Ineko Kato

Endogenous erythropoietin from astrocyte protects the oligodendrocyte precursor cell against hypoxic and reoxygenation injury

The hypoxia‐responsive cytokine erythropoietin (EPO) provides neuroprotective effects in the damaged brain during ischemic events and neurodegenerative diseases. The purpose of the present study is to evaluate the EPO/EPO receptor (EPOR) endogenous system between astrocyte and oligodendrocyte precursor cell (OPC) under hypoxia. We report here elevated EPO mRNA levels and protein release in cultured astrocytes following hypoxic stimulation by quantitative RT‐PCR and ELISA. Furthermore, the EPOR gene expressions were detected in cultured OPCs as in astrocytes and microglias by quantitative RT‐PCR. Cell staining revealed the EPOR expression in OPC. To evaluate the protective effect of endogenous EPO from astrocyte to OPCs, EPO/EPOR signaling was blocked by EPO siRNA or EPOR siRNA gene silencing in in vitro study. The suppression of endogenous EPO production in astrocytes by EPO siRNA decreased the protection to OPCs against hypoxic stress. Furthermore, OPC with EPOR siRNA had less cell survival after hypoxic/reoxygenation injury. This suggested that EPO/EPOR signaling from astrocyte to OPC could prevent OPC damage under hypoxic/reoxygenation condition. Our present finding of an interaction between astrocytes and OPCs may lead to a new therapeutic approach to OPCs for use against cellular stress and injury.

Hemodynamics of the cerebral arteries of infants with periventricular leukomalacia.

OBJECTIVE. This study investigated the developmental changes in blood flow in each cerebral artery among infants with and without periventricular leukomalacia (PVL), to elucidate the time of onset of PVL. METHODS. Eight of 67 low birth weight infants were diagnosed through ultrasonography as having PVL with cyst formation. The mean cerebral blood flow velocities (CBFVs) in the anterior cerebral artery, middle cerebral arteries (MCAs), posterior cerebral arteries (PCAs), internal carotid arteries (ICAs), and basilar artery were measured with Doppler ultrasonography at postnatal days 0, 1, 2, 3, 4, 5, 7, 10, 14, 21, 28, 42, 56, and 70. Four of 8 infants with cyst formation and 1 of 59 infants without cyst formation developed cerebral palsy. RESULTS. The mean CBFVs of infants with PVL were significantly lower in the anterior cerebral artery (days 14–70), the right MCA (days 14–70), the left MCA (days 14–70), the right PCA (days 7–70), the left PCA (days 5–70), the right ICA (days 7–70), the left ICA (days 7–70), and the basilar artery (days 14 and 28–70). The CBFVs in all arteries were also lower among those with PVL than among intact infants on day 0. The CBFVs increased postnatally in the PCAs of infants with intact brains, whereas they remained unchanged after day 14 or 21 among infants with PVL. There was a significant difference in the prevalence of cerebral palsy between the 2 groups. CONCLUSIONS. We suggest that the total cerebral blood supply is decreased in cases of cystic PVL and that this reduction occurs just after birth, in a defined sequence, in the cerebral arteries. We conclude that the insult resulting in PVL might occur close to the time of birth.

Total hydroperoxide and biological antioxidant potentials in a neonatal sepsis model.

Oxidant/antioxidant imbalance plays an important role in septic shock. The present study examined changes in circulating oxidative components in a neonatal sepsis model. Subjects were 14 newborn mixed-strain piglets randomly divided into two groups: a cecal ligation and perforation (CLP) model (n = 7) and sham (n = 7). Blood samples for total hydroperoxide (TH), biological antioxidant potential (BAP), tumor necrosis factor (TNF) α, interleukin (IL)-6, and IL-10 were collected pre-CLP and at 1, 3, and 6 h post-CLP. TH and BAP levels at 1 h post-CLP were significantly higher in the CLP group than in the sham group. In the CLP group, TH decreased gradually and reached baseline levels by 6 h post-CLP, while BAP remained elevated. Linear correlations were identified between serum TH and BAP at 1 h post-CLP, serum TH and TNF-α at 1 h post-CLP, and BAP and IL-6 at 6 h post-CLP. Changes in and correlations between circulating oxidative and inflammatory state components in a neonatal sepsis model were clarified. This is the first study to reveal that the presence of oxidant/antioxidant imbalance in sepsis and septic shock changes during the disease course.

Arousal from sleep mechanisms in infants

Arousals from sleep allow sleep to continue in the face of stimuli that normally elicit responses during wakefulness and also permit awakening. Such an adaptive mechanism implies that any malfunction may have clinical importance. Inadequate control of arousal in infants and children is associated with a variety of sleep-related problems. An excessive propensity to arouse from sleep favors the development of repeated sleep disruptions and insomnia, with impairment of daytime alertness and performance. A lack of an adequate arousal response to a noxious nocturnal stimulus reduces an infants chances of autoresuscitation, and thus survival, increasing the risk for Sudden Infant Death Syndrome (SIDS). The study of arousability is complicated by many factors including the definition of an arousal; the scoring methodology; the techniques used (spontaneous arousability versus arousal responses to endogenous or exogenous stimuli); and the confounding factors that complicate the determination of arousal thresholds by changing the sleepers responses to a given stimulus such as prenatal drug, alcohol, or cigarette use. Infant age and previous sleep deprivation also modify thresholds. Other confounding factors include time of night, sleep stages, the sleepers body position, and sleeping conditions. In this paper, we will review these different aspects for the study of arousals in infants and also report the importance of these studies for the understanding of the pathophysiology of some clinical conditions, particularly SIDS.

Edaravone, a novel free radical scavenger, reduces high-mobility group box 1 and prolongs survival in a neonatal sepsis model.

Free radicals play an important role in the inflammatory process of sepsis. We hypothesized that edaravone, a novel free radical scavenger, can suppress pathophysiological events and prolong survival in a neonatal sepsis cecal ligation and perforation (CLP) model. Of 32 3-day-old anesthetized and mechanically ventilated piglets, 11 received CLP only, 10 received CLP and edaravone treatment starting 30 min after CLP, and 11 constituted a sham (control) group. Mean arterial pressure (MAP), heart rate, cardiac output, arterial blood gas, serum total hydroperoxide, nitrite and nitrate, TNF-&agr;, and high-mobility group box 1 (HMGB1) were measured before CLP and at 1, 3, and 6 h after CLP. Compared with the CLP group, the edaravone group showed higher MAP at 6 h, lower heart rate at 1 and 3 h, lower total hydroperoxide at 1 h, lower nitrite and nitrate at 3 and 6 h, and higher (although not significantly so) mean cardiac output at 1, 3, and 6 h. TNF-&agr; elevation was delayed from 1 h in the CLP group to 3 h in the edaravone group. In the edaravone group, HMGB1 did not change significantly at any time, whereas in the CLP group, it increased at 6 h. Survival times were longer in the edaravone group than in the CLP group (15.4 ± 1.4 vs. 10.2 ± 1 h; P < 0.005). In addition, each of the serial dilutions of edaravone had a higher biological antioxidant potential than tempol does. In conclusion, edaravone suppressed free radicals, delayed the TNF-&agr; surge, and prevented HMGB1 elevation, thereby maintaining MAP and prolonging survival time in a neonatal sepsis CLP model.

Effect of hemoperfusion using polymyxin B-immobilized fiber on IL-6, HMGB-1, and IFN gamma in a neonatal sepsis model.

To evaluate effects of polymyxin B direct hemoperfusion (PMX-DHP) on a neonatal sepsis cecal ligation and perforation (CLP) model, in 24 anesthetized and mechanically ventilated 3-d-old piglets, 16 were assigned to CLP and an arteriovenous extracorporeal circuit from 3 h until 6 h post-CLP, with a PMX-column in PMX-DHP–treated group (8 piglets) and 8 as sham. Plasma lipopolysaccharide (LPS) was measured at before CLP and at 3 and 9 h. Changes in mean systemic blood pressure (mSBP), mean pulmonary blood pressure, serum IL-6, tumor necrosis factor alpha, interferon gamma, and highly mobile group-1 box protein were measured before CLP and at 1, 3, 6, and 9 h. LPS was lower in the sham and PMX-DHP groups than in the control at 9 h. The mSBP was higher in the sham and PMX-DHP groups than in the control at both 6 h. IL-6 was lower in the sham and PMX-DHP groups than in the control at 6 h. HMGB-1 was lower in the PMX-DHP group than in the control at 6 h. IFN-γ was only detected in the control group at 9 h. Survival times in the PMX-DHP group were longer than in the control. Thus, PMX-DHP improved septic shock in a neonatal septic model.

Development and characterization of a novel porcine model of neonatal sepsis.

Sepsis and its sequela remain a major source of morbidity and mortality in neonates despite advances in antimicrobials and aggressive supportive care. Many models of neonatal sepsis have been developed for investigating the pathophysiology of this disease and application of therapy, and a model with an infectious focus is closer to clinical reality. To establish an animal model that mimics the clinical characteristics of neonatal sepsis, the cecal devascularization and perforation procedure was implemented on 15 mixed-strain newborn piglets, which produced an infectious focus that acted as a continuous source of microorganisms to the peritoneal cavity. The mean survival time in animals with sepsis was 10.4 h (range 5.5-17.9 h), whereas all of the sham-operated control animals survived more than 24 h. Animals with sepsis showed a gradual significant decrease in the mean systemic blood pressure (mSBP; 71 ± 3 mmHg in sepsis vs. 64 ± 3 mmHg in control at 3 h, 38 ± 7 mmHg in sepsis vs. 59 ± 4 mmHg in control at 6 h, mean ± SEM). They also showed an increase of serum levels of endotoxin (5.6 × 105 ± 4.5 × 105 pg/mL in sepsis vs. 6.0 × 102 ± 3.8 × 102 pg/mL in control at 6 h). Serum levels of TNF-α in the animals with sepsis became significantly higher than the control animals at 0 h (96 ± 31 pg/mL in sepsis vs. 12 ± 1 pg/mL in control) and remained significantly higher than all through the experiment. Serum levels of IL-6 in animals with sepsis showed a gradual increase (484 ± 231 pg/mL in sepsis in its peak at 6 h vs. 24 ± 5 pg/mL in control), however, there were no significant differences in serum IL-10 levels between the groups. Microorganisms detected in the blood of animals with sepsis were gram-negative enteric and anaerobic organisms. These results suggested that this model mimics the clinical state of neonatal sepsis and hence may have significant implications for the treatment of sepsis, including its use as a model in further investigations.

High cerebrospinal fluid antioxidants and interleukin 8 are protective of hypoxic brain damage in newborns

Abstract The objective was to explain the discrepancy in the development of hypoxic ischemic brain injury (HIE) in some asphyxiated newborns rather than others. Forty newborns were classified according to their cerebrospinal neuron-specific-enolase (CSF-NSE) levels on their 5th-day of life; group 1 with low-NSE (n = 25). The remaining 15 newborns had high-NSE and were further divided into a group with no HIE (n = 10, group 2) and another with HIE (n = 5, group 3). CSF-NSE, totalhydroperoxide (TH), biological-antioxidant-potentials (BAPs), 12 cytokines and Erythropoietin (EPO) were measured. The TH/BAP gave the oxidative-stress-index (OSI). The BAPs of serial dilutions of three types of EPO were tested. CSF-NSE and TH and mean OSIs were higher in group 3. IL-8 and mean BAPs were higher in group 2 than in group 1. EPO was less detected in group 3. Serial EPO dilutions correlated with their BAPs. Compensatory antioxidants and IL-8 elevation could be protective of perinatal asphyxic brain injury. Antioxidative effect of EPO could be neuroprotective.

High postnatal oxidative stress in neonatal cystic periventricular leukomalacia

Oxidative stress plays an important role in cystic periventricular leukomalacia (PVL). We performed a case-control study of preterm infants delivered at <35 weeks of gestation between January 2003 and December 2006. Patients were stratified into three groups, according to age at which cysts were initially identified: 10 days old (early cystic PVL; n=10), >10 days old (late cystic PVL; n=12); and no cystic PVL (controls; n=22). Serum total hydroperoxide, biological antioxidant potential and oxidative stress index (calculated as total hydroperoxide/biological antioxidant potential) were measured within 3h after birth. Frequencies of preterm rupture of membrane and chorioamnionitis were significant higher in early cystic PVL than in late cystic PVL or controls. Duration of oxygen treatment and mechanical ventilation and frequency of apnea were significantly higher in late cystic PVL than in controls or early cystic PVL. Serum total hydroperoxide levels and oxidative stress index were significantly higher in early cystic PVL than in late cystic PVL or controls (p<0.05, respectively). Postnatal duration until cyst identification displayed a significant negative correlation with oxidative stress index and total hydroperoxide level (r=-0.497, p<0.05; r=-0.50, p<0.05, respectively). These findings suggest that early onset of cystic PVL might be due to either antenatal or intrapartum factors, but late onset might be due to postnatal factors. In the pathophysiology and therapy of cystic PVL, oxidative stress and onset timing appear crucial. This is the first study to reveal that neonates experiencing much more oxidative stress at birth show earlier onset of cystic PVL.

Longitudinal Evaluation of Patients with a Homozygous R450H Mutation of the TSH Receptor Gene

Background/Aim: The R450H mutation of the TSH receptor (TSHR) gene has been frequently observed in Japanese patients with resistance to TSH. The purpose of this study was to clarify the phenotype of patients with a homozygous R450H mutation of the TSHR gene; the mutant receptor has previously demonstrated moderately impaired function in vitro. Methods: We performed a clinical investigation of 5 Japanese patients who had hyperthyrotropinemia as neonates, in whom a homozygous R450H mutation of the TSHR gene had been demonstrated by genetic sequencing analysis. Results: The thyroid hormone levels of the patients were normal in early infancy, although their serum levels of TSH were mildly elevated. After supplemental treatment with levothyroxine sodium (L-T4) was started, we had to increase the dose to maintain the level of TSH within the normal range in all patients. Thyroid dysfunction became obvious in one patient at reexamination during adolescence when L-T4 treatment was stopped for 1 month. Four patients were examined for intelligence quotient and their scores were normal. Conclusions: Thyroid hormone replacement therapy should be considered based on biological data in patients with hyperthyrotropinemia who have a homozygous R450H mutation of the TSHR gene even if they do not exhibit obvious hypothyroidism in infancy.