A site‐specific PEGylated analog of exendin‐4 with improved pharmacokinetics and pharmacodynamics in vivo

Objectives Our aim was to improve the in vivo pharmacokinetics and pharmacodynamics of exendin‐4 by using site‐specific PEGylation. Methods We designed the PEGylated peptide based on its structure and activity relationship and prepared the conjugate by two steps of chromatographic purification. After obtained the conjugate we confirmed its glucose‐lowering activity in normal mice and determined its half‐life in SD rats. Then we evaluated its anti‐diabetic activity in a multiple low‐dose Streptozocin (STZ)‐induced diabetic mice model. Key findings With the process established in this study the product conjugate was obtained with a yield of over 60% and purity of above 99%. The conjugate maintained its original conformation after modification. In SD rats its half‐life was prolonged to 27.12 ± 5.75 h which was 17.61‐fold longer than that of the natural exendin‐4 for which the half‐life was only 1.54 ± 0.47 h. Its anti‐diabetic activity was significantly improved in the diabetic mice. Conclusions Compare with native exendin‐4, the C‐terminal site‐specific PEGylated analog of exendin‐4 obtained in this study has an improved pharmacokinetics and pharmacodynamics in vivo and could be regarded as a potential candidate for the future development of anti‐diabetic drugs.     

The natural flavonoid galangin ameliorates dextran sulphate sodium–induced ulcerative colitis in mice: Effect on Toll‐like receptor 4, inflammation and oxidative stress

This study was carried out to investigate the potential therapeutic effect of galangin, a promising active principle of honeybee propolis, in dextran sulphate sodium (DSS)–induced colitis in mice. We explored the possible underlying mechanisms for galangin action and the therapeutic benefit of adding galangin to the standard therapy sulphasalazine. A galangin dose of 40 mg/kg was selected based on a preliminary dose‐selection study for investigation in a 4‐week cyclical model of DSS‐induced colitis. Mice received 3% DSS in their drinking water during the first and third weeks and were administered the treatments (40 mg/kg galangin, 100 mg/kg sulphasalazine and a combination of 20 mg/kg galangin and 50 mg/kg sulphasalazine) daily starting from the second week. Galangin significantly ameliorated DSS‐induced histopathological alterations and tissue injury, down‐regulated Toll‐like receptor 4 expression, suppressed NF‐κB p65 activation, lowered inflammatory cytokine levels and demonstrated antioxidant effects. The combination of galangin and sulphasalazine at half doses yielded comparable results to either drug alone at full dose. This study highlights galangin as a promising therapy for colitis management.     

Toll‐like receptor 4 ablation rescues against paraquat‐triggered myocardial dysfunction: Role of ER stress and apoptosis

Paraquat is a nitrogen herbicide imposing severe organ toxicity in human leading to acute lung injury and heart failure. The present study was designed to examine the impact of ablation of the innate proinflammatory mediator toll‐like receptor 4 (TLR4) in paraquat‐induced cardiac contractile dysfunction and the underlying mechanisms involved with a focus on endoplasmic reticulum (ER) stress and apoptosis. Adult male wild‐type (WT) and TLR4 knockout (TLR4^?/?) mice were challenged with paraquat (45 mg/kg, i.p.) for 48 h prior to the assessment of myocardial and cardiomyocyte sarcomere function, ER stress, apoptosis and inflammation. Acute paraquat challenge exerted myocardial functional and geometric alterations including enlarged left ventricular end systolic diameter (LVESD), reduced fractional shortening, decreased sarcomere shortening, maximal velocities of sarcomere shortening and relengthening associated with unchanged LV posterior wall thickness, septal thickness, LV end diastolic diameter (LVEDD), heart rate, sarcomere length, time‐to‐peak shortening and time‐to‐90% relengthening. Although TLR4 ablation did not affect mechanical properties in the heart, it significantly attenuated or ablated paraquat‐induced cardiac contractile anomalies. Moreover, paraquat imposed overt ER stress, apoptosis and inflammation as evidenced by upregulation of Bip, CHOP, Caspase‐3, ?9, Bax, Bad, and IL‐1β, phosphorylation of PERK, eIF2α and IΚB, as well as activation of the stress molecules ERK and p38, with unchanged Caspase‐8, Bcl2, TNF‐α, p53, HMGB1, MyD88 and phosphorylation of Akt, GSK3β and JNK, the effects of which were attenuated or negated by TLR4 knockout. Taken together, our results suggested that TLR4 ablation alleviated paraquat‐induced myocardial contractile dysfunction possibly through attenuation of ER stress, apoptosis and inflammation. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 656–668, 2017.     

Protective effects of melatonin and glucagon‐like peptide‐1 receptor agonist (liraglutide) on gastric ischaemia–reperfusion injury in high‐fat/sucrose‐fed rats

Ischaemia–reperfusion (I–R) injury is a serious pathology that is often encountered with thrombotic events, during surgery when blood vessels are cross‐clamped, and in organs for transplantation. Increased oxidative stress is the main pathology in I–R injury, as assessed in studies on the heart, kidney, and brain with little data available on gastric I–R (GI–R). Liraglutide is a GLP‐1 receptor agonist that has insulinotropic and weight reducing actions, and melatonin that has been much studied as a chronotropic hormone; have also studied as being anti‐oxidative stress agents. Herein, we aimed to explore the effects of liraglutide and melatonin on GI–R injury with high‐fat/sucrose diet. Rats were divided into six groups; two diet‐control, two melatonin‐ and two liraglutide‐pretreated groups. All rats were subjected to 30 minutes of gastric ischaemia followed by 1 hour of reperfusion. Gastric tissues were assessed for the percentage of DNA fragmentation, myeloperoxidase activity, total oxidant status, total antioxidant capacity, oxidative stress index, BMI and histopathological examination. We showed that high‐fat feeding for four weeks prior to GI–R significantly increased BMI, oxidative stress indices and decreased total antioxidant capacity, with a neutral effect on apoptosis compared to controls. Pretreatment with either melatonin (10 mg/kg per day orally) or liraglutide (25 μg/kg per day ip) reverses these effects. Furthermore, both drugs reduced weight only in HFS‐fed rats. Both liraglutide and melatonin have nearly similar protective effects on gastric I–R injury through decreasing the oxidative stress and apoptosis.     

Lycopene inhibits cyclic strain‐induced endothelin‐1 expression through the suppression of reactive oxygen species generation and induction of heme oxygenase‐1 in human umbilical vein endothelial cells

Lycopene is the most potent active antioxidant among the major carotenoids, and its use has been associated with a reduced risk for cardiovascular disease (CVD). Endothelin‐1 (ET‐1) is a powerful vasopressor synthesized by endothelial cells and plays a crucial role in the pathophysiology of CVD. However, the direct effects of lycopene on vascular endothelial cells have not been fully described. This study investigated the effects of lycopene on cyclic strain‐induced ET‐1 gene expression in human umbilical vein endothelial cells (HUVECs) and identified the signal transduction pathways that are involved in this process. Cultured HUVECs were exposed to cyclic strain (20% in length, 1 Hz) in the presence or absence of lycopene. Lycopene inhibited strain‐induced ET‐1 expression through the suppression of reactive oxygen species (ROS) generation through attenuation of p22^phox mRNA expression and NAD(P)H oxidase activity. Furthermore, lycopene inhibited strain‐induced ET‐1 secretion by reducing ROS‐mediated extrace‐llular signal‐regulated kinase (ERK) phosphorylation. Conversely, lycopene treatment enhanced heme oxygenase‐1 (HO‐1) gene expression through the activation of phosphoinositide 3‐kinase (PI3K)/Akt pathway, followed by induction of the nuclear factor erythroid 2‐related factor 2 (Nrf2) nuclear translocation; in addition, HO‐1 silencing partially inhibited the repressive effects of lycopene on strain‐induced ET‐1 expression. In summary, our study showed, for the first time, that lycopene inhibits cyclic strain‐induced ET‐1 gene expression through the suppression of ROS generation and induction of HO‐1 in HUVECs. Therefore, this study provides new valuable insight into the molecular pathways that may contribute to the proposed beneficial effects of lycopene on the cardiovascular system.     

MiR‐30a‐5p ameliorates spinal cord injury‐induced inflammatory responses and oxidative stress by targeting Neurod 1 through MAPK/ERK signalling

Spinal cord injury (SCI) is a major disability requiring more effective treatment than is currently available. MicroRNAs have been shown to effectively regulate gene expression at the translational level. The aim of the present study was to explore the potential role of miR‐30‐5p and possible mechanism in SCI. We found that miR‐30‐5p was notably down‐regulated, while Neurod 1 expression was highly elevated in microglia from the mouse model of SCI. Additionally, overexpression of miR‐30a‐5p significantly suppressed inflammatory responses as reflected by a decrease in the secretion of the cytokines TNF‐α, IL‐1β and IL‐10 triggered by SCI. Furthermore, introduction of miR‐30a‐5p strengthened the scavenging of oxygen free radicals accompanied by an increase in the expression of SEPN1, TXNL1 and GPX1. More importantly, our study explored that Neurod 1 was a direct and functional target of miR‐30a‐5p, which was validated by the dual luciferase reporter assay. qRT‐PCR and western blot analysis further validated that miR‐30a‐5p negatively regulated the expression of Neurod 1. Mechanistically, overexpression of miR‐30a‐5p or silencing of the Neurod 1 gene prevented the MAPK/ERK signalling and inhibited inflammatory responses, meanwhile activated SEPN1, TXNL1 and GPX1. These findings indicate that miR‐30a‐5p ameliorates inflammatory responses and oxidative stress by targeting Neurod 1 through MAPK/ERK signalling.     

Iptakalim prevents rat pulmonary hypertension induced by endothelin‐1 through the activation of KATP channel in vivo

Iptakalim has been previously characterized as a novel, selective ATP‐sensitive potassium channel opener. In the present study, to determine whether iptakalim can prevent the pulmonary hypertension induced by endothelin‐1 (ET‐1) through the activation of K_ATP channel in vivo, the effects of iptakalim and glibenclamide (a selective K_ATP channel blocker) on the mean pulmonary pressure (mPAP) induced by ET‐1 were examined in rats. Treatment of the animals with exogenous ET‐1 (via the pulmonary artery at a dose of 1.5 µg/kg) induced a pulmonary hypertension in vivo, whereas the administration of iptakalim (via the pulmonary artery at doses of either 0.5 mg or 1.0 mg/kg) prior to ET‐1 prevented pulmonary hypertension induced by ET‐1 in vivo. The ability of iptakalim to prevent pulmonary hypertension induced by ET‐1 was abolished by glibenclamide (via the femoral artery at a dose of 20 mg/kg) in vivo. These findings provide strong evidence that iptakalim acts as a specific K_ATP channel opener to antagonize the vasoconstrictor effect of ET‐1 in the pulmonary circulation. Thus, iptakalim may be developed as a therapeutic option for the treatment of pulmonary hypertension. Drug Dev Res 69: 89–94, 2008. © 2008 Wiley‐Liss, Inc.     

Fisetin‐induced apoptosis of human oral cancer SCC‐4 cells through reactive oxygen species production,endoplasmic reticulum stress,caspase‐, and mitochondria‐dependent signaling pathways

Oral cancer is one of the cancer‐related diseases in human populations and its incidence rates are rising worldwide. Fisetin, a flavonoid from natural products, has been shown to exhibit anticancer activities in many human cancer cell lines but the molecular mechanism of fisetin‐induced apoptosis in human oral cancer cells is still unclear; thus, in this study, we investigated fisetin‐induced cell death and associated signal pathways on human oral cancer SCC‐4 cells in vitro. We examined cell morphological changes, total viable cells, and cell cycle distribution by phase contrast microscopy and flow cytometry assays. Reactive oxygen species (ROS), Ca²⁺, mitochondria membrane potential (ΔΨ_m), and caspase‐8, ‐9, and ‐3 activities were also measured by flow cytometer. Results indicate that fisetin induced cell death through the cell morphological changes, caused G2/M phase arrest, induction of apoptosis, promoted ROS and Ca²⁺ production, and decreased the level of ΔΨ_m and increased caspase‐3, ‐8, and ‐9 activities in SCC‐4 cells. DAPI staining and DNA gel electrophoresis were also used to confirm fisetin‐induced cell apoptosis in SCC‐4 cells. Western blotting also found out that Fisetin increased the proapoptotic proteins such as Bax and Bid and decreased the antiapoptotic proteins such as Bcl‐2. Furthermore, results also showed that Fisetin increased the cytochrome c, AIF, and Endo G release from mitochondria in SCC‐4 cells. We also used ATF‐6α, ATF‐6β, GADD153, and GRP78 which indicated that fisetin induced cell death through ER stress. Based on those observations, we suggest that fisetin induced cell apoptosis through ER stress, mitochondria‐, and caspase‐dependent pathways.     

Angiotensin‐(1–7) treatment ameliorates angiotensin II‐induced apoptosis of human umbilical vein endothelial cells

相似文献   

Epigenetic modification of H3K4 and oxidative stress are involved in MC‐LR‐induced apoptosis in testicular cells of SD rats

Microcystin‐leucine arginine (MC‐LR) is a cyclic heptapeptide, produced by aquatic cyanobacteria such as microcystis, with strong reproductive toxicity which poses greater threat to the reproductive abilities of humans and animals. By exploring the role of trimethylation of histone H3 at lysine 4 (H3K4me3) and the role of oxidative stress in MC‐LR‐induced apoptosis in testicular Sertoli cells in Sprague‐Dawley (SD) rats, this study indicated that MC‐LR increased the expression levels of apoptosis‐related genes by raising the levels of H3K4me3. 5′‐Deoxy‐5′‐methylthioadenosine (MTA), the inhibitor of H3K4me3, reduced apoptosis, indicating for the first time that epigenetic modification is closely related to the testicular reproductive toxicity induced by MC‐LR. MC‐LR also induced oxidative stress by stimulating the generation of reactive oxygen species (ROS), and subsequently triggering mitochondria‐mediated apoptotic pathway by decreasing mitochondrial membrane potential and increasing the levels of Bax, Bcl‐2, Caspase‐3, and so on. MC‐LR‐induced apoptosis of testicular cells could be decreased after pretreatment with oxidative stress inhibitor N‐acetyl‐cysteine (NAC). Furthermore, the pathological damage to mitochondria and testes were observed in SD rats. These results show that MC‐LR can induce apoptosis by raising the levels of H3K4me3, and pretreatment with MTA can ameliorate the MC‐LR‐induced apoptosis of cocultured cells by lowering the levels of H3K4me3. Furthermore, NAC has a protective effect on MC‐LR‐induced apoptosis of testicular cells in SD rats by inhibiting the oxidative stress.     

Specific α7 nicotinic acetylcholine receptor agonist ameliorates isoproterenol‐induced cardiac remodelling in mice through TGF‐β1/Smad3 pathway

It is well‐accepted that inflammation plays an important role in the development of cardiac remodelling and that therapeutic approaches targeting inflammation can inhibit cardiac remodelling. Although a large amount of evidence indicates that activation of α7 nicotinic acetylcholine receptor (α7nAChR) causes an anti‐inflammatory effect, the role of α7nAChR in cardiac remodelling and the underlying mechanism have not been established. To investigate the effect of the specific α7nAChR agonist, PNU282987, on cardiac remodelling induced by isoproterenol (ISO 60 mg/kg per day) in mice, the cardiomyocyte cross‐sectional area (CSA) and collagen volume fraction were evaluated by hematoxylin and eosin (HE) and Masson staining, respectively. Cardiac function and ventricular wall thickness were measured by echocardiography. The protein expressions of collagen I, matrix metalloproteinase 9 (MMP‐9), transforming growth factor β1 (TGF‐β1), and Smad3 were analyzed by Western blot. ISO‐induced cardiac hypertrophy, characterized by an increase in the heart weight/body weight ratio, CSA and ventricular wall thickness. Moreover, cardiac fibrosis indices, such as collagen volume fraction, MMP‐9 and collagen I protein expression, were also increased by ISO. PNU282987 not only attenuated cardiac hypertrophy but also decreased the cardiac fibrosis induced by ISO. Furthermore, PNU282987 suppressed TGF‐β1 protein expression and the phosphorylation of Smad3 induced by ISO. In conclusion, PNU282987 ameliorated the cardiac remodelling induced by ISO, which may be related to the TGF‐β1/Smad3 pathway. These data imply that the α7nAChR may represent a novel therapeutic target for cardiac remodelling in many cardiovascular diseases.     

The role of Krüppel‐like factor 4 in transforming growth factor‐β–induced inflammatory and fibrotic responses in human proximal tubule cells

Krüppel‐like factor 4 (KLF4) is known to mitigate inflammation in several cell types. Using human proximal tubule cells, the present study aimed to investigate the role of KLF4 in regulating transforming growth factor (TGF)‐β₁ induced inflammatory and fibrotic responses. Human kidney proximal tubular cells were exposed to high glucose, or TGF‐β₁ and KLF4 expressions were determined. Cells were then transfected with empty vector or KLF4 and exposed to 2‐ng/mL TGF‐β₁ for up to 72 h. Inflammatory proteins (macrophage migration inhibitory factor and monocyte chemoattractant protein‐1) and pro‐fibrotic proteins (fibronectin and collagen IV) were measured after 72 h by enzyme‐linked immunosorbent assay and western blot, respectively. To determine the relevance to in vivo models of chronic kidney disease, KLF4 protein expression in streptozotocin‐induced diabetic mice was determined. Krüppel‐like factor 4 messenger RNA (mRNA) levels were significantly reduced in high glucose‐treated human kidney proximal tubular cells. High glucose increased TGF‐β₁ mRNA expression, which significantly increased migration inhibitory factor and monocyte chemoattractant protein‐1 protein secretion. Transforming growth factor‐β₁ significantly increased fibronectin and collagen IV protein expression. The overexpression of KLF4 significantly reduced TGF‐β–mediated increases in migration inhibitory factor and monocyte chemoattractant protein‐1 but had no effect on TGF‐β–mediated fibronectin and collagen IV mRNA and protein expression. The levels of KLF4 mRNA were significantly reduced in the diabetic kidney, and diabetic animals had a significant reduction in renal tubular expression of KLF4 proteins. This data suggest that KLF4 reduces inflammation induced by TGF‐β₁, suggesting a therapeutic role for KLF4 in diabetic nephropathy.     

Therapeutic effects of CPU 86017 on acute and chronic congestive cardiac failure mediated by reducing ET‐1?NOS and oxidative stress in rats

CPU 86017, a derivative of berberine, was administered to rats in which acute and chronic heart failure was induced by left coronary artery ligation for 3 h and 8 weeks, respectively. The rats were divided into the following groups: sham operation, coronary artery ligation (CAL), CAL+ CPU 86017 (80?40 and 20 mg/kg, ig) and CAL+ captopril (60 mg/kg, ig). In the acute model, the systolic parameters of LVSP and LV+dp/dtmax as well as the diastolic parameters of LVEDP and LV‐dp/dtmin improved significantly on pretreatment of CPU 86017 (80 mg/kg). Reductions in elevated serum CPK?LDH?MDA?GOT?GPT?infarcted area and blood viscosity were also significant (P < 0.01). In the chronic model, CPU 86017 (80 mg/kg) preserved the systolic parameters of LVSP and LV+dp/dtmax and the diastolic function of the LVEDP and LV‐dp/dtmin. CPU 86017 completely suppressed elevated plasma ANP and ET‐1, serum and tissue iNOS?NO and MDA, whereas the decreased SOD was improved. CPU 86017 and captopril improved cardiac failure performance and regressed cardiac remodeling in CHF by reducing tissue weight index: lung weight/body weight (BW), right ventricular weight/BW, and left ventricular weight/BW. CPU 86017 exerted beneficial actions in cardiac performance in models of both acute and chronic heart failure, mainly by suppressing ET‐1, iNOS, and oxidative stress in infarcted tissue. Drug Dev Res 63:22–32, 2004. © 2004 Wiley‐Liss, Inc.     

Exogenous recombinant human thioredoxin‐1 prevents acetaminophen‐induced liver injury by scavenging oxidative stressors,restoring the thioredoxin‐1 system and inhibiting receptor interacting protein‐3 overexpression

Thioredoxin‐1 (Trx‐1) is a potent therapeutic agent against a variety of diseases because of its actions as an antioxidant and regulator of apoptosis. N‐acetyl‐p‐aminophenol (APAP), commonly known as acetaminophen, generates excessive oxidative stress and triggers hepatocyte cell death, exemplified by regulated necrosis. In the present study, we investigated whether APAP‐induced liver injury in a mouse model is associated with “necroptosis,” and if pretreatment with recombinant Trx‐1 prevents the hepatic injury caused by APAP overdose. We also explored the mechanism underlying the preventive action of Trx‐1 against APAP‐induced hepatic injury. In a prevention study, C3H/he mice received different doses (0, 10, 50 or 100 mg kg^–1 body weight) of recombinant human Trx‐1 intraperitoneally, followed by a single oral dose of 300 mg kg^–1 of APAP. In this experimental paradigm, liver injury and lethality were markedly decreased in rhTrx‐1–pretreated mice. In survival experiments, mice received rhTrx‐1 followed by oral administration of a lethal dose of APAP. APAP overdose caused a series of liver toxicity‐associated events, beginning with overexpression of c‐fos, excessive production of reactive oxygen species and reactive nitrogen species (RNS) and leading to decreased endogenous Trx‐1 expression and activation of JNK signaling pathways. Pretreatment with rhTrx‐1 inhibited all of these toxicological manifestations of APAP. In addition, rhTrx‐1 significantly reduced the expression of RIP‐3, a critical necrosome component. Taken together, our findings indicate that rhTrx‐1 prevents APAP‐induced liver injury through multiple action mechanisms, including scavenging reactive oxygen species and reactive nitrogen species, restoring endogenous Trx‐1 levels and inhibiting RIP‐3 overexpression.     

Synthesis and evaluation of a 18F‐labeled 4‐phenylpiperidine‐4‐carbonitrile radioligand for σ1 receptor imaging

We report the design and synthesis of several 4‐phenylpiperidine‐4‐carbonitrile derivatives as σ₁ receptor ligands. In vitro radioligand competition binding assays showed that all the ligands exhibited low nanomolar affinity for σ₁ receptors (K_i(σ₁) = 1.22–2.14 nM) and extremely high subtype selectivity (K_i(σ₂) = 830–1710 nM; K_i(σ₂)/K_i(σ₁) = 680–887). [¹⁸F]9 was prepared in 42–46% isolated radiochemical yield, with a radiochemical purity of >99% by HPLC analysis after purification, via nucleophilic ¹⁸F^‐ substitution of the corresponding tosylate precursor. Biodistribution studies in mice demonstrated high initial brain uptakes and high brain‐to‐blood ratios. Administration of SA4503 or haloperidol 5 min prior to injection of [¹⁸F]9 significantly reduced the accumulation of radiotracers in organs known to contain σ₁ receptors. Two radioactive metabolites were observed in the brain at 30 min after radiotracer injection. [¹⁸F]9 may serve as a lead compound to develop suitable radiotracers for σ₁ receptor imaging with positron emission tomography.     

Orchidectomy attenuates high‐salt diet‐induced increases in blood pressure,renovascular resistance,and hind limb vascular dysfunction: role of testosterone

Sex hormone‐dependent vascular reactivity is an underlying factor contributing to sex differences in salt‐dependent hypertension. This study evaluated the role of androgens (testosterone) in high salt‐induced increase in blood pressure (BP) and altered vascular reactivity in renal blood flow and perfused hind limb preparation. Weanling male rats (8 weeks old, 180–200 g) were bilaterally orchidectomised or sham operated with or without testosterone replacement (Sustanon 250, 10 mg/kg intramuscularly once in 3 weeks) and placed on a normal (0.3%) or high (4.0%) NaCl diet for 6 weeks. The high‐salt diet (HSD) increased arterial BP, renal vascular resistance (RVR) and positive fluid balance (FB). These changes were accompanied by decreased plasma nitric oxide levels. The increased BP, RVR and FB observed in the rats fed a HSD were reversed by orchidectomy while testosterone replacement prevented the reversal. Phenylephrine (PE)‐induced increased vascular resistance in the perfused hind limb vascular bed was enhanced by HSD, the enhanced vascular resistance was prevented by orchidectomy and testosterone replacement reversed orchidectomy effect. Vasorelaxation responses to acetylcholine (ACh) and sodium nitroprusside (SNP) were impaired in HSD groups, orchidectomy attenuated the impairment, while testosterone replacement prevented the orchidectomy attenuation. These data suggested that eNOS‐dependent and independently‐mediated pathways were equally affected by HSD in vascular function impairment and this effect is testosterone‐dependent in male Sprague‐Dawley rats.     

Involvement of opioid system in antidepressant‐like effect of the cannabinoid CB1 receptor inverse agonist AM‐251 after physical stress in mice

Cannabinoid inverse agonists possess antidepressant‐like properties, but the mechanism of this action is unknown. Numerous studies have reported the interaction between opioid and cannabinoid pathways. In this study, acute foot‐shock stress was used in mice to investigate the involvement of the opioid pathway in the antidepressant‐like effect of the cannabinoid CB₁ receptor inverse agonist AM‐251. Stress was induced by intermittent foot‐shock stimulation for 30 min. Then, using the forced swimming test (FST) and tail suspension test (TST), the immobility time was measured. Results show that the immobility time was significantly prolonged in animals subjected to foot‐shock stress, compared with non‐stressed controls (P < 0.01). Also, the serum corticosterone level was significantly increased after stress induction (P < 0.001). Administration of AM‐251 (0.5 and 0.3 mg/kg, intraperitoneally (i.p.)), significantly decreased the immobility time of stressed mice in the FST (P < 0.001 and P < 0.01, respectively) and TST (P < 0.01 and P < 0.05, respectively). The lowest dose of AM‐251 (0.1 mg/kg), naltrexone (0.3 mg/kg), and morphine (1.0 mg/kg) did not show any significant effect on stressed animals (P > 0.05). Co‐administration of AM‐251 with sub‐effective dose of naltrexone decreased the effective dose of this cannabinoid inverse agonist, to 0.1 mg/kg (P < 0.01). On the other hand, administration of the sub‐effective dose of morphine reversed the anti‐immobility effect of AM‐251 (0.5 mg/kg; P < 0.001). In conclusion, the present study for the first time reveals the possible role of opioid signalling in the antidepressant‐like properties of AM‐251 in a foot‐shock stress model.     

GLP-1Ra通过抑制NOX2来源的ROS产生减少高糖诱导的β细胞凋亡

目的 探讨胰高血糖素样肽-1 （GLP-1） 受体激动剂 （GLP-1Ra） 减少高糖诱导的β细胞凋亡作用的可能机制。方法 正常对照 （N, 普通饲料喂养） 组、 2 型糖尿病 （T2DM） 组和 GLP-1 Ra 组[利拉鲁肽 200 μg/ （kg·d） ]大鼠干预12 周。比较各组大鼠造模前、 造模后给药前 （0 周） 及 12 周末血糖水平。高压液相色谱分析法测定糖化血红蛋白（HbA1c）; 全自动生化分析仪测定天冬氨酸转氨酶 （AST）、 肌酐 （CR） 及尿素氮 （BUN） 等; TUNEL染色观察胰岛细胞凋亡情况; 免疫组化法测定 cleaved caspase 3; DCFH-DA 荧光探针检测胰岛活性氧簇 （ROS）; 免疫组织化学法检测NADPH氧化酶（NOX） 催化亚基 （NOX2）。结果 12周时, GLP-1Ra组的血糖、 HbA1c、 总胆固醇 （TC） 及低密度脂蛋白胆固醇 （LDL-c） 水平均低于T2DM组 （P＜0.05）; GLP-1Ra组胰岛细胞凋亡率和cleaved caspase 3水平较T2DM组下降（P＜0.05）; 应用 Apocynin 抑制前, GLP-1Ra 组胰岛 ROS 水平明显低于 T2DM 组, 并与 N 组差异无统计学意义 （P＞0.05）, 应用Apocynin 抑制后, 各组间差异均无统计学意义 （P＞0.05）。GLP-1Ra 组胰岛NOX2水平较T2DM 组下降（P＜0.05）。结论 GLP-1Ra能抑制糖尿病大鼠β细胞的凋亡, 抑制NOX2来源的ROS产生可能是重要的潜在机制之一。