Long-term exposure of chemokine CXCL10 causes bronchiolitis-like inflammation

CXCR3-independent role of CXCL10 in alveolar epithelial repair

The alveolar type II epithelial cells (AEC2s) act as stem cells in the lung for alveolar epithelial maintenance and repair. Chemokine C-X-C motif chemokine 10 (CXCL10) is expressed in injured tissues, modulating multiple cellular functions. AEC2s, previously reported to release chemokines to recruit leukocytes, were found in our study to secrete CXCL10 after bleomycin injury. We found that Sftpc-Cxcl10 transgenic mice were protected from bleomycin injury. The transgenic mice showed an increase in the AEC2 population in the lung by flow cytometry analysis. Both endogenous and exogenous CXCL10 promoted the colony formation efficiency of AEC2s in a three-dimensional (3-D) organoid growth assay. We identified that the regenerative effect of CXCL10 was CXCR3 independent using Cxcr3-deficient mice, but it was related to the TrkA pathway. Binding experiments showed that CXCL10 interacted with TrkA directly and reversibly. This study demonstrates a previously unidentified AEC2 autocrine signaling of CXCL10 to promote their regeneration and proliferation, probably involving a CXCR3-independent TrkA pathway.NEW & NOTEWORTHY CXCL10 may aid in lung injury recovery by promoting the proliferation of alveolar stem cells and using a distinct regulatory pathway from the classical one.

CXCL10 deficiency limits macrophage infiltration, preserves lung matrix, and enables lung growth in bronchopulmonary dysplasia

Preterm infants with oxygen supplementation are at high risk for bronchopulmonary dysplasia (BPD), a neonatal chronic lung disease. Inflammation with macrophage activation is central to the pathogenesis of BPD. CXCL10, a chemotactic and pro-inflammatory chemokine, is elevated in the lungs of infants evolving BPD and in hyperoxia-based BPD in mice. Here, we tested if CXCL10 deficiency preserves lung growth after neonatal hyperoxia by preventing macrophage activation. To this end, we exposed Cxcl10 knockout (Cxcl10-/-) and wild-type mice to an experimental model of hyperoxia (85% O2)-induced neonatal lung injury and subsequent regeneration. In addition, cultured primary human macrophages and murine macrophages (J744A.1) were treated with CXCL10 and/or CXCR3 antagonist. Our transcriptomic analysis identified CXCL10 as a central hub in the inflammatory network of neonatal mouse lungs after hyperoxia. Quantitative histomorphometric analysis revealed that Cxcl10-/- mice are in part protected from reduced alveolar. These findings were related to the preserved spatial distribution of elastic fibers, reduced collagen deposition, and protection from macrophage recruitment/infiltration to the lungs in Cxcl10-/- mice during acute injury and regeneration. Complimentary, studies with cultured human and murine macrophages showed that hyperoxia induces Cxcl10 expression that in turn triggers M1-like activation and migration of macrophages through CXCR3. Finally, we demonstrated a temporal increase of macrophage-related CXCL10 in the lungs of infants with BPD. In conclusion, our data demonstrate macrophage-derived CXCL10 in experimental and clinical BPD that drives macrophage chemotaxis through CXCR3, causing pro-fibrotic lung remodeling and arrest of alveolarization. Thus, targeting the CXCL10-CXCR3 axis could offer a new therapeutic avenue for BPD.

Acute vaping in a golden Syrian hamster causes inflammatory response transcriptomic changes

E-cigarette vaping is a major aspect of nicotine consumption, especially for children and young adults. Although it is branded as a safer alternative to cigarette smoking, murine and rat models of subacute and chronic e-cigarette vaping exposure have shown many proinflammatory changes in the respiratory tract. An acute vaping exposure paradigm has not been demonstrated in the golden Syrian hamster, and the hamster is a readily available small animal model that has the unique benefit of becoming infected with and transmitting respiratory viruses, including SARS-CoV-2, without genetic alteration of the animal or virus. Using a 2-day, whole body vaping exposure protocol in male golden Syrian hamsters, we evaluated serum cotinine, bronchoalveolar lavage cells, lung, and nasal histopathology, and gene expression in the nasopharynx and lung through reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Depending on the presence of nonnormality or outliers, statistical analysis was performed by ANOVA or Kruskal-Wallis tests. For tests that were statistically significant (P < 0.05), post hoc Tukey-Kramer and Dunn's tests, respectively, were performed to make pairwise comparisons between groups. In nasal tissue, RT-qPCR analysis revealed nicotine-dependent increases in gene expression associated with type 1 inflammation (CCL-5 and CXCL-10), fibrosis [transforming growth factor-β (TGF-β)], nicotine-independent increase oxidative stress response (SOD-2), and a nicotine-independent decrease in vasculogenesis/angiogenesis (VEGF-A). In the lung, nicotine-dependent increases in the expression of genes involved in the renin-angiotensin pathway [angiotensin-converting enzyme (ACE), ACE2], coagulation (tissue factor, Serpine-1), extracellular matrix remodeling (MMP-2, MMP-9), type 1 inflammation (IL-1β, TNF-α, and CXCL-10), fibrosis (TGF-β and Serpine-1), oxidative stress response (SOD-2), neutrophil extracellular traps release (ELANE), and vasculogenesis and angiogenesis (VEGF-A) were identified. To our knowledge, this is the first demonstration that the Syrian hamster is a viable model of e-cigarette vaping. In addition, this is the first report that e-cigarette vaping with nicotine can increase tissue factor gene expression in the lung. Our results show that even an acute exposure to e-cigarette vaping causes significant upregulation of mRNAs in the respiratory tract from pathways involving the renin-angiotensin system, coagulation, extracellular matrix remodeling, type 1 inflammation, fibrosis, oxidative stress response, neutrophil extracellular trap release (NETosis), vasculogenesis, and angiogenesis.

Dysregulation of the Immune Environment in the Airways During HIV Infection

HIV-1 increases susceptibility to pulmonary infection and disease, suggesting pathogenesis in the lung. However, the lung immune environment during HIV infection remains poorly characterized. This study examined T cell activation and the cytokine milieu in paired bronchoalveolar lavage (BAL) and blood from 36 HIV-uninfected and 32 HIV-infected participants. Concentrations of 27 cytokines were measured by Luminex, and T cells were phenotyped by flow cytometry. Blood and BAL had distinct cytokine profiles (p=0.001). In plasma, concentrations of inflammatory cytokines like IFN-γ (p=0.004) and TNF-α (p=0.004) were elevated during HIV infection, as expected. Conversely, BAL cytokine concentrations were similar in HIV-infected and uninfected individuals, despite high BAL viral loads (VL; median 48,000 copies/ml epithelial lining fluid). HIV-infected individuals had greater numbers of T cells in BAL compared to uninfected individuals (p=0.007); and BAL VL positively associated with CD4+ and CD8+ T cell numbers (p=0.006 and p=0.0002, respectively) and CXCL10 concentrations (p=0.02). BAL T cells were highly activated in HIV-infected individuals, with nearly 2-3 fold greater frequencies of CD4+CD38+ (1.8-fold; p=0.007), CD4+CD38+HLA-DR+ (1.9-fold; p=0.0006), CD8+CD38+ (2.8-fold; p=0.0006), CD8+HLA-DR+ (2-fold; p=0.022) and CD8+CD38+HLA-DR+ (3.6-fold; p<0.0001) cells compared to HIV-uninfected individuals. Overall, this study demonstrates a clear disruption of the pulmonary immune environment during HIV infection, with readily detectable virus and activated T lymphocytes, which may be driven to accumulate by local chemokines.

Effect of Vitamin D3 on Lung Damage Induced by Cigarette Smoke in Mice

Cigarette smoking is known to induce serious lung diseases, but there is not an effective method to solve this problem. The present study investigated vitamin D3 on over-expression of CXCR3 and CXCL10 in mice induced by cigarette smoking. A pulmonary airway model was designed, and morphological assessment of emphysema, IL-4, IFN-γ and CXCL10 concentration in bronchoalveolar lavage fluids, expression of CXCR3 and CXCL10 were detected. Emphysema of the mice only exposed to cigarette smoke was significant, and concentration of IL-4, IFN-γ and CXCL10 was also increased. In addition, CXCR3 and CXCL10 were over-expressed. The degree of emphysema, concentration of IL-4, IFN-γ and CXCL10, and expression of CXCR3 and CXCL10 in mice administrated with low dose vitamin D3 were similar to the normally treated mice. Low dose of vitamin D3 can effectively protect the lung from the damage induced by cigarette smoke.

Nontypeable Haemophilus influenzae DNA stimulates type I interferon expression via STING signaling pathway

Nontypeable Haemophilus influenzae (NTHI) is one of the leading causes of acute exacerbations of COPD (AECOPD). Although the immunoregulation function of NTHI outer member protein and endotoxin were confirmed, the role of NTHI DNA in activating immune responses remains to be elucidated. In this study, we found expression of IFN-β and IFN stimulated gene CXCL10 in host cells was forcefully elevated after treating with NTHI and NTHI DNA. Interestingly, we tested increased level of STING in NTHI infected mice lung. Meanwhile, STING expression in lung of mimic COPD murine model was higher than healthy mice after NTHI infection. Importantly, knockout of STING or overexpression of STING, TBK1 and IRF3 respectively impaired or enhanced IFN-β and CXCL10 expression during treating with NTHI and NTHI DNA. NTHI and NTHI DNA-induced I-IFN response appeared to be mediated by cGAS. Collectively, we suggested that NTHI DNA as a PAMP triggered I-IFN response, which was STING/TBK1/IRF3 dependent.

SUMMARY

NTHI is the leading cause of acute exacerbations of COPD (AECOPD). Since AECOPD is an immune event, it is meaningful to elucidate the mechanism under NTHI induced immune response. It has been revealed that lipooligosaccharides and protein of NTHI could induce host immune response, but the function of NTHI nuclide acid during infection is unclear. In this research, we demonstrate NTHI DNA is a trigger for I-IFN expression, and the STING/TBK1/IRF3 pathway plays an integral role in sensing NTHI DNA to induce I-IFN expression. Moreover, by long-term intrabronchial infection of LPS, we constructed a mimic COPD murine model, in which the STING expression in lung tissues were higher than healthy mice after NTHI infection, which led us to surmise that NTHI cause AECOPD by inducing I-IFN production via STING signal pathway.

TLR2 Activation Limits Rhinovirus-Stimulated CXCL-10 by Attenuating IRAK-1-Dependent IL-33 Receptor Signaling in Human Bronchial Epithelial Cells

Airway epithelial cells are the major target for rhinovirus (RV) infection and express proinflammatory chemokines and antiviral cytokines that play a role in innate immunity. Previously, we demonstrated that RV interaction with TLR2 causes ILR-associated kinase-1 (IRAK-1) depletion in both airway epithelial cells and macrophages. Further, IRAK-1 degradation caused by TLR2 activation was shown to inhibit ssRNA-induced IFN expression in dendritic cells. Therefore, in this study, we examined the role of TLR2 and IRAK-1 in RV-induced IFN-β, IFN-λ1, and CXCL-10, which require signaling by viral RNA. In airway epithelial cells, blocking TLR2 enhanced RV-induced expression of IFNs and CXCL-10. By contrast, IRAK-1 inhibition abrogated RV-induced expression of CXCL-10, but not IFNs in these cells. Neutralization of IL-33 or its receptor, ST2, which requires IRAK-1 for signaling, inhibited RV-stimulated CXCL-10 expression. In addition, RV induced expression of both ST2 and IL-33 in airway epithelial cells. In macrophages, however, RV-stimulated CXCL-10 expression was primarily dependent on TLR2/IL-1R. Interestingly, in a mouse model of RV infection, blocking ST2 not only attenuated RV-induced CXCL-10, but also lung inflammation. Finally, influenza- and respiratory syncytial virus-induced CXCL-10 was also found to be partially dependent on IL-33/ST2/IRAK-1 signaling in airway epithelial cells. Together, our results indicate that RV stimulates CXCL-10 expression via the IL-33/ST2 signaling axis, and that TLR2 signaling limits RV-induced CXCL-10 via IRAK-1 depletion at least in airway epithelial cells. To our knowledge, this is the first report to demonstrate the role of respiratory virus-induced IL-33 in the induction of CXCL-10 in airway epithelial cells.

Secretion of IL-16 through TNFR1 and calpain-caspase signaling contributes to MRSA pneumonia

Staphylococcus aureus is a major cause of severe pneumonia. Multiple mechanisms of proinflammatory signaling are activated to recruit immune cells into the airway in response to S. aureus. We found that interleukin-16 (IL-16), a T cell cytokine that binds CD4, is potently activated by S. aureus, specifically by protein A (SpA), and to a much greater extent than by Gram-negative pathogens or lipopolysaccharide. IL-16 production involved multiple signals including ligation of tumor necrosis factor receptor (TNFR) family members or epidermal growth factor receptor, both receptors for SpA and generation of Ca(2+) fluxes to activate calpains and caspase-3. Although human airway epithelial cells, vascular endothelial cells, THP-1 and Jurkat T cells released IL-16 in response to S. aureus in vitro, in a murine model of pneumonia, CD4(+) cells were the major source of IL-16 suggesting the involvement of an autocrine signaling pathway. The production of IL-16 contributed to lung damage as neutralization of IL-16 enhanced S. aureus clearance and resulted in diminished lung pathology in S. aureus pneumonia. Our results suggest that the ability of S. aureus to activate TNFR1 and Ca(2+)/calpain signaling contribute to T cell activation and excessive inflammation in the setting of acute pneumonia.

Synergy of IL-27 and TNF-α in regulating CXCL10 expression in lung fibroblasts

IL-27 is involved in inflammatory reactions. CXCL10 is an important chemokine contributing to airway inflammatory disease. In this study, we investigated whether IL-27 modulated the synthesis of CXCL10 in primary human lung fibroblasts (HLFs). HLFs were activated by IL-27 alone, or in combination with other cytokines. CXCL10 synthesis was measured by real-time PCR and ELISA. An examination of transcriptional regulation was performed via the transient transfection of promoter constructs, whereas mRNA stability was assessed by actinomycin D chase and real-time PCR. The underlying signaling pathways were studied by Western blotting and intracellular staining, using flow cytometry. Our results demonstrated that IL-27 induced and synergized with TNF-α to up-regulate CXCL10 mRNA and protein concentrations in a steroid-insensitive manner. This synergistic CXCL10 production was dependent on the transcriptional regulation of CXCL10 gene promoter activity and the enhanced stability of CXCL10 mRNA because of IL-27 and TNF-α, and this synergism was regulated by the activation of p38 mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-OH kinase (PI3K)-Akt dominantly, and in small part via NF-κB. Interestingly, IL-27 promoted the basal and enhanced TNF-α-induced phosphorylation of p38 MAPK and Akt, but not IκBα. Moreover, enhanced CXCL10 mRNA stability occurred via a p38 MAPK-dependent pathway. Finally, clinical analysis showed that IL-27 was detected in the bronchoalveolar lavage of patients with asthma, chronic obstructive pulmonary disease (COPD), and pulmonary tuberculosis (PTB), and increased IL-27 concentrations were correlated with increased CXCL10 concentrations in patients with COPD and PTB. Our findings suggest that IL-27 has the potential to amplify airway inflammation via the induction of CXCL10 from HLFs, in combination with TNF-α.