Upregulated selenoprotein I during lipopolysaccharide-induced B cell activation promotes lipidomic changes and is required for effective differentiation into IgM-secreting plasma B cells.

The mechanisms driving metabolic reprogramming during B cell activation are unclear, particularly roles for enzymatic pathways involved in lipid remodeling. We found that murine B cell activation with lipopolysaccharide (LPS) led to a 1.6-fold increase in total lipids that included higher levels of phosphatidylethanolamine (PE) and plasmenyl PE. Selenoprotein I (SELENOI) is an ethanolamine phospholipid transferase involved in the synthesis of both PE and plasmenyl PE, and SELENOI expression was also upregulated during activation. Selenoi knockout (KO) B cells exhibited decreased levels of plasmenyl PE, which plays an important antioxidant role. Lipid peroxidation was measured and found to increase ∼2-fold in KO vs. wild-type (WT) B cells. Cell death was not impacted by KO in LPS-treated B cells and proliferation was only slightly reduced, but differentiation into CD138 + Blimp-1+ plasma B cells was decreased ∼2-fold. This led to examination of B cell receptors important for differentiation that recognize the ligand B cell activating factor, and levels of TACI (transmembrane activator, calcium-modulator, and cytophilin ligand interactor) (CD267) were significantly decreased on KO B cells compared with WT control cells. Vaccination with ovalbumin/adjuvant led to decreased ovalbumin-specific immunoglobulin M (IgM) levels in sera of KO mice compared with WT mice. Real-time polymerase chain reaction analyses revealed a decreased switch from surface to secreted IgM in spleens of KO mice induced by vaccination or LP-BM5 retrovirus infection. Overall, these findings detail the lipidomic response of B cells to LPS activation and reveal the importance of upregulated SELENOI for promoting differentiation into IgM-secreting plasma B cells.

Optic nerve hydropic axonal degeneration and blocked retrograde axoplasmic transport: histopathologic features in human high-pressure secondary glaucoma.

OBJECTIVE: To describe histopathologic features of anterior optic nerves of 12 eyes enucleated for sustained high ocular pressure from iris-ciliary body melanomas in 10 and choroidal melanomas with chronic angle closure in 2. METHODS: In this retrospective study, we analyzed cases indexed in 2 eye pathology laboratories and reviewed the pertinent literature. Cases were identified from diagnostic indexes; microscopic study of slides stained with hematoxylin-eosin and Verhoeff-van Gieson, Mallory trichrome, periodic acid-Schiff, alcian blue, or colloidal iron for acid mucopolysaccharide; review of available clinical documentation; and analysis of features and photography. The main outcome measures were description of optic nerve heads, prelaminar atrophy, laminar posterior bowing, locations and density of hydropic axonal degeneration, blocked retrograde axoplasmic transport, posterior atrophy, and optic nerve disorganization with glial proliferation. RESULTS: Hydropic axonal degeneration was present in front of, within, and posterior to the lamina cribrosa in all 12 eyes. This degeneration extended diffusely and posteriorly from the peripheral lamina and was most dense centrally in 10 eyes. Retrolaminar changes compatible with blockage of retrograde axoplasmic transport were seen in 9 eyes. Posterior atrophy with disorganization and glial proliferation was seen in 10 eyes. No eye had classic glaucomatous atrophic cupping. CONCLUSIONS: Diffuse and centrally intense hydropic axonal degeneration and central blocked retrograde axoplasmic transport explain loss of central acuity, generalized contraction of visual field, and generalized optic atrophy without glaucomatous cupping in eyes with prolonged high-pressure secondary glaucoma.