Local synthesis of amyloid fibril precursor in AL amyloidosis of the urinary tract

Amyloidosis and the lung

Amyloidosis is a disorder of protein folding in which normally soluble plasma proteins aggregate in an abnormal fibrillar form causing progressive disruption to tissue structure and organ function. This review covers systemic AA and AL amyloidosis which may arise as a consequence of chronic respiratory conditions; the manifestations of both systemic and of localised amyloid deposition within the respiratory tract and provides a summary of current approaches to diagnosis and management.

Localized amyloidosis of the genitourinary tract: report of 5 new cases and review of the literature

Primary localized amyloidosis of the genitourinary tract is a rare entity characterized by small pseudotumors localized in the renal pelvis, ureters, or bladder. Amyloid fibrils are derived from immunoglobulin light chains, but no systemic plasma cell proliferation is detected. The clinical and radiologic features mimic urinary tract cancer, and local treatment is indicated. The prognosis is excellent in most cases, although disease recurrence is possible. We report 5 new cases of localized amyloidosis of the urinary tract, with lambda (4/5), or kappa (1/5) chain amyloid protein, involving the bladder (5/5), and the ureter and renal pelvis (1/5), with multiple, bilateral lesions in 1 case. The presenting complaint was painless hematuria in 4 cases. All cases were of primary (AL)-type amyloidosis. All patients underwent extensive investigation, and none presented any signs of generalized amyloidosis. A favorable outcome was observed in every case. We performed a comprehensive review of the literature, and summarize the data.

The systemic amyloidoses: clearer understanding of the molecular mechanisms offers hope for more effective therapies

Knowledge about the systemic amyloidoses has increased considerably during the last few years. This group of diseases is characterized by great biochemical variability, including at least 11 different amyloid fibril proteins and a remarkable range of clinical manifestations. With the understanding that the pathogenesis is different in the various forms of amyloidosis, it is now being increasingly accepted that an early and accurate diagnosis, including that of the underlying biochemical nature, is crucial for a successful treatment. The elucidation of the molecular mechanisms involved in amyloidogenesis is at the basis of the recent blossoming of new, innovative and more effective therapeutic approaches.

Light chain amyloidosis of the urinary bladder. A site restricted deposition of an externally produced immunoglobulin

AIMS

To identify the amyloid protein in a patient with amyloidosis localised to the urinary bladder, and to see whether subtyping of the protein by sequence analysis increases the understanding of the selection of the urinary bladder as the site of amyloid deposition.

METHODS

A patient with gross haematuria and a congophilic mass in his urinary bladder was evaluated further. Characterisation of the amyloid protein was performed using conventional histological and immunohistochemical methods. Determination of the N-terminal amino acid sequence of the amyloid protein was performed using protein sequencers.

RESULTS

The patient's history, physical examination, and laboratory evaluation excluded the involvement of other organs, justifying a diagnosis of amyloidosis localised to the urinary bladder. Histological and immunological studies showed that the amyloid protein deposited in the urinary bladder of the patient was probably of the amyloid light chain type. No plasma cells or lymphocytes were seen in sections of the urinary bladder and lower ureter adjacent to the amyloid deposits. Molecular analysis showed the sequence NFMLTQPHSISGSPG, which assigned the amyloid protein to either the Vlambda(I) or the Vlambda(VI) immunoglobulin (Ig) light chain families.

CONCLUSIONS

The findings suggest that the amyloid protein in this patient originated outside the urinary bladder. The heterogeneity of the Ig proteins in known cases of amyloidosis of the lower urinary tract suggests that the amino acid residues, which determine the Vlambda subtyping, have no major role in restricting the deposited protein to the urinary bladder.

Useful polyclonal antibodies against synthetic peptides corresponding to immunoglobulin light chain constant region for immunohistochemical detection of immunoglobulin light chain amyloidosis

For the immunohistochemical detection of immunoglobulin (Ig) light chain amyloidosis on formalin-fixed, paraffin-embedded tissue sections, we prepared polyclonal antibodies against synthetic peptides corresponding to positions 118-134 of Ig lambda light chain and positions 116-133 of Ig kappa light chain. Nineteen cases of systemic Ig lambda light chain amyloidosis (Alambda amyloidosis), 10 cases of systemic Ig kappa light chain amyloidosis (Akappa amyloidosis), one case of immunohistochemically unclassified systemic amyloidosis and five cases of localized Alambda amyloidosis were tested with these antibodies. Anti-lambda (118-134) antiserum and the affinity-purified antibody both reacted with 18 of the 19 cases of systemic Alambda amyloidosis and all cases of localized Alambda amyloidosis, although the immunoexpression was somewhat variable in intensity in different areas within the same specimen in both systemic and localized amyloidosis. The signal intensities in plasma cells and serum reacted for anti-lambda (118-134) antiserum were weaker than signals obtained with commercially available anti-Ig lambda light chain antibodies. Anti-kappa (116-133) antiserum and the affinity-purified antibody reacted with nine of the 10 cases of systemic Akappa amyloidosis. We conclude that these antibodies against synthetic peptides corresponding to the Ig light chain constant region are useful for the classification of amyloidosis on formalin-fixed, paraffin-embedded tissue sections.

Primary localized amyloidosis of the urinary bladder: a case series of 31 patients

OBJECTIVE

To evaluate the presentation and prognosis of primary localized amyloidosis of the urinary bladder.

PATIENTS AND METHODS

The medical records of 31 patients with primary localized amyloidosis of the urinary bladder were reviewed. Immunohistochemical amyloid typing was performed on bladder biopsy specimens from 27 patients.

RESULTS

The median age of the 22 men and 9 women was 55 years. Twenty-four patients (77%) presented with gross hematuria (associated with irritative urinary tract symptoms in 6 patients), and 7 (23%) had only irritative lower urinary tract symptoms. Multiple bladder areas were involved in 20 patients (65%), a single area was involved in 8 (26%), and diffuse involvement was present in 3 (10%). Twenty-four patients had immunoglobulin light chain, and 3 had transthyretin-related amyloid. Local recurrences were common. None of the patients developed systemic amyloidosis.

CONCLUSION

Primary localized amyloidosis of the urinary bladder can be easily confused with a neoplasm. Immunohistochemical amyloid typing is important. Transthyretin-related amyloid of the bladder requires no further work-up. Repeated work-ups for systemic amyloidosis are unnecessary for patients with light chain-related amyloidosis of the urinary bladder. Early eradication with fulguration or laser therapy is indicated. Cystoscopic follow-up is necessary.

Analysis of plasma cell clonality in localized AL amyloidosis

AL amyloidosis is characterized by fibrillar tissue deposits composed of monoclonal immunoglobulin light chains(IgLs). It has been speculated that clonal expansion of plasma cells may occur locally and produce amyloidogenic IgLs. Both immunohistochemistry and molecular genetics are useful for examining plasma cell clonality from paraffin-embedded tissue sections, which are easy to obtain. We evaluated plasma cell clonality in 16 biopsy cases of localized AL amyloidosis using these two methods. A clonal excess of plasma cells was detected in 6 (37.5%) cases immunohistochemically, in 10 (62.5%) cases molecularly, and in 13 (81.3%) cases by at least one of the two methods. These results support local synthesis of the light chain proteins in localized AL amyloidosis.

Tracheobronchial amyloidosis. The Boston University experience from 1984 to 1999

Tracheobronchial amyloidosis (TBA), an idiopathic disorder characterized by deposition of fibrillar proteins in the tracheobronchial tree, occurred in 10 patients referred to the Amyloid Program at Boston University over the past 15 years. Fewer than 100 cases of TBA have been described; only 1 series encompassed more than 3 patients. We analyzed our experience with biopsy-proven TBA to define better its natural history. Follow-up averaged approximately 8 years and was obtained in all cases, making this outcome reporting the largest and most complete to date. Three of these patients were prospectively studied for up to 24 months to examine the utility of bronchoscopy, computerized tomography (CT) imaging, and pulmonary function tests (PFTs) in monitoring disease progression. No patient with TBA developed signs or symptoms of systemic amyloidosis during the period reviewed. Conversely, tracheobronchial disease was not diagnosed in 685 patients with primary systemic (AL) amyloidosis during the 15-year study period at Boston University. Bronchoscopy proved most useful in establishing the diagnosis by biopsy. Narrowing of major airways limited its inspection of the tracheobronchial tree, however. In contrast, CT imaging provided quantitative assessment of airway narrowing and mural thickening--2 major consequences of amyloid infiltration. These CT features, in the presence of mural calcifications sparing the posterior tracheal membrane, have been reported in few disorders other than TBA. The ability of CT to map airway involvement and identify extraluminal manifestations of TBA made it the study of choice for establishing disease extent. Three patterns of disease were evident by CT imaging and bronchoscopic examination: proximal, mid, and distal airways involvement. Those with severe proximal disease had significantly decreased air flows, air trapping, and fixed upper airway obstruction on PFTs. Patients with distal disease had normal airflows. PFTs could not clearly distinguish proximal from severe mid airways disease. Thirty percent of patients died within 7-12 years after diagnosis, all having proximal or severe mid airways disease. Repeated rigid bronchoscopic debridement and laser treatments did not prevent progressive airways narrowing in patients dying from TBA. Most patients with mid airways involvement, and all distal airway cases, had either stagnant disease or slowly increasing amyloid deposits when followed for up to 14 years. In a small subset of patients followed prospectively, serial PFTs were most sensitive to disease progression. CT-derived measures of airway lumen diameter and wall thickness did not change significantly despite marked improvements in airflow after rigid bronchoscopy. Our experience suggests that serial PFTs and CT imaging together offer the best assessment of airway involvement and disease progression in patients with TBA. In the future, radiation therapy may provide more definitive treatment of TBA than debulking procedure have to date.

What is the role of giant cells in AL-amyloidosis?

AL-amyloidosis is one of the most common amyloidoses and can be found in a localized and a systemic form. The precursor protein is an immunoglobulin light chain which as AL-protein in both localized and systemic AL-amyloidosis shows the same pattern of fragmentation and changes of primary structure. In this work it is shown that that there is a difference between localized and systemic amyloidosis in respect to accompanying giant cells which constantly are found associated with amyloid deposits in localized AL-amyloidosis. In addition, giant cells were found together with amyloid deposits in lymph nodes of some cases of systemic AL-amyloidosis. Based on these findings and electron microscopic studies, it is discussed whether the giant cells actively participate in amyloid fibril formation by uptake and modification of the precursor protein or the giant cells are part of a foreign body reaction. Included in this work are two new cases of localized lung (lambda I) and ureteric (kappa I) AL-amyloidosis.

Organ-Specific (Localized) Synthesis of Ig Light Chain Amyloid

Ig amyloidosis is usually a systemic disease with multisystem involvement. However, in a significant number of cases amyloid deposition is limited to one specific organ. It has not been determined if the Ig light chain (LC) amyloid precursor protein in localized amyloidosis is synthesized by circulating plasma cells with targeting of the amyloid fibril-forming process to one specific organ, or whether the synthesis of Ig LC and fibril formation occurs entirely as a localized process. In the present study local synthesis of an amyloid fibril precursor LC was investigated. Amyloid fibrils were isolated from a ureter that was obstructed by extensive infiltration of the wall with amyloid. Amino acid sequence analysis of the isolated fibril subunit protein proved it to be derived from a λII Ig LC. Plasma cells within the lesion stained positively with labeled anti-λ Ab and by in situ hybridization using an oligonucleotide probe specific for λ-LC mRNA. RT-PCR of mRNA extracted from the tumor and direct DNA sequencing gave the nucleotide sequence coding specifically for the λII amyloid subunit protein, thus confirming local synthesis of the LC protein.

A novel apolipoprotein A-1 variant, Arg173Pro, associated with cardiac and cutaneous amyloidosis

An American kindred was found to have hereditary amyloidosis with cutaneous and cardiac involvement. Characterization of fibrils isolated from skin identified the amyloid protein as the N-terminal 90 to 100 residues of apolipoprotein A-1. Sequence of the apolipoprotein A-1 gene was normal except for a G/C transversion at position 1638 which predicts an Arg to Pro substitution at residue 173. This mutation, unlike previously described amyloidogenic mutations is not in the N-terminal fragment which is incorporated into the fibril. The mutation is at the same residue as in apolipoprotein A-1 Milano (Arg173Cys) which does not result in amyloid formation. Decreased plasma HDL cholesterol levels in carriers of the Arg173Pro mutation suggest an increased rate of catabolism as has been shown for the amyloidogenic Gly26Arg mutation. This suggests that altered metabolism caused by the mutation may be a significant factor in apolipoprotein A-1 fibrillogenesis.

Hereditary amyloid cardiomyopathy caused by a variant apolipoprotein A1

Autosomal dominant hereditary amyloidosis with a unique cutaneous and cardiac presentation and death from heart failure by the sixth or seventh decade was found to be associated with a previously unreported point mutation (thymine to cytosine, nt 1389) in exon 4 of the apolipoprotein A1 (apoA1) gene. The predicted substitution of proline for leucine at amino acid position 90 was confirmed by structural analysis of amyloid protein isolated from cardiac deposits of amyloid. The subunit protein is composed exclusively of NH2-terminal fragments of the variant apoA1 with the longest ending at residue 94 in the wild-type sequence. Amyloid fibrils derived from four previously described apoA1 variants are composed of similar fragments with carboxyl-terminal heterogeneity, but contrary to those variants, which all carry one extra positive charge, the substitution Leu90Pro does not result in any charge modification. It is unlikely, therefore, that amyloid fibril formation is related to change of charge for a specific residue of the precursor protein. This is in agreement with studies on transthyretin amyloidosis in which no unifying factor such as change of charge for amino acid residues has been noted.