Elevation in sphingolipid upon SARS-CoV-2 infection: possible implications for COVID-19 pathology

Understanding pathways that might impact coronavirus disease 2019 (COVID-19) manifestations and disease outcomes is necessary for better disease management and for therapeutic development. Here, we analyzed alterations in sphingolipid (SL) levels upon infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). SARS-CoV-2 infection induced elevation of SL levels in both cells and sera of infected mice. A significant increase in glycosphingolipid levels was induced early post SARS-CoV-2 infection, which was essential for viral replication. This elevation could be reversed by treatment with glucosylceramide synthase inhibitors. Levels of sphinganine, sphingosine, GA1, and GM3 were significantly increased in both cells and the murine model upon SARS-CoV-2 infection. The potential involvement of SLs in COVID-19 pathology is discussed.

Preclinical pharmacology of glucosylceramide synthase inhibitor venglustat in a GBA-related synucleinopathy model

Mutations in GBA, the gene encoding the lysosomal enzyme glucocerebrosidase (GCase), represent the greatest genetic risk factor for developing synucleinopathies including Parkinson’s disease (PD). Additionally, PD patients harboring a mutant GBA allele present with an earlier disease onset and an accelerated disease progression of both motor and non-motor symptoms. Preclinical studies in mouse models of synucleinopathy suggest that modulation of the sphingolipid metabolism pathway via inhibition of glucosylceramide synthase (GCS) using a CNS-penetrant small molecule may be a potential treatment for synucleinopathies. Here, we aim to alleviate the lipid storage burden by inhibiting the de novo synthesis of the primary glycosphingolipid substrate of GCase, glucosylceramide (GlcCer). We have previously shown that systemic GCS inhibition reduced GlcCer and glucosylsphingosine (GlcSph) accumulation, slowed α-synuclein buildup in the hippocampus, and improved cognitive deficits. Here, we studied the efficacy of a brain-penetrant clinical candidate GCS inhibitor, venglustat, in mouse models of GBA-related synucleinopathy, including a heterozygous Gba mouse model which more closely replicates the typical GBA-PD patient genotype. Collectively, these data support the rationale for modulation of GCase-related sphingolipid metabolism as a therapeutic strategy for treating GBA-related synucleinopathies.

Multislice Spiral Computed Tomography under Hybrid Iterative Reconstruction Algorithm in Staging Diagnosis of Bladder Cancer and Ceramide Glycosylation

This study was to discuss the application of multislice spiral computed tomography (CT) in the staging diagnosis of bladder cancer and the effect of ceramide glycosylation. The hybrid iterative reconstruction algorithm was applied. Immunohistochemistry and western blot were used to detect the normal bladder tissues (30 cases) of GCS in group 1 (100 cases) and group 2. The scanned images of all the research objects were obtained, the images with the iterative reconstruction algorithm were reconstructed, and statistical analysis on the CT value under the algorithm was conducted. The results showed that the image quality, blood vessel sharpness, average image score, signal-to-noise ratio, and radiation dose after the spiral CT and iterative reconstruction algorithm all increased, while the noise value decreased. The optical density value of glucosylceramide synthase in group 2 patients increased by 71%, and the optical density value of group 1 increased by 29%. The optical density expression of glucosylceramide synthase in group 1 patients was significantly higher than that in the control group, and there was a statistical difference between the two ( P < 0.05 ). Among the results of multislice spiral CT for tumor staging, the lesions larger than 5 cm and in the range of 1.1–2 cm in diameter were more sensitive. In 41 patients, there were multiple lesions. A total of 142 cancer lesions were found. The diameter of the tissue ranged from 0.5 to 6.8 cm, with an average diameter of 2.03 ± 0.35 cm. The optical density of glucosylceramide synthase in the group 1 was 5526, and the optical density in group 2 was 2576. The OD expression of GCS in group 1 was greatly higher in contrast to that in group 2, and there was a statistical difference between the two groups ( P < 0.05 ). The multislice spiral CT examination under this algorithm found that the diagnosis and staging accuracy of lesions with a diameter greater than 5 cm and tumor diameters in the range of 1.1 to 2 cm was higher. The image processed by the hybrid iterative reconstruction algorithm had good effect, high definition, and accuracy.

Glucosylceramide synthase regulates hepatocyte repair after concanavalin A-induced immune-mediated liver injury

Background Sphingolipids produce pleiotropic signaling pathways, and participate in the pathological mechanism of hepatocyte apoptosis and necrosis during liver injury. However, the role of glucosylceramide synthase (GCS)–key enzyme that catalyzes the first glycosylation step, in liver injury is still vague. Methods All experiments were conducted using 7–9-week-old pathogen-free male C57BL/6 mice. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were detected in murine models of liver disease, in addition to histological characterization of liver injuries. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the relative expression of the GCS, matrix metallopeptidase-1 (MMP-1), and tissue inhibitor of metalloproteinase-1 (TIMP-1) genes. The GCS was observed through a fluorescence microscope, and the flow cytometry was used to detect hepatocyte apoptosis. The concentrations of serum IL-4, IL-6, and IL-10 were measured using enzyme-linked immune-sorbent assay (ELISA) kit. MMP-1 and TIMP-1 protein expression was measured via western blot (WB) analysis. Results Con A is often used as a mitogen to activate T lymphocytes and promote mitosis. A single dose of Con A injected intravenously will cause a rapid increase of ALT and AST, which is accompanied by the release of cytokines that cause injury and necrosis of hepatocytes. In this study, we successfully induced acute immune hepatitis in mice by Con A. Con A administration resulted in GCS upregulation in liver tissues. Moreover, the mice in the Con A group had significantly higher levels of ALT, AST, IL-4, IL-6, IL-10 and increased hepatocyte apoptosis than the control group. In contrast, all of the aforementioned genes were significantly downregulated after the administration of a GCS siRNA or Genz-123346 (i.e., a glucosylceramide synthase inhibitor) to inhibit the GCS gene. Additionally, the histopathological changes observed herein were consistent with our ALT, AST, IL-4, IL-6, and IL-10 expression results. However, unlike this, hepatocyte apoptosis has been further increased on the basis of the Con A group. Moreover, our qRT-PCR and WB results indicated that the expression of MMP-1 in the Con A group was significantly lower than that in the control group, whereas TIMP-1 exhibited the opposite trend. Conversely, MMP-1 expression in the GCS siRNA and Genz-123346 groups was higher than that in the Con A group, whereas TIMP-1 expression was lower. Conclusions GCS inhibition reduces Con A-induced immune-mediated liver injury in mice, which may be due to the involvement of GCS in the hepatocyte repair process after injury.

Improving bone health via modulation of glycosphingolipid metabolism and autophagy

Patients with multiple myeloma (MM), an incurable malignancy of plasma cells, frequently develop osteolytic bone lesions. In this study, glycosphingolipids were essential in promoting autophagic degradation of the signaling molecule TRAF3, a key step in bone-resorbing osteoclast differentiation. Specifically altering the glycosphingolipid composition with eliglustat, an FDA approved glucosylceramide synthase inhibitor, arrested osteoclast differentiation; this could be rescued by exogenous addition of the missing glycosphingolipids. Eliglustat significantly reduced bone disease in several preclinical models of MM by inhibiting osteoclastogenesis and, due to its unique mode of action, it was able to act in combination with existing bone protective drugs. Furthermore, eliglustat arrested osteoclast differentiation from the bone marrow of MM patients in a glycosphingolipid-dependent way. This work identifies both the mechanism by which glucosylceramide synthase inhibition blocks autophagic degradation of TRAF3 to reduce osteoclastogenesis as well as highlighting the translational potential of eliglustat to be combined with current treatments.