METHODS: Animals were divided into three groups: (i) normal non-diabetic (NDM), (ii) diabetic treated (tocotrienol-rich fractions - TRF) and (iii) diabetic untreated (non-TRF). The treatment group received oral administration of tocotrienol-rich fractions (200 mg/kg body weight) daily for eight weeks. The normal non-diabetic and the diabetic untreated groups were fed standard rat feed. Blood glucose and lipid profiles, oxidative stress markers and morphological changes of the thoracic aorta were evaluated.
RESULTS: Tocotrienol-rich fractions treatment reduced serum glucose and glycated hemoglobin concentrations. The tocotrienol-rich fractions group also showed significantly lower levels of plasma total cholesterol, low-density lipoprotein cholesterol, and triglyceride, as compared to the untreated group. The tocotrienol-rich fractions group had higher levels of high-density lipoprotein cholesterol, as compared to the untreated group. Superoxide dismutase activity and levels of vitamin C in plasma were increased in tocotrienol-rich fractions-treated rats. The levels of plasma and aorta malondealdehyde + 4-hydroxynonenal (MDA + 4-HNE) and oxidative DNA damage were significant following tocotrienol-rich fractions treatment. Electron microscopic examination showed that the normal morphology of the thoracic aorta was disrupted in STZ-diabetic rats. Tocotrienol-rich fractions supplementation resulted in a protective effect on the vessel wall.
CONCLUSION: These results show that tocotrienol-rich fractions lowers the blood glucose level and improves dyslipidemia. Levels of oxidative stress markers were also reduced by administration of tocotrienol-rich fractions. Vessel wall integrity was maintained due to the positive effects mediated by tocotrienol-rich fractions.
METHODS: A crude methanol extract of the aerial parts of Isodon rugosus (Ir.Cr.) was used for both in vitro and in vivo experiments. The plant extract was tested on isolated rabbit jejunum preparations for possible presence of spasmolytic activity. Moreover, isolated rabbit tracheal and aorta preparations were used to ascertain the relaxant effects of the extract. Acetylcholinesterase and butyrylcholinesterase inhibitory activities of Ir.Cr were also determined as well as its antioxidant activity. The in vivo antiemetic activity of the extract was evaluated by using the chick emesis model, while the analgesic and antipyretic activities were conducted on albino mice.
RESULTS: The application of the crude extract of I. rugosus to isolated rabbit jejunum preparations exhibited relaxant effect (0.01-0.3 mg/ml). The Ir.Cr also relaxed K+(80 m M)-induced spastic contractions in isolated rabbit jejunum preparations and shifted the Ca+2 concentration response curves towards right (0.01-0.3 mg/ml). Similarly, the extract, when applied to the isolated rabbit tracheal preparations relaxed the carbachol (1 μM)--as well as K+ (80 mM)-induced contractions in a concentration range of 0.01-1.0 mg/ml. Moreover, it also relaxed (0.01-3.0 mg/ml) the phenylephrine (1 μM)- and K+ (80 mM)-induced contractions in isolated rabbit aorta preparations. The Ir.Cr (80 mg/kg) demonstrated antipyretic activity on pyrogen-induced pyrexia in rabbits as compared to aspirin as standard drug. The Ir.Cr also exhibited anti-oxidant as well as inhibitory effect on acetyl- and butyryl-cholinesterase and lipoxygenase (0.5 mg/ml).
CONCLUSIONS: The observed relaxant effect on isolated rabbit jejunum, trachea and aorta preparations caused by Ir.Cr is possibly to be mediated through Ca+2 channel blockade and therefore may provided scientific basis to validate the folkloric uses of the plant in the management of gastrointestinal, respiratory and cardiovascular ailments. The observed antioxidant activity as well as the lipoxygenase inhibitory activity may validate its traditional use in pain and inflammations.
METHODS AND RESULTS: Selective agonists of PKA and EPAC synergistically inhibited Egr1 expression, which was essential for VSMC proliferation. Forskolin, adenosine, A2B receptor agonist BAY60-6583 and Cicaprost also inhibited Egr1 expression in VSMC but not in endothelial cells. Inhibition of Egr1 by cAMP was independent of cAMP response element binding protein (CREB) activity but dependent on inhibition of serum response element (SRE) activity. SRF binding to the Egr1 promoter was not modulated by cAMP stimulation. However, Egr1 expression was dependent on the SRF co-factors Elk1 and 4 but independent of MAL. Inhibition of SRE-dependent Egr1 expression was due to synergistic inhibition of Rac1 activity by PKA and EPAC, resulting in rapid cytoskeleton remodelling and nuclear export of ERK1/2. This was associated with de-phosphorylation of the SRF co-factor Elk1.
CONCLUSION: cAMP inhibits VSMC proliferation by rapidly inhibiting Egr1 expression. This occurs, at least in part, via inhibition of Rac1 activity leading to rapid actin-cytoskeleton remodelling, nuclear export of ERK1/2, impaired Elk1-phosphorylation and inhibition of SRE activity. This identifies one of the earliest mechanisms underlying the anti-mitogenic effects of cAMP in VSMC but not in endothelial cells, making it an attractive target for selective inhibition of VSMC proliferation.