Neural mechanism of acute stress regulation by trace aminergic signalling in the lateral habenula in male mice.

Stress management is necessary for vertebrate survival. Chronic stress drives depression by excitation of the lateral habenula (LHb), which silences dopaminergic neurons in the ventral tegmental area (VTA) via GABAergic neuronal projection from the rostromedial tegmental nucleus (RMTg). However, the effect of acute stress on this LHb-RMTg-VTA pathway is not clearly understood. Here, we used fluorescent in situ hybridisation and in vivo electrophysiology in mice to show that LHb aromatic L-amino acid decarboxylase-expressing neurons (D-neurons) are activated by acute stressors and suppress RMTg GABAergic neurons via trace aminergic signalling, thus activating VTA dopaminergic neurons. We show that the LHb regulates RMTg GABAergic neurons biphasically under acute stress. This study, carried out on male mice, has elucidated a molecular mechanism in the efferent LHb-RMTg-VTA pathway whereby trace aminergic signalling enables the brain to manage acute stress by preventing the hypoactivity of VTA dopaminergic neurons.

Phosphorylation of CLK2 at serine 34 and threonine 127 by AKT controls cell survival after ionizing radiation.

AKT phosphorylates components of the intrinsic cell survival machinery and promotes survival to various stimuli. In the present study, we identified CDC-like kinase 2 (CLK2) as a new substrate of AKT activation and elucidated its role in cell survival to ionizing radiation. AKT directly binds to and phosphorylates CLK2 on serine 34 and threonine 127, in vitro and in vivo. CLK2 phosphorylation was detected in HeLa cells overexpressing active AKT. In addition, we demonstrated that ionizing radiation induces CLK2 phosphorylation via AKT activation. In contrast, the suppression of endogenous AKT expression by siRNA inhibited CLK2 phosphorylation in response to 2 gray of γ-ray or insulin. Furthermore, we examined the effect of CLK2 on the survival of irradiated CCD-18Lu cells overexpressing Myc-CLK2. CLK2 overexpression significantly increased cell growth and inhibited cell death induced by 2 gray. The role of CLK2 in cell survival to ionizing radiation was dependent on the phosphorylation of serine 34 and threonine 127. Our results suggest that AKT activation controls cell survival to ionizing radiation by phosphorylating CLK2, revealing an important regulatory mechanism required for promoting cell survival.

A novel inhibitor of apoptosis protein (IAP)-interacting protein, Vestigial-like (Vgl)-4, counteracts apoptosis-inhibitory function of IAPs by nuclear sequestration.

The inhibitors of apoptosis proteins (IAP), which include cIAP1, cIAP2 and XIAP, suppress apoptosis through the inhibition of caspases, and the activity of IAPs is regulated by a variety of IAP-binding proteins. Herein, we report the identification of a Vestigial-like 4 (Vgl-4), which functions as a transcription cofactor in cardiac myocytes, as a new IAP binding protein. Vgl-4 is expressed predominantly in the nucleus and its overexpression triggers a relocalization of IAPs from the cytoplasm to the nucleus. cIAP1/2-interacting protein TRAF2 (TNF receptor-associated factor 2) prevented the Vgl-4-driven nuclear localization of cIAP2. Accordingly, the forced relocation of IAPs to the nucleus by Vgl-4 significantly reduced their ability to prevent Bax- and TNFα-induced apoptosis, which can be recovered by co-expression with TRAF2. Our results suggest that Vgl-4 may play a role in the apoptotic pathways by regulating translocation of IAPs between different cell compartments.

Down-regulation of habenular calcium-dependent secretion activator 2 induces despair-like behavior.

Calcium-dependent secretion activator 2 (CAPS2) regulates the trafficking and exocytosis of neuropeptide-containing dense-core vesicles (DCVs). CAPS2 is prominently expressed in the medial habenula (MHb), which is related to depressive behavior; however, how MHb neurons cause depressive symptoms and the role of CAPS2 remains unclear. We hypothesized that dysfunction of MHb CAPS neurons might cause defects in neuropeptide secretion and the activity of monoaminergic centers, resulting in depressive-like behaviors. In this study, we examined (1) CAPS2 expression in the habenula of depression animal models and major depressive disorder patients and (2) the effects of down-regulation of MHb CAPS2 on the animal behaviors, synaptic transmission in the interpeduncular nucleus (IPN), and neuronal activity of monoamine centers. Habenular CAPS2 expression was decreased in the rat chronic restraint stress model, mouse learned helplessness model, and showed tendency to decrease in depression patients who died by suicide. Knockdown of CAPS2 in the mouse habenula evoked despair-like behavior and a reduction of the release of DCVs in the IPN. Neuronal activity of IPN and monoaminergic centers was also reduced. These results implicate MHb CAPS2 as playing a pivotal role in depressive behavior through the regulation of neuropeptide secretion of the MHb-IPN pathway and the activity of monoaminergic centers.

Remote ischemic preconditioning ameliorates indirect acute lung injury by modulating phosphorylation of IκBα in mice.

OBJECTIVE: Acute lung injury is responsible for mortality in seriously ill patients. Previous studies have shown that systemic inflammation is attenuated by remote ischemic preconditioning (RIPC) via reducing nuclear factor-kappa B (NF-κB). Therefore, we investigated whether lipopolysaccharide (LPS)-induced indirect acute lung injury (ALI) can be protected by RIPC. METHODS: RIPC was accomplished by 10 minutes of occlusion using a tourniquet on the right hind limb of mice, followed by 10 minutes of reperfusion. This process was repeated three times. Intraperitoneal LPS (20 mg/kg) was administered to induce indirect ALI. Inflammatory cytokines in bronchoalveolar lavage fluid were analyzed using an enzyme-linked immunosorbent assay. Pulmonary tissue was excised for histological examination, and for examining NF-κB activity and phosphorylation of inhibitor of κBα (IκBα). RESULTS: NF-κB activation and LPS-induced histopathological changes in the lungs were significantly alleviated in the RIPC group. RIPC reduced phosphorylation of IκBα in lung tissue of ALI mice. CONCLUSIONS: RIPC attenuates endotoxin-induced indirect ALI. This attenuation might occur through modification of NF-κB mediation of cytokines by modulating phosphorylation of IκBα.

Early red blood cell abnormalities as a clinical variable in sepsis diagnosis.

BACKGROUND: Sepsis is a medical emergency during which early detection is closely associated with mortality. In sepsis, red blood cell (RBC) abnormalities have been reported. However, it is not known how early RBC abnormalities are expressed compared with various clinical manifestations used in sepsis-related organ failure assessment (SOFA). OBJECTIVE: Therefore, using a lipopolysaccharide (LPS)-induced sepsis model we investigated the clinical significance of RBC abnormalities as an early indicator in the detection of septic injury compared with clinical variables. METHODS: Sprague-Dawley rats received LPS (20 mg/kg) intraperitoneally. Aggregation indices (AIs) and aggregation half-time (T1/2), and elongation indices (EI max) were measured. Clinical data-related SOFA and lactate were measured at 2 h, 4 h, 8 h and 12 h after LPS injection. RESULTS: AIs increased at 4 h, and T1/2 decreased at 2 h after LPS injection. Platelet counts decreased at 4 h, and lactate increased at 2 h after LPS injection. AIs showed strong correlations with T1/2 and platelets, EI max increased at 2 h after LPS injection, while EI max had a positive correlation with lactate. CONCLUSIONS: RBC aggregation appears to be an early indicator of clinical deterioration in sepsis and may represent a diagnostic indicator in sepsis.

Identification of cellular responses to low-dose radiation by the profiling of phosphorylated proteins in human B-lymphoblast IM-9 cells.

PURPOSE: The aim of this study was to explore the potential for radiation-specific signaling of various LDIR-induced effects in human B-lymphoblast IM-9 cells. MATERIALS AND METHODS: Human lymphoblast IM-9 cells were exposed to ionizing radiation at 0.1 and 2 Gy using a 137Cs γ-irradiator at a dose rate of 0.8 Gy/min. Cell viability and DNA fragmentation were determined using MTT assay and TUNEL assay at 24 h after irradiation. Profiling of protein phosphorylation by radiation was identified using a phospho-antibody array at 4 h after irradiation and Dataset of the profiling was analyzed by IPA. RESULTS: Cell survival and apoptotic signaling were not affected by 0.1 Gy of radiation, whereas 2 Gy induced cellular damage. The analysis of low-dose ionizing radiation (LDIR) or high-dose ionizing radiation (HDIR)-specific responses by IPA generated different results. Various cell maintenance functions were only apparent following the analysis of increased protein phosphorylation by LDIR, whereas several cancer formation- and development-related functions were only detected following the analysis of increased protein phosphorylation by HDIR. CONCLUSIONS: The LDIR-induced protein phosphorylation patterns might be involved in various cell survival responses or cellular maintenance functions, which provide important insight into our understanding of the different effects of LDIR and HDIR.

Role of AKT and ERK pathways in controlling sensitivity to ionizing radiation and adaptive response induced by low-dose radiation in human immune cells.

Despite many studies of the effect of ionizing radiation, biological mechanisms of action might differ greatly depend on dose, dose rate, and cell type. This study was performed to explore the effects of low- and high-dose radiation in human immune cell lines. We examined cell sensitivity after irradiation with 0.05, 0.1, or 2Gy in two normal cell lines and three tumor cell lines. Low-dose radiation of 0.05 and 0.1Gy had no effect on cell survival in any tested cell line, with the exception of IM-9 cells, whose viability was transiently increased. However, IM-9 and C1R-sB7 cells were very sensitive to high-dose radiation-induced cell death, whereas Jurkat and JM1 cells showed moderate sensitivity, and THP-1 cells were completely resistant. This radiosensitivity was correlated with basal AKT activation, which is induced by phosphorylation. In radiosensitive IM-9 cells, priming with chronic low-dose irradiation blocked cell death induced by high-dose radiation challenge via inhibition of caspase activation and PARP cleavage. AKT phosphorylation was not altered in IM-9 cells, but ERK phosphorylation was greatly elevated immediately after chronic low-dose irradiation. Taken together, our results suggest that the different responses of normal and tumor cells to low-dose and high-dose radiation depend on AKT activation, which is regulated by protein phosphatase 2 (PP2A). In radiosensitive normal cells lacking basal AKT activity, chronic low-dose radiation increases activation of the ERK pathway, which plays an important role in the adaptive response to radiation, providing a very important insight into understanding the effects of ionizing radiation on health.

Chronic low-dose radiation inhibits the cells death by cytotoxic high-dose radiation increasing the level of AKT and acinus proteins via NF-κB activation.

PURPOSE: This study explored the effects of low-dose and low-dose-rate irradiation in human lung fibroblast CCD-18Lu cells and examined the role of AKT (protein kinase B, PKB) in cellular responses. MATERIALS AND METHODS: We examined cell survival after chronic low-dose irradiation (0.01 Gy or 0.05 Gy) with challenging high-dose (2 or 10 Gy) irradiation. We examined the effect of AKT activation on cell survival after chronic low-dose radiation using transduced cells with retroviral vector expressing constitutively active AKT (CA-AKT). RESULTS: Chronic low-dose priming irradiation increased cells viability against the challenging high-dose irradiation. Irradiation at 0.05 Gy increased cellular levels of AKT and acinus long form (L) and short form (S). The chronic low-dose radiation promoted cells proliferation in the exogenously expressed CA-AKT cells. It also increased nuclear factor-kappa B (NF-κB) activity in a biphasic induction pattern. Suppression of NF-κB activation by mutant form of inhibitor of kappa B alpha (IκBαM) antagonized the radiation-induced expression of AKT and acinus L and S. CONCLUSIONS: Chronic low-dose radiation increases the levels of AKT and acinus proteins via NF-κB activation, and the NF-κB/AKT pathway responding to chronic low-dose irradiation plays an important role in the radiation adaptive response.

A critical role for AKT activation in protecting cells from ionizing radiation-induced apoptosis and the regulation of acinus gene expression.

Although AKT activation leads to the activation of various pathways related to cell survival, the roles of AKT in modulating cellular responses induced by ionizing radiation in normal human cells remain unclear. Here we show that low-dose radiation of 0.05Gy did not affect cell death, but high-dose radiation (> 0.2Gy) induced apoptosis through the activation of caspases and acinus cleavage. Ionizing radiation induced acinus phosphorylation via AKT activation. Thus, we examined the effect of AKT activation on radiation-induced cell death using CCD-18Lu cells transduced with a retroviral vector expressing constitutively active AKT (CA-AKT). The overexpression of CA-AKT rendered the cells resistant to ionizing radiation and prevented the proteolytic cleavage of acinus via phosphorylation. In addition, overexpression of CA-AKT resulted in the upregulation of acinus expression by activation of the NF-kappaB pathway. On the other hand, suppression of endogenous AKT expression by siRNA resulted in the reduction of acinus expression and enhanced the radiation-induced apoptosis in both CCD-18Lu and IM-9 cells. Our results suggest that AKT activation inhibits cell death during radiation-induced apoptosis through the regulation of phosphorylation and expression of acinus. The AKT/NF-kappaB/acinus pathway functions as one of the important regulatory mechanisms required for modulating ionizing radiation sensitivity.