Synthesis and biological evaluation of novel cytoprotective heterocycles

The small heterocyclic compounds pifithrin-alpha, also called PFT-alpha (1), and its closed-ring counterpart IBT ( 2) have been described in the literature as p53 and STAT6 inhibitors, respectively. We investigated both events and prepared novel compounds, structurally related to 1 and 2, with enhanced bioactivity.; IL-4 and IL-13 signaling through the STAT6 pathway are crucial cytokines for the regulation of protective immune responses. Moreover, recent data indicates that they inhibit apoptosis in malignant B cells and other cancer cells. Using various survival/proliferation assays we report that certain of our compounds induce death in chronic lymphocytic leukemia (CLL) and Hodgkin's lymphoma (HL) cells by inhibiting the IL-4/IL-13 pathway linked to the enhanced survival of the malignant cells. Moreover, we confirm the relationship to this pathway by showing a decrease in expression of the STAT6-dependent 12/15-lipoxygenase (-LOX) gene by our compounds.; The chemoprotection of cells from apoptosis induced by toxins or ionizing radiation could be important for biodefense, and in the treatment of acute injuries. We report that some of our small heterocyclic analogs, including fused benzothiazoles, benzimidazoles and related compounds, abrogated thymocyte apoptosis induced by dexamethasone and gamma-irradiation. Optimization of the structure, based on the findings from our screen, lead to the preparation of several compounds that showed increased bioactivity. In general, the PFT-alpha and aromatic IBT analogs were less inherently toxic to mouse thymocytes and had greater cytoprotective ability than other isosteric ring systems. However, the most potent compound was a quinolinium salt (95), which was at least 300 fold more potent than the reference compound PFT-alpha, with an IC50 value of 0.013 muM compared to 4.16 muM for 1 in the DEX-induced apoptosis assay. Those compounds also provided significant protection against gamma-radiation-induced apoptosis of thymocytes and protected mice from gamma-radiation.; Investigation of the mechanism of action of these novel compounds lead us to examine the Bcl2-family proteins, especially the BH3-only protein PUMA, linked to both glucocorticoid (p53-independent) and the gamma-radiation (p53-dependent) apoptosis pathways. We report here that the induction of PUMA expression by either stimulus can be inhibited by our compounds, enhancing cell survival.