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Tag: inflammation (Page 1 of 2)

Hepatic stellate cell activation markers are regulated by the vagus nerve in systemic inflammation

Osman Ahmed, April S. Caravaca, María Crespo, Wanmin Dai, Ting Liu, Qi Guo , Magdalena Leiva, Guadalupe Sabio, Vladimir S. Shavva, Stephen G. Malin & Peder S. Olofsson.

The liver is an important immunological organ and liver inflammation is part of the pathophysiology of non-alcoholic steatohepatitis, a condition that may promote cirrhosis, liver cancer, liver failure, and cardiovascular disease. Despite dense innervation of the liver parenchyma, little is known about neural regulation of liver function in inflammation. Here, we study vagus nerve control of the liver response to acute inflammation.

Detection by FACS of activated hepatic stellate cells (Image: María Crespo).

Methods: Male C57BL/6 J mice were subjected to either sham surgery, surgical vagotomy, or electrical vagus nerve stimulation followed by intraperitoneal injection of the TLR2 agonist zymosan. Animals were euthanized and tissues collected 12 h after injection. Samples were analyzed by qPCR, RNAseq, flow cytometry, or ELISA.

Results: Hepatic mRNA levels of pro-inflammatory mediators Ccl2, Il-1β, and Tnf-α were significantly higher in vagotomized mice compared with mice subjected to sham surgery. Differences in liver Ccl2 levels between treatment groups were largely reflected in the plasma chemokine (C-C motif) ligand 2 (CCL2) concentration. In line with this, we observed a higher number of macrophages in the livers of vagotomized mice compared with sham as measured by flow cytometry. In mice subjected to electrical vagus nerve stimulation, hepatic mRNA levels of Ccl2, Il1β, and Tnf-α, and plasma CCL2 levels, were significantly lower compared with sham. Interestingly, RNAseq revealed that a key activation marker for hepatic stellate cells (HSC), Pnpla3, was the most significantly differentially expressed gene between vagotomized and sham mice. Of note, several HSC-activation associated transcripts were higher in vagotomized mice, suggesting that signals in the vagus nerve contribute to HSC activation. In support of this, we observed significantly higher number of activated HSCs in vagotomized mice as compared with sham as measured by flow cytometry.

Conclusions: Signals in the cervical vagus nerve controlled hepatic inflammation and markers of HSC activation in zymosan-induced peritonitis.

Conventional type 1 dendritic cells protect against age-related adipose tissue dysfunction and obesity

Elena Hernández-García, Francisco J. Cueto, Emma C. L. Cook, Ana Redondo-Urzainqui, Sara Charro-Zanca, Iñaki Robles-Vera, Ruth Conde-Garrosa, Ivana Nikolić, Guadalupe Sabio, David Sancho & Salvador Iborra.

Conventional dendritic cells (cDCs) scan and integrate environmental cues in almost every tissue, including exogenous metabolic signals. While cDCs are critical in maintaining immune balance, their role in preserving energy homeostasis is unclear.

Body composition by MRI.

Here, we showed that Batf3-deficient mice lacking conventional type 1 DCs (cDC1s) had increased body weight and adiposity during aging. This led to impaired energy expenditure and glucose tolerance, insulin resistance, dyslipidemia, and liver steatosis. cDC1 deficiency caused adipose tissue inflammation that was preceded by a paucity of NK1.1+ invariant NKT (iNKT) cells. Accordingly, among antigen-presenting cells, cDC1s exhibited notable induction of IFN-γ production by iNKT cells, which plays a metabolically protective role in lean adipose tissue. Flt3L treatment, which expands the dendritic cell (DC) compartment, mitigated diet-induced obesity and hyperlipidemia in a Batf3-dependent manner. This effect was partially mediated by NK1.1+ cells.

These results reveal a new critical role for the cDC1-iNKT cell axis in the regulation of adipose tissue homeostasis.

Resident macrophage-dependent immune cell scaffolds drive anti-bacterial defense in the peritoneal cavity

Adrián Vega-Pérez, Laura H. Villarrubia, Cristina Godio, Alejandra Gutiérrez-González, Lidia Feo-Lucas, Margarita Ferriz, Natalia Martínez-Puente, Julieta Alcaín, Alfonso Mora, Guadalupe Sabio, María López-Bravo, Carlos Ardavín.

Peritoneal immune cells reside unanchored within the peritoneal fluid in homeostasis. Here, we examined the mechanisms that control bacterial infection in the peritoneum using a mouse model of abdominal sepsis following intraperitoneal Escherichia coli infection.

Whole-mount immunofluorescence and confocal microscopy of the peritoneal wall and omentum revealed that large peritoneal macrophages (LPMs) rapidly cleared bacteria and adhered to the mesothelium, forming multilayered cellular aggregates composed by sequentially recruited LPMs, B1 cells, neutrophils, and monocyte-derived cells (moCs). The formation of resident macrophage aggregates (resMφ-aggregates) required LPMs and thrombin-dependent fibrin polymerization. E. coli infection triggered LPM pyroptosis and release of inflammatory mediators. Resolution of these potentially inflammatory aggregates required LPM-mediated recruitment of moCs, which were essential for fibrinolysis-mediated resMφ-aggregate disaggregation and the prevention of peritoneal overt inflammation.

Thus, resMφ-aggregates provide a physical scaffold that enables the efficient control of peritoneal infection, with implications for antimicrobial immunity in other body cavities, such as the pleural cavity or brain ventricles

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