Leukocyte chemotactic factor 2 (LECT2)-associated renal amyloidosis

LECT2: A pleiotropic and promising hepatokine, from bench to bedside

LECT2 (leucocyte cell-derived chemotaxin 2) is a 16-kDa protein mainly produced by hepatocytes. It was first isolated in PHA-activated human T-cell leukaemia SKW-3 cells and originally identified as a novel neutrophil chemotactic factor. However, many lines of studies suggested that LECT2 was a pleiotropic protein, it not only functioned as a cytokine to exhibit chemotactic property, but also played multifunctional roles in some physiological conditions and pathological abnormalities, involving liver regeneration, neuronal development, HSC(haematopoietic stem cells) homeostasis, liver injury, liver fibrosis, hepatocellular carcinoma, metabolic disorders, inflammatory arthritides, systemic sepsis and systemic amyloidosis. Among the above studies, it was discovered that LECT2 could be a promising molecular biomarker and therapeutic target. This review summarizes LECT2-related receptors and pathways, basic and clinical researches, primarily in mice and human, for a better comprehension and management of these diseases in the future.

A stepwise data interpretation process for renal amyloidosis typing by LMD-MS

Backgrounds

Systemic amyloidosis is classified according to the deposited amyloid fibril protein (AFP), which determines its best therapeutic scheme. The most common type of AFP found are immunoglobulin light chains. The laser microdissection combined with mass spectrometry (LMD-MS) technique is a promising approach for precise typing of amyloidosis, however, the major difficulty in interpreting the MS data is how to accurately identify the precipitated AFP from background.

Objectives

The objective of the present study is to establish a complete data interpretation procedure for LMD-MS based amyloidosis typing.

Methods

Formalin-fixed paraffin-embedded specimens from patients with renal amyloidosis and non-amyloid nephropathies (including diabetic nephropathy, fibrillary glomerulonephritis, IgA nephropathy, lupus nephritis, membranous nephropathy, and normal tissue adjacent to tumors) were analyzed by LMD-MS. Forty-two specimens were used to train the data interpretation procedure, which was validated by another 50 validation specimens. Area under receiver operating curve (AUROC) analysis of amyloid accompanying proteins (AAPs, including apolipoprotein A-IV, apolipoprotein E and serum amyloid P-component) for discriminating amyloidosis from non-amyloid nephropathies was performed.

Results

A stepwise data interpretation procedure that includes or excludes the types of amyloidosis group by group was established. The involvement of AFPs other than immunoglobulin was determined by P-score, as well as immunoglobulin light chain by variable of λ-κ, and immunoglobulin heavy chain by H-score. This achieved a total of 88% accuracy in 50 validation specimens. The AAPs showed significantly different expression levels between amyloidosis specimens and non-amyloid nephropathies. Each of the single AAP had a AUROC value more than 0.9 for diagnosis of amyloidosis from non-amyloid control, and the averaged level of the three AAPs showed the highest AUROC (0.966), which might be an alternative indicator for amyloidosis diagnosis.

Conclusions

The proteomic data interpretation procedure for LMD-MS based amyloidosis typing was established successfully that has a high practicability in clinical application.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-022-02785-9.

A case of renal and splenic LECT 2 amyloidosis: A recently recognized cause of renal and systemic amyloidosis

Amyloidosis has traditionally been of a few defined varieties, most commonly including light-chain amyloidosis (AL amyloidosis) and secondary amyloidosis due to chronic inflammation (AA amyloidosis). Apolipoprotein A-I/A-II cystatin C, gelsolin, lysozyme, fibrinogen alpha chain, beta 2 microglobulin, and transthyretin familial amyloidosis represent rarer but reported varieties. Ten years ago, the first reports linked leukocyte chemotactic factor 2 (LECT2) amyloidosis as a pathological agent identified as a novel class of amyloid-generating protein. Epidemiology suggested that this was a new cause of amyloidosis that is especially common in Hispanic patients and somewhat common among patients from the Middle East-North Africa (MENA) region. We report a case of splenic and renal LECT 2 amyloidosis in a 62-year- old Hispanic male with diabetes mellitus. After an unremarkable serological workup, LECT 2 amyloidosis was diagnosed on renal biopsy. The case presentation is reviewed as a typical presentation, and the literature is reviewed regarding this newly reported entity, resulting in infiltrative renal amyloidosis and chronic renal disease.

Delving into the amyloidogenic core of human leukocyte chemotactic factor 2

ALECT2 (leukocyte chemotactic factor 2) amyloidosis is one of the most recently identified amyloid-related diseases, with LECT2 amyloids commonly found in different types of tissues. Under physiological conditions, LECT2 is a 16 kDa multifunctional protein produced by the hepatocytes and secreted into circulation. The pathological mechanisms causing LECT2 transition into the amyloid state are still largely unknown. In the case of ALECT2 patients, there is no disease-causing mutation, yet almost all patients carry a common polymorphism that appears to be necessary but not sufficient to directly trigger amyloidogenesis. In this work, we followed a reductionist methodology in order to detect critical amyloidogenic "hot-spots" during the fibrillation of LECT2. By associating experimental and computational assays, this approach reveals the explicit amyloidogenic core of human LECT2 and pinpoints regions with distinct amyloidogenic properties. The fibrillar architecture of LECT2 polymers, based on our results, provides a wealth of detailed information about the amyloidogenic "hot-spot" interactions and represents a starting point for future peptide-driven intervention in ALECT2 amyloidosis.

Amyloidosis: Insights from Proteomics

Amyloidoses are a spectrum of disorders caused by abnormal folding and extracellular deposition of proteins. The deposits lead to tissue damage and organ dysfunction, particularly in the heart, kidneys, and nerves. There are at least 30 different proteins that can cause amyloidosis. The clinical management depends entirely on the type of protein deposited, and thus on the underlying pathogenesis, and often requires high-risk therapeutic intervention. Application of mass spectrometry-based proteomic technologies for analysis of amyloid plaques has transformed the way amyloidosis is diagnosed and classified. Proteomic assays have been extensively used for clinical management of patients with amyloidosis, providing unprecedented diagnostic and biological information. They have shed light on the pathogenesis of different amyloid types and have led to identification of numerous new amyloid types, including ALECT2 amyloidosis, which is now recognized as one of the most common causes of systemic amyloidosis in North America.

Systemic amyloidosis

Tissue deposition of protein fibrils causes a group of rare diseases called systemic amyloidoses. This Seminar focuses on changes in their epidemiology, the current approach to diagnosis, and advances in treatment. Systemic light chain (AL) amyloidosis is the most common of these conditions, but wild-type transthyretin cardiac amyloidosis (ATTRwt) is increasingly being diagnosed. Typing of amyloid fibrils, a critical determinant of therapy, has improved with the wide availability of laser capture and mass spectrometry from fixed histological tissue sections. Specific and accurate evaluation of cardiac amyloidosis is now possible using cardiac magnetic resonance imaging and cardiac repurposing of bone scintigraphy tracers. Survival in AL amyloidosis has improved markedly as novel chemotherapy agents have become available, but challenges remain in advanced disease. Early diagnosis, a key to better outcomes, still remains elusive. Broadening the amyloid-specific therapeutic landscape to include RNA inhibitors, fibril formation stabilisers and inhibitors, and immunotherapeutic targeting of amyloid deposits holds promise to transform outcomes in systemic amyloidoses.

Leukocyte cell-derived chemotaxin 2 (LECT2)–associated amyloidosis is a frequent cause of hepatic amyloidosis in the United States

Leukocyte cell-derived chemotaxin-2–associated amyloidosis (ALect2) is a common cause of systemic amyloidosis involving the liver. Recognition and accurate diagnosis of hepatic ALect2 amyloidosis is essential for accurate management of patients with hepatic amyloidosis.