Clinical strategies for amyloid A amyloidosis secondary to rheumatoid arthritis

The potential role of glycosaminoglycans in serum amyloid A fibril formation by in silico approaches

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SAA dimer binds GAGs stronger than its monomer.

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Due to its net negative charge SAA prefers to bind short GAG sequences.

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GAG binding by SAA is electrostatics-driven and rather unspecific.

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GAG binding site is constituted predominantly by the N-terminal helix residues.

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GAG binding could potenitally attenuate unfolding of the N-terminal helix.

Serum amyloid A (SAA) is actively involved in such pathological processes as atherosclerosis, rheumatoid arthritis, cancer and Alzheimer's disease by its aggregation. One of the factors that can attenuate its aggregation and so affects its physiological role is its interactions with glycosminoglycans (GAGs), linear anionic periodic polysaccharides. These molecules located in the extracellular matrix of the cell are highly variable in their chemical composition and sulfation patterns. Despite the available experimental evidence of SAA-GAG interactions, no mechanistic details at atomic level have been reported for these systems so far. In our work we aimed to apply diverse computational tools to characterize SAA-GAG complexes formation and to answer questions about their potential specificity, energetic patterns, particular SAA residues involved in these interactions, favourable oligomeric state of the protein and the potential influence of GAGs on SAA aggregation. Molecular docking, conventional and replica exchange molecular dynamics approaches were applied to corroborate the experimental knowledge and to propose the corresponding molecular models. SAA-GAG complex formation was found to be electrostatics-driven and rather unspecific of a GAG sulfation pattern, more favorable for the dimer than for the monomer when binding to a short GAG oligosaccharide through its N-terminal helix, potentially contributing to the unfolding of this helix, which could lead to the promotion of the protein aggregation. The data obtained add to the specific knowledge on SAA-GAG systems and deepen the general understanding of protein-GAG interactions that is of a considerable value for the development of GAG-based approaches in a broad theurapeutic context.

A 16-year Survey of Clinicopathological Findings, Electron Microscopy, and Classification of Renal Amyloidosis

Background

Electron microscopy (EM) is a valuable tool in the diagnosis of renal amyloidosis, particularly in the early stages of the disease. In Iran, studies on EM and the clinical features of renal amyloidosis are scarce. The objective of the present study was to survey EM investigations, pathological classifications, and clinical features of renal amyloidosis.

Methods

This cross-sectional study was performed in Shiraz, Iran, during 2001-2016. Out of 2,770 kidney biopsies, 27 cases with a diagnosis of renal amyloidosis were investigated. EM investigation and six staining procedures for light microscopy (LM) were performed. Two pathological classifications based on glomerular, peritubular, perivascular, and interstitial involvement were made. Finally, the association between these classifications and the clinical features was assessed. Chi-square, Fisher's exact, Independent t test, and Multiple logistic regression analysis were used. P values<0.05 were considered statistically significant.

Results

In 51.9% of the cases, the clinical diagnosis was nephrotic syndrome. Proteinuria and edema were the most prevalent clinical manifestations. The role of EM investigation for diagnosis was graded "necessary" or "supportive" in 48.2% of the patients. In the classification based on glomerular classes, variables such as the mean blood pressure (P=0.003), history of hypertension (P=0.02), creatinine >1.5 (P=0.03), and severe tubular atrophy (P=0.03) were significantly higher in class B (advanced amyloid depositions).

Conclusion

EM plays an important role in the diagnosis of renal amyloidosis. EM in conjunction with LM investigation with Congo red staining is recommended, to prevent misdiagnosis of patients with a clinical suspicion of renal amyloidosis. Among different pathological features of renal amyloidosis, the severity of glomerular amyloid depositions had a clear relationship with clinical presentations.

Rituximab Therapy in Renal Amyloidosis Secondary to Rheumatoid Arthritis

Secondary amyloid A (AA) amyloidosis is a late and serious complication of poorly controlled, chronic inflammatory diseases. Rheumatoid arthritis (RA) patients with poorly controlled, longstanding disease and those with extra-articular manifestations are under risk for the development of AA amyloidosis. Although new drugs have proven to be significantly effective in the treatment of secondary AA amyloidosis, no treatment modality has proven to be ideal. To date, only in small case series preliminary clinical improvement have been shown with rituximab therapy for AA amyloidosis secondary to RA that is refractory to TNF-α inhibitors (TNF-i) therapy. In these case series, we assessed the efficacy and safety of rituximab therapy for patients with RA and secondary amyloidosis. Hacettepe University Biologic Registry was developed at 2005. The data of the RA patients who were prescribed a biological drug were recorded regularly. Patients with biopsy proven AA amyloidosis patients were screened. Of 1022 RA patients under biologic therapy, 0.7% patients had clinically apparent histologically confirmed amyloidosis. Four of seven patients who were prescribed rituximab at least one infusion enrolled to those case series. Two of four patients showed significant clinical improvement and one of them also had decrease in proteinuria and the other one had stable renal function and proteinuria. The main goal for the treatment of AA amyloidosis is to control the activity of the underlying disorder. In this study, we showed that rituximab may be an effective treatment in RA patients with amyloidosis who were unresponsive to conventional disease modifying anti-rheumatic drugs (DMARDs) and/or TNFi.

Diagnosis of secondary amyloidosis in alkaptonuria

Background

Alkaptonuria (AKU) is an inborn error of catabolism due to a deficient activity of homogentisate 1,2-dioxygenase. Patients suffer from a severe arthropathy, cardiovascular and kidney disease but other organs are affected, too. We found secondary amyloidosis as a life-threatening complication in AKU, thus opening new perspectives for its treatment. We proved that methotrexate and anti-oxidants have an excellent efficacy to inhibit the production of amyloid in AKU model chondrocytes. Owing to the progressive and intractable condition, it seems important to detect amyloid deposits at an early phase in AKU and the choice of specimens for a correct diagnosis is crucial.

Methods

Ten AKU subjects were examined for amyloidosis; abdominal fat pad aspirates, labial salivary gland, cartilage and synovia specimens were analysed by CR, Th-T, IF, TEM.

Results

Amyloid was detected in only one abdominal fat pad specimen. However, all subjects demonstrated amyloid deposition in salivary glands and in other organ biopsies, indicating salivary gland as the ideal specimen for early amyloid detection in AKU.

Conclusions

This is, at the best of our knowledge, the first report providing correct indications on the diagnosis of amyloidosis in AKU, thus offering the possibility of treatment of such co-morbidity to AKU patients.

Virtual slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_185

Therapeutic Benefits of Tocilizumab Vary in Different Organs of a Patient with AA Amyloidosis

Systemic reactive AA amyloidosis is a life-threatening complication of chronic inflammatory diseases. Anti-interleukin-6 receptor, tocilizumab (TCZ), has been shown to improve clinical symptoms of patients with AA amyloidosis, accompanied with regression of the amyloid deposition. We report a case of AA amyloidosis evaluated by histology of multiple organs before and after TCZ treatment. A woman in her 60s with rheumatoid arthritis was referred to our hospital because of cardiac and renal dysfunction. A gastric and renal biopsy revealed the deposition of AA amyloid, and echocardiography revealed concentric left ventricular hypertrophy. Her estimated glomerular filtration rate was decreased to 8.6 mL/min/1.73 m², and B-type natriuretic peptide, C-reactive protein, and serum amyloid A protein were significantly elevated. TCZ treatments markedly decreased her serum amyloid A protein and C-reactive protein levels, but hemodialysis was required 1 year later. Endoscopic gastric rebiopsy 3 years after initiation of TCZ treatments revealed the regression of amyloid deposition and echocardiography revealed improvement of her left ventricular hypertrophy. However, a renal rebiopsy revealed that the amyloid deposition had not regressed. In conclusion, these observations suggest that the therapeutic effects of TCZ can vary among organs in patients with AA amyloidosis.

Interaction of serum amyloid A with human cystatin C--assessment of amino acid residues crucial for hCC-SAA formation (part II)

Secondary amyloid A (AA) amyloidosis is an important complication of some chronic inflammatory diseases, primarily rheumatoid arthritis (RA). It is a serious, potentially life-threatening disorder caused by the deposition of AA fibrils, which are derived from the circulatory, acute-phase-reactant, serum amyloid A protein (SAA). Recently, a specific interaction between SAA and the ubiquitous inhibitor of cysteine proteases--human cystatin C (hCC)--has been proved. Using a combination of selective proteolytic excision and high-resolution mass spectrometry, the binding sites in the SAA and hCC sequences were assessed as SAA(86-104) and hCC(96-102), respectively. Here, we report further details concerning the hCC-SAA interaction. With the use of affinity tests and florescent ELISA-like assays, the amino acid residues crucial for the protein interaction were determined. It was shown that all amino acid residues in the SAA sequence, essential for the formation of the protein complex, are basic ones, which suggests an electrostatic interaction character. The idea is corroborated by the fact that the most important residues in the hCC sequence are Ser-98 and Tyr-102; these residues are able to form hydrogen bonds via their hydroxyl groups. The molecular details of hCC-SAA complex formation might be helpful for the design of new compounds modulating the biological role of both proteins.

Effectiveness of etanercept vs cyclophosphamide as treatment for patients with amyloid A amyloidosis secondary to rheumatoid arthritis

OBJECTIVES

To compare the effectiveness of an alkylating agent with that of a biologic agent in the treatment of patients with amyloid A (AA) amyloidosis secondary to RA and to assess the association of the serum AA (SAA) 1.3 allele with treatment.

METHODS

CYC and etanercept (ETN) were administered to 62 and 24 RA patients, respectively, who were confirmed with biopsy as having AA amyloidosis. We evaluated whether the SAA1.3 allele, a factor indicating genetic risk and poor prognosis of Japanese RA patients with AA amyloidosis, influenced treatments and retrospectively analysed the effectiveness of both agents via statistical methods.

RESULTS

Two treatment groups were similar, except for the SAA1.3 genotype (P = 0.015) and duration of AA amyloidosis since diagnosis (P < 0.001). Also, patients given ETN had somewhat worse renal function, i.e. 24-h proteinuria (P = 0.02), at the initiation of treatment. ETN demonstrated greater effectiveness than CYC, as shown by significantly improved levels of serum CRP and serum albumin (both P < 0.01) and estimated glomerular filtration rate (eGFR; P = 0.032). ETN improved survival (P = 0.025), and the hazard ratios for the risk of death endpoint with eGFR and 24-h proteinuria were significant by P = 0.024 and P = 0.025, respectively. The SAA1.3 allele did not affect the response to medications in AA amyloidosis secondary to RA.

CONCLUSION

ETN treatment was more effective than CYC treatment, and CRP, albumin and eGFR may be valuable biomarkers for analysis. The SAA1.3 allele was not a factor affecting treatment in Japanese patients with AA amyloidosis secondary to RA.

Alkaptonuria is a novel human secondary amyloidogenic disease

Alkaptonuria (AKU) is an ultra-rare disease developed from the lack of homogentisic acid oxidase activity, causing homogentisic acid (HGA) accumulation that produces a HGA-melanin ochronotic pigment, of unknown composition. There is no therapy for AKU. Our aim was to verify if AKU implied a secondary amyloidosis. Congo Red, Thioflavin-T staining and TEM were performed to assess amyloid presence in AKU specimens (cartilage, synovia, periumbelical fat, salivary gland) and in HGA-treated human chondrocytes and cartilage. SAA and SAP deposition was examined using immunofluorescence and their levels were evaluated in the patients' plasma by ELISA. 2D electrophoresis was undertaken in AKU cells to evaluate the levels of proteins involved in amyloidogenesis. AKU osteoarticular tissues contained SAA-amyloid in 7/7 patients. Ochronotic pigment and amyloid co-localized in AKU osteoarticular tissues. SAA and SAP composition of the deposits assessed secondary type of amyloidosis. High levels of SAA and SAP were found in AKU patients' plasma. Systemic amyloidosis was assessed by Congo Red staining of patients' abdominal fat and salivary gland. AKU is the second pathology after Parkinson's disease where amyloid is associated with a form of melanin. Aberrant expression of proteins involved in amyloidogenesis has been found in AKU cells. Our findings on alkaptonuria as a novel type II AA amyloidosis open new important perspectives for its therapy, since methotrexate treatment proved to significantly reduce in vitro HGA-induced A-amyloid aggregates.

Significant association between renal function and area of amyloid deposition in kidney biopsy specimens in reactive amyloidosis associated with rheumatoid arthritis

The kidney is a major target organ for systemic amyloidosis, resulting in proteinuria and an elevated serum creatinine level. In patients with reactive amyloidosis associated with rheumatoid arthritis, a correlation between the amount of amyloid deposits and clinical parameters is not known. The purpose of this study was to clarify the association between various factors including renal function and the area of amyloid deposition in these patients. Fifty-eight patients with an established diagnosis of reactive AA amyloidosis were studied. We retrospectively investigated the correlation between clinical data and the area occupied by amyloid in renal biopsy specimens. All the patients showed amyloid deposits in renal tissues, and the percentage of the area occupied by amyloid was <10% in 54 of them. Mesangial proliferative glomerulonephritis and membranous nephropathy were frequently combined with renal amyloidosis. For statistical analyses, the percentage of the area occupied by amyloid was transformed to a common logarithmic value (Log(10) % amyloid), as the histograms showed a log-normal distribution. Log(10) % amyloid was found to be correlated with age, creatinine (Cr) level, creatinine clearance (Ccr), blood urea nitrogen (BUN) level, and the estimated glomerular filtration rate (eGFR). Multiple linear regression analyses were then performed to examine the sex- and age-adjusted association between Log(10) % amyloid and each of the clinical variables. Cr, Ccr, BUN, UA, CRP, and eGFR were significantly correlated with Log(10) % amyloid, but urinary protein was not. There was a significant correlation between the area of amyloid deposition in renal tissue and parameters of renal function, especially Cr and Ccr. If amyloid deposition in renal tissue can be arrested or prevented, then it may be possible to maintain renal function at an acceptable level.

Extra-articular manifestations of rheumatoid arthritis: An update

Rheumatoid arthritis (RA) is an immune-mediated disease involving chronic low-grade inflammation that may progressively lead to joint destruction, deformity, disability and even death. Despite its predominant osteoarticular and periarticular manifestations, RA is a systemic disease often associated with cutaneous and organ-specific extra-articular manifestations (EAM). Despite the fact that EAM have been studied in numerous RA cohorts, there is no uniformity in their definition or classification. This paper reviews current knowledge about EAM in terms of frequency, clinical aspects and current therapeutic approaches. In an initial attempt at a classification, we separated EAM from RA co-morbidities and from general, constitutional manifestations of systemic inflammation. Moreover, we distinguished EAM into cutaneous and visceral forms, both severe and not severe. In aggregated data from 12 large RA cohorts, patients with EAM, especially the severe forms, were found to have greater co-morbidity and mortality than patients without EAM. Understanding the complexity of EAM and their management remains a challenge for clinicians, especially since the effectiveness of drug therapy on EAM has not been systematically evaluated in randomized clinical trials.

Serum amyloid A induces reactive oxygen species (ROS) production and proliferation of fibroblast

Serum amyloid A (SAA) levels are elevated highly in acute phase response and elevated slightly and persistently in chronic diseases such as rheumatoid arthritis and diabetes. Given that fibroblasts exert profound effects on progression of inflammatory chronic diseases, the aim of this study was to investigate the response of fibroblasts to SAA. A dose-dependent increase in O(2) (-) levels was observed by treatment of fibroblasts with SAA (r = 0·99 and P ≤ 0·001). In addition, the expression of p47-phox was up-regulated by SAA (P < 0·001) and diphenyliodonium (DPI), a nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor, reduced the release of O(2) (-) by 50%. Also, SAA raised fibroblast proliferation (P < 0·001) and this effect was completely abolished by the addition of anti-oxidants (P < 0·001). These findings support the notion that, in chronic inflammatory sites, SAA activated fibroblast proliferation and ROS production.

Therapeutic anti-inflammatory potential of formyl-peptide receptor agonists

The need for novel anti-inflammatory drugs justifies the search for innovative targets that could satisfy this goal. For quite some time now, we have proposed the study of endogenous anti-inflammation as a distinctive approach to the discovery of new drugs. This approach requires development of new compounds that activate specific receptor targets to downregulate the cellular and tissue pathways operative in the host during inflammation. Here we dwell on a family of G-protein coupled receptors (GPCR) termed FPRs, acronym for formyl-peptide receptors. With three and seven members in man and mouse, respectively, these receptors harness many biological functions, spanning odour perception and hair growth, to the control of multiple facets (pain; cell migration; oxidative burst; xenobiotic engulfment) of the inflammatory reaction. We focus on FPR biology with particular attention to molecules able to produce pharmacological effects by interacting with these GPCRs, describing endogenous agonists of FPRs and, more relevantly, the current development of synthetic agonists. Besides being potential leads for the development of the anti-inflammatory therapeutics of the future, these compounds could also help clarify the properties and roles that each FPR might play in the complex network of pathways that is inflammation. We conclude that FPR2 agonists could be valid warhorses for defining a novel philosophy for anti-inflammatory drug discovery programmes: mimicking - with new compounds - the way our body disposes of inflammation could be a viable approach to regulate aberrant inflammatory responses as in the case of several chronic rheumatic and cardiovascular pathologies.

Recent advances in neutralizing the IL-6 pathway in arthritis

Recent advances in understanding the mechanism(s) of how IL-6 trans-signaling regulates immune cell function and promotes inflammation in autoimmune arthritis are critically reviewed. Serum and/or synovial fluid (SF) IL-6 is markedly elevated in adult and juvenile rheumatoid arthritis (RA), psoriatic arthritis (PsA), ankylosing spondylitis (AS) and osteoarthritis (OA). IL-6, in concert with IL-17, determines the fate of CD4⁺ lymphocytes and therefore TH₁₇ cell differentiation. IL-6 also plays a critical role in modulating B-lymphocyte activity. The recognition that IL-6 trans-signaling regulates inflammation resulted in the development of tocilizumab, a fully humanized monoclonal antibody that neutralizes the biological activity of the IL-6-receptor (IL-6R). Significant clinical benefit was demonstrated as well as reduced serum IL-6 levels with suppression of X-ray progression of disease in several clinical trials in which juvenile or adult RA patients were treated with tocilizumab monotherapy or tocilizumab plus methotrexate. However, levels of serum and/or SF IL-6 cytokine protein superfamily members, adiponectin, oncostatin M, pre-B-cell colony enhancing factor/visfatin and leukemia inhibitory factor are also elevated in RA. Additional studies will be required to determine if anti-IL-6 trans-signaling inhibition strategies with tocilizumab or recombinant soluble IL-6R reduce the level of these cytokines.

Effective Anti-TNF-α Therapy Can Induce Rapid Resolution and Sustained Decrease of Gastroduodenal Mucosal Amyloid Deposits in Reactive Amyloidosis Associated with Rheumatoid Arthritis

Objective.

To examine the effect of anti-tumor necrosis factor-α (anti-TNF) therapy in patients with reactive AA amyloidosis associated with rheumatoid arthritis (RA).

Methods.

Fourteen patients with reactive AA amyloidosis associated with RA were prospectively evaluated. Four patients were treated with infliximab and 10 with etanercept. The mean period of anti-TNF therapy was 20.1 ± 13.8 months. Laboratory findings and renal function were examined before and after initiation of anti-TNF therapy. In 9 patients the area of amyloid deposits in serial gastroduodenal mucosal biopsy specimens was examined and image analysis was performed.

Results.

C-reactive protein and serum amyloid A protein levels were significantly reduced after initiation of anti-TNF therapy. Twenty-four hour creatinine clearance improved in 4 patients, did not change in 5, and deteriorated in 3. Twenty-four hour urinary protein excretion was significantly decreased in 3 patients, not exacerbated in 6, and increased in 3 after initiation of anti-TNF therapy. The biopsy specimens from the 9 patients who underwent serial gastroduodenal biopsies showed significant decreases in the area of amyloid deposits, from 8.8% ± 6.4% to 1.6% ± 0.6% (p = 0.003) after initiation of anti-TNF therapy. Four patients showed a sustained decrease in the areas of amyloid deposits in their third biopsy specimens, and amyloid deposits were not detectable in 2.

Conclusion.

Our results indicate a striking effect of anti-TNF therapy for rapid removal and sustained disappearance of amyloid deposits in gastric mucosal tissue with amelioration of renal functions in patients with reactive amyloidosis due to RA.