Amyloid contained in the knee joint meniscus is formed from apolipoprotein A-I

Age-related amyloidosis outside the brain: A state-of-the-art review

Inside and outside the brain, accumulation of amyloid fibrils plays key roles in the pathogenesis of fatal age-related diseases such as Alzheimer's and Parkinson's diseases and wild-type transthyretin amyloidosis. Although the incidence of all amyloidoses increases with age, for some types of amyloidosis aging is known as the main direct risk factor, and these types are typically diseases of elderly people. More than 10 different precursor proteins are known to cause age-associated amyloidosis; these proteins include amyloid β protein, α-synuclein, transthyretin, islet amyloid polypeptide, atrial natriuretic factor, and the newly discovered epidermal growth factor-containing fibulin-like extracellular matrix protein 1. Except for intracerebral amyloidoses, most age-related amyloidoses have been little studied. Indeed, in view of the increasing life expectancy in our societies, understanding how aging is involved in the process of amyloid fibril accumulation and the effects of amyloid deposits on the aging body is extremely important. In this review, we summarize current knowledge about the nature of amyloid precursor proteins, the prevalence, clinical manifestations, and pathogenesis of amyloidosis, and recent advances in our understanding of age-related amyloidoses outside the brain.

Transthyretin amyloid deposits in lumbar spinal stenosis and assessment of signs of systemic amyloidosis

BACKGROUND

Wild-type transthyretin (ATTRwt) amyloidosis is the most common systemic amyloidosis in Western countries and manifests mainly as progressive restrictive cardiomyopathy.

OBJECTIVE

To study the prevalence of ATTR deposits in ligament tissue in patients undergoing surgery for lumbar spinal stenosis and to assess whether these deposits are associated with cardiac amyloidosis.

MATERIALS AND METHODS

A total of 250 patients, aged 50-89 (57% women), none with known cardiovascular disease, were included. Ligaments were investigated microscopically for amyloid. ATTR type was determined by immunohistochemistry and fibril type by Western blot. The amount of amyloid was graded 0-4. All patients with grade 3-4 ATTR deposits were offered cardiac investigation including ECG, cardiac ultrasound, plasma NT-proBNP and cardiac magnetic resonance (CMR), including modern tissue characterization.

RESULTS

Amyloid was identified in 221 of the samples (88.4%). ATTR appeared in 93 samples (37%) of whom 42 (17 women and 25 men) were graded 3-4; all had fibril type A (mixture of full-length TTR and fragmented TTR). Twenty-nine of 42 patients with grade 3-4 ATTR deposits accepted cardiovascular investigations; none of them had definite signs of cardiac amyloidosis, but five men had a history of carpal tunnel syndrome.

CONCLUSIONS

The prevalence of ATTR deposits in ligamentum flavum in patients with lumbar spinal stenosis was high but not associated with manifest ATTR cardiac amyloidosis. However, the findings of fibril type A, the prevalence of previous carpal tunnel syndrome and ATTR amyloid in surrounding adipose and vascular tissue indicate that amyloid deposits in ligamentum flavum may be an early manifestation of systemic ATTR disease.

Apolipoprotein AI amyloid deposits in the ligamentum flavum in patients with lumbar spinal canal stenosis

Amyloidosis is a protein-misfolding disease characterised by insoluble amyloid deposits in the extracellular space of various organs and tissues, such as the brain, heart, kidneys, and ligaments. We previously reported the frequent occurrence of amyloid deposits in the ligament flavum in the presence of lumbar spinal canal stenosis (LSCS), which is a common spinal disorder in older individuals. Our earlier clinicopathological studies revealed that amyloid deposits derived from transthyretin (TTR) were involved in the pathogenesis of LSCS. ATTR amyloid was the most common form in the ligamentum flavum, but amyloid deposits that were not identified still existed in more than 50% of patients with LSCS. In this study, we found apolipoprotein AI (AApoAI) amyloid deposits in the ligamentum flavum of patients with LSCS. The deposits occurred in 12% of patients with LSCS. Biochemical studies revealed that the amyloid deposits consisted mainly of full-length ApoAI. As a notable finding, the lumbar ligamentum flavum of patients who had LSCS with double-positive amyloid deposits-positive for both ATTR and AApoAI-was significantly thicker than that of patients who had LSCS with single-positive-that is, positive for either ATTR or AApoAI-amyloid deposits. We thus suggest that lumbar AApoAI amyloid formation may enhance the pathological changes of lumbar ATTR amyloidosis in patients with LSCS.

Localised foot and ankle amyloid deposition

BACKGROUND

Localised (transthyretin-associated) amyloid is commonly seen in articular/periarticular tissues of elderly individuals. Whether age-associated, amyloid deposition occurs in foot and ankle (F&A) tissues has not previously been investigated. In this study we assessed the nature and frequency of F&A amyloid deposition and determined whether it is associated with age and/or specific articular/periarticular F&A lesions.

METHODS

Histological sections of twenty five normal F&A articular/periarticular tissues (16-71 years) and a range of F&A lesions were stained by Congo Red. The amyloid protein was identified by immunohistochemistry and type of matrix glycosaminoglycans determined by Alcian Blue (critical electrolyte concentration) histochemistry.

RESULTS

Amyloid deposits were found in the joint cartilage and capsule of 3/25 normal specimens (57, 62 and 78 years). Amyloid deposits were small, contained transthyretin, and found in areas of matrix degeneration associated with the presence of highly sulphated glycosaminoglycans. In patients older than 47 years, small amyloid deposits were noted in some F&A lesions, including osteoarthritis, Charcot arthropathy, bursa, ganglion, chondrocalcinosis, gout, calcific tendonitis and Achilles tendonitis.

CONCLUSION

Small localised amyloid deposits in F&A tissues contain transthyretin and occur in areas of matrix degeneration associated with the presence of highly sulphated glycosaminoglycans; these deposits are age-associated and, although seen more commonly in some F&A lesions, are small and unlikely to be of pathogenic significance.

Accelerated pre-senile systemic amyloidosis in PACAP knockout mice - a protective role of PACAP in age-related degenerative processes

Dysregulation of neuropeptides may play an important role in aging‐induced impairments. Among them, pituitary adenylate cyclase‐activating polypeptide (PACAP) is a potent cytoprotective peptide that provides an endogenous control against a variety of tissue‐damaging stimuli. We hypothesized that the progressive decline of PACAP throughout life and the well‐known general cytoprotective effects of PACAP lead to age‐related pathophysiological changes in PACAP deficiency, supported by the increased vulnerability to various stressors of animals partially or totally lacking PACAP. Using young and aging CD1 PACAP knockout (KO) and wild type (WT) mice, we demonstrated pre‐senile amyloidosis in young PACAP KO animals and showed that senile amyloidosis appeared accelerated, more generalized, more severe, and affected more individuals. Histopathology showed age‐related systemic amyloidosis with mainly kidney, spleen, liver, skin, thyroid, intestinal, tracheal, and esophageal involvement. Mass spectrometry‐based proteomic analysis, reconfirmed with immunohistochemistry, revealed that apolipoprotein‐AIV was the main amyloid protein in the deposits together with several accompanying proteins. Although the local amyloidogenic protein expression was disturbed in KO animals, no difference was found in laboratory lipid parameters, suggesting a complex pathway leading to increased age‐related degeneration with amyloid deposits in the absence of PACAP. In spite of no marked inflammatory histological changes or blood test parameters, we detected a disturbed cytokine profile that possibly creates a pro‐inflammatory milieu favoring amyloid deposition. In summary, here we describe accelerated systemic senile amyloidosis in PACAP gene‐deficient mice, which might indicate an early aging phenomenon in this mouse strain. Thus, PACAP KO mice could serve as a model of accelerated aging with human relevance. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Methionine oxidized apolipoprotein A-I at the crossroads of HDL biogenesis and amyloid formation

Apolipoprotein A-I (apoA-I) shares with other exchangeable apolipoproteins a high level of structural plasticity. In the lipid-free state, the apolipoprotein amphipathic α-helices interact intra- and intermolecularly, providing structural stabilization by self-association. We have reported that lipid-free apoA-I becomes amyloidogenic upon physiologically relevant (myeloperoxidase-mediated) Met oxidation. In this study, we established that Met oxidation promotes amyloidogenesis by reducing the stability of apoA-I monomers and irreversibly disrupting self-association. The oxidized apoA-I monomers also exhibited increased cellular cholesterol release capacity and stronger association with macrophages, compared to nonoxidized apoA-I. Of physiologic relevance, preformed oxidized apoA-I amyloid fibrils induced amyloid formation in nonoxidized apoA-I. This process was enhanced when self-association of nonoxidized apoA-I was disrupted by thermal treatment. Solid state NMR analysis revealed that aggregates formed by seeded nonoxidized apoA-I were structurally similar to those formed by the oxidized protein, featuring a β-structure-rich amyloid fold alongside α-helices retained from the native state. In atherosclerotic lesions, the conditions that promote apoA-I amyloid formation are readily available: myeloperoxidase, active oxygen species, low pH, and high concentration of lipid-free apoA-I. Our results suggest that even partial Met oxidation of apoA-I can nucleate amyloidogenesis, thus sequestering and inactivating otherwise antiatherogenic and HDL-forming apoA-I.-Witkowski, A., Chan, G. K. L., Boatz, J. C., Li, N. J., Inoue, A. P., Wong, J. C., van der Wel, P. C. A., Cavigiolio, G. Methionine oxidized apolipoprotein A-I at the crossroads of HDL biogenesis and amyloid formation.

Transthyretin deposition promotes progression of osteoarthritis

Deposition of amyloid is a common aging-associated phenomenon in several aging-related diseases. Osteoarthritis (OA) is the most prevalent joint disease, and aging is its major risk factor. Transthyretin (TTR) is an amyloidogenic protein that is deposited in aging and OA-affected human cartilage and promotes inflammatory and catabolic responses in cultured chondrocytes. Here, we investigated the role of TTR in vivo using transgenic mice overexpressing wild-type human TTR (hTTR-TG). Although TTR protein was detected in cartilage in hTTR-TG mice, the TTR transgene was highly overexpressed in liver, but not in chondrocytes. OA was surgically induced by destabilizing the medial meniscus (DMM) in hTTR-TG mice, wild-type mice of the same strain (WT), and mice lacking endogenous Ttr genes. In the DMM model, both cartilage and synovitis histological scores were significantly increased in hTTR-TG mice. Further, spontaneous degradation and OA-like changes in cartilage and synovium developed in 18-month-old hTTR mice. Expression of cartilage catabolic (Adamts4, Mmp13) and inflammatory genes (Nos2, Il6) was significantly elevated in cartilage from 6-month-old hTTR-TG mice compared with WT mice as was the level of phospho-NF-κB p65. Intra-articular injection of aggregated TTR in WT mice increased synovitis and significantly increased expression of inflammatory genes in synovium. These findings are the first to show that TTR deposition increases disease severity in the murine DMM and aging model of OA.

Apolipoprotein A-1-related amyloidosis 2 case reports and review of the literature

RATIONALE

Apolipoprotein A-1 (ApoA-1)-related amyloidosis is characterized by the deposition of ApoA-1 in various organs and can be either hereditary or nonhereditary. It is rare and easily misdiagnosed. Renal involvement is common in hereditary ApoA-1 amyloidosis, but rare in the nonhereditary form.

PATIENT CONCERNS

We reported two cases with ApoA-1 amyloidosis, a 64-year-old man suffering from nephrotic syndrome and a 40-year-old man with nephrotic syndrome and splenomegaly. Renal biopsies revealed glomerular, interstitial and vascular amyloid deposits and positive phospholipase A2 receptor staining in the glomerular capillary loop in case 1, and mesangial amyloid deposits in case 2.

DIAGNOSES

After immunostaining failed to determine the specific amyloid protein, proteomic analysis of amyloid deposits by mass spectrometry was performed and demonstrated the ApoA-1 origin of the amyloid. Genetic testing revealed no mutation of the APOA1 gene in case 1 but a heterozygous mutation, Trp74Arg, in case 2. Case 1 was thus diagnosed as nonhereditary ApoA-1 associated renal amyloidosis with membranous nephropathy, and case 2 as hereditary ApoA-1 amyloidosis with multiorgan injuries (kidney and spleen) and a positive family history.

INTERVENTIONS

Case 1 was treated with glucocorticoid combined with cyclosporine. Case 2 was treated with calcitriol and angiotensin converting enzyme inhibitors.

OUTCOMES

Two cases were followed up for 5 months and 2 years, respectively; and case 1 was found to have attenuated proteinuria while case 2 had an elevation of cholestasis indices along with renal insufficiency.

LESSONS

Proteomic analysis by mass spectrometry of the amyloid deposits combined with genetic analysis can provide accurate diagnosis of ApoA-1 amyloidosis. Besides, these 2 cases expand our knowledge of ApoA-1-related renal amyloidosis.

Serum Apo A-1 and Its Role as a Biomarker of Coronary Artery Disease

Objectives

To evaluate the role of apolipoprotein(Apo A-1) as a biomarker of coronary artery disease (CAD) and its comparison with the traditional marker high-density lipoprotein (HDL).

Methodology

One hundred patients proven to have coronary artery disease by angiography were recruited and their serum biomarkers were compared with 100 normal individuals adjusted for age and sex.

Result

The mean +/-standard deviation (SD) value of plasma Apo A-1 levels in the normal individuals were observed to be 207.42 +/- 41.35 (mg/dL) against 90.69 +/- 20.77 (mg/dL) in the cardiac patients. On the other hand the serum HDL levels were 52.93 +/-33.58 (mg/dL) in the normal individuals and 37.86 +/- 23.19 (mg/dL) in the cardiac patients. Both of these differences were statistically significant (p < 0.001). For Apo A-1, a large proportion of patients (85%) were found to be in the abnormal range when compared to the control group in which only 7% had an abnormal value. For HDL, a majority (70%) of the cardiac patients had abnormal values while 40% of the normal individuals also had abnormal values. The sensitivity of Apo A-1 for detecting CAD was 85%, while for HDL, it was only 69%. Similarly, the specificity of Apo A-1 for detecting CAD was 93%, while for HDL, it was 60%. When plotted on a receiver operating characteristic (ROC) curve, Apo A-1 had a much larger area under the curve when compared to HDL.

Conclusion

This study suggests that Apo A-1 may, in fact, be more sensitive than HDL as a predictor of CAD. However, to completely elucidate its role as a biomarker, to set target serum levels and to increase its clinical use, further studies are required.

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.

Recipient aging accelerates acquired transthyretin amyloidosis after domino liver transplantation

Domino liver transplantation (DLT) with liver grafts from patients with hereditary transthyretin (TTR) amyloidosis has been performed throughout the world because of a severe liver graft shortage. Reports of acquired systemic TTR amyloidosis in domino liver recipients have been increasing; however, the precise pathogenesis and clinical course of acquired TTR amyloidosis remains unclear. We analyzed the relationship between the occurrence of acquired amyloidosis and clinical features in 22 consecutive domino liver donors with hereditary TTR amyloidosis (10 males and 12 females; mean age at DLT: 37.2 years; TTR mutations: V30M [n = 19], Y114C [n = 1], L55P [n = 1], and S50I [n = 1]) and 22 liver recipients (16 males and 6 females; mean age at DLT, 46.2 years). The mean times from DLT to amyloid first appearance and transplant recipient symptom onset were 8.2 years and 9.9 years, respectively. Kaplan-Meier analysis and quantification of the amyloid deposition revealed aging of recipients correlated with early de novo amyloid deposition. The sex of donors and recipients and the age, disease duration, and disease severity of donors had no significant effect on the latency of de novo amyloid deposition. In conclusion, our results demonstrate that recipient aging is associated with the early onset de novo amyloidosis. Because acquired amyloidosis will likely increase, careful follow-up for early amyloidosis detection and new treatments, including TTR stabilizers and gene-silencing therapies, are required. Liver Transplantation 22 656-664 2016 AASLD.

Knee osteoarthritis associated with different kinds of amyloid deposits and the impact of aging on type of amyloid

Amyloidosis is a protein conformational disorder in which amyloid fibrils accumulate in the extracellular space and induce organ dysfunction. Recently, two different amyloidogenic proteins, transthyretin (TTR) and apolipoprotein A-I (Apo A-I), were identified in amyloid deposits in knee joints in patients with knee osteoarthritis (OA). However, clinicopathological differences related to those two kinds of amyloid deposits in the knee joint remain to be clarified. Here, we investigated the clinicopathological features related to these knee amyloid deposits associated with knee OA and the biochemical characteristics of the amyloid deposits. We found that all of our patients with knee OA had amyloid deposits in the knee joints, especially in the meniscus, and those deposits were primarily derived from TTR and/or Apo A-I. Some patients with knee OA, however, had unclassified amyloid deposits. One of our interesting observations concerned the different effects of aging on each type of amyloid formed. The frequency of formation of ATTR deposits clearly increased with age, but that of AApo A-I deposits decreased. Furthermore, we found that ∼16% of patients with knee OA developed ATTR/AApo A-I double deposits in the meniscus. Amyloid deposition may therefore be a common histopathological feature associated with knee OA. Also, aging may induce ATTR formation in the knee joint in elderly patients with knee OA, whereas AApo A-I formation may be inversely correlated with age.

Apolipoprotein-A1 as a damage-associated molecular patterns protein in osteoarthritis: ex vivo and in vitro pro-inflammatory properties

Osteoarthritis (OA) is associated with a local inflammatory process. Dyslipidemia is known to be an underlying cause for the development of OA. Therefore, lipid and inflammatory levels were quantified ex vivo in blood and synovial fluid of OA patients (n=29) and compared to those of rheumatoid arthritis (RA) patients (n=27) or healthy volunteers (HV) (n=35). The role of apolipoprotein A-I (ApoA1) was investigated in vitro on inflammatory parameters using human joint cells isolated from cartilage and synovial membrane obtained from OA patients after joint replacement. Cells were stimulated with ApoA1 in the presence or not of serum amyloid A (SAA) protein and/or lipoproteins (LDL and HDL) at physiological concentration observed in OA synovial fluid. In our ex vivo study, ApoA1, LDL-C and total cholesterol levels were strongly correlated to each other inside the OA joint cavity whereas same levels were not or weakly correlated to their corresponding serum levels. In OA synovial fluid, ApoA1 was not as strongly correlated to HDL as observed in OA serum or in RA synovial fluid, suggesting a dissociative level between ApoA1 and HDL in OA synovial fluid. In vitro, ApoA1 induced IL-6, MMP-1 and MMP-3 expression by primary chondrocytes and fibroblast-like synoviocytes through TLR4 receptor. HDL and LDL attenuated joint inflammatory response induced by ApoA1 and SAA in a ratio dependent manner. In conclusion, a dysregulated lipidic profile in the synovial fluid of OA patients was observed and was correlated with inflammatory parameters in the OA joint cavity. Pro-inflammatory properties of ApoA1 were confirmed in vitro.

Myeloperoxidase-mediated Methionine Oxidation Promotes an Amyloidogenic Outcome for Apolipoprotein A-I

High plasma levels of apolipoprotein A-I (apoA-I) correlate with cardiovascular health, whereas dysfunctional apoA-I is a cause of atherosclerosis. In the atherosclerotic plaques, amyloid deposition increases with aging. Notably, apoA-I is the main component of these amyloids. Recent studies identified high levels of oxidized lipid-free apoA-I in atherosclerotic plaques. Likely, myeloperoxidase (MPO) secreted by activated macrophages in atherosclerotic lesions is the promoter of such apoA-I oxidation. We hypothesized that apoA-I oxidation by MPO levels similar to those present in the artery walls in atherosclerosis can promote apoA-I structural changes and amyloid fibril formation. ApoA-I was exposed to exhaustive chemical (H2O2) oxidation or physiological levels of enzymatic (MPO) oxidation and incubated at 37 °C and pH 6.0 to induce fibril formation. Both chemically and enzymatically oxidized apoA-I produced fibrillar amyloids after a few hours of incubation. The amyloid fibrils were composed of full-length apoA-I with differential oxidation of the three methionines. Met to Leu apoA-I variants were used to establish the predominant role of oxidation of Met-86 and Met-148 in the fibril formation process. Importantly, a small amount of preformed apoA-I fibrils was able to seed amyloid formation in oxidized apoA-I at pH 7.0. In contrast to hereditary amyloidosis, wherein specific mutations of apoA-I cause protein destabilization and amyloid deposition, oxidative conditions similar to those promoted by local inflammation in atherosclerosis are sufficient to transform full-length wild-type apoA-I into an amyloidogenic protein. Thus, MPO-mediated oxidation may be implicated in the mechanism that leads to amyloid deposition in the atherosclerotic plaques in vivo.

Clinical and laboratory characteristics of patients having amyloidogenic transthyretin deposition in osteoarthritic knee joints

OBJECTIVE

Our aim was to investigate clinical and laboratory characteristics of osteoarthritic patients who had amyloid deposition in their knee joints.

METHODS

Synovial membranes were obtained from 36 patients with knee osteoarthritis (OA) who underwent joint replacement surgery. From this sample, the diagnosis of amyloid was determined by Congo red staining, which demonstrated apple-green birefringence under a polarized microscope. All synovial membranes were immunohistochemically characterized for the expressions of amyloid immunoglobulin light chain (AL-κ and AL-λ), serum amyloid-A (SAA), amyloidogenic transthyretin (ATTR), and amyloidogenic β2-microglobulin (Aβ2M). Matrix-assisted laser desorption-ionizaton/time of flight mass spectrometry (MALDI-TOF MS) was used to analyze transthyretin (TTR) isoforms in the serum of each patient.

RESULTS

Nine cases (25%) were found to be amyloid-positive. Immunohistochemically, eight cases (88.9%) had ATTR deposition, and one sample (11.1%) was shown to be AL-κ-positive. MALDI-TOF MS identified that the TTR in the serum of the patients was unmodified wild-type TTR, TTR-Cys-S-S-Cys, and TTR-Cys-S-S-CysGly. The age at surgery and the disease duration were significantly higher in the ATTR-positive group than in the ATTR-negative group. Knee score and function score were significantly lower in the ATTR-positive group than in the ATTR-negative group.

CONCLUSIONS

Amyloid deposition in synovial membranes of OA patients was found to be ATTR and AL-κ. TTR in the serum of the patients was unmodified wild-type TTR together with two isoforms. The high age at surgery, long disease duration, and a deteriorated knee function were associated with ATTR amyloid deposition in the osteoarthritic knee joints.

Transthyretin-derived amyloidosis: probably a common cause of lumbar spinal stenosis

BACKGROUND

Senile systemic amyloidosis (SSA) derived from wild-type transthyretin is a fairly common condition of old individuals, particularly men. The main presentation is by cardiac involvement, which can lead to severe restrictive cardiomyopathy. SSA is, however, a systemic disease, and amyloid deposits may appear in many other tissues but are thought to be without clinical symptoms outside the heart. Amyloid is a very common finding in cartilage and ligaments of elderly subjects, and transthyretin has been demonstrated in some deposits. Lumbar spinal stenosis is also a condition of usually elderly individuals in whom narrowing of the lumbar spinal canal leads to compression of nerves to the lower limbs.

RESULTS

We questioned whether lumbar spinal stenosis sometimes could be a manifestation of undiagnosed SSA. In this first report we have studied the presence of amyloid in material obtained at surgery for spinal stenosis in 26 patients. Amyloid was found in 25 subjects. Transthyretin was demonstrated immunohistochemically in 5 out of 15 studied resected tissues. Four of the positive materials were analyzed with Western blot revealing both full-length transthyretin (TTR) and C-terminal TTR fragments, typically seen in SSA.

CONCLUSION

We conclude that lumbar spinal stenosis quite frequently may be a consequence of SSA and that further studies are warranted.

Mass spectrometry analysis reveals non-mutated apolipoprotein A1 lumbosacral radiculoplexus amyloidoma

INTRODUCTION

In rare instances, amyloidosis presents as a focal, macroscopic lesion involving peripheral neural tissues (amyloidoma). In all known reported cases, peripheral nerve amyloidomas have had immunoglobulin light-chain fibril composition and occurred in the context of paraproteinemia.

METHODS

A 46-year-old man presented with progressive insidious-onset right lumbosacral radiculoplexus neuropathy without paraproteinemia. MRI-targeted fascicular nerve biopsy was performed on an enlarged sciatic nerve after earlier distal fibular nerve biopsy was nondiagnostic. Laser dissected mass spectroscopy of the discovered amyloid protein was performed after immunohistochemistry failed to identify the specific amyloid protein. Complete gene sequencing of apolipoprotein A1 (ApoA1) was performed.

RESULTS

Only wild-type ApoA1 amyloid was found in the congophilic component in the nerve.

CONCLUSIONS

This case highlights the utility of MRI-guided fascicular nerve biopsy combined with laser-dissected mass spectrometric analysis. Importantly, the case expands the known causes of amyloidomas to include wild-type ApoA1.

Proteome of skeletal muscle lipid droplet reveals association with mitochondria and apolipoprotein a-I

The lipid droplet (LD) is a universal organelle governing the storage and turnover of neutral lipids. Mounting evidence indicates that elevated intramuscular triglyceride (IMTG) in skeletal muscle LDs is closely associated with insulin resistance and Type 2 Diabetes Mellitus (T2DM). Therefore, the identification of the skeletal muscle LD proteome will provide some clues to dissect the mechanism connecting IMTG with T2DM. In the present work, we identified 324 LD-associated proteins in mouse skeletal muscle LDs through mass spectrometry analysis. Besides lipid metabolism and membrane traffic proteins, a remarkable number of mitochondrial proteins were observed in the skeletal muscle LD proteome. Furthermore, imaging by fluorescence microscopy and transmission electronic microscopy (TEM) directly demonstrated that mitochondria closely adhere to LDs in vivo. Moreover, our results revealed for the first time that apolipoprotein A-I (apo A-I), the principal apolipoprotein of high density lipoprotein (HDL) particles, was also localized on skeletal muscle LDs. Further studies verified that apo A-I was expressed endogenously by skeletal muscle cells. In conclusion, we report the protein composition and characterization of skeletal muscle LDs and describe a novel LD-associated protein, apo A-I.

Human apolipoprotein A-I-derived amyloid: its association with atherosclerosis

Amyloidoses constitute a group of diseases in which soluble proteins aggregate and deposit extracellularly in tissues. Nonhereditary apolipoprotein A-I (apoA-I) amyloid is characterized by deposits of nonvariant protein in atherosclerotic arteries. Despite being common, little is known about the pathogenesis and significance of apoA-I deposition. In this work we investigated by fluorescence and biochemical approaches the impact of a cellular microenvironment associated with chronic inflammation on the folding and pro-amyloidogenic processing of apoA-I. Results showed that mildly acidic pH promotes misfolding, aggregation, and increased binding of apoA-I to extracellular matrix elements, thus favoring protein deposition as amyloid like-complexes. In addition, activated neutrophils and oxidative/proteolytic cleavage of the protein give rise to pro amyloidogenic products. We conclude that, even though apoA-I is not inherently amyloidogenic, it may produce non hereditary amyloidosis as a consequence of the pro-inflammatory microenvironment associated to atherogenesis.

ODAM Expression Inhibits Human Breast Cancer Tumorigenesis

We have posited that Odontogenic Ameloblast Associated Protein (ODAM) serves as a novel prognostic biomarker in breast cancer and now have investigated its potential role in regulating tumor growth and metastasis. Human breast cancer MDA-MB-231 cells were transfected with a recombinant ODAM plasmid construct (or, as a control, the plasmid vector alone). ODAM expression increased adhesion and apoptosis of the transfected MDA-MB-231 cells and suppressed their growth rate, migratory activity, and capability to invade extracellular matrix-coated membranes. Implantation of such cells into mouse mammary fat pads resulted in significantly smaller tumors than occurred in animals that received control cells; furthermore, ODAM-expressing cells, when injected intravenously into mice, failed to metastasize, whereas the control-transfected counterparts produced extensive lung lesions. Our finding that induction of ODAM expression in human breast cancer cells markedly inhibited their neoplastic properties provides further evidence for the regulatory role of this molecule in tumorigenesis and, consequently, is of potential clinical import.

Proteomic analysis of articular cartilage vesicles from normal and osteoarthritic cartilage

OBJECTIVE

Articular cartilage vesicles (ACVs) are extracellular organelles found in normal articular cartilage. While they were initially defined by their ability to generate pathologic calcium crystals in cartilage of osteoarthritis (OA) patients, they can also alter the phenotype of normal chondrocytes through the transfer of RNA and protein. The purpose of this study was to analyze the proteome of ACVs from normal and OA human cartilage.

METHODS

ACVs were isolated from cartilage samples from 10 normal controls and 10 OA patients. We identified the ACV proteomes using in-gel trypsin digestion, nanospray liquid chromatography tandem mass spectrometry analysis of tryptic peptides, followed by searching an appropriate subset of the Uniprot database. We further differentiated between normal and OA ACVs by Holm-Sidak analysis for multiple comparison testing.

RESULTS

More than 1,700 proteins were identified in ACVs. Approximately 170 proteins satisfied our stringent criteria of having >1 representative peptide per protein present, and a false discovery rate of ≤5%. These proteins included extracellular matrix components, phospholipid binding proteins, enzymes, and cytoskeletal components, including actin. While few proteins were seen exclusively in normal or OA ACVs, immunoglobulins and complement components were present only in OA ACVs. Compared to normal ACVs, OA ACVs displayed decreases in matrix proteoglycans and increases in transforming growth factor β-induced protein βig-H3, DEL-1, vitronectin, and serine protease HtrA1 (P < 0.01).

CONCLUSION

These findings lend support to the concept of ACVs as physiologic structures in articular cartilage. Changes in OA ACVs are largely quantitative and reflect an altered matrix and the presence of inflammation, rather than revealing fundamental changes in composition.

The adsorption of biomolecules to multi-walled carbon nanotubes is influenced by both pulmonary surfactant lipids and surface chemistry

BACKGROUND

During production and processing of multi-walled carbon nanotubes (MWCNTs), they may be inhaled and may enter the pulmonary circulation. It is essential that interactions with involved body fluids like the pulmonary surfactant, the blood and others are investigated, particularly as these interactions could lead to coating of the tubes and may affect their chemical and physical characteristics. The aim of this study was to characterize the possible coatings of different functionalized MWCNTs in a cell free environment.

RESULTS

To simulate the first contact in the lung, the tubes were coated with pulmonary surfactant and subsequently bound lipids were characterized. The further coating in the blood circulation was simulated by incubating the tubes in blood plasma. MWCNTs were amino (NH2)- and carboxyl (-COOH)-modified, in order to investigate the influence on the bound lipid and protein patterns. It was shown that surfactant lipids bind unspecifically to different functionalized MWCNTs, in contrast to the blood plasma proteins which showed characteristic binding patterns. Patterns of bound surfactant lipids were altered after a subsequent incubation in blood plasma. In addition, it was found that bound plasma protein patterns were altered when MWCNTs were previously coated with pulmonary surfactant.

CONCLUSIONS

A pulmonary surfactant coating and the functionalization of MWCNTs have both the potential to alter the MWCNTs blood plasma protein coating and to determine their properties and behaviour in biological systems.

Age-related changes in the musculoskeletal system and the development of osteoarthritis

Osteoarthritis (OA) is the most common cause of chronic disability in older adults. Although classically considered a "wear and tear" degenerative condition of articular joints, recent studies have demonstrated an inflammatory component to OA that includes increased activity of several cytokines and chemokines in joint tissues that drive production of matrix-degrading enzymes. Rather than directly causing OA, aging changes in the musculoskeletal system contribute to the development of OA by making the joint more susceptible to the effects of other OA risk factors that include abnormal biomechanics, joint injury, genetics, and obesity. Age-related sarcopenia and increased bone turnover may also contribute to the development of OA. Understanding the basic mechanisms by which aging affects joint tissues should provide new targets for slowing or preventing the development of OA.

Impaired expression of genes regulating cholesterol efflux in human osteoarthritic chondrocytes

Altered lipid metabolism has been implicated as a critical player in osteoarthritis (OA). Our study aimed to investigate the expression of genes regulating cholesterol efflux in human chondrocytes and to study the effect of an LXR agonist on cholesterol efflux and lipid accumulation in osteoarthritic chondrocytes. ATP-binding-cassette transporter A1 (ABCA1), apolipoprotein A1 (ApoA1), and liver X receptors (LXRalpha and LXRbeta) mRNA expression levels were evaluated using real-time polymerase chain reaction (PCR) and ApoA1 protein levels by Western blot analysis in normal and osteoarthritic articular cartilage samples. Cholesterol efflux was evaluated in osteoarthritic chondrocytes radiolabeled with [1,2(n)-(3)H] cholesterol after LXR treatment, while intracellular lipid accumulation was studied after Oil-red-O staining. Cholesterol efflux gene expressions were significantly lower in osteoarthritic cartilage compared to normal. Treatment of osteoarthritic chondrocytes with the LXR agonist TO-901317 significantly increased ApoA1 and ABCA1 expression levels, as well as cholesterol efflux. Additionally, osteoarthritic chondrocytes presented intracellular lipids deposits, while no deposits were found after treatment with TO-901317. Our findings suggest that impaired expression of genes regulating cholesterol efflux may be a critical player in osteoarthritis, while the ability of the LXR agonist to facilitate cholesterol efflux suggests that it may be a target for therapeutic intervention in osteoarthritis.

Hereditary apolipoprotein AI-associated amyloidosis in surgical pathology specimens: identification of three novel mutations in the APOA1 gene

Apolipoprotein AI-derived (AApoAI) amyloidosis may present either as a non-hereditary form with wild-type protein deposits in atherosclerotic plaques or as a hereditary form due to germline mutations in the APOA1 gene. Currently, more than 50 apoAI variants are known, and 13 are associated with amyloidosis. We describe six patients with AApoAI amyloidosis due to APOA1 germline mutations that affect the larynx, small intestine, large intestine, heart, liver, kidney, uterus, ovary, or pelvic lymph nodes. In each patient, the amyloid showed a characteristic apple green birefringence when viewed under polarized light after Congo red staining and was immunoreactive with antibodies against apoAI. Sequence analyses revealed one known (p.Leu75Pro) and three novel APOA1 mutations that included gene variations leading to two different frameshifts (p.Asn74fs and p.Ala154fs) and one amino acid exchange (p.Leu170Pro). These three novel mutations extend our knowledge about both the location of the mutations and the organ distribution in hereditary AApoAI amyloidosis. Thirteen of the now sixteen amyloidogenic mutations are localized in two hot-spot regions that span residues 50 to 93 and 170 to 178. The organ distribution and clinical presentation of AApoAI amyloidosis seems to depend on the position of the mutation. Patients with alterations in codons 1 to 75 mostly develop hepatic and renal amyloidosis, while carriers of mutations in residues 173 to 178 mainly suffer from cardiac, laryngeal, and cutaneous amyloidosis.

Expression of odontogenic ameloblast-associated protein (ODAM) in dental and other epithelial neoplasms

We previously have communicated our discovery that the amyloid associated with calcifying epithelial odontogenic tumors is composed of N-terminal fragments of the structurally novel odontogenic ameloblast-associated protein designated ODAM. Subsequently, it was shown by other investigators that ODAM is expressed in rodent enamel organ and is likely involved in dental development. We now report that this molecule also is found in certain human tissues, principally the salivary gland and trachea, as evidenced by RNA array analysis and immunohistochemistry-utilizing antibodies prepared against synthetic ODAM-related peptides and recombinant protein. Notably, these reagents immunostained normal and malignant ameloblasts and other types of human neoplastic cells, including those of gastric, lung, and breast origin where the presence in the latter was confirmed by in situ hybridization using gene-specific molecular probes. Moreover, significant titers of anti-ODAM IgG antibodies were detected in the sera of patients with these malignancies. Our studies have provided the first evidence in humans for the cellular expression of ODAM in normal and diseased states. Based on our findings, we posit that ODAM is a developmental antigen that has an essential role in tooth maturation and in the pathogenesis of certain odontogenic and other epithelial neoplasms; further, we suggest that ODAM may serve as a novel prognostic biomarker, as well as a potential diagnostic and therapeutic target for patients with breast and other epithelial forms of cancer.

Odontogenic ameloblast-associated protein nature of the amyloid found in calcifying epithelial odontogenic tumors and unerupted tooth follicles

We have previously reported that the amyloid found in three patients with calcifying epithelial odontogenic tumors (CEOT) was composed of N-terminal fragments of a putative 153-residue protein specified by a gene designated FLJ20513 now known to represent exons 5 through 10 of the odontogenic ameloblast-associated protein (ODAM) locus that encodes a 279-residue polypeptide. Confirmation of the amyloidogenic potential of ODAM has resulted from analyses of four other cases where we found, in addition, a 74-residue segment specified by exon 4. Through preparation of ODAM-related synthetic peptides, it was possible to localize the fibril-forming region of this molecule, as well as generate a monoclonal antibody that reacted specifically with the amyloid associated with CEOT. Notably, we also detected green birefringent congophilic material in unerupted tooth follicles - a precursor of CEOT - and demonstrated through immunologic and chemical analyses the ODAM nature of the deposits. Our studies have provided further evidence for this unique form of odontogenic amyloid that we provisionally designate "AODAM".