Florencia Rosetti

Circulating TNF Receptors 1 and 2 Predict ESRD in Type 2 Diabetes

Levels of proinflammatory cytokines associate with risk for developing type 2 diabetes but whether chronic inflammation contributes to the development of diabetic complications, such as ESRD, is unknown. In the 1990s, we recruited 410 patients with type 2 diabetes for studies of diabetic nephropathy and recorded their characteristics at enrollment. During 12 years of follow-up, 59 patients developed ESRD (17 per 1000 patient-years) and 84 patients died without ESRD (24 per 1000 patient-years). Plasma markers of systemic inflammation, endothelial dysfunction, and the TNF pathway were measured in the study entry samples. Of the examined markers, only TNF receptors 1 and 2 (TNFR1 and TNFR2) associated with risk for ESRD. These two markers were highly correlated, but ESRD associated more strongly with TNFR1. The cumulative incidence of ESRD for patients in the highest TNFR1 quartile was 54% after 12 years but only 3% for the other quartiles (P<0.001). In Cox proportional hazard analyses, TNFR1 predicted risk for ESRD even after adjustment for clinical covariates such as urinary albumin excretion. Plasma concentration of TNFR1 outperformed all tested clinical variables with regard to predicting ESRD. Concentrations of TNFRs moderately associated with death unrelated to ESRD. In conclusion, elevated concentrations of circulating TNFRs in patients with type 2 diabetes at baseline are very strong predictors of the subsequent progression to ESRD in subjects with and without proteinuria.

Circulating TNF Receptors 1 and 2 Predict Stage 3 CKD in Type 1 Diabetes

Elevated plasma concentrations of TNF receptors 1 and 2 (TNFR1 and TNFR2) predict development of ESRD in patients with type 2 diabetes without proteinuria, suggesting these markers may contribute to the pathogenesis of renal decline. We investigated whether circulating markers of the TNF pathway determine GFR loss among patients with type 1 diabetes. We followed two cohorts comprising 628 patients with type 1 diabetes, normal renal function, and no proteinuria. Over 12 years, 69 patients developed estimated GFR less than 60 mL/min per 1.73 m(2) (16 per 1000 person-years). Concentrations of TNFR1 and TNFR2 were strongly associated with risk for early renal decline. Renal decline was associated only modestly with total TNFα concentration and appeared unrelated to free TNFα. The cumulative incidence of estimated GFR less than 60 mL/min per 1.73 m(2) for patients in the highest TNFR2 quartile was 60% after 12 years compared with 5%-19% in the remaining quartiles. In Cox proportional hazards analysis, patients with TNFR2 values in the highest quartile were threefold more likely to experience renal decline than patients in the other quartiles (hazard ratio, 3.0; 95% confidence interval, 1.7-5.5). The risk associated with high TNFR1 values was slightly less than that associated with high TNFR2 values. TNFR levels were unrelated to baseline free TNFα level and remained stable over long periods within an individual. In conclusion, early GFR loss in patients with type 1 diabetes without proteinuria is strongly associated with circulating TNF receptor levels but not TNFα levels (free or total).

T cell apoptosis at the maternal-fetal interface in early human pregnancy, involvement of galectin-1.

The human fetus is not rejected by the maternal immune system despite expressing paternal antigens. Natural killer cells, the major lymphocyte population of the human decidua (dNKs), express genes with immunomodulatory potential. These include galectin-1 (gal1), a lectin with apoptotic activity on activated CD8+ T cells, Th1 and Th17 CD4+ cells. Although many cell types at the maternal–fetal interface also produce gal1, its production by dNKs has been used here to study its function in pregnancy. Media conditioned by dNKs containing gal1 induced apoptosis of activated T cells. This effect was blocked by anti-gal1 antibodies. Decidual T (dT) cells but not peripheral T (pT) cells bound gal1 and presented a distinct glycophenotype compatible with sensitivity to gal1. Annexin V staining, TUNEL, and hypodiploidy showed a substantial proportion of apoptotic dT cells. Immunohistochemistry revealed widespread expression of gal1 as well as periglandular apoptotic dT foci that colocalized with dNKs. Thus, secretion of gal1 by dNKs and other decidual cells contributes to the generation of an immune-privileged environment at the maternal–fetal interface.

Human Lupus Serum Induces Neutrophil-Mediated Organ Damage in Mice That Is Enabled by Mac-1 Deficiency

Systemic lupus erythematosus (SLE) is a chronic, multiorgan inflammatory autoimmune disorder associated with high levels of circulating autoantibodies and immune complexes. We report that passive transfer of human SLE sera into mice expressing the uniquely human FcγRIIA and FcγRIIIB on neutrophils induces lupus nephritis and in some cases arthritis only when the mice additionally lack the CD18 integrin, Mac-1. The prevailing view is that Mac-1 on macrophages is responsible for immune complex clearance. However, disease permitted by the absence of Mac-1 is not related to enhanced renal immune complex deposition or in situ C1q/C3 complement activation and proceeds even in the absence of macrophages. Instead, disease is associated with increased FcγRIIA-induced neutrophil accumulation that is enabled by Mac-1 deficiency. Intravital microscopy in the cremasteric vasculature reveals that Mac-1 mitigates FcγRIIA-dependent neutrophil recruitment in response to deposited immune complexes. Our results provide direct evidence that human SLE immune complexes are pathogenic, demonstrate that neutrophils are primary mediators of end organ damage in a novel humanized lupus mouse model, and identify Mac-1 regulation of FcγRIIA-mediated neutrophil recruitment as a key step in development of target organ damage.

Cutting edge: protein phosphatase 2A confers susceptibility to autoimmune disease through an IL-17-dependent mechanism.

The contribution of individual molecular aberrations to the pathogenesis of systemic lupus erythematosus (SLE), an autoimmune disease that affects multiple organs, is often difficult to evaluate because of the presence of abundant confounding factors. To assess the effect of increased expression of the phosphatase protein phosphatase 2A (PP2A) in T cells, as recorded in SLE patients, we generated a transgenic mouse that overexpresses the PP2Ac subunit in T cells. The transgenic mouse displays a heightened susceptibility to immune-mediated glomerulonephritis in the absence of other immune defects. CD4+ T cells produce increased amounts of IL-17 while the number of neutrophils in the peripheral blood is increased. IL-17 neutralization abrogated the development of glomerulonephritis. We conclude that increased PP2Ac expression participates in SLE pathogenesis by promoting inflammation through unchecked IL-17 production and facilitating the development of end-organ damage.

The many faces of Mac-1 in autoimmune disease

Mac‐1 (CD11b/CD18) is a β2 integrin classically regarded as a pro‐inflammatory molecule because of its ability to promote phagocyte cytotoxic functions and enhance the function of several effector molecules such as FcγR, uPAR, and CD14. Nevertheless, recent reports have revealed that Mac‐1 also plays significant immunoregulatory roles, and genetic variants in ITGAM, the gene that encodes CD11b, confer risk for the autoimmune disease systemic lupus erythematosus (SLE). This has renewed interest in the physiological roles of this integrin and raised new questions on how its seemingly opposing biological functions may be regulated. Here, we provide an overview of the CD18 integrins and how their activation may be regulated as this may shed light on how the opposing roles of Mac‐1 may be elicited. We then discuss studies that exemplify Mac‐1s pro‐inflammatory versus regulatory roles particularly in the context of IgG immune complex‐mediated inflammation. This includes a detailed examination of molecular mechanisms that could explain the risk‐conferring effect of rs1143679, a single nucleotide non‐synonymous Mac‐1 polymorphism associated with SLE.

Neutrophils: game changers in glomerulonephritis?

Glomerulonephritides represent a diverse array of diseases that have in common immune cell-mediated effector mechanisms that cause organ damage. The contribution of neutrophils to the pathogenesis of proliferative glomerulonephritis (GN) is not well recognized. Most equate neutrophils with killing pathogens and causing collateral tissue damage during acute inflammation. However, these phagocytes are endowed with additional characteristics that have been traditionally reserved for cells of the adaptive immune system. They communicate with other cells, exhibit plasticity in their responses and have the potential to coordinate and inform the subsequent immune response, thus countering the notion that they arrive, destroy and then disappear. Therefore, neutrophils, which are the first to arrive at a site of inflammation, are potential game changers in GN.

A Lupus-Associated Mac-1 Variant Has Defects in Integrin Allostery and Interaction with Ligands under Force

Leukocyte CD18 integrins increase their affinity for ligand by transmitting allosteric signals to and from their ligand-binding αI domain. Mechanical forces induce allosteric changes that paradoxically slow dissociation by increasing the integrin/ligand bond lifetimes, referred to as catch bonds. Mac-1 formed catch bonds with its ligands. However, a Mac-1 gene (ITGAM) coding variant (rs1143679, R77H), which is located in the β-propeller domain and is significantly associated with systemic lupus erythematosus risk, exhibits a marked impairment in 2D ligand affinity and affinity maturation under mechanical force. Targeted mutations and activating antibodies reveal that the failure in Mac-1 R77H allostery is rescued by induction of cytoplasmic tail separation and full integrin extension. These findings demonstrate roles for R77, and the β-propeller in which it resides, in force-induced allostery relay and integrin bond stabilization. Defects in these processes may have pathological consequences, as the Mac-1 R77H variant is associated with increased susceptibility to lupus.

ICER is requisite for Th17 differentiation

Inducible cAMP early repressor (ICER) has been described as a transcriptional repressor isoform of the cAMP response element modulator (CREM). Here we report that ICER is predominantly expressed in Th17 cells through the IL-6–STAT3 pathway and binds to the Il17a promoter, where it facilitates the accumulation of the canonical enhancer RORγt. In vitro differentiation from naive ICER/CREM-deficient CD4+ T cells to Th17 cells is impaired but can be rescued by forced overexpression of ICER. Consistent with a role of Th17 cells in autoimmune and inflammatory diseases, ICER/CREM-deficient B6.lpr mice are protected from developing autoimmunity. Similarly, both anti-glomerular basement membrane-induced glomerulonephritis and experimental encephalomyelitis are attenuated in ICER/CREM-deficient mice compared with their ICER/CREM-sufficient littermates. Importantly, we find ICER overexpressed in CD4+ T cells from patients with systemic lupus erythematosus. Collectively, our findings identify a unique role for ICER, which affects both organ-specific and systemic autoimmunity in a Th17-dependent manner.

The mechanisms of up-regulation of dendritic cell activity by oxidative stress

Whereas DC have increasingly been recognized for their role in activating the inflammatory cascades during IRIs, the mechanisms by which oxidative stress enhances DC activation remain to be explored. We examined the role of oxidative stress on two important features of DC: T cell activation and trafficking. Bone marrow‐derived OS‐DC were compared with untreated DC. DC exposed to oxidative stress augmented allogeneic T cell proliferation and showed increased migration in a chemotaxis chamber. These results were confirmed by using hypoxanthine and xanthine oxidase as another inducer of oxidative stress. We used OT‐II and OT‐I mice to assess the effect of oxidative stress on DC activation of OVA‐specific CD4+ and CD8+ T cells, respectively. Oxidative stress increased DC capacity to promote OVA‐specific CD4+ T cell activity, demonstrated by an increase in their proliferation and production of IFN‐γ, IL‐6, and IL‐2 proinflammatory cytokines. Whereas oxidative stress increased the DC ability to stimulate IFN‐γ production by OVA‐specific CD8+ T cells, cellular proliferation and cytotoxicity were not affected. Compared with untreated DC, oxidative stress significantly reduced the capacity of DC to generate Tregs, which were restored by using anti‐IL‐6. With regard to DC trafficking, whereas oxidative stress increased DC expression of p‐Akt and p‐NF‐κB, targeting PI3Kγ and NF‐κB pathways abrogated the observed increase in DC migration. Our data propose novel insights on the activation of DC by oxidative stress and provide rationales for targeted therapies, which can potentially attenuate IRI.