scholarly journals Role of β-arrestin-2 in short- and long-term opioid tolerance in the dorsal root ganglia

2020 ◽  
Author(s):  
Karan H. Muchhala ◽  
Joanna C. Jacob ◽  
William L. Dewey ◽  
Hamid I. Akbarali
Keyword(s):  
G Protein ◽  
Dorsal Root Ganglia ◽  
Dorsal Root ◽  
Opioid Tolerance ◽  
Male Mice ◽  
Wild Type ◽  
Drg Neurons ◽  
Antinociceptive Tolerance

Abstractβ-arrestin-2 has been implicated in the mechanism of opioid-induced antinociceptive tolerance. G-protein-biased agonists with reduced β-arrestin-2 activation are being investigated as safer alternatives to clinically-used opioids. Opioid-induced analgesic tolerance is classically considered as centrally-mediated, but recent reports implicate nociceptive dorsal root ganglia (DRG) neurons as critical mediators in this process. Here, we investigated the role of β-arrestin-2 in the mechanism of opioid tolerance in DRG nociceptive neurons using β-arrestin-2 knockout mice and the G-protein-biased μ-opioid receptor agonist, TRV130. Whole-cell current-clamp electrophysiology experiments revealed that 15-18-hour overnight exposure to 10 μM morphine in vitro induced acute tolerance in β-arrestin-2 wild-type but not knockout DRG neurons. Furthermore, in wild-type DRG neurons circumventing β-arrestin-2 activation by overnight treatment with 200 nM TRV130 attenuated tolerance. Similarly, in β-arrestin-2 knockout male mice acute antinociceptive tolerance induced by 100 mg/kg morphine s.c. was prevented in the warm-water tail-withdrawal assay. Treatment with 30 mg/kg TRV130 s.c. also inhibited antinociceptive tolerance in wild-type mice. Alternately, in β-arrestin-2 knockout DRG neurons tolerance induced by 7-day in vivo exposure to 50 mg morphine pellet was conserved. Likewise, β-arrestin-2 deletion did not mitigate in vivo antinociceptive tolerance induced by 7-day exposure to 25 mg or 50 mg morphine pellet in both female or male mice, respectively. Consequently, these results indicated that β-arrestin-2 mediates acute but not chronic opioid tolerance in DRG neurons and to antinociception. This suggests that opioid-induced antinociceptive tolerance may develop even in the absence of β-arrestin-2 activation, and thus significantly affect the clinical utility of biased agonists.

scholarly journals Loss of SUR1 subtype KATP channels alters antinociception and locomotor activity after opioid administration

2020 ◽  
Author(s):  
Gerald Sakamaki ◽  
Kayla Johnson ◽  
Megan Mensinger ◽  
Eindray Hmu ◽  
Amanda H. Klein
Keyword(s):  
Dorsal Root Ganglia ◽  
Dorsal Root ◽  
Katp Channels ◽  
Acute Administration ◽  
Superficial Dorsal Horn ◽  
Wild Type ◽  
Opioid Administration ◽  
Potassium Flux ◽  
Μ Opioid Receptor

AbstractBackgroundOpioid signaling can occur through several downstream mediators and influence analgesia as well as reward mechanisms in the nervous system. KATP channels are downstream targets of the μ opioid receptor and contribute to morphine-induced antinociception.AimsThe aim of the present work was to assess the role of SUR1-subtype KATP channels in antinocicpetion and hyperlocomotion of synthetic and semi-synthetic opioids.MethodsAdult male and female mice wild-type (WT) and SUR1 deficient (KO) mice were assessed for mechanical and thermal antinociception after administration of either buprenorphine, fentanyl, or DAMGO. Potassium flux was assessed in the dorsal root ganglia and superficial dorsal horn cells in WT and KO mice. Hyperlocomotion was also assessed in WT and KO animals after buprenorphine, fentanyl, or DAMGO administration.ResultsSUR1 KO mice had attenuated mechanical antinociception after systemic administration of buprenorphine, fentanyl, and DAMGO. Potassium flux was also attenuated in the dorsal root ganglia and spinal cord cells after acute administration of buprenorphine and fentanyl. Hyperlocomotion after administration of morphine and buprenorphine was potentiated in SUR1 KO mice, but was not seen after administration of fentanyl or DAMGO.ConclusionsThese results suggest SUR1-subtype KATP channels mediate the antinociceptive response of several classes of opioids (alkaloid and synthetic/semi-synthetic), but may not contribute to the “drug-seeking” behaviors of all classes of opioids.

scholarly journals The role of pruriceptors in enhancing sensitivity to pruritogens in a murine chronic compression model of dorsal root ganglion

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Tao Wang ◽  
Jin Tao ◽  
Yehong Fang ◽  
Chao Ma
Keyword(s):  
Dorsal Root Ganglion ◽  
Dorsal Root ◽  
Neurological Diseases ◽  
Histamine Receptor ◽  
Drg Neurons ◽  
Itch Sensation ◽  
Chronic Pruritus ◽  
In Vivo Calcium Imaging

AbstractChronic pruritus is a symptom that commonly observed in neurological diseases. It has been hypothesized that the chronic pruritus may result from sensitization of itch-signaling pathways but the mechanisms remain obscure. In this study, we established a mouse model of chronic compression of dorsal root ganglion (CCD) and injected various pruritogenic and algogenic agents intradermally to the calf skin ipsilateral to the compressed dorsal root ganglion (DRG). Compared to the naïve mice, a significant increase in itch-related behaviors was observed in the CCD mice after the injection of pruritogens including histamine and BAM8-22, but not after the injection of capsaicin, although all the above agents evoked enhanced pain-related behaviors toward the injected site. In addition, we investigated if pruritogen-evoked activities of DRG neurons were enhanced in this model. In vivo calcium imaging revealed that compressed DRG neurons exhibited enhanced responses to histamine and BAM8-22. Immunoflorescent staining also showed that the histamine receptor H1 and the capsaicin receptor TRPV1 were significantly upregulated in DRG neurons. Our findings indicated that the sensitization of primary pruriceptive neurons may underlie the enhanced itch sensation after chronic compression of DRG in the mice, and may play a role in chronic pruritus in neurological diseases.

scholarly journals Role of β-arrestin-2 in short- and long-term opioid tolerance in the dorsal root ganglia

2021 ◽  
Vol 899 ◽  
pp. 174007
Author(s):  
Karan H. Muchhala ◽  
Joanna C. Jacob ◽  
William L. Dewey ◽  
Hamid I. Akbarali
Keyword(s):  
Dorsal Root Ganglia ◽  
Dorsal Root ◽  
Opioid Tolerance ◽  
Short And Long Term

scholarly journals The Role of Pruriceptors in Enhancing Sensitivity to Pruritogens in a Murine Chronic Compression Model of Dorsal Root Ganglion

2020 ◽  
Author(s):  
Tao Wang ◽  
Jin Tao ◽  
Yehong Fang ◽  
Chao Ma
Keyword(s):  
Dorsal Root Ganglion ◽  
Dorsal Root ◽  
Neurological Diseases ◽  
Histamine Receptor ◽  
Drg Neurons ◽  
Itch Sensation ◽  
Chronic Pruritus ◽  
In Vivo Calcium Imaging

Abstract Chronic pruritus is a symptom that commonly observed in neurological diseases. It has been hypothesized that the chronic pruritus may result from sensitization of itch-signaling pathways but the mechanisms remain obscure. In this study, we established a mouse model of chronic compression of dorsal root ganglion (CCD) and injected various pruritogenic and algogenic agents intradermally to the calf skin ipsilateral to the compressed dorsal root ganglion (DRG). Compared to the naïve mice, a significant increase in itch-related behaviors was observed in the CCD mice after the injection of pruritogens including histamine and BAM8-22, but not after the injection of capsaicin, although all the above agents evoked enhanced pain-related behaviors toward the injected site. In addition, we investigated if pruritogen-evoked activities of DRG neurons are enhanced in this model. In vivo calcium imaging revealed that compressed DRG neurons exhibited significant enhanced responses to histamine and BAM8-22. Immunoflorescent staining also showed that the histamine receptor H1 and the capsaicin receptor TRPV1 were significantly upregulated in DRG neurons. Our findings indicated that in mice modeling the sensitization of primary pruriceptive neurons may underlie the enhanced itch sensation after chronic compression of DRG neurons, and may play a role in chronic pruritus in neurological diseases.

scholarly journals Arabidopsis Disulfide Reductase, Trx-h2, Functions as an RNA Chaperone under Cold Stress

2021 ◽  
Vol 11 (15) ◽  
pp. 6865
Author(s):  
Eun Seon Lee ◽  
Joung Hun Park ◽  
Seong Dong Wi ◽  
Ho Byoung Chae ◽  
Seol Ki Paeng ◽  
...  
Keyword(s):  
Cold Stress ◽  
Wild Type ◽  
Rna Chaperone ◽  
E Coli ◽  
Cold Sensitive ◽  
Thioredoxin H ◽  
Functional Rnas

The thioredoxin-h (Trx-h) family of Arabidopsis thaliana comprises cytosolic disulfide reductases. However, the physiological function of Trx-h2, which contains an additional 19 amino acids at its N-terminus, remains unclear. In this study, we investigated the molecular function of Trx-h2 both in vitro and in vivo and found that Arabidopsis Trx-h2 overexpression (Trx-h2OE) lines showed significantly longer roots than wild-type plants under cold stress. Therefore, we further investigated the role of Trx-h2 under cold stress. Our results revealed that Trx-h2 functions as an RNA chaperone by melting misfolded and non-functional RNAs, and by facilitating their correct folding into active forms with native conformation. We showed that Trx-h2 binds to and efficiently melts nucleic acids (ssDNA, dsDNA, and RNA), and facilitates the export of mRNAs from the nucleus to the cytoplasm under cold stress. Moreover, overexpression of Trx-h2 increased the survival rate of the cold-sensitive E. coli BX04 cells under low temperature. Thus, our data show that Trx-h2 performs function as an RNA chaperone under cold stress, thus increasing plant cold tolerance.

scholarly journals Expression of Cholinergic Markers and Characterization of Splice Variants during Ontogenesis of Rat Dorsal Root Ganglia Neurons

2021 ◽  
Vol 22 (11) ◽  
pp. 5499
Author(s):  
Veronica Corsetti ◽  
Carla Perrone-Capano ◽  
Michael Sebastian Salazar Intriago ◽  
Elisabetta Botticelli ◽  
Giancarlo Poiana ◽  
...  
Keyword(s):  
Dorsal Root Ganglia ◽  
Dorsal Root ◽  
Splice Variants ◽  
Multiple Roles ◽  
Pcr Analysis ◽  
Drg Neurons ◽  
Embryonic Developmental Stage ◽  
Embryo Stage ◽  
Dorsal Root Ganglia Neurons ◽  
Cholinergic Markers

Dorsal root ganglia (DRG) neurons synthesize acetylcholine (ACh), in addition to their peptidergic nature. They also release ACh and are cholinoceptive, as they express cholinergic receptors. During gangliogenesis, ACh plays an important role in neuronal differentiation, modulating neuritic outgrowth and neurospecific gene expression. Starting from these data, we studied the expression of choline acetyltransferase (ChAT) and vesicular ACh transporter (VAChT) expression in rat DRG neurons. ChAT and VAChT genes are arranged in a “cholinergic locus”, and several splice variants have been described. Using selective primers, we characterized splice variants of these cholinergic markers, demonstrating that rat DRGs express R1, R2, M, and N variants for ChAT and V1, V2, R1, and R2 splice variants for VAChT. Moreover, by RT-PCR analysis, we observed a progressive decrease in ChAT and VAChT transcripts from the late embryonic developmental stage (E18) to postnatal P2 and P15 and in the adult DRG. Interestingly, Western blot analyses and activity assays demonstrated that ChAT levels significantly increased during DRG ontogenesis. The modulated expression of different ChAT and VAChT splice variants during development suggests a possible differential regulation of cholinergic marker expression in sensory neurons and confirms multiple roles for ACh in DRG neurons, both in the embryo stage and postnatally.

scholarly journals Essential role of glucose transporter GLUT3 for post-implantation embryonic development

2008 ◽  
Vol 200 (1) ◽  
pp. 23-33 ◽  
Author(s):  
S Schmidt ◽  
A Hommel ◽  
V Gawlik ◽  
R Augustin ◽  
N Junicke ◽  
...  
Keyword(s):  
Essential Role ◽  
Glucose Transporter ◽  
Growth Arrest ◽  
Complete Loss ◽  
Transporter Gene ◽  
Wild Type ◽  
Post Implantation ◽  
Time Point

Deletion of glucose transporter geneSlc2a3(GLUT3) has previously been reported to result in embryonic lethality. Here, we define the exact time point of growth arrest and subsequent death of the embryo.Slc2a3−/−morulae and blastocysts developed normally, implantedin vivo, and formed egg-cylinder-stage embryos that appeared normal until day 6.0. At day 6.5, apoptosis was detected in the ectodermal cells ofSlc2a3−/−embryos resulting in severe disorganization and growth retardation at day 7.5 and complete loss of embryos at day 12.5. GLUT3 was detected in placental cone, in the visceral ectoderm and in the mesoderm of 7.5-day-old wild-type embryos. Our data indicate that GLUT3 is essential for the development of early post-implanted embryos.

scholarly journals A reassessment of the role of B7-1 expression in tumor rejection.

1995 ◽  
Vol 182 (5) ◽  
pp. 1415-1421 ◽  
Author(s):  
T C Wu ◽  
A Y Huang ◽  
E M Jaffee ◽  
H I Levitsky ◽  
D M Pardoll
Keyword(s):  
T Cells ◽  
Tumor Cells ◽  
Cd8 T Cells ◽  
Tumor Rejection ◽  
Type B ◽  
Wild Type ◽  
Systemic Immunity ◽  
Murine Tumor

Introduction of the B7-1 gene into murine tumor cells can result in rejection of the B7-1 transductants and, in some cases, systemic immunity to subsequent challenge with the nontransduced tumor cells. These effects have been largely attributed to the function of B7-1 as a costimulator in directly activating tumor specific, major histocompatibility class I-restricted CD8+ T cells. We examined the role of B7-1 expression in the direct rejection as well as in the induction of systemic immunity to a nonimmunogenic murine tumor. B-16 melanoma cells with high levels of B7-1 expression did not grow in C57BL/6 recipient mice, while wild-type B-16 cells and cells with low B7-1 expression grew progressively within 21 d. In mixing experiments with B7-1hi and wild-type B-16 cells, tumors grew out in vivo even when a minority of cells were B7-1-. Furthermore, the occasional tumors that grew out after injection of 100% B-16 B7-1hi cells showed markedly decreased B7-1 expression. In vivo antibody depletions showed that NK1.1 and CD8+ T cells, but not CD4+ T cells, were essential for the in vivo rejection of tumors. Animals that rejected B-16 B7-1hi tumors did not develop enhanced systemic immunity against challenge with wild-type B-16 cells. These results suggest that a major role of B7-1 expression by tumors is to mediate direct recognition and killing by natural killer cells. With an intrinsically nonimmunogenic tumor, this direct killing does not lead to enhanced systemic immunity.

scholarly journals Expression of lysophosphatidic acid receptor 5 is necessary for the regulation of intestinal Na+/H+ exchanger 3 by lysophosphatidic acid in vivo

2018 ◽  
Vol 315 (4) ◽  
pp. G433-G442 ◽  
Author(s):  
Kayte A. Jenkin ◽  
Peijian He ◽  
C. Chris Yun
Keyword(s):  
Epithelial Cells ◽  
Lysophosphatidic Acid ◽  
Direct Evidence ◽  
Intestinal Epithelial Cells ◽  
Regulatory Role ◽  
Intestinal Epithelial ◽  
Fluid Absorption ◽  
Wild Type

Lysophosphatidic acid (LPA) is a bioactive lipid molecule, which regulates a broad range of pathophysiological processes. Recent studies have demonstrated that LPA modulates electrolyte flux in the intestine, and its potential as an antidiarrheal agent has been suggested. Of six LPA receptors, LPA5 is highly expressed in the intestine. Recent studies by our group have demonstrated activation of Na+/H+ exchanger 3 (NHE3) by LPA5. However, much of what has been elucidated was achieved using colonic cell lines that were transfected to express LPA5. In the current study, we engineered a mouse that lacks LPA5 in intestinal epithelial cells, Lpar5ΔIEC, and investigated the role of LPA5 in NHE3 regulation and fluid absorption in vivo. The intestine of Lpar5ΔIEC mice appeared morphologically normal, and the stool frequency and fecal water content were unchanged compared with wild-type mice. Basal rates of NHE3 activity and fluid absorption and total NHE3 expression were not changed in Lpar5ΔIEC mice. However, LPA did not activate NHE3 activity or fluid absorption in Lpar5ΔIEC mice, providing direct evidence for the regulatory role of LPA5. NHE3 activation involves trafficking of NHE3 from the terminal web to microvilli, and this mobilization of NHE3 by LPA was abolished in Lpar5ΔIEC mice. Dysregulation of NHE3 was specific to LPA, and insulin and cholera toxin were able to stimulate and inhibit NHE3, respectively, in both wild-type and Lpar5ΔIEC mice. The current study for the first time demonstrates the necessity of LPA5 in LPA-mediated stimulation of NHE3 in vivo. NEW & NOTEWORTHY This study is the first to assess the role of LPA5 in NHE3 regulation and fluid absorption in vivo using a mouse that lacks LPA5 in intestinal epithelial cells, Lpar5ΔIEC. Basal rates of NHE3 activity and fluid absorption, and total NHE3 expression were not changed in Lpar5ΔIEC mice. However, LPA did not activate NHE3 activity or fluid absorption in Lpar5ΔIEC mice, providing direct evidence for the regulatory role of LPA5.

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