SSHTN resulting from Ang II infusion is associated with infiltration and activation of immune cells that produce Ang II. MMF treatment reduces these features and prevents the development of SSHTN.

Recent studies have suggested that subtle microvascular and tubulointerstitial injury in the kidney can cause salt-sensitive hypertension. To test this hypothesis, we determined whether the mild renal disease induced by transient blockade of nitric oxide (NO) synthesis would result in salt-sensitive hypertension and whether prevention of the renal injury by coadministration of the immunosuppressive agent mycophenolate mofetil (MMF) would block the development of salt sensitivity. N(omega)-nitro-L-arginine-methyl ester (L-NAME; 70 mg/100 ml in the drinking water) was administered for 3 wk to rats with or without MMF (30 mg x kg(-1) x day(-1) by gastric gavage), followed by a 1-wk "washout" period in which the MMF was continued, which was followed in turn by placement on a high-salt (4% NaCl) diet for an additional 4 wk. Renal histology was examined at 3 and 8 wk, and blood pressure was measured serially. L-NAME treatment resulted in acute hypertension and the development of mild renal injury. During the washout period, blood pressure returned to normal, only to return to the hypertensive range on exposure of the animals to a high-salt diet. MMF treatment prevented the development of hypertension in response to a high-salt diet. This correlated with the ability of MMF to inhibit specific aspects of the renal injury, including the development of segmental glomerulosclerosis, the infiltration of T cells and ANG II-positive cells, and the thickening of afferent arterioles.

Abstract-The mechanisms by which persistent proteinuria induces interstitial inflammation and fibrosis are not well known, although nuclear factor-B (NF-B), which regulates the transcription of many genes involved in renal injury, could be implicated. In rats with intense proteinuria, we studied the renal activation of NF-B as well as the potential involvement of the vasoactive hormones angiotensin II (Ang II) and endothelin-1 (ET-1). Uninephrectomized Wistar-Kyoto rats receiving 1 g/d of BSA had proteinuria but no renal morphological lesions at day 1. By contrast, tubular atrophy and/or dilation and mononuclear cell infiltration were observed after 8 or 28 days of BSA administration, coinciding with maximal proteinuria. In relation to control uninephrectomized rats, the renal cortex of nephritic rats showed an increment in the activation of NF-B at all time periods studied. By in situ Southwestern histochemistry, NF-B activity was mainly localized in proximal tubules, interstitial mononuclear cells, and, to a lesser extent, the glomeruli. The administration of the ACE inhibitor quinapril plus the ET A /ET B receptor antagonist bosentan during 28 days to BSA-overloaded animals diminished proteinuria, renal lesions, and NF-B activity more markedly than single drugs. Cultured tubular epithelial cells exposed to BSA revealed an intense NF-B activation in a time-and dose-dependent manner. Incubation of cells with receptor antagonists of Ang II (AT 1 : losartan and AT 2 : PD-123,319) or ET-1 (ET A : BQ123 and ET B : IRL1038) inhibited significantly the BSA-induced NF-B activity (90%, 75%, 90%, and 60% of inhibition versus basal, respectively). Our results show that overload proteinuria causes NF-B activation in tubular epithelial cells both in vivo and in vitro. The vasoactive peptides Ang II and ET-1 appear to be implicated in this effect. The results reveal a novel mechanism of perpetuation of renal damage induced by persistent proteinuria.

Mesangial cell growth and accumulation of extracellular matrix proteins constitute key features of progressive glomerular injury. Endothelin-1 (ET-1) and angiotensin II (Ang II), two potent vasoconstrictor agents, evoke a number of similar responses in mesangial cells. In rat mesangial cells, we compared ET-1 and Ang II effects on matrix protein production and cell proliferation as well as the potential interaction between the two hormones. When cells in 0.5% fetal calf serum were incubated for 24 hours with various concentrations of ET-1 or Ang II, both peptides stimulated, in a dose-dependent manner, fibronectin and type IV collagen mRNA expression, fibronectin synthesis, and mitogenesis. Incubation with specific receptor antagonists of both hormones demonstrated that endothelin subtype A (ETA) and angiotensin type 1 (AT1) receptors were involved. Preincubation of cells with two different protein kinase C inhibitors or with a neutralizing anti-transforming growth factor-beta antibody, but not an unrelated IgG, diminished the peptide-induced fibronectin synthesis. A dual interrelation seems to exist between ET-1 and Ang II. Thus, the AT1 receptor antagonist losartan and the angiotensin-converting enzyme inhibitors quinaprilat and captopril diminished the ET-1-mediated effects, whereas, the ETA receptor antagonist BQ-123 diminished the Ang II-induced fibronectin synthesis and mesangial cell proliferation. Our results suggest that ET-1 and Ang II stimulate matrix protein synthesis and mesangial cell mitogenesis through ETA and AT1 receptors, respectively, by complicated mechanisms, implicating protein kinase C activation, synthesis of transforming growth factor-beta, and release of one peptide by the other. These data could be important for a better understanding of the participation of vasoactive substances in the pathogenesis of glomerulosclerosis.

Abstract-Persistent proteinuria is considered a deleterious prognostic factor in most progressive renal diseases. However, the mechanisms by which proteinuria induces renal damage remain undetermined. Since proximal tubular cells possess all the machinery to generate angiotensin II (Ang II), we approached the hypothesis that proteinuria could elicit the renal activation of the renin-angiotensin system in a model of intense proteinuria and interstitial nephritis induced by protein overload. After uninephrectomy (UNX), Wistar-Kyoto rats received daily injections of 1 g BSA or saline for 8 days. The mean peak of proteinuria was observed at the fourth day (538Ϯ89 versus 3Ϯ1 mg/24 h in UNX controls; nϭ12; PϽ0.05) and was increased during the whole study period (at the eighth day: 438Ϯ49 mg/24 h; nϭ12; PϭNS). Morphological examination of the kidneys at the end of the study showed marked tubular lesions (atrophy, vacuolization, dilation, and casts), interstitial infiltration of mononuclear cells, and mesangial expansion. In relation to UNX control rats, renal cortex of BSA-overloaded rats showed an increment in the gene expression of angiotensinogen (2.4-fold) and angiotensin-converting enzyme (ACE) (2.1-fold), as well as a diminution in renin gene expression. No changes were observed in angiotensin type 1 (AT 1 ) receptor mRNA expression in both groups of rats. By in situ reverse transcription-polymerase chain reaction and immunohistochemistry, ACE expression (gene and protein) was mainly localized in proximal and distal tubules and in the glomeruli. By immunohistochemistry, angiotensinogen was localized only in proximal tubules, and AT 1 receptor was localized mainly in proximal and distal tubules. In the tubular brush border, an increase in ACE activity was also seen (5.5Ϯ0.5 versus 3.1Ϯ0.7 U/mg protein ϫ10 Ϫ4 in UNX control; nϭ7; PϽ0.05). Our results show that in the kidney of rats with intense proteinuria, ACE and angiotensinogen were upregulated, while gene expression of renin was inhibited and AT 1 was unmodified. On the whole, these data suggest an increase in Ang II intrarenal generation. Since Ang II can elicit renal cell growth and matrix production through the activation of AT 1 receptor, this peptide may be responsible for the tubulointerstitial lesions occurring in this model. These results suggest a novel mechanism by which proteinuria may participate in the progression of renal diseases. (Hypertension. 1999;33:732-739.)