NORA Manufacturing Sector Strategic Goals
927ZGFT - Neuroinflammation, Glial Signaling and NeurotoxicityStart Date: 10/1/2008
End Date: 9/30/2013
Principal Investigator (PI)Name: James O'callaghan
Funded By: NIOSH
Primary Goal Addressed9.0
Secondary Goal AddressedNone
Attributed to Manufacturing50%
This laboratory-based research project will be conducted to characterize novel molecular changes associated with gliosis, a sensitive cellular index of neurotoxicity. A large number of workplace-related chemicals, and the physiological and environmental factors with which they interact, are associated with subtle neurological effects. Establishing the adverse (i.e. neurotoxicological) nature of these effects is hampered by the lack of available biomarkers of neurotoxicity. Anti-inflammatory and proinflammatory agents will be employed to validate the role of neuroinflammation in the induction of gliosis and neurotoxicity. These studies will evaluate the utility of neuroinflammatory mediators as early biomarkers of neurotoxicity in preclinical assessments, research that directly address the needs described under the neurological component of the Cancer, Reproductive and Cardiovascular Cross-Sector Goals and Health Hazard Evaluation Goals. NIOSH neurotoxicity assessment guidelines are expected outcome.
Glial activation represents a dominant cellular response to all types of damage to the central nervous system (CNS). The generality of the glial reaction to injury, despite the regional- and cell-type specific targets of individual neurotoxic insults, implies there are common signals underlying this cellular response. Discovery and characterization of these signals offer the potential for developing biomarkers of neurotoxicity that can be used as preclinical indicators of any workplace neurotoxic exposure. Signal transduction, especially in the CNS, rely on numerous messengers, receptors and protein phosphorylation cascades. Knowledge of protein phosphorylation sites on a given phosphoprotein permits the accurate prediction of the upstream effectors involved (the Greengardian Model). Previously, we used this approach to discover and characterize glial activation associated phosphorylation of signal transducer and activator of transcription 3 (STAT3). Known upstream effectors for STAT3 include proinflammatory cytokines and chemokines involved in inflammation in the periphery and that are suspected to be involved in "neuroinflammation" in diseases of the CNS. Using genomic and proteomic profiling and qrtPCR, we discovered a rapid and large induction in the expression of a variety of proinflammatory mediators was associated with phosphorylation of STAT3 and activation of both microglia and astroglia (gliosis). While our initial findings make it clear that gliosis and the attendant expression of proinflammatory mediators are associated with toxicant-induced damage to the CNS, it is by no means clear that a cause-and-effect relationship exists between the presence of a neuroinflammatory process and neural damage. For example, workplace related events, such as stress, anxiety, depression, obesity, systemic infections, autonomic dysfunction and disrupted sleep-wake cycles all are associated with changes in the expression of CNS cytokines and chemokines in the absence of evidence of neural damage. Thus, "neuroinflammation"-related events in the CNS must be carefully defined with respect to involvement in neurotoxic responses and not just as a reflection of altered neural physiological responses. This is not just an issue of semantics because a presumed role of inflammation can influence the course of research in an entire field and can consume enormous resources without having the benefit of sound and substantial scientific footing. Therefore, in this project we will use a variety of known neurotoxic agents to induce glial activation and the expression of proinflammatory mediators in the brains of experimental animals. Our preliminary data indicate that antinflammatory agents can suppress neural inflammatory events without affecting neurotoxicity and gliosis. Thus, to examine the linkage between "neuroinflammation" mediators, neural (neuronal or glial) damage and subsequent gliosis, we will examine the effects of anti- and proinflammatory agents on neuroinflammatory responses associated with glial activation and neurotoxicity. Thus, on the one hand, we will evaluate the effects of actue and chronic glucocoritoids on neuroinflammation and neurotoxicity endpoints. On the other hand we will evaluate the effects of acute and chronic lipopolysacharide, as a proinflammogen, on neuroinflammation and neurotoxicity. Finally, we will evaluate animal models of the workplace-related events listed above, either alone, or in combination with known neurotoxic exposures, to determine their influence on neuroinflammtory responses associated with neurotoxicty and subsequent gliosis. In aggregate, these studies will serve to determine if proinflammatory mediators can serve as potential early and sensitive biomarkers of neurotoxicity that ultimately can be applied in a risk assessment context relevant to adverse workplace exposures.
• Develop a comprehensive battery of neurotoxicity biomarkers, i.e. biomarkers applicable to the assessment of broad classes of known and suspected neurotoxic agents.
A large number of workplace-related chemicals, and the physiological and environmental factors with which they interact, are associated with subtle neurological effects. Establishing the potential adverse (i.e. neurotoxicological) nature of these effects is hampered by the lack of neurotoxicity biomarkers. Microglia and astroglia, sub-types of central nervous system glia, have been shown to serve as microsensors of neurotoxic insult. Using tissue from experimental animals and humans, combined with the implementation of novel assay procedures, we have shown that enhanced expression of astrocytic and microglial genes, and their corresponding proteins, can be used to quantify toxicant-induced glial activation (glosis) resulting from dosages of a given agent below those that result in overt cytopathology or behavioral abnormalities. The generality of the glial reaction to injury that we observed, despite the target selectivity of specific neurotoxic insults, implied that there are common signals underlying this cellular reaction, signals that would serve as novel and early biomarkers of neurotoxicity. Cytokines, neurotrophins, neurohormones, and their down-stream signaling effector modules have been linked to toxicant-induced gliosis, as well as to neurological disease states such as Parkinson's and Alzheimer's disease. Consistent with these observations, we have discovered that a variety of proinflammatory cytokines and chemokines are associated with the early stages of exposure to a wide variety of known and suspected neurotoxicants, findings implicating these messenger molecules as early biomarkers of neurotoxicity. While it is becoming clear that activation of microglia and astroglia and the attendant expression of proinflammatory cytokines and chemokines often are associated with disease-, trauma- and, based on our findings, toxicant-induced damage to the CNS, it is by no means clear that a cause-and-effect relationship exists between the presence of a neuroinflammatory process and neural damage. Determining if the expression of specific neuroinflammation-related molecules in the brain is linked in a casual way to neural damage resulting from administration of a variety of known and suspected neurotoxic agents, will provide the information needed to move forward with further validation studies of these potentially sensitive and early biomarkers of neurotoxicity. In this project we will use experimental animals treated with known neurotoxicants and assess brain neuroinflammtory responses with and without pretreatment with anti-inflammatory agents. We then will determine if suppression of inflammation suppresses neurotoxicity using a variety of neuronal and glial biomarkers of neural injury previously established in this laboratory.