Evaluation of the Effect of Captopril and Losartan on Tacrolimus-induced Nephrotoxicity in Rats

Background Tacrolimus is an immunosuppressive drug. Activation of the renin-angiotensin system (RAS) and associated inflammations may exacerbate the toxic effects of tacrolimus. Given the significant role of the kidney in RAS this study aimed to evaluate the effect of captopril as an angiotensin-converting enzyme (ACE) blocker and losartan as an angiotensin II receptor blocker on tacrolimus-induced nephrotoxicity. Materials and Methods In total, 36 adult male rats weighing 200–250 gr were completely randomized and divided into six groups (control, tacrolimus, tacrolimus and losartan, tacrolimus and captopril, losartan, and captopril) for 30 days. Afterwards, blood urea nitrogen (BUN), creatinine (Cr) and ACE2 enzyme were measured. Also, both kidneys were collected for histological examinations. Results The level of BUN and Cr significantly increased in tacrolimus group. The level of BUN and Cr were lower in the groups treated with a combination of tacrolimus and losartan or captopril. While ACE2 level increased in the groups receiving a combination of tacrolimus and losartan or captopril, the level of increase was insignificant, compared to the group treated with tacrolimus alone. The glomerulus diameter and the thickness of the renal proximal tubular epithelium significantly decreased in the group treated with tacrolimus alone. the mentioned variables increased in the group treated with a combination of tacrolimus and losartan or captopril, compared to the tacrolimus group. Conclusion According to this study, tacrolimus increased the BUN and Cr levels while decreasing the ACE2 levels. However, tacrolimus in combination with losartan or captopril seemed to decrease the nephrotoxicity of the drug.

The renal tubular acidoses

Renal tubular acidosis (RTA) arises when the kidneys either fail to excrete sufficient acid, or are unable to conserve bicarbonate, with both circumstances leading to metabolic acidosis of varying severity with altered serum potassium. Proximal and distal types of RTA can be differentiated according to which nephron segment is malfunctioning. Proximal RTA: aetiology and diagnosis—the condition may be (1) secondary to generalized proximal tubular dysfunction (part of the renal Fanconi’s syndrome), or rarely (2) due to an inherited mutation of a single transporter (NBC1) located at the basolateral surface of the proximal tubular epithelium. The combination of normal anion gap acidosis with other features of proximal tubular dysfunction such as renal phosphate wasting (and hypophosphataemia), renal glycosuria, hypouricaemia (due to uricosuria), aminoaciduria, microalbuminuria, and other low molecular weight proteinuria suggests the diagnosis. Management—this requires large quantities of oral alkali with (in most cases) potassium supplements to prevent severe hypokalaemia. Distal RTA: aetiology/diagnosis—two main classes are differentiated by whether (1) the acid-handling cells in the collecting ducts are themselves functioning inadequately, in which case there is associated hypokalaemia (this is ‘classic’ distal RTA); or (2) the main abnormality is of the salt-handling principal cells in the same nephron segment, in which case hyperkalaemia occurs and the acidosis is a secondary phenomenon—this is hyperkalaemic distal RTA. The combination of normal anion gap acidosis with a urine pH higher than 5.5 suggests classic distal RTA. Management—(1) classic distal RTA—1 to 3 mg/kg per day of oral alkali; (2) hyperkalaemic distal RTA—treatment is with sodium bicarbonate, but fludrocortisone and/or potassium-lowering measures may also be necessary. Precipitating drugs should be stopped.

Deletion of UNC5B in Kidney Epithelium Exacerbates Diabetic Nephropathy in Mice

Background: Guidance cue netrin-1 was shown to have protective effects in diabetic nephropathy. However, the role of its receptor UNC5B in diabetic kidney disease is unknown. Moreover, whether netrin-1 is protective against diabetic kidney disease in a genetic model of nephropathy and in the nephropathy prone DBA background is also unknown. The aim of this study was to determine the significance of UNC5B in tubular epithelial cells in chronic kidney disease due to diabetes and evaluate whether netrin-1 is also protective in the case of a nephropathy-prone mouse. Methods: Proximal tubular epithelium-specific UNC5B knockout mice as well as heterozygous UNC5B knockout mice were used to determine the roles of UNC5B in nephropathy. Diabetes was induced in these tissue-specific knockout, heterozygous and WT mice, and albuminuria was then monitored. Results: WT and heterozygous diabetic mice developed significant albuminuria at 8 weeks after induction of diabetes as compared to buffer-treated control mice. However, albuminuria was significantly more pronounced in mice with proximal tubule specific deletion of UNC5B. Transgenic overexpression of netrin-1 in proximal tubules in the DBA background and administration of recombinant netrin-1 to Ins2Akita mice also significantly reduced diabetes-induced albuminuria and suppressed glomerular and interstitial lesions. Conclusion: Our data suggested that netrin-1 signaling in proximal tubular epithelium may play a critical role in the protection of kidney against diabetic kidney disease.