Mechanosensitive Ion Channel TMEM63A Gangs Up with Local Macrophages to Modulate Chronic Post-amputation Pain / 神经科学通报·英文版

Post-amputation pain causes great suffering to amputees, but still no effective drugs are available due to its elusive mechanisms. Our previous clinical studies found that surgical removal or radiofrequency treatment of the neuroma at the axotomized nerve stump effectively relieves the phantom pain afflicting patients after amputation. This indicated an essential role of the residual nerve stump in the formation of chronic post-amputation pain (CPAP). However, the molecular mechanism by which the residual nerve stump or neuroma is involved and regulates CPAP is still a mystery. In this study, we found that nociceptors expressed the mechanosensitive ion channel TMEM63A and macrophages infiltrated into the dorsal root ganglion (DRG) neurons worked synergistically to promote CPAP. Histology and qRT-PCR showed that TMEM63A was mainly expressed in mechanical pain-producing non-peptidergic nociceptors in the DRG, and the expression of TMEM63A increased significantly both in the neuroma from amputated patients and the DRG in a mouse model of tibial nerve transfer (TNT). Behavioral tests showed that the mechanical, heat, and cold sensitivity were not affected in the Tmem63a-/- mice in the naïve state, suggesting the basal pain was not affected. In the inflammatory and post-amputation state, the mechanical allodynia but not the heat hyperalgesia or cold allodynia was significantly decreased in Tmem63a-/- mice. Further study showed that there was severe neuronal injury and macrophage infiltration in the DRG, tibial nerve, residual stump, and the neuroma-like structure of the TNT mouse model, Consistent with this, expression of the pro-inflammatory cytokines TNF-α, IL-6, and IL-1β all increased dramatically in the DRG. Interestingly, the deletion of Tmem63a significantly reduced the macrophage infiltration in the DRG but not in the tibial nerve stump. Furthermore, the ablation of macrophages significantly reduced both the expression of Tmem63a and the mechanical allodynia in the TNT mouse model, indicating an interaction between nociceptors and macrophages, and that these two factors gang up together to regulate the formation of CPAP. This provides a new insight into the mechanisms underlying CPAP and potential drug targets its treatment.

Cardiac image segmentation using generalized polynomial chaos expansion and level set function.

Cardiovascular Magnetic Resonance (CMR) images involves a great amount of uncertainties. Such uncertainties may originate from either intrinsic measurement limitations or heterogeneities among patients. Without properly considering these uncertainties, image analysis may provide inaccurate estimations of cardiac functions, and ultimately lead to false diagnosis and inappropriate treatment strategy. In this work, a stochastic image segmentation algorithm is developed to separate cardiac chambers from the background of CMR images. To account for noise and uncertainties in pixel values, a generalized polynomial chaos (gPC) expansion is integrated with a level set function to dynamically evolve boundaries of cardiac chambers. Two consecutive steps are developed: a deterministic segmentation to identify an immediate neighborhood of boundary, of which pixel values are used to calibrate the gPC model; and a stochastic segmentation applied to the neighborhood region to evolve boundaries of cardiac chambers in a stochastic manner. The proposed method can provide a probabilistic description of the segmented heart boundary, which will greatly improve the reliability of image analysis, and potentially enhanced cardiac function evaluation.

Global sensitivity analysis for developing biological models: Application to K+ channel model in mouse ventricular myocytes.

Mathematical models of cardiac myocytes are highly nonlinear and involve a large number of model parameters. The parameters are estimated using experimental data, which are often corrupted by noise and uncertainty. Such uncertainty can be propagated onto model parameters during model calibration, which further affects model reliability and credibility. In order to improve model accuracy, it is important to quantify and reduce the uncertainty in model response resulting from parametric uncertainty. Sensitivity analysis is a key technique to investigate the significance of parametric uncertainty and its effect on model responses. This can identify and rank most sensitive parameters, and evaluate the effect of uncertainty on model outputs. In this work, a global sensitivity analysis is developed to determine the significance of parametric uncertainty on model responses using Sobol indices. This method is applied to nonlinear K+ channel models of mouse ventricular myocytes to demonstrate the efficacy of the developed algorithm.

Propagation of parametric uncertainty for the K+ channel model in mouse ventricular myocytes.

Cardiac potassium (K+) channel plays an important role in cardiac electrical signaling. Mathematical models have been widely used to investigate the effects of K+ channels on cardiac functions. However, the model of K+ channel involves parametric uncertainties, which can be induced by fitting the model's parameters that best capture experimental data. Since the prediction of cardiac functions are highly parameter-dependent, it is critical to quantify the influence of parametric uncertainty on the model responses to provide the more reliable predictions. This paper presents a new method to efficiently propagate the uncertainty on the model's parameters of K+ channel to the gating variables as well as the current density. In this way, we can estimate the model predictions and their corresponding confidence intervals simultaneously. A generalized polynomial chaos (gPC) expansion approximating the parametric uncertainty is used in combination with the physical models to quantify and propagate the parametric uncertainties onto the modeled predictions of steady state activation and steady state inactivation of the K+ channel. Using Galerkin projection, the variation (i.e., confidence interval) of the gating variables resulting from the uncertainty of model parameters can then be estimated in a computationally efficient fashion. As compared with the Monte Carlo (MC) simulations, the proposed methodology shows it's advantageous in terms of computational efficiency and accuracy, thus demonstrating the potential for dealing with more complicated cardiac models.

Detection of the propagating direction of electrical wavefront in atrial fibrillation.

Atrial Fibrillation (AF) is one of the most common sustained arrhythmia, which can increase the risk of heart failure and stroke. Understanding the complex electrical dynamics of AF and correctly targeting AF sources for ablation therapies remain challenging in clinical practice. This is due to the incapability to reconstruct the electrical dynamic of AF, and lack of efficient approach for AF source identification. This paper builds a multi-sale framework for modeling of the abnormal electrical propagation in AF initiated by triggers from Pulmonary Veins (PVs). A new algorithm is developed to detect the propagating direction of electrical wavefronts. The detection algorithm is further validated using modeling results. The developed multi-scale framework and the detection algorithm will contribute to AF diagnosis and potentially improve the treatment outcomes of AF ablations.

Parallel computing simulation of electrical excitation and conduction in the 3D human heart.

A correctly beating heart is important to ensure adequate circulation of blood throughout the body. Normal heart rhythm is produced by the orchestrated conduction of electrical signals throughout the heart. Cardiac electrical activity is the resulted function of a series of complex biochemical-mechanical reactions, which involves transportation and bio-distribution of ionic flows through a variety of biological ion channels. Cardiac arrhythmias are caused by the direct alteration of ion channel activity that results in changes in the AP waveform. In this work, we developed a whole-heart simulation model with the use of massive parallel computing with GPGPU and OpenGL. The simulation algorithm was implemented under several different versions for the purpose of comparisons, including one conventional CPU version and two GPU versions based on Nvidia CUDA platform. OpenGL was utilized for the visualization / interaction platform because it is open source, light weight and universally supported by various operating systems. The experimental results show that the GPU-based simulation outperforms the conventional CPU-based approach and significantly improves the speed of simulation. By adopting modern computer architecture, this present investigation enables real-time simulation and visualization of electrical excitation and conduction in the large and complicated 3D geometry of a real-world human heart.

Effect of microglia inhibition on GABAB receptor expression in the spinal cord in a rat model of neuropathic pain / 中华麻醉学杂志

Objective To investigate the effects of minocycline,a selective microglia inhibitor on dorsal GABAB receptor expression in the spinal cord in a rat model of neuropathic pain and the possible mechanism.Methods Forty-eight male SD rats weighing 220-260 g were used in this study.Neuropathic pain was induced by ligation of L5 spinal nerve(SNL).The animals were randomly divided into 4 groups(n=12 each):Ⅰ sham operation;Ⅱ SNL;Ⅲ sham operation+intrathecal(IT)minocycline 50 μg;IV SNL+IT minecycline 50 μg.Paw withdrawal threshold to von Frey hair stimulation was measured before operation(baseline)and at post-surgery days 1,2,4,6,8,10,12,14,16,18 in 6 animals in each group.The GABABR2 expression in dorsal horn of spinal cord was detected by Western blot at the time point when paw withdrawal threshold to mechanical stimulation was the lowest in another six animals which did not undergo yon Frey hair stimulation test.Results The paw withdrawal threshold to mechanical stimuli and the GABABR2 expression in the dorsal horn of spinal cord were significantly lower in SNL group than in sham operation group.The decreased paw withdrawal threshold to von Frey hair stimulation and the down-regulated GABABR2 expression in the spinal cord induced by SNL were ameliorated by intrathecal administration of micmglia inhibitor- minocycline in group Ⅳ.Conclusion The mechanism of neuropathic pain mediated by microglia activation may be related to the inhibition of GABAB receptor activation.

Combined inhibitory effects of propofol and midazolam on macroscopic sodium currents in rat sympathetic ganglion neurons / 中国临床药理学与治疗学

AIM: To study the interactions of propofol and midazolam on the whole cell sodium channel currents in rat sympathetic ganglion neurons. METHODS: Whole cell patch clamp recordings were made from enzymatically isolated rat (7- 10 d ) superior cervical sympathetic ganglion neurons. Isobolographic analysis was applied to evaluate the potency of combinations of propofol and midazolam on Na + channel currents. RESULTS: Under V h= 80 mV and V t= 0 mV . Propofol and midazolam dose dependently blocked Na + currents with a mean drug concentration required to produce 50% current inhibition (IC 50 ): 33.12 ?mol?L -1 and 18.35 ?mol?L -1 ; clinically relevant concentrations of propofol and midazolam reduced Na + peak currents by 27.66 % (P

Inhibitory mechanisms of diazepam on macroscopic sodium currents in rat sympathetic ganglion neurons / 中国临床药理学与治疗学

Aim The effects of diazepam on the whole cell sodium currents in rat sympathetic ganglion neurons were studied to investigate the mechanisms by diazepam mediates hypotension. Methods Whole cell patch clamp recordings were performed on enzymatically isolated rat superior cervical sympathetic ganglion neurons. Results Diazepam dose dependently blocked the whole cell sodium currents. Under a V t of 0 mV and a V h of 80 mV 0.3 ?mol?L -1 diazepam reduced sodium peak currents by 14.76 %(P

The inhibition of sodium channel currents in rat sympathetic ganglion neurons by ropivacaine / 中华麻醉学杂志

Objective To investigate the effects of ropivacaine on the whole cell sodium currents in rat sympathetic ganglion neurons in order to determine whether sympathetic ganglion is involved in the ropivacaine cardiotoxity. Methods The sympathetic neurons were enzymatically isolated from the superior cervical ganglion. The effects of ropivacaine on the whole cell sodium channel currents were assessed using patch clamp technique. Results Ropivacaine blocked the whole cell sodium channel currents dose dependently. When the holding potential (Vh) was -80mV and Vt Omv , 0.01?mol/L ropivacaine reduced peak currents by 30.02% with a mean IC50 of 2.68?mol/L. The blockade was also potential dependent. When Vh was -60mv, the mean IC50 was 1.55?mol/l. 1.0?mol/L ropivacaine reduced the peak value of I V curve by 30.66% but did not affect the shape of I V curve and caused 2.56mv shift of voltage dependence activation curve to depolarized potentials and 3.56mv shift of steady state inactivation curve to more hyperdepolarized potentials.The conditioning pulse potential at which half maximal channels were activated (V1/2), changed from -52.99mv to -56.44mv and the test potential at which half maximal channels were activated (V1/2), changed from -25.2mv to -22.64mv. Conclusions Subconvulsive concentration of ropivacaine significantly inhibits sympathetic ganglion neurons in a dose dependent and potential dependent way through the inactivation of sodium channel,indicating that sympathetic ganglion neurons may contribute to the cardiotoxity of ropivacaine.

Expression of mRNA for isoforms of GABA_B receptor in the spinal cord in a rat model of chronic neuropathic pain / 中华麻醉学杂志

Objective To investigate the effect of GABAB receptor in spinal cord by detecting semi-quantitatively the mRNA for isoforms of GABAB receptor in a chronic neuropathic pain model. Methods Twenty-four male SD rats weighing 200-250g were anesthetized with intraperitoneal pentobarbital. Lamina of L5 vertebra and superior articular process of L6 were removed and posterior root of left L5 spinal nerve was exposed and tightly ligated with 7/0 atraumatic suture. The animals were randomly divided into 4 groups of 6 animals in each group: group A in which animals were observed for 7 days after sham operation; group B in which animals were observed for 7 days after ligation of posterior root of L5 spinal nerve; in group C animals were observed for 14 days after sham operation and in group D animals were observed for 14 days after ligation. Pain threshold was measured by heat stimulation of bilateral hindlimbs before and on the 1st , 3rd , 7th , 10th and 14th day after operation. Lumbar spinal cord was removed on the 7th or 14th day after operation and mRNA for isoforms of GABAB receptor in the spinal cord was detected semi-quantitatively by digoxin hybridization in situ.Results Pain threshold of left hindlimb (ligated side) was significantly lower than that of right hindlimb on the 7th, 10th and 14th day after operation as measured by heat stimulation. There were less mRNA for three isoforms of GABAB receptor in group B and D as compared with group A and C respectively. Conclusion The gene expression of three isoforms of GABAB receptor in the spinal cord has plasticity and is reduced during chronic neuropathic pain.

Clinical assessment of the effect of intravenous PCA and epidural PCA in postoperative analgesia / 中华麻醉学杂志

To compare the clinical effect and side-effect of intravenous PCA(PCIA) with epidural PCA (PCEA). Method: One hundred and eighty postoperative patients, who were randomly divided into three groups: group PCIA, group PCEA and control, were observed for 3 days after operation. Result: Overall patients in two PCA groups were satisfied with the postoperative analgesia. The incidence of urinary retention in group PCIA were significantly lower than that in group PCEA (P0.05). 10% in group PCIA were in medium sedation whereas no eases in group PCEA were in sedation. At 6th hour after operation,serum cortisol level of control patients was much higher than that of PCA patients. Conclusion=Both PCIA and PCEA have excellent analgesia and reduce stress response after operation. PClA has lower incidence of urinary retention and is performed easily,but inhibits gastrointestinal motility much more and has higher sedative incidence compared with PCEA.