Quantitative proteomics analysis of COVID-19 infected hamster lung tissue

The mechanistic interplay between SARS-CoV-2 infection, inflammation, and oxygen homeostasis is not well defined. Here we show that the hypoxia-inducible factor (HIF-1α) transcriptional pathway is activated, perhaps due to a lack of oxygen or an accumulation of mitochondrial reactive oxygen species (ROS) in the lungs of adult Syrian hamsters infected with SARS-CoV-2. Prominent nuclear localization of HIF-1 and increased expression of HIF-1α target proteins, including glucose transporter 1 (Glut1), lactate dehydrogenase (LDH), and pyruvate dehydrogenase kinase-1 (PDK1), were observed in areas of lung consolidation filled with infiltrating monocytes/macrophages. Upregulation of these HIF-1α target proteins was accompanied by a rise in glycolysis as measured by extracellular acidification rate (ECAR) in lung homogenates. A concomitant marginal reduction in mitochondrial respiration was also observed as seen by a partial loss of oxygen consumption rates (OCR) in both coupled and uncoupled states of respiration in isolated mitochondrial fractions of SARS-CoV-2 infected hamster lungs. Proteomics analysis revealed specific deficits in the mitochondrial ATP synthase (Atp5a1) within complex V and in the ATP/ADP translocase (Slc25a4). The activation of HIF-1 in inflammatory macrophages may also drive proinflammatory cytokines production, complement activation, and oxidative stress in infected lungs. Together, these findings support a role for HIF-1 as a central mediator of the metabolic reprogramming, inflammation, and mitochondrial dysfunction associated with COVID-19 disease.