Neutrophil extracellular traps are a source of extracellular HMGB1 in lupus nephritis: associations with clinical and histopathological features

OBJECTIVE

This study aimed to analyze the expression of the high mobility group box-1 (HMGB1) protein in neutrophil extracellular traps (NETs) of patients with lupus nephritis (LN) and its association with clinical and histopathological features of the disease.

METHODS

Twenty-three patients with biopsy-confirmed LN and 14 systemic lupus erythematosus (SLE) patients with active disease (SLE Disease Activity Index (SLEDAI) score ≥ 6) and no evidence of LN were included. Clinical and laboratory features were recorded. NETs and the expression of HMGB1 were assessed by confocal microscopy, and serum HMGB1 levels were measured by ELISA.

RESULTS

In comparison to patients without kidney disease, patients with LN had a higher expression of HMGB1 in spontaneous (57 vs. 30.4; p = 0.027) and lipopolysaccharide (LPS)-induced (55.8 vs. 24.9; p = 0.005) NETs. We found a positive correlation between serum HMGB1 and the expression of HMGB1 in LPS-induced NETs (r = 0.447, p = 0.017). The expression of HMGB1 in spontaneous NETs correlated with SLEDAI score (r = 0.514, p = 0.001), anti-dsDNA antibodies (r = 0.467, p = 0.004), the rate of glomerular filtration descent (r = 0.543, p = 0.001), and diverse histopathological components of active nephritis in the kidney biopsy, such as the activity index (r = 0.581, p = 0.004), fibrinoid necrosis (r = 0.603, p = 0.002), and cellular crescents (r = 0.486, p = 0.019).

CONCLUSIONS

In patients with SLE, NETs are a source of extracellular HMGB1. The expression of HMGB1 in NETs is higher among patients with LN, which correlates with clinical and histopathological features of active nephritis and suggest a possible role of this alarmin in the pathophysiology of kidney damage in SLE.

Air Travel, Circadian Rhythms/Hormones, and Autoimmunity

Biological rhythms are fundamental for homeostasis and have recently been involved in the regulatory processes of various organs and systems. Circadian cycle proteins and hormones have a direct effect on the inflammatory response and have shown pro- or anti-inflammatory effects in animal models of autoimmune diseases. The cells of the immune system have their own circadian rhythm, and the light-dark cycle directly influences the inflammatory response. On the other hand, patients with autoimmune diseases characteristically have sleep disorders and fatigue, and in certain disease, such as rheumatoid arthritis (RA), a frank periodicity in the signs and symptoms is recognized. The joint symptoms predominate in the morning, and apparently, subjects with RA have relative adrenal insufficiency, with a cortisol peak unable to control the late night load of pro-inflammatory cytokines. Transatlantic flights represent a challenge in the adjustment of biological rhythms, since they imply sleep deprivation, time zone changes, and potential difficulties for drug administration. In patients with autoimmune diseases, the use of DMARDs and prednisone at night is probably best suited to lessen morning symptoms. It is also essential to sleep during the trip to improve adaptation to the new time zone and to avoid, as far as possible, works involving flexible or nocturnal shifts. The study of proteins and hormones related to biological rhythms will demonstrate new pathophysiological pathways of autoimmune diseases, which will emphasize the use of general measures for sleep respect and methods for drug administration at key daily times to optimize their anti-inflammatory and immune modulatory effects.

Ro52/TRIM21-deficient expression and function in different subsets of peripheral blood mononuclear cells is associated with a proinflammatory cytokine response in patients with idiopathic inflammatory myopathies

The presence of anti-Ro52/tripartite motif 21 (Trim21) autoantibodies has been associated with a distinctive clinical profile and has gained value as a prognostic marker in idiopathic inflammatory myopathies (IIM). The aim of the present work was to analyse Ro52/Trim21 expression in different subsets of peripheral blood mononuclear cells (PBMCs) of patients with IIM, as well as the ubiquitination profile and its association with proinflammatory cytokine production. We included 18 patients with recent-onset IIM and 18 age- and gender-matched healthy donors. PBMCs were isolated and different subsets (CD4⁺ , CD8⁺ , CD14⁺ ) were purified by magnetic selection. The expression of Ro52/Trim21 in different PBMC subsets of patients with IIM and healthy donors was analysed by Western blot. We assessed the presence of myositis-specific and associated autoantibodies by enzyme-linked immunosorbent assay (ELISA). Cytokine levels were measured by cytometric bead array. Patients with IIM showed decreased protein expression of Ro52/Trim21 in comparison to healthy controls in PBMC (0·97 ± 0·60 versus 1·84 ± 0·92, P = 0·016), CD4⁺ lymphocytes (0·79 ± 0·54 versus 2·41 ± 0·78, P = 0·017), and monocytes (0·87 ± 0·35 versus 1·89 ± 0·20, P < 0·001). There were no significant differences among IIM groups. Also, a lower K48-mediated ubiquitination profile was found, predominantly in CD4⁺ lymphocytes. Furthermore, after mitogenic stimulation, there was a higher synthesis of proinflammatory cytokines by T cells [interleukin (IL)-17A and tumour necrosis factor (TNF)-α] and monocytes [IL-6 and interferon (IFN)-α] from IIM patients compared with healthy controls. Our data suggest that patients with IIM, mainly DM, are characterized by a deficient expression of Ro52/TRIM21 in different PBMC subsets (CD4⁺ lymphocytes and monocytes), along with lower K48-mediated ubiquitination, which is associated with a proinflammatory cytokine response.

The nature of L8 and L8S8 forms of ribulose bisphosphate carboxylase/oxygenase from Chromatium vinosum

L8 and L8S8 forms of ribulose bisphosphate carboxylase/oxygenase (RubisCO) have been prepared from Chromatium vinosum by the extremely mild method of centrifugal fractionation. Only the L8S8 form is detectable in crude extracts of this organism. Both forms show immunological identify in double diffusion studies using antibody to L subunits of the L8S8 form. L subunits from both L8 and L8S8 enzymes are identical by the criteria of peptides observed after limited proteolysis and N-terminal sequence analysis. In addition, these subunits show regions of homology with L subunits from Rhodospirillum rubrum, Anacystis nidulans, and spinach. S subunits of the C. vinosum enzyme are completely homologous to those from A. nidulans and higher plants from the 18th through 25th residue, a stretch preceded in all cases by two basic amino acids.

Interaction, functional relations and evolution of large and small subunits in Rubisco from prokaryota and eukaryota

In early biological evolution anoxygenic photosynthetic bacteria may have been established through the acquisition of ribulose bisphosphate carboxylase-oxygenase (Rubisco). The establishment of cyanobacteria may have followed and led to the production of atmospheric oxygen. It has been postulated that a unicellular cyanobacterium evolved to cyanelles which were evolutionary precursors of chloroplasts of both green and non-green algae. The latter probably diverged from ancestors of green algae as evidenced by the occurrence of large (L) and small (S) subunit genes for Rubisco in the chloroplast genome of the chromophytic algae Olisthodiscus luteus. In contrast, the gene for the S subunit was integrated into the nucleus in the evolution of green algae and higher plants. The evolutionary advantages of this integration are uncertain because the function of S subunits is unknown. Recently, two forms of Rubisco (L8 and L8S8) of almost equivalent carboxylase and oxygenase activity have been isolated from the photosynthetic bacterium Chromatium vinosum. This observation perpetuates the enigma of S subunit function. Current breakthroughs are imminent, however, in our understanding of the function of catalytic L subunits because of the application of deoxyoligonucleotide-directed mutagenesis. Especially interesting mutated Rubisco molecules may have either enhanced carboxylase activity or higher carboxylase:oxygenase ratios. Tests of expression, however, must await the insertion of modified genes into the nucleus and chloroplasts. Methodology to accomplish chloroplast transformation is as yet unavailable. Recently, we have obtained the first transformation of cyanobacteria by a colE1 plasmid. We regard this transformation as an appropriate model for chloroplast transformation.