N-phenacylthiazolium bromide decreases renal and increases urinary advanced glycation end products excretion without ameliorating diabetic nephropathy in C57BL/6 mice

AIMS

Advanced glycation end products (AGE), which form from the non-enzymatic reaction of proteins and sugars, have been implicated in the pathogenesis of diabetic nephropathy. Recently, a compound [N-phenacylthiazolium bromide (PTB)] has been described which cleaves alpha,beta-dicarbonyl compounds. In the present study we used diabetic C57BL/6 mice to determine if PTB altered renal AGE levels and reduced diabetic glomerulosclerosis.

METHODS

Mice with stable hyperglycaemia induced by streptozotocin were given daily subcutaneous injections of either PTB (10 microg/g) or saline for 12 weeks. Renal-collagen bound AGE and urinary AGE-peptides were measured by ELISA using an anti-AGE-RNase antibody. Renal collagen-released Nepsilon(carboxymethyl)lysine (CML) and pentosidine were determined by high pressure liquid chromatography (HPLC). Glomerular lesions (volume and mesangial/total surface area) were evaluated by computer-assisted image analysis. We determined urinary protein/creatinine ratio as a functional parameter. AGE localization was examined by immunohistochemistry using the anti-AGE-RNase antibody.

RESULTS

Renal collagen-bound AGE were decreased and urinary AGE excretion was increased in PTB-treated diabetic mice. However, collagen-released CML and pentosidine were similar in both groups. Glomerular histology and morphometric analysis revealed also no differences between PTB-and saline-treated diabetic mice. The urinary protein/creatinine ratio was unaffected by PTB-treatment. AGE staining by anti-AGE-RNase antibody was present in Bowman's capsules, glomerular basement membranes and cortical tubules. It was decreased in all structures in PTB-treated diabetic mice.

CONCLUSION

In summary, PTB decreased renal AGE accumulation but did not ameliorate glomerular lesions or proteinuria. Thus, cleavage of AGE by PTB is not sufficient to prevent development of diabetic nephropathy in C57BL/6 mice.

Pentosan polysulfate treatment reduces cyclosporine-induced nephropathy in salt-depleted rats

BACKGROUND

Long-term cyclosporine (CsA) treatment leads to a decreased glomerular filtration rate, hyalinosis of afferent arterioles, and striped cortical tubulo-interstitial fibrosis. We showed previously that pentosan polysulfate (SP54) prevented the development of microvascular and interstitial lesions in mouse models of progressive glomerulosclerosis. In this study, we examined the effect of pentosan polysulfate on the development of CsA nephropathy.

METHODS

Pair-fed Sprague-Dawley rats were fed a low-sodium (0.03%) diet and received CsA (15 mg/kg, subcutaneously, in olive oil)/5% glucose, pentosan polysulfate (10 mg/kg, subcutaneously in 5% glucose) plus CsA, olive oil/pentosan polysulfate, or olive oil/5% glucose for 30 days. Creatinine clearance (CrCl) was determined at three time points. Afferent arteriolar lesions, glomerular volume, and tubulo-interstitial lesions were quantitated. RNA was extracted from cortex.

RESULTS

Severe lesions were found in the CsA group. A reduction in the number of affected arterioles (32%) and the degree of chronic tubulo-interstitial lesions (44%) was found in pentosan polysulfate/CsA-treated rats. A 20% decrease in glomerular volume was found in CsA rats, but not in pentosan polysulfate/CsA-treated rats. Pentosan polysulfate treatment did not prevent the CsA-induced decrease in CrCl (approximately 30%) at 4 weeks. CsA did not affect cortical endothelial or neuronal nitric-oxide synthase or mRNA levels, but there was small increase in neuronal nitric-oxide synthase mRNA levels in the pentosan polysulfate/CsA-treated group.

CONCLUSIONS

Pentosan polysulfate reduced structural renal lesions in CsA-treated, salt-depleted Sprague-Dawley rats.

Nephrotoxin exposure in utero reduces glomerular number in sclerosis-prone but not sclerosis-resistant mice

BACKGROUND

We have previously found that nephron number was not fixed, that is, there was a direct correlation between low birth weight and decreased nephron number in infants. In sclerosis-prone rats, we found that gentamicin exposure in utero induced a reduction in glomerular number and aggravated glomerulosclerosis in adults. In mice, we found that an inborn 50% reduction in nephron number, caused by the Os mutation, was associated with glomerulosclerosis in sclerosis-prone (ROP+/+) mice, but not in sclerosis-resistant (C57BL/6J) mice. Because the genetic background determined the response to decreased nephron number, we asked whether the susceptibility changes in glomerular number and glomerulosclerosis were linked.

METHODS

Gentamicin was administered before and after the onset of fetal nephrogenesis. (1) Prior to the onset of nephrogenesis, two groups of pregnant mice were treated from embryonic day (E) E8 to E12. In group A, early glomerular development was studied by placing ureteric ridges removed on E12 in vitro for four days, following which the ureteric bud branches and glomeruli were counted using lectin staining. In group B, nephron number was determined in spontaneously delivered 14-day-old (14PN) pups by counting glomeruli. (2) After the onset of nephrogenesis, to determine the direct effects of gentamicin on nephron induction, ureteric ridges were placed in organ culture at E12 of normal gestation, in the presence or absence of gentamicin. The number of glomeruli and ureteric bud branches were counted after six days in culture.

RESULTS

A decrease in glomerular number and ureteric bud branches was observed in sclerosis-prone (ROP+/+) mice, irrespective of whether gentamicin was administered prior to or after the onset of nephrogenesis. Glomerular number and ureteric bud branching were not decreased by gentamicin in sclerosis-resistant (C57BL/6) mice.

CONCLUSIONS

These data provide evidence that there is a positive correlation between the susceptibility to glomerulosclerosis in adulthood and a reduction in nephron number in utero. Thus, exposure to nephrotoxins in utero compounds the risk of renal failure as an adult in sclerosis-prone individuals.