PrP(c) deficiency and dasatinib protect mouse intestines against radiation injury by inhibiting of c-Src

FG-4592 alleviates Radiation-Induced Intestinal Injury by facilitating recovery of intestinal stem cell and reducing damage of intestinal epithelial

Damage of Intestinal Stem Cells (ISCs) is the main cause of radiation induced-intestinal injury (RIII). Recently, hypoxia Inducible factor (HIF) was verified to be critical for promoting proliferation of ISCs, which suggested a protective role of HIF in the RIII. Thus, we investigated the effect of FG-4592, a novel up-regulator of HIF, on the protection of RIII. With/without FG-4592 treatment, the abdomen of mice was radiated, and intestinal injury was assessed. Especially, by intestinal organoid culture, the multiplication capacity and differentiation features of ISCs were detected. As a result, FG-4592, a novel up-regulator of HIF could remit RIII and promote regeneration and differentiation of ISCs after radiation, which were depended on HIF-2 rather than HIF-1.

Tyrosine kinase inhibitors protect the salivary gland from radiation damage by increasing DNA double-strand break repair

We have previously shown that the tyrosine kinase inhibitors (TKIs) dasatinib and imatinib can protect salivary glands from irradiation (IR) damage without impacting tumor therapy. However, how they induce this protection is unknown. Here we show that TKIs mediate radioprotection by increasing the repair of DNA double-stranded breaks. DNA repair in IR-treated parotid cells, but not oral cancer cells, occurs more rapidly following pretreatment with imatinib or dasatinib and is accompanied by faster formation of DNA damage-induced foci. Similar results were observed in the parotid glands of mice pretreated with imatinib prior to IR, suggesting that TKIs "prime" cells for DNA repair. Mechanistically, we observed that TKIs increased IR-induced activation of DNA-PK, but not ATM. Pretreatment of parotid cells with the DNA-PK inhibitor NU7441 reversed the increase in DNA repair induced by TKIs. Reporter assays specific for homologous recombination (HR) or nonhomologous end joining (NHEJ) verified regulatation of both DNA repair pathways by imatinib. Moreover, TKIs also increased basal and IR-induced expression of genes associated with NHEJ (DNA ligase 4, Artemis, XLF) and HR (Rad50, Rad51 and BRCA1); depletion of DNA ligase 4 or BRCA1 reversed the increase in DNA repair mediated by TKIs. In addition, TKIs increased activation of the ERK survival pathway in parotid cells, and ERK was required for the increased survival of TKI-treated cells. Our studies demonstrate a dual mechanism by which TKIs provide radioprotection of the salivary gland tissues and support exploration of TKIs clinically in head and neck cancer patients undergoing IR therapy.

Novel Pentapeptide Derived from Chicken by-Product Ameliorates DSS-Induced Colitis by Enhancing Intestinal Barrier Function via AhR-Induced Src Inactivation

Managing patients with refractory inflammatory bowel diseases (IBD) is a common clinical challenge. Galli Gigeriae Endothelium Corneum (GGEC), a chicken by-product, has been used for centuries in Asian countries as a functional food and supplement for the treatment of gastrointestinal disorders. In this study, a novel peptide (LNLYP, LP-5) with gastrointestinal stability that can enhance the intestinal barrier function that was first identified in GGEC. Our work demonstrated that aryl hydrocarbon receptor (AhR) activation by LP-5 could inhibit the Src kinase to increase tight junction protein levels and down-regulate the expression of inflammatory cytokines to protect the intestinal barrier and finally alleviate dextran sulfate sodium (DSS)-induced colitis. This study revealed that LP-5 had the potential to develop into a therapeutic agent for the treatment of colitis and provided new high-valued utilization of GGEC.

Prion protein deficiency impairs hematopoietic stem cell determination and sensitizes myeloid progenitors to irradiation

Highly conserved among species and expressed in various types of cells, numerous roles have been attributed to the cellular prion protein (PrPC). In hematopoiesis, PrPC regulates hematopoietic stem cell self-renewal but the mechanisms involved in this regulation are unknown. Here we show that PrPC regulates hematopoietic stem cell number during aging and their determination towards myeloid progenitors. Furthermore, PrPC protects myeloid progenitors against the cytotoxic effects of total body irradiation. This radioprotective effect was associated with increased cellular prion mRNA level and with stimulation of the DNA repair activity of the Apurinic/pyrimidinic endonuclease 1, a key enzyme of the base excision repair pathway. Altogether, these results show a previously unappreciated role of PrPC in adult hematopoiesis, and indicate that PrPC-mediated stimulation of BER activity might protect hematopoietic progenitors from the cytotoxic effects of total body irradiation.

Tyrosine Kinase Inhibitors Protect the Salivary Gland from Radiation Damage by Inhibiting Activation of Protein Kinase C-δ

In patients undergoing irradiation (IR) therapy, injury to nontumor tissues can result in debilitating, and sometimes permanent, side effects. We have defined protein kinase C-δ (PKCδ) as a regulator of DNA damage-induced apoptosis and have shown that phosphorylation of PKCδ by c-Abl and c-Src activates its proapoptotic function. Here, we have explored the use of tyrosine kinase inhibitors (TKI) of c-Src and c-Abl to block activation of PKCδ for radioprotection of the salivary gland. Dasatinib, imatinib, and bosutinib all suppressed tyrosine phosphorylation of PKCδ and inhibited IR-induced apoptosis in vitro To determine whether TKIs can provide radioprotection of salivary gland function in vivo, mice were treated with TKIs and a single or fractionated doses of irradiation. Delivery of dasatinib or imatinib within 3 hours of a single or fractionated dose of irradiation resulted in >75% protection of salivary gland function at 60 days. Continuous dosing with dasatinib extended protection to at least 5 months and correlated with histologic evidence of salivary gland acinar cell regeneration. Pretreatment with TKIs had no impact on clonogenic survival of head and neck squamous cell carcinoma (HNSCC) cells, and in mice harboring HNSCC cell-derived xenografts, combining dasatinib or imatinib with fractionated irradiation did not enhance tumor growth. Our studies indicate that TKIs may be useful clinically to protect nontumor tissue in HNC patients undergoing radiotherapy, without negatively impacting cancer treatment. Mol Cancer Ther; 16(9); 1989-98. ©2017 AACR.