Protein kinase C plays an essential role in sildenafil-induced cardioprotection in rabbits

Sildenafil citrate (Viagra) is the most widely used pharmacological drug for treating erectile dysfunction in men. It has potent cardioprotective effects against ischemia-reperfusion injury via nitric oxide and opening of mitochondrial ATP-sensitive K(+) channels. We further investigated the role of protein kinase C (PKC)-dependent signaling pathway in sildenafil-induced cardioprotection. Rabbits were treated (orally) with sildenafil citrate (1.4 mg/kg) 30 min before index ischemia for 30 min and reperfusion for 3 h. The PKC inhibitor chelerythrine (5 mg/kg i.v.) was given 5 min before sildenafil. Infarct size (% of risk area) reduced from 33.65 +/- 2.17 in the vehicle (saline) group to 15.07 +/- 0.63 in sildenafil-treated groups, a 45% reduction compared with vehicle (mean +/- SE, P < 0.05). Chelerythrine abolished sildenafil-induced protection, as demonstrated by increase in infarct size to 31.14 +/- 2.4 (P < 0.05). Chelerythrine alone had an infarct size of 33.5 +/- 2.5, which was not significantly different compared with DMSO-treated group (36.8 +/- 1.7, P > 0.05). Western blot analysis demonstrated translocation of PKC-alpha, -, and -delta isoforms from cytosol to membrane after treatment with sildenafil. However, no change in the PKC-beta and -epsilon isoforms was observed. These data provide direct evidence of an essential role of PKC, and potentially PKC-alpha, -, and -delta, in sildenafil-induced cardioprotection in the rabbit heart.     

Furanoflavonoids from Pongamia pinnata fruits

Fruits of Pongamia pinnata afforded four new furanoflavonoids, pongapinnol A-D (1-4), and a new coumestan, pongacoumestan (5) along with thirteen known compounds 6-18. Compounds 16 and 17 are isolated for the first time from this plant. The structures of isolated compounds were elucidated on the basis of spectroscopic data interpretation.     

The role of adapter protein Shc in estrogen non-genomic action

Breast cancer is one of the most common malignancies in the United States. Seventy percent of breast cancers are hormone-responsive due to the presence of estrogen receptors ERalpha and ERbeta, which are important diagnostic and therapeutic targets in cancer treatment. Estrogen acts through its receptors, which reside on the cell membrane as demonstrated recently and in the nucleus, leading to cancer cell proliferation and protection from cell death. The membrane ERalpha has been reported in MCF-7 human breast cancer cells and is believed to mediate estrogen effects to activate mitogen-activated protein (MAP) kinase and phosphoinositide 3-kinase (PI3-kinase). Activation of many growth factor receptors require adapter proteins to delivery the upstream signals to downstream kinases, such as MAP kinase. Both Shc and the p85alpha subunit of PI3-kinase are adapter proteins. In addition to their roles in transducing signals from membrane growth factor receptors, they have been demonstrated to interact with ERalpha in an estrogen dependent manner. In this review, the role of Shc in mediating estrogen effects on MAP Kinase regulation, cell growth and anti-apoptosis will be discussed. The possible role of PI3-kinase in estrogen rapid action is also reviewed in brief.     

Lipid rafts in cytokine signaling

Lipid rafts are established as critical structures for a variety of cellular processes, including immune cell activation. Beyond their importance for initial immune cell activation at the immunological synapse, lipid rafts are now also being recognized as important sites for cytokine and growth factor signal transduction, both in immune cells as part of secondary regulatory processes, and in non-immune cells. This review summarizes current knowledge regarding the roles of rafts in cytokine signaling and emphasizes the need for measures to better standardize the study of rafts.     

Plant regeneration in cotton: A short-term inositol starvation promotes developmental synchrony in somatic embryogenesis

Summary Despite high commercial interest, the success of biotechnological applications in cotton (Gossypium hirsutum) has been limited due to difficulties in genetic transformation. Major problems have been genotype dependence and low frequency of somatic embryogenesis, making it difficult to regenerate plants from transgenic tissue. This study reports an increase in somatic embryogenesis efficiency and the induction of developmental synchrony in embryogenic callus cultures of cotton by a single cycle of myo-inositol depletion in liquid culture. Calluses were initiated on hypocotyl or cotyledon explants of cultivar Coker 312 by culturing these explants on callus-inducing solid medium [Murashige and Skoog salts plus vitamins of Gamborg's B₅ medium, 30 g l⁻¹ glucose, 100 mg l⁻¹ myo-inositol, 2.2 μM 2,4-dichlorophenoxyacetic acid, and 0.88 μM 6-benzyladenine]. The calluses were transferred to an identical liquid basal medium devoid of plant growth regulators. This induced the development of embryogenic cells. Friable clumps of cells formed after 20 d in the medium were selectively collected over filter mesh 40 subjected to one cycle of myo-inositol starvation. This induced a highly synchronized embryogenesis in the culture. The optimized protocol gave 100% embryos at the globular stage, out of which more than 80% developed into bipolar torpedo-stage embryos. About 68% of these were converted to plantlets by subculturing onto a simplified solid medium, and finally grown into healthy, fertile plants.     

Two-photon fluorescence correlation microscopy reveals the two-phase nature of transport in tumors

Transport parameters determine the access of drugs to tumors. However, technical difficulties preclude the measurement of these parameters deep inside living tissues. To this end, we adapted and further optimized two-photon fluorescence correlation microscopy (TPFCM) for in vivo measurement of transport parameters in tumors. TPFCM extends the detectable range of diffusion coefficients in tumors by one order of magnitude, and reveals both a fast and a slow component of diffusion. The ratio of these two components depends on molecular size and can be altered in vivo with hyaluronidase and collagenase. These studies indicate that TPFCM is a promising tool to dissect the barriers to drug delivery in tumors.     

Chaperone-Assisted Overexpression of an Active -Carbamoylase from Agrobacterium tumefaciens AM 10

The N-carbamoyl- -amino acid amidohydrolase ( -carbamoylase) gene (dcb) from Agrobacterium tumefaciens AM 10 was cloned by polymerase chain reaction in plasmid pET28a and was overexpressed in Escherichia coli JM109 (DE3). However, almost 80% of the enzyme remained trapped in inclusion bodies. To facilitate the expression of the properly folded active enzyme, the chaperones GroEL/ES were coexpressed in plasmid pKY206. This resulted in a 43-fold increase in active enzyme production compared to the wild-type strain. The histidyl-tagged -carbamoylase was purified by a single step nickel-affinity chromatography to a specific activity of 9.5 U/mg protein.     

Effects of sodium intake on cardiovascular variables in humans during posture changes and ambulatory conditions

The hypothesis was tested that cardiac output (CO) and stroke volume (SV) are increased by a moderate physiological elevation in sodium intake with a more pronounced effect in the ambulatory upright seated than supine position. Fourteen healthy males were investigated during ambulatory and controlled laboratory conditions at the end of two consecutive 5-day periods with sodium intakes of 70 (low) and 250 (high) mmol/24 h or vice versa, respectively. Comparing high and low sodium intake, plasma volume and plasma protein concentrations were 9 and 8% higher in the seated and the supine position, respectively. When seated during laboratory conditions, CO was 5.3 +/- 0.2 l/min on the high sodium intake vs. 4.8 +/- 0.2 l/min on the low (P < 0.05), and SV was 81 +/- 3 vs. 68 +/- 3 ml (P < 0.05). In the supine position, SV was 107 +/- 3 ml on the high vs. 99 +/- 3 ml (P < 0.05) on the low sodium intake, while CO remained unchanged. The difference in CO and SV induced by the change in sodium intake was significantly higher in the seated than in the supine position (P < 0.05). During upright ambulatory conditions, CO was 5.9 +/- 0.2 l/min during the high and 5.2 +/- 0.2 l/min during the low sodium intake (P < 0.05), and SV was 84 +/- 3 and 69 +/- 3 ml (P < 0.05), respectively. Mean arterial pressure was unchanged by the variations in sodium intake. In conclusion, increments in sodium intake within the normal physiological range increase CO and SV and more so in the seated vs. the supine position. These changes are readily detectable during upright, ambulatory conditions. The results indicate that the higher SV and CO could constitute an arterial baroreflex stimulus for the augmented renal sodium excretion.     

Evidence that NOS2 acts as a trigger and mediator of late preconditioning induced by acute systemic hypoxia

Chronic systemic hypoxia (SH) enhances myocardial ischemic tolerance in mammals. We studied the delayed cardioprotection caused by acute SH and associated signaling mechanism. Conscious adult male mice were exposed to one or two cycles of hypoxia (H; 10% O(2)) or normoxia (21% O(2)) for various durations (30 min, 2 h, 4 h) followed by 24 h of reoxygenation. Hearts were isolated 24 h later and subjected to ischemia-reperfusion in a Langendorff model. Infarct size was reduced in mice pretreated with one (H4h) or two cycles (H4hx2) of 4 h SH compared with normoxia mice (P < 0.05), which was abolished by an inducible nitric oxide synthase (NOS2) inhibitor (S-methylisothiourea, 3 mg/kg) given before SH or ischemia. H4hx2 also failed to reduce infarct size in NOS2 knockout mice. Cyclooxygenase-2 (COX-2) inhibitor (NS-398, 10 mg/kg) did not block the protection given either before H4hx2 or ischemia. A two- to three fold increase in myocardial NOS2 expression was observed in H4h, H2hx2, and H4hx2 (P < 0.05), whereas endothelial NOS (NOS3) or COX-2 remained unchanged. We conclude that acute SH induces delayed cardioprotection, which is triggered and mediated by NOS2, but not by NOS3 or COX-2.