Eiji Masaki

Gi-coupled γ-aminobutyric acid-B receptors cross-regulate phospholipase C and calcium in airway smooth muscle.

γ-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian central nervous system, and exerts its actions via both ionotropic (GABA(A)) and metabotropic (GABA(B)) receptors. Although the functional expression of GABA(B) receptors coupled to the G(i) protein was reported for airway smooth muscle, the role of GABA(B) receptors in airway responsiveness remains unclear. We investigated whether G(i)-coupled GABA(B) receptors cross-regulate phospholipase C (PLC), an enzyme classically regulated by G(q)-coupled receptors in human airway smooth muscle cells. Both the GABA(B)-selective agonist baclofen and the endogenous ligand GABA significantly increased the synthesis of inositol phosphate, whereas GABA(A) receptor agonists, muscimol, and 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol exerted no effect. The baclofen-induced synthesis of inositol phosphate and transient increases in [Ca(2+)](i) were blocked by CGP35348 and CGP55845 (selective GABA(B) antagonists), pertussis toxin (PTX, which inactivates the G(i) protein), gallein (a G(βγ) signaling inhibitor), U73122 (an inhibitor of PLC-β), and xestospongin C, an inositol 1,4,5-triphosphate receptor blocker. Baclofen also potentiated the bradykinin-induced synthesis of inositol phosphate and transient increases in [Ca(2+)](i), which were blocked by CGP35348 or PTX. Moreover, baclofen potentiated the substance P-induced contraction of airway smooth muscle in isolated guinea pig tracheal rings. In conclusion, the stimulation of GABA(B) receptors in human airway smooth muscle cells rapidly mobilizes intracellular Ca(2+) stores by the synthesis of inositol phosphate via the activation of PLC-β, which is stimulated by G(βγ) protein liberated from G(i) proteins coupled to GABA(B) receptors. Furthermore, crosstalk between GABA(B) receptors and G(q)-coupled receptors potentiates the synthesis of inositol phosphate, transient increases in [Ca(2+)](i), and smooth muscle contraction through G(i) proteins.

Perioperative infusion of dexmedetomidine at a high dose reduces postoperative analgesic requirements: a randomized control trial

PurposeWe hypothesized that a high dose of dexmedetomidine (1xa0μg/kg/h) could reduce postoperative analgesic requirements of patients.MethodsThis was a prospective, randomized, double-blind, placebo-controlled study carried out in Tohoku University Hospital. Thirty-two patients who underwent open gynecological abdominal surgery were randomly divided into a control (group C) and a dexmedetomidine group (group D). In both groups of patients, an epidural catheter was put in position prior to the induction of anesthesia, and continuous epidural infusion was started using a patient-controlled epidural analgesia (PCEA) pump. During the induction of anesthesia, group D patients received a loading dose of dexmedetomidine (1xa0μg/kg over 10xa0min), followed by a continuous infusion at a rate of 1xa0μg/kg/h. The patients in group C received a volume-matched infusion of normal saline as placebo. Consumption of PCEA bolus (local anesthetics) during the first postoperative 24xa0h, postoperative pain scores, and side effects related to the use of dexmedetomidine were recorded.ResultsDexmedetomidine (1xa0μg/kg/h) significantly reduced PCEA bolus consumption [15.9xa0±xa06.5 (group C) vs. 5.3xa0±xa05.0xa0ml (group D); Pxa0=xa00.0001] and postoperative pain scores. The infusion of dexmedetomidine produced no serious side effects, such as hemodynamic changes.ConclusionsAmong this small patient cohort, perioperative infusion of dexmedetomidine (1xa0μg/kg/h) resulted in antinociception without severe side effects. These results suggest that this method could be of interest with respect to improving postoperative pain status.

Modified versus conventional ultrafiltration in pediatric cardiac surgery: a meta-analysis of randomized controlled trials comparing clinical outcome parameters.

OBJECTIVEnAlthough previous studies have demonstrated that modified ultrafiltration improves laboratory parameters in pediatric cardiac surgery, the clinical outcome data have been inconsistent. We performed a meta-analysis of randomized controlled trials comparing modified versus conventional ultrafiltration.nnnMETHODSnWe conducted a comprehensive search of the literature to identify clinical trials that met our inclusion criteria. To be included, studies had to be prospective randomized trials that compared modified ultrafiltration and conventional ultrafiltration in pediatric cardiac surgery using cardiopulmonary bypass. We focused on the following outcome variables: hematocrit and mean arterial blood pressure after cardiopulmonary bypass, amount of chest tube drainage after surgery, time to extubation, and length of stay in the intensive care unit. The random effects model was used to determine the pooled effect estimates. The estimators of treatment effects were expressed as the weighted mean difference with 95% confidence intervals. The heterogeneity of collected data was also evaluated.nnnRESULTSnWe screened 54 studies, 8 of which satisfied our inclusion criteria. Combined analysis revealed that modified ultrafiltration resulted in significantly higher postbypass hematocrit and higher mean arterial blood pressure. Benefits in postoperative blood loss, ventilator time, and intensive care unit stay were not apparent. There was significant heterogeneity among the studies surveyed.nnnCONCLUSIONSnThe advantage of modified ultrafiltration over conventional ultrafiltration consists of significant improvement of clinical conditions in the immediate postbypass period. The postoperative outcome parameters were not significantly influenced. We should also take into account possible clinical or methodologic variations in the currently available ultrafiltration studies.

Pentax Airway Scope® vs Macintosh laryngoscope for tracheal intubation in adult patients: a systematic review and meta‐analysis

The Pentax Airway Scope® is a single‐use optical videolaryngoscope designed to assist with difficult tracheal intubation. We systematically reviewed the efficacy of the Pentax Airway Scope with that of a conventional laryngoscope for tracheal intubation in adults with ‘normal’ and ‘difficult’ airways. We included 17 randomised controlled trials with a total of 1801 participants. We used the DerSimonian and Laird random‐effects model to calculate pooled relative risk or weighted mean differences. The relative risk (95% CI) of a Cormack–Lehane grade‐1 laryngeal view was 2.40 (1.76–2.49) with the Pentax Airway Scope compared with the Macintosh laryngoscope, p < 0.00001. We found no other differences between the two laryngoscopes. Despite a superior laryngeal view, the Pentax Airway Scope provides little clinical benefit over the conventional laryngoscope.

Novel identification of the free fatty acid receptor FFAR1 that promotes contraction in airway smooth muscle

Obesity is one of the major risk factors for asthma. Previous studies have demonstrated that free fatty acid levels are elevated in the plasma of obese individuals. Medium- and long-chain free fatty acids act as endogenous ligands for the free fatty acid receptors FFAR1/GPR40 and FFAR4/GPR120, which couple to Gq proteins. We investigated whether FFAR1 and FFAR4 are expressed on airway smooth muscle and whether they activate Gq-coupled signaling and modulate airway smooth muscle tone. We detected the protein expression of FFAR1 and FFAR4 in freshly dissected native human and guinea pig airway smooth muscle and cultured human airway smooth muscle (HASM) cells by immunoblotting and immunohistochemistry. The long-chain free fatty acids (oleic acid and linoleic acid) and GW9508 (FFAR1/FFAR4 dual agonist) dose-dependently stimulated transient intracellular Ca(2+) concentration ([Ca(2+)]i) increases and inositol phosphate synthesis in HASM cells. Downregulation of FFAR1 or FFAR4 in HASM cells by small interfering RNA led to a significant inhibition of the long-chain free fatty acids-induced transient [Ca(2+)]i increases. Oleic acid, linoleic acid, or GW9508 stimulated stress fiber formation in HASM cells, potentiated acetylcholine-contracted guinea pig tracheal rings, and attenuated the relaxant effect of isoproterenol after an acetylcholine-induced contraction. In contrast, TUG-891 (FFAR4 agonist) did not induce the stress fiber formation or potentiate acetylcholine-induced contraction. These results suggest that FFAR1 is the functionally dominant free fatty acid receptor in both human and guinea pig airway smooth muscle. The free fatty acid sensors expressed on airway smooth muscle could be an important modulator of airway smooth muscle tone.

The dopamine D1 receptor is expressed and facilitates relaxation in airway smooth muscle

BackgroundDopamine signaling is mediated by Gs protein-coupled “D1-like” receptors (D1 and D5) and Gi-coupled “D2-like” receptors (D2-4). In asthmatic patients, inhaled dopamine induces bronchodilation. Although the Gi-coupled dopamine D2 receptor is expressed and sensitizes adenylyl cyclase activity in airway smooth muscle (ASM) cells, the Gs-coupled dopamine D1-like receptor subtypes have never been identified on these cells. Activation of Gs-coupled receptors stimulates cyclic AMP (cAMP) production through the stimulation of adenylyl cyclase, which promotes ASM relaxation. We questioned whether the dopamine D1-like receptor is expressed on ASM, and modulates its function through Gs-coupling.MethodsThe mRNA and protein expression of dopamine D1-like receptor subtypes in both native human and guinea pig ASM tissue and cultured human ASM (HASM) cells was measured. To characterize the stimulation of cAMP through the dopamine D1 receptor, HASM cells were treated with dopamine or the dopamine D1-like receptor agonists (A68930 or SKF38393) before cAMP measurements. To evaluate whether the activation of dopamine D1 receptor induces ASM relaxation, guinea pig tracheal rings suspended under isometric tension in organ baths were treated with cumulatively increasing concentrations of dopamine or A68930, following an acetylcholine-induced contraction with or without the cAMP-dependent protein kinase (PKA) inhibitor Rp-cAMPS, the large-conductance calcium-activated potassium (BKCa) channel blocker iberiotoxin, or the exchange proteins directly activated by cAMP (Epac) antagonist NSC45576.ResultsMessenger RNA encoding the dopamine D1 and D5 receptors were detected in native human ASM tissue and cultured HASM cells. Immunoblots confirmed the protein expression of the dopamine D1 receptor in both native human and guinea pig ASM tissue and cultured HASM cells. The dopamine D1 receptor was also immunohistochemically localized to both human and guinea pig ASM. The dopamine D1-like receptor agonists stimulated cAMP production in HASM cells, which was reversed by the selective dopamine D1-like receptor antagonists SCH23390 or SCH39166. A68930 relaxed acetylcholine-contracted guinea pig tracheal rings, which was attenuated by Rp-cAMPS but not by iberiotoxin or NSC45576.ConclusionsThese results demonstrate that the dopamine D1 receptors are expressed on ASM and regulate smooth muscle force via cAMP activation of PKA, and offer a novel target for therapeutic relaxation of ASM.

The dopamine D2 receptor is expressed and sensitizes adenylyl cyclase activity in airway smooth muscle

Dopamine receptors are G protein-coupled receptors that are divided into two subgroups, D(1)-like receptors (D(1) and D(5)) that couple to the G(s) protein and D(2)-like receptors (D(2), D(3), and D(4)) that couple to G(i). Although inhaled dopamine has been reported to induce bronchodilation in patients with asthma, functional expression of dopamine receptor subtypes has never been described on airway smooth muscle (ASM) cells. Acute activation of G(i)-coupled receptors inhibits adenylyl cyclase activity and cAMP synthesis, which classically impairs ASM relaxation. In contrast, chronic activation of G(i)-coupled receptors produces a paradoxical enhancement of adenylyl cyclase activity referred to as heterologous sensitization. We questioned whether the dopamine D(2)-like receptor is expressed on ASM, whether it exhibits classical G(i)-coupling, and whether it modulates ASM function. We detected the mRNA encoding the dopamine D(2) receptor in total RNA isolated from native human ASM and from cultured human airway smooth muscle (HASM) cells. Immunoblots identified the dopamine D(2) receptor protein in both native human and guinea pig ASM and cultured HASM cells. The dopamine D(2) receptor protein was immunohistochemically localized to both human and guinea pig ASM. Acute activation of the dopamine D(2) receptor by quinpirole inhibited forskolin-stimulated adenylyl cyclase activity in HASM cells, which was blocked by the dopamine D(2) receptor antagonist L-741626. In contrast, the chronic pretreatment (1 h) with quinpirole potentiated forskolin-stimulated adenylyl cyclase activity, which was inhibited by L-741626, the phospholipase C inhibitor U73122, or the protein kinase C inhibitor GF109203X. Quinpirole also stimulated inositol phosphate synthesis, which was inhibited by L-741626 or U73122. Chronic pretreatment (1 h) of the guinea pig tracheal rings with quinpirole significantly potentiated forskolin-induced airway relaxation, which was inhibited by L-741626. These results demonstrate that functional dopamine D(2) receptors are expressed on ASM and could be a novel therapeutic target for the relaxation of ASM.

Weekend versus weekday admission and short-term mortality: A meta-analysis of 88 cohort studies including 56,934,649 participants

Abstract It is widely accepted that higher mortality related to weekend admissions basically exists; however, there has been no systematic exploration of whether weekend admissions are associated with higher risk of death in patients on the basis of certain diagnoses, geographic regions, and study subtypes. A meta-analysis was performed according to the reporting guidelines of the Meta-analysis of Observational Studies in Epidemiology (MOOSE Compliant). Literature search was conducted using electronic databases. Primary outcome was short-term (⩽30-day) mortality. Patients were divided into 7 regions (North America, South America, Europe, Asia, Oceania, Africa, and Antarctica) for subgroup analyses and into 7 categories evaluating 24 major diagnoses. Pooled odds ratio (OR) with 95% confidence interval (CI) was calculated with DerSimonian and Laird random-effects models. Eighty-eight studies including 56,934,649 participants met our inclusion criteria. Overall pooled adjusted and crude OR of weekend to weekday admission for short-term mortality was 1.12 (95% CI, 1.07–1.18; I2u200a=u200a97%) and 1.16 (95% CI, 1.14–1.19; I2u200a=u200a97%), respectively. In subgroup analyses, higher risk of death on the weekend was significantly identified in patients living in all five continents (North America, South America, Europe, Asia, and Oceania). However, significant weekend effect was identified only in 15 of 24 diagnostic groups. Patients admitted on the weekend were more likely to die in an emergency situation (crude ORu200a=u200a1.17, 95% CI, 1.12–1.22). Although weekend admissions were associated with higher risk of death compared with weekday admissions on all five continents, the effect was limited to certain diagnostic groups and admission subtypes. Weekend effect remains highly heterogeneous and limited, suggesting that further well-conducted cohort studies might be informative.

Early Postoperative Nociceptive Threshold and Production of Brain-Derived Neurotrophic Factor Induced by Plantar Incision Are Not Influenced with Minocycline in a Rat: Role of Spinal Microglia.

Background: Brain-derived neurotrophic factor (BDNF) from spinal microglia is crucial for aberrant nociceptive signaling in several pathological pain conditions, including postoperative pain. We assess the contribution of spinal microglial activation and associated BDNF overexpression to the early post-incisional nociceptive threshold. Methods: Male Sprague-Dawley rats were implanted with an intrathecal catheter. A postoperative pain model was established by plantar incision. Thermal and mechanical nociceptive responses were assessed by infrared radiant heat and von Frey filaments before and after plantar incision. Rats were injected intrathecally the microglial activation inhibitor minocycline before incision, 24 h after incision, or both. Other groups were subjected to the same treatments and the L4-L5 spinal cord segment removed for immunohistochemical analysis of microglia activation and BNDF expression. Results: Plantar incision reduced both thermal latency and mechanical threshold, indicating thermal hypersensitivity and mechanical allodynia. Minocycline temporally reduced thermal withdrawal latency but had no effect on mechanical withdrawal threshold, spinal microglial activity, or dorsal horn BDNF overexpression during the early post-incision period. Conclusion: These results suggest that spinal microglia does not contribute substantially to post-incisional nociceptive threshold. The BDNF overexpression response that may contribute to postoperative hyperalgesia and allodynia is likely derived from other sources.

Esmolol modulates inhibitory neurotransmission in the substantia gelatinosa of the spinal trigeminal nucleus of the rat

Backgroundβ1-adrenaline receptor antagonists are often used to avoid circulatory complications during anesthesia in patients with cardiovascular diseases. Of these drugs, esmolol, a short-acting β antagonist, is also reported to exert antinociceptive and anesthetic sparing effects. This study was designed to identify the central mechanism underlying the antinociceptive effect of esmolol.MethodsWistar rats (7-21 d, 17-50 g) were anesthetized with ketamine (100-150 mg/kg) or isoflurane (5%) and decapitated. Horizontal slices (400-μm thick) of the lower brainstem containing the substantia gelatinosa (SG) of the caudal part of the spinal trigeminal nucleus (Sp5c), in which the nociceptive primary afferents form the first intracranial synapses, were made with a vibrating slicer. The miniature inhibitory and excitatory postsynaptic currents (mIPSCs and mEPSCs, respectively) were simultaneously recorded from visually identified SG neurons of the Sp5c in the presence of tetrodotoxin (1 μM). Additionally, mIPSCs were recorded during pharmacological isolation of GABA- and glycine-mediated mIPSCs with kynurenic acid (1 mM).ResultsEsmolol (500 μM) significantly and selectively increased the mIPSC frequency (to 214.2% ± 34.2% of the control, mean ± SEM, n = 35; P < 0.001), but not that of mEPSCs, without changing their amplitude. The increase in mIPSC frequency with esmolol was not affected by prior activation of β receptors with isoproterenol (100 μM) but it was significantly attenuated by removal of extracellular Ca2+.ConclusionsThese data suggest that esmolol modulates inhibitory transmitter release in the Sp5c through a mechanism involving Ca2+-entry but in a β1-adrenoceptor-independent manner. The present results suggest that the facilitation of inhibitory transmitter release in the central nociceptive network underlies, at least in part, the antinociceptive effect of esmolol.