Bilateral acute pyogenic conjunctivitis with iritis induced by unilateral topical application of bacterial peptidoglycan muramyl dipeptide in adult rabbits

• Published in: Experimental eye research 2013-11, Vol.116, p.324-336
• Main Authors: Langford, Marlyn P., Foreman, Bridgett D., Srur, Lana, Ganley, James P., Redens, Thomas B.
• Format: Article
• Language: English
• Subjects: Acetylmuramyl-Alanyl-Isoglutamine - administration & dosage; Acetylmuramyl-Alanyl-Isoglutamine - toxicity; Acute Disease; Administration, Topical; Animals; Bacteria; calreticulin; conjunctivitis; Conjunctivitis - metabolism; Conjunctivitis - microbiology; Conjunctivitis - pathology; Cytokines - metabolism; Disease Models, Animal; efferocytosis; Eye Infections, Bacterial - chemically induced; Eye Infections, Bacterial - metabolism; Eye Infections, Bacterial - microbiology; Female; gamma-glutamyltranspeptidase; iritis; Iritis - metabolism; Iritis - microbiology; Iritis - pathology; Male; muramyl dipeptide; neutrophils; Rabbits; Tears - chemistry
• ISSN: 0014-4835; 1096-0007
• DOI: 10.1016/j.exer.2013.10.005

The factors responsible for the conjunctivitis and iritis associated with acute ocular infection and post enteric inflammatory disease are not fully known. The pro-inflammatory activity of unilateral topical application of muramyl dipeptide (MDP; the smallest bio-active Gram-positive and Gram-negative bacterial cell wall component) was investigated in adult rabbits. The resultant bilateral conjunctivitis/iritis and pyogenic responses were characterized. Bilateral symptoms were graded by slit lamp examinations; tear fluid, Schirmer tests (tear production), blood and aqueous humor (AH) samples were obtained from MDP-treated and untreated rabbits. MDP concentration, gamma-glutamyltranspeptidase activity (GGT; key enzyme in glutathione recapture, xenobiotic detoxification, eicosanoid synthesis and neutrophil function), protein concentration, and tear cell density, cytology, and immunofluorescent antibody reactivity to GGT and calreticulin (CRT; MDP-binding protein) were determined. MDP was cleared from ipsilateral tears and serum by 6 h, but was undetected in mock-treated contralateral tears. Bilateral signs of acute transient pyogenic conjunctivitis, characterized by tearing, lid edema, conjunctival hyperemia, chemosis and leukocytic infiltrate with iritis (erythema and aqueous flare) were detected. Milder symptoms occurred in the mock-treated contralateral eyes. Bilateral symptoms, tear production, tear protein, GGT activity, and mucopurulent discharge (containing up to 2.5–5.0 × 106 cells/mL) were elevated 4–8 h post MDP and resolved to near pre-treatment levels by 24 h. Tear GGT activity and protein levels were higher in MDP-treated and mock-treated contralateral eyes than in eyes of untreated adult rabbits (p's