Spantide I decreases type I cytokines, enhances IL-10, and reduces corneal perforation in susceptible mice after Pseudomonas aeruginosa infection

Purpose: To determine the effects of blocking substance P (SP) interactions with its major receptor (NK1-R) using the antagonist spantide I in susceptible mice infected with Pseudomonas aeruginosa.

Methods: Immunohistochemistry and Enzyme immunosorbent assay (EIA) tested levels of SP in the cornea of B6 and BALB/c mice. B6 mice were treated with spantide, and after Infection, slit lamp examination; clinical score; Bacterial counts; and myeloperoxidase (MPO), RT-PCR, ELISA, and polymorphonuclear (PMN) cell chemotaxis assays were performed.

Results: SP corneal levels were significantly elevated constitutively and after Infection in the B6 more than in BALB/c mice. Spantide treatment of B6 mice significantly decreased the number of perforated corneas, Bacterial counts, and PMNs. mRNA levels for type I cytokines (e.g., IFN-gamma) as well as MIP-2, IL-6, TNF-alpha, and IL-1beta (mRNA and protein) also were significantly reduced after spantide treatment. The type II cytokine IL-10 (mRNA and protein) was elevated, whereas TGF-beta mRNA levels were unchanged after spantide treatment. PMN chemotaxis was induced by SP and other neuropeptides in vitro, but was not affected by spantide I. mRNA for neurokinin-1-receptor-1 (NK-1R) was detected in the normal and infected corneas and on macrophages (Mphis), but not on PMNs (unstimulated or stimulated with endotoxin [LPS]). Spantide treatment of Mphis reduced IL-1beta after LPS+SP treatment but not after either alone.

Conclusions: The SP antagonist Spantide provides a novel approach to reduce type 1 and enhance the type 2 cytokine IL-10 in the infected cornea of B6 mice, leading to a significant reduction in corneal perforation and improved disease outcome.