The relationships between seasonal variations in the concentration of urea in bulk milk and the production and fertility of dairy herds

The retinal pigment epithelium (RPE) is clinically involved in diverse ocular inflammatory diseases. Because perturbed RPE cells produce a variety of inflammatory substances, RPE cells may play an integral part in these diseases. Interleukin-1 (IL-1) and granulocyte-macrophage colony-stimulating factor (GM-CSF) are pleiotropic cytokines with the ability to trigger numerous inflammatory responses. This report shows that cultured human RPE cells synthesize interleukin-1 beta (IL-1 beta) and GM-CSF in response to the potentially inflammatory cytokine, IL-1 alpha, but not to E. coli endotoxin. Control RPE cells made little or no mRNA or protein for either IL-1 beta or GM-CSF. Upon stimulation of the cells by IL-1 alpha, both IL-1 beta and GM-CSF mRNAs were readily apparent by 3 hours, persisted for over 24 hours, and were translated into immunologically detectable proteins. GM-CSF protein was secreted into the culture medium, whereas IL-1 beta protein remained cell associated. The IL-1 alpha-induced mRNA and protein production were inhibited by dexamethasone. These observations provide additional evidence that RPE cells are capable of playing a pivotal role during ocular inflammation.