Jiwan Woo

Reducing agents sensitize C-type nociceptors by relieving high-affinity zinc inhibition of T-type calcium channels

Recent studies have demonstrated an important role for T-type Ca2+ channels (T-channels) in controlling the excitability of peripheral pain-sensing neurons (nociceptors). However, the molecular mechanisms underlying the functions of T-channels in nociceptors are poorly understood. Here, we demonstrate that reducing agents as well as endogenous metal chelators sensitize C-type dorsal root ganglion nociceptors by chelating Zn2+ ions off specific extracellular histidine residues on Cav3.2 T-channels, thus relieving tonic channel inhibition, enhancing Cav3.2 currents, and lowering the threshold for nociceptor excitability in vitro and in vivo. Collectively, these findings describe a novel mechanism of nociceptor sensitization and firmly establish reducing agents, as well as Zn2+, Zn2+-chelating amino acids, and Zn2+-chelating proteins as endogenous modulators of Cav3.2 and nociceptor excitability.

Taurine in drinking water recovers learning and memory in the adult APP/PS1 mouse model of Alzheimer's disease

Alzheimers disease (AD) is a lethal progressive neurological disorder affecting the memory. Recently, US Food and Drug Administration mitigated the standard for drug approval, allowing symptomatic drugs that only improve cognitive deficits to be allowed to accelerate on to clinical trials. Our study focuses on taurine, an endogenous amino acid found in high concentrations in humans. It has demonstrated neuroprotective properties against many forms of dementia. In this study, we assessed cognitively enhancing property of taurine in transgenic mouse model of AD. We orally administered taurine via drinking water to adult APP/PS1 transgenic mouse model for 6 weeks. Taurine treatment rescued cognitive deficits in APP/PS1 mice up to the age-matching wild-type mice in Y-maze and passive avoidance tests without modifying the behaviours of cognitively normal mice. In the cortex of APP/PS1 mice, taurine slightly decreased insoluble fraction of Aβ. While the exact mechanism of taurine in AD has not yet been ascertained, our results suggest that taurine can aid cognitive impairment and may inhibit Aβ-related damages.

Intrathecal RGS4 inhibitor, CCG50014, reduces nociceptive responses and enhances opioid-mediated analgesic effects in the mouse formalin test

BACKGROUND:The regulator of G-protein signaling protein type 4 (RGS4) accelerates the guanosine triphosphatase activity of G&agr;i and G&agr;o, resulting in the inactivation of G-protein–coupled receptor signaling. An opioid receptor (OR), a G&agr;i-coupled receptor, plays an important role in pain modulation in the central nervous system. In this study, we examined whether (1) spinal RGS4 affected nociceptive responses in the formalin pain test, (2) this RGS4-mediated effect was involved in OR activation, and (3) the µ-OR agonist–induced antinociceptive effect was modified by RGS4 modulation. METHODS:Formalin (1%, 20 µL) was injected subcutaneously into the right hindpaws of male 129S4/SvJae×C57BL/6J (RGS4+/+ or RGS4−/−) mice, and the licking responses were counted for 40 minutes. The time periods (seconds) spent licking the injected paw during 0 to 10 minutes (early phase) and 10 to 40 minutes (late phase) were measured as indicators of acute nociception and inflammatory pain response, respectively. An RGS4 inhibitor, CCG50014, and/or a µ-OR agonist, [D-Ala2, N-MePhe4, Gly-ol]-enkephalin (DAMGO), were intrathecally injected 5 minutes before the formalin injection. A nonselective OR antagonist, naloxone, was intraperitoneally injected 30 minutes before the CCG50014 injection. RESULTS:Mice that received the formalin injection exhibited typical biphasic nociceptive behaviors. The nociceptive responses in RGS4-knockout mice were significantly decreased during the late phase but not during the early phase. Similarly, intrathecally administered CCG50014 (10, 30, or 100 nmol) attenuated the nociceptive responses during the late phase in a dose-dependent manner. The antinociceptive effect of the RGS4 inhibitor was totally blocked by naloxone (5 mg/kg). In contrast, intrathecal injection of DAMGO achieved a dose-dependent reduction of the nociceptive responses at the early and late phases. This analgesic effect of DAMGO was significantly enhanced by the genetic depletion of RGS4 or by coadministration of CCG50014 (10 nmol). CONCLUSIONS:These findings demonstrated that spinal RGS4 inhibited the endogenous or exogenous OR-mediated antinociceptive effect in the formalin pain test. Thus, the inhibition of RGS4 activity can enhance OR agonist–induced analgesia. The enhancement of OR agonist–induced analgesia by coadministration of the RGS4 inhibitor suggests a new therapeutic strategy for the management of inflammatory pain.

Age-dependent inverse correlations in CSF and plasma amyloid-β(1-42) concentrations prior to amyloid plaque deposition in the brain of 3xTg-AD mice.

Amyloid-β (Aβ) plays a critical role as a biomarker in Alzheimer’s disease (AD) diagnosis. In addition to its diagnostic potential in the brain, recent studies have suggested that changes of Aβ level in the plasma can possibly indicate AD onset. In this study, we found that plasma Aβ(1–42) concentration increases with age, while the concentration of Aβ(1–42) in the cerebrospinal fluid (CSF) decreases in APPswe, PS1M146V and TauP301L transgenic (3xTg-AD) mice, if measurements were made before formation of ThS-positive plaques in the brain. Our data suggests that there is an inverse correlations between the plasma and CSF Aβ(1–42) levels until plaques form in transgenic mice’s brains and that the plasma Aβ concentration possesses the diagnostic potential as a biomarker for diagnosis of early AD stages.

Combined Rho-kinase inhibition and immunogenic cell death triggers and propagates immunity against cancer

Activation of T cell immune response is critical for the therapeutic efficacy of cancer immunotherapy. Current immunotherapies have shown remarkable clinical success against several cancers; however, significant responses remain restricted to a minority of patients. Here, we show a therapeutic strategy that combines enhancing the phagocytic activity of antigen-presenting cells with immunogenic cell death to trigger efficient antitumour immunity. Rho-kinase (ROCK) blockade increases cancer cell phagocytosis and induces antitumour immunity through enhancement of T cell priming by dendritic cells (DCs), leading to suppression of tumour growth in syngeneic tumour models. Combining ROCK blockade with immunogenic chemotherapy leads to increased DC maturation and synergistic CD8+ cytotoxic T cell priming and infiltration into tumours. This therapeutic strategy effectively suppresses tumour growth and improves overall survival in a genetic mouse mammary tumour virus/Neu tumour model. Collectively, these results suggest that boosting intrinsic cancer immunity using immunogenic killing and enhanced phagocytosis is a promising therapeutic strategy for cancer immunotherapy.Activation of an immune response is critical for the efficacy of cancer therapies. Here, the authors show that combination of ROCK inhibitor with chemotherapeutics that induce immunogenic cell death of cancer cells leads to increased dendritic cells’ maturation and synergistic CD8+ cytotoxic T cell priming and infiltration into the tumours, leading to suppressed tumour growth and improved overall survival in syngeneic and genetically engineered tumour models.

Four-week individual caging of male ICR mice alters body composition without change in body mass

Understanding the physiological implications of caging conditions for mice is crucial in improving the replicability and reliability of animal research. Individual caging of mice is known to alter mouse psychology, such as triggering depression-like symptoms in mice, suggesting that caging conditions could have negative effects on mice. Therefore, we hypothesized that individual caging could affect the physical composition of outbred mice. To investigate this, dual X-ray absorptiometry (DXA) was used to compare the mass, bone mineral content (BMC), bone mineral density (BMD), lean tissue percentage and fat tissue percentage between group and individual caged mice. We also conducted open field test to compare mouse activities in different caging conditions. Our results showed significantly reduced BMD and lean tissue percentage and significantly increased fat tissue percentage in individually-caged male mice. Furthermore, there were no differences in body mass and activity between the grouped and individual mice, suggesting that these physical alterations were not induced by group-related activity. In this study, we conclude that individual caging could alter the body composition of mice without affecting external morphology.

A new MEMS neural probe system integrated with push-pull microfluidic channels and biosensors for real-time monitoring of neurochemicals

We present a new MEMS neural probe integrated with two microfluidic channels, a mixer, and biosensors for real-time monitoring of neurochemicals and neural activities. The microfluidic channels for push-pull operation of fluids enable infusion of drugs and extraction of brain fluid at the same time. Also, we can simultaneously monitor neural activities modulated by the infused drug. The real-time monitoring of neurochemicals using the monolithically integrated sensors is a new concept we propose which is enabled through the MEMS technology. The proposed system will provide an important new set of information for brain disease investigation and functional brain-mapping.