Citrullination Licenses Calpain to Decondense Nuclei in Neutrophil Extracellular Trap Formation.

Neutrophils respond to various stimuli by decondensing and releasing nuclear chromatin characterized by citrullinated histones as neutrophil extracellular traps (NETs). This achieves pathogen immobilization or initiation of thrombosis, yet the molecular mechanisms of NET formation remain elusive. Peptidyl arginine deiminase-4 (PAD4) achieves protein citrullination and has been intricately linked to NET formation. Here we show that citrullination represents a major regulator of proteolysis in the course of NET formation. Elevated cytosolic calcium levels trigger both peptidylarginine deiminase-4 (PAD4) and calpain activity in neutrophils resulting in nuclear decondensation typical of NETs. Interestingly, PAD4 relies on proteolysis by calpain to achieve efficient nuclear lamina breakdown and chromatin decondensation. Pharmacological or genetic inhibition of PAD4 and calpain strongly inhibit chromatin decondensation of human and murine neutrophils in response to calcium ionophores as well as the proteolysis of nuclear proteins like lamin B1 and high mobility group box protein 1 (HMGB1). Taken together, the concerted action of PAD4 and calpain induces nuclear decondensation in the course of calcium-mediated NET formation.

[Prevalence of antinuclear envelope antibodies and their isotypes in sera positive for antinuclear antibodies]. / Prevalencia de anticuerpos anti envoltura nuclear y sus isotipos en sueros positivos para anticuerpos antinucleares.

Antinuclear antibodies detected in HEp-2 cells by indirect immunofluorescence assay display a great variety of images, including the nuclear envelope pattern. This is quite a less frequent finding. Two thousand five hundred and ninety-four sera were processed, and 37.6% of ANA were detected. The prevalence of anti-nuclear envelope antibodies (ANEA) was of 1.2%, with a high association with autoimmune liver diseases (83%) and a low association with systemic lupus erythematosus. In 21 sera of patients with ANEA, no anti-DNAn antibodies were found; but 28.6% of anti-smooth muscle antibodies and 19% of anti-mitochondrial antibodies were detected. The triple rodent tissue section proved to be a less sensitive substrate than HEp-2 for the detection of ANEA. When using conjugates against different isotypes of antibodies for the detection of ANA, 90.5% of IgG, 66.6% of IgA and 9.5% of IgM. Two patients had ANEA-IgA at high titers (> or = 1:160) without ANEA-IgG. In this work, the importance of performing complementary tests for the detection of anti-smooth muscle antibodies, anti-mitochondrial antibodies and anti-DNAn is highlighted in order to apply these tests as guidelines for the clinical diagnosis of patients with ANEA. Besides, this study expresses the need of using total anti-Ig antibodies as conjugate for IIF-HEp-2 instead of anti-lgG; until the role of IgA antibodies in these autoimmune diseases is clarified.

Prevalencia de anticuerpos anti envoltura nuclear y sus isotipos en sueros positivos para anticuerpos antinucleares / Prevalence of antinuclear envelope antibodies and their isotypes in sera positive for antinuclear antibodies

Antinuclear antibodies detected in HEp-2 cells by indirect immunofluorescence assay display a great variety of images, including the nuclear envelope pattern. This is quite a less frequent finding. Two thousand five hundred and ninety-four sera were processed, and 37.6% of ANA were detected. The prevalence of anti-nuclear envelope antibodies (ANEA) was of 1.2%, with a high association with autoimmune liver diseases (83%) and a low association with systemic lupus erythematosus. In 21 sera of patients with ANEA, no anti-DNAn antibodies were found; but 28.6% of anti-smooth muscle antibodies and 19% of anti-mitochondrial antibodies were detected. The triple rodent tissue section proved to be a less sensitive substrate than HEp-2 for the detection of ANEA. When using conjugates against different isotypes of antibodies for the detection of ANA, 90.5% of IgG, 66.6% of IgA and 9.5% of IgM. Two patients had ANEA-IgA at high titers (> or = 1:160) without ANEA-IgG. In this work, the importance of performing complementary tests for the detection of anti-smooth muscle antibodies, anti-mitochondrial antibodies and anti-DNAn is highlighted in order to apply these tests as guidelines for the clinical diagnosis of patients with ANEA. Besides, this study expresses the need of using total anti-Ig antibodies as conjugate for IIF-HEp-2 instead of anti-lgG; until the role of IgA antibodies in these autoimmune diseases is clarified.

Autoantigens of the nuclear pore complex.

The nuclear envelope (NE) is one of many intracellular targets of the autoimmune response in patients with autoimmune liver disease, systemic lupus erythematosus, and related conditions. In eukaryotic organisms the NE consists of five interconnected regions: an outer nuclear membrane (ONM) that is continuous with the endoplasmic reticulum, an intermembrane or perinuclear space, an inner nuclear membrane (INM) with a unique set of integral membrane proteins, the underlying nuclear lamina, and the pore domains that are regions where the ONM and INM come together. The pore domains are sites of regulated continuity between the cytoplasm and nucleus that are occupied by supramolecular structures, termed nuclear pore complexes (NPCs). Human autoantibodies identified to date bind to specific components in three of the five NE compartments. Autoantigen targets include the lamins A, B, and C of the nuclear lamina, gp210, p62 complex proteins, Nup153, and Tpr within the NPC, and LBR, MAN1, LAP1, and LAP2 that are integral proteins of the INM. Autoantibodies to these NE targets have been shown to be correlated with various autoimmune diseases such as primary biliary cirrhosis, other autoimmune liver diseases and systemic rheumatic diseases. Now that the proteome of the NE is more clearly defined, other autoantibodies to components in this cell compartment are likely to be defined.