Browse by Audience
Dysbiosis of gut microbiota is associated with many pathologies, yet host factors modulating microbiota remain unclear. Interstitial cystitis/bladder pain syndrome (IC/BPS) is a debilitating condition of chronic pelvic pain often with co-morbid urinary dysfunction and anxiety/depression, and recent studies find fecal dysbiosis in IC/BPS patients. We identified the locus encoding acyloxyacyl hydrolase, Aoah, as a modulator of pelvic pain severity in a murine IC/BPS model. AOAH-deficient mice spontaneously develop rodent correlates of pelvic pain, increased responses to induced pelvic pain models, voiding dysfunction, and anxious/depressive behaviors. Here, we report that AOAH-deficient mice exhibit dysbiosis of GI microbiota. AOAH-deficient mice exhibit an enlarged cecum, a phenotype long associated with germ-free rodents, and a "leaky gut" phenotype. AOAH-deficient ceca showed altered gene expression consistent with inflammation, Wnt signaling, and urologic disease. 16S sequencing of stool revealed altered microbiota in AOAH-deficient mice, and GC-MS identified altered metabolomes. Co-housing AOAH-deficient mice with wild type mice resulted in converged microbiota and altered predicted metagenomes. Co-housing also abrogated the pelvic pain phenotype of AOAH-deficient mice, which was corroborated by oral gavage of AOAH-deficient mice with stool slurry of wild type mice. Converged microbiota also alleviated comorbid anxiety-like behavior in AOAH-deficient mice. Oral gavage of AOAH-deficient mice with anaerobes cultured from IC/BPS stool resulted in exacerbation of pelvic allodynia. Together, these data indicate that AOAH is a host determinant of normal gut microbiota, and dysbiosis associated with AOAH deficiency contributes to pelvic pain. These findings suggest that the gut microbiome is a potential therapeutic target for IC/BPS.
Learn More >Endogenous lipid mediators are proposed to contribute to headache and facial pain by activating trigeminal neurons (TN). We recently identified 11-hydroxy-epoxide- and 11-keto-epoxide derivatives of linoleic acid (LA) that are present in human skin and plasma and potentially contribute to nociception. Here we expand upon initial findings by examining the effects of 11-hydroxy- and 11-keto-epoxide-LA derivatives on TN activation in comparison to LA, the LA derivative [9-hydroxy-octadecadienoic acid (9-HODE)] and prostaglandin E (PGE). 11-hydroxy- and 11-keto-epoxide-LA derivatives elicited Ca transients in TN subpopulations. The proportion of neurons responding to test compounds (5 μM, 5 min) ranged from 16.2 ± 3.8 cells (11 K-9,10E-LA) to 34.1 ± 2.4 cells (11H-12,13E-LA). LA and 9-HODE (5 μM, 5 min) elicited responses in 11.6 ± 3.1% and 9.7 ± 3.4% of neurons, respectively. 11H-12,13E-LA, 11K-12,13E-LA, and 11H-9,10E-LA produced Ca responses in significantly higher proportions of neurons compared to either LA or 9-HODE (F (6, 36) = 5.12, P = 0.0007). 11H-12,13E-LA and 11H-9,10E-LA increased proportions of responsive neurons in a concentration-dependent fashion, similar to PGE. Most sensitive neurons responded to additional algesic agents (32.9% to capsaicin, 40.1% to PGE, 58.0% to AITC), however 20.6% did not respond to any other agent. In summary, 11-hydroxy-epoxide derivatives of LA increase trigeminal neuron excitability, suggesting a potential role in headache or facial pain.
Learn More >We explored the atypical functional connectivity (FC) between the anterior cingulate cortex (ACC) and other brain areas in rats subjected to repeated meningeal nociception. The rat model was established by infusing an inflammatory soup (IS) through supradural catheters in conscious rats. Rats were subdivided according to the frequency of the IS infusions. FC analysis seeded on the ACC was performed on rats 21 days after IS infusion. Glyceryl trinitrate was injected following baseline scanning in the low-frequency IS (LF-IS) group and magnetic resonance imaging (MRI) data were acquired 1 hour after the injection. The rats exhibited nociceptive behavior after high-frequency IS (HF-IS) infusion. The ACC showed increased FC with the cerebellum in the IS groups. The medulla showed increased FC with the ACC in the ictal period in the LF-IS rats. Several areas showed increased FC with the ACC in the HF-IS group, including the pontine tegmentum, midbrain, thalamus, corpus callosum, hippocampus, and retrosplenial, visual, sensory, and motor cortices. This study indicated that the medulla participates in the early stage of a migraine attack and may be associated with the initiation of migraine. Sensitization of the trigeminal nociceptive pathway might contribute to the cutaneous allodynia seen in chronic migraine. Brain areas important for memory function may be related to the chronification of migraine. Electrophysiological studies should examine those migraine-related areas and provide new targets for migraine treatment and prevention.
Learn More >Memantine (MEM) is one of the important clinical medications in treating moderate to severe Alzheimer disease. The effect of MEM on preventing or treating punctate allodynia has been thoroughly studied but not on the induction of dynamic allodynia. The aim of this study is to investigate whether MEM could prevent the induction of dynamic allodynia and its underlying spinal mechanisms. 1)in vivo SNI pain model, pretreatment with MEM at a lower dose (10nmol, i.t.; MEM-10) selectively prevented the induction of dynamic allodynia, but not the punctate allodynia. 2) Pretreatment with either MK801-10 (MK801-10nmol, i.t.) or higher dose of MEM (30nmol, i.t.; MEM-30) prevented the induction of both dynamic and punctate allodynia. 3) MEM-10 showed significant effect on the inhibition of the SNI induced overactivation of microglia in spinal dorsal horn. 4) In contrast, in CFA model, MEM-10 neither affected the CFA injection induced activation of microglia in spinal dorsal horn nor the induction of dynamic allodynia. 5) Immunohistology studies showed Kir2.1 channel distributed widely and co-localized with microglia in the spinal dorsal horn of mice. 6) Pretreatment with either minocycline, a microglia inhibitor, or ML133, a Kir2.1 inhibitor, both selectively prevented the overactivation of microglia in spinal dorsal horn, and the induction of dynamic allodynia following SNI. The selectively inhibitory effect on the induction of dynamic allodynia in SNI model by low dose of the memantine (MEM-10) was tightly correlated with the blockade of microglia Kir2.1 channel to suppress the microglia activation.
Learn More >The incidence of bortezomib-induced neuropathic pain hampers the progress of therapy for neoplasia, and also negatively affects the quality of life of patients. However, the molecular mechanism underlying bortezomib-induced neuropathic pain remains unknown. In the present study, we found that the application of bortezomib significantly increased the expression of GATA binding protein 3 (GATA3) in the spinal dorsal horn, and intrathecal administration of GATA3 siRNA attenuated mechanical allodynia. Furthermore, ChIP-sequencing showed that bortezomib treatment induced the redistribution of GATA3 to transcriptional relevant regions. Notably, combined with the results of mRNA microarray, we found that C-C motif chemokine ligand 21 (CCL21) had an increased GATA3 binding and upregulated mRNA expression in the dorsal horn after bortezomib treatment. Next, we found that bortezomib treatment induced CCL21 upregulation in the spinal neurons, which was significantly reduced upon GATA3 silencing. Blockade of CCL21 using the neutralizing antibody or special siRNA ameliorated mechanical allodynia induced by bortezomib. In addition, bortezomib treatment increased the acetylation of histone H3 and the interaction between GATA3 and CREB-binding protein (CBP). GATA3 siRNA suppressed the CCL21 upregulation by decreasing the acetylation of histone H3. Together, these results suggested that activation of GATA3 mediated the epigenetic upregulation of CCL21 in dorsal horn neurons, which contributed to the bortezomib-induced neuropathic pain.
Learn More >Neuropathic pain results from nerve injuries that cause ectopic firing and increased nociceptive signal transmission due to activation of key membrane receptors and channels. The dysregulation of trafficking of voltage-gated ion channels is an emerging mechanism in the etiology of neuropathic pain. We identify increased phosphorylation of collapsin response mediator protein 2 (CRMP2), a protein reported to regulate presynaptic voltage-gated calcium and sodium channels. A spared nerve injury (SNI) increased expression of a cyclin dependent kinase 5 (Cdk5)-phosphorylated form of CRMP2 in the dorsal horn of the spinal cord and the dorsal root ganglia (DRG) in the ipsilateral (injured) versus the contralateral (non-injured) sites. Biochemical fractionation of spinal cord from SNI rats revealed the increase in Cdk5-mediated CRMP2 phosphorylation to be enriched to pre-synaptic sites. CRMP2 has emerged as a central node in assembling nociceptive signaling complexes. Knockdown of CRMP2 using a small interfering RNA (siRNA) reversed SNI-induced mechanical allodynia implicating CRMP2 expression as necessary for neuropathic pain. Intrathecal expression of a CRMP2 resistant to phosphorylation by Cdk5 normalized SNI-induced mechanical allodynia, whereas mimicking constitutive phosphorylation of CRMP2 resulted in induction of mechanical allodynia in naïve rats. Collectively, these results demonstrate that Cdk5-mediated CRMP2 phosphorylation is both necessary and sufficient for peripheral neuropathic pain.
Learn More >Dependence on opioids and the number of opioid overdose deaths are serious and escalating public health problems, but medication-assisted treatments for opioid addiction remain inadequate for many patients. Glucagon-like pepide-1 (GLP-1) is a gut hormone and neuropeptide with actions in peripheral tissues and in the brain, including regulation of blood glucose and food intake. GLP-1 analogs, which are approved diabetes medications, can reduce the reinforcing and rewarding effects of alcohol, cocaine, amphetamine, and nicotine in rodents. Investigations on effects of GLP-1 analogs on opioid reward and reinforcement have not been reported. We assessed the effects of the GLP-1 receptor agonist Exendin-4 (Ex4) on opioid-related behaviors in male mice, i.e., morphine-conditioned place preference (CPP), intravenous self-administration (IVSA) of the short-acting synthetic opioid remifentanil, naltrexone-precipitated morphine withdrawal, morphine analgesia (male and female mice), and locomotor activity. Ex4 treatment had no effect on morphine-induced CPP, withdrawal, or hyperlocomotion. Ex4 failed to decrease remifentanil self-administration, if anything reinforcing effects of remifentanil appeared increased in Ex4-treated mice relative to saline. Ex4 did not significantly affect analgesia. In contrast, Ex4 dose dependently decreased oral alcohol self-administration, and suppressed spontaneous locomotor activity. Taken together, Ex4 did not attenuate the addiction-related behavioral effects of opioids, indicating that GLP-1 analogs would not be useful medications in the treatment of opioid addiction. This difference between opioids and other drug classes investigated to date may shed light on the mechanism of action of GLP-1 receptor treatment in the addictive effects of alcohol, central stimulants, and nicotine.
Learn More >The box jellyfish Chironex fleckeri is extremely venomous, and envenoming causes tissue necrosis, extreme pain and death within minutes after severe exposure. Despite rapid and potent venom action, basic mechanistic insight is lacking. Here we perform molecular dissection of a jellyfish venom-induced cell death pathway by screening for host components required for venom exposure-induced cell death using genome-scale lenti-CRISPR mutagenesis. We identify the peripheral membrane protein ATP2B1, a calcium transporting ATPase, as one host factor required for venom cytotoxicity. Targeting ATP2B1 prevents venom action and confers long lasting protection. Informatics analysis of host genes required for venom cytotoxicity reveal pathways not previously implicated in cell death. We also discover a venom antidote that functions up to 15 minutes after exposure and suppresses tissue necrosis and pain in mice. These results highlight the power of whole genome CRISPR screening to investigate venom mechanisms of action and to rapidly identify new medicines.
Learn More >Since the failure of specific substance P antagonists to induce analgesia, the role of tachykinins in the development of neuropathic pain states has been discounted. This conclusion was reached without studies on the role of tachykinins in normal patterns of primary afferents response and sensitization or the consequences of their absence on the modulation of primary mechano-nociceptive afferents after injury. Nociceptive afferents from animals lacking tachykinins (Tac1 knockout: KO) showed a disrupted pattern of activation to tonic suprathreshold mechanical stimulation. These nociceptors failed to encode the duration and magnitude of natural pronociceptive stimuli or to develop mechanical sensitization as consequence of this stimulation. Moreover, paw edema, hypersensitivity, and weight bearing were also reduced in Tac1 KO mice 24 hours after paw incision surgery. At this time, nociceptive afferents from these animals did not show the normal sensitization to mechanical stimulation or altered membrane electrical hyperexcitability as observed in wild type animals. These changes occurred despite a similar increase in CGRP immunoreactivity in sensory neurons in Tac1 KO and normal mice. Based on these observations we conclude that tachykinins are critical modulators of primary nociceptive afferents, with a preeminent role in the electrical control of their excitability with sustained activation or injury.
Learn More >Trigeminal neuralgia (TN) commonly results in pain behaviors and cognitive impairment. Convincing evidence suggests that TWIK-related spinal cord K+ (TRESK) exerts antinociceptive and neuroprotective effects. However, its possible potentials in TN remain unclear. TN model was established in rats by generating an infraorbital nerve chronic constriction injury (ION-CCI), and rats received intrathecal injections of TRESK overexpressing lentivirus (LV-TRESK) and siRNA expression vector targeted against TRESK (si-TRESK) into the trigeminal ganglions. Mechanical allodynia was evaluated by mechanical withdrawal threshold (MWT). Cognitive capacity was tested using Morris water maze (MWM). The TRESK expression was determined by quantitative real-time PCR (qRT-PCR) and western blotting. Results showed that the mRNA and protein levels of TRESK were significantly downregulated in trigeminal ganglions in injured rats. Intrathecal treatment with TRESK reduced mechanical allodynia and relieved learning and memory deficits in TN rats, while si-TRESK injection caused neuropathic pain and cognitive deficits. In summary, the present study concluded that TRESK ameliorated pain-associated behaviors and cognitive deficits, which was useful as an alternative approach in management of TN.
Learn More >