Phosphoinositide 3-kinase signalling and FoxO transcription factors in rheumatoid arthritis

Identification of potential ferroptosis key genes and immune infiltration in rheumatoid arthritis by integrated bioinformatics analysis

Objective

Ferroptosis is of vital importance in the development of Rheumatoid arthritis (RA). The purpose of this project is to clarify the potential ferroptosis-related genes, pathways, and immune infiltration in RA by bioinformatics analysis.

Methods

We acquired ferroptosis-related genes (FRGs) from Ferroptosis database (FerrDb). We obtained the Gene dataset of RA (GSE55235) from the Gene Expression Omnibus (GEO) Database, screened the differentially expressed genes (DEGs) in RA and control samples, and then took the intersection of it and FRGs. Aiming to construct the protein-protein interaction (PPI) networks of the FRGs-DEGs, STRING database and Cytoscape software 3.7.0 would be used. Furthermore, hub genes were identified by CytoNCA, a Cytoscape plug-in. The gene ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment of FRGs-DEGs were performed.

Results

We identified 34 FRGs-DEGs, including 7 upregulated and 27 downregulated genes by taking the intersection of the FRGs and DEGs. PPI analysis identified a total of 3 hub genes(VEGFA, PTGS2, and JUN). GO enrichment analyses and KEGG Pathway enrichment displayed that the FRGs-DEGs are involved in the response to oxidative stress and corticosteroid, heme binding, FoxO-signal pathway. Results of immune infiltration displayed that increased infiltration of T cells, while Macrophages M2 less may be related to the occurrence of RA.

Conclusion

The hub genes involved in ferroptosis in RA may be VEGFA, PTGS2, and JUN, which are mainly involved in FoxO-signal pathway. T cell, Mac, and plasma cells may be involved in the regulation of RA-joints-synovial-inflammation.

One of the active ingredients in Paeoniae Radix Alba functions as JAK1 inhibitor in rheumatoid arthritis

Objective: We aimed to explore and verify the mechanism underlying the action of the active ingredients of Paeoniae Radix Alba (PRA) in the treatment of rheumatoid arthritis (RA).

Methods: The protein targets of PRA’s six active ingredients and RA were identified. Then, the intersection of the two groups was studied. The drug–target network was constructed, visualized, and analyzed by Cytoscape software. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment were performed to analyze these genes. Furthermore, we validated our predictions of the potential targets through a docking study. Finally, the anti-inflammatory effect of Palbinone (PB), one of the active ingredients of PRA, was tested by conducting in vitro and in vivo studies.

Results: Six active ingredients of PRA were identified, and 103 overlapping genes were discovered. Functional enrichment analysis indicated that the genes are mostly enriched in IL-17 signaling pathway, Th17 cell differentiation, and the FoxO, ErbB, and TNF signaling pathways. 10 hub genes and two gene cluster modules were identified by Cytoscape. Molecular docking analysis proved that PB was able to bind to the ATP binding site of Janus kinase (JAK)1, thereby acting as a potential inhibitor of JAK1. In vitro and in vivo studies demonstrated that PB exerts its anti-inflammatory role via the inhibition of JAK1.

Conclusion: We constructed a multitarget pharmacological network of PRA in RA treatment. PB, one of the active compounds of PRA, was demonstrated to be a promising inhibitor of JAK1.

Role of Tripartite Motif-Containing 3 Protein (TRIM3) in Rheumatoid Arthritis and Its Mechanism

Aim: To discuss TRIM3’s effects and relative mechanisms in RA development. Materials and methods: Using FLS as research object in our study. Present study divided into two steps, first step, discussing TRIM3 depressing effects in normal FLS cell; next, using IL-1β stimulating to make RA cell model, TRIM3 overexpression in RA model to observe cell biological activities. Measuring IL-6 and TNF-α levels by ELISA kit; evaluating cell proliferation by MTT and EdU assay; relative proteins including TRIM3, TAB2 and NF-κB(p65) proteins expression using WB method. Results: With TRIM3 knockdown, FLS cell proliferation were significantly increased with IL-6, TNF-α levels significantly up-regulation (P < 0.001, respectively). Meanwhile, TAB2 protein expression significantly depressing and NF-κB(p65) protein significantly increasing; those were similar as IL-1β stimulating RA cell model in FLS cell line. In RA cell model, transfection TRIM3 in FLS cell, the cell proliferation was significantly depressed with IL-1β, TNF-α levels depressing, and TAB2 protein expression significantly increasing and NF-κB(p65) protein significantly depressing. Conclusion: TRIM3 knockdown might be a result to RA development; with TRIM3 overexpression, RA induced FLS hyperproliferation significantly improved with TAB2 up-regulation and NF-κB(p65) down-regulation in vitro.

Rapamycin reduces podocyte damage by inhibiting the PI3K/AKT/mTOR signaling pathway and promoting autophagy

Objective: Rapamycin is a potent inducer of autophagy in podocytes. However, we still understand very little about how autophagy is regulated under podocyte injury conditions. This study aimed to investigate the role of autophagy in podocyte injury and the regulatory mechanism of the PI3K/Akt/mTOR signaling pathway in this process. Methods: The podocytes were cultured in vitro, and the apoptosis rate of each group was determined by flow cytometry. The protein expression and distribution of LC3-II were examined by immunofluorescence. The phosphorylation levels of Akt, LC3-II, mTOR, 4EBP1, and P70S6K were measured using Western Blot. Transmission electron microscopy was used to examine the changes in autophagosomes in each group. Results: Compared with the control group, the puromycin group (PAN) increased podocyte apoptosis, decreased numbers of autophagosomes, and downregulated LC3-II protein expression. Compared with the PAN group, the podocyte apoptosis rate decreased in the Rapamycin group (RAPA), the number of autophagosomes increased, and LC3-II protein expression was upregulated. In addition, PAN evoked an increase in p-Akt expressions, RAPA treatment induced a reversal of PAN-induced p-Akt upregulation, and the phosphorylation levels of mTOR, 4EBP1, and P70S6K were downregulated. Conclusion: PAN can damage podocytes by inhibiting podocyte autophagic activity and promoting apoptosis. Rapamycin can ameliorate PAN-induced podocyte damage by activating autophagy. This effect may be related to rapamycin-mediated PI3K/AKT/mTOR signaling pathway and autophagy.

Transcriptome-Based Network Analysis Reveals Hirudin Potentiates Anti-Renal Fibrosis Efficacy in UUO Rats

Background: Hirudin has been widely used in the treatment of antifibrosis. Previous studies have shown that hirudin can effectively improve the clinical remission rate of chronic kidney disease. However, the mechanism of its renal protection has not been systematically investigated.

Methods: In this study, the reliability of UUO-induced renal interstitial fibrosis was evaluated by histopathological verification. High-throughput transcriptome sequencing was used to elucidate the molecular mechanism of hirudin, differentially expressed mRNAs were identified, and their functions were analyzed by GO analysis and GSEA. In addition, the RNA-seq results were validated by in vitro and vivo experiments.

Results: We found 322 identical differential expressed genes (IDEs) in the UUO hirudin-treated group compared with the sham group. Functional enrichment analysis indicated that cellular amino acid metabolic processes were the most obvious enrichment pathways in biological processes. In terms of molecular functional enrichment analysis, IDEs were mainly enriched in coenzyme binding, pyridoxal phosphate binding and other pathways. In addition, microbody is the most obvious pathway for cellular components. A total of 115 signaling pathways were enriched, and AMPK, JAK-STAT, and PI3K-Akt signaling pathways were the important signaling pathways enriched. We found that PI3K, p-Akt, and mTOR expression were significantly reduced by hirudin treatment. In particular, our results showed that hirudin could induce a decrease in the expression of autophagy-related proteins such as P62, LC3, Beclin-1 in TGF-β1-induced NRK-52E cells.

Conclusion: Our results suggest that hirudin may protect the kidney by ameliorating renal autophagy impairment through modulating the PI3K/Akt pathway.

Identification and validation of hub genes of synovial tissue for patients with osteoarthritis and rheumatoid arthritis

Background

Osteoarthritis (OA) and rheumatoid arthritis (RA) were two major joint diseases with similar clinical phenotypes. This study aimed to determine the mechanistic similarities and differences between OA and RA by integrated analysis of multiple gene expression data sets.

Methods

Microarray data sets of OA and RA were obtained from the Gene Expression Omnibus (GEO). By integrating multiple gene data sets, specific differentially expressed genes (DEGs) were identified. The Gene Ontology (GO) functional annotation, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways and protein–protein interaction (PPI) network analysis of DEGs were conducted to determine hub genes and pathways. The “Cell Type Identification by Estimating Relative Subsets of RNA Transcripts (CIBERSORT)” algorithm was employed to evaluate the immune infiltration cells (IICs) profiles in OA and RA. Moreover, mouse models of RA and OA were established, and selected hub genes were verified in synovial tissues with quantitative polymerase chain reaction (qPCR).

Results

A total of 1116 DEGs were identified between OA and RA. GO functional enrichment analysis showed that DEGs were enriched in regulation of cell morphogenesis involved in differentiation, positive regulation of neuron differentiation, nuclear speck, RNA polymerase II transcription factor complex, protein serine/threonine kinase activity and proximal promoter sequence-specific DNA binding. KEGG pathway analysis showed that DEGs were enriched in EGFR tyrosine kinase inhibitor resistance, ubiquitin mediated proteolysis, FoxO signaling pathway and TGF-beta signaling pathway. Immune cell infiltration analysis identified 9 IICs with significantly different distributions between OA and RA samples. qPCR results showed that the expression levels of the hub genes (RPS6, RPS14, RPS25, RPL11, RPL27, SNRPE, EEF2 and RPL19) were significantly increased in OA samples compared to their counterparts in RA samples (P < 0.05).

Conclusion

This large-scale gene analyses provided new insights for disease-associated genes, molecular mechanisms as well as IICs profiles in OA and RA, which may offer a new direction for distinguishing diagnosis and treatment between OA and RA.

The Role of Forkhead Box Family in Bone Metabolism and Diseases

Forkhead box (Fox) family, an evolutionarily conserved family of transcription factors carrying the "Forkhead" motif, plays an indispensable role in human health and disease. Fox family genes are involved in cell differentiation, proliferation and apoptosis, embryonic development, aging, glucose and lipid metabolism, and immune regulation. The regulatory role of the Fox family in the context of bone metabolism and orthopedic diseases is an emerging research hotspot. In this review, we highlight the major molecular mechanisms underlying the regulatory role of Fox factors in bone metabolism, bone development, bone homeostasis, and bone diseases associated with inhibition or upregulation of Fox factors. In addition, we discuss the emerging evidence in the realm of Fox factor-based therapeutics.

Photobiomodulation with 630-nm LED radiation inhibits the proliferation of human synoviocyte MH7A cells possibly via TRPV4/PI3K/AKT/mTOR signaling pathway

Phototherapy has been used to treat postoperative pain and inflammatory response in rheumatoid arthritis. Confidence in this approach, however, is impaired by lack of understanding of the light-triggered cellular and molecular mechanisms. The purpose of this study was to characterize the response of human synoviocyte MH7A cells to visible LED red light in an attempt to elucidate the associated action mechanism. Human synoviocyte MH7A cells were treated with 630-nm LED light after stimulation of tumor necrosis factor-α (TNF-α). The effects of light radiation on cell proliferation and migration were detected by MTT assay and scratch test. The expressions of inflammatory cytokines were measured using RT-qPCR. This was followed by detection of the levels of extracellular proteins IL-6 and IL-8 after differential radiation. Furthermore, the expression levels and activation of proteins on PI3K/AKT/mTOR signaling pathway were examined with Western blot. In terms of the proliferation and migration, repeated radiation with LED red light (630 nm, 26 and 39 J/cm²) exerted an inhibitory effect on synoviocyte MH7A cells. Expression of inflammatory factors (IL-6, IL-1β, IL-8, and MMP-3) was reduced; meanwhile, the expression of anti-inflammatory factor IL-10 was promoted. At the protein level, treatment with 39 J/cm² of LED red light could decrease the level of extracellular protein (IL-6 and IL-8) and affect the expression and phosphorylation of proteins on TRPV4/PI3K/AKT/mTOR signaling pathway induced by TNF-α. These results demonstrated that LED red light (630 nm) inhibits proliferation and migration of MH7A cells. The growth-inhibiting effects of LED red light on human synoviocyte MH7A cells appear to be associated with regulation of the TRPV4/PI3K/AKT/mTOR signaling pathway.

A Network Pharmacology Approach to Explore Mechanism of Action of Longzuan Tongbi Formula on Rheumatoid Arthritis

Longzuan Tongbi Formula (LZTB) is an effective proved prescription in Zhuang medicine for treating active rheumatoid arthritis (RA). However, its active ingredients, underlying targets, and pharmacological mechanism are still not clear in treating RA. We have applied network pharmacology to study LZTB and found that 8 herbs in LZTB and 67 compounds in the 8 herbs are involved in the regulation of RA-related genes; we have conducted pathway analysis of overlapping genes and found that 7 herbs participate in the regulations of 24 pathways associated with RA and that 5 herbs in the 7 herbs and 25 compounds in the 5 herbs participate in the regulation of hsa05323 (rheumatoid arthritis). The results indicated that all herbs in LZTB and some compounds in those herbs participate in the treatment of RA; 25 compounds are main active ingredients and hsa05323 (rheumatoid arthritis) is the major pathway in the treatment of RA. We have also found that three pathways (inflammatory mediator regulation of TRP channels, PPAR signaling pathway, and mTOR signaling pathway) might have some effect on the treatment of RA.

FOXO3a promotes gastric cancer cell migration and invasion through the induction of cathepsin L

Forkhead box O3A (FOXO3a) is an important transcription factor involved in various human cancers. However, the role of FOXO3a in regulating the invasion and metastasis of gastric cancer cells has not been clarified. Here, we report that FOXO3a overexpression promoted migration and invasion of gastric cancer cells by upregulating cathepsin L. FOXO3a knockdown suppressed migration and invasion and also downregulated cathepsin L expression in gastric cancer cells. Silencing cathepsin L in these cells suppressed FOXO3a overexpression-induced cell migration and invasion. Mechanistic studies revealed that FOXO3a increased cathepsin L promoter activation, and cathepsin L overexpression repressed E-cadherin expression, causing gastric cancer cells to undergo epithelial-mesenchymal transition (EMT). Our data reveal a previously unexplored function of FOXO3a in gastric cancer invasion by regulating proteins involved in extracellular matrix (ECM) degradation and EMT. We suggest that FOXO3a may be of prognostic value and a potential therapeutic target in blocking tumor metastasis.

FOXM1 facilitates gastric cancer cell migration and invasion by inducing Cathepsin D

Forkhead box M1 (FOXM1) has been reported as a vital transcription factor in different human malignancies. To date, the mechanisms of FOXM1 in modulating the invasion and metastasis of gastric cancer cells have not been elucidated. In the present study, we found that overexpression of FOXM1 prompted cell migration and invasion of gastric cancer, and increased the expression of Cathepsin D (Cath-D). However, FOXM1 siRNA repressed cell migration and invasion, and also decreased the expression of Cath-D in gastric cancer cells. Blocking of Cath-D repressed FOXM1 overexpression-mediated cell migration and invasion. Mechanically, FOXM1 facilitated the activation of Cath-D promoter. Furthermore, overexpression of Cath-D affected the expression of E-cadherin, leading to epithelial-mesenchymal transition (EMT) of gastric cancer cells. In conclusion, this study demonstrated that FOXM1 promotes gastric cancer cell migration and invasion through inducing expression of Cath-D in gastric cancer. Thus, FOXM1 may be recommended as a potential therapeutic target for gastric cancer patients.

Resveratrol inhibits TNF-α-induced IL-1β, MMP-3 production in human rheumatoid arthritis fibroblast-like synoviocytes via modulation of PI3kinase/Akt pathway

Resveratrol (trans-3,4'-trihydroxystilbene), a natural phytoalexin, possesses anti-inflammatory, anti-proliferative, and immunomodulatory properties and has the potential for treating inflammatory disorders. The present study was designed to investigate the effects of resveratrol on TNF-α-induced inflammatory cytokines production of IL-1β and MMP3 in Rheumatoid arthritis (RA) Fibroblast-like synoviocytes (FLS) and further to explore the role of PI3K/Akt signaling pathway by which resveratrol modulates those cytokines production. The levels of IL-1β, MMP-3 in cultural supernatants among groups were measured by enzyme-linked immunosorbent assay. Messenger RNA expression of IL-1β and MMP-3 in RA FLS was analyzed using a reverse transcription-polymerase chain reaction. Western blot analysis was used to detect proteins expression in RA FLS intervened by resveratrol. Resveratrol inhibited both mRNA and proteins expressions of IL-1β and MMP-3 on RA FLS in a dose-dependent manner. Resveratrol also decreased significantly the expression of phosphorylated Akt dose dependently. Activation of PI3K/Akt signaling pathway exists in TNF-α-induced production of IL-1β and MMP3 on RA FLS, which is hampered by PI3K inhibitor LY294002. Immunofluorescence staining showed that TNF-α alone increased the production of P-Akt, whereas LY294002 and 50 μM resveratrol suppressed the TNF-α-stimulated expression of P-Akt. Resveratrol attenuates TNF-α-induced production of IL-1β and MMP-3 via inhibition of PI3K-Akt signaling pathway in RA FLS, suggesting that resveratrol plays an anti-inflammatory role and might have beneficial effects in preventing and treating RA.

The diversity of sex steroid action: the role of micro-RNAs and FOXO transcription factors in cycling endometrium and cancer

The rise and fall in ovarian oestrogen and progesterone production orchestrates a series of events that are indispensable for reproduction, including ovulation, implantation, decidualisation and menstruation. In the uterus, these events involve extensive tissue remodelling, characterised by waves of endometrial cell proliferation, differentiation, recruitment of inflammatory cells, apoptosis, tissue breakdown, menstruation and regeneration. The ability of ovarian hormones to trigger such diverse physiological responses is foremost dependent upon interaction of activated steroid receptors with specific transcription factors, such as Forkhead box class O (FOXO) proteins, involved in cell fate decisions. Furthermore, micro-RNAs (miRNAs), small non-coding RNAs that function as posttranscriptional regulators of gene expression, have emerged as a major regulator system of steroid hormone responses in the female reproductive tract. Consequently, increasing evidence shows that deregulated uterine miRNA expression underpins a spectrum of common reproductive disorders, ranging from implantation failure to endometriosis. Furthermore, by targeting FOXO transcription factors and other key regulators of tissue homeostasis, oncogenic endometrial miRNAs promote tumourigenesis and cancer progression.

FOXO3a represses VEGF expression through FOXM1-dependent and -independent mechanisms in breast cancer

Vascular endothelial growth factor (VEGF) plays a central role in breast cancer development and progression, but the mechanisms that control its expression are poorly understood. Breast cancer tissue microarrays revealed an inverse correlation between the Forkhead transcription factor FOXO3a and VEGF expression. Using the lapatinib-sensitive breast cancer cell lines BT474 and SKBR3 as model systems, we tested the possibility that VEGF expression is negatively regulated by FOXO3a. Lapatinib treatment of BT474 or SKBR3 cells resulted in nuclear translocation and activation of FOXO3a, followed by a reduction in VEGF expression. Transient transfection and inducible expression experiments showed that FOXO3a represses the proximal VEGF promoter whereas another forkhead member, FOXM1, induces VEGF expression. Chromatin immunoprecipitation and oligonucleotide pull-down assays demonstrated that both FOXO3a and FOXM1 bind a consensus Forkhead response element (FHRE) in the VEGF promoter. Upon lapatinib stimulation, activated FOXO3a displaces FOXM1 bound to the FHRE before recruiting histone deacetylase 2 (HDAC2) to the promoter, leading to decreased histones H3 and H4 acetylation, and concomitant transcriptional inhibition of VEGF. These results show that FOXO3a-dependent repression of target genes in breast cancer cells, such as VEGF, involves competitive displacement of DNA-bound FOXM1 and active recruitment of transcriptional repressor complexes.

Role of GILZ in immune regulation, glucocorticoid actions and rheumatoid arthritis

Glucocorticoids have been exploited therapeutically for more than six decades through the use of synthetic glucocorticoids as anti-inflammatory agents, and are still used in as many as 50% of patients suffering from inflammatory diseases such as rheumatoid arthritis (RA). Better understanding of the mechanisms of action of glucocorticoids could enable the development of therapies that dissociate the broad-spectrum benefits of glucocorticoids from their adverse metabolic effects. The glucocorticoid-induced leucine zipper protein (GILZ; also known as TSC22 domain family protein 3) is a glucocorticoid-responsive molecule whose interactions with signal transduction pathways, many of which are operative in RA and other inflammatory diseases, suggest that it is a key endogenous regulator of the immune response. The overlap between the observed effects of GILZ on the immune system and those of glucocorticoids strongly suggest GILZ as a critical mediator of the therapeutic effects of glucocorticoids. Observations of the immunomodulatory effects of GILZ in human RA synovial cells, and in an in vivo model of RA, support the hypothesis that GILZ is a key glucocorticoid-induced regulator of inflammation in RA. Moreover, evidence that the effect of GILZ on bone loss might be in contrast to those of glucocorticoids suggests manipulation of GILZ as a potential means of dissociating the beneficial anti-inflammatory effects of glucocorticoids from their negative metabolic repercussions.

Histone deacetylase inhibitors suppress inflammatory activation of rheumatoid arthritis patient synovial macrophages and tissue

Macrophages contribute significantly to the pathology of many chronic inflammatory diseases, including rheumatoid arthritis (RA), asthma, and chronic obstructive pulmonary disease. Macrophage activation and survival are tightly regulated by reversible acetylation and deacetylation of histones, transcription factors, and structural proteins. Although histone deacetylase (HDAC) inhibitors (HDACis) demonstrate therapeutic effects in animal models of chronic inflammatory disease, depressed macrophage HDAC activity in patients with asthma, chronic obstructive pulmonary disease, or RA may contribute to inflammation in these diseases, potentially contraindicating the therapeutic administration of HDACis. In this study, we directly examined whether HDACis could influence the activation of macrophages derived from the inflamed joints of patients with RA. We found that inhibition of class I/II HDACs or class III sirtuin HDACs potently blocked the production of IL-6 and TNF-alpha by macrophages from healthy donors and patients with RA. Two HDACis, trichostatin A and nicotinamide, selectively induced macrophage apoptosis associated with specific downregulation of the antiapoptotic protein Bfl-1/A1, and inflammatory stimuli enhanced the sensitivity of macrophages to HDACi-induced apoptosis. Importantly, inflammatory and angiogenic cytokine production in intact RA synovial biopsy explants was also suppressed by HDACis. Our study identifies redundant, but essential, roles for class I/II and sirtuin HDACs in promoting inflammation, angiogenesis, and cell survival in RA.

PI3K p110delta regulates T-cell cytokine production during primary and secondary immune responses in mice and humans

We have previously described critical and nonredundant roles for the phosphoinositide 3-kinase p110delta during the activation and differentiation of naive T cells, and p110delta inhibitors are currently being developed for clinical use. However, to effectively treat established inflammatory or autoimmune diseases, it is important to be able to inhibit previously activated or memory T cells. In this study, using the isoform-selective inhibitor IC87114, we show that sustained p110delta activity is required for interferon-gamma production. Moreover, acute inhibition of p110delta inhibits cytokine production and reduces hypersensitivity responses in mice. Whether p110delta played a similar role in human T cells was unknown. Here we show that IC87114 potently blocked T-cell receptor-induced phosphoinositide 3-kinase signaling by both naive and effector/memory human T cells. Importantly, IC87114 reduced cytokine production by memory T cells from healthy and allergic donors and from inflammatory arthritis patients. These studies establish that previously activated memory T cells are at least as sensitive to p110delta inhibition as naive T cells and show that mouse models accurately predict p110delta function in human T cells. There is therefore a strong rationale for p110delta inhibitors to be considered for therapeutic use in T-cell-mediated autoimmune and inflammatory diseases.

Targeting histone deacetylase activity in rheumatoid arthritis and asthma as prototypes of inflammatory disease: should we keep our HATs on?

Cellular activation, proliferation and survival in chronic inflammatory diseases is regulated not only by engagement of signal trans-duction pathways that modulate transcription factors required for these processes, but also by epigenetic regulation of transcription factor access to gene promoter regions. Histone acetyl trans-ferases coordinate the recruitment and activation of transcription factors with conformational changes in histones that allow gene promoter exposure. Histone deacetylases (HDACs) counteract histone acetyl transferase activity through the targeting of both histones as well as nonhistone signal transduction proteins important in inflammation. Numerous studies have indicated that depressed HDAC activity in patients with inflammatory airway diseases may contribute to local proinflammatory cytokine production and diminish patient responses to corticosteroid treatment. Recent observations that HDAC activity is depressed in rheumatoid arthritis patient synovial tissue have predicted that strategies restoring HDAC function may be therapeutic in this disease as well. Pharmacological inhibitors of HDAC activity, however, have demonstrated potent therapeutic effects in animal models of arthritis and other chronic inflammatory diseases. In the present review we assess and reconcile these outwardly paradoxical study results to provide a working model for how alterations in HDAC activity may contribute to pathology in rheumatoid arthritis, and highlight key questions to be answered in the preclinical evaluation of compounds modulating these enzymes.

Foxo in the immune system

In addition to their key roles in cellular survival, death, proliferation and metabolism, the Foxo subfamily of forkhead (Fox) transcription factors play critical roles in the homeostasis of immune-relevant cells, including T cells, B cells, neutrophils and other non-lymphoid lineages that modulate inflammation in disease states such as inflammatory arthritis and systemic lupus erythematosus. This review summarizes such current and expanding knowledge of the Foxo family members in immunity, and their potential as therapeutic targets in inflammatory disease.

Immune regulation by Foxo transcription factors

The Foxo subfamily of forkhead (Fox) transcription factors are mammalian homologues of the Caenorhabditis elegans DAF-16 longevity gene, and play key roles in cellular and organism survival, death, proliferation and metabolism. A growing body of evidence indicates that Foxo proteins furthermore play critical roles in immune cell homeostasis, modulating inflammation in some disease states such as inflammatory arthritis and systemic lupus erythematosus (SLE), via fundamental roles in T cells, B cells, neurophils and other myeloid lineages. This review summarizes current knowledge of the Foxo family members in general and in immunity, including their potential use as therapeutic targets.

The role of Ras signaling in lupus T lymphocytes: biology and pathogenesis

Ras is a GTP-binding protein that plays multiple important roles in cell activation, including proliferative and inflammatory responses. Ras regulation is complex and depends upon post-translational processing, organelle-specific localization and the activation/deactivation of Ras by a number of regulatory molecules. Ras activation in T lymphocytes demonstrates unique features, including its dependence on the T cell receptor and the ability of Ras to signal from both the plasma membrane and the Golgi. Abnormalities of Ras expression, activation and signaling pathways in T lymphocytes appear to play important roles in the development of autoimmunity in general, and systemic lupus erythematosus in particular. In this manuscript, we review the basic biology of Ras in T lymphocytes, and the ways in which T lymphocyte Ras abnormalities may contribute to the development of a lupus phenotype.

P-selectin primes leukocyte integrin activation during inflammation

Selectins mediate leukocyte rolling and prime leukocytes for integrin-mediated leukocyte adhesion. However, neither the in vivo importance of nor the signaling pathway by which selectin-mediated integrin activation occurs has been determined. We report here that P-selectin-deficient mice manifested impaired leukocyte adhesion, which was 'rescued' by soluble P-selectin. Mechanistically, the cytoplasmic domain of P-selectin glycoprotein ligand 1 formed a constitutive complex with Nef-associated factor 1. After binding of P-selectin, Src kinases phosphorylated Nef-associated factor 1, which recruited the phosphoinositide-3-OH kinase p85-p110delta heterodimer and resulted in activation of leukocyte integrins. Inhibition of this signal-transduction pathway diminished the adhesion of leukocytes to capillary venules and suppressed peritoneal infiltration of leukocytes. Our data demonstrate the functional importance of this newly identified signaling pathway mediated by P-selectin glycoprotein ligand 1.

Inhibition of forkhead box class O family member transcription factors in rheumatoid synovial tissue

OBJECTIVE

Phosphatidylinositol 3-kinase-dependent activation of protein kinase B (PKB) has been observed in rheumatoid arthritis (RA) synovial tissue, and mechanisms that interfere with this process are protective in animal models of arthritis. PKB can regulate cell survival and proliferation via phosphorylation-dependent inactivation of forkhead box class O (FoxO) transcription factors. The present study was undertaken to examine whether FoxO transcription factors are differentially inactivated in RA synovial tissue, and whether this inactivation correlates with laboratory and clinical parameters of disease activity.

METHODS

The expression and phosphorylation of FoxO family members were assessed in synovial biopsy tissue from 12 patients with RA and 9 patients with inflammatory osteoarthritis (OA), by immunohistochemistry and quantitative computer-assisted image analysis. Immunoblotting was used to assess the interleukin-1beta (IL-1beta)- and tumor necrosis factor alpha (TNFalpha)-induced phosphorylation of FoxO1 and FoxO4 in cultured fibroblast-like synoviocytes (FLS) and macrophages.

RESULTS

FoxO1, FoxO3a, and FoxO4 were expressed and phosphorylated in synovial tissue from both RA patients and OA patients. In RA synovial tissue, phosphorylation of FoxO1 was observed in both FLS and macrophages, FoxO3a in T lymphocytes, and FoxO4 in macrophages alone. Following stimulation with IL-1beta and TNFalpha, FoxO1 and FoxO4 were phosphorylated in both RA and OA FLS and synovial macrophages, respectively. Inactivation of FoxO4 was significantly enhanced in the RA as compared with the OA synovial sublining. There was a strong negative correlation between inactivation of FoxO4 in RA synovial tissue and increased serum C-reactive protein levels and a raised erythrocyte sedimentation rate in RA patients.

CONCLUSION

All 3 FoxO family members examined were phosphorylated in both RA and OA synovial tissue; in particular, inactivation of FoxO4 was significantly enhanced in macrophages from RA synovial tissue. Thus, cell-specific inactivation of FoxO family members appears to differentially regulate cell survival and proliferation in the RA synovium.