SARS-CoV-2 Infection Impacts Carbon Metabolism and Depends on Glutamine for Replication in Syrian Hamster Astrocytes

Abstract

Coronaviruses belong to a well-known family of enveloped RNA viruses and are the causative agent of the common cold. Although the seasonal coronaviruses do not pose a threat to human life, three members of this family, i.e., SARS-CoV, MERS-CoV and recently, SARS-CoV2, may cause severe acute respiratory syndrome and lead to death. Unfortunately, COVID-19 has already caused more than 4.4 million deaths worldwide. Although much is better understood about the immunopathogenesis of the lung disease, important information about systemic disease is still missing, mainly concerning neurological parameters. In this context, we sought to evaluate immunometabolic changes using in vitro and in vivo models of hamsters infected with SARS-CoV-2. Here we show that, besides infecting hamsters astrocytes, SARS-CoV-2 induces changes in protein expression and metabolic pathways involved in carbon metabolism, glycolysis, mitochondrial respiration, and synaptic transmission. Interestingly, many of the differentially expressed proteins are concurrent with proteins that correlate with neurological diseases, such as Parkinsons's disease, multiple sclerosis, amyotrophic lateral sclerosis, and Huntington's disease. Metabolic analysis by high resolution real-time respirometry evidenced hyperactivation of glycolysis and mitochondrial respiration. Further metabolomics analysis confirmed the consumption of many metabolites, including glucose, pyruvate, glutamine, and alpha ketoglutarate. Interestingly, we observed that glutamine was significantly reduced in infected cultures, and the blockade of mitochondrial glutaminolysis significantly reduced viral replication and pro-inflammatory response. SARS-CoV-2 was confirmed in vivo as hippocampus, cortex, and olfactory bulb of intranasally infected hamsters were positive for viral genome several days post-infection. Altogether, our data reveals important changes in overall protein expression, mostly of those related to carbon metabolism and energy generation, causing an imbalance in important metabolic molecules and neurotransmitters. This may suggest that some of the neurological features observed during COVID-19, as memory and cognitive impairment, may rely on altered energetic profile of brain cells, as well as an unbalanced glutamine/glutamate levels, whose importance for adequate brain function is unquestionable.

Morphological, cellular and molecular basis of brain infection in COVID-19 patients

“…In line with the potential neurotropic properties of SARS-CoV-2, recent evidence has demonstrated the presence of viral proteins in brain regions of COVID-19 patients as well as in the brains of K18-ACE2 transgenic mice infected with SARS-CoV-2 21–23 and syrian hamsters 24 . The presence of SARS-CoV-2 in the human brain has been associated with significant astrogliosis, microgliosis and immune cell accumulation 21 .…”

“…Moreover, astrocytes are responsible for maintaining glutamate levels in the brain 69,70 . Recently, de Oliveira et al showed that glutamine levels were reduced in mixed glial cells infected with SARS-CoV-2 and that the inhibition of glutaminolysis decreased viral replication and pro-inflammatory response 24 . Hence, given the importance of the coupling between astrocytes and neurons, alterations in astrocytic glucose and glutamine metabolism are expected to compromise neuronal function, affecting neuronal metabolism and synaptic function and plasticity 71 .…”

Metabolomics analysis identifies glutamic acid and cystine imbalances in COVID-19 patients without comorbid conditions. Implications on redox homeostasis and COVID-19 pathophysiology

“…The main complications derived from SARS-CoV-2 infection are related to systemic oxygen shortage due to lung tissue damage as a result of exacerbated immune activation and virus replication, which lead to metabolic changes that prepare target organs and tissues to reduced oxygen supply [ 39 ]. Leaving aside the metabolic reshaping provoked by the virus on infected cells [ 40 , 41 ], it has been proposed that critical metabolic changes occur in endothelial and immune cells in the early stages of lung damage [ 40 ]. Moreover, if oxygen levels do not recover, the decrement in oxygen supply may lead to further damage to critical organs such as brain, kidneys, and liver [ 42 , 43 ], as observed in critical COVID-19 patients.…”

TOM70 in Glial Cells as a Potential Target for Treatment of COVID-19

“…Interestingly, it was verified that ACE2 was predominantly localized in the pericytes from the mouse microvessels (Wenzel et al, 2021). Further studies showed that SARS-CoV-2 is able to directly infect neural stem cell-derived astrocytes (Crunfli et al, 2020) and hamster astrocytes (de Oliveira et al, 2021), and that SARS-CoV-2 spike protein was present in different cells from brain of patients, the majority of these cells being astrocytes (Crunfli et al, 2020).…”