Chorionic gonadotropin alleviates thioglycollate-induced peritonitis by affecting macrophage function

Human chorionic gonadotrophin (hCG) is a hormone produced during pregnancy and present at the implantation site and in the maternal blood. Pregnancy has been proposed to represent a controlled state of inflammation at an early stage at the implantation site and later, systemically extended to the maternal circulation. Earlier, we reported that hCG can inhibit the development of diabetes in NOD mice and LPS-induced septic shock in a murine model. We hypothesize that hCG can contribute to the reduction of inflammation by modifying Mphi function. Here, the TG-induced peritonitis model for inflammation was used to investigate the effect of hCG on cytokine production and cell recruitment in vivo. hCG pretreatment in TG-induced peritonitis increased the number of peritoneal cells, especially PMN and monocytes, compared with mice injected with TG only. This increased cell number was partially explained by increased cell survival induced by hCG. Despite the cellular infiltrate, hCG pretreatment decreased i.p. TNF-alpha, IL-6, PTX3, CCL3, and CCL5 levels. By depleting peritoneal resident Mphi using clodronate liposomes prior to the application of hCG and the TG trigger, we established that Mphi are the main responsive cells to hCG, as the suppressed TNF-alpha and IL-6 production and increased PMN influx are abolished in their absence. Together, these data suggest that hCG contributes to the controlled inflammatory state of pregnancy by regulating Mphi proinflammatory function.

An increased MRP8/14 expression and adhesion, but a decreased migration towards proinflammatory chemokines of type 1 diabetes monocytes

In the early development of type 1 diabetes macrophages and dendritic cells accumulate around the islets of Langerhans at sites of fibronectin expression. It is thought that these macrophages and dendritic cells are derived from blood monocytes. Previously, we showed an increased serum level of MRP8/14 in type 1 diabetes patients that induced healthy monocytes to adhere more strongly to fibronectin (FN). Here we show that MRP8/14 is expressed and produced at a higher level by type 1 diabetes monocytes, particularly after adhesion to FN, creating a positive feedback mechanism for a high fibronectin-adhesive capacity. Also adhesion to endothelial cells was increased in type 1 diabetes monocytes. Despite this increased adhesion the transendothelial migration of monocytes of type 1 diabetes patients was decreased towards the proinflammatory chemokines CCL2 and CCL3. Because non-obese diabetic (NOD) mouse monocytes show a similar defective proinflammatory migration, we argue that an impaired monocyte migration towards proinflammatory chemokines might be a hallmark of autoimmune diabetes. This hampered monocyte response to proinflammatory chemokines questions whether the early macrophage and dendritic cell accumulation in the diabetic pancreas originates from an inflammatory-driven influx of monocytes. We also show that the migration of type 1 diabetes monocytes towards the lymphoid tissue-related CCL19 was increased and correlated with an increased CCR7 surface expression on the monocytes. Because NOD mice show a high expression of these lymphoid tissue-related chemokines in the early pancreas it is more likely that the early macrophage and dendritic cell accumulation in the diabetic pancreas is related to an aberrant high expression of lymphoid tissue-related chemokines in the pancreas.

Evidence for an enhanced adhesion of DC to fibronectin and a role of CCL19 and CCL21 in the accumulation of DC around the pre-diabetic islets in NOD mice

The non-obese diabetic (NOD) mouse is a widely used animal model for the study of human diabetes. The lymphocytic (peri-)insulitis is preceded by an early accumulation of dendritic cells (DC) around the islets of Langerhans. This DC accumulation is thought to derive from an influx of monocytes attracted by pro-inflammatory chemokines. Besides chemokines, extracellular matrix (ECM) proteins play an important role in the accumulation of leukocytes in tissues. We studied the expression of the chemokines CCL2, CCL5, CXCL10, CCL19 and CCL21 over time in pancreases of NOD and control mice by ELISA on pancreas lysates as well as by immunohistochemistry. In addition, we studied the adhesive capacity of bone marrow-derived DC (BMDC) to ECM components. DC in the NOD pancreas accumulated at sites with an intense expression of fibronectin. In vitro, NOD BMDC showed increased fibronectin adhesion and increased VLA-5 expression. At the time of early DC accumulation (<10 wk), the lymphoid tissue-related chemokines CCL19 and CCL21 were increased. Our findings support the view that the early accumulation of DC around the NOD islets is not the consequence of an enhanced attraction of precursors and immature DC by pro-inflammatory chemokines. It rather might be the consequence of an aberrantly enhanced adhesion and retention of NOD DC.

NOD mice have a severely impaired ability to recruit leukocytes into sites of inflammation

The accumulation of macrophages (M Phi) and dendritic cells (DC) in the pancreas plays a crucial role in the pathogenesis of autoimmune diabetes. We studied the recruitment of monocytes, M Phi and DC to sites of inflammation, i.e. the peritoneal cavity and a subcutaneously elicited air pouch in the NOD mouse model of autoimmune diabetes. The leukocyte recruitment was studied from 1 to 7 days after injection of thioglycollate (peritoneum), C5a (peritoneum, air pouch), CCL2 and CCL3 (air pouch). C57BL/6 and BALB/c mice served as controls. Morphological and flow cytometric analysis of the recruited cells was performed, IL-1 beta, TNF-alpha, IL-6, IL-12 and IL-10 in exudates measured, and in vitro CCL2-chemotaxis of exudate M Phi (Boyden chamber) determined. NOD mice were strongly impaired in the recruitment of M Phi, DC, monocytes, and granulocytes. Chemokine-injected air pouches of NOD mice showed an increased IL-10 and a decreased IL-1 beta level, while the other cytokines were normally or very lowly expressed. In addition, NOD exudate M Phi displayed an impaired in vitro CCL2-induced migration. Our data show that NOD mice have an impaired ability to recruit leukocytes into sites of inflammation elicited in the peritoneum and the air pouch. A raised IL-10/IL-1 beta ratio at these sites and a deficient migratory capacity of NOD monocytes are important determinants in this impairment.