Protein kinase-dependent and Ca2+-independent cAMP inhibition of ANP release in beating rabbit atria

2002 ◽  
Vol 282 (5) ◽  
pp. R1477-R1489 ◽  
Author(s):  
Xun Cui ◽  
Jin Fu Wen ◽  
Jing Yu Jin ◽  
Wen Xie Xu ◽  
Sung Zoo Kim ◽  
...  

Regulation of atrial release of atrial natriuretic peptide (ANP) is coupled to changes in atrial dynamics. However, the mechanism by which mechanical stretch controls myocytic ANP release must be defined. The purpose of this study was to define the mechanism by which cAMP controls myocytic ANP release in perfused, beating rabbit atria. The cAMP-elevating agents forskolin and 3-isobutyl-1-methylxanthine (IBMX) inhibited myocytic ANP release. The activation of adenylyl cyclase with forskolin inhibited ANP release, which was a function of an increase in cAMP production. Inhibitors for L-type Ca2+ channels and protein kinase A (PKA) attenuated a minor portion of the forskolin-induced inhibition of ANP release. Gö-6976 and KN-62, which are specific inhibitors for protein kinase C-α and Ca2+/calmodulin kinase, respectively, failed to modulate forskolin-induced inhibition of ANP release. The nonspecific protein kinase inhibitor staurosporine blocked forskolin-induced inhibition of ANP release in a dose-dependent manner. Staurosporine but not nifedipine shifted the relationship between cAMP and ANP release. Inhibitors for L-type Ca2+ channels and PKA and staurosporine blocked forskolin-induced accentuation of atrial dynamics. These results suggest that cAMP inhibits atrial myocytic release of ANP via protein kinase-dependent and L-type Ca2+-channel-dependent and -independent signaling pathways.

2001 ◽  
Vol 280 (4) ◽  
pp. R1230-R1239 ◽  
Author(s):  
Kasiani C. Pozios ◽  
Jun Ding ◽  
Brian Degger ◽  
Zee Upton ◽  
Cunming Duan

Insulin-like growth factor (IGF)-I and -II have been cloned from a number of teleost species, but their cellular actions in fish are poorly defined. In this study, we show that both IGF-I and -II stimulated zebrafish embryonic cell proliferation and DNA synthesis in a concentration-dependent manner, whereas insulin had little mitogenic activity. Affinity cross-linking and immunoblotting studies revealed the presence of IGF receptors with the characteristics of the mammalian type I IGF receptor. Competitive binding assay results indicated that the binding affinities of the zebrafish IGF-I receptors to IGF-I, IGF-II, and insulin are 1.9, 2.6, and >190 nM, indicating that IGF-I and -II bind to the IGF-I receptor(s) with approximately equal high affinity. To further investigate the cellular mechanism of IGF actions, we have studied the effects of IGFs on two major signal transduction pathways: mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3 kinase). IGFs activated MAPK in zebrafish embryonic cells in a dose-dependent manner. This activation occurred within 5 min of IGF-I stimulation and disappeared after 1 h. IGF-I also caused a concentration-dependent activation of protein kinase B, a downstream target of PI3 kinase, this activation being sustained for several hours. Inhibition of MAPK activation by the MAPK kinase inhibitor PD-98059 inhibited the IGF-I-stimulated DNA synthesis. Similarly, use of the PI3 kinase inhibitor LY-294002 also inhibited IGF-I-stimulated DNA synthesis. When both the MAPK and PI3 kinase pathways were inhibited using a combination of these compounds, the IGF-I-stimulated DNA synthesis was completely negated. These results indicate that both IGF-I and -II are potent mitogens for zebrafish embryonic cells and that activation of both the MAPK and PI3 kinase-signaling pathways is required for the mitogenic action of IGFs in zebrafish embryonic cells.


2019 ◽  
Author(s):  
Nicola M. Blythe ◽  
Vasili Stylianidis ◽  
Melanie J. Ludlow ◽  
Hamish T. J. Gilbert ◽  
Elizabeth L. Evans ◽  
...  

AbstractPiezo1 is a mechanosensitive cation channel with widespread physiological importance; however its role in the heart is poorly understood. Cardiac fibroblasts are responsible for preserving the structural integrity of the myocardium and play a key role in regulating its repair and remodeling following stress or injury. We investigated expression and function of Piezo1 in cultured human and mouse cardiac fibroblasts. RT-PCR studies confirmed expression ofPiezo1mRNA in cardiac fibroblasts at similar levels to endothelial cells. Fura-2 intracellular Ca2+measurements validated Piezo1 as a functional ion channel that was activated by the Piezo1 agonist, Yoda1. Yoda1-induced Ca2+entry was inhibited by Piezo1 blockers (gadolinium, ruthenium red) and the Ca2+response was reduced proportionally by Piezo1 siRNA knockdown or in cells fromPiezo1+/−mice. Investigation of Yoda1 effects on selected remodeling genes indicated that Piezo1 activation opposed cardiac fibroblast differentiation; data confirmed by functional collagen gel contraction assays. Piezo1 activation using Yoda1 or mechanical stretch also increased the expression of interleukin-6 (IL-6), a mechanosensitive pro-hypertrophic and pro-fibrotic cytokine, in a Piezo1-dependent manner. Multiplex kinase activity profiling combined with kinase inhibitor studies and phospho-specific western blotting, established that Piezo1 activation stimulated IL-6 secretion via a pathway involving p38 MAP kinase, downstream of Ca2+entry. In summary, this study reveals that cardiac fibroblasts express functional Piezo1 channels coupled to reduced myofibroblast activation and increased secretion of paracrine signaling molecules that can modulate cardiac remodeling.


2003 ◽  
Vol 89 (3) ◽  
pp. 1387-1401 ◽  
Author(s):  
L. Liu ◽  
S. A. Simon

When capsaicin, the pungent compound in hot pepper, is applied to epithelia it produces pain, allodynia, and hyperalgesia. We investigated, using whole cell path clamp, whether some of these responses induced by capsaicin could be a consequence of capsaicin blocking I Acurrents, a reduction in which, such as occurs in injury, increases neuronal excitability. In capsaicin-sensitive (CS) rat trigeminal ganglion (TG) neurons, capsaicin inhibited I A currents in a dose-dependent manner. I A currents were reduced 49% by 1 μM capsaicin. In capsaicin-insensitive (CIS) rat TG neurons, or small-diameter mouse VR1−/− neurons, 1 μM capsaicin inhibited I A currents 9 and 3%, respectively. These data suggest that in CS neurons the vast majority of the capsaicin-induced inhibition of I Acurrents occurs as a consequence of the activation of vanilloid receptors. Capsaicin (1 μM) did not alter the I A conductance-voltage relationship but shifted the inactivation-voltage curve about 15 mV to hyperpolarizing voltages, thereby increasing the number of inactivated I A channels at the resting potential. I A currents were relatively unaffected by 1 mM CTP-cAMP or 500 nM phorbol-12, 13-dibuterate (a protein kinase C agonist) but were inhibited by 20–30% with either 1 mM CTP-cGMP or 25 μM N-(6-aminohexyl)-5-chloro-1-napthalenesulfonamide HCl (a calcium-calmodulin kinase inhibitor). In the presence of 0.5 μM KT5823, an inhibitor of protein kinase G (PKG) pathways, 1 μM capsaicin inhibited I A by only 26%. In summary, in CS neurons, capsaicin decreases I A currents through the activation of vanilloid receptors. That activation, partially through the activation of cGMP-PKG and calmodulin-dependent pathways should result in increased excitability of capsaicin-sensitive nociceptors.


2003 ◽  
Vol 90 (5) ◽  
pp. 3201-3212 ◽  
Author(s):  
Zhaoping Liu ◽  
E. Bradshaw Bunney ◽  
Sarah B. Appel ◽  
Mark S. Brodie

Dopaminergic neurons of the ventral tegmental area (VTA) have been implicated in the rewarding properties of drugs of abuse and in the etiology of schizophrenia; serotonin modulation of these neurons may play a role in these phenomena. Whole cell patch-in-the-slice recording in rat brain slices was used to investigate modulation of the hyperpolarization-activated cationic current Ih by serotonin in these neurons. Serotonin (50-500 μM) reduced the amplitude of Ih in a concentration-dependent manner; this effect was reversible after prolonged washout of serotonin. This effect was mimicked by the 5-HT2 agonist α-methylserotonin (25 μM) and reversed by the 5-HT2 antagonist ketanserin (25 μM). Serotonin reduced the maximal Ih current and conductance (measured at -130 mV) and caused a negative shift in the voltage dependence of Ih activation. The serotonin-induced reduction in Ih amplitude was antagonized by intracellular administration of the nonspecific protein kinase inhibitor H-7 (75 μM) and the selective protein kinase C inhibitor chelerythrine (25 μM). The protein kinase C activator phorbol 12, 13 diacetate (PDA, 2 μM) reduced Ih amplitude; when PDA and serotonin were applied together, the effect on Ih was less than additive. These data support the conclusion that serotonin reduces Ih in dopaminergic VTA neurons by acting at serotonin 5-HT2 receptors, which activate protein kinase C. This reduction of Ih may be physiologically important, as the selective inhibitor of Ih, ZD7288, significantly increased dopamine inhibition of firing rate of dopaminergic VTA neurons, an effect that we previously demonstrated with serotonin.


1990 ◽  
Vol 10 (5) ◽  
pp. 646-653 ◽  
Author(s):  
Hideaki Hara ◽  
Hiroshi Onodera ◽  
Mikio Yoshidomi ◽  
Yuzuru Matsuda ◽  
Kyuya Kogure

The protective effects of protein kinase inhibitors and a calmodulin kinase inhibitor (W-7) against ischemic neuronal damage were examined in the CA1 subfield of the hippocampus. Staurosporine, KT5720, and KT5822 were used as inhibitors of protein kinase C (PKC), cyclic AMP–dependent protein kinase, and cyclic GMP–dependent protein kinase, respectively. All test compounds were injected topically into the CA1 subfield of the hippocampus. In the gerbil ischemia model, staurosporine (0.1–10 ng) administered 30 min before ischemia prevented neuronal damage in a dose-dependent manner. However, KT5720, KT5822, and W-7 were ineffective, even at a dose of 10 ng. In the rat ischemia model, staurosporine (10 ng) also prevented neuronal damage when administered before ischemic insult, although staurosporine administered 10 or 180 min after recirculation was ineffective. These results suggest the involvement of PKC in CA1 pyramidal cell death after ischemia and that the fate of vulnerable CA1 pyramidal cells through PKC-mediated processes could be determined during the early recirculation period.


1997 ◽  
Vol 272 (3) ◽  
pp. G401-G407 ◽  
Author(s):  
M. J. Bragado ◽  
A. Dabrowski ◽  
G. E. Groblewski ◽  
J. A. Williams

The presence of the 90-kDa ribosomal S6 protein kinase (p90(rsk)) in isolated rat pancreatic acini was demonstrated by Western blotting and immunoprecipitation with anti-p90(rsk). Cholecystokinin (CCK) activated p90(rsk) activity in a time- and dose-dependent manner and increased its phosphorylation. The threshold concentration of CCK was 10 pM and the maximal effect was seen at 1 nM. An increase in p90(rsk) was observed 1 min after 1 nM CCK stimulation, reaching a maximum at 10 min, when p90(rsk) activity was increased 5.4-fold. Carbachol and bombesin, but not vasoactive intestinal peptide, also activated p90(rsk). CCK-induced activation of p90(rsk) appears to be mediated by protein kinase C (PKC), since 12-O-tetradecanoylphorbol-13-acetate increased p90(rsk) activity 5.3-fold. GF-109293X, a potent inhibitor of PKC, strongly inhibited CCK-evoked p90(rsk) activity. Treatment of acini with ionomycin or 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid had no effect, indicating that mobilization of intracellular Ca2+ by CCK is not important in p90(rsk) activation. Although there were some quantitative differences in the extent of inhibition, the specific inhibitors [rapamycin, wortmannin, mitogen-activated protein kinase (MAPK) kinase inhibitor PD98059, and GF-109293X] had parallel effects on p90(rsk) and p42(mapk) activities, consistent with a model in which p90(rsk) can be regulated in acini by MAPK.


Blood ◽  
1993 ◽  
Vol 82 (9) ◽  
pp. 2890-2898 ◽  
Author(s):  
C Combadiere ◽  
J el Benna ◽  
E Pedruzzi ◽  
J Hakim ◽  
A Perianin

Abstract Stimulation of polymorphonuclear neutrophils (PMN) by phorbol esters or formyl peptides (fMLP) generates large quantities of superoxide anion, the so-called respiratory burst (RB), a phenomenon associated with intense phosphorylation of a 47-kD protein (p47 phox). Staurosporine, a potent protein kinase C (PKC) antagonist, inhibits both responses when PMN are stimulated by phorbol myristate acetate (PMA), suggesting a positive role of PKC. In this study, we reassessed these PMN responses in fMLP-stimulated cells and found that staurosporine had opposite effects depending on the duration of PMN treatment with staurosporine. Short PMN incubation (0.5 to 3 minutes) with 25 to 100 nmol/L staurosporine inhibited the fMLP-induced RB, whereas longer treatment (15 to 20 minutes) enhanced it by up to about 200% relative to controls. In contrast, the PMA-mediated RB was depressed by staurosporine in a time-dependent manner. A primed fMLP-induced RB was also observed after long (15 minutes) PMN treatment with 5 to 100 mumol/L H-7, whereas shorter treatment (5 minutes) resulted in a small decrease in RB. By contrast, the tyrosine kinase inhibitor genistein (2 to 80 mumol/L) depressed fMLP-induced RB whatever the duration of PMN treatment. Analysis of 32P-phosphorylated proteins in fMLP-stimulated cells showed that short PMN treatment (< 8 minutes) with staurosporine abolished the phosphorylation of the 47-kD protein, which was identified as p47 phox, whereas long treatment partially restored p47 phox phosphorylation up to approximately 50% of the control value. In PMA-stimulated PMN, phosphorylation was reduced in a time-dependent manner. Furthermore, the staurosporine-primed RB and the staurosporine- induced recovery of phosphorylation were inhibited by sphingosine but not by genistein. Thus, in addition to its known depressive effect, staurosporine markedly potentiated fMLP-stimulated RB as a function of the duration of PMN treatment. The restoration of p47 phox phosphorylation suggests that staurosporine may alter the interactions between different protein kinases, producing marked time-dependent changes in signalling pathways. These data emphasize the care that should be taken in interpreting data obtained using this kinase inhibitor that may, however, be helpful analyzing in signalling pathways.


2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Seung Ju Kim ◽  
Hye Yoom Kim ◽  
Yun Jung Lee ◽  
Hao Zhen Cui ◽  
Ji Yeon Jang ◽  
...  

The seeds ofLepidium apetalumWilldenow (called “Tinglizi” in China and “Jungryukza” in Korea) have been used to discharge phlegm and improve dropsy in Oriental medicine. The present study investigated the effects of ethanol extract of the seeds ofLepidium apetalum(ELA) on atrial dynamics and atrial natriuretic peptide (ANP) secretion in beating rabbit atria. ELA increased atrial stroke volume, pulse pressure, and cAMP efflux, concomitantly attenuating ANP secretion in a dose-dependent manner. ELA-induced increases in atrial stroke volume, pulse pressure, and cAMP levels and decrease in ANP secretion were not inhibited by pretreatment with staurosporine, a nonspecific protein kinase inhibitor, or diltiazem and verapamil, the L-type Ca2+channel blockers, respectively. Helveticoside, a well-known digitalis-like cardiac glycosidic constituent of ELA, also increased atrial dynamics, including stroke volume and pulse pressure, without changing cAMP efflux and ANP secretion, and the effects of helveticoside were not inhibited by pretreatment with staurosporine, diltiazem, and verapamil. These results suggest that the ELA-induced positive inotropic activity in beating rabbit atria might, at least partly, be due to the digitalis-like activity of helveticoside rather than an increase in cAMP efflux.


Endocrinology ◽  
2011 ◽  
Vol 152 (3) ◽  
pp. 751-763 ◽  
Author(s):  
Yewei Xing ◽  
Anthony Cohen ◽  
George Rothblat ◽  
Sandhya Sankaranarayanan ◽  
Ginny Weibel ◽  
...  

Adrenal aldosterone production is regulated by physiological agonists at the level of early and late rate-limiting steps. Numerous studies have focused on the role of lipoproteins including high-density lipoprotein (HDL) as cholesterol providers in this process; however, recent research suggests that HDL can also act as a signaling molecule. Herein, we used the human H295R adrenocortical cell model to study the effects of HDL on adrenal aldosterone production and CYP11B2 expression. HDL, especially HDL2, stimulated aldosterone synthesis by increasing expression of CYP11B2. HDL treatment increased CYP11B2 mRNA in both a concentration- and time-dependent manner, with a maximal 19-fold increase (24 h, 250 μg/ml of HDL). Effects of HDL on CYP11B2 were not additive with natural agonists including angiotensin II or K+. HDL effects were likely mediated by a calcium signaling cascade, because a calcium channel blocker and a calmodulin kinase inhibitor abolished the CYP11B2-stimulating effects. Of the two subfractions of HDL, HDL2 was more potent than HDL3 in stimulating aldosterone and CYP11B2. Further studies are needed to identify the active components of HDL, which regulate aldosterone production.


Endocrinology ◽  
1999 ◽  
Vol 140 (6) ◽  
pp. 2850-2858 ◽  
Author(s):  
Shinichi Suzuki ◽  
Isao Yamamoto ◽  
Jun Arita

Abstract Intracellular cAMP regulates cell proliferation as a second messenger of extracellular signals in a number of cell types. We investigated, by pharmacological means, whether an increase in intracellular cAMP levels changes proliferation rates of lactotrophs in primary culture, whether there are interactions between signal transduction pathways of cAMP and the growth factor insulin, and where the dopamine receptor agonist bromocriptine acts in the cAMP pathway to inhibit lactotroph proliferation. Rat anterior pituitary cells, cultured in serum-free medium, were treated with cAMP-increasing agents, followed by 5-bromo-2′-deoxyuridine (BrdU) to label proliferating pituitary cells. BrdU-labeling indices indicative of the proliferation rate of lactotrophs were determined by double immunofluorescence staining for PRL and BrdU. Treatment with forskolin (an adenylate cyclase activator) or (Bu)2cAMP (a membrane-permeable cAMP analog) increased BrdU-labeling indices of lactotrophs in a dose- and incubation time-dependent manner. The cAMP-increasing agents were also effective in increasing BrdU-labeling indices in populations enriched for lactotrophs by differential sedimentation. The stimulatory action of forskolin was observed, regardless of concentrations of insulin that were added in combination with forskolin. Inhibition of the action of endogenous cAMP by H89 or KT5720, a protein kinase A inhibitor, attenuated an increase in BrdU-labeling indices by insulin treatment. On the other hand, the specific mitogen-activated protein kinase inhibitor PD98059, which was effective in blocking the mitogenic action of insulin, markedly suppressed the forskolin-induced increase in BrdU-labeling indices. (Bu)2cAMP antagonized not only inhibition of BrdU labeling indices but also changes in cell shape induced by bromocriptine treatment, although forskolin did not have such an antagonizing effect. These results suggest that: 1) intracellular cAMP plays a stimulatory role in the regulation of lactotroph proliferation; 2) cAMP and insulin/mitogen-activated protein kinase signalings require each other for their mitogenic actions; and 3) the antimitogenic action of bromocriptine is, at least in part, caused by inhibition of cAMP production.


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