K. Connolly1, P. J. Matheson2, J. A. Shepherd2, J. W. Smith2, R. N. Garrison2, C. D. Downard2 1University Of Louisville,School Of Medicine,Louisville, KY, USA 2University Of Louisville,Department Of Surgery,Louisville, KY, USA
Introduction: Macrophages clear bacteria from the gut in the early stages of necrotizing enterocolitis (NEC), a potentially lethal inflammatory bowel disease of premature infants. Chemokine (C-C) ligand 3 (CCL3 or macrophage inflammatory protein-1a, MIP-1a) and Interleukin-12 (IL-12) are key chemokines/cytokines in this process. CCL3, a chemokine, recruits immune cells such as monocytes and neutrophils to the site of injury and induces the release of other pro-inflammatory cytokines including IL-1, IL-6, and tumor necrosis factor-a (TNF-a). IL-12, a pro-inflammatory cytokine, recruits and activates immune cells including T cells and NK cells.. We hypothesized that CCL3 and IL-12 expression in the ileum might be increased in the context of NEC-associated inflammation.
Methods: Sprague-Dawley rats were randomized to groups by litter. CONTROLS were delivered vaginally and dam-fed. NEC groups were delivered by C-section 12 hours prematurely, formula fed, exposed to intermittent cold and hypoxia, and given a single oral dose of lipopolysaccharide. Ileum samples were obtained at 0, 12, 24, 48, 72 and 96 hours of life and western blots were performed with antibodies against CCL3, IL-12, and b-actin for normalization by individual animal. Statistical analysis was performed using 2-way ANOVA and a priori P<0.05.
Results: Ileal CCL3 and IL-12 protein expression (see Figure) in NEC was below Control levels at 24 hours, but increased at 72 hours versus Controls (*P<0.05). The change in ileal protein expression occurred between the 24 and 48 hour time points for both mediators.
Conclusion: These data support our prior studies that demonstrated a similar pattern of CCL3 and IL-12 expression in the serum of NEC rats versus Control. Since macrophage function plays a key role in the early development of NEC, down-regulation of IL-12 in the setting of increased CCL3 might represent deranged or inhibited macrophage function in the NEC disease process.
