The discovery of novel experimental therapies for inflammatory arthritis. Mediators Inflamm. 2009;2009:698769. [PMID: 20339519 PMCID: PMC2842969 DOI: 10.1155/2009/698769]

HEV ORF3 downregulatesCD14 and CD64 to impair macrophages phagocytosis through inhibiting JAK/STAT pathway

Hepatitis E virus (HEV) could induce chronic hepatitis and liver failure with high mortality through unknown mechanisms. The previous study showed that the HEV open reading frames 3 (ORF3) could inhibit macrophages inflammatory response. Impaired macrophages phagocytosis was also found in patients infected with HEV and its nucleic acids could be detected in macrophages. To elucidate the role of HEV ORF3 on phagocytosis, the phagocytosis activation was measured by phagocytosis test, flow cytometry, and phalloidin staining. Meanwhile, the expression of key phagocytic receptors and the activation of transduction pathway were investigated by using reverse transcription real-time quantitative polymerase chain reaction (RT-qPCR) and Western blot analysis. Results of phagocytosis test showed that the HEV ORF3 could significantly impair the absorption capacity of latex beads. Furthermore, results of RT-qPCR and Western blot analysis showed that the expression of CD14 and CD64 decreased. Afterward, the present study showed that the activation of Janus kinase-signal transducer and activator of transcription (JAK/STAT) signaling pathway was inhibited by HEV ORF3 and downregulation of CD14 and CD64 could be reversed by interferon γ, one activator of the JAK1/STAT1 signaling pathway. In conclusion, HEV ORF3 could significantly impair the phagocytosis of macrophage by downregulating expression of CD14 and CD64, which may function by inhibiting the activation of the JAK1/STAT1 signaling pathway.

The role of PI3K/AKT/FOXO signaling in psoriasis

Phosphatidylinositol 3-kinase (PI3K) and protein kinase B (AKT) signaling pathway play a central role in multiple cellular functions such as cell proliferation and survival. The forkhead box O (FOXO) transcription factors are negatively regulated by the PI3K/AKT signaling pathway and considered to have inhibitory effect on cell proliferation. Psoriasis is a multifactorial disease with a strong genetic background and characterized by hyperproliferative keratinocyte. PI3K signaling regulates proliferation of keratinocyte by activating AKT and other targets, and by inducing FOXO downregulation. The amplification of PI3K and AKT and the loss of the FOXO are gradually being recognized in psoriatic lesions. The upstream and downstream of PI3K/AKT signaling molecules such as tumor suppressor phosphatase and tensin homolog (PTEN) and mammalian target of Rapamycin (mTOR), respectively, are also frequently altered in psoriasis. In this review, we highlight the recent studies on the roles and mechanisms of PI3K and AKT in regulating hyperproliferation of keratinocyte, and the roles of the downstream targets FOXO in psoriasis. Finally, we summarized that PI3K/AKT/FOXO signaling and its upstream and downstream molecule which could be underlying therapeutic target for psoriasis. This article is part of a special issue entitled: PI3K-AKT-FOXO axis in psoriasis.

The PI3K/Akt/PTEN/mTOR pathway: a fruitful target for inducing cell death in rheumatoid arthritis?

PI3K/Akt/mTOR signaling regulates diverse cellular processes. Abnormal PI3K/Akt/mTOR signaling is a characteristic feature of cancer. As such inhibition of PI3K/Akt/mTOR signaling using small molecule inhibitors has been a focus of recently developed anticancer drugs. Rheumatoid arthritis and psoriatic arthritis are autoimmune-mediated inflammatory diseases. PI3K signaling could now be targeted to determine its contribution to rheumatoid and psoriatic arthritis where deregulated proliferation and aberrant survival of activated immune cells, macrophages, monocytes, dendritic cells and synovial fibroblasts significantly overlap with abnormal growth of cancer cells. The results of some recent studies in psoriatic arthritis using PI3K signaling inhibitors suggests that small molecule inhibitor strategies directed at PI3K signaling may be a useful future therapy for immune-mediated arthritis.

MicroRNA Regulation of Epithelial to Mesenchymal Transition

Epithelial to mesenchymal transition (EMT) is a central regulatory program that is similar in many aspects to several steps of embryonic morphogenesis. In addition to its physiological role in tissue repair and wound healing, EMT contributes to chemo resistance, metastatic dissemination and fibrosis, amongst others. Classically, the morphological change from epithelial to mesenchymal phenotype is characterized by the appearance or loss of a group of proteins which have come to be recognized as markers of the EMT process. As with all proteins, these molecules are controlled at the transcriptional and translational level by transcription factors and microRNAs, respectively. A group of developmental transcription factors form the backbone of the EMT cascade and a large body of evidence shows that microRNAs are heavily involved in the successful coordination of mesenchymal transformation and vice versa, either by suppressing the expression of different groups of transcription factors, or otherwise acting as their functional mediators in orchestrating EMT. This article dissects the contribution of microRNAs to EMT and analyzes the molecular basis for their roles in this cellular process. Here, we emphasize their interaction with core transcription factors like the zinc finger enhancer (E)-box binding homeobox (ZEB), Snail and Twist families as well as some pluripotency transcription factors.

Protein kinase small molecule inhibitors for rheumatoid arthritis: Medicinal chemistry/clinical perspectives

Medicinal chemistry strategies have contributed to the development, experimental study of and clinical trials assessment of the first type of protein kinase small molecule inhibitor to target the Janus kinase/Signal Transducers and Activators of Transcription (JAK/STAT) signaling pathway. The orally administered small molecule inhibitor, tofacitinib, is the first drug to target the JAK/STAT pathway for entry into the armamentarium of the medical therapy of rheumatoid arthritis. The introduction of tofacitinib into general rheumatologic practice coupled with increasing understanding that additional cellular signal transduction pathways including the mitogen-activated protein kinase and phosphatidylinositide-3-kinase/Akt/mammalian target of rapamycin pathways as well as spleen tyrosine kinase also contribute to immune-mediated inflammatory in rheumatoid arthritis makes it likely that further development of orally administered protein kinase small molecule inhibitors for rheumatoid arthritis will occur in the near future.

Myrsine seguinii ethanolic extract and its active component quercetin inhibit macrophage activation and peritonitis induced by LPS by targeting to Syk/Src/IRAK-1

ETHNOPHARMACOLOGICAL RELEVANCE

Myrsine seguinii H. LÉVEILLÉ (syn. Rapanea neriifolia) (Myrsinaceae) is a medicinal plants traditionally used in Myanmar to treat infectious and inflammatory diseases. Since none of reports have systematically demonstrated the anti-inflammatory activity of this plant, we aimed to mechanistically understand the regulatory roles of the plant in inflammatory responses using the ethanolic extract of Myrsine seguinii (Ms-EE).

MATERIALS AND METHODS

Activated macrophages and peritonitis symptoms induced by lipopolysaccharide (LPS) were employed. HPLC analysis was used to identify active components. To characterize direct target enzymes, kinase assay was established.

RESULTS

Ms-EE inhibited the production of nitric oxide (NO) and prostaglandin (PG)E2 in RAW264.7 cells and peritoneal macrophages stimulated by LPS. This extract suppressed the mRNA expression of the inducible NO synthase (iNOS) and cyclooxygenase (COX)-2 genes by down-regulating the activation of nuclear factor (NF)-κB and activator protein (AP-1). Interestingly, it was found that Ms-EE can directly suppress the enzyme activities of Syk, Src, and interleukin-1 receptor-associated kinase-1 (IRAK-1). Similarly, orally administered Ms-EE inhibited the phosphorylation of Src and Syk in peritoneal exudate-derived cells prepared from peritonitis. Finally, HPLC analysis clearly demonstrated that quercetin is a major active component with suppressing activity on the release of inflammatory mediators (NO and PGE2), and the enzyme activities of Src, Syk, and IRAK-1.

CONCLUSION

Ms-EE containing quercetin negatively modulates macrophage-mediated in vitro inflammatory responses and LPS-induced peritonitis by blocking the Src/Syk/NF-κB and IRAK-1/AP-1 pathways, which contributes to its major ethnopharmacological use as an anti-inflammatory herbal medicine.

Prospects for treating osteoarthritis: enzyme-protein interactions regulating matrix metalloproteinase activity

Primary osteoarthritis (OA) is a musculoskeletal disorder of unknown etiology. OA is characterized by an imbalance between anabolism and catabolism in, and altered homeostasis of articular cartilage. Matrix metalloproteinases (MMPs) and a disintegrin and metalloproteinase with thrombospondin motif are upregulated in OA joints. Extracellular matrix (ECM) proteins are critical for resistance to compressive forces and for maintaining the tensile properties of the tissue. Tissue inhibitor of metalloproteinases (TIMPs) is the endogenous inhibitor of MMPs, but in OA, TIMPs do not effectively neutralize MMP activity. Upregulation of MMP gene expression occurs in OA in a milieu of proinflammatory cytokines such as interleukin (IL)-1, IL-6 and tumor necrosis factor α. Presently, the medical therapy of OA includes mainly nonsteroidal anti-inflammatory drugs and corticosteroids which dampen pain and inflammation but appear to have little effect on restoring joint function. Experimental interventions to restore the imbalance between anabolism and catabolism include small molecule inhibitors of MMP subtypes or inhibitors of the interaction between IL-1 and its receptor. Although these agents have some positive effects on reducing MMP subtype activity they have little efficacy at the clinical level. MMP-9 is one MMP subtype implicated in the degradation of articular cartilage ECM proteins. MMP-9 was found in OA synovial fluid as a complex with neutrophil gelatinase-associated lipocalin (NGAL) which protected MMP-9 from autodegradation. Suppressing NGAL synthesis or promoting NGAL degradation may result in reducing the activity of MMP-9. We also propose initiating a search for enzyme-protein interactions to dampen other MMP subtype activity which could suppress ECM protein breakdown.

CC chemokine receptors and chronic inflammation--therapeutic opportunities and pharmacological challenges

Chemokines are a family of low molecular weight proteins with an essential role in leukocyte trafficking during both homeostasis and inflammation. The CC class of chemokines consists of at least 28 members (CCL1-28) that signal through 10 known chemokine receptors (CCR1-10). CC chemokine receptors are expressed predominantly by T cells and monocyte-macrophages, cell types associated predominantly with chronic inflammation occurring over weeks or years. Chronic inflammatory diseases including rheumatoid arthritis, atherosclerosis, and metabolic syndrome are characterized by continued leukocyte infiltration into the inflammatory site, driven in large part by excessive chemokine production. Over years or decades, persistent inflammation may lead to loss of tissue architecture and function, causing severe disability or, in the case of atherosclerosis, fatal outcomes such as myocardial infarction or stroke. Despite the existence of several clinical strategies for targeting chronic inflammation, these diseases remain significant causes of morbidity and mortality globally, with a concomitant economic impact. Thus, the development of novel therapeutic agents for the treatment of chronic inflammatory disease continues to be a priority. In this review we introduce CC chemokine receptors as critical mediators of chronic inflammatory responses and explore their potential role as pharmacological targets. We discuss functions of individual CC chemokine receptors based on in vitro pharmacological data as well as transgenic animal studies. Focusing on three key forms of chronic inflammation--rheumatoid arthritis, atherosclerosis, and metabolic syndrome--we describe the pathologic function of CC chemokine receptors and their possible relevance as therapeutic targets.

Intracellular Signaling Pathways in Rheumatoid Arthritis

Dysfunctional intracellular signaling involving deregulated activation of the Janus Kinase/Signal Transducers and Activators of Transcription (JAK/STAT) and "cross-talk" between JAK/STAT and the stress-activated protein kinase/mitogen-activated protein kinase (SAPK/MAPK) and Phosphatidylinositide-3-Kinase/AKT/mammalian Target of Rapamycin (PI-3K/AKT/mTOR) pathways play a critical role in rheumatoid arthritis. This is exemplified by immune-mediated chronic inflammation, up-regulated matrix metalloproteinase gene expression, induction of articular chondrocyte apoptosis and "apoptosis-resistance" in rheumatoid synovial tissue. An important consideration in the development of novel therapeutics for rheumatoid arthritis will be the extent to which inhibiting these signal transduction pathways will sufficiently suppress immune cell-mediated inflammation to produce a lasting clinical remission and halt the progression of rheumatoid arthritis pathology. In that regard, the majority of the evidence accumulated over the past decade indicated that merely suppressing pro-inflammatory cytokine-mediated JAK/ STAT, SAPK/MAPK or PI-3K/AKT/mTOR activation in RA patients may be necessary but not sufficient to result in clinical improvement. Thus, targeting aberrant enzyme activities of spleen tyrosine kinase, sphingosine kinases-1, -2, transforming growth factor β-activated kinase-1, bone marrow kinase, and nuclear factor-κB-inducing kinase for intervention may also have to be considered.