Biphasic effects of dopamine on 86rubidium uptake in rat renal proximal tubules

The mechanism(s) by which dopamine inhibits Na+-K+-ATPase activity in the renal proximal tubule is still controversial. We studied the short-term effects of dopamine on the sodium pump in rat renal proximal tubule suspensions with the 86Rb uptake method. Dopamine and the D1-like agonist, SKF81297, initially stimulated Na+-K+-ATPase activity at 5 min and subsequently inhibited it at 10 min and 20 min; the inhibition by 10 microM dopamine at 20 min was 21.3 +/- 4.5%. The inhibitory effect of dopamine on Na+-K+-ATPase activity was mimicked by thymeleatoxin (a classical protein kinase C [PKC] agonist) while Sp-8-CPT-cAMPS (a protein kinase A [PKA] agonist) had no effect. However, the combination of the PKC and PKA agonists mimicked the biphasic effects of dopamine and SKF81297. Rp-8-CPT-cAMPS (a PKA inhibitor), U-73122 (a phospholipase C inhibitor), or calphostin C (a PKC inhibitor), blocked the dopamine-mediated biphasic effects on Na+-K+-ATPase activity. It is suggested that the biphasic effects of dopamine on Na+-K+-ATPase activity (an initial stimulation and a subsequent inhibition) are transduced by activating both PKA and PKC through a D1-like receptor.

Estradiol-17beta-BSA stimulates Ca(2+) uptake through nongenomic pathways in primary rabbit kidney proximal tubule cells: involvement of cAMP and PKC

The effect of estradiol-17beta-BSA (E(2)-BSA) on Ca(2+) uptake and its related signal pathways were examined in the primary cultured rabbit kidney proximal tubule cells. E(2)-BSA (10(-9) M) significantly stimulated Ca(2+) uptake from 2 h by 13% and at 8 h by 35% as compared to control, respectively. This stimulatory effect of E(2)-BSA was not inhibited by tamoxifen (10(-8) M, an intracellular estrogen receptor antagonist), actinomycin D (10(-7) M, a transcription inhibitor), and cycloheximide (4 x 10(-5) M, a protein synthesis inhibitor). However, E(2)-BSA-induced stimulation of Ca(2+) uptake was blocked by methoxyverapamil (10(-6) M, an L-type calcium channel blocker) and 5-(N-ethyl-N-isopropyl)-amiloride (10(-5) M, a Na(+)/H(+) antiporter blocker). These results suggest that E(2)-BSA stimulates Ca(2+) uptake through nongenomic pathways. Thus, we investigated which signal pathways were related to E(2)-BSA-induced stimulation of Ca(2+) uptake. 8-Br-cAMP (10(-6) M) alone increased Ca(2+) uptake by 22% compared to control. When E(2)-BSA combined with 8-Br-cAMP, Ca(2+) uptake was not significantly stimulated compared to E(2)-BSA. SQ 22536 (10(-6) M, an adenylate cyclase inhibitor) and myristoylated protein kinase A inhibitor amide 14-22 (10(-6) M, a protein kinase A inhibitor) blocked E(2)-BSA-induced stimulation of Ca(2+) uptake and E(2)-BSA also increased cAMP generation by 26% of that of control. In addition, TPA (0.02 ng/ml, an artificial PKC promoter) stimulated the Ca(2+) uptake by 14%, and the cotreatment of TPA and E(2)-BSA did not significantly stimulate Ca(2+) uptake compared to E(2)-BSA. E(2)-BSA-induced stimulation of Ca(2+) uptake was blocked by U 73122 (10(-6) M, a phospholipase C inhibitor) or bisindolylmaleimide I (10(-6) M, a protein kinase C inhibitor). Indeed, E(2)-BSA stimulated PKC activity by 26%. In conclusion, E(2)-BSA (10(-9) M) stimulated Ca(2+) uptake by nongenomic action, which is mediated by cAMP and PKC pathways.

Novel effects of propranolol. Release of internal Ca(2+) followed by activation of capacitative Ca(2+) entry in Madin Darby canine kidney cells

The effect of propranolol on Ca(2+) signalling in Madin Darby canine kidney (MDCK) cells was investigated by using fura-2 as a Ca(2+) probe. Propranolol increased cytosolic free Ca(2+) levels ([Ca(2+)](i)) in a concentration-dependent manner between 0.1 and 1 mM. The response was partly inhibited by external Ca(2+) removal. In Ca(2+)-free medium pretreatment with 0.2 mM propranolol partly inhibited the [Ca(2+)](i) rise induced by 1 microM thapsigargin, an inhibitor of the endoplasmic reticulum Ca(2+) pump; but pretreatment with thapsigargin abolished propranolol-induced Ca(2+) release. Addition of 3 mM Ca(2+) induced a [Ca(2+)](i) rise after pretreatment with 0.2 mM propranolol in Ca(2+)-free medium. Propranolol (0.2 mM) inhibited 25% of thapsigargin-induced capacitative Ca(2+) entry. Suppression of 1,4,5-trisphosphate (IP(3)) formation by 2 microM U73122, a phospholipase C inhibitor, did not alter 0.2 mM propranolol-induced internal Ca(2+) release. Propranolol (1 mM) also increased [Ca(2+)](i) in human neutrophils. Collectively, we have found that 0.2 mM propranolol increased [Ca(2+)](i) in MDCK cells by releasing Ca(2+) from thapsigargin-sensitive Ca(2+) stores in an IP(3)-independent manner, followed by Ca(2+) influx from external space. Independently, propranolol was able to inhibit thapsigargin-induced capacitative Ca(2+) entry.

Tachykinins increase [3H]acetylcholine release in mouse striatum through multiple receptor subtypes

Tachykinins have been suggested to play a significant role in the mammalian striatum, at least in part by the control of acetylcholine release from cholinergic interneurons. In the present study, we have examined the ability of known tachykinin agonists and antagonists to modulate the activity of these interneurons in mouse striatal slices. Using whole-cell patch-clamp recordings, the selective neurokinin-1, neurokinin-2 and neurokinin-3 receptor agonists [sar9,Met(O2)11]substance P, [beta-ala8]neurokinin A(4-10) and senktide each produced a dose-dependent depolarization of visually identified cholinergic interneurons that was retained under conditions designed to interrupt synaptic transmission. The nature of these neurons and the expression of multiple tachykinin receptors was confirmed using single-cell reverse transcriptase-polymerase chain reaction analysis. Using in vitro superfusion techniques, the selective neurokinin-1, neurokinin-2 and neurokinin-3 receptor agonists [sar9,Met(O2)11]substance P, [beta-ala8]neurokinin A(4-10) and senktide, respectively, each produced a dose-dependent increase in acetylcholine release, the selectivity of which was confirmed using the neurokinin-1, neurokinin-2 and neurokinin-3 receptor antagonists SR140333, GR94800 and SR142801 (100 nM). U73122 (10 microM), a phospholipase C inhibitor, blocked [sar9,Met(O2)11]substance P- and senktide-induced acetylcholine release, but had no effect on [beta-ala8]neurokinin A(4-10)-induced release. The protein kinase C inhibitors chelerythrine and Ro-31-8220 (both 1 microM) significantly inhibited responses induced by all three agonists. These findings indicate that tachykinins modulate the activity of mouse striatal cholinergic interneurons. Furthermore, neurokinin-2 receptors are shown to perform a role in mouse that has not been identified previously in other species.

Inhibitors of phospholipase C prevent glutamate neurotoxicity in primary cultures of cerebellar neurons

The role of phospholipase C in the molecular mechanism of glutamate neurotoxicity was assessed in primary cultures of cerebellar neurons. It is shown that 1-[6-[[(17b)-3-methoxyestra-1,3, 5(10)-trien-17-yl]amino] hexyl]-1H-pyrrole-2,5-dione (U-73122) and 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphorylcholine (Et-18-OCH(3)), two agents that inhibit phospholipase C, prevent glutamate and N-methyl-D-aspartic acid (NMDA) neurotoxicity. It is shown that both compounds prevent glutamate neurotoxicity at concentrations lower than those required to inhibit carbachol-induced hydrolysis of inositol phospholipids. In contrast, it was a good correlation between the concentrations of U-73122 and Et-18-OCH(3) required to inhibit NMDA-induced hydrolysis of phospholipids and those required to prevent glutamate and NMDA neurotoxicity. NMDA-induced hydrolysis of phospholipids is inhibited by nitroarginine, an inhibitor of nitric-oxide synthase, and is mimicked by the nitric oxide-generating agent S-nitroso-N-acetylpenicillamine. The results reported indicate that glutamate neurotoxicity would be mediated by activation of NMDA receptors, leading to activation of nitric-oxide synthase and increased formation of nitric oxide, which results in increased activity of phospholipase C. Inhibition of phospholipase C by U-73122 or Et-18-OCH(3) prevents glutamate-induced neuronal death.

Cyclosporin-A-induced effects on the free Ca2+ concentration in LLC-PK1-cells and their mechanisms

Here we have examined the effects of Cyclosporin A (CyA) on the free intracellular Ca2+ concentration ([Ca2+]i) of LLC-PK1/PKE20 cells to evaluate mechanisms of CyA nephrotoxicity using Fura-2 microspectrofluorometry or digital fluorescence video imaging. The CyA-associated changes were compared to the effects of tacrolimus (Tac), a structurally unrelated immunosuppressant with similar cellular pathways which also causes nephrotoxicity. CyA (EC50(: 1 nmol/l, n=16) and Tac (EC50: 1 nmol/l, n=5) caused a concentration-dependent increase of [Ca2+]i which was substantially attenuated by reducing the external Ca2+ concentration (10(-6) mol/l). Similarly Cyclosporin H, a non-immunosuppressive analogue of CyA, stimulated a Ca2+ influx. Nicardipine (10(-6) mol/l) reduced the CyA- and the Tac-induced Ca2+ influx to 52+/-16% (n=10) and 13+/-10% (n=13) of control respectively. Diltiazem and verapamil (10(-6) mol/l) were also effective, but flufenamate (10(-4) mol/l), Gd3+ (10(-5) mol/l) and La3+ (10(-5) mol/l) were not. In the absence of extracellular Ca2+ CyA led to a small but significant [Ca2+]i increase, indicating additional release from internal stores. Depletion of inositol-1,4,5-trisphosphate-(InsP3-) sensitive Ca2+ stores by extracellular ATP (10(4) mol/l) in low-Ca2+ solution completely suppressed the CyA-induced [Ca2+]i rise. CyA had no effect on the cellular InsP3 concentration. Furthermore, inhibition of phospholipase-Cbeta (PLCbeta) by U73122 (2x10(-5) mol/l) did not alter the CyA-stimulated [Ca2+]i rise. A direct effect of CyA on InsP3-sensitive Ca2+ stores, the InsP3 receptor, the Ca2+ content of the stores or involvement of additional stores is assumed. Incubation with CyA for 1, 12 and 24 h enhanced the rise in [Ca2+]i peak induced by ATP, arginine vasopressin (AVP) and angiotensin II. In summary, CyA stimulated a [Ca2+]i increase in LLC-PK1 cells through Ca2+ release from InsP3-sensitive stores and Ca2+ influx via a nicardipine-sensitive pathway. The CyA-mediated [Ca2+]i increase is independent of PLCbeta activity and InsP3 metabolism. CyA caused long-term enhancement of the agonist-induced rise in [Ca2+]i. The effects of CyA on Ca2+ signaling appear to be independent of its immunosuppressive action.

PDGF and FGF-2 signaling in oligodendrocyte progenitor cells: regulation of proliferation and differentiation by multiple intracellular signaling pathways

In this paper we address the linking of platelet-derived growth factor (PDGF) and basic fibroblast growth factor (FGF-2) to intracellular signaling molecules in oligodendrocyte progenitors. It is demonstrated that both growth factors activate downstream targets similar to those shown for protein kinase C (PKC) activation. Yet, neither the arrest of terminal oligodendrocyte differentiation nor the proliferation induced by PDGF or FGF-2 can be antagonized by inhibition of PKC. Rather, p42/p44 mitogen-activated protein kinase (MAPK), p38 MAPK, and pp70 S6 kinase were found to be necessary for the mitogenic activity of PDGF and FGF-2. Paradoxically, these kinases were also necessary for the onset of oligodendrocyte differentiation in control cells. In addition, cAMP-dependent kinase A (PKA) activation inhibited the mitogenic response of oligodendrocyte progenitors to FGF-2. Taken together, the molecular mechanism that controls oligodendrocyte lineage progression is operated by at least two signal pathways, which interfere either with proliferation and/or differentiation of oligodendrocyte progenitors.

Effect of aging on the mechanisms of PTH-induced calcium influx in rat intestinal cells

We have investigated the effects of aging on parathyroid hormone (PTH) modulation of intracellular calcium homeostasis and their relationship to signal transduction pathways in isolated rat duodenal cells (enterocytes). PTH (10(-8)-10(-9) M) increased enterocyte (45)Ca(2+) influx and intracellular Ca(2+) concentration ([Ca(2+)](i)) to a greater extent (twofold and 50%, respectively) in aged (24 months) than in young (3 months) animals. The [Ca(2+)](i) response of old cells to the hormone was slower, lacking the early phase of changes in cytosolic Ca(2+). Ca(2+) influx induced by PTH was prevented by the protein kinase A antagonist Rp-cAMPS in both young and aged enterocytes, whereas neomycin and compound U73122, inhibitors of PLC-catalyzed phosphoinositide hydrolysis, abolished hormone-dependent Ca(2+) influx in young but had no effect on aged cells. Higher basal adenylyl cyclase (AC) activity and cAMP content were detected in old enterocytes. PTH increased the absolute levels of cAMP in aged cells and AC activity of microsomes isolated therefrom to a greater extent (>/= twofold) than in young enterocytes/membranes. In young cells, the hormone also induced a rapid and transient release of inositoltrisphosphate (IP(3)) and diacylglycerol (neomycin-sensitive) at 45 sec, and a delayed phase of DAG at 5 min (neomycin-insensitive). The early formation of IP(3) and DAG was blunted in aged animals. These results suggest that both the PLC and adenylyl cyclase cascades are involved in PTH stimulation of Ca(2+) influx in duodenal cells. During aging, however, only the cAMP pathway is operative, mediating a potentiation of the effects of the hormone. Additional studies are required to establish the relative role of PTH-dependent messenger systems in the regulation of intestinal calcium absorption and age-related abnormalities.

Comparison of the effects of antiprogestins RU38486, ZK98299 and ORG31710 on periovulatory hypophysial, ovarian and adrenal hormone secretion in the rat

The antiprogestin (AP) RU38486 (RU) blocks progesterone (P) and glucocorticoid (G) actions. Administration of 4 mg RU on proestrous morning to cyclic rats dissociates LH and FSH secretion on proestrous afternoon, early estrus and on estrous afternoon. In order to ascertain which action blocked by RU is predominant in the control of periovulatory LH and FSH secretion, a study was made on the effects of: a) 1 or 4 mg of ZK98299 (ZK) (type I P antagonist; Schering), b) 2 or 8 mg of Org31710 (OR) (type II P antagonist lacking anti-G actions; Organon) or c) 1 or 4 mg of RU (type II P antagonist; Exelgyn) to 4-day cyclic rats on proestrous morning on serum concentrations of LH, FSH, inhibin-alpha (I), estradiol-17beta (E), progesterone (P) and corticosterone (B) at 18:30 h on proestrus and at 02:00 and 18:30 h on estrus. Controls, receiving 0.2 ml oil, had elevated serum concentrations of all six hormones on proestrous afternoon; at early estrus, only serum concentrations of FSH and P remained elevated, and, on estrous afternoon, all hormones but I and B, that peaked again, had reached their lowest serum levels. All AP treatments except 1 mg ZK had the same effects. On proestrous afternoon serum LH concentrations were reduced and serum FSH concentrations were suppressed whereas serum levels of I, E, P and B were unaffected. At early estrus, basal serum concentrations of LH and E increased while FSH secretion was abolished. Serum levels of I, P and B did not differ from controls. AP treatments increased basal LH concentration, hyperstimulated FSH secretion and reduced serum I concentration on the afternoon of estrus. E, P and B serum levels did not differ from controls at this stage. Treatment with 1 mg ZK was less effective in reducing serum FSH on proestrous afternoon and at early estrus, and had no effect on serum concentrations of any hormone on estrous afternoon. These results indicate that blockade of P receptor activation by P is, predominantly, the mechanism of AP action on periovulatory gonadotropin secretion in rats.

Purinoceptor-mediated calcium mobilization and cellular proliferation in cultured bovine corneal endothelial cells

In the present study, we investigated the effect of adenosine triphosphate (ATP) on cytosolic free calcium mobilization and mitogenic activity in cultured bovine corneal endothelial cells (BCEC). The [Ca2+]i was determined using a Ca2+ sensitive indicator, Fura-2/AM, and cell proliferation was evaluated by counting the cell number. ATP, its metabolites and analogs caused transient increase in [Ca2+]i in a concentration-dependent manner (10(-7) M-10(-3) M) and the potency of agonists was ordered as follows: 2-methylthio-ATP > uridine triphosphate > ATP > adenosine diphosphate. Adenosine monophosphate and adenosine did not affect [Ca2+]i. ATP (10(-4) M) also promoted the accumulation of inositol trisphosphate (IP3). The ATP-induced transient [Ca2+]i increase and IP3 accumulation were attenuated by pretreatment with a phospholipase C inhibitor, U-73122 (5 microM), for 30 min. ATP (10(-5) M) significantly enhanced the proliferation of BCEC. ATP-induced [Ca2+]i increase and cell proliferation were inhibited by a purinoceptor antagonist, suramin (10(-4) M). Thus, the present study indicates that BCEC contain P2 purinoceptors that regulate their proliferation.

A fundamental role for the nitric oxide-G-kinase signaling pathway in mediating intercellular Ca(2+) waves in glia

In this study, we highlight a role for the nitric oxide-cGMP-dependent protein kinase (NO-G-kinase) signaling pathway in glial intercellular Ca(2+) wave initiation and propagation. Addition of the NO donor molsidomine (100-500 microM) or puffing aqueous NO onto primary glial cell cultures evoked an increase in [Ca(2+)](i) in individual cells and also local intercellular Ca(2+) waves, which persisted after removal of extracellular Ca(2+). High concentrations of ryanodine (100-200 microM) and antagonists of the NO-G-kinase signaling pathway essentially abrogated the NO-induced increase in [Ca(2+)](i), indicating that NO mobilizes Ca(2+) from a ryanodine receptor-linked store, via the NO-G-kinase signaling pathway. Addition of 10 microM nicardipine to cells resulted in a slowing of the molsidomine-induced rise in [Ca(2+)](i), and inhibition of Mn(2+) quench of cytosolic fura-2 fluorescence mediated by a bolus application of 2 microM aqueous NO to cells, indicating that NO also induces Ca(2+) influx in glia. Mechanical stress of individual glial cells resulted in an increase in intracellular NO in target and neighboring cells and intercellular Ca(2+) waves, which were NO, cGMP, and G-kinase dependent, because incubating cells with nitric oxide synthase, guanylate cyclase, and G-kinase inhibitors, or NO scavengers, reduced Delta[Ca(2+)](i) and the rate of Ca(2+) wave propagation in these cultures. Results from this study suggest that NO-G-kinase signaling is coupled to Ca(2+) mobilization and influx in glial cells and that this pathway plays a fundamental role in the generation and propagation of intercellular Ca(2+) waves in glia.

Inositol phosphate metabolism and nitric-oxide synthase activity in endothelial cells are involved in the vasorelaxant activity of nebivolol

Nebivolol is a recently developed beta-blocker provided with vasodilator properties. Because the mechanism of the putative endothelium-dependent effect of this beta-adrenoceptor blocker has not been completely elucidated, the aim of this study was to investigate the effects of nebivolol on an isolated resistance vascular bed and on cell messengers and constitutive nitric-oxide synthase activity (cNOS) in endothelial cells. Experiments were carried out using the rat mesenteric vascular bed and cultured bovine coronary postcapillary venular endothelial cells from bovine heart (CVEC). In mesenteric vascular bed preconstricted by 30 microM noradrenaline and 0.3 microM U46619, dl-nebivolol induced a concentration-dependent relaxing effect at concentrations between 3 and 30 microM; this effect was changed to a concentration-dependent vasoconstrictor response either in endothelium-denuded preparations or in intact preparations pretreated with 100 microM N(omega)-nitro-L-arginine methyl ester plus 3 microM indomethacin. The vasorelaxant effect of dl-nebivolol in preconstricted preparations was completely blocked by pretreatment either with the phospholipase C inhibitor U73122 (1 microM) or with the endoplasmic reticulum Ca(2+)-ATPase inhibitor thapsigargin (1 microM) for 30 min. The cellular level of the inositol trisphosphate metabolite inositol monophosphate in coronary postcapillary venular endothelial cells was not affected by dl-nebivolol in the concentration range 100 nM to 1 microM, but it was concentration dependently increased after exposure for 15 min to 10 and 30 microM dl-nebivolol. The activity of cNOS was almost doubled after a 5-min exposure to 10 microM dl-nebivolol and was significantly impaired by thapsigargin and N(omega)-nitro-L-arginine methyl ester treatment, although it was unaffected by N(omega)-nitro-D-arginine methyl ester. These findings demonstrate that nebivolol, in micromolar concentrations, induces vasorelaxation through activation of inositol phosphate metabolism and stimulation of cNOS activity in endothelial cells.

Cerebellin stimulates the secretory activity of the rat adrenal gland: in vitro and in vivo studies

Cerebellin is a 16-aminoacid peptide widely distributed in the central nervous system, where it exerts neuromodulatory functions. Cerebellin is contained in human adrenal medulla, and it has been recently demonstrated that cerebellin elicits catecholamine release by human adrenal in vitro. Aim of the present study was to ascertain whether cerebellin affects adrenal function in the rat. Cerebellin concentration-dependently (from 10(-9)to 10(-7)M) increased norepinephrine (but not epinephrine) and cyclic-AMP production by adrenomedullary tissue in vitro. The norepinephrine response to 10(-7)M cerebellin was blocked by the protein kinase (PK) A inhibitor H-89, but not by the phospholipase C inhibitor U-73122 or the PKC inhibitor calphostin-C. Cerebellin did not affect aldosterone and corticosterone secretion of dispersed zona glomerulosa and zona fasciculata-reticularis adrenocortical cells. Cerebellin concentration-dependently (from 10(-8)to 10(-7)M) enhanced norepinephrine release by in situ perfused rat adrenals. Cerebellin (10(-7)M) also elicited a significant rise in aldosterone and corticosterone output, and this effect was annulled by either the beta1-adrenoceptor antagonist l -alprenolol or H-89. Collectively, the present findings allow us to conclude that cerebellin 1) directly stimulates norepinephrine release via the adenylate cyclase/PKA-dependent signaling pathway; and 2) indirectly enhances adrenocortical secretion in vivo, through a paracrine mechanism involving medullary catecholamine release.

Regulation of calcium signalling by docosahexaenoic acid in human T-cells. Implication of CRAC channels

We elucidated the role of docosahexaenoic acid (DHA) on the increases in free intracellular calcium concentrations, [Ca(2+)]i, in human (Jurkat) T-cell lines. DHA evoked an increase in [Ca(2+)]i in a dose-dependent manner in these cells. Anti-CD3 antibody, known to stimulate increases in Ca(2+) from endoplasmic reticulum (ER) via the production of inositol trisphosphate, also evoked increases in [Ca(2+)]i in Jurkat T-cells. We also used thapsigargin which inhibits Ca(2+)-ATPase of the ER and, therefore, increases Ca(2+) in the cytosol. Interestingly, addition of DHA during the thapsigargin-induced peak response exerted an additive effect on the increases in [Ca(2+)]i in human T-cells, indicating that the mechanisms of action of these two agents are different. However, the DHA-induced calcium response was not observed when this agent was added during the anti-CD3-induced calcium peak, though its addition resulted in a prolonged and sustained calcium response as a function of time, suggesting that DHA recruits calcium, in part, from the ER pool and the prolonged response may be due to Ca(2+) influx. In the medium containing 0% Ca(2+), the DHA-evoked response on the increases in [Ca(2+)]i was significantly curtailed as compared to that in 100% Ca(2+) medium, supporting the notion that the response of the DHA is also due, in part, to the opening of calcium channels. Furthermore, preincubation of cells with tyrphostin A9, an inhibitor of Ca(2+) release-activated Ca(2+) (CRAC) channels also significantly curtailed the DHA-induced sustained response on the increases in [Ca(2+)]i in these cells. These results suggest that DHA induces an increase in [Ca(2+)]i via the ER pool and the opening of CRAC channels in human T-cells.

Psychological state and mood effects of steroidal chemosignals in women and men

We tested the hypothesis that isolated steroids, claimed to act like pheromones, affect human psychological state or mood. In the first experiment, we established that two steroids, Delta4, 16-androstadien-3-one and 1,3,5(10)16-estratetraen-3-ol, modulated emotional states within 6 min of exposure. In men and women, neither steroid had specific effects on states of alertness or negative-confused mood. However, both steroids increased positive stimulated mood state in women but decreased it in men. These psychological findings do not parallel the reported sexually specific effects of these two steroids on the surface potential activity of putative vomeronasal epithelium. In a second experiment on women, we replicated that Delta4,16-androstadien-3-one modulated their general mood state, even when women were not aware of its odor and gave identical olfactory descriptions for the steroid and the control carrier solutions. In this within-subjects, repeated-measures experiment, androstadienone prevented the deterioration in general mood which occurred during exposure to the clove oil carrier solution in the laboratory environment. Thus, androstadienone appears to modulate affect, rather than releasing stereotyped behaviors or emotions. It is premature to call these steroids human pheromones. They are nonetheless psychologically potent, mandating future work delineating their function-i.e., whether these steroids are communicative chemosignals, context specific, or related to unconscious associations. In light of these modulatory effects and the complexity of human behavior, the function of chemosignals and pheromonal systems in a variety of species may need to be expanded to include the concept of modulators, as well as the traditional releasers, primers, and signaling compounds.

Purinergic activation of spontaneous transient outward currents in guinea pig taenia colonic myocytes

Spontaneous transient outward currents (STOCs) were recorded from smooth muscle cells of the guinea pig taenia coli using the whole cell patch-clamp technique. STOCs were resolved at potentials positive to -50 mV. Treating cells with caffeine (1 mM) caused a burst of outward currents followed by inhibition of STOCs. Replacing extracellular Ca(2+) with equimolar Mn(2+) caused STOCs to "run down. " Iberiotoxin (200 nM) or charybdotoxin (ChTX; 200 nM) inhibited large-amplitude STOCs, but small-amplitude "mini-STOCs" remained in the presence of these drugs. Mini-STOCs were reduced by apamin (500 nM), an inhibitor of small-conductance Ca(2+)-activated K(+) channels (SK channels). Application of ATP or 2-methylthioadenosine 5'-triphosphate (2-MeS-ATP) increased the frequency of STOCs. The effects of 2-MeS-ATP persisted in the presence of charybdotoxin but were blocked by combination of ChTX (200 nM) and apamin (500 nM). 2-MeS-ATP did not increase STOCs in the presence of pyridoxal phosphate 6-azophenyl-2',4'-disulfonic acid, a P(2) receptor blocker. Similarly, pretreatment of cells with U-73122 (1 microM), an inhibitor of phospholipase C (PLC), abolished the effects of 2-MeS-ATP. Xestospongin C, an inositol 1,4,5-trisphosphate (IP(3)) receptor blocker, attenuated STOCs, but these events were not affected by ryanodine. The data suggest that purinergic activation through P(2Y) receptors results in localized Ca(2+) release via PLC- and IP(3)-dependent mechanisms. Release of Ca(2+) is coupled to STOCs, which are composed of currents mediated by large-conductance Ca(2+)-activated K(+) channels and SK channels. The latter are thought to mediate hyperpolarization and relaxation responses of gastrointestinal muscles to inhibitory purinergic stimulation.

Activation of human neutrophils by Mycobacterium tuberculosis H37Ra involves phospholipase C gamma 2, Shc adapter protein, and p38 mitogen-activated protein kinase

Recent studies have shown that human neutrophils play a significant protective role in mycobacteria infection. When encountered with mycobacteria, neutrophils exhibit the typical early bactericidal responses including phagocytosis and generation of reactive oxygen intermediates (ROI), but the underlying mechanisms are largely unknown. The present study shows that stimulation of neutrophils with an attenuated strain of Mycobacterium tuberculosis H37Ra (Mtb) led to a tyrosine kinase-dependent ROI production in these cells. Stimulation with Mtb induces a rapid and transient tyrosine phosphorylation of several proteins, one of which was identified as phospholipase C gamma 2 (PLC gamma 2). Several tyrosine-phosphorylated proteins were associated with the PLC gamma 2 precipitates from Mtb-stimulated neutrophils, of which pp46 was characterized as the Shc adapter protein. A role for PLC gamma 2-Shc association in the generation of ROI is supported by the observations that stimulation with Mtb causes the activation of p38 mitogen-activated protein kinase (MAPK), a downstream target of the Shc/Ras signaling cascade, and that the effect of genistein on ROI production coincided with its ability to inhibit both PLC gamma 2-Shc association and p38 MAPK activation. Moreover, pretreatment of neutrophils with a PLC inhibitor markedly suppresses the Mtb-stimulated ROI production as well as p38 MAPK activation in these cells. Taken together, these results indicate that stimulation of neutrophils with Mtb triggers the tyrosine phosphorylation of PLC gamma 2 and its association with Shc, and that such association is critical for the Mtb-stimulated ROI production through activating p38 MAPK.

Bradykinin-induced inhibition of cell proliferation and tyrosine kinase activity in rat mesangial cells

The relationship between cell proliferation, protein tyrosine phosphorylation, phosphotyrosine kinase activity and bradykinin receptor activation in rat mesangial cells was investigated. We demonstrated that bradykinin (BK), through the B2 receptor, induced a dose-dependent inhibition of mesangial cell proliferation stimulated by fetal calf serum. We next found that BK induced a dose-dependent inhibition of phospho-tyrosine kinase activity. Treatments with pertussis-toxin, inhibition of phospholipase C and protein kinase C inhibitors and chelation of free cytosolic calcium did not change the bradykinin-induced inhibition of phosphotyrosine kinase. Western blot analysis of phosphotyrosinated proteins demonstrated that BK reduced tyrosine phosphorylation of several proteins among which we identified the 125-focal adhesion kinase. Taken together, these data suggest for the first time that, in proliferating rat mesangial cells, B2 receptor stimulation is able to induce, via a pertussis insensitive pathway, the inhibition of tyrosine kinase activity and mesangial cell proliferation.

Lysophosphatidic acid rapidly induces protein kinase D activation through a pertussis toxin-sensitive pathway

Protein kinase D (PKD) is a serine-threonine protein kinase with distinct structural features and enzymological properties. Herein we demonstrate that lysophosphatidic acid (LPA) induces rapid PKD activation in mouse Swiss 3T3 and Rat-1 cells. LPA induced PKD activation in a concentration-dependent fashion with maximal stimulation (7.6-fold) achieved at 5 microM. Treatment of Swiss 3T3 cells with the protein kinase C (PKC) inhibitors GF-I, Ro-31-8220, and Gö-7874 completely abrogated PKD activation induced by LPA at concentrations that did not inhibit PKD activity when added directly to the in vitro kinase assays. PKD activation induced by LPA was attenuated markedly and selectively by prior exposure of either Swiss 3T3 or Rat-1 cells to pertussis toxin (PTx) in a concentration-dependent manner. In contrast, treatment with the protein tyrosine kinase inhibitor genistein, the MEK inhibitor PD-098059, or the phosphoinositide 3-kinase inhibitor wortmannin did not affect PKD activation in response to LPA. These results provide the first example of PTx-sensitive and PKC-dependent PKD activation and identify a novel G(i)-dependent event in the action of LPA.

W-7 induces [Ca(2+)](i) increases in Madin-Darby canine kidney (MDCK) cells

The effect of W-7 [N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride] on Ca(2+) signaling in Madin-Darby canine kidney cells was investigated. W-7 (0.1-1 mM) induced a [Ca(2+)](i) increase, which comprised an initial increase and a plateau. Ca(2+) removal inhibited the Ca(2+) signals by 80%, suggesting that W-7 activated external Ca(2+) influx and internal Ca(2+) release. Pretreatment with the mitochondrial uncoupler carbonylcyanide m-chlorophenylhydrazone (2 microM) and the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin (1 microM) abolished the internal Ca(2+) release induced by 0.5 mM W-7; conversely, pretreatment with W-7 prevented thapsigargin and carbonylcyanide m-chlorophenylhydrazone from releasing internal Ca(2+). W-7 (0.2 mM) induced Mn(2+) quench of fura-2 fluorescence, which was inhibited by La(3+) (0.1 mM) by 80%. La(3+) (0.1 mM) partly inhibited 0.2 mM W-7-induced [Ca(2+)](i) increase. Addition of 5 mM Ca(2+) induced a significant [Ca(2+)](i) increase after pretreating with 0.2 to 1 mM W-7 in Ca(2+)-free medium for 5 min, suggesting that W-7 induced capacitative Ca(2+) entry. W-7 (0.5 mM) potentiated the capacitative Ca(2+) entry induced by 1 microM thapsigargin by 15%. Pretreatment with aristolochic acid (40 microM) to inhibit phospholipase A(2) reduced 0.5 mM W-7-induced internal Ca(2+) release and external Ca(2+) influx by 25 and 80%, respectively. Inhibition of phospholipase C with U73122 (2 microM) or inhibition of phospholipase D with propranolol (0.1 mM) had no effect on the internal Ca(2+) release induced by 0.5 mM W-7. It remains unclear whether W-7 induced [Ca(2+)](i) increases via inhibition of calmodulin. Three other calmodulin inhibitors (phenoxybenzamine, trifluoperazine, and fluphenazine-N-chloroethane) did not alter resting [Ca(2+)](i).

Characteristics of collagen-induced Ca2+ mobilization in bovine platelets

We characterized the collagen-induced increase in cytosolic Ca2+ ([Ca2+]i) of bovine platelets loaded with the Ca2+ indicator Fura-PE3/AM. Collagen (10 micrograms/ml)-induced increase in [Ca2+]i was only partially inhibited by aspirin, a cyclooxygenase inhibitor, or adenosine 3'-phosphate 5'-phosphosulfate (A3P5PS, a P2Y1 receptor antagonist), while in human platelets it was almost completely suppressed by aspirin. Collagen-induced increase in [Ca2+]i of bovine platelets was inhibited by U73122 (0.3-5 microM), a phospholipase C inhibitor. Collagen (10 micrograms/ml) increased production of inositol 1,4,5-trisphosphate, which was prevented by pretreatment with U73122 (5 microM). Collagen (10 micrograms/ml) accelerated Mn2+ entry, since the rate of Fura-PE3 quenching by Mn2+ was enhanced by 13-fold following stimulation with collagen. U73122 inhibited the acceleration of Mn2+ entry induced by collagen. PGE1 (2.5 microM) partially inhibited the collagen (50 micrograms/ml)-induced increase in [Ca2+]i in bovine platelets but not in human platelets. The data suggest that collagen-induced Ca2+ mobilization in bovine platelets is mediated by phospholipase C. The Ca2+ mobilization in bovine platelets is different from that in human ones as to the dependency on arachidonic acid metabolites and sensitivity to PGE1.

Hyperosmolality induces activation of cPKC and nPKC, a requirement for ERK1/2 activation in NIH/3T3 cells

Protein kinase C (PKC) has been reported to be associated with the activation of extracellular signal-regulated kinase (ERK) by hyperosmolality. However, it is unclear whether hyperosmolality induces PKC activation and which PKC isoforms are involved in ERK activation. In this study, we demonstrate that NaCl increases total PKC activity and induces PKCalpha, PKCdelta, and PKCepsilon translocation from the cytosol to the membrane in NIH/3T3 cells, suggesting that hyperosmotic stress activates conventional PKC (cPKC) and novel PKC (nPKC). Further studies show that NaCl-inducible ERK1 and ERK2 (ERK1/2) activation is a consequence of cPKC and nPKC activation, because either downregulation with 12-O-tetradecanoylphorbol 13-acetate or selective inhibition of cPKC and nPKC by GF-109203X and rottlerin largely inhibited the stimulation of ERK1/2 phosphorylation by NaCl. In addition, we show that NaCl increases diacylglycerol (DAG) levels and that a phospholipase C (PLC) inhibitor, U-73122, inhibits NaCl-induced ERK1/2 phosphorylation. These results, together, suggest that a hyperosmotic NaCl-induced signaling pathway that leads to activation of ERK1/2 may sequentially involve PLC activation, DAG release, and cPKC and nPKC activation.

Mechanisms of AVP-induced glucagon release in clonal alpha-cells in-R1-G9: involvement of Ca(2+)-dependent and -independent pathways

1. The mechanisms underlying AVP-induced increase in [Ca(2+)](i) and glucagon release in clonal alpha-cells In-R1-G9 were investigated. 2. AVP increased [Ca(2+)](i) and glucagon release in a concentration-dependent manner. After the administration of AVP, glucagon was released within 30 s, quickly reached the maximum within 2 min, and maintained a steady-state concentration for at least 15 min. 3. In Ca(2+)-containing medium, AVP increased [Ca(2+)](i) in a biphasic pattern; a peak followed by a sustained plateau. In Ca(2+)-free medium, the Ca(2+) response to AVP became monophasic with lower amplitude and no plateau. Both the basal and AVP-induced glucagon releases were lower in the absence than in the presence of extracellular Ca(2+). When [Ca(2+)](i) was stringently deprived by BAPTA, a Ca(2+) chelator, AVP still significantly increased glucagon release. 4. Pretreatment with thapsigargin, a microsomal Ca(2+) ATPase inhibitor, abolished both the Ca(2+) peak and sustained plateau. 5.AVP increased intracellular concentration of IP(3). 6. U-73122 (8 microM), a phospholipase C inhibitor, abolished AVP-induced increases in [Ca(2+)](i), but only reduced AVP-induced glucagon release by 39%. 7. Pretreatment with nimodipine, an L-type Ca(2+) channel blocker failed to alter AVP-induced glucagon release or increase in [Ca(2+)](i). 8. The results suggest that AVP causes glucagon release through both Ca(2+)-dependent and -independent pathways. For the Ca(2+)-dependent pathway, the G(q) protein activates phospholipase C, which catalyzes the formation of IP(3). IP(3) induces Ca(2+) release from the endoplasmic reticulum, which, in turn, triggers Ca(2+) influx. Both Ca(2+) release and Ca(2+) influx may contribute to AVP-induced glucagon release.