Nephrotoxic and peroxidative potential of meropenem and imipenem/cilastatin in rat and human renal cortical slices and microsomes.

BACKGROUND

Carbapenems are a relatively new class of beta-lactam antibiotics characterized by a broad spectrum of antibacterial activity. Meropenem (MER), a new carbapenem has shown a lower nephrotoxic potential compared to imipenem (IMI). IMI is used in a fixed one-to-one combination with the nephroprotective agent cilastatin (CIL). The present studies examined whether MER and IMI/CIL produce peroxidative and nephrotoxic alterations including oxidative changes in rat and human renal cortical slices and microsomes.

MATERIALS AND METHODS

Untreated slices and microsomes were incubated in vitro for various periods of time in phosphate-buffered media containing various concentrations of MER, IMI/CIL or for comparison cephaloridine (CPH). Lipid peroxidation was monitored by the determination of malondialdehyde (MDA) in incubation media and slices in the presence or absence of antioxidants. Total glutathione, oxidized glutathione (GSSG), pyruvate-stimulated gluconeogenesis and paraaminohippurate (PAH) accumulation were measured in slices.

RESULTS

In rat renal cortical slices, MER, IMI/CIL and CPH induced a time- and concentration-dependent MDA production (content in incubation media plus slices). 5 mM MER, 5 mM IMI/CIL and 3 mM CPH were the lowest concentrations which caused a significant MDA production after 3 hs compared to control (control 61.5+/-15.3 nmol MDA/g tissue, MER 75.4+/-10.9, p<0.001; control 48.0+/-8.7, IMI/CIL 65.1+/-11.7, p<0.001; control 61.5+/-15.3, CPH 113.0+/-28.2, p<0.001). 20 mM MER, 20 mM IMI/CIL and 12 mM CPH revealed marked MDA production after 3 hs in human renal cortical slices (control 29.8+/-4.2 nmol MDA/g tissue, MER 49.4+/-8.7, p<0.01; control 27.6+/-7.0, IMI/CIL 68.3+/-9.9, p<0.001; control 32.5+/-7.7, CPH 93.8+/-31.6, p<0.001) and in human renal microsomes (control 1.0+/-0.9 nmol MDA/mg protein, MER 2.9+/-1.0, p<0.05; IMI/CIL 6.8+/-2.2, p<0.001; CPH 8.4+/-2.2, p<0.001), respectively. The corresponding MDA production was about 2-fold higher in rat renal cortical slices and almost the same in rat renal microsomes. Antioxidants reduced the MER-induced increase in MDA content in rat renal cortical slices by 48% (alpha-tocopherol, 10(-4) M), 72% ((+)-cyanidanol-3, 10(-5) M) and 100% (DPPD, N, N'-diphenyl-p-phenylendiamine, 10(-6) M). In rat renal cortical slices, MER and IMI/CIL induced an increase up to 50% in the content of GSSG and a corresponding %-decrease in reduced glutathione (GSH). In rat renal cortical slices, MER and IMI/CIL induced a time- and concentration-dependent decrease in PAH accumulation and gluconeogenesis. PAH accumulation was already reduced by 5 mM MER after 1 h (control slice to medium ratio 18.3+/-6.8, MER 10.7+/-1.9, p<0.05) and by 10 mM IMI/CIL after 3 h (control 16.9+/-5.6, IMI/CIL 5.5+/-1.3, p<0.001). Pyruvate-stimulated gluconeogenesis after 3 hs was already reduced by 2.5 mM MER (control 5.7+/-2.1 micromol glucose/g tissue/h, MER 3.9+/-1.1, p<0.05) and by 10 mM IMI/CIL (control 5.7+/-2.1, IMI/CIL 2.8+/-1.0, p<0.001).

CONCLUSION

Thus, MER and IMI/CIL (at concentrations more than 10-fold higher as peak plasma concentrations achieved in humans) revealed an oxidative change (depletion of GSH, production of GSSG), a peroxidative potential (production of MDA) and a nephrotoxic potential (reduction in pyruvate-stimulated gluconeogenesis and PAH accumulation). Human kidney seems to be less susceptible to beta-lactam antibiotic-induced lipid peroxidation than rat kidney.