Dosimetry can change mechanistic models:

1
Dosimetry can change mechanistic models

• The challenge of scrutinizing the source before
  gathering and analyzing the data

Owen R. Moss, Ph.D.
2
Particulate Matter Health Effects

• Dosimetry of pulmonary hypersensitivity
• Macrophage uptake of nanoparticles
• Biomarkers of long-term response

3
Nanoparticle Toxicology

• Warheit (2005)
• Toxicity depends on surface characteristics,
• particularly surface area and free radical
  generation by interaction of particles with
  cells

4
When nanoparticles get in the way Impact of
projected area on in vivo and in vitro
macrophage function.

• Moss, O. R. and Wong, V. A. (2006) Inhalation
  Toxicology
• (in review January 2006)

5
Frontiers in the application of nanoparticle
dosimetry

• Application in experimental design to determine
  mechanisms of action of inhaled nanoparticles.
• Two examples
• In vivo example from the toxicology literature.
• In vitro example from confocal microscopy.

6
Oberdorster et al. 1994

• Oberderster et al. (1994) Correlation between
  Particle Size, in Vivo Particle Persistence, and
  Lung Injury, Environmental Health Perspectives
  Vol. (102), Supplement 5, 1-11
• A correlation between particle surface area
  and impairment of macrophage function was
  observed.
• Was that chemical interaction or physical
  obstruction?
• Was that particle surface area or particle
  projected surface?

7
A story of 4 spheres

• 12,400 nm diameter macrophage
• 3,000 nm diameter PSL particles
• 250 nm diameter TiO2 particles
• 20 nm diameter TiO2 particles

8
Coverage
250 nm TiO2
10,000
9
Oberdorster 1994

• Experimental Design (12 week TiO2 exposure 29
  week clearance)

250 nm diameter TiO2 particles
Mass deposition of 250 nm and 20 nm diameter
particles the same. Target no-overload
Alveolar space TiO2 particle volume lt 6 of
macrophage volume.
10
Macrophage toxicity and surface area
(PSL clearance half-time for controls 66 d)
11
Impact of masking on macrophage mediated
clearance.
(PSL clearance half-time for controls 66 d)
12
Impact of masking on macrophage mediated
clearance.
(PSL clearance half-time for controls 66 d)
13
In vitro tests

• 2x1013 fluorescent 26 nm diameter PSL beads per
  ml
• 0.2 ml injected
• 300,000 cells
• 1.3x107 fluorescent particles per cell
• time-lapse photography on confocal scope
• resolution 300x increase in concentration.

14
Confocal images
15
0 seconds
16
20 seconds
17
40 seconds
18
60 seconds
19
80 seconds
20
160 seconds
21
240 seconds
22
300 seconds
23
Number of Beads per Cell
24
Nanometer particle uptake
26 nm PSL
Minutes -
25
Dose metrics

• Impairment of macrophage function can be directly
  related to the potential for TiO2 particles to
  mask the surface of the macrophage.
• Nanoparticle deposition modeling is needed in
  resolving chemical and physical impact on cell
  and organ function.

26
The Toxicology of Numbers

• The Avalanche Scenario implies that
• snowflakes are toxic because avalanches are
  lethal
• The toxicology of nanoparticles includes
• the impact of individual nanoparticles
• the impact of the composite

27
Dosimetry CountsMolecular hypersensitivity may
not drive pulmonary hyperresponsiveness
Moss, O. R.(1) and Oldham, M. J.(2) (2006) J.
Aerosol Med (in second review February 2006)
(1) CIIT Centers for Health Research (2)
University of California, Irvine
28
Reanalysis of Previous Research

• DeLorme, M.P. and O.R. Moss. 2002. Pulmonary
  function assessment by whole-body plethysmography
  in restrained versus unrestrained mice. J.
  Pharmacol. Toxicol. Meth. 47110.
• Oldham, M.J. and R.F. Phalen, 2002. Dosimetry
  implications of upper tracheobronchial airway
  anatomy in two mouse varieties. Anat. Rec.
  2685965.
• Oldham, M.J., R.F. Phalen, G.M. Schum, and D.S.
  Daniels. 1994. Predicted nasal and
  tracheobronchial particle deposition efficiencies
  for the mouse. Ann. Occup. Hyg. 38 (Supp.
  1)135141.

29
Airway response

• Bronchoconstrictive agonist
• Murine model

Most Responsive
Least Responsive
AJ gt BALB/c gt CD-1 gt B6C3F1
30
Airway Response Measurement

• Change in airway resistance
• Based on pulmonary function values
• Change in enhanced pause (Penh) reflects change
  in resistance
• DeLorme and Moss (2002) J Pharm Tox. Methods
  471-10.

31
Airway Response
Generator
Chamber
32
Whole Body Plethysmograph
33
Enhanced Pause

• Penh ( Te/Tr 1)( PEP/PIP )

34
PC200R (BALB/c)
BALB/c
35
Methacholine for 200 increase in resistance
12x
36
Airway Diameters
Oldham and Phalen, 2002, Anatomical Record
26859-65
37
Particle deposition at PC200R
38
Different aerosols
39
Size Distribution at PC200R
40
PD200R
3.6x
41
3.6x difference in hypersensitivity

• Airway resistance from nasal tissue
• response time
• Close enough
• possible but dosimetry seems incomplete
• Molecular biology component
• genomic component may be morphometry

42
Smooth Muscle Constriction
43
Smooth Muscle Constriction
44
? in Resistance to Flow
45
Comparing equal resistance ?
46
Representative airway generation

• By Volume
• By Sensitivity

47
Airway Volumes
48
Airway Generation Sensitivity
Sensitivity as a multiple of the sensitivity of
generation 1, the trachea.
49
Airway Generation Sensitivity
Sensitivity as a multiple of the sensitivity of
generation 1, the trachea.
50
Airway Generation Sensitivity
Sensitivity as a multiple of the sensitivity of
generation 1, the trachea.
51
Physiological dose for 200 ?R
52
Microdosimetry

• Time delay in nasal response
• Constant Smooth Muscle Response
• Deposition models

53
Pharyngeal Aspirationaerosol deposition
54
Changing Mechanistic Models

• Diameter-squared has three meanings
• chemical reactivity
• physical obstruction
• or both.
• Dose Counts
• pulmonary morphometry can impact response