Cell assay for the identification of amyloid inhibitors in systemic AA amyloidosis

Deactivation of the Unfolded Protein Response Aggravated Renal AA Amyloidosis in HSF1 Deficiency Mice

Systemic amyloid A (AA) amyloidosis, which is considered the second most common form of systemic amyloidosis usually takes place several years prior to the occurrence of chronic inflammation, generally involving the kidney. Activated HSF1, which alleviated unfolded protein response (UPR) or enhanced HSR, is the potential therapeutic target of many diseases. However, the effect of HSF1 on AA amyloidosis remains unclear. This study focused on evaluating effect of HSF1 on AA amyloidosis based on HSF1 knockout mice. As a result, aggravated amyloid deposits and renal dysfunction have been found in HSF1 knockout mice. In progressive AA amyloidosis, HSF1 deficiency enhances serum amyloid A production might to lead to severe AA amyloid deposition in mice, which may be related to deactivated unfolded protein response as well as enhanced inflammation. Thus, HSF1 plays a significant role on UPR related pathway impacting AA amyloid deposition, which can mitigate amyloidogenic proteins from aggregation pathologically and is the possible way for intervening with the pathology of systemic amyloid disorder. In conclusion, HSF1 could not only serve as a new target for AA amyloidosis treatment in the future, but HSF1 knockout mice also can be considered as a valuable novel animal model for renal AA amyloidosis.

Human lysozyme inhibits the fibrillation of serum amyloid a protein from systemic AA amyloidosis

BACKGROUND

Systemic AA amyloidosis is a world-wide occurring protein misfolding disease in humans and animals that arises from the formation of amyloid fibrils from serum amyloid A (SAA) protein and their deposition in multiple organs.

OBJECTIVE

To identify new agents that prevent fibril formation from SAA protein and to determine their mode of action.

MATERIALS AND METHODS

We used a cell model for the formation of amyloid deposits from SAA protein to screen a library of peptides and small proteins, which were purified from human hemofiltrate. To clarify the inhibitory mechanism the obtained inhibitors were characterised in cell-free fibril formation assays and other biochemical methods.

RESULTS

We identified lysozyme as an inhibitor of SAA fibril formation. Lysozyme antagonised fibril formation both in the cell model as well as in cell-free fibril formation assays. The protein binds SAA with a dissociation constant of 16.5 ± 0.6 µM, while the binding site on SAA is formed by segments of positively charged amino acids.

CONCLUSION

Our data imply that lysozyme acts in a chaperone-like fashion and prevents the aggregation of SAA protein through direct, physical interactions.

Lung cancer combined with diffuse peritoneal and mesenteric amyloidosis detected on 18F-FDG PET/CT: A case report

RATIONALE

Amyloidosis is a heterogeneous group of diseases characterized by extracellular deposition of amyloid fibrils. Lung carcinoma is rarely reported to be associated with AA amyloidosis. With regard to the manifestation of amyloidosis infiltrating organs, most of the cases focus on the heart, liver, kidneys, and peripheral nervous system. Amyloidosis with diffuse abdominal involvement in combination with pulmonary squamous cell carcinoma carcinoma is an exceptionally rare occurrence.

PATIENT CONCERNS

A 70-year-old man was admitted to hospital for a 2-month history of repeated cough, low grade fever, hemoptysis and left back shoulder pain, which was not relieved by nonsteroid anti-inflammatory drugs. Meanwhile, he complained of intermittent diffuse abdominal discomfort and chronic persistent constipation.

DIAGNOSES

The patient was diagnosed with poorly differentiated lung squamous cell carcinoma and diffuse peritoneal and mesenteric amyloidosis based on the pathological biopsy.

INTERVENTIONS

The patient received surgery and chemotherapy for lung tumor. He did not receive any treatment against amyloidosis.

OUTCOMES

The patient died of a severe respiratory infection.

LESSONS

This case indicates that lung carcinoma is suspected to play a causative role in the development of amyloidosis. In addition, amyloidosis should be considered in the differential diagnosis in cases in which diffuse greater omentum, peritoneal, and mesenteric calcifications on 18F-2-fluoro-2-deoxy-D-glucose(18F-FDG) photon emission computed tomography (PET/CT).

Structural Basis for Vital Function and Malfunction of Serum Amyloid A: an Acute-Phase Protein that Wears Hydrophobicity on Its Sleeve

PURPOSE OF REVIEW

This review addresses normal and pathologic functions of serum amyloid A (SAA), an enigmatic biomarker of inflammation and protein precursor of AA amyloidosis, a life-threatening complication of chronic inflammation. SAA is a small, highly evolutionarily conserved acute-phase protein whose plasma levels increase up to one thousand-fold in inflammation, infection, or after trauma. The advantage of this dramatic but transient increase is unclear, and the complex role of SAA in immune response is intensely investigated. This review summarizes recent advances in our understanding of the structure-function relationship of this intrinsically disordered protein, outlines its newly emerging beneficial roles in lipid transport and inflammation control, and discusses factors that critically influence its misfolding in AA amyloidosis.

RECENT FINDINGS

High-resolution structures of lipid-free SAA in crystals and fibrils have been determined by x-ray crystallography and electron cryo-microscopy. Low-resolution structural studies of SAA-lipid complexes, together with biochemical, cell-based, animal model, genetic, and clinical studies, have provided surprising new insights into a wide range of SAA functions. An emerging vital role of SAA is lipid encapsulation to remove cell membrane debris from sites of injury. The structural basis for this role has been proposed. The lysosomal origin of AA amyloidosis has solidified, and its molecular and cellular mechanisms have emerged. Recent studies have revealed molecular underpinnings for understanding complex functions of this Cambrian protein in lipid transport, immune response, and amyloid formation. These findings help guide the search for much-needed targeted therapies to block the protein deposition in AA amyloidosis.