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Publications (11)44.02 Total impact

  • Sungjae Yoo, Ji Yeon Lim, Sun Wook Hwang
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    ABSTRACT: Lipids have long been studied as constituents of the cellular architecture and energy stores in the body. Evidence is now rapidly growing that particular lipid species are also important for molecular and cellular signaling. Here we review the current information on interactions between lipids and transient receptor potential (TRP) ion channels in nociceptive sensory afferents that mediate pain signaling. Sensory neuronal TRP channels play a crucial role in the detection of a variety of external and internal changes, particularly with damaging or pain-eliciting potentials that include noxiously high or low temperatures, stretching, and harmful substances. In addition, recent findings suggest that TRPs also contribute to altering synaptic plasticity that deteriorates chronic pain states. In both of these processes, specific lipids are often generated and have been found to strongly modulate TRP activities, resulting primarily in pain exacerbation. This review summarizes three standpoints viewing those lipid functions for TRP modulations as second messengers, intercellular transmitters, or bilayer building blocks. Based on these hypotheses, we discuss perspectives that account for how the TRP-lipid interaction contributes to the peripheral pain mechanism. Still a number of blurred aspects remain to be examined, which will be answered by future efforts and may help to better control pain states.
    Molecules 01/2014; 19(4):4708-44. · 2.43 Impact Factor
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    ABSTRACT: Oxidative stress induces numerous biological problems. Lipid oxidation and peroxidation appear to be important steps by which exposure to oxidative stress leads the body to a disease state. For its protection, the body has evolved to respond to and eliminate peroxidation products through the acquisition of binding proteins, reducing and conjugating enzymes, and excretion systems. During the past decade, researchers have identified a group of ion channel molecules that are activated by oxidized lipids: transient receptor potential (TRP) channels expressed in sensory neurons. These ion channels are fundamentally detectors and signal converters for body-damaging environments such as heat and cold temperatures, mechanical attacks, and potentially toxic substances. When messages initiated by TRP activation arrive at the brain, we perceive pain, which results in our preparing defensive responses. Excessive activation of the sensory neuronal TRP channels upon prolonged stimulations sometimes deteriorates the inflammatory state of damaged tissues by promoting neuropeptide release from expresser neurons. These same paradigms may also work for pathologic changes in the internal lipid environment upon exposure to oxidative stress. Here, we provide an overview of the role of TRP channels and oxidized lipid connections during abnormally increased oxidative signaling, and consider the sensory mechanism of TRP detection as an alert system.
    International Journal of Molecular Sciences 01/2014; 15(9):16430-16457. · 2.46 Impact Factor
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    Sungjae Yoo, Ji Yeon Lim, Sun Wook Hwang
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    ABSTRACT: The efficacy of many of pain-relieving drugs is based on mechanisms by which the drugs interfere with the body's natural pain-mediating pathways. By contrast, although it is less popular, other drugs including opioids exert more powerful analgesic actions by augmenting endogenous inhibitory neural circuits for pain mediation. Recently, a novel endogenous pain-inhibitory principle was suggested and is now attracting both scientific and clinical attentions. The central players for the actions are particular body lipids: resolvins. Although research is in the preclinical phase, multiple hypotheses have actively been matured regarding the potency and molecular and neural processes of the analgesic effects of these substances. Consistently, accumulating experimental evidence has been demonstrating that treatment with these lipid substances is strongly effective at controlling diverse types of pain. Treatment of resolvins does not appear to disturb the body homeostasis as severely as many other therapeutic agents that interrupt the body's natural signaling flow, which enables us to predict their fewer adverse effects. This paper serves as a review of currently documented painkilling actions of resolvins, summarizes the potential cellular and receptor-mediated mechanisms to date, and discusses the many clinical uses for these therapeutic lipids that have not yet been tested. Future scientific efforts will more concentrate to unveil such aspects of the substances and to construct clear proofs of concept for pain relief.
    Current Neuropharmacology 12/2013; 11(6):664-76. · 2.03 Impact Factor
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    ABSTRACT: Butamben (n-butyl-p-aminobenzoic acid) is a pain-relieving local anesthetic for topical use. Blockade of voltage-gated channel expressed in the peripheral sensory neurons has been suggested as a mechanism of action. Its effects on another sensory neuronal channel family, transient receptor potential (TRP) have remained unclear. In this study we attempted to address this question using six sensory neuronal TRP channel-expressing heterologous systems, cultured sensory neurons and TRP-mediated acute animal pain tests. In Ca(2+) imaging and whole cell electrophysiology, TRPA1 and TRPV4 were blocked by micromolar butamben. Butamben also activated TRPA1 at millimolar concentrations. The inhibitory effects on the two TRP channels were reproducible in sensory neurons. Moreover, butamben attenuated acute animal pain behaviors in a TRPA1- or TRPV4-dependent manner. Para-aminobenzoic acid (PABA), an analog of a simpler chemical structure, displayed similar in vitro and in vivo properties, suggestive that chemical structure is important for the two TRP-specificity. Our findings suggest that inhibition of TRPA1 and TRPV4 contribute to the peripheral analgesic mechanisms of butamben.
    Neuroscience Letters 11/2011; 506(2):297-302. · 2.03 Impact Factor
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    ABSTRACT: Transient receptor potential ion channels (TRPs) expressed in the periphery sense and electrically transduce noxious stimuli to transmit the signals to the brain. Many natural and synthetic ligands for the sensory TRPs have been found, but little is known about endogenous inhibitors of these TRP channels. Recently, we reported that farnesyl pyrophosphate, an endogenous substance produced in the mevalonate pathway, is a specific activator for TRPV3. Here, we show that isopentenyl pyrophosphate (IPP), an upstream metabolite in the same pathway, is a dual inhibitor for TRPA1 and TRPV3. By using Ca(2+) imaging and voltage clamp experiments with human embryo kidney cell heterologous expression system, cultured sensory neurons, and epidermal keratinocytes, we demonstrate that micromolar IPP suppressed responses to specific agonists of TRPA1 and TRPV3. Consistently, peripheral IPP administration attenuated TRPA1 and TRPV3 agonist-specific acute pain behaviors. Furthermore, local IPP pretreatment significantly reversed mechanical and thermal hypersensitivity of inflamed animals. Taken together, the present study suggests that IPP is a novel endogenous TRPA1 and TRPV3 inhibitor that causes local antinociception. Our results may provide useful chemical information to elucidate TRP physiology in peripheral pain sensation.
    Pain 02/2011; 152(5):1156-64. · 5.64 Impact Factor
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    ABSTRACT: Environmental or internal noxious stimuli excite the primary sensory nerves in our body. The sensory nerves relay these signals by electrical discharges to the brain, leading to pain perception. Six transient receptor potential (TRP) ion channels are expressed in the sensory nerve terminals and play a crucial role in sensing diverse noxious stimuli. Cation influx through activated TRP ion channels depolarizes the plasma membrane, resulting in neuronal excitation and pain. Natural and synthetic compounds have been found to act on these sensory TRP channels to alter the nociception. Evidence is growing that lipidergic substances are also cable of modifying TRP ion channel activity by direct binding. Here, we focus on endogenously generated lipids that modulate the sensory TRP activities. Unsaturated fatty acids or their metabolites via lipoxygenase, cyclooxygenase or epoxygenase are able to modulate (activate, inhibit or potentiate) the function of specific TRPs. Isoprene lipids, diacylglycerol, resolvin, and lysophospholipids also show distinct activities on sensory TRP channels. Outcomes caused by the interactions between sensory TRPs and lipid ligands are also discussed. The knowledge we collected here implicates that information on lipidergic ligands may contribute to our understanding of peripheral pain mechanism and provide an opportunity to design novel therapeutic strategies.
    Archives of Pharmacal Research 10/2010; 33(10):1509-20. · 1.54 Impact Factor
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    ABSTRACT: Polymodal nociceptors detect noxious stimuli, including harsh touch, toxic chemicals and extremes of heat and cold. The molecular mechanisms by which nociceptors are able to sense multiple qualitatively distinct stimuli are not well understood. We found that the C. elegans PVD neurons are mulitidendritic nociceptors that respond to harsh touch and cold temperatures. The harsh touch modality specifically required the DEG/ENaC proteins MEC-10 and DEGT-1, which represent putative components of a harsh touch mechanotransduction complex. In contrast, responses to cold required the TRPA-1 channel and were MEC-10 and DEGT-1 independent. Heterologous expression of C. elegans TRPA-1 conferred cold responsiveness to other C. elegans neurons and to mammalian cells, indicating that TRPA-1 is a cold sensor. Our results suggest that C. elegans nociceptors respond to thermal and mechanical stimuli using distinct sets of molecules and identify DEG/ENaC channels as potential receptors for mechanical pain.
    Nature Neuroscience 07/2010; 13(7):861-8. · 15.25 Impact Factor
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    ABSTRACT: Temperature-sensitive transient receptor potential ion channels (thermoTRPs) expressed in epidermal keratinocytes and sensory afferents play an important role as peripheral pain detectors for our body. Many natural and synthetic compounds have been found to act on the thermoTRPs leading to altered nociception, but little is known about endogenous painful molecules activating TRPV3. Here, we show that farnesyl pyrophosphate (FPP), an intermediate metabolite in the mevalonate pathway, specifically activates TRPV3 among six thermoTRPs using Ca(2+) imaging and electrophysiology with cultured keratinocytes and TRPV3-overexpressing cells. Agonistic potencies of related compounds in the FPP metabolism were ignorable. Voltage-dependence of TRPV3 was shifted by FPP, which appears to be the activation mechanism. An intraplantar injection of FPP acutely elicits nociceptive behaviors in inflamed animals, indicating that FPP is a novel endogenous pain-producing substance via TRPV3 activation. Co-culture experiments demonstrated that this FPP-evoked signal in the keratinocytes is transmitted to sensory neurons. In addition, FPP reduced TRPV3 heat threshold resulting in heightened behavioral sensitivity to noxious heat. Taken together, our data suggest that FPP is the firstly identified endogenous TRPV3 activator that causes nociception. Our results may provide useful chemical information to elucidate TRPV3 physiology and novel pain-related metabolisms.
    Journal of Biological Chemistry 06/2010; 285(25):19362-71. · 4.65 Impact Factor
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    ABSTRACT: Lipoxygenase (LO) metabolites are generated in inflamed tissues. However, it is unclear whether the inhibition of the LO activity regulates the expression of c-Fos protein, a pain marker in the spinal cord. Here we used a carrageenan-induced inflammation model to examine the role of LO in the development of c-Fos expression. Intradermally injected carrageenan caused elevated number of cells exhibiting Fos-like immunoreactivity (Fos-LI) in the spinal dorsal horn, and decreased the thermal and mechanical threshold in Hargreaves and von Frey tests. Pretreatment with an inhibitor of phospholipase A2, that generates the LO substrate, prior to the carrageenan injection significantly reduced the number of Fos-(+) cells. A general LO inhibitor NDGA, a 5-LO inhibitor AA-861 and a 12-LO inhibitor baicalein also exhibited the similar effects. Moreover, the LO inhibitors suppressed carrageenan-induced thermal and mechanical hyperalgesic behaviors, which inidcates that the changes in Fos expression correlates with those in the nociceptive behaviors in the inflamed rats. LO products are endogenous TRPV1 activators and pretreatment with BCTC, a TRPV1 antagonist inhibited the thermal but not the mechanical hypersensitivity. Overall, our results from the Fos-LI and behavior tests suggest that LO products released from inflamed tissues contribute to nociception during carrageenan-induced inflammation, indicating that the LO pathway is a possible target for modulating inflammatory pain.
    Molecules and Cells 05/2009; 27(4):417-22. · 2.21 Impact Factor
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    ABSTRACT: Six transient receptor potential (TRP) ion channels expressed in the sensory afferents play an important role as body thermosensors and also as peripheral pain detectors. It is known that a number of natural compounds specifically activate those sensory neuronal TRP channels, and a well-known example is cinnamaldehyde for TRPA1. Here we show that human and mouse TRPA1 are activated by acetaldehyde, an intermediate substance of ethanol metabolism, in the HEK293T cell heterologous expression system and in cultured mouse trigeminal neurons. Acetaldehyde failed to activate other temperature-sensitive TRP channels expressed in sensory neurons. TRPA1 antagonists camphor and gadolinium, and a general TRP blocker ruthenium red inhibited TRPA1 activation by acetaldehyde. Camphor, gadolinium and ruthenium red also suppressed the acute nociceptive behaviors induced by the intradermal administration of acetaldehyde into the mouse footpads. Intradermal co-application of prostaglandin E2 and acetaldehyde greatly potentiated the acetaldehyde-induced nociceptive responses, and this effect was reversed by treatment with the TRPA1 antagonist camphor. These results suggest that acetaldehyde causes nociception via TRPA1 activation. Our data may also help elucidate the mechanisms underlying acetaldehyde-related pathological symptoms such as hangover pain.
    European Journal of Neuroscience 12/2007; 26(9):2516-23. · 3.75 Impact Factor
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    ABSTRACT: Temperature-activated transient receptor potential ion channels (thermoTRPs) are known to function as ambient temperature sensors and are also involved in peripheral pain sensation. The thermoTRPs are activated by a variety of chemicals, of which specific activators have been utilized to explore the physiology of particular channels and sensory nerve subtypes. The use of capsaicin for TRPV1 is an exemplary case for nociceptor studies. In contrast, specific agents for another vanilloid subtype channel, TRPV2 have been lacking. Here, we show that probenecid is able to activate TRPV2 using electrophysiological and calcium imaging techniques with TRPV2-expressing HEK293T cells. Five other sensory thermoTRPs-TRPV1, TRPV3, TRPV4, TRPM8 and TRPA1-failed to show a response to this drug in the same heterologous expression system, suggesting that probenecid is a specific activator for TRPV2. Probenecid-evoked responses were also reproduced in a distinct subset of cultured trigeminal neurons that were responsive to 2-aminoethoxydiphenyl borate, a TRPV1-3 activator. The probenecid-sensitive neurons were mainly distributed in a medium to large-diameter population, in agreement with previous observations with TRPV2 immunolocalization. Under inflammation, probenecid elicited nociceptive behaviors in in vivo assays. These results suggest that TRPV2 is specifically activated by probenecid and that this chemical might be useful for investigation of pain-related TRPV2 function.
    Neuroscience Letters 10/2007; 425(2):120-5. · 2.03 Impact Factor