The role of eicosanoids in cyclosporine nephrotoxicity in the rat

Treatment With Dimethyl Fumarate Attenuates Calcineurin Inhibitor-induced Nephrotoxicity

BACKGROUND

Cyclosporine A (CsA) is an immunosuppressive drug which has been widely used to prevent rejection after organ transplantation. However, its therapeutic use is limited by nephrotoxicity, in part mediated by oxidative stress. The present study aims to investigate the protective effects of dimethyl fumarate (DMF) on CsA-induced nephrotoxicity by enhancing the antioxidant defense system.

METHODS

Male Sprague-Dawley rats were treated with CsA (n = 8, 20 mg/kg per day intraperitoneally) or CsA + DMF (n = 7, 50 mg/kg per day orally) for 28 days. Renal function, histopathology, malondialdehyde (MDA), myeloperoxidase levels, and antioxidant enzyme expression were determined.

RESULTS

The DMF cotreatment ameliorated CsA-induced renal dysfunction as evidenced by significant decrease in serum creatinine (CsA 0.79 ± 0.02 mg/dL vs CsA + DMF 0.62 ± 0.04 mg/dL, P = 0.001) and urea (CsA 66.9 ± 0.4 mg/dL vs CsA + DMF 53.3 ± 2.6 mg/dl, P < 0.0001) levels, as well as improvement of creatinine clearance. Dimethyl fumarate also significantly decreased serum MDA and renal tissue MDA and myeloperoxidase contents. The protein expression of NAD(P)H quinone oxidoreductase-1, a major cellular antioxidant and detoxifying enzyme, was significantly enhanced by DMF administration in kidney.

CONCLUSIONS

Administration of DMF has a protective potential against CsA nephrotoxicity. The protection afforded by DMF is mediated in part through inhibiting oxidative stress and inflammation and enhancing the antioxidant capacity.

Expression of renal distal tubule transporters TRPM6 and NCC in a rat model of cyclosporine nephrotoxicity and effect of EGF treatment

Renal magnesium (Mg2+) and sodium (Na+) loss are well-known side effects of cyclosporine (CsA) treatment in humans, but the underlying mechanisms still remain unclear. Recently, it was shown that epidermal growth factor (EGF) stimulates Mg2+ reabsorption in the distal convoluted tubule (DCT) via TRPM6 (Thébault S, Alexander RT, Tiel Groenestege WM, Hoenderop JG, Bindels RJ. J Am Soc Nephrol 20: 78–85, 2009). In the DCT, the final adjustment of renal sodium excretion is regulated by the thiazide-sensitive Na+-Cl− cotransporter (NCC), which is activated by the renin-angiotensin-aldosterone system (RAAS). The aim of this study was to gain more insight into the molecular mechanisms of CsA-induced hypomagnesemia and hyponatremia. Therefore, the renal expression of TRPM6, TRPM7, EGF, EGF receptor, claudin-16, claudin-19, and the NCC, and the effect of the RAAS on NCC expression, were analyzed in vivo in a rat model of CsA nephrotoxicity. Also, the effect of EGF administration on these parameters was studied. CsA significantly decreased the renal expression of TRPM6, TRPM7, NCC, and EGF, but not that of claudin-16 and claudin-19. Serum aldosterone was significantly lower in CsA-treated rats. In control rats treated with EGF, an increased renal expression of TRPM6 together with a decreased fractional excretion of Mg2+ (FE Mg2+) was demonstrated. EGF did not show this beneficial effect on TRPM6 and FE Mg2+ in CsA-treated rats. These data suggest that CsA treatment affects Mg2+ homeostasis via the downregulation of TRPM6 in the DCT. Furthermore, CsA downregulates the NCC in the DCT, associated with an inactivation of the RAAS, resulting in renal sodium loss.

Yolk sac concentration of prostaglandin E2 in diabetic pregnancy: further clues to the etiology of diabetic embryopathy

Fetal malformation associated with maternal diabetes occurs before the seventh week of pregnancy. Current hypotheses suggest that the diabetic milieu causes a reduction in phosphatidylinositol turnover, leading to a disruption in the arachidonic acid cascade and resulting in a deficiency of prostaglandins, particularly prostaglandin E2. This in turn results in a wide variety of congenital anomalies. This hypothesis has not been tested experimentally in humans. The yolk sac is thought to be the most important source of nutrition in early pregnancy. We sought to compare yolk sac prostaglandin levels in normal and diabetic women. Under ultrasonographic guidance, yolk sacs were aspirated form 8 normal and 12 diabetic women ranging from 8 to 10 weeks gestational age prior to elective abortion. Prostaglandin E2 levels were determined using RIA. The mean prostaglandin E2 level in normal controls was 3605 pg/mL, and was undetected in all of the yolk sacs aspirated from diabetic women (P < 0.001). Yolk sac diameter in diabetic pregnancies was 1.2 mm larger than that of normal pregnancies. The functional and morphological changes demonstrated in this study may increase our understanding of the pathophysiology of diabetic embryopathy.

Diurnal rhythm of prostanoid secretion from bone/marrow organ in the rat

The secretion of prostanoids from an adult diaphysial rat bone organ was assessed throughout a 24 h period at 4 h intervals as well as the 24 h activities of bone alkaline phosphatase isoenzyme and serum corticosterone levels. Femurs were removed from 16 rats at each interval and incubated in the absence or presence of indomethacin (100 micrograms). The levels of prostaglandin E2 (PGE2) prostaglandin F2 alpha (PGF2 alpha), and the stable metabolites of thromboxane and prostacyclin, thromboxane B2 (TxB2), and 6-keto prostaglandin F1 alpha (6-keto PGF1 alpha) were measured by radioimmunoassay (RIA). The patterns for each of the variables was subjected to cosinor analysis for predetermined various periods. The chronograms obtained indicated that PGF2 alpha, PGE2, and TxB2 showed 24 h rhythms with computed peak hour acrophases at 1700, 1800, and 2200 h, respectively, and prostacyclin demonstrated a 19 h rhythm with a peak secretion at 1100 h. Corticosterone levels and bone alkaline phosphatase isoenzyme activity in the serum were at peak at 1630 and 2200 h, and at nadir at 0500 and 1000 h, respectively, both exhibiting 24 h rhythms similar to those of PGF2 alpha, PGE2, and TxB2. Bone alkaline phosphatase isoenzyme activity in the femurs' incubation media showed a 12 h diurnal rhythm with peaks at 1230 and 2330 h and nadirs at 0600 and 2330 h (p < 0.01). In summary, this study demonstrated for the first time a 24 h rhythm of prostanoid secretion from diaphysial bone.(ABSTRACT TRUNCATED AT 250 WORDS)

Prostanoids and cyclosporin-mediated nephrotoxicity in rats: a critical appraisal

The involvement of arachidonic acid metabolism in cyclosporin (CsA) nephrotoxicity depending on CsA vehicle has been explored in this study. For this purpose creatinine clearance, urinary excretion and renal levels of eicosanoids were measured in the following rat experimental groups: group I, control; group II, CsA was administered in olive oil by gavage at 15 mg/kg/d for 7 d; group III, same as group II but 30 mg/kg/d; group IV, CsA was administered in fish oil by gavage at 15 mg/kg/d for 7 d; group V, same as group IV but 30 mg/kg/d; group VI, CsA was administered in olive oil at 15 mg/kg/d with prednisolone (1 mg/kg/d). The results indicate that (1) CsA nephrotoxicity and prostanoid alterations seem to be greatly improved when fish results indicate that (1) CsA nephrotoxicity and prostanoid alterations seem to be greatly improved when fish oil substitutes olive oil as a vehicle for CsA administration and (2) a correlation was found between eicosanoids measured and renal function, except in group II in which creatinine clearance remains unmodified but eicosanoids were altered, thus suggesting that other factors play a role in mediating nephrotoxicity due to cyclosporin.

Alleviation of experimental cyclosporin A nephrotoxicity by low dose aspirin in the rat

Groups of male Sprague-Dawley rats received either cyclosporin A (CsA; 25 mg/kg by gavage), low dose aspirin (ASP; 20 mg/kg by gavage), a combination of both, or the appropriate drug vehicles daily for 14 days. Renal structure and function were assessed on day 0 (pretreatment) and on days 7 and 14. Compared to pretreatment results, CsA nephrotoxicity was characterized by increased plasma urea and creatinine concentrations and by moderate to severe microcalcification (MC) at the corticomedullary junction by day 14. The development of nephrotoxicity was also associated with a 5-fold increase in urine thromboxane B2 (TxB2) excretion by day 10, while that of 6-ketoprostaglandin F1 alpha remained relatively constant. Although both ASP and saline (ASP vehicle) -cotreated animals demonstrated significantly lower plasma urea and creatinine concentrations compared to treatment with CsA alone, the severity of MC observed on day 14, was reduced only in the ASP cotreatment group. Though whole blood CsA concentrations were similar at around 2400 ng/mL in all experimental groups. In addition, although a 2-fold increase in urine TxB2 excretion was observed on days 7 and 10 following treatment with CsA/ASP, levels were significantly reduced compared to treatment with either CsA alone or CsA/saline (both P < 0.05).

De novo hypertension after liver transplantation

Hypertension develops in most patients after transplantation when immunosuppression is based on cyclosporine and prednisone. The pathogenesis appears to be multifactorial but involves rapidly rising vasoconstrictor tone in renal and systemic vascular beds. Much of this tone reflects abnormal vascular function, characterized by impaired prostacyclin and EDRF effects, in conjunction with increased vasoconstriction due to endothelin and possibly other factors. Effective management of the transplant recipient depends on preventing excessive vasoconstriction, usually with calcium channel blocking agents.

The reversal of experimental cyclosporin A nephrotoxicity by thromboxane synthetase inhibition

The ability of thromboxane synthetase inhibition to reverse acute cyclosporin A (CsA)-induced nephrotoxicity in the rat was investigated. CsA administration (50 mg/kg/day p.o. for 14 days) to male Sprague-Dawley rats caused a significant 50% decline in creatinine clearance rates, an increase in N-acetyl-beta-D-glucosaminidase (NAG) enzymuria and renal tubulointerstitial damage by day 14. These changes were associated with a 5-6-fold increase in urinary thromboxane B2 excretion (from pretreatment values of 28.1 +/- 7.9 to 122.6 +/- 38.9 and 165.8 +/- 39.0 eta g/24 hr body weight on days 7 and 14, respectively). Excretion rates of 6-keto-prostaglandin F1 alpha and prostaglandin E2 were, however, unaffected by CsA administration. Co-treatment with a thromboxane synthetase inhibitor (CGS 12970; 8-[3-methyl-2-(3-pyridyl)-1-indolyl]-octanoic acid) from day 7 (10 mg/kg/day) normalized thromboxane B2 excretion, resulted in creatine clearance rates which were similar to pretreatment values on days 10 and 14, reduced NAG enzymuria on day 10 and prevented acute proximal tubular vacuolation. However, the severity of chronic CsA nephrotoxicity, namely chronic tubular damage and microcalcification at the corticomedullary junction, was not diminished by the thromboxane synthetase inhibition. These results demonstrate that (i) elevated thromboxane synthesis plays an important role in the development of acute CsA nephrotoxicity and (ii) that different and/or additional mechanisms are involved in the pathogenesis of chronic nephrotoxicity.

Importance of endogenous prostaglandins for the toxicity of cyclosporin A to rat endocrine and exocrine pancreas?

Previous work has shown that cyclosporin A is toxic to the endocrine and exocrine pancreas. The aim of this study was to examine whether endogenous eicosanoids play a role in controlling cyclosporin A induced toxicity. Rats were treated for eight days with indomethacin (2 mg/kg, twice daily) in addition to cyclosporin A (5 or 10 mg/kg daily). Effects of drug treatments on exocrine (as assessed by amylase and protein secretion into the pancreatic juice) and endocrine (as assessed by the glucose dependent insulin release) pancreatic functions, and pancreatic formation of prostaglandins and thromboxane were evaluated. Treatment with cyclosporin A in the doses used did not inhibit eicosanoid formation by the pancreatic tissue ex vivo. Indomethacin caused significant inhibition of pancreatic formation of prostaglandin E2, 6k prostaglandin F1 alpha and thromboxane B2. Combined treatment with indomethacin and cyclosporin A (5 or 10 mg/kg) augmented cyclosporin A induced pancreatic toxicity with further impairment of insulin release, amylase secretion, and pancreatic juice protein content, but did not result in more pronounced inhibition of pancreatic eicosanoid formation. The increased toxicity of the combined treatment was, however, associated with raised cyclosporin A whole blood concentrations. The data suggest that the potentiation of pancreatic toxicity of cyclosporin A observed during coadministration of indomethacin is not the result of suppression of endogenous pancreatic eicosanoid biosynthesis, but more likely results from altered cyclosporin A pharmacokinetic which may be caused by an interference of indomethacin with the hepatic cytochrome P-450 dependent monooxygenase involved in cyclosporin A metabolism. The possibility that coadministration of non-steroidal antiinflammatory drugs aggravates toxic effects in cyclosporin A treated patients should be considered.

In vivo assessment by videomicroscopy of acute renal microvascular responses to cyclosporin

Nephrotoxicity limits the use of cyclosporin A for immunosuppression after organ transplantation and may be caused by glomerular hypoperfusion. Indirect studies have shown that cyclosporin A increases renal vascular resistance and reduces total renal blood flow. This study used direct in vivo videomicroscopy to define the effects of the drug on the renal microcirculation of the rat. An intravenous infusion of cyclosporin A (20 mg per kg body-weight) caused a 13 per cent acute constriction of the proximal interlobular artery and an associated 29 per cent reduction in preglomerular interlobular arterial blood flow. There was a simultaneous increase in mean arterial blood pressure of 34 per cent caused by cyclosporin A and a 23 per cent increase in systemic vascular resistance. Cyclosporin acutely reduces renal microvascular blood flow by vasoconstriction and affects the central circulation, suggesting that a generalized peripheral vasoconstriction is induced.

Effect of autacoid modulation on N-(3,5-dichlorophenyl)succinimide (NDPS) and NDPS metabolite nephrotoxicity

N-(3,5-Dichlorophenyl)succinimide (NDPS) is an agricultural fungicide which has been shown to induce acute tubular necrosis. The purpose of the present study was to determine if creatinine clearance was altered early in the development of NDPS nephrotoxicity. This study also examined the effect of autacoid modulation on the renal effects induced by NDPS and two metabolites of NDPS, N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS) and N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (NDHSA). In one set of experiments, male Fischer 344 rats (4 rats/group) were administered a single intraperitoneal (i.p.) injection of NDPS (1.0 mmol/kg) or vehicle and creatinine clearance was determined at 3 and 6 h post-treatment. NDPS administration resulted in a marked decrease in creatinine clearance at both time points. In a second set of experiments, rats (4-8 rats/group) were pretreated with the cyclooxygenase inhibitor indomethacin (3.0 or 5.0 mg/kg, i.p.) or the thromboxane synthase inhibitor dazmegrel (20 mg/kg, i.p.) 1 h before the i.p. administration of NDPS (0.2 or 0.4 mmol/kg), NDHS (0.05 or 0.1 mmol/kg), NDHSA (0.05 or 0.1 mmol/kg) or vehicle. Indomethacin pretreatment potentiated the nephrotoxic potential of NDPS and its two metabolites, while dazmegrel pretreatment attenuated NDPS nephrotoxicity without marked effects on NDHS or NDHSA nephropathy. These results indicate that renal hemodynamic changes occur early in the development of NDPS nephrotoxicity and that autacoids are important modulators of NDPS- and NDPS metabolite-induced renal effects.

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.

Cyclosporin A treatment enhances angiotensin converting enzyme activity in lung and serum of rats

Nephrotoxicity and arterial hypertension are the most common side effects of treatment with cyclosporin A (CSA). Its effects on angiotensin converting enzyme (ACE) activity in the renal cortex, lung and serum of nephrotoxic rats have been investigated. Wistar rats were treated with CSA (20 mg kg-1 day-1 i.p.) or vehicle (olive oil containing 10% ethanol) for 14 days. On day 15, the rats were killed and ACE activity determined by radiometric assay using [3H]hippuryl-glycyl-glycine as substrate. CSA treatment resulted in a decrease in creatinine clearance, urine flow and body weight and a significant increase in serum and lung ACE activities (436 +/- 9 vs 391 +/- 7 nmol mL-1 min-1, P less than 0.001; 184 +/- 8 vs 142 +/- 10 nmol mg-1 min-1 P less than 0.01, respectively). In contrast, renal cortex ACE activity was reduced in the CSA-treated rats (0.35 +/- 0.02 vs 0.51 +/- 0.02 nmol mg-1 min-1, P less than 0.01). ACE activities in the renal cortex and serum were not affected by treatment with gentamicin (80 mg kg-1 day-1) for 11 days. In rats treated simultaneously with CSA and captopril (50 mg kg-1 day-1) ACE activity in the serum, lung and renal cortex was inhibited by 95, 93 and 92%, respectively. These changes in ACE activity were associated with a decreased systolic blood pressure in the rats receiving CSA and captopril. Therefore, ACE activity in the serum and lung of CSA-treated rats was increased, while its activity in the renal cortex was reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

Decrease in cyclosporin-mediated prostacyclin production in renal versus carotid arteries: a mechanism for cyclosporin-induced hypertension

Although the mechanism of cyclosporin (CsA)-induced hypertension is unknown, it has been shown to inhibit prostacyclin (PGI2) production directly, which may be a factor. We determined whether CsA had a differential effect on PGI2 production from the carotid artery (CA) and internal jugular vein (JV) compared to that from the renal artery (RA) and vein (RV) as a possible contributing factor to renovascular hypertension based upon the ability of organs to regulate their own blood flow according to local circumstances. The neck and renal vessels were removed from anesthetized adult female dogs (N = 8) and placed in a stimulation chamber, with Cell I being control (Hepes buffer), Cell II containing 0.3 mg/ml CsA, and Cell III containing CsA and 25 microM arachidonic acid (AA). Following serial stimulation periods, the supernatant was evaluated for PGI2 production by radioimmunoassay. PGI2 production from CA was significantly higher than that from RA following control and AA stimulation, 1474 +/- 382 pg/cm2-min vs 733 +/- 173 pg/cm2-min (P less than 0.05) and 2236 +/- 347 vs 1090 +/- 217 (P less than 0.01), respectively. CsA-induced PGI2 production from the carotid arteries was significantly greater than that from the renal arteries, 2944 +/- 586 vs 1003 +/- 235 (P less than 0.005). However, stimulation with AA following CsA resulted in sustained PGI2 production in both arteries that was similar to stimulation with CsA alone, 3014 +/- 600 vs 2944 +/- 586 for the carotids and 1278 +/- 280 vs 1003 +/- 235 for the renal arteries.(ABSTRACT TRUNCATED AT 250 WORDS)