The underlying mechanisms and strategies of DNA damage and repair in radiation sialadenitis

Immunomodulation of salivary gland function due to cancer therapy

Functional salivary glands (SG) are essential for maintaining oral health, and salivary dysfunction is a persistent major clinical challenge. Several cancer therapies also have off-target effects leading to SG dysfunction. Recent advances highlight the role of SG immune populations in homeostasis, dysfunction and gland regeneration. Here, we review what is known about SG immune populations during development and postnatal homeostasis. We summarize recent findings of immune cell involvement in SG dysfunction following cancer treatments such as irradiation (IR) for head and neck cancers, immune transplant leading to graft-versus-host-disease (GVHD) and immune checkpoint inhibitor (ICI) treatment. The role of immune cells in SG in both homeostasis and disease, is an emerging field of research that may provide important clues to organ dysfunction and lead to novel therapeutic targets.

Radiation-induced changes in energy metabolism result in mitochondrial dysfunction in salivary glands

Salivary glands are indirectly damaged during radiotherapy for head and neck cancer, resulting in acute and chronic hyposalivation. Current treatments for radiation-induced hyposalivation do not permanently restore function to the gland; therefore, more mechanistic understanding of the damage response is needed to identify therapeutic targets for lasting restoration. Energy metabolism reprogramming has been observed in cancer and wound healing models to provide necessary fuel for cell proliferation; however, there is limited understanding of alterations in energy metabolism reprogramming in tissues that fail to heal. We measured extracellular acidification and oxygen consumption rates, assessed mitochondrial DNA copy number, and tested fuel dependency of irradiated primary salivary acinar cells. Radiation treatment leads to increases in glycolytic flux, oxidative phosphorylation, and ATP production rate at acute and intermediate time points. In contrast, at chronic radiation time points there is a significant decrease in glycolytic flux, oxidative phosphorylation, and ATP production rate. Irradiated salivary glands exhibit significant decreases in spare respiratory capacity and increases in mitochondrial DNA copy number at days 5 and 30 post-treatment, suggesting a mitochondrial dysfunction phenotype. These results elucidate kinetic changes in energy metabolism reprogramming of irradiated salivary glands that may underscore the chronic loss of function phenotype.

Radiation-Induced Changes in Energy Metabolism Result in Mitochondrial Dysfunction in Salivary Glands

Salivary glands are indirectly damaged during radiotherapy for head and neck cancer, resulting in acute and chronic hyposalivation. Current treatments for radiation-induced hyposalivation do not permanently restore function to the gland; therefore, more mechanistic understanding of the damage response is needed to identify therapeutic targets for lasting restoration. Energy metabolism reprogramming has been observed in cancer and wound healing models to provide necessary fuel for cell proliferation; however, there is limited understanding of alterations in energy metabolism reprogramming in tissues that fail to heal. We measured extracellular acidification and oxygen consumption rates, assessed mitochondrial DNA copy number, and tested fuel dependency of irradiated primary salivary acinar cells. Radiation treatment leads to increases in glycolytic flux, oxidative phosphorylation, and ATP production rate at acute and intermediate time points. In contrast, at chronic radiation time points there is a significant decrease in glycolytic flux, oxidative phosphorylation, and ATP production rate. Irradiated salivary glands exhibit significant decreases in spare respiratory capacity and increases in mitochondrial DNA copy number at days 5 and 30 post-treatment, suggesting a mitochondrial dysfunction phenotype. These results elucidate kinetic changes in energy metabolism reprogramming of irradiated salivary glands that may underscore the chronic loss of function phenotype.

Polydopamine-Coated Radiolabeled Microspheres for Combinatorial Radioembolization and Photothermal Cancer Therapy

Transarterial radioembolization (TARE) is a local radionuclide therapy and is successfully used in hepatocellular carcinoma (HCC) treatment. Radioactive microspheres have been widely studied for TARE. Preparation of ideal radioactive microspheres is significant for clinical research and patient treatment. In this study, we have designed a novel multifunctional microsphere, i.e., polydopamine (PDA)-coated ¹⁷⁷Lu-radiolabeled silica microspheres (MS) denoted as ¹⁷⁷Lu-MS@PDA, which can be used for TARE and photothermal therapy (PTT). The radiostability of ¹⁷⁷Lu-MS@PDA was significantly improved by coating ¹⁷⁷Lu-MS with PDA. In addition, the coating of PDA makes microspheres have excellent photothermal performance. MicroSPECT/CT images showed that ¹⁷⁷Lu-MS@PDA was accurately embolized and remained in the tumor during the observation time. At the time, it also showed that ¹⁷⁷Lu-MS@PDA was very stable in vivo. Furthermore, the anti-tumor results demonstrated that TARE combined with PTT of ¹⁷⁷Lu-MS@PDA can significantly inhibit tumor growth without obvious side effects. ¹⁷⁷Lu-MS@PDA holds great potential as a promising radioactive microsphere for HCC.

Tetrahedral framework nucleic acids alleviate irradiation-induced salivary gland damage

In this study, we investigated the role of tetrahedral framework nucleic acids (tFNAs) in irradiation-induced salivary gland damage in vitro and in vivo. Irradiation-damaged submandibular gland cells (SMGCs) were treated with different concentrations of tFNAs. Cell activity was measured by CCK-8 assay. Cell death was detected by Calcein-AM/PI double staining. Cell apoptosis was assessed by flow cytometry. The expression of apoptosis proteins and inflammatory cytokines were detected by western blot. Body weight, drinking volume, saliva flow rate and lag time was measured 8 weeks after irradiation. Micromorphological changes of submandibular gland were assessed by haematoxylin-eosin and masson staining. Cell proliferation, apoptosis and microvessel density of submandibular gland were evaluated by immunohistochemical staining. tFNAs could promote cell proliferation, inhibit cell apoptosis of irradiation-damaged SMGCs and reduce irradiation induced cell death. Mechanism studies revealed that tFNAs inhibited cell apoptosis through regulating the Bcl-2/Bax/Caspase-3 signalling pathway and inhibited the release of TNF-α, IL-1β and IL-6 to reduce cell damage caused by inflammation. Animal experiments showed that tFNAs could alleviate irradiation-induced weight loss, increased water intake, decreased saliva production and prolonged salivation lag time and could ameliorate salivary gland damage. tFNAs have a positive effect on alleviating irradiation-induced salivary gland damage and might be a promising agent for the treatment of this disease.