Renal transplantation relieves the symptoms but does not reverse beta 2-microglobulin amyloidosis

Uremic Toxicity: Present State of the Art

The uremic syndrome is a complex mixture of organ dysfunctions, which is attributed to the retention of a myriad of compounds that under normal condition are excreted by the healthy kidneys (uremic toxins). In the area of identification and characterization of uremic toxins and in the knowledge of their pathophysiologic importance, major steps forward have been made during recent years. The present article is a review of several of these steps, especially in the area of information about the compounds that could play a role in the development of cardiovascular complications. It is written by those members of the Uremic Toxins Group, which has been created by the European Society for Artificial Organs (ESAO). Each of the 16 authors has written a state of the art in his/her major area of interest.

Dialysis-related amyloidosis: challenges and solutions

Amyloidosis refers to the extracellular tissue deposition of fibrils composed of low-molecular-weight subunits of a variety of proteins. These deposits may result in a wide range of clinical manifestations depending upon their type, location, and the amount of deposition. Dialysis-related amyloidosis is a serious complication of long-term dialysis therapy and is characterized by the deposition of amyloid fibrils, principally composed of β2 microglobulins (β2M), in the osteoarticular structures and viscera. Most of the β2M is eliminated through glomerular filtration and subsequent reabsorption and catabolism by the proximal tubules. As a consequence, the serum levels of β2M are inversely related to the glomerular filtration rate; therefore, in end-stage renal disease patients, β2M levels increase up to 60-fold. Serum levels of β2M are also elevated in several pathological conditions such as chronic inflammation, liver disease, and above all, in renal dysfunction. Retention of amyloidogenic protein has been attributed to several factors including type of dialysis membrane, prolonged uremic state and/or decreased diuresis, advanced glycation end products, elevated levels of cytokines and dialysate. Dialysis treatment per se has been considered to be an inflammatory stimulus, inducing cytokine production (such as interleukin-1, tumor necrosis factor-α, interleukin-6) and complement activation. The released cytokines are thought to stimulate the synthesis and release of β2M by the macrophages and/or augment the expression of human leukocyte antigens (class I), increasing β2M expression. Residual renal function is probably the best determinant of β2M levels. Therefore, it has to be maintained as long as possible. In this article, we will focus our attention on the etiology of dialysis-related amyloidosis, its prevention, therapy, and future solutions.

Hematologic manifestations of kidney disease

Physiologically, there is an intimate link between the kidney and the blood. Many of the kidney diseases are the result of alteration in the blood such as dysproteinemia, microangiopathic hemolytic anemia (MAHA), hemolysis, etc. On the other hand, the kidney is the organ responsible for the regulation of hematopoiesis. Renal dysfunction can lead to both anemia and polycythemia. In addition, recent understanding of the MAHA process reveals that the renal microvasculature plays a key role in the pathogenesis. Finally, the failure of the kidney to clear toxins from the body can result in alteration involving hemostasis, as well as leukocyte function and survival.

The peptidic middle molecules: is molecular weight doing the trick?

Chronic kidney disease (CKD) is characterized by a gradual endogenous intoxication caused by the progressive accumulation of bioactive compounds that in normal conditions would be excreted and/or metabolized by the kidney. Uremic toxicity now is understood as one of the potential causes for the excess of cardiovascular disease and mortality observed in CKD. An important family of uremic toxins is that of the peptidic middle molecules, with a molecular weight ranging between 500 and 60,000 Da, which makes them, as a consequence, difficult to remove in the process of dialysis unless the dialyzer pore size is large enough. This review provides an overview of the main and best-characterized peptidic middle molecules and their role as potential culprits of the cardiometabolic complications inherent to CKD patients.

Benefit of doxycycline treatment on articular disability caused by dialysis related amyloidosis

Abstract Doxycycline inhibits amyloid formation in vitro and its therapeutic efficacy is under evaluation in clinical trials for different protein conformational diseases, including prion diseases, Alzheimer's disease and transthyretin amyloidosis. In patients on chronic hemodialysis, a persistently high concentration of β2-microglobulin causes a form of amyloidosis (dialysis-related amyloidosis, DRA) localized in bones and ligaments. Since doxycycline inhibits β2-microglobulin fibrillogenesis in vitro and accumulates in bones, DRA represents an ideal form of amyloidosis where doxycycline may reach a therapeutic concentration at the site of amyloid deposition. Three patients on long-term dialysis with severe articular impairment and uncontrollable pain due to DRA were treated with 100 mg of doxycycline daily. Pharmacokinetics and safety of treatment were conducted. Plasmatic levels of the drug reached a plateau after one week (1.1-2.3 µg/ml). Treatment was well tolerated in two patients for a year, while one was suspended after 5 months due to mild esophagitis. Treatment was associated with a significant reduction in articular pain and with a significant and measurable improvement in passive and active movements in all cases, despite the persistence of unchanged amyloid deposits measured by magnetic resonance imaging.

Serum β2-microglobulin at discharge predicts mortality and graft loss following kidney transplantation

Serum β(2)-microglobulin (β(2)M), a novel marker of kidney function, predicts mortality and kidney failure in the general population, and its elevation following transplantation is a marker of acute rejection. The association between post-transplant serum β(2)M and outcomes following kidney transplantation, however, is unknown. To help determine this, we conducted a retrospective cohort study of 2190 individuals receiving a primary kidney transplant with serum β(2)M measured at discharge. A total of 452 deaths and 347 graft failures before death (669 total graft losses) occurred over a median of 4.1 years of follow-up. After adjustment, the highest quintile of β(2)M (5.0 mg/l and above), compared with the lowest quintile (<2.3 mg/l), was associated with a hazard ratio of 4.6 (95% confidence interval 2.8, 7.5) for death, 4.1 (2.4, 7.0) for death-censored graft loss, and 3.8 (2.5, 5.6) for total graft loss. Serum β(2)M was more strongly associated with each outcome than was serum creatinine. Higher serum β(2)M at discharge was independently associated with each outcome in models stratified by the presence of delayed graft function, donor type, or estimated glomerular filtration rate at discharge. Thus, serum β(2)M at discharge is a potent predictor of long-term mortality and graft loss in kidney transplant recipients, providing information on allograft function beyond that of serum creatinine.

β(2)-microglobulin amyloidosis

Dialysis-related amyloidosis (DRA) is a clinical syndrome of pain, loss of function and other symptoms due to the deposition of amyloid consisting of β(2)-microglobulin (β(2)m) in the musculoskeletal system. The condition is seen in patients who suffer from chronic kidney disease and are treated with hemodialysis for a long time. Even though β(2)m easily can be manipulated to form amyloid in laboratory experiments under non-physiological conditions the precise mechanisms involved in the formation of β(2)m-amyloid in patients with DRA have been difficult to unravel. The current knowledge which is reviewed here indicates that conformational fluctuations centered around the D-strand, the DE-loop, and around the cis-configured Pro32 peptide bond are involved in β(2)m amyloidosis. Also required are highly increased concentrations of circulating β(2)m and possibly various post-translational modifications mediated by the pro-inflammatory environment in uremic blood, together with the influence of divalent metal ions (specifically Cu(2 +)), uremic toxins, and dialysis-enhanced redox-processes. It seems plausible that domain-swapped β(2)m dimers act as building blocks of β-spine cross-β -sheet fibrils consisting of otherwise globular, roughly natively folded protein. An activated complement system and cellular activation perpetuate these reactions which due to the affinity of β(2)m-amyloid for the collagen of synovial surfaces result in the DRA syndrome.

beta(2)-microglobulin: from physiology to amyloidosis

beta(2)-microglobulin (beta(2)m) is capable of forming amyloid in osteoarticular structures in kidney failure patients that undergo chronic hemodialysis treatment. Although sophisticated analytical methods have yielded comprehensive data about the conformation of the native protein both as a monomer and as the light chain of the type I major histocompatibility complex, the cause and mechanisms leading to the transformation of beta(2)m into amyloid deposits in patients with dialysis-related amyloidosis are unsettled. The impact on conformational stability of various truncations, cleavages, amino acid substitutions, and divalent cations, especially Cu(2+), however, are highly relevant for understanding beta(2)m unfolding pathways leading to amyloid formation. This review describes the current knowledge about such conformationally destabilizing and amyloidogenic factors and links these to the structure and function of beta(2)m in normal physiology and pathology. Tables listing modifications of beta(2)m found in amyloid from patients and a systematic overview of laboratory conditions conducive to beta(2)m-fibrillogenesis are also included.

Sonographic evaluation of entheseal sites of the lower extremity in patients undergoing hemodialysis

PURPOSE

To evaluate the entheseal sites of the lower extremities in patients on hemodialysis using the Glasgow Ultrasound Enthesitis Scoring System (GUESS) and to correlate the findings with the duration of hemodialysis and patient scores.

METHODS

Forty-nine patients who were on hemodialysis for at least 2 years were grouped according to duration of hemodialysis. Total GUESS scores; total enthesophyte, erosion, and bursitis scores; and tendon thicknesses were calculated, compared between groups, and correlated with duration of dialysis.

RESULTS

There was a statistically significant correlation between duration of hemodialysis and total GUESS score (p < 0.001, r = 0.81) and also between the total enthesophyte and erosion scores (p < 0.001). If severe enthesitis was defined as a total GUESS score of more than 18, receiver operating characteristic (ROC) curve analysis revealed that a cutoff point of 10 years for the duration of hemodialysis would predict severe enthesal damage with 83% sensitivity and 93% specificity (area under the ROC curve, 0.92; 95% confidence interval, 0.83-1.00).

CONCLUSION

Hemodialysis results in entheseal site changes that worsen with extended duration of hemodialysis, especially after 10 years.

Historical background and clinical treatment of dialysis-related amyloidosis

Dialysis-related amyloidosis (DRA) is a frequent and serious complication in patients on long-term dialysis. The amyloid has a marked affinity for joint tissues, and carpal tunnel syndrome, polyarthralgia, destructive spondyloarthropathy, and bone cysts are the major clinical manifestations of DRA. beta(2)-Microglobulin (beta(2)-m) was identified as the major protein constituent of the amyloid fibrils. Risk factors for the development of DRA include age, duration of dialysis treatment, use of low-flux dialysis membrane, use of low purity dialysate, monocyte chemoattractant protein-1 GG genotype, and apolipoprotein E4 allele, although the retention of beta(2)-m in the plasma appears to be prerequisite. Clinical therapeutic strategies for DRA include dialysis, medical or surgical therapy, and renal transplantation. Preventive measures have attempted to remove beta(2)-m from the serum by using high-flux membranes and a beta(2)-m adsorption column in hemodialysis. Renal transplantation is a radical approach to treating the arthralgias attributed to the amyloid deposits while the regression of dialysi-related amyloid deposits is not identified after successful renal transplantation in many studies. It is necessary to elucidate the pathogenesis of DRA and to establish more effective prevention and therapy in the future.

Neurological complications in renal failure: a review

Neurological complications whether due to the uremic state or its treatment, contribute largely to the morbidity and mortality in patients with renal failure. Despite continuous therapeutic advances, many neurological complications of uremia, like uremic encephalopathy, atherosclerosis, neuropathy and myopathy fail to fully respond to dialysis. Moreover, dialytic therapy or kidney transplantation may even induce neurological complications. Dialysis can directly or indirectly be associated with dialysis dementia, dysequilibrium syndrome, aggravation of atherosclerosis, cerebrovascular accidents due to ultrafiltration-related arterial hypotension, hypertensive encephalopathy, Wernicke's encephalopathy, hemorrhagic stroke, subdural hematoma, osmotic myelinolysis, opportunistic infections, intracranial hypertension and mononeuropathy. Renal transplantation itself can give rise to acute femoral neuropathy, rejection encephalopathy and neuropathy in graft versus host disease. The use of immunosuppressive drugs after renal transplantation can cause encephalopathy, movement disorders, opportunistic infections, neoplasms, myopathy and progression of atherosclerosis. We address the clinical, pathophysiological and therapeutical aspects of both central and peripheral nervous system complications in uremia.

Beta-2 microglobulin in ESRD: an in-depth review

Beta-2 microglobulin is the most widely studied low-molecular-weight protein in end-stage renal disease. It is known to cause dialysis-related amyloidosis (DRA), by virtue of its retention when renal function fails, its deposition in tissues, its aggregation into fibrils, and its ability to become glycosylated. The onset of DRA may be protracted by the use of noncellulosic membranes, especially when high-volume hemodiafiltration is used in the treatment of renal failure. Adsorptive methods have been developed to improve the removal of beta-2 microglobulin. There seems to be a relative risk reduction in mortality when patients are treated with dialysis membranes that have a higher clearance of beta-2 microglobulin.

Bone disease after renal transplantation

Bone disease is common after renal transplantation. The main syndromes are bone loss with a consequent fracture rate of 3% per year, osteonecrosis of the hip, and bone pain. The causes of disease include preexisting uremic osteodystrophy (hyperparathyroidism, aluminum osteomalacia, beta2-associated amyloidosis, and diabetic osteopathy), postoperative glucocorticoid therapy, poor renal function, and ongoing hyperparathyroidism, as the result of either autonomous transformation of the parathyroid gland or ongoing physiologic stimuli. Cyclosporine A treatment, hyperphosphaturia, and a pathogenic vitamin D allele have also been implicated. Bone loss is particularly pronounced during the first year after operation, amounting to up to 9% of bone mass. The clinical and biochemical picture is consistent with a high turnover bone disease, but histomorphometric studies do not completely support this. Principal prophylactic options include preoperative osteodystrophy prophylaxis; postoperative calcium, vitamin D, or calcitriol therapy; estrogen therapy for postmenopausal women; and parathyroidectomy for medically intractable hyperparathyroidism. Recently, prophylactic biphosphonate treatment has shown promise, but the exact indications for treatment remain to be determined.

Dialysis-related amyloidosis after renal transplantation

There is no effective therapy for dialysis-related amyloidosis (DRA). The restoration of renal function with a functional graft seems the most reasonable therapy for this disturbing disease. Although there are not many prospective series on the efficacy of renal transplantation for DRA, all the studies agree that most of the patients experienced a significantly clinical improvement of the articular symptoms after a successful renal transplantation. Nevertheless, radiologic (bone cysts) and histologic lesions did not disappear after long-term follow-up.

beta2-microglobulin-derived amyloidosis: an update

The present review attempts to summarize recent developments in the field of beta2-microglobulin-derived amyloidosis (A(beta2)m amyloidosis) in patients on chronic dialysis therapy. A key factor in the pathogenesis is the uremic retention of the precursor molecule, beta2-microglobulin (beta2m). However, secondary modifications of the molecule such as limited proteolysis, conformational changes, and the formation of advanced glycation end products have also been described. Finally, in order to explain the striking predilection of the disease for synovial and periarticular structures, a role of local predisposing factors within the synovial membrane (for example, of the particular constituents of the extracellular matrix) must also be postulated. With respect to clinical symptomatology, recent data have confirmed that clinically manifest signs of the amyloidosis represent only the tip of the iceberg, since histologically amyloid deposition is much more widespread. Noninvasive diagnosing of the disease has been advanced by technical changes of the beta2m scintigraphy. Finally, there is accumulating evidence that prevention of the disease not only includes the usage of high-flux synthetic membranes for hemodialysis or hemodiafiltration, but that other factors contribute to the clinical manifestations of amyloidosis such as the dialysate composition and its microbacteriological quality. Such factors, which have changed over the last years as part of general improvements in dialysis care, may explain why the prevalence of the amyloidosis appears to decrease.

Osteoarticular disorders of renal origin: disease-related and iatrogenic

Osteoarticular disorders significantly limit the quality of long-term survival with chronic renal failure. beta 2M amyloidosis is a complication of chronic renal failure that has been recognized mostly in patients receiving long-term haemodialysis. Patients with beta 2M amyloidosis typically present with the triad of shoulder periarthritis, carpal tunnel syndrome, and flexor tenosynovitis of the hands. Other musculoskeletal manifestations of beta 2M amyloidosis include destructive spondyloarthropathy, cervico-occipital pseudotumours, bone cysts, and pathological fractures. At present, only renal transplantation may slow or halt the progession of beta 2M amyloidosis. Crystal-induced arthropathy, most commonly caused by basic calcium phosphate crystals, is an important cause of acute joint inflammation in the patient with renal failure. The incidence of bone and joint infection is increased in patients undergoing dialysis. Haemodialysis and peritoneal dialysis are also associated with an erosive or destructive arthropathy of finger joints, which is not explained by local amyloid deposition.

beta2-microglobulin induces MMP-1 but not TIMP-1 expression in human synovial fibroblasts

BACKGROUND

beta2-Microglobulin (beta2m) amyloidosis is a destructive articular disease that causes significant morbidity in patients undergoing hemodialysis. The amyloid deposits contain beta2m, some of which is altered with advanced glycation end products (AGE-beta2m). The deposits are located principally in joint structures, with adjacent degradation of cartilage and bone. We hypothesized that one of the mechanisms by which beta2m induces joint destruction is to induce the release of matrix metalloproteinase-1 (MMP-1), but not tissue inhibitor of metalloproteinase-1 (TIMP-1), from synovial fibroblasts.

METHODS

To test this hypothesis and determine the role of AGE-beta2m, we incubated human osteoarthritic synovial fibroblasts in the presence and absence of beta2m and AGE-beta2m and measured the release of interstitial collagenase (MMP-1) and/or TIMP-1 by enzyme-linked immunosorbent assay and Northern blot analysis.

RESULTS

beta2m and AGE-beta2m at 10 and 25 microg/mL induced the release of MMP-1 from human osteoarthritic synovial fibroblasts at 24 hours. In contrast, there was no increased release of TIMP-1, leading to an increase in the MMP-1/TIMP-1 ratio indicative of uncontrolled collagenolysis. A similar dose response was observed at 48 hours, except that AGE-beta2m had no effect over control cultures. MMP-1 mRNA expression by Northern blot analysis paralleled these findings. The source of the fibroblasts did not alter the results. Finally, we demonstrated that doxycycline, a treatment for arthritis, can inhibit the release of MMP-1 from synovial fibroblasts incubated with beta2m.

CONCLUSION

beta2m, at physiologically relevant concentrations, induces the release of MMP-1 without concomitant release of TIMP-1 from human synovial fibroblasts, leading to uncontrolled collagenolysis. The alteration of beta2m with AGE did not alter this effect at 24 hours, but blocked the effect at 48 hours. These findings may account for the tissue destruction seen in beta2m amyloidosis.

Symptomatic carpal tunnel syndrome after orthotopic liver transplantation: a retrospective analysis

BACKGROUND

Carpal tunnel syndrome (CTS) is an entrapment neuropathy of the median nerve and has been reported after renal transplantation; there are no reports of CTS after liver transplantation.

METHODS

The incidence of and the risk factors for CTS were assessed in 1350 liver allograft recipients.

RESULTS

Seventeen women and two men with CTS were identified. Women developed symptoms at a median time of 6.8 months, and all but one received transplants because of primary biliary cirrhosis (PBC). All 17 patients were taking cyclosporine. The only risk factor for CTS was the pretransplant diagnosis of PBC (6.7% of 240 PBC patients surviving 6 months or more compared with 0.4% of 717 patients who received grafts for other indications).

CONCLUSIONS

CTS may occur in patients early after liver transplantation; because in many cases the symptoms were attributed to cyclosporine neurotoxicity, the diagnosis should be considered, especially in patients who received grafts because of PBC.