Comparative study between trimetazidine and ice slush hypothermia in protection against renal ischemia/reperfusion injury in a porcine model

Trimetazidine an emerging paradigm in renal therapeutics: Preclinical and clinical insights

Trimetazidine (TMZ) is a well-known anti-ischemic agent used for the treatment of angina pectoris. In the past decades, the efficacy of this drug has been tested in a wide range of kidney injuries, including drug-induced nephrotoxicity (DIN), radio-contrast agent-induced nephropathy, and surgically induced renal ischemic injury. TMZhas renoprotective effects by attenuating oxidative stress, inflammatory cytokine release, maintaining oxygen and energy balance. Moreover, TMZ administration prevented kidney graft rejection in the porcine model by suppressing the infiltration of mononuclear cells, preserving mitochondrial functions, and maintaining Ca+ homeostasis. In DIN and diabetic kidney diseases,TMZ treatment prevents renal injury by inactivating immune cells, attenuating renal fibrosis, inflammation, apoptosis, and histological abnormalities. Interestingly, the clinical therapeutic efficacy of TMZ has also been documented in pre-existing kidney disease patients undergoing contrast exposure for diagnostic intervention. However, the mechanistic insights into the TMZ mediated renoprotective effects in other forms of renal injuries, including type-2 diabetes, drug-induced nephrotoxicity, and hypertension-induced chronic kidney diseases, remain uninvestigated and incomplete. Moreover, the clinical utility of TMZ as a renoprotective agent in radio-contrast-induced nephrotoxicity needs to be tested in a large patient population. Nevertheless, the available pieces of evidence suggest that TMZ is a promising and emerging renal therapy for the treatment and management of kidney diseases of variable etiologies. This review discusses the various pre-clinical and clinical findings and provides mechanistic insights into the TMZ mediated beneficial effects in various kidney diseases.

Testing Danegaptide Effects on Kidney Function after Ischemia/Reperfusion Injury in a New Porcine Two Week Model

INTRODUCTION

Ischemia/reperfusion injury (I/R-I) is a leading cause of acute kidney injury (AKI) and is associated with increased mortality. Danegaptide is a selective modifier of the gap junction protein connexion 43. It has cytoprotective as well as anti-arrhythmic properties and has been shown to reduce the size of myocardial infarct in pigs. The aim of this study was to investigate the ischemia-protective effect of Danegaptide in a porcine renal I/R-I model with two weeks follow up.

METHODS

Unilateral renal I/R-I was induced in pigs by clamping the left renal artery over a two hour period. The model allowed examination of renal blood flow by magnetic resonance imaging (MRI) and the measurement of single kidney GFR two weeks after injury. Eleven animals were randomized to Danegaptide-infusion while nine animals received placebo. Kidney histology and urinary neutrophil gelatinase-associated lipocalin (NGAL) excretion were included as markers of AKI.

RESULTS

Unilateral kidney I/R-I resulted in an immediate ~50% GFR reduction, associated with a four-fold increase in urinary NGAL-excretion. Fourteen days after I/R-I, the total GFR was ~75% of baseline with a significantly lower GFR in the injured left kidney compared to the right kidney. No differences in GFR were observed between the treated and non-treated animals immediately after I/R-I or at Day 14. Furthermore, no differences were observed in the urinary excretion of NGAL, renal blood flow or other markers of renal function.

CONCLUSIONS

As expected this porcine renal I/R-I model was associated with reduced GFR two weeks after injury. Danegaptide did not improve renal function after I/R-I.

Ineffectiveness of remote ischemic renal preconditioning in a porcine solitary-kidney model

PURPOSE

Our study sought to demonstrate the effects of remote ischemic preconditioning (R-IPC) on renal function in a large animal (porcine) solitary-kidney model.

METHODS

Twelve pigs were assigned to two groups: Each underwent a right nephrectomy followed by a week of recovery. Group 1 (No-IPC) underwent left renal hilar clamping for 90 minutes. Group 2 underwent right and left iliac artery clamping for 10 minutes each (R-IPC), followed by left hilar clamping for 90 minutes. Serum creatinine was drawn for both groups before ischemia (preoperative), then at 6 hours, 24 hours, 3 days, and 7 days after. Kidneys were harvested at 24 hours or 7 days for histologic analysis, and the degree of acute tubular necrosis (ATN) or lymphocyte invasion was quantified.

RESULTS

Paired serum creatinine values were analyzed between time points. For Group 1, paired differences existed at 24 hours (P=0.008) but not at 3 days or 7 days. For Group 2, paired differences existed at 24 hours (P=0.006) but not at 3 days or 7 days. The mean preoperative serum creatinine level was similar between groups (P>0.05). The change in serum creatinine level was not significantly different between groups at any time point. Histologic analysis revealed rare evidence of ATN at 24 hours in Group 2, but not in Group 1. At 7 days, neither group showed ATN, and both showed 1-2+evidence of lymphocytic infiltrates.

CONCLUSION

R-IPC in a solitary-kidney porcine model does not confer renal protection from warm ischemia either as evidenced by renal function measures or on histologic analysis.

Carbamylated erythropoietin-FC fusion protein and recombinant human erythropoietin during porcine kidney ischemia/reperfusion injury

PURPOSE

To test the hypothesis that a carbamylated EPO-FC fusion protein (cEPO-FC) or recombinant human erythropoietin (rhEPO) would protect against kidney ischemia/reperfusion (I/R) injury in pigs with atherosclerosis.

METHODS

Anesthetized and mechanically ventilated animals received cEPO-FC (50 μg kg(-1)), rhEPO (5,000 IU kg(-1)), or vehicle (n = 9 per group) prior to 120 min of aortic occlusion and over 4 h of reperfusion. During aortic occlusion, mean arterial pressure (MAP) was maintained at 80-120 % of baseline values by esmolol, nitroglycerin, and ATP. During reperfusion, noradrenaline was titrated to keep MAP at pre-ischemic levels. Blood creatinine and neutrophil gelatinase-associated lipocalin (NGAL) levels, creatinine clearance, fractional Na(+) excretion, and HE and PAS staining were used to assess kidney function and histological damage. Plasma interleukin-6, tumor necrosis factor-α, nitrate + nitrite and 8-isoprostane levels were measured to assess systemic inflammation, and nitrosative and oxidative stress.

RESULTS

I/R caused acute kidney injury with reduced creatinine clearance, increased fractional Na(+) excretion and NGAL levels, moderate to severe glomerular and tubular damage and apoptosis, systemic inflammation and oxidative and nitrosative stress, but there were no differences between the treatment groups. Pre-ischemia nitrate + nitrite and 8-isoprostanes levels were lower and higher, respectively, than in healthy animals of a previous study, and immune histochemistry showed higher endothelial nitric oxide synthase and lower EPO receptor expression in pre-ischemia kidney biopsies than in biopsies from healthy animals.

CONCLUSIONS

In swine with atherosclerosis, rhEPO and cEPO-FC failed to attenuate prolonged ischemia-induced kidney injury within an 8-h reperfusion period, possibly due to reduced EPO receptor expression resulting from pre-existing oxidative stress and/or reduced NO release.