Correlative increasing expressions of KIF5b and Nav1.7 in DRG neurons of rats under neuropathic pain conditions.

Nav1.7, one of tetrodotoxin-sensitive voltage-gated sodium channels, mainly expressed in the small diameter dorsal root ganglion (DRG) neurons. The expression and accumulation on neuronal membrane of Nav1.7 increased following peripheral tissue inflammation or nerve injury. However, the mechanisms for membrane accumulation of Nav1.7 remained unclear. We report that KIF5b, a highly expressed member of the kinesin-1 family in DRGs, promoted the translocation of Nav1.7 to the plasma membrane in DRG neurons of the rat. Following nociceptive behaviors in rats induced by peripheral spared nerve injury (SNI), synchronously increased KIF5b and Nav1.7 expressions were observed in DRGs. Immunohistochemistry staining demonstrated the co-expressions of KIF5b and Nav1.7 in the same DRG neurons. Immunoprecipitation experiments further confirmed the interactions between KIF5b and Nav1.7. Moreover, intrathecal injections of KIF5b shRNA moderated the SNI-induced both mechanical and thermal hyperalgesia. The rescued analgesic effects also alleviated SNI-induced anxiety-like behaviors. In sum, KIF5b was required for the membrane localizations of Nav1.7, which suggests a novel mechanism for the trafficking of Nav1.7 involved in neuropathic pain.

Morphological investigations of endomorphin-2 and spinoparabrachial projection neurons in the spinal dorsal horn of the rat.

It has been proved that endomorphin-2 (EM2) produced obvious analgesic effects in the spinal dorsal horn (SDH), which existed in our human bodies with remarkable affinity and selectivity for the µ-opioid receptor (MOR). Our previous study has demonstrated that EM2 made synapses with the spinoparabrachial projection neurons (PNs) in the SDH and inhibited their activities by reducing presynaptic glutamate release. However, the morphological features of EM2 and the spinoparabrachial PNs in the SDH have not been completely investigated. Here, we examined the morphological features of EM2 and the spinoparabrachial PNs by using triple fluorescence and electron microscopic immunohistochemistry. EM2-immunoreactive (-ir) afferents directly contacted with the spinoparabrachial PNs in lamina I of the SDH. Immunoelectron microscopy (IEM) were used to confirm that these contacts were synaptic connections. It was also observed that EM2-ir axon terminals contacting with spinoparabrachial PNs in lamina I contained MOR, substance P (SP) and vesicular glutamate transporter 2 (VGLUT2). In lamina II, MOR-ir neurons were observed to receive direct contacts from EM2-ir varicosities. The synaptic connections among EM2, MOR, SP, VGLUT2, and the spinoparabrachial PNs were also confirmed by IEM. In sum, our results supply morphological evidences for the analgesic effects of EM2 on the spinoparabrachial PNs in the SDH.

Various BDNF administrations attenuate SPS-induced anxiety-like behaviors.

Post-traumatic stress disorder (PTSD) has become epidemic following severely stressful incidents. Previous studies have shown that brain-derived neurotrophic factor (BDNF) has anxiolytic effects on various anxiety or depression disorders including PTSD. However, the detailed mechanisms of BDNF for treating PTSD were rarely investigated. In the current study, single-prolonged stress (SPS) was used as an animal model recapitulating specific aspects for a PTSD-like phenotype. The effects of BDNF on SPS-induced anxiety-like behaviors were investigated. We showed that the levels of BDNF in the cerebro-spinal fluid (CSF) were significantly reduced after the rats experienced SPS. The SPS-induced reductions of percentages of time spent in the central area to total time in the open field test, were dose-dependently mitigated after BDNF intracerebroventricular (i.c.v.) injections. BDNF i.c.v. administration also dose-dependently increased the preference of the light box in the light-dark box test. Both expressions of tyrosine kinase receptor B (TrkB) protein and mRNA in the prefrontal cortex (PFC) and amygdala were significantly increased after SPS challenges. BDNF i.c.v. administration attenuated these compensatory increases of TrkB. At last, the anxiolytic effects of BDNF on SPS model were also observed by using other two injection methods. These results inspired us to study that different administrations of BDNF were used in patients with PTSD in the future, in-depthly.

Effect of ulinastatin, a human urinary protease inhibitor, on heatstroke-induced apoptosis and inflammatory responses in rats.

Ulinastatin has been demonstrated to protect against heatstroke by reducing cerebral ischemia and damage in rats. In order to extend these observations, apoptosis and systemic inflammatory responses were assessed in rats treated with ulinastatin prior to the initiation of heatstroke. Following the onset of heatstroke, histological analysis revealed that the hippocampal tissues displayed edema and damage. In addition, upregulation of malondialdehyde, inducible nitric oxide synthase (iNOS) and reactive oxygen species and downregulation of superoxide dismutase were observed compared with the respective levels in the control group. Furthermore, TUNEL staining and western blotting assays indicated that heatstroke induced cell apoptosis by increasing the Bax/Bcl-2 ratio and caspase-3 levels, and upregulating the protein expression levels of nuclear factor-κB, cyclooxygenase-2 and iNOS. However, the injury induced by heatstroke was significantly inhibited by ulinastatin pretreatment at doses of 5,000 and 10,000 IU/kg. Survival analysis of the rats subjected to heatstroke demonstrated that rats treated with ulinastatin at a dose of 10,000 IU/kg lived longer than those that did not receive ulinastatin treatment. These observations indicate that ulinastatin may protect against heatstroke by reducing apoptosis and systemic inflammatory responses.

JAK2/STAT3 pathway mediating inflammatory responses in heatstroke-induced rats.

Heatstroke not only directly induces cell injury, but also causes large amounts of inflammatory mediators release and cells with extensive biological activities to induce a systemic inflammatory response and immune dysfunction. This study aimed to observe the effects of JAK2 inhibitor AG490 on the brain injury and inflammatory responses of rats with systemic heatstroke. Under the light microscope, the hippocampus tissues of rat with heatstroke were edema and apoptotic rate was increased. Up-regulation of malondialdehyde (MDA), nitric oxide synthase (iNOS), reactive oxygen species (ROS) and down-regulation of superoxide dismutase (SOD) were also found after heatstroke in rats, which compared with that of the control group. Heatstroke induced inflammation factors secretions and up-regulated levels of matrix metallopeptidase 2 and 9 (MMP2 and MMP-9) and systemic inflammatory response molecules including intercellular adhesion molecule-1 (ICAM-1), tumor necrosis factor-beta 1 (TNF-ß1) and cyclooxygenase-2 (COX-2). However, the JAK2 inhibitor AG490 was significantly attenuated the brain injury and inflammatory responses induced by heatstroke in rats. The survival time of heatstroke rats showed that AG490 notably lived longer than heatstroke rats without AG490 treatment. These findings suggest that AG490 may prevent the occurrence of heatstroke via inhibiting the JAK2/STAT3 pathway and the systemic inflammatory responses.