Editorial: The CXCR4 Ligand/Receptor Family and the DPP4 Protease in High-Risk Cardiovascular Patients

SARS-CoV-2: Receptor and Co-receptor Tropism Probability

The recent pandemic which arose from China, is caused by a pathogenic virus named "severe acute respiratory syndrome-related coronavirus-2 (SARS-CoV-2)". Its rapid global expansion has inflicted an extreme public health concern. The attachment of receptor-binding domains (RBD) of the spike proteins (S) to the host cell's membrane, with or without the help of other cellular components such as proteases and especially co-receptors, is required for the first stage of its pathogenesis. In addition to humans, angiotensin-converting enzyme 2 (ACE2) is found on a wide range of vertebrate host's cellular surface. SARS-CoV-2 has a broad spectrum of tropism; thus, it can infect a vast range of tissues, organs, and hosts; even though the surface amino acids of the spike protein conflict in the receptor-binding region. Due to the heterogeneous ACE2 distribution and the presence of different domains on the SARS-CoV-2 spike protein for binding, the virus entry into diverse host cell types may depend on the host cells' receptor presentation with or without co-receptors. This review investigates multiple current types of receptor and co-receptor tropisms, with other molecular factors alongside their respective mechanisms, which facilitate the binding and entry of SARS-CoV-2 into the cells, extending the severity of the coronavirus disease 2019 (COVID-19). Understanding the pathogenesis of COVID-19 from this perspective can effectively help prevent this disease and provide more potent treatment strategies, particularly in vulnerable people with various cellular-level susceptibilities.

COVID-19 and comorbidities: A role for dipeptidyl peptidase 4 (DPP4) in disease severity?

The coronavirus disease 2019 (COVID-19) pandemic is caused by a novel betacoronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), similar to SARS-CoV and Middle East respiratory syndrome (MERS-CoV), which cause acute respiratory distress syndrome and case fatalities. COVID-19 disease severity is worse in older obese patients with comorbidities such as diabetes, hypertension, cardiovascular disease, and chronic lung disease. Cell binding and entry of betacoronaviruses is via their surface spike glycoprotein; SARS-CoV binds to the metalloprotease angiotensin-converting enzyme 2 (ACE2), MERS-CoV utilizes dipeptidyl peptidase 4 (DPP4), and recent modeling of the structure of SARS-CoV-2 spike glycoprotein predicts that it can interact with human DPP4 in addition to ACE2. DPP4 is a ubiquitous membrane-bound aminopeptidase that circulates in plasma; it is multifunctional with roles in nutrition, metabolism, and immune and endocrine systems. DPP4 activity differentially regulates glucose homeostasis and inflammation via its enzymatic activity and nonenzymatic immunomodulatory effects. The importance of DPP4 for the medical community has been highlighted by the approval of DPP4 inhibitors, or gliptins, for the treatment of type 2 diabetes mellitus. This review discusses the dysregulation of DPP4 in COVID-19 comorbid conditions; DPP4 activity is higher in older individuals and increased plasma DPP4 is a predictor of the onset of metabolic syndrome. DPP4 upregulation may be a determinant of COVID-19 disease severity, which creates interest regarding the use of gliptins in management of COVID-19. Also, knowledge of the chemistry and biology of DPP4 could be utilized to develop novel therapies to block viral entry of some betacoronaviruses, potentially including SARS-CoV-2.

Stromal Cell-derived Factor-1 and CXC Chemokine Receptor Type-4 are Associated with Cardiovascular Disease in Patients under Hemodialysis

Background

Cardiovascular disease (CVD) is the most common cause of death among patients with end-stage renal disease especially whom under hemodialysis (HD). Stromal cell-derived factor-1 (SDF-1) and its receptor CXC chemokine receptor type-4 (CXCR4) could contribute to CVD. The main aim of this study was to evaluate the association between SDF-1 and CXCR4 with CVD and its related risk factors in patients under HD.

Methods

Sixty patients under HD and 29 healthy subjects were recruited in the study. The serum levels and relative messenger RNA (mRNA) expressions of SDF-1 and CXCR4 were measured using enzyme-linked immunosorbent assay and real-time polymerase chain reaction in patients and controls, respectively. CVD history of the patients was obtained.

Results

Twenty patients (33.3%) had a history of CVD. The mean levels of serum and relative mRNA expressions of SDF-1 and CXCR4 were higher in patients than controls and also in patients with a history of CVD than patients without it. The serum levels and relative expressions of SDF-1 and CXCR4 were positively correlated with blood urea nitrogen, parathyroid hormone, and high-sensitivity C-reactive protein and inversely correlated with hemoglobin. The history of CVD was the independent predictor of serum levels of SDF-1 and CXCR4 and also relative mRNA expression of CXCR4.

Conclusions

The higher levels of serum and relative mRNA expressions of SDF-1 and CXCR4 were associated with CVD in patients under HD. Furthermore, SDF-1 and CXCR4 were associated with several traditional and uremia-related CVD risk factors in such patients.