Direct actions of urotensin II on the heart: implications for cardiac fibrosis and hypertrophy

Urotensin II (UII) is a somatostatin-like peptide recently identified as a potent vasoconstrictor. In this study, we examined whether UII promotes cardiac remodeling through nonhemodynamic effects on the myocardium. In a rat model of heart failure after myocardial infarction (MI), increased UII peptide and UII receptor protein expression was observed in both infarct and noninfarct regions of the left ventricle compared with sham. Moreover, post-MI remodeling was associated with a significant 75% increase in UII receptor gene expression in the heart (P<0.05 versus sham controls), with this increase noted in both regions of the left ventricle. In vitro, UII (10-7 mol/L) stimulation of neonatal cardiac fibroblasts increased the level of mRNA transcripts for procollagens alpha1(I), alpha1(III), and fibronectin by 139+/-15% (P<0.01), 59+/-5% (P<0.05), and 141+/-14% (P<0.01), respectively, with a concomitant 23+/-2% increase in collagen peptide synthesis as determined by 3H-proline incorporation (P<0.01). UII had no effect on cellular hypertrophy, as determined by changes in total protein content in isolated neonatal cardiomyocytes. However, expression of recombinant rat UII receptor in neonatal cardiomyocytes resulted in significant UII-dependent activation of hypertrophic signaling as demonstrated by increased total protein content (unstimulated, 122.4+/-4.0 microg/well; rat UII, 147.6+/-7.0 microg/well; P<0.01) and activation of the hypertrophic phenotype through Galpha(q)- and Ras-dependent pathways. These results indicate that, in addition to potent hemodynamic effects, UII may be implicated in myocardial fibrogenesis through increased collagen synthesis by cardiac fibroblasts and may also be an important determinant of pathological cardiac hypertrophy in conditions characterized by UII receptor upregulation.

Adenoviral-directed expression of the type 1A angiotensin receptor promotes cardiomyocyte hypertrophy via transactivation of the epidermal growth factor receptor

Angiotensin II (Ang II) may cause cardiac hypertrophy via type 1 Ang II receptors (AT(1)) on cardiomyocytes and through growth factors released from cardiac fibroblasts. Whereas cardiomyocyte-specific AT(1) receptor expression produces cardiac hypertrophy and remodeling in vivo, delineation of the signals that mediate growth to Ang II is challenging because the prevailing in vitro model (cultured neonatal cardiomyocytes) expresses low levels of AT(1) receptor and responds inconsistently to Ang II. In this study, when AT(1A) receptors were expressed using adenovirus in cultured neonatal cardiomyocytes, Ang II stimulated a robust hypertrophy that was not secondary to the release of cardiac fibroblast-derived factors, specifically endothelin-1. Hypertrophy was accompanied by the induction of the immediate-early response genes, c-fos and c-jun, and reexpression of atrial natriuretic peptide (ANP). Ang II-induced activation of an ANP promoter-reporter was inhibited by the dominant/negative mutants, GalphaqI and N17Ras, indicating that hypertrophic signaling by the AT(1A) receptor is via heterotrimeric G protein coupling and downstream Ras pathways. AT(1A)-mediated cardiomyocyte hypertrophy and mitogen-activated protein kinase (MAPK) activation were inhibited by the MAPK kinase inhibitor, PD98059, and the epidermal growth factor (EGF) receptor kinase antagonist, AG1478, but not by PKC inhibitor, bisindolylmaleimide-1. Moreover, Ang II-induced MAPK activation was prevented by treatment with a matrix metalloproteinase inhibitor, consistent with the tyrosine phosphorylation of the EGF receptor in response to AT(1A) receptor activation. These data unequivocally demonstrate that Ang II can directly promote cardiac myocyte growth via AT(1A) receptors expressed on these cells and reveal for the first time the important contribution of EGF receptor-transactivated MAPK signaling to this process.

beta(2)-adrenergic receptor overexpression exacerbates development of heart failure after aortic stenosis

BACKGROUND

Beta-adrenergic signaling is downregulated in the failing heart, and the significance of such change remains unclear.

METHODS AND RESULTS

To address the role of beta-adrenergic dysfunction in heart failure (HF), aortic stenosis (AS) was induced in wild-type (WT) and transgenic (TG) mice with cardiac targeted overexpression of beta(2)-adrenergic receptors (ARs), and animals were studied 9 weeks later. The extents of increase in systolic arterial pressure (P<0.01 versus controls), left ventricular (LV) hypertrophy (TG, 94+/-6 to 175+/-7 mg; WT, 110+/-6 to 168+/-10 mg; both P<0.01), and expression of ANP mRNA were similar between TG and WT mice with AS. TG mice had higher incidences of premature death and critical illness due to heart failure (75% versus 23%), pleural effusion (81% versus 45%), and left atrial thrombosis (81% versus 36%, all P<0.05). A more extensive focal fibrosis was found in the hypertrophied LV of TG mice (P<0.05). These findings indicate a more severe LV dysfunction in TG mice. In sham-operated mice, LV dP/dt(max) and heart rate were markedly higher in TG than WT mice (both P<0.01). dP/dt(max) was lower in both AS groups than in sham-operated controls, and this tended to be more pronounced in TG than WT mice (-32+/-5% versus -16+/-6%, P=0.059), although dP/dt(max) remained higher in TG than WT groups (P<0.05).

CONCLUSIONS

Elevated cardiac beta-adrenergic activity by beta(2)-AR overexpression leads to functional deterioration after pressure overload.

The cryptome: a subset of the proteome, comprising cryptic peptides with distinct bioactivities

There is increasing evidence that proteolytic cleavage gives rise to 'hidden' peptides with bioactivities that are often unpredicted and totally distinct to the parent protein. So far, the liberation of these cryptic peptides, or crypteins, has been shown to be prevalent in proteins associated with endocrine signalling, the extracellular matrix, the complement cascade and milk. A broad spectrum of proteases has been implicated in the generation of natural crypteins that appear to play a role in modulating diverse biological processes, such as angiogenesis, immune function and cell growth. The proteolytic liberation of crypteins with novel activities represents an important mechanism for increasing diversity of protein function and potentially offers new opportunities for protein-based therapeutics.

Selective activation of alpha1A-adrenergic receptors in neonatal cardiac myocytes is sufficient to cause hypertrophy and differential regulation of alpha1-adrenergic receptor subtype mRNAs

Prolonged stimulation of cardiac alpha1-adrenergic receptors causes myocyte hypertrophy, although the receptor subtypes involved remain controversial. We have used a potent and selective alpha1A agonist, A-61603, to test whether activation of the alpha1A-adrenergic receptor subtype is sufficient to mediate the morphological, biochemical and molecular alterations associated with cardiomyocyte hypertrophy. In neonatal rat cardiomyocyte cultures, 48 h incubation with 50 nm A-61603 led to a marked increase in myocardial cell size that was associated with a significant elevation in the rate of protein synthesis. The increased rate of incorporation of radiolabelled amino acids into protein stimulated by A-61603 was totally abolished by the selective alpha1A antagonist KMD-3213. A-61603 increased ANF secretion three-fold, and ANF mRNA 12-fold above control levels in cardiomyocyte cultures. RNase protection analysis demonstrated a A-61603-mediated two to three-fold increase in alpha1A-adrenergic receptor mRNA with a concomitant 50% decrease in alpha1B mRNA levels by 48 h. Identical responses of differential regulation of alpha1A- and alpha1B-adrenergic receptor mRNA were observed with phenylephrine. Both the stimulation of alpha1A- and repression alpha1B-adrenergic receptor mRNA caused by A-61603 could be abolished by 10-20 nm KMD-3213. The present data provide evidence that selective activation of alpha 1A-adrenergic receptors on cardiomyocytes is sufficient to mediate the phenotypic changes associated with cardiac hypertrophy. In addition, the differential regulation of alpha1A and alpha1B mRNA in response to selective alpha1A-adrenergic receptor stimulation suggests that cross-talk between receptor subtypes may be involved in regulating receptor populations during chronic agonist exposure.

Sex hormones and cardiomyopathic phenotype induced by cardiac beta 2-adrenergic receptor overexpression

Sex differences in cardiomyopathic phenotype and the role of gonadal status were studied in mice with cardiac overexpression of beta(2)-adrenergic receptors (ARs) over 6-15 months (mo) of age. Survival to 15 mo was 96% in wild-type mice but was poorer in transgenic (TG) mice and lower for males than females (13% vs. 56%, P < 0.001). Echocardiography demonstrated progressive left ventricular (LV) dilatation and reduction in LV fractional shortening in male but much less marked changes in female TG mice. Incidences of atrial thrombosis, pleural effusion and lung congestion were higher and myocyte size and fibrosis in the LV were greater in TG males than females. Deprivation of testicular hormones by castration during 3-15 mo of age improved survival and significantly ameliorated LV dysfunction, remodeling, and hypertrophy compared with intact TG males. No significant effect, except for a trend of a better survival, was detected by ovariectomy in TG females. In conclusion, cardiac beta(2)-AR overexpression at a high level leads to cardiomyopathy and heart failure with aging. Female mice had less cardiac remodeling, dysfunction, and pathology and a marked survival advantage over male mice, and this was independent of prevailing levels of ovarian hormones. TG males showed benefit from orchiectomy, suggesting a contribution by testicular hormones to the progression of the cardiomyopathic phenotype.

Phase II biomarker trial of a multimarker diagnostic for ovarian cancer

Purpose

The primary hypothesis to be tested in this study was that the diagnostic performance (as assessed by the area under the receiver operator characteristic curve, AUC) of a multianalyte panel to correctly identify women with ovarian cancer was significantly greater than that for CA-125 alone.

Methods

A retrospective, case–control study (phase II biomarker trial) was conducted that involved 362 plasma samples obtained from women with ovarian cancer (n = 150) and healthy controls (n = 212). A multivariate classification model was developed that incorporated five biomarkers of ovarian cancer, CA-125; C-reactive protein (CRP); serum amyloid A (SAA); interleukin 6 (IL-6); and interleukin 8 (IL-8) from a modelling cohort (n = 179). The performance of the model was evaluated using an independent validation cohort (n = 183) and compared with of CA-125 alone.

Results

The AUC for the biomarker panel was significantly greater than the AUC for CA-125 alone for a validation cohort (p < 0.01) and an early stage disease cohort (i.e. Stages I and II; p < 0.01). At a threshold of 0.3, the sensitivity and specificity of the multianalyte panel were 94.1 and 91.3%, respectively, for the validation cohort and 92.3 and 91.3%, respectively for an early stage disease cohort.

Conclusions

The use of a panel of plasma biomarkers for the identification of women with ovarian cancer delivers a significant increase in diagnostic performance when compared to the performance of CA-125 alone.

Adrenomedullin stimulates cAMP accumulation and inhibits atrial natriuretic peptide gene expression in cardiomyocytes

Adrenomedullin (ADM) is a novel vasodilating and natriuretic peptide which may play an important role in cardiovascular regulation. In neonatal cardiomyocyte cultures we have shown that ADM leads to dose-dependent inceases in cAMP accumulation and subsequent inhibition of atrial natriuretic peptide (ANP) gene expression and secretion. Forskolin-mediated elevation of intracellular cAMP levels led to a qualitatively similar inhibitory effect on both ANP gene expression and secretion. These data show that ADM has direct effects on expression of ANP in the cardiomyocyte by a mechanism that may involve the activation of adenylate cyclase, lending further support to the hypothesis that ADM may act in vivo as an important endocrine or paracrine modulator of cardiovascular function.

Immunoreactive arginine-vasopressin in Brattleboro rat ovary

Homozygous (di/di) Brattleboro rats have normal hypothalamic levels of oxytocin and neurophysin I, but undetectable levels of neurophysin II and arginine-vasopressin (AVP). This defect has been presumed to be at the genomic or transcriptional level, as AVP messenger is reported to be drastically reduced, if not absent, from the hypothalamus of Brattleboro rats. Recent studies suggest de novo production of various neuropeptides in the mammalian gonad, including AVP. We report here the detection and localization of immunoreactive (ir) AVP in the luteal cells of adult homozygous Brattleboro rats, and the modulation of this ovarian ir-AVP by gonadotropins. These findings are thus consistent with a tissue-specific defect of AVP expression in the magnocellular neurones of the Brattleboro rat, and suggest that a comparable defect does not occur in the ovaries of such animals.

In vivo and in vitro evidence for impaired arginine transport in human heart failure

BACKGROUND

The clinical features of congestive heart failure (CHF) result from a complex interaction between reduced ventricular function, neurohormonal activation, and impaired endothelial function. Although endothelial dysfunction has been well documented, the mechanisms that contribute to this abnormality remain unknown. Recent studies, however, indicate a potential therapeutic role for supplemental L-arginine, suggesting the presence of an underlying disorder of L-arginine metabolism.

METHODS AND RESULTS

We used 2 complementary approaches to assess L-arginine transport in control subjects and patients with CHF. During a steady-state intra-arterial infusion of [(3)H]L-arginine (100 nCi/min), forearm clearance of [(3)H]L-arginine was significantly reduced in CHF patients compared with forearm kinetics in control subjects (64+/-2 versus 133+/-14 mL/min, P=0.002). In conjunction with this, [(3)H]L-arginine uptake by peripheral blood mononuclear cells (PBMCs) was also substantially reduced in heart failure patients compared with controls (V(max) 10. 1+/-1.3 versus 49.8+/-7.1 pmol/10(5) cells per 5 minutes, P<0.001). In association with this finding, we observed a 76% (P<0.01) reduction in mRNA expression for the cationic amino acid transporter CAT-1, as assessed by ribonuclease protection assay.

CONCLUSIONS

These data document both in vivo and in vitro evidence for a marked depression of L-arginine transport in human CHF and therefore provide an explanation for the restorative actions of supplemental L-arginine on vascular function in CHF.

Corticotropin-releasing factor differentially regulates anterior and intermediate pituitary lobe proopiomelanocortin gene transcription, nuclear precursor RNA and mature mRNA in vivo

The proopiomelanocortin (POMC) gene and its peptide products are under complex regulation in the pituitary by multiple hormonal, neurohormonal and neurotransmitter factors. Corticotropin-releasing factor (CRF) stimulates the release of POMC-derived peptides in both anterior and intermediate lobes of the pituitary, while having differential long-term effects on levels of POMC mRNA in the two pituitary lobes in vivo. In the present study, we have analyzed the release of POMC-derived peptides, as well as changes in POMC gene transcription, primary transcript, nuclear mRNA and cytoplasmic mRNA levels following acute and chronic in vivo CRF administration in an attempt to elucidate the mechanism whereby this tissue-specific differential regulation occurs. Subcutaneous injection of CRF led to a substantial increase in plasma adrenocorticotropin, but only a minor sustained rise in plasma alpha-melanocyte-stimulating hormone. CRF was shown to induce rapid, time-dependent increases in POMC gene transcription in both anterior and intermediate pituitary lobes, which were reflected by increases in the level of POMC primary transcript in the nucleus. POMC primary transcript remained 2-fold elevated in the anterior lobe for at least 4 h after a single injection of CRF; in contrast, CRF stimulation of POMC primary transcript in the intermediate lobe was short-lived, and had returned to control values by 60 min after injection. After 7 days of repetitive CRF administration, POMC primary transcript, mature nuclear mRNA and cytoplasmic mRNA were 2.5 to 3.0-fold elevated in the anterior pituitary.(ABSTRACT TRUNCATED AT 250 WORDS)

Cross talk between corticosteroids and alpha-adrenergic signalling augments cardiomyocyte hypertrophy: a possible role for SGK1

OBJECTIVE

Mineralocorticoids and glucocorticoids have been implicated in the pathogenesis of cardiac diseases; however, both in vivo and in vitro studies indicate that changes in the cellular milieu of either the cardiomyocyte and/or cells of the vasculature is required for corticosteroid signalling to be pathological. The aim of the current study was to directly address whether signalling pathways that are activated during myocyte hypertrophy alter corticosteroid signalling and thus enable these steroids to significantly impact on the hypertrophic response.

METHODS

Neonatal rat ventricular cardiomyocytes were treated with phenylephrine or phorbol ester for 48 h to induce myocyte hypertrophy. Following treatment, the expression of glucocorticoid receptor, mineralocorticoid receptor, and 11beta-hydroxysteroid dehydrogenase were determined by ribonuclease protection assay. In addition, the activity of 11beta-hydroxysteroid dehydrogenase and the ability of glucocorticoid and mineralocorticoid receptors to induce serum- and glucocorticoid-induced kinase 1 (SGK1) gene transcription were assessed. Corticosteroid effects on phenylephrine and phorbol ester-induced hypertrophy were determined by measuring atrial natriuretic peptide (ANP) mRNA expression, protein synthesis, or induction of rDNA transcription.

RESULTS

Incubation of cardiomyocytes with phenylephrine and phorbol ester for 48 h led to a hypertrophic response with an associated 8- to 12-fold increase in ANP mRNA and 2-fold increase in rDNA transcription. Cardiomyocyte hypertrophy led to a significant 2-fold increase in glucocorticoid receptor and mineralocorticoid receptor expression that resulted in enhanced receptor signaling as judged via the ability of corticosterone and aldosterone to induce SGK1 gene transcription. 11beta-Hydroxysteroid dehydrogenase2 was not detected in normal or hypertrophied cardiomyocytes, and 11beta-hydroxysteroid dehydrogenase exclusively demonstrated reductase activity, converting the inactive 11-ketometabolite back to active glucocorticoid. 11beta-Hydroxysteroid dehydrogenase1 expression and reductase activity were increased with phorbol ester-induced hypertrophy but not phenylephrine-induced hypertrophy. In basal cardiomyocytes, either aldosterone or corticosterone induced only a minor increase in ANP mRNA and protein synthesis; however, in cardiomyocytes primed with phenylephrine, both corticosteroids significantly potentiated phenylephrine-mediated effects via activation of the glucocorticoid receptor.

CONCLUSION

In the present study we demonstrate that significant cross talk exists in the cardiomyocyte between corticosteroid receptor-activated pathways and both protein kinase C and alpha-adrenergic signalling. Cellular changes associated with the hypertrophic response promote corticosteroid signalling and allow for corticosteroid-mediated potentiation of alpha-adrenergic receptor signalling. Such augmentation of cardiomyocyte hypertrophy may in part explain the role that corticosteroid hormones play in the pathophysiological progression of heart disease.

Dopamine D2-receptor messenger RNA is differentially regulated by dopaminergic agents in rat anterior and neurointermediate pituitary

Hypothalamic dopamine (DA), acting at DA D2-receptors (D2-R) on pituitary target cells, mediates peptide release and biosynthesis of rat pituitary anterior lobe (AL) prolactin, and neurointermediate lobe (NIL) pro-opiomelanocortin (POMC). We were interested in determining if dopamine agonists and antagonists were capable of modifying D2-R gene expression in these pituitary cells. Utilizing the recently published sequence of the rat D2-R, we isolated a rat D2-R cDNA clone by polymerase chain reaction, and have synthesized RNA probes to quantitate levels of D2-R mRNA by solution hybridization/nuclease protection assay. We report here that 5-day administration of the DA antagonist haloperidol led to significant increases in both D2-R mRNA and POMC mRNA in the NIL; the DA agonist bromocriptine caused a significant decrease in NIL POMC mRNA with no parallel change in D2-R mRNA. In contrast, no significant changes in D2-R mRNA in AL were observed following treatment with either the DA agonist or antagonist. These data provide evidence for tissue-specific regulation of D2-R mRNA in response to dopaminergic manipulation.

11Beta-hydroxysteroid dehydrogenase 1 transforms 11-dehydrocorticosterone into transcriptionally active glucocorticoid in neonatal rat heart

The ability of cells to directly respond to glucocorticoids and aldosterone is a function of GR and MR expression, and coexpression of 11beta-hydroxysteroid dehydrogenases (11betaHSDs), which convert glucocorticoids and their 11-ketometabolites into either receptor inactive or active derivatives. The aim of the present study was to determine the cellular expression of GR, MR, 11betaHSD1, and 11betaHSD2 in neonatal rat heart and determine the role these enzymes play in modulating glucocorticoid and aldosterone action. Ribonuclease protection analysis and steroid binding assays showed that GR is expressed in both cardiac myocytes and fibroblasts, whereas MR is expressed only in myocytes. 11betaHSD2 was not detected in cardiac cells, but 11betaHSD1 was expressed at high levels in both cardiac myocytes and fibroblasts. Enzyme activity studies demonstrated that 11betaHSD1 acted as a reductase only, converting biologically inactive 11-dehydrocorticosterone to corticosterone, which then stimulated serum and glucocorticoid-induced kinase gene transcription via GR. In both cardiac myocytes and fibroblasts, aldosterone stimulated serum and glucocorticoid-induced kinase gene expression exclusively via GR, but not MR, indicating that aldosterone can have glucocorticoid-like actions in heart. The ability of cardiac cells to use both circulating corticosterone and 11-dehydrocorticosterone as a source of glucocorticoid suggests that the heart is under tonic glucocorticoid control, implying that glucocorticoids play important homeostatic roles in the heart.

Reduced reperfusion-induced Ins(1,4,5)P3 generation and arrhythmias in hearts expressing constitutively active alpha1B-adrenergic receptors

Reperfusion of globally ischemic rat hearts causes the generation of inositol(1,4,5)trisphosphate [Ins(1,4,5)P3] and the initiation of arrhythmias. These responses are mediated by alpha1-adrenergic receptors (ARs), but the subtype of receptor involved has not been identified. Under normoxic conditions, hearts from transgenic animals expressing constitutively active alpha1B-ARs in heart (alpha1B-constitutively active mutant [CAM]) showed higher [3H] inositol phosphate responses to norepinephrine (2.3-fold) than hearts from nontransgenic animals (alpha1B-WT) (1.6-fold). alpha1B-WT hearts responded to 2 minutes of reperfusion after 20 minutes of global ischemia by generation of Ins(1,4,5)P3 (5301+/-1310 to 11 413+/-1597 CPM/g tissue; mean+/-SEM; n=6; P<0.01 in [3H] labeling studies and 3.8+/-0.2 to 6.3+/-0.6 nmol/g by mass analysis, n=6; P<0.05). In contrast to findings in normoxia, hearts from alpha1B-CAM animals showed no Ins(1,4,5)P3 response in early reperfusion. In parallel studies, alpha1B-WT hearts developed ventricular tachycardia and ventricular premature beats (VPB) during 5 minutes of reperfusion after 20 minutes of ischemia. The incidence of these arrhythmias was reduced in the alpha1B-CAM hearts (95% to 62% for VPB and 47% to 12% for ventricular tachycardia; both P<0.05). The resistance of the alpha1B-CAM hearts was not due to alpha1B-AR-mediated preconditioning, as the Ins(1,4,5)P3 response to thrombin receptor activation during reperfusion was not different between the 2 groups. To investigate the possibility of reduced alpha1A-receptor activity in the alpha1B-CAM hearts, expression of the mRNA for alpha1A- and alpha1B-receptors was measured. alpha1B-WT hearts contained mRNA for both receptor subtypes, but the levels of alpha1B-receptor mRNA were 5-fold higher than alpha1A-receptor mRNA. alpha1B-CAM hearts contained very high levels of alpha1B-receptor mRNA (26-fold increase), but the expression of mRNA for the alpha1A-receptors (0.141+/-0.035 amol/ microg RNA; mean+/-SEM; n=6) was reduced by 50% relative to alpha1B-WT controls (0.276+/-0.046 amol/ microg RNA; n=6; P<0.01). The reduction in arrhythmogenic and Ins(1,4,5)P3 responses in alpha1B-CAM hearts provides evidence that these response are not mediated by alpha1B-receptors.

Adverse effects of constitutively active alpha(1B)-adrenergic receptors after pressure overload in mouse hearts

Cardiac hypertrophy and function were studied 6 wk after constriction of the thoracic aorta (TAC) in transgenic (TG) mice expressing constitutively active mutant alpha(1B)-adrenergic receptors (ARs) in the heart. Hearts from sham-operated TG animals and nontransgenic littermates (WT) were similar in size, but hearts from TAC/TG mice were larger than those from TAC/WT mice, and atrial natriuretic peptide mRNA expression was also higher. Lung weight was markedly increased in TAC/TG animals, and the incidence of left atrial thrombus formation was significantly higher. Ventricular contractility in anesthetized animals, although it was increased in TAC/WT hearts, was unchanged in TAC/TG hearts, implying cardiac decompensation and progression to failure in TG mice. There was no increase in alpha(1A)-AR mRNA expression in TAC/WT hearts, and expression was significantly reduced in TAC/TG hearts. These findings show that cardiac expression of constitutively actively mutant alpha(1B)-ARs is detrimental in terms of hypertrophy and cardiac function after pressure overload and that increased alpha(1A)-AR mRNA expression is not a feature of the hypertrophic response in this murine model.

Evaluation of midkine and anterior gradient 2 in a multimarker panel for the detection of ovarian cancer

The aims of this study were: to characterise and compare plasma concentrations of midkine (MDK) in normal healthy women with concentrations observed in women with ovarian cancer; and to establish and compare the performance of MDK with that of anterior gradient 2 protein (AGR2) and CA125 in the development of multi-analyte classification algorithms for ovarian cancer. Median plasma concentrations of immunoreactive MDK, AGR2 and CA125 were significantly greater in the case cohort (909 pg/ml, 765 pg/ml and 502 U/ml, respectively n = 46) than in the control cohort (383 pg/ml, 188 pg/ml and 13 U/ml, respectively n = 61) (p < 0.001). The area under the receiver operator characteristic curve (AUC) for MDK and AGR2 was not significantly different (0.734 ± 0.046 and 0.784 ± 0.049, respectively, mean ± SE) but were both significantly less than the AUC for CA125 (0.934 ± 0.030, p < 0.003). When subjected to stochastic gradient boosted logistic regression modelling, the AUC of the multi-analyte panel (MDK, AGR2 and CA125, 0.988 ± 0.010) was significantly greater than that of CA125 alone (0.934 ± 0.030, p = 0.035). The sensitivity and specificity of the multi-analyte algorithm were 95.2 and 97.7%, respectively. Within the study cohort, CA125 displayed a sensitivity and specificity of 87.0 and 94.6%, respectively. The data obtained in this study confirm that both MDK and AGR2 individually display utility as biomarkers for ovarian cancer and that in a multi-analyte panel significantly improve the diagnostic utility of CA125 in symptomatic women.

Ovarian immunoreactive beta-endorphin and estrous cycle in the rat

Adult female Sprague-Dawley rats were killed at different stages of a 4-day estrous cycle, and ovaries and anterior pituitaries examined for content of immunoreactive beta-endorphin by RIA and for localization by indirect immunofluorescence. Two anti-beta-endorphin antisera, both recognizing different antigenic determinants of human-beta-endorphin, showed intense immunofluorescence staining of cells localized predominantly in ovarian corpora lutea. At proestrus, both large and small luteal cells stained positively but only the large luteal cells were immunofluorescence positive at other stages of the estrous cycle. In addition, less intense staining of granulosa cells was occasionally observed in secondary and antral follicles; scattered cells in the interstitium were also weakly positive. In contrast, cells of primordial and primary follicles, and those of theca tissue were consistently negative. Ovarian levels of immunoreactive beta-endorphin were found to be lowest at estrus (2.1 +/- 0.18 ng/g; n = 8, mean +/- SE) and significantly raised in stepwise manner over metestrus and diestrus to a peak (approximately 4 X estrous levels) at proestrus; in contrast, immunoreactive beta-endorphin content of anterior pituitaries remained unaltered during the same period. Sephadex G-50 gel chromatography of ovarian extracts revealed three distinct peaks of immunoreactive beta-endorphin, a minor peak in the void volume, and two major peaks of unequal size eluting at mol wt approximately 11.5K and approximately 3.5K. The major species of low molecular weight immunoreactive beta-endorphin on reverse phase HPLC was beta-endorphin1-31. We conclude from the findings that, in adult rat ovaries, luteal, granulosa, and interstitial cells are responsible for the production of immunoreactive beta-endorphin and that this production, being related to the estrous cycle, is presumably under the direct or indirect influence of gonadotropins.

Intervening sequence-specific in situ hybridization: detection of the pro-opiomelanocortin gene primary transcript in individual neurons

We describe here the in situ hybridization procedure which we have used to detect the pro-opiomelanocortin (POMC) gene primary transcript in nuclei of individual neurons in the periarcuate region of the hypothalamus. An exon-intron RNA probe was used to detect POMC primary transcript and mature mRNA in nuclear extracts of nucleic acids using a sensitive S1 nuclease protection assay. The levels per cell of nuclear primary transcript were similar to those seen in the anterior pituitary, suggesting that intervening sequence in situ hybridization should be feasible. A nonrepetitive complementary RNA probe specific for the first intervening sequence of the rat POMC gene (POMC IVS-A) was used to detect the POMC primary transcript in hypothalamic tissue sections by in situ hybridization. The distribution of nuclear localized autoradiographic grains was similar to that previously reported for immunocytochemically defined POMC neurons, suggesting that the procedure is also effective in brain cells.

Adrenomedullin expression in rat uterus is correlated with plasma estradiol

Levels of expression of adrenomedullin (AM) in the uterus have been reported to vary with the reproductive cycle. This study examines the relationships among uterine AM mRNA, the stage of the estrous cycle, and circulating estradiol and progesterone in cycling rats and in ovariectomized (OVX) rats without or with estrogen replacement (ER). Strong AM mRNA, AM immunoreactivity, and pro-AM NH2-terminal 20 peptide (PAMP) immunoreactivity were observed in endometrial stroma by use of in situ hybridization and immunocytochemistry. Endometrial expression was particularly intense at proestrus and estrus, with weaker expression in the myometrium. By RNase protection assay, significant differences in AM mRNA between the stages of the estrous cycle could not be established. However, levels of AM mRNA were positively correlated with plasma estradiol in cycling rats (r = 0.56, P < 0.005) and in OVX and ER rats (r = 0.92, P < 0.001) and were not correlated with plasma progesterone. Levels of AM mRNA were significantly reduced after OVX compared with cycling rats, and ER restored AM mRNA to levels equivalent to those seen at the peak of the cycle (proestrus). In conclusion, although AM expression in the uterus varies throughout the estrous cycle, it is more closely correlated with circulating estradiol levels than with the stage of the cycle itself.

Co-expression of adrenomedullin and adrenomedullin receptors in rat epididymis: distinct physiological actions on anion transport

Adrenomedullin (AM) has been found in the brain as well as in various peripheral tissues, including reproductive organs such as the testis and the prostate. Here, we report the expression of AM in the rat epididymis and its role in anion secretion. Whole-epididymal extracts had 35.3 +/- 1.4 fmol of immunoreactive AM per mg of protein, and immunocytochemical studies showed positive AM immunostaining in the epithelial cells. By solution-hybridization-RNase protection assay, preproAM mRNA was detected at high levels in the epididymis. Gel filtration chromatography of AM showed two peaks, with the predominant one eluting at the position of authentic rat AM (1-50). Specific binding of AM to the epididymis, which could be displaced by calcitonin gene-related peptide, was observed. The epididymis also bound to calcitonin gene-related peptide, and this was displaceable by AM. Furthermore, the epididymis was shown to co-express mRNA encoding the calcitonin receptor-like receptor and receptor activity-modifying proteins, RAMP1/RAMP2. The corpus region had the highest AM level and gene expression and the lowest active peptide:precursor ratio. However, mRNA levels of the receptor and the receptor activity-modifying proteins were similar in all regions. In monolayer cultures derived from the rat epididymal cells, AM stimulated short-circuit current on the luminal side in a dose-dependent manner. Our results demonstrate the presence of AM, preproAM mRNA, AM receptors, and specific-binding sites in the rat epididymis as well as the possible role of AM in the regulation of electrolyte and fluid secretion in the epididymis.

Changes in rat pituitary nuclear and cytoplasmic pro-opiomelanocortin RNAs associated with adrenalectomy and glucocorticoid replacement

While the transcriptional effects of glucocorticoid hormone manipulation on the pituitary pro-opiomelanocortin (POMC) gene have been documented, it is not yet clear whether glucocorticoids activate additional post-transcriptional mechanisms to regulate POMC gene expression. We have used RNA probes that span exon/intron junctions in sensitive nuclease protection assays in order to examine changes in POMC precursor RNA as well as mature mRNA in nucleus and cytoplasm following both adrenalectomy (ADX) and administration of exogenous glucocorticoids. ADX led to a rapid and sustained 8- to 10-fold increase in the level of POMC primary transcript in the anterior lobe (AL), from 1 to 14 days after ADX. Stimulation of mature POMC mRNA in the nucleus was also rapid, with 7- to 8-fold increases evident by 1 day after ADX. In sharp contrast, the time-dependent accumulation of POMC mRNA in the cytoplasm was slow in comparison, reaching levels approximately 2-fold higher than sham-operated animals by 1 day post-ADX and 12-fold higher by 14 days after ADX. Despite the constant elevated level of nuclear POMC precursor RNA, the rate of accumulation of POMC mRNA in the corticotroph cytoplasm after ADX was not linear, with the greatest increase occurring within the first 1-4 days post-ADX. This led to alterations in the molar ratio of POMC primary transcript: nuclear mRNA: cytoplasmic mRNA in the AL at 1 and 4 days after ADX and showed a relative increase in the proportion of POMC RNA transcripts within the nucleus. Acute administration of dexamethasone to ADX rats resulted in rapid 80-90% inhibition of POMC primary transcript levels in the AL that was maximal by 30 min but with no associated change in mature mRNA. No significant changes in POMC RNA were seen in neurointermediate lobe in any of these studies. These studies suggest that following ADX, time-dependent alterations in nuclear transport of mature POMC mRNA and/or changes in POMC mRNA stability, in addition to changes in gene transcription may account for the overall level of POMC mRNA expressed in the AL. Furthermore, we have illustrated the use of exon/intron probes for accurately quantitating rapid alterations in steady-state levels of nuclear precursor RNA that may reflect transcriptional responses and/or changes in post-transcriptional processing of the primary transcript.

Concomitant dopaminergic and glucocorticoid control of pituitary proopiomelanocortin messenger ribonucleic acid and beta-endorphin levels

Synthesis and secretion of POMC-derived peptides appear to be differentially regulated in the anterior pituitary (AP) and neurointermediate lobe (NIL). In the AP, glucocorticoids inhibit, and CRF and arginine vasopressin stimulate, synthesis of POMC and release of immunoreactive (ir)-beta-endorphin (beta EP); in the NIL, synthesis and release of POMC and its derivatives are under tonic inhibitory dopaminergic control. There is, however, evidence for some overlap of these control mechanisms under certain circumstances. In the present study we have used specific RIA and Northern blot analysis to examine the effects of chronic treatment with dopaminergic agents and dexamethasone (DM) (both alone and in combination) on AP and NIL content of ir-beta EP and POMC messenger RNA (mRNA), and/or hypothalamic ir-arginine vasopressin and ir-CRF content. In the NIL, the dopamine agonist bromocriptine reduced and the antagonist haloperidol raised both POMC mRNA and ir-beta EP content. Long term DM treatment did not alter NIL ir-beta EP content in the intact rat, but increased levels of POMC mRNA. DM abolished the haloperidol-induced increase in NIL ir-beta EP content but further increased the haloperidol-induced rise in POMC mRNA. DM treatment lowered both ir-beta EP and POMC mRNA in the AP as well as lowering levels of hypothalamic ir-CRF. In DM-treated rats, haloperidol partially restored AP ir-beta EP and POMC mRNA to control untreated levels. These findings further support the proposition that both dopaminergic agents and glucocorticoids can modulate POMC mRNA levels and/or tissue content of ir-beta EP in both the NIL and AP of the rat. The effects of DM on the NIL, both alone or with haloperidol, suggest that glucocorticoids may have both direct and indirect effects on POMC gene expression in this tissue.

Adrenomedullin induces expression of c-fos and AP-1 activity in rat vascular smooth muscle cells and cardiomyocytes

The recently described hypotensive peptide adrenomedullin has been shown to activate various second messenger pathways in cells of the cardiovascular system though no genomic actions have yet been described. In cultured rat vascular smooth muscle cells, cardiomyocytes, and cardiac fibroblasts, adrenomedullin caused a rapid, but transient induction of c-fos mRNA expression in all three cell types that varied in magnitude. Adrenomedullin increased AP-1 DNA binding activities in vascular smooth muscle cells and cardiomyocytes, but not in cardiac fibroblasts. These data suggest that cardiomyocytes and vascular smooth muscle cells may be important genomic targets for this novel hormone.