OBJECTIVE: Dexmedetomidine (DEX), the most specific α ₂-adrenergic receptor agonist widely used for its sedative and analgesic properties, has been reported to upregulate HIF-1α expression to protect hypoxic and ischemic tissues. However, it is largely unclear whether DEX can also upregulate Hypoxia-inducible factor-1 alpha (HIF-1α) expression and its downstream vascular endothelial growth factor-A (VEGFA) in cancer tissues with oxygen-deficient tumor microenvironment. METHODS: We used SMMC-7721 cells, MHCC97-H cells, and a mouse model of orthotopic hepatic carcinoma to explore the effect of DEX on angiogenesis and vasculogenic mimicry (VM) and its mechanism. Under normoxic (20% O ₂) and hypoxic (1% O ₂) conditions, DEX was used to intervene cells, and yohimbine was used to rescue them. RESULTS: The results showed that DEX promoted angiogenesis and VM in human liver cancer cells within a certain dose range, and the addition of yohimbine inhibited this effect. DEX could activate HIF-1α/VEGFA pathway, which was further verified by silencing HIF-1α. Consistently, in vivo results also showed that DEX can up-regulate HIF-1α/VEGFA expression, and enhance the number of VM channels and microvessel density (MVD). CONCLUSION We believe that HIF-1α/VEGFA might be an important signaling pathway by which DEX promotes angiogenesis and VM formation in human hepatocellular carcinoma, whereas α ₂-adrenergic receptor mediation might be the critical mechanisms.
Animals ; Humans ; Mice ; Adrenergic alpha-2 Receptor Agonists/pharmacology* ; Carcinoma, Hepatocellular ; Cardiovascular Physiological Phenomena ; Dexmedetomidine/pharmacology* ; Hypoxia ; Liver Neoplasms/drug therapy* ; Oxygen ; Tumor Microenvironment ; Vascular Endothelial Growth Factor A/genetics* ; Receptors, Adrenergic, alpha-2/metabolism*

The purpose of this study was to investigate the effects of α₂ adrenergic receptor agonist dexmedetomidine on withdrawal symptoms in alcohol-dependent rats and the underlying mechanism, so as to provide a scientific basis for the treatment of alcohol withdrawal syndrome (AWS). Adult Sprague-Dawley (SD) male rats were orally administered with 6% aqueous alcohol continuously for 28 d to establish alcohol drinking model, and then stopped drinking to induce AWS. Enzyme-linked immunosorbent assay (ELISA) was used to determine the content of norepinephrine (NE) in the locus coeruleus and hippocampus of rats. Dexmedetomidine (5, 10, and 20 μg/kg) was intraperitoneally injected respectively when the rats showed significant AWS. In some rats, α₂ adrenergic receptor antagonist yohimbine was injected into hippocampus in advance. The results showed that, compared with the control group, the 6 h withdrawal group exhibited significantly increased AWS score and amount of repeat drinking. The NE contents in hippocampus and locus coeruleus of the last drinking and the 6 h withdrawal groups were significantly increased compared with those of the control group. Dexmedetomidine intervention significantly decreased AWS score and hippocampus NE content in the 6 h withdrawal group, while yohimbine could reverse these effects of dexmedetomidine. These results suggest that dexmedetomidine might improve the withdrawal symptoms in alcohol-dependent rats via activating α₂ adrenergic receptor.
Adrenergic alpha-2 Receptor Agonists/therapeutic use* ; Alcoholism/drug therapy* ; Animals ; Dexmedetomidine/therapeutic use* ; Hippocampus/metabolism* ; Male ; Norepinephrine ; Rats ; Rats, Sprague-Dawley ; Receptors, Adrenergic, alpha-2/metabolism* ; Substance Withdrawal Syndrome/drug therapy* ; Yohimbine/pharmacology*

It is known that stimulation of the α(2A)-adrenoceptors (α(2A)-ARs) by the selective α(2A)-AR agonist guanfacine produces an important and beneficial influence on prefrontal cortical (PFC) cognitive functions such as spatial working memory and selective attention. However, it is unclear whether stimulation of the α(2A)-ARs has a similar effect on fear conditioning that involves the amygdala and hippocampus. Here, we show that systemically administered guanfacine significantly enhances spatial learning of rats in the Lashley maze: compared with controls, the rats treated with guanfacine required significantly fewer trials and made significantly fewer errors to reach learning criterion. However, guanfacine produced no effect on acquisition of contextual and auditory fear memories. The present study suggests that beneficial effect of α(2A)-AR stimulation is task-dependent: guanfacine improves spatial learning but not fear conditioning.
Adrenergic alpha-2 Receptor Agonists ; pharmacology ; Animals ; Behavior, Animal ; drug effects ; Conditioning (Psychology) ; drug effects ; Fear ; drug effects ; Guanfacine ; pharmacology ; Maze Learning ; drug effects ; Memory ; drug effects ; Rats ; Spatial Behavior ; drug effects

Objective: To explore the protective effects of dexmedetomidine (Dex) against high glucose-induced epithelial-mesenchymal transition in HK-2 cells and relevant mechanisms. Methods: HK-2 cells were exposed to either glucose or glucose+Dex for 6 h. The production of ROS, morphology of HK-2 cells, and cell cycle were detected. Moreover, the expression of AKT, p-AKT, ERK, p-ERK, PI3K, E-Cadherin, Claudin-1, and α-SMA were determined and compared between HK-2 cells exposed to glucose and those exposed to both glucose and Dex with or without PI3K/AKT pathway inhibitor LY294002 and ERK pathway inhibitor U0126. Results: Compared with HK-2 cells exposed to high level of glucose, the HK-2 cells exposed to both high level of glucose and Dex showed: (1) lower level of ROS production; (2) cell morphology was complete; (3) more cells in G1 phase; (4) lower expression of p-AKT, p-ERK and α-SMA, higher expression of E-Cadherin and Claudin-1. PI3K/AKT inhibitor LY294002 and ERK inhibitor U0126 decreased the expression of p-AKT, p-ERK and α-SMA, and increased the expression of E-Cadherin and Claudin-1. Conclusion Dex can attenuate high glucose-induced HK-2 epithelial-mesenchymal transition by inhibiting AKT and ERK.
Adrenergic alpha-2 Receptor Agonists ; pharmacology ; Cell Line ; Dexmedetomidine ; pharmacology ; Epithelial-Mesenchymal Transition ; drug effects ; Glucose ; metabolism ; Humans ; MAP Kinase Signaling System ; drug effects ; Proto-Oncogene Proteins c-akt ; antagonists & inhibitors ; Signal Transduction ; drug effects

OBJECTIVETo demonstrate the inhibitory effect of kappa-opioid receptor activation by U50488H on hypertrophy induced by NE in cultured neonatal rat cardiac myocytes and compare its effect with that of prazosin and propranolol.

METHODSThe cellular proliferation was determined with crystal violet staining. The protein content was assayed with Lowry's method. The cardiomyocytes volumes were measured by computer photograph analysis system. The protein synthesis was assayed with [3H]-lencine incorporation method.

RESULTS(1) NE significantly induced the increase of protein content, [3H]-leucine incorporation and cell size without a concomitant increase in cell number in low serum medium. OThese responses were partially suppressed by prazosin or propranolol alone and completely abolished by both in combination. U50488H significantly inhibited the NE-induced increase of protein content, [3H]-leucine incorporation and cell size. The inhibitory effects of U50488H on NE-induced cardiac hypertrophy were greater than either prazosin or propranolol, but comparable to combination of both.

CONCLUSIONNE, acting via both alpha1- and beta-adrenergic pathway, stimulates myocyte hypertrophy. Stimulating kappa-opioid receptor significantly inhibits NE-induced cardiac hypertrophy, which may be related with alpha1- and beta1-adrenergic pathway.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer ; pharmacology ; Adrenergic alpha-1 Receptor Antagonists ; pharmacology ; Adrenergic beta-Antagonists ; pharmacology ; Animals ; Animals, Newborn ; Cardiomegaly ; chemically induced ; pathology ; prevention & control ; Cell Enlargement ; drug effects ; Cells, Cultured ; Female ; Male ; Myocytes, Cardiac ; cytology ; Norepinephrine ; Prazosin ; pharmacology ; Propranolol ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Receptors, Opioid, kappa ; agonists

This study aims to elucidate the mechanisms by which dexmedetomidine alleviates pulmonary edema in rats with acute lung injury induced by lipopolysaccharide (LPS). Male Wistar rats were randomly divided into five groups: normal saline control (NS) group, receiving intravenous 0.9% normal saline (5 mL/kg); LPS group, receiving intravenous LPS (10 mg/kg); small-dose dexmedetomidine (S) group, treated with a small dose of dexmedetomidine (0.5 μg · kg(-1) · h(-1)); medium-dose dexmedetomidine (M) group, treated with a medium dose of dexmedetomidine (2.5 μg · kg(-1) · h(-1)); high-dose dexmedetomidine (H) group, treated with a high dose of dexmedetomidine (5 μg · kg(-1) · h(-1)). The rats were sacrificed 6 h after intravenous injection of LPS or NS, and the lungs were removed for evaluating histological characteristics and determining the lung wet/dry weight ratio (W/D). The levels of tumor necrosis factor-alpha (TNF-&alpha;) and interleukin-1β (IL-1β) in the lung tissues were assessed by enzyme- linked immunosorbent assay (ELISA). The mRNA and protein expression levels of aquaporin-1 (AQP1) and aquaporin-5 (AQP5) were detected by RT-PCR, immunohistochemistry, and Western blotting. The lung tissues from the LPS groups were significantly damaged, which were less pronounced in the H group but not in the small-dose dexmedetomidine group or medium-dose dexmedetomidine group. The W/D and the concentrations of TNF-&alpha; and IL-1β in the pulmonary tissues were increased in the LPS group as compared with those in NS group, which were reduced in the H group but not in S group or M group (P<0.01). The expression of AQP1 and AQP5 was lower in the LPS group than in the NS group, and significantly increased in the H group but not in the S group or M group (P<0.01). Our findings suggest that dexmedetomidine may alleviate pulmonary edema by increasing the expression of AQP-1 and AQP-5.
Acute Lung Injury ; chemically induced ; drug therapy ; genetics ; pathology ; Adrenergic alpha-2 Receptor Agonists ; pharmacology ; Animals ; Aquaporin 1 ; agonists ; genetics ; immunology ; Aquaporin 5 ; agonists ; genetics ; immunology ; Dexmedetomidine ; pharmacology ; Dose-Response Relationship, Drug ; Drug Administration Schedule ; Gene Expression Regulation ; Injections, Intravenous ; Interleukin-1beta ; antagonists & inhibitors ; genetics ; immunology ; Lipopolysaccharides ; Lung ; drug effects ; immunology ; pathology ; Male ; Organ Size ; drug effects ; Pulmonary Edema ; chemically induced ; drug therapy ; genetics ; pathology ; Rats ; Rats, Wistar ; Signal Transduction ; Transcription, Genetic ; Tumor Necrosis Factor-alpha ; antagonists & inhibitors ; genetics ; immunology

PURPOSE: Dexmedetomidine, a full agonist of alpha2B-adrenoceptors, is used for analgesia and sedation in the intensive care units. Dexmedetomidine produces an initial transient hypertension due to the activation of post-junctional alpha2B-adrenoceptors on vascular smooth muscle cells (SMCs). The aims of this in vitro study were to identify mitogen-activated protein kinase (MAPK) isoforms that are primarily involved in full, alpha2B-adrenoceptor agonist, dexmedetomidine-induced contraction of isolated rat aortic SMCs. MATERIALS AND METHODS: Rat thoracic aortic rings without endothelium were isolated and suspended for isometric tension recording. Cumulative dexmedetomidine (10(-9) to 10(-6) M) dose-response curves were generated in the presence or absence of extracellular signal-regulated kinase (ERK) inhibitor PD 98059, p38 MAPK inhibitor SB 203580, c-Jun NH2-terminal kinase (JNK) inhibitor SP 600125, L-type calcium channel blocker (verapamil and nifedipine), and alpha2-adrenoceptor inhibitor atipamezole. Dexmedetomidine-induced phosphorylation of ERK, JNK, and p38 MAPK in rat aortic SMCs was detected using Western blotting. RESULTS: SP 600125 (10(-6) to 10(-5) M) attenuated dexmedetomidine-evoked contraction in a concentration-dependent manner, whereas PD 98059 had no effect on dexmedetomidine-induced contraction. SB 203580 (10(-5) M) attenuated dexmedetomidine-induced contraction. Dexmedetomidine-evoked contractions were both abolished by atipamezole and attenuated by verapamil and nifedipine. Dexmedetomidine induced phosphorylation of JNK and p38 MAPK in rat aortic SMCs, but did not induce phosphorylation of ERK. CONCLUSION: Dexmedetomidine-induced contraction involves a JNK- and p38 MAPK-mediated pathway downstream of alpha2-adrenoceptor stimulation in rat aortic SMCs. In addition, dexmedetomidine-induced contractions are primarily dependent on calcium influx via L-type calcium channels.
Adrenergic alpha-2 Receptor Agonists/*pharmacology ; Animals ; Anthracenes/pharmacology ; Aorta/cytology ; Dexmedetomidine/*pharmacology ; Enzyme Inhibitors/pharmacology ; Extracellular Signal-Regulated MAP Kinases/antagonists & inhibitors/physiology ; Flavonoids/pharmacology ; Imidazoles/pharmacology ; JNK Mitogen-Activated Protein Kinases/antagonists & inhibitors/*physiology ; Male ; *Muscle Contraction ; Muscle, Smooth, Vascular/drug effects/enzymology/*physiology ; Protein Isoforms/antagonists & inhibitors/physiology ; Pyridines/pharmacology ; Rats ; Rats, Sprague-Dawley ; p38 Mitogen-Activated Protein Kinases/antagonists & inhibitors/physiology