Molecular indicators of stress-induced neuroinflammation in a mouse model simulating features of post-traumatic stress disorder

A social-stress mouse model was used to simulate features of post-traumatic stress disorder (PTSD). The model involved exposure of an intruder (male C57BL/6) mouse to a resident aggressor (male SJL) mouse for 5 or 10 consecutive days. Transcriptome changes in brain regions (hippocampus, amygdala, medial prefrontal cortex and hemibrain), blood and spleen as well as epigenome changes in the hemibrain were assayed after 1- and 10-day intervals following the 5-day trauma or after 1- and 42-day intervals following the 10-day trauma. Analyses of differentially expressed genes (common among brain, blood and spleen) and differentially methylated promoter regions revealed that neurogenesis and synaptic plasticity pathways were activated during the early responses but were inhibited after the later post-trauma intervals. However, inflammatory pathways were activated throughout the observation periods, except in the amygdala in which they were inhibited only at the later post-trauma intervals. Phenotypically, inhibition of neurogenesis was corroborated by impaired Y-maze behavioral responses. Sustained neuroinflammation appears to drive the development and maintenance of behavioral manifestations of PTSD, potentially via its inhibitory effect on neurogenesis and synaptic plasticity. By contrast, peripheral inflammation seems to be directly responsible for tissue damage underpinning somatic comorbid pathologies. Identification of overlapping, differentially regulated genes and pathways between blood and brain suggests that blood could be a useful and accessible brain surrogate specimen for clinical translation.

Transcriptome characterization of immune suppression from battlefield-like stress

Transcriptome alterations of leukocytes from soldiers who underwent 8 weeks of Army Ranger training (RASP, Ranger Assessment and Selection Program) were analyzed to evaluate impacts of battlefield-like stress on the immune response. About 1400 transcripts were differentially expressed between pre- and post-RASP leukocytes. Upon functional analysis, immune response was the most enriched biological process, and most of the transcripts associated with the immune response were downregulated. Microbial pattern recognition, chemotaxis, antigen presentation and T-cell activation were among the most downregulated immune processes. Transcription factors predicted to be stress-inhibited (IRF7, RELA, NFκB1, CREB1, IRF1 and HMGB) regulated genes involved in inflammation, maturation of dendritic cells and glucocorticoid receptor signaling. Many altered transcripts were predicted to be targets of stress-regulated microRNAs. Post-RASP leukocytes exposed ex vivo to Staphylococcal enterotoxin B showed a markedly impaired immune response to this superantigen compared with pre-RASP leukocytes, consistent with the suppression of the immune response revealed by transcriptome analyses. Our results suggest that suppression of antigen presentation and lymphocyte activation pathways, in the setting of normal blood cell counts, most likely contribute to the poor vaccine response, impaired wound healing and infection susceptibility associated with chronic intense stress.

Study of proinflammatory responses induced by Yersinia pestis in human monocytes using cDNA arrays

Yersinia pestis, the causative agent of plague, is known to develop strategies to overcome the host immune mechanisms and survive in the host. The molecular changes induced by Y. pestis in the host are not well delineated. Here, we examined the early events triggered after the intracellular infection of Y. pestis in human monocytes and lymphocytes by analyzing the host transcriptional profiles using cDNA arrays. We found that sets of genes that, especially at early time periods, were highly upregulated in monocytes alone when compared with a mixed culture of lymphocytes and monocytes. Gene expression responses revealed genes coding for cytokines, chemokines, transcription factors, inflammatory and apoptosis-related genes. Protein levels were measured, and real-time polymerase chain reaction was used to validate the microarray results. Our data suggest that intracellular infection of human monocytes with Y. pestis results in a strong inflammatory response at early time periods and a downregulation of genes such as thromobomodulin, which may play a role in coagulation, resulting in disseminated intravascular coagulation, a primary cause of death in plague infected hosts. We provide evidence that genomic analysis can provide a solid foundation to mechanistic insights to explain some of the symptoms induced by Y. pestis.

Transcriptional response signature of human lymphoid cells to staphylococcal enterotoxin B

Two shock-inducing toxins that result in similar eventual outcome of disease were studied to determine host gene expression responses, for correlation of both similar and unique gene patterns. We initially used differential display (DD)-PCR and identified 859 cDNA fragments that were differentially expressed after 16 h of in vitro exposure of human peripheral blood mononuclear cells (PBMC) to staphylococcal enterotoxin B (SEB). Upon further examination using custom cDNA microarrays and RT-PCR analysis, we found unique set of genes to each toxin (SEB or lipopolysaccharide (LPS)), especially at early time periods. By 16 h, there was a convergence of some gene expression responses and many of those genes code for proteins such as proteinases, transcription factors, vascular tone regulators, and respiratory distress. In an attempt to replicate the findings in vivo, monkeys were challenged with SEB and the resultant gene expression responses indicated a pattern typical of SEB exposure when compared to LPS, with a similar outcome. We provide evidence that vastly diverse global gene analysis techniques used in unison can not only effectively identify pathogen-specific genomic markers and provide a solid foundation to mechanistic insights but also explain some of the toxin-related symptoms through gene functions.

Expression pattern of fatty acid-binding proteins in human normal and cancer prostate cells and tissues

PURPOSE

Fatty acid-binding protein (FABP) expression patterns were evaluated as potential markers and therapeutic targets for prostate cancer.

EXPERIMENTAL DESIGN

FABP expression levels were determined by reverse transcription-PCR in cultured prostate normal and tumor cells and in human biopsy samples. Regulation of cellular processes was examined using FABP antisense constructs.

RESULTS

Prostate cells express a variety of different FABPs. Liver (L)- and intestine-FABPs were elevated 5-9-fold in prostate cancer compared with normal primary prostate cells. In contrast, adipose- and epidermal-FABPs were markedly down-regulated (3-20-fold) in cancer versus normal cells. Similar expression patterns were found in human tissue biopsy samples. However, brain-FABP had a distinct pattern of expression: it was overexpressed only in LNCaP cells and in well-differentiated tissue samples, suggesting a stage-specific expression profile. Secretion of L-FABP protein was observed from DU 145 prostate cancer cells, but not in the culture fluid of normal prostate epithelial cells. Antisense oligodeoxynucleotides, designed to block production of epidermal-FABP (a marker for normal prostate cells), caused increased proliferation in DU 145 prostate cancer cells. In vivid contrast, antisense oligodeoxynucleotides to L-FABP (overexpressed in prostate cancer) decreased proliferation and caused apoptosis.

CONCLUSIONS

We propose that there is a distinct balance between these groups of FABPs, whose altered regulation in cells may play a role in prostate cancer. Furthermore, the pattern of expression and secretion of FABPs have the potential to serve as a diagnostic marker for an aggressive phenotype of prostate cancer.

Magnesium ion-mediated binding to tRNA by an amino-terminal peptide of a class II tRNA synthetase

Aspartyl-tRNA synthetase is a class II tRNA synthetase and occurs in a multisynthetase complex in mammalian cells. Human Asp-tRNA synthetase contains a short 32-residue amino-terminal extension that can control the release of charged tRNA and its direct transfer to elongation factor 1 alpha; however, whether the extension binds to tRNA directly or interacts with the synthetase active site is not known. Full-length human AspRS, but not amino-terminal 32 residue-deleted, fully active AspRS, was found to bind to noncognate tRNA(fMet) in the presence of Mg(2+). Synthetic amino-terminal peptides bound similarly to tRNA(fMet), whereas little or no binding of polynucleotides, poly(dA-dT), or polyphosphate to the peptides was found. The apparent binding constants to tRNA by the peptide increased with increasing concentrations of Mg(2+), suggesting Mg(2+) mediates the binding as a new mode of RNA.peptide interactions. The binding of tRNA(fMet) to amino-terminal peptides was also observed using fluorescence-labeled tRNAs and circular dichroism. These results suggest that a small peptide can bind to tRNA selectively and that evolution of class II tRNA synthetases may involve structural changes of amino-terminal extensions for enhanced selective binding of tRNA.