Effects of radiographic contrast media on proliferation and apoptosis of human vascular endothelial cells

The aim of the study was to determine the effects of radiographic contrast media (RCM) on proliferation and apoptosis of human vascular endothelial cells. Human umbilical vein endothelial cells (HUVECs) were exposed for either 1 min or 15 min to RCM (diatrizoate, ioxaglate, iopromide, iotrolan) at an iodine concentration of 250 mgl ml-1. Controls were complete growth medium (CGM) and saturated mannitol (osmotic control). [3H]thymidine incorporation was used to determine cell proliferation 24 h after exposure. Apoptosis was determined at 1 h and 6 h by terminal uridine nick end labelling (TUNEL), time lapse video microscopy (TLVM) and DNA electrophoresis. Mean proliferation rates (%) (+/- SEM) (p-values compared with the CGM control) at 1 min and 15 min, respectively, were: diatrizoate: 31.9 (10.6), 5.8 (1.5) (p < 0.001); ioxaglate: 48.4 (10.9), 20.4 (4.5) (p < 0.001); iopromide: 63.4 (8.7), 58.2 (10.2) (p < 0.05); iotrolan: 84.7 (7.3), 72.8 (12.4) (p = ns); saturated mannitol 50.5 (9.6), 45.9 (10.0) (p < 0.001). Mean apoptotic indices (%) (+/- SEM) at 1 h and 6 h following 1 min exposure, respectively, were: CGM: 0.25 (0.13), 0.23 (0.08); diatrizoate: 2.18 (0.19), 2.69 (0.34) (p < 0.001); ioxaglate: 1.90 (0.23), 1.69 (0.02) (p < 0.05); iopromide: 0.59 (0.04), 0.33 (0.02) (p = ns); iotrolan: 0.30 (0.07), 0.27 (0.1) (p = ns); saturated mannitol 2.11 (0.24), 1.4 (0.1) (p < 0.05). After 15 min exposure, apoptosis rates at both 1 h and 6 h, respectively, were: iotrolan: 0.29 (0.17), 0.51 (0.16) (p = ns); diatrizoate: 3.19 (0.81), 11.66 (1.75) (p < 0.001); ioxaglate: 1.88 (0.14), 2.87 (0.20) (p < 0.05); iopromide: 1.06 (0.11), 1.52 (0.15) (p < 0.05); saturated mannitol 1.62 (0.09), 4.63 (0.74) (p < 0.05). TLVM and DNA electrophoresis confirmed the occurence of apoptosis after exposure to RCM. In conclusion, saturated mannitol and all tested RCM, with the exception of iotrolan, (diatrizoate > ioxaglate > iopromide) reduced proliferation and increased apoptosis of HUVECs. The effects were more pronounced with ionic RCM and seem to depend on osmolality as well as the chemical structure of these agents. Endothelial injury and apoptosis may be responsible for some of the side effects associated with intravascular use of RCM.

Anionic PAMAM dendrimers rapidly cross adult rat intestine in vitro: a potential oral delivery system?

PURPOSE

To investigate systematically the effect of polyamidoamine (PAMAM) dendrimer size, charge, and concentration on uptake and transport across the adult rat intestine in vitro using the everted rat intestinal sac system.

METHODS

Cationic PAMAM dendrimers (generations 3 and 4) and anionic PAMAM dendrimers (generations 2.5, 3.5, and 5.5) that were modified to include on average a single pendant amino group were radioiodinated using the Bolton and Hunter Reagent. 125I-Labelled dendrimers were incubated with everted sacs in vitro and the transfer of radioactivity into the tissue and serosal fluid was followed with time.

RESULTS

The serosal transfer rates seen for all anionic generations were extremely high with Endocytic Indices (EI) in the range 3.4-4.4 microL/mg protein/h. The concentration-dependence of serosal transfer was linear over the dendrimer concentration range 10-100 microg/mL. For 125I-labelled generation 5.5 the rate of tissue uptake was higher (EI = 2.48+/-0.51 microL/mg protein/h) than seen for 125I-labelled generations 2.5 and 3.5 (0.6-0.7 microL/mg protein/h) (p < 0.05). The 125I-labelled cationic PAMAM dendrimers (generations 3 and 4) displayed a tissue uptake (EI = 3.3-4.8 microL/mg protein/h) which was higher (p < 0.05) than the rate of serosal transfer (EI = 2.3-2.7 microL/mg protein/h), probably due to nonspecific adsorption of cationic dendrimer to the mucosal surface.

CONCLUSIONS

As the anionic PAMAM dendrimers displayed serosal transfer rates that were faster than observed for other synthetic and natural macromolecules (including tomato lectin) studied in the everted sac system, these interesting nanoscale structures may have potential for further development as oral drug delivery systems.

Characterisation of autoantibodies to peripheral myelin protein 22 in patients with hereditary and acquired neuropathies

To investigate the possibility that an autoimmune mechanism may play a role in the hereditary neuropathy Charcot-Marie-Tooth type 1A (CMT1A), sera were analysed by Western blot for anti-peripheral myelin protein 22 (PMP22) autoantibodies. These sera were compared with sera from patients with CMT type 2 (CMT2), acquired peripheral neuropathies such as chronic inflammatory demyelinating neuropathy (CIDP), anti-MAG IgM neuropathy, Miller-Fisher syndrome (MFS), diabetic neuropathy and with control blood donors. Anti-PMP22 positive sera were detected in 70% of patients with CMT1 and unexpectedly in 60% of patients with CMT2. Interestingly, 44% of the patients with other peripheral neuropathies and 23% of the apparently healthy controls showed also anti-PMP22 antibody reactivity. Immunohistochemical analysis of the human anti-PMP22 antisera on healthy sural nerve sections and on PMP22-expressing COS cells revealed that these sera did not recognise endogenous PMP22. Our results indicate that anti-PMP22 autoantibodies are found in sera of patients with different types of peripheral neuropathies, but their role in the pathogenesis of these diseases remains to be determined.

Perirenal mass: an unusual presentation of malignant lymphoma

Perirenal masses are an uncommon manifestation of malignant lymphoma. We report a 73-year-old patient who had this very unusual pattern of renal involvement in non-Hodgkin's lymphoma. Diagnosis was made on the basis of characteristic ultrasound and computed tomography findings and confirmed by histology from a specimen obtained by ultrasound guided biopsy.

Dendrimers: relationship between structure and biocompatibility in vitro, and preliminary studies on the biodistribution of 125I-labelled polyamidoamine dendrimers in vivo

Dendrimers are highly branched macromolecules of low polydispersity that provide many exciting opportunities for design of novel drug-carriers, gene delivery systems and imaging agents. They hold promise in tissue targeting applications, controlled drug release and moreover, their interesting nanoscopic architecture might allow easier passage across biological barriers by transcytosis. However, from the vast array of structures currently emerging from synthetic chemistry it is essential to design molecules that have real potential for in vivo biological use. Here, polyamidoamine (PAMAM, Starburst), poly(propyleneimine) with either diaminobutane or diaminoethane as core, and poly(ethylene oxide) (PEO) grafted carbosilane (CSi-PEO) dendrimers were used to study systematically the effect of dendrimer generation and surface functionality on biological properties in vitro. Generally, dendrimers bearing -NH(2) termini displayed concentration- and in the case of PAMAM dendrimers generation-dependent haemolysis, and changes in red cell morphology were observed after 1 h even at low concentrations (10 microg/ml). At concentrations below 1 mg/ml CSi-PEO dendrimers and those dendrimers with carboxylate (COONa) terminal groups were neither haemolytic nor cytotoxic towards a panel of cell lines in vitro. In general, cationic dendrimers were cytotoxic (72 h incubation), displaying IC(50) values=50-300 microg/ml dependent on dendrimer-type, cell-type and generation. Preliminary studies with polyether dendrimers prepared by the convergent route showed that dendrimers with carboxylate and malonate surfaces were not haemolytic at 1 h, but after 24 h, unlike anionic PAMAM dendrimers they were lytic. Cationic 125I-labelled PAMAM dendrimers (gen 3 and 4) administered intravenously (i.v.) to Wistar rats ( approximately 10 microg/ml) were cleared rapidly from the circulation (<2% recovered dose in blood at 1 h). Anionic PAMAM dendrimers (gen 2.5, 3.5 and 5.5) showed longer circulation times ( approximately 20-40% recovered dose in blood at 1 h) with generation-dependent clearance rates; lower generations circulated longer. For both anionic and cationic species blood levels at 1 h correlated with the extent of liver capture observed (30-90% recovered dose at 1 h). 125I-Labelled PAMAM dendrimers injected intraperitoneally were transferred to the bloodstream within an hour and their subsequent biodistribution mirrored that seen following i.v. injection. Inherent toxicity would suggest it unlikely that higher generation cationic dendrimers will be suitable for parenteral administration, especially if they are to be used at a high dose. In addition it is clear that dendrimer structure must also be carefully tailored to avoid rapid hepatic uptake if targeting elsewhere (e.g. tumour targeting) is a primary objective.

Improved PCR detection of Campylobacter jejuni from chicken rinses by a simple sample preparation procedure

Many food samples and enrichment media are inhibitory to the PCR, thereby lowering its detection capacity. A simple sample preparation method based on buoyant density centrifugation was examined for its application in PCR detection of Campylobacter jejuni from chicken rinse samples. Bacterial cells were spiked at different levels in a mixture of Preston broth and chicken rinse (4:1 ratio) and 0.9 ml of these mixtures were layered over 0.6 ml of gradient medium made from Percoll. PCR sensitivity for bacterial samples treated with this procedure was approximately 10-100 times higher than for samples without treatment. This sample preparation method allowed for the detection of C. jejuni from 26 of 31 naturally contaminated chicken samples after a 20-24-h enrichment period in Preston broth, compared with only 14 positives for untreated samples. In addition, the effect of Oxyrase on the growth and PCR detection of C. jejuni was examined. While Oxyrase significantly enhanced the growth and the PCR signals of C. jejuni in pure culture, it appeared not to improve the PCR detection of C. jejuni in naturally contaminated chickens.

Capillary electrophoresis in clinical and forensic analysis: recent advances and breakthrough to routine applications

This paper is a comprehensive review article on capillary electrophoresis (CE) in clinical and forensic analysis. It is based upon the literature of 1997 and 1998, presents CE examples in major fields of application, and provides an overview of the key achievements encountered, including those associated with the analysis of drugs, serum proteins, hemoglobin variants, and nucleic acids. For CE in clinical and forensic analysis, the past two years witnessed a breakthrough to routine applications. As most coauthors of this review are associated with diagnostic or forensic laboratories now using CE on a routine basis, this review also contains data from routine applications in drug, protein, and DNA analysis. With the first-hand experience of providing analytical service under stringent quality control conditions, aspects of quality assurance, assay specifications for clinical and forensic CE and the pros and cons of this maturing, cost-and pollution-controlled age technology are also discussed.

Transfer of YACs up to 2.3 Mb intact into human cells with polyethylenimine

The transfer of large YAC DNA into human cells is a laborious procedure. High quality pulsed field gel purified DNA is required, which is easily sheared during manipulation before transfection or degraded in the endosome of the cell following transfection. NaCl and polyamines compact and prevent DNA from shearing, but may not consistently protect DNA after transfection. We investigated if other polycations such as poly-L-lysine (PLL) and polyethylenimine (PEI) could condense and protect large YAC DNA (up to 2.3 Mb) from being degraded after lipofection. DNA condensation was monitored by a gel retardation assay, and atomic force microscopy (AFM). DNA was retarded in the gel when complexed with high concentrations of PLL and PEI, indicating that DNA had condensed. However, AFM images of PLL-DNA complexes showed aggregates of DNA molecules resulting from incomplete condensation, whereas PEI-DNA complexes produced condensed particles approximately 30-60 nm. Exogenous PLL-DNA remained intact in 36% of positive clones after lipofection, whereas PEI-DNA was intact in 100% of positive clones. PEI is a better condensing reagent than PLL, protecting DNA from shearing and endosomal degradation, and assists in delivering YACs up to 2.3 Mb intact into human cells.

Dendrimer-platinate: a novel approach to cancer chemotherapy

A polyamidoamine (PAMAM) dendrimer generation 3.5 with a sodium carboxylate surface was conjugated to cisplatin giving a dendrimer-platinate (dendrimer-Pt; 20-25 wt% platinum) which was highly water soluble and released platinum slowly in vitro. In vivo the dendrimer-Pt and cisplatin were equi-active i.p. against i.p. L1210, and at high dose dendrimer-Pt given i.p. showed activity against i.p. B16F10 whereas cisplatin did not. Additionally, when administered i.v. to treat a palpable s.c. B16F10 melanoma, the dendrimer-Pt displayed antitumor activity whereas cisplatin was inactive. Measurement of platinum levels in blood and tissues after i.v. injection of cisplatin (1 mg/kg) or dendrimer-Pt (15 mg/kg)-the maximum tolerated dose (MTD) of these compounds-showed selective accumulation of the dendrimer-Pt in solid tumor tissue by the EPR effect (a 50-fold increase in area under curve compared with cisplatin). The dendrimer-Pt was also less toxic (3- to 15-fold) than cisplatin and thus has potential for further investigation as a novel antitumor approach.

Designing of peptides with left handed helical structure by incorporating the unusual amino acids

The conformational behaviour of delta Ala has been investigated by quantum mechanical method PCILO in the model dipeptide Ac-delta Ala-NHMe and in the model tripeptides Ac-X-delta Ala-NHMe with X = Gly, Ala, Val, Leu, Abu and Phe and is found to be quite different. The computational results suggest that in the model tripeptides the most stable conformation corresponds to phi 1 = -30 degrees, psi 1 = 120 degrees and phi 2 = psi 2 = 30 degrees in which the > C = 0 of the acetyl group is involved in hydrogen bond formation with N-H of the amide group. Similar results were obtained for the conformational behaviour of D-Ala in Ac-D-Ala-NHMe and Ac-Ala-D-Ala-NHMe. The conformational behaviour of the amino acids delta Ala, D-Ala, Val and Aib in model tripeptides have been utilized in the designing of left handed helical peptides. It is shown that the peptide HCO-(Ala-D-Ala)3-NHMe can adopt both left and right handed helix whereas in the peptide Ac-(Ala-delta Ala)3-NHMe the lowest energy conformer is beta-bend ribbon structure. Left handed helical structure with phi = 30 degrees, psi = 60 degrees for D-Ala residues and phi = psi = 30 degrees for delta Ala is found to be more stable by 4 kcal mole-1 than the corresponding right handed helical structure for the peptide Ac-(D-Ala-delta Ala)3-NHMe. In both the peptides Ac-(Val-delta Ala)3-NHMe and Ac-(D-Val-delta Ala)3-NHMe the most stable conformer is the left handed helix. Comparisons of results for Ac-(Ala-delta Ala)3-NHMe and Ac(Val-delta Ala)3-NHMe and Ac-(D-Ala-delta Ala)3-NHMe and Ac-(D-Val-delta Ala)3-NHMe also reveal that the Val residues facilitate the population of 3(10) left handed helix over the other conformers. It is also shown that the conformational behaviour of Aib residue depends on the chirality of neighbouring amino acids, i.e. Ac-(Aib-Ala)3-NHMe adopts right handed helical structure whereas Ac-(Aib-D-Ala)3-NHMe is found to be in left handed helical structure.

Quantitative enzymuria following aorto-renal angiography

Quantitative estimation of urinary enzymes has been advocated as a more sensitive marker than conventional renal function tests to assess radio-contrast media induced nephrotoxicity. We studied 27 subjects with normal renal functions who underwent abdominal aortography for varied indications. Among these, 8 also required selective renal arteriography and 3 underwent arch aortography in addition. Sodium iothalamate was used as a radio-contrast medium and the average amount injected was 73 ml (45 to 120 ml) per subject. Standard renal function assessment including urinalysis, 24 hour urinary protein excretion, creatinine clearance done both before and after aortography did not show any significant alteration. Urinary excretion of tubular enzymes including leucine aminopeptidase (LAP), alkaline phosphatase (ALP), gamma-glutamyl transpeptidase (GGT) and maltase (MAL) was estimated before and 2, 24 and 48 hours after aortography. All enzymes showed a significant rise at 2 hours. Urinary excretion of LAP, ALP and GGT peaked at 24 hours after aortography without a further change in MAL levels. Enzymuria returned to baseline values 48 hours following the procedure. It is concluded that an increase in the urinary excretion of the brush-border enzymes within 24 hours of contrast media administration may suggest an early nephrotoxicity.

Intravascular stents: a new technique for tissue processing for histology, immunohistochemistry, and transmission electron microscopy

BACKGROUND

Study of the vascular response to stent implantation has been hampered by difficulties in sectioning metal and tissue without distortion of the tissue stent interface. The metal is often removed before histochemical processing, causing a loss of arterial architecture. Histological and immunohistochemical sections should be 5 microns with an intact tissue stent interface.

OBJECTIVES

To identify the most suitable cutting and grinding equipment, embedding resin, and slides for producing thin sections of stented arteries with the stent wires in situ for histological, immunohistochemical, and transmission electron microscopic (TEM) analyses.

METHODS

20 balloon stainless steel stents were implanted in the coronary arteries of 10 pigs. Twenty eight days later the stented arterial segments were excised, formalin fixed, embedded in five different resins (Epon 812, LR white, T9100, T8100, and JB4), and sectioned with two different high speed saws and a grinder for histological, immunohistochemical, and TEM analyses. Five stented human arteries were obtained at necropsy and processed using the best of the reported methods.

RESULTS

The Isomet precision saw and grinder/polisher unit reliably produced 5 microns sections with most embedding resins; minimum section thickness with the horizontal saw was 400 microns. Resin T8100, a glycol methacrylate, enabled satisfactory sectioning, grinding, and histological (toluidine blue, haematoxylin and eosin, and trichromatic and polychromatic stains) and immunohistochemical analyses (alpha smooth muscle actin, von Willebrand factor, vimentin, proliferating cell nuclear antigen, and CD68 (mac 387)). T9100 and T8100 embedded stented sections were suitable for ultrastructural examination with TEM. Stented human arterial sections showed preserved arterial architecture with the struts in situ.

CONCLUSION

This study identified the optimal methods for embedding, sawing, grinding, and slide mounting of stented arteries to achieve 5 microns sections with an intact tissue metal interface, excellent surface qualities, histological and immunohistochemical staining properties, and suitability for TEM examination. The technique is applicable to experimental and clinical specimens.

Apoptosis and cell proliferation after porcine coronary angioplasty

BACKGROUND

Angioplasty initiates a number of responses in the vessel wall including cellular migration, proliferation, and matrix accumulation, all of which contribute to neointima formation and restenosis. Cellular homeostasis within a tissue depends on the balance between cell proliferation and apoptosis.

METHODS AND RESULTS

Profiles of apoptosis and proliferation were therefore examined in a porcine PTCA injury model over a 28-day period. Forty-two arteries from 21 pigs, harvested at the site of maximal injury at 1, 6, and 18 hours, and 3, 7, 14, and 28 days after PTCA, were examined (n=3 animals per time point). Uninjured arteries were used as controls. Apoptosis was demonstrated by the terminal uridine nick-end labeling (TUNEL) method, transmission electron microscopy (TEM), and DNA fragmentation. Cells traversing the cell cycle were identified by immunostaining for proliferating cell nuclear antigen (PCNA). Apoptosis was not detected in control vessels at all time points nor at 28 days after PTCA. Apoptotic cells were identified at all early time points with a peak at 6 hours (5.1+/-0.26%; compared to uninjured artery, P<0.001) and confirmed by characteristic DNA ladders and TEM findings. Regional analysis showed apoptosis within the media, adventitia, and neointima peaked at 18 hours, 6 hours, and 7 days after PTCA, respectively. In comparison, PCNA staining peaked at 3 days after PTCA (7.16+/-0.29%; compared to 1.78+/-0.08% PCNA-positive cells in the uninjured artery, P<0.001). Profiles of apoptosis and cell proliferation after PTCA were discordant in all layers of the artery except the neointima. These profiles also differed between traumatized and nontraumatized regions of the arterial wall. Immunostaining with cell-type specific markers and TEM analysis revealed that apoptotic cells included vascular smooth muscle cells (VSMCs), inflammatory cells, and adventitial fibroblasts.

CONCLUSIONS

These results suggest that the profile of apoptosis and proliferation after PTCA is regional and cell specific, and attempts to modulate either of these events for therapeutic benefit requires recognition of these differences.

Biomimicry 1: PC

The surface properties of stents can be modified by coating them, for example with a polymer. Phosphorylcoline (PC) is the major component of the outer layer of the cell membrane. The haemo- and biocompatibility of a PC-containing polymer is thus based on biomimicry, and has been confirmed by several experiments showing much reduced thrombogenicity of PC-coated surfaces, and porcine coronary artery implants showing no sign of adverse effect. Clinical experience with the PC-coated BiodivYsio appears favourable. The PC coating can be tailored for take up and controlled elution of various drugs for stent-based local delivery, a property which is being actively explored.

Structural organization and chromosomal localization of the human Na,K-ATPase beta 3 subunit gene and pseudogene

We have cloned and characterized the Na,K-ATPase beta 3 subunit gene (ATP1B3), and a beta 3 subunit pseudogene (ATP1B3P1), from a human PAC genomic library. The beta 3 subunit gene is > 50 kb in size and is split into 7 exons. The exon/intron organization of the beta 3 subunit gene is identical to that of the Na,K-ATPase beta 3 subunit gene, indicating that these two genes evolved from a common evolutionary ancestor. Comparison of the promoter region of the human and mouse beta 3 subunit gene reveals a high degree of homology within a 300-bp segment located immediately upstream of the translation start site, suggesting that control elements that serve to regulate the cell-specific expression of the beta 3 subunit gene are likely to be located within this conserved region. Dot blot analysis of beta 3 subunit transcripts revealed expression within virtually all human tissues, while in situ hybridization showed expression of beta 3 mRNA in both neurons and glia of rat brain. Fluorescence in situ hybridization with PAC DNA clones localized ATP1B3 to the q22-->23 region of Chromosome (Chr) 3, and the beta 3 pseudogene to the p13-->15 region of Chr 2.

Specific detection and confirmation of Campylobacter jejuni by DNA hybridization and PCR

Conventional detection and confirmation methods for Campylobacter jejuni are lengthy and tedious. A rapid hybridization protocol in which a 1,475-bp chromogen-labelled DNA probe (pDT1720) and Campylobacter strains filtered and grown on 0.22-micron-pore-size hydrophobic grid membrane filters (HGMFs) are used was developed. Among the environmental and clinical isolates of C. jejuni, Campylobacter coli, Campylobacter jejuni subsp. doylei, Campylobacter lari, and Arcobacter nitrofigilis and a panel of 310 unrelated bacterial strains tested, only C. jejuni and C. jejuni subsp. doylei isolates hybridized with the probe under stringent conditions. The specificity of the probe was confirmed when the protocol was applied to spiked skim milk and chicken rinse samples. Based on the nucleotide sequence of pDT1720, a pair of oligonucleotide primers was designed for PCR amplification of DNA from Campylobacter spp. and other food pathogens grown overnight in selective Mueller-Hinton broth with cefoperazone and growth supplements. All C. jejuni strains tested, including DNase-producing strains and C. jejuni subsp. doylei, produced a specific 402-bp amplicon, as confirmed by restriction and Southern blot analysis. The detection range of the assay was as low as 3 CFU per PCR to as high as 10(5) CFU per PCR for pure cultures. Overnight enrichment of chicken rinse samples spiked initially with as little as approximately 10 CFU/ml produced amplicons after the PCR. No amplicon was detected with any of the other bacterial strains tested or from the chicken background microflora. Since C. jejuni is responsible for 99% of Campylobacter contamination in poultry, PCR and HGMF hybridization were performed on naturally contaminated chicken rinse samples, and the results were compared with the results of conventional cultural isolation on Preston agar. All samples confirmed to be culture positive for C. jejuni were also identified by DNA hybridization and PCR amplification, thus confirming that these DNA-based technologies are suitable alternatives to time-consuming conventional detection methods. DNA hybridization, besides being sensitive, also has the potential to be used in direct enumeration of C. jejuni organisms in chicken samples.

A new mutation, 3905insT, accounts for 4.8% of 1173 CF chromosomes in Switzerland and causes a severe phenotype

We have analysed 1173 cystic fibrosis (CF) chromosomes from Switzerland for eight mutations in the CF transmembrane conductance regulator (CFTR) gene. This permitted the identification of 88.5% of all mutations present. A novel insertion mutation in exon 20 of the CFTR gene, 3905insT, was discovered. This mutation accounted for 4.8% of CFTR gene mutations in Switzerland and has since been identified in other populations of probable Swiss descent. It is associated with a highly variable clinical phenotype but always with pancreatic insufficiency. Haplotype analysis with three intragenic microsatellites in the CFTR gene showed that the mutation is associated with a haplotype rarely identified on other CFTR alleles and, therefore, that the frequency of the mutation in Switzerland is explained by a founder effect of a relatively recent mutation event.

DNA-dependent protein kinase is a target for a CPP32-like apoptotic protease

We demonstrate that the catalytic subunit of the DNA-dependent protein kinase (DNA-PKcs) is specifically, proteolytically cleaved in HL-60 cells treated with staurosporine (STS), a potent inducer of apoptosis. The proteolysis of DNA-PKcs correlated with or preceded apoptotic chromosomal DNA degradation. Cell-free extracts prepared from STS-treated HL-60 cells recapitulated the proteolysis of DNA-PKcs in an in vitro assay using purified DNA-PK as the substrate. Western blot analyses of the apoptotic cell extract showed that the 32-kDa precursor of CPP32 is expressed in HL-60 cells and processed following STS treatment. In addition, whereas the DNA-PKcs protease activity was not inhibitable by many conventional protease inhibitors, it was inhibitable by a highly selective peptide-derived inhibitor of CPP32. These data strongly suggest that CPP32, or a CPP32-like protease, is responsible for DNA-PKcs proteolysis. Finally, our results demonstrated that the cleavage of DNA-PKcs in vitro proceeded in the presence of Bcl-2, indicating that the function provided by Bcl-2 lies upstream the proteolysis of DNA-PKcs.