Expression of surfactant protein D in human corneal epithelial cells is upregulated by Pseudomonas aeruginosa.
We reported previously that surfactant protein D (SP-D) was present in human tears and corneal epithelial cells, and that it contributed to tear fluid protection of those cells against Pseudomonas aeruginosa invasion. This suggested a role in ocular innate immunity. Here, we explored the effects of bacterial challenge on SP-D expression by human corneal epithelial cells. Results showed that these cells produced and secreted SP-D constitutively in culture, and that production (mRNA, protein) and secretion of SP-D were upregulated after exposure to heat-killed P. aeruginosa or to purified flagellin or lipopolysaccharide. To begin exploring the mechanism for flagellin-mediated SP-D induction, cells were exposed to purified flagellin or flagellin mutated in the TLR-5-binding domain (L94A, L88A) which reduces IL-8 secretion by A549 respiratory cells. Mutated flagellin did not upregulate IL-8 expression in corneal epithelial cells, but did induce SP-D responses. Mitogen-activated protein kinase inhibitors, especially the JNK inhibitor SP600125, reduced secretion of SP-D, but not production, in the presence of P. aeruginosa. These data show that while SP-D and IL-8 corneal responses are each induced by P. aeruginosa or its antigens, they can involve different regions of the same ligand. The data suggest that separate mechanisms may regulate SP-D secretion and production by human corneal epithelia.
Ni
Minjian
M
School of Optometry, University of California, Berkeley, CA 94720, USA.
Tam
Connie
C
Verma
Amrisha
A
Ramphal
Reuben
R
Hawgood
Samuel
S
Evans
David J
DJ
Fleiszig
Suzanne M J
SM
D000704:Analysis of Variance; D000942:Antigens, Bacterial / Q000235:genetics / Q000378:metabolism; D002461:Cell Line, Transformed; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019573:Epithelium, Corneal / Q000276:immunology* / Q000378:metabolism* / Q000382:microbiology; D005408:Flagellin / Q000235:genetics / Q000276:immunology; D005786:Gene Expression Regulation; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism; D008024:Ligands; D008070:Lipopolysaccharides / Q000276:immunology; D017354:Point Mutation; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000276:immunology*; D037663:Pulmonary Surfactant-Associated Protein D / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation
D000942:Antigens, Bacterial; D004791:Enzyme Inhibitors; D016209:Interleukin-8; D008024:Ligands; D008070:Lipopolysaccharides; D037663:Pulmonary Surfactant-Associated Protein D; D005408:Flagellin