# Presentation: 391224

## Division of Neurotoxicology/NCTR:Neurotoxicological Research in Support of Science-Based Decisions

**William Slikker, Jr., Ph.D.**
**Director, Division of Neurotoxicology**
**National Center for Toxicological Research**
** ****Food and Drug Administration**
**Jefferson, Arkansas 72079**

## Mission Statement

**     ****The mission of the Division of Neuro-toxicology is to develop and validate quantitative biomarkers of neurotoxicity **
**and utilize them to elucidate toxic mechanisms and increase the certainty of assumptions underlying risk assessment **
**for neurotoxicants.**

## Neurotoxicity

**Neurotoxicity may be defined as any adverse effect on the structure or function of the central and/or peripheral nervous system by a biological, chemical, or physical agent.**
**Adverse effects can include both unwanted effects and any alteration from baseline that diminishes the ability of an organism to survive, reproduce or adapt to its environment.**
**Neurotoxic effects may be permanent or reversible, produced by neuropharmacological or neuro-degenerative properties of a neurotoxicant, or the result of direct or indirect actions on the nervous system.**

## Incidence of brain related disorders:  Social Impact

**One out of four Americans will suffer**
**   ****from a brain-related disorder during their lifetime.**
**One out of ten school-age children**
**   ****has a functional deficit.**

## Incidence of brain-related disorders:  Economic Impact

**In the U.S., brain-related disorders account for more hospitalizations than any other major disease group.**
**Estimated cost of treatment, rehabilitation, and related consequences is $400 billion each year.**
**Thus, brain-related toxicity results in long-lasting costs to human health and our national economy.**

## Multidisciplinary Research Approach

**Many of the relevant effects can be measured by neurochemical, neurophysiological, neuropathological or behavioral techniques.**
**A multidisciplinary approach is necessary to assess neurotoxicity because of the complex and diverse functions of the nervous system.**

## Discipline - Continuum Approach

**Neurochemical**

**Morphological**

**Physiological**

**Behavioral**

**Psychological**

_**Discipline - Continuum Approach**_

**Genomics, Proteomics**

**Computational Modeling**

## Research Approach

**Evaluation of Available Endpoints**

**Neuropathology         Neurobiology         Neurophysiology        Behavior**

**Light microscopy**
**Histochemistry**
**Immunohistochem.**
**Electron **
**         ****Microscopy**

**Neurochemistry**
**Molecular Biol.**
**Microdialysis**
**Protein Biochem.**
**Cell Culture**

**Neurotoxicity Profile**

**EEG**
**Evoked Potentials**
**Single-unit**
**       ****Recordings**

**Spontaneous**
**Schedule-**
**     ****controlled**
**“****Challenge”**

## Division of Neurotoxicology Senior Staff

**Syed Ali, Ph.D.****	****	****	****	****Neurochemical Toxicology**
**Zbigniew Binienda, D.V.M., Ph.D.****	****Neurophysiological **
**                                                                    ****Toxicology**
**John Bowyer, Ph.D.****	****	****	****Neurobiological Toxicology**
**Sherry Ferguson, Ph.D.****	****	****Developmental Neuro-****	****	****	****	****	****	****	****   behavioral Toxicology**
**Merle Paule, Ph.D.****	****	****	****Behavioral Neurotoxicology**
**Andy Scallet, Ph.D.****	****	****	****Experimental Neurohistology**
**Larry Schmued, Ph.D.****	****	****	****Neuroanatomical Histo-****	****	****	****	****	****	****   chemistry**

## Slide 10

## Slide 11

## NCTR/FDA Nonhuman Primate Center

**Capability****	****  **
**General toxicology and pharmacokinetics **
**Breeding colony**
**Neurotoxicology **
**Behavior**
**Extramural Funding**
**Averaged over one-half million dollars per year during last 13 years**
**Productivity**
**Over ten publications per year, unique to FDA**

## Learning Task:  Accuracy

**Notes:**
Orient graph
Point out control group 
“under control conditions, subjects show improvements on performance from roughly 20% at the start of testing to nearly 60% by the end of the 18 month dosing period.  
The same can be said for the low-dose MK-801 group (indicate), the high-dose MK-801 group (indicate) and the low-dose remacemide group.
Among subjects in the high-dose remacemide group (indicate), there were significant impairments in behavioral acquisition over the 18 months of chronic drug treatment. 
 These effects emerged as significant during the 11th block of test sessions and persisted for the remainder of the 18 month dosing period.

When you see an effect that persists through the end of treatment, it is logical to ask whether the effect is due to acute effects owing to the presence of the drug in the animal or does it reflect a long-term, irreversible effect of early drug exposure.  And, in fact, the purpose of the withdrawal phases of the present experiment was to get at that very question.”

(Based on Richard Allen’s data (from raw transaction files) and analyzed 
using Wald statistics based on the chi-square distribution).

## Cases of comparable behavioral effects of drugs in humans and animals (monkeys)

## Evaluation of Pediatric Anticonvulsants/ NMDA Antagonists 

**NCTR, CFSAN and CDER are collaborating on a volumetric MRI imaging approach to detect drug effects on apoptosis in the developing brain.**

## Domoic Acid Neurotoxicity

**Domoic Acid Neurotoxicity**

## Slide 17

## Acceptable doses of domoic acid based on silver stain grain counts in hippocampus (CA2 region)

## Conclusions

**Quantitative biomarkers of neurotoxicity can be determined.**
**Continuous (nonquantal) data can be used in quantitative risk assessment.**
**Outcome from several risk assessment approaches can be compared.**

##    The locations of the brain regions sensitive to substituted amphetamine-induced somatic neurodegeration can be used as a map for the areas in which:

More subtle types of long-term effects can be examined (and possibly used as biomarkers for neurotoxicity):
mRNA species changes as detected by cDNA arrays.
Changes in protein species detected by proteomics.
Lower doses of substituted amphetamines, that do not produce overt signs of neurotoxicity, may produce long-term ultrastructural and neurochemical changes.

** **
**More subtle types of long-term effects can be examined (and possibly used as biomarkers for neurotoxicity):**
**mRNA species changes as detected by cDNA arrays.**
**Changes in protein species detected by proteomics.**
**Lower doses of substituted amphetamines, that do not produce overt signs of neurotoxicity, may produce long-term ultrastructural and neurochemical changes.**

## RNA from the Substantia Nigra 14 days Post Dosing

**RNA from the Substantia Nigra 14 days Post Dosing**
**	**
**	****Control (Saline)****	****	****Amphetamine**

## Publication and                    Review Activities

**Publication and                    Review Activities**

**Peer-reviewed Publications**
**Book Chapters**
**40 per year**

## Reviews: FDA Guidance and Harmonization Documents

**Red Book II (CFSAN)**
**Reproductive and Developmental Toxicity (CDER)**
**USEPA Food Quality Protection Act,  **
**    ****10X Factor**
**OECD Guidance Document for Neurotoxicity Testing**
**WHO, IARC Working Group on Pharmaceutical Agents**

## A Diversified Portfolio of Leveraging is Important

**CRADA/UALR - Effects of Prenatal Cocaine on Behavioral Plasticity - Paule - $250,000 - 5  years**
**NTP/IAG- Endocrine Disruptors (Ongoing) - Ferguson and Scallet**
**EPA/ IAG - Quantitative Procedures for Neurotoxicity Risk Assessment - Slikker - $200,000 - 2 years**
**CRADA/AstraZeneca - Development of a Nonhuman Primate Model for Studying the Consequences of Long-term Anticonvulsant Medication on Complex Brain Functions - Paule - $1.1 million - 5 years**

## Ongoing Approved Protocol

**   ****Multiple cDNA Array Analysis of the Temporal Changes in mRNA Species after Neurotoxic Events**
**   **John F. Bowyer, John Tor-Agbidye, A.W. Tank (Univ. Rochester), James P. O’Callaghan (NIOSH), Willard Freeman and Kent Vrana (Wake Forest Univ.), Syed Ali, Angela Harris, William Slikker, Jr.

## Ongoing Approved Protocol

**CRADA**
**NCTR/ AstraZeneca**
**  **
**    ****Development of a nonhuman primate model for studying the consequences of long-term anticonvulsant medication on complex brain functions: Rodent equivalent**
-    Merle G. Paule (NCTR) and Edwin Pearson (AstraZeneca)

## Protocol Under Review

**   ****Neurotoxicity Assessment of Ephedra-Containing Dietary Supplements:  Application of cDNA Array and Neurochemical Approaches**
**   **Syed F. Ali, Bill Gurley (UAMS), Syed Z. Imam, Tucker Patterson, Helen Duhart, Saber Hussain (Mantech), Glenn Newport, Angela Harris, John Bowyer, Zbigniew Binienda, William Slikker, Jr.

## Concept Papers Approved

**   ****Study on Alteration of the Programming of the 5-HT System by Nicotine Exposure During Development**
**   **Zengjun Xu, Theodore Slotkin and Frederic J. Seidler (Duke University), John F. Bowyer, William Slikker, Jr.

## Concept Papers Approved

**   ****Enhancement of mitochondrial energy metabolism by carnitines and related dietary supplements: Application of cDNA microarrays, neurophysiological, and neurochemical approaches**
-    Zbigniew Binienda (NCTR), Franco Gaetani and M. Ashraf Virmani (Sigma-Tau Health Science, S.P.A.), Chung S. Kim (CFSAN), Syed Ali and William Slikker, Jr. (NCTR)

## Future Directions

**Thimerosal (CBER, CDER)**
**Nutritional Supplements, e.g. infant formula (CFSAN)**
**Therapeutics, e.g. anticonvulsants, neuroprotectants (CDER, CFSAN)**

## Future Directions-Resource Development

**Imaging (CFSAN, CDER, CDRH)**
**Animal models, e.g. transgenic, nonhuman primates (CFSAN, CBER, CDER)**
**Genomics and proteomics (CDER, CBER, CFSAN)**

## FDA Intercenter Neurotoxicity Working Group

**The FDA is a  science-based regulatory agency with broad responsibilities for promoting and protecting public health.**
**The credibility of and confidence in the FDA’s regulatory decisions are based on the agency’s ability to apply sound science in its review and regulatory process.**
**Efforts are needed to ensure that regulators have the appropriate expertise and necessary information in various scientific disciplines for making appropriate decisions based on high quality science.**
**To assist the FDA in addressing regulatory concerns related to neurotoxicity, personnel from the Centers within the agency, who are actively involved in neuroscience research or regulatory activities, have organized an Inter-center Neurotoxicity Working Group.**