Cystathionine β-synthase deficiency: different changes in proteomes of thrombosis-resistant Cbs-/- mice and thrombosis-prone CBS-/- humans

Deciphering pathophysiological mechanisms underlying cystathionine beta-synthase-deficient homocystinuria using targeted metabolomics, liver proteomics, sphingolipidomics and analysis of mitochondrial function

BACKGROUND

Cystathionine β-synthase (CBS)-deficient homocystinuria (HCU) is an inherited disorder of sulfur amino acid metabolism with varying severity and organ complications, and a limited knowledge about underlying pathophysiological processes. Here we aimed at getting an in-depth insight into disease mechanisms using a transgenic mouse model of HCU (I278T).

METHODS

We assessed metabolic, proteomic and sphingolipidomic changes, and mitochondrial function in tissues and body fluids of I278T mice and WT controls. Furthermore, we evaluated the efficacy of methionine-restricted diet (MRD) in I278T mice.

RESULTS

In WT mice, we observed a distinct tissue/body fluid compartmentalization of metabolites with up to six-orders of magnitude differences in concentrations among various organs. The I278T mice exhibited the anticipated metabolic imbalance with signs of an increased production of hydrogen sulfide and disturbed persulfidation of free aminothiols. HCU resulted in a significant dysregulation of liver proteome affecting biological oxidations, conjugation of compounds, and metabolism of amino acids, vitamins, cofactors and lipids. Liver sphingolipidomics indicated upregulation of the pro-proliferative sphingosine-1-phosphate signaling pathway. Liver mitochondrial function of HCU mice did not seem to be impaired compared to controls. MRD in I278T mice improved metabolic balance in all tissues and substantially reduced dysregulation of liver proteome.

CONCLUSION

The study highlights distinct tissue compartmentalization of sulfur-related metabolites in normal mice, extensive metabolome, proteome and sphingolipidome disruptions in I278T mice, and the efficacy of MRD to alleviate some of the HCU-related biochemical abnormalities.

Homocysteine metabolites inhibit autophagy by upregulating miR-21-5p, miR-155-5p, miR-216-5p, and miR-320c-3p in human vascular endothelial cells

Nutritional and genetic deficiencies in homocysteine (Hcy) metabolism lead to hyperhomocysteinemia (HHcy) and cause endothelial dysfunction, a hallmark of atherosclerosis, which is a major cause of cardiovascular disease (CVD). Impaired autophagy causes the accumulation of damaged proteins and organelles and is associated with CVD. Biochemically, HHcy is characterized by elevated levels of Hcy and its metabolites, Hcy-thiolactone and N-Hcy-protein. However, whether these metabolites can dysregulate mTOR signaling and autophagy in endothelial cells is not known. Here, we examined the influence of Hcy-thiolactone, N-Hcy-protein, and Hcy on autophagy human umbilical vein endothelial cells. We found that treatments with Hcy-thiolactone, N-Hcy-protein, or Hcy significantly downregulated beclin 1 (BECN1), autophagy-related 5 (ATG5), autophagy-related 7 (ATG7), and microtubule-associated protein 1 light chain 3 (LC3) mRNA and protein levels. We also found that these changes were mediated by upregulation by Hcy-thiolactone, N-Hcy-protein, and Hcy of autophagy-targeting microRNA (miR): miR-21, miR-155, miR-216, and miR-320c. The effects of these metabolites on levels of miR targeting autophagy as well as on the levels of BECN1, ATG5, ATG7, and LC3 mRNA and protein were abrogated by treatments with inhibitors of miR-21, miR-155, miR-216, and mir320c. Taken together, our findings show that Hcy metabolites can upregulate miR-21, miR-155, miR-216, and mir320c, which then downregulate autophagy in human endothelial cells, important for vascular homeostasis.

Establishment and validation of a predictive model of preeclampsia based on transcriptional signatures of 43 genes in decidua basalis and peripheral blood

Preeclampsia (PE) has an increasing incidence worldwide, and there is no gold standard for prediction. Recent progress has shown that abnormal decidualization and impaired vascular remodeling are essential to PE pathogenesis. Therefore, it is of great significance to analyze the decidua basalis and blood changes of PE to explore new methods. Here, we performed weighted gene co-expression network analysis based on 9553 differentially expressed genes of decidua basalis data (GSE60438 includes 25 cases of PE and 23 non-cases) from Gene Expression Omnibus to screen relevant module-eigengenes (MEs). Among them, MEblue and MEgrey are the most correlated with PE, which contains 371 core genes. Subsequently, we applied the logistic least absolute shrinkage and selection operator regression, screened 43 genes most relevant to prediction from the intersections of the 371 genes and training set (GSE48424 includes 18 cases of PE and 18 non-cases) genes, and built a predictive model. The specificity and sensitivity are illustrated by receiver operating characteristic curves, and the stability was verified by two validation sets (GSE86200 includes 12 cases of PE and 48 non-cases, and GSE85307 includes 47 cases of PE and 110 non-cases). The results demonstrated that our predictive model shows good predictions, with an area under the curve of 0.991 for the training set, 0.874 and 0.986 for the validation sets. Finally, we found the 43 key marker genes in the model are closely associated with the clinically accepted predictive molecules, including FLT1, PIGF, ENG and VEGF. Therefore, this predictive model provides a potential approach for PE diagnosis and treatment.

Thromboses and Hemostasis Disorders Associated with COVID-19: The Possible Causal Role of Cross-Reactivity and Immunological Imprinting

By examining the issue of the thromboses and hemostasis disorders associated with severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) through the lens of cross-reactivity, it was found that 60 pentapeptides are shared by SARS-CoV-2 spike glycoprotein (gp) and human proteins that— when altered, mutated, deficient or, however, improperly functioning— cause vascular diseases, thromboembolic complications, venous thrombosis, thrombocytopenia, coagulopathies, and bleeding, inter alia. The peptide commonality has a relevant immunological potential as almost all of the shared sequences are present in experimentally validated SARS-CoV-2 spike gp-derived epitopes, thus supporting the possibility of cross-reactions between the viral gp and the thromboses-related human proteins. Moreover, many of the shared peptide sequences are also present in pathogens to which individuals have previously been exposed following natural infection or vaccinal routes, and of which the immune system has stored imprint. Such an immunological memory might rapidly trigger anamnestic secondary cross-reactive responses of extreme affinity and avidity, in this way explaining the thromboembolic adverse events that can associate with SARS-CoV-2 infection or active immunization.

Proteomic exploration of cystathionine β-synthase deficiency: implications for the clinic

Introduction: Homocystinuria due to cystathionine β-synthase (CBS) deficiency, the most frequent inborn error of sulfur amino acid metabolism, is characterized biochemically by severely elevated homocysteine (Hcy) and related metabolites, such as Hcy-thiolactone and N-Hcy-protein. CBS deficiency reduces life span and causes pathological abnormalities affecting most organ systems in the human body, including the cardiovascular (thrombosis, stroke), skeletal/connective tissue (osteoporosis, thin/non-elastic skin, thin hair), and central nervous systems (mental retardation, seizures), as well as the liver (fatty changes), and the eye (ectopia lentis, myopia). Molecular basis of these abnormalities were largely unknown and available treatments remain ineffective. Areas covered: Proteomic and transcriptomic studies over the past decade or so, have significantly contributed to our understanding of mechanisms by which the CBS enzyme deficiency leads to clinical manifestations associated with it. Expert opinion: Recent findings, discussed in this review, highlight the involvement of dysregulated proteostasis in pathologies associated with CBS deficiency, including thromboembolism, stroke, neurologic impairment, connective tissue/collagen abnormalities, hair defects, and hepatic toxicity. To ameliorate these pathologies, pharmacological, enzyme replacement, and gene transfer therapies are being developed.

Genetic Attenuation of Paraoxonase 1 Activity Induces Proatherogenic Changes in Plasma Proteomes of Mice and Humans

High-density lipoprotein (HDL), in addition to promoting reverse cholesterol transport, possesses anti-inflammatory, antioxidative, and antithrombotic activities. Paraoxonase 1 (PON1), carried on HDL in the blood, can contribute to these antiatherogenic activities. The PON1-Q192R polymorphism involves a change from glutamine (Q variant) to arginine (R variant) at position 192 of the PON1 protein and affects its enzymatic activity. The molecular basis of PON1 association with cardiovascular and neurological diseases is not fully understood. To get insight into the function of PON1 in human disease, we examined how genetic attenuation of PON1 levels/activity affect plasma proteomes of mice and humans. Healthy participants (48.9 years old, 50% women) were randomly recruited from the Poznań population. Four-month-old Pon1^−/− (n = 17) and Pon1^+/+ (n = 8) mice (50% female) were used in these experiments. Plasma proteomes were analyzed using label-free mass spectrometry. Bioinformatics analysis was carried out using the Ingenuity Pathway Analysis (IPA) resources. PON1-Q192R polymorphism and Pon1^−/− genotype induced similar changes in plasma proteomes of humans and mice, respectively. The top molecular network, identified by IPA, affected by these changes involved proteins participating in lipoprotein metabolism. Other PON1 genotype-dependent proteomic changes affect different biological networks in humans and mice: “cardiovascular, neurological disease, organismal injury/abnormalities” in PON1-192QQ humans and “humoral immune response, inflammatory response, protein synthesis” and “cell-to-cell signaling/interaction, hematological system development/function, immune cell trafficking” in Pon1^−/− mice. Our findings suggest that PON1 interacts with molecular pathways involved in lipoprotein metabolism, acute/inflammatory response, and complement/blood coagulation that are essential for blood homeostasis. Modulation of those interactions by the PON1 genotype can account for its association with cardiovascular and neurological diseases.

Telomere length and mtDNA copy number in human cystathionine β-synthase deficiency

Telomere shortening and mitochondrial DNA (mtDNA) copy number are associated with human disease and a reduced life span. Cystathionine β-synthase (CBS) is a housekeeping enzyme that catalyzes the first step in metabolic conversion of homocysteine (Hcy) to cysteine. Mutations in the CBS gene cause CBS deficiency, a rare recessive metabolic disease, manifested by severe hyperhomocysteinemia (HHcy) and thromboembolism, which ultimately reduces the life span. However, it was not known whether telomere shortening or mtDNA is involved in the pathology of human CBS deficiency. We quantified leukocyte telomere length (TL), mtDNA copy number, and plasma Hcy levels in CBS^-/- patients (n = 23) and in sex- and age-matched unaffected CBS^+/+ control individuals (n = 28) 0.08-57 years old. We found that TL was significantly increased in severely HHcy CBS^-/- female patients but unaffected in severely HHcy CBS^-/- male patients, relative to the corresponding CBS^+/+ controls who had normal plasma Hcy levels. In multiple regression analysis TL was associated with CBS genotype in women but not in men. MtDNA copy number was not significantly affected by the CBS^-/- genotype. Taken together, these findings identify the CBS gene as a new locus in human DNA that affects TL in women and illustrate a concept that a housekeeping metabolic gene can be involved in telomere biology. Our findings suggest that neither telomere shortening nor reduced mtDNA copy number contribute to the reduced life span in CBS^-/- patients.