ABSTRACT
BACKGROUND: As an indispensable clinical inhalation anesthetic, sevoflurane is widely used for peri-operative sedation. The neuroprotective effect of sevoflurane pre-conditioning against cerebral ischemia/reperfusion has been gradually realized, but the underlying mechanism during the early reperfusion period has not been established. METHOD: Primary cultured cortical neurons were treated with 2% sevoflurane pre-conditioning for 30min, exposed to oxygen-glucose deprivation for 90min, and followed by 60min of reperfusion (OGD/R). Additionally, neuronal cells were treated with an inhibitor of extracellular signal-related kinases 1 and 2 (Erk1/2) phosphorylation (PD98059), a mPTP opener (atractyloside), or a mPTP opening inhibitor (cyclosporine A) before sevoflurane pre-conditioning. RESULT: Sevoflurane pre-conditioning decreased neuronal apoptosis (assessed by TUNEL), oxidative stress (assessed by malondialdehyde [MDA], superoxide dismutase [SOD], and heme oxygenase [HO]-1), and opening of mitochondrial permeability transition pores [mPTPs] (assessed by calcein-cobalt), but increased neuronal viability (assessed by MTT) and mitochondrial membrane potential (assessed by JC-1) after OGD/R exposure compared with OGD/R treatment alone. Pre-treatment with the mPTP opener and inhibitor of Erk1/2 phosphorylation abolished the protective effect induced by sevoflurane pre-conditioning. Pre-treatment with the mPTP opener attenuated the phosphorylation of Erk1/2 in mitochondria of neuronal cultures exposed to OGD/R induced by sevoflurane pre-conditioning. The mPTP opening inhibitor, like sevoflurane pre-conditioning, increased phosphorylation of Erk1/2 after OGD/R exposure, while PD98059 failed to reverse inhibition of mPTP opening in cultures exposed to OGD/R induced by sevoflurane pre-conditioning. CONCLUSION: The neuroprotective mechanism of sevoflurane pre-conditioning might be associated with increased Erk1/2 phosphorylation in mitochondria via inhibition of mPTP opening in the early reperfusion period.
Subject(s)
Heme Oxygenase (Decyclizing)/metabolism , MAP Kinase Signaling System/drug effects , Methyl Ethers/pharmacology , Mitochondrial Membrane Transport Proteins/antagonists & inhibitors , Neurons/drug effects , Neuroprotective Agents/pharmacology , Animals , Apoptosis/drug effects , Apoptosis/physiology , Atractyloside/pharmacology , Cell Hypoxia/drug effects , Cell Hypoxia/physiology , Cells, Cultured , Cerebral Cortex/drug effects , Cerebral Cortex/metabolism , Cyclosporine/pharmacology , Disease Models, Animal , Drug Evaluation, Preclinical , Enzyme Inhibitors/pharmacology , Flavonoids/pharmacology , Glucose/deficiency , Heme Oxygenase (Decyclizing)/antagonists & inhibitors , MAP Kinase Signaling System/physiology , Mitochondrial Membrane Transport Proteins/metabolism , Mitochondrial Permeability Transition Pore , Mitogen-Activated Protein Kinase 1/antagonists & inhibitors , Mitogen-Activated Protein Kinase 1/metabolism , Mitogen-Activated Protein Kinase 3/antagonists & inhibitors , Mitogen-Activated Protein Kinase 3/metabolism , Neurons/metabolism , Phosphorylation/drug effects , Rats, Sprague-Dawley , SevofluraneABSTRACT
Phytantriol (PT), ethanol (ET) and water were used to prepare in situ cubic liquid crystal (ISV2). The pseudo-ternary phase diagram of PT-ET-water was constructed and isotropic solution formulations were chosen for further optimization. The physicochemical properties of isotropic solution formulations were evaluated to optimize the composition of ISV2. In situ hexagonal liquid crystals (ISH2) were prepared based on the composition of ISV2 with the addition of vitamin E acetate (VitEA) and the amount of VitEA was optimized by in vitro release behavior. The phase structures of liquid crystalline gels formed by ISV2 and ISH2 in excess water were confirmed by crossed polarized light microscopy and small angle X-ray scattering, respectively. Rheological properties of ISV2 and ISH2 were studied by a DHR-2 rheometer. In vitro drug release studies were conducted by using a dialysis membrane diffusion method. Pharmacokinetics was investigated by determination of sinomenine hydrochloride (SMH) concentration in synovial membrane after intra-articular injection of SMH-loaded ISH2 in adjuvant-induced arthritis rats. The optimal ISV2 (PT/ET/water, 64 : 16 : 20, w/w/w) loaded with 6 mg x g(-1) of SMH showed a suitable pH, injectable and formed a cubic liquid crystalline gel in situ with minimum water absorption in the shortest time. The optimal ISV2 was able to sustain the drug release for 144 h. The optimal ISH2 system was prepared by addition of 5% VitEA into PT in the optimal ISV2 system. This ISH2 (PT/VitEA/ET/water, 60.8 : 3.2 : 16 : 20, w/w/w/w) was an injectable isotropic solution with suitable pH. The new ISH2 was able to sustain the drug release for more than 240 h. Local pharmacokinetics study indicated that the retention time and AUC(0-∞) of ISH2 group were increased significantly compared with that of SMH solution group and the AUC(0-∞) of ISH2 group was 6.01 times higher than that of SMH solution group. The developed ISH2 was suitable for intra-articular injection that may apply to patients in the treatment of rheumatoid arthritis.