Quantitative susceptibility mapping in rats with minimal hepatic encephalopathy: Does iron overload aggravate cognitive impairment by promoting neuroinflammation?

BACKGROUND AND AIMS: Minimal hepatic encephalopathy (MHE) is a mild form of hepatic encephalopathy that lacks observable signs and symptoms. Nevertheless, MHE can cause neurocognitive dysfunction, although the neurobiological mechanisms are not fully understood. Here, the effects of hippocampal iron deposition on cognitive function and its role in MHE were investigated. MATERIALS AND METHODS: Eighteen rats were assigned to experimental and control groups. MHE was induced by thioacetamide. Spatial memory and exploratory behavior were assessed by the Morris water and elevated plus mazes. Hippocampal susceptibility was measured by quantitative susceptibility mapping, iron deposition in the hippocampus and liver by Prussian blue staining, and inflammatory cytokine and ferritin levels in the hippocampus were measured by ELISA. RESULTS: MHE rats showed impaired spatial memory and exploratory behavior (P < 0.05 for all parameters). The bilateral hippocampal susceptibility values were significantly raised in MHE rats, together with evidence of neuroinflammation (increased pro-inflammatory and reduced anti-inflammatory cytokine levels (all P < 0.05). Further analysis indicated good correlations between hippocampal susceptibility values with latency time and inflammatory cytokine levels in MHE but not in control rats. CONCLUSION: MHE induced by thioacetamide was associated with hippocampal iron deposition and inflammation, suggesting that iron overload may be an important driver of neuroinflammatory responses.

Research Progress in Polypeptoids Prepared by Controlled Ring-Opening Polymerizations.

Polypeptoids, structural mimics of polypeptides, have attracted considerable attention due to their biocompatibility, proteolytic stability, thermal processability, good solubility, synthetic accessibility, and structural diversity. Polypeptoids have emerged as an interesting material in both polymer science and biological field. This review primarily discusses the research progress of polypeptoids prepared by controlled ring-opening polymerizations in the past decade, including synthetic strategies of monomers, polymerizations by different initiators, postfunctionalization, fundamental properties, crystallization-driven self-assembly, and potential biological applications.

Investigated diagnostic value of synthetic relaxometry, three-dimensional pseudo-continuous arterial spin labelling and diffusion-weighted imaging in the grading of glioma.

BACKGROUND: To investigate the performance of synthetic relaxometry, three-dimensional pseudo-continuous arterial spin labelling (pCASL) and diffusion-weighted imaging (DWI) in differentiating high-grade gliomas (HGGs) from low-grade gliomas (LGGs) and to compare with the conventional MRI. METHODS: Seventy-two patients with gliomas (including 27 LGGs and 45 HGGs) were studied using synthetic magnetic resonance imaging (sy-MRI), pCASL, and DWI with a 3.0 T MR scanner. T1 relaxometry (T1), T2 relaxometry (T2), as well as proton density (PD) from sy-MRI, cerebral blood flow (CBF) from pCASL, apparent diffusion coefficient (ADC) from DWI and enhancement quality (EQ), proportion enhancing (PE) from conventional contrast enhanced image based Visually-Accessible-Rembrandt-Images (VASARI) scoring system, were all analyzed by two radiologists. The Student's t-test, Mann-Whitney U test or Fisher's exact test was used to compare the parameters between LGGs and HGGs. The diagnostic performance of each parameter and their combination for glioma grading were analyzed. RESULTS: Significant statistical differences in T1, PD, CBF, ADC, EQ and PE are observed between LGGs and HGGs (all P < 0.001). The ADC values have higher discrimination abilities compared with other univariable parameters, with the AUC of 0.905. AUC values for conventional contrast-enhanced method, EQ and PE from VASARI, and conventional contrast-free method, CBF + ADC, are 0.873 and 0.912 respectively. The combined T1, PD, CBF and ADC model had the best performance for differentiating LGGs and HGGs with AUC, sensitivity and specificity of 0.993, 95.5%, 100%, respectively. CONCLUSIONS: Relaxometry parameters derived from synthetic MRI contributed to the discrimination of low-grade gliomas from high-grade gliomas. Proposed contrast-free approach combining T1, PD, CBF and ADC showed a strong discriminative power, and outperformed conventional approaches.

Differential Replication and Cytokine Response between Vaccine and Very Virulent Marek's Disease Viruses in Spleens and Bursas during Latency and Reactivation.

Marek's disease virus (MDV) infection results in Marek's disease (MD) in chickens, a lymphoproliferative and oncogenic deadly disease, leading to severe economic losses. The spleen and bursa are the most important lymphoid and major target organs for MDV replication. The immune response elicited by MDV replication in the spleen and bursa is critical for the formation of latent MDV infection and reactivation. However, the mechanism of the host immune response induced by MDV in these key lymphoid organs during the latent and reactivation infection phases is not well understood. In the study, we focused on the replication dynamics of a vaccine MDV strain MDV/CVI988 and a very virulent MDV strain MDV/RB1B in the spleen and bursa in the latent and reactivation infection phases (7-28 days post-inoculation [dpi]), as well as the expression of some previously characterized immune-related molecules. The results showed that the replication ability of MDV/RB1B was significantly stronger than that of MDV/CVI988 within 28 days post-infection, and the replication levels of both MDV strains in the spleen were significantly higher than those in the bursa. During the latent and reactivation phase of MDV infection (7-28 dpi), the transcriptional upregulation of chicken IL-1ß, IL6, IL-8L1 IFN-γ and PML in the spleen and bursa induced by MDV/RB1B infection was overall stronger than that of MDV/CVI988. However, compared to MDV/RB1Binfection, MDV/CVI988 infection resulted in a more effective transcriptional activation of CCL4 in the latent infection phase (7-14 dpi), which may be a characteristic distinguishing MDV vaccine strain from the very virulent strain.

The RNA helicase DDX5 promotes viral infection via regulating N6-methyladenosine levels on the DHX58 and NFκB transcripts to dampen antiviral innate immunity.

Multi-functional DEAD-box helicase 5 (DDX5), which is important in transcriptional regulation, is hijacked by diverse viruses to facilitate viral replication. However, its regulatory effect in antiviral innate immunity remains unclear. We found that DDX5 interacts with the N6-methyladenosine (m6A) writer METTL3 to regulate methylation of mRNA through affecting the m6A writer METTL3-METTL14 heterodimer complex. Meanwhile, DDX5 promoted the m6A modification and nuclear export of transcripts DHX58, p65, and IKKγ by binding conserved UGCUGCAG element in innate response after viral infection. Stable IKKγ and p65 transcripts underwent YTHDF2-dependent mRNA decay, whereas DHX58 translation was promoted, resulting in inhibited antiviral innate response by DDX5 via blocking the p65 pathway and activating the DHX58-TBK1 pathway after infection with RNA virus. Furthermore, we found that DDX5 suppresses antiviral innate immunity in vivo. Our findings reveal that DDX5 serves as a negative regulator of innate immunity by promoting RNA methylation of antiviral transcripts and consequently facilitating viral propagation.

DEAD/DEAH-box helicase 5 is hijacked by an avian oncogenic herpesvirus to inhibit interferon beta production and promote viral replication.

DEAD-box helicase 5 (DDX5) plays a significant role in tumorigenesis and regulates viral replication of several viruses. An avian oncogenic herpesvirus, Marek's disease virus (MDV), is widely known to cause immunosuppression and lymphoma in chickens. However, the underlying mechanisms of how DDX5 plays a role in viral replication remain unclear. In this study, we show that MDV inhibits the production of interferon beta (IFN-ß) in chicken embryo fibroblasts (CEFs) by increasing the expression level and promoting the nuclear aggregation of DDX5. We further reveal how DDX5 down-regulates melanoma differentiation-associated gene 5/toll-like receptor 3 signaling through the fundamental transcription factor, interferon regulatory factor 1. MDV replication is suppressed, and the production of IFN-ß is promoted in the DDX5 absented CEFs. Taken together, our investigations demonstrate that MDV inhibits IFN-ß production by targeting DDX5-mediated signaling to facilitate viral replication, which offers a novel insight into the mechanism by which an avian oncogenic herpesvirus replicates in chicken cells.

Transcriptional Profiles Associated with Marek's Disease Virus in Bursa and Spleen Lymphocytes Reveal Contrasting Immune Responses during Early Cytolytic Infection.

Marek's disease virus (MDV), an alpha herpes virus, causes a lymphoproliferative state in chickens known as Marek's disease (MD), resulting in severe monetary losses to the poultry industry. Because lymphocytes of bursa of Fabricius and spleen are prime targets of MDV replication during the early cytolytic phase of infection, the immune response in bursa and spleen should be the foundation of late immunity induced by MDV. However, the mechanism of the MDV-mediated host immune response in lymphocytes in the early stage is poorly understood. The present study is primarily aimed at identifying the crucial genes and significant pathways involved in the immune response of chickens infected with MDV CVI988 and the very virulent RB1B (vvRB1B) strains. Using the RNA sequencing approach, we analyzed the generated transcriptomes from lymphocytes isolated from chicken bursa and spleen. Our findings validated the expression of previously characterized genes; however, they also revealed the expression of novel genes during the MDV-mediated immune response. The results showed that after challenge with CVI988 or vvRB1B strains, 634 and 313 differentially expressed genes (DEGs) were identified in splenic lymphocytes, respectively. However, 58 and 47 DEGs were observed in bursal lymphocytes infected with CVI988 and vvRB1B strains, respectively. Following MDV CVI988 or vvRB1B challenge, the bursal lymphocytes displayed changes in IL-6 and IL-4 gene expression. Surprisingly, splenic lymphocytes exhibited an overwhelming alteration in the expression of cytokines and cytokine receptors involved in immune response signaling. On the other hand, there was no distinct trend between infection with CVI988 and vvRB1B and the expression of cytokines and chemokines, such as IL-10, IFN-γ, STAT1, IRF1, CCL19, and CCL26. However, the expression profiles of IL-1ß, IL-6, IL8L1, CCL4 (GGCL1), and CCL5 were significantly upregulated in splenic lymphocytes from chickens infected with CVI988 compared with those of chickens infected with vvRB1B. Because these cytokines and chemokines are considered to be associated with B cell activation and antigenic signal transduction to T cells, they may indicate differences of immune responses initiated by vaccinal and virulent strains during the early phase of infection. Collectively, our study provides valuable data on the transcriptional landscape using high-throughput sequencing to understand the different mechanism between vaccine-mediated protection and pathogenesis of virulent MDV in vivo.

Neuroprotection of cordycepin in NMDA-induced excitotoxicity by modulating adenosine A1 receptors.

Cerebral ischemia impairs physiological form of synaptic plasticity such as long-term potentiation (LTP). Clinical symptoms of cognitive dysfunction resulting from cerebral ischemia are associated with neuron loss and synaptic function impairment in hippocampus. It has been widely reported that cordycepin displays neuroprotective effect on ameliorating cognitive dysfunction induced by cerebral ischemia. Therefore, it is necessary to study whether cordycepin recovers cognitive function after brain ischemia through improving LTP induction. However, there has been very little discussion about the effects of cordycepin on LTP of cerebral ischemia so far. In the present study, we investigated the effects of cordycepin on LTP impairment and neuron loss induced by cerebral ischemia and excitotoxicity, using electrophysiological recording and Nissl staining techniques. The models were obtained by bilateral common carotid artery occlusion (BCCAO) and intrahippocampal NMDA microinjection. We also explored whether adenosine A1 receptors involve in the neuroprotection of cordycepin by using western blot. We found that cordycepin remarkably alleviated LTP impairment and protected pyramidal cell of hippocampal CA1 region against cerebral ischemia and excitotoxicity. Meanwhile, cordycepin prevented the reduction on adenosine A1 receptor level caused by ischemia but did not alter the adenosine A2A receptor level in hippocampal CA1 area. The improvement of LTP in the excitotoxic rats after cordycepin treatment could be blocked by DPCPX, a selective antagonist of adenosine A1 receptor. In summary, our findings provided new insights into the mechanisms of cordycepin neuroprotection in excitotoxic diseases, which is through regulating adenosine A1 receptor to improve LTP formation and neuronal survival.

Effects of cordycepin on spontaneous alternation behavior and adenosine receptors expression in hippocampus.

Cordycepin, an adenosine analogue, has been reported to improve cognitive function. Important roles on learning and memory of adenosine and its receptors, such as adenosine A1 and A2A receptors (A1R and A2AR), also have been shown. Therefore, we assume that the improvement of learning and memory induced by cordycepin is likely related to hippocampal adenosine content and adenosine receptor density. Here we investigated the effects of cordycepin on the short-term spatial memory by using a spontaneous alternation behavior (SAB) test in Y-maze, and then examined hippocampal adenosine content and A1R and A2AR densities. We found that orally administrated cordycepin (at dosages of 5 and 10mg/kg twice daily for three weeks) significantly increased the percent of relative alternation of mice in SAB but not altered body weight, hippocampus weight and hippocampal adenosine content. Furthermore, cordycepin decreased A2AR density in hippocampal subareas; however, cordycepin only reduced the A1R density in DG but not CA1 or CA3 region. Our results suggest that cordycepin exerts a nootropic role possibly through modulating A2AR density of hippocampus, which further support the concept that it is mostly A2AR rather than A1R to control the adaptive processes of memory performance. These findings would be helpful to provide a new window into the pharmacological properties of cordycepin for cognitive promotion.

RNA-seq reveals the critical role of CspA in regulating Brucella melitensis metabolism and virulence.

Brucella melitensis is a facultative intracellular bacterium that replicates within macrophages. The ability of Brucella to survive and multiply in the hostile environment of host macrophages is essential for its virulence. The cold shock protein CspA plays an important role in the virulence of B. melitensis. To analyze the genes regulated by CspA, the whole transcriptomes of B. melitensis NIΔcspA and its parental wild-type strain, B. melitensis NI, were sequenced and analyzed using the Solexa/Illumina sequencing platform. A total of 446 differentially expressed genes were identified, including 324 up-regulated and 122 down-regulated genes. Numerous genes identified are involved in amino acid, fatty acid, nitrogen, and energy metabolism. Interestingly, all genes involved in the type IV secretion system and LuxR-type regulatory protein VjbR were significantly down-regulated in NIΔcspA. In addition, an effector translocation assay confirmed that the function of T4SS in NIΔcspA is influenced by deletion of the cspA gene. These results revealed the differential phenomena associated with virulence and metabolism in NIΔcspA and NI, providing important information for understanding detailed CspA-regulated interaction networks and Brucella pathogenesis.

The effects of MucR on expression of type IV secretion system, quorum sensing system and stress responses in Brucella melitensis.

MucR is a transcriptional regulator in many bacterial pathogens and is required for virulence in mice and macrophages, resistance to stress responses, and modification of the cell envelope in Brucella spp. To determine why the mucR deleted mutant is attenuated in vivo and in vitro, we performed RNA-seq analysis using Brucella melitensis RNA obtained from B. melitensis 16M and 16MΔmucR grown under the same conditions. We found 442 differentially expressed genes; 310 were over expressed, and 132 were less expressed in 16MΔmucR. Many genes identified are involved in metabolism, cell wall/envelope biogenesis, replication, and translation. Notably, genes involved in type IV secretion system and quorum sensing system were down-regulated in 16MΔmucR. In addition, genes involved in tolerance to acid and iron-limitation were also affected and experimentally verified in this study. The effects of MucR on Brucella survival and persistence in mice and macrophages were related to type IV secretion system, quorum sensing system, and stress tolerance, which also provide added insight to the MucR regulon.

Tenuigenin ameliorates learning and memory impairments induced by ovariectomy.

Estrogen deficiency is associated with cognitive impairment. Hormone replacement therapy (HRT) has proven to be effective in preventing and reversing the memory and learning deficiencies. However, conventional estrogenic treatment could increase the risks of breast cancer and venous thromboembolism. Tenuigenin (TEN) is putatively believed as the active component extracted from a Chinese herb Polygala tenuifolia root. Although TEN has been shown to enhance learning and memory in healthy mice, it remains unknown whether or not TEN could ameliorate learning and memory impairments. In the present study, mice were divided into four groups: sham-operated (sham), ovariectomized (OVX), OVX+estradiol benzoate (EB) and OVX+TEN groups. Step-through passive avoidance and Y-maze tests were used to assess learning and memory abilities, and the number of nitric oxide synthase (NOS) positive neurons and the synaptic measurement of hippocampal CA1 area were examined. The results showed that TEN was given orally to OVX mice, leading to the improvement of learning and memory in step-through passive avoidance and Y-maze tests. TEN could reduce the loss of NOS positive neurons and prevent the synaptic morphological changes induced by ovariectomy. Our results suggest that TEN may exert a potential therapeutic value for menopause cognitive dysfunction.

Cordycepin decreases activity of hippocampal CA1 pyramidal neuron through membrane hyperpolarization.

Cordycepin (3'-deoxyadenosine) is the main functional component of Cordycepins militaris, a renowned traditional Chinese medicine, which has been shown to possess anti-tumor, anti-inflammatory, anti-diabetic and neuro-protective effects. However, the effect of cordycepin on the central nervous system (CNS) remains unclear. In this study, the effects of cordycepin on neuronal activity were investigated on the CA1 pyramidal neurons in rat hippocampal brain slices using a whole-cell patch clamp technique. Our results revealed that cordycepin significantly decreased the frequency of both the spontaneous and evoked action potential (AP) firing. While AP spike width, the amplitude of fast after hyperpolarization (fAHP), and membrane input resistance were not altered by cordycepin, the neuronal membrane potential was hyperpolarized by cordycepin. Collectively, these results demonstrate that cordycepin reduces neuronal activity by inducing membrane hyperpolarization, indicating that cordycepin may be a potential therapeutic strategy for ischemic and other excitotoxic disorders.