Targeting the PI3K/STAT3 axis modulates age-related differences in macrophage phenotype in rats with myocardial infarction.

Ageing is associated with impaired repair mechanisms in cardiovascular diseases. Macrophages contribute to cardiac fibrosis after myocardial infarction (MI). The phosphatidyl-inositol-3-kinase (PI3K) pathway has been shown to play a role in cardiac remodelling after MI. It remained unclear whether n-butylidenephthalide, a major component of Angelica sinensis, can attenuate cardiac fibrosis by regulating the PI3K/signal transducer and activator of transcription 3 (STAT3)-mediated macrophage phenotypes in ageing rats after MI. Twenty-four hours after ligation of the left anterior descending artery, young (2-month-old) and ageing (18-month-old) male Wistar rats were treated with either vehicle or n-butylidenephthalide for 4 weeks. There were similar infarct sizes in both age groups. Compared with young rats, ageing rats exhibited significant increased cardiac fibrosis after MI, which can be attenuated after administering n-butylidenephthalide. MI was associated with decreased activities of PI3K and STAT3 in ageing rats compared with young rats. In both age groups, n-butylidenephthalide effectively provided a significant increase of STAT3 phosphorylation, STAT3 activity, STAT3 nuclear translocation, myocardial IL-10 levels and the percentage of M2c macrophage and a decrease of myofibroblast infiltration. The effects of n-butylidenephthalide on increased IL-10 levels were reversed by LY294002 or S3I-201. Furthermore, LY294002 abolished the STAT3 phosphorylation, whereas PI3K activity was not affected following the inhibition of STAT3. In conclusions, the host environment is responsible for ageing-related myofibroblast dysregulation in response to MI which can be improved by administering n-butylidenephthalide via macrophage differentiation towards M2 phenotype by targeting the PI3K/STAT3 axis.

The role of the chemical burns caused by hydroxide ion in the toxicity of dermal exposure to tetramethylammonium ion in a rat model.

OBJECTIVE: To evaluate the role of the chemical burns caused by hydroxide ion in the fatal effects of tetramethylammonium ion (TMA) in dermal exposure to tetramethylammonium hydroxide (TMAH), we conducted a rat study consisting of two-step treatments with dermal exposure to NaOH and tetramethylammonium chloride (TMACl). METHODS: In the first step, NaOH or saline was administered in the gauze on the shaved skin for 5 min, and in the second step, TMAH, TMACl, or saline was administered in the same way. The mean blood pressure (MBP), heart rate (HR), and survival in rats were compared among seven groups. RESULTS: Dermal exposure to saline and then 2.75 M TMACl introduced limited and temporary non-fatal effects. Exposure to 2.75 M NaOH and then saline had almost no effects and caused no deaths. Treatments with more concentrated NaOH or TMACl resulted in suppressions of MBP and HR, and deaths were observed after the dosing of TMACl. CONCLUSION: The toxicity of dermal exposure to TMA alone is limited, but fatal effects can be introduced by pre-treatment with hydroxide ion. Therefore, the chemical burn caused by hydroxide ion plays an essential role in the toxicity, implicating that effective neutralizing may help decreasing the fatality rate.

K ATP channel agonists preserve connexin43 protein in infarcted rats by a protein kinase C-dependent pathway.

Downward remodelling of gap junctional proteins between myocytes may trigger ventricular arrhythmia after myocardial infarction. We have demonstrated that ATP-sensitive potassium (K(ATP)) channel agonists attenuated post-infarction arrhythmias. However, the involved mechanisms remain unclear. The purpose of this study was to determine whether K(ATP) channel agonists can attenuate arrhythmias through preserving protein kinase C (PKC)-(ε)dependent connexin43 level after myocardial infarction. Male Wistar rats after ligating coronary artery were randomized to either vehicle, nicorandil, pinacidil, glibenclamide or a combination of nicorandil and glibenclamide or pinacidil and glibenclamide for 4 weeks. To elucidate the role of PKC(ε) in the modulation of connexin43 level, carbachol and myristoylated PKC(ε) V1-2 peptide were also assessed. Myocardial connexin43 level was significantly decreased in vehicle-treated infarcted rats compared with sham. Attenuated connexin43 level was blunted after administering K(ATP) channel agonists, assessed by immunofluorescent analysis, Western blotting, and real-time quantitative reverse transcription-PCR of connexin43. Arrhythmic scores during programmed stimulation in the K(ATP) channel agonists-treated rats were significantly lower than those treated with vehicle. The beneficial effects of K(ATP) channel agonists were blocked by either glibenclamide or 5-hydroxydecanoate. Addition of the PKC activator, phorbol 12-myristate 13-acetate and the specific PKC(ε) agonist, carbachol, blocked the effects of nicorandil on connexin43 phosphorylation and dye permeability. The specific PKC(ε) antagonist, myristoylated PKC(ε) V1-2 peptide, did not have additional beneficial effects on connexin43 phosphorylation compared with rats treated with nicorandil alone. Chronic use of K(ATP) channel agonists after infarction, resulting in enhanced connexin43 level through a PKC(ε)-dependent pathway, may attenuate the arrhythmogenic response to programmed electrical stimulation.

Antitumor effect of BPR-DC-2, a novel synthetic cyclic cyanoguanidine derivative, involving the inhibition of MDR-1 expression and down-regulation of p-AKT and PARP-1 in lung cancer.

In our previous study, a series of novel cyclic cyanoguanidine compounds, eg. 5-substituted 2-cyanoimino-4-imidazodinone and 2-cyanoimino-4- pyrimidinone derivatives have been successfully synthesized and showed remarkable cytotoxicity in several cancer cell lines. In this present study, it is our aim to screen more potential candidates among the cyclic pyridyl cyanoguanidine compounds (BPR-DC-1, 2, 3) by in vitro and in vivo studies for the therapy of lung cancer, alternatively. Our results showed that BPR-DC-2 significantly inhibited proliferation of tumor cells with an IC50 of 3.60 ± 1.27 and 14.81 ± 4.23 µM in human lung carcinoma cells, H69 and A549, respectively by the MTT assay at 48 hr; BPR-DC-2 also obviously suppressed the tumor proliferation and MDR-1 gene expression, even induced cell apoptosis in the ex vivo histocultured lung tumor. We further demonstrated that, in the nude mouse model of metastatic lung cancer, BPR-DC-2 could diminish the tumor mass, retard the progression of metastasis, and prolong the survival time. In addition, it was found that BPR-DC-2 exerted its anti-tumor effects through the inhibition of MDR-1 gene expression and down-regulation of tumor anti-apoptosis signals (activated p-AKT and over-expression of PARP-1) by western blotting analysis. In conclusion, in this present study we have demonstrated that BPR-DC-2, derived from a series of novel synthetic cyclic cyanoguanidine compounds, has proved its potential as an anti-tumor drug candidate in treating lung cancer.

Effect of pravastatin on ventricular arrhythmias in infarcted rats: role of connexin43.

Epidemiologic studies showed that men treated with statins appear to have a lower incidence of sudden death than men without statins. However, the specific factor for this remained disappointingly elusive. We assessed whether pravastatin enhanced connexin43 expression after myocardial infarction through attenuation of endothelin-1. Twenty-four hours after ligation of the anterior descending artery, male Wistar rats were randomized to vehicle, pravastatin, mevalonate, bosentan, or a combination of pravastatin and mevalonate or pravastatin and bosentan for 4 wk. Myocardial endothelin-1 levels were significantly elevated in vehicle-treated rats at the border zone compared with sham-operated rats. Myocardial connexin43 expression at the border zone was significantly decreased in vehicle-treated infarcted rats compared with sham-operated rats. Attenuated connexin43 expression was blunted after administration of pravastatin, as assessed by immunofluorescence analysis, Western blotting, and real-time quantitative RT-PCR of connexin43. Bosentan enhanced connexin43 amount in infarcted rats and did not have additional beneficial effects on pravastatin-treated rats. Arrhythmic scores during programmed stimulation in vehicle-treated rats were significantly higher than scores in those treated with pravastatin. In contrast, the beneficial effects of pravastatin-induced connexin43 were abolished by the addition of mevalonate and a protein kinase C inducer. In addition, the amount of connexin43 showed significant increase after addition of bisindolylmaleimide, implicating that protein kinase C is a relevant target in endothelin-1-mediated connexin43 expression. Thus chronic use of pravastatin after infarction, resulting in enhanced connexin43 amount by attenuation of mevalonate-dependent endothelin-1 through a protein kinase C-dependent pathway, may attenuate the arrhythmogenic response to programmed electrical stimulation.