The Role of IL-33 on LPS-Induced Acute Lung Injury in Mice

THE IL-33/ST2 AXIS PROMOTES ACUTE RESPIRATORY DISTRESS SYNDROME BY NATURAL KILLER T CELLS

ABSTRACT

Acute respiratory distress syndrome (ARDS) is characterized by uncontrolled inflammation, which manifests as leukocyte infiltration and lung injury. However, the molecules that initiate this infiltration remain incompletely understood. We evaluated the effect of the nuclear alarmin IL-33 on lung damage and the immune response in LPS-induced lung injury. We established a LPS-induced lung injury mouse model. We used genetically engineered mice to investigate the relationship among the IL-33/ST2 axis, NKT cells, and ARDS. We found that IL-33 was localized to the nucleus in alveolar epithelial cells, from which it was released 1 h after ARDS induction in wild-type (WT) mice. Mice lacking IL-33 (IL-33 - / - ) or ST2 (ST2 - / - ) exhibited reduced neutrophil infiltration, alveolar capillary leakage, and lung injury in ARDS compared with WT mice. This protection was associated with decreased lung recruitment and activation of invariant nature killer (iNKT) cells and activation of traditional T cells. Then, we validated that iNKT cells were deleterious in ARDS in CD1d - / - and Vα14Τg mice. Compared with WT mice, Vα14Τg mice exhibited increased lung injury in ARDS, and the CD1d - / - mice showed outcomes opposite those of the Vα14Τg mice. Furthermore, we administered a neutralizing anti-ST2 antibody to LPS-treated WT and Vα14Τg mice 1 h before LPS administration. We found that IL-33 promoted inflammation through NKT cells in ARDS. In summary, our results demonstrated that the IL-33/ST2 axis promotes the early uncontrolled inflammatory response in ARDS by activating and recruiting iNKT cells. Therefore, IL-33 and NKT cells may be therapeutic target molecules and immune cells, respectively, in early ARDS cytokine storms.

Inhalable Jojoba Oil Dry Nanoemulsion Powders for the Treatment of Lipopolysaccharide- or H2O2-Induced Acute Lung Injury

Jojoba (Simmondsia chinensis (Link) C.K. Schneid) is a dioecious plant in desert and semi-desert areas, e.g., the Ismailia Desert in Egypt. Jojoba oil (JJBO) is a natural slight yellow oil with the functions of skin barrier repairing and wound healing, which is dermally applied as a traditional medication or cosmetic in the Middle East. The objective of this study was to prepare JJBO dry nanoemulsion powders (JNDs) and investigate their anti-acute lung injury effects. JJBO nanoemulsions (JNEs) were prepared and then lyophilized to JNDs and the properties and simulated lung deposition were measured. Rat acute lung injury (ALI) models were established after intratracheal (i.t.) administration of lipopolysaccharide (LPS) or hydrogen peroxide (H₂O₂). JNDs and dexamethasone (DXM) solutions were also i.t. administered to the rats. The pathological states of lung tissues were checked. Inflammatory and oxidative factors in the lung tissues were determined using ELISA methods. NF-κB p65 and caspase-3 were measured with a Western blotting method and an immunohistochemical method, respectively. JNDs had an appropriate mass median aerodynamic diameter (MMAD) of 4.17 µm and a fine particle fraction (FPF) of 39.11%. JNDs showed higher anti-inflammatory effect on LPS-induced ALI than DXM with a decrease in total protein content and down-regulation of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6) and NF-κB p65. JNDs also showed higher anti-inflammatory and anti-oxidation effect on H₂O₂-induced ALI than DXM with elimination of reactive oxygen species (ROS), increasing of superoxide dismutase (SOD), decrease in of lipid peroxide malondialdehyde (MDA) and glutathione (GSH), and inhibition of caspase-3 expression. Moreover, i.t. JNDs attenuated bleeding and infiltrations of the inflammatory cells in the two ALI models. JNDs are a promising natural oil-contained inhalable medication for the treatment of LPS- or H₂O₂-induced ALI.

Salvia miltiorrhiza Injection Alleviates LPS-Induced Acute Lung Injury by Adjusting the Balance of MMPs/TIMPs Ratio

Salvia miltiorrhiza injection (SMI) is a classical traditional Chinese medicine, which plays an active role in the treatment of many diseases such as promoting blood circulation, removing blood stasis, reducing inflammatory reaction, and improving acute lung injury (ALI). Previous studies have shown that matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) are involved in the pathophysiological process of ALI. However, the relationship between SMI and MMPs/TIMPs remains unclear. In this study, Wistar rats were randomly divided into control group (NC), Salvia miltiorrhiza group (SM), lipopolysaccharide group (LPS), and Salvia miltiorrhiza treatment group (Tsm). The four groups were subdivided into four time points (2, 6, 12, and 24 hours), and specimens were collected after animal sacrifice at each time point. Serum TNF-α and IL-6 levels were detected by ELISA. The degree of lung injury was determined by lung tissue hematoxylin-eosin staining, lung wet/dry weight (W/D) ratio, and lung permeability index. The changes in lung MMPs/TIMPs protein and mRNA were detected by Western blot and real-time quantitative PCR. The results showed that rats injected with LPS experience acute lung injury, and the ratio of MMPs/TIMPs in lung tissues increased gradually with time. In the Tsm group, the ratio of MMPs/TIMPs decreased gradually, and likewise, the balance was gradually restored, while indicators related to lung injury were gradually declined. These data suggest that SMI alleviates LPS-induced acute lung injury; this protective effect may be related to regulation of the balance of MMPs/TIMPs ratio.

Pulmonary Neutrophilic Inflammation and Noncommunicable Diseases: Pathophysiology, Redox Mechanisms, Biomarkers, and Therapeutics

Significance: Pulmonary neurophilic inflammation (PNI) is the homing and activation of neutrophil with damage to the microvasculature. This process is involved in pulmonary damage in patients exposed to airborne pollutants (exogenous stressors) and also to systemic inflammation/oxidative stress (endogenous stressors) associated with noncommunicable diseases (NCDs). Recent Advances: PNI is an important trigger of the early onset and progression of NCD in susceptible patients exposed to airborne pollutants. Irritation of the lung microvasculature by exogenous and endogenous stressors causes PNI. Circulating endogenous stressors in NCD can cause PNI. Critical Issues: Air pollution-triggered PNI causes increased circulating endogenous stressors that can trigger NCD in susceptible patients. Systemic inflammation/oxidative stress associated with NCD can cause PNI. Inflammation/end-oxidation products of macromolecules are also potential biomarkers and therapeutic targets for NCD-triggered PNI- and PNI-triggered NCD. Future Directions: Understanding the molecular mechanism of PNI triggered by exogenous or endogenous stressors will help explain the early onset of NCD in susceptible patients exposed to air pollution. It can also help undercover biomarkers and mechanism-based therapeutic targets in air pollutant-triggered PNI, PNI-triggered NCD, and NCD-triggered PNI.

Different intensity of autophagy regulate interleukin-33 to control the uncontrolled inflammation of acute lung injury

OBJECTIVES

Cytokines participate in the progression of acute respiratory distress syndrome (ARDS), and uncontrolled inflammation is a central issue of acute lung injury (ALI). Interleukin (IL)-33 is a nuclear protein that has been reported to have a proinflammatory role in ARDS. Studies have shown that excessive autophagy may lead to the increased mortality of patients with ARDS, while several investigations indicated that IL-33 and autophagy interact with one another. The present study sought to clarify the relation between autophagy and IL-33's proinflammatory role in ARDS.

METHODS

We built a lipopolysaccharide (LPS)-induced lung injury mouse model. To study the relationship between IL-33 and autophagy, mice were pretreated with rapamycin (RAPA; a promoter of autophagy) and 3-methyladenine (3-MA; an inhibitor of autophagy) prior to LPS administration. The expression of IL-33 in serum and bronchoalveolar lavage fluid (BALF) was measured. Immunohistochemistry of IL-33 in lung tissue was examined. Th1,Th2 cytokines/chemokine levels in serum and BALF were tested. Further, the severity of lung injury was evaluated. And the nuclear factor-kappa B (NF-κB)'s nuclear translocation in lung tissue was detected.

RESULTS

In comparison with the control group, the levels of IL-33 in serum and BALF were increased after LPS injection. Th1 cytokines/chemokine levels were significantly increased in serum and BALF, while Th2 cytokine levels changed only a little. The levels of IL-33 in serum and BALF of the RAPA group was significantly increased after LPS was injected as compared with the LPS group; additionally, the levels of IL-33 in serum and BALF of the 3-MA group was significantly reduced after LPS was injected as compared with the LPS group, and that lung injury was ameliorated after 3-MA pretreatment. Th1 cytokines and chemokines in both serum and BALF were also decreased in the 3-MA group. Furthermore, we found that the nuclear translocation of NF-κB increased after LPS administration, and NF-κB's nuclear translocation was significantly increased in comparison with the LPS group after RAPA pretreatment. In contrast, NF-κB's nuclear translocation decreased after 3-MA pretreatment as compared with the LPS group.

CONCLUSIONS

These findings showed that autophagy might regulate IL-33 by activating or inhibiting NF-κB to control the uncontrolled inflammation of acute lung injury.

Role of the IL-33/ST2/p38 signaling pathway in the immune response of corneal epithelial cells to Aspergillus fumigatus infection

AIM

To investigate the expression of interleukin (IL)-33 in the cornea and human corneal epithelial cells (HCECs) exposed to Aspergillus fumigatus (A. fumigatus), and to determine the function of IL-33/ST2/p38 signaling pathway in the immune response of corneal epithelial cells to A. fumigatus infection.

METHODS

The mRNA and protein expression of IL-33 in HCECs and mice corneas were examined by quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) and Western blot analysis, respectively. IL-33 expression was also detected in cornea samples from healthy donors and patients with fungal keratitis with immunohistochemistry. The cultured HCECs were treated with inactive A. fumigatus hyphae at various concentrations with or without recombinant human IL-33 protein, soluble recombinant ST2 protein, specific ST2 neutralizing antibody, or the mitogen-activated protein kinase (MAPK) p38 inhibitor SB203580 for evaluation of the expression and activation of IL-33/ST2/p38 signaling in the regulation of proinflammatory cytokines. The production levels of IL-6 and IL-1β were determined by qRT-PCR and enzyme-linked immunosorbent assay (ELISA). The proliferation of HCECs was determined by a Cell Counting Kit-8 (CCK8) assay and cell count.

RESULTS

IL-33 expression levels increased in the corneal tissues of patients with fungal keratitis and in mice corneas of experimental A. fumigatus infection, as well as in HCECs with infection of A. fumigatus. A. fumigatus strongly stimulated HCECs-generated proinflammatory cytokine (IL-6 and IL-1β) production at both the mRNA and protein levels. This production of pro-inflammatory mediators stimulated by A. fumigatus was further stimulated by IL-33 and was prevented by soluble ST2 protein or ST2 neutralizing antibody. Moreover, IL-33 naturally promoted the p38 phosphorylation induced by A. fumigatus, which was suppressed by soluble ST2 protein. The MAPK p38 inhibitor SB203580 also inhibited the A. fumigatus-induced proinflammatory cytokine production. IL-33 administration for 48h and 72h promoted the proliferation of HCECs, which was attenuated by treatment with soluble recombinant human ST2 protein.

CONCLUSION

A. fumigatus elevates IL-33 expression in human and mice corneas and HCECs. Thus, IL-33/ST2/p38 signaling may play an important role in amplifying the immune response of corneal epithelial cells to A. fumigatus infection. Besides, IL-33 promotes the cell proliferation of HCECs via its receptor ST2. These findings suggest a novel autocrine mechanism of amplification of the fungal-induced inflammatory response in the corneal epithelium, highlighting a potential therapeutic target for fungal keratitis.

Elevated IL-33 promotes expression of MMP2 and MMP9 via activating STAT3 in alveolar macrophages during LPS-induced acute lung injury

Background

Pulmonary inflammation and endothelial barrier permeability increase in acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) induced by pro-inflammatory cytokines and matrix metalloproteinases (MMPs). However, the relationship between pro-inflammatory cytokines and MMPs in ALI/ARDS remains poorly understood.

Methods

A lipopolysaccharide (LPS)-induced ALI rat model was established through intratracheal instillation. The wet/dry ratios of lung tissues were measured, and bronchoalveolar lavage fluid (BALF) was collected to test protein concentrations, total cell/macrophage numbers, and pro-inflammatory cytokine levels. LPS-treated alveolar macrophages were utilized in in vitro experiments. The expression and secretion of MMPs were respectively detected using quantitative PCR, Western blotting and ELISA assays.

Results

The levels of IL-33 and MMP2/9 in BALF increased in all the ALI rats with severe lung injury. LPS-induced IL-33 autocrine upregulated the expression of MMP2 and MMP9 through activating STAT3. Neutralizing IL-33 in culture medium with specific antibodies suppressed the expression and secretion of MMP2 and MMP9 in LPS-treated alveolar macrophages. Consistently, eliminating IL-33 decreased the levels of MMP2 and MMP9 in BALF and alleviated lung injury in ALI rats.

Conclusion

The IL-33/STAT3/MMP2/9 regulatory pathway is activated in alveolar macrophages during acute lung injury, which may exacerbate the pulmonary inflammation.