Haeme oxygenase-1 overexpression via nAChRs and the transcription factor Nrf2 has antinociceptive effects in the formalin test

Epibatidine has shown antinociceptive effects in various pain models, being 200-fold more potent than morphine. Previous results from our laboratory demonstrated that HO-1 overexpression has an antinociceptive effect in the formalin test. Furthermore, epibatidine was able to induce haeme oxygenase-1 (HO-1). So, the aim of this study was to investigate the effect of HO-1 overexpression induced by epibatidine in nociception elicited by formalin injection in the mice hindpaw. Administration of epibatidine (4 μg/kg) 24 h before the test reduced the nociceptive response during the first phase and second phase of the formalin test. This effect was prevented by treatment with tin protoporphyrin (SnPP, an inhibitor of HO-1 activity) administered via intraplantar 5 min before the test, suggesting a main role of HO-1. Western blot analysis revealed that epibatidine treatment increased by 2-fold HO-1 expression in the paw; this effect was lost in knockout mice for nuclear factor-erythroid 2-related factor 2 (Nrf2) and was accompanied by the loss of its antinociceptive effect. Furthermore, the antinociceptive effect of epibatidine was related to the activation of alpha7 and/or alpha9 nAChRs since methyllycaconitine (MLA) and mecamylamine but not dihydro-β-erythroidine (DHβE) reverted this effect. Finally, we showed by flow cytometry and by immunofluorescence that white blood cells of the animals injected with epibatidine expressed more HO-1 than control animals, and this expression was also reverted by MLA pre-treatment. These findings demonstrate that HO-1 induction by epibatidine has antinociceptive and anti-inflammatory effects by the activation of MLA-sensitive nAChRs.     

背根神经节血红素加氧酶1过表达缓解小鼠神经病理性疼痛

目的:探讨背根神经节(dorsal root ganglion,DRG)中血红素加氧酶1(heme oxygenase 1,HO-1)的表达分布及在DRG中过表达HO-1对神经病理性疼痛的作用。方法:构建保留性坐骨神经损伤(spared nerve injury,SNI)诱导的神经病理性疼痛模型;行为学检测机械性触诱发痛;免疫荧光染色检测DRG中HO-1在神经元中表达和分布;免疫印迹检测DRG中HO-1表达。结果:免疫荧光染色显示DRG中HO-1阳性神经元在SNI后数量显著减少;DRG中HO-1阳性神经元主要是IB4阳性的小型神经元(<300μm2);连续5天腹腔注射原卟啉IX氯化钴(cobalt protoporphyrin-IX,CoPP)能增加神经病理性疼痛小鼠的机械缩足阈值;鞘内注射过表达HO-1的腺病毒相关病毒(adenovirus associated virus,AAV)能特异性浸染DRG神经元,并上调HO-1表达;同时能有效提高神经病理性疼痛小鼠的机械缩足阈值,此效应持续21天以上。结论:DRG中HO-1主要表达在IB4阳性的小型神经元;过表达DRG神经元中HO-1能有效缓解SNI诱导的神经病理性疼痛。     

血红素加氧酶-1对心肌缺血再灌注损伤的保护作用

目的:探讨血红素加氧酶-1(HO-1)对心肌缺血再灌注损伤的保护作用及机制。方法:采用HO-1的诱导剂钴原卟啉(CoPP)和抑制剂锌原卟啉(ZnPP)分别进行干预处理后,建立大鼠的心肌缺血/再灌注损伤模型。观察大鼠再灌注后心肌形态变化,检测HO-1基因在大鼠心肌的表达情况,测定大鼠左心室心肌组织超氧化物歧化酶(SOD)活性及丙二醛(MDA)含量。结果:再灌注前使用CoPP进行预处理,可以诱导HO-1蛋白的表达上调;HO-1蛋白表达上调可以减少缺血再灌注后的心肌细胞坏死,提高心肌组织中SOD含量并降低MDA的含量。结论:CoPP诱导的HO-1过表达可以抑制心肌缺血再灌注损伤后的细胞坏死,从而减轻心肌的再灌注损伤,其主要机制与抗氧自由基有关。     

Oxidative stress fuels Trypanosoma cruzi infection in mice

Oxidative damage contributes to microbe elimination during macrophage respiratory burst. Nuclear factor, erythroid-derived 2, like 2 (NRF2) orchestrates antioxidant defenses, including the expression of heme-oxygenase-1 (HO-1). Unexpectedly, the activation of NRF2 and HO-1 reduces infection by a number of pathogens, although the mechanism responsible for this effect is largely unknown. We studied Trypanosoma cruzi infection in mice in which NRF2/HO-1 was induced with cobalt protoporphyrin (CoPP). CoPP reduced parasitemia and tissue parasitism, while an inhibitor of HO-1 activity increased T. cruzi parasitemia in blood. CoPP-induced effects did not depend on the adaptive immunity, nor were parasites directly targeted. We also found that CoPP reduced macrophage parasitism, which depended on NRF2 expression but not on classical mechanisms such as apoptosis of infected cells, induction of type I IFN, or NO. We found that exogenous expression of NRF2 or HO-1 also reduced macrophage parasitism. Several antioxidants, including NRF2 activators, reduced macrophage parasite burden, while pro-oxidants promoted it. Reducing the intracellular labile iron pool decreased parasitism, and antioxidants increased the expression of ferritin and ferroportin in infected macrophages. Ferrous sulfate reversed the CoPP-induced decrease in macrophage parasite burden and, given in vivo, reversed their protective effects. Our results indicate that oxidative stress contributes to parasite persistence in host tissues and open a new avenue for the development of anti-T. cruzi drugs.     

钴原卟啉诱导大鼠骨髓间充质干细胞血红素加氧酶-1过表达及其对IL-10分泌的影响

本研究探讨不同浓度钴原卟啉(CoPP)诱导大鼠骨髓间充质干细胞(BMMSC)血红素加氧酶-1(hemeoxygenase-1,HO-1)过表达的效应关系及其对BMMSC分泌IL-10的影响。分离培养BMMSC,用流式细胞术检测BMMSC中CD34、CD45、CD44和CD71的表达;应用茜素红染色和油红染色检测BMMSC向成骨及成脂诱导情况。BMMSC随机分为4组,分别置于CoPP浓度为0、25、50和75μmol/L的培养液中进行诱导。用MTT法分析BMMSC增殖情况。采用RT-PCR检测各试验组HO-1的表达水平,筛选出诱导HO-1表达上调的最适合的CoPP浓度。用ELISA试剂盒检测各组IL-10的分泌量。结果表明,体外分离培养的BMMSC中CD34、CD45表达呈阴性,CD44和CD71表达呈阳性;BMMSC经成骨及成脂诱导后出现钙沉积和脂滴,茜素红染色和油红染色呈阳性。各个浓度的CoPP对细胞增殖无显影响,CoPP 50μmol/L能强烈诱导BMMSC的HO-1表达,其在试验组的表达高于对照组,与此同时IL-10分泌量也较对照组增多。结论:CoPP对细胞增殖活性无促进作用,CoPP50μmol/L是诱导BMMSC HO-1表达上调的最适合的浓度,HO-1表达上调可诱导IL-10分泌增加。     

Local interactions between anandamide, an endocannabinoid, and ibuprofen, a nonsteroidal anti-inflammatory drug, in acute and inflammatory pain

Anandamide, an endocannabinoid, is degraded by the enzyme fatty acid amide hydrolase which can be inhibited by nonsteroidal anti-inflammatory drugs (NSAIDs). The present work was designed to study the peripheral interactions between anandamide and ibuprofen (a non-specific cyclooxygenase inhibitor) in the rat formalin test. We first determined the ED50 for anandamide (0.018 microg +/- 0.009), ibuprofen (0.18 microg +/- 0.09), and their combination (0.006 microg +/- 0.002). Drugs were given 15 min before a 2.5% formalin injection into the dorsal surface of the right hind paw. Results were analyzed using isobolographic analysis. The antinociceptive interaction between anandamide and ibuprofen was synergistic. To further investigate the mechanisms by which the combination of anandamide with ibuprofen produced their antinociceptive effects, we used specific antagonists for the cannabinoid CB1 (AM251; 80 microg) and CB2 (AM630; 25 microg) receptors. We demonstrated that the antinociceptive effects of ibuprofen were not antagonized by either AM251 or AM630 and that those of anandamide were antagonized by AM251 but not by AM630. The synergistic antinociceptive effects of the combination of anandamide with ibuprofen were completely antagonized by AM251 but only partially inhibited by AM630. In conclusion, locally (hind paw) injected anandamide, ibuprofen or combination thereof decreased pain behavior in the formalin test. The combination of anandamide with ibuprofen produced synergistic antinociceptive effects involving both cannabinoid CB1 and CB2 receptors. Comprehension of the mechanisms involved needs further investigation.     

Peripheral and central antinociceptive action of Na+-K+-2Cl- cotransporter blockers on formalin-induced nociception in rats

The possible local peripheral and spinal (intrathecal) antinociceptive effect of Na(+)-K(+)-2Cl(-) cotransporter (NKCC) inhibitors was investigated in the rat formalin test. Nociceptive flinching behavior induced by formalin (1%) injection in the hind paw was assessed following administration of cotransporter inhibitors. Local peripheral pretreatment in the ipsilateral paw with bumetanide (ED(30), 27.1+/-12.7 microg/paw), piretanide (ED(30), 109.2+/-21.6 microg/paw) or furosemide (ED(30), 34.3+/-5.0 microg/paw), but not vehicle (DMSO 100%), produced dose-dependent antinociception in phase 2 of the test. Local bumetanide had the greatest effect (approximately 70% antinociception). Bumetanide also inhibited formalin-induced flinching behavior during phase 1 (ED(30), 105.6+/-99.1 microg/paw). Spinal intrathecal pretreatment with bumetanide (ED(30), 194.6+/-97.9 microg), piretanide (ED(30), 254.4+/-104.9 microg) or furosemide (ED(30), 32.0+/-6.9 microg), but not vehicle (DMSO 100%), also produced antinociception in phase 2. In this case, only intrathecal furosemide reduced flinching behavior during phase 1 (ED(30), 99.4+/-51.4 microg) and had the maximal antinociceptive effect in phase 2 (approximately 65% antinociception). The opioid receptor-antagonist naloxone (2 mg/kg, s.c.) did not reverse antinociception induced by either peripheral or spinal administration of NKCC blockers. Our data suggest that the Na(+)-K(+)-2Cl(-) cotransporter localized in sensory neurons at intraspinal and peripheral sites is involved in formalin-induced nociception.     

Systemic capsaicin and olvanil reduce the acute algogenic and the late inflammatory phase following formalin injection into rodent paw.

Systemic capsaicin and an analogue, olvanil (NE-19550, 4-hydroxy-3-methoxyphenyl methyl-9Z-octadecenamide), were tested for antinociceptive activity in a model of persistent pain produced by the subcutaneous injection of formalin into the rodent hind paw. Formalin induced a biphasic nociceptive response in mice and rats which was measured (a) by the time spent licking the injected paw in mice and (b) by making electrophysiological recordings of single nociceptive neurone discharges in L1-L3 of the spinal dorsal horn of halothane-anaesthetised rats. In mice the initial phase of the response was reduced by systemic administration of morphine, capsaicin and olvanil but not by indomethacin. The second, more prolonged, inflammatory phase of the response was reduced by each agent. In rats, similar concentrations of capsaicin and olvanil reduced both the first and second components of the formalin response. These data show that capsaicin and a non-pungent analogue, olvanil, are efficacious antinociceptive agents in a model of prolonged chemical nociception induced by formalin. Their activity compares favourably with that of morphine and appears superior to that of indomethacin.     

血红素加氧酶-1对高糖诱导大鼠腹膜间皮细胞转化生长因子β1和纤维连接蛋白表达的影响

目的研究血红素加氧酶-1（HO-1）对高糖作用下体外培养的大鼠腹膜间皮细胞（RPMC）转化生长因子β1（TGF-β1）和纤维连接蛋白（FN）表达的影响。方法将原代培养的第3代RPMC随机分为对照组、高糖组、钴原卟啉（CoPP）＋高糖组和CoPP组。同步培养72h后,以反转录聚合酶链反应（RT-PCR）法检测各组细胞TGF-β1和FNmRNA表达情况;酶联免疫吸附法（ELISA）检测细胞上清液中TGF-β1和FN的蛋白质水平。结果高糖组、CoPP＋高糖组和CoPP组的HO-1mRNA及蛋白表达水平均显著高于对照组,其中CoPP＋高糖组显著高于高糖组;高糖组和CoPP＋高糖组的FNmRNA及蛋白表达水平显著高于对照组及CoPP组;高糖组、CoPP＋高糖组TGF-β1mRNA及蛋白表达水平显著高于对照组及CoPP组,其中CoPP＋高糖组显著低于高糖组。结论 HO-1可抑制高糖诱导的RPMCTGF-β1和FN的表达,具有抗腹膜纤维化的作用。     

Synergistic interaction between meloxicam and aminoguanidine in formalin‐induced nociception in mice

Objectives: The objective of this study was to examine the nature of interaction between cyclooxygenase‐2 inhibitor meloxicam and inducible nitric oxide synthase inhibitor aminoguanidine in formalin‐induced nociception in mice and the possible therapeutic advantage. Methods: Antinociceptive effect of meloxicam (1, 3, 10 and 30mg/kg, oral) and aminoguanidine (10, 30, 100 and 300mg/kg, oral) and their combinations was examined in formalin‐induced paw licking model in mice. Analysis of variance and isobolographic method were employed to identify the nature of antinociceptive interaction. Results: Higher doses of meloxicam (10 and 30mg/kg) and aminoguanidine (100 and 300mg/kg) produced significant reduction in paw licking time (antinociceptive) in late phase of formalin‐induced nociception. Combination of sub‐threshold dose of meloxicam (3mg/kg) with increasing doses of aminoguanidine (10, 30, 100 and 300mg/kg) resulted in synergistic antinociceptive effect. Similarly, co‐administration of sub‐threshold dose of aminoguanidine (30mg/kg) with increasing doses of meloxicam (1, 3, 10 and 30mg/kg) produced significant reduction in formalin‐induced paw licking behaviour. The experimental ED₅₀ for combination with their confidence limits are below the confidence interval of theoretical line of additive interaction, suggesting synergistic nature of interaction between meloxicam and aminoguanidine in isobolographic analysis. Conclusion: Co‐administration of meloxicam and aminoguanidine showed synergistic antinociceptive effect which might possibly reduce gastrointestinal toxicity associated with the use of meloxicam.     

Endogenous nociceptin/orphanin FQ signalling produces opposite spinal antinociceptive and supraspinal pronociceptive effects in the mouse formalin test: pharmacological and genetic evidences

Nociceptin/orphanin FQ (N/OFQ) has been demonstrated to modulate nociceptive transmission via selective activation of N/OFQ peptide (NOP) receptors. Despite huge research efforts, the role(s) of the endogenous N/OFQ-NOP receptor system in pain processing remains incompletely understood. In the present study, we investigated the role of endogenous N/OFQ in the processing of tonic nociceptive input. To address this issue the effects of NOP-selective antagonists [Nphe1,Arg14,Lys15]N/OFQ-NH2 (UFP-101) and J-113397 on nociceptive behaviour, and the nociceptive phenotype of NOP receptor-deficient mice were tested in the mouse formalin test. Twenty microliters of 1.5% formalin solution was injected subcutaneously into the right hind paw causing a characteristic pattern of nociceptive behaviours (licking, biting and lifting of the injected paw). In control mice, the injection of formalin resulted in a classical biphasic nociceptive response with the first phase lasting from 0 to 10 min and the second phase from 15 to 45 min. UFP-101 at 10 nmol/mouse (but not at 1 nmol/mouse) produced antinociceptive action when injected intracerebroventricularly and a pronociceptive action when given intrathecally. Systemic administration of J-113397 (10 mg/kg, intravenously) and the genetic ablation of the NOP receptor gene both produced a significant increase of mouse nociceptive behaviour. Collectively, these results demonstrate that endogenous N/OFQ-NOP receptor signalling is activated during the mouse formalin test producing spinal antinociceptive and supraspinal pronociceptive effects. The overall effect of blocking NOP receptor signalling, by either systemic pharmacological antagonism or genetic ablation, indicates that the spinal antinociceptive action prevails over supraspinal pronociceptive effects.     

Dimethoxycurcumin, a Synthetic Curcumin Analogue, Induces Heme Oxygenase-1 Expression through Nrf2 Activation in RAW264.7 Macrophages

Curcumin [1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione] induces heme oxygenase-1 (HO-1) expression via activation of the nuclear factor-erythroid-2-related factor 2 (Nrf2), whereas tetrahydrocurcumin [1,7-bis(4-hydroxy-3-methoxyphenyl)-3,5-heptanedione], one of curcumin in vivo metabolites, has no effect on HO-1 expression and Nrf2 activation. The aim of this study was to investigate whether dimethoxycurcumin [1,7-bis(4,3-dimethoxyphenyl)-1,6-heptadiene-3,5-dione], a synthetic curcumin analogue with higher metabolic stability over curcumin, could induce HO-1 expression to the same extent as curcumin in RAW264.7 macrophages. Dimethoxycurcumin and curcumin, but not tetrahydrocurcumin, induced HO-1 expression and Nrf2 nuclear translocation, suggesting that the unsaturated nature of the diarylheptanoid chain of the compounds are crucial for HO-1 expression and Nrf2 activation. Blockage of Nrf2 synthesis by small interfering RNA abolished HO-1 expression by dimethoxycurcumin, indicating that dimethoxycurcumin may induce HO-1 expression via Nrf2 activation. In comparison, dimethoxycurcumin and curcumin had about the same effect on HO-1 expression, suggesting that dimethoxycurcumin retains the HO-1-inducing activity of its parent compound curcumin in RAW264.7 macrophages.     

The Expression of Heme Oxygenase-1 Induced by Lansoprazole

Our previous studies have demonstrated that lansoprazole inhibits acute inflammatory reactions as well as intestinal mucosal injuries induced by ischemia-reperfusion or indomethacin administration in rats. Thus, proton pump inhibitors such as lansoprazole have been demonstrated to prevent gastrointestinal mucosal injury by mechanisms independent of acid inhibition. In our in vitro study, lansoprazole induced the expression of heme oxygenase-1 (HO-1) on rat gastric epithelial cells (RGM-1 cells), and exerted anti-inflammatory effect on the dependent of HO-1 expression. Furthermore, NF-E2-related factor-2 (Nrf2) played an important role in HO-1 expression induced by lansoprazole. In this review, we focused on lansoprazole-induced HO-1 expression, its anti-inflammatory action, and the role of Nrf2 in its expression.     

Possible role of NMDA receptors in antinociception induced by rilmenidine in mice in the formalin test.

OBJECTIVES: The aim of the study was to investigate the possible role of MK-801, an NMDA antagonist, in analgesia induced by rilmenidine, an imidazoline (I(1)) agonist, in mice in the formalin test. METHODS: 25 microl of formalin 2.5% was injected into the dorsal surface of the right hind paw of the mouse. Pain response was scored after formalin injection for a period of 50 min. A weighted average of nociceptive score, ranging from 0 to 3, was calculated. The mean +/-SEM of scores between 0-5 and 15-40 min after formalin injection was presented. RESULTS: The study showed that rilmenidine (1.25, 2.5 and 5 mg/kg, i.p.) produced analgesia dose-dependently (p<0.001) in formalin test. In addition, the results demonstrated that efaroxan (0.1 and 1 mg/kg, i.p.) could reduce the antinociceptive effect of rilmenidine (2.5 mg/kg, i.p.) (p<0.01) in animals, however, yohimbine (0.1 and 0.2 mg/kg, i.p.) could not block the analgesia induced by rilmenidine (2.5 mg/kg, i.p.) (p>0.05). On the other hand, MK-801 (0.05 mg/kg, i.p.) reduced the pain related behaviors in mice (p>0.05). Moreover, our findings demonstrated that MK-801 (0.01 mg/kg, i.p.) could potentiate the analgesic effect of rilmenidine (1.25 mg/kg, i.p.) significantly (p<0.01). CONCLUSIONS: The present study suggests that imidazoline (I(1)) receptors play an important role in mediating the antinociception induced by rilmenidine in formalin test. Furthermore, it may be concluded that there is an interaction between NMDA receptors and imidazoline (I(1)) binding sites.     

原发性胆汁性胆管炎患者血清核因子相关因子2、血红素加氧酶1的含量与熊去氧胆酸短期应答的相关性

目的观察核因子相关因子2(Nrf2)、血红素加氧酶1(HO-1)在原发性胆汁性胆管炎(PBC)患者治疗前后血清中的水平变化,并探讨二者与熊去氧胆酸(UDCA)短期疗效的相关性。方法纳入山西医科大学第一医院PBC患者及健康对照者各80例。收集PBC患者治疗前后的临床资料及血清样本,采用ELISA法检测样本中Nrf2及HO-1的含量,硫代巴比妥酸法、黄嘌呤氧化酶法分别检测丙二醛(MDA)及超氧化物歧化酶(SOD)的含量,并进一步分析UDCA治疗前后PBC患者血清中Nrf2、HO-1的水平变化及临床意义。结果治疗前PBC患者血清Nrf2、HO-1含量分别为(626.07±103.95)U/L、(16.62±5.06)U/L显著高于健康对照者[分别为(164.45±35.12)U/L、(11.74±2.0)U/L],差异均有统计学意义(P均<0.001);与治疗前比较,UDCA治疗后1个月PBC患者血清中Nrf2[(754.30±104.36)U/L]、HO-1[(22.60±5.51)U/L]含量显著增加(P均<0.001),肝功能各项指标也得到改善(P均<0.001)。患者治疗前血清中Nrf2水平(r=0.751,P=0.012)、HO-1水平(r=0.621,P=0.038)与治疗效果均呈正相关。以治疗前Nrf2=586.17 U/L作为阈值,预测的UDCA短期疗效的敏感度为84.6%,特异度为77.5%,曲线下面积为0.824(P<0.05);以治疗前HO-1=14.92 U/L作为阈值,预测的UDCA短期疗效的敏感度为88.5%,特异度为75.0%,曲线下面积为0.861(P<0.05)。结论Nrf2、HO-1在PBC患者疾病过程中发挥重要作用,二者在血清中的基线水平及动态变化同UDCA疗效相关,可以提示PBC患者对UDCA短期治疗的应答情况。     

厄多司坦对急性肺损伤小鼠肺内Nrf2表达的影响

[目的]探讨厄多司坦对脂多糖(LPS)诱导的小鼠急性肺损伤(ALI)小鼠肺内抗氧化转录因子Nrf2表达的影响.[方法]健康雄性C57bl/6小鼠24只随机分为对照组、ALI组和厄多司坦组,每组8只.采用气管注射LPS(5mg/kg)复制小鼠ALI动物模型.厄多司坦组通过提前30min灌胃(150mg/kg)给予预处理,造模12h后处理小鼠.HE染色观察小鼠肺组织形态学改变;检测丙二醛(MDA)含量和超氧歧化物(SOD)活性反映肺组织氧化应激;Western blot法检测肺组织核内Nrf2的表达;Real-time PCR检测肺组织hO-1和SOD mRNA含量.[结果]厄多司坦可改善LPS诱导的ALI小鼠肺组织病理形态学改变,降低肺组织内MDA含量,而增加SOD活性.厄多司坦亦可显著性增加ALI小鼠肺组织细胞核内Nrf2的表达,并显著增加Nrf2下游靶基因HO-1和SOD mRNA的表达.[结论]厄多司坦能减轻LPS诱导的小鼠ALI,通过增强ALI小鼠肺内抗氧化转录因子Nrf2的核转位及转录活性可能是其机制所在.     

Heme oxygenase type 2 plays a role in formalin-induced nociception

Although much attention has been focused in recent years on nitric oxide synthase (NOS) as an enzyme intimately involved in many types of nociceptive signaling, the enzyme heme oxygenase (HO) has received little attention. Yet, HO produces gaseous second messenger molecule CO which, like NO, has proven to be an important neurotransmitter in the CNS. In these studies we provide detailed evidence that HO activity is critical to formalin-induced licking behavior in mice. The HO inhibitor tin protoporphyrin (Sn-P) dose-dependently reduced formalin-stimulated licking behavior in both phases of the formalin assay. This apparent analgesic effect was unlikely due to the non-specific effects of this agent as Sn-P did not alter rotarod performance, and the blood-brain barrier impermeant HO inhibitor zinc protoporphyrin (Zn-P) had little effect on licking times. We also hypothesized that heme oxygenase type 2 (HO-2) was the specific isoform of HO involved in nociception. Mice with a targeted disruption of the HO-2 gene were found to have greatly reduced licking times. Furthermore, Sn-P did not further reduce licking times when administered to HO-2 knockout animals. Taken together our evidence indicates that HO plays an important role in nociceptive signaling related to inflammatory-type pain, and that HO-2 is the isozyme mediating this nociception.     

Heme oxygenase-mediated increases in adiponectin decrease fat content and inflammatory cytokines tumor necrosis factor-alpha and interleukin-6 in Zucker rats and reduce adipogenesis in human mesenchymal stem cells

Adiponectin, an abundant adipocyte-derived plasma protein that modulates vascular function in type 2 diabetes, has been shown to provide cytoprotection to both pancreatic and vascular systems in diabetes. Therefore, we examined whether up-regulation of heme oxygenase (HO)-1 ameliorates the levels of inflammatory cytokines and influences serum adiponectin in Zucker fat (ZF) rats. ZF rats displayed a decrease in both HO activity and HO-1 and HO-2 protein levels and an increase in tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 compared with Zucker lean (ZL) rats. Treatment of ZF animals with 2 mg/kg cobalt protoporphyrin IX (CoPP) increased protein levels of HO-1 and HO activity, but HO-2 was unaffected. The increase in HO-1 was associated with a decrease in superoxide levels (p < 0.05) and an increase in plasma adiponectin (p < 0.005), compared with untreated ZF rats. CoPP treatment decreased visceral and s.c. fat content, and it reduced weight gain (p < 0.01). In addition, the inflammatory cytokines TNF-alpha and IL-6 were decreased (p < 0.04 and p < 0.008, respectively). Treatment of human bone marrow-derived adipocytes cultured with CoPP resulted in an increase in HO-1 and a decrease in superoxide levels. Up-regulation of HO-1 caused adipose remodeling, smaller adipocytes, and increased adiponectin secretion in the culture medium of human bone marrow-derived adipocytes. In summary, this study demonstrates that the antiobesity effect of HO-1 induction results in an increase in adiponectin secretion, in vivo and in vitro, a decrease in TNF-alpha and IL-6, and a reduction in weight gain. These findings highlight the pivotal role and symbiotic relationship of HO-1 and adiponectin in the modulation of the metabolic syndrome phenotype.     

Influence of formalin concentration on the antinociceptive effects of anti-inflammatory drugs in the formalin test in rats: Separate mechanisms underlying the nociceptive effects of low-and high-concentration formalin

The present study has assessed the relationship between formalin-induced nociception and formalin-induced inflammation by comparing the dose-related effects of anti-inflammatory treatments on both nociceptive scores and plasma extravasation in the rat hind paw in response to high and low concentrations of formalin. The degree of plasma extravasation produced by 1% formalin did not differ significantly from that produced by the same volume of saline, and was not significantly affected by either of the anti-inflammatory agents. The 5% formalin injection produced significant plasma extravasation that was dose-dependently reduced by both dexamethasone and ibuprofen. The early-phase nociceptive responses to either 1 or 5% formalin were not affected significantly by either of the anti-inflammatory agents. In contrast, the late-phase nociceptive responses to 5%, but not 1%, formalin were dose-dependently reduced by both dexamethasone and ibuprofen. The present study suggests that there is a positive correlation between the nociceptive and inflammatory effects of formalin in the rat hind paw. However, only a high concentration of formalin, which produces significant plasma extravasation, is capable of demonstrating the antinociceptive effects of anti-inflammatory agents, and the effects are restricted to the late phase of the formalin test.