This study tested the hypothesis that depressor responses caused by tempol are not associated with reductions in vascular O2- levels in urethane-anesthetized deoxycorticosterone acetate (DOCA)-salt hypertensive rats. We compared the effects of intravenous (IV) administration of tempol, apocynin, superoxide dismutase-polyethylene glycol (PEG-SOD), and SOD on mean arterial blood pressure (MAP), heart rate (HR), and renal sympathetic nerve activity (RSNA). In DOCA-salt rats, tempol (30 to 300 micromol/kg) dose-dependently decreased RSNA, MAP, and HR. Tempol (300 micromol/kg) decreased MAP from 140+/-5 to 83+/-4 mm Hg (P<0.05). HR decreased from 435+/-15 to 390+/-12 bpm (P<0.05). RSNA was reduced by 54%+/-6% from baseline. However, in the same rats, tempol did not reduce dihydroethidium-induced fluorescent signals in the aorta and vena cava. Apocynin (200 micromol/kg) did not lower MAP (142+/-5 mm Hg versus 140+/-6 mm Hg) or HR (428+/-15 bpm versus 420+/-13 bpm) and apocynin did not potentiate depressor responses caused by tempol. PEG-SOD (10 000 U/kg, bolus or 5000 U/kg bolus followed by a 30-minutes infusion of 500 U/kg/min) or SOD (25 000 U/kg, bolus or 10 000 U/kg bolus followed by a 30-minutes infusion of 1000 U/kg per minute) did not alter MAP or HR. It is concluded that depressor responses and decreases in HR and RSNA caused by acute tempol treatment are caused by direct sympathetic nerve activity inhibition that is not accompanied by SOD-mimetic action in the aorta or vena cava.

Down-regulation of miR-146b-5p contributes to tumorigenesis in several human cancers. However, the relevance of miR-146b-5p to prognosis, proliferation and apoptosis in gliomas remains unknown. In the present study, we demonstrated that miR-146b-5p expression was inversely correlated with grades and Ki-67 index in 147 human glioma specimens, but positively correlated with patients’ survival. Furthermore, two distinct subgroups of patients with grade I-IV gliomas with different prognoses were identified according to miR-146b-5p expression in our specimens. Cox regression showed that miR-146b-5p was an independent predictor for patients’ survival. Overexpression of miR-146b-5p dramatically suppressed glioma cell proliferation and induced apoptosis. Mechanistically, we validated TRAF6 as a direct functional target of miR-146b-5p and found that miR-146b-5p overexpression significantly decreased phosphorylated TAK1 and IκBα, the pivotal downstream effectors of TRAF6. Moreover, TRAF6 expression was positively correlated with glioma grades and Ki-67 index but inversely correlated with miR-146b-5p expression and predicted poor prognosis of glioma patients. In glioblastoma cell lines, silencing of TRAF6 could mimic the anti-tumor effect of miR-146b-5p. Our findings identify miR-146b-5p as a tumor suppressor and novel prognostic biomarker of gliomas, and suggest miR-146b-5p and TRAF6 as potential therapeutic candidates for malignant gliomas.

The role of sympathetic nerves and nitric oxide (NO) in tempol-induced cardiovascular responses was evaluated in urethane-anesthetized sham and deoxycorticosterone acetate (DOCA)-salt-treated (DOCA-salt) rats. Tempol (30-300 micromol/kg iv), a superoxide (O) scavenger, decreased renal sympathetic nerve activity (RSNA), mean arterial pressure (MAP), and heart rate (HR) in DOCA-salt and sham rats. The antioxidants tiron and ascorbate did not alter MAP, HR, or RSNA in any rat. Tempol responses were unaffected after sham rats were treated with N(G)-nitro-L-arginine (L-NNA, 13 mg/kg). In DOCA-salt rats, L-NNA reduced tempol-induced depressor responses but not the inhibition of HR or RSNA. Tempol did not significantly decrease MAP, HR, or RSNA after hexamethonium (30 mg/kg iv) treatment in any rat. Dihydroethidine histochemistry revealed increased O levels in arteries and veins from DOCA-salt rats. Tempol treatment in vitro reduced O levels in arteries and veins from DOCA-salt rats. In conclusion, tempol-induced depressor responses are mediated largely by NO-independent sympathoinhibition in sham and DOCA-salt rats. There is an additional interaction between NO and tempol that contributes to depressor responses in DOCA-salt rats.

The role of the sympathetic nervous system in 4-hydroxy-2,2,6,6-tetramethyl piperidinoxyl (tempol)-induced cardiovascular responses in urethane-anesthetized, normotensive rats was evaluated. Tempol caused dose-dependent (30-300 micromol/kg iv) decreases in renal sympathetic nerve activity (RSNA), mean arterial blood pressure (MAP), and heart rate (HR). Similar responses were obtained after sinoaortic denervation and cervical vagotomy. These responses were not blocked following treatment with the nitric oxide synthase inhibitor NG-nitro-L-arginine (2.6 mg x kg(-1) x min(-1) iv for 5 min) or the alpha2-adrenergic receptor antagonist idazoxan (0.3 mg/kg iv bolus). Idazoxan blocked the effects of clonidine (10 miccrog/kg iv) on HR, MAP, and RSNA. Hexamethonium (30 mg/kg iv) inhibited RSNA, and tempol did not decrease RSNA after hexamethonium. The effects of tempol on HR and MAP were reduced by hexamethonium. In conclusion, depressor responses caused by tempol are mediated, partly, by sympathoinhibition in urethane-anesthetized, normotensive rats. Nitric oxide does not contribute to this response, and the sympathoinhibitory effect of tempol is not mediated via alpha2-adrenergic receptors. Finally, tempol directly decreases HR, which may contribute to the MAP decrease.

No abstract

Large-conductance Ca2+-activated K+ (BK) channels are composed of pore-forming α-subunits and accessory β1-subunits that modulate Ca2+ sensitivity. BK channels regulate arterial myogenic tone and renal Na+ clearance/K+ reabsorption. Previous studies using indirect or short-term blood pressure measurements found that BK channel β1-subunit knockout (BK β1-KO) mice were hypertensive. We evaluated 24-h mean arterial pressure (MAP) and heart rate in BK β1-KO mice using radiotelemetry. BK β1-KO mice did not have a higher 24-h average MAP when compared with wild-type (WT) mice, although MAP was ∼10 mmHg higher at night. The dose-dependent peak declines in MAP by nifedipine were only slightly larger in BK β1-KO mice. In BK β1-KO mice, giving 1% NaCl to mice to drink for 7 days caused a transient (5 days) elevation of MAP (∼5 mmHg); MAP returned to pre-saline levels by day 6. BK β1-KO mesenteric arteries in vitro demonstrated diminished contractile responses to paxilline, increased reactivity to Bay K 8644 and norepinephrine (NE), and maintained relaxation to isoproterenol. Paxilline and Bay K 8644 did not constrict WT or BK β1-KO mesenteric veins (MV). BK β1-subunits are not expressed in MV. The results indicate that BK β1-KO mice are not hypertensive on normal or high-salt intake. BK channel deficiency increases arterial reactivity to NE and L-type Ca2+ channel function in vitro, but the L-type Ca2+ channel modulation of MAP is not altered in BK β1-KO mice. BK and L-type Ca(2+) channels do not modulate murine venous tone. It appears that selective loss of BK channel function in arteries only is not sufficient to cause sustained hypertension.

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BackgroundCeramides are a class of sphingolipids that form the structural component of the cell membrane and also act as second messengers in cell signaling pathways. Emerging results suggest that ceramide induces growth arrest and apoptosis in various human cancer cells. However, the mechanisms underlying its antitumor activity are yet to be identified. Endoplasmic reticulum stress (ER stress), a cellular adaptive response, is believed to initially compensate for damage but can eventually trigger cell death if the stimulus is severe or prolonged. In this study, we investigated whether ceramide induces cell death in human salivary adenoid cystic carcinoma (ACCs) through activation of the apoptotic ER stress.ResultsRT-PCR, real-time PCR and western blot demonstrated that exogenous ceramide treatment up-regulated GRP78 and p-eIF2α expression and XBP1 splicing. Moreover, the ceramide synthase inhibitor FB1 abolished ceramide-induced ER stress. Up-regulation of the ER stress-associated apoptosis promoting transcription factor CHOP and p-JNK suggested that the antitumor activity of ceramide is owing to activation of apoptotic ER stress. Mechanistically, [Ca2+]ER depletion and SERCA inhibition by ceramide treatment suggested that it induces ER stress by disrupting [Ca2+]ER homeostasis. The chemical chaperone TUDCA inhibited ceramide-induced ER stress and cell death. In addition, the downstream metabolite of ceramide, S1P, cannot activate ER stress.ConclusionsThese results demonstrated that exogenous ceramide induces cancer cell death through a mechanism involving severe ER stress triggered by the disruption of ER Ca2+ homeostasis.