Non-cell autonomous influence of the astrocyte system xc? on hypoglycaemic neuronal cell death

Despite longstanding evidence that hypoglycaemic neuronal injury is mediated by glutamate excitotoxicity, the cellular and molecular mechanisms involved remain incompletely defined. Here, we demonstrate that the excitotoxic neuronal death that follows GD (glucose deprivation) is initiated by glutamate extruded from astrocytes via system x_c⁻ – an amino acid transporter that imports l-cystine and exports l-glutamate. Specifically, we find that depriving mixed cortical cell cultures of glucose for up to 8 h injures neurons, but not astrocytes. Neuronal death is prevented by ionotropic glutamate receptor antagonism and is partially sensitive to tetanus toxin. Removal of amino acids during the deprivation period prevents – whereas addition of l-cystine restores – GD-induced neuronal death, implicating the cystine/glutamate antiporter, system x_c⁻. Indeed, drugs known to inhibit system x_c⁻ ameliorate GD-induced neuronal death. Further, a dramatic reduction in neuronal death is observed in chimaeric cultures consisting of neurons derived from WT (wild-type) mice plated on top of astrocytes derived from sut mice, which harbour a naturally occurring null mutation in the gene (Slc7a11) that encodes the substrate-specific light chain of system x_c⁻ (xCT). Finally, enhancement of astrocytic system x_c⁻ expression and function via IL-1β (interleukin-1β) exposure potentiates hypoglycaemic neuronal death, the process of which is prevented by removal of l-cystine and/or addition of system x_c⁻ inhibitors. Thus, under the conditions of GD, our studies demonstrate that astrocytes, via system x_c⁻, have a direct, non-cell autonomous effect on cortical neuron survival.     

Selective and specific inhibition of the plasmodium falciparum lysyl-tRNA synthetase by the fungal secondary metabolite cladosporin

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Highlights? The fungal secondary metabolite Cladosporin inhibits liver- and blood-stage malaria parasites ? Cladosporin specifically targets lysyl-tRNA synthetase (Krs1) ? Cladosporin is >100-fold more potent against parasite Krs1 relative to the human enzyme ? Two amino acids in the Krs1 ATP-binding pocket confer species-selective inhibition     

Evaluation of Oxidative Stress in Overweight Subjects With or Without Metabolic Syndrome

Although oxidative stress is considered the underlying mechanism by which dysfunctional metabolism occurs in obese subjects, there are few studies on oxidative stress in overweight subjects. The objective of this study was to verify the influence of metabolic syndrome (MetS) on oxidative stress and antioxidant defense in overweight subjects. There were 123 subjects (50 in the control group and 73 in the overweight group) chosen to participate in this cross‐sectional study. The control group included 50 healthy individuals with a BMI between 20 and 24.9 kg/m² and without MetS. The overweight group included 73 subjects with a BMI between 25 and 29.9 kg/m². Overweight subjects were divided into two groups: with MetS (29 subjects) and without MetS (44 subjects). Control group and overweight group subjects without MetS showed no differences in oxidative stress parameters and total antioxidant capacity (TRAP). Overweight subjects with MetS had higher hydroperoxide concentrations measured by chemiluminescence compared to the control group (P < 0.05), higher hydroperoxide and hydrogen peroxide concentrations determined by ferrous oxidation‐xylenol orange assay compared to overweight subjects without MetS (P < 0.001), and higher advanced oxidation protein product (AOPP) concentrations (P < 0.001) compared to the other groups. AOPP was directly correlated with uric acid concentrations. Overweight subjects with MetS had lower TRAP concentrations compared to the control group (P < 0.001). In conclusion, this study showed that overweight subjects with MetS, in contrast to overweight subjects without MetS, have a redox imbalance characterized by increased plasma oxidation and reduced antioxidant capacity.     

Gender differences in UV-induced inflammation and immunosuppression in mice reveal male unresponsiveness to UVA radiation

Immunosuppression attributed mainly to the UVB (290-320 nm) waveband is a prerequisite for skin cancer development in mice and humans. The contribution of UVA (320-400 nm) is controversial, but in mice UVA irradiation has been found to antagonise immunosuppression by UVB. In other studies of photoimmune regulation, protection mediated via oestrogen receptor-β signalling was identified as a normal endogenous defence in mice, and was shown to depend on UVA irradiation. A gender bias in photoimmune responsiveness was thus suggested, and is tested in this study by comparing the UV-induced inflammatory and immune responses in male and female hairless mice. We report that male mice, which show greater skin thickness than females, developed a less intense but slower resolving sunburn inflammatory oedema, correlated with reduced epidermal expression of pro-inflammatory IL-6 than females following solar simulated UV (SSUV, 290-400 nm) exposure. On the other hand, the contact hypersensitivity reaction (CHS) was more severely suppressed by SSUV in males, correlated with increased epidermal expression of immunosuppressive IL-10. Exposure to the UVB waveband alone, or to cis-urocanic acid, suppressed CHS equally in males and females. However, whereas UVA irradiation induced immunoprotection against either UVB or cis-urocanic acid in females, this protection was significantly reduced or abrogated in males. The results indicate that males are compromised by a relative unresponsiveness to the photoimmune protective effects of UVA, alone or as a component of SSUV. This could explain the known gender bias in skin cancer development in both mice and humans.     

Mitochondrial proteomic analysis of Cisplatin resistance in ovarian cancer

Epithelial ovarian cancer (EOC) is the leading cause of death among women with gynecologic malignancies and accounts for approximately 6% of cancer deaths among women. Cisplatin and its analogues form the backbone of the most active chemotherapy regimens in advanced EOC; however, development of platinum resistance is common and typically marks a transition in which curing the patient is no longer possible. An emerging theme in many cancers is that mitochondrial dysfunction contributes to an aggressive carcinogenic phenotype. We hypothesized that changes in the mitochondrial proteome are required to support development of cisplatin resistance in human EOC. To investigate this hypothesis, an organellar proteomics approach was utilized to quantify alterations in protein abundance in mitochondria enriched from isogenic cisplatin-sensitive (A2780) and -resistant (A2780-CP20) human EOC cells. Protein isolates from mitochondria-enriched fractions were analyzed by high resolution liquid chromatography-tandem mass spectrometry (LC-MS/MS), and relative abundance of identified proteins was quantified by spectral counting. Pathway analyses revealed significant increases in notch signaling pathways, cell survival, and alternate apoptotic pathways in the A2780-CP20 subtype. Among the alterations identified in the mitochondrial proteomic composition in cisplatin-resistant EOC cells, activated leukocyte cell adhesion molecule (AKAP12) and A kinase anchoring protein 12 (AKAP12) were elevated, while nestin was diminished in the mitochondrial fraction of A2780-CP20 relative to A2780. This was verified by immunoblot analysis. These results confirm that important changes in the mitochondrial proteome, many of which promote evasion of apoptosis and tumor invasiveness and metastasis, are present in cisplatin-resistant EOC.     

The origin and evolutionary history of HIV-1 subtype C in Senegal

Background

The classification of HIV-1 strains in subtypes and Circulating Recombinant Forms (CRFs) has helped in tracking the course of the HIV pandemic. In Senegal, which is located at the tip of West Africa, CRF02_AG predominates in the general population and Female Sex Workers (FSWs). In contrast, 40% of Men having Sex with Men (MSM) in Senegal are infected with subtype C. In this study we analyzed the geographical origins and introduction dates of HIV-1 C in Senegal in order to better understand the evolutionary history of this subtype, which predominates today in the MSM population

Methodology/Principal Findings

We used a combination of phylogenetic analyses and a Bayesian coalescent-based approach, to study the phylogenetic relationships in pol of 56 subtype C isolates from Senegal with 3,025 subtype C strains that were sampled worldwide. Our analysis shows a significantly well supported cluster which contains all subtype C strains that circulate among MSM in Senegal. The MSM cluster and other strains from Senegal are widely dispersed among the different subclusters of African HIV-1 C strains, suggesting multiple introductions of subtype C in Senegal from many different southern and east African countries. More detailed analyses show that HIV-1 C strains from MSM are more closely related to those from southern Africa. The estimated date of the MRCA of subtype C in the MSM population in Senegal is estimated to be in the early 80''s.

Conclusions/Significance

Our evolutionary reconstructions suggest that multiple subtype C viruses with a common ancestor originating in the early 1970s entered Senegal. There was only one efficient spread in the MSM population, which most likely resulted from a single introduction, underlining the importance of high-risk behavior in spread of viruses.     

Familial longevity is marked by lower diurnal salivary cortisol levels: the Leiden Longevity Study

Background

Reported findings are inconsistent whether hypothalamic-pituitary-adrenal (HPA) signaling becomes hyperactive with increasing age, resulting in increasing levels of cortisol. Our previous research strongly suggests that offspring from long-lived families are biologically younger. In this study we assessed whether these offspring have a lower HPA axis activity, as measured by lower levels of cortisol and higher cortisol feedback sensitivity.

Methods

Salivary cortisol levels were measured at four time points within the first hour upon awakening and at two time points in the evening in a cohort comprising 149 offspring and 154 partners from the Leiden Longevity Study. A dexamethasone suppression test was performed as a measure of cortisol feedback sensitivity. Age, gender and body mass index, smoking and disease history (type 2 diabetes and hypertension) were considered as possible confounding factors.

Results

Salivary cortisol secretion was lower in offspring compared to partners in the morning (Area Under the Curve = 15.6 versus 17.1 nmol/L, respectively; p = 0.048) and in the evening (Area Under the Curve = 3.32 versus 3.82 nmol/L, respectively; p = 0.024). Salivary cortisol levels were not different after dexamethasone (0.5 mg) suppression between offspring and partners (4.82 versus 5.26 nmol/L, respectively; p = 0.28).

Conclusion

Offspring of nonagenarian siblings are marked by a lower HPA axis activity (reflected by lower diurnal salivary cortisol levels), but not by a difference in cortisol feedback sensitivity. Further in-depth studies aimed at characterizing the HPA axis in offspring and partners are needed.