Treatment of the arthropathy of familial hypercholesterolaemia

Familial Hypercholesterolemia with Tendinous Xanthomas and Achilles Tendinitis – A Forgotten Dermato-Rheumatologic Association

Familial hypercholesterolemia (FH) is a disorder of lipoprotein metabolism with dermatological and rhematological manifestations. Tendinous xanthomata (TX) are a hallmark of this disease. They are associated with recurrent tendinitis and tendon damage, an aspect of the clinical presentation, which is not well-known among dermatologists. We report two cases of heterozygous familial hypercholesterolemia, where the patients started developing tendinous xanthomata early in their life, with progressive increase in the number and size of lesions. However, they presented late, only when the recurrent attacks of tendinitis became severe. We present these cases to highlight the rheumatologic features, which may be the first symptom of heterozygous familial hypercholesterolemia.

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.

Possible involvement of the oxidized low-density lipoprotein/lectin-like oxidized low-density lipoprotein receptor-1 system in pathogenesis and progression of human osteoarthritis

OBJECTIVE

Using human cartilage samples and cultured chondrocytes, to assess the possible involvement of oxidized low-density lipoprotein (ox-LDL) and lectin-like ox-LDL receptor-1 (LOX-1) in pathogenesis and progression of osteoarthritis (OA).

METHODS

Thirty-two cartilage samples were obtained from 16 patients with knee OA, and 12 Control samples from six with femoral neck fracture. LOX-1 mRNA expressions in 12 OA and six Control samples were analyzed by reverse transcription-polymerase chain reaction (RT-PCR). Immunohistochemistry for ox-LDL and LOX-1 was performed in all samples. The histological OA grade was assessed with the modified Mankin score. The relative percentage of the ox-LDL and LOX-1 immunopositive chondrocytes was calculated in all samples. The effects of ox-LDL on cell viability in cultured human chondrocytes were investigated by the 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) assay and on proteoglycan synthesis by monitoring [35S] sulfate incorporation.

RESULTS

There was a statistically significant difference between mean LOX-1/GAPDH (LOX-1/human glyceraldehyde-3-phosphate dehydrogenase) ratio of OA samples and that of Control samples (40.6%+/-10.3 and 11.9%+/-2.8, respectively, P<0.0001). The mean percentage of ox-LDL-positive cells was 23.0+/-15.7% in OA and 4.3+/-3.7% in Control cells (P=0.0002). The mean percentage of LOX-1-positive cells was 51.7+/-29.5% in OA and 10.0+/-8.1% in Control cells (P<0.0001). Both the ox-LDL immunoreactivity and the LOX-1 immunoreactivity were significantly correlated with the modified Mankin scores (R2=0.67 and 0.48, respectively; P<0.0001 for each). ox-LDL significantly reduced the human chondrocyte viability and proteoglycan synthesis, and pretreatment with anti-human LOX-1 monoclonal antibody reversed these effects.

CONCLUSION

The ox-LDL/LOX-1 system may be involved in human OA.

Oxidized low-density lipoprotein (ox-LDL) binding to lectin-like ox-LDL receptor-1 (LOX-1) in cultured bovine articular chondrocytes increases production of intracellular reactive oxygen species (ROS) resulting in the activation of NF-kappaB

OBJECTIVE

To examine the effect of oxidized low-density lipoprotein (ox-LDL) on the intracellular production of reactive oxygen species (ROS) in bovine articular chondrocytes (BACs) and to investigate whether this increase occurs through binding to the receptor lectin-like ox-LDL receptor-1 (LOX-1). Furthermore, to ascertain whether the binding of ox-LDL to LOX-1 results in NF-kappaB activation.

DESIGN

BACs were preincubated with 2',7'-dichlorofluorescin diacetate (DCFH-DA), a dye that allows the monitoring of intracellular ROS production for DCF by spectrofluorometry. BACs were incubated with native LDL and ox-LDL (10, 50, and 100 microg/ml) for 5 min at 37 degrees C and DCF formation was observed. BACs were also preincubated with anti-LOX-1 mAb (40 microg/ml) or ascorbic acid (10 microM). Nuclear extracts from BACs treated for the indicated periods with 50 microg/ml ox-LDL, and preincubated with anti-LOX-1 mAb or ascorbic acid, were prepared and analyzed by electrophoretic mobility shift assay (EMSA).

RESULTS

ox-LDL induced a significant dose-dependent increase in ROS production after 5-min incubation with BACs (P < 0.001). ROS formation was markedly reduced in BACs preincubated with anti-LOX-1 mAb and ascorbic acid (P < 0.001). Activation in BACs of the transcription factor NF-kappaB was evident after 5-min incubation with ox-LDL and was attenuated by anti-LOX-1 mAb and ascorbic acid.

CONCLUSION

ox-LDL binding to LOX-1 in BACs increased the production of intracellular ROS and activated NF-kappaB. Reduction of NF-kappaB activation by ascorbic acid indicates that the activation, at least in part, is ROS-dependent. These observations support the hypothesis that hypercholesterolemia is one of several risk factors for arthritis, and that lipid peroxidation products such as ox-LDL are involved in cartilage matrix degradation.

[Hyperlipidemia and osteoarticular manifestations]

Hyperlipoproteinaemia, notably types II and IV, may give rise to various musculoskeletal disorders. Mono-, oligo- or polyarthritis, or even simple arthralgias, are often encountered in patients with severe type IIa hyperlipoproteinaemia, the most satisfactory tentative explanation for this being a microcrystalline pathology. Tendinitis is also frequent, particularly in children. The same manifestations have also been reported, although more occasionally, in type IV hyperlipoproteinaemia. Skeletal lesions, such as xanthoma or lipoma ossificans, are extremely rare. Other musculoskeletal disorders, including gout and aseptic osteonecrosis, are often associated with hyperlipidaemia. Some diseases may induce secondary hyperlipidaemia but have their own rheumatological manifestations. Finally, lipid-lowering drugs, such as fibrates and statines, sometimes induce disabling myalgias.

Articular manifestations of familial hypercholesterolaemia

Familial hypercholesterolaemia is characterised by a decreased removal of low density lipoproteins and premature coronary artery disease. Tendinous xanthomata are a hallmark of the disease. The affected joints may also be the sites of inflammation and pain. Arthropathy has been associated mainly with the homozygous form of familial hypercholesterolaemia, but it is also known to occur in the heterozygous form. We report on the articular manifestations in 73 patients with heterozygous familial hypercholesterolaemia. About 40% of these patients had at least one episode of articular symptoms. The observed articular manifestations may be classified into four types: Achilles pain (18%), Achilles tendinitis (11%), oligoarticular arthritis (7%), polyarticular or rheumatic fever-like arthritis (4%). It is concluded that in heterozygous familial hypercholesterolaemia articular manifestations are frequent, diverse, and may be the first symptom of this metabolic disorder.