Analysis of the time course for organ culture-induced endothelin ET B receptor upregulation in rat mesenteric arteries

Reduced Mechanical Stretch Induces Enhanced Endothelin B Receptor-Mediated Contractility via Activation of Focal Adhesion Kinase and Extracellular Regulated Kinase 1/2 in Cerebral Arteries from Rat

Cerebral ischaemia results in enhanced endothelin B (ETB ) receptor-mediated contraction and receptor protein expression in the affected cerebrovascular smooth muscle cells (SMC). Organ culture of cerebral arteries is a method to induce similar alterations in ETB receptor expression. We suggest that rapid and sustained reduction in wall tension/stretch is a possible trigger mechanism for this vascular remodelling. Isolated rat middle cerebral artery (MCA) segments were incubated in a wire myograph with or without mechanical stretch, prior to assessment of their contractile response to the selective ETB receptor agonist sarafotoxin 6c. The involvement of extracellular regulated kinase (ERK) 1/2 and focal adhesion kinase (FAK) was studied by their specific inhibitors U0126 and PF-228, respectively. Compared with their stretched counterparts, unstretched MCA segments showed a significantly increased ETB receptor-mediated contractile response after 12 hr of incubation, which was attenuated by either U0126 or PF-228. The functionally increased ETB -mediated contractility could be attributed to two different mechanisms: (i) a difference in ETB receptor localization from primarily endothelial expression to SMC expression and (ii) an increased calcium sensitivity of the SMCs due to an increased expression of the calcium channel transient receptor potential canonical 1. Collectively, our results present a possible mechanism linking lack of vessel wall stretch/tension to changes in ETB receptor-mediated contractility via triggering of an early mechanosensitive signalling pathway involving ERK1/2 and FAK signalling. A mechanism likely to be an initiating factor for the increased ETB receptor-mediated contractility found after cerebral ischaemia.

Cerebral ischemia induces microvascular pro-inflammatory cytokine expression via the MEK/ERK pathway

BACKGROUND

Cerebral ischemia from middle cerebral artery wall (MCA) occlusion results in increased expression of cerebrovascular endothelin and angiotensin receptors and activation of the mitogen-activated protein kinase (MAPK) pathway, as well as reduced local cerebral blood flow and increased levels of pro-inflammatory mediators in the infarct region. In this study, we hypothesised that inhibition of the cerebrovascular inflammatory reaction with a specific MEK1/2 inhibitor (U0126) to block transcription or a combined receptor blockade would reduce infarct size and improve neurological score.

METHODS

Rats were subjected to a 2-hours middle cerebral artery occlusion (MCAO) followed by reperfusion for 48 hours. Two groups of treated animals were studied; (i) one group received intraperitoneal administration of a specific MEK1/2 inhibitor (U0126) starting at 0, 6, or 12 hours after the occlusion, and (ii) a second group received two specific receptor antagonists (a combination of the angiotensin AT1 receptor inhibitor Candesartan and the endothelin ETA receptor antagonist ZD1611), given immediately after occlusion. The middle cerebral arteries, microvessels and brain tissue were harvested; and the expressions of tumor necrosis factor-alpha (TNF-alpha), interleukin-1ss (IL-1ss), interleukin-6 (IL-6), inducible nitric oxide synthase (iNOS) and phosphorylated ERK1/2, p38 and JNK were analysed using immunohistochemistry.

RESULTS

We observed an infarct volume of 25 +/- 2% of total brain volume, and reduced neurological function 2 days after MCAO followed by 48 hours of recirculation. Immunohistochemistry revealed enhanced expression of TNF-alpha, IL-1ss, IL-6 and iNOS, as well as elevated levels of phosphorylated ERK1/2 in smooth muscle cells of ischemic MCA and in associated intracerebral microvessels. U0126, given intraperitoneal at zero or 6 hours after the ischemic event, but not at 12 hours, reduced the infarct volume (11.7 +/- 2% and 15 +/- 3%, respectively), normalized pERK1/2, and prevented elevation of the expressions of TNF-alpha IL-1ss, IL-6 and iNOS. Combined inhibition of angiotensin AT1 and endothelin ETA receptors decreased the volume of brain damaged (12.3 +/- 3; P < 0.05) but only slightly reduced MCAO-induced enhanced expression of iNOS and cytokines

CONCLUSION

The present study shows elevated microvascular expression of TNF-alpha, IL-1ss, IL-6 and iNOS following focal ischemia, and shows that this expression is transcriptionally regulated via the MEK/ERK pathway.

Involvement of calcium-calmodulin-dependent protein kinase II in endothelin receptor expression in rat cerebral arteries

Experimental cerebral ischemia and organ culture of cerebral arteries result in the enhanced expression of endothelin ET(B) receptors in smooth muscle cells via increased transcription. The present study was designed to evaluate the involvement of calcium-calmodulin-dependent protein kinase (CAMK) in the transcriptional expression of endothelin receptors after organ culture. Rat basilar arteries were incubated for 24 h with or without the CAMK inhibitor KN93 or ERK1/2 inhibitor U0126. The contractile responses to endothelin-1 (ET-1; ET(A) and ET(B) receptor agonist) and sarafotoxin 6c (S6c; ET(B) receptor agonist) were studied using a sensitive myograph. The mRNA levels of the ET(A) and ET(B) receptors and CAMKII were determined by real-time PCR, and their protein levels were evaluated by immunohistochemistry and Western blot. The mRNA levels of CAMKII and the ET(B) receptor increased during organ culture, but there was no change in the expression of the ET(A) receptor. This effect was abolished by coincubation with KN93 or U0126. In functional studies, both inhibitors attenuated the S6c-induced contraction. Incubating the arteries with KN93, but not U0126, decreased the amount of phosphorylated CAMKII. The inhibitors had no effect on the levels of myosin light chain during organ culture, as measured by Western blot. CAMKII is involved in the upregulation of the endothelin ET(B) receptor and interacts with the ERK1/2 pathway to enhance receptor expression. CAMKII has no effect on the contractile apparatus in rat cerebral arteries.

Gene expression and molecular changes in cerebral arteries following subarachnoid hemorrhage in the rat

Object

The authors investigated early changes in the cerebral arteries of rats that occur after subarachnoid hemorrhage (SAH).

Methods

Messenger RNA was investigated by performing microarray and quantitative real-time polymerase chain reaction (PCR) analyses, and protein expression was shown by performing immunohistochemical studies. The array data indicated that the initial processes that occur after SAH involve activation of genes involved in angiogenesis, inflammation, and extracellular matrix (ECM) remodeling. The real-time PCR investigation confirmed upregulation of genes that were observed using the microarray to be regulated, including iNOS, MMP13, and cxcl2. The authors also verified the upregulation of previously implicated genes for G-protein–coupled receptors (endothelin B [ETB], angiotensin 1 [AT1], and AT2) and metalloproteinase 9. The results of an immunohistochemical study confirmed that receptor genes that were seen to be regulated produced an increase in protein expression. Double immunostaining of rat cerebral arteries with endothelial cell– or smooth-muscle cell–specific antibodies verified that an increase in ETB, 5-hydrotryptamine (5-HT1B), and 5-HT1D receptor expression occurs in smooth-muscle cells.

Conclusions

Processes occurring after SAH lead to enhanced arterial contractility and ECM remodeling either directly or through angiogenesis and inflammation. These processes are active via an increase in metalloproteinase expression, the presence of proangiogenic factors, and the expression of proinflammatory genes.

ERK1/2 inhibition attenuates cerebral blood flow reduction and abolishes ET(B) and 5-HT(1B) receptor upregulation after subarachnoid hemorrhage in rat

Upregulation of endothelin B (ET(B)) and 5-hydroxytryptamine 1B (5-HT(1B)) receptors via transcription has been found after experimental subarachnoid hemorrhage (SAH), and this is associated with enhanced phosphorylation of the mitogen-activated protein kinase (MAPK) extracellular signal-regulated kinase (ERK1/2). In the present study, we hypothesized that inhibition of ERK1/2 alters the ET(B) and 5-HT(1B) receptor upregulation and at the same time prevents the sustained cerebral blood flow (CBF) reduction associated with SAH. The ERK1/2 inhibitor SB386023-b was injected intracisternally in conjunction with and after the induced SAH in rats. At 2 days after the SAH, cerebral arteries were harvested for quantitative real-time polymerase chain reaction, immunohistochemistry and analysis of contractile responses to endothelin-1 (ET-1; ET(A) and ET(B) receptor agonist) and 5-carboxamidotryptamine (5-CT; 5-HT1 receptor agonist) in a sensitive myograph. To investigate if ERK1/2 inhibition had an influence on the local and global CBF after SAH, an autoradiographic technique was used. At 48 h after induced SAH, global and regional CBF were reduced by 50%. This reduction was prevented by treatment with SB386023-b. The ERK1/2 inhibition also decreased the maximum contraction elicited by application of ET-1 and 5-CT in cerebral arteries compared with SAH. In parallel, ERK1/2 inhibition downregulated ET(B) and 5-HT(1B) receptor messenger ribonucleic acid and protein levels compared with the SAH. Cerebral ischemia after SAH involves vasoconstriction and subsequent reduction in the CBF. The results suggest that ERK1/2 inhibition might be a potential treatment for the prevention of cerebral vasospasm and ischemia associated with SAH.

Upregulation of endothelin ETB receptor-mediated vasoconstriction in rat coronary artery after organ culture

The aim of this study was to examine if endothelin ET(B) receptor-mediated contraction occurred in isolated segments of rat coronary arteries during organ culture. Presence of contractile endothelin ET(B) receptors was studied by measuring the change in isometric tension in rings of left anterior descending coronary arteries isolated from hearts of rats as response to application of the selective endothelin ET(B) receptor agonist, Sarafotoxin 6c and endothelin-1. In segments cultured 1 day in serum free Dulbecco's Modified Eagle's Medium, Sarafotoxin 6c induced a concentration dependent contraction with a pEC(50) value of 10.4+/-0.21 and a maximal response of 3.9+/-0.25 mN/mm (n=15). The maximal contraction was significantly larger than the responses measured in fresh tissue, where the mean value of the maximal contractions was 0.22+/-0.03 mN/mm (n=17). The increased contraction to Sarafotoxin 6c after culturing could be eliminated with addition of the transcriptional blocker, actinomycin D, to the culture medium or be significantly attenuated by application of the translational inhibitor, cycloheximide. The vasoconstrictor effect of endothelin-1 or to depolarisation by high K(+)-solution was not modified after 1 day in culture medium. The experiments indicate that organ culture of rat coronary arteries upregulate endothelin ET(B) receptor-mediated contraction by inducing synthesis of new protein.

Involvement of protein kinases on the upregulation of endothelin receptors in rat basilar and mesenteric arteries

Endothelin(B) (ET(B)) receptors are upregulated in experimental stroke or after 24 hrs of organ culture. This upregulation is manifested both as stronger contraction and as an increase in ET(B) receptor messenger RNA (mRNA) levels. The present study was designed to evaluate the importance of protein kinases (c-Jun N-terminal kinase [JNK], protein kinase C [PKC], and extracellular signal-regulated kinase [ERK1/2]) in ET(B) receptor upregulation after organ culture. Rat basilar and mesenteric arteries were incubated for 24 hrs in Dulbecco's modified Eagle's medium (DMEM) with or without the PKC inhibitor, RO-31-7549; the ERK1/2 inhibitor, SB386023; or the JNK inhibitor, SP600125, added 3, 6, or 12 hrs after initiation of incubation. Subsequently, vessel segments were mounted in myographs and the contractile responses to ET-1 and sarafotoxin 6c were studied. The ET(B) and ET(A) receptor mRNA levels were determined with a real-time polymerase chain reaction (PCR). The cellular localization and protein level of ET(B) receptors were evaluated by immunohistochemistry. The PKC and ERK1/2 inhibitors attenuated the contraction induced by S6c in the basilar arteries more than in the mesenteric arteries. The efficiency of the inhibitors was proportional to the incubation time. Real-time PCR showed a decrease in the ET(B) receptor mRNA levels in arteries treated with PKC or ERK inhibitors. The JNK inhibitor had a significant inhibitory effect on ET(B) receptor upregulation in the basilar arteries. Immunohistochemistry revealed that the ET(B) receptor upregulation occured in the smooth-muscle cells and that it had the same pattern as in the quantitative PCR. Our results show that the PKC, ERK1/2, and JNK are more important for the upregulation of contractile ET(B) receptors in cerebral arteries compared with mesenteric arteries. ERK1/2 seems to be more important for the ET(B) receptor upregulation, as compared with PKC and JNK. The evaluation of the time dependency suggests that the phenomenon can be reversed even after its initiation.

Vascular endothelin ET(B) receptor-mediated contraction requires phosphorylation of ERK1/2 proteins

In cardiovascular diseases, endothelin type B (ET(B)) receptors in arterial smooth muscle cells are upregulated. The present study revealed that organ culture of rat mesenteric artery segments enhanced endothelin ET(B) receptor-mediated contraction paralleled with increase in the receptor mRNA and protein expressions. The endothelin ET(B) receptor-mediated contraction was associated with increase in phosphorylation of extracellular regulation kinase 1 and 2 (ERK1/2) proteins and elevated levels of intracellular calcium. The elevation curve of intracellular calcium consisted of two phases: one rapid and one sustained. Inhibition of ERK1/2 phosphorylation by SB386023 or blockage of calcium channels by nifedipine significantly reduced the endothelin ET(B) receptor-mediated contraction (P<0.05) and decreased the sustained phase of intracellular calcium level, but not the rapid phase. Thus, phosphorylation of ERK1/2 proteins and elevation of intracellular calcium level are required for endothelin ET(B) receptor-mediated contraction in rat mesenteric artery.

Effect of short-term organoid culture on the pharmaco-mechanical properties of rat extra- and intrapulmonary arteries

1 Organoid cultured explants from differentiated tissues have gained renewed interest in the undertaking of physiological and pharmacological studies. In the work herein, we examined the pharmaco-mechanical properties of an in vitro model consisting of organoid cultured rings derived from rat extra- and intrapulmonary arteries, over a period of 4 days in culture. 2 Mechanical changes were quantified using isometric tension measurements on both fresh and cultured pulmonary arterial tissues, with experiments performed in the presence or absence of 10% foetal calf serum. Conventional histochemical and immunofluorescent stainings were also performed to assess tissue structure integrity and apoptosis. 3 The explants developed spontaneous rhythmic contractions (SRC) in approximately half of the vessels. SRC amplitude and time course were modified by conditions and agents acting on membrane potential (high-potassium solutions--levcromakalim, a potassium channel opener), while nitrendipine, an L-type calcium channel blocker, suppressed SRC. 4 Cultured explants also developed a hyper-reactivity to high potassium challenges (10-40 mM). Whereas contraction to serotonin (5-HT) was enhanced in intrapulmonary arteries, contraction to endothelin-1 remained unchanged after 4 days of culture. Serum did not alter contractile properties during the culture period. 5 Endothelial-dependent relaxation was maintained in response to A23187 500 microM, but was abolished in response to 10 microM carbamylcholine. 6 Histological and immuno-histological analyses revealed the absence of hypertrophied vascular wall or apoptosis. 7 In conclusion, the contractile phenotype as well as tissue structure integrity of organoid explants remain essentially intact during short-term culture, making this model suitable for pharmaco-genomic studies.

Up-Regulation of alpha1A-Adrenoceptors in Rat Mesenteric Artery Involves Intracellular Signal Pathways

The aim of the present study was to investigate if there is an altered expression of alpha-adrenoceptors during organ culture of rat mesenteric artery segments by using a sensitive pharmacological method and molecular biological techniques. Noradrenalin (NA) induced contraction via alpha1-adrenoceptors. The contraction and alpha1A-adrenoceptor mRNA levels were elevated during organ culture. Transcriptional inhibitor actinomycin D, translational inhibitor cycloheximide, protein kinase C inhibitors (staurosporine and RO31-8220) and mitogen-activated protein kinase (MAPK) pathway inhibitors (SB386023, U0126 and SB239063) prevented the increase in NA-induced contractions. The amount of alpha1A-adrenoceptor mRNA was significantly lower in the artery segments cultured for 1 day in the presence of specific MAPK extracellular signal-regulated protein kinase1/2 pathway inhibitor SB386023 than that of the cultured controls. SB386023 did not affect alpha2-adrenoceptor mRNA level. Our results suggest that the up-regulation of alpha1A-adrenoceptors involves transcription and intracellular signal transduction via the protein kinase C and the ERK 1/2 pathways.

Screening, analysis and in vitro vasodilatation of effective components from Ligusticum Chuanxiong

Effective components, ligustilide and butylidenephthalide, from Ligusticum Chuanxiong (Ligusticum wallichii Franchat, Umbelliferae) were screened and identified by using a cell membrane chromatography (CMC) and a gas chromatography/mass spectrometry (GC/MS). The components showed the effects of inhibiting vasoconstriction in vitro on rat abdominal aorta segments. The screening procedure was performed in a rat artery CMC column (50 mm x 2.0 mm I.D.) with a sodium phosphate buffer (pH 7.4) as mobile phase at 37 degrees C. The identification was accomplished by a DB-5MS 30 m capillary column (0.25 mm I.D., 0.25 microm film thickness) with helium as carrier gas operating under program control temperature and electron impact ionization mass spectrometer in a scan mode. Results demonstrated that ligustilide and butylidenephthalide can act on rat artery cell membrane similar to verapamil in CMC system. They significantly inhibited the vasoconstrictions induced by norepinephrine bitartrate (NE) and calcium chloride (CaCl2). The relaxing effect of ligustilide on the NE- and CaCl2-induced constrictions is more potent than that of butylidenephthalide. Ligustilide and butylidenephthalide seem to be the two main effective components of Ligusticum Chuanxiong as a traditional Chinese medicine for treating blood vessel diseases.

Increased alphaCGRP potency and CGRP-receptor antagonist affinity in isolated hypoxic porcine intramyocardial arteries

1. This study describes the effects of hypoxia on relaxing responses and cAMP production induced by the known vasodilator peptides: alphaCGRP, amylin (AMY) and adrenomedullin (AM) on isolated pig coronary arteries in vitro. 2. Hypoxic incubation increased the vasorelaxant effect of alphaCGRP (four-fold; P<0.05), AMY (3.2-fold; P<0.05), but not significantly for AM (two-fold; NS). 3. Whereas hypoxia had no effect on arterial cAMP levels, it significantly potentiated the production of cAMP stimulated of alphaCGRP and AMY, but not of AM. 4. The antagonist alphaCGRP(8-37) also exerted an increased effect in hypoxia. The Schild plot-derived pK(B) values revealed an increase in the apparent affinity of the antagonist for the CGRP(1) receptor from 7.0 to 7.2 under control conditions versus 8.0 in hypoxia. 5. Removal of endothelium, peptidase inhibitors, preincubation with the adenosine A(2A) receptor antagonist CSC (10(-3) M), the ATP-sensitive K-channel inhibitor glibenclamide (10(-5) M), the cyclooxygenase inhibitor indomethacin (10(-3) M) or NG-monomethyl-L-arginine (10(-4) M) had no effect on the alphaCGRP-induced vasorelaxation in hypoxia; neither did hypoxia influence the levels of CGRP and AM receptor mRNA. 6. We conclude that hypoxic incubation increases the relaxation and cAMP production induced by alphaCGRP and AMY in rings of porcine coronary arteries in vitro. A concomitant release of adenosine, a cyclooxygenase product, an endothelium-derived substance, activation of vascular ATP-sensitive K-channels, peptidase inhibitors or changes in CGRP and AM receptor mRNA cannot account for the changes observed in hypoxia. Moreover, alphaCGRP(8-37) showed increased affinity at the CGRP(1) receptor during hypoxia, possibly due to a conformational change at the CGRP(1) receptor site.

Enhanced transcription of contractile 5-hydroxytryptamine 2A receptors via extracellular signal-regulated kinase 1/2 after organ culture of rat mesenteric artery

5-Hydroxytryptamine (5-HT) has been found to elicit enhanced contractile effects in some vascular disorders. The present study was designed to examine if vascular 5-HT2A receptors are up-regulated during organ culture and if the extracellular signal-regulated protein kinase 1/2 (ERK1/2) pathways are involved. Compared with fresh rat mesenteric artery ring segments, the contractile responses to 5-HT were significantly increased in the segments cultured for 6, 24 or 48 hr (P<0.05, P<0.01, P<0.01, respectively). The 5-HT-induced contraction occurred via 5-HT2A receptors, since the selective 5-HT2A antagonist ketanserin blocked the 5-HT-induced contraction in the fresh segments with a pA2 value 9.5 (slope was 0.98 with 95% confidence intervals from 0.8 to 1.1). A similar result was obtained in the segments cultured for 24 hr with a pA2 value of 9.43 (slope=0.91 and 95% confidence intervals between 0.45 to 2.3). In addition, the enhanced 5-HT2A receptor contraction occurred with a significant increase of 5-HT2A receptor mRNA (P<0.05). Organ culture of the mesenteric artery was found to activate ERK1/2 already within 1 and 3 hr. It is likely that the ERK1/2 pathways were involved as a initial switch, since the selective ERK1/2 pathway inhibitor SB386023 abolished both up-regulation of 5-HT2A mRNA transcription and the enhanced contractile response to 5-HT. These data reveal a role of ERK1/2 in up-regulation of 5-HT2A receptors and suggest a possibility to inhibit the enhanced responses to 5-HT by inhibition of the ERK1/2 pathway.

Triptan-induced contractile (5-HT1B receptor) responses in human cerebral and coronary arteries: relationship to clinical effect

Triptans are agonists at 5-HT1B and 5-HT1D (where 5-HT is 5-hydroxytryptamine; serotonin) receptors and cause vasoconstriction of isolated blood vessels. The aim of the present study was to determine vasoconstrictor potency (EC50) of triptans in human coronary and cerebral arteries and to examine whether there was any relationship with the maximal plasma concentrations (Cmax; nM) of the drugs achieved following oral administration of clinically relevant doses to man using values reported in the literature. We also examined the expression of 5-HT1B receptors in atherosclerotic and normal coronary arteries. The vasocontractile responses to sumatriptan, rizatriptan or eletriptan were characterized by in vitro pharmacology. The ratio of Cmax/EC50 was calculated. 5-HT1B and 5-HT1D receptors were visualized by immunohistochemical techniques in coronary arteries. Sumatriptan, rizatriptan and eletriptan were powerful vasoconstrictors in cerebral artery. The rank order of agonist potency was eletriptan=rizatriptan=sumatriptan. In the coronary artery, the triptans were weaker vasoconstrictors. The rank order of potency was similar. In cerebral artery the ratio of Cmax/EC50 was not significantly different from unity, indicating a relationship between these two parameters. In general for the coronary artery, the ratios were significantly less than unity, indicating no direct relationship. Immunohistochemistry showed expression of 5-HT1B receptors in the medial layer, but did not reveal any obvious difference in 5-HT1B receptor expression between normal and atherosclerotic coronary arteries. The results support the notion that triptans are selective vasoconstrictors of cerebral arteries over coronary arteries and that there is a relationship between vasoconstrictor potency in cerebral arteries and clinically relevant plasma levels.

Interleukin-1beta attenuates endothelin B receptor-mediated airway contractions in a murine in vitro model of asthma: roles of endothelin converting enzyme and mitogen-activated protein kinase pathways

BACKGROUND

Asthma is a chronic airway disease, known to involve several inflammatory mediators. Little is known about how these mediators interact in order to produce or attenuate even basic features of the disease, like airway hyper-reactivity and remodelling. Endothelin-1 (ET-1) and IL-1beta are two mediators suggested to play important roles in the induction of airway inflammation.

OBJECTIVE

To investigate the interactions between ET-1 and IL-1beta, using a novel in vitro model of asthma, focusing on airway smooth muscle contractility.

METHODS

Isolated murine tracheal segments were cultured from 1 to 8 days in the absence and presence of IL-1beta. The subsequent contractile responses to sarafotoxin 6c (S6c) (selective agonist for ETB receptor) and sarafotoxin 6b (S6b) (ETA and ETB receptor agonist) were recorded by a myographs system. In all experiments, ETB receptors were desensitized before the contractile response to S6b was recorded. Thus, the response to S6b is only mediated by ETA receptors in the present study. The mRNA expressions for ET-1 and endothelin (ET) receptors were quantified by real-time PCR.

RESULTS

Organ culture in the presence of IL-1beta attenuated the maximal contraction induced by S6c, but not S6b. This reduction was concentration-dependent and was significant after 2, 4 and 8 days of culture. To investigate the mechanisms behind this, inhibitors for endothelin converting enzyme (ECE) phosphoramidon, c-JUN N-terminal kinase (JNK) SP600125, extracellular-signal-regulated kinase 1/2(ERK 1/2) PD98059 and p38 pathway SB203580 were used. Individually, SP600125 and PD98059, but not SB203580, could partly reverse the reduction induced by IL-1beta. An additional effect was obtained when SP600125 and PD98059 were combined. The mRNA expressions for ET-1 and ETB receptor were up- and down-regulated, respectively, by IL-1beta.

CONCLUSION

Presence of IL-1beta in the airways attenuate the contractile response mediated via ETB receptors, an effect dependent on ECE, JNK and ERK 1/2 pathways.

Role of mitogen-activated protein kinases in endothelin ETB receptor up-regulation after organ culture of rat mesenteric artery

Organ culture of isolated arteries results in increased levels of endothelin ET(B) (ET(B)) receptor mRNA and in enhanced ET(B) receptor mediated contraction. The present study was designed to pinpoint the mitogen-activated protein kinase (MAPK) subtype involved in up-regulation of ET(B) receptors after organ culture of rat mesenteric arteries. Western blot and selective antibodies towards constitutional and phosphorylated MAPKs revealed the appearance of phosphorylated MAPK of the extracellular signal-regulated kinases (ERK) 1/2 type at 3 h of organ culture. The functional ET(B) receptor and its mRNA expression were up-regulated after 24 h of organ culture. Following incubation with the MEK 1/2 specific inhibitor SB408039 or the raf inhibitor SB386023b the up-regulation was attenuated both for ET(B) receptor responses and in ET(B) receptor mRNA expression in the vessel segments. Neither Western blot nor myograph or mRNA analysis showed involvement of the other MAPKs studied. Our results suggest that the ERK1/2 MAPKs are involved in the endothelin ET(B) receptor up-regulation following organ culture.

Effects of a topical enamel matrix derivative on skin wound healing

Enamel matrix derivative, obtained from developing porcine teeth, is composed mainly of amelogenin proteins and used topically in periodontal surgery for advanced periodontitis to regenerate lost connective tissues. The primary objective of this study was to investigate the effects of enamel matrix derivative on skin wound healing. Secondly, in vitro effects of enamel matrix derivative on dermal fibroblasts and microvascular endothelial cells were examined. Full-thickness, circular 2-cm skin wounds in white 16-week-old rabbits were treated thrice weekly with enamel matrix derivative (30 mg/ml) in the vehicle propylene glycol alginate or with vehicle alone. Enamel matrix derivative treatment increased the amount of granulation tissue and accelerated time to complete epithelialization by 3 days (p < 0.001) compared to vehicle treatment. In cultured fibroblasts, vascular endothelial growth factor levels in conditioned media were increased more than fivefold (p < 0.001) with enamel matrix derivative treatment (0.1mg/ml) over control, measured by specific enzyme-linked immunosorbent assay. Enamel matrix derivative also increased release of matrix metalloproteinase-2 more than threefold from fibroblasts (p < 0.001) and from endothelial cells (p < 0.001). Thus, enamel matrix derivative significantly accelerated wound closure in rabbits, possibly by increasing levels of growth factors and proteinases important for granulation tissue formation and remodeling.

Ischemic heart disease induce upregulation of endothelin receptor mRNA in human coronary arteries

Endothelin has been implicated in the pathogenesis of ischemic heart disease and congestive heart failure. The aims were to quantify endothelin type A (ETA) and type B (ETB) receptor mRNA levels in human coronary arteries from patients with ischemic heart disease, congestive heart failure and controls using real-time polymerase chain reaction (real-time PCR). In addition, the suitability of organ culture as a model mimicking endothelin receptor changes in cardiovascular disease was evaluated by in vitro pharmacology and real-time PCR. Endothelin ETA and ETB receptor mRNA levels were significantly higher in arteries from patients with ischemic heart disease (0.23+/-0.04 and 0.35+/-0.06) as compared to congestive heart failure (0.09+/-0.02 and 0.07+/-0.01) and controls (0.08+/-0.02 and 0.08+/-0.01). After organ culture, the endothelin ETB receptor mRNA levels were elevated, and the sarafotoxin 6c-induced vasoconstriction was more efficacious. Increased endothelin receptor activity may contribute to the increased vascular tone and development of atherosclerotic disease in ischemic heart disease in man.

Receptor changes in cerebral arteries after subarachnoid haemorrhage

Subarachnoid haemorrhage (SAH), occurring with a delay of 4-10 days is linked to cerebral vasospasm (CVS), a pathological constriction of the cerebral arteries. Several agents have been suggested as being responsible - amongst these perhaps 5-hydroxytryptamine (5-HT) and endothelin-1 (ET-1) are the most prominent, given their ability to elicit powerful constriction of arteries. Investigating both 5-HT and ET receptors we observed distinct changes in the receptor phenotype after experimental SAH - namely upregulation of the ETB and 5-HT1B receptors - linked to a higher sensitivity to the endogenous agonists. This multiple receptor upregulation may explain the failure in treating CVS using single receptor antagonists, and may also significantly change our understanding of the effector mechanism behind CVS. So far only the ET and 5-HT receptors have been studied in this regard, but other receptor systems may also undergo changes.