Endogenous nitric oxide inhibits spinal NMDA receptor activity and pain hypersensitivity induced by nerve injury.

The role of nitric oxide (NO) in nociceptive transmission at the spinal cord level remains uncertain. Increased activity of spinal N-methyl-d-aspartate (NMDA) receptors contributes to development of chronic pain induced by peripheral nerve injury. In this study, we determined how endogenous NO affects NMDA receptor activity of spinal cord dorsal horn neurons in control and spinal nerve-ligated rats. Bath application of the NO precursor l-arginine or the NO donor S-nitroso-N-acetylpenicillamine (SNAP) significantly inhibited NMDA receptor currents of spinal dorsal horn neurons in both sham control and nerve-injured rats. Inhibition of neuronal nitric oxide synthase (nNOS) or blocking the S-nitrosylation reaction with N-ethylmaleimide abolished the inhibitory effects of l-arginine on NMDA receptor currents recorded from spinal dorsal horn neurons in sham control and nerve-injured rats. However, bath application of the cGMP analog 8-bromo-cGMP had no significant effects on spinal NMDA receptor currents. Inhibition of soluble guanylyl cyclase also did not alter the inhibitory effect of l-arginine on spinal NMDA receptor activity. Furthermore, knockdown of nNOS with siRNA abolished the inhibitory effects of l-arginine, but not SNAP, on spinal NMDA receptor activity in both groups of rats. Additionally, intrathecal injection of l-arginine significantly attenuated mechanical or thermal hyperalgesia induced by nerve injury, and the l-arginine effect was diminished in rats treated with a nNOS inhibitor or nNOS-specific siRNA. These findings suggest that endogenous NO inhibits spinal NMDA receptor activity through S-nitrosylation. NO derived from nNOS attenuates spinal nociceptive transmission and neuropathic pain induced by nerve injury.

Risk Factor Analysis for In-hospital Mortality in Patients With Non-ST Segment Elevation Myocardial Infarction in China / 中国循环杂志

Objective:To explore the risk factors for in-hospital mortality in patients with non-ST segment elevation myocardial infarction (NSTEMI) in China.Methods:The information of 5816 NSTEMI patients from 2013-01 to 2014-09 by China Acute Myocardial Infarction (CAMI) registry were extracted.Our research included in 2 groups:In-hospital death group,n=352 and In-hospital survival group,n=5464.The baseline condition,laboratory examination,treatment and the in-hospital outcomes were collected;the independent risk factors for in-hospital mortality were studied by multivariable Logistic regression analysis.Results:6.05％ (352/5816) patients died during hospitalization.The baseline conditions were different between 2 groups.Multivariable Logistic regression analysis indicated that age,BMI,systolic blood pressure,Killip classification,heart arrest,ST-segment depression in ECG,new onset of Complete left bundle branch block,serum creatinine,white blood cells,Count nonsmoker,previous history of MI and PCI were the independent risk factors for in-hospital mortality in NSTEMI patients.Conclusion:The above 12 variables were the independent risk factors for in-hospital mortality in NSTEMI patients which should be helpful for identifying the high risk patients at the early stage in clinical practice.

Risk Factor Analysis for In-hospital Mortality in Patients With Non-ST Segment Elevation Myocardial Infarction in China / 中国循环杂志

Objective:To explore the risk factors for in-hospital mortality in patients with non-ST segment elevation myocardial infarction (NSTEMI) in China.Methods:The information of 5816 NSTEMI patients from 2013-01 to 2014-09 by China Acute Myocardial Infarction (CAMI) registry were extracted.Our research included in 2 groups:In-hospital death group,n=352 and In-hospital survival group,n=5464.The baseline condition,laboratory examination,treatment and the in-hospital outcomes were collected;the independent risk factors for in-hospital mortality were studied by multivariable Logistic regression analysis.Results:6.05％ (352/5816) patients died during hospitalization.The baseline conditions were different between 2 groups.Multivariable Logistic regression analysis indicated that age,BMI,systolic blood pressure,Killip classification,heart arrest,ST-segment depression in ECG,new onset of Complete left bundle branch block,serum creatinine,white blood cells,Count nonsmoker,previous history of MI and PCI were the independent risk factors for in-hospital mortality in NSTEMI patients.Conclusion:The above 12 variables were the independent risk factors for in-hospital mortality in NSTEMI patients which should be helpful for identifying the high risk patients at the early stage in clinical practice.

Nitric oxide inhibits nociceptive transmission by differentially regulating glutamate and glycine release to spinal dorsal horn neurons.

Nitric oxide (NO) is involved in many physiological functions, but its role in pain signaling remains uncertain. Surprisingly, little is known about how endogenous NO affects excitatory and inhibitory synaptic transmission at the spinal level. Here we determined how NO affects excitatory and inhibitory synaptic inputs to dorsal horn neurons using whole-cell recordings in rat spinal cord slices. The NO precursor L-arginine or the NO donor SNAP significantly increased the frequency of glycinergic spontaneous and miniature inhibitory postsynaptic currents (IPSCs) of lamina II neurons. However, neither L-arginine nor SNAP had any effect on GABAergic IPSCs. L-arginine and SNAP significantly reduced the amplitude of monosynaptic excitatory postsynaptic currents (EPSCs) evoked from the dorsal root with an increase in paired-pulse ratio. Inhibition of the soluble guanylyl cyclase abolished the effect of L-arginine on glycinergic IPSCs but not on evoked monosynaptic EPSCs. Also, inhibition of protein kinase G blocked the increase in glycinergic sIPSCs by the cGMP analog 8-bromo-cGMP. The inhibitory effects of L-arginine on evoked EPSCs and high voltage-activated Ca(2+) channels expressed in HEK293 cells and dorsal root ganglion neurons were abolished by blocking the S-nitrosylation reaction with N-ethylmaleimide. Intrathecal injection of L-arginine and SNAP significantly increased mechanical nociceptive thresholds. Our findings suggest that spinal endogenous NO enhances inhibitory glycinergic input to dorsal horn neurons through sGC-cGMP-protein kinase G. Furthermore, NO reduces glutamate release from primary afferent terminals through S-nitrosylation of voltage-activated Ca(2+) channels. Both of these actions probably contribute to inhibition of nociceptive transmission by NO at the spinal level.

Variants of neural nitric oxide synthase in the spinal cord of neuropathic rats and their effects on nuclear factor-kappaB (NF-kappaB) activity in PC12 cells.

UNLABELLED: Neuropathic pain due to nerve injury is associated with overactivity of spinal N-methyl-D-aspartate (NMDA) receptors and nitric oxide synthases (NOS). Spinal NOS and NMDA receptors could act in a concerted manner to excite each other in nociceptive signaling. Among the 3 major NOS isoforms, neuronal NOS (nNOS) has the most functional relationship with NMDA receptors through a PDZ-PDZ (PSD-95, Dlg, ZO-1 homology) postsynapse interaction. However, some nNOS variants lack the PDZ domain, which may result in the changes in the interaction with the NMDA receptor and subsequent localization and enzymatic activity. The aim of this study was to determine which nNOS variants are expressed in the spinal cord in neuropathic rats and deduce their role in neuropathic pain by testing the effects of these kinds of nNOS on nuclear factor-kappaB (NF-kappaB) activity in PC12 cells. Western blot analysis revealed that there were at least 3 bands of nNOS (155, 135, and 125 kDa) in the spinal cord and, moreover, that nNOS at 135 kDa decreased significantly after development of neuropathic pain. 5'-RACE-PCR and Southern blots determined that the nNOS at 155 and 135 kDa corresponded to nNOSalpha and nNOSbeta, respectively, which was confirmed by RT-PCR. PC12 cells transfected with the nNOSalpha gene had no effect on NF-kappaB activity, but nNOSbeta without the PDZ domain significantly decreased that in PC12 cells. Considering the importance of spinal NF-kappaB signaling in neuropathic rat, it could be concluded that changes in spinal nNOS variants and quantity after peripheral nerve injury implicate nNOS in the generation of neuropathic pain. PERSPECTIVE: This article presents data demonstrating that nNOS variants change in the spinal cord of the rats after neuropathic pain and result in differential effects on NF-kappaB activity in PC12 cells. These changes in nNOS variants and their different characteristics may account for the spinal NO paradox role in neuropathic pain. Furthermore, these data suggest that nNOSbeta may represent a new therapeutic target for the treatment of chronic neuropathic pain.

[The cellular location and significance of p38alpha/beta isoforms in the lumbar spinal cord of the bone cancer pain rats].

OBJECTIVE: To examine the cellular distribution and location of p38alpha/beta isoforms in the lumbar spinal cord of the bone cancer pain rats. METHODS: Twenty SD female rats weighing 180 - 220 g were randomly divided into 2 groups (n = 10 each): group A (control group): intra-tibial injection of 3 microl Hank's solution; group B (model group): intra-tibial injection of 3 microl MADB-106 mammary gland carcinoma cells of rats (4.8 x 10(3)/microl). Mechanical withdrawal threshold and radiant heat threshold of rats' hind paws were measured every other day from one day before operation until 14 days later. The lumbar 4 ~ 5 spinal cord was removed on the 14th day. The cellular distribution and location of the spinal p38alpha/beta immunoreactivity were detected by immunohistochemistry SABC and double immunofluorescence methods. RESULTS: No significant differences in mechanical withdrawal threshold and radiant heat threshold were found at all time points in group A. During the first 6 days of post-operation there was obvious difference in radiant heat stimulus between group A and B (P < 0.05); on the 14th day after operation, mechanical pain threshold and radiant heat threshold in group B were significantly different from that of group A (P < 0.05). The p38alpha/beta immunoreactivity of group B in laminae I approximately IV of dorsal horn showed stronger staining than group A (P < 0.05). Double immunofluorescence confocal micrographs showed that spinal p38alpha and the neuronal marker neuronal N (NeuN) were colocalized in the dorsal horn, indicating that p38alpha was expressed in neurons. Double immunofluorescence micrographs demonstrated that antibodies against p38beta and the microglia marker OX42 labeled the same cell, indicating that p38beta was expressed in microglia. CONCLUSION: Our studies indicate that p38alpha and p38beta are involved in the generation and maintenance of bone cancer pain states. p38alpha is predominantly expressed in neurons, while p38beta is expressed in microglia.

[Analgesic effect of intrathecal transplant of immortalized rat astrocyte strain genetically modified by human preproenkephalin gene on rat chronic neuropathic pain].

OBJECTIVE: To observe the analgesic effect of intrathecal transplant of immortalized rat astrocyte genetically modified by human preproenkephalin gene (IAST/hPPE) on chronic neuropathic pain. METHODS: 40 adult male Sprague-Dawley rats were randomly divided into four groups, 10 rats for each group. Naive group, SNI group, SNI + IAST group and SNI + IAST/hPPE group. The immortalized rat astrocyte (IAST) or IAST/hPPE co-incubated with bromodeoxyuridine (BrdU) in vitro were transplanted in the lumbar 4 to 6 subarachnoid space near the spinal cord 1 week after right side spared nerve injury (SNI). All animals were tested for bilateral 50% hindpaw withdrawal threshold (PWT) to a graded series of Von Frey hairs stimulation once a week from one week before SNI to six weeks after transplant, the difference value for right 50% PWT minus left 50% PWT was calculated and the effect of intraperitoneal naloxone on the analgesic efficacies was also observed. The content of L-EK in the spinal cord of L4 - 6 and was determined using immunohistochemistry and radioimmunoassay, and the expression of BrdU in grafts was determined using immunohistochemistry. RESULTS: Allodynia-like behaviour after 1 week following SNI was observed. As compared with Naive group, the difference value for the right 50% PWT minus left 50% PWT in the other three groups was higher significantly (P < 0.01). The tactile allodynia induced by SNI was significantly alleviated during the 1 to 6 week period after transplantation of IAST/hPPE cells, but transplants of IAST cells had no effect on the allodynia-like behaviour. The difference value for the right 50% PWT minus left 50% PWT in SNI + IAST/hPPE group was lower significantly than that in the SNI and SNI +I AST group (P < 0.01), but there was no significant difference between SNI and SNI + IAST group (P > 0.05). The efficacies were reversed by intraperitoneal naloxone in SNI + IAST/hPPE group. The content of L-EK in the lumbar spinal cord in IAST/hPPE group (108.1 pg/mg +/- 12.5 pg/mg) was significantly higher than that in other three groups (P < 0.01), but there was no significant difference between SNI and SNI + IAST group (25.4 pg/mg +/- 1.9 pg/mg vs 28.0 pg/mg +/- 2.1 pg/mg, P > 0.05). Furthermore, The grafts in the surface of dorsal horn were still stained positively for BrdU, they survived greater than 6 weeks on the pia mater around the spinal cord. CONCLUSION: Intrathecal transplant of IAST/hPPE cells could alleviate the allodynia-like behaviour after chronic neuropathic pain, which is associated with enkephalin secreted continuously from the grafts and conducted via opiate receptors.