Sympatho-Vagal Dysfunction in Patients with End-Stage Lung Disease Awaiting Lung Transplantation

Trichosanthin-derived peptide Tk-PQ attenuates immune rejection in mouse tracheal allotransplant model by suppressing PI3K-Akt and inducing type II immune polarization

Obliterative bronchiolitis (OB) is one of the main complications affecting long-term survival of post-lung transplantation patients. In this study, we evaluated the efficacy of Tk-PQ (a peptide derived from trichosanthin) in alleviating OB in a mouse ectopic tracheal transplant model. We found that post-transplantation treatment of Tk-PQ significant ameliorated OB symptoms including luminal occlusion, epithelial cells loss and fibrosis in the allograft. In addition, Tk-PQ promoted immune suppressive environment by inducing Th2 polarization and increasing Treg population which in turn led to elevated levels of anti-inflammatory cytokines IL-4, IL-10, IL-33 and decreased levels of pro-inflammatory IL-1β. Mechanistically, we used transcriptome analysis of splenic T cells from allografted mice to show that Tk-PQ treatment down-regulated the PI3K-Akt signaling pathway. Indeed, the immune suppression phenotypes of Tk-PQ was recapitulated by a PI3K inhibitor LY294002. Taken together, Tk-PQ regulates post-transplantation immuno-rejection by modulating the balance of T cell response via the PI3K-Akt pathway, making it a promising peptide based immune rejection suppressant for patients receiving allotransplant.

Cardiac autonomic control in Rett syndrome: Insights from heart rate variability analysis

Rett syndrome (RTT) is a rare and severe neurological disorder mainly affecting females, usually linked to methyl-CpG-binding protein 2 (MECP2) gene mutations. Manifestations of RTT typically include loss of purposeful hand skills, gait and motor abnormalities, loss of spoken language, stereotypic hand movements, epilepsy, and autonomic dysfunction. Patients with RTT have a higher incidence of sudden death than the general population. Literature data indicate an uncoupling between measures of breathing and heart rate control that could offer insight into the mechanisms that lead to greater vulnerability to sudden death. Understanding the neural mechanisms of autonomic dysfunction and its correlation with sudden death is essential for patient care. Experimental evidence for increased sympathetic or reduced vagal modulation to the heart has spurred efforts to develop quantitative markers of cardiac autonomic profile. Heart rate variability (HRV) has emerged as a valuable non-invasive test to estimate the modulation of sympathetic and parasympathetic branches of the autonomic nervous system (ANS) to the heart. This review aims to provide an overview of the current knowledge on autonomic dysfunction and, in particular, to assess whether HRV parameters can help unravel patterns of cardiac autonomic dysregulation in patients with RTT. Literature data show reduced global HRV (total spectral power and R-R mean) and a shifted sympatho-vagal balance toward sympathetic predominance and vagal withdrawal in patients with RTT compared to controls. In addition, correlations between HRV and genotype and phenotype features or neurochemical changes were investigated. The data reported in this review suggest an important impairment in sympatho-vagal balance, supporting possible future research scenarios, targeting ANS.

Sympatho-Vagal Dysfunction in Systemic Sclerosis: A Follow-Up Study

Systemic sclerosis (SSc) patients often present cardiovascular autonomic dysfunction, which is associated with the risk of arrhythmic complications and mortality. However, little is known regarding the progression of cardiac autonomic impairment over time. We aimed to evaluate the cardiac autonomic modulation among SSc with limited cutaneous (lcSSc), diffuse cutaneous (dcSSc) subset, and age-matched healthy control (HC) at baseline (t0) and five-year follow-up (t1). In this follow-up study, ECG was recorded at t0 and t1 in twenty-four SSc patients (dcSSc; n = 11 and lcSSc; n = 13) and 11 HC. The heart rate variability (HRV) analysis was conducted. The spectral analysis identified two oscillatory components, low frequency (LF) and high frequency (HF), and the sympatho-vagal balance was assessed by the LF/HF ratio. The LF/HF increased (p = 0.03), and HF reduced at t1 compared to t0 in dcSSc (p = 0.03), which did not occur in the lcSSc and HC groups. Otherwise, both lcSSc and dcSSc groups presented augmented LF/HF at t0 and t1 compared to HC (p < 0.01). In conclusion, a worsening of cardiac autonomic dysfunction is related to the dcSSc subset, in which a more extent of skin fibrosis and internal organs fibrosis is present.

Women have a greater cardiac vagal withdrawal to heat stress compared to men

The heated environment shifts the sympatho-vagal balance toward sympathetic predominance and vagal withdrawal. Women's heart is more reliant on vagal autonomic control, while men's heart is more dependent on sympathetic control. However, sex differences in cardiovascular autonomic responses to heat stress remain unknown. We aimed to investigate the cardiovascular autonomic regulation under heat stress between sexes. Thirty-two young participants (27 ± 4 years old; 16 women) were enrolled in a single visit, resting for 30min at baseline (thermal reference condition TC; ∼24°C) and 30min under a heated environment (HOT; ∼38°C). Blood pressure (BP), skin temperature, electrocardiogram, and respiratory oscillations were continuously recorded. The heart rate variability (HRV) was assessed by spectral analysis (low-frequency [LFnu; sympathetic and vagal] and high-frequency [HFnu; vagal]), and symbolic analysis (0 V% [sympathetic] and 2UV%, and 2LV% [vagal]). The spontaneous baroreflex sensitivity (BRS) was calculated by the gain between BP and R-R within the LF band (αLF). The estimated maximal aerobic capacity and body surface area were employed as covariates in sex comparisons. The effects of HOT were the following: 1) Women have a greater cardiac vagal withdrawal to heat stress compared to men; 2) Sex differences on cardiac autonomic response to heat stress exist after controlling for the effect of estimated physical fitness and body surface area. Therefore, heat stress provokes a higher vagal withdrawal to the heart in women compared to men. It could be attributed to sex per se since significant differences between men and women were not modified after covariate analysis.

Orthostatic Hypotension and Concurrent Autonomic Dysfunction: A Novel Complication of Lung Transplantation

Background

Persistent orthostatic hypotension (OH) is a lesser-known complication of lung transplantation (LTx). In this retrospective case series, we describe the clinical manifestations, complications, and treatment of persistent OH in 13 LTx recipients.

Methods

We identified LTx recipients who underwent transplantation between March 1, 2018, and March 31, 2020, with persistent symptomatic OH and retrospectively queried the records for clinical information.

Results

Thirteen patients were included in the analysis, 9 (69%) had underlying pulmonary fibrosis, and 12 (92%) were male. The median age, height, and body mass index at LTx were 68 years, 70 inches, and 27 kg/m², respectively. Six (46%) patients were deceased at the time of chart abstraction with a median (IQR) posttransplant survival of 12.6 months (6, 21); the 7 remaining living patients were a median of 19.6 months (18, 32) posttransplant. Signs and symptoms of OH developed a median of 60 (7, 75) days after transplant. Patients were treated with pharmacological agents and underwent extensive physical therapy. Most patients required inpatient rehabilitation (n = 10, 77%), and patients commonly developed comorbid conditions including weight loss, renal insufficiency with eGFR <50 (n = 13, 100%), gastroparesis (n = 7, 54%), and tachycardia-bradycardia syndrome (n = 2, 15%). Falls were common (n = 10, 77%). The incidence of OH in LTx recipients at our center during the study period was 5.6% (13/234).

Conclusions

Persistent OH is a lesser-known complication of LTx that impacts posttransplant rehabilitation and may lead to comorbidities and shortened survival. In addition, most LTx recipients with OH at our center were tall, thin men with underlying pulmonary fibrosis, which may offer an opportunity to instate pretransplant OH screening of at-risk patients.

The interplay between heated environment and active standing test on cardiovascular autonomic control in healthy individuals

Objective.To investigate the interplay between active standing and heat stress on cardiovascular autonomic modulation in healthy individuals.Approach.Blood pressure (BP) and ECG were continuously recorded during 30 min in supine (SUP) and 6 min in orthostatic position (ORT) under thermal reference (TC; ∼24 °C) or heated environment (HOT; ∼36 °C) conditions, in a randomized order. All data collection was performed during the winter and spring seasons when typical outdoor temperatures are ∼23 °C. Spectral analysis was employed by the autoregressive model of R-R and systolic blood pressure (SBP) time series and defined, within each band, in low (LF, 0.04 to 0.15 Hz) and high (0.15-0.40 Hz) frequencies. The indices of cardiac sympathetic (LF) and cardiac parasympathetic (HF) were normalized (nu) dividing each band power by the total power subtracted the very-low component (<0.04 Hz), obtaining the cardiac autonomic balance (LF/HF) modulation. The gain of the relationship between SBP and R-R variabilities within the LF band was utilized for analysis of spontaneous baroreflex sensitivity (alpha index;αLF). Nonlinear analysis was employed through symbolic dynamics of R-R, which provided the percentage of sequences of three heart periods without changes in R-R interval (0V%; cardiac sympathetic modulation) and two significant variations (2UV% and 2LV%; cardiac vagal modulation).Main results.HOT increased 0V% and HR, and decreasedαLF and 2UV% during SUP compared to TC. During ORT, HOT provokes a greater increment on HR, LF/HF and 0V%, indexes compared to ORT under TC.Significance.At rest, heat stress influences both autonomic branches, increasing sympathetic and decreasing vagal modulation and spontaneous baroreflex sensitivity. The augmented HR during active standing under heat stress seems to be mediated by a greater increment in cardiac sympathetic modulation, showing an interplay between gravitational and thermal stimulus.

Effects of oxygen supplementation in autonomic nervous system function during exercise in patients with idiopathic pulmonary fibrosis and exertional desaturation

INTRODUCTION

Patients with idiopathic pulmonary fibrosis (IPF) have reduced exercise capacity and often present exertional dyspnea and desaturation. The role of autonomic nervous system (ANS) as a pathogenetic contributor to this dysfunction has not been evaluated.

OBJECTIVE

To evaluate whether improvement of arterial oxygen saturation (SpO₂ ) via oxygen supplementation results to ANS function improvement, during steady state submaximal exercise.

METHODS

This is a secondary analysis of a single-blind, randomized, placebo-controlled, cross-over trial, including 12 IPF patients, with isolated exertional desaturation. Following a maximal cardiopulmonary test, participants underwent two submaximal steady state tests during which they received either supplementary oxygen or medical air. Continuous beat-to-beat blood pressure measurements were recorded (Finapres Medical Systems, Amsterdam, The Netherlands). Autonomic function was assessed non-invasively by heart rate variability (HRV); root mean square of successive differences (RMSSD) and standard-deviation-Poincare-plot (SD1) were used as indices of parasympathetic output. Entropy and detrended fluctuation analysis (DFA) were also used.

RESULTS

During rest, oxygen supplementation did not significantly alter RMSSD and SD1. During exercise, subjects presented no significant alterations compared with baseline, in most HRV indices examined. There was no improvement of this behavior with O₂ -supplementation. Approximate-entropy increased during exercise, with no differences between protocols.

CONCLUSIONS

IPF patients presented an inadequate adaptive response of their ANS to exercise and recovery. Although oxygen supplementation significantly prolonged exercise duration and prevented the substantial exertional desaturation, the blunted vagal response to steady-state exercise in these patients was not improved, suggesting that acute oxygen supplementation does not sufficiently improve ANS dysfunction in these patients.

Effects of bilateral lung transplantation on cardiac autonomic modulation and cardiorespiratory coupling: a prospective study

Background

Although cardiac autonomic modulation has been studied in several respiratory diseases, the evidence is limited on lung transplantation, particularly on its acute and chronic effects. Thus, we aimed to evaluate cardiac autonomic modulation before and after bilateral lung transplantation (BLT) through a prospective study on patients enrolled while awaiting transplant.

Methods

Twenty-two patients on the waiting list for lung transplantation (11 women, age 33 [24–51] years) were enrolled in a prospective study at Ospedale Maggiore Policlinico Hospital in Milan, Italy. To evaluate cardiac autonomic modulation, ten minutes ECG and respiration were recorded at different time points before (T0) and 15 days (T1) and 6 months (T2) after bilateral lung transplantation. As to the analysis of cardiac autonomic modulation, heart rate variability (HRV) was assessed using spectral and symbolic analysis. Entropy-derived measures were used to evaluate complexity of cardiac autonomic modulation. Comparisons of autonomic indices at different time points were performed.

Results

BLT reduced HRV total power, HRV complexity and vagal modulation, while it increased sympathetic modulation in the acute phase (T1) compared to baseline (T0). The HRV alterations remained stable after 6 months (T2).

Conclusion

BLT reduced global variability and complexity of cardiac autonomic modulation in acute phases, and these alterations remain stable after 6 months from surgery. After BLT, a sympathetic predominance and a vagal withdrawal could be a characteristic autonomic pattern in this population.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-021-01752-6.