Prostaglandin E2 receptor PTGER4-expressing macrophages promote intestinal epithelial barrier regeneration upon inflammation.

OBJECTIVE: Dysfunctional resolution of intestinal inflammation and altered mucosal healing are essential features in the pathogenesis of inflammatory bowel disease (IBD). Intestinal macrophages are vital in the process of inflammation resolution, but the mechanisms underlying their mucosal healing capacity remain elusive. DESIGN: We investigated the role of the prostaglandin E2 (PGE2) receptor PTGER4 on the differentiation of intestinal macrophages in patients with IBD and mouse models of intestinal inflammation. We studied mucosal healing and intestinal epithelial barrier regeneration in Csf1r-iCre Ptger4fl/fl mice during dextran sulfate sodium (DSS)-induced colitis. The effect of PTGER4+ macrophage secreted molecules was investigated on epithelial organoid differentiation. RESULTS: Here, we describe a subset of PTGER4-expressing intestinal macrophages with mucosal healing properties both in humans and mice. Csf1r-iCre Ptger4fl/fl mice showed defective mucosal healing and epithelial barrier regeneration in a model of DSS colitis. Mechanistically, an increased mucosal level of PGE2 triggers chemokine (C-X-C motif) ligand 1 (CXCL1) secretion in monocyte-derived PTGER4+ macrophages via mitogen-activated protein kinases (MAPKs). CXCL1 drives epithelial cell differentiation and proliferation from regenerating crypts during colitis. Specific therapeutic targeting of macrophages with liposomes loaded with an MAPK agonist augmented the production of CXCL1 in vivo in conditional macrophage PTGER4-deficient mice, restoring their defective epithelial regeneration and favouring mucosal healing. CONCLUSION: PTGER4+ intestinal macrophages are essential for supporting the intestinal stem cell niche and regeneration of the injured epithelium. Our results pave the way for the development of a new class of therapeutic targets to promote macrophage healing functions and favour remission in patients with IBD.

Newly Synthesized DNA Methyltransferase Inhibitors as Radiosensitizers for Human Lung Cancer and Glioblastoma Cells.

BACKGROUND/AIM: Improvement of the efficacy of radiotherapy for lung cancer and glioblastoma is urgently needed. MATERIALS AND METHODS: We synthesized several novel DNA methyltransferase inhibitors and evaluated their potentials as possible radiosensitizers. Eleven non-nucleoside compounds were synthesized and evaluated along with one known compound using human lung cancer (A549) and glioblastoma (U373MG) cells. Cytotoxicity and radiosensitizing effects were evaluated using clonogenic assay. Sensitizer enhancement ratios at a survival fraction of 0.5 were calculated, and statistical analysis was performed using the ratio paired t-test. The inhibitory effects of three selected compounds on the activity of DNA methyltransferase 1 (DNMT1) and the pharmacokinetic profiles were analyzed. RESULTS: All twelve compounds demonstrated various levels of cytotoxicity. Of the twelve compounds, eleven and eight compounds radiosensitized A549 and U373MG cells, respectively, with at least marginal significance (p<0.10). The sensitizer enhancement ratios in A549 and U373MG ranged 1.166-2.537 and 1.083-1.743 among compounds with radiosensitizing effects, respectively. The three selected compounds inhibited DNMT1 activity by 26.5-78.5%. Elimination half-lives ranged from 0.3 to 1.3 h. CONCLUSION: Novel DNA methyltransferase inhibitors with significant radiosensitizing capacity and improved biostability were synthesized. These materials will serve as a basis for the development of novel radiosensitizers.

Radiosensitization of Glioblastoma Cells by a Novel DNA Methyltransferase-inhibiting Phthalimido-Alkanamide Derivative.

BACKGROUND/AIM: Strategies to enhance the therapeutic ratio of radiotherapy in glioblastoma are warranted. Our aim was to report a novel DNA methyltransferase inhibitor as a potential radiosensitizing agent in glioblastoma. MATERIALS AND METHODS: Four glioblastoma cell lines and one normal astrocyte cell line were incubated with a newly-synthetized phthalimido-alkanamide derivative, MA17, and its radiosensitizing effects were assessed. We performed a tumor growth delay assay in two glioblastoma lines: U87MG and U138MG. We evaluated DNA methyltransferase (DNMT) inhibition, apoptosis, autophagy, DNA damage repair, and FANCA expression. RESULTS: MA17 radiosensitized all glioblastoma cells (all p<0.05), but it did not affect normal astrocytes (p=0.193). MA17 significantly prolonged the mean tumor doubling time in vivo, in cells treated in addition with radiotherapy, compared to radiotherapy alone (p<0.05). DNMT activity was down-regulated, and apoptosis and autophagy were induced by MA17. Double-stranded DNA break foci were observed for prolonged periods in cells treated with MA17. FANCA expression was also inhibited. CONCLUSION: A novel phthalimido-alkanamide derivative demonstrated significant radiosensitization in glioblastoma cells in vitro and in vivo. Further investigation is needed to translate these results to the clinic.