- Email: [email protected]
Silicone Gel and Animal Models of Autoimmune Disease
CLINICAL IMMUNOLOGY AND IMMUNOPATHOLOGY
Vol. 87, No. 3, June, pp. 205–206, 1998 Article No. II984567
EDITORIAL Silicone Gel and Animal Models of Autoimmune Disease Kimber L. White, Jr. Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia 23298
This issue of Clinical Immunology and Immunopathology features an interesting paper by McDonald et al., in which the authors conclude that exposure to silicone gel can exacerbate autoimmune disease in New Zealand Black (NZB) mice and that it may play a similar role in the development of autoimmune disease in a small percentage of women who are genetically susceptible to such disease. Their experimental observations and conclusion that exposure to silicone gel exacerbates autoimmune glomerulonephritis in NZB mice is in marked contrast to the negative findings of numerous other investigators who have studied the effects of silicone gel in various animal models of autoimmune disease. In studies reported by Chang (1) silicone gel, with or without heat-killed Mycobacterium tuberculosis, failed to induce arthritis in the Lewis rat model of adjuvant arthritis. Similar negative results with silicone gel were reported by Naim et al. (2) in the Lewis rat model. In the Dark Agouti rat, which is highly susceptible to developing arthritis, silicone gel also failed to produce arthritis in studies conducted by Naim et al. (3). In more recent studies, Sverdrup et al. (4) reported that in the Dark Agouti rat silicone gel did not cause arthritis; however, intradermal injection of five of eight cosmetic products also evaluated produced arthritis in the rat model. Negative findings, following exposure to silicone gel, have also been observed in mouse models of autoimmune disease. A scleroderma-like syndrome is one of the connective tissue disorders which has been associated with silicone gel breast-implant patients (5). However, in elegant studies conducted by Frondoza et al. (6, 7), using the tight skin (TSK//) mouse model for human scleroderma, silicone gel administration did not enhance development of skin fibrosis nor synthesis of autoantibodies to RNA polymerase and topoisomerase. Furthermore, in the mouse model of type II collageninduced arthritis, Schaefer et al. (8) reported that silicone gel implantation did not increase the incidence or severity of the disease compared with sham-operated controls. In addition to the autoimmune studies, exten-
sive evaluation of the effects of silicone gel on the immune system of B6C3F1 mice, following either 10 days of exposure (9) or 180 days (10), failed to demonstrate adverse effects with the possible exception of decreased natural killer (NK) cell activity. McDonald et al. indicated that the New Zealand Black strain of mice is used as a model for spontaneous development of murine systemic lupus erythematosus (SLE), especially when crossed with the New Zealand White (NZW) mice. In actuality, as indicated in the references cited by the authors, the NZB is a more appropriate model of autoimmune hemolytic anemia, the major cause of death for this strain of mice. This point is alluded to by the authors in their statement that, when not crossed with the NZW mice, NZB mice produce autoantibodies later in life and rarely suffer from a fatal version of lupus-like nephritis, citing Yoshida et al. (11) as reference. Since the NZB strain was used in the study, one would expect, if silicone gel did exacerbate the autoimmune disease, that exacerbation of autoimmune hemolytic anemia would be observed. While a decrease in hematocrit was observed in the silicone- and pristanetreated groups, no increase in anti-erythrocyte antibody levels, the hallmark of autoimmune hemolytic anemia, was observed in silicone-treated animals as determined by hemagglutination (HA) titers. The highest HA titers were observed in the untreated animals and the control animals receiving three injections of Hanks’ balanced salt solution. Animals receiving the greatest amount of silicone gel, 0.6 ml, had the lowest HA titers. An explanation for the lack of effect on HA titer, as purposed by the authors, was that autoantibodies were either more hemolytic or produced at an earlier age. With the rapid turnover of erythrocytes and the decrease in hematocrit levels being observed at the time of sacrifice, production of antibodies at an earlier age does not seem like a viable explanation. However, the lack of effect observed on NZB HA titers may be simply a result of BALB/c erythrocytes (RBCs) being used in the HA assay instead of NZB RBCs. Our laboratory has been studying the NZBWF1
205
AID
Clin 4567
/
a520$$$381
05-27-98 18:23:09
0090-1229/98 $25.00 Copyright q 1998 by Academic Press All rights of reproduction in any form reserved.
clina
AP: Clin
206
EDITORIAL
(NZB1NZW) as an animal model to identify compounds capable of inducing autoimmune disease in humans. As indicated earlier, the NZBWF1 is a well-characterized animal model for SLE in humans. In our studies (12), we have been able to show, as have others, that compounds such as mercuric chloride and D-penicillamine, known inducers of SLE-like autoimmune disease in humans and animals, can exacerbate the autoimmune disease in this model system. Furthermore, our recent studies (13) demonstrate that exposure to potent adjuvants, such as Freund’s complete adjuvant (FCA) and Freund’s incomplete adjuvant (FIA), also exacerbate the development of the SLE autoimmune disease in the NZBWF1 mouse model. The NZBWF1 mouse model of human SLE is characterized by elevated titers of antinuclear antibodies, raised levels of serum IgG, polyclonal activation of Bcells, and the subsequent development of fatal, immune-complex-mediated glomerulonephritis. We have been able to quantitate these effects by developing ELISA assays to evaluate increased serum total IgG levels, as well as increased IgG antibody levels, to dinitrophenol–human serum albumin (DNP–HSA) and sheep erythrocytes, all characteristic of the polyclonal activation of B-cells. Increased antinuclear antibodies were evaluated by determining serum IgG antibody levels to dsDNA. Development of glomerulonephritis was detected with increased levels of IgG antibodies to laminin, altered kidney weights, and increases in urinary protein. Kidneys were flash frozen at the time of sacrifice for future histochemical evaluation of IgG and complement C3 deposition. It has been our experience that the semiquantitative evaluation of urinary protein using dip sticks lacks the necessary sensitivity to conduct rigorous scientific and statistical analysis. Accordingly, we have moved to using an ELISA procedure to quantitate the amount of albumin present in the urine of NZBWF1 mice as an indicator of urinary protein and kidney damage. In addition to the compounds and adjuvants listed above, our laboratory has also evaluated silicone gel in the NZBWF1 model (12, 13). Silicone gel was obtained from a Dow Corning Silastic mammary implant. Animals were implanted subcutaneously with 1, 2, or 3 ml of silicone gel in the mammary region. Sham control animals received 3 ml of saline in the mammary region. After 78 days of exposure, animals were sacrificed and immunological and toxicological parameters described above were evaluated. In contrast to what was observed in the mercuric chloride-, D-penicillamine-, FCA-, or FIA-treated
AID
Clin 4567
/
a520$$$381
05-27-98 18:23:09
NZBWF1 mice, no significant difference was observed between sham control animals and animals implanted with any dose of silicone gel for any of the immunological and toxicological parameters evaluated. At the high dose level (3 ml), our mice were administered five times the amount of silicone gel used in the McDonald et al. study. Furthermore, the silicone gel was implanted in the mammary region in a manner consistent with that occurs clinically. The results of our studies, in the NZBWF1 model of SLE, are consistent with the results of other animal models which reported the inability of silicone gel to exacerbate autoimmune disease and in contrast with the findings of McDonald et al. REFERENCES 1. Chang, Y.-H., Adjuvanticity and arthritogenicity of silicone. Plast. Reconstr. Surg. 92, 469, 1993. 2. Naim, J., Lanzafame, R., and van Oss, C., The effects of siliconegel on the immune response. J. Biomaterials Sci. Polymer Ed. 7(2), 123, 1995. 3. Nalm, J., Ippolito, K., Lanzafame, R., and van Oss, C., Induction of type II collagen arthritis in the DA rat using silicone gels and oils as adjuvant. J. Autoimmun. 8, 751, 1995. 4. Sverdrup, B., Klareskog, L., and Kleinau, S., Common commercial cosmetic products induce arthritis in DA rat. Environ. Health Perspect. 106, 27, 1998. 5. Marik, P., Kark, A., and Zambakides, A., Scleroderma after silicone augmentation mammoplasty. SAM J. 77, 212, 1990. 6. Frondoza, C., Jones, L., Rose, N., Hatakeyama, A., Phelps, R., and Bona, C., Silicone does not potentiate development of the scleroderma-like syndrome in tight skin (TSK//) mice. J. Autoimmun. 9, 473, 1996. 7. Frondoza, C., Jones, L., Rose, N., Hatakeyama, A., Phelps, R., and Bona, C., Development of scleroderma-like syndrome in TsK// mice is not enhanced by silicone administration. Curr. Top. Microbiol. Immunol. 210, 299, 1996. 8. Schaefer, C., Whalen, J., Knapp, T., and Wooley, P., The influence of silicone implantation on type II collagen-induced arthritis in mice. Arthritis Rheum. 48, 1864, 1997. 9. Bradley, S. G., Munson, A. E., McCay, J. A., Brown, R. D., Musgrove, D. L., Wilson, S., Stern, M., Luster, M. I., and White, K. L., Jr., Subchronic 10 day immunotoxicity of polydimethylsiloxane (silicone) fluid, gel and elastomer and polyurethane disks in female B6C3F1 mice. Drug Chem. Toxicol. 17, 175, 1994. 10. Bradley, S. G., White, K. L., Jr., McCay, J. A., Brown, R. D., Musgrove, D. L., Wilson, S., Stern, M., Luster, M. I., and Munson, A. E., Immunotoxicity of 180 day exposure to polydimethylsiloxane (silicone) fluid, gel and elastomer and polyurethane disks in female B6C3F1 mice. Drug Chem. Toxicol. 17, 221, 1994. 11. Yoshida, S., Castles, J. J., and Gerschwin, M. E., The pathogenesis of autoimmunity in the New Zealand mice. Semin. Arthritis Rheum. 19, 224, 1990. 12. White, K. L., Jr., Butterworth, L. F., David, D. W., and Klykken, P. C., Failure of silicone gel to exacerbate autoimmune responses in female NZB/W mice. Toxicologist 36, 265, 1997. 13. White, K. L., Jr., Use of Brown Norway rat and NZB1W mouse model of systemic lupus erythematosus to assess effects of silicone gel, metals, and other xenobiotics on autoimmune disease. Toxicologist 42, 403, 1998.
clina
AP: Clin
Vol. 87, No. 3, June, pp. 205–206, 1998 Article No. II984567
EDITORIAL Silicone Gel and Animal Models of Autoimmune Disease Kimber L. White, Jr. Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia 23298
This issue of Clinical Immunology and Immunopathology features an interesting paper by McDonald et al., in which the authors conclude that exposure to silicone gel can exacerbate autoimmune disease in New Zealand Black (NZB) mice and that it may play a similar role in the development of autoimmune disease in a small percentage of women who are genetically susceptible to such disease. Their experimental observations and conclusion that exposure to silicone gel exacerbates autoimmune glomerulonephritis in NZB mice is in marked contrast to the negative findings of numerous other investigators who have studied the effects of silicone gel in various animal models of autoimmune disease. In studies reported by Chang (1) silicone gel, with or without heat-killed Mycobacterium tuberculosis, failed to induce arthritis in the Lewis rat model of adjuvant arthritis. Similar negative results with silicone gel were reported by Naim et al. (2) in the Lewis rat model. In the Dark Agouti rat, which is highly susceptible to developing arthritis, silicone gel also failed to produce arthritis in studies conducted by Naim et al. (3). In more recent studies, Sverdrup et al. (4) reported that in the Dark Agouti rat silicone gel did not cause arthritis; however, intradermal injection of five of eight cosmetic products also evaluated produced arthritis in the rat model. Negative findings, following exposure to silicone gel, have also been observed in mouse models of autoimmune disease. A scleroderma-like syndrome is one of the connective tissue disorders which has been associated with silicone gel breast-implant patients (5). However, in elegant studies conducted by Frondoza et al. (6, 7), using the tight skin (TSK//) mouse model for human scleroderma, silicone gel administration did not enhance development of skin fibrosis nor synthesis of autoantibodies to RNA polymerase and topoisomerase. Furthermore, in the mouse model of type II collageninduced arthritis, Schaefer et al. (8) reported that silicone gel implantation did not increase the incidence or severity of the disease compared with sham-operated controls. In addition to the autoimmune studies, exten-
sive evaluation of the effects of silicone gel on the immune system of B6C3F1 mice, following either 10 days of exposure (9) or 180 days (10), failed to demonstrate adverse effects with the possible exception of decreased natural killer (NK) cell activity. McDonald et al. indicated that the New Zealand Black strain of mice is used as a model for spontaneous development of murine systemic lupus erythematosus (SLE), especially when crossed with the New Zealand White (NZW) mice. In actuality, as indicated in the references cited by the authors, the NZB is a more appropriate model of autoimmune hemolytic anemia, the major cause of death for this strain of mice. This point is alluded to by the authors in their statement that, when not crossed with the NZW mice, NZB mice produce autoantibodies later in life and rarely suffer from a fatal version of lupus-like nephritis, citing Yoshida et al. (11) as reference. Since the NZB strain was used in the study, one would expect, if silicone gel did exacerbate the autoimmune disease, that exacerbation of autoimmune hemolytic anemia would be observed. While a decrease in hematocrit was observed in the silicone- and pristanetreated groups, no increase in anti-erythrocyte antibody levels, the hallmark of autoimmune hemolytic anemia, was observed in silicone-treated animals as determined by hemagglutination (HA) titers. The highest HA titers were observed in the untreated animals and the control animals receiving three injections of Hanks’ balanced salt solution. Animals receiving the greatest amount of silicone gel, 0.6 ml, had the lowest HA titers. An explanation for the lack of effect on HA titer, as purposed by the authors, was that autoantibodies were either more hemolytic or produced at an earlier age. With the rapid turnover of erythrocytes and the decrease in hematocrit levels being observed at the time of sacrifice, production of antibodies at an earlier age does not seem like a viable explanation. However, the lack of effect observed on NZB HA titers may be simply a result of BALB/c erythrocytes (RBCs) being used in the HA assay instead of NZB RBCs. Our laboratory has been studying the NZBWF1
205
AID
Clin 4567
/
a520$$$381
05-27-98 18:23:09
0090-1229/98 $25.00 Copyright q 1998 by Academic Press All rights of reproduction in any form reserved.
clina
AP: Clin
206
EDITORIAL
(NZB1NZW) as an animal model to identify compounds capable of inducing autoimmune disease in humans. As indicated earlier, the NZBWF1 is a well-characterized animal model for SLE in humans. In our studies (12), we have been able to show, as have others, that compounds such as mercuric chloride and D-penicillamine, known inducers of SLE-like autoimmune disease in humans and animals, can exacerbate the autoimmune disease in this model system. Furthermore, our recent studies (13) demonstrate that exposure to potent adjuvants, such as Freund’s complete adjuvant (FCA) and Freund’s incomplete adjuvant (FIA), also exacerbate the development of the SLE autoimmune disease in the NZBWF1 mouse model. The NZBWF1 mouse model of human SLE is characterized by elevated titers of antinuclear antibodies, raised levels of serum IgG, polyclonal activation of Bcells, and the subsequent development of fatal, immune-complex-mediated glomerulonephritis. We have been able to quantitate these effects by developing ELISA assays to evaluate increased serum total IgG levels, as well as increased IgG antibody levels, to dinitrophenol–human serum albumin (DNP–HSA) and sheep erythrocytes, all characteristic of the polyclonal activation of B-cells. Increased antinuclear antibodies were evaluated by determining serum IgG antibody levels to dsDNA. Development of glomerulonephritis was detected with increased levels of IgG antibodies to laminin, altered kidney weights, and increases in urinary protein. Kidneys were flash frozen at the time of sacrifice for future histochemical evaluation of IgG and complement C3 deposition. It has been our experience that the semiquantitative evaluation of urinary protein using dip sticks lacks the necessary sensitivity to conduct rigorous scientific and statistical analysis. Accordingly, we have moved to using an ELISA procedure to quantitate the amount of albumin present in the urine of NZBWF1 mice as an indicator of urinary protein and kidney damage. In addition to the compounds and adjuvants listed above, our laboratory has also evaluated silicone gel in the NZBWF1 model (12, 13). Silicone gel was obtained from a Dow Corning Silastic mammary implant. Animals were implanted subcutaneously with 1, 2, or 3 ml of silicone gel in the mammary region. Sham control animals received 3 ml of saline in the mammary region. After 78 days of exposure, animals were sacrificed and immunological and toxicological parameters described above were evaluated. In contrast to what was observed in the mercuric chloride-, D-penicillamine-, FCA-, or FIA-treated
AID
Clin 4567
/
a520$$$381
05-27-98 18:23:09
NZBWF1 mice, no significant difference was observed between sham control animals and animals implanted with any dose of silicone gel for any of the immunological and toxicological parameters evaluated. At the high dose level (3 ml), our mice were administered five times the amount of silicone gel used in the McDonald et al. study. Furthermore, the silicone gel was implanted in the mammary region in a manner consistent with that occurs clinically. The results of our studies, in the NZBWF1 model of SLE, are consistent with the results of other animal models which reported the inability of silicone gel to exacerbate autoimmune disease and in contrast with the findings of McDonald et al. REFERENCES 1. Chang, Y.-H., Adjuvanticity and arthritogenicity of silicone. Plast. Reconstr. Surg. 92, 469, 1993. 2. Naim, J., Lanzafame, R., and van Oss, C., The effects of siliconegel on the immune response. J. Biomaterials Sci. Polymer Ed. 7(2), 123, 1995. 3. Nalm, J., Ippolito, K., Lanzafame, R., and van Oss, C., Induction of type II collagen arthritis in the DA rat using silicone gels and oils as adjuvant. J. Autoimmun. 8, 751, 1995. 4. Sverdrup, B., Klareskog, L., and Kleinau, S., Common commercial cosmetic products induce arthritis in DA rat. Environ. Health Perspect. 106, 27, 1998. 5. Marik, P., Kark, A., and Zambakides, A., Scleroderma after silicone augmentation mammoplasty. SAM J. 77, 212, 1990. 6. Frondoza, C., Jones, L., Rose, N., Hatakeyama, A., Phelps, R., and Bona, C., Silicone does not potentiate development of the scleroderma-like syndrome in tight skin (TSK//) mice. J. Autoimmun. 9, 473, 1996. 7. Frondoza, C., Jones, L., Rose, N., Hatakeyama, A., Phelps, R., and Bona, C., Development of scleroderma-like syndrome in TsK// mice is not enhanced by silicone administration. Curr. Top. Microbiol. Immunol. 210, 299, 1996. 8. Schaefer, C., Whalen, J., Knapp, T., and Wooley, P., The influence of silicone implantation on type II collagen-induced arthritis in mice. Arthritis Rheum. 48, 1864, 1997. 9. Bradley, S. G., Munson, A. E., McCay, J. A., Brown, R. D., Musgrove, D. L., Wilson, S., Stern, M., Luster, M. I., and White, K. L., Jr., Subchronic 10 day immunotoxicity of polydimethylsiloxane (silicone) fluid, gel and elastomer and polyurethane disks in female B6C3F1 mice. Drug Chem. Toxicol. 17, 175, 1994. 10. Bradley, S. G., White, K. L., Jr., McCay, J. A., Brown, R. D., Musgrove, D. L., Wilson, S., Stern, M., Luster, M. I., and Munson, A. E., Immunotoxicity of 180 day exposure to polydimethylsiloxane (silicone) fluid, gel and elastomer and polyurethane disks in female B6C3F1 mice. Drug Chem. Toxicol. 17, 221, 1994. 11. Yoshida, S., Castles, J. J., and Gerschwin, M. E., The pathogenesis of autoimmunity in the New Zealand mice. Semin. Arthritis Rheum. 19, 224, 1990. 12. White, K. L., Jr., Butterworth, L. F., David, D. W., and Klykken, P. C., Failure of silicone gel to exacerbate autoimmune responses in female NZB/W mice. Toxicologist 36, 265, 1997. 13. White, K. L., Jr., Use of Brown Norway rat and NZB1W mouse model of systemic lupus erythematosus to assess effects of silicone gel, metals, and other xenobiotics on autoimmune disease. Toxicologist 42, 403, 1998.
clina
AP: Clin