Features and mechanisms of propofol-induced protein kinase C (PKC) translocation and activation in living cells.

Background and purpose: In this study, we aimed to elucidate the action mechanisms of propofol, particularly those underlying propofol-induced protein kinase C (PKC) translocation. Experimental approach: Various PKCs fused with green fluorescent protein (PKC-GFP) or other GFP-fused proteins were expressed in HeLa cells, and their propofol-induced dynamics were observed using confocal laser scanning microscopy. Propofol-induced PKC activation in cells was estimated using the C kinase activity receptor (CKAR), an indicator of intracellular PKC activation. We also examined PKC translocation using isomers and derivatives of propofol to identify the crucial structural motifs involved in this process. Key results: Propofol persistently translocated PKCα conventional PKCs and PKCδ from novel PKCs (nPKCs) to the plasma membrane (PM). Propofol translocated PKCδ and PKCη of nPKCs to the Golgi apparatus and endoplasmic reticulum, respectively. Propofol also induced the nuclear translocation of PKCζ of atypical PKCs or proteins other than PKCs, such that the protein concentration inside and outside the nucleus became uniform. CKAR analysis revealed that propofol activated PKC in the PM and Golgi apparatus. Moreover, tests using isomers and derivatives of propofol predicted that the structural motifs important for the induction of PKC and nuclear translocation are different. Conclusion and implications: Propofol induced the subtype-specific intracellular translocation of PKCs and activated PKCs. Additionally, propofol induced the nuclear translocation of PKCs and other proteins, probably by altering the permeability of the nuclear envelope. Interestingly, propofol-induced PKC and nuclear translocation may occur via different mechanisms. Our findings provide insights into the action mechanisms of propofol.

Identification of protein kinase C domains involved in its translocation induced by propofol.

Propofol is widely used for general anesthesia and sedation; however, the mechanisms of its anesthetic and adverse effects are not fully understood. We have previously shown that propofol activates protein kinase C (PKC) and induces its translocation in a subtype-specific manner. The purpose of this study was to identify the PKC domains involved in propofol-induced PKC translocation. The regulatory domains of PKC consist of C1 and C2 domains, and the C1 domain is subdivided into the C1A and C1B subdomains. Mutant PKCα and PKCδ with each domain deleted were fused with green fluorescent protein (GFP) and expressed in HeLa cells. Propofol-induced PKC translocation was observed by time-lapse imaging using a fluorescence microscope. The results showed that persistent propofol-induced PKC translocation to the plasma membrane was abolished by the deletion of both C1 and C2 domains in PKCα and by the deletion of the C1B domain in PKCδ. Therefore, propofol-induced PKC translocation involves the C1 and C2 domains of PKCα and the C1B domain of PKCδ. We also found that treatment with calphostin C, a C1 domain inhibitor, abolished propofol-induced PKCδ translocation. In addition, calphostin C inhibited the propofol-induced phosphorylation of endothelial nitric oxide synthase (eNOS). These results suggest that it may be possible to modulate the exertion of propofol effects by regulating the PKC domains involved in propofol-induced PKC translocation.

Characterization of intracellular calcium mobilization induced by remimazolam, a newly approved intravenous anesthetic.

Many anesthetics, including Propofol, have been reported to induce elevation of intracellular calcium, and we were interested to investigate the possible contribution of calcium elevation to the mechanism of the newly approved remimazolam actions. Remimazolam is an intravenous anesthetic first approved in Japan in July 2020, and is thought to exert its anesthetic actions via γ-aminobutyric acid A (GABAA) receptors; however, the precise mechanisms of how remimazolam elevates intracellular calcium levels remains unclear. We examined the remimazolam-induced elevation of intracellular calcium using SHSY-5Y neuroblastoma cells, COS-7 cells, HEK293 cells, HeLa cells, and human umbilical vein endothelial cells (HUVECs) loaded with fluorescent dyes for live imaging. We confirmed that high concentrations of remimazolam (greater than 300 µM) elevated intracellular calcium in a dose-dependent manner in these cells tested. This phenomenon was not influenced by elimination of extracellular calcium. The calcium elevation was abolished when intracellular or intraendoplasmic reticulum (ER) calcium was depleted by BAPTA-AM or thapsigargin, respectively, suggesting that calcium was mobilized from the ER. Inhibitors of G-protein coupled receptors (GPCRs)-mediated signals, including U-73122, a phospholipase C (PLC) inhibitor and xestospongin C, an inositol 1,4,5-triphosphate receptors (IP3R) antagonist, significantly suppressed remimazolam-induced calcium elevation, whereas dantrolene, a ryanodine receptor antagonist, did not influence remimazolam-induced calcium elevation. Meanwhile, live imaging of ER during remimazolam stimulation using ER-tracker showed no morphological changes. These results suggest that high doses of remimazolam increased intracellular calcium concentration in a dose-dependent manner in each cell tested, which was predicted to be caused by calcium mobilization from the ER. In addition, our studies using various inhibitors revealed that this calcium elevation might be mediated by the GPCRs-IP3 pathway. However, further studies are required to identify which type of GPCRs is involved.

Propofol induces the elevation of intracellular calcium via morphological changes in intracellular organelles, including the endoplasmic reticulum and mitochondria.

Propofol, most frequently used as a general anesthetic due to its versatility and short-acting characteristics, is thought to exert its anesthetic actions via GABAA receptors; however, the precise mechanisms of its adverse action including angialgia remain unclear. We examined the propofol-induced elevation of intracellular calcium and morphological changes in intracellular organelles using SHSY-5Y neuroblastoma cells, COS-7 cells, HEK293 cells, and HUVECs loaded with fluorescent dyes for live imaging. Although propofol (>50 µM) increased intracellular calcium in a dose-dependent manner in these cells, it was not influenced by the elimination of extracellular calcium. The calcium elevation was abolished when intracellular or intraendoplasmic reticulum (ER) calcium was depleted by BAPTA-AM or thapsigargin, respectively, suggesting that calcium was mobilized from the ER. Studies using U-73122, xestospongin C, and dantrolene revealed that propofol-induced calcium elevation was not mediated by G-protein coupled receptors, IP3 receptors, or ryanodine receptors. We performed live imaging of the ER, mitochondria and Golgi apparatus during propofol stimulation using fluorescent dyes. Concomitant with the calcium elevation, the structure of the ER and mitochondria was fragmented and aggregated, and these changes were not reversed during the observation period, suggesting that propofol-induced calcium elevation occurs due to calcium leakage from these organelles. Although the concentration of propofol used in this experiment was greater than that used clinically (30 µM), it is possible that the concentration exceeds 30 µM at the site where propofol is injected, leading the idea that these phenomena might relate to the various propofol-induced adverse effects including angialgia.

Assessment of postoperative nutritional status and physical function between open surgical aortic valve replacement and transcatheter aortic valve implantation in elderly patients.

Background and aims : Severe aortic stenosis (AS) has been normally treated with surgical aortic valve replacement (AVR) whereas recently, transcatheter aortic valve implantation (TAVI) has been introduced as a minimally invasive operation for patients with high surgical risk and frailty. In this study, we have evaluated postoperative physical function and nutrition intake in the patients following AVR and TAVI. Methods : This prospective observational study involved 9 patients with surgical aortic valve replacement (AVR) and 7 patients with transcatheter aortic valve implantation (TAVI). Body composition was measured one day prior surgery, postoperative day (POD) 1, POD 3, POD 5 and POD 7. Hand grip strength, calf circumference and gait speed were measured one day before surgery and on the day of discharge. Results : Skeletal muscle was significantly decreased in AVR patients at postoperative day 3 and 7, while there was no change in TAVI patients. Patients with TAVI showed higher dietary intake after surgery compared to patients with AVR, and they maintained hand grip strength and calf circumference at discharge. Conclusions : In elderly patients with AS, TAVI can improve post-operative recovery maintaining nutritional status and physical function even. J. Med. Invest. 67 : 139-144, February, 2020.

SKF-10047, a prototype Sigma-1 receptor agonist, augmented the membrane trafficking and uptake activity of the serotonin transporter and its C-terminus-deleted mutant via a Sigma-1 receptor-independent mechanism.

The serotonin transporter (SERT) is functionally regulated via membrane trafficking. Our previous studies have demonstrated that the SERT C-terminal deletion mutant (SERTΔCT) showed a robust decrease in its membrane trafficking and was retained in the endoplasmic reticulum (ER), suggesting that SERTΔCT is an unfolded protein that may cause ER stress. The Sigma-1 receptor (SigR1) has been reported to attenuate ER stress via its chaperone activity. In this study, we investigated the effects of SKF-10047, a prototype SigR1 agonist, on the membrane trafficking and uptake activity of SERT and SERTΔCT expressed in COS-7 cells. Twenty-four hours of SKF-10047 treatment (>200 µM) accelerated SERT membrane trafficking and robustly upregulated SERTΔCT activity. Interestingly, these effects of SKF-10047 on SERT functions were also found in cells in which SigR1 expression was knocked down by shRNA, suggesting that SKF-10047 exerted these effects on SERT via a mechanism independent of SigR1. A cDNA array study identified several candidate genes involved in the mechanism of action of SKF-10047. Among them, Syntaxin3, a member of the SNARE complex, was significantly upregulated by 48 h of SKF-10047 treatment. These results suggest that SKF-10047 is a candidate for ER stress relief.

[The Analgesic Sparing Effect of Ketamine for Postoperative Pain Management after Pediatric Surgery on the Body Surface].

BACKGROUND: It is reported that ketamine, a N-methyl-D-aspertate (NMDA) receptor antagonist, can provide analgesic effect improving postoperative pain management and decrease the supplementary analgesic requirement. We investigated the analgesic sparing effect of ketamine for postoperative pain in children undergoing surgery of body surface. METHODS: Fifty eight patients (0-9 yrs) who had surgery of body surface were divided into two groups (ketamine : n = 27, Group K or control : n = 31, Group N). Postoperative analgesia extracted from charts was retrospectively evaluated by the times patients used analgesics until discharge after the operations. Chi-square and Mann-Whitney U tests were used for statistical analysis. Results : The ketamine group received an intrave- nous bolus of ketamine (1 mg - kg-1) before surgical skin incision. However, there were no significant differ- ences of usage (Group K vs Group N : 4/27 vs 7/31, P=0.45) and frequency of supplementary analgesic us- ages (P=0.85) among groups. In addition, there were also no significant demographic differences between the two groups. Conclusions : Our investigation suggests that the intravenous bolus of ketamine (1 mg - kg-1) before surgical skin incision does not decrease the supple- mentary analgesic requirements on postoperative pain management in pediatric surgery of the body surface.

[The Influence of Flurbiprofen on the Frequency of Postoperative Shivering].

BACKGROUND: Many methods to prevent postoperative shivering (POS) has been reported. However, there are few reports demonstrating the effect of flurbiprofen on POS which affects the set point in the thermocenter of the hypothalamus. METHODS: One hundred and forty six patients undergoing lung lobectomy or segmentectomy under video-assisted thoracic surgery were divided into a flurbiprofen-treated group (Group F) and a non-treated group (Group N). We retrospectively investigated the incidence of POS associated with total intravenous anesthesia with epidural anesthesia compared with or without flurbiprofen. We weighed the incidence of POS against age, body mass index, the effective site concentration of fentanyl on extubation, the mean dose of remifentanil, the minimum rectal temperature, the surgical duration and total hemorrhage volume based on the anesthetic chart Chi-square and Student t-test were used for statistical analysis. RESULTS: Although the surgical duration in Group F was shorter than that in Group N (223±83 vs. 165±80 (min), P<0.01), the incidence of POS in Group F was higher than that in Group N (1/32 vs. 28/114, P<0.01). There were no significant differences in another items between the two groups. CONCLUSIONS: The results of the study indicates that flurbiprofen has a possible beneficial effect in preventing POS.

[Case of drug-induced angioedema (DIAE) on induction of anesthesia with difficult ventilation due to oropharyngeal edema].

A 69-year-old man with a past history of hypertension on angiotensin II receptor blocker (ARB) for three months presented for radical prostatectomy. Immediately after induction of anesthesia with fentanyl and propofol, mask ventilation became difficult, although no significant hemodynamic changes occurred. Fiberoptic examination revealed severe oropharyngeal edema, but, the trachea was successfully intubated. Afterward, the operation proceeded without complications. He stayed in the ICU for 4 days until the trachea was extubated successfully. He was diagnosed with DIAE because of his history of dyspnea with exclusion of other possible pathophysiological conditions.