NF-κB dependent anti-inflammatory activity of chlorojanerin isolated from Saussurea heteromalla.

Medicinal plants have shown great promise as a source of novel drug compounds for the treatment of inflammatory disorders. In our search for new entities with anti-inflammatory potential, the extracts of the whole plant of Saussurea heteromalla (family-Asteraceae), collected from Himalayas, were evaluated in the high throughput screen for TNF-α and IL-6 inhibitors. The extract blocked TNF-α and IL-6 production in LPS stimulated THP-1 cells (human acute monocyte leukemia cell line) completely at 10 and 30 µg/ml. The plant has been found as a new source of chlorojanerin, a guaianolide type of sesquiterpene lactone. Chlorojanerin was shown to be significantly effective in inhibiting TNF-α and IL-6 production in LPS-stimulated THP-1 cells (IC(50)=2.3±0.2 µM and 1.8±0.7 µM respectively). The compound also blocked TNF-α and IL-6 production from LPS-stimulated human monocytes (IC(50)=1.5±0.4 and 0.7±0.2 µM respectively) and synovial cells from a patient with rheumatoid arthritis (IC(50)<0.03 and 0.5 µM respectively). Transcriptional profiling of the LPS stimulated THP-1 cells revealed that chlorojanerin exerted its anti-inflammatory effect by inhibiting the expression of 8 genes involved in activating the transcription factor - NF-κB. Real time analysis of these genes validated the effect of chlorojanerin on the classical downstream targets of NF-κB. Thus, this study clearly delineated 8 genes which were specifically mitigated due to the effect of chlorojanerin on NF-κB induced signaling at the mRNA level. Further, chlorojanerin at 5 µM also inhibited the binding of NF-κB in a GFP reporter assay system by 55.5% thus validating the microarray gene expression data. This work is a step towards the isolation and characterization of lead anti-inflammatory agents from the extract of Saussurea heteromalla, which can be developed into better therapeutic molecules targeted towards some specific inflammatory diseases.

Diversity in the C3b [corrected] contact residues and tertiary structures of the staphylococcal complement inhibitor (SCIN) protein family.

To survive in immune-competent hosts, the pathogen Staphylococcus aureus expresses and secretes a sophisticated array of proteins that inhibit the complement system. Among these are the staphylococcal complement inhibitors (SCIN), which are composed of three active proteins (SCIN-A, -B, and -C) and one purportedly inactive member (SCIN-D or ORF-D). Because previous work has focused almost exclusively on SCIN-A, we sought to provide initial structure/function information on additional SCIN proteins. To this end we determined crystal structures of an active, N-terminal truncation mutant of SCIN-B (denoted SCIN-B18-85) both free and bound to the C3c fragment of complement component C3 at 1.5 and 3.4 Å resolution, respectively. Comparison of the C3c/SCIN-B18-85 structure with that of C3c/SCIN-A revealed that both proteins target the same functional hotspot on the C3b/C3c surface yet harbor diversity in both the type of residues and interactions formed at their C3b/C3c interfaces. Most importantly, these structures allowed identification of Arg44 and Tyr51 as residues key for SCIN-B binding to C3b and subsequent inhibition of the AP C3 convertase. In addition, we also solved several crystal structures of SCIN-D to 1.3 Å limiting resolution. This revealed an unexpected structural deviation in the N-terminal α helix relative to SCIN-A and SCIN-B. Comparative analysis of both electrostatic potentials and surface complementarity suggest a physical explanation for the inability of SCIN-D to bind C3b/C3c. Together, these studies provide a more thorough understanding of immune evasion by S. aureus and enhance potential use of SCIN proteins as templates for design of complement targeted therapeutics.

A preferential p110alpha/gamma PI3K inhibitor attenuates experimental inflammation by suppressing the production of proinflammatory mediators in a NF-kappaB-dependent manner.

A promising therapeutic approach to diminish pathological inflammation is to inhibit the increased production and/or biological activity of proinflammatory cytokines (e.g., TNF-alpha, IL-6). The production of proinflammatory cytokines is controlled at the gene level by the activity of transcription factors, such as NF-kappaB. Phosphatidylinositol 3-kinase (PI3K), a lipid kinase, is known to induce the activation of NF-kappaB. Given this, we hypothesized that inhibitors of PI3K activation would demonstrate anti-inflammatory potential. Accordingly, we studied the effects of a preferential p110alpha/gamma PI3K inhibitor (compound 8C; PIK-75) in inflammation-based assays. Mechanism-based assays utilizing human cells revealed that PIK-75-mediated inhibition of PI3K activation is associated with dramatic suppression of downstream signaling events, including AKT phosphorylation, IKK activation, and NF-kappaB transcription. Cell-based assays revealed that PIK-75 potently and dose dependently inhibits in vitro and in vivo production of TNF-alpha and IL-6, diminishes the induced expression of human endothelial cell adhesion molecules (E-selectin, ICAM-1, and VCAM-1), and blocks human monocyte-endothelial cell adhesion. Most importantly, PIK-75, when administered orally in a therapeutic regimen, significantly suppresses the macroscopic and histological abnormalities associated with dextran sulfate sodium-induced murine colitis. The efficacy of PIK-75 in attenuating experimental inflammation is mediated, at least in part, due to the downregulation of pertinent inflammatory mediators in the colon. Collectively, these results provide first evidence that PIK-75 possesses anti-inflammatory potential. Given that PIK-75 is known to exhibit anti-cancer activity, the findings from this study thus reinforce the cross-therapeutic functionality of potential drugs.

A fluorinated analog of ISO-1 blocks the recognition and biological function of MIF and is orally efficacious in a murine model of colitis.

A promising therapeutic approach to diminish pathological inflammation is to inhibit the synthesis and/or biological activity of macrophage migration inhibitory factor (MIF). Prior studies have shown that intraperitoneal administration of small-molecule inhibitors targeting the catalytic pocket of MIF (e.g., ISO-1) elicits a therapeutic effect in mouse inflammation models. However, it remains to be elucidated whether these tautomerase activity inhibitors block the synthesis and/or biological activity of MIF. In this study, we investigated and compared the activity of representative MIF inhibitors from isoxazole series (fluorinated analog of ISO-1; ISO-F) and substituted quinoline series (compound 7E; 7E). Our results demonstrate that ISO-F is a more potent MIF inhibitor than 7E. Both ISO-F and 7E do not inhibit MIF synthesis but "bind-onto" MIF thereby blocking its recognition. However, in contrast to 7E, ISO-F docks well in the active site of MIF and also has a stronger binding affinity towards MIF. In line with these observations, ISO-F, but not 7E, robustly inhibits the biological function of MIF. Most importantly, ISO-F, when administered orally in a therapeutic regimen, significantly suppresses dextran sulphate sodium (DSS)-induced murine colitis. This study, which provides mechanistic insights into the anti-inflammatory efficacy of ISO-F, is the first documented report of in vivo anti-inflammatory efficacy of a MIF inhibitor upon oral administration. Moreover, the findings from this study reinforce the potential of catalytic site of MIF as a target for eliciting therapeutic effect in inflammatory disorders. Compounds (e.g., ISO-F) that block not only the recognition but also the biological function of MIF are potentially attractive for reducing pathological inflammation.