Ellen K. Silbergeld, PhDJohns Hopkins UniversityBloomberg School of Public Health

ENVIRONMENTAL EXPOSURES AS “CO-CONSPIRATORS” IN AUTOIMMUNE DISEASE

AUTOIMMUNE DISEASES: A WOMEN’S HEALTH ISSUE

• DIFFERENTIAL INCIDENCE– 1.5 to 50 times more frequent

• INTERACTIONS WITH PREGNANCY, STEROIDS and MENOPAUSE– Cause or exacerbation?

• IMPACTS ON HEALTH and QUALITY OF LIFE– Symptomatic treatment, no cures

Table I Female:Male Ratios in Autoimmune Diseases

Hashimoto's disease/hypothyroiditis 0:1Systemic lupus erythematosus 10:1 Sjogren's syndrome 9:1 Antiphospholipid syndrome 9:1 Primary biliary cirrhosis 9:1 Mixed connective tissue disease 8:1Chronic active hepatitis 8:1Graves' disease/hyperthyroiditis 7:1Rheumatoid arthritis 4:1Scleroderma 3:1Myasthenia gravis 2:1Multiple sclerosis 2:1Chronic idiopathic thrombocytopenic purpura 2:1

AUTOIMMUNE DISEASES

• SYSTEMIC or TARGET ORGAN SPECIFIC DISEASES

• SEXUALLY DIMORPHIC – incidence? Severity? Both?

• COMPLEX GENE:ENVIRONMENT INTERACTIONS

GENE:ENVIRONMENT INTERACTIONS

• GENETICS: FAMILIAL PATTERNS OF DISEASE

• SEX – GENES and ENDOCRINOLOGY• ACQUIRED RISK FACTORS

– DRUGS

– INFECTIONS

– ENVIRONMENTAL CHEMICALS?

ENVIRONMENTAL EXPOSURES AS CAUSES

• INFECTIONS

– AUTOIMMUNE MYOCARDITIS

• CHEMICALS/METALS

– TOXIC OIL SYNDROME

– GOLD + IODINE and SELENIUM DEFICIENCY

– MERCURY….

MERCURY and the IMMUNE SYSTEM

• IMMUNOSUPPRESSION– Decreased resistance to malaria– Impaired immunity to malaria

• NEUROIMMUNOTOXICOLOGY– Interrupted cerebellar neural migration

• AUTOIMMUNITY– Lupus-like disease in rodents– Increased [auto]antibodies in humans

MERCURY AND AUTOIMMUNE DISEASE

• CAN MERCURY CAUSE AI DISEASE?– HUMAN DATA?

• NEPHROTOXICITY MAY INVOLVE AUTOIMMUNE MECHANISMS

• FRANK AI DISEASE NOT DEMONSTRATED BUT EPI DATA ARE LIMITED

• NEUROTOXICITY MORE SENSITIVE OUTCOME

– EXPERIMENTAL DATA – YES• INBRED RODENT STRAINS ARE SUSCEPTIBLE• RESPONSE CAN INCLUDE AUTOANTIBODIES,

VASCULITIS, NEPHROPATHY• DOSES ARE RELATIVELY HIGH COMPARED TO

HUMAN EXPOSURES

CAN MERCURY ACCELERATE AI DISEASE?

• HUMAN DATA

– HgU higher in patients with more severe

scleroderma + antifibrillarin Ab

• EXPERIMENTAL DATA

– Hg accelerates pathology in lupus-prone

strains of mice - NZB, Palmerston North, etc

ANIMAL MODELS OF AI DISEASE

• SPONTANEOUS

– INBRED STRAINS – NZB, PN

• ACQUIRED

– GRAFT versus HOST DISEASE

ADVANTAGES OF ACQUIRED DISEASE MODEL

• TIME COURSE OF DISEASE CAN BE PREDICTED

• MECHANISTIC INFORMATION IS AVAILABLE• SEVERITY OF DISEASE CAN BE MODULATED

GRAFT vs HOST DISEASE (GVHD)

• C57Bl/6 x DBA/2 F1

– INJECTION OF PARENTAL SPLENOCYTES

INTO B6xD2 F1 OFFSPRING

• DBA/2 CELLS into F1 produces chronic lupus like disease• Bl/6 CELLS into F1 produces acute lupus

like disease

EXPERIMENTAL PROTOCOL

• Hg exposure: 20 or 200 ug/kg for 3 weeks every other day, donor and host

• Transfer cells• Follow development of disease – proteinuria,

morbidity, serum antibodies• Postmortem histopathology of kidney and

vasculature

MERCURY & AUTOIMMUNE MYOCARDITIS

• MYOCARDITIS IS A MAJOR CAUSE OF HEART FAILURE AND SUDDEN DEATH IN YOUNG ADULTS

• MYOCARDITIS CAN RESULT IN CHRONIC CARDIOMYOPATHY

• MANY CASES ARE AUTOIMMUNE DISEASE• INFECTIONS ARE ASSOCIATED WITH AUTOIMMUNE

MYOCARDITIS

CARDIAC MYOSIN MODEL OF AIM

• INFECTION-ASSOCIATED AIM ASSOCIATED WITH POST-EXPOSURE CARDIOTOXICITY

• IMMUNE MIMICRY [CHAGAS DISEASE] OR UNCOVERING INTRACELLULAR EPITOPES IN CARDIOMYOCYTES

• CARDIAC MYOSIN A MAJOR AUTOANTIGEN

EAM in MICE

• A/J MICE [male or female]• Immunization with cardiac myosin peptide• Disease course – 21 days

– Dilated cardiomyopathy: myocardial infiltration and cardiomyocyte death

– Immune complex deposition in heart– CM-specific IgG in sera– Pathophysiologic cardiac function

Mercury + EAM

• Pretreat A/J mice with 10 or 100 mcg/kg HgCl2

• Immunize with CMP + adjuvant• Follow disease course for 21 days

MERCURY – CAUSE OR CO-CONSPIRATOR

• MERCURY CAN CAUSE AI DISEASE IN SUSCEPTIBLE RODENTS

• MERCURY CAN ACCELERATE LUPUS IN DISEASE-PRONE MICE

• MERCURY BY ITSELF CANNOT CAUSE AI DISEASE IN NONSUSCEPTIBLES

MECHANISMS OF MERCURY:AI INTERACTIONS

• Mercury alters lymphocyte subsets– No evidence for cell loss or altered ratios

• Mercury is a “superantigen”– But no effects by itself

• Mercury alters cell:cell signalling– Effects observed on Th1 and Th2 cytokines– Decreases in NO-mediated cell death– NFB binding

• Mercury alters costimulatory “support”– B7 family may be target

RESEARCH QUESTIONS

• WHAT IS THE LOWEST EFFECTIVE DOSE OF MERCURY AS A CO-CONSPIRATOR IN AUTOIMMUNITY?

• DOES MERCURY INTERACT WITH SEX/ENDOCRINOLOGY?

• WHAT ARE THE CONSEQUENCES OF PRENATAL EXPOSURES TO MERCURY ON LATER SUSCEPTIBILITY TO AUTOIMMUNE DISEASE

• IS MERCURY TOXICITY AN AUTOIMMUNE DISEASE?

BALTIMORE MERCURY RESEARCH GROUP

• Dr CHARLES VIA’S LAB (Univ MD Med Sch)

– Phuong Nguyen

– John Papadimitriou

• DR NOEL ROSE’S LAB (JHMI)

– Dr Marina Afanasyeva

• DR ELLEN SILBERGELD’S LAB (BSPH)

– Dr Jennifer Nyland

– Ines Silva

– Dr Dennis Hoover

RESEARCH SUPPORT

• CURE AUTISM NOW FOUNDATION

• ARTHRITIS FOUNDATION

• NATIONAL INSTITUTES OF HEALTH

• HEINZ FAMILY FOUNDATION