Correction of lung inflammation in a F508del CFTR murine cystic fibrosis model by the sphingosine-1-phosphate lyase inhibitor LX2931

Abstract

Progressive lung disease with early onset is the main cause of mortality and morbidity in cystic fibrosis patients. Here we report a reduction of sphingosine-1-phosphate (S1P) in the lung of unchallenged Cftr F508del CFTR mutant mice. This correlates with enhanced infiltration by inducible nitric oxide synthase (iNOS)-expressing granulocytes, B cells, and T cells. Furthermore, the ratio of macrophage-derived dendritic cells (MoDC) to conventional dendritic cells (cDC) is higher in mutant mouse lung, consistent with unprovoked inflammation. Oral application of a S1P lyase inhibitor (LX2931) increases S1P levels in mutant mouse tissues. This normalizes the lung MoDC/cDC ratio and reduces B and T cell counts. Lung granulocytes are enhanced, but iNOS expression is reduced in this population. Although lung LyC6+ monocytes are enhanced by LX2931, they apparently do not differentiate to MoDC and macrophages. After challenge with bacterial toxins (LPS-fMLP) we observe enhanced levels of proinflammatory cytokines TNF-α, KC, IFNγ, and IL-12 and the inducible mucin MUC5AC in mutant mouse lung, evidence of deficient resolution of inflammation. LX2931 does not prevent transient inflammation or goblet cell hyperplasia after challenge, but it reduces MUC5AC and proinflammatory cytokine levels toward normal values. We conclude that lung pathology in homozygous mice expressing murine F508del CFTR, which represents the most frequent mutation in CF patients, is characterized by abnormal behavior of infiltrating myeloid cells and delayed resolution of induced inflammation. This phenotype can be partially corrected by a S1P lyase inhibitor, providing a rationale for therapeutic targeting of the S1P signaling pathway in CF patients.

Elastase Exocytosis by Airway Neutrophils Is Associated with Early Lung Damage in Children with Cystic Fibrosis

“…Together, our findings suggest that neutrophils recruited to the airway lumen of children with CF are conditioned to adopt an activated state with distinguishing features (increased CD63 expression). This is consistent with the notion that the CF airway environment can trigger early inflammation, as previously proposed in select mouse models of CF (38,47,48), human CF fetal xenografts (15), CF ferrets (18,49), and children with CF (13). A Figure 1.…”

“…A prime target for intervention is NE, for which inhibitors (53) should be tested for their ability to block not only extracellular, but also surface-associated forms. Alternative strategies include reducing the number of neutrophils recruited from blood (54,48) and their ability to exocytose primary granules (55).…”

Sphingolipids role in the regulation of inflammatory response: From leukocyte biology to bacterial infection

“…In the context of CF airways pathology, new interest has recently emerged for S1P as regulator of CFTR activity, as well as from the intriguing relationship between altered S1P content and inflammatory response to bacterial infection . The involvement of S1P in CF pathology is supported by evidence that inhibition of S1P degradation is associated with decreased lung inflammatory response to P. aeruginosa in a CF mouse model . In brief, abnormally elevated signaling downstream S1PRs could have detrimental effects on CF lung pathophysiology, thus making regulation of S1P/S1PR pathway a potentially relevant molecular target.…”

“…52 The involvement of S1P in CF pathology is supported by evidence that inhibition of S1P degradation is associated with decreased lung inflammatory response to P. aeruginosa in a CF mouse model. 65 In brief, abnormally elevated signaling downstream S1PRs could have detrimental effects on CF lung pathophysiology, thus making regulation of S1P/S1PR pathway a potentially relevant molecular target. The concept of S1P as a critical regulator of host antimicrobial effector pathways has been earlier provided by Garg et al, 66 who showed that S1P reduced mycobacterial growth and pulmonary damage both in vitro and in vivo.…”

Sphingosine 1-Phosphate: A Novel Target for Lung Disorders

“…However, treatment with SPL inhibitor (LX2931) could restore the S1P levels. Moreover, the CF phenotype of CFTR mutant mice was partially corrected by LX2931 further confirming the possible therapeutic targeting of S1P signaling in CF (50). …”