Increased renal thromboxane production in murine lupus nephritis

To determine whether the amount of cyclooxygenase metabolites correlates with the development of lupus nephritis, intrarenal eicosanoid production was measured in autoimmune mice. Disease progression was related to the renal biosynthesis of prostaglandin (PGE2), prostacyclin (6 keto PGF1 alpha), and thromboxane (TXB2) using the MRL-lpr and NZB X NZW F1 hybrid mouse strains with predictably progressive forms of renal disease that mimic the human illness. Mice were evaluated for renal disease by measuring urinary protein excretion and renal immunopathological conditions and these features were related to renal eicosanoid production. These studies show that: (a) intrarenal synthesis of TXB2 increased incrementally in MRL-lpr and NZB X NZW F1 hybrid mice as renal function deteriorated and renal pathologic events progressed; (b) there were no consistent increases in the levels of two other cyclooxygenase metabolites, PGE2 or 6 keto PGF1 alpha; (c) increased TXB2 production occurred in the renal medulla, cortex, and within enriched preparations of cortical glomeruli; (d) when renal disease was prevented by pharmacologic doses of PGE2, intrarenal TXB2 did not increase; (e) administration of a dose of ibuprofen (9 mg/kg), a cyclooxygenase inhibitor capable of reducing 90% of platelet TXB2 without affecting intrarenal levels, did not retard the progression of renal damage. Taken together, these data indicate that the intrarenal level of TXB2 rises in relation to the severity of murine lupus nephritis. Furthermore, because of the potential deleterious effects of TXA2, enhanced production of this eicosanoid may be an important mediator of renal injury.