Systemic enzyme therapy in chronic glomerulonephritis

AIM: To try polyenzyme drug vobenzim in chronic glomerulonephritis (CGN). MATERIALS AND METHODS: 174 CGN patients were randomized into 2 groups. The study group of 39 patients received conventional pathogenetic treatment plus vobenzim (initial dose 18-24, maintenance 12-15 dragees a day). Control group of 135 patients were given only pathogenetic therapy. 67 patients appeared ineligible. RESULTS: 3-6 months after the treatment the response was seen in 61.5% patients of the study and 17.8% patients of the control group. Side effects of vobenzim in CGN treatment were absent. CONCLUSION: Enzyme therapy with vobenzim in CGN is safe and effective.     

Effect of renovascular hypertension on experimental glomerulonephritis in rats.

Systemic hypertension is a major risk factor that determines the rate of progression of kidney disease. The underlying mechanisms, however, are incompletely understood. To gain insight into these mechanisms, the present study was undertaken to characterize the effects of renovascular hypertension on the course of anti-thymocyte antibody-induced glomerulonephritis. Glomerulonephritis was induced in rats 6 weeks after the initiation of two-kidney, one-clip hypertension, when blood pressure was already increased. Structure and function of the clipped and the nonclipped kidney were examined 5 days later. Glomerular filtration rate (GFR) was measured by inulin clearance. The induction of nephritis did not alter the blood pressure in either hypertensive rats or normotensive controls. Albuminuria increased slightly in normotensive rats after the induction of nephritis, whereas no significant differences were found between hypertensive rats with or without nephritis. No significant differences were found for the GFR values of normotensive controls and nephritic animals or for values in the clipped kidney with or without nephritis. However, the GFR of the nonclipped kidney was significantly reduced in nephritic animals as compared with all other groups. Morphologic evaluation revealed that hypertensive rats with nephritis exhibited a combination of characteristics of nephritis and hypertensive glomerular injury. Histologic findings of nephritis, such as glomerular binding of rabbit IgG and glomerular proliferation and mesangial matrix expansion, were similar after the induction of nephritis in controls and in the clipped and nonclipped kidneys of hypertensive animals. However, intraglomerular microaneurysms were significantly more often found in the non-clipped kidneys after the induction of nephritis. Hypertension-induced deterioration of glomerular function was not associated with marked morphologic deterioration but rather with a combination of the characteristics of nephritis and hypertensive glomerular injury.     

Brain angiotensin-converting enzyme activity in experimental hypertensive rats

Angiotensin-converting enzyme (ACE) activity was measured in six areas of the brain of normotensive and experimental hypertensive rats; one-clip, one-kidney (1-c, 1-k) and one-clip, two-kidney (1-c, 2-k) Goldblatt hypertensive (GH) rats. ACE activity was consistently high in the thalamus of normotensive and both 1-c, 1-k and 1-c, 2-k GH rats. However, the enzyme activity in the hypothalamus of 1-c, 2-k GH rats was significantly higher than that of normotensive rats, while there was no significant difference in the enzyme activity between normotensive and 1-c, 1-k GH rats. These results demonstrate that in 1-c, 2-k GH rats, increased ACE activity in the brain may play a central role in the hypertension.     

Cryoglobulins in acute experimental immune complex glomerulonephritis.

The relationship between cold-insoluble complexes, or cryoglobulins, and renal disease was studied in rabbits with acute serum sickness produced with BSA. The onset of serum creatinine elevation correlated well with the appearance of cryoglobulins. The average interval between the appearance of cryoglobulins and the elevation in serum creatinine was 0.87 day. In no animal did creatinine elevation precede cryoglobulinemia, even though immune complexes were detectable much earlier by other methods. The level of cryoglobulin correlated significantly with the level of serum creatinine (r = 0.71, p less than 0.01). Cryoglobulins may be of immunopathologic significance in acute experimental immune complex glomerulonephritis.     

Effects of various antiplatelet drugs and defibrinating agent on experimental glomerulonephritis in rats

Two types of experimental GN induced by immunological procedures. Heymann-type AIC-GN and NTN, were treated with anticoagulant agents. Dipyridamole, aspirin, ticlopidine or batroxobin was administered either to rats with AIC-GN for 14 to 28 days or to NTN rats 2 days prior to injection with NTS and 14 to 21 days thereafter. A significant decrease in the amount of urinary protein was observed only in rats treated with 12.5 to 50.0 mg/kg dipyridamole daily, whereas no significant decrease in proteinuria was observed in either AIC-GN or NTN rats treated with the other agents. Histopathologically, no improvement in the light and electron microscopic findings was noted in AIC-GN rats treated with these agents, even with dipyridamole. On the other hand, in NTN rats, light and electron microscopic study of the kidneys from rats sacrificed 30 to 60 min after NTS injection revealed that platelet aggregation and inflammatory changes in the glomeruli were remarkable reduced in rats pretreated with 56.4 mg/kg aspirin or 50.0 mg/tg triclopidine daily, but no difference in the renal lesions between rats treated with aspirin or triclopidine and control animals were observed 2 weeks after NTS injection. No histological improvement was observed in rats pretreated with dipyridamole. It would be reasonable to conclude from these results that the favorable effect of dipyridamole on proteinuria is not related to its antiplatelet activity and that platelet aggregation is not essential to the development of renal lesions in rat AIC-GN and NTN. (J Lab Clin Med 99:428, 1982.)     

Control of proximal tubule fluid reabsorption in experimental glomerulonephritis.

We have recently shown that in the early autologous phase of nephrotoxic serum nephritis (NSN) single nephron glomerular filtration rate is unchanged from values in normal hydropenic control rats, but that single nephron filtration fraction and efferent arteriolar oncotic pressure (piE) are reduced because of a marked reduction in the glomerular capillary ultrafiltration coefficient. The present study was undertaken to examine the influence of this decline in piE as well as the other known determinants of peritubular capillary fluid exchange on absolute proximal fluid reabsorption (APR) in NSN. The findings indicate that APR and proximal fractional reabsorption are reduced significantly in NSN, relative to values in a separate group of age and weight-matched normal hydropenic control rats studied concurrently. In addition to the measured decline in piE, efferent arteriolar plasma flow (Qe) and peritubular capillary hydraulic pressure (Pc) were found to increase significantly, while interstitial oncotic pressure, estimated from hilar lymph, was not significantly different from values in control rats. Using a mathematical model of peritubular capillary fluid uptake we found that, assuming that the capillary permeability-surface area product and interstitial hydraulic pressure are unchanged in NSN, the observed changes in piE and Pc are sufficient to offset the effect of the increase in QE, yielding a calculated reduction in APR of approximately 4 nl/min, in excellent agreement with the observed mean decline of 4.1 nl/min. These findings suggest that control of APR in NSN is mediated by the same factors that regulate APR under normal physiological conditions, namely, the imbalance of forces governing peritubular capillary uptake of isotonic reabsorbate.     

Determinants of glomerular filtration in experimental glomerulonephritis in the rat.

Pressures and flows were measured in surface glomerular capillaries, efferent arterioles, and proximal tubules of 22 Wistar rats in the early autologous phase of nephrotoxic serum nephritis (NSN). Linear deposits of rabbit and rat IgG and C3 component of complement were demonstrated in glomerular capillary walls by immunofluorescence microscopy. Light microscopy revealed diffuse proliferative glomerulonephritis, and proteinuria was present. Although whole kidney and single nephron glomerular filtration rate (GFR) in NSN (0.8 plus or minus 0.04 SE2 ml/min and 2 plus or minus 2 nl/min, respectively) remained unchanged from values in 16 weight-matched NORMAL HYDROPENIC control rats (0.8 plus or minus 0.08 and 28 plus or minus 2), important alterations in glomerular dynamics were noted. Mean transcapillary hydraulic pressure difference (deltaP) averaged 41 plus or minus 1 mm Hg in NSN versus 32 plus or minus 1 in controls (P LESS THAN 0.005). Oncotic pressures at the afferent (piA) end of the glomerular capillary were similar in both groups ( 16 mm /g) but increased much less by the efferent end (piE) in NSN (to 29 plus or minus 1 mm Hg) than in controls (33 plus or minus 1, P less than 0.025). Hence, equality between deltaP and piE, denoting filtration pressure equilibrium, obtained in control but not in NSN rats. While glomerular plasma flow rate was slightly higher in NSN (88 plus or minus 8 nl/min) than in controls (76 plus or minus 6, P greater than 0.2), the failure to achieve filtration equilibrium in NSN rats was primarily the consequence of a marked fall in the glomerular capillary ultrafiltration coefficient, Kf, to a mean value of 0.03 nl/(s times mm Hg), considerably lower than that found recently for the normal rat, 0.08 nl/(s times mm Hg). Thus, despite extensive glomerular injury, evidenced morphologically and by the low Kf, GFR remained normal. This maintenance of GFR resulted primarily from increases in deltaP, which tended to increase the net driving force for filtration, and thereby compensate for the reduction in Kf.     

Strain specific responses of inbred rats on the severity of experimental autoimmune glomerulonephritis

Experimental autoimmune glomerulonephritis with pulmonary hemorrhage was induced in rats of 4 inbred strains, F344/DuCrj, LEW/Crj, WKY/NCrj and SHR/NCrj, by the injection of a nephritogenic antigen from bovine glomerular basement membrane. The severity and clinical course of glomerulonephritis within the strains were very similar, but those between the strains were different. Among them, F344 rats demonstrated mild glomerulonephritis with petechial pulmonary hemorrhage. LEW rats showed more severe symptoms from pulmonary hemorrhage than F344 rats and had heavy, long-lasting proteinuria that caused nephrotic syndrome. WKY rats showed very severe glomerulonephritis with pulmonary hemorrhage, and had azotemia by 4 weeks after the injection. SHR rats had both severe glomerulonephritis and severe pulmonary hemorrhage. Investigation of the dose-effect relationship of the nephritogenic antigen in F344 and WKY rats revealed that the minimum dose required to induce nephritis in F344 and WKY rats was 10 micrograms and 3 micrograms respectively, and that the injection of more than a certain amount (i.e., 30 micrograms in F344, 10 micrograms in WKY) of the antigenic material induced almost the same severity of disease. These results indicate that genetic differences in experimental animals influence the severity of renal damage, suggesting that the use of inbred strains is necessary for adequate study of experimental glomerulonephritis.     

Therapeutic effect of glucocorticoid on experimental crescentic glomerulonephritis.

Crescentic glomerulonephritis shows active and progressive glomerular changes with rapid deterioration in kidney function. A large dose of glucocorticoid (pulse therapy) is clinically used for the treatment, but its efficacy has not been fully estimated. In this study we assessed the therapeutic effect of a large dose of methyl-prednisolone (MP) on a rat model of crescentic glomerulonephritis that had been induced in WKY rats by an injection of anti-glomerular basement membrane antibody. The infiltration of CD8+ cells and monocytes was manifest by day 3, proteinuria appeared on days 4 and 5, and cellular crescents were diffusely formed by day 7. The gene expression of MCP-1, a chemokine for monocytes and T lymphocytes, was enhanced within 4 hours and peaked on day 3. Daily administration of MP (30 mg/kg/d) from day 3 through day 6 reduced the gene expression of MCP-1 and the numbers of glomerular leukocytes and largely prevented both crescent formation and proteinuria. When daily MP treatment started on day 7, the numbers of glomerular CD8+ cells and monocytes, crescents, and urinary protein were significantly reduced by day 11. In addition, continuing treatment with a small dose of MP (3 mg/kg/d) begun on day 11 completely prevented the increase in blood urea nitrogen and serum creatinine levels. These results indicate that treatment with a large dose of MP histologically and clinically ameliorates crescentic glomerulonephritis in a rat model, supporting the efficacy of pulse MP therapy for the treatment of the disease in human subjects.     

B-cell-targeted therapy in adult glomerulonephritis

Introduction: There are many mechanisms through which B lymphocytes have been implicated in the pathogenesis of glomerulonephritis. There are a number of trials and clinical studies in glomerulonephritis involving depletion of CD20⁺ B lymphocytes using rituximab. Newer anti-CD20 agents are currently under evaluation, as are drugs targeting alternative B-cell targets such as B lymphocyte stimulator. Such selective, targeted B-cell therapies, if shown to be effective, may be of value in minimising toxicity from more conventional agents.

Areas covered: This article reviews the role of B cells as a target for therapy in adult renal disease resulting from primary glomerulonephritis and that occurring secondary to systemic disease. It will not address intracellular signalling or co-stimulatory pathways as therapeutic targets.

Expert opinion: There are indications for B-cell targeted therapies in a number of adult glomerulonephritides, with varying degrees of evidence. Further understanding of the mechanisms of B-cell depletion and repletion, and interplay with B-cell survival factors, is necessary in order to identify patients who will respond favourably.     

Macrophage-induced glomerular fibrin deposition in experimental glomerulonephritis in the rabbit.

Glomerular fibrin deposition is important in the pathogenesis of renal failure and crescent formation in glomerulonephritis. The mechanisms of glomerular fibrin deposition are unknown. The current studies explored the role of macrophages in this process. Methods were developed for measuring glomerular fibrin deposition and glomerular procoagulant activity in a passive model of the autologous phase of antiglomerular basement membrane antibody-induced glomerulonephritis in rabbits. Significant fibrin deposition was observed to be associated with glomerular macrophage accumulation. Leukocyte ablation with mustine hydrochloride prevented both glomerular macrophage accumulation and fibrin deposition without affecting the coagulation system or the deposition of disease-inducing antibodies and complement. Repletion with mononuclear inflammatory cells produced significant fibrin deposition. To examine the role of tissue injury per se in glomerular fibrin deposition, a macrophage-independent model of glomerular injury (heterologous phase glomerulonephritis) was also studied. Although a similar degree of glomerular injury occurred, there was no significant fibrin deposition. This suggests that macrophages, rather than injury alone, are responsible for fibrin deposition. Lysates of isolated glomeruli containing macrophages demonstrated greatly enhanced procoagulant activity compared with lysates of glomeruli without macrophages. Thus macrophages appear to be directly responsible for glomerular fibrin deposition in antiglomerular basement membrane antibody-induced glomerulonephritis, and this appears to be due to their ability to express procoagulant activity rather than their propensity to cause glomerular injury.     

Activation of extracellular signal-regulated kinase in proliferative glomerulonephritis in rats.

Multiple extracellular mitogens are involved in the pathogenesis of proliferative forms of glomerulonephritis (GN). In vitro studies demonstrate the pivotal role of extracellular signal-regulated kinase (ERK) in the regulation of cellular proliferation in response to extracellular mitogens. In this study, we examined whether this kinase, as a convergence point of mitogenic stimuli, is activated in proliferative GN in vivo. Two different proliferative forms of anti-glomerular basal membrane (GBM) GN in rats were induced and whole cortical tissue as well as isolated glomeruli examined using kinase activity assays and Western blot analysis. Administration of rabbit anti-rat GBM serum to rats, preimmunized with rabbit IgG, induced an accelerated crescentic anti-GBM GN. A significant increase in cortical, and more dramatically glomerular ERK activity was detected at 1, 3, and 7 d after induction of GN. Immunization of Wistar-Kyoto rats with bovine GBM also induced a crescentic anti-GBM GN with an increase of renal cortical ERK activity after 4, 6, and 8 wk. ERK is phosphorylated and activated by the MAP kinase/ERK kinase (MEK). We detected a significant increase in the expression of glomerular MEK in the accelerated form of anti-GBM GN, providing a possible mechanism of long-term activation of ERK in this disease model. In contrast to ERK, activation of stress-activated protein kinase was only detectable at early stages of proliferative GN, indicating these related kinases to serve distinct roles in the pathogenesis of GN. Our observations point to ERK as a putative mediator of the proliferative response to immune injury in GN and suggest that upregulation of MEK is involved in the long-term regulation of ERK in vivo.     

New avian model of experimental glomerulonephritis consistent with mediation by cellular immunity. Nonhumorally mediated glomerulonephritis in chickens

The present study examined the role of cell-mediated immunity (CMI) in the production of experimental autoimmune glomerulonephritis (EAG) in chickens deficient in humorally mediated immunity (HMI). Cyclophosphamide bursectomized (Bsx) and normal control chickens were used. Bsx chickens were used only if they had severe depression of HMI, which was evidenced by marked reduction in bursal weights (0.89 +/- 0.23 vs. 2.92 +/- 0.9 g), decreased serum IgG to less than or equal to 10% of normal, and total lack of HMI to immunization with sheep red blood cells. EAG was produced by immunizing chickens with bovine glomerular basement membrane (GBM) in complete Freund's adjuvant. CMI manifested by wattle thickness increments to PPD was not different, 3.89 +/- 0.45 mm for Bsx compared with 3.73 +/- 0.75 mm for controls. No circulating antibodies to GBM developed in 68% of Bsx chickens, and the anti-GBM titers were less than 1:312 in those Bsx chickens positive for antibody compared with greater than 2,000 for controls. GBM deposits of IgG by fluorescence were much decreased, 0.53 +/- 0.16 compared with 2.19 +/- 0.32 for controls, and were absent in 64% of Bsx chickens. Nonetheless, proliferative nephritis with crescents was present and was even more severe in Bsx chickens than in controls, with glomerular sizes of 20.8 +/- 0.6 U for Bsx-GBM, 19.8 +/- 1.2 for control-GBM, 14.9 +/- 1.5 for Bsx, and 13.6 +/- 0.8 for normal chickens. Nephritic eluates did not produce disease in normal chickens, while administration of sensitized cells with [H3]thymidine to naive birds was associated with increased mesangial grain counts by autoradiography. These findings suggest that CMI plays a major role in the pathogenesis of EAG in chickens in the absence of HMI. By implication, CMI may be crucial in the development of other types of glomerulonephritis as well.     

Targeted therapy in colorectal cancer

Advances in chemotherapeutic agents have led to improved outcomes for patients with metastatic colorectal cancer (CRC). Chemotherapies, however, are limited by their toxicities and lack of specificity. Aberrations in the regulation and expression of growth factors have been implicated in the development of CRC, and this understanding has led to the development of targeted agents. In 2004, two novel agents, bevacizumab and cetuximab, were approved by the US Food and Drug Administration for the treatment of metastatic CRC. Bevacizumab, a humanized monoclonal antibody to vascular endothelial growth factor, and cetuximab, a human-mouse chimeric monoclonal antibody to the epidermal growth factor receptor, have changed the field dramatically. Bevacizumab appears to augment the efficacy of combination chemotherapy regimens for the treatment of metastatic CRC in both the first- and second-line settings, and the role of bevacizumab as part of adjuvant treatment is the subject of ongoing trials. However, because of the increased incidence of serious arterial thromboembolic events, gastrointestinal perforations, bleeding complications, and hypertension associated with bevacizumab, this agent is probably not indicated in all circumstances. Combination treatment with cetuximab and irinotecan appears appropriate in patients with advanced CRC who have failed irinotecan. Patients who are unable to receive additional irinotecan may be treated with cetuximab monotherapy. Positive epidermal growth factor receptor status by immunohistochemistry of a tumor specimen is presently mandated to determine candidacy for this therapy, although this assay appears to be suboptimal and newer assessment techniques to determine suitability for therapy must be developed. Phase III trials should shed light on the role of cetuximab in the first-line metastatic and adjuvant settings. Multitargeted strategies in CRC combining chemotherapy with bevacizumab and cetuximab are currently being explored. Further advances in the treatment of CRC are expected through continued scientific investigation and well-designed clinical trials.     

Colloid solution therapy of experimental ischemic intestinal shock in rats

This study evaluated the effects of varying colloid concentrations and infusion volumes on survival and plasma volume expansion in rats subjected to an intestinal ischemic shock. Up to 10% solutions of albumin and dextran-40 in lactated Ringer's solution, infused over a 6-h period, had the same effects on hematocrit (Hct) changes and survival patterns. Mean Hct values (45% to 50%) were independent of colloid solution concentration. With lactated Ringer's solution alone, Hct was 55%, despite the very large volume used; and less than 3% of the infused lactated Ringer's solution remained as plasma volume at 3 and 6 h of infusion. With increasing colloid concentration a greater proportion of the infused volume contributed to plasma volume. Of a 10% colloid solution, 50% and 34% remained as plasma volume at 3 and 6 h. For colloid concentrations between 1% and 3%, there was an equal distribution of infused fluid between the extracellular fluid space and the plasma. Survival rate, as measured by blood volume expansion, was greater with colloid solution concentrations between 2% and 4%.     

Helping antibodies. Targeted antithrombotic and fibrinolytic therapy

The development of monoclonal antibodies facilitated an enormous progress in modern medicine in the last years. The targeted inhibition of defined molecular structures allows therapeutic concepts, which before were inconceivable. There are numerous antibodies in clinical use within the area of tumour therapy, chronically inflammatory diseases, transplantation, infections and also in cardiovascular medicine. Different antibody formats are used such as IgG molecules, Fab fragments and single chain antibodies. Single chain antibodies represent the smallest functional form of the antibody and are used preferentially as recombinant antibodies. The therapeutic possibilities of antibody technology are extended by fusion to radioactive or therapeutically active substances. This review focuses on the application of antibodies and fusion proteins as antithrombotic and fibrinolytic drugs. The use of antibodies allows the development of inhibitory agents with clearly defined functional properties, as for example for activation-specific GPIIb/IIIa-blockade. In addition antibodies can be used for targeting antithrombotic and fibrinolytic agents to the thrombus, allowing an effective local action with less bleeding complications.