The Spike Protein of SARS-CoV-2 Impairs Lipid Metabolism and Increases Susceptibility to Lipotoxicity: Implication for a Role of Nrf2.

Coronavirus disease 2019 (COVID-19) patients show lipid metabolic alterations, but the mechanism remains unknown. In this study, we aimed to investigate whether the Spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) impairs lipid metabolism in host cells. We generated a Spike cell line in HEK293 using the pcDNA vector carrying the Spike gene expression cassette. A control cell line was generated using the empty pcDNA vector. Gene expression profiles related to lipid metabolic, autophagic, and ferroptotic pathways were investigated. Palmitic acid (PA)-overload was used to assess lipotoxicity-induced necrosis. As compared with controls, the Spike cells showed a significant increase in lipid depositions in cell membranes as well as dysregulation of expression of a panel of molecules involving lipid metabolism, autophagy, and ferroptosis. The Spike cells showed an upregulation of nuclear factor erythroid 2-related factor 2 (Nrf2), a multifunctional transcriptional factor, in response to PA. Furthermore, the Spike cells exhibited increased necrosis in response to PA-induced lipotoxicity compared to control cells in a time- and dose-dependent manner via ferroptosis, which could be attenuated by the Nrf2 inhibitor trigonelline. We conclude that the Spike protein impairs lipid metabolic and autophagic pathways in host cells, leading to increased susceptibility to lipotoxicity via ferroptosis which can be suppressed by a Nrf2 inhibitor. This data also suggests a central role of Nrf2 in Spike-induced lipid metabolic impairments.

Spike protein of SARS-CoV-2 activates macrophages and contributes to induction of acute lung inflammation in male mice.

The spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) plays a crucial role in mediating viral entry into host cells. However, whether it contributes to pulmonary hyperinflammation in patients with coronavirus disease 2019 is not well known. In this study, we developed a spike protein-pseudotyped (Spp) lentivirus with the proper tropism of the SARS-CoV-2 spike protein on the surface and determined the distribution of the Spp lentivirus in wild-type C57BL/6J male mice that received an intravenous injection of the virus. Lentiviruses with vesicular stomatitis virus glycoprotein (VSV-G) or with a deletion of the receptor-binding domain (RBD) in the spike protein [Spp (∆RBD)] were used as controls. Two hours postinfection (hpi), there were 27-75 times more viral burden from Spp lentivirus in the lungs than in other organs; there were also about 3-5 times more viral burden from Spp lentivirus than from VSV-G lentivirus in the lungs, liver, kidney, and spleen. Deletion of RBD diminished viral loads in the lungs but not in the heart. Acute pneumonia was observed in animals 24 hpi. Spp lentivirus was mainly found in SPC+ and LDLR+ pneumocytes and macrophages in the lungs. IL6, IL10, CD80, and PPAR-γ were quickly upregulated in response to infection in the lungs as well as in macrophage-like RAW264.7 cells. Furthermore, forced expression of the spike protein in RAW264.7 cells significantly increased the mRNA levels of the same panel of inflammatory factors. Our results demonstrated that the spike protein of SARS-CoV-2 confers the main point of viral entry into the lungs and can induce cellular pathology. Our data also indicate that an alternative ACE2-independent viral entry pathway may be recruited in the heart and aorta.

Spike Protein of SARS-CoV-2 Activates Macrophages and Contributes to Induction of Acute Lung Inflammations in Mice

Background Coronavirus disease 2019 (COVID-19) patients exhibit multiple organ malfunctions with a primary manifestation of acute and diffuse lung injuries. The Spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is crucial to mediate viral entry into host cells;however, whether it can be cellularly pathogenic and contribute to pulmonary hyper-inflammations in COVID-19 is not well known. Methods and Findings In this study, we developed a Spike protein-pseudotyped (Spp) lentivirus with the proper tropism of SARS-CoV-2 Spike protein on the surface and tracked down the fate of Spp in wild type C57BL/6J mice receiving intravenous injection of the virus. A lentivirus with vesicular stomatitis virus glycoprotein (VSV-G) was used as the control. Two hours post-infection (hpi), Spp showed more than 27-75 times more viral burden in the lungs than other organs;it also exhibited about 3-5 times more viral burden than VSV-G lentivirus in the lungs, liver, kidney and spleen. Acute pneumonia was evident in animals 24 hpi. Spp lentivirus was mainly found in LDLR+ macrophages and pneumocytes in the lungs, but not in MARC1+ macrophages. IL6, IL10, CD80 and PPAR-? were quickly upregulated in response to infection of Spp lentivirus in the lungs in vivo as well as in macrophage-like RAW264.7 cells in vitro. We further confirmed that forced expression of the Spike protein in RAW264.7 cells could significantly increase the mRNA levels of the same panel of inflammatory factors. Conclusions Our results demonstrate that the Spike protein of SARS-CoV-2 alone can induce cellular pathology, e.g. activating macrophages and contributing to induction of acute inflammatory responses.

Follow-up study on serum cholesterol profiles and potential sequelae in recovered COVID-19 patients.

BACKGROUND: COVID-19 patients develop hypolipidemia. However, it is unknown whether lipid levels have improved and there are potential sequlae in recovered patients. OBJECTIVE: In this follow-up study, we evaluated serum lipidemia and various physiopathological laboratory values in recovered patients. METHODS: A 3-6 month follow-up study was performed between June 15 and September 3, 2020, to examine serum levels of laboratory values in 107 discharged COVID-19 patients (mild = 59; severe/critical = 48; diagnoses on admission). Sixty-one patients had a revisit chest CT scan. A Wilcoxon signed-rank test was used to analyze changes in laboratory values at admission and follow-up. RESULTS: LDL-c and HDL-c levels were significantly higher at follow-up than at admission in severe/critical cases (p <  0.05). LDL-c levels were significantly higher at follow-up than at admission in mild cases (p <  0.05). Coagulation and liver functional values were significantly improved at follow-up than at admission for patients (p <  0.05). Increases in HDL-c significantly correlated with increases in numbers of white blood cells (p <  0.001) during patients' recovery. With exclusion of the subjects taking traditional Chinese medicines or cholesterol-lowering drugs, LDL-c and HDL-c levels were significantly increased at follow-up than at admission in severe/critical cases (p <  0.05). Residue lesions were observed in CT images in 72% (44 of 61) of follow-up patients. CONCLUSIONS: Improvements of LDL-c, HDL-c, liver functions, and incomplete resolution of lung lesions were observed at 3-6 month follow-up for recovered patients, indicating that a long-term recovery process could be required and the development of sequelae such as pulmonary fibrosis could be expected in some patients.

Fecal occult blood and urinary cytology tests for rapid screening of inflammatory infection in the gastrointestinal and urological systems in patients with Coronavirus disease 2019.

BACKGROUND: Gastrointestinal infections (GI) and urological infections (UI) have not been fully addressed in COVID-19 patients. We aimed to evaluate the values of routine fecal occult blood (FOB) test and urinary cytology test (UCT) for screening of GI and UI in COVID-19 patients. METHODS: In this retrospective study, COVID-19 patients without associated comorbidities were divided into FOB- or UCT-positive or FOB- or UCT-negative groups. Their clinical characteristics and laboratory findings were then compared. RESULTS: A total of 13.6% of patients (47 of 345) tested positive for FOB, and 57.4% (27 of 47) of these patients lacked gastrointestinal symptoms. A total of 30.1% of patients (104 of 345) exhibited gastrointestinal symptoms, and 38.0% (131 of 345) were positive for either FOB or gastrointestinal symptoms. FOB-positive patients possessed significantly higher levels of C-reactive protein and fewer lymphocytes than FOB-negative patients. A total of 36.9% of patients (80 of 217) exhibited positive UCT, and 97.5% (78 of 80) of these patients possessed normal levels of serum markers for renal injuries. Significant differences in age and sex ratios were observed between the UCT-positive and UCT-negative groups, and 72.4% (42 of 58) of female patients over 60 years old were UCT-positive. CONCLUSIONS: Fecal occult blood test in combination with gastrointestinal symptoms could serve as a simple and useful screening approach for GI diagnoses for COVID-19. Age and sex are risk factors for UI in COVID-19 patients. UCT could be a sensitive tool for assessing early UI at a stage in which serum markers for renal injuries appear normal.

Cholesterol: A new game player accelerating vasculopathy caused by SARS-CoV-2?

The pandemic of coronavirus disease (COVID-19) has become a global threat to public health. Functional impairments in multiple organs have been reported in COVID-19, including lungs, heart, kidney, liver, brain, and vascular system. Patients with metabolic-associated preconditions, such as hypertension, obesity, and diabetes, are susceptible to experiencing severe symptoms. The recent emerging evidence of coagulation disorders in COVID-19 suggests that vasculopathy appears to be an independent risk factor promoting disease severity and mortality of affected patients. We recently found that the decreased levels of low-density lipoprotein cholesterols (LDL-c) correlate with disease severity in COVID-19 patients, indicating pathological interactions between dyslipidemia and vasculopothy in patients with COVID-19. However, this clinical manifestation has been unintentionally underestimated by physicians and scientific communities. As metabolic-associated morbidities are generally accompanied with endothelial cell (EC) dysfunctions, these pre-existing conditions may make ECs more vulnerable to SARS-CoV-2 attack. In this mini-review, we summarize the metabolic and vascular manifestations of COVID-19 with an emphasis on the association between changes in LDL-c levels and the development of severe symptoms as well as the pathophysiologic mechanisms underlying the synergistic effect of LDL-c and SARS-CoV-2 on EC injuries and vasculopathy.

Letter to the Editor: Low-density lipoprotein is a potential predictor of poor prognosis in patients with coronavirus disease 2019.

BACKGROUND: The pandemic of coronavirus disease 2019 (COVID-19) has become a global threat to public health. The lipid pathophysiology in COVID-19 is unknown. METHODS: In this retrospective longitudinal study, we monitored the serum lipids in 17 surviving and 4 non-surviving COVID-19 cases prior to their viral infections and duration the entire disease courses. RESULTS: In surviving cases, the low-density lipoprotein (LDL) levels decreased significantly on admission as compared with the levels before infection; the LDL levels remained constantly low during the disease progression and resumed to the original levels when patients recovered (pre-infection: 3.5 (3.0-4.4); on admission: 2.8 (2.3-3.1), p < 0.01; progression: 2.5 (2.3-3.0); discharge: 3.6 (2.7-4.1); median (IQR), in mmol/L). In non-surviving patients, LDL levels showed an irreversible and continuous decrease until death (1.1 (0.9-1.2), p = 0.02 versus the levels on admission). The ratio changes of LDL levels inversely correlated with ratio changes of high-sensitivity C-reactive protein levels. Logistic regression analysis showed increasing odds of lowered LDL levels associated with disease progression (odds ratio: 4.48, 95% IC: 1.55-12.92, p = 0.006) and in-hospital death (odds ratio: 21.72, 95% IC: 1.40-337.54, p = 0.028). CONCLUSIONS: LDL levels inversely correlated to disease severities, which could be a predictor for disease progress and poor prognosis.

Elevations of serum cancer biomarkers correlate with severity of COVID-19.

In this retrospective study, we evaluated the levels of a series of serum biomarkers in coronavirus disease 2019 (COVID-19) patients (mild: 131; severe: 98; critical: 23). We found that there were significant increases in levels of human epididymis protein 4 (HE4) (73.6 ± 38.3 vs 46.5 ± 14.7 pmol/L; P < .001), cytokeratin-19 fragment (CYFRA21-1) (2.2 ± 0.9 vs 1.9 ± 0.8 µg/L; P < .001), carcinoembryonic antigen (CEA) (3.4 ± 2.2 vs 2.1 ± 1.2 µg/L; P < .001), carbohydrate antigens (CA) 125 (18.1 ± 13.5 vs 10.5 ± 4.6 µg/L; P < .001), and 153 (14.4 ± 8.9 vs 10.1 ± 4.4 µg/L; P < .001) in COVID-19 mild cases as compared to normal control subjects; their levels showed continuous and significant increases in severe and critical cases (HE4, CYFRA21-1, and CA125: P < .001; CEA and CA153: P < .01). Squamous cell carcinoma antigen (SCC) and CA199 increased significantly only in critical cases of COVID-19 as compared with mild and severe cases and normal controls (P < .01). There were positive associations between levels of C-reactive protein and levels of HE4 (R = .631; P < .001), CYFRA21-1 (R = .431; P < .001), CEA (R = .316; P < .001), SCC (R = .351; P < .001), CA153 (R = .359; P < .001) and CA125 (R = .223; P = .031). We concluded that elevations of serum cancer biomarkers positively correlated with the pathological progressions of COVID-19, demonstrating diffuse and acute pathophysiological injuries in COVID-19.