Disruption of DNA-PKcs-mediated cGAS retention on damaged chromatin potentiates DNA damage-inducing agent-induced anti-multiple myeloma activity.

BACKGROUND: Targeting DNA damage repair factors, such as DNA-dependent protein kinase catalytic subunit (DNA-PKcs), may offer an opportunity for effective treatment of multiple myeloma (MM). In combination with DNA damage-inducing agents, this strategy has been shown to improve chemotherapies partially via activation of cGAS-STING pathway by an elevated level of cytosolic DNA. However, as cGAS is primarily sequestered by chromatin in the nucleus, it remains unclear how cGAS is released from chromatin and translocated into the cytoplasm upon DNA damage, leading to cGAS-STING activation. METHODS: We examined the role of DNA-PKcs inhibition on cGAS-STING-mediated MM chemosensitivity by performing mass spectrometry and mechanism study. RESULTS: Here, we found DNA-PKcs inhibition potentiated DNA damage-inducing agent doxorubicin-induced anti-MM effect by activating cGAS-STING signaling. The cGAS-STING activation in MM cells caused cell death partly via IRF3-NOXA-BAK axis and induced M1 polarization of macrophages. Moreover, this activation was not caused by defective classical non-homologous end joining (c-NHEJ). Instead, upon DNA damage induced by doxorubicin, inhibition of DNA-PKcs promoted cGAS release from cytoplasmic chromatin fragments and increased the amount of cytosolic cGAS and DNA, activating cGAS-STING. CONCLUSIONS: Inhibition of DNA-PKcs could improve the efficacy of doxorubicin in treatment of MM by de-sequestrating cGAS in damaged chromatin.

Resveratrol attenuates inflammatory hyperalgesia by inhibiting glial activation in mice spinal cords.

The present study aimed to investigate the effect of resveratrol on inflammatory pain. Mice were injected intraperitoneally with lipopolysaccharide (LPS) for 5 consecutive days to induce subacute systemic inflammation. Acetic acid­induced writhing tests and tail­flick tests were performed following the final LPS injection. Glial fibrillary acidic protein (GFAP; an astrocyte­specific activation marker), ionized calcium binding adapter molecule 1 (Iba­1; a microglia­specific activation marker) and sirtuin 1 (SIRT1) protein expression levels were detected using immunohistochemistry analysis or western blotting. Following administration of LPS for 5 days, the number of writhes increased and the tail­flick latency decreased. Resveratrol (10 or 20 mg/kg) partly inhibited LPS­induced hyperalgesia and prevented the increase in tumor necrosis factor­α and interleukin 6 levels induced by LPS. LPS injection reduced the SIRT1 protein expression and increased the number of GFAP­positive and Iba­1­positive cells in the spinal cord. Resveratrol increased the SIRT1 protein expression levels and decreased the number of GFAP­positive and Iba­1­positive cells in LPS­treated mice. The protective effect of resveratrol was partly blocked by a selective SIRT1 inhibitor, EX­257. Results from the present study suggest that subacute treatment with LPS induced the activation of glial cells and hyperalgesia. Resveratrol was demonstrated to inhibit the activation of glial cells and attenuate inflammatory hyperalgesia in a SIRT1­dependent manner.