The neuroprotective effects of isoflurane preconditioning in a murine transient global cerebral ischemia-reperfusion model: the role of the Notch signaling pathway.

Inhalational anesthetic preconditioning can induce neuroprotective effects, and the notch signaling pathway plays an important role in neural progenitor cell differentiation and the inflammatory response after central nervous system injury. This study evaluated whether the neuroprotective effect of isoflurane preconditioning is mediated by the activation of the notch signaling pathway. Mice were divided into two groups consisting of those that did or did not receive preconditioning with isoflurane. The expression levels of notch-1, notch intracellular domain (NICD), and hairy and enhancer of split (HES-1) were measured in mice subjected to transient global cerebral ischemia-reperfusion injury. The notch signaling inhibitor DAPT and conditional notch-RBP-J knockout mice were used to investigate the mechanisms of isoflurane preconditioning-induced neuroprotection. Immunohistochemical staining, real-time polymerase chain reaction assays, and Western blotting were performed. Isoflurane preconditioning induced neuroprotection against global cerebral ischemia. Preconditioning up-regulated the expression of notch-1, HES-1, and NICD after ischemic-reperfusion. However, these molecules were down-regulated at 72 h after ischemic-reperfusion. The inhibition of notch signaling activity by DAPT significantly attenuated the isoflurane preconditioning-induced neuroprotection, and similar results were obtained using notch knockout mice. Our results demonstrate that the neuroprotective effects of isoflurane preconditioning are mediated by the pre-activation of the notch signaling pathway.

Estrogen and its receptor enhance mechanobiological effects in compressed bone mesenchymal stem cells.

Mechanical stimulation and estrogen have been proven to be two important factors in promoting mesenchymal stem cell activity, which is closely associated with bone formation, mass maintenance and remodeling. However, the superposition effects of mechanical stimulation and estrogen on stem cells remain unknown. It is also unclear if the estrogen receptor (ER) plays only a key role in estrogen signaling or if it is also involved in the mechanotransduction of stem cells. To investigate the role of estrogen and its receptors in the mechanobiological effects in bone mesenchymal stem cells (BMSCs), isolated mesenchymal stem cells from bone marrow were exposed to mechanical pressure under additional estrogen treatment or ER blockade. Cell proliferation was examined using an MTT assay and alkaline phosphatase (ALP) activity was determined by a modified enzyme kinetic method. Alignment of the cytoskeleton was observed by Coomassie brilliant blue staining and F-actin fluorescent staining. Cellular ultrastructure was observed under transmission electron microscope. Expression of ERα was investigated using Western blot analysis. Results indicated that mechanical pressure promoted cell proliferation, ALP activity, ERα expression and F-actin stress fiber formation. Overall, this effect was enhanced by the addition of estrogen and inhibited by ER blockade. We concluded that pressure stimulated proliferation and differentiation capability via F-actin transduction in BMSCs. The effects were enhanced by the addition of estrogen, and the ER plays an important role in regulating mechanobiological effects and the mechanotransduction processes of BMSCs.

Effect of mechanical pressure on the thickness and collagen synthesis of mandibular cartilage and the contributions of G proteins.

To investigate the role of mechanical pressure on cartilage thickness and type II collagen synthesis, and the role of G protein in that process, in vitro organ culture of mandibular cartilage was adopted in this study. A hydraulic pressure-controlled cellular strain unit was used to apply hydrostatic pressurization to explant cultures. The explants were compressed by different pressure values (0 kPa, 100 kPa, and 300 kPa) after pretreatment with or without a selective and direct antagonist (NF023) for the G proteins. After 4, 8 and 12 h of cell culture under each pressure condition, histological sections of the explants were stained with hematoxylin-eosin to investigate the thickness of the cartilage. Immunohistochemical staining was used to observe type II collagen expressions. The results showed that a hydrostatic pressure of 100 kPa significantly reduced the thickness of the proliferative layer in condylar cartilage without affecting the thickness of the transitional layer. Hydrostatic pressures of 100 kPa and 300 kPa significantly enhanced the synthesis of type II collagen. G proteins are involved not only in the proliferation and differentiation of condylar cartilage regulated by prolonged pressure, but also in the process of collagen production in condylar cartilage stimulated by pressure.

Neuroprotective effect of orexin-A is mediated by an increase of hypoxia-inducible factor-1 activity in rat.

BACKGROUND: Recent studies suggest that the novel neuropeptide orexin-A may play an essential role during neuronal damage. However, the function of orexin-A during brain ischemia remains unclear. Recently, hypoxia-inducible factor-1α (HIF-1α) was shown to be activated by orexin-A. The aim of the current study is to test the hypothesis that administration of exogenous orexin-A can attenuate ischemia-reperfusion injury through the facilitation of HIF-1α expression. METHODS: Sprague-Dawley rats were subjected to transient middle cerebral artery occlusion for 120 min. Rats were treated with different doses of orexin-A or vehicle before the ischemia and at the onset of reperfusion. To investigate the action of HIF-1α in the neuroprotective effects of orexin-A, the HIF-1α inhibitor YC-1 was used alone or combined with orexin-A. Neurologic deficit scores and infarct volume were assessed. Brains were harvested for immunohistochemical staining and western blot analysis. RESULTS: Orexin-A significantly ameliorated neurologic deficit scores and reduced infarct volume after cerebral ischemia reperfusion. Administration of 30 µg/kg orexin-A showed optimal neuroprotective effects. This effect was still present 7 days after reperfusion. Furthermore, orexin-A decreased the number of apoptotic cells and significantly enhanced HIF-1α expression after cerebral ischemia reperfusion. Moreover, the facilitation of HIF-1α expression was accompanied with inhibition of von Hippel-Lindau expression. Administration of HIF-1α inhibitor suppressed the increase of HIF-1α and reversed the neuroprotective effects of orexin-A. CONCLUSIONS: Orexin-A has a neuroprotective effect against cerebral ischemia-reperfusion injury. These effects may be mediated through the HIF-1α pathway.

Ibandronate promotes osteogenic differentiation of periodontal ligament stem cells by regulating the expression of microRNAs.

Bisphosphonates (BPs) have a profound effect on bone resorption and are widely used to treat osteoclast-mediated bone diseases. They suppress bone resorption by inhibiting the activity of mature osteoclasts and/or the formation of new osteoclasts. Osteoblasts may be an alternative target for BPs. Periodontal ligament stem cells (PDLSCs) exhibit osteoblast-like features and are capable of differentiating into osteoblasts or cementoblasts. This study aimed to determine the effects of ibandronate, a nitrogen-containing BP, on the proliferation and the differentiation of PDLSCs and to identify the microRNAs (miRNAs) that mediate these effects. The PDLSCs were treated with ibandronate, and cell proliferation was measured using the MTT (3-dimethylthiazol-2,5-diphenyltetrazolium bromide) assay. The expression of genes and miRNAs involved in osteoblastic differentiation was assayed using quantitative real-time reverse-transcription polymerase chain reaction (qRT-PCR). Ibandronate promoted the proliferation of PDLSCs and enhanced the expression of alkaline phosphatase (ALP), type I collagen (COL-1), osteoprotegerin (OPG), osteocalcin (OCN), and Runx2. The expression of miRNAs, including miR-18a, miR-133a, miR-141 and miR-19a, was significantly altered in the PDLSCs cultured with ibandronate. In PDLSCs, ibandronate regulates the expression of diverse bone formation-related genes via miRNAs. The exact mechanism underlying the role of ibandronate in osteoblasts has not been completely understood. Ibandronate may suppress the activity of osteoclasts while promoting the proliferation of osteoblasts by regulating the expression of miRNAs.

Isoflurane preconditioning induces neuroprotection by attenuating ubiquitin-conjugated protein aggregation in a mouse model of transient global cerebral ischemia.

BACKGROUND: In this study, we sought to clarify the role of inhibiting ubiquitin-conjugated protein aggregation in the formation of a neuroprotective effect after isoflurane preconditioning using a transient global cerebral ischemia-reperfusion injury mouse model. METHODS: C57BL/6 mice were randomly assigned to 3 groups (isoflurane preconditioning [IsoPC] group, control [Con] group, and sham group, n = 24 in each group). Mice in the IsoPC group and sham group were placed in a chamber and pretreated with isoflurane (1.2% isoflurane, 98% O(2), 1 hour/day) for 5 days. Mice in the Con group were placed in the same chamber but pretreated with oxygen only (98% O(2), 2% N(2), 1 hour/day) for 5 days. Twenty-four hours after the last preconditioning day, bilateral common carotid artery occlusion was performed as a model of global cerebral ischemia for 20 minutes in the IsoPC group and Con group. The total motor scores, number of viable neurons in the CA1 region of the hippocampus, and expression levels of conjugated ubiquitin or free ubiquitin were assessed by neurological assessment, immunohistochemistry, and Western blotting (at 24 and 72 hours) after reperfusion, respectively. RESULTS: The total motor scores in the IsoPC group were better than the Con group (P < 0.05). Morphological observations showed that the IsoPC group had better neuron structure than in the Con group. The numbers of viable neurons in the CA1 region were significantly increased by isoflurane preconditioning compared with those in the Con group (P < 0.05). The numbers of TUNEL-positive neurons in the CA1 region were significantly decreased after isoflurane preconditioning. The density of conjugated ubiquitin staining in the CA1 region of the IsoPC group was significantly lower than in the Con group (P < 0.05) and the expression of conjugated ubiquitin in the IsoPC group was lower than in the Con group (P < 0.05). CONCLUSION: Inhibition of ubiquitin-conjugated protein aggregation may have an essential role in inducing cerebral ischemic tolerance by isoflurane preconditioning in a transient global cerebral ischemia-reperfusion injury mouse model.