Dopamine agonists in restless leg syndrome treatment and their effects on sleep parameters: A systematic review and meta-analysis

BACKGROUND

Dopamine agonists (DAs) constitute the standard therapeutic scheme for restless leg syndrome (RLS) because they have been proven to be effective. However, DAs may change sleep parameters, thus having adverse effects on patient condition. This meta-analysis clarified the effects of DAs used in RLS treatment on the sleep architecture.

METHODS

PubMed, Embase, and Cochrane Central databases were searched for randomized control trials (RCT) (up to October 2023) that discussed the effects of DAs on sleep architecture in patients with RLS. A meta-analysis employing a random-effects model was conducted. The patients were divided into subgroups according to individual DAs and treatment duration (1 day or ≥4 weeks).

RESULTS

Thirteen eligible randomized placebo-controlled trials were included in the assessment. The effects of three DAs (i.e., pramipexole, ropinirole, and rotigotine) on rapid eye movement (REM) sleep, slow-wave sleep (SWS), and sleep efficiency (SE) were analyzed. Overall, pramipexole significantly improved SE but decreased the percentage of REM sleep among treated patients. Ropinirole also enhanced SE compared with the placebo group. Rotigotine did not affect SE and REM sleep. Subgroup analysis found that pramipexole used for 1 day and ≥4 weeks significantly diminished the percentage of REM sleep. Ropinirole used for 1 day showed similar REM sleep patterns. Finally, none of the three DAs affected SWS.

CONCLUSIONS

This meta-analysis demonstrated that DAs significantly affect sleep parameters.

Association of low serum ferritin levels with augmentation in patients with restless legs syndrome: A systematic review and meta-analysis

BACKGROUND

Augmentation of restless legs syndrome (RLS) is an iatrogenic side effect induced by dopaminergic agents, and it is a major cause of therapeutic failure. Iron deficiency is a risk factor for RLS, but its effects on the development of RLS augmentation are unclear. This meta-analysis aimed to elucidate the association between serum ferritin and RLS augmentation.

METHODS

We searched the PubMed, Cochrane Library, Embase, ClinicalKey, ScienceDirect, and ProQuest databases for studies comparing the serum ferritin levels of patients with augmented RLS and nonaugmented RLS. A meta-analysis based on a random-effects model was conducted. Levodopa equivalent dose (LED), International Restless Legs Study Group Severity Rating Scale (IRLS), and serum hemoglobin levels were also analyzed.

RESULTS

Six observational studies fulfilled the eligibility criteria of this meta-analysis. A total of 220 RLS patients with augmentation and 687 RLS patients without augmentation were included. The results revealed that augmented RLS was significantly associated with low serum ferritin levels (p = 0.002), high LEDs (p = 0.026), and nonsignificantly associated with high IRLS scores (p = 0.227).

CONCLUSIONS

A low serum ferritin level is associated with RLS augmentation. For patients with RLS who are iron deficient, iron supplements can not only relieve their fundamental RLS symptoms but also lower the risk of RLS augmentation. Moreover, non-dopminergic agents should be considered as the first-line treatment for patients with persistent low serum ferritin levels or those with moderate to severe RLS to prevent augmentation.

Association between subclinical epileptiform discharge and the behavioral and psychological symptoms in patients with Alzheimer's dementia

OBJECTIVES

Behavioral and psychological symptoms of dementia (BPSD) are highly prevalent in patients with Alzheimer's disease (AD), causing burdens on caregivers. Behavioral and psychological symptoms of dementia and subclinical epileptiform discharge (SED) increased with the disease course of AD. However, the interaction between them was still unknown. The present study aimed to evaluate the associations between SED and BPSD.

METHODS/DESIGN

Patients with AD from Kaohsiung Municipal Ta-tung Hospital were included in this study. International 10-20 system scalp electroencephalography (EEG) for 13 min was performed to detect SED. Behavioral and psychological symptoms of dementia was assessed by neuropsychiatric inventory (NPI) questionnaires. The occurrence of BPSD subsyndromes was compared between patients with and without SED.

RESULTS

Two hundred sixty-three adult patients qualified for the inclusion criteria and were enrolled in this study. The mean age of patients was 80.2 years, and approximately 62% were women. 17.1% of patients showed SED on EEG. Apathy was the most commonly reported BPSD subsyndrome in this cohort. There was no significant difference in the prevalence of BPSD between patients with and without SED. (75.6% vs. 67.4%, p = 0.2806). However, the NPI score of irritability subsyndrome was significantly higher in the SED (+) group (2.6 ± 3.7 vs. 1.2 ± 2.7, p = 0.0028). In addition, subclinical epileptiform discharge in the frontal lobe was associated with a considerably higher occurrence of hyperactivity subsyndrome, including irritability.

CONCLUSIONS

SED may not be a direct cause of BPSD, but the presence of SED may affect the manifestation of BPSD.

Reduction in the propensity of rapid eye movement sleep and phasic-to-tonic ratio in patients with refractory epilepsy

STUDY OBJECTIVES

Patients with epilepsy exhibit disturbed sleep architecture and shorter rapid eye movement (REM) sleep compared with healthy controls. REM sleep consists of two microstates, phasic and tonic REM. Studies suggest that epileptic activity is suppressed in phasic but not in tonic REM. However, changes in the REM microstructure in patients with epilepsy are still unknown. Therefore, this study evaluated the differences in REM microstructure between patients with refractory and medically controlled epilepsy.

METHODS

This retrospective case-control study included patients with refractory and medically controlled epilepsy. Sleep parameters of the patients were recorded by standard polysomnography. In addition, the microstructures of sleep and REM sleep were compared between the two epilepsy groups.

RESULTS

Forty-two patients with refractory epilepsy and 106 with medically controlled epilepsy were evaluated. The refractory group showed significantly decreased REM sleep (p = 0.0062), particularly in the first and second sleep cycles (p = 0.0028 and 0.00482, respectively), as well as longer REM latency (p = 0.0056). Eighteen and 28 subjects in the refractory and medically controlled epilepsy groups, respectively, with comparable REM sleep percentages, underwent REM microstructure examination. Phasic REM sleep was significantly lower in the refractory group (4.5% ± 2.1% vs. 8.0% ± 4.1%; p = 0.002). In addition, the phasic-to-tonic ratio was significantly decreased (4.8 ± 2.3 vs. 8.9 ± 4.9; p = 0.002) and negatively associated with refractory epilepsy (coefficient = -0.308, p = 0.0079).

CONCLUSION

Patients with refractory epilepsy exhibited REM sleep disturbance at both macro and microstructure levels.

Restless Legs Syndrome in Patients with Epilepsy: Risk analysis, Polysomnography, and Quality of Life evaluation

STUDY OBJECTIVES

Restless legs syndrome (RLS) is a circadian rhythm related sensorimotor disorder due to brain iron deficiency, with lesion sites at the putamen and substantia nigra. However, epilepsy is a disease with abnormal electric discharge from the cortex and can be triggered with iron disequilibrium. We designed a case-control study to discover the association between epilepsy and RLS.

METHODS

A total of 24 patients with epilepsy and RLS and 72 patients with epilepsy without RLS were included. Most of the patients underwent polysomnography and video electroencephalogram tests and took sleep questionnaires. We collected information on seizure characteristics, including general or focal onset, epileptogenic focus, current antiseizure medications, medically responsive epilepsy or refractory epilepsy, and nocturnal attacks. The sleep architectures of the two groups were compared. We analyzed the risk factors for RLS using multivariate logistic regression.

RESULTS

Among the patients with epilepsy, the occurrence of RLS was associated with refractory epilepsy (OR 6.422, P = 0.002) and nocturnal seizures (OR 4.960, P = 0.005). Sleep parameters were not significantly associated with RLS status. Quality of life was significantly impaired in the group with RLS in both the physical and mental domains.

CONCLUSIONS

Refractory epilepsy and nocturnal seizures were strongly correlated with RLS in patients with epilepsy. RLS should be considered a predictable comorbidity in patients with epilepsy. The management of RLS not only led to better control of the patient's epilepsy but also improved their quality of life.

Association between Subclinical Epileptiform Discharge and the Severity of Cognitive Decline in Alzheimer’s Disease: A Longitudinal Cohort Study

Background: Alzheimer’s disease (AD) is the most common type of dementia. Aging is a risk factor for both AD and seizures. Subclinical epileptiform discharge (SED) has no evident clinical manifestation in patients with AD. Therefore, SED is liable to be overlooked in these patients since electroencephalography is not routinely performed in clinical settings. Previous studies about the association between SED and AD have yielded inconsistent results. Objective: The current study aimed to evaluate the prevalence of SED and its effect on AD severity and clinical outcomes. Methods: Patients with AD from Kaohsiung Municipal Ta-tung Hospital were included in this study. International 10–20 system scalp electroencephalography for 13 minutes was performed to detect SED. Clinical outcomes of patients with and without SED were assessed by neuropsychological tests [Cognitive Abilities Screening Instrument (CASI), Mini-Mental State Examination (MMSE), and Clinical Dementia Rating Scale Sum of Boxes (CDR-SOB)]. Results: 288 patients (mean age 80.5 years, 60.4% female) were enrolled in this study. Fifty-seven (19.8%) out of 288 patients with AD had SED. The prevalence of SED increased with the severity of cognitive impairment. Compared with patients without SED, those with SED showed significantly greater decline in CASI (–9.32 versus –3.52 points, p = 0.0001) and MMSE (–2.52 versus –1.12 points, p = 0.0042) scores in one year. Conclusion: SED may play a significant role in AD progression and is a potential therapeutic target.

Static postural stability and neuropsychological performance after awakening from REM and NREM sleep in patients with chronic insomnia: a randomized, crossover, overnight polysomnography study

STUDY OBJECTIVES

Chronic insomnia disorder (CID) is a common sleep disorder, with a prevalence ranging from 6% to 10% worldwide. Individuals with CID experience more fragmented sleep than healthy controls do. They awaken frequently during the night and have a higher risk of injury from falling. Awakening from different sleep stages may have different effects on postural stability and waking performance. However, limited research has been conducted on this topic.

METHODS

This prospective randomized crossover study was conducted between January 2015 and January 2017. We included 20 adults aged 20-65 years who fulfilled diagnosis criteria for CID. Participants underwent two overnight polysomnography studies with an interval of at least 7 days. They were awakened during either rapid eye movement (REM) sleep or N1/N2 sleep alternatively. We compared measurements of static postural stability, vigilance scores, and neuropsychological tests between REM and N1/N2 sleep awakening.

RESULTS

Polysomnography parameters between the two nights were comparable. Participants who were awakened from REM sleep had worse static postural stability than those with N1/N2 awakening. Compared with N1/N2 awakening, larger mean sway areas of center of pressure (COP; p = 0.0413) and longer COP mean distances (p = 0.0139) were found in REM sleep awakening. There were no statistically significant differences in vigilance scores or neuropsychological tests between the two nights.

CONCLUSIONS

REM sleep awakening was associated with worse static postural stability than was N1/N2 awakening. No statistically significant differences were found in waking performance in alertness or in neuropsychological tests between N1/N2 and REM sleep awakening.

Non-rapid eye movement sleep instability in adults with epilepsy: a systematic review and meta-analysis of cyclic alternating pattern

STUDY OBJECTIVES

Epilepsy is characterized by disrupted sleep architecture. Studies on sleep macro- and microstructure revealed that patients with epilepsy experience disturbed rapid eye movement (REM) sleep; however, no consensus has been reached on non-REM (NREM) sleep changes. Cyclic alternating pattern (CAP) is a marker of sleep instability that occurs only during NREM sleep. This meta-analysis investigated CAP differences between patients with epilepsy and healthy controls.

METHODS

This study followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines in searching PubMed, Embase, and Cochrane Central database for studies comparing polysomnographic sleep microstructures between patients with epilepsy and healthy controls. A meta-analysis using a random-effects model was performed. We compared CAP rates, percentages of phase A1, A2, A3 subtypes, and phase B durations between patients with epilepsy and healthy controls.

RESULTS

A total of 11 studies, including 209 patients with epilepsy and 197 healthy controls, fulfilled the eligibility criteria. Compared with healthy controls, patients with epilepsy had significantly increased CAP rates and decreased A1 subtype percentages, and patients with sleep-related epilepsy had increased A3 subtype percentages. Subgroup analyses revealed that antiseizure medications (ASMs) decreased CAP rates and increased phase B durations but did not affect the microstates of phase A in patients with sleep-related epilepsy.

CONCLUSIONS

This meta-analysis detected statistically significant differences in CAP parameters between patients with epilepsy and healthy controls. Our findings suggest patients with epilepsy experience NREM sleep instability. ASMs treatment may decrease NREM instability but did not alter the microstates of phase A.

Exploring factors associated with interictal heart rate variability in patients with medically controlled focal epilepsy

PURPOSE

Heart rate variability (HRV) reflects the balance between the functional outputs of the sympathetic and parasympathetic nervous systems. It is lower in patients with epilepsy than in the healthy controls. However, HRV has been inadequately studied in different patient subgroups with medically controlled epilepsy. Hence, this study aimed to investigate factors associated with interictal HRV in patients with medically controlled epilepsy.

METHODS

This retrospective cohort study included 54 patients (24 males and 30 females) with medically controlled focal epilepsy who only received monotherapy to eliminate the confounding effect of different antiseizure medications (ASMs). Patients with major systemic or psychiatric disorder comorbidities were excluded. For HRV analysis, electroencephalography and 5-minute well-qualified electrocardiogram segment recording were conducted during stage N1 or N2 sleep. In addition, the association between age, gender, seizure onset type, ASMs, and the time domain and frequency-domain HRV measures was analyzed.

RESULTS

HRV negatively correlated with advanced age. Patients with focal to bilateral tonic-clonic seizure (FBTCS) had a significantly lower HRV than focal impaired awareness seizures (FIAS). HRV was not associated with any gender and ASMs.

CONCLUSIONS

HRV negatively correlated with age, and patients with FBTCS had a decreased HRV. Thus, these patients may have a declining autonomic function. Therefore, different seizure types may carry different risks of autonomic dysfunction in patients with medically controlled focal epilepsy.

Quantitative evaluation of the microstructure of rapid eye movement sleep in refractory epilepsy: a preliminary study using electroencephalography and heart rate variability analysis

INTRODUCTION

Patients with epilepsy have a disturbed sleep architecture. Polysomnographic studies have shown that patients with refractory epilepsy have decreased rapid eye movement (REM) sleep and longer REM latency than those with medically controlled epilepsy. However, little is known about the differences in the REM sleep microstructure between these patient groups.

METHODS

We conducted a retrospective case-control study of 20 patients with refractory epilepsy (refractory group) and 28 patients with medically controlled epilepsy (medically controlled group). All patients completed sleep questionnaires and underwent overnight in-lab polysomnography. Five-minute electroencephalogram recordings at the C3 and C4 electrodes from each REM sleep were selected for spectral analysis, and 5-min electrocardiogram segments recorded during REM sleep were used for heart rate variability analysis. The groups' scores on the sleep questionnaires, polysomnographic sleep parameters, indices of sleep-related breathing disorders, and REM sleep electroencephalogram spectra were compared.

RESULTS

The refractory group had decreased REM sleep (p < 0.001) and longer REM latency (p = 0.0357) than those of the medically controlled group. Moreover, electroencephalogram spectral analysis revealed that the refractory group had decreased absolute beta power (p = 0.0039) and relative beta power (p = 0.0035) as well as increased relative delta power (p = 0.0015) compared with the medically controlled group.

CONCLUSIONS

Differences in the polysomnographic macrostructure and REM sleep microstructure between the study groups suggest REM sleep dysregulation in patients with refractory epilepsy.

The impact of antiseizure medications on polysomnographic parameters: a systematic review and meta-analysis

BACKGROUND

Oral antiseizure medications (ASMs) are first-line treatments for patients with epilepsy. However, ASMs may alter sleep architecture, adversely affecting patient outcomes. The meta-analysis aimed to elucidate the effect of ASMs on sleep architecture.

METHODS

PubMed, Embase, and Cochrane Central database (up to Febrary 2021) were searched for randomized control trials (RCT) with effects of ASMs on polysomnography parameters. A meta-analysis using a random-effects model was performed. We did not set limitation to the participants with underlying diagnosis of epilepsy.

RESULTS

Eighteen randomized-controlled trials fulfilled the eligibility criteria. The effects of five main groups of ASMs (sodium channel blockers, calcium channel blockers, GABA enhancers, synaptic vesicle glycoprotein 2A [SV2A] ligand, and broad-spetrum ASMs) on slow-wave sleep (SWS), rapid eye movement (REM) sleep, and sleep efficiency (SE) were analyzed. Compared with placebo, calcium channel blockers and GABA enhancers significantly increased SWS. GABA enhancers also decreased REM sleep percentage, whereas calcium channel blockers significantly increased SE. Sodium channel blockers, SV2A ligand and broad-spectrum ASMs did not affect SWS, REM sleep, or SE. The subgroup analysis revealed that gabapentin, pregabalin, and tiagabine increased the percentage of SWS. Tiagabine also decreased REM sleep, whereas pregabalin increased SE. Finally, levetiracetam did not affect SWS, REM sleep, and SE.

CONCLUSIONS

This meta-analysis indicated that ASMs can have a statistically significant effect on sleep parameters; the effect differs between ASMs.

Rapid eye movement sleep disturbance in patients with refractory epilepsy: A polysomnographic study

OBJECTIVE/BACKGROUND

Patients with epilepsy have disrupted sleep architecture and a higher prevalence of sleep disturbance. Moreover, obstructive sleep apnea (OSA) is more common among patients with refractory epilepsy. Few studies have compared subjective sleep quality, sleep architecture, and prevalence of OSA between patients with refractory epilepsy and those with medically controlled epilepsy. Therefore, this study aimed to evaluate the differences in sleep quality, sleep architecture, and prevalence of OSA between patients with refractory epilepsy and patients with medically controlled epilepsy.

PATIENTS

This retrospective case-control study included 38 patients with refractory epilepsy and 96 patients with medically controlled epilepsy. Sleep parameters and indices of sleep-related breathing disorders were recorded by standard in-laboratory polysomnography. The scores from sleep questionnaires on sleep quality and daytime sleepiness were compared between the two groups.

RESULTS

Patients with refractory epilepsy versus medically controlled epilepsy had statistically significantly decreased rapid eye movement (REM) sleep (13.5 ± 6.1% vs. 16.2 ± 6.1%) and longer REM latency (152.2 ± 84.1 min vs. 117.2 ± 61.9 min). Further, no differences were found in the prevalence of sleep-related breathing disorders, subjective sleep quality, prevalence of daytime sleepiness, and quality of life. Although not statistically significant, patients with refractory epilepsy have a lower rate of OSA compared with those with medically controlled epilepsy (21.1% vs. 30.2%).

CONCLUSIONS

Patients with refractory epilepsy had more disrupted REM sleep regulation than those with medically controlled epilepsy. Although patients with epilepsy have a higher risk of OSA, in this study patients with refractory epilepsy were not susceptible to OSA.

Posterior reversible encephalopathy syndrome with ischemic infarction complicated with intrauterine fetal death: A case report

RATIONALE

Posterior reversible encephalopathy syndrome (PRES), a rare neurologic disorder, manifests as headache, altered mental status, seizures, visual disturbances, and other focal neurologic signs with typically reversible clinical symptoms and image changes. Although the underlying mechanism remains unknown, a current theory indicates cerebral autoregulation failure as the primary cause. We report a case of PRES with stroke in an adult with intrauterine fetal death (IUFD).

PATIENT CONCERNS

A 35-year-old Asian woman with twin pregnancy underwent cesarean section at 32 weeks of gestation because of IUFD. She presented with focal seizures and visual field defect 2 days after undergoing cesarean section. Her blood pressure and kidney, liver, and coagulation functions were normal without proteinuria.

DIAGNOSIS

PRES was diagnosed based on a series of brain magnetic resonance imaging findings. Ischemic infarction in the right frontal lobe eventually developed to encephalomalacia.

INTERVENTIONS

The patient received levetiracetam and valproate for seizure management.

OUTCOMES

Five days after the onset, seizures were under control. All neurologic deficits completely improved after 21 days of admission.

LESSONS

PRES can occur in women with IUFD without preeclampsia or eclampsia symptoms. Although most cases result in vasogenic edema of the brain and exhibit good prognosis, PRES can cause cytotoxic edema and permanently damage the brain.

M(1)-like muscarinic acetylcholine receptors regulate fast-spiking interneuron excitability in rat dentate gyrus

Cholinergic transmission through muscarinic acetylcholine receptors (mAChRs) plays a key role in cortical oscillations. Although fast-spiking (FS), parvalbumin-expressing basket cells (BCs) are proposed to be the cellular substrates of gamma oscillations, previous studies reported that FS nonpyramidal cells in neocortical areas are unresponsive to cholinergic modulation. Dentate gyrus (DG) is an independent gamma oscillator in the hippocampal formation. However, in contrast to other cortical regions, the direct impact of mAChR activation on FS BC excitability in this area has not been investigated. Here, we show that bath-applied muscarine or carbachol, two mAChR agonists, depolarize DG BCs in the acute brain slices, leading to action potential firing in the theta-gamma bands in the presence of blockers of ionotropic glutamate and gamma-aminobutyric acid type A receptors at physiological temperatures. The depolarizing action persists in the presence of tetrodotoxin, a voltage-gated Na(+) channel blocker. In voltage-clamp recordings, muscarine markedly reduces background K(+) currents. These effects are mimicked by oxotremorine methiodide, an mAChR-specific agonist, and largely reversed by atropine, a non-selective mAChR antagonist, or pirenzepine, an M(1) receptor antagonist, but not by gallamine, an M(2/4) receptor antagonist. Interestingly, in contrast to M(1)-receptor-mediated depolarization, M(2) receptor activation by the specific agonist arecaidine but-2-ynyl ester tosylate down-regulates GABA release at BC axons-the effect is occluded by gallamine, an M(2) receptor antagonist. Overall, muscarinic activation results in a net increase in phasic inhibitory output to the target cells. Thus, cholinergic activation through M(1)-like receptor enhances BC activity and promotes the generation of nested theta and gamma rhythms, thereby enhancing hippocampal function and associated performance.

Critical roles of TRAF2 and TRAF5 in tumor necrosis factor-induced NF-kappa B activation and protection from cell death

Tumor necrosis factor (TNF) receptor-associated factors (TRAFs) were identified as signal transducers for the TNF receptor superfamily. However, the exact roles of TRAF2 and TRAF5 in TNF-induced NF-kappaB activation still remain controversial. To address this issue, we generated TRAF2 and TRAF5 double knockout (DKO) mice. TNF- but not interleukin-1-induced nuclear translocation of NF-kappaB was severely impaired in murine embryonic fibroblasts (MEFs) derived from DKO mice. Moreover, DKO MEFs were more susceptible to TNF-induced cytotoxicity than TRAF2 knockout MEFs. Collectively, these results indicate that both TRAF2 and TRAF5 are involved in TNF-induced NF-kappaB activation and protection from cell death.

FADD Null Mouse Embryonic Fibroblasts Undergo Apoptosis after Photosensitization with the Silicon Phthalocyanine Pc 4

Oxidative stress, such as photodynamic therapy with the silicon phthalocyanine Pc 4 (Pc 4-PDT), can induce apoptosis and tumor necrosis factor alpha (TNF) production. TNF receptors, as well as other death receptors, have been implicated in stress-induced apoptosis. To assess directly the role of FADD, a death receptor-associated protein, in induction of apoptosis post-Pc 4-PDT, embryonic fibroblasts from FADD knock out (k/o) and wild-type (wt) mice were used. Pc 4-PDT induced casp-3 activation and apoptosis in both cell types. In the presence of zVAD, a pancaspase inhibitor, Pc 4-PDT-induced apoptosis was abrogated in both cell lines. Fumonisin B1 (FB), an inhibitor of ceramide synthase, had no effect on apoptosis after Pc 4-PDT in either cell line. Similar to Pc 4-PDT, exogenous C6-ceramide bypassed FADD deficiency and induced zVAD-sensitive apoptosis. In contrast to Pc 4 photosensitization, TNF did not induce either apoptosis or ceramide accumulation in FADD k/o cells. In the absence of FADD deficiency, TNF-induced apoptosis was zVAD-sensitive and FB-insensitive. Induced ceramide levels remained elevated after cotreatment with TNF and zVAD in FADD wt cells. Taken together, these data provide genetic evidence for a lack of FADD requirement in Pc 4-PDT- or C6-ceramide-induced apoptosis. FB-sensitive ceramide production accompanies, but does not suffice, for apoptosis after Pc 4 photosensitization or TNF.

Tumor necrosis factor receptor-associated factor 6 (TRAF6) deficiency results in exencephaly and is required for apoptosis within the developing CNS

Tumor necrosis factor receptor-associated factors (TRAFs) are adaptor proteins important in mediating intracellular signaling. We report here that targeted deletion of traf6 greatly increases the frequency of failure of neural tube closure and exencephaly in traf6 (-/-) mice. The penetrance of this defect is influenced by genetic background. Neural tube fusion requires the coordination of several biological processes, including cell migration invoked by contact-dependent signaling, cell proliferation, and programmed cell death (PCD). To gain greater insight into the role of TRAF6 in these processes, neural development and migration within the CNS of traf6 (-/-) mice and controls were assessed through temporal examination of a number of immunohistochemical markers. In addition, relative levels of cellular proliferation and PCD were examined throughout embryonic development using bromodeoxyuridine (BrdU) and in situ terminal deoxynucleotidyl transferase-mediated dUTP biotinylated nick end labeling (TUNEL), respectively. The data suggest that loss of TRAF6 does not significantly alter the level of cellular proliferation or the pattern of neural differentiation per se, but rather regulates the level of PCD within specific regions of the developing CNS. Substantial reductions in TUNEL were observed within the ventral diencephalon and mesencephalon in exencephalic traf6 (-/-) embryos. Our results demonstrate a novel and prominent role for TRAF6 in the regional control of PCD within the developing CNS.

Deficiency of T2K leads to apoptotic liver degeneration and impaired NF-kappaB-dependent gene transcription

Induction of NF-kappaB-dependent transcription requires phosphorylation and subsequent degradation of I-kappaB, an inhibitor of NF-kappaB, followed by nuclear translocation and DNA binding of NF-kappaB. Tumor necrosis factor receptor-associated factor 2 (TRAF2) plays a role in NF-kappaB activation in response to cytokines such as tumor necrosis factor alpha (TNFalpha). In this study, we purified and characterized a novel kinase (T2K, also known as TBK1 or NAK), which associates with TRAF2 and exhibits kinase activity towards I-kappaBalpha in vitro. The physiological function of T2K was investigated using T2K-deficient mice. Heterozygotes appear normal, but t2k(-/-) animals die at approximately E14.5 of massive liver degeneration and apoptosis. Never theless, hematopoietic progenitors from T2K-deficient fetal liver support normal lymphocyte development. Furthermore, t2k(-/-) embryonic fibroblasts and thymocytes do not display increased sensitivity to TNFalpha-induced apoptosis. In response to either TNFalpha or IL-1 induction, t2k(-/-) embryonic fibroblasts exhibit normal degradation of I-kappaB and kappaB-binding activity. However, NF-kappaB-directed transcription is dramatically reduced. These results demonstrate that, like I-kappaB kinase beta and the RelA subunit of NF-kappaB, T2K is critical in protecting embryonic liver from apoptosis. However, T2K has a unique role in the activation of NF-kappaB-directed transcription, apparently independent of I-kappaB degradation and NF-kappaB DNA binding.

Low frequency of bacteremia after endoscopic mucosal resection

BACKGROUND

Endoscopic mucosal resection has become a popular alternative for the treatment of early-stage neoplasia of the gastrointestinal tract. However, there are still no data on the frequency of bacteremia associated with this form of treatment.

METHODS

We conducted a prospective study of 21 men and 17 women undergoing endoscopic mucosal resection with a cap-fitted panendoscope for upper gastrointestinal lesions. Blood cultures were performed before, 10 minutes after, and 4 hours after the procedure for both aerobic and anaerobic bacteria.

RESULTS

Blood culture at baseline was negative in all the patients. Two of 38 patients (5.3 %) had positive blood culture at 10 minutes after the procedure. The isolated microorganisms were Streptococcus salivarius and Corynebacterium species. All patients had negative blood cultures 4 hours later. None of these 38 patients had any symptoms or signs associated with infection.

CONCLUSIONS

Bacteremia associated with endoscopic mucosal resection is infrequent and transient.

Requirement for Casper (c-FLIP) in regulation of death receptor-induced apoptosis and embryonic development

Casper (c-FLIP) associates with FADD and caspase-8 in signaling complexes downstream of death receptors like Fas. We generated Casper-deficient mice and cells and noted a duality in the physiological functions of this molecule. casper-/- embryos do not survive past day 10.5 of embryogenesis and exhibit impaired heart development. This phenotype is reminiscent of that reported for FADD-/- and caspase-8-/- embryos. However, unlike FADD-/- and caspase-8-/- cells, casper-/- embryonic fibroblasts are highly sensitive to FasL- or TNF-induced apoptosis and show rapid induction of caspase activities. NF-kappaB and JNK/SAPK activation is intact in TNF-stimulated casper-/- cells. These results suggest that Casper has two distinct roles: to cooperate with FADD and caspase-8 during embryonic development and to mediate cytoprotection against death factor-induced apoptosis.

Severe liver degeneration and lack of NF-kappaB activation in NEMO/IKKgamma-deficient mice

Phosphorylation of IkappaB, an inhibitor of NF-kappaB, is an important step in the activation of the transcription factor NF-kappaB. Phosphorylation is mediated by the IkappaB kinase (IKK) complex, known to contain two catalytic subunits: IKKalpha and IKKbeta. A novel, noncatalytic component of this kinase complex called NEMO (NF-kappaB essential modulator)/IKKgamma was identified recently. We have generated NEMO/IKKgamma-deficient mice by gene targeting. Mutant embryos die at E12.5-E13.0 from severe liver damage due to apoptosis. NEMO/IKKgamma-deficient primary murine embryonic fibroblasts (MEFs) lack detectable NF-kappaB DNA-binding activity in response to TNFalpha, IL-1, LPS, and Poly(IC) and do not show stimulus-dependent IkappaB kinase activity, which correlates with a lack of phosphorylation and degradation of IkappaBalpha. Consistent with these data, mutant MEFs show increased sensitivity to TNFalpha-induced apoptosis. Our data provide in vivo evidence that NEMO/IKKgamma is the first essential, noncatalytic component of the IKK complex.

Mediation of TNF receptor-associated factor effector functions by apoptosis signal-regulating kinase-1 (ASK1)

Tumor necrosis factor-alpha (TNF), a major inflammatory cytokine, generates a wide variety of cellular responses via key cytoplasmic adaptor molecules named TNF receptor-associated factors (TRAFs). We report that TRAF2, TRAF5 and TRAF6 associate with apoptosis signal-regulating kinase 1 (ASK1), and a catalytically-inactive ASK1 mutant blocks stress-activated protein kinase (SAPK)/Jun NH2-terminal kinase (JNK) activation by these TRAFs. A truncated derivative of TRAF2, which inhibits SAPK activation by TNF, blocks TNF-induced ASK1 activation. Furthermore, protection from TNF-induced cell death conferred by an ASK1 mutant is dependent upon TRAF2. Hence, ASK1 is a common mediator of TRAF-regulated SAPK and apoptosis signaling, and the TRAF2 - ASK1 connection completes the signaling cascade from TNF to SAPK/JNK activation.

TRAF2 deficiency results in hyperactivity of certain TNFR1 signals and impairment of CD40-mediated responses

Tumor necrosis factor (TNF) receptor-associated factor 2 (TRAF2) can interact with various members of the TNF receptor family. Previously, we reported that TRAF2-deficient mice die prematurely and have elevated serum TNF levels. In this study, we demonstrate that TRAF2-deficient macrophages produce increased amounts of nitric oxide (NO) and TNF in response to TNF stimulation. Furthermore, we could enhance the survival of TRAF2-deficient mice by eliminating either TNF or TNFR1. Using these double-knockout mice, we show that in the absence of TRAF2, the T helper-dependent antibody response, CD40-mediated proliferation, and NF-kappaB activation are defective. These data demonstrate two important roles of TRAF2, one as a negative regulator of certain TNFR1 signals and the other as a positive mediator of CD40 signaling.

Interleukin 13 is secreted by and stimulates the growth of Hodgkin and Reed-Sternberg cells

Gene expression patterns can provide vital clues to the pathogenesis of neoplastic diseases. We investigated the expression of 950 genes in Hodgkin's disease (HD) by analyzing differential mRNA expression using microarrays. In two independent microarray experiments, the HD-derived cell lines L428 and KMH2 were compared with an Epstein-Barr virus (EBV)-immortalized lymphoblastoid B cell line, LCL-GK. Interleukin (IL)-13 and IL-5 were found to be highly expressed in the HD-derived cell lines. Examination of IL-13 and IL-5 expression by Northern blot analysis and enzyme-linked immunosorbent assay confirmed these results and revealed the expression of IL-13 in a third HD-derived cell line, HDLM2. Control LCL and EBV-negative non-Hodgkin lymphoma-derived cell lines did not express IL-13. In situ hybridization of lymph node tissue from HD patients showed that elevated levels of IL-13 were specifically expressed by Hodgkin/Reed-Sternberg (H/RS) tumor cells. Treatment of a HD-derived cell line with a neutralizing antibody to IL-13 resulted in a dose-dependent inhibition of H/RS cell proliferation. These data suggest that H/RS cells produce IL-13 and that IL-13 plays an important role in the stimulation of H/RS cell growth, possibly by an autocrine mechanism. Modulation of the IL-13 signaling pathway may be a logical objective for future therapeutic strategies.

Gene targeting in the analysis of mammalian apoptosis and TNF receptor superfamily signaling

Apoptosis, or programmed cell death (PCD), is the subject of much current investigative interest. Developing embryos and many adult organ systems require the tight coupling of cellular proliferation and PCD to ensure proper organogenesis and optimal tissue function. Over the past decade, our knowledge of the genetic basis underlying the execution of apoptosis in mammals has progressed enormously, thanks largely to groundbreaking studies performed in the nematode Caenorhabditis elegans. In contrast, the components of the signaling apparatus that links the various death stimuli and the receptors they stimulate to the execution mechanism remain relatively unknown. It is only in the past 4 years that studies of signal transduction via members of the tumor necrosis factor (TNF) receptor superfamily have identified a plethora of novel signaling proteins, including molecules that are directly involved in apoptosis signaling, and others that regulate the induction of cell death. This two-part review focuses on the biology of apoptosis and signaling through members of the TNF receptor superfamily as revealed by the study of gene-targeted "knockout" mice. These genetic mutant animals are invaluable tools not only for confirming or refuting a proposed function of a particular gene in an in vivo setting, but also for uncovering novel functions for a gene that were not anticipated from conventional in vitro experiments. In the field of apoptosis, as for many other areas of biomedical research, knockout mice and cell lines can be used as models for studying human disease, with the ultimate goal of developing therapeutic strategies.

Preoperative sonographic diagnosis of midgut malrotation with volvulus in adults: the "whirlpool" sign

Midgut malrotation and volvulus, found mostly in children, are rare and difficult to diagnose preoperatively in adults. We report 2 cases in which a 68-year-old man and a 75-year-old woman presented with intermittent cramping abdominal pain, abdominal distention, and vomiting. Abdominal sonography demonstrated wrapping of the superior mesenteric vein and bowel loops around the superior mesenteric artery (the "whirlpool sign") in both patients. Abdominal CT revealed similar findings. The diagnoses of midgut volvulus and mesenteric malrotation were made, and the patients underwent laparotomy. The man was confirmed to have duodenojejunal malrotation and volvulus, and the woman had cecal volvulus. The whirlpool sign is valuable for the preoperative diagnosis of mesenteric vessel malrotation and midgut volvulus.

TRAF6 deficiency results in osteopetrosis and defective interleukin-1, CD40, and LPS signaling

Bone resorption and remodeling is an intricately controlled, physiological process that requires the function of osteoclasts. The processes governing both the differentiation and activation of osteoclasts involve signals induced by osteoprotegerin ligand (OPGL), a member of tumor necrosis factor (TNF) superfamily, and its cognate receptor RANK. The molecular mechanisms of the intracellular signal transduction remain to be elucidated. Here we report that mice deficient in TNF receptor-associated factor 6 (TRAF6) are osteopetrotic with defects in bone remodeling and tooth eruption due to impaired osteoclast function. Using in vitro assays, we demonstrate that TRAF6 is crucial not only in IL-1 and CD40 signaling but also, surprisingly, in LPS signaling. Furthermore, like TRAF2 and TRAF3, TRAF6 is essential for perinatal and postnatal survival. These findings establish unexpectedly diverse and critical roles for TRAF6 in perinatal and postnatal survival, bone metabolism, LPS, and cytokine signaling.

Requirement of FADD for tumor necrosis factor-induced activation of acid sphingomyelinase

The generation of mice strains deficient for select members of the signaling complex of the 55-kDa tumor necrosis factor receptor (TNF-R55) has allowed the assignment of specific cellular responses to distinct TNF-R55-associated proteins. In particular, the TNF-R55-associated protein FADD seems to be responsible for recruitment and subsequent activation of caspase 8. In this report we demonstrate the requirement of FADD for TNF-induced activation of endosomal acid sphingomyelinase (A-SMase). In primary embryonic fibroblasts from FADD-deficient mice the activation of A-SMase by TNF-R55 ligation was almost completely impaired. This effect is specific in that other TNF responses like activation of NF-kappaB or neutral (N-)SMase remained unaffected. In addition, interleukin-1-induced activation of A-SMase in FADD-deficient cells was unaltered. In FADD-/- embryonic fibroblasts reconstituted by transfection with a FADD cDNA expression construct, the TNF responsiveness of A-SMase was restored. The results of this study suggest that FADD, in addition to its role in triggering a proapoptotic caspase cascade, is required for TNF-induced activation of A-SMase.

E1A-induced processing of procaspase-8 can occur independently of FADD and is inhibited by Bcl-2

Expression of the 243-residue form of the adenovirus E1A protein in the absence of other viral proteins triggers apoptosis by a pathway that requires p53. This pathway includes processing and activation of initiator procaspase-8, redistribution of cytochrome c, and activation of procaspase-3. Bcl-2 functions at or upstream of procaspase-8 processing to inhibit all of these events and prevent cell death. This contrasts with the anti-apoptotic influence of Bcl-2 family proteins in the cell death pathway induced by Fas ligand or tumor necrosis factor (TNF), in which Bcl-2 typically acts downstream of Fas/TNFR1-mediated activation of caspase-8. Moreover, E1A induces procaspase-8 processing and cell death in cells deleted of FADD, an adaptor protein critical for Fas/TNFR1 activation of caspase-8. The results indicate that E1A is capable of activating caspase-8 by a Bcl-2-inhibitable pathway that does not involve autocrine stimulation of FADD-dependent death receptor pathways.

Activation of the dsRNA-dependent protein kinase, PKR, induces apoptosis through FADD-mediated death signaling

The dsRNA-dependent protein kinase (PKR) is considered to play a key role in interferon-mediated host defense against viral infection and conceivably malignant transformation. To investigate further the mechanisms of PKR-induced growth inhibition, we have developed tetracycline-inducible murine cell lines that express wild-type PKR or a catalytically inactive PKR variant, PKRdelta6. Following induction, the growth of the wild-type PKR-expressing cells was similar to that of cells transfected with vector alone, while cells expressing PKRdelta6 became malignantly transformed. Significantly, treatment with dsRNA caused the wild-type PKR-overexpressing cells to undergo programed cell death while, conversely, cells expressing PKRdelta6 were completely resistant. Our studies demonstrated that activation of PKR induces the expression of members of the tumor necrosis factor receptor (TNFR) family, including Fas (CD95/Apo-1) and pro-apopotic Bax. In contrast, transcripts representing Fas, TNFR-1, FADD (Fas-associated death domain), FLICE, Bad and Bax were ablated in cells expressing PKRdelta6. The involvement of the death receptors in PKR-induced apoptosis was underscored by demonstrating that murine fibroblasts lacking FADD were almost completely resistant to dsRNA-mediated cell death. Thus, PKR, a key cellular target for viral repression, is a receptor/inducer for the induction of pro-apoptotic genes by dsRNA and probably functions in interferon-mediated host defense to trigger cell death in response to virus infection and perhaps tumorigenesis.

CD28-independent, TRAF2-dependent costimulation of resting T cells by 4-1BB ligand

4-1BB ligand (4-1BBL) is a member of the tumor necrosis factor (TNF) family expressed on activated antigen-presenting cells. Its receptor, 4-1BB, is a member of the TNF receptor family expressed on activated CD4 and CD8 T cells. We have produced a soluble form of 4-1BBL using the baculovirus expression system. When coimmobilized on plastic with anti-CD3, soluble 4-1BBL induces interleukin (IL)-2 production by resting CD28+ or CD28- T cells, indicating that 4-1BBL can function independently of other cell surface molecules, including CD28, in costimulation of resting T cell activation. At low concentrations of anti-CD3, 4-1BBL is inferior to anti-CD28 in T cell activation. However, when 4-1BB ligand is provided together with strong TCR signals, then 4-1BBL and anti-CD28 are equally potent in stimulation of IL-2 production by resting T cells. We find that TNF receptor-associated factor (TRAF)1 or TRAF2 associate with a glutathione S-transferase-4-1BB cytoplasmic domain fusion protein in vitro. In T cells, we find that association of TRAF1 and TRAF2 with 4-1BB requires 4-1BB cross-linking. In support of a functional role for TRAF2 in 4-1BB signaling, we find that resting T cells isolated from TRAF2-deficient mice or from mice expressing a dominant negative form of TRAF2 fail to augment IL-2 production in response to soluble 4-1BBL. Thus 4-1BB, via the TRAF2 molecule, can provide CD28-independent costimulatory signals to resting T cells.

FADD: essential for embryo development and signaling from some, but not all, inducers of apoptosis

FADD (also known as Mort-1) is a signal transducer downstream of cell death receptor CD95 (also called Fas). CD95, tumor necrosis factor receptor type 1 (TNFR-1), and death receptor 3 (DR3) did not induce apoptosis in FADD-deficient embryonic fibroblasts, whereas DR4, oncogenes E1A and c-myc, and chemotherapeutic agent adriamycin did. Mice with a deletion in the FADD gene did not survive beyond day 11.5 of embryogenesis; these mice showed signs of cardiac failure and abdominal hemorrhage. Chimeric embryos showing a high contribution of FADD null mutant cells to the heart reproduce the phenotype of FADD-deficient mutants. Thus, not only death receptors, but also receptors that couple to developmental programs, may use FADD for signaling.

Early lethality, functional NF-kappaB activation, and increased sensitivity to TNF-induced cell death in TRAF2-deficient mice

TRAF2 is an intracellular signal-transducing protein recruited to the TNFR1 and TNFR2 receptors following TNF stimulation. To investigate the physiological role of TRAF2, we generated TRAF2-deficient mice. traf2-/- mice appeared normal at birth but became progressively runted and died prematurely. Atrophy of the thymus and spleen and depletion of B cell precursors also were observed. Thymocytes and other hematopoietic progenitors were highly sensitive to TNF-induced cell death and serum TNF levels were elevated in these TRAF2-deficient animals. Examination of traf2-/- cells revealed a severe reduction in TNF-mediated JNK/SAPK activation but a mild effect on NF-kappaB activation. These results suggest that TRAF2-independent pathways of NF-kappaB activation exist and that TRAF2 is required for an NF-kappaB-independent signal that protects against TNF-induced apoptosis.

Regulation of adipose maturation and energy homeostasis

The adipose tissue of mammals represents a dynamic organ disseminated throughout the body. It fluctuates in abundance according to the availability of metabolic energy supplies. Mature adipose tissue communicates with the central nervous system via a hormonal circuit that controls satiety. Adipogenesis can be recapitulated in cell culture, thus facilitating molecular biological studies of the regulatory proteins that control this process. Such studies have led to the identification of two families of transcription factors that regulate adipogenesis and mammalian energy homeostasis.

Rapamycin inhibits clonal expansion and adipogenic differentiation of 3T3-L1 cells

Differentiating 3T3-L1 cells express an immunophilin early during the adipocyte conversion program as described in this issue [Yeh, W.-C., Li, T.-K., Bierer, B. E. & McKnight, S. L. (1995) Proc. Natl. Acad. Sci. USA 92, 11081-11085]. The temporal expression profile of this protein, designated FK506-binding protein (FKBP) 51, is concordant with the clonal-expansion period undertaken by 3T3-L1 cells after exposure to adipogenic hormones. Having observed FKBP51 synthesis early during adipogenesis, we tested the effects of three immunosuppressive drugs--cyclosporin A, FK506, and rapamycin--on the terminal-differentiation process. Adipocyte conversion was not affected by either cyclosporin A or FK506 and yet was significantly reduced by rapamycin at drug concentrations as low as 10 nM. Clonal expansion was impeded in drug-treated cultures, as was the accumulation of cytoplasmic lipid droplets normally seen late during differentiation. Rapamycin treatment likewise inhibited the expression of CCAAT/enhancer binding protein alpha, a transcription factor required for 3T3-L1 cell differentiation. All three of these effects were reversed by high FK506 concentrations, indicating that the operative inhibitory event was mediated by an immunophilin-rapamycin complex.

Identification and characterization of an immunophilin expressed during the clonal expansion phase of adipocyte differentiation

Mouse 3T3-L1 cells differentiate into fat-laden adipocytes in response to a cocktail of adipogenic hormones. This conversion process occurs in two discrete steps. During an early clonal expansion phase, confluent 3T3-L1 cells proliferate and express the products of the beta and delta members of the CCAAT/enhancer binding protein (C/EBP) family of transcription factors. The cells subsequently arrest mitotic growth, induce the expression of the alpha form of C/EBP, and acquire the morphology of fully differentiated adipocytes. Many of the genes induced during the terminal phase of adipocyte conversion are directly activated by C/EBP alpha, and gratuitous expression of this transcription factor is capable of catalyzing adipose conversion in a number of different cultured cell lines. The genetic program undertaken during the clonal expansion phase of 3T3-L1 differentiation, controlled in part by C/EBP beta and C/EBP delta, is less clearly understood. To study the molecular events occurring during clonal expansion, we have identified mRNAs that selectively accumulate during this phase of adipocyte conversion. One such mRNA encodes an immunophilin hereby designated FKBP51. In this report we provide the initial molecular characterization of FKBP51.

Cascade regulation of terminal adipocyte differentiation by three members of the C/EBP family of leucine zipper proteins

Terminal differentiation of cultured 3T3-L1 fibroblasts to the adipogenic phenotype is potently stimulated by dexamethasone (DEX) and methylisobutylxanthine (MIX). Previous studies have shown that these hormones induce the expression of genes encoding two members of the CCAAT/enhancer binding protein (C/EBP) family of transcription factors. In the absence of new protein synthesis DEX activates the gene encoding C/EBP delta. Likewise, MIX is a direct inducer of C/EBP beta gene expression. Optimal conditions for differentiation entail a 2-day period wherein confluent fibroblasts are exposed to DEX and MIX, followed by removal of the hormones and subsequent culture in the presence of insulin and fetal bovine serum. During the early phase of differentiation, high levels of C/EBP delta and C/EBP beta accumulate. These transcription factors diminish during the terminal phase of differentiation and come to be replaced by a third member of the C/EBP family, C/EBP alpha. Conclusive evidence has already shown that C/EBP alpha regulates terminal adipocyte differentiation, turning on the battery of fat-specific genes required for the synthesis, uptake, and storage of long chain fatty acids. Here we provide evidence that C/EBP delta and C/EBP beta play early catalytic roles in the differentiation pathway, relaying the effects of the hormonal stimulants DEX and MIX in a cascade-like fashion, leading to the activation of the gene encoding C/EBP alpha. Conditions facilitating the precocious expression of either C/EBP delta or C/EBP beta were observed to accelerate adipogenesis and, in the case of C/EBP beta, relieve dependence on the early hormonal stimulants. Likewise, conditions that prevented the expression of functional C/EBP beta effectively blocked terminal differentiation. Finally, we have discovered that ectopic expression of C/EBP beta in multipotential NIH-3T3 cells results in their conversion into committed adipoblasts capable, upon hormonal stimulation, of synchronous and uniform differentiation into fat-laden adipocytes.