El cateterismo vesical intermitente en la insuficiencia contráctil del detrusor / The role of clean intermittent catheterization in the treatment for detrusor underactivity

OBJETIVOS: Estudiar la influencia del cateterismo vesical intermitente (CVI) sobre la función del tracto urinario inferior (TUI) en pacientes con retención urinaria (RU) por insuficiencia contráctil (IC) del detrusor. MATERIAL Y MÉTODOS: Estudio longitudinal. Cuarenta y nueve pacientes (28 hombres/21 mujeres; edad media: 55 años) sometidos a CVI por RU por IC (frecuencia media 3,15 veces/día). El único criterio de inclusión fue la realización de CVI asociada a IC. Se realizó historia clínica y dos estudios urodinámicos con un intervalo de 4 años de media. Se compararon los datos urodinámicos pre y post CVI mediante test exacto de Fisher para variables dicotómicas y test de la t de Student para datos pareados (estudios antes y después del CVI) e independientes (comparación entre diferentes grupos) en el caso de las variables paramétricas. El nivel de significación se fijó en 5% bilateral. RESULTADOS: Se observó aumento significativo de la acomodación vesical, del índice de obstrucción (BOOI) y del índice de contractilidad vesical (BCI), sin alcanzar significación estadística. Respecto de los pacientes en los que su BCI mejoró después del CVI se observó un porcentaje significativamente mayor de pacientes con hiperplasia benigna de próstata (HBP) y detrusor acontráctil comparado con los pacientes en los que el BCI no mejoró después del CVI. El tiempo en que los pacientes estaban sometidos a CVI fue significativamente menor en el grupo de mejoría. CONCLUSIONES: El CVI mejoró la acomodación vesical en los pacientes de nuestra serie. El BCI mejoró en varones con HBP y en pacientes con detrusor acontráctil

OBJECTIVE: To study the influence of clean intermittent catheterization (CIC) on the lower urinary tract function in patients with urinary retention (UR) due to detrusor underactivity (DU). MATERIAL AND METHODS: A longitudinal study was carried out on 49 patients (28 men, 21 women) of mean age 55 years, who underwent CIC for UR secondary to DU. The mean CIC frequency was 3.15 times/day. Patients' clinical data were collected, and they underwent urodynamic study before and after CIC, with a mean interval of 4 years. Fisher's exact test was used for the analysis of categorical variables and Student's t test for parametric variables. The level of significance was set at 0.05 for a two-tailed test. RESULTS: The second urodynamic study showed a significantly increased bladder compliance, the Bladder Outlet Obstruction Index (BOOI) and the Bladder Contractility Index (BCI) also increased but without reaching statistical significance. There was a significantly higher percentage of benign prostatic hyperplasia (BPH) and acontractile detrusor cases among the group of patients whose BCI improved after CIC, with significantly lower CIC time. CONCLUSIONS: CIC improved bladder compliance in the patients of our series. The BCI improved in BPH patients and in patients with acontractile detrusor

The role of clean intermittent catheterization in the treatment for detrusor underactivity. / El cateterismo vesical intermitente en la insuficiencia contráctil del detrusor.

OBJECTIVE: To study the influence of clean intermittent catheterization (CIC) on the lower urinary tract function in patients with urinary retention (UR) due to detrusor underactivity (DU). MATERIAL AND METHODS: A longitudinal study was carried out on 49 patients (28 men, 21 women) of mean age 55years, who underwent CIC for UR secondary to DU. The mean CIC frequency was 3.15 times/day. Patients' clinical data were collected, and they underwent urodynamic study before and after CIC, with a mean interval of 4years. Fisher's exact test was used for the analysis of categorical variables and Student's t test for parametric variables. The level of significance was set at 0.05 for a two-tailed test. RESULTS: The second urodynamic study showed a significantly increased bladder compliance, the Bladder Outlet Obstruction Index (BOOI) and the Bladder Contractility Index (BCI) also increased but without reaching statistical significance. There was a significantly higher percentage of benign prostatic hyperplasia (BPH) and acontractile detrusor cases among the group of patients whose BCI improved after CIC, with significantly lower CIC time. CONCLUSIONS: CIC improved bladder compliance in the patients of our series. The BCI improved in BPH patients and in patients with acontractile detrusor.

Terapia combinada con bevacizumab y alteplasa para el tratamiento de hemorragias submaculares / Combined therapy with bevacizumab and alteplasa for the treatment of submacular hemorrhages

INTRODUCCIÓN: El uso combinado de bevacizumab y alteplasa intrarretiniano supone una alternativa de tratamiento de las hemorragias maculares que adquiere cada vez más relevancia. Además, su utilización en una única jeringa evita una inyección intrarretiniana reduciendo los posibles riesgos que conllevan. OBJETIVO: Confirmar la efectividad y seguridad de la combinación de bevacizumab y alteplasa in vivo para el tratamiento de hemorragias submaculares en pacientes con degeneración macular asociada a la edad y determinar si supone una alternativa de tratamiento válida. METODOLOGÍA: Estudio retrospectivo observacional de pacientes tratados con bevacizumab y alteplasa para hemorragias submaculares desde febrero de 2017 a febrero de 2018. Se revisó la situación clínica pre-intervención y a los 3 meses. Las variables revisadas para determinar la efectividad del tratamiento fueron el tamaño de la superficie de la hemorragia, el grosor retiniano y la agudeza visual. La seguridad se evaluó con la aparición de reacciones adversas. RESULTADOS: Fueron incluidos cinco pacientes, cuatro con un ojo afectado y uno con ambos, 60% hombres, con una mediana de edad de 78 años (68-89). Objetivamente se redujo el porcentaje de ocupación de la hemorragia de una media del 70% al 6% tras la intervención. El grosor retiniano disminuyó de 1.531 micras (1.891-1.195) a 516,8 micras (324-667). La agudeza visual mejoró en dos pacientes manteniéndose en el resto. Todos los pacientes refirieron subjetivamente mejoría tras la intervención. El tratamiento fue seguro por la ausencia de aparición de reacciones adversas. CONCLUSIONES: El tratamiento estudiado ha demostrado ser efectivo y seguro clínicamente

INTRODUCTION: The combined use of bevacizumab and intraretinal alteplase is an alternative treatment for macular hemorrhage that is becoming more and more relevant. In addition, its use in a single syringe prevents an intraretinal injection reducing the possible risks involved. OBJECTIVE: To confirm the effectiveness and safety of the combination of bevacizumab and alteplase in vivo for submacular hemorrhage in patients with macular degeneration associated with age and to determine whether it is a valid treatment alternative. MATERIAL AND METHODS: Observational retrospective study of patients treated with bevacizumab and alteplase for submacular hemorrhages from February 2017 to February 2018. The clinical situation was reviewed pre-intervention and at 3 months later. The variables reviewed to determine the effectiveness of the treatment were the size of the hemorrhage surface, the retinal thickness and the visual acuity. Safety was determined with the appearance of adverse reactions. RESULTS: Six eyes of five patients were included, 60% men, with a median age of 78 years (68-89). Objectively the percentage of occupation of the hemorrhage was reduced from an average of 70% to 6% after the intervention. The retinal thickness decreased from 1,531 microns (1,891-1,195) to 516.8 microns (324-667). Visual acuity improved in two patients and remained in the rest. All patients reported subjectively improvement after the intervention. The treatment was safe due to the absence of adverse reactions. CONCLUSIONS: The reviewed treatment has shown to be clinically effective and safe

Vólvulo cecal: características en imagen / Cecal volvulus: imaging features

Objetivo. El objetivo de este estudio es analizar la sensibilidad de los hallazgos de la radiografía simple y de la tomografía computarizada (TC) en el diagnóstico del vólvulo cecal. Material y métodos. Se revisaron las historias clínicas de 11 pacientes con diagnóstico endoscópico o quirúrgico de vólvulo cecal. Dos radiólogos analizaron por consenso los hallazgos en la radiografía simple y en la TC y calcularon la sensibilidad. Se realizó de forma retrospectiva un diagnóstico de certeza, probable o indeterminado de vólvulo cecal sobre la base de la presencia o ausencia de signos previamente descritos. Los signos de sufrimiento parietal en la TC se compararon con los hallazgos anatomopatológicos. Resultados. Los hallazgos más sensibles en la radiografía simple fueron la presencia de un asa desproporcionadamente dilatada y un patrón de oclusión de intestino delgado distal (91%), seguidos de un nivel hidroaéreo único en el ciego y colapso del colon distal (82%). En la TC, el signo del grano de café con un único nivel hidroaéreo y el colapso de colon izquierdo mostraron una sensibilidad del 100%. El signo del remolino se observó en el 86%. De forma retrospectiva se pudo realizar un diagnóstico de certeza en el 36 y el 86% de los casos en la radiografía simple y en la TC, respectivamente. Aunque todos los casos con isquemia tenían signos de deterioro vascular en la TC, no se encontró correlación significativa entre ambos parámetros. Conclusiones. La utilización de los signos descritos de vólvulo cecal permite hacer un diagnóstico de certeza con la radiografía simple en un tercio de los pacientes y en la mayoría de los casos con la TC. La valoración de otros hallazgos adicionales incrementa la posibilidad de realizar un diagnóstico correcto (AU)

Objective. To determine the sensitivity of plain-film radiography and computed tomography (CT) in the diagnosis of cecal volvulus. Material and methods. We reviewed the clinical histories of 11 patients diagnosed with cecal volvulus at endoscopy or surgery. Two radiologists working in consensus analyzed the findings at plain-film radiography and at CT and calculated the sensitivities. The plain-film and CT studies were retrospectively classified as certain, probable, or indeterminate for cecal volvulus on the basis of the presence or absence of previously reported signs. Signs of wall suffering at CT were compared to the histologic findings. Results. The most sensitive findings at plain-film radiography were the presence of a disproportionately dilated bowel loop and a pattern of distal small bowel occlusion (91%), followed by a single air-fluid level in the cecum and collapse of the distal colon (82%). At CT, the “coffee bean” sign with a single air-fluid level and collapse of the left colon had a sensitivity of 100%. The whirl sign was present in 86%. Retrospectively, 36% of the plain-film studies and 86% of the CT studies were classified as certain for cecal volvulus. Although all cases with ischemia had signs of vascular compromise on CT, no significant correlation was observed between these variables. Conclusions. The plain-film signs reported for cecal volvulus enable a certain diagnosis in a third of all cases; the CT signs enable a certain diagnosis in most cases. The evaluation of additional findings increases the chances of reaching the correct diagnosis (AU)

Patrón en mosaico de la pared del colon en un caso con vólvulo de ciego: hallazgos en TC / Polygonal mosaic-like pattern of the colonic mucosa in cecal volvulus: CT findings

El patrón en mosaico de la mucosa colónica es un hallazgo radiológico poco frecuente, que se ha descrito previamente en los estudios de enema de bario. Describimos la apariencia de este patrón en la TC en un paciente con vólvulo de ciego (AU)

A polygonal mosaic-like pattern of colonic mucosa is a rare radiological finding that was first described in studies using barium enema. We describe the CT findings of this pattern in a case of cecal volvulus (AU)

[Cecal volvulus: imaging features]. / Vólvulo cecal: características en imagen.

OBJECTIVE: To determine the sensitivity of plain-film radiography and computed tomography (CT) in the diagnosis of cecal volvulus. MATERIAL AND METHODS: We reviewed the clinical histories of 11 patients diagnosed with cecal volvulus at endoscopy or surgery. Two radiologists working in consensus analyzed the findings at plain-film radiography and at CT and calculated the sensitivities. The plain-film and CT studies were retrospectively classified as certain, probable, or indeterminate for cecal volvulus on the basis of the presence or absence of previously reported signs. Signs of wall suffering at CT were compared to the histologic findings. RESULTS: The most sensitive findings at plain-film radiography were the presence of a disproportionately dilated bowel loop and a pattern of distal small bowel occlusion (91%), followed by a single air-fluid level in the cecum and collapse of the distal colon (82%). At CT, the "coffee bean" sign with a single air-fluid level and collapse of the left colon had a sensitivity of 100%. The whirl sign was present in 86%. Retrospectively, 36% of the plain-film studies and 86% of the CT studies were classified as certain for cecal volvulus. Although all cases with ischemia had signs of vascular compromise on CT, no significant correlation was observed between these variables. CONCLUSIONS: The plain-film signs reported for cecal volvulus enable a certain diagnosis in a third of all cases; the CT signs enable a certain diagnosis in most cases. The evaluation of additional findings increases the chances of reaching the correct diagnosis.

[Polygonal mosaic-like pattern of the colonic mucosa in cecal volvulus: CT findings]. / Patrón en mosaico de la pared del colon en un caso con vólvulo de ciego: hallazgos en TC.

A polygonal mosaic-like pattern of colonic mucosa is a rare radiological finding that was first described in studies using barium enema. We describe the CT findings of this pattern in a case of cecal volvulus.

Topiramato en el tratamiento del dolor neuropático enpacientes previamente tratados con AINEs / Topiramate for the management of neuropathic pain in patients previously treated with NSAIs

Introducción: el topiramato es un nuevo fármaco antiepiléptico que por su buena tolerancia se está empezando a utilizar como alternativa a otros anticomiciales en el tratamiento del dolor neuropático. Objetivos: con este estudio pretendemos ver su eficacia como alternativa a otros fármacos anticonvulsivantes en el tratamiento del dolor neuropático periférico, en pacientes que previamente estaban consumiendo AINE, evaluando la evolución en el dolor mediante la escala visual analógica (VAS) y la aparición de efectos secundarios.Material y métodos: presentamos un seguimiento con dicho fármaco llevado a cabo en nuestro centro, de carácter descriptivo prospectivo sobre 200 pacientes con dolor neuropático periférico puro o asociado a dolor somático, que previamente habían recibido tratamiento con AINEs o analgésicos sin presentar mejoría en la intensidad del dolor, a los que se les administra topiramato en dosis iniciales de 25 mg.12 h-1 que se van aumentando semanalmente hasta llegar a dosis máximas de 100200 mg.día-1 según el caso, asociando AINEs y/o analgésicos y reevaluándose como mínimo al mes y a los tres meses del comienzo del tratamiento. Se compara el grado de dolor respecto a la primera visita por medio del VAS y se recogen los casos de suspensión de tratamiento y sus causas, así como los principales efectos adversos aparecidos. Resultados: en la primera revisión se objetiva un descenso de más de dos puntos en el VAS tanto en los pacientes con dolor neuropático puro como en el asociado a dolor somático, apreciándose también mejoría en la segunda revisión con respecto a la primera. Aparecen efectos adversos en un 16,4 por ciento de los pacientes de predominio en la primera semana de tratamiento, siendo los principales y por este orden las náuseas y vómitos, la somnolencia y la pérdida de peso. Se suspende el tratamiento en un 6,8 por ciento de ellos por intolerancia o inefectividad. Conclusiones: topiramato es un fármaco efectivo como alternativa a otros anticomiciales en el tratamiento del dolor neuropático. En general sus efectos adversos son escasos y bien tolerados por los pacientes (AU)

The disintegrins ADAM10 and TACE contribute to the constitutive and phorbol ester-regulated normal cleavage of the cellular prion protein.

We showed previously that PrPc undergoes constitutive and phorbol ester-regulated cleavage inside the 106-126 toxic domain of the protein, leading to the production of a fragment referred to as N1. Here we show by a pharmacological approach that o-phenanthroline, a general zinc-metalloprotease inhibitors, as well as BB3103 and TAPI, the inhibitors of metalloenzymes ADAM10 (A disintegrin and metalloprotease); and TACE, tumor necrosis factor alpha-converting enzyme; ADAM17), respectively, drastically reduce N1 formation. We set up stable human embryonic kidney 293 transfectants overexpressing human ADAM10 and TACE, and we demonstrate that ADAM10 contributes to constitutive N1 production whereas TACE mainly participates in regulated N1 formation. Furthermore, constitutive N1 secretion is drastically reduced in fibroblasts deficient for ADAM10 whereas phorbol 12,13-dibutyrate-regulated N1 production is fully abolished in TACE-deficient cells. Altogether, our data demonstrate for the first time that disintegrins could participate in the catabolism of glycosyl phosphoinositide-anchored proteins such as PrPc. Second, our study identifies ADAM10 and ADAM17 as the protease candidates responsible for normal cleavage of PrPc. Therefore, these disintegrins could be seen as putative cellular targets of a therapeutic strategy aimed at increasing normal PrPc breakdown and thereby depleting cells of the putative 106-126 "toxic" domain of PrPc.

Constitutive alpha-secretase cleavage of the beta-amyloid precursor protein in the furin-deficient LoVo cell line: involvement of the pro-hormone convertase 7 and the disintegrin metalloprotease ADAM10.

The beta-amyloid precursor protein (betaAPP) undergoes a physiological cleavage triggered by one or several proteolytic activities referred to as alpha-secretases, leading to the secretion of sAPPalpha. Several lines of evidence indicate that the alpha-secretase cleavage is a highly regulated process. Thus, besides constitutive production of sAPPalpha, several studies have reported on protein kinase C-regulated sAPPalpha secretion. Studies aimed at identifying alpha-secretase(s) candidates suggest the involvement of enzymes belonging to the pro-hormone convertases and disintegrin families. The delineation of respective contributions of proteolytic activities in constitutive and regulated sAPPalpha secretion is rendered difficult by the fact that the overall regulated response always includes the basal constitutive counterpart that cannot be selectively abolished. Here we report on the fact that the furin-deficient LoVo cells are devoid of regulated PKC-dependent sAPPalpha secretion and therefore represent an interesting model to study exclusively the constitutive sAPPalpha secretion. We show here, by a pharmacological approach using selective inhibitors, that pro-hormone convertases and proteases of the ADAM (disintegrin metalloproteases) family participate in the production/secretion of sAPPalphas in LoVo cells. Transfection analysis allowed us to further establish that the pro-hormone convertase 7 and ADAM10 but not ADAM17 (TACE, tumour necrosis factor alpha-converting enzyme) likely contribute to constitutive sAPPalpha secretion by LoVo cells.

Overexpression of Rab11 or constitutively active Rab11 does not affect sAPPalpha and Abeta secretions by wild-type and Swedish mutated betaAPP-expressing HEK293 cells.

Presenilins 1 and 2 are two homologous proteins which, when mutated, appear responsible for most of the early-onset familial forms of Alzheimer's disease. Among various functional aspects, presenilins appear to behave as chaperoning partners of a series of proteins including the beta-amyloid precursor protein. Recently, presenilins were shown to interact with Rab11, a GTPase involved in intracellular transport. This suggested that Rab11-presenilin interaction could influence the routing of betaAPP and thereby modulate its maturation. In this context, we examined whether overexpression of Rab11 or its constitutively active mutant Rab11Q70L could affect betaAPP maturation in human HEK293 cells. We show here that the overexpression of both Rab11-related proteins does not modify the recovery of secreted sAPPalpha or Abeta in HEK293 cells expressing wild-type betaAPP or betaAPP harboring the Swedish double mutation. These data indicate that Rab11 does not influence betaAPP processing in HEK293 cells. However, it does not preclude the possibility for Rab11 to modulate other presenilin-mediated functions in human cells.

Role of the proteasome in Alzheimer's disease.

The proteasome is a multicatalytic complex involved in the degradation of polyubiquitinated proteins. Here we review the clues of a possible involvement of the proteasome in Alzheimer's disease neuropathology. Thus, we discuss the fact that the proteasome modulates the intracellular concentrations of presenilins 1 and 2. These two proteins, when mutated, appear responsible for most of early onset forms of Alzheimer's disease and this is thought to be due to the exacerbation of the pathogenic pathway of the maturation of the beta-amyloid precursor protein. Controlling presenilins concentrations could have drastic repercussions on cell physiology as suggested by the fact that proteasome inhibitors drastically potentiate the 'normal' or 'pathogenic' presenilins phenotype related with betaAPP processing. The possibility of considering the proteasome as a potential target for therapeutic intervention in Alzheimer's disease is discussed.

Proprotein convertase activity contributes to the processing of the Alzheimer's beta-amyloid precursor protein in human cells: evidence for a role of the prohormone convertase PC7 in the constitutive alpha-secretase pathway.

The physiological maturation of the beta-amyloid precursor protein (betaAPP) leads to the secretion of a fragment termed APPalpha, after cleavage by a proteolytic enzyme called-secretase. In Alzheimer's disease, betaAPP undergoes exacerbated proteolytic attacks by beta- and gamma-secretases, which liberate a readily aggregatable 40-42-amino acid peptide called AP. We show here that overexpression of the prohormone convertase PC7 triggers increased secretion of APPalpha and lowers both Abeta40 and Abeta42 recoveries. Overexpression of alpha1-antitrypsin Portland (alpha1-PDX), which blocks mammalian precursor convertases of the constitutive secretory pathway, reverses the PC7-induced APPalpha increase as well as the decrease of Abeta40/42 in HEK293 cells. It is interesting that alpha1-PDX also lowers the level of APPalpha endogenously produced by mock-transfected HEK293 cells. Finally, a Jurkat clone stably expressing alpha1-PDX produces noticeably lower amounts of APPalpha. Therefore, this serpin affects endogenous a-secretase activity/pathway in distinct cell types. By contrast, alpha1-PDX does not alter the processing of presenilin 1 or its mutated congeners linked to some familial forms of Alzheimer's disease. Altogether, we demonstrate that a prohormone convertase participates in the alpha-secretase pathway of betaAPP maturation in human cells and concomitantly contributes to slowing the pathogenic route leading to the formation of Abeta. Our data strongly suggest that PC7 could fulfill such a role.

[Strategies for identification of secretases implicated in Alzheimer's disease]. / Stratégies d'identification des sécrétases impliquées dans la maladie d'Alzheimer.

In Alzheimer's disease, cortical areas of affected patients are invaded by extracellular proteinous deposits called senile plaques, the main component of which is called amyloid beta-peptide or A beta. This peptide derives from the proteolytic attack of a precursor, the beta-amyloid precursor protein, by two enzymes called beta- and gamma-secretases. Alternatively, beta APP can be cleaved by an additional activity named alpha-secretase that occurs inside the A beta sequence, thereby precluding its formation, and concomitantly liberating a secreted fragment, namely APP alpha. Therefore, secretases seem to play a key role in the control of physiological and potentially pathogenic beta APP catabolites and could be envisioned as possible therapeutic targets in Alzheimer's disease. Here, we describe possible experimental approaches to identify such proteolytic activities.

Bipolar-shape response of human neutrophils to corticotropin-releasing factor.

Human neutrophils in whole blood become bipolar in shape after exposure to chemokinetic stimuli. In normal blood, the proportion of non-spherical neutrophils was 1.2 +/- 0.07% (n = 101). After incubation of blood samples with corticotropin-releasing hormone (CRF, 1 to 20 microM) 36 of 101 subjects exhibited a > or = 10% bipolar-shape ellipsoid response. This ellipsoid response was more frequent in female than in male subjects (32/75 vs. 4/26, p < 0.01). Female Caucasian subjects were more sensitive to CRF than female East Asian subjects (25/48 vs. 2/15, p < 0.01). Age was not a factor in sensitivity to CRF. In young female East Asian subjects (23 +/- 0.4 years, n = 8) that did not manifest the ellipsoid response to CRF, formyl-Met-Leu-Phe (fMLP), a chemotactic peptide, 10(-9) M increased non-spherical neutrophils to 31 +/- 0.8%. In these individuals, the fMLP response was inhibited in a dose-dependent manner by CRF. The pharmacological profile of the stimulatory and fMLP-inhibitory actions of CRF on neutrophil shape was consistent with that of a CRF1-receptor mediated response. Expression of mRNA for the CRF1-receptor was detected in hematopoietic cell lines (e.g., HL-60) using a reverse transcriptase polymerase chain-reaction method. The bipolar-shape response of human neutrophils to CRF has the potential to be a useful indicator of the functional state of this hormone-receptor system in inflammation.

Proteasome inhibitors prevent the degradation of familial Alzheimer's disease-linked presenilin 1 and potentiate A beta 42 recovery from human cells.

BACKGROUND: Several lines of evidence suggest that most of the early-onset forms of familial Alzheimer's disease (FAD) are due to inherited mutations borne by a chromosome 14-encoded protein, presenilin 1 (PS1). This is likely related to an increased production of amyloid beta-peptide (A beta) 42, one of the main components of the extracellular deposits called senile plaques that invade human cortical areas during the disease. MATERIALS AND METHODS: We set up stably transfected HEK293 cells overexpressing wild-type (wt) and various FAD-linked mutated PS1. By Western blot analysis, we examined the influence of specific proteasome inhibitors on PS1-like immunoreactivities. Furthermore, by means of metabolic labeling and immunoprecipitation with A beta 40 and A beta 42-directed specific antibodies, we assessed the effect of the inhibitors on the production of A beta s by wt and mutated PS1-expressing cells transiently transfected with beta APP751. RESULTS: We show that two distinct proteasome inhibitors, Z-IE (Ot-Bu)A-Leucinal and lactacystin, increase in a time- and dose-dependent manner the immunoreactivities of both wt and mutated PS1. Furthermore, we demonstrate that PS1 is polyubiquitinated in these cells. Other inhibitors, ineffective on the proteasome, fail to protect wt and mutated PS1-like immunoreactivities. We also establish that the FAD-linked mutations of PS1 trigger a selective increased formation of A beta 42 as reflected by higher A beta 42 over total A beta ratios when compared with wtPS1-expressing cells. Interestingly, this augmentation was further amplified by proteasome inhibitors in cells expressing mutated but not wtPS1. CONCLUSION: Altogether, our data indicate that PS1 undergoes polyubiquitination in HEK293 cells and that the proteasome contributes to the degradation of wt and FAD-linked PS1, thereby directly influencing the A beta production in human cells.

Constitutive and protein kinase C-regulated secretory cleavage of Alzheimer's beta-amyloid precursor protein: different control of early and late events by the proteasome.

The physiological processing of the beta-amyloid precursor protein (betaAPP) by a protease called alpha-secretase gives rise to APP alpha, a C-terminally truncated fragment of betaAPP with known neurotrophic and cytoprotective properties. Several lines of evidence indicate that protein kinase C (PKC)-mediated events regulate this physiological pathway. We show here that the proteasome multicatalytic complex modulates the phorbol 12,13-dibutyrate-stimulated APP alpha secretion at several levels in human kidney 293 (HK293) cells. Two blocking agents of the proteasome, namely, Z-IE(Ot-Bu)A-leucinal and lactacystin, elicit a dual effect on PKC-regulated APP alpha secretion by metabolically labeled HK293 cells. Thus, short periods of preincubation (2-5 h) of the cells with the inhibitors trigger a drastic potentiation of APP alpha recovery, whereas long-term treatment of the cells (15-20 h) with the blocking agents leads to an overall decrease in the secretion of APP alpha. Such a dual effect was not observed on constitutive APP alpha secretion and intracellular formation generated by HK293 cells, which both only increase upon inhibitor treatments. Similar effects on the constitutive and PKC-regulated APP alpha secretion were observed with PC12 cells. Altogether, these data suggest distinct mechanisms underlying basal and PKC-regulated APP alpha production, indicating that this multicatalytic complex appears as a key contributor of the alpha-secretase pathway.