The stress-activated protein kinase pathway mediates cell death following injury induced by cis-platinum, UV irradiation or heat

BACKGROUND: Stimuli that stress cells, including inflammatory cytokines, ultra-violet irradiation, DNA-damaging chemotherapeutic drugs and heat shock, stimulate a recently identified cytoplasmic signaling system that is structurally related to the mitogen-activated protein kinase pathway. This pathway consists of a cascade of protein kinases including stress-activated protein kinase (SAPK), also termed Jun N-terminal kinase (JNK), and two kinases that activate it, MEKK and SEK/MKK4. Despite rapid progress in delineating the components of this pathway, the cellular consequence of its activation remains to be defined. RESULTS: We have screened cells for defects in SAPK signaling and identified a cell line, previously characterized for its thermotolerance properties, as being more refractive to SAPK activation induced by heat stress than its thermosensitive parental line. Stable expression of dominant inhibiting SEK mutants in thermosensitive parental cells specifically and effectively blocked SAPK activation after heat shock. These lines also became markedly resistant to the cytocidal effects of thermal stress, confirming the phenotype of the thermotolerant line. These cell lines defective in SAPK activation were also resistant to the lethal effects of the DNA-damaging drug cis-platinum. CONCLUSIONS: Experimentally induced stable blockade of SAPK activation in cells with normal thermosensitivity is sufficient to confer resistance to cell death induced by diverse stimuli including heat and the chemotherapeutic agent cis-platinum. These results suggest that activation of the SAPK pathway by diverse cell stressors plays a critical part in mediating the toxicity of these treatments and inducing cell death. SAPK activation in this context could broadly influence cellular response to stress, modulate apoptosis during development or determine the clinical response of tumor cells to cytotoxic therapies.     

Neuronal Ca2+ sensor 1, the mammalian homologue of frequenin, is expressed in chromaffin and PC12 cells and regulates neurosecretion from dense-core granules

Neuronal Ca2+ sensor 1 (NCS-1) is the mammalian homologue of the Ca2+-binding protein frequenin previously implicated in regulation of neurotransmission in Drosophila (Pongs, O., Lindemeier, J., Zhu, X. R., Theil, T., Endelkamp, D., Krah-Jentgens, I., Lambrecht, H.-G., Koch, K. W., Schwemer, J., Rivosecchi, R., Mallart, A., Galceran, J. , Canal, I., Barbas, J. A., and Ferrus, A. (1993) Neuron 11, 15-28). NCS-1 has been considered to be expressed only in neurons, but we show that NCS-1 expression can be detected in bovine adrenal chromaffin and PC12 cells, two widely studied model neuroendocrine cells. NCS-1 was present in both cytosolic and membrane fractions including purified chromaffin granules, and in immunofluorescence, its distribution overlapped with peripheral punctate staining seen with the synaptic-like microvesicle marker synaptophysin in PC12 cells. The possible functional role of NCS-1 in exocytosis of dense-core granules was tested using transient transfection in PC12 cells and assay of co-transfected growth hormone (GH) release. Overexpression of NCS-1 increased evoked GH release in intact cells in response to ATP. No effect of overexpression was seen on GH release because of Ca2+ in permeabilized cells suggesting that NCS-1 may have a regulatory but not direct role in neurosecretion.     

Design and synthesis of m1-selective muscarinic agonists: (R)-(-)-(Z)-1-Azabicyclo[2.2.1]heptan-3-one, O-(3-(3'-methoxyphenyl)-2-propynyl)oxime maleate (CI-1017), a functionally m1-selective muscarinic agonist

The synthesis and SAR of a series of (Z)-(+/-)-1-azabicyclo[2.2. 1]heptan-3-one, O-(3-aryl-2-propynyl)oximes are described. The biochemistry and pharmacology of 24Z (PD 142505) and its enantiomers are highlighted. 24Z is functionally an m1-selective muscarinic agonist. Efficacy and m1 selectivity reside in the R enantiomer, (R)-24Z (CI-1017).     

Mutants of Pseudomonas aeruginosa that show specific hypersensitivity to aminoglycosides

A class of mutants in Pseudomonas aeruginosa have been found that are tolerant to aeruginocin 41 and also hypersensitive to aminoglycosides. They do not show any changes in susceptibility to a wide range of other toxic agents, including antibiotics and surfactants. This tol locus, tolA, has been mapped at 10 min from the FP2 origin and linked to carA (carbamyl phosphate synthetase) by transduction and conjugation. By selecting for revertants of the hypersensitivity phenotype, revertants to tol(+) were found, indicating that it is the tolA locus that is responsible for this specific hypersensitivity. The results indicate that a specific mechanism exists for the intrinsic resistance of P. aeruginosa to aminoglycosides.     

Comparative evaluation of modified m-FC and m-TEC media for membrane filter enumeration of Escherichia coli in water

Two media used to detect fecal coliforms in water by membrane filtration, m-FC and m-TEC, were modified and supplemented with the chromogenic substrate 5-bromo-6-chloro-3-indoyl-beta-D-glucuronide (BCIG) and were compared for quantitative recovery of Escherichia coli. Student's t test of data from 181 water samples of sewage, rivers, lakes, and wells did not demonstrate any statistically significant differences (P = 0.05) in the enumeration of E. coli with these media. Target colonies were confirmed to be E. coli at rates of 98.6 and 97.3% by using FC-BCIG and TEC-BCIG media, respectively. Glucuronidase-negative isolates of E. coli were encountered at the same frequency (6.0%) on both media. This collaborative study demonstrated that either modified basal medium could be used successfully for detection of E. coli in various nontreated waters within 24 h.     

Drug misuse in a special clinic patient population in Glasgow

Defibrination with ancrod in nephrotoxic nephritis in rabbits. In rabbits with nephrotoxic nephritis, defibrination with ancrod provided protection when administered during the autologous phase, after extensive glomerular fibrin deposition had occurred and crescents and renal failure were developing. When further glomerular fibrin deposition was prevented by defibrination, deposited fibrin was rapidly removed, indicating that glomerular fibrin-clearing mechanisms are retained in crescentic nephritis. Defibrination had no effect on the extent of glomerular C3 deposition or on the amount of proteinuria.     

Crystal structure of an engineered Cro monomer bound nonspecifically to DNA: possible implications for nonspecific binding by the wild-type protein

The structure has been determined at 3.0 A resolution of a complex of engineered monomeric Cro repressor with a seven-base pair DNA fragment. Although the sequence of the DNA corresponds to the consensus half-operator that is recognized by each subunit of the wild-type Cro dimer, the complex that is formed in the crystals by the isolated monomer appears to correspond to a sequence-independent mode of association. The overall orientation of the protein relative to the DNA is markedly different from that observed for Cro dimer bound to a consensus operator. The recognition helix is rotated 48 degrees further out of the major groove, while the turn region of the helix-turn-helix remains in contact with the DNA backbone. All of the direct base-specific interactions seen in the wild-type Cro-operator complex are lost. Virtually all of the ionic interactions with the DNA backbone, however, are maintained, as is the subset of contacts between the DNA backbone and a channel on the protein surface. Overall, 25% less surface area is buried at the protein DNA interface than for half of the wild-type Cro-operator complex, and the contacts are more ionic in character due to a reduction of hydrogen bonding and van der Waals interactions. Based on this crystal structure, model building was used to develop a possible model for the sequence-nonspecific interaction of the wild-type Cro dimer with DNA. In the sequence-specific complex, the DNA is bent, the protein dimer undergoes a large hinge-bending motion relative to the uncomplexed form, and the complex is twofold symmetric. In contrast, in the proposed nonspecific complex the DNA is straight, the protein retains a conformation similar to the apo form, and the complex lacks twofold symmetry. The model is consistent with thermodynamic, chemical, and mutagenic studies, and suggests that hinge bending of the Cro dimer may be critical in permitting the transition from the binding of protein at generic sites on the DNA to binding at high affinity operator sites.     

A multicenter trial of 6-aminocaproic acid (Amicar) in the prevention of bleeding in infants on ECMO

BACKGROUND/PURPOSE: Intracranial hemorrhage (ICH), is a major source of morbidity and the leading cause of death in neonates treated with extracorporeal membrane oxygenation (ECMO). Anecdotal reports have suggested that epsilon-aminocaproic acid (EACA) can decrease the risk of ICH. The purpose of this study was to evaluate, in a multiinstitutional, prospective, randomized, blinded fashion, the effect of EACA on the incidence of hemorrhagic complications in neonates receiving ECMO. METHODS: All neonates (except congenital diaphragmatic hernia) who met criteria for ECMO at three institutions were eligible for enrollment. EACA (100 mg/kg) or placebo was given at the time of cannulation followed by 25 mg/kg/h for 72 hours. Bleeding complications, transfusion requirements, and thrombotic complications were recorded. Post-ECMO imaging included head ultrasound scan computed tomography (CT) scan, and duplex ultrasound scan of the inferior vena cava and renal vessels. RESULTS: Twenty-nine neonates were enrolled (EACA, 13 and placebo, 16). Five (17.2%) patients had a significant (grade 3 or larger) ICH. There was no statistical difference in the incidence of significant ICH in patients who received EACA (23%) versus placebo (12.5%). Septic patients accounted for all of the ICH in the EACA group. Thrombotic complications (aortic thrombus and SVC syndrome) developed in two patients from the placebo group. There was no difference in thrombotic circuit complications between groups. CONCLUSIONS: Our results suggest that the use of EACA in neonates receiving ECMO is safe but may not decrease the overall incidence of hemorrhagic complications.