167 research outputs found
SIRT1 directly activates autophagy in human chondrocytes
© 2020, The Author(s). Osteoarthritis (OA) is the most common form of arthritis worldwide with no effective treatment. Ageing is the primary risk factor for OA. We sought to investigate if there is a distinct and functional convergence of ageing-related mechanisms SIRT1 and autophagy in chondrocytes. Our results show that, levels of SIRT1 are decreased in human normal aged and OA cartilage compared with young cartilage. Moreover, silencing SIRT1 in chondrocytes lead to decreased expression of chondrogenic markers but did not alter the expression of catabolic proteases. In contrast, activation of SIRT1 increased autophagy in chondrocytes by the deacetylation of lysine residues on crucial autophagy proteins (Beclin1, ATG5, ATG7, LC3). This activation was shown to be mTOR/ULK1 independent. Our results indicate that maintenance of autophagy in chondrocytes by SIRT1 is essential for preserving cartilage integrity throughout life and therefore is a target for drug intervention to protect against OA
RNA binding proteins regulate anabolic and catabolic gene expression in chondrocytes
This study demonstrates for the first time how RNABPs are able to affect the balance of anabolic and catabolic gene expression in human chondrocytes. The post-transcriptional mechanisms controlled by RNABPs present novel avenues of regulation and potential points of intervention for controlling the expression of SOX9 and MMP13 in chondrocytes
Targeted inhibition of aggrecanases prevents articular cartilage degradation and augments bone mass in the STR/Ort spontaneous model of osteoarthritis
BACKGROUND:Cartilage destruction in osteoarthritis (OA) is mediated mainly by MMPs and ADAMTSs. The therapeutic candidature of targeting aggrecanases has not yet been defined in joints where spontaneous OA arises due to genetic susceptibility, without a traumatic or load- induced aetiology such as the STR/Ort mouse. Nor do we know the long-term effect of aggrecanase inhibition on bone. METHODS:Using the STR/Ort spontaneously OA background, we have generated transgenic mice that overexpress [-1A]TIMP-3, either ubiquitously or conditionally in chondrocytes. [-1A]TIMP-3 is a variant of tissue inhibitor of metalloproteinase-3 (TIMP-3) that has an extra alanine at the N- terminus that selectively inhibits ADAMTSs, but not MMPs. We analysed a range of OA-related measures in all mice at 40 weeks of age. RESULTS:Mice expressing high [-1A]TIMP-3 levels were protected against the development of the OA whilst low expressers were not. Interestingly, we also found that high levels of [-1A]TIMP-3 transgene overexpression resulted in raised bone mass particularly in females. This regulation of bone mass is, at least, partly direct as primary adult osteoblasts infected with [-1A]TIMP-3 in vitro show elevated rates of mineralisation. CONCLUSIONS:The results provide evidence that [-1A]TIMP-3-mediated inhibition of aggrecanases can protect from cartilage degradation in naturally occurring OA mouse model and highlight a novel role that aggrecanases' inhibition may play in increased bone mass. This article is protected by copyright. All rights reserved
Dietary restriction of tyrosine and phenylalanine lowers tyrosinaemia associated with nitisinone therapy of alkaptonuria.
BACKGROUND: Alkaptonuria (AKU) is caused by homogentisate 1,2-dioxygenase deficiency that leads to homogentisic acid (HGA) accumulation, ochronosis and severe osteoarthropathy. Recently, nitisinone treatment, which blocks HGA formation, has been effective in AKU patients. However, a consequence of nitisinone is elevated tyrosine that can cause keratopathy. The effect of tyrosine and phenylalanine dietary restriction was investigated in nitisinone-treated AKU mice, and in an observational study of dietary intervention in AKU patients. METHODS: Nitisinone-treated AKU mice were fed tyrosine/phenylalanine-free and phenylalanine-free diets with phenylalanine supplementation in drinking water. Tyrosine metabolites were measured pre-nitisinone, post-nitisinone, and after dietary restriction. Subsequently an observational study was undertaken in 10 patients attending the National Alkaptonuria Centre (NAC), with tyrosine >700ÎŒmol/L who had been advised to restrict dietary protein intake and where necessary, to use tyrosine/phenylalanine-free amino acid supplements. RESULTS: Elevated tyrosine (813ÎŒmol/L) was significantly reduced in nitisinone-treated AKU mice fed a tyrosine/phenylalanine-free diet in a dose responsive manner. At 3âdays of restriction, tyrosine was 389.3ÎŒmol/L, 274.8ÎŒmol/L and 144.3ÎŒmol/L with decreasing phenylalanine doses. In contrast, tyrosine was not effectively reduced in mice by a phenylalanine-free diet; at 3âdays tyrosine was 757.3ÎŒmol/L, 530.2ÎŒmol/L and 656.2ÎŒmol/L, with no dose response to phenylalanine supplementation. In NAC patients, tyrosine was significantly reduced (p=0.002) when restricting dietary protein alone, and when combined with tyrosine/phenylalanine-free amino acid supplementation; 4 out of 10 patients achieved tyrosine <700ÎŒmol/L. CONCLUSION: Tyrosine/phenylalanine dietary restriction significantly reduced nitisinone-induced tyrosinaemia in mice, with phenylalanine restriction alone proving ineffective. Similarly, protein restriction significantly reduced circulating tyrosine in AKU patients
Data on CUX1 isoforms in idiopathic pulmonary fibrosis lung and systemic sclerosis skin tissue sections
This data article contains complementary figures related to the
research article entitled, âTransforming growth factor-ÎČ-induced
CUX1 isoforms are associated with fibrosis in systemic sclerosis
lung fibroblastsâ (Ikeda et al. (2016) [2], http://dx.doi.org/10.1016/j.
bbrep.2016.06.022), which presents that TGF-ÎČ increased CUX1
binding in the proximal promoter and enhancer of the COL1A2 and
regulated COL1. Further, in the scleroderma (SSc) lung and diffuse
alveolar damage lung sections, CUX1 localized within the α-
smooth muscle actin (α-SMA) positive cells (Fragiadaki et al., 2011)
[1], âHigh doses of TGF-beta potently suppress type I collagen via
the transcription factor CUX1â (Ikeda et al., 2016) [2]. Here we
show that CUX1 isoforms are localized within α-smooth muscle
actin-positive cells in SSc skin and idiopathic pulmonary fibrosis
(IPF) lung tissue sections. In particular, at the granular and prickle
cell layers in the SSc skin sections, CUX1 and α-SMA are colocalized.
In addition, at the fibrotic loci in the IPF lung tissue
sections, CUX1 localized within the α-smooth muscle actin (α-
SMA) positive cells
Anatomical Distribution of Ochronotic Pigment in Alkaptonuric Mice is Associated with Calcified Cartilage Chondrocytes at Osteochondral Interfaces
Alkaptonuria (AKU) is characterised by increased circulating homogentisic acid and deposition of ochronotic pigment in collagen-rich connective tissues (ochronosis), stiffening the tissue. This process over many years leads to a painful and severe osteoarthropathy, particularly affecting the cartilage of the spine and large weight bearing joints. Evidence in human AKU tissue suggests that pigment binds to collagen. The exposed collagen hypothesis suggests that collagen is initially protected from ochronosis, and that ageing and mechanical loading causes loss of protective molecules, allowing pigment binding. Schmorlâs staining has previously demonstrated knee joint ochronosis in AKU mice. This study documents more comprehensively the anatomical distribution of ochronosis in two AKU mouse models (BALB/c Hgdâ/â, Hgd tm1aâ/â), using Schmorlâs staining. Progression of knee joint pigmentation with age in the two AKU mouse models was comparable. Within the knee, hip, shoulder, elbow and wrist joints, pigmentation was associated with chondrons of calcified cartilage. Pigmented chondrons were identified in calcified endplates of intervertebral discs and the calcified knee joint meniscus, suggesting that calcified tissues are more susceptible to pigmentation. There were significantly more pigmented chondrons in lumbar versus tail intervertebral disc endplates (pâ=â0.002) and clusters of pigmented chondrons were observed at the insertions of ligaments and tendons. These observations suggest that loading/strain may be associated with increased pigmentation but needs further experimental investigation. The calcified cartilage may be the first joint tissue to acquire matrix damage, most likely to collagen, through normal ageing and physiological loading, as it is the first to become susceptible to pigmentation
Joint replacement risk is markedly increased in alkaptonuria (AKU) in those with prior arthroplasty
BackgroundIncreased homogentisic acid (HGA) in alkaptonuria (AKU) causes severe arthritis. Nitisinone reduces the production of HGA, but whether it also decreases arthroplasty was examined in 237 AKU patients.Patients and methodsPatients attending the United Kingdom National Alkaptonuria Centre (NAC) and the Suitability of Nitisinone in Alkaptonuria 2 (SONIA 2) study were studied. Assessments included questionnaires eliciting details of arthroplasty. Nitisinone was administered from baseline, 2 mg in the NAC and 10 mg in SONIA 2. In SONIA 2, subgroups consisted of those with baseline arthroplasty on and not on nitisinone (BR + N+, BR + N-), as well as those without baseline arthroplasty on and not on nitisinone (BR-N+, BR-N-).ResultsIn the SONIA2 subgroups, new joint replacement (JR) probabilities after baseline were significantly different (BR + N+, BR + N-, BR-N+, BR-N-) (Ï2 = 23.3, p p p (7.0) years at baseline but 57.7 (8.7) years at final follow up during nitisinone therapy and showed only 7 incident JR. The BR+ group had an age at baseline of 57.4 (8.5) years and had undergone 94 JRs at baseline.ConclusionThe incidence of arthroplasty was earlier and more frequent after the first JR and was not affected by nitisinone
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