The effects of androgen deprivation therapy on cardiac function and heart failure: implications for management of prostate cancer

Cardiovascular Events and Androgen Receptor Signaling Inhibitors in Advanced Prostate Cancer: A Systematic Review and Meta-Analysis

Importance

Cardiovascular (CV) events remain a substantial cause of mortality among men with advanced and metastatic prostate cancer (PCa). The introduction of novel androgen receptor signaling inhibitors (ARSI) has transformed the treatment landscape of PCa in recent years; however, their associated CV toxic effects remains unclear.

Objective

To assess the incidence of CV events with addition of ARSI to standard of care (SOC) in locally advanced (M0) and metastatic (M1) PCa.

Data Sources

Systematic searches of PubMed, Scopus, Web of Science, EMBASE, and ClinicalTrials.gov were performed from inception up to May 2023.

Study Selection

Randomized clinical trials of ARSI agents (abiraterone, apalutamide, darolutamide, enzalutamide) that reported CV events among individuals with M0 and M1, hormone-sensitive prostate cancer (HSPC) and castration-resistant prostate cancer (CRPC).

Data Extraction and Synthesis

A systematic review was performed in accordance with PRISMA guidance. Two authors screened and independently evaluated studies eligible for inclusion. Data extraction and bias assessment was subsequently performed.

Main Outcomes and Measures

A random-effects meta-analysis was performed to estimate risk ratios for the incidence of all grade and grade 3 or higher CV events (primary outcomes), in addition to hypertension, acute coronary syndrome (ACS), cardiac dysrhythmia, CV death, cerebrovascular event, and venous thromboembolism (secondary outcomes). Sources of heterogeneity were explored using meta-regression.

Results

There were 24 studies (n = 22 166 patients; median age range, 63-77 years; median follow-up time range, 3.9-96 months) eligible for inclusion. ARSI therapy was associated with increased risk of all grade CV event (risk ratio [RR], 1.75; 95% CI, 1.50-2.04; P < .001) and grade 3 or higher CV events (RR, 2.10; 95%, 1.72-2.55; P < .001). ARSI therapy also was associated with increased risk for grade 3 or higher events for hypertension (RR, 2.25; 95% CI, 1.74-2.90; P < .001), ACS (RR, 1.93; 95% CI, 1.43-1.60; P < .01), cardiac dysrhythmia (RR, 1.64; 95% CI, 1.23-2.17; P < .001), cerebrovascular events (RR, 1.86; 95% CI, 1.34-2.59; P < .001) and for CV-related death (RR, 2.02; 95% CI, 1.32-3.10; P = .001). Subgroup analysis demonstrated increased risk of all CV events across the disease spectrum (M0 HSPC: RR, 2.26; 95% CI, 1.36-3.75; P = .002; M1 HSPC: RR, 1.85; 95% CI, 1.47-2.31; P < .001; M0 CRPC: RR, 1.79; 95% CI, 1.13-2.81; P = .01; M1 CRPC: RR, 1.46; 95% CI, 1.16-1.83; P = .001).

Conclusions and Relevance

This systematic review and meta-analysis found that the addition of ARSIs to traditional ADT was associated with increased risk of CV events across the prostate cancer disease spectrum. These results suggest that patients with prostate cancer should be advised about and monitored for the potential of increased risk of CV events with initiation of ARSI therapy alongside conventional hormonal therapy.

Testosterone deficiency impairs cardiac interfibrillar mitochondrial function and myocardial contractility while inducing oxidative stress

Introduction

Clinical studies have shown that low levels of endogenous testosterone are associated with cardiovascular diseases. Considering the intimate connection between oxidative metabolism and myocardial contractility, we determined the effects of testosterone deficiency on the two spatially distinct subpopulations of cardiac mitochondria, subsarcolemmal (SSM) and interfibrillar (IFM).

Methods

We assessed cardiac function and cardiac mitochondria structure of SSM and IFM after 12 weeks of testosterone deficiency in male Wistar rats.

Results and Discussion

Results show that low testosterone reduced myocardial contractility. Orchidectomy increased total left ventricular mitochondrial protein in the SSM, but not in IFM. The membrane potential, size and internal complexity in the IFM after orchidectomy were higher compared to the SHAM group. However, the rate of oxidative phosphorylation with all substrates in the IFM after orchidectomy was lower compared to the SHAM group. Testosterone replacement restored these changes. In the testosterone-deficient SSM group, oxidative phosphorylation was decreased with palmitoyl-L-carnitine as substrate; however, the mitochondrial calcium retention capacity in IFM was increased. There was no difference in swelling of the mitochondria in either group. These changes in IFM were followed by a reduction in phosphorylated form of AMP-activated protein kinase (p-AMPK-α), peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) translocation to mitochondria and decreased mitochondrial transcription factor A (TFAM). Testosterone deficiency increased NADPH oxidase (NOX), angiotensin converting enzyme (ACE) protein expression and reduced mitochondrial antioxidant proteins such as manganese superoxide dismutase (Mn-SOD) and catalase in the IFM. Treatment with apocynin (1.5 mM in drinking water) normalized myocardial contractility and interfibrillar mitochondrial function in the testosterone depleted animals. In conclusion, our findings demonstrate that testosterone deficiency leads to reduced myocardial contractility and impaired cardiac interfibrillar mitochondrial function. Our data suggest the involvement of reactive oxygen species, with a possibility of NOX as an enzymatic source.

Population-based Assessment of Intermittent Androgen Deprivation Therapy Utilization for Relapsed, Nonmetastatic, Hormone-sensitive Adenocarcinoma of the Prostate

OBJECTIVES

Androgen deprivation therapy (ADT) is the standard of care for men with nonmetastatic hormone-sensitive prostate cancer (nmHSPC) after treatment failure. Although intermittent ADT (iADT) is noninferior to continuous ADT for prostate cancer outcomes, with superior quality of life and cost-to-benefit ratio, little is known regarding its real-world utilization. The authors aimed to determine the utilization of iADT in a Canadian Provincial Cancer Program for relapsed nmHSPC and identified risk factors associated with the nonreceipt of iADT.

MATERIALS AND METHODS

This retrospective population-based cohort study used linked administrative databases to identify all patients with relapsed nmHSPC from 2012 to 2016 and quantified ADT prescription history. Patients were defined as iADT eligible if prostate-specific antigen (PSA) was <4 ng/mL and trending downwards on ≥2 sequential PSAs after ≥6 months of ADT. Univariable and multivariable logistic regression analyses were performed to determine factors associated with nonreceipt of iADT.

RESULTS

A total of 601 men with relapsed, nmHSPC were included with a median age at relapse of 73 (range, 46 to 96), pre-ADT PSA of 12.2 ng/mL, and a median pre-ADT PSA doubling time of 7.8 months. 80.9% of the cohort were eligible to receive iADT and 74.4% were treated with iADT. On multivariable analysis, patients originally treated with surgery (odds ratio [OR], 0.19; 95% confidence interval [CI], 0.08-0.46) or having a Gleason Score ≥8 (OR, 0.30; 95% CI, 0.12-0.78) had decreased odds of receipt of iADT. Patients with longer PSA doubling times were more likely to receive iADT (OR, 2.71; 95% CI, 1.17-6.31).

CONCLUSIONS

The utilization of iADT was relatively common for men in Manitoba during the study period, however, the uptake of iADT can be improved among identified subgroups.

Impact of Medical Castration on Malignant Arrhythmias in Patients With Prostate Cancer

Background

Medical castration, gonadotropin‐releasing hormone agonists, and antiandrogens have been widely applied as a treatment for prostate cancer. Sex steroid hormones influence cardiac ion channels. However, few studies have examined the proarrhythmic properties of medical castration.

Methods and Results

This study included 149 patients who underwent medical castration using gonadotropin‐releasing hormones with/without antiandrogen for prostate cancer. The changes in the ECG findings during the therapy and associations of the electrocardiographic findings with malignant arrhythmias were studied. The QT and corrected QT (QTc) intervals prolonged during the therapy compared with baseline (QT, 394±32 to 406±39 ms [P<0.001]; QTc, 416±27 to 439±31 ms [P<0.001]). The QTc interval was prolonged in 119 (79.9%) patients during the therapy compared with baseline. In 2 (1.3%) patients who had no structural heart disease, torsade de pointes (TdP) and ventricular fibrillation (VF) occurred ≥6 months after starting the therapy. In patients with TdP/VF, the increase in the QTc interval from the pretreatment value was >80 ms. However, in patients without TdP/VF, the prevalence of an increase in the QTc interval from the pretreatment value of >50 ms was 11%, and an increase in the QTc interval from the pretreatment value >80 ms was found in only 4 (3%) patients.

Conclusions

Medical castration prolongs the QT/QTc intervals in most patients with prostate cancer, and it could cause TdP/VFs even in patients with no risk of QT prolongation before the therapy. An increase in the QTc interval from the pretreatment value >50 ms might become a predictor of TdP/VF. Much attention should be paid to the QTc interval throughout all periods of medical castration to prevent malignant arrhythmias.

Androgen Deprivation Therapy Use Increases the Risk of Heart Failure in Patients With Prostate Cancer: A Population-Based Cohort Study

The aim of this study was to investigate the relationship between androgen deprivation therapy and heart failure among prostate cancer patients. This cohort study used the data from the Taiwan Longitudinal Health Insurance Database 2005. In the full cohort study, we identified 1244 prostate cancer patients who had received androgen deprivation therapy as the study cohort and 1806 prostate cancer patients who did not receive androgen deprivation therapy as the comparison cohort. To eliminate potential bias, we performed a propensity score-matched cohort study. Each prostate cancer patient was tracked for 1 year from the index date to ascertain whether they were subsequently diagnosed with heart failure. In the full cohort study, incidence rates of heart failure per 100 person-years within the 1-year follow-up period were 4.00 (95%CI, 2.95-5.30) and 1.89 (95%CI, 1.30-2.66) for androgen deprivation therapy users and nonusers, respectively. In addition, the multivariable Cox regression indicated that the hazard ratio (HR) of heart failure among androgen deprivation therapy users was 1.72 (95%CI, 1.08-2.73) compared with those androgen deprivation therapy nonusers. In the propensity score-matched cohort study, the adjusted HR for heart failure among androgen deprivation therapy users was 1.92 (95%CI, 1.15-3.18) compared with propensity score-matched nonusers. In conclusion, this study found that androgen deprivation therapy users had a higher risk of heart failure than nonusers among prostate cancer patients in both the full cohort study and the propensity score-matched study.

Cancer and the Broken Heart: Complications and Implications of Therapy-Related Cardiotoxicity

The growing number of adult long-term cancer survivors has expanded our knowledge of negative physiologic sequelae associated with curative therapies. Of note are the cardiovascular corollaries of chest radiotherapy and some commonly used chemotherapy agents. A contemporary understanding of risk factors has facilitated the development of guidelines for prevention and surveillance of cardiac compromise. The future holds promise with enhanced opportunities to use cardioprotectant drugs and biomarkers to prevent and detect early myocardial changes. Infusion therapy nurses must keep abreast of these developments to facilitate their roles as patient educators and advocates in the face of this toxicity's prevalence.

Cardiovascular safety of abiraterone acetate in metastatic castration-resistant prostate cancer patients: a prospective evaluation

AIM

The aim of this study is to evaluate cardiotoxicity of abiraterone acetate (AA) in metastatic castration-resistant prostate cancer patients (pts) with cardiovascular comorbidities or coronary artery disease (CAD) risk factors.

PATIENTS & METHODS

We prospectively analyzed pts receiving AA in order to evaluate correlations between cardiotoxicity onset and CAD risk factors or cardiovascular comorbidities.

RESULTS

Eighty-seven pts were enrolled, with median treatment duration of 9 months (1-44). At baseline, 84 pts (96%) had CAD risk factors. During treatment four pts (4; 6%) developed hypertension and 26 pts (30%) worsened the preexisting hypertension. Median left ventricular ejection fraction were 64 and 63% at baseline and after treatment, respectively.

CONCLUSION

AA appears to be safe in pts with cardiovascular comorbidities or CAD risk factors.

[Antihormonal therapy in prostate cancer : Side effects]

Androgen deprivation is still standard therapy for prostate cancer, either as primary androgen deprivation therapy or with the use of secondary hormonal drugs including abiraterone and enzalutamide. However, especially the clinically occult side effects like metabolic changes or cardiovascular complications and effects on the psyche of the patient are often not recognized in daily practice. Active monitoring of such side effects is essential for prevention and early intervention. In addition, the efficacy of androgen deprivation therapies is limited by primary and secondary resistance. The underlying molecular mechanism including splice variants of the androgen receptor in contrast to mutations are usually reversible and should be regarded as a sign of efficacy of the current treatment. Therefore, the clever, timely use of androgen deprivation or even the use of a bipolar androgen therapy should enable reversal of resistance to again render tumor cells sensitive to androgen-deprivation therapy.

Cardiovascular toxicities of systemic treatments of prostate cancer

Prostate cancer is the most common cancer in men, with an incidence that is expected to increase in the coming years. Prostate cancer is usually diagnosed in men >65 years of age, thus the concurrent presence of cardiovascular diseases might influence the treatment, owing to the increased risk of cardiovascular mortality. The introduction of new drugs, such as abiraterone and enzalutamide for the management of metastatic disease has created further interest in treatment-related cardiovascular toxicities, although limited data from trials specifically designed to identify cardiovascular toxicities of these agents are currently available. The only available data are derived from published phase II-III study reports, expanded access or compassionate use programmes and meta-analyses of the effects of systemic therapies that are already approved for use in clinical practice or are in the early phases of development. These data are conflicting, although they seem to suggest that certain drugs are associated with an increased risk of cardiovascular adverse events. Clinical trial methodology could be improved by the enrolment of greater numbers of patients >65 years of age, and the use of comprehensive cardiological evaluations. Moreover, closer collaboration between oncologists and cardiologists is essential for the identification and/or management of cardiovascular adverse events in patients with prostate cancer.

[Cardiovascular risk patients under androgen deprivation therapy: Lower risk with GnRH antagonists compared to LHRH agonists?]

BACKGROUND

Androgen deprivation therapy (ADT) with gonadotropin-releasing hormone (GnRH) agonists or GnRH antagonists is the mainstay of treatment for metastatic prostate cancer (mCaP). However, ADT is associated with serious cardiovascular events. Only a few studies that directly compare the cardiovascular risk of LHRH agonists versus GnRH antagonists have been published.

OBJECTIVES

This review aims to compare the cardiovascular risk of LHRH agonists versus GnRH antagonists based on the literature.

METHODS

A literature search that considered full publications and abstracts published before December 10, 2014 was performed. Due to their high evidence quality, only meta-analyses and pooled studies were included in this review.

RESULTS

Four studies were included. These investigated the cardiovascular risk of patients receiving an ADT with LHRH agonists and/or GnRH antagonists. However, only one of these directly compared the cardiovascular risk of ADT with LHRH agonists versus GnRH antagonists. This meta-analysis showed a significant reduction in cardiovascular risk for patients receiving a GnRH antagonist compared to those patients receiving a LHRH agonist (HR: 0.597; 95 % CI: 0.380-0.938; P = 0.0253). Subgroup analyses showed that, in particular, patients with pre-existing cardiovascular diseases who were treated with a GnRH antagonist have a significantly lower risk of experiencing a cardiovascular event when compared with patients receiving a GnRH agonist (HR: 0.44; 95 % CI: 0.26-0.74; P = 0.002).

CONCLUSION

In conclusion, GnRH antagonists are associated with a lower risk of cardiovascular events, compared with LHRH agonists, when administered as ADT in CaP patients, and particularly in patients with a history of cardiovascular disease. Thus, patients with a history of cardiovascular disease may benefit from ADT with a GnRH antagonist.

Molecular mechanisms underlying resistance to androgen deprivation therapy in prostate cancer

Prostate cancer (PCa) is the most widely diagnosed male cancer in the Western World and while low- and intermediate-risk PCa patients have a variety of treatment options, metastatic patients are limited to androgen deprivation therapy (ADT). This treatment paradigm has been in place for 75 years due to the unique role of androgens in promoting growth of prostatic epithelial cells via the transcription factor androgen receptor (AR) and downstream signaling pathways. Within 2 to 3 years of ADT, disease recurs-at which time, patients are considered to have castration-recurrent PCa (CR-PCa). A universal mechanism by which PCa becomes resistant to ADT has yet to be discovered. In this review article, we discuss underlying molecular mechanisms by which PCa evades ADT. Several major resistance pathways center on androgen signaling, including intratumoral and adrenal androgen production, AR-overexpression and amplification, expression of AR mutants, and constitutively-active AR splice variants. Other ADT resistance mechanisms, including activation of glucocorticoid receptor and impairment of DNA repair pathways are also discussed. New therapies have been approved for treatment of CR-PCa, but increase median survival by only 2-8 months. We discuss possible mechanisms of resistance to these new ADT agents. Finally, the practicality of the application of "precision oncology" to this continuing challenge of therapy resistance in metastatic or CR-PCa is examined. Empirical validation and clinical-based evidence are definitely needed to prove the superiority of "precision" treatment in providing a more targeted approach and curative therapies over the existing practices that are based on biological "cause-and-effect" relationship.

Sex differences in the regulation of spatially distinct cardiac mitochondrial subpopulations

Spatially distinct mitochondrial subpopulation may mediate myocardial pathology through permeability transition pore opening (MPTP). The goal of this study was to assess sex differences on the two spatially distinct mitochondrial subpopulations: subsarcolemmal mitochondria (SSM) and intermyofibrillar mitochondria (IFM) based on morphology, membrane potential, mitochondrial function, oxidative phosphorylation, and MPTP. Aged matched Wistar rats were used to study SSM and IFM. Mitochondrial size was larger in SSM than in IFM in both genders. However, SSM internal complexity, yield, and membrane potential were higher in male than in female. The maximal rate of mitochondrial respiration, states 3 and 4, using glutamate + malate as substrate, were higher in IFM and SSM in the male group compared to female. The respiratory control ratio (RCR-state3/state 4), was not different in both SSM and IFM with glutamate + malate. The ADP:O ratio was found higher in IFM and SSM from female compared to males. When pyruvate was used, state 3 was found unchanged in both IFM and SSM, state 4 was also greater in male IFM compared to female. The RCR increased in the SSM while IFM remained the same. State 4 was higher in male SSM while in the IFM remained the same. The IFM presented a higher Ca(2+) retention capacity compared with SSM, however, there was a greater sensitivity to Ca(2+)-induced MPTP in SSM and IFM in the male group compared to female. In conclusion, our data show that spatially distinct mitochondrial subpopulations have sex-based differences in oxidative phosphorylation, morphology, and calcium retention capacity.

Will testosterone replacement therapy become a new treatment of chronic heart failure? A review based on 8 clinical trials

BACKGROUND

According to the present evidences suggesting association between low testosterone level and prediction of reduced exercise capacity as well as poor clinical outcome in patients with heart failure, we sought to determine if testosterone replacement therapy (TRT) improves clinical and cardiovascular conditions as well as quality of life status in patients with stable chronic heart failure (CHF).

METHODS

We carried out a review based on 8 published clinical trials to determine whether TRT will benefit patients with CHF. Information of exercise capacity, hemodynamic parameters, electrocardiogram indicators, muscle strength, echocardiography guidelines and laboratory indexes were collected to assess clinical outcomes.

RESULTS

We found that TRT could improve significantly exercise capacity, muscle strength and electrocardiogram indicators but no significant changes in ejection fraction (EF), systolic blood pressure (SBP), diastolic blood pressure (DBP), N-terminal pro-brain natriuretic peptide (NT-proBNP), tumor necrosis factor-α (TNF-α), high-sensitivity C-reactive protein (hs-CRP) and interleukin-6 (IL-6).

CONCLUSIONS

High-quality studies are required to better understand the clinical effects of testosterone.

[Cardiovascular risk of androgen deprivation therapy for treatment of hormone-dependent prostate cancer : Differences between GnRH antagonists and GnRH agonists]

BACKGROUND

Several studies have indicated that reduction of testosterone levels in patients with prostate cancer undergoing androgen deprivation therapy (ADT) with gonadotropin-releasing hormone (GnRH) agonists can be associated with an increased risk of cardiovascular events. The GnRH antagonists have a different mode of action compared with GnRH agonists and may be preferred in ADT for patients with cardiovascular disease.

OBJECTIVE

This review article discusses potential mechanisms underlying the development of cardiovascular events associated with ADT when using GnRH agonists and explains the differences in mode of action between GnRH agonists and GnRH antagonists. Additionally, relevant studies are presented and practical recommendations for the clinical practice are provided.

MATERIAL AND METHODS

A literature search was performed. Full publications and abstracts published in the last 10 years up to September 2015 were considered to be eligible.

RESULTS

The GnRH antagonists were associated with a decreased risk of cardiovascular events compared with GnRH agonists in prostate cancer patients undergoing ADT and particularly in patients with cardiovascular risk factors or a history of cardiovascular disease. This decrease may be due to the different mode of action of GnRH antagonists compared with GnRH agonists.

CONCLUSION

Prostate cancer patients with either cardiovascular disease or an increased risk of experiencing a cardiovascular event undergoing ADT should be preferentially treated with GnRH antagonists.

Therapeutic Rationales, Progresses, Failures, and Future Directions for Advanced Prostate Cancer

Patients with localized prostate cancer (PCa) have several therapeutic options with good prognosis. However, survival of patients with high-risk, advanced PCa is significantly less than patients with early-stage, organ-confined disease. Testosterone and other androgens have been directly linked to PCa progression since 1941. In this review, we chronicle the discoveries that led to modern therapeutic strategies for PCa. Specifically highlighted is the biology of androgen receptor (AR), the nuclear receptor transcription factor largely responsible for androgen-stimulated and castrate-recurrent (CR) PCa. Current PCa treatment paradigms can be classified into three distinct but interrelated categories: targeting AR at pre-receptor, receptor, or post-receptor signaling. The continuing challenge of disease relapse as CR and/or metastatic tumors, destined to occur within three years of the initial treatment, is also discussed. We conclude that the success of PCa therapies in the future depends on targeting molecular mechanisms underlying tumor recurrence that still may affect AR at pre-receptor, receptor, and post-receptor levels.

Dual-5α-Reductase Inhibition Promotes Hepatic Lipid Accumulation in Man

CONTEXT

5α-Reductase 1 and 2 (SRD5A1, SRD5A2) inactivate cortisol to 5α-dihydrocortisol in addition to their role in the generation of DHT. Dutasteride (dual SRD5A1 and SRD5A2 inhibitor) and finasteride (selective SRD5A2 inhibitor) are commonly prescribed, but their potential metabolic effects have only recently been identified.

OBJECTIVE

Our objective was to provide a detailed assessment of the metabolic effects of SRD5A inhibition and in particular the impact on hepatic lipid metabolism.

DESIGN

We conducted a randomized study in 12 healthy male volunteers with detailed metabolic phenotyping performed before and after a 3-week treatment with finasteride (5 mg od) or dutasteride (0.5 mg od). Hepatic magnetic resonance spectroscopy (MRS) and two-step hyperinsulinemic euglycemic clamps incorporating stable isotopes with concomitant adipose tissue microdialysis were used to evaluate carbohydrate and lipid flux. Analysis of the serum metabolome was performed using ultra-HPLC-mass spectrometry.

SETTING

The study was performed in the Wellcome Trust Clinical Research Facility, Queen Elizabeth Hospital, Birmingham, United Kingdom.

MAIN OUTCOME MEASURE

Incorporation of hepatic lipid was measured with MRS.

RESULTS

Dutasteride, not finasteride, increased hepatic insulin resistance. Intrahepatic lipid increased on MRS after dutasteride treatment and was associated with increased rates of de novo lipogenesis. Adipose tissue lipid mobilization was decreased by dutasteride. Analysis of the serum metabolome demonstrated that in the fasted state, dutasteride had a significant effect on lipid metabolism.

CONCLUSIONS

Dual-SRD5A inhibition with dutasteride is associated with increased intrahepatic lipid accumulation.

Testosterone modulates cardiac contraction and calcium homeostasis: cellular and molecular mechanisms

The incidence of cardiovascular disease rises dramatically with age in both men and women. Because a woman's risk of cardiovascular disease rises markedly after the onset of menopause, there has been growing interest in the effect of estrogen on the heart and its role in the pathophysiology of these diseases. Much less attention has been paid to the impact of testosterone on the heart, even though the levels of testosterone also decline with age and low-testosterone levels are linked to the development of cardiovascular diseases. The knowledge that receptors for all major sex steroid hormones, including testosterone, are present on individual cardiomyocytes suggests that these hormones may influence the heart at the cellular level. Indeed, it is well established that there are male-female differences in intracellular Ca(2+) release and contraction in isolated ventricular myocytes. Growing evidence suggests that these differences arise from effects of sex steroid hormones on processes involved in intracellular Ca(2+) homeostasis. This review considers how myocardial contractile function is modified by testosterone, with a focus on the impact of testosterone on processes that regulate Ca(2+) handling at the level of the ventricular myocyte. The idea that testosterone regulates Ca(2+) handling in the heart is important, as Ca(2+) dysregulation plays a key role in the pathogenesis of a variety of different cardiovascular diseases. A better understanding of sex hormone regulation of myocardial Ca(2+) homeostasis may reveal new targets for the treatment of cardiovascular diseases in all older adults.

Binding site of activators of the cystic fibrosis transmembrane conductance regulator in the nucleotide binding domains

The use of substances that could activate the defective chloride channels of the mutant cystic fibrosis transmembrane conductance regulator (CFTR) has been suggested as possible therapy for cystic fibrosis. Using epithelia formed by cells stably transfected with wildtype or mutant (G551D, G1349D) CFTR, we estimated the apparent dissociation constant, K(D), of a series of CFTR activators by measuring the increase in the apical membrane current. Modification of apparent K(D) of CFTR activators by mutations of the nucleotide-binding domains (NBDs) suggests that the binding site might be in these regions. The human NBD structure was predicted by homology with murine NBD1. An NBD1-NBD2 complex was constructed by overlying monomers to a bacterial ABC transporter NBD dimer in the "head-to-tail" conformation. Binding sites for CFTR activators were predicted by molecular docking. Comparison of theoretical binding free energy estimated in the model to free energy estimated from the apparent dissociation constants, K(D), resulted in a remarkably good correlation coefficient for one of the putative binding sites, located in the interface between NBD1 and NBD2.