Nitric oxide as a double-edged sword in pulmonary viral infections: Mechanistic insights and potential therapeutic implications

In the face of the global pandemic caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), researchers are tirelessly exploring novel therapeutic approaches to combat coronavirus disease 2019 (COVID-19) and its associated complications. Nitric oxide (NO) has appeared as a multifaceted signaling mediator with diverse and often contrasting biological activities. Its intricate biochemistry renders it a crucial regulator of cardiovascular and pulmonary functions, immunity, and neurotransmission. Perturbations in NO production, whether excessive or insufficient, contribute to the pathogenesis of various diseases, encompassing cardiovascular disease, pulmonary hypertension, asthma, diabetes, and cancer. Recent investigations have unveiled the potential of NO donors to impede SARS-CoV- 2 replication, while inhaled NO demonstrates promise as a therapeutic avenue for improving oxygenation in COVID-19-related hypoxic pulmonary conditions. Interestingly, NO's association with the inflammatory response in asthma suggests a potential protective role against SARS-CoV-2 infection. Furthermore, compelling evidence indicates the benefits of inhaled NO in optimizing ventilation-perfusion ratios and mitigating the need for mechanical ventilation in COVID-19 patients. In this review, we delve into the molecular targets of NO, its utility as a diagnostic marker, the mechanisms underlying its action in COVID-19, and the potential of inhaled NO as a therapeutic intervention against viral infections. The topmost significant pathway, gene ontology (GO)-biological process (BP), GO-molecular function (MF) and GO-cellular compartment (CC) terms associated with Nitric Oxide Synthase (NOS)1, NOS2, NOS3 were arginine biosynthesis (p-value = 1.15 x 10-9) regulation of guanylate cyclase activity (p-value = 7.5 x 10-12), arginine binding (p-value = 2.62 x 10-11), vesicle membrane (p-value = 3.93 x 10-8). Transcriptomics analysis further validates the significant presence of NOS1, NOS2, NOS3 in independent COVID-19 and pulmonary hypertension cohorts with respect to controls. This review investigates NO's molecular targets, diagnostic potentials, and therapeutic role in COVID-19, employing bioinformatics to identify key pathways and NOS isoforms' significance.

Polyaspartic acid increases potassium content and reduces the ratio of total sugar to nicotine in tobacco leaves

Tobacco is an important cash crop in China, but the low potassium (K) content and high ratio of total sugar to nicotine in tobacco leaves have seriously affected the quality of tobacco leaves. As a fertilizer synergist, polyaspartic acid (PASP) can improve the K content in tobacco leaves, but it is unknown how it affects the K content in different parts of tobacco leaves, and how PASP affects the ratio of total sugar to nicotine in tobacco leaves has not been reported. Therefore, "Zhongyan 100" was selected for pot experiments with 5 different PASP addition levels: CK (0.0 %), P1 (0.1 %), P2 (0.2 %), P3 (0.4 %) and P4 (0.6 %), to reveal the effects of PASP on tobacco growth, K content, sugar content, nicotine content and the ratio of total sugar to nicotine in different tobacco parts, and determine the optimal PASP dosage for regulating the K content and the ratio of total sugar to nicotine in tobacco. The results showed that P1 (0.1 %) and P2 (0.2 %) only had slighter effects on tobacco growth and quality, while P3 (0.4 %) and P4 (0.6 %)treatments significantly promoted dry matter accumulation, increased K and nicotine content in leaves, decreased reducing sugar and total soluble sugar content in leaves, thereby reducing the ratio of total sugar to nicotine in tobacco leaves, especially in upper leaves. Considering the economic cost savings, 0.4% PASP was determined as the best application level to improve the growth and quality of tobacco. Thus, proper application of PASP is beneficial to improve tobacco leaf quality and reduce chemical K fertilizer application, thereby decreasing agricultural environmental risks of chemical fertilizer and alleviating the rapid depletion of potash in the world.

Outcome of Patients With Cardiogenic Shock and Previous Right Ventricular Impairment Represented by Decreased Tricuspid Annular Plane Systolic Excursion and Tricuspid Annular Plane Systolic Excursion to Pulmonary Artery Systolic Pressure Ratio

This study investigates the prognostic impact of known decreased ratio of tricuspid annular plane systolic excursion (TAPSE) to pulmonary artery systolic pressure (PASP) and TAPSE in patients with cardiogenic shock (CS). In patients with pulmonary artery hypertension and in critically ill patients, decreased TAPSE and TAPSE/PASP ratio are known to be negative predictors. However, studies regarding the prognostic impact in patients with CS are limited. Consecutive patients with CS from June 2019 to May 2021 treated at a single center were included. Medical history including echocardiographic parameters such as TAPSE and PASP was documented for each patient. The primary endpoint was all-cause mortality at 30 days. Statistical analyses included univariable t test, Spearman's correlation, C-statistics, Kaplan-Meier analyses, and Cox proportional regression analyses. A total of 90 patients with CS and measurement of TAPSE and TAPSE/PASP ratio were included. TAPSE and TAPSE/PASP ratio measured several months before intensive care unit admission were both able to predict 30-day survival in CS patients, and were both lower in 30-day nonsurvivors. TAPSE/PASP ratio <0.4 mm/mmHg (log-rank p = 0.006) and TAPSE <18 mm (log-rank p = 0.004) were associated with increased risk of 30-day all-cause mortality. After multivariable adjustment, TAPSE/PASP ratio <0.4 mm/mmHg was not able to predict 30-day all-cause mortality, whereas TAPSE <18 mm was still significantly associated with the primary endpoint (hazard ratio 2.336, confidence interval 1.067 to 5.115, p = 0.034). In consecutive patients presenting with CS, compared to TAPSE alone, previously determined TAPSE/PASP ratio did not improve risk prediction for 30-day all-cause mortality.

Relevance of the TAPSE/PASP ratio in pulmonary arterial hypertension

BACKGROUND

The ratio of echocardiography-derived tricuspid annular plane systolic excursion (TAPSE) and pulmonary arterial systolic pressure (PASP) has recently been reported as an independent prognostic parameter in heart failure. The TAPSE/PASP ratio has not been evaluated in detail in patients with pulmonary arterial hypertension (PAH).

METHODS

We analyzed TAPSE/PASP in 290 patients with PAH entered into the Giessen Pulmonary Hypertension Registry between November 2003 and July 2014. The prognostic relevance of TAPSE/PASP was assessed with multivariate Cox regression models, adjusting for clinical covariates, echocardiographic parameters, or hemodynamics, and was confirmed by Kaplan-Meier analyses.

RESULTS

When stratified by tertile of TAPSE/PASP (low: <0.19 mm/mmHg; middle: 0.19-0.32 mm/mmHg; high: >0.32 mm/mmHg), patients in the low tertile showed significantly compromised hemodynamic, functional, and echocardiographic status compared with patients in the middle and high tertiles. In all multivariate models, TAPSE/PASP remained independently associated with overall mortality: the hazard ratio (95% confidence interval) was 1.87 (1.35-2.59) when adjusting for clinical covariates (p < .001), 5.21 (2.17-12.5) when adjusting for echocardiographic parameters (p < .001), 1.92 (1.30-2.83) when adjusting for hemodynamics (p = .001), and 4.13 (2.02-8.48) when adjusting for a selection of previously identified independent echocardiographic and hemodynamic prognostic indicators (p < .001). Kaplan-Meier analyses showed better overall survival in the middle and high tertiles versus the low tertile (log-rank p < .001).

CONCLUSIONS

The TAPSE/PASP ratio is a meaningful prognostic parameter in patients with PAH and is associated with hemodynamics and functional class.

Clinical and echocardiographic diagnosis, follow up and management of right-sided cardiac thrombi

BACKGROUND

Right-sided cardiac masses are infrequent and have varied clinical presentation. The present study describes the clinical features, echocardiographic findings and management of 19 patients presenting with right-sided cardiac thrombi in a tertiary care center in north India.

METHODS

This is a retrospective, single center observational study of consecutive patients over the period January 2003-2008 admitted in our emergency intensive care unit (EICU). We identified 38 patients with right-sided cardiac masses admitted to EICU diagnosed by transthoracic echocardiography of which 19 patients had right-sided thrombus. The echocardiographic findings were reviewed by two cardiologists in all patients. Treatment was not standardized and choice of therapy was based on judgment of attending physician.

RESULTS

The mean age of patients with cardiac thrombus was 36.6 ± 11.8 years. Right atrial (n = 17) and right ventricle (n = 2) thrombi were associated with deep vein thrombosis (DVT) in 7 (36.8%) and pulmonary embolism in 3 (15%) patients. 13 (68.4%) patients appeared to have in situ mural thrombus. 12 patients were managed with oral anticoagulants, 3 patients underwent surgery and 4 patients were thrombolysed. All the survivors had a mean follow-up of 40 ± 6 months (range--18-50 months).

CONCLUSIONS

Prompt echocardiographic examination in an appropriate clinical setting facilitates faster diagnosis and management of patients with right-sided cardiac thrombi. High incidence of in situ mural thrombus and varied comorbidities predisposing to right-sided cardiac thrombi besides DVT and pulmonary embolism need to be recognized. Oral anticoagulation and thrombolysis appear to be the mainstay of treatment with surgery limited for selected patients.

Doppler echocardiography inaccurately estimates right ventricular pressure in children with elevated right heart pressure

BACKGROUND

Doppler echocardiography (DE) is widely used as a surrogate for right heart catheterization (RHC), the gold standard, to assess and monitor elevated right heart pressure in children. However, its accuracy has not been prospectively validated in children. The objectives of this study were to evaluate the accuracy of DE in predicting simultaneously measured right ventricular (RV) pressure by RHC in pediatric patients and to determine if the degree of RV hypertension affects the accuracy of DE in assessing right heart pressure.

METHODS

Eighty children (age range, 0-17.9 years; median age, 5.5 years) with two-ventricle physiology and a wide range of right heart pressures underwent simultaneous DE and RHC. The pressure gradient between the right ventricle and the right atrium was directly measured by RHC and simultaneously estimated by DE using tricuspid regurgitation. Patients were then grouped on the basis of RHC-measured RV systolic pressure (RVSP): group 1 (n = 43), with RVSP < 1/2 systemic systolic blood pressure (SBP); group 2 (n = 37), with RVSP ≥ 1/2 SBP; group 3 (n = 56), with RVSP < 2/3 SBP; and group 4 (n = 24), with RVSP ≥ 2/3 SBP. Correlation and Bland-Altman analyses were performed on all groups. Accuracy was predefined as 95% limits of agreement within ±10 mm Hg.

RESULTS

Despite a reasonable correlation between DE and RHC in all groups, there was poor agreement between techniques as RVSP/SBP increased. DE was inaccurate in one of 43 patients in group 1 (2%) versus nine of 37 in group 2 (24%) and was inaccurate in one of 56 patients in group 3 (2%) versus eight of 24 in group 4 (33%). Overestimation and underestimation occurred equally in all groups.

CONCLUSION

DE inaccurately estimates RV pressure in children with elevated right heart pressure. It should not be relied on as the sole method of assessing right heart hemodynamics in children with RV hypertension.

Pressure reflection in the pulmonary circulation by echocardiography in patients with left heart disease indicates reactive pulmonary hypertension

OBJECTIVES

The two hemodynamic profiles in left heart disease (LHD) with pulmonary hypertension (PH), passive PH with increased pulmonary venous pressure and reactive PH with increased pulmonary vascular resistance (PVR > 3 Wood units, WU), are difficult to distinguish non-invasively. We hypothesized that echocardiographic signs of pressure reflection (PR) in the pulmonary circulation can be used to diagnose reactive PH.

MATERIAL AND METHODS

The study comprised 122 patients divided into three groups: patients without PH (No PH, n = 61), patients with LHD, PH and normal PVR (passive PH, n = 29) and patients with LHD, PH and increased PVR (reactive PH, n = 32). Echocardiography and right heart catheterization were performed within 24 h. Three parameters were selected related to PR [the acceleration of flow in the right ventricular outflow tract (RVOT), the interval and the augmentation of pressure between peak RVOT flow and peak RV pressure]. Cutoff values aiming at ruling in (high positive likelihood ratio, PLR) and ruling out (low negative likelihood ratio, NLR) increased PVR were determined using receiver operator characteristic (ROC) curves.

RESULTS

The proportions of the patients with PH and PVR > 3 WU were 50% and 29%. Twenty-one percent had both increased pulmonary capillary wedge pressure and PVR. The area under the ROC curve for the PR parameters was 0.82-0.89. The PLR with ruling in cutoff values ranged from 4.7 to 9.4. The NLR with ruling out cutoff values ranged from 0.20 to 0.12.

CONCLUSIONS

Echocardiographic assessment of PR in patients with LHD can be used to identify or exclude reactive PH.

Echocardiographic estimation of pulmonary arterial systolic pressure in acute heart failure. Prognostic implications

BACKGROUND

Prognostic implications of echocardiographic assessment of pulmonary hypertension (PH) in non-selected patients hospitalized for acute heart failure (AHF) are not clearly defined. The aim of this study was to evaluate the association between echocardiography-derived PH in AHF and 1-year all-cause mortality.

METHODS

We prospectively included 1210 consecutive patients admitted for AHF. Patients with significant heart valve disease were excluded. Pulmonary arterial systolic pressure (PASP) was estimated using transthoracic echocardiography during hospitalization (mean time after admission 96±24h). Patients were categorized as follows: non-measurable, normal PASP (PASP≤35mmHg), mild (PASP 36-45mmHg), moderate (PASP 46-60mmHg) and severe PH (PASP >60mmHg). The independent association between PASP and 1-year mortality was assessed with Cox regression analysis.

RESULTS

At 1-year follow-up, 232 (19.2%) deaths were registered. PASP was measured in 502 (41.6%) patients with a median of 46 [38-55] mmHg. The distribution of population was: 708 (58.5%), 76 (6.3%), 147 (12.1%), 190 (15.7%) and 89 (7.4%) for non-measurable, normal PASP, mild, moderate and severe PH, respectively. One-year mortality was lower for patients with normal PASP (1.32 per 10 person-years), intermediate for patients with non-measurable, mild and moderate PH (2.48, 2.46 and 2.62 per 10 persons-year, respectively) and higher for those with severe PH (4.89 per 10 person-years). After multivariate adjustment, only patients with PASP >60mmHg displayed significant adjusted increase in the risk of 1-year all-cause mortality, compared to patients with normal PASP (HR=2.56; CI 95%: 1.05-6.22, p=0.038).

CONCLUSIONS

In AHF, severe pulmonary hypertension derived by echocardiography is an independent predictor of 1-year-mortality.