The Concise Guide to PHARMACOLOGY 2013/14: enzymes

AMPK-mediated autophagy pathway activation promotes ΔFosB degradation to improve levodopa-induced dyskinesia

BACKGROUND

Parkinson's disease patients on chronic levodopa often suffer from motor complications, which tend to reduce their quality of life. Levodopa-induced dyskinesia (LID) is one of the most prevalent motor complications, often characterized by abnormal involuntary movements, and the pathogenesis of LID is still unclear but recent studies have suggested the involvement of autophagy.

METHODS

The onset of LID was mimicked by chronic levodopa treatment in a unilateral 6-hydroxydopamine (6-OHDA) -lesion rat model. Overexpression of ΔFosB in HEK293 cells to mimic the state of ΔFosB accumulation. The modulation of the AMP-activated protein kinase (AMPK)-mediated autophagy pathway using by metformin, AICAR (an AMPK activator), Compound C (an AMPK inhibitor) and chloroquine (an autophagy pathway inhibitor). The severity of LID was assessed by axial, limb, and orofacial (ALO) abnormal involuntary movements (AIMs) score and in vivo electrophysiology. The activity of AMPK pathway as well as autophagy markers and FosB-ΔFosB levels were detected by western blotting. RT-qPCR was performed to detect the transcription level of FosB-ΔFosB. The mechanism of autophagy dysfunction was further explored by immunofluorescence and transmission electron microscopy.

RESULTS

In vivo experiments demonstrated that chronic levodopa treatment reduced AMPK phosphorylation, impaired autophagosome-lysosomal fusion and caused FosB-ΔFosB accumulation in the striatum of PD rats. Long-term metformin intervention improved ALO AIMs scores as well as reduced the mean power of high gamma (hγ) oscillations and the proportion of striatal projection neurons unstable in response to dopamine for LID rats. Moreover, the intervention of metformin promoted AMPK phosphorylation, ameliorated the impairment of autophagosome-lysosomal fusion, thus, promoting FosB-ΔFosB degradation to attenuate its accumulation in the striatum of LID rats. However, the aforementioned roles of metformin were reversed by Compound C and chloroquine. The results of in vitro studies demonstrated the ability of metformin and AICAR to attenuate ΔFosB levels by promoting its degradation, while Compound C and chloroquine could block this effect.

CONCLUSIONS

In conclusion, our results suggest that long-term metformin treatment could promote ΔFosB degradation and thus attenuate the development of LID through activating the AMPK-mediated autophagy pathway. Overall, our results support the AMPK-mediated autophagy pathway as a novel therapeutic target for LID and also indicate that metformin is a promising therapeutic candidate for LID.

Acute Administration of Metformin Protects Against Neuronal Apoptosis Induced by Cerebral Ischemia-Reperfusion Injury via Regulation of the AMPK/CREB/BDNF Pathway

Metformin is a first-line anti-diabetic agent with a powerful hypoglycemic effect. Several studies have reported that metformin can improve the prognosis of stroke patients and that this effect is independent of its hypoglycemic effect; however, the specific mechanism remains unclear. In this research, we explored the effect and specific mechanism of metformin in cerebral ischemia-reperfusion (I/R) injury by constructing a transient middle cerebral artery occlusion model in vivo and a glucose and oxygen deprivation/reoxygenation (OGD/R) model in vitro. The results of the in vivo experiments showed that acute treatment with low-dose metformin (10 mg/kg) ameliorated cerebral edema, reduced the cerebral infarction volume, improved the neurological deficit score, and ameliorated neuronal apoptosis in the ischemic penumbra. Moreover, metformin up-regulated the brain-derived neurotrophic factor (BDNF) expression and increased phosphorylation levels of AMP-activated protein kinase (AMPK) and cAMP-response element binding protein (CREB) in the ischemia penumbra. Nevertheless, the above-mentioned effects of metformin were reversed by Compound C. The results of the in vitro experiments showed that low metformin concentrations (20 μM) could reduce apoptosis of human umbilical vein endothelial cells (HUVECs) under OGD/R conditions and promote cell proliferation. Moreover, metformin could further promote BDNF expression and release in HUVECs under OGD/R conditions via the AMPK/CREB pathway. The Transwell chamber assay showed that HUVECs treated with metformin could reduce apoptosis of SH-SY5Y cells under OGD/R conditions and this effect could be partially reversed by transfection of BDNF siRNA in HUVECs. In summary, our results suggest that metformin upregulates the level of BDNF in the cerebral ischemic penumbra via the AMPK/CREB pathway, thereby playing a protective effect in cerebral I/R injury.

In vivo effects of nitrosyl hydrogen on cardiac function and sarcoplasmic reticulum calcium pump (SERCA2a) in rats with heart failure after myocardial infarction

Background

Abnormal Ca2+ circulation in cardiomyocytes is an important cause of decreased myocardial contractility in failing hearts. Nitroxyl hydrogen (HNO) can oxidize Ca²⁺ cycle-related proteins, alter their biological functions, promote Ca²⁺ recovery as well as release, and enhance myocardial contractility. In this study, we aim to observe the effect of nitrosyl hydrogen (HNO) on the cardiac function of rats with heart failure and elucidate the underlying mechanism.

Methods

Twenty six male Wistar rats were randomly divided into heart failure group (HF group), Angeli's salt treatment group (HF + AS group) and sham operation group (Sham group). The HF + AS group rats were treated with HNO donor Angeli's salt by intraperitoneal injection of 1 mg/kg/d, and the rats in the HF group and the Sham group were given the same amount of normal saline. Cardiac function was measured by echocardiography before and after treatment. NT-proBNP was measured by enzyme immunoassay (ELISA) kit after treatment. Western blot were used to measure the expression of sarcoplasmic reticulum Ca²⁺-ATPase (SERCA) in protein levels in rats. The activities of SERCA2a were detected by the biochemical kit finally.

Results

We found that Nitrosyl hydrogen could significantly increase LVEF, +dp/dt, -dp/dt (P<0.05), significantly decrease NT-ProBNP and LVEDP (P<0.01), and significantly enhance the activities of SERCA2a protein (P<0.05).

Conclusions

These findings suggest that Nitrosyl hydrogen could improve the cardiac function possibly by increasing protein activities of SERCA2a in rats.

Transgelin interacts with PARP1 in human colon cancer cells

Background

Transgelin, an actin-binding protein, is associated with cytoskeleton remodeling. Findings from our previous studies demonstrated that transgelin was up-regulated in node-positive colorectal cancer (CRC) versus node-negative disease. Over-expression of TAGLN affected the expression of 256 downstream transcripts and increased the metastatic potential of colon cancer cells in vitro and in vivo. This study aims to explore the mechanisms through which transgelin participates in the metastasis of colon cancer cells.

Methods

Immunofluorescence and immunoblotting analysis were used to determine the cellular localization of endogenous and exogenous transgelin in colon cancer cells. Co-immunoprecipitation and subsequently high-performance liquid chromatography/tandem mass spectrometry were performed to identify the proteins that were potentially interacting with transgelin. The 256 downstream transcripts regulated by transgelin were analyzed with bioinformatics methods to discriminate the specific key genes and signaling pathways. The Gene-Cloud of Biotechnology Information (GCBI) tools were used to predict the potential transcription factors (TFs) for the key genes. The predicted TFs corresponded to the proteins identified to interact with transgelin. The interaction between transgelin and the TFs was verified by co-immunoprecipitation and immunofluorescence.

Results

Transgelin was found to localize in both the cytoplasm and nucleus of the colon cancer cells. Approximately 297 proteins were identified to interact with transgelin. The overexpression of TAGLN led to the differential expression of 184 downstream genes. Network topology analysis discriminated seven key genes, including CALM1, MYO1F, NCKIPSD, PLK4, RAC1, WAS and WIPF1, which are mostly involved in the Rho signaling pathway. Poly (ADP-ribose) polymerase-1 (PARP1) was predicted as the unique TF for the key genes and concurrently corresponded to the DNA-binding proteins potentially interacting with transgelin. The interaction between PARP1 and transgelin in human RKO colon cancer cells was further validated by immunoprecipitation and immunofluorescence assays.

Conclusions

Our results suggest that transgelin binds to PARP1 and regulates the expression of downstream key genes, which are mainly involved in the Rho signaling pathway, and thus participates in the metastasis of colon cancer.

Metformin inhibits angiogenesis of endothelial progenitor cells via miR-221-mediated p27 expression and autophagy

Aim: To explore the underlying mechanisms of metformin on the angiogenic capacity of endothelial progenitor cells (EPCs). Results: EPC growth and miR-221 expression decreased concentration-dependence with metformin, and a negative correlation was observed between miR-221 expression and metformin concentration (p < 0.001). miR-221 overexpression using a mimic decreased the metformin-mediated angiogenic effects in EPCs (p < 0.01). Metformin increased p27 and LC3II expression and AMP-activated protein kinase (AMPK) phosphorylation, and decreased p62 expression, while miR-221 overexpression reversed the effects of metformin. Additionally, AMPK inhibition by compound C reversed the increase in p27 and LC3II levels and AMPK phosphorylation or miR-221 siRNA treatment. Conclusion: Metformin inhibits the angiogenic capacity of EPCs. The underlying mechanism involves AMPK-mediated autophagy pathway activity and increases miR-221-mediated p27 expression.

Erythropoietin induces miRNA-210 by JAK2/STAT5 signaling in PBMCs of End-stage Renal Disease patients

Anemia of chronic kidney disease is associated with blunted response/resistance to erythropoietin-stimulating agents (ESAs) in hemodialysis (HD) patients. Several molecules have been successfully associated with ESA responsiveness; however, none of them is now considered a valid therapeutic biomarker of erythropoietin resistance in these patients. We performed an evaluation of the level of specific plasma circulating miRNAs in blood samples of HD patients, in relation to ESA treatment, with a follow-up of 1 year (T0-T3). We found significantly lower circulating levels of all miRNAs analyzed at baseline (T0) in HD patients vs. healthy control (HC). The plasmatic levels of miRNA-210 resulted significantly and negatively associated with Erythropoietin Resistance Index (ERI), and the variance of ΔmiRNA-210 (miRNA-210_T3 minus miRNA-210_T0 ) explained significant percentage of ΔERI (ERI_T3 minus ERI_T0 ) variance. The receiver operating characteristic analysis at T0 showed that the plasmatic level of miRNA-210 could distinguish HD patients with positive or negative trend in ERI at T3. In vitro, recombinant human erythropoietin (EPO) induced significant release of miRNA-210 from cultured peripheral blood mononuclear cells, through the activation of Janus kinase 2 (JAK2)/ signal transducer and activator of transcription 5 (STAT5) signaling, but not by the activation of the MAPK protein 38α and extracellular signal-regulated kinase ½. Accordingly, HD patients with negative ΔERI showed higher level of phosphor-Janus kinase 2 and nuclear translocation of phosphor-signal transducer and activator of transcription 5. vs. patients with positive ΔERI or HC. Our data highlighted that chronic HD significantly reduces the circulating level of the miRNAs evaluated; within the targets analyzed, the miRNA-210 could be considered as a prognostic indicator of ESA responsiveness and index for anemia management.

Mechanisms and Characteristics of Sulfonylureas and Glinides

BACKGROUND

Type 2 diabetes mellitus is a complex progressive endocrine disease characterized by hyperglycemia and life-threatening complications. It is the most common disorder of pancreatic cell function that causes insulin deficiency. Sulfonylurea is a class of oral hypoglycemic drugs. Over the past half century, these drugs, together with the subsequent non-sulfonylureas (glinides), have been the main oral drugs for insulin secretion.

OBJECTIVE

Through in-depth study, the medical profession considers it as an important drug for improving blood sugar control.

METHODS

The mechanism, characteristics, efficacy and side effects of sulfonylureas and glinides were reviewed in detail.

RESULTS

Sulfonylureas and glinides not only stimulated the release of insulin from pancreatic cells, but also had many extrapanular hypoglycemic effect, such as reducing the clearance rate of insulin in liver, reducing the secretion of glucagon, and enhancing the sensitivity of peripheral tissues to insulin in type 2 diabetes mellitus.

CONCLUSION

Sulfonylureas and glinides are effective first-line drugs for the treatment of diabetes mellitus. Although they have the risk of hypoglycemia, weight gain and cardiovascular disease, their clinical practicability and safety can be guaranteed as long as they are reasonably used.

Acute interaction between oral glucose (75 g as Lucozade) and inorganic nitrate: Decreased insulin clearance, but lack of blood pressure-lowering

AIMS

Dietary inorganic nitrate (NO₃ ^- ) lowers peripheral blood pressure (BP) in healthy volunteers, but lacks such effect in individuals with, or at risk of, type 2 diabetes mellitus (T2DM). Whilst this is commonly assumed to be a consequence of chronic hyperglycaemia/hyperinsulinaemia, we hypothesized that acute physiological elevations in plasma [glucose]/[insulin] blunt the haemodynamic responses to NO₃ ^- , a pertinent question for carbohydrate-rich Western diets.

METHODS

We conducted an acute, randomized, placebo-controlled, double-blind, crossover study on the haemodynamic and metabolic effects of potassium nitrate (8 or 24 mmol KNO₃ ) vs. potassium chloride (KCl; placebo) administered 1 hour prior to an oral glucose tolerance test in 33 healthy volunteers.

RESULTS

Compared to placebo, there were no significant differences in systolic or diastolic BP (P = 0.27 and P = 0.30 on ANOVA, respectively) with KNO₃ , nor in pulse wave velocity or central systolic BP (P = 0.99 and P = 0.54 on ANOVA, respectively). Whilst there were significant elevations from baseline for plasma [glucose] and [C-peptide], no differences between interventions were observed. A significant increase in plasma [insulin] was observed with KNO₃ vs. KCl (n = 33; P = 0.014 on ANOVA) with the effect driven by the high-dose cohort (24 mmol, n = 13; P < 0.001 on ANOVA; at T = 0.75 h mean difference 210.4 pmol/L (95% CI 28.5 to 392.3), P = 0.012).

CONCLUSIONS

In healthy adults, acute physiological elevations of plasma [glucose] and [insulin] result in a lack of BP-lowering with dietary nitrate. The increase in plasma [insulin] without a corresponding change in [C-peptide] or [glucose] suggests that high-dose NO₃ ^- decreases insulin clearance. A likely mechanism is via NO-dependent inhibition of insulin-degrading enzyme.

The genome of tapeworm Taenia multiceps sheds light on understanding parasitic mechanism and control of coenurosis disease

Coenurosis, caused by the larval coenurus of the tapeworm Taenia multiceps, is a fatal central nervous system disease in both sheep and humans. Though treatment and prevention options are available, the control of coenurosis still faces presents great challenges. Here, we present a high-quality genome sequence of T. multiceps in which 240 Mb (96%) of the genome has been successfully assembled using Pacbio single-molecule real-time (SMRT) and Hi-C data with a N50 length of 44.8 Mb. In total, 49.5 Mb (20.6%) repeat sequences and 13, 013 gene models were identified. We found that Taenia spp. have an expansion of transposable elements and recent small-scale gene duplications following the divergence of Taenia from Echinococcus, but not in Echinococcus genomes, and the genes underlying environmental adaptability and dosage effect tend to be over-retained in the T. multiceps genome. Moreover, we identified several genes encoding proteins involved in proglottid formation and interactions with the host central nervous system, which may contribute to the adaption of T. multiceps to its parasitic life style. Our study not only provides insights into the biology and evolution of T. multiceps, but also identifies a set of species-specific gene targets for developing novel treatment and control tools for coenurosis.

Ceramide kinase regulates the migration of bone marrow-derived mesenchymal stem cells

Endogenous bone marrow-derived mesenchymal stem cells (BM-MSCs) are mobilized into peripheral blood and injured tissues by various growth factors and cytokines that are expressed in the injured tissues, such as substance P (SP), stromal cell derived factor-1 (SDF-1), and transforming growth factor-beta (TGF-β). Extracellular bioactive lipid metabolites such as ceramide-1-phosphate and sphingosine-1-phosphate also modulate BM-MSC migration as SP, SDF-1, and TGF-β. However, the roles of intrinsic lipid kinases of BM-MSCs in the stem cell migration are unclear. Here, we demonstrated that ceramide kinase mediates the chemotactic migration of BM-MSCs in response to SP, SDF-1, or TGF-β. Furthermore, a specific inhibitor of ceramide kinase inhibited TGF-β-induced migration of BM-MSCs and N-cadherin that is necessary for BM-MSCs migration in response to TGF-β. Therefore, these results suggest that the intracellular ceramide kinase is required for the BM-MSCs migration and the roles of the intrinsic ceramide kinase in the migration are associated with N-cadherin regulation.

New Insights into the Potential Roles of 3-Iodothyronamine (T1AM) and Newly Developed Thyronamine-Like TAAR1 Agonists in Neuroprotection

3-Iodothyronamine (T1AM) is an endogenous high-affinity ligand of the trace amine-associated receptor 1 (TAAR1), detected in mammals in many organs, including the brain. Recent evidence indicates that pharmacological TAAR1 activation may offer a novel therapeutic option for the treatment of a wide range of neuropsychiatric and metabolic disorders. To assess potential neuroprotection by TAAR1 agonists, in the present work, we initially investigated whether T1AM and its corresponding 3-methylbiaryl-methane analog SG-2 can improve learning and memory when systemically administered to mice at submicromolar doses, and whether these effects are modified under conditions of MAO inhibition by clorgyline. Our results revealed that when i.p. injected to mice, both T1AM and SG-2 produced memory-enhancing and hyperalgesic effects, while increasing ERK1/2 phosphorylation and expression of transcription factor c-fos. Notably, both compounds appeared to rely on the action of ubiquitous enzymes MAO to produce the corresponding oxidative metabolites that were then able to activate the histaminergic system. Since autophagy is key for neuronal plasticity, in a second line of experiments we explored whether T1AM and synthetic TAAR1 agonists SG1 and SG2 were able to induce autophagy in human glioblastoma cell lines (U-87MG). After treatment of U-87MG cells with 1 μM T1AM, SG-1, SG-2 transmission electron microscopy (TEM) and immunofluorescence (IF) showed a significant time-dependent increase of autophagy vacuoles and microtubule-associated protein 1 light chain 3 (LC3). Consistently, Western blot analysis revealed a significant increase of the LC3II/LC3I ratio, with T1AM and SG-1 being the most effective agents. A decreased level of the p62 protein was also observed after treatment with T1AM and SG-1, which confirms the efficacy of these compounds as autophagy inducers in U-87MG cells. In the process to dissect which pathway induces ATG, the effects of these compounds were evaluated on the PI3K-AKT-mTOR pathway. We found that 1 μM T1AM, SG-1 and SG-2 decreased pAKT/AKT ratio at 0.5 and 4 h after treatment, suggesting that autophagy is induced by inhibiting mTOR phosphorylation by PI3K-AKT-mTOR pathway. In conclusion, our study shows that T1AM and thyronamine-like derivatives SG-1 and SG-2 might represent valuable tools to therapeutically intervene with neurological disorders.

The anti-inflammatory effects of Yunnan Baiyao are involved in regulation of the phospholipase A2/arachidonic acid metabolites pathways in acute inflammation rat model

The traditional Chinese medicine Yunnan Baiyao (YNB) has been reported to possess anti-inflammatory properties, however its mechanism of action remains unclear. It was previously reported that YNB ameliorated depression of arachidonic acid (AA) levels in a rat model of collagen-induced arthritis. In the current study, the capacity of YNB to ameliorate inflammation was compared in carrageenan-induced and AA-induced acute inflammation of the rat paw with celecoxib and mizolastine, respectively (n=24 per group). The capacity of YNB to affect the phospholipase A2 (PLA2)/AA pathway (using reverse transcription-quantitative polymerase chain reaction) and release of inflammatory lipid mediators (by ELISA) were investigated. Celecoxib ameliorated carrageenan-induced paw edema, and mizolastine ameliorated AA-induced rat paw edema. YNB alleviated paw edema and inhibited inflammatory cell infiltration in the two models. YNB inhibited production of 5-LOX AA metabolite leukotriene B4 (LTB4), and suppressed expression of 5-LOX, cytosolic PLA2 (cPLA2), 5-LOX-activating protein, and LTB4 receptor mRNA in the AA-induced inflammation model (P<0.05). YNB Inhibited the production of the COX-2 AA metabolite prostaglandin E2 (PGE2) and suppressed expression of COX-2, cPLA2, PGE2 mRNA in the carrageenan-induced inflammation mode (P<0.05). Taken together, the data suggest that modulation of COX and LOX pathways in AA metabolism represent a novel anti-inflammatory mechanism of YNB.

Erythropoietin ameliorates diabetes-associated cognitive dysfunction in vitro and in vivo

Several studies indicate that erythropoietin (EPO) has remarkable neuroprotective effects in various central nervous system disorders, while little is known about the effects of EPO in diabetes-associated cognitive dysfunction. Therefore, the present study aimed to investigate whether EPO ameliorates diabetes-associated cognitive dysfunction in vivo and in vitro. We investigated the protective effects of EPO on high-glucose (HG)-induced PC12 cell death and oxidative stress. The effects of EPO (300 U/kg administered three times a week for 4 weeks) on diabetes-associated cognitive decline were investigated in diabetic rats. EPO significantly increased cell viability, increased the activity of superoxide dismutase, decreased the production of malondialdehyde and reactive oxygen species, and decreased the apoptosis rate. Additionally, LY294002, a phosphatidylinositol 3-kinase (PI3K) inhibitor, abolished the protective effects of EPO in HG-treated PC12 cells. In diabetic rats, EPO prevented deficits in spatial learning and memory in the Morris water maze test. The results of real-time PCR and Western blotting showed that EPO upregulated EPO receptor, PI3K, and phosphorylated Akt2 relative to unphosphorylated Akt2 (p-Akt2/Akt2) and downregulated glycogen synthase kinase-3β (GSK-3β). These studies demonstrate that EPO is an effective neuroprotective agent in the context of diabetes-associated cognitive dysfunction and show that this effect involves the PI3K/Akt/GSK-3β pathway.

Pharmacological inhibition of MAGL attenuates experimental colon carcinogenesis

Colorectal cancer (CRC) is a major health problem in Western countries. The endocannabinoid 2-arachidonoyl-glycerol (2-AG) exerts antiproliferative actions in a number of tumoral cell lines, including CRC cells. Monoacylglycerol lipase (MAGL), a serine hydrolase that inactivates 2-AG, is highly expressed in aggressive human cancer cells. Here, we investigated the role of MAGL in experimental colon carcinogenesis. The role of MAGL was assessed in vivo by using the xenograft and the azoxymethane models of colon carcinogenesis; MAGL expression was evaluated by RT-PCR and immunohistochemistry; 2-AG levels were measured by liquid chromatography mass spectrometry; angiogenesis was evaluated in tumor tissues [by microvessel counting and by investigating the expression of vascular endothelial growth factor (VEGF) and fibroblast growth factor-2 (FGF-2) proteins] as well as in human umbilical vein endothelial cells (HUVEC); cyclin D1 was evaluated by RT-PCR. MAGL and 2-AG were strongly expressed in tumor tissues. The MAGL inhibitor URB602 reduced xenograft tumor volume, this effect being associated to down-regulation of VEGF and FGF-2, reduction in the number of vessels and down-regulation of cyclin D1. In HUVEC, URB602 exerted a direct antiangiogenic effect by inhibiting FGF-2 induced proliferation and migration, and by modulating pro/anti-angiogenic agents. In experiments aiming at investigating the role of MAGL in chemoprevention, URB602 attenuated azoxymethane-induced preneoplastic lesions, polyps and tumors. MAGL, possibly through modulation of angiogenesis, plays a pivotal role in experimental colon carcinogenesis. Pharmacological inhibition of MAGL could represent an innovative therapeutic approach to reduce colorectal tumor progression.

Inflammation: maladies, models, mechanisms and molecules

The continued focus of attention on the diversity of mechanisms underpinning inflammation has improved our understanding of the potential to target specific pathways in the inflammatory network to achieve meaningful therapeutic gains. In this themed issue of the British Journal of Pharmacology our scope was deliberately broad, ranging across both acute and chronic disease in various organs. Pro- and anti-inflammatory mechanisms receive attention as does the phenotype of macrophages. Whilst the manifestations of neuro-inflammation are less obvious than those in peripheral tissues, central innate and adaptive immunity in brain and the M1/M2 phenotypes of microglia are topics of special interest. The contributions to the inflammatory milieu of cytokines, chemokines and associated signalling cascades are considered. Overall, the coverage herein advances the basic science underpinning our understanding of inflammation and emphasizes its importance in different pathologies.

Mechanisms by which the thiazolidinedione troglitazone protects against sucrose-induced hepatic fat accumulation and hyperinsulinaemia

BACKGROUND AND PURPOSE

Thiazolidinediones (TZD) are known to ameliorate fatty liver in type 2 diabetes. To date, the underlying mechanisms of their hepatic actions remain unclear.

EXPERIMENTAL APPROACH

Hepatic triglyceride content and export rates were assessed in 2 week high-sucrose-fed Wistar rats treated with troglitazone and compared with untreated high-sucrose rodent controls. Fractional de novo lipogenesis (DNL) contributions to hepatic triglyceride were quantified by analysis of triglyceride enrichment from deuterated water. Hepatic insulin clearance and NO status during a meal tolerance test were also evaluated.

KEY RESULTS

TZD significantly reduced hepatic triglyceride (P < 0.01) by 48%, decreased DNL contribution to hepatic triglyceride (P < 0.01) and increased postprandial non-esterified fatty acids clearance rates (P < 0.01) in comparison with the high-sucrose rodent control group. During a meal tolerance test, plasma insulin AUC was significantly lower (P < 0.01), while blood glucose and plasma C-peptide levels were not different. Insulin clearance was increased (P < 0.001) by 24% and was associated with a 22% augmentation of hepatic insulin-degrading enzyme activity (P < 0.05). Finally, hepatic NO was decreased by 24% (P < 0.05).

CONCLUSIONS

Overall, TZD show direct actions on liver by reducing hepatic DNL and increasing hepatic insulin clearance. The alterations in hepatic insulin clearance were associated with changes in insulin-degrading enzyme activity, with possible modulation of NO levels.

Down-regulation of IL-8 by high-dose vitamin D is specific to hyperinflammatory macrophages and involves mechanisms beyond up-regulation of DUSP1

BACKGROUND AND PURPOSE

There is current interest in vitamin D as a potential anti-inflammatory treatment for chronic inflammatory lung disease, including cystic fibrosis (CF). Vitamin D transcriptionally up-regulates the anti-inflammatory gene DUSP1, which partly controls production of the inflammatory chemokine IL-8. IL-8 is overabundant in CF airways, potentially due to hyperinflammatory responses of CF macrophages. We tested the ability of vitamin D metabolites to down-regulate IL-8 production in CF macrophages.

EXPERIMENTAL APPROACH

CF and healthy monocyte-derived macrophages (MDM) were treated with two vitamin D metabolites, 25-hydroxyvitamin D3 (25OHD3 ) and 1,25-dihydroxyvitamin D3 (1,25(OH)2 D3 ), or paricalcitol, synthetic analogue of 1,25(OH)2 D3 . 25OHD3 was tested at doses of 25-150 nM, whereas 1,25(OH)2 D3 and paricalcitol at doses of up to 100 nM. IL-8 was stimulated by bacterial virulence factors. As potential anti-inflammatory mechanism of vitamin D metabolites, we assessed up-regulation of DUSP1.

KEY RESULTS

MDM from patients with CF and some healthy donors showed excessive production of stimulated IL-8, highlighting their hyperinflammatory phenotype. Vitamin D metabolites down-regulated stimulated IL-8 only in those hyperinflammatory MDM, and only when used at high doses (>100 nM for 25OHD3 , or >1 nM for 1,25(OH)2 D3 and paricalcitol). The magnitude of IL-8 down-regulation by vitamin D metabolites or paricalcitol was moderate (∼30% vs. >70% by low-dose dexamethasone). Transcriptional up-regulation of DUSP1 by vitamin D metabolites was seen in all tested MDM, regardless of IL-8 down-regulation.

CONCLUSIONS AND IMPLICATIONS

Vitamin D metabolites and their analogues moderately down-regulate IL-8 in hyperinflammatory macrophages, including those from CF. This down-regulation appears to go through DUSP1-independent mechanisms.

The phytocannabinoid, Δ⁹-tetrahydrocannabivarin, can act through 5-HT₁A receptors to produce antipsychotic effects

BACKGROUND AND PURPOSE

This study aimed to address the questions of whether Δ(9)-tetrahydrocannabivarin (THCV) can (i) enhance activation of 5-HT1 A receptors in vitro and (ii) induce any apparent 5-HT₁A receptor-mediated antipsychotic effects in vivo.

EXPERIMENTAL APPROACH

In vitro studies investigated the effect of THCV on targeting by 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) of 5-HT₁A receptors in membranes obtained from rat brainstem or human 5-HT₁A CHO cells, using [(35)S]-GTPγS and 8-[(3)H]-OH-DPAT binding assays. In vivo studies investigated whether THCV induces signs of 5-HT₁A receptor-mediated antipsychotic effects in rats.

KEY RESULTS

THCV (i) potently, albeit partially, displaced 8-[(3) H]-OH-DPAT from specific binding sites in rat brainstem membranes; (ii) at 100 nM, significantly enhanced 8-OH-DPAT-induced activation of receptors in these membranes; (iii) produced concentration-related increases in 8-[(3)H]-OH-DPAT binding to specific sites in membranes of human 5-HT₁A receptor-transfected CHO cells; and (iv) at 100 nM, significantly enhanced 8-OH-DPAT-induced activation of these human 5-HT₁A receptors. In phencyclidine-treated rats, THCV, like clozapine (i) reduced stereotyped behaviour; (ii) decreased time spent immobile in the forced swim test; and (iii) normalized hyperlocomotor activity, social behaviour and cognitive performance. Some of these effects were counteracted by the 5-HT₁A receptor antagonist, WAY100635, or could be reproduced by the CB₁ antagonist, AM251.

CONCLUSIONS AND IMPLICATIONS

Our findings suggest that THCV can enhance 5-HT₁A receptor activation, and that some of its apparent antipsychotic effects may depend on this enhancement. We conclude that THCV has therapeutic potential for ameliorating some of the negative, cognitive and positive symptoms of schizophrenia.

Ketamine coadministration attenuates morphine tolerance and leads to increased brain concentrations of both drugs in the rat

Background and Purpose

The effects of ketamine in attenuating morphine tolerance have been suggested to result from a pharmacodynamic interaction. We studied whether ketamine might increase brain morphine concentrations in acute coadministration, in morphine tolerance and morphine withdrawal.

Experimental Approach

Morphine minipumps (6 mg·day^–1) induced tolerance during 5 days in Sprague–Dawley rats, after which s.c. ketamine (10 mg·kg^–1) was administered. Tail flick, hot plate and rotarod tests were used for behavioural testing. Serum levels and whole tissue brain and liver concentrations of morphine, morphine-3-glucuronide, ketamine and norketamine were measured using HPLC-tandem mass spectrometry.

Key Results

In morphine-naïve rats, ketamine caused no antinociception whereas in morphine-tolerant rats there was significant antinociception (57% maximum possible effect in the tail flick test 90 min after administration) lasting up to 150 min. In the brain of morphine-tolerant ketamine-treated rats, the morphine, ketamine and norketamine concentrations were 2.1-, 1.4- and 3.4-fold, respectively, compared with the rats treated with morphine or ketamine only. In the liver of morphine-tolerant ketamine-treated rats, ketamine concentration was sixfold compared with morphine-naïve rats. After a 2 day morphine withdrawal period, smaller but parallel concentration changes were observed. In acute coadministration, ketamine increased the brain morphine concentration by 20%, but no increase in ketamine concentrations or increased antinociception was observed.

Conclusions and Implications

The ability of ketamine to induce antinociception in rats made tolerant to morphine may also be due to increased brain concentrations of morphine, ketamine and norketamine. The relevance of these findings needs to be assessed in humans.

The novel, orally available and peripherally restricted selective cannabinoid CB2 receptor agonist LEI-101 prevents cisplatin-induced nephrotoxicity

BACKGROUND AND PURPOSE

Here, we have characterized 3-cyclopropyl-1-(4-(6-((1,1-dioxidothiomorpholino)methyl)-5-fluoropyridin-2-yl)benzyl)imidazolidine-2,4-dione hydrochloride (LEI-101) as a novel, peripherally restricted cannabinoid CB2 receptor agonist, using both in vitro and in vivo models.

EXPERIMENTAL APPROACH

We investigated the effects of LEI-101 on binding and functional activity. We assessed its in vitro and in vivo selectivity. Efficacy of LEI-101 was determined in a mouse model of cisplatin-induced nephrotoxicity.

KEY RESULTS

LEI-101 behaved as a partial agonist at CB2 receptors using β-arrestin and GTPγS assays and was ~100-fold selective in CB2 /CB1 receptor-binding assays. It did not display any activity on endocannabinoid hydrolases and nor did it react with serine hydrolases in an activity-based protein profiling assay. In mice, LEI-101 had excellent oral bioavailability reaching high concentrations in the kidney and liver with minimal penetration into the brain. LEI-101 up to a dose of 60 mg·kg(-1) (p.o.) did not exert any CNS-mediated effects in the tetrad assay, in mice. LEI-101 (p.o. or i.p.) at 3 or 10 mg·kg(-1) dose-dependently prevented kidney dysfunction and/or morphological damage induced by cisplatin in mice. These protective effects were associated with improved renal histopathology, attenuated oxidative stress and inflammation in the kidney. These effects were absent in CB2 receptor knockout mice.

CONCLUSION AND IMPLICATIONS

These results indicate that LEI-101 is a selective, largely peripherally restricted, orally available CB2 receptor agonist with therapeutic potential in diseases that are associated with inflammation and/or oxidative stress, including kidney disease.

COPD and squamous cell lung cancer: aberrant inflammation and immunity is the common link

Cigarette smoking has reached epidemic proportions within many regions of the world and remains the highest risk factor for chronic obstructive pulmonary disease (COPD) and lung cancer. Squamous cell lung cancer is commonly detected in heavy smokers, where the risk of developing lung cancer is not solely defined by tobacco consumption. Although therapies that target common driver mutations in adenocarcinomas are showing some promise, they are proving ineffective in smoking-related squamous cell lung cancer. Since COPD is characterized by an excessive inflammatory and oxidative stress response, this review details how aberrant innate, adaptive and systemic inflammatory processes can contribute to lung cancer susceptibility in COPD. Activated leukocytes release increasing levels of proteases and free radicals as COPD progresses and tertiary lymphoid aggregates accumulate with increasing severity. Reactive oxygen species promote formation of reactive carbonyls that are not only tumourigenic through initiating DNA damage, but can directly alter the function of regulatory proteins involved in host immunity and tumour suppressor functions. Systemic inflammation is also markedly increased during infective exacerbations in COPD and the interplay between tumour-promoting serum amyloid A (SAA) and IL-17A is discussed. SAA is also an endogenous allosteric modifier of FPR2 expressed on immune and epithelial cells, and the therapeutic potential of targeting this receptor is proposed as a novel strategy for COPD-lung cancer overlap.

Progressive inflammation-mediated neurodegeneration after traumatic brain or spinal cord injury

Traumatic brain injury (TBI) has been linked to dementia and chronic neurodegeneration. Described initially in boxers and currently recognized across high contact sports, the association between repeated concussion (mild TBI) and progressive neuropsychiatric abnormalities has recently received widespread attention, and has been termed chronic traumatic encephalopathy. Less well appreciated are cognitive changes associated with neurodegeneration in the brain after isolated spinal cord injury. Also under-recognized is the role of sustained neuroinflammation after brain or spinal cord trauma, even though this relationship has been known since the 1950s and is supported by more recent preclinical and clinical studies. These pathological mechanisms, manifested by extensive microglial and astroglial activation and appropriately termed chronic traumatic brain inflammation or chronic traumatic inflammatory encephalopathy, may be among the most important causes of post-traumatic neurodegeneration in terms of prevalence. Importantly, emerging experimental work demonstrates that persistent neuroinflammation can cause progressive neurodegeneration that may be treatable even weeks after traumatic injury.

Bcl-2 phosphorylation confers resistance on chronic lymphocytic leukaemia cells to the BH3 mimetics ABT-737, ABT-263 and ABT-199 by impeding direct binding

BACKGROUND AND PURPOSE

Although the ongoing clinical trials of ABT-263 and ABT-199 in chronic lymphocytic leukaemia (CLL) have indicated that BH3 mimetics hold considerable promise, understanding the mechanism of CLL resistance to BH3 mimetics remains a challenge.

EXPERIMENTAL APPROACH

The LD50 values of ABT-737, ABT-263 and ABT-199 in a number of primary CLL cells from 40 patients, were determined. The levels of Bcl-2 family proteins, including phosphorylated Bcl-2 (pBcl-2) and their interactions were measured by immunoblotting and co-immunoprecipitation. In vitro binding assays were performed by isothermal titration calorimetry and ELISA. BH3 profiling in isolated mitochondria was analysed.

KEY RESULTS

The ratio of (Mcl-1 + pBcl-2) to Bcl-2 expression provided the most significant predictive marker for the cytotoxic potential of ABT-737, ABT-263 and ABT-199 in the panel of CLL samples. Mechanistically, pBcl-2 inhibited the effects of the ABT compounds on the displacement of Bax and Bim from Bcl-2, thereby suppressing mitochondrial apoptosis. The ABT compounds exhibited 100-300-fold lower binding affinity to the glutamic acid, phosphomimetic, mutant of Bcl-2 (T69E, S70E and S87E; EEE-Bcl-2). BH3 peptides exhibited different rank orders of binding affinities to full-length WT-Bcl-2 and full-length EEE-Bcl-2.

CONCLUSIONS AND IMPLICATIONS

Our study suggested that a structural alteration in the BH3-binding groove was induced by phosphorylation of Bcl-2. Our data also provided a framework to overcome resistance of CLL cells to the ABT compounds by combining pBcl-2 kinase inhibitors with the ABT compounds.

Microglial activation and progressive brain changes in schizophrenia

Schizophrenia is a debilitating disorder that typically begins in adolescence and is characterized by perceptual abnormalities, delusions, cognitive and behavioural disturbances and functional impairments. While current treatments can be effective, they are often insufficient to alleviate the full range of symptoms. Schizophrenia is associated with structural brain abnormalities including grey and white matter volume loss and impaired connectivity. Recent findings suggest these abnormalities follow a neuroprogressive course in the earliest stages of the illness, which may be associated with episodes of acute relapse. Neuroinflammation has been proposed as a potential mechanism underlying these brain changes, with evidence of increased density and activation of microglia, immune cells resident in the brain, at various stages of the illness. We review evidence for microglial dysfunction in schizophrenia from both neuroimaging and neuropathological data, with a specific focus on studies examining microglial activation in relation to the pathology of grey and white matter. The studies available indicate that the link between microglial dysfunction and brain change in schizophrenia remains an intriguing hypothesis worthy of further examination. Future studies in schizophrenia should: (i) use multimodal imaging to clarify this association by mapping brain changes longitudinally across illness stages in relation to microglial activation; (ii) clarify the nature of microglial dysfunction with markers specific to activation states and phenotypes; (iii) examine the role of microglia and neurons with reference to their overlapping roles in neuroinflammatory pathways; and (iv) examine the impact of novel immunomodulatory treatments on brain structure in schizophrenia.

Immunoinflammatory diseases of the central nervous system - the tale of two cytokines

Cytokines are potent mediators of cellular communication that have crucial roles in the regulation of innate and adaptive immunoinflammatory responses. Clear evidence has emerged in recent years that the dysregulated production of cytokines may in itself be causative in the pathogenesis of certain immunoinflammatory disorders. Here we review current evidence for the involvement of two different cytokines, IFN-α and IL-6, as principal mediators of specific immunoinflammatory disorders of the CNS. IFN-α belongs to the type I IFN family and is causally linked to the development of inflammatory encephalopathy exemplified by the genetic disorder, Aicardi-Goutières syndrome. IL-6 belongs to the gp130 family of cytokines and is causally linked to a number of immunoinflammatory disorders of the CNS including neuromyelitis optica, idiopathic transverse myelitis and genetically linked autoinflammatory neurological disease. In addition to clinical evidence, experimental studies, particularly in genetically engineered mouse models with astrocyte-targeted, CNS-restricted production of IFN-α or IL-6 replicate many of the cardinal neuropathological features of these human cytokine-linked immunoinflammatory neurological disorders giving crucial evidence for a direct causative role of these cytokines and providing further rationale for the therapeutic targeting of these cytokines in neurological diseases where indicated.

Microglial M1/M2 polarization and metabolic states

Microglia are critical nervous system-specific immune cells serving as tissue-resident macrophages influencing brain development, maintenance of the neural environment, response to injury and repair. As influenced by their environment, microglia assume a diversity of phenotypes and retain the capability to shift functions to maintain tissue homeostasis. In comparison with peripheral macrophages, microglia demonstrate similar and unique features with regards to phenotype polarization, allowing for innate immunological functions. Microglia can be stimulated by LPS or IFN-γ to an M1 phenotype for expression of pro-inflammatory cytokines or by IL-4/IL-13 to an M2 phenotype for resolution of inflammation and tissue repair. Increasing evidence suggests a role of metabolic reprogramming in the regulation of the innate inflammatory response. Studies using peripheral immune cells demonstrate that polarization to an M1 phenotype is often accompanied by a shift in cells from oxidative phosphorylation to aerobic glycolysis for energy production. More recently, the link between polarization and mitochondrial energy metabolism has been considered in microglia. Under these conditions, energy demands would be associated with functional activities and cell survival and thus, may serve to influence the contribution of microglia activation to various neurodegenerative conditions. This review examines the polarization states of microglia and their relationship to mitochondrial metabolism. Additional supporting experimental data are provided to demonstrate mitochondrial metabolic shifts in primary microglia and the BV-2 microglia cell line induced under LPS (M1) and IL-4/IL-13 (M2) polarization.

Mirabegron relaxes urethral smooth muscle by a dual mechanism involving β3 -adrenoceptor activation and α1 -adrenoceptor blockade

LINKED ARTICLE

This article is commented on by Michel, M. C., pp. 429-430 of this issue. To view this commentary visit http://dx.doi.org/10.1111/bph.13379.

BACKGROUND AND PURPOSE

Mirabegron is the first β3 -adrenoceptor agonist approved for treatment of overactive bladder syndrome. This study aimed to investigate the effects of β3 -adrenoceptor agonist mirabegron in mouse urethra. The possibility that mirabegron also exerts α1 -adrenoceptor antagonism was also tested in rat smooth muscle preparations presenting α1A - (vas deferens and prostate), α1D - (aorta) and α1B -adrenoceptors (spleen).

EXPERIMENTAL APPROACH

Functional assays were carried out in mouse and rat isolated tissues. Competition assays for the specific binding of [(3) H]prazosin to membrane preparations of HEK-293 cells expressing each of the human α1 -adrenoceptors, as well as β-adrenoceptor mRNA expression and cyclic AMP measurements in mouse urethra, were performed.

KEY RESULTS

Mirabegron produced concentration-dependent urethral relaxations that were shifted to the right by the selective β3 -adrenoceptor antagonist L-748,337 but unaffected by β1 - and β2 -adrenoceptor antagonists (atenolol and ICI-118,551 respectively). Mirabegron-induced relaxations were enhanced by the PDE4 inhibitor rolipram, and the agonist stimulated cAMP synthesis. Mirabegron also produced rightward shifts in urethral contractions induced by the α1 -adrenoceptor agonist phenylephrine. Schild regression analysis revealed that mirabegron behaves as a competitive antagonist of α1 -adrenoceptors in urethra, vas deferens and prostate (α1A -adrenoceptor, pA2  ≅ 5.6) and aorta (α1D -adrenoceptor, pA2  ≅ 5.4) but not in spleen (α1B -adrenoceptor). The affinities estimated for mirabegron in functional assays were consistent with those estimated in radioligand binding with human recombinant α1A - and α1D -adrenoceptors (pKi  ≅ 6.0).

CONCLUSION AND IMPLICATIONS

The effects of mirabegron in urethral smooth muscle are the result of β3 -adrenoceptor agonism together with α1A and α1D -adrenoceptor antagonism.

Enhanced serelaxin signalling in co-cultures of human primary endothelial and smooth muscle cells

BACKGROUND AND PURPOSE

In the phase III clinical trial, RELAX-AHF, serelaxin caused rapid and long-lasting haemodynamic changes. However, the cellular mechanisms involved are unclear in humans.

EXPERIMENTAL APPROACH

This study examined the effects of serelaxin in co-cultures of human primary endothelial cells (ECs) and smooth muscle cells (SMCs) on cAMP and cGMP signalling.

KEY RESULTS

Stimulation of HUVECs or human coronary artery endothelial cells (HCAECs) with serelaxin, concentration-dependently increased cGMP accumulation in co-cultured SMCs to a greater extent than in monocultures of either cell type. This was not observed in human umbilical artery endothelial cells (HUAECs) that do not express the relaxin receptor, RXFP1. Treatment of ECs with l-N(G) -nitro arginine (NOARG; 30 μM, 30 min) inhibited serelaxin-mediated (30 nM) cGMP accumulation in HUVECs, HCAECs and co-cultured SMCs. In HCAECs, but not HUVECs, pre-incubation with indomethacin (30 μM, 30 min) also inhibited cGMP accumulation in SMCs. Pre-incubation of SMCs with the guanylate cyclase inhibitor ODQ (1 μM, 30 min) had no effect on serelaxin-mediated (30 nM) cGMP accumulation in HUVECs and HCAECs but inhibited cGMP accumulation in SMCs. Serelaxin stimulation of HCAECs, but not HUVECs, increased cAMP accumulation concentration-dependently in SMCs. Pre-incubation of HCAECs with indomethacin, but not l-NOARG, abolished cAMP accumulation in co-cultured SMCs, suggesting involvement of prostanoids.

CONCLUSIONS AND IMPLICATIONS

In co-cultures, treatment of ECs with serelaxin caused marked cGMP accumulation in SMCs and with HCAEC also cAMP accumulation. Responses involved EC-derived NO and with HCAEC prostanoid production. Thus, serelaxin differentially modulates vascular tone in different vascular beds.

Threonine532 phosphorylation in ClC-3 channels is required for angiotensin II-induced Cl(-) current and migration in cultured vascular smooth muscle cells

BACKGROUND AND PURPOSE

Angiotensin II (AngII) induces migration and growth of vascular smooth muscle cell (VSMC), which is responsible for vascular remodelling in some cardiovascular diseases. Ang II also activates a Cl(-) current, but the underlying mechanism is not clear.

EXPERIMENTAL APPROACH

The A10 cell line and primary cultures of VSMC from control, ClC-3 channel null mice and WT mice made hypertensive with AngII infusions were used. Techniques employed included whole-cell patch clamp, co-immunoprecipitation, site-specific mutagenesis and Western blotting,

KEY RESULTS

In VSMC, AngII induced Cl(-) currents was carried by the chloride ion channel ClC-3. This current was absent in VSMC from ClC-3 channel null mice. The AngII-induced Cl(-) current involved interactions between ClC-3 channels and Rho-kinase 2 (ROCK2), shown by N- or C-terminal truncation of ClC-3 protein, ROCK2 siRNA and co-immunoprecipitation assays. Phosphorylation of ClC-3 channels at Thr(532) by ROCK2 was critical for AngII-induced Cl(-) current and VSMC migration. The ClC-3 T532D mutant (mutation of Thr(532) to aspartate), mimicking phosphorylated ClC-3 protein, significantly potentiated AngII-induced Cl(-) current and VSMC migration, while ClC-3 T532A (mutation of Thr(532) to alanine) had the opposite effects. AngII-induced cell migration was markedly decreased in VSMC from ClC-3 channel null mice that was insensitive to Y27632, an inhibitor of ROCK2. In addition, AngII-induced cerebrovascular remodelling was decreased in ClC-3 null mice, possibly by the ROCK2 pathway.

CONCLUSIONS AND IMPLICATIONS

ClC-3 protein phosphorylation at Thr(532) by ROCK2 is required for AngII-induced Cl(-) current and VSMC migration that are involved in AngII-induced vascular remodelling in hypertension.

APT070 (mirococept), a membrane-localizing C3 convertase inhibitor, attenuates early human islet allograft damage in vitro and in vivo in a humanized mouse model

Background and Purpose

A major obstacle to islet cell transplantation is the early loss of transplanted islets resulting from the instant blood‐mediated inflammation reaction (IBMIR). The activation of complement pathways plays a central role in IBMIR. The aim of this study was to test the inhibitory effect of “painting” human islets with APT070, a membrane‐localizing C3 convertase inhibitor, on inflammation evoked by exposure to human serum in vitro and by transplantation in vivo in a humanized diabetic mouse model.

Experimental Approach

In vitro, human islets pre‐incubated with APT070 were exposed to allogeneic whole blood. In vivo, similarly treated islets were transplanted underneath the kidney capsule of streptozotocin‐induced diabetic NOD‐SCID IL2rγ^−/− mice that had been reconstituted with human CD34⁺ stem cells. Complement activation and islet hormone content were assayed using enzyme‐linked immunosorbent assays. Supernatants and sera were assayed for cytokines using cytometric beads array. Morphology of the islets incubated with human serum in vitro and in graft‐bearing kidney were evaluated using immunofluorescence staining.

Key Results

Pre‐incubation with APT070 decreased C‐peptide release and iC3b production in vitro, with diminished deposition of C4d and C5b‐9 in islets embedded in blood clots. In vivo, the APT070‐treated islets maintained intact structure and showed less infiltration of inflammatory cells than untreated islets. The pretreatments also significantly reduced pro‐inflammatory cytokines in supernatants and sera.

Conclusions and Implications

Pre‐treatment of islets with APT070 could reduce intra‐islet inflammation with accompanying preservation of insulin secretion by beta cells. APT070 could be as a potential therapeutic tool in islet transplantation.

Hydrogen sulfide: physiological properties and therapeutic potential in ischaemia

Hydrogen sulfide (H2 S) has become a molecule of high interest in recent years, and it is now recognized as the third gasotransmitter in addition to nitric oxide and carbon monoxide. In this review, we discuss the recent literature on the physiology of endogenous and exogenous H2 S, focusing upon the protective effects of hydrogen sulfide in models of hypoxia and ischaemia.

Unravelling the theories of pre-eclampsia: are the protective pathways the new paradigm?

Pre-eclampsia is a vascular disorder of pregnancy where anti-angiogenic factors, systemic inflammation and oxidative stress predominate, but none can claim to cause pre-eclampsia. This review provides an alternative to the ‘two-stage model’ of pre-eclampsia in which abnormal spiral arteries modification leads to placental hypoxia, oxidative stress and aberrant maternal systemic inflammation. Very high maternal soluble fms-like tyrosine kinase-1 (sFlt-1 also known as sVEGFR) and very low placenta growth factor (PlGF) are unique to pre-eclampsia; however, abnormal spiral arteries and excessive inflammation are also prevalent in other placental disorders. Metaphorically speaking, pregnancy can be viewed as a car with an accelerator and brakes, where inflammation, oxidative stress and an imbalance in the angiogenic milieu act as the ‘accelerator’. The ‘braking system’ includes the protective pathways of haem oxygenase 1 (also referred as Hmox1 or HO-1) and cystathionine-γ-lyase (also known as CSE or Cth), which generate carbon monoxide (CO) and hydrogen sulphide (H₂S) respectively. The failure in these pathways (brakes) results in the pregnancy going out of control and the system crashing. Put simply, pre-eclampsia is an accelerator–brake defect disorder. CO and H₂S hold great promise because of their unique ability to suppress the anti-angiogenic factors sFlt-1 and soluble endoglin as well as to promote PlGF and endothelial NOS activity. The key to finding a cure lies in the identification of cheap, safe and effective drugs that induce the braking system to keep the pregnancy vehicle on track past the finishing line.

Exogenous administration of thiosulfate, a donor of hydrogen sulfide, attenuates angiotensin II-induced hypertensive heart disease in rats

BACKGROUND AND PURPOSE

Hypertension is an important mediator of cardiac damage and remodelling. Hydrogen sulfide (H2S) is an endogenously produced gasotransmitter with cardioprotective properties. However, it is not yet in clinical use. We, therefore, investigated the protective effects of sodium thiosulfate (STS), a clinically applicable H2 S donor substance, in angiotensin II (Ang II)-induced hypertensive cardiac disease in rats.

EXPERIMENTAL APPROACH

Male Sprague Dawley rats were infused with Ang II (435 ng kg min(-1)) or saline (control) for 3 weeks via s.c. placed osmotic minipumps. During these 3 weeks, rats received i.p. injections of either STS, NaHS or vehicle (0.9% NaCl).

KEY RESULTS

Compared with controls, Ang II infusion caused an increase in systolic and diastolic BP with associated cardiac damage as evidenced by cardiac hypertrophy, an increase in atrial natriuretic peptide (ANP) mRNA, cardiac fibrosis and increased oxidative stress. Treatment with NaHS and STS prevented the development of hypertension and the increase in ANP mRNA levels. Furthermore, the degree of cardiac hypertrophy, the extent of histological fibrosis in combination with the expression of profibrotic genes and the levels of oxidative stress were all significantly decreased.

CONCLUSIONS AND IMPLICATIONS

Ang II-induced hypertensive cardiac disease can be attenuated by treatment with STS and NaHS. Although BP regulation is the most plausible mechanism of cardiac protection, the antifibrotic and antioxidant properties of released sulfide may also contribute to their effects. Our data show that H2 S might be a valuable addition to the already existing antihypertensive and cardioprotective therapies.

Identification of a resveratrol tetramer as a potent inhibitor of hepatitis C virus helicase

BACKGROUND AND PURPOSE

Hepatitis C virus (HCV) infection is responsible for various chronic inflammatory liver diseases. Here, we have identified a naturally occurring compound with anti-HCV activity and have elucidated its mode of antiviral action.

EXPERIMENTAL APPROACH

Luciferase reporter and real-time RT-PCR assays were used to measure HCV replication. Western blot, fluorescence-labelled HCV replicons and infectious clones were employed to quantitate expression levels of viral proteins. Resistant HCV mutant mapping, in vitro NS3 protease, helicase, NS5B polymerase and drug affinity responsive target stability assays were also used to study the antiviral mechanism.

KEY RESULTS

A resveratrol tetramer, vitisin B from grapevine root extract showed high potency against HCV replication (EC50 = 6 nM) with relatively low cytotoxicity (EC50 >10 μM). Combined treatment of vitisin B with an NS5B polymerase inhibitor (sofosbuvir) exhibited a synergistic or at least additive antiviral activity. Analysis of a number of vitisin B-resistant HCV variants suggested an NS3 helicase as its potential target. We confirmed a direct binding between vitisin B and a purified NS3 helicase in vitro. Vitisin B was a potent inhibitor of a HCV NS3 helicase (IC50 = 3 nM). In vivo, Finally, we observed a preferred tissue distribution of vitisin B in the liver after i.p. injection in rats, at clinically attainable concentrations. Conclusion and Implications Vitisin B is one of the most potent HCV helicase inhibitors identified so far. Vitisin B is thus a prime candidate to be developed as the first HCV drug derived from natural products.

Identification of N-arachidonoyl dopamine as a highly biased ligand at cannabinoid CB1 receptors

BACKGROUND AND PURPOSE

N-arachidonyl dopamine (NADA) has been identified as a putative endocannabinoid, but there is little information about which signalling pathways it activates. The purpose of this study was to identify the signalling pathways activated by NADA in vitro.

EXPERIMENTAL APPROACH

Human or rat cannabinoid CB1 receptors were expressed in AtT20, CHO or HEK 293 cells. NADA displacement of radiolabelled cannabinoids, and CB1 receptor mediated activation of K channels or ERK phosphorylation, release of intracellular calcium ([Ca]i ) and modulation of adenylyl cyclase were measured in addition to NADA effects on CB1 receptor trafficking.

KEY RESULTS

At concentrations up to 30 μM, NADA failed to activate any signalling pathways via CB1 receptors, with the exception of mobilization of [Ca]i . The elevations of [Ca]i were insensitive to pertussis toxin, and reduced or abolished by blockers of Gq /11 -dependent processes including U73122, thapsigargin and a peptide antagonist of Gq /11 activation. Prolonged NADA incubation produced modest loss of cell surface CB1 receptors. The prototypical cannabinoid agonist CP55940 signalled as expected in all assays.

CONCLUSIONS AND IMPLICATIONS

NADA is an ineffective agonist at most canonical cannabinoid receptor signalling pathways, but did promote mobilization of [Ca]i via Gq -dependent processes and some CB1 receptor trafficking. This signalling profile is distinct from that of any known cannabinoid, and suggests that NADA may have a unique spectrum of effects in vivo. Our results also indicate that it may be possible to identify highly biased CB1 receptor ligands displaying a subset of the pharmacological or therapeutic effects usually attributed to CB1 ligands.

Knockdown of the small conductance Ca(2+) -activated K(+) channels is potently cytotoxic in breast cancer cell lines

BACKGROUND AND PURPOSE

Small conductance calcium-activated potassium (KCa 2.x) channels have a widely accepted canonical function in regulating cellular excitability. In this study, we address a potential non-canonical function of KCa 2.x channels in breast cancer cell survival, using in vitro models.

EXPERIMENTAL APPROACH

The expression of all KCa 2.x channel isoforms was initially probed using RT-PCR, Western blotting and microarray analysis in five widely studied breast cancer cell lines. In order to assess the effect of pharmacological blockade and siRNA-mediated knockdown of KCa 2.x channels on these cell lines, we utilized MTS proliferation assays and also followed the corresponding expression of apoptotic markers.

KEY RESULTS

All of the breast cancer cell lines, regardless of their lineage or endocrine responsiveness, were highly sensitive to KCa 2.x channel blockade. UCL1684 caused cytotoxicity, with LD50 values in the low nanomolar range, in all cell lines. The role of KCa 2.x channels was confirmed using pharmacological inhibition and siRNA-mediated knockdown. This reduced cell viability and also reduced expression of Bcl-2 but increased expression of active caspase-7 and caspase-9. Complementary to these results, a variety of cell lines can be protected from apoptosis induced by staurosporine using the KCa 2.x channel activator CyPPA.

CONCLUSIONS AND IMPLICATIONS

In addition to a well-established role for KCa 2.x channels in migration, blockade of these channels was potently cytotoxic in breast cancer cell lines, pointing to modulation of KCa 2.x channels as a potential therapeutic approach to breast cancer.

Trimetazidine prevents macrophage-mediated septic myocardial dysfunction via activation of the histone deacetylase sirtuin 1

BACKGROUND AND PURPOSE

Sepsis is a systemic inflammatory response accompanied by excessive production of inflammatory cytokines and cardiovascular dysfunction. Importantly, macrophage-derived pro-inflammatory agents play a key role in cardiovascular impairment in sepsis. Here we have investigated the effects of trimetazidine (TMZ) on pro-inflammatory responses of macrophages in endotoxin-induced myocardial dysfunction.

EXPERIMENTAL APPROACH

Mice pretreated with TMZ were injected i.p. with LPS and cardiac function evaluated. Levels of macrophage infiltration, macrophage inflammatory response and cardiomyocyte apoptosis were measured using immunohistochemical staining, elisa, real-time RT-PCR, Western blot, TUNEL and flow cytometry assays.

KEY RESULTS

Pretreatment with TMZ prevented LPS-induced myocardial dysfunction and apoptosis. TMZ also lowered levels of pro-inflammatory cytokines in serum and cardiac tissue and myocardial macrophage infiltration. Bone marrow transplantation indicated that TMZ alleviated LPS-induced myocardial dysfunction via decreasing macrophage infiltration. TMZ reduced expression of pro-inflammatory cytokines in LPS-stimulated cardiac and peritoneal macrophages. Co-culture of TMZ-pretreated macrophages with cardiomyocytes and conditioned media from TMZ-pretreated macrophages both decreased LPS-induced cardiomyocyte apoptosis. The anti-apoptosis effects of TMZ resulted from decrease of pro-inflammatory cytokines, partly due to normalizing the sirtuin 1 (Sirt1)/AMP-activated protein kinase (AMPK)/Nrf2/haem oxygenase-1 and Sirt1/PPARα pathways in macrophages. Cytokine secretion was also regulated by ROS, which were attenuated by TMZ via activation of Sirt1, AMPK and PPARα.

CONCLUSIONS AND IMPLICATIONS

TMZ protected against LPS-induced myocardial dysfunction and apoptosis, accompanied by inhibition of macrophage pro-inflammatory responses. Our studies suggest that TMZ might represent a novel therapeutic agent to prevent and treat sepsis-induced myocardial dysfunction.

All-trans retinoic acid protects against doxorubicin-induced cardiotoxicity by activating the ERK2 signalling pathway

BACKGROUND AND PURPOSE

Doxorubicin is a powerful antineoplastic agent for treating a wide range of cancers. However, doxorubicin cardiotoxicity of the heart has largely limited its clinical use. All-trans retinoic acid (ATRA) plays an important role in many cardiac biological processes, but its protective effects on doxorubicin-induced cardiotoxicity remain unknown. Here, we studied the effect of ATRA on doxorubicin cardiotoxicity and the underlying mechanisms.

EXPERIMENTAL APPROACHES

Cellular viability assays, Western blotting and mitochondrial respiration analyses were employed to evaluate the cellular response to ATRA in H9c2 cells and primary cardiomyocytes. Quantitative PCR and gene knockdown were performed to investigate the underlying molecular mechanisms of ATRA's effects on doxorubicin cardiotoxicity.

KEY RESULTS

ATRA significantly inhibited doxorubicin-induced apoptosis in H9c2 cells and primary cardiomyocytes. ATRA was more effective against doxorubicin cardiotoxicity than resveratrol and dexrazoxane. ATRA also suppressed reactive oxygen species generation and restored expression levels of mRNA and proteins in the phase II detoxifying enzyme system: nuclear factor-E2-related factor 2, manganese superoxide dismutase, haem oxygenase-1, and mitochondrial function (mitochondrial membrane integrity, mitochondrial DNA copy numbers and mitochondrial respiration capacity, biogenesis and dynamics). Both a ERK1/2 inhibitor (U0126) and ERK2 siRNA, but not ERK1 siRNA, abolished the protective effect of ATRA against doxorubicin-induced toxicity in H9c2 cells. Remarkably, ATRA did not compromise the anticancer efficacy of doxorubicin in gastric carcinoma cells.

CONCLUSIONS AND IMPLICATIONS

ATRA protected cardiomyocytes against doxorubicin-induced toxicity, by activating the ERK2 pathway, without compromising its anticancer efficacy. Therefore, ATRA is a promising candidate as a cardioprotective agent against doxorubicin cardiotoxicity.

PPARγ agonists regulate bidirectional transport of amyloid-β across the blood-brain barrier and hippocampus plasticity in db/db mice

BACKGROUND AND PURPOSE

There is emerging evidence suggesting that abnormal transport of amyloid-β (Aβ) across the blood-brain barrier (BBB) is involved in diabetes-associated cognitive decline. We investigated whether PPARγ agonists restore Aβ transport across the BBB and hippocampal plasticity in db/db mice.

EXPERIMENTAL APPROACH

Efflux and influx of Aβ across the BBB were determined by stereotaxic intra-cerebral or i.a. infusion of [(125) I]-Aβ1-40 respectively. Receptor for advanced glycation end products (RAGE) and low-density lipoprotein receptor-related protein 1 (LRP1), which are involved in Aβ influx and efflux, PPARγ and NF-κB p65 at the BBB, as well as hippocampal Aβ, caspase-3, Bax and Bcl-2 were assayed by Western blot, immunohistochemistry and RT-PCR. In vivo, hippocampal LTP was recorded, and Morris water maze and Y-maze tasks were performed.

KEY RESULTS

Treatment with PPARγ agonists, rosiglitazone (0.8 mg·kg(-1) ) and pioglitazone (9.0 mg·kg(-1) ), for 6 weeks significantly increased Aβ efflux and decreased Aβ influx across the BBB in db/db mice. Concomitantly, they decreased hippocampal Aβ1-40 and Aβ1-42 , suppressed neuronal apoptosis, as indicated by decreased caspase-3 activity and increased ratio of Bcl-2/Bax, and increased hippocampal plasticity, characterized by an enhanced in vivo LTP and better performance in behavioural tests. Furthermore, the PPARγ agonists induced the expression of LRP1 gene by activation of PPARγ and suppressed RAGE gene expression by inactivation of NF-κB signalling at the BBB of db/db mice.

CONCLUSIONS AND IMPLICATIONS

PPARγ agonists modify abnormal Aβ transport across the BBB and this is accompanied by amelioration of β-amyloidosis and an improvement in hippocampal plasticity in diabetic mice.

CREB, AP-1, ternary complex factors and MAP kinases connect transient receptor potential melastatin-3 (TRPM3) channel stimulation with increased c-Fos expression

BACKGROUND AND PURPOSE

The rise in intracellular Ca(2+) stimulates the expression of the transcription factor c-Fos. Depending on the mode of entry of Ca(2+) into the cytosol, distinct signal transducers and transcription factors are required. Here, we have analysed the signalling pathway connecting a Ca(2+) influx via activation of transient receptor potential melastatin-3 (TRPM3) channels with enhanced c-Fos expression.

EXPERIMENTAL APPROACH

Transcription of c-Fos promoter/reporter genes that were integrated into the chromatin via lentiviral gene transfer was analysed in HEK293 cells overexpressing TRPM3. The transcriptional activation potential of c-Fos was measured using a GAL4-c-Fos fusion protein.

KEY RESULTS

The signalling pathway connecting TRPM3 stimulation with enhanced c-Fos expression requires the activation of MAP kinases. On the transcriptional level, three Ca(2+) -responsive elements, the cAMP-response element and the binding sites for the serum response factor (SRF) and AP-1, are essential for the TRPM3-mediated stimulation of the c-Fos promoter. Ternary complex factors are additionally involved in connecting TRPM3 stimulation with the up-regulation of c-Fos expression. Stimulation of TRPM3 channels also increases the transcriptional activation potential of c-Fos.

CONCLUSIONS AND IMPLICATIONS

Signalling molecules involved in connecting TRPM3 with the c-Fos gene are MAP kinases and the transcription factors CREB, SRF, AP-1 and ternary complex factors. As c-Fos constitutes, together with other basic region leucine zipper transcription factors, the AP-1 transcription factor complex, the results of this study explain TRPM3-induced activation of AP-1 and connects TRPM3 with the biological functions regulated by AP-1.

Prostaglandin E2 inhibits neutrophil extracellular trap formation through production of cyclic AMP

BACKGROUND AND PURPOSE

Upon stimulation, neutrophils release their nuclear contents called neutrophil extracellular traps (NETs), which contain unfolded chromatin and lysosomal enzymes. NETs have been demonstrated to play a critical role in host defence, although the role of PGE2 , a bioactive substance generated in inflammatory tissues, in the formation of NETs remains unclear.

EXPERIMENTAL APPROACH

The effects of PGE2 , agonists and antagonists of its receptors, and modulators of the cAMP-PKA pathway on the formation of NETs were examined in vitro in isolated neutrophils and in vivo in a newly established mouse model.

KEY RESULTS

PGE2 inhibited PMA-induced NET formation in vitro through EP2 and EP4 Gαs-coupled receptors. Incubation with a cell-permeable cAMP analogue, dibutyryl cAMP, or various inhibitors of a cAMP-degrading enzyme, PDE, also suppressed NET formation. In the assay established here, where an agarose gel was s.c. implanted in mice and NET formation was detected on the surface of the gel, the extent of the NET formed was inhibited in agarose gels containing rolipram, a PDE4 inhibitor, and butaprost, an EP2 receptor agonist.

CONCLUSIONS AND IMPLICATIONS

PGE2 inhibits NET formation through the production of cAMP. These findings will contribute to the development of novel treatments for NETosis-related diseases.

A novel approach to inhibit bone resorption: exosite inhibitors against cathepsin K

BACKGROUND AND PURPOSE

Cathepsin K (CatK) is a major drug target for the treatment of osteoporosis. Potent active site-directed inhibitors have been developed and showed variable success in clinical trials. These inhibitors block the entire activity of CatK and thus may interfere with other pathways. The present study investigates the antiresorptive effect of an exosite inhibitor that selectively inhibits only the therapeutically relevant collagenase activity of CatK.

EXPERIMENTAL APPROACH

Human osteoclasts and fibroblasts were used to analyse the effect of the exosite inhibitor, ortho-dihydrotanshinone (DHT1), and the active site inhibitor, odanacatib (ODN), on bone resorption and TGF-ß1 degradation. Cell cultures, Western blot, light and scanning electron microscopy as well as energy dispersive X-ray spectroscopy, molecular modelling and enzymatic assays were used to evaluate the inhibitors.

KEY RESULTS

DHT1 selectively inhibited the collagenase activity of CatK, without affecting the viability of osteoclasts. Both inhibitors abolished the formation of resorption trenches, with DHT1 having a slightly higher IC50 value than ODN. Maximal reductions of other resorption parameters by DHT1 and ODN were comparable, respectively 41% and 33% for total resorption surface, 46% and 48% for resorption depths, and 83% and 61% for C-terminal telopetide fragment (CTX) release. DHT1 did not affect the turnover of fibrosis-associated TGF-ß1 in fibroblasts, whereas 500 nM ODN was inhibitory.

CONCLUSIONS AND IMPLICATIONS

Our study shows that an exosite inhibitor of CatK can specifically block bone resorption without interfering with other pathways.

Honokiol sensitizes breast cancer cells to TNF-α induction of apoptosis by inhibiting Nur77 expression

BACKGROUND AND PURPOSE

The orphan nuclear receptor Nur77 is implicated in the survival and apoptosis of cancer cells. The purpose of this study was to determine whether and how Nur77 serves to mediate the effect of the inflammatory cytokine TNF-α in cancer cells and to identify and characterize new agents targeting Nur77 for cancer therapy.

EXPERIMENTAL APPROACH

The effects of TNF-α on the expression and function of Nur77 were studied using in vitro and in vivo models. Nur77 expression was evaluated in tumour tissues from breast cancer patients. The anticancer effects of honokiol and its mechanism of action were assessed by in vitro, cell-based and animal studies.

KEY RESULTS

TNF-α rapidly and potently induced the expression of Nur77 in breast cancer cells through activation of IκB kinase and JNK. Knocking down Nur77 resulted in TNF-α-dependent apoptosis, while ectopic Nur77 expression in MCF-7 cells promoted their growth in animals. Levels of Nur77 were higher in tumour tissues than the corresponding tissues surrounding the tumour in about 50% breast cancer patients studied. Our in vitro and animal studies also identified honokiol as an effective sensitizer of TNF-α-induced apoptosis by inhibiting TNF-α-induced Nur77 mRNA expression, which could be attributed to its interference of TNFR1's interaction with receptor-interacting protein 1 (RIPK1).

CONCLUSIONS AND IMPLICATIONS

TNF-α-induced Nur77 serves as a survival factor to attenuate the death effect of TNF-α in cancer cells. With its proven human safety profile, honokiol represents a promising agent that warrants further clinical development.

Actions of the dual FAAH/MAGL inhibitor JZL195 in a murine neuropathic pain model

BACKGROUND AND PURPOSE

While cannabinoids have been proposed as a potential treatment for neuropathic pain, they have limitations. Cannabinoid receptor agonists have good efficacy in animal models of neuropathic pain; they have a poor therapeutic window. Conversely, selective fatty acid amide hydrolase (FAAH) inhibitors that enhance the endocannabinoid system have a better therapeutic window, but lesser efficacy. We examined whether JZL195, a dual inhibitor of FAAH and monacylglycerol lipase (MAGL), could overcome these limitations.

EXPERIMENTAL APPROACH

C57BL/6 mice underwent the chronic constriction injury (CCI) model of neuropathic pain. Mechanical and cold allodynia, plus cannabinoid side effects, were assessed in response to systemic drug application.

KEY RESULTS

JZL195 and the cannabinoid receptor agonist WIN55212 produced dose-dependent reductions in CCI-induced mechanical and cold allodynia, plus side effects including motor incoordination, catalepsy and sedation. JZL195 reduced allodynia with an ED50 at least four times less than that at which it produced side effects. By contrast, WIN55212 reduced allodynia and produce side effects with similar ED50s. The maximal anti-allodynic effect of JZL195 was greater than that produced by selective FAAH, or MAGL inhibitors. The JZL195-induced anti-allodynia was maintained during repeated treatment.

CONCLUSIONS AND IMPLICATIONS

These findings suggest that JZL195 has greater anti-allodynic efficacy than selective FAAH, or MAGL inhibitors, plus a greater therapeutic window than a cannabinoid receptor agonist. Thus, dual FAAH/MAGL inhibition may have greater potential in alleviating neuropathic pain, compared with selective FAAH and MAGL inhibitors, or cannabinoid receptor agonists.

Chinese innovation in cardiovascular drug discovery

This article is part of a themed section on Chinese Innovation in Cardiovascular Drug Discovery. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-23

Emerging role of hydrogen sulfide in hypertension and related cardiovascular diseases

Hydrogen sulfide (H2 S) has traditionally been viewed as a highly toxic gas; however, recent studies have implicated H2 S as a third member of the gasotransmitter family, exhibiting properties similar to NO and carbon monoxide. Accumulating evidence has suggested that H2 S influences a wide range of physiological and pathological processes, among which blood vessel relaxation, cardioprotection and atherosclerosis have been particularly studied. In the cardiovascular system, H2 S production is predominantly catalyzed by cystathionine γ-lyase (CSE). Decreased endogenous H2 S levels have been found in hypertensive patients and animals, and CSE(-/-) mice develop hypertension with age, suggesting that a deficiency in H2 S contributes importantly to BP regulation. H2 S supplementation attenuates hypertension in different hypertensive animal models. The mechanism by which H2 S was originally proposed to attenuate hypertension was by virtue of its action on vascular tone, which may be related to effects on different ion channels. Both H2 S and NO cause vasodilatation and there is cross-talk between these two molecules to regulate BP. Suppression of oxidative stress may also contribute to antihypertensive effects of H2 S. This review also summarizes the state of research on H2 S and hypertension in China. A better understanding of the role of H2 S in hypertension and related cardiovascular diseases will allow novel strategies to be devised for their treatment.