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Possible utilization of extracorporeal hemoperfusion in the treatment of coronary artery disease A hypothesis and proposal for animal studies
313
Atherosclerosis, 26 (1977) 373-377 0 Elsevier/North-Holland Biomedical Press
POSSIBLE UTILIZATION OF EXTRACORPOREAL HEMOPERFUSION THE TREATMENT OF CORONARY ARTERY DISEASE A HYPOTHESIS
AND PROPOSAL
IN
FOR ANIMAL STUDIES
MEIR STRAHILEVITZ Department Ill. (U.S.A.)
of Psychiatry, Southern Illinois University School of Medicine, Springfield,
(Received 16 June, 1976) (Revised, received 14 September, 1976) (Accepted 15 September, 1976)
Summary It is proposed that in vivo immunoadsorption may be utilized in the treatment of coronary artery disease. The proposed method is based on binding of low density lipoproteins and cholesterol to antibodies directed against low density lipoproteins which are bound to a matrix in an extracorporeal hemoperfusion column. The various observations that suggest the hypothesis are presented. The feasibility of the proposed method and some of the problems that may be encountered in its utilization are discussed. The method should be evaluated in animal studies prior to consideration of clinical trials in patients. Key words:
Atherosclerosis - Coronary artery disease - Extracorporal Immunoadsorption -Low density lipoproteins
hemoperfusion
-
Increased concentration of cholesterol and low density lipoproteins (LDL) in the serum are major factors both in the induction of experimental atherosclerosis (AS) in animals and spontaneous AS and Coronary Artery Disease (CAD) in humans [l-3]. The surgical treatment of CAD involves high risk and expense. Its general effectiveness in prolonging life has not yet been clearly established [4]. Advanced fibrotic AS plaques probably can be removed only by surgery [5]. How-
374
ever, the possibility should be considered that if LDL and serum cholesterol were to be reduced significantly below normal levels, even relatively advanced lesions in CAD may regress to the extent that cholesterol and lipoprotein arterial wall infiltration and the associated edema [6] are contributing significantly to the arterial-lumen narrowing. This lipid infiltration may trigger further fibrotic changes [ 51. Regression of experimental atherosclerosis in Rhesus monkeys was observed after a therapeutic diet [ 71. In man, Strazi et al. obtained arteriographic evidence of regression of atherosclerosis in the coronary arteries following a portocaval shunt for treatment of hyperlipidemia [8]. Thompson et al. [9] noticed loss of angina and obtained evidence of influx of tissue cholesterol into plasma, following plasma exchange, in two patients with homozygous familial hypercholesterolemia. All of these procedures were associated with decreased level of serum cholesterol and LDL. It is proposed that the gradient of concentration between LDL and cholesterol in the blood and in the arterial wall may reach such a critical level that will lead to significant absorption of cholesterol (primarily in esterified form) which is distributed in droplets or diffuse form in the middle and outer layers of the atherosclerotic intima. To a great extent this cholesterol is associated with LDL and is therefore accessible for exchange with the plasma [lo]. Drugs that are utilized for reducing blood level of cholesterol are capable to induce only a moderate (6-10%) reduction in blood cholesterol [ 11,121. Only in some individuals with type 2 and type 4 hyperlipoproteinemia can reduction in serum cholesterol be achieved by dietary measures and the reduction is often relatively small [13,14]. The major part of serum cholesterol (50-60%) is bound to LDL [2]. An efficient method for the removal of LDL, cholesterol and other lipids as well as other compounds that may be involved in the etiology of CAD in some cases (such as antibodies to heat-dried cow’s milk and value in the nonsurgical treatboiled egg-white [ 151) may be of therapeutic ment of CAD. The hypothesis is hereby proposed that Hemoperfusion-Immunoadsorption, in which specific antigens and antibodies (such as antibodies to human LDL) are bound to suitable matrix in a hemoperfusion column may be utilized for the absorption of LDL and cholesterol, in particular, from the blood and body stores of individuals with CAD, with the result that a reduction in the arterial wall infiltration of LDL and cholesterol and an increase in lumen size of affected coronary arteries may be achieved. The column will be connected to the circulation of the individual being treated. The antibodies may be regenerated by elution of bound antigen by change in PH [16] for continuous use. The eluted antigens (such as LDL and the cholesterol bound to it) may then be removed from the system. Materials that are capable of relative specific adsorption of LDL (for example, glass powder [17]), cholesterol and other lipids may be incorporated in the column matrix as well. Resin column hemoperfusion (using as resin Amberlite XAD-2) has been used successfully for the treatment of acute barbiturate intoxication in man [ 181. Thus the instrumentation and technology for column hemoperfusion are presently available. Antihuman LDL activity was found in human monoclonal immunoglobulins and was associated with hypolipidemia. No antihuman HDL
315
activity was present in these sera [19]. Immunochemical characterization of intact lipoproteins indicate that LDL is antigenically distinct from HDL and that human plasma lipoproteins are immunochemically distinct from the nonlipid containing plasma protein fraction [20]. Antiserum to LDL and HDL respectively is available commercially [ 191. Bailey et al. were able to obtain a reduction in AS plaques in immunized rabbits, as well as a reduction in the level of serum cholesterol and total lipids, using an immunogen that was prepared by conjugating Sebacyl ChlorideCholesterol to Bovine Serum Albumin (BSA) or to human P-lipoprotein [21,22]. They suggested that their observations demonstrate the feasibility of immunological manipulation of serum lipid and cholesterol levels by use of antibodies directed against specific serum lipoprotein constituents [ 221. Active immunization of humans with immunogenic conjugates of cholesterol with lipoproteins or BSA, with or without the utilization of adjuvants during the immunization, may be associated with undesirable or- even serious side effects, such as anaphylaxis, serum sickness, immune complex disease or autoimmune phenomena. It would be preferable to utilize methods in which immunological specific and selective binding of antigens, antibodies and haptens in human blood takes place without having to introduce heterologous antigens or antibodies into the circulation or other part of the body of the subject being treated. This goal can be achieved by utilization of an extracorporeal hemoperfusion immunoadsorption method. That such a method be quantitatively efficient in removing relatively large amounts of antigen from the circulation is suggested by the work of Lye1 et al. These investigators inserted Human Serum Albumin (HSA) and Ovalbumin (OA)-conjugated nylon tubing into the inferior vena cava of heparinized dogs and demonstrated in vivo selective binding of ‘*‘Iantibodies to HSA and 1311-antibodies to OA to the HSA- and OA-conjugated nylon tubing respectively. Kinetic measurements indicated that if the tubing were cycled continuously through the venous system, it would be possible theoretically to remove milligram amounts of antibody over a 24-hour period [23]. However, it is rather unlikely that such a procedure with antibody or antigen conjugated nylon tubing could be safely used in humans repetitively over relatively long periods of time. It is proposed that the utilization of a column immunoadsorption hemoperfusion device may be a safer, simpler and more efficient procedure for removal of LDL and cholesterol from the blood and body stores. Burstein was able to obtain by immunization of rabbits antiserum to LDL, 1 ml of which neutralized 3.5-7 mg of LDL. This would mean that 1 ml of antiserum will be capable to neutralize the LDL in l-2 ml of adult normal human serum [24]. VLDL may be the source of some of serum LDL [21].Thus adsorption of VLDL may also lead to reduction in serum LDL. Considering the MW of VLDL (5-10 X 106) and the normal serum concentration in the adult (150 mg/lOO ml), it can be concluded that if one could obtain anti VLDL serum of similar strength to the anti LDL serum obtained by Burstein, 1 ml of antiserum will be able to neutralize the amount of VLDL in 6-10 ml of normal that the antibodies in the immunoadsorption human serum. Considering column can be regenerated, that one could by repeated bleeding obtain from
376
one rabbit more than 100 ml of serum and that one may be able to immunize larger animals, such as sheep, it would seem that it may be feasible to obtain sufficient amounts of antibodies for preparation of the immunoadsorbent column. Miller and Miller [25] summarized the observations indicating that a reduction in plasma high density lipoproteins (HDL) concentration may accelerate the development of atherosclerosis, possibly by impairing the clearance of cholesterol from the arterial wall. They presented evidence for the regulation of tissue-cholesterol pools by HDL and draw attention to the association of low plasma HDL concentrations with clinical ischemic heart disease and with several coronary risk factors. They proposed that the development of atherosclerosis might be successfully prevented by increasing plasma HDL. In view of these observations, it would seem that a method capable of removing LDL without removing significant amount of HDL from the plasma and body stores is desirable. In fact, one may consider the possible combination of specific removal of LDL while increasing in the same time, as suggested by Miller and Miller, the level of HDL. The proposed hemoperfusion treatment may be capable of relative selective and specific removal of LDL from the blood and body stores. Thus, one may utilize in the hemoperfusion antibody specific to LDL that does not cross-react to any significant extent with HDL [19,26]. Plasma exchange, particularly with the utilization of continuous flow blood cell separator, was used effectively for the reduction of plasma cholesterol and LDL in patients with homozygous familial hypercholesterolemia [ 91. However, the long-term repeated utilization of plasmapheresis involves repeated administration of large amounts of human plasma products which may lead to various complications [ 271. It is possible that the proposed hemoadsorption method could be utilized more frequently and for longer periods, than is the case with plasmapheresis because it is based on the selective removal of LDL and cholesterol without a significant removal of useful substances (such as HDL) and without the addition of exogenous plasma products. It is also possible that the proposed method will be more efficient in removing larger amounts of LDL and VLDL as compared to plasmapheresis. The proposed hemoperfusion adsorption method should be evaluated first in animal experiments in order to test its safety and efficiency before any clinical evaluation of the method in patients is being contemplated. Only animal experimentation and if feasible, pilot clinical trials will be able to determine whether or not the proposed hemoperfusion-adsorption method is advantageous over plasmapheresis. The “half life” of LDL in plasma is 2.2-3.7 days [28]. This observation would indicate that treatment may have to be performed frequently. Takeuchi and Yamamura found that plasmapheresis in the rat was associated with an increase in liver incorporation of amino acids into LDL and VLDL. However, no increase in hepatic lipid synthesis was observed by previous feeding of the rats with 2% erotic acid [29]. Orotic acid is, however, toxic to the liver [30] and therefore cannot be used in humans. It is not known if selective removal of LDL and VLDL from the plasma by hemoperfusion immunoadsorption will also be associated with an increase in their rate of synthesis by the liver. It is likely that such would indeed be the
377
case and in that event concurrent administration of a compound that is capable to inhibit liver synthesis of LDL may be needed. In humans nicotinic acid may reduce LDL synthesis [ 311. References 1 KIimov, A.N., P&ova-Maslakova, L.G., Rodionova, L.P. and Sinitzina, T.A.. The Reticuloendothelizd System and Atherosclerosis, Plenum Press, New York, N.Y.. 1967. P. 442. 2 Levy, R.I. and Stone, N.J.. The Pathogenesis of Atherosclerosis, Wiihams and Wilkins, Baltimore, Md., 1972. P. 227. 3 Kannel, W.B., Castelii, W.P., Gordon, T. and McNamara, P.M., Serum cholesterol, lipoproteins and the risk of coronary heart disease, Ann. Intern. Med., 74 (1971) 1. 4 Dunkman, W.B., Perloff, J.K., Kastor, J.A. and Shelburne, J.C., Medical perspectives in coronary artery surgery - A caveat, Ann. Intern. Med., 81 (1974) 817. 5 Friedman, M.. Pathogenesis of Coronary Artery Disease, McGraw-Hill, New York, N.Y., 1969, p. 71. 6 Poston, R.N. and Davies, D.F., Immunity and inflammation in the pathogenesis of atherosclerosis. Atherosclerosis, 19 (1974) 353. in atheromatous coronary arteries in rhesus I Armstrong. M.L. and Megan. M.B., Lipid depletion monkeys after regression diets, Circ. Res.. 30 (1970) 675. 8 Strati, T.E., Chase, H.P., Putnam, C.W. and Nora, J.J., Follow-up of patient with porticavai shunt for the treatment of hyperhpidaemia. Lance& 2 (1974) 714. 9 Thompson, G.R., Lowenthal, R. and Myant, N.B., Plasma exchange in the management of homozygous familial hypercholesterolemia, Lancet, 1 (1975) 1208. 10 Adams, C.W.M.. Lipoproteins and the reversibility of atherosclerosis, Lancet, 1 (1972) 635. 11 Detre, K.M. and Shaw, L.. Long term changes of serum cholesterol with cholesterol-altering drugs in patients with coronary heart disease - Veterans Administration drug-lipid cooperative study, Circulation, 50 (1974) 998. 12 Gustafson, A. and Lanner. A., Treatment of hypedipoproteinemia type II A with a new anion exchange resin Secholex, Europ. J. Ciin. Pharmacol., 7 (1974) 65. 13 Rifkind, B.M., Clinical aspects of hyperhpoproteinemia. In: R.M.S. Smellie (Ed.): Plasma Lipoproteins Biochemical Society Symposium No. 33, Academic Press, London and New York, 1971. P. 137. 14 Schonfeld, G. and Kudzama, D.J.. Type IV hyperlipoproteinemia, Arch. Intern. Med., 132 (1973) 55. 15 Davies, D.F., Rees, B.W.G., Johnson. A.P. and Elwwod. P.C., Food antibodies and myocardiai infarction, Lancet. 1 (1974) 1012. 16 Boyd, W.C.. Fundamentals of Immunology, 4th edition, Interscience, New York, London, Sydney, 1966. p. 318. 17 Carlson. L.A., Chromatographic separation of serum lipoproteins on glass powder columns - Description of the method and some applications, Clin. Chim. Acta. 5 (1960) 528. 18 Rosenbaum, J.L.. Kramer, M.S., Raja, R. and Boreyko, C., Resin hemoperfusion - A new treatment for acute drug intoxication, New Engl. J. Med., 284 (1971) 874. 19 Riesen. W., Noseda, G. and Biitler. R., Anti-P-lipoprotein activity of human myoclonal immunoglobulins. VOX Sang., 22 (1972) 420. 20 Aladjem. F., Lieberman. M. and Gofman. J.W., Immunochemical studies of human plasma lipoproteins, J. Exp. Med., 105 (1957) 49. with a synthetic cholesterol-ester antigen and 21 Bailey, J.M.. Bright, R. and Tomar, R.. Immunization induced atherosclerosis in rabbits, Nature (Lond.), 201 (1964) 407. 22 Bailey, J.M. and Butler, J., Synthetic cholesterol-ester antigens in experimental atherosclerosis. In: N.R. Di Luzio and R. Paoletti, (Eds.): The Reticuloendotheiiai System and Atherosclerosis, Plenum Press, New York, N.Y.. 1967, p. 433. 23 Lyle, L.R.. Parker, B.M. and Parker. C.W.. The use of protein-substituted nylon catheters for selective immunoadsorption in viva, J. Immunol., 113 (2) (1974) 517. 24 Burstein. M., Antiserum de lapin immunise contre les lipoprot6ines humaines de faible densite (1.006-1.063). Nouv. Rev. Franc. Hematol., 12 (2) (1972) 251. concentration and development of 25 Miller. G.J. and Miller, N.E.. Plasma-high-density-lipoprotein ischaemic heart-disease, Lancet, 1 (1975) 16. Schonfeld, G., Lees, R.S.. George, P.K. and Peleger, B.. Assay of total plasma apoliPoProtein 6 concentration in human subjects, J. Chn. Invest., 53 (1974) 1458. in Clinical Medicine, 4th edition, Blackwell. Oxford and Edin27 MoIIison, P.L., Blood, Transfusion burgh, 1967, p. 590. 28 Walton, K.W., Scott, P.J., Verrier, J.J., Fletcher, R.F. and Whitehead, T., Studies on low density IiPoprotein turnover in relation to atromid therapy, J. Atheroscler. Res., 3 (1963) 396. 29 Takeuchi, N. and Yamamura, Y., The effect of plasmapheresis on cholesterol synthesis in the rat Relationship to protein synthesis, J. Lab. Clin. Med., 79 (5) (1972) 801. 30 Standerfer, S.B. and Handler, P., Fatty liver induced by erotic acid feeding, Proc. SOC. ExP. Biol. Med., 90 (1955) 270. 31 Myant. N.B., The metabolism of LDL. Adv. Exp. Med. Bioi., 38 (1973) 53.
26
Atherosclerosis, 26 (1977) 373-377 0 Elsevier/North-Holland Biomedical Press
POSSIBLE UTILIZATION OF EXTRACORPOREAL HEMOPERFUSION THE TREATMENT OF CORONARY ARTERY DISEASE A HYPOTHESIS
AND PROPOSAL
IN
FOR ANIMAL STUDIES
MEIR STRAHILEVITZ Department Ill. (U.S.A.)
of Psychiatry, Southern Illinois University School of Medicine, Springfield,
(Received 16 June, 1976) (Revised, received 14 September, 1976) (Accepted 15 September, 1976)
Summary It is proposed that in vivo immunoadsorption may be utilized in the treatment of coronary artery disease. The proposed method is based on binding of low density lipoproteins and cholesterol to antibodies directed against low density lipoproteins which are bound to a matrix in an extracorporeal hemoperfusion column. The various observations that suggest the hypothesis are presented. The feasibility of the proposed method and some of the problems that may be encountered in its utilization are discussed. The method should be evaluated in animal studies prior to consideration of clinical trials in patients. Key words:
Atherosclerosis - Coronary artery disease - Extracorporal Immunoadsorption -Low density lipoproteins
hemoperfusion
-
Increased concentration of cholesterol and low density lipoproteins (LDL) in the serum are major factors both in the induction of experimental atherosclerosis (AS) in animals and spontaneous AS and Coronary Artery Disease (CAD) in humans [l-3]. The surgical treatment of CAD involves high risk and expense. Its general effectiveness in prolonging life has not yet been clearly established [4]. Advanced fibrotic AS plaques probably can be removed only by surgery [5]. How-
374
ever, the possibility should be considered that if LDL and serum cholesterol were to be reduced significantly below normal levels, even relatively advanced lesions in CAD may regress to the extent that cholesterol and lipoprotein arterial wall infiltration and the associated edema [6] are contributing significantly to the arterial-lumen narrowing. This lipid infiltration may trigger further fibrotic changes [ 51. Regression of experimental atherosclerosis in Rhesus monkeys was observed after a therapeutic diet [ 71. In man, Strazi et al. obtained arteriographic evidence of regression of atherosclerosis in the coronary arteries following a portocaval shunt for treatment of hyperlipidemia [8]. Thompson et al. [9] noticed loss of angina and obtained evidence of influx of tissue cholesterol into plasma, following plasma exchange, in two patients with homozygous familial hypercholesterolemia. All of these procedures were associated with decreased level of serum cholesterol and LDL. It is proposed that the gradient of concentration between LDL and cholesterol in the blood and in the arterial wall may reach such a critical level that will lead to significant absorption of cholesterol (primarily in esterified form) which is distributed in droplets or diffuse form in the middle and outer layers of the atherosclerotic intima. To a great extent this cholesterol is associated with LDL and is therefore accessible for exchange with the plasma [lo]. Drugs that are utilized for reducing blood level of cholesterol are capable to induce only a moderate (6-10%) reduction in blood cholesterol [ 11,121. Only in some individuals with type 2 and type 4 hyperlipoproteinemia can reduction in serum cholesterol be achieved by dietary measures and the reduction is often relatively small [13,14]. The major part of serum cholesterol (50-60%) is bound to LDL [2]. An efficient method for the removal of LDL, cholesterol and other lipids as well as other compounds that may be involved in the etiology of CAD in some cases (such as antibodies to heat-dried cow’s milk and value in the nonsurgical treatboiled egg-white [ 151) may be of therapeutic ment of CAD. The hypothesis is hereby proposed that Hemoperfusion-Immunoadsorption, in which specific antigens and antibodies (such as antibodies to human LDL) are bound to suitable matrix in a hemoperfusion column may be utilized for the absorption of LDL and cholesterol, in particular, from the blood and body stores of individuals with CAD, with the result that a reduction in the arterial wall infiltration of LDL and cholesterol and an increase in lumen size of affected coronary arteries may be achieved. The column will be connected to the circulation of the individual being treated. The antibodies may be regenerated by elution of bound antigen by change in PH [16] for continuous use. The eluted antigens (such as LDL and the cholesterol bound to it) may then be removed from the system. Materials that are capable of relative specific adsorption of LDL (for example, glass powder [17]), cholesterol and other lipids may be incorporated in the column matrix as well. Resin column hemoperfusion (using as resin Amberlite XAD-2) has been used successfully for the treatment of acute barbiturate intoxication in man [ 181. Thus the instrumentation and technology for column hemoperfusion are presently available. Antihuman LDL activity was found in human monoclonal immunoglobulins and was associated with hypolipidemia. No antihuman HDL
315
activity was present in these sera [19]. Immunochemical characterization of intact lipoproteins indicate that LDL is antigenically distinct from HDL and that human plasma lipoproteins are immunochemically distinct from the nonlipid containing plasma protein fraction [20]. Antiserum to LDL and HDL respectively is available commercially [ 191. Bailey et al. were able to obtain a reduction in AS plaques in immunized rabbits, as well as a reduction in the level of serum cholesterol and total lipids, using an immunogen that was prepared by conjugating Sebacyl ChlorideCholesterol to Bovine Serum Albumin (BSA) or to human P-lipoprotein [21,22]. They suggested that their observations demonstrate the feasibility of immunological manipulation of serum lipid and cholesterol levels by use of antibodies directed against specific serum lipoprotein constituents [ 221. Active immunization of humans with immunogenic conjugates of cholesterol with lipoproteins or BSA, with or without the utilization of adjuvants during the immunization, may be associated with undesirable or- even serious side effects, such as anaphylaxis, serum sickness, immune complex disease or autoimmune phenomena. It would be preferable to utilize methods in which immunological specific and selective binding of antigens, antibodies and haptens in human blood takes place without having to introduce heterologous antigens or antibodies into the circulation or other part of the body of the subject being treated. This goal can be achieved by utilization of an extracorporeal hemoperfusion immunoadsorption method. That such a method be quantitatively efficient in removing relatively large amounts of antigen from the circulation is suggested by the work of Lye1 et al. These investigators inserted Human Serum Albumin (HSA) and Ovalbumin (OA)-conjugated nylon tubing into the inferior vena cava of heparinized dogs and demonstrated in vivo selective binding of ‘*‘Iantibodies to HSA and 1311-antibodies to OA to the HSA- and OA-conjugated nylon tubing respectively. Kinetic measurements indicated that if the tubing were cycled continuously through the venous system, it would be possible theoretically to remove milligram amounts of antibody over a 24-hour period [23]. However, it is rather unlikely that such a procedure with antibody or antigen conjugated nylon tubing could be safely used in humans repetitively over relatively long periods of time. It is proposed that the utilization of a column immunoadsorption hemoperfusion device may be a safer, simpler and more efficient procedure for removal of LDL and cholesterol from the blood and body stores. Burstein was able to obtain by immunization of rabbits antiserum to LDL, 1 ml of which neutralized 3.5-7 mg of LDL. This would mean that 1 ml of antiserum will be capable to neutralize the LDL in l-2 ml of adult normal human serum [24]. VLDL may be the source of some of serum LDL [21].Thus adsorption of VLDL may also lead to reduction in serum LDL. Considering the MW of VLDL (5-10 X 106) and the normal serum concentration in the adult (150 mg/lOO ml), it can be concluded that if one could obtain anti VLDL serum of similar strength to the anti LDL serum obtained by Burstein, 1 ml of antiserum will be able to neutralize the amount of VLDL in 6-10 ml of normal that the antibodies in the immunoadsorption human serum. Considering column can be regenerated, that one could by repeated bleeding obtain from
376
one rabbit more than 100 ml of serum and that one may be able to immunize larger animals, such as sheep, it would seem that it may be feasible to obtain sufficient amounts of antibodies for preparation of the immunoadsorbent column. Miller and Miller [25] summarized the observations indicating that a reduction in plasma high density lipoproteins (HDL) concentration may accelerate the development of atherosclerosis, possibly by impairing the clearance of cholesterol from the arterial wall. They presented evidence for the regulation of tissue-cholesterol pools by HDL and draw attention to the association of low plasma HDL concentrations with clinical ischemic heart disease and with several coronary risk factors. They proposed that the development of atherosclerosis might be successfully prevented by increasing plasma HDL. In view of these observations, it would seem that a method capable of removing LDL without removing significant amount of HDL from the plasma and body stores is desirable. In fact, one may consider the possible combination of specific removal of LDL while increasing in the same time, as suggested by Miller and Miller, the level of HDL. The proposed hemoperfusion treatment may be capable of relative selective and specific removal of LDL from the blood and body stores. Thus, one may utilize in the hemoperfusion antibody specific to LDL that does not cross-react to any significant extent with HDL [19,26]. Plasma exchange, particularly with the utilization of continuous flow blood cell separator, was used effectively for the reduction of plasma cholesterol and LDL in patients with homozygous familial hypercholesterolemia [ 91. However, the long-term repeated utilization of plasmapheresis involves repeated administration of large amounts of human plasma products which may lead to various complications [ 271. It is possible that the proposed hemoadsorption method could be utilized more frequently and for longer periods, than is the case with plasmapheresis because it is based on the selective removal of LDL and cholesterol without a significant removal of useful substances (such as HDL) and without the addition of exogenous plasma products. It is also possible that the proposed method will be more efficient in removing larger amounts of LDL and VLDL as compared to plasmapheresis. The proposed hemoperfusion adsorption method should be evaluated first in animal experiments in order to test its safety and efficiency before any clinical evaluation of the method in patients is being contemplated. Only animal experimentation and if feasible, pilot clinical trials will be able to determine whether or not the proposed hemoperfusion-adsorption method is advantageous over plasmapheresis. The “half life” of LDL in plasma is 2.2-3.7 days [28]. This observation would indicate that treatment may have to be performed frequently. Takeuchi and Yamamura found that plasmapheresis in the rat was associated with an increase in liver incorporation of amino acids into LDL and VLDL. However, no increase in hepatic lipid synthesis was observed by previous feeding of the rats with 2% erotic acid [29]. Orotic acid is, however, toxic to the liver [30] and therefore cannot be used in humans. It is not known if selective removal of LDL and VLDL from the plasma by hemoperfusion immunoadsorption will also be associated with an increase in their rate of synthesis by the liver. It is likely that such would indeed be the
377
case and in that event concurrent administration of a compound that is capable to inhibit liver synthesis of LDL may be needed. In humans nicotinic acid may reduce LDL synthesis [ 311. References 1 KIimov, A.N., P&ova-Maslakova, L.G., Rodionova, L.P. and Sinitzina, T.A.. The Reticuloendothelizd System and Atherosclerosis, Plenum Press, New York, N.Y.. 1967. P. 442. 2 Levy, R.I. and Stone, N.J.. The Pathogenesis of Atherosclerosis, Wiihams and Wilkins, Baltimore, Md., 1972. P. 227. 3 Kannel, W.B., Castelii, W.P., Gordon, T. and McNamara, P.M., Serum cholesterol, lipoproteins and the risk of coronary heart disease, Ann. Intern. Med., 74 (1971) 1. 4 Dunkman, W.B., Perloff, J.K., Kastor, J.A. and Shelburne, J.C., Medical perspectives in coronary artery surgery - A caveat, Ann. Intern. Med., 81 (1974) 817. 5 Friedman, M.. Pathogenesis of Coronary Artery Disease, McGraw-Hill, New York, N.Y., 1969, p. 71. 6 Poston, R.N. and Davies, D.F., Immunity and inflammation in the pathogenesis of atherosclerosis. Atherosclerosis, 19 (1974) 353. in atheromatous coronary arteries in rhesus I Armstrong. M.L. and Megan. M.B., Lipid depletion monkeys after regression diets, Circ. Res.. 30 (1970) 675. 8 Strati, T.E., Chase, H.P., Putnam, C.W. and Nora, J.J., Follow-up of patient with porticavai shunt for the treatment of hyperhpidaemia. Lance& 2 (1974) 714. 9 Thompson, G.R., Lowenthal, R. and Myant, N.B., Plasma exchange in the management of homozygous familial hypercholesterolemia, Lancet, 1 (1975) 1208. 10 Adams, C.W.M.. Lipoproteins and the reversibility of atherosclerosis, Lancet, 1 (1972) 635. 11 Detre, K.M. and Shaw, L.. Long term changes of serum cholesterol with cholesterol-altering drugs in patients with coronary heart disease - Veterans Administration drug-lipid cooperative study, Circulation, 50 (1974) 998. 12 Gustafson, A. and Lanner. A., Treatment of hypedipoproteinemia type II A with a new anion exchange resin Secholex, Europ. J. Ciin. Pharmacol., 7 (1974) 65. 13 Rifkind, B.M., Clinical aspects of hyperhpoproteinemia. In: R.M.S. Smellie (Ed.): Plasma Lipoproteins Biochemical Society Symposium No. 33, Academic Press, London and New York, 1971. P. 137. 14 Schonfeld, G. and Kudzama, D.J.. Type IV hyperlipoproteinemia, Arch. Intern. Med., 132 (1973) 55. 15 Davies, D.F., Rees, B.W.G., Johnson. A.P. and Elwwod. P.C., Food antibodies and myocardiai infarction, Lancet. 1 (1974) 1012. 16 Boyd, W.C.. Fundamentals of Immunology, 4th edition, Interscience, New York, London, Sydney, 1966. p. 318. 17 Carlson. L.A., Chromatographic separation of serum lipoproteins on glass powder columns - Description of the method and some applications, Clin. Chim. Acta. 5 (1960) 528. 18 Rosenbaum, J.L.. Kramer, M.S., Raja, R. and Boreyko, C., Resin hemoperfusion - A new treatment for acute drug intoxication, New Engl. J. Med., 284 (1971) 874. 19 Riesen. W., Noseda, G. and Biitler. R., Anti-P-lipoprotein activity of human myoclonal immunoglobulins. VOX Sang., 22 (1972) 420. 20 Aladjem. F., Lieberman. M. and Gofman. J.W., Immunochemical studies of human plasma lipoproteins, J. Exp. Med., 105 (1957) 49. with a synthetic cholesterol-ester antigen and 21 Bailey, J.M.. Bright, R. and Tomar, R.. Immunization induced atherosclerosis in rabbits, Nature (Lond.), 201 (1964) 407. 22 Bailey, J.M. and Butler, J., Synthetic cholesterol-ester antigens in experimental atherosclerosis. In: N.R. Di Luzio and R. Paoletti, (Eds.): The Reticuloendotheiiai System and Atherosclerosis, Plenum Press, New York, N.Y.. 1967, p. 433. 23 Lyle, L.R.. Parker, B.M. and Parker. C.W.. The use of protein-substituted nylon catheters for selective immunoadsorption in viva, J. Immunol., 113 (2) (1974) 517. 24 Burstein. M., Antiserum de lapin immunise contre les lipoprot6ines humaines de faible densite (1.006-1.063). Nouv. Rev. Franc. Hematol., 12 (2) (1972) 251. concentration and development of 25 Miller. G.J. and Miller, N.E.. Plasma-high-density-lipoprotein ischaemic heart-disease, Lancet, 1 (1975) 16. Schonfeld, G., Lees, R.S.. George, P.K. and Peleger, B.. Assay of total plasma apoliPoProtein 6 concentration in human subjects, J. Chn. Invest., 53 (1974) 1458. in Clinical Medicine, 4th edition, Blackwell. Oxford and Edin27 MoIIison, P.L., Blood, Transfusion burgh, 1967, p. 590. 28 Walton, K.W., Scott, P.J., Verrier, J.J., Fletcher, R.F. and Whitehead, T., Studies on low density IiPoprotein turnover in relation to atromid therapy, J. Atheroscler. Res., 3 (1963) 396. 29 Takeuchi, N. and Yamamura, Y., The effect of plasmapheresis on cholesterol synthesis in the rat Relationship to protein synthesis, J. Lab. Clin. Med., 79 (5) (1972) 801. 30 Standerfer, S.B. and Handler, P., Fatty liver induced by erotic acid feeding, Proc. SOC. ExP. Biol. Med., 90 (1955) 270. 31 Myant. N.B., The metabolism of LDL. Adv. Exp. Med. Bioi., 38 (1973) 53.
26