Effects of treatment with a carbon monoxide-releasing molecule and a heme oxygenase 1 inducer in the antinociceptive effects of morphine in different models of acute and chronic pain in mice

Rationale

Treatment with a carbon monoxide-releasing molecule (tricarbonyldichlororuthenium(II) dimer, CORM-2) or a classical heme oxygenase 1 inducer (cobalt protoporphyrin IX, CoPP) has potent anti-inflammatory effects, but the role played by these treatments in the antinociceptive effects of morphine during acute and chronic pain was not evaluated.

Objectives

In wild type (WT), neuronal (NOS1-KO), or inducible (NOS2-KO) nitric oxide synthases knockout mice, we evaluated the effects of CORM-2 and CoPP treatments in the antinociceptive actions of morphine and their interaction with nitric oxide during acute, visceral, and chronic inflammatory or neuropathic pain.

Methods

Acute and visceral pain was assessed through formalin and acid acetic writhing tests. Chronic inflammatory pain induced by the intra-articular administration of complete Freund’s adjuvant and neuropathic pain by partial ligation of sciatic nerve were evaluated by measuring allodynia and hyperalgesia using the von Frey filaments, plantar, or cold plate tests.

Results

While nitric oxide, synthetized by NOS1 and/or NOS2, increased the local antinociceptive effects of morphine during acute and chronic pain, it decreased the inhibitory effects of morphine after visceral pain. Moreover, while CORM-2 or CoPP treatments did not alter or reduced the antinociceptive effects of morphine during acute and visceral pain, both treatments improved the local antiallodynic and antihyperalgesic effects of morphine after chronic inflammatory or neuropathic pain in WT, but not in KO mice.

Conclusions

CORM-2 and CoPP treatments improved the local antinociceptive effects of morphine during chronic inflammatory and neuropathic pain by interaction with nitric oxide synthetized by NOS1 and NOS2 isoforms.     

Carbon monoxide-releasing molecules (CO-RMs) attenuate the inflammatory response elicited by lipopolysaccharide in RAW264.7 murine macrophages

The enzyme heme oxygenase-1 (HO-1) is a cytoprotective and anti-inflammatory protein that degrades heme to produce biliverdin/bilirubin, ferrous iron and carbon monoxide (CO). The anti-inflammatory properties of HO-1 are related to inhibition of adhesion molecule expression and reduction of oxidative stress, while exogenous CO gas treatment decreases the production of inflammatory mediators such as cytokines and nitric oxide (NO). CO-releasing molecules (CO-RMs) are a novel group of substances identified by our group that are capable of modulating physiological functions via the liberation of CO. We aimed in this study to examine the potential anti-inflammatory characteristics of CORM-2 and CORM-3 in an in vitro model of lipopolysaccharide (LPS)-stimulated murine macrophages. Stimulation of RAW264.7 macrophages with LPS resulted in increased expression of inducible NO synthase (iNOS) and production of nitrite. CORM-2 or CORM-3 (10-100 microM) reduced nitrite generation in a concentration-dependent manner but did not affect the protein levels of iNOS. CORM-3 also decreased nitrite levels when added 3 or 6 h after LPS exposure. CORM-2 or CORM-3 did not cause any evident cytotoxicity and produced an increase in HO-1 expression and heme oxygenase activity; this effect was completely prevented by the thiol donor N-acetylcysteine. CORM-3 also considerably reduced the levels of tumor necrosis factor-alpha, another mediator of the inflammatory response. The inhibitory effects of CORM-2 and CORM-3 were not observed when the inactive compounds, which do not release CO, were coincubated with LPS. These results indicate that CO liberated by CORM-2 and CORM-3 significantly suppresses the inflammatory response elicited by LPS in cultured macrophages and suggest that CO carriers can be used as an effective strategy to modulate inflammation.     

Sigma-1 receptor inhibition reverses acute inflammatory hyperalgesia in mice: role of peripheral sigma-1 receptors

Rationale

Sigma-1 (σ₁) receptor inhibition ameliorates neuropathic pain by inhibiting central sensitization. However, it is unknown whether σ₁ receptor inhibition also decreases inflammatory hyperalgesia, or whether peripheral σ₁ receptors are involved in this process.

Objective

The purpose of this study was to determine the role of σ₁ receptors in carrageenan-induced inflammatory hyperalgesia, particularly at the inflammation site.

Results

The subcutaneous (s.c.) administration of the selective σ₁ antagonists BD-1063 and S1RA to wild-type mice dose-dependently and fully reversed inflammatory mechanical (paw pressure) and thermal (radiant heat) hyperalgesia. These antihyperalgesic effects were abolished by the s.c. administration of the σ₁ agonist PRE-084 and also by the intraplantar (i.pl.) administration of this compound in the inflamed paw, suggesting that blockade of peripheral σ₁ receptors in the inflamed site is involved in the antihyperalgesic effects induced by σ₁ antagonists. In fact, the i.pl. administration of σ₁ antagonists in the inflamed paw (but not in the contralateral paw) was sufficient to completely reverse inflammatory hyperalgesia. σ₁ knockout (σ₁-KO) mice did not develop mechanical hyperalgesia but developed thermal hypersensitivity; however, the s.c. administration of BD-1063 or S1RA had no effect on thermal hyperalgesia in σ₁-KO mice, supporting on-target mechanisms for the effects of both drugs. The antiedematous effects of σ₁ inhibition do not account for the decreased hyperalgesia, since carrageenan-induced edema was unaffected by σ₁ knockout or systemic σ₁ pharmacological antagonism.

Conclusions

σ₁ receptors play a major role in inflammatory hyperalgesia. Targeting σ₁ receptors in the inflamed tissue may be useful for the treatment of inflammatory pain.     

Peripheral antinociceptive effects of µ- and δ-opioid receptor agonists in NOS2 and NOS1 knockout mice during chronic inflammatory pain

The aim of this study is to investigate the involvement of nitric oxide synthesized by the inducible (NOS2) or neuronal (NOS1) nitric oxide synthases in the local antinociceptive effects produced by µ- and δ-opioid receptor agonists during chronic inflammatory pain. Peripheral inflammatory pain was induced in NOS2 and NOS1 knockout mice and their wild type littermates by the subplantar administration of complete Freund's adjuvant (30 µl). The presence of paw inflammation, mechanical allodynia and thermal hyperalgesia induced by complete Freund's adjuvant were assessed by measuring paw diameter and using the von Frey filaments and plantar tests, respectively. During chronic inflammation, NOS2 deficient mice have a more rapid recovery of paw edema and a reduced thermal hyperalgesia compared to wild type. In contrast, a reduced paw edema and mechanical allodynia, as well as a modest rapid recovery from thermal hyperalgesia were observed in NOS1 knockout mice compared to wild type. The thermal hyperalgesia induced by complete Freund's adjuvant was not completely reversed by the subplantar administration of morphine (days 4 and 7) or [d-Pen ^2,5] enkephalin (DPDPE) (days 1 and 4) in NOS2 knockout mice as occurs in wild type mice. Moreover, the local administration of morphine or DPDPE also failed to reverse the decrease of ipsilateral paw withdrawal latency induced by complete Freund's adjuvant in NOS1 knockout mice throughout 10 days of peripheral inflammation. These results indicate the different roles played by nitric oxide synthesized by NOS2 or NOS1 in the maintenance of mechanical allodynia and thermal hyperalgesia induced by chronic inflammatory pain as well as, in the antinociceptive effects produced by µ- and δ-opioid receptor agonists during peripheral inflammatory pain.     

Exogenous carbon monoxide suppresses Escherichia coli vitality and improves survival in an Escherichia coli-induced murine sepsis model

Aim:

Endogenous carbon monoxide (CO) has been shown to modulate inflammation and inhibit cytokine production both in vivo and in vitro. The aim of this study was to examine whether exogenous carbon monoxide could suppress the vitality of Escherichia coli (E coli) and improve the survival rate in an E coli-induced murine sepsis model.

Methods:

ICR mice were infected with E coli, and immediately injected intravenously with carbon monoxide releasing molecule-2 (CORM-2, 8 mg/kg) or inactive CORM-2 (8 mg/kg). The survival rate was monitored 6 times daily for up to 36 h. The blood samples, liver and lung tissues were collected at 6 h after the infection. Bacteria in peritoneal lavage fluid, blood and tissues were enumerated following culture. Tissue iNOS mRNA expression was detected using RT-PCR. NF-κB expression was detected with Western blotting.

Results:

Addition of CORM-2 (200 and 400 μmol/L) into culture medium concentration-dependently suppressed the growth of E coli and decreased the colony numbers, but inactive CORM-2 had no effect. Treatment of the infected mice with CORM-2 significantly increased the survival rate to 55%, while all the infected mice treated with inactive CORM-2 died within 36 h. E coli infection caused severe pathological changes in liver and lungs, and significantly increased serum transaminases, lipopolysaccharide, TNF-α and IL-1β levels, as well as myeloperoxidase activity, TNF-α and IL-1β levels in the major organs. Meanwhile, E coli infection significantly increased the number of colonies and the expression of iNOS mRNA and NF-κB in the major organs. All these abnormalities were significantly attenuated by CORM-2 treatment, while inactive CORM-2 was ineffective.

Conclusion:

In addition directly suppressing E coli, CORM-2 protects the liver and lungs against E coli-induced sepsis in mice, thus improving their survival.     

Sex-influence of nicotine and nitric oxide on motor coordination and anxiety-related neurophysiological responses

Rationale

Nitric oxide (NO) is a messenger synthesized in both the neuronal and glial populations by nitric oxide synthase type 1 (NOS1). Nicotine regulates NO production in a sex-dependent manner, both molecules being involved in motor function.

Objective

The present study evaluates sex differences in motor coordination, general movement, and anxiety-related responses resulting from both constant and continuous nicotine treatment and the genetic depletion of NOS1 activity.

Methods

Male and female mice were analyzed with the open-field and the rotarod tests. To understand the role of NO, knockout mice for NOS1 (NOS1?/?) were analyzed. Nicotine was administered continuously at a dose of 24 mg/kg/day via osmotic mini-pumps over 14 days because the behavioral effects elicited are similar to those observed with discontinuous administration.

Results

Data analyses revealed noteworthy sex differences derived from NOS1 depletion. Control NOS1?/? males exhibited an exacerbated anxiety-related response in relation to control NOS1?/? females and control wild-type (WT) males; these differences disappeared in the nicotine-administered NOS1?/? males. Additionally, nicotine administration differentially affected the horizontal movements of NOS1?/? females with respect to WT animals. NO depletion affected male but not female motor coordination improvement along the test days. However, the drug affected female motor coordination only at the end of the administration period.

Conclusions

We show for the first time that NO affects motor and anxiety behaviors in a sex-dependent manner. Moreover, the behavioral effects of constant nicotine administration are dimorphic and dependent on NO production.     

HO-1/CO 信号通路对切口痛大鼠炎症因子的调控作用

目的 观察脊髓血红素氧合酶-1（HO-1）/CO 信号通路对切口痛大鼠炎症因子的调节作用及可能机制。方法 切口痛模型大鼠 36 只在实验即刻（0 h）, 术后 1、4、8、12 及 24 h 各处死 6 只, 取患侧脊髓腰膨大处, Western blot 法检测 HO-1 蛋白表达, 酶联免疫吸附试验（ELISA）法检测炎症因子肿瘤坏死因子-α（TNF-α）、白细胞介素（IL）-1β、IL-6 和高迁移率族蛋白 1（HMGB1）。 另外, 对照（C）组 36 只大鼠不做切口痛模型;切口痛模型大鼠 144 只按处理方式不同分为切口痛（IP）组, 切口痛+HO-1 诱导剂（IP+hemin）组, 术前给予腹腔注射大鼠 100 mg/kg 血红素（hemin）; 切口痛+HO-1 抑制剂（IP+Znpp-IX）组, 术前给予腹腔注射大鼠 45 μmoL/kg 锌原卟啉（Znpp）-IX; 切口痛+ CO 释放剂（IP+CORM-2）组, 于术前经腹腔注射给予 10 mg/kg 一氧化碳释放分子（CORM）-2。 各组于实验即刻（0 h）, 术后 1、4、8、12 及 24 h 行机械缩足阈值（PWMT）和热缩足潜伏期（PWTL）的检测, 应用 ELISA 法检测各组 TNF- α、IL-1β、IL-6 和 HMGB1 的表达情况。 结果 与 0 h 比较, 术后 1、4、8、12 及 24 h HO-1 蛋白表达水平和 TNF-α、 IL-1β、IL-6 和 HMGB1 均增高（P＜ 0.05）。 与 C 组比较, 其余组大鼠各时间点 PWMT 值和 PWTL 值减少, TNF-α、 IL-1β、IL-6 和 HMGB1 表达增加（P＜ 0.05）; 与 IP 组比较, IP+hemin 组和 IP+CORM-2 组大鼠 1、4、8、12 及 24 h 时 PWMT 值和 PWTL 值均增高, 而 TNF-α、IL-1β、IL-6 和 HMGB1 表达减少, IP+Znpp-IX 组 PWMT 值和 PWTL 值降低, 但 TNF-α、IL-1β、IL-6 和 HMGB1 表达增加（P＜ 0.05）。 结论 切口痛可诱发大鼠 HO-1 表达增加, 而 HO-1/CO 信号通路在调控切口痛大鼠炎症因子的释放方面发挥重要作用。     

Alteration of neuropathic and visceral pain in female C57BL/6J mice lacking the PPAR-α gene

Rationale

Peroxisome proliferator-activated receptors (PPARs) participate in the control of chronic neuropathic and inflammatory pain, and these receptors could play a role on acute pain.

Objectives

We used null (PPAR-?? ?/?) and wild-type female mice and the PPAR-?? blocker GW6471 to evaluate (1) the role of PPAR-?? on neuropathic pain, (2) the involvement of PPAR-?? on visceral and acute thermal nociception, and (3) tissue levels of pro-inflammatory factors.

Methods

Neuropathic pain was induced by sciatic nerve ligature. Acute thermal nociception was evaluated through hot-plate, tail-immersion, and writhing tests. The pro-inflammatory factors nitric oxide, TNF-??, and interleukins-1?? and -3 were measured.

Results

Regarding neuropathic pain, higher sensitivity to thermal and mechanical non-noxious and noxious stimuli was observed in mice lacking PPAR-??. Cold and mechanical allodynia and heat hyperalgesia were augmented in null mice. With respect to visceral nociception, writhes after acetic acid were enhanced in mutant mice. Although basal thermal sensitivity was enhanced in PPAR-?? ?/? mice, cutaneous thermal nociception did not differ between genotypes. Blockade of PPAR-?? was devoid of effects on acute thermal and writhing tests. Finally, nerve ligature enhanced pro-inflammatory factors in plantar tissue, levels being higher in null mice. No changes in pro-inflammatory factors were observed in the hot-plate test.

Conclusions

Genetic ablation of PPAR-?? is involved in neuropathic and visceral nociception. Lack of PPAR-?? is not involved in acute thermal pain, but it is involved in basal thermal reaction. Changes are biological adaptations to receptor deletion because blockade of PPAR-?? does not affect inflammatory pain or thermal reactions.     

Attenuation of TNF production and experimentally induced inflammation by PDE4 inhibitor rolipram is mediated by MAPK phosphatase-1

Background and Purpose

3′,5′-Cyclic nucleotide PDE4 is expressed in several inflammatory and immune cells, and PDE4 catalyses the hydrolysis of cAMP to 5′AMP, down-regulating cAMP signalling in cells. MAPK phosphatase-1 (MKP-1) is an endogenous p38 MAPK signalling suppressor and limits inflammatory gene expression and inflammation. In the present study, we investigated the effect of a PDE4 inhibitor rolipram on MKP-1 expression and whether MKP-1 is involved in the anti-inflammatory effects of rolipram.

Experimental Approach

The effect of rolipram on TNF production was investigated in J774 mouse macrophage cell line and in primary mouse peritoneal macrophages (PM) from wild-type (WT) and MKP-1(–/–) mice. We also investigated the effect of rolipram on carrageenan-induced paw inflammation in WT and MKP-1(–/–) mice.

Key Results

MKP-1 expression was enhanced by rolipram, by a non-selective PDE inhibitor IBMX and by a cAMP analogue 8-Br-cAMP in J774 cells and in PM. Enhanced MKP-1 mRNA expression by rolipram was reversed by a PKA inhibitor. Rolipram, IBMX and 8-Br-cAMP also inhibited TNF production in activated macrophages. Accordingly, rolipram inhibited TNF production in PMs from WT mice but, interestingly, not in PMs from MKP-1(–/–) mice. Furthermore, rolipram attenuated carrageenan-induced paw inflammation in WT but not in MKP-1(–/–) mice.

Conclusions and Implications

PDE4 inhibitor rolipram was found to enhance the expression of MKP-1, and MKP-1 mediated, at least partly, the anti-inflammatory effects of PDE4 inhibition. The results suggest that compounds that enhance MKP-1 expression and/or MKP-1 activity hold potential as novel anti-inflammatory drugs.     

Protection of protease-activated receptor 2 mediated vasodilatation against angiotensin II-induced vascular dysfunction in mice

Background

Under conditions of cardiovascular dysfunction, protease-activated receptor 2 (PAR2) agonists maintain vasodilatation activity, which has been attributed to increased cyclooxygenase-2, nitric oxide synthase and calcium-activated potassium channel (SK3.1) activities. Protease-activated receptor 2 agonist mediated vasodilatation is unknown under conditions of dysfunction caused by angiotensin II. The main purpose of our study was to determine whether PAR2-induced vasodilatation of resistance arteries was attenuated by prolonged angiotensin II treatment in mice. We compared the vasodilatation of resistance-type arteries (mesenteric) from angiotensin II-treated PAR2 wild-type mice (WT) induced by PAR2 agonist 2-furoyl-LIGRLO-amide (2fly) to the responses obtained in controls (saline treatment). We also investigated arterial vasodilatation in angiotensin II-treated PAR2 deficient (PAR2^-/-) mice.

Results

2fly-induced relaxations of untreated arteries from angiotensin II-treated WT were not different than saline-treated WT. Treatment of arteries with nitric oxide synthase inhibitor and SK3.1 inhibitor (L-NAME + TRAM-34) blocked 2fly in angiotensin II-treated WT. Protein and mRNA expression of cyclooxygenase-1 and -2 were increased, and cyclooxygenase activity increased the sensitivity of arteries to 2fly in only angiotensin II-treated WT. These protective vasodilatation mechanisms were selective for 2fly compared with acetylcholine- and nitroprusside-induced relaxations which were attenuated by angiotensin II; PAR2^-/- were protected against this attenuation of nitroprusside.

Conclusions

PAR2-mediated vasodilatation of resistance type arteries is protected against the negative effects of angiotensin II-induced vascular dysfunction in mice. In conditions of endothelial dysfunction, angiotensin II induction of cyclooxygenases increases sensitivity to PAR2 agonist and the preserved vasodilatation mechanism involves activation of SK3.1.     

Relationship between serum IL10 level and p38MAPK enzyme activity on behavioral and cellular aspects of variation of hyperalgesia during different stages of arthritis in rats

Objects and design

Regarding to anti-inflammatory role of interleukin (IL) 10, its inhibitory effects on p38MAPK activity and, different pro and anti-inflammatory roles of activated p38MAPK in cells, this study was aimed to investigate relationship between serum IL10 level and p38MAPK enzyme activity on behavioral and cellular aspects variation of hyperalgesia during different stages of arthritis in rats.

Materials and methods

Adjuvant arthritis (AA) was induced by a single subcutaneous injection of complete Freund’s adjuvant into the rats’ hind paw. Behavioral and inflammatory responses were assessed at 0, 3, 7, 14, and 21 days of study. Receptor and other protein enzyme expression variations were detected by western blotting. Anti-IL10 and p38MAPK inhibitor were administered daily during the 21 days of study.

Result

Daily treatment with anti-IL10 antibody significantly increased paw edema and hyperalgesia in the AA group compared with the AA control group. Administration of anti-IL10 antibody caused significant increase in the ratio of phosphorylated p38 to p38MAPK enzyme level expression on 14th and 21st days of study compared with the AA control group.

Conclusion

Our study confirmed that a part of anti- inflammatory effects of serum IL10 during AA inflammation was mediated via inhibition of p38MAPK enzyme phosphorylation. Moreover, these findings suggest that increase in the level of spinal mu opioid receptor expression during AA inflammation is not mediated via the direct effect of serum IL10 on spinal p38MAPK.     

Involvement of interleukin-1 in lead nitrate-induced hypercholesterolemia in mice

Hepatic 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) and cholesterol 7α-hydroxylase (Cyp7a1) are rate-limiting enzymes for cholesterol biosynthesis and catabolism, respectively. Involvement of inflammatory cytokines, particularly interleukin-1 (IL-1), in alterations of HMGR and Cyp7a1 gene expression during development of lead nitrate (LN)-induced hypercholesterolemia was examined in IL-1α/β-knockout (IL-1-KO) and wild-type (WT) mice. Lead nitrate treatment of WT mice led to not only a marked downregulation of the Cyp7a1 gene at 6-12 h, but also a significant upregulation of the HMGR gene at 12 h. However, such changes were not observed at significant levels in IL-1-KO mice, although a slight, transient downregulation of the Cyp7a1 gene and a minimal upregulation of the HMGR gene occurred at 6 h and 24 h, respectively. Consequently, LN treatment led to development of hypercholesterolemia at 24 h in WT mice, but not in IL-1-KO mice. Furthermore, in WT mice, significant LN-mediated increases were observed at 3-6 h in hepatic IL-1 levels, which can modulate gene expression of Cyp7a1 and HMGR. These findings indicate that, in mice, LN-mediated increases in hepatic IL-1 levels contribute, at least in part, to altered expressions of Cyp7a1 and HMGR genes, and eventually to hypercholesterolemia development.     

Contributions of HO-1-Dependent MAPK to Regulating Intestinal Barrier Disruption

The mitogen-activated protein kinase (MAPK) pathway controls intestinal epithelial barrier permeability by regulating tight junctions (TJs) and epithelial cells damage. Heme oxygenase-1 (HO-1) and carbon monoxide (CO) protect the intestinal epithelial barrier function, but the molecular mechanism is not yet clarified. MAPK activation and barrier permeability were studied using monolayers of Caco-2 cells treated with tissue necrosis factor α (TNF-α) transfected with FUGW-HO-1 or pLKO.1-sh-HO-1 plasmid. Intestinal mucosal barrier permeability and MAPK activation were also investigated using carbon tetrachloride (CCl₄) administration with CoPP (a HO-1 inducer), ZnPP (a HO-1 inhibitor), CO releasing molecule 2 (CORM-2), or inactived-CORM-2-treated wild-type mice and mice with HO-1 deficiency in intestinal epithelial cells. TNF-α increased epithelial TJ disruption and cleaved caspase-3 expression, induced ERK, p38, and JNK phosphorylation. In addition, HO-1 blocked TNF-α-induced increase in epithelial TJs disruption, cleaved caspase-3 expression, as well as ERK, p38, and JNK phosphorylation in an HO-1-dependent manner. CoPP and CORM-2 directly ameliorated intestinal mucosal injury, attenuated TJ disruption and cleaved caspase-3 expression, and inhibited epithelial ERK, p38, and JNK phosphorylation after chronic CCl₄ injection. Conversely, ZnPP completely reversed these effects. Furthermore, mice with intestinal epithelial HO-1 deficient exhibited a robust increase in mucosal TJs disruption, cleaved caspase-3 expression, and MAPKs activation as compared to the control group mice. These data demonstrated that HO-1-dependent MAPK signaling inhibition preserves the intestinal mucosal barrier integrity by abrogating TJ dysregulation and epithelial cell damage. The differential targeting of gut HO-1-MAPK axis leads to improved intestinal disease therapy.     

Neuropeptide Y Y5 receptor antagonism attenuates cocaine-induced effects in mice

Rationale

Several studies suggest a role for neuropeptide Y (NPY) in addiction to drugs of abuse, including cocaine. However, the NPY receptors mediating addiction-related effects remain to be determined.

Objectives

To explore the potential role of Y5 NPY receptors in cocaine-induced behavioural effects.

Methods

The Y5 antagonist L-152,804 and Y5-knockout (Y5-KO) mice were tested in two models of cocaine addiction-related behaviour: acute self-administration and cocaine-induced hyperactivity. We also studied effects of Y5 receptor antagonism on cocaine-induced c-fos expression and extracellular dopamine with microdialysis as well as dopamine transporter-mediated uptake of dopamine in vitro. Immunocytochemistry was used to determine whether dopamine neurons express Y5-like immunoreactivity.

Results

In self-administration, L-152,804 prominently decreased nose-poking for the peak dose of cocaine and shifted the dose–response curve for cocaine downward. Y5-KO mice also showed modestly attenuated self-administration. Cocaine-induced hyperactivity was attenuated by L-152,804 and in Y5-KO mice. Cocaine failed to increase c-fos expression in the nucleus accumbens and striatum of L-152,804-treated mice, indicating that the Y5 antagonist could act by influencing neural activity in these regions. Accordingly, the cocaine-induced increase in accumbal extracellular dopamine was attenuated by L-152,804 and in Y5-KO mice, suggesting that Y5 antagonism influences cocaine-induced behaviour by regulating dopamine. Consistent with this concept, dopamine neurons in the ventral tegmental area appeared to contain Y5 receptors. In contrast, neither L-152,804 nor NPY influenced dopamine transporter-mediated dopamine uptake.

Conclusions

The present data indicate that Y5 antagonism may attenuate cocaine-induced behavioural effects, suggesting that Y5 receptors could be a potential therapeutic target in cocaine addiction.     

Nicotine exposure during adolescence: cognitive performance and brain gene expression in adult heterozygous reeler mice

Rationale

We have recently reported nicotine-induced stimulation of reelin and glutamic acid decarboxylase 67 (GAD67) mRNA expression levels in the brain of heterozygous reeler mice (HRM), a putative animal model for the study of symptoms relevant to major behavioral disorders.

Objectives

We aimed to evaluate long-term behavioral effects and brain molecular changes as a result of adaptations to nicotine exposure in the developing HRM males.

Methods

Adolescent mice (pnd 37–42) were exposed to oral nicotine (10 mg/l) in a 6-day free-choice drinking schedule. As expected, no differences in total nicotine intake between WT (wild-type) mice and HRM were found.

Results

Long-term behavioral effects and brain molecular changes, as a consequence of nicotine exposure during adolescence, were only evidenced in HRM. Indeed, HRM perseverative exploratory behavior and poor cognitive performance were modulated to WT levels by subchronic exposure to nicotine during development. Furthermore, the expected reduction in the expression of mRNA of reelin and GAD67 in behaviorally relevant brain areas of HRM appeared persistently restored by nicotine. For brain-derived neurotrophic factor (BDNF) mRNA expression, no genotype-dependent changes appeared. However, expression levels were increased by previous nicotine in brains from both genotypes. The mRNA encoding for nicotine receptor subunits (α7, β2 and α4) did not differ between genotypes and as a result of previous nicotine exposure.

Conclusion

These findings support the hypothesis of pre-existing vulnerability (based on haploinsufficiency of reelin) to brain and behavioral disorders and regulative short- and long-term effects associated with nicotine modulation.     

The role of alpha5 nicotinic acetylcholine receptors in mouse models of chronic inflammatory and neuropathic pain

The aim of the present study was to determine the impact of α₅ nicotinic acetylcholine receptor (nAChR) subunit deletion in the mouse on the development and intensity of nociceptive behavior in various chronic pain models.The role of α₅-containing nAChRs was explored in mouse models of chronic pain, including peripheral neuropathy (chronic constriction nerve injury, CCI), tonic inflammatory pain (the formalin test) and short and long-term inflammatory pain (complete Freund's adjuvant, CFA and carrageenan tests) in α₅ knock-out (KO) and wild-type (WT) mice.The results showed that paw-licking time was decreased in the formalin test, and the hyperalgesic and allodynic responses to carrageenan and CFA injections were also reduced. In addition, paw edema in formalin-, carrageenan- or CFA-treated mice were attenuated in α₅-KO mice significantly. Furthermore, tumor necrosis factor-alpha (TNF-α) levels of carrageenan-treated paws were lower in α₅-KO mice. The antinociceptive effects of nicotine and sazetidine-A but not varenicline were α₅-dependent in the formalin test. Both hyperalgesia and allodynia observed in the CCI test were reduced in α₅-KO mice. Nicotine reversal of mechanical allodynia in the CCI test was mediated through α₅-nAChRs at spinal and peripheral sites.In summary, our results highlight the involvement of the α₅ nAChR subunit in the development of hyperalgesia, allodynia and inflammation associated with chronic neuropathic and inflammatory pain models. They also suggest the importance of α₅-nAChRs as a target for the treatment of chronic pain.     

Inflammation in the pleural cavity following injection of multi-walled carbon nanotubes is dependent on their characteristics and the presence of IL-1 genes

Upon inhalation, multi-walled carbon nanotubes (MWCNTs) may reach the subpleura and pleural spaces, and induce pleural inflammation and/or mesothelioma in humans. However, the mechanisms of MWCNT-induced pathology after direct intrapleural injections are still only partly elucidated. In particular, a role of the proinflammatory interleukin-1 (IL-1) cytokines in pleural inflammation has so far not been published. We examined the MWCNT-induced pleural inflammation, gene expression abnormalities, and the modifying role of IL-1α and β cytokines following intrapleural injection of two types of MWCNTs (CNT-1 and CNT-2) compared with crocidolite asbestos in IL-1 wild-type (WT) and IL-1α/β KO (IL1-KO) mice. Histopathological examination of the pleura 28?days post-exposure revealed mesothelial cell hyperplasia, leukocyte infiltration, and fibrosis occurring in the CNT-1 (Mitsui-7)-exposed group. The pleura of these mice also showed the greatest changes in mRNA and miRNA expression levels, closely followed by CNT-2. In addition, the CNT-1-exposed group also presented the greatest infiltrations of leukocytes and proliferation of fibrous tissue. WT mice were more prone to development of sustained inflammation and fibrosis than IL1-KO mice. Prominent differences in genetic and epigenetic changes were also observed between the two genotypes. In conclusion, the fibrotic response to MWCNTs in the pleura depends on the particles’ physico-chemical properties and on the presence or absence of the IL-1 genes. Furthermore, we found that CNT-1 was the most potent inducer of inflammatory responses, followed by CNT-2 and crocidolite asbestos.     

Deletion of thioredoxin-interacting protein preserves retinal neuronal function by preventing inflammation and vascular injury

BACKGROUND AND PURPOSE

Retinal neurodegeneration is an early and critical event in several diseases associated with blindness. Clinically, therapies that target neurodegeneration fail. We aimed to elucidate the multiple roles by which thioredoxin-interacting protein (TXNIP) contributes to initial and sustained retinal neurodegeneration.

EXPERIMENTAL APPROACH

Neurotoxicity was induced by intravitreal injection of NMDA into wild-type (WT) and TXNIP-knockout (TKO) mice. The expression of apoptotic and inflammatory markers was assessed by immunohistochemistry, elisa and Western blot. Microvascular degeneration was assessed by periodic acid-Schiff and haematoxylin staining and retinal function by electroretinogram.

KEY RESULTS

NMDA induced early (1 day) and significant retinal PARP activation, a threefold increase in TUNEL-positive nuclei and 40% neuronal loss in ganglion cell layer (GCL); and vascular permeability in WT but not TKO mice. NMDA induced glial activation, expression of TNF-α and IL-1β that co-localized with Müller cells in WT but not TKO mice. In parallel, NMDA triggered the expression of NOD-like receptor protein (NLRP3), activation of caspase-1, and release of IL-1β and TNF-α in primary WT but not TKO Müller cultures. After 14 days, NMDA induced 1.9-fold microvascular degeneration, 60% neuronal loss in GCL and increased TUNEL-labelled cells in the GCL and inner nuclear layer in WT but not TKO mice. Electroretinogram analysis showed more significant reductions in b-wave amplitudes in WT than in TKO mice.

CONCLUSION AND IMPLICATIONS

Targeting TXNIP expression prevented early retinal ganglion cell death, glial activation, retinal inflammation and secondary neuro/microvascular degeneration and preserved retinal function. TXNIP is a promising new therapeutic target for retinal neurodegenerative diseases.