Norepinephrine-induced downregulation of GLT-1 mRNA in rat astrocytes.

AIM OF THE RESEARCH: Glutamate transporter-1 (GLT-1; also known as excitatory amino acid transporter 2) plays an important role in the maintenance of glutamate homeostasis in the synaptic cleft. Downregulation of GLT-1 in the spinal cord has been reported in chronic pain models, which suggests that GLT-1 is involved in the development of chronic pain. However, the mechanism by which GLT-1 is downregulated in the spinal cord is still unknown. We hypothesized that norepinephrine is involved in the regulation of GLT-1. The aim of this study was to investigate the effect of norepinephrine on GLT-1 expression in cultured astrocytes. METHODS: This study involved both in vivo and in vitro experiments. We first validated changes in GLT-1 mRNA expression in the spinal cord of rats with spared nerve injury (SNI) using real-time RT-PCR. Next, cultured primary astrocytes from the rat spinal cord were stimulated with norepinephrine, and GLT-1 mRNA was subsequently quantitated. RNB cells, an astrocytic cell line, were also stimulated with norepinephrine and other α-adrenoceptor agonists. RESULTS: SNI resulted in bilateral downregulation of GLT-1 in rat spinal cord. The in vitro study showed that norepinephrine and phenylephrine dose-dependently downregulated GLT-1 in primary astrocytes and RNB cells. Furthermore, the effect of norepinephrine was reversed by an α-adrenoceptor antagonist. CONCLUSION: Norepinephrine downregulates GLT-1 mRNA expression in astrocytes via the α1-adrenoceptor. Our results provide new insight into the mechanisms involved in downregulation of GLT-1 in the chronic pain models.

Quercetin Attenuates Neuropathic Pain in Rats with Spared Nerve Injury.

Quercetin is a flavonoid widely found in plants and marketed to the public as a supplement. Several studies have reported its effect on glial cells. This study aimed to examine the effect of quercetin on the development of neuropathic pain and the underlying mechanism in a spared nerve injury (SNI) rat model. Male Sprague-Dawley rats randomly assigned to the control or the quercetin group were subjected to SNI of the sciatic nerve. We measured pain behaviors on the hind paw and glial fibrillary acidic protein (GFAP) in the dorsal root ganglion (DRG) and spinal cord. Oral administration of 1% quercetin, begun before surgery, attenuated mechanical allodynia compared to the control group at days 7 and 10 after SNI. On the other hand, established pain was not attenuated in a post-dose group in which quercetin was begun 7 days after SNI. Quercetin inhibited GFAP in the satellite glial cells of the ipsilateral L5 DRG on day 7 compared to the control group. Quercetin suppressed the development of neuropathic pain through a mechanism partly involving the inhibition of satellite glial cells. As its safety is well established, quercetin has great potential for clinical use in pain treatment.

Urinary Albumin Levels Predict Development of Acute Kidney Injury After Pediatric Cardiac Surgery: A Prospective Observational Study.

OBJECTIVE: Mortality and morbidity of acute kidney injury (AKI) after cardiac surgery still remain high. The authors undertook the present study to evaluate the utility of early postoperative urinary albumin (uAlb) as a diagnostic marker for predicting occurrence of AKI and its severity in pediatric patients undergoing cardiac surgery. DESIGN: A prospective observational study. SETTING: A single-institution university hospital. PARTICIPANTS: All patients<18 years of age who underwent repair of congenital heart disease with cardiopulmonary bypass between July 2010 and July 2012 were included in the study. Neonates age<1 month were excluded from the study population. INTERVENTIONS: The association between uAlb and occurrence of AKI within 3 days after admission to the intensive care unit was investigated. Criteria from pediatric-modified Risk Injury Failure Loss and End-stage kidney disease (pRIFLE) were used to determine the occurrence of AKI. The value of uAlb was measured at intensive care unit admission immediately after cardiac surgery in all participants from whom a 5-mL urine sample was obtained. MEASUREMENTS AND MAIN RESULTS: Of 376 patients, AKI assessed by pRIFLE was identified in 243 (64.6%): 172 for risk (R; 45.7%), 44 for injury (I; 11.7%), and 27 for failure (F; 7.2%). One hundred thirty-three patients (35.4%) were classified as being without AKI (normal [N]) by pRIFLE. The concentration of uAlb was significantly higher in AKI patients than in non-AKI patients (median [interquartile range]): uAlb (µg/mL): 13.5 (6.4-39.6) v 6.0 (3.4-16), p<0.001; uAlb/Cr (mg/gCr): 325 (138-760) v 121 (53-269), p< 0.001. CONCLUSIONS: The utility of uAlb for prompt diagnosis of AKI was shown. Obtaining uAlb measurements early after pediatric cardiac surgery may be useful for predicting the occurrence and severity of AKI.

Methylation and intratumoural heterogeneity of 14-3-3 sigma in oral cancer.

14-3-3 sigma has been a major G2/M checkpoint control gene and has demonstrated that its inactivation in various cancers occurs mostly by epigenetic hypermethylation, not by genetic change. This study investigated the methylation status and expression of the 14-3-3 sigma gene in 46 oral squamous cell carcinomas by methylation-specific polymerase chain reaction, reverse transcriptase-polymerase chain reaction, Western blotting and immunohistochemistry. Exons of the p53 gene were examined for mutations by sequencing analysis and CyclinD1 by immunohistochemistry. Methylation of the 14-3-3 sigma gene was detected in 13% (6/46) of the oral tumours, but not in corresponding adjacent non-malignant and normal gingival tissues. Intratumoural heterogeneity was found in the tumour tissues including three 14-3-3 sigma-methylated samples. Methylation of 14-3-3 sigma was detected in 3 SCC with p53 mutations and 3 with wild-type p53. Our major findings are: (a) methylation of 14-3-3 gene promoter is a rare event in oral cancer; (b) it is not always associated with 14-3-3 protein levels and there is no clear relationship between its methylation and p53 mutation; (c) loss of 14-3-3 sigma expression is associated with reduced CyclinD1 gene expression.

Up-regulation of brain-derived neurotrophic factor in the dorsal root ganglion of the rat bone cancer pain model.

Metastatic bone cancer causes severe pain, but current treatments often provide insufficient pain relief. One of the reasons is that mechanisms underlying bone cancer pain are not solved completely. Our previous studies have shown that brain-derived neurotrophic factor (BDNF), known as a member of the neurotrophic family, is an important molecule in the pathological pain state in some pain models. We hypothesized that expression changes of BDNF may be one of the factors related to bone cancer pain; in this study, we investigated changes of BDNF expression in dorsal root ganglia in a rat bone cancer pain model. As we expected, BDNF mRNA (messenger ribonucleic acid) and protein were significantly increased in L3 dorsal root ganglia after intra-tibial inoculation of MRMT-1 rat breast cancer cells. Among the eleven splice-variants of BDNF mRNA, exon 1-9 variant increased predominantly. Interestingly, the up-regulation of BDNF is localized in small neurons (mostly nociceptive neurons) but not in medium or large neurons (non-nociceptive neurons). Further, expression of nerve growth factor (NGF), which is known as a specific promoter of BDNF exon 1-9 variant, was significantly increased in tibial bone marrow. Our findings suggest that BDNF is a key molecule in bone cancer pain, and NGF-BDNF cascade possibly develops bone cancer pain.