cGAS-like receptors put a sting into the evolution of immune defence

A sequential scheme including PTT and 2'3'-cGAMP/CQ-LP reveals the antitumor immune function of PTT through the type I interferon pathway

Photothermal therapy (PTT) is a promising antitumor treatment that is easy to implement, minimally invasive, and precisely controllable, and evokes strong antitumor immunity. We believe that a thorough elucidation of its underlying antitumor immune mechanisms would contribute to the rational design of combination treatments with other antitumor strategies and consequently potentiate clinical use. In this study, PTT using indocyanine green (ICG) induced STING-dependent type I interferon (IFN) production in macrophages (RAW264.7 and bone marrow-derived macrophages (BMDMs)), as proven by the use of a STING inhibitor (C178), and triggered STING-independent type I IFN generation in tumor cells (CT26 and 4T1), which was inhibited by DNase pretreatment. A novel liposome coloaded with the STING agonist 2'3'-cGAMP (cGAMP) and chloroquine (CQ) was constructed to achieve synergistic effect with PTT, in which CQ increased cGAMP entrapment efficiency and prevented STING degradation after IFN signaling activation. The sequential combination treatment caused a significant increase in tumor cell apoptosis, probably due to interferon stimulating gene products 15 and 54 (ISG15 and ISG 54), and achieved a more striking antitumor inhibition effect in the CT26 tumor model than the 4T1 model, likely due to higher STAT1 expression and consequently more intense IFN signal transduction. In the tumor microenvironment, the combination treatment increased infiltrating CD8+T cells (4-fold) and M1-like TAMs (10-fold), and decreased M-MDSCs (over 2-fold) and M2-like TAMs (over 4-fold). Above all, in-depth exploration of the antitumor mechanism of PTT provides guidance for selecting sensitive tumor models and designing reasonable clinical schemes.

Inhibition of cGAS ameliorates acute lung injury triggered by zinc oxide nanoparticles

PURPOSE

Zinc oxide nanoparticles (ZnONPs) have been widely used in various industrial and biomedical fields. Occupational or accidental inhalation exposure to ZnONPs might lead to acute lung injury (ALI). Cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING) are critical for the initiation and expansion of inflammation and contribute to tissue injury; however, the role and mechanism of the cGAS-STING pathway in ALI-induced by ZnONPs are unclear.

METHODS

Male C57BL/6 J mice were intratracheally injected with ZnONPs (0.6 mg/kg) or mock. The mice were euthanized and the degree of lung injury was determined 3 days after the instillation of ZnONPs. The BEAS-2B cell line was used as a cell model to investigate the cytotoxicity of ZnONPs in vitro.

RESULTS

We found that ZnONPs inhalation induced ALI in mice, manifested by exacerbated lung pathological changes, mitochondrial damage, oxidative stress and inflammation. Interestingly, cGAS and STING were activated in the lung tissues of the mice and BEAS-2B lung epithelial cells treated with ZnONPs. More importantly, we illustrated that the cGAS inhibitor RU.521 inhibited the activation of the cGAS-STING pathway, further decreased oxidative stress and inflammation, and led to ameliorated lung injury in mice treated with ZnONPs.

CONCLUSION

This study demonstrated that ZnONPs trigger the activation of the cGAS-STING pathway, which plays an important role in ZnONPs-induced ALI. Inhibition of cGAS with RU.521 mitigates the oxidative stress induced by ZnONPs, suggesting that targeting the cGAS-STING pathway may be a feasible strategy to ameliorate the pulmonary injury caused by nanoparticles.

Drosophila as a Model for Human Viral Neuroinfections

The study of human neurological infection faces many technical and ethical challenges. While not as common as mammalian models, the use of Drosophila (fruit fly) in the investigation of virus–host dynamics is a powerful research tool. In this review, we focus on the benefits and caveats of using Drosophila as a model for neurological infections and neuroimmunity. Through the examination of in vitro, in vivo and transgenic systems, we highlight select examples to illustrate the use of flies for the study of exogenous and endogenous viruses associated with neurological disease. In each case, phenotypes in Drosophila are compared to those in human conditions. In addition, we discuss antiviral drug screening in flies and how investigating virus–host interactions may lead to novel antiviral drug targets. Together, we highlight standardized and reproducible readouts of fly behaviour, motor function and neurodegeneration that permit an accurate assessment of neurological outcomes for the study of viral infection in fly models. Adoption of Drosophila as a valuable model system for neurological infections has and will continue to guide the discovery of many novel virus–host interactions.