Is the Endothelium the Missing Link in the Pathophysiology and Treatment of COVID-19 Complications?

Reversible central adrenal insufficiency in survivors of COVID-19: results from a 24-month longitudinal study

Objective

We studied the temporal course of hypothalamic-pituitary-adrenal (HPA) dysfunction in patients with coronavirus disease 2019 (COVID-19).

Methods

Three hundred and two patients (median age 54 years (interquartile range (IQR) 42-64), 76% males) were recruited. The HPA axis was evaluated by morning cortisol and adrenocorticotrophic hormone (ACTH) at admission (n = 232). Adrenal insufficiency (AI) during acute illness was defined using a morning cortisol <83 nmol/L. AI at 12 months follow-up was defined using a peak cortisol <406 nmol/L in the ACTH stimulation test (APST) (n = 90). Those with AI at 12 months were further assessed by APST every 6 months for recovery of hypoadrenalism.

Results

The median morning cortisol and ACTH levels during COVID-19 were 295 (IQR 133-460) nmol/L and 3.9 (0.8-6.9) pmol/L, respectively. AI was present in 33 (14%) patients; ACTH was elevated in three and low or inappropriately normal in the rest 30 patients. At 12 months, AI was seen in 13% (12/90) patients, with all cases being hypothalamic-pituitary in origin; five (42%) of them had not met the diagnostic criteria for AI during COVID-19. AI diagnosed at admission persisted at 12 months in seven patients and recovered in seven; the remaining 19 patients were lost to follow-up. The presence of AI at 12 months was independent of severity and steroid use during COVID-19. A morning cortisol <138 nmol/L during COVID-19 predicted the presence of AI at 12 months. All patients showed recovery of the HPA axis in the ensuing 12 months.

Conclusion

Central AI was common during acute COVID-19 and at 12 months of follow-up. AI can be late onset, developing after recovery from COVID-19, and was transient in nature.

COVID-19 and Long COVID: Disruption of the Neurovascular Unit, Blood-Brain Barrier, and Tight Junctions

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), could affect brain structure and function. SARS-CoV-2 can enter the brain through different routes, including the olfactory, trigeminal, and vagus nerves, and through blood and immunocytes. SARS-CoV-2 may also enter the brain from the peripheral blood through a disrupted blood-brain barrier (BBB). The neurovascular unit in the brain, composed of neurons, astrocytes, endothelial cells, and pericytes, protects brain parenchyma by regulating the entry of substances from the blood. The endothelial cells, pericytes, and astrocytes highly express angiotensin converting enzyme 2 (ACE2), indicating that the BBB can be disturbed by SARS-CoV-2 and lead to derangements of tight junction and adherens junction proteins. This leads to increased BBB permeability, leakage of blood components, and movement of immune cells into the brain parenchyma. SARS-CoV-2 may also cross microvascular endothelial cells through an ACE2 receptor-associated pathway. The exact mechanism of BBB dysregulation in COVID-19/neuro-COVID is not clearly known, nor is the development of long COVID. Various blood biomarkers could indicate disease severity and neurologic complications in COVID-19 and help objectively diagnose those developing long COVID. This review highlights the importance of neurovascular and BBB disruption, as well as some potentially useful biomarkers in COVID-19, and long COVID/neuro-COVID.

IgA Anti-β2-Glycoprotein I Antibodies as Markers of Thrombosis and Severity in COVID-19 Patients

Patients with COVID-19 may develop a hypercoagulable state due to tissue and endothelial injury, produced by an unbalanced immune response. Therefore, an increased number of thromboembolic events has been reported in these patients. The aim of this study is to investigate the presence of antiphospholipid antibodies (aPL) in COVID-19 patients, their role in the development of thrombosis and their relationship with the severity of the disease. In this retrospective study, serum samples from 159 COVID-19 patients and 80 healthy donors were analysed for the presence of aPL. A total of 29 patients (18.2%) and 14 healthy donors (17.5%) were positive for aPL. Nineteen COVID-19 patients (12%) but no healthy donor presented a positive percentage of the IgA isotype aPL. IgA anti-β2-glycoprotein I antibodies (anti-β2GPI) were the most frequent type (6.3%) in patients but was not detected in any healthy donor. The positivity of this antibody was found to be significantly elevated in patients with thromboembolic events (25% vs. 5%, p = 0.029); in fact, patients with positive IgA anti-β2GPI had an incidence of thrombosis over six times higher than those who had normal antibody concentrations [OR (CI 95%) of 6.67 (1.5-30.2), p = 0.014]. Additionally, patients with moderate-severe disease presented a higher aPL positivity than patients with mild disease according to the Brescia (p = 0.029) and CURB-65 (p = 0.011) severity scales. A multivariate analysis showed that positivity for IgA anti-β2GPI is significantly associated with disease severity measured by CURB-65 [OR (CI 95%) 17.8 (1.7-187), p = 0.0016]. In conclusion, COVID-19 patients have a significantly higher positive percentage of the IgA isotype aPL than healthy donors. IgA anti-β2GPI antibodies were the most frequently detected aPL in COVID-19 patients and were associated with thrombosis and severe COVID-19 and are thus proposed as a possible marker to identify high-risk patients.

Endothelial injury and dysfunction with emerging immunotherapies in multiple myeloma, the impact of COVID-19, and endothelial protection with a focus on the evolving role of defibrotide

Patients with multiple myeloma (MM) were among the groups impacted more severely by the COVID-19 pandemic, with higher rates of severe disease and COVID-19-related mortality. MM and COVID-19, plus post-acute sequelae of SARS-CoV-2 infection, are associated with endothelial dysfunction and injury, with overlapping inflammatory pathways and coagulopathies. Existing treatment options for MM, notably high-dose therapy with autologous stem cell transplantation and novel chimeric antigen receptor (CAR) T-cell therapies and bispecific T-cell engaging antibodies, are also associated with endothelial cell injury and mechanism-related toxicities. These pathologies include cytokine release syndrome (CRS) and neurotoxicity that may be exacerbated by underlying endotheliopathies. In the context of these overlapping risks, prophylaxis and treatment approaches mitigating the inflammatory and pro-coagulant effects of endothelial injury are important considerations for patient management, including cytokine receptor antagonists, thromboprophylaxis with low-molecular-weight heparin and direct oral anticoagulants, and direct endothelial protection with defibrotide in the appropriate clinical settings.

The critical role of endothelial cell in the toxicity associated with chimeric antigen receptor T cell therapy and intervention strategies

Chimeric antigen receptor (CAR)-T cell therapy has shown promising results in patients with hematological malignancies. However, many patients still have poor prognoses or even fatal outcomes due to the life-threatening toxicities associated with the therapy. Moreover, even after improving the known influencing factors (such as number or type of CAR-T infusion) related to CAR-T cell infusion, the results remain unsatisfactory. In recent years, it has been found that endothelial cells (ECs), which are key components of the organization, play a crucial role in various aspects of immune system activation and inflammatory response. The levels of typical markers of endothelial activation positively correlated with the severity of cytokine release syndrome (CRS) and immune effector cell-associated neurotoxic syndrome (ICANS), suggesting that ECs are important targets for intervention and toxicity prevention. This review focuses on the critical role of ECs in CRS and ICANS and the intervention strategies adopted.

What Role Does Microthrombosis Play in Long COVID?

Soon after the outbreak of coronavirus disease 2019 (COVID-19), unexplained sustained fatigue, cognitive disturbance, and muscle ache/weakness were reported in patients who had recovered from acute COVID-19 infection. This abnormal condition has been recognized as "long COVID (postacute sequelae of COVID-19 [PASC])" with a prevalence estimated to be from 10 to 20% of convalescent patients. Although the pathophysiology of PASC has been studied, the exact mechanism remains obscure. Microclots in circulation can represent one of the possible causes of PASC. Although hypercoagulability and thrombosis are critical mechanisms of acute COVID-19, recent studies have reported that thromboinflammation continues in some patients, even after the virus has cleared. Viral spike proteins and RNA can be detected months after patients have recovered, findings that may be responsible for persistent thromboinflammation and the development of microclots. Despite this theory, long-term results of anticoagulation, antiplatelet therapy, and vascular endothelial protection are inconsistent, and could not always show beneficial treatment effects. In summary, PASC reflects a heterogeneous condition, and microclots cannot explain all the presenting symptoms. After clarification of the pathomechanisms of each symptom, a symptom- or biomarker-based stratified approach should be considered for future studies.

Molecular cross-talk between long COVID-19 and Alzheimer's disease

The long COVID (coronavirus disease), a multisystemic condition following severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection, is one of the widespread problems. Some of its symptoms affect the nervous system and resemble symptoms of Alzheimer's disease (AD)-a neurodegenerative condition caused by the accumulation of amyloid beta and hyperphosphorylation of tau proteins. Multiple studies have found dependence between these two conditions. Patients with Alzheimer's disease have a greater risk of SARS-CoV-2 infection due to increased levels of angiotensin-converting enzyme 2 (ACE2), and the infection itself promotes amyloid beta generation which enhances the risk of AD. Also, the molecular pathways are alike-misregulations in folate-mediated one-carbon metabolism, a deficit of Cq10, and disease-associated microglia. Medical imaging in both of these diseases shows a decrease in the volume of gray matter, global brain size reduction, and hypometabolism in the parahippocampal gyrus, thalamus, and cingulate cortex. In some studies, a similar approach to applied medication can be seen, including the use of amino adamantanes and phenolic compounds of rosemary. The significance of these connections and their possible application in medical practice still needs further study but there is a possibility that they will help to better understand long COVID.

Serum from COVID-19 patients promotes endothelial cell dysfunction through protease-activated receptor 2

BACKGROUND

Endothelial dysfunction plays a central role in the pathophysiology of COVID-19 and is closely linked to the severity and mortality of the disease. The inflammatory response to SARS-CoV-2 infection can alter the capacity of the endothelium to regulate vascular tone, immune responses, and the balance between anti-thrombotic and pro-thrombotic properties. However, the specific endothelial pathways altered during COVID-19 still need to be fully understood.

OBJECTIVE

In this study, we sought to identify molecular changes in endothelial cells induced by circulating factors characteristic of COVID-19.

METHODS AND RESULTS

To this aim, we cultured endothelial cells with sera from patients with COVID-19 or non-COVID-19 pneumonia. Through transcriptomic analysis, we were able to identify a distinctive endothelial phenotype that is induced by sera from COVID-19 patients. We confirmed and expanded this observation in vitro by showing that COVID-19 serum alters functional properties of endothelial cells leading to increased apoptosis, loss of barrier integrity, and hypercoagulability. Furthermore, we demonstrated that these endothelial dysfunctions are mediated by protease-activated receptor 2 (PAR-2), as predicted by transcriptome network analysis validated by in vitro functional assays.

CONCLUSION

Our findings provide the rationale for further studies to evaluate whether targeting PAR-2 may be a clinically effective strategy to counteract endothelial dysfunction in COVID-19.

Endothelial activation and damage as a common pathological substrate in different pathologies and cell therapy complications

The endothelium is a biologically active interface with multiple functions, some of them common throughout the vascular tree, and others that depend on its anatomical location. Endothelial cells are continually exposed to cellular and humoral factors, and to all those elements (biological, chemical, or hemodynamic) that circulate in blood at a certain time. It can adapt to different stimuli but this capability may be lost if the stimuli are strong enough and/or persistent in time. If the endothelium loses its adaptability it may become dysfunctional, becoming a potential real danger to the host. Endothelial dysfunction is present in multiple clinical conditions, such as chronic kidney disease, obesity, major depression, pregnancy-related complications, septic syndromes, COVID-19, and thrombotic microangiopathies, among other pathologies, but also in association with cell therapies, such as hematopoietic stem cell transplantation and treatment with chimeric antigen receptor T cells. In these diverse conditions, evidence suggests that the presence and severity of endothelial dysfunction correlate with the severity of the associated disease. More importantly, endothelial dysfunction has a strong diagnostic and prognostic value for the development of critical complications that, although may differ according to the underlying disease, have a vascular background in common. Our multidisciplinary team of women has devoted many years to exploring the role of the endothelium in association with the mentioned diseases and conditions. Our research group has characterized some of the mechanisms and also proposed biomarkers of endothelial damage. A better knowledge would provide therapeutic strategies either to prevent or to treat endothelial dysfunction.

Long COVID-19 Pathophysiology: What Do We Know So Far?

Long COVID-19 is a recognized entity that affects millions of people worldwide. Its broad clinical symptoms include thrombotic events, brain fog, myocarditis, shortness of breath, fatigue, muscle pains, and others. Due to the binding of the virus with ACE-2 receptors, expressed in many organs, it can potentially affect any system; however, it most often affects the cardiovascular, central nervous, respiratory, and immune systems. Age, high body mass index, female sex, previous hospitalization, and smoking are some of its risk factors. Despite great efforts to define its pathophysiology, gaps remain to be explained. The main mechanisms described in the literature involve viral persistence, hypercoagulopathy, immune dysregulation, autoimmunity, hyperinflammation, or a combination of these. The exact mechanisms may differ from system to system, but some share the same pathways. This review aims to describe the most prevalent pathophysiological pathways explaining this syndrome.

Ultrastructural Reorganization of Endotheliocytes of Pulmonary Blood Capillaries in COVID-19

The ultrastructural organization endotheliocytes of pulmonary blood capillaries in COVID-19 was studied on autopsy material using electron microscopy. Swelling of the cytoplasm and mitochondria with destruction of the cristae, dilation of the Golgi complex cisternae, a decrease in the volume density of the luminal and basal caveolae and free transport vesicles, an increase of the rough endoplasmic reticulum, as well as the presence of elements of coronavirus replication (reticulovesicular structures, zippered endoplasmic reticulum, electron-dense particles in the Golgi cisternae, and vacuoles with viral particles) were revealed. Further studies of the intracellular mechanisms used by the virus to replicate could help to develop antiviral drugs for the treatment of the new coronavirus infection.

Beyond Acute COVID-19: A Review of Long-term Cardiovascular Outcomes

Statistics Canada estimated that approximately 1.4 million Canadians suffer from long COVID. Although cardiovascular changes during acute SARS-CoV-2 infection are well documented, long-term cardiovascular sequelae are less understood. In this review, we sought to characterize adult cardiovascular outcomes in the months after acute COVID-19 illness. In our search we identified reports of outcomes including cardiac dysautonomia, myocarditis, ischemic injuries, and ventricular dysfunction. Even in patients without overt cardiac outcomes, subclinical changes have been observed. Cardiovascular sequelae after SARS-CoV-2 infection can stem from exacerbation of preexisting conditions, ongoing inflammation, or as a result of damage that occurred during acute infection. For example, myocardial fibrosis has been reported months after hospital admission for COVID-19 illness, and might be a consequence of myocarditis and myocardial injury during acute disease. In turn, myocardial fibrosis can contribute to further outcomes including dysrhythmias and heart failure. Severity of acute infection might be a risk factor for long-term cardiovascular consequences, however, cardiovascular changes have also been reported in young, healthy individuals who had asymptomatic or mild acute disease. Although evolving evidence suggests that previous SARS-CoV-2 infection might be a risk factor for cardiovascular disease, there is heterogeneity in existing evidence, and some studies are marred by measured and unmeasured confounders. Many investigations have also been limited by relatively short follow-up. Future studies should focus on longer term outcomes (beyond 1 year) and identifying the prevalence of outcomes in different populations on the basis of acute and long COVID disease severity.

Long COVID and the cardiovascular system-elucidating causes and cellular mechanisms in order to develop targeted diagnostic and therapeutic strategies: a joint Scientific Statement of the ESC Working Groups on Cellular Biology of the Heart and Myocardial and Pericardial Diseases

Long COVID has become a world-wide, non-communicable epidemic, caused by long-lasting multiorgan symptoms that endure for weeks or months after SARS-CoV-2 infection has already subsided. This scientific document aims to provide insight into the possible causes and therapeutic options available for the cardiovascular manifestations of long COVID. In addition to chronic fatigue, which is a common symptom of long COVID, patients may present with chest pain, ECG abnormalities, postural orthostatic tachycardia, or newly developed supraventricular or ventricular arrhythmias. Imaging of the heart and vessels has provided evidence of chronic, post-infectious perimyocarditis with consequent left or right ventricular failure, arterial wall inflammation, or microthrombosis in certain patient populations. Better understanding of the underlying cellular and molecular mechanisms of long COVID will aid in the development of effective treatment strategies for its cardiovascular manifestations. A number of mechanisms have been proposed, including those involving direct effects on the myocardium, microthrombotic damage to vessels or endothelium, or persistent inflammation. Unfortunately, existing circulating biomarkers, coagulation, and inflammatory markers, are not highly predictive for either the presence or outcome of long COVID when measured 3 months after SARS-CoV-2 infection. Further studies are needed to understand underlying mechanisms, identify specific biomarkers, and guide future preventive strategies or treatments to address long COVID and its cardiovascular sequelae.

Coagulopathy is Initiated with Endothelial Dysfunction and Disrupted Fibrinolysis in Patients with COVID-19 Disease

A substantial group of patients suffer from Covid-19 (CAC) coagulopathy and are presented with thrombosis. The pathogenesis involved in CAC is not fully understood. We evaluated the hemostatic and inflammatory parameters of 51 hospitalized Covid-19 adult patients and 21 controls. The parameters analyzed were danger signal molecule (High molecular weight group box protein-1/HMGBP-1), platelet count, prothrombin time (PT), activated partial thromboplastin time (aPTT), D-dimer, fibrinogen, endothelial protein C receptor (EPCR), soluble E-selectin, soluble P-selectin, thrombomodulin, tissue plasminogen activator (TPA), plasminogen activator inhibitor-1 (PAI-1), soluble fibrin monomer complex (SFMC), platelet-derived microparticles (PDMP), β-thromboglobulin, antithrombin and protein C. The main objective of our study was to investigate which part of the hemostatic system was mostly affected at the admission of Covid-19 patients and whether these parameters could differentiate intensive care unit (ICU) and non-ICU patients. In this prospective case-control study, 51 patients ≥ 18 years who are hospitalized with the diagnosis of Covid-19 and 21 healthy control subjects were included. We divided the patients into two groups according to their medical progress, either in ICU or non-ICU group. Regarding the outcome, patients were again categorized as a survivor and non-survivor groups. Blood samples were collected from patients at admission at the time of hospitalization before the administration of any treatment for Covid-19. The analyzes of the study were made with the IBM SPSS V22 program. p < 0.05 was considered statistically significant. A total of 51 adult patients (F/M: 24/27) (13 ICU and 38 non-ICU) were included in the study cohort. The mean age of the patients was 68.1 ± 14.4 years. The control group consisted of 21 age and sex-matched healthy individuals. All of the patients were hospitalized. In a group of 13 patients, Covid-19 progressed to a severe form, and were hospitalized in ICU. We found out that the levels of fibrinogen, prothrombin time (PT), endothelial protein-C receptor (EPCR), D-dimer, soluble E-selectin, soluble P-selectin, plasminogen activator inhibitor-1 (PAI-1), and tissue plasminogen activator (TPA) were increased; whereas, the levels of soluble fibrin monomer complex (SFMC), platelet-derived microparticles (PDMP), antithrombin and protein-C were decreased in Covid-19 patients compared to the control group at hospital admission. Tissue plasminogen activator was the only marker with a significantly different median level between ICU and non-ICU groups (p < 0.001). In accordance with the previous literature, we showed that Covid-19 associated coagulopathy is distinct from sepsis-induced DIC with prominent early endothelial involvement and fibrinolytic shut-down. Reconstruction of endothelial function at early stages of infection may protect patients from progressing to ICU hospitalization. We believe that after considering the patient's bleeding risk, early administration of LMWH therapy for Covid-19, even in an outpatient setting, may be helpful both for restoring endothelial function and anticoagulation. The intensity of anticoagulation in non-ICU and ICU Covid-19 patients should be clarified with further studies.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12291-023-01118-3.

Clinical assessment of endothelial function in convalescent COVID-19 patients: a meta-analysis with meta-regressions

BACKGROUND

Endothelial dysfunction has been proposed to play a key role in the pathogenesis of coronavirus disease 2019 (COVID-19) and its post-acute sequelae. Flow-mediated dilation (FMD) is recognized as an accurate clinical method to assess endothelial function. Thus, we performed a meta-analysis of the studies evaluating FMD in convalescent COVID-19 patients and controls with no history of COVID-19.

METHODS

A systematic literature search was conducted in the main scientific databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Using the random effects method, differences between cases and controls were expressed as mean difference (MD) with 95% confidence intervals (95% CI). The protocol was registered on PROSPERO with reference number CRD42021289684.

RESULTS

Twelve studies were included in the final analysis. A total of 644 convalescent COVID-19 patients showed significantly lower FMD values as compared to 662 controls (MD: -2.31%; 95% CI: -3.19, -1.44; p < 0.0001). Similar results were obtained in the sensitivity analysis of the studies that involved participants in either group with no cardiovascular risk factors or history of coronary artery disease (MD: -1.73%; 95% CI: -3.04, -0.41; p = 0.010). Interestingly, when considering studies separately based on enrolment within or after 3 months of symptom onset, results were further confirmed in both short- (MD: -2.20%; 95% CI: -3.35, -1.05; p < 0.0001) and long-term follow-up (MD: -2.53%; 95% CI: -4.19, -0.86; p = 0.003). Meta-regression models showed that an increasing prevalence of post-acute sequelae of COVID-19 was linked to a higher difference in FMD between cases and controls (Z-score: -2.09; p = 0.037).

CONCLUSIONS

Impaired endothelial function can be documented in convalescent COVID-19 patients, especially when residual clinical manifestations persist. Targeting endothelial dysfunction through pharmacological and rehabilitation strategies may represent an attractive therapeutic option.Key messagesThe mechanisms underlying the post-acute sequelae of coronavirus disease 2019 (COVID-19) have not been fully elucidated.Impaired endothelial function can be documented in convalescent COVID-19 patients for up to 1 year after infection, especially when residual clinical manifestations persist.Targeting endothelial dysfunction may represent an attractive therapeutic option in the post-acute phase of COVID-19.

Endothelial Dysfunction in COVID-19: Potential Mechanisms and Possible Therapeutic Options

SARS-CoV-2, a novel coronavirus found in Wuhan (China) at the end of 2019, is the etiological agent of the current pandemic that is a heterogeneous disease, named coronavirus disease 2019 (COVID-19). SARS-CoV-2 affects primarily the lungs, but it can induce multi-organ involvement such as acute myocardial injury, myocarditis, thromboembolic eventsandrenal failure. Hypertension, chronic kidney disease, diabetes mellitus and obesity increase the risk of severe complications of COVID-19. There is no certain explanation for this systemic COVID-19 involvement, but it could be related to endothelial dysfunction, due to direct (endothelial cells are infected by the virus) and indirect damage (systemic inflammation) factors. Angiotensin-converting enzyme 2 (ACE2), expressed in human endothelium, has a fundamental role in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. In fact, ACE2 is used as a receptor by SARS-CoV-2, leading to the downregulation of these receptors on endothelial cells; once inside, this virus reduces the integrity of endothelial tissue, with exposure of prothrombotic molecules, platelet adhesion, activation of coagulation cascades and, consequently, vascular damage. Systemic microangiopathy and thromboembolism can lead to multi-organ failure with an elevated risk of death. Considering the crucial role of the immunological response and endothelial damage in developing the severe form of COVID-19, in this review, we will attempt to clarify the underlying pathophysiological mechanisms.

Serum of Post-COVID-19 Syndrome Patients with or without ME/CFS Differentially Affects Endothelial Cell Function In Vitro

A proportion of COVID-19 reconvalescent patients develop post-COVID-19 syndrome (PCS) including a subgroup fulfilling diagnostic criteria of Myalgic encephalomyelitis/Chronic Fatigue Syndrome (PCS/CFS). Recently, endothelial dysfunction (ED) has been demonstrated in these patients, but the mechanisms remain elusive. Therefore, we investigated the effects of patients’ sera on endothelia cells (ECs) in vitro. PCS (n = 17), PCS/CFS (n = 13), and healthy controls (HC, n = 14) were screened for serum anti-endothelial cell autoantibodies (AECAs) and dysregulated cytokines. Serum-treated ECs were analysed for the induction of activation markers and the release of small molecules by flow cytometry. Moreover, the angiogenic potential of sera was measured in a tube formation assay. While only marginal differences between patient groups were observed for serum cytokines, AECA binding to ECs was significantly increased in PCS/CFS patients. Surprisingly, PCS and PCS/CFS sera reduced surface levels of several EC activation markers. PCS sera enhanced the release of molecules associated with vascular remodelling and significantly promoted angiogenesis in vitro compared to the PCS/CFS and HC groups. Additionally, sera from both patient cohorts induced the release of molecules involved in inhibition of nitric oxide-mediated endothelial relaxation. Overall, PCS and PCS/CFS patients′ sera differed in their AECA content and their functional effects on ECs, i.e., secretion profiles and angiogenic potential. We hypothesise a pro-angiogenic effect of PCS sera as a compensatory mechanism to ED which is absent in PCS/CFS patients.

Complement Mediated Endothelial Damage in Thrombotic Microangiopathies

Thrombotic microangiopathies (TMA) constitute a group of different disorders that have a common underlying mechanism: the endothelial damage. These disorders may exhibit different mechanisms of endothelial injury depending on the pathological trigger. However, over the last decades, the potential role of the complement system (CS) has gained prominence in their pathogenesis. This is partly due to the great efficacy of complement-inhibitors in atypical hemolytic syndrome (aHUS), a TMA form where the primary defect is an alternative complement pathway dysregulation over endothelial cells (genetic and/or adquired). Complement involvement has also been demonstrated in other forms of TMA, such as thrombotic thrombocytopenic purpura (TTP) and in Shiga toxin-producing Escherichia coli hemolytic uremic syndrome (STEC-HUS), as well as in secondary TMAs, in which complement activation occurs in the context of other diseases. However, at present, there is scarce evidence about the efficacy of complement-targeted therapies in these entities. The relationship between complement dysregulation and endothelial damage as the main causes of TMA will be reviewed here. Moreover, the different clinical trials evaluating the use of complement-inhibitors for the treatment of patients suffering from different TMA-associated disorders are summarized, as a clear example of the entry into a new era of personalized medicine in its management.

Chromogranin A plasma levels predict mortality in COVID-19

Background

Chromogranin A (CgA) and its fragment vasostatin I (VS-I) are secreted in the blood by endocrine/neuroendocrine cells and regulate stress responses. Their involvement in Coronavirus 2019 disease (COVID-19) has not been investigated.

Methods

CgA and VS-I plasma concentrations were measured at hospital admission from March to May 2020 in 190 patients. 40 age- and sex-matched healthy volunteers served as controls. CgA and VS-I levels relationship with demographics, comorbidities and disease severity was assessed through Mann Whitney U test or Spearman correlation test. Cox regression analysis and Kaplan Meier survival curves were performed to investigate the impact of the CgA and VS-I levels on in-hospital mortality.

Results

Median CgA and VS-I levels were higher in patients than in healthy controls (CgA: 0.558 nM [interquartile range, IQR 0.358–1.046] vs 0.368 nM [IQR 0.288–0.490] respectively, p = 0.0017; VS-I: 0.357 nM [IQR 0.196–0.465] vs 0.144 nM [0.144–0.156] respectively, p<0.0001). Concentration of CgA, but not of VS-I, significantly increased in patients who died (n = 47) than in survivors (n = 143) (median 0.948 nM [IQR 0.514–1.754] vs 0.507 nM [IQR 0.343–0.785], p = 0.00026). Levels of CgA were independent predictors of in-hospital mortality (hazard ratio 1.28 [95% confidence interval 1.077–1.522], p = 0.005) when adjusted for age, number of comorbidities, respiratory insufficiency degree, C-reactive protein levels and time from symptom onset to sampling. Kaplan Meier curves revealed a significantly increased mortality rate in patients with CgA levels above 0.558 nM (median value, log rank test, p = 0.001).

Conclusion

Plasma CgA levels increase in COVID-19 patients and represent an early independent predictor of mortality.

Elevated plasma levels of epithelial and endothelial cell markers in COVID-19 survivors with reduced lung diffusing capacity six months after hospital discharge

BACKGROUND

Some COVID-19 survivors present lung function abnormalities during follow-up, particularly reduced carbon monoxide lung diffusing capacity (DLCO). To investigate risk factors and underlying pathophysiology, we compared the clinical characteristics and levels of circulating pulmonary epithelial and endothelial markers in COVID-19 survivors with normal or reduced DLCO 6 months after discharge.

METHODS

Prospective, observational study. Clinical characteristics during hospitalization, and spirometry, DLCO and plasma levels of epithelial (surfactant protein (SP) A (SP-A), SP-D, Club cell secretory protein-16 (CC16) and secretory leukocyte protease inhibitor (SLPI)), and endothelial (soluble intercellular adhesion molecule 1 (sICAM-1), soluble E-selectin and Angiopoietin-2) 6 months after hospital discharge were determined in 215 COVID-19 survivors.

RESULTS

DLCO was < 80% ref. in 125 (58%) of patients, who were older, more frequently smokers, had hypertension, suffered more severe COVID-19 during hospitalization and refer persistent dyspnoea 6 months after discharge. Multivariate regression analysis showed that age ≥ 60 years and severity score of the acute episode ≥ 6 were independent risk factors of reduced DLCO 6 months after discharge. Levels of epithelial (SP-A, SP-D and SLPI) and endothelial (sICAM-1 and angiopoietin-2) markers were higher in patients with reduced DLCO, particularly in those with DLCO ≤ 50% ref. Circulating SP-A levels were associated with the occurrence of acute respiratory distress syndrome (ARDS), organizing pneumonia and pulmonary embolisms during hospitalization.

CONCLUSIONS

Reduced DLCO is common in COVID-19 survivors 6 months after hospital discharge, especially in those older than 60 years with very severe acute disease. In these individuals, elevated levels of epithelial and endothelial markers suggest persistent lung damage.

Impact of COVID-19 on vascular patients worldwide: analysis of the COVIDSurg data

BACKGROUND

The COVIDSurg collaborative was an international multicenter prospective analysis of perioperative data from 235 hospitals in 24 countries. It found that perioperative COVID-19 infection was associated with a mortality rate of 24%. At the same time, the COVER study demonstrated similarly high perioperative mortality rates in vascular surgical patients undergoing vascular interventions even without COVID-19, likely associated with the high burden of comorbidity associated with vascular patients. This is a vascular subgroup analysis of the COVIDSurg cohort.

METHODS

All patients with a suspected or confirmed diagnosis of COVID-19 in the 7 days prior to, or in the 30 days following a vascular procedure were included. The primary outcome was 30-day mortality. Secondary outcomes were pulmonary complications (adult respiratory distress syndrome, pulmonary embolism, pneumonia and respiratory failure). Logistic regression was undertaken for dichotomous outcomes.

RESULTS

Overall, 602 patients were included in this subgroup analysis, of which 88.4% were emergencies. The most common operations performed were for vascular-related dialysis access procedures (20.1%, N.=121). The combined 30-day mortality rate was 27.2%. Composite secondary pulmonary outcomes occurred in half of the vascular patients (N.=275, 45.7%).

CONCLUSIONS

Mortality following vascular surgery in COVID positive patients was significantly higher than levels reported pre-pandemic, and similar to that seen in other specialties in the COVIDSurg cohort. Initiatives and surgical pathways that ensure vascular patients are protected from exposure to COVID-19 in the peri-operative period are vital to protect against excess mortality.

Peripheral microcirculatory alterations are associated with the severity of acute respiratory distress syndrome in COVID-19 patients admitted to intermediate respiratory and intensive care units

Background

COVID-19 is primarily a respiratory disease; however, there is also evidence that it causes endothelial damage in the microvasculature of several organs. The aim of the present study is to characterize in vivo the microvascular reactivity in peripheral skeletal muscle of severe COVID-19 patients.

Methods

This is a prospective observational study carried out in Spain, Mexico and Brazil. Healthy subjects and severe COVID-19 patients admitted to the intermediate respiratory (IRCU) and intensive care units (ICU) due to hypoxemia were studied. Local tissue/blood oxygen saturation (StO₂) and local hemoglobin concentration (THC) were non-invasively measured on the forearm by near-infrared spectroscopy (NIRS). A vascular occlusion test (VOT), a three-minute induced ischemia, was performed in order to obtain dynamic StO₂ parameters: deoxygenation rate (DeO₂), reoxygenation rate (ReO₂), and hyperemic response (H_AUC). In COVID-19 patients, the severity of ARDS was evaluated by the ratio between peripheral arterial oxygen saturation (SpO₂) and the fraction of inspired oxygen (FiO₂) (SF ratio).

Results

Healthy controls (32) and COVID-19 patients (73) were studied. Baseline StO₂ and THC did not differ between the two groups. Dynamic VOT-derived parameters were significantly impaired in COVID-19 patients showing lower metabolic rate (DeO₂) and diminished endothelial reactivity. At enrollment, most COVID-19 patients were receiving invasive mechanical ventilation (MV) (53%) or high-flow nasal cannula support (32%). Patients on MV were also receiving sedative agents (100%) and vasopressors (29%). Baseline StO₂ and DeO₂ negatively correlated with SF ratio, while ReO₂ showed a positive correlation with SF ratio. There were significant differences in baseline StO₂ and ReO₂ among the different ARDS groups according to SF ratio, but not among different respiratory support therapies.

Conclusion

Patients with severe COVID-19 show systemic microcirculatory alterations suggestive of endothelial dysfunction, and these alterations are associated with the severity of ARDS. Further evaluation is needed to determine whether these observations have prognostic implications. These results represent interim findings of the ongoing HEMOCOVID-19 trial.

Trial registration ClinicalTrials.gov NCT04689477. Retrospectively registered 30 December 2020.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-021-03803-2.

COVID-19 Associated Choroidopathy

The aim of the study is to report on the indocyanine green angiography (ICGA) and OCT findings in patients hospitalized for severe COVID infection. In this observational prospective monocentric cohort study, we included patients hospitalized for severe COVID infection. The main outcomes were ICGA and OCT findings. A total of 14 patients with a mean age of 58.2 ± 11.4 years and a male predominance (9/14 patients; 64%) were included. The main ICGA findings included hypofluorescent spots in 19 eyes (68%), intervortex shunts in 10 eyes (36%), and characteristic "hemangioma-like" lesions in five eyes (18%). "Hemangioma-like" lesions were both unique and unilateral, and showed no washout on the late phase of the angiogram. The main OCT findings included focal choroidal thickening in seven eyes (25%), caverns in six eyes (21%) and paracentral acute middle maculopathy lesions in one eye (4%). All patients hospitalized for severe COVID infection had anomalies on ICGA and OCT. Lesions to both retinal and choroidal vasculature were found. These anomalies could be secondary to vascular involvement related directly or indirectly to the SARS-CoV2 virus.

Resveratrol as an Adjunctive Therapy for Excessive Oxidative Stress in Aging COVID-19 Patients

The coronavirus disease 2019 (COVID-19) pandemic continues to burden healthcare systems worldwide. COVID-19 symptoms are highly heterogeneous, and the patient may be asymptomatic or may present with mild to severe or fatal symptoms. Factors, such as age, sex, and comorbidities, are key determinants of illness severity and progression. Aging is accompanied by multiple deficiencies in interferon production by dendritic cells or macrophages in response to viral infections, resulting in dysregulation of inflammatory immune responses and excess oxidative stress. Age-related dysregulation of immune function may cause a more obvious pathophysiological response to SARS-CoV-2 infection in elderly patients and may accelerate the risk of biological aging, even after recovery. For more favorable treatment outcomes, inhibiting viral replication and dampening inflammatory and oxidative responses before induction of an overt cytokine storm is crucial. Resveratrol is a potent antioxidant with antiviral activity. Herein, we describe the reasons for impaired interferon production, owing to aging, and the impact of aging on innate and adaptive immune responses to infection, which leads to inflammation distress and immunosuppression, thereby causing fulminant disease. Additionally, the molecular mechanism by which resveratrol could reverse a state of excessive basal inflammatory and oxidative stress and low antiviral immunity is discussed.