Photobiomodulation therapy's effects on cardiac fibrosis activation after experimental myocardial infarction.

INTRODUCTION: Ischemic heart disease is the leading cause of death worldwide, and interventions to reduce myocardial infarction (MI) complications are widely researched. Photobiomodulation therapy (PBMT) has altered multiple biological processes in tissues and organs, including the heart. OBJECTIVES: This study aimed to assess the temporal effects of PBMT on cardiac fibrosis activation after MI in rats. In this proof-of-concept study, we monitored the change in expression patterns over time of genes and microRNAs (miRNAs) involved in the formation of cardiac fibrosis post-MI submitted to PBMT. MATERIALS AND METHODS: Experimental MI was induced, and PBMT was applied shortly after coronary artery ligation (laser light of wavelength 660 nm, 15 mW of power, energy density 22.5 J/cm2 , 60 seconds of application, irradiated area 0.785 cm2 , fluence 1.1 J/cm2 ). Ventricular septal samples were collected at 30 minutes, 3, 6, 24 hours, and 3 days post-MI to determine temporal PBMT's effects on messenger RNA (mRNA) expression associated with cardiac fibrosis activation and miRNAs expression. RESULTS: PBMT, when applied after ischemia, reversed the changes in mRNA expression of myocardial extracellular matrix genes induced by MI. Surprisingly, PBMT modified cardiac miRNAs expression related to fibrosis replacement in the myocardium. Expression correlations between myocardial mRNAs were assessed. The correlation coefficient between miRNAs and target mRNAs was also determined. A positive correlation was detected among miR-21 and transforming growth factor beta-1 mRNA. The miR-29a expression negatively correlated to Col1a1, Col3a1, and MMP-2 mRNA expressions. In addition, we observed that miR-133 and Col1a1 mRNA were negatively correlated. CONCLUSION: The results suggest that PBMT, through the modulation of gene transcription and miRNA expressions, can interfere in cardiac fibrosis activation after MI, mainly reversing the signaling pathway of profibrotic genes.

Physicians' Attitudes Toward Telemedicine Consultations During the COVID-19 Pandemic: Cross-sectional Study.

BACKGROUND: To mitigate the effect of the COVID-19 pandemic, health care systems worldwide have implemented telemedicine technologies to respond to the growing need for health care services during these unprecedented times. In the United Arab Emirates, video and audio consultations have been implemented to deliver health services during the pandemic. OBJECTIVE: This study aimed to evaluate whether differences exist in physicians' attitudes and perceptions of video and audio consultations when delivering telemedicine services during the COVID-19 pandemic. METHODS: This survey was conducted on a cohort of 880 physicians from outpatient facilities in Abu Dhabi, which delivered telemedicine services during the COVID-19 pandemic between November and December 2020. In total, 623 physicians responded (response rate=70.8%). The survey included a 5-point Likert scale to measure physician's attitudes and perceptions of video and audio consultations with reference to the quality of the clinical consultation and the professional productivity. Descriptive statistics were used to describe physicians' sociodemographic characteristics (age, sex, designation, clinical specialty, duration of practice, and previous experience with telemedicine) and telemedicine modality (video vs audio consultations). Regression models were used to assess the association between telemedicine modality and physicians' characteristics with the perceived outcomes of the web-based consultation. RESULTS: Compared to audio consultations, video consultations were significantly associated with physicians' confidence toward managing acute consultations (odds ratio [OR] 1.62, 95% CI 1.2-2.21; P=.002) and an increased ability to provide patient education during the web-based consultation (OR 2.21, 95% CI 1.04-4.33; P=.04). There was no significant difference in physicians' confidence toward managing long-term and follow-up consultations through video or audio consultations (OR 1.35, 95% CI 0.88-2.08; P=.17). Video consultations were less likely to be associated with a reduced overall consultation time (OR 0.69, 95% CI 0.51-0.93; P=.02) and reduced time for patient note-taking compared to face-to-face visits (OR 0.48, 95% CI 0.36-0.65; P<.001). Previous experience with telemedicine was significantly associated with a lower perceived risk of misdiagnosis (OR 0.46, 95% CI 0.3-0.71; P<.001) and an enhanced physician-patient rapport (OR 2.49, 95% CI 1.26-4.9; P=.008). CONCLUSIONS: These results indicate that video consultations should be adopted frequently in the new remote clinical consultations. Previous experience with telemedicine was associated with a 2-fold confidence in treating acute conditions, less than a half of the perceived risk of misdiagnosis, and an increased ability to provide patients with health education and enhance the physician-patient rapport. Additionally, these results show that audio consultations are equivalent to video consultations in providing remote follow-up care to patients with chronic conditions. These findings may be beneficial to policymakers of e-health programs in low- and middle-income countries, where audio consultations may significantly increase access to geographically remote health services.

The action of aripiprazole and brexpiprazole at the receptor level in singultus.

The hiccup (Latin singultus) is an involuntary periodic contraction of the diaphragm followed by glottic closure, which can be a rare side effect of aripiprazole. In contrast to the structurally closely related aripiprazole, brexpiprazole was not associated with this particular adverse drug reaction. Having two very similar drugs that differ in their ability to induce hiccups represents a unique opportunity to gain insight into the receptors involved in the pathophysiology of the symptom and differences in clinical effects between aripiprazole and brexpiprazole. The overlap between maneuvers used to terminate paroxysmal supraventricular tachycardia and those employed to terminate bouts of hiccups suggests that activation of efferent vagal fibers can be therapeutic in both instances. Recent work seems to support a pivotal role for serotonin receptors in such vagal activation. It is unlikely that a unique receptor-drug interaction could explain the different effects of the examined drugs on hiccup. The different effect is most likely the consequence of several smaller effects at more than one receptor. Brexpiprazole is a highly affine (potent) α2C antagonist and, therefore, also an indirect 5-HT1A agonist. In contrast, aripiprazole is a partial 5-HT1A agonist (weak antagonist) and an HT3 antagonist. Activation of 5-HT1A receptors enhances vagal activity while HT3 blockade reduces it. Vagus nerve activation is therapeutic for hiccups. A definitive answer continues to be elusive.

Cardiovascular and Quality of Life Outcomes of a 3-Month Physical Exercise Program in Two Brazilian Communities.

Background: A reduction in physical activity levels in older people is associated with declining quality of life and lower cardiorespiratory fitness levels associated with cardiovascular disease outcomes and mortality from all causes. Evidence supports the positive effect of community-based exercise (CEXE) programs on cardiovascular health and quality of life. This research aimed to examine the effects of a 3-month CEXE on health-related quality of life and cardiovascular risk factors in two Brazilian populations. Methods: Adults with an average age of 70.2 ± 5.4 years were recruited to engage in an individually designed group based CEXE program two to three times/week (aerobic exercise, circuit resistance training, and stretching exercises for 1 h each time). Once a week, competitions were held to improve socialization and collaboration capacity among group members. The CEXE group was compared with a sedentary group. Cardiovascular outcomes were blood pressure, triglycerides, body mass index, waist circumference, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol, total cholesterol, and glycemia. Health-related quality of life was evaluated using the Short Form-36. Results: Of the cardiovascular outcomes studied, the CEXE program significantly reduced systolic blood pressure [5.7 (95% CI 0.2 to 11.3), p < 0.05] and the triglyceride-HDL-C ratio [0.8 (95% CI 0.05 to 1.5), p < 0.05], whereas HDL-C was significantly increased [4.4 (95% CI 0.02 to 8.8), p < 0.05]. A significant improvement in the Short Form-36 subscales occurred in CEXE but not in the control group: physical functioning score [increase of 24.2 (95% CI 11.8 to 36.5) vs. -9.2 (95% CI -21.5 to 3.2), p < 0.001], physical role functioning score [increase of 35.4 (95% CI 12.8 to 58.0) vs. 16.7 (95% CI -6.0 to 39.3), p < 0.01], and general health score [increase of 23.7 (95% CI: 36.9. to 10.4) vs. 2.4 (95% CI -10.9 to 15.7), p < 0.001]. Conclusion: This study shows that in older adults, a 12-week physical activity program can significantly decrease cardiovascular risk and improve health-related quality of life measures. An important transferable sociocultural strategy of our exercise program was to establish social interactions during and outside the CEXE program.

Melatonin, mitochondria and hypertension.

Melatonin, due to its multiple means and mechanisms of action, plays a fundamental role in the regulation of the organismal physiology by fine tunning several functions. The cardiovascular system is an important site of action as melatonin regulates blood pressure both by central and peripheral interventions, in addition to its relation with the renin-angiotensin system. Besides, the systemic management of several processes, melatonin acts on mitochondria regulation to maintain a healthy cardiovascular system. Hypertension affects target organs in different ways and cellular energy metabolism is frequently involved due to mitochondrial alterations that include a rise in reactive oxygen species production and an ATP synthesis decrease. The discussion that follows shows the role played by melatonin in the regulation of mitochondrial physiology in several levels of the cardiovascular system, including brain, heart, kidney, blood vessels and, particularly, regulating the renin-angiotensin system. This discussion shows the putative importance of using melatonin as a therapeutic tool involving its antioxidant potential and its action on mitochondrial physiology in the cardiovascular system.

Association between Carotid Intima Media Thickness and Heart Rate Variability in Adults at Increased Cardiovascular Risk.

Background: Atherosclerotic carotid intima-media thickness (IMT) may be associated with alterations in the sensitivity of carotid baroreceptors. The aim of this study was to investigate the association between carotid IMT and the autonomic modulation of heart rate variability (HRV). Methods: A total of 101 subjects were enrolled in this prospective observational study. The carotid IMT was determined by duplex ultrasonography. The cardiac autonomic function was determined through HRV measures during the Deep Breathing Test. Linear regression models, adjusted for demographics, comorbidities, body mass index, waist-hip-ratio, and left ventricular ejection fraction were used to evaluate the association between HRV parameters and carotid IMT. Results: Participants had a mean age of 60.4 ± 13.4 years and an estimated 10-year atherosclerotic cardiovascular disease (ASCVD) risk score (using the Pooled Cohort Equations) of 16.4 ± 17. The mean carotid media thickness was highest (0.90 ± 0.19 mm) in the first quartile of the standard deviation of all RR intervals (SDNN) (19.7 ± 5.1 ms) and progressively declined in each subsequent quartile to 0.82 ± 0.21 mm, 0.81 ± 0.16 mm, and 0.68 ± 0.19 in quartiles 2 (36.5 ± 5.9 ms), 3 (57.7 ± 6.2 ms) and 4 (100.9 ± 22.2 ms), respectively. In multivariable adjusted models, there was a statistical significant association between SDNN and carotid IMT (OR -0.002; 95%CI -0.003 to -0.001, p = 0.005). The same significant association was found between carotid IMT and other measures of HRV, including coefficient of variation of RR intervals (CV) and dispersion of points along the line of identity (SD2). Conclusions: In a cohort of individuals at increased cardiovascular risk, carotid IMT as a marker of subclinical atherosclerosis was associated with alterations of HRV indicating an impaired cardiac autonomic control, independently of other cardiovascular risk factors.

Quantifying Effects of Pharmacological Blockers of Cardiac Autonomous Control Using Variability Parameters.

Objective: The aim of this study was to identify the most sensitive heart rate and blood pressure variability (HRV and BPV) parameters from a given set of well-known methods for the quantification of cardiovascular autonomic function after several autonomic blockades. Methods: Cardiovascular sympathetic and parasympathetic functions were studied in freely moving rats following peripheral muscarinic (methylatropine), ß1-adrenergic (metoprolol), muscarinic + ß1-adrenergic, α1-adrenergic (prazosin), and ganglionic (hexamethonium) blockades. Time domain, frequency domain and symbolic dynamics measures for each of HRV and BPV were classified through paired Wilcoxon test for all autonomic drugs separately. In order to select those variables that have a high relevance to, and stable influence on our target measurements (HRV, BPV) we used Fisher's Method to combine the p-value of multiple tests. Results: This analysis led to the following best set of cardiovascular variability parameters: The mean normal beat-to-beat-interval/value (HRV/BPV: meanNN), the coefficient of variation (cvNN = standard deviation over meanNN) and the root mean square differences of successive (RMSSD) of the time domain analysis. In frequency domain analysis the very-low-frequency (VLF) component was selected. From symbolic dynamics Shannon entropy of the word distribution (FWSHANNON) as well as POLVAR3, the non-linear parameter to detect intermittently decreased variability, showed the best ability to discriminate between the different autonomic blockades. Conclusion: Throughout a complex comparative analysis of HRV and BPV measures altered by a set of autonomic drugs, we identified the most sensitive set of informative cardiovascular variability indexes able to pick up the modifications imposed by the autonomic challenges. These indexes may help to increase our understanding of cardiovascular sympathetic and parasympathetic functions in translational studies of experimental diseases.

ICU Blood Pressure Variability May Predict Nadir of Respiratory Depression After Coronary Artery Bypass Surgery.

OBJECTIVES: Surgical stress induces alterations on sympathovagal balance that can be determined through assessment of blood pressure variability. Coronary artery bypass graft surgery (CABG) is associated with postoperative respiratory depression. In this study we aimed at investigating ICU blood pressure variability and other perioperative parameters that could predict the nadir of postoperative respiratory function impairment. METHODS: This prospective observational study evaluated 44 coronary artery disease patients subjected to coronary artery bypass surgery (CABG) with cardiopulmonary bypass (CPB). At the ICU, mean arterial pressure (MAP) was monitored every 30 min for 3 days. MAP variability was evaluated through: standard deviation (SD), coefficient of variation (CV), variation independent of mean (VIM), and average successive variability (ASV). Respiratory function was assessed through maximal inspiratory (MIP) and expiratory (MEP) pressures and peak expiratory flow (PEF) determined 1 day before surgery and on the postoperative days 3rd to 7th. Intraoperative parameters (volume of cardioplegia, CPB duration, aortic cross-clamp time, number of grafts) were also monitored. RESULTS: Since, we aimed at studying patients without confounding effects of postoperative complications on respiratory function, we had enrolled a cohort of low risk EuroSCORE (European System for Cardiac Operative Risk Evaluation) with < 2. Respiratory parameters MIP, MEP, and PEF were significantly depressed for 4-5 days postoperatively. Of all MAP variability parameters, the ASV had a significant good positive Spearman correlation (rho coefficients ranging from 0.45 to 0.65, p < 0.01) with the 3-day nadir of PEF after cardiac surgery. Also, CV and VIM of MAP were significantly associated with nadir days of MEP and PEF. None of the intraoperative parameters had any correlation with the postoperative respiratory depression. CONCLUSIONS: Variability parameters ASV, CV, and VIM of the MAP monitored at ICU may have predictive value for the depression of respiratory function after cardiac surgery as determined by peak expiratory flow and maximal expiratory pressure. ClinicalTrials.gov Identifier: NCT02074371.

Avosentan is protective in hypertensive nephropathy at doses not causing fluid retention.

Multiple studies indicate that endothelin antagonism may have a protective effect for chronic kidney disease. Despite that, clinical studies using avosentan have been halted due to adverse effects including fluid overload. Therefore, we aimed at investigating whether avosentan may have protective effects against hypertensive nephropathy at doses below those inducing fluid-retention. We used double transgenic rats (dTGR), overexpressing both the human renin and angiotensinogen gene, which develop malignant hypertension. Effects of avosentan alone or in combination with low-dose of valsartan (angiotensin AT1 receptor antagonist) on end-organ damage were studied. Avosentan induced a decrease of diuresis (18.3%) with a consequent decrease in hematocrit (8.3%) only at the highest dose investigated (100mg/kg). Treatment with the combination of avosentan and valsartan (10 and 0.1mg/kg, once daily by gavage, respectively) decreased albuminuria to a greater extent than each compound given alone (avosentan: 19.6mg/24h; valsartan: 12.9mg/24h; avosentan+valsartan: 1.7mg/24h, data are median values). Histological severity score also showed a drastic reduction of kidney damage. Furthermore, avosentan alone or in combination therapy dramatically decreased mortality compared to the 100% in untreated animals. These data support a therapeutic effect of avosentan at doses below those inducing fluid overload.

The Angiotensin-melatonin axis.

Accumulating evidence indicates that various biological and neuroendocrine circadian rhythms may be disrupted in cardiovascular and metabolic disorders. These circadian alterations may contribute to the progression of disease. Our studies direct to an important role of angiotensin II and melatonin in the modulation of circadian rhythms. The brain renin-angiotensin system (RAS) may modulate melatonin synthesis, a hormone with well-established roles in regulating circadian rhythms. Angiotensin production in the central nervous system may not only influence hypertension but also appears to affect the circadian rhythm of blood pressure. Drugs acting on RAS have been proven effective in the treatment of cardiovascular and metabolic disorders including hypertension and diabetes mellitus (DM). On the other hand, since melatonin is capable of ameliorating metabolic abnormalities in DM and insulin resistance, the beneficial effects of RAS blockade could be improved through combined RAS blocker and melatonin therapy. Contemporary research is evidencing the existence of specific clock genes forming central and peripheral clocks governing circadian rhythms. Further research on the interaction between these two neurohormones and the clock genes governing circadian clocks may progress our understanding on the pathophysiology of disease with possible impact on chronotherapeutic strategies.

Cardiovascular responses evoked by activation or blockade of GABA(A) receptors in the hypothalamic PVN are attenuated in transgenic rats with low brain angiotensinogen.

Previous evidence indicates that a balance between inhibitory gabaergic and excitatory angiotensinergic factors in the PVN is important for cardiovascular control. We investigated the cardiovascular response evoked from activation or blockade of GABA(A) receptors in the paraventricular nucleus (PVN), in transgenic rats with low brain angiotensinogen [TGR(ASrAOGEN)]. Brain Ang II and Ang-(1-7) levels were also determined. In functional experiments, TGR(ASrAOGEN) and Sprague-Dawley rats (SD, control) were anesthetized with urethane and blood pressure (BP), heart rate (HR) and renal sympathetic nerve activity (RSNA) were recorded. Brain Ang II and Ang-(1-7) levels were largely reduced in TGR(ASrAOGEN) compared with SD rats. Inhibition of PVN neurons with the GABA(A) agonist, muscimol (1 nmol/100 nL), resulted in an attenuated fall in all cardiovascular variables in TGR(ASrAOGEN) compared with SD rats. This difference was particularly pronounced in HR (TGR Mus -23±6 bpm vs. -77±9 bpm SD Mus; P<0.05) and RSNA (TGR -3±10% vs.-29±8% SD; P<0.05). Furthermore, the sympathetic response evoked by blockade of GABA(A) receptors in the PVN of TGR(ASrAOGEN) was also largely suppressed. The present data indicate that the sympathetic outflow mediated by PVN neurons under basal conditions is suppressed in TGR(ASrAOGEN) rats corroborating the functional significance of brain angiotensin production in the central regulation of sympathetic output to the cardiovascular system.

Differential diagnosis between experimental endophthalmitis and uveitis in vitreous with Raman spectroscopy and principal components analysis.

Raman spectroscopy has been used for the diagnosis of various eye diseases. A diagnostic tool based on Raman spectroscopy has been developed to discriminate endophthalmitis from uveitis in vitreous tissues of rabbits' eyes in vitro. Twenty-two New Zealand rabbits suffering from endophthalmitis induced by Staphylococcus aureus (n=10), non-infectious uveitis induced by lipopolysaccharide from Escherichia coli (LPS) (n=10 animals) and control (n=2) were included in the study. After eye inoculation, vitreous tissues were dissected and a fragment was submitted to dispersive Raman spectroscopy using near-infrared laser excitation (830 nm, 100 mW) and spectrograph/CCD camera for detection of Raman signal with integration time of 50 s. A routine was developed to classify the spectra of endophthalmitis and uveitis using principal components analysis (PCA) and Mahalanobis distance. The mean Raman spectra of tissues with uveitis and endophthalmitis showed several bands in the region of 800-1800 cm(-1), which have been attributed to nucleic acids, amino acids and proteins from inflamed tissue and proliferating bacteria. The bands at 1004, 1258, 1339, 1451 and 1635 cm(-1) showed statistically significant differences between both diseases. It was observed that principal components PC1, PC3 and PC4 showed statistically significant differences for the two tissue types, indicating that these PCs can be used to discriminate between the two groups. The diagnostic model showed 94% sensitivity, 95% specificity and 95% accuracy using PC3×PC4. The Raman spectroscopy technique has been shown to be useful in differentiating uveitis and endophthalmitis in vitreous tissues in vitro, and these results may be clinically relevant for differentiating vitreous tissues to optimise the diagnosis of inflammatory and infectious vitreoretinal diseases.

Effect of SPP 635, a renin inhibitor, on intraocular pressure in glaucomatous monkey eyes.

The effect of topical application of SPP 635, a renin inhibitor, on intraocular pressure (IOP) was evaluated in the eyes of monkeys with laser induced unilateral glaucoma. A multiple-dose study was performed in 8 glaucomatous monkey eyes with 3 concentrations of SPP 635, 0.2%, 0.3% and 0.4%. IOP was measured hourly for 6 h on each day of the study beginning at 9:30 a.m. Following one baseline day (untreated) and one vehicle-treated day (50 µl drop of vehicle to the glaucomatous eye at 9:30 a.m.), a 50 µl drop (25 µl × 2) of SPP 635, 0.2%, 0.3% or 0.4%, was topically applied to the glaucomatous eye at 9:30 a.m. and 3:30 p.m. for 5 consecutive days. Twice daily administration of each of the 3 concentrations of SPP 635 for 5 days significantly (p < 0.05) reduced IOP. The maximum reduction in IOP occurred 3 or 4 h after morning dosing and was 4.3 ± 0.8 (mean ± SEM) mmHg (14%) for 0.2% SPP 635, 5.3 ± 1.0 mmHg, (19%) for 0.3% SPP 635, and 8.0 ± 1.3 mmHg (25%) for 0.4% SPP 635. The longest duration of IOP reduction was for 6 h with 0.2% or 0.3% SPP 635, and was for at least 18 h with 0.4% concentration. Compared to 0.2% or 0.3% concentrations, 0.4% SPP 635 produced a greater (p < 0.05) and longer duration of IOP reduction (18 vs. 6 h). Mild conjunctival discharge appeared in 2 of 8 eyes, and hyperemia appeared in 2 eyes with the 0.3% and 0.4% concentrations on treatment days 3 and 5. Topically applied SPP 635, a new renin inhibitor, reduces IOP in glaucomatous monkeys in a dose-dependent manner. Renin inhibitors, are a novel class of compounds which may have potential for the treatment of glaucoma.

Local renin-angiotensin system and the brain--a continuous quest for knowledge.

The ancient renin-angiotensin system (RAS) was discovered more than a hundred years ago by identifying the rate-limiting enzyme of the system and its relevance to blood pressure regulation. Forty years ago, Detlev Ganten et al. postulated the existence of a tissue RAS. In these forty years, he kept developing the knowledge of these systems either directly or by training or attracting the interest of many researchers. Through the present review, we try to highlight recent advancements that originated from the postulation of local brain RAS. Although a large amount of knowledge accumulated, this system continues to intrigue and stimulate the interest and imagination of many researchers.

Effect of SPP 301, an endothelin antagonist, on intraocular pressure in glaucomatous monkey eyes.

PURPOSE: To evaluate the effect of topical application of avosentan (SPP 301), endothelin receptor type A antagonist, on intraocular pressure (IOP) in monkey eyes with laser-induced unilateral glaucoma. MATERIALS AND METHODS: A multiple-dose study was performed in eight glaucomatous monkey eyes that were topically treated with SPP 301 by applying a 50 µl drop (25 µl × 2) at 9:30 a.m. and 3:30 p.m. for 5 consecutive days at three concentrations (0.003%, 0.03%, or 0.3%). IOP was measured hourly for 6 hrs on each day of the study beginning at 9:30 a.m. for one baseline day, one vehicle-treated day, and treatment days 1, 3, and 5. RESULTS: Twice daily administration of each of the three concentrations of SPP 301 for 5 days significantly (p < 0.05) reduced IOP. The maximum reduction in IOP occurred 2 or 3 hrs after morning dosing and was 1.8 ± 0.8 (mean ± SEM) mmHg (6%) for 0.003% SPP 301, 4.1 ± 0.7 mmHg (13%) for 0.03% SPP 301, and 7.1 ± 1.3 mmHg (21%) for 0.3% SPP 301. The longest duration of IOP reduction was for 2 hrs with 0.003% SPP 301, and was for at least 6 hrs with 0.03% and 0.3% concentrations. Compared to 0.03% or 0.003% concentrations, 0.3% SPP 301 produced a greater (p < 0.05) IOP reduction. IOP was reduced in fellow untreated normal eyes 2 hr after morning dosing with 0.3% SPP 301, maximum reduction in IOP (11%) occurred on day 1. Of the eyes treated with 0.3% SPP 301, one eye demonstrated mild conjunctival discharge and one eye was closed for 5 min after dosing. CONCLUSION: Topically applied SPP 301, an endothelin antagonist, reduced IOP in glaucomatous monkey eyes in a dose-dependent manner. Endothelin antagonists, a novel class of compound, may have potential for the treatment of glaucoma.

Nigral and striatal regulation of angiotensin receptor expression by dopamine and angiotensin in rodents: implications for progression of Parkinson's disease.

The basal ganglia have a local renin-angiotensin system and it has been shown that the loss of dopaminergic neurons induced by neurotoxins is amplified by local angiotensin II (AII) via angiotensin type 1 receptors (AT1) and nicotinamide adenine dinucleotide phosphate (NADPH) complex activation. Recent studies have revealed a high degree of counter-regulatory interactions between dopamine and AII receptors in non-neural cells such as renal proximal tubule cells. However, it is not known if this occurs in the basal ganglia. In the striatum and nigra, depletion of dopamine with reserpine induced a significant increase in the expression of AT1, angiotensin type 2 receptors (AT2) and the NADPH subunit p47(phox) , which decreased as dopamine function was restored. Similarly, 6-hydroxydopamine-induced chronic dopaminergic denervation induced a significant increase in expression of AT1, AT2 and p47(phox) , which decreased with L-dopa administration. A significant reduction in expression of AT1 mRNA was also observed after administration of dopamine to cultures of microglial cells. Transgenic rats with very low levels of brain AII showed increased AT1, decreased p47 (phox) and no changes in AT2 expression, whereas mice deficient in AT1 exhibited a decrease in the expression of p47 (phox) and AT2. The administration of relatively high doses of AII (100 nm) decreased the expression of AT1, and the increased expression of AT2 and p47(phox) in primary mesencephalic cultures. The results reveal an important interaction between the dopaminergic and local renin-angiotensin system in the basal ganglia, which may be a major factor in the progression of Parkinson's disease.

Transgenic angiotensin-converting enzyme 2 overexpression in vessels of SHRSP rats reduces blood pressure and improves endothelial function.

Rat models of hypertension, eg, spontaneously hypertensive stroke-prone rats (SHRSP), display reduced angiotensin-converting enzyme 2 (ACE2) mRNA and protein expression compared with control animals. The aim of this study was to investigate the role of ACE2 in the pathogenesis of hypertension in these models. Therefore, we generated transgenic rats on a SHRSP genetic background expressing the human ACE2 in vascular smooth muscle cells by the use of the SM22 promoter, called SHRSP-ACE2. In these transgenic rats vascular smooth muscle expression of human ACE2 was confirmed by RNase protection, real-time RT-PCR, and ACE2 activity assays. Transgene expression leads to significantly increased circulating levels of angiotensin-(1-7), a prominent product of ACE2. Mean arterial blood pressure was reduced in SHRSP-ACE2 compared to SHRSP rats, and the vasoconstrictive response to intraarterial administration of angiotensin II was attenuated. The latter effect was abolished by previous administration of an ACE2 inhibitor. To evaluate the endothelial function in vivo, endothelium-dependent and endothelium-independent agents such as acetylcholine and sodium nitroprusside, respectively, were applied to the descending thoracic aorta and blood pressure was monitored. Endothelial function turned out to be significantly improved in SHRSP-ACE2 rats compared to SHRSP. These data demonstrate that vascular ACE2 overexpression in SHRSP reduces hypertension probably by locally degrading angiotensin II and improving endothelial function. Thus, activation of the ACE2/angiotensin-(1-7) axis may be a novel therapeutic strategy in hypertension.

Increased susceptibility to endotoxic shock in transgenic rats with endothelial overexpression of kinin B(1) receptors.

Two kinin receptors have been described, the inducible B(1) and the constitutive B(2). B(1) receptors are important in cardiovascular homeostasis and inflammation. To further clarify their vascular function, we have generated transgenic rats (TGR(Tie2B(1))) overexpressing the B(1) receptor exclusively in the endothelium. Endothelial cell-specific expression was confirmed by B(1)-agonist-induced relaxation of isolated aorta, which was abolished by endothelial denudation of the vessel. This vasodilatation was mediated by nitric oxide (NO) and K(+) channels. TGR(Tie2B(1)) rats were normotensive but, in contrast to controls, reacted with a marked fall in blood pressure and increased vascular permeability after intravenous injection of a B(1) agonist. After lipopolysaccharide treatment, they present a more pronounced hypotensive response and marked bradycardia associated with increased mortality when compared to non-transgenic control animals. Thus, the transgenic rats overexpressing kinin B(1) receptors exclusively in the endothelium generated in this study support an important role of this receptor in the vasculature during the pathogenesis of endotoxic shock.

Mice deficient for both kinin receptors are normotensive and protected from endotoxin-induced hypotension.

Kinins play a central role in the modulation of cardiovascular function and in the pathophysiology of inflammation. These peptides mediate their effects by binding to two specific G-protein coupled receptors named B1 and B2. To evaluate the full functional relevance of the kallikrein-kinin system, we generated mice lacking both kinin receptors (B1B2-/-). Because of the close chromosomal position of both kinin receptor genes, B1B2-/- mice could not be obtained by simple breeding of the single knockout lines. Therefore, we inactivated the B1 receptor gene by homologous recombination in embryonic stem cells derived from B2-deficient animals. The B1B2-/- mice exhibited undetectable levels of mRNAs for both receptors and a lack of response to bradykinin (B2 agonist) and des-Arg9-bradykinin (B1 agonist), as attested by contractility studies with isolated smooth muscle tissues. B1B2-/- mice are healthy and fertile, and no sign of cardiac abnormality was detected. They are normotensive but exhibit a lower heart rate than controls. Furthermore, kinin receptor deficiency affects the pathogenesis of endotoxin-induced hypotension. While blood pressure decreased markedly in wild-type mice and B2-/- and moderately in B1-/- mice after bacterial lipopolysaccharide (LPS) injection, blood pressure remained unchanged in B1B2-/- mice. These results clearly demonstrate a pivotal role of kinins and their receptors in hypotension induced by endotoxemia in mice.