Hong-Bing Xiang

Activation of spinal chemokine receptor CXCR3 mediates bone cancer pain through an Akt-ERK crosstalk pathway in rats

Previously, we showed that activation of the spinal CXCL9, 10/CXCR3 pathway mediated bone cancer pain (BCP) in rats. However, the cellular mechanism involved is poorly understood. Here, we found that the activated CXCR3 was co-localized with either neurons, microglia, and astrocytes in the spinal cord, or non-peptidergic-, peptidergic-, and A-type neurons in the dorsal root ganglion. The inoculation of Walker-256 mammary gland carcinoma cells into the rats tibia induced a time-dependent phosphorylation of Akt and extracellular signal-regulated kinase (ERK1/2) in the spinal cord, and CXCR3 was necessary for the phosphorylation of Akt and ERK 1/2. Meanwhile, CXCR3 was co-localized with either pAkt or pERK1/2. Blockage of either Akt or ERK1/2 prevented or reversed the mechanical allodynia in BCP rats. Furthermore, there was cross-activation between PI3K/Akt and Raf/MEK/ERK pathway under the BCP condition. Our results demonstrated that the activation of spinal chemokine receptor CXCR3 mediated BCP through Akt and ERK 1/2 kinase, and also indicated a crosstalk between PI3K/Akt and Raf/MEK/ERK signaling pathways under the BCP condition.

The cuneiform nucleus may be involved in the regulation of skeletal muscle tone by motor pathway: a virally mediated trans-synaptic tracing study in surgically sympathectomized mice

ARTICLE Sir, The review article entitled ‘The pedunculopontine nucleus area: critical evaluation of interspecies differences relevant for its use as a target for deep brain stimulation’ by Alam et al. (2011), addressed that the cuneiform nucleus, an adjacent region of the pedunculopontine nucleus, was the important area of the mesencephalic locomotor region and played a major role in the initiation of gait. It has been suggested by many studies that neurons in the cuneiform nucleus are involved in the generation of locomotion, and signals from the cuneiform nucleus activate central pattern generators in the spinal cord, mainly through the medullary reticulospinal tract (Takakusaki et al. , 2003). The understanding of neuroanatomical motor circuitry and neuronal connections from cuneiform nucleus to skeletal muscle is important for studying the possible mechanism of cuneiform nucleus involved in the regulation of skeletal muscle tone by motor pathway. We would like to further complete the discussion of Alam et al. (2011) by introducing a virally-mediated trans-synaptic tracing study. Deep brain stimulation has become a remarkable treatment option for several different movement disorders, such as neuropsychiatric disorders, intractable pain, epilepsy, restless legs syndrome, Parkinson’s disease, and Alzheimer’s disease (Wichmann and Delong, 2006; Halpern et al. , 2007; Lyons, 2011; Thevathasan et al. , 2011). The mesencephalic pedunculopontine tegmental nucleus has been suggested as a target for deep brain stimulation, but the exact mechanism of deep brain stimulation in the pedunculopontine tegmental nucleus area is not fully understood. Because clinical data have demonstrated that the outcome of deep brain stimulation in the pedunculopontine nucleus area can be quite variable, there is great controversy about the …

Activation of CXCL10/CXCR3 Signaling Attenuates Morphine Analgesia: Involvement of Gi Protein

Morphine is a potent agonist of μ-opioid receptor and is widely used to relieve severe pain, including cancer pain. Some chemokines, for example, CX3CL1 and CCL2, participate in the regulation of opioid santinociception. In our previous study, we found overexpression of chemokine CXCL10/CXCR3 in spinal cord participated in the development of cancer-induced bone pain, so we supposed that CXCL10 may have influence in morphine analgesia in cancer pain relief. In this study, we found that a single dose of morphine could transiently increase the expression of CXCL10 in spinal cord. Blocking the function of CXCL10 enhanced morphine antinociception in cancer-induced bone pain rats. However, overexpression of CXCL10 induced acute algesia and decreased the analgesic effect of morphine in normal mice. The algesic effect of CXCL10 was blocked by inhibition of CXCR3 and Gi protein. These results suggested that CXCL10 in spinal cord serves as a novel negative regulator of morphine analgesia and provided evidence that activation of CXCL10/CXCR3 in spinal cord may attenuate antinociceptive potency of morphine in cancer pain relief.

Deep brain stimulation of the pedunculopontine tegmental nucleus may influence renal function

Deep brain stimulation of the pedunculopontine tegmental nucleus (PPTg) had usually been reported to improve the symptoms of advanced Parkinsons disease. Previous studies showed that neurons in the PPTg involved in the control of the sympathetic outflow to the kidneys. Our recent studies using transneuronal labeling pseudorabies virus (PRV)-614 supported the sympathetic nature of the caudal PPTg. We propose a hypothesis that deep brain stimulation of the PPTg may influence renal function by serotonergic and catecholaminergic pathways. Because PRV-614/tryptophan hydroxylase and PRV-614/tyrosine hydroxylase double-labeled neurons in the compact parts of PPTg (cpPPTg) were not detected, deep brain stimulation of the cpPPTg might not influence renal function.

Laterodorsal tegmentum and pedunculopontine tegmental nucleus circuits regulate renal functions: Neuroanatomical evidence in mice models

Neurons in the laterodorsal tegmentum (LDTg) and pedunculopontine tegmental nucleus (PPTg) play important roles in central autonomic circuits of the kidney. In this study, we used a combination of retrograde tracers pseudorabies virus (PRV)-614 and fluorescence immunohistochemistry to characterize the neuroanatomic substrate of PPTg and LDTg innervating the kidney in the mouse. PRV-614-infected neurons were retrogradely labeled in the rostral and middle parts of LDTg, and the middle and caudal parts of PPTg after tracer injection in the kidney. PRV-614/TPH double-labeled neurons were mainly localized in the rostral of LDTg, whereas PRV-614/TH neurons were scattered within the three parts of LDTg. PRV-614/TPH and PRV-614/TH neurons were located predominantly in the caudal of PPTg (cPPTg). These data provided direct neuroanatomical foundation for the identification of serotonergic and catecholaminergic projections from the mid-brain tegmentum to the kidney.SummaryNeurons in the laterodorsal tegmentum (LDTg) and pedunculopontine tegmental nucleus (PPTg) play important roles in central autonomic circuits of the kidney. In this study, we used a combination of retrograde tracers pseudorabies virus (PRV)-614 and fluorescence immunohistochemistry to characterize the neuroanatomic substrate of PPTg and LDTg innervating the kidney in the mouse. PRV-614-infected neurons were retrogradely labeled in the rostral and middle parts of LDTg, and the middle and caudal parts of PPTg after tracer injection in the kidney. PRV-614/TPH double-labeled neurons were mainly localized in the rostral of LDTg, whereas PRV-614/TH neurons were scattered within the three parts of LDTg. PRV-614/TPH and PRV-614/TH neurons were located predominantly in the caudal of PPTg (cPPTg). These data provided direct neuroanatomical foundation for the identification of serotonergic and catecholaminergic projections from the mid-brain tegmentum to the kidney.

Motor Cortex-Periaqueductal Gray-Spinal Cord Neuronal Circuitry May Involve in Modulation of Nociception: A Virally Mediated Transsynaptic Tracing Study in Spinally Transected Transgenic Mouse Model

Several studies have shown that motor cortex stimulation provided pain relief by motor cortex plasticity and activating descending inhibitory pain control systems. Recent evidence indicated that the melanocortin-4 receptor (MC4R) in the periaqueductal gray played an important role in neuropathic pain. This study was designed to assess whether MC4R signaling existed in motor cortex- periaqueductal gray- spinal cord neuronal circuitry modulated the activity of sympathetic pathway by a virally mediated transsynaptic tracing study. Pseudorabies virus (PRV)-614 was injected into the left gastrocnemius muscle in adult male MC4R-green fluorescent protein (GFP) transgenic mice (n = 15). After a survival time of 4–6 days, the mice (n = 5) were randomly assigned to humanely sacrifice, and spinal cords and brains were removed and sectioned, and processed for PRV-614 visualization. Neurons involved in the efferent control of the left gastrocnemius muscle were identified following visualization of PRV-614 retrograde tracing. The neurochemical phenotype of MC4R-GFP-positive neurons was identified using fluorescence immunocytochemical labeling. PRV-614/MC4R-GFP dual labeled neurons were detected in spinal IML, periaqueductal gray and motor cortex. Our findings support the hypothesis that MC4R signaling in motor cortex-periaqueductal gray-spinal cord neural pathway may participate in the modulation of the melanocortin-sympathetic signaling and contribute to the descending modulation of nociceptive transmission, suggesting that MC4R signaling in motor cortex- periaqueductal gray-spinal cord neural pathway may modulate the activity of sympathetic outflow sensitive to nociceptive signals.

Activation of spinal phosphatidylinositol 3-kinase/protein kinase B mediates pain behavior induced by plantar incision in mice.

The etiology of postoperative pain may be different from antigen-induced inflammatory pain and neuropathic pain. However, central neural plasticity plays a key role in incision pain. It is also known that phosphatidylinositol 3-kinase (PI3K) and protein kinase B/Akt (PKB/Akt) are widely expressed in laminae I-IV of the spinal horn and play a critical role in spinal central sensitization. In the present study, we explored the role of PI3K and Akt in incision pain behaviors. Plantar incision induced a time-dependent activation of spinal PI3K-p110γ and Akt, while activated Akt and PI3K-p110γ were localized in spinal neurons or microglias, but not in astrocytes. Pre-treatment with PI3K inhibitors, wortmannin or LY294002 prevented the activation of Akt brought on by plantar incision in a dose-dependent manner. In addition, inhibition of spinal PI3K signaling pathway prevented pain behaviors (dose-dependent) and spinal Fos protein expression caused by plantar incision. These data demonstrated that PI3K signaling mediated pain behaviors caused by plantar incision in mice.

Role of Spinal Cord in Regulating Mouse Kidney: A Virally Mediated Trans-synaptic Tracing Study

OBJECTIVE To determine the spinal innervation and neuronal connections is important for studying renal metabolic responses. MATERIALS AND METHODS In this study, the spinal cords of 10 adult male C57BL/6J strain mice were mapped retrograde using injections of pseudorabies virus (PRV)-614. The virus, injected into the kidney, was specifically transported to the spinal cord. RESULTS At 5 days after injection of the PRV-614, PRV-614-positive cells were found in the intermediolateral cell column, the intercalates nucleus, or the central autonomic nucleus of spinal cord segments T4-L1, and most PRV-614-labeled cells were found in the T9 segment. CONCLUSION Our results revealed neuroanatomical circuits between kidney and the spinal intermediolateral cell column neurons.

Melanocortin-4 receptor expression in the rostral ventromedial medulla involved in modulation of nociception in transgenic mice

The rostral ventromedial medulla (RVM) is a prominent component of the descending modulatory system involved in the control of spinal nociceptive transmission. In the current study, we investigated melanocortin-4 receptor (MC4R) expression in the RVM, where the neurons involved in modulation of nociception reside. Using a line of mice expressing green fluorescent protein (GFP) under the control of the MC4R promoter, we found a large number of GFP-positive neurons in the RVM [nucleus raphe magnus (NRM) and nucleus gigantocellularis pars α (NGCα)]. Fluorescence immunohistochemistry revealed that approximately 10% of MC4R-GFP-positive neurons coexpressed tyrosine hydroxylase, indicating that they were catecholaminergic, whereas 50%–75% of those coexpressed tryptophan hydroxylase, indicating that they were serotonergic. Our findings support the hypothesis that MC4R signaling in RVM may modulate the activity of serotonergic sympathetic outflow sensitive to nociceptive signals, and that MC4R signaling in RVM may contribute to the descending modulation of nociceptive transmission.SummaryThe rostral ventromedial medulla (RVM) is a prominent component of the descending modulatory system involved in the control of spinal nociceptive transmission. In the current study, we investigated melanocortin-4 receptor (MC4R) expression in the RVM, where the neurons involved in modulation of nociception reside. Using a line of mice expressing green fluorescent protein (GFP) under the control of the MC4R promoter, we found a large number of GFP-positive neurons in the RVM [nucleus raphe magnus (NRM) and nucleus gigantocellularis pars α (NGCα)]. Fluorescence immunohistochemistry revealed that approximately 10% of MC4R-GFP-positive neurons coexpressed tyrosine hydroxylase, indicating that they were catecholaminergic, whereas 50%–75% of those coexpressed tryptophan hydroxylase, indicating that they were serotonergic. Our findings support the hypothesis that MC4R signaling in RVM may modulate the activity of serotonergic sympathetic outflow sensitive to nociceptive signals, and that MC4R signaling in RVM may contribute to the descending modulation of nociceptive transmission.

Stimulation of the pedunculopontine tegmental nucleus may affect renal function by melanocortinergic signaling

Deep brain stimulation of the pedunculopontine tegmental nucleus (PPTg) has been reported to improve gait disturbance in animal models of Parkinsonism and among patients with Parkinsons disease. Evidence suggests that neurons in the PPTg are involved in the control of the sympathetic outflow to the kidneys, and sympathetic regulation is a major component of central melanocortin action. Our recent studies using transneuronal labeling pseudorabies virus (PRV)-614 and melanocortin-4 receptor (MC4R)-green fluorescent protein (GFP) transgenic mice supported the melanocortinergic nature of the middle and caudal PPTg (mPPTg and cPPTg). Because PRV-614/MC4R-GFP double-labeled neurons in the mPPTg and cPPTg were detected, we propose a hypothesis that deep brain stimulation of the PPTg may influence renal function by the melanocortinergic pathway.