Changes in biochemical markers of joint tissue metabolism in a randomized controlled trial of glucocorticoid in early rheumatoid arthritis

OBJECTIVE

To determine the effects of low-dose prednisolone on joint tissue metabolism in early rheumatoid arthritis (RA).

METHODS

In addition to a range of biochemical markers of cartilage, bone and synovial tissue turnover, levels of pro-matrix metalloproteinase 3 (pro-MMP-3), pro-MMP-1, and cytidine deaminase (CD) were measured in serum from 79 of 128 patients with early RA who took part in the Arthritis and Rheumatism Council Low-Dose Glucocorticoid Study. Serum concentrations of joint tissue metabolites on treatment and off treatment were compared using Student's t-test.

RESULTS

Levels of the keratan sulfate epitope, 5D4, and glycosaminoglycan (GAG) were similar on and off treatment. However, the levels of synovium-derived markers, hyaluronate (HA) and N-propeptide of type III procollagen (PIIINP), were reduced by 23.9% (P < 0.01) and 25.2% (P < 0.001), respectively, during treatment with prednisolone. Serum osteocalcin (OC) was reduced by 25.8% (P < 0.001), while the levels of CD and pro-MMP-3 increased by 31.2% (P < 0.01) and 53.7% (P < 0.001) during prednisolone treatment compared with the off-treatment period.

CONCLUSION

Low-dose prednisolone had no significant effect on markers of cartilage turnover (GAG, 5D4) in early RA, suggesting that early erosions do not involve cartilage surfaces. The reduction in the markers of bone turnover (OC) and synovial tissue turnover (HA and PIIINP) support the general view that prednisolone reduces synovitis and suppresses bone turnover.

Mitogenic signaling by substance P and bombesin-like neuropeptide receptors in astrocytic/glial brain tumor-derived cell lines

Neuropeptides such as substance P (SP) and bombesin regulate many biological processes through binding to and activating their respective cell surface receptors. Recently, we reported that many astrocytic/glial-derived brain tumor cell lines express functional SP and bombesin receptors (43% and 85%, respectively). Activation of these neuropeptide receptors stimulates several signaling pathways that regulate transcription and translation leading to the induction of mitogenesis in several cell types including astrocytic brain tumor-derived cell lines. We have also shown that a number of signaling pathways are induced by SP and/or bombesin receptors in astrocytic/glial-derived brain tumor cell lines and demonstrated that inhibiting these path-ways by selective compounds such as PD 098059, tamoxifen, CGP 41251, and rapamycin blocks cell growth. In summary, mitogenic signaling by neuropeptides may play a role in brain tumor growth and/or tumor progression, and selective compounds capable of blocking mitogenic signaling have potential to be useful in the treatment of brain tumors.

CGP 41251 and tamoxifen selectively inhibit mitogen-activated protein kinase activation and c-Fos phosphoprotein induction by substance P in human astrocytoma cells

The substance P (SP) receptor (NK-1 subtype) is widely expressed in primary human astrocytomas and glioblastomas and many brain tumor-derived cell lines. SP receptor activation stimulates the mitogen-activated protein (MAP) kinase pathway and the expression of immediate-early genes (e.g., c-Fos and c-Myc), resulting in an increase in DNA synthesis in human astrocytoma U-373 MG cells. In this study, we investigated the role of protein kinase C (PKC) in SP receptor activation of the MAP kinase pathway. SP peptide, epidermal growth factor, and the PKC activator 12-O-tetradecanoylphorbol-13-acetate (TPA) induced the tyrosine phosphorylation of the Erk1 and Erk2 MAP kinases in a concentration-dependent manner in U-373 MG cells. Pretreatment of the cells with PKC inhibitors, CGP 41251 or tamoxifen, inhibited tyrosine phosphorylation of Erk1 and Erk2 MAP kinases induced by low concentrations of SP or TPA and significantly attenuated phosphorylation at high concentrations of SP or TPA. The inhibitory effect exhibited by tamoxifen on SP-induced MAP kinase activation is similar to that exhibited by the selective PKC inhibitor CGP 41251, suggesting that the PKC enzyme is the in situ target for both inhibitors. Furthermore, SP-induced c-Fos phosphoprotein expression is inhibited by CGP 41251 or tamoxifen with similar efficacy. Importantly, neither CGP 41251 nor tamoxifen has any detectable effect on the MAP kinase activation by epidermal growth factor, consistent with the ability of this growth factor to activate the MAP kinase pathway by a PKC-independent mechanism. Prolonged treatment with TPA resulted in down-regulation of PKC and selective inhibition of TPA- and SP-induced Erk1 and Erk2 tyrosine phosphorylation in U-373 MG cells. Consistent with the in situ results, CGP 41251 and tamoxifen significantly inhibited endogenous PKC enzymatic activity from U-373 MG cells in vitro. In contrast to CGP 41251 and tamoxifen, Gö 6976, a highly selective inhibitor for PKC alpha and PKC beta 1 isozymes, did not inhibit SP- or TPA-induced tyrosine phosphorylation of Erk1 and Erk2 MAP kinases; rather, it inhibited a signaling pathway leading to the phosphorylation of cAMP-responsive element binding protein in U-373 MG cells. To investigate whether selective PKC isozyme(s) are involved in the activation of the MAP kinase pathway by SP, we determined the expression of PKC isozymes in U-373 MG cells. We found that U-373 MG cells express nine different PKC isozymes (alpha, beta I, beta II, epsilon, delta, eta, zeta, iota, and mu) and that stimulation with SP results in significant and selective translocation of PKC epsilon isozyme from cytosolic to membrane fraction. This establishes a correlation between the ability of SP to activate the MAP kinase pathway and its ability to translocate PKC epsilon. In conclusion, the results presented in this study demonstrate that SP receptor activation of PKC, possibly PKC epsilon, leads to the activation of the MAP kinase pathway, and that this pathway can be inhibited by known PKC inhibitors.

Relations between synovial fluid and serum concentrations of osteocalcin and other markers of joint tissue turnover in the knee joint compared with peripheral blood

OBJECTIVE

To determine if osteocalcin (OC) is locally produced in the joint and to study the relation between markers of bone, cartilage, and synovial tissue turnover.

METHODS

The concentrations of OC, keratan sulphate epitope (5D4), and hyaluronate (HA) were measured in paired serum and synovial fluid in 10 healthy volunteers and 15 patients with osteoarthritis (OA) and 16 with rheumatoid arthritis (RA). OC was measured with a commercial immunoradiometric assay and concentrations of 5D4 and HA were measured using enzyme linked immunosorbent inhibition assays.

RESULTS

Synovial fluid OC was found to be significantly lower than serum (p < 0.001) in all patients and controls. Synovial fluid OC concentrations were directly correlated with serum concentrations (r = 0.63, p < 0.001) and with age (r = 0.48, p < 0.01). There were also some relations between OC, HA, and 5D4 in patients with OA and RA. The OC concentrations were directly correlated with HA (r = 0.68, p < 0.01) in OA serum and there was a similar correlation in RA synovial fluid (r = 0.69, p < 0.01). A weak negative correlation was found between OC and 5D4 in OA serum (r = -0.55, p = 0.035) while a weak positive correlation was found in RA serum (r = 0.53, p = 0.034).

CONCLUSIONS

These results show that more OC is present in the circulation than in knee joint fluids suggesting that synovial fluid OC may be derived from the blood.

Functional expression of bombesin receptor in most adult and pediatric human glioblastoma cell lines; role in mitogenesis and in stimulating the mitogen-activated protein kinase pathway

Functional bombesin receptors were identified in most human glioblastoma cell lines examined (approximately 85% of lines). Bombesin stimulated the release of intracellular Ca2+ in human adult (U-373MG, D-247MG, U-118MG, U-251MG, D-245MG, U-105MG, D-54MG, A-172MG, and D-270MG lines) and pediatric (SJ-S6 and SJ-G2 lines) glioblastoma cell lines. Stimulation of the glioblastoma cell line U-373MG with bombesin or gastrin-releasing peptide (GRP) induced mitogenesis, measured by [3H]thymidine incorporation into DNA, and stimulated the tyrosine phosphorylation of the mitogen-activated protein (MAP) kinases (Erk1 and Erk2). The stimulation of the MAP kinase phosphorylation in U-373MG cells was time- and peptide concentration-dependent. Both bombesin and GRP showed similar potencies in stimulation of intracellular Ca2+ release and activation of the MAP kinase pathway in U-373MG cells, whereas neuromedin B (NMB) peptide was less potent. Bombesin and GRP induced the release of cytosolic Ca2+ in a concentration-dependent manner. Because bombesin and GRP were more potent than NMB peptide in increasing the cytosolic Ca2+ levels in U-373MG cells, we concluded that the BB2 subtype (also known as GRP-preferring receptor subtype) of the bombesin receptor is expressed in this cell line. The bombesin receptor antagonist ([Leu13-psi(CH2NH)Leu14]bombesin) blocked bombesin induced Ca2+ release and attenuated MAP kinase activation in U-373MG cells demonstrating that bombesin is acting through a receptor-dependent mechanism. This study indicates that functional bombesin receptors are widely expressed in human glioblastoma cell lines.

Bromocriptine transcriptionally activates the multidrug resistance gene (pgp2/mdr1b) by a novel pathway

The P-glycoprotein (Pgp) reversing agent, reserpine, induces MDR1 mRNA and PGP protein in human colon carcinoma cells (Schuetz, E. G., Beck, W. T., and Schuetz, J. D. (1996) Mol. Pharmacol. 49, 311-318) and in H35 rat hepatoma cells. Reserpine's interference with cellular dopamine utilization suggested that dopamine and dopaminergics might be important physiological regulators of PGP expression. Initial studies demonstrated that the H35 cells express the D2 dopamine receptor. Pgp protein and pgp2/mdr1b mRNA was increased (maximum of 10- and 8-fold, respectively) by the potent D2 dopamine receptor agonists bromocriptine, R(-)-propylnorapomorphine hydrochloride, and quinpirole, and Pgp protein induction was blocked by D2 receptor antagonists spiperone and clozapine. D2 receptor agonist induction of pgp2/mdr1b mRNA was paralleled by transcriptional activation of the pgp2/mdr1b promoter but blocked by pretreatment with the D2 dopamine receptor antagonists, spiperone, eticlopride, and clozapine. Co-transfection of a D2 dopamine receptor expression vector enhanced bromocriptine's transcriptional activation of the pgp2/mdr1b promoter. The G-protein, Galphai2, is required for bromocriptine transcriptional activation because the G-protein inhibitor, pertussis toxin, suppressed bromocriptine's activation of pgp2/mdr1b transcription and co-transfection of a dominant negative Galphai2 abrogated bromocriptine activation of pgp2/mdr1b. Gi proteins can transduce signals by activation of mitogen-activated protein kinases (MAPKs), and because Raf-1 is a known activator of MDR1, we tested for Raf-1 involvement. Co-transfection of a dominant negative Raf-1 failed to block bromocriptine induction of pgp2/mdr1b, and bromocriptine treatment caused no phosphorylation of the MAP kinase kinase substrates p42 and p44, demonstrating that the MAP kinase pathway was not involved. These are the first studies demonstrating transcriptional activation of an MDR gene by dopamine receptor agonists and that this activation occurs by a signal transduction pathway requiring the D2 dopamine receptor coupled to a functional G-protein.

Substance P-induced mitogenesis in human astrocytoma cells correlates with activation of the mitogen-activated protein kinase signaling pathway

The neuropeptide substance P (SP) regulates many biological processes through binding to and activating the SP receptor (NK-1 subtype). Activation of the SP receptor induces mitogenesis in several cell types. In this study, we characterized the mitogenic response induced by SP peptide in the U-373MG astrocytoma cell line and showed that activation of the SP receptor induces [3H]thymidine incorporation into DNA. We also found that SP potently induces c-myc mRNA and protein in the U-373MG cells. Tyrphostin A25, which blocks activity of tyrosine kinases, significantly inhibited SP-induced mitogenesis, suggesting that the mitogenic response induced by SP peptide involves phosphorylation by tyrosine kinases. Furthermore, stimulation of the SP receptor activates tyrosine phosphorylation and enzymatic activity of extracellular signal-regulated kinases (Erk1 and Erk2), also called the mitogen-activated protein kinases (MAPKs). This result suggests that MAPKs participate in the SP peptide-induced signaling pathway. The addition of CP 96,345 ([(2S,3S)-cis-2-(diphenylmethyl)-N-[(2-methoxyphenyl)-methyl]-1 -azabicyclo[2.2.2]octan-3-amine]; an NK-1 receptor antagonist) or PD 098059 (MEK1 inhibitor) inhibited both DNA synthesis and activation of the MAPK pathway, substantiating that SP stimulates mitogenesis by activating the MAPK pathway through receptors of the NK-1 subtype. Our results demonstrate that SP peptide is a strong mitogen in the U-373MG astrocytoma cell line and establish a clear correlation between SP-induced mitogenesis and activation of MAPK signaling pathway.

Variation of an epitope of keratan sulphate and total glycosaminoglycans in normal equine joints

An epitope of keratan sulphate (KS) and total glycosaminoglycans (GAG) were measured in synovial fluid samples from joints of 53 horses immediately following humane destruction. Internal examination of the joints post mortem ensured that there was no gross evidence of osteoarthritis or other joint disease. Joints sampled were distal interphalangeal (DIP), proximal interphalangeal (PIP), metacarpophalangeal (MCP), metatarsophalangeal (MTP), tarsometatarsal (TMT), tarsocrural (TC), femoropatellar (FP) and antebrachiocarpal (ABC) joints. The age of each horse was assessed by examination of the teeth. Samples were analysed for the KS epitope using a monoclonal antibody 5D4 and an inhibition ELISA and for total GAG level by a direct dye binding technique. There was no significant correlation between KS or GAG concentration and age. However, there were significant differences in the concentrations of KS and GAG in different joints. The median level (+semi interquartile range) of KS:GAG ratio in the MCP was significantly lower than the PIP (0.25 [0.05] vs. 0.35 [0.08]; P < 0.007) and also the DIP joints (0.25 [0.05] vs. 0.47 [0.09] P < 0.001). This study provides information which is both valuable in the investigation of normal joint metabolism and essential in the interpretation of synovial fluid KS and GAG values in their potential role as aids in the evaluation of joint disease.

The relevance of chondroitin and keratan sulphate markers in normal and arthritic synovial fluid

This study investigated the synovial fluid concentrations of glycosaminoglycan (GAG), keratan sulphate (KS) epitope 5D4 and chondroitin sulphate (CS) sulphation patterns in healthy volunteers and patients with osteoarthritis (OA) and rheumatoid arthritis (RA). Synovial fluids were collected from knee joints of healthy volunteers (n = 24), and patients with OA (n = 28) and RA (n = 29). Concentrations of GAG and the keratan sulphate epitope 5D4 were measured in 15 of the healthy volunteers, and all of the OA and RA synovial fluids. Total GAG was measured using a dye-binding method and 5D4 by an ELISA. The unsaturated CS disaccharides delta C4 and delta C6 were measured by capillary electrophoresis in all synovial fluids. The concentrations of GAG, 5D4 and delta C6 in the normal synovial fluid were higher but that of delta C4 lower than those of the disease groups. The delta C6:delta C4 ratios correlated with age (r = -0.437, P < 0.001) and the mean value was lower in females than males (2.92 compared with 5.22, P < 0.001). After allowing for age and sex, the delta C6:delta C4 ratio in the control group was significantly elevated (P < 0.001) compared to both OA and RA. The ratio was also related to proteoglycan markers (r = 0.383 for 5D4 and r = 0.357 for GAG). The finding that 5D4 and delta C6:delta C4 ratios are higher in synovial fluid from healthy volunteers compared to OA and RA suggests that they may be markers of the susceptibility of articular cartilage to early damage in arthritis.

Recent advances in osteoarthritis

Osteoarthritis (OA) is a very common affliction and is associated with much disability. In the past decade important advances have been made in our understanding and treatment of OA. New technology in imaging and biochemistry have helped towards the identification of prognostic markers of disease and providing sensitive techniques to test the effects of new exciting drugs for intervention. New information regarding the heterogeneity and aetiopathogenesis of OA adds to this excitement. It may not be long before we will be in a position to predict the progression of the disease and contemplate intervention with disease modifying agents. This review discusses these latest advances in the study and management of OA.

Cytokines in osteoarthritis: mediators or markers of joint destruction?

OBJECTIVE

The integrity of articular cartilage is maintained by the balance between cytokine-driven anabolic and catabolic processes. Unregulated or excess influences of these molecules are thought to play a part in the pathophysiology of many joint diseases. However, the role of cytokines in osteoarthritis (OA) is not well established. Our aims are twofold: firstly to consider the evidence for the contribution of cytokines to the pathophysiology of OA and secondly to evaluate their potential as markers of disease activity in OA.

METHODS

Cytokine homeostasis, the role of catabolic and anabolic cytokines in maintaining cartilage integrity, and the contribution of such cytokines to destructive processes in OA were examined. Consideration was given to the interrelationship between cartilage, bone, and synovium in OA; metabolites produced by such structures were compared with cytokines as indicators of disease activity.

RESULTS

The evidence reviewed suggests that interleukin-1 (IL-1) and the less potent tumor necrosis factor alpha (TNF alpha) are mediators of joint damage in OA. The cytokines interleukin-6 (IL-6) and leukemia inhibitory factor (LIF) were implicted in both destructive and protective mechanisms, suggesting a dual role. Metabolites of the different components of the joint provided a better measure of disease activity than cytokines.

CONCLUSIONS

Experimental evidence is emerging that catabolic cytokines are mediators of joint damage in OA, although their usefulness as markers of disease activity is limited because of the need to monitor a wide range of ligands and their inhibitors simultaneously. In contrast, metabolites released from cells within bone, synovium, and cartilage related to disease activity and provided prognostic information.

Synovial fluid and serum concentrations of aminoterminal propeptide of type III procollagen in healthy volunteers and patients with joint disease

OBJECTIVES

To analyse synovial fluid and serum concentrations of the amino-propeptide of the type III procollagen (PIIINP) in normal individuals and patients with joint disease, and to explore the relationship between synovial fluid PIIINP concentrations and the rheumatological diagnosis, local inflammation, and joint disease.

METHODS

A radioimmunoassay was used to measure the PIIINP concentrations in serum and knee joint synovial fluid from 16 healthy volunteers and patients with osteoarthritis (OA) (n = 40), rheumatoid arthritis (RA) (n = 30), and psoriatic arthritis (PsA) (n = 12). The PIIINP measurements were related to demographic data, synovial fluid leucocyte counts, and radiographic changes at the knee.

RESULTS

Serum PIIINP concentrations were greater in each of the disease groups than in control subjects, but there were no differences between the disease groups. Synovial fluid concentrations of PIIINP were much greater than those in serum, indicating local production, and were significantly greater in RA than in other disease groups (p < 0.001). There was only a weak positive correlation between synovial fluid leucocyte counts, some radiographic changes, and synovial fluid PIIINP concentrations.

CONCLUSIONS

These data suggest that synovial fluid PIIINP concentrations may reflect local synovial proliferative processes in joint disease, and that they could be of diagnostic and prognostic value in inflammatory arthropathies.

Serum hyaluronic acid level as a predictor of disease progression in osteoarthritis of the knee

OBJECTIVE

To investigate the prognostic value of serum hyaluronic acid (HA) and keratan sulfate (KS) levels in relation to tibiofemoral osteoarthritis (OA) of the knee.

METHODS

Clinical and demographic data were collected on 94 patients. Radiographs were obtained at study entry and at 5-year followup. Disease progression was defined as 2 mm of joint space narrowing of any tibiofemoral compartment, and/or knee joint surgery during the study period. Serum HA and KS were measured and levels were correlated with entry data and disease progression.

RESULTS

At entry, HA levels were significantly related to disease duration (P = 0.036), minimum joint space (P = 0.049), and previous surgery (P = 0.001). After these variables were taken into account, patients whose disease had progressed were shown to have had significantly higher levels of HA at baseline compared with those whose disease had not progressed (P = 0.019). However, there were no significant differences in levels of serum KS between those with and those without disease progression, at entry (P = 0.779) or at subsequent visits.

CONCLUSION

These results suggest that serum HA levels predict disease outcome in OA of the knee and confirm that a single measurement of the serum level of KS is not useful as a prognostic marker in OA.

Relationship between serum cartilage oligomeric matrix protein levels and disease progression in osteoarthritis of the knee joint

The value of serum cartilage oligomeric matrix protein (COMP) as a marker of disease progression was investigated in 81 hospital out-patients with clinical knee osteoarthritis (OA). Progressing patients were defined by a decrease of > or = 2 mm in joint space on X-ray or requiring knee surgery during the 5 yr of follow-up. Of the 57 patients for whom full data were available, 20 progressed and 37 did not progress. Serum COMP levels increased during the first year in those who progressed (mean 6.42 micrograms/ml) (S.D. 6.64) compared to those who did not progress [mean 0.07 microgram/ml (S.D. 4.99); P < 0.001]. Changes in COMP during the first year were related to baseline COMP (r = -0.672, P < 0.001) and weight-to-height ratio (r = 0.272, P = 0.47). After allowing for these variables, serum COMP increased during the first year in progressive patients by 5.04 micrograms/ml [95% confidence interval (CI): (2.61, 7.46)] more than in non-progressive patients. Discriminant analysis gave a sensitivity of 70% and specificity of 78% at a cut-off value of 3.17 micrograms/ml. Baseline serum COMP levels did not differ between the groups but were related to late phase scintigraphy scan abnormalities. These observations suggest that the changes in serum COMP may have prognostic significance and are consistent with a model of OA in which early signs of episodic clinical progression can be found in the cartilage as well as in subchondral bone.

Correlation between synovial fluid markers of cartilage and bone turnover and scintigraphic scan abnormalities in osteoarthritis of the knee

OBJECTIVE

To test the hypothesis that scintigraphic evidence of bone activity will correlate with biochemical evidence of increased matrix turnover in osteoarthritis (OA).

METHODS

Keratan sulfate epitope (5D4), chondroitin sulfate epitope (3B3), and osteocalcin (OC) were measured in synovial fluid (SF) from 35 patients with knee OA, within 1 month of bone scan.

RESULTS

SF OC levels correlated with 5D4 levels (r = 0.32, P = 0.047) and with abnormalities on scintigraphic scan. Mean OC levels were 47% higher (P = 0.016) in patients with severely abnormal findings on scans compared with levels in patients with mildly abnormal scan findings. No significant association of 5D4 or 3B3 levels and perfusion- or late (bone)-phase scintigraphic abnormalities was found.

CONCLUSION

These data support the hypothesis that there is an association between late-phase bone scan abnormalities and SF biochemical markers of bone turnover in OA.

Attenuation of agonist-induced desensitization of the rat substance P receptor by microinjection of inositol pentakis-and hexakisphosphates in Xenopus laevis oocytes

Recently, inositol hexakisphosphate (phytic acid) was shown to bind to photoreceptor arrestin and block its interaction with rhodopsin. Such an interaction might predict that inositol polyphosphates could alter G protein-coupled receptor desensitization. To investigate the possible roles of higher inositol polyphosphates on receptor desensitization, we have expressed the rat substance P receptor in Xenopus laevis oocytes. The functional expression of substance P receptor was monitored by voltage-clamp recording of substance P-induced Ca(2+)-dependent Cl- currents. When control oocytes were stimulated with substance P (30 nM), after 10 min of washing the second responses to substance P were approximately 15% of the first responses. Cytosolic injection of inositol pentakisphosphate (100 microM) or inositol hexakisphosphate (100 microM) inhibited the reduction of the second substance P-induced current responses, maintaining the second responses to 57-58% of the initial responses. The protective effects of inositol pentakisphosphate and inositol hexakisphosphate against agonist-induced desensitization were concentration and time dependent and structurally specific, in that inositol hexasulfate and inositol tris- and tetrakisphosphate isomers were inactive. Microinjection of inositol hexakisphosphate did not (a) change the potency of substance P or the sensitivity of the expressed substance P receptor to substance P, (b) inhibit 12-O-tetradecanoylphorbol-13-acetate-induced loss of substance P-induced current responses, or (c) alter the currents elicited by microinjection of inositol-1,4,5-trisphosphate. These results suggest that inositol pentakisphosphate and inositol hexakisphosphate have specific inhibitory effects on the agonist-induced loss of responsiveness of the rat substance P receptor. Moreover, these protective effects of inositol hexakisphosphate against desensitization were also observed with the endogenous lysophosphatidic acid/phosphatidic acid receptor, indicating that this mechanism is not specific to ectopic receptors. These results suggest that inositol pentakisphosphate and inositol hexakisphosphate may be novel pharmacological tools for the study of agonist-induced desensitization.

Attenuation of agonist-induced desensitization of the rat substance P receptor by progressive truncation of the C-terminus

We have investigated the C-terminal tail of the rat substance P receptor (SPR) as a domain essential for agonist-induced desensitization. Four progressively shorter mutants, using premature termination in the C-terminus, were constructed and compared with the unaltered SPR using ectopic expression of wild-type and mutant receptors in Xenopus oocytes. These mutants were designated D16, D47, D70 and D96 with 16, 47, 70 and 96 amino acids residues deleted from the tail, respectively. Wild type SPR, D16 and D47 exhibited normal current responses when challenged with substance P, but D70 and D96 had reduced maximal current responses (70% and 5% of wild type SPR, respectively). D70, however, exhibited substantial resistance to substance P-induced desensitization in that 55%, versus 8% for wild type SPR, of the peak current of the first response was preserved on second challenge with substance P. Therefore, a domain from residues 338 to 360 of the rat SPR, though not necessary for the functional activity of the receptor, plays an essential role in agonist-induced desensitization.

Intra-articular hyaluronic acid in osteoarthritis of the knee: an investigation into mechanisms of action

The objective of this study was to investigate mechanisms of action of intra-articular hyaluronic acid in osteoarthritis (OA) of the knee. Twelve patients with bilateral knee OA and synovial effusions entered a randomized, single-blind, blind observer study. Hyaluronic acid ("Hyalgan", Fidia SpA, Italy) or placebo were given by intra-articular injection weekly for 5 weeks. Assessments included clinical indices and imaging (magnetic resonance imaging (MRI) and 99m Tc bone scanning) before and after the course of injections. In addition, synovial fluid keratan sulfate (KS), chondroitin sulfate (CS) and C-propeptide of type II collagen (CPII) were measured. MRI and 99m Tc scanning showed no change in either treated or placebo knees over the 6-week study period. A fall in KS levels occurred in treated knees compared with placebo (Wilcoxon paired test, P = 0.1), although this did not reach significance perhaps due to small sample numbers). Ten out of 12 treated knees showed a fall in KS, compared with four out of 12 placebo knees. CS and CPII levels did not change significantly. Intra-articular injection of hyaluronic acid did not result in any improvement in the clinical indices compared to the placebo. In conclusion, assessment of cartilage markers may be of value when studying novel therapies in OA. MRI appearances remain remarkably stable over a 6-week period.

Expression of the MAS proto-oncogene in the retinal pigment epithelium of the rhesus macaque

The MAS proto-oncogene codes for a seven transmembrane protein which has been previously localized to specific regions of the hippocampus and cerebral cortex in the rat central nervous system. Because MAS has biological properties related to the growth and differentiation of cells of neuroectodermal origin, we investigated the distribution of MAS expression in the rhesus macaque retina by in situ hybridization. A 330 base pair (bp) segment of the human MAS sequence was subcloned and used to generate single-stranded cRNA probes for these studies. Our results demonstrated little, if any, positive signal over the neurons of the retina. The use of epi-polarization microscopy, however, revealed a distinct positive labelling of retinal pigment epithelial (RPE) cells. These studies suggest the use of MAS as a possible marker for the retinal pigment epithelium.

Nuclear hormone receptors involved in neoplasia: erb A exhibits a novel DNA sequence specificity determined by amino acids outside of the zinc-finger domain

The erb A oncogene is a dominant negative allele of a thyroid hormone receptor gene and acts in the cancer cell by encoding a transcriptional repressor. We demonstrate here that the DNA sequence recognition properties of the oncogenic form of the erb A protein are significantly altered from those of the normal thyroid hormone receptors and more closely resemble those of the retinoic acid receptors; this alteration appears to play an important role in defining the targets of erb A action in neoplasia. Unexpectedly, the novel DNA recognition properties of erb A are encoded by an N-terminal region not previously implicated as playing this function in current models of receptor-DNA interaction. Two N-terminal erb A amino acids in particular, histidine 12 and cysteine 32, contribute to this phenomenon, acting in conjunction with amino acids in the zinc finger domain. The effects of the N-terminal domain can be observed at the level of both DNA binding and transcriptional modulation. Our results indicate that unanticipated determinants within the nuclear hormone receptors participate in DNA sequence recognition and may contribute to the differential target gene specificity displayed by different receptor forms.

v-erbA acts on retinoic acid receptors in immature avian erythroid cells

The v-erbA oncogene of avian erythroblastosis virus (AEV) encodes an aberrant version of a gene for a thyroid hormone receptor (c-erbA) and functions in neoplasia by blocking erythroid differentiation and altering the growth properties of fibroblasts. The v-erbA gene has been proposed to act as a dominant negative allele, functioning by interfering with the actions of its normal cell homologs, the thyroid hormone receptors. The v-erbA protein can also, however, interfere with the actions of other members of the nuclear hormone receptor family, and it has been proposed that interference with a retinoic acid-mediated response may be a crucial determinant of v-erbA's function in the cancer cell. Here we report that the ability of v-erbA to interfere with retinoic acid receptor (RAR) action extends to the neoplastic erythroid cell and that v-erbA can inhibit transcriptional activation by all three isoforms (alpha, beta, and gamma) of RAR. Overexpression of RAR-alpha was found to partially overcome the presumptive v-erbA block to transcription in the erythroleukemic cell. These results are consistent with our hypothesis that v-erbA can act in neoplasia by interfering with a retinoic acid-mediated signal transduction pathway.

The development of monoclonal antibodies to the human mitochondrial 60-kd heat-shock protein, and their use in studying the expression of the protein in rheumatoid arthritis

OBJECTIVE

To assess the claim that the human 60-kd heat-shock protein (HSP) is highly expressed in the joints of patients with rheumatoid arthritis (RA), but is not readily detected in normal tissues.

METHODS

Monoclonal antibodies were raised against the human 60-kd mitochondrial heat-shock protein (P1 protein; hsp60), and their specificity was established. They were then applied to synovial tissue.

RESULTS

HSP was expressed similarly in normal, osteoarthritic, and RA synovium. Low levels of hsp60 were detected in synovial fluid by immunoprecipitation.

CONCLUSION

Minor differences in the distribution of hsp60 in synovium from RA joints were attributable to increased cellularity and to the disorganization of the tissue architecture.

V-erbA and c-erbA proteins enhance transcriptional activation by c-jun

The ability of different transcription factors to interact with one another is an important means by which the eucaryotic cell can integrate separate growth and differentiation signals into a coherent response. We report here an analysis of the interactions of transcription factors that are also the products of oncogenes: the erbA, jun and fos proteins. We demonstrate that the c-jun polypeptide can functionally interact with the c-erbA protein (thyroid hormone receptor) to yield an enhanced activity greater than that of either factor individually. Although the avian erythroblastosis v-erbA allele is generally thought to act as a transcriptional repressor in vertebrate cells, we also report the existence of promoter contexts where v-erbA, as well as c-erbA, can serve as 'co-activators' of c-jun function. V-erbA appears to augment retinoic acid receptor function in the same context. Our results suggest that v-erbA may have unanticipated positive effect on transcription in the neoplastic cell in addition to the repressor functions previously characterized.

v-erbA oncogene function in neoplasia correlates with its ability to repress retinoic acid receptor action

The v-erbA oncoprotein of avian erythroblastosis virus is an aberrant version of a thyroid hormone receptor and functions in neoplasia by blocking erythroid differentiation and by modifying the growth properties of fibroblasts. v-erbA has been proposed to represent a novel dominant negative oncogene, acting in the cancer cell by interfering with the actions of its normal cell homologs, the thyroid hormone receptors. We report here that v-erbA can actually interfere with the actions of a variety of members of the steroid/retinoid receptor family and that the ability of v-erbA to act in neoplasia best correlates not with suppression of c-erbA action, but with interference with the retinoic acid receptor response. We suggest that v-erbA may act in neoplasia by promiscuously interfering with a retinoid-mediated differentiation process.

Ontogeny of the v-erbA oncoprotein from the thyroid hormone receptor: an alteration in the DNA binding domain plays a role crucial for v-erbA function

The avian erythroblastosis virus v-erbA oncogene is imprecisely derived from a cellular gene (c-erbA) encoding a thyroid hormone receptor: the v-erbA protein has sustained both small terminal deletions and internal amino acid sequence changes relative to c-erbA. We report here that one of these missense differences between v- and c-erbA proteins, located in a zinc finger DNA binding domain, has dramatic effects on the biological activities of the encoded protein. Back mutation of the viral coding sequence to resemble c-erbA at this site severely impairs erythroid transformation and produces subtle changes in DNA binding by the encoded protein, suggesting that differences in DNA binding by the viral and cellular proteins may be involved in the activation of v-erbA as an oncogene.

The viral erbA oncogene protein, a constitutive repressor in animal cells, is a hormone-regulated activator in yeast

The v-erbA oncogene is a retrovirus-transduced and altered copy of a cellular gene for a thyroid hormone receptor. In animal cells, the v-erbA protein fails to respond to hormone and acts as a dominant negative allele, inhibiting gene activation normally conferred by the wild-type thyroid hormone receptor. We report here that, unexpectedly, the v-erbA protein acts as a hormone-regulated transcriptional activator in S. cerevisiae. We suggest that the ability of v-erbA protein to function as a transcriptional repressor or an activator is determined by interaction with, or modification by, other cellular factors, and that this phenomenon may be relevant to understanding ligand regulation of the normal thyroid and steroid hormone receptors.

Immunity to heat shock proteins in rheumatoid arthritis

Heat shock proteins (hsp) or "stress proteins" are a group of highly conserved proteins which are important in the day to day function of all cells. Early studies by others have indicated that immunity to the 65 kDa hsp of mycobacteria is important in the development of arthritis in the adjuvant arthritis model in rats. In this paper, we review the evidence suggesting that, as for the rat model, immune reactivity to hsp is of importance in the human disease. Elevated levels of IgG antibodies to the 65 kDa hsp of mycobacteria are characteristic of rheumatoid arthritis (RA) patients. Much of this antibody cross-reacts with human 65 kDa hsp and is therefore autoreactive. The 65 kDa hsp is found in synovial fluid and is therefore a potential target for antibody. Antibodies to the 70 kDa hsp (both of mycobacterial and human origin) are elevated, but not specifically, in RA. Increased T cell responses to the 65 kDa hsp are also found in synovial fluid of RA patients. Although gamma delta T cells are present in the synovial joint of RA patients, they do not appear to be particularly increased in frequency although the subset distribution of these cells is clearly different from that seen in the circulation. In fact, the synovium looks like the "gut" with regard to these subsets!

Terminal N-acetylglucosamine in chronic synovitis

The distribution of terminal GlcNAc residues in normal and diseased synovial tissue has been studied using a mouse monoclonal antibody (mAb) which binds to terminal N-acetylglucosamine (GlcNAc). Normal human connective tissue, including synovium, showed no staining for terminal GlcNAc. Normal epithelial tissues, including tonsillar epithelium, skin, small intestinal epithelium and salivary epithelium showed cellular staining. Synovium from patients with definite rheumatoid arthritis showed dense granular staining of macrophages. In addition, synovium from 9 of 12 patients with definite rheumatoid arthritis showed reticular extracellular staining indicating deposition of material bearing terminal GlcNAc in the connective tissue stroma. The extracellular staining was not seen in synovium from patients with osteoarthritis. Extracellular material bearing terminal GlcNAc may act as an inflammatory stimulus in rheumatoid arthritis, either by acting as antigen or by interaction with receptors on macrophage membranes which also recognize GlcNAc on bacterial material, thus triggering biochemical pathways normally occurring in response to the presence of micro-organisms.

Preliminary studies on enzootic bovine leukosis in Saudi dairy farms

The occurrence of sporadic cases of enzootic bovine leukosis in commercial dairy farms in Saudi Arabia was recently confirmed and found to be associated with importation of breeding heifers. Immunodiffusion test was applied to screen the prevalence of infection with bovine leukemia virus among local traditional and dairy cattle. All the 102 examined local cattle were negative, while out of the 1329 tested dairy animals (originating from 23 farms), 268 (from 16 farms) showed precipitating activity. As an epizootiological model, all animals of an infected dairy farm were serologically examined. Out of the 560 originally imported cows and the 1849 animals born locally in the farm, 217 (39%) and 468 (25%) animals, respectively, were found positive. The correlation between the age of locally born animals and the occurrence of antibodies against bovine leukemia virus was discussed.

Membrane N-acetylglucosamine: expression by cells in rheumatoid synovial fluid, and by pre-cultured monocytes

After 21-48 h in culture, 2-8% of human peripheral blood monocytes strongly express terminal N-acetylglucosamine (GlcNAc) on their membranes. This can be detected with a monoclonal antibody selected for binding to asialo-agalacto-fetuin, and is eliminated by incubating the cells in pure N-acetylglucosaminidase. Expression of GlcNAc is transient, and can no longer be detected by day 4. These cells are a subset of macrophages since they are positive for non-specific esterase and stained by the monoclonal antibody EBM 11. GlcNAc-positive cells showing double staining with monoclonal antibodies UCHM1 and RFD7 were detected. Their numbers were not influenced by the addition of GM-CSF, IFN-gamma, 1,25-(OH)2 cholecalciferol or indomethacin. Macrophages which give membrane staining for terminal GlcNAc were also found in rheumatoid synovial fluid, and in synovial tissue, though in the peripheral blood their frequency was the same in samples from normal donors and from patients with rheumatoid arthritis. Immunoblots of 24-48-h monocyte cultures or of fresh synovial fluid cells using the anti-GlcNAc monoclonal, show the anticipated agalactosyl IgG heavy chains, and an additional band of 70-80kDa.