Transcript Chemical Toxicants and Chronic Inflammation

Chemical Toxicants and
Chronic Inflammation
Kristen Dostie
April 8, 2015
Cadmium (Cd)
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Toxic heavy metal
Found naturally in environment
Extremely long biological half-life of 18-33 years
Intoxication leads to a variety of adverse effects
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Oxidative stress
Genotoxicity
Nephrotoxicity
Osteotoxicity
Pulmonary toxicity
Hepatoxocity
Reproductive toxicity
Carcenogenicity
• Currently no treatment for Cd-intoxication
What are the main sources of Cd?
• Natural sources
• Erosion of rocks and soils, forest fires,
volcanic eruptions
• Man-made processes
• Usage of phosphate fertilizers, presence in
sewage sludge, industrial uses
• Industrial Uses
• Metal plating, producing pigments, NiCd
batteries, stabilizers in plastics
Routes of Cd Exposure
• Inhalation
• Occupational exposure- mining, metal
plating, paint production, welding
• Non-occupational exposure- cigarette
smoking
• Ingestion
• Plant products that take up Cd in the soil
• Skin absorption
• Negligible amounts absorbed through
the skin
Known adverse effects of Cd on human health
• Toxic to many organs such as kidney, liver, lungs, pancreas, testes, placenta, brain,
and bones
• Cellular mechanisms of Cd toxicity in cells:
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Decrease in antioxidant potential
Decrease in thiol status
Activation of signaling pathways
Inhibition of DNA methylation and DNA repair
Cell damage
• Class I human carcinogen
• Can induce inflammatory response
Cd and oxidative stress
Cuypers et al 2010
Cd exposure leads to upregulation of many inflammatory
mediators such as:
Transcription factors
• NF-κB
• AP-1
Proinflammatory cytokines
• IL-6
• TNF-α
• IL-1β
• IL-8
Adhesion molecules
• ICAM-1
• PECAM-1
Other inflammatory mediators
• MPO
• iNOS
• MMPs
• COX-2 and PGE2
• CRP
Miley Cyrus poisons the youth of America in
more ways than one
Quick Background
• Acute inhalation of Cd as soluble ion or particle
• Bronchial inflammation, ↑ MMP-9 in BALF (Bolognin et al 2009)
• ↑IL-6, ↑ macrophage inflammatory protein-2 (MIP-2) in primary rat lung epithelial
cells (Lag et al 2010)
• ↑TNF-α, ↑IL-1β, ↑MIP-2 in alveolar macrophages (Lag et al 2010)
• Chronic Cd exposure
• 90% inhaled dose absorbed in lungs (Kundu et al 2009)
• Lung cell proliferation (Kundu et al 2009)
• Lung inflammation (Kundu et al 2009)
• Cadmium oxide nanoparticles (CdO NPs)
• Nanoparticle: has at least 1 dimension <100nm
• Used for medical imaging and directing pharmaceutical agents to target sites
Approach
1. Exposed mice to ~1.7µg CdO NP per day
(below OSHA Action level)
2. Euthanized 24h after final exposure or
allowed to recover for 6 days prior to
euthanasia
CdO
CdO
CdO
3. Measured various markers of inflammation
and tissue damage
CdO
CdO
Objective: to determine the effects of inhaled CdO NPs at an occupationally relevant
concentration on pulmonary injury and repair, and on systemic immunity in adult mice.
Effects of inhaled CdO NP on body and lung weights
Cd exposure causes an increase in relative lung weight that persists for longer than 7 days after cessation of
exposure.
Inhaled CdO NP leads to pulmonary inflammation
Filtered air
Fluid/inflammatory cell infiltration
1d post-cessation of Cd exposure
7d post-cessation of Cd exposure
BALT= bronchus-associated lymphoid tissue
Site of septum wall thickening
Area of increased BALT
BALT and septum wall thickening persist 7 days after cessation of CdO NP exposure.
Effects of inhaled CdO NPs on lavagable cell number and
viability
Number of cells in BALF increase 7 days after cessation of CdO exposure consistent with leukocyte
infiltration into lung tissues associated with inflammation.
Effects of inhaled CdO NP on lavagable protein and LDH
activity
Although total protein in BALF decreases 7 days following cessation of Cd treatment, indicators of cell
damage persist.
Effects of exposure to NPs on lavagable pro-inflammatory
cytokines
Short-term inhalation of CdO NPs continues to alter the release of pro-inflammatory cytokines 7 days after
exposure has ceased.
Effects of inhaled CdO NPs on BALF MMP-2 and MMPactivity
ND= none
detected?
Metalloproteinase activity persists 7 days after CdO NP exposure has ceased.
Effects of CdO NP inhalation on peripheral white blood
cell profiles
Circulating neutrophils decrease 7 days post cessation of exposure compared to 24h timepoint and to
control; this could be attributed to neutrophils adhering to/exiting vasculature.
Effects of inhaled CdO NPs on blood leukocyte populations and
bacterial uptake by circulating phagocytes
Phagocytic index of circulating blood phagocytes suggests that inhaled CdO may be translocating from
lung tissue into the blood
Conclusions of Paper 1
• Short-term inhalation of CdO NPs can:
• Lead to persistent pulmonary cell damage
• Affect lung histology and systemic immune function
• Some markers of inflammation were reversible
• Others persisted for ≥7 days
• LDH
• Release of certain proinflammatory cytokines
• MMP-2
Short-term CdO NP inhalation can lead to continued lung tissue injury
or decreased ability to repair damage
Dietary sources of Cadmium
• Little is known about the impact of
chronic ingestion of Cd on small
intestine and colon health
• We do not know how passage of
Cd influences mucosal
homeostasis
• Link between Cd ingestion and
IBD?
Wolk et al, 2012
Approach
• Age- and sex-matched BALB/c mice
• Exposed mice to various doses of Cd and Pb chloride salts in drinking
water
• Cd: 5, 20, and 100 ppm
• Pb: 100 and 500 ppm
• 4, 8, or 12 weeks of exposure
• Measured:
• Cd and Pb accumulation in various tissues
• Essential metal content (Zn, Fe, Cu) in various tissues
• DNA damage in intestinal tissues
Cd and Pb contents in various regions of small and large
intestine
Cd accumulates in the ileum and duodenum, but is cleared 4 weeks after cessation of Cd exposure.
Impact of Cd and Pb on essential metal content in
distinct tissues
Cd accumulates in the ileum and duodenum, but is cleared 4 weeks after cessation of Cd exposure.
Genotoxic effects of chronic Cd exposure in the intestine
of mice
Cd has genotoxic effects on colonic cells and at low concentrations in the duodenum
Paper 2 Conclusions
• Continuous exposure to low and intermediate levels of Cd and Pb
have minimal biological impact on the intestinal microenvironment
• Cannot conclude impact of environmental Cd or Pb on susceptibility
to IBD
• Cannot conclude potential role of Cd or Pb exposure in the
pathogenesis of IBD
• Chronic Cd ingestion does disturb essential metal homeostasis in the
gut
• Zn, Fe
• These could have potential implications on intestinal immunity
What we still don’t know about Cd and inflammation
From Paper #1:
• Mechanisms associated with CdO NP-induced pulmonary injury
• Mechanisms leading to the onset and persistence of these effects
• Relationship between Cd exposure, induction of MMP-2 and -9 and
pulmonary disease
From Paper #2:
• Consequences of Zn and Fe homeostasis on mucosal immune function
• Relationship between Cd exposure and pathogenesis of colitis
• If metal homeostasis and metallothioneins influences susceptibility to
chronic inflammatory diseases
Specific aim and future directions
Specific Aim
To determine the role of the metal-binding protein metallothionein in the
pathogenesis of chronic pulmonary inflammation induced by Cd.
Approach
• Mouse model
• C57BL/6J (wild type)
• C57BL/6J-Mt1tmBriMt2tmBri mice (Mt1 and Mt2 deficient)
• C57BL/6J-TgN(Mt1)174Bri mice (overexpress Mt1)
• Chronic exposure of mice to Cd
• Inhaled-aerosol
• Ingested- spike drinking water
• Measure molecular and clinical markers of inflammation during and
after cessation of exposure
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Histology
PMN infiltration
Proteinase activity
Adhesion molecule expression
Inflammatory cytokine expression
Questions? Comments? Suggestions?