Reactive (secondary) amyloidosis and its pathogenesis

Renal amyloidosis in dogs: a retrospective study of 91 cases with comparison of the disease between Shar-Pei and non-Shar-Pei dogs

BACKGROUND

Renal amyloidosis (RA) is a progressive and fatal renal disease.

HYPOTHESIS

Clinical and pathologic manifestations of RA differ between Chinese Shar-Pei (CSPs) and non-Shar-Pei (NSPs) dogs.

ANIMALS

91 client-owned dogs.

METHODS

Retrospective review of medical records of dogs with a histological diagnosis of RA. Clinical and clinicopathologic data, hospitalization, complications, and outcome were compared between CSPs and NSPs.

RESULTS

Comorbid diseases were present in 64% of all dogs. CSPs were significantly younger compared to NSPs (median, 4.8 years; range: 3.6-17 versus median: 9.0 years; range: 2.4-11.1; P < .0001). The frequency of hypoalbuminemia, the most common biochemical abnormality, was higher in NSPs compared to CSPs (100% versus 64.7%, respectively; P < .001). Median serum creatinine concentration at presentation was 5.5 mg/dL, and was 3-fold higher in CSPs compared to NSPs (P = .005). Increased urine protein : creatinine ratio was present in 96% of all dogs. Nephrotic syndrome was present in 10% of NSPs but not in CSPs. Glomerular amyloid deposition, present in both CSPs (78.6%) and NSPs (95.6%) was most commonly diffuse, global, and severe. Renal medullar amyloidosis was more common in CSPs (100%) compared to NSPs (49.0%, P = .002), as was extrarenal amyloid deposition. The median survival time of all dogs was 5 days (range: 0-443 days). Serum creatinine concentration was significantly and negatively associated with survival (P = .025).

CONCLUSIONS AND CLINICAL RELEVANCE

The clinical and pathologic manifestations of amyloidosis differ between CSPs and NSPs. The survival time observed herein was unexpectedly low, and argues for early surveillance and management of the underlying predisposing conditions.

The putative role of alpha-1-antitrypsin in the disaggregation of amyloid lambda fibrils

BACKGROUND AND OBJECTIVES

Interactions between hydrophobic compounds like cholesterol and lithocholic acid and alpha-1-antitrypsin (alpha-1-AT) have previously been described. We studied the putative interaction between alpha-1-AT and the insoluble, hydrophobic, beta-pleated sheet, light-chain-derived fibrils that predominate the tissue deposits in primary immunocytic (AL) related amyloidosis.

SUBJECTS AND METHODS

Amyloid fibrils were isolated from two cases with lambda and two cases with kappa AL amyloidosis.

RESULTS

The lambda fibrils could be completely disaggregated (as shown by light and electron microscopy and Congo red uptake) by alpha-1-AT added in the molar ratio 1:5, whereas fibrils with predominantly kappa chains remained unaffected. The lambda-chain interaction was accompanied by characteristic changes of the physicochemical and biological properties of alpha-1-AT apparent in an increased thermal stability and loss of elastase-inhibitory activity. These findings are compatible with a transition of alpha-1-AT from a native, stressed conformation to a relaxed form.

CONCLUSIONS

Disaggregation of lambda AL amyloid fibrils can be achieved by addition of alpha-1-AT. The findings may have therapeutic implications in primary amyloidosis.

beta 2-Microglobulin amyloidosis. A systemic amyloid disease affecting primarily synovium and bone in long-term dialysis patients

A number of rheumatic disorders occur in patients on long-term hemodialysis treatment. In recent years a clinical syndrome comprising carpal tunnel syndrome, destructive arthropathy, and cystic bone lesions has been recognized in these patients. Congo-red staining and microscopy in polarized light reveal a high frequency of amyloid in the affected tissues. Amino acid sequence data of the isolated major amyloid fibril protein show its identity with beta 2-microglobulin. beta 2-microglobulin amyloid has a predilection for synovial tissues and bone, but visceral deposits may also occur indicating the systemic nature of the disease. The clinicopathological features, pathogenesis, and diagnosis of beta 2-microglobulin amyloidosis are reviewed, and the therapeutic and prophylactic measures discussed. The identification of beta 2-microglobulin as an amyloidogenic protein has in an important way contributed to the understanding of the mechanisms of amyloidogenesis in general and emphasized the complexity of amyloid disease and the diversity of proteins capable of forming congophilic fibrillar deposits in human tissues.

Amyloid in central nervous system disease

A review is presented of diseases of the central nervous system associated with amyloid deposition. The name amyloid is given to substances with particular physical characteristics which are independent of the chemical constitution of the proteins in the substance. Ideally, a classification of amyloid diseases should be based on the chemical composition of the amyloid deposits; this has only been partially realized. The best documented group of diseases with amyloid deposition in the central nervous system is the group of 'cerebral beta amyloid diseases', characterized by the deposition of beta-protein. This group includes: Alzheimer's disease, sporadic cerebral amyloid angiopathy, Down's syndrome, Parkinson-dementia of Guam, hereditary cerebral hemorrhage with amyloidosis-Dutch type and age-related asymptomatic amyloid angiopathy.

The pathogenesis of reactive systemic amyloidosis

The diagnosis of amyloidosis is based on the presence of extracellular tissue deposits of proteinaceous material that demonstrate a characteristic green color when stained with Congo red and viewed under polarized light. Several different proteins are amyloidogenic but, in domestic animals, spontaneously occurring systemic amyloidosis is reactive in nature and characterized by the presence of amyloid protein AA. This type of systemic amyloidosis may occur secondary to chronic inflammatory or neoplastic disease, but in many instances no predisposing disease is found. A sustained increase in the serum concentration of serum amyloid A protein (SAA) is necessary but not sufficient for the development of reactive amyloidosis. Other inherited and acquired host-related factors are likely to be important in the development of reactive amyloidosis because this condition develops in few patients with chronic inflammatory disease. The tissue tropism of amyloid deposits varies with the amyloid protein itself and species affected. The consequences of amyloidosis for the host depend upon the tissues involved and the response of these tissues to the presence of the amyloid deposits. In domestic animals, reactive systemic amyloidosis is nephropathic, leading to end-stage renal disease, and the clinical presentation is that of uremia.

Urinary protein excretion patterns in reactive (secondary) systemic amyloidosis

The urinary excretion of immunoglobulin light chains kappa and lambda, immunoglobulin G, transferrin, and beta-2-microglobulin was studied in 21 patients with nonimmunoglobulin-related amyloid nephropathy (secondary, type AA) associated with rheumatic disease and in 39 patients with glomerulopathy of nonamyloid origin, as well as in 22 patients with rheumatic disease without signs of nephropathy and in 15 healthy subjects. Patients with amyloidosis were found to have a higher ratio of excreted lambda/kappa light chains than patients with diabetic nephropathy or chronic glomerulonephritis. The increased lambda/kappa ratio was not dependent on the grade of proteinuria and was evident in patients with mild as well as heavy proteinuria. The ratio of lambda/kappa light chains in serum of patients with amyloidosis did not differ from that in healthy controls. The results suggest that amyloid deposition in the kidneys is associated with a selective alternation of the immunoglobulin light chain excretion in the urine.

Class-specific rheumatoid factors, DR antigens, and amyloidosis in patients with rheumatoid arthritis

Class-specific rheumatoid factors (RFs) were measured by enzyme immunoassay in 59 patients with rheumatoid arthritis complicated by systemic amyloidosis (RA+A), 47 patients with rheumatoid arthritis without amyloid (RA), 106 patients with other rheumatic diseases (juvenile rheumatoid arthritis, systemic lupus erythematosus, Sjögren's syndrome), and 55 blood donors. The patients with RA+A were characterised by a high prevalence of RF negativity; the IgM RF concentration was raised in only 18 of the 59 patients (31%, p less than 0.001 v RA), the IgG RF concentration in 20 of 59 (34%, p less than 0.001 v RA), and the IgA RF concentration in 24 of 59 (41%, p less than 0.001 v RA). A higher prevalence of HLA-DR4 (p less than 0.001) and a lower prevalence of DR2 (p less than 0.05) were found among 48 tested patients with RA+A when compared with a control panel consisting of 500 blood donors. No significant differences in the prevalence of DR1-DR7 or B27 antigens were observed, however, between patients with RA with or without amyloid.

Antibodies to amyloid A protein in rheumatic diseases

Circulating autoantibodies against amyloid A protein (AA) were demonstrated by enzyme immunoassay in 18/62 patients with rheumatoid arthritis (RA) and in 9/27 patients with systemic lupus erythematosus (SLE). In the subset of RA patients who had developed amyloid, the frequency of antibodies to AA was lower than in those without amyloid (P less than 0.05). The antibody levels showed some variation in serial serum samples during follow-up (1-4 years) of patients with amyloidosis or SLE, but did not correlate with disease activity. In contrast to the patients with rheumatic diseases, patients with inflammatory bowel disease and acute bacterial peritonitis had antibody levels within the range of the healthy control subjects. The results show that autoantibodies to protein AA may occur in rheumatic diseases; their occurrence does not, however, identify subjects with tissue amyloid deposits. Absorption experiments suggest that the antibodies may be directed to circulating amyloid A protein.

Amyloidosis

Recent studies have provided new insight into the pathogenesis of amyloidosis and have broadened our knowledge of the mechanisms of deposition and resolution of amyloid. In particular, the structure, synthesis and plasma clearance of the inflammation-associated amyloid precursor, SAA, have been extensively studied and the precursor-product relationship between circulating SAA, protein AA and fibrillar amyloid A clarified. Information has been accumulating about the enzymatic processes involved in the cleavage of SAA and the degradation of protein AA and a new view has been presented on the possible role of amyloid P component in AA amyloidogenesis. The current model of AA pathogenesis emphasizes the dynamic character of amyloid.

Serum amyloid A protein, albumin and prealbumin in Alzheimer's disease and in demented patients with Down's syndrome

The concentrations of serum amyloid A (SAA) protein, albumin and prealbumin were measured in 22 patients with Alzheimer's disease (AD), in 21 demented patients with Down's syndrome (DS), and in age-matched control subjects for both groups in a 2-year follow-up study. The concentration of SAA was initially elevated in 9 of 22 (41%) patients with AD and in 8 of 21 (38%) patients with DS. After 2-years, 10 of 12 (83%) AD patients and 11 of 14 (79%) DS patients had elevated SAA levels but with fluctuation of the values. None of the controls revealed increase in the SAA level. The concentration of SAA did not correlate with the duration of AD or AD-like process although the highest values were found in cachectic AD patients confined to bed. Although neoplasm or infection were not diagnosed, the presence of occult neoplasm or subclinical infection as a cause of SAA elevation, especially in the DS group susceptible to infection, could not be excluded. Moreover, the fluctuation of SAA values in DS seems likely to be associated with an infection. Albumin and prealbumin levels were decreased in both AD and DS; the prealbumin levels in AD was lower than that in DS.