The Activity of JAK/STAT and NF-κB in Patients with Rheumatoid Arthritis

BACKGROUND

Research is still being conducted in order to determine the mechanisms responsible for the initiation of rheumatoid arthritis (RA) as well as for its persistence and progression.

OBJECTIVES

The aim of this work was to establish the expression of the signal transducer and activator of transcription (STAT) transcription factors and the nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) transcription factor in peripheral blood leukocytes and synovial fluid cells. The correlations between the activation level of the transcription factors and the activity of the disease were also analyzed.

MATERIAL AND METHODS

In total, the study included 34 RA patients and 19 healthy individuals as controls. The expression of NFκB, STAT1, STAT3, STAT4, STAT5 and STAT6 in peripheral blood leukocytes and synovial fluid cells was established. The immunocytochemistry method was used to determine the degree of activation of STAT and NF-κB transcription factors. For the location of the factors, primary polyclonal anti-STATs and monoclonal anti-NF-κB antibodies were used.

RESULTS

The expression of STAT1, STAT3, STAT4, STAT5, STAT6 and NFκB was significantly higher in the group of RA patients than in the controls. No statistically significant differences were found between the expression of STATs in peripheral blood leukocytes and synovial fluid cells.

CONCLUSIONS

In comparison with the control group, the expression of the STAT and NFκB transcription factors in RA patients was higher, which may be helpful in better understanding the etiopathogenesis of the disease in the future, and may potentially have important therapeutic implications.

Ex Vivo Signaling Protein Mapping in T Lymphocytes in the Psoriatic Arthritis Joints

We assessed signaling protein mapping in total T cells, to analyze the proportions of T regulatory (Treg) and TCD4+ effector (Teff) cell phenotypes, and the respective interleukin 6Rα (IL-6Rα) expression in the inflammatory microenvironment of synovial fluid (SF) of patients with sustained psoriatic arthritis (PsA). Our approach was to measure the IL-6 level in SF using a multiplex bead immunoassay. Reverse-phase protein array was used to assess Janus kinase (JAK) 1 and JAK2, extra-cellular regulated kinase (ERK) 1 and 2, protein kinase Cδ (PKCδ), signal transducer and activator and transcription (STAT) 1, STAT3, and STAT5 phosphoproteins in total T cell lysates from SF of patients with PsA. Frequencies of CD4+IL-17A-F+IL-23+ CD4+ Th cells producing IL-17A and IL-17F (Th17) and CD4+CD25high intracellular forkhead box transcription factor+ (FOXP3+) phenotypes, and the percentage of Treg- and Teff- cells were quantified in SF and matched peripheral blood (PB) of patients with PsA and PB of healthy controls (HC) by flow cytometry. Our results were the following: In PsA SF samples, a coordinate increase of JAK1, ERK1/2, STAT1, STAT3, and STAT5 phosphoproteins was found in total T cells in SF of PsA; where IL-6 levels were higher than in PB from HC. Expanded CD4+IL-17A-F+IL-23+ Th17, CD4+ CD25- Teff- and CD4+CD25(high) FoxP3+Treg subsets, showing similar levels of enhanced IL-6Rδ expression, were confined to PsA joints. In our studies, the transcriptional network profile identified by ex vivo signaling protein mapping in T lymphocytes in PsA joints revealed the complex interplay between IL-1, IL-6, and IL-23 signaling and differentiation of Th17 cells and CD4+Tregs in sustained joint inflammation in PsA.

Developmental changes in the human GH receptor and its signal transduction pathways

We previously reported the presence of functional human GH receptors (hGHRs) in the human fetal hepatocyte (FH) as early as the first trimester. Interestingly, fetal serum levels of hGH are in the acromegalic range, yet certain hGH-dependent factors are expressed at very low levels (IGF-I, IGF-binding protein-3), suggesting that fetal liver has limited responsiveness to hGH. To determine whether this is due to the fetal tissue levels of hGHR or factors in the hGH/hGHR axis that might influence hGHR function, we compared hGHR isoforms and downstream signaling proteins in FH versus human adult liver (HAL). Immunoprecipitation/immunoblotting (IB) analyses found similar precursor and mature hGHR forms while RT-PCR assays of truncated (T) hGHR(1-279), dominant negative for the full-length (FL) receptor, showed similar T/FL mRNA ratios in FH and HAL. IB demonstrated that Janus kinase (JAK) 2, signal transducers and activators of transcription (STAT(1, 3, 5A/B)), and suppressors of cytokine signaling (SOCS(1, 2, 3, cytokine-inducible SH2-containing protein (CIS))) proteins were detectable in all FH and HAL tested (12 weeks of fetal age to 60 years); the levels were similar (STAT5B) or lower (JAK2/STAT1/STAT3/STAT5A: 38-53%, SOCS/CIS: 58-76%) in FH compared with HAL. Our studies to date demonstrate that, during hepatocyte development, hGHR levels are lower in the fetal cells but the hGHR isoforms, including the relative amount of truncated versus FL, remain unchanged. The JAK2/STAT/SOCS signaling molecules are present in the FH as early as the first trimester. However, they are generally at <50% level in postnatal liver. These data suggest that low expression of both hGHR and major hGHR signaling components may explain the limited responsiveness of the fetal cells to the high circulating levels of hGH.

Beta-glucosylceramide: a novel method for enhancement of natural killer T lymphoycte plasticity in murine models of immune-mediated disorders

BACKGROUND

beta-Glucosylceramide, a naturally occurring glycolipid, exerts modulatory effects on natural killer T (NKT) lymphocytes.

AIM

To determine whether beta-glucosylceramide can alter NKT function in opposite directions, colitis was induced by intracolonic installation of trinitrobenzenesulphonic acid, and hepatocellular carcinoma (HCC) was induced by transplantation of Hep3B cells.

METHODS

The immunological effect of beta-glucosylceramide was assessed by analysis of intrahepatic and intrasplenic lymphocyte populations, serum cytokines and STAT protein expression.

RESULTS

Administration of beta-glucosylceramide led to alleviation of colitis and to suppression of HCC, manifested by improved survival and decreased tumour volume. The beneficial effects were associated with an opposite immunological effect in the two models: the peripheral:intrahepatic CD4:CD8 lymphocyte ratio increased in the colitis model and decreased in the HCC group. The peripheral:intrahepatic NKT lymphocyte ratio decreased in beta-glucosylceramide-treated mice solely in the HCC model. The effect of beta-glucosylceramide was associated with decreased STAT1 and 4 expression, and with overexpression of STAT6, along with decreased interferon gamma levels in the colitis model, whereas an opposite effect was noted in the HCC model.

CONCLUSIONS

beta-glucosylceramide alleviates immunologically incongruous disorders and may be associated with "fine tuning" of immune responses, by changes in plasticity of NKT lymphocytes.

Disruption of the ifkA and ifkB genes results in altered cell adhesion, morphological defects and a propensity to form pre-stalk O cells during development of Dictyostelium

IfkA and ifkB are two GCN2-like genes present in Dictyostelium. Disruption of either gene alone results in subtle developmental defects. However, disruption of ifkA and ifkB within the same strain results in severe morphological and patterning defects in the developing double null cells. The mutant cells aggregate in streams that give tightly clumped mounds. Fingers form from the mounds but remain attached to one another, especially at their bases. The fingers culminate to give fused and entangled structures lacking proper stalk but containing some spores. The morphological defects are consistent with an enhanced cell-cell and cell-substrate adhesiveness of the developing double null cells, which may result in inappropriate cell contacts and altered cell motility and sorting properties. In ifkA/ifkB nulls, cell type proportioning and patterning is altered in favor of ALC/pstO cell types. The bias toward the ALC/pstO cell types may be due, in part, to the nuclear localization of the transcription factor STATc in growing ifkA/ifkB null cells. STATc normally becomes localized to the nucleus during finger formation and only within the pre-stalk O zone. The precocious nuclear localization seen in the mutant cells may predispose the cells to a ALC/pstO cell fate. The findings indicate that IfkA and IfkB have redundant functions in Dictyostelium morphogenesis that involve maintaining proper cell-cell and cell-substrate adhesion and the equilibrium between different cell types for proper spatial patterning.