Abstract
Purpose: :
CXC chemokines are well known PMN agonists that play an important role in the activation of chemotaxis, PMN degranulation and angiogenesis through CXCR1 and CXCR2. We propose to study the expression of a 10 kDa CXC chemokine called platelet binding protein (PBP) which is the precursor of connective tissue activating peptide–III (CTAP–III), beta–thromboglobulin antigen (B–TG) and neutrophil activating peptide (NAP–2) in the murine eye before and during corneal infection with Pseudomonas aeruginosa.
Methods: :
We used RT–PCR, western blots and immunohistochemistry to determine if CXC chemokines were expressed in the eyes of C57BL/6J mice before and after corneal infection with P. aeruginosa using a seven day post–infection holding period.
Results: :
Using RT–PCR, we detected the constitutive expression of the 10 kDa corneal PBP which was upregulated during corneal infection, but less so in immunized mice. Western blot studies yielded similar results as well as the proteolytic PBP end product termed NAP–2. An 80 kDa protein band was also expressed suggesting that it shared partial homology with PBP. Immunohistochemical studies indicated that PBP expression was constitutively present in the uninfected corneas, retinas and lens and was upregulated in the corneas and lens during infection. PBP expression was detected in the three major layers of the cornea and retina prior to infection as well as in corneal PBP positive infiltrating cells during infection.
Conclusions: :
PBP shares a common C–terminal domain with other CXC cytokines and is the precursor of CTAP–III and NAP–2 residues after N–processing. PBP was constitutively expressed in the corneas, retinas and lens and was upregulated during corneal infection. These PMN agonists may play an important role in regulating innate immunity as well as in chemotaxis and angiogenesis during infection.
Keywords: Pseudomonas • keratitis • cytokines/chemokines