Polystyrene microplastics induce pulmonary fibrosis by promoting alveolar epithelial cell ferroptosis through cGAS/STING signaling

Polystyrene microplastics (PS-MPs) are new types of environmental pollutant that have garnered significant attention in recent years since they were found to cause damage to the human respiratory system when they are inhaled. The pulmonary fibrosis is one of the serious consequences of PS-MPs inhalation. However, the impact and underlying mechanisms of PS-MPs on pulmonary fibrosis are not clear. In this study, we studied the potential lung toxicity and PS-MPs-developed pulmonary fibrosis by long-term intranasal inhalation of PS-MPs. The results showed that after exposing to the PS-MPs, the lungs of model mouse had different levels of damage and fibrosis. Meanwhile, exposing to the PS-MPs resulted in a markedly decrease in glutathione (GSH), an increase in malondialdehyde (MDA), and iron overload in the lung tissue of mice and alveolar epithelial cells (AECs). These findings suggested the occurrence of PS-MP-induced ferroptosis. Inhibitor of ferroptosis (Fer-1) had alleviated the PS-MPs-induced ferroptosis. Mechanically, PS-MPs triggered cell ferroptosis and promoted the development of pulmonary fibrosis via activating the cGAS/STING signaling pathway. Inhibition of cGAS/STING with G150/H151 attenuated pulmonary fibrosis after PS-MPs exposure. Together, these data provided novel mechanistic insights of PS-MPs-induced pulmonary fibrosis and a potential therapeutic paradigm.

The interplay between autophagy and cGAS-STING signaling and its implications for cancer

Autophagy is an intracellular process that targets various cargos for degradation, including members of the cGAS-STING signaling cascade. cGAS-STING senses cytosolic double-stranded DNA and triggers an innate immune response through type I interferons. Emerging evidence suggests that autophagy plays a crucial role in regulating and fine-tuning cGAS-STING signaling. Reciprocally, cGAS-STING pathway members can actively induce canonical as well as various non-canonical forms of autophagy, establishing a regulatory network of feedback mechanisms that alter both the cGAS-STING and the autophagic pathway. The crosstalk between autophagy and the cGAS-STING pathway impacts a wide variety of cellular processes such as protection against pathogenic infections as well as signaling in neurodegenerative disease, autoinflammatory disease and cancer. Here we provide a comprehensive overview of the mechanisms involved in autophagy and cGAS-STING signaling, with a specific focus on the interactions between the two pathways and their importance for cancer.

Perillaldehyde ameliorates lipopolysaccharide-induced acute lung injury via suppressing the cGAS/STING signaling pathway

Acute lung injury (ALI) is a common life-threatening illness characterized by a lung inflammatory response and oxidative stress, and effective agent therapies are currently lacking. mtDNA can be recognized by cGAS/STING, the dysregulation of which leads to inflammatory diseases, such as ALI. Perillaldehyde(PAH), one of the major active components of traditional Chinese medicine made from Perilla frutescens, has antioxidant and antiinflammatory effects. The aim of this study was to explore whether PAH can protect against lipopolysaccharide (LPS)-induced ALI and whether its protective effect is exerted through the regulation of cGAS/STING signaling. We found that PAH significantly inhibited lung histological changes, inflammatory cell infiltration, and the overproduction of inflammatory cytokines induced by LPS. Moreover, PAH inhibited LPS-induced oxidative stress, as shown by the deceases in superoxide dismutase (SOD) and glutathione(GSH) levels and increased in malondialdehyde (MDA) and lactate dehydrogenase (LDH) levels. In addition, PAH markedly downregulated the expression of cGAS, STING, p-TBK, p-IRF3, p-P65, and p-IκB, and pharmacological inhibition of cGAS/STING inhibited ALI- induced by LPS. Furthermore, the levels of mitochondrial ROS (mROS) and mtDNA were increased, and cGAS/STING-mediated IRF3/NF-κB signaling was activated during the inflammatory response- induced by LPS in RAW264.7 cells. In addition, pretreatment with the STING activator partially abolished the inhibitory effect of PAH on the inflammation and activation of STING-mediated IRF3/NF-κB signaling induced by LPS. Overall, the results revealed that PAH can effectively alleviate ALI by inhibiting cGAS/STING-mediated IRF3/NF-κB signaling, and that PAH may be a potential candidate agent for the treatment of ALI.

Administration of a glypican-3 peptide increases the infiltration and cytotoxicity of CD8+ T cells against testicular yolk sac tumor, associated with enhancing the intratumoral cGAS/STING signaling

BACKGROUND

Glypican-3 (GPC3) is highly expressed in testicular yolk sac tumor (TYST). GPC3 has been evaluated as a cancer vaccine for some types of tumors, but little is known on the effects of GPC3 peptide-based therapy on TYST. Here, we evaluated the antitumor effect of GPC3144-152 on TYST and its potential mechanisms.

METHODS

GPC3144-152 -specific CD8+ T cells were induced by vaccine immunization and examined by ELISPOT. The CD8+ T cells were purified for testing their cytotoxicity in vitro against TYST cells by CCK-8 and TUNEL assays and in vivo against tumor growth. The influence of GPC3144-152 loading and/or cGAS silencing on the tumor growth, apoptosis and cGAS/STING signaling was tested by immunohistochemistry, immunofluorescence, flow cytometry, and Western blot.

RESULTS

Vaccination with GPC3144-152 induced tumor-specific CD8+ T cells that secreted high levels of IFN-γ and granzyme B, and had potent cytotoxicity against TYST in a dose-dependent manner. Adoptive transfer of CD8+ T cells and treatment with GPC3144-152 significantly inhibited the growth of TYST tumors, but less effective for cGAS-silenced TYST tumors in vivo. Treatment with GPC3144-152 enhanced the infiltration of CD8+ T cells into the tumor environment and their cytotoxicity against TYST tumors in vivo by up-regulating granzyme B and IFN-β expression, but down-regulating GPC3 expression in the tumors. Co-culture of CD8+ T cells with TYST in the presence of exogenous GPC3144-152 enhanced peptide-specific CD8+ T-cell cytotoxicity in vitro, accompanied by enhancing cGAS, γH2AX, TBK1, and IRF3 phosphorylation in TYST cells, but less effective in cGAS-silenced TYST cells.

CONCLUSIONS

These data indicated that GPC3 peptide-specific CD8+ T cells had potent antitumor activity against TYST tumor, particularly for combined treatment with the peptide, which was partially dependent on the intratumoral cGAS/STNG signaling. GPC3 peptide vaccine may be valuable for the combination treatment of TYST.

A Dihydroartemisinin-Loaded Nanoreactor Motivates Anti-Cancer Immunotherapy by Synergy-Induced Ferroptosis to Activate Cgas/STING for Reprogramming of Macrophage

Infiltration of tumor-associated macrophages (TAM) characterized by an M2 phenotype is an overriding feature in malignant tumors. Reprogramming TAM is the most cutting-edge strategy for cancer therapy. In the present study, an iron-based metal-organic framework (MOF) nanoreactor loaded with dihydroartemisinin (DHA) is developed, which provides high uptake by TAM and retains their viability, thus effectively addressing the inefficiency of the DHA at low concentrations. Impressively, DHA@MIL-101 can selectively accumulate in tumor tissues and remodel TAM to the M1 phenotype. The results of RNA sequencing further suggest that this nanoreactor may regulate ferroptosis, a DNA damage signaling pathway in TAM. Indeed, the outcomes confirm that DHA@MIL-101 triggers ferroptosis in TAM. In addition, the findings reveal that DNA damage induced by DHA nanoreactors activates the intracellular cGAS sensor, resulting in the binding of STING to IRF3 and thereby up-regulating the immunogenicity. In contrast, blocking ferroptosis impairs DHA@MIL-101-induced activation of STING signaling and phenotypic remodeling. Finally, it is shown that DHA nanoreactors deploy anti-tumor immunotherapy through ferroptosis-mediated TAM reprogramming. Taken together, immune efficacy is achieved through TAM's remodeling by delivering DHA and iron ions into TAM using nanoreactors, providing a novel approach for combining phytopharmaceuticals with nanocarriers to regulate the immune microenvironment.

Pharmacological targeting of cGAS/STING-YAP axis suppresses pathological angiogenesis and ameliorates organ fibrosis

Organ fibrosis is accompanied by pathological angiogenesis. Discovering new ways to ameliorate pathological angiogenesis may bypass organ fibrosis. The cyclic guanosine monophosphate (GMP)-adenosine monophosphate (AMP) synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway has been implicated in organ injuries and its activation inhibits endothelial proliferation. Currently, a controversy exists as to whether cGAS/STING activation exacerbates inflammation and tissue injury or mitigates damage, and whether one of these effects predominates under specific context. This study unveiled a new antifibrotic cGAS/STING signaling pathway that suppresses pathological angiogenesis in liver and kidney fibrosis. We showed that cGAS expression was induced in fibrotic liver and kidney, but suppressed in endothelial cells. cGAS genetic deletion promoted liver and kidney fibrosis and pathological angiogenesis, including occurrence of endothelial-to-mesenchymal transition. Meanwhile, cGAS deletion upregulated profibrotic Yes-associated protein (YAP) signaling in endothelial cells, which was evidenced by the attenuation of organ fibrosis in mice specifically lacking endothelial YAP. Pharmacological targeting of cGAS/STING-YAP signaling by both a small-molecule STING agonist, SR-717, and a G protein-coupled receptor (GPCR)-based antagonist that blocks the profibrotic activity of endothelial YAP, attenuated liver and kidney fibrosis. Together, our data support that activation of cGAS/STING signaling mitigates organ fibrosis and suppresses pathological angiogenesis. Further, pharmacological targeting of cGAS/STING-YAP axis exhibits the potential to alleviate liver and kidney fibrosis.

Increased cGAS/STING signaling components in patients with Mooren's ulcer

AIM

To explore the expression of cGAS/STING signaling components in Mooren's ulcer (MU).

METHODS

Samples were obtained from ten MU patients, and eight residual corneal-scleral rings of healthy donor corneas for controls. Human corneal epithelial cells (HCECs) were used to evaluate the effect of cGAS/STING signaling pathway. Immunohistochemistry (IHC) and Western blot were used to examine the expression of cGAS, STING, and phosphorylated interferon regulatory factor 3 (p-IRF3) in MU tissues. The expression of interferon-β (IFN-β) and interferon-stimulated genes (ISGs) was quantified by real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA).

RESULTS

The protein levels of cGAS and STING in MU samples were significantly elevated when compared with the healthy controls by Western blot and IHC. After stimulation with cGAMP, real-time PCR and ELISA showed a dramatic increase of IFN-β and ISGs (containing CXCL10, IFIT1, and IL-6) in HCECs. Moreover, HCECs treated with cGAMP was characterized by increased phosphorylation and more nuclear translocation of IRF3. Meanwhile, increased p-IRF3 was observed in MU samples via IHC and Western blot.

CONCLUSION

The pronounced expression of cGAS/STING signaling components in the patients with MU and probably contribute to the onset and development of MU.