Proteolysis of the N-methyl-d-aspartate receptor by calpain in situ

N-Methyl-D-aspartate (NMDA) receptors are calcium-permeable glutamate receptors that play putative roles in learning, memory, and excitotoxicity. NMDA receptor-mediated calcium entry can activate the calcium-dependent protease calpain, leading to substrate degradation. The major NMDA receptor 2 (NR2) subunits of the receptor are in vitro substrates for calpain at selected sites in the C-terminal region. In the present study, we assessed the ability of calpain-mediated proteolysis to modulate the NR1a/2A subtype in a heterologous expression system. Human embryonic kidney (HEK293t) cells, which endogenously express calpain, were cotransfected with NR1a/2A in addition to the calpain inhibitor calpastatin or empty vector as control. Receptor activation by glutamate and glycine as co-agonists led to calpain activation as measured by succinyl-L-leucyl-L-leucyl-L-valyl-L-tyrosyl-aminomethyl coumarin (Suc-LLVY-AMC). Calpain activation also resulted in the degradation of NR2A and decreased binding of (125)I-MK-801 ((125)I-dizocilpine) to NR1a/2A receptors. No stable N-terminal fragment of the NMDA receptor was formed after calpain activation, suggesting calpain regulation of NMDA receptor levels in ways distinct from that previously observed with in vitro cleavage. NR2 subunit constructs lacking the final 420 amino acids were not degraded by calpain. Agonist-stimulated NR1a/2A-transfected cells also had decreased calcium uptake and produced lower changes in agonist-stimulated intracellular calcium compared with cells cotransfected with calpastatin. Calpastatin had no effect on either calcium uptake or intracellular calcium levels when the NR2A subunit lacked the final 420 amino acids. These studies demonstrate that NR2A is a substrate for calpain in situ and that this proteolytic event can modulate NMDA receptor levels.     

Inhibitory oligonucleotides specifically block effects of stimulatory CpG oligonucleotides in B cells

Reaction to certain motifs in bacterial DNA is an important function of natural immunity. For example, single stranded oligonucleotides (ODN) containing the motif "not C, unmethylated C, G, not G" are powerful mitogens and apoptosis inhibitors for mouse spleen B cells. But replacing GCGTT or ACGTT with GCGGG or ACGGG converted a stimulatory 15-mer ODN into an inhibitory ODN. All inhibitory ODN had three consecutive G, and a fourth G increased inhibitory activity, but a deazaguanosine substitution to prevent planar stacking did not affect activity. Inhibitory ODN blocked apoptosis protection and cell-cycle entry induced by stimulatory ODN, but not that induced by lipopolysaccharide, anti-CD40 or anti-IgM+IL-4. ODN-driven up-regulation of cyclin D(2), c-Myc, c-Fos, c-Jun and Bcl(XL) and down-regulation of cyclin kinase inhibitor p27(kip1) were all blocked by inhibitory ODN. The relative potency of a series of stimulatory and inhibitory ODN was the same for all readouts measured. Interference with uptake of stimulatory ODN could not account for their inhibitory effects. Even if addition of inhibitory ODN was delayed several hours, partial inhibition of stimulatory ODN effects occurred. Inhibitory ODN hold potential as antidotes for excessive ODN stimulation in the clinical setting and provide an important tool for studying ODN recognition.     

1H-MR spectroscopy of normal brain tissue before and after postoperative radiotherapy because of primary brain tumors

PURPOSE: Brain metabolism after surgery and postoperative radiotherapy (pRT) because of primary brain tumors was assessed by proton magnetic resonance spectroscopy ((1)H-MRS) in vivo. The study was designed to reveal the impact of pRT on normal brain tissue metabolism, which may potentially help in delineating the target volumes for reirradiated patients. METHODS AND MATERIALS: Spectra of 43 patients ages 16-63 years treated with pRT for primary glial tumors in the Center of Oncology Maria Curie Memorial Institute Branch in Gliwice were analyzed. The control group consisted of spectra acquired for 30 healthy volunteers. All patients were treated with 3D conformal techniques using 6-20 MV photons to total doses of 60 Gy. Spectra were acquired from the control region before pRT and from three uninvolved regions 9-12 months after the end of pRT. Voxels were located in the region of low (<6 Gy), medium (29-39 Gy), and high radiation dose ( approximately 60 Gy). Relative intensities of the signals relating to N-acetyl-aspartate (NAA), choline-based compounds, creatine and phosphocreatine (Cr), mio-Inositol, lactate, and lipids were obtained. RESULTS: The spectra of "normal brain" taken 9 months after pRT are significantly different from those obtained for control volunteers and from the spectra acquired before radiotherapy. The lactate and lipids signals are very strong; however, they are not correlated with absorbed dose. NAA/Cr ratios are significantly lower than before radiotherapy even for the low-dose regions. Differences increase with radiation dose: the NAA/Cr ratio is significantly lower for the regions of brain receiving a high dose of radiation than for the low-dose areas. CONCLUSION: Combined treatment of primary brain tumors (surgery + postoperative radiotherapy) causes alteration of brain metabolism, even in regions of the brain far from the postoperative tumor bed and receiving relatively low total doses of radiation. Single voxel MRS spectroscopy in vivo cannot help in delineating target volumes for secondary irradiation.     

Evaluation of granulocyte-colony stimulating factor (Filgrastim) in infected diabetic foot ulcers

AIMS/HYPOTHESIS: To re-evaluate the use of Granulocyte-Colony Stimulating Factor (G-CSF) in the treatment of infected diabetic foot ulcers. METHODS. Thirty-seven diabetic subjects were randomised to Granulocyte-Colony Stimulating Factor (G-CSF) (n=20) or placebo (n=17). The primary endpoint was resolution of cellulitis, which was evaluated clinically and with an infection summary score. Patients were hospitalised for 10 days and received subcutaneously either 5 microg/kg G-CSF or placebo daily. Ulcers were treated with a standard wound protocol and the patients were instructed to stay in bed. All subjects received antibiotics (clindamycin and ciprofloxacin) intravenously until the inflammation had subsided. RESULTS: Patients who received G-CSF did not have an earlier resolution of clinically defined cellulitis (p=0.57). The infection summary score declined, but comparably, in both groups (G-CSF: 29.5+/-18.4 to 6.7+/-6.3 p<0.001, placebo: 24.2+/-16.9 to 8.9+/-7.2 p<0.001). The ulcer volume, which was not greater among placebo patients, was reduced by 59% in G-CSF and by 35% in placebo patients. CONCLUSION/INTERPRETATION: We conclude that antibiotic and non weight-bearing therapy (bed rest) accelerated the resolution of cellulitis in infected foot ulcers. Additional treatment with G-CSF had no further beneficial effect.     

Survival after first esophageal variceal hemorrhage in patients with biliary atresia

OBJECTIVE: To determine the influence of the new onset of esophageal variceal hemorrhage (EVH) on transplant-free survival in children with biliary atresia and to examine variables that predicted survival after the onset of EVH. METHODS: Retrospective chart review of 134 patients with biliary atresia who underwent portoenterostomy between 1973 and 1992 at a single institution; 29% had EVH. RESULTS: The risk of death or need for liver transplantation was 50% at 6 years after the initial episode of EVH. Patients with a serum bilirubin concentration < or =4 mg/dL at the first episode of EVH had transplant-free survival of >80% for 4 years after this episode, those with bilirubin levels >4 to 10 mg/dL had 50% survival at 1 year, and those with bilirubin levels >10 mg/dL had 50% survival at 4 months. The risk of death or transplant for a child with EVH and total serum bilirubin levels >10 mg/dL was 12.0 (95% CI: 6.0, 24.1), 4 to 10 mg/dL was 7.2 (3.1, 16.7), and < or =4 mg/dL was 0.6 (0.1, 3.1) times the risk of a same-aged child who did not have EVH. CONCLUSIONS: Children with biliary atresia and first EVH episode have a variable prognosis related to total serum bilirubin concentration at the time of the episode.