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.

Antioxidants inhibit SAA formation and pro-inflammatory cytokine release in a human cell model of alkaptonuria.

OBJECTIVE: Alkaptonuria (AKU) is an ultra-rare autosomal recessive disease that currently lacks an appropriate therapy. Recently we provided experimental evidence that AKU is a secondary serum amyloid A (SAA)-based amyloidosis. The aim of the present work was to evaluate the use of antioxidants to inhibit SAA amyloid and pro-inflammatory cytokine release in AKU. METHODS: We adopted a human chondrocytic cell AKU model to evaluate the anti-amyloid capacity of a set of antioxidants that had previously been shown to counteract ochronosis in a serum AKU model. Amyloid presence was evaluated by Congo red staining. Homogentisic acid-induced SAA production and pro-inflammatory cytokine release (overexpressed in AKU patients) were evaluated by ELISA and multiplex systems, respectively. Lipid peroxidation was evaluated by means of a fluorescence-based assay. RESULTS: Our AKU model allowed us to prove the efficacy of ascorbic acid combined with N-acetylcysteine, taurine, phytic acid and lipoic acid in significantly inhibiting SAA production, pro-inflammatory cytokine release and membrane lipid peroxidation. CONCLUSION: All the tested antioxidant compounds were able to reduce the production of amyloid and may be the basis for establishing new therapies for AKU amyloidosis.

Biochemical and proteomic characterization of alkaptonuric chondrocytes.

Alkaptonuria (AKU) is a rare genetic disease associated with the accumulation of homogentisic acid (HGA) and its oxidized/polymerized products which leads to the deposition of melanin-like pigments (ochronosis) in connective tissues. Although numerous case reports have described ochronosis in joints, little is known on the molecular mechanisms leading to such a phenomenon. For this reason, we characterized biochemically chondrocytes isolated from the ochronotic cartilage of AKU patients. Based on the macroscopic appearance of the ochronotic cartilage, two sub-populations were identified: cells coming from the black portion of the cartilage were referred to as "black" AKU chondrocytes, while those coming from the white portion were referred to as "white" AKU chondrocytes. Notably, both AKU chondrocytic types were characterized by increased apoptosis, NO release, and levels of pro-inflammatory cytokines. Transmission electron microscopy also revealed that intracellular ochronotic pigment deposition was common to both "white" and "black" AKU cells. We then undertook a proteomic and redox-proteomic analysis of AKU chondrocytes which revealed profound alterations in the levels of proteins involved in cell defence, protein folding, and cell organization. An increased post-translational oxidation of proteins, which also involved high molecular weight protein aggregates, was found to be particularly relevant in "black" AKU chondrocytes.

Evaluation of antioxidant drugs for the treatment of ochronotic alkaptonuria in an in vitro human cell model.

Alkaptonuria (AKU) is a rare autosomal recessive disease, associated with deficiency of homogentisate 1,2-dioxygenase activity in the liver. This leads to an accumulation of homogentisic acid (HGA) and its oxidized derivatives in polymerized form in connective tissues especially in joints. Currently, AKU lacks an appropriate therapy. Hence, we propose a new treatment for AKU using the antioxidant N-acetylcysteine (NAC) administered in combinations with ascorbic acid (ASC) since it has been proven that NAC counteracts the side-effects of ASC. We established an in vitro cell model using human articular primary chondrocytes challenged with an excess of HGA (0.33 mM). We used this experimental model to undertake pre-clinical testing of potential antioxidative therapies for AKU, evaluating apoptosis, viability, proliferation, and metabolism of chondrocytes exposed to HGA and treated with NAC and ASC administered alone or in combination addition of both. NAC decreased apoptosis induced in chondrocytes by HGA, increased chondrocyte growth reduced by HGA, and partially restored proteoglycan release inhibited by HGA. A significantly improvement in efficacy was found with combined addition of the two antioxidants in comparison with NAC and ASC alone. Our novel in vitro AKU model allowed us to demonstrate the efficacy of the co-administration of NAC and ASC to counteract the negative effects of HGA for the treatment of ochronotic arthropathy.

Biochemical investigation of the effects of human platelet releasates on human articular chondrocytes.

The aim of the present study was to demonstrate the mitogenic and differentiating properties of platelet-rich plasma releasates (PRPr) on human chondrocytes in mono- and three-dimensional cultures. In order to assess if PRPr supplementation could maintain the chondrocyte phenotype or at least inhibit the cell de-differentiation even after several days in culture, we performed a proteomic study on several cell cultures independently grown, for different periods of time, in culture medium with FCS, human serum (HS), and releasates obtained from PRP and platelet-poor plasma (PPP). We found that PRP treatment actually induced in chondrocytes the expression of proteins (some of which novel) involved in differentiation.

Human platelet releasates combined with polyglycolic acid scaffold promote chondrocyte differentiation and phenotypic maintenance.

In the present study, we aimed to demonstrate the differentiating properties of platelet-rich plasma releasates (PRPr) on human chondrocytes seeded on a polygtlycolic acid (PGA) 3D scaffold. Gene expression and biochemical analysis were carried out to assess the improved quality of our PGA-based cartilage constructs supplemented with PRPr. We observed that the use of PRPr as cell cultures supplementation to PGA-chondrocyte constructs may promote chondrocyte differentiation, and thus may contribute to maintaining the chondrogenic phenotype longer than conventional supplementation by increasing high levels of important chondrogenic markers (e.g. sox9, aggrecan and type II collagen), without induction of type I collagen. Moreover, our constructs were analysed for the secretion and deposition of important ECM molecules (sGAG, type II collagen, etc.). Our results indicate that PRPr supplementation may synergize with PGA-based scaffolds to stimulate human articular chondrocyte differentiation, maturation and phenotypic maintenance.

Serum amyloid A circulating levels and disease activity in patients with juvenile idiopathic arthritis.

The aim of our study was to evaluate the association between circulating levels of serum amyloid A protein (SAA) and disease activity in patients with juvenile idiopathic arthritis (JIA). Our study group included 41 JIA patients (9 male, 32 female), classified according to the International League of Associations for Rheumatology (ILAR) criteria (5); 16 had polyarticular onset disease and 25 had oligoarticular onset disease. Among 25 patients with oligoarticular disease, three had extended oligoarthritis. Serum amyloid A (SAA), erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were measured in both patients and 26 healthy controls. SAA levels were higher in JIA patients versus healthy controls (p<0.001). Significant positive correlations were found between SAA and the presence of active joints (rho=0.363, p<0.05), the number of active joints (rho=0.418, p<0.05), ESR (R=0.702, p<0.05) and CRP (R=0.827, p<0.05). No significant correlations between ESR and the presence of active joints (rho=0.221, p=0.225) or between ESR and the number of active joints (rho=0.118, p=0.520) were demonstrated in JIA patients. No significant correlations were obtained between CRP and the presence of active joints (rho=0.034, p=0.855) or between CRP and the number of active joints (rho=0.033, p=0.859). We discovered a significant increase in SAA levels in JIA patients, compared to controls, and a strong positive correlation between SAA level and JIA disease activity. We also discerned SAA to be a more sensitive laboratory marker than ESR and CRP for evaluating the presence and number of active joints. We suggest that SAA can be used as an additional indicator of disease activity in JIA.