A20/TNFAIP3 heterozygosity predisposes to behavioral symptoms in a mouse model for neuropsychiatric lupus.

Background: Neuropsychiatric lupus (NPSLE) refers to the neurological and psychiatric manifestations that are commonly observed in patients with systemic lupus erythematosus (SLE). An important question regarding the pathogenesis of NPSLE is whether the symptoms are caused primarily by CNS-intrinsic mechanisms or develop as a consequence of systemic autoimmunity. Currently used spontaneous mouse models for SLE have already contributed significantly to unraveling how systemic immunity affects the CNS. However, they are less suited when interested in CNS primary mechanisms. In addition, none of these models are based on genes that are associated with SLE. In this study, we evaluate the influence of A20, a well-known susceptibility locus for SLE, on behavior and CNS-associated changes in inflammatory markers. Furthermore, given the importance of environmental triggers for disease onset and progression, the influence of an acute immunological challenge was evaluated. Methods: Female and male A20 heterozygous mice (A20+/-) and wildtype littermates were tested in an extensive behavioral battery. This was done at the age of 10±2weeks and 24 â€‹± â€‹2 weeks to evaluate the impact of aging. To investigate the contribution of an acute immunological challenge, LPS was injected intracerebroventricularly at the age of 10±2weeks followed by behavioral analysis. Underlying molecular mechanisms were evaluated in gene expression assays on hippocampus and cortex. White blood cell count and blood-brain barrier permeability were analyzed to determine whether peripheral inflammation is a relevant factor. Results: A20 heterozygosity predisposes to cognitive symptoms that were observed at the age of 10 â€‹± â€‹2 weeks and 24 â€‹± â€‹2 weeks. Young A20+/- males and females showed a subtle cognitive phenotype (10±2weeks) with distinct neuroinflammatory phenotypes. Aging was associated with clear neuroinflammation in female A20+/- mice only. The genetic predisposition in combination with an environmental stimulus exacerbates the behavioral impairments related to anxiety, cognitive dysfunction and sensorimotor gating. This was predominantly observed in females. Furthermore, signs of neuroinflammation were solely observed in female A20+/- mice. All above observations were made in the absence of peripheral inflammation and of changes in blood-brain barrier permeability, thus consistent with the CNS-primary hypothesis. Conclusions: We show that A20 heterozygosity is a predisposing factor for NPSLE. Further mechanistic insight and possible therapeutic interventions can be studied in this mouse model that recapitulates several key hallmarks of the disease.

Rare presentation of idiopathic duodenoduodenal intussusception.

Enteroenteric intussusception is a condition in which the full-thickness bowel wall becomes telescoped into the lumen of distal bowel. Intussusception in adult occurs infrequently and varies from childhood intussusception, particularly in its presentation, aetiology and treatment. Duodenoduodenal intussusception is rare because the duodenum is fixed in the retroperitoneal position. It usually occurs secondary to tumour, lipoma, Brunner's gland hamartomatous polyp or adenoma. The diagnosis in adults is usually made at laparotomy, where presentation is with intestinal obstruction. In non-emergency presentation, it may be difficult to arrive at an accurate diagnosis as symptoms may be vague, self-limiting intermittent abdominal pain. Clinical examinations and investigations may not be conclusive and another working diagnosis such as irritable bowel syndrome would be made. We describe a case where a patient initially presented with symptoms mimicking pancreatitis but his symptoms persisted over the course of 2 weeks. When a laparotomy was performed, duodenoduodenal intussusception was discovered and confirmed with histopathology. In this case, a discernible leading point could not be identified.

A20 prevents chronic liver inflammation and cancer by protecting hepatocytes from death.

An important regulator of inflammatory signalling is the ubiquitin-editing protein A20 that acts as a break on nuclear factor-κB (NF-κB) activation, but also exerts important cytoprotective functions. A20 knockout mice are cachectic and die prematurely due to excessive multi-organ inflammation. To establish the importance of A20 in liver homeostasis and pathology, we developed a novel mouse line lacking A20 specifically in liver parenchymal cells. These mice spontaneously develop chronic liver inflammation but no fibrosis or hepatocellular carcinomas, illustrating an important role for A20 in normal liver tissue homeostasis. Hepatocyte-specific A20 knockout mice show sustained NF-κB-dependent gene expression in the liver upon tumor necrosis factor (TNF) or lipopolysaccharide injection, as well as hepatocyte apoptosis and lethality upon challenge with sublethal doses of TNF, demonstrating an essential role for A20 in the protection of mice against acute liver failure. Finally, chronic liver inflammation and enhanced hepatocyte apoptosis in hepatocyte-specific A20 knockout mice was associated with increased susceptibility to chemically or high fat-diet-induced hepatocellular carcinoma development. Together, these studies establish A20 as a crucial hepatoprotective factor.

Predicting discharge outcomes after total knee replacement using the Risk Assessment and Predictor Tool.

OBJECTIVE: To explore the use of the Risk Assessment and Predictor Tool (RAPT) as a pre-operative tool to predict postoperative discharge destination and length of stay for patients undergoing total knee replacement (TKR) in Singapore. PARTICIPANTS AND SETTING: A cohort of 569 patients undergoing primary TKR at the Singapore General Hospital were recruited prospectively from November 2009 to June 2010. INTERVENTION: All patients completed a modified RAPT questionnaire pre-operatively, and underwent standard clinical pathway guidelines for TKR throughout the study. MAIN OUTCOME MEASURES: Actual discharge destination (ADDest) and length of stay (LOS). DESIGN: Total RAPT score and preferred discharge destination (PDD) were recorded pre-operatively, while ADDest and LOS were obtained immediately after discharge. Multivariable logistic regression and multivariable regression analysis were used to determine whether the RAPT items and score could predict the discharge outcomes. RESULTS: Total RAPT score was a significant predictor of LOS for patients following TKR (R=0.24, P<0.001); the higher the RAPT score, the longer the LOS. Total RAPT score was also a significant predictor of actual discharge to home [odds ratio (OR) 2.32, 95% confidence interval (CI) 1.11 to 4.85]. PDD was a significant predictor for LOS (R=0.22, P<0.001) and ADDest (R=0.33, P<0.001). Patients who chose to be discharged home were more likely to be directly discharged home (OR 9.79, 95% CI 5.07 to 18.89, P<0.001). CONCLUSION: Total RAPT score and PDD were significant predictors of ADDest and LOS for patients following TKR in Singapore. The ability to predict discharge outcomes following TKR could assist caregivers, healthcare professionals and administrators in optimising care and resource allocations for patients.

Impact of antioxidants on the ability of phenolic phytochemicals to kill HCT116 colon cancer cells.

Certain phenolic phytochemicals can kill cancer cells. Possible interference from antioxidants is a concern, and this issue has not been studied appreciably. Therefore, the effect of ascorbate and N-acetylcysteine on the ability of epigallocatechin gallate (EGCG) and curcumin to kill HCT116 colon cancer cells was examined. EGCG and curcumin each caused DNA damage in the cells. The DNA-damaging ability of EGCG, but not curcumin, was hindered by either ascorbate or NAC, which was also shown in HT29 and SW480 colon cancer cells. Also, iron chelators (deferoxamine and 2,2'-dipyridyl) inhibited the ability of EGCG, but not curcumin, to cause damage to the DNA in HCT116 cells. Interestingly, curcumin, but not EGCG, increased the expression of growth arrest and DNA damage-inducible gene 153 and also heme oxygenase-1, and this stress gene upregulation by curcumin was antioxidant-insensitive. With prolonged incubation of HCT116 cells with either EGCG or curcumin, cell shrinkage, membrane blebbing, apoptotic bodies, and chromatin condensation/fragmentation were observed. These morphological changes were not apparent in EGCG-treated cells that had been pretreated with either ascorbate or NAC. However, the ascorbate and NAC pretreatments did not prevent the occurrence of the morphological changes in curcumin-treated cells. Thus, these findings suggest that ascorbate and NAC interfere with the ability of EGCG, but not curcumin, to kill HCT116 cells. This basic knowledge may help to better plan and optimize strategies for chemoprevention or chemotherapy.

Keratinocyte-specific ablation of the NF-κB regulatory protein A20 (TNFAIP3) reveals a role in the control of epidermal homeostasis.

The ubiquitin-editing enzyme A20 (tumor necrosis factor-α-induced protein 3) serves as a critical brake on nuclear factor κB (NF-κB) signaling. In humans, polymorphisms in or near the A20 gene are associated with several inflammatory disorders, including psoriasis. We show here that epidermis-specific A20-knockout mice (A20(EKO)) develop keratinocyte hyperproliferation, but no signs of skin inflammation, such as immune cell infiltration. However, A20(EKO) mice clearly developed ectodermal organ abnormalities, including disheveled hair, longer nails and sebocyte hyperplasia. This phenotype resembles that of mice overexpressing ectodysplasin-A1 (EDA-A1) or the ectodysplasin receptor (EDAR), suggesting that A20 negatively controls EDAR signaling. We found that A20 inhibited EDAR-induced NF-κB signaling independent from its de-ubiquitinating activity. In addition, A20 expression was induced by EDA-A1 in embryonic skin explants, in which its expression was confined to the hair placodes, known to be the site of EDAR expression. In summary, our data indicate that EDAR-induced NF-κB levels are controlled by A20, which functions as a negative feedback regulator, to assure proper skin homeostasis and epidermal appendage development.

Caspases are not localized in mitochondria during life or death.

Caspases are crucial for the initiation, propagation and execution of apoptosis. They normally exist as proenzymes, which can be activated through recruitment into activating complexes and by proteolytic cleavage by other caspases or proteases. Perturbation of organelles such as nuclei, endoplasmatic reticulum and mitochondria results in the activation of caspases. A number of caspases (-2, -3, -8 and -9) were published as being localized in the intermembrane space of mitochondria. However, in three different models of apoptosis (anti-Fas-induced cell death in murine hepatocytes, Fas ligand-induced apoptosis in Jurkat cells and apoptosis induced by growth factor withdrawal in Ba/F3 cells) we could not identify a mitochondrial location of caspases, neither under control nor under apoptotic conditions. In all three apoptotic models caspases were found in the cytosolic (caspases-2, -3, -6, -7, -8, -9) and nuclear subcellular fractions (caspases-2, -3). In another approach we treated isolated liver mitochondria with truncated Bid. Although tBid-dependent release of Cytochrome c, AIF, adenylate kinase, Smac/DIABLO and Omi/HtrA2 could be demonstrated, none of the caspases were detectable both in the supernatant and the mitochondrial fraction after treatment. Our results demonstrate that, in contrast to previous studies, no caspases-2, -3, -8 and -9 are associated with the mitochondrial fraction. These findings support the concept of a separate compartmentalization between proapoptotic cofactors in the mitochondria and silent precursor caspases in the cytosol.

The role of mitochondrial factors in apoptosis: a Russian roulette with more than one bullet.

Mitochondria are 'life-essential' organelles for the production of metabolic energy in the form of ATP. Paradoxically mitochondria also play a key role in controlling the pathways that lead to cell death. This latter role of mitochondria is more than just a 'loss of function' resulting in an energy deficit but is an active process involving different mitochondrial proteins. Cytochrome c was the first characterised mitochondrial factor shown to be released from the mitochondrial intermembrane space and to be actively implicated in apoptotic cell death. Since then, other mitochondrial proteins, such as AIF, Smac/DIABLO, endonuclease G and Omi/HtrA2, were found to undergo release during apoptosis and have been implicated in various aspects of the cell death process. Members of the Bcl-2 protein family control the integrity and response of mitochondria to apoptotic signals. The molecular mechanism by which mitochondrial intermembrane space proteins are released and the regulation of mitochondrial homeostasis by Bcl-2 proteins is still elusive. This review summarises and evaluates the current knowledge concerning the complex role of released mitochondrial proteins in the apoptotic process.

Tipping the balance between necrosis and apoptosis in human and murine cells treated with interferon and dsRNA.

Interferons enhance the cellular antiviral response by inducing expression of protective proteins. Many of these proteins are activated by dsRNA, a typical by-product of viral infection. Here we show that type-I and type-II interferons can sensitize cells to dsRNA-induced cytotoxicity. In caspase-8- or FADD-deficient Jurkat cells dsRNA induces necrosis, instead of apoptosis. In L929sA cells dsRNA-induced necrosis involves high reactive oxygen species production. The antioxidant butylated hydroxyanisole protects cells from necrosis, but shifts the response to apoptosis. Treatment with the caspase inhibitor benzyloxycarbonyl-Val-Ala-DL-Asp(OMe)-fluoromethylketone or overexpression of Bcl-2 prevent this shift and promote necrosis. Our results suggest that a single stimulus can initiate different death-signaling pathways, leading to either necrotic or apoptotic cell death. Inhibition of key events in these signaling pathways, such as caspase activation, cytochrome c release or mitochondrial reactive oxygen species production, tips the balance between necrosis and apoptosis, leading to dominance of one of these death programs.

A matrix-assisted laser desorption ionization post-source decay (MALDI-PSD) analysis of proteins released from isolated liver mitochondria treated with recombinant truncated Bid.

A crucial event in the process of apoptosis is caspase-dependent generation of truncated Bid (tBid), inducing release of cytochrome c. In an in vitro reconstitution system we combined purified recombinant tBid with isolated liver mitochondria and identified the released proteins using a proteomic matrix-assisted laser desorption ionization post-source decay (MALDI-PSD) approach. In order to meet physiological conditions, the concentration of tBid was chosen such that it was unable to induce cytochrome c release in mitochondria derived from liver-specific Bcl-2-transgenic mice. Several mitochondrial proteins were identified to be released in a tBid-dependent way, among which cytochrome c, DIABLO/Smac, adenylate kinase 2, acyl-CoA-binding protein, endonuclease G, polypyrimidine tract-binding protein, a type-I RNA helicase, a WD-40 repeat-containing protein and the serine protease Omi. Western blotting confirmed the absence of adenylate kinase 3, a matrix mitochondrial protein. These results demonstrate that a physiologically relevant concentration of tBid is sufficient to induce release of particular intermembrane mitochondrial proteins belonging to a broad molecular-mass range.

The serine protease Omi/HtrA2 is released from mitochondria during apoptosis. Omi interacts with caspase-inhibitor XIAP and induces enhanced caspase activity.

Proteome analysis of supernatant of isolated mitochondria exposed to recombinant tBid, a proapoptotic Bcl-2 member, revealed the presence of the serine protease Omi, also called HtrA2. This release was prevented in mitochondria derived from Bcl-2-transgenic mice. Release of Omi under apoptotic conditions was confirmed in vivo in livers from mice injected with agonistic anti-Fas antibodies and was prevented in livers from Bcl-2 transgenic mice. Omi release also occurs in apoptotic dying but not in necrotic dying fibrosarcoma L929 cells, treated with anti-Fas antibodies and TNF, respectively. The amino acid sequence reveals the presence of an XIAP interaction motif at the N-terminus of mature Omi. We demonstrate an interaction between endogeneous Omi and recombinant XIAP. Furthermore we show that endogenous Omi is involved in enhanced activation of caspases in cytosolic extracts.

Endonuclease G: a mitochondrial protein released in apoptosis and involved in caspase-independent DNA degradation.

A hallmark of apoptosis is the fragmentation of nuclear DNA. Although this activity involves the caspase-3-dependent DNAse CAD (caspase-activated DNAse), evidence exists that DNA fragmentation can occur independently of caspase activity. Here we report on the ability of truncated Bid (tBid) to induce the release of a DNAse activity from mitochondria. This DNAse activity was identified by mass spectrometry as endonuclease G, an abundant 30 kDa protein released from mitochondria under apoptotic conditions. No tBid-induced endonuclease G release could be observed in mitochondria from Bcl-2-transgenic mice. The in vivo occurrence of endonuclease G release from mitochondria during apoptosis was confirmed in the liver from mice injected with agonistic anti-Fas antibody and is completely prevented in Bcl-2 transgenic mice. These data indicate that endonuclease G may be involved in CAD-independent DNA fragmentation during cell death pathways in which truncated Bid is generated.

Factors influencing the patterns of injuries and outcomes in car versus car crashes compared to sport utility, van, or pick-up truck versus car crashes: Crash Injury Research Engineering Network Study.

BACKGROUND: Data using crash dummies suggest that motor vehicle crashes (MVCs) involving passenger sedans (S) vs sport utility, vans, or light trucks (SUVTs) produce more severe injuries than those involving two sedans (SvS). However, no detailed data regarding pattern of injuries or force mechanisms involved have been presented in real patients. METHODS: The relationship of injury patterns and severities with MVC reconstruction data were obtained in 412 MVC patients, drivers or front seat passengers. Crashes were examined with regard to impact direction, frontal (F) or lateral (L) crashes, vehicle mass ratio, ISS, DELTA V, seat belt use, and airbag deployment (AB). RESULTS: In 309 F-MVC, AB reduced overall ISS (24.3 to 17.9) with a reduction in the mean severity of traumatic brain injury (TBI) GCS < or = 12, from 48% to only 28%. This AB protection from TBI was preserved as DELTA V increased to > 30 mph even though non-AB protected body areas (thorax, lung, liver, and lower extremity injuries) all increased. When vehicles of incompatible size and mass (SUVT) had F-MVC with sedans the incidence of severe TBI rose as did face lacerations despite AB or belt use. In L-MVC between SUVT and sedans compared with SvS MVC, there was a cephalad shift in body injuries with increased thorax, but decreased lower extremity injuries. The incidence of TBI increased. Analysis of injury contact sites (hits) showed more hits and a wider distribution of contract sites in SUVT vs sedan MVC. These appeared due to the greater mass excess and larger mass ratio, hood height, and width in the F-SUVT vs S crashes. All of these factors plus the increased bumper height above the body frame side-door sill were injury causal factors in the L-SUVT vs S MVCs. CONCLUSION: Both F and L crashes between sedans and SUVT with a high mass ratio shift the pattern of injury cephalad with increased thorax and intrathoracic organ injuries, and more severe TBI. These data suggest that improved head and thorax side-impact buffering and design features which transmit MVC forces from the higher front end of the larger mass SUVT to the frame of the sedan may better protect sedan occupants from side-impacts.

Disparate effects of similar phenolic phytochemicals as inhibitors of oxidative damage to cellular DNA.

Phenolic phytochemicals are natural plant substances whose cellular effects have not been completely determined. Nordihydroguaiaretic acid (NDGA) and curcumin are two phenolic phytochemicals with similar molecular structures, suggesting that they possess comparable chemical properties particularly in terms of antioxidant activity. To examine this possibility in a cellular system, this study evaluated the capacities of NDGA and curcumin to function as antioxidants in inhibiting oxidative damage to DNA. Jurkat T-lymphocytes were pre-incubated for 30 min with 0-25 microM of either NDGA or curcumin to allow for uptake. The phenolic phytochemical-treated cells were then oxidatively challenged with 25 microM hydrogen peroxide (H2O2). Afterwards, cells were subjected to alkaline micro-gel electrophoresis (i.e. comet assay) to assess the extent of single-strand breaks in DNA. In a concentration-dependent manner, NDGA inhibited H2O2-induced DNA damage, whereas curcumin did not. In fact, incubating Jurkat T-lymphocytes with curcumin alone actually induced DNA damage. This effect of curcumin on DNA did not appear to reflect the DNA fragmentation associated with apoptosis because there was no proteolytic cleavage of poly-(ADP-ribose)-polymerase, which is considered an early marker of apoptosis. Curcumin-induced damage to DNA was prevented by pre-treatment of the cells with the lipophilic antioxidant, alpha-tocopherol, suggesting that curcumin damaged DNA through oxygen radicals. Therefore, it is concluded that NDGA has antioxidant activity but curcumin has prooxidant activity in cultured cells based on their opposite effects on DNA.

Death receptor-induced apoptotic and necrotic cell death: differential role of caspases and mitochondria.

In L929sAhFas cells, tumor necrosis factor (TNF) leads to necrotic cell death, whereas agonistic anti-Fas antibodies elicit apoptotic cell death. Apoptosis, but not necrosis, is correlated with a rapid externalization of phosphatidylserine and the appearance of a hypoploid population. During necrosis no cytosolic and organelle-associated active caspase-3 and -7 fragments are detectable. The necrotic process does not involve proteolytic generation of truncated Bid; moreover, no mitochondrial release of cytochrome c is observed. Bcl-2 overexpression slows down the onset of necrotic cell death. In the case of apoptosis, active caspases are released to the culture supernatant, coinciding with the release of lactate dehydrogenase. Following necrosis, mainly unprocessed forms of caspases are released. Both TNF-induced necrosis and necrosis induced by anti-Fas in the presence of the caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp(OMe)-fluoromethylketone are prevented by the serine protease inhibitor N-tosyl-L-phenylalanine chloromethylketone and the oxygen radical scavenger butylated hydroxyanisole, while Fas-induced apoptosis is not affected.

Different effects of genistein on molecular markers related to apoptosis in two phenotypically dissimilar breast cancer cell lines.

The association between consumption of genistein-containing soybean products and lower risk of breast cancer suggests a cancer chemopreventive role for genistein. Consistent with this suggestion, exposing cultured human breast cancer cells to genistein inhibits cell proliferation, although this is not completely understood. To better understand how genistein works, the ability of genistein to induce apoptosis was compared in phenotypically dissimilar MCF-7 and MDA-MB-231 human breast cancer cells that express the wild-type and mutant p53 gene, respectively. After 6 days of incubation with 50 microM genistein, MCF-7 but not MDA-MB-231 cells, showed morphological signs of apoptosis. Marginal proteolytic cleavage of poly-(ADP-ribose)-polymerase and significant DNA fragmentation were also detected in MCF-7 cells. In elucidating these findings, it was determined that after 2 days of incubation with genistein, MCF-7 but not MDA-MB-231 cells, had significantly higher levels of p53. Accordingly, the expression of certain proteins modulated by p53 was studied next. Levels of p21 increased in both of the genistein-treated cell lines, suggesting that p21 gene expression was activated but in a p53-independent manner, whereas no significant changes in levels of the pro-apoptotic protein, Bax, were found. In MCF-7 cells, levels of the anti-apoptotic protein, Bcl-2, decreased slightly at 18-24 h but then increased considerably after 48 h. Hence, the Bax:Bcl-2 ratio initially increased but later decreased. These data suggest that at the genistein concentration tested, MCF-7 cells in contrast to MDA-MB-231 cells were sensitive to the induction of apoptosis by genistein, but Bax and Bcl-2 did not play clear roles.

Epigallocatechin gallate protects U937 cells against nitric oxide-induced cell cycle arrest and apoptosis.

Ingesting phenolic phytochemicals in many plant products may promote health, but the effects of phenolic phytochemicals at the cellular level have not been fully examined. Thus, it was determined if the tea phenolic phytochemical, epigallocatechin gallate (EGCG), protects U937 human pro-monocytic cells against the nitrogen free radical, nitric oxide (*NO). Cells were incubated for 4-6 h with 500 microM S-nitrosoglutathione (GSNO), which generates *NO, but this did not induce single-strand breaks in DNA. Nevertheless, 82 +/- 4% of GSNO-treated cells, compared to only 39 +/- 1% of untreated cells, were arrested in the G(1)-phase of the cell cycle. However, dosing the GSNO-treated cells with 9, 14, or 18 microg/ml of EGCG resulted in only 74 +/- 8%, 66 +/- 1%, and 43 +/- 3% of the cells, respectively, in the G(1)-phase. Exposing cells to GSNO also resulted in the emergence of a sub-G(1) apoptotic cell population numbering 14 +/- 3%, but only 5 +/- 2%, 5 +/- 1%, and 2 +/- 0% upon dosing of the GSNO-treated cells with 9, 14, and 18 microg/ml of EGCG, respectively. Furthermore, exposing cells to GSNO resulted in greater cell surface binding of annexin V-FITC, but binding was 41-89% lower in GSNO-treated cells dosed with EGCG. Collectively, these data suggest that *NO or downstream products induced cell cycle arrest and apoptosis that was not due to single-strand breaks in DNA, and that EGCG scavenged cytotoxic *NO or downstream products, thus reducing the number of cells in a state of cell cycle arrest or apoptosis.

Lithium sensitizes tumor cells in an NF-kappa B-independent way to caspase activation and apoptosis induced by tumor necrosis factor (TNF). Evidence for a role of the TNF receptor-associated death domain protein.

We have previously shown that lithium salts can considerably increase the direct cytotoxic effect of tumor necrosis factor (TNF) on various tumor cells in vitro and in vivo. However, the underlying mechanism has remained largely unknown. Here we show that the TNF-sensitizing effect of lithium chloride (LiCl) is independent of the type of cell death, either necrosis or apoptosis. In the case of apoptosis, TNF/lithium synergism is associated with an enhanced activation of caspases and mitochondrial cytochrome c release. Sensitization to apoptosis is specific for TNF-induced apoptosis, whereas Fas-mediated or etoposide-induced apoptosis remains unaffected. LiCl also potentiates cell death induced by artificial oligomerization of a fusion protein between FKBP and the TNF receptor-associated death domain protein. TNF-induced activation of NF-kappa B-dependent gene expression is not modulated by LiCl treatment. These results indicate that LiCl enhances TNF-induced cell death in an NF-kappa B-independent way, and suggest that the TNF receptor-associated death domain protein plays a crucial role in the TNF-sensitizing effect of LiCl.