Understanding inorganic pyrophosphate metabolism: toward prevention of calcium pyrophosphate dihydrate crystal deposition.
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Adenosine Monophosphate↗
Biomedical subjects
L M Ryan
Publications and source records attributed to L M Ryan.
A unique ectonucleotide pyrophosphohydrolase associated with porcine chondrocyte-derived vesicles.
Previous studies have shown increased nucleotide pyrophosphohydrolase (EC 3.6.1.8) (NTPPHase) activity in detergent extracts of degenerated human cartilage containing calcium pyrophosphate dihydrate (CPPD) crystals relative to those from osteoarthritis or normal cartilage. NTPPHase was later shown to be an ectoenzyme and its activity was increased in synovial fluid from patients with CPPD crystal deposits relative to fluids from other types of arthritis. We have purified a soluble 61-kD NTPPHase from conditioned media of organ-cultured porcine articular cartilage to electrophoretic homogeneity. Its NH2-terminal sequence through 26 cycles showed < 30% homology to any previously reported protein sequence. An antibody raised to a synthetic peptide corresponding to this sequence reacted with denatured but not native enzyme. This antibody reacted against a sedimentable vesicle-associated 127-kD protein in conditioned media from cultured articular cartilage or from chondrocytes in primary monolayer culture and against a series of soluble proteins in conditioned media supernatant, including a 61-kD protein representing our original isolate. No reactivity was found in 1% SDS extracts of washed cultured chondrocytes, although these contained greater NTPPHase activity than the conditioned media. Antibody to PC-1, another ectoNTPPHase, reacted with 1% SDS extracts of whole chondrocytes but not against those chromatographic fractions containing the major portion of NTPPHase activity. Release of the vesicle-associated 127-kD enzyme into conditioned medium was stimulated three- to sevenfold by TGF beta 1. The antibody also reacted with a series of soluble proteins and with 127-kD sedimentable protein in human synovial fluid. Kinetic studies supported the existence of a unique vesicle-associated NTPPHase; apparent Km (mM) of chondrocyte membrane NTPPHase was 1.5 and 3.0 at pH 7.3 and 9.88, respectively; apparent Km (mM) of vesicle associated NTPPHase was 0.83 and 1.28 at pH 7.3 and 9.88. The data suggest the existence of a unique ecto-NTPPHase associated with vesicles derived from normal articular cartilage.
Amino Acid Sequence↗
Correction: A unique ectonucleotide pyrophosphohydrolase associated with porcine chondrocyte-derived vesicles.
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Amino Acid Sequence↗
Alkaline phosphatase: placental and tissue-nonspecific isoenzymes hydrolyze phosphoethanolamine, inorganic pyrophosphate, and pyridoxal 5'-phosphate. Substrate accumulation in carriers of hypophosphatasia corrects during pregnancy.
Hypophosphatasia features selective deficiency of activity of the tissue-nonspecific (liver/bone/kidney) alkaline phosphatase (ALP) isoenzyme (TNSALP); placental and intestinal ALP isoenzyme (PALP and IALP, respectively) activity is not reduced. Three phosphocompounds (phosphoethanolamine [PEA], inorganic pyrophosphate [PPi], and pyridoxal 5'-phosphate [PLP]) accumulate endogenously and appear, therefore, to be natural substrates for TNSALP. Carriers for hypophosphatasia may have decreased serum ALP activity and elevated substrate levels. To test whether human PALP and TNSALP are physiologically active toward the same substrates, we studied PEA, PPi, and PLP levels during and after pregnancy in three women who are carriers for hypophosphatasia. Hypophosphatasemia corrected during the third trimester because of PALP in maternal blood. Blood or urine concentrations of PEA, PPi, and PLP diminished substantially during that time. After childbirth, maternal circulating levels of PALP decreased, and PEA, PPi, and PLP levels abruptly increased. In serum, unremarkable concentrations of IALP and low levels of TNSALP did not change during the study period. We conclude that PALP, like TNSALP, is physiologically active toward PEA, PPi, and PLP in humans. We speculate from molecular/crystallographic information, indicating significant similarity of structure of the substrate-binding site of ALPs throughout nature, that all ALP isoenzymes recognize these same three phosphocompound substrates.
Alkaline Phosphatase↗
Consequences of prolonged inhalation of ozone on F344/N rats: collaborative studies. Part XI: Integrative Summary.
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Administration, Inhalation↗
Consequences of prolonged inhalation of ozone on F344/N rats: collaborative studies. Part X: Robust composite scores based on median polish analysis.
This report describes some of the statistical methods used to analyze data from the National Toxicology Program/Health Effects Institute Collaborative Ozone Project. The purpose of the collaborative study was to assess the health effects of chronic ozone inhalation. Data were obtained from a subset of 164 F344/N rats dedicated to use by the Health Effects Institute from a standard ozone inhalation study conducted by Battelle Pacific Northwest Laboratories for the National Toxicology Program. The study involved eight groups of investigators, each assessing different types of ozone-related health effects. These included studies of respiratory function and of structural, cellular, and biochemical changes in the lungs and airways. Designing and analyzing a study with several groups of investigators raises many statistical challenges. The highest design priority for this study was that each investigation be individually interpretable as an independent study. This meant that each investigator had to receive an adequate number of animals, balanced with respect to level of ozone exposure and other factors such as the gender of the rats and the time they were killed. Another feature of the collaborative study was the opportunity it provided to assess and quantify the effect of ozone exposure on a broad spectrum of endpoints, and to explore the relations between the different types of effect. Maximizing the potential to assess these correlations required that the individual animals studied by the different groups of investigators overlap as much as possible. This aspect of the statistical design required careful consideration of the compatibility between various investigations. Fortunately, the degree of compatibility was substantial. In many cases, for example, it was possible to assess respiratory function in the animals before they were killed, and then to divide the tissue among several different investigators. This report concentrates on the methods that were specially developed to analyze the data for multiple endpoints collected in the study. Nonstandard techniques were required to accommodate the complex pattern of missing data that was inherent in the study design because no animals were measured by all investigators.
Administration, Inhalation↗
Treatment of refractory crystal-associated arthritis.
Crystal-associated arthritis includes gout, calcium pyrophosphate deposition (CPPD) disease, and the basic calcium phosphate (BCP)-related syndromes. In this article, the authors discuss the use of drug combinations and steroids for refractory gout patients and recommend management strategies for gout in the organ transplant recipient. Difficult cases of CPPD disease can be treated with colchicine and intra-articular steroids. The BCP-associated syndromes are best managed with NSAIDs and intraarticular measures. Experimental therapies for all forms of crystal-related arthritis are also discussed.
Acute Disease↗
Anticonvulsant teratogenesis: 2. Statistical methods for multiple birth outcomes.
The purpose of this paper is to demonstrate the application of generalized estimating equations to assess an exposure effect using multiple birth outcomes. This multivariate approach provides the flexibility of regression modeling and improved power, as compared to series of univariate analyses or collapsing the multiple end-points to a single indicator of affectedness. Motivating the discussion will be a large cohort study designed to assess the effects of anticonvulsant medications on a variety of birth outcomes, including major malformations, and growth and weight parameters, as well as a broad spectrum of minor physical anomalies. Because the study is still in progress, the aim here is not to present a definitive analysis, but to present and describe the application of these recently developed statistical methods to analyze studies with multiple outcomes. For simplicity, we will focus on the control and drug-exposed groups only from that study (ignoring the seizure history group), and we will concentrate on an analysis of minor physical anomalies.
Abnormalities, Drug-Induced↗
Synovial fluid and plasma levels of cartilage matrix glycoprotein in arthritis.
As cartilage matrix glycoprotein (CMGP) is a prominent matrix constituent, we analyzed the relationship of levels in plasma (CMGPP) and synovial fluid (CMGPS) to each other, to clinical diagnosis, and to degree of radiographic cartilage degeneration. CMGP was measured in matched synovial fluid and plasma specimens from 67 patients with various forms of arthritis using an ELISA technique. CMGPS consistently exceeded CMGPP, CMGPP levels correlated significantly with CMGPS levels, and CMGP retention in joint fluid, as calculated by the ratio CMGPS: CMGPP, was significantly higher in patients whose synovial fluids contain basic calcium phosphate crystals. No correlation of CMGPP or CMGPS with diagnosis or degree of cartilage degeneration was observed. CMGP measurements are not useful diagnostically in patients with chronic arthritis and do not predict degree of radiographic degeneration. The association of basic calcium phosphate crystals with intraarticular retention of CMGP warrants further study.
Arthritis, Rheumatoid↗
Ageing increases growth factor-induced inorganic pyrophosphate elaboration by articular cartilage.
Advanced age is the most common risk factor for the development of calcium pyrophosphate dihydrate (CPPD) crystal-associated arthritis. However, the link between ageing and CPPD crystal formation in cartilage remains unexplained. In CPPD deposition disease, excess extracellular inorganic pyrophosphate (ePPi), generated by articular chondrocytes, accumulates in affected joints and contributes to CPPD crystallogenesis. Transforming growth factor beta 1 (TGF beta 1) is the first known physiologic stimulant of ePPi elaboration by adult porcine and human cartilage. We hypothesized that sensitivity of articular cartilage to the ePPi-stimulatory effects of TGF beta 1 may increase with ageing. Accordingly, we compared the effects of TGF beta 1 on cartilage ePPi elaboration from juvenile, young adult, and old adult pigs. Cartilage organ cultures from old animals increased ePPi elaboration in response to TGF beta 1 to a greater extent than did cartilage from juvenile and young adult animals. Similar results were seen in chondrocyte monolayers. Concurrent exposure to epidermal growth factor (EGF) augmented, but was not necessary for TGF beta 1-induced ePPi elaboration by adult cartilage. In contrast, in juvenile cartilage, concurrent exposure to EGF was required to permit TGF beta 1-induced ePPi elaboration. Thus, increased cartilage responsiveness to the ePPi-stimulatory effects of TGF beta 1 occurs with ageing, and may explain the link between advanced age and CPPD deposition disease.
Aging↗
Insulin-like growth factor-1 suppresses pyrophosphate elaboration by transforming growth factor beta1-stimulated chondrocytes and cartilage.
Our objective was to examine the effect of insulin-like growth factor-1 (IGF-1) on extracellular pyrophosphate (ePPi) elaboration by porcine cartilage. These studies further define the factors influencing ePPi accrual, a key step in calcium pyrophosphate dihydrate (CPPD) crystal formation. ePPi was measured in adult porcine organ and monolayer culture media in the presence of IGF-1, transforming growth factor beta-1 (TGFbeta-1), IGF-1 antibody and synovial fluid (SF). As previously shown, TGFbeta-1 stimulated ePPi elaboration by cartilage and chondrocytes. IGF-1 significantly inhibited the stimulatory effect of TGFbeta-1 on ePPi elaboration by both cartilage explants and chondrocytes. Anti-IGF-1 antibody blocked this inhibition. Anti-IGF-1 antibody also decreased the inhibitory effect of SF on ePPi elaboration, suggesting the presence of active IGF-1. These results support an important regulatory role for IGF-1 in cartilage ePPi elaboration. IGF-1 inhibited the effects of the ePPi-stimulatory factor TGFbeta-1 and thus may protect normal joints from excess accumulation of ePPi and subsequent CPPD crystal formation.
Animals↗
A comparison of continuous- and discrete- time three-state models for rodent tumorigenicity experiments.
The three-state illness-death model provides a useful way to characterize data from a rodent tumorigenicity experiment. Most parametrizations proposed recently in the literature assume discrete time for the death process and either discrete or continuous time for the tumor onset process. We compare these approaches with a third alternative that uses a piecewise continuous model on the hazards for tumor onset and death. All three models assume proportional hazards to characterize tumor lethality and the effect of dose on tumor onset and death rate. All of the models can easily be fitted using an Expectation Maximization (EM) algorithm. The piecewise continuous model is particularly appealing in this context because the complete data likelihood corresponds to a standard piecewise exponential model with tumor presence as a time-varying covariate. It can be shown analytically that differences between the parameter estimates given by each model are explained by varying assumptions about when tumor onsets, deaths, and sacrifices occur within intervals. The mixed-time model is seen to be an extension of the grouped data proportional hazards model [Mutat. Res. 24:267-278 (1981)]. We argue that the continuous-time model is preferable to the discrete- and mixed-time models because it gives reasonable estimates with relatively few intervals while still making full use of the available information. Data from the ED01 experiment illustrate the results.
Animals↗
Probenecid inhibits transforming growth factor-beta 1 induced pyrophosphate elaboration by chondrocytes.
OBJECTIVE: The elaboration of excess extracellular inorganic pyrophosphate (ePPi) by cartilage contributes to calcium pyrophosphate dihydrate (CPPD) crystal deposition disease. Transforming growth factor-beta 1 (TGF beta 1) is the only defined physiologic stimulant of cartilage ePPi elaboration. The mechanism of ePPi generation by chondrocytes is unknown, but current evidence suggests that TGF beta 1 induced ePPi is made intracellularly. An active transport mechanism such as an anion transporter would then be necessary to export ePPi to the matrix where crystals form. We determined the effect of probenecid (PB), an anion transport inhibitor, on TGF beta 1 induced ePPi elaboration. METHODS: Porcine hyaline articular chondrocytes in high density monolayer cultures were exposed to serum-free media with and without TGF beta 1 and/or PB. ePPi was measured in the media after 48-96 h of exposure. Cell injury was measured by examining the release of 3H-deoxyglucose from chondrocytes. The activity of the ePPi generating ectoenzyme nucleoside triphosphate pyrophosphohydrolase (NTPPPH) and media lactate concentrations were measured with standard colorimetric assays. As PB may inhibit phosphodiesterase (PDE), its effects on ePPi generation were compared with isobutylmethylxanthine (IBMX), a specific PDE inhibitor. RESULTS: PB inhibited TGF beta 1 induced ePPi elaboration by chondrocytes. PB did not cause membrane injury or decrease NTPPPH activity. Lactate production was decreased by PB but did not correlate with the effects of PB on ePPi elaboration. IBMX did not inhibit TGF beta 1 effect on ePPi elaboration. CONCLUSION: PB blocks TGF beta 1 induced ePPi elaboration. This effect is independent of cell membrane injury, decreased NTPPPH activity, or PDE inhibition. Our data implicate a role for anion transport in TGF beta 1 induced ePPi elaboration, and suggest a potential therapy for CPPD disease.
1-Methyl-3-isobutylxanthine↗
Evidence that a 550,000-dalton cartilage matrix glycoprotein is a chondrocyte membrane-associated protein closely related to ceruloplasmin.
Cartilage matrix glycoprotein (CMGP) is a disulfide-bonded 550,000-dalton protein that is synthesized by chondrocytes and ciliary epithelial cells. We have purified the protein from bovine and porcine articular cartilage and have sequenced two peptides, which both have significant homology with human ceruloplasmin, a copper-binding oxidase. Immunolocation analysis indicates that a commercial polyclonal antiserum to human ceruloplasmin reacts with bovine cartilage CMGP. Chelating columns made with copper bind CMGP from bovine cartilage extracts. CMGP is present in bovine chondrocyte membrane preparations purified from sucrose density gradients. Oligonucleotide probes have been synthesized based on the published sequence of the 3'-untranslated region and a portion of the C terminus of human ceruloplasmin and have been used to amplify a cDNA fragment from bovine cartilage and human liver libraries. CMGP demonstrates oxidase activity towards p-phenylenediamine similar to that of ceruloplasmin. These studies suggest that CMGP is closely related to, if not identical with, ceruloplasmin. It is possible that CMGP may be involved in metal transport into and/or within the chondrocyte.
Amino Acid Sequence↗
A comparison of the effect of transforming growth factor beta 1 on pyrophosphate elaboration from various articular tissues.
OBJECTIVE: The purpose of this study was to determine the effect of transforming growth factor beta 1 (TGF beta 1) on inorganic pyrophosphate (PPi) elaboration from articular tissues to better understand the pathophysiology of calcium pyrophosphate dihydrate (CPPD) crystal deposition in the joint. METHODS: PPi was measured in the media of adult porcine articular tissue in organ culture and monolayer cultures. RESULTS: TGF beta 1 strongly stimulated PPi elaboration by porcine fibrocartilage and hyaline cartilage. It modestly increased PPi elaboration by ligament, and had no effect on PPi elaborated by synovium. Of all cell types tested in cell culture, only chondrocytes responded to TGF beta 1 by significantly increasing PPi elaboration. CONCLUSION: TGF beta 1 stimulates PPi elaboration from hyaline cartilage, fibrocartilage, and ligament, indicating that there is in situ CPPD crystal formation in these tissues. The ability of tissues to respond to TGF beta 1 by increasing PPi elaboration correlates with the prevalence of CPPD crystal deposition found clinically. The unique response of chondrocyte monolayers to TGF beta 1 reinforces the key role of the chondrocyte in PPi elaboration in the joint. These findings support an etiologic role for responsiveness to TGF beta 1 in CPPD disease.
Animals↗
Statistical model for fetal death, fetal weight, and malformation in developmental toxicity studies.
The purpose of this paper is to present a statistical model for analyzing the joint effects of exposure on fetal death, fetal weight, and malformation in a developmental toxicity study. In addition to allowing for the usual litter effect, the model allows for correlations between different outcomes measured on the same fetus. Fitting the model requires first focusing on non-live outcomes by modeling the probability of fetal death or resorption as a function of dose. Then outcomes among live fetuses are modeled using a two-stage regression approach. The first stage models fetal weight as a function of dose and the second stage models fetal malformation as a function of dose, as well as residuals from the weight model. The regression coefficients from the malformation model have intuitive interpretations in terms of correlations between littermates and between different outcomes measured within the same fetus. Not only does the approach provide a useful way to investigate the relationship between adverse fetal outcomes, it also yields a natural framework for conducting quantitative risk assessment. A procedure is proposed for quantifying overall risk by incorporating the three outcomes in order to estimate safe dose levels and corresponding lower confidence limits. The method is illustrated using data from an experiment in mice conducted through the National Toxicology Program.
Abnormalities, Drug-Induced↗
Calcium pyrophosphate dihydrate crystal deposition and other crystal deposition diseases.
Recent advances in understanding the pathogenesis and mechanisms of tissue damage related to calcium-containing crystals are highlighted in this review. The clinical spectrum of diseases related to crystal deposition has broadened and includes distinct neurologic syndromes associated with hypertrophy and calcification of the ligamentum flavum or posterior longitudinal ligament in the cervical spine. Diagnostic methods of crystal identification are also reviewed.
Aged↗
Randomized comparison of doxorubicin alone versus ifosfamide plus doxorubicin or mitomycin, doxorubicin, and cisplatin against advanced soft tissue sarcomas.
PURPOSE: This three-armed phase III study in adults with advanced soft tissue sarcomas was planned as a comparison of objective regression rates, toxicity, and survival of patients receiving doxorubicin alone, ifosfamide plus doxorubicin, and mitomycin plus doxorubicin plus cisplatin. PATIENTS AND METHODS: Between December 1987 and July 1990, 279 patients with histologically confirmed sarcomas were enrolled to receive treatment A (doxorubicin 80 mg/m2), treatment B (ifosfamide 7.5 g/m2 plus doxorubicin 60 mg/m2), or treatment C (mitomycin 8 mg/m2 plus doxorubicin 40 mg/m2 plus cisplatin 60 mg/m2). RESULTS: Of 262 assessable patients, 74 (29%) achieved objective tumor regression. Objective regression occurred in 20% of the 90 patients who received doxorubicin alone (complete remission [CR] rate, 2%), in 34% of the 88 who received ifosfamide plus doxorubicin (CR rate, 3%), and in 32% of the 84 who received mitomycin plus doxorubicin plus cisplatin (CR rate, 7%). With grade 3 or greater myelosuppression in 53% of group A, 80% of group B, and 55% of group C, regimen B was significantly more myelosuppressive than either regimen A or C (P = .01) with two, three, and one treatment-related deaths, respectively. Synovial sarcomas were responsive to ifosfamide plus doxorubicin, especially among patients younger than 40 years of age. CONCLUSION: Ifosfamide plus doxorubicin produced a significantly higher regression rate (P = .03) than did doxorubicin alone; however, this was achieved at a level of myelosuppression significantly more intense than that produced by the single agent or by the three-drug combination. Mitomycin, doxorubicin, and cisplatin also appeared to be more active than the single agent; however, at a myelosuppression level similar to that of doxorubicin alone, this trend (P = .07) did not attain the usual level for significance. No significant survival differences were observed.
Adult↗