Effect of PD-1 Inhibitor Combined with X-Ray Irradiation on the Inflammatory Microenvironment and Lung Tissue Injury in Mice

The involvement of Sting in exacerbating acute lung injury in sepsis via the PARP-1/NLRP3 signaling pathway

BACKGROUND

Interferon gene stimulator (Sting) is an indispensable adaptor protein that plays a crucial role in acute lung injury (ALI) induced by sepsis, and the PARP-1/NLRP3 signaling pathway may be an integral component of the inflammatory response mediated by Sting. However, the regulatory role of Sting in the PARP-1/NLRP3 pathway in ALI remains insufficiently elucidated.

METHODS

Using lipopolysaccharide (LPS) to induce ALI in C57BL/6 mice and HUVEC cells, an in vivo and in vitro model was established. In vivo, Sting agonists and inhibitors were administered, while in vitro, Sting was knocked down using siRNA. ELISA was employed to quantify the levels of IL-1β, IL-6, and TNF-α. TUNEL staining was conducted to assess cellular apoptosis, while co-immunoprecipitation was utilized to investigate the interaction between Sting and NLRP3. Expression levels of Sting, NLRP3, PARP-1, among others, were assessed via Western blotting and RT-qPCR. Lung HE staining and lung wet/dry ratio were evaluated in the in vivo mouse model. To validate the role of the PARP-1/NLRP3 signaling pathway, PARP-1 inhibitors were employed both in vivo and in vitro.

RESULTS

In vitro experiments revealed that the Sting agonist group exacerbated LPS-induced pulmonary pathological damage, pulmonary edema, inflammatory response (increased levels of IL-6, TNF-α, and IL-1β), and cellular injury, whereas the Sting inhibitor group significantly ameliorated the aforementioned injuries, with further improvement observed in the combination therapy of Sting inhibitor and PARP-1 inhibitor. Western blotting and RT-qPCR results demonstrated significant suppression of ICAM-1, VCAM-1, NLRP3, and PARP-1 expression in the Sting inhibitor group, with this reduction further enhanced in the Sting inhibitor + PARP-1 inhibitor treatment group, exhibiting opposite outcomes to the agonist. Furthermore, in vitro experiments using HUVEC cell lines validated these findings.

CONCLUSIONS

Our study provides new insights into the roles of Sting and the PARP-1/NLRP3 signaling pathway in inflammatory responses, offering novel targets for the development of therapeutic interventions against inflammatory reactions.

Vitamin E stabilizes iron and mitochondrial metabolism in pulmonary fibrosis

Introduction: Pulmonary fibrosis (PF) is a fatal chronic lung disease that causes structural damage and decreased lung function and has a poor prognosis. Currently, there is no medicine that can truly cure PF. Vitamin E (VE) is a group of natural antioxidants with anticancer and antimutagenic properties. There have been a few reports about the attenuation of PF by VE in experimental animals, but the molecular mechanisms are not fully understood. Methods: Bleomycin-induced PF (BLM-PF) mouse model, and cultured mouse primary lung fibroblasts and MLE 12 cells were utilized. Pathological examination of lung sections, immunoblotting, immunofluorescent staining, and real-time PCR were conducted in this study. Results: We confirmed that VE significantly delayed the progression of BLM-PF and increased the survival rates of experimental mice with PF. VE suppressed the pathological activation and fibrotic differentiation of lung fibroblasts and epithelial-mesenchymal transition and alleviated the inflammatory response in BLM-induced fibrotic lungs and pulmonary epithelial cells in vitro. Importantly, VE reduced BLM-induced ferritin expression in fibrotic lungs, whereas VE did not exhibit iron chelation properties in fibroblasts or epithelial cells in vitro. Furthermore, VE protected against mitochondrial dysmorphology and normalized mitochondrial protein expression in BLM-PF lungs. Consistently, VE suppressed apoptosis in BLM-PF lungs and pulmonary epithelial cells in vitro. Discussion: Collectively, VE markedly inhibited BLM-induced PF through a complex mechanism, including improving iron metabolism and mitochondrial structure and function, mitigating inflammation, and decreasing the fibrotic functions of fibroblasts and epithelial cells. Therefore, VE presents a highly potential therapeutic against PF due to its multiple protective effects with few side effects.

Effect of X-ray irradiation combined with PD-1 inhibitor treatment on lung tissue injury in mice

PURPOSE

To determine the effect of X-ray irradiation combined with PD-1 immune checkpoint inhibitor administration on lung tissue injury in a mouse model and its potential mechanism.

METHODS

In all, 20 C57BL/6J mice were randomly divided into four groups with five mice in each group: control group, PD-1 inhibitor group, irradiation group, and irradiation combined with PD-1 inhibitor group. Hematoxylin-eosin staining of the lung tissue was performed 30 days after the end of irradiation to evaluate the morphological and pathological changes in the tissue. Masson staining and analysis of hydroxyproline were used to evaluate the degree of pulmonary fibrosis. The levels of transforming growth factor-β1 (TGF-β1) and tumor necrosis factor α(TNF-α) were evaluated by Enzyme-Linked immunosorbent assay (ELISA). CD3+, CD4+, and CD8+ T lymphocytes in the lung tissue were detected by immunohistochemistry. The expression levels of TGF-β1, Smad3, cGAS, and STING in the lung tissue were evaluated by Western blotting.

RESULTS

The lung injury scores and pulmonary fibrosis indices in the irradiation group were higher than those in the control group. Meanwhile, lung pneumonia score, pulmonary fibrosis index, percentage of CD4 cells and expression of TGF-β1, p-Smad3, and STING in the lung tissue of mice in irradiation combined with PD-1 inhibitor group were higher than those in the other three groups.

CONCLUSION

Lung injury and pulmonary fibrosis were induced by whole chest X-ray irradiation in mice, and PD-1 inhibitor could aggravate lung injury and pulmonary fibrosis in mice. Thus, radiotherapy combined with PD-1 inhibitors may affect the immune inflammatory microenvironment in the lung tissues of mice by activating TGF-β1/Samd3 and cGAS/STING signaling pathways, thus aggravating lung tissue damage induced by radiation.

The occurrence and development of radiation-induced lung injury after interstitial brachytherapy and stereotactic radiotherapy in SD rats

BACKGROUND

To compare the severity of radiation-induced lung injury (RILI) after the right lung of SD rats received interstitial brachytherapy and stereotactic radiotherapy (SBRT).

METHODS

RILI rat model was established using interstitial brachytherapy and SBRT methods, respectively. CT scan was performed to analyze the lung volume and the CT value difference between the left and right lungs in rats. Then the lung tissues were analyzed through H&E staining, peripheral blood was extracted to detect the expression levels of serum inflammatory cytokines, pro-fibrotic cytokines, and fibrotic-inhibiting cytokines by ELISA.

RESULTS

The difference between right and left lung CT values was significantly elevated in the SBRT group when compared with the control group and the interstitial brachytherapy group (P < 0.05). The IFN-γ expression in the interstitial brachytherapy group was significantly different from that in the SBRT group at week 1, 4, 8 and 16. Besides, the expressions of IL-2, IL-6 and IL-10 in SBRT group were significantly higher than that of interstitial brachytherapy group (P < 0.05). The TGF-β expression in interstitial brachytherapy group reached its peak with the increase of time from week 1 to week 16, and it was significantly lower than SBRT group (P < 0.05). The mortality rate in the SBRT group was 16.7%, which was significantly higher than that in the interstitial brachytherapy group.

CONCLUSION

The treatment method of interstitial brachytherapy is considered as an effective and safe tool by reducing the side effects of radiotherapy and increasing the radiation dose of radiotherapy.

The role of PD-1/PD-L1 axis in idiopathic pulmonary fibrosis: Friend or foe?

Idiopathic pulmonary fibrosis (IPF) is a devastating interstitial lung disease with a bleak prognosis. Mounting evidence suggests that IPF shares bio-molecular similarities with lung cancer. Given the deep understanding of the programmed cell death-1 (PD-1)/programmed death-ligand 1 (PD-L1) pathway in cancer immunity and the successful application of immune checkpoint inhibitors (ICIs) in lung cancer, recent studies have noticed the role of the PD-1/PD-L1 axis in IPF. However, the conclusions are ambiguous, and the latent mechanisms remain unclear. In this review, we will summarize the role of the PD-1/PD-L1 axis in IPF based on current murine models and clinical studies. We found that the PD-1/PD-L1 pathway plays a more predominant profibrotic role than its immunomodulatory role in IPF by interacting with multiple cell types and pathways. Most preclinical studies also indicated that blockade of the PD-1/PD-L1 pathway could attenuate the severity of pulmonary fibrosis in mice models. This review will bring significant insights into understanding the role of the PD-1/PD-L1 pathway in IPF and identifying new therapeutic targets.

Therapeutic targets and biomarkers of tumor immunotherapy: response versus non-response

Cancers are highly complex diseases that are characterized by not only the overgrowth of malignant cells but also an altered immune response. The inhibition and reprogramming of the immune system play critical roles in tumor initiation and progression. Immunotherapy aims to reactivate antitumor immune cells and overcome the immune escape mechanisms of tumors. Represented by immune checkpoint blockade and adoptive cell transfer, tumor immunotherapy has seen tremendous success in the clinic, with the capability to induce long-term regression of some tumors that are refractory to all other treatments. Among them, immune checkpoint blocking therapy, represented by PD-1/PD-L1 inhibitors (nivolumab) and CTLA-4 inhibitors (ipilimumab), has shown encouraging therapeutic effects in the treatment of various malignant tumors, such as non-small cell lung cancer (NSCLC) and melanoma. In addition, with the advent of CAR-T, CAR-M and other novel immunotherapy methods, immunotherapy has entered a new era. At present, evidence indicates that the combination of multiple immunotherapy methods may be one way to improve the therapeutic effect. However, the overall clinical response rate of tumor immunotherapy still needs improvement, which warrants the development of novel therapeutic designs as well as the discovery of biomarkers that can guide the prescription of these agents. Learning from the past success and failure of both clinical and basic research is critical for the rational design of studies in the future. In this article, we describe the efforts to manipulate the immune system against cancer and discuss different targets and cell types that can be exploited to promote the antitumor immune response.