Regulation of proliferation by vasopressin in aortic smooth muscle cells: function of protein kinase C

Vasopressin augments TNBS-induced colitis through enteric neuronal V1a receptor-mediated COX-2-dependent prostaglandin release from mast cells in mice

BACKGROUND

Inflammatory bowel disease (IBD) is a functional disorder with chronic and relapsing clinical features. Vasopressin (VP) is a hormone responsible for water and stress homeostasis and also regulates gastrointestinal inflammation and motility. We explored whether VP was related to IBD pathogenesis and its possible pathway.

METHODS

Colitis was induced by 2,4,6-trinitrobenzenesulfonic acid (TNBS) in mice. The disease activity and colonic damage were evaluated through a scoring system. Locations of the V_1a receptor were revealed by immunochemistry method in colon. Ussing chamber technique was performed for the electrophysiological characterization by using rat ileum. The (Arg⁸ )-Vasopressin (AVP)-evoked short-circuit current (Isc) was recorded in the presence of conivaptan (V_1a and V₂ receptor antagonist), tolvaptan (V_1b receptor antagonist), tetrodotoxin (TTX), atropine, cyclooxygenase (COX) inhibitors (indomethacin, nonspecific COX antagonist; SC560, COX-1 antagonist; NS560, COX-2 antagonist), and a stabilizer of mast cell (cromolyn sodium), respectively.

KEY RESULTS

TNBS resulted in the obvious loss of body weight and tissue damages in mice. AVP significantly aggravated the TNBS-induced colitis, which was attenuated by conivaptan but not tolvaptan. V_1a receptors were found immunopositive in neurons among the enteric nervous system. AVP evoked a pulsatile response in Isc. Its amplitude, frequency, and cycle duration were around 8-15 µA/cm² , 10-11 mHz, and 1.5 minutes, respectively. Notably, the AVP-evoked change in Isc was abolished by TTX, atropine, conivaptan, indomethacin, NS560, and cromolyn sodium, respectively.

CONCLUSIONS AND INFERENCES

VP-V_1a receptor played the proinflammatory role in TNBS-induced colitis by promoting COX-2-dependent prostaglandin release from mucosal mast cells, which was mediated by the cholinergic pathway.

Possible involvement of phosphatidylinositol 3-kinase/Akt signal pathway in vasopressin-induced HSP27 phosphorylation in aortic smooth muscle A10 cells

We previously reported that p38 mitogen-activated protein (MAP) kinase takes a part in arginine vasopressin (AVP)-induced heat shock protein 27 (HSP27) phosphorylation in aortic smooth muscle A10 cells. In the present study, we investigated whether phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) is involved in the phosphorylation of HSP27 in these cells. AVP time-dependently induced the phosphorylation of PI3K and Akt. Akt inhibitor, 1l-6-hydroxymethyl-chiro-inositol 2-(R)-2-O-methyl-3-O-octadecylcarbonate, partially suppressed the phosphorylation of HSP27. The AVP-induced HSP27 phosphorylation was attenuated by LY294002, a PI3K inhibitor. The combination of Akt inhibitor and SB203580, a p38 MAP kinase inhibitor, completely suppressed the AVP-induced phosphorylation of HSP27. Furthermore, LY294002 or Akt inhibitor did not affect the AVP-induced phosphorylation of p38 MAP kinase and SB203580 did not affect the phosphorylation of PI3K or Akt. These results suggest that PI3K/Akt plays a part in the AVP-induced phosphorylation of HSP27, maybe independently of p38 MAP kinase, in aortic smooth muscle A10 cells.

Modulation of ANP-C receptor signaling by arginine-vasopressin in A-10 vascular smooth muscle cells: role of protein kinase C

We have previously shown that pretreatment of A-10 vascular smooth muscle cells (VSMC) with angiotensin II (Ang II) attenuated atrial natriuretic peptide receptor-C (ANP-C)-mediated inhibition of adenylyl cyclase without altering [125I]ANP binding. In the present studies, we have investigated the modulation of ANP-C receptor signaling by arginine-vasopressin (AVP). Pretreatment of A-10 VSMC with AVP for 24h resulted in a reduction in ANP receptor binding activity by about 50% (B(max); control cells, 22.9+/-2.5 fmol/mg protein, AVP-treated cells, 11.4+/-1.2 fmol/mg protein). In addition, the expression of ANP-C receptor as determined by immunoblotting was also decreased by about 50% by AVP treatment, which was prevented by GF109203X, an inhibitor of protein kinase C (PKC). The decreased expression of ANP-C receptor was reflected in an attenuation of ANP-C receptor-mediated inhibition of adenylyl cyclase. C-ANP(4-23) [des(Gln(18),Ser(19),Gln(20),Leu(21),Gly(22))ANP(4-23)-NH(2)], a ring deleted peptide of ANP that interacts specifically with ANP-C receptor, inhibited adenylyl cyclase activity by about 30% in control cells, which was completely attenuated in AVP-treated cells. This attenuated inhibition was significantly restored by GF 109203X. In addition, AVP treatment augmented the levels of Gialpha-2 and Gialpha-3 proteins; however, the Gi functions were completely attenuated. The increased expression of Gialpha proteins induced by AVP was inhibited by GF109203X as well as by actinomycin D treatments. In addition, AVP treatment also enhanced the expression of Gsalpha protein and Gsalpha-mediated stimulation of adenylyl cyclase by GTPgammaS, N-ethylcarboxamide adenosine (NECA), and forskolin (FSK), whereas the levels of Gbeta were not altered by AVP treatment. These results indicate that AVP-induced PKC signaling may be responsible for the down-regulation of ANP-C receptor that results in the attenuation of C-ANP(4-23)-mediated inhibition of adenylyl cyclase activity, and suggest a cross-talk between vasopressin V(1) and ANP-C receptor-mediated signaling pathways.

Effects of arginine vasopressin in the heart are mediated by specific intravascular endothelial receptors

Arginine vasopressin induces vascular, inotropic and arrhythmogenic effects in the heart. Existing evidence, obtained indirectly, suggests that these effects occur through paracrine endothelial mechanisms. To demonstrate this, vasopressin was confined to the intravascular space by covalent coupling to high molecular weight (2x10(6) Da, vasopresin-dextran) dextran. Isolated guinea pig hearts were infused with equivalent concentrations of vasopressin and vasopressin-dextran. The negative inotropic and coronary vasopressor effects of vasopressin-dextran were similar to those evoked by vasopressin; in both cases effects were reversible. Free dextran had no effect on vascular resistance nor in ventricular developed pressure. The inotropic and vascular effects of both vasopressin and vasopressin-dextran were blocked by the vasopressin receptor antagonist [Adamantaneacetyl(1), o-Et-D-Tyr(2), Val(4), Aminobutyryl(6), Arg(8,9)]vasopressin (Adam-vasopressin), indicating that the effects of the two agonists were vasopressin receptor-mediated. To elucidate possible endothelial intermediaries of these effects, isolated guinea pig hearts were infused simultaneously with vasopressin or vasopressin-dextran and several inhibitors either of synthesis or blockers of receptors of possible endothelial mediators. Only reactive blue 2, a P(2y) purinoceptor antagonist, and suramin, a P(2y) and a P(2x) purinoceptor antagonist, caused a total reversal of vascular and inotropic effects of vasopressin and vasopressin-dextran. Pyridoxalphosphate-6-Azophenyl-2'-4'disulphonic acid, a P(2x) purinoceptor antagonist, was without effect. Our results provide direct evidence that the short-term cardiac effects of vasopressin are due to selective activation of intravascular purinoceptors and suggest that an intermediary of these effects is ATP.

Prostanoids regulate proliferation of vascular smooth muscle cells induced by arginine vasopressin

The aim of the present study was to investigate the effect of arginine [Arg(8)]vasopressin (vasopressin) on proliferation of vascular smooth muscle cells and the mechanisms underlying the action of vasopressin. To clarify these issues, we used two different types of vascular smooth muscle cells, cultured adult rat aortic smooth muscle cells and A10 cells, a cell line derived from fetal rat aorta. Vasopressin (10(-8) to 10(-6) M) significantly stimulated the proliferation of rat aortic smooth muscle cells in a dose-dependent manner. In contrast, vasopressin significantly inhibited the proliferation of A10 cells. This inhibition was abolished when A10 cells were treated with indomethacin. Vasopressin stimulated the production of prostanoids several-fold in A10 cells but not in rat aortic smooth muscle cells. These effects were completely blocked by the vasopressin V(1) receptor antagonist, 1-¿1-[4-(3-acetylamino-propoxy)benzoyl]4-piperidyl¿-3, 4-dihydro-2(1H)-quinolinone (OPC21268), but not by the vasopressin V(2) receptor antagonist, (+/-)-5-dimethylamino-1-[4-(2-methylbenzoylamino)benzol]-2, 3,4,5-tetrahydro-1H-benzazepine hydrochloride (OPC31260). These results indicate that vasopressin has diverse effect on proliferation of vascular smooth muscle cells through the vasopressin V(1) receptor, depending on the production of growth regulatory prostanoids.

Interactive computerized microscopy as a tool for quantifying vascular remodelling effects of diabetes and V1a receptor antagonist SR 49059 on rat mesenteric arterial bed

A methodology using interactive computerized microscopy (ICM) was developed to quantify in the mesenteric arterial bed the morphometric changes associated with diabetes and the influence of treatment with SR 49059, an antagonist of vasopressin V1a receptors. Four groups of rats were studied: untreated normal (N) or streptozotocin- (60 mg/kg i.v.) induced diabetic (D), and treated (0.4 mg/g SR 49059 included in food) normal (NT) or diabetic (DT) animals. Treatment was initiated 4 days after diabetes induction and continued for 3 weeks. Nested (hierarchical) analysis of variance of ICM data was performed on raw diameter or after logarithmic normalization of area and nuclei values. Diabetes was associated with an increase in arterial diameters, and in total vessel, wall, media, adventitia, and lumen areas. The same parameters, with the exception of the lumen, were also increased in DT as compared to D. The number of nuclei in the media or adventitia was increased in D as compared to N, and in DT as compared to D. In summary, ICM is allowed to further characterize the vascular mesenteric changes and describe for the first time the enlargement of adventitia associated with diabetes. Our study also suggested that the blockade of Via receptors is unable to prevent diabetes-related vascular changes, although the slight increase in food intake associated with SR 49059 treatment may have had an indirect influence on angiopathy development.

Evidence for a vasopressin system in the rat heart

Traditionally, a hypothalamo-neurohypophysial system is thought to be the exclusive source of arginine vasopressin (AVP), a potent antidiuretic, vasoconstricting, and growth-stimulating neuropeptide. We have identified de novo synthesis of AVP in the heart as well as release of the hormone into the cardiac effluents. Specifically, molecular cloning of sequence tags amplified from isolated, buffer-perfused, and pressure-overloaded rat hearts allowed the detection of cardiac AVP mRNA. Subsequent experiments revealed a prominent induction of AVP mRNA (peak at 120 minutes, 59-fold, P<0. 01 versus baseline) and peptide (peak at 120 minutes, 11-fold, P<0. 01 versus baseline) in these isolated hearts. Newly induced vasopressin peptide was localized most prominently to endothelial cells and vascular smooth muscle cells of arterioles and perivascular tissue using immunohistochemistry. In addition to pressure overload, nitric oxide (NO) participated in these alterations, because inhibition of NO synthase by Nomega-nitro-L-arginine methyl ester markedly depressed cardiac AVP mRNA and peptide induction. Immediate cardiac effects related to cardiac AVP induction in isolated, perfused, pressure-overloaded hearts appeared to be coronary vasoconstriction and impaired relaxation. These functional changes were observed in parallel with AVP induction and largely prevented by addition of a V1 receptor blocker (10(-8) mol/L [deamino-Pen1, O-Me-Tyr2, Arg8]-vasopressin) to the perfusion buffer. Even more interesting, pressure-overloaded, isolated hearts released the peptide into the coronary effluents, offering the potential for systemic actions of AVP from cardiac origin. We conclude that the heart, stressed by acute pressure overload or NO, expresses vasopressin in concentrations sufficient to cause local and potentially systemic effects.

Rat aortic smooth-muscle cell proliferation is bidirectionally regulated in a cell cycle-dependent manner via PACAP/VIP type 2 receptor

In the cardiovascular system, vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase activating polypeptide (PACAP) have been well characterized as potent vasodepressors or vasodilators. However, their pathophysiological implication in proliferation of vascular smooth muscle cells has not yet been elucidated. In the present study, we have first identified PACAP/VIP type 2 receptor as a dominant type in rat vascular smooth muscle cell (VSMC) by RT-PCR. PACAP and VIP increased cyclic AMP accumulation with similar potency. In 24-h [3H]thymidine incorporation assay, PACAP or VIP exhibited a suppressive effect on the DNA synthesis of rat VSMC stimulated by serum when added at the late G1 phase. In contrast, when added at G0/G1 phase of the cell cycle, PACAP or VIP enhanced the serum-induced DNA synthesis. In 24-h incubation, PACAP alone has little mitogenic activity. However, when incubated up to 48 h, PACAP stimulated significantly the DNA synthesis and the cell proliferation of rat VSMC. These results suggest that PACAP and VIP regulate the proliferation of rat VSMC by enhancing or suppressing in a cell cycle-dependent manner and induce delayed mitogenesis and cell proliferation.

Identification of arginine vasopressin mRNA in rat aortic smooth muscle cells

We investigated the expression of mRNA for arginine vasopressin in vascular smooth muscle cells and A10 cells using reverse transcription-polymerase chain reaction and Northern blot analysis. Arginine vasopressin mRNA was identified both in rat aortic smooth muscle cells and A10 cells, suggesting that arginine vasopressin is locally produced in vascular smooth muscle cells. Arginine vasopressin, a potent vasoconstrictor, may modulate vascular function in an autocrine or paracrine fashion.

Involvement of phosphatidylcholine hydrolysis by phospholipase D in extracellular ATP-induced arachidonic acid release in aortic smooth muscle cells

We investigated the effect of extracellular ATP on phosphatidylcholine-hydrolyzing phospholipase D activity and the role of phospholipase D activation in extracellular ATP-induced arachidonic acid release in cultured rat aortic smooth muscle cells. ATP significantly stimulated the formation of choline in a dose-dependent manner in the range between 0.01 and 0.5 mmol/L. However, ATP had no effect on the formation of phosphocholine. Staurosporine, an inhibitor of protein kinases, did not affect the ATP-induced formation of choline. ATP significantly stimulated arachidonic acid release in a dose-dependent manner in the range between 0.01 and 0.5 mmol/L. DL-Propranolol hydrochloride (propranolol), an inhibitor of phosphatidic acid phosphohydrolase, significantly inhibited the ATP-induced release of arachidonic acid. 1,6-Bis(cyclohexyloximinocarbonylamino)-hexane (RHC-80267), a potent and selective inhibitor of diacylglycerol lipase, reduced ATP-induced arachidonic acid release. Quinacrine, a phospholipase A2 inhibitor, suppressed ATP-induced arachidonic acid release. Both propranolol and RHC-80267 markedly inhibited the ATP-induced synthesis of 6-ketoprostaglandin F1 alpha, a stable metabolite of prostacyclin. These results strongly suggest that extracellular ATP activates phosphatidylcholine-hydrolyzing phospholipase D independently of protein kinase C in aortic smooth muscle cells and that the arachidonic acid release induced by extracellular ATP is mediated, at least in part, through phosphatidylcholine hydrolysis by phospholipase D activation.

Roles of vasodilatory prostaglandins in mitogenesis of vascular smooth muscle cells

Vasodilatory prostaglandins (PGI2, PGE1) and synthetic prostacyclin mimetics inhibit smooth muscle cell proliferation in vitro after stimulation by growth factors. Similar results are obtained in vivo after endothelial injury, suggesting that vasodilatory prostaglandins might also control smooth muscle cell proliferation in vivo. However, available data from clinical trials are conflicting and currently do not support the concept that these compounds might be successfully used to suppress excessive smooth muscle cell growth in response to tissue injury, specifically restenosis after PTCA. One possible explanation for these different results is an agonist-induced down-regulation of prostacyclin receptors in vascular smooth muscle cells. It is possible that enhanced endogenous prostacyclin biosynthesis, subsequent to induction of COX-2 and/or in relation to the formation of a neointima from media smooth muscle cells, might have a similar effect. There is still uncertainty regarding the cellular signal transduction pathways and their possibly complex interaction, although cAMP-dependent reactions are probably involved. In addition, vasodilatory prostaglandins might also interfere with the generation and action of other growth modulating factors, including PDGF, hepatocyte growth factor and nitric oxide. In conclusion, vasodilatory prostaglandins might be considered as growth modulating endogenous mediators in vascular smooth muscle cells.

Glucocorticoid inhibits cAMP production induced by vasoactive agents in aortic smooth muscle cells

It is well-known that atherosclerotic change and hypertension are common manifestations in patients with glucocorticoid excess. We previously reported that pituitary adenylate cyclase activating polypeptide (PACAP), prostaglandin E2 (PGE2) and carbacyclin, a stable analog of prostacyclin, have suppressive effects on vasopressin-induced DNA synthesis of rat aortic smooth muscle cells through cAMP production (Murase et al., J. Hypertens., 10 (1992) 1505; Oiso et al., Biochem. Cell. Biol., 71 (1993) 156). In the present study, we investigated the effect of glucocorticoid on cAMP production induced by PACAP, PGE2 and carbacyclin in aortic smooth muscle cells. The pretreatment with dexamethasone significantly inhibited cAMP accumulation induced by these vasoactive agents in a dose dependent manner in the range between 10 pM and 10 nM. These inhibitory effects of dexamethasone were dependent on the time of pretreatment up to 8 h. Dexamethasone inhibited cAMP accumulation induced by NaF, a GTP-binding protein activator, and forskolin which directly activates adenylate cyclase. Moreover, forskolin-induced adenylate cyclase activity was significantly reduced in membranes prepared from the cells treated with dexamethasone. These results strongly suggest that glucocorticoid inhibits cAMP production induced by vasoactive agents in primary cultured rat aortic smooth muscle cells and the inhibitory effect is exerted at the level of adenylate cyclase.

Vasopressin induces arachidonic acid release through pertussis toxin-sensitive GTP-binding protein in aortic smooth muscle cells: independence from phosphoinositide hydrolysis

We previously reported that pertussis toxin (PTX) had little effect on arginine vasopressin-induced formation of inositol trisphosphate (IP3) in rat aortic smooth muscle cells [Kondo et al.: Biochemical and Biophysical Research Communications 161:677-682, 1989]. In the present study, we investigated the mechanism of vasopressin-induced arachidonic acid release in rat aortic smooth muscle cells. Vasopressin stimulated both the release of arachidonic acid and the formation of IP3 dose dependently in the range between 10 pM and 1 microM. The effect of vasopressin on arachidonic acid release was more potent than that on the formation of IP3. Quinacrine, a phospholipase A2 inhibitor, significantly suppressed the vasopressin-induced arachidonic acid release but had little effect on the formation of inositol phosphates. NaF, a GTP-binding protein activator, mimicked vasopressin by stimulating the arachidonic acid release. The arachidonic acid release stimulated by a combination of vasopressin and NaF was not additive. PTX partially but significantly suppressed the vasopressin-induced arachidonic acid release. In the cell membranes, PTX catalyzed ADP-ribosylation of a protein with an M(r) of about 40,000. Pretreatment of membranes with 0.1 microM vasopressin in the presence of 2.5 mM MgCl2 and 100 microM GTP markedly attenuated this PTX-catalyzed ADP-ribosylation of the protein in a time-dependent manner. These results strongly suggest that PTX-sensitive GTP-binding protein is involved in the coupling of vasopressin receptor to phospholipase A2 in primary cultured rat aortic smooth muscle cells.