Biomedical subjects

M L Wu

Publications and source records attributed to M L Wu.

At least 55 records · Page 3Linked to original sources

PubMed1998

Regulation of acetylcholine release by intracellular acidification of developing motoneurons in Xenopus cell cultures.

1. The effects of intracellular pH changes on the acetylcholine (ACh) release and cytoplasmic Ca2+ concentration at developing neuromuscular synapses were studied in Xenopus nerve-muscle co-cultures. 2. Spontaneous and evoked ACh release of motoneurons was monitored by using whole-cell voltage-clamped myocytes. Intracellular alkalinization with 15 mM NH4Cl slightly reduced the frequency of spontaneous synaptic currents (SSCs). However, cytosolic acidification following withdrawal of extracellular NH4Cl caused a marked and transient increase in spontaneous ACh release. 3. Another method of cytosolic acidification was used in which NaCl in Ringer solution was replaced with weak organic acids. The increase in spontaneous ACh release paralleled the level of intracellular acidification resulting from addition of these organic acids. Acetate and propionate but not isethionate, methylsulphate and glucuronate, caused an increase in intracellular pH and a marked increase in spontaneous ACh release. 4. Impulse-evoked ACh release was slightly augmented by intracellular alkalinization and inhibited by cytosolic acidification. 5. Cytosolic acidification was accompanied by an elevation in the cytoplasmic Ca2+ concentration ([Ca2+]i), resulting from both external Ca2+ influx and intracellular Ca2+ mobilization. In contrast, the increase in [Ca2+]i induced by high K+ was inhibited by cytosolic acidification. 6. We conclude that cytosolic acidification regulates spontaneous and evoked ACh release differentially in Xenopus motoneurons, increasing spontaneous ACh release but inhibiting evoked ACh release.

Acetylcholine↗

PubMed1998

Differential osmosensing signalling pathways and G-protein involvement in human cervical cells with different tumour potential.

Previous studies show that the regulatory volume decrease (RVD) in human cervical cells with different tumour potential may be mediated by different ion channels. The signalling events involved in regulating these channel activities are not clear. To screen the possible mechanisms involved in cell volume regulation in these cells, we examine intracellular mechanisms and second messengers listed as follows: phospholipase C (PLC), phospholipase A2 (PLA2), tyrosine kinase (TK), protein kinase C (PKC), protein kinase A (PKA), and cAMP. The involvement of G-protein was also studied. Our results showed that PLC signalling with downstream activation of PKC was involved in the cell volume regulation of cervical cancer cells. On the other hand, different PKC isoforms that were not related to upstream PLC regulation were involved in the RVD of human papillomavirus (HPV)-immortalised and normal cervical epithelia. Furthermore, GTP-gamma S facilitated the process of RVD in cervical cancer cells, while pertussis toxin retarded this process. In contrast, neither GTP-gamma S nor pertussis toxin showed effect on the RVD responses of HPV-immortalised and normal cervical cells.

Cell Line, Transformed↗

PubMed1998

Expression and export of Pseudomonas putida NTU-8 creatinase by Escherichia coli using the chitinase signal sequence of Aeromonas hydrophila.

The gene for the creatinase from Pseudomonas putida NTU-8 was sequenced and revealed an open reading frame (ORF) of 1209 base pairs encoding a polypeptide of 403 amino acids with a calculated molecular weight (M(r)) of 45,691. The deduced amino acid sequence is very similar to that of the creatinase of Pseudomonas putida and Flavobacterium sp. An overproduction system for the chitinase signal peptide--creatinase hybrid gene was constructed by using the pQE-51 expression vector in E. coli JM109. The amount of this fusion enzyme was about 50% exported into the periplasmic space of E. coli.

Aeromonas hydrophila↗

PubMed1998

Ciliated hepatic foregut cyst mimicking neoplasm.

We describe a ciliated hepatic foregut cyst that was clinically considered neoplastic because it was large, bilocular, and associated with a high serological level of carbohydrate antigen 19-9 (CA 19-9). Histologically, the wall of the cyst showed characteristic pseudopapillae lined by ciliated stratified columnar epithelium with interspersed goblet cells and underlying smooth muscle. The epithelium was strongly immunoreactive for CA 19-9. We therefore conclude that large size, multilocularity, and elevated CA 19-9 do not exclude ciliated hepatic foregut cysts from diagnostic consideration.

Adult↗

PubMed1998

Desiccant recovered, Crohn's disease discovered.

Foreign bodies occasionally lodge in strictures due to Crohn's disease. Most cases involve patients known to have Crohn's disease. However, some patients deny or cannot recall ingestion of foreign bodies. Gastrointestinal obstruction caused by a foreign body is a rare presentation of Crohn's disease. We report the first case of Crohn's disease presenting as gastrointestinal obstruction resulting from accidental ingestion of a pharmaceutical desiccant.

Adult↗

PubMed1998

Lipoxygenase metabolites as mediators of UTP-induced intracellular acidification in mouse RAW 264.7 macrophages.

In previous studies, we have shown that mouse RAW 264.7 macrophages possess pyrimidinoceptors, coupled to a phosphoinositide-specific phospholipase C, with a higher specificity for UTP than for ATP. In the current study, we explored the mechanism involved in the UTP-induced intracellular acidification seen in this cell line. UTP (30 microM) caused a reversible pHi decrease of 0.16 +/- 0.01 unit; this effect was not influenced by the removal of extracellular Cl- or Na+ ions or by pretreatment with 5-(N-ethyl-N-isopropyl)-amiloride (10 microM), 5-nitro-2-(3-phenylpropylamino)benzoic acid (100 microM), staurosporine (1 microM), or Ro 31-8220 (1 microM) but was completely abolished by the removal of extracellular Ca2+. UTP (30 microM), thapsigargin (1 microM), and ionomycin (1 microM) each induced a similar extent of external Ca2+-dependent acidification with a similar time-dependency, but the effects were nonadditive. To further investigate the Ca2+-dependent mechanism, we studied the involvement of arachidonic acid (AA) and eicosanoid metabolites. The addition of AA (10 microM) but not arachidic acid (100 microM) produced a reduction in pHi. UTP, thapsigargin, and ionomycin induced Ca2+-dependent AA release. Furthermore, 4-bromo-phenacyl bromide [30 microM, a phospholipase A2 (PLA2) inhibitor-, nordihydroguaiaretic acid (50 microM, a lipoxygenase inhibitor), and MK-886 (10 microM, a 5-lipoxygenase-activating protein inhibitor) abolished the UTP- or ionomycin-induced responses, whereas indomethacin (30 microM, a cyclooxygenase inhibitor) and baicalein (10 microM, a selective 12-lipoxygenase inhibitor) had no effect. MAFP (a cPLA2 inhibitor) and REV 5901 (a 5-lipoxygenase inhibitor as well as a competitive antagonist of peptide leukotrienes), but not RHC 80267 (a diacylglycerol lipase inhibitor), also inhibited the UTP-induced response. In contrast, the pHi response to AA was unaffected by the presence of 4-bromo-phenacyl bromide or the removal of extracellular Ca2+ ions but abolished by addition of NDGA. Exogenous 5-hydroperoxyeicosatetraenoic acid (2 microM) also produced marked acidification, and UTP and ionomycin both induced peptide leukotriene formation. In conclusion, this is the first report indicating that lipoxygenase metabolites act as mediators of the Ca2+-dependent acidification seen in macrophages in response to UTP or ionomycin via activation of cPLA2 and AA release.

Animals↗

PubMed1998

PKC activation is required by EGF-stimulated Na(+)-H+ exchanger in human pleural mesothelial cells.

Epidermal growth factor (EGF) stimulates the Na(+)-H+ exchanger, leading to enhanced cell proliferation. In human pleural mesothelial cells (PMCs), the intracellular signaling mechanism mediating the EGF-induced stimulation of the Na(+)-H+ exchanger has not yet been identified. Using a pH-sensitive fluorescent probe, 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein, to measure changes in intracellular pH (pHi), we found that 1) EGF and 12-O-tetradecanoylphorbol 13-acetate (TPA; a phorbol ester) both stimulate the ethylisopropyl amiloride-sensitive Na(+)-H+ exchanger; 2) TPA-induced alkalosis can be blocked by protein kinase C (PKC) inhibitors (chelerythrine and staurosporine) or by PKC down-regulation, indicating that PKC activation is involved in the stimulation of the Na(+)-H+ exchanger. However, TPA-induced alkalosis is not blocked by tyrosine kinase inhibitors; and 3) the stimulatory effect of EGF on the Na(+)-H+ exchanger acts via stimulation of tyrosine kinase-receptor activity because it is inhibited by tyrosine kinase inhibitors (genistein, lavendustin A, and herbimycin A). It also involves PKC activation because EGF-induced alkalosis was blocked by PKC inhibitors. These results suggest that PKC activation is one of the downstream signals for EGF-induced activation of the Na(+)-H+ exchanger in primary cultures of human pleural mesothelial cells.

Cells, Cultured↗

PubMed1998

The clinical significance of hyperamylasemia in organophosphate poisoning.

OBJECTIVE: Hyperamylasemia with a presumptive diagnosis of acute pancreatitis has been reported following organophosphate poisoning but there are no large-scale studies incorporating more specific diagnostic criteria. METHODS: Retrospective review of the medical records of 159 patients with a diagnosis of organophosphate poisoning over 3 years. Serum amylase, pancreatic amylase, salivary amylase, lipase and cholinesterase levels, and the clinical manifestations were analyzed. RESULTS: Serum amylase data was available for 121 of the 159 study patients. Hyperamylasemia (amylase > or = 360 U/L) was found in 44 patients (36%). Lipase was measured in 28 patients with hyperamylasemia; 9 of 28 had hyperlipasemia (lipase > or = 380 U/L). The finding of hyperamylasemia was closely related to clinical severity and presence of shock. A presumptive diagnosis of painless acute pancreatitis was diagnosed by hyperlipasemia associated with hyperamylasemia, clinical severity, serum LDH, and leukocyte counts. Two patients with presumptive pancreatitis died. Shock, coma, and hypoalbuminemia were the factors predicting fatality. CONCLUSIONS: Hyperamylasemia is frequent in severe organophosphate poisoning. However, hyperamylasemia is not synonymous with acute pancreatitis and pancreatic amylase is not a reliable parameter in the diagnosis of organophosphate-induced pancreatitis due to its low sensitivity and specificity. Lipase assay is indicated in patients with hyperamylasemia for early diagnosis of pancreatitis. Proper image studies and even pathological examination are also needed to confirm the extent of pancreatic injury. With prompt diagnosis and appropriate treatment, a complete recovery can be anticipated unless the patient has otherwise unrelated complications.

Acute Disease↗

PubMed1998

A fatal case of acute ferric chloride poisoning.

Death from ferric chloride poisoning has never been reported in Taiwan. We report a fatality from the suicidal ingestion of ferric chloride solution used as an etching agent for printed circuitry. A 25-y-old woman presented with vomiting after ingestion of 200 ml ferric chloride solution (pH 1.0). She had hypoxemia and severe metabolic acidosis with respiratory alkalosis initially. Three hours after her ingestion she presented with drowsy consciousness, tachycardia, tachypnea and protracted vomiting. Laboratory studies showed leukocytosis, elevated glucose, aspartate aminotransferase, amylase, lactate dehydrogenase, and total bilirubin, coagulation defect and hemolysis. Aspiration pneumonia and vision loss were also noted. Four hours after ingestion cardiopulmonary arrest suddenly occurred after severe vomiting and she expired. Toxicological studies showed marked elevation of serum iron (2440 micrograms/dl); the estimated oral dose of ferric chloride was equivalent to 11.52 g (230 mg/kg) of elemental iron. This patient did not receive deferoxamine due to rapid deterioration and a late diagnosis. Deferoxamine should be given in any symptomatic patient or in the presence of anion gap metabolic acidosis with a history of ferric chloride ingestion.

Acidosis↗

PubMed1998

Concentrated cresol intoxication.

Cresol, a commonly used disinfectant, may cause gastrointestinal corrosive injury, central nervous system and cardiovascular disturbances, and renal and hepatic injury following intoxication. We report a case of acute severe cresol poisoning after a suicide attempt with ingestion of a cresol-soap solution used as a toilet disinfectant. A 44-y-old male was found unconscious after ingesting 300 ml of 50% cresol-soap solution. Endotracheal intubation, gastric lavage and activated charcoal were given immediately which reversed his conscious. He had dermal burns, esophageal and gastric erosion, pneumonia, mixed metabolic acidosis and respiratory aklalosis, renal and liver function impairment, leucocytosis and dark urine. Acute renal failure and hemolysis developed, but he recovered after hemodialysis and intensive supportive care. Urine levels of p-cresol, m-cresol, o-cresol and phenol were respectively 2083, 2059, 125 and 68 mg/g creatinine at 7 h post-ingestion. Though the amount cresol claimed ingested by the patient (150 g) far exceeded the reported lethal dose (30-60 g), and multiple complications developed after massive ingestion, this patient recovered. The renal, pulmonary and hematological effects in this patient might have resulted from the direct toxicity of cresol and its metabolites.

Adult↗

PubMed1997

Regulation of cyclin D1 by calpain protease.

Cyclin D1, a critical positive regulator of G1 progression, has been implicated in the pathogenesis of certain cancers. Regulation of cyclin D1 occurs at the transcriptional and posttranscriptional level. Here we present evidence that cyclin D1 levels are regulated at the posttranscriptional level by the Ca2+-activated protease calpain. Serum starvation of NIH 3T3 cells resulted in rapid loss of cyclin D1 protein that was completely reversible by calpain inhibitors. Actinomycin D and lovastatin induced rapid loss of cyclin D1 in prostate and breast cancer cells that was reversible by calpain inhibitors and not by phenylmethylsulfonyl fluoride, caspase inhibitors, or lactacystin, a specific inhibitor of the 26 S proteasome. Treatment of intact NIH 3T3, prostate, and breast cancer cells with a calpain inhibitor dramatically increased the half-life of cyclin D1 protein. Addition of purified calpain to PC-3-M lysates resulted in Ca2+-dependent cyclin D1 degradation. Transient expression of the calpain inhibitor calpastatin increased cyclin D1 protein in serum-starved NIH 3T3 cells. Cyclins A, E, and B1 have been reported to be regulated by proteasome-associated proteolysis. The data presented here implicate calpain in cyclin D1 posttranslational regulation.

3T3 Cells↗

PubMed1997

Mechanism of oxidative stress-induced intracellular acidosis in rat cerebellar astrocytes and C6 glioma cells.

1. Following ischaemic reperfusion, large amounts of superoxide anion (.O2-), hydroxyl radical (.OH) and H2O2 are produced, resulting in brain oedema and changes in cerebral vascular permeability. We have found that H2O2 (100 microM) induces a significant intracellular acidosis in both cultured rat cerebellar astrocytes (0.37 +/- 0.04 pH units) and C6 glioma cells (0.33 +/- 0.07 pH units). 2. Two membrane-crossing ferrous iron chelators, phenanthroline and deferoxamine, almost completely inhibited H2O2-induced intracellular acidosis, while the non-membrane-crossing iron chelator apo-transferrin had no effect. Furthermore, the acidosis was completely inhibited by two potent membrane-crossing .OH scavengers, N-(2-mercaptopropionyl)-glycine (N-MPG) and dimethyl thiourea (DMTU). Since .OH can be produced during iron-catalysed H2O2 breakdown (Fenton reaction), we have shown that a large reduction in pH1 in glial cells can result from the production of intracellular .OH via H2O2 oxidation. 3. We have ruled out the possible involvement of: (i) an increase in intracellular Ca2+ levels; and (ii) inhibition of oxidative phosphorylation. 4. Our results suggest that .OH inhibits glycolysis, leading to ATP hydrolysis and intracellular acidosis. This conclusion is based on the following observations: (i) in glucose-free medium, or in the presence of iodoacetate or 2-deoxy-D-glucose, H2O2-induced acidosis is completely suppressed; (ii) H2O2 and iodoacetate both produce an increase in levels of intracellular free Mg2+, an indicator of ATP breakdown; and (iii) direct measurement of intracellular ATP levels and lactate production show 50 and 55% reductions in ATP content and lactate production, respectively, following treatment with 100 microM H2O2. 5. Inhibition of the pH1 regulators (i.e. the Na(+)-H+ exchange and possibly the Na(+)-HCO3(-)-dependent pH1 transporters) resulting from H2O2-induced intracellular ATP reduction may also be involved in the H2O2-evoked intracellular acidosis in glial cells.

Acidosis↗

PubMed1997

Capacitative Ca2+ influx in glial cells is inhibited by glycolytic inhibitors.

In non-excitable cells, stimulation of phosphoinositide (PI) turnover and inhibition of the endoplasmic reticulum (ER) Ca2+-ATPase are methods commonly used to deplete calcium stores, resulting in a capacitative Ca2+ influx (i.e., Ca2+ release-activated Ca2+ influx). Since this Ca2+ influx in glial cells has not been thoroughly investigated, we have used C6 glioma cells as a glial cell model to study this phenomenon. On adding cyclopiazonic acid (CPA) or thapsigargin (TG) (two ER Ca2+-ATPase inhibitors) in Ca2+-free medium, only a small transient increase in intracellular Ca2+ was seen. After depletion of the stored Ca2+, a marked Ca2+ influx, followed by a prolonged plateau, was seen on re-addition of extracellular Ca2+ ions (2 mM), i.e., capacitative Ca2+ influx. A similar effect was seen on adding ATP, known to deplete the inositol triphosphate (IP3)-sensitive Ca2+ store in C6 cells. After various degrees of store depletion, the amplitude of the capacitative Ca2+ influx was found to be highly dependent on the amount of Ca2+ remaining in the store. This Ca2+ influx was markedly inhibited by (1) La3+ and Ni2+, (2) SK&F 96365, econazole, and miconazole, and (3) membrane depolarization, clearly showing that this Ca2+ influx after store depletion in C6 cells is a capacitative mechanism. Interestingly, the capacitative Ca2+ influx can be inhibited by a reduction in intracellular ATP (ATPi) levels in glial cells. The role of ATPi in the capacitative Ca2+ influx is discussed.

Adenosine Triphosphate↗

PubMed1997

Interaction between Na+ and H+ ions on Na-H exchange in sheep cardiac Purkinje fibers.

The interaction between Na+ and H+ ions upon Na-H exchange (NHE) was examined in sheep cardiac Purkinje fibers. Acid equivalent fluxes through NHE were examined using recordings of intracellular pH and Na+ in isolated preparations measured with ion selective microelectrodes. The extent of acid-extrusion by NHE was estimated from pH(i) recovery-rate, multiplied by beta(i) (intracellular buffering power) in response to an internal acid load induced by 20 mm NH4Cl removal (nominally HCO3- free media). A mixed inhibitory effect was found of extracellular H+ on external Na+-activation of NHE (i.e. an increase, at low pH(o), in the apparent Michaelis constant for external Na+ ions [K(Nao)(0.5)] and a decrease in the maximum transport rate [V(Nao)(max)]). In addition, we confirmed that the stoichiometry of Na(o) binding is unaffected by the pH(o) (between 7.5 and 6.5), showing a Hill coefficient close to one. The interaction between Na+ and H+ ions at the internal face of the cardiac NHE was also studied. Our evidence suggests that an increase in the intracellular Na+ ion concentration ([Na+]i) inhibits acid efflux and that this inhibition can be approximated by the decrease in thermodynamic driving force caused by reducing the transmembrane Na+ gradient. It appears, however, that small variations in [Na+]i from the normal resting level (intracellular sodium activity, a(i)Na = 7 to 13 mm) have little or no effect on acid efflux, suggesting that variation of a(i)Na is not a physiologically important controller of NHE activity in heart.

Animals↗

PubMed1997

Incipient speciation by sexual isolation in Drosophila melanogaster: extensive genetic divergence without reinforcement.

The collection of Drosophila melanogaster from Zimbabwe and nearby regions (the Z-type) yield females who would not mate with the cosmopolitan D. melanogaster males (the M-type). To dissect the genetic basis of this sexual isolation, we constructed 16 whole-chromosome substitution lines between two standard Z- and M-lines. The results were as follows: (1) All substitution lines appear normal in viability and fertility in both sexes, indicating no strong postmating isolation. (2) The genes for the behaviors are mapped to all three major chromosomes with the same ranking and comparable magnitude of effects for both sexes: III > II >> X > or = 0 (III, II and X designate the effects of the three chromosomes). The results suggest less evolution on the X than on autosomes at loci of sexual behavior. (3) The genes for "Z-maleness" are many and somewhat redundant. Whole-chromosome effects for Z-maleness appear nearly additive and show little dominance. (4) In contrast, "Z-femaleness" has less redundancy as partial genotypes never exhibit full phenotypic effects. Epistatic interactions and incomplete dominance can sometimes be detected. (5) The extensive genetic divergence underlying sexual isolation has evolved in the absence of detectable reduction in hybrid fitnesses. Sexual selection has apparently been a driving force of multiple facets of speciation at the nascent stage without reinforcement.

Animals↗

PubMed1997

Intracellular pH regulation in cultured human pleural mesothelial cells.

The human pleural space is lined by a single layer of mesothelial cells, the intracellular pH (pH(i)) of which has never been investigated. In the present study, the intrinsic buffering power of H+ ions (beta(i)) and the pH(i) regulatory systems were investigated in primary cultures of human pleural mesothelial cells (PMCs) with microspectrofluorimetry. We found: (1) that at the resting pH(i), the beta(i) was low and increased as the pH(i) decreased; (2) that the pH(i) recovery was largely inhibited either with Na+-free medium or nominally HCO3 free medium containing ethyl-isopropyl amiloride (EIPA); (3) a 4-4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS)-sensitive, Na+/HCO3-dependent, but Cl(-)-independent acid extrusion mechanism in CO2/HCO3 buffer; and (4) that in the same buffer, a DIDS- sensitive but Na+-independent alkalosis was induced by intracellular Cl- depletion. We therefore conclude that at least three membrane pH(i) regulators are involved in regulating the pH(i) in PMCs, these being the EIPA-sensitive Na+-H+ exchanger; a novel electroneutral, DIDS-sensitive Na+-HCO3 cotransporter; and the DIDS-sensitive Cl(-)-HCO3 exchanger. Furthermore, under physiologic conditions, the Na+-HCO3 cotransporter plays a more important role in extrusion of excess intracellular H+ ions than does the Na+-H+ exchanger.

Amiloride↗

PubMed1997

Scombroid fish poisoning: an overlooked marine food poisoning.

Scombroid fish poisoning is a food-borne chemical intoxication caused by certain spoiled fish that contain a large amount of histamine and some biogenic diamines. It has gradually become a world-wide medical problem and probably is the most common cause of fish poisoning. As the data on the incidents of scombroid fish poisoning in Taiwan remains scarce, we report 2 incidents of scombroid fish poisoning in Northern Taiwan. We collected data of the 2 outbreaks of suspected fish poisoning which were reported to us in 1996. An epidemiological investigation was undertaken. Questionnaire interviews were given to persons who ate lunch in the same cafeteria in outbreak 2. The leftover fish were sent for species identification and toxin analysis. The first incident involving 4 women occurred in March 1996. All cases experienced flush, dizziness, blurred vision and skin rashes after eating lunch. A non-scombroid fish of Makaira with histamine levels as high as 84.13 mg/100 g flesh was implicated in this incident. In August 1996, another incident involving some cases who ate lunch at the same cafeteria were investigated. A total of 146 questionnaires were distributed with a return of 132 questionnaires (90.4%). Fifty-five employees reported positive signs or symptoms; 48 persons who ate fish and 7 women who did not eat fish were ill. Fish was the only food associated with the illness with an attack rate of 73.8% (p < 0.001). The incriminated fish was later identified as a scombroid fish of Euthynnus with a histamine content of 271.9 mg/100 g flesh in 1 leftover piece and 118.5 mg/100 g flesh in another piece. Most cases in these 2 outbreaks received treatment with antihistamines and had rapid and complete recovery. The diagnosis of scombroid fish poisoning could be misdiagnosed as food allergy or bacterial food poisoning if physicians are not aware of such poisoning. The nonspecific but characteristic symptomatology of histamine food poisoning and previous consumption of fish should alert physicians to the possibility of scombroid fish poisoning. Unless complicated with shock or respiratory distress, supportive treatment with antihistamines usually concludes with a good prognosis. Toxin analysis of the fish flesh remains the most important step in approaching a confirmed diagnosis.

Adolescent↗

PubMed1996

Different interleukin-1 beta converting enzyme (ICE) family protease requirements for the apoptotic death of T lymphocytes triggered by diverse stimuli.

Two cell permeable peptide fluoromethyl ketone inhibitors of Interleukin-1 beta converting enzyme (ICE) family proteases were tested as inhibitors of apoptotic cell death of T lymphocytes at various stages of differentiation. The CPP-32-like protease activity in apoptotic cell lysates was blocked by both the ICE inhibitor Cbz-Val-Ala-Asp(OMe)-fluoromethyl ketone (ZVAD-FMK) as well as its truncated analog Boc-Asp(OMe)-fluoromethyl ketone (BD-FMK), which failed to block ICE. In vitro apoptotic death in murine thymocytes triggered by the independent agents dexamethasone, etoposide, radiation, anti-Fas, and anti-CD3 was blocked equally well by BD-FMK and ZVAD-FMK, but not by the control reagent Cbz-Phe-Ala-fluoromethyl ketone. In activated T cell blasts, while anti-CD3/ Fas-induced death was almost completely inhibited by both ZVAD-FMK, and BD-FMK, death induced by dexamethasone, etoposide, or irradiation was more sensitive to inhibition by BD-FMK. In the murine T cell line CTLL-2, apoptotic death induced by IL-2 withdrawal, etoposide, or dexamethasone was inhibited by BD-FMK, while ZVAD-FMK was without effect. These data indicate that ICE-family proteases comprise a common functional step in distinct T cell apoptotic death pathways, but suggest that different family members are likely to be critical in various differentiated T cell types, even when triggered by the same stimulus.

Amino Acid Chloromethyl Ketones↗