Steroids

Head of Research Program: Jana Oklešťková
Team Members: Lucie Rárová, Miroslav Kvasnica

 

Steroids group is focused to synthesis and study of biological and immunological activities of brassinosteroids, plant and animal steroids and related compounds.

 

Brassinosteroids are involved in control of many important physiological and developmental processes, but their concentrations in plants are extremely low (pg.g^-1 fresh weight, FW). For several years we have study brassinosteroid structure-activity relationships. We try to generate a library of available and/or synthesiable brassinosteroid- like ligands and dock the prepared library into BRI1 crystal structure and evaluate their biological activities in both plant and animal systems.  The biological activities of BRs analogues in planta can be evaluated in two bioassays: the bean second internode bioassay and the pea inhibition bioassay. In the international cooperation we can study BRI1-ligand-BAK1 interaction in vitro and Brs receptor and co receptor interaction based on fluorescent BR probes. In cooperation with foreign partners, we have recently studied  BR biosynthetic pathways. Progress in plant steroids chemistry and biology would have been impossible without sensitive and specific methods for their detection in plant tissues. Series of polyclonal or monoclonal antibodies against brassinosteroids and vertebrate-type steroid hormones have been also developed and used in ELISA tests for detection of steroids in body fluids (e.g. cow milk) and for immunoaffinity chromatography (IAC). Combination of IAC with UHPLC/MS/MS can be used for determination of steroids in various plant species.

The cytotoxic effect of natural brassinosteroids and their synthetic analogues on human cancer cells derived from tumours were determined in vitro recently. The cellular and molecular mechanisms of action of these phytohormones in human cells remain unknown. Both natural brassinosteroids and their synthetic analogues could inhibit proliferation of human cancer cells, caused changes in the cell cycle or apoptosis. We have been developing assays over the past few years for the activity of BRs in human steroid receptors (AR, ER, PR, GR, MR). Based on molecular docking, we are choosing BRs analogues for testing on steroid receptors from steroid library.

Angiogenesis, the growth of new blood vessels in animals, is essential for organ growth as well as for growth of solid tumors and metastasis. Endothelial cells are the main players in angiogenesis and could be a target for antiangiogenic therapy because they are non-transformed and easily accessible to achievable concentrations of antiangiogenic agents. Vascularization of tumors plays a crucial role in cell nutrition and oxygen distribution. Tumor angiogenesis targeting in the sense of discovery of novel drugs includes inhibition of proteolytic enzymes that break down the extracellular matrix surrounding existing capillaries, inhibition of endothelial cell proliferation, migration and enhancement of tumor endothelial cell apoptosis. Potent angiogenic inhibitors capable of blocking tumor growth may have potential for the development of novel generations of anticancer drugs. Brassinosteroids and their derivatives also could inhibit proliferation, migration and tube formation of human endothelial cells HUVEC (Human Umbilical Vein Endothelial Cells. The cellular and molecular mechanisms of action of these phytohormones in animal and human cells are still unknown. Our results suggest that tested brassinosteroids are promising leads for the development of a new generation of potential anticancer drugs.