Influence of the rate of infusion on cyclosporine nephrotoxicity in the rat

Establishing a Clinically Relevant Large Animal Model Platform for TBI Therapy Development: Using Cyclosporin A as a Case Study

We have developed the first immature large animal translational treatment trial of a pharmacologic intervention for traumatic brain injury (TBI) in children. The preclinical trial design includes multiple doses of the intervention in two different injury types (focal and diffuse) to bracket the range seen in clinical injury and uses two post-TBI delays to drug administration. Cyclosporin A (CsA) was used as a case study in our first implementation of the platform because of its success in multiple preclinical adult rodent TBI models and its current use in children for other indications. Tier 1 of the therapy development platform assessed the short-term treatment efficacy after 24 h of agent administration. Positive responses to treatment were compared with injured controls using an objective effect threshold established prior to the study. Effective CsA doses were identified to study in Tier 2. In the Tier 2 paradigm, agent is administered in a porcine intensive care unit utilizing neurological monitoring and clinically relevant management strategies, and intervention efficacy is defined as improvement in longer term behavioral endpoints above untreated injured animals. In summary, this innovative large animal preclinical study design can be applied to future evaluations of other agents that promote recovery or repair after TBI.

Effect of oxypurinol on cyclosporine toxicity in cultured EA, LLC-PK1 and MDCK cells

It has been proposed that cyclosporin (CsA) toxicity may in part be due to the action of oxygen-based free radicals. We compared the response of cultured endothelial (EA) and epithelial (LLC-PK1 and MDCK) cells to CsA, 250 or 1000 ng/mL for 24 or 72 h, with or without the xanthine oxidase inhibitor oxypurinol (Oxy), 10 mg/mL. CsA-induced alterations were seen on phase contrast and electron microscopy. In EA cells, swollen mitochondria and large cytoplasmic vacuoles surrounded by a thin membrane containing ribosomes were present at the periphery of the cell. In LLC-PK1 cells no vacuoles were present while in MDCK cells, the vacuoles were smaller and more centrally located. In both epithelial cell lines, mitochondria were distorted with loss of cristae. In all three cell lines, CsA depressed cell counts and decreased 3H-thymidine incorporation. Also, LDH release was accelerated. The addition of Oxy minimized the morphologic effect of CsA on all three cell lines with the effect more apparent in EA cells. The CsA-induced reduction of cell replication and increase in LDH release were also attenuated by Oxy. These results support the notion that the peroxidative properties of CsA may be responsible in part for CsA-induced nephrotoxicity.

NMR spectroscopy as a novel approach to the monitoring of renal transplant function

High field 1H NMR spectroscopy was used for the rapid multicomponent analysis of low molecular wt compounds in urine in order to investigate the patterns of metabolic changes associated with early renal allograft dysfunction. Urine samples were collected daily for 14 days from 33 patients who underwent primary renal allograft transplantation, and analyzed by 500 and/or 600 MHz 1H NMR spectroscopy. All patients received 20 mg prednisolone and 5 mg/kg b.d. oral cyclosporin A (CsA) solution. In this study no patient showed clinical or histopathological evidence of CsA nephrotoxicity. For each patient the NMR-generated metabolite data were correlated with the clinical observations, graft biopsy pathology, and data from conventional laboratory techniques for assessing renal function. The NMR spectra of urine from patients with immediate functioning grafts were similar with respect to their patterns of amino acids, organic acids and organic amines, whereas the patients with delayed or non-functioning grafts showed significantly different metabolite excretion patterns. In longitudinal studies on individual patients there were increased urinary levels of trimethylamine-N-oxide (TMAO), dimethylamine (DMA), lactate, acetate, succinate, glycine and alanine during episodes of graft dysfunction. However, only the urinary concentration of TMAO was statistically significantly higher (P < 0.025) in the urine collected from patients during episodes of graft dysfunction (410 +/- 102 microM TMAO/mM creatinine) than in patients with good graft function (91 +/- 18 microM TMAO/mM creatinine) or healthy control subjects (100 +/- 50 microM TMAO/mM creatinine). These findings suggest that graft dysfunction is associated with damage to the renal medulla which causes the release of TMAO into the urine from the damaged renal medullary cells. This provides a possible novel urinary marker for post-transplant graft dysfunction. This study shows that NMR spectroscopy of biofluids, when used in combination with conventional laboratory techniques, is a valuable aid to renal transplant monitoring.

The pathophysiology of Sandimmune (cyclosporine) in man and animals

Part I: The side-effects of Sandimmune that have been of most significance clinically are renal dysfunction, renal vascular damage and arterial hypertension. To examine the nature and the origin of such effects, the actions of Sandimmune on the renal tubule, the renal vessels and systemic vessels have been analyzed. To evaluate whether common vasoconstrictory systems may be involved, changes in the renin-angiotensin-aldosterone system and prostaglandin-thromboxane system have been assessed. Comparison between animal and human data obtained in vivo and in vitro shows the actions of Sandimmune on the renal tubule to be modest and involve only a few specific effects. The major action of Sandimmune is on the vessels, vasoconstriction being the major cause of renal dysfunction and also the cause of arterial hypertension. Neither the circulating renin-angiotension-aldosterone system nor the prostaglandin-thromboxane system is clearly responsible for vasoconstriction. Although not itself a vasoconstrictor, Sandimmune seems to modulate the constrictory and dilatory response to other agents in several vascular beds.

Primary renovascular effects of erythromycin in the rat: relationship to cyclosporine nephrotoxicity

Erythromycin is known to exacerbate cyclosporine nephrotoxicity. This has been attributed to the potential of erythromycin to reduce the hepatic microsomal metabolism and clearance of cyclosporine. Erythromycin may also be nephrotoxic. We tested the hypothesis that erythromycin may have direct effects on the renal vasculature which are additive or synergistic with the effects of cyclosporine. Sprague-Dawley rats were administered graded doses of either erythromycin, 2.5, 5, 7.5, and 10 mg/kg BW/min i.v. over consecutive 10-min intervals; cyclosporine, 1, 2, 3, and 4 mg/kg BW/min i.v. over consecutive 10-min intervals; or both drugs simultaneously. In separate experiments, identical doses of erythromycin or cyclosporine were infused intravenously following acute unilateral renal denervation. Infusion of erythromycin led to an initial decline in arterial blood pressure whereas infusion of cyclosporine resulted in a dose-related increase in arterial blood pressure. Despite these different systemic effects, each drug alone produced a striking decrease in renal blood flow. This effect was more pronounced when the drugs were infused concomitantly. The reduction in renal blood flow occurred in an additive manner as a direct consequence of increased renal vascular resistance. Prior renal denervation did not modify the response to either erythromycin or cyclosporine. These results demonstrate that cyclosporine-induced vasoconstriction is exacerbated by erythromycin and suggest that the decline in renal function observed in patients coadministered these drugs may be due in part to additive renovascular toxicity.