Hiroyuki Kinoshita

Inhibiting NADPH oxidase protects against long-term memory impairment induced by neonatal sevoflurane exposure in mice

BACKGROUNDnNeonatal exposure to anaesthetics such as sevoflurane has been reported to result in behavioural deficits in rodents. However, while oxidative injury is thought to play an underlying pathological role, the mechanisms of neurotoxicity remain unclear. In the present study, we investigated whether the NADPH oxidase inhibitor apocynin protects against long-term memory impairment produced by neonatal sevoflurane exposure in mice.nnnMETHODSnPostnatal day six mice were divided into four groups; (1) non-anaesthesia, (2) intraperitoneal apocynin (50 mg kg(-1)) treatment, (3) 3% sevoflurane exposure for 6 h, and (4) apocynin treatment combined with sevoflurane exposure. Superoxide concentrations and NADPH oxidase expression in the brain were determined using dihydroethidium fluorescence and immunoblotting, respectively. Cleaved caspase-3 immunoblotting was used for the detection of apoptosis, and cytochrome c immunoblotting was performed to evaluate mitochondrial function. Long-term cognitive impairment was evaluated using the fear conditioning test in adulthood.nnnRESULTSnSevoflurane exposure increased concentrations of superoxide (109%) and the NADPH oxidase subunit p22phox (39%) in the brain, and apocynin abolished these increases. Neonatal sevoflurane exposure caused learning deficits in adulthood. Apocynin also maintained long-term memory function in mice given neonatal sevoflurane exposure, and it reduced apoptosis and decreased cytochrome c concentrations in the brains of these mice.nnnCONCLUSIONSnApocynin reduces neuronal apoptosis and protects against long-term memory impairment in mice, neonatally exposed to sevoflurane by reducing superoxide concentrations. These findings suggest that NADPH oxidase inhibitors may protect against cognitive dysfunction resulting from neonatal anaesthesia.

Kynurenine causes vasodilation and hypotension induced by activation of KCNQ-encoded voltage-dependent K(+) channels.

Kynurenine is a potential contributor to hypotension in animal and human sepsis. The present study was designed to examine whether the voltage-dependent K(+) channels encoded by the KCNQ gene family (Kv7 channels) mediate vasodilator effects of kynurenine and whether modulation of these channels ameliorates hypotension caused by this compound. Rat aortas and mesenteric arteries or human omental arteries without endothelium were used. Some rings were incubated with the selective Kv7 channel inhibitor linopirdine (10xa0μM). l-Kynurenine (10xa0μM-1xa0mM) induced concentration-dependent relaxation in rat aortas and mesenteric arteries as well as human omental arteries, whereas linopirdine abolished the relaxation. l-Kynurenine (1xa0mM) produced hyperpolarization of vascular smooth muscle, which was reversed by linopirdine (10xa0μM). Wistar rats received l-kynurenine (1xa0mM) iv and subsequent linopirdine (10xa0μM) iv under 3% sevoflurane inhalation. l-Kynurenine iv caused hypotension, whereas linopirdine iv partially reversed it. In conclusion, kynurenine dilates arteries from rats as well as humans via Kv7 channels in the vascular smooth muscle. In rats, this tryptophan metabolite causes hypotension, which is partly counteracted by Kv7 channel inhibition. These results suggest that modulation of Kv7 channels may be a novel strategy to treat hypotension induced by the kynurenine.

The supine-to-prone position change induces modification of endotracheal tube cuff pressure accompanied by tube displacement

STUDY OBJECTIVESnTo determine whether the supine-to-prone position change displaced the endotracheal tube (ETT) and, if so, whether the displacement related to this change modified ETT cuff pressure.nnnDESIGNnProspective study.nnnSETTINGnOperating room of a university hospital.nnnPATIENTSn132 intubated, adult, ASA physical status 1, 2, and 3 patients undergoing lumbar spine surgery.nnnINTERVENTIONS AND MEASUREMENTSnAfter induction of anesthesia, each patients trachea was intubated. The insertion depth of each ETT was 23 cm for men and 21 cm for women at the upper incisors. In the supine position and after the supine-to-prone position change with the head rotated to the right, the length from the carina to ETT tip and ETT cuff pressure were measured.nnnMAIN RESULTSnAfter the supine-to-prone position change, 91.7% patients had ETT tube displacement. Of these, 48% of patients ETT moved ≥ 10 mm, whereas 86.3% of patients had changes in tube cuff pressure. There was a slight but significant correlation between ETT movement and change in cuff pressure. Depending on the position change, ETT cuff pressure decreased and the ETT tended to withdraw.nnnCONCLUSIONSnAfter the supine-to-prone position change, patients had ETT tube displacement. Such ETT movement may be accompanied by a decrease in cuff pressure.

Intermittent local periodontal inflammation causes endothelial dysfunction of the systemic artery via increased levels of hydrogen peroxide concomitantly with overexpression of superoxide dismutase

BACKGROUNDnThe present study was designed to examine whether the intermittent local periodontal inflammation induces endothelial dysfunction of the systemic artery caused by oxidative stress and if increased levels of hydrogen peroxide coexisted with overexpression of superoxide dismutase (SOD) as well as NADPH oxidase contribute to the oxidative stress.nnnMETHODSnThe rats in lipopolysaccharides (LPS) group received 1500μg LPS injection to bilateral gingiva of the lower jaw a week interval from eight- to eleven-week-old. Isolated mandibles or aortas were subjected to the evaluation of histopathological changes, isometric force recordings, reactive oxygen species using 2,7-dichlorofluorescin diacetate (10(-5)mol/L) and protein expression of NADPH oxidase subunits and SOD, respectively.nnnRESULTSnMandible sections demonstrated the periodontal inflammation only in the LPS group at three days, but not seven days, after the LSP injection. Acetylcholine (10(-9) to 10(-5)mol/L)-induced relaxation was reduced only in aortas from the LPS group. Gp91ds-tat and PEG-catalase restored the impaired dilation in arteries from the LPS group. Levels of reactive oxygen species were enhanced in aortas from the LPS group, whereas the increment was abolished by the treatment with gp91-ds-tat or PEG-catalase. Expression of a NADPH oxidase subunit p47phox and CuZn-SOD increased in the LPS group.nnnCONCLUSIONSnThe intermittent local periodontal inflammation induces systemic endothelial dysfunction caused by overproduction of reactive oxygen species in the systemic artery of rats and that overexpression of CuZn-SOD as well as a NADPH oxidase cytosolic subunit contributes to increased levels of hydrogen peroxide in blood vessels of this animal model.

Cerebral oxygenation in the beach chair position before and during general anesthesia in patients with and without cardiovascular risk factors

STUDY OBJECTIVESnTo evaluate changes in cerebral tissue oxygen index (TOI) values under the beach chair position before and during general anesthesia in surgical patients with or without cardiovascular risk factors.nnnDESIGNnProspective study.nnnSETTINGnOperating room in the university hospital.nnnPATIENTSnNinety-one patients undergoing surgery, including healthy patients (n = 28), patients with 1 cardiovascular risk factor (n = 33), and those with more than 1 risk factor (n = 30).nnnINTERVENTIONS AND MEASUREMENTSnCerebral TOI the day before and during general anesthesia was evaluated using a near-infrared spectroscopy NIRO-200 (Hamamatsu Photonics, Hamamatsu, Japan) for each patient. The initial TOI measurement in the supine position after a 10-minute rest or 10 minute after the endotracheal intubation was followed by measurements in 30° and subsequent 60° upright position for 5 minutes. Phenylephrine 0.1 mg and/or ephedrine 4 mg was administered intravenously to maintain mean blood pressure above 60 mm Hg accordingly.nnnMAIN RESULTSnThe beach chair position decreased mean arterial blood pressure and heart rate under general anesthesia, although patients with more than 1 cardiovascular risk factor needed significantly more phenylephrine doses to maintain mean blood pressure above 60 mm Hg. Values of TOI were within the normal range of about 70% before and during anesthesia in all groups.nnnCONCLUSIONSnThe beach chair position under general anesthesia did not alter cerebral oxygenation in patients with or without cardiovascular risk factors showing normal preoperative cerebral TOI values when the mean blood pressure was maintained above 60 mm Hg. The careful management using the cerebral oxygenation monitoring appears to maintain cerebral perfusion in the beach chair position during general anesthesia.

Human serum albumin and oxidative stress in preeclamptic women and the mechanism of albumin for stress reduction

Aims The present study to address one of the mechanisms in preeclampsia, examined whether levels of oxidative stress, human serum albumin, and endothelial function correlate in pregnant women and whether human serum albumin reduces levels of superoxide produced by NADPH oxidase activation in the human vascular smooth muscle cells. Materials and methods Pregnant women with (Preeclampsia group, n = 33) and without preeclampsia (Normal group, n = 37) were recruited to determine levels of reactive oxygen species (serum diacron-reactive oxygen metabolite [d-ROM]), and the flow-mediated dilation (FMD). Human coronary arterial smooth muscle cells or omental arteries were subjected to evaluate isometric force recordings, levels of superoxide, western immunoblotting, and immunohistochemistry. The superoxide scavenging assay was also performed in a cell-free system. Key findings Women in the preeclampsia group demonstrated lower FMD and higher serum d-ROM values than those in the normal group. There were the inverse correlations between serum levels of d-ROM and the degree of FMD and between serum levels of albumin and those of d-ROM. D-glucose reduced the levcromakalim-induced dilation of human omental arteries, and it increased levels of superoxide and the recruitment of the NADPH oxidase subunit p47phox in human coronary arterial smooth muscle cells. Human serum albumin (0.05 to 0.5 g/dL) prevented these alterations whereas it exerted no superoxide scavenging effect. Significance Serum albumin relates to oxidative stress inversely, but to the endothelial function positively, in pregnant women. Human serum albumin appears to reduce oxidative stress via NADPH oxidase inhibition in the human vascular smooth muscle, indicating that the serum level may be a critical determinant of vascular oxidative stress in some human diseases.

High oxygen modifies vasodilator effect of cysteine via enhanced oxidative stress and thromboxane production in the rat mesenteric artery

Whether high oxygen is harmful to the vascular function is unclear. The present study examined if high oxygen modifies vasodilator effect of cysteine via enhanced oxidative stress and thromboxane production. Rat mesenteric arteries with endothelium at 95 or 50xa0% oxygen were subjected to isometric force recordings, measurement of thromboxane B2 levels, determination of superoxide and peroxynitrite levels and evaluation of NADPH oxidase subunit protein expression, respectively. L-cysteine (0.01–3xa0mM) constricted or dilated arteries at 95 and 50xa0% oxygen, respectively. Thromboxane receptor antagonist SQ-29,548 (1xa0μM) abolished the constriction at 95xa0% oxygen. L-cysteine (3xa0mM) increased levels of thromboxane B2 in arteries upon 95xa0% oxygen application. L-cysteine relaxed arteries treated with superoxide inhibitor tiron (2xa0mM) or NADPH oxidase inhibitor gp91ds-tat (1xa0μM) irrespective of the oxygen concentration while ATP-sensitive K+ channel inhibitor glibenclamide (1xa0μM) and cystathionine-γ-lyase (CSE) inhibitor DL-propargylglycine (10xa0mM) similarly abolished the relaxation. L-cysteine (3xa0mM) with 95xa0% oxygen augmented levels of superoxide as well as nitrotyrosine within the artery, concomitantly with enhanced membrane protein expression of NADPH oxidase subunit p47phox. The higher concentration of oxygen attenuates L-cysteine-induced vasodilation via superoxide production mediated by NADPH oxidase along with thromboxane A2 production, resulting in vasoconstriction. The increased levels of superoxide, as well as peroxynitrite, coexist with the impaired vasodilation related to ATP-sensitive K+ channels and CSE. Higher oxygen with plasma cysteine may cause oxidative stress and vasoconstrictor prostanoid production in blood vessels.

Propofol reduces liver dysfunction caused by tumor necrosis factor-α production in Kupffer cells.

PurposeThe present study, conducted in rats, investigated whether propofol attenuates lipopolysaccharide (LPS)-triggered liver dysfunction via regulation of tumor necrosis factor (TNF)-α production in activated Kupffer cells.MethodsRats received LPS (500xa0μg/kg) under Urethane™ sedation (1xa0g/kg) in combination with propofol (5xa0mg/kg/h) or Intralipid™ from 1xa0h before to 6xa0h after LPS administration. Some rats were treated with 10 mg/kg gadolinium chloride (GdCl3) to induce Kupffer cell depletion. The serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), TNF-α mRNA and protein expression, caspase-3 activation and apoptosis were evaluated in hepatocytes. Immunofluorescence staining revealed expression of the pan-macrophage marker CD68 as well as TNF-α in Kupffer cells.ResultsALT and AST serum levels increased approximately four-fold in LPS-exposed rats compared with Intralipid™-treated rats at 6xa0h after LPS administration, whereas propofol and GdCl3 reduced the LPS-induced increases. LPS simultaneously augmented TNF-α expression in Kupffer cells, followed by increased caspase-3 activity and apoptosis in hepatocytes. Immunofluorescence staining and immunoblotting assay showed that TNF-α expression in Kupffer cells was inhibited by propofol and GdCl3, resulting in a reduction of caspase-3 activity and apoptosis in LPS-treated rat hepatocytes.ConclusionsPropofol (5xa0mg/kg/h) attenuated LPS-triggered liver dysfunction via inhibition of TNF-α production in activated Kupffer cells. These results suggest that propofol is capable of inhibiting inflammation-induced liver dysfunction in vivo.

Phosphatidylinositol 3-kinase inhibition induces vasodilator effect of sevoflurane via reduction of Rho kinase activity

Aims: This study was aimed to examine whether a volatile anesthetic sevoflurane in clinical doses reduces vasoconstriction under the inhibition of phosphatidylinositol 3‐kinase (PI3K) in the rat and human arteries and whether the intravenous administration of the PI3K inhibitor decreases blood pressure in rats under the sevoflurane inhalation. Materials and methods: Rat arteries (n = 5–6) and human omental arteries (n = 5–6) were subjected to isometric force recordings and western immunoblotting for Rho kinase, mitogen‐activated protein kinase, and protein kinase C. Some arteries were incubated with sevoflurane (1.5% or 3%), a selective PI3K inhibitor LY294002 (3 × 10− 6 mol/L) or the combination. Mean arterial pressure (MAP) and heart rate (HR) in rats (n = 7) were evaluated with or without intravenous injection of LY294002 (3 × 10− 6 mol/L) under 2% sevoflurane inhalation. Key findings: Sevoflurane with LY294002, but not sevoflurane or LY294002 solely, inhibited the phenylephrine‐induced contraction (32% to 52% decrease at phenylephrine [3 × 10− 6 mol/L] in rat arteries and [3 × 10− 5 mol/L] in human arteries). Sevoflurane (3%) only with LY294002 decreased Rho kinase activity in the rat aorta into 30%. Intravenous LY294002 reduced MAP (8.1–12.4 mm Hg decrease), but not HR, in rats under 2% sevoflurane inhalation. Significance: Clinical sevoflurane doses with PI3K inhibition reduce the contraction of rat and human arteries ex vivo resulting from Rho kinase inhibition, and systemic blood pressure of rats in vivo. These results suggest that sevoflurane potentially causes vasodilation and hypotension in patients receiving anti‐cancer therapy that inhibits PI3K.

Sevoflurane preconditioning ameliorates lipopolysaccharide-induced cognitive impairment in mice

Systemic inflammation induces brain neuronal inflammation, in turn causing acute cognitive disorders. Furthermore, neuronal inflammation is one cause of postoperative cognitive disorder (POCD) and delirium. However, no sufficiently established pharmacological treatment is available for neurocognitive inflammation. This study evaluated the possible neuroprotective effects of preconditioning with sevoflurane anesthesia on cognition and neuroinflammatory changes in an animal model of lipopolysaccharide (LPS)-induced systemic inflammation. Adult mice were randomly divided into (1) control, (2) 2% sevoflurane preconditioning for 1 h, (3) intraperitoneal 5 mg/kg LPS injection, and (4) 2% sevoflurane preconditioning for 1 h + LPS injection groups. At 24 h after 5 mg/kg LPS injection, microglial activation based on ionized calcium-binding adapter molecule 1 (Iba-1) expression in the hippocampus was determined using immunostaining and immunoblotting. IL-1β and IL-6 immunoblotting were used as inflammation markers, and β-site of amyloid precursor protein cleaving enzyme 1 (BACE1) immunoblotting was performed to evaluate amyloid β-protein (Aβ) accumulation. Long-term cognitive impairment was evaluated using fear conditioning tests. Intraperitoneal LPS increased levels of Iba-1 (150%), inflammation markers (160%), and Aβ accumulation (350%), and sevoflurane preconditioning suppressed these increases. Systemic LPS caused learning deficits. Sevoflurane also maintained long-term memory in mice receiving LPS injection. Sevoflurane preconditioning prevented long-term memory impairment in the mouse model administered systemic LPS by decreasing excessive microglial activation, inflammation, and Aβ accumulation. This study supports the hypothesis that sevoflurane preconditioning might also be beneficial for neuronal inflammation. Sevoflurane might be beneficial for reducing delirium and POCD.