COREGULATED EXPRESSION OF GLOMERULAR 12 15-LIPOXYGENASE AND INTERLEUKIN-4 MESSENGER-RNAS IN RAT NEPHROTOXIC NEPHRITIS/

Arachidonate 12- and 15-lipoxygenase (LO) products are generated in ex perimental glomerulonephritis. 15-S-HETE (a 15-LO product) and lipoxin s (interaction products between 5-LO and either 12-LO or 15-LO) counte ract the proinflammatory actions of leukotrienes. IL-4 has been shown to up-regulate 15-LO gene expression in human leukocytes. Based on hom ology with human 15-LO, we cloned a 0.76 kbp fragment of a rat LO cDNA from leukocytes stimulated by interleukin-4 (IL-4). The deduced amino acid sequence shows 71.0% and 60.1% homology to human 15-LO and 12-LO , respectively, and 100% homology to a recently cloned ''leukocyte typ e'' rat 12-lipoxygenase enzyme, which possesses significant 15-lipoxyg enase activity (heretofore referred to as ''12/15-LO''). A deletion mu tant was utilized to generate internal standard cRNA in quantitative P CR assays. Glomerular 12/15-LO mRNA increased significantly over contr ols 24 and 48 hours after NTS injection, then decreased at 72 hours. R NA from NTS glomeruli contained higher levels of 12/15-LO mRNA than th at from unstimulated peripheral leukocytes, suggesting that 12/15-LO t ranscription is up-regulated locally in native and/or infiltrating glo merular cells. Glomerular IL-4 mRNA increased markedly 16 hours post-N TS, and was then reduced, suggesting a potential role for T cell-deriv ed IL-4 in directing the expression of 12/15-LO during glomerulonephri tis. This represents the first demonstration of tandem regulated in vi vo gene expression for a lymphokine (IL-4) and a lipoxygenase, both of which promote counter-inflammatory influences in immune complex-media ted injury.