LRRK2 kinase inhibition reverses G2019S mutation-dependent effects on tau pathology progression

BACKGROUND

Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most common cause of familial Parkinson's disease (PD). These mutations elevate the LRRK2 kinase activity, making LRRK2 kinase inhibitors an attractive therapeutic. LRRK2 kinase activity has been consistently linked to specific cell signaling pathways, mostly related to organelle trafficking and homeostasis, but its relationship to PD pathogenesis has been more difficult to define. LRRK2-PD patients consistently present with loss of dopaminergic neurons in the substantia nigra but show variable development of Lewy body or tau tangle pathology. Animal models carrying LRRK2 mutations do not develop robust PD-related phenotypes spontaneously, hampering the assessment of the efficacy of LRRK2 inhibitors against disease processes. We hypothesized that mutations in LRRK2 may not be directly related to a single disease pathway, but instead may elevate the susceptibility to multiple disease processes, depending on the disease trigger. To test this hypothesis, we have previously evaluated progression of α-synuclein and tau pathologies following injection of proteopathic seeds. We demonstrated that transgenic mice overexpressing mutant LRRK2 show alterations in the brain-wide progression of pathology, especially at older ages.

METHODS

Here, we assess tau pathology progression in relation to long-term LRRK2 kinase inhibition. Wild-type or LRRK2G2019S knock-in mice were injected with tau fibrils and treated with control diet or diet containing LRRK2 kinase inhibitor MLi-2 targeting the IC50 or IC90 of LRRK2 for 3-6 months. Mice were evaluated for tau pathology by brain-wide quantitative pathology in 844 brain regions and subsequent linear diffusion modeling of progression.

RESULTS

Consistent with our previous work, we found systemic alterations in the progression of tau pathology in LRRK2G2019S mice, which were most pronounced at 6 months. Importantly, LRRK2 kinase inhibition reversed these effects in LRRK2G2019S mice, but had minimal effect in wild-type mice, suggesting that LRRK2 kinase inhibition is likely to reverse specific disease processes in G2019S mutation carriers. Additional work may be necessary to determine the potential effect in non-carriers.

CONCLUSIONS

This work supports a protective role of LRRK2 kinase inhibition in G2019S carriers and provides a rational workflow for systematic evaluation of brain-wide phenotypes in therapeutic development.

Early inflammation precedes cardiac fibrosis and heart failure in desmoglein 2 murine model of arrhythmogenic cardiomyopathy

The study of a desmoglein 2 murine model of arrhythmogenic cardiomyopathy revealed cardiac inflammation as a key early event leading to fibrosis. Arrhythmogenic cardiomyopathy (AC) is an inherited heart muscle disorder leading to ventricular arrhythmias and heart failure due to abnormalities in the cardiac desmosome. We examined how loss of desmoglein 2 (Dsg2) in the young murine heart leads to development of AC. Apoptosis was an early cellular phenotype, and RNA sequencing analysis revealed early activation of inflammatory-associated pathways in Dsg2-null (Dsg2^-/-) hearts at postnatal day 14 (2 weeks) that were absent in the fibrotic heart of adult mice (10 weeks). This included upregulation of iRhom2/ADAM17 and its associated pro-inflammatory cytokines and receptors such as TNFα, IL6R and IL-6. Furthermore, genes linked to specific macrophage populations were also upregulated. This suggests cardiomyocyte stress triggers an early immune response to clear apoptotic cells allowing tissue remodelling later on in the fibrotic heart. Our analysis at the early disease stage suggests cardiac inflammation is an important response and may be one of the mechanisms responsible for AC disease progression.

Cardiovascular risk assessment in women - an update

Cardiovascular disease is the leading cause of morbidity and mortality in postmenopausal women. Although it is a disease of aging, vascular disease initiates much earlier in life. Thus, there is a need to be aware of the potential to prevent the development of the disease from an early age and continue this surveillance throughout life. The menopausal period and early menopause present an ideal opportunity to assess cardiovascular risk and plan accordingly. Generally in this period, women will be seen by primary health-care professionals and non-cardiovascular specialists. This review addresses female-specific risk factors that may contribute to the potential development of cardiovascular disease. It is important for all health-care professionals dealing with women in midlife and beyond to be cognisant of these risk factors and to initiate female-specific preventative measures or to refer to a cardiovascular specialist.

Eating-related anxiety in individuals with eating disorders

Although previous research has supported the importance of anxiety as an etiological and maintenance factor for eating disorders, the specific mechanisms are not well understood. The role of anxiety in the context of eating behavior is especially unclear. The purpose of this study was to identify anxiety-eliciting eating situations and anxiety management strategies patients use to mitigate anxiety experienced in the context of eating as determined by diagnostic groups and symptom patterns. Fifty-three eating disorder outpatients were administered the Eating and Anxiety Questionnaire (EAQ) and the Eating Disorder Diagnostic Scale. Ratings indicated significant anxiety in most eating situations, whereas management strategies were more limited yet regularly employed. Factor analysis of the EAQ revealed a 6-factor solution for anxiety management strategies and a 4-factor solution for anxiety-eliciting situations. These results indicate patients with eating disorders report high levels of anxiety associated with eating behaviors but utilize limited yet consistent anxiety management strategies. Effective intervention strategies for managing eating-related anxiety should be incorporated into treatment and may need to be specified for different diagnostic subgroups.

Fluorescence-labeled reporter gene in transgenic mice provides a useful tool for investigating cutaneous innervation

B6.Cg-Tg(Thy1-YFP)16Jrs/J transgenic mice were created to express the yellow fluorescent protein gene driven by a mouse Thy1 promoter that labeled motor and sensory neurons such that individual nerves could be followed. These mice were used to identify nerves in the skin that innervate the erector pili and panniculus carnosus muscle. Whole mounts demonstrated yellow fluorescent protein expression in nerves of the skin, which was confirmed by labeling the neuromuscular junction with fluorescinated α-bungarotoxin. Frozen and paraffin-embedded skin sections revealed innervation of the panniculus carnosus muscle. Paraffin sections labeled with an anti-green fluorescent protein antibody revealed innervation of the panniculus carnosus as well as the erector pili muscle and around the hair follicle bulge.

Group support to improve psychosocial well-being and primary-care demands among women with cardiac syndrome X

BACKGROUND

Women with angina pectoris, a positive exercise electrocardiogram (ECG) for myocardial ischemia and angiographically smooth coronary arteries (cardiac syndrome X), are often characterized by unresolved symptomatology and a poor quality of life. Psychological morbidity and quality of life appear to be related to social support and social isolation. An investigation of group support as an aid to treatment for cardiac syndrome X was therefore undertaken.

METHODS

Forty-nine women with cardiac syndrome X (mean ± standard deviation 61.8 ± 8 years) were randomized to 12 monthly support group meetings or usual care control. The Health Anxiety Questionnaire (HAQ), Hospital Anxiety and Depression Scale (HADS), SF-36, York Angina Beliefs scale, ENRICHD Social Support Instrument (ESSI) and a demographic information scale, along with hospital admissions, general practitioner (GP) or cardiologist appointments were measured at baseline, 6 months and 12 months.

RESULTS

Support group participants maintained higher levels of social support than controls (ESSI score, 17.18 ± 5.35 vs. 14.45 ± 6.98, p = 0.008). Near significant improvements in health beliefs total score (p = 0.068) and threat perception (p = 0.062) were found among the support group compared to the control; 29% of support patients had made one or more GP visits over the duration of the study, compared with 54% of the control group (p = 0.06).

CONCLUSION

Support group participation maintains social support and may reduce health-care demands and misconceived health beliefs among patients with cardiac syndrome X.

Esterified estrogens combined with methyltestosterone improve emotional well-being in postmenopausal women with chest pain and normal coronary angiograms

OBJECTIVE

The cardiac syndrome X is described as the triad of angina pectoris, a positive exercise test for myocardial ischemia, and angiographically smooth coronary arteries. Although syndrome X does not result in an increased risk of cardiovascular mortality, the symptoms are often troublesome and unresponsive to conventional antianginal therapy. The majority of patients are postmenopausal, and estrogen therapy can alleviate anginal symptoms. We investigated the effect of esterified estrogens combined with methyltestosterone (Estratest) on quality of life in postmenopausal women with syndrome X.

DESIGN

Patients were withdrawn from antianginal therapy. Sublingual nitrates were allowed for treatment of anginal episodes. Patients underwent treadmill testing, and quality of life was assessed by using the Short Form-36 and Cardiac Health Profile questionnaires after the women had received 8 weeks of Estratest or identical placebo in a randomized, double-blind, cross-over study.

RESULTS

Nineteen patients were randomized, and 16 patients completed the protocol. Plasma 17beta-estradiol concentrations were significantly increased by Estratest; however, total testosterone levels were not. The "emotional" score of the Cardiac Health Profile questionnaire was significantly improved after Estratest use compared with placebo (p = 0.03); however, there was no significant change in the Short Form-36 questionnaire for any variable. Estratest significantly increased systolic blood pressure and rate pressure product at rest but had no effect on exercise parameters. Time to onset of chest pain during exercise was also unaffected.

CONCLUSIONS

We have demonstrated a beneficial effect of Estratest on emotional well-being in postmenopausal women with cardiological syndrome X. There was no significant treatment effect on exercise parameters, including time to onset of chest pain.

Effect of sex hormones on cardiac mass

Increased left-ventricular mass is an important cardiovascular risk factor for morbidity and mortality. Apart from obvious differences in cardiac size, the changes in left-ventricular mass in response to age and hypertrophic stimuli are very different in men and women. Whereas left-ventricular mass increases with age in apparently healthy women, it remains constant in men. Under increased cardiac loading conditions, such as hypertension or aortic stenosis, this disparity between sexes is even more striking. Findings are especially pronounced in people aged 50 years or older, in whom reproductive hormone concentrations have fallen. Whether the differences in left-ventricular mass changes are related to endogenous sex-hormone concentrations has never been shown. Androgens have anabolic effects on cardiac cells, and oestrogens have antiproliferative properties, we therefore postulate that the normal decline in endogenous sex hormones with age has contrary effects on ventricular mass in men and women in normal and pathological states.

Natural progesterone, but not medroxyprogesterone acetate, enhances the beneficial effect of estrogen on exercise-induced myocardial ischemia in postmenopausal women

OBJECTIVES

We sought to compare the effects of estrogen/transvaginal progesterone gel with estrogen/medroxyprogesterone acetate (MPA) on exercise-induced myocardial ischemia in postmenopausal women with coronary artery disease or previous myocardial infarction, or both.

BACKGROUND

Estrogen therapy beneficially affects exercise-induced myocardial ischemia in postmenopausal women; however, women with an intact uterus also take progestin to protect against uterine malignancies. The effects of combination estrogen/progestin therapy on myocardial ischemia are unknown.

METHODS

Eighteen postmenopausal women (mean +/- SD age 59+/-7 years) were given 17-beta-estradiol in single-blinded manner for four weeks (1 mg/day for three weeks then 2 mg/day for one week). Estradiol (2 mg/day) was then continued, and the patients were randomized (double-blind) for 12 days to either transvaginal progesterone gel (90 mg on alternate days) and oral MPA placebo (10 mg/day), or vice versa. After another two weeks on estradiol alone, the patients crossed over to progestin treatment and repeated the protocol on the opposite treatment. Patients underwent treadmill exercise testing after each estradiol phase and at day 10 of each progestin phase.

RESULTS

Exercise time to myocardial ischemia increased after the first estrogen phase as compared with baseline (mean difference with 95% confidence interval [CI]: 72 s [34 to 110], p = 0.001), and was increased by combination estradiol/progesterone therapy as compared with estradiol/MPA therapy (92 s [35 to 149], p = 0.001)). Two patients (11%) were withdrawn while taking estradiol/MPA owing to unstable angina.

CONCLUSIONS

Combination estrogen/transvaginal progesterone gel increases exercise time to myocardial ischemia, as compared with estrogen/MPA. These results imply that the choice of progestin in women at higher cardiovascular risk requires careful consideration.

Tamoxifen acutely relaxes coronary arteries by an endothelium-, nitric oxide-, and estrogen receptor-dependent mechanism

In epidemiological studies tamoxifen has been associated with a reduction in the incidence of fatal myocardial infarction in women. However, the effects of tamoxifen on coronary artery reactivity are unknown. We hypothesized that tamoxifen would relax precontracted isolated rabbit coronary arteries. Rings of coronary artery from adult male and nonpregnant female New Zealand White rabbits were suspended in organ baths containing Krebs' solution; isometric tension was measured. Tamoxifen (0.1-100 microM) induced significant endothelium-dependent relaxation in precontracted rabbit coronary arteries. This relaxation was inhibited by N(omega)-nitro-L-arginine methyl ester and the estrogen receptor antagonist ICI 182,780. There was no significant effect on calcium concentration-dependent contraction curves. These data suggest that tamoxifen has beneficial effects on coronary reactivity that could, at least in part, account for the reduction in risk of fatal myocardial infarction in women taking tamoxifen.

17beta-estradiol decreases endothelin-1 levels in the coronary circulation of postmenopausal women with coronary artery disease

BACKGROUND

Estrogen reverses acetylcholine-induced coronary vasoconstriction via the possible facilitation of endothelium-derived NO. Estrogen also affects endothelium-derived constrictor factors. We therefore investigated the effects of 17beta-estradiol on coronary vasomotor responses to substance P (SP), and coronary sinus endothelin-1 and NO metabolite levels in postmenopausal women with coronary heart disease.

METHODS AND RESULTS

We studied 20 women; 14 received estrogen (mean age 65+/-2 years) and 6 served as ethanol control subjects (age 63+/-3 years). Intracoronary infusions of papaverine (8 mg) and SP were administered before and 20 minutes after 50 pg/min 17beta-estradiol or 0.2 microL/min control. Coronary blood flow was calculated from the diameter, as measured with quantitative coronary angiography, and flow velocity, as measured with intracoronary Doppler. Coronary sinus plasma endothelin-1 and nitrite/nitrate (NO(2)/NO(3)) were measured at baseline, at peak velocity response to each infusion, and every 5 minutes during the estradiol infusion. Endothelin-1 levels were decreased after 20 minutes of estradiol (1.12+/-0.18 versus 0.86+/-0.17 pmol/L baseline2 versus estradiol, P:=0.05). Endothelin-1 levels to SP decreased after 17beta-estradiol (1.29+/-0. 18 versus 1.04+/-0.15 and 1.3+/-0.16 versus 0.99+/-0.17 pmol/L for before versus after estradiol, 10 and 25 pmol/min SP; both P:<0.05). NO(2)/NO(3) levels did not change. There was no change in vasomotor responses to estradiol alone or to papaverine or SP before versus after estradiol.

CONCLUSIONS

Short-term intracoronary 17beta-estradiol administration decreases coronary endothelin-1 levels. There was no enhancement of vasomotor responses to SP after the administration of estrogen, suggesting that the effects of estrogen on coronary acetylcholine responses may be a specific and not a generalized effect on coronary vasoreactivity.

Plant-derived estrogens relax coronary arteries in vitro by a calcium antagonistic mechanism

OBJECTIVES

To investigate the potential for plant derived estrogens (phytoestrogens) genistein, phloretin, biochanin A and zearalanone to relax rabbit coronary arteries in vitro and to determine the mechanism(s) of such relaxation.

BACKGROUND

Epidemiological data suggests a reduction in the incidence of coronary heart disease in humans who have a high intake of phytoestrogens.

METHODS

Isolated rabbit coronary artery rings were suspended in individual organ baths, precontracted with potassium chloride (30 mM), and the relaxing effects and mechanisms of relaxation to genistein, phloretin, biochanin A and zearalanone were determined by measurement of isometric tension.

RESULTS

Genistein, phloretin and biochanin A induced significant gender-independent relaxation in rings with and without endothelium. Inhibition of nitric oxide and prostaglandin synthesis with L-NAME and indomethacin had no effect on genistein-induced relaxation. Relaxation was unaffected by the specific estrogen receptor antagonist ICI 182,780, the ATP-sensitive potassium channel inhibitor glibenclamide and the potassium channel inhibitor, barium chloride. Calcium concentration-dependent contraction curves in high potassium depolarization medium were significantly shifted to the right and downward after incubation with genistein and zearalanone. An inhibitory effect of genistein (2 microM) on L-type calcium current in guinea-pig ventricular myocytes confirmed a calcium antagonist relaxing mechanism of action. In healthy volunteers, plasma genistein levels of approximately 2 microM are achieved after ingestion of a commercially available soy protein drink (Supro) containing 37 mg genistein.

CONCLUSIONS

This study demonstrates that phytoestrogens induce endothelium-independent relaxation of coronary arteries; the mechanism involves calcium antagonism. These mechanisms may contribute to the potential long-term cardiovascular protective effect of these substances.

Testosterone enhances flow-mediated brachial artery reactivity in men with coronary artery disease

Acute administration of high-dose testosterone in men with coronary artery disease improves endothelial function.

Effects of testosterone on coronary vasomotor regulation in men with coronary heart disease

BACKGROUND

The increased incidence of coronary artery disease in men compared with premenopausal women suggests a detrimental role of male hormones on the cardiovascular system. However, testosterone has direct relaxing effects on coronary arteries in animals, as shown both in vitro and in vivo. The effect of testosterone on the human coronary circulation remains unknown.

METHODS AND RESULTS

We studied 13 men (aged 61+/-11 years) with coronary artery disease. They underwent measurement of coronary artery diameter and blood flow after a 3-minute intracoronary infusion of vehicle control (ethanol) followed by 2-minute intracoronary infusions of acetylcholine (10(-7) to 10(-5) mol/L) until peak velocity response. A dose-response curve to 3-minute infusions of testosterone (10(-10) to 10(-7) mol/L) was then determined, and the acetylcholine infusions were repeated. Finally, an intracoronary bolus of isosorbide dinitrate (1000 microgram) was given. Coronary blood flow was calculated from measurements of blood flow velocity using intracoronary Doppler and coronary artery diameter using quantitative coronary angiography. Testosterone significantly increased coronary artery diameter compared with baseline (2.78+/-0. 74 mm versus 2.86+/-0.72 mm [P=0.05], 2.87+/-0.71 mm [P=0.038], and 2.90+/-0.75 mm [P=0.005] for baseline versus testosterone 10(-9) to 10(-7) mol/L, respectively). A significant increase in coronary blood flow occurred at all concentrations of testosterone compared with baseline (geometric mean [95% CI]: 32 [25, 42] versus 36.3 [27, 48] (P=0.006), 35.3 [26, 47] (P=0.029), 36.8 [28, 49] (P=0.002), and 37 [28, 48] (P=0.002), mL/min for baseline versus testosterone 10(-10) to 10(-7) mol/L, respectively). No differences existed in coronary diameter or blood flow responses to acetylcholine before versus after testosterone.

CONCLUSIONS

Short-term intracoronary administration of testosterone, at physiological concentrations, induces coronary artery dilatation and increases coronary blood flow in men with established coronary artery disease.

Raloxifene acutely relaxes rabbit coronary arteries in vitro by an estrogen receptor-dependent and nitric oxide-dependent mechanism

BACKGROUND

Selective estrogen receptor modulators (SERMs) have been defined as compounds that display tissue specificity with regard to estrogenic effects. They appear to share the beneficial effects of estrogen on bone and lipids but are not associated with an increased risk of breast or uterine carcinoma. Estrogen relaxes coronary arteries and has long-term protective effects on the vascular system. The effect of SERMs on the coronary vasculature is unknown. We therefore investigated the effects of the SERM raloxifene on isolated rabbit coronary arteries.

METHODS AND RESULTS

Rings of coronary artery from adult male and nonpregnant female New Zealand White rabbits were suspended in organ baths containing Krebs solution; isometric tension was then measured. Raloxifene induced coronary arterial relaxation in male and female coronary arteries by an endothelium-dependent and estrogen receptor-dependent mechanism involving nitric oxide. Raloxifene also had a direct calcium antagonistic effect on the coronary myocyte. Estrogen, however, induced only endothelium-independent coronary arterial relaxation. The endothelium-dependent component of relaxation induced by raloxifene 10(-6) mol/L resulted in almost 100% (79+/-7% versus 43+/-3%, P<0.001) more relaxation than that induced by estrogen 10(-6) mol/L.

CONCLUSIONS

These data demonstrate that raloxifene has vascular relaxing properties. The surprising finding is that the receptor-dependent effects via the endothelium are observed in coronary arteries from both male and female animals.

Effect of acute testosterone on myocardial ischemia in men with coronary artery disease

The effect of acute testosterone administration on exercise-induced myocardial ischemia was assessed in 14 men with coronary artery disease and low plasma testosterone concentrations in a study of randomized, double-blind, crossover design. Testosterone increased time to 1-mm ST-segment depression compared with placebo by 66 (15 to 117) seconds (p = 0.016), suggesting a beneficial effect of testosterone on myocardial ischemia in these patients.

The effect of angiotensin converting enzyme inhibition on myocardial function and blood pressure after coronary artery bypass surgery--a randomised study

OBJECTIVE

To investigate the effect of 6 weeks' pre-operative treatment with the angiotensin converting enzyme inhibitor, quinapril, on left ventricular function when measured 3 months after coronary artery bypass graft surgery and to examine the safety of such treatment.

PATIENTS AND METHODS

Patients (96) [86 males, 10 females; mean age 61 years] with chronic stable angina, on the waiting list for coronary artery bypass graft surgery, underwent measurement of left ventricular function by resting radionuclide ventriculography. Patients were then randomised to quinapril 20 mg once daily or placebo in a double-blind fashion, in addition to existing anti-anginal therapy and this regimen was continued for up to 6 weeks prior to operation. Measurement of left ventricular function was repeated 3 months following surgery, after recommencement of pre-surgery anti-anginal therapy for 1 week. Effects on systemic vascular resistance (SVR) during bypass were calculated from perfusion records and vasoconstrictor use during operation was documented. The safety of the addition of quinapril to the anti-anginal regimen was assessed by measurement of systemic blood pressure (BP) after the first dose of study medication, measurement of intra-operative BP, administration of inotropes and any intra-operative complications.

RESULTS

There was no difference between treatment groups in the pre-study left ventricular ejection fraction (mean (S.D.); 54.9 (13.8)% versus 55.6 (13.2)%, quinapril versus placebo, respectively), or 3 months after surgery (58.1 (13.6)%, versus 56.9 (12.6)%, quinapril versus placebo, respectively). Left ventricular ejection fraction 3 months after surgery did not change significantly from pre-treatment in either group (2.8 (10.7)% and 1.5 (10.1)%; quinapril and placebo, respectively). There was no first-dose hypotension (systolic BP < 100 mmHg). The intra-operative BP and the SVR during bypass in the two treatment groups were not significantly different. The ischaemic time (mean = 56 min) and the use of inotropes were the same in both groups and there was no mortality.

CONCLUSIONS

Angiotensin converting enzyme inhibitor treatment before coronary artery bypass graft surgery does not have a significant beneficial effect on left ventricular function following coronary artery bypass graft surgery. Angiotensin converting enzyme inhibition, administered in addition to anti-anginal therapy, does not cause first-dose hypotension or increase morbidity or mortality and can safely be used in patients with coronary heart disease prior to coronary artery bypass graft surgery.

Short-term anti-ischemic effect of 17beta-estradiol in postmenopausal women with coronary artery disease

BACKGROUND

Short-term administration of 17beta-estradiol improves effort-induced myocardial ischemia in female patients with coronary artery disease. 17Beta-estradiol also has direct and indirect coronary vascular smooth muscle relaxing properties. The aim of the present study was to evaluate the effect of short-term administration of 17beta-estradiol on pacing-induced myocardial ischemia by means of continuous monitoring of coronary sinus pH in 16 postmenopausal female patients with coronary artery disease.

METHODS AND RESULTS

Patients underwent incremental atrial pacing starting at a rate of 100 bpm and increments of 20 bpm every 2 minutes up to 160 bpm before and 20 minutes after either 17beta-estradiol (1 mg sublingual, 9 patients) or placebo (sublingual, 7 patients). The time to the onset of myocardial ischemia during pacing was significantly increased by 17beta-estradiol (mean+/-SD, 254+/-36 versus 298+/-23 seconds; P<.02) but not by placebo (262+/-45 versus 256+/-34 seconds; P=NS) The pH shift was significantly reduced by 17beta-estradiol but not by placebo at every step of the pacing protocol. The maximum pH shift at peak pacing was significantly reduced by the administration of 17beta-estradiol by 0.022 pH units (95% CI, 0.001, 0.043; P<.04) but not by sublingual placebo (-0.002 pH units; 95% CI, -0.0073, 0.0021; P=NS). The maximum pH shift at maximum comparable pacing was also reduced by 17beta-estradiol by 0.015 pH units (95% CI, 0.012, 0.017; P<.001) but not by placebo (-0.0022 pH units; 95% CI, -0.006, 0.0015; P=NS).

CONCLUSIONS

17Beta-estradiol reduces the degree of pacing-induced myocardial ischemia in postmenopausal patients with coronary artery disease. The reduction of pacing-induced coronary sinus pH shift is consistent with an anti-ischemic effect of the hormone and is not due to preconditioning, as evidenced by the absence of improvement after placebo.

Expression of tenascin-C in bones responding to mechanical load

A number of early biochemical responses of bone cells to mechanical loading have been identified, but the full sequence of events from the sensing of strain to the formation of new bone is poorly characterized. Extracellular matrix proteins can modulate cell behavior and would be ideal molecules to amplify the early response to loading. The extracellular matrix protein, tenascin-C, supports differentiation of cultured osteoblast-like cells. The current study was carried out to investigate whether expression patterns of tenascin-C in loaded bones support a role for this protein as a mediator of the osteoregulatory response to loading. Tenascin-C expression was investigated by Northern blot analysis in rat ulnae subjected to an established noninvasive loading regimen engendering physiological strain levels. RNA extracted from loaded compared with contralateral control bones 6 h after loading showed a significant increase in tenascin-C transcript expression. The presence of tenascin-C was investigated by immunohistochemistry in bones of animals killed 3, 5, or 15 days after the initiation of daily loading. In animals killed at 3 or 5 days, periosteal surfaces undergoing load-induced reversal from resorption to formation showed enhanced tenascin-C staining. In animals killed at 15 days, the bone formed in response to loading was clearly demarcated from old bone by strong tenascin-C staining of reversal lines. Within this new bone, tenascin-C staining was seen in the lacunae of older but not more recently embedded osteocytes. The results presented here indicate that tenascin-C expression by bone cells is enhanced in the early osteogenic response to loading. This may indicate that tenascin-C acts as a mediator of the mechanically adaptive response.

Antianginal, hemodynamic and coronary vascular effects of captopril in stable angina pectoris

A pilot study was performed to assess the short-term effects of intravenous captopril on anginal threshold and systemic and coronary hemodynamics in patients with stable angina pectoris. Twelve patients with documented coronary artery disease, stable angina pectoris and normal left ventricular function were studied by an incremental atrial pacing stress test before and after intravenous captopril (n = 8) or placebo (n = 4). There were no significant differences in the extent of coronary disease or left ventricular function between the 2 groups and resting plasma-renin levels were normal. Captopril increased the time to angina (14 +/- 4 to 9 +/- 5 minutes, p less than 0.05), increased heart rate at development of angina (126 +/- 7 to 142 +/- 7 beats/min, p less than 0.05) and tended to increase coronary blood flow (229 +/- 154 to 296 +/- 259 ml/min, p = 0.11) and decrease coronary vascular resistance (53 +/- 10 to 47 +/- 3 dynes s cm-5/1,000, p = 0.11) at peak stress without alteration in systemic hemodynamics. No significant changes were seen after placebo administration. Therefore, intravenous captopril appears to cause a short-term increase of coronary vascular reserve, and anginal threshold in patients with chronic stable angina. This effect appears to be independent of inhibition of the systemic renin-angiotensin system or systemic hemodynamic changes.

The cardiac lymphatics

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