1986 — 1988 |
Vasko, Michael R |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Regulation of Afferent Neurotransmitter Release @ University of Texas SW Med Ctr/Dallas
The overall goal of this work is to detemrine which neurotransmitters are important in regulating nociception at the level of the spinal cord and the mechanism of the regulations. Evidence from the literature shows that norepinephrine, opioids, and gamma aminobutyric acid are involved in regulation of nociception at the level of the dorsal horn of the spinal cord. Although the mechanisms of this antinociception remain unknown, preliminary evidence suggests that norepinephrine and morphine may act in part by inhibiting the release of the putative afferent neurotransmitter substance P. The purpose of the proposed studies is to determine if norepinephrine, opioid agonists, and gamma-aminobutyric acid inhibit the release of the afferent nociceptive neurotransmitters, substance P, and somatostatin. Peptide release will be induced in superfused rat spinal cord slices using high extracellular potassium and veratridine. Substance P and somatostatin in the perfusate will be measured by radioimmunoassay. Dose-response relationships for norepinephrine, opioids, and gamma aminobutyric acid agonists will be determined. Specific receptor antagonists will be used to determine which receptors mediate any observed inhibition of transmitter release. Studies will also be performed in spinal cord slices taken from rats made tolerant to analgesic doses of morphine to determine if tolerance develops to the inhibition of peptide release. Finally, studies will be performed in rats pretreated with the neurotoxin, capsaicin, to determine if the observed effects on peptide release are occurring on primary afferent neurons. Understanding neurotransmitter interactions at the level of the dorsal horn of the spinal cord is critical in determining what mechanisms regulate nociception and ultimately in designing clinical strategies for the management of pain. The proposed experiments will provide new information regarding the neurochemistry of regulation of afferent neurotransmitter release and will complement previous electrophysiological and immunohistochemical studies.
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0.943 |
1991 — 1993 |
Vasko, Michael R |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Tolerance to Opioid Actions On Sensory Neurons @ Indiana Univ-Purdue Univ At Indianapolis
It is widely accepted that intrathecal injection of opioids and alpha2 adrenergic drugs produce antinociception in animal models of pain and in man. The sites and mechanism of action of these drugs at the level of the spinal cord, however remains unknown. one possible mechanism to explain this spinal action of opioids and alpha2-agonists is by inhibition of neurotransmitter release from nociceptive sensory neurons. The purpose of this work is to determine whether tolerance and cross-tolerance develop to the inhibitory effects of opioids and alpha2-agonists on transmitter release from sensory neurons. Two techniques will be used to study tolerance and cross-tolerance, release evoked from spinal cord slices and release from rat sensory neurons. Regulation of release of substance P and calcitonin gene-related peptide are the endpoints of the studies. The use of spinal cord slices will allow correlation between tolerance to antinociception and tolerance to inhibition of transmitter release. Use of sensory neurons in culture will provide a model for studying tolerance mechanisms. Regulation of potassium-stimulated release will be measured in spinal cords from non-tolerant rats and rats tolerant to the antinociceptive effects of opioids or alpha2 agonists. Dose-response curves for inhibition of release will be generated for both groups and will be compared to determine if tolerance and cross-tolerance develop. Similar experiments will be performed in rat sensory grown in cells in grown culture. Regulation of release of peptides in cells chronically exposed to morphine will be compared with naive cells. In addition, selective studies will be performed on cells in culture to determine if G-proteins and/or cyclic AMP are involved in acute regulation of transmitter release and in the development of tolerance. From these studies we will gain knowledge as to the sites and mechanisms by which opioids and alpha2-agonists produce antinociception and on the mechanisms of tolerance development.
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0.925 |
1995 — 2004 |
Vasko, Michael R |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Eicosanoid Mechanisms Initiating Neurogenic Inflammation @ Indiana Univ-Purdue Univ At Indianapolis
DESCRIPTION: (Adapted from the Investigator's Abstract) Increasing evidence suggests that a major component of the inflammatory actions of prostaglandins is through augmenting the activity of small diameter sensory neurons. This activation and the subsequent release of neuropeptides from these neurons results in neurogenic inflammation and enhanced pain sensation. The studies outlined in this proposal will determine which prostaglandin receptor subtypes mediate sensitization of sensory neurons. The investigators will also examine the effects of inflammation and long-term exposure to inflammatory mediators on the expression and function of prostaglandin receptor subtypes. Finally, studies will elucidate the role of calcium/calmodulin dependent protein kinase in mediating sensitization after acute and long term exposure to prostaglandins. Alterations in receptor expression and function will be studied using two experimental models, 1) rat sensory neurons grown in culture and 2) spinal cord slices and dorsal root ganglia(DRGs) from rats with unilateral inflammation. The former model provides a unique opportunity to examine the mechanisms of eicosanoid action on sensory neurons without significant interference from other types of cells, whereas the latter affords the opportunity to study eicosanoid actions at the level of sensory input to the spinal cord during chronic inflammation. To assess receptor expression real time PCR detection, radioligand binding and immunoblotting will be used. To establish a causal relationship between activation of receptor subtypes and the sensitizing actions of prostaglandins, antisense technology will be used to reduce expression of specific receptor subtypes. The ability of prostaglandins to augment evoked release of substance P and calcitonin gene-related peptide from sensory neurons and to increase cAMP will be used as indices of sensitization. These studies will provide basic information as to the mechanisms of eicosanoid actions on sensory neurons and establish which prostaglandin receptor subtypes are important in altering neuronal sensitivity during inflammation. This knowledge is critically important for understanding the process of neurogenic inflammation and in ultimately designing new drug therapies for the management of inflammatory diseases.
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0.925 |
2005 — 2008 |
Vasko, Michael R |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Lipase Products Mediate Sensitization of Sensory Neurons @ Indiana Univ-Purdue Univ At Indianapolis
DESCRIPTION (provided by applicant): Lipases are critically important in signal transduction in that they produce a number of first and second messengers that mediate numerous physiological processes. These lipases include phospholipase A2s which liberate arachidonic acid (the rate limiting step in eicosanoid biosynthesis), phospholipase Cs which liberate inositol trisphosphate and diacylglycerols (DAGs), and phospholipase Ds which synthesize phosphatidic acids (PAs) and lysophosphatidic acids (LPAs). Although much work has focused on the involvement of products of PLA2s in pain and inflammation, few studies have examined whether other lipase products modulate neurogenic inflammation and nociception. A major mechanism to account for both neurogenic inflammation and enhanced pain sensitization involves augmenting the activity of small diameter sensory neurons with the subsequent release of neuropeptides from these neurons. Consequently, the studies outlined in this proposal will examine the effects of various lipase products on sensitization of sensory neurons. We also will determine whether select inflammatory mediators augment peptide release from sensory neurons and whether these actions are mediated by lipase products. Studies also will determine whether peripheral inflammation increases the activity of the PLC and PLD signaling pathways and thus contributes to long-term sensitization. The role of lipase products will be studied using two experimental models: (1) rat sensory neurons grown in culture, and (2) spinal cord and dorsal root ganglia (DRGs) from rats with unilateral inflammation. The former model provides a unique opportunity to examine the mechanisms of action of lipase products on sensory neurons and the transduction cascades activated by inflammatory mediators without significant interference from other types of cells. The latter model affords the opportunity to study actions of lipases at the level of sensory input to the central nervous system in naive animals or during chronic inflammation. We will manipulate the lipase transduction cascades by using drugs that inhibit specific enzymes in the pathways, by reducing expression of specific proteins with small linterfering RNA, and by over expressing proteins by infection with adenoviral constructs. The ability of lipase products to augment stimulated release of the neuropeptides, substance P (SP) and calcitonin gene-related peptide (CGRP) from sensory neurons and to increase excitability will be used as indices of sensitization. These studies will provide basic information as to the transduction cascades that mediate neuronal sensitivity during inflammation. This knowledge is critically important for understanding the process of neurogenic inflammation and in ultimately designing new drug therapies for the management of inflammatory diseases.
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0.925 |
2010 — 2013 |
Vasko, Michael R |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
An Intracellular Signaling Switch For Maintaining Peripheral Sensitization @ Indiana Univ-Purdue Univ At Indianapolis
DESCRIPTION (provided by applicant): Peripheral sensitization (i.e. increased sensitivity of sensory neurons) is initiated by the acute inflammatory response, and under pathological conditions this sensitization is maintained producing chronic inflammatory pain. Of major importance in this phenomenon is the production and release of proinflammatory prostaglandins which occurs at the onset of injury and is maintained throughout the course of inflammatory diseases. Although much work has focused on cellular mechanisms mediating the acute sensitizing actions of prostaglandins, there is little understanding of the mechanisms by which these eicosanoids can maintain peripheral sensitization. Recent studies performed in our laboratory suggest a novel mechanism to maintain sensitization, whereby a cooperative interaction occurs between the inflammatory mediator nerve growth factor (NGF) and prostaglandins. Through this mechanism, NGF switches the intracellular signaling cascade that mediates prostaglandin-induced sensitization from the canonical cAMP-dependent protein kinase (PKA) pathway to exchange factors directly activated by cAMP (Epacs). In this way, inflammation (by increasing NGF production and release) enables sensory neurons to continue to respond to prostaglandins over time. Thus, we hypothesize that inflammation or long-term exposure to inflammatory mediators switches the signaling pathways that mediate the sensitizing actions of prostaglandins. To test this hypothesis, we propose three specific aims. In aim 1, we will determine the mechanism(s) by which NGF switches the intracellular signaling pathways mediating the PGE2-induced peripheral sensitization from activation of PKA to activation of Epacs. In aim 2, we will determine whether inflammation also switches the intracellular signaling pathways mediating the PGE2-induced peripheral sensitization from cAMP-induced activation of PKA to cAMP-induced activation of Epacs. In aim 3, we will determine the downstream signaling pathway(s) mediating Epac-induced sensitization of sensory neurons. Overall, the knowledge gained from these studies is critical to understanding the process of sustained pain and hypersensitivity in chronic arthritic diseases. In addition, if we demonstrate that Epac2 activation only occurs during inflammation, our findings have important implications for elucidating a novel therapeutic target for treating chronic pain during inflammation.
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0.925 |
2015 — 2016 |
Fehrenbacher, Jill C (co-PI) [⬀] Kelley, Mark R. (co-PI) [⬀] Vasko, Michael R |
R21Activity Code Description: To encourage the development of new research activities in categorical program areas. (Support generally is restricted in level of support and in time.) |
Dna Damage and Repair in Inflammation-Induced Peripheral Sensitization @ Indiana Univ-Purdue Univ At Indianapolis
? DESCRIPTION (provided by applicant): Although inflammation-induced peripheral sensitization (i.e. increased sensitivity of sensory neurons) can resolve as an injury heals, under pathological conditions this sensitization is maintained and contributes to chronic inflammatory pain. Studies of the cellular mechanisms mediating this maintenance of peripheral sensitization have focused on transcriptional changes that alter protein expression or post-translational modulation of various proteins, especially ion channels. To date, however, these studies have not resulted in new therapeutic approaches for treating chronic inflammatory pain. For this R21 application, we propose a novel mechanism for maintaining sensitization of sensory neurons, i.e. inflammation-induced DNA damage. This damage could result in an alteration in the phenotype of neurons from normal to the sensitized state. Recent studies performed in our laboratory provide support for examining this mechanism, since we have shown that augmenting DNA repair mechanism reverses toxicity in sensory neurons induced by cancer therapies. Furthermore, our preliminary data suggest that inflammation and the inflammatory mediators LPS, MCP-1, and, PGE2, can produce DNA damage in sensory neurons. Thus, we hypothesize that inflammation and inflammatory mediators produce oxidative DNA damage in sensory neurons that contributes to hypersensitivity and that augmenting the base excision repair pathway protects neurons from this damage and thus attenuates the enhanced excitability. To test this hypothesis we propose two specific aims. In studies for the first aim, w will determine whether CFA-induced inflammation or long-term exposure to inflammatory mediators (LPS, MCP-1 or PGE2) in isolated sensory neurons produces reactive oxygen species (ROS) and DNA damage in sensory neurons. We also will determine whether antioxidants or increasing APE1 repair activity (by overexpressing it in sensory neurons) prevents or reverses the DNA damage. In aim 2, we will determine whether augmenting APE1 activity with overexpression in sensory neurons prevents or reverses peripheral sensitization induced by CFA injection into the rat hindpaw or by long-term exposure to inflammatory mediators (LPS, MCP-1 or PGE2) in isolated sensory neurons. If we demonstrate that DNA repair reverses peripheral sensitization that occurs during inflammation, our findings have important implications for elucidating a novel therapeutic target for treating chronic pain.
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0.925 |