T-bet as a possible therapeutic target in autoimmune disease

Computation of Robust Minimal Intervention Sets in Multi-Valued Biological Regulatory Networks

Enabled by rapid advances in computational sciences, in silico logical modeling of complex and large biological networks is more and more feasible making it an increasingly popular approach among biologists. Automated high-throughput, drug target identification is one of the primary goals of this in silico network biology. Targets identified in this way are then used to mine a library of drug chemical compounds in order to identify appropriate therapies. While identification of drug targets is exhaustively feasible on small networks, it remains computationally difficult on moderate and larger models. Moreover, there are several important constraints such as off-target effects, efficacy and safety that should be integrated into the identification of targets if the intention is translation to the clinical space. Here we introduce numerical constraints whereby efficacy is represented by efficiency in response and robustness of outcome. This paper introduces an algorithm that relies on a Constraint Satisfaction (CS) technique to efficiently compute the Minimal Intervention Sets (MIS) within a set of often complex clinical safety constraints with the aim of identifying the smallest least invasive set of targets pharmacologically accessible for therapy that most efficiently and reliably achieve the desired outcome.

Therapeutic and immunoregulatory effect of GATA-binding protein-3/T-box expressed in T-cells ratio of astragalus polysaccharides on 2,4,6-trinitrobenzene sulfonic acid-induced colitis in rats

OBJECTIVE

To analyze the immunological characteristics of 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis model and examine the therapeutic effects and mechanisms of Astragalus polysaccharides (APS) treatment.

METHODS

Thirty-two male specific pathogen free Spragne-Dawley rats were randomly equally assigned to four groups: control, TNBS, APS and prednisone groups. Experimental colitis was induced by enema administration of TNBS. Then rats were treated with APS (0.5 g•kg^-1•day^-1, once daily) or prednisone (1.0 mg•kg^-1•day^-1, once daily) by gavage for 14 days. Macroscopic lesion and histological damage were determined, and activity of myeloperoxidase (MPO) was measured in the colonic tissues. Expressions of T-box expressed in T-cells (T-bet) and GATA-binding protein-3 (GATA-3) were determined by immunohistochemistry analysis and western blot.

RESULTS

Both macroscopic lesion and histological colonic damage induced by TNBS were reduced by APS and prednisone treatment. These were accompanied by significant attenuation of MPO activity (P=0.03). TNBS intervention enhanced the expression of both GATA-3 and T-bet, but the expression of T-bet was significantly enhanced than that of GATA-3, resulting in significant reduction of GATA-3/T-bet ratio (P=0.025). APS administration enhanced the expression of T-bet (P=0.04) and GATA-3 (P=0.019) in comparison to TNBS group, and resulting in an up-regulated GATA-3/T-bet ratio. Prednisone treatment inhibited both expressions; however it also resulted in up-regulation of the GATA-3/T-bet ratio.

CONCLUSIONS

These results demonstrated that APS exerted a beneficial immune regulatory effect on experimental colitis. It promoted the expression of T helper cell 1 (Th1) and T helper cell 2 (Th2) specific transcription factors but ultimately favor a shift toward Th2 phenotype, suggesting that APS possessed therapeutic potential in experimental colitis.

Efficient computation of minimal perturbation sets in gene regulatory networks

In the last few decades, technological and experimental advancements have enabled a more precise understanding of the mode of action of drugs with respect to human cell signaling pathways and have positively influenced the design of new drug compounds. However, as the design of compounds has become increasingly target-specific, the overall effects of a drug on adjacent cellular signaling pathways remain difficult to predict because of the complexity of the interactions involved. Off-target effects of drugs are known to influence their efficacy and safety. Similarly, drugs which are more target-specific also suffer from lack of efficacy because their scope might be too limited in the context of cellular signaling. Even in situations where the signaling pathways targeted by a drug are known, the presence of point mutations in some of the components of the pathways can render a therapy ineffective in a considerable target subpopulation. Some of these issues can be addressed by predicting Minimal Intervention Sets (MIS) of elements of the signaling pathways that when perturbed give rise to a pre-defined cellular phenotype. These minimal gene perturbation sets can then be further used to screen a library of drug compounds in order to discover effective drug therapies. This manuscript describes algorithms that can be used to discover MIS in a gene regulatory network that can lead to a defined cellular phenotype. Algorithms are implemented in our Boolean modeling toolbox, GenYsis. The software binaries of GenYsis are available for download from http://www.vital-it.ch/software/genYsis/.

Clinical efficacy of Lactobacillus acidophilus against experimental murine colitis and its effects on the expression of STAT1, T-bet and GATA3

AIM: To investigate the therapeutic efficacy of Lactobacillus acidophilus against experimental murine colitis and its effects on the expression of STAT1, T-bet and GATA3.

METHODS: Experimental murine colitis was induced with 2.5% dextran sulfate sodium (DSS). A total of 70 mice were randomly and equally divided into seven groups: model control group, negative control group, mesalamine group, low-dose Lactobacillus acidophilus group, medium-dose Lactobacillus acidophilus group, high-dose Lactobacillus acidophilus group and normal control group. The expression of STAT1, T-bet and GATA3 mRNAs in colonic mucosa was measured by reverse transcription-polymerase chain reaction (RT-PCR). The expression of T-bet protein was measured by Western blot and immunohistochemistry (IHC). Colonic tissue damage was assessed using histopathologic score. The body weight and disease activity index (DAI) of all rats were evaluated daily.

RESULTS: Compared with the normal control group, the disease activity index and histopathologic scores were significantly increased (both P < 0.05) in the model control group. All doses of Lactobacillus acidophilus and mesalamine could significantly reduce disease activity index and histopathologic scores when compared to the model control group (6.20 ± 2.64, 5.00 ± 1.21, 5.72 ± 2.63 and 5.81 ± 1.32 vs 7.81 ± 1.02; 4.25 ± 2.05, 2.56 ± 1.81, 2.20 ± 1.12 and 3.10 ± 2.60 vs 5.80 ± 2.94; all P < 0.05). The expression levels of STAT1 and T-bet mRNAs in all Lactobacillus acidophilus groups (low-, medium- and high-dose) and mesalazine group were lower than that in the model control group (all P < 0.05). Moreover, the expression levels of T-bet protein in all Lactobacillus acidophilus groups and mesalazine group were also significantly lower than that in the model control group (0.27 ± 0.04, 0.23 ± 0.02, 0.18 ± 0.04 and 0.27 ± 0.11 vs 0.30 ± 0.04; 0.263 ± 0.045, 0.234 ± 0.015, 0.114 ± 0.025 and 0.252 ± 0.024 vs 0.322 ± 0.064; all P < 0.05). Optimum effects were achieved in the high-dose Lactobacillus acidophilus group.

CONCLUSION: Inhibition of transcriptional factors STAT1/T-bet activation maybe one mechanism contributing to the therapeutic effects of Lactobacillus acidophilus against ulcerative colitis.

Polarization of B effector cells in Sjögren's syndrome

Analysis of salivary glands of patients with primary Sjögren's syndrome has yielded conflicting results with respect to T helper (Th)1/Th2 polarization. This balance might parallel the progress of the local lesions. B-cells are now taking center stage in this disease. They can also be primed to differentiate into two cytokine-production pathways, dubbed B effector (Be) 1 and Be2 cells. This is discussed in the light of our recent finding that Be1 accompany Th1, while Be2 accompany in the tissue lesions.

IL-28A is a key regulator of T-cell-mediated liver injury via the T-box transcription factor T-bet

BACKGROUND & AIMS

T-cell-mediated fulminant hepatitis is a potentially life-threatening event for which the underlying pathogenic mechanisms are not fully understood. Here, we demonstrate a key regulatory role of IL-28A in T-cell-mediated hepatitis.

METHODS

We cloned the murine IL-28A gene by reverse-transcription polymerase chain reaction, assessed the effects of recombinant IL-28A, and generated IL-28A-transgenic mice.

RESULTS

IL-28A induced TH1 cytokine production by CD4+ T lymphocytes in a T-bet-dependent manner and was up-regulated in a murine model of T-cell-mediated hepatitis upon Con A administration. In vivo, CD4+ T cells from newly created IL-28A-transgenic animals revealed an increased proliferation and proinflammatory TH1 cytokine production, as compared with wild-type mice. In addition, IL-28A-transgenic mice showed markedly augmented Con A-induced hepatitis with up-regulated interferon-gamma cytokine production, as compared with wild-type mice. Transgenic mice exhibited an up-regulation of the interferon-gamma-T-bet signaling pathway in Con A hepatitis, and augmented hepatitis in these mice was suppressed by crossing them with T-bet-deficient mice. In addition, in vivo blockade of interferon-gamma but not IL-4 suppressed augmented liver inflammation in transgenic mice, suggesting that IL-28A induces the T-bet signaling pathway in T-cell-induced hepatitis. Finally, IL-28A-specific antisense phosphorothioate oligonucleotides suppressed liver pathology in Con A-treated wild-type mice, as compared with the case of control oligonucleotides.

CONCLUSIONS

IL-28A emerges as a key regulatory cytokine with pathogenic function in T-cell-mediated liver injury. Thus, targeting of IL-28A represents a potential novel approach for therapy of Th1-mediated inflammatory diseases such as T-cell-mediated hepatitis.

T-bet, a Th1 transcription factor, is up-regulated in T cells from patients with aplastic anemia

In aplastic anemia, immune destruction of hematopoietic cells results in bone marrow failure. Type 1 cytokines, especially IFN-gamma, have been implicated in the pathophysiology of T-cell-mediated, Fas-mediated stem cell apoptosis of hematopoietic cells. Here, we show that the transcription factor T-bet (T-box expressed in T cells) is increased in T cells from patients with aplastic anemia. Patients' T-bet bound directly to the proximal site of the IFN-gamma promoter without any prior stimulation, in contrast to healthy controls. Increased levels of Itk kinase participated in T-bet up-regulation and active transcription of the IFN-gamma gene observed in these patients. Blocking PKC-, a kinase that lies downstream of Itk kinase, decreased T-bet protein and IFN-gamma intracellular levels. These data suggest that the increased IFN-gamma levels observed in aplastic anemia patients are the result of active transcription of the IFN-gamma gene by T-bet. Blocking the transcription of the IFN-gamma gene with kinase inhibitors might lead to the development of novel therapeutic agents for patients with aplastic anemia and other autoimmune diseases.