Differences and similarities between COVID-19 related-headache and COVID-19 vaccine related-headache. A case-control study

INTRODUCTION

Headache is a frequent symptom at the acute phase of coronavirus disease 2019 (COVID-19) and also one of the most frequent adverse effects following vaccination. In both cases, headache pathophysiology seems linked to the host immune response and could have similarities. We aimed to compare the clinical phenotype and the frequency and associated onset symptoms in patients with COVID-19 related-headache and COVID-19 vaccine related-headache.

SUBJECTS AND METHODS

A case-control study was conducted. Patients with confirmed COVID-19 infection and COVID-19-vaccine recipients who experienced new-onset headache were included. A standardised questionnaire was administered, including demographic variables, prior history of headaches, associated symptoms and headache-related variables. Both groups were matched for age, sex, and prior history of headache. A multivariate regression analysis was performed.

RESULTS

A total of 238 patients fulfilled eligibility criteria (143 patients with COVID-19 related-headache and 95 subjects experiencing COVID-19 vaccine related-headache). Patients with COVID-19 related-headache exhibited a higher frequency of arthralgia, diarrhoea, dyspnoea, chest pain, expectoration, anosmia, myalgia, odynophagia, rhinorrhoea, cough, and dysgeusia. Further, patients with COVID-19 related-headache had a more prolonged daily duration of headache and described the headache as the worst headache ever experienced. Patients with COVID-19 vaccine-related headache, experienced more frequently pain in the parietal region, phonophobia, and worsening of the headache by head movements or eye movements.

CONCLUSION

Headache caused by SARS-CoV-2 infection and COVID-19 vaccination related-headache have more similarities than differences, supporting a shared pathophysiology, and the activation of the innate immune response. The main differences were related to associated symptoms.

Inhibition of Mertk Signaling Enhances Bone Healing after Tooth Extraction

Regeneration of alveolar bone is an essential step in restoring healthy function following tooth extraction. Growth of new bone in the healing extraction socket can be variable and often unpredictable when systemic comorbidities are present, leading to the need for additional therapeutic targets to accelerate the regenerative process. One such target is the TAM family (Tyro3, Axl, Mertk) of receptor tyrosine kinases. These proteins have been shown to help resolve inflammation and maintain bone homeostasis and thus may have therapeutic benefits in bone regeneration following extraction. Treatment of mice with a pan-TAM inhibitor (RXDX-106) led to accelerated alveolar bone fill following first molar extraction in a mouse model without changing immune infiltrate. Treatment of human alveolar bone mesenchymal stem cells with RXDX-106 upregulated Wnt signaling and primed the cells for osteogenic differentiation. Differentiation of human alveolar bone mesenchymal stem cells with osteogenic media and TAM-targeted inhibitor RXDX-106 (pan-TAM), ASP-2215 (Axl specific), or MRX-2843 (Mertk specific) showed enhanced mineralization with pan-TAM or Mertk-specific inhibitors and no change with Axl-specific inhibitor. First molar extractions in Mertk-/- mice had increased alveolar bone regeneration in the extraction socket relative to wild type controls 7 d postextraction. Flow cytometry of 7-d extraction sockets showed no difference in immune cell numbers between Mertk-/- and wild type mice. RNAseq of day 7 extraction sockets showed increased innate immune-related pathways and genes associated with bone differentiation in Mertk-/- mice. Together, these results indicate that TAM receptor signaling, specifically through Mertk, can be targeted to enhance bone regeneration after injury.

A specific gene-microbe interaction drives the development of Crohn's disease-like colitis in mice

Bacterial dysbiosis is associated with Crohn's disease (CD), a chronic intestinal inflammatory disorder thought to result from an abnormal immune response against intestinal bacteria in genetically susceptible individuals. However, it is unclear whether dysbiosis is a cause or consequence of intestinal inflammation and whether overall dysbiosis or specific bacteria trigger the disease. Here, we show that the combined deficiency of NOD2 and phagocyte NADPH oxidase, two CD susceptibility genes, triggers early-onset spontaneous T_H1-type intestinal inflammation in mice with the pathological hallmarks of CD. Disease was induced by Mucispirillum schaedleri, a Gram-negative mucus-dwelling anaerobe. NOD2 and CYBB deficiencies led to marked accumulation of Mucispirillum, which was associated with impaired neutrophil recruitment and killing of the bacterium by luminal neutrophils. Maternal immunoglobulins against Mucispirillum protected mutant mice from disease during breastfeeding. Our results indicate that a specific intestinal microbe triggers CD-like disease in the presence of impaired clearance of the bacterium by innate immunity.

[Comparison of rapid anesthetic induction with sevoflurane vs target-controlled infusion of propofol]

OBJECTIVE

To determine whether inhalation induction is faster than target-controlled infusion (TCI).

MATERIAL AND METHODS

Patients in ASA physical status 1 or 2 who were scheduled for elective surgery were randomized to a propofol TCI group or a sevoflurane group. Both groups received a TCI of 5 ng L(-1) of remifentanil. Rapid induction was performed using an effect-site TCI of 2.8 microg mL(-1) of propofol in the propofol group and 8% sevoflurane in the sevoflurane group. We recorded time until loss of the palpebral reflex, hemodynamic variables, respiratory variables, hypnotic depth of anesthesia using the auditory evoked potentials index (AAI), and the moment the anesthesiologist decided to intubate. Also recorded was the time taken to reach an AAI of less than 40, which was established as the threshold of hypnotic depth sufficient for tracheal intubation.

RESULTS

Forty-four patients were enrolled in the trial. The palpebral reflex loss time was 60 (44-90) seconds in the TCI-propofol group and 72 (38-265) seconds in the sevoflurane group (P<.05). An AAI of less than 40 was reached in 105 (90-195) seconds in the TCI-propofol group and in 230 (125-355) seconds in the sevoflurane group. The variation in the calculated effect-site concentration (Ce) was consistent with the direction of change in the AAI value, which decreased as Ce increased; the variation in the expired fraction of sevoflurane did not show the same relationship. The anesthesiologist was not authorized to intubate 2 patients in the sevoflurane group as the AAI threshold was not reached. The decrease in blood pressure was significantly greater in patients in the sevoflurane group than in those in the propofol group.

CONCLUSION

Anesthetic induction is faster with a TCI of propofol based on Ce than with sevoflurane. The propofol Ce was consistent with the direction of change in the AAI.

Cancer gene therapy with iCaspase-9 transcriptionally targeted to tumor endothelial cells

Antiangiogenic therapies have shown varying results partly because each tumor type secretes a distinct panel of angiogenic factors to sustain its own microvascular network. In addition, recent evidence demonstrated that tumors develop resistance to antiangiogenic therapy by turning on alternate angiogenic pathways when one pathway is therapeutically inhibited. Here, we test the hypothesis that expression of a caspase-based artificial death switch in tumor-associated endothelial cells will disrupt tumor blood vessels and slow down tumor progression irrespective of tumor type. Adenoviral vectors expressing inducible Caspase-9 (iCaspase-9) under transcriptional regulation with the endothelial cell-specific vascular endothelial growth factor receptor-2 (VEGFR2) promoter (Ad-hVEGFR2-iCaspase-9) induced apoptosis of proliferating human dermal microvascular endothelial cells (HDMECs), but not human tumor cells (UM-SCC-17B, head and neck squamous cell carcinoma; HepG2, hepatocellular carcinoma; PC-3, prostate adenocarcinoma; SLK, Kaposi's sarcoma; MCF-7, breast adenocarcinoma). Notably, apoptosis was dependent upon activation of iCaspase-9 with the dimerizer drug AP20187. Local delivery of Ad-hVEGFR2-iCaspase-9 followed by intraperitoneal injection of AP20187 ablated tumor microvessels and inhibited xenografted tumor growth in all tumor models evaluated here. We conclude that a cancer gene therapy strategy based on a transcriptionally targeted viral vector expressing an inducible caspase allows for selective and controlled ablation of microvessels of histopathologically diverse tumor types.

Unidirectional crosstalk between Bcl-xL and Bcl-2 enhances the angiogenic phenotype of endothelial cells

Expression of Bcl-x(L) correlates with the clinical outcomes of patients with cancer. While the role of Bcl-2 in angiogenesis is becoming increasingly evident, the function of Bcl-x(L) in angiogenesis is unclear. Here, we showed that epidermal growth factor (EGF) induces in vitro capillary sprouting and Bcl-x(L) expression in primary endothelial cells. Bcl-x(L)-transduced human dermal microvascular endothelial cells (HDMEC-Bcl-x(L)), but not empty vector control cells, spontaneously organize into capillary-like sprouts. Searching for a mechanism to explain these responses, we observed that Bcl-x(L) induced expression of the pro-angiogenic chemokines CXC ligand-1 (CXCL1) and CXC ligand-8 (CXCL8), and that blockade of CXC receptor-2 (CXCR2) signaling inhibited spontaneous sprouting of HDMEC-Bcl-x(L). Bcl-x(L) led to Bcl-2 upregulation, but Bcl-2 did not upregulate Bcl-x(L), suggesting the existence of a unidirectional crosstalk from Bcl-x(L) to Bcl-2. EGF and Bcl-x(L) activate the mitogen-activated protein kinase/ERK pathway resulting in upregulation of vascular endothelial growth factor (VEGF), a known inducer of Bcl-2 in endothelial cells. Inhibition of VEGF receptor signaling in HDMEC-Bcl-x(L) prevented Bcl-2 upregulation and demonstrated the function of a VEGF-mediated autocrine loop. Bcl-2 downregulation by RNAi blocked CXCL1 and CXCL8 expression downstream of Bcl-x(L), and markedly decreased angiogenesis in vivo. We conclude that Bcl-x(L) functions as a pro-angiogenic signaling molecule controlling Bcl-2 and VEGF expression. These results emphasize a complex interplay between Bcl-2 family members beyond their classical roles in apoptosis.

STR data for 11 autosomal STR markers from Costa Rica, Central America

Allele frequencies for 11 STR autosomal loci (F13A01, F13B, FESFPS, LPL, CSF1PO, TH01, TPOX, VWA, D16S539, D7S820 and D13S317) were obtained from a sample of 200 unrelated individuals from Costa Rica, Central America.

Antiangiogenic gene therapy: disruption of neovascular networks mediated by inducible caspase-9 delivered with a transcriptionally targeted adenoviral vector

The activation of an inducible caspase (iCaspase-9) mediates apoptosis of neovascular endothelial cells, and overcomes the prosurvival effect of vascular endothelial growth factor or basic fibroblast growth factor. The potential utilization of direct activation of caspases as an antiangiogenic strategy for treatment of angiogenesis-dependent diseases (eg cancer) requires expression of the inducible caspase primarily in the tumor endothelium. The objective of this work was to develop and characterize a transcriptionally targeted adenoviral vector that mediates expression of iCaspase-9 specifically in neovascular endothelial cells. We observed that adenoviral vectors containing the human VEGFR2 promoter induced reporter gene expression primarily in proliferating human dermal microvascular endothelial cells (HDMEC). HDMEC transduced with recombinant adenoviral vectors containing iCaspase-9 under regulation of the VEGFR2 promoter (Ad-hVEGFR2-iCaspase-9) and exposed to a cell-permeable dimerizer drug (AP20187), presented higher caspase-3 activity and apoptosis than controls (P < or = 0.05). Using the SCID Mouse Model of Human Angiogenesis, we observed that local delivery of Ad-hVEGFR2-iCaspase-9 followed by intraperitoneal injection of AP20187 resulted in endothelial cell apoptosis and local ablation of microvessels. We believe that this constitutes the first report of a transcriptionally targeted antiangiogenic adenoviral vector that mediates neovascular disruption upon activation of a caspase-based artificial death switch.

Ablation of microvessels in vivo upon dimerization of iCaspase-9

Anti-angiogenic therapies based on targeted disruption of the tumor microvascular network have been proposed for cancer treatment. Inhibitors of the endothelial cell pro-survival pathway mediated by VEGF were shown to activate caspases and cause microvascular regression, but the efficacy of this strategy can be hindered by the engagement of redundant survival pathways. Alternatively, if direct activation of an apical pro-apoptotic caspase is sufficient to disrupt microvessels in vivo, such a strategy could potentially override upstream endothelial cell survival inputs and disrupt tumor neovascular networks. Here, we fused caspase-9 to a mutated FKBP12 domain to express an inducible caspase-9 molecule (iCaspase-9) that can be activated by a cell-permeable dimerizer drug, and transduced this construct into primary endothelial cells. We found that drug-induced dimerization of iCaspase-9 is sufficient to activate endogenous caspase-3 and trigger apoptosis even when endothelial cells are treated with the pro-survival factors VEGF or bFGF. A single intraperitoneal injection of the dimerizer drug induced apoptosis of endothelial cells expressing iCaspase-9 and elimination of human microvessels engineered in immunodeficient mice. These results demonstrate that the activation of iCaspase-9 disrupts microvessels in vivo, and suggest a novel anti-angiogenic strategy based on the expression and controlled activation of an inducible death gene in neovascular endothelial cells.

Bimp1, a MAGUK family member linking protein kinase C activation to Bcl10-mediated NF-kappaB induction

Bcl10 and MALT1, products of distinct chromosomal translocations in mucosa-associated lymphoid tissue lymphoma, cooperate in activating NF-kappaB. Mice lacking Bcl10 demonstrate severe immunodeficiency associated with failure of lymphocytes to activate nuclear factor kappaB (NF-kappaB) in response to antigen receptor stimulation and protein kinase C activation. We characterize Bimp1, a new signaling protein that binds Bcl10 and activates NF-kappaB. Bimp1-mediated NF-kappaB activation requires Bcl10 and IkappaB kinases, indicating that Bimp1 acts upstream of these mediators. Bimp1, Bcl10, and MALT1 form a ternary complex, with Bcl10 bridging the Bimp1/MALT1 interaction. A dominant negative Bimp1 mutant inhibits NF-kappaB activation by anti-CD3 ligation, phorbol ester, and protein kinase C expression. These results suggest that Bimp1 links surface receptor stimulation and protein kinase C activation to Bcl10/MALT1, thus leading to NF-kappaB induction.

An induced proximity model for NF-kappa B activation in the Nod1/RICK and RIP signaling pathways

Nod1 is an Apaf-1-like molecule composed of a caspase-recruitment domain (CARD), nucleotide-binding domain, and leucine-rich repeats that associates with the CARD-containing kinase RICK and activates nuclear factor kappaB (NF-kappaB). We show that self-association of Nod1 mediates proximity of RICK and the interaction of RICK with the gamma subunit of the IkappaB kinase (IKKgamma). Similarly, the RICK-related kinase RIP associated via its intermediate region with IKKgamma. A mutant form of IKKgamma deficient in binding to IKKalpha and IKKbeta inhibited NF-kappaB activation induced by RICK or RIP. Enforced oligomerization of RICK or RIP as well as of IKKgamma, IKKalpha, or IKKbeta was sufficient for induction of NF-kappaB activation. Thus, the proximity of RICK, RIP, and IKK complexes may play an important role for NF-kappaB activation during Nod1 oligomerization or trimerization of the tumor necrosis factor alpha receptor.

Disruption of the CED-9.CED-4 complex by EGL-1 is a critical step for programmed cell death in Caenorhabditis elegans

In the nematode Caenorhabditis elegans, the apoptotic machinery is composed of four basic elements: the caspase CED-3, the Apaf-1 homologue CED-4, and the Bcl-2 family members CED-9 and EGL-1. The ced-9(n1950) gain-of-function mutation prevents most, if not all, somatic cell deaths in C. elegans. It encodes a CED-9 protein with a glycine-to-glutamate substitution at position 169, which is located within the highly conserved Bcl-2 homology 1 domain. We performed biochemical analyses with the CED-9G169E protein to gain insight into the mechanism of programmed cell death. We find that CED-9G169E retains the ability to bind both EGL-1 and CED-4, although its affinity for EGL-1 is reduced. In contrast to the behavior of wild-type CED-9, the interaction between CED-9G169E and CED-4 is not disrupted by expression of EGL-1. Furthermore, CED-4 and CED-9G169E co-localizes with EGL-1 to the mitochondria in mammalian cells, and expression of EGL-1 does not induce translocation of CED-4 to the cytosol. Finally, the ability of EGL-1 to promote apoptosis is impaired by the replacement of wild-type CED-9 with CED-9G169E, and this effect is correlated with the inability of EGL-1 to induce the displacement of CED-4 from the CED-9.CED-4 complex. These studies suggest that the release of CED-4 from the CED-9.CED-4 complex is a necessary step for induction of programmed cell death in C. elegans.

Expression and functional analysis of Apaf-1 isoforms. Extra Wd-40 repeat is required for cytochrome c binding and regulated activation of procaspase-9

Apaf-1 is an important apoptotic signaling molecule that can activate procaspase-9 in a cytochrome c/dATP-dependent fashion. Alternative splicing can create an NH(2)-terminal 11-amino acid insert between the caspase recruitment domain and ATPase domains or an additional COOH-terminal WD-40 repeat. Recently, several Apaf-1 isoforms have been identified in tumor cell lines, but their expression in tissues and ability to activate procaspase-9 remain poorly characterized. We performed analysis of normal tissue mRNAs to examine the relative expression of the Apaf-1 forms and identified Apaf-1XL, containing both the NH(2)-terminal and COOH-terminal inserts, as the major RNA form expressed in all tissues tested. We also identified another expressed isoform, Apaf-1LN, containing the NH(2)-terminal insert, but lacking the additional WD-40 repeat. Functional analysis of all identified Apaf-1 isoforms demonstrated that only those with the additional WD-40 repeat activated procaspase 9 in vitro in response to cytochrome c and dATP, while the NH(2)-terminal insert was not required for this activity. Consistent with this result, in vitro binding assays demonstrated that the additional WD-40 repeat was also required for binding of cytochrome c, subsequent Apaf-1 self-association, binding to procaspase-9, and formation of active Apaf-1 oligomers. These experiments demonstrate the expression of multiple Apaf-1 isoforms and show that only those containing the additional WD-40 repeat bind and activate procaspase-9 in response to cytochrome c and dATP.

Drob-1, a Drosophila member of the Bcl-2/CED-9 family that promotes cell death

The Bcl-2/CED-9 family of proteins, which includes both antiapoptotic and proapoptotic members, plays key regulating roles in programmed cell death. We report here the identification and characterization of Drob-1, the first Drosophila member of the Bcl-2/CED-9 family to be isolated. Drob-1 contains four conserved Bcl-2 homology domains (BH1, BH2, BH3, and BH4) and a C-terminal hydrophobic domain. Ectopic expression of Drob-1 in the developing Drosophila eye resulted in a rough-eye phenotype. Furthermore, when overexpressed in Drosophila S2 cells, Drob-1 induced apoptosis accompanied by elevated caspase activity. This Drob-1-induced cell death, however, could not be antagonized by baculovirus p35, a broad-spectrum caspase inhibitor. Drob-1 was localized to the intracytoplasmic membranes, predominantly to the mitochondrial membranes, and a mutant Drob-1 lacking the hydrophobic C terminus lost both its mitochondrial localization and its proapoptotic activity. These results suggest that Drob-1 promotes cell death by inducing both caspase-dependent and -independent pathways at the mitochondria. Our identification of Drob-1 and further genetic analysis should provide increased understanding of the universal mechanisms by which the Bcl-2/CED-9 family members and other related proteins regulate apoptosis.

ARC inhibits cytochrome c release from mitochondria and protects against hypoxia-induced apoptosis in heart-derived H9c2 cells

Ischemia induces apoptosis as well as necrosis of cardiac myocytes. We recently reported the cloning of a cDNA that encodes an apoptotic inhibitor, ARC, that is expressed predominantly in cardiac and skeletal muscle. In the present study, we examined the ability of ARC to protect rat embryonic heart-derived H9c2 cells from apoptosis induced by hypoxia, a component of ischemia. We found that H9c2 cells express ARC and that exposure to hypoxia substantially reduces ARC expression while inducing apoptosis. Transfected H9c2 cells in which cytosolic ARC protein levels remain elevated during hypoxia were significantly more resistant to hypoxia-induced apoptosis than parental H9c2 cells or H9c2 cells transfected with a control vector. Loss of endogenous ARC in the cytosol of H9c2 cells was associated with translocation of ARC from the cytosol to intracellular membranes, release of cytochrome c from the mitochondria, activation of caspase-3, poly(ADP-ribose)polymerase (PARP) cleavage, and DNA fragmentation. All of these events were inhibited in H9c2 cells overexpressing ARC when compared with control cells. In contrast, caspase inhibitors prevented PARP cleavage but not cytochrome c release, suggesting that exogenously expressed ARC acts upstream of caspase activation in this model of apoptosis. These results demonstrate that ARC can protect heart myogenic H9c2 cells from hypoxia-induced apoptosis, and that ARC prevents cytochrome c release by acting upstream of caspase activation, perhaps at the mitochondrial level.

Regulation of the forkhead transcription factor FKHR, but not the PAX3-FKHR fusion protein, by the serine/threonine kinase Akt

Akt, a proto-oncogene that encodes a cytosolic serine/threonine kinase, can phosphorylate and modulate the activity of several proteins involved in cellular metabolism and survival. Recently, two mammalian highly related forkhead transcription factors FKHRL1 and AFX and their nematode homologue Daf-16 have been found to be targets of this kinase. Here we show that Akt, but not inactive Akt, represses the transcriptional activity of FKHR, another member of the forkhead family. FKHR mutants with alanine substitutions at three Akt phosphorylation consensus sites (T24, S256 and S319) were inhibited by Akt, but mutation of all three sites rendered FKHR resistant to suppression. By contrast, the transcriptional activity of the oncogenic PAX3-FKHR fusion protein, containing two consensus phosphorylation sites, was not inhibited by Akt. Importantly, Akt inhibited the translocation of FKHR to the nucleus, providing a mechanism by which Akt might regulate the transcriptional activity of FKHR. Consistent with this model, the localization of the PAX3-FKHR fusion protein was nuclear and was not altered by Akt. These results provide evidence that Akt inhibits the transcriptional activity of FKHR by controlling its trafficking into the nucleus and that oncogenic PAX3-FKHR can escape this negative regulation by Akt.

Overexpression of Bcl-x(L) promotes chemotherapy resistance of mammary tumors in a syngeneic mouse model

Bcl-x(L), a prosurvival member of the Bcl-2 family that is expressed in many tumors, represses apoptosis induced by chemotherapeutic drugs in vitro. However, the contribution of apoptosis and prosurvival Bcl-2-related proteins to chemotherapy resistance in vivo is unknown and has been challenged by recent results with clonogenic survival assays. To test the ability of Bcl-x(L) to provide chemotherapy resistance to tumors, we transfected the mouse bcl-x(L) gene into the tumorigenic SCK mammary cell line and assessed the response of tumor cells to chemotherapeutic drugs in clonogenic assays and in a syngeneic mouse model. Bcl-x(L) conferred protection on SCK cells against methotrexate at certain drug concentrations, but not at all against 5-fluorouracil in clonogenic survival assays in vitro. Injection of SCK cells transfected with Bcl-x(L) or control plasmid in the mammary fat pads of syngeneic recipient mice resulted in tumors of similar size. However, although the volume of control tumors regressed up to 80% after 4 to 5 days of chemotherapy, SCK tumors expressing Bcl-x(L) did not regress and continued to grow in the presence of methotrexate or 5-fluorouracil. In addition, numbers of apoptotic cells were significantly higher in control tumors as compared to Bcl-x(L)-expressing tumors in animals treated with methotrexate or 5-fluorouracil. These results provide evidence that inhibition of apoptosis through Bcl-x(L) overexpression can promote resistance to chemotherapy in tumors in vivo.

Role of cytochrome c and dATP/ATP hydrolysis in Apaf-1-mediated caspase-9 activation and apoptosis

Apaf-1 plays a critical role in apoptosis by binding to and activating procaspase-9. We have identified a novel Apaf-1 cDNA encoding a protein of 1248 amino acids containing an insertion of 11 residues between the CARD and ATPase domains, and another 43 amino acid insertion creating an additional WD-40 repeat. The product of this Apaf-1 cDNA activated procaspase-9 in a cytochrome c and dATP/ATP-dependent manner. We used this Apaf-1 to show that Apaf-1 requires dATP/ATP hydrolysis to interact with cytochrome c, self-associate and bind to procaspase-9. A P-loop mutant (Apaf-1K160R) was unable to associate with Apaf-1 or bind to procaspase-9. Mutation of Met368 to Leu enabled Apaf-1 to self-associate and bind procaspase-9 independent of cytochrome c, though still requiring dATP/ATP for these activities. The Apaf-1M368L mutant exhibited greater ability to induce apoptosis compared with the wild-type Apaf-1. We also show that procaspase-9 can recruit procaspase-3 to the Apaf-1-procaspase-9 complex. Apaf-1(1-570), a mutant lacking the WD-40 repeats, associated with and activated procaspase-9, but failed to recruit procaspase-3 and induce apoptosis. These results suggest that the WD-40 repeats may be involved in procaspase-9-mediated procaspase-3 recruitment. These studies elucidate biochemical steps required for Apaf-1 to activate procaspase-9 and induce apoptosis.

Nod1, an Apaf-1-like activator of caspase-9 and nuclear factor-kappaB

Ced-4 and Apaf-1 belong to a major class of apoptosis regulators that contain caspase-recruitment (CARD) and nucleotide-binding oligomerization domains. Nod1, a protein with an NH2-terminal CARD-linked to a nucleotide-binding domain and a COOH-terminal segment with multiple leucine-rich repeats, was identified. Nod-1 was found to bind to multiple caspases with long prodomains, but specifically activated caspase-9 and promoted caspase-9-induced apoptosis. As reported for Apaf-1, Nod1 required both the CARD and P-loop for function. Unlike Apaf-1, Nod1 induced activation of nuclear factor-kappa-B (NF-kappaB) and bound RICK, a CARD-containing kinase that also induces NF-kappaB activation. Nod1 mutants inhibited NF-kappaB activity induced by RICK, but not that resulting from tumor necrosis factor-alpha stimulation. Thus, Nod1 is a leucine-rich repeat-containing Apaf-1-like molecule that can regulate both apoptosis and NF-kappaB activation pathways.

CIPER, a novel NF kappaB-activating protein containing a caspase recruitment domain with homology to Herpesvirus-2 protein E10

We have identified and characterized CIPER, a novel protein containing a caspase recruitment domain (CARD) in its N terminus and a C-terminal region rich in serine and threonine residues. The CARD of CIPER showed striking similarity to E10, a product of the equine herpesvirus-2. CIPER formed homodimers via its CARD and interacted with viral E10 but not with several apoptosis regulators containing CARDs including ARC, RAIDD, RICK, caspase-2, caspase-9, or Apaf-1. Expression of CIPER induced NF-kappaB activation, which was inhibited by dominant-negative NIK and a nonphosphorylable IkappaB-alpha mutant but not by dominant-negative RIP. Mutational analysis revealed that the N-terminal region of CIPER containing the CARD was sufficient and necessary for NF-kappaB-inducing activity. Point mutations in highly conserved residues in the CARD of CIPER disrupted the ability of CIPER to activate NF-kappaB and to form homodimers, indicating that the CARD is essential for NF-kappaB activation and dimerization. We propose that CIPER acts in a NIK-dependent pathway of NF-kappaB activation.

[Opioids and the immune system]

The immune response is partly regulated by the nervous system, that involves endogenous opioids, stimulating or depressing immune responses. Opioids modulate immune response by indirect and direct mechanisms. Indirect modulation occurs when the activation of opioid receptors within the nervous system modifies the activity of neuroendocrine axes or neurotransmission pathways. Direct modulation results from the effects of opioids on immune system cells. This requires the expression of membrane opioid receptors in these cells. Immunomodulating effects of morphine would be a result of the integration of indirect and direct effects. In animal models, morphine transiently depresses cellular and humoral immunity. In humans, morphine has similar effects; however, the real impact of morphine administration on the immune response in clinical situations in not yet known.

Identification of regulatory and catalytic domains in the apoptosis nuclease DFF40/CAD

The DNA fragmentation factor (DFF) is composed of two subunits, the 40-kDa caspase-3-activated nuclease (DFF40/CAD) and its 45-kDa inhibitor (DFF45/ICAD). During apoptosis, DFF-40/CAD is activated by caspase-3-mediated cleavage of DFF45/ICAD. Mutational analysis of DFF40/CAD revealed that DFF40/CAD is composed of a C-terminal catalytic domain and an N-terminal regulatory domain. Deletion of the catalytic domain (residues 290-345) abrogated the caspase-3-induced nuclease activity of DFF40/CAD but not its ability to interact with DFF45/ICAD. Conversely, removal of the regulatory domain (residues 1-83) yielded a constitutively active DFF40/CAD nuclease that neither bound to its inhibitor nor required caspase-3 for activation. Amino acid alignment revealed that the regulatory domain of DFF40/CAD has homology to the N-terminal region of mammalian and Drosophila DFF45/ICAD and CIDE-N, a regulatory domain previously identified in pro-apoptotic CIDE proteins. Mutational analysis of the N-terminal region revealed mutants with diminished nuclease activity but with intact ability to bind DFF45/ICAD. Thus, CIDE-N represents a new type of domain that is associated with the regulation of the apoptosis/DNA fragmentation pathway.

Caenorhabditis elegans EGL-1 disrupts the interaction of CED-9 with CED-4 and promotes CED-3 activation

In the nematode Caenorhabditis elegans, programmed cell death is implemented by the protease CED-3 whose activity is inhibited by CED-9 through physical associations with the regulator CED-4. The product of a recently described gene, egl-1, binds to and inhibits CED-9. In the present studies, we have addressed the molecular mechanism by which EGL-1 regulates CED-9 function and promotes cell death. Expression of CED-4 and CED-3 resulted in decreased survival and apoptosis of mammalian cells, activities that could be inhibited by CED-9. Importantly, this protective effect of CED-9 was antagonized by EGL-1. Immunoprecipitation analysis showed that EGL-1 binding to CED-9 disrupts the association between CED-4 and CED-9, an activity that required the BH3 motif of EGL-1. Consistent with these results, expression of EGL-1 promoted CED-4-dependent processing of CED-3, and this activity of EGL-1 was mediated through inhibition of CED-9. In mammalian cells, CED-9 is known to target the subcellular localization of CED-4 from the cytosol to intracellular membranes. Expression of EGL-1 resulted in redistribution of CED-4 from intracellular membranes, where it co-localized with CED-9, to the cytoplasm, providing further evidence that EGL-1 regulates CED-4 through CED-9. Finally, the levels of EGL-1 were greatly enhanced by co-expression of CED-9 in both mammalian cells and in a cell-free system, suggesting a role for CED-9 in the expression and/or stabilization of EGL-1. These studies provide a mechanism for how EGL-1 functions to antagonize pro-survival of CED-9 and to promote CED-3 activation and programmed cell death.

WD-40 repeat region regulates Apaf-1 self-association and procaspase-9 activation

The casp9 protein plays a critical role in apoptosis induced by a variety of death stimuli. A regulator of apoptosis, Apaf-1, binds to and activates pro-casp9 in the presence of cytochrome c and dATP, a requirement that is bypassed by deletion of the WD-40 repeats located in the C-terminal half of Apaf-1. In this report, we used constitutively active Apaf-1 mutant lacking the WD-40 repeat region to study the mechanism and regulation of pro-casp9 activation. Mutational analysis revealed that only a small portion of the CED-4 homologous region (residues 456-559) could be deleted without destroying the ability of Apaf-1-(1-559) to activate pro-casp9. Apaf-1 can self-associate to form oligomers. Disruption of Apaf-1 self-association by deletion (Delta109-559) or mutation of the P-loop region (K149R) abrogated Apaf-1-mediated pro-casp9 activation. Forced oligomerization of the caspase recruitment domain of Apaf-1 was sufficient for pro-casp9 activation. Dimerization of chimeric Fpk-pro-casp9 protein with the dimerizer drug FK1012 induced pro-casp9 processing and apoptosis in cells. Significantly, the C-terminal region containing WD-40 repeats interacted with its N-terminal CED-4 homologous region, as determined by immunoprecipitation experiments. Importantly, expression of the WD-40 repeat region inhibited Apaf-1 self-association and proteolytic activation of pro-casp9. These studies provide a mechanism by which Apaf-1 promotes autoactivation of pro-casp9 through Apaf-1 self-association, a process that is negatively regulated by the WD-40 repeats.

Diva, a Bcl-2 homologue that binds directly to Apaf-1 and induces BH3-independent cell death

We have identified and characterized Diva, which is a novel regulator of apoptosis. Sequence analysis revealed that Diva is a member of the Bcl-2 family of proteins containing Bcl-2 homology domain 1, 2, 3, and 4 (BH1, BH2, BH3, and BH4) regions and a carboxyl-terminal hydrophobic domain. The expression of Diva mRNA was detected in multiple embryonic tissues but was restricted to the ovary and testis in adult mice. The expression of Diva promoted the death of 293T, Ramsey, and T47D cells as well as that of primary sensory neurons, indicating that Diva is a proapoptotic protein. Significantly, Diva lacks critical residues in the conserved BH3 region that mediate the interaction between BH3-containing proapoptotic Bcl-2 homologues and their prosurvival binding partners. Consistent with this, Diva did not bind to cellular Bcl-2 family members including Bcl-2, Bcl-XL, Bcl-w, Mcl-1, and A1/Bfl-1. Furthermore, mutants of Diva lacking the BH3 region fully retained their proapoptotic activity, confirming that Diva promotes apoptosis in a BH3-independent manner. Significantly, Diva interacted with a viral Bcl-2 homologue (vBcl-2) encoded by the Kaposi's sarcoma-associated herpesvirus. Consistent with these associations, apoptosis induced by Diva was inhibited by vBcl-2 but not by Bcl-XL. Importantly, Diva interacted with Apaf-1, an adapter molecule that activates caspase-9, a central death protease of the apoptotic pathway. The expression of Diva inhibited the binding of Bcl-XL to Apaf-1, as determined by immunoprecipitation assays. Thus, Diva represents a novel type of proapoptotic Bcl-2 homologue that promotes apoptosis independently of the BH3 region through direct binding to Apaf-1, thus preventing Bcl-XL from binding to the caspase-9 regulator Apaf-1.

[Mechanism of action of general anesthetics. Effect on ion channel proteins or on membrane phospholipids?]

General anesthesia is defined by reversible unconsciousness, lack of response to noxious stimuli, and amnesia, induced by chemical agents. Mechanisms underlying the anesthetic effect are not known. The most prevalent belief was that anesthetic drugs acted on the lipid cell membranes, based on the correlation between oil solubility and anesthetic potency. Later, it has been proposed that anesthetic agents act on specific proteins of the cellular membrane of neurons. Voltage-gated ionic channels are inhibited by anesthetic agents, being some subtypes more sensitive. Clinical concentration of anesthetic agents inhibit or stimulate excitatory or inhibitory neurotransmitter receptors, respectively. Specific receptor agonists and antagonists modify this effect. Intercellular channels (gap junctions) are also affected by anesthetic agents through direct interaction with some of their protein subunits. Thus, anesthesia would result from combined effects on specific proteins acting on neural cell excitability as well as transmission and propagation of nerve impulses.

Targeting cancer cell death with a bcl-XS adenovirus

Transformation is a complex cellular process that requires several genetic abnormalities. In many cases, one of these abnormalities is an inhibition of PCD, which provides a selective advantage for tumor cells. This has been recently shown in an in vivo model, where overexpression of Bcl-XL, is a crucial step in the progression from hyperplasia to neoplasia and is accompanied by a significant decrease in tumor apoptosis [56]. Frequently, overexpression of a member of the Bcl-2 family results in a block in cell death and appears to nullify many built-in cellular defense mechanisms against cancer. Such a block presents a problem because radiation and chemotherapy, standard cancer treatments, ultimately exert their effect by induction of apoptosis and would also be made less effective. Therefore, to better treat cancer it may be necessary to develop novel methods to overcome the effects of the Bcl-2 family. One way to approach this problem is to target the cause--the molecular machinery that allows a cancer cell to survive. Advances in our understanding of apoptosis has identified the Bcl-2 family as a mediator of most apoptosis pathways, including those initiated by oncogenes, tumor suppressor genes, growth factor withdrawal, and external damaging signals. Therefore, functional inhibition of Bcl-2 family members is lethal to many cancer cells. Using gene transfer technology, we can now deliver genes that accomplish this goal. Further investigation will reveal whether this translates to improved therapy in the future.

RICK, a novel protein kinase containing a caspase recruitment domain, interacts with CLARP and regulates CD95-mediated apoptosis

Signaling through the CD95/Fas/APO-1 death receptor plays a critical role in the homeostasis of the immune system. RICK, a novel protein kinase that regulates CD95-mediated apoptosis was identified and characterized. RICK is composed of an N-terminal serine-threonine kinase catalytic domain and a C-terminal region containing a caspase-recruitment domain. RICK physically interacts with CLARP, a caspase-like molecule known to bind to Fas-associated protein with death domain (FADD) and caspase-8. Expression of RICK promoted the activation of caspase-8 and potentiated apoptosis induced by Fas ligand, FADD, CLARP, and caspase-8. Deletion mutant analysis revealed that both the kinase domain and caspase-recruitment domain were required for RICK to promote apoptosis. Significantly, expression of a RICK mutant in which the lysine of the putative ATP-binding site at position 38 was replaced by a methionine functioned as an inhibitor of CD95-mediated apoptosis. Thus, RICK represents a novel kinase that may regulate apoptosis induced by the CD95/Fas receptor pathway.

CIDE, a novel family of cell death activators with homology to the 45 kDa subunit of the DNA fragmentation factor

DFF45 is a subunit of the DNA fragmentation factor (DFF) that is cleaved by caspase-3 during apoptosis. However, the mechanism by which DFF45 regulates apoptotic cell death remains poorly understood. Here we report the identification and characterization of two mammalian genes, CIDE-A and CIDE-B, encoding highly related proteins with homology to the N-terminal region of DFF45. CIDE-A and CIDE-B were found to activate apoptosis in mammalian cells, which was inhibited by DFF45 but not by caspase inhibitors. Expression of CIDE-A induced DNA fragmentation in 293T cells, which was inhibited by DFF45, further suggesting that DFF45 inhibits the apoptotic activities of CIDEs. In addition to mammalian CIDE-A and CIDE-B, we identified DREP-1, a Drosophila melanogaster homolog of DFF45 that could inhibit CIDE-A-mediated apoptosis. Mutant analysis revealed that the C-terminal region of CIDE-A was necessary and sufficient for killing whereas the region with homology to DFF45 located in the N-terminus was required for DFF45 to inhibit CIDE-A-induced apoptosis. CD95/Fas-mediated apoptosis was enhanced by CIDEs but inhibited by DFF45. These studies suggest that DFF45 is evolutionarily conserved and implicate CIDEs as DFF45-inhibitable effectors that promote cell death and DNA fragmentation.

ARC, an inhibitor of apoptosis expressed in skeletal muscle and heart that interacts selectively with caspases

We have identified and characterized ARC, apoptosis repressor with caspase recruitment domain (CARD). Sequence analysis revealed that ARC contains an N-terminal CARD fused to a C-terminal region rich in proline/glutamic acid residues. The CARD domain of ARC exhibited significant homology to the prodomains of apical caspases and the CARDs present in the cell death regulators Apaf-1 and RAIDD. Immunoprecipitation analysis revealed that ARC interacts with caspase-2, -8, and Caenorhabditis elegans CED-3, but not with caspase-1, -3, or -9. ARC inhibited apoptosis induced by caspase-8 and CED-3 but not that mediated by caspase-9. Further analysis showed that the enzymatic activity of caspase-8 was inhibited by ARC in 293T cells. Consistent with the inhibition of caspase-8, ARC attenuated apoptosis induced by FADD and TRADD and that triggered by stimulation of death receptors coupled to caspase-8, including CD95/Fas, tumor necrosis factor-R1, and TRAMP/DR3. Remarkably, the expression of human ARC was primarily restricted to skeletal muscle and cardiac tissue. Thus, ARC represents an inhibitor of apoptosis expressed in muscle that appears to selectively target caspases. Delivery of ARC by gene transfer or enhancement of its endogenous activity may provide a strategy for the treatment of diseases that are characterized by inappropriately increased cell death in muscle tissue.

Bcl-XL interacts with Apaf-1 and inhibits Apaf-1-dependent caspase-9 activation

Recent studies indicate that Caenorhabditis elegans CED-4 interacts with and promotes the activation of the death protease CED-3, and that this activation is inhibited by CED-9. Here we show that a mammalian homolog of CED-4, Apaf-1, can associate with several death proteases, including caspase-4, caspase-8, caspase-9, and nematode CED-3 in mammalian cells. The interaction with caspase-9 was mediated by the N-terminal CED-4-like domain of Apaf-1. Expression of Apaf-1 enhanced the killing activity of caspase-9 that required the CED-4-like domain of Apaf-1. Furthermore, Apaf-1 promoted the processing and activation of caspase-9 in vivo. Bcl-XL, an antiapoptotic member of the Bcl-2 family, was shown to physically interact with Apaf-1 and caspase-9 in mammalian cells. The association of Apaf-1 with Bcl-XL was mediated through both its CED-4-like domain and the C-terminal domain containing WD-40 repeats. Expression of Bcl-XL inhibited the association of Apaf-1 with caspase-9 in mammalian cells. Significantly, recombinant Bcl-XL purified from Escherichia coli or insect cells inhibited Apaf-1-dependent processing of caspase-9. Furthermore, Bcl-XL failed to inhibit caspase-9 processing mediated by a constitutively active Apaf-1 mutant, suggesting that Bcl-XL regulates caspase-9 through Apaf-1. These experiments demonstrate that Bcl-XL associates with caspase-9 and Apaf-1, and show that Bcl-XL inhibits the maturation of caspase-9 mediated by Apaf-1, a process that is evolutionarily conserved from nematodes to humans.

Mtd, a novel Bcl-2 family member activates apoptosis in the absence of heterodimerization with Bcl-2 and Bcl-XL

We have identified and characterized Mtd, a novel regulator of apoptosis. Sequence analysis revealed that Mtd is a member of the Bcl-2 family of proteins containing conserved BH1, BH2, BH3, and BH4 regions and a carboxyl-terminal hydrophobic domain. In adult tissues, Mtd mRNA was predominantly detected in the brain, liver, and lymphoid tissues, while in the embryo Mtd mRNA was detected in the liver, thymus, lung, and intestinal epithelium. Expression of Mtd promoted the death of primary sensory neurons, 293T cells and HeLa cells, indicating that Mtd is a proapoptotic protein. Unlike all other known death agonists of the Bcl-2 family, Mtd did not bind significantly to the survival-promoting proteins Bcl-2 or Bcl-XL. Furthermore, apoptosis induced by Mtd was not inhibited by Bcl-2 or Bcl-XL. A Mtd mutant with glutamine substitutions of highly conserved amino acids in the BH3 domain retained its ability to promote apoptosis, further indicating that Mtd does not promote apoptosis by heterodimerizing with Bcl-2 or Bcl-XL. Mtd-induced apoptosis was not blocked by broad range synthetic caspase inhibitors z-VAD-fmk or a viral protein CrmA. Mtd is the first example of a naturally occurring Bcl-2 family member that can activate apoptosis independently of heterodimerization with survival-promoting Bcl-2 and Bcl-XL.

Increase in Bcl-2 level promoted by CD40 ligation correlates with inhibition of B cell apoptosis induced by vacuolar type H(+)-ATPase inhibitor

We have previously demonstrated that cell death of WEHI-231 cells induced by specific inhibitors of vacuolar type H(+)-ATPase (V-ATPase) occurs through apoptosis. CD40 is involved in regulating activation, differentiation, and apoptosis of B cells. Here we show that the CD40 ligation rescues WEHI-231 cells from apoptotic cell death induced by a specific V-ATPase inhibitor, concanamycin A. CD40 signaling with anti-CD40 antibody resulted in the induction of Bcl-2 and Bcl-XL proteins in WEHI-231 cells. Constitutive expression of Bcl-2 but not Bcl-XL inhibited concanamycin A-induced apoptosis. These findings suggest that the expression of Bcl-2 mediated through CD40 signaling rescues the apoptotic cell death induced by blockade of V-ATPase. Interestingly, the acidification of intracellular acidic compartments was completely inhibited when WEHI-231 cells were cultured with concanamycin A, even in the presence of anti-CD40 antibody. In addition, apoptosis in WEHI-231 cells induced by concanamycin A was strongly suppressed when cultured with imidazole, a cell-permeable base, suggesting that apoptosis induced by concanamycin A is preceded by intraacidification.

CLARP, a death effector domain-containing protein interacts with caspase-8 and regulates apoptosis

We have identified and characterized CLARP, a caspase-like apoptosis-regulatory protein. Sequence analysis revealed that human CLARP contains two amino-terminal death effector domains fused to a carboxyl-terminal caspase-like domain. The structure and amino acid sequence of CLARP resemble those of caspase-8, caspase-10, and DCP2, a Drosophila melanogaster protein identified in this study. Unlike caspase-8, caspase-10, and DCP2, however, two important residues predicted to be involved in catalysis were lost in the caspase-like domain of CLARP. Analysis with fluorogenic substrates for caspase activity confirmed that CLARP is catalytically inactive. CLARP was found to interact with caspase-8 but not with FADD/MORT-1, an upstream death effector domain-containing protein of the Fas and tumor necrosis factor receptor 1 signaling pathway. Expression of CLARP induced apoptosis, which was blocked by the viral caspase inhibitor p35, dominant negative mutant caspase-8, and the synthetic caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-(OMe)-fluoromethylketone (zVAD-fmk). Moreover, CLARP augmented the killing ability of caspase-8 and FADD/MORT-1 in mammalian cells. The human clarp gene maps to 2q33. Thus, CLARP represents a regulator of the upstream caspase-8, which may play a role in apoptosis during tissue development and homeostasis.

harakiri, a novel regulator of cell death, encodes a protein that activates apoptosis and interacts selectively with survival-promoting proteins Bcl-2 and Bcl-X(L)

Programmed cell death is essential in organ development and tissue homeostasis and its deregulation is associated with the development of several diseases in mice and humans. The precise mechanisms that control cell death have not been elucidated fully, but it is well established that this form of cellular demise is regulated by a genetic program which is activated in the dying cell. Here we report the identification, cloning and characterization of harakiri, a novel gene that regulates apoptosis. The product of harakiri, Hrk, physically interacts with the death-repressor proteins Bcl-2 and Bcl-X(L), but not with death-promoting homologs, Bax or Bak. Hrk lacks conserved BH1 and BH2 regions and significant homology to Bcl-2 family members or any other protein, except for a stretch of eight amino acids that exhibits high homology with BH3 regions. Expression of Hrk induces cell death which is inhibited by Bcl-2 and Bcl-X(L). Deletion of 16 amino acids including the conserved BH3 region abolished the ability of Hrk to interact with Bcl-2 and Bcl-X(L) in mammalian cells. Moreover, the killing activity of this mutant form of Hrk (Hrk deltaBH3) was eliminated or dramatically reduced, suggesting that Hrk activates cell death at least in part by interacting with and inhibiting the protection afforded by Bcl-2 and Bcl-X(L). Because Hrk lacks conserved BH1 and BH2 domains that define Bcl-2 family members, we propose that Hrk and Bik/Nbk, another BH3-containing protein that activates apoptosis, represent a novel class of proteins that regulate apoptosis by interacting selectively with survival-promoting Bcl-2 and Bcl-X(L).

A1 demonstrates restricted tissue distribution during embryonic development and functions to protect against cell death

Members of the bcl-2 gene family are essential regulators of cell survival in a wide range of biological processes. A1, a member of the family, is known to be expressed in certain adult tissues. However, the precise tissue distribution and function of A1 remains poorly understood. We show here that A1 is expressed in multiple tissues during murine embryonic development. In the embryo, A1 was detected first at embryonic day 11.5 in liver, brain, and limbs. At day 13.5 of gestation, A1 expression was observed in the central nervous system, liver, perichondrium, and digital zones of developing limbs in a pattern different from that of bcl-X. In the central nervous system of 15.5-day embryos, A1 was expressed at high levels in the ventricular zone and cortical plate of brain cortex. Significantly, the interdigital zones of limbs and the intermediate region of the developing brain cortex, two sites associated with extensive cell death, were devoid of A1 and bcl-X. The expression of A1 was retained in many adult tissues. To assess the ability of A1 to modulate cell death, stable transfectants expressing different amounts of A1 protein were generated in K562 cells. Expression of A1 was associated with retardation of apoptotic cell death induced by actinomycin D and cycloheximide as well as by okadaic acid. Confocal microscopy showed that the A1 protein was localized to the cytoplasm in a pattern similar to that of Bcl-2. These results demonstrate that the expression of A1 is wider than previously reported in adult tissues. Furthermore, its distribution in multiple tissues of the embryo suggests that A1 plays a role in the regulation of physiological cell death during embryonic development.

A computer program for quantification of SH groups generated after reduction of monoclonal antibodies

Reduction of disulfide bonds to sulfhydryl (SH) groups for direct radiolabeling of antibodies for immunoscintigraphic studies of colorectal and other cancers continues to be of considerable research interest. We have developed a general strategy and a versatile computer program for the quantification of the number of SH per molecule of antibody (Ab) generated after the treatment of monoclonal antibodies (MAbs) with reducing agents such as 2-mercaptoethanol (2-ME), stannous chloride (SnCl2), dithiothreitol (DTT), dithioerythritol (DTE), ascorbic acid (AA), and the like. The program we describe here performs an unweighted least-squares regression analysis of the cysteine standard curve and interpolates the cysteine concentration of the samples. The number of SH groups per molecule of antibody in the 2-mercaptoethanol and in the other reducing agents was calculated from the cysteine standard curve using Ellman's reagent to develop the yellow color. The linear least-squares method fit the standard data with a high degree of accuracy and with the correlation coefficient r of 0.999. A program has been written for the IBM PC compatible computer utilizing a friendly menu to interact with the users. The package allows the user to change parameters of the assay, to calculate regression coefficients slope, intercept and its standard errors, to perform statistical analysis, together with detailed analysis of variance, and to produce an output of the results in a printed format.

Micromethod for quantification of SH groups generated after reduction of monoclonal antibodies

A simple, rapid, and reproducible micromethod for quantification of sulfhydryl (SH) groups generated after reduction of monoclonal antibody (MAb) disulfide bonds with 2-mercaptoethanol (2-ME) is described. The number of SH groups per molecule of antibody in the 2-ME and in the other reducing agents was calculated from the cysteine standard curve using Ellman's reagent to develop the yellow color. Results were plotted as absorbance at 405 nm vs. cysteine concentration (microgram/mL). After subtraction of the background due to Ellman's reagent, a straight-line relationship passing through the origin was obtained. Absorption spectrum of the yellow products was controlled, and no significative differences were found between optical density at 412 nm and 405 nm. Using a small quantity of antibody in the order of 37 micrograms, the lowest detection limit for cysteine quantification was 0.03 microgram. An excellent linear correlation was found between both cysteine concentration and absorbance (r = 0.999), and the mean value of the relative error in the quantification of cysteine from samples was 2.8%. A statistical Student t-test showed an excellent linearity and parallelism between cysteine standard and samples.

Constitutive expression of bcl-2 in B cells causes a lethal form of lupuslike autoimmune disease after induction of neonatal tolerance to H-2b alloantigens

The bcl-2 protooncogene has been shown to provide a survival signal to self-reactive B cells, but it fails to override their developmental arrest after encounter with antigen. Furthermore, constitutive expression of bcl-2 in B cells does not promote the development of autoimmune disease in most strains of mice, indicating that signals other than those conferred by bcl-2 are required for long-term survival and differentiation of self-reactive B cells in vivo. To further examine the factors that are required for the pathogenesis of autoimmune disease, we have assessed the effect of bcl-2 overexpression on the development of host-versus-graft disease, a self-limited model of systemic autoimmune disease. In this model, injection of spleen cells from (C57BL/6 x BALB/c)F1 hybrid mice into BALB/c newborn parental mice induces immunological tolerance to donor tissues and activation of autoreactive F1 donor B cells through interactions provided by allogeneic host CD4+ T cells. BALB/c newborns injected with spleen cells from (C57BL/6 x BALB/c)F1 mice expressing a bcl-2 transgene in B cells developed high levels of anti-single-stranded DNA and a wide range of pathogenic autoantibodies that were not or barely detectable in mice injected with nontransgenic spleen cells. In mice injected with transgenic B cells, the levels of pathogenic autoantibodies remained high during the course of the study and were associated with long-term persistence of donor B cells, development of a severe autoimmune disease, and accelerated mortality. These results demonstrate that bcl-2 can provide survival signals for the maintenance and differentiation of autoreactive B cells, and suggest that both increased B cell survival and T cell help play critical roles in the development of certain forms of systemic autoimmune disease.

Amplified ELISA to detect autoantibodies to N-glycolyl-GM3 ganglioside

Numerous immunochemical methods are now available for the detection of antibodies to gangliosides. An amplified ELISA method for detection of autoantibodies to NGcGM3 ganglioside in the sera of patients with various type of renal diseases was developed. IgM antibodies were found in 39 out of 53 sera of patients using 30 normal healthy blood donor as a negative control. For human IgG conjugate no reactivity to NGcGM3 was seen in the sera. Positive ELISA results were confirmed by TLC-immunostaining using GM3, NGcGM3, NGcGM2 and Standard bovine gangliosides (GM1, GD1a, GD1b and GT1b). All sera were also assayed for reactivity with GM3 in ELISA to determine the line specificity of these antibodies. Based on these results, a protocol for a sensitive and reproducible amplification ELISA system for serum anti-NGcGM3 antibodies in patients with renal or other diseases is presented. The ELISA method described here in appear to be useful adjunt to measure antiNGcGM3 antibodies in sera of patients with various type of renal or other diseases.

Bcl-XL displays restricted distribution during T cell development and inhibits multiple forms of apoptosis but not clonal deletion in transgenic mice

The survival of T lymphocytes is tightly controlled during development. Here, we show that Bcl-xL, a protein homologue of Bcl-2, is highly regulated in the thymus in a pattern different than that of Bcl-2. The maximum expression was in CD4+CD8+ thymocytes, a developmental stage where Bcl-2 is downregulated. To assess the role of Bcl-xL in thymocyte apoptosis, we generated mice overexpressing an E mu-bcl-x transgene within the T cell compartment. Constitutive expression of Bcl-xL resulted in accumulation of thymocytes and mature T cells in lymphoid organs. Thymocytes overexpressing Bcl-xL exhibited increased viability in vitro and were resistant to apoptosis induced by different signals, including glucocorticoid, gamma irradiation, calcium ionophore, and CD3 cross-linking. However, Bcl-xL was unable to block clonal deletion of thymocytes reactive with self-superantigens or H-Y antigen. These studies demonstrate that Bcl-2 and Bcl-xL, two functionally related proteins, are regulated independently during T cell development. In contrast to Bcl-2, which has been implicated in the maintenance of mature T cells, Bcl-xL appears to provide a survival signal for the maintenance of more immature CD4+CD8+ thymocytes before positive selection.

A recombinant bcl-x s adenovirus selectively induces apoptosis in cancer cells but not in normal bone marrow cells

Many cancers overexpress a member of the bcl-2 family of inhibitors of apoptosis. To determine the role of these proteins in maintaining cancer cell viability, an adenovirus vector that expresses bcl-xs, a functional inhibitor of these proteins, was constructed. Even in the absence of an exogenous apoptotic signal such as x-irradiation, this virus specifically and efficiently kills carcinoma cells arising from multiple organs including breast, colon, stomach, and neuroblasts. In contrast, normal hematopoietic progenitor cells and primitive cells capable of repopulating severe combined immunodeficient mice were refractory to killing by the bcl-xs adenovirus. These results suggest that Bcl-2 family members are required for survival of cancer cells derived from solid tissues. The bcl-xs adenovirus vector may prove useful in killing cancer cells contaminating the bone marrow of patients undergoing autologous bone marrow transplantation.

Modulation of anti-IgM-induced B cell apoptosis by Bcl-xL and CD40 in WEHI-231 cells. Dissociation from cell cycle arrest and dependence on the avidity of the antibody-IgM receptor interaction

The demise of B cell progenitors expressing functional IgM receptors for self appears to be the main mechanism by which B cell tolerance is accomplished. The genetic mechanisms that regulate the death process during this critical step of B cell development are still poorly understood. We have studied the regulation of apoptosis in WEHI-231 lymphoma cells after treatment with a panel of anti-IgM mAbs as an in vitro model of clonal B cell deletion. We showed that a product of bcl-x, Bcl-xL, can inhibit anti-IgM-induced apoptosis but not cell cycle arrest in a dose-dependent manner. Bcl-xL was efficient in protecting B cells from low but not high avidity anti-IgM mAbs. In contrast to that observed with Bcl-xL, CD40 stimulation was efficient in inhibiting both cell cycle arrest and apoptosis after IgM cross-linking regardless of the binding avidity of the anti-IgM Ab. Moreover, activation through IgM receptors but not CD40 induced up-regulation followed by rapid down-modulation of Bcl-xL. Thus, the capacity of Bcl-xL to modulate anti-IgM-induced apoptosis in WEHI-231 cells is highly dependent on the avidity of the Ab-IgM receptor interaction.

Modulation of anti-IgM-induced B cell apoptosis by Bcl-xL and CD40 in WEHI-231 cells. Dissociation from cell cycle arrest and dependence on the avidity of the antibody-IgM receptor interaction

The demise of B cell progenitors expressing functional IgM receptors for self appears to be the main mechanism by which B cell tolerance is accomplished. The genetic mechanisms that regulate the death process during this critical step of B cell development are still poorly understood. We have studied the regulation of apoptosis in WEHI-231 lymphoma cells after treatment with a panel of anti-IgM mAbs as an in vitro model of clonal B cell deletion. We showed that a product of bcl-x, Bcl-xL, can inhibit anti-IgM-induced apoptosis but not cell cycle arrest in a dose-dependent manner. Bcl-xL was efficient in protecting B cells from low but not high avidity anti-IgM mAbs. In contrast to that observed with Bcl-xL, CD40 stimulation was efficient in inhibiting both cell cycle arrest and apoptosis after IgM cross-linking regardless of the binding avidity of the anti-IgM Ab. Moreover, activation through IgM receptors but not CD40 induced up-regulation followed by rapid down-modulation of Bcl-xL. Thus, the capacity of Bcl-xL to modulate anti-IgM-induced apoptosis in WEHI-231 cells is highly dependent on the avidity of the Ab-IgM receptor interaction.

A personal computer-based system for parallel line analysis of bioassay data

A program is described for symmetric parallel line analysis of bioassay data with a logistic dose-response relationship. Dose-response relationship is transformed to semilog or log-log. A regression line can be calculated for the dose-response curve for standard and test samples, and produces potency estimate of test sample preparation relative to the standard preparation based on parallel-line bioassay statistical methods [3,4], together with detailed analysis of variance, estimates of slope, intercept and chi 2 test which permits a very sensitive test for linearity and parallelism of standard and test sample and facilitates detection of 'outliers', i.e. samples exhibiting non-parallelism. The general comparison of dose-response relationships produced by the program are a feature of particular interest.

bcl-x is expressed in embryonic and postnatal neural tissues and functions to prevent neuronal cell death

Previous studies have implicated the bcl-2 protooncogene as a potential regulator of neuronal survival. However, mice lacking functional bcl-2 exhibited normal development and maintenance of the central nervous system (CNS). Since bcl-2 appears dispensable for neuronal survival, we have examined the expression and function of bcl-x, another member of the bcl-2 family of death regulatory genes. Bcl-2 is expressed in neuronal tissues during embryonic development but is down-regulated in the adult CNS. In contrast, Bcl-xL expression is retained in neurons of the adult CNS. Two different forms of bcl-x mRNA and their corresponding products, Bcl-xL and Bcl-x beta, were expressed in embryonic and adult neurons of the CNS. Microinjection of bcl-xL and bcl-x beta cDNAs into primary sympathetic neurons inhibited their death induced by nerve growth factor withdrawal. Thus, Bcl-x proteins appear to play an important role in the regulation of neuronal survival in the adult CNS.

Discordant expression of Bcl-x and Bcl-2 by keratinocytes in vitro and psoriatic keratinocytes in vivo

Apoptosis is a required event in maintaining kinetic homeostasis within continually renewing tissues such as skin. However, no systematic study of the apoptotic process in epidermal keratinocytes of the skin has been performed. In this report, we examined the expression of proteins associated with promoting (Fas) or preventing (Bcl-2, Bcl-x, CD40) apoptosis in the normal, psoriatic, and malignant keratinocyte. Immunohistochemical staining and flow cytometry analysis revealed that normal cultured keratinocytes express low levels of Fas, CD40, and Bcl-x that was enhanced by cytokines including gamma-interferon (IFN-gamma) and a phorbol ester tumor promoter, TPA. Only faint Bcl-2 staining was detected in cultured keratinocytes exposed to IFN-gamma and TPA compared with the prominent expression of Bcl-x. Biopsies of normal skin, psoriatic plaques, and basal cell carcinomas were examined to extend the in vitro observations. Immunohistochemical staining revealed that while keratinocytes in normal epithelium express low to absent levels of Fas and Bcl-x, psoriatic keratinocytes expressed significantly higher levels of Fas and Bcl-x. In contrast, malignant keratinocytes in basal cell carcinomas expressed high levels of Bcl-2, but minimal Bcl-x, and no Fas. Immunoblot analysis revealed that the long form of Bcl-x (Bcl-xI), which prevents apoptosis in lymphocytes, is expressed by cultured keratinocytes and psoriatic plaque keratinocytes. We conclude that normal cytokine-activated keratinocytes can express an apoptotic (Fas) and an anti-apoptotic protein (Bcl-x). The overexpression of Bcl-x in psoriasis, or Bcl-2 in basal cell carcinomas, may contribute to the longevity of these cells by blocking the normal apoptotic process involved in the terminal differentiation program of epidermal keratinocytes.

Bcl-2 and Bcl-x: regulatory switches for lymphoid death and survival

The survival and death of lymphoid cells is under the control of a genetic program. Cell death is activated at different stages of development and serves to remove unnecessary and autoreactive lymphocytes, as well as to limit the immune response. The survival of cells is regulated by a set of genes that act as repressors of the cell death mechanism. Of these, bcl-2 and bcl-x exhibit a striking pattern of regulation during lymphoid maturation and can inhibit several forms of apoptotic cell death. Here, Gabriel Núñez and colleagues review recent developments in the field, particularly focusing on the role of the Bcl-2 and Bcl-x proteins in regulating lymphoid death and survival.