Chromatin damage generated by DNA intercalators leads to degradation of RNA Polymerase II.

In cancer therapy, DNA intercalators are mainly known for their capacity to kill cells by inducing DNA damage. Recently, several DNA intercalators have attracted much interest given their ability to inhibit RNA Polymerase I transcription (BMH-21), evict histones (Aclarubicin) or induce chromatin trapping of FACT (Curaxin CBL0137). Interestingly, these DNA intercalators lack the capacity to induce DNA damage while still retaining cytotoxic effects and stabilize p53. Herein, we report that these DNA intercalators impact chromatin biology by interfering with the chromatin stability of RNA polymerases I, II and III. These three compounds have the capacity to induce degradation of RNA polymerase II and they simultaneously enable the trapping of Topoisomerases TOP2A and TOP2B on the chromatin. In addition, BMH-21 also acts as a catalytic inhibitor of Topoisomerase II, resembling Aclarubicin. Moreover, BMH-21 induces chromatin trapping of the histone chaperone FACT and propels accumulation of Z-DNA and histone eviction, similarly to Aclarubicin and CBL0137. These DNA intercalators have a cumulative impact on general transcription machinery by inducing accumulation of topological defects and impacting nuclear chromatin. Therefore, their cytotoxic capabilities may be the result of compounding deleterious effects on chromatin homeostasis.

Downregulated eosinophil activity in ulcerative colitis with concomitant primary sclerosing cholangitis.

Primary sclerosing cholangitis (PSC) is a chronic bile duct inflammation strongly connected to ulcerative colitis (UC). PSC is associated with an increased risk of colon cancer, but the link between the intestinal and the bile duct inflammation is still unknown. Also, the involvement of intestinal immune cells in the pathogenesis of PSC remains to be determined. The eosinophil granulocyte is one of the immune cells implicated in the inflammatory process of ulcerative colitis. This study was performed to determine how the accumulation and activation of intestinal eosinophils may differ between UC with and without concomitant PSC, and how this may be influenced by the cytokine/chemokine profile of the intestinal compartment. Eosinophils from peripheral blood and multiple parts of the colon were analyzed by flow cytometry. The intestinal level of inflammatory mediators was assessed using a multiplex proximity extension assay and a quantitative immunoassay. We found that colonic eosinophils were more abundant in both UC and PSC-UC compared with controls, but that their expression of activation markers was significantly increased in UC only. The colonic level of pro-inflammatory cytokines was increased in active UC but not in PSC-UC. In conclusion, we show for the first time that eosinophil activation phenotype discriminates between UC and PSC-UC, and that this may depend on the local cytokine profile of the colonic mucosa.