THE ISOLATION OF A MUCOPOLYSACCHARIDE FROM SYNOVIAL FLUID*

Transcription

1 THE ISOLATION OF A MUCOPOLYSACCHARIDE FROM SYNOVIAL FLUID* BY KARL MEYER, ELIZABETH M. SMYTH, AND MARTIN H. DAWSON (From the Department of Ophthalmology, College of Physicians and Surgeons, Columbia University, and the Institute of Ophthalmology and the Edward Daniels Faulkner Arthritis Clinic, Presbyierian Hospital, New York) (Received for publication, January 30, 1939) It has been known for a long time that synovial fluid on acidification yields a stringy precipitate, the so called synovial mucin, which redissolves in alkali to form a viscous solution. Much work has been done on the distribution and properties of this fraction and its production by special cells of the synovial lining. Even its formation in tissue cultures of synovial tissue has been demonstrated. (For literature see (2).) Some authors have contended that the synovial fluid is a secretion of specific cells of the synovial lining; others have thought it to be a dialysate of the blood stream modified by products of degenerated tissue. In view of the importance and frequency of diseases such as rheumatic fever and arthritis, much attention has been devoted to the quantity and the viscosity of the fluid and the mucin isolated from it. It seems doubtful, however, whether the method of isolation of the mucin (precipitation with 2 per cent acetic acid) gives a quantitative yield of unaltered material. No information was available about the chemical nature of synovial mucin other than data on the nitrogen and sulfur content and the appearance of a reducing substance after hydrolysis. In order to isolate the substance responsible for the viscosity of the synovial fluid we have used a method similar to that employed in the isolation of chondroitinsulfuric acid (3), avoiding strong alkali and acid. A polysaccharide acid of high molecular weight was thus obtained from bovine synovial mucin, possessing most of the viscosity of the starting material. * A preliminary report of this work has been published (1). 319

2 Synovial Fluid Mucopolysaccharide It is obvious from the methods of preparation that the polysaccharide acid occurs in the fluid either free or united to protein in salt linkage only. Such a salt should dissociate in weakly alkaline solution, and a separation of the protein cation and its polysaccharide anion should be possible if the two constituents possess different solubilities. This proves to be the case. The synovial mucin can be separated into its protein and carbohydrate components by salting-out the protein in weak ammoniacal solution. The protein is precipitated by half saturation with ammonium sulfate and the carbohydrate can be obtained from the viscous supernatant solution by alcohol precipitation. The polysaccharide acid consists of equimolar parts of hexosamine, hexuronic acid, and acetyl, the latter apparently as N- acetylglucosamine. The yield varied from 200 to 300 mg. per liter of synovial fluid. The concentration of polysaccharide calculated from the hexosamine content of the mucin was about 25 per cent greater than that accounted for by the isolated polysaccharide acid. The remaining hexosamine is apparently part of the protein moiety. The protein isolated by the salting-out method gave after several reprecipitations 1.5 per cent hexosamine on analysis. On the basis of the uranic acid determinations of the mucin, the hexosamine content of the protein was calculated as 1.8 per cent instead of the 1.5 per cent found. In its hexosamine content as well as in its physical properties, the protein resembles serum globulin. The polysaccharide acid constitutes about 13 to 14 per cent of the mucin complex. It has been shown (4) that acid polysaccharides form true salts with the basic amino groups of proteins, which precipitate if the lat#ter are ionized, i.e. in acid solution. In addition to the hexosamine contained in the polysaccharide acid and the globulin fraction, a still larger amount of the hexosamine (about 60 per cent) found in the original synovial fluid is contained in fractions not accounted for by isolation. The hexosamine content of this residual fraction is in close agreement with the hexosamine content of normal serum, calculated on the basis of total solids. It is interesting to point out that this finding contrasts with the results obtained with aqueous and vitreous humor, where the polysaccharide isolated accounts for about 90 per cent of the total hexosamine in these fluids. Two possible

3 Meyer, Smyth, and Dawson 321 explanations for the discrepancy may be offered: (1) the proteins found in synovial fluid may be the normal serum proteins, (2) they may result from inflammatory and traumatic processes. In composition and rotation the polysaccharide acid of synovial fluid appears to be identical with the polysaccharide acid of vitreous humor, umbilical cord (5), and the mucoid phase of Group A hemolytic streptococcus (6). This is also borne out by the enzymatic hydrolysis of the new polysaccharide, by a specific enzyme obtained from pneumococcus (7),l into acetylglucosamine and glucuronic acid. The amount of reducing sugar liberated accounts for 96 to 100 per cent of the analytically determined component carbohydrates. Whether the polysaccharide acid of synovial fluid from species other than cattle is identical with the one described is not definitely known at present. However, from 160 cc. of an exudate from an inflamed human knee joint, we isolated 53.9 mg. of an impure polysaccharide having properties similar to the bovine fractions. This polysaccharide was also hydrolyzed by the pneumococcus enzyme. Experiments on the immunological properties of the polysaccharide acid indicate that it does not possess the properties of a hapten. All attempts to obtain antisera to the carbohydrate have failed, as have experiments designed to increase the antigenicity of synovial fluid (8). Attempts to produce precipitating sera against the polysaccharide of hemolytic streptococci by immunizing rabbits with Group A organisms according to Loewenthal s method (9) have also met with failure. EXPERIMENTAL Preparation of the Polysaccharide Acid-The synovial fluid was obtained in the slaughter-house by aspiration of the astragalotibia1 joints of freshly killed cattle, mostly 1 year-old steers.2 Usually 2 to 5 liters were worked up in each lot. In some in- 1 We have obtained uniformly highly active enzyme preparations from autolyzed pneumococci. The enzyme has also been prepared from cultures of Group A hemolytic streptococci. This work will be reported in a separate communication. 2 We wish to thank the management of Wilson and Company for their splendid cooperation.

4 322 Synovial Fluid Mucopolysaccharide stances the fluid was filtered. The fluid was diluted with 2.5 volumes of distilled water and the protein salt of the polysaccharide was formed by adding 10 per cent acetic acid to give a concentration of 0.2 per cent. This concentration, instead of the 2 to 3 per cent recommended by others, is sufficient to precipitate all of the polysaccharide. After 18 hours at O-5, the fibrous and sticky precipitate was partly removed by a glass rod and the rest by filtration. It was washed several times with distilled water and brought into solution with 10 per cent calcium chloride. Sodium hydroxide was added from time to time to keep the solution just alkaline to phenolphthalein (ph 9). On being stirred mechanically, the material slowly goes into solution. From this solution the bulk of the protein was removed by repeated shaking with chloroform-amyl alcohol mixture (5, 10). When the solution had become almost clear, it was treated with 1.25 volumes of alcohol. The centrifuged precipitate was washed with alcohol and dissolved in 5 per cent sodium acetate solution. If the solution was turbid, the treatment with chloroform-amyl alcohol was repeated. A further amount of protein was then removed by adding an 8 per cent zinc acetate solution and neutralizing with normal sodium hydroxide. Care must be taken at this stage to work in dilute solution (about 0.5 per cent with respect to carbohydrate), as otherwise the polysaccharide itself precipitates as a zinc salt. To remove zinc and sodium acetate the centrifuged solution was again treated with alcohol acidified with acetic acid. The precipitate was dissolved in a minimum amount of water and reprecipitated with 5 volumes of glacial acetic acid or alcohol acidified with glacial acetic acid. The voluminous, gelatinous mass was removed by centrifuging, washed on a filter with alcohol, acetone, and ether, and dried over phosphorus pentoxide. The free acid thus isolated consists of white fibers of considerable tensile strength. The neutralized 0.25 per cent solution of one sample (No. 82) in 0.9 per cent sodium chloride had a viscosity, determined at 20 in an Ostwald viscosimeter, of 9.33 relative to 0.9 per cent sodium chloride. The separation of the protein salt into the protein and carbohydrate fractions was carried out on a once reprecipitated sample, which after dehydration with alcohol gave the following

5 Meyer, Smyth, and Dawson 323 analysis: Sample 76Ia, N 12.63, hexosamine 7.55, uranic acid 6.17, acetyl 1.74, hexuronic acid to hexosamine ratio 0.75, acetyl to hexosamine ratio The protein separated out on addition of an equal volume of saturated ammonium sulfate solution and on making it alkaline with strong ammonia water to ph 9. The precipitate was filtered off through folded filter paper. Sulfate was removed from the clear, viscous solution by adding solid barium acetate and acidifying with a small amount of acetic acid, and the supernatant was treated with 2 volumes of alcohol. The precipitate was extracted with 5 per cent sodium acetate solution; the solution cleared by zinc hydroxide precipitation and again treated with alcohol. After one reprecipitation from alcohol, Sample 7811 was obtained (Table I). The ammonium sulfate precipitate containing the protein fractions was taken up in water, neutralized, and fractioned by ammonium sulfate solution. Four fractions were obtained. For analysis the solutions were precipitated with 5 per cent trichloroacetic acid, washed three times with 2 per cent trichloroacetic acid, and dried. Nitrogen Hemsamine Analysis of the polysaccharide fractions is shown in Table I. The analytical methods have been described previously (5, 11). The high ash content is of special importance when one is considering whether the polysaccharide is originally, all or in part, a sulfuric acid ester. It has been claimed that the mucin of synovial fluid is a protein compound of chondroitinsulfuric acid (2). Analysis of Sample 69 (38 mg.) gave no volatile sulfur and in the ash 0.47 per cent sulfur. (The sulfur content of chondroitinsulfuric acid prepared by a similar method varied between 5.6 and 6.1 per cent, half of which appears as volatile sulfur.) Phosphorus was present in traces too small to determine. The ash content is probably explained by the difficulty experienced in washing the extremely voluminous slimy precipitates. Another indication of the absence of appreciable quantities of chondroitinsulfuric acid is found in the rotation of the hexosamine

6 324 Synovial Fluid Mucopolysaccharide hydrochloride isolated from the polysaccharide gm. of a preparation containing 33.1 per cent hexosamine was hydrolyzed with hydrochloric acid and the amino sugar hydrochloride isolated as described previously (5). The gm. of hexosamine hydrochloride isolated accounted for 88.1 per cent of the amount TABLE Analysis of Synovial Fluid Polysaccharide Corrected for Ash and Moisture - Equivalents lent per equivaweight s*i?e I & k -- z.- Per cent Per cent : : 77AI t : 3 $.s - 8 Per cent 41.: ; : 44.: Pm cent 9.4 1o.e I [ai, 5 f ~- iz iegrees gt C C a 3 Pm ent.9;.01.9!.11.5(.9( TABLE II Enzymatic Hydrolysis of Polysaccharide from Synovial Fluid The concentration of the polysaccharide was 0.5 per cent. Hydrolysis shows 96 per cent of the theoretical amount calculated from reducing values for acetylglucosamine and glucuronic acid. Concentration of eneyme in mixture Glucose (theoretical = mg.) from 1 mg. polysaccharide (Hegedorn-Jensen method) corrected for controls 2 hrs. I 17 hrs. I 41 hrs. per cent ma. mg found by analysis. The nitrogen content was 6.40 per cent (theoretical 6.47), and the rotation at equilibrium was f70.1 (theoretical for d-glucosamine hydrochloride, ). The hexosamine was therefore d-glucosamine. In the presence of chondroitinsulfuric acid, the isolated hexosamine would have shown a

7 Meyer, Smyth, and Dawson 325 rotation intermediate between glucosamine and chondrosamine, as shown previously (5). The enzymatic hydrolysis of the polysaccharide from synovial fluid is illustrated in Table II. In Fig. 1 is shown a comparison of the hydrolysis of the polysaccharides from synovial fluid and from Group A hemolytic streptococci with two dilutions of enzyme. The enzyme employed in this experiment was prepared from a non-type-specific I.- '/TREPTOCOCCW x--+jynovial POLWACCHARIDE FLUID POLVJACWARIDE POLVJACC~IARIDE FIG. 1. Comparison of the rate of hydrolysis of polysaccharides from synovial fluid and from Group A hemolytic streptococci. The substrate concentration was 0.25 per cent and the enzyme concentrations and per cent. I variant of Type II pneumococcus. At the intervals indicated in the graph 0.2 cc. was pipetted out and reducing sugar determined by the Hagedorn-Jensen method. Both the enzyme and substrates were incubated in buffer solution separately and the very small amount of reduction in these blanks subtracted. The course of the hydrolysis for the two polysaccharides runs parallel within the limits of error of the method. This together with the similarity in the chemical and physical properties of the substance indicates their identity. ) The streptococcus polysaccharide was a sodium salt obtained from Dr. Kendall.

8 326 Synovial Fluid Mucopolysaccharide The hexuronic acid present in the polysaccharides of vitreous humor and umbilical cord had been demonstrated as glucuronic acid by. the isolation of its oxidation product saccharic acid (5). From the synovial polysaccharide the attempt was made to isolate glucuronic acid after enzymatic hydrolysis of the polysaccharide with the pneumococcus enzyme gm. of polysaccharide was incubated in the presence of toluene for 66 hours with 10 mg. of a purified enzyme preparation (as flavianate) from Type II pneumococcus. The reducing value at that time indicated that the polysaccharide had been hydrolyzed about 100 per cent. Glucuronic acid was precipitated as the basic lead salt. From this fraction the thiosemicarbazone was prepared by Neuberg s method (12), having a melting point of (m.p. found by Neuberg 223 ). According to Neuberg the thiosemicarbazone is typical for glucuronic acid. Acetylglucosamine was not isolated. An attempt was made to follow the hydrolysis of the polysaccharide by the pneumococcus enzyme by the quantitative acetylglucosamine determination of Morgan and Elson (13). Neither the polysaccharide nor the enzyme gave a blank value after incubation, while the mixture of the two gave an increasingly intense color after incubation. However, it has not been possible to get satisfactory data by this method. SUMMARY From the stringy precipitate which settles out from synovial fluid after acidification, the so called synovial mu&, a polysaccharide acid has been prepared. This polysaccharide consists of equimolar parts of a hexosamine, a hexuronic acid, and acetyl. The hexosamine has been demonstrated as d-glucosamine and the uranic acid as glucuronic acid. The polysaccharide acid is apparently identical with the polysaccharides previously isolated from vitreous humor and umbilical cord, and with that present in Group A hemolytic streptococcus. All four polysaccharides contain the same components in equimolar amounts, have a similar optical rotation, and are hydrolyzed at the same rate by a specific enzyme. The protein component of the carbohydrate-protein complex has been obtained by precipitation with ammonium sulfate in weakly alkaline solution. It appears to

9 Meyer, Smyth, and Dawson 327 be a globulin which apparently forms an insoluble salt with the acid polysaccharide on acidification. We wish to acknowledge the assistance of Mr. Arthur Stempel and Miss Eleanor Chaffee during the latter part of this work. BIBLIOGRAPHY 1. Meyer, K., Smyth, E. M., and Dawson, M. H., Science, 88, 129 (1938). 2. Kling, D. H., The synovial membrane and the synovial fluid, Los Angeles (1938). 3. Meyer, K., and Smyth, E. M., J. Biol. Chem., 119, 507 (1937). 4. Meyer, K., Palmer, J. W., and Smyth, E. M., J. Biol. Chem., 119, 501 (1937). 5. Meyer, K., and Palmer, J. W., J. Biol. Chem., 114, 689 (1936). 6. Kendall, F. E., Heidelberger, M., and Dawson, M. H., J. Biol. Chem., 118, 61 (1937). 7. Meyer, K.? Dubos, R., and Smyth, E. M., J. BioZ. Chem., 118,71 (1937). 8. Swift, H. F., and Schultz, M. P., J. Exp. Med., 63, 703, (1936). 9. Loewenthal, H., Bit. J. Exp. Path., 19, 164 (1938). 10. Sevag, M. G., Biochem. Z., 273, 419 (1934). 11. Palmer, J. W., Smyth, E. M., and Meyer, K., J. BioZ. Chem., 119, 491 (1937). 12. Neuberg, C., Ber. them. Ges., 33, 3322 (1900). 13. Morgan, W. T. J., and Elson, L. A., Biochem. J., 28, 988 (1934).

10 THE ISOLATION OF A MUCOPOLYSACCHARIDE FROM SYNOVIAL FLUID Karl Meyer, Elizabeth M. Smyth and Martin H. Dawson J. Biol. Chem. 1939, 128: Access the most updated version of this article at Alerts: When this article is cited When a correction for this article is posted Click here to choose from all of JBC's alerts This article cites 0 references, 0 of which can be accessed free at tml#ref-list-1