Renin-angiotensin system function and blood pressure in adult rats after perinatal salt overload

BACKGROUND AND AIM

To study the influence of high salt intake during pregnancy and lactation on body weight, blood pressure, and the function of the renin-angiotensin system in adult rats.

METHODS AND RESULTS

Female Wistar rats received a low (0.15 NaCl), normal (1.30), or high (8% diet) salt diet. Mating occurred on the 12th week of age. From weaning, the offspring received normal salt diet. Weekly tail-cuff blood pressure and body weight measurements were performed during pregnancy and in the offspring (body weight since weaning and tail-cuff blood pressure between the 8th and the 12th week of age). Salt sensitivity of the blood pressure was evaluated and plasma renin activity determinations were performed in the 12-week-old offspring. Immunohistochemistry for renal angiotensin II was performed in the adult offspring. Renal mass and the number of glomeruli were determined. Tail-cuff blood pressure was higher in salt overloaded dams than in normal and low salt ones. In the adult offspring from the high salt dams, lower body weight, higher tail-cuff blood pressure, lower salt sensitivity in females, and increased kidney angiotensin II were observed. Plasma renin activity did not change with changes in salt intake in the adult offspring submitted to high salt environment during the perinatal period. In the offspring, renal mass and the number of glomeruli were not influenced by the dams' salt intake.

CONCLUSIONS

Salt overload during pregnancy and/or lactation has long-term effects on offspring's body weight and blood pressure. In addition, high salt diet during the perinatal period induced renin-angiotensin system functional disturbances in the offspring.

Predominant IL-10 production in indirect alloreactivity is not associated with rejection

In a prospective study of indirect alloresponse in renal transplantation, we detected proliferation and cytokine production to donor and third-party HLA-DR peptides unrelated to rejection. Twenty of 28 patients (71%) presented proliferation, 29% before and 71% after transplantation. Half of the patients also presented proliferation to third-party peptides. Indirect alloresponse was also detected in 75% of healthy individuals (HI). Variability of response was observed in patients and HI for both proliferation and cytokine production. IL-10 predominance was observed in indirect alloresponses to donor peptides pre- and post-Tx, in contrast with more IFN-gamma and TGF-beta being detected in HI. IL-10 production was frequently detected without proliferation, in contrast with more frequent proliferation being found with IFN-gamma and TGF-beta production. The lack of association of either cytokine or proliferation with rejection, together with the predominance of IL-10 unrelated to proliferation, suggests that regulatory cells may be part of the T cell repertoire involved in indirect alloreactivity.

Cyclosporine-induced interstitial fibrosis and arteriolar TGF-beta expression with preserved renal blood flow

BACKGROUND

Cyclosporine A (CsA)-induced chronic nephrotoxicity is characterized by interstitial fibrosis and afferent arteriole hyalinosis. CsA lesion has been linked to maintained renal vasoconstriction and narrowing of the afferent arteriole lumen diameter, leading to preglomerular ischemia. We investigated the role of renal hemodynamics in CsA-induced transforming growth factor (TGF-beta) expression and interstitial fibrosis.

METHODS

Groups of rats fed a low salt diet were given CsA 5 mg/kg/day (CsA) or the vehicle (olive oil, [VH]) s.c. and had the renal blood flow (RBF), glomerular filtration rate (GFR), mean arterial pressure, renal vascular resistance, renal histologic changes, and immunohistochemical features for macrophages and TGF-beta evaluated after 1, 2, and 8 weeks of treatment.

RESULTS

At week 1, despite normal renal hemodynamics and MAP, there was a significant macrophage interstitial influx in CsA-treated rats (70+/-16 vs. 29+/-4 cells+/0.5 mm2, in CsA vs. VH, P=0.02) that was progressive with treatment (80+/-13 vs. 32+/-8 cells+/0.5 mm2, P=0.016 and 197+/-36 vs. 23+/-3 cells+/0.5 mm2, P=0.0002, CsA vs. VH at 2 and 8 weeks, respectively). After 2 weeks of treatment, CsA animals developed a significant interstitial fibrosis, with preserved RBF, even when it was assessed 2 hr after CsA injection. There was a significant increase in the immunostaining for TGF-beta in the juxtaglomerular arterioles in CsA-treated rats (48.6+/-3.8 vs. 35.1+/-1.1%, CsA vs. VH at 2 weeks, P<0.05 and 59.0+/-3.2 vs. 37.0+/-2.1%, CsA vs. VH at 8 weeks, P=0.0001). A significant and progressive GFR decrease followed the renal structural injury of CsA treatment. Arteriolar and glomerular anatomic injury were not found throughout the study.

CONCLUSIONS

Low CsA doses might generate interstitial fibrosis without any decrease in RBF or structural arteriolar lesion evidence, possibly through early macrophage influx and increased TGF-beta expression. It clearly seems that CsA-induced ischemia and tubulointerstitial injury may occur independently, suggesting that chronic CsA nephrotoxicity may be very hard to prevent or even not be preventable at all.

Mycophenolate mofetil attenuates renal injury in the rat remnant kidney

BACKGROUND

Mycophenolate mofetil (MMF), an inhibitor of lymphocyte proliferation, has been used to prevent allograft rejection. We investigated whether MMF also limits progressive renal injury in rats with 5/6 renal ablation, a model not primarily related to immunologic mechanisms.

METHODS

Eighty-eight adult male Munich-Wistar rats underwent ablation and received either vehicle (N = 42) or oral MMF (N = 46), 10 mg/kg/day. Forty-seven sham-operated rats were also studied.

RESULTS

Thirty days after surgery, remnant kidneys exhibited glomerular hypertension and hypertrophy. MMF treatment did not correct these abnormalities. Immunohistochemistry revealed interstitial lymphocyte infiltration 7 and 30 days after ablation. Proliferating cells abounded seven days after ablation, especially in tubules, declining in number along the following weeks. By contrast, the number of macrophages was moderately increased in the first weeks, attaining values eightfold as high as control 60 days after ablation. MMF attenuated these cellular events at all phases of the study. Sixty days after ablation, marked albuminuria, glomerulosclerosis and interstitial expansion were prominent in untreated rats. MMF treatment largely attenuated glomerular and interstitial injury without changing proteinuria.

CONCLUSION

This is the first evidence that MMF may impact favorably on progressive renal diseases of "nonimmunologic" origin.

Nitroflurbiprofen, a new nonsteroidal anti-inflammatory, ameliorates structural injury in the remnant kidney

Cyclooxygenase derivatives and nitric oxide (NO) may influence the pathogenesis of progressive nephropathies. We investigated the effect of nitroflurbiprofen (NOF), a NO-releasing nonsteroidal anti-inflammatory drug (NSAID) without gastrointestinal toxicity, in rats with 5/6 ablation (NX). The following four groups were studied: Sham, sham-operated rats; Sham + NOF, Sham receiving oral NOF two times daily; NX, rats subjected to NX; and NX + NOF, NX receiving NOF. NOF was barely detected in plasma but released the parent compound flurbiprofen. At 30 days, glomerular hydraulic pressure (PGC) was 76 +/- 3 mmHg in NX (52 +/- 1 in Sham, P < 0.05). NOF slightly reduced PGC to 69 +/- 2 mmHg in NX + NOF (P > 0.05 vs. NX). Glomerular volumes behaved similarly. At 60 days, tail cuff pressure was 152 +/- 6 mmHg, glomerulosclerosis index was 22.1 +/- 9.5, and interstitial fractional area was 9.9 +/- 1.2% in NX. NOF reduced these parameters to 137 +/- 4 mmHg, 3.5 +/- 0.7, and 6.4 +/- 0.8%, respectively (P < 0.05), without causing growth stunting or anemia. These beneficial effects could not be ascribed to NO donation and may reflect cyclooxygenase inhibition. This is the first evidence that chronic NSAID treatment may ameliorate progressive nephropathies.

Acute renal failure due to hemolytic uremic syndrome in adult patients

Hemolytic uremic syndrome is characterized by the simultaneous occurrence of hemolytic anemia, thrombocytopenia, and renal failure. Clinical/ pathologic data, along with the treatment and outcome of 8 adult patients with HUS, are described. There were 7 females and 1 male, age 30.7 +/- 12 years; 7 were White and 1 Black. Three patients were kidney graft recipients, 2 of whom were receiving cyclosporine; 2 patients were postpartum; 1 case followed an abortion; 1 occurred with prodromic infection; and 1 case was without a causal factor. All patients presented with hematuria and 6 with oligoanuria. Laboratory data showed hemolytic anemia with schistocytes, LDH values were 2584 +/- 2191 U/L, platelets were 79,000 +/- 40,000/mL, creatinine concentrations were 5.9 +/- 2.5 mg/dL. Renal biopsy showed thrombotic microangiopathy. Two had predominant glomerular involvement. 2 showed renal cortical necrosis, 4 were marked by predominant arteriolar involvement. In 5 patients dialytic therapy was performed. All were treated with fresh-frozen plasma infusion and 6 with plasmapheresis. Three patients died, 2 without recovery of renal function. In conclusion, the trigger events were related to renal transplant in 3.2 of them taking cyclosporine; 3 with pregnancy; 1 to precedent infection; and 1 with no causal factor. There was no correlation between histological form and outcome in this group of patients. The benefit of plasmapheresis was evident in the recovery of the extrarenal manifestations, although it did not change the renal outcome. The prognosis is poor, with a high mortality (37.5%) and/or end-stage renal failure (37.5%). Complete recovery of renal function was obtained in 25%.

Effect of salt intake and inhibitor dose on arterial hypertension and renal injury induced by chronic nitric oxide blockade

Long-term nitric oxide blockade by N omega -nitro-L-arginine methyl ester (L-NAME) leads to severe and progressive hypertension. The role of salt intake in this model is unclear. To verify whether salt dependence in this model is related to the extent of nitric oxide inhibition, we gave adult male Munich-Wistar rats a low salt, standard salt, or high salt diet and oral L-NAME treatment at either 3 or 25 mg/kg per day. At 10 to 15 days of treatment, the slope of the pressure-natriuresis line was decreased in rats receiving low-dose L-NAME compared with untreated controls. In rats treated with the higher dose, the line was shifted to the right but remained parallel to that obtained in untreated controls. Renal vascular resistance was moderately increased in rats receiving low-dose L-NAME, whereas high-dose L-NAME induced a marked vasoconstriction that was aggravated by salt overload. Low-dose L-NAME treatment induced hypertension only when associated with sodium overload. In rats receiving high-dose L-NAME, hypertension was aggravated by sodium excess but was not ameliorated by sodium restriction. Long-term (6 weeks) L-NAME treatment was associated with progressive hypertension, which was aggravated by salt overload, and with the development of albuminuria, focal glomerular collapse, glomerulosclerosis, and renal interstitial expansion. These abnormalities were worsened by salt overload and largely prevented by salt restriction. In the model of chronic nitric oxide blockade, salt dependence is a function of the inhibitor dose, and renal injury varies directly with the level of salt intake.