High Concentration Hydrogen Mitigates Sepsis-Induced Acute Lung Injury in Mice by Alleviating Mitochondrial Fission and Dysfunction

Hydrogen therapy promotes macrophage polarization to the M2 subtype in radiation lung injury by inhibiting the NF-κB signalling pathway

Background

Radiotherapy has become a standard treatment for chest tumors, but a common complication of radiotherapy is radiation lung injury. Currently, there is still a lack of effective treatment for radiation lung injury.

Methods

A mouse model of radioactive lung injury (RILI) was constructed and then treated with different cycles of hydrogen inhalation. Lung function tests were performed to detect changes in lung function.HE staining was used to detect pathological changes in lung tissue. Immunofluorescence staining was used to detect the polarization of macrophages in lung tissue. Immunohistochemistry was used to detect changes in cytokine expression in lung tissues. Western Blot was used to detect the expression of proteins related to the NF-κB signalling pathway.

Results

Lung function test results showed that lung function decreased in the model group and improved in the treatment group.HE staining showed that inflammatory response was evident in the model group and decreased in the treatment group. Immunohistochemistry results showed that the expression of pro-inflammatory factors was significantly higher in the model group, and the expression of pro-inflammatory factors was significantly higher in the treatment group. The expression of pro-inflammatory factors in the treatment group was significantly lower than that in the model group, and the expression of anti-inflammatory factors in the treatment group was higher than that in the model group. Immunofluorescence showed that the expression of M1 subtype macrophages was up-regulated in the model group and down-regulated in the treatment group. The expression of M2 subtype macrophages was up-regulated in the treatment group relative to the model group. Western Blot showed that P-NF-κB p65/NF-κB p65 was significantly increased in the model group, and P-NF-κB p65/NF-κB p65 was decreased in the treatment group.

Conclusion

Hydrogen therapy promotes macrophage polarization from M1 to M2 subtypes by inhibiting the NF-κB signalling pathway, thereby attenuating the inflammatory response to radiation lung injury.

Protective Effect of Vitamin K2 (MK-7) on Acute Lung Injury Induced by Lipopolysaccharide in Mice

Vitamin K2 (MK-7) has been shown to cause significant changes in different physiological processes and diseases, but its role in acute lung injury (ALI) is unclear. Therefore, in this study, we aimed to evaluate the protective effects of VK2 against LPS-induced ALI in mice. The male C57BL/6J mice were randomly divided into six groups (n = 7): the control group, LPS group, negative control group (LPS + Oil), positive control group (LPS + DEX), LPS + VK2 (L) group (VK2, 1.5 mg/kg), and LPS + VK2 (H) group (VK2, 15 mg/kg). Hematoxylin-eosin (HE) staining of lung tissue was performed. Antioxidant superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) activities, and the Ca2+ level in the lung tissue were measured. The effects of VK2 on inflammation, apoptosis, tight junction (TJ) injury, mitochondrial dysfunction, and autophagy were quantitatively assessed using Western blot analysis. Compared with the LPS group, VK2 improved histopathological changes; alleviated inflammation, apoptosis, and TJ injury; increased antioxidant enzyme activity; reduced Ca2+ overload; regulated mitochondrial function; and inhibited lung autophagy. These results indicate that VK2 could improve tight junction protein loss, inflammation, and cell apoptosis in LPS-induced ALI by inhibiting the mitochondrial dysfunction and excessive autophagy, indicating that VK2 plays a beneficial role in ALI and might be a potential therapeutic strategy.

Tangeretin attenuates acute lung injury in septic mice by inhibiting ROS-mediated NLRP3 inflammasome activation via regulating PLK1/AMPK/DRP1 signaling axis

OBJECTIVE

NLRP3 inflammasome-mediated pyroptosis of macrophage acts essential roles in the progression of sepsis-induced acute lung injury (ALI). Tangeretin (TAN), enriched in citrus fruit peel, presents anti-oxidative and anti-inflammatory effects. Here, we aimed to explore the potentially protective effect of TAN on sepsis-induced ALI, and the underlying mechanism of TAN in regulating NLRP3 inflammasome.

MATERIAL AND METHODS

The effect of TAN on sepsis-induced ALI and NLRP3 inflammasome-mediated pyroptosis of macrophage were examined in vivo and in vitro using a LPS-treated mice model and LPS-induced murine macrophages, respectively. The mechanism of TAN regulating the activation of NLRP3 inflammasome in sepsis-induced ALI was investigated with HE staining, Masson staining, immunofluorescent staining, ELISA, molecular docking, transmission electron microscope detection, qRT-PCR, and western blot.

RESULTS

TAN could evidently attenuate sepsis-induced ALI in mice, evidenced by reducing pulmonary edema, pulmonary congestion and lung interstitial fibrosis, and inhibiting macrophage infiltration in the lung tissue. Besides, TAN significantly suppressed inflammatory cytokine IL-1β and IL-18 expression in the serum or bronchoalveolar lavage fluid (BALF) samples of mice with LPS-induced ALI, and inhibited NLRP3 inflammasome-mediated pyroptosis of macrophages. Furthermore, we found TAN inhibited ROS production, preserved mitochondrial morphology, and alleviated excessive mitochondrial fission in LPS-induced ALI in mice. Through bioinformatic analysis and molecular docking, Polo-like kinase 1 (PLK1) was identified as a potential target of TAN for treating sepsis-induced ALI. Moreover, TAN significantly inhibited the reduction of PLK1 expression, AMP-activated protein kinase (AMPK) phosphorylation, and Dynamin related protein 1 (Drp1) phosphorylation (S637) in LPS-induced ALI in mice. In addition, Volasertib, a specific inhibitor of PLK1, abolished the protective effects of TAN against NLRP3 inflammasome-mediated pyroptosis of macrophage and lung injury in the cell and mice septic models.

CONCLUSION

TAN attenuates sepsis-induced ALI by inhibiting ROS-mediated NLRP3 inflammasome activation via regulating PLK1/AMPK/DRP1 signaling axis, and TAN is a potentially therapeutic candidate against ALI through inhibiting pyroptosis.

Mitochondria: one of the vital hubs for molecular hydrogen's biological functions

As a novel antioxidant, a growing body of studies has documented the diverse biological effects of molecular hydrogen (H2) in a wide range of organisms, spanning animals, plants, and microorganisms. Although several possible mechanisms have been proposed, they cannot fully explain the extensive biological effects of H2. Mitochondria, known for ATP production, also play crucial roles in diverse cellular functions, including Ca2+ signaling, regulation of reactive oxygen species (ROS) generation, apoptosis, proliferation, and lipid transport, while their dysfunction is implicated in a broad spectrum of diseases, including cardiovascular disorders, neurodegenerative conditions, metabolic disorders, and cancer. This review aims to 1) summarize the experimental evidence on the impact of H2 on mitochondrial function; 2) provide an overview of the mitochondrial pathways underlying the biological effects of H2, and 3) discuss H2 metabolism in eukaryotic organisms and its relationship with mitochondria. Moreover, based on previous findings, this review proposes that H2 may regulate mitochondrial quality control through diverse pathways in response to varying degrees of mitochondrial damage. By combining the existing research evidence with an evolutionary perspective, this review emphasizes the potential hydrogenase activity in mitochondria of higher plants and animals. Finally, this review also addresses potential issues in the current mechanistic study and offers insights into future research directions, aiming to provide a reference for future studies on the mechanisms underlying the action of H2.