Organoids as a novel tool in modelling infectious diseases.

Infectious diseases worldwide affect human health and have important societal impacts. A better understanding of infectious diseases is urgently needed. In vitro and in vivo infection models have brought notable contributions to the current knowledge of these diseases. Organoids are multicellular culture systems resembling tissue architecture and function, recapitulating many characteristics of human disease and elucidating mechanisms of host-infectious agent interactions in the respiratory and gastrointestinal systems, the central nervous system and the skin. Here, we discuss the applicability of the organoid technology for modeling pathogenesis, host response and features, which can be explored for the development of preventive and therapeutic treatments.

Exercise training ameliorates adrenergic control in spontaneously hypertensive rats.

The goal of this study was to examine vascular control after sympathetic stimulation by tyramine infusion in hypertensive rats submitted to swimming training. To this end, male rats were assigned to the following groups: sedentary (SN) and trained normotensive (TN), sedentary (SH) and trained hypertensive (TH). Arterial pressure (AP), heart rate (HR), HR variability (HRV), AP variability (APV), and cardiac autonomic function were recorded. Following, infusion of tyramine was administrated. The TN and TH showed a lower resting HR compared with their respective sedentary groups (p < .05). Pressure levels were less in TH than SH (p < .05). The TH showed a higher HRV together with a lower APV in comparison to SH (p < .05). The sympathetic modulation of HRV and APV was lower in TH than in SH (p < .05). Both trained groups presented an increased parasympathetic modulation of HRV compared with their respective sedentary groups (p < .05). The TN and TH groups had a higher vagal effect in comparison with their respective sedentary groups (p < .001). The sympathetic effect was lower in TH than in SH (p < .001). Pressor and HR responses to tyramine in different doses were attenuated in TH (p < .001). Further analysis showed a significant association between infusion of tyramine and normalized LF component of HRV (r = 0.84, p < .001), systolic APV (r = 0.58, p < .001) and diastolic APV (r = 0.49, p < .001). In conclusion, exercise training provokes less pressor response variation by tyramine infusion in hypertensive animals suggesting sympathetic nerve endings adjustments and decrease of the vasoconstrictor effect attenuates injury caused by hypertension improving cardiovascular autonomic dysfunction, which can be associated with sympathetic attenuation.

Cardiac autonomic modulation and long-term use of amiodarone in patients with chronic Chagasic cardiopathy.

BACKGROUND: Patients with chronic Chagas cardiopathy (CCC), which may be associated with cardiac arrhythmias, frequently use amiodarone, an antiarrhythmic drug that, experimentally, appears to modulate the cardiac autonomic function. OBJECTIVE: The present cross-sectional observational study aimed to evaluate autonomic cardiac modulation in patients with CCC undergoing chronic amiodarone therapy. METHODS: Three groups were investigated: Group 1 included patients with CCC not treated with amiodarone (n = 27); Group 2 included patients with CCC with prolonged use (at least 6 months) of amiodarone (n = 16); and Group 3 included non-Chagasic control patients (n = 23). All patients underwent a complete clinical and laboratory assessment, followed by autonomic function tests, consisting of a basal continuous electrocardiogram in the resting supine position for 10 minutes, followed by a change the orthostatic posture for a further 5 minutes. Heart rate variability (HRV) parameters (median and interquartile interval) were quantified using linear methods in the time- and frequency-domains (autoregressive spectral analysis) and nonlinear methods, including symbolic analysis. RESULTS: Patients with CCC using amiodarone had changes in HRV suggestive of an offset in the sympatho-vagal balance with a vagal modulation predominance (normalized HF, 49.7[27.4] vs 31.1[22.8] [P < 0.05]; and percentage 2V, 40.1 [14.6] vs 21.5 [13.4] [P < 0.05] vs untreated CCC group). These changes were further accompanied by increases in parameters indicative of greater complexity of HRV. CONCLUSIONS: The deviation in the sympatho-vagal balance and the increase in the complexity of HRV strongly suggest that amiodarone may have a cardioprotective effect, in addition to its antiarrhythmic effects, which could increase the survival of these patients.

Long-term anabolic steroids in male bodybuilders induce cardiovascular structural and autonomic abnormalities.

OBJECTIVE: The aims of this study were to examine the hypothesis that users of anabolic androgenic steroids (AAS) would have cardiac autonomic disorders and that there is a correlation between sympathetic modulation, high blood pressure (BP) and alterations to cardiac dimensions. METHODS: Forty-five male subjects were enrolled in the study. They were categorized into three groups comprising bodybuilders actively using AAS (AAS users; n = 15), bodybuilders who had never used AAS (nonusers; n = 15) and age-paired healthy sedentary controls (n = 15). Hemodynamic parameters, linear and nonlinear analyses of heart rate variability and electrocardiography and echocardiography analyses were performed at rest. RESULTS: Bodybuilders in the AAS group had a higher mean BP than those in the ASS nonuser group (p < 0.05) and the sedentary controls (p < 0.001). Cardiac sympathetic modulation was higher in AAS users than in AAS nonusers (p < 0.05) and the sedentary controls (p < 0.001), and parasympathetic modulation was lower in AAS users than in nonusers and the sedentary controls (p < 0.05). Shannon entropy was lower in AAS users than in the sedentary (p < 0.05) controls, and the corrected QT interval and QT dispersion were higher in AAS users than in the sedentary controls (p < 0.05). The interventricular septal thickness, left ventricle posterior wall thickness and relative diastolic wall thickness were higher in AAS users than in AAS nonusers and the sedentary controls (p < 0.001). AAS users showed a positive correlation between increased sympathetic modulation and high BP (r = 0.48, p < 0.005), as well as sympathetic modulation and cardiac hypertrophy (r = 0.66, p < 0.001). CONCLUSION: There was a marked cardiac autonomic alteration in AAS users, with a shift toward sympathetic modulation predominance and vagal attenuation. The high BP observed in our group of bodybuilders using AAS was associated with increased sympathetic modulation, and this increased sympathetic modulation was associated with structural alterations in the heart. This association may constitute an important mechanism linking AAS abuse to increased cardiovascular risk.

Amiodarone and itraconazole improve the activity of pentavalent antimonial in the treatment of experimental cutaneous leishmaniasis.

Leishmaniasis affect millions of people, causing morbidity and mortality, especially in developing tropical and subtropical countries. Unfortunately, the possibilities of treatment for these infections are still quite limited and most of the available drugs present serious side effects. The objective of this paper was to evaluate the therapeutic role of amiodarone and itraconazole in the treatment of cutaneous leishmaniasis caused by Leishmania (Leishmania) amazonensis. In order to perform this evaluation, hamsters were infected with 1 × 106 metaciclic promastigotes of the parasite in the hind footpad and, after the onset of the lesions, were treated with glucantime, amiodarone, itraconazole, glucantime and amiodarone, glucantime and itraconazole or amiodarone and itraconazole. The treatments' efficacy was evaluated per analysis of the size of the cutaneous lesions and by parasitic investigation of the infected foot (by histopathological examination and PCR) and possible side effects were analyzed taking into account the weight of the animals and some biochemical and metabolic parameters (glucose, urea, creatinine, AST, ALT and ALP). The results have shown that, in hamsters, amiodarone and itraconazole, either used isolated or in combination, are unable to stop the development of cutaneous lesions caused by L. (L.) amazonensis, but improve the activity of glucantime in the treatment of these lesions and seem to present no evident side effects. More studies are necessary in order to investigate the clinical potential of these combinations, so there can be the possibility of broadening the therapeutic options available, especially in resistant cases.

Priming Mesenchymal Stem Cells with Endothelial Growth Medium Boosts Stem Cell Therapy for Systemic Arterial Hypertension.

Systemic arterial hypertension (SAH), a clinical syndrome characterized by persistent elevation of arterial pressure, is often associated with abnormalities such as microvascular rarefaction, defective angiogenesis, and endothelial dysfunction. Mesenchymal stem cells (MSCs), which normally induce angiogenesis and improve endothelial function, are defective in SAH. The central aim of this study was to evaluate whether priming of MSCs with endothelial growth medium (EGM-2) increases their therapeutic effects in spontaneously hypertensive rats (SHRs). Adult female SHRs were administered an intraperitoneal injection of vehicle solution (n = 10), MSCs cultured in conventional medium (DMEM plus 10% FBS, n = 11), or MSCs cultured in conventional medium followed by 72 hours in EGM-2 (pMSC, n = 10). Priming of the MSCs reduced the basal cell death rate in vitro. The administration of pMSCs significantly induced a prolonged reduction (10 days) in arterial pressure, a decrease in cardiac hypertrophy, an improvement in endothelium-dependent vasodilation response to acetylcholine, and an increase in skeletal muscle microvascular density compared to the vehicle and MSC groups. The transplanted cells were rarely found in the hearts and kidneys. Taken together, our findings indicate that priming of MSCs boosts stem cell therapy for the treatment of SAH.

Modulation of sympathetic activity and heart rate variability by ivabradine.

AIMS: Bradycardic agents are currently used in the treatment of angina and heart failure; direct information on their effects on cardiac sympathetic nerve activity (SNA) may be relevant to their chronic use. The present study evaluates the effect of pacemaker inhibition on SNA; direct nerve recordings and indirect autonomic indexes are compared. METHODS AND RESULTS: Experiments were performed in 18 anaesthetized rats. SNA (direct nerve recording) and heart rate variability (HRV) indexes were evaluated in parallel. All parameters were recorded 10 min before to 60 min after administration of the If blocker ivabradine (IVA; 2 mg/kg, i.v.; n = 8) or vehicle (VEH; n = 5). IVA-induced RR interval (RR) prolongation (at 60 min +15.0 ± 7.1%, P < 0.01) was associated with decreased diastolic arterial pressure (DAP; -17.3 ± 8.4%, P < 0.05) and increased SNA (+51.1 ± 12.3%, P < 0.05). These effects were accompanied by increased RR variance (RRσ(2)), which showed strong positive correlation with RR. Frequency-domain HRV indexes (in normalized units) were unchanged by IVA. After baroreceptor reflexes had been eliminated by sino-aortic denervation (n = 5), similar IVA-induced RR prolongation (at 60 min +14.3 ± 5.9%, NS vs. intact) was associated with a larger DAP reduction (-30.9 ± 4.1%, P < 0.05 vs. intact), but failed to affect SNA. CONCLUSIONS: (i) IVA-induced bradycardia was associated with increased SNA, resulting from baroreceptor unloading; if this applied to chronic IVA use in humans, it would be of relevance for therapeutic use of the drug. (ii) Whenever mean HR is concomitantly changed, time-domain HRV indexes should not be unequivocally interpreted in terms of autonomic balance.

Endogenous resident c-Kit cardiac stem cells increase in mice with an exercise-induced, physiologically hypertrophied heart.

Physical activity evokes well-known adaptations in the cardiovascular system. Although exercise training induces cardiac remodeling, whether multipotent stem cells play a functional role in the hypertrophic process remains unknown. To evaluate this possibility, C57BL/6 mice were subjected to swimming training aimed at achieving cardiac hypertrophy, which was morphologically and electrocardiographically characterized. Subsequently, c-Kit(+)Lin(-) and Sca-1(+)Lin(-) cardiac stem cells (CSCs) were quantified using flow cytometry while cardiac muscle-derived stromal cells (CMSCs, also known as cardiac-derived mesenchymal stem cells) were assessed using in vitro colony-forming unit fibroblast assay (CFU-F). Only the number of c-Kit(+)Lin(-) cells increased in the hypertrophied heart. To investigate a possible extracardiac origin of these cells, a parabiotic eGFP transgenic/wild-type mouse model was used. The parabiotic pairs were subjected to swimming, and the wild-type heart in particular was tested for eGFP(+) stem cells. The results revealed a negligible number of extracardiac stem cells in the heart, allowing us to infer a cardiac origin for the increased amount of detected c-Kit(+) cells. In conclusion, the number of resident Sca-1(+)Lin(-) cells and CMSCs was not changed, whereas the number of c-Kit(+)Lin(-) cells was increased during physiological cardiac hypertrophy. These c-Kit(+)Lin(-) CSCs may contribute to the physiological cardiac remodeling that result from exercise training.

Remodeling of elastic layer of aortic artery after training by swimming in spontaneously hypertensive rats.

Hypertension is a major risk factor for cardiovascular diseases, in which the elastic properties of arteries are subjected to high pressure levels, and networks of elastic fibers may develop cleft longitudinal, transverse, breaks and fragmentation, and such structural changes (fibrosis and degradation of elastin) may lead to a decrease in the elasticity of the artery. The descending thoracic aortas of normotensive Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHRs) subjected to physical training through swimming or those of sedentary rats were prepared with hematoxylin-eosin and Verhoff to assess the artery medial. The images were captured with a videocamera coupled to an ordinary light microscope and the images were analyzed with the same program. SHRs showed a larger area of the medial layer of the thoracic aorta (F = 25,764, P < 0.001), and it was observed that rats submitted to physical training through swimming showed a larger area of the thoracic aorta (t = 3.206, P = 0.011). There was a higher percentage of elastic trained (F = 6.536, P = 0.019). To conclude, this study aimed to determine the elastic component of the aortic artery in animals that underwent exercise when compared with those that did not perform the activity, and analyze the relationship between the area of the aortic wall in trained and sedentary animals. The principal conclusion is that the rigidity of the aorta is not increased in SHRs subjected to physical training compared with that of trained WKY animals; however, when sedentary SHRs were analyzed there was a decrease in the elasticcomponent, which can characterize the aortic arterial stiffness in SHRs.

Autonomic nervous system modulation affects the inflammatory immune response in mice with acute Chagas disease.

The aim of the present study was to evaluate the effects of changes to the autonomic nervous system in mice during the acute phase of Chagas disease, which is an infection caused by the parasite Trypanosoma cruzi. The following types of mice were inoculated with T. cruzi (CHG): wild-type (WT) and vesicular acetylcholine transporter knockdown (KDVAChT) C57BL/6j mice; wild-type non-treated (NT) FVB mice; FVB mice treated with pyridostigmine bromide (PYR) or salbutamol (SALB); and ß(2)-adrenergic receptor knockout (KOß2) FVB mice. During infection and at 18-21 days after infection (acute phase), the survival curves, parasitaemia, electrocardiograms, heart rate variability, autonomic tonus and histopathology of the animals were evaluated. Negative control groups were matched for age, genetic background and treatment. The KDVAChT-CHG mice exhibited a significant shift in the electrocardiographic, autonomic and histopathological profiles towards a greater inflammatory immune response that was associated with a reduction in blood and tissue parasitism. In contrast, the CHG-PYR mice manifested reduced myocardial inflammation and lower blood and tissue parasitism. Similar results were observed in CHG-SALB animals. Unexpectedly, the KOß2-CHG mice exhibited less myocardial inflammation and higher blood and tissue parasitism, which were associated with reduced mortality. These findings could have been due to the increase in vagal tone observed in the KOß2 mice, which rendered them more similar to the CHG-PYR animals. In conclusion, our results indicate a marked immunomodulatory role for the parasympathetic and sympathetic autonomic nervous systems, which inhibit both the inflammatory immune response and parasite clearance during the acute phase of experimental Chagas heart disease in mice.

Autonomic neuroimmunomodulation in chagasic cardiomyopathy.

Chagas disease is an endemic parasitic disease, caused by the flagellate protozoan Trypanosoma cruzi, with a high prevalence in Latin America. During its chronic phase, chronic chagasic cardiomyopathy is the most apparent clinical form, affecting 25-30% of patients. This clinical form may present as congestive heart failure, thromboembolic phenomena, cardiac arrhythmias and sudden death. Pathological findings in the heart include mononuclear inflammatory infiltrate, focal myocarditis, epicarditis and neuroganglionitis, associated with variable focal fibrosis and widely variable autonomic dysfunction. The immune-inflammatory response has been considered to be the cause of the autonomic dysfunction, which may trigger life-threatening arrhythmias and sudden death. In the last few years, several reports in the literature have described the marked role played by the autonomic nervous system in the modulation of the immune-inflammatory response in some experimental models of infectious, ischaemic and autoimmune diseases. However, nothing is known about this autonomic neural modulation of the immune response in Chagas disease. In the present report, we discuss several sets of evidence suggesting that changes in the autonomic drive directed towards the heart could modify blood and tissue parasitism, as well as inflammatory infiltration, in chagasic cardiomyopathy. The pathogenic implications of these potential neural immune manipulations are also discussed.

Heart rate and arterial pressure variability and baroreflex sensitivity in ovariectomized spontaneously hypertensive rats.

AIMS: The present study evaluated the effects of ovariectomy on heart rate and arterial pressure variability and cardiac baroreflex sensitivity (BRS) in female spontaneously hypertensive (SHR) and Wistar-Kyoto rats (WKY). MAIN METHODS: Sham-surgery animals were used as control. Sixteen weeks after ovariectomy or sham-surgery, animals were recorded. Time series of pulse interval (PI) and systolic AP (SAP) were analyzed by means of autoregressive spectral analysis, which quantifies the power of very low (VLF=0.01-0.25 Hz), low (LF=0.25-0.75 Hz) and high frequency (HF=0.75-2.5 Hz) bands. BRS was assessed by means of linear regression between changes of PI and SAP induced by vasoactive drugs or calculation of alpha-index, a spontaneous BRS index. KEY FINDINGS: There was no difference in baseline PI or SAP between ovariectomized and sham SHR. Spectral analysis of heart rate variability suggested a shift of sympatho-vagal balance toward sympathetic predominance in ovariectomized SHR (LF/HF=1.8+/-0.2 versus 0.7+/-0.2 in sham SHR, p<0.05). Ovariectomy increased total variance and VLF power of SAP in SHR (29.1+/-9.6 mmHg2 and 18.6+/-6.3 mmHg2 versus 9.1+/-2.1 mmHg2 and 4.3+/-1.4 mmHg2, respectively, in sham SHR, p<0.05). In addition, ovariectomy reduced reflex bradycardia in SHR (0.18+/-0.03 ms/mmHg versus 0.34+/-0.06 ms/mmHg in sham SHR, p<0.05). Ovariectomy did not affect heart rate and SAP variability or BRS in WKY. SIGNIFICANCE: These data showed that ovarian hormones deprivation induced marked changes on cardiovascular control, increasing SAP variability and cardiac sympatho-vagal balance and blunting BRS in female hypertensive animals, which reinforce the possible protective role of ovarian hormones on the cardiovascular system.

Effects of long-term angiotensin converting enzyme inhibition on cardiovascular variability in aging rats.

We studied the effects of chronic (4 weeks) angiotensin converting enzyme inhibition with captopril on arterial pressure (AP) and heart rate (HR) variability, as well as on cardiac baroreflex sensitivity (BRS), in aged (20 months) rats. Series of basal RR interval (RRi) and systolic AP (SAP) were studied by autoregressive spectral analysis with oscillations quantified in low (LF: 0.2-0.8 Hz) and high frequency (HF: 0.8-2.5 Hz). BRS was measured by linear regression between HR and MAP changes. Captopril did not affect the spectra of RRi or SAP in young rats. Aged rats presented a reduction in variance (time domain) and in LF and HF oscillations of RRi and SAP. Captopril induced, in aged rats, a decrease in absolute and normalized LF oscillations and in LF/HF ratio of RRi. Captopril also reduced the variance, without changing its LF or HF components of SAP. Reflex tachycardia was reduced in aged as compared to young rats (-1.1+/-0.2 versus -3.4+/-0.5 bpm/mm Hg) and captopril did not affect it. Reflex bradycardia was also reduced in aged rats (-0.7+/-0.5 versus -2.0+/-0.4 bpm/mm Hg), but captopril prevented this attenuation in aged rats (-2.3+/-0.3 versus -0.7+/-0.5 bpm/mm Hg). These data indicate that there is a reduction in HR and SAP variability during aging, suggesting impairment of cardiovascular autonomic control. Captopril was able to change the power of oscillatory components of RRi, suggesting a shift in cardiac sympatho/vagal balance toward parasympathetic predominance. In addition, blockage of ACE improved the reflex bradycardia, but not the reflex tachycardia in aged rats.

Cardiac autonomic modulation in hypertensive patients with Chagas' disease.

BACKGROUND: Arterial hypertension and Chagas' disease are prevalent pathologies in Latin America. It has been demonstrated that each one of them may cause cardiac autonomic dysfunction. This study aimed to investigate the pattern of cardiac autonomic modulation in chagasic-hypertensive patients. METHODS: Subjects (n=120) without left ventricular dysfunction were distributed in four groups: healthy control (n=30); hypertensive (n=30); chagasic (n=30) and chagasic-hypertensive (n=30). Patients were evaluated by autoregressive spectral analysis of heart rate variability in three different conditions: baseline, cold face and passive tilt tests. Power spectral densities in low (0.04-0.15 Hz) and high (0.15-0.50 Hz) frequency bands were estimated in both absolute and normalized units. RESULTS: Baseline median values (percentile 25 to percentile 75) of mean arterial pressure (in mmHg) were 93.3 (85.0-96.7), 116.7 (*, #) (110.0-129.2), 86.7 (83.3-92.5) and 106.7 (*, #) (106.7-110.0) for healthy control, hypertensive, chagasic and chagasic-hypertensive patients, respectively (*p<0.05 versus healthy control, #p<0.05 against chagasic group). Heart rate at rest did not differ among groups. Regarding to spectral parameters in baseline conditions, the absolute power of high frequency component of heart rate variability of the chagasic-hypertensive group was significantly lower than that found in healthy control and hypertensive patients. There were no differences in spectral parameters responses during cold face test. After passive tilt test, however, decreases in high frequency oscillations and increases in sympathovagal balance (low and high frequency ratio) were significantly lower in hypertensive, chagasic and chagasic-hypertensive patients as compared with healthy control. CONCLUSIONS: These data indicate that chagasic-hypertensive patients presented an impairment of cardiac parasympathetic modulation at baseline conditions as well as in response to passive orthostatic stress.

Opposite effects of iv amiodarone on cardiovascular vagal and sympathetic efferent activities in rats.

It is unknown whether amiodarone exerts a direct central action on the cardiovascular autonomic nervous system. This study was designed to evaluate the effects of acute amiodarone administration on vagal and sympathetic efferent nerve discharges. Experiments were carried out in 25 decerebrate unanesthetized rats. In one group, vagal activity was recorded from preganglionic fibers isolated from the cervical vagus nerve. In another group, sympathetic recordings were obtained from fibers isolated from the cervical sympathetic trunk in intact conditions or after barodenervation. Recordings were performed before and for 60 min after amiodarone (50 mg/kg iv) administration. In all groups, amiodarone induced bradycardia and hypotension. Vagal activity increased immediately, reaching a significant difference after 20 min (260 +/- 131% from 16.4 +/- 3.3 spikes/s) and was unmodified by the barodenervation. At difference, sympathetic activity after an initial and short-lasting increase (150 +/- 83% from 24.8 +/- 5.7 spikes/s) began to decrease significantly after 20 min (36 +/- 17%) throughout the experiment. The initial increase in sympathetic activity was not observed in barodenervated animals. These changes in vagal and sympathetic activity could play an important role in contributing to the antiarrhythmic action of amiodarone.

Intravenous amiodarone modifies autonomic balance and increases baroreflex sensitivity in conscious rats.

Amiodarone is an antiarrhythmic agent commonly used to treat cardiac arrhythmias. This study was designed to investigate the effects of intravenous amiodarone on the neural control of heart rate and arterial pressure and spontaneous baroreflex sensitivity (BRS). Experiments were carried out on conscious freely moving normotensive Wistar (WR) and spontaneously hypertensive rats (SHR). Arterial pressure was continuously monitored before and after amiodarone (50 mg/kg i.v.) or vehicle for 30 min. Heart rate (expressed as the pulse interval, PI) and systolic arterial pressure (SAP) variabilities were assessed using autoregressive spectral analysis. BRS was calculated as the alpha-index (the square root of the ratio between the PI and SAP powers). Amiodarone induced bradycardia and hypotension in both strains, with these effects being more intense in SHR. The variability profile of PI was characterized by a significant reduction of normalized low frequency (LF) and LF/HF ratio, while the high frequency (HF) component both in absolute and normalized units (nu) was increased in both WR and SHR strains. A significant decrease in SAP variance and its LF oscillation was observed. In addition, BRS was also increased in both groups, being more intense in SHR. In both WR and SHR, intravenous amiodarone had a considerable effect on heart rate variabilities (HRV), shifting cardiac sympathovagal balance toward a sympathetic inhibition and/or vagal activation, which were associated with an increase in spontaneous BRS. Decreases of SAP variance and LF(SAP) suggest sympatholytic effects on peripheral vessels. Besides the direct ion channel effects, these changes in the autonomic balance could contribute to the antiarrhythmic action of the intravenous amiodarone.