Potentials and Limitations of the Low-Molecular-Weight Protein Lysozyme as a Carrier for Renal Drug Targeting

Abstract

Selective targeting of drugs to the kidney may enable an increased renal effectiveness combined with a reduction of extrarenal toxicity. Intrarenal delivery to the proximal tubular cell can be achieved using low-molecular-weight proteins, such as lysozyme. Administration of high dosages of lysozyme, required to study the effects of such conjugates in vivo, however, is restricted since a partial escape of the renal reabsorption and the occurrence of unwanted effects on systemic blood pressure and renal function may occur. The purpose of this study was to investigate the optimal parenteral administration schedule and the maximum dose of lysozyme, providing the most optimal tubular reabsorption and at the same time a minimal effect on blood pressure and renal hemodynamics, comparing continuous infusion of lysozyme with single dose injections. Urinary lysozyme excretion increased dose-dependently, both during continuous infusion and intravenous bolus injections. However, this loss of intact lysozyme into the urine was much higher after 3 injections of in total 250 mg x kg(-1) x 6 h(-1) (51.8+/-3.7% of the dose) compared to the same dose administered by continuous infusion (11.7+/-2.4%, P < 0.001). Continuous infusion of lysozyme up to 1000 mg x kg(-1) in 6 hours had no effect on systemic blood pressure, whereas a bolus injection of lysozyme (167 mg x kg(-1)) resulted in reversible blood pressure lowering of 52.2+/-2.2% (P<0.001). A dose-dependent decline of the glomerular filtration rate was observed at dosages of lysozyme higher than 100 mg x kg(-1) x 6 h(-1), with a maximal reduction of 53.0+/-3.7% after infusion of 1000 mg x kg(-1) x 6 h(-1). Effective renal plasma flow was less affected and only lowered statistically significant at dosages of 500 (-12.6+/-3.3%, P<0.05) to 1000 mg x kg(-1) x 6 h(-1) (-17.2+/-3.9%, P<0.01). We conclude that bolus injections of lysozyme should not be used for renal targeting purposes since it results in considerable tubular loss of lysozyme in the urine as well as cardiovascular side effects. In contrast, continuous infusion of lysozyme using dosages sufficient for renal drug targeting (maximally 15 mg x kg(-1) x h(-1)) only has minimal effects on blood pressure and renal hemodynamics, with a minimal urinary lysozyme loss as well.

Targeting of Captopril to the Kidney Reduces Renal Angiotensin-Converting Enzyme Activity without Affecting Systemic Blood Pressure

“…In a previous study, we demonstrated that this slow continuous infusion allows for the administration of high doses of lysozyme without affecting systemic and renal physiology (Haverdings et al, 2001a). As expected from the literature, intravenous infusion of free captopril resulted in an acute lowering of systemic blood pressure (Cushman et al, 1989).…”

Renal-Selective Delivery and Angiotensin-Converting Enzyme Inhibition by Subcutaneously Administered Captopril-Lysozyme

“…In addition, renal disease will damage the glomerulus, leading to filtration of plasma proteins, which subsequently are also reabsorbed by these receptors (Leheste et al, 1999). High concentrations of lysozyme or plasma proteins in the preurine may saturate the megalin receptors and reduce the efficiency of the reabsorption process (Haverdings et al, 2001). Indeed, we observed this phenomenon when we administered different doses of lysozyme in healthy and proteinuric rats.…”

Anti-Inflammatory Effects of Lysozyme Against HMGB1 in Human Endothelial Cells and in Mice

“…Because the average weight of used mouse is 27 g, and the average blood volume is 2 mL, the amount of lysozyme (0.57, 1.43, 2.86, or 5.72 μg per mouse) injected yielded a maximum concentration of 20, 50, 100, or 200 nM in the peripheral blood. Maximum amounts of used lysozyme (5.72 μg per mouse=212 μg/kg) administrated into mouse is safe because previous reports used up to 100 mg/kg [31], 300 mg/kg [32], or 1000 mg/kg [33]. To determine the molecular mechanism by which lysozyme inhibited the release of LPS-mediated HMGB1, we tested the effects of lysozyme on the transcriptional regulation of HMGB1 by LPS in HUVECs.…”