Plasmodium falciparum Merozoite Surface Protein 3: OLIGOMERIZATION,SELF-ASSEMBLY,AND HEME COMPLEX FORMATION*

Merozoite surface protein 3 of Plasmodium falciparum, a 40-kDa protein that also binds heme, has been biophysically characterized for its tendency to form highly elongated oligomers. This study aims to systematically analyze the regions in MSP3 sequence involved in oligomerization and correlate its aggregation tendency with its high affinity for binding with heme. Through size exclusion chromatography, dynamic light scattering, and transmission electron microscopy, we have found that MSP3, previously known to form elongated oligomers, actually forms self-assembled filamentous structures that possess amyloid-like characteristics. By expressing different regions of MSP3, we observed that the previously described leucine zipper region at the C terminus of MSP3 may not be the only structural element responsible for oligomerization and that other peptide segments like MSP3(192–196) (YILGW) may also be required. MSP3 aggregates on incubation were transformed to long unbranched amyloid fibrils. Using immunostaining methods, we found that 5–15-μm-long fibrillar structures stained by anti-MSP3 antibodies were attached to the merozoite surface and also associated with erythrocyte membrane. We also found MSP3 to bind several molecules of heme by UV spectrophotometry, HPLC, and electrophoresis. This study suggested that its ability to bind heme is somehow related to its inherent characteristics to form oligomers. Moreover, heme interaction with a surface protein like MSP3, which does not participate in hemozoin formation, may suggest a protective role against the heme released from unprocessed hemoglobin released after schizont egress. These studies point to the other roles that MSP3 may play during the blood stages of the parasite, in addition to be an important vaccine candidate.     

Attenuation of Reactive Gliosis Does Not Affect Infarct Volume in Neonatal Hypoxic-Ischemic Brain Injury in Mice

Background

Astroglial cells are activated following injury and up-regulate the expression of the intermediate filament proteins glial fibrillary acidic protein (GFAP) and vimentin. Adult mice lacking the intermediate filament proteins GFAP and vimentin (GFAP^−/−Vim^−/−) show attenuated reactive gliosis, reduced glial scar formation and improved regeneration of neuronal synapses after neurotrauma. GFAP^−/−Vim^−/− mice exhibit larger brain infarcts after middle cerebral artery occlusion suggesting protective role of reactive gliosis after adult focal brain ischemia. However, the role of astrocyte activation and reactive gliosis in the injured developing brain is unknown.

Methodology/Principal Findings

We subjected GFAP^−/−Vim^−/− and wild-type mice to unilateral hypoxia-ischemia (HI) at postnatal day 9 (P9). Bromodeoxyuridine (BrdU; 25 mg/kg) was injected intraperitoneally twice daily from P9 to P12. On P12 and P31, the animals were perfused intracardially. Immunohistochemistry with MAP-2, BrdU, NeuN, and S100 antibodies was performed on coronal sections. We found no difference in the hemisphere or infarct volume between GFAP^−/−Vim^−/− and wild-type mice at P12 and P31, i.e. 3 and 22 days after HI. At P31, the number of NeuN⁺ neurons in the ischemic and contralateral hemisphere was comparable between GFAP^−/−Vim^−/− and wild-type mice. In wild-type mice, the number of S100⁺ astrocytes was lower in the ipsilateral compared to contralateral hemisphere (65.0±50.1 vs. 85.6±34.0, p<0.05). In the GFAP^−/−Vim^−/− mice, the number of S100⁺ astrocytes did not differ between the ischemic and contralateral hemisphere at P31. At P31, GFAP^−/−Vim^−/− mice showed an increase in NeuN⁺BrdU⁺ (surviving newly born) neurons in the ischemic cortex compared to wild-type mice (6.7±7.7; n = 29 versus 2.9±3.6; n = 28, respectively, p<0.05), but a comparable number of S100⁺BrdU⁺ (surviving newly born) astrocytes.

Conclusions/Significance

Our results suggest that attenuation of reactive gliosis in the developing brain does not affect the hemisphere or infarct volume after HI, but increases the number of surviving newborn neurons.     

Major depressive disorder diagnosis based on effective connectivity in EEG signals: a convolutional neural network and long short-term memory approach

Deep learning techniques have recently made considerable advances in the field of artificial intelligence. These methodologies can assist psychologists in early diagnosis of mental disorders and preventing severe trauma. Major Depression Disorder (MDD) is a common and serious medical condition whose exact manifestations are not fully understood. So, early discovery of MDD patients helps to cure or limit the adverse effects. Electroencephalogram (EEG) is prominently used to study brain diseases such as MDD due to having high temporal resolution information, and being a noninvasive, inexpensive and portable method. This paper has proposed an EEG-based deep learning framework that automatically discriminates MDD patients from healthy controls. First, the relationships among EEG channels in the form of effective brain connectivity analysis are extracted by Generalized Partial Directed Coherence (GPDC) and Direct directed transfer function (dDTF) methods. A novel combination of sixteen connectivity methods (GPDC and dDTF in eight frequency bands) was used to construct an image for each individual. Finally, the constructed images of EEG signals are applied to the five different deep learning architectures. The first and second algorithms were based on one and two-dimensional convolutional neural network (1DCNN–2DCNN). The third method is based on long short-term memory (LSTM) model, while the fourth and fifth algorithms utilized a combination of CNN with LSTM model namely, 1DCNN-LSTM and 2DCNN-LSTM. The proposed deep learning architectures automatically learn patterns in the constructed image of the EEG signals. The efficiency of the proposed algorithms is evaluated on resting state EEG data obtained from 30 healthy subjects and 34 MDD patients. The experiments show that the 1DCNN-LSTM applied on constructed image of effective connectivity achieves best results with accuracy of 99.24% due to specific architecture which captures the presence of spatial and temporal relations in the brain connectivity. The proposed method as a diagnostic tool is able to help clinicians for diagnosing the MDD patients for early diagnosis and treatment.     

Flavonoid Baicalein Modulates H<Subscript>2</Subscript>O<Subscript>2</Subscript>-Induced Mitogen-Activated Protein Kinases Activation and Cell Death in SK-N-MC Cells

It is believed that ROS-induced oxidative stress triggers numerous signaling pathways which are involved in neurodegenerative diseases, including Alzheimer’s disease. To find the effective drugs for neurodegenerative diseases, the deep delve into molecular mechanisms underlie these diseases is necessary. In the current study, we investigated the effects of flavonoid baicalein on H₂O₂-induced oxidative stress and cell death in SK-N-MC cells. Our results revealed that the treatment of SK-N-MC cells with H₂O₂ led to a decrease in cell viability through phosphorylation and activation of extracellular signal-regulated kinases (ERKs) and c-Jun N-terminal kinases (JNKs) pathways followed by increase in Bax/Bcl2 ratio and initiation of caspase-dependent apoptotic pathways. In addition, our results showed that the exposure of SK-N-MC cells to H₂O₂ ended up in reduction of glutathione (GSH) levels of SK-N-MC cells via JNK/ERK-mediated down-regulation of γ-glutamyl-cysteine synthetase (γ-GCS) expression. Our results demonstrated that flavonoid baicalein protected against H₂O₂-induced cell death by inhibition of JNK/ERK pathways activation and other key molecules in apoptotic pathways, including blockage of Bax and caspase-9 activation, induction of Bcl-2 expression and prevention of cell death. Baicalein supported intracellular defense mechanisms through maintaining GSH levels in SK-N-MC cells by the removal of inhibition effects of JNK/ERK pathways from γ-GCS expression. In addition, baicalein attenuated lipid and protein peroxidation and intracellular reactive oxygen species in SK-N-MC cells. In accordance with these observations, baicalein can be a promising candidate in antioxidant therapy and designing of natural-based drug for ROS-induced neurodegenerative disorders.     

Effect of ovarian tissue vitrification method on mice preantral follicular development and gene expression

Vitrification is considered a viable method for cryopreservation of ovarian tissue and selection of methods that minimize follicular damage is important. The objective of the present study was to evaluate the effects of two vitrification methods on ovarian tissue morphology, preantral follicles survival rate during in vitro culture, and relative expression of genes associated with oocyte maturation and cumulus expansion. Ovaries from 12-day-old mice were vitrified in media containing ethylene glycol, dimethyl sulphoxide, and sucrose. Before plunging in liquid nitrogen, ovaries were first loaded into an acupuncture needle (needle immersion vitrification [NIV]) or placed on a cold steel surface for 10 to 20 seconds (solid surface vitrification [SSV]). The integrity of the ovarian tissue was well-preserved after vitrification and was similar controls. Follicle viability in the SSV group was lower (P < 0.05) than in the control group after 6 days of culture and the NIV group after 10 day of culture. Follicle viability after 12 day of culture was 92.8%, 82.1%, and 58.4% in control, NIV, and SSV groups, respectively. Bmp15, Gdf9, BmprII, Alk6, Alk5, Has2, and Ptgs2 gene expression patterns were similar among groups. However, the level of gene expression in the vitrification groups during Days 6 to 10 were higher compared with the control group. In conclusion, ovarian tissue morphologic integrity was well-preserved, regardless of the vitrification method. Vitrification using the needle immersion method resulted in greater follicular survival after 12 day of culture than the SSV method. Gene expression patterns during culture did not seem to explain the reduced survival rate observed in the solid surface group.     

Thioredoxin 1 overexpression attenuated diabetes-induced endoplasmic reticulum stress in Müller cells via apoptosis signal-regulating kinase 1

As one of the common and serious chronic complications of diabetes mellitus (DM), the related mechanism of diabetic retinopathy (DR) has not been fully understood. Müller cell reactive gliosis is one of the early pathophysiological features of DR. Therefore, exploring the manner to reduce diabetes-induced Müller cell damage is essential to delay DR. Thioredoxin 1 (Trx1), one of the ubiquitous redox enzymes, plays a vital role in redox homeostasis via protein–protein interactions, including apoptosis signal-regulating kinase 1 (ASK1). Previous studies have shown that upregulation of Trx by some drugs can attenuate endoplasmic reticulum stress (ERS) in DR, but the related mechanism was unclear. In this study, we used DM mouse and high glucose (HG)-cultured human Müller cells as models to clarify the effect of Trx1 on ERS and the underlying mechanism. The data showed that the diabetes-induced Müller cell damage was increased significantly. Moreover, the expression of ERS and reactive gliosis was also upregulated in diabetes in vivo and in vitro. However, it was reversed after Trx1 overexpression. Besides, ERS-related protein expression, reactive gliosis, and apoptosis were decreased after transfection with ASK1 small-interfering RNA in stable Trx1 overexpression Müller cells after HG treatment. Taken together, Trx1 could protect Müller cells from diabetes-induced damage, and the underlying mechanism was related to inhibited ERS via ASK1.     

A Meta-Analysis of Site-Specific Effects of Cathodal Transcranial Direct Current Stimulation on Sensory Perception and Pain

The primary aim of our meta-analysis was to evaluate the effects of cathodal transcranial direct current stimulation (c-tDCS) on sensory and pain thresholds (STh and PTh) in healthy individuals and pain level (PL) in patients with chronic pain. Electronic databases were searched for c-tDCS studies. Methodological quality was evaluated using the PEDro and Downs and Black (D&B) assessment tools. C-tDCS of the primary motor cortex (S1) increases both STh (P<0.001, effect size of 26.84%) and PTh (P<0.001, effect size of 11.62%). In addition, c-tDCS over M1 led to STh increase (P<0.005, effect size of 30.44%). Likewise, PL decreased significantly in the patient group following application of c-tDCS. The small number of studies precluded subgroup analysis. Nevertheless, meta-analysis showed that in all groups (except c-tDCS of S1) active c-tDCS and sham stimulation produced significant differences in STh/PTh in healthy and PL in patient group. This review provides evidence for the site-specific effectiveness of c-tDCS in increasing STh/PTh in healthy individuals and decreasing PL in patients with chronic pain. However, due to small sample sizes in the included studies, our results should be interpreted with caution. Given that the level of blinding was not considered in the inclusion criteria, the results of the current study should be interpreted with caution.