Phorbol esters inhibit ionomycin-induced hydrolysis of phosphoinositides and phosphatidylcholine in bovine corneal epithelial cells

Evaluation of smoking cessation intervention in patients with chronic diseases in smoking cessation clinics

This study aimed to evaluate the effects of psychological intervention and psychological plus drug intervention on smoking cessation among male smokers with single chronic diseases.A total of 509 male smokers were divided into psychological group (n = 290) and psychological plus drugs (n = 219) groups according to their will. The physicians provided free individual counseling and follow-up interviews with brief counseling for all the subjects. In addition to mental intervention, patients in psychological plus drug group also received bupropion hydrochloride or varenicline tartrate to quit smoking. Outcomes were self-reported, regarding the 7-day point prevalence on abstinence rate and continuous abstinence rates at 1-, 3-, and 6-month follow-up period. Data analyses were performed using intention-to-treat analysis and per protocol analysis.With regards to the 3 follow-up time points, 7-day point-prevalence abstinence rate in psychological plus drugs group was all higher than that in the psychological intervention group. Additionally, the 3-month continuous abstinence rate (21.4%) of the 6-month follow-up in the psychological group was not significantly higher than that (26.9%) in the psychological plus drugs group (P >.05 for all). Fagerström test score, stage of quitting smoking, perceived confidence or difficulty in quitting, and chronic disease types were independently correlated with 3-month continuous abstinence in the 6-month follow up (P <.05 for all). The results were similar between intentional analysis and protocol analysis.The psychological intervention and psychological plus drugs intervention exerted good effects on smoking cessation in a short time (1 month). Nevertheless, the advantages did not appear during long-time (6 months) follow-up.

Identification and characterization of differentially active pools of type IIalpha phosphatidylinositol 4-kinase activity in unstimulated A431 cells

The seven known polyphosphoinositides have been implicated in a wide range of regulated and constitutive cell functions, including cell-surface signalling, vesicle trafficking and cytoskeletal reorganization. In order to understand the spatial and temporal control of these diverse cell functions it is necessary to characterize the subcellular distribution of a wide variety of polyphosphoinositide synthesis and signalling events. The predominant phosphatidylinositol kinase activity in many mammalian cell types involves the synthesis of the signalling precursor, phosphatidylinositol 4-phosphate, in a reaction catalysed by the recently cloned PI4KIIalpha (type IIalpha phosphatidylinositol 4-kinase). However the regulation of this enzyme and the cellular distribution of its product in different organelles are very poorly understood. This report identifies the existence, in unstimulated cells, of two major subcellular membrane fractions, which contain PI4KIIalpha possessing different levels of intrinsic activity. Separation of these membranes from each other and from contaminating activities was achieved by density gradient ultracentrifugation at pH 11 in a specific detergent mixture in which both membrane fractions, but not other membranes, were insoluble. Kinetic comparison of the purified membrane fractions revealed a 4-fold difference in K (m) for phosphatidylinositol and a 3.5-fold difference in V (max), thereby indicating a different mechanism of regulation to that described previously for agonist-stimulated cells. These marked differences in basal activity and the occurrence of this isozyme in multiple organelles emphasize the need to investigate cell signalling via PI4KIIalpha at the level of individual organelles rather than whole-cell lysates.

Platelet-activating factor preferentially stimulates the phospholipase A2/cyclooxygenase cascade in the rabbit cornea

Platelet-activating factor (PAF) is formed in the cornea after injury as well as by infiltrating inflammatory cells. We have studied the effects of PAF on the release and metabolism of arachidonic acid (AA) in the rabbit cornea. Corneal lipids were labeled in vivo by injecting [3H]AA and subsequently incubated in vitro with 100 nM PAF in the presence or absence of 10 microM BN50727, a PAF antagonist. The AA and eicosanoids released by incubated corneas were analyzed by high-performance liquid chromatography (HPLC). Tissue lipids were examined by mono- and bidimensional thin-layer chromatography (TLC). Within 5 min, PAF stimulated AA release to 76% above control levels. BN50727 inhibited the AA release elicited by PAF at all time points studied. The decreased content of [3H]AA in phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI) following PAF exposure and the lack of stimulation by PAF on the release of [3H] linoleic acid suggest that the cytosolic phospholipase A2 was activated. PAF also stimulated depletion of AA from the inositol lipids, phosphatidylinositol-4-phosphate (PIP) and phosphatidylinositol-4,5-biphosphate (PIP2) and increased content of [3H]AA into diacylglycerol (DAG) and phosphatidic acid (PA). This reaction indicates that PAF could also mediate activation of other phospholipases in the cornea. In addition, PAF preferentially stimulated the cyclooxygenase pathway. The PAF antagonist BN50727 mainly suppressed the PAF-stimulated release of PGE2. The antagonist did not inhibit lipoxygenase activity even after 30 min of PAF stimulation. These results suggest that PAF activate a phospholipase A2/cyclooxygenase pathway in the cornea via a PAF-receptor mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

Activation of phospholipase D by guanosine 5'[gamma-thio]triphosphate and AlF4- in bovine corneal epithelial cells

We have investigated the regulation of phospholipase D (PLD) by guanine nucleotides and AlF4- in bovine corneal epithelial cells (BCEC) prelabeled with [3H]myristic acid. In the presence of ethanol, AlF4- increased the production of [3H]PA and [3H]PET indicating activation of PLD in these cells. The effects of AlF4- were time- and dose-dependent. Addition of guanosine 5[gamma-thio]triphosphate (GTP gamma S), to streptolysin O-permeabilized cells also resulted in increased accumulation of [3H]PA and [3H]PEt. Other guanine and adenine nucleotides were ineffective, and guanosine thiodiphosphate inhibited the GTP gamma S-induced activation of PLD. Direct addition of GTP gamma S to microsomal fraction prepared from [3H]myristate-labeled BCEC resulted in increased formation of [3H]PEt in a time- and dose-dependent manner. The activation of PLD by GTP gamma S in the microsomal fraction was absolutely dependent on the presence of Ca2+ > 0.5 microM. Addition of Ca2+ (10-100 microM) alone dose-dependently stimulated the PLD activity. Treatment of the microsomal fraction with phorbol esters had no effect on the ability of GTP gamma S to stimulate PLD. Addition of isoproterenol to BCEC resulted in several-fold stimulation of cAMP, but it had no effect on basal or PDBu-induced stimulation of PLD. Taken together, the data suggest that a GTP-binding protein is involved in regulation of PLD in BCEC, and that maximal stimulation of PLD probably results from an interaction between Ca2+, PKC and G-protein in BCEC.