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


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.


CONCLUSIONS
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.
Windt
Willemijn A K M
WA
Department of Clinical Pharmacology, Groningen University, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands. w.a.k.m.windt@med.umcg.nl
Prakash
Jai
J
Kok
Robbert Jan
RJ
Moolenaar
Frits
F
Kluppel
C Alex
CA
de Zeeuw
Dick
D
van Dokkum
Richard P E
RP
Henning
Robert H
RH
D000806:Angiotensin-Converting Enzyme Inhibitors / Q000008:administration & dosage* / Q000097:blood / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002216:Captopril / Q000008:administration & dosage* / Q000097:blood / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin; D016503:Drug Delivery Systems; D007668:Kidney / Q000187:drug effects*; D007674:Kidney Diseases / Q000097:blood / Q000139:chemically induced* / Q000378:metabolism / Q000652:urine*; D008297:Male; D009113:Muramidase; D007703:Peptidyl-Dipeptidase A / Q000097:blood / Q000378:metabolism; D011507:Proteinuria / Q000503:physiopathology*; D051381:Rats; D017208:Rats, Wistar; D012982:Sodium, Dietary / Q000008:administration & dosage / Q000494:pharmacology
D000806:Angiotensin-Converting Enzyme Inhibitors; D012982:Sodium, Dietary; D004317:Doxorubicin; D002216:Captopril; D009113:Muramidase; D007703:Peptidyl-Dipeptidase A