The stress-activated protein kinase subfamily of c-Jun kinases

The mitogen-activated protein (MAP) kinases Erk-1 and Erk-2 are proline-directed kinases that are themselves activated through concomitant phosphorylation of tyrosine and threonine residues. The kinase p54 (M(r) 54,000), which was first isolated from cycloheximide-treated rats, is proline-directed like Erks-1/2, and requires both Tyr and Ser/Thr phosphorylation for activity. p54 is, however, distinct from Erks-1/2 in its substrate specificity, being unable to phosphorylate pp90rsk but more active in phosphorylating the c-Jun transactivation domain. Molecular cloning of p54 reveals a unique subfamily of extracellularly regulated kinases. Although they are 40-45% identical in sequence to Erks-1/2, unlike Erks-1/2 the p54s are only poorly activated in most cells by mitogens or phorbol esters. However, p54s are the principal c-Jun N-terminal kinases activated by cellular stress and tumour necrosis factor (TNF)-alpha, hence they are designated stress-activated protein kinases, or SAPKs. SAPKs are also activated by sphingomyelinase, which elicits a subset of cellular responses to TNF-alpha (ref. 9). SAPKs therefore define a new TNF-alpha and stress-activated signalling pathway, possibly initiated by sphingomyelin-based second messengers, which regulates the activity of c-Jun.

Raf-1 activates MAP kinase-kinase

The normal cellular homologue of the acutely transforming oncogene v-raf is c-raf-1, which encodes a serine/threonine protein kinase that is activated by many extracellular stimuli. The physiological substrates of the protein c-Raf-1 are unknown. The mitogen-activated protein (MAP) kinases Erk1 and 2 are also activated by mitogens through phosphorylation of Erk tyrosine and threonine residues catalysed by a protein kinase of relative molecular mass 50,000, MAP kinase-kinase (MAPK-K). Here we report that MAPK-K as well as Erk1 and 2 are constitutively active in v-raf-transformed cells. MAPK-K partially purified from v-raf-transformed cells or from mitogen-treated cells can be deactivated by phosphatase 2A. c-Raf-1 purified after mitogen stimulation can reactivate the phosphatase 2A-inactivated MAPK-K over 30-fold in vitro. c-Raf-1 reactivation of MAPK-K coincides with the selective phosphorylation at serine/threonine residues of a polypeptide with M(r) 50,000 which coelutes precisely on cation-exchange chromatography with the MAPK-K activatable by c-Raf-1. These results indicate that c-Raf-1 is an immediate upstream activator of MAPK-K in vivo. To our knowledge, MAPK-K is the first physiological substrate of the c-raf-1 protooncogene product to be identified.

Epidermal growth factor (EGF)-like repeats of human tenascin-C as ligands for EGF receptor

Signaling through growth factor receptors controls such diverse cell functions as proliferation, migration, and differentiation. A critical question has been how the activation of these receptors is regulated. Most, if not all, of the known ligands for these receptors are soluble factors. However, as matrix components are highly tissue-specific and change during development and pathology, it has been suggested that select growth factor receptors might be stimulated by binding to matrix components. Herein, we describe a new class of ligand for the epidermal growth factor (EGF) receptor (EGFR) found within the EGF-like repeats of tenascin-C, an antiadhesive matrix component present during organogenesis, development, and wound repair. Select EGF-like repeats of tenascin-C elicited mitogenesis and EGFR autophosphorylation in an EGFR-dependent manner. Micromolar concentrations of EGF-like repeats induced EGFR autophosphorylation and activated extracellular signal-regulated, mitogen-activated protein kinase to levels comparable to those induced by subsaturating levels of known EGFR ligands. EGFR-dependent adhesion was noted when the ligands were tethered to inert beads, simulating the physiologically relevant presentation of tenascin-C as hexabrachion, and suggesting an increase in avidity similar to that seen for integrin ligands upon surface binding. Specific binding to EGFR was further established by immunofluorescence detection of EGF-like repeats bound to cells and cross-linking of EGFR with the repeats. Both of these interactions were abolished upon competition by EGF and enhanced by dimerization of the EGF-like repeat. Such low affinity behavior would be expected for a matrix-"tethered" ligand; i.e., a ligand which acts from the matrix, presented continuously to cell surface EGF receptors, because it can neither diffuse away nor be internalized and degraded. These data identify a new class of "insoluble" growth factor ligands and a novel mode of activation for growth factor receptors.

Identification of a full-length cDNA for an endogenous retrovirus of miniature swine

Endogenous retroviruses of swine are a concern in the use of pig-derived tissues for xenotransplantation into humans. The nucleotide sequence of porcine endogenous retrovirus taken from lymphocytes of miniature swine (PERV-MSL) has been characterized. PERV-MSL is a type C retrovirus of 8,132 bp with the greatest nucleic acid sequence identity to gibbon ape leukemia virus and murine leukemia virus. Constitutive production of PERV-MSL RNA has been detected in normal leukocytes and in multiple organs of swine. The copy numbers of full-length PERV sequences per genome (approximately 8 to 15) vary among swine strains. The open reading frames for gag, pol, and env in PERV-MSL have over 99% amino acid sequence identity to those of Tsukuba-1 retrovirus and are highly homologous to those of endogenous retrovirus of cell line PK15 (PK15-ERV). Most of the differences in the predicted amino acid sequences of PK15-ERV and PERV-MSL are in the SU (cell attachment) region of env. The existence of these PERV clones will enable studies of infection by endogenous retroviruses in xenotransplantation.

The Size and Duration of the Sumatra-Andaman Earthquake from Far-Field Static Offsets

The 26 December 2004 Sumatra earthquake produced static offsets at continuously operating GPS stations at distances of up to 4500 kilometers from the epicenter. We used these displacements to model the earthquake and include consideration of the Earth's shape and depth-varying rigidity. The results imply that the average slip was >5 meters along the full length of the rupture, including the approximately 650-kilometer-long Andaman segment. Comparison of the source derived from the far-field static offsets with seismically derived estimates suggests that 25 to 35% of the total moment release occurred at periods greater than 1 hour. Taking into consideration the strong dip dependence of moment estimates, the magnitude of the earthquake did not exceed Mw = 9.2.

Molecular structure of a major insulin/mitogen-activated 70-kDa S6 protein kinase

The molecular structure of a rat hepatoma 70-kDa insulin/mitogen-stimulated S6 protein kinase, obtained by molecular cloning, is compared to that of a rat homolog of the 85-kDa Xenopus S6 protein kinase alpha; both kinases were cloned from H4 hepatoma cDNA libraries. The 70-kDa S6 kinase (calculated molecular mass of 59,186 Da) exhibits a single catalytic domain that is most closely related in amino acid sequence (56% identity) to the amino-terminal, kinase C-like domain of the rat p85 S6 kinase (calculated molecular mass of 82,695 Da); strong similarity extends through a further 67 residues carboxyl-terminal to the catalytic domain (40% identity), corresponding to a region also conserved among the kinase C family. Outside of this segment of approximately 330 amino acids, the structures of the p70 and p85 S6 kinases diverge substantially. The p70 S6 kinase is known to be activated through serine/threonine phosphorylation by unidentified insulin/mitogen-activated protein kinases. A model for the regulation of p70 S6 protein kinase activity is proposed wherein the low activity of the unphosphorylated enzyme results from the binding of a basic, inhibitory pseudosubstrate site (located carboxyl-terminal to the extended catalytic domain) to an acidic substrate binding region (located amino-terminal to the catalytic domain); substrate binding is thereby prevented. S6 kinase activation requires displacement of this inhibitory segment, which is proposed to occur consequent to its multiple phosphorylation. The putative autoinhibitory segment contains several serine and threonine residues, each followed directly by a proline residue. This motif may prevent autophosphorylation but permit transphosphorylation; two of these serine residues reside in a maturation promoting factor (MPF)/cdc-2 consensus motif. Thus, hormonal regulation of S6 kinase may involve the action of MPF/cdc-2 or protein kinases with related substrate specificity.

An association study of 43 SNPs in 16 candidate genes with atorvastatin response

Variation in individual response to statin therapy has been widely studied for a potential genetic component. Multiple genes have been identified as potential modulators of statin response, but few study findings have replicated. To further examine these associations, 2735 individuals on statin therapy, half on atorvastatin and the other half divided among fluvastatin, lovastatin, pravastatin and simvastatin were genotyped for 43 SNPs in 16 genes that have been implicated in statin response. Associations with low-density lipoprotein cholesterol (LDL-C) lowering, total cholesterol lowering, HDL-C elevation and triglyceride lowering were examined. The only significant associations with LDL-C lowering were found with apoE2 in which carriers of the rare allele who took atorvastatin lowered their LDL-C by 3.5% more than those homozygous for the common allele and with rs2032582 (S893A in ABCB1) in which the two groups of homozygotes differed by 3% in LDL-C lowering. These genetic effects were smaller than those observed with the demographic variables of age and gender. The magnitude of all the differences found is sufficiently small that genetic data from these genes should not influence clinical decisions on statin administration.

Pharmacodynamics of fluconazole in a murine model of systemic candidiasis

In this study we defined the pharmacodynamic parameter that optimizes outcome in deep-seated Candida albicans infections treated with fluconazole. Using a murine model of systemic candidiasis, we conducted single-dose dose-ranging studies with fluconazole to determine the dosage of this drug that resulted in a 50% reduction in fungal densities (50% effective dose [ED50]) in kidneys versus the fungal densities in the kidneys of untreated controls. We found that the ED50 of fluconazole given intraperitoneally was 4.56 mg/kg of body weight/day (95% confidence interval, 3.60 to 5.53 mg/kg/day), and the dose-response relationship was best described by an inhibitory sigmoid maximal effect (Emax) curve. To define the pharmacodynamics of fluconazole, we gave dosages lower than, approximating, and higher than the ED50 of fluconazole (range, 3.5 to 5.5 mg/kg/day, equivalent to the ED16 to the ED75) to various groups of infected animals using three dose-fractionation schedules. For each total dose of fluconazole examined, the dose-fractionation schedules optimized the ratio of the area under the concentration-time curve (AUC) to the MIC (the AUC/MIC ratio), the ratio of the maximum concentration of drug in serum (Cmax) to the MIC, and the time that the drug remained above the MIC for the infecting C. albicans isolate. Similar reductions in fungal densities in kidneys were seen between groups that received the same total dose of fluconazole in one, two, or four equally divided doses. Thus, dose-fractionation studies demonstrated that the pharmacodynamic parameter of fluconazole that best predicted outcome was the AUC/MIC ratio.

Is oral rice electrolyte solution superior to glucose electrolyte solution in infantile diarrhoea?

In a controlled trial of oral rehydration therapy, a rice-based electrolyte solution was evaluated in a group (n=26) of infants and young children aged between 3 months and 5 years with moderate to severe dehydration owing to acute diarrhoea, and the results were compared with a matched control group (n=26) receiving WHO recommended glucose electrolyte solution. The former was found to be more effective than the latter as shown by an appreciably lower rate of stool output, a shorter duration of diarrhoea, and a smaller intake of rehydration fluid.

Differential solubilization of lipids along with membrane proteins by different classes of detergents

Membrane proteins are typically extracted by detergent concentrations of 0.5-2.0%, using detergent/protein ratios of 1:1 to 3:1. We have compared the ability of 14 different detergents from seven different structural and ionic classes, at a concentration of 2.0% and a detergent/protein ratio of 2:1, to extract an integral membrane protein (the serotonin 5-HT1A receptor) in active form and have observed profound differences in both lipids and proteins. All extracts were freed from detergents and dialyzed to form vesicles containing 95-100% of the extracted lipids, prior to [3H]8-hydroxy-2-(N,N-di-n-propylamino)tetralin ([3H]8-OH-DPAT) binding. The most efficient detergents in extracting active 5-HT1A receptor protein were the zwitterionic 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) and 3-[(cholamidopropyl)dimethylammonio]-2-hydroxy-1-propanesulfonate (CHAPSO), followed by the neutral n-dodecyl-beta-D-maltoside. Zwitterionic detergents also produced the highest solubilized lipid/protein ratio (3.0 and 2.5, respectively) and in general the relative amounts of extracted lipids and proteins followed inverse profiles. Thus, hydrophobic detergents such as Tritons (with critical micelle concentrations similar to CHAPS) and Thesit (structurally similar to Lubrol) extracted the most protein, but relatively little lipid (ratios of less than 0.2) and very little active 5-HT receptor. Dramatic differences were also observed in the ratios of individual lipids extracted by the same concentrations of different detergents and resolved by high-performance thin-layer chromatography. For example, galactosylceramide (GalCer) content ranged from 2.7% (CHAPSO) to 13.4% (sodium cholate) of the total lipid extract and cholesterol ranged from 0% (digitonin) to 17.9% (Triton X-100). The detergent-extractability profile for phosphatidylethanolamine (PE) (range 15-40% of total lipid) paralleled that of phosphatidylinositol (PI) (range 4-10%), but was inverse to that for GalCer and cholesterol. Detergent-extractability profiles for phosphatidylcholine (PC) and phosphatidylserine (PS) also followed inverse profiles, with zwitterionic detergents giving high PS/PC and high PE/PC ratios (approximately 2:1), whereas the Tritons and digitonin gave ratios of 1:2. We believe that differential solubilization of lipids, as well as proteins, by detergents is important for the biological activity of the extracted proteins, and lipid extractability should be taken into account when purifying membrane proteins.

TULP1 mutation in two extended Dominican kindreds with autosomal recessive retinitis pigmentosa

The RP14 autosomal recessive Retinitis pigmentosa (arRP) locus has been mapped to a 2cM region of chromosome 6p21.3. TULP1 (the gene encoding tubby-like protein 1) is a candidate target for the disease mutation because it maps to the RP14 minimum genetic region and because a mutation in the highly homologous mouse tub gene leads to obesity, deafness and early progressive retinal degeneration. Here we report a splice-site mutation (IVS14+1, G-->A) that is homozygous in all affected individuals (N=33) and heterozygous in all obligate carriers (N=50) from two RP14-linked kindreds. The mutation was not observed in 210 unrelated controls. The data indicate that impairment of TULP1 protein function is a rare cause of arRP and that the normal protein plays an essential role in the physiology of the retina.

cbl-3: a new mammalian cbl family protein

We have cloned a new human gene, cbl-3, which encodes a protein with marked homology to the cbl family of proteins. The predicted protein encoded by this gene retains the conserved phosphotyrosine binding domain (PTB) in the N-terminal and the zinc finger but is significantly shorter (MW 52.5 kDa) than the other mammalian cbl proteins. The protein lacks the extensive proline rich domain and leucine zipper seen in c-cbl and cbl-b and structurally most resembles the C. elegans and Drosophila cbl proteins. The gene is ubiquitously expressed with highest expression in the aerodigestive tract, prostate, adrenal gland, and salivary gland. The protein is phosphorylated and recruited to the EGFR upon EGF stimulation and inhibits EGF stimulated MAP kinase activation. In comparison to the other mammalian cbl proteins (e.g. cbl-b), cbl-3 interacts with a restricted range of proteins containing Src Homology 3 regions. An alternatively spliced form of the cbl-3 protein was also identified which deletes a critical region of the PTB domain and which does not interact with the EGFR nor inhibit EGF stimulated MAP kinase activation. These data demonstrate that cbl-3, a novel mammalian cbl protein, is a regulator of EGFR mediated signal transduction.

Bedtime H2 blockers improve nocturnal gastric acid control in GERD patients on proton pump inhibitors

AIM

Proton pump inhibitors taken twice daily before meals (proton pump inhibitor b.d. AC) effectively controls daytime gastric pH; however, nocturnal gastric acid breakthrough (NAB) occurs in more than 75% of patients. Adding an H2-blocker at bedtime decreases NAB in normal subjects. The efficacy of this regimen has not been evaluated in GERD patients. The aim of this study was to assess the effects of proton pump inhibitor b.d., both with and without bedtime H2-blocker on intragastric pH and the occurrence of NAB in GERD patients.

METHODS

Prolonged ambulatory pH studies in GERD patients were reviewed. Group A: 60 patients (mean age 53 years, male 30) taking either omeprazole 20 mg or lansoprazole 30 mg b.d. Group B: 45 patients (mean age 49 years, male 23) on proton pump inhibitor b.d. (omeprazole 20 mg or lansoprazole 30 mg) plus an H2-blocker at bedtime (ranitidine 300 mg, famotidine 40 mg or nizatidine 300 mg). Eleven patients were evaluated during treatment with both regimens (group C). The percentage time of nocturnal and daytime intragastric pH > 4 and per cent of patients with gastric NAB were analysed. In the patients with NAB, its duration and associated oesophageal acid exposure also were analysed.

RESULTS

Median percentage time intragastric pH > 4 overnight was 51% in group A, compared to 96% in group B (P < 0.0001). Median percentage daytime pH > 4 was 73% in group A and 79.8% in group B (P=0.14). Median percentage time intragastric pH >p 4 overnight increased from 54.6% without H2RA to 96.5% after adding bedtime H2RA (P=0.0013) in group C patients. NAB occurred in 82% patients in group A and 40% in group B (P < 0.0001). The mean duration of oesophageal acid exposure during NAB was significantly shorter in group B (18 +/- 6 min) than in group A (42 +/- 9 min, P=0.04).

SUMMARY

Adding a bedtime H2-blocker to the treatment enhanced nocturnal gastric pH control and decreased NAB compared to the proton pump inhibitor b.d. regimen. A bedtime H2-blocker also decreased oesophageal acid exposure during NAB.

CONCLUSION

Adding a bedtime H2-blocker to a proton pump inhibitor b.d. regimen should be considered in patients who require continued nocturnal gastric acid control whilst taking proton pump inhibitor b.d.

Inhibition of NF-kappaB activity enhances TRAIL mediated apoptosis in breast cancer cell lines

Most breast cancer cell lines are resistant to TNF-related apoptosis inducing ligand (TRAIL) induced apoptosis. In sensitive breast cancer cell lines TRAIL rapidly induces the cleavage and activation of caspases leading to the subsequent cleavage of downstream caspase substrates. In contrast, there is no caspase activation in the resistant cell lines. The transcription factor NF-KB can inhibit apoptosis induced by a variety of stimuli including activation of death receptors. We investigated whether NF-kappaB contributes to the resistance of breast cancer cells to TRAIL induced apoptosis. All of the resistant breast cancer cell lines expressed NF-kappaB and had detectable NF-kappaB activity in nuclear extracts prior to treatment with TRAIL. Upon TRAIL treatment, a significant increase in NF-kappaB activity was seen in most of the cell lines. To directly test if NF-kappaB activity contributes to the resistance of these cell lines to TRAIL, we transiently transfected the resistant cell lines with an inhibitor of NF-kappaB (IkappaBdeltaN) and measured TRAIL induced apoptosis in control and transfected cells. All of the resistant cell lines tested showed an increase in TRAIL induced apoptosis when transfected with the IKBdeltaN. These results demonstrate that TRAIL resistant breast cancer cells fail to rapidly activate the apoptotic machinery but they do activate NF-kappaB. Inhibition of NF-kappaB activity increases the sensitivity to TRAIL mediated apoptosis in resistant cells. These results suggest that agents which inhibit NF-kappaB should increase the clinical efficacy of TRAIL in breast cancer cells.

Polymer latexes for cell-resistant and cell-interactive surfaces

Novel polymer latexes were prepared that can be applied in several ways for the control and study of cell behavior on surfaces. Acrylic latexes with glass transitions ranging from -30 to 100 degrees C were synthesized by dispersion polymerization in a water and alcohol solution using an amphiphilic comb copolymer as a stabilizing agent. The comb had a poly(methyl methacrylate) backbone and hydrophilic poly(ethylene glycol) (PEG) side chains, which served to stabilize the dispersion and create a robust hydrophilic coating on the final latex particles. The end groups of the comb stabilizer can be selectively functionalized to obtain latex particles with a controlled density of ligands tethered to their surfaces. Latexes were prepared with adhesion peptides (RGD) linked to the surface of the acrylic beads to induce attachment and spreading of cells. Coalesced films obtained from the RGD-bearing latex particles promoted attachment of WT NR6 fibroblasts, while films from unmodified latex particles were resistant to these cells. Additionally, RGD-linked beads were embedded in cell-resistant comb polymer films to create cell-interactive surfaces with discrete clustered-ligand domains. Cell attachment and morphology were seen to vary with the surface density of the RGD-bearing latex beads.

Regulation of an epitope-tagged recombinant Rsk-1 S6 kinase by phorbol ester and erk/MAP kinase

Phorbol ester tumor promoters (TPA) activate the endogenous erk/MAP kinases and Rsk S6 kinases but not the p70S6 kinase in COS cells. DNA sequences encoding the rat Rsk-1 S6 kinase (homologous to Xenopus rsk alpha), modified by insertion of a peptide epitope at the polypeptide aminoterminus, were expressed transiently in COS cells. TPA stimulates the 40S and peptide kinase activity of the recombinant epitope-tagged Rsk-1, as well as the extent of Rsk-1 autophosphorylation in vitro (32P-Ser >> 32P-Thr). Indications that the conformation of the recombinant Rsk-1 polypeptide is substantially changed after activation by TPA in situ include a retarded mobility of the Rsk-1 polypeptide on SDS-PAGE and the appearance of new 32P-peptides during autophosphorylation in vitro. All these features of the TPA-activated Rsk-1 S6 kinase are abolished by dephosphorylation of the kinase in vitro with Ser/Thr phosphatase-2A. TPA increases 32P incorporation into recombinant Rsk-1 by 2-3-fold (32P-Ser >> 32P-Thr). Peptide mapping exhibits a single major 32P-peptide in Rsk-1 isolated from unstimulated cells and 10-12 additional 32P peptides after TPA treatment in situ. Phosphorylation of basal or phosphatase-2A-treated recombinant Rsk-1 in vitro with erk2/MAP kinase increases Rsk-1 40S kinase, peptide kinase, and autophosphorylating activity, retards migration of Rsk-1 polypeptides on SDS-PAGE, and generates new sites of Rsk-1 autophosphorylation in vitro. By contrast, TPA-activated Rsk-1 is not altered in these properties by autophosphorylation in vitro. By contrast, TPA-activated Rsk-1 is not altered in these properties by phosphorylation in vitro with erk2/MAP kinase. Activation of Rsk-1 in situ with TPA diminishes by over 90% the extent of Rsk-1 phosphorylation achieved in vitro by erk2/MAP kinase, as compared to the parallel phosphorylation of a phosphatase-2A-treated Rsk-1; basal Rsk-1 is intermediate. Peptide maps of phosphatase-2A-treated Rsk-1 after phosphorylation in vitro with erk2/MAP kinase exhibit 32P-peptides that comigrate with nearly all of the 32P-peptides present in TPA-activated-32P Rsk-1 labeled in situ, plus several 32P-peptides characteristic of Rsk-1 autophosphorylation in vitro.(ABSTRACT TRUNCATED AT 400 WORDS)

Identification of a locus, distinct from RDS-peripherin, for autosomal recessive retinitis pigmentosa on chromosome 6p

We performed a genomic search for linkage to autosomal recessive retinitis pigmentosa in a large pedigree obtained from the Dominican Republic using microsatellite markers. Regions of the genome known to contain genes for retinitis pigmentosa were preferentially tested. One of these regions, on chromosome 6p, which contains the gene for peripherin, gave positive lod scores. Use of a mononucleotide repeat polymorphism in the peripherin gene excluded this locus. Two- and multi-point analyses suggest that the most likely location for the disease gene is near D6S291, which is located approximately 20 centimorgans telomeric from peripherin.

Externalization of phosphatidylserine may not be an early signal of apoptosis in neuronal cells, but only the phosphatidylserine-displaying apoptotic cells are phagocytosed by microglia

Earlier reports on nonneural cells have shown that the normally inner plasma membrane lipid, phosphatidylserine (PS), flip-flops out during the early stages of apoptosis, whereas DNA laddering and plasma membrane permeabilization occur during the late stages. In this study, the applicability of these parameters to CNS-derived neuronal cells was tested using hippocampal HN2-5, cells that undergo apoptosis under anoxia. Because such insults on unsynchronized cells, e.g., undifferentiated HN2-5 cells, result in both early and late apoptotic cells, we mechanically separated these cells into three fractions containing (a) cells that had completely detached during anoxia, (b) cells that remained weakly attached to the tissue culture dish and, once detached by trituration in serum-containing medium, did not reattach, and (c) cells that reattached in 2-3 h. Fractions a and b contained cells that showed pronounced DNA laddering, whereas cells in fraction c did not show any DNA laddering. Double staining with fluorescein isothiocyanate-annexin V (which binds to PS) and propidium iodide (which stains the DNA in cells with a permeable cell membrane) revealed that all cells in fraction a had a permeable cell membrane (propidium iodide-positive) and PS molecules in the outer leaflet of the plasma membrane (fluorescein isothiocyanate-annexin V-positive). By contrast, fractions b and c contained cells with no externalized PS molecules. Cells in fractions a-c also showed, respectively, 50-, 21-, and 5.5-fold higher caspase-3 (CPP32) activity than that in healthy control cells. All these results show that fraction a contained late apoptotic cells, which also had the highest CPP32 activity; cells in fraction b were at an intermediate stage, when DNA laddering had already occurred; and fraction c contained very early apoptotic cells, in which no DNA laddering had yet occurred. Therefore, in the neuronal HN2-5 cells, externalization of PS occurs only during the final stages of apoptosis when the cells have completely lost their adhesion properties. Further experiments showed that ameboid microglial cells isolated from neonatal mouse brain phagocytosed only the cells in fraction a. These results show that in CNS-derived HN2-5 cells, (a) PS externalization is a late apoptotic event and is concomitant with a complete loss of surface adhesion of the apoptotic cells and (b) PS externalization is crucial for microglial recognition and phagocytosis of the apoptotic HN2-5 cells. Thus, PS externalization could be causally linked to the final detachment of apoptotic neuronal cells, which in turn prepares them for rapid phagocytosis by microglia.

Agonist stimulation of the serotonin1A receptor causes suppression of anoxia-induced apoptosis via mitogen-activated protein kinase in neuronal HN2-5 cells

Previous studies have indicated that stimulation of neuronal inhibitory receptors, such as the serotonin1A receptor (5-HT1A-R), could cause attenuation of the activity of both N-type Ca2+ channels and N-methyl-D-aspartic acid receptors, thus resulting in protection of neurons against excitotoxicity. The purpose of this study was to investigate if the 5-HT1A-R is also coupled to an alternative pathway that culminates in suppression of apoptosis even in cells that are deficient in Ca2+ channels. Using a hippocampal neuron-derived cell line (HN2-5) that is Ca2+ channel-deficient, we demonstrate here that an alternative pathway is responsible for 5-HT1A-R-mediated protection of these cells from anoxia-triggered apoptosis, assessed by deoxynucleotidyl-transferase-mediated dUTP nick end-labeling (TUNEL). The 5-HT1A-R agonist-evoked protection was eliminated in the presence of pertussis toxin and also required phosphorylation-mediated activation of mitogen-activated protein kinase (MAPK), as evidenced by the elimination of the agonist-elicited rescue of neuronal cells by the MAPK kinase inhibitor PD98059 but not by the phosphatidylinositol 3-kinase (PI-3K) inhibitor wortmannin. Furthermore, agonist stimulation of the 5-HT1A-R caused a 60% inhibition of anoxia-stimulated caspase 3-like activity in the HN2-5 cells, and this inhibition was abrogated by PD98059 but not by wortmannin. Although agonist stimulation of the 5-HT1A-R caused an activation of PI-3Kgamma in HN2-5 cells, our results showed that this PI-3Kgamma activity was not linked to the 5-HT1A-R-promoted regulation of caspase activity and suppression of apoptosis. Thus, in the neuronal HN2-5 cells, agonist binding to the 5-HT1A-R results in MAPK-mediated inhibition of a caspase 3-like enzyme and a 60-70% suppression of anoxia-induced apoptosis through a Ca2+ channel-independent pathway.

Ovarian steroids and modulation of morphine-induced analgesia and catalepsy in female rats

The influence of ovarian steroids on modulation of antinociceptive and cataleptic responses to morphine in female rats was evaluated. The sensitivity of the animals to morphine varied at different stages of the estrous cycle. The responses of postpartum and ovariectomized rats to morphine was attenuated. The test doses of estradiol-17 beta or progesterone, either alone or in combination, did not alter this attenuated morphine sensitivity. Testosterone, however, sensitized post-partum as well as ovariectomized rats to morphine. Unlike progesterone, 17-alpha-hydroxy progesterone antagonized testosterone. Collectively these data implicate ovarian testosterone as a physiological modulator of actions of morphine in female rats.