Autoreactive responses to an environmental factor: 1. phthalate induces antibodies exhibiting anti‐DNA specificity

Abstract

SUMMARYEnvironmental factors have been implicated in the induction of autoimmune disorders. We report here that a common chemical, phthalate, used widely in synthetic polymers and cosmetics induces serum anti-self DNA antibodies in BALB/c, NZB and autoimmune-prone NZB/W F1 mice. The latter group experiences a high mortality, and signi®cantly higher anti-DNA antibody levels along with nephritis and other histopathologic changes in kidney.Comparison of amino acid sequences of an anti-phthalate BALB/c B-cell hybrid, 2C3 with the known database at the National Center for Biotechnology Information reveals a striking homology between the variable regions of 2C3-Ig (g 1 , k) and an anti-DNA antibody, BV04-01 (g2b,k) isolated from the lupus-prone NZB/W F1 mice. The homology is 98% for k light chain and 70% for g heavy chain. Like 2C3-Ig, BV04-01 also has speci®city for d(pT)4. Furthermore, the light chains of both 2C3-Ig and BV04-01 are products of Vk1 gene. To understand the nature of anti-phthalate responses in general, hybridomas generated from phthalate± keyhole limpet haemocyanin-primed BALB/c splenocytes were characterized. The study identi®es cross-reactive populations that strongly bind phthalate, DNA, or both. Of the 14 hybridomas evaluated, six express the same Vk1 gene-derived light chain as 2C3, and bind both phthalate and ds and ss-DNA. They speci®cally recognize the oligonucleotides, d(pT)4, and d(pT)10. Additionally, when antisera raised against idiopeptides corresponding to 2C3-Ig hypervariable regions are allowed to react with 2C3-Ig, their binding is blocked speci®cally by both d(pT)4 and phthalate. This study clearly demonstrates that phthalate exposure leads to activation of a signi®cant number of autoreactive B-cells, with the consequence of a signi®cant pathogenic progression in susceptible NZB/W F1 mice but not in non-autoimmune-prone BALB/c.

Is lipstick associated with the development of systemic lupus erythematosus (SLE)?

“…Eosin is a red dye that has been implicated in photosensitivity [9] and lupus flares [5]. Phthalate, another common ingredient in lipsticks, can induce anti-DNA antibody responses and SLE-like syndromes in lupus-prone mice [6][7][8]. 2-Octynoic acid is a xenobiotic that can modify the immunodominant E2 component of pyruvate dehydrogenase complexes (PDC-E2) and induce the antimitochondrial antibody response in primary biliary cirrhosis [4].…”

“…Lipsticks, in particular, contain a variety of chemical agents whose properties might increase the risk for SLE. These include eosin, 2-octynoic acid (a xenobiotic), and phthalate isomers that have been linked to lupus and other autoimmune disorders in vitro and in animals [4][5][6][7][8]. The privileged absorption of the lipstick through the buccal mucosa and oral ingestion may further aggravate the negative effects of these chemicals.…”

Autoreactive responses to environmental factors: 3. Mouse strain-specific differences in induction and regulation of anti-DNA antibody responses due to phthalate-isomers

“…Phthalateeprotein conjugates were prepared by coupling the diazotized phthalate-isomers to proteins (KLH or BSA) as described by Bloor et al [29] and Lim and Ghosh [21]. Briefly, amino groups of aminophthalates were diazotized by HNO 2 and the resulting diazonium salt, when added to KLH or BSA, was covalently linked to proteins by azo-coupling.…”

“…Antibodies induced by phthalate administration display cross-reactivity toward single and double-stranded DNA in both nonautoimmune BALB/c and lupus-prone NZB/W F1 mice [21]. These anti-phthalate antibodies also share idiotype identity with a well described anti-DNA mAb, BV-04 [22].…”

“…We have recently described molecular mimicry by ortho-phthalate of self-DNA and particularly, d(pT)4 nucleotides [21]. Antibodies induced by phthalate administration display cross-reactivity toward single and double-stranded DNA in both nonautoimmune BALB/c and lupus-prone NZB/W F1 mice [21].…”