Stimulatory type A CpG-DNA induces a Th2-like response in human endothelial cells

pVAXhsp65 Vaccination Primes for High IL-10 Production and Decreases Experimental Encephalomyelitis Severity

Experimental autoimmune encephalomyelitis (EAE) is a demyelinating pathology of the central nervous system (CNS) used as a model to study multiple sclerosis immunopathology. EAE has also been extensively employed to evaluate potentially therapeutic schemes. Considering the presence of an immune response directed to heat shock proteins (hsps) in autoimmune diseases and the immunoregulatory potential of these molecules, we evaluated the effect of a previous immunization with a genetic vaccine containing the mycobacterial hsp65 gene on EAE development. C57BL/6 mice were immunized with 4 pVAXhsp65 doses and 14 days later were submitted to EAE induction by immunization with myelin oligodendrocyte glycoprotein (MOG_35–55) emulsified in Complete Freund's Adjuvant. Vaccinated mice presented significant lower clinical scores and lost less body weight. MOG_35–55 immunization also determined less inflammation in lumbar spinal cord but did not change CD4+CD25+Foxp3+ T cells frequency in spleen and CNS. Infiltrating cells from the CNS stimulated with rhsp65 produced significantly higher levels of IL-10. These results suggest that the ability of pVAXhsp65 vaccination to control EAE development is associated with IL-10 induction.

Proinflammatory Stimulation of Toll-Like Receptor 9 with High Dose CpG ODN 1826 Impairs Endothelial Regeneration and Promotes Atherosclerosis in Mice

Background

Toll-like receptors (TLR) of the innate immune system have been closely linked with the development of atherosclerotic lesions. TLR9 is activated by unmethylated CpG motifs within ssDNA, but also by CpG motifs in nucleic acids released during vascular apoptosis and necrosis. The role of TLR9 in vascular disease remains controversial and we sought to investigate the effects of a proinflammatory TLR9 stimulation in mice.

Methods and Findings

TLR9-stimulation with high dose CpG ODN at concentrations between 6.25nM to 30nM induced a significant proinflammatory cytokine response in mice. This was associated with impaired reendothelialization upon acute denudation of the carotid and increased numbers of circulating endothelial microparticles, as a marker for amplified endothelial damage. Chronic TLR9 agonism in apolipoprotein E-deficient (ApoE^-/-) mice fed a cholesterol-rich diet increased aortic production of reactive oxygen species, the number of circulating endothelial microparticles, circulating sca-1/flk-1 positive cells, and most importantly augmented atherosclerotic plaque formation when compared to vehicle treated animals. Importantly, high concentrations of CpG ODN are required for these proatherogenic effects.

Conclusions

Systemic stimulation of TLR9 with high dose CpG ODN impaired reendothelialization upon acute vascular injury and increased atherosclerotic plaque development in ApoE^-/- mice. Further studies are necessary to fully decipher the contradictory finding of TLR9 agonism in vascular biology.

Circulating cell-free mitochondrial DNA as the probable inducer of early endothelial dysfunction in the prediabetic patient

Recent evidence has shown that 346million people in the world have diabetes mellitus (DM); this number will increase to 439million by 2030. In addition, current data indicate an increase in DM cases in the population between 40 and 59years of age. Diabetes is associated with the development of micro- and macro-vascular complications, derived from chronic hyperglycemia on the endothelium. Some reports demonstrate that people in a prediabetic state have a major risk of developing early endothelial dysfunction (ED). Today, it is accepted that individuals considered as prediabetic patients are in a pro-inflammatory state associated with endothelial and mitochondrial dysfunction. It is important to mention that impaired mitochondrial functionality has been linked to endothelial apoptosis and release of mitochondrial DNA (mtDNA) in patients with sepsis, cardiac disease, or atherosclerosis. This free mtDNA could promote ED, as well as other side effects on the vascular system through the activation of the toll-like receptor 9 (TLR9). TLR9 is expressed in different cell types (e.g., T or B lymphocytes, mastocytes, and epithelial and endothelial cells). It is localized intracellularly and recognizes non-methylated dinucleotides of viral, bacterial, and mitochondrial DNA. Recently, it has been reported that TLR9 is associated with the pathogenesis of lupus erythematosus, rheumatoid arthritis, and autoimmune diabetes. In this work, it is hypothesized that the increase in the levels of circulating mtDNA is the trigger of early ED in the prediabetic patient, and later on in the older patient with diabetes, through activation of the TLR9 present in the endothelium.

Immune complexes activate human endothelium involving the cell-signaling HMGB1-RAGE axis in the pathogenesis of lupus vasculitis

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the formation of immune complexes (ICs), which contain a complex mixture of autoantigens nucleic acids, nucleic acids-associated proteins and corresponding autoantibodies. In SLE, ICs are deposited in multiple organs. Vasculopathy and vasculitis in SLE are typical complications and are associated with deposition of ICs on endothelium, endothelial activation and inflammatory cell infiltration. However, the effects of ICs on endothelial cells and the mechanisms involved remain unclear. In this study, we have demonstrated for the first time that ICs upregulated cell surface expression of the receptor for advanced glycation end products (RAGE), the expression of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), increased the secretion of the chemokines interleukin 8 (IL-8), monocyte chemoattractant protein-1 (MCP-1), the proinflammatoy cytokines interleukin 6 (IL-6), tumor necrosis factor-α (TNF-α) and promoted the activation of the transcription factor NF-κB p65 in human endothelial cells (P<0.05). ICs also increased transendothelial migration of monocytes (P<0.05). One of the mechanisms underlying these activating effects of ICs on human endothelial cells involves cell signaling by high-mobility group box 1 protein (HMGB1)-RAGE axis, as these effects can be partially blocked by HMGB1 A-box, soluble RAGE (sRAGE), SB203580, PD98059, Bay 117082 (P<0.05) and co-treatment with these agents (P<0.05). In conclusion, ICs elicit proinflammatory responses in human endothelial cells and alter their function involving cellular signaling via the HMGB1-RAGE axis in the pathogenesis of SLE vasculitis.