Chronic glucocorticoid therapy amplifies glomerular injury in rats with renal ablation

Adrenocorticotropic hormone analog use for podocytopathies

BACKGROUND

Adrenocorticotropic hormone is being increasingly studied for treatment of various glomerulopathies, most notably membranous nephropathy. Less data are available regarding its use in idiopathic nephrotic syndrome (INS) secondary to minimal change disease (MCD) or focal segmental glomerulosclerosis (FSGS). We report here our experience with H.P. Acthar(®) Gel (repository corticotropin injection) as first-line or subsequent therapy in patients with INS.

METHODS

Data were taken from three patients with MCD and ten patients with FSGS from around the US, who were treated with Acthar Gel as initial or subsequent therapy. Treatment was solely at the discretion of the primary nephrologist without a specific protocol. A complete response (CR) was defined as final urine protein-to-creatinine ratio <500 mg/g and a partial response (PR) as 50% decrease without rise of serum creatinine. Side effects and tolerability were noted.

RESULTS

All three patients with MCD received Acthar Gel as second-line or later immunosuppressive (IS) therapy and all responded (one CR and two PRs). Two of the ten patients with FSGS received Acthar Gel as first-line IS therapy, while the other eight had failed multiple agents. Four of the ten patients with FSGS had responses, including two CRs and two PRs. The three patients with MCD tolerated therapy well without side effects. Five patients with FSGS tolerated therapy well, while five had various steroid-like side effects, resulting in therapy discontinuation in two patients.

CONCLUSION

Acthar Gel is a viable alternative IS agent for treatment of INS in patients intolerant or resistant to conventional therapy. More data are needed to better define its appropriate place.

Leveraging melanocortin pathways to treat glomerular diseases

The melanocortin system is a neuroimmunoendocrine hormone system that constitutes the fulcrum in the homeostatic control of a diverse array of physiological functions, including melanogenesis, inflammation, immunomodulation, adrenocortical steroidogenesis, hemodynamics, natriuresis, energy homeostasis, sexual function, and exocrine secretion. The kidney is a quintessential effector organ of the melanocortin hormone system with melanocortin receptors abundantly expressed by multiple kidney parenchymal cells, including podocytes, mesangial cells, glomerular endothelial cells, and renal tubular cells. Converging evidence unequivocally demonstrates that the melanocortin-based therapy using the melanocortin peptide adrenocorticotropic hormone (ACTH) is prominently effective in inducing remission of steroid-resistant nephrotic syndrome caused by various glomerular diseases, including membranous nephropathy, minimal change disease and focal segmental glomerulosclerosis, suggesting a steroidogenic-independent mechanism. Mechanistically, ACTH and other synthetic melanocortin analogues possess potent proteinuria-reducing and renoprotective activities that could be attributable to direct protection of glomerular cells and systemic immunomodulation. Thus, leveraging melanocortin signaling pathways using ACTH or novel synthetic melanocortin analogues represents a promising and pragmatic therapeutic strategy for glomerular diseases. This review article introduces the biophysiology of the melanocortin hormone system with an emphasis on the kidney as a target organ, discusses the existing data on melanocortin therapy for glomerular diseases, and elucidates the potential mechanisms of action.

The renaissance of corticotropin therapy in proteinuric nephropathies

Refractory nephrotic syndrome continues to be a therapeutic challenge despite advances in immunosuppression and blockade of the renin-angiotensin-aldosterone cascade. Adrenocorticotropic hormone (ACTH), a pituitary neuroimmunoendocrine polypeptide, was widely used in the 1950s as an effective therapy for childhood nephrotic syndrome, but has since been replaced by synthetic glucocorticoid analogues. In addition to controlling steroidogenesis, ACTH also acts as an important physiological agonist of the melanocortin system. Clinical and experimental evidence now suggests that ACTH has antiproteinuric, lipid-lowering and renoprotective properties, which are not fully explained by its steroidogenic effects. ACTH therapy is effective in inducing remission of nephrotic syndrome in patients with a variety of proteinuric nephropathies, even those resistant to steroids and other immunosuppressants. This Perspectives article describes the biophysiology of ACTH, with an emphasis on its melanocortin actions, particularly in renal parenchymal cells, which could potentially explain the therapeutic effects of ACTH in nephrotic glomerulopathies.

Glomerular involution in children with frequently relapsing minimal change nephrotic syndrome: An unrecognized form of glomerulosclerosis?

Global glomerulosclerosis can be divided in the vascular (obsolescent) type and the glomerulopathic (solidified) type. In biopsies from children with recurrent nephrotic syndrome owing to minimal change nephropathy (MCN), we noticed small, globally sclerosed glomeruli that appeared to be distinct from global glomerulosclerosis. These small sclerosed glomeruli are best described as involuted glomeruli. We have characterized these involuted glomeruli in detail. We studied biopsies of 18 children (11 male, 7 female) with frequently relapsing MCN and evaluated possible explanatory variables. The involuted glomeruli can be differentiated from the other types of global glomerulosclerosis. Most notable is the presence of vital podocytes and parietal epithelial cells, which have retained their staining characteristics, in between the matrix, and the absence of periglomerular and tubulo-interstitial fibrosis. We observed involuted glomeruli in 12 out of 18 biopsies; the median percentage of involuted glomeruli was 6% (range 0-33%). The percentage of involuted glomeruli correlated with age at renal biopsy and the interval between onset of disease and time of renal biopsy, but not with gender, age at onset of disease, or prednisone dose. Multivariate analysis revealed that the interval between onset of disease and time of renal biopsy was the only independent predictor. In conclusion, glomerular involution is a special form of global glomerulosclerosis. The absence of periglomerular and tubulo-interstitial fibrosis suggests a different pathogenesis. Glomerular involution is a slow process. The clinical data suggest that involution is related to the duration of the disease process.

Glucocorticoid diminishes vascular endothelial growth factor and exacerbates proteinuria in rats with mesangial proliferative glomerulonephritis

Glucocorticoids are widely prescribed for renal diseases. It is believed that glucocorticoids attenuate immune-mediated renal diseases by suppressing the cell-mediated immune system. However, there is evidence that glucocorticoids influence the expression of such growth factors as vascular endothelial growth factor (VEGF), transforming growth factor-beta1 (TGF-beta1), and connective tissue growth factor (CTGF), which are known to influence the development or progression of renal diseases. Therefore, we undertook this study to determine whether glucocorticoids regulate proteinuria or extracellular matrix (ECM) production by altering these growth factors. Mesangial proliferative glomerulonephritis was induced in rats by intravenous injection of monoclonal antibody (OX-7), and dexamethasone (20 mg/kg) was administered intraperitoneally from the third to seventh disease day. Glomerular expression of VEGF, TGF-beta1, and CTGF, the amount of urinary protein, and glomerular ECM were measured on the seventh disease day. The nephritic group showed proteinuria and greater VEGF, TGF-beta1, and ECM production. Dexamethasone aggravated proteinuria (protein, 0.4 +/- 0.1 mg/mg creatinine in the NC group, 6.3 +/- 2.0 mg/mg creatinine in the DC group, and 21.1 +/- 1.9 mg/mg creatinine in the D-Dex group; P < 0.05) and diminished VEGF release (22 +/- 3 pg/mg total protein in the NC group, 292 +/- 26 pg/mg total protein in the DC group, and 198 +/- 23 pg/mg total protein in the D-Dex group; P < 0.05). Expression of TGF-beta1, CTGF, and ECM was not altered significantly by dexamethasone treatment. We found that glucocorticoid diminishes VEGF release and at the same time exacerbates proteinuria in rats with this type of glomerulonephritis.

Glomerular hypertension and hyperfiltration in adrenocorticotrophin-induced hypertension in rats: the role of nitric oxide

OBJECTIVE

To determine the effects on pre- and post-glomerular vascular resistance of adrenocorticotrophin (ACTH)-induced hypertension in rats, before and after blockade of nitric oxide formation.

DESIGN

Four groups of Sprague-Dawley rats were studied. Measurements were made in ACTH- (Synacthen Depot, 0.25 mg/kg twice daily for 8 days) and sham-treated anaesthetized rats, before and after either Nomega-nitro-L-arginine (L-NNA, 6 mg/kg) or vehicle.

METHODS

Whole-kidney and single-nephron haemodynamics and function were measured. Glomerular capillary pressure was estimated from tubular stop-flow pressure measurements.

RESULTS

Blood pressure (P < 0.001), renal blood flow (RBF, P < 0.05) and glomerular filtration rate (P < 0.01) were increased following ACTH treatment compared with sham. There were no differences in either total renal, or pre- or post-glomerular vascular resistances, but stop-flow-estimated glomerular capillary pressure was elevated (P < 0.001) as was single-nephron glomerular filtration rate (SNGFR) (P < 0.001) and single-nephron blood flow (P < 0.01 ) in the ACTH- compared to the sham-treated rats. L-NNA treatment increased blood pressure by a similar extent in both ACTH- and sham-treated rats, but reduced RBF (P < 0.05) and glomerular filtration rate (GFR) (P < 0.05) more in the ACTH group; similar changes were seen in single-nephron values. L-NNA increased pre- and post-glomerular resistances to a greater extent in the ACTH group.

CONCLUSIONS

ACTH-induced hypertension produced glomerular hypertension and hyperfiltration, which may be due to nitric oxide-related vasodilatation of the renal vasculature.

Insights Into Glucocorticoid-Associated Hypertension

The association between excess glucocorticoids and hypertension has been much discussed but poorly understood. From both clinical observations and laboratory studies, it is clear that glucocorticoids exert their effects at many different sites responsible for blood pressure regulation. Isoforms of the enzyme 11ss-hydroxysteroid dehydrogenase (11ss-HSD), located in steroid-responsive tissues, metabolize endogenously produced glucocorticoids. These enzymes limit steroid access to mineralocorticoid and/or glucocorticoid receptors. In the kidney, synthetic and endogenous glucocorticoids are capable of enhancing transepithelial sodium transport in the presence of 11ss-HSD inhibition. Proximal tubule reabsorption of sodium can be indirectly augmented after chronic exposure to glucocorticoids. In this segment, steroids have a permissive effect, increasing the expression of both Na(+), K(+) adenosine triphosphatase along the basolateral membrane and Na(+)-H(+) exchanger along the apical membrane of epithelial cells. Although glucocorticoids themselves produce no increase in sodium reabsorption in this segment, angiotensin II-stimulated sodium transport is significantly greater in proximal tubular cells pretreated with glucocorticoids. The increased transport in distal renal segments is more direct and stems in part from glucocorticoid cross-over binding to mineralocorticoid receptors. In vascular tissue, synthetic and endogenous glucocorticoids, after inhibition of the dehydrogenase reaction, magnify the response to circulating vasoconstrictors. The effects of glucocorticoids in vascular tissue is indirect, upregulating the expression of receptors to many vasoconstrictors and downregulating the effects of potential vasodilators. Thus, glucocorticoids have the potential to alter both circulating volume and vascular resistance.

Cellular and molecular mediators in common pathway mechanisms of chronic renal disease progression

Injury mechanisms activated by the hemodynamic adaptations to nephron loss are considered to represent a final common pathway that underlies the progressive nature of chronic renal disease. In this article, we review experimental evidence that the induction of cell adhesion molecule, cytokine and profibrotic growth factor gene expression and the resultant renal infiltration by inflammatory cells, especially macrophages, are important components of these common pathway mechanisms. Interventions aimed at inhibiting these mechanisms may offer new treatments for slowing or arresting the progression of chronic renal disease.

Chronic allograft nephropathy: An update

Chronic allograft nephropathy is the most prevalent cause of renal transplant failure in the first post-transplant decade, but its pathogenesis has remained elusive. Clinically, it is characterized by a slow but variable loss of function, often in combination with proteinuria and hypertension. The histopathology is also not specific, but transplant glomerulopathy and multilayering of the peritubular capillaries are highly characteristic. Several risk factors have been identified, such as advanced donor age, delayed graft function, repeated acute rejection episodes, vascular rejection episodes, and rejections that occur late after transplantation. A common feature of chronic allograft nephropathy is that it develops in grafts that have undergone previous damage, although the mechanism(s) responsible for the progressive fibrosis and tissue remodeling has not yet been defined. Hypotheses to explain chronic allograft nephropathy include the immunolymphatic theory, the cytokine excess theory, the loss of supporting architecture theory, and the premature senescence theory. The most effective option to prevent chronic allograft nephropathy is to avoid graft injury from both immune and nonimmune mechanisms.

Effect of glucocorticoids on renal dopamine production

This study assess the effects of glucocorticoids on dopamine excretion and evaluates the participation of renal dopamine in the effects of glucocorticoids on renal function and Na+ excretion. Dexamethasone (i.m.; 0.5 mg/kg) was administered to male Wistar rats on day 2 or on days 2 and 5. Daily urinary excretions of Na+, dihydroxyphenylalanine (DOPA), dopamine and dihydroxyphenylacetic acid were determined from day 1 to day 7. Renal function was evaluated 8 h after dexamethasone administration in a separate group. The first dose of dexamethasone increased about 100% diuresis and natriuresis, increased urinary DOPA and renal plasma flow, and did not affect urinary dopamine or the other parameters evaluated. These effects were not affected by previous administration of haloperidol. The second dexamethasone dose increased about 200% diuresis and natriuresis, increased urinary dopamine, DOPA, dihydroxyphenylacetic acid, Uosm x V and both glomerular filtration rate and renal plasma flow. Carbidopa administered before the second dexamethasone dose blunted both the diuretic and the natriuretic response whereas haloperidol abolished or blunted all the effects of the second dexamethasone dose. These results show that modifications in renal dopamine production produced by corticoids may contribute to the effects of these hormones on Na+ balance and diuresis and suggest that regardless the factor that promotes an increase in renal perfusion and glomerular filtration rate during long term administration of glucocorticoids, a dopaminergic mechanism is actively involved in the maintenance of these hemodynamic changes.

Chronic rejection: increasing evidence for the importance of allogen-independent factors

Chronic rejection is a process caused by an interplay of different risk factors. Early injury regardless of type, seems to be an important prognostic event. Later insults appear to contribute. As the individual components of the process are increasingly dissected and understood, means to modulate or normalize them will be forthcoming.

Nephroprotective effect of antihypertensive drugs in essential hypertension

BACKGROUND

Effective antihypertensive treatment has prevented target-organ involvement in hypertension, markedly reducing morbidity and mortality from strokes, coronary heart disease, cardiac failure, and hypertensive emergencies. However, the incidence of hypertension-related end-stage renal disease continues to increase, suggesting that therapeutic reduction in arterial pressure by itself is not sufficient to prevent the development of hypertensive renal failure.

OBJECTIVE

To examine experimental and clinical data concerning the protective effect of reduction of arterial pressure on the progression of hypertension-related renal disease, and the evidence indicating that some antihypertensive agents may afford more nephroprotection, over and above that attributable to reduction of arterial pressure.

RESULTS

Results of numerous studies clearly indicate that adequate control of arterial pressure, irrespective of the antihypertensive agent used, slowed the progression of renal disease. Results of some studies suggest that lowering arterial pressure below the level that is usually considered adequate has an additional beneficial effect by slowing the progression of renal injury.

CONCLUSION

Results of a number of studies evaluating nephroprotective effects of various drugs and regimens have indicated that certain agents, most notably angiotensin converting enzyme inhibitors and their combination with calcium antagonists, afford more protection than do others at similar levels of reduction of arterial pressure. Results of still other studies suggest that certain agents that exert greater nephroprotection are more efficient at controlling arterial pressure. Therefore, further data are needed before any final conclusion can be drawn. However, it is clear that, in order to establish nephroprotection in patients with essential hypertension, the problem should not be further complicated by additional comorbid diseases such as diabetes mellitus.

Contribution of early acute rejection episodes to chronic rejection in a rat kidney retransplantation model

Chronic graft rejection represents the single most important risk factor for unsatisfactory long-term results after organ transplantation. In addition to various alloantigen dependent and independent factors, acute rejection episodes have been cited as a major immunological risk factor. However, the effects of acute rejection episodes on long-term graft outcome remains unknown. To examine the influence of a single early rejection event on ultimate graft outcome, acutely rejecting rat kidney grafts were retransplanted sequentially into syngeneic rats and their functional and structural behavior assessed over time. LEWxBNF1 kidney allografts and LEW isografts were removed from their LEW recipients after three, four, five and seven days (N = 12/group/time period) and retransplanted into donor strain hosts. The grafts were followed functionally and harvested four, eight, and 32 weeks later. Urinary protein excretion was measured weekly. Kidneys were examined morphologically and immunohistologically using monoclonal antibodies (mAbs) against macrophages (ED-1), T cells and their subsets (CD5, CD4, CD8), MHC class II expression (OX3) and adhesion molecules (ICAM-1 and LFA-1alpha). The mean standard time +/- SD of non-retransplanted allografts was 14.5 +/- two days; isografts functioned indefinitely. At five and seven days, acutely rejecting allografts showed massive cellular infiltrates associated with extensive necrosis. These changes could not be reversed by retransplantation and the syngeneic recipients later died of renal failure. In contrast, most allografts retransplanted earlier in the process recovered completely when retransplanted after three (12 of 12 allografts) and four (7 of 12 allografts) days. During the subsequent follow-up period, urinary protein excretion was comparable in retransplanted allografts and isografts. The increased mononuclear cell infiltration in non-retransplanted allografts seen at three and four days was only occasionally observed during the follow-up period after retransplantation. Only a few sclerosed glomeruli (approximately 15%), mild arterial changes and minimal cellular infiltrates were observed by 32 weeks, which were similar to that seen in retransplanted isografts. A single acute rejection episode was completely reversible and did not progress to chronic rejection if retransplanted into syngeneic donors when the inflammatory changes are still early. Those results demonstrate the critical effect of alloantigen-dependent events on chronic graft deterioration, and indicate that prompt and aggressive treatment of initial acute rejection episodes are beneficial to protect against late deleterious changes in the graft.

Paediatric kidney transplantation

Renal transplantation is the optimal form of renal replacement therapy leading to substantial improvement in the quality of life. It has rapidly become the standard treatment for end-stage renal disease in children. However, despite impressive short-term results significant long-term problems remain unsolved. Because of the lack of effective treatment for chronic rejection and common recipient noncompliance, allograft half-life has not improved significantly during the last decade. A paediatric recipient is likely to need several retransplantations in adulthood. Moreover, the immunosuppressive drugs used today have potentially serious side-effects including nephrotoxicity and de novo malignancy. These are especially relevant for paediatric recipients who will continue to receive therapy for several decades. Most therapeutic protocols used for children are derived from those used for adults. However, the metabolic differences between an adult and a growing and developing paediatric transplant recipient are not always adequately appreciated before these new therapies are initiated. In the near future, we are likely to see new and more efficient drugs become available. It is important that we try to understand their properties in children and use them and our current arsenal on an individual basis aiming at optimal graft survival but also at avoiding unnecessary adverse effects.

Effects of glucocorticoid therapy on urine protein-to-creatinine ratios and renal morphology in dogs

Glomerulonephritis has been associated with exogenous glucocorticoid administration and spontaneous hyperadrenocorticism in the dog. The purpose of this study was to determine the effects of long-term glucocorticoid therapy on urine protein:creatinine ratios (UP/Cs) and renal morphology. Nine young-adult male dogs were determined to be healthy and have normal renal function as assessed by physical examination, CBC, serum biochemistry analysis, Knott's test for Dirofilaria immitis, urinalysis, urine culture, urine protein electrophoresis, endogenous creatinine clearance, 24-hour urinary protein excretion, and UP/C. Prednisone was administered to each dog at a dosage of 2.2 mg/kg PO bid for 42 days. Urinalysis and UP/C were performed on days 0, 7, 14, 21, 28, and 42 of treatment. Mean UP/C on day 0 was 0.29 +/- 0.10. Mean UP/C increased progressively to a maximum of 1.27 +/- 1.02 on day 28. Mean UP/C on day 42 decreased slightly (0.92 +/- 0.56) but remained significantly increased above baseline. The most consistent renal light microscopic finding on necropsy examination was generalized hypercellular glomerular tufts, suggestive of mesangial cell proliferation. Four dogs also had occasional adhesions of glomerular tufts to Bowman's capsule, accompanied by thickening of the capsule. Direct immunofluorescence for immunoglobulin deposition was negative in all dogs. Electron microscopy, evaluated in 7 dogs, was characterized by occasional mild segmental thickening of basement membranes, fusion of visceral cell foot processes, and glomerular adhesions. The results of this study indicate that long-term administration of glucocorticoids results in significant proteinuria and glomerular changes in the dog.

Chronic allograft failure: the clinical problem

Long-term survival statistics for organ allografts have not improved substantially over time, despite improved immunosuppression and organ preservation and better surgical and perioperative management. Chronic rejection is the most important long-term limitation in allografts and increasingly seems to be caused by a multifactorial series of antigen-dependent and antigen-independent factors. Early injury is critical to late events, whether antigen driven (early acute rejection episodes and human leukocyte antigen mismatching) or antigen independent (ischemia/reperfusion injury and brain death). Ongoing alloimmunologic injury to the host and inadequate organ mass functioning (donor age, gender, race, and organ size) also seem to be important to this persisting process. Associated recipient conditions, which includes hypertension and hyperlipidemia, and postoperative complications, which include drug nephrotoxicity and infections, may affect this late-phase graft loss. These deleterious risk factors for chronic rejection of long-functioning allografts are an important subject for future investigation.

Antihypertensive drug treatment in chronic renal allograft rejection in the rat. Effect on structure and function

To gain insight into the contribution of immunologic and hemodynamic factors in the progressive demise of structure and function in chronic renal allograft dysfunction, we studied the histological changes, the immunostainable glomerular anionic sites, and glomerular capillary hydrostatic pressures of rat renal allografts with chronic rejection. Recipient animals were left untreated, received 8 weeks of treatment with the immunosuppressive drug cyclosporine, or received antihypertensive drugs consisting of the combination of reserpine, hydralazine and hydrochlorothiazide, the angiotensin-converting enzyme inhibitor cilazapril, or the angiotensin II receptor blocker L-158,809. Grafts in untreated recipients developed chronic interstitial inflammation, as well as vascular and glomerular lesions consistent with chronic rejection. These lesions were associated with immunohistochemical loss of the negatively charged heparan sulfate proteoglycan side chain. All treatment regimens decreased the systemic and glomerular capillary pressures and were associated with no loss of function, decreased proteinuria, and a tendency to improved graft function. Cyclosporine prevented all histological manifestations of rejection, and antihypertensive drugs decreased the extent of glomerular mesangiolysis and glomerulosclerosis; L-158,809 and cilazapril also inhibited graft atherosclerosis and tubular atrophy. We conclude that chronic rejection is primarily an immune-mediated process, but hemodynamic and angiotensin II-mediated effects may play a pivotal role in the expression of immune-mediated lesions.

Proteinuria and albumin homeostasis in the nephrotic syndrome: effect of dietary protein intake

Nephrotic syndrome is analyzed in the light of interventions designed to decrease proteinuria and renal injury. The effect of dietary protein intake on urinary protein losses and albumin homeostasis are discussed on the basis of the pathophysiologic mechanisms known to account for changes in renal function of nephrotic patients. In addition, the effect of angiotensin-converting enzyme inhibitors for reduction of proteinuria is discussed in terms of the modulation of glomerular permselectivity and hemodynamics.

Hyperfiltration nephropathy as a cause of late graft loss in renal transplantation

Despite improved immunosuppression and early allograft survival, long-term survival of allografts remains unchanged. Late renal allograft loss has traditionally been considered to result from repeated or unresolved episodes of acute rejection that lead to chronic immune-mediated allograft rejection. However, late renal allograft loss is known to occur in the absence of prior episodes of acute rejection. It is therefore proposed that factors other than histocompatibility influence long-term allograft survival. Evidence for nonimmunologic factors contributing to late allograft loss is presented. The central hypothesis is that following renal allograft mass reduction (from any etiology), glomerular hyperperfusion and hyperfiltration develop and lead to progressive renal dysfunction, proteinuria, histopathologic allograft changes, and late allograft failure. Multiple nonimmunologic factors that could contribute to reduced renal mass and ultimately promote chronic allograft loss as a result of hyperfiltration nephropathy are presented along with possible therapeutic strategies for the prevention and treatment of glomerular hyperfiltration.

Chronic rejection and late renal allograft dysfunction

Renal transplantation is currently standard therapy for end-stage kidney disease for children. Despite the considerable improvement in short-term results, the expected allograft half-life has remained the same. This is due to chronic rejection/late graft dysfunction which has proved resistant to therapeutic attempts. During the last few years the multifactorial pathogenesis of chronic renal allograft rejection has been clarified to some extent. Early injury by immunological and non-immunological mechanisms is followed by vascular remodelling due to repetitive cycles of cytokine release, upregulation of growth factors, and vascular smooth muscle cell proliferation. This leads to typical concentric arteriosclerosis and ischemia. Secondary kidney-specific mechanisms are initiated by the reduction in functioning renal mass and lead to gradual progression of chronic rejection. There is no single optimal therapy. Several attempts to influence the pathophysiological cascade have been promising. Attention should be focused on minimizing early immunological/non-immunological injury in order to attenuate future progression of chronic rejection. A significant prolongation of allograft half-life may be achieved during the next decade with the introduction of new therapeutic agents and comprehensive approach to treatment. This would be especially beneficial for pediatric recipients, reducing the need for retransplantation in adulthood.

Abnormal permeability to proteins and glomerular lesions: a meta-analysis of experimental and human studies

Whether abnormal protein traffic through the glomerular capillary is one of the possible causes of glomerular injury has been a matter of considerable controversy. Experimental and clinical evidence indicate an association between the two, and several explanations of potential pathophysiologic pathways are available that may explain protein-dependent forms of renal injury. However, none of the mechanisms suggested thus far have been definitely proven. A meta-analytic review was used to further explore the relationship between urinary protein excretion and glomerular injury in experimental and human proteinuric nephropathies. In experimental models a definite positive association (P < 0.0001) was found between urinary protein excretion and glomerulosclerosis. The overall effect size d for this relationship was 2.36 (95% confidence interval, 2.13 to 2.60), corresponding to a correlation coefficient of r = 0.76. Similarly, the correlation between albuminuria and glomerular sclerotic lesions was highly significant (overall d = 2.88; 95% confidence interval, 2.33 to 3.42; P < 0.0001; correlation coefficient, r = 0.82). In humans the meta-analytic correlation yielded analogous, although less striking, results (overall d = 0.58; 95% confidence interval, 0.43 to 0.73; P < 0.0001; correlation coefficient, r = 0.28). In conclusion, meta-analysis of data from studies examining urinary protein excretion revealed a significant positive correlation with glomerular sclerosis in both experimental models and human diseases. This study supports the role of abnormal protein traffic through the glomerular capillary as one of the possible causes of renal injury. However, the strong relationship found does not necessary establish a cause-and-effect relationship.

Glomerular hemodynamic responses to pregnancy in rats with severe reduction of renal mass

These studies investigate glomerular hemodynamic responses to pregnancy in rats with 5/6th reduction of renal mass of four weeks duration. Both preglomerular and efferent arteriolar resistances (RA and RE) fell significantly at midterm although single nephron glomerular filtration rate (SNGFR) and glomerular plasma flow (QA) were unchanged versus virgins. In late pregnant rats with reduction of renal mass, the gestational fall in RA and RE was maintained and GFR, RPF, SNGFR and QA were higher compared to virgins. The gestational renal vasodilation was prolonged in this model of hypertension versus normals and a peripheral vasodilation is also indicated by the late fall in blood pressure. In virgins with 5/6th reduction of renal mass, PGC is elevated but in pregnant rats PGC fell towards term. The value of Kf was doubled in late pregnancy compared to virgins. All three groups of rats with reduction of renal mass showed similar proteinuria and similar levels of focal glomerular sclerosis, suggesting that pregnancy did not exacerbate the glomerular damage in this model of hypertension and renal disease. A decrease in hematocrit in late pregnancy compared with both virgin and midterm pregnancy indicated a plasma volume expansion. We conclude that when superimposed on hypertension with glomerular damage due to 5/6th reduction of renal mass, pregnancy induced gestational renal and peripheral vasodilation and plasma volume expansion. Since pregnancy was antihypertensive and lowered PGC, there was no hemodynamic basis for pregnancy-associated exacerbation of damage in this model of glomerular injury.

PC:PS liposomes induce a recruitment of neutrophils and the release of TNF alpha in the lungs of mice sensitized with Saccharopolyspora rectivirgula

The aim of this study was to verify the effect of nasally instilled liposomes (L) or dexamethasone-containing L (Ldexa) on normal or inflamed lung tissue. Three groups of mice were studied. Group I was given saline instillations for 3 weeks prior to the instillation with liposomes. In groups II and III lung inflammation was induced by repeated instillations of Saccharopolyspora rectivirgula before the instillation of liposomes (group II) or liposomes containing dexamethasone (group III). Animals from all groups were killed at regular time intervals for up to 48 h after the instillation of liposomes. The total cell count in bronchoalveolar lavage fluid did not differ significantly between groups I and II. However, in group III it decreased rapidly from 6.2 to 2.8 x 10(5) cells mL-1 within 2 h. Differential counts did not change in group I, but in group II a transient neutrophilia was observed 180 min after the instillation of liposomes. In group III, the instillation of dexamethasone-containing liposomes depleted all neutrophils and lymphocytes after 4 h. No TNF alpha was found in samples of lavage fluid from any of the groups at time 0. In group I, liposomes induced the production of 0.03 ng mL-1 of TNF alpha in the 1 h sample only. In group II, TNF alpha peaked to 1 ng mL-1 at 1 h and had decreased to 0.35 ng mL-1 by 3 h. In group III, TNF alpha peaked at 1 h, but only reached a level of 0.1 ng mL-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Fundamental concepts and immunosuppressive treatment in the various forms of glomerulonephritis

Immunosuppressive treatment in glomerulonephritis (GN) is still controversial. Most of the secondary forms of glomerulonephritis have the histologic features of one of the primary types of glomerulonephritis. Eight histologic expressions of primary glomerulonephritis can be distinguished and ordered in terms of severity of symptoms and prognosis: endocapillary GN, minimal change GN, mesangioproliferative GN, membranous GN, focal-sclerosing GN, membranoproliferative GN, focal-necrotizing GN, and rapidly progressive GN. Agreement exists only to the extent that immunosuppression is not required in endocapillary glomerulonephritis, although it is recommended in the other extreme of rapidly progressive GN. Primarily, an indication for immunosuppression is given by the severity of symptoms with a urinary protein excretion > 3.5 g per day and/or serum creatinine > 150 mumol per liter. As for anti-GBM, the type of glomerulonephritis is more important than the severity of symptoms in guiding therapy, whereas for IgA nephropathy it is controversial whether the prospective prognosis of even inexorably deteriorating renal function justifies immunosuppression. Renal biopsy is required to identify the type of glomerulonephritis so as to establish the specific immunosuppressive concept with different intensity and duration of treatment. Immunosuppression can reduce urinary protein excretion and improve deterioration of renal function; however, the proportion of patients responding varies with and depends on the different forms of GN.

Do calcium channel blockers have renal protective effects?

Calcium channel blockers are used in the treatment of hypertension because of their ability to decrease peripheral vascular resistance. Recent research has suggested that these drugs also preserve or improve renal function in patients with essential hypertensive renal disease or diabetic renal disease, and in renal transplant recipients with or without cyclosporin therapy. In general, studies in animal models of hypertension and in hypertensive humans have demonstrated reduction in renal vascular resistance, and preservation or enhancement of renal plasma flow and glomerular filtration rate. In addition, calcium channel blockers appear to have a positive effect on renal addition, calcium channel blockers appear to have a positive effect on renal haemodynamic function in the setting of diabetes mellitus; prospective trials have also demonstrated reductions in urinary protein excretion in these patients. Current evidence suggests that calcium channel blockers are well-suited for the treatment of patients with hypertensive disease even in the presence of renal impairment, a clinical scenario common in the elderly population.

Methylprednisolone dosage effects on peripheral lymphocyte subpopulations and eicosanoid synthesis

Glucocorticoids have a major role in the treatment of glomerular diseases. Despite recent advances in understanding of their mechanism of action, very few studies have addressed the relative advantage of the wide range of different dose regimens employed in clinical practice. We studied the effects of methylprednisolone given intravenously for three consecutive days at the doses of 1 mg/kg (group 1, N = 7; group 2, N = 5), 5 mg/kg (group 3, N = 5) or 15 mg/kg (group 4, N = 6) on total blood peripheral leukocytes and on lymphocyte subsets in patients with glomerular diseases, and investigated whether such effects were a function of the drug concentration in the blood. Since glucocorticoids have an inhibitory effect on the formation of eicosanoids in different cells, we also investigated in the same patients the effect of 1 and 15 mg/kg methylprednisolone on systemic and renal eicosanoid synthesis. Results of pharmacokinetic study showed that the three different doses of methylprednisolone we used resulted in major differences in patient's exposure to the drug, and within the same dose there was a great individual variability. By contrast the three different doses of methylprednisolone induced a comparable drop in the absolute number of lymphocytes six hours after the first injection of methylprednisolone, while 24 hours later blood lymphocyte counts returned to the pre-injection values in all patients. Analysis of lymphocyte subsets showed a selective decrease in the number of circulating CD4+ and CD8+ cells six hours after methylprednisolone which was comparable in the four groups of patients studied. As for the effect of methylprednisolone on systemic and renal eicosanoid synthesis in patients with glomerular diseases, 1 and 15 mg/kg were equally unable to reduce thromboxane A2 (TxA2) and prostaglandin E2 (PGE2) release by circulating polimorphonuclear cells (PMNs). By contrast, methylprednisolone partially inhibited eicosanoid synthesis by PMNs in vitro. Consistent with the data on PMNs, urinary excretion of TxA2 and prostacyclin (PGI2) metabolites were unaltered by the different doses of methylprednisolone. By contrast urinary PGE2 was markedly and significantly reduced in patients given 15 but not 1 mg/kg. We conclude that 1 mg/kg methylprednisolone given to patients with glomerular diseases has the same effect on peripheral total blood leukocyte count and lymphocyte subsets than 5 and 15 mg/kg. The same is true for eicosanoid synthesis by PMNs. Renal synthesis of PGE2 is inhibited by 15 mg/kg but not by 1 mg/kg.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenalectomy ameliorates ablative nephropathy in the rat independently of corticosterone maintenance level

The roles of the adrenal gland and of dietary protein level in ablative nephropathy in the rat were examined by comparing adrenalectomized rats, replaced with corticosterone at low physiological (1 and 2) or high physiological (3 and 4) levels with intact rats (5 and 6). All groups were subjected to 5/6 nephrectomy and followed 12 weeks on a regular diet (2, 4 and 6) or a reduced protein diet (1, 3 and 5). Groups 1, 2, 5 and 6 all grew at the same rate but groups 3 and 4 grew less, though food intake was nearly the same in all. Higher dietary protein, higher corticosterone maintenance level, and the presence of intact adrenal glands all increased proteinuria significantly. Extracellular fluid volume (82Br space) was identical in all groups at 8 and 12 weeks, because the animals were given a choice of water or saline to drink. Mortality was highest (50%) in Group 6 and lowest (11%) in Group 1, but these differences were not significant. Final inulin clearance was significantly improved by adrenalectomy when non-survivors were scored as having zero clearance, but not if the analysis was limited to survivors. It was not affected by diet or by corticosterone level. Renal histopathological scores were also improved significantly by adrenalectomy and by protein restriction, but were not influenced by corticosterone level. Thus adrenalectomy and dietary protein restriction independently ameliorate ablative nephropathy, but corticosterone replacement level has no effects, except on proteinuria.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of growth hormone in the development of experimental renal scarring

Recent experimental data has implicated growth hormone in the development of glomerular sclerosis. In this study, we have examined the development and progression of glomerular and tubulointerstitial scarring in Wistar and Dwarf rats, selectively growth hormone-deficient, following subtotal nephrectomy. Wistar rats showed progressive proteinuria, hypertension and renal failure as well as severe renal scarring 120 days after subtotal nephrectomy. In contrast, growth hormone-deficient Dwarf rats had minimal proteinuria, mild renal functional impairment and moderate renal histological scarring. The difference in these functional and structural parameters between the two strains is highly significant, although both experimental groups had comparable food consumption and systemic blood pressure. The significantly smaller glomeruli and limited kidney hypertrophy over 120 days observed in Dwarf rats may account for some of the protection against glomerular sclerosis and tubulointerstitial scarring observed in that strain.

The aging hypertensive kidney: pathophysiology and therapeutic options

The aging kidney undergoes hemodynamic changes characterized by reductions in glomerular filtration rate and effective renal plasma flow. These functional changes are associated with loss of renal mass related to changes in the intrarenal vasculature. The reduced glomerular filtration surface area and subsequent microcirculatory adaptations enhance the risk for development of renal diseases associated with systemic diseases. Hypertensive nephrosclerosis accounts for 26% of all end-stage renal disease in the United States; the median age of those affected is 67 years. Hemodynamic and structural changes observed in the essential hypertensive kidney suggest an accentuation of the physiologic aging process. Initially observed hemodynamic changes, which may be reversible with specific drug therapy, suggest that excessive production of angiotensin II plays a role. Progressive renal impairment may occur despite control of systemic hypertension. Renal protection appears to require therapeutic normalization of both systemic and glomerular capillary pressures. The latter may depend on a drug's ability to attenuate the intrarenal effects of angiotensin II on the renal microcirculation. Drug classes with renal protective potential include angiotensin-converting enzyme inhibitors and calcium antagonists. However, long-term clinical trials are required to assess the potential advantages of specific drug therapies in preventing the development and/or progression of hypertensive arteriolar nephrosclerosis.

Fosinopril prevents hyperfiltration and decreases proteinuria in post-transplant hypertensives

Hypertension and renal mass reduction induce glomerular hypertension (GH), hyperfiltration (HF) and renal injury. GH may contribute to allograft loss in post-transplant hypertensive patients (PT x HT). HF and GH may be evaluated by renal response to acute protein intake (API). Since ACE inhibition may prevent GH, the effects of fosinopril (Fos) were evaluated in 10 PT X HT on azathioprine and prednisone. Patients received 5 to 40 mg/day of Fos during 12 months. Baseline MAP (111.1 +/- 2.9 mm Hg) was significantly reduced by 10 to 12 mm Hg, rising to 114.7 +/- 2.7 mm Hg after Fos was administered. GFR (63.7 +/- 5.9 ml/min) decreased after 4 (48.1 +/- 4.6, P less than 0.05) and 12 months (50.7 +/- 4.6, P less than 0.05), rising to 59.4 +/- 5.6 after Fos was given. There was no GFR response to API before and after one month of Fos, however, a clear response became apparent at 4 (+ 27% P less than 0.05), and 12 months (+ 18%, P less than 0.05), disappearing after Fos discontinuation. Proteinuria (918.8 +/- 710.6 mg/d) decreased after 4 (72.3 +/- 21.6 mg/d, P less than 0.05) and 12 months, rising to 297.8 +/- 172.3 mg/day after therapy. GFR response to API in 22 controls and 17 uninephrectomized donors was 13 and 11%, respectively. Lack of response to API in PT x HT suggests HF and GH. Reduction of GFR, restoration of response to API and reduction of proteinuria, indicate that ACE inhibition with fosinopril ameliorates HF and GH. This effect may be beneficial in preventing hemodynamic-mediated allograft injury.

The renal functional and structural consequences of corticosteroid and angiotensin-converting enzyme inhibitor therapy in chronic puromycin aminonucleoside nephropathy

Glomerular diseases are characterized by increased urinary protein excretion. Treatment of this abnormality frequently involves administration of corticosteroids and angiotensin-converting enzyme inhibitors. There has been much recent interest in the potential impact of these drugs on progressive renal dysfunction, since they have opposing effects on intraglomerular hemodynamics. Therefore, we investigated the effect of methylprednisolone or captopril treatment on animals with chronic puromycin aminonucleoside nephropathy. In rats given a single injection of puromycin aminonucleoside, 15 mg/100 g body weight, both methylprednisolone and captopril significantly reduced proteinuria at 6 months [83 +/- 14 untreated (n = 7), 34 +/- 6 with methylprednisolone (n = 8), and 6 +/- 1 mg/24 h with captopril (n = 5), P less than 0.001]. Segmental glomerulosclerosis occurred with equal frequency in the untreated (7.8 +/- 2.3%) and methylprednisolone-treated rats (5.0 +/- 1.11%), but was significantly reduced by the administration of captopril (1.0 +/- 0.5%, P less than 0.001). We conclude that in chronic puromycin aminonucleoside nephropathy, treatment with corticosteroids reduces proteinuria without increasing the incidence of segmental glomerulosclerosis. Therapy with an angiotensin-converting enzyme inhibitor substantially decreases proteinuria and lessens the severity of glomerular scarring.

On the natural tendency to progressive loss of remaining kidney function in patients with impaired renal function

Patients who lose more than 50% of their functioning renal mass are at risk to develop progressive deterioration of their remaining kidney function, even though the process that caused the original loss of kidney function may no longer be present. The glomerular capillary hyperperfusion, hypertension, and hyperfiltration that occur in the surviving nephrons may play an important role in the natural tendency for renal function to deteriorate. Nevertheless, recent studies suggest that these glomerular hemodynamic events may not be the final common pathway for the natural deterioration of renal function, as was once thought. With regard to the general management of patients with impaired renal function, recent evidence suggests that controlling systemic blood pressure, reducing dietary protein and phosphorus intake, and controlling hyperlipidemia may be effective in slowing the loss of renal function.

Contribution of mononuclear leucocytes to the progression of experimental focal glomerular sclerosis

Uninephrectomized Sprague-Dawley rats repeatedly administered with aminonucleoside of puromycin and protamine sulfate developed progressive focal glomerular sclerosis (FGS). The contribution to disease progression of both glomerular and interstitial infiltrating leucocytes was studied throughout the disease evolution. Leucocyte subsets were quantitated with an immunoperoxidase technique using monoclonal antibodies for rat leucocyte surface antigens: OXI (total leucocytes) OX6 (Ia positive cells), OX8 (suppressor/cytotoxic T cells), OX19 (total T cells), OX22 (B cells and subsets of T cells), and ED1 (macrophages/monocytes). In the glomeruli, macrophages and Ia positive cells were significantly increased when sclerotic lesions appeared, but T lymphocytes and subsets of T lymphocytes were not found. However, in the interstitium, all leucocytes were identified and increased in number throughout the disease evolution. Early in the disease, monocytes and lymphocytes were both present in large numbers, but at the end stage of the process, the predominant infiltrating leucocytes were CD4+ve T cells. In FGS rats treated throughout the disease with oral prednisolone (begun after disease induction), renal function was significantly better than in the untreated group, whereas the sclerosis and leucocyte accumulation in the glomeruli were unchanged. However, prednisolone treatment resulted in significantly fewer interstitial leucocytes and especially reduced the numbers of CD4+vc cells. These results suggest that the glomerular sclerotic lesions are related to the participation of macrophages independent of T cells, and that immune mechanisms mediated by T cells in the interstitium have an important role in the progression of this disease to end-stage renal failure.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute and chronic effects of angiotensin converting enzyme inhibitors on the essential hypertensive kidney

The natural course of essential hypertensive renal disease is characterized by a slowly progressive impairment of renal function. Initially, the changes are functional and reversible; however, structural changes gradually occur, leading to hypertensive nephrosclerosis. Similarities exist between the early functional hemodynamic changes observed in the essential hypertensive kidney and the physiologic renal effects of angiotensin II. To the degree that the initial functional changes are the result of excessive endogenous production of angiotensin II, interruption of the integrity of this humoral system could be expected to reverse the pathophysiologic sequence of events leading to hypertensive nephrosclerosis. This review focuses on the pathophysiology of the essential hypertensive kidney, the intrarenal effects of angiotensin II, and the acute and chronic effects of angiotensin converting enzyme (ACE) inhibition therapy on the essential hypertensive kidney. The data reviewed suggest that ACE inhibition therapy does reverse the initial functional hemodynamic changes observed in the essential hypertensive kidney and may protect the glomerulus from hemodynamically mediated injury.

Calcium channel blocker nisoldipine in chronic renal failure

Patients with a stable progression of chronic renal failure with a creatinine clearance of 15-45 mL/min were randomly assigned to two groups of antihypertensive therapy: 1--nisoldipine as the only antihypertensive agent and 2--antihypertensive drugs without calcium channel blockers and a placebo tablet instead of nisoldipine. The patients were already on a low-protein diet and some form of antihypertensive therapy but without calcium channel blockers. There were 18 patients in the placebo group and 20 patients in the nisoldipine group. The follow-up period averaged 23.7 +/- 10.6 (SD) months in the placebo group and 23 +/- 11.3 months in the nisoldipine group. The slopes of the reciprocal of serum creatinine were calculated for the period prior to and following our intervention. The number of patients whose slopes improved following intervention was 6/18 in the placebo group and 15/20 in the nisoldipine group (p less than .02). The patients whose slopes improved had a significant fall in systolic and diastolic BP, as well as in the MAP. Those whose slopes did not improve had a significant decrease in systolic BP, but no change in diastolic BP and no significant difference in the MAP. When all 38 patients are analyzed together, regardless of their grouping, the correlation between the difference percent in the slope, and the difference percent in the MAP, was significant. Furthermore, punch biopsies of the skin showed a markedly different calcium content in the two groups, which was significantly less in the nisoldipine-treated patients as compared with the patients not receiving calcium blockers.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of iron in the tubulo-interstitial injury in nephrotoxic serum nephritis

We studied the possibility that tubule fluid iron could be involved in the pathogenesis of the tubulo-interstitial injury associated with primary glomerular disease. Tubule fluid iron is determined by the magnitude of the glomerular leak for transferrin and the iron saturation of transferrin. To minimize tubule fluid iron in an experimental model of glomerulonephritis, iron deficiency was induced in rats prior to the induction of nephrotoxic serum nephritis. Iron deficiency did not effect the development of glomerular disease as determined by proteinuria, but had a marked effect on preventing the development of tubulo-interstitial disease and renal functional deterioration. There was also a strong correlation between the amount of functional deterioration and extent of tubulo-interstitial disease and urinary iron excretion in both the control and iron deficient animals. It is proposed that injury results from iron being dissociated from transferrin at the more acid pH of the tubule fluid. Iron, a transition element, is able to catalyze the Haber-Weiss reaction with the formation of free hydroxyl radicals which causes renal tubule cell injury. This tubulo-interstitial injury is the major determinate of progressive renal functional deterioration in this experimental model of glomerulonephritis.

Short and long term effects of antihypertensive therapy in the diabetic rat

To compare the impact of differing antihypertensive regimens on the development of renal injury, studies were performed in three groups of moderately hyperglycemic diabetic rats, and one group of non-diabetic control (C) rats. One diabetic group (DM) received no therapy except insulin. The remaining diabetic groups received insulin and either the angiotensin I converting enzyme inhibitor captopril (CAP), or triple therapy (TRX) with reserpine, hydralazine and hydrochlorothiazide. CAP and TRX modestly and comparably lowered blood pressure. At 6 to 10 weeks, DM rats exhibited elevation of the single nephron glomerular filtration rate (SNGFR), due to elevations of the glomerular capillary plasma flow rate (QA) and the glomerular capillary hydraulic pressure (PGC). In both DM/CAP and DM/TRX rats, blood pressure reduction was associated with selective normalization of PGC, without change in SNGFR or QA. In long-term (70 weeks) studies, DM rats exhibited progressive albuminuria and marked glomerular sclerosis. CAP limited albuminuria and injury to values even lower than those in C rats, whereas TRX served only to delay, but not to prevent, the increase in albuminuria. TRX reduced glomerular sclerosis, but was less effective than CAP. At 70 weeks, CAP and TRX still reduced systemic blood pressure; PGC remained at normal levels with CAP but was no longer controlled with TRX. These results confirm the clinical observation that antihypertensive therapy slows diabetic glomerulopathy, but also suggest that CAP affords superior long-term protection as compared to the other antihypertensive drug regimen studied.

Normotensive renal failure in systemic sclerosis

Of 140 patients with "scleroderma renal crisis" encountered during a 33-year period, 15 of 131 (11%) whose blood pressures were recorded were normotensive during this complication. In comparison with 116 patients with hypertension, the normotensive patients significantly more often had microangiopathic hemolytic anemia (90% versus 38%) and thrombocytopenia (83% versus 21%). Pulmonary hemorrhage occurred in 6 normotensive patients. More normotensive patients had received high doses of corticosteroids (prednisone greater than or equal to 30 mg/day) during the 2 months immediately preceding renal crisis (64% versus 16%). A role for corticosteroids in precipitating renal crisis is suggested. The 12-month survival was significantly reduced in the normotensive patients (13% versus 35%).