Is chymase 1 a therapeutic target in cardiovascular disease?

INTRODUCTION

Non-angiotensin converting enzyme mechanisms of angiotensin II production remain underappreciated in part due to the success of current therapies to ameliorate the impact of primary hypertension and atherosclerotic diseases of the heart and the blood vessels. This review scrutinize the current literature to highlight chymase role as a critical participant in the pathogenesis of cardiovascular disease and heart failure.

AREAS COVERED

We review the contemporaneous understanding of circulating and tissue biotransformation mechanisms of the angiotensins focusing on the role of chymase as an alternate tissue generating pathway for angiotensin II pathological mechanisms of action.

EXPERT OPINION

While robust literature documents the singularity of chymase as an angiotensin II-forming enzyme, particularly when angiotensin converting enzyme is inhibited, this knowledge has not been fully recognized to clinical medicine. This review discusses the limitations of clinical trials' that explored the benefits of chymase inhibition in accounting for the failure to duplicate in humans what has been demonstrated in experimental animals.

Development and experimental test of support vector machines virtual screening method for searching Src inhibitors from large compound libraries

BACKGROUND

Src plays various roles in tumour progression, invasion, metastasis, angiogenesis and survival. It is one of the multiple targets of multi-target kinase inhibitors in clinical uses and trials for the treatment of leukemia and other cancers. These successes and appearances of drug resistance in some patients have raised significant interest and efforts in discovering new Src inhibitors. Various in-silico methods have been used in some of these efforts. It is desirable to explore additional in-silico methods, particularly those capable of searching large compound libraries at high yields and reduced false-hit rates.

RESULTS

We evaluated support vector machines (SVM) as virtual screening tools for searching Src inhibitors from large compound libraries. SVM trained and tested by 1,703 inhibitors and 63,318 putative non-inhibitors correctly identified 93.53%~ 95.01% inhibitors and 99.81%~ 99.90% non-inhibitors in 5-fold cross validation studies. SVM trained by 1,703 inhibitors reported before 2011 and 63,318 putative non-inhibitors correctly identified 70.45% of the 44 inhibitors reported since 2011, and predicted as inhibitors 44,843 (0.33%) of 13.56M PubChem, 1,496 (0.89%) of 168 K MDDR, and 719 (7.73%) of 9,305 MDDR compounds similar to the known inhibitors.

CONCLUSIONS

SVM showed comparable yield and reduced false hit rates in searching large compound libraries compared to the similarity-based and other machine-learning VS methods developed from the same set of training compounds and molecular descriptors. We tested three virtual hits of the same novel scaffold from in-house chemical libraries not reported as Src inhibitor, one of which showed moderate activity. SVM may be potentially explored for searching Src inhibitors from large compound libraries at low false-hit rates.

Inhibitory effect of eriodictyol on IgE/Ag-induced type I hypersensitivity

Mast cells are the principal effector cells involved in the allergic response, through the release of histamine. We investigated the effect of eriodictyol, derived from the painted maple and yerba santa, on mast cell degranulation and on an allergic response in an animal model. We also investigated its effect on the expression of the ceramide kinase (CERK) involved in calcium-dependent degranulation, and on ceramide activation by multiple cytokines. Eriodictyol suppressed the release of beta-hexosaminidase, a marker of degranulation, and the expression of interleukin (IL)-4 mRNA. It inhibited the expression of CERK mRNA, reduced the ceramide concentration in antigen-stimulated mast cells, and suppressed the passive cutaneous anaphylaxis (PCA) reaction in mice in a dose-dependent manner. These results suggest that eriodictyol can inhibit mast cell degranulation through inhibition of ceramide kinase, and that it might potentially serve as an anti-allergic agent.

Tryptanthrin inhibits Th2 development, and IgE-mediated degranulation and IL-4 production by rat basophilic leukemia RBL-2H3 cells

ETHNOPHARMACOLOGICAL RELEVANCE

Tryptanthrin is a compound isolated from Polygonum tinctorium, which is a known folk medicine with various biological activities.

AIM OF THE STUDY

Allergic diseases are initiated by the development of allergen-specific T helper type 2 (Th2) cells and amplified by the degranulation of and cytokine release from basophils and mast cells during an effector phase. We found that Tryptanthrin could down-regulate IL-4 production by Th2 cells, while IFN-γ production by Th1 cells was not affected. Since IL-4 produced by basophils and effector Th2 cells has been shown to play important roles in the development and amplification of Th2-dominated allergic responses, we examined the effects of Tryptanthrin on the initiation and effector phase responses of Type I allergy in vitro.

MATERIALS AND METHODS

To determine the mechanisms of Tryptanthrin-induced down-regulation of IL-4 production, the expression of Th2-specific transcription factors, c-Maf and GATA-3, was analyzed by RT-PCR. The effects of Tryptanthrin on Th cell differentiation were evaluated using CD4(+) T cells purified from spleen cells of Sugi basic protein (SBP)-immunized BALB/c mice. In primary cultures, cells were stimulated with SBP and antigen-presenting cells under neutral or Th2-skewing conditions in the presence or absence of Tryptanthrin. Cytokines produced by differentiated Th cells in secondary cultures were analyzed by ELISA. The effects of Tryptanthrin on IgE-mediated degranulation and IL-4 production were determined using rat basophilic leukemia (RBL-2H3) cells. Phosphorylation of ERK1/2 and Akt in Tryptanthrin-treated RBL-2H3 cells was analyzed to determine the mechanism of Tryptanthrin actions.

RESULTS

Tryptanthrin suppressed c-Maf mRNA expression in Th2 clone cells, and even under Th2-skewing conditions, Tryptanthrin inhibited differentiation toward the Th2 phenotype, which is an essential event for the initiation phase of allergic diseases. Tryptanthrin also inhibited the IgE-mediated degranulation of and IL-4 production by RBL-2H3 cells, probably due to inhibiting IgE-mediated signaling pathways, including the phosphorylation of ERK1/2 and Akt.

CONCLUSION

These findings suggest that Tryptanthrin effectively inhibits the effector and exacerbation responses, as well as the initiator responses, of Type I allergy. Thus, Tryptanthrin may have beneficial effects for immediate-type allergic responses.