Renal targeting of captopril using captopril-lysozyme conjugate enhances its antiproteinuric effect in adriamycin-induced nephrosis

Abstract

Introduction High-sodium intake blunts the renoprotective efficacy of angiotensin-converting enzyme (ACE) inhibitors. We investigated whether targeting the drug to the kidneys may attenuate the inferior response to ACE inhibitor (ACE-I) under high-sodium conditions. The ACE-I, captopril, was coupled to the low molecular weight protein (LMWP) lysozyme, yielding captopril-lysozyme conjugates that accumulate specifically in the proximal tubular cells of the kidneys.We compared the antiproteinuric efficacy of captopril to that of the captopril-lysozyme conjugate in adriamycin-induced proteinuric rats fed with a high-sodium diet. Materials and methods Rats with adriamycin (single injection 2 mg/kg)-induced proteinuria were put on a high-sodium diet (HS; 3% NaCl). When stable proteinuria developed at 5.5 weeks, animals were assigned to the following subcutaneous treatments: (1) vehicle (n=7); (2) lysozyme (equivalent to the amount in conjugate) (n=7); (3) captopril (5 mg/kg/24 hours) (n=8); (4) captopril-lysozyme conjugate (captopril content equivalent to 1mg captopril/kg/24 hours) (n=7). Blood pressure and proteinuria were monitored. After 10 days of treatment the rats were sacrificed and kidneys and plasma were removed. Results Results are given as mean + S.E.M. After injection with adriamycin at t=0, stable proteinuria developed, amounting to 547+79 mg/24 hours at week 5.5. Subsequently, after seven and nine days of treatment, no reduction of proteinuria was observed in the captopril-treated group. In contrast, a significant reduction in proteinuria, amounting to 35+4% (day seven) and 25+2% (day nine), was observed in the captopril-lysozyme conjugate group (p<0.05 compared with the captopril group). In contrast, blood pressure was reduced in the captopril-treated group by 13.9+2.9 mmHg, while in the captopril-lysozyme treated group, an increase of 7.9+3.3 mmHg was found. Renal ACE activity was lowered by 30% in the captopril, as well as in the captopril-lysozyme conjugate treated group, compared with control. Furthermore, the ratio of kidney: plasma levels of captopril almost doubled as a consequence of coupling to lysozyme. Conclusion In proteinuric rats fed with a high-sodium diet, captopril induced a reduction in blood pressure without an effect on proteinuria. In contrast, renal targeting of a five times lower dose of the ACE-I with the captopril-lysozyme conjugate reduced proteinuria without reducing blood pressure. Therefore, renal targeting of ACE-I may be a promising strategy to optimise the therapeutic response of ACE-I.

Renal Targeting: Peptide-Based Drug Delivery to Proximal Tubule Cells

“…In the case of a captopril− lysozyme conjugate, only 1.5% of such a system is the active drug. 23 For diseases which need a high drug concentration, e.g., infections with antibiotics, such a payload ratio is not feasible to handle. In the case of lysozyme, bolus injections can result in cardiovascular side effects.…”

“…The relatively high molecular weight of LMWP leads to an unfavorable drug-to-carrier ratio. In the case of a captopril–lysozyme conjugate, only 1.5% of such a system is the active drug . For diseases which need a high drug concentration, e.g., infections with antibiotics, such a payload ratio is not feasible to handle.…”

“…18,19 LMWP were used for the delivery of various small molecule drugs such as doxorubicin, 20 triptolide, 21 naproxen, 17,22 indomethacin, and captopril. 23 Depending on the drug linkage, the active component can be released from the carrier either enzymatically or by chemical cleavage. Unfortunately, the clinical value of lysozyme as a renal carrier is hampered by significant cardiovascular side effects.…”

“…LMWP are excreted by glomerular filtration and subsequently reabsorbed by receptor-mediated endocytosis into proximal tubular cells. Following internalization and transfer into lysosomes, they are catabolized to small peptides and single amino acids. , LMWP were used for the delivery of various small molecule drugs such as doxorubicin, triptolide, naproxen, , indomethacin, and captopril . Depending on the drug linkage, the active component can be released from the carrier either enzymatically or by chemical cleavage.…”

Novel Therapeutic Targets for the Treatment of Tubulointerstitial Fibrosis

“…zyme conjugate could be administered through the subcutaneous route which provided a slow and prolonged accumulation of the conjugate in kidneys [189]. Prolonged treatment of this captopril conjugate exhibited a significant reduction in proteinuria without affecting systolic blood pressure in adriamycin induced nephrotic animals [190]. Using the same renal carrier system, we have recently delivered the p38 MAPK inhibitor SB202190 to the kidneys [191].…”