Enforced dimerization of BAX results in its translocation, mitochondrial dysfunction and apoptosis

Expression of the pro-apoptotic molecule BAX has been shown to induce cell death. While BAX forms both homo- and heterodimers, questions remain concerning its native conformation in vivo and which moiety is functionally active. Here we demonstrate that a physiologic death stimulus, the withdrawal of interleukin-3 (IL-3), resulted in the translocation of monomeric BAX from the cytosol to the mitochondria where it could be cross-linked as a BAX homodimer. In contrast, cells protected by BCL-2 demonstrated a block in this process in that BAX did not redistribute or homodimerize in response to a death signal. To test the functional consequence of BAX dimerization, we expressed a chimeric FKBP-BAX molecule. Enforced dimerization of FKBP-BAX by the bivalent ligand FK1012 resulted in its translocation to mitochondria and induced apoptosis. Caspases were activated yet caspase inhibitors did not block death; cytochrome c was not released detectably despite the induction of mitochondrial dysfunction. Moreover, enforced dimerization of BAX overrode the protection by BCL-XL and IL-3 to kill cells. These data support a model in which a death signal results in the activation of BAX. This conformational change in BAX manifests in its translocation, mitochondrial membrane insertion and homodimerization, and a program of mitochondrial dysfunction that results in cell death.

Apomorphine enantiomers protect cultured pheochromocytoma (PC12) cells from oxidative stress induced by H2O2 and 6-hydroxydopamine

A significant body of evidence has been provided to support the hypothesis that oxidant stress may be responsible for the degeneration of dopaminergic neurons in the substantia nigra pars compacta in Parkinson's disease. Apomorphine, a dopamine D1/D2-receptor agonist in the clinical therapy of Parkinson's disease, has been found to be a potent antioxidant and to prevent free radical reaction in rat brain mitochondrial fraction. In this article we show that 1-10 microM of apomorphine protects rat pheochromocytoma (PC12) cells from the toxic effects of H2O2 (0.6 mM) and the neurotoxin 6-hydroxydopamine (150 microM). Neither of these effects were exhibited by ascorbic acid, desferal, lisuride, or bromocriptine. Although pergolide exhibited some protection of PC12 cells against H2O2 toxicity, it was not as potent as apomorphine. In light of the present findings and the clinical reports that parkinsonian patients on long-term apomorphine therapy stabilize clinically and can be weaned off L-dopa, one may assume that apomorphine can exert a neuroprotective activity by way of its potent antioxidant properties.

Autism and autistic epileptiform regression with occipital spikes

The electroencephalographic abnormalities seen in Landau-Kleffner syndrome (LKS) (language deterioration) are non-specific, and consist of a variety of epileptiform discharge patterns including continuous slow spike-wave discharges during sleep, focal sharp waves with spikes, and centrotemporal (rolandic) spikes. Similarly, the EEG abnormalities seen in autistic epileptiform regression (language and social/behavioral deterioration) are non-specific and overlap with those seen in LKS. By contrast, distinct epilepsy syndromes in otherwise normal children occur in the EEG-defined benign focal epilepsies of childhood. Occipital spikes or spike-wave present either in the older child with visual symptoms and headache or in the younger child with autonomic symptoms followed by brief or prolonged partial motor seizures. Seven young children (five from a consecutive series of 42) presenting clinically with autism or autistic regression and possible or definite seizures, whose EEGs revealed occipital spikes or spike-wave characteristic of the benign epilepsies, are reported. Although occipital spikes are commonly seen in young children as an age-dependent EEG-defined benign focal epilepsy, their high frequency in this population with cognitive difficulties suggests a possible causal relation. The effects of the epileptiform discharge on cognitive functioning presumably reflect extension into temporal and parietal lobes, rather than occipital disturbances per se.

Urinary cadmium as indicator of renal cadmium in humans: an autopsy study

OBJECTIVE

To estimate the equivalent cadmium levels in renal cortex and in urine, as based on autopsy analysis of subjects not exposed to cadmium occupationally.

METHODS

The levels of Cd were determined in renal cortex, liver, urine and urinary bladder of 39 subjects deceased at the age 42 +/- 14 years. Flame atomic absorption spectrometry (kidneys, liver) and flameless AAS (urine, bladder) were used.

RESULTS

The urinary cadmium level determined post mortem is strongly correlated with the renal Cd levels. Eliminating cases with high urinary proteins and extrapolating from sets of data with elevated urinary protein concentration to its normal range yielded a value of 1.7 microg/g creatinine as equivalent to the renal level of 50 microg/g w.w.

CONCLUSIONS

It seems possible to use monitoring data for cadmium in urine and in renal cortex in a coherent way.

Expression and bactericidal activity of nitric oxide synthase in Brucella suis-infected murine macrophages

We examined the expression and activity of inducible nitric oxide synthase (iNOS) in both gamma interferon (IFN-gamma)-treated and untreated murine macrophages infected with the gram-negative bacterium Brucella suis. The bacteria were opsonized with a mouse serum containing specific antibrucella antibodies (ops-Brucella) or with a control nonimmune serum (c-Brucella). The involvement of the produced NO in the killing of intracellular B. suis was evaluated. B. suis survived and replicated within J774A.1 cells. Opsonization with specific antibodies increased the number of phagocytized bacteria but lowered their intramacrophage development. IFN-gamma enhanced the antibrucella activity of phagocytes, with this effect being greater in ops-Brucella infection. Expression of iNOS, interleukin-6, and tumor necrosis factor alpha (TNF-alpha) mRNAs was induced in both c-Brucella- and ops-Brucella-infected cells and was strongly potentiated by IFN-gamma. In contrast to that of cytokine mRNAs, iNOS mRNA expression was independent of opsonization. Similar levels of iNOS mRNAs were expressed in IFN-gamma-treated cells infected with c-Brucella or ops-Brucella; however, expression of iNOS protein and production of NO were detected only in IFN-gamma-treated cells infected with ops-Brucella. These discrepancies between iNOS mRNA and protein levels were not due to differences in TNF-alpha production. The iNOS inhibitor N omega-nitro-L-arginine methyl ester increased B. suis multiplication specifically in IFN-gamma-treated cells infected with ops-Brucella, demonstrating a microbicidal effect of the NO produced. This observation was in agreement with in vitro experiments showing that B. suis was sensitive to NO killing. Together our data indicate that in B. suis-infected murine macrophages, the posttranscriptional regulation of iNOS necessitates an additive signal triggered by macrophage Fcgamma receptors. They also support the possibility that in mice, NO favors the elimination of Brucella, providing that IFN-gamma and antibrucella antibodies are present, i.e., following expression of acquired immunity.

Influence of endogenous and environmental factors on variations of serum lipoprotein (a) concentrations in a large population of insulin-treated diabetic patients

Variations of serum Lp(a) concentrations were studied in a large population of insulin-treated diabetic patients in relation to the type of diabetes, insulin treatment and long-term complications. Lp(a) concentrations were measured by immunonephelometry in 740 diabetic patients [493 insulin-dependent diabetic (IDDM) patients and 247 insulin-treated Type 2 diabetic (ITD) patients]. Concentrations and distributions were compared with those of 128 non-diabetic controls. Correlations were investigated with lipidic and glycaemic parameters, daily lipid intake, body mass index (BMI), macrovascular and nephropathic complications, and insulin therapy. Both groups of insulin-treated patients (IDDM and ITD) displayed significantly higher Lp(a) concentrations when compared to controls. No relationship was found with macrovascular complications and nephropathy, except in IDDM patients in whom Lp(a) was elevated when creatinine concentration was above 120 mumol/L. Mean variations of Lp(a) were correlated with BMI and triglyceride variations in IDDM patients and only with triglycerides in ITD patients. These results suggest a direct and/or indirect (via serum triglycerides) potential role of exogenous insulin in the modulation of serum Lp(a) concentrations. BMI and lipid daily fat intake could be considered as additional modulating factors of Lp(a) serum concentrations in ITD patients.

Apomorphine enantiomers protect cultured pheochromocytoma (PC12) cells from oxidative stress induced by H2O2 and 6-hydroxydopamine

A significant body of evidence has been provided to support the hypothesis that oxidant stress may be responsible for the degeneration of dopaminergic neurons in the substantia nigra pars compacta in Parkinson's disease. Apomorphine, a dopamine D1/D2-receptor agonist in the clinical therapy of Parkinson's disease, has been found to be a potent antioxidant and to prevent free radical reaction in rat brain mitochondrial fraction. In this article we show that 1-10 microM of apomorphine protects rat pheochromocytoma (PC12) cells from the toxic effects of H2O2 (0.6 mM) and the neurotoxin 6-hydroxydopamine (150 microM). These effects were not exhibited by ascorbic acid, desferal, lisuride, or bromocriptine. Although pergolide exhibited some protection of PC12 cells against H2O2 toxicity, it was not as potent as apomorphine. In light of the present findings and the clinical reports that parkinsonian patients on long-term apomorphine stabilize clinically and can be weaned off L-dopa, one may assume that apomorphine can exert a neuroprotective activity via its potent antioxidant properties.

Nitric oxide production in human macrophagic cells phagocytizing opsonized zymosan: direct characterization by measurement of the luminol dependent chemiluminescence

When differentiated into mature macrophages by the combination of all-trans retinoic acid and 1,25-dihydroxyvitamin D3, the human promonocytic cell lines U937 and THP-1 expressed inducible nitric oxide synthase (iNOS) transcripts. During their differentiation, the cells acquired the capacity to produce not only superoxide anion (O2.-) but also nitric oxide (.NO) in response to IgG (or IgE)-opsonized zymosan. The inhibitors of the iNOS pathway, aminoguanidine and NG-monomethyl-L-arginine (L-NMMA), suppressed the production of .NO and enhanced the steady-state concentration of O2.- determined. Conversely, superoxide dismutase (SOD) scavenged the O2.- released and increased the .NO-derived nitrite concentration detected. These data suggested a possible interaction between O2.- and .NO. In differentiated U937 (or THP-1) cells, IgG or IgE-opsonized zymosan induced a strong time-dependent luminol-dependent chemiluminescence (LDCL), which was abrogated by SOD and partially inhibited by aminoguanidine or L-NMMA. Since the iNOS inhibitors did not directly scavenge O2.-, LDCL determination in the presence or absence of SOD and/or iNOS inhibitors demonstrated a concomitant production of O2.- and .NO. These radicals induced the formation of a .NO-derived product(s), probably peroxynitrite (ONOO-), which was required to elicit maximal LDCL. Finally, LDCL measurement provided a convenient tool to characterize iNOS triggering and demonstrated an interaction between NADPH oxidase and iNOS products in human macrophagic cells phagocytizing opsonized-zymosan. These findings show that in activated macrophages, iNOS activity can be involved in LDCL and support the debated hypothesis of iNOS participation to the microbicidal activity of human macrophages.

Comparison of the ion channel characteristics of proapoptotic BAX and antiapoptotic BCL-2

The BCL-2 family of proteins is composed of both pro- and antiapoptotic regulators, although its most critical biochemical functions remain uncertain. The structural similarity between the BCL-XL monomer and several ion-pore-forming bacterial toxins has prompted electrophysiologic studies. Both BAX and BCL-2 insert into KCl-loaded vesicles in a pH-dependent fashion and demonstrate macroscopic ion efflux. Release is maximum at approximately pH 4.0 for both proteins; however, BAX demonstrates a broader pH range of activity. Both purified proteins also insert into planar lipid bilayers at pH 4.0. Single-channel recordings revealed a minimal channel conductance for BAX of 22 pS that evolved to channel currents with at least three subconductance levels. The final, apparently stable BAX channel had a conductance of 0.731 nS at pH 4. 0 that changed to 0.329 nS when shifted to pH 7.0 but remained mildly Cl- selective and predominantly open. When BAX-incorporated lipid vesicles were fused to planar lipid bilayers at pH 7.0, a Cl--selective (PK/PCl = 0.3) 1.5-nS channel displaying mild inward rectification was noted. In contrast, BCL-2 formed mildly K+-selective (PK/PCl = 3.9) channels with a most prominent initial conductance of 80 pS that increased to 1.90 nS. Fusion of BCL-2-incorporated lipid vesicles into planar bilayers at pH 7.0 also revealed mild K+ selectivity (PK/PCl = 2.4) with a maximum conductance of 1.08 nS. BAX and BCL-2 each form channels in artificial membranes that have distinct characteristics including ion selectivity, conductance, voltage dependence, and rectification. Thus, one role of these molecules may include pore activity at selected membrane sites.

Decrease in phosphocreatine level in skeletal muscle of SIV-infected rhesus macaques correlates with decrease in intracellular glutathione

Loss of skeletal muscle tissue (cachexia) is one of the hallmarks of HIV infection. It has been found (1) that creatine kinase, i.e., an enzyme of pivotal importance in muscular mitochondrial energy metabolism, is inhibited by oxidative glutathiolation, and (2) that reduced glutathione (GSH) is decreased in skeletal muscle of SIV-infected rhesus monkeys. We, therefore, have studied the phosphocreatine (P-Cr) levels. Muscle tissue from SIV-infected macaques showed significantly decreased P-Cr but normal creatine (Cr), ATP, and ADP when compared with uninfected macaques. Individual P-Cr levels were significantly correlated with GSH. Our findings may explain the dysregulation of energy metabolism in cachexia.

Short-term intensive insulin therapy in insulin-requiring diabetes: effectiveness and factors predicting success

Insulin-requiring diabetes (IRD) is a condition of permanent blood glucose imbalance which occurs despite a regulated diet and treatment with maximum doses of oral anti-diabetic drugs (glibenclamide 15 mg/d + metformin 1,700 mg/d). This report describes the results of a 2-year prospective study in 75 IRD patients treated to eliminate their insulin requirement. All had residual endogenous insulin secretion (REIS) (urinary C peptide > 80 micrograms/24 h and/or basal C peptide > 2.4 ng/ml) and were treated for 10 days by subcutaneous insulin infusion via a portable pump. REIS was measured, and insulin resistance was determined by an insulin tolerance test (ITT) to define their insulin sensitivity index (DG/G) before and after 10-day intensive therapy. The patients were monitored as outpatients, and the attempt at remission was considered to be a failure (F) or a success (S). Thirty of the 75 patients (40%) were in remission at 1 year, and 14/67 (21%) at 2 years. No clinical criterion differentiated successes from failures at 1 year, nor was the initial degree of blood glucose imbalance or the REIS predictive of the metabolic changes that occurred after insulin therapy. However, the drop in the insulin requirement (IR) (-26% for F and -39% for S, p < 0.05) and the increases in the DG/G index (+68 +/- 51% for F and 176 +/- 50% for S, p < 0.01) after insulin therapy were indicative of their condition 1 year later. Receiving operating characteristic curves showed that a 35% decrease in IR and an 80% increase in DG/G were indicative of a successful outcome at 1 year, with a specificity and sensitivity of about 70%. It is concluded that a decrease in daily IR and an increase in the DG/G index during insulin treatment are prognostic indicators of the course of insulin-requiring diabetics after temporary intensive insulin treatment.

The ankle clonus test for assessment of the integrity of the spinal cord during operations for scoliosis

The ankle clonus test, a method for evaluating the integrity of the spinal cord during operations for scoliosis, is predicated on the finding that patients recovering from general anesthesia normally have temporary ankle clonus bilaterally. An absence of transient ankle clonus has been shown to indicate neurological compromise. The test was performed for 1006 patients who were being managed with spinal arthrodesis and instrumentation and 115 control patients who had an operation under general anesthesia because of a condition that was unrelated to the spine. The six patients in whom a neurological deficit developed all had had a so-called positive result on the ankle clonus test (that is, an absence of transient ankle clonus). There were no false-negative results and three false-positive results; the test therefore had a sensitivity of 100 per cent and a specificity of 99.7 per cent. The ankle clonus test was found to be more accurate than the wake-up test and monitoring of somatosensory evoked potentials for predicting neurological compromise.

mRNAs encoding CCKB but not CCKA receptors are expressed in human T lymphocytes and Jurkat lymphoblastoid cells

We previously reported the existence of pharmacologically related gastrin/CCKB type receptors (CCKB-R) in a variant of Jurkat T lymphoblastoid cells (JK(CD3- CD4+)). We studied here the expression of mRNAs encoding CCKA and CCKB receptors in various human white cells by means of Reverse Transcription-Polymerase Chain Reaction (RT-PCR). Using CCKB-R specific primers, we detected a significant expression of CCKB-R mRNA in JK(CD3- CD4+) cells. These transcripts were also expressed, at a lower level, in two other Jurkat clones (JK(CD3+ CD4-) and JK(CD3+ CD4+)), in peripheral blood lymphocytes (PBL) and in purified CD4+ and CD8+ lymphocytes. Activation of Jurkat cells and PBL by T cells mitogenic lectins (jacalin, phytohemaglutinin) did not modify CCKB-R mRNA expression. In all these cells, using CCKA-R specific primers, we could not amplify any specific cDNA fragment corresponding to this receptor. Neither CCKB-R nor CCKA-R mRNAs could be detected in monocytic cells. Our data show for the first time a constitutive expression of CCKB-R transcripts in lymphoid cells. Moreover, the modulation of immunocyte functions by cholecystokinin-related peptides could occur through CCKB-R rather than CCKA-R and affect lymphocytes rather than monocytes.

Ectopic production and processing of atrial natriuretic peptide in a small cell lung carcinoma cell line and tumor from a patient with hyponatremia

BACKGROUND

Tumors and tumor cell lines from two patients with small cell lung carcinoma (SCLC) (one with and one without hyponatremia) were studied. Ectopic production and prohormone processing of atrial natriuretic peptide (ANP) were investigated to determine if a biologically active peptide was produced in a tumor cell line from a patient with hyponatremia and no evidence of arginine vasopressin (AVP) production.

METHODS

Ribonuclease (RNase) protection assays were performed on mRNA isolated from tumors and tumor cell lines established from two SCLC patients, one with and one without hyponatremia. Cellular extracts and conditioned media were studied using reversed-phase high performance liquid chromatography (HPLC) to determine the immunoreactive form of ANP. Tumor cell line sonicates were studied for subcellular localization of enzymatic activity that cleaved pro-ANP peptide substrates.

RESULTS

RNase protection assays showed a 200-base pair protected fragment in the mRNA isolated from the tumor and tumor cell line from the patient with hyponatremia (Patient 4). HPLC characterization of the cellular extract and conditioned medium from the tumor and tumor cell line from Patient 4 demonstrated ANP immunoreactivity in the same fraction as ANP- (S99-Y126). The tumor cell line extract that localizes to a subcellular fraction enriched for lysosomes and secretory organelles contains a 60-kilodalton molecular weight protein with enzyme activity that hydrolyzes synthetic pro-ANP substrates and catalyzes the formation of ANP-(S99-Y126).

CONCLUSIONS

A tumor cell line from a patient with hyponatremia was able ectopically to produce, process, and secrete ANP in the same immunoreactive form as the biologically active molecule. Preliminary studies show that tumor cell line NCI-H1284 contains an enzyme that can cleave precursors at the same amino acid sequences needed to produce ANP-(S99-Y126) from pro-ANP.

Elevated hepatic gamma-glutamylcysteine synthetase activity and abnormal sulfate levels in liver and muscle tissue may explain abnormal cysteine and glutathione levels in SIV-infected rhesus macaques

To establish whether the low cysteine and glutathione levels in HIV-infected patients and SIV-infected rhesus macaques may be consequences of an abnormal cysteine catabolism, we analyzed sulfate and glutathione levels in macaques. Muscle tissue (m. vastus lateralis and m. gastrocnemius) of SIV-infected macaques (n = 25) had higher sulfate and lower glutathione and glutamate levels than that of uninfected controls (n =9). Hepatic tissue, in contrast, showed decreased sulfate and glutathione disulfide (GSSG) levels, and increased gamma-glutamylcysteine synthetase (gamma-GCS) activity. These findings suggest drainage of the cysteine pool by increased cysteine catabolism in skeletal muscle tissue, and by increased hepatic glutathione biosynthesis. Cachectic macaques also showed increased urea levels and decreased glutamine/urea ratios in the liver, which are obviously related to the abnormal urea excretion and negative nitrogen balance commonly observed in cachexia. As urea production and net glutamine synthesis in the liver are strongly influenced by proton-generating processes, the abnormal hepatic urea production may be the direct consequence of the cysteine deficiency and the decreased catabolic conversion of cysteine into sulfate and protons in the liver.

Serum lipoprotein (a) concentrations in a population of 819 non-insulin-dependent diabetic patients

Variations in serum Lp(a) concentrations were studied in a large population of non-insulin-dependent diabetic (NIDDM) patients in relation to long-term complications. Lp(a) concentrations were measured by immunonephelometry in 819 NIDDM subjects and compared with those of 128 controls. Correlations were investigated relative to plasma lipid and glycaemic parameters, body mass index (BMI) and macro- and microvascular complications. Mean absolute and relative variations of Lp(a) concentrations were studied in a subgroup of 245 patients over a one-year period. No significant differences were found between Lp(a) concentrations in NIDDM and control subjects. No relationship was evidenced with macrovascular and microvascular complications or glycaemic control. Mean relative Lp(a) variations were correlated with BMI and absolute and relative variations in triglyceridaemia. These results confirm the absence of any alterations of Lp(a) concentrations in a large cohort of NIDDM patients, either with or without micro- and macrovascular complications, but suggest a particular modulatory role for BMI and serum triglyceride variations.

Abnormal glutathione and sulfate levels after interleukin 6 treatment and in tumor-induced cachexia

Excessive urea excretion associated with a negative nitrogen balance and massive loss of skeletal muscle mass (cachexia) is a frequent life threatening complication in malignancies and HIV infection. As these patients have often elevated interleukin-6 (IL-6) and abnormally low cystine levels, we have now determined the intracellular levels of glutathione and other cysteine derivatives in the liver and muscle tissue of IL-6-treated or tumor-bearing C57BL/6 mice. IL-6 treatment or inoculation of the MCA-105 fibrosarcoma caused a significant increase in hepatic gamma-glutamyl-cysteine synthetase activity and a decrease in the sulfate level, glutamine/urea ratio, and glutamine/glutamate ratio, suggesting that a decrease of the proton generating cysteine catabolism in the liver may increase carbamoyl-phosphate synthesis and urea formation at the expense of net glutamine synthesis. Treatment with cysteine, conversely, caused an increase in sulfate, glutamine/urea ratios, and glutamine/glutamate ratios and may thus be a useful therapeutic tool in clinical medicine. In contrast to the liver, muscle tissue of tumor-bearing mice showed decreased glutathione and increased sulfate levels, suggesting that the cysteine pool may be drained by an increased cysteine catabolism in this tissue. The findings indicate that tumor cachexia is triggered initially by IL-6 and is later sustained by processes driven by an abnormal cysteine metabolism in different organs.-Hack, V., Gross, A., Kinscherf, R., Bockstette, M., Fiers, W., Berke, G., and Dröge, W. Abnormal glutathione and sulfate levels after interleukin 6 treatment and in tumor-induced cachexia.