COVID-19 and its clinical severity are associated with alterations of plasma sphingolipids and enzyme activities of sphingomyelinase and ceramidase

Abstract

AbstractIn the current pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2; COVID-19), a better understanding of the underlying mechanisms is essential to reduce morbidity and mortality and treat post-COVID-19 disease. Here, we analyzed alterations of sphingolipids and their metabolizing enzymes in 125 men and 74 women tested positive for SARS-CoV-2 and hospitalized with mild, moderate or severe symptoms or after convalescence.The activities of acid and neutral sphingomyelinases (ASM, NSM), which hydrolyze sphingomyelin to ceramide, were significantly increased in COVID-19 patients, while the activity of neutral ceramidase (NC), which hydrolyzes ceramide to sphingosine, was reduced. These alterations could each contribute to elevated ceramide levels in patients. Accordingly, liquid chromatography tandem-mass spectrometry (LC-MS/MS) yielded increased levels of ceramides 16:0 and 18:0 with highest levels in severely affected patients and similar effects for dihydroceramides 16:0 and 18:0, whereas levels of (dihydro-)ceramides 24:0 were reduced. Furthermore, sphingomyelin 20:0; 22:0 and 24:0 as substrates of ASM and NSM as well as their dihydrosphingomyelin counterparts were reduced in patients as well as sphingosine-1-phosphate further downstream of NC activity. Effects of NSM, NC, ceramides and sphingomyelins remained significant after Bonferroni correction. SARS-CoV-2 antibody levels in convalescent patients were associated with age but none of the sphingolipid parameters. Based on our data, COVID-19 is associated with a dysregulation of sphingolipid homeostasis in a severity-dependent manner, particularly focused around a reduction of sphingomyelins and an accumulation of ceramides by increased enzyme activities leading to ceramide elevation (ASM, NSM) combined with a decreased activity of enzymes (NC) reducing ceramide levels. The potential of a combined sphingolipid/enzyme pattern as a diagnostic and prognostic marker and therapeutic target deserves further exploration.