Methylation of Retinoic Acid Receptor, Beta (RARB) Gene Increases Risk for Prostate Cancer in African-American Men

DNA methylation is an indicator of the initiation of prostate carcinogenesis and as such has utility as a marker of risk in pathologically negative prostate tissue samples. We conducted a matched case-control study nested in a historical cohort of over 6,000 men with pathologically benign prostate specimens identified between January 1991 and November 2002 with no previous history of prostate cancer. Eligible cases were diagnosed with prostate cancer at least one year after cohort entry. Controls were selected through incidence density sampling and matched to cases on date and age at cohort entry, race, and type of specimen. In 310 matched prostate cancer case-control pairs (65% white; 35% African American), we assayed the DNA of the benign prostate specimen for presence of methylation in a five-gene panel (APC, RARB, CCND2, RASSF1, MGMT) and then estimated the risk of developing prostate cancer associated with methylation at each gene for the whole sample and stratified by race. Overall, methylation of RARB had the strongest association with prostate cancer risk (HR = 1.94; 95% CI = 1.30 – 2.91). In race-stratified analyses, the majority of the increased risk associated with RARB was found in the African-American sample (HR = 3.40; 95% CI = 1.68–6.88). In addition, APC was also associated with increased risk for prostate cancer in the African-American sample (HR = 2.17; 95% CI = 1.09–4.29). In a model that included both genes, only RARB remained statistically significantly associated with prostate cancer (HR = 3.14; 95% CI = 1.54–6.44). In whites, methylation was not associated with prostate cancer for any of the five genes assayed. In summary, positive methylation status at RARB and APC in pathologically benign prostate is associated with significant increased risk for subsequent prostate cancer, but primarily in African-American men. Whether this race-specific risk is due to racial differences in environmental stimuli and/or biology is unclear, but further study of DNA methylation in the earliest stages of prostate carcinogenesis may help explain the disproportionate burden of this disease among African-American men.

Activated factor XI and tissue factor in chronic obstructive pulmonary disease: links with inflammation and thrombin generation

INTRODUCTION

Increased cardiovascular mortality and risk of venous thromboembolism are serious extra-pulmonary complications of chronic obstructive pulmonary disease (COPD). Previously, circulating active tissue factor (TF) and factor XIa (FXIa) have been reported to be associated with acute coronary syndromes.

OBJECTIVE

To measure plasma FXIa and active TF, prothrombin fragment 1.2 (F1.2), and markers of systemic inflammation (C-reactive protein [CRP], interleukin-6 [IL-6], tumor necrosis factor α [TNFα] and matrix metalloproteinase 9 [MMP-9]) in 60 patients with documented stable COPD free of previous thromboembolic events.

METHODS

In-house clotting assays using inhibitory monoclonal antibodies against FXIa and TF.

RESULTS

FXIa was detected in 9 (15%) and TF activity in 7 (11.7%) COPD patients. Subjects positive for FXIa and/or TF (n=10; 16.7%) had higher F1.2 (median [interquartile range], 398 [216] vs 192 [42] pM, p<0.000001), fibrinogen (5.58 [2.01] vs 3.97 [2.47] g/L, p=0.0007), CRP (14.75 [1.20] vs 1.88 [2.95] mg/L, p<0.000001), IL-6 (8.14 [4.74] vs 2.45 [2.24] pg/mL, p=0.00002), and right ventricular systolic pressure (47 [15] vs 38 [12] mmHg, p=0.023), and lower vital capacity (66 [15] vs 80 [17] % predicted, p=0.04) than COPD patients without detectable FXIa and TF. COPD severity was not associated with the presence of circulating FXIa and active TF.

CONCLUSIONS

This is the first study to show that active FXIa and TF are present in stable COPD patients, who exhibit enhanced systemic inflammation and thrombin generation. Our findings suggest a new prothrombotic mechanism which might contribute to elevated risk of thromboembolic complications in COPD.

Downregulation of oxytocin receptors in right ventricle of rats with monocrotaline-induced pulmonary hypertension

AIM

pulmonary hypertension (PH) in the rat leads to right ventricular (RV) hypertrophy, inflammation and increased natriuretic peptide (NP) levels in plasma and RV. Because the release of nitric oxide (NO) and atrial natriuretic peptide (ANP) is a function of the oxytocin receptor (OTR), we examined the effect of PH on gene and protein expression of OTR, NP (A, atrial; B, brain) and receptors (NPRs), nitric oxide synthases (NOS), interleukin (IL)-1β, IL-6 and tumour necrosis factor-α in the hypertrophied RV in a model of PH.

METHODS

RV hypertrophy was induced in male Sprague-Dawley rats with monocrotaline (MCT; 60 mg kg(-1) ) and was confirmed by the presence of an increased RV weight and RV-to-[left ventricle (LV) and septum] ratio.

RESULTS

in the RV of MCT-treated rats, a approximately 40% reduction in OTR mRNA and protein was observed compared with the RV of control rats. This reduction was associated with increased transcripts of ANP and BNP in both ventricles and a corresponding increase in NP receptor mRNA expression for receptors A, B and C. Protein expression of inducible NOS was increased in the RV, whereas endothelial NOS transcripts were increased only in the LV of MCT-treated rats. In the RV of MCT-treated rats, downregulation of OTR was also associated with increased mRNA expression of IL-1β and IL-6.

CONCLUSION

our results show that downregulation of the OTR in the RV of MCT-treated rats is associated with increased expression of NP and their receptors as well as IL-1β and IL-6. This reduction in OTR in RV myocardium may have an impact on cardiac function in the MCT-induced model of PH.

An improved manufacturing process for Xyntha/ReFacto AF

SUMMARY

ReFacto Antihemophilic Factor is a second-generation antihaemophilia A product manufactured using a process that includes therapeutic grade human serum albumin (HSA) in the cell culture medium, but is formulated without HSA as a stabilizer. Even though this second-generation antihaemophilia product has a good safety profile, a programme was implemented to eliminate all animal- and human-derived raw materials from the production process, thus producing a third-generation product. To that end, HSA has been removed from the master and working cell banks and from the culture medium. The hybridoma-derived monoclonal antibody formerly used in the purification process has been replaced by a chemically synthesized affinity peptide, and a virus-retaining filtration step has been added to enhance the clearance of large viruses, such as retroviruses. The purification process has been validated for the removal of a panel of model viruses and provides significant clearance of all viruses tested. Host cell- and process-derived impurity removal validations also were conducted, including host cell DNA and protein, in addition to the affinity peptide. Compared with the product manufactured according to the original process, these changes had no detectable effect on the structural integrity, stability or clinical efficacy of this antihaemophilia A product. The product produced by the improved manufacturing process is named Xyntha/ReFacto AF.

Cannabidiol-induced lymphopenia does not involve NKT and NK cells

The major non-psychoactive compound of cannabis plant, cannabidiol, has been reported to be a promising therapeutic agent for many inflammatory, autoimmune and neurodegenerative diseases. In spite of growing interest in therapeutic use of cannabidiol very little is known about its influence on the immune system. Present study aimed to evaluate lymphocyte subsets distribution in peripheral blood after repeated, systemic administration of cannabidiol. Adult male Wistar rats received intraperitoneal injections of vehicle or cannabidiol at dose of 2.5 or 5 mg/kg/day, for 14 consecutive days. Blood samples were collected one hour after the last injection. Three-color immunofluorescent antibody staining procedure (CD3-FITC/CD45RA-PC7/CD161A-APC and CD3-FITC/CD4-PC7/CD8-APC) was used for determination of T, B, NK, NKT, T helper, and T cytotoxic lymphocyte subsets. Total leukocyte number and percentage numbers of leukocyte subpopulations were also assessed. Administration of cannabidiol at dose of 5 mg/kg caused a significant decrease in total leukocyte number and a significant fall in total numbers of T, B, and both T helper and T cytotoxic lymphocyte subsets. This immunosuppressive effect did not affect the total numbers of NK and NKT cells that are responsible for the primary, nonspecific antiviral and antitumor immune response. In contrast, administration of cannabidiol at dose of 2.5 mg/kg increased the total and percentage NKT cells numbers, and the percentage number of NK cells. The results suggest that repeated treatment with cannabidiol inhibits specific immunity by reduction of T, B, T cytotoxic, and T helper cell numbers, and may enhance nonspecific antiviral and antitumor immune response related to NK and NKT cells.

How to develop guidelines for clinical practice

Recent decades have seen an explosion of clinical practice guidelines documents developed to inform clinicians about the best options for managing treatment, with the explicit intent to influence behaviour. As our exposure to guidelines has increased it has become clear that the process of guideline development should follow specific rules in order to avoid disagreement, misunderstanding, misleading recommendations, and confusion. In this article, we review the approach to developing clinical practice guidelines suggested by an international Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) workgroup. This approach suggests several steps for guideline development: 1. determine the purpose, scope, and intended audience; 2. select the panel of guideline authors; 3. specify the main focused clinical questions that the recommendations will address; 4. decide on the relative importance of outcomes; 5. find and summarize the evidence supporting each recommendation; 6. determine the quality of the available evidence; 7. evaluate the balance of desirable and undesirable consequences for a particular course of action; 8. formulate recommendations, including their strenght; and 9. consider a system for subsequent guideline implementation and evaluation. We aim to help the readers of practice guidelines asses those guidelines' quality and validity, as well as to assist the authors of future guidelines in systematically generating clinical recommendations.

The use of insulin and the effect on survival of non-small cell lung cancer patients

e22073

Background: Diabetes mellitus (DM) is one of the common morbidities in United States. Insulin therapy has been frequently used in its treatment. Some studies have postulated that activation of Insulin and Insulin-like growth factor (IGF) pathway may contribute to cancer proliferation, growth and resistance to anticancer therapies. The impact of insulin on diabetic patients with non-small cell lung cancer (NSCLC) has not been reported. Methods: 1,233 patients with NSCLC diagnosed between January 1999 and December 2004 were identified from the Tumor Registry at Henry Ford Health System. Based on inclusion criteria, data from 1,206 patients were extracted from the electronic medical records. Statistical analyses were performed between insulin and non insulin users. Results: Out of 1,206 patients, 193 patients had NSCLC and DM. Data was available from 192 patients. Sixty (31.3%) were on insulin at the time of NSCLC diagnosis and defined as insulin users, while 132 were not on insulin and defined as non- users (68.7%). Demographics, co-morbidities, disease stage at diagnosis, therapeutic interventions, and laboratory values were analyzed for overall and cancer-specific survival. More insulin users (81%) than non-users (64%) presented with advanced disease (stage ≥ 3) at diagnosis (P=0.02). Although no significant difference of Hemoglobin A1c was observed, the median survival from all causes of death was 6.5 months for insulin-users versus 9.9 months for non-users (P=0.08). When survival time was calculated from cancer-specific death, the median survival between insulin and non-insulin users was 7.2 months versus 38.7 months, respectively (P=0.002), with a hazard ratio (HR) for insulin use equals 1.91. Results from our univariable and multivariable analyses will be presented at the ASCO annual meeting in detail. Conclusions: This data indicates that the use of insulin may adversely affect the biology and clinical course of NSCLC with a tendency of advanced disease stage at diagnosis and a shorter cancer-specific survival time. Prospective study of DM with NSCLC or other cancer diagnosis will improve our understanding of this potential adverse effect on cancer biology and provide scientific rational to target IGF-pathway especially in diabetic patients.

No significant financial relationships to disclose.

Purinergic regulation of glomerular microvasculature and tubular function

Purinergic molecules: ATP, ADP and adenosine regulate physiological processes through activation of purinoceptors in the plasma membrane. Experimental evidence supports the view that purinergic molecules affect glomerular and tubular functions. Purinergic molecule-induced changes of tension of mesangial cells and/or podocytes may influence GFR by affecting the glomerular ultrafiltration coefficient. On the other hand, purinoceptors are crucial for electrolyte and fluid homeostasis by modulating activity of sodium-potassium-ATPase, voltage-independent or -dependent ion channels and cAMP-dependent water channels.

Dissociation between the effects of P1, P4-diadenosine tetraphosphate (Ap4A) on renal haemodynamics and tubular function in anaesthetized rats

Previous studies from our laboratory have reported a marked reduction in glomerular filtration rate (GFR) and sodium reabsorption in renal proximal tubule during intravenous infusion of P(1),P(4)-diadenosine tetraphosphate (Ap(4)A) at dose of 1.0 micromol/kg + 10 nmol/kg/min (i.v., injection followed by infusion) in anaesthetized Wistar rats. In the present study, the changes of GFR and urine sodium excretion were investigated in response to systemic infusion of Ap(4)A at different doses. Ap(4)A at dose of 0.1 micromol/kg + 1.0 nmol/kg/min did not change GFR and sodium urinary excretion whereas 2-fold higher dose produced significant (3.4-fold) increase in sodium excretion without changes in GFR. Significant but transient reduction in GFR by approximately 21% was observed during infusion of Ap(4)A at dose of 0.5 micromol/kg + 5.0 nmol/kg/min. Higher doses of Ap(4)A (1.0 micromol/kg + 10 nmol/kg/min and 2.0 micromol/kg + 20 nmol/kg/min) reduction in GFR and marked natriuresis. Our results suggest that tubular sodium transport systems are more sensitive to Ap(4)A than systems involved in GFR regulation.

Damage to the nucleus accumbens shell but not core impairs ventral tegmental area stimulation-induced feeding

Food intake is regulated not only by homeostatic requirements but also by emotional factors (e.g. palatability of food, alleviation of emotional tension etc.). The nucleus accumbens (Acb) is a part of the mesolimbic dopaminergic system which is responsible for a positive emotional aspect of various homeostasis-relevant stimuli. In the present work, we tested the Acb involvement in feeding behaviour using an experimental paradigm specifically designed to assess motivational vs motor aspect of food ingestion. In rats, feeding was evoked by electrical stimulation of the midbrain ventral tegmental area (a somatodendritic region of mesolimbic system) and assessed quantitatively with the use of the latency to feed/stimulation frequency curve-shift paradigm before and after electrolytic lesion of Acb. An impairment of stimulation-induced feeding manifesting as an elevation of the reaction threshold and a rightward, parallel shift of the stimulation frequency/reaction latency curve in the range of frequency which is sensitive to motivational aspects of food occurred after lesions localized mainly in the Acb shell. The lesions situated mainly in the Acb core were ineffective. The results obtained indicate that the Acb shell connected with the limbic system but not the motor-related Acb core affects motivational aspects of feeding behaviour.

The use of statins may prolong survival of non-small cell lung cancer patients: Final update from 1,205 cases

7638

Background: Hypercholesterolemia is one of the most common morbidities in United States. Statins have been proven as effective cholesterol-lowering agents and have been widely used in this country. They have been reported reducing the incidence and risk of various cancer types. However, the impact of using statins on the survival of 407 patients with diagnosed non-small cell lung cancer (NSCLC) was initially reported (Wang, et al. Abstract #7149, ASCO Meeting 2006). Methods: 1,233 patients with diagnosed non-small cell lung cancer were identified from the Tumor Registry at Henry Ford Health System between January 1999 and December 2004. The data from 1,206 patients were extracted from their available electronic medical records. Statistical analyses were performed and stratified for statin users versus non statin users. Results: Data from 1,205 eligible patients were included in this updated report. There were 391 patients with hypercholesterolemia, 250 of them were statin users at the time of their non-small cell lung cancer diagnosis. Average age was 68 (range 46–90) years for statin users and 65.9 (range 29–94) years for non statin users. Overall median survival of 1,205 subjects was 9.85 months. After stratifying for statin use, the median survival of statin users was 13.9 (95% C.I. 9.9 - 17.4) months while the median survival of non statin users was 9.6 (95% C.I. 8.1 - 10.4) months, with a P value of 0.0001. After having several prognostic variables (age, stage, co-morbids, other cancers, performance status, anti-cancer therapies, and serum albumin, etc.) adjusted, statin use still demonstrated protection from death with a hazard ratio of 0.74 (95% C.I. 0.59 - 0.95, P=0.017). Conclusion: The trend of survival benefit from NSCLC among statin users was shown in our previous report and it has maintained with further enhanced statistical significance in this update. Though statin use will unlikely become an independent anti-cancer regimen by itself, the choice of continuation of statin among NSCLC patients may still provide survival benefit to this population. The favorable impact of statin use on NSCLC patients is intriguing; a prospective study of co-morbidity management with statins in patients with non-small cell lung cancer is warranted.

No significant financial relationships to disclose.

The use of statins may prolong survival of non-small cell lung cancer patients

7149

Background: Hypercholesterolemia is one of the most common morbidities in United States. Statins have been proven as effective cholesterol-lowering agents and have been widely used in this country. They have been reported reducing the incidence and risk of various cancer types. However, the impact of using statins on the survival of patients with diagnosed non-small cell lung cancer is unknown. Methods: Ongoing retrospective study involves a cohort of 1,233 patients with diagnosed non-small cell lung cancer. Patients were identified from the Tumor Registry at Henry Ford Health System between January 1999 and December 2004. To date, the electronic medical records from 407 of the 1,233 cases were reviewed. Statistical analyses were performed and stratified for statin users versus non statin users. Results: Data from 407 patients were included in this analysis. There were 109 patients with hypercholesterolemia, 54 of them were statin users at the time of their non-small cell lung cancer diagnosis. Average age was 70 (range 46–85) years for statin users and 65 (range 29–93) years for non statin users. Median survival of 407 subjects was 9.82 months. After stratifying for statin use, the median survival of statin users was 12.38 months while the median survival of non statin users was 9.75 months, with a p value of 0.012. Conclusion: Though small sample size, this study is the first time ever suggesting a possible survival benefit of statin use in patients with non-small cell lung cancer who have received their standard anti-tumor regimens. Other variables that may contribute to this result will be further clarified and discussed after completing the data collection and analysis of this entire cohort. Based on our preliminary result, a prospective study of co-morbidity management with statins in patients with non-small cell lung cancer is warranted.

No significant financial relationships to disclose.

The use of statins and the effect on survival in patients with small cell lung cancer

17121

Background: Hypercholesterolemia is one of the most common morbidities in United States. Statins have been proven as effective cholesterol-lowering agents and have been widely used in this country. They have been reported reducing the incidence and risk of various cancer types. However, the impact of using statins on the survival of patients with diagnosed small cell lung cancer is unknown. Methods: A retrospective study involved a cohort of 282 patients with diagnosed small cell lung cancer. Patients were identified from the Tumor Registry at Henry Ford Health System between January 1995 and December 2002. Electronic medical records of these patients were reviewed. Statistical analyses were performed and stratified for statin users versus non statin users. Results: Out of 282 patients, there were 73 patients with hypercholesterolemia, 37 of them were statin users at the time of their small cell lung cancer diagnosis. Average age was 65 (range 34–87) years for non statin users and 69 (range 52–85) years for statin users. Median survival of 282 subjects was 7.37 months. After stratifying for statin use, the median survival of statin users was 8.66 months while the median survival of non statin users was 7.17 months (p = 0.29). Conclusion: Though slightly prolonged median survival in statin-users was observed, no survival benefit is demonstrated from this patient population. Factors that may have contributed to this result will be further discussed. With the trend of an increase in median survival among statin users, whenever possible, continuation of statins as co-morbidity management may still benefit patients with small cell lung cancer, during their receiving standard anti-tumor therapies.

No significant financial relationships to disclose.

Plasma homocysteine affects fibrin clot permeability and resistance to lysis in human subjects

OBJECTIVE

Homocysteine (Hcy) is a risk factor for thrombosis. We investigated a hypothesis that the clot permeability and its resistance to fibrinolysis is associated with plasma total Hcy (tHcy) in human subjects.

METHODS AND RESULTS

We studied healthy men not taking any medication (n=76), male patients with advanced coronary artery disease (CAD) taking low-dose aspirin (n=33), men with diabetes mellitus diagnosed recently (median hemoglobin A(1c) 7.65%; n=16), and patients with isolated hypercholesterolemia (>7.0 mmol/L; n=15). We assessed clot permeability and turbidimetric lysis time as the determinants of fibrin clot structure. In a regression model, including age and fibrinogen, plasma tHcy was an independent predictor of clot permeation and fibrinolysis time in healthy subjects (R2=0.88, P<0.0001 and R2=0.54, P<0.0001, respectively). In CAD patients, tHcy and fibrinogen were stronger predictors of the permeation coefficient (R2=0.84; P<0.0001) than was fibrinogen alone (R2=0.66; P<0.0001), whereas tHcy was the only predictor of lysis time (R2=0.69; P<0.0001). Elevated tHcy levels observed after methionine load were not associated with any of the fibrin clot properties. In patients with diabetes or hypercholesterolemia, the influence of Hcy on permeation and, to a lesser extent, on the lysis time was obscured by dominant effects of glucose and cholesterol. In 20 asymptomatic men with hyperhomocysteinemia treated with folic acid, reduction in tHcy levels resulted in increased clot permeability (P=0.0002) and shorter lysis time (P<0.0001).

CONCLUSIONS

Our results indicate that plasma tHcy predicts clot permeation and susceptibility to fibrinolysis in healthy men and CAD patients. Our data are consistent with a mechanism of thrombosis in hyperhomocysteinemia, which involves modification of fibrinogen by Hcy-thiolactone.

Understanding the antiphospholipid syndrome and its treatment

The antiphospholipid syndrome (APS) is a clinicopathologic disorder characterized by the persistent presence of anticardiolipin antibodies, lupus anticoagulants, or both in the plasma of patients with arterial or venous thrombosis or obstetric complications. The antiphospholipid antibodies involved in this syndrome have a relatively weak affinity for phospholipid-binding proteins such as b(2) glycoprotein I and prothrombin. In certain conditions they form bivalent antibody-protein complexes that bind with a relatively high affinity to negatively charged phospholipid surfaces. Evidence is accumulating for a pathogenetic role of antiphospholipid antibodies via interference with surface-mediated anticoagulant and procoagulant processes. The syndrome is characterized by the recurrence of thrombotic and obstetric complications. Retrospective studies have suggested that patients with APS and thrombosis need a high-intensity anticoagulant treatment. A few small prospective studies support treatment with a targeted INR of 2 to 3.

Effect of cAMP analogues on glomerular inulin space of isolated rats renal glomeruli

Cyclic AMP has been generally recognised as activator of cAMP-dependent protein kinases. However, there is little evidence about role of cAMP-dependent protein kinase (PKA), in particular izoenzymes PKA-I and PKA-II, in glomeruli contractility. We measured changes of glomerular inulin space (GIS) as a marker of its contractility in the presence of phosphodiesterase resistance cAMP analogues; activators and inhibitors of PKA. Activator of PKA i.e. (Sp) 8-Cl-cAMPS (0.1-100 microM) decreased GIS. (Rp) 8-Cl-cAMPS (0.1-100 microM), inhibitor of PKA, was ineffective but shifted concentration-response curve of (Sp) 8-Cl-cAMPS to right at 50 microM. Specific A site activation by N6-benzoyl-cAMP decreased GIS with maximum at 0.1 microM. Activation of B site by 8-aminobutyloamino-cAMP (0.1-100 microM) had no effect. However, specific activation of both sites on PKA-I or PKA-II by site-selective analogue pairs e.g. 8-aminobutyloamino-cAMP plus 8-piperidino-cAMP or N6-benzoyl-cAMP plus 8-piperidino-cAMP respectively, significantly increased sensitivity of glomeruli to analogues. Our data suggest that activation of PKA-I or PKA-II might have an important role in the regulation of glomerular contractility.

Pregnancy alters nitric oxide synthase and natriuretic peptide systems in the rat left ventricle

Cyclic guanosine monophosphate (cGMP), which is implicated in cardiac cell growth and function, is synthesized by cytoplasmic soluble guanylyl cyclase (GC) stimulated via nitric oxide (NO) and by particulate membrane-bound GC activated via natriuretic peptides. We investigated possible cGMP elevation in the left ventricle (LV) of rats developing physiologic LV hypertrophy during gestation. Furthermore, expression of estrogen receptors (ER) and oxytocin receptors (OTR) was evaluated because their activation stimulates NO and atrial natriuretic peptide (ANP) release from the heart. Compared with nonpregnant controls, Sprague-Dawley rats on day 7 of gestation had similar heart weights, but, on days 14 and 21, ventricular mass increased by 12% and 28% respectively (P< 0.05). LV cGMP concentration was elevated at day 14 of gestation (3.25 +/- 0.12 vs 4.65 +/- 0.17 pmol/g wet weight, P< 0.01) but decreased at day 21 (2.45 +/- 0.09 pmol/g, P< 0.05) to increase again on postpartum day 1 (6.01 +/- 0.15 pmol/g) and day 4 (9.21 +/- 1.79 pmol/g). Changes in endothelial nitric oxide synthase (eNOS), inducible NOS (iNOS), OTR and ERalpha, but not ERbeta, proteins paralleled the pregnancy-related cGMP changes in the LV. In contrast, ANP mRNA of the LV remained at control level throughout gestation but increased postpartum, whereas brain natriuretic peptide (BNP) expression declined at term and increased postpartum. The particulate GC natriuretic peptide receptors (GC-A and GC-B) transcripts were already lower at day 14 of gestation. Natriuretic peptide clearance receptor (NPR-C) transcript was not altered on days 7 and 14, but increased at term. We conclude that cGMP concentration in the rat LV is influenced by both NOS and natriuretic peptide systems and may be involved in the changes of LV contractility and hypertrophy that occur during rat gestation.

The Cardiovascular and Renal Effects of the Potent and Highly Selective μ Opioid Agonist [Dmt1]DALDA

The cardiovascular and renal effects of a mu opioid agonist, [Dmt]DALDA, were studied in conscious Sprague-Dawley rats. During the first hour postinjection, [Dmt]DALDA (0.025-250 microg/rat, IV) evoked a dose-dependent diuresis. The dose of 2.5 microg increased urine volume from 1.0 +/- 0.2 to 3.4 +/- 0.3 mL/h (P < 0.001, n = 30), urinary excretion of sodium, potassium, and cGMP, and induced a mild antihypertensive effect. This dose increased cumulative 4-hour urine volume but significantly inhibited sodium and potassium excretions. The renal and cardiovascular effects were abolished by naloxone (4 mg/kg), but not by naloxonazine (35 mg/kg SC), a selective mu-1 receptor antagonist. Pretreatment with 8 mg/kg naloxone methiodide, an opioid antagonist with limited access to the brain, partially inhibited the renal effects of [Dmt]DALDA. Inhibition of nitric oxide synthases with L-NAME (1 mg/kg) had no effect on the renal and cardiovascular actions of [Dmt]DALDA. Plasma ANP and AVP, measured at 20 and 120 minutes after injection, were not altered by 2.5 and 25 microg [Dmt]DALDA. Therefore, [Dmt]DALDA evokes renal and cardiovascular effects that may primarily be mediated by central naloxonazine-insensitive mu opioid receptors (non-mu-1). These findings indicate that the central mu opioid system is involved in the regulatory mechanism of renal handling of sodium and water.

Changes of atrial natriuretic peptide in rat supraoptic neurones during pregnancy

To better understand the role of atrial natriuretic peptide (ANP) in the central regulation of hydro-mineral homeostasis, we analysed its expression in rat hypothalamic neurones during gestation and postpartum. These physiological events are characterized by opposing body fluid regulations. Quantitative in situ hybridization analysis showed that starting from mid-pregnancy, ANP mRNA declined in neurones of the preoptic area, periventricular area, lateral hypothalamus and endorhinal nucleus, and remained low at postpartum. By contrast, magnocellular cells in the supraoptic nucleus (SON) showed four- and 10-fold more ANP mRNA in sections from preterm and postpartum rats, respectively, compared to nonpregnant controls (P < 0.001). Oxytocin mRNA paralleled ANP mRNA expression in the SON, whereas vasopressin mRNA rose in early pregnancy and declined thereafter. High hypothalamic ANP concentration at day 21 of gestation versus nonpregnant rats (3.1 +/- 0.5 versus 1.8 +/- 0.4 ng/mg protein, P < 0.05) suggested that ANP transcript accumulation in the SON is associated with increased utilization of the peptide. The elevation of hypothalamic ANP (two-fold) and ANP receptors by treatment of ovariectomized rats with 17beta-oestradiol (25 micro g/rat, 10 days) was abolished by coadministration of progesterone. Thus, we concluded that elevated oestradiol at term stimulates ANP synthesis and paracrine ANP activation in the hypothalamus. Overall, we provide experimental, anatomical and molecular evidence for ANP regulation in hypothalamic neurones at preterm and after 17beta-oestradiol stimulation. Our study supports the concept that ANP expressed in the SON acts as a peptidergic neurotransmitter involved in water and salt regulation during pregnancy and postpartum.

Cardiac Effects of Moxonidine in Spontaneously Hypertensive Obese Rats

Moxonidine, an imidazoline receptor agonist that acts centrally to inhibit sympathetic activity, has been shown to reduce effectively blood pressure, fasting insulin levels, and free fatty acids. In this study, we investigated the long-term effects of moxonidine treatment on cardiac natriuretic peptides (ANP and BNP) in Spontaneously Hypertensive Obese Rats (SHROBs), a rat model that resembles human Syndrome X. SHROBs expressing spontaneous hypertension, insulin resistance, and genetic obesity (weight 590 +/- 20 g, at 30 weeks) received moxonidine in chow at 4 mg/kg/day for 15 days. Moxonidine significantly reduced not only systolic blood pressure (187 +/- 6 versus 156 +/- 5 mm Hg, P < 0.05) but also plasma ANP (1595 +/- 371 versus 793 +/- 131 pg/mL, P < 0.05) and BNP (22 +/- 3 versus 14 +/- 1 pg/mL, P < 0.04), without influencing cardiac content of either peptide. Semi-quantitative PCR revealed that atrial ANPmRNA/GAPDHmRNA decreased to 39% 6 10% of pair-fed controls, P < 0.03. In left ventricles, moxonidine also decreased ANP mRNA to 69% +/- 7% and BNP mRNA to 74% +/- 6% of control, P < 0.02, but right ventricular ANP and BNP mRNA were not affected. These findings indicate that chronic inhibition of sympathetic activity with moxonidine in SHROB is associated with decreased ventricular natriuretic peptide transcription, consistent with the cardioprotective effects of moxonidine given the role of ANP and BNP as markers of cadiac disease. Moxonidine also improves the metabolic profile in these rats, thus it may be considered the drug of choice in treatment of metabolic syndrome X.

Renal haemodynamics and natriuretic responses to intravenous administration of diadenosine tetraphosphate (Ap4A) and nicotinamide adenine dinucleotide (NAD) in rat

Effects of Ap4A and NAD--precursor of adenosine, on renal plasma flow (RPF), glomerular filtration rate (GFR) and urine excretion were determined in the anaesthetised rats. Infusion of Ap4A or NAD (i.v., bolus--1 micromol/kg followed by 10 nmol/min/kg) decreased RPF and GFR (by 30 and 40%, respectively). In spite of GFR reduction during Ap4A infusion, the significant increase in sodium excretion and urine flow was noticed: fractional sodium (FENa) and urine excretion (FEurine) rose 15-fold and 2.5-fold in comparison with the control value, respectively. In contrast to Ap4A, NAD-induced decrease in GFR was associated with parallel decrease in sodium and urine excretion, thus the FENa and FEurine did not significantly change. Pretreatment with adenosine deaminase (adenosine degrading enzyme, 2 U/min/kg) or theophylline (P1-receptors antagonist, 0.2 mmol/min/kg) ceased responses to NAD, whereas Ap4A-induced changes were not affected. Pre-treatment with suramin (P2-receptors antagonist, (i.v., bolus--12 mg/kg followed by 1.2 mg/min/kg) completely abolished the renal effects of Ap4A. We conclude that Ap4A may exert specific action on renal function. It acts different from NAD that modified renal function through its hydrolysis product--adenosine. Ap4A might reduce glomerular filtration rate and evoke natriuresis and diuresis, and its effects are probably mediated through stimulation of P2-receptors.

Involvement of Rho-kinase in P2Y-receptor-mediated contraction of renal glomeruli

The involvement of Rho-kinase in P2Y-receptor induced contraction of isolated rat renal glomeruli was investigated. The contraction effects have been investigated based on changes in the intracapillary volume of isolated glomeruli. ATP was found to induce time- and concentration-dependent contraction of isolated glomeruli. Other tested nucleotides (ADP, UTP) and ATP analogues (beta,gamma-methylene-ATP, 2-methylothio-ATP) contracted glomeruli in similar magnitude whereas AMP had no effect. Furthermore, the contractive effect of ATP was prevented in the presence of an antagonist of P2Y-receptors, reactive blue 2. However, a selective antagonist of A1-receptors, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), had no effect. Contraction induced by ATP, ADP, and UTP, in contrast to 2-methylothio-ATP and beta,gamma-methylene-ATP, was prevented in the presence of Rho-kinase's inhibitor, (R)-(+)-trans-N-(4-pyridyl)-4-(1-aminoethyl)-cyclohexanecarboxamide dihydrochloride monohydrate (Y-27632). These findings suggest the involvement of Rho-kinase pathways in P2Y-induced contraction of isolated glomeruli.