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| TITLE: | EMF Effects on Brain Cell Cultures | ||
| Principal Investigator |
Michael McMillian, Ph.D. | Laboratory of Environmental Neurosciences, NIEHS | |
| Health Relevance |
Neurobehavioral Dysfunction | ||
| Research Categories |
Short term whole animal studies | Neurobehavior | Neuronal Development |
| FY95 Funds | DIR-6 $ 30,000 | Start Date 10/93 | End Date 9/95 |
| Rationale and Summary |
The central nervous system (CNS) is dependent on electrical signaling to form appropriate,
complex connections and networks. The developing CNS is thus potentially among the most
important targets for electromagnetic field (EMF) effects. Immune cells are reportedly among the
most sensitive cells to EMF effects. Brain microglia, the resident immune cells of the CNS, arise
from the same lineage as the monocytes of the peripheral immune system. Microglia can be
stimulated to produce a number of cytokines, (including TNF alpha, IL-1,IL-6, and TGF beta) that
have been shown to be important in certain aspects of brain development, as well as in
inflammatory and neurotoxic responses to brain injury in adults. Additionally there are clinical
reports of an increased incidence of rapidly growing astrocytomas after EMF exposure. We have
developed mixed brain cell cultures as model systems to study mechanisms involved in
neurotoxicity. Pronounced changes are seen in these cultures after exposure of neonatal rat pups
to drugs, such as the NMDA receptor blocker MK801, and this model system should provide a
useful screen for long-lived effects of EMF exposure on the developing brain. The main purpose
of this project was to examine the effects of EMF exposure in mixed brain cell cultures from
neonatal pups. The cell culture studies yielded a number of differences between groups, but
correlations with EMF dose-exposure were generally lacking. Basal [3H]pdBu binding, which
serves as an index for the number of neurons, was higher in cultures from EMF-exposed brains.
This suggests that high EMF exposures did not kill neurons. EMF exposure increased the
lipopolysaccharide (LPS)-induced activation of microglia. LPS-induced releases of IL-1 beta
(primarily microglia-derived) and {Met5} enkephalin (primarily astrocyte-derived) were not
significantly different between groups. In summary, this study showed that EMF exposure affects
microglia responses which, in turn, may influence the neuro-immune functions during brain
development.
The goal of this research project is to evaluate the effects of electromagnetic field (EMF) exposure on neuronal development. |
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| Experimental Design and Exposure Conditions |
The Sprague-Dawley rats that were utilized in the study "Evaluate the toxic and carcinogenic potential of 60Hz magnetic fields in laboratory animals for the National Toxicology Program" were studied in this proposal. In these experiments conducted in IIT Research Institute in Chicago, several pups were not used and were designated to be sacrificed. This study utilized these additional rats. The pregnant rats were exposed to continuous(18.5 hours/day) or intermittent (one hour on/one hour off during the exposure period) fields of EMF. Ten rat pups at postnatal day 1 were sacrificed from groups of rats exposed of EMF. Five groups of rat pups were studied: A): Control B): 20 mGauss continuous exposure C): 2 Gauss continuous exposure D): 10 Gauss intermittent exposure E): 10 Gauss continuous exposure Mixed brain cell cultures were prepared according to the published method (McMillian et al., 1992) and cells were incubated for 7-14 days before use. {3H}pdBu binding which binds to protein kinase C, was used as a marker for neurons. Immunocytochemical studies using a specific marker (ox-42) were used for the activation of microglia. Levels of {Met5}-enkephalin and IL-1 beta were measured by radioimmunoassay and ILISA, respectively. | ||
| Quality Assurance Measures |
All exposure parameters were independently verified by the National Institute of Standards and Technology (NIST). All cell cultures were done on blinded samples. The code was broken only after all of the results were analyzed. | ||
| Results and Discussion |
The cell culture studies yielded a number of significant differences between the five groups (A:
sham, B: 20mG, C: 2G, D: 10G intermittent, E: 10G continuous), but correlations with EMF dose-
exposure were generally lacking. Basal [3H]pdBu binding, which binds to protein kinase C and
can be used as an index for the number of neurons was higher in cultures from EMF-exposed
brains. This suggests that EMF exposures did not kill neurons, but rather may have interfered
with normal developmental loss of neurons. Group B plates showed the highest [3H]pdBu
binding in response to activation of protein kinase C by phorbol ester. Treatment with
lipopolysaccharides (LPS), which activate microglia, decreased [3H]pdBu binding in group C, D,
and E, presumably due to the loss of neurons by microglia. This notion was consistent with the
finding that microglia in these three groups were more activated than group A and B. Levels of
{Met5}-enkephalin (predominantly reflecting astrocytes) were not altered in EMF-exposed
groups, suggesting that astrocytes were not affected. Therefore, most of the changes observed in
this study can be attributed to EMF effects on microglia responses. This notion supports the
findings that immune cells are among the most sensitive cell to EMF effect because microglia
arise from the same lineage as the monocytes of the peripheral immune system. Thus results
obtained from this study suggest that EMF exposure during gestation may alter the neuro-immune
function which may influence the brain development.
The results from this pilot project do not support further studies. This project will not be continued. |
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| Recent Publications |
None | ||