Dexmedetomidine prevents post-ischemic LTP via presynaptic and postsynaptic mechanisms.

Increasing evidence indicates that dexmedetomidine (DEX), a selective α2-adrenergic receptor agonist, has a neuroprotective effect against cerebral injury. However, it remains unknown whether and how DEX functionally prevents the pathological form of synaptic plasticity caused by ischemia in the hippocampal CA1 neurons. To address this issue, we analyzed the role of DEX using a model of brain ischemia (oxygen and glucose deprivation, OGD) referred to as post-ischemic LTP (i-LTP). We found that DEX could reduce i-LTP by selectively activating α2 receptors. To clarify its detailed mechanisms, the presynaptic and postsynaptic roles of DEX were investigated. The activation of the α2 receptors of DEX decreased the frequency spontaneous mEPSCs, which exerted its presynaptic mechanisms. In addition, DEX also decreased the amplitude of mEPSCs and prevented the depolarization of postsynaptic membranes during OGD treatment, which exerted its postsynaptic mechanisms. More importantly, our results indicate that postsynaptic ß receptors, not α1 receptors, participated in i-LTP. Therefore, these results demonstrated that decreasing ß receptors activation by DEX-medicated pre- and post-synaptic α2 receptors activation is responsible for i-LTP. Because of the NMDARs required for i-LTP, we further examined the critical roles of postsynaptic ß receptors downstream PKA regulation of NMDA receptor-mediated EPSCs (NMDA EPSC). We clarified that it is attributable to the direct effect of DEX on NMDA EPSC as mediated by PKA inactivation. These findings suggest that DEX can protect neurons from functional damage caused by a relatively mild degree of transient cerebral ischemia, and this effect is mediated by both presynaptic reduction of NE and glutamate release and postsynaptic suppression of NMDAR activation by ß receptors and downstream PKA regulation.

Oestrogen changed cardiomyocyte contraction and beta-adrenoceptor expression in rat hearts subjected to ischaemia-reperfusion.

Women with functional ovaries have a lower cardiovascular risk than men and postmenopausal women. However, oestrogen replacement therapy remains controversial. This study examined the effect of ovarian hormone deficiency and oestrogen replacement on ventricular myocyte contractile function and expression of beta-adrenoceptors (beta-ARs). Female Sprague-Dawley rats were subjected to bilateral ovariectomy (OVX) or sham operation (Sham). A subgroup of OVX rats received oestrogen (E2) replacement (40 microg kg(-1) day(-1)) for 4 weeks. Cardiomyocyte shortening was evaluated in basal conditions and in the presence of isoprenaline (ISO). The expression of beta-ARs was assessed by Western blotting. The presence of lactate dehydrogenase (LDH) activity in the coronary effluent was determined. Ovariectomy promoted body weight gain associated with reduced serum E2 and uterine weight, all of which were abolished by treatment with E2. Ovariectomy increased the amplitude of both basal and ISO-stimulated contractions, increased LDH release, upregulated beta1-AR expression and downregulated beta2-AR expression, all of which were restored by treatment with E2. A beta1-AR antagonist, CGP20712A, but not a beta2-AR antagonist, ICI118,551, significantly decreased the amplitude of ventricular myocyte shortening. Oestrogen decreased cardiomyocyte contraction and the expression of beta1-AR, and increased expression of beta2-AR, and all these effects were abolished by the E2 receptor antagonist, ICI182,780. These data suggest that oestrogen plays a cardioprotective role in female rat hearts subjected to ischaemia-reperfusion injury, and the effects of oestrogen are associated with decreased cardiomyocyte contraction and expression of beta1-AR, and increased expression of beta2-AR.

Fumagillin treatment of hepatocellular carcinoma in rats: an in vivo study of antiangiogenesis.

AIM: To investigate the effect and possible mechanisms of antiangiogenesis therapy for HCC in rats. METHODS: Adult male LEW/SsN rats were divided into 3 groups, 25 animals each. Group A was the control group. Groups B and C were given diethylnitrosamine, 5 mg/kg/d. In addition, group C rats received an intraperitoneal injection of fumagillin, 30 mg/(kg x d). Five animals in each group were killed at 6th, 12th, 18th, 20th and 24th wk to evaluate the development of HCC and metastasis. Weight of the rats, liver tumors, and number of organs involved by HCC were measured at each stage. We compared methionine aminopeptidase-2 (MetAP-2) mRNA, Bcl-2 mRNA, telomerase mRNA, and telomerase activity at 24th wk in the liver tissue of group A rats and tumor tissue of HCC from group B and C rats. RESULTS: No HCC developed in group A, but tumors were present in group B and C rats by the 18th wk. At wk 20 and 24, the median liver weight in group B was 0.64 g (range: 0.58-0.70 g) and 0.79 g (range: 0.70-0.90 g) (P = 0.04), and that in group C was 0.37 g (range: 0.35-0.42 g) and 0.39 g (range: 0.35-0.47 g) (P = 0.67). The liver weight in group C rats was significantly lower than that in group B rats (P = 0.009). At the same time, the median metastasis score (number of organ systems involved) was 3 (range2-3) in group B, and 1 (range 1-2) in group C, a significant difference between the groups (P = 0.007, 0.004). The levels of MetAP-2 mRNA were significantly higher in groups B and C than in group A (P = 0.025), and significantly higher in group C than in group B (P = 0.047). The level of Bcl-2 mRNA was significantly higher in group B than in group A (P = 0.024), but lower in group C than in group B, although not significantly (P = 0.072). Telomerase mRNA was significantly higher in group B than in group A (P = 0.025), but significantly lower in group C than in group B (P = 0.016). The same inter-group relationship was also true for telomerase activity (P = 0.025 and 0.046). CONCLUSION: Fumagillin effectively inhibits both liver tumor growth and metastasis in rats in vivo. A possible mechanism is fumagillin-induced inhibition of MetAP-2, which plays an essential role in endothelial cell proliferation. Inhibition of MetAP-2 also results in inhibition of Bcl-2 and telomerase activity.

Prognostic significance of preoperative circulating vascular endothelial growth factor messenger RNA expression in resectable hepatocellular carcinoma: a prospective study.

AIM: To investigate the prognostic value of vascular endothelial growth factor messenger RNA (VEGF mRNA) in the peripheral blood (PB) of patients with hepatocellular carcinoma (HCC) undergoing curative resection. METHODS: Using a reverse-transcription polymerase chain reaction (RT-PCR)-based assay, VEGF mRNA in the PB was determined prospectively in 50 controls and in 50 consecutive patients undergoing curative resection for HCC. RESULTS: Among the isoforms of VEGF mRNA, VEGF(165) and VEGF(121) were expressed. By multivariate analysis, a higher level of VEGF(165) in preoperative PB correlated with a risk of HCC recurrence with borderline significance (P=0.050) and significantly with recurrence-related mortality (P=0.048); while VEGF(121) did not. Other significant predictors of HCC recurrence included cellular dedifferentiation (P=0.033), an absent or incomplete capsule (P=0.020), vascular permeation (P=0.018), and daughter nodules (P=0.006). The other significant parameter of recurrence related mortality was cellular dedifferentiation (P=0.053). The level of circulating VEGF mRNA, however, did not significantly correlate with tumor size, cellular differentiation, capsule, daughter nodules, vascular permeation, necrosis and hemorrhage of tumors. CONCLUSION: The preoperative level of circulating VEGF mRNA, especially isoform VEGF(165), plays a significant role in the prediction of postoperative recurrence of HCC.

Is the vascular endothelial growth factor messenger RNA expression in resectable hepatocellular carcinoma of prognostic value after resection?

AIM: To study whether vascular endothelial growth factor messenger RNA (VEGF mRNA) in the hepatocellular carcinoma (HCC) tissues obtained after curative resection has a prognostic value. METHODS: Using a reverse-transcription polymerase chain reaction (RT-PCR)-based assay, VEGF mRNA was determined prospectively in liver tissues of 50 controls and in HCC tissues of 50 consecutive patients undergoing curative resection for HCC. RESULTS: Among the isoforms of VEGF mRNA, VEGF(165) and VEGF(121) were expressed. By multivariate analysis, a higher level of VEGF(165) in HCC tissue correlated with a significant risk of HCC recurrence (P=0.038) and significantly with recurrence-related mortality (P=0.045); while VEGF(121) did not. Other significant predictors of HCC recurrence included cellular dedifferentiation (P=0.033), an absent or incomplete capsule (P=0.020), vascular permeation (P=0.018), and daughter nodules (P=0.006). The other significant variables of recurrence related mortality consisted of vascular permeation (P=0.045), and cellular dedifferentiation (P=0.053). The level of VEGF mRNA in HCC tissues, however, did not significantly correlate with tumor size, cellular differentiation, capsule, daughter nodules, vascular permeation, necrosis and hemorrhage of tumors. CONCLUSION: The expression of VEGF mRNA, especially isoform VEGF(165), in HCC tissues, may play a significant and independent role in the prediction of postoperative recurrence of HCC.