Adenosine influences the high-affinity uptake of transmitter glutamate and aspartate under conditions of hepatic encephalopathy

The high-affinity uptake of transmitter glutamate and aspartate in hippocampal slices incubated in sera from patients with hepatic encephalopathy was dramatically reduced in neuropil areas by more than 50 % compared with the control level. Adenosine compensates for these reduction in reuptake capacity in a concentration-dependent fashion reaching normal values at 500 M adenosine. The renormalization of glutamate and aspartate uptake caused by adenosine might reasonably be expected to have potential therapeutic implications for the treatment of hepatic encephalopathy.     

Attenuation of Ethanol Withdrawal by Ceftriaxone-Induced Upregulation of Glutamate Transporter EAAT2

Alcohol withdrawal syndrome (AWS) is a potentially fatal outcome of severe alcohol dependence that presents a significant challenge to treatment. Although AWS is thought to be driven by a hyperglutamatergic brain state, benzodiazepines, which target the GABAergic system, comprise the first line of treatment for AWS. Using a rat model of ethanol withdrawal, we tested whether ceftriaxone, a β-lactam antibiotic known to increase the expression and activity of glutamate uptake transporter EAAT2, reduces the occurrence or severity of ethanol withdrawal manifestations. After a 2-week period of habituation to ethanol in two-bottle choice, alcohol-preferring (P) and Wistar rats received ethanol (4.0 g/kg) every 6 h for 3–5 consecutive days via gavage. Rats were then deprived of ethanol for 48 h during which time they received ceftriaxone (50 or 100 mg/kg, IP) or saline twice a day starting 12 h after the last ethanol administration. Withdrawal manifestations were captured by continuous video recording and coded. The evolution of ethanol withdrawal was markedly different for P rats vs Wistar rats, with withdrawal manifestations occurring >12 h later in P rats than in Wistar rats. Ceftriaxone 100 mg/kg per injection twice per day (200 mg/kg/day) reduced or abolished all manifestations of ethanol withdrawal in both rat variants and prevented withdrawal-induced escalation of alcohol intake. Finally, ceftriaxone treatment was associated with lasting upregulation of ethanol withdrawal-induced downregulation of EAAT2 in the striatum. Our data support the role of ceftriaxone in alleviating alcohol withdrawal and open a novel pharmacologic avenue that requires clinical evaluation in patients with AWS.     

Acute desipramine restores presynaptic cortical defects in murine experimental autoimmune encephalomyelitis by suppressing central CCL5 overproduction

Background and Purpose

Altered glutamate exocytosis and cAMP production in cortical terminals of experimental autoimmune encephalomyelitis (EAE) mice occur at the early stage of disease (13 days post-immunization, d.p.i.). Neuronal defects were paralleled by overexpression of the central chemokine CCL5 (also known as RANTES), suggesting it has a role in presynaptic impairments. We propose that drugs able to restore CCL5 content to physiological levels could also restore presynaptic defects. Because of its efficacy in controlling CCL5 overexpression, desipramine (DMI) appeared to be a suitable candidate to test our hypothesis.

Experimental Approach

Control and EAE mice at 13 d.p.i. were acutely or chronically administered DMI and monitored for behaviour and clinical scores. Noradrenaline and glutamate release, cAMP, CCL5 and TNF-α production were quantified in cortical synaptosomes and homogenates. Peripheral cytokine production was also determined.

Key Results

Noradrenaline exocytosis and α₂-adrenoeceptor-mediated activity were unmodified in EAE mice at 13 d.p.i. when compared with control. Acute, but not chronic, DMI reduced CCL5 levels in cortical homogenates of EAE mice at 13 d.p.i., but did not affect peripheral IL-17 and TNF-α contents or CCL5 plasma levels. Acute DMI caused a long-lasting restoration of glutamate exocytosis, restored endogenous cAMP production and impeded the shift from inhibition to facilitation of the CCL5-mediated control of glutamate exocytosis. Finally, DMI ameliorated anxiety-related behaviour but not motor activity or severity of clinical signs.

Conclusions

We propose DMI as an add-on therapy to normalize neuropsychiatric symptoms in multiple sclerosis patients at the early stage of the disease.     

Repeated Baclofen treatment ameliorates motor dysfunction,suppresses reflex activity and decreases the expression of signaling proteins in reticular nuclei and lumbar motoneurons after spinal trauma in rats

The interruption of supraspinal input to the spinal cord leads to motor dysfunction and the development of spasticity. Clinical studies have shown that Baclofen (a GABA_B agonist), while effective in modulating spasticity is associated with side-effects and the development of tolerance. The aim of the present study was to assess if discontinued Baclofen treatment and its repeated application leads antispasticity effects, and whether such changes affect neuronal nitric oxide synthase (nNOS) in the brainstem, nNOS and parvalbumin (PV) in lumbar α-motoneurons and glial fibrillary acidic protein in the ventral horn of the spinal cord. Adult male Wistar rats were exposed to Th9 spinal cord transection. Baclofen (30 mg/b.w.) diluted in drinking water, was administered for 6 days, starting at week 1 after injury and then repeated till week 4 after injury. The behavior of the animals was tested (tail-flick test, BBB locomotor score) from 1 to 8 weeks. Our results clearly indicate the role of nitric oxide, produced by nNOS in the initiation and the maintenance of spasticity states 1, 6 and 8 weeks after spinal trauma. A considerable decrease of nNOS staining after Baclofen treatment correlates with improvement of motor dysfunction. The findings also show that parvalbumin and astrocytes participate in the regulation of ion concentrations in the sub-acute phase after the injury.     

Metaplastic control of the endocannabinoid system at inhibitory synapses in hippocampus

The modifiability of neuronal response plasticity is called "metaplasticity." In suppressing synaptic inhibition and facilitating induction of long-term excitatory synaptic plasticity, endocannabinoids (eCBs) act as agents of metaplasticity. We now report the discovery of a calcium-dependent mechanism that regulates eCB mobilization by metabotropic glutamate receptor (mGluR) activation. The switch-like mechanism primes cells to release eCBs and requires a transient rise in intracellular Ca2+ concentration ([Ca2+]i) but not concurrent activation of mGluRs. Conversely, short-term, [Ca2+]i-dependent eCB release can be persistently enhanced by mGluR activation. Hence, eCBs are also objects of metaplasticity, subject to higher levels of physiological control.     

Time Course Analysis of the Effects of Botulinum Neurotoxin Type A on Pain and Vasomotor Responses Evoked by Glutamate Injection into Human Temporalis Muscles

The effect of botulinum neurotoxin type A (BoNTA) on glutamate-evoked temporalis muscle pain and vasomotor responses was investigated in healthy men and women over a 60 day time course. Subjects participated in a pre-BoNTA session where their responses to injection of glutamate (1 M, 0.2 mL) and saline (0.2 mL) into the temporalis muscles were assessed. On Day 1, BoNTA (5 U) was injected into one temporalis muscle and saline into the contralateral temporalis muscle, in a randomized order. Subjects then received intramuscular injections of glutamate (1 M, 0.2 mL) into the left and right temporalis muscles at 3 h and subsequently 7, 30 and 60 days post-injection of BoNTA. Pain intensity, pain area, and neurogenic inflammation (skin temperature and skin blood perfusion) were recorded. Prior to BoNTA treatment, glutamate evoked significantly greater pain and vasomotor reactions (P < 0.001) than saline. BoNTA significantly reduced glutamate-evoked pain intensity (P < 0.05), pain area (P < 0.01), skin blood perfusion (P < 0.05), and skin temperature (P < 0.001). The inhibitory effect of BoNTA was present at 3 h after injection, peaked after 7 days and returned to baseline by 60 days. Findings from the present study demonstrated a rapid action of BoNTA on glutamate-evoked pain and neurogenic inflammation, which is in line with animal studies.     

老年糖尿病患者血清GAD-Ab、ICA、IAA和IA-2-Ab联合检测的临床应用价值

[目的]探讨谷氨酸脱羧酶抗体（GAD-Ab）、胰岛细胞抗体（ICA）、胰岛自身抗体（IAA）和蛋白酪氨酸磷酸酶抗体（IA-2-Ab）联合检测对老年糖尿病患者的应用价值.[方法]采用免疫印迹法检测330例老年糖尿病患者和40例正常人血清中GAD-Ab、ICA、IAA和IA-2-Ab,并对四项自身抗体全阴患者与有一项以上阳性患者的空腹血糖（FBG）、餐后两小时血糖（2hPBG）和糖化血红蛋白（HbA1c）等血液生化指标进行比较.[结果]430例老年糖尿病患者GAD-Ab、ICA、IAA和IA-2-Ab的阳性率分别为39.7%、28.5%、17.0%和16.4%,四项自身抗体全阴患者124例,占37.6%,与有一项以上阳性患者比较,其FPG、2hPBG和HbA1c水平无显著差异（P〉0.05）.[结论]四项联合检测对老年糖尿病患者的诊断及治疗方案的制定有重要意义     

谷氨酸转运体-1在H2S保护PC12细胞对抗化学性低氧损伤中的作用

目的探讨谷氨酸转运体-1（GLT-1）在硫化氢（H2S）保护PC12细胞对抗化学性低氧损伤中的作用。方法应用化学性低氧模拟剂氯化钴（CoCl2）处理PC12细胞建立化学性低氧损伤模型作为研究对象。实验分为6组,正常对照组：未经任何药物处理的PC12细胞;CoCl2处理组：PC12细胞用600μmol/L的CoCl2处理24h或48h;H2S单独处理组;H2S预处理组：400μmol/L NaHS（H2S的供体）提前30min作用PC12细胞,然后与CoCl2一起再作用24h或48h;DHK（一种GLT-1抑制剂）单独处理组;DHK阻断组：在NaHS预处理前30min,给以400μmol/L DHK,然后按H2S预处理组继续处理。应用蛋白免疫印迹法（Western bolt）检测GLT-1蛋白表达;CCK-8比色法测定细胞存活率;Hoechst33258核染色法检测细胞凋亡的形态学改变及数量改变;罗丹明123（Rh123）染色及荧光显微镜照相测定线粒体膜电位（MMP）。结果 600μmol/L CoCl2处理PC12细胞24h可使GLT-1表达明显减少;在CoCl2处理PC12细胞前应用400μmol/L NaHS预处理30min能明显地阻断CoCl2对GLT-1表达的抑制作用;400μmol/L的GLT-1抑制剂DHK能阻断H2S保护PC12细胞对抗CoCl2诱导的损伤作用,使细胞存活率降低,凋亡细胞数量及MMP丢失增多。结论上调GLT-1表达可能是H2S保护PC12细胞对抗CoCl2损伤的作用机制之一。     

氯胺酮对谷氨酸诱导大鼠大脑皮层星形胶质细胞自噬的影响

目的观察氯胺酮对谷氨酸诱导的大鼠大脑皮层星形胶质细胞自噬的影响。方法取新生大鼠大脑皮层,原代混合培养、分离、纯化获得星形胶质细胞。实验分3个组：对照组（C组,加入D-Hank＇s液）;谷氨酸组（G组,加入谷氨酸至终浓度125μmol/L）;谷氨酸和氯胺酮组（GK组,先加入谷氨酸至终浓度125μmol/L,30 min后加入氯胺酮至终浓度1 mmol/L）。用相差显微镜观察细胞形态变化,免疫荧光染色鉴定细胞种类及LC3蛋白在细胞内的表达,通过Western blot法检测beclin-1、bcl-2、LC3蛋白的表达变化。结果 G组细胞内beclin-1、beclin-1/bcl-2、LC3Ⅱ/LC3Ⅰ蛋白表达较C组上升,bcl-2蛋白表达较C组下降（均P〈0.05）。GK组细胞内beclin-1、beclin-l/bcl-2、LC3Ⅱ/LC3Ⅰ蛋白表达较G组下降,bcl-2蛋白表达较G组上升（均P〈0.05）。结论 125μmol/L谷氨酸能促进星形胶质细胞发生自噬和凋亡,1 mmol/L氯胺酮可抑制谷氨酸诱导星形胶质细胞发生的自噬和凋亡。