂O₂ for 2 h. To evaluate the effect on autophagy, a separate group of cells were incubated with 1 mM 3-methyladenine (3-MA) before treatment with remifentanil and H₂O₂. Cell viability and apoptotic cell death were determined via MTT assay and Hoechst staining, respectively. Mineralized matrix formation was visualized using alizarin red S staining. Western blot analysis was used to determine the expression levels of bone-related genes.

RESULTS

Cell viability and mineralized matrix formation increased on remifentanil pretreatment before exposure to H₂O₂-induced oxidative stress. As determined via western blot analysis, remifentanil pretreatment increased the expression of bone-related genes (Col I, BMP-2, osterix, and TGF-β). However , pretreatment with 3-MA before exposure to remifentanil and H₂O₂ inhibited remifentanil's protective effects on hFOB cells during oxidative stress.

CONCLUSIONS

We showed that remifentanil prevents oxidative damage in hFOB cells via a mechanism that may be highly related to autophagy. Further clinical studies are required to investigate its potential as a therapeutic agent.