Mitsuko Numazaki

Structural determinant of TRPV1 desensitization interacts with calmodulin.

The capsaicin receptor, TRPV1 (VR1), is a sensory neuron-specific ion channel that serves as a polymodal detector of pain-producing chemical and physical stimuli. Extracellular Ca2+-dependent desensitization of TRPV1 observed in patch–clamp experiments when using both heterologous expression systems and native sensory ganglia is thought to be one mechanism underlying the paradoxical effectiveness of capsaicin as an analgesic therapy. Here, we show that the Ca2+-binding protein calmodulin binds to a 35-aa segment in the C terminus of TRPV1, and that disruption of the calmodulin-binding segment prevents TRPV1 desensitization. Compounds that interfere with the 35-aa segment could therefore prove useful in the treatment of pain.

Increased sensitivity of desensitized TRPV1 by PMA occurs through PKCε-mediated phosphorylation at S800

Abstract Important mechanisms that regulate inhibitory and facilitatory effects on TRPV1‐mediated nociception are desensitization and phosphorylation, respectively. Using Ca2+‐imaging, we have previously shown that desensitization of TRPV1 upon successive capsaicin applications was reversed by protein kinase C activation in dorsal root ganglion neurons and CHO cells. Here, using both Ca2+‐imaging and patch‐clamp methods, we show that PMA‐induced activation of PKC&egr; is essential for increased sensitivity of desensitized TRPV1. TRPV1 has two putative substrates S502 and S800 for PKC&egr;‐mediated phosphorylation. Patch‐clamp analysis showed that contribution of single mutant S502A or S800A towards increased sensitivity of desensitized TRPV1 is indistinguishable from that observed in a double mutant S502A/S800A. Since S502 is a non‐specific substrate for TRPV1 phosphorylation by kinases like PKC, PKA or CAMKII, evidence for a role of PKC specific substrate S800 was investigated. Evidence for in vivo phosphorylation of TRPV1 at S800 was demonstrated for the first time. We also show that the expression level of PKC&egr; paralleled the amount of phosphorylated TRPV1 protein using an antibody specific for phosphorylated TRPV1 at S800. Furthermore, the anti‐phosphoTRPV1 antibody detected phosphorylation of TRPV1 in mouse and rat DRG neurons and may be useful for research regarding nociception in native tissues. This study, therefore, identifies PKC&egr; and S800 as important therapeutic targets that may help regulate inhibitory effects on TRPV1 and hence its desensitization.

DIP (mDia interacting protein) is a key molecule regulating Rho and Rac in a Src‐dependent manner

Cell movement is driven by the coordinated regulation of cytoskeletal reorganization through Rho GTPases downstream of integrin and growth‐factor receptor signaling. We have reported that mDia, a target protein of Rho, interacts with Src and DIP. Here we show that DIP binds to p190RhoGAP and Vav2, and that DIP is phosphorylated by Src and mediates the phosphorylation of p190RhoGAP and Vav2 upon EGF stimulation. When endogenous DIP was inhibited by expressing dominant‐negative mutants of DIP or siRNA, phosphorylation of p190RhoGAP and Vav2 upon EGF stimulation was diminished, and EGF‐induced actin organization, distribution of p190RhoGAP and Vav2, and cell movement were affected. Therefore, DIP seems to transfer the complex of the three proteins from cytosol to beneath the membrane, and the three proteins, in turn, can be phosphorylated by Src. DIP inactivated Rho and activated Rac following EGF stimulation in the membrane fraction. Thus, DIP acts as a regulatory molecule causing Src kinase‐dependent feedback modulation of Rho GTPases downstream of Rho‐mDia upon EGF stimulation, and plays an important role in cell motility.

RETRACTED: Reduction of emetic symptoms during cesarean delivery with antiemetics: propofol at subhypnotic dose versus traditional antiemetics

STUDY OBJECTIVE To evaluate the efficacy and safety of propofol (at a subhypnotic dose), droperidol, and metoclopramide in reducing emetic symptoms during cesarean delivery. DESIGN Randomized, double-blinded, placebo-controlled study. SETTING University hospital. PATIENTS 100 ASA physical status I and II parturients undergoing cesarean delivery with spinal anesthesia. INTERVENTIONS Patients received placebo (saline) followed by placebo (Intralipid(R)), placebo (saline) followed by propofol at a subhypnotic dose (1.0 mg/kg/hr), droperidol 1.25 mg followed by placebo (Intralipid(R)), or metoclopramide 10 mg followed by placebo (Intralipid(R)) intravenously (IV) immediately after clamping of the umbilical cord. MEASUREMENT AND MAIN RESULTS The percentage of patients who were emesis-free, which was defined as experiencing no nausea, retching, or vomiting, in the intraoperative, postdelivery period was 80% with propofol, 80% with droperidol, and 78% with metoclopramide (p < 0.05), compared with placebo (40%). Severity of nausea was less inpatients who received propofol than in those who received placebo (p < 0.05), and there were no differences seen among the droperidol, metoclopramide, and placebo groups. No clinically serious adverse events as a result of the study drugs were observed in any of the groups. CONCLUSIONS Prophylactic antiemetic efficacy of propofol at a subhypnotic dose (1.0 mg/kg/hr), droperidol 1.25 mg, and metoclopramide 10 mg is comparable in parturients undergoing cesarean delivery. Moreover, propofol at a subhypnotic dose is effective in the prevention of severe nausea.

Dose-range effects of propofol for reducing emetic symptoms during cesarean delivery

OBJECTIVE To evaluate the efficacy and safety of propofol at subhypnotic doses for reducing emetic symptoms in parturients undergoing cesarean delivery under spinal anesthesia. METHODS In a randomized, double‐masked trial, 80 patients received lidocaine intravenously 0.1 mg/kg (for injection pain relief) followed by either placebo or propofol at three different doses (0.5 mg/kg per hour, 1.0 mg/kg per hour, 2.0 mg/kg per hour) (n = 20 in each group) immediately after clamping of the umbilical cord. Emetic episodes and safety assessments were performed during spinal anesthesia for cesarean delivery. To estimate a sufficient sample size, it was calculated that 20 patients per group would be required with &agr; = .05 and β = .2. RESULTS The rate of patients experiencing no emetic symptoms in an intraoperative, postdelivery period was 45% with propofol 0.5 mg/kg per hour (P = .5), 80% with propofol 1.0 mg/kg per hour (P = .011), and 80% with propofol 2.0 mg/kg per hour (P = .011), compared with placebo (40%). No clinically serious adverse events caused by the study drugs were observed. CONCLUSION Propofol 1.0 mg/kg per hour is the minimum effective subhypnotic dose for reducing emetic symptoms during cesarean delivery. Increasing the dose to 2.0 mg/kg per hour provides no further benefit.

Randomized, double-blind comparison of subhypnotic-dose propofol alone and combined with dexamethasone for emesis in parturients undergoing cesarean delivery

BACKGROUND Nausea, retching, and vomiting are common in parturients undergoing cesarean delivery performed under regional anesthesia. Subhypnotic-dose propofol 1.0 mg/kg per hour has been used to reduce the incidence of these emetic symptoms. Dexamethasone has been shown to reduce chemotherapy-induced emesis when added to an antiemetic regimen. OBJECTIVE The aim of this study was to examine the difference in efficacy and tolerability between subhypnoticdose propofol 1.0 mg/kg per hour alone and combined with dexamethasone 8 mg for reducing postdelivery emetic episodes in parturients undergoing cesarean delivery. METHODS In a randomized, double-blind trial, parturients received IV placebo (saline) or dexamethasone 8 mg followed by a continuous infusion of propofol at subhypnotic dose (1.0 mg/kg per hour) immediately after clamping of the umbilical cord. Intraoperative, postdelivery emetic episodes and safety assessments were performed by an investigator. RESULTS One hundred twenty parturients (mean [SD] age, 29 [5] years; age range, 21-38 years; mean [SD] height, 158 [7] cm; height range, 145-172 cm; mean [SD] body weight, 72 [8] kg; weight range, 54-90 kg) were enrolled in the study, 60 in each treatment group. The treatment groups were comparable with respect to maternal demographics and operative management. The rate of emetic symptoms (nausea, retching, and vomiting) in an intraoperative, postdelivery period was lower in patients who received the combination regimen than in those who received subhypnotic-dose propofol 1.0 mg/kg per hour alone (5% [3/60] vs 20% [12/60], respectively; P = 0.012). No clinically important adverse events attributable to the study drug were observed in either group. CONCLUSION In the parturients undergoing cesarean delivery performed under spinal anesthesia in this study, the combination of subhypnotic-dose propofol 1.0 mg/kg per hour and dexamethasone 8 mg was more effective than propofol alone for reducing the incidence of postdelivery emetic symptoms.

Retraction Note to: Antiemetic efficacy of propofol at small doses for reducing nausea and vomiting following thyroidectomy

To our readers: Further to the Expression of Concern* posted online on February 15, 2013, it is with considerable regret that the Canadian Journal of Anesthesia hereby retracts the abovecited article by Dr. Yoshitaka Fujii as a result of: 1) overwhelming evidence of fabrication relating to the fact that the distributions of many variables reported by Dr. Fujii in these studies are exceedingly unlikely; and 2) the inability of Dr. Fujii’s institution to attest to the integrity of the study and/or the data conducted under its auspices, as set out in the Joint Editors-in-Chief Request for Determination of April 9, 2012. We extend our sincere appreciation to University of Tsukuba Institute of Clinical Medicine for their review of the status of Dr. Fujii’s research and to the investigating committee for their review of his research findings.