Mark E. Rosenberg

Induction of heme oxygenase is a rapid, protective response in rhabdomyolysis in the rat.

Heme proteins such as myoglobin or hemoglobin, when released into the extracellular space, can instigate tissue toxicity. Myoglobin is directly implicated in the pathogenesis of renal failure in rhabdomyolysis. In the glycerol model of this syndrome, we demonstrate that the kidney responds to such inordinate amounts of heme proteins by inducing the heme-degradative enzyme, heme oxygenase, as well as increasing the synthesis of ferritin, the major cellular repository for iron. Prior recruitment of this response with a single preinfusion of hemoglobin prevents kidney failure and drastically reduces mortality (from 100% to 14%). Conversely, ablating this response with a competitive inhibitor of heme oxygenase exacerbates kidney dysfunction. We provide the first in vivo evidence that induction of heme oxygenase coupled to ferritin synthesis is a rapid, protective antioxidant response. Our findings suggest a therapeutic strategy for populations at a high risk for rhabdomyolysis.

CLUSTERIN : PHYSIOLOGIC AND PATHOPHYSIOLOGIC CONSIDERATIONS

Clusterin is a heterodimeric glycoprotein produced by a wide array of tissues and found in most biologic fluids. A number of physiologic functions have been proposed for clusterin based on its distribution and in vitro properties. These include complement regulation, lipid transport, sperm maturation, initiation of apoptosis, endocrine secretion, membrane protection, and promotion of cell interactions. A prominent and defining feature of clusterin is its induction in such disease states as glomerulonephritis, polycystic kidney disease, renal tubular injury, neurodegenerative conditions including Alzheimers disease, atherosclerosis, and myocardial infarction. The expression of clusterin in these states is puzzling, from the specific molecular species and cellular pathways eliciting such expression, to the roles subserved by clusterin once induced. This review will discuss these physiologic and pathophysiologic aspects of clusterin and speculate on its role in disease.

Isolation and Characterization of Kidney-Derived Stem Cells

Acute kidney injury is followed by regeneration of damaged renal tubular epithelial cells. The purpose of this study was to test the hypothesis that renal stem cells exist in the adult kidney and participate in the repair process. A unique population of cells that behave in a manner that is consistent with a renal stem cell were isolated from rat kidneys and were termed multipotent renal progenitor cells (MRPC). Features of these cells include spindle-shaped morphology; self-renewal for >200 population doublings without evidence for senescence; normal karyotype and DNA analysis; and expression of vimentin, CD90 (thy1.1), Pax-2, and Oct4 but not cytokeratin, MHC class I or II, or other markers of more differentiated cells. MRPC exhibit plasticity that is demonstrated by the ability of the cells to be induced to express endothelial, hepatocyte, and neural markers by reverse transcriptase-PCR and immunohistochemistry. The cells can differentiate into renal tubules when injected under the capsule of an uninjured kidney or intra-arterially after renal ischemia-reperfusion injury. Oct4 expression was seen in some tubular cells in the adult kidney, suggesting these cells may be candidate renal stem cells. It is proposed that MRPC participate in the regenerative response of the kidney to acute injury.

Surveillance and prevention of residential-fire injuries

BACKGROUND The majority of severe and fatal burn injuries result from residential fires. We studied the effectiveness of a smoke-alarm-giveaway program in the prevention of burn injuries in an area with a high rate of such injuries. METHODS We collected data on burn injuries in Oklahoma City from September 1987 through April 1990. The target area for the intervention was an area of 24 square miles (62 km2) with the highest rate of injuries related to residential fires in the city. We distributed smoke alarms door to door in the target area and then surveyed alarm use and function in a sample of the homes that had received an alarm. We also calculated the rates of fire injury per 100,000 population and per 100 fires for both the target area and the rest of the city before and after the smoke-alarm giveaway. RESULTS Before the intervention the rate of burn injuries per 100,000 population was 4.2 times higher in the target area than in the rest of Oklahoma City. An initial survey indicated that 11,881 of the 34,945 homes in the target area (34 percent) did not have smoke alarms. A total of 10,100 smoke alarms were distributed to 9291 homes; 45 percent were functioning four years later. The annualized fire-injury rates declined by 80 percent in the target area during the four years after the intervention (from 15.3 to 3.1 per 100,000 population), as compared with a small increase in the rest of the city (from 3.6 to 3.9 per 100,000 population). There was also a 74 percent decline in the target area in the injury rate per 100 fires (from 5.0 to 1.3; rate ratio, 0.3; 95 percent confidence interval, 0.1 to 0.6), as compared with a small increase in the rest of the city. CONCLUSIONS A targeted intervention involving a smoke-alarm-giveaway program can reduce the incidence of injuries from residential fires.

Transplant tourism: Outcomes of United States residents who undergo kidney transplantation overseas.

Background. Although international commerce in kidney transplantation is a reality, little is known about U.S. residents who travel abroad for kidney transplantation. Methods. We retrospectively reviewed the clinical outcomes of patients who were evaluated at the University of Minnesota Medical Center or Hennepin County Medical Center, but then surreptitiously underwent kidney transplantation overseas. Results. We identified 10 patients who underwent kidney transplantation outside the United States between September 16, 2002 and June 30, 2006 and then returned for care in our programs. Eight were transplanted in Pakistan (all Somali), one was transplanted in China (Chinese), and one was transplanted in Iran (Iranian). All but one had a living donor. Mean age was 36.8±12.5 years with median follow-up of 2.0 years (range 0.4–3.7). Three patients communicated their intent to travel abroad before transplantation. Induction immunosuppressive therapy (if any) was available in 3/10, and initial maintenance immunosuppression was known in 5/10. Complications were primarily infectious, with six potentially life-threatening infections in four patients. At last follow-up, mean serum creatinine was 1.13±0.34 mg/dL, acute rejection occurred in 2/10, 1/10 grafts failed due to acute rejection, and 9/10 patients were alive. Conclusions. Kidney function and graft survival were generally good after surreptitious overseas kidney transplantation. Major problems included incomplete perioperative information communicated to the posttransplant care facility and a high incidence of posttransplant infections. Longer follow-up and detailed cost analysis are needed to better understand the implications of the growing phenomenon of transplant tourism.

Progression of kidney disease in chronic renal transplant rejection

The rate of progression of renal insufficiency was quantitated from reciprocal of serum creatinine versus time plots in patients with clinical and histologic evidence of chronic renal transplant rejection. The plots were evaluated by the breakpoint test. This method identifies breakpoints in a linear plot and compares the statistical significance of the fit provided by two intersecting lines with that of a single straight line. The breakpoint test when applied to the 22 patients with a significant linear correlation between the reciprocal of serum creatinine versus time detected a change in the slope in 20 cases (90.9%) indicating the presence of a breakpoint. The average diastolic, systolic, and mean arterial pressures before the breakpoint were significantly correlated with the value of the serum creatinine at the time of the change of the slope (r = 0.45, P less than 0.05; r = 0.58, P less than 0.01; r = 0.56, P less than 0.05, respectively) demonstrating more severe hypertension in those patients with the more severe renal dysfunction. The slope after the breakpoint was significantly correlated with the mean diastolic blood pressure values after the breakpoint (r = 0.48, P less than 0.05) with higher pressures being found in those patients with faster rates of decline in renal function. Both before and after the breakpoint occurred, the rate of progression of the renal disease, as estimated by the reciprocal of serum creatinine versus time plot, was greater when the mean diastolic blood pressure was higher than 90 mmHg. In conclusion, the vast majority of patients with proven chronic rejection progress linearly although a change in the rate of progression was frequent. Higher levels of blood pressure correlate with greater rates of progression of renal insufficiency, and a faster progression associates with a diastolic blood pressure greater than 90 mmHg.

Apolipoprotein J/Clusterin Prevents a Progressive Glomerulopathy of Aging

ABSTRACT Apoliprotein J (apoJ)/clusterin has attracted considerable interest based on its inducibility in multiple injury processes and accumulation at sites of remodeling, regression, and degeneration. We therefore sought to investigate apoJ/clusterins role in kidney aging, as this may reveal the accumulated effects of diminished protection. Aging mice deficient in apoJ/clusterin developed a progressive glomerulopathy characterized by the deposition of immune complexes in the mesangium. Up to 75% of glomeruli in apoJ/clusterin-deficient mice exhibited moderate to severe mesangial lesions by 21 months of age. Wild-type and hemizygous mice exhibited little or no glomerular pathology. In the apoJ/clusterin-deficient mice, immune complexes of immunoglobulin G (IgG), IgM, IgA, and in some cases C1q, C3, and C9 were detectable as early as 4 weeks of age. Electron microscopy revealed the accumulation of electron-dense material in the mesangial matrix and age-dependent formation of intramesangial tubulo-fibrillary structures. Even the most extensively damaged glomeruli showed no evidence of inflammation or necrosis. In young apoJ/clusterin-deficient animals, the development of immune complex lesions was accelerated by unilateral nephrectomy-induced hyperfiltration. Injected immune complexes localized to the mesangium of apoJ/clusterin-deficient but not wild-type mice. These results establish a protective role of apoJ/clusterin against chronic glomerular kidney disease and support the hypothesis that apoJ/clusterin modifies immune complex metabolism and disposal.

Effect of dietary protein on rat renin and angiotensinogen gene expression.

Plasma renin activity varies with the level of dietary protein, being higher on a high protein diet. To explore the molecular mechanisms underlying this relationship we first examined the effect of dietary protein on renin and angiotensinogen gene expression at the level of steady state mRNA in male Sprague-Dawley rats. Renal renin mRNA was higher on a 50% (high) compared to a 6% (low) protein diet both 3 d (9.4 +/- 1.1 vs. 5.3 +/- 0.4 pg/micrograms of total RNA; P less than 0.02) and 21 d (6.8 +/- 1.0 vs. 3.5 +/- 0.4 pg/micrograms of total RNA; P less than 0.02) after dietary change. No change occurred in either renal or liver angiotensinogen mRNA. When three levels of dietary protein were examined, renal renin mRNA was elevated on a 50% and lowered on a 6% protein diet compared to a more standard 20% protein diet. Kidney weights and renal protein, RNA, and RNA/DNA increased with the level of dietary protein reflecting protein-induced renal hypertrophy. Uninephrectomy resulted in no change in renin mRNA compared to sham operation (3.7 +/- 0.1 vs. 3.4 +/- 0.1 pg/micrograms RNA; P = NS) despite renal growth in the uninephrectomy group implicating dietary protein and not hypertrophy as the major factor for stimulating renin mRNA. In conclusion, the level of dietary protein is a novel and specific stimulus for changes in renal renin mRNA. The increased plasma renin activity on a high protein diet is due at least in part to increased renin synthesis.

Clusterin promotes the aggregation and adhesion of renal porcine epithelial cells.

The function of clusterin, a heterodimeric glycoprotein markedly induced in renal and other organ injuries, is unclear. Since renal injury is accompanied by alterations in cell attachment, it is possible that clusterin functions to promote cell-cell and cell-substratum interactions. In this study, a single cell suspension of renal epithelial (LLC-PK1) cells was treated with purified human clusterin, resulting in time- and dose-dependent cell aggregation. Electron microscopy of the cell aggregates demonstrated cell junction and lumen formation. To determine the effect of clusterin on cell adhesion, tissue culture plates were coated with clusterin, fibronectin, PBS, or albumin. Clusterin and fibronectin promoted cell adhesion to the same extent. The adhesion to clusterin was dose dependent and specific, as a monoclonal antibody against clusterin inhibited cell adhesion to clusterin but not fibronectin. Perterbations of the cytoskeleton may underlie the alterations in cell attachment which occur in renal injury. Induction of clusterin mRNA was seen after disruption of both microtubules and microfilaments and after inhibition of cell-substratum interactions. In conclusion, clusterin is a potent renal epithelial cell aggregation and adhesion molecule. We speculate that clusterin functions to promote cell-cell and cell-substratum interactions which are perturbed in the setting of renal injury, thereby preserving the integrity of the renal epithelial barrier.

Renin expression in renal ablation

To determine whether expression of the renin-angiotensin system (RAS) is influenced by the degree of renal ablation, male Sprague-Dawley rats underwent uninephrectomy, 1 1/3 nephrectomy, or sham operation. Renin and angiotensinogen messenger RNA (mRNA) were not different among the three groups 2 weeks after surgery. The time course of expression of renin mRNA after 1 1/3 nephrectomy showed no difference versus controls at 2 and 4 weeks and a decrease at 6 weeks after surgical ablation. Because nephrons adjacent to the infarcted area in the 1 1/3 nephrectomy may be hypoperfused and a source of increased renin synthesis, intrarenal distribution of tissue renin content, renin mRNA, and immunostainable renin were examined in separate groups of rats subjected to 1 1/3 nephrectomy. The kidney was divided into two pieces, one containing the scar and scar-adjacent tissue and the other portion the tissue distant from the scar. Tissue renin content, renin mRNA, and immunostainable renin were significantly greater in the scar-adjacent tissue compared with the nonscar tissue. Immunoreactive renin was seen in the juxtaglomerular apparatuses as well as in vascular elements proximal to the juxtaglomerular apparatus and within mesangial cells of some glomeruli of the scar-adjacent tissue. In conclusion, immunostainable renin, tissue renin content, and renin mRNA were increased in scar-adjacent tissue after 1 1/3 nephrectomy. We speculate that this unique scar-associated redistribution of renin may play a pathophysiological role in the progression of renal disease.