ABSTRACT
Purpose : Background: Despite being primarily a respiratory disease, COVID-19 can lead to non-respiratory complications, including myocardial infarction and acute ischemic stroke. Moreover, COVID-19 spike protein (SP) was reported in the retina of deceased patients with COVID-19. Retinal microvascular abnormalities as loss of microvasculature and distinct thinning of the microcapillaries were reported in patients who recovered from COVID-19. We are still in the midst of the COVID-19 pandemic, with more deaths and cases every day. Therefore investigating the impact of COVID-19 on the retinal neurovascular environment and the long-term effect of this virus on vision is of great interest. Purpose: To study the contribution of COVID-19 SP to retinal inflammation and vascular death. Methods : Methods: COVID-19 SP, a highly glycosylated protein that allows the virus to penetrate the cell and cause infection, was injected intravitreally in 6-8 weeks global h-ACE2 knock-in mice and wild-type mice. Mice were sacrificed after 14 days, then vascular cell death and inflammation were evaluated by the presence of acellular capillaries and the expression of inflammatory and apoptotic markers. To complement our in-vivo studies, Human Microvascular Endothelial Cells (HMEC) were treated with 100 nM COVID-19 SP for 48 hours. The expression of inflammatory and apoptotic markers was assessed by PCR western blot. Results : Results: Our results showed that HMEC exposed to COVID-19 SP for 48 hours displayed an increase in inflammatory and apoptotic markers expression including TNF-α, IL-1β, IL-6, and cleaved caspase-3 compared to control conditions. Additionally, COVID-19 SP enhanced the oxidative stress in HMEC, evident by the increase in nitro-tyrosine formation, superoxide dismutase, and NADPH oxidase complex 1 (NOX1 and NOX5) expression. The in-vivo findings came in agreement with our in-vitro studies. We found that intravitreal injection of the COVID-19 SP-induced 1) strong activation of the retinal glial cells, assessed by GFAP radial staining, and 2) increased vascular death, assessed by acellular capillaries formation 14 days after the injection. Conclusions : Conclusions: Our findings highlight the possible role of COVID-19 SP in inducing retinal inflammation and vascular death. Further studies are required to reveal the impact of COVID-19 SP on visual acuity and the possibility of causing visual impairment using various animal models.
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Background: Acute respiratory infection (ARI) is the leading infectious cause of pediatric death worldwide, comprising 15% of all deaths in children under 5 years old. Human metapneumovirus (HMPV) is a primary cause of ARI, and accounts for a major portion of ARI-related hospitalizations in infants and young children. Although nearly every person is infected with HMPV during early childhood, re-infections occur often, highlighting the difficulty in building long-term immunity. There are no approved vaccines or antiviral therapies. Early host responses to HMPV are poorly characterized, and further understanding could identify important antiviral pathways and potential therapeutic targets. Type I (IFN-α/β) and III interferons (IFN-λ) display antiviral activity against numerous respiratory viruses and are currently being investigated for therapeutic use in several respiratory infections including SARS-CoV-2. However, their roles in HMPV infection remain largely unknown. Our laboratory has previously shown that type I IFN is critical for HMPV pathogenesis, as loss of IFN-α/β signaling reduces lung inflammation and lessens HMPV disease severity in mice. Here, we describe distinct antiviral roles for type I and III IFNs during HMPV infection using an established mouse model. Methods: In vivo studies were conducted using mice lacking either the IFN-α/ β receptor (IFNAR-/-) or IFN-λ receptor (IFNLR-/-). Early immune responses to HMPV strains TN/94-49 and C2-202 were assessed by clinical disease scoring, plaque assay, Luminex immunoassay, and spectral cytometry of mouse lung samples. In vitro studies were performed using CMT 64-61 mouse bronchial epithelial cells. Responses to TN/94-49 and C2-202 were measured by qPCR, plaque assay, and Luminex immunoassay of cell lysates and supernatants. Results: IFNAR-/- mice exhibited lower clinical disease scores, reduced lung levels of inflammatory cytokines IL6, MIP-1α, and MCP-1, and decreased numbers of lung interstitial macrophages during HMPV infection, highlighting their critical role in HMPV immune-mediated pathogenesis. IFNLR-/- mice with intact IFNAR showed moderate clinical disease, higher lung levels of inflammatory cytokines IL-6, MCP-1, and IFN-γ, and increased lung interstitial macrophage recruitment. A reduction in HMPV disease was also recapitulated by IFNAR-neutralizing antibody treatment of IFNLR-/- mice. Interestingly, IFNLR-/- showed higher HMPV viral titers, while IFNAR-/- mice showed no differences or slightly lower viral titers, compared to wild-type mice. Moreover, IFN-λ pre-treatment of infected CMT 64-61 cells reduced HMPV viral titers and decreased supernatant levels of inflammatory cytokines IL-6, IL-1β, TNFα, and MCP-1. Conclusion: These findings suggest that type I IFN is necessary for HMPV pathogenesis, while type III IFN is critical for limiting HMPV replication in the lungs but does not contribute to HMPV inflammatory disease. This work uncovers key functional differences between type I and III IFNs during HMPV infection, an important feature of innate immune responses to HMPV that may be utilized to inform treatment.
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Introduction and Rationale: No targeted therapies exist that improve the outcomes of patients with Acute Respiratory Distress Syndrome (ARDS), in part to the multifactorial etiology of this devastating disease. Infectious agents remain the most common initiating insults, and besides SARS-CoV-2, Influenza-A virus (IAV) is responsible for more ARDS cases and deaths than any other agent. In fact, IAV increases the risk of mortality in ARDS patients three-fold, and accounts for almost half of all ARDS deaths. We recently identified TREK-1 potassium channels on epithelial cells as important regulators of alveolar inflammation and barrier function, two hallmarks of ARDS, and found that pharmacological activation of TREK-1 protects against hyperoxia-induced lung injury. However, whether TREK-1 channels convey similar protection in a clinically more relevant IAVinduced lung injury model, remains unknown. Methods: We infected adult C57BL/6 wildtype mice intra-tracheally (i.t.) with IAV (PR8 strain;TCID50 400), followed by once-daily i.t. injections (days 5, 6 and 7 post-IAV) with the novel TREK-1 activating compounds ML335 (60mcg/kg), BL1249 (100mcg/kg), or a vehicle control, to create a clinically-relevant treatment model. To evaluate the role of epithelial cells in this model, we infected primary human alveolar epithelial cells (HAEC) with IAV (0.01 pfu) for 24 hours. Endpoint analysis consistent in quantification of quasi-static lung compliance;BAL fluid total protein, cell counts, and ROS concentrations;cytokine levels in BAL fluid and cell supernatants;and HAEC viability (XTT assay). In addition, we measured alterations in epithelial potassium currents (fluorometric FLIPR assays) and in IAV-induced signaling cascades (real-time PCR) following IAV infection and treatment with our TREK-1 activators. Results: Oncedaily treatment of mice with the TREK-1 activating compounds ML335 or BL1249 following IAV infection improved lung compliance, and BAL fluid total protein levels, cell counts, IL-6, CXCL-10, MIP-1alpha, and TNF-alpha concentrations, but not ROS, CCL-2 or IL-10 levels. In HAEC, TREK-1 activation improved IAV-induced IL-6, CXCL-10, and CCL-2 levels, while MIP-1alpha, TNF-alpha and IL-10 levels remained unchanged. XTT assays confirmed that in our model IAV infection did not cause significant cell death. Interestingly, IAV infection decreased HAEC potassium currents, which could be counteracted by TREK-1 activation and cell hyperpolarization. Finally, TREK-1 activationmediated cell hyperpolarization inhibited TLR4- and TNFSF13-mediated downstream signaling in IAV-infected HAEC, whereas NFkB, RIG1, TLR3, and TLR7 signaling was not affected. Conclusions: TREK-1 potassium channel activation may represent a novel approach to protect against IAV-induced acute lung injury.
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Rationale: In severe COVID-19 patients, decrease of ATP production caused by mitochondrial dysfunction thought to induce the lung injury. Febuxostat, which is a therapeutic medicine for hyperuricemia, is thought to have the effect of improving mitochondrial dysfunction and enhances the production of ATP. The purpose of this study is to investigate the effect of febuxostat in LPS induced lung injury mouse model. Methods: C57BL/6 WT mice (8-12 wk-old males) were exposed to lipopolysaccharide (LPS) intratracheally to develop the murine model of LPS-induced lung injury. For the treatment, 100 μg of febuxostat was administered twice a day from 2 days before the exposure of LPS. Bronchial lavage fluid (BALF) and lung tissue were collected 24 hours and 7 days after the LPS exposure. The BALF were analyzed for total and differential cell counts. The lung tissues were stained with Masson's trichrome staining and analyzed for lung fibrosis. Results: Twenty-four hours after the LPS exposure, the number of total cells and neutrophils in the BALF was increased. In the group receiving febuxostat, the number of total cells and neutrophils were significantly decreased at 24 hours after the LPS exposure. At 7 days after the LPS exposure, the number of total cells and neutrophils in both LPS and LPS + Febuxostat group returned to almost the same level as control group. Additionally, the percentage of collagen deposition area representing lung fibrosis in the entire lung field was enhanced in LPS group compared to control group at 7 days after the LPS exposure. Moreover, the treatment of febuxostat inhibited the fibrosis in LPS group. Conclusions: Administration of febuxostat inhibited the lung inflammation in the acute phase and improved the lung fibrosis in LPS-induced lung injury model. This study suggests that the treatment of febuxostat may inhibit the lung injury caused in severe COVID-19 patients.
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Introduction: Management of acute respiratory distress including COVID-19 pneumonia involves O2 supplementation, which is lifesaving, but causes severe hyperoxic acute lung injury (HALI). AT2 cells are the most affected cell type in hyperoxia (HO). NADPH oxidase (NOX) is a major source of reactive oxygen species (ROS) in HO. NOX4, the only functionally active NOX present in mitochondria, and primarily produces H2O2 as well as mtROS has been shown to be involved in several human pathologies. Not much is known about NOX4-induced mitochondrial injury in HALI. The current study aims to determine the role of AT2 epithelial cell NOX4 in HALI and the impact of HO on the modulation of mtROS and mitochondrial dynamics in HALI. Methods: Nox4-/-Spc-Cre animals were generated using tamoxifen induction and the knockdown was validated. The Nox4- /-Spc-Cre knockout (KO) and wild type (WT) mice were exposed to room air (NO) or 95% O2 (HO) for 66h to study the structural and functional changes in the lung. Transmission Electron Microscopy (TEM) was used to study the HO-induced changes in mitochondria. Isolated primary AT2 and/ mouse lung epithelial (MLE) cell line was investigated for mtROS, mt dynamics and apoptosis. Mitochondrial injury was assessed in Nox4 WT and Nox4 silenced cells. Results: C57BL/6J WT animals subjected to HO for 66h showed increased expression of NOX4, determining the role of NOX4 in HALI. The H&E staining demonstrated significant HALI in Nox4 WT animals exposed to HO compared to Nox4 KO as determined by increased infiltration of neutrophils, alveolar wall thickening and presence of proteinaceous debris in the alveolar space. Further, increased BAL cell count and protein levels, increased AT2 cell death and elevation of the proinflammatory cytokine IL- 6 and the chemokine KC was seen in WT animals compared to Nox4 KO. Analysis of lung tissues by TEM showed mitochondrial swelling, cristae damage and mitophagy in AT2 cells due to HO. Changes in mt injury markers were also observed. HO-induced NOX4 increase in primary AT2/ MLE-12 cells resulted in increased mtROS production and apoptosis, which was reduced with Nox4 siRNA silencing. Conclusion: This study suggests that the HO induced NOX4 expression in mouse lung, and deletion of Nox4 gene in AT2 cells reduced mtROS production and apoptosis and protected the lungs from severe hyperoxic lung injury. These results suggest NOX4 as a potential target for the treatment of HALI.
ABSTRACT
COVID-19 pandemic has affected our health and economy. Clinical trials confirmed multiple neurological symptoms due to COVID-19, ranging from headaches, insomnia to stroke, and encephalopathy. More studies are required to unravel the cellular and molecular mechanisms to find a cure for these neurological symptoms. Here, we investigate the effect of COVID-19 spike protein (S-protein) on the cerebrovasculature and cognitive functions in two mouse models that express humanized ACE-2 (h ACE2), a receptor essential for cellular infection and COVID-19 internalization. We hypothesize that COVID-19 S-protein causes cognitive dysfunction via the deterioration of cerebrovascular functions. Methods: S-protein was either injected intravenously or directly into the hippocampus of K-18 (h ACE2 in epithelial cells) or global h-ACE2 knock-in (h ACE2 KI) mice or wild-type mice. Cognitive functions were assessed by Y-maze and Barnes maze. Cerebrovascular density was determined using confocal 3-D image reconstruction. Human brain microvascular endothelial cells (HBMVEC) were treated with S-protein and assessed for apoptosis and inflammatory markers using immunoblotting and RT-PCR. K-18 and h-ACE2 KI mice received intraocular injections of S-protein;retinas were evaluated for vascular cell death and inflammation. Results: S-protein injections caused significant deterioration in memory and learning function of K-18 and h-ACE2 KI mice but not in the wild-type mice (P<0.05). S-protein significantly increased inflammatory mediators, cytokine production, and apoptosis in the brains and HBMVECs (P<0.05). Significant cerebrovascular rarefaction was detected only in K-18 and h-ACE2 KI mice compared to wild-type mice (P<0.05). Retinal vascular cell death and inflammation were significantly increased after S-protein injection. (P<0.05) Conclusions: COVID-19 spike protein decreases cognitive function via increased endothelial cell inflammation, apoptosis, and cerebrovascular rarefaction. Humanized ACE2 animal models are excellent and reliable for investigating the neurological symptoms of COVID-19.