Molecular mechanisms involved in HIV-1 Tat-mediated induction of IL-6 and IL-8 in astrocytes

Background

Two families of polyunsaturated fatty acid (PUFA), omega-3 (ω-3) and omega-6 (ω-6), are required for physiological functions. The long chain ω-3 PUFAs, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have significant biological effects. In particular, DHA is a major component of cell membranes in the brain. It is also involved in neurotransmission. Spinal cord injury (SCI) is a highly devastating pathology that can lead to catastrophic dysfunction, with a significant reduction in the quality of life. Previous studies have shown that EPA and DHA can exert neuroprotective effects in SCI in mice and rats. The aim of this study was to analyze the mechanism of action of ω-3 PUFAs, such as DHA, in a mouse model of SCI, with a focus on the early pathophysiological processes.

Methods

In this study, SCI was induced in mice by the application of an aneurysm clip onto the dura mater via a four-level T5 to T8 laminectomy. Thirty minutes after compression, animals received a tail vein injection of DHA at a dose of 250 nmol/kg. All animals were killed at 24 h after SCI, to evaluate various parameters implicated in the spread of the injury.

Results

Our results in this in-vivo study clearly demonstrate that DHA treatment reduces key factors associated with spinal cord trauma. Treatment with DHA significantly reduced: (1) the degree of spinal cord inflammation and tissue injury, (2) pro-inflammatory cytokine expression (TNF-α), (3) nitrotyrosine formation, (4) glial fibrillary acidic protein (GFAP) expression, and (5) apoptosis (Fas-L, Bax, and Bcl-2 expression). Moreover, DHA significantly improved the recovery of limb function. Furthermore, in this study we evaluated the effect of oxidative stress on dorsal root ganglion (DRG) cells using a well-characterized in-vitro model. Treatment with DHA ameliorated the effects of oxidative stress on neurite length and branching.

Conclusions

Our results, in vivo and in vitro, clearly demonstrate that DHA treatment reduces the development of inflammation and tissue injury associated with spinal cord trauma.     

HIV-1 integration: an interplay between HIV-1 integrase, cellular and viral proteins

To achieve a productive infection, the reverse transcribed cDNA of the human immunodeficiency virus type 1 (HIV-1) has to be inserted in the host cell genome. The main protein required to accomplish this reaction is the virally encoded integrase. In vitro, the recombinant integrase is capable of catalyzing the two subsequent reactions of the integration process, namely the 3' processing followed by the strand transfer, without other viral and/or cellular proteins. However, a number of studies indicate that the in vivo integration process also involves cellular proteins, assisting the virus to integrate in the cellular genome. These cellular proteins can play a role during different steps of the integration process, including nuclear import, integrase catalysis, integration site selection and DNA gap repair. In this review we summarize the candidate cellular proteins involved in the HIV-1 integration process identified so far and discuss their potential roles during HIV-1 replication.     

Ig/EBP-1: a ubiquitously expressed immunoglobulin enhancer binding protein that is similar to C/EBP and heterodimerizes with C/EBP

We report the isolation and characterization of cDNA clones that encode a protein with the same DNA binding specificity as the immunoglobulin heavy chain enhancer binding protein E (muEBP-E). We call the gene encoding this protein Ig/EBP-1. A fusion protein encoded by the cDNA binds specifically to muEBP-E-binding sites (E sites) in both the IgH enhancer and the VH1 promoter. Sequence analysis reveals that Ig/EBP-1 is a member of the "basic-zipper" family of DNA-binding proteins that are characterized by basic regions and heptad repeats of leucine residues. Among known family members, Ig/EBP-1 demonstrates highest homology to C/EBP throughout the DNA-binding domain and leucine repeat region. Ig/EBP-1 and C/EBP have highly overlapping binding specificities; both cloned proteins bind to the IgH enhancer and the VH1 promoter E sites, and Ig/EBP-1 binds to previously characterized C/EBP binding sites in the Rous sarcoma virus (RSV) LTR and the murine albumin promoter. Consistent with their homology in the leucine repeat region, Ig/EBP-1 and C/EBP form heterodimers; Ig/EBP-1 is the first member of this family that has been found to heterodimerize with the well-characterized C/EBP. Ig/EBP-1 mRNA is present in all tissues and cell lines examined, although its levels vary almost 20-fold from different sources, with highest levels in early B cells. In tissues where Ig/EBP-1 and C/EBP are both present, heterodimers may be functionally important. The presence of Ig/EBP-1 in fibroblasts and other tissues where C/EBP is not expressed suggests that Ig/EBP-1 may be functionally important for the activity of the RSV enhancer in these cell types. Finally, elevated expression of Ig/EBP-1 in early B cells may explain in part the enhancer-independent activity of VH promoters early in B-cell development.     

HIV-1B’/C重组病毒感染者Vif、Vpr和Vpu特异性细胞免疫应答研究

目的 探讨我国HIV-1 B'/C重组病毒感染者针对HIV-1调节蛋白的细胞免疫反应特征及其与病毒复制控制的关系.方法 以覆盖HIV-1 C亚型Vpr、Vpu和Vif蛋白全长的重叠肽段作为刺激抗原,利用ELISPOT方法检测新疆HIV-1 B'/C重组病毒感染者的特异性细胞免疫反应.使用SIGMAPLOT 10.0和SIGMASTAT 3.5进行统计分析,用双尾t检验比较组间差异,用Spearmam秩相关分析免疫反应与病毒载量及CD4细胞计数的关系.结果 在检测的60名HIV-1 B'/C重组病毒感染者中,能够识别Vif、Vpr和Vpu蛋白产生CIL应答者分别为68%、52%和8%,Vpr和Vif蛋白存在多个强CIL反应的免疫优势区域.研究中还发现针对Vpr、Vif和Vpu蛋白的CTL反应强度和广度与HIV感染者的病毒载量及CD4细胞数量无明显的相关性.结论 HIV-1 Vpr和Vif蛋白包含多个可被机体免疫系统特异性T细胞识别的免疫优势区域.对这些免疫优势区所包含的CIL表位进行鉴定并探讨其在自然感染过程中的作用,对新一代的HIV疫苗设计有重要的参考意义.