Lysosomal dysfunction in osteoarthritis and aged cartilage triggers apoptosis in chondrocytes through BAX mediated release of Cytochrome c

OBJECTIVE

Lysosomes are the major catabolic organelle of the cell and regulate the macromolecular and organelle turnover and programmed cell death. Here, we investigated the lysosome dysfunction in cartilage and its role in chondrocytes apoptosis and the associated mechanism.

DESIGN

Lysosomal acidification in Osteoarthritis (OA) and aged cartilage was determined by LysoSensor staining. Lysosomal function in chondrocytes was blocked by siRNA mediated depletion of Lysosomal Associated Membrane Protein 2 (LAMP2) or with lysosome inhibitors. Chondrocyte apoptosis was determined by LDH release, Caspase-3/7 activation, TUNEL and PI uptake assays. Loss of mitochondrial membrane potential (MMP/ΔΨM) and mitochondrial superoxide level was determined by JC-1 and MitoSOX staining, respectively. Colocalization of mitochondria with BCL2 associated X (BAX) and Cytochrome c was determined by immunostaining. Destabilization of medial meniscus (DMM) was performed to induce OA in mice.

RESULTS

Lysosomal acidification was found to be significantly decreased in aged mouse and human and mouse OA cartilage which also showed increased chondrocyte apoptosis. Inhibition of lysosomal function resulted in increased oxidative stress, accumulation of dysfunctional mitochondria and apoptosis in chondrocytes in monolayer and in cartilage explant cultures. Depletion of LAMP2 expression or treatment of chondrocytes with lysosomal function inhibitors increased the expression and mitochondrial translocation of BAX leading to Cytochrome c release. Lysosomal dysfunction-induced apoptosis in chondrocytes was not blocked by antioxidants MitoTempo or Diphenyleneiodonium (DPI) but was abrogated by inhibiting BAX.

CONCLUSION

Lysosomal dysfunction induce apoptosis in chondrocytes through BAX-mediated mitochondrial damage and release of Cytochrome c. Our data points to lysosomal function restoration and/or BAX inhibition in chondrocytes as a therapeutic approach for OA.

tRNA-derived fragments (tRFs) regulate post-transcriptional gene expression via AGO-dependent mechanism in IL-1β stimulated chondrocytes

OBJECTIVES

Recent studies have shown that tRNA-derived RNA fragments (tRFs) are novel regulators of post-transcriptional gene expression. However, the expression profiles and their role in post-transcriptional gene regulation in chondrocytes is unknown. Here, we determined tRFs expression profile and explored tRF-3003a role in post-transcriptional gene regulation in IL-1β stimulated chondrocytes.

METHODS

We used qPCR arrays to determine tRNAs and tRFs expression in age- and sex-matched primary human OA chondrocytes and TC28/I2 cells stimulated with IL-1β. Chondrocytes were transfected with tRNA-Cys^GCA overexpression plasmid or tRF-3003a mimic and 3'UTR luciferase reporter plasmids of mRNAs harboring predicted tRF target "seed sequence". The AGO-RNA-induced silencing complex (AGO-RISC)-dependent repressive activity of tRF-3003a was determined by siRNA-mediated knockdown of AGO2.

RESULTS

IL-1β increased the expression levels of specific tRNAs and of tRF-3003a, a type 3 tRF produced by the cleavage of tRNA-Cys^GCA. tRF-3003a "seed sequence" was identified in the 3'UTR of JAK3 mRNA and tRNA-Cys^GCA overexpression or transfection of a tRF-3003a mimic in chondrocytes downregulated JAK3 expression and significantly reduced the activity of the 3'UTR reporter. RIP assay showed enrichment of tRF-3003a into AGO2/RISC in IL-1β treated chondrocytes. The suppressive effect of tRF-3003a on JAK3 3'UTR reporter was abrogated with siRNA-mediated depletion of AGO2.

CONCLUSIONS

We demonstrate that under pathological conditions chondrocytes display perturbations in the expression profile of specific tRNAs and tRFs. Furthermore, a specific tRF namely tRF-3003a can post-transcriptionally regulate JAK3 expression via AGO/RISC formation in chondrocytes. Identification of this novel mechanism may be of value in the design of precision therapies for OA.

Expression profile of protein tyrosine kinase genes in human osteoarthritis chondrocytes

OBJECTIVE

To determine the expression profile of protein kinase (PK) and protein tyrosine kinase (PTK) genes in human primary osteoarthritis (OA) chondrocytes and to compare it with that of immortalized human chondrocytes T/C 28a4 with a view to learning whether T/C 28a4 cells can be used for elucidating signal transduction pathways in human chondrocytes.

DESIGN

We used the Atlas Human cDNA Array and a method based on PCR with degenerate primers to analyse the expression profile of protein kinase genes in primary human OA chondrocytes and compared it with that of immortalized human chondrocyte cell line T/C 28a4 using RT-PCR and Western blotting.

RESULTS

A total of 21 PTK genes were identified and several of these have never been shown to be expressed in human OA chondrocytes. Comparative expression analysis of some selected kinase genes showed that the mRNA expression pattern of many protein kinase genes in OA chondrocytes was identical to that of T/C 28a4 cells. However, there were differences in the level of protein expression of selected protein kinases in these cells. For example, mRNA expression of the novel kinase HCK was detected in OA chondrocytes and in the cell lines analysed but by Western blotting HCK protein was not detected in OA chondrocytes. In these studies, we also identified a novel mutant form of the discoidin domain receptor 2 (DDR2) transcript from chondrocyte-like cell line HTB-94.

CONCLUSIONS

Our results provide novel information about protein kinase gene expression in OA chondrocytes and indicate that the transformed chondrocyte cell line T/C 28a4 may be suitable for elucidating signal transduction pathways in chondrocytes and to investigate how they regulate chondrocyte function in inflammatory and degenerative joint diseases.

Immunization with TCR Vbeta10 peptide reduces the frequency of type-II collagen-specific Th1 type T cells in BUB/BnJ (H-2q) mice

OBJECTIVE

Collagen induced arthritis (CIA) in mice is mediated by synergistic T cell and humoral immune responses specific for type II collagen (CII). We have previously shown that in arthritic joints of BUB mice (TCR Vbetaa, H-2q) the TCR repertoire is enrichedfor Vbeta10 expressing T cells, and that immunization with a Vbeta10 peptide (Vbeta10p) prevents the phenotypic expression of disease. The objective of the present study was to understand how immunization with a synthetic TCR Vbeta peptide affected the development of the pathogenic CII-specific immune response in BUB mice.

METHODS

Arthritic and protected animals were tested for Vbeta10p- and CII-specific cytokine production by a highly specific and sensitive ELISA spot assay, andfor CII-specific antibody production by standard ELISA. In adoptive transfer experiments, Vbeta10p-specific LN cells (INF-gamma producing) were injected into naive mice prior to immunization with type-II collagen/CFA.

RESULTS

Immune cells from arthritic animals produced IFN-gamma and IL-2, without IL-4 and IL-5 in response to CII and an immunodominant epitope, A2, derivedfrom CII. Serum from these mice contained anti-CII antibodies of both IgGI and IgG2a subtypes. Our results show for thefirst time that immunization with Vbeta10p resulted in Vbeta10p-specific IFN-gamma and IL-2 production that was restricted to the CD4+ T cell subset. Emergence of this Vbeta10p-specific immune response was associated with a dramatic decrease in the frequency of CII and A2-specific, cytokine producing T cells in arthritis protected mice. Protective immunity was cell mediated and could be adoptively transferred. In contrast, the protective immunization had only a marginal effect on the anti-CII antibody response indicating that the CII specific humoral immune response was not significantly affected.

CONCLUSION

Immunization with TCR Vbeta10p leads to expansion of a population of Vbeta10p- specific CD4+ Tcells. This anti-TCR Vbeta10p specific type 1 cytokine producing immune response was protective in adoptive transfer studies and appears to inhibit the expansion of the pathogenic anti-CII cellular immunity. Additionally, the anti-TCR Vbeta10p-specific cellular immune response was mediated by CD4+ T cells and these T cells did not produce IL-4 or IL-5. Thus, our results suggest that protection against CIA in mice immunized with synthetic TCR Vbeta10p was achieved by a specific down-regulation of the CII-specific Thl type cellular immune response and not via immune deviation.

Involvement of caspase-3 in epigallocatechin-3-gallate-mediated apoptosis of human chondrosarcoma cells

Green tea polyphenol-(-)epigallocatechin-3-gallate (EGCG)-is a potent chemopreventive agent in many test systems and has been shown to inhibit tumor promotion and induce apoptosis. In this study we describe a novel observation that EGCG displayed strong inhibitory effects on the proliferation and viability of HTB-94 human chondrosarcoma cells in a dose-dependent manner and induced apoptosis. Investigation of the mechanism of EGCG-induced apoptosis revealed that treatment with EGCG resulted in DNA fragmentation, induction of caspase-3/CPP32 activity, and cleavage of the death substrate poly(ADP-ribose)polymerase (PARP). Pretreatment of cells with a synthetic pan-caspase inhibitor (Z-VAD-FMK) and a caspase-3-specific inhibitor (DEVD-CHO) prevented EGCG-induced PARP cleavage. The induction of apoptosis by EGCG via activation of caspase-3/CPP32-like proteases may provide a mechanistic explanation for its antitumor effects.

Tumour necrosis factor alpha enhances the expression of hydroxyl lyase, cytoplasmic antiproteinase-2 and a dual specificity kinase TTK in human chondrocyte-like cells

Tumour necrosis factor alpha (TNF-alpha) is a cytokine with pleiotropic effects on cells ranging from proliferation to apoptosis. These biological effects of TNF-alpha are believed to be elicited by the induction or enhancement of the expression of TNF-alpha responsive genes in the target cells. TNF-alpha is pro-inflammatory and a principal mediator in the pathogenesis of arthritis. The activation of an inflammatory cascade by TNF-alpha in arthritis results in the degradation of cartilage, joint destruction and loss of function. Because TNF-alpha is an important mediator in the pathogenesis of arthritis, the present study addresses the identification of novel TNF-alpha responsive genes in HTB-94 cell line which is of human origin and maintains a chondrocytic phenotype. The three identified cDNAs were previously not known to be induced or upregulated by TNF-alpha in chondrocytes or cells of chondrocytic lineage. One of the identified cDNAs had sequence similarity to human hydroxyl lyase mRNA (PLOD), an enzyme involved in collagen biosynthesis and its metabolism; the second cDNA had sequence similarity to the human cytoplasmic anti-proteinase-2 mRNA (CAP-2), a member of a group of proteins shown to be associated with protecting cells from TNF-alpha-induced apoptosis; and the third cDNA had sequence similarity to a dual specificity kinase, TTK, which is associated with cell proliferation. Relative gene expression level analysis by PCR and by Northern blotting revealed that treatment with TNF-alpha enhanced the expression of PLOD, CAP2 and TTK transcripts which confirmed the results obtained with display gels. Furthermore, TTK mRNA expression was also induced in human articular chondrocytes treated with TNF-alpha but not in untreated chondrocytes. Our results suggest that these genes may play a role in chondrocytic responses to TNF-alpha-mediated stimuli affecting the cartilage homeostasis.

Prevention of collagen-induced arthritis in mice by a polyphenolic fraction from green tea

Identification of common dietary substances capable of affording protection or modulating the onset and severity of arthritis may have important human health implications. An antioxidant-rich polyphenolic fraction isolated from green tea (green tea polyphenols, GTPs) has been shown to possess anti-inflammatory and anticarcinogenic properties in experimental animals. In this study we determined the effect of oral consumption of GTP on collagen-induced arthritis in mice. In three independent experiments mice given GTP in water exhibited significantly reduced incidence of arthritis (33% to 50%) as compared with mice not given GTP in water (84% to 100%). The arthritis index also was significantly lower in GTP-fed animals. Western blot analysis showed a marked reduction in the expression of inflammatory mediators such as cyclooxygenase 2, IFN-gamma, and tumor necrosis factor alpha in arthritic joints of GTP-fed mice. Histologic and immunohistochemical analysis of the arthritic joints in GTP-fed mice demonstrated only marginal joint infiltration by IFN-gamma and tumor necrosis factor alpha-producing cells as opposed to massive cellular infiltration and fully developed pannus in arthritic joints of non-GTP-fed mice. The neutral endopeptidase activity was approximately 7-fold higher in arthritic joints of non-GTP-fed mice in comparison to nonarthritic joints of unimmunized mice whereas it was only 2-fold higher in the arthritic joints of GTP-fed mice. Additionally, total IgG and type II collagen-specific IgG levels were lower in serum and arthritic joints of GTP-fed mice. Taken together our studies suggest that a polyphenolic fraction from green tea that is rich in antioxidants may be useful in the prevention of onset and severity of arthritis.

T cells reactive to a single immunodominant self-restricted allopeptide induce skin graft rejection in mice

Alloreactive T lymphocytes can respond to foreign MHC complexed with foreign peptides through the direct pathway of allorecognition and can additionally recognize allopeptides expressed in the context of recipient (self) MHC through the indirect pathway. To better elucidate how indirect pathway-responsive CD4(+) T cells mediate allograft rejection, we isolated and characterized a TH1 T cell line from BALB/c recipients of B10.A skin that responds to a defined immunodominant, self-restricted allopeptide, I-Abetak58-71. When transferred into BALB/c severe combined immunodeficiency recipients of B10.A skin allografts, this cell line specifically induced a form of skin graft rejection characterized by the presence of TH1 cytokines, macrophage infiltration, and extensive fibrosis. Recall immune responses and immunofluorescence of the rejecting skin revealed only the presence of the peptide-specific T cells within the recipient animals, with no evidence of a direct pathway alloresponse. These studies demonstrate that T cells reactive to a single self-restricted allopeptide can mediate a form of allogeneic skin graft rejection that exhibits characteristics of a chronic, fibrosing process.

Experimental autoimmune myasthenia gravis in B10.BV8S2 transgenic mice: preferential usage of TCRAV1 gene by lymphocytes responding to acetylcholine receptor

Multiple TCRBV genes have been implicated in experimental autoimmune myasthenia gravis (EAMG) pathogenesis in susceptible H-2(b) strains of mice. We studied the contribution of specific TCRBV and AV genes in EAMG pathogenesis using B10.BV8S2 transgenic mice (H-2[b]). The TCR transgenic mice predominantly have TCRBV8S2 transgene, but can use any of the endogenous AV gene repertoire. The transgenic mice were immunized with acetylcholine receptor (AChR) in CFA and evaluated for EAMG pathogenesis. Although the lymphocyte responses to AChR in B10.BV8S2 transgenic and nontransgenic TCR wild-type mice were equivalent, a marked reduction in lymphocyte response to the dominant AChR alpha chain peptide 146-162 was observed in the TCR transgenic mice. After boosting with AChR in CFA, anti-AChR Abs were detected in the serum, and 14 of 42 (33%) of the TCR transgenic mice developed clinical EAMG. Furthermore, EAMG in TCR transgenic mice was prevented by treatment with mAb to TCRBV8, which depleted BV8-expressing T cells. Cloning and sequencing of TCRAV genes from AChR-reactive T cells from B10.BV8S2 transgenic mice revealed a pattern of restricted TCRAV gene usage. The majority (60%) of the clones sequenced showed a sequence identical with that of the TCRAV1S8 gene. In the normal spleen cells of TCR transgenic mice, AV gene usage was more random. Thus, despite the presence of a complete endogenous TCRAV repertoire in B10.BV8S2 transgenic mice, T cells responding to AChR preferentially used a single endogenous TCRAV gene, thus implicating the involvement of the TCRAV1S8 gene in EAMG pathogenesis.

Experimental autoimmune myasthenia gravis in B10.BV8S2 transgenic mice: preferential usage of TCRAV1 gene by lymphocytes responding to acetylcholine receptor

Multiple TCRBV genes have been implicated in experimental autoimmune myasthenia gravis (EAMG) pathogenesis in susceptible H-2(b) strains of mice. We studied the contribution of specific TCRBV and AV genes in EAMG pathogenesis using B10.BV8S2 transgenic mice (H-2[b]). The TCR transgenic mice predominantly have TCRBV8S2 transgene, but can use any of the endogenous AV gene repertoire. The transgenic mice were immunized with acetylcholine receptor (AChR) in CFA and evaluated for EAMG pathogenesis. Although the lymphocyte responses to AChR in B10.BV8S2 transgenic and nontransgenic TCR wild-type mice were equivalent, a marked reduction in lymphocyte response to the dominant AChR alpha chain peptide 146-162 was observed in the TCR transgenic mice. After boosting with AChR in CFA, anti-AChR Abs were detected in the serum, and 14 of 42 (33%) of the TCR transgenic mice developed clinical EAMG. Furthermore, EAMG in TCR transgenic mice was prevented by treatment with mAb to TCRBV8, which depleted BV8-expressing T cells. Cloning and sequencing of TCRAV genes from AChR-reactive T cells from B10.BV8S2 transgenic mice revealed a pattern of restricted TCRAV gene usage. The majority (60%) of the clones sequenced showed a sequence identical with that of the TCRAV1S8 gene. In the normal spleen cells of TCR transgenic mice, AV gene usage was more random. Thus, despite the presence of a complete endogenous TCRAV repertoire in B10.BV8S2 transgenic mice, T cells responding to AChR preferentially used a single endogenous TCRAV gene, thus implicating the involvement of the TCRAV1S8 gene in EAMG pathogenesis.

Hereditary osteoarthritis with mild spondyloepiphyseal dysplasia--are there "hot spots" on COL2A1?

OBJECTIVE

To define the genetic basis of a family with an autosomal, dominantly inherited form of spondyloepiphyseal dysplasia (SED) associated with tall stature.

METHODS

A 6 generation family with early onset osteoarthritis (OA) associated with mild SED was studied. 14 individuals were examined clinically and radiologically, and DNA analysis was performed on 5. As the clinical pattern of joint involvement and tall stature of affected individuals resembled a family recently reported with an exon 11 mutation in COL2A1, this same mutation was specifically sought. In 2 clinically affected and 3 unaffected family members, exon 11 was amplified by polymerase chain reaction (PCR) followed by restriction enzyme digestion with Asp H1, the enzyme recognition sequence of which is altered by the mutation. The PCR product containing exon 11 was then directly sequenced.

RESULTS

OA with widespread involvement of peripheral joints, in addition to spondylodysplasia, was seen in 14 members of the kindred. Affected family members had brachydactyly and were of average to above average height. Asp H1 digestion of the PCR product containing exon 11 in those with clinical disease was consistent with the presence of a mutation. Direct sequencing of this PCR product conclusively showed that a single base substitution was present in those with clinical disease, resulting in an arginine 75-cysteine (Arg75-Cys) mutation.

CONCLUSION

We describe a 3rd family with an Arg75-Cys mutation with precocious generalized OA and mild SED. This finding supports the concept of mutational hot spots on COL2A1 related to the hypermutability of the cytosine-guanine doublet.

Immunization with T cell receptor V beta chain peptides deletes pathogenic T cells and prevents the induction of collagen-induced arthritis in mice

Collagen-induced arthritis (CIA) in susceptible strains of mice is an animal model of T cell-mediated inflammatory polyarthritis. Analysis of T cell receptor (TCR) V beta gene usage in cells isolated from arthritic joints of BUB/BnJ (BUB) mice (H-2q, TCR V beta a) showed that TCR V beta chain gene usage was limited to TCR V beta 3 and V beta 10 gene families. All of the BUB mice immunized with a mixture of TCR V beta 3 and TCR V beta 10 peptides, but not with control TCR V beta 14 peptide, were refractory to the induction of CIA. Immunization with TCR V beta 3 and V beta 10 peptides completely blocked the development of clinical and subclinical inflammation, formation of pannus and synovial hyperplasia, and the erosion of cartilage and bone. Further studies revealed that preimmunization of BUB mice with V beta 10 peptide alone was sufficient to render the mice resistant to CIA. Analysis of TCR V beta chain gene expression in lymph node cells from arthritic and arthritis-protected mice showed the expression of TCR V beta 10 subfamily in all of the arthritic mice, but not in arthritis-protected mice. Immunization with TCR V beta peptides did not diminish the humoral responses to chicken type-II collagen and also elicited significant levels of anti-V beta 3 and anti-V beta 10 peptide antibodies. Antibodies cross-reactive with mouse chicken type-II collagen were detected in both the arthritic and arthritis-protected mice. Adoptive transfer of serum from arthritis-protected BUB mice significantly delayed the onset (P < 0.005) of arthritis in recipient BUB mice. In contrast, mice injected with serum from arthritic mice had early onset of arthritis. These results demonstrate that immunization of BUB mice with TCR V beta chain peptides elicited antibodies reactive with the self-TCR and prevented the induction of collagen-induced arthritis by eliminating or downregulating pathogenic T cells and consequently blocking the development of humoral immune response. These findings may have clinical applications in treating human autoimmune diseases characterized by common TCR gene usage.

Phenotypic modulation of newly synthesized proteoglycans in human cartilage and chondrocytes

The proteoglycans synthesized by human osteoarthritic femoral head cartilage and nonarthritic articular cartilage age-matched to the osteoarthritic cartilage specimens was studied in explant cultures and in chondrocytes generated by explant outgrowth from the cartilages. Twenty-four hours after explanation, both nonarthritic articular cartilage and osteoarthritic cartilage synthesized principally one large proteoglycan core protein that migrated on 3-5% acrylamide gels with an apparent molecular mass (M(r)) of approximately 520 kDa after enzymatic digestion with chondroitinase ABC and keratanase. The proteoglycan was found in both the explant itself and in the medium compartment of the culture as well. This proteoglycan contained chondroitin-6-sulfate, keratan sulfate and the hyaluronan binding region as evidenced by immunoblotting with murine anti-proteoglycan monoclonal antibodies indicating that the proteoglycan was aggrecan. To a much lesser extent two additional proteoglycan core proteins were also found in the explant but were not seen in the culture medium compartment. These proteoglycans possessed apparent M(r)'s of approximately 480 kDa and approximately 390 kDa on 3-5% acrylamide gels after chondroitinase ABC and keratanase digestion. The medium compartment contained principally the approximately 520 kDa proteoglycan core protein. In osteoarthritic cartilage explants, the pattern of newly synthesized proteoglycans recovered from the tissue as assessed on 3-16% polyacrylamide gradient gels remained relatively the same from day 1 after explantation up to 36 days of culture. By contrast, the proteoglycans recovered from the culture medium contained chondroitin sulfate and keratan sulfate after 1, 7, and 21 days in culture but by 36 days appeared to contain only chondroitin sulfate. Chondrocytes generated from osteoarthritic cartilage and age-matched nonarthritic articular cartilage synthesized different patterns of large (greater than 200 kDa) proteoglycan. Whereas chondrocytes derived from osteoarthritic cartilage continued to synthesize principally the approximately 520 kDa proteoglycan core protein, the chondrocytes derived from nonarthritic cartilage synthesized in addition to this proteoglycan, abundant amounts of the other two proteoglycan core proteins as well.

Limited heterogeneity in T-cell receptor V beta chain gene expression in arthritic joints of BUB/BnJ (H-2q) mice--a T-cell receptor V beta a strain

We have earlier shown that T-cells in arthritic joints and LNs of B10.Q mice (H-2q, TCR V beta b) use a restricted number of TCR V beta chain genes (V beta 6, 8, 9). In the present study, we have investigated the TCR V beta chain gene expression in arthritic joints and LN of BUB/BnJ mice (H-2q, TCR V beta a). Mice were immunized with [table: see text] chicken type-II collagen, and arthritic joints and draining LNs were removed at the onset of arthritis and the TCR V beta chain gene expression was studied by PCR. A restricted usage of TCR V beta was observed in both the tissues. A dominant usage of TCR V beta 4, 7, and 15 was found in the LNs while TCR V beta 3 and 10 were predominantly expressed in arthritic joints in the majority of the arthritic mice (5/7). Our results indicate that (a) in H-2q mice with CIA there is a restricted usage of TCR V beta chain genes regardless of the TCR V beta genotype; and (b) in the absence of TCR V beta 8 and 9, TCR V beta 3 and 10 are predominantly used by joint-infiltrating T-cells.

Clinical correlations of osteoarthritis associated with single base mutations in the type II procollagen gene

There are increasing numbers of mutations described in the gene for type II collagen (COL2A1). Recently, COL2A1 mutations were shown to be associated with milder forms of chondrodysplasia, which may present with precocious generalized osteoarthritis (OA). The arginine519-cysteine and the arginine75-cysteine mutations are 2 such sites on COL2A1 where multiple unrelated families have been reported presenting with early onset, generalized OA and chondrodysplasia. The observation of multiple sites where recurrent mutations occur suggests that certain areas of COL2A1 are more prone to mutational events.

Type II procollagen gene (COL2A1) mutation in exon 11 associated with spondyloepiphyseal dysplasia, tall stature and precocious osteoarthritis

OBJECTIVE

To define the clinical, pathological and molecular genetic characteristics of a family with mild spondyloepiphyseal dysplasia (SED) and precocious osteoarthritis.

METHODS

The proband was a 46-year-old man with precocious generalized OA, tall stature, mild chondrodysplasia and moderate deafness. His daughter, aged 21, showed similar clinical features. Electron microscopic (EM) analysis of collagen from an affected joint of the proband was performed. DNA was extracted from whole blood on the proband, his affected daughter, unaffected wife and second daughter, to look for a mutation in exons 31 or 11, sites where point mutations have been previously described in mild forms of SED. After finding no mutation in exon 31, exon 11 of COL2A1 was further analyzed. Exon 11 was amplified using polymerase chain reaction (PCR), and screening for the mutation was undertaken using a restriction enzyme digestion, the recognition sequence of which is altered by this point mutation. Sequence analysis was then performed.

RESULTS

Electron microscopic (EM) analysis of cartilage from the proband showed thin appearing collagen fibrils organized into parallel lamellar structures. DNA studies revealed a single base change in one allele of exon 11 which produced an arginine to cysteine mutation at position 75 of the triple helix of type II collagen in the proband and his affected daughter.

CONCLUSION

This is the 2nd example of an Arginine75-Cysteine mutation associated with SED; in our case, however, contrasting clinical features were present. Recurrent mutations at a few specific sites of COL2A1 suggest the possibility of susceptibility "hot spots" for mutational events.

Restricted expression of T cell receptor V beta and lymphokine genes in arthritic joints of a TCR V beta a (H-2q) mouse strain-BUB/BnJ-with collagen-induced arthritis

Type II collagen-induced arthritis (CIA) is an animal model of inflammatory polyarthritis with clinical and pathological features resembling rheumatoid arthritis (RA). We compared the expression of T cell receptor (TCR) V beta genes in T cells isolated from the inflamed joints, draining lymph nodes and the spleens of BUB/BnJ (H-2q) mice (BUB) during the early phase of CIA. We also investigated the profiles of cytokine gene expression in T cells obtained from the same tissues. We found that the expression of TCR V beta s, in arthritic joints of mice, during the early phase of the disease was limited to TCR V beta 3 and 10 gene families. In contrast, TCR V beta 4, 7, and 15 were predominant in the draining lymph nodes (LNs) and TCR V beta 2, 6, and 14 were predominant in the spleens of arthritic mice. Molecular cloning and sequence analysis revealed that the T cell populations in the arthritic joints were oligoclonal as determined by the limited N-D-N region diversity observed in the sequenced clones. These results demonstrate, for the first time, that (1) joint infiltrating T cells in TCR V beta a genotype mice use a restricted repertoire of TCR V beta genes; (2) there was oligoclonal expansion of infiltrating T cells in arthritic joints in mice with collagen-induced arthritis. Our results on cytokine gene expression in the arthritic joints of BUB mice indicate that Th-1-like T cell derived cytokines may be the predominant cytokines in the arthritic joints as illustrated by the presence of transcripts for IL-2 and IFN-gamma but not IL-4. In summary, our results provide evidence that T cells with restricted specificities, and more specificially, Th-1 type T cells, are crucial in the early phase of collagen induced arthritis in mice.

Biochemical and molecular characterization of stromelysin synthesized by human osteoarthritic chondrocytes stimulated with recombinant human interleukin-1

OBJECTIVE

To study the biochemical and molecular characterization of stromelysin synthesized by human chondrocytes derived from osteofemoral heads.

METHODS

First passage human chondrocyte cultures were incubated with recombinant human interleukin-1 alpha or recombinant human interleukin-1 beta (10-1000 pg ml-1) for either 24 or 48 hrs. The medium compartment of these cultures was assayed for stromelysin activity. Total cellular RNA was used to determine: (i) the molecular structure of the stromelysin synthesized by these cells; and (ii) whether or not these chondrocytes expressed the Type II procollagen gene (COL2A1).

RESULTS

Human osteoarthritic chondrocytes released into the medium on enzyme requiring tryspin activation that possessed Substance P (SP) cleaving activity. SP cleaving activity was completely inhibited by EDTA. Casein zymography showed lysis zones produced by trypsin-activated chondrocyte culture medium that co-migrated with casein lysis zones produced by recombinant human prostromelysin. The majority of SP cleaving activity was eluted from a Zn-Sepharose column with 0.25 M glycine. Enzyme activity eluted from Zn-Sepharose produced casein lysis zones which co-migrated with lysis zones produced by recombinant human prostromelysin. Immunoblotting revealed the presence of prostromelysin (M(r), 55-57 kDa) in the pooled chondrocyte culture media applied to Zn-Sepharose and in the 0.25 M glycine eluate. Trypsin-activation converted prostromelysin to a mature stromelysin form (M(r), 45-47 kDa). Polymerase chain reaction (PCR) amplification of human chondrocyte cDNA demonstrated COL2A1 transcripts. A PCR product of expected size (680 bp) was produced by amplification of chondrocyte cDNA using stromelysin-1 oligonucleotide primers. The cloned and sequenced PCR product showed 100% homology between the chondrocyte stromelysin-1 mRNA-derived cDNA and the stromelysin-1 mRNA-derived cDNA of cultured human synovial, gingival and skin fibroblasts.

CONCLUSIONS

By several criteria, human osteoarthritic chondrocytes synthesized stromelysin which was biochemically and antigenically identical, and molecularly homologous with human fibroblast stromelysin-1. These results suggest that a quantitative imbalance between stromelysin-1 and endogenous stromelysin-1 inhibitors rather than the transcription of a new stromelysin gene is the mechanism underlying the increased proteoglycan degradation seen in osteoarthritic cartilage.

BUB/BnJ (H-2q) is a TCR deletion mutant mouse strain (TCR V beta a, KJ16-) that is susceptible to type II collagen-induced arthritis

Type II collagen-induced arthritis (CIA) in mice is an animal model of autoimmune inflammatory arthritis. Arthritis is induced in susceptible strains of mice (H-2q and H-2r) after immunization with heterologous or autologous type II collagen in CFA. Induction of CIA is T cell dependent and a restricted usage of TCR V beta genes has been found in the arthritic joints and lymph nodes of mice with CIA. However, genes within the MHC are not the only determinants of susceptibility to CIA as SWR/j, AU/ssJ (both H-2q) and RIIIS/J(H-2r) mice are resistant to the induction of CIA. These strains of mice are TCR V beta chain genes deletion mutants (TCR V beta a and TCR V beta c haplotypes) and it was hypothesized that these mice are resistant to CIA because of the absence of a particular set of V beta TCR genes that are genomically deleted in these strains of mice. We now show that BUB/BnJ mice (H-2q) are T cell subsets deficient because of the genomic deletion of TCR V beta 5, 8, 9, 11, 12, and 13 sub-families. Our data demonstrate that despite the deficiency in T cell subsets from genomic deletion of TCR V beta genes, BUB mice are highly susceptible to the development of CIA. These results indicate that genomic deletion of certain TCR V beta genes alone is not in itself sufficient to confer resistance to CIA. These results further suggest that other unknown gene(s) must also contribute to the induction of CIA.

BUB/BnJ (H-2q) is a TCR deletion mutant mouse strain (TCR V beta a, KJ16-) that is susceptible to type II collagen-induced arthritis

Type II collagen-induced arthritis (CIA) in mice is an animal model of autoimmune inflammatory arthritis. Arthritis is induced in susceptible strains of mice (H-2q and H-2r) after immunization with heterologous or autologous type II collagen in CFA. Induction of CIA is T cell dependent and a restricted usage of TCR V beta genes has been found in the arthritic joints and lymph nodes of mice with CIA. However, genes within the MHC are not the only determinants of susceptibility to CIA as SWR/j, AU/ssJ (both H-2q) and RIIIS/J(H-2r) mice are resistant to the induction of CIA. These strains of mice are TCR V beta chain genes deletion mutants (TCR V beta a and TCR V beta c haplotypes) and it was hypothesized that these mice are resistant to CIA because of the absence of a particular set of V beta TCR genes that are genomically deleted in these strains of mice. We now show that BUB/BnJ mice (H-2q) are T cell subsets deficient because of the genomic deletion of TCR V beta 5, 8, 9, 11, 12, and 13 sub-families. Our data demonstrate that despite the deficiency in T cell subsets from genomic deletion of TCR V beta genes, BUB mice are highly susceptible to the development of CIA. These results indicate that genomic deletion of certain TCR V beta genes alone is not in itself sufficient to confer resistance to CIA. These results further suggest that other unknown gene(s) must also contribute to the induction of CIA.

Clinical correlations of osteoarthritis associated with a single-base mutation (arginine519 to cysteine) in type II procollagen gene. A newly defined pathogenesis

OBJECTIVE

To investigate the occurrence and clinical correlation of the arg519-to-cys mutation in the type II procollagen gene in patients with osteoarthritis (OA).

METHODS

Sixty-six subjects from 7 families with a strong family history of generalized OA and 13 patients with erosive OA were evaluated clinically and radiologically. Blood samples from 58 subjects in the familial OA group and from all 13 patients with erosive OA were obtained for DNA analysis. Exon 31 of COL2A1, which spans residue 519, was amplified by polymerase chain reaction.

RESULTS

The arg519-to-cys mutation was detected in 2 of the 7 families with generalized OA. In these 2 families, the mutation was present in the 2 probands and in 19 other clinically affected family members, as well as in 3 (so-far) clinically unaffected family members (ages 25, 14, and 11 years). It was absent in 18 clinically unaffected members tested. The mutation was associated with a distinctive pattern of early-onset, aggressive, generalized OA with a mild spinal chondrodysplasia. Inheritance was autosomal dominant. No mutation was found in any of the patients with erosive OA.

CONCLUSION

The arg519-to-cys mutation defines a new pathogenic factor in generalized OA with characteristic clinical and radiologic features. The demonstration of a mutation in 3 of 8 families with OA studied thus far suggests a significant incidence of genetically related clinical OA.

Human cartilage from late stage familial osteoarthritis transcribes type II collagen mRNA encoding a cysteine in position 519

A single base change resulting in the substitution of Cys for Arg at position 519 of the type II collagen triple helix is a predisposing factor in the pathogenesis of a precocious-onset form of familial osteoarthritis associated with a mild chondrodysplasia. Cartilage obtained at the time of total knee replacement in a patient with the Arg-Cys519 mutation was used to investigate the expression of Col2A1 alleles. Using PCR assisted amplification of mRNA with specific amplification of a region of Col2A1 message encompassing exons 31-34, followed by single strand conformation polymorphism and sequence analyses, we have found transcription products of both mutant and normal type II collagen alleles. Further analysis of the sequence of these exons provides evidence that the Arg-Cys519 mutation arose independently in at least two of the three known affected families. The presence of both mutant and normal alleles of Col2A1 in cDNA derived from cartilage obtained from this patient suggests that Cys519-containing type II collagen may continue to be produced even in advanced stages of osteoarthritis.

The effect of circulating serum factors from patients with systemic lupus erythematosus on protein kinase A (PKA) activity and PKA-dependent protein phosphorylation in T lymphocytes

T lymphocytes from subjects with active systemic lupus erythematosus (SLE) exhibit reduced cAMP-inducible, protein kinase A (PKA)-dependent phosphorylation of several intracellular substrates compared with healthy and disease controls. To ascertain whether the persistent T cell activation observed during active SLE can result in impaired PKA-dependent protein phosphorylation, normal T cells were activated in vitro by monoclonal anti-CD3-epsilon antibody and recombinant IL1-alpha (rIL1-alpha) for 24 hr. T cell activation, verified by IL2 mRNA, IL2 receptor-alpha (IL2R-alpha) mRNA, and IL2R-beta mRNA expression, did not diminish cAMP-inducible, PKA-dependent protein phosphorylation. We also tested the hypothesis that circulating factors present in active SLE serum can decrease cAMP-inducible total PKA phosphotransferase activity and PKA-dependent protein phosphorylation in normal T lymphocytes. T cells cultured for 24 hr in medium supplemented with 10% active SLE sera (from subjects who exhibited the defect of PKA-dependent protein phosphorylation) exhibited similar total PKA phosphotransferase activity and substrate phosphorylation as cells cultured in normal AB serum. Moreover, the addition of interferon-alpha (IFN-alpha) and/or immune complexes (IC) did not diminish either total PKA activity or PKA-dependent substrate phosphorylation. Lastly, we found that the defect of PKA-dependent protein phosphorylation in active SLE T cells could not be reversed by culturing the cells in culture medium supplemented with 10% AB serum for 24 hr. In conclusion, (a) deficient cAMP-inducible, PKA-dependent phosphorylation in SLE T cells is not reversible by culturing cells in vitro; (b) there is no evidence to support the concept that serum factors, including IC and IFN-alpha, can induce a defect of PKA-dependent protein phosphorylation in normal T cells.

Chemical carcinogens increase IL-1 alpha and IL-6 gene transcripts in human keratinocytes

Using reverse transcriptase-linked polymerase chain reaction, the effect of polycyclic aromatic hydrocarbons (PAHs) on IL-1 alpha, IL-1 beta and IL-6 gene expression in cultured human keratinocytes was studied. Exposure to beta-naphthoflavone and benz(a)anthracene resulted in a higher copy number of IL-1 alpha and IL-6 mRNA while lower level of IL-1 beta mRNA was detected in these cells. These data suggest that, like ultraviolet B (UVB) radiation, ubiquitous environmental carcinogenic PAHs are potent inducers of IL-1 alpha and IL-6 cytokines and, unlike UVB, they downregulate IL-1 beta in human keratinocytes.

Induction of CYP1A1 mRNA in rat epidermis and cultured human epidermal keratinocytes by benz(a)anthracene and beta-naphthoflavone

Cytochrome P-4501A1 (CYP1A1) plays a major role in the bioactivation of procarcinogens in target tissues, including skin. However, the factors controlling CYP1A1 expression in mammalian skin are unknown. Utilizing the reverse transcriptase-linked polymerase chain reaction, we analyzed the effect of treatment with beta-naphthoflavone (beta-NF) and benz(a)anthracene on the expression of CYP1A1 mRNA in rat epidermis and normal human epidermal keratinocytes (NHEK). Inducer treatment of rats and NHEKs resulted in several-fold increases in aryl hydrocarbon hydroxylase activity. Following inducer treatment of adult or neonatal rats, increase in CYP1A1 gene message occurred as compared with that in controls. Higher basal level and inducibility were detected in mature rather than in 4-day-old rats. This induction occurred as early as 4 hr after beta-NF application. Exposure to beta-NF and benz(a)anthracene also resulted in substantial increases in gene message in NHEK. Northern blot analyses complemented the polymerase chain reaction data. These results indicate that CYP1A1 gene expression is increased in mammalian epidermis by inducers of epidermal aryl hydrocarbon hydroxylase activity.

Restricted heterogeneity in T-cell antigen receptor V beta gene usage in the lymph nodes and arthritic joints of mice

We have used PCR to study the expression of T-cell antigen receptor beta RNA containing particular variable region (V) elements from transcripts directly in the cells isolated from joints and lymph nodes of B10.Q mice (H-2q) immunized with chicken type II collagen. Our data show that the T cells present in arthritic joints expressed only a few V beta transcripts--V beta 2, -6, -7, -8.2, -9, -10, and -15. V beta 6 and -8.2 were expressed predominantly (six out of seven animals) while others were expressed at a relatively low level in different animals. In lymph node cells, transcripts for V beta 6, -8.2, and -9 were detected in four out of seven animals. The data indicate that in collagen-induced arthritis there is a restrictive usage of TCR V beta elements and that V beta 6 and -8.2 are probably used preferentially.

RIII S/J (H-2r). An inbred mouse strain with a massive deletion of T cell receptor V beta genes

We have identified an inbred strain of mouse, RIII S/J (H-2r), that has the largest known deletion of the TCR V beta genes by screening with mAb and TCR V beta specific probes. Upon screening of PBL with mAb F23.1, which is specific for V beta 8 TCR, RIII S/J was found to be negative. On further screening with mAb KJ 23a, which is specific for V beta 17a TCR, RIII S/J was completely negative. We next tested RIII S/J with mAb 44-22-1, which is specific for V beta 6 TCR, and found it also to be negative. The (B10 X RIII)F1 mice showed a 50% expression of V beta 6 gene, indicating a genomic rather than a clonal deletion. mAb KJ25, detecting V beta 3, was positive in RIII S/J, denoting the downstream boundary for the deletion. Southern blot analysis of liver DNA using TCR V beta-specific probes confirmed the deletion of V beta 8 gene subfamily and V beta 5 gene subfamily, along with V beta 9, V beta 11, V beta 12, and V beta 13 genes similar to the known TCR V beta deletion mutants (SWR, SJL, C57L, and C57Br). In addition, RIII S/J is missing V beta 6, V beta 15, and V beta 17 genes. Our mapping of the deletion indicates that RIII S/J has lost approximately 130 kb of V beta chromosome and with it 13 V beta genes out of the known 21 V beta genes of the TCR. The deletion is marked by the presence of V beta 10 gene upstream and V beta 3 gene downstream.

Identification of T-cell receptor V beta deletion mutant mouse strain AU/ssJ (H-2q) which is resistant to collagen-induced arthritis

Our laboratory is involved in investigating the role of T-cell receptor (Tcr) in collagen-induced arthritis (CIA). During these studies we found AU/ssJ (H-2q) mice to be resistant to CIA like SWR (H-2q), as compared with other H-2q strains with wild-type Tcr like DBA/1 and B10.Q. Upon screening with monoclonal antibodies F23.1 and KJ23a, AU/ssJ was found to be F23.1 negative (V beta 8 Tcr negative) and KJ23a positive (V beta 17a Tcr positive). Southern blot analysis on liver DNA using specific Tcr-V beta probes confirmed the deletion of V beta 8 gene family and also showed that AU/ssJ mice have deletions of V beta 9, V beta 13, V beta 12, and V beta 11 genes of Tcr. Further, these mice show a restriction fragment length polymorphism pattern with V beta 10, V beta 6, and V beta 17 probes similar to SWR mice as compared with B10 mice. Since SWR and AU/ssJ are from different backgrounds, these studies indicate that specific variable region beta chain genes of Tcr are crucial for susceptibility to CIA in mice. Furthermore, these studies identify an additional inbred strain which has also deleted 50% of its Tcr-V beta genes.

Specific amplification with PCR of a refractory segment of genomic DNA

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Possible role of V beta T cell receptor genes in susceptibility to collagen-induced arthritis in mice

Arthritis was induced by immunization of type II collagen in adjuvant in mice from H-2q-bearing crosses between SWR (H-2q/q) and B10 (H-2b/b mice), two strains known to be resistant to collagen-induced arthritis (CIA). The resistance of B10 is known to be due to its MHC haplotype, but it was postulated that the resistance of SWR mice which expresses the susceptible MHC haplotype could be due to the deletion of close to 50% of the V beta genes of the T cell receptor (TCR) in them. 17% of the F1 hybrids, 33% of the SWR backcrosses, 68% of the B10 backcrosses, and 52% of the F2 hybrids developed arthritis on follow-up to 5 mo after primary immunization with collagen. There was no significant difference in anti-type II collagen antibody titers between the arthritic and nonarthritic mice in each of these crosses. The segregation of the TCR genes with arthritis was determined in the F2 population by typing with F23.1 mAb that reacts with T cells using V beta 8 subfamily genes in their TCRs. SWR mice are F23.1- as V beta 8 genes are deleted in them. All six of arthritic mice homozygous for H-2q, and thus with an H-2 haplotype similar to SWR mice, expressed the F23.1 marker. These studies indicate that for complete susceptibility to collagen-induced arthritis, not only is a susceptible MHC haplotype (H-2q) important, but possibly also the presence of a subset of T cells using certain specific V beta genes in their TCRs. Other background genes may, however, modulate the severity of arthritis.

The inducible cytotoxic T-lymphocyte-associated gene transcript CTLA-1 sequence and gene localization to mouse chromosome 14

Classical phenomenological approaches to the study of the mechanism of T-cell-mediated cytotoxicity have now given way to a search for molecules involved in this function; this is attempted either by subcellular and biochemical fractionation of material from cytotoxic cells, or through the characterization of molecules recognized by cytotoxicity-inhibiting monoclonal antibodies Molecules having a role in cytotoxicity may also be identified by detecting the corresponding messenger RNA transcripts. Such an approach may include, as a first step, the search for transcripts as specific as possible to cytotoxic T cells; only secondarily can their actual relevance to cytotoxicity be investigated. We report here the preparation and systematic screening of a differential complementary DNA bank, in which we detected three distinct messenger RNA transcripts (CTLA-1, CTLA-2 and CTLA-3) present in various cytotoxic T cells but not (or less so) in a range of non-cytotoxic lymphoid cells. We describe the co-inducibility of these transcripts and of cytotoxicity in thymocytes and hybridoma cells, the sequence of CTLA-1 cDNA, its protein homology with serine esterases and the localization of the corresponding gene to mouse chromosome 14.

Sister-chromatid exchanges and chromosomal aberrations in lymphocytes of male albino rats treated with an alkylating agent, apholate (NSC 26, 812; ENT 26, 316)

A lymphocyte culture system was used to study the frequency of chromosomal aberrations and SCEs at various time intervals after an intraperitoneal injection of apholate (0.5 mg/kg b.w.) in male albino rats. Treatment with apholate increased the frequency of chromosomal aberrations significantly (P less than 0.001). The majority of chromosomal aberrations were single chromatid breaks, although other aberrations were also present. The distribution of chromatid breaks was non-random and the large chromosomes were affected to a greater extent. SCEs frequency in lymphocytes of apholate-treated rats was more than 5-fold higher in comparison to controls. The highest number of chromosomal aberrations and SCEs/rat was recorded at 48 h post-treatment, after which there was a gradual decline in both SCE and chromosomal aberration frequency. The results indicate that apholate is a mutagenic compound and it may also be carcinogenic.

Studies with chlorambucil. I. Effect on lactate dehydrogenase in the testes of albino rabbits treated with multiple doses of chlorambucil

Treatment with multiple sub-lethal doses of chlorambucil resulted in lower activity levels and specific activity of LDH and low protein content in the testes of albino rabbits. Electrophoretic analysis and assay of individual isozymes eluted from DEAE-Sephadex A-50 indicated that this loss in activity was related to the differential and/or selective action of chlorambucil on LDH4, which was affected most, while LDH3 and LDH5 were affected to a lesser degree. Kinetic inhibitory studies on purified rabbit muscle LDH in vitro revealed that chlorambucil in the reaction mixture binds to non-active enzyme sites resulting in non-competitive irreversible inhibition of LDH.

Testicular damage and change in serum LDH isozyme pattern induced by multiple sub-lethal doses of apholate in albino rats

Treatment with apholate caused degenerative changes in the testes of albino rats. No histological changes were observed in Leydig cells. LDH-X activity was present in the serum of treated rats and absent in controls. Electrophoresis indicates that the activity band present in serum was similar to the activity band found in testes. A colorimetric method for assaying LDH-X activity is reported.