Renal vascular and tubulointerstitial inflammation and proliferation in Cyp1a1-Ren2 transgenic rats with inducible ANG II-dependent malignant hypertension

Abstract

Graciano ML, Mouton CR, Patterson ME, Seth DM, Mullins JJ, Mitchell KD. Renal vascular and tubulointerstitial inflammation and proliferation in Cyp1a1-Ren2 transgenic rats with inducible ANG II-dependent malignant hypertension. Am J Physiol Renal Physiol 292: F1858 -F1866, 2007. First published March 6, 2007;doi:10.1152/ajprenal.00469.2006.-Transgenic rats with inducible ANG II-dependent malignant hypertension [TGR(Cyp1a1Ren2)] were generated by inserting the mouse Ren2 renin gene into the genome of the rat. The present study was performed to assess renal morphological changes occurring during the development of ANG IIdependent malignant hypertension in these rats. Male Cyp1a1-Ren2 rats (n ϭ 10) were fed normal rat food containing indole-3-carbinol (I3C; 0.3%) for 10 days to induce malignant hypertension. Rats induced with I3C had higher mean arterial pressures (173 Ϯ 9 vs. 112 Ϯ 11 mmHg, P Ͻ 0.01) than noninduced normotensive rats (n ϭ 9). Glomerular damage was evaluated by determination of the glomerulosclerosis index (GSI) in tissue sections stained with periodic acid-Schiff. Kidneys of hypertensive rats had a higher GSI than normotensive rats (21.3 Ϯ 5.6 vs. 3.5 Ϯ 1.31 units). Quantitative analysis of macrophage ED-1-positive cells and proliferating cell nuclear antigen using immunohistochemistry demonstrated increased macrophage numbers in the renal interstitium (106.4 Ϯ 11.4 vs. 58.7 Ϯ 5.0 cells/mm 2 ) and increased proliferating cell number in cortical tubules (37.8 Ϯ 5.7 vs. 24.2 Ϯ 2.1 cells/mm 2 ), renal cortical vessels (2.2 Ϯ 0.5 vs. 0.13 Ϯ 0.07 cells/vessel), and the cortical interstitium (33.6 Ϯ 5.7 vs. 4.2 Ϯ 1.4 cells/mm 2 ) of hypertensive rat kidneys. These findings demonstrate that the renal pathological changes that occur during the development of malignant hypertension in Cyp1a1-Ren2 rats are characterized by inflammation and cellular proliferation in cortical vessels and tubulointerstitium. kidney; glomerulosclerosis; renal injury; immunohistochemistry; renin-angiotensin system; renal pathology; peptide hormones TRANSGENIC RATS WITH INDUCIBLE activation of extrarenal renin gene expression [TGR(Cyp1a1Ren2)] were generated using a renin transgene under the transcriptional control of the cytochrome P-450 (Cyp1a1) promoter (23). This transgenic rat line was created by inserting a mouse Ren2 renin gene, fused to an 11.5-kb fragment of the Cyp1a1 promoter, into the genome of the Fischer 344 rat (23). Cyp1a1, which catalyzes the oxidation of a wide range of endogenous lipophilic compounds and xenobiotics (7, 10, 43), is not constitutively expressed but is highly inducible on exposure to various aryl hydrocarbons such as indole-3-carbinol (I3C) (7,10,14,21,26,33,43). Induction of Cyp1a1 is mediated by the aryl hydrocarbon receptor, which is a basic helix-loop-helix-transcription factor that binds to specific DNA elements in the Cyp1a1 promoter (7, 13, 43). Rats transgenic for the Cyp1a1-Ren2 construct do not constitutively express the Ren2 renin gene. Rather, the Ren2 gene is expressed, primarily i...

AT1 receptor-mediated augmentation of angiotensinogen, oxidative stress, and inflammation in ANG II-salt hypertension

“…Kidney sections (3 m), paraffin embedded, were stained with 1) Masson's trichrome (Mass Histology, Worcester, MA) for assessment of glomerular and interstitial fibrosis and 2) periodic acid-Schiff (PAS) for the determination of glomerular lesions. Morphometry of glomeruli and the extent of the interstitial fibrotic-positive area were evaluated quantitatively using computerized image analysis, as described (7,26). Mesangial expansion was quantified in 20 glomeruli per kidney per rat by dividing the PAS-positive stained area by the total area of the glomerulus and expressed as means Ϯ SE of the 20 measurements in percentage values, as previously described (7,26).…”

“…Morphometry of glomeruli and the extent of the interstitial fibrotic-positive area were evaluated quantitatively using computerized image analysis, as described (7,26). Mesangial expansion was quantified in 20 glomeruli per kidney per rat by dividing the PAS-positive stained area by the total area of the glomerulus and expressed as means Ϯ SE of the 20 measurements in percentage values, as previously described (7,26). For the immunoexpression of proliferating cell nuclear antigen (PCNA) and CD68, markers of cell proliferation and macrophage infiltration, respectively, monoclonal antibodies for PCNA and CD68 were used at 1:1,000 dilutions (7,26), respectively.…”

“…Mesangial expansion was quantified in 20 glomeruli per kidney per rat by dividing the PAS-positive stained area by the total area of the glomerulus and expressed as means Ϯ SE of the 20 measurements in percentage values, as previously described (7,26). For the immunoexpression of proliferating cell nuclear antigen (PCNA) and CD68, markers of cell proliferation and macrophage infiltration, respectively, monoclonal antibodies for PCNA and CD68 were used at 1:1,000 dilutions (7,26), respectively. Data were expressed as fold-changes in the number of nuclei in proliferation (for PCNA) or number of macrophages (for CD68).…”

Intrarenal angiotensin II and angiotensinogen augmentation in chronic angiotensin II-infused mice

“…telemetry; mouse kidney; hypertension CHRONIC INFUSIONS OF ANGIOTENSIN II (ANG II) lead to elevations in intrarenal ANG II content associated with reductions in renal function and sodium excretion and hypertension (26,29,31,35). An increase in intrarenal ANG II content is also associated with enhanced oxidative stress and chronic proinflammatory and proliferative responses that result in progressive tissue injury (7,18). Indeed, every model of experimental ANG II-dependent hypertension is characterized by augmentation of intrarenal ANG II content to levels much greater than can be explained on the basis of equilibration with the systemic circulation (8,23,39).…”

Signal transduction of the (pro)renin receptor as a novel therapeutic target for preventing end-organ damage

“…50 In contrast, an inducible, transgenic, hepatic prorenin overexpression using indole-3-carbinol was associated with hypertension, moderate renal vasculopathy and moderate cardiac hypertrophy, but not with cardiac fibrosis and glomerulosclerosis, 51,52 whereas a similar transgenic experiment observed glomerular damage. 53 A recent, sophisticated approach used transgenic mice expressing site-mutated prorenin eliminating its enzymatic activity. 54 These animals did not exhibit cardiac fibrosis or renal glomerular sclerosis.…”