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Sphingosine kinase 2 Generated Nuclear S1P is an Epigenetic Co‐Regulator of Pseudomonas aeruginosa ‐Induced Lung Inflammation
Author(s) -
Ebenezer David Lenin,
Fu Panfeng,
Berdyshev Evgeny,
Natarajan Viswanathan
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.1053.6
Subject(s) - sphingosine , sphingosine kinase , biology , inflammation , sphingosine kinase 1 , sphingosine 1 phosphate , cancer research , kinase , microbiology and biotechnology , immunology , biochemistry , receptor
Pseudomonas aeruginosa (PA ) , a gram‐negative, opportunistic, aerobic bacilli is associated with rapid deterioration of the cystic fibrotic lung and is the significant cause of pneumonia in immunocompromised and mechanical ventilated patients. A distinctive feature of P. aeruginosa lung infection is the incessant inflammation‐driven respiratory failure that contributes to increased morbidity and mortality. Our research aims to define the epigenetic role of Sphingolipids in regulating immunological events in P. aeruginosa ‐induced lung inflammation that has remained undefined so far. Sphingosine‐1‐Phosphate (S1P), is a bioactive sphingolipid that plays a key role in regulating signaling pathways modulating inflammatory responses in cells. Sphingosine Kinase (SphK) 1 & 2 generate intracellular S1P and Sphingosine‐1‐Phosphate Lyase (S1PL) and S1P Phosphatase (SPP) catalyze its degradation. Our murine model studies, as evident from decreased levels of inflammatory cytokines, proteins and cell counts in bronchoalveolar lavage and neutrophil migration to the alveolar space, suggest that knocking out SphK2, but not SphK1, offers protection against PA‐induced lung inflammation. PA infection also induced phosphorylation of SphK2 and subsequent translocation to the nucleus in mouse lung tissues and mouse lung epithelial cell line (MLE‐12). PA‐induced SphK2 phosphorylation resulted in increased acetylation of Histone H3 and H4 that correlated with increased IL‐6 gene expression at mRNA and protein levels. Moreover, PA infection decreased Histone Deacetylase (HDAC) activity in a time dependent manner in mouse alveolar type II cells and we validated SphK2 association with HDAC 1 & 2 by co‐immuno precipitation with nuclear HDAC repressor complex proteins. Nuclear fractions isolated from MLE‐12 cells exhibited significant levels of sphingosine and ceramide and stimulation with PA enhanced nuclear S1P in the presence of S1P lyase inhibitor, 4‐deoxypyridoxine. Interaction of sphingosine and S1P with HDAC1 and 2 in MLE‐12 nuclear fraction was confirmed by bio‐conjugate technique using biotin tagged sphingosine and S1P. Furthermore, using MLE‐12 nuclear fraction, we were able to demonstrate, that inhibition of nuclear HDAC activity by S1P is as potent as the inhibition obtained using Trichostatin A (TSA), a HDAC inhibitor. To examine the therapeutic potential of targeting SphK2‐S1P signaling axis in the treatment of PA‐induced lung inflammation, we evaluated ABC 294640, a specific SphK2 inhibitor in mice and observed reduction in PA‐induced inflammation. Taken together, these results emphasize the novel role of nuclear S1P in PA‐induced lung inflammation and targeting SphK2 could be a therapeutic option to treat bacterial infection of the lung. Support or Funding Information This work is supported by NIH/HLBI P01 HL98050 to VN.