Role of the Kidney in Metabolic Change of Interleukin-2

Abstract

The metabolic change of human recombinant interleukin-2 (IL-2) was investigated by the use of ¹²⁵I-labeled IL-2 (¹²⁵I-IL-2). After intravenous injection into mice, the distribution of ¹²⁵I-IL-2 in various organs revealed that the major portion of injected ¹²⁵I-IL-2 was rapidly accumulated in the kidney. Simultaneous injection of an excess amount of cold IL-2 greatly reduced the distribution of ¹²⁵I-IL-2 to the kidney, suggesting that the accumulation of ¹²⁵I-IL-2 by the kidney was a specific reactivity between ¹²⁵I-IL-2 and the kidney. The gel filtration profile of ¹²⁵I-IL-2 in the serum specimens remained the same as that of the originally injected sample, and differed completely from that in the urine specimens, suggesting that ¹²⁵I-IL-2 was metabolized in the kidney. To confirm this notion, ¹²⁵I-IL-2 was incubated in vitro with kidney homogenate, which degraded ¹²⁵I-IL-2 in acidic pH. After subcellular fractionation, the cytosol fraction of the kidney was shown to hydrolyze ¹²⁵I-IL-2 with an optimal pH of 4. The reactivity of the kidney cytosol fraction with ¹²⁵I-IL-2 was inhibitable by pepstatin, an acid protease inhibitor, but not by TLCK or TPCK. Additional experiments using a heat-treated kidney cytosol fraction plus cathepsin D, and pepstatin inhibition on the degradation of ¹²⁵I-IL-2 by cathepsin D, a major acid protease in the kidney, resulted in the identification of this enzyme to be responsible for the degradation of ¹²⁵I-IL-2. Overall, these results demonstrated that the kidney is the organ to metabolize IL-2 and that cathepsin D, a renal acid protease, is involved in the degradation of IL-2.

Treatment of metastatic renal cell carcinoma with subcutaneous interleukin 2: evidence for non-renal clearance of cytokines

“…It is possible that the cytokines detected in urine may be proteolytic fragments as found in mice following i.v. IL-2 (Ohnishi et al, 1989(Ohnishi et al, , 1990, and it is possible that much larger amounts of proteolytically degraded cytokines are present but not detected by the assays used.…”

“…Evidence from animal and human studies clearly demonstrates a renal clearance of IL-2 following i.v. administration (Donohue and Rosenberg, 1983;Donohue et al, 1984;Lotze et al, 1985;Ohnishi et al, 1989Ohnishi et al, , 1990Konrad et al, 1990; Gibbons et al, 1995;Nadeau et al, 1995), with a very rapid initial clearance followed by a more delayed clearance thought to be due to the slower release from the extravascular space back to the plasma. In rats, double nephrectomy produces an approximate twofold increase in the half-life of IL-2, a 10-to 20-fold increase in initial plasma levels and a 75% reduction in the clearance of IL-2 (Gibbons et al, 1995), which supports the existence of an British Journal of Cancer (1997) additional but less efficient clearance mechanism.…”

“…The calculated plasma clearance of 120 ml min-m is consistent with renal clearance (Lotze et al, 1985). This is supported by animal studies showing a rapid renal accumulation of radiolabelled IL-2 (Koths and Halenbeck, 1985;Ohnishi et al, 1989) and marked prolongation of the half-life by double nephrectomy or ligation of the ureters or renal pedicles (Donohue and Rosenberg 1983;Gibbons et al, 1995). If the hydrodynamic size of IL-2 is comparable to that predicted by its covalent structure, glomerular filtration would be expected to occur.…”

“…administration, fragments of IL-2 have been found. These are thought to occur as a result of catabolism by renal cathepsin D with the specific inhibitor pepstatin decreasing the renal accumulation of IL-2 and increasing the t,/2 (Ohnishi et al, 1989;Ohnishi et al, 1990 …”

“…administration, fragments of IL-2 have been found. These are thought to occur as a result of catabolism by renal cathepsin D with the specific inhibitor pepstatin decreasing the renal accumulation of IL-2 and increasing the t,/2 (Ohnishi et al, 1989;Ohnishi et al, 1990 depending on the dose used (Konrad et al, 1990), but it is not known whether the same mechanisms of clearance apply. In support of an alternative clearance mechanism at lower doses are the brief reports of the treatment of three anephric patients with s.c. IL-2, two of whom experienced similar toxicity to that experienced by many patients with normal renal function apart from more pronounced hypotension (Buter et al, 1992) and the other experiencing more severe toxicity (OMS .…”