Sphingosine kinase 1 activation enhances epidermal innate immunity through sphingosine-1-phosphate stimulation of cathelicidin production

J Dermatol Sci. 2015 Sep;79(3):229-34. doi: 10.1016/j.jdermsci.2015.06.007. Epub 2015 Jun 19.


Background: The ceramide metabolite, sphingosine-1-phosphate (S1P), regulates multiple cellular functions in keratinocytes (KC). We recently discovered that production of a key innate immune element, cathelicidin antimicrobial peptide (CAMP), is stimulated via a NF-κB-dependent mechanism that is activated by S1P when S1P is generated by sphingosine kinase (SPHK) 1.

Objective: We investigated whether pharmacological modulation of SPHK1 activity, using a novel synthetic SPHK1 activator, (S)-methyl 2-(hexanamide)-3-(4-hydroxyphenyl) propanoate (MHP), stimulates CAMP expression.

Methods: MHP-mediated changes in both S1P and CAMP downstream mediators were analyzed in normal cultured human KC by qRT-PCR, Western immunoblot, ELISA, confocal microscopy for immunohistochemistry, HPLC and ESI-LC/MS/MS, and microbial pathogen invasion/colonization in a human epidermal organotypic model.

Results: Treatment with MHP directly activated SPHK1 and increased cellular S1P content in normal cultured human KC. Because MHP did not inhibit S1P lyase activity, which hydrolyses S1P, augumented S1P levels could be attributed to increased synthesis rather than blockade of S1P degradation. Next, we found that exogenous MHP significantly stimulated CAMP mRNA and protein production in KC, increases that were significantly suppressed by siRNA directed against SPHK1, but not by a scrambled control siRNA. NF-κB activation, assessed by nuclear translocation of NF-κB, occurred in cells following incubation with MHP. Conversely, pretreatment with a specific inhibitor of SPHK1 decreased MHP-induced nuclear translocation of NF-κB, and significantly attenuated the MHP-mediated increase in CAMP production. Finally, topical MHP significantly suppressed invasion of the virulent Staphylococcus aureus into murine skin explants.

Conclusion: MHP activation of SPHK1, a target enzyme of CAMP production, can stimulate innate immunity.

Keywords: Antimicrobial defense; Cathelicidin antimicrobial peptide; Small molecule; Sphingosine kinase 1.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antimicrobial Cationic Peptides / biosynthesis*
  • Antimicrobial Cationic Peptides / genetics
  • Bacterial Physiological Phenomena / drug effects
  • Cathelicidins
  • Cells, Cultured
  • Enzyme Activators / pharmacology
  • Enzyme Inhibitors / pharmacology
  • Epidermis / enzymology
  • Epidermis / immunology*
  • Humans
  • Immunity, Innate*
  • Keratinocytes / chemistry
  • Keratinocytes / enzymology*
  • Keratinocytes / immunology
  • Lysophospholipids / metabolism*
  • Mice
  • NF-kappa B / metabolism
  • Phosphotransferases (Alcohol Group Acceptor) / genetics
  • Phosphotransferases (Alcohol Group Acceptor) / metabolism*
  • RNA, Messenger / metabolism
  • RNA, Small Interfering / pharmacology
  • Sphingosine / analogs & derivatives*
  • Sphingosine / metabolism
  • Staphylococcus aureus / drug effects
  • Staphylococcus aureus / physiology
  • Tyrosine / analogs & derivatives
  • Tyrosine / pharmacology


  • Antimicrobial Cationic Peptides
  • Enzyme Activators
  • Enzyme Inhibitors
  • Lysophospholipids
  • NF-kappa B
  • RNA, Messenger
  • RNA, Small Interfering
  • methyl 2-(hexanamide)-3-(4-hydroxyphenyl)propanoate
  • sphingosine 1-phosphate
  • Tyrosine
  • Phosphotransferases (Alcohol Group Acceptor)
  • sphingosine kinase
  • Sphingosine
  • Cathelicidins