Addressing the 'hypoxia paradox' in severe COVID-19: literature review and report of four cases treated with erythropoietin analogues

Parameters and Morphological Changes of Erythrocytes and Platelets of COVID-19 Subjects: A Longitudinal Cohort Study

Purpose

Information about dynamic changes occurring in the parameters and morphology of erythrocytes and platelets during the coronavirus disease 2019 (COVID-19) infection and convalescence is scarce. To explore potential associations between dynamic erythrocyte and platelet parameters, morphological changes, and the course or severity of the disease is essential.

Patients and Methods

From January 17th, 2020, to February 20th, 2022, we followed up on 35 patients with non-severe and 11 patients with severe COVID-19 following their discharge. We collected clinical features, dynamic complete blood count (CBC), and peripheral blood smears (PBS) and analyzed parameter and morphological changes of erythrocytes and platelets depending on the course or severity of the disease. The course of the disease included four periods, namely onset (T1), discharge (T2), 1-year follow-up (T3), and 2-year follow-up (T4).

Results

Red blood cell (RBC) counts and hemoglobin were the lowest in T2, followed by T1, and lower in T1 and T2 than in T3 and T4. Inversely, the red blood cell distribution width (RDW) was the highest in T2, followed by T1, and higher than in T3 and T4. Compared to non-severe patients, the platelet of severe patients was lower in T1 and T2. In contrast, the mean platelet volume (MPV) and platelet distribution width (PDW) tended to be higher in severe patients. Similarly, anisocytosis was more common in peripheral blood smears at early stages and in severe patients. Finally, large platelets were more common in severe patients.

Conclusion

Anisocytosis of erythrocytes and large platelets are found in patients with severe COVID-19, these changes may help primary hospitals to identify patients with a high risk of severe COVID-19 at an early stage.

The Impact of Recombinant Human Erythropoietin Administration in Critically ill COVID-19 Patients: A Multicenter Cohort Study

The use of erythropoietin-stimulating agents (ESAs) as adjunctive therapy in critically ill patients with COVID-19 may have a potential benefit. This study aims to evaluate the effect of ESAs on the clinical outcomes of critically ill COVID-19 patients. A multicenter, retrospective cohort study was conducted from 01-03-2020 to 31-07-2021. We included adult patients who were ≥ 18 years old with a confirmed diagnosis of COVID-19 infection and admitted to intensive care units (ICUs). Patients were categorized depending on ESAs administration during their ICU stay. The primary endpoint was the length of stay; other endpoints were considered secondary. After propensity score matching (1:3), the overall included patients were 120. Among those, 30 patients received ESAs. A longer duration of ICU and hospital stay was observed in the ESA group (beta coefficient: 0.64; 95% CI: 0.31-0.97; P = < .01, beta coefficient: 0.41; 95% CI: 0.12-0.69; P = < .01, respectively). In addition, the ESA group's ventilator-free days (VFDs) were significantly shorter than the control group. Moreover, patients who received ESAs have higher odds of liver injury and infections during ICU stay than the control group. The use of ESAs in COVID-19 critically ill patients was associated with longer hospital and ICU stays, with no survival benefits but linked with lower VFDs.

Significance of Catecholamine Biosynthetic/Metabolic Pathway in SARS-CoV-2 Infection and COVID-19 Severity

The SARS-CoV-2 infection was previously associated with the expression of the dopamine biosynthetic enzyme L-Dopa decarboxylase (DDC). Specifically, a negative correlation was detected between DDC mRNA and SARS-CoV-2 RNA levels in in vitro infected epithelial cells and the nasopharyngeal tissue of COVID-19 patients with mild/no symptoms. However, DDC, among other genes related to both DDC expression and SARS-CoV-2-infection (ACE2, dACE2, EPO), was upregulated in these patients, possibly attributed to an orchestrated host antiviral response. Herein, by comparing DDC expression in the nasopharyngeal swab samples of severe/critical to mild COVID-19 cases, we showed a 20 mean-fold reduction, highlighting the importance of the expression of this gene as a potential marker of COVID-19 severity. Moreover, we identified an association of SARS-CoV-2 infection with the expression of key catecholamine biosynthesis/metabolism-related genes, in whole blood samples from hospitalized patients and in cultured cells. Specifically, viral infection downregulated the biosynthetic part of the dopamine pathway (reduction in DDC expression up to 7.5 mean-fold), while enhanced the catabolizing part (increase in monoamine oxidases A and B expression up to 15 and 10 mean-fold, respectively) in vivo, irrespectively of the presence of comorbidities. In accordance, dopamine levels in the sera of severe cases were reduced (up to 3.8 mean-fold). Additionally, a moderate positive correlation between DDC and MAOA mRNA levels (r = 0.527, p < 00001) in the blood was identified upon SARS-CoV-2-infection. These observations were consistent to the gene expression data from SARS-CoV-2-infected Vero E6 and A549 epithelial cells. Furthermore, L-Dopa or dopamine treatment of infected cells attenuated the virus-derived cytopathic effect by 55% and 59%, respectively. The SARS-CoV-2 mediated suppression of dopamine biosynthesis in cell culture was, at least in part, attributed to hypoxia-like conditions triggered by viral infection. These findings suggest that L-Dopa/dopamine intake may have a preventive or therapeutic value for COVID-19 patients.

Are hemoglobin-derived peptides involved in the neuropsychiatric symptoms caused by SARS-CoV-2 infection?

Follow-up of patients affected by COVID-19 has unveiled remarkable findings. Among the several sequelae caused by SARS-CoV-2 viral infection, it is particularly noteworthy that patients are prone to developing depression, anxiety, cognitive disorders, and dementia as part of the post-COVID-19 syndrome. The multisystem aspects of this disease suggest that multiple mechanisms may converge towards post-infection clinical manifestations. The literature provides mechanistic hypotheses related to changes in classical neurotransmission evoked by SARS-CoV-2 infection; nonetheless, the interaction of peripherally originated classical and non-canonic peptidergic systems may play a putative role in this neuropathology. A wealth of robust findings shows that hemoglobin-derived peptides are able to control cognition, memory, anxiety, and depression through different mechanisms. Early erythrocytic death is found during COVID-19, which would cause excess production of hemoglobin-derived peptides. Following from this premise, the present review sheds light on a possible involvement of hemoglobin-derived molecules in the COVID-19 pathophysiology by fostering neuroscientific evidence that supports the contribution of this non-canonic peptidergic pathway. This rationale may broaden knowledge beyond the currently available data, motivating further studies in the field and paving ways for novel laboratory tests and clinical approaches.

The influence of renin angiotensin aldosterone system (RAAS), endothelial nitric oxide synthase (eNOS) and erythropoietin (EPO) on COVID-19 complications

Certain aspects of the renin-angiotensin-aldosterone system (RAAS) have eluded deserved attention such as the role of erythropoietin (EPO) and nitric oxide (NO) both of which appear to significantly modulate COVID-19 disease course. Furthermore, renin-angiotensin-aldosterone system (RAAS) and endothelial NO synthase (eNOS) genetic polymorphisms additionally impact on EPO and NO homeostasis and have extensive implications on pharmacological disease management.

Introducing the brain erythropoietin circle to explain adaptive brain hardware upgrade and improved performance

Executive functions, learning, attention, and processing speed are imperative facets of cognitive performance, affected in neuropsychiatric disorders. In clinical studies on different patient groups, recombinant human (rh) erythropoietin (EPO) lastingly improved higher cognition and reduced brain matter loss. Correspondingly, rhEPO treatment of young rodents or EPO receptor (EPOR) overexpression in pyramidal neurons caused remarkable and enduring cognitive improvement, together with enhanced hippocampal long-term potentiation. The 'brain hardware upgrade', underlying these observations, includes an EPO induced ~20% increase in pyramidal neurons and oligodendrocytes in cornu ammonis hippocampi in the absence of elevated DNA synthesis. In parallel, EPO reduces microglia numbers and dampens their activity and metabolism as prerequisites for undisturbed EPO-driven differentiation of pre-existing local neuronal precursors. These processes depend on neuronal and microglial EPOR. This novel mechanism of powerful postnatal neurogenesis, outside the classical neurogenic niches, and on-demand delivery of new cells, paralleled by dendritic spine increase, let us hypothesize a physiological procognitive role of hypoxia-induced endogenous EPO in brain, which we imitate by rhEPO treatment. Here we delineate the brain EPO circle as working model explaining adaptive 'brain hardware upgrade' and improved performance. In this fundamental regulatory circle, neuronal networks, challenged by motor-cognitive tasks, drift into transient 'functional hypoxia', thereby triggering neuronal EPO/EPOR expression.