Ioana Inta

IL-6 knockout mice exhibit resistance to stress-induced development of depression-like behaviors.

Cytokine-dependent mechanisms in the CNS have been implicated in the pathogenesis of depression. Interleukin-6 is upregulated in depressed patients and dowregulated by antidepressants. It is, however, unknown whether IL-6 is involved in the pathogenesis of depression. We subjected IL-6-deficient mice (IL-6(-/-)) to depression-related tests (learned helplessness, forced swimming, tail suspension, sucrose preference). We also investigated IL-6 in the hippocampus of stressed wild-type mice. IL-6(-/-) mice showed reduced despair in the forced swim, and tail suspension test, and enhanced hedonic behavior. Moreover, IL-6(-/-) mice exhibited resistance to helplessness. This resistance may be caused by the lack of IL-6, because stress increased IL-6 expression in wild-type hippocampi. This suggests that IL-6 is a component in molecular mechanisms in the pathogenesis of depression. IL-6(-/-) mice represent tools to study IL-6-dependent signaling pathways in the pathophysiology of depression in vivo. Moreover, these mice may support the screening of compounds for depression by altering cytokine-mediated signaling.

Bim and Noxa Are Candidates to Mediate the Deleterious Effect of the NF-κB Subunit RelA in Cerebral Ischemia

The transcription factor nuclear factor κB (NF-κB) is well known for its antiapoptotic action. However, in some disorders, such as cerebral ischemia, a proapoptotic function of NF-κB has been demonstrated. To analyze which subunit of NF-κB is functional in cerebral ischemia, we induced focal cerebral ischemia in mice with a germline deletion of the p52 or c-Rel gene or with a conditional deletion of RelA in the brain. Only RelA deficiency reduced infarct size. Interestingly, expression of the proapoptotic BH3 (Bcl-2 homology domain 3)-only genes Bim and Noxa in cerebral ischemia depended on RelA and the upstream kinase IKK (IκB kinase). RelA stimulated Bim and Noxa gene transcription in primary cortical neurons and bound to the promoter of both genes. Thus, the deleterious function in cerebral ischemia is specific for the NF-κB subunit RelA and may be mediated through Bim and Noxa.

NF‐κB p50/RelA and c‐Rel‐containing dimers: opposite regulators of neuron vulnerability to ischaemia

Diverse nuclear factor‐κB subunits mediate opposite effects of extracellular signals on neuron survival. While RelA is activated by neurotoxic agents, c‐Rel drives neuroprotective effects. In brain ischaemia RelA and p50 factors rapidly activate, but how they associate with c‐Rel to form active dimers and contribute to the changes in diverse dimer activation for neuron susceptibility is unknown. We show that in both cortical neurons exposed to oxygen glucose deprivation (OGD) and mice subjected to brain ischaemia, activation of p50/RelA was associated with inhibition of c‐Rel/RelA dimer and no change p50/c‐Rel. Targeting c‐Rel and RelA expression revealed that c‐Rel dimers reduced while p50/RelA enhanced neuronal susceptibility to anoxia. Activation of p50/RelA complex is known to induce the pro‐apoptotic Bim and Noxa genes. We now show that c‐Rel‐containing dimers, p50/c‐Rel and RelA/c‐Rel, but not p50/RelA, promoted Bcl‐xL transcription. Accordingly, the OGD exposure induced Bim, but reduced Bcl‐xL promoter activity and decreased the content of endogenous Bcl‐xL protein. These findings demonstrate that within the same neuronal cell, the balance between activation of p50/RelA and c‐Rel‐containing complexes fine tunes the threshold of neuron vulnerability to the ischaemic insult. Selective targeting of different dimers will unravel new approaches to limit ischaemia‐associated apoptosis.

NF-κB signalling in cerebral ischaemia

In acute stroke, neuronal apoptosis and inflammation are considered to be important mechanisms on the road to tissue loss and neurological deficit. Both apoptosis and inflammation depend on gene transcription. We have identified a signalling pathway that regulates transcription of genes involved in apoptosis and inflammation. In a mouse model of focal cerebral ischaemia, there is an induction of the cytokine TWEAK (tumour necrosis factor-like weak inducer of apoptosis) and its membrane receptor Fn14. TWEAK promotes neuronal cell death and activates the transcription factor NF-kappaB (nuclear factor kappaB) through the upstream kinase IKK [IkappaB (inhibitory kappaB) kinase]. In vivo, IKK is activated in neurons. Neuron-specific deletion of the subunit IKK2 or inhibition of IKK activity reduced the infarct size and neuronal cell loss. A pharmacological inhibitor of IKK also showed neuroprotective properties. IKK-dependent ischaemic brain damage is likely to be mediated by NF-kappaB, because neuron-specific inhibition of NF-kappaB through transgenic expression of the NF-kappaB superrepressor was found to reduce the infarct size. In summary, there is evidence that IKK/NF-kappaB signalling contributes to ischaemic brain damage and may provide suitable drug targets for the treatment of stroke.

Induction of the cytokine TWEAK and its receptor Fn14 in ischemic stroke

Stroke outcome is determined by delayed neuronal cell death and edema formation. TWEAK, a cytokine of the TNF superfamily, and its membrane receptor Fn14 promote ischemia-induced neuronal apoptosis and leakage of the blood-brain barrier. Both TWEAK and Fn14 are upregulated in experimental stroke models. In this study, we investigated whether TWEAK and Fn14 are upregulated in stroke patients. We measured serum concentrations of TWEAK in stroke patients and matched control subjects by ELISA. Expression of Fn14 in the brain was evaluated by real-time RT-PCR and immunohistochemistry. TWEAK serum concentrations were elevated in stroke patients. In autopsy samples, we found elevated mRNA levels of the receptor Fn14 and a trend towards higher TWEAK mRNA levels. In the infarcted and peri-infarct tissue immunostaining for Fn14 was enhanced. These data show that the cytokine TWEAK and its membrane receptor Fn14 are upregulated in stroke and suggest that they contribute to stroke outcome.

Neuronal NF-κB influences thermoregulation and survival in a sepsis model

Gene regulation in sepsis is known to be controlled by the transcription factor NF-kappaB. However, the function of neuronal NF-kappaB in sepsis is not well defined. In a mouse model of sepsis induced by i.p. injection of lipopolysaccharides (LPS), we found an activation of NF-kappaB in the brain as shown by the induction of a transgenic NF-kappaB reporter. Inhibition of neuronal NF-kappaB by cell-specific expression of the NF-kappaB super-repressor IkappaBalpha-SR improved LPS-induced hypothermia and survival but had no effect on body weight or on the humoral response to LPS. In contrast, glial inhibition of NF-kappaB did not influence body temperature and survival. By immunohistochemistry, we detected the active NF-kappaB subunit RelA in neuronal nuclei of the organum vasculosum of the lamina terminalis. Our data reveal an important role of neuronal NF-kappaB in thermoregulation and survival. The upcoming group of NF-kappaB inhibitors may have a place in the treatment of the acute-phase response.

Minocycline does not evoke anxiolytic and antidepressant-like effects in C57BL/6 mice

Minocycline is a broad-spectrum tetracycline antibiotic with multiple actions, including anti-inflammatory and neuroprotective effects, that was proposed as novel treatment for several psychiatric disorders including schizophrenia and depression. However, there are contradictory results regarding antidepressant effects of minocycline in rodent models. Additionally, the possible anxiolytic effect of minocycline is still poorly investigated. Therefore, we aimed to clarify in the present study the influence of minocycline on behavioral correlates of mood disorders in standard tests for depression and anxiety, the Porsolt Forced Swim Test (FST), Elevated O-Maze, Dark-Light Box Test and Openfield Test in adult C57BL/6 mice. We found, unexpectedly, that mice treated with minocycline (20-40mg/kg, i.p.) did not display antidepressant- or anxiolytic-like behavioral changes in contrast to mice treated with diazepam (0.5mg/kg, anxiety tests) or imipramine (20mg/kg, depressive-like behavior). These results are relevant for future studies, considering that C57BL/6 mice, the most widely used strain in pharmacological and genetic animal models, did not react as expected to the treatment regime applied.

Analyses of Gonadoblastoma Y (GBY)-locus and of Y centromere in Turner syndrome patients.

BACKGROUND Mosaicism with cytogenetically visible Y chromosome is found in 5-6% of Turner Syndrome (TS) patients. Additionally, occult Y-chromosome derived material is increasingly found in patients with monosomy X when using more sensitive molecular techniques. These TS patients are at risk of developing gonadoblastomas when the Y genes presumed to be involved in gonadoblastoma development (Gonadoblastoma-Y-locus; GBY) are present. AIM To find occult Y-chromosome material in TS patients and to correlate the patients phenotype to Y-chromosome material. METHODS We studied 60 TS-patients for presence of the Y chromosome with focus on the Gonadoblastoma Y-locus and its extension in Yp and Yq using sensitive Y centromere and Y gene deletion PCR assays. In addition, we evaluated their individual clinical and auxological characteristics. RESULTS We identified presence of the GBY-locus in 7 patients (11.7%) including 4 patients without evidence for a Y chromosome in their preceding standard karyotype analyses. Clinical and auxological characteristics were similar in GBY-positive and GBY-negative patients. CONCLUSIONS Presence of the GBY locus in Turner patients with no indication of the Y chromosome in standard cytogenetic chromosome analysis can be revealed by sensitive molecular PCR assays screening for presence of the Y centromere and the GBY-candidate-genes in proximal Yp11 and Yq11, respectively.

Height Gain in Ullrich-Turner Syndrome after Early and Late Growth Hormone Treatment Start: Results from a Large Retrospective German Study and Potential Basis for an Individualized Treatment Approach

Background: Ullrich-Turner syndrome (UTS) girls often present with short stature in adolescence to the endocrinologist when the efficacy of growth hormone (GH) to improve growth remains unknown and parameters to estimate individual GH responsiveness have yet to be determined. Objective: Retrospective evaluation of adult height (AH) and predicted adult height at GH start (descriptive model of Ranke, Model PredAH) in early and late GH-treated German UTS patients. Subjects/Methods: 313 patients treated with GH, early [chronological age (CA) at GH start <12 years, n = 259] or late (CA at GH start ≥12 years, n = 54) who reached AH were selected from KIGS (Pfizer International Growth Database). Results: AH (152.5 ± 5.9 vs. 151.1 ± 5.4 cm, p = n.s.) after GH treatment for 7.5 ± 2.12 years (GH start early) and for 5.2 ± 1.2 years (GH start late) were similar (p = n.s.) as Model PredAH (155.7 ± 4.8 vs. 154.7 ± 4.8 cm; p = n.s.) but higher (p < 0.001) than projected adult height (Ranke, ProjAH; 148.2 ± 5.5 vs. 145.2 ± 6.7 cm; p = 0.001). Total height gain over ProjAH was 4.3 ± 4.6 cm (GH start early) and 5.8 ± 4.7 cm (GH start late, p = 0.021), respectively. Conclusions: GH may improve AH in UTS patients even when started late. The individual growth response could be estimated by the descriptive Model PredAH independent of age at treatment start.

Puberty marks major changes in the hippocampal and cortical c-Fos activation pattern induced by NMDA receptor antagonists.

ABSTRACT Non‐selective and subunit (GluN2B)‐specific N‐methyl‐d‐aspartate receptor (NMDAR) antagonists represent promising alternative antidepressant drugs with fast onset of the therapeutic action. The neuronal activation pattern induced by NMDAR antagonists is well characterized by c‐Fos expression analysis only in the adult rodent brain. In contrast, there is little information available regarding their effects during postnatal development. Here we performed a systematic c‐Fos brain mapping of the non‐selective NMDAR antagonist MK‐801 and the GluN2B‐specific antagonist Ro 25–6981 from postnatal day 16 (P16) to P40. We found significant regional differences with gender‐specificity in the activation pattern compared to the adult. Surprisingly, in the hippocampus, MK‐801 triggered at pre‐pubertal stages (especially at P24) very strong c‐Fos expression, followed by low levels after P30, the approximate time point of puberty onset in mice. The cortical distribution of MK‐801‐triggered c‐Fos expression before puberty differed also substantially from the adult brain, showing high levels only in deep cortical layers at pre‐pubertal stages. In comparison, the cortical activation induced by Ro 25–6981 diminished from high pre‐pubertal levels and was in comparison with that triggered by MK‐801 low in the hippocampus. These results reveal highly dynamic changes in the c‐Fos activation pattern induced by NMDAR antagonists during puberty. This article is part of the Special Issue entitled ‘Ionotropic glutamate receptors’. HIGHLIGHTSThe brain activation pattern induced by NMDAR blockade during puberty is unknown.We found high hippocampal c‐Fos activation by MK‐801 at postnatal day 24.Cortical MK‐801‐induced activation changed from deep to all layers during puberty.GluN2B‐specific antagonists triggered activation patterns distinct from MK‐801.