Pseudomonas aeruginosa corneal infection affects cholinergic enzymes in rat lacrimal gland

Since the increased use of extended-wear contact lenses, Pseudomonas aeruginosa has emerged as a primary etiological agent of ulcerative keratitis. Clinical isolates have been classified into two types: cytotoxic and non-cytotoxic. This study revealed significant immune and neuro-enzymatic changes elicited by the two types of P. aeruginosa in the lacrimal gland of rats. The humoral immune response in the lacrimal gland to the non-cytotoxic strain was significantly lower than to the cytotoxic strain, possibly due to the immunogenicity of the extracellular toxin; however, the same effect was not seen in the serum. Choline acetyltransferase and acetylcholinesterase are known to be responsible for synthesis and degradation of acetylcholine, respectively, binding receptors on acini and plasma cells, modulating their activity, and constituting the principle regulator of tear secretion. Following infection, neuro-enzyme activities were significantly modified to reduce the concentration of acetylcholine and therefore potentially reduce secretion from the glands. The data lead to the hypothesis that P. aeruginosa may have the potential to reduce the protective barrier provided by the lacrimal gland to benefit pathogenicity. It was also observed that the neuro-enzyme response of the lacrimal glands of uninfected eyes of the test animals was the same as that of infected eyes, implying that the signal may be relayed by common lymphoidal tissue or the central nervous system and a measurable response returned to both eyes.