Gene therapy with AAV9-SGPL1 in an animal model of lung fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a progressive scarring disease of the lung that leads rapidly to respiratory failure. Novel approaches to treatment are urgently needed. The bioactive lipid sphingosine-1-phosphate (S1P) is increased in IPF lungs and promotes proinflammatory and profibrotic TGF-ß signaling. Hence, decreasing lung S1P represents a potential therapeutic strategy for IPF. S1P is degraded by the intracellular enzyme S1P lyase (SPL). Here we find that a knock-in mouse with a missense SPL mutation mimicking human disease resulted in reduced SPL activity, increased S1P, increased TGF-ß signaling, increased lung fibrosis, and higher mortality after injury compared to wild type (WT). We then tested adeno-associated virus 9 (AAV9)-mediated overexpression of human SGPL1 (AAV-SPL) in mice as a therapeutic modality. Intravenous treatment with AAV-SPL augmented lung SPL activity, attenuated S1P levels within the lungs, and decreased injury-induced fibrosis compared to controls treated with saline or only AAV. We confirmed that AAV-SPL treatment led to higher expression of SPL in the epithelial and fibroblast compartments during bleomycin-induced lung injury. Additionally, AAV-SPL decreased expression of the profibrotic cytokines TNFα and IL1ß as well as markers of fibroblast activation, such as fibronectin (Fn1), Tgfb1, Acta2, and collagen genes in the lung. Taken together, our results provide proof of concept for the use of AAV-SPL as a therapeutic strategy for the treatment of IPF. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

SARS-CoV-2 ORF3a expression in brain disrupts the autophagy-lysosomal pathway, impairs sphingolipid homeostasis, and drives neuropathogenesis.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection causes injury to multiple organ systems, including the brain. SARS-CoV-2's neuropathological mechanisms may include systemic inflammation and hypoxia, as well as direct cell damage resulting from viral infections of neurons and glia. How the virus directly causes injury to brain cells, acutely and over the long term, is not well understood. In order to gain insight into this process, we studied the neuropathological effects of open reading frame 3a (ORF3a), a SARS-CoV-2 accessory protein that is a key pathological factor of the virus. Forced ORF3a brain expression in mice caused the rapid onset of neurological impairment, neurodegeneration, and neuroinflammation-key neuropathological features found in coronavirus disease (COVID-19, which is caused by SARS-CoV-2 infection). Furthermore, ORF3a expression blocked autophagy progression in the brain and caused the neuronal accumulation of α-synuclein and glycosphingolipids, all of which are linked to neurodegenerative disease. Studies with ORF3-expressing HeLa cells confirmed that ORF3a disrupted the autophagy-lysosomal pathway and blocked glycosphingolipid degradation, resulting in their accumulation. These findings indicate that, in the event of neuroinvasion by SARS-CoV-2, ORF3a expression in brain cells may drive neuropathogenesis and be an important mediator of both short- and long-term neurological manifestations of COVID-19.

Sirolimus to treat chronic and steroid-resistant allograft rejection-related fibrosis in pediatric liver transplantation.

This study aimed to report our experience with the use of sirolimus in pediatric liver transplant patients with chronic rejection or steroid-resistant rejection with hepatic fibrosis, focusing on their histological evolution. All pediatric liver transplant recipients who received off-label treatment with sirolimus for chronic ductopenic rejection or cortico-resistant rejection between July 2003 and July 2022 were included in the study. All nine patients included in the study showed improvement in liver enzymes and cholestasis parameters as soon as 1-month after postsirolimus introduction. A decrease in fibrosis stage was observed in 7/9 (77.7%) patients at 36 months. All but one patient experienced an improvement in the Rejection Activity Index and ductopenia at 12 months. A single patient had to discontinue sirolimus treatment owing to nephrotic proteinuria. In conclusion, sirolimus may be a safe and effective treatment for chronic and steroid-resistant rejection and may improve allograft rejection-related fibrosis and ductal damage.

Sialidase NEU3 action on GM1 ganglioside is neuroprotective in GM1 gangliosidosis.

GM1 gangliosidosis is a neurodegenerative disorder caused by mutations in the GLB1 gene, which encodes lysosomal ß-galactosidase. The enzyme deficiency blocks GM1 ganglioside catabolism, leading to accumulation of GM1 ganglioside and asialo-GM1 ganglioside (GA1 glycolipid) in brain. This disease can present in varying degrees of severity, with the level of residual ß-galactosidase activity primarily determining the clinical course. Glb1 null mouse models, which completely lack ß-galactosidase expression, exhibit a less severe form of the disease than expected from the comparable deficiency in humans, suggesting a potential species difference in the GM1 ganglioside degradation pathway. We hypothesized this difference may involve the sialidase NEU3, which acts on GM1 ganglioside to produce GA1 glycolipid. To test this hypothesis, we generated Glb1/Neu3 double KO (DKO) mice. These mice had a significantly shorter lifespan, increased neurodegeneration, and more severe ataxia than Glb1 KO mice. Glb1/Neu3 DKO mouse brains exhibited an increased GM1 ganglioside to GA1 glycolipid ratio compared with Glb1 KO mice, indicating that NEU3 mediated GM1 ganglioside to GA1 glycolipid conversion in Glb1 KO mice. The expression of genes associated with neuroinflammation and glial responses were enhanced in Glb1/Neu3 DKO mice compared with Glb1 KO mice. Mouse NEU3 more efficiently converted GM1 ganglioside to GA1 glycolipid than human NEU3 did. Our findings highlight NEU3's role in ameliorating the consequences of Glb1 deletion in mice, provide insights into NEU3's differential effects between mice and humans in GM1 gangliosidosis, and offer a potential therapeutic approach for reducing toxic GM1 ganglioside accumulation in GM1 gangliosidosis patients.

Dysfunctional mitochondrial translation and combined oxidative phosphorylation deficiency in a mouse model of hepatoencephalopathy due to Gfm1 mutations.

Hepatoencephalopathy due to combined oxidative phosphorylation deficiency type 1 (COXPD1) is a recessive mitochondrial translation disorder caused by mutations in GFM1, a nuclear gene encoding mitochondrial elongation factor G1 (EFG1). Patients with COXPD1 typically present hepatoencephalopathy early after birth with rapid disease progression, and usually die within the first few weeks or years of life. We have generated two different mouse models: a Gfm1 knock-in (KI) harboring the p.R671C missense mutation, found in at least 10 patients who survived more than 1 year, and a Gfm1 knock-out (KO) model. Homozygous KO mice (Gfm1-/- ) were embryonically lethal, whereas homozygous KI (Gfm1R671C/R671C ) mice were viable and showed normal growth. R671C mutation in Gfm1 caused drastic reductions in the mitochondrial EFG1 protein content in different organs. Six- to eight-week-old Gfm1R671C/R671C mice showed partial reductions of in organello mitochondrial translation and respiratory complex IV enzyme activity in the liver. Compound heterozygous Gfm1R671C/- showed a more pronounced decrease of EFG1 protein in liver and brain mitochondria, as compared with Gfm1R671C/R671C mice. At 8 weeks of age, their mitochondrial translation rates were significantly reduced in both tissues. Additionally, Gfm1R671C/- mice showed combined oxidative phosphorylation deficiency (reduced complex I and IV enzyme activities in liver and brain), and blue native polyacrylamide gel electrophoresis analysis revealed lower amounts of both affected complexes. We conclude that the compound heterozygous Gfm1R671C/- mouse presents a clear dysfunctional molecular phenotype, showing impaired mitochondrial translation and combined respiratory chain dysfunction, making it a suitable animal model for the study of COXPD1.

Transforming growth factor-beta 1: A new factor reducing hepatic SHBG production in liver fibrosis.

Low plasma sex hormone-binding globulin (SHBG) levels are present in fatty liver disease, which represents a spectrum of diseases ranging from hepatocellular steatosis through steatohepatitis to fibrosis and irreversible cirrhosis. We have previously determined that fat accumulation reduces SHBG production in different nonalcoholic fatty liver disease mouse models. In the present work, we are interested in elucidating the molecular mechanisms reducing SHBG plasma levels in liver fibrosis. For this purpose, in vivo studies were performed using the human SHBG transgenic mice developing liver fibrosis induced by carbon tetrachloride (CCl4 ). Our results clearly showed that CCl4 induced liver fibrosis and reduced SHBG production by reducing hepatocyte nuclear factor 4 alpha (HNF-4α). The SHBG reduction could be influenced by the increase in transforming growth factor-beta 1 (TGF-ß1), which was increased in mice developing liver fibrosis. Therefore, we decided to evaluate the role of TGF-ß1 in regulating hepatic SHBG production. Results obtained in both HepG2 cells and human SHBG transgenic mice showed that TGF-ß1 reduced significantly SHBG messenger RNA and protein levels. Mechanistically TGF-ß1 downregulated P1-HNF-4α isoforms and increased P2-HNF-4α isoforms via Smad3 and Stat3 pathways through TGF-ß1 receptor I, resulting in transcriptional repression of the SHBG gene. Taken together, we found for the first time that TGF-ß1 is a new factor regulating hepatic SHBG production in liver fibrosis. Further research is needed to determine the role of this reduction in hepatic SHBG production in the progression of nonalcoholic steatohepatitis.

The sphingosine 1-phosphate receptor 1 causes tissue retention by inhibiting the entry of peripheral tissue T lymphocytes into afferent lymphatics.

Although much is known about the migration of T cells from blood to lymph nodes, less is known about the mechanisms regulating the migration of T cells from tissues into lymph nodes through afferent lymphatics. Here we investigated T cell egress from nonlymphoid tissues into afferent lymph in vivo and developed an experimental model to recapitulate this process in vitro. Agonism of sphingosine 1-phosphate receptor 1 inhibited the entry of tissue T cells into afferent lymphatics in homeostatic and inflammatory conditions and caused the arrest, mediated at least partially by interactions of the integrin LFA-1 with its ligand ICAM-1 and of the integrin VLA-4 with its ligand VCAM-1, of polarized T cells at the basal surface of lymphatic but not blood vessel endothelium. Thus, the increased sphingosine 1-phosphate present in inflamed peripheral tissues may induce T cell retention and suppress T cell egress.

Transient elastography in DAA era. Relation between post-SVR LSM and histology.

The natural history of HCV chronic infection has drastically changed after direct-acting antiviral treatment. Due to the high sustained virological response (SVR) achieved, noninvasive estimation of liver fibrosis regression has become a major key point. The present study tries to evaluate the relation between liver histology and liver stiffness measurement (LSM) by transient elastography (TE) after SVR.

Parvovirus B19 Myocarditis: Looking Beyond the Heart.

Human parvovirus B19 represents the most common etiology of myocarditis in the pediatric population. Although it usually causes a benign exanthematic viral infection, parvovirus B19 may also present as disseminated disease with tropism for the myocardium, causing heart failure with high mortality. We present the case of a 2-year-old patient with fulminating acute myocarditis in whom the histological, immunophenotypic, and microbiological findings in necropsy showed multiorgan involvement caused by parvovirus B19. The autopsy revealed changes due to infection with parvovirus B19 as well as hypoxic-ischemic and secondary autoimmune changes. Medullary aplasia was observed, transmural lymphocyte myocarditis, lymphocytosis in the dermis with endothelial cells positive for parvovirus B19 in immunohistochemistry, cholestatic hepatitis due to ischemia and autoimmune hepatitis, lymphadenitis, and signs of hemophagocytosis. We also found hypoxic-ischemic encephalopathy.

Cerebral organoids derived from Sandhoff disease-induced pluripotent stem cells exhibit impaired neurodifferentiation.

Sandhoff disease, one of the GM2 gangliosidoses, is a lysosomal storage disorder characterized by the absence of ß-hexosaminidase A and B activity and the concomitant lysosomal accumulation of its substrate, GM2 ganglioside. It features catastrophic neurodegeneration and death in early childhood. How the lysosomal accumulation of ganglioside might affect the early development of the nervous system is not understood. Recently, cerebral organoids derived from induced pluripotent stem (iPS) cells have illuminated early developmental events altered by disease processes. To develop an early neurodevelopmental model of Sandhoff disease, we first generated iPS cells from the fibroblasts of an infantile Sandhoff disease patient, then corrected one of the mutant HEXB alleles in those iPS cells using CRISPR/Cas9 genome-editing technology, thereby creating isogenic controls. Next, we used the parental Sandhoff disease iPS cells and isogenic HEXB-corrected iPS cell clones to generate cerebral organoids that modeled the first trimester of neurodevelopment. The Sandhoff disease organoids, but not the HEXB-corrected organoids, accumulated GM2 ganglioside and exhibited increased size and cellular proliferation compared with the HEXB-corrected organoids. Whole-transcriptome analysis demonstrated that development was impaired in the Sandhoff disease organoids, suggesting that alterations in neuronal differentiation may occur during early development in the GM2 gangliosidoses.

De Novo Sphingolipid Biosynthesis Is Required for Adipocyte Survival and Metabolic Homeostasis.

Sphingolipids are a diverse class of essential cellular lipids that function as structural membrane components and as signaling molecules. Cells acquire sphingolipids by both de novo biosynthesis and recycling of exogenous sphingolipids. The individual importance of these pathways for the generation of essential sphingolipids in differentiated cells is not well understood. To investigate the requirement for de novo sphingolipid biosynthesis in adipocytes, a cell type with highly regulated lipid metabolism, we generated mice with an adipocyte-specific deletion of Sptlc1 Sptlc1 is an obligate subunit of serine palmitoyltransferase, the enzyme responsible for the first and rate-limiting step of de novo sphingolipid biosynthesis. These mice, which initially developed adipose tissue, exhibited a striking age-dependent loss of adipose tissue accompanied by evidence of adipocyte death, increased macrophage infiltration, and tissue fibrosis. Adipocyte differentiation was not affected by the Sptlc1 deletion. The mice also had elevated fasting blood glucose, fatty liver, and insulin resistance. Collectively, these data indicate that de novo sphingolipid biosynthesis is required for adipocyte cell viability and normal metabolic function and that reduced de novo sphingolipid biosynthesis within adipocytes is associated with adipocyte death, adipose tissue remodeling, and metabolic dysfunction.

Sphingosine-1-phosphate Phosphatase 2 Regulates Pancreatic Islet ß-Cell Endoplasmic Reticulum Stress and Proliferation.

Sphingosine-1-phosphate (S1P) is a sphingolipid metabolite that regulates basic cell functions through metabolic and signaling pathways. Intracellular metabolism of S1P is controlled, in part, by two homologous S1P phosphatases (SPPases), 1 and 2, which are encoded by the Sgpp1 and Sgpp2 genes, respectively. SPPase activity is needed for efficient recycling of sphingosine into the sphingolipid synthesis pathway. SPPase 1 is important for skin homeostasis, but little is known about the functional role of SPPase 2. To identify the functions of SPPase 2 in vivo, we studied mice with the Sgpp2 gene deleted. In contrast to Sgpp1(-/-) mice, Sgpp2(-/-) mice had normal skin and were viable into adulthood. Unexpectedly, WT mice expressed Sgpp2 mRNA at high levels in pancreatic islets when compared with other tissues. Sgpp2(-/-) mice had normal pancreatic islet size; however, they exhibited defective adaptive ß-cell proliferation that was demonstrated after treatment with either a high-fat diet or the ß-cell-specific toxin, streptozotocin. Importantly, ß-cells from untreated Sgpp2(-/-) mice showed significantly increased expression of proteins characteristic of the endoplasmic reticulum stress response compared with ß-cells from WT mice, indicating a basal islet defect. Our results show that Sgpp2 deletion causes ß-cell endoplasmic reticulum stress, which is a known cause of ß-cell dysfunction, and reveal a juncture in the sphingolipid recycling pathway that could impact the development of diabetes.

Utility Serum Marker HE4 for the Differential Diagnosis Between Endometriosis and Adnexal Malignancy.

OBJECTIVE: The aim of the study was to assess the utility of serum human epididymal secretory protein E4 (HE4) biomarker in the differential diagnosis of endometriosis and adnexal malignancies. METHODS: Multicentric prospective observational study between January 2010 and December 2011 in 4 European centers (Italy, Portugal, Latvia, and Spain) was carried out. We collected 981 healthy patients diagnosed with adnexal patology and selected 65 patients diagnosed with endometriosis and analyzed their serum markers CA125, HE4, and Risk of Ovarian Malignancy Algorithm (ROMA) index. We also analyzed all cases of malignant histology and divided them according to CA125 levels (negative, ≤35 U/mL; intermediate, >35-150 U/mL; and highly positive, >150 U/mL). RESULTS: HE4 was positive only in 1.5% of cases, CA125 in 64.6%, and ROMA index in 14.1%. In the subgroup intermediate CA125 values, positive HE4 is very specific (91.2%) correctly classifying patients with benign disease, but with lower sensibility (66.1%); however, ROMA index showed a high sensibility (89.3%), with a false-positive rate of 42.8%. CONCLUSIONS: HE4 can be a very useful biomarker to exclude malignant disease in patients with endometriosis.

Prognostic value of the dynamics of M-type phospholipase A2 receptor antibody titers in patients with idiopathic membranous nephropathy treated with two different immunosuppression regimens.

CONTEXT: The dynamics of anti-phospholipase A2 antibody titers during treatment could predict clinical responses in patients with membranous nephropathy. OBJECTIVES: We analyzed the predictive value of the dynamics of these antibodies on clinical responses. MATERIALS AND METHODS: The serum antibody levels were measured before and during treatment in 79 patients with anti-phospholipase A2 receptor antibody membranous nephropathy treated with two different immunosuppression regimens RESULTS: In both groups of patients, the relative reduction in antibody titers at 3 and 6 months preceded and predicted the clinical responses. CONCLUSIONS: Antibody titer dynamics was useful for predicting clinical responses.

Sphingosine-1-phosphate phosphatase 1 regulates keratinocyte differentiation and epidermal homeostasis.

Sphingosine 1-phosphate (S1P) is a bioactive lipid whose levels are tightly regulated by its synthesis and degradation. Intracellularly, S1P is dephosphorylated by the actions of two S1P-specific phosphatases, sphingosine-1-phosphate phosphatases 1 and 2. To identify the physiological functions of S1P phosphatase 1, we have studied mice with its gene, Sgpp1, deleted. Sgpp1(-/-) mice appeared normal at birth, but during the 1st week of life they exhibited stunted growth and suffered desquamation, with most dying before weaning. Both Sgpp1(-/-) pups and surviving adults exhibited multiple epidermal abnormalities. Interestingly, the epidermal permeability barrier developed normally during embryogenesis in Sgpp1(-/-) mice. Keratinocytes isolated from the skin of Sgpp1(-/-) pups had increased intracellular S1P levels and displayed a gene expression profile that indicated overexpression of genes associated with keratinocyte differentiation. The results reveal S1P metabolism as a regulator of keratinocyte differentiation and epidermal homeostasis.

Shaping the landscape: metabolic regulation of S1P gradients.

Sphingosine-1-phosphate (S1P) is a lipid that functions as a metabolic intermediate and a cellular signaling molecule. These roles are integrated when compartments with differing extracellular S1P concentrations are formed that serve to regulate functions within the immune and vascular systems, as well as during pathologic conditions. Gradients of S1P concentration are achieved by the organization of cells with specialized expression of S1P metabolic pathways within tissues. S1P concentration gradients underpin the ability of S1P signaling to regulate in vivo physiology. This review will discuss the mechanisms that are necessary for the formation and maintenance of S1P gradients, with the aim of understanding how a simple lipid controls complex physiology. This article is part of a Special Issue entitled Advances in Lysophospholipid Research.

Simplifying complexity: genetically resculpting glycosphingolipid synthesis pathways in mice to reveal function.

Glycosphingolipids (GSLs) are a group of plasma-membrane lipids notable for their extremely diverse glycan head groups. The metabolic pathways for GSLs, including the identity of the biosynthetic enzymes needed for synthesis of their glycans, are now well understood. Many of their cellular functions, which include plasma-membrane organization, regulation of cell signaling, endocytosis, and serving as binding sites for pathogens and endogenous receptors, have also been established. However, an understanding of their functions in vivo had been lagging. Studies employing genetic manipulations of the GSL synthesis pathways in mice have been used to systematically reduce the large numbers and complexity of GSL glycan structures, allowing the in vivo functions of GSLs to be revealed from analysis of the resulting phenotypes. Findings from these studies have produced a clearer picture of the role of GSLs in mammalian physiology, which is the topic of this review.

The significant IgG4 infiltrate in autoimmune hepatitis is associated with a greater ductular reaction and more advanced liver disease.

BACKGROUND: Sclerosing cholangitis is the typical IgG4-related disease digestive involvement. However, the role of the IgG4 liver expression in autoimmune hepatitis remains unknown. AIMS: to assess whether the expression of IgG4 plasma cells in patients with autoimmune hepatitis (AIH) was associated with different outcomes. METHODS: Retrospective study including patients diagnosed with AIH by biopsy from January-2009 to June-2021. At least mild IgG4 expression (>10 IgG4+-plasma cells per field) was considered as significant. RESULTS: 85 patients with AIH were included. Overall, 58.8% were women, mean age 54 years. Nine (10.6%) presented cirrhosis at diagnosis. Fifteen (17.6%) had significant IgG4 liver expression. Patients with IgG4 infiltrate were older (p = 0.021), presented liver cirrhosis more frequently (33.3% vs. 5.7%, p = 0.007), greater IgG plasma values (p = 0.008) and atypical ANCAs (p = 0.086); ductular reaction was also more common (p = 0.009). Complete remission rate was similar regardless of the IgG4 infiltrate. Time to corticosteroids discontinuation was longer in subjects with IgG4 infiltrate (p = 0.068), but second-line therapy tended to be less frequent (p = 0.187). CONCLUSION: Significant IgG4 liver infiltrate in patients with autoimmune hepatitis is associated with more advanced liver disease. The greater ductular reaction mediated by the IgG4 infiltrate may be the cause for this finding, though this finding should be prospectively assessed.

Sphingosine-1-phosphate lyase deficiency produces a pro-inflammatory response while impairing neutrophil trafficking.

Sphingosine-1-phosphate (S1P) lyase catalyzes the degradation of S1P, a potent signaling lysosphingolipid. Mice with an inactive S1P lyase gene are impaired in the capacity to degrade S1P, resulting in highly elevated S1P levels. These S1P lyase-deficient mice have low numbers of lymphocytes and high numbers of neutrophils in their blood. We found that the S1P lyase-deficient mice exhibited features of an inflammatory response including elevated levels of pro-inflammatory cytokines and an increased expression of genes in liver associated with an acute-phase response. However, the recruitment of their neutrophils into inflamed tissues was impaired and their neutrophils were defective in migration to chemotactic stimulus. The IL-23/IL-17/granulocyte-colony stimulating factor (G-CSF) cytokine-controlled loop regulating neutrophil homeostasis, which is dependent on neutrophil trafficking to tissues, was disturbed in S1P lyase-deficient mice. Deletion of the S1P4 receptor partially decreased the neutrophilia and inflammation in S1P lyase-deficient mice, implicating S1P receptor signaling in the phenotype. Thus, a genetic block in S1P degradation elicits a pro-inflammatory response but impairs neutrophil migration from blood into tissues.

Plasma cell S1P1 expression determines secondary lymphoid organ retention versus bone marrow tropism.

After induction in secondary lymphoid organs, a subset of antibody-secreting cells (ASCs) homes to the bone marrow (BM) and contributes to long-term antibody production. The factors determining secondary lymphoid organ residence versus BM tropism have been unclear. Here we demonstrate that in mice treated with FTY720 or that lack sphingosine-1-phosphate (S1P) receptor-1 (S1P1) in B cells, IgG ASCs are induced and localize normally in secondary lymphoid organs but they are reduced in numbers in blood and BM. Many IgG ASCs home to BM on day 3 of the secondary response and day 3 splenic ASCs exhibit S1P responsiveness, whereas the cells remaining at day 5 are unable to respond. S1P1 mRNA abundance is higher in ASCs isolated from blood compared to spleen, whereas CXCR4 expression is lower. Blood ASCs also express higher amounts of Kruppel-like factor (KLF)2, a regulator of S1P1 gene expression. These findings establish an essential role for S1P1 in IgG plasma cell homing and they suggest that differential regulation of S1P1 expression in differentiating plasma cells may determine whether they remain in secondary lymphoid organs or home to BM.