The role of VIP in cornea.
OBJECTIVE
Exogenous vasoactive intestinal peptide (VIP) down-regulates pro-inflammatory but up-regulates anti-inflammatory cytokines, growth factors (GFs) and Toll-like receptors promoting healing in experimental Pseudomonas aeruginosa (P. aeruginosa) keratitis. Whether VIP is required for GF or GF receptor (R) expression in normal and infected corneas is unknown and is the purpose of this study.


METHODS
VIP knockout ((-/-)) and wild-type (WT) C57BL/6 (B6) mice were infected and tested using PCR array, real-time RT-PCR, ELISA, and immunostaining. VIP antagonist treatment studies also were done using B6 and BALB/c mice.


RESULTS
Infected corneas of VIP(-/-) versus WT B6 mice perforated earlier (2 vs. 5 days postinfection [p.i.]), and array data showed that GFs were differentially changed between groups. RT-PCR revealed that the infected cornea of VIP(-/-) versus WT mice expressed higher mRNA levels of epidermal growth factor (EGF) and hepatocyte growth factor (HGF), reduced FGF, EGFR, and HGFR, with no difference in FGFR; differences between groups were not seen in normal cornea. Immunostaining for GF and GFR in the normal cornea of VIP(-/-) versus WT mice was similar. However, at 1 day p.i., VIP(-/-) versus WT mice had more intense EGF and HGF, similar FGFR, and reduced FGF, EGFR, and HGFR staining. VIP antagonist treatment decreased protein levels for GFR at 5 days p.i. in both B6 and BALB/c mice, with no significant changes in normal cornea.


CONCLUSIONS
The data showed that endogenous VIP is not requisite for GF or GFR expression in the normal cornea but, after infection, its absence or reduction is critical for their regulation.
Department of Anatomy & Cell Biology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
Xiaoyu
X
Jiang
Sharon A
SA
McClellan
Ronald P
RP
Barrett
Yunfan
Y
Zhang
Megan E
ME
Foldenauer
Linda D
LD
Hazlett
D000818:Animals; D015169:Colony Count, Microbial; D003315:Cornea / Q000378:metabolism* / Q000382:microbiology / Q000473:pathology; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D015818:Eye Infections, Bacterial / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects*; D007634:Keratitis / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D018696:Neuroprotective Agents / Q000627:therapeutic use; D011552:Pseudomonas Infections / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D011550:Pseudomonas aeruginosa / Q000302:isolation & purification; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics*; D017978:Receptors, Growth Factor / Q000096:biosynthesis / Q000187:drug effects / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051193:Toll-Like Receptors / Q000096:biosynthesis / Q000235:genetics; D014660:Vasoactive Intestinal Peptide / Q000627:therapeutic use*
D018696:Neuroprotective Agents; D012333:RNA, Messenger; D017978:Receptors, Growth Factor; D051193:Toll-Like Receptors; D014660:Vasoactive Intestinal Peptide