Glucocorticoid effects on Fos immunoreactivity and NADPH-diaphorase histochemical staining following spinal cord injury

Antinociceptive effects of vitamin B-complex: A behavioral and histochemical study in rats

B-vitamins have been evaluated as a useful adjuvant therapy to treat pain. In spite of clinical and experimental evidence indicating the analgesic effect of B-vitamins, few studies have investigated their effect on aspects of the inflammatory pain response. In the present study, we investigated the analgesic effect of chronic application of B-complex vitamins (Neurobion) using an inflammatory experimental pain model in rats. Nociceptive behavioral responses were evaluated in male Wistar rats after plantar injection of formalin, comparing the treatment group (TG) with Neurobion pretreatment to the control group (CG) without the pretreatment. In addition, neuronal activity in the central pain pathway was evaluated using c-Fos immunohistochemical reactivity and NADPH-d histochemistry. A highly significant reduction of painful behaviors such as licking and flinching were observed in TG, especially during the secondary phase of the formalin test compared to CG. Results suggest that long-term pre-treatment using Neurobion can have a beneficial effect in reducing the chronic phase of pain. In addition, we observed a downregulation of c-Fos and NADPH-d in dorsal spinal neurons, suggesting that the antinociceptive effect induced by Neurobion could be due to a suppression of nociceptive transmission at the spinal level, particularly in the afferent regions of the dorsal spinal horn, which these neurons utilizing nitric oxide at least as one of their pain neurotransmitters.

Preoperative anxiety induces chronic postoperative pain by activating astrocytes in the anterior cingulate cortex region

OBJECTIVE

The study aims to explore the relationship between preoperative anxiety and chronic postoperative pain.

METHODS

A total of forty rats were divided into four groups, control, single-prolonged stress alone, Hysterectomy alone, and SPS+ Hysterectomy. The paw withdrawal mechanical thresholds (PWMT) were examined. qRT-PCR and western blotting assay were performed to detect the GFAP expression in astrocytes isolated from the anterior cingulate cortex (ACC) region. In addition, the long-term potentiation (LTP) in ACC was examined.

RESULTS

Rats in the SPS group or the Hysterectomy alone group had no significant effect on chronic pain formation, but SPS can significantly induce chronic pain after surgery. Astrocytes were still active, and the LTP was significantly increased three days after modeling in the SPS+Hysterectomy group.

CONCLUSIONS

anxiety can induce chronic pain by activating astrocytes in the ACC region.

Spinal neuronal activation during locomotor-like activity enabled by epidural stimulation and 5-hydroxytryptamine agonists in spinal rats

The neural networks that generate stepping in complete spinal adult rats remain poorly defined. To address this problem, we used c-fos (an activity-dependent marker) to identify active interneurons and motoneurons in the lumbar spinal cord of adult spinal rats during a 30-min bout of bipedal stepping. Spinal rats were either step trained (30 min/day, 3 days/week, for 7.5 weeks) or not step trained. Stepping was enabled by epidural stimulation and the administration of the serotonergic agonists quipazine and 8-OHDPAT. A third group of spinal rats served as untreated (no stimulation, drugs, or stepping) controls. The numbers of activated cholinergic central canal cluster cells and partition neurons were higher in both step-trained and nontrained rats than in untreated rats and were higher in nontrained than in step-trained rats. The latter finding suggests that daily treatment with epidural stimulation plus serotonergic agonist treatment without step training enhances the excitability of a broader cholinergic interneuronal population than does step training. The numbers of activated interneurons in laminae II-VI of lumbar cross-sections were higher in both step-trained and nontrained rats than in untreated rats, and they were highest in step-trained rats. This finding suggests that this population of interneurons is responsive to epidural stimulation plus serotonergic treatment and that load-bearing induced when stepping has an additive effect. The numbers of activated motoneurons of all size categories were higher in the step-trained group than in the other two groups, reflecting a strong effect of loading on motoneuron recruitment. In general, these results indicate that the spinal networks for locomotion are similar with and without brain input.

SIGNIFICANCE

We identified neurons within the spinal cord networks that are activated during assisted stepping in paraplegic rats. We stimulated the spinal cord and administered a drug to help the rats step. One group was trained to step and another was not trained. We observed a lower percentage of activated neurons in specific spinal cord regions in trained rats than in nontrained rats after a 1-hr stepping bout, suggesting that step training reduces activation of some types of spinal neurons. This observation indicates that training makes the spinal networks more efficient and suggests a "learning" phenomenon in the spinal cord without any brain input.

NADPH-d and Fos reactivity in the rat spinal cord following experimental spinal cord injury and embryonic neural stem cell transplantation

AIMS

The aim of this study is to determine the role of nitric oxide (NO) in neuropathic pain and the effect of embryonic neural stem cell (ENSC) transplantation on NO content in rat spinal cord neurons following spinal cord injury (SCI).

MAIN METHODS

Ninety adult male Sprague-Dawley rats were divided into 3 groups (n=30, each): control (laminectomy), SCI (hemisection at T12-T13 segments) and SCI+ENSC. Each group was further divided into sub-groups (n=5 each) based on the treatment substance (L-NAME, 75 mg/kg/i.p.; L-arginine, 225 mg/kg/i.p.; physiological saline, SF) and duration (2h for acute and 28 days for chronic groups). Pain was assessed by tail flick and Randall-Selitto tests. Fos immunohistochemistry and NADPH-d histochemistry were performed in segments 2 cm rostral and caudal to SCI.

KEY FINDINGS

Tail-flick latency time increased in both acute and chronic L-NAME groups and increased in acute and decreased in chronic L-arginine groups. The number of Fos (+) neurons decreased in acute and chronic L-NAME and decreased in acute L-arginine groups. Following ENSC, Fos (+) neurons did not change in acute L-NAME but decreased in the chronic L-NAME groups, and decreased in both acute and chronic L-arginine groups. NADPH-d (+) neurons decreased in acute L-NAME and increased in L-arginine groups with and without ENSC transplantation.

SIGNIFICANCE

This study confirms the role of NO in neuropathic pain and shows an improvement following ENSC transplantation in the acute phase, observed as a decrease in Fos(+) and NADPH-d (+) neurons in spinal cord segments rostral and caudal to injury.

NADPH-d/NOS reactivity in the lumbar dorsal horn of congenitally hypothyroid pups before and after formalin pain induction

We have previously demonstrated that congenitally hypothyroid rat pups exhibit altered behavioral response to formalin pain induction during postnatal period. In the present study, using NADPH-diaphorase histochemistry and NOS immunostaining, we investigated the effect of congenital hypothyroidism on the NOS expression in spinal cord of intact neonates at postnatal days of 15 and 21. We also examined the effect of thyroid dysfunction on the NADPH-d/NOS expression in response to formalin nociception. Congenital hypothyroidism induced by propylthiouracil (PTU) treatment started from gestational day 16 and continued to postnatal day 15 or 21. Congenitally hypothyroid pups exhibited marked reduction in NADPH-d reactive cells (84% and 66% in P15 and P21, respectively; P<0.001) and NOS-ir cells (52% and 91% in P15 and P21, respectively; P<0.001) in superficial lumbar dorsal horn laminae (I-II) as compared to that of normal pups. Moreover, in congenitally hypothyroid pups the NADPH-d/NOS expression following hindpaw formalin injection did not change significantly. Our results demonstrate that congenital hypothyroidism affect developmental expression of NOS in spinal dorsal horn, which may in part explain the altered behavioral pain response as we previously reported in hypothyroid pups.

Combination of dexamethasone and etanercept reduces secondary damage in experimental spinal cord trauma

The aim of our study was to evaluate the therapeutic efficacy of combination therapy with etanercept and dexamethasone (DEX) in vivo in experimental murine model of spinal cord trauma, which was induced by the application of vascular clips (force of 24 g) to the dura via a four-level T5-T8 laminectomy. Spinal cord injury in mice resulted in severe trauma characterized by edema, neutrophil infiltration, and cytokine production followed by recruitment of other inflammatory cells, production of inflammation mediators, tissue damage, apoptosis and disease. Treatment of the mice with etanercept (1.25 mg/kg) and DEX (0.025 mg/kg) when administered as a combination therapy but not as a single treatment significantly reduced the degree of (1) spinal cord inflammation and tissue injury (histological score), (2) infiltration of neutrophils (MPO evaluation), (3) inducible nitric oxide synthase, nitrotyrosine, and cytokines expression (tumor necrosis factor-alpha and interleukin-1 beta), (4) and apoptosis (Terminal deoxynucleotidyltransferase-mediated UTP end labeling staining, Fas-ligand expression and Bax and Bcl-2 expression). In a separate set of experiments we have also clearly demonstrated that the combination therapy significantly ameliorated the recovery of limb function (evaluated by motor recovery score). Taken together, our results clearly demonstrate for the first time that strategies targeting multiple proinflammatory pathways may be more effective than a single effector molecule for the treatment of spinal cord trauma.

Identification of corticosteroid-regulated genes in cardiomyocytes by serial analysis of gene expression

Corticosteroids (aldosterone, cortisol/corticosterone) exert direct functional effects on cardiomyocytes. However, gene networks activated by corticosteroids in cardiomyocytes, as well as the involvement of the mineralocorticoid receptor (MR) vs the glucocorticoid receptor (GR) in these effects, remain largely unknown. Here we characterized the corticosteroid-dependent transcriptome in primary culture of neonatal mouse cardiomyocytes treated with 10(-6) M aldosterone, a concentration predicted to occupy both MR and GR. Serial analysis of gene expression revealed 101 aldosterone-regulated genes. The MR/GR specificity was characterized for one regulated transcript, namely ecto-ADP-ribosyltransferase-3 (Art3). Using cardiomyocytes from GR(null/null) or MR(null/null) mice we demonstrate that in GR(null/null) cardiomyocytes the response is abrogated, but it is fully maintained in MR(null/null) cardiomyocytes. We conclude that Art3 expression is regulated exclusively via the GR. Our study identifies a new set of corticosteroid-regulated genes in cardiomyocytes and demonstrates a new approach to studying the selectivity of MR- vs GR-dependent effects.

DT-diaphorase: a target for new anticancer drugs

DT-diaphorase (DTD) is an obligate two-electron reductase which bioactivates chemotherapeutic quinones. DTD levels are elevated in a number of tumour types, including non-small cell lung carcinoma, colorectal carcinoma, liver cancers and breast carcinomas, when compared to the surrounding normal tissue. The differential in DTD between tumour and normal tissue should allow targeted activation of chemotherapeutic quinones in the tumour whilst minimising normal tissue toxicity. The prototypical bioreductive drug is Mitomycin C (MMC) which is widely used in clinical practice. However, MMC is actually a relatively poor substrate for DTD and its metabolism is pH-dependent. Other bioreductive drugs have failed because of poor solubility and inability to surpass other agents in use. RH1, a novel diaziridinylbenzoquinone, is a more efficient substrate for DTD. It has been demonstrated to have anti-tumour effects both in vitro and in vivo and demonstrates a relationship between DTD expression levels and drug response. RH1 has recently entered a phase I clinical trial in solid tumours under the auspices of Cancer Research UK. Recent work has demonstrated that DTD is present in the nucleus and is associated with both p53 and the heat shock protein, HSP-70. Furthermore, DTD is inducible by several non-toxic compounds and therefore much interest has focussed on increasing the differential in DTD levels between tumour and normal tissues.

Acute and delayed restraint stress-induced changes in nitric oxide producing neurons in limbic regions

RATIONALE

Microinjection into the dentate gyrus of the hippocampus of N(omega)-nitro-l-arginine methyl ester hydrochloride (l-NAME), a nitric oxide synthase (NOS) inhibitor, induces antinociceptive effect 5 days after a single restraint episode. The mechanisms of this stress-antinociceptive modulatory effect have not been investigated but may involve plastic changes in the hippocampal formation (HF).

OBJECTIVE

The objective of the present study was to investigate possible mechanisms of the stress-modulating effect on antinociception induced by NOS inhibition in the hippocampus. We analyzed the effects of restraint stress on neuronal NOS (nNOS) expression and nicotinamide adenine dinucleotide phosphate-diaphorase histochemical activity (NADPH-d) in the HF and related brain regions.

METHODS

Male Wistar rats (n=6-11/group) were submitted to a single (acute stress) or repeated (5 days) episodes of 2-h restraint. Control animals remained in their home cages being all animals daily handled during this period. In the fifth day, animals received unilateral microinjection of l-NAME (150 nmol/0.2 microl) or saline (control) into the dentate gyrus of the dorsal hippocampus (DG). Immediately before and after drug microinjection tail-flick reflex latency or hotplate licking reaction was measured. Animals were killed i. immediately; ii. 5 days after acute stress; or iii. after repeated stress. NADPH-d and nNOS expression were quantified in the HF, caudate-putamen, secondary somatosensorial, entorhinal and piriform cortices and amygdaloid complex.

RESULTS

Five days after one or five restraint episodes l-NAME microinjection into the DG elicited antinociceptive effect (analysis of variance [ANOVA], P<0.05). Acute restraint stress induced a significant increase in the density of neurons expressing NADPH-d and nNOS in the amygdaloid nuclei. nNOS expression increased also in the DG and piriform cortex. Five days after a single or repeated restraint stress there was an additional increase in NADPH-d- and nNOS-positive neurons in CA1, CA3, and entorhinal cortex. No changes were seen in non-limbic regions such as the caudate-putamen and secondary somatosensorial cortex.

CONCLUSION

The results confirm that the dorsal hippocampus participates in the modulation of stress consequences. They also show that a single stress episode causes acute changes in nitric oxide system in the amygdala complex and delayed modifications in the HF. The delayed (5 days) antinociceptive effect of NOS inhibition in the HF after a single restraint episode suggests that those latter modifications may have functional consequences. It remains to be tested if the acute amygdala and delayed hippocampal changes are causally related.

Influence of estradiol on NADPH diaphorase/neuronal nitric oxide synthase activity and colocalization with progesterone or type II glucocorticoid receptors in ovine hypothalamus

Nitric oxide (NO) has been shown to play an important role in both the neuroendocrine reproductive and stress axes, which are closely linked. Because progesterone (P4) receptors (PRs) and glucocorticoid receptors (GRs) are not found in GnRH neurons and the NOergic system has been implicated in the control of GnRH secretion, this study aimed to ascertain whether steroids altered the NOergic system. Our first objective was to map the distribution of NO synthase (NOS) cells in the ovine preoptic area (POA) and hypothalamus and to determine whether NOS activity is enhanced by estradiol (E2) treatment. Using NADPH diaphorase (NADPHd) histochemistry, we found that NADPHd-positive neurons were spread throughout the ovine POA and hypothalamus, and that all NADPHd cells were immunoreactive for NOS. In response to estradiol, a significant increase in the number of NADPHd cells was noted only in the ventrolateral region of the ventromedial nucleus (VMNvl), with no significant difference in the POA or arcuate nucleus. Progesterone and glucocorticoid receptors were colocalized with NADPHd reactive neurons in the POA, arcuate nucleus, and VMNvl of ewes in both treatment groups. In ewes receiving estradiol, the number of NADPHd-positive cells containing steroid receptors in the POA (PR, 81%; GR, 79%) and arcuate nucleus (PR, 89%; GR, 84%) was similar, but in the VMNvl, fewer NADPHd-positive cells contained GR (PR, 88%, GR, 31%). These data show that estradiol up-regulates NOS activity in a site-specific manner and that the influence and possible interaction of progesterone and corticosteroids on NO producing cells may differ according to the neural location.