The astrocyte glutamate transporter, GLT1, is responsible for the vast majority of glutamate uptake in the adult central nervous system (CNS), thereby regulating extracellular glutamate homeostasis and preventing excitotoxicity. Glutamate dysregulation plays a central role in outcome following traumatic spinal cord injury (SCI). To determine the role of GLT1 in secondary cell loss following SCI, mice heterozygous for the GLT1 astrocyte glutamate transporter (GLT1+/−) and wild-type mice received thoracic crush SCI. Compared to wild-type controls, GLT1+/− mice had an attenuated recovery in hindlimb motor function, increased lesion size, and decreased tissue sparing. GLT1+/− mice showed a decrease in intraspinal GLT1 protein and functional glutamate uptake compared to wild-type mice, accompanied by increased apoptosis and neuronal loss following crush injury. These results suggest that astrocyte GLT1 plays a role in limiting secondary cell death following SCI, and also show that compromise of key astrocyte functions has significant effects on outcome following traumatic CNS injury. These findings also suggest that increasing intraspinal GLT1 expression may represent a therapeutically relevant target for SCI treatment.

Glutamate is the predominant excitatory amino acid neurotransmitter in the mammalian central nervous system (CNS). Glutamate transporter EAAT2 /GLT-1 is the physiologically dominant astroglial protein that inactivates synaptic glutamate. Previous studies have shown that EAAT2 dysfunction leads to excessive extracellular glutamate and may contribute to various neurological disorders including amyotrophic lateral sclerosis (ALS). The recent discovery of the neuroprotective properties of ceftriaxone, a beta lactam antibiotic, suggested that increasing EAAT2 /GLT-1 gene expression might be beneficial in ALS and other neurological/psychiatric disorders by augmenting astrocytic glutamate uptake. Here we report our efforts to develop a new screening assay for identifying compounds that activate EAAT2 gene expression. We generated fetal derived-human immortalized astroglial cells that are stably expressing a firefly luciferase reporter under the control of the human EAAT2 promoter. When screening a library of 1040 FDA approved compounds and natural products, we identified harmine, a naturally occurring beta-carboline alkaloid, as one of the top hits for activating the EAAT2 promoter. We further tested harmine in our in vitro cell culture systems and confirmed its ability to increase EAAT2/GLT1 gene expression and functional glutamate uptake activity. We next tested its efficacy in both wild type animals and in an ALS animal model of disease and demonstrated that harmine effectively increased GLT-1 protein and glutamate transporter activity in vivo. Our studies provide potential novel neurotherapeutics by modulating the activity of glutamate transporters via gene activation.

Shilajit, a medicine herb commonly used in Ayurveda, has been reported to contain at least 85 minerals in ionic form that act on a variety of chemical, biological, and physical stressors. The substantia gelatinosa (SG) neurons of the trigeminal subnucleus caudalis (Vc) are involved in orofacial nociceptive processing. Shilajit has been reported to be an injury and muscular pain reliever but there have been few functional studies of the effect of Shilajit on the SG neurons of the Vc. Therefore, whole cell and gramicidin-perfotrated patch clamp studies were performed to examine the action mechanism of Shilajit on the SG neurons of Vc from mouse brainstem slices. In the whole cell patch clamp mode, Shilajit induced short-lived and repeatable inward currents under the condition of a high chloride pipette solution on all the SG neurons tested. The Shilajit-induced inward currents were concentration dependent and maintained in the presence of tetrodotoxin (TTX), a voltage gated Na+ channel blocker, CNQX, a non-NMDA glutamate receptor antagonist, and AP5, an NMDA receptor antagonist. The Shilajit-induced responses were partially suppressed by picrotoxin, a GABAA receptor antagonist, and totally blocked in the presence of strychnine, a glycine receptor antagonist, however not affected by mecamylamine hydrochloride (MCH), a nicotinic acetylcholine receptor antagonist. Under the potassium gluconate pipette solution at holding potential 0 mV, Shilajit induced repeatable outward current. These results show that Shilajit has inhibitory effects on the SG neurons of Vc through chloride ion channels by activation of the glycine receptor and GABAA receptor, indicating that Shilajit contains sedating ingredients for the central nervous system. These results also suggest that Shilajit may be a potential target for modulating orofacial pain processing.

A survey was conducted to determine the extent of intestinal parasite infection in Bat Dambang, Cambodia in March 2004. A total of 623 fecal specimens was collected from kindergarten and schoolchildren and examined using the formalin-ether sedimentation technique. The overall infection rate of intestinal parasites was 25.7% (boys, 26.2%; girls, 25.1%), and the infection rates of intestinal helminthes by species were as follows: Echinostoma sp. 4.8%, hookworm 3.4%, Hymenolepis nana 1.3%, and Rhabditis sp. 1.3%. The infection rates of intestinal protozoa were; Entamoeba coli 4.8%, Giardia lamblia 2.9%, Iodamoeba butschlii 1.4%, Entamoeba polecki 1.1%, and Entamoeba histolytica 0.8%. There were no egg positive cases of Ascaris lumbricoides or Trichuris trichiura. All children infected were treated with albendazole, praziquantel, or metronidazole according to parasite species. The results showed that intestinal parasites are highly endemic in Bat Dambang, Cambodia.

Susceptibilities of 5 different mice strains, including C3H/HeN, BALB/c, C57BL6, FvB and ICR, to Echinostoma hortense infection, was evaluated. The worm expulsion rate, worm size and egg production were observed from 1 to 8 weeks after infection with 30 metacercariae. C3H/HeN and ICR mice showed the highest worm maturation rates. The worm recovery rate and the number of eggs per gram (EPG) of feces was also higher in C3H/HeN and ICR mice than in BALB/c, C57BL6, and FvB mice. It is suggested that E. hortense is highly infectious to ICR and C3H/HeN mice, but not to the other strains of mice. Based on the results obtained, we believe that the susceptibility of different mouse strains to E. hortense infection is dependent on the genetic and immunologic background of mice.