Veronesi study and SCIENCE and NATURE

On June 15th, Science published an article "New Nano-headache" discussing research by B. Veronesi and on the following day, not to be out done, Nature published a similar article with the less fanciful title "Nanoparticles in sun creams can stress brain cells."

The source is Veronesi's research published in Environmental Science and Technology on June 7th. In her results and discussions she makes the following claims. "...[T]hese data demonstrate that nanosize P25 particles stimulate microglia to produce ROS (reactive oxygen species) through the oxidative burst and through intefererence with mitochondrial ETC (electron transport chain). Neverthless, the microglia remained viable at all concentrations of P25....

Whether the microglia's release of ROS translates into neuronal damage in situ is not addressed in this study, but pilot data indicates P25 stimulates apoptotic ( a genetically directed process of cell self-destruction that is marked by the fragmentation of nuclear DNA) pathways in cultured neurons (she references pilot data by Long et al, in The Toxicologist 2006). It is an abstract from the SOT 2006 Annual Meeting and in it Veronesi and team claim "both FeO (zero valent iron and TiO2 (both bare and surface modified with sodium dodecylbenezene sulfonate) ... stimulated the oxidation burst in both neurons and microglia." Presumably, the microglia results were presented at the meeting. It is difficult to discern how the findings associated with this abstract better evidence the claim of neuronal damage per se. We will be looking forward to more data being published.

Based on observations made from airborne particulate matter, she argues that it is "plausible that similar physical properties of engineered nanoparticles could affect biological targets...."

Then she writes that a primary focus of nanotoxicity studies should involve defining the causal mechanisms linking the physical properties of engineered nanoparticles with biological effects which is being done in a series of studies though more funded research may be prudent.

Technically, the TiO2 may affect microglia. Microglia are phagocytic cells, generally inactive, unless confronted by some exogenous stimuli. Even Veronesi reports they remained viable though stimulated by the presence nanosized titanium oxide, even viable after 18 hours of exposure.

SCIENCE - While there may have been some oxidative stress, it is unclear how the engaged microglia translates into Noreen Park's (SCIENCE) nano-headache! Free radicals are not harmful if they activate microglia and the response chemical reactions are transitory (oxygen anions to hydrogen peroxide to H2O). Presumably, this team found that the response was more prolonged.

Park adds that prolonged exposure [to free radicals] can damage neurons which seems at odds with the language in the EST article ..."not addressed in this study." True, unless they are dispatched. Park then adds a reference to both Parkinson's and Alzheimer's as rhetorical fear tags.

NATURE - Ball (NATURE) begins his article with the caveat "[t]he research does not necessarily imply that these microscopic grains (see above) ... are harmful in the human body." And adds that size matters in many cases because size affects reactivity.

Ball's metaphor is charming. "It's a bit like releasing poison gas in a room containing invaders (microglia) and hoping (actually the process is a little less random than that) that it won't seep out into the rest of the building." While I wouldn't characterize microglia as invaders, the metaphor allows me to approach the exposure issue.

If TiO2 are problematic to microglia and neurons, they need to get there first and we have not seen anything close to definitiveness in terms of exposure pathways. Applying a sunscreen and brain damage from damaged neurons remains a major leap.

Finally Ball adds references to both Parkinson's and Alzheimer's as well. If you add that poison reference that gives him three fear tags to two from Park. He wins??

OBSERVATIONS

The last sentence in Ball's article is worth repeating here. "And there is no firm evidence that this oxidative stress could damage neurons, although Veronesia says they have preliminary results showing that titania nanoparticles can trigger cell death in neurons."

Gunter Oberdorster, a sound mind, added it was "premature to conclude TiO2 damges the brain" and care must be used in "extrapolating [the results] to live organisms."

This is not to say the research should not be taken seriously. It should and needs to be vetted and replicated and extended.