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Summary: Activated macrophages must carefully calibrate their inflammatory responses to balance efficient pathogen control with inflammation-mediated tissue damage, but the molecular underpinnings of this “balancing act” remain unclear. Using genetically engineered mouse models and primary macrophage cultures, we show that Toll-like receptor (TLR) signaling induces the expression of the transcription factor Spic selectively in patrolling monocytes and tissue macrophages by a nuclear factor κB (NF-κB)-dependent mechanism. Functionally, Spic downregulates pro-inflammatory cytokines and promotes iron efflux by regulating ferroportin expression in activated macrophages. Notably, interferon-gamma blocks Spic expression in a STAT1-dependent manner. High levels of interferon-gamma are indicative of ongoing infection, and in its absence, activated macrophages appear to engage a “default” Spic-dependent anti-inflammatory pathway. We also provide evidence for the engagement of this pathway in sterile inflammation. Taken together, our findings uncover a pathway wherein counter-regulation of Spic by NF-κB and STATs attune inflammatory responses and iron metabolism in macrophages.

Pancreatic β-cell survival remains poorly understood despite decades of research. GATA transcription factors broadly regulate embryogenesis and influence survival of several cell types, but their role in adult β-cells remains undefined. To investigate the role of GATA factors in adult β-cells, we derived β-cell-inducible Gata4- and Gata6-knockout mice, along with whole-body inducible Gata4 knockouts. β-Cell Gata4 deletion modestly increased the proportion of dying β-cells in situ with ultrastructural abnormalities suggesting endoplasmic reticulum (ER) stress. Notably, glucose homeostasis was not grossly altered in Gata4- and Gata6-knockout mice, suggesting that GATA factors do not have essential roles in β-cells. Several ER stress signals were up-regulated in Gata4 and Gata6 knockouts, most notably CHOP, a known regulator of ER stress-induced apoptosis. However, ER stress signals were not elevated to levels observed after acute thapsigargin administration, suggesting that GATA deficiency only caused mild ER stress. Simultaneous deletion of Gata4 and CHOP partially restored β-cell survival. In contrast, whole-body inducible Gata4 knockouts displayed no evidence of ER stress in other GATA4-enriched tissues, such as heart. Indeed, distinct GATA transcriptional targets were differentially expressed in islets compared with heart. Such β-cell-specific findings prompted study of a large meta-analysis dataset to investigate single nucleotide polymorphisms harbored within the human GATA4 locus, revealing several variants significantly associated with type 1 diabetes mellitus. We conclude that GATA factors have important but nonessential roles to promote ER integrity and β-cell survival in a tissue-specific manner and that GATA factors likely contribute to type 1 diabetes mellitus pathogenesis.

The existence of adult β-cell progenitors remains the most controversial developmental biology topic in diabetes research. It has been reported that β-cell progenitors can be activated by ductal ligation–induced injury of adult mouse pancreas and apparently act in a cell-autonomous manner to double the functional β-cell mass within a week by differentiation and proliferation. Here, we demonstrate that pancreatic duct ligation (PDL) does not activate progenitors to contribute to β-cell mass expansion. Rather, PDL stimulates massive pancreatic injury, which alters pancreatic composition and thus complicates accurate measurement of β-cell content via traditional morphometry methodologies that superficially sample the pancreas. To overcome this potential bias, we quantified β-cells from the entire pancreas and observed that β-cell mass and insulin content are totally unchanged by PDL-induced injury. Lineage-tracing studies using sequential administration of thymidine analogs, rat insulin 2 promoter–driven cre-lox, and low-frequency ubiquitous cre-lox reveal that PDL does not convert progenitors to the β-cell lineage. Thus, we conclude that β-cells are not generated in injured adult mouse pancreas.

The majority of Wiskott–Aldrich syndrome protein (WASP) in T cells is in a complex with WASP interacting protein (WIP), a 503 a.a. long proline rich protein. Here we demonstrate that a novel anti-WIP mAb, 3D10, recognizes an epitope in the N-terminal domain of the WIP protein, within the sequence 13 PTFALA 18 . mAb 3D10 competes with actin, but not with WASP or Nck, for WIP binding. Analysis of 3D10 immunoprecipitates failed to demonstrate dissociation of the WASP–WIP complex after TCR ligation that we previously reported using a polyclonal anti-WIP anti-serum raised against a C-terminal peptide (a.a. 459–503) that spanned the WASP binding site. 3D10 mAb allowed the detection of a novel isoform of WIP consisting of a truncated 403 a.a. long protein that includes the 377 a.a. encoded by the first 4 exons of WIP followed by a 26 a.a. sequence encoded by intron 4.