Expression of adhesion molecules in rat renal cortex during experimental hydronephrosis

Unilateral ureteral obstruction (UUO) is associated with an early and steadily increasing infiltration of macrophages into the renal cortical interstitium. As adhesion molecules may play an important role in macrophage recruitment following the mechanical disturbance after UUO, we delineated the time course of intercellular adhesion molecule (ICAM)-1 and vascular adhesion molecule (VCAM)-1 mRNA and protein expression. A significant 6.6- (P < 0.001), 2.6- (P < 0.025), 2.6- (P < 0.01), and 2.0-fold (P < 0.005) increase in ICAM-1 mRNA expression was observed at 12, 24, 48, and 96 hours after obstruction, respectively, in comparison to the contralateral unobstructed kidney (CUK). Despite an apparent relief of obstruction, four weeks following reversal of obstruction mRNA levels of ICAM-1 remained equivalent to the 96-hour obstructed kidney group. No significant difference in VCAM-1 mRNA expression was observed between the obstructed kidneys and CUK specimens. Immunohistochemistry revealed focal labeling of ICAM-1 on the apical and basolateral surface of the renal tubules, peritubular interstitium, and vessels of the renal cortex by 12 hours after UUO. In contrast, only faint staining for ICAM-1 protein was observed in the cortex from CUK specimens. The obstructed and CUK specimens exhibited diffuse immunolocalization of VCAM-1 in the cortical tubules and Bowman's capsular epithelium. In situ hybridization showed mRNA transcription for ICAM-1 localized in the peritubular interstitium and cortical tubules from obstructed kidneys. To lend mechanistic insight into the response of ICAM-1 to the mechanical disturbance after UUO, the expression of ICAM-1 mRNA was examined when freshly isolated proximal tubules were exposed to angiotensin II (1 to 100 microM) immediately after preparation. Levels of ICAM-1 mRNA were elevated 1.4-, 7.1-, and 3.7-fold when exposed to 10 microM, 100 microM, and 1000 microM of angiotensin II for one hour, respectively, when compared to control cultures. The addition of losartan to proximal tubules for one hour prior to angiotensin II stimulation decreased ICAM-1 levels to control values. In summary, this investigation demonstrates that ICAM-1 is important in the initiation of macrophage recruitment into the renal cortex of the obstructed kidney. These findings provide evidence that angiotensin II, produced after ureteral ligation as a result of tubular injury and dysfunction, may play a central role in the release of ICAM-1 from the proximal tubule epithelial cells.

Expression of subunits of the metalloendopeptidase meprin in renal cortex in experimental hydronephrosis

Meprin A is a metalloendopeptidase in the proximal tubular epithelium of rodents that is capable of hydrolyzing a great variety of peptides and proteins. The aim of the present investigation was to investigate effects of ureteral ligation on the expression of meprin subunits. Ureteral ligation resulted in marked decreases in the expression of both alpha- and beta-meprin subunits within 12 h of ureteral obstruction. Even greater downregulation of expression of meprin alpha- and beta-mRNA was noted at 24, 48, and 96 h after ureteral ligation. The greatest decrease in meprin mRNA expression in obstructed kidneys over contralateral unobstructed control kidneys (CUK) occurred at 24 h postunilateral ureteral obstruction (post-UUO) for the meprin alpha-subunit (20-fold decrease compared with controls) and at 48 h for the meprin beta-subunit (90-fold decrease). On immunolabeling, the intensity for the two meprin subunits at the corticomedullary junction was dramatically decreased at 24 to 96 h after ureteral ligation in contrast to the CUK specimens. Results of in situ hybridization indicated that the CUK specimens expressed meprin beta-mRNA at the corticomedullary junction, whereas the obstructed kidneys exhibited a decrease in mRNA signal for meprin beta-subunit. There was a steady increase in the interstitial macrophage number in UUO rat kidneys over the 96 h of evaluation post-UUO. ED-1-positive macrophages were observed almost exclusively in the peritubular cortical interstitial space in a ringlike pattern with a preponderance of macrophage clusters around glomeruli. Unexpectedly, after reversal of UUO, the interstitial macrophage number remained higher than controls, despite the demonstrable decompression of the renal pelvis and caliceal system. In summary, this investigation demonstrates downregulation of meprin alpha and beta within hours of UUO and indicates a novel tubular response to ureteral obstruction.

Relative fasting hypoinsulinaemia and ultrasonically measured early arterial disease in type 2 diabetes. The SENDCAP Study Group, St. Mary's, Ealing, Northwick Park Diabetes Cardiovascular Disease Prevention Study

Macrovasular disease is the most important cause of morbidity and mortality in Type 2 (non-insulin-dependent) diabetes. Dyslipidaemia and hyperinsulinaemia have been proposed as aetiological factors. This paper describes the interrelationships between fasting serum insulin, serum lipids, and the extent of ultrasonically measured early arterial disease in Type 2 diabetic subjects screened for entry into a prospective study set up to ascertain whether improving serum lipids can alter the progress of arterial disease in Type 2 diabetes. Measurements were made of the initima media thickness (IMT) in the carotid artery, and an arterial ultrasound score (AUS) based on appearances of both carotid and femoral arteries was calculated for 192 established Type 2 diabetic subjects, males and females, mean age 51 (range 35-66) years, median duration of diabetes 3.5 years, with no known cardiovascular disease. Multiple regression analysis showed that carotid IMT increased with age and was inversely related to serum insulin (variance accounted for, R2, = 8.8%, p = 0.0002). AUS increased with age and was related inversely to serum insulin, or to C-peptide when this was substituted in the model. In addition to age and serum insulin, AUS was positively associated with non-HDL cholesterol and negatively with HDL 3 cholesterol (R2 = 26%, p = 0.0001). Early thickening and damage to the arterial wall in Type 2 diabetes may be related to relative fasting hypoinsulinaemia.

Atypical hyperlipidemia and nephropathy associated with apolipoprotein E homozygosity

Hyperlipidemia has been implicated in the pathogenesis of experimental progressive glomerulosclerosis, but its role in human renal injury is controversial. This report describes a 12-yr-old boy presenting with massive proteinuria, hepatomegaly, anemia, severe mixed hyperlipidemia, and progressive renal failure. The initial renal biopsy disclosed large numbers of foam cells that were shown to be monocytes. Evidence is presented suggesting that apoprotein-E2 homozygosity in our patient, together with an 88% reduction in plasma lipoprotein lipase activity associated with severe nephrotic syndrome, is responsible for the atypical clinical features, lipoprotein phenotype III with chylomicronemia, and renal lipidosis. A regimen of dietary lipid restriction, gemfibrozil, and niacin resulted in significant but partial improvement of the dyslipidemia and resolution of the hepatomegaly and ascites. This report stresses the importance of characterizing unique lipid disorders in patients with nephrotic syndrome in order to prescribe effective lipid-lowering strategies. Moreover, the striking resemblance of the clinical and nephrohistologic features of this patient to those occurring in experimental models of coexisting glomerular injury and hyperlipidemia led to the speculation that, in this setting, the hyperlipidemia may contribute to the development of progressive glomerulosclerosis.

Macrophages and progressive renal disease in experimental hydronephrosis

Many recent clinical and experimental studies have clearly demonstrated that one of the initial events taking place in the process of progressive renal injury is monocytic infiltration of the glomerular and tubulointerstitial compartments. In this report, experimental data supporting the role of the infiltrating renal macrophage (M phi) as a mediator of interstitial fibrosis during the course of obstructive nephropathy will be reviewed as it pertains to the unilateral ureteral obstruction model in the rat. The central pathobiologic theme drawn on data from this model is that fibrogenic cytokines, especially transforming growth factor-beta, are, in part, M phi-derived and represent pivotal links between the initial postobstructive renal inflammation and the late development of renal scarring. The tubular epithelium, as a consequence of the mechanical disturbance produced by ureteral obstruction, may elaborate a host of M phi chemoattractant moieties. Many substances can be released by these infiltrating M phi; however, our studies have focused on transforming growth factor-beta 1. Transforming growth factor-beta is an important regulator of extracellular matrix, through its direct effects and modulation of other growth factors to maintain matrix homeostasis. We propose that the markedly increased expression of transforming growth factor-beta 1 following ureteral ligation, as detected by a number of laboratories, induces a profibrogenic state and initiates a cascade of dysregulatory events, including the upregulation of tissue inhibitors of metalloproteinase. Transforming growth factor-beta 1 also may serve as a potent stimulus for the modulation of quiescent interstitial fibroblasts into myofibroblasts. From a therapeutic standpoint, targeting these early cellular and molecular events may be extremely important in interrupting the interstitial fibrotic response to long-term obstructive uropathy.

Renal revascularization in patients on dialysis

Five patients requiring dialysis for acute pulmonary edema and uremia from severe renal artery occlusive disease underwent surgical revascularization. Three patients with oliguria had excellent outcomes and remain dialysis-independent as long as twenty-four months following operation (mean serum creatinine 2.0 mg/dl). The two patients who were anuric both had technically successful operations but remained dialysis-dependent. Diagnostic evaluation of the azotemic patient suspected to have renal arterial occlusive disease should include a history and physical examination, urinalysis, renal ultrasound, and duplex scan of the renal arteries. In appropriate patients, arteriography should then be considered if other diagnoses appear unlikely. This algorithm may help identify those patients who might benefit from renal revascularization. It appears that oliguria rather than anuria and the angiographic demonstration of a patent distal vessel and nephrogram suggest a better functional outcome after revascularization. Unfortunately, the response to surgery cannot be reliably predicted and patient selection remains a challenge, but retrieval of renal function can be achieved in some cases even if patients are already being hemodialyzed.

Early and persistent up-regulated expression of renal cortical osteopontin in experimental hydronephrosis

The mechanical disturbance after unilateral ureteral obstruction (UUO) is a nonimmune stimulus that is capable of eliciting a florid macrophage infiltration of the kidney and subsequent post-inflammatory renal scarring. Osteopontin has potential chemoattractant activity and, for this reason, we delineated the kinetics of its expression in the renal cortex of rats with UUO. Whole body X-irradiation and reversal of UUO were utilized as interventional maneuvers to give additional pathobiological insight into this protein's role in the response of the kidneys to ureteral obstruction. Increased osteopontin mRNA levels in obstructed kidneys versus contralateral unobstructed specimens were evident as early as 4 hours after UUO and steadily increased at 12, 24, 48, and 96 hours after UUO. Both X-irradiation and reversal of UUO failed to significantly modulate renal cortical osteopontin mRNA expression at all of the above time points. Paralleling the increments in renal cortical osteopontin mRNA levels were significant elevations in the cortical renal interstitial macrophage number, which was significantly diminished by previous X-irradiation but not reversal of UUO. Focal labeling of osteopontin was noted in both tubular and Bowman's capsular epithelium in obstructed kidneys as early as 4 hours after UUO, whereas, in the contralateral unobstructed specimens, there was only faint staining in Bowman's capsule. By 96 hours after UUO, obstructed kidneys exhibited intense, diffuse staining for osteopontin in both tubules and Bowman's capsule. Osteopontin's immunolocalization was not modulated by X-irradiation or reversal of UUO. These data support the contention that osteopontin is involved in the accumulation of macrophages within the peritubular and periglomerular interstitium in the obstructed renal cortex.

Differential mRNA expression of renal cortical tissue inhibitor of metalloproteinase-1, -2, and -3 in experimental hydronephrosis

The pathophysiologic sequelae of both acute and chronic experimental unilateral ureteral obstruction (UUO) in the rat are the result of a variety of complex humoral and cellular interactions. The development of interstitial fibrosis is dependent on the tightly coupled regulation of synthesis and degradation of extracellular matrix proteins. This laboratory, among others, has shown an up-regulated expression of renal cortical transforming growth factor (TGF)-beta 1 within hours of the onset of UUO. Because a potential contribution of TGF-beta to fibrosis may be its ability to increase the expression of proteinase inhibitors such as members of the tissue inhibitor of metalloproteinase (TIMP) family, this laboratory now sought to delineate the kinetics of TIMP-1, TIMP-2, and TIMP-3 mRNA expression in the renal cortex after UUO. There was a marked elevation of TIMP-1 mRNA expression after UUO, which was first noted at 12 h after ureteral ligation. By 96 h after UUO; there was a 30-fold increment in TIMP-1 mRNA in the obstructed kidneys compared with the contralateral unobstructed kidney or sham-operated rat specimens. In contradistinction to TIMP-1, a decrease in TIMP-3 mRNA levels was noted at 12 h after ureteral obstruction and persisted at the 24-, 48-, and 96-h time intervals. TIMP-2 gene expression remained at a relatively constant level during the entire study. It is proposed that the increased expression of TGF-beta 1 post-UUO induces a profibrogenic state and initiates a cascade of dysregulatory events including the up-regulation of TIMP-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Myofibroblasts in experimental hydronephrosis

Interstitial fibrosis is a common outcome of longterm ureteral obstruction. One pathological arm of the fibrotic reaction in diverse tissue loci and experimental models is the retraction of granulation tissue. The role of the myofibroblast in granulation tissue contraction and fibrocontractive diseases has been well established, but the mechanisms leading to differentiation of fibroblastic cells into myofibroblasts during the evolution of inflammation are not yet fully clarified. Investigators using other model systems have shown that macrophage-derived transforming growth factor-beta 1 (TGF-beta 1) may be pivotal in the process of myofibroblast modulation. Our laboratory has shown that the unilateral ureteral obstruction in the rat is characterized by a 20-fold increment in infiltrating renal cortical interstitial macrophages, an increase in cortical TGF-beta 1 gene expression, which parallels the infiltrating macrophage burden, and immunolocalization of this peptide growth factor in close proximity to resident interstitial fibroblasts. Because of this model's features, it was our aim to assess whether a myofibroblastic modulation was operant in the renal cortex of obstructed rat kidneys versus the control contralateral unobstructed kidney specimens. Immunolabeling for alpha-smooth muscle actin and the intermediate filament protein, desmin, was detected and steadily intensified from 24 to 96 hours after unilateral ureteral obstruction in obstructed kidneys only. In temporal concert with the detection of alpha-smooth muscle actin protein, the mRNA expression for this cytoskeletal component exhibited 3.7-, 15.7-, and 4.1-fold increments in the renal cortex of obstructed kidneys versus the contralateral unobstructed kidney specimens at 24, 48, and 96 hours after unilateral ureteral obstruction, respectively. Whole body X-irradiation, administered to rats 11 days before proximal left ureteral ligation, significantly lowered cortical interstitial macrophage number, cortical TGF-beta and alpha-smooth muscle actin mRNA levels as well as the intensity of immunolabeling for alpha-smooth muscle actin from 12 to 96 hours after unilateral ureteral obstruction. These data support a postulate that renal cortical TGF-beta 1, derived from the infiltrating macrophage, in part, contributes to the subsequent interstitial fibrosis response to renal injury by fostering the modulation of fibroblasts to myofibroblasts within the renal cortex after ureteral obstruction.

Transforming growth factor-beta expression in macrophages during hypercholesterolemic states

Macrophage infiltration into the glomerular mesangium is a prominent feature of various glomerulopathies. Recent evidence suggests that infiltrating macrophages may play a role in propagating initial glomerular injury to the development of glomerulosclerosis via transforming growth factor-beta (TGF-beta)-stimulating matrix accumulation. Rats with the acute puromycin aminonucleoside (PA) nephrosis exhibit an elevated gene expression of glomerular TGF-beta 1; however, the cellular origin of this upregulation is unknown. Using polymerase chain reaction (PCR), we detected that the TGF-beta 1 isoform is expressed in glomerular macrophages isolated from experimental rats made hypercholesterolemic by either diet or by induction of PA nephrosis. Peritoneal macrophages from nephrotic or dietary-hypercholesterolemic animals also exhibited a significant increment in the expression of TGF-beta 1 mRNA on Northern analysis, in contrast to similar cells obtained from normal control rats. PCR analysis of glomerular RNA also detected the expression of the TGF-beta 2 mRNA isoform. TGF-beta 2 mRNA expression was not observed in isolated glomerular macrophages from either glomeruli of PA-nephrotic rats or from glomeruli of animals with dietary hypercholesterolemia. Expression of the TGF-beta 3 mRNA isoform was only observed by PCR in J774 A.1 cells. Thus the as a cellular source for the enhanced expression of TGF-beta 1 during the acute nephrotic phase of our toxic, progressive glomerulopathy model and within several days of inducing only hypercholesterolemia by dietary means.

Macrophages and renal disease

In this multimodel overview, we have provided the seminal experimental evidence for the crucial contribution of macrophages in the progression of glomerular and interstitial fibrosis. Although all the experimental data provided in this review definitely increase our understanding of the progress of renal disease, we have been mindful to use caution in extrapolating data from animal experiments to the clinical setting (109). In addition, uncertainty still exists as to whether macrophages activation entails a generalized mechanism in which the cells release growth factors and other mediators such as bioactive lipids and nitric oxide simultaneously, or a selective mechanism in which the cells release some but not all macrophage products (110). However, we anticipate that further substantial clinical and experimental observations are on the horizon. Novel therapeutic strategies in these models must be concerned with the prevention of renal macrophage recruitment and/or the suppression of the fibrogenic ability of this pluripotential inflammatory cell.

Macrophages, monocyte chemoattractant peptide-1, and TGF-beta 1 in experimental hydronephrosis

Early cellular and molecular derangements have been evaluated as potential pivotal factors for the late development of interstitial fibrosis after experimental hydronephrosis. In this study, we delineated the kinetics of renal cortical macrophage infiltration as well as the cortical expression of transforming growth factor-beta 1 (TGF-beta 1) and monocyte chemoattractant peptide-1 (MCP-1) at 12, 48, and 96 h after unilateral ureteral obstruction (UUO). Interstitial macrophage number in the obstructed kidney versus the contralateral unobstructed kidney (CUK) significantly increased by 12 (11.1 +/- 0.9 vs. 4.5 +/- 0.6), 48 (27.5 +/- 0.9 vs. 4.0 +/- 0.8), and 96 h (71.4 +/- 4.6 vs. 3.2 +/- 0.4) after UUO. MCP-1 mRNA was detected from 12 to 96 h in the obstructed kidney but was absent in the CUK specimens at all time points. Apical tubular MCP-1 expression, on immunolabeling, was present from 12 through 96 h after UUO in the obstructed kidney but not the CUK specimen. On Northern analysis, there were highly significant 2.6-, 5.8-, and 7.0-fold increments in renal cortical TGF-beta 1 mRNA levels at 12, 48, and 96 h, respectively, in the obstructed kidney versus the CUK specimen. Intracellular TGF-beta 1, on immunolabeling, was detected only in the obstructed kidneys of UUO rats at all three time points and was confined to peritubular cells of the renal interstitium. A significant (P < 0.005) correlation (r = 0.95) between interstitial macrophage number and cortical TGF-beta 1 mRNA levels was noted.(ABSTRACT TRUNCATED AT 250 WORDS)

The adverse effects of cholesterol in progressive glomerular injury

Accumulating experimental evidence indicates that hypercholesterolemia is an aggravating factor in the progression of initial glomerular injury to glomerulosclerosis. Many features of progressive glomerular disease share biological properties with atherosclerosis and emerging data suggest a noxious role for oxidized low density lipoprotein in the glomerulosclerosis process. This article reviews these issues and examines the pathobiology of cholesterol-induced glomerular injury.

Cholesterol, macrophages, and gene expression of TGF-beta 1 and fibronectin during nephrosis

Hypercholesterolemia aggravates experimental progressive glomerular injury. Evidence suggests the infiltrating glomerular macrophage (M phi) is a potential effector mechanism for the noxious effects of hypercholesterolemia. Because transforming growth factor (TGF)-beta 1 is secreted by activated M phi s and also stimulates fibronectin production by glomerular cells, we evaluated the kinetics of gene expression for these moieties in glomeruli isolated from nephrotic rats at 3, 7, 11, and 42 days after the delivery of puromycin aminonucleoside (PA). We also assessed whether cholesterol feeding, which raises the glomerular M phi number, alters the glomerular mRNA levels for TGF-beta 1 and fibronectin. Glomerular mRNA levels for TGF-beta 1 and fibronectin in nephrotic rats exhibited a biphasic temporal pattern, decreasing significantly below control at 3 and 7 days after PA but increasing significantly at 11 and 42 days after PA. The upregulated gene expression for TGF-beta 1 and fibronectin at 11 days after PA temporally corresponded to the phase of mesangial M phi infiltration in this model. Cholesterol feeding to both normal and nephrotic rats significantly increased glomerular TGF-beta 1 and fibronectin mRNA levels at 11 days after PA. Immunohistochemical labeling for M phi s and intracellular TGF-beta 1 demonstrated both mesangial and cortical interstitial localization with the TGF-beta1-positive cells possessing M phi nuclear morphology. These findings identify a novel interaction between hypercholesterolemia, augmented glomerular M phi accumulation, and upregulated glomerular TGF-beta 1 and fibronectin gene expression. These perturbations within the acutely injured glomerulus constitute an early pathobiological determinant for the later development of mesangial matrix expansion and glomerulosclerosis.

Relationship between hyperlipidemia, lipid mediators, and progressive glomerulosclerosis in the nephrotic syndrome

Nephrotic syndrome is defined by proteinuria, hypoalbuminemia, edema and hypercholesterolemia. Evidence from both the experimental and clinical literature suggests that high lipid levels are not only a marker of disease, but also contribute to the process of glomerulosclerosis. Lipid mediators, including eicosanoids, platelet-activating factor, and chemotactic factors, can contribute by effecting leukocyte infiltration, mesangial proliferation, extracellular matrix protein production, vasoreactivity, and coagulation. Infiltrating macrophages may play a central role in these processes. Therapeutic maneuvers aimed at the correction of lipid abnormalities may halt or slow the progression of nephrotic syndrome to end-stage renal disease.

Macrophages mediate adverse effects of cholesterol feeding in experimental nephrosis

We tested whether the deleterious effects of hypercholesterolemia, in a progressive glomerular disease model, may be mediated by infiltrating renal macrophages. A single sublethal dose of whole body X-irradiation (XI) delivered to rats with acute puromycin aminonucleoside (PA) nephrosis fed a high-cholesterol (HC) diet resulted in significantly greater inulin and p-aminohippurate (PAH) clearances at 11 days after PA without any alterations in circulating lipid levels, in contrast to nonirradiated HC-fed nephrotic controls. This functional protection was associated with significant declines in both glomerular and cortical interstitial macrophage number. Over the course of this 16-wk model, HC-fed PA rats had significantly less albuminuria as well as significantly fewer glomerulosclerosis (GS) lesions and less mesangial matrix expansion at the end of the study despite an equivalent degree of sustained hypercholesterolemia. This data suggests that reducing the infiltrating glomerular and cortical interstitial macrophage burden with XI during acute PA nephrosis, unaccompanied by any hypolipidemic effect, produces not only early salutary effects on renal function but also a significant amelioration of the progressive glomerulopathic features of this model. This is consistent with the hypothesis that the infiltrating renal macrophage, in large part, directly mediates the adverse effects of hypercholesterolemia in this model.

Glomerular macrophages and the mesangial proliferative response in the experimental nephrotic syndrome

Mesangial cell proliferation, which is a harbinger of glomerulosclerosis, occurs in both immune and nonimmune glomerulopathies. The proximity of infiltrating glomerular macrophages to the contractile mesangial cells during acute puromycin aminonucleoside (PA) nephrosis suggests the possibility of a paracrine effect on mesangial cell growth. To test this, three maneuvers to either raise or lower the glomerular macrophage number during acute PA nephrosis (2 weeks after PA) were employed: 1) an essential fatty acid-deficient (EFAD) diet; 2) a cholesterol-supplemented diet (CSD); and 3) a single dose (600 rad) whole-body X-irradiation (XI) given to CSD-fed PA rats. Both the glomerular macrophage number and proliferation within the mesangium were evaluated immunohistochemically with ED-1, a mouse monoclonal anti-rat macrophage label, and 19A2, a mouse monoclonal anti-proliferating cell nuclear antigen (PCNA)/cyclin antibody, respectively. Immunohistochemical detection of 5'-bromo-2'-deoxyuridine (BrdU) incorporation confirmed that proliferation was occurring within the mesangial zones. The EFAD diet significantly reduced both the glomerular macrophage and PCNA/cyclin-positive cell number at 2 weeks after PA with a positive correlation (r = 0.89, P < 0.05). The CSD maneuver significantly increased both the glomerular macrophage and PCNA/cyclin cell number with a strong degree of correlation (r = 0.95, P < 0.01). X-irradiation administered to CSD-fed PA rats significantly lowered both the glomerular macrophage and PCNA/cyclin-positive cell number at 2 weeks. In all groups, the glomerular tufts did not express muscle actin using HHF 35, a specific immunolabel, suggesting that the proliferation in this model is not related to direct mesangial cell injury. This study shows that maneuvers that modulate the glomerular macrophage number are also associated with corresponding changes in the number of proliferating cells within the mesangium, suggesting a paracrine growth stimulation by the infiltrating macrophage during acute PA nephrosis. The infiltrating glomerular macrophage may be an effector mechanism for the propagation of initial glomerular injury to glomerulosclerosis by augmenting mesangial cell proliferation early in the course of this nonimmune progressive glomerulopathy.

Progressive albuminuria and glomerulosclerosis in a rat model of chronic renal allograft rejection

A significant proportion of renal allografts fail within several months or years after transplantation, primarily because of chronic rejection. The etiology and pathophysiology of this condition remain unclear. We studied the renal function, morphology, and immunohistology, in parallel, among F344-to-Lewis allografts (n = 23) and isografts (n = 13) over the course of 24 weeks. Only an initial 10-day course of CsA (5 mg/kg/day) was given to both groups to prevent acute rejection. Hypertension did not develop, although awake systolic blood pressure was significantly higher in allografts at the end of the study. Significant differences in urine albumin excretion (UalbV) between isografts and allografts were evident as early as 4 weeks after engraftment but rose dramatically by 20 weeks (3.3 +/- 0.7 vs. 21.2 +/- 3.7 mg/day, respectively, P < .001). This pattern continued until the conclusion of the study (5.0 +/- 1.1 vs. 53.5 +/- 7.6 mg/day, P < .001). Serum creatinine values were only significantly elevated in allografts at 16 weeks, which temporally corresponded to the dramatic increase in UalbV. However, renal blood flow and glomerular filtration rate, measured by paraaminohippurate and inulin clearances, respectively, were significantly lower in allografted organs, at 24 weeks. The frequency of glomerulosclerosis lesions was significantly increased in allografted kidneys at 24 weeks and correlated with UalbV values. Glomerular localization of mononuclear leukocyte subsets were equivalent between allografts and isografts; however, the numbers of interstitial macrophages, CD8+, and pan-T-cells were all significantly greater in allografts at 24 weeks. The infiltration of significantly greater numbers of macrophages and lymphocytes into the tubulointerstitium of the allograft group suggests a mononuclear leukocyte effector cell mediation of the progressive glomerular abnormalities in this model of chronic renal allograft rejection in the rat.

Diabetic glomerulosclerosis and chronic renal failure with absent-to-minimal microalbuminuria

We report the case of an elderly black woman with a 20-year history of insulin-independent diabetes mellitus (IDDM), chronic renal failure, hypertension, proliferative retinopathy, and classical histologic features of diabetic glomerulosclerosis on renal biopsy. Repeat determinations of urinary albumin excretion rates failed to disclose significant microalbuminuria. This presentation should remind the clinician that a small minority of patients with IDDM of long duration may have severe diabetic glomerulosclerosis and renal insufficiency without detectable microalbuminuria.

The role of reactive oxygen species in animal models of glomerular disease

Reactive oxygen metabolites have been demonstrated to play a pathobiologic role in a number of experimental models of both immune and nonimmune glomerular injury. Using scavenging substances, enzyme inhibitors, and transition metal chelators, all of the major reactive oxygen metabolites have been implicated in glomerular injury. In addition, in neutrophil-dependent models, interaction between neutrophil-derived myeloperoxidase and halide anions has been shown to be involved in glomerular damage, as well as halogenation of the glomerular basement membrane (GBM). Finally, recent attention has focused on the role of cytokines (perhaps elaborated by infiltrating monocytes/macrophages) in stimulating mesangial cells (MC) to produce reactive oxygen species. Theoretically, this pathobiologic sequence could further enhance an inflammatory state within the glomerular tuft and enable the propagation of initial glomerular injury, which may be associated with an increase in monocyte infiltration into the mesangium, to glomerulosclerosis in experimental models that manifest this transition.

A putative role of hypercholesterolemia in progressive glomerular injury

Recently, much experimental evidence has accumulated contending that hypercholesterolemia is an aggravating factor in the progression of initial glomerular injury to glomerulosclerosis. Many of the features of progressive glomerular disease share biological properties with those of atherosclerosis, and data suggesting a noxious role for oxidized low-density lipoprotein in the glomerulosclerosis process are emerging. This review discusses these issues and examines the pathobiology of cholesterol-induced glomerular injury.