Hypertension after pancreas-kidney transplantation: role of bladder versus enteric pancreatic drainage.

BACKGROUND: Recent reports suggest that hypertension may be less common after simultaneous pancreas-kidney transplantation than after kidney transplantation alone. However, the mechanisms for this beneficial effect have not been delineated. We hypothesize that lower blood pressures may result from chronic volume depletion in patients with bladder-drained pancreatic allografts. METHODS: We compared the incidence and severity of hypertension 12 months after transplantation in 79 bladder-drained pancreas-kidney recipients and 46 diabetic kidney-only recipients. These two groups were compared with a smaller group of enterically drained pancreas-kidney recipients. Blood pressure was also compared before and after surgical conversion from bladder to enteric drainage in 10 patients. RESULTS: Hypertension was significantly less common and less severe after pancreas-kidney transplantation than after kidney transplantation alone, but the benefit of the pancreas transplant was evident only in bladder-drained patients. Logistic regression analysis of the bladder-drained pancreas-kidney patients confirmed the independent impact of the pancreatic allograft on the presence of hypertension, indicated an independent association with serum creatinine concentration and donor age, but suggested no correlation with recipient age, race, or number of rejection episodes. A comparison of blood pressures before and after pancreatic conversion from bladder to enteric drainage indicated no significant change in the prevalence or severity of hypertension. CONCLUSIONS: We conclude that the beneficial effect of a pancreas transplant on the prevalence and severity of hypertension after simultaneous pancreas-kidney transplantation is limited to bladder-drained patients. Although it is possible that the effect is mediated by chronic volume depletion, the observation that blood pressure does not increase after conversion from bladder to enteric drainage suggests that other factors may be involved.

Azathioprine monotherapy in HLA-identical live donor kidney transplant recipients.

The high success rate of HLA-identical sibling transplants and our previous experience with steroid-free immunosuppressive regimens and cyclosporine withdrawal prompted us to evaluate the safety and efficacy of monotherapy with azathioprine in 12 HLA-identical kidney transplant recipients with a serum creatinine concentration less than 176.8 mumol/L, a 1-way stimulatory index less than 2.0 in a post-transplant mixed lymphocyte culture, and a demonstrated tolerance of a minimum azathioprine dose of 1.0 mg/kg per day without leukopenia. Eleven of 12 patients were successfully converted to azathioprine monotherapy without a significant change in serum creatinine concentration for as long as 76 months. Benefits of steroid and cyclosporine withdrawal included a significant reduction in mean systolic and diastolic blood pressure, number of blood pressure medications, total serum cholesterol, and glycohemoglobin in diabetic subjects. Our results suggest that azathioprine monotherapy is safe and effective in a select group of HLA-identical sibling transplants, but these benefits must be carefully balanced against an associated risk of precipitating acute allograft rejection.

Benefits of pre-emptive dose reduction for Sandimmune to Neoral conversion in stable renal transplant recipients.

In an effort to minimize nephrotoxicity resulting from greater exposure to cyclosporine after Sandimmune to Neoral conversion, we compared two conversion regimens using different dosing ratios. Serial serum creatinine concentrations and trough cyclosporine levels were measured in 26 patients converted from Sandimmune to Neoral using a 1:0.8 dosing ratio (Group 1) and compared to those of 26 patients converted using a 1:1 dosing ratio (Group 2). The percentage change in peak serum creatinine concentration after conversion was greater in Group 2. However, at last follow-up, the dose reductions in each group were comparable. Following conversion, patients in Group 1 required fewer dose adjustments and follow-up blood tests. Compared to conversion using a 1:1 dosing ratio, conversion from Sandimmune to Neoral using a 1:0.8 ratio results in comparable dose reductions and less short-term nephrotoxicity, while requiring less frequent laboratory monitoring.

Immunosuppressive drugs in pregnancy.

Successful pregnancies are now common in female organ transplant recipients. Despite high rates of success, pregnancy in an organ transplant recipient should be managed as a high-risk condition with emphasis on prevention and prompt treatment of rejection episodes. The number of immunosuppressive drugs and drug combinations has increased in recent years. Data accrued by a national registry indicate that pregnancy is generally successful in patients maintained on some combination of cyclosporine, azathioprine, and steroids. Relatively little information is available regarding the safety of some of the newer immunosuppressive agents in pregnancy. Until additional information is collected, transplant physicians and obstetricians must balance the efficacy of immunosuppressants in preventing allograft rejection in the mother against possible adverse drug reactions in both the mother and fetus.

Long-term renal function in type I diabetics after kidney or kidney-pancreas transplantation: influence of number, timing, and treatment of acute rejection episodes.

BACKGROUND: Previous studies comparing renal function in diabetic subjects receiving either a kidney or kidney-pancreas transplant generally have indicated no differences; however, these studies have been limited by inclusion of either a small number of patients or selected patients followed for relatively short periods of time. METHODS: To compare long-term renal function and factors affecting renal function in type I diabetic patients receiving either kidney or kidney-pancreas transplants, the slopes of regression lines generated by plotting the reciprocal of serum creatinine (1/Cr) versus time were measured in 109 consecutive patients followed for at least 12 and up to 102 months after transplantation. Multivariate analyses included linear regression using the slope of 1/Cr versus time as the dependent variable and logistic regression using a positive or negative slope as the dependent variable. RESULTS: Significant differences between kidney-pancreas (n=64) and kidney recipients (n=45) included a smaller proportion of African-Americans, lower rates of HLA matching, lower levels of panel-reactive antibodies, shorter cold ischemia times, a lower incidence of delayed graft function, and a higher incidence of acute renal allograft rejection episodes in the kidney-pancreas group. Trough cyclosporine blood levels were significantly higher in the kidney-pancreas group for the first 12 posttransplant months. The slopes of 1/Cr versus time were negative in each group with a trend toward a more negative slope in the kidney-pancreas group. Multivariate analyses indicated that a concomitant pancreas allograft did not influence long-term renal function. The total number of renal rejection episodes was the best independent predictor of a negative slope of 1/Cr versus time. However, use of OKT3 for the treatment of rejection within the first 3 months of transplantation exerted a surprisingly beneficial effect on long-term renal function, a phenomenon that was most apparent in the kidney-alone group. CONCLUSIONS: The frequency and timing of acute rejection episodes are more important than the influence of a simultaneously transplanted pancreatic allograft in determining long-term function of the transplanted kidney. A concerning trend toward late deterioration of renal function in kidney-pancreas recipients suggests that the benefits of sustained euglycemia, shorter cold ischemia times, lower rates of sensitization, and early use of OKT3 ultimately may be outweighed by the negative effects of more frequent renal rejection episodes.

Influence of steroid withdrawal on proteinuria in renal allograft recipients.

The ratio of urine protein/urine creatinine in spot urine specimens was measured to determine the influence of steroid withdrawal and other clinical variables on urinary protein excretion in 135 primary renal transplant recipients, including 73 patients in whom steroid withdrawal was never attempted and 62 patients in whom steroid withdrawal was attempted at various times following transplantation. Both univariate and multivariate analyses showed that steroid withdrawal per se did not directly influence proteinuria. However, patients who renewed steroid therapy because of acute allograft rejection following attempted steroid withdrawal exhibited significantly more proteinuria than was encountered either in patients who remained steroid-free or in those for whom steroid withdrawal was never attempted. This study suggests that steroid withdrawal itself does not lead to proteinuria, however, acute rejection following steroid withdrawal clearly accelerates urinary protein excretion that may be the harbinger of chronic allograft rejection.

Renal function following conversion from Sandimmune to Neoral in stable renal transplant recipients.

Conversion of stable renal transplant patients from Sandimmune to Neoral may pose a risk of short-term nephrotoxicity. Serial serum creatinine concentrations were measured in 141 kidney and simultaneous kidney-pancreas transplant recipients converted from Sandimmune to Neoral on a 1:1 dosing basis and followed for up to 11 months. Following conversion, cyclosporine dose was reduced in 74% of patients with a mean dose reduction of 22.6% for the entire cohort. Serum creatinine concentrations transiently increased to more than 30% above baseline in 48% of patients and remained more than 30% above baseline in 16% of patients. Multivariate analyses suggested that acute rejection, maintenance steroid therapy, young age, Sandimmune dose prior to conversion, and an increment in trough cyclosporine levels after conversion were positive predictors of renal insufficiency following conversion. Lower doses of Neoral should be considered at the time of conversion to minimize nephrotoxicity.

Effects of fluvastatin on hyperlipidemia after renal transplantation: influence of steroid therapy.

OBJECTIVE: To assess the efficacy and safety of fluvastatin in hypercholesterolemic, cyclosporine-treated, renal transplant recipients, and to determine whether concomitant steroid therapy in such patients alters the lipid-lowering effects of fluvastatin. DESIGN: An open-label, prospective, parallel study was performed in 20 cyclosporine-treated renal transplant recipients with hypercholesterolemia defined by a low-density lipoprotein (LDL) concentration greater than 160 mg/dL or a total cholesterol/high-density lipoprotein (HDL) concentration ratio greater than 5.0. Lipid profiles were measured before and 1 month after treatment with fluvastatin 20 mg/d. Lipid profiles in a group of patients receiving concomitant therapy with prednisone (n = 12) were compared with those of patients who had not received steroids for at least 6 months (n = 8). SETTING: The Renal Transplant Clinic at University Hospitals of Cleveland. MAIN OUTCOME MEASURES: The main outcome measures were serum concentrations of total cholesterol, LDL, HDL, and triglycerides. Treatment failure was defined by LDL concentrations persistently above 160 mg/dL after 1 month of fluvastatin therapy. Safety was assessed clinically and by serial measurements of liver enzymes and creatine phosphokinase. RESULTS: LDL concentrations decreased significantly in both the steroid-treated and steroid-free groups after 1 month of fluvastatin therapy. There was no significant change in HDL concentrations or serum triglycerides in either group. Treatment failure was more common in patients receiving steroids (4/12 patients) than in steroid-free patients (1/8 patients). After 1 month of therapy, LDL cholesterol was significantly lower in the steroid-free group (126 +/- 18 mg/dL) than in the steroid-treated group (147 +/- 23 mg/dL) (p < 0.05). There was no clinical or laboratory evidence of myonecrosis in either group. CONCLUSIONS: Low dosages of fluvastatin appear to be safe in cyclosporine-treated renal transplant recipients. Steroid-free patients exhibit a response to fluvastatin that is qualitatively similar to that of steroid-treated patients, consisting of a significant decrease in LDL concentrations and no change in HDL or serum triglyceride concentrations.

Unique C1 inhibitor dysfunction in a kindred without angioedema. I. A mutant C1 INH that inhibits C1-s but not C1-r.

We have described hereditary incomplete deficiency of the fourth component of complement (C4) in 10 members of a large kindred. C4 deficiency in this kindred is not linked to C4 loci in the HLA region. C4 synthesis is decreased, and C4 catabolism is normal in kindred members with low serum C4 levels. We have discovered a uniquely dysfunctional C1 inhibitor in all C4-deficient members of this kindred. C1 inhibitor dysfunction is revealed by incubating sera of affected members with EDTA, which destroys all C4 activity in these sera, but not in normal sera or sera from individuals with partial C4 deficiencies. The M(r) of C1 inhibitor purified from affected members is normal, but approximately 50% of this C1 inhibitor resists cleavage by trypsin (0.14 microM) at arg444, suggesting a substitution at this position. Moderate increases in trypsin, however, result in cleavage of the resistant molecules, which would not be expected if arg444 were the site of the mutation. All molecules in C1 inhibitor purified from affected members' plasma bind to activated C1s (C1-s), but approximately 50% of molecules in these preparations do not bind to activated C1r (C1r). These findings show that affected kindred members have a unique mutation in C1 inhibitor. The mutant C1 inhibitor does not prevent the activation of C1s by C1-r when serum Ca2+ is chelated by EDTA, but its inhibition of C1-s is normal in vivo, as shown by normal C2 levels, normal C4 catabolism, and absence of angioedema in C4-deficient members. The nature of the mutation, its selective failure to inhibit C1-r, and its relationship to decreased C4 synthesis remain to be defined.

A cationic region of the platelet-derived growth factor (PDGF) A-chain (Arg159-Lys160-Lys161) is required for receptor binding and mitogenic activity of the PDGF-AA homodimer.

Platelet-derived growth factor-AA and -BB homodimers and -AB heterodimers bind with high affinity to the platelet-derived growth factor (PDGF) alpha-receptor. Basic polypeptides such as polylysine and protamine sulfate compete with PDGF for receptor binding, suggesting a role for ligand positive charge in the binding interaction. A pentapeptide amino acid sequence with a cationic tripeptide core is perfectly conserved between the A- and B-chains (Val158-Arg159-Lys160-Lys161-Pro162) and was therefore considered as a possible alpha-receptor-binding domain. We have investigated the functional importance of positive charge within this region of the PDGF A-chain by using site-directed mutagenesis to convert the cationic core amino acids to the acidic sequence triglutamic acid. cDNAs encoding wild-type (PDGF-AAwt) and charge mutant (PDGF-AAcm) proteins were expressed following stable transfection of Chinese hamster ovary cells. Proper assembly and secretion of PDGF-AAcm was verified by metabolic labeling with [35S]cysteine, immunoprecipitation, and SDS-polyacrylamide gel electrophoresis analysis under nonreducing and reducing conditions. PDGF-AAcm was secreted as two major species of disulfide-linked A-chain homodimers identical in molecular mass to those observed for PDGF-AAwt (32 and 35 kDa). Secreted PDGF-AAwt and PDGF-AAcm proteins were purified to homogeneity and subjected to structural and functional analyses. Compared to purified PDGF-AAwt, PDGF-AAcm displayed a marked reduction in both binding affinity for PDGF alpha-receptors and mitogenic activity in Swiss 3T3 cells. Large reductions were also observed in the ability of semipurified PDGF-AAcm to stimulate calcium influx and the production of inositol phosphates. Measurement of circular dichroism spectra of highly purified PDGF-AAcm and PDGF-AAwt revealed no significant difference in secondary structure. Collectively, these results indicate that the cationic Arg159-Lys160-Lys161 region plays a critical role in the biological activity of PDGF-AA by direct participation in ligand binding to the PDGF alpha-receptor.

Mitogenic signals for platelet-derived growth factor isoforms in liver fat-storing cells.

Platelet-derived growth factor (PDGF), a key mitogen for liver fat-storing cells (FSC), is a dimeric molecule that occurs as homodimers or heterodimers of related polypeptide chains (PDGF-BB, -AB, and -AA). In chronic inflammation of the liver lobule, any of the three dimeric forms of PDGF derived from multiple sources could potentially interact with FSC. We explored the effects of the three different PDGF isoforms on DNA synthesis and early signal transduction pathways potentially related to PDGF mitogenicity in rat liver FSC. PDGF-BB homodimer and -AB heterodimer induced a marked increase in DNA synthesis, whereas the effect of PDGF-AA homodimer was considerably lower. Moreover, the mitogenicity of each isoform proportionally correlated with their effects on phosphoinositide turnover and intracellular Ca2+. Both the PDGF-BB and -AB dimers likely interact with the PDGF-beta-receptor, although PDGF-AB requires at least one alpha-receptor. The low responsiveness to PDGF-AA could not be accounted for by downregulation of the PDGF-alpha-receptor because FSC expressed very low levels of PDGF-A- and B-chain mRNAs and did not secrete detectable amounts of PDGF activity in the conditioned media. In addition, preincubation of FSC with suramin, a potent inhibitor of PDGF binding to its receptor, failed to increase PDGF-AA-induced DNA synthesis. These results are consistent with a predominant expression of PDGF-beta-receptor in liver FSC, that is linked to phospholipase C activation.

Endothelin stimulates PDGF secretion in cultured human mesangial cells.

Endothelin, a 17-DKa peptide originally described as a potent vasoconstrictor, also stimulates the release of important regulators of glomerular hemodynamics such as atrial natriuretic factor and renin. In the present study we investigated the role of endothelin in the release of another potent vasoconstrictor and mitogen of human mesangial cells, the platelet-derived growth factor. Endothelin stimulated PDGF release at 12 hours and the effect was sustained for 36 hours. This effect was associated with the enhanced induction of mRNAs encoding PDGF A- and B-chain. Endothelin also induced mitogenesis in human mesangial cells which was accompanied by activation of phospholipase C with increased inositol phosphate turnover. These data suggest a mechanism by which endothelin may regulate mesangial cell function in disease states.

Phosphatidic acid modulates DNA synthesis, phospholipase C, and platelet-derived growth factor mRNAs in cultured mesangial cells. Role of protein kinase C.

Increases in cell phosphatidic acid content occur in response to a wide variety of agonists, many of which have growth promoting properties. These changes have correlated with calcium flux, enzyme activation, gene induction, or cell proliferation. In the current studies we show that exogenous phosphatidic acid (PA) and phosphatidylserine stimulate phosphoinositide hydrolysis and DNA synthesis in cultured human renal mesangial cells. These phospholipids also induce mRNAs for platelet-derived growth factor (PDGF). The activation of phospholipase C by PA appears to be desensitized via protein kinase C as brief preincubation with phorbol ester abrogates the effect. PA-induced DNA synthesis is only partly mediated via protein kinase C as co-incubation with the inhibitor staurosporine blunts DNA synthesis by only one-third. In contrast, induction of PDGF A-chain mRNA is almost totally inhibited by staurosporine. We propose that changes in endogenous phospholipids such as PA or phosphatidylserine may serve as common signaling pathway for a variety of growth factors. Induction of PDGF proto-oncogenes via protein kinase C may represent one mechanism by which this cell activation occurs.

Immune complex activation of rat glomerular mesangial cells: dependence on the Fc region of antibody.

Glomerulonephritis is frequently associated with immunoglobulin deposition in the mesangium. We had previously shown that contractile, rat mesangial cells in culture synthesize superoxide anion after binding immune complexes (IC) in a manner dependent on the Fc region of immunoglobulin G (IgG). We now studied the effects of soluble IC on mesangial cell cytosolic free calcium ([Ca2+]i) and phosphatidylinositol turnover as putative mechanisms of transmembrane signaling as well as prostaglandin biosynthesis and contraction. IC (500 micrograms specific antibody) raised [Ca2+]i in mesangial cells loaded with fura-2 from resting levels of 100.4 +/- 8.0 to a peak of 282.3 +/- 31.5 nM in a dose-dependent manner. Removal of extracellular Ca2+ by ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid only slightly reduced peak, IC-stimulated [Ca2+]i to 236 +/- 18 nM but prevented the sustained phase of the response, indicating that IC both mobilized Ca2+ from intracellular stores and increased the influx of Ca2+ across the plasma membrane. IC did not increase water-soluble inositol phosphates, measured by anion-exchange chromatography of trichloroacetic acid-extracted cells but markedly stimulated PGE2 and thromboxane B2 synthesis in a dose- and time-dependent manner. Finally, IC (250 micrograms specific antibody) induced 45.8 +/- 10.1% of the cells to contract with an average decrease in cross-sectional surface area of 20.0 +/- 1.8% of basal as assessed by image-analysis microscopy. IC formed with F(ab')2 fragments of antibody and antigen or mixtures of antigen and nonimmune whole molecule antibody did not alter [Ca2+]i, induce prostaglandin synthesis, or stimulate mesangial cell contraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Mitogenic signals for thrombin in mesangial cells: regulation of phospholipase C and PDGF genes.

Thrombin is a proteolytic enzyme of diverse biological activities, which is produced during activation of the coagulation pathway. In addition, thrombin is a mitogen for fibroblasts and endothelial cells. Intraglomerular thrombosis and cell proliferation are common pathological features of several glomerular diseases. We studied the effect of thrombin on deoxyribonucleic acid (DNA) synthesis in cultured human mesangial cells and explored mechanisms of signal transduction involved. Bovine and human thrombin caused dose-dependent increases in DNA synthesis, inositol trisphosphate, and cytosolic calcium [(Ca2+)i]. A threefold increase in inositol-3-trisphosphate (IP3) levels was observed as early as 10 s after the addition of thrombin, whereas increases in (Ca2+)i occurred within 5-10 s and declined rapidly. Stimulation of mesangial cells by thrombin resulted in induction of messenger ribonucleic acids (mRNAs) encoding platelet-derived growth factor (PDGF) A- and B-chains. This was associated with an enhanced secretion of PDGF-like protein. These data provide mechanisms by which thrombin may regulate mesangial cell function in disease states.

Characterization of Ca2+ transport in rat renal brush-border membranes and its modulation by phosphatidic acid.

The Ca2+ transport process by isolated renal brush-border membranes was characterized and the influence of the acidic phospholipid phosphatidic acid (PtdA) on this transport process was assessed. Ca2+ uptake by brush-border membranes exhibited saturation kinetics. It was inhibitable by a variety of multivalent cations, as well as by Ca2+-entry inhibitors, including verapamil, Ruthenium Red and gentamicin. It was selective for Ca2+ compared with Mg2+. This process was also electrophoretic since generation of K+ and anion-diffusion potentials, negative inside the vesicle, increased Ca2+ uptake. Elevations in PtdA content of brush-border membranes by either exogenous addition or endogenous generation of PtdA by incubating brush-border membranes with MgATP2- elevated the rate of Ca2+ uptake. This ATP effect could not be attributed to (Ca2+ + Mg2+)-dependent ATPase or contaminating membrane fragments. PtdA also increased the magnitude and rate of Ca2+ efflux from brush-border membranes preloaded with Ca2+. These modulations in uptake and efflux were not observed with phosphatidylcholine or phosphatidylinositol. In summary, these results are consistent with the presence of an electrophoretic uniport system for Ca2+ in renal brush-border membranes, and demonstrate that PtdA uniquely among phospholipids tested appears to facilitate transmembrane flux of Ca2+ across this membrane preparation.

Alterations in renal cortical phospholipid content induced by gentamicin: time course, specificity, and subcellular localization.

Increasing evidence suggests that membrane phospholipids are a major site of interaction between gentamicin and renal tubular cells. To help assess the impact of this interaction on renal tubular cell phospholipid metabolism, renal cortical phospholipid levels were assessed serially during treatment with nephrotoxic doses of gentamicin in the rat. Within 15 h of treatment with a single 100 mg/kg dose of gentamicin, significant increases in phosphatidylinositol and phosphatidic acid occurred, and further increases in these acidic phospholipids were seen 24 h after two and four daily doses. No consistent sustained changes were observed in total phospholipid levels or in levels of other phospholipids. None of these gentamicin treatment regimens was associated with wide-spread tubular cell necrosis in the rat at the intervals studied. In contrast, during models of acute renal failure secondary to HgCl2 and glycerol, increases in phosphatidylinositol and phosphatidic acid were found only after the development of wide-spread tubular cell necrosis. Subcellular fractionation studies showed that the increase in phosphatidylinositol produced by gentamicin involved multiple cell membranes, including mitochondria, brush border membranes, endoplasmic reticulum, and lysosomes, suggesting that the effects of gentamicin on renal cortical acidic phospholipid metabolism are not limited to inhibition of intralysosomal degradative processes but, rather, occur in such fashion as to influence the phospholipid composition of multiple subcellular membranes.

Clinical and pathophysiologic aspects of aminoglycoside nephrotoxicity.

Aminoglycoside antibiotics continue to be a mainstay of therapy in the clinical management of gram negative infections, but a major factor in the clinical use of aminoglycosides is their nephrotoxicity. With gram negative organisms accounting for the majority of hospital acquired infections, the occurrence of aminoglycoside induced acute renal failure has become commonplace. Presently at least 10% of all cases of acute renal failure can be attributed to these antibiotics. This article will cover the renal handling of the aminoglycosides, the pathogenetic mechanisms of nephrotoxicity, and the clinical aspects of aminoglycoside induced acute renal failure with particular emphasis on recent data which have increased our understanding of the interaction of aminoglycosides with the renal tubular cell and the effects of this interaction on cellular function and integrity.