No abstract available.
Calcium Channels/metabolism* ; Calcium Signaling/physiology* ; Cyclic AMP-Dependent Protein Kinases/metabolism* ; Pancreas/enzymology* ; Periodicity ; Phosphorylation ; Receptors, Cytoplasmic and Nuclear/metabolism*

BACKGROUNDAdipocytes behave like a rich source of pro-inflammatory cytokines including monocyte chemoattractant protein-1 (MCP-1). Oxidized low-density lipoprotein (oxLDL) participates in the local chronic inflammatory response, and high-density lipoprotein could counterbalance the proinflammatory function of oxLDL, but the underlying mechanism is not completely understood. This study aimed to evaluate the effect of apolipoprotein A-I mimetic peptide L-4F on the secretion and expression of MCP-1 in fully differentiated 3T3-L1 adipocytes induced by oxLDL and to elucidate the possible mechanisms.

METHODSFully differentiated 3T3-L1 adipocytes were incubated in the medium containing various concentration of L-4F (0-50 μg/ml) with oxLDL (50 μg/ml) stimulated, with/without protein kinase A (PKA) inhibitor H-89 (10 μmol/L) preincubated. The concentrations of MCP-1 in the supernatant, the mRNA expression of MCP-1, the levels of CCAAT/enhancer binding protein α (C/EBPα), and CCAAT/enhancer binding protein β (C/EBPβ) were evaluated. The monocyte chemotaxis assay was performed by micropore filter method using a modified Boyden chamber.

RESULTSOxLDL stimulation induced a significant increase of MCP-1 expression and secretion in 3T3-L1 adipocytes, which were inhibited by L-4F preincubation in a dose-dependent manner. PKA inhibitor H-89 markedly reduced the oxLDL-induced MCP-1 expression, but no further decrease was observed when H-89 was used in combination with L-4F (50 μg/ml) (P > 0.05). OxLDL stimulation showed no significant effect on C/EBPα protein level but increased C/EBPβ protein level in a time-dependent manner. H-89 and L-4F both attenuated C/EBPβ protein level in oxLDL-induced 3T3-L1 adipocytes.

CONCLUSIONSOxLDL induces C/EBPβ protein synthesis in a time-dependent manner and enhances MCP-1 secretion and expression in 3T3-L1 adipocytes. L-4F dose-dependently counterbalances the pro-inflammatory effect of oxLDL, and cyclic AMP/PKA-C/EBPβ signaling pathway may participate in it.

3T3-L1 Cells ; Animals ; CCAAT-Enhancer-Binding Protein-beta ; analysis ; physiology ; Chemokine CCL2 ; genetics ; secretion ; Cyclic AMP ; physiology ; Cyclic AMP-Dependent Protein Kinases ; physiology ; Humans ; Lipoproteins, LDL ; antagonists & inhibitors ; pharmacology ; Mice ; Peptides ; pharmacology ; Signal Transduction ; physiology

The study aims to identify the role of cAMP-PKA pathway in the group Ⅱ metabotropic glutamate receptors (mGluRs)-mediated regulation of respiratory rhythm from the brainstem slice. Neonatal (aged 0-3 d) Sprague-Dawley rats of either sex were used. The brainstem slice containing the medial region of the nucleus retrofacialis (mNRF) and the hypoglossal nerve rootlets was prepared, and the surgical procedure was performed in the modified Kreb's solution (MKS) with continuous carbogen (95% O2 and 5% CO2) bubbling, and ended in 3 min. Respiratory rhythmical discharge activity (RRDA) of the hypoglossal nerve rootlets was recorded by suction electrode. Eighteen brainstem slice preparations were divided into 3 groups. In group 1, group Ⅱ mGluRs specific antagonist (2S)-α-ethylglutamic acid (EGLU) was added into the perfusion solution for 10 min. In group 2, after application of Forskolin for 10 min, washout with MKS, the slice was perfused with Rp-cyclic 3', 5'-hydrogen phosphorothioate adenosine triethylammonium salt (Rp-cAMPS) alone for another 10 min. In group 3, after application of Rp-cAMPS for 10 min, additional EGLU was added into the perfusion for another 10 min. The results showed EGLU shortened respiratory cycle (RC), but the changes of integral amplitude (IA) and inspiratory time (TI) were not statistically significant. Forskolin induced significant decreases in RC, and increased TI, IA. Rp-cAMPS could make the opposite effect compared with the changes of RRDA with Forskolin. The effect of EGLU on the RRDA was inhibited after blocking the cAMP-PKA pathway. Taken together, cAMP-PKA pathway may play an important role in the group Ⅱ mGluRs-mediated regulation of RRDA in the brainstem slice of neonatal rats.
Animals ; Animals, Newborn ; Brain Stem ; physiology ; Cyclic AMP-Dependent Protein Kinases ; metabolism ; Female ; In Vitro Techniques ; Male ; Rats ; Rats, Sprague-Dawley ; Receptors, Metabotropic Glutamate ; physiology ; Respiration ; Signal Transduction ; physiology

OBJECTIVETo investigate the role of transient receptor potential melastatin 8 (TRPM8) channels in migraine mechanism in rats by measuring the changes in expression of TRPM8 in the trigeminal nerve of rats with migraine.

METHODSTwenty male Sprague-Dawley rats were randomly and equally divided into a blank control group and a model group. Nitroglycerin (10 mg/kg) was injected subcutaneously in the back of the neck once a week for 5 weeks, to prepared a rat model of migraine without aura. Normal saline was injected subcutaneously instead of nitroglycerin in the control group. At 4 hours after the final injection, behavior scoring of all rats was performed, and then the trigeminal nerve ganglions of rats in both groups were collected for measurement of expression of N-methyl-D-aspartate receptor (NMDAR), protein kinase A (PKA), and TRPM8 using immunohistochemical staining, immunofluorescence, and Western blot, respectively.

RESULTSThe behavior score in each week during the rat model preparing was significantly higher in the model group than in the control group (P<0.05). The expression of NMDAR, PKA, and TRPM8 in the model group was significantly higher than in the control group (P<0.01). Both the behavior score and the expression of NMDAR were positively correlated with the expression of TRPM8 (r=0.822 and 0.794 respectively; P<0.01).

CONCLUSIONSTRPM8 may be involved in migraine mechanism probably by activation of the NMDAR pathway.

Animals ; Cyclic AMP-Dependent Protein Kinases ; analysis ; Male ; Migraine Disorders ; etiology ; Rats ; Rats, Sprague-Dawley ; Receptors, N-Methyl-D-Aspartate ; analysis ; physiology ; TRPM Cation Channels ; physiology

PURPOSE: beta-adrenoceptors have been demonstrated in human corporal smooth muscles by the receptor binding assays, and have been known to elicit relaxation of the precontracted corporal tissues. Despite these findings, it is not clear whether the beta-adrenoceptors have any role in the control of penile erection. Potassium channels play an important role in the physiology of the corporal smooth muscle. The maxi-K+ channel subtypes are thought to be the most physiologically relevant K+ channels expressed in this tissue. The goal of this study was to clarify the contribution of the beta-adrenoceptors to the modulation of the corporal smooth muscle tone. MATERIALS AND METHODS: Patch-clamp technique was applied to the cultured human corporal smooth muscle cells. RESULTS: Maxi-K+ channel was activated by the application of the beta-adrenoceptor stimulator, isoproterenol (ISO). ISO increased the open probability (nP0) by 512+/-53% and the mean open time by 214+/-12% in the cell-attached patch recording. The whole cell patch recording indicated that the application of ISO in the bath solution increased the peak amplitude of the whole cell outward K+-current during the step depolarization (from -70 to + 130 mV). The presence of a specific protein kinase A inhibitor (PKI) in the pipette tip suppressed the ISO-induced increase of the whole cell outward K+-current. CONCLUSIONS: These studies showed that the beta-adrenoceptor activation contributed to the modulation of the corporal smooth muscle tone by activating the potassium channels, and moreover, that the activation of the potassium channels by the beta-adrenoceptors was related to the protein kinase A pathway.
Baths ; Cyclic AMP-Dependent Protein Kinases ; Humans* ; Isoproterenol ; Male ; Muscle, Smooth* ; Myocytes, Smooth Muscle* ; Patch-Clamp Techniques ; Penile Erection ; Physiology ; Potassium Channels ; Relaxation

OBJECTIVETo investigate the impact of rheumatoid arthritis (RA)-associated HLA-DRbeta1 * 0401, * 0402, * 0403, * 0404 and * 0101 subtypes on the protein kinase A (PKA) signaling pathway.

METHODSAdenylate cyclase (AC), cAMP and PKA activity in transfectants expressing RA-associated HLA-DRbeta1 subtypes and their mutants were detected.

RESULTSCompared to HLA-DRbeta1 * 0402 transfectants, the RA-associated HLA-DRbeta1 * 0401, * 0404 and * 0101 transfectants produced significantly lower levels of AC, cAMP and PKA.

CONCLUSIONRA-associated HLA-DRbeta1 molecules are involved in the pathogenesis of RA through down-regulation of the PKA signaling pathway.

Adenylyl Cyclases ; analysis ; Arthritis, Rheumatoid ; etiology ; genetics ; immunology ; Cyclic AMP ; analysis ; genetics ; Cyclic AMP-Dependent Protein Kinases ; physiology ; Down-Regulation ; HLA-DR Antigens ; analysis ; genetics ; Immunophenotyping ; In Vitro Techniques ; Signal Transduction

Lysophosphatidic acid (LPA) is a phospholipid growth factor that acts through G-protein-coupled receptors. Previously, we demonstrated an altered profile of LPA-dependent cAMP content during the aging process of human diploid fibroblasts (HDFs). In attempts to define the molecular events associated with the age-dependent changes in cAMP profiles, we determined the protein kinase A (PKA) activity, phosphorylation of cAMP-response element binding protein (CREB), and the protein expression of CRE-regulatory genes, c-fos and COX-2 in young and senescent HDFs. We observed in senescent cells, an increase in mRNA levels of the catalytic subunit a of PKA and of the major regulatory subunit Ia. Senescence-associated increase of cAMP after LPA treatment correlated well with increased CREB phosphorylation accompanying activation of PKA in senescent cells. In senescent cells, after LPA treatment, the expression of c-fos and COX-2 decreased initially, followed by an increase. In young HDFs, CREB phosphorylation decreased following LPA treatment, and both c-fos and COX-2 protein levels increased rapidly. CRE-luciferase assay revealed higher basal CRE-dependent gene expression in young HDFs compared to senescent HDFs. However, LPA-dependent slope of luciferase increased more rapidly in senescent cells than in young cells, presumably due to an increase of LPA-induced CREB phosphorylation. CRE-dependent luciferase activation was abrogated in the presence of inhibitors of PKC, MEK1, p38MAPK, and PKA, in both young and senescent HDFs. We conclude that these kinase are coactivators of the expression of CRE-responsive genes in LPA-induced HDFs and that their changed activities during the aging process contribute to the final expression level of CRE-responsive genes.
Time Factors ; Protein Kinase Inhibitors/pharmacology ; Phosphorylation ; Male ; Lysophospholipids/*pharmacology ; Luciferases/genetics/metabolism ; Humans ; Gene Expression/drug effects ; Fibroblasts/cytology/*drug effects/metabolism ; Diploidy ; Cyclic AMP-Dependent Protein Kinases/genetics/metabolism ; Cyclic AMP Response Element-Binding Protein/metabolism ; Cyclic AMP/*metabolism ; Cells, Cultured ; Cell Aging/physiology ; Catalytic Domain/genetics

Isoproterenol (ISO), a beta agonist, causes hyperpolarization of coronary smooth muscle cells via an increase in K+ conductance. This hyperpolarization may cause the coronary vasorelaxation by decreasing the cytoplasmic Ca2+ concentration. It is well known that the activation of beta adrenoreceptors stimulates the adenylate cyclase activity, and the resulting K+ channel phosphorylation by cAMP-dependent protein kinase may be responsible for ISO-induced increase in K+ channel activity. However, it is not clear whether the increase in K+ channel activity by ISO is exclusively due to the activation of adenylate cyclase or not. In this research, the effect of ISO on the isometric tension and the mechanism of ISO-induced K+ channel activation were investigated in various patch clamp conditions. The summarized results are as follows. ISO- and pinacidil induced vasorelaxation was significantly inhibited by the application of TEA or by increasing the external K+ concentration. In the whole cell clamp mode, application of ISO increased K+ outward current, and this effect was completely eliminated by propranolol. In the cell-attached patch, application of ISO or forskolin increased Ca(2+)-activated K+ channel activity. Application of ISO to the bath in the outside-out patches or GTP in the inside-out patches stimulated Ca(2+)-activated K+ channels. From the above results, both A-kinase dependent channel phosphorylation and direct GTP-binding protein mediated effect might be responsible for the the activation of Ca(2+)-activated K+ channel by ISO in rabbit coronary smooth muscle cells. And this K+ channel activation also contributes to the ISO-induced vasorelaxation.
Animal ; Calcium/*metabolism ; Coronary Vessels/*drug effects/physiology ; Cyclic AMP-Dependent Protein Kinases/physiology ; Female ; GTP-Binding Proteins/physiology ; Isoproterenol/*pharmacology ; Male ; Muscle, Smooth, Vascular/*drug effects/physiology ; Potassium Channels/*drug effects ; Rabbits ; Support, Non-U.S. Gov't ; Vasodilation/drug effects

In the heart, stimulation of beta-adrenergic receptors (betaAR) serves as the most powerful means to increase cardiac contractility and relaxation in response to stress or a "fight-or-flight" situation. However, sustained beta-adrenergic stimulation promotes pathological cardiac remodeling such as myocyte hypertrophy, apoptosis and necrosis, thus contributing to the pathogenesis of chronic heart failure. Over the past decade, compelling evidence has demonstrated that coexisting cardiac betaAR subtypes, mainly beta(1)AR and beta (2)AR, activate markedly different signaling cascades. As a result, acute beta(1)AR stimulation activates the G(s) -adenylyl cyclase-cAMP-PKA signaling that can broadcast throughout the cell, whereas beta(2)AR-evoked cAMP signaling is spatially and functionally compartmentalized, due to concurrent G(i) activation. Chronic stimulation of beta(1)AR and beta(2)AR elicits opposing effects on the fate of cardiomyocytes: beta(1)AR induces hypertrophy and apoptosis; but beta(2)AR promotes cell survival. The cardiac protective effect of beta(2)AR is mediated by a signaling pathway sequentially involving G(i), G(betagamma), PI3K and Akt. Unexpectedly, beta(1)AR-induced myocyte hypertrophy and apoptosis are independent of the classic cAMP/PKA pathway, but require activation of Ca(2+)/calmodulin-dependent kinase II (CaMK II). The outcomes of cardiac-specific transgenic overexpression of either beta AR subtype in mice have reinforced the fundamentally different functional roles of these betaAR subtypes in governing cardiac remodeling and performance. These new insights regarding betaAR subtype stimulation not only provide clues as to cellular and molecular mechanisms underlying the beneficial effects of beta AR blockers in patients with chronic heart failure, but also delineate rationale for combining selective beta(1)AR blockade with moderate beta(2)AR activation as a potential novel therapy for the treatment of chronic heart failure.
Adenylyl Cyclases ; metabolism ; Animals ; Cyclic AMP-Dependent Protein Kinases ; metabolism ; GTP-Binding Proteins ; metabolism ; Heart ; physiology ; Heart Failure ; physiopathology ; Humans ; Myocardium ; metabolism ; Receptors, Adrenergic, beta ; classification ; physiology ; Receptors, Adrenergic, beta-1 ; physiology ; Receptors, Adrenergic, beta-2 ; physiology ; Signal Transduction

Estrogen is a steroid and the predominant female sex hormone in the body. Ovariectomised (OVX) adult female rats exhibit greater myocardial injury compared to the sham rats following ischemic insult in the presence of beta-adrenoceptor stimulation. Estrogen replacement restores the response of OVX female rats to ischemic/beta-adrenoceptor stimulation to that of normal female rats, providing evidence for a cardioprotective role of estrogen during ischemic insult. The protective effect is due to down-regulation of the beta(1)-adrenoceptor. There is also evidence that estrogen suppresses the expression and activity of protein kinase A (PKA), a second messenger of the G(s) protein/adenylyl cyclase/cAMP/PKA pathway which ultimately influences contractile function. There is also preliminary evidence that estrogen may suppress the activity of Ca(2+)/calmodulin kinase II deltac isoform (CaMKII-deltac), another downstream second messenger of the beta(1)-adrenoceptor pathway, which is involved in PKA-independent cell apoptosis. Acute administration of estrogen at physiological level could inhibit myocardial beta(1)-adrenoceptor and attenuate Ca(2+) influx independent of the estrogen receptor. In addition, brain studies also show estrogen inhibits the activities activated by the beta-adrenoceptor in brain regions responsible for the regulation of arterial blood pressure. Thus, it can be appreciated that the interaction between estrogen and the beta(1)-adrenoceptor and its signaling pathways is a complex one. Estrogen plays an important role not only in reproduction but also in other regulatory functions such as cardioprotection.
Animals ; Cyclic AMP-Dependent Protein Kinases ; Down-Regulation ; Estrogens ; physiology ; Female ; Gonadal Steroid Hormones ; Heart ; physiology ; Heart Diseases ; prevention & control ; Myocardium ; Rats ; Rats, Sprague-Dawley ; Receptors, Adrenergic, beta-1 ; physiology ; Signal Transduction