Productos de activación del complemento (C3a y C5b-9) como marcadores de actividad de la dermatomiositis. Comparación con parámetros bioquímicos tradicionales

Inhibiting B cell activating factor attenuates preeclamptic symptoms in placental ischemic rats

PROBLEM

Preeclampsia (PE), new-onset hypertension during pregnancy, is associated with a pro-inflammatory state with activated T cells, cytolytic natural killer (NK) cells, dysregulated complement proteins, and B cells secreting agonistic autoantibodies to the angiotensin II type-1 receptor (AT1-AA). The reduced uterine perfusion pressure (RUPP) model of placental ischemia recapitulates these features of PE. Blocking CD40L-CD40 communication between T and B cells or B cell depletion with Rituximab prevents hypertension and AT1-AA production in RUPP rats. This suggests that T cell-dependent B cell activation contributes to the hypertension and AT1-AA associated with PE. B2 cells maturing into antibody producing plasma cells are the product of T cell-dependent B cell-interactions and B cell Activating Factor (BAFF) is an integral cytokine in the development of B2 cells specifically. Thus, we hypothesize that BAFF blockade will selectively deplete B2 cells, therefore reducing blood pressure, AT1-AA, activated NK Cells, and complement in the RUPP rat model of PE.

METHOD OF STUDY

Gestational Day (GD) 14 pregnant rats underwent the RUPP procedure, and a subset were treated with 1 mg/kg Anti-BAFF antibodies via jugular catheters. On GD19, blood pressure was measured, B cells and NK cells were measured by flow cytometry, AT1-AA was measured by cardiomyocyte bioassay, and complement activation was measured by ELISA.

RESULTS

Anti-BAFF therapy attenuated hypertension, AT1-AA, NK cell activation, and APRIL levels in RUPP rats without negatively impacting fetal outcomes.

CONCLUSIONS

This study demonstrates that B2 cells contribute to hypertension, AT1-AA, and NK cell activation in response to placental ischemia during pregnancy.

Pathophysiological Mechanisms and Treatment of Dermatomyositis and Immune Mediated Necrotizing Myopathies: A Focused Review

Idiopathic inflammatory myopathies (IIM), collectively known as myositis, are a composite group of rare autoimmune diseases affecting mostly skeletal muscle, although other organs or tissues may also be involved. The main clinical feature of myositis is subacute, progressive, symmetrical muscle weakness in the proximal arms and legs, whereas subtypes of myositis may also present with extramuscular features, such as skin involvement, arthritis or interstitial lung disease (ILD). Established subgroups of IIM include dermatomyositis (DM), immune-mediated necrotizing myopathy (IMNM), anti-synthetase syndrome (ASyS), overlap myositis (OM) and inclusion body myositis (IBM). Although these subgroups have overlapping clinical features, the widespread variation in the clinical manifestations of IIM suggests different pathophysiological mechanisms. Various components of the immune system are known to be important immunopathogenic pathways in IIM, although the exact pathophysiological mechanisms causing the muscle damage remain unknown. Current treatment, which consists of glucocorticoids and other immunosuppressive or immunomodulating agents, often fails to achieve a sustained beneficial response and is associated with various adverse effects. New therapeutic targets have been identified that may improve outcomes in patients with IIM. A better understanding of the overlapping and diverging pathophysiological mechanisms of the major subgroups of myositis is needed to optimize treatment. The aim of this review is to report on recent advancements regarding DM and IMNM.

International Union of Basic and Clinical Pharmacology. [corrected]. LXXXVII. Complement peptide C5a, C4a, and C3a receptors

The activation of the complement cascade, a cornerstone of the innate immune response, produces a number of small (74-77 amino acid) fragments, originally termed anaphylatoxins, that are potent chemoattractants and secretagogues that act on a wide variety of cell types. These fragments, C5a, C4a, and C3a, participate at all levels of the immune response and are also involved in other processes such as neural development and organ regeneration. Their primary function, however, is in inflammation, so they are important targets for the development of antiinflammatory therapies. Only three receptors for complement peptides have been found, but there are no satisfactory antagonists as yet, despite intensive investigation. In humans, there is a single receptor for C3a (C3a receptor), no known receptor for C4a, and two receptors for C5a (C5a₁ receptor and C5a₂ receptor). The most recently characterized receptor, the C5a₂ receptor (previously known as C5L2 or GPR77), has been regarded as a passive binding protein, but signaling activities are now ascribed to it, so we propose that it be formally identified as a receptor and be given a name to reflect this. Here, we describe the complex biology of the complement peptides, introduce a new suggested nomenclature, and review our current knowledge of receptor pharmacology.

Membrane attack by complement: the assembly and biology of terminal complement complexes

Complement system activation plays an important role in both innate and acquired immunity. Activation of the complement and the subsequent formation of C5b-9 channels (the membrane attack complex) on the cell membranes lead to cell death. However, when the number of channels assembled on the surface of nucleated cells is limited, sublytic C5b-9 can induce cell cycle progression by activating signal transduction pathways and transcription factors and inhibiting apoptosis. This induction by C5b-9 is dependent upon the activation of the phosphatidylinositol 3-kinase/Akt/FOXO1 and ERK1 pathways in a Gi protein-dependent manner. C5b-9 induces sequential activation of CDK4 and CDK2, enabling the G1/S-phase transition and cellular proliferation. In addition, it induces RGC-32, a novel gene that plays a role in cell cycle activation by interacting with Akt and the cyclin B1-CDC2 complex. C5b-9 also inhibits apoptosis by inducing the phosphorylation of Bad and blocking the activation of FLIP, caspase-8, and Bid cleavage. Thus, sublytic C5b-9 plays an important role in cell activation, proliferation, and differentiation, thereby contributing to the maintenance of cell and tissue homeostasis.

Plasma C3a-des-Arg levels in women with and without endometriosis

PROBLEM

The lack of a reliable method for early non-invasive detection of endometriosis often results in delayed diagnosis. The aim of this study was to test the hypothesis that the plasma concentration of complement factor C3a (anaphylatoxin) can be used as a non-invasive test in the diagnosis of endometriosis.

METHOD OF STUDY

The C3a concentration was analyzed using ELISA in 160 patients with (n = 109) or without (n = 51) endometriosis during menstruation (n = 49), follicular phase (n = 55), and luteal (n = 56) phase.

RESULTS

Plasma C3a concentration was comparable between patients with [102 (27-2213) ng/mL] and without [105 (32-2340) ng/mL] (P = 0.84) endometriosis, also when assessed separately during menstruation, follicular phase, and luteal phase.

CONCLUSION

We found no difference in C3a levels between women with and without endometriosis and did not confirm our hypothesis that plasma C3a levels can be used as diagnostic test for endometriosis.