Propofol Anesthesia Depth Monitoring Based on Self-Attention and Residual Structure Convolutional Neural Network.

METHODS: We compare nine index values, select CNN+EEG, which has good correlation with BIS index, as an anesthesia state observation index to identify the parameters of the model, and establish a model based on self-attention and dual resistructure convolutional neural network. The data of 93 groups of patients were selected and randomly grouped into three parts: training set, validation set, and test set, and compared the best and worst results predicted by BIS. RESULT: The best result is that the model's accuracy of predicting BLS on the test set has an overall upward trend, eventually reaching more than 90%. The overall error shows a gradual decrease and eventually approaches zero. The worst result is that the model's accuracy of predicting BIS on the test set has an overall upward trend. The accuracy rate is relatively stable without major fluctuations, but the final accuracy rate is above 70%. CONCLUSION: The prediction of BIS indicators by the deep learning method CNN algorithm shows good results in statistics.

Exhaled Propofol Concentrations Correlate With Plasma and Brain Tissue Concentrations in Rats.

BACKGROUND: Propofol can be measured in exhaled gas. Exhaled and plasma propofol concentrations correlate well, but the relationship with tissue concentrations remains unknown. We thus evaluated the relationship between exhaled, plasma, and various tissue propofol concentrations. Because the drug acts in the brain, we focused on the relationship between exhaled and brain tissue propofol concentrations. METHODS: Thirty-six male Sprague-Dawley rats were anesthetized with propofol, ketamine, and rocuronium for 6 hours. Animals were randomly assigned to propofol infusions at 20, 40, or 60 mg·kg·h (n = 12 per group). Exhaled propofol concentrations were measured at 15-minute intervals by multicapillary column-ion mobility spectrometry. Arterial blood samples, 110 µL each, were collected 15, 30, and 45 minutes, and 1, 2, 4, and 6 hours after the propofol infusion started. Propofol concentrations were measured in brain, lung, liver, kidney, muscle, and fat tissue after 6 hours. The last exhaled and plasma concentrations were used for linear regression analyses with tissue concentrations. RESULTS: The correlation of exhaled versus plasma concentrations (R = 0.71) was comparable to the correlation of exhaled versus brain tissue concentrations (R = 0.75) at the end of the study. In contrast, correlations between plasma and lung and between lung and exhaled propofol concentrations were poor. Less than a part-per-thousand of propofol was exhaled over 6 hours. CONCLUSIONS: Exhaled propofol concentrations correlate reasonably well with brain tissue and plasma concentrations in rats, and may thus be useful to estimate anesthetic drug effect. The equilibration between plasma propofol and exhaled gas is apparently independent of lung tissue concentration. Only a tiny fraction of administered propofol is eliminated via the lungs, and exhaled quantities thus have negligible influence on plasma concentrations.

The role of propofol hydroxyl group in 5-lipoxygenase recognition.

Propofol is a clinically important intravenous anesthetic. We previously reported that it directly inhibited 5-lipoxygenase (5-LOX), a key enzyme for leukotriene biosynthesis. Because the hydroxyl group in propofol (propofol 1-hydroxyl) is critical for its anesthetic effect, we examined if its presence would be inevitable for 5-lipoxygenase recognition. Fropofol is developed by substituting the hydroxy group in propofol with fluorine. We found that propofol 1-hydroxyl was important for 5-lipoxygenase recognition, but it was not absolutely necessary. Azi-fropofol bound to 5-LOX at one of the two propofol binding sites of 5-LOX (pocket around Phe-187), suggesting that propofol 1-hydroxyl is important for 5-LOX inhibition at the other propofol binding site (pocket around Val-431). Interestingly, 5-hydroperoxyeicosatetraenoic acid (5-HpETE) production was significantly increased by stimulation with calcium ionophore A23187 in HEK293 cells expressing 5-LOX, suggesting that the fropofol binding site is important for the conversion from 5-HpETE to leukotriene A4. We also indicated that propofol 1-hydroxyl might have contributed to interaction with wider targets among our body.

Pharmacogenomics of poor drug metabolism in Greyhounds: Cytochrome P450 (CYP) 2B11 genetic variation, breed distribution, and functional characterization.

Greyhounds recover more slowly from certain injectable anesthetics than other dog breeds. Previous studies implicate cytochrome P450 (CYP) 2B11 as an important clearance mechanism for these drugs and suggest Greyhounds are deficient in CYP2B11. However, no CYP2B11 gene mutations have been identified that explain this deficiency in Greyhounds. The objectives of this study were to provide additional evidence for CYP2B11 deficiency in Greyhounds, determine the mechanisms underlying this deficiency, and identify CYP2B11 mutations that contribute to this phenotype in Greyhounds. Greyhound livers metabolized CYP2B11 substrates slower, possessed lower CYP2B11 protein abundance, but had similar or higher mRNA expression than other breeds. Gene resequencing identified three CYP2B11 haplotypes, H1 (reference), H2, and H3 that were differentiated by mutations in the gene 3'-untranslated region (3'-UTR). Compared with 63 other dog breeds, Greyhounds had the highest CYP2B11-H3 allele frequency, while CYP2B11-H2 was widely distributed across most breeds. Using 3'-UTR luciferase reporter constructs, CYP2B11-H3 showed markedly lower gene expression (over 70%) compared to CYP2B11-H1 while CYP2B11-H2 expression was intermediate. Truncated mRNA transcripts were observed in CYP2B11-H2 and CYP2B11-H3 but not CYP2B11-H1 transfected cells. Our results implicate CYP2B11 3'-UTR mutations as a cause of decreased CYP2B11 enzyme expression in Greyhounds through reduced translational efficiency.

The Binding Mechanisms and Inhibitory Effect of Intravenous Anesthetics on AChE In Vitro and In Vivo: Kinetic Analysis and Molecular Docking.

Inhibitors of acetylcholinesterase (AChE), which have an important role in the prevention of excessive AChE activity and ß-amyloid (Aß) formation are widely used in the symptomatic treatment of Alzheimer's disease (AD). The inhibitory effect of anesthetic agents on AChE was determined by several approaches, including binding mechanisms, molecular docking and kinetic analysis. Inhibitory effect of intravenous anesthetics on AChE as in vitro and in vivo have been discovered. The midazolam, propofol and thiopental have shown competitive inhibition type (midazolam > propofol > thiopental) and Ki values were found to be 3.96.0 ± 0.1, 5.75 ± 0.12 and 29.65 ± 2.04 µM, respectively. The thiopental and midazolam showed inhibition effect on AChE in vitro, whereas they showed activation effect in vivo when they are combined together. The order of binding of the drugs to the active site of the 4M0E receptor was found to be midazolam > propofol > thiopental. This study on anesthetic agents that are now widely used in surgical applications, have provided a molecular basis for investigating the drug-enzyme interactions mechanism. In addition, the study is important in understanding the molecular mechanism of inhibitors that are effective in the treatment of AD.

Binding site location on GABAA receptors determines whether mixtures of intravenous general anaesthetics interact synergistically or additively in vivo.

BACKGROUND AND PURPOSE: General anaesthetics can act on synaptic GABAA receptors by binding to one of three classes of general anaesthetic sites. Canonical drugs that bind selectively to only one class of site are etomidate, alphaxalone, and the mephobarbital derivative, R-mTFD-MPAB. We tested the hypothesis that the general anaesthetic potencies of mixtures of such site-selective agents binding to the same or to different sites would combine additively or synergistically respectively. EXPERIMENTAL APPROACH: The potency of general anaesthetics individually or in combinations to cause loss of righting reflexes in tadpoles was determined, and the results were analysed using isobolographic methods. KEY RESULTS: The potencies of combinations of two or three site-selective anaesthetics that all acted on a single class of site were strictly additive, regardless of which single site was involved. Combinations of two or three site-selective anaesthetics that all bound selectively to different sites always interacted synergistically. The strength of the synergy increased with the number of separate sites involved such that the percentage of each agent's EC50 required to cause anaesthesia was just 35% and 14% for two or three sites respectively. Propofol, which binds non-selectively to the etomidate and R-mTFD-MPAB sites, interacted synergistically with each of these agents. CONCLUSIONS AND IMPLICATIONS: The established pharmacology of the three anaesthetic binding sites on synaptic GABAA receptors was sufficient to predict whether a mixture of anaesthetics interacted additively or synergistically to cause loss of righting reflexes in vivo. The principles established here have implications for clinical practice.

Propofol specifically reduces PMA-induced neutrophil extracellular trap formation through inhibition of p-ERK and HOCl.

Neutrophil extracellular traps (NETs) are net-like chromatin fibers that can trap and kill microorganisms. Although several anti-inflammatory effects of intravenous anesthetics have been reported, it has not been investigated whether intravenous anesthetics influence NET formation. AIMS: To compare the effects of four intravenous anesthetics (propofol, thiamylal sodium, midazolam, and ketamine) on phorbol myristate acetate (PMA)-induced NET formation and analyze the associated signaling pathways. MATERIALS AND METHODS: PMA-stimulated NETs formed in the absence or presence of intravenous anesthetics were stained with SYTOX Green and then quantified. Inhibitors were applied to investigate the related mechanism, which was confirmed by western blotting, and ROS were detected. KEY FINDINGS: The neutrophils incubated with propofol showed the lowest degree of NET formation compared with those incubated with the other intravenous anesthetics. Propofol significantly reduced the level of myeloperoxidase (MPO)-derived HOCl but not that of superoxide. Aminopyrine, an MPO inhibitor, markedly decreased the number of PMA-induced NETs, indicating the involvement of HOCl in the inhibitory effect of propofol on NET formation. According to western blotting results, the level of p-ERK was reduced by propofol during PMA-induced NET formation. The ERK inhibitor PD98059 decreased NET formation but did not inhibit PMA-induced HOCl generation, and aminopyrine did not reduce ERK phosphorylation. SIGNIFICANCE: Through this study, we define a new anti-inflammatory effect of intravenous anesthetics. Of the four intravenous anesthetics tested, propofol was the most potent inhibitor of NET formation. Moreover, propofol resulted in a decrease in PMA-induced NET formation by two independent mechanisms: inhibition of HOCl and p-ERK.

Characterization of Intestinal and Hepatic CYP3A-Mediated Metabolism of Midazolam in Children Using a Physiological Population Pharmacokinetic Modelling Approach.

PURPOSE: Changes in drug absorption and first-pass metabolism have been reported throughout the pediatric age range. Our aim is to characterize both intestinal and hepatic CYP3A-mediated metabolism of midazolam in children in order to predict first-pass and systemic metabolism of CYP3A substrates. METHODS: Pharmacokinetic (PK) data of midazolam and 1-OH-midazolam from 264 post-operative children 1-18 years of age after oral administration were analyzed using a physiological population PK modelling approach. In the model, consisting of physiological compartments representing the gastro-intestinal tract and liver,intrinsic intestinal and hepatic clearances were estimated to derive values for bioavailability and plasma clearance. RESULTS: The whole-organ intrinsic clearance in the gut wall and liver were found to increase with body weight, with a 105 (95% confidence interval (CI): 5-405) times lower intrinsic gut wall clearance than the intrinsic hepatic clearance (i.e. 5.08 L/h (relative standard error (RSE) 10%) versus 527 L/h (RSE 7%) for a 16 kg individual, respectively). When expressed per gram of organ, intrinsic clearance increases with increasing body weight in the gut wall, but decreases in the liver, indicating that CYP3A-mediated intrinsic clearance and local bioavailability in the gut wall and liver do not change with age in parallel. The resulting total bioavailability was found to be age-independent with a median of 20.8% in children (95%CI: 3.8-50.0%). CONCLUSION: In conclusion, the intrinsic CYP3A-mediated gut wall clearance is substantially lower than the intrinsic hepatic CYP3A-mediated clearance in children from 1 to 18 years of age, and contributes less to the overall first-pass metabolism compared to adults.

Excitatory Pathways from the Lateral Habenula Enable Propofol-Induced Sedation.

The lateral habenula has been widely studied for its contribution in generating reward-related behaviors [1, 2]. We have found that this nucleus plays an unexpected role in the sedative actions of the general anesthetic propofol. The lateral habenula is a glutamatergic, excitatory hub that projects to multiple targets throughout the brain, including GABAergic and aminergic nuclei that control arousal [3-5]. When glutamate release from the lateral habenula in mice was genetically blocked, the ability of propofol to induce sedation was greatly diminished. In addition to this reduced sensitivity to propofol, blocking output from the lateral habenula caused natural non-rapid eye movement (NREM) sleep to become highly fragmented, especially during the rest ("lights on") period. This fragmentation was largely reversed by the dual orexinergic antagonist almorexant. We conclude that the glutamatergic output from the lateral habenula is permissive for the sedative actions of propofol and is also necessary for the consolidation of natural sleep.

High Constitutive Activity Accounts for the Combination of Enhanced Direct Activation and Reduced Potentiation in Mutated GABAA Receptors.

GABAA receptors activated by the transmitter GABA are potentiated by several allosterically acting drugs, including the intravenous anesthetic propofol. Propofol can also directly activate the receptor, albeit at higher concentrations. Previous functional studies have identified amino acid residues whose substitution reduces potentiation of GABA-activated receptors by propofol while enhancing the ability of propofol to directly activate the receptor. One interpretation of such observations is that the mutation has specific effects on the sites or processes involved in potentiation or activation. We show here that divergent effects on potentiation and direct activation can be mediated by increased constitutive open probability in the mutant receptor without any specific effect on the interactions between the allosteric drug and the receptor. By simulating GABAA receptor activity using the concerted transition model, we demonstrate that the predicted degree of potentiation is reduced as the level of constitutive activity increases. The model further predicts that a potentiating effect of an allosteric modulator is a computable value that depends on the level of constitutive activity, the amplitude of the response to the agonist, and the amplitude of the direct activating response to the modulator. Specific predictions were confirmed by electrophysiological data from the binary α1ß3 and concatemeric ternary ß2α1γ2L+ß2α1 GABAA receptors. The corollaries of reduced potentiation due to increased constitutive activity are isobolograms that conform to simple additivity and a loss of separation between the concentration-response relationships for direct activation and potentiation.

Propofol Is an Allosteric Agonist with Multiple Binding Sites on Concatemeric Ternary GABAA Receptors.

GABAA receptors can be directly activated and potentiated by the intravenous anesthetic propofol. Previous photolabeling, modeling, and functional data have identified two binding domains through which propofol acts on the GABAA receptor. These domains are defined by the ß(M286) residue at the ß"+"-α"-" interface in the transmembrane region and the ß(Y143) residue near the ß"-" surface in the junction between the extracellular and transmembrane domains. In the ternary receptor, there are predicted to be two copies of each class of sites, for a total of four sites per receptor. We used ß2α1γ2L and ß2α1 concatemeric constructs to determine the functional effects of the ß(Y143W) and ß(M286W) mutations to gain insight into the number of functional binding sites for propofol and the energetic contributions stemming from propofol binding to the individual sites. A mutation of each of the four sites affected the response to propofol, indicating that each of the four sites is functional in the wild-type receptor. The mutations mainly impaired stabilization of the open state by propofol, i.e., reduced gating efficacy. The effects were similar for mutations at either site and were largely additive and independent of the presence of other Y143W or M286W mutations in the receptor. The two classes of sites appeared to differ in affinity for propofol, with the site affected by M286W having about a 2-fold higher affinity. Our analysis indicates there may be one or two additional functionally equivalent binding sites for propofol, other than those modified by substitutions at ß(Y143) and ß(M286).

Propofol attenuates cytokine-mediated upregulation of expression of inducible nitric oxide synthase and apoptosis during regeneration post-partial hepatectomy.

PURPOSE:: To determine the effects of propofol and ketamine anesthesia on liver regeneration in rats after partial hepatectomy (PHT). METHODS:: Male Wistar albino rats were assigned randomly to four groups of 10. Anesthesia was induced and maintained with propofol in groups 1 and 2, and with ketamine in groups 3 and 4. PHT was undertaken in groups 1 and 3. Rats in groups 2 and 4 (control groups) underwent an identical surgical procedure, but without PHT. At postoperative day-5, rats were killed. Regenerated liver was removed, weighed, and evaluated (by immunohistochemical means) for expression of inducible nitric oxide synthase (iNOS), endothelial NOS (eNOS), apoptosis protease-activating factor (APAF)-1, and proliferating cell nuclear antigen (PCNA). Also, blood samples were collected for measurement of levels of tumor necrosis factor (TNF)-α and interleukin (IL)-6. RESULTS:: Between groups 2 and 4, there were no differences in tissue levels of iNOS, eNOS, and APAF-1 or plasma levels of TNF-α and IL-6. eNOS expression was similar in group 1 and group 3. Expression of iNOS and APAF-1 was mild-to-moderate in group 1, but significantly higher in group 3. Groups 1 and 3 showed an increase in PCNA expression, but expression in both groups was comparable. Plasma levels of TNF-α and IL-6 increased to a lesser degree in group 1 than in group 3. CONCLUSION:: Propofol, as an anesthetic agent, may attenuate cytokine-mediated upregulation of iNOS expression and apoptosis in an animal model of liver regeneration after partial hepatectomy.

Green discolouration of urine following propofol infusion in a dog.

A three-year-old, female neutered Weimaraner was presented with a history of neck pain and tetraparesis. MRI revealed an extradural mass at the level of C3 vertebra, which was thought to be a spinal abscess, and the dog was scheduled for surgical exploration the following morning. Overnight the dog developed an exaggerated ventilatory pattern, with paradoxical inward movement of the thorax on inspiration. Arterial blood gas analysis revealed respiratory acidosis and ventilator support was initiated to prevent excessive respiratory fatigue. During mechanical ventilation, anaesthesia was maintained using a propofol target-controlled infusion system and, subsequently, the dog produced bright green urine in the urine collection system. Although previously documented in humans, this appears to be the first report of green urine in a dog following propofol use.

Propofol attenuates cytokine-mediated upregulation of expression of inducible nitric oxide synthase and apoptosis during regeneration post-partial hepatectomy

Abstract Purpose: To determine the effects of propofol and ketamine anesthesia on liver regeneration in rats after partial hepatectomy (PHT). Methods: Male Wistar albino rats were assigned randomly to four groups of 10. Anesthesia was induced and maintained with propofol in groups 1 and 2, and with ketamine in groups 3 and 4. PHT was undertaken in groups 1 and 3. Rats in groups 2 and 4 (control groups) underwent an identical surgical procedure, but without PHT. At postoperative day-5, rats were killed. Regenerated liver was removed, weighed, and evaluated (by immunohistochemical means) for expression of inducible nitric oxide synthase (iNOS), endothelial NOS (eNOS), apoptosis protease-activating factor (APAF)-1, and proliferating cell nuclear antigen (PCNA). Also, blood samples were collected for measurement of levels of tumor necrosis factor (TNF)-α and interleukin (IL)-6. Results: Between groups 2 and 4, there were no differences in tissue levels of iNOS, eNOS, and APAF-1 or plasma levels of TNF-α and IL-6. eNOS expression was similar in group 1 and group 3. Expression of iNOS and APAF-1 was mild-to-moderate in group 1, but significantly higher in group 3. Groups 1 and 3 showed an increase in PCNA expression, but expression in both groups was comparable. Plasma levels of TNF-α and IL-6 increased to a lesser degree in group 1 than in group 3. Conclusion: Propofol, as an anesthetic agent, may attenuate cytokine-mediated upregulation of iNOS expression and apoptosis in an animal model of liver regeneration after partial hepatectomy.

Guía de práctica clínica para la elección del fluido de restauración volémica perioperatoria en los pacientes adultos intervenidos de cirugía no cardiaca / Clinical practice guide for the choice of perioperative volume-restoring fluid in adult patients undergoing non-cardiac surgery

Esta Guía de Práctica Clínica responde a preguntas clínicas sobre seguridad en la elección de fluido (cristaloide, coloide o Hidroxietilalmidón 130) en pacientes que precisan restauración volémica en el periodo perioperatorio de cirugía no cardiaca. A partir del resumen de la evidencia, se elaboraron las recomendaciones siguiendo la metodología GRADE. En esta población se sugiere la fluidoterapia basada en la administración de cristaloides, (recomendación débil, calidad de la evidencia baja). En las situaciones en las que la restauración volémica no se alcance sólo con cristaloides, se sugiere utilizar coloides sintéticos (Hidroxietilalmidón 130 o gelatina fluida modificada) en lugar de Albúmina 5% (recomendación débil, calidad de la evidencia baja). La elección y dosificación de coloide deberán basarse en las características del producto, comorbilidad del paciente y experiencia del anestesiólogo (AU)

The present Clinical practice guide responds to the clinical questions about security in the choice of fluid (crystalloid, colloid or hydroxyethyl starch 130) in patients who require volume replacement during perioperative period of non-cardiac surgeries. From the evidence summary, recommendations were made following the GRADE methodology. In this population fluid therapy based on crystalloids is suggested (weak recommendation, low quality evidence). In the events where volume replacement is not reached with crystalloids, the use of synthetic colloids (hydroxyethyl starch 130 or modified fluid gelatin) is suggested instead of 5% albumin (weak recommendation, low quality evidence). The choice and dosage of the colloid should be based in the product characteristics, patient comorbidity and anesthesiologist's experience (AU)

Drug Pharmacokinetics Determined by Real-Time Analysis of Mouse Breath.

Noninvasive, real-time pharmacokinetic (PK) monitoring of ketamine, propofol, and valproic acid, and their metabolites was achieved in mice, using secondary electrospray ionization and high-resolution mass spectrometry. The PK profile of a drug influences its efficacy and toxicity because it determines exposure time and levels. The antidepressant and anaesthetic ketamine (Ket) and four Ket metabolites were studied in detail and their PK was simultaneously determined following application of different sub-anaesthetic doses of Ket. Bioavailability after oral administration vs. intraperitoneal injection was also investigated. In contrast to conventional studies that require many animals to be sacrificed even for low-resolution PK curves, this novel approach yields real-time PK curves with a hitherto unmatched time resolution (10 s), and none of the animals has to be sacrificed. This thus represents a major step forward not only in animal welfare, but also major cost and time savings.

Online breath analysis of propofol during anesthesia: clinical application of membrane inlet-ion mobility spectrometry.

BACKGROUND: Breath analysis of propofol is a potential noninvasive method for approximating the plasma propofol concentration. There have been various reported techniques for measuring the exhaled propofol concentration at steady state; however, the propofol concentration undergoes marked changes during clinical anesthesia. Therefore, this study investigated the use of membrane inlet-ion mobility spectrometry (MI-IMS) to monitor exhaled propofol discontinuously and continuously during propofol anesthesia. METHODS: The study included 19 patients of American Society of Anesthesiologists physical status I or II. In experiment I (discontinuous study), breath and blood samples were collected discontinuously, with stable target propofol concentrations of 2.8 µg/ml, 3.2 µg/ml, 3.5 µg/ml, and 3.8 µg/ml. In experiment II (continuous study), propofol concentration was maintained at 3.5 µg/ml after induction, and exhaled breath was collected continuously every 3 min during propofol infusion. Relationships of the exhaled propofol concentration with the plasma propofol concentration, measured by high-performance liquid chromatography and the continuously measured bispectral (BIS) index were investigated. RESULTS: Comparison of the exhaled and plasma propofol concentrations revealed a bias ± precision of 2.1% ± 14.6% (95% limits of agreement: - 26.5-30.7%) in experiment I and - 10.4% ± 13.2 (- 36.3-15.4%) in experiment II. In both experiments, exhaled propofol concentrations measured by MI-IMS were consistent with, the propofol effect represented by the BIS index. CONCLUSIONS: MI-IMS may be a suitable method to predict plasma propofol concentration online during propofol anesthesia. Monitoring exhaled propofol may improve the safety of propofol anesthesia.

Structural comparisons of ligand-gated ion channels in open, closed, and desensitized states identify a novel propofol-binding site on mammalian γ-aminobutyric acid type A receptors.

BACKGROUND: Most anesthetics, particularly intravenous agents such as propofol and etomidate, enhance the actions of the neurotransmitter γ-aminobutyric acid (GABA) at the GABA type A receptor. However, there is no agreement as where anesthetics bind to the receptor. A novel approach would be to identify regions on the receptor that are state-dependent, which would account for the ability of anesthetics to affect channel opening by binding differentially to the open and closed states. METHODS: The open and closed structures of the GABA type A receptor homologues Gloeobacter ligand-gated ion channel and glutamate-gated chloride channel were compared, and regions in the channels that move on channel opening and closing were identified. Docking calculations were performed to investigate possible binding of propofol to the GABA type A ß3 homomer in this region. RESULTS: A comparison between the open and closed states of the Gloeobacter ligand-gated ion channel and glutamate-gated chloride channel channels identified a region at the top of transmembrane domains 2 and 3 that shows maximum movement when the channels transition between the open and closed states. Docking of propofol into the GABA type A ß3 homomer identified two putative binding cavities in this same region, one with a high affinity and one with a lower affinity. Both cavities were adjacent to a histidine residue that has been photolabeled by a propofol analog, and both sites would be disrupted on channel closing. CONCLUSIONS: These calculations support the conclusion of a recent photolabeling study that propofol acts at a site at the interface between the extracellular and transmembrane domains, close to the top of transmembrane domain 2.

Propofol attenuated acute kidney injury after orthotopic liver transplantation via inhibiting gap junction composed of connexin 32.

BACKGROUND: Postliver transplantation acute kidney injury (AKI) severely affects patient survival, whereas the mechanism is unclear and effective therapy is lacking. The authors postulated that reperfusion induced enhancement of connexin32 (Cx32) gap junction plays a critical role in mediating postliver transplantation AKI and that pretreatment/precondition with the anesthetic propofol, known to inhibit gap junction, can confer effective protection. METHODS: Male Sprague-Dawley rats underwent autologous orthotopic liver transplantation (AOLT) in the absence or presence of treatments with the selective Cx32 inhibitor, 2-aminoethoxydiphenyl borate or propofol (50 mg/kg) (n = 8 per group). Also, kidney tubular epithelial (NRK-52E) cells were subjected to hypoxia-reoxygenation and the function of Cx32 was manipulated by three distinct mechanisms: cell culture in different density; pretreatment with Cx32 inhibitors or enhancer; Cx32 gene knock-down (n = 4 to 5). RESULTS: AOLT resulted in significant increases of renal Cx32 protein expression and gap junction, which were coincident with increases in oxidative stress and impairment in renal function and tissue injury as compared to sham group. Similarly, hypoxia-reoxygenation resulted in significant cellular injury manifested as reduced cell growth and increased lactate dehydrogenase release, which was significantly attenuated by Cx32 gene knock-down but exacerbated by Cx32 enhancement. Propofol inhibited Cx32 function and attenuated post-AOLT AKI. In NRK-52E cells, propofol reduced posthypoxic reactive oxygen species production and attenuated cellular injury, and the cellular protective effects of propofol were reinforced by Cx32 inhibition but cancelled by Cx32 enhancement. CONCLUSION: Cx32 plays a critical role in AOLT-induced AKI and that inhibition of Cx32 function may represent a new and major mechanism whereby propofol reduces oxidative stress and subsequently attenuates post-AOLT AKI.